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Long term follow up of clinical outcome between patellar resurfacing and nonresurfacing in total knee arthroplasty: Chinese experience

Feng, Bin; Weng, Xisheng; Lin, Jin; Jin, Jin; Qian, Wenwei; Wang, Wei; Qiu, Guixing

doi: 10.3760/cma.j.issn.0366-6999.20141845
Original article
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Background The long term outcome of patellar resurfacing in Chinese has not been well described. This study evaluated more than 10-year clinical outcomes and survivorship of patellar resurfacing or nonresurfacing in total knee arthroplasty.

Methods From January 1993 to December 2002, 265 patients accepted total knee arthroplasty in Department of Orthopaedic Surgery, Peking Union Medical College Hospital. Among them, 226 patients (246 knees) were successfully followed up, with 176 knees for patellar resurfacing and 70 knees for nonresurfacing. The survivorship of total knee arthroplasty between two groups and the hospital for special surgery knee score (HSS), patellar score, patellar related complication and radiological results were studied at the latest follow-up.

Results The HSS knee score increased from 55.9±12.2 preoperatively to 92.0±10.9 postoperatively for patellar resurfacing group and from 56.6±9.9 to 94.2±11.4 for nonresurfacing group after average 11.4-year follow-up. Patellar score increased from 13.93±2.42 preoperatively to 28.33±2.20 for resurfacing group and from 13.55±2.73 to 27.8±2.37 for nonresurfacing group. There was no statistically significant difference for both HSS score, patellar score between the two groups with higher rate of anterior knee pain for nonresurfacing group. Patellar nonresurfacing had higher lateral subluxation than resurfacing group according to radiological evaluation. Patients with rheumatoid arthritis had 5.5 fold patellar related complication than patients with osteoarthritis. The 10-year survival rate was not statistically significant different between the two groups (P=0.12).

Conclusions There was no significant difference of long-term clinical outcome and survivorship between patellar resurfacing and nonresurfacing. Patellar nonresurfacing can be advisable during primary total knee arthroplasty especially in Chinese patients with osteoarthritis. Selective patellar resurfacing for patients with rheumatoid arthritis can achieve lower patella related complication.

Department of Orthopaedic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100730, China (Feng B, Weng XS, Lin J, Jin J, Qian WW, Wang W and Qiu GX)

Correspondence to: Weng Xisheng, Department of Orthopaedic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100730, China (Tel & Fax: 86–10–69152809. Email: xshweng@medmail.com.cn)

(Received August 6, 2014)

Edited by Guo Lishao

Patellar resurfacing has been recommended on the basis of anterior knee pain (AKP) associated with the patella after total knee arthroplasty (TKA). However, with patellar resurfacing, complications such as polyethylene wearing, patellar fracture, patellar clunk syndrome may occur.1 Up to now, three approaches are currently used for patellar strategy during primary TKA, (1) never resurface, (2) always resurface, and (3) selectively resurface the patella.2 As for whether or not the patella should be routinely resurfaced during primary TKA and the criteria for resurfacing, the decision still remains controversial and can not decide clear superiority of one approach over the other. According to some randomized control trials (RCTs), patellar resurfacing had no statistically significant difference with nonresurfacing, as for clinical outcome, knee score and re-operation rate.3–5 While other studies, even meta-analysis, reported the patellar resurfacing may demonstrated superiority over the opposite side.2,6,7 Because the anatomy of Chinese population knees was different from the western with the relatively thinner patellar and thinner anterior femoral condyles.8 And there was limited report in literature about the long term outcome of patellar resurfacing in Chinese. It is necessary to study the outcome of patellar resurfacing versus nonresurfacing in Chinese population. The purposes of our study were to evaluate the clinical and radiographic outcome after 10 postoperative years between patellar resurfacing group and nonresurfacing group during primary TKA and the survivorship of more than 10 years follow-up. Our hypothesis is that the patellar resurfacing in Chinese may has different outcome than that in Western Caucasian.

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METHODS

This was a retrospective study. The study protocol was approved by the Institutional Review Board of Peking Union Medical College Hospital. Ethics Committee approval was taken from the regional Ethics Committee, and consent was obtained from all the patients in this study.

Totally, 265 patients underwent primary cemented fixed bearing TKAs by three chief knee surgeons from January 1993 to December 2002 in Department of Orthopaedic Surgery, Peking Union Medical College Hospital. Thirty-nine patients with rheumatoid arthritis (RA), 222 patients with knee osteoarthritis (OA), 4 patients with miscellaneous had indications for surgery. There were 221 female and 44 male patients. The average age at surgery was (62.2±9.4) years (39 to 79 years) and the average body mass index (BMI) was (24.7±3.8) kg/m2 (13.9 to 40.2). Follow-up concluded in December 2012.

