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Should the patella be resurfaced at total knee replacement?
The Knee 7 Ž2000. 199᎐204
Review article
Should the patella be resurfaced at total knee replacement? Jonathan NobleU Department of Orthopaedic Surgery, Uni¨ ersity of Manchester Medical School, Hope Hospital, Eccles Old Road, Salford, Greater Manchester, UK Received 14 January 2000; received in revised form 25 August 2000; accepted 15 September 2000
Abstract Total knee replacement ŽTKR. presumably is replacement of the total knee articular surface. Sometimes it is and sometimes it is not. It is this author’s firm conviction that the patella should be resurfaced in the vast majority of cases. Such advocacy must be critically justified and the potential drawbacks and alternatives examined. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Total knee replacement; Patella; Resurfacing
1. Historical considerations Hinged arthroplasty without patella resurfacing had a high incidence of post-operative retro-patella pain, w10x. Gunston w16x reported a 39% incidence of patello-femoral problems with a polycentric design, which also omitted patella resurfacing. High rates of patello-femoral pain, where resurfacing was not accomplished, persisted with second generation designs, such as the Geomedic w19,44x, the Duocondylar w40,53x, as well as the Spherocentric w22x and Attenborough w51x. Further literature review revealed an incidence of patello-femoral pain of approximately 25% with a variety of prostheses w9,11,13,14,18,23,32,52x. Of these prostheses only Insall’s posterior stabilised, approaches modern design practice, but a pattern of frequent patello-femoral pain clearly emerged, during the 1980s. Soudry et al. in 1986 w55x compared total condylar arthroplasty with and without resurfacing. This is a U
Corresponding author. Tel.: q44-1565-722871; fax: q44-161227-9405.
seminal paper in that the total condylar was the forerunner of modern knee replacement, the goldstandard and ‘Charnley of the Knee’. They found a similar incidence of retro-patella pain, or of pain relief, but poorer function with those in whom the patella was not resurfaced. Thirty-three percent of that group could not ascend stairs unaided. Using the same prosthesis in a patient series, two thirds of whom suffered from rheumatoid disease, and all but one of whom were routinely resurfaced, only 16% were unable to climb stairs w38x. Similarly, Enis et al. w12x reported on 25 patients with a bilateral Townley replacement, one side only with patellar resurfacing. The majority preferred their resurfaced side, which they reported to be stronger and more comfortable in relation to stair climbing. Boyd et al. w7x compared 396 knees in which the duo-patellar prosthesis included resurfacing, with 495 in whom the patella was left unresurfaced. The decision whether or not to resurface was based upon the appearance of the patella at surgery. They concluded by recommending resurfacing for both inflammatory and degenerative arthritis.
0968-0160r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 6 8 - 0 1 6 0 Ž 0 0 . 0 0 0 6 7 - 3
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J. Noble r The Knee 7 (2000) 199᎐204
2. The state of the patello-femoral joint The evident disregard paid to the status of the patello-femoral articulation by the Oxford group, when pre-operatively they decide whether or not to insert an Oxford unicompartmental replacement for various osteoarthritis w33x. Can science help us to decide which patella to replace and which not? In a tissue culture model, Steinberg et al. w56x showed that active rheumatoid synovium can only function in the presence of active chondrocytes and suggest that removing all residual chondrocytes Žand thus resurfacing the patella. was a deterrent to subsequent synovitis. Following this work it was suggested w43x that the same interaction occurred with the synovium from osteoarthritis. In unicompartmental arthritis, Obeid et al. w36x found that ‘unaffected’ cartilage at unicompartmental replacement was significantly thinner and softer than control cartilage. They concluded that it was mechanically inferior to normal cartilage, despite appearing to be sound. This would seem to counter the view of Scott and Reilly w50x that patellar resurfacing should be avoided in cases with ‘normal’ articular cartilage. It is very unusual to encounter a patient whose knee symptoms are severe enough to warrant a TKR in which the patella articular cartilage is normal. This is not surprising. In a random autopsy study w35x of a group of patients who died of medical causes, and who were of a similar age range to an average TKR series, 79% had patello-femoral osteoarthritis. In 1982, Armstrong and Mow w1x concluded that the visual and histological appearance of patella cartilage was a poor indicator of its ability to function normally in an intact joint. Recently, Newman et al. w34x found that ‘perfect’ articular cartilage did not guarantee a comfortable patello-femoral joint. The resurfaced patella seems more forgiving of misalignment than the unresurfaced w34x. However, a maltracking polyethylene button in almost any situation leads to debris and therefore, osteolysis. In cadaveric experiments Whiteside’s group w27x have shown that conforming patellae had higher contact stresses, at flexion angles greater than 90⬚. This is a worry for the future, now that 105᎐115⬚ of flexion are commonplace post-operatively. Can materials other than high-density polyethylene ŽHDPE. be used to resurface the patella?
