Patellar resurfacing in total knee arthroplasty: a prospective, randomized trial

BACKGROUND: The management of the patella in total knee arthroplasty is still problematic. We aimed to identify differences in the clinical outcome of total knee arthroplasty according to whether or not patellar resurfacing had been performed in a prospective, randomized study of 220 osteoarthritic knees. METHODS: Two hundred and twenty total knee arthroplasties in 201 patients were randomly assigned to be performed with either resurfacing or retention of the patella, and the results were followed for a mean of forty-eight months (range, thirty-six to seventy-nine months) in a double-blind (both patient and clinical evaluator blinded), prospective study. Evaluation was performed annually by an independent observer and consisted of assessment with the Knee Society clinical rating system, specific evaluation of anterior knee pain, a stair-climbing test, and radiographic examination. RESULTS: Fifteen (12%) of the 128 knees without patellar resurfacing and nine (10%) of the ninety-two knees with patellar resurfacing underwent a revision or another type of reoperation related to the patellofemoral articulation. This difference was not significant (chi square with one degree of freedom = 0.206, p = 0.650). At the time of the latest follow-up, there was a significantly higher incidence of anterior pain (chi square with one degree of freedom = 5.757, p = 0.016) in the knees that had not had patellar resurfacing. CONCLUSIONS: Patients who underwent patellar resurfacing had superior clinical results in terms of anterior knee pain and stair descent. However, anterior knee pain still occurred in patients with patellar resurfacing, and nine (10%) of the ninety-two patients in that group underwent a revision or another type of reoperation involving the patellofemoral joint. Weight but not body mass index was associated with the development of anterior knee pain in the patients without patellar resurfacing, a finding that suggests that patellofemoral dysfunction may be a function of joint loading rather than obesity.     

Patellar resurfacing in total knee arthroplasty

Routine patella resurfacing in total knee arthroplasty has been debated for decades. The early total knee designs and surgical techniques lead to a high complication rate following patellar resurfacing. This lead to many surgeons abandoning this practice and either leaving the patella unresurfaced routinely or selectively resurfacing. Modern day randomized control trials and meta-analyses of these trials reveal a higher incidience of anterior knee pain and a resultant higher reoperation rate in nonresurfaced patellae. We argue that with modern day designs and surgical techniques, there is a low complication rate to resurfacing and little downside to resurfacing.     

Patellar resurfacing in total knee arthroplasty

Whether or not to resurface the patella when performing a primary total knee arthroplasty remains an open question. A number of recent studies have added new information relevant to this controversy. Anatomic studies show that there is normally substantial variability in the anatomy of the trochlear groove. Implanting a femoral component therefore results in a change in the surface topography of the knee in a high percentage of cases. Even though a number of intraoperative techniques have been described in an attempt to accurately reproduce femoral and tibial component rotation, studies of the application of these techniques reveal that component malpositioning or malrotation of a measurable degree occurs in 10% to 30% of cases, depending on the surgical technique and landmarks used. There has been substantial change in the design of both femoral and patellar components in recent years. Even with current designs, biomechanical studies indicate that some degree of change in kinematics and contact stresses occurs following total knee arthroplasty. However, the results of clinical studies have been extremely variable, with most showing either no difference or very little difference between resurfaced and nonresurfaced patellae in osteoarthritic knees. The decision to resurface the patella or not must be individualized on the basis of the surgeon's training and experience and an intraoperative assessment of the patellofemoral articulation.     

Patellar resurfacing in total knee arthroplasty

Technical errors in patellar resurfacing at the time of total knee arthroplasty (TKA) are responsible for many of the complications that affect the patellofemoral joint. Instability, patellar fracture, and wear of metal-backed patellar implants are significantly affected by errors of patellar resurfacing. A review of 50 TKAs using a condylar prosthesis and a standardized technique for patellar resurfacing was performed to evaluate the accuracy of the technique. The patients were evaluated at a mean of 2.5 years (range, two to five years) after surgery. The Hospital for Special Surgery Knee Score improved from a preoperative mean of 56 to 92 at the last evaluation. The Hospital for Special Surgery Knee Scores were excellent in 92% and good in 8%. The Knee Society Knee Score improved from a preoperative mean of 28 for pain and 49 for function to a last evaluation mean of 96 for pain and 85 for function. None of the patients had symptoms referable to the patellofemoral joint. There were no patellar fractures, dislocations, or instances of implant loosening of the patella. Roentgenograms revealed nine asymmetrically resurfaced patellae and five tilted patellae. There were no patellar subluxations. Patellar thickness was maintained at the preoperative level of 21 mm. Joint-line height was elevated 1 mm. The patellar height was decreased 2 mm from the preoperative height. Using a standard technique, satisfactory clinical results can be achieved, but minor errors in resurfacing and alignment will still occur.     

