Summary

BDDH often presents with a significant incidence of osseous impingement, and certain symptoms and signs exhibited similarities with Cam-type FAI. it is suggested that BDDH with osseous impingement should be classified as a distinct entity between femoroacetabular impingement and developmental dysplasia of the hip (and separate from BDDH without impingement), while excluding joint instability.

Abstract

Background

Borderline developmental dysplasia of the hip (BDDH) accompanied by Cam deformity and subspinous impingement has been found to potentially benefit from arthroscopic labrum repair, subspinous decompression, femoroplasty and capsular closure. However, the research comparing BDDH combined with osseous impingement to femoroacetabular impingement (FAI) without borderline dysplasia remains limited.

Methods

Data were retrospectively collected from a consecutive cohort of patients who underwent primary hip arthroscopy between September 2016 and October 2020. Patients were divided based on the preoperative lateral center-edge angle (LCEA) into 2 distinct groups: (1) borderline dysplasia (LCEA 18°-25°) and (2) Cam-type FAI without borderline dysplasia (LCEA 25°-40°and α > 55°).Inclusion criteria were patients aged 18-50 years who showed no significant improvement following conservative treatment. Exclusion criteria involved a positive joint instability examination, FEAR index > 5°, previous hip surgery, avascular necrosis, fracture, Tönnis grade ≥ 2. Disparities in symptoms and signs, preoperative examinations, intraoperative findings and procedures were thoroughly examined and analyzed. The patient-reported outcome scores (PROs) were compared.

Results

Follow-up was available for 61 (91.0%) patients with BDDH and 125 (86.2%) patients with
Cam-type FAI. The preoperative characteristics, including the location, nature, and severity of hip
pain, hip flexion, adductor and abductor range of motion, as well as intraoperative findings such as labral and articular cartilage injury location and severity were found to be similar between the groups (P > .05). However, preoperative internal and external motion of the hip joint, Tönnis angle, femoro-epiphyseal acetabular roof (FEAR) index, labral size, capsule thickness and the percentage of ligamentum teres tear in the BDDH group were significantly higher than those in the FAI group, and the percentage of pain aggravating factor, Cam deformity and type II/III anterior inferior iliac spine (AIIS) between groups had statistical significance (P < .05). The percentages of intraoperative minimal acetabuloplasty, subspinous decompression, labral repair, ligamentum teres debridement and capsular closure in BDDH group were significantly higher than those in FAI group, except for femoroplasty (P < .05). Postoperation PROs were significantly improvement over preoperation in both groups. However, there were no significant differences between groups in preoperative and postoperative VAS, mHHS and IHOT-12 scores, postoperative realization of minimal clinically important difference (MCID) and patient acceptable symptom status (PASS) (P >0.05).