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Patellofemoral arthroplasty
Patellofemoral Arthroplasty 2-12-year Follow-up Study
P h i l i p p e C a r t i e r , M D , * J e a n - L o u i s S a n o u i l l e r , MD,-]- a n d R o n a l d Grelsamer, MDt
Abstract: Seventy-two patellofemoral arthroplasties in 65 patients were fol-
lowed an average of 4 years (range, 2-12 years). In 69 cases concomitant surgery was performed, including soft tissue realignments, tibial tubercle transfers, and unicompartmental femorotibial reconstructions. Twenty-two patients had already had knee procedures, 18 of which addressed their patellofemoral joint. The implant used in all cases features a deep, nonanatomic trochlear component. Using the Mansat scoring system, 85% of the results were good to excellent, with nearly 50% of these excellent. Fourteen complications were noted, seven related to the implant itself and seven associated with extrapatellar pathology. The authors have found patellofemoral arthroplasty to be a viable solution to end-stage patellofemoral arthritis, keeping in mind a nonforgiving surgical technique and the necessity to address all extraarticular pathology. Key words: patellofemoral, arthroplasty, unicompartmental, femorotibial, extensor alignment.
3. "Spongialization," whereby all subchondral bone is removed. We have found the results of this procedure, first espoused by Ficat (11), to be unpredictable. 4. Patella resurfacing. First reported by Duncan and MacKeever in 1955 (10), this procedure has always been controversial. The initial results were encouraging (1, 9, 10, 18, 26) but with one exception (22) did not withstand the test of time (12, 14, 27).
Conventional surgery about the soft tissues, tibial tuberosity, and patellar cartilage can address the problem of mild patellofemoral arthritis. However, this surgery will fail in the face of near total cartilage loss. The options in such cases include: 1. Patellectomy. This procedure is irreversible and leads to considerable stresses across the femorotibial joint. Thought to be more successful for posttraumatic arthritis than for other arthritidies, it has continued to draw mixed reviews (6, 8, 9, 18, 23, 24). 2. Tibial tuberosity elevation (Maquet) (17). The elevation must be significant ( 15 ram) to be effective, can threaten the overlying skin, and decreases quadriceps strength. We have been disappointed with our results using this procedure, especially in patients whose occupation or hobbies require kneeling.
This conceptually led to the final option, the object of our study: 5. Patellofemoral (trochlear) arthroplasty, as first reported by Bechtol and Lubinus (15).
Materials and Methods
* From Clinique des Maussins, Paris, France. t From Hopital St. Michel, Paris, France. From Cohtmbia-Presbyterian Medical Center New York, New York.
Eighty-seven patellofemoral arthroplasties were carried out between 1975 and 1986. At the time of this study, 5 patients had died and 10 had been lost
Reprint requests: Philippe Cartier, MD, Clinique des Maussins, 67 rue de Romainville, 75019 Paris, France.
49
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
to follow-up study. In the 72 remaining cases there were 65 patients (56 women, 9 men); 7 patients had bilateral procedures. Their average age at the time of surgery was 65 years (range, 23-89 years), and the average follow-up period was 4 years (range, 2-12 years). In three cases, we revised an existing patellofemoral implant. Etiologies included arthritis from: ( 1) isolated malalignment secondary to femoropatellar dysplasia (27 cases); (2) malalignment associated with medial or lateral femorotibial degeneration (medial, 31 cases; lateraI, 6 cases); (3) trauma (3 cases); and (4) chondrocalcinosis (5 cases). Except for patients in the latter two categories, only patients with global grade IV chondromalacia and complete disappearance of the patellofemoral joint line were elected for prosthetic replacement. Contrary to Brobeck and Johansson (5), we saw no indication for an arthroplasty in simple chondromalacia. Eighteen knees had already had at least one procedure to the extensor mechanism, including 10 fibial tuberosity transfers, 5 soft tissue procedures, 3 patellofemoral replacements, and 3 Maquet procedures. In addition, four knees had had nonpatellar surgery (3 osteotomies and 1 lysis of adhesions). Four knees had had two or more procedures. To assess fully each compartment radiographically, we obtained the following radiographs: standing AP, standing AP in flexion, varus-valgus stress views, lateral in extension and in 60 ° of flexion, axial