The impact of a total hip replacement on jaw position, upper body posture and body sway

Objectives: The purpose of this study was to examine whether, and to what extent, a total hip replacement can influence the position and the movement of the jaw, the upper body posture and body sway. Methods: Twenty test subjects (6 females, 14 males) participated in this study pre- and post-total hip replacement, in addition to a healthy control group of 20 subjects (5 females, 15 males). The measurements were conducted by means of an ultrasound system to measure jaw condyle position and movement of the lower jaw, a three-dimensional back scan to analyze upper back posture, and a static and dynamic force plate to measure body sway. For statistical analysis the Wilcoxon-Matched-Pairs-Test or Man-Whitney-U-Test, including a Bonferroni-Holm correction, respectively, was used. Results: After surgery, the mean values of the left and right jaw condyles of the test group moved posterior, and the left condyle position was located more caudally. There were no significant differences concerning the jaw position between the two groups. There was little change in upper body posture in both groups. The test group had a more anteriorly inclined thoracic spine and a less pronounced lumbar lordosis. During static body sway measurements, increased fluctuations in the test group after surgery could be seen. Conclusion: Differences between both groups in the pre- and post-surgical condition could be detected. These differences were more prominent when the measured body segments were more distally located with respect to the hip region.