Sequential Resection of the Distal Clavicle and Its Effects on Horizontal Acromioclavicular Joint Translation

Background: Reconstructions of the coracoclavicular (CC) ligament in an open or arthroscopically assisted procedure are often combined with a resection of the distal clavicle to prevent or treat osteoarthritic degenerations of the acromioclavicular (AC) joint. However, increased horizontal translation leading to symptomatic instability may be associated with resection of the distal clavicle. Hypothesis: Horizontal translation increases in direct correlation to subsequent resection of the distal clavicle. Study Design: Controlled laboratory study. Methods: Twelve fresh-frozen specimens (mean age, 82.0 +/- 5 years) were examined using a servohydraulic testing system. A 70-N force was applied in the anterior, posterior, and superior directions, and the translations were quantified for all directions. After native testing, sequential resection of the distal clavicle at 5 and 10 mm was performed after incision of the inferior capsule, and anterior-posterior loads were retested. Finally, the AC ligaments were incised, and repeated testing was performed. Results: Native mean (+/- standard deviation) anterior translation was 7.90 +/- 2.62 mm. After section of the inferior AC capsule, anterior translation was 8.05 +/- 2.62 mm (P = 1.0). After clavicle resection of 5 mm, anterior translation was 10.75 +/- 2.38 mm (P = .122), and after resection of 10 mm, anterior translation was significantly increased to 11.6 +/- 2.37 mm (P = .012). Complete AC capsule sectioning led to significantly greater amounts of anterior translation (12.12 +/- 3.0 mm; P = .003). Posterior translation for the native specimen was 8.88 +/- 2.63 mm. Sectioning of the inferior AC capsule resulted in 9.21 +/- 2.71-mm translation (P = 1.0). After clavicle resection of 5 mm, posterior translation was 10.42 +/- 2.42 mm (P = 1.0), and after 10-mm resection, it was 11.31 +/- 2.86 mm (P = .39). Sectioning of the complete AC capsule led to significantly greater amounts of posterior translation (12.31 +/- 3.12 mm; P = .043). Conclusion: Ten millimeters of resection increased anterior translation of the distal clavicle with both the superior and posterior AC capsules as well as the CC ligaments intact. Both anterior and posterior translations increased after 10-mm resection and complete AC capsule sectioning. Clinical Relevance: These results suggest that resection of the distal clavicle leads to increased horizontal translation despite an intact superior and posterior AC capsule. Only sparing resection of the distal clavicle should be performed and only if strictly indicated. Violation of the AC capsule further increases horizontal translation and should therefore be avoided, or if indicated in AC joint dislocations, a reconstruction of the AC capsule should be considered.