Catherine Niyada Petchprapa MD, Presenter: Nothing to Disclose

Christina Levchook MD, Abstract Co-Author: Nothing to Disclose

José Raya MSc, Abstract Co-Author: Nothing to Disclose

Jenny T. Bencardino MD, Abstract Co-Author: Nothing to Disclose

Determine the prevalence of the notch sign in patients with non specific hip pain versus patients with clinical/radiographic femoroacetabular impingement (FAI).  Determine the association of other FAI morphological features with the notch sign.

Retrospective review of our department database was performed for consecutive studies of the hip including AP, frog lateral and cross table lateral views during a 6 months’ time frame. Exclusion criteria included prior surgery, OA, DDH and poor technique. Fifty-three patients with history of non specific hip pain (F29:M24; F: M = 1.2:1; age range= 21-87, mean 58.71) and 53 patients with clinical/radiographic FAI findings were identified (F20:M33; F: M=1:1.6; age range = 17-87-mean: 60). The following variables were recorded by two readers blinded to clinical history: notch sign visible in AP, frog and/or crosstable in both groups for prevalence calculation. In the FAI group, additional measurements included: cam deformity, subcortical head/neck cysts, coxa profunda, acetabular protusion, acetabular retroversion and crossover sign. The association of these measurements with the presence of a notch sign was calculated using Chi-square analysis.

The notch sign was best demonstrated on cross table lateral view. The prevalence of the notch sign was significantly (P=0.004) higher in FAI patients (19%=10/53) than in patients with non specific hip pain (2%=1/53). The notch sign has an associated odd ratio of 10 (95%-confidence interval= [1.5, 18.5]) of having FAI. Patients with clinical FAI/positive notch sign had associated cam deformity 20% (2/10), cysts 10% (1/10), profunda 80% (8/10), acetabular protrusion 0% (0/10) and crossover 80% (8/10). In patients with clinical/radiographic FAI with a negative notch sign, the prevalence of cam was 42% (18/43), cysts 14% (6/43), profunda 58% (25/43), acetabular protusion 5% (2/43), and crossover 60% (26/43). However, none of these FAI morphological features were significantly associated with the notch sign (chi square test, P>0.05)

The notch sign shows great promise as a reliable radiographic marker of FAI.  There is no significant association of a positive notch sign with specific features of type cam or type pincer morphology.

Visualization of a positive notch sign on cross table lateral views should prompt the interpreting radiologist to search for other radiographic findings of FAI morphology.

Petchprapa, C, Levchook, C, Raya, J, Bencardino, J, The Notch Sign: Is It a Reliable Radiographic Marker of Femoroacetabular Impingement?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12027274.html