WO2010077309A2

WO2010077309A2 - External fixation apparatus with adjustable pin clamping means and convergent bone pins

Info

Publication number: WO2010077309A2
Application number: PCT/US2009/006566
Authority: WO
Inventors: Mohammed A. Hajianpour
Original assignee: Nutek Orthopaedics, Inc.
Priority date: 2008-12-17
Filing date: 2009-12-16
Publication date: 2010-07-08
Also published as: WO2010077309A3

Abstract

An external fixation device for holding bone fragments in place includes a housing having a number of internal mounting surfaces, in which rotationally adjustable pin holders are held by individual clamping members that simultaneously clamp the pin holder and a bone pin within the pin holder. Some of the internal surfaces are arranged to hold bone pins converging in a region of convergence spaced apart from the housing. One embodiment is arranged to hold bone fragments in place within a fractured distal radius, while another embodiment includes a rounded portion shaped as an arc.

Description

THE DESCRIPTION

EXTERNAL FIXATION APPARATUS WITH ADJUSTABLE PIN CLAMPING MEANS AND CONVERGENT BONE PINS

TECHNICAL FIELD

This invention relates to apparatus for the external fixation of fractured bones, and, more particularly, to such apparatus having means for adjustably mounting and clamping a number of bone pins to a housing.

BACKGROUND ART

External fixation often provides the best method for holding bone fragments in place during he healing of a severe bone fracture, in which multiple bone fragments are formed. In the external fixation process, bone pins or wires ate surgically attached to the individual bone fragments and to intact sections of bone, so that a desired alignment of multiple fragments can be maintained during the healing process. The individual bone pins or wires are also attached to a frame that is external to the body to be held in a fixed configuration. Then, after the bone fragments have joined to one another in a satisfactory manner, the bone pins or wires are removed from the bones and from the body in another surgical procedure, With external fixation, an ability to hold individual bone fragments in place often makes in possible to achieve results that cannot be achieved using other conventional techniques, such as casting.

Since serious bone fractures can occur in many different ways in various parts of the body, forming various configuration of bone fragments, it is highly desirable that a device for external fixation should be configured in a variety of different ways, reducing the number of different types of fixation devices that need to be held in inventory to meet expected demands. To this end, the patent literature includes a number of descriptions of fixation devices that can be assembled from multiple elements in various ways or that can be adjusted to provide various configurational features. For example, a fixture may include several holes for clamping members to hold bone pins disposed within an elongated portion and a number of holes in a rectangular pattern, which can accommodate a variety of pin configurations. Such an arrangement may be used, for example, to fasten the elongated portion of the fixture to the shaft of the radius bone within the arm and to attach various fragments within a broken wrist to a pattern of pins clamped within the rectangular array. A configuration for applying external fixation to a fractured tibia is also described as including a frame an elongated lower section for fastening the frame to the shaft of the tibia using bone pins extending along a straight line and an arcuate section extending from each side of the upper end of the elongated lower section for clamping bone pins extending into bone fragments within the upper portion of the tibia.

Another method for obtaining flexibility within an external fixation device is to provide a number of clamping elements holding one or more bone pins, with the clamping elements being attached to one another by devices providing for pivotal adjustment. For example, a fixture may include a number of clamping elements, each of which clamps a pair of bone pins extending parallel to one another and a rod to which the clamping elements are attached by means of a pair of pivoting clamps providing for rotational adjustment and clamping about two axes perpendicular to one another. Alternately, a fixation device may have a pair of elongated carriers, each of which supports a pair of bone screws that are movable along the carrier by rotating a spindle. The carriers are joined to one another by a connector including a rigid rod and a ball at each end. The balls are received by partly spherical sockets that can be fixed relative to the balls through screws. An external fixation may include a fixation block from which one or more arms extend, with a ball and socket joint connecting each arm to the block for universal movement thereabout. Setscrews are then provided for tightening the ball and socket joints. A fixation device may have a pair of clamping members, each of which includes a row of holes into which bone pins may be inserted and clamped, with the clamping members being connected by a tube, into which a rod extends from one of the clamping members, while a ball from the other connecting member extends into a partially spherical hole within the tube.

Setscrews are then provided for clamping the rod and ball in place within the tube. A common method for the treatment of a fractured distal radius involves the use of standard immobilizing cast techniques, preventing movement of the radiocarpal joint throughout the course of rehabilitation. A problem with this method is that it sometimes results in inadequate internal fixation, which can cause deformity, pain, and prolonged disability.

The process of external pin fixation is alternately used in the repair of a fractured distal radius. This process initially involves the surgical insertion of skeletal traction pins on both sides of the fracture, with a frame being connected to the pins for immobilizing the bones, and for holding them together until the fracture is mended. Conventional methods for applying external pin fixation for the treatment of a fractured distal radius provide for the immobilization of the radiocarpal joint, so that the hand cannot be flexed. For example, frames used for this type of external fixation rigidly but adjustably connects a pair of pins extending into the metacarpal bones with a pair of pins extending into the radius on the proximal side of the fracture. While this type of fixation often provides an improvement over conventional casting techniques in the management of severe fractures of the distal radius, immobilization of the radiocarpal joint during the treatment period typically results in a long period of stiffness and disability after the external fixation device is removed. Typically the external fixation device is left in place during the healing process for six to eight weeks. After the fixation device is removed, three to six months are required for the patient to regain motion of his hand.

A fixation device may be configured to provide adequate fixation during the healing process while allowing flexure in the radiocarpal joint. Such a fixation device includes a number of pins clamped within pin mounting holes. Each pin extends through a flexible sleeve and through a clamping nut. Each pin-mounting hole includes a pilot hole guiding the pin and an internally threaded portion engaging an externally threaded portion of the clamping nut. As the clamping nut istightened, the flexible sleeve is longitudinally compressed, so that it expands transversely to clamp itself within the pin-mounting hole and to clamp the pin within itself. The fixation device, which is configured particularly for external fixation of a fractured distal radius, includes a first number of such pins configured for attachment within a shaft portion of the radius and a second number of such pins configured to attachment to one or more fragments of the fractured radius. The fixation device also includes a sliding attachment block supporting a number of pins extending for lateral attachment to such a fragment.