cant difference in complication and revision rates when comparing those, which were resurfaced with those which were not w47x. However, we can confidently conjecture that those resurfaced were the more badly affected knees and patellae. It is comforting to find so little difference between the bad and not so bad cases. A more persuasive argument in favour of not resurfacing the patella is that, as a revision procedure, resurfacing secondarily is technically less demanding and more reliable than revising a failed patella component. Berry and Rand w4x warned of high complication and failure rates in procedures to revise just the patellar component. Rand w42x also indicated that extensor mechanism problems are the commonest cause of re-operation after the implantation of total condylar type prostheses. At least part of their problem is related to metal-backing, now a largely discredited procedure. Moreover, it has previously been suggested w38x that resurfacing the patella, certainly in rheumatoid disease, may protect the bone stock. It may otherwise be eroded to produce the so-called ‘sea-gull sign’ ŽFig. 1. or even near disappearance of the patella ŽFig. 2.. I accept the potential pitfalls of patella component revision. However, in my own 8᎐13-year follow-up of total condylar prosthesis with patella resurfacing w30x there was a 98% survivorship at 8᎐13 years, and also in the surviving patients followed up to 19 years w28x. Wright et al. w58x reported 5᎐8 year follow-up results with 518 cemented Kinemax knees, with patellar resurfacing. They had but four Ž0.76%. complications. Bugbee et al. w8x reported 186 consecutive anatomic modular knee arthroplasties at a 4᎐10-year review, with two component revisions and no complications related to the patello-femoral articulation. Clearly, well-executed articular resurfacing of the patella is followed by a very low incidence of patello-femoral complications. Thus, technique and probably component design are all important.
3. Not resurfacing the patella There are surgeons who quite happily and unequivocally do not resurface the patella w54,31x. The Swedish Knee Arthroplasty Register, reporting on 4381 primary TKRs for rheumatoid disease, found no signifi-
Fig. 1. Wear of an unresurfaced patella causing the ‘sea gull sign’.
J. Noble r The Knee 7 (2000) 199᎐204
Fig. 2. An unresurfaced patella that has been almost totally worn away.
4. Surgical technique and component design The extensor mechanism is assuredly the Achilles heel of knee replacement. Complications such as patellar fracture ŽFig. 3., a vascular necrosis, patella ligament rupture ŽFig. 4. and component loosening have all been incriminated by those opposed to patella resurfacing. Firstly, let us consider the complications of metalbacked patella components. Several authors have reported unfavourably on metal-backing which resulted in very thin HPDE and led to premature failure due to early wear w3,20,25,49,57x. However, Laskin and Bucknell w24x believe that the problems of failure with metal-backing could be solved by converting the implant from an onlay to an inlay design. This surely is to replace the need to accommodate metal at the expense of plastic but now doing so at the expense of bone stock. As Insall and Kelly w17x stated, few serious
Fig. 3. Patella fracture following resurfacing.
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Fig. 4. A high-riding patella following petallar tendon rupture after resurfacing.
complications have been associated with the use of all plastic patellae. Petrie et al. w37x contrasted 843 patients with a metal-backed patella to 994 with an all HDPE patella. The infection rate was almost twice as high with the metal-back group, presumably because of more wear debris. Marton, Scott and Thornhill w26x reviewed 1378 PFC knees, and after excluding the complications directly and solely attributable to metal-backing, their re-operation rate dropped from 4.5% to 2.9%. Metal-backed patella buttons should be consigned to history. Ranawat et al. w41x reported 95% excellent or good results from patella resurfacing, two or more years after total condylar arthroplasty. In discussion they emphasised that there had been no subluxation, dislocations or fractures and only one case of patella component loosening. There were no patella ligament ruptures. They attributed this success to quadriceps re-alignment, minimal patella bone excision with subchondral bone preservation and conservation of the fat pad. Ranawat reported w39x on 100 knees with patella resurfacing, more than half with rheumatoid disease, 5᎐10 years after a total condylar prosthesis. There were no patella dislocations although 14 were tilted on X-ray analysis. There was one case of loosening and one of osteonecrosis, with over 90% having good or excellent results. My own results, with an almost identical case mix and the same prosthesis are similar w38x. However, I removed every fat pad and was careful to cut the retro-patella surface flush with the quadriceps tendon thus, exposing cancellous bone. This avoided overstuffing the resurfaced patellofemoral joint. There was also a 40% lateral release
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rate. I had one fracture after a fall and one patella ligament ruptured when passive knee flexion was forced in physiotherapy! I am a strong advocate of the no-thumb test, as an indicator for or against lateral release. This is because patella mal-tracking is a common cause of wear after TKR w29x. Gerba and Maenza Ž1998. w15x reviewed this topic, pointing out that many good, pain free, long term results co-exist with a tilted, resurfaced patella. Bindelglass w5x reviewed patella tracking in 234 primary TKRs and found it to be central in only 55% with 14% frankly subluxed. They concluded that neither pain scores, nor fixation were affected by patella tracking, nor by lateral release at surgery. Ritter and Campbell w46x suggested that the incidence of patella fracture, with resurfacing was significantly reduced by lateral release, however, Ritter’s enthusiasm for lateral release has recently diminished w45x. Clearly the picture is mixed and I conclude that: 1. Metal-backed patellae should not be used. 2. Fat pad excision facilitates proper exposure of the lateral tibial plateau and thus, allows accurate cuts with correct femoral component placement. This includes rotation of the femoral component which is important for patella stability. 3. Advocates of carefully chosen and well executed lateral release clearly have good results with few resultant complications. There is a suggestion that patella tilt is not so important. My instincts are against this view and I worry about the long-term implications in terms of HDPE wear.
