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Patellar Resurfacing Reduces Pain after TKA for Juvenile Rheumatoid Arthritis

Lybäck, C O*; Lehto, M U K; Hämäläinen, M M J; Belt, E A§

Clinical Orthopaedics and Related Research: June 2004 - Volume 423 - Issue - p 152-156
doi: 10.1097/01.blo.0000127118.98129.6d
SECTION II: ORIGINAL ARTICLES
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Influence of patellar resurfacing after knee replacement and the frequency of patella infera and its relation to the postoperative appearance of the knee pain were assessed in patients with juvenile rheumatoid arthritis. Seventy-seven total knee arthroplasties using the AGC prosthesis with nonconstrained components were done on 52 patients with a mean followup of 7.3 years (range, 3–13 years). Anterior knee pain was present in 14 of 30 patients (47%) with an unreplaced patella and in two of 18 patients (11%) with patella resurfacing. The patella was replaced in 18 patients (35%) and in 23 of 77 knees (30%). Neither revision surgery of implanted patellar components nor any later resurfacing of an unreplaced patella were done during the followup. Preoperatively using the Insall-Salvati ratio, the majority of knees (54 of 77) had a low-riding patella. Patella infera occurred commonly in patients with juvenile rheumatoid arthritis. No connection between patella infera and anterior knee pain was found.

From the *Porvoo District Hospital, Porvoo, Finland; †Coxa, Hospital for Joint Replacement, Tampere and Tampere University Hospital, Finland; ‡Oulu University Hospital, Oulu Finland; and the §Rheumatism Foundation Hospital, Heinola, Finland.

Received: April 8, 2002

Revised: October 25, 2002; April 14, 2003; August 20, 2003

Accepted: October 20, 2003

Correspondence to: Eero Belt, MD, PhD, Rheumatism Foundation Hospital, FIN-18120 Heinola, Finland. Phone: 358 3849 1821; Fax: 038 4918 1512; E-mail: eero.belt@reuma.fi.

Resurfacing of the patella in total knee arthroplasty (TKA) is controversial, and some authors do not routinely recommend it.2,26 However, some authors have reported that patellar resurfacing always should be done in association with TKA.17,18 Patients with juvenile rheumatoid arthritis differ in many respects from other candidates for knee replacement. Many morphologic differences exist between juvenile rheumatoid arthritis and adult onset rheumatoid arthritis.1,15,24,35 Total knee arthroplasty in patients with juvenile rheumatoid arthritis often is a challenging procedure with many technical problems because of more severe deformities, small bone size,15,30 and patella infera which often is seen in patients with juvenile rheumatoid arthritis.33

In several studies, resurfacing of the patella has been recommended in patients with juvenile rheumatoid arthritis.15,30,33 Fern et al12 reported a significant relationship between patella infera and anterior knee pain in patients with rheumatoid arthritis, and recommended selective resurfacing of the patella only in patients with a low-riding patella.

The aim of the current study was to elucidate whether patellar resurfacing would reduce pain after TKA in juvenile rheumatoid arthritis. Frequency of patella infera and its impact on anterior knee pain also was assessed.

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MATERIALS AND METHODS

From 1985 to 1995, 77 knee replacements were done in 52 patients (45 females and seven males) fulfilling the criteria of juvenile rheumatoid arthritis7 at our institutions. The mean age of the patients at the onset of disease was 7.8 years (range, 1.5–16 years) and their mean age at the time of surgery was 32.7 years (range, 16–64 years). All patients received the AGC prosthesis (Anatomical Graduated Component; Biomet, Warsaw, IN). The mean followup was 7.3 years (range, 3–13 years). Standard or small components were implanted in 72 knees and custom-made components were implanted in five knees. Knee replacements were done using nonconstrained components with careful soft tissue balancing and filling of the bone defects with autologous cancellous bone from resections (either blocks or morselized bone). Bone grafts were used in 15 knees. Cementless fixation was preferred because of the young age of the patients and because of prevailing general recommendations. Cemented fixation was used in only four of 77 knees. The patella was replaced in 23 of 77 knees.

