The role of patellar resurfacing in TKA. Point

While controversy persists, scientific evidence favoring patellar resurfacing in primary TKA is abundant. The literature demonstrates a substantially higher incidence of anterior knee pain and reoperation rates if the patella is not resurfaced primarily. Prospective, randomized studies have reported reoperation rates to convert unresurfaced patellas to resurfaced patellas exceed those for complications after patellar resurfacing. When resurfacing the patella, strict surgical principles are paramount to avoid complications. These include duplicating the original patella thickness, maintaining the patellar blood supply, achieving central patellar tracking, and properly positioning the femoral, tibial, and patellar components. Optimum prosthetic design features for patella resurfacing include an anatomic, asymmetric trochlear groove that is broad, extended, (distally and posteriorly) and deeper compared with first-generation designs.     

The Outcome of Total Knee Arthroplasty With and Without Patellar Resurfacing up to 17 Years: A Report From the Australian Orthopaedic Association National Joint Replacement Registry

BackgroundPatellar resurfacing in total knee arthroplasty (TKA) remains a controversial issue after more than 4 decades of TKA. Despite a growing body of evidence from registry data, resurfacing is still based largely on a surgeon’s preference and training. The purpose of this study is to provide long-term outcomes for patellar resurfaced compared to when the patella is not resurfaced.MethodsData from the Australian Orthopaedic Association National Joint Replacement Registry (1999-2017) were used for this study. The analysis included 570,735 primary TKAs undertaken for osteoarthritis. Hazard ratios (HRs) and 17-year cumulative percent revision rates were used to compare revision rates between 4 subgroups: minimally stabilized (MS) patellar resurfacing, posterior stabilized (PS) patellar resurfacing, MS unresurfaced, and PS unresurfaced patella. Additional analyses of the patellar implant type and a comparison of inlay and onlay patellar resurfacing were also performed.ResultsFor all primary TKA, procedures where the patella was not resurfaced have a higher rate of revision compared to procedures where the patella was resurfaced (HR, 1.31; confidence interval, 1.28-1.35; P < .001). Unresurfaced PS knees have the highest cumulative percent revision at 17 years (11.1%), followed by MS unresurfaced (8.8%), PS resurfaced (7.9%), and MS resurfaced (7.1%). Inlay patellar resurfacing has a higher rate of revision compared to onlay patellar resurfacing (HR, 1.27; confidence interval, 1.17-1.37; P < .001).ConclusionResurfacing the patella reduces the rate of revision for both MS and PS knees. MS knees with patellar resurfacing have the lowest rate of revision. Onlay patella designs are associated with a lower revision rate compared to inlay patella designs.     

The role of patellar resurfacing in total knee arthroplasty

The ideal treatment of the patella in primary total knee arthroplasty (TKA) for osteoarthritis (OA) remains unclear. Although data exist in the literature to support either resurfacing or not resurfacing the patella, evidence continues to emerge that unresurfaced patellas deteriorate with time. Recent prospective, randomized studies also favor patellar resurfacing over retaining the native patella, reporting reoperation rates to convert unresurfaced to resurfaced patellas exceeding those for complications after patellar resurfacing. In addition, the incidence of residual patellofemoral pain after secondary resurfacing is substantially higher than when patellofemoral resurfacing is done primarily. Patient selection criteria are critical in the decision-making process. Patellofemoral complications, the greatest argument against resurfacing, have been diminished with improved surgical techniques and implant design.     

The influence of patellar resurfacing on patellar kinetics and retropatellar contact characteristics

Background

Femoropatellar complications are one of the most common problems after total knee arthroplasty (TKA). However, the question of whether to resurface the patella remains controversial. Therefore, we evaluated the kinetics and the retropatellar contact characteristics of patella resurfacing with fixed and gliding surfaces.

Methods

Eight Thiel-embalmed cadaver knees were tested—first intact, then after TKA without patellar resurfacing, and finally with additional patellar resurfacing—while flexing the knee from 0° to 100°. We tested a fixed as well as a gliding patella surface. During the examination, quadriceps and hamstring forces were applied. The retropatellar pressure was determined with a special patella sensor, and the patellar kinetics were measured using an optical three-dimensional motion analysis system.

Results

Resurfacing the patella caused a significant increase in retropatellar pressure and a significant decrease in retropatellar contact area. Using a fixed patella, the retropatellar pressure nearly quadrupled in higher flexion compared to the native patella. Furthermore, the lateral movement of the patella increased after TKA, especially after additional patellar resurfacing.