The Bristol knee group w34x conducted a slightly different study, with three groups of patients, randomly allocated. Group A, had patella resurfacing, group B did not. In group C the operating surgeon exercised his own discretion and decided, at the time of operation, whether or not to resurface the patella. The patients all had osteoarthritus and the case-mix was well matched, although in follow-ups there were slightly fewer lateral releases Ž18%. in group C, than in A Ž24%., or B Ž27%.. In group A, no case has required any type of revision. In group B, six underwent secondary resurfacing and 4 more were under observation, for persistent anterior knee pain. In group C, one resurfaced patella had to be revised for patella loosening. Newman w34x, like others, observed that resurfaced patellae tolerated minor degrees of mal-tracking far better than unresurfaced patellae and gave more comfortable knees. It is clear from these studies that the need for re-operation is much higher if the patella is left than if it is resurfaced. Respective rates of 5᎐10% for secondary resurfacing are unacceptable and are unlikely to be as successful as a primary resurfacing. The only justification is the argument that a secondary procedure is easier than a failed primary procedure. I also question whether initial patella resurfacing, carried out secondarily, will be as successful as that carried out at the same time as resurfacing the femur and tibia.
6. Conclusions 5. Prospective studies Kajino et al. w21x reported 26 patients with bilateral TKR, for rheumatoid disease. One side was randomly allocated for patella resurfacing. At 4᎐7.5 year followup scores for pain, function and range of movement revealed no significant difference, though pain on standing and on stairs was worse without patella resurfacing. Bourne et al. w6x published a prospective randomised trial of 100 anatomic medullary knees, reviewed at 2 years, half with and half without patella resurfacing. The knee scores were even better in the unresurfaced than the resurfaced group, but 4% of the unresurfaced group had to undergo secondary resurfacing within 2 years. I understand that at 5 years this figure has doubled to 8%. Bourne and Rorabeck now resurface all patellae, which are 10 mm or more in thickness w48x. In a similar study of 118 Miller-Galante knees, no resurfaced case had had to undergo a revision at a 2᎐4 year follow-up whereas 10% of the unresurfaced group had w2x.
1. Historically the literature generally shows a high incidence of anterior knee pain, if the patella is not resurfaced. 2. Follow up studies of well executed condylar tricompartmental knees, with patella resurfacing, reveal a very low rate of patello-femoral pain, complications, and revision of the patella component. 3. In cases where the results of resurfacing and not resurfacing the patella have been similar, there is a higher rate of pain or disability in relation to standing for a long time, or the use of stairs, with the unresurfaced group. 4. Metal-backed patellae are unnecessary and should be avoided because of high failure and complication rates. 5. The early re-operation rate in those prospective studies where half the patellae have been left unresurfaced have an unacceptably high early reoperation rate. 6. The complications of patella resurfacing although
J. Noble r The Knee 7 (2000) 199᎐204
rare in well executed series are technically difficult to resolve, with quite a high failure rate themselves. 7. The resurfaced patella is more forgiving than the unresurfaced patella, in terms of symptoms from maltracking, but I am concerned regarding HDPE wear, long term. 8. As overall ranges of movement improve with newer TKR designs we will need to be vigilant for the possibility of an increased rate of polyethylene wear. Finally whilst always urging critical caution I have very little hesitation in advocating routine patella resurfacing. Quite simply total knee replacement should be just that, always providing that there is sufficient bone stock to accommodate the patella ‘button’. References w1x Armstrong CG, Mow VC. Variations in intrinsic mechanical properties of human articular cartilage with age, degeneration and water content. J Bone Jt Surg 1982;64A:94᎐99. w2x Barrack RL, Wolfe MW, Waldman DA, Milicic M, Bertot AJ, Myers L. Resurfacing of the patella in total knee arthroplasty. J Bone Jt Surg 1997;79A:1121᎐1131. w3x Bayley JC, Scott RD, Ewald FC, Holmes GB. Failure of the metal backed patellar component after total knee replacement. J Bone Jt Surg 1988;70A:668᎐674. w4x Berry DJ, Rand JA. Isolated patellar component revisions of total knee replacement. Clin Orthop Rel Res 1993;286: 110᎐115. w5x Bindelglass DF, Cohen JL, Dorr LD. Patellar tilt and subluxation in total knee arthroplasty. Relationship to pain fixation and design. Clin Orthop Rel Res 1993;286:103᎐109. w6x Bmy ne RB, Rorabeck CH, Vaz M, Kramer J, Hardie R, Robertson D. Resurfacing vs not resurfacing the patella during total knee replacement. Clin Orthop Rel Res 1995; 321:156᎐161. w7x Boyd AD, Ewald FC, Thomas WH, Poss R, Sledge CB. Long term complications after total knee arthroplasty with or without resurfacing of the patella. J Bone Jt Surg 1993;75A: 674᎐681. w8x Bugbee WD, Ammeen DJ, Parks NL, Engh GA. Fmy to ten year results with the anatomic modular knee. Clin Orthop Rel Res 1998;348:158᎐165. w9x Clayton M, Thirupathi R. Patellar complications after total condylar arthroplasty. Clin Orthop Rel Res 1982;170:152᎐156. w10x Craig DM, Lettin AWF, Scales JT. Stanmore total knee replacement. J Bone Jt Surg 1983;65B:225. w11x Efkekhar NS. Adjustable intramedullary replacement of the knee joint. J Bone Jt Surg 1983;65A:293᎐309. w12x Enis JE, Gardener R, Robledo MA, Latta L, Smith R. Comparison of patellar resurfacing vs non-resurfacing in bilateral total knee arthroplasty. Clin Orthop Rel Res 1990;260:38᎐42. w13x Evanski PM, Waugh TR, Orofino CF, Anzel SH. UCI knee replacement. Clin Orthop Rel Res 1976;120:33᎐38. w14x Freeman MAR, Todd RC, Bambert P, Day WH. ICLH arthroplasty of the knee. J Bone Jt Surg 1978;60B:339᎐344. w15x Gerba BE, Maenza F. Shift and tilt of the bony patella in total knee replacement. Orthopaedics 1998;27:629᎐636.
