Landmark Study Details Key THA Outcome for Women

A team of Finnish researchers recently examined 65 postmenopausal women with hip osteoarthritis (OA) and Dorr type-A or B femoral anatomy who had total hip arthroplasty (THA) with a tapered, single-wedge femoral stem. Their study, “Volumetric Bone Mineral Density in Cementless Total Hip Arthroplasty in Postmenopausal Women: Effects on Primary Femoral Stem Stability and Clinical Recovery,” was published in the June 16, 2021 edition of The Journal of Bone and Joint Surgery.

Hannu Aro, M.D., Ph.D., Professor Emeritus of Orthopaedic Surgery and Traumatology and the University of Turku, gave background on the prospective cohort to OTW, saying, “To our knowledge, our project represents the first-ever attempt to delineate the impact of skeletal health on the success of cementless total hip arthroplasty in postmenopausal women.”

The researchers measured femoral stem translation and rotation using model-based radiostereometric analysis (RSA) within 3 days postop and then at 3, 5, and 11 months. Postoperatively, the investigators collected walking speed, walking activity, and patient‐reported outcomes data. Using the data, the researchers selected two groups, the first with less than 2mm of stem subsidence after 5 months and the second with stem subsidence equal to or greater than 2mm.

Dr. Aro detailed the study’s methodology to OTW, “The project utilized model-based radiostereometric analysis of implant migration, high-resolution QCT [quantitative computed tomography] analysis of local volumetric bone density, advanced analysis of functional recovery with an office-based inertial sensor gait analysis system and pedometer-analysis of walking activity, pulse-echo ultrasound measurements of the distal radius and serum measurements of bone turnover markers.”

The study, which was a prospective base-study and two randomized placebo-controlled trials, was sponsored by the Academy of Finland and Stryker Corporation, Novartis AG and Amgen Inc.

According to Dr. Aro, the data collected from the study seemed to indicate that, “Hip implant stability dictates the speed of functional and subjective recovery from cementless total hip arthroplasty.”

“Women with high femoral stem stability (no or minimal micromotion measured by radiostereometric analysis) had faster improvement of spontaneous walking speed and greater walking activity. Clinical recovery was slower and patient-reported outcome was less satisfactory in women with initial implant migration.”

“Implant (femoral stem) migration occurred during the first 12 weeks after surgery. Implant migration was prominent in women with low volumetric bone density in the intertrochanteric region of the proximal femur. These subjects were characterized also by high serum levels of bone turnover markers. Stem migration was temporary and did not prevent the ultimate osseointegration with the host bone. All stems were radiographically healed (osseointegrated) at two years. None of the stems has been revised during the four-year postoperative follow-up.”

“The skeletal status must be evaluated if a postmenopausal woman is scheduled to have total hip arthroplasty. Unexpectedly, it is difficult to define adequate bone stock for cementless total hip arthroplasty based on routine hip DXA [dual-energy x-ray absorptiometry] imaging. Hip DXA seems to be insensitive in detection of women at high risk of implant migration, probably due to osteoarthritic pathology of the femoral head and neck.”

“Based on preoperative plain hip radiographs, women with Dorr type-C femoral anatomy can be excluded. Dorr type-C is associated with a high rate of osteoporosis and an increased risk of periprosthetic fracture. It is concerning that our study was unable to define inadequate bone stock based on DXA-defined thresholds of osteoporosis and osteopenia.”

“However, proximal femur quantitative CT as well as the measurement of the cortical-bone thickness of the distal radius by pulse-echo ultrasound attain moderate accuracy in distinguishing women at high risk for initial implant migration. During surgery, meticulous broaching technique minimizes the risk of radiographic stem subsidence. Our randomized placebo-controlled trials have shown that femoral stem migration is resistant to antiresorptive treatment with zoledronic acid or denosumab.”