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Abstract Presented at the 29th Annual Meeting of the Arthroscopy Association of North America| Volume 26, ISSUE 6, SUPPLEMENT , e10-e11, June 01, 2010

Subcoracoid Impingement: Factors associated with the size and location of the Coracohumeral Interval (SS-21)

      Introduction

      A narrowing of the subcoracoid space may lead to mechanical conflicts that result in injury to the rotator cuff, biceps, and biceps pulley. The coracohumeral interval (CHI) is associated with age and gender but has not been standardized to size and anatomic location. The purpose of this study therefore was to determine clinical and anatomic factors associated with the size and location of the CHI.

      Methods

      Data were collected prospectively in 81 consecutive patients undergoing arthroscopic shoulder surgery for various pathologies. The CHI from this cohort was then compared to a cohort of 44 patients that were surgically treated for coracoid impingement with a coracoidplasty. There were 91 men and 38 women with an average age of 48.4 years old (range 15-75). The Coracoid-humeral interval (CHI) was measured on axial preoperative MRIs and was defined as the most narrow point between the coracoid and the humeral head. To standardize the CHI measurement, the interval location was evaluated in relation to the equator of the humeral head. CHI was the dependent variable and multivariate analysis was used to assess the relationship with various surgical and preoperative subjective factors.

      Results

      The location of the CHI was consistently just superior to the equator of the humeral head. There was no significant difference in CHI between gender, men had 12.6mm (SD3.9) vs women 11.6mm (SD3.3) (p=0.22; power70%). CHI did not change with age (r=−0.047; p=0.63). Patients with instability had a significantly larger CHI of 15.1mm (SD3.3) than patients without instability of 11.6mm (SD3.6) (p=0.000). When the CHI of the instability patients was removed from the analysis, there was no difference in the CHI across genders but age was significantly correlated with the interval size(r=−0.215; p=0.01). Patients with coracoid impingement had a significantly narrowed CHI of 9.8mm (SD2.5) versus 13.3mm (SD3.7) compared to patients without coracoid impingement (p=0.000). Patients with complete supraspinatus tears had significantly narrower CHI of 10.4mm (SD3.6) vs 12.2mm (SD3.5) (p=0.04) in those without cuff tears. ASES score was significantly associated with the CHI (r=.381; p=.002)

      Conclusion

      The CHI was uniformly located just proximal to the equator of the humeral head. CHI in women and men were not significantly different, but age did have an effect. Patients with instability had a significantly larger CHI than patients without instability. In our analysis those with coracoid impingement and those with complete supraspinatus tears had narrowed CHI's. Patients with a narrowed CHI had lower preoperative ASES scores. In conclusion, the type of shoulder pathology affects the CHI more than gender and age.