Mild generalised hypermobility (Beighton score ≥2) is the most accurate preoperative indicator of intraoperatively-confirmed microinstability in 622 primary hip arthroscopies.

Purpose: To identify the preoperative diagnostic accuracy of routine hip arthroscopy clinical assessments for intraoperatively confirmed microinstability. Methods: Image indices, clinical assessments and operation details from 622 consecutive primary hip arthroscopies undertaken by a single surgeon between January 2018 and December 2020 were extracted from the surgeon's database. Microinstability diagnosis was retrospectively confirmed by the presence of any of four intraoperative criteria: increased ease of distraction of the hip, isolated straight anterior labral tear, inside-out chondral lesion or a lateral Seldes 2 or 3 labral tear in the absence of cam or pincer morphology. Optimal thresholds for numerical measures were determined using receiver operating characteristic curve (ROC) analyses by minimising the distance from the point of perfect sensitivity and specificity. Diagnostic parameters, calculated from contingency tables, were evaluated for individual and combinations of demographic, examination and imaging indices, including age, self-reported gender, risk-sport participation, positive log roll/hip dial test, Beighton score, hip range-of-motion, lateral centre-edge angle (LCEA), Tonnis angle, crossover sign and ischial sign. Results: A total of 622 hips (533 patients) aged 35.5 ± 11.8 years, 56%:44% female:male ratio were identified. Female patients were 2.08 times more likely than male to have microinstability (sensitivity 0.93, specificity 0.55). A Beighton score ≥2 was the best overall indicator of microinstability (sensitivity 0.85, specificity 0.82, positive likelihood ratio 4.73, negative likelihood ratio 0.18). Presence of female gender, with either LCEA < 35° or Beighton score ≥2, increased sensitivity to 0.93, at the expense of specificity (0.69) and no combination of indices surpassed Beighton score alone in the Youden index (sensitivity + specificity - 1). Conclusion: Among the individual and combined presurgical indicators evaluated, Beighton score ≥2 was the most accurate test for intraoperatively-confirmed microinstability in primary hip arthroscopy patients. Mild generalised laxity, particularly in female patients with a slightly shallow acetabulum (LCEA < 35°), should raise suspicion of microinstability to minimise missed diagnoses. Level of Evidence: Level III, diagnostic study.