Conclusions

Resurfacing the patella routinely is not advised. When osteoarthritis of the patella is found, the gliding patella should be preferred.     

Asymmetric patella resurfacing in total knee arthroplasty

Three hundred consecutive primary, cemented, condylar total knee arthroplasties (TKAs) were reviewed for the presence of asymmetric patella resurfacing using a postoperative Merchant or sunrise patellar radiograph. Twenty-one knees in 14 patients were found to have the patella asymmetrically resurfaced. Asymmetric resurfacing typically involved the inadvertent preferential resurfacing of the lateral facet with underresection of bone from the medial patellar facet. All patients underwent follow-up for a minimum of 5 years, with a mean follow-up of 7.5 years. Of the 21 knees, 3 revisions were required for patellar complications. One patellar component was loose on radiographs and there was marked patellofemoral pain in 6 knees. Overall, 11 of 21 knees (52%) underwent revision or were recommended for revision for patellar complications or had anterior knee pain that limited activities. Inadvertent asymmetric patella resurfacing using the kinematic condylar implant adversely affects the outcome after TKA.     

Treatment of the patella at reimplantation for septic total knee arthroplasty

The results of treatment of the patella at the time of aseptic revision of a total knee arthroplasty (TKA) have been better with resurfacing of the patella than other modes of treatment such as leaving a bony shell. Treatment of the patella at the time of reimplantation of a TKA has not been addressed in prior studies. The ability to resurface the patella will be determined by the amount of bone remaining, integrity of the patella, vascularity, the location of the joint line, and soft tissue coverage for wound closure. The current review addresses the technique of patellar resurfacing and patellar bone defect treatment at the time of reimplantation of a TKA.     

The patellofemoral component of total knee arthroplasty

Patellofemoral complications continue to form a large proportion (up to 50%) of total knee arthroplasty (TKA) complications. If adequate attention is paid intraoperatively to patellar tracking and component position, the incidence of subluxation, component loosening, and fracture should decrease. When treating patellar subluxation and dislocation, tibial tubercle transfer should be avoided because there is an unacceptably high incidence of complications. Care should be taken to treat the underlying cause of dislocation with either a soft tissue procedure or component revision. Fracture of the patella may be treated nonoperatively in 50% and 80% of patients. Cysts, if large, may be bone-grafted to avoid the potential complications of stress fracture and component loosening. Loosening of the patellar component is likely to be symptomatic and to require surgery in up to 75% of cases. A displaced patellar component may cause attritional wear of the quadriceps tendon or patellar ligament. All rheumatoid patellae should be resurfaced. The present trend in the osteoarthritic patella is toward resurfacing more often. With improved implant design and a predicted decrease in complications, resurfacing in the osteoarthritic patella may become routine. Osteoarthritic patellae that maintain good cartilage, normal anatomic shape, and congruent tracking need not be resurfaced.     

Outcomes of patellar resurfacing versus nonresurfacing in total knee arthroplasty: a 9-year experience based on a case series of scorpio PS knees

Patellar resurfacing during total knee arthroplasty (TKA) is an actively debated issue. This prospective study addresses fundamental questions regarding whether to resurface the patella. To do this, we compared clinical results of Scorpio PS knees with and without patellar resurfacing to determine whether there was any statistically significant difference in survivorship, function, pain, and radiographic analyses. Our study failed to demonstrate any statistical difference between the 2 groups (resurfaced versus nonresurfaced) according to knee pain, walking abilities, stair climbing, range of motion, and radiologic findings, as well as cross-correlations between patellar pain and age, gender, obesity, or etiology. Our radiologic findings did not reveal any failures of bony structures facing the metallic flange. Some knee designs can thus be seen as "patella friendly." Given the significant cost of patella resurfacing and the resulting well-known complications, we continue to avoid systematic resurfacing of the patella during Scorpio TKA.     

Effect of patella thickness on patella strain following total knee arthroplasty

Patellar complications following total knee arthroplasty (TKA) have begun to emerge as a major cause of failure. In an effort to understand some of the mechanical factors that might contribute to patellar component failure, a biomechanical study was performed. Quadriceps force and anterior patellar strain were measured during dynamic flexion in 10 fresh, paired human cadaver knee joints. First, tests were performed in the intact knee, followed by either posterior cruciate ligament (PCL) retention or sacrifice of TKA without patellar resurfacing. Tests were then performed following patellar resurfacing with an overly thick, optimum and thin, bony patella. Patellar strain increased in each specimen (with flexion angles of up to 80 degrees), was most pronounced as the bony patella became thinner, was closest to the intact knee when the patella was not resurfaced, and was unaffected by PCL retention or sacrifice. Patellar osteotomy, resulting in a bony patellar thickness of less than 15 mm, resulted in significantly increased strain. TKA systems should include instrumentation that allows precise restoration of overall patellar thickness while maintaining a bony patellar thickness of at least 15 mm.     

