Bi-unicondylar arthroplasty

Aims Bi-unicondylar arthroplasty (Bi-UKA) is a bone and anterior cruciate ligament (ACL)-preserving alternative to total knee arthroplasty (TKA) when the patellofemoral joint is preserved. The aim of this study is to investigate the clinical outcomes and biomechanics of Bi-UKA. Methods Bi-UKA subjects (n = 22) were measured on an instrumented treadmill, using standard gait metrics, at top walking speeds. Age-, sex-, and BMI-matched healthy (n = 24) and primary TKA (n = 22) subjects formed control groups. TKA subjects with preoperative patellofemoral or tricompartmental arthritis or ACL dysfunction were excluded. The Oxford Knee Score (OKS) and EuroQol five-dimension questionnaire (EQ-5D) were compared. Bi-UKA, then TKA, were performed on eight fresh frozen cadaveric knees, to investigate knee extensor efficiency under controlled laboratory conditions, using a repeated measures study design. Results Bi-UKA walked 20% faster than TKA (Bi-UKA mean top walking speed 6.7 km/h (SD 0.9),TKA 5.6 km/h (SD 0.7), p < 0.001), exhibiting nearer-normal vertical ground reaction forces in maximum weight acceptance and mid-stance, with longer step and stride lengths compared to TKA (p < 0.048). Bi-UKA subjects reported higher OKS (p = 0.004) and EQ-5D (p < 0.001). In vitro, Bi-UKA generated the same extensor moment as native knees at low flexion angles, while reduced extensor moment was measured following TKA (p < 0.003). Conversely, at higher flexion angles, the extensor moment of TKA was normal. Over the full range, the extensor mechanism was more efficient following Bi-UKA than TKA (p < 0.028). Conclusion Bi-UKA had more normal gait characteristics and improved patient-reported outcomes, compared to matched TKA subjects. This can, in part, be explained by differences in extensor efficiency. Cite this article: Bone Joint Res 2021;10(11):723–733.

Classification of combined partial knee arthroplasty

Aims There has been a recent resurgence in interest in combined partial knee arthroplasty (PKA) as an alternative to total knee arthroplasty (TKA). The varied terminology used to describe these procedures leads to confusion and ambiguity in communication between surgeons, allied health professionals, and patients. A standardized classification system is required for patient safety, accurate clinical record-keeping, clear communication, correct coding for appropriate remuneration, and joint registry data collection. Materials and Methods An advanced PubMed search was conducted, using medical subject headings (MeSH) to identify terms and abbreviations used to describe knee arthroplasty procedures. The search related to TKA, unicompartmental (UKA), patellofemoral (PFA), and combined PKA procedures. Surveys were conducted of orthopaedic surgeons, trainees, and biomechanical engineers, who were asked which of the descriptive terms and abbreviations identified from the literature search they found most intuitive and appropriate to describe each procedure. The results were used to determine a popular consensus. Results Survey participants preferred “bi-unicondylar arthroplasty” (Bi-UKA) to describe ipsilateral medial and lateral unicompartmental arthroplasty; “medial bi-compartmental arthroplasty” (BCA-M) to describe ipsilateral medial unicompartmental arthroplasty with patellofemoral arthroplasty; “lateral bi-compartmental arthroplasty” (BCA-L) to describe ipsilateral lateral unicompartmental arthroplasty with patellofemoral arthroplasty; and tri-compartmental arthroplasty (TCA) to describe ipsilateral patellofemoral and medial and lateral unicompartmental arthroplasties. “Combined partial knee arthroplasty” (CPKA) was the favoured umbrella term. Conclusion We recommend bi-unicondylar arthroplasty (Bi-UKA), medial bicompartmental arthroplasty (BCA-M), lateral bicompartmental arthroplasty (BCA-L), and tricompartmental arthroplasty (TCA) as the preferred terms to classify CPKA procedures. Cite this article: Bone Joint J 2019;101-B:922–928.

Higher Function Scores and Satisfaction in Patients with Anteromedial Osteoarthritis Compared with Other Wear Patterns of the Knee: 2 Years after Both Total and Unicondylar Knee Arthroplasties

Anteromedial osteoarthritis (AMOA) is a common wear pattern in primary osteoarthritic knees. In patients with bone-on-bone disease, the most appropriate surgical intervention is still a matter of debate. Knee arthroplasty is a well-accepted treatment to relieve symptoms and regain function. Unfortunately, satisfaction is limited, especially related to activities. A cross-sectional study was performed among patients treated with total knee arthroplasty (TKA) and unicondylar arthroplasty (UKA) to determine if the osteoarthritis wear pattern or type of prosthesis affects knee-specific function scores and satisfaction related to activities. All UKA patients (N = 100) were treated for AMOA. Based on radiological assessment of the wear pattern, TKA patients were divided into two groups: TKA for AMOA (N = 68) and true TKA (N = 99). The Knee injury and Osteoarthritis Outcomes Score (KOOS), new Knee Society score (KSS), anterior knee pain scale, visual analog scales (VASs) for satisfaction about activities, and net promoter score were collected. After 2 years' follow-up, the anterior knee pain scale and VAS satisfaction showed significantly better scores for patients treated with TKA for AMOA compared with the true TKA group. Also in the KOOS subscales, some differences were seen in favor of the TKA for AMOA group. The new KSS was not in favor of a specific wear pattern, but patients with AMOA treated with UKA performed better on the symptoms subscale compared with patients treated with TKA. In conclusion, patients treated with TKA for AMOA showed better knee-specific function scores and satisfaction scores compared with patients treated with TKA for other wear patterns, and only slight differences were found between both the AMOA groups (TKA for AMOA and UKA). Thus, the radiologic assessment of wear patterns might be useful to take into account the shared decision-making process, when discussing expectations, timing, and outcomes with knee osteoarthritis patients considering knee arthroplasty. When AMOA is present, it might be beneficial to choose UKA over TKA.

Early Failure in Medial Unicondylar Arthroplasty: Radiographic Analysis on the Importance of Joint Line Restoration

Survivorship of unicondylar knee arthroplasty (UKA) remains a drawback, especially compared with the outcome of total knee arthroplasty. This could be improved by identifying and correcting failure mechanisms. To this purpose, this study aimed at exploring failure modalities of UKA, with particular focus on the role of joint line (JL) position and alignment as variable to be optimized for a successful outcome. This study explored modes of failure in 266 medial UKAs. Radiological comparison was performed between 24 failures and 24 matched controls, to determine the importance of UKA positioning in terms of femorotibial angle (FTA), tibial plateau angle, and posterior tibial slope (PTS). Radiographic comparative analysis showed statistically significant differences in the failure group compared with the control group in terms of variation in FTA (p = 0.0222), PTS (p = 0.0025), and JL height (p = 0.0022). Variations not only in FTA but also PTS and JL height were correlated with failures observed in this series. Thus, based on the results of this study, it emerges that JL position should be carefully controlled in all planes while implanting a UKA. This is a Level III, case–control study.