However, in the holes used in such a device to mount pins within the first number of pins, what is needed is a somewhat more simple, and therefore cost- effective, method for holding the pins in place. Such a method would preferably eliminate the need for the flexible sleeves to translate longitudinal compression into transverse clamping forces. In the holes used to mount pins within the second number of pins, what is needed is a more simple method, which will preferably clamp all of the pins in use simultaneously. Two or more of these pins may be used to clamp a single bone fragment in two or more places, or several pins may be used to clamp several bone fragments. Furthermore, since the process of setting a distal radius fracture typically includes an application of extension to the distal fragment(s), what is needed is a feature simplifying the application of such extension forces as the fixation device is installed on the fractured radius. What is needed is a method for adjusting the angular relationships between certain individual pins in such a fixture and a more simple method to hold pins directed laterally into the bone fragment(s).

What is needed is a bone fixation device having the flexibility of adjusting the angle at which individual bone pins extend from a housing or frame, preferably with such an adjustment being provided through a clamping device that simultaneously clamps both the linear extension of the bone pin, along its length, and its angle relative to the housing or frame.

DISCLOSURE OF INVENTION

In accordance with one aspect of the invention, apparatus for external fixation of bone fragments is provided, with the apparatus including a housing, a plurality of bone pins, and a plurality of clamping members. The housing includes first and second pluralities of internal mounting surfaces and first and second pluralities of apertures, with each of the internal mounting surfaces and each of the apertures being formed as rounded surfaces extending around and along a central axis of the internal mounting surface. Each of the deformable pin holders, which are held within the housing, includes a spherical external surface engaging one of the internal mounting surfaces within the housing, a pin mounting hole extending in a straight line through a center of the spherical external surface, and a first slot extending in a direction perpendicular to the pin mounting hole across the pin mounting hole and partially across the pin holder, displaced inward from a first end of the pin mounting hole, and forming a first deflectable portion of the pin holder between the first slot and the first end of the pin mounting hole. The bone pins are each held within the pin mounting hole in one of the deformable pin holders to extend through one of the apertures. An angle, relative to the housing, at which each of the bone pins extends through the aperture, is varied by pivoting the pin holder within the housing, with each of the bone pins being adjustable within a conical region about the central axis of the internal mounting surface. The central axes of the first plurality of pin holders extend parallel to one another, while the central axes of the second plurality of pin holders extend along the housing through a first distance at acute angles relative to one another to hold bone pins to converge within a region of convergence spaced apart from the elongated portion and substantially shorter than the first distance. The clamping members each engage ome of the deformable pin holders to hold the pin holder in place within the housing, while simultaneously deflecting the first deformable portion of the pin holder to hold the bone pin in place within the pin holder.

Preferably, each of the deformable pin holders additionally includes a second slot extending in a direction perpendicular to the pin mounting hole across the pin mounting hole and partially across the pin holder, displaced inward from a second end of the pin mounting hole, forming a second deflectable portion of the pin holder between the second slot and the second end of the pin mounting hole. The clamping member then simultaneously deflects the second deformable portion of the pin holder to hold the bone pin in place within the pin holder.

Preferably, each clamping member includes a threaded surface and an annular surface engaging the first deformable portion of one of the deformable pin holders, while the housing includes a plurality of threaded surfaces, each disposed adjacent an aperture in the plurality of apertures, with the threaded surface of each of the clamping members engaging one of the threaded surfaces of the housing. Then, as each of the clamping members is rotated in a first direction, an engagement force between the spherically rounded surface of the pin holder clamped in place within the housing by the clamping member and the internal mounting surface within the housing is increased to hold the pin holder in place within the housing, and deflection of the deformable portion of the pin holder is increased to hold the bone pin in place within the pin holder. As each of the clamping members is rotated opposite the first direction, the engagement force between the spherically rounded surface of the pin holder and the internal mounting surface within the housing is decreased to allow rotation of the spherically rounded surface of the pin holder within the internal mounting surface of the housing and to allow movement of the bone pin within the pin mounting hole of the pin holder.

In accordance with another aspect of the invention, apparatus is provided for the external fixation of bone fragments within a fractured distal radius, with the apparatus including a housing, a plurality of deformable pin holders, a plurality of bone pins that are each held within one of the deformable pin holders, a plurality of shank attachment pins, a plurality of fragment attachment pins, and a clamping bracket.: The housing includes an elongated shank mounting portion, a fragment attachment pin array section at a first end of the elongated shank mounting portion, and a lateral fragment mounting section extending parallel to the elongated shank mounting portion and downward from an edge of the fragment attachment pin array section. The elongated shank mounting portion of the housing includes a plurality of pin mounting structures. The fragment attachment pin array section of the housing includes a first array of fragment attachment pin holes extending through the housing,

The lateral fragment mounting section includes a plurality of internal mounting surfaces and a plurality of apertures, with each of the internal mounting surfaces and each of the apertures being formed as rounded surfaces extending around and along a central axis of the internal mounting surface.

The plurality of deformable pin holders, which are held within the housing, each includes a spherical external surface engaging one of the internal mounting surfaces within the housing, a pin mounting hole extending in a straight line through a center of the spherical external surface, and a first slot. The first slot extends in a direction perpendicular to the pin mounting hole across the pin mounting hole and partially across the pin holder, being displaced inward from a first end of the pin mounting hole, forming a first deflectable portion of the pin holder between the first slot and the first end of the pin mounting hole. The plurality of bone pins, each extend through an aperture in the plurality of apertures, with an angle, relative to the housing, at which each of the bone pins extends through the aperture being varied by pivoting the pin holder within the housing. The shank attachment pins are invividually held within the plurality of pin mounting structures within the shank mounting portion of the housing. The plurality of fragment attachment pins extends through the first array of fragment attachment pin holes. The clamping bracket includes a second array of fragment attachment pin holes. The clamping bracket is mounted on the fragment attachment pin array section to be moved between a position in which the first and second arrays of fragment attachment pin holes are aligned with one another and a position in which the first and second arrays of fragment attachment pin holes are moved out of alignment with one another to clamp the plurality of fragment attachment pins within the fragment attachment array section.

Preferably, one of the pin mounting structures within the elongated shank mounting portion includes an additional internal mounting surface and an additional aperture as described above, with the apparatus additionally including an additional deformable pin holder, held within the additional internal mounting surface, and an additional clamping member engaging the additional pin holder, and with one of the shank attachment pins being held within the pin mounting hole in the additional deformable pin holder.

Preferably, the clamping bracket includes a first clamping plate having the second array of fragment attachment pin holes and a second clamping plate having a third array of fragment attachment pin holes, aligned with the first array of fragment attachment pin holes, with the first and second clamping plates being disposed on opposite sides of the fragment attachment pin array section of the housing.

