Acetabular Rim Reduction for the Treatment of Femoroacetabular Impingement Correlates With Preoperative and Postoperative Center-Edge Angle

Clinical Research, Steadman Philippon Research Institute, 181 W. Meadow Drive, Vail, CO 81657, U.S.A.
Arthroscopy The Journal of Arthroscopic and Related Surgery (Impact Factor: 3.21). 06/2010; 26(6):757-61. DOI: 10.1016/j.arthro.2009.11.003
Source: PubMed


The purpose of this study was to quantify the change in degrees in the center-edge (CE) angle for each millimeter of acetabular rim resected in hips undergoing arthroscopic acetabular rim trimming.
Preoperative and postoperative CE angle and millimeters of rim reduction were prospectively collected in 58 hips that underwent arthroscopic rim reduction. There were 35 women and 23 men. The mean age was 32 years. The inclusion criterion was hip arthroscopy for femoroacetabular impingement in patients without dysplastic hips. Two orthopaedic surgeons made independent measurements of the CE angle on preoperative and postoperative anteroposterior pelvis radiographs. To determine the amount of rim reduction intraoperatively, the lunate surface was measured with an arthroscopic ruler at the 12-o'clock position before and after rim trimming. The rim trimming was performed by a single surgeon using a 5.5-mm motorized bur.
For the 58 hips included in this study, the mean rim reduction performed was 3.2 mm (range, 1 to 9 mm). The mean change in CE angle was 3.9 degrees (range, 0 degrees to 17 degrees ). All numbers were normally distributed. By use of a regression model, the change in the CE angle could be determined by the following formula: Change in CE angle = 1.8 + (0.64 x rim reduction in millimeters). The interobserver intraclass correlation coefficient for radiographic measurement of the CE angle was 0.92 (95% confidence interval, 0.87 to 0.95), indicating excellent interobserver reliability.
The amount of change in the CE angle can be estimated by the amount of bony resection performed at the 12-o'clock position on the lunate surface in the arthroscopic treatment of femoroacetabular impingement. We found that 1 mm of bony resection equals 2.4 degrees of change in the CE angle and 5 mm of bony resection equals 5 degrees of change in the CE angle.
Level II, diagnostic study.

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    • "The measured postoperative alpha angle was below 46 • in all cases, except for two patients operated early on (cases 1 and 5) who needed additional surgery, which suggests that the volume and position of the bone being resected can be adequately evaluated under direct surgical view. The labrum was reinserted only once with suture in this series; the published reinsertion rate is much higher because acetabular resection is performed by detaching the base of the labrum and then resuturing it, which seems deleterious to us [39]. Laude et al. [26] and Larson and Giveans [40] have shown that this procedure does not improve the result, and can even be painful. "
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    • "On the acetabular side, while the crossover sign indicates retroversion, this does not systematically mean excessive coverage, as seen in the possible association with dysplasia 43—45. While the dysplasia parameters and angular values are well defined, the same is not yet true for the characteristics and limits of excess coverage [46] [47]. In the present study, retroversion had to be associated with anterior and/or lateral coverage angles greater than 25 • for excessive coverage to be diagnosed and acetabuloplasty indicated. "
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