Patient-Specific Parameters Associated With Traction in Primary and Revision Hip Arthroscopic Surgery

Background: Distraction of the hip joint is a necessary step during hip arthroscopic surgery. The force of traction needed to distract the hip is not routinely measured, and little is known about which patient factors may influence this force. Purpose: To quantify the force of traction required for adequate distraction of the hip during arthroscopic surgery and explore the relationship between hip joint stiffness and patient-specific demographics, flexibility, and anatomy. Study Design: Case series; Level of evidence, 4. Methods: A total of 101 patients (61 female) undergoing primary hip arthroscopic surgery were prospectively enrolled. A load cell attached to the traction boot continuously measured traction force. Fluoroscopic images were obtained before and after traction to measure joint displacement. The stiffness coefficient was calculated as the force of traction divided by joint displacement. Relationships between the stiffness coefficient and patient demographics and clinical parameters were investigated using a univariable regression model. The regression analysis was repeated separately by patient sex. Variables significant at P < .05 were included in a multivariable regression model. Results: The instantaneous peak force averaged 80 +/- 18 kilogram-force (kgf), after which the force required to maintain distraction decreased to 57 +/- 13 kgf. In univariable regression analysis, patient sex, alpha angle, hamstring flexibility, and Beighton hypermobility score were each correlated to stiffness. However, patient sex was the only significant variable in the multivariable regression model. Intrasex analysis demonstrated that increased hamstring flexibility correlated with decreased final holding stiffness in male patients and that higher Beighton scores correlated with decreased maximal stiffness in female patients. Conclusion: Male patients undergoing primary arthroscopic surgery have greater stiffness to hip distraction during arthroscopic surgery compared with female patients. In male patients, stiffness increased with decreasing hamstring flexibility. In female patients, increased Beighton scores corresponded to decreased stiffness. The presence of a labral tear was not correlated with stiffness to distraction. These data may be used to identify patients in whom a specific focus on capsular repair and/or plication may be warranted.