patellofemoral views in 30 ° of flexion (quadriceps relaxed and contracted, leg in neutral, internal, and external rotation) and axial views in 60 ° of flexion. These radiographs are obtained for all patients considered for reconstructive surgery and for all patients in this series. Concomitant procedures performed at the time of our arthroplasty included femorotibial reconstruct i o n - 3 6 unicompartmental replacements (30 medial, 6 lateral) and 1 valgus osteotomy--and extensor realignment procedures. Although the design of the implant used is relatively constrained, it cannot be relied upon to contain a malaligned patella. Accordingly, patients with malalignment had a proximal realignment operation to which a tibial tuberosity transfer was added in the presence of a significant Q angle. Patients who had had surgery previous to their tuberosity had further surgery if the tubercle was felt to be in a suboptimal position. Accordingly, there were 34 tibial tuberosity transfers (18 medially, 13 cephalad, 1 laterally, 2 reversals of Maquets) and 27 isolated proximal soft tissue realignment procedures. Blazina's Patella II (Richards) was used in 64 cases and the Patella III in 8 cases. The former features a cental peg on the trochlear implant and is conser-
vatively replaced by three fine points in the latter. The choice between the two is predicted on the quality of the bone. Both will easily tolerate an accompanying unicompartmental femorotibial replacement. The trochlear component is symmetric, rides quite proximally on the femur, and is deep (retentive). Accordingly, it demands a patellar implant featuring a significant ridge. The surgical technique is that described by Bechtol, with significant modifications. A median parapatellar approach is used, a lateral release is routinely performed, and the fat p a d - - a n important vascular supply to the patella--is preserved. Osteophytes in the intercondylar notch are removed so as to restore normal anatomy. This step is critical since under no circumstance should the tip of the trochlear implant protrude into the notch. The outline of the trochlear trial is outlined with the cautery. Gouges, osteotomes, and the oscillating saw are used to create a new trochlear bed. The proximal portion of the implant will rest on the femoral metaphysis, which usually requires shaping. Ideally, the medial-lateral wings of the implant will lie flush on the condyles. However, there is often significant dysplasia, in which case the implant will touch just one condyle (usually the lateral condyle) with the contralateral condyle requiring cement augmentation. There should be no impingement of the tibial spines on the trochlear implant. Attention can then be turned to the more conventional patellar replacement, with attention to the following details: 1. The amount of bone removed should approximate the thickness of the implant. 2. A line drawn between the two fixation holes should be absolutely perpendicular to the trochlear axis, both in extension and in the first few degrees of flexion. 3. The patellar trial should track perfectly to the extent that (a) the ridge on the patellar button remain perfectly parallel to the trochlear groove throughout the range of motion, and (b) there be no catching of the component as the knee goes from flexion to extension. Such catching is usually indicative of a relative patella baja, which requires a proximal transfer of the tibial tuberosity.
Results Patients were evaluated according to the Mansat 20-point rating scale (16), which includes the following parameters: pain, stability, range of motion,
Patellofemoral Arthroplasty
function, and quadriceps strength. Points are deducted for recurvatum and flexion contractures. Before surgery, 82% of patients had a poor rating. The remaining 18% had either pain without instability or instability without pain. After surgery, we recorded the following results: 38% excellent, 47% good or very good, and 15% fair or poor. We found a close correlation between patients' subjective impressions and our o w n rating, as 85% of patients were found to be satisfied and 15% unsatisfied. Of these, four patients developed symptomatic degeneration of the medial compartment and one suffered from sympathetic dystrophy. Not included in the above as satisfactory results are five other patients (7%) w h o felt dramatic improvement after further remedial surgery and considered themselves very satisfied with the final result. Were they to be included in the good to excellent group, as they
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Cartier et al.
