RESUMO
INTRODUCTION: We sought to assess if the medullary diameter to cortical width ratio (MD:CW), canal flair index (CFI), and canal fill (CF) of the proximal radius were associated with the presence of Stress shielding (SS) after a MoPyC radial head arthroplasty (RHA). MATERIAL & METHOD: We conducted a retrospective, international, multicenter (4 centers) study. A total of 100 radial head arthroplasties in 64 women and 36 men with a mean age of 58.40 years ±14.90 (range, 25.00; 91.00) were included. Radiographic measurements, including MD:CW, CFI, CF, and postoperative SS were captured at a mean follow-up of 3.9 years ±2.8 (range, 0.5-11). RESULTS: Stress shielding was identified in 60 patients. Mean preoperative MD:CW, CFI, and CF were 0.55 ±0.09, 1.05 ±0.18 and 0.79±0.11, respectively. The presence of SS was significantly associated with MD:CW (aOR=13.66; p=0.001), and expansion of the stem (aOR=3.78; p=0.001). The amount of the SS was significantly correlated with expansion of the stem (aß 4.58; p<0.001). CONCLUSIONS: Our study found that MD:CW was an independent risk factor of SS after Mopyc RHA. Patients with longer and larger diameter (auto-expansion) Mopyc stems were also at significantly increased risk of SS. Further studies involving multiple implants designs are needed to confirm the preliminary observations presented in the current study.