In one version of the apparatus for external fixation of a fractured distal radius, one of the pin mounting structures within the elongated shank mounting portion includes a pin adjustment slot, with the apparatus additionally including a nut mounted to slide within the pin adjustment slot, a collet screw, a distraction clamp, and a distraction screw. The nut includes inclined surfaces engaging the pin adjustment slot to prevent rotation of the nut within the pin adjustment slot and to prevent removal of the nut from the pin adjustment slot. The collet screw additionally slides within the pin adjustment slot. One of the shank attachment pins forms a linearly adjustable bone pin extending through a hole within the collet screw, which includes a deformable threaded portion engaging the nut. As the collet screw is rotated in a first direction, an engagement force between the collet screw and the linearly adjustable bone pin is increased to hold the linearly adjustable bone pin in place collet screw and to hold the nut in place within the pin adjustment slot. Then, as the collet screw is rotated opposite the first direction, the engagement force between the collet screw and the linearly adjustable bone pin is decreased to release the linearly adjustable bone pin to move within the collet screw and the nut is released to slide within the pin adjustment slot. The distraction clamp removably holds the linearly adjustable bone pin; and the distraction screw engaging the distraction clamp and the housing. Turning the distraction screw in a second direction moves the linearly adjustable bone pin toward a proximal end of the housing, hile turning the distraction screw opposite the second direction allows the linearly adjustable bone pin to move away from the proximal end of the housing.

In accordance with yet another aspect of the invention, apparatus is provided for the external fixation of bone fragments, with the apparatus including a housing having a curved portion, extending in an arc around an arc axis, a plurality of internal mounting surfaces, with a first plurality of the internal mounting surfaces and apertures as described above disposed within the curved portion. The central axis of . each of the internal mounting surfaces within the first plurality extends to the arc axis, a plurality of deformable pin holders as described above. Pluralities of deformable pin holders, bone pins, and clamping members are disposed within the individual internal mounting surfaces.

The housing may also include a first linear portion, extending in a straight line parallel to the arc axis, including a second plurality of internal mounting surfaces. The first linear portion may extend from a first end of the curved portion, with a second liner portion, including a third plurality of internal mounting surfaces, extending from the second end of the curved portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG 1 is a perspective view of a device for external fixation of bone fragments, shown as used for a proximal fracture of the humerus;

FIG. 2 is a perspective view of a device similar to the device of FIG. 1, shown as used for a proximal fracture of the tibia;

FIG. 3 is a fragmentary front elevation of the device of FIG. 1 ;

FIG. 4 is a perspective view of a pin holder within the device of FIG. 1 ;

FIG. 5 is a transverse cross-sectional elevation of a pin mounting structure within a housing built in accordance with the invention;

FIG. 6 is a perspective view of the pin mounting structure of FIG. 5;

FIG. 7. is a lateral cross-sectional view of a bone fixation device built in accordance with a first embodiment of the invention, including a number of the pin mounting structures of FIG. 5;

FIG. 8 is a perspective view of a fixation device built in accordance with a second embodiment of the invention, shown as used with a distal fracture of the humerus;

FIG. 9 is a perspective view of the fixation device of FIG. 8, shown as used with a distal fracture of the tibia;

FIG. 10 is a perspective view of the fixation device of FIG. 8, shown as used with a proximal fracture of the tibia;

FIG. 1 1 is a perspective view of an alternative fixation device housing additionally built in accordance with the second embodiment; and

FIG. 12 is an elevation of a fixation device using the housing of FIG. 11 , shown as used with a fractured phalange.

FIG. 13 is a perspective view of a device built in accordance with a third embodiment of the invention for the external fixation of fragments within a fractured distal radius;

FIG. 14 is a longitudinal cross-sectional view of the device of FIG. 13, taken as indicated by section lines 14-14 therein;

FIG. 15 is a transverse cross-sectional view of the device of FIG. 13, taken as indicated by section lines 15-15 therein;

FIG. 16 is a transverse cross-sectional view of the device of FIG. 13, taken as indicated by section lines 16-16 therein; and

FIG. 17 is a perspective view of a device built in accordance with an alternative version of the third embodiment of the invention for the external fixation of fragments within a fractured distal radius.

MODES FOR CARRYING OUT THE INVENTION

FIG. 1 is a perspective view of a device 10 for the external fixation of bone fragments, including a housing 12 having a vertically elongated central portion 14 and a lateral portion 16 extending outward, in the directions of arrows 18, and rearward, in the direction of arrow 20, from each side of an upper end 22 of vertically elongated central portion 14: The vertically elongated central portion 14 includes a first plurality of the internal mounting surfaces 24; each of which extends outwardly from an aperture 25 within the housing 12, while each lateral portion 16 includes at least one of the internal mounting surfaces 24 extending from an aperture 25. Some of the internal mounting surfaces 24 mount pin holders 28 holding bone pins 28, with the pin holders 28 being held in place by clamping members 30 engaging threaded surfaces 32 of the housing 12. This arrangement provides for the placement of bone pins 28 at various levels extending downward from the upper end 22 of the vertically elongated central portion 14, with the lateral portions 16 being inclined relative to one another so that bone pins 28 can extend inward around a fracture area from these portions 16.

In the example of FIG. 1, the device 10 is shown with various bone pins 28 attached to a fractured humerus bone 34, holding a number of fragments 36 in place at an upper end 38 of the humerus bone 34, with bone pins 28 held within the vertically elongated central portion 14 of the housing 12 attached to the shaft portion 40 of the humerus bone 34. Each of the bone pins 28 includes a threaded end 42 that is driven into engagement with a portion of the bone 34 by a driving tool (not shown) rotating a non-circular-surface (not shown) at an end of the bone pin 28 opposite the threaded end 42. After the bone pin 28 is fastened into place, the bone pin 28 is preferably cut off outwardly adjacent the pin holder 26 in which it is held to limit the distance through which the bone pin 28 extends outwardly from the device 10. The configuration of the device 10 is adjustable in several ways, with pin holders 26 being placed in a subset of the internal mounting surfaces 24, so that bone pins 28 are placed at locations appropriate for the external fixation of a particular fractured bone. In addition, the individual pin holders 26 are angularly adjustable so that each bone pin 28 can be adjusted and clamped in place through a vertical angle of adjustment 44 and through a horizontal angle of adjustment 46, with the bone pin 28 additionally being adjustable along its axis in the directions of arrows 48.

