The Femoral Head “Divot” Sign: A Useful Arthroscopic Sign of Hip Microinstability

Abstract

Background: A femoral head “divot” is a rare finding during hip arthroscopy. A linear chondral indentation can be observed on the femoral head, just lateral and parallel to the acetabular labrum. Purpose/Hypothesis: The purpose of this study was to describe a novel arthroscopic sign and retrospectively review patients with this finding. We hypothesized that this sign would be found in patients with characteristics consistent with hip microinstability. Study Design: Case series; Level of evidence, 4. Methods: Intraoperative images of patients undergoing primary hip arthroscopy between July 2017 and July 2019 were reviewed for evidence of a femoral head divot. Preoperative characteristics, physical examination findings, radiographic measurements, and magnetic resonance imaging (MRI) findings were described. Results: Of 690 available cases, 14 cases (13 patients; 2.0%) had evidence of a femoral head divot. The mean patient age was 29.1 years, and all but 1 patient (92.3%) were female. Ligamentous laxity was present in 81.8% of patients, anterior apprehension test was positive in 78.6%, and painful internal snapping was present in 50.0%. The mean lateral center-edge angle, anterior center-edge angle, and Tönnis angle were 19.2°, 20.3°, and 12.4°, respectively. The divot was identified in 5 of 12 available MRI scans, most commonly on axial proton density sequence. Intraoperatively, all hips had labral tears, iliopsoas bursitis was demonstrated in 78.6%, and the ligamentum teres was damaged in 42.9%. Labral repair was performed in 12 of the 14 hips, with 2 patients undergoing labral reconstruction. Iliopsoas fractional lengthening was performed in 50.0%, capsular plication was performed in 78.6%, and capsular repair was performed in the remainder. Conclusion: The femoral head divot sign is a rare arthroscopic finding during hip arthroscopy. The results of this study demonstrated that patients who have a divot also present with characteristic radiographic or physical examination findings of hip microinstability due to either acetabular dysplasia or ligamentous laxity. Recognition of a femoral head divot may be valuable for the diagnosis of microinstability during hip arthroscopy and may help guide appropriate management, such as capsular plication. Further studies are needed to determine the exact prevalence of the femoral head divot in patients with microinstability and to evaluate the effect of this finding on patient outcomes.

Female gender, decreased lateral center edge angle and a positive hyperextension–external rotation test are associated with ease of hip distractability at time of hip arthroscopy

“…Both studies found that male sex was correlated with higher traction forces required for adequate hip distraction, thus increasing their risk of traction‐related injury. Similarly, prior investigations of hip microinstability have described majority female populations [12, 13, 20, 24]. Hormonal differences, particularly in serum relaxin concentrations, have been proposed as a cause of higher incidences of ligamentous laxity in female patients [8].…”

Central Femoral Head Chondromalacia Is Associated with a Diagnosis of Hip Instability

“…described a femoral head divot sign in 14 patients, identifying a linear chondral indentation on the femoral head just lateral and parallel to the acetabular labrum in patients identified to have hip microinstability. 10 They proposed that, in the setting of microinstability, this area may experience repetitive edge loading leading to the head deformation.…”

“…2 , 8 Making the diagnosis of microinstability is based on a multitude of factors that are identified through a thorough history and physical exam, imaging studies, and intraoperative findings. 1 , 2 , 4 , 5 , 9 , 10 Moreover, the diagnosis of hip microinstability can occur with normal radiographs or be a concurrent diagnosis with labral injuries, femoroacetabular impingement (FAI), hip dysplasia or borderline dysplasia. Therefore, a high index of suspicion is necessary to make the diagnosis.…”

Pre- and intraoperative decision-making challenges in hip arthroscopy for femoroacetabular impingement

“…113,114 Arthroscopic evaluation of the joint can show classical patterns of inside-out chondral wear of the acetabulum and central femoral head wear or the 'divot' sign. 115 In addition, fluoroscopic assessment of the hip joint to analyze the degree and ease of femoral head distraction can be informative. 110 Initial treatment involves activity modification, strengthening the surrounding hip musculature and core muscles through physiotherapy.…”