Tourniquets were used in all cases. A midline skin incision was used with a medial parapatellar capsular incision. The bone cuts were made using prosthesis specific instruments with measured resection and carefully planned soft tissue technique. The intramedullary and extramedullary guide systems were used for distal femoral and proximal tibial bone resection respectively.

In this series, the patellar thickness, bone quality were considered for determining either patella resurfacing or non-resurfacing. The average thickness of patella was (21.3±2.1) mm (17.0 to 26.0 mm) in our series, with mean thickness of 20.6 mm for female and 23.0 mm for male. Patella resurfacing was used in cases of severe cartilage damage, serious deformity and mal-tracking; and generally the residual bone thickness of more than 12.0 mm was required.9 The mean thickness of patella after resurfacing was 20.5 mm for female and 22.8 for male. For patellar non-resurfacing group, patellarplasty consisting of articular surface smoothing, osteophyte removal and patellar rim denervation were performed. Patellofemoral tracking was assessed after implantation of implants by ‘no thumb test’. Lateral release was performed when patellofemoral maltracking was assessed. All the patellofemoral tracking was adjusted well before wound closure.

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Clinical and radiological evaluation

The Hospital for Special Surgery (HSS) knee score questionnaire was used for clinical evaluation. The symptoms of anterior knee pain when climbing stairs, range of motion (ROM), patellar clunk, instability, and reason for revision were recorded at the latest follow-up. The patellar score was evaluated according to Fellar's system.10 The patients underwent clinical evaluation at the outpatient clinic. Whenever it was not possible to come to the outpatient clinic (mainly because of transportation problems), these patients were visited by the examiner of local hospital and were interviewed by telephonic questionnaire. For the patients who had died at the time of the study, date of death and the status of knees as well as knee scores were noted from the family.

X-rays were taken immediately after operation. And X-rays of weight bearing in the anteroposterior (AP), laterolateral (LL) and skyline view were evaluated at the latest follow-up (Figures 1, 2). Skyline views of patella were evaluated for patellar tracking. Insall-Salvati index was used to evaluate the relationship of the patella with the joint line, which was measured by the ratio of the length of the patellar joint surface (P) to the length of the patellar tendon (T) (P/T ratio) from lateral view.

Figure 1.

Figure 1.

Figure 2.

Figure 2.

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Statistical analysis

SPSS 15.0 (SPSS Inc., Chicago, IL, USA) was used for statistical analysis. Clinical data were analyzed using means±standard deviation (SD). The level of statistical significance was set at P <0.05. Paired t-tests were performed to determine the difference of HSS knee score, ROM. The influence of different patellar strategy to the clinical outcome was evaluated in analysis of variance (ANOVA) with covariance model. The patellar related complication was analyzed with Chi-square test.

The Kaplan-Meier method was used for survivorship analysis. There were two definitions of failure for survivorship analysis in our study. One was defined as reoperation of the implant for any reason: including infection, aseptic loosening, instability, patellar complication. Another was defined as the occurrence of patellar complication with or without reoperation. For the patients who could not fulfill with the clinical evaluation during the latest follow up, if no problems with the TKA were described at the last visit, we presumed that the implants worked well in situ. The survivorship between different factors was evaluated in a log rank test. The risk factor of patellar related complication was analyzed with Cox's Proportional Hazard Model. Risk ratio (RR) was used to evaluate the relative risk between RA and OA groups.

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RESULTS

In this cohort, thirty-nine patients (account for 14%) were lost during less than 10 years follow-up, with average age of (64.9±5.2) years at index operation, with 7 males and 32 females, with diagnoses of OA for 35 patients and RA for 4 patients. These patients had an average ROM of 95.9°±9.3° (range, 80° to 120°) at an average 4.32 years follow-up (range, 2 to 8 years). Totally 226 patients (246 knees) were successfully followed. Within them, fifty-one patients (54 knees) died or had paraplegia or paralysis to impair ambulation because of cerebrovascular disease within less than 10 years after index operation. All the 54 knees had TKAs in situ at latest follow-up. Fifteen patients (15 knees) had reoperation because of the implant failure during follow up. Totally, 160 patients (177 knees) presented implants with good performance in situ after more than 10 postoperative years, with average 11.9 years follow-up (10 to 18 years). As for patellar strategy, patellar resurfacing with polyethylene dome patella was used in 134 knees and non-resurfacing was used in 43 knees. The indications for TKA, were 30 knees for RA, 147 knees for primary or secondary OA. The Ortholoc knee system (Dow Corning Wright Medical, USA) was used for 82 knees, and PFC system (DePuy Orthopaedics, Inc, Warsaw, IN, USA) for 39 knees, Kinemax (Howmedica, Rutherford, NJ, USA) for 19 knees, domestic manufactured products for 14 knees and others for 23 knees.

In this study, eighty patients (96 knees) fulfilled with the evaluation of clinical outcome with HSS knee score system and patellar score.

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Clinical results

Clinical outcomes were successfully evaluated for 96 knees with HSS knee score for an average 11.4 years (10 to 18 years) follow-up (Table 1). There was no statistically significant difference for the postoperative HSS knee score among three chief knee surgeons after ANOVA analysis (F=2.9, P=0.06). The total HSS knee score increased from 56.58±11.05 (range, 28 to 80) preoperatively to 92.29±10.95 (range, 69 to 112) postoperatively. The ROM improved from 84.8°±24° (range, 10° to 120°) to 99.7°±17.6° (range, 30° to 120°). All the items had statistically significant differences (P <0.01).

Table 1

Table 1

In our group, totally 15 patients (15 knees) underwent reoperation during follow-up, only one patient underwent reoperation for patellar complication, which had patellar dislocation 11 years after index operation. Ten knees had reoperations for septic loosening, three knees for aseptic loosening, one knee for postoperative stiffness. In our series, HSS knee score increased from 55.9±12.2 (range, 28 to 80) preoperatively to 92.0±10.9 (range, 70 to 111) postoperatively for the patellar resurfacing group, and from 56.6±9.9 (33 to 77) to 94.2±11.4 (69 to 112) for the nonresurfacing group. The patellar score increased from 13.9±2.4 to 28.3±2.2 for the resurfacing group, and from 13.6±2.7 to 27.8±2.4 for the nonresurfacing group (Table 1). There was no statistically significant different clinical outcome improvement between patellar resurfacing and patellar non-resurfacing group. Three patients experienced patellar complication in resurfacing group, with one for patellar dislocation who underwent reoperation, two with anterior knee pain. Four patients experienced patellar complication in nonresurfacing group, with three for AKP and one for patellar clunk. Six of the seven patients did not accept reoperation. The patellar nonresurfacing group experienced higher rate of AKP compared with resurfacing one (7.9% vs. 3.6%). Nevertheless, the difference was not statistically significant both for patellar complication (χ2=0.684, P=0.408) and anterior knee pain (χ2=0.679, P=0.41).

According to the Cox's Proportional Hazard Model, there was statistical difference of patellar related complication between RA and OA patients (P=0.030), while no statistically significant difference of patellar related complication between patellar resurfacing and nonresurfacing patients (P=0.199), between CR and PS patients (P=0.887). RA patients experienced a 5.5 fold of patellar related complication compared with OA patients (RR=5.5). Patellar nonresurfacing experienced a 2.7 fold of patellar related complication compared with resurfacing patients (RR=2.74). RA patients who underwent patellar resurfacing experienced 0.36 fold of complication compared with who underwent patellar nonresurfacing. Patients with CR prothesis experienced 0.89 fold of complication compared with patients with PS prothesis.

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Radiological results

Radiological evaluation was possible for 64 knees in our group (Figures 1, 2). The Insall-Salviti index of resurfacing group was 1.2 (range, 0.8 to 1.4), nonresurfacing group was 1.12 (rang, 0.8 to 1.5) (Table 1). When the edge of patella presented lateralization over edge of lateral condyle on skyline view, it was considered patella lateral subluxation. Chi-square test showed non-resurfacing group had higher and statistically significant rate of lateral subluxation at follow-up than resurfacing group (χ2=4.814, P=0.028) (Table 2).

Table 2

Table 2

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Survivorship analysis

In our cohort, 246 knees were enrolled for the survivorship analysis. Taking failure with reoperation of the implant as the endpoint, the cumulative average survival rate at 10 years was (93.6±1.7)%, with (91.3±2.2)% for resurfacing group and (95.0±2.4)% for nonresurfacing group. The difference was not statistically significant (P=0.12) (Figure 3). Taking failure with the patellar related complication, the cumulative average survival rate at 10 years was (97.7±1.3)% for patellar resurfacing group, and (94.2±2.8)% for nonresurfacing group. The difference was not statistically significant either (P=0.098) (Figure 4).

Figure 3.

Figure 3.

Figure 4.

Figure 4.

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DISCUSSION

TKA is a highly effective procedure that provides reliable relief from pain, improves physical function in patients with advanced knee arthropathy. Long-term follow-up study has been reported for Western Caucasian in literature with more than 90% of survivor rate after 10 postoperative years.11 It was also reported a 92.7% survival rate at 10 years follow-up with improved clinical outcome and pain relief for TKA in Chinese people.12 But as for whether or not the patella should be routinely resurfaced during primary TKA and the criteria for resurfacing, the decision still remains controversial.

The most frequently adopted criteria for patellar resurfacing in literature were the presence of advanced patellofemoral arthritis, damage to the cartilage of the patellar joint surface and patellofemoral incongruency.13–15 Other criteria included the inflammatory OA, preoperative anterior knee pain and cases with the advanced deformity.14,15 For patients with small and osteopenic patella, active and young patients with a moderate damage to the patellar cartilage, the patellar resurfacing was not suggested.15 The criteria to resurface the patellar during primary TKA in this study were the degree of damage to the cartilage during operation, the patellofemoral incongruency and the patellar bone quality. The criteria were consistent with the literature and we indicated to refer the status of patella at operation as the definitive decision of patellar resurfacing or not.

We found the clinical outcome evaluation with HSS knee score, anterior knee pain, patellar complication were not statistically different after more than 10 years follow-up between the patellar resurfacing and nonresurfacing group. The nonresurfacing group had higher rate of lateral subluxation according to radiographic evaluation. The nonresurfacing group also had higher rate of AKP. Our opinion was supported by the study by Li et al.16 as well as other studies of outcome of patellar resurfacing after TKA.3,5,8,17 Li et al conducted a systematic review of patellar resurfacing in TKA, in which the indication of operation included both OA and RA, and demonstrated the average incidence of AKP of nonresurfacing group and resurfacing group was 24.1% and 12.9% respectively, patellar resurfacing in TKA can reduce the risk of reoperation with no benefit to postoperative knee function or patient satisfaction than in TKA without patellar resurfacing.16 The authors of other studies also concluded that although the nonresurfacing group had more cases of revision due to patellar cause, there was no difference of clinical outcome between different patellar strategy both for OA and RA patients.3,5,8,17 Furthermore, according to 700 cases study of Arnold et al,18 the patella remodeled over the years and matched the condylar design of the femoral prosthesis after primary TKA without patellar resurfacing. The author concluded even TKA without patellar resurfacing gave excellent long term results. In this study, patellar scoring system was adopted to evaluate the outcome of patellar resurfacing. The result also demonstrated no statistical difference between the two groups, with 27.8 point for nonresurfacing group and 28.33 for resurfacing group. Our result was consistent with the study of Fellar et al's.10 Our study also indicated that the long term survivorship was not statistically different between the two groups. The unique to this study was the using patellar related complication as the extra definition of failure for survivorship analysis. So we could study more accurately the impact of patellar strategy to long term survivorship after primary TKA. To consider the studies in literature up to now, more knee surgeon concluded it was not necessary to regularly resurface the patella during primary TKA.5,8,10,19

In this study, no difference was present for relationship of patella with the joint line between two groups. Although patellar non-resurfaced group had higher incidence of lateral subluxation from radiological results, there was no difference of anterior knee pain and HSS knee score between patients with patellar resurfacing and those without. In literature, many studies have focused on the impacting factor to clinical outcome and patellofemoral complication after TKA, but the results were controversial. It was reported the postoperative patellofemoral complication was mainly correlated with the patellar malalignment and with the impaired mechanical axis of the lower extremity.19,20 So, the patellofemoral congruency was essential to overcome the patellar related complication in TKA procedures.20 Nevertheless, other study reported there was no significant difference between the knees with no patellar incongruence and the knees with incongruence,21 and patellar strategy was not associated with the patellar congruence angle and clinical outcome.22 In future, with more high level evidence be available, it will help to answer the question.

Because thinner patellar is at higher risk of fracture given the high mechanical pressures subjected. For successful patellar resurfacing, a residual bone thickness of 15 mm was suggested after patellar osteotomy according to literature in Caucasian.23 The average thickness of patella was 20.6 mm for female and 23 mm for male in our series. The thickness was less than that of Western population, which was 22.5 mm for female and 25.3 mm for male.24 Our result was supported by the study by Li et al.8 We preferred the residual bone thickness of 12 mm for patellar resurfacing in Chinese in our practice. This opinion was also supported by the study of Kim et al.9 Furthermore, in our practice, we found the anterior femoral condyle was relatively thinner.8 With the morphological features of the knee joint in Chinese, we predicted the pressure in the patellofemoral joint in Chinese was lower than in Western patients and the incidence of patellofemoral complication was also lower.8 This may be the reason of lower AKP rate in our study than in other studies,3,13,25 with 7.3% AKP rate in patellar nonresurfacing group and 3.6% in resurfacing group, and this is what we hypothesized in the introduction of this study. Furthermore, in order to reduce the patellar related complication, the lower extremity mechanical axis should be adjusted within the physiological limits following the total knee arthroplasty.26 Jeffery et al26 reported that when the mechanical axis passed through the middle 1/3 of the prosthesis, the subsequent loosening was 3% in all of the cases; and when the mechanical axis passed through other parts of the prosthesis, the incidence of loosening was increased to 24%.26 In our practice, the lateralization of femoral component was preferred to adjust the mechanical axis within the physiological limits. Because the postoperative patellofemoral complication was mainly correlated with the patellar malalignment,20 patellofemoral tracking should be assessed after implantation of implants by ‘no thumb test’, and patellar congruence should be acquired before wound closure. Furthermore, internal rotation of the femoral or tibial component, failure to balance the soft tissue, proximally elevating of joint line and extreme valgus position of the knee should be avoided in TKA procedure with or without patellar resurfacing.14,19

For the impacting factor to the patellar complication, which included the preoperative diagnosis and the PCL strategy, the diagnosis of RA was more significant in this study according to the ‘Cox's Hazard Model’. The patellar related complication was higher in RA patients than in OA patients in our series. Patellar resurfacing during TKA was considered to have the effect to eliminate the reaction between patellar cartilage and inflamed synovium and to reduce the postopearative patellar related complication.14,15,27 So RA knee was considered an indication for patellar resurfacing in some studies. It was reported that RA patients with TKA and patellar resurfacing were more satisfied with the clinical outcome and had lower rate of AKP than the opposite side.13,27 On the contrary, some other studies reported there were no difference in terms of pain relief and patellar related complication between the two groups for RA patients.28,29 Furthermore, Fern et al29 reported even the postoperative moderate to severe AKP for RA patients who underwent TKA with patellar nonresurfacing was about 13.5%, none had secondary resurfacing. One more factor when considering the patellar resurfacing for RA patients was that the patients were reported to have high incidence of osteopenia and small patellar, according to Shoji et al's study,28 which increased the risk and difficulty for patellar resurfacing. The author concluded when RA patients had little or no deformity of patellar, it was not advisable for patellar resurfacing.28 According to our study, we more preferred that RA can be an indication of patellar resurfacing during TKA with lower postoperative complication, when the patellar bone was competent for resurfacing procedure. The knee surgeon should refer the patellar thickness, bone quality, patellar deformity after intraoperative inspection as the selection criteria of patellar resurfacing. Selective patellar resurfacing can be a reasonable strategy during TKA for RA patients.

The main limitations of the present study were that the data were collected retrospectively and the relatively higher rate of lost to follow-up. Our results were similar to the other long-term studies which had high patient attrition by 10 years.5,17 Nevertheless, in our study, the lost to follow-up had an average ROM of 95.9° at their latest follow-up which was comparable to patients completing follow-up. Furthermore, referred to the Joshi et al's study which reported a lower rate of failure for revision surgery and higher satisfactory results even in “lost to follow-up” compared with patients completing follow-up.30 Furthermore, this study represented a mixture sample of TKA with various prostheses, and the patella-friendly design and non-patella-friendly designs were not easily separated in this study. We conclude further long-term follow-up of modern prostheses in randomized studies is needed in future. However, as for the result in this study, we thought it reflected a common set-up in which many patients were treated, thus providing a typical representative of early TKAs in China. Furthermore, the power of this study was the limited long-term follow-up study in the mainland of China. We concluded, at the least, our study could provide the information about the long term follow-up outcome of patellar resurfacing and nonresurfacing in Chinese.

According to our study, we concluded that there was no difference between patellar resurfacing and nonresurfacing as for the long term clinical outcome and survivorship in Chinese. The patellar nonresurfacing can be advisable during primary TKA especially in Chinese OA patients with good clinical outcome and long term survivorship. Selective patellar resurfacing was more reasonable during TKA in RA patients with lower patellar related complication.

Acknowledgments: The authors are grateful to Dr. Bian Yanyan and Zhao Lijuan for the data collection in the study. The authors also are grateful to Margaret D and Leyna D from American Journal Experts for their editing service of the manuscript.

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Keywords:

total knee arthroplasty; patellar resurfacing; Chinese

© 2014 Chinese Medical Association