GB2447018A - Artificial hip joint - Google Patents

Abstract

An artificial hip joint which addresses all prior disadvantages. Preferably the hip joint comprises a titanium plate with a roughened surface, screw thread and underlying acetabulum cap. The plate may be attached with a three-part fastener comprising a screw-threaded base, spiked inner part and conical locking nut with side apertures. The femoral portion may comprise a shaft mounted to a detachable head and neck. The shaft may comprise an outer thistle with holes and inner thistle with a spiky outer surface which fit together and encourage knitting and the circulation of nutrients. The spikes may have pronged tips. The prosthesis may have optimum dimensions and angles. The bone cement used for fixing the prosthesis may include boron.

Description

L 2447018 Advanced Artificial Hip Joint

Background

Evolution of hip joint; a) 1925 (M. Smith -Peterson) ,-hemispherical glass attachment applied to degenerated ba/I on neck of femur, this broke.

b) 1936 Introduction of Cobalt-chmmium alloy, 1938 application of dental actylic resulting in limited movement and osteo (mechanical) arthritic degeneration of acetabulum cup.

C) Sir John Chamley first introduces a Teflon then a high density polyethylene socket with a dental bone cement to fasten cup to pelvis. (Clinical studies revealed inevitable severe failure over time).

d) Nick Spensor observed that polyethylene is hydrophobic (repels lubricating sync via).

Results welcomed by Hugh Phillips (Pres RCS). Decided that a hydrophilic additive to articulating surfaces would be a viable improvement. (2001).

e) Patent established for "femoral endoproSfhe)-is for artificial hip joint' comprising of 3D lattice structure attached to upper femoral shaft and connecting dome of cup (to underlying human trabeculae). The intention to pmvide a 3D trabecular structure for bone to "knit" into and prevent movement.

Problems 1) Detachment of acetabulum plate to pelvis. Inept cement and holding screws.

2) Synovial fluid entering between acetabulum plate and peMs.

3) Outer ace tabular cup (peculators I metal) thicker than normal, resulting in narrower diameter /smaller head, or attachment to less dense bone in pelvis (further away from hard outer bone). Diameter of ball of head (considering redistribution of pressure parameters between a football size object and the head of a needle (also round), excess repetitive stress on ace tabular cup facet.) - 4) Lack of lubrication around ball and cup. Hydrophobic action of polyethylene.

4) Ball wearing down with excess space, movement and forces on joint.

5) Deposits entering joint area from head and cup causing inflammatory analysis. (noted with post Charnley devices (high density polyethylene)).

6) Alteration of normal gait with unnatural forces occurring. Incorrect coxa varum/valgum wrong angle of neck of femur to shaft of artificial hip joint to individual.

7) Longer shaft need during revision surgery.

8) Lack of interconnection between artificial shaft to surrounding bone.

9) Alteration of normal gait with unnatural forces occurring. Incorrect coax arum/val gum.

10) Femoral shaft (standard operation) splinting or femoral neck (less common style of operation) exacerbated by rotation of femur to inner shaft of artificial joint (with constant body weight/ground reaction forces).

11) Unnatural, stiff and heavy materials taking space normally occupied by spongy,porous bone, blood vessels etc. Entrapment! atrophy of upper nutrient arteries (medialllateral circumflex arteries) between fat dagger-like shaft" and body weight forces and inner wall of upper femoral shaft. Quality of bone deteriorating (like a tree dying from the top I consider avascular necrosis of femoral head).

12) No consideration for elastic retention of potential gait energy.

Where components are invarIably over nd under engineered.

Discussion 2.

Consider someone hanging a picture on a screw into wall plaster near a train line.

Inner porous bone isn't that tough. It was nev9r designed to withhold the forces of body weight -ground reaction forces. It is also in a constant state of flux -remodeling as osteo..

clasts/blasts, minerals etc pass through the porous channels, It is simply not built for the job. Attempting to hold an artifidI fhiitr rk+ ar.c...-._-_i _L.tL * a small but significant discrepancy of up to 2 degrees (possibly more in some cases / its difficult to get clear data on this, and I'm cynical about accepted clinical assumptions, as I've yet to find any clear studies in this area). An inclination out of alignment by 2 degrees would possibly exacerbate normal biomechanical loading (to that individual) with excess loading occurring at focal points on ball/head and retaining cup.

(N.B. 4 dimensional Finite Element Analysis: Plumbing in known materiaUdesign, stresses and time degradation factors, could help evak'ae wieci creak-downs might occur in current systems.) Lf-Guide to Diagrams Diagrams I Fig 1) Cross section of titanium plate with screw thread and underlying acetabulum cup, with 1) Titanium plate, la) rough surface, 2) Inner thread (a), and 2a) acetabulum cup.

