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Revision Patellofemoral Arthroplasty
The Journal of Arthroplasty Vol. 23 No. 7 2008
Revision Patellofemoral Arthroplasty Three- to Seven-Year Follow-Up Michiel R.G. Hendrix, MMed (Orth),* Christopher E. Ackroyd, FRCS,y and Jess H. Lonner, MDz
Abstract: In this series, a failed first-generation patellofemoral arthroplasty was revised to a second-generation prosthesis. Fourteen knees were prospectively followed up for a mean of 60 months. Primary procedure failure was due to component malposition, subluxation, polyethylene wear, or overstuffing. Mean Bristol knee scores improved from 58 (range, 36-86) to 79 (range, 38-100) (P b .001). Mild femorotibial arthritis (Ahlbach stage I) was present in 5 knees and predicted a poorer outcome. At most recent follow-up, there was no evidence of wear, loosening, or subluxation. Significant improvement can be obtained when revising the failed patellofemoral arthroplasty, provided there is no femorotibial arthritis. Key words: revision, patellofemoral, arthroplasty, design. © 2008 Elsevier Inc. All rights reserved.
otibial arthritis. Loosening and wear of the components have not been reported with great frequency [2-12]. Early-generation implants, in particular, had a relatively high tendency for failures related directly to patellar maltracking [2,4,5,7,8]. Although many of these failures have been attributed to component malposition or soft tissue imbalance, the likelihood is that many of these were in fact hastened by particular design features of the trochlear components, which put the patella at risk for catching, snapping, and subluxation on its proximal and lateral edges. Several series have reported a relatively high incidence of secondary surgery, such as soft tissue realignment, tibial tubercle realignment, or revision of the patellar and/or trochlear components to correct patella maltracking [2-4,7,10,12]. Although several studies have discussed a need for patellofemoral revisions, details of those revisions and an analysis of the results have not been provided. The purpose of this study was to review the results of revision patellofemoral arthroplasty from a firstgeneration to a second-generation design and describe the indications and technical issues associated with those revisions.
Isolated patellofemoral arthroplasty is an acceptable treatment option for patients with isolated patellofemoral arthritis, with results that are superior to other traditional methods, such as patellectomy and tibial tubercle unloading procedures [1]. This procedure is advocated for patients with degenerative arthritis of the patellofemoral compartment. Success of patellofemoral arthroplasty has varied at all durations of follow-up, depending on issues such as patient selection, component malposition, soft tissue alignment, and implant design [2-12]. Typical failure mechanisms of patellofemoral arthroplasty include patellar maltracking and progressive femorFrom the *Department of Orthopaedic Surgery, Stirling Royal Infirmary, Stirling, UK; yDepartment of Orthopaedic Surgery, Bristol Nuffield Hospital, Bristol, UK; and zBooth Bartolozzi Balderston Orthopaedics, Pennsylvania Hospital, Philadelphia, Pennsylvania. Submitted June 20, 2007; accepted October 4, 2007. Benefits or funds were received in partial or total support of the research material described in this article. These benefits or support were received from Stryker. Reprint requests: Jess H. Lonner, MD, Booth Bartolozzi Balderston Orthopaedics, Pennsylvania Hospital, 800 Spruce Street, Philadelphia, PA 19107. © 2008 Elsevier Inc. All rights reserved. 0883-5403/08/2307-0006$34.00/0 doi:10.1016/j.arth.2007.10.019
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978 The Journal of Arthroplasty Vol. 23 No. 7 October 2008
Materials and Methods Between 1996 and 2002, the 2 senior authors (JHL and CEA) have revised 14 Lubinus patellofemoral arthroplasties in 11 patients (Waldermar Link, Hamburg, Germany) to 14 Avon patellofemoral arthroplasties (Stryker, Mahwah, NJ, and Limerick, Ireland). Outcomes were evaluated using the Bristol knee score (BKS) [13]. The BKS has a maximum total score of 100, a component score for pain (maximum of 40), another component score for function (maximum of 27), and other components for movement, alignment, and collateral laxity in extension. Radiographic assessment involved routine weight-bearing anteroposterior, lateral, and axial radiographs with 30° of knee flexion. An analysis of covariance or a 2-sample t test was used to establish statistical significance in outcomes. The mean age at the time of revision was 71 years (range, 36-80 years). The time to onset of symptoms leading to revision after primary arthroplasty varied from 6 weeks to 36 months (Table 1). The 3 youngest patients became symptomatic between 6 and 12 weeks postoperatively. The interval from primary to revision patellofemoral arthroplasty was a mean 67 months (range, 7-128 months). Indications for revision surgery included component malalignment and patellar subluxation (8 knees), polyethylene wear and synovitis (9 knees), trochlear component malposition (3 knees), patellar malposition (2 knees), and overstuffing (1 knee). None was revised for loosening. Radiographs before revision arthroplasty confirmed malposition of the trochlear
Fig. 1. Anteroposterior view of a Lubinus prosthesis.