Radiographs of the patients’ knees were taken preoperatively and during the immediate postoperative period. Preoperatively, the grade of destruction in the knees was assigned using the method of Larsen et al.22 Patients were followed up clinically after 3 months, and clinically and radiographically after 1, 4, and 8 years.24 In the clinical control the functional status of the patient and knee was assessed and the range of motion and stability of the knee were checked. Thirty-eight patients were available for the 4-year followup and 10 patients were available for the 8-year followup. In the radiographic evaluation of January 2000, the following parameters were measured using a tangential perspective view (skyline) (Fig 1): lateral patellar displacement,23 sulcus angle,6 sulcus width,21 and patellar width.21 Patellar thickness, length of the patella, and the length of the patellar tendon were measured on the lateral radiographs (Fig 2). Assessment of the position of the patella was based on the Insall-Salvati index, which is defined as the ratio length of the patellar tendon/length of the patella.16 The patellar tilt angle (Fig 3) was measured in the group of resurfaced patellas.14

Fig 1.

Fig 1.

Fig 2.

Fig 2.

Fig 3.

Fig 3.

At the end of 1998, 3 to 13 years after surgery, an interview was arranged with patients to assess knee pain and longevity of replaced knees. Two patients could not be contacted and two patients died during the followup. Therefore, this information was collected on 48 patients (71 replaced knees). In the statistical analysis (painfulness) the difference between resurfaced and unreplaced patellas was assessed using Fisher-Freeman-Halton Test.13

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RESULTS

The overall survival for TKA was 99% (95% confidence interval, 92–100) during the 13 years followup using revision surgery or death of the patient as an end point. One knee with preoperative valgus angulation of 33° was revised 4 years after implantation because of marked instability and loosening of the components.24 The patella was resurfaced in 18 patients, and in 23 of 77 knees (30%), using all-polyethylene components in three knees and metal-backed components in 20 knees. No revision surgery or component failures of the patella were detected during the followup. Mild radiolucency (radiolucent lines < 1.5 mm) around the patellar component was observed in five knees with metal-backed components and in one knee with an all-polyethylene implant. Marked radiolucency (≥ 1.5 mm) was seen in one knee with a metal-backed component.

Preoperatively the majority of knees (54 of 77; 70%) had a low-riding patella—patella infera (Fig 4) with an Insall-Salvati ratio less than 1.0,16 but no connection between patella infera and anterior knee pain was seen in our study. The index was less than 0.9 in 46 (60%), and less than 0.8 in 28 knees (36%). Postoperatively (3–13 years after surgery) the corresponding figures were less than 1 in 54 knees (70%), less than 0.9 in 48 knees (62%), and less than 0.8 in 33 of 77 knees (43%) (Table 1). The length of the patella was unchanged during the followup. Lateral patellar displacement was seen in 17 knees preoperatively and in 23 knees postoperatively. Medial displacement was observed in 11 knees preoperatively and in five knees postoperatively, respectively. In the remaining knees the patellas were neutral (Table 1). The mean preoperative Larsen grade was 4.2 (range, 3–5).

Table 1

Table 1

Fig 4.

Fig 4.

Anterior knee pain was present in 14 of 30 patients (47%) with an unreplaced patella and in two of 18 patients (11%) with patella resurfacing (25% of the knees: in 33% with unreplaced patellas and in 9% with resurfaced patellas (p = 0.05)). Only two of 18 painful knees (11%) (both with a metal-backed patella) had a replaced patella. Painless knees occurred in 53 of 71 knees (75%) and in 32 of 48 patients (67%). Thirty-four of 48 patients (71%) did not need any walking aids. Mild anterior knee pain was present in 17 knees and moderate pain was present in one knee.

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DISCUSSION

Our previous study of 77 TKAs in 52 patients with juvenile rheumatoid arthritis seems to be the most extensive study in literature.24 The aim of the current study was to elucidate the appearance of postoperative anterior knee pain with the replaced and unreplaced patellas and the changes of the patella and patellar tendon in the same series. We evaluated the frequency of patella infera and assessed whether it had impact on anterior knee pain. However, patellar resurfacing was done only when it was considered necessary (in 30% of knees) to minimize the complication rate in this young patient group, and no matched groups were used.

