Biomechanical Analysis of Distal Clavicle Excision With Acromioclavicular Joint Reconstruction

BACKGROUND: Acromioclavicular (AC) joint separation is a common injury, usually affecting young adults. Controversy exists regarding whether to excise the distal clavicle when surgical intervention is required. PURPOSE: To evaluate the biomechanical strength of AC and coracoclavicular (CC) ligament reconstruction with and without concurrent distal clavicle excision. STUDY DESIGN: Controlled laboratory study. METHODS: Nine matched pairs of cadaver shoulders were used. All shoulders were tested with intact CC and AC ligaments, and the ligaments were sectioned. For 1 shoulder in each pair, a 7-mm distal clavicle excision was performed. The contralateral distal clavicle was left intact. Single-tunnel CC ligament reconstruction was performed, and excess graft length was extended and secured across the AC joint to reconstruct the superior AC joint ligaments in all specimens. Specimens were then potted and cyclically loaded for 500 cycles in the anterior-posterior and superior-inferior planes using an MTS Minibionix load frame to evaluate displacement across the AC joint. RESULTS: Regarding the clavicle-intact reconstructed versus the intact state, there was significantly greater AC joint translation in the reconstructed state in the anterior-posterior (20.2 ± 7.0 mm vs 6.0 ± 1.5 mm; P < .001) and superior-inferior directions (12.3 ± 3.3 mm vs 4.2 ± 1.2 mm; P < .001). In the clavicle-excised reconstructed versus the intact state, there was also significantly greater translation in the reconstructed state in the anterior-posterior (21.7 ± 5.1 mm vs 8.9 ± 4.3 mm; P < .001) and superior-inferior directions (12.3 ± 6.1 mm vs 5.8 ± 3.1 mm; P < .001). When the difference in translation between the reconstructed and intact groups in the clavicle-intact versus the clavicle-excised group was compared, no statistically significant difference was noted in anterior-posterior (14.2 ± 7.8 mm vs 12.8 ± 5.0 mm; P = .67) or superior-inferior translation (8.1 ± 2.9 mm vs 6.6 ± 3.9 mm; P = .39). CONCLUSION: Excision of the distal clavicle did not have a significant effect on anterior-posterior or superior-inferior motion at the AC joint following single-tunnel CC and AC ligament reconstruction. CLINICAL RELEVANCE: The study suggests that excision of the distal clavicle in this procedure is not associated with increased anterior-posterior or superior-inferior instability in this model.