Morphology of Proximal Ulna Bare Area: A Guide for Olecranon Osteotomy.

PURPOSE: Olecranon osteotomy is commonly used to obtain access to the distal humerus for fracture fixation. The goal of this study was to accurately describe the anatomy of the bare area to minimize articular cartilage damage while performing olecranon osteotomies. METHODS: Twenty cadaveric ulnae were denuded to expose the bare area. Laser surface mapping was used to create 3-dimensional models, and the nonarticular portions of the ulnae were digitally measured. RESULTS: The morphology of the bare area from all aspects of the proximal ulna was defined. The central bare area was consistent in its location, 4.9 ± 1.5 mm distal to the deepest portion of the trochlear notch and 23.2 ± 2.3 mm distal to the olecranon tip. The maximum chevron osteotomy apical angle to stay within the bare area averaged 110° ± 11.8°. However, there was little tolerance for error without the risk of violating the articular cartilage. With transverse osteotomy, averaging 18° ± 10.6° in the coronal plane, there is less risk of damaging the articular cartilage. CONCLUSIONS: Transverse osteotomy perpendicular to the posterior surface of the ulna aiming at the visible bare area on the medial and lateral sides of the greater sigmoid notch may reduce the chances of violating the nonvisible articular cartilage of the proximal ulna. Based on the findings of this study, if chevron osteotomy is used, a shallow apex distal angle of more than 110° is recommended. CLINICAL RELEVANCE: This study provides intraoperative landmarks to guide surgeons performing olecranon osteotomies to stay within the bare area.

Comparing internal fixation constructs for scapular spine insufficiency fractures following reverse shoulder arthroplasty.

INTRODUCTION: There is limited research on the surgical management techniques for scapular spine fractures after reverse shoulder arthroplasty (RTSA). As such, the purpose of this in vitro biomechanical study was to compare 4 fixation constructs to stabilize scapular spine insufficiency fractures. METHODS: Twelve paired fresh-frozen cadaveric scapulae (N = 24) were randomized into 4 fixation groups: subcutaneous border plating (± hook) and supraspinatus fossa plating (± hook). A Levy type II fracture was simulated. Each specimen was cyclically loaded incrementally up to 700 N in 50 N steps or until failure. Between 50 and 200 N construct stiffness was measured, and stability failure was defined as displacement greater than 2.5 mm. RESULTS: Seventy-nine percent (19 of 24) of the specimens failed before the maximum load of 700 N. The average survival force with subcutaneous border plating was 480 ± 80 N compared with 380 ± 30 N for supraspinatus fossa plating (P = .3). Fixation construct failure was significantly more likely with fossa plating over subcutaneous plating (P = .012). The presence of the lateral plate hook was beneficial in preventing failure of the lateral acromion (P = .016). CONCLUSION: When appropriately surgically indicated, a dorsally applied plate to the subcutaneous border of the scapular spine with a lateral inferior supporting hook may be advantageous for internal fixation of type II scapular spine insufficiency fractures after RTSA.