Clinical utility of markerless motion capture for kinematic evaluation of sit-to-stand during 30 s-CST at one year post total knee arthroplasty: a retrospective study.

BACKGROUND: Although the importance of kinematic evaluation of the sit-to-stand (STS) test of total knee arthroplasty (TKA) patients is clear, there have been no reports analyzing STS during the 30-s chair sit-up test (30 s-CST) with a focus on kinematic characteristics. This study aimed to demonstrate the clinical utility of kinematic analysis of STS during the 30 s-CST by classifying STS into subgroups based on kinematic parameters, and to determine whether differences in movement strategies are expressed as differences in clinical outcomes. METHODS: The subjects were all patients who underwent unilateral TKA due to osteoarthritis of the knee and were followed up for one year postoperatively. Forty-eight kinematic parameters were calculated using markerless motion capture by cutting STS in the 30 s-CST. The principal components of the kinematic parameters were extracted and grouped by kinematic characteristics based on the principal component scores. Clinical significance was examined by testing whether differences in patient-reported outcome measures (PROMs) were observed. RESULTS: Five principal components were extracted from the 48 kinematic parameters of STS and classified into three subgroups (SGs) according to their kinematic characteristics. It was suggested that SG2, using a kinematic strategy similar to the momentum transfer strategy shown in previous studies, performed better in PROMs and, in particular, may be associated with achieving a "forgotten joint", which is considered the ultimate goal after TKA. CONCLUSIONS: Clinical outcomes differed according to kinematic strategies used STS, suggesting that kinematic analysis of STS in 30 s-CST may be useful in clinical practice. TRIAL REGISTRATION: This study was approved by the Medical Ethical Committee of the Tokyo Women's Medical University (approval number: 5628 on May 21, 2021).

Noise after total knee arthroplasty has limited effect on joint awareness and patient-reported clinical outcomes: retrospective study.

BACKGROUND: Some patients complain of noise after total knee arthroplasty (TKA). Controversy still exists on how the noise affects the clinical outcomes, including joint awareness, after TKA. The Forgotten Joint Score-12 (FJS-12) measures the clinical outcomes focusing on joint awareness after surgery. The Knee Society Scoring System-2011 (KSS-2011) includes questionnaires for satisfaction, expectation, and functional activities. The aim of this study is to clarify the relationship among FJS-12, KSS-2011, and the noise. Furthermore, the relationship between FJS-12 and KSS-2011 was validated. METHODS: Using FJS-12 and KSS-2011, 295 knees from 225 patients who underwent TKA were retrospectively evaluated. Noise perception was evaluated by a questionnaire with five grades, a method that follows the questionnaire form of FJS-12 ("Are you aware of the noise of your artificial joint?"; never, almost never, seldom, sometimes, mostly). Correlations among FJS-12, KSS-2011, and noise were analyzed. The patients were divided into four groups based on the mechanism of their implant [cruciate retaining, posterior stabilized, cruciate sacrificed, and bicruciate stabilized (BCS)]. FJS-12, KSS-2011, and noise were compared among the groups. RESULTS: A strong correlation was found between FJS-12 and total score of KSS-2011 (0.70; P < 0.001). FJS-12 correlated with KSS-2011 subcategories of "symptoms," "satisfaction," and "standard activities," with correlation coefficients at approximately 0.60. Noise had weak correlations with FJS-12 (0.28; P < 0.001) and KSS-2011 (0.20 P < 0.001). In comparing the TKA mechanisms, BCS had remarkably better KSS-2011 and greater movement range but worse noise scores. CONCLUSIONS: Noise perception after TKA had limited effect on joint awareness and clinical outcomes. FJS-12 correlated strongly with KSS-2011 and associated with satisfaction, residual symptoms, and daily activities, as assessed by KSS-2011 subscores. TRIAL REGISTRATION: This study was approved by the Medical Ethical Committee of the Tokyo Women's Medical University (approval number: 4681 on March 2, 2018).

Awareness of Stress Concentration Points for Prevention and Management of Periprosthetic Fractures Following Plate Installation Reinforcement: A Case Report.

Introduction: In an aging society, the incidence of periprosthetic fractures will increase owing to the increasing number of patients undergoing joint replacement surgery. We experienced a case of recurrent periprosthetic fracture in a patient who had undergone ipsilateral hip bipolar hemiarthroplasty (BHA) and total knee arthroplasty. Based on our experience, we discuss the treatment strategy for periprosthetic fractures in patients at a high risk of fall. Case Report: An 84-year-old woman, who had undergone total knee arthroplasty 9 years ago and ipsilateral hip BHA 2 years ago, sustained a knee condylar fracture (Su classification type III) due to fall. This knee periprosthetic fracture posed a challenge for osteosynthesis; therefore, revision total knee arthroplasty was performed using a hinge-type prosthesis. During this surgery, we installed a reinforcement plate on the femoral shaft to prevent fractures because of the short stem tip distance between the hip and knee prosthesis (53 mm). The procedure was successful, and the patient regained her walking ability. However, 6 months after surgery, the patient sustained a hip periprosthetic fracture (Vancouver type B2) due to a fall, despite precautionary plate installation. In case of hip stem insertion, the stress caused by fall is concentrated on the infratrochanteric region, as reflected in her fracture site. From a mechanical perspective, this fracture was not accidental. The plate reinforcement procedure may have been inadequate because the top of the plate was located at the infratrochanteric region. Conclusion: Periprosthetic fractures may occur despite the installation of a plate for fracture prevention. With a total hip arthroplasty or hip BHA stem inserted, a fall could result in a subtrochanteric fracture.