[Translated article] Comparison of leg length discrepancy correction after the use of a modular neck stem and its monoblock homologue in total primary hip arthroplasty.

INTRODUCTION AND OBJECTIVE

Dual modularity stems seek to more precisely restore anatomy by allowing intraoperative adjustments thanks to modular necks. Our aim is to compare the radiographic length correction with the H MAX-M® Stem versus its monoblock counterpart H MAX-S®.

MATERIAL AND METHODS

A prospective cohort study was carried out through consecutive sampling on patients who underwent primary total hip arthroplasty with coxarthrosis diagnosis between 2011 and 2015. One arm of the cohort included patients who were operated with a modular stem and the other with a monobloc stem. Length was measured on the anteroposterior pelvic-bearing radiograph at 6 months. The mean of the measurements obtained for each arm of the cohort were compared with each other.

RESULTS

No statistically significant differences were observed in the correction of asymmetry between both groups, determined as the difference in length between the operated hip and the contralateral hip (p=.106). Nor were differences observed in postoperative length values (p=.053). It should be noted that for both the modular stem and the monobloc stem, the majority group is the one with restored length (84.1% and 80.4%, respectively; p=.001).

CONCLUSION

Despite the theoretical advantage of modularity and that having interchangeable parts could be of great interest, in our study, we have not been able to demonstrate a superiority of modular designs compared to monoblock for control of postoperative leg length discrepancy.