Unicondylar Knee Replacement - OWLS 2 26/10/2001

-            Advantages over TKR :

1. Preservation of bone stock

2. Preservation of ACL, Lateral compartment and PF joint

3. Preservation of kinematics and proprioception of knee

4. Easy to revise to TKR

-            Compared to High Tibial osteotomy

1. Higher rate of early and long term success

2. Fewer early post op complications

3. No immobilization; earlier return to full mobility

4. Uni is more likely to increase ROM (remove adhesions/osteophytes)

5. Easier conversion to TKR

-            Demanding to get resection and placement just right

-            Excessive wear and loosening has been a historical problem. ( Incongrous surfaces need at least 8mm to withstand high pressures which result from high pressure areas)

-            Oxford Uni : Fem component is spherical, tibial component is flat “ both are cemented. Polyethelene meniscal bearing conforms with the metal components ( i.e. is congruent). It is unconstrained and is retained by its shape and soft tissue tension. Meniscal bearing range from 3.5 to 11.5 mm.

-            Oxford Uni provides congruous articular surfaces with areas of about 6 sq. cm in all positions. Oxford mean penetration 0.01 mm per annum therefore less reported   wear and less reported aseptic loosening

Brief

Insall et al.                JBJS(A)    1980

Author

Insall J, Aglietti P

Title

A five to seven year follow up of unicondylar arthroplasty

Reference

JBJS (A)    1980   62-A, 8, 1329 -1337.

Summary

22 (from 32) knees, average age 66 (47-80), 25 medial and 7 lateral, 1excellent, 7 good, 4 fair and 10 poor; 7 revised (4 Tib. loose, 1 fem. loose, 2 OA progression). 18 patients had patellectomy > did worse. Lat did better than medial. Problems: component fixation, OA progression, patella, pain relief not as good as TKR. Conclusions: high tib osteotomy is better and only use may be in lateral disease.

Critique

Small numbers. No independent rad review. Selection criteria limited to medial OA, < 10 deg of FF, 90 deg of flexion. Patella excised if signs of PF OA (!)These poor results killed off the use of Uni's during much of the '80s

Brief

Goodfellow et al.                  JBJS(Br) 1988

Author

Goodfellow JW, Kershaw CJ, Benson MK and O'Connor JJ.

Title

The Oxford Knee for Unicompartmental OA; the first 103 cases

Reference

JBJS(Br) 1988   70-B, 5, 692-701

Summary

Oxford Uni . 98 (from 103) knees, average age 70, 76 medial & 27 lateral, FU 21-56 months. Failures: 7 medial and 2 lateral (5 loose,1 collapse,1 OA progression, 2 bearing dislocation), 16.2% failed with deficient ACL cf with 4.8% if normal ACL. No relationship with failure and state of PF joint. Selection should be : > 65 years, intact ACL, severe uni disease, varus-valgus correctable preoperatively otherwise disease too advanced.

Critique

Included all of the first 100. Prospective. All aspects of postop recovery assessed; pain relief, ROM, deformity, stability, function, rads and failures. This paper establishes the importance of the ACL in the ( Oxford ) Uni.

Brief

Christensen             Clin Ortho   1991

Arhor

Christensen NO

Title

Unicompartmental Protheseis for Gonarthrosis. A nine year series of 575 knees from a Swedish hospital.

Reference

Clin Orthop 1991; 273: 165-9.

Summary

St Georg “ Schlitten ; 575 in 415 pts. 56% (320) bilateral. 521 medial and 51 lateral. Rev at 3,6,10 years. Age 70 “79. 7 (1.2%) revisions (4 tib loose, 1 tib/fem loose, 1 infection, 1 lig instability) 14 case had secondary procedure . Selection criteria; excessive weight and state of ACL not a problem. Only 10% of knee OA pts. needed TKR.

Critique

Retrospective, rad evaluation by independent radiologist. Otherwise poor paper but seems to have good results. other than revision rate author fails to explain how pts did and what function they have. Don't bear up to other authors survivor stats for the St Georg - 80%

Brief

Murray et al,                    JBJS(Br)    1998

Arhor

Murray DW, Goodfellow JW, O'Connor JJ

Title

The Oxford   medial   unicompartmental arthroplasty; A ten year survival

Reference

  JBJS(Br) 1998; 80(B), 6, 983-989.

Summary

Oxford Uni . 143 knees, Average 7.6 year FU (max 13.8). 5 revisions (1 infection, 2 OA progression, 1 loose fem, 1 pain+, 1 meniscal dislocation). Cumulative survival 98% at 10 yrs ( 97% if include lost to FU). Guidelines: Stress rads to see full thickness of lateral cartilage and to confirm deformity is correctable; lat compartment fibrillation, medial margin fem condyle erosions or osteophytes not contraindications; normal ACL (no longitudinal splits and a normal synovium); Intact PCL; PF not a problem; Pt weight not a problem. Excluded: ACL(28), revisions(2), Previous Tib osteotomy(9), Post trauma OA(2), AVN(1).    Pt selection is crucial     

Critique

Questionnaire based, one surgeon, good numbers, specific parameters and inclusion criteria.   Sets out patient selection well and therefore has the highest % survival compared to any other series ( highest 10 yr survival score for TKR is 98.7% - Colizza, Insall et al)

Brief

Weale et al.            JBJS(Br)    1999

Arhor

Weale AE, Murray DW, Crawfoed R, Psychoyios V, Bonomo A,   Howell G, O'Connor J, Goodfellow JW.

Title

Does arthritis progress in the retained compartments after 'Oxford' medial unicompartment arthroplasty. A clinical and rad review with 10 year FU.

Reference

JBJS(B)   1999, 81-B, 5, 783-789

Summary

Oxford Uni: 56 knees in 45 pts but only 29 reviewed. FU 11.4 years (10-14). Clinical outcome : Knee scores, ROM, range of deformity not significantly different than at 2 yrs post op. Flexion had improved. Rads: showed no change in lat compartment. Conclusion; medial compartment disease is focal disorder and Oxford Uni preserved joint structures

Critique

Again good paper out of the Oxford camp.



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