Fig 2) Cross section of titanium plate with screw thread and attenuated conical retaining sheath and locking nut"-:-1) Titanium plate, 2b) Inner thread (a), 3) "Attenuated conical retaining sheath", 4) Oval holes within 3) (more could be present), 5) Locking nut attached to end of 2), 6) Inner thread (b) and 6a) "attenuated conical sheath" Fig 2a Enlargement of Fig 1. without acetabulum cup.

Diagrams Ia Fig 3) "Inner spike leaves and holding cyUnoer base "-:-7) Inner spike leaves portion, 8) Holding cylinder base portion, 9) smooth / rounded friction reduced circular base.

Fig 4) "Internal locking clamp and screw' -:-10) Inner screw thread,1l) "Pushing upper base plate to retaining spike leaves and holding cylinder base", 12) "Upper screw thread" to "attenuated conical retaining sheave locking nut" and porous bone. 12a) thinner shaft.

Diagram lb Fig 5) Assembled "3 Part "Advanced Surgk:a Retaining Screw".

Diagram 2 Fig 6 Cross section of "Advanced Artificial Hp Joint' -:*-13) mid-line of femur,14) mid-line of neck of "Advanced Artificial Hip Joint" for neutra'/average position of neck inclination to mid-line of external femur, 15) mid-line of adjustable neck for patient with coxa valgum, 16) mid-line with coxa varum, 17) neutral angle around 27 degrees, 18) valgum angle around 25.5 degrees, 19) varum angle around 28.5 degrees, 20) Join between attachable head and neck, 21) diameter of head the same as fndivicuals being replaced or slightly wider.

Diagram 2a Fig 7) Cross sections of head and neck attachrner,s -:-22) base of neck, with 23) screw thread space and screw thread, 24) upper portion of neck with conical screw, 25) mid-line of upper portion of neck, 26) circular base of upper portion of neck perpendicular to 25), 27) upper portion of neck where cicar base is at an angle to 25), 28) oblique view of base of neck with 29) marker to enable sugeon to ?lace upper portion in line with 30) upper marker on upoer portion of neck before screwing into place to ensure correct end position.

Diagram 3 Fig 8) "Showing 31) "Outer Thistle shaft. sheath'S with 31a) "Oval-like" holes (not to scale or in correct place), where 32) recess in outer sheave (and inner sheath portion) allows a very small but essential amount of internal/external rotation, as occurs naturally within the long fibers of the femur during elastic retention of potential energy of gait. The top supporting portion (cylinderlike) s thicker than 25) the tapered lower portion, 36) allows space for circulation/ soft bone/trabecuization anc 37) allows space for branches from the circumflex artery entering and nourishing this tpe: section of the femur.

Diagram 4 Fig 9) Shows Inner Thistle shaft sheath" (no exactly to scale) with 38) lip that snugly its over "Outer Thistle shaft sheath"ancl uz bp of eiur, and 39) "Thistle spikes".

Diagrams 4a Fig 10) Shows 31ayO'aI like hole", Fig 11) Shows 40)'Er.argernent of e'd c ti-1:sie ike" with 41)"DuaI prongs", 42) "Skived/thinner portion" in 40) and 45) 1oldir, recess" Fig 12) Presents 43) hard outer bone ci izmur eiiq penetrated by 41), passing through 31)31a) and 44) porol's bone.

Claims (18)

1. Claims 1) An Advanced Artificiel Hio Joint (AAHJ) that addresses aD

   issues from; a) the internal screws within the retaining acetabulum plate, b) the bone cement C) the thickness of the acetabulum plate and diameter of ball of head d) the correct choice of materials for all components within AAHJ.

   e) the optimum angle of inclination i9tween mid-line of neck of AAHJ and mid-line of individual patients femur.

   f optimum design of AAHJ to ow spice and passage of branches off the circumflex aiterV, nutrients etc, to ioJi and maintain bone health.

   g) optimum design of AAHJ shaft inecha,ism to prevent sinking of AAHJ /limb length discrepancy or splitting of femur.

