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No link found between component position in hip resurfacing arthroplasty, metal ion levels
Adequate placement of femoral and acetabular components in computer-navigated hip resurfacing was not associated with elevated metal ion levels, according to recently published results.
Researchers prospectively identified 114 patients who underwent computer-assisted metal-on-metal hip resurfacing arthroplasty. Investigators determined cobalt and chromium ion levels by drawing a plasma sample at 1 year postoperatively and then repeated the process at either 1-year or 2-year intervals in asymptomatic patients and performed it more often in patients with clinical or radiographic concerns. With the chromium and cobalt ion levels, investigators performed two separate multiple regression analyses. The Harris hip score, University of California, Los Angeles activity score, acetabular component positon, femoral acetabular position and femoral and acetabular angles were also recorded.
Results showed the position of the acetabular component significantly changed compared with that of the native acetabulum. Investigators noted there was a 6-mm increase in the femoral vertical onset; however, the femoral horizontal offset did not change. The global offset decreased from 87.5 mm to 81.6 mm.
According to researchers, the mean gluteus medius activation angle went from 7.8° to 6.1 °. The mean abductor arm changed from 72.8 mm to 71.3 mm. There were no significant predictors seen for cobalt ion levels and chromium ion levels using regression analyses. ‒ by Monica Jaramillo
Disclosures: Mann reports no relevant financial disclosures. Please the see the full study for a list of all other authors’ relevant financial disclosures.
Perspective
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Hip arthroplasty is among the best surgeries in orthopedics and has favorable long-term outcomes. However, there is always room for improvement. This study aimed to determine acetabular and femoral component position in mechanically stable hips that underwent computer-navigated hip resurfacing and to evaluate if these were related to metal ion levels.
With mean follow-up of 4.5 years, they found the resurfaced hip had a significant increase in femoral vertical offset and a decrease in global offset, gluteus medius activation angle and abductor arm angle compared to preoperative measurements. In addition, they found no predictors of metal ion level.
In recent years, robotic and computer-navigