Ultrasound measurement of the effects of high, medium and low hip long-axis distraction mobilization forces on the joint space width and its correlation with the joint strain

Abstract

Background: No study has evaluated the mechanical effect of different magnitudes of long axis-distraction mobilization (LADM) force on hip joint space width (JSW) or the association between the separation of joint surfaces and the strain on hip capsular ligaments.

Objective: To compare the joint separation when applying three different magnitudes of LADM forces (low, medium and high) and to analyse the correlation between joint separation, strain on the inferior ilio-femoral ligament and magnitude of applied force.

Design: Repeated measures controlled laboratory cadaveric study.

Methods: Three magnitudes of force were applied to 11 cadaveric hip joints (mean age 73 years). Ultrasound images were used to measure joint separation, and strain gauges recorded inferior ilio-femoral ligament strain during each condition.

Results: The magnitude of joint separation was significantly different between low (0.23 ± 0.19 mm), medium (0.72 ± 0.22 mm) and high (2.62 ± 0.43 mm) forces (p < 0.001). There were significant associations between magnitude of force, joint separation and the strain on the inferior ilio-femoral ligament during LADM (r > 0.723; p < 0.001).

Conclusion: Hip joint separation and ligament strain during LADM are associated with the magnitude of the applied force.