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are below, the success rate would increase from 85% to 92%. The results varied according to etiology and n u m ber of prior procedures. For arthritis secondary to isolated end-stage malalignment (27 cases) there were 85% good to excellent results in primary surgery. W h e n a concomitant femorotibial unicompartmentaI was required there were 86% good to excellent results. The results were good to excellent in all five cases of chondrocalcinosis cases and in two of the three patients with posttraumatic arthritis. Broken d o w n by scoring category, the results were as follows. Ninety-two percent of patients had satisfactory pain relief (compared to the 96% with severe preoperative pain). Sixty percent had unlimited ambulation capacity and another 33% could walk 1 mile (1,600 m) (vs. limited ambulation in 97% of patients before surgery, half of w h o m could not walk
r d
Fig. 1. Failure of joint replacement as a result of patella baja. (Top left) Preoperative. (Top right) Correction of patella baja. (Bottom left and right) Progressive return to patella baja.
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
500 m). Flexion greater than 100 ° was obtained in every case and reached 130 ° in two-thirds of patients. There were 16 flexion contractures noted, all less than I0 °. Stability in all planes was obtained in every patient except one with a neuropathy whose patella was stable but whose knee was still weak. Such stability helped to account for an ability to climb stairs without the use of a ramp in 70% of cases and an ability to climb stairs two by two in 44% of patients. Gait was symmetric but " p r u d e n t " with the use of the ramp in 23% and remained halting and asymmetric in 7%. Before surgery, 96% of patients found stairs impossible or climbed in a halting, asymmetric manner. Finally, deep squatting--forbidden in patients whose tibial tuberosity was transferred proximally for patella b a j a - - w a s possible in 55%.
Complications We noted two early complications: one phlebitis and one case of skin necrosis treated by gastrocnemius flap. There were six complications mechanical in nature, which occurred early in our experience: two persistent lateral subluxations, three patients with persistent pain palpably due to an excessively large patellar button, and one "catching" of the patella secondary to a patella baja (Fig. 1). These resulted in one tibial tuberosity transfer, one lateral release, one patellar button exchange, and one patellectomy. There was one asymptomatic avascular necrosis of the patella and five complications not related to the patella: three cases o f p e s tendinitis (one of which required a p e s release) and two Sudeck's dystrophies. Five of the above procedures rapidly led to satisfactory results and the patients could reasonably be included in the good to excellent group. We noted no sepsis and no loosening at either the patellar or trochlear level. As previously noted, four patients subsequently had symptomatic degeneration of a previously asymptomatic femorotibial compartment. To date there has been only one case of asymptomatic radiographic degeneration (Fig. 2).
pathology about the knee. In certain cases implants were used that we do not consider judicious, and certain investigators placed their implant in a suboptimal position. The indications for the procedure include symptomatic degeneration of the patellofemoral joint, with or without involvement of one of the other compartments. We consider age less than 50 years to be a relative contraindication. Patella baja is a serious contraindication, because symptomatic "catching" of the components is likely to occur. The use of a patellofemoral replacement in conjunction with a unicompartmental femorotibial replacement is clearly a controversial procedure, considering the availability of total knee arthroplasty. Total knee arthroplasty has the advantage of k n o w n durability in older patients and it lies within the arm a m e n t a r i u m of most orthopaedic surgeons. However, the combined procedures described in this article offer a degree of bone preservation, range of motion, and proprioception that cannot be overlooked, especially in younger patients. The choice of implant is critical. The normal trochlea is far from ideal, and it is an error to duplicate its morphology. Implants that have done so have not met with success (3, 13, 25). Patella instability has been noted as a result of insufficient geometric retention by the trochlear implant. We therefore agree with Renard (19) that a nonanatomic trochlear design is best.
Discussion Our results support the contention of others (2, 4, 5, 19, 21) that patellofemoral replacement surgery can be a viable procedure. Our review of series reporting disappointing results indicates that the authors may have paid too little attention to coexisting
Fig. 2. Patellofemoral replacement with excellent clinical and radiologic results. (A) Preoperative view. (Figure continues)
Patellofemoral Arthroplasty
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Cartier et al.
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Fig. 2. (B) Postoperative view at 12 years. The patient's clear medial compartment pathology is as yet asymptomatic.
