Plateau–Patella Angle in Evaluation of Patellar Height After Total Knee Arthroplasty

The plateau–patella angle (PPA) has been proposed as a new and simpler method to describe patellar height. This method has not been used or validated in knees following total knee arthroplasty (TKA). A modified PPA (mPPA) was developed for use in this population. The method was validated by determining the interobserver and intraobserver reliability of the technique in 50 consecutive patients compared to three well-described methods of describing patellar height after TKA. Three observers then evaluated the mPPA of 297 post-operative radiographs to describe a normal range after TKA for a given technique and implant. The interobserver reliability was the highest for the mPPA compared to the other methods. The mean mPPA for the entire cohort was 21.06, 20.49, and 19.94 for the three observers. The modified plateau–patella angle is a reliable way to evaluate patellar height in patients who have undergone total knee arthroplasty.     

Patellar Eversion Does Not Adversely Affect Quadriceps Recovery Following Total Knee Arthroplasty

Although avoiding patellar eversion during a total knee arthroplasty (TKA) has theoretical benefit in quadriceps recovery, there has been paucity of supportive objective clinical results. We prospectively designed the study whether TKA without patellar eversion has better quadriceps recovery in an objective, dynamometer study. Seventy-two knees undergoing TKA with midvastus approach were randomized into two groups according to patellar eversion or not. Clinical data and objective quadriceps recovery using a dynamometer were investigated preoperatively and postoperative at 6 weeks, 3 months, 6 months and 1 year. There were no statistical differences between two groups throughout the follow-up periods in recovery of quadriceps force or power and clinical data. Choosing to evert patella during TKA using midvastus approach would not adversely affect postoperative quadriceps recovery.     

Total Patellar Skin Loss From Cryotherapy After Total Knee Arthroplasty

The use of cryotherapy after total knee arthroplasty is a very common therapeutic adjunct accepted as routine postoperative care. We present 2 cases of total patellar skin loss due to cryotherapy after total knee arthroplasty. Substantial soft tissue defects were created after the initial debridement of the necrotic tissue. Both patients were evaluated for frostbite, and the wounds were sharply debrided. Application of an advanced wound management technique involves the use of a collagen-glycosaminoglycan biodegradable bilayer matrix, silver impregnated antimicrobial dressing, and low-pressure vacuum device, followed by delayed split thickness skin grafting and low-pressure vacuum device. We find that this technique provided durable soft tissue coverage for necrotic wounds of the knee that do not involve the joint capsule.     

Patellar Fracture After Total Knee Arthroplasty for Rheumatoid Arthritis

Patellar fracture is one of the most challenging complications of total knee arthroplasty, but relatively, little is known about it in patients with rheumatoid arthritis. We retrospectively analyzed 329 total knee arthroplasties performed in 230 female patients with rheumatoid arthritis to identify the incidence and risk factors for postoperative patellar fractures. The mean age was 61.8 years, and the mean follow-up period was 6.2 years. Patellar resurfacing was performed in all cases. Five postoperative patellar fractures (1.51%) were identified, and a thin residual patellar thickness and the use of posterior-stabilizing components were identified as significant risk factors, although the number of fractures was small in both groups. There was also tendency of higher age and greater joint line change observed in patients with fracture compared with those without fracture.     

全膝置换术后髌骨髌腱角的变化

目的 研究全膝置换术后相同屈膝角度下矢状位髌骨和髌腱之间的角度变化,及其与术后活动度的关系.方法 材料为2002年5月～2003年12月期间做了初次全膝置换的33个关节(30例),诊断包括29个膝骨关节炎、4个类风湿性关节炎,其中20个关节置换了髌骨.男5例,女25例;年龄平均67.3岁.术前和术后1年摄0°、45°、90°侧位X线片,记录术后1年的活动度,测量术前术后不同屈膝度下的髌骨纵轴和髌韧带的夹角,并进行分析.结果 术后1年在屈膝90°时,髌骨与髌腱的角度较术前增大(P＜0.01).更换髌骨和保留髌骨组术后都发生了相似的角度变化(P＜0.01).术后屈膝90°的髌骨髌腱角和术后活动度呈负相关(r=-0.506,P=0.003).结论 全膝置换术后在屈膝活动时的髌骨髌腱角变化规律发生改变,与置换髌骨无关;术后屈膝90°时髌骨髌腱角的改变幅度与术后活动度限制有关.     

Infection and Instability Increasing the Risk of Patella Baja and Pseudo-Patella Baja after Revision Total Knee Arthroplasty

BackgroundPatella baja with patellar tendon shortening due to traumatic or ischemic injury is a widely known complication after primary total knee arthroplasty (TKA). Pseudo-patella baja may arise from the elevation of the joint line after excessive distal femoral resection. The maintenance of original patellar height is important in revision TKA because postoperative patella baja and pseudo-patella baja can cause inferior biomechanical and clinical results. We investigated the incidence and risk factors of patella baja and pseudo-patella baja after revision TKA.MethodsWe retrospectively reviewed data for 180 revision TKAs. Patella baja was defined as a truly low-lying patella with an Insall-Salvati ratio (ISR) of < 0.8 and a Blackburne-Peel ratio (BPR) of < 0.54. Pseudo-patella baja was defined as a relatively low-lying patella compared to the joint line within the normal range of ISR and with a BPR of < 0.54. Clinically, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM) were evaluated. Risk factors increasing the incidence of patella baja and pseudo-patella baja after revision TKA were evaluated using multiple regression analysis.ResultsBefore revision TKA, 169 knees did not exhibit patella baja or pseudo-patella baja, while 9 knees showed patella baja and 2 knees exhibited pseudo-patella baja. At 2 years after revision TKAs, 25 knees (13.9%) showed patella baja and 23 knees (12.8%) exhibited pseudo-patella baja. Despite no differences in the postoperative WOMAC score between groups with and without patella baja and pseudo-patella baja, the postoperative ROM was significantly smaller in the group with patella baja (113.3°) or pseudo patella baja (110.5°) than in the normal group (122.0°). Infection as the cause of revision TKA increased the risk of patella baja (odds ratio, 10.958; p < 0.001), and instability increased the risk of pseudo-patella baja (odds ratio, 11.480; p < 0.001).ConclusionsInfection and instability resulted in increases in the incidence of patella baja and pseudo-patella baja after revision TKA. Information about the risk factors of patella baja and pseudo-patella baja will help TKA surgeons plan the height of the patella after revision TKA and improve clinical outcomes.     

Patellar Height After Total Knee Arthroplasty: Comparison of 3 Methods

Background

Total knee arthroplasty (TKA) is the gold standard procedure for knee osteoarthritis. However, there have been conflicting reports concerning whether TKA is associated with modifications in patellar height. This controversy might be partially explained by the diversity of methods used to measure patellar height. Therefore, we aimed at assessing the reproducibility of 3 radiological indices commonly used to evaluate patellar height—Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) ratios. Additionally, we aimed at evaluating the short-term differences between preoperative and postoperative patellar heights as measured by those 3 methods.

Tibial Tubercle-Trochlear Groove Distance Influences Patellar Tilt After Total Knee Arthroplasty

BackgroundTibial tubercle-trochlear groove (TT-TG) distance is associated with a greater risk of recurrent patellar dislocation in young, active patients. However, the effect of TT-TG distance after total knee arthroplasty (TKA) has not been investigated. The purpose is to analyze the effect of TT-TG distance and component rotation on patellar tilt and patellar shift after TKA.MethodsAfter TKA, axial computed tomography scans and axial radiograph were taken in 115 consecutive knees. TT-TG distance was measured between the most anterior point of the tibial tuberosity and the deepest point of the femoral component relative to a line connecting the anterior condyles. Femoral and tibial component rotation was measured relative to the femoral and tibial rotational axis, respectively. Pearson correlation coefficients were calculated.ResultsTT-TG distance had a significant correlation with patellar tilt in extension (R = 0.220, P = .018), patellar tilt in flexion (R = 0.438, P < .001), and patellar shift (R = 0.330, P < .001). Tibial component rotation had a significant correlation with patellar tilt in flexion (R = −0.251, P = .007) and patellar shift (R = −0.360, P < .001). Femoral component rotation had no significant correlations. Tibial component rotation had a significant correlation with TT-TG distance (R = −0.573, P < .001), whereas femoral component rotation had no correlation (P = .192).ConclusionTT-TG distance had a significant correlation with patellar tilt and patellar shift. Surgeons need to understand the factors affecting TT-TG distance and to pay attention to avoiding excessive TT-TG distance after TKA.     

Patellar Denervation Reduces Postoperative Anterior Knee Pain After Patellar Resurfacing Total Knee Arthroplasty: A Randomized Controlled Trial

BackgroundThe benefit of patellar denervation (PD) in patellar resurfacing total knee arthroplasty (TKA) is still debatable. This prospective, randomized controlled trial investigated whether circumferential PD should be performed in patellar resurfacing TKA.MethodsA total of 241 patients who underwent unilateral TKA were randomized into PD or non-PD groups. Incidence, intensity, and presentation time of anterior knee pain (AKP) and clinical outcomes were evaluated at 3, 6, 9, 12, 18, and 24 months postoperatively.ResultsThe incidence of AKP was significantly lower in the PD group (6.4% vs 16.2%, P = .032). The intensity of AKP and patient satisfaction scores were significantly better in the PD group at 3 months but not after 3 months. The presentation time of AKP mostly occurs at 3 months after surgery. The Knee Society score, range of motion, Oxford score, patellar score, activity of daily living score, and visual analog scale of overall knee pain were not significantly different between the two groups during the follow-up period.ConclusionGiven that PD can improve AKP and patient satisfaction at an early period postoperatively without jeopardizing clinical outcomes at no additional cost, this inexpensive procedure readily available in nearly every operation room is strongly recommended during primary TKA with patellar resurfacing.     

Arthroscopic Treatment of Patellar Clunk and Synovial Hyperplasia After Total Knee Arthroplasty

Patellofemoral pain, crepitus, and locking are infrequent symptoms after total knee arthroplasty (TKA). We performed a retrospective review of 25 patients who underwent arthroscopic debridement after primary TKA to treat the patellar clunk syndrome (15 knees) or patellofemoral synovial hyperplasia (10 knees). After surgery, patient-reported knee pain and crepitus as well as Knee Society knee and function scores improved in both groups. Postoperative knee range of motion remained unchanged. Arthroscopic debridement of symptomatic patellofemoral synovium after TKA is a safe and effective procedure.     

Influence of Patellar Morphology Classified by Wiberg Classification on Knee Joint Function and Patellofemoral Tracking After Total Knee Arthroplasty Without Patellar Resurfacing

BackgroundTo evaluate the influence of patellar morphology on knee joint function and patellofemoral tracking in patients with primary osteoarthritis after total knee arthroplasty (TKA) without patellar resurfacing.MethodsWe performed a retrospective study of 156 patients with primary osteoarthritis who underwent TKA without patellar resurfacing from April 2018 to July 2019. As per Wiberg classification, patients were divided into Wiberg type I (group A, n = 38), II (group B, n = 88), and III (group C, n = 30) groups. The clinical data, postoperative follow-up data, and radiological data between three groups were compared.ResultsThere was no statistically significant difference in the HSS score and Feller score between the three groups before surgery and at each follow-up point after surgery (P > .05). At the last follow-up, there were no significant differences in the height and relative thickness of the patella between the three groups (P > .05). However, the incidence of anterior knee pain was significantly higher in group C than in the group B (P < .05). The patellar tilt angle was significantly larger in group C than in the groups A and B (both P < .05). The patellar facet angle was significantly larger in group A than in group B and C, which was also significantly larger in group B than in group C (both P < .05).ConclusionPatients with three different morphologic types of the patella both exhibited improved knee joint function after TKA, however, patients with Wiberg type Ⅲ patella were more prone to have poor patellofemoral tracking and anterior knee pain after surgery.     

Lateral Patellar Facet Impingement After Primary Total Knee Arthroplasty: It Does Exist

The existence of the diagnosis “lateral patellar facet impingement” (LPFI) is controversial and the outcomes for surgical revision for symptomatic LPFI uncertain. We found that of the 3361 index knee revisions performed at our institution from 1995 to 2008, eleven were done for symptomatic LPFI. Their clinical histories and radiographic imaging were reviewed before and after revision TKA and were also compared to a group of control patients. We found no statistically significant differences between the groups in preoperative KS pain and function scores or radiographic features. However, the combined findings of pain in the subpatellar/lateral aspect of the knee post TKA and radiographic lateral facet contact were significantly associated with revision due to LPFI. Surgical revision results were variable, but ~ 2/3 of the patients were satisfied with the operation and had a significant improvement in KS function scores.     

全膝关节置换术后的手法松解

背景：全膝关节置换术后初期对部分屈曲角度不能超过90°的患者可能须进行麻醉下的手法松解，以改善关节活动度。本目的是评价全膝置换术后手法松解的治疗效果。方法：90例患者（113膝）因术后平均10周时患膝屈曲角度≤90。而进行了手法松解。分别于全膝关节置换术之前、手术、手法松解前、手法松解后即刻以及术后6个月、1年、3年、5年以量角器测量膝关节的屈曲角度。黑：90例患者中81例（90％）在手法松解后膝关节屈曲角度获得改善。膝关节平均屈曲角度在全膝关节置换术前102°，中皮肤缝合后111°，手法松解前70°。术后5年随访时膝关节屈曲角度较手法松解前平均提高35°（p〈0．0001，配对t检）。术后12周之内进行手法松解的患者与术后12周之后进行手法松解的患者相比，平均屈膝角度的改善程度无显著差，最终仍进行手法松解的患者其术前膝关节协会疼痛评分明显低于未进行手法松解的患者（更痛，p=0．0027）。结论手法松解可以改善全膝关节置换术后膝关节屈曲角度。术前疼痛明显的患者术后更趋向于须手法松解。可信水平：治疗性研究，Ⅲ级。进一步可信度参见作者介绍。     

Patellar Rebar Augmentation in Revision Total Knee Arthroplasty

BackgroundIn revision total knee arthroplasty, osteolysis, mechanical abrasion, and infection may leave patellar bone stock severely attenuated with cavitary and/or segmental rim deficiencies that compromise fixation of patellar implant pegs. The purpose of this study was to retrospectively review the use of cortical “rebar” screws to augment cement fixation in revision patelloplasty.MethodsFrom 2006 to 2018, dorsal patellar rebar technique was used for patellar reconstruction in 128 of 1037 revision total knee arthroplasty cases (12.3%). Follow-up was achieved with serial radiographs and prospective comparison of Knee Society Scores (KSSs) for clinical outcome. Complications and implant failures requiring reoperation or modified rehabilitation were also assessed.ResultsOf the 128 patellar revisions performed using the rebar technique, 69 patients were women and 59 patients were men. The average age of the group was 69.5 years (range, 32-83 years). The mean follow-up of the cohort was 37 months (range, 13-109 months). The most common causes for revision were kinematic conflict, periprosthetic joint infection, and aseptic loosening. The median number of rebar screws used was 5 (range, 1-13). Preoperative KSSs for the study cohort averaged 50 (range, 0-90) At latest follow-up, mean KSS was 85 (range, 54-100). There were 4 patellar-related complications (3.1%) with no implant failures at study conclusion. Retrieval analysis revealed rigid fixation of the reconstructed patellar component in all cases.ConclusionsPatellar rebar screw augmentation is a useful technique when there are significant cavitary deficiencies and limited segmental rim deficiencies. This technique allows the surgeon to extend indications for patellar revision arthroplasty.