Anterior knee pain following primary total knee arthroplasty

Despite improvements in technique and technology for total knee arthroplasty (TKA), anterior knee pain impacts patient outcomes and satisfaction. Addressing the prosthetic and surgical technique related causes of pain after TKA, specifically as it relates to anterior knee pain, can aid surgeons in addressing these issues with their patients. Design features of the femoral and patellar components which have been reported as pain generators include: Improper femoral as well as patellar component sizing or designs that result in patellofemoral stuffing; a shortened trochlear groove distance from the flange to the intercondylar box; and then surgical technique related issues resulting in: Lateral patellar facet syndrome; overstuffed patella/flange combination; asymmetric patellar resurfacing, improper transverse plane component rotation resulting in patellar subluxation/tilt. Any design consideration that allows impingement of extensor mechanism anatomical elements has the possibility of impacting outcome by becoming a pain generator. As the number of TKA procedures continues to increase, it is increasingly critical to develop improved, evidence based prostheses that maximize function and patient satisfaction while minimizing pain and other complications.     

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.     

Use of a trabecular metal patella for marked patella bone loss during revision total knee arthroplasty

This study evaluates the short-term results following patellar resurfacing with a trabecular metal patella shell in the setting of marked patellar bone loss at the time of revision total knee arthroplasty (TKA). Twenty consecutive patients undergoing revision TKA with the use of a trabecular metal patella were evaluated at a mean 23-month follow-up. All patients had marked patellar bone loss at surgery precluding resurfacing with a standard cemented patellar button. Results were good or excellent in 17 of 20 patients. There were no displacements of any trabecular metal patella shells, and the fixation appeared excellent despite the poor quality of bone remaining. Complications included 3 patients with polar patella fractures postoperatively. Qualitatively, these results compare favorably with patellar resection arthroplasty in this setting.     

Finite Element Analysis of Resurfacing Depth and Obliquity on Patella Stress and Stability in TKA

Patella resurfacing in total knee arthroplasty (TKA) reduces postoperative complications and revisions; however, the optimal cutting depth and angle that minimize patellar strain and fracture remain unclear. We performed three-dimensional finite element analysis (FEA) of resurfacing cutting depth and obliquity to assess the stresses in each component of the knee joint, and fatigue testing to determine cyclic loading conditions over the expected life span of the implant. Maximum stress on the patella increased as cutting depth increased up to 8 mm; peak stresses on the idealized button further increased at 10-mm depth. Medial superior obliquities below 3° showed the lowest stress on the patella and button and the highest fatigue life. An oblique cut of 3° with respect to the inferior end increased patellar stress and reduced fatigue life, making this the least successful approach. Taken together, our FEA supports the use of minimal cutting depths at − 3° with respect to the superior end for patellar resurfacing in TKA in order to minimize stresses in the structure and improve TKA durability. Future studies will assess the effect of patella button placement to account for real-world practice variations.     

The effect of an augmentation patella prosthesis versus patelloplasty on revision patellar kinematics and quadriceps tendon force: an ex vivo study

The purpose of this study was to assess the effect of 2 revision reconstructive interventions on patellofemoral joint mechanics in comparison to control. We flexed 8 cadaver knee specimens from 0 degrees to 60 degrees of flexion in a test rig designed to simulate weight-bearing flexion and extension (Oxford rig). Quadriceps tendon extensor force and patellar kinematics were recorded for control total knee arthroplasty (TKA) (normal primary TKA with patella resurfaced) and then for each of the 2 revision patellar interventions (after patelloplasty of typical revision knee patellar bone defect to leave a simple bony shell, and after TKA with augmentation patella resurfacing). Our results demonstrate that patellar kinematics and quadriceps extensor force are optimized when the patella is reconstructed to normal anteroposterior thickness.     