FIG. 2 shows the device 10 with various bone pins 28 attached to a fractured tibia 49, holding a number of fragments 49a in place at the upper end 49b of the tibia, with bone pins 28 held within the vertically elongated portion 14 of the housing 12 attached to the shaft portion 49c of the tibia 49. To achieve non-bridging fixation, allowing movement of the leg and knee while maintaining the fixation of fragments 49a of the tibia 49, all bone pins 28 are fastened into the tibia 49 and fragments thereof 49a, with no bone pins being fastened into the fibia 49d or other bones.

FIG. 3 is a fragmentary front elevation of the device 10, showing one of the clamping members 30, which is provided with a noncircular surface 64 to facilitate rotation of the clamping member 30. As the clamping member 30 is tightened by rotation in a first direction, indicated by arrow 66, an engagement force between the spherically rounded surface 52 of the pin holder 26 clamped in place within the housing 12 by the clamping member 30 and the internal mounting surface 24 within the housing 12 is increased to hold the pin holder 26 in place within the housing 12 and deflection of the deformable portions 54 of the pin holder is increased to hold the bone pin 28 in place within the pin holder 26. As each of the clamping members 30 is rotated opposite the first direction of arrow 66, the engagement force between the spherically rounded surface 52 of the pin holder 26 and the internal mounting surface 24 within the housing 12 is decreased to allow rotation of the spherically rounded surface 52 of the pin holder 26 within the internal mounting surface 24 of the housing 12 and to allow movement of the bone pin 28 within the pin mounting hole 50 of the pin holder 26.. For example, the device 10 may be provided with a box wrench (not shown) for loosening and tightening the clamping members 30.

FIG. 4 is a perspective view of one of one of the pin holders 26, which has a spherical external surface 68. The clamping member 30 includes a pair of slots 58 extending perpendicular to the pin mounting hole 50, inward across the pin mounting hole 50 and partly across the pin holder 26, so that a deformable portion 54 is formed between each end 56 of the pin mounting hole 50 and the slot 58 that is nearer to the end 56.

FIG. 5 is a transverse cross-sectional elevation of a pin mounting structure 200 within a housing 202 built in accordance with the invention. Parts similar to those described above in reference to FIGS. 1 -4, are accorded like reference numbers. A pin 28 is held within a pin holder 26, which is configured as described above in reference to FIG. 3, and which is clamped in place by a clamping member 30 having an outer threaded surface 206 engaging an inner threaded surface 208 within a mounting hole 210 of the housing 202. The mounting hole 210 includes a spherically rounded inner surface 211, engaging a spherical surface 52 of the pin holder 28, and an aperture 212, extending to a surface 213 of the housing 202. Within the mounting hole 210, the inner threaded surface 208, the spherically rounded inner surface 21 1 , and the aperture 212 are coaxial with one another about a central axis 214. The aperture 212 and a clearance hole 215, extending through the clamping member 30, include truncated conical surfaces 216, 218. These truncated conical surfaces 216, 218 together allow movement of the pin 28 between the position indicated by dashed lines 219 and the position indicated by dashed lines 220. For example, the pin 28 may be moved through an angle 222 of thirty degrees from the central axis 214 of the mounting hole 210 and at any angle 226 around the central axis 214.

The pin mounting hole 50 extends through a center of the spherical external surface 68, being divided by the slots 58 into a deflectable part 223 within each of the deformable portions 54 and a central part 224 extending between the slots 58. When the clamping member 30 is tightened by rotation in the direction of arrow

66 to increase an engagement force holding the pin holder 26 in place, the deformable portions 54 are deflected inward, bring the deflectable parts 223 of the pin mounting hole 50 out of alignment with the central part 224 thereof, so that the bone pin 28 is clamped in place within the pin mounting hole. Them, when the clamping member is loosened by rotation opposite the opposite the direction of arrow 66 to decrease the engagement force holding the pin holder 20 in place, the deformable portions 54 return outward, so that the deflectable parts 223 of the pin mounting hole 50 return into alignment with the central part 224 thereof, allowing movement of the bone pin 28 within the pin mounting hole 50.

FIG. 6 is a perspective view of the pin mounting structure 200, showing the bone pin 28 as being adjustable within a conical region 227 about the central axis 214.

FIG. 7 is a lateral cross-sectional view of a bone fixation device 230 built in accordance with a first embodiment of the invention to include a housing 232 having an elongated portion 233 with a number of pin mounting structures 234, each configured as described above in reference to FIG. 6, except that the central axes 214 of the mounting holes 231 are disposed at various angles 236 relative to a surface 238 of the housing 232. The pin mounting structures 234 are additionally arranged so that the central axes 214 converge within a region of convergence 240 that is spaced apart from the elongated portion 233. In addition, as described above in reference to FIG.

6, the bone pins 28 may be individually adjusted within conical regions 227 about the central axes 214, allowing further movement of the pins 28 within the region of convergence 240. This arrangement provides for placing a number of pins within the region of convergence 240, with the pins 28 entering the region from a wide variety of angles. For example, the region of convergence 240 may be located in a region of one or more fractures occurring within a bone, with the pins 28 being variously employed to hold bone fragments in place during the healing process. The housing 232 extends in a first direction of arrow 242, with the pin mounting structures 234 being disposed within a first distance 244. The region of convergence 240 is substantially shorter, in the first direction of arrow 242, than the first distance 244, allowing a concentration of the bone pins 28 within the region of convergence 240 to be much greater than the concentration of the bone pins along the surface 238 of the elongated portion 233.

In the example of FIG. 7, the bone fixation device 230 is shown providing fixation for a proximal fracture 248 of the humerus 250, with surrounding tissues not being shown for clarity. In addition to the pin mounting structures 234, the bone fixation device 230 includes various features, such as outward extending sections 252 of the housing 232 supporting additional bone pins 28, and such as a pin mounting structure 254 that is outside the first distance 244. Due to the adjustability provided within the pin mounting structure 254 a pin 28 held by this structure 254 extends into the region of convergence 240 after entering the shaft portion 256 of the humerus 250 at a low angle 258. Using the flexibility of bone pin placement provided within the bone fixation device 230, regions 260 within the tissue adjacent to the fracture 248 having concentrations of nerves, ligaments, blood vessels, etc. that cannot be disturbed without significant damage to the patient can readily be avoided in the placement of bone pins 28. Since all of the bone pins 28 are fastened into the humerus 250, the fixation device 230 does not bridge the shoulder joint, allowing movement while holding various bone fragments in place.

