ePoster #717 - ISHA Annual Scientific Meeting 2016

The Impingement-Instability Index For Mechanical Hip Pain

Eilish O'sullivan, PT, DPT, OCS, SCS, New York, NY UNITED STATES
Bryan Talmadge Kelly, MD, New York, NY UNITED STATES

Hospital for Special Surgery, New York, NY, UNITED STATES

FDA Status Not Applicable

Summary: The Impingement-Instability Index looks to describe patients in term of the femoral side, by combining the Alpha Angle and the femoral version.

Abstract:
Purpose
We have previously described the Morphologic Matrix to classify patients with mechanical hip pain. One of the more difficult parameters to easily quantify is acetabular coverage. The Impingement-Instability Index looks to describe patients in term of the femoral side, by combining the Alpha Angle and the femoral version.
Methods
A retrospective analysis was conduct from a prospectively enrolled Hip Preservation Registry with available computed tomography (CT) data undergoing hip arthroscopy for mechanical hip pain between October 2010 and July 2014. Surgery was indicated for labral injury and femoroacetabular impingement. The Index is calculated based upon measurements derived from CT Scan, and is found by subtracting the femoral version from the alpha angle. Those with large indices (Impingement Index) have greater cam morphology and decreased femoral version. Those with low indices (Instability Index) have little or no cam morphology and increase femoral version. These patients were then grouped into 10 categories based upon their Index (in 10 degree increments) for ease of comparison.


Results

Criteria were met for 1080 patients (1330 hips), 60% were male, and average age was 27.1 years. The range was 5-103. The frequency of patients was normally distributed throughout the groups. There were significant differences between males and females, with the average Index for Males of 56 (range 8-103), and the average for females 45 (rage 5-82). Those patients with greater than or equal to 2 years’ patient-reported outcomes were then compared by group (N=514). There were significant differences between groups in terms of Modified Harris Hip Score, Hip Outcome Score, and International Hip Outcome Tool (p<0.05), with significant post-operative increases in all groups (p<0.005). The extremes on either end of the spectrum noted lower outcome scores overall.


Conclusions

The Impingement-Instability Index allows for easy and reliable categorization of patients with mechanical hip pain. Understanding of the mechanical pattern of injury is paramount for optimal surgical management and successful outcomes in this patient group.