The Journal of Arthroplasty

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1 The Journal of Arthroplasty 28 (2013) Contents lists available at ScienceDirect The Journal of Arthroplasty journal homepage: Long-Term Follow-Up of Cemented Fixed-Bearing Total Knee Arthroplasty in a Chinese Population: A Survival Analysis of More Than 10 Years Bin Feng, MD, Xisheng Weng, MD, Jin Lin, MD, Jin Jin, MD, Wei Wang, MD, Guixing Qiu, MD Department of Orthopaedic Surgery, Peking Union Medical College Hospital, Peking Union Medical College, Beijing, China article info abstract Article history: Received 23 December 2012 Accepted 14 March 2013 Keywords: primary total knee arthroplasty fixed bearing platform long term follow up clinical outcome survivorship analysis The aims of this study were to evaluate the long term clinical outcomes and survival rate of total knee arthroplasty (TKA) in Chinese population and the risk factors for failure. Between 1985 to 2001, 297 patients underwent primary TKAs with cemented fixed bearing platform in our center. Survival rate was 92.7% at 10 years, with reoperation of the implant as the endpoint, and 90.4% at 15 years. Main reasons for failure were infection and aseptic loosening. Clinical evaluation of 96 knees with HSS knee score showed the mean scores increased from ± preoperatively to ± postoperatively. RA patients had lower longterm survivorship compared with OA patients. Younger patients had better HSS scores. Patella strategy and posterior-cruciate-ligament (PCL) strategy had no effect on implant survivorship and clinical outcome. In conclusion, this was one of first studies showing valid long-term outcomes of primary TKA in Chinese Elsevier Inc. All rights reserved. Total knee arthroplasty (TKA) is a highly effective procedure that provides reliable relief from pain, improves physical function, and provides a high level of patient satisfaction in patients with advanced knee arthropathy. Long-term follow-up studies have been reported for Western Caucasian in literatures [1 3]. Although the procedure has been introduced in China for more than twenty years, no longterm follow-up has been reported for Chinese people up-to-date. It was reported the Chinese population knees were too small for some western prothesis [4] and anatomy of tibia was different from the western [5]. Nevertheless, most TKA prostheses used in China mainland were made for Western Caucasian subjects, and the limited protheses from domestic company were also manufactured according to western design. It was necessary to study the long term follow-up of TKA in the Chinese population. The purpose of our study was to evaluate the survivorship and clinical and radiographic results of primary cemented fixed-bearing TKA in the Chinese population during more than 10 years of follow-up. Materials and Methods This was a retrospective study. In total, 297 patients underwent primary cemented fixed bearing TKAs with metal-backed tibial components by three chief knee surgeons between 1985 and 2001 in Peking Union Medical College Hospital, China. Indications to surgery were: 47 patients with rheumatoid arthritis (RA), 243 The Conflict of Interest statement associated with this article can be found at dx.doi.org/ /j.arth Reprint requests: Xisheng Weng, MD, Department of Orthopaedic Surgery, Peking Union Medical College Hospital, Peking Union Medical College,, Beijing, China, patients with knee osteoarthritis (OA), 7 patients with miscellaneous. There were 246 female and 51 male patients. The sex distribution of arthritis and operation was a common finding in a Chinese ethnic group and was caused by the racial difference of disease demographics and sex distinction of bow leg incidence. Follow-up concluded in December The study was approved by the local medical ethical committee. In our series, fifty-six (accounting for 18.8%) patients were lost during the follow-up. Furthermore, sixtythree patients died or had comorbidity to influence normal ambulance (such as cerebrovascular disease) with less than 10 years follow-up and without signs or symptoms of implant failure. In total, 178 patients were successfully followed up for more than 10 years. The average age at surgery was ± 9.94 years (39 79 years) and the average body mass index (BMI) was 24.7 ± 3.8 kg/m 2 ( ). The selection of specific type of implants was based on the various considerations, including sex, preoperative deformity, anatomical geometry and supply flow of implant. At times, it was necessarily required to change to other implants when the import of prosthesis was discontinued or when the implant with expected size was not prepared. In this series, cemented protheses were used for all the cases, and hybrid TKAs with all-polyethylene tibial components were excluded from our study. The patients age, preoperative deformity and contracture, and intraoperative evaluation of the posterior cruciate ligament (PCL) were taken into consideration for determining either a cruciate-retaining (CR) or a posterior stabilizing (PS) design. 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 / $36.00/0 see front matter 2013 Elsevier Inc. All rights reserved.

