Relationship Between Subacromial Bone Erosion and Hook Position of Clavicular Plate in Distal Clavicle Fractures.

OBJECTIVES To evaluate the influence of posterior hook position on subacromial bone erosion during surgical treatment of distal clavicle fractures with locking compression plate (LCP) clavicle hook plate (CHP). DESIGN Single-center retrospective study. SETTING Level V trauma center (university hospital). PATIENTS Twenty-one patients (mean age, 45.8 years) treated with CHP were included. One, three, 15, and two patients had Neer type I, IIa, IIb, and V fractures, respectively. INTERVENTION Open reduction and internal fixation were performed with LCP CHP. All implants were removed after a mean of 6.1 months postoperatively. MAIN OUTCOME MEASUREMENTS Japanese Orthopaedic Association (JOA) shoulder scores were used to assess recovery. Radiographically, the coracoclavicular distance (CCD) was measured as the distance between the tip of the coracoid process and the undersurface of the clavicle. Three-dimensional computed tomography was performed to identify bone erosion at the hook tips after implant removal. The distance from the acromioclavicular joint center to the bone erosion was divided into five areas at 5-mm intervals, and the position and depth of bone erosion were measured in each area. RESULTS The mean follow-up period was 17.4 months; mean ± standard deviation (SD) JOA score was 75.9 ± 4.7 at the final follow-up, while the mean duration of bony union was 4.4 ± 1.0 (SD) months. Delayed bony union was observed in one patient, while a second surgery was required in another due to acromion cut-out. Radiography showed over reduction in 95% of cases. The correlation coefficient showed a difference between CCD and the position of bone erosion measured by CT (Rs=0.32, p=0.006). Erosion under the acromion surface was found in all patients. The depth of erosion correlated with the posterior hook position (Rs = 0.29, P = 0.023). CONCLUSIONS Posterior hook tip placement increased the likelihood of bone erosion and complications due to over reduction. CHP should be set more anteriorly beneath the acromion to prevent complications. LEVEL OF EVIDENCE Therapeutic level IV. See Instructions for Authors for a complete description of levels of evidence.