In Vivo Evaluation of Hemiarthroplasty Bearing Materials Using Animal Models: A Scoping Review (Part II)

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.