FIG. 8 is a perspective view of a fixation device 270 built in accordance with a second embodiment of the invention with a housing 272 including an arcuate elongated portion 274 formed as an arc having an arc axis 276. A plurality of bone pins 28 extend from an arcuate surface 278, also formed about the arc axis 276, Each of the bone pins 28 is adjustably held in place by a pin mounting structure 200, configured as described above in reference to FIG. 12. The central axis 214 of each of the pin mounting structures 200 passes through the arc axis 276, so that the central axes 214 are seen to converge upon a region of convergence 280 extending around the arc axis 276. In addition, the housing 270 includes a linearly elongated portion 282 extending from each end of the arcuate elongated structure 274. The linearly elongated portions 282 extend in the same direction, indicated by arrow 284, parallel to the arc axis 276. Each of the linearly elongated portions 282 includes another plurality of bone pins 28, extending toward the arc axis 276, with each of the bone pins 28 being adjustably held in place by a pin mounting structure 200.

In the example of FIG. 8, the fixation device 270 is shown as used to treat a fractured distal humerus 286, with the arcuate elongated portion 274 extending partly around the fractured area 288 at the distal end of the humerus 286 to hold various bone fragments 290 in place, and with the linearly elongated portions 282 extending along the bone shaft 292 to hold the fixation device 270 itself in place using bone pins 28 extending into the bone shaft 292. Since none of the bone pins 28 extend into the radius 294 or the ulna 296, the fixation device does not bridge across the elbow joint, allowing movement at the joint while holding the fragments together.

FIG. 9 is a perspective view of the fixation device 270 as used to provide fixation for a fractured distal tibia 300, with the arcuate elongated portion 274 extending partly around the fractured area 302 to hold various bone fragments 304 in place, and with the linearly elongated portions 282 extending along the bone shaft 306 to hold the fixation device 270 in place using bone pins 28 extending into the bone shaft 306. Since none of the bone pins 28 extend into the fibia 308 or other bones, except for the tibia 300, non-bridging fixation is achieved.

FIG. 10 is a perspective view of the fixation device 270 as used to provide fixation for a fractured proximal tibia 310, as shown in a dorsal view, with the arcuate elongated portion 274 extending partly around the fractured area 312 to hold various bone fragments 314 in place, and with the linearly elongated portions 282 extending along the bone shaft 316 to hold the fixation device 270 in place using bone pins 28 extending into the bone shaft 316. Again, since none of the bone pins 28 extend into the fibia 318 or other bones, except for the tibia 310, non-bridging fixation is achieved.

FlG. 1 1 is a perspective view of a housing 320 for a fixation device, additionally built in accordance with the second embodiment of the invention, with only a single linearly elongated portion 322, extending from one of the ends of an arcuate elongated portion 324. Such fixation devices may be built in various sizes, with larger devices being used for attachment to bones of the arms and legs, and with smaller devices being used to provide fixation for fractured phalanges. Both the overall size of the fixation device and the size of the mounting devices 200 (shown in FIGS. 12 and 13) may be reduced to provide a greater density of smaller pins for use with a fractured phalange. In addition, the housings 272, 320 are preferably composed of a thermoplastic resin that can be easily cut if it is necessary to shorten a part of the housing.

FIG. 12 is a perspective view of a fixation device 326, including the housing 320, as used to provide fixation for a fractured phalange 328, with the arcuate elongated portion 324 extending partly around the fractured area 330 to hold various bone fragments 332 in place, and with the linearly elongated portion 322 extending along a bone shaft 334 to hold the fixation device 326 in place using bone pins 28 extending into the bone shaft 334. Again, since all of the bone pins 28 extend through the phalange 328 and fragments thereof, non-bridging fixation is achieved.

FIG. 13 is a perspective view of a device 400 built in accordance with a third embodiment of the invention for the external fixation of fragments 401 within a fractured distal end 402 of a radius 403. The device 400 includes an elongated shank mounting section 404, a fragment attachment pin array section 406, and a lateral fragment mounting section 408. The elongated shank mounting section 404 includes an angularly adjustable shank mounting pin 410 extending downward, in the direction of arrow 411 , to be fastened into a shank portion 412 of the distal radius 402 and a linearly adjustable shank mounting pin 416, also extending downward, in the direction of arrow 41 1, to be fastened into the shank portion 412. The fragment attachment pin array section 406 includes a plurality of attachment pins 418 extending downward, in the direction of arrow 41 1, to be fastened into a number of the bone fragments 401. The lateral fragment mounting section 408 includes a number of angularly adjustable fragment mounting pins 420 extending laterally, generally in the direction of arrow 422 into a number of the bone fragments 401. (The directions described herein are established according to an assumption that the hand, not shown, but attached to the radius 412, is held outward with the palm facing downward, in the direction of arrow 41 1.)

Non-bridging fixation is achieved by fastening all of the pins 410, 416, 418, 420 of the device 400 into the fragments 401 and the shank portion 412 of the radius 403. None of these pins 410, 416, 418, 420 are fastened into the carpal bones, not shown, but adjacent to the fragments 401, or the bones of the hand, so that the hand and wrist can be flexed and moved normally, without a loss of mobility during the healing process requiring fixation.

FIG. 14 is a longitudinal cross-sectional view of the device 400, taken as indicated by section lines 14-14 in FIG. 13 to show means for attaching the angularly adjustable shank mounting pin 410 and the linearly adjustable shank mounting pin 416 to a shank mounting section 424 within a housing 430 of the device 400. The angularly adjustable shank mounting pin 410 is rotatably mounted and clamped in place as described above in reference to FIGS. 4-4, with various similar elements being accorded like reference numerals.

FIG. 15 is a transverse cross-sectional view of the device 400, taken as indicated be section lines 15-15 in FIG. 16, showing means for attaching the linearly adjustable shank mounting pin 416, the angularly adjustable shank mounting pin 410, and the fragment attachment pins 412. The linearly adjustable shank mounting pin

416 is mounted to slide along the shank mounting housing section 424 in the axial directions of arrows 432, 433, with a collet screw 436 sliding within an adjustment slot 434 in the housing section 424. The collet screw 436 includes a non-circular section 438, a flange 440, a barrel 441 sliding within the slot 434, and a threaded section 442 engaging a nut 443. The nut 443 slides within a slot 444, with dovetail surfaces 446 of the nut 443 engaging dovetail surfaces 448 of the slot 444 to prevent rotation of the nut 443 while allowing the nut 443 to slide within the slot 444. The threaded section 442 of the collet screw 436. includes a plurality of threaded clamping members 450, which move inward to clamp the adjustable shank mounting pin 416 in place within the collet screw 436 as the as the collet screw 436 is rotated into engagement with the nut 443 using the non-cylindrical surface 438 of the collet screw 436.