Accordingly, we have chosen to use the Richards Patella II, which features a deep "retentive" trochlear design. This requires the use of a patellar implant with a prominent ridge to match the trochlear counterpart. Such a patellar implant is more difficult to position than would be a smooth button, because the ridge must match the trochlea perfectly in all planes throughout a full range of motion. The trochlear c o m p o n e n t is symmetric. The very narrow distal aspect of the trochlear component allows for easy simultaneous implantation of a unicondylar replacement. Our experience with three patients w h o developed pain because the patella button was too wide led us to develop a " m i n i " size. Since then we have been able to fit every patient appropriately. In the newer Patella III model the lone central trochlear peg is replaced by smaller pegs, potentially
minimizing the difficulties in case of a revision to a total knee arthroplasw. It is important to avoid the following surgical errors: 1. Encroachment of the trochlear c o m p o n e n t into a poorly delineated notch. 2. Maintenance of a significant Q angle and sole reliance on the geometry of the implant for patellar stability. 3. Failure to check for "catching" of the components with the knee flexed past 110 °. 4. Failure to align the patellar ridge with the trochlear groove. The patellofemoral replacement must ahvays be performed in conjunction with any measures required to obtain a satisfactory alignment of the ex-
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
Fig. 3. Patellofemoral replacement in conjunction with femorotibial replacement. (A) Preoperative view. (B) Postoperative view at 4 years. (Figure continues)
tensor mechanism in the sagittal, frontal, and axial planes. We concur with Blazina (4) on the frequent necessity for realignment procedures, especially those involving the tibial tuberosity. A thorough preoperative evaluation of tile femorotibial compartments is essential. This should include observing the patient during stair climbing. The radiologic evaluation must include varus-valgus views and standing flexion views with the knees flexed 20 °. A preoperative arthroscopy is not unreasonable in doubtful cases. W h e n considerable femorotibial degeneration is noted, it must be addressed surgically. Our success rate did not drop w h e n the patellar arthroplasty was combined with a femorotibial unicompartmental replacement (Fig. 3). Although we are firm believers in standard patellar realignment procedures, our 8 5 - 9 2 % success rate going back as far as 12 years leads us to carry out a patellofemoral replacement w h e n we note major cartilage destruction or severe patellofemoral chon-
3U Fig. 3. (C) Postoperative view at 4 years.
o/
Patellofemoral Arthroplasty
drocalcinosis in patients older than 50 years. In cases of severe anatomic incongruency we are willing to compromise on this age limit. Our success has caused us to reevaluate our indications for patellectomies and for the Maquet procedure, which we have performed with decreasing frequency. We hope that our results with future patellofemoral replacements will continue to improve as we further refine the indications for the procedure, the detection of associated pathology, and the positioning of the components.
References 1. Aglietti P, Insall JN, Walker PS, Trent P: A new patella prosthesis. Clin O n h o p 107:175, 1975 2. Arciero R, Toomey H: Patello-femoral arthroplasty: a three to nine year follow-up study. Clin Orthop 236:60, 1988 3. Aubriot JH, Levy G: Proth6se totale f6moro patellaire dans l'arthrose isol6e. In: L'appareil extenseur du genou. Masson, Paris, 1985 4. Blazina ME, Fox JM, Del Pizzo W e t al: Patellofemoral replacement. Clin Orthop 144:98, 1979 5. Brobeck L, Johansson E: Long term results with Richards patello-femoral knee prosthesis. Presented at the International Society of the Knee Meeting, Sydney, 1987 6. Castaing J, Castellani L, Plisson JL, Delpace J: La patellectomie totale: technique et resultats. Rev Chir Orthop 55:259, 1969 7. Cistac C: lnt6r6t de la chirurgie des parties molles perirotulienne dans les syndromes d'instabilite femoropatellaires: ~ propos de 311 cas. Thesis. Nantes, 1985 8. Compere CL, Hill JA, Lewinnek GE, Thompson RG: A new method of patellectomy for patellofemoral arthritis. J Bone Joint Surg 61A:714, 1979 9. De Palma A, Sawyer B, Hoffman JD: Reconsideration of lesions affecting the patellofemoral joint. Clin Orthop 18:63, 1960
