Patients in this study showed good fixation and no revision hip arthroplasty surgeries at 10-year and 12-year follow-up, but researchers noted severe stress shielding in almost half of the cases.
Tomofumi Nishino, MD, and colleagues followed 41 patients who underwent total hip arthroplasty (THA) using Synergy stems [Smith & Nephew; Memphis, Tenn.] with a minimum 10-year follow-up, according to the abstract. They noted first-degree stress shielding in 8 hips, second-degree stress shielding in 20 hips, third-degree stress shielding in 13 hips and fourth-degree stress shielding in 9 hips. They also noticed spot welds in Gruen zone 3 in 35 hips and zone 5 in 32 hips.
“Total hip arthroplasty using Synergy stems for 50 hips showed favorable results even at 10 [years] to 12 years after surgery, with follow-ups conducted in 94% of cases,” Nishino and colleagues wrote in the study. “Although roentgenology showed favorable fixation and no reimplantations were performed, severe stress shielding was observed in nearly half of the cases. Stress was concentrated at the border of the distal stem surface coating in 80% of cases, and bone remodeling was observed.”
The researchers found that the degree of stress shielding was higher for patients with distal bone remodeling.
“Multiple regression analysis showed that stem size and short patient height, which arises because of a mismatch in the size of the stem and the femoral bone, are the stress shielding determinants,” Nishino and colleagues wrote.
Disclosure: The authors have no relevant financial disclosures.