A distraction clamp 460 is provided to apply a distraction force in the direction of arrow 433 through the fragment mounting pins 418, 420 to the bone fragments 401 within the fractured distal end 402 of the distal radius 403 (shown in FlG. 19). The distraction clamp 460 includes a pair of hooks 462 engaging the linearly adjustable shank mounting pin 416 and a threaded hole 464 engaging a distraction adjustment screw 466. This distraction force is applied, after the surgical placement of the fragment mounting pins 418, 420 within the bone fragments 401 and after the surgical placement of the shank mounting pin 416 within the bone shank portion 412, but before the surgical placement of the adjustable shank mounting pin 410 within the bone shank portion 412, by turning the distraction adjustment screw 466 by means of a non-circular surface 468 to move the housing 430 in the distraction direction of arrow 433. Then, when a suitable level of distraction has been achieved, the linearly adjustable shank mounting pin 416 is clamped into place using the collet screw 436, and the adjustable shank mounting pin 410 is surgically installed within the bone shank portion 412 and clamped to the housing 430 using the clamping member 50. Finally, the distraction clamp 460 is removed from the fixation device 401 by turning the distraction screw 466 so that it is disengaged from the proximal end 470 of the housing 430, and by disengaging the distraction clamp 460 from the linearly adjustable shank mounting pin 416, with the pin 416 passing through slots 472 of the distraction clamp 460.

FIG. 16 is a transverse cross-sectional view of the device 400, taken as indicated by section lines 16-16 in FIG. 13 to show means for mounting and clamping the plurality of fragment attachment pins 418 and the angularly adjustable fragment mounting pins 420. For mounting the fragment attachment pins 418, similar patterns of holes 480 are provided within a distal portion 482 of the housing 430, within a top plate 484 of a U-shaped pin clamping bracket 486, and within a bottom plate 488 of the clamping bracket 486. The U-shaped pin clamping bracket 486 is mounted to slide in and opposite the lateral direction of arrow 422, with inclined sides 494 of the plates 484, 486 within the clamping bracket 486 sliding along inclined sides 496 of the housing 430. The alignment between the patterns of holes 480 within the clamping bracket 486 and the holes 480 within the housing 430 is adjusted using a pair of screws 500, each engaging a threaded hole 502 within the clamping bracket 486 to press an adjacent surface 504 of the housing 430. As the screws 500 are tightened, the holes 480 within the clamping bracket 486 are moved in the direction of arrow 41 1 relative to the holes 480 within the housing 430, so that forces from the surfaces of the holes 480 engaging the fragment attachment pins 418 in opposite directions hold these pins 418 in place.

Preferably, a clamp retaining means 504 is additionally provided to hold the pin clamping bracket 486 in place on the housing 430 in the absence of any

' fragment attachment pins 418. For example, the clamp retaining means 504 includes a pin 506 extending from the housing 430 within a hole 508 in each of the plates 484,

488 of the pin clamping bracket 486, with the hole 508 being large enough to allow the movement of the plates 484, 488 as described above A ramp surface 510 is provided at an edge of each of the plates 484, 488 so that the pin clamping bracket 486 can be snapped in place over the pins 506.

The angularly adjustable fragment mounting pins 420 are each attached rotatably mounted and clamped in place as described above in reference to FIGS. 4-4, with various similar elements being accorded like reference numbers.

In the treatment of a particular facture, fragment mounting pins 418, 420 will be placed in only some of the positions provided for such pins within the device

400. A larger number of such positions are provided, and the angular adjustability of the fragment mounting pins 420 is further provided, so that the device 400 can be used to treat a wide number of different fracture conditions.

FIG. 17 is a perspective view of a device 520 built in accordance with an alternative version of the third embodiment of the invention to have an elongated shank mounting section 522 having two angularly adjustable shank mounting pins

410 instead of one angularly adjustable shank mounting pin 410 and a linearly adjustable shank mounting pin 416. Other aspects of the device 520 are as described above in reference to FIGS. 10-24.

While versions of the devices 400, 520 adapted for providing fixation for a fractured distal radius of the right arm has been shown and described, it is understood that a similar device, having a housing that is a mirror image of the housing 430 described herein, may be configured for providing fixation for a fractured distal radius of the left arm, and that such a device is within the spirit and scope of the invention. It is further understood that apparatus in accordance with the third embodiment of this invention may be readily employed to provide fixation for bone fragments at an end of another bone. While the invention has been described in terms of its preferred embodiments with some degree of particularity, it is understood that this description has been given only by way of example, and that many variations can be made without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

THE CLAIMSWhat is claimed is

1. Apparatus for external fixation of bone fragments, wherein the apparatus comprises: a housing including first and second pluralities of internal mounting surfaces and first and second pluralities of apertures, wherein each of the internal mounting surfaces and each of the apertures are formed as rounded surfaces extending around and along a central axis of the internal mounting surface; a plurality of deformable pin holders held within the housing, wherein each of the deformable pin holders includes a spherical external surface engaging one of the internal mounting surfaces within the housing and a pin mounting hole extending in a straight line through a center of the spherical external surface, and deformable portion; a plurality of bone pins, each held within the pin mounting hole in one of the deformable pin holders to extend through one of the apertures, wherein an angle, relative to the housing, at which each of the bone pins extends through the aperture is varied by pivoting the pin holder within the housing, wherein each of the bone pins is adjustable within a conical region about the central axis of the internal mounting surface, wherein the central axes of the first plurality of pin holders extend parallel to one another, and wherein the central axes of the second plurality of pin holders extend along the housing through a first distance at acute angles relative to one another to hold bone pins to converge within a region of convergence spaced apart from the elongated portion and substantially shorter than the first distance; and a plurality of clamping members, each engaging a deformable pin holder in the plurality of deformable pin holders to hold the deformable pin holder in place within the housing while simultaneously deforming the deformable portion of the pin holder to hold the bone pin in place within the pin holder.

