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.