A CADAVERIC STUDY OF ARTHROSCOPIC HIP CAM IMPINGEMENT TREATMENT: BIOCHEMICAL COMPARISON OF CONTACT PRESSURES BETWEEN PARTIAL AND COMPLETE FEMORAL OSTEOPLASTY

Purpose

To determine the differences of biomechanical properties in three conditions including 1) native cam deformity 2) cam deformity with incomplete resection and 3) cam deformity with complete resection.

Methods

A cadaveric study was performed using 8 frozen, hemi-pelvises with cam-type deformity (alpha angle >55°) measured on CT scan and an intact labrum. Intraarticular pressure maps were produced for each specimen under the following conditions: 1) native cam deformity, 2) cam deformity with incomplete resection and 3) cam deformity with complete resection. A 5.5-mm burr was used to resect the lateral portion of the cam deformity to a depth of 3–4 mm. The specimen was placed in a custom designed jig in the MTS electromechanical test system to create pressure and area map measurements. In each condition, three biomechanical parameters were obtained including contact pressure, contact area and peak force within a region-of-interest (ROI). Repeated measurements were performed for three times in each condition and the average value of each parameter was used for statistical analysis. ANOVA was used to compare biomechanical parameters between three conditions.

Results

Repeated measures ANOVA analysis demonstrated that the pressures averages of hips with complete resection of cam lesions were significantly lower when compared to averages of hips with incomplete femoral cam lesion and intact cam deformity (2.48+0.56 kg/cm³ vs 2.32+0.50 kg/cm³ vs 2.02+0.54 kg/cm³, respectively; p-value=0.01). Percentage reduction of contact pressure in the complete resection and incomplete resection groups compared to the native CAM deformity groups were 18.49% and 1.58% respectively. There was no statistically significant difference in contact pressures between the incomplete resection and unoperated groups. Contact area and peak force showed no statistically significant differences across three conditions.

Conclusion

There are lower intraarticular hip contract pressures in complete resection of the cam lesions when compared to an incomplete resection and intact hip without resection. These observations underscore the importance of ensuring complete resection of femoral cam lesions in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome.

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