Morphologic and angular planning for cam resection in femoro-acetabular impingement: value of the omega angle

Abstract

This study showed that alpha angle, measured in one plane, was not a predictor of the radial extension of cam deformity. To achieve a full resection, it was frequently necessary to extend the femoral head osteoplasty over the retinacular area. Pre-operative determination of the omega angle and location of the vascular foramina helped improve cam resection safety and accuracy.

Cam deformity and the omega angle, a novel quantitative measurement of femoral head-neck morphology: a 3D CT gender analysis in asymptomatic subjects

“…Although 3D imaging can identify larger α°than 2D imaging, these differences are mainly the result of measurement location [19]. Furthermore, there is an increased risk of residual impingement and vascular insult resulting from surgical treatment based on inaccurate data regarding the extent of deformities [27,28,51]. Intervals for the α°were significantly different between genders, coherent with results reported by Hack et al [35] but divergent from other studies [25,30] (Table 7).…”

“…Current 2D imaging protocols for FAI do not permit complete consideration of these features. The radial extension of cam deformity has been described using MRI to compare bone resection using different surgical techniques [27], but 3D imaging might provide more accurate estimates. However, the optimal method for using 3D CT in this setting has not been well defined.…”

Femoroacetabular Impingement: What the Surgeon Wants to Know

“…26 With recent detailed knowledge of the vascular supply to the femoral head, resection of lateral cam deformities overlapping the vascular area is no longer an absolute isolated indication for open surgery. 17,18 The literature is very scarce concerning recommendations for the amount and shape of resection at the head-neck junction and acetabular margin. Few publications define the amount of safe bone resection on the femoral side before creating an increased risk of stress fracture, and there is no consensus about the depth and extension of resection.…”

“…For example, in cam impingement, the surgical treatment goal of restoring head sphericity can be difficult to accomplish considering the frequent overlap of cam deformity with the area of perforation of the superior retinacular arteries. [15][16][17][18] In the last decade, the number of performed hip arthroscopies has increased dramatically, much more than osteotomies or other hip-preserving procedures. Some studies point to an increase of 250 to 365% in the last 10 years.…”

Femoral Head Avascular Necrosis Is Not Caused by Arthroscopic Posterolateral Femoroplasty

“…On the contrary, Rupp and Rupp 1 explicitly condoned disrupting these vessels despite the fact that neither localization nor extension of the femoroplasties was adequately defined. 4,5 One could assume that violation of a single retinacular vessel would not cause AVN of the femoral head, but it should serve as a warning to surgeons to cease further violation of the posterolateral vascularity. It is interesting that institutional ethical approval for this research was not presented by Rupp …”