Revision of the Unicompartmental Knee Replacement - Dushan Atkinson 25/9/2008

10 year PubMed Literature Search 1998-2008


Keywords: Revision, Knee, Arthroplasty, Unicompartmental



What is the survival of UKRs?

Why/how do they fail?

Are they more complex then revising a TKR?

What are the long-term outcomes following revision to re-UKR or TKR?

What are the problems encountered during revision?


UKR Survival



1) UKR for primary osteoarthritis: a prospective follow-up study of 1,819 patients from the Finnish Arthroplasty Register. Koskinen et al. Acta Orthop. 2007 Feb;78(1):128-35


73% Kaplan-Meier survival of 10 yrs with revision as end-point

Oxfords 81%

MG II 79%

Duracon 78%

Younger patients (<65yrs) 1.5 x failure rate


2) Results of UKR at a minimum of ten years of follow-up

Berger et al.   J Bone Joint Surg Am. 2005 May;87(5):999-1006


62 consecutive UKRs (MG)

49 UKRs10 year f/u

HSS 92; 80% excellent, 12% good, 8% fair

2 revisions for progressive OA

No loosening or osteolysis at 10 yrs!

Kaplan-Meier 98% 10 yr; 95% 13 yr


3) The Oxford unicompartmental knee prosthesis: an independent 10-year survival analysis

Vorlat P, Knee Surg Sports Traumatol Arthrosc. 2006 Jan;14(1):40-5


149 UKRs 1988-1996. Mean f/u 6.5 yrs

16 revised

Cumulative survival 82% at 10 yrs


4) Unicompartmental or total knee arthroplasty?: Results from a matched study.

Amin, Clin Orthop Relat Res. 2006 Oct;451:101-6


54 consecutive UKRs and 54 TKRs. Matched

5 year survival 88% UKR; 100% TKR

TKR more reliable procedure.

Midterm clinical outcomes similar for both

Complication rate may be greater for UKR.



How/Why do Uni’s fail?


Usual early/late rates of infection with implants

Undercorrection of varus  => excessive load on prosthesis, loosening and failure

Malpositioning => tibial subluxation or patella impingement

Poly wear => bone defects (osteolysis) (less with mobile bearings)

Overcorrection of varus => accelerated lateral OA

Bearing dislocations (esp lateral Uni’s); Over-distraction of soft-tissues


5) Fixed or mobile bearing unicompartmental knee replacement? A comparative cohort study

Gleeson RE, Knee. 2004 Oct;11(5):379-84


47 Oxfords, 57 St Georg Sleds

2 yr functional scores similar

Pain scores better in SGS

4 Oxford revised at 3 yrs

3 SGS revised at 3.4 yrs

Mobile-bearing higher reoperation rate


6) Comparison of a mobile with a fixed-bearing unicompartmental knee implant

Emerson   Clin Orthop Relat Res. 2002 Nov;(404):62-70


51 fixed bearing; mean 7.7 yrs f/u

50 meniscal bearing; mean 6.8 yrs f/u

Fixed bearing survival 93% at 11 yrs

Mobile bearing survival 99% at 11 yrs

Fixed => tibial component failure

Mobile => trend of lateral OA  


Converting UKR’s to TKR’s

More difficult than performing primary TKR?

Results may be not as good as primary TKR?

Technically easier than revising a failed TKR?



7) Revision of Oxford medial UKR to TKR -   results of a multicentre study

Saldanha KA   Knee. 2007 Aug;14(4):275-9


15 yr period. 1060 Uni’s. 3 Centres

36 revised to TKR for aseptic loosening- 28 standard TKRs, 6 constrained, 2 semi-constrained

30 cases TKRs no stems. 6 stems.

30 cases minimal bone loss. 2 metal augments. 2 cement filled cavities. 2 BG

Mean f/u 2 years.

Total knee score 86.3. function score 78.5

UKR revision comparable to TKR revision



8) Revision TKR after UKR: 54 cases

Neyret et al. Rev Chir Orthop Reparatrice 2004; 90(1):49-57.