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w16x Gunston FH. Ten year results of polycentric knee arthroplasty. J Bone Jt Surg 1980;62B:133. w17x Insall J, Kelly M. The total condylar prosthesis. Clin Orthop Rel Res 1986;205:43᎐48. w18x Insall J, Lachiewics P, Burnstein E. The posterior stabilised condylar prosthesis modification of the total condylar design: two and five year clinical experience. J Bone Jt Surg 1982;62A:1317᎐1323. w19x Insall J, Ranawat CS, Aglietti P, Shine J. A comparison of four models of total knee replacement prosthesis. J Bone Jt Surg 1976;58A:754᎐765. w20x Johnson DF, Eastwood DM. Patellar complications after knee arthroplasty. A prospective study of 56 cases using the Kinematic prosthesis. Acta Orthop Scand 1992;63:74᎐79. w21x Kajino A, Yoshinos Kameyama S, Kahdo M, Nagashima S. Comparison of the results of bilateral total knee arthroplasty with and without patella replacement for rheumatoid arthritis. J Bone Jt Surg 1997;79A:570᎐574. w22x Kauffer H, Matthews L. Spherocentric arthroplasty of the knee. J Bone Jt Surg 1981;63A:545᎐559. w23x Kettlekamp DB, Pryer P, Brady TA. A selective use of the variable axis knee. Orthop Trans 1979;3:301᎐302. w24x Laskin RS, Bucknell A. The use of metal back patellar prostheses in total knee arthroplasty. Clin Orthop Rel Res 1990;260:52᎐55. w25x Lombardi AV, Engh GA, Votz RG, Albrigo JL, Brainard BJ. Fracturerdislocation of the polyethylene in metal-backed patellar components in total knee arthroplasty. J Bone Jt Surg 1988;70A:675᎐679. w26x Marton SD, McManus JL, Scott RD, Thornhill TS. Press-fit condylar total knee arthroplasty, five to nine year follow-up evaluation. J Arthro 1997;12:603᎐614. w27x Matsuda S, Ishinishi T, White SE, Whiteside LA. Patellofemoral joint after total knee arthroplasty. Effect on contact area and contact stress. J Arthro 1997;12:790᎐797. w28x Mirza H, Noble J, Jayem M. Ten to nineteen year follow-up of total condylar knee replacements.-Presentation to the British Orthopaedic Association Glasgow; September, 1999. w29x Mochizuki RM, Schurmann DJ. Patellar complications following total knee arthroplasty. J Bone Jt Surg 1979; 61A:879᎐883. w30x Monsall F, Noble J, Obeid EM. Eight to thirteen year followup of total condylar knee replacements.-Presentation to the Joint Meeting of the British Association for Rheumatoid Surgery and the British Orthopaedic Association. Westminster Conference Centre, 1993. w31x Moran CG, Pinder IM, Lees TA, Midwinter MJ. Survivorship analysis of the uncemented porous-coated anatomic knee replacement. J Bone Jt Surg 1991;73A:848᎐857. w32x Murray DG, Webster DA. Variable axis knee prosthesis. J Bone Jt Surg 1981;63A:687᎐694. w33x Murray DW, Goodfellow JW, O’Connor JJ. The Oxford medial unicompartmental arthroplasty. A 10 year review. J Bone Jt Surg 1998;80B:983᎐989. w34x Newman JH, Ackroyd CE, Shah NA, Karachalios T. Should the patella be resurfaced during total knee replacement? The Knee 2000;7:17᎐23. w35x Noble J, Hamblen DL. The pathology of the degenerative meniscus lesion. J Bone Jt Surg 1975;57B:180᎐185. w36x Obeid EMH, Adams MA, Newman JH. Mechanical properties of articular cartilage in knees with unicompartmental osteoarthritis. J Bone Jt Surg 1994;76B:315᎐319. w37x Petrie RS, Hanssen AD, Osmon DR, Ilstrup D. Metal-backed patellar component failure in total knee arthroplasty: a possible risk for late infection. Am J Orthop 1998;27:172᎐176.