2, The apparatus of claim 1, wherein each of the deformable pin holders additionally includes a first slot extending in a direction perpendicular to the pin mounting hole to form a first portion of the deformable portion and a second slot, spaced apart from the first slot and extending in a direction perpendicular to the pin mounting hole to form a second portion of the deformable portion, the pin mounting hole within each of the pin holders includes a first deflectable portion extending between a first end of the pin mounting hole and the first slot, a second deflectable portion extending between a second end of the pin mounting hole and the second slot, and a central portion extending between the first and second slots, and engaging each of the pin holders with a clamping member in the plurality of clamping members deforms the first and second portions of the deformable portion to move the first and second deflectable portions of the pin mounting hole out of alignment with the central portion of the pin mounting hole.

3. The apparatus of claim 2 wherein each clamping member includes a threaded surface and an annular surface engaging the first deformable portion of one of the deformable pin holders, the housing includes a plurality of threaded surfaces, each disposed adjacent an aperture in the plurality of apertures, the threaded surface of each of the clamping members engages one of the threaded surfaces of the housing, as each of the clamping members is rotated in a first direction, an engagement force between the spherically rounded surface of the pin holder clamped in place within the housing by the clamping member and the internal mounting surface within the housing is increased to hold the pin holder in place within the housing, and deflection of the deformable portion of the pin holder is increased to hold the bone pin in place within the pin holder, and as each of the clamping members is rotated opposite the first direction, the engagement force between the spherically rounded surface of the pin holder and the internal mounting surface within the housing is decreased to allow rotation of the spherically rounded surface of the pin holder within the internal mounting surface of the housing and to allow movement of the bone pin within the pin mounting hole of the pin holder.

4. The apparatus of claim 1 , wherein the housing comprises a curved portion extending in an arc around an arc axis and including the second plurality of the internal mounting surfaces, the central axis of each internal mounting surface within the second plurality extends to the arc axis.

5. The apparatus of claim 1, wherein the housing additionally includes an elongated shank mounting portion, a fragment attachment pin array section at a first end of the elongated shank mounting portion, and a lateral fragment mounting section extending parallel to the elongated shank mounting portion and downward from an edge of the fragment attachment pin array section; the first plurality of internal mounting surfaces extend along the elongated shank mounting portion, the second plurality of internal mounting surfaces extend along the lateral fragment mounting section; the fragment attachment pin array section includes a first array of fragment attachment pin holes extending through the housing, the apparatus additionally comprises a clamping bracket including a second array of fragment attachment pin holes, a plurality of fragment attachment pins extending through the first and second arrays of fragment attachment pin holes, a first plurality of the deformable pin holders held within the first plurality of the internal mounting surfaces, a first plurality of the bone pins held within the first plurality of deformable pin holders, and a first plurality of the clamping members engaging the first plurality of the deformable pin holders, and the clamping bracket is mounted on the fragment attachment pin array section to be moved between a position in which the first and second arrays of fragment attachment pin holes are aligned with one another and a position in which the first and second arrays of fragment attachment pin holes are moved out of alignment with one another to clamp the plurality of fragment attachment pins within the fragment attachment array section.

6. Apparatus for the external fixation of bone fragments within a fractured distal radius, wherein the apparatus comprises: a housing including an elongated shank mounting portion, a fragment attachment pin array section at a first end of the elongated shank mounting portion, and a lateral fragment mounting section extending parallel to the elongated shank mounting portion and downward from an edge of the fragment attachment pin array section, wherein the elongated shank mounting portion includes a plurality of pin mounting structures, wherein the fragment attachment pin array section includes a first array of fragment attachment pin holes extending through the housing, wherein the lateral fragment mounting section includes a plurality of internal mounting surfaces and a plurality of apertures, wherein each of the internal mounting surfaces and each of the apertures are formed as rounded surfaces extending around and along a central axis of the internal mounting surface; a plurality of deformable pin holders held within the housing, wherein each of the deformable pin holders includes a spherical external surface engaging one of the internal mounting surfaces within the housing, a pin mounting hole extending in a straight line through a center of the spherical external surface, and a deflectable portion of the pin holder; a plurality of bone pins, each held within the pin mounting hole in a deformable pin holder within the plurality of deformable pin holders to extend through an aperture in the plurality of apertures, wherein an angle, relative to the housing, at which each of the bone pins extends through the aperture is varied by pivoting the pin holder within the housing; a plurality of clamping members, each engaging a deformable pin holder in the plurality of deformable pin holders to hold the deformable pin holder in place within the housing while simultaneously deforming the deformable portion of the pin holder to hold the bone pin in place within the pin holder; a plurality of shank attachment pins held within the plurality of pin mounting structures within the shank mounting portion of the housing; a plurality of fragment attachment pins extending through the first array of fragment attachment pin holes; and a clamping bracket including a second array of fragment attachment pin holes, wherein the clamping bracket is mounted on the fragment attachment pin array section to be moved between a position in which the first and second arrays of fragment attachment pin holes are aligned with one another and a position in which the first and second arrays of fragment attachment pin holes are moved out of alignment with one another to clamp the plurality of fragment attachment pins within the fragment attachment array section.

7. The apparatus of claim 6, wherein one of the pin mounting structures within the elongated shank mounting portion includes an additional internal mounting surface and an additional aperture, wherein the additional internal mounting surface and the additional aperture are formed as rounded surfaces extending around and along a central axis of the internal mounting surface, the apparatus additionally includes an additional deformable pin holder, held within the additional internal mounting surface and an additional clamping member engaging the additional pin holder, one of the shank attachment pins is held within the pin mounting hole in the additional deformable pin holder to extend through the additional aperture, and an angle, relative to the housing, at which the shank attachment pin held within the pin mounting hole in the additional deformable pin holder is varied by pivoting the pin holder within the housing.

8. The apparatus of claim 6, wherein the clamping bracket includes a first clamping plate having the second array of fragment attachment pin holes and a second clamping plate having a third array of fragment attachment pin holes, aligned with the first array of fragment attachment pin holes, and the first and second clamping plates are disposed on opposite sides of the fragment attachment pin array section of the housing.

