Martin Beck

Background: Degenerative osteoarthritis (OA) of the hip often arises from structural abnormalities that alter load distribution, which leads to progressive chondrolabral damage. Although substantial advances have been made, the existing terminology in the field of hip preservation remains heterogeneous and inconsistently applied, limiting scientific communication and treatment standardization. The aim of this article is to link evidence from existing literature to develop a framework in the form of a structured lexicon, one that defines the morphological features and pathomechanical mechanisms that are relevant to the symptomatic, pre-arthritic hip. Methods: This descriptive framework was developed through the synthesis of current biomechanical, radiographic, and clinical evidence, combined with expert consensus from an international, multidisciplinary panel. Foundational concepts were derived from basic science research, including tribology, mechanobiology, and contact mechanics, to establish a unified terminology. Results: Three principal wear modes—instability, impingement, and mixed mechanisms—are proposed, corresponding to distinct pathological loading environments. Wear mechanisms include dysplasia with rim overload and stress-related cartilage failure, impingement with cam-induced shear or pincer rim conflict, and secondary inflammatory degeneration. Wear damage is classified by tissue involvement, encompassing labral degeneration, chondrolabral detachment, staged cartilage delamination, and subchondral bone changes (sclerosis, cystic change). By linking lesion topography to underlying mechanics, this framework has diagnostic and therapeutic relevance as well as encompasses radiographic measurements and clinical features of wear that are pertinent to hip instability and femoroacetabular impingement. Conclusions: This lexicon provides a coherent framework for pre-arthritic hip disease, establishing a shared terminology to guide basic-science research integration and the interpretation of current clinical practice in hip preservation.

Background: Periprosthetic femoral fractures (PFFs) are an increasingly common indication for revision total hip arthroplasty (THA). While patient-related risk factors are well documented, the influence of femoral stem design on PFF risk remains poorly characterized. In this study using nationwide data, we assessed the association between stem design and PFF risk. Methods: We analyzed 182,118 primary THAs (performed from 2015 to 2023) from the Swiss National Joint Registry (SIRIS). Cementless stems were categorized according to the Kheir classification, and cemented stems were categorized as double-tapered polished, triple-tapered polished, composite-beam, or custom. A multivariable Cox regression model, including variables such as age, sex, American Society of Anesthesiologists (ASA) class, body mass index (BMI), surgical indication, prior ipsilateral hip surgery, stem design, collar, dual-mobility cup, bearing, and head size, was analyzed. Hazard ratios (HRs) with 95% confidence intervals (CIs) are reported. Results: Among 182,118 THAs (mean patient age, 68.9 ± 11.5 years; female sex in 53.1% of cases), 1,226 (0.7%) were complicated by PFF. The cumulative incidence of PFF reached 0.7% at 5 years and 1.3% at 10 years. Higher PFF risk was associated with an age of 75 to 84 years (HR = 1.68 [95% CI = 1.44 to 1.96]) and ≥85 years (HR = 1.86 [95% CI = 1.47 to 2.35]), ASA class of 3 to 5 (females, HR = 1.70; males, HR = 1.73), BMI of 2 (HR = 1.61) or ≥40 kg/m ² (HR = 1.64), prior ipsilateral hip surgery (HR = 1.32), and use of a dual-mobility cup (HR = 1.56). Elective procedures (HR = 0.36) and collared stems (HR = 0.26) were associated with a lower risk. Compared with cementless type-3 stems, cementless type-7 (anatomic) stems showed a higher risk of PFF (HR = 1.88), whereas cementless type-1B (HR = 0.62) and composite-beam cemented stems (HR = 0.45) were protective. Conclusions: In this large nationwide registry study, femoral stem design independently influenced PFF risk after primary THA. Cementless anatomic stems increased the risk, whereas composite-beam cemented stems and the presence of a collar conferred a protective effect. These findings support personalized implant selection, particularly for older patients or those with frailty. Level of Evidence: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Currently, much is debated on the optimal treatment of borderline hips, being in the continuum between stable and unstable hips. The diagnosis of stability is often difficult but is a prerequisite for further treatment. Analysis includes a variety of radiographic parameters. We observed that unstable hips often had a crescent-like gadolinium collection in the postero-inferior joint space. We therefore questioned if the ‘crescent sign’ could be an indicator for hip instability? A retrospective comparative study was conducted including 56 hips in the instability group (treated with PAO) and 70 hips with femoroacetabular impingement (FAI) as control group. Based on standard radiographic parameters and magnetic resonance imaging (MRI), the association between hip instability and the ‘crescent sign’ was analyzed. For univariate group comparisons, the non-parametric Wilcoxon two sample test was used. Association between discrete variables was examined by means of chi-square tests. To examine predictive variables, logistic regression models were carried out. Most hips with a crescent sign belong to the instability group. A crescent sign has a sensitivity of 73.3% and specificity of 93% for instability. Based on our results, the crescent sign is a factor that is more prevalent in unstable hips. However, its absence does not exclude instability of the hip. If present, the specificity speaks strongly in favor for instability of the hip.