Detection and influence factor of serum metal ions concentration level after resurfacing arthroplasty of the hip

Abstract

To observe the tendency of serum cobalt (Co), chromium (Cr), and molybdenum (Mo) ions concentration level after resurfacing arthroplasty of the hip (RSAH) by inductively coupled plasma mass spectrometer (ICP-MS), and analyze the influence factors. Forty-seven patients (55 hips) underwent RSAH between June 2005 and November 2014 who had good joint function (Harris score were >85) at every review time were selected in the study. There were 25 males and 22 females, with the mean age of 49.7 years (range, 18-64 years). The disease causes included developmental dysplasia of the hip (DDH) in 18 cases (22 hips) and non-DDH in 29 cases (33 hips). The follow-up time was 6 months to 5 years (mean, 3.2 years). The concentrations of Co, Cr, and Mo ions were measured by ICP-MS, and were compared with those of 6 normal controls. Based on the analysis of the measured results, patients were chosen and grouped according to prosthesis position and femoral head prosthesis diameter. A correlative analysis was made between serum metal ions concentration and various factors (age, body mass index, pre- and post-operative Harris scores, neck-shaft angle, and stem-shaft angle). The concentration of serum Co ion reached the peak at 1 year after operation ( P<0.05), and then slowly decreased, increased again at 4 years after operation and was close to the 2nd-year level at 5 years. The concentration of serum Cr ion reached its peak at 9 months after operation ( P<0.05), and then gradually decreased, and was close to normal level at 5 years. The concentration of serum Mo ion kept increase trend and reached the peak at 5 years ( P<0.05). Thirty-five hips of 29 patients followed up 9 months and 1 year were grouped. For DDH and non-DDH patients, Co and Cr ion concentrations of 40-45° abduction angle of acetabular component were significantly lower than those of <40° and >45° ( P<0.05), but there was no significant difference in Mo ion concentration ( P>0.05). For all patients, Co, Cr, and Mo ion concentrations of 15-20° anteversion angle of acetabular component were significantly lower than those of <15° and >20° ( P<0.05). Co, Cr, and Mo ion concentrations of ≥48 mm diameter of the femoral component were significantly lower than those of <48 mm ( P<0.05). There was a negative correlation between Co ion and postoperative Harris score ( r=-0.486, P=0.041). The serum Co and Cr ions concentrations increase obviously at 1 year and 9 months after RSAH operation, and Mo ion concentration displays an increase trend. The metal ions concentrations have close relationship with the position of acetabular component.