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10. Duncan C, McKeever D: Patellar prosthesis. J Bone Joint Surg 37A:I074, 1955 11. Ficat RP, Ficat C, Gedeon P, Toussaint JB: Spongialization: a new treatment for diseased patcllae. Clin Orthop 144:74, 1979 12. Insall JN, Tria A J, Aglietti P: Resurfacing of the patella. J Bone Joint Surg 62A:933, 1980 13. Jouan JP, club Farabeuf: La proth~se f6moro patellaire de Lubinus: considerations techniques et premiers resultats. Ann Orthop de l'Ouest 18:45, 1986 14. Levitt RL: A long-term evaluation of patellar prostheses. Clin Orthop 97:153, 1973 15. Lubinus: Patella glide bearing total replacement. Orthopedics 2:119, 1979 16. Mansat C, Rufo D: Contribution h I'dtude des arthroplasties du genou type Marmor: h propos de 61 cas. Thesis. Toulouse, 1977 17. Maquet P: Advancement of the tibial tuberosity. C/in Orthop 115:225, 1976 18. Pickett J, Stoll D: Patellaplasty or patellectomy? Olin Orthop 144:103, 1979 19. Renard JF: Prothhses autocentriques de rotule. Thesis. Dijon, 1986 20. Scott RD: Prosthetic replacement of the patellofemoral joint. Orthop Clin North Am 10:129, 1979 21. Tomer Baduell CE, Moline SM, Bascompte Nadal A: Arthroplastie femoro-patellaire. Acta Orthop Belg 51:553, 1985 22. Vermuelen H, De Doncker E, Watillon M: Les prothhses rotuliennes de MacKeever dans l'arthrose f6moropatellaire. Acta Orthop Belg 39:79, 1973 23. West F, Soto-Hall R: Recurrent dislocation of the patella in the adult. J Bone Joint Surg 40A:386, 1958 24. West F: End results ofpatellectomy. J Bone Joint Surg 44A: 1089, 1962 25. Witvoet J, Benslama R, Orengo P et al: La prothese f6moro-patellaire du groupe GUEPAR. Rev Chir Orthop 69 (Suppl II):156, 1983 26. Worrell RV: Prosthetic resurfacing of the patella. Clin Orthop 144:91, 1979 27. Worrell RV: Resurfacing of the patella in young patients. Orthop Clin North Am 17:303, 1986
P h i l i p p e C a r t i e r , M D , * J e a n - L o u i s S a n o u i l l e r , MD,-]- a n d R o n a l d Grelsamer, MDt
Abstract: Seventy-two patellofemoral arthroplasties in 65 patients were fol-
lowed an average of 4 years (range, 2-12 years). In 69 cases concomitant surgery was performed, including soft tissue realignments, tibial tubercle transfers, and unicompartmental femorotibial reconstructions. Twenty-two patients had already had knee procedures, 18 of which addressed their patellofemoral joint. The implant used in all cases features a deep, nonanatomic trochlear component. Using the Mansat scoring system, 85% of the results were good to excellent, with nearly 50% of these excellent. Fourteen complications were noted, seven related to the implant itself and seven associated with extrapatellar pathology. The authors have found patellofemoral arthroplasty to be a viable solution to end-stage patellofemoral arthritis, keeping in mind a nonforgiving surgical technique and the necessity to address all extraarticular pathology. Key words: patellofemoral, arthroplasty, unicompartmental, femorotibial, extensor alignment.
3. "Spongialization," whereby all subchondral bone is removed. We have found the results of this procedure, first espoused by Ficat (11), to be unpredictable. 4. Patella resurfacing. First reported by Duncan and MacKeever in 1955 (10), this procedure has always been controversial. The initial results were encouraging (1, 9, 10, 18, 26) but with one exception (22) did not withstand the test of time (12, 14, 27).
Conventional surgery about the soft tissues, tibial tuberosity, and patellar cartilage can address the problem of mild patellofemoral arthritis. However, this surgery will fail in the face of near total cartilage loss. The options in such cases include: 1. Patellectomy. This procedure is irreversible and leads to considerable stresses across the femorotibial joint. Thought to be more successful for posttraumatic arthritis than for other arthritidies, it has continued to draw mixed reviews (6, 8, 9, 18, 23, 24). 2. Tibial tuberosity elevation (Maquet) (17). The elevation must be significant ( 15 ram) to be effective, can threaten the overlying skin, and decreases quadriceps strength. We have been disappointed with our results using this procedure, especially in patients whose occupation or hobbies require kneeling.