component in 3 knees (Figs. 1 and 2) and patellar component in 2. Patellar subluxation was evident in 8 knees. Intraoperative findings included polyethylene wear in 11 knees, synovitis in 9, femoral malposition in 3, and patellar malposition in 2. There was more than one indication for surgery and/or intraoperative abnormality in most of the knees. There was no evidence of loosening of either the trochlear or patellar components of the Lubinus prosthesis in any case. In 11 of 14 knees, both the trochlear and patellar components were revised; in 3 knees, only the trochlear component was revised, leaving the
Table 1. Demographics
Knee Limb Sex 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean
R L R L R R L R L R L R R L
M M M F F F F F F F F M F F
Age at Revision (y)
Reason for Revision
Time Between PFA and Revision PFA (mo)
72.9 72.2 70.8 70.9 64.9 79.4 80.4 61.3 70.9 67.3 68.3 53.6 35.9 49.3 65.6
1+2 1+2 2+3 5 1+3 1+2 1+2 2 2 2 2 1+4 1+4 1+4
94 85 103 128 50 51 78 26 112 86 97 7 10 14 67
Reason for revision: 1, maltracking/subluxation; 2, synovitis; 3, patellar component malposition; 4, femoral component malposition; 5, overstuffing. PFA indicates patellofemoral arthroplasty.
Fig. 2. Lateral view of a Lubinus prosthesis. The component was flexed to ensure that it had been implanted flush with the distal condylar surfaces, leaving a step-off between the anterior flange of the prosthesis and the anterior femoral cortex proximally.
Revision Patellofemoral Arthroplasty Hendrix et al
Fig. 3. Anteroposterior view of the same knee after revision to an Avon prosthesis. This demonstrates broader coverage anteriorly and more proximal extension of the femoral component.
unworn and well-positioned patellar component in place. One patient required a small bone graft of the distal femur in one knee. The conservative nature of the preparation for the Lubinus implant lent itself well to the more substantial femoral resection for the Avon component, without compromised bone support or significantly exposed bone on its margins. Patients were considered Charnley class A in 8 knees, Charnley class B in 1 knee, and Charnley class C in 5 knees. Charnley class A considers that other joints are normal or had successful prior knee arthroplasty and that the patients have no significant medical comorbidities. Charnley class B consists of patients with poor function in the contralateral knee with no other joint involvement and no other medical comorbidities. Charnley class C consists of patients with painful joints other than the knees and/or with other nonjoint factors causing infirmity.
979
(which does not mate well with many distal femora), and its anterior flange is short, not extending beyond the articular cartilage margin of the native femoral trochlea. The sulcus angle of the trochlear component is relatively constrained, particularly in the smaller sizes, in which it is about 110° (although it can be as high as 150° in the larger sizes, which are used infrequently). The patellar component is an all-polyethylene modified central dome [14]. There is limited congruity between the patellar button and the femoral component. The Avon trochlear prosthesis (Figs. 3 and 4), introduced in 1996, is a symmetric design, which is implanted by an onset technique whereby the anterior trochlea is resected, and the implant lies flush with the anterior femoral cortex. The intercondylar extension of the implant is then inset, flush with the articular cartilage surfaces of the femoral condyles. Its sizes tend to be significantly broader than the Lubinus, covering most of the anterior surface of the resected femur. The sagittal radius of curvature is approximately 90°, which mates well with most distal femora. The Avon prosthesis extends significantly more proximally than the Lubinus, so that in extension the patellar component articulates entirely on the metallic surface of the femoral component, without having to glide from the native anterior femoral cortex onto the prosthetic surface. The sulcus angle of the Avon is approximately 125° in
Implant Designs The Lubinus trochlear component (Figs. 1 and 2), introduced in 1975, is an asymmetric inset design that allows very conservative preparation of subchondral bone [14]. Each of its sizes tend to be very narrow, the sagittal radius of curvature very obtuse
Fig. 4. Lateral view of the same knee after revision to an Avon prosthesis. The femoral component mates well with the distal femur.
980 The Journal of Arthroplasty Vol. 23 No. 7 October 2008 all sizes, less constraining than the smaller Lubinus trochlear component sizes [5,6].
Results Patients were followed for a mean 60 months (range, 36-87 months) after revision. No patients were lost to follow-up. The results are depicted in Tables 2 and 3. There were no early postoperative problems such as infection or venous thromboembolic complications. Mean BKSs (total) improved from 58 (range, 36-86) to 79 (range, 38100) (P b .001; 95% confidence interval, +10 to +31); pain component of the BKSs improved from 9 (range, 0-35) to 28 (range, 0-40) (P = .001; 95% confidence interval, +8 to +24); and the BKS function component improved from 15 (range, 1220) to 19 (range, 9-27) (P = .014; 95% confidence interval, +1 to +7). These improvements were all statistically significant. The broad 95% confidence interval for each measure indicates the limited power of this study in a small cohort. At most recent follow-up after revision, mean flexion was 115° (70°-130°). Full extension was present in all but 2 knees, which had 5° and 10° flexion contractures, respectively. The average flexion contracture was 1°. There were no cases of patellofemoral instability at most recent follow-up. Three patients had worse BKSs postoperatively compared with preoperative values, with declines ranging from 2 to 7 points. Those patients with declining BKSs were Charnley C patients with multiple comorbidities, polyarticular joint involvement, and an average age of 75 years (range, 6580 years). Excluding Charnley class C patients from Table 2. Clinical Outcomes Knee 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean
Charnley Class
FollowUp (mo)
a a a a c c c a c a a b a c
55 62 53 24 46 87 75 84 64 48 48 36 40 56
Pre Rev Post Rev BKS BKS 58 86 51 57 48 55 58 67 36 46 47 70 88 47 58
89 94 80 93 38 75 53 69 74 91 93 87 100 69 79
Femorotibial Arthrosis No No Yes No No Yes Yes Yes No No No No No Yes No
Pre rev BKS indicates pre-revision BKS; post rev BKS, postrevision BKS.