   h) allowance by design for a very small but significant amount of internal/external rotation within structure of shaft ernbeodea firmly into porous bone and slightly into hard bone) to work with the:atural rotation (3ccurring mm by mm down the external longitudinal fibers of the hard bone) within elastic retention of potential gait energy. As opused to a lat cagger-like" solid titanium shaft rammed into the femur.
2. 2) A claim as claimed in claim la), where a more complex tn-part screw with steel/titanium any other appropriate metal is inserted into the acetabulum portion of the hip.
3. 3) A claim as claimcd in 2), whera skrt drill hole is made through screw hole space of the retaining back cetabulum rltt rnayb 3mm diameter at a depth of 4mm) and a "retair'ir,a outer attenu3fec, co;ic.i sheath' is screwed into the outer screw thread within the metal plate.
4. 4) A claim as claned in 2), where ar "inner sp!ke leaves and attenuated conical base"is screwed into place via the Internal iocking clamp and screw" held fast into the retaining nut portion of the Tetainng cuter attenuated conical sheath".
5. 5) A claim as claimed n 2), wnere "spike.:i'ss are pushed through the "Oval-like slots" within the "retaining outer actenu&ted ecnical sheath" enabling better retention of the tn..part screw nv v;rue o near perpendicular movement and position of "spike leaves o centre' iine of ietairtng outer attenuated conical sheath" within the porous bone. in short, the tn-part screw assembly holds against a greater surface area within the peivic region behind he acetabulum.
6. 6) A claim as cai!ned in 10), v/here pnicr t application of claims 2-5, bone cement containing Boron is sieved gently into siuticn (with or without a small amount of broad spectrum r,tibiotic [with resçe t breatn passing through surgical mask]) and gently poucd over bach. Cl rot4.neci ourtion behind back of metal thin back acetabulurn rlate Using s lb i'vir'.ir en and sterile technique to prevent any risk of infection.
7. 7) A ciaim as cia.ied in ic)1 vhere v.a tr.in metal acetabulum holding plate and thin covering high density polyethvleie oct ":iemispherical-Iike" cup allows space for a wider diameter ball (corrpred crtnt tesign in "trabeculised" artificial hip joints.
8. 8) A claim:s ciir-ii 1) ?lhOr riy:. ;...rer ball nelps redistribute loading pressure wit,r at nii:ip. tTcHçj an e;a9me parameter consideration/analogy of the differcnc between e pressure of a football size object or the hen'sphericl.irfaca of a edle'.Air:iig at reducing wear and tear with sboughing -micro deposi3 i i associated inf'a ?Irnto y degradation around joint.
9. 9) A claim as caned in id). whr high nsity polyethylene is impregnated with Boron to attrici iubricair.;ro i.-d'c nyc1roph:iic action. Further preventing degradation within joint facets.
10. 10) A claim as claimed in le), where the a,gIe o inclination can be selected for the individual prior to operatioi, assessed by radiography and by consultant biomechanics expert.
11. 11) A claim as &ned in 10), where the hall/head/upper neck portion of AAHJ can be selected anc' sciewed firmly r,to piace in it correct position by markers to enable the surgeon i.o contact sce' titrcs -io' tation before rotating.
12. 12) A claim as dairned in it) wher- r9cs,r te medial sides of the two shaft components allows space ard redistributes pressure away from upper nutrient branches off the circumflex artery ano th hoilow nature of the device allows circulation and flow of minerals etc to r.ourish and maintain bone health of the upper portion of the femur and also allow entry of natural trabeculae.
13. 13) A claim as claimed in ig) where aH "Thistle spikes" from "Inner Thistle shaft sheath" pass through all matcrtirg OvJ-like holes" within "Outer Thistle shaft sheath". Also. wnere, when the sureoi is confident inner portion is in correct place, a sharp tp from rubber sterila sLrgial mallet forces it firmly into place by locking pressure of upper part of ouiet Ova) like hole" surrounding "Holding recess gaps towards ends of the metal (Titanium/steel or other appropriate meal)'Thistle spikes".
14. 14) A ciaim as c:-,ec in 13, where th Dual prongs" at the end of the "Thistle spikes" are dr;wr, together (vi: exrnl;essure from "Oval-like hole") and "Skived pot tion" betven ial pro,s" e rinç folding.
15. 15) A claim as;b'med in 13), whe crc fr:; together "Dual prongs" penetrate into the porous bc. arid slighti inic. oier bone.
16. 16) A claim as dairned in 13), where tce theft assembly has a wider beam-age thus from an engi ieertng perspectiie is more effective in its structural integrity and ability to hok fs within femur.
17. 17) A clam as cliimd in I 3i, where te saft assembly can be selected according to the weight ar of i,idvftli atU:.. (cq., Wider components for stocky robust in ivi!tits, USInQ sliii tt.r r ciaIs for increased loading requiremens. rr mere slender componits'sheaths for lighter individuals.
18. 18) A airn as u':ied in lii). wt-ere the desigr allows a small degree of internal/ external rotian (in transverse plane) ir accordance with the natural biomechanical elastic retention of potential energy of human gait.