The contribution of the posterolateral capsule to elbow joint stability: a cadaveric biomechanical investigation.

BACKGROUND: Elbow posterolateral rotatory instability occurs after an injury to the lateral collateral ligament complex (LCLC) in isolation or in association with an osteochondral fracture of the posterolateral margin of the capitellum (Osborne-Cotterill lesion [OCL]). The contribution to elbow stability of the posterolateral capsule, attached to this lesion, is unknown. This study quantified the displacement of the radial head on simulated posterior draw with sectioning of the posterior capsule (a simulated OCL) or LCLC. METHODS: Biomechanical testing of the elbow was performed in 8 upper limb cadavers. With the elbow 0°, 30°, 60°, and 90° degrees of flexion, posterior displacement of the radius was measured at increments of a load of 5 N up to 50 N. A simulated OCL and LCLC injury was then performed. RESULTS: A simulated OCL results in significantly more displacement of the radial head compared with the intact elbow at 30° to 60° of elbow flexion. LCLC resection confers significantly more displacement. An OCL after LCLC resection does not create further displacement. CONCLUSIONS: The degree of radial head displacement is greater after a simulated OCL at 30° to 60° of flexion compared with the intact elbow with the same load but not as great as seen with sectioning of the LCLC. This study suggests that the posterior capsule attaching to the back of the capitellum is important to elbow stability and should be identified as the Osborne-Cotterill ligament. Clinical studies are required to determine the importance of these biomechanical findings.

Assessing the required glenoid peg penetration in native scapula when bone graft is used during primary and revision shoulder arthroplasty.

Aims: Achieving purchase in native glenoid bone is essential for the stability of the glenoid baseplate when bone graft is used to address bone loss in both primary and revision shoulder arthroplasty procedures. The aim of this study is to assess the required depth of the baseplate peg in native bone when bone graft is used to result in satisfactory integration. Patients and methods: The CT scans of patients who underwent either primary or revision arthroplasty procedures with bone graft using the SMR Axioma Trabecular Titanium (TT) Metal Backed glenoid system were assessed. We measured the depth of the glenoid peg in native glenoid bone. Measurements were taken by two authors separately. Results: The scans of 53 patients (mean age 68 years) with a minimum follow-up of two years were reviewed. Implants included 12 anatomical and 41 reverse geometry prostheses. There were 17 primaries and 36 revisions: hemiarthroplasties (20) total (14) and reverse (2) implants. Bone grafts were from humeral head (15), iliac crest (34) and allograft (4). The mean depths were 8.8 mm (first assessor) and 9.10 mm (second assessor). The glenoid peg violated the glenoid vault in 32 patients and this did not adversely affect the outcome. There were three failures of implants all of which were aseptic failures and had peg penetration of less than 6 mm. Conclusions: The mean depth of glenoid peg in native bone was 9 mm (variation between 0.2 and 0.52 mm at 95% confidence interval). Aseptic loosening was seen with peg penetration less than 6 mm in native bone. Glenoid vault violation was not associated with loosening.