2 1702 B. Feng et al. / The Journal of Arthroplasty 28 (2013) intramedullary and extramedullary guide systems were used for distal femoral and proximal tibial bone resection, respectively. In our series, the varus and valgus deformity were corrected intraarticularly. After the bone resection, the contracted amount of soft tissue was carefully evaluated with palpation, and the selective release was performed as required. The patella thickness, bone quality were considered for determining either patella resurfacing or nonresurfacing. The average thickness of patella was ± 2.09mm (26 17mm) in our series, with mean thickness of 20.6 mm for female and 23 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 around 15mm was required [6]. For patella non-resurfacing group, articular surface smoothing, osteophyte removal and patella rim denervation were performed. the outpatient clinic (mainly because of transportation problems), these patients were visited by the examiner of local hospital and were interviewed by telephonic questionnaire. This was in agreement with the literature that supported the quality of data obtained using the telephonic method [8]. For the patients who had died at the time of the study, date of death and the status of knees as well as probable knee scores were noted from the family. X-rays were taken immediately after operation. X-rays of weight bearing in the anteroposterior (AP), laterolateral (LL) and skyline view were evaluated at the latest follow-up [Fig. 1]. Radiolucent lines were recorded (defining radiolucent lines as the distance of the bone prosthesis interface N 2 mm) and a more than 4 mm radiolucent line was significant and should be closely followed up for progression[9]. Skyline views of patella were evaluated for patella subluxation. Clinical and radiological evaluation The Hospital for Special Surgery (HSS) knee score questionnaire was used for clinical evaluation [7]. The symptoms of anterior knee pain, instability when climbing stairs and reason for revision were recorded at the latest follow-up. Patients underwent clinical evaluation at the outpatient clinic. Whenever it was not possible to come to Statistical analysis SPSS (SPSS Inc.) was the program used for statistical analysis. Clinical data were analyzed using means and standard deviation (SD). The level of statistical significance was set at P b Paired t-tests were performed to determine the difference of HSS knee score, range of motion (ROM), and flexion contracture. The influence of indication Fig. 1. F/52, rheumatoid arthritis, she underwent one stage bilateral TKA with PFC knees. (A1-A4) anterior posterior (AP), lateral and skyline plain X view of bilateral knee before operation. (B1-B3) AP and lateral view after index of operation. (C1-C4) AP, lateral, skyline view of bilateral knees at 10 years after operation. (C5) Weight bearing view of lower limbs at 10 years after operation.

