Clinical Outcomes After Arthroscopic Treatment of Extraspinal Diffuse Idiopathic Skeletal Hyperostosis (DISH) Involving the Hip Joint.

Objective: The hip joint can be affected by extraspinal diffuse idiopathic skeletal hyperostosis (DISH). This study aimed to compare the clinical characteristics of hips with DISH to those with mixed-type femoroacetabular impingement symptoms (FAIS). In addition, patient-reported outcome (PRO) scores were reported among patients with DISH involving the hip joint who underwent arthroscopic treatment.

Methods: A retrospective analysis was performed using data from patients who underwent hip arthroscopy between 2017 and 2021. Patients who had a preoperative diagnosis of extraspinal DISH of the hip joint and postoperative Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports Subscale (HOS-SSS), International Hip Outcome Tool 12-component form (iHOT-12), modified Harris Hip Score (mHHS) and visual analog scale (VAS) for pain scores were enrolled in the study. The patients' characteristics were compared with those of a control group (1:2) consisting of mixed-type patients with FAIS. The control group was matched in terms of age, sex, body mass index (BMI), and symptom duration.

Results: Eleven hips (0.87%) with extraspinal DISH (study group) were matched to 22 FAIS hips (control group). All the patients were male. The mean age of patients was 42.0 ± 8.0 in the study group. The study group was characterized by a larger preoperative alpha angle (79.1 ± 6.8 vs 64.8 ± 9.7, P < .001), lateral center-edge angle (LCEA) (49.7 ± 6.0 vs 40.7 ± 3.2, P < .001), and postoperative LCEA (36.6 ± 3.0 vs 34.2 ± 2.0, P = .013). In addition, a higher proportion of acetabular (81.8% vs 31.8%, P = .007) and femoral head chondral lesions (45.5% vs 9.1%, P = .016). Cartilage damage has the potential to affect the prognosis of arthroscopic treatment. Nevertheless, at the final follow-up, patients with DISH experienced a significant increase in range of motion (ROM), notable enhancements in all PROs, and favorable rates of minimal clinically important difference (MCID) for the PROs.

Conclusion: The occurrence of DISH in the hip joint is considerably infrequent, characterized by hip pain and limited ROM. Despite increased alpha angle and LCEA, and more acetabular and femoral head chondral damage noted at the time hip arthroscopy, patients with DISH observed a significant improvement in ROM, notable enhancements in all PROs, and favorable rates of MCID for the PROs.