Periprosthetic bone mineral density after total hip arthroplasty with an AMIStem or Quadra femoral component performed by a minimally invasive anterior approach (AMIS): a prospective randomized clinical dual-energy X-ray absorptiometry study

Introduction

This prospective 12 months of dual-energy X-ray absorptiometry (DEXA) study evaluated differences in periprosthetic bone mineral density in 40 patients undergoing cementless total hip arthroplasty (THA) by a minimally invasive anterior approach (AMIS), using Medacta AMIStem or Quadra stems. Both stems are straight rectangular. AMIStem shows reduced lateral flare and length in comparison to Quadra.

Objectives

The main goal of the study is to verify if bone mineral density is equivalent following THA with the AMIStem and Quadra femoral components.

Methods

Forty patients were randomly allocated to the Quadra and AMIStem groups. Three patients were lost to follow-up because they moved to another town, and revision surgery was performed on one patient due to periprosthetic fracture after a car accident. Patients were examined clinically and underwent DEXA preoperatively and at 1 week, 6 weeks, 6 months, and 1 year after THA. Patients enrolled had no preexisting lower limb arthroplasty and no osteoporosis.

Results

Harris hip score increased significantly for Quadra stem 5.3?±?14.1 and AMIStem 41.0?±?13.4. The high-activity hip score increased significantly for Quadra stem 3.8 ±2.2 and AMIStem 4.1?±?2.4. Considering 0.15 mg/cm² as an acceptable difference, bone mineral density for AMIStem and Quadra groups was statistically equivalent. A limited remodeling process with slight bone loss in the proximal calcar region R7, as expected after implantation of uncemented components, was observed for both stems.

Conclusions

The study demonstrates that the two stems are statistically equivalent in all zones at all time points investigated.