Table 3. Effect of Femorotibial Osteoarthritis on Mean Outcome Scores of Revision PFA Femorotibial OA (Ahlbach Grade 1)
Mean Increase in BKS − t
Mean Increase in BKS − p
Mean Increase in BKS − f
Present (n = 5 knees) Absent (n = 9 knees)
14 (range, (−)5 to 29) 25 (range, (−)10 to 46)
15 (range, 5-25) 17 (range, (−)10 to 35)
−1 (range, (−)5 to 7) 7 (range, 0-11)
OA indicates osteoarthritis; BKS − t, BKS − total (maximum points, 40); BKS − p, BKS − pain component (maximum points, 15); BKS − f, BKS − function component (maximum points, 25); (−), decrease in score.
the analysis, improvements in overall BKSs, function scores, and pain scores were all statistically significant (P = .002, P = .010, and P = .004, respectively). Mild femorotibial arthritis (Ahlbach grade 1) had developed in the medial and lateral compartments of 4 knees (3 patients). Isolated grade 1 Ahlbach changes were noted in the lateral compartment in one knee. Development of femorotibial osteoarthritis was predictive of a poorer outcome (Table 3). Two knees have been revised to a total knee arthroplasty for femorotibial arthritis. At the most recent follow-up, there was no radiographic evidence of component malposition, patellar subluxation, polyethylene wear, or aseptic loosening.
Discussion Although newer designs are reducing considerably the incidence of patellofemoral complications after patellofemoral arthroplasty, some earlier-generation implants were fraught with a relatively high incidence of complications directly related to the patellofemoral articulation, such as catching of the patellar component on the edge of the trochlear component that results in subluxation [4,5,7,8]. Although these problems have often been attributed to component malposition and soft tissue imbalance, the likelihood is that shape and design of the trochlear components often are responsible for these problems. This series, which reviews revisions of a number of failed Lubinus implants, highlights how successfully some patellar maltracking problems can be treated by revision to a trochlear implant with a design that is more conducive to unimpeded patellar tracking. Given the design characteristics of the Lubinus trochlear component, it is difficult to implant it completely flush with the surrounding articular cartilage and the anterior surface of the femur, which accounts for the catching and snapping of the patella on the proximal
Revision Patellofemoral Arthroplasty Hendrix et al
Fig. 5. Intraoperative view of the same knee after removal of the Lubinus prosthesis. There has been minimal loss of bone from the femur.
edge and lateral flange of the trochlea as the patella courses from the native femur onto the trochlear component that is often observed with that implant [5]. With newer and evolving implants, there has been a reduction in the incidence of these mechanical complications at short and midterm [5,6]. Revision patellofemoral arthroplasty can be entertained for isolated patellofemoral failures and problems such as loosening, patella maltracking, patella wear, or component malalignment. Although revision patellofemoral arthroplasty is more conservative than revision to a total knee arthroplasty, it should only be done if bone stock is reasonable and accommodating of the new revision implant and if the femorotibial compartments are not arthritic or symptomatic. In addition, the trochlear component should have design features that are conducive to patellar tracking so that the problems that prompted revision are not recreated [5]. In this series, component malalignment and malposition, and patellar catching and subluxation had been satisfactorily addressed by revision with use of a trochlear component that is more accommodating of patella tracking and better mated with most of distal femora than the revised implant. Considerable bone stock loss in the trochlear region may compromise the ability to successfully reimplant a trochlear component without risking premature subsidence or loosening. In the case of the Lubinus implant, which is implanted by the inlay technique and is quite conservative of under-
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lying bone stock, revision to an Avon trochlear component, which requires a transverse anterior cut flush with the anterior femoral cortex and is broader than the Lubinus implant, is easy; and implant stability and support have not been a problem in these cases (Figs. 5 and 6). Although some trochlear geometries are more accommodating of subtle abnormalities of patellar tracking, significant malalignment must be corrected to expect reasonable patellar tracking without subluxation or polyethylene wear [7]. In this series, although pain was typically reduced and clinical and function scores commonly improved, those patients with substantial comorbidities (Charnley C) or femorotibial arthritis did not improve as much after revision to a more contemporary patellofemoral design as those without. Our study found that those patients who developed femorotibial arthritis had a decrease in mean Bristol knee function scores and would have been better treated with revision to a total knee arthroplasty, which has yielded results comparable to primary total knee arthroplasty [15]. Those patellofemoral arthroplasties that fail because of femorotibial degeneration are not amenable to revision to an alternate design of patellofemoral arthroplasty but in fact should be revised to a total knee arthroplasty or a unicompartmental arthroplasty can be performed to resurface the arthritic compartment, leaving the patellofemoral arthroplasty in place. One of the patients in this series with a poor end
Fig. 6. Intraoperative view of the same knee after cementation of the Avon prosthesis.
