My name is Richard Van Tienderen, and Dr. Westerman and I would like to thank ANA for the opportunity to contribute this section on subspine impingement to the ANA HIP toolkit. Dr. Westerman has the following disclosures. Surgical treatment of femoral acetabular impingement, or FAI, has demonstrated superior outcomes in comparison to conservative care and physical therapy. It has been shown to lead to high patient satisfaction and rates of return to sport in several prospective multicenter randomized controlled trials. In addition, correction of intraarticular hip impingement has been shown to normalize contact stresses within the hip joint. So, as long as we adequately fix the labral pathology and correct the intraarticular impingement, everyone can high-five and go home, right? Well, sometimes it's more complicated. An adequate evaluation of hip pain needs to also take into consideration various causes of extraarticular hip pain to include psoas pathology and subspine, ischiofemoral, and greater trochanteric impingement. For the purposes of this presentation, we will be focusing on the identification and treatment of subspine impingement. The identification and correction of subspine impingement is important in optimizing patient outcomes. This study by Larson from AJSM in 2014 found that nearly 46% of revision hip arthroscopy cases had subspine impingement morphology, and the identification and treatment of subspine impingement was associated with significant improvement in patient outcome scores after revision hip surgery. Subspine impingement has been defined as irregular contact between the anterior inferior iliac spine and the femoral neck. Morphologic changes to the anterior inferior iliac spine often contribute to this form of impingement. On physical examination, patients experience pain in the typical hip impingement position of flexion, adduction, and internal rotation. But subspine impingement also commonly elicits pain and limits functionality with maximum hip flexion. Radiographically, the false profile view gives the best view of subspine morphology. A dumb lateral view can also be utilized. 3DCT is often utilized to further characterize the deformity. Anterior inferior iliac spine morphology has previously been classified into types I, II, or III. Type I morphology is defined as a smooth ilium wall between the anterior inferior iliac spine and acetabular rim. With type II morphology, the anterior inferior iliac spine prominence extends to the acetabular rim. And type III morphology is when the prominence extends distally to the acetabular rim. This study out of arthroscopy in 2019 was a retrospective observational study that utilized CT scan and 3D modeling to analyze subspine morphology and impingement in patients with a previous diagnosis of FAI. They observed abnormal contact consistent with subspine impingement in approximately 24% of patients. Type I subspine morphology was the most common at 52%. 41% had type II, and 6.5% had type III morphology. An additional finding of interest was the association between femoral version and subspine impingement. The median femoral version for patients with subspine impingement was less than 6 degrees, and the optimal cutoff value to suspect subspine impingement morphology was less than 8 degrees with 82% sensitivity and 70% specificity. This relationship between femoral version and FAI is important as previous literature has reported on the high rate of abnormal femoral version in patients with symptomatic FAI. Measurements for femoral version can be obtained from CT scans that include both the femoral neck and the femoral condyles. Femoral version is then measured by the angle formed by the long axis of the femoral neck and aligned parallel to the posterior aspect of the femoral condyles. Prone evaluation to measure passive hip internal rotation can also be utilized to estimate femoral version. Gait evaluation will demonstrate neutral to outward foot progression. This study published in AJSM in 2019 by Lerch found that low femoral version in combination with FAI presented with significant decreases in hip flexion and internal rotation, 32% combined intra and extra articular impingement with hip flexion and high rates of subspine impingement in the fader position with the area of impingement extending to the distal aspect of the femoral neck. The anterior inferior iliac spine serves as the attachment site for the direct head of the rectus as well as the iliocapsularis and lies just proximal to the hip capsule as well as the anterior and superior labrum. Labral bruising can be an arthroscopic finding of subspine impingement. Subspine decompression begins with standard diagnostic arthroscopy with an interportal capsulotomy. Interoptive fluoroscopic imaging is utilized concurrently to verify instrument position. A window is developed between the labrum and the anterior inferior iliac spine while protecting the capsule. A burr is introduced through the interportal capsulotomy for distal decompression. To gain more proximal access without capsule disruption, a pericapsular window is created by making a window through the rectus tendon and the proximal capsule. This allows for proximal decompression. Sometimes two or three pericapsular windows are needed to complete a comprehensive decompression. All other intraarticular hip pathology can be addressed concurrently. This case involved an anterior inferior iliac spine fracture with fragment instability and therefore required a more thorough release of the rectus tendon. A burr was then introduced through multiple pericapsular windows for complete fracture removal. This technique allows for decompression of subspine impingement while allowing for treatment of intra-articular hip impingement and labral pathology concurrently. It is important to keep in mind that subspine impingement extends distally on the femoral neck, and therefore distal camera section is also necessary for a complete decompression. In conclusion, subspine impingement is a form of extra-articular hip impingement that frequently occurs concurrently with intra-articular hip impingement and is associated with low femoral anteversion. Impingement can occur in both terminal flexion and the fader positions. Not addressing subspine impingement is commonly associated with the need for revision surgery. Finally, the use of pericapsular windows allows for proximal decompression of the anterior inferior iliac spine while allowing for capsule preservation. Thank you.

subspine impingement

hip pain evaluation

femoral acetabular impingement

surgical correction

comprehensive treatment