Patellar resurfacing in total knee arthroplasty. A meta-analysis

BACKGROUND: Patellar resurfacing during total knee arthroplasty remains controversial. We aimed to evaluate the effectiveness of this technique through an evaluation of the current literature. METHODS: We performed a meta-analysis of randomized controlled trials comparing total knee arthroplasties performed with and without patellar resurfacing. Outcomes of interest included the number of reoperations, the prevalence of postoperative anterior knee pain, and the improvement in various knee scores. RESULTS: Ten trials assessing 1223 knees were eligible. The absolute risk of reoperation was reduced by 4.6% (95% confidence interval, 1.9% to 7.3%) in the patellar resurfacing arm (between-study heterogeneity, p < 0.01; I(2) = 60%), implying that one would have to resurface twenty-two patellae (95% confidence interval, fourteen to fifty-two patellae) in order to prevent one reoperation. Patellar resurfacing reduced the absolute risk of postoperative anterior knee pain by 13.8% (95% confidence interval, 6.4% to 21.2%), implying that one would have to resurface seven patellae (95% confidence interval, five to sixteen patellae) in order to prevent one case of postoperative anterior knee pain. Only four trials provided adequate data for a quantitative synthesis of the changes in the various knee scores; on the basis of those four trials, there was no difference in the mean improvement in the knee scores (standardized mean difference, 0.03; 95% confidence interval, -0.50 to 0.56). CONCLUSIONS: The available evidence indicates that patellar resurfacing reduces the risks of reoperation and anterior knee pain after total knee arthroplasty. The observed effects are clinically important despite their modest magnitude. Additional, carefully designed randomized trials are required to strengthen this claim.     

Patellar resurfacing in total knee arthroplasty. A prospective, randomized, double-blind study with five to seven years of follow-up

BACKGROUND: Whether to resurface the patella during a primary total knee arthroplasty performed for the treatment of degenerative osteoarthritis remains a controversial issue. Parameters that have been suggested as being useful in guiding this decision include patient height and weight, the presence of anterior knee pain preoperatively, and the grade of chondromalacia encountered intraoperatively. The purpose of this study was to determine whether these parameters were predictive of the clinical result following total knee arthroplasty with or without patellar resurfacing. METHODS: Eighty-six patients (118 knees) undergoing primary total knee arthroplasty for the treatment of osteoarthritis were enrolled in a prospective, randomized, double-blind study. All patients received the same posterior-cruciate-sparing total knee prosthetic components. Patients were randomized to treatment with or without resurfacing of the patella. Evaluations consisted of the determination of a Knee Society clinical score, the completion of a patient satisfaction questionnaire, specific questions relating to patellofemoral symptoms, and radiographs. Sixty-seven patients (ninety-three knees) were followed for a minimum of five years (range, sixty to eighty-four months; average, 70.5 months). RESULTS: With the numbers available, there was no significant difference between the groups treated with and without resurfacing with regard to the overall Knee Society score or the pain and function subscores. Obesity, the degree of patellar chondromalacia, and the presence of preoperative anterior knee pain did not predict postoperative clinical scores or the presence of postoperative anterior knee pain. CONCLUSIONS: The occurrence of anterior knee pain could not be predicted with any clinical or radiographic parameter studied. On the basis of these results, it seems likely that postoperative anterior knee pain is related either to the component design or to the details of the surgical technique, such as component rotation, rather than to whether or not the patella is resurfaced.     

Patellar resurfacing complications in total knee arthroplasty

Purpose

The ideal management of the patella during total knee arthroplasty (TKA) is still controversial. Patellar retention is generally associated with an increased rate of anterior knee pain; however, patient satisfaction is similar in cases of replacement or retention. When the patella is replaced, potential severe complications can occur. Aim of this study was to retrospectively review results of a continuous series of patients having been treated with TKA and patella resurfacing.

Methods

The charts of 1,600 consecutive total knee prostheses were analysed to evaluate the rate of patellar resurfacing. All implants were posterior stabilized; 310 patients having received a patellar replacement were reviewed at follow-up (FU) examination. Complete physical examination as well as administration of the Hospital for Special Surgery (HSS) score was performed. X-rays analysis included weightbearing anteroposterior (AP) and lateral views of the injured knee and bilateral skyline views at 30° flexion.

Results

Two hundred and eighty patients were available for clinical and imaging investigation at an average FU of 96 (58–144) months. Mean age at the time of surgery was 70 (62–80) years. Mean HSS score was 85.9 ± 7.6. The overall rate of patellofemoral complications was 7 % (19 cases); 13 patients claimed anterior knee pain, five had symptomatic patellar maltracking and one had patellar component loosening.

Conclusion

Our data are in accordance with those available in the literature. Recent meta-analyses demonstrated lower risk of re-operation after patellar resurfacing. However, when complications of the resurfaced patella occur, they can be potentially catastrophic events.     