982 The Journal of Arthroplasty Vol. 23 No. 7 October 2008 result was noted to have a valgus and hyperextended knee at the time of revision. Although other series have alluded to the need for revision patellofemoral arthroplasty, details of the outcomes have not been provided [8,9,10]. KrajcaRadcliffe and Coker [3] reviewed the results of 16 patellofemoral arthroplasties with the Richards I or II implant. One patellofemoral revision arthroplasty, with patellar realignment, was necessary for patellar malalignment and subluxation. This patient has had a successful outcome at 16.6 years. It is unclear whether the same implant was used. Arciero and Toomey [2] reported on 2 revision patellofemoral arthroplasties in a series of 22 patients for trochlear malpositioning that caused patellar clicking and subluxation. Those patients had satisfactory results at 4 and 6 years after revision. Blazina et al [10], in a series of 57 knees, reported a need for 5 isolated trochlear revision, 1 isolated patellar revision, and 3 revisions of both the trochlear and patellar components, all for malpositioning. The disparate results between the 2 implants reported in this series are highlighted by data published previously [5-7]. In a series by Lonner [5], 30 consecutive patellofemoral arthroplasties using the Lubinus implant were compared to a consecutive series of 25 patellofemoral arthroplasties using the Avon trochlear component. The author noted 17% fair and poor results from patellar catching, subluxation, and pain with the Lubinus compared to less than 4% with the Avon design. Although there were no cases of patellar subluxation or catching with the Avon patellofemoral arthroplasty, 4% had moderate anterior knee pain from soft tissue crepitus or inflammation. Ackroyd [6] reported an incidence of patellar maltracking of less than 1% with the Avon trochlear component. This design with a broader anterior flange is more accommodating of patellar tracking than the Lubinus, which had a 32% incidence of patellofemoral complications in the author's earlier series [7]. In that series, 28% required revision either to an alternate patellofemoral arthroplasty or to total knee arthroplasty [7]. Smith et al [8] reported on 45 patellofemoral arthroplasties with a mean follow-up of 45 months (range, 6-90 months), of which 5 knees were revised to total knee arthroplasty (1 due to patellar instability) and 2 to another patellofemoral arthroplasty for patellar component maltracking. Appropriately aligning the revised trochlear component parallel with the epicondylar axis or perpendicular to the anteroposterior axis of the trochlear groove is paramount in helping to ensure accurate tracking of the patella, both in primary and revision patellofemoral arthroplasties.
The patella can be retained if there is no wear and only slight cold flow deformation, but it should be revised when substantially worn, loose, or malpositioned [16]. In addition, an asymmetrically resected patella or overstuffed patellofemoral articulation would require revision of the patellar component. The weaknesses of this study include a small number of patients and the fact that a generic knee score was used to assess the results, the BKS, which does not specifically identify outcomes, problems, or symptoms related to the patellofemoral joint. Excluding those patients who had some degree of femorotibial arthritis at the time of revision patellofemoral arthroplasty, this series has demonstrated improved outcomes in patients after revision patellofemoral arthroplasty to a design more accommodating to patellar tracking. Specifically, patellofemoral catching and instability were resolved in all patients without need for tibial tubercle realignment, highlighting the value of newer designs in enhancing patellar tracking after patellofemoral arthroplasty.
Acknowledgments The authors thank Sue Miller for her help with the database, Rob Elton for statistical analysis, and Beverly Thomas, RN, for manuscript preparation.
References 1. Saleh KJ, Arendt EA, Eldridge J, et al. Symposium. Operative treatment of patellofemoral arthritis. J Bone Joint Surg Am 2005;87:659. 2. Arciero R, Toomey H. Patellofemoral arthroplasty. A three to nine year follow-up study. Clin Orthop Relat Res 1988;236:60. 3. Krajca-Radcliffe JB, Coker TP. Patellofemoral arthroplasty. A 2- to 18-year followup study. Clin Orthop Relat Res 1996;330:143. 4. Board TN, Mahmood A, Ryan WG, et al. The Lubinus patellofemoral arthroplasty: a series of 17 cases. Arch Orthop Trauma Surg 2004;124:285. 5. Lonner JH. Patellofemoral arthroplasty: pros, cons, and design considerations. Clin Orthop Relat Res 2004;428:158. 6. Ackroyd CE, Newman JH, Evans R, et al. The Avon patellofemoral arthroplasty. Five-year survivorship and functional results. J Bone Joint Surg 2007;89B:310. 7. Tauro B, Ackroyd CE, Newman JH, et al. The Lubinus patellofemoral arthroplasty. A 5 to 10 year prospective study. J Bone Joint Surg Br 2001;83:696. 8. Smith AM, Peckett WR, Butler-Manuel PA, et al. Treatment of patello-femoral arthritis using the
Revision Patellofemoral Arthroplasty Hendrix et al
9.
