RÉSUMÉ
INTRODUCTION: The MoPyc radial head arthroplasty (RHA) is a monopolar implant with a pyrocarbon head that obtains rigid fixation via controlled expansion of the titanium stem. The aim of this study was to evaluate the short to midterm outcomes of MoPyc RHA. MATERIALS AND METHODS: Between 2002 and 2021, 139 MoPyc RHA were implanted in 139 patients with a RH fracture. The mean follow-up was 5.9 years ±3.5 (range 1-16). Range of motion, mean Mayo Elbow Performance score (MEPS), quick disabilities of the Arm, Shoulder and Hand (quickDASH) score, visual analog scale (VAS), radiographic outcome, and reason for failure were recorded. RESULTS: The mean MEP, QuickDASH, and VAS scores were 89.1± 2.2(range, 45-100), 17.5±16.7(range, 0-78), and 0.8±1.6(range, 0-50), respectively. Stress shielding (SS) and osteolysis around the stem (OAS) were identified in 92(66%) and 20(14%) patients. A total of 47(29%) patients experienced at least one complication; and 29(21%) of them required re-intervention. Persistent stiffness (n=12;9%) was the most common complication. No painful loosening was noted. Osteolysis around the stem, presence of an autoexpanding stem, and overstuffing were associated with a lower MEPS and an increase in VAS (p<0.05). Stress shielding (SS) was associated with an increase in MEPS (aß=6.92; p<0.001) and lower VAS (aß=-0.69; p=0.016). The auto-expending stem increased the likelihood of SS after RHA (aOR=1.49; p=0.001). CONCLUSIONS: A well-fixed MoPyc RHA provided satisfactory short to midterm outcomes, without painful loosening. However, the autoexpanding stem system was associated with poorer functional outcomes and increased the likelihood of SS.
RÉSUMÉ
BACKGROUND: 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. MATERIALS AND METHODS: 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: SS 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 (adjusted odds ratio = 13.66; P = .001), and expansion of the stem (adjusted odds ratio = 3.78; P = .001). The amount of the SS was significantly correlated with expansion of the stem (aß 4.58; P < .001). CONCLUSIONS: Our study found that MD:CW was an independent risk factor of SS after MoPyc radial head arthroplasty. Autoexpansion of the MoPyc stem significantly increased the risk of SS and its extent. Further studies involving multiple implants designs are needed to confirm the preliminary observations presented in the current study.