Multicentre. 54 revisions (45 medial , 9 lateral UKR); mean failure was at 4 years for aseptic loosening

82% of revisions were “easy”

Mean f/u of 4 years

Subjective Outcomes: very satisfactory 56%; satis 36%

IKS scores 85; Flexion 113 degs

5 re-revisions (9% at 4 years)




9) Registry outcomes of UKR revisions

Dudley et al. Clin Orthop Relat Res 2008; 466 (7):1666-70


7587 knee implants 1991-2005 registry

68 UKR revised to UKR, 112 TKRs revised to TKR


Rev TKRs more complex based on proxies

Operative time greater, poly thickness greater

More use of stems and augments

More expensive: implants and hospital costs


No difference in survival between the 2 types

4 UKRs re-revised, 7 TKRs re-revised


Survival following revision from UKR to TKR


10) The survivorship and results of total knee replacements converted from UKR

Johnson et al Knee. 2007 Mar;14(2):154-7.

77 patients Bristol , mean age 66.1 years

Mean f/u 6.9 years

91% 10 year Kaplan Meier Survival

Bristol Knee scores 78.2

16 excellent, 11 good, 5 fair, 3 failed

Safe, reliable, repeatable, not technically difficult, comparable to Primary TKR


11) Revision surgery after failed UKR: a study of 35 cases.

Bohm J Arthroplasty. 2000 Dec;15(8):982-9

35 revisions to TKR (mean age 71 yrs)

Aseptic loosening major cause

Mean f/u 4 years

HSS scores 78.2

11 excellent, 13 good, 4 fair, 7 poor

6 re-revisions for aseptic loosening! (17%)

83% 4 year survival


12) Revision of UKR: outcome in 1,135 cases from the Swedish Knee Arthroplasty study

Lewold   Acta Orthop Scand. 1998 Oct;69(5):469-74.

1,135 or 14,772 UKRs revised 1975-1995

Mean age at revision 71 yrs

232 rev-UKR; 750 revised to TKR; 153 other bits

At 5 yrs re-revision rate 3x higher in rev-UKR (26% c/w 7%)


Once failed, the knee should be revised to a TKR.

Don’t add contralateral components (17% fail at 5yrs, c/w 7% TKR)


13) Results of Revision of UKR to TKR

Estour et al 2008 June Int Orthop

33 UKRs with tibial bone loss revised to TKR

15 tibial loosening;   5 femoral loosening; 2 both

5 polyethylene wear

4 progressive OA (2 lateral, 2 PFJ)

13 needed metallic wedge for tibial defect

8 needed femoral head allograft

F/u   mean 6 years. 5 died; 1 lost to f/u

All grafts integrated/ no osteolysis.                                

(100% 6 year cumulative survival)


Problems encountered during revision

Despite initial conservative bone cuts in UKR

Bone loss (from component removal)

Bone loss from osteolysis

          Small contained defects; no cortical loss: Bone graft, cement, metal augments

          Large defects; cortical bone loss: Stemmed components plus above


14) Revision of unicompartmental arthroplasty of the knee. Clinical and technical considerations

Chakrabarty   J Arthroplasty. 1998 Feb;13(2):191-6.

836 UKRs, 73 revised at 56 months.   71% med

27 Progressive OA, 16 poly wear, 27 loose

64 revised to TKR; 79% exc/good function 4.5 yrs

42 % no bone loss

24 % F or T bone loss; 34 % both F and T bone loss

2/3 small contained defects

1/3 large defects requiring reconstruction

4.1% re-revision rate



Incise through previous scar, or most lateral scar

May need quads turn-down

Debridement and synovectomy

Cut-out components with oscillating saw. Preserve bone

Prepare femoral and tibial surfaces to accept revision implant

Note bone loss: small <8cm3; large >8cm3

Small contained defects– bone graft

Large defect – Stem

Peripheral defects – bone graft and Stem or metal wedges/steps and stems

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