10. 11.
12.
Lubinus patello-femoral arthroplasty: a retrospective review. Knee 2002;9:27. Kooijman HJ, Driesen AP, van Horn JR. Long-term results of patellofemoral arthroplasty. A report of 56 arthroplasties with 17 years of follow-up. J Bone Joint Surg Br 2003;85:836. Blazina ME, Fox JM, Del Pizzo W, et al. Patellofemoral replacement. Clin Orthop Relat Res 1979;144:98. Argenson JNA, Flecher X, Parratte S, et al. Patellofemoral arthroplasty: an update. Clin Orthop Relat Res 2005;440:50. Cartier P, Sanouiller JL, Khefacha A. Long-term results with the first patellofemoral prosthesis. Clin Orthop Relat Res 2005;436:47.
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13. Newman JH, Ackroyd CE, Shah A. Unicompartmental or total knee replacement? Five-year results of a prospective, randomized trial of 102 osteoarthritic knees with unicompartmental arthritis. J Bone Joint Surg Br 1998;80:862. 14. Lubinus HH. Patella glide bearing total replacement. Orthopedics 1979;2:119. 15. Lonner JH, Jasko JG, Booth Jr RE. Revision of a failed patellofemoral arthroplasty to a total knee replacement. J Bone Joint Surg Am 2006;88:2337. 16. Lonner JH, Mont MA, Sharkey PF, et al. Fate of the unrevised all-polyethylene patellar component in revision total knee arthroplasty. J Bone Joint Surg Am 2003;85:56.
Revision Patellofemoral Arthroplasty Three- to Seven-Year Follow-Up Michiel R.G. Hendrix, MMed (Orth),* Christopher E. Ackroyd, FRCS,y and Jess H. Lonner, MDz
Abstract: In this series, a failed first-generation patellofemoral arthroplasty was revised to a second-generation prosthesis. Fourteen knees were prospectively followed up for a mean of 60 months. Primary procedure failure was due to component malposition, subluxation, polyethylene wear, or overstuffing. Mean Bristol knee scores improved from 58 (range, 36-86) to 79 (range, 38-100) (P b .001). Mild femorotibial arthritis (Ahlbach stage I) was present in 5 knees and predicted a poorer outcome. At most recent follow-up, there was no evidence of wear, loosening, or subluxation. Significant improvement can be obtained when revising the failed patellofemoral arthroplasty, provided there is no femorotibial arthritis. Key words: revision, patellofemoral, arthroplasty, design. © 2008 Elsevier Inc. All rights reserved.
otibial arthritis. Loosening and wear of the components have not been reported with great frequency [2-12]. Early-generation implants, in particular, had a relatively high tendency for failures related directly to patellar maltracking [2,4,5,7,8]. Although many of these failures have been attributed to component malposition or soft tissue imbalance, the likelihood is that many of these were in fact hastened by particular design features of the trochlear components, which put the patella at risk for catching, snapping, and subluxation on its proximal and lateral edges. Several series have reported a relatively high incidence of secondary surgery, such as soft tissue realignment, tibial tubercle realignment, or revision of the patellar and/or trochlear components to correct patella maltracking [2-4,7,10,12]. Although several studies have discussed a need for patellofemoral revisions, details of those revisions and an analysis of the results have not been provided. The purpose of this study was to review the results of revision patellofemoral arthroplasty from a firstgeneration to a second-generation design and describe the indications and technical issues associated with those revisions.
Isolated patellofemoral arthroplasty is an acceptable treatment option for patients with isolated patellofemoral arthritis, with results that are superior to other traditional methods, such as patellectomy and tibial tubercle unloading procedures [1]. This procedure is advocated for patients with degenerative arthritis of the patellofemoral compartment. Success of patellofemoral arthroplasty has varied at all durations of follow-up, depending on issues such as patient selection, component malposition, soft tissue alignment, and implant design [2-12]. Typical failure mechanisms of patellofemoral arthroplasty include patellar maltracking and progressive femorFrom the *Department of Orthopaedic Surgery, Stirling Royal Infirmary, Stirling, UK; yDepartment of Orthopaedic Surgery, Bristol Nuffield Hospital, Bristol, UK; and zBooth Bartolozzi Balderston Orthopaedics, Pennsylvania Hospital, Philadelphia, Pennsylvania. Submitted June 20, 2007; accepted October 4, 2007. Benefits or funds were received in partial or total support of the research material described in this article. These benefits or support were received from Stryker. Reprint requests: Jess H. Lonner, MD, Booth Bartolozzi Balderston Orthopaedics, Pennsylvania Hospital, 800 Spruce Street, Philadelphia, PA 19107. © 2008 Elsevier Inc. All rights reserved. 0883-5403/08/2307-0006$34.00/0 doi:10.1016/j.arth.2007.10.019
977
978 The Journal of Arthroplasty Vol. 23 No. 7 October 2008
Materials and Methods Between 1996 and 2002, the 2 senior authors (JHL and CEA) have revised 14 Lubinus patellofemoral arthroplasties in 11 patients (Waldermar Link, Hamburg, Germany) to 14 Avon patellofemoral arthroplasties (Stryker, Mahwah, NJ, and Limerick, Ireland). Outcomes were evaluated using the Bristol knee score (BKS) [13]. The BKS has a maximum total score of 100, a component score for pain (maximum of 40), another component score for function (maximum of 27), and other components for movement, alignment, and collateral laxity in extension. Radiographic assessment involved routine weight-bearing anteroposterior, lateral, and axial radiographs with 30° of knee flexion. An analysis of covariance or a 2-sample t test was used to establish statistical significance in outcomes. The mean age at the time of revision was 71 years (range, 36-80 years). The time to onset of symptoms leading to revision after primary arthroplasty varied from 6 weeks to 36 months (Table 1). The 3 youngest patients became symptomatic between 6 and 12 weeks postoperatively. The interval from primary to revision patellofemoral arthroplasty was a mean 67 months (range, 7-128 months). Indications for revision surgery included component malalignment and patellar subluxation (8 knees), polyethylene wear and synovitis (9 knees), trochlear component malposition (3 knees), patellar malposition (2 knees), and overstuffing (1 knee). None was revised for loosening. Radiographs before revision arthroplasty confirmed malposition of the trochlear
Fig. 1. Anteroposterior view of a Lubinus prosthesis.