3 B. Feng et al. / The Journal of Arthroplasty 28 (2013) being primary OA or RA, age at the time of operation, PCL retention or substitution, patella resurfacing or non-resurfacing and protheses from western manufactured products or domestic ones were evaluated in analyses of variance (ANOVA) with covariance model. With such model, the preoperative knee score was considered to be covariant to avoid its confounding effect. Levene statistic was used to test for the homogeneity of variances with all the variables. Therefore, all continuous variables were confirmed to have the assumption of equal variances in ANOVA test (P N 0.05). The Kaplan Meier method was used for survivorship analysis. Failure was defined as reoperation of the implant for any reason: including infection, aseptic loosening, instability, patella complication, etc. 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. Results In this cohort, fifty-six patients were lost during less than 10 years follow-up, with average age of 64.7 ± 5.7 years, with 11 males and 45 females, with diagnoses of OA for 47 patients and RA for 9 patients. These patients had an average ROM of 96.3 ± 9.3 (range, 80 to 120 ) at an average 4.11 years follow-up (range, 2 to 8 years). In total, 241 patients were successfully followed. Within them, forty-nine patients died and 14 patients had paraplegia or paralysis to impair ambulation because of cerebrovascular disease within 10 years after index operation. All the 63 patients had TKAs in situ at latest followup. Eighteen patients (19 knees) had reoperation because of the implant failure during follow up. In total, 160 patients (193 knees) were followed for more than 10 years. And 75 patients (96 knees) fulfilled with the evaluation of clinical outcome with HSS knee score system. For the 193 knees and the reoperated 19 knees, implants from western manufactured products were used for 194 knees, including Ortholoc (Dow Corning Wright Medical, Arlington, TN) for 92 knees, PFC (DePuy Orthopaedics, Inc, Warsaw, IN, USA) for 39 knees, Kinemax (Howmedica, Rutherford, NJ, USA) for 19 knees, others for 33 knees, unknown for 11 knees. Implants from domestic manufactured products were used for 18 knees. The CR prostheses were used in 173 knees and the PS prosthesis in 39 knees. As for patella strategy, patella resurfacings with polyethylene dome patella were used in 150 knees in our group and patella non-resurfacing was used in 62 knees. The indications for TKA were 38 knees for rheumatoid arthritis and 174 knees for primary or secondary osteoarthritis. Clinical Results The average follow-up period was 12.4 years ± 2.27 years (10 to 25 years) in our group. Clinical outcomes were successfully evaluated for 96 knees with HSS knee score for an average 11.4 years (10 18 years) follow up. The total HSS knee score increased from (range, 28 80) preoperatively to (range, ) postoperatively. The ROM improved from 84.8 (range, 10 to 120 ) to 99.7 (range, 30 to 120 ). The flexion contracture was corrected from 8.4 (range, 0 to 40 ) preoperatively to 0.5 (range, 0 to 10 ) postoperatively. All the items had statistically significant differences (P b 0.01). In our group, 18 patients (19 knees) underwent reoperation during follow-up. Ten knees (3.0% of all the operated knees) had reoperations for septic loosening. Within them, seven had infection less than 3 years after index operation, three had late infection more than six years after index operation. All were treated by two-stage revision surgery. Six (1.8%) had reoperations for aseptic loosening, all of which happened at 5 years later after index operation and were treated by one-stage revision. Two patients had reoperation because of postoperative stiffness in one year. One patient had patella dislocation 11 years after index operation and underwent reoperation. In our series three patients experienced instability during stair climbing at 10, 11, 13 years after operation and one patient had patella crepitus. All the 4 patients could fulfill with daily life without obvious difficulty and did not agree with reoperation. In our cases, no revision was done because of extensive wear of the polyethylene. ANOVA analysis showed there were no statistically different HSS improvement between CR and PS group, between protheses from western manufactured products and from domestic manufactured ones, between age N65 years at operation and age less than 65 years (Table 1). Nevertheless, those with age less than 65 years at operation had obvious higher HSS knee scores compared with the opposite ones. There was also no different HSS score improvement between the patella resurfacing and patella non-resurfacing groups, as well as anterior knee pain (result not shown). Indication of RA had better HSS score improvement when compared with preoperative knee score than OA patients (P = 0.015) (Table 1). The group of protheses from western manufactured products had better but not statistically significant postoperative ROM (average ) than protheses from domestic manufactured ones (average 93.5 )(P = 0.173).As for improvement of flexion contracture, prothesis from western products was statistically significant than the latter, with 0.43 to 1.83 (P =0.039). Radiological Results Radiological evaluation was possible for 52 knees in our group. Radiolucent lines were found in 10 knees (19.2%), and eight of them presented only at tibial side; two presented at both tibial and femoral sides. None of the cases was observed with progression of the radiolucent lines during follow-up. 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 rate of lateral subluxation at follow-up than resurfacing group, but the difference of the two groups was not statistically significant (P = 0.051) (Table 2), as well as anterior knee pain between the two groups. Table 1 Covariance ANOVA Analysis of Factors Affecting Long Term Follow-Up HSS Scores After TKA. Item Impacting Factor Number of Knees Preoperative HSS Postoperative HSS P value PCL strategy PS ± ± 10.5 P = CR ± ± 11.2 patella resurfacing ± ± 10.9 P = non-resurfacing ± ± 11.4 Diagnosis RA ± ± 5.2 P = OA ± ± 11.4 Implant Local company ± ± 11.3 P = 0.69 From abroad ± ± 10.1 Age at operation age ± ± 10.8 P = 0.55 age b ± ± 10.9 CR: cruciate retaining, PS: posterior substituting, RA: rheumatoid arthritis, OA: osteoarthritis.

