Biomechanical evaluation of acromion and scapular spine fracture repair techniques systematic review.

Background: The incidence of reverse total shoulder arthroplasty (rTSA) is rising. Acromion and scapular spine fractures (ASFs) are a known complication following rTSA with an incidence rate of around 5%. The purpose of this study was to review biomechanical studies that have explored fixation techniques for ASFs following rTSA. Methods: PubMed, CENTRAL, Embase, and MEDLINE were searched from January 1, 2000, to August1, 2025, to identify biomechanical studies evaluating fixation techniques of acromion or scapular spine fractures following rTSA. Study characteristics, specimen type, sample size, Levy fracture classification, fixation methods, and mechanical outcomes were extracted. Results: The initial literature search yielded 202 studies with 3 duplications. Of the remaining 199 studies, 5 studies met criteria. The 5 studies tested a total of 89 shoulders, 53 synthetic scapulae (Sawbones) and 40 human cadaveric scapulae. Four of 5 studies examined Levy type III fractures. Three studies compared the efficacy of double plating to single plating, including a 90-90 configured 3.5-mm small fragment locking plate with a 2.7-mm small fragment locking plate (Katthagen et al), 2 3.5-mm small fragment locking plates (Hollensteiner et al), and a 90-90 configured 3.5-mm small fragment locking plate with a 3.5-mm one-third tubular locking plate (Pastor et al). Only Hollensteiner et al showed double plating to be statistically superior to single plating. Pastor et al could not show double plating with a 3.5-mm small fragment locking plate and a 3.5-mm one-third tubular locking plate to be superior to single plating. Kicinski et al compared a 3.5-mm small fragment locking plate to a 3.5-mm clavicle plate and a 3.5-mm reconstruction plate and showed a small fragment locking plate to provide significantly better fixation. Discussion: There exists a great need for further biomechanical exploration of fixation techniques for ASFs following rTSA. There is not currently enough research to draw many true conclusions to guide treatment for clinicians. Three point five mm small fragment locking plates are superior to clavicle plates or reconstruction plates. There current biomechanical evidence suggesting double plating is superior to dorsal single plating is weak for those with poor bone quality and nonexistent for those with normal bone quality or those without Levy type III fractures. No biomechanical studies are available to evaluate repair methods/constructs for type I fractures, and only one study is available for type II fractures.