The effect of perceived LLD on lower limb load characteristics during early postoperative static standing in patients who underwent THA

Abstract

Background: Many patients complain about Perceived LegLengthDiscrepancy (P-LLD) followingTHA, regardless of the degree of actual LLD evaluated by X-ray (XP-LLD). Purpose: To clarify the effect of P-LLD on lower limb load characteristics during early postoperative static standing following THA. Methods:The subjects of this studywere 15 unilateral hip osteoarthritis patients who underwent THA. The subjects’ P-LLD, lower limb load characteristics in a static standing position (operated side lower limb load ratio, pelvic inclination angle, trunk inclination angle, pelvis/trunk inclination angle, operated side hip adduction ROM, and operated side hip adduction moment), and patient characteristics (Operated side hip extension ROM, operated side hip abduction torque, pain, and satisfaction) were measured on day 7, 14, and 21 post-operation (POD7, 14, 21). Patients who felt a LLD of 0.5 cm or more were considered as having P-LLD. Subjects with an actual LLD of 0.5 cm or more were considered as having XP-LLD. In statistical analysis, subjects were divided into three groups on each measurement day: subjects with both XP-LLD and P-LLD (Group A), subjects with no XP-LLD but with P-LLD (Group B), and subjects with no XP-LLD and no P-LLD (Group C) and compared with each item. Results:Significant differenceswere observed in operated side lower limb load ratio and operated side hip adduction moment on POD7.Namely, the operated side lower limb load ratio was significantly lower in Group B compared to Group C, and the operated side hip adduction moment was lower in Groups A and B compared to Group C. The operated side hip adduction ROM was also more limited in Groups A and B compared to Group C, although the difference was not statistically significant (p= 0.082). A significant difference was observed in operated side hip adductionmoment on POD14 – the operated side hip adduction moment was lower in Groups A and B compared to Group C. The operated side lower limb load ratio was also lower in Groups A and B compared to Group C, although the difference was not statistically significant (p= 0.074). Significant differences were observed in pain and satisfaction on POD 21 – Group B had significantly stronger pain and lower levels of satisfaction than Group C. Conclusion(s): Subjects with P-LLD on POD7 find it difficult to create an adduction moment with load on the abducted operated side hip, and their adduction moment is also reduced as a result of the lower operated side lower limb load. Although there were improvements with respect to load on the abducted operated side hip on POD14, groups with P-LLD had reduced adduction moment as a result of their continued low operated side lower limb load. From results of POD21, sustained postoperative pain has an effect on the persistence of P-LLD, and the persistence of P-LLD also affects satisfaction during the early postoperative period. Implications: It was suggested that increasing the amount of load on the abducted operated side hip during static standing in the early postoperative period to promote creation of an adduction moment on the operated side hip can improve P-LLD.