Hip Capsulolabral Complex: Anatomy, Disease, MRI Features, and Postoperative Appearance.

The hip is a uniquely constrained joint with critical static stability provided by the labrum, capsule and capsular ligaments, and ligamentum teres. The labrum is a fibrocartilaginous structure along the acetabular rim that encircles most of the femoral head. Labral tears are localized based on the clock-face method, which determines the extent of the tear while providing consistent terminology for reporting. Normal labral variants can mimic labral disease and can be differentiated by assessment of thickness or width, shape, borders, location, and associated abnormalities. The Lage and Czerny classification systems are currently the most well-known arthroscopic and imaging systems, respectively. Femoroacetabular impingement is a risk factor for development of labral tears and is classified according to bone dysmorphisms of the femur ("cam") or acetabulum ("pincer") or combinations of both (mixed). The capsule consists of longitudinal fibers reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral) and circular fibers. Capsular injuries occur secondary to hip dislocation or iatrogenically after capsulotomy. Capsular repair improves hip stability at the expense of capsular overtightening and inadvertent chondral injury. The ligamentum teres is situated between the acetabular notch and the fovea of the femoral head. Initially considered to be inconsequential, recent studies have recognized its role in hip rotational stability. Existing classification systems of ligamentum teres tears account for injury mechanism, arthroscopic findings, and treatment options. Injuries to the labrum, capsule, and ligamentum teres are implicated in symptoms of hip instability. The authors discuss the labrum, capsule, and ligamentum teres, highlighting their anatomy, pathologic conditions, MRI features, and postoperative appearance. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Soft Tissue Structures Differ in Patients With Prearthritic Hip Disease.

BACKGROUND: Clinically, understanding how the soft tissue envelope adapts to various forms of hip dysfunction could enhance both surgical and nonsurgical management. Very few studies have looked at soft tissue structures as preoperative discriminators between varying underlying etiologies of hip conditions. PURPOSE: To demonstrate that the magnetic resonance arthrography assessment of soft tissue structures of the hip will preoperatively differ in patients with different underlying hip joint diseases. METHODS: Fifty-seven patients who underwent preoperative magnetic resonance arthrography and corrective hip surgery were retrospectively identified yielding 3 groups: 17 with developmental dysplasia of the hip (DDH) (11 F, 6 M; mean age 35.1 years, range 19.6-53.6); 20 with isolated labral tears (LTs) (17 F, 3 M; mean age 38.4 years, range 15.2-62.1), and 20 with cam-type femoroacetabular impingement (FAI) (11 F, 9 M; mean age 38.8 years, range 18.9-51.2). Measurements of the hip labral length, capsule thickness, and psoas, rectus femoris, and gluteal muscle dimensions were performed, with normalization of the values for statistical analysis. RESULTS: The superior labral length was significantly greater in the DDH group [normalized value (NV): 0.30] compared with the FAI group (NV: 0.25, P < 0.05). In addition, the superior (12 o'clock) capsular thickness (NV: 0.24) was significantly greater compared with the LT group (NV: 0.15, P < 0.05) and the FAI group (NV: 0.16, P < 0.05). The DDH group also had a significantly greater anterior (3 o'clock) capsular thickness (NV: 0.18) compared with the LT group (NV: 0.13, P < 0.05). The transverse dimension of the rectus femoris was larger in the DDH group (NV: 1.39) compared with the FAI group (NV: 1.14, P < 0.05). CONCLUSION: An enlarged rectus femoris and thicker hip capsule as well as an enlarged labrum are characteristic findings in hip dysplasia. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Bone and soft tissue ablation.

Bone and soft tissue tumor ablation has reached widespread acceptance in the locoregional treatment of various benign and malignant musculoskeletal (MSK) lesions. Many principles of ablation learned elsewhere in the body are easily adapted to the MSK system, particularly the various technical aspects of probe/antenna design, tumoricidal effects, selection of image guidance, and methods to reduce complications. Despite the common use of thermal and chemical ablation procedures in bone and soft tissues, there are few large clinical series that show longitudinal benefit and cost-effectiveness compared with conventional methods, namely, surgery, external beam radiation, and chemotherapy. Percutaneous radiofrequency ablation of osteoid osteomas has been evaluated the most and is considered a first-line treatment choice for many lesions. Palliation of painful metastatic bone disease with thermal ablation is considered safe and has been shown to reduce pain and analgesic use while improving quality of life for cancer patients. Procedure-related complications are rare and are typically easily managed. Similar to all interventional procedures, bone and soft tissue lesions require an integrated approach to disease management to determine the optimum type of and timing for ablation techniques within the context of the patient care plan.