component in 3 knees (Figs. 1 and 2) and patellar component in 2. Patellar subluxation was evident in 8 knees. Intraoperative findings included polyethylene wear in 11 knees, synovitis in 9, femoral malposition in 3, and patellar malposition in 2. There was more than one indication for surgery and/or intraoperative abnormality in most of the knees. There was no evidence of loosening of either the trochlear or patellar components of the Lubinus prosthesis in any case. In 11 of 14 knees, both the trochlear and patellar components were revised; in 3 knees, only the trochlear component was revised, leaving the
Table 1. Demographics
Knee Limb Sex 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean
R L R L R R L R L R L R R L
M M M F F F F F F F F M F F
Age at Revision (y)
Reason for Revision
Time Between PFA and Revision PFA (mo)
72.9 72.2 70.8 70.9 64.9 79.4 80.4 61.3 70.9 67.3 68.3 53.6 35.9 49.3 65.6
1+2 1+2 2+3 5 1+3 1+2 1+2 2 2 2 2 1+4 1+4 1+4
94 85 103 128 50 51 78 26 112 86 97 7 10 14 67
Reason for revision: 1, maltracking/subluxation; 2, synovitis; 3, patellar component malposition; 4, femoral component malposition; 5, overstuffing. PFA indicates patellofemoral arthroplasty.
Fig. 2. Lateral view of a Lubinus prosthesis. The component was flexed to ensure that it had been implanted flush with the distal condylar surfaces, leaving a step-off between the anterior flange of the prosthesis and the anterior femoral cortex proximally.
Revision Patellofemoral Arthroplasty Hendrix et al
Fig. 3. Anteroposterior view of the same knee after revision to an Avon prosthesis. This demonstrates broader coverage anteriorly and more proximal extension of the femoral component.
unworn and well-positioned patellar component in place. One patient required a small bone graft of the distal femur in one knee. The conservative nature of the preparation for the Lubinus implant lent itself well to the more substantial femoral resection for the Avon component, without compromised bone support or significantly exposed bone on its margins. Patients were considered Charnley class A in 8 knees, Charnley class B in 1 knee, and Charnley class C in 5 knees. Charnley class A considers that other joints are normal or had successful prior knee arthroplasty and that the patients have no significant medical comorbidities. Charnley class B consists of patients with poor function in the contralateral knee with no other joint involvement and no other medical comorbidities. Charnley class C consists of patients with painful joints other than the knees and/or with other nonjoint factors causing infirmity.
979
(which does not mate well with many distal femora), and its anterior flange is short, not extending beyond the articular cartilage margin of the native femoral trochlea. The sulcus angle of the trochlear component is relatively constrained, particularly in the smaller sizes, in which it is about 110° (although it can be as high as 150° in the larger sizes, which are used infrequently). The patellar component is an all-polyethylene modified central dome [14]. There is limited congruity between the patellar button and the femoral component. The Avon trochlear prosthesis (Figs. 3 and 4), introduced in 1996, is a symmetric design, which is implanted by an onset technique whereby the anterior trochlea is resected, and the implant lies flush with the anterior femoral cortex. The intercondylar extension of the implant is then inset, flush with the articular cartilage surfaces of the femoral condyles. Its sizes tend to be significantly broader than the Lubinus, covering most of the anterior surface of the resected femur. The sagittal radius of curvature is approximately 90°, which mates well with most distal femora. The Avon prosthesis extends significantly more proximally than the Lubinus, so that in extension the patellar component articulates entirely on the metallic surface of the femoral component, without having to glide from the native anterior femoral cortex onto the prosthetic surface. The sulcus angle of the Avon is approximately 125° in
Implant Designs The Lubinus trochlear component (Figs. 1 and 2), introduced in 1975, is an asymmetric inset design that allows very conservative preparation of subchondral bone [14]. Each of its sizes tend to be very narrow, the sagittal radius of curvature very obtuse
Fig. 4. Lateral view of the same knee after revision to an Avon prosthesis. The femoral component mates well with the distal femur.