The outcome of this series using the nonconstrained AGC prosthesis with a followup of 13 years was encouraging with a survival rate of 99%. Only one revision TKA was done because of instability, but no revision procedures were done for replaced patellas, and no later resurfacing was done for unreplaced patellas. Radiolucencies around the patellar component were present in 13% of knees.

Fourteen of 30 patients (47%) with an unreplaced patella and two of 18 patients (11%) with patella resurfacing had anterior knee pain. Only two of 18 painful knees (11%) (both with metal-backed components) had a replaced patella. Metal-backed components were used in 87% of replaced patellas in the current series. One significant radiolucency was encountered around the implant, but no revision procedures were done. The risk of complication has been reported to be high especially with the use of metal-backed patellar implants.3,4,9,20,29 Typically, the failure has been caused by wear, polyethylene dissociation, and metal-induced synovitis or fracture.3 It also has been shown that metal debris may play a role in the pathogenesis of late prosthesis infection.29 Schroder et a132 reported similar results with metal-backed components in their series of 51 AGC knee replacements in patients with rheumatoid arthritis. In the current study the low body mass of the patients with decreased demand in ambulation and restrictions from other weightbearing joints probably contributed to the good results.

The outcome of TKA in patients with juvenile rheumatoid arthritis was first reported in a series by Sarokhan et al30 in 1983 comprising 29 knee replacements. Four of six reoperations (18% in that series) were done because of patellofemoral pain subsequently requiring patellar resurfacing. In the study by Boublik et al,5 one reoperation was done because of failure of a metal-backed patellar component. Dalury et al10 published a followup of TKAs in patients younger than 45 years. That series comprised 103 knees, and 29% of patients had a diagnosis of juvenile rheumatoid arthritis. The patella was replaced in all patients with inflammatory joint disease. In two knees, the patellar component was revised, one for loosening and one for an acute avulsion fracture of the quadriceps insertion.

Patella infera may occur after knee fractures,25 high tibial osteotomy,28 reconstruction of the anterior cruciate ligament,11 and TKA.19,36 Patella infera is suggested to exist when the Insall-Salvati index has decreased by 10%, or more.19,27,36 Schlenzka and Schwesinger31 assessed the variation of this index in a healthy population and found a large distribution: from 0.72 to 1.38. Fern et al12 reported a significant relationship between patella infera and anterior knee pain in patients with rheumatoid arthritis, and recommended selective resurfacing of the patella only in patients with a low-riding patella. Except as a consequence of surgery, patella infera occurs rarely, but it often is seen in patients with juvenile rheumatoid arthritis.33 In the current study, the patella was low-riding in most patients preoperatively (Fig 5). The Insall-Salvati index was less than 1 in 70% of the knees. Patella infera reflects problems with the extensor system and predisposes to flexion restrictions. Patella infera also favors resurfacing and thinning of the thickened patella seen in juvenile rheumatoid arthritis. Severe patella infera may cause perioperative difficulties, and an osteotomy of the tibial tubercle may be necessary.8

Fig 5.

Fig 5.

Whether to resurface the patella in knee replacement is a concern for many orthopaedic surgeons. Two studies have proved that routine resurfacing has not yielded a real benefit in patients with osteoarthritis.2,26 However, the situation is different among patients with rheumatoid arthritis and resurfacing frequently is preferred in these patients.17,34 Patients with juvenile rheumatoid arthritis differ in many aspects from other patients.1,15,24,30,35 There are strong advocates of routine resurfacing of the patella in patients with juvenile rheumatoid arthritis.15,30,33 In the current series patient contentment was higher with the replaced patella, no complications related to resurfacing occurred, and patella infera was common. Therefore, we agree with resurfacing the patella in patients with juvenile rheumatoid arthritis.

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Acknowledgment

We thank Hannu Kautiainen for statistical analysis.

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References

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