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w38x Rae PJ, Noble J, Hodgkinson JP. Patellar resurfacing in total condylar knee arthroplasty. J Arthro 1990;5:259᎐265. w39x Ranawat CS. The patello-femoral joint in total condylar knee arthroplasty. Clin Orthop Rel Res 1986;205:93᎐99. w40x Ranawat CS, Insall J, Shine J. Duo-condylar knee arthroplasty. Clin Orthop Rel Res 1976;120:76᎐82. w41x Ranawat CS, Rose HA, Bryan WJ. Replacement of the patello-femoral joint with total condylar knee arthroplasty. Int Orthop 1984;8:61᎐65. w42x Rand JA. The patello-femoral joint in total knee arthroplasty. J Bone Jt Surg 1994;76A:612᎐620. w43x Read L, Alexander KL, Noble J, Collins RF. The action of diseased synovium on cartilage substrate. J Bone Jt Surg 1982;64B:383. w44x Riley LH, Hungerford DS. Geomedic total knee replacement for treatment of the rheumatoid knee. J Bone Jt Surg 1978;60A:523᎐527. w45x Ritter MA. Presentation to Current Controversies in Knee Surgery. Royal Society of Medicine. London, June 1999. w46x Ritter MA, Campbell ED. Post-operative patellar complications with or without release during total knee arthroplasty. Clin Orthop Rel Res 1987;219:163᎐169. w47x Robertson O, Knutson K, Lewold S, Goodman S, Lidgren L. Knee arthroplasty in rheumatoid arthritis. A report from the Swedish Knee Arthroplasty Register on 4381 primary operations 1985᎐1995. Acta Orthop Scand 1997;68:545᎐553. w48x Rorabeck CH. Personal communication, 1999. w49x Rosenberg AG, Andriacchi TP, Barden R, Galante JO. Patel-
w50x w51x w52x w53x w54x w55x w56x w57x w58x
lar component failure in cementless total knee arthroplasty. Clin Orthop Rel Res 1998;236:106᎐114. Scott RD, Reilly DT. Pros and cons of patellar resurfacing in total knee replacement. Orthop Trans 1980;4:328. Simison AJM, Noble J, Hardinge K. Complications of the Attenborough knee replacement. J Bone Jt Surg 1986;68B:100᎐105. Sheehan J. Arthroplasty of the knee. Clin Orthop Rel Res 1979;145:101᎐109. Sledge CB, Ewald FC. Total knee arthroplasty. Experience at the Robert Breck Brigham Hospital. Clin Orthop Rel Res 1979;145:78᎐84. Smith SR, Stuart P, Pinder IM. Non-resurfaced patella in total knee arthroplasty. J Arthroplasty 1989;?:581᎐586. Supplement. Soudry M, Mestriner LA, Binazzu R, Insall J. Total arthroplasty without patellar resurfacing. Clin Orthop Rel Res 1986;205:166᎐170. Steinberg J, Sledge CB, Noble J, Stirratt CR. A tissue culture model of cartilage breakdown in rheumatoid arthritis. Biochem J 1979;80:403᎐408. Stulberg SD, Stulberg BN, Hamati Y, Tsao A. Failure mechanism of metal-backed patellar components. Clin Orthop Rel Res 1988;236:88᎐105. Wright J, Ewald FC, Poss R, Sledge CB, Thomas WH. Patello-femoral joint in symmetrical total knee arthoplasty. Presentation to the Combined Meeting of the British and Irish Orthopaedic Associations. Dublin, 1998.
Review article
Should the patella be resurfaced at total knee replacement? Jonathan NobleU Department of Orthopaedic Surgery, Uni¨ ersity of Manchester Medical School, Hope Hospital, Eccles Old Road, Salford, Greater Manchester, UK Received 14 January 2000; received in revised form 25 August 2000; accepted 15 September 2000
Abstract Total knee replacement ŽTKR. presumably is replacement of the total knee articular surface. Sometimes it is and sometimes it is not. It is this author’s firm conviction that the patella should be resurfaced in the vast majority of cases. Such advocacy must be critically justified and the potential drawbacks and alternatives examined. 䊚 2000 Elsevier Science B.V. All rights reserved. Keywords: Total knee replacement; Patella; Resurfacing
1. Historical considerations Hinged arthroplasty without patella resurfacing had a high incidence of post-operative retro-patella pain, w10x. Gunston w16x reported a 39% incidence of patello-femoral problems with a polycentric design, which also omitted patella resurfacing. High rates of patello-femoral pain, where resurfacing was not accomplished, persisted with second generation designs, such as the Geomedic w19,44x, the Duocondylar w40,53x, as well as the Spherocentric w22x and Attenborough w51x. Further literature review revealed an incidence of patello-femoral pain of approximately 25% with a variety of prostheses w9,11,13,14,18,23,32,52x. Of these prostheses only Insall’s posterior stabilised, approaches modern design practice, but a pattern of frequent patello-femoral pain clearly emerged, during the 1980s. Soudry et al. in 1986 w55x compared total condylar arthroplasty with and without resurfacing. This is a U
Corresponding author. Tel.: q44-1565-722871; fax: q44-161227-9405.