4 1704 B. Feng et al. / The Journal of Arthroplasty 28 (2013) Table 2 Patella Tracking Between Patella Resurfacing Group and Non-Resurfacing Group n = 52). Item Survivorship analysis In our cohort, 241 patients 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 92.7% ± 1.7% and 90.4% ± 2.1% for 15 years of follow-up. Twenty knees survived for more than 15 years with implants in situ in our group. Four knees survived for more than twenty years. Indication for OA had statistically higher survival rate for more than 10 years than indication for RA (Fig. 2B) (P = 0.032). Ten years and fifteen years survival rate of OA patients were 93.6% ± 1.8% and 92.7% ± 2% respectively in our series, and 88% ± 5%, 78.3% ± 7.9% for RA patients respectively. No statistically significant differences were found for survival more than 10 years between the CR and PS groups (Fig. 2A) (P = 0.776), between the patella resurfacing and non-resurfacing groups (Fig. 2C) (P = 0.176), between OA patients 65 years old and OA patients b65 years old (Fig. 2D)(P = 0.676), and between protheses from western manufactured products and from domestic ones (P = 0.304). Discussion Number of Knees Normal Patella Tracking Subluxation Ratio of Subluxation Patellar non-resurfacing % Patellar resurfacing % P = Efforts had been made continuously to elucidate the long term follow up of TKA in literature (Table 3) [1 3,10 13,15], however, the literature provided heterogenous data. The reason may be that durability of TKA is affected by many factors such as patient selection, implant design, and surgical technique [14] and that the definition of failure of TKA has not been consistent in literature. For instance, Dixon et al. [2] presented a 93% survivorship of the PFC system (DePuy) at 15 years with re-operation for any reason as the endpoint in a single surgeon study. While, Ma et al. [15] reported a 20 years survival of 91.9% of total Condylar (Howmedica, Rutherford, NJ) TKA using revision for mechanical failure as an end point in a multisurgeon study. The limitation of this study was that it represented a nonselected sample of TKA with various cemented fixed bearing prostheses. However, it reflected a common set-up in which many patients were treated, thus providing a typical representative of early TKAs in China. Taking failure with reoperation of the implant as the endpoint, the 10-year survival rate of 92.7% was comparable with results in literature [1 3,10 13]. In our study, 18.8% patients were lost in follow-up. The reason was due to the incomplete follow-up system and rapid human transportation in developing China. Nevertheless, Joshi et al. [16] 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. In our study, the lost to follow-up had an average ROM of 96.3 at their latest follow-up which was comparable to patients completing follow-up. We concluded, at the least, our result could provide representative data in terms of long term survivorship of cemented fixed-bearing TKA in population of China mainland, even with the patients who were lost to follow-up. Furthermore, the power of this study was the first long-term followup of TKA in Chinese population in the mainland. In literature, the long term outcome of TKA presented with significant relief of knee pain, but as for the functional score, there was a drop because of the aging despite of no loosening or other significant complications at long term follow-up [10]. Ritter et al.[17] reported the functional component of the KSS score declined significantly at an Fig. 2. Kaplan-Meier survival analysis of TKA with reoperation for the implant as the endpoint. Time reported in years. (A) Survival analysis between PS and CR prosthesis (P = 0.776). (B) Survival analysis between RA and OA patients (P = 0.032). (C) Survival analysis between patellar resurfacing group and non-resurfacing group (P = 0.176). (D) Survival analysis between OA patients b 65years old and 65 years old (P = 0.676).