Patellar resurfacing versus no resurfacing in Scorpio total knee arthroplasty

This retrospective study compared the results of patellar resurfacing versus no resurfacing in 121 patients (142 knees) who underwent Scorpio total knee arthroplasty (TKA) between January 2002 and September 2004. Mean follow-up was 33 months in the nonresurfaced group and 18 months in the resurfaced group. The 2 groups were similar in age and gender. The incidence of anterior knee pain was 25% in the nonresurfaced group compared to 7% in the resurfaced group (P = 0.05), and the rate of revision was 10% in the nonresurfaced group compared to zero in the resurfaced group (P = 0.013). Mean Euroquol score was 91 in the nonresurfaced group compared to 95 in the resurfaced group (P = 0.26). Euroquol score, Knee Society score, knee instability, return to preoperative functional level, ability to kneel, use of a walking aid, and presence of limp were not significantly different between the 2 groups. The results of this study suggest a more consistent outcome can be achieved with patellar resurfacing in TKA with the Scorpio prosthesis.     

全膝关节置换术中髌骨面修整与髌骨置换的比较研究

目的比较全膝关节置换术髌骨面修整和髌骨置换的临床结果。方法2002年1月至12月对60例（60膝）行初次全膝关节置换术的骨性关节炎患者进行前瞻性、随机化研究。所有患者接受相同的后交叉韧带替代型全膝关节假体（PFC）,患者随机行髌骨面修整（髌骨面修整组）或髌骨置换（髌骨置换组）。58例患者平均随访54个月（40～60个月）,对其进行临床评价,包括膝关节协会评分（KSS）、膝关节活动度（ROM）、患者满意度和X线检查。结果两组患者KSS总评分（P=0．12）、KSS疼痛评分（P=0．90）、患者满意度（P=0．22）无明显差异;两组术后膝前痛的发生率均为10％亦无明显差异。两组ROM（P=0．028）和KSS功能评分（P=0．0098）差异有统计学意义。结论全膝关节置换术不论是髌骨面修整还是髌骨置换均能明显减轻疼痛和改善功能。术后膝前痛可能与假体设计和手术技术有关,并非与是否置换髌骨有关。     

Patellar resurfacing in total condylar knee arthroplasty. Technique and results

One hundred thirty-two total condylar knee arthroplasties with a 3-8-year follow-up period were studied prospectively with particular reference to the patellofemoral joint. All patients had significant patellofemoral disease and underwent primary patellar resurfacing. After operation 96% of patients had little or no pain and 98% had functional improvement. There were seven (5%) complications related to the patellofemoral joint. The importance of careful attention to preparation of the patella, the technique of prosthetic implantation and correct patellar tracking were emphasized. Routine patellar resurfacing proved highly successful with minimal complications.     

Patellar clunk syndrome in total knee arthroplasty without patellar resurfacing

In a series of 647 total knee arthroplasties, the patella was not resurfaced if bony geometry of the patella was good enough to maintain good congruency of the patella undersurface to the femoral component and the patella was tracking normally at the femoral component groove at the time of surgery. Three hundred seventy-two total knee arthroplasties were done with a femoral component that had the same geometry as the original total condylar prosthesis. None of these knees resulted in patellar catching, whether the patella was resurfaced or not. Two hundred seventy-five total knee arthroplasties were done with a more contemporary femoral component with wider intercondylar space and shorter posterior extension of the intercondylar notch. Eleven of these 275 knees demonstrated catching of the patella at 60° to 90° of flexion when the knee was tested from flexion to extension during the surgery. All of these 11 knees did not have patellar resurfacing during surgery at first. Of these 11 knees with patellar catching noted during surgery, at first, patellar catching was eliminated with patellar resurfacing in 4 and by shaving of the superior pole of the patella in 7. None of the knees with the patella resurfacing in this series showed patellar catching.     

Patellar resurfacing in total knee arthroplasty leads to better isokinetic performance

BackgroundFor decades there have been concerns about patellar resurfacing (PR) in total knee arthroplasty (TKA) and the individual preference of the surgeon is still the main determinant of whether or not resurfacing is applied. According to preference, surgeons can be categorized in 3 main groups of those who usually, selectively, or rarely resurface. The aim of this prospective, randomized, controlled study was to compare the isokinetic performance and clinical outcome of TKAs with PR and without PR.MethodsA total of 50 patients scheduled to undergo TKA for primary osteoarthritis of the knee were randomly assigned to either the PR or non-PR groups. There were no significant differences between the groups in respect of age, BMI, gender and preoperative Knee Society Score (KSS) and isokinetic performance. Patients were evaluated at postoperative 3, 6, and 12 months with KSS and at 6 months and 1 year with isokinetic measurements.ResultsThe PR group had a higher mean score, especially in the functional component of KSS, but the difference was not statistically significant. Knee extension peak torque was significantly higher in the PR group at 6 months (p = 0.029) and 1 year (p = 0.004) postoperatively. There were no significant differences between the groups in respect of knee flexion peak torque values following TKA.ConclusionsThe results of this study demonstrated that PR during TKA is associated with better isokinetic performance and higher knee scores. These results support routine/usually resurfacing of the patella. For surgeons who selectively resurface the patella, the advantage of better isokinetic performance may be taking into consideration in favor of resurfacing the patella where they are undecided.Level of evidenceLevel I, therapeutic study.     

