Computer-assisted correction of cam-type femoroacetabular impingement: a Sawbones study.

BACKGROUND: Assessing the adequacy of bone resection when correcting cam-type femoroacetabular impingement can be difficult when the surgeon is inexperienced or when less-invasive arthroscopic surgical techniques are used. The primary purpose of the present study was to compare, using a Sawbones model, the results of computer-assisted navigated osteochondroplasty of the femoral neck junction with correction with use of femoral head spherometer gauges. The second objective was to compare the results of computer-assisted osteochondroplasty performed by surgeons who had varied experience with the procedure. METHODS: We calculated and compared the post-resection alpha angle in custom-molded Sawbones models with cam-type impingement following both surgical techniques, performed by three surgeons with varied experience with the procedure. The alpha angle was measured at two positions (the three o'clock and one-thirty positions of the femoral head-neck junction) before and after resection. RESULTS: At the three o'clock position, there were no significant differences between the computer-navigation and spherometer groups (p = 0.83). There was undercorrection at the one-thirty position, with the median alpha angle being greater in the navigation group as compared with the spherometer group (71.0 compared with 58.6; p = 0.05). In the navigation group, there were no significant differences in the post-resection mean alpha angle among the three surgeons at either the one-thirty plane or the three o'clock plane. CONCLUSIONS: Navigation enabled the inexperienced surgeon to perform an equivalent amount of bone resection as the more experienced surgeons. However, all surgeons did not sufficiently resect the cam deformity as compared with the gold-standard open technique at the one-thirty position.

Validity of the alpha angle measurement on plain radiographs in the evaluation of cam-type femoroacetabular impingement.

BACKGROUND: Cam-type femoroacetabular impingement is secondary to lack of concavity at the anterosuperior femoral head-neck junction, resulting in reduced femoral head-neck offset and femoral head asphericity. This morphologic deformity can be detected by MRI and plain radiographs and quantified using the alpha angle. QUESTIONS/PURPOSES: We evaluated the accuracy and reproducibility of plain radiography in the diagnosis of cam-type deformity. METHODS: Sixty-eight patients (37 females, 31 males) with a mean age of 38 years (range, 17-60 years) were treated for intraarticular hip pathology with 43 hips having cam-type femoroacetabular impingement and 25 having isolated labral tears. All patients had alpha angle measurements made on plain radiographs (AP pelvis, crosstable lateral, Dunn view) and multiplanar MRI using an alpha angle of more than 50.5° as the gold standard. RESULTS: The Dunn view had a sensitivity of 91%, specificity of 88%, positive predictive value of 93%, negative predictive value of 84%, and accuracy of 90% for diagnosing the cam deformity associated with femoroacetabular impingement. The Pearson correlation coefficients between the MRI and plain radiography values were 0.702, 0.552, and 0.349 for the Dunn, crosstable lateral, and AP views, respectively. CONCLUSIONS: Our observations validate the clinical use of the Dunn view in the evaluation of the femoral head-neck contour in cam-type femoroacetabular impingement. LEVEL OF EVIDENCE: Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Complications of the direct anterior approach for total hip arthroplasty.

With the direct anterior approach gaining in popularity, it is important to appreciate the complications that are specific to it. The authors outline these potential complications and offer advice on the ways and the techniques to avoid them. This information is especially useful to the surgeon considering using this approach for the first time or to the surgeon who may already have encountered some of these complications as a result of using this approach.

Anterior Hueter approach in the treatment of femoro-acetabular impingement: rationale and technique.

In the last decade, femoro-acetabular impingement (FAI) has been recognized as a cause of pain and early arthrosis in the young adult hip. Carl Hueter first described the anterior approach in 1881. This article discusses the indications and diagnostic criteria and the surgical technique and early clinical results for the combined arthroscopic/Hueter approach.