This conceptually led to the final option, the object of our study: 5. Patellofemoral (trochlear) arthroplasty, as first reported by Bechtol and Lubinus (15).
Materials and Methods
* From Clinique des Maussins, Paris, France. t From Hopital St. Michel, Paris, France. From Cohtmbia-Presbyterian Medical Center New York, New York.
Eighty-seven patellofemoral arthroplasties were carried out between 1975 and 1986. At the time of this study, 5 patients had died and 10 had been lost
Reprint requests: Philippe Cartier, MD, Clinique des Maussins, 67 rue de Romainville, 75019 Paris, France.
49
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
to follow-up study. In the 72 remaining cases there were 65 patients (56 women, 9 men); 7 patients had bilateral procedures. Their average age at the time of surgery was 65 years (range, 23-89 years), and the average follow-up period was 4 years (range, 2-12 years). In three cases, we revised an existing patellofemoral implant. Etiologies included arthritis from: ( 1) isolated malalignment secondary to femoropatellar dysplasia (27 cases); (2) malalignment associated with medial or lateral femorotibial degeneration (medial, 31 cases; lateraI, 6 cases); (3) trauma (3 cases); and (4) chondrocalcinosis (5 cases). Except for patients in the latter two categories, only patients with global grade IV chondromalacia and complete disappearance of the patellofemoral joint line were elected for prosthetic replacement. Contrary to Brobeck and Johansson (5), we saw no indication for an arthroplasty in simple chondromalacia. Eighteen knees had already had at least one procedure to the extensor mechanism, including 10 fibial tuberosity transfers, 5 soft tissue procedures, 3 patellofemoral replacements, and 3 Maquet procedures. In addition, four knees had had nonpatellar surgery (3 osteotomies and 1 lysis of adhesions). Four knees had had two or more procedures. To assess fully each compartment radiographically, we obtained the following radiographs: standing AP, standing AP in flexion, varus-valgus stress views, lateral in extension and in 60 ° of flexion, axial patellofemoral views in 30 ° of flexion (quadriceps relaxed and contracted, leg in neutral, internal, and external rotation) and axial views in 60 ° of flexion. These radiographs are obtained for all patients considered for reconstructive surgery and for all patients in this series. Concomitant procedures performed at the time of our arthroplasty included femorotibial reconstruct i o n - 3 6 unicompartmental replacements (30 medial, 6 lateral) and 1 valgus osteotomy--and extensor realignment procedures. Although the design of the implant used is relatively constrained, it cannot be relied upon to contain a malaligned patella. Accordingly, patients with malalignment had a proximal realignment operation to which a tibial tuberosity transfer was added in the presence of a significant Q angle. Patients who had had surgery previous to their tuberosity had further surgery if the tubercle was felt to be in a suboptimal position. Accordingly, there were 34 tibial tuberosity transfers (18 medially, 13 cephalad, 1 laterally, 2 reversals of Maquets) and 27 isolated proximal soft tissue realignment procedures. Blazina's Patella II (Richards) was used in 64 cases and the Patella III in 8 cases. The former features a cental peg on the trochlear implant and is conser-
vatively replaced by three fine points in the latter. The choice between the two is predicted on the quality of the bone. Both will easily tolerate an accompanying unicompartmental femorotibial replacement. The trochlear component is symmetric, rides quite proximally on the femur, and is deep (retentive). Accordingly, it demands a patellar implant featuring a significant ridge. The surgical technique is that described by Bechtol, with significant modifications. A median parapatellar approach is used, a lateral release is routinely performed, and the fat p a d - - a n important vascular supply to the patella--is preserved. Osteophytes in the intercondylar notch are removed so as to restore normal anatomy. This step is critical since under no circumstance should the tip of the trochlear implant protrude into the notch. The outline of the trochlear trial is outlined with the cautery. Gouges, osteotomes, and the oscillating saw are used to create a new trochlear bed. The proximal portion of the implant will rest on the femoral metaphysis, which usually requires shaping. Ideally, the medial-lateral wings of the implant will lie flush on the condyles. However, there is often significant dysplasia, in which case the implant will touch just one condyle (usually the lateral condyle) with the contralateral condyle requiring cement augmentation. There should be no impingement of the tibial spines on the trochlear implant. Attention can then be turned to the more conventional patellar replacement, with attention to the following details: 1. The amount of bone removed should approximate the thickness of the implant. 2. A line drawn between the two fixation holes should be absolutely perpendicular to the trochlear axis, both in extension and in the first few degrees of flexion. 3. The patellar trial should track perfectly to the extent that (a) the ridge on the patellar button remain perfectly parallel to the trochlear groove throughout the range of motion, and (b) there be no catching of the component as the knee goes from flexion to extension. Such catching is usually indicative of a relative patella baja, which requires a proximal transfer of the tibial tuberosity.