The need for patellar resurfacing in total knee arthroplasty: a literature review

The controversy over whether or not to routinely resurface the patella during a total knee arthroplasty has persisted despite three decades of successful joint replacement procedures. Advocates for routine patellar resurfacing admit the occasional need for secondary patellar resurfacing and declare increased incidence of anterior knee pain in patients with non‐resurfaced patellae as a cause for worry. Surgeons that leave the patella unresurfaced cite avoidance of complications that include patellar fracture, avascular necrosis, patellar tendon injury and instability. This review discusses the available literature on patellar resurfacing through an evidence‐based analysis of randomized and pseudo‐randomized controlled trials and published meta‐analyses to date. The published literature seems to favour resurfacing the patellar routinely. Selective patellar resurfacing would be the ideal solution if sound pre‐operative criteria could be established. So far, a method for accurately predicting which patients can avoid patellar resurfacing has not been found. Future research looking at patellar resurfacing should concentrate on developing criteria for selecting those patients that would benefit from patellar resurfacing and those that would do as well without resurfacing, and thus, limiting potential surgical complications.     

髌骨软骨退变分级对保留髌骨型全膝关节置换术疗效的影响

 目的 探讨髌骨软骨退变Outerbridge分级对保留髌骨型全膝关节置换术疗效的影响。方法 对2007年2月至2010年1月因膝关节退变性骨关节炎行保留髌骨型全膝关节置换术的151例进行回顾性分析。男65例,女86例;年龄56～82岁,平均(65±5.0)岁。随访时间2～5年,平均3.5年。术中对髌骨软骨退变分级的评定采用Outerbridge标准,统计末次随访时不同髌骨软骨退变分级患者的满意度及膝前痛发生情况,视觉模拟评分(visual analogue scale,VAS)>3分判定为有膝前痛;比较不同髌骨软骨退变分级患者的美国膝关节学会评分(Knee Society Scale,KSS)及髌骨评分。结果 OuterbridgeⅠ级18例、Ⅱ级36例、Ⅲ级62例、Ⅳ级35例。膝前痛发生率4.0%(6/151),其中轻度疼痛4例、中度2例。无翻修病例,总体满意率96.7%(146/151)。不同髌骨软骨退变分级患者的满意度(H=5.54,P=0.14)、膝前痛发生率(H=0.56, P=0.91)、KSS膝评分(F=1.95, P=0.12)、功能评分(F=2.11,P=0.10)及髌骨评分(F=1.35, P=0.26)的差异均无统计学意义。结论 不同髌骨软骨退变分级患者行保留髌骨型全膝关节置换术后疗效无差异,对退变性骨关节炎患者行全膝关节置换术时无须置换髌骨。     

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.     

膝关节骨关节炎患者初次全膝关节置换术中选择髌骨置换的Meta分析

目的探讨膝关节骨关节炎(OA)进行初次全膝关节置换术(TKA)中选择髌骨置换与否的疗效,评价两种不同治疗选择的差异。方法检索Medline、Embase、Cochranelibrary、CBM,收集膝关节OA行初次TKA术中髌骨置换与否的临床对照试验,提取数据分析,采用RevMan5.0.18进行Meta分析。结果纳入8个前瞻性随机对照试验,共822例手术,其中髌骨置换组373例,髌骨非置换组444例。髌骨置换与非置换组比较,前膝痛与KSS评分均无明显的统计学意义(P0.5),置换组的因髌股关节问题而再次手术率低于非置换组[RR=0.53,95%CI(0.29,0.96),P=0.04],但置换组再次手术的原因除了常见的前膝痛,还包括髌骨假体相关的并发症。结论膝关节OA的患者行初次TKA术中选择髌骨置换与否的前膝痛与KSS评分无明显的统计学意义,置换组的因髌股关节问题再次手术率低于非置换组,但置换组再次手术的复杂性大于非置换组。     

Management of periprosthetic patellar fractures. A systematic review of literature

Despite advances in surgical technique and implant design, complications involving the extensor mechanism and patellofemoral joint after total knee arthroplasty (TKA) continue to be the most common cause of pain and the most commonly cited reason for revision surgery. Periprosthetic patellar fractures occur in 1.19% of all reported cases after TKA, with a clear correlation with resurfacing of the patella. In 88.32% of the cases reported the fracture is not associated with a traumatic event and it is identified at the follow-up examination during the first 2 years after knee replacement. Predisposing factors for fracture include lateral release, excessive bone removal, peg fixation and cementation, improper patellar tracking and prosthesis malpositioning. More than 50% of fractures are associated with a loose implant which complicates the fracture management. Non-operative treatment seems to offer acceptable functional results and pain relief, especially in cases of minimal displacement and stable implant fixation. However, when surgical reconstruction is undertaken, open reduction and internal fixation with tension band or cerclage wiring should not be the first choice of treatment as the rate of failure and subsequent non-union may be as high as 90%.