9. The apparatus of claim 6, wherein one of the pin mounting structures within the elongated shank mounting portion includes a pin adjustment slot, and wherein the apparatus additionally comprises: a nut slidably mounted within the pin adjustment slot, including inclined surfaces engaging the pin adjustment slot to prevent rotation of the nut within the pin adjustment slot and to prevent removal of the nut from the pin adjustment slot a collet screw additionally sliding within the pin adjustment slot, wherein one of the shank attachment pins forms a linearly adjustable bone pin extending through a hole within the collet screw, wherein the collet screw includes a deformable threaded portion engaging the nut, wherein, as the collet screw is rotated in a first direction, an engagement force between the collet screw and the linearly adjustable bone pin is increased to hold the linearly adjustable bone pin in place collet screw and to hold the nut in place within the pin adjustment slot, and wherein, as the collet screw is rotated opposite the first direction, the engagement force between the collet screw and the linearly adjustable bone pin is decreased to release the linearly adjustable bone pin to move within the collet screw and the nut is released to slide within the pin adjustment slot, a distraction clamp removably holding the linearly adjustable bone pin; and a distraction screw engaging the distraction clamp and the housing, wherein turning the distraction screw in a second direction moves the linearly adjustable bone pin toward a proximal end of the housing, and wherein turning the distraction screw opposite the second direction allows the linearly adjustable bone pin to move away from the proximal end of the housing.

10. The apparatus of claim 6, wherein each of the deformable pin holders additionally includes a first slot extending in a direction perpendicular to the pin mounting hole to form a first portion of the deformable portion and a second slot, spaced apart from the first slot and extending in a direction perpendicular to the pin mounting hole to form a second portion of the deformable portion, the pin mounting hole within each of the pin holders includes a first deflectable portion extending between a first end of the pin mounting hole and the first slot, a second deflectable portion extending between a second end of the pin mounting hole and the second slot, and a central portion extending between the first and second slots, and engaging each of the pin holders with a clamping member in the plurality of clamping members deforms the first and second portions of the deformable portion to move the first and second deflectable portions of the pin mounting hole out of alignment with the central portion of the pin mounting hole.

1 1. The apparatus of claim 10, wherein each clamping member includes a threaded surface and an annular surface engaging the first deformable portion of a pin holder in the plurality of deformable pin holders, the housing includes a plurality of threaded surfaces, each disposed adjacent an aperture in the plurality of apertures, the threaded surface of each of the clamping members engages one of the threaded surfaces of the housing, as each of the clamping members is rotated in a first direction, an engagement force between the spherically rounded surface of the pin holder clamped in place within the housing by the clamping member and the internal mounting surface within the housing is increased to hold the pin holder in place within the housing, and deflection of the deformable portion of the pin holder is increased to hold the bone pin in place within the pin holder, and as each of the clamping members is rotated opposite the first direction, the engagement force between the spherically rounded surface of the pin holder and the internal mounting surface within the housing is decreased to allow rotation of the spherically rounded surface of the pin holder within the internal mounting surface of the housing and to allow movement of the bone pin within the pin mounting hole of the pin holder.

12. Apparatus for external fixation of bone fragments, wherein the apparatus comprises: a housing including a curved portion, extending in an arc around an arc axis, a plurality of internal mounting surfaces, and a plurality of apertures, wherein each of the internal mounting surfaces and each of the apertures are formed as rounded surfaces extending around and along a central axis of the internal mounting surface, wherein the plurality of internal mounting surfaces includes a first plurality of internal mounting surfaces, each disposed within the curved portion, and wherein the central axis of each of the internal mounting surfaces in the first plurality extends to the arc axis; a plurality of deformable pin holders held within the housing, wherein each of the deformable pin holders includes a spherical external surface engaging one of the internal mounting surfaces within the housing, a pin mounting hole extending in a straight line through a center of the spherical external surface, and a deflectable portion; a plurality of bone pins, each held within the pin mounting hole in a deformable pin holder within the plurality of deformable pin holders to extend through an aperture in the plurality of apertures, wherein an angle, relative to the housing, at which each of the bone pins extends through the aperture is varied by pivoting the pin holder within the housing, wherein each of the bone pins is adjustable within a conical region about the central axis of the internal mounting surface, and a plurality of clamping members, each engaging a deformable pin holder in the plurality of deformable pin holders to hold the pin holder in place within the housing while simultaneously deflecting the deformable portion of the pin holder to hold the bone pin in place within the pin holder.

13. The apparatus of claim 12, wherein the housing additionally includes a first linear portion, extending in a straight line parallel to the arc axis, and the plurality of internal mounting surfaces additionally includes a second plurality of internal mounting surfaces, each disposed within the first linear portion, the central axis of each of the internal mounting surfaces in the second plurality extends to the arc axis.

14. The apparatus of claim 13, wherein the first linear portion extends from a first end of the curved portion.

15. The apparatus of claim 14, wherein the housing additionally includes a second linear portion, extending in a straight line parallel to the arc axis, and the plurality of internal mounting surfaces additionally includes a third plurality of internal mounting surfaces, each disposed within the second linear portion, the central axis of each of the internal mounting surfaces in the third plurality extends to the arc axis.

16. The apparatus of claim 14, wherein each of the deformable pin holders additionally includes a first slot extending in a direction perpendicular to the pin mounting hole to form a first portion of the deformable portion and a second slot, spaced apart from the first slot and extending in a direction perpendicular to the pin mounting hole to form a second portion of the deformable portion, the pin mounting hole within each of the pin holders includes a first deflectable portion extending between a first end of the pin mounting hole and the first slot, a second deflectable portion extending between a second end of the pin mounting hole and the second slot, and a central portion extending between the first and second slots, and engaging each of the pin holders with a clamping member in the plurality of clamping members deforms the first and second portions of the deformable portion to move the first and second deflectable portions of the pin mounting hole out of alignment with the central portion of the pin mounting hole.

17. The apparatus of claim 16 wherein each clamping member includes a threaded surface and an annular surface engaging the first deformable portion of a pin holder in the plurality of deformable pin holders, the housing includes a plurality of threaded surfaces, each disposed adjacent an aperture in the plurality of apertures, the threaded surface of each of the clamping members engages one of the threaded surfaces of the housing, as each of the clamping members is rotated in a first direction, an engagement force between the spherically rounded surface of the pin holder clamped in place within the housing by the clamping member and the internal mounting surface within the housing is increased to hold the pin holder in place within the housing, and deflection of the deformable portion of the pin holder is increased to hold the bone pin in place within the pin holder, and as each of the clamping members is rotated opposite the first direction, the engagement force between the spherically rounded surface of the pin holder and the internal mounting surface within the housing is decreased to allow rotation of the spherically rounded surface of the pin holder within the internal mounting surface of the housing and to allow movement of the bone pin within the pin mounting hole of the pin holder.