seminal paper in that the total condylar was the forerunner of modern knee replacement, the goldstandard and ‘Charnley of the Knee’. They found a similar incidence of retro-patella pain, or of pain relief, but poorer function with those in whom the patella was not resurfaced. Thirty-three percent of that group could not ascend stairs unaided. Using the same prosthesis in a patient series, two thirds of whom suffered from rheumatoid disease, and all but one of whom were routinely resurfaced, only 16% were unable to climb stairs w38x. Similarly, Enis et al. w12x reported on 25 patients with a bilateral Townley replacement, one side only with patellar resurfacing. The majority preferred their resurfaced side, which they reported to be stronger and more comfortable in relation to stair climbing. Boyd et al. w7x compared 396 knees in which the duo-patellar prosthesis included resurfacing, with 495 in whom the patella was left unresurfaced. The decision whether or not to resurface was based upon the appearance of the patella at surgery. They concluded by recommending resurfacing for both inflammatory and degenerative arthritis.
0968-0160r00r$ - see front matter 䊚 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 6 8 - 0 1 6 0 Ž 0 0 . 0 0 0 6 7 - 3
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J. Noble r The Knee 7 (2000) 199᎐204
2. The state of the patello-femoral joint The evident disregard paid to the status of the patello-femoral articulation by the Oxford group, when pre-operatively they decide whether or not to insert an Oxford unicompartmental replacement for various osteoarthritis w33x. Can science help us to decide which patella to replace and which not? In a tissue culture model, Steinberg et al. w56x showed that active rheumatoid synovium can only function in the presence of active chondrocytes and suggest that removing all residual chondrocytes Žand thus resurfacing the patella. was a deterrent to subsequent synovitis. Following this work it was suggested w43x that the same interaction occurred with the synovium from osteoarthritis. In unicompartmental arthritis, Obeid et al. w36x found that ‘unaffected’ cartilage at unicompartmental replacement was significantly thinner and softer than control cartilage. They concluded that it was mechanically inferior to normal cartilage, despite appearing to be sound. This would seem to counter the view of Scott and Reilly w50x that patellar resurfacing should be avoided in cases with ‘normal’ articular cartilage. It is very unusual to encounter a patient whose knee symptoms are severe enough to warrant a TKR in which the patella articular cartilage is normal. This is not surprising. In a random autopsy study w35x of a group of patients who died of medical causes, and who were of a similar age range to an average TKR series, 79% had patello-femoral osteoarthritis. In 1982, Armstrong and Mow w1x concluded that the visual and histological appearance of patella cartilage was a poor indicator of its ability to function normally in an intact joint. Recently, Newman et al. w34x found that ‘perfect’ articular cartilage did not guarantee a comfortable patello-femoral joint. The resurfaced patella seems more forgiving of misalignment than the unresurfaced w34x. However, a maltracking polyethylene button in almost any situation leads to debris and therefore, osteolysis. In cadaveric experiments Whiteside’s group w27x have shown that conforming patellae had higher contact stresses, at flexion angles greater than 90⬚. This is a worry for the future, now that 105᎐115⬚ of flexion are commonplace post-operatively. Can materials other than high-density polyethylene ŽHDPE. be used to resurface the patella?
cant difference in complication and revision rates when comparing those, which were resurfaced with those which were not w47x. However, we can confidently conjecture that those resurfaced were the more badly affected knees and patellae. It is comforting to find so little difference between the bad and not so bad cases. A more persuasive argument in favour of not resurfacing the patella is that, as a revision procedure, resurfacing secondarily is technically less demanding and more reliable than revising a failed patella component. Berry and Rand w4x warned of high complication and failure rates in procedures to revise just the patellar component. Rand w42x also indicated that extensor mechanism problems are the commonest cause of re-operation after the implantation of total condylar type prostheses. At least part of their problem is related to metal-backing, now a largely discredited procedure. Moreover, it has previously been suggested w38x that resurfacing the patella, certainly in rheumatoid disease, may protect the bone stock. It may otherwise be eroded to produce the so-called ‘sea-gull sign’ ŽFig. 1. or even near disappearance of the patella ŽFig. 2.. I accept the potential pitfalls of patella component revision. However, in my own 8᎐13-year follow-up of total condylar prosthesis with patella resurfacing w30x there was a 98% survivorship at 8᎐13 years, and also in the surviving patients followed up to 19 years w28x. Wright et al. w58x reported 5᎐8 year follow-up results with 518 cemented Kinemax knees, with patellar resurfacing. They had but four Ž0.76%. complications. Bugbee et al. w8x reported 186 consecutive anatomic modular knee arthroplasties at a 4᎐10-year review, with two component revisions and no complications related to the patello-femoral articulation. Clearly, well-executed articular resurfacing of the patella is followed by a very low incidence of patello-femoral complications. Thus, technique and probably component design are all important.