980 The Journal of Arthroplasty Vol. 23 No. 7 October 2008 all sizes, less constraining than the smaller Lubinus trochlear component sizes [5,6].
Results Patients were followed for a mean 60 months (range, 36-87 months) after revision. No patients were lost to follow-up. The results are depicted in Tables 2 and 3. There were no early postoperative problems such as infection or venous thromboembolic complications. Mean BKSs (total) improved from 58 (range, 36-86) to 79 (range, 38100) (P b .001; 95% confidence interval, +10 to +31); pain component of the BKSs improved from 9 (range, 0-35) to 28 (range, 0-40) (P = .001; 95% confidence interval, +8 to +24); and the BKS function component improved from 15 (range, 1220) to 19 (range, 9-27) (P = .014; 95% confidence interval, +1 to +7). These improvements were all statistically significant. The broad 95% confidence interval for each measure indicates the limited power of this study in a small cohort. At most recent follow-up after revision, mean flexion was 115° (70°-130°). Full extension was present in all but 2 knees, which had 5° and 10° flexion contractures, respectively. The average flexion contracture was 1°. There were no cases of patellofemoral instability at most recent follow-up. Three patients had worse BKSs postoperatively compared with preoperative values, with declines ranging from 2 to 7 points. Those patients with declining BKSs were Charnley C patients with multiple comorbidities, polyarticular joint involvement, and an average age of 75 years (range, 6580 years). Excluding Charnley class C patients from Table 2. Clinical Outcomes Knee 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Mean
Charnley Class
FollowUp (mo)
a a a a c c c a c a a b a c
55 62 53 24 46 87 75 84 64 48 48 36 40 56
Pre Rev Post Rev BKS BKS 58 86 51 57 48 55 58 67 36 46 47 70 88 47 58
89 94 80 93 38 75 53 69 74 91 93 87 100 69 79
Femorotibial Arthrosis No No Yes No No Yes Yes Yes No No No No No Yes No
Pre rev BKS indicates pre-revision BKS; post rev BKS, postrevision BKS.
Table 3. Effect of Femorotibial Osteoarthritis on Mean Outcome Scores of Revision PFA Femorotibial OA (Ahlbach Grade 1)
Mean Increase in BKS − t
Mean Increase in BKS − p
Mean Increase in BKS − f
Present (n = 5 knees) Absent (n = 9 knees)
14 (range, (−)5 to 29) 25 (range, (−)10 to 46)
15 (range, 5-25) 17 (range, (−)10 to 35)
−1 (range, (−)5 to 7) 7 (range, 0-11)
OA indicates osteoarthritis; BKS − t, BKS − total (maximum points, 40); BKS − p, BKS − pain component (maximum points, 15); BKS − f, BKS − function component (maximum points, 25); (−), decrease in score.
the analysis, improvements in overall BKSs, function scores, and pain scores were all statistically significant (P = .002, P = .010, and P = .004, respectively). Mild femorotibial arthritis (Ahlbach grade 1) had developed in the medial and lateral compartments of 4 knees (3 patients). Isolated grade 1 Ahlbach changes were noted in the lateral compartment in one knee. Development of femorotibial osteoarthritis was predictive of a poorer outcome (Table 3). Two knees have been revised to a total knee arthroplasty for femorotibial arthritis. At the most recent follow-up, there was no radiographic evidence of component malposition, patellar subluxation, polyethylene wear, or aseptic loosening.
Discussion Although newer designs are reducing considerably the incidence of patellofemoral complications after patellofemoral arthroplasty, some earlier-generation implants were fraught with a relatively high incidence of complications directly related to the patellofemoral articulation, such as catching of the patellar component on the edge of the trochlear component that results in subluxation [4,5,7,8]. Although these problems have often been attributed to component malposition and soft tissue imbalance, the likelihood is that shape and design of the trochlear components often are responsible for these problems. This series, which reviews revisions of a number of failed Lubinus implants, highlights how successfully some patellar maltracking problems can be treated by revision to a trochlear implant with a design that is more conducive to unimpeded patellar tracking. Given the design characteristics of the Lubinus trochlear component, it is difficult to implant it completely flush with the surrounding articular cartilage and the anterior surface of the femur, which accounts for the catching and snapping of the patella on the proximal
Revision Patellofemoral Arthroplasty Hendrix et al
Fig. 5. Intraoperative view of the same knee after removal of the Lubinus prosthesis. There has been minimal loss of bone from the femur.
