Victoria P. Marino

Hemiarthroplasty is commonly used to treat damage localized to one side of a synovial joint, maximally preserving the patient's opposing healthy bone and cartilage; however, challenges remain due to accelerated wear of the cartilage articulating with the implant surface. This scoping review summarized investigations of hemiarthroplasty bearing materials (HBMs) utilizing animal models. The review focused on HBMs tested, animal models used, duration of animal survival, and outcome assessments (e.g., gait analysis, image analysis, histological staining, and cartilage scoring). The initial search was designed to broadly capture all studies evaluating HBMs articulating against articular cartilage. A total of 1798 studies were identified, which after screening yielded 72 that met the inclusion criteria. Of these, 24 were classified as in vivo and were included in this review. The HBMs evaluated included metals (63%), hard and soft polymers (33%), ceramics (17%), and synthetic carbons (17%). HBMs were predominantly studied in canines (46%), rabbits (25%), and sheep (21%), with survival durations from 2 to 104 weeks. Outcome assessment of cartilage wear varied across studies and histological staining was performed in all studies with the most common stains being Safranin‐O (58%) and Hematoxylin and Eosin (54%). Commonly used cartilage scoring systems were Mankin and Modified Mankin (38%); however, among all studies, scales and sub‐categories for scoring criteria varied drastically. While similarities were identified with respect to HBMs, animal models, and some outcome measures, the diversity of testing methodologies and lack of comparative evaluations limited the ability to identify the best practice for evaluating HBM performance.

Hemiarthroplasty is used to treat joint damage confined to one side, aiming to preserve the remaining healthy cartilage and bone while addressing conditions like femur fractures and osteonecrosis; however, challenges persist due to cartilage wear and inconsistent clinical outcomes. This scoping review evaluates in vitro studies on hemiarthroplasty bearing materials (HBM), focusing on the HBM tested, cartilage specimens, experimental setups, outcome variables, and the comparability of results. Of 1798 identified studies, 72 met the inclusion criteria, with 48 classified as in vitro. HBMs tested included metals (42%) and soft polymers (30%) and 45% of studies utilized multiple distinct HBMs. Cartilage specimens were predominantly bovine (65%), mostly from the tibial‐femoral joint (69%). The two most common experimental set ups were tribometers (75%) and simulators (25%) both using commercial and custom‐built rigs. Tribometer configurations included pin‐on‐disc and pin‐on‐plate models and simulators highlighted ball‐on‐joint set ups. Tribometer motions included linear reciprocating (62%) or multidirectional reciprocating (24%). Input parameters included contact stress (8.8 kPa to 23.3 MPa, mean 2.1 MPa), velocity (0.5‐100 mm/s, mean 16.46 mm/s), testing duration (0.03–33.8 h, mean 5.4 h), and distance (5.4 cm to 9000 m, mean 393 m). Simulators used inputs of loads ranging from 25 N to 1.5 kN, 500 to 500,000 cycles and a variety of flexion‐extension profiles together with secondary motions. Lubricants were mostly bovine calf serum (38%) and saline‐based solutions (21%). Outcome variables mainly included coefficient of friction and damage to cartilage and/or HBM, but the methods to assess these outputs varied. Methodological differences and inconsistent reporting of outcomes limited the ability to draw firm conclusions about the relative performance of HBMs.