Anatomical Conoid Ligament Reconstruction Improves Posterior Stability in Neer Type IIB Distal Clavicle Fractures: A Cadaveric Biomechanical Study.

HYPOTHESIS: This biomechanical study aimed to compare suture button tape (SBT) fixation techniques using different clavicular drill-hole positions in a Neer type IIB distal clavicle fracture (DCF) model. We hypothesized that anatomical conoid ligament reconstruction would provide greater posterior stability than that provided by anterior reconstruction without compromising superior stability.

METHODS: A Neer type IIB DCF model was created using 12 fresh-frozen cadaver shoulders and tested using the following three groups: conoid group (intact conoid ligament); anatomical group (drill hole placed at the posterior aspect of the clavicle over the conoid tubercle); and anterior group (drill hole placed at the anterior one-third of the clavicular width). Reduction accuracy was assessed by measuring displacement rates (superior, anteroposterior, and combined) at the reduced positions. Mechanical stability was evaluated by applying 70-N superior and posterior loads to the proximal clavicle and measuring displacement relative to the reduced position. A statistical analysis using Friedman tests was performed; if the results were significant, then pairwise Wilcoxon signed-rank tests were subsequently performed. Bonferroni correction was applied across all 21 pairwise comparisons. An adjusted P < .05 was considered significant.

RESULTS: No significant pairwise differences in reduction accuracy were detected after Bonferroni correction. Under superior loading, the median displacement rates were 33.2%, 4.2%, and 12.6% in the conoid, anatomical, and anterior groups, respectively. The displacement rate in the anatomical group was lower than that in the conoid group (adjusted P = .021). No significant difference between the two reconstruction groups was detected. Under posterior loading, median displacement rates were 48.1%, 16.5%, and 23.7% in the conoid, anatomical, and anterior groups, respectively. The displacement rate in the anatomical group was lower than that in the conoid and anterior groups (adjusted P = .010 and .031, respectively). The mean within-specimen difference in posterior displacement between the anterior and anatomical groups was 1.8 mm (95% confidence interval, 0.6-2.9 mm).

CONCLUSION: Anatomical reconstruction using SBT provided greater resistance to posterior displacement than that provided by anterior reconstruction, with a mean within-specimen reduction in posterior displacement of 1.8 mm under a 70-N posterior load. No statistically significant difference in superior displacement was detected between the two reconstruction groups. The clinical relevance of the observed posterior displacement difference has not yet been established.

LEVEL OF EVIDENCE: Basic Science Study, Biomechanics.