5 B. Feng et al. / The Journal of Arthroplasty 28 (2013) Table 3 Summary of Survival Studies of TKA in Literature about the Survival Rate, Clinical Outcome, ROM and Comparison between Our Study. Patients at Index Operation Patients at Follow Up Follow Up (Years) Survival Rate Knee Score Evaluation System Pre-op Post-op ROM (Pre-op) ROM (Post-OP) Our study % HSS Rand [3] % Chalidis [1] % KSS KFS Dixon [2] % KSS KFS Huizinga [10] % Bistolfi [11] % HSS Bae [12] % HSS Meding [13] KSS KFS Ma [15] % HSS : no comment; Pre-OP: preoperative; Post-OP: postoperative; KSS: knee society score; KFS: Knee Function Score; HSS: Hospital For Special Surgery Knee Score; ROM: range of motion. average 0.88 points per year between the third and 12th years mainly because of the deterioration in gait and the decreased walking distance. According to our result, clinical results of TKA were good, with a significant increase in HSS scores and patients' range of motion and walking ability improving significantly, thus confirming the validity of the TKA procedure in Chinese people. The improvement of knee score in our study was comparable with results in literature, but the postoperative ROMs of the operated knees were less than that in literature (Table 3). We concluded the reason may be Chinese people were less required for the high flexion knee and were relatively limited in daily living activity after TKA operation compared with western Caucasian. In literature, the infection was considered to be the initial cause of failure after primary TKA and always happened at an early stage, while polyethylene wear was the primary cause of failure after the fifth postoperative year [12,18]. Bae et al. [12] reported infection accounted for 0.4% of 3014 TKAs, polyethylene wear accounted for 3.8% and aseptic loosening accounted for 0.8%, respectively. Pijls [19] reported a 1 mm less thickness of insert was accompanied by a 3-fold rate for revision of insert. Huizinga [10] reported 17 of 211 TKAs were revised during more than 15 years of follow up and 5 TKAs were revised because of infection; eleven were reoperated because of aseptic loosening. Other studies meanwhile reported infection as the most common reasons for revision TKAs. Hossain et al. [20] reported the infection was the most common etiology leading to revision, which accounted for 30% of 349 revision cases. Our date was in agreement with the latter rather than the former studies. We noticed that main reason for failure in this series was infection and the aseptic loosening was not the most frequent indication for reoperation but was the main reason of failure after 5 years. Furthermore, there were no obvious polyethylene wear and instability in our series. Although three patients experienced instability but they could fulfill with daily lives and did not accept revision. Our results were different from those in literature[10,12,18]. We noticed the BMI and postoperative ROM in our series was lower than western civilizations (see Table 3) [1,9,21]. Although Odland et al. [21] and Bourne et al. [9] reported the BMI was not associated with revision rate for wear and postoperative outcome. According to Hossain's study of a large cohort of revision TKAs, younger patients and increasing BMI played a role in aseptic loosening as the cause for revision [20]. We predicted the lower BMI of our group may be the reason of the less revision for polyethylene wear in Chinese population. Furthermore, the less postoperative ROM and the less demand of daily life can also be the reasons of the less polyethylene wear in our series. Because of the limited cases of wear and instability in our study, further analysis was not feasible. Future studies may help us to find a more persuading conclusion. The other purpose of this study was to evaluate the factors influencing clinical outcome and survival rate, with variables of age, diagnosis and producing area of prostheses. It was reported in literature that female patients, older than 60 years, patients with rheumatoid arthritis, and metal-backed tibial condylar prosthesis had higher survival rates [3,12], while aligned or malaligned postoperative mechanical axis had no effect on survival rates [12,22]. On the contrary, Attar et al. [23] stated that sex, age, and diagnosis had no significant effects on the survival rates. In our series, we found the indication of RA had a lower survival rate than OA patients, for which the finding was inconsistent