Results Patients were evaluated according to the Mansat 20-point rating scale (16), which includes the following parameters: pain, stability, range of motion,
Patellofemoral Arthroplasty
function, and quadriceps strength. Points are deducted for recurvatum and flexion contractures. Before surgery, 82% of patients had a poor rating. The remaining 18% had either pain without instability or instability without pain. After surgery, we recorded the following results: 38% excellent, 47% good or very good, and 15% fair or poor. We found a close correlation between patients' subjective impressions and our o w n rating, as 85% of patients were found to be satisfied and 15% unsatisfied. Of these, four patients developed symptomatic degeneration of the medial compartment and one suffered from sympathetic dystrophy. Not included in the above as satisfactory results are five other patients (7%) w h o felt dramatic improvement after further remedial surgery and considered themselves very satisfied with the final result. Were they to be included in the good to excellent group, as they
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Cartier et al.
51
are below, the success rate would increase from 85% to 92%. The results varied according to etiology and n u m ber of prior procedures. For arthritis secondary to isolated end-stage malalignment (27 cases) there were 85% good to excellent results in primary surgery. W h e n a concomitant femorotibial unicompartmentaI was required there were 86% good to excellent results. The results were good to excellent in all five cases of chondrocalcinosis cases and in two of the three patients with posttraumatic arthritis. Broken d o w n by scoring category, the results were as follows. Ninety-two percent of patients had satisfactory pain relief (compared to the 96% with severe preoperative pain). Sixty percent had unlimited ambulation capacity and another 33% could walk 1 mile (1,600 m) (vs. limited ambulation in 97% of patients before surgery, half of w h o m could not walk
r d
Fig. 1. Failure of joint replacement as a result of patella baja. (Top left) Preoperative. (Top right) Correction of patella baja. (Bottom left and right) Progressive return to patella baja.
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
500 m). Flexion greater than 100 ° was obtained in every case and reached 130 ° in two-thirds of patients. There were 16 flexion contractures noted, all less than I0 °. Stability in all planes was obtained in every patient except one with a neuropathy whose patella was stable but whose knee was still weak. Such stability helped to account for an ability to climb stairs without the use of a ramp in 70% of cases and an ability to climb stairs two by two in 44% of patients. Gait was symmetric but " p r u d e n t " with the use of the ramp in 23% and remained halting and asymmetric in 7%. Before surgery, 96% of patients found stairs impossible or climbed in a halting, asymmetric manner. Finally, deep squatting--forbidden in patients whose tibial tuberosity was transferred proximally for patella b a j a - - w a s possible in 55%.
Complications We noted two early complications: one phlebitis and one case of skin necrosis treated by gastrocnemius flap. There were six complications mechanical in nature, which occurred early in our experience: two persistent lateral subluxations, three patients with persistent pain palpably due to an excessively large patellar button, and one "catching" of the patella secondary to a patella baja (Fig. 1). These resulted in one tibial tuberosity transfer, one lateral release, one patellar button exchange, and one patellectomy. There was one asymptomatic avascular necrosis of the patella and five complications not related to the patella: three cases o f p e s tendinitis (one of which required a p e s release) and two Sudeck's dystrophies. Five of the above procedures rapidly led to satisfactory results and the patients could reasonably be included in the good to excellent group. We noted no sepsis and no loosening at either the patellar or trochlear level. As previously noted, four patients subsequently had symptomatic degeneration of a previously asymptomatic femorotibial compartment. To date there has been only one case of asymptomatic radiographic degeneration (Fig. 2).