3. Not resurfacing the patella There are surgeons who quite happily and unequivocally do not resurface the patella w54,31x. The Swedish Knee Arthroplasty Register, reporting on 4381 primary TKRs for rheumatoid disease, found no signifi-
Fig. 1. Wear of an unresurfaced patella causing the ‘sea gull sign’.
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Fig. 2. An unresurfaced patella that has been almost totally worn away.
4. Surgical technique and component design The extensor mechanism is assuredly the Achilles heel of knee replacement. Complications such as patellar fracture ŽFig. 3., a vascular necrosis, patella ligament rupture ŽFig. 4. and component loosening have all been incriminated by those opposed to patella resurfacing. Firstly, let us consider the complications of metalbacked patella components. Several authors have reported unfavourably on metal-backing which resulted in very thin HPDE and led to premature failure due to early wear w3,20,25,49,57x. However, Laskin and Bucknell w24x believe that the problems of failure with metal-backing could be solved by converting the implant from an onlay to an inlay design. This surely is to replace the need to accommodate metal at the expense of plastic but now doing so at the expense of bone stock. As Insall and Kelly w17x stated, few serious
Fig. 3. Patella fracture following resurfacing.
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Fig. 4. A high-riding patella following petallar tendon rupture after resurfacing.
complications have been associated with the use of all plastic patellae. Petrie et al. w37x contrasted 843 patients with a metal-backed patella to 994 with an all HDPE patella. The infection rate was almost twice as high with the metal-back group, presumably because of more wear debris. Marton, Scott and Thornhill w26x reviewed 1378 PFC knees, and after excluding the complications directly and solely attributable to metal-backing, their re-operation rate dropped from 4.5% to 2.9%. Metal-backed patella buttons should be consigned to history. Ranawat et al. w41x reported 95% excellent or good results from patella resurfacing, two or more years after total condylar arthroplasty. In discussion they emphasised that there had been no subluxation, dislocations or fractures and only one case of patella component loosening. There were no patella ligament ruptures. They attributed this success to quadriceps re-alignment, minimal patella bone excision with subchondral bone preservation and conservation of the fat pad. Ranawat reported w39x on 100 knees with patella resurfacing, more than half with rheumatoid disease, 5᎐10 years after a total condylar prosthesis. There were no patella dislocations although 14 were tilted on X-ray analysis. There was one case of loosening and one of osteonecrosis, with over 90% having good or excellent results. My own results, with an almost identical case mix and the same prosthesis are similar w38x. However, I removed every fat pad and was careful to cut the retro-patella surface flush with the quadriceps tendon thus, exposing cancellous bone. This avoided overstuffing the resurfaced patellofemoral joint. There was also a 40% lateral release
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rate. I had one fracture after a fall and one patella ligament ruptured when passive knee flexion was forced in physiotherapy! I am a strong advocate of the no-thumb test, as an indicator for or against lateral release. This is because patella mal-tracking is a common cause of wear after TKR w29x. Gerba and Maenza Ž1998. w15x reviewed this topic, pointing out that many good, pain free, long term results co-exist with a tilted, resurfaced patella. Bindelglass w5x reviewed patella tracking in 234 primary TKRs and found it to be central in only 55% with 14% frankly subluxed. They concluded that neither pain scores, nor fixation were affected by patella tracking, nor by lateral release at surgery. Ritter and Campbell w46x suggested that the incidence of patella fracture, with resurfacing was significantly reduced by lateral release, however, Ritter’s enthusiasm for lateral release has recently diminished w45x. Clearly the picture is mixed and I conclude that: 1. Metal-backed patellae should not be used. 2. Fat pad excision facilitates proper exposure of the lateral tibial plateau and thus, allows accurate cuts with correct femoral component placement. This includes rotation of the femoral component which is important for patella stability. 3. Advocates of carefully chosen and well executed lateral release clearly have good results with few resultant complications. There is a suggestion that patella tilt is not so important. My instincts are against this view and I worry about the long-term implications in terms of HDPE wear.
The Bristol knee group w34x conducted a slightly different study, with three groups of patients, randomly allocated. Group A, had patella resurfacing, group B did not. In group C the operating surgeon exercised his own discretion and decided, at the time of operation, whether or not to resurface the patella. The patients all had osteoarthritus and the case-mix was well matched, although in follow-ups there were slightly fewer lateral releases Ž18%. in group C, than in A Ž24%., or B Ž27%.. In group A, no case has required any type of revision. In group B, six underwent secondary resurfacing and 4 more were under observation, for persistent anterior knee pain. In group C, one resurfaced patella had to be revised for patella loosening. Newman w34x, like others, observed that resurfaced patellae tolerated minor degrees of mal-tracking far better than unresurfaced patellae and gave more comfortable knees. It is clear from these studies that the need for re-operation is much higher if the patella is left than if it is resurfaced. Respective rates of 5᎐10% for secondary resurfacing are unacceptable and are unlikely to be as successful as a primary resurfacing. The only justification is the argument that a secondary procedure is easier than a failed primary procedure. I also question whether initial patella resurfacing, carried out secondarily, will be as successful as that carried out at the same time as resurfacing the femur and tibia.