edge and lateral flange of the trochlea as the patella courses from the native femur onto the trochlear component that is often observed with that implant [5]. With newer and evolving implants, there has been a reduction in the incidence of these mechanical complications at short and midterm [5,6]. Revision patellofemoral arthroplasty can be entertained for isolated patellofemoral failures and problems such as loosening, patella maltracking, patella wear, or component malalignment. Although revision patellofemoral arthroplasty is more conservative than revision to a total knee arthroplasty, it should only be done if bone stock is reasonable and accommodating of the new revision implant and if the femorotibial compartments are not arthritic or symptomatic. In addition, the trochlear component should have design features that are conducive to patellar tracking so that the problems that prompted revision are not recreated [5]. In this series, component malalignment and malposition, and patellar catching and subluxation had been satisfactorily addressed by revision with use of a trochlear component that is more accommodating of patella tracking and better mated with most of distal femora than the revised implant. Considerable bone stock loss in the trochlear region may compromise the ability to successfully reimplant a trochlear component without risking premature subsidence or loosening. In the case of the Lubinus implant, which is implanted by the inlay technique and is quite conservative of under-
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lying bone stock, revision to an Avon trochlear component, which requires a transverse anterior cut flush with the anterior femoral cortex and is broader than the Lubinus implant, is easy; and implant stability and support have not been a problem in these cases (Figs. 5 and 6). Although some trochlear geometries are more accommodating of subtle abnormalities of patellar tracking, significant malalignment must be corrected to expect reasonable patellar tracking without subluxation or polyethylene wear [7]. In this series, although pain was typically reduced and clinical and function scores commonly improved, those patients with substantial comorbidities (Charnley C) or femorotibial arthritis did not improve as much after revision to a more contemporary patellofemoral design as those without. Our study found that those patients who developed femorotibial arthritis had a decrease in mean Bristol knee function scores and would have been better treated with revision to a total knee arthroplasty, which has yielded results comparable to primary total knee arthroplasty [15]. Those patellofemoral arthroplasties that fail because of femorotibial degeneration are not amenable to revision to an alternate design of patellofemoral arthroplasty but in fact should be revised to a total knee arthroplasty or a unicompartmental arthroplasty can be performed to resurface the arthritic compartment, leaving the patellofemoral arthroplasty in place. One of the patients in this series with a poor end
Fig. 6. Intraoperative view of the same knee after cementation of the Avon prosthesis.
982 The Journal of Arthroplasty Vol. 23 No. 7 October 2008 result was noted to have a valgus and hyperextended knee at the time of revision. Although other series have alluded to the need for revision patellofemoral arthroplasty, details of the outcomes have not been provided [8,9,10]. KrajcaRadcliffe and Coker [3] reviewed the results of 16 patellofemoral arthroplasties with the Richards I or II implant. One patellofemoral revision arthroplasty, with patellar realignment, was necessary for patellar malalignment and subluxation. This patient has had a successful outcome at 16.6 years. It is unclear whether the same implant was used. Arciero and Toomey [2] reported on 2 revision patellofemoral arthroplasties in a series of 22 patients for trochlear malpositioning that caused patellar clicking and subluxation. Those patients had satisfactory results at 4 and 6 years after revision. Blazina et al [10], in a series of 57 knees, reported a need for 5 isolated trochlear revision, 1 isolated patellar revision, and 3 revisions of both the trochlear and patellar components, all for malpositioning. The disparate results between the 2 implants reported in this series are highlighted by data published previously [5-7]. In a series by Lonner [5], 30 consecutive patellofemoral arthroplasties using the Lubinus implant were compared to a consecutive series of 25 patellofemoral arthroplasties using the Avon trochlear component. The author noted 17% fair and poor results from patellar catching, subluxation, and pain with the Lubinus compared to less than 4% with the Avon design. Although there were no cases of patellar subluxation or catching with the Avon patellofemoral arthroplasty, 4% had moderate anterior knee pain from soft tissue crepitus or inflammation. Ackroyd [6] reported an incidence of patellar maltracking of less than 1% with the Avon trochlear component. This design with a broader anterior flange is more accommodating of patellar tracking than the Lubinus, which had a 32% incidence of patellofemoral complications in the author's earlier series [7]. In that series, 28% required revision either to an alternate patellofemoral arthroplasty or to total knee arthroplasty [7]. Smith et al [8] reported on 45 patellofemoral arthroplasties with a mean follow-up of 45 months (range, 6-90 months), of which 5 knees were revised to total knee arthroplasty (1 due to patellar instability) and 2 to another patellofemoral arthroplasty for patellar component maltracking. Appropriately aligning the revised trochlear component parallel with the epicondylar axis or perpendicular to the anteroposterior axis of the trochlear groove is paramount in helping to ensure accurate tracking of the patella, both in primary and revision patellofemoral arthroplasties.
The patella can be retained if there is no wear and only slight cold flow deformation, but it should be revised when substantially worn, loose, or malpositioned [16]. In addition, an asymmetrically resected patella or overstuffed patellofemoral articulation would require revision of the patellar component. The weaknesses of this study include a small number of patients and the fact that a generic knee score was used to assess the results, the BKS, which does not specifically identify outcomes, problems, or symptoms related to the patellofemoral joint. Excluding those patients who had some degree of femorotibial arthritis at the time of revision patellofemoral arthroplasty, this series has demonstrated improved outcomes in patients after revision patellofemoral arthroplasty to a design more accommodating to patellar tracking. Specifically, patellofemoral catching and instability were resolved in all patients without need for tibial tubercle realignment, highlighting the value of newer designs in enhancing patellar tracking after patellofemoral arthroplasty.
Acknowledgments The authors thank Sue Miller for her help with the database, Rob Elton for statistical analysis, and Beverly Thomas, RN, for manuscript preparation.
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