pathology about the knee. In certain cases implants were used that we do not consider judicious, and certain investigators placed their implant in a suboptimal position. The indications for the procedure include symptomatic degeneration of the patellofemoral joint, with or without involvement of one of the other compartments. We consider age less than 50 years to be a relative contraindication. Patella baja is a serious contraindication, because symptomatic "catching" of the components is likely to occur. The use of a patellofemoral replacement in conjunction with a unicompartmental femorotibial replacement is clearly a controversial procedure, considering the availability of total knee arthroplasty. Total knee arthroplasty has the advantage of k n o w n durability in older patients and it lies within the arm a m e n t a r i u m of most orthopaedic surgeons. However, the combined procedures described in this article offer a degree of bone preservation, range of motion, and proprioception that cannot be overlooked, especially in younger patients. The choice of implant is critical. The normal trochlea is far from ideal, and it is an error to duplicate its morphology. Implants that have done so have not met with success (3, 13, 25). Patella instability has been noted as a result of insufficient geometric retention by the trochlear implant. We therefore agree with Renard (19) that a nonanatomic trochlear design is best.
Discussion Our results support the contention of others (2, 4, 5, 19, 21) that patellofemoral replacement surgery can be a viable procedure. Our review of series reporting disappointing results indicates that the authors may have paid too little attention to coexisting
Fig. 2. Patellofemoral replacement with excellent clinical and radiologic results. (A) Preoperative view. (Figure continues)
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Fig. 2. (B) Postoperative view at 12 years. The patient's clear medial compartment pathology is as yet asymptomatic.
Accordingly, we have chosen to use the Richards Patella II, which features a deep "retentive" trochlear design. This requires the use of a patellar implant with a prominent ridge to match the trochlear counterpart. Such a patellar implant is more difficult to position than would be a smooth button, because the ridge must match the trochlea perfectly in all planes throughout a full range of motion. The trochlear c o m p o n e n t is symmetric. The very narrow distal aspect of the trochlear component allows for easy simultaneous implantation of a unicondylar replacement. Our experience with three patients w h o developed pain because the patella button was too wide led us to develop a " m i n i " size. Since then we have been able to fit every patient appropriately. In the newer Patella III model the lone central trochlear peg is replaced by smaller pegs, potentially
minimizing the difficulties in case of a revision to a total knee arthroplasw. It is important to avoid the following surgical errors: 1. Encroachment of the trochlear c o m p o n e n t into a poorly delineated notch. 2. Maintenance of a significant Q angle and sole reliance on the geometry of the implant for patellar stability. 3. Failure to check for "catching" of the components with the knee flexed past 110 °. 4. Failure to align the patellar ridge with the trochlear groove. The patellofemoral replacement must ahvays be performed in conjunction with any measures required to obtain a satisfactory alignment of the ex-
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The Journal of Arthroplasty Vol. 5 No. 1 March 1990
Fig. 3. Patellofemoral replacement in conjunction with femorotibial replacement. (A) Preoperative view. (B) Postoperative view at 4 years. (Figure continues)
tensor mechanism in the sagittal, frontal, and axial planes. We concur with Blazina (4) on the frequent necessity for realignment procedures, especially those involving the tibial tuberosity. A thorough preoperative evaluation of tile femorotibial compartments is essential. This should include observing the patient during stair climbing. The radiologic evaluation must include varus-valgus views and standing flexion views with the knees flexed 20 °. A preoperative arthroscopy is not unreasonable in doubtful cases. W h e n considerable femorotibial degeneration is noted, it must be addressed surgically. Our success rate did not drop w h e n the patellar arthroplasty was combined with a femorotibial unicompartmental replacement (Fig. 3). Although we are firm believers in standard patellar realignment procedures, our 8 5 - 9 2 % success rate going back as far as 12 years leads us to carry out a patellofemoral replacement w h e n we note major cartilage destruction or severe patellofemoral chon-
3U Fig. 3. (C) Postoperative view at 4 years.
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drocalcinosis in patients older than 50 years. In cases of severe anatomic incongruency we are willing to compromise on this age limit. Our success has caused us to reevaluate our indications for patellectomies and for the Maquet procedure, which we have performed with decreasing frequency. We hope that our results with future patellofemoral replacements will continue to improve as we further refine the indications for the procedure, the detection of associated pathology, and the positioning of the components.
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