6. Conclusions 5. Prospective studies Kajino et al. w21x reported 26 patients with bilateral TKR, for rheumatoid disease. One side was randomly allocated for patella resurfacing. At 4᎐7.5 year followup scores for pain, function and range of movement revealed no significant difference, though pain on standing and on stairs was worse without patella resurfacing. Bourne et al. w6x published a prospective randomised trial of 100 anatomic medullary knees, reviewed at 2 years, half with and half without patella resurfacing. The knee scores were even better in the unresurfaced than the resurfaced group, but 4% of the unresurfaced group had to undergo secondary resurfacing within 2 years. I understand that at 5 years this figure has doubled to 8%. Bourne and Rorabeck now resurface all patellae, which are 10 mm or more in thickness w48x. In a similar study of 118 Miller-Galante knees, no resurfaced case had had to undergo a revision at a 2᎐4 year follow-up whereas 10% of the unresurfaced group had w2x.
1. Historically the literature generally shows a high incidence of anterior knee pain, if the patella is not resurfaced. 2. Follow up studies of well executed condylar tricompartmental knees, with patella resurfacing, reveal a very low rate of patello-femoral pain, complications, and revision of the patella component. 3. In cases where the results of resurfacing and not resurfacing the patella have been similar, there is a higher rate of pain or disability in relation to standing for a long time, or the use of stairs, with the unresurfaced group. 4. Metal-backed patellae are unnecessary and should be avoided because of high failure and complication rates. 5. The early re-operation rate in those prospective studies where half the patellae have been left unresurfaced have an unacceptably high early reoperation rate. 6. The complications of patella resurfacing although
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rare in well executed series are technically difficult to resolve, with quite a high failure rate themselves. 7. The resurfaced patella is more forgiving than the unresurfaced patella, in terms of symptoms from maltracking, but I am concerned regarding HDPE wear, long term. 8. As overall ranges of movement improve with newer TKR designs we will need to be vigilant for the possibility of an increased rate of polyethylene wear. Finally whilst always urging critical caution I have very little hesitation in advocating routine patella resurfacing. Quite simply total knee replacement should be just that, always providing that there is sufficient bone stock to accommodate the patella ‘button’. References w1x Armstrong CG, Mow VC. Variations in intrinsic mechanical properties of human articular cartilage with age, degeneration and water content. J Bone Jt Surg 1982;64A:94᎐99. w2x Barrack RL, Wolfe MW, Waldman DA, Milicic M, Bertot AJ, Myers L. Resurfacing of the patella in total knee arthroplasty. J Bone Jt Surg 1997;79A:1121᎐1131. w3x Bayley JC, Scott RD, Ewald FC, Holmes GB. Failure of the metal backed patellar component after total knee replacement. J Bone Jt Surg 1988;70A:668᎐674. w4x Berry DJ, Rand JA. Isolated patellar component revisions of total knee replacement. Clin Orthop Rel Res 1993;286: 110᎐115. w5x Bindelglass DF, Cohen JL, Dorr LD. Patellar tilt and subluxation in total knee arthroplasty. Relationship to pain fixation and design. Clin Orthop Rel Res 1993;286:103᎐109. w6x Bmy ne RB, Rorabeck CH, Vaz M, Kramer J, Hardie R, Robertson D. Resurfacing vs not resurfacing the patella during total knee replacement. Clin Orthop Rel Res 1995; 321:156᎐161. w7x Boyd AD, Ewald FC, Thomas WH, Poss R, Sledge CB. Long term complications after total knee arthroplasty with or without resurfacing of the patella. J Bone Jt Surg 1993;75A: 674᎐681. w8x Bugbee WD, Ammeen DJ, Parks NL, Engh GA. Fmy to ten year results with the anatomic modular knee. Clin Orthop Rel Res 1998;348:158᎐165. w9x Clayton M, Thirupathi R. Patellar complications after total condylar arthroplasty. Clin Orthop Rel Res 1982;170:152᎐156. w10x Craig DM, Lettin AWF, Scales JT. Stanmore total knee replacement. J Bone Jt Surg 1983;65B:225. w11x Efkekhar NS. Adjustable intramedullary replacement of the knee joint. J Bone Jt Surg 1983;65A:293᎐309. w12x Enis JE, Gardener R, Robledo MA, Latta L, Smith R. Comparison of patellar resurfacing vs non-resurfacing in bilateral total knee arthroplasty. Clin Orthop Rel Res 1990;260:38᎐42. w13x Evanski PM, Waugh TR, Orofino CF, Anzel SH. UCI knee replacement. Clin Orthop Rel Res 1976;120:33᎐38. w14x Freeman MAR, Todd RC, Bambert P, Day WH. ICLH arthroplasty of the knee. J Bone Jt Surg 1978;60B:339᎐344. w15x Gerba BE, Maenza F. Shift and tilt of the bony patella in total knee replacement. Orthopaedics 1998;27:629᎐636.
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