髌骨置换与否对全膝关节置换术疗效影响的Meta分析

[目的]系统评价髌骨置换与不置换髌骨的全膝关节置换术的术后疗效.[方法]收集1966～2010发表的所有比较髌骨置换与不置换髌骨伞膝关节置换后疗效的随机对照试验,对其逐个进行质量评价,提取关于置换后再手术率、前膝痛发生率、患者满意率及各种评分系统测评的膝关节评分的改善,并作系统评价.[结果]11个随机对照试验共纳入1 473例膝,置换髌骨与未置换组的再次手术率差异有显著性意义(相对危险度=0.54,95%可信区间为0.35～0.84);未置换髌骨组再次接受手术的概率比较大.置换髌骨与未置换组的置换后前膝疼痛发生率差异有显著性意义(相对危险度=0.53,95%可信区间为0.39～0.71).置换髌骨与未置换组的术后患者满意率差异无显著性意义(相对危险度=1.14,95%可信区间为0.74～1.76).置换髌骨与未置换组的术后KSS评分差异无显著性意义(加权均数差=1.15,95%可信区间为-0.23～2.53).[结论]置换髌骨的全膝关节置换术中,远期随访再手术率、置换后前膝痛发生率低于未置换髌骨组,患者满意率及置换后膝关节KSS评分方面,两种髌骨处理方式无显著性差异.由于纳入文献质量差异较大,对此结论的解释应保持谨慎.     

Patellar contact forces with and without patellar resurfacing in total knee arthroplasty.

Patellar contact forces were measured in 7 fresh-frozen cadaver knees during continuous flexion-extension cycling for the normal knee and after total knee arthroplasty without and with patellar resurfacing using 2 prosthesis systems with different designs for the femoral and patellar components. Analysis of variance with specimen as a repeated measure was used to examine the effect of contact surface. When compared to normal knees, total knee arthroplasty without patellar resurfacing resulted in no change in patellar contact forces. The magnitude of the inferosuperior patellar shear force increased significantly after patellar replacement with an oval, biconcave patellar component and increased further after replacement with an oval, domed patellar component. There were no significant changes in the mediolateral and anteroposterior contact force components after patellar replacement.     

Patellar resurfacing in total knee arthroplasty, the current state of the controversy

Summary This article reviews the current controversy of resurfacing the patella in total knee arthroplasty. Up-to-date knowledge of experimental and biomechanical studies as well as the different types of implants and specifics of the patella preaparation are described in detail. The author furthermore discusses the relevant clinical studies dealing with patellar resurfacing and tries to guide the reader in evaluating the results. Finally is summarized why the indication for resurfacing the patella is so controversial and how a differentiated indication for resurfacing the patella could be specified.      

Patellar prosthesis positioning in total knee arthroplasty. A roentgenographic study

Patellar prosthesis positioning in 40 primary total knee replacements was evaluated with regard to (1) patellar tilt, (2) angle between the patellar component and patellar bony remnant, (3) lateral versus medial placement, (4) patellar height, and (5) size of the patellar component versus patellar length. Two different designs were evaluated. Twenty knees that were resurfaced with a patellar button prosthesis and implanted with conventional surgical technique constituted Group A. Twenty knees that were resurfaced with a new biconvex prosthesis and implanted with specially designed instrumentation constituted Group B. For Group A, the patellar tilt averaged 4.25 degrees preoperative and 8.35 degrees postoperative. For Group B the patellar tilt averaged 4.60 degrees preoperative and 1.83 degrees postoperative. In Group B, there was significant improvement in patellar position, with only two patients showing values exceeding the neutral range (p = 0.0409). The angle between the patellar component and the bony remnant in Group A averaged 5.975 degrees, and in Group B, 1.447 degrees. Two patients in Group A and 18 patients in Group B had values in the normal range for patellar tilt and the angle between the prosthesis and the bone. The prosthesis was inserted medial to the patellar center in six patients in Group A and one patient in Group B. A significant decrease in patellar height was noted for both groups, but values were still within the normal range. Both groups showed significant increase in the postoperative articular length, indicating that oversized prostheses were inserted and excess bone removed.