with results in literature [3]. This could be due to difference of activity of patients, osteoporosis around the knee joint, disorder of other joints, and age at surgery for RA patients [24]. We also found the RA patients had better improvement of clinical outcome according to preoperative knee score and predicted the better satisfaction for these patients. This might be the relatively lower preoperative knee score for RA patients. We concluded further studies were needed to illustrate these findings. Bae et al. [12] reported patients older than 60 years had higher survival rate at 15 years follow-up with 90% compared to 80%. Odland et al. [21] concluded the reasons for high failure rate (16% at 10 year follow up) in the young OA patients were wear and lysis because of more daily living activity. Nevertheless, because of mild active of elder patients, the elders had a higher survival rate after TKA with the compromise of mild postoperative clinical outcome, as reported by Parsch et al. [14] that the knee functional score at 10 years follow-up was 55.6 for patients b65 years while it was 34 points for patients 65 years. Parsch [14] also reported the patients affected with the contralateral side or with other comorbidities had lower Knee Function score. O'Connor et al. [25] reported the women achieved less level of physical function and less favorable final pain score than men at 10 years follow up after primary TKA. In our series, we did not find such significance for patients older than 65 both for survival rate and clinical outcome. This was likely due to limited daily activity, even for relatively young Chinese patients after the index operation of TKA. One limitation of our study was that the adopted HSS questionnaire could not provide more detailed assessment of the postoperative knee function than the KSS questionnaire did. We found there were no different survival rate and HSS knee score improvement between prostheses from western manufactured products and domestic ones, but the former one had better ROM and flexion contracture improvement than the latter. Because of the limited case numbers of protheses from domestic products, it was hard to draw a solid conclusion and we need mores cases in the future to elucidate the difference. Up to now, we thought the protheses from western manufactured products may achieve better ROM function than domestic ones. In literature, the patella non-resurfacing would be followed with higher rate of reoperation for patellofemoral related complication [11,12]. Nevertheless, Burnett [26] reported equivalent clinical results

6 1706 B. Feng et al. / The Journal of Arthroplasty 28 (2013) for resurfaced and non-resurfaced patella in TKA as for Knee Society Clinical Rating Score, satisfaction, revision rates, or anterior knee pain in a 10-year randomized clinical trial. He et al. [27] concluded, according to meta-analysis, although reoperation for patellofemoral problems was significantly more likely in the nonresurfacing group, there was no difference in terms of anterior knee pain rate, knee society score and knee function score. In this study, the selective patella resurfacings were adopted with good results. Although patella non-resurfaced group had higher incidence of subluxation from radiological results, there was no difference of anterior knee pain between patients with patella resurfacing and those without. Furthermore, no statistically meaningful differences were observed in terms of implant failure and clinical results between two groups. Because the Chinese patients undergoing TKA had thinner patella than western patients [28], we concluded the patella non-resurfacing could be a preferable choice for Chinese people. So far, there was no solid basis for the decision to either retain or sacrifice the PCL during primary TKA [3,29 31]. Recent meta-analyses were undertaken to pool the results and to compare the outcome of PS and CR group [30,32], and results indicated no differences for survival rate, knee scores or incidence of complications with medium-term follow-up, while the postoperative ROM and patients satisfaction in PS design were superior to that of the CR design [31,32]. In our series, there were also no statistically significant differences in terms of implant failure and clinical results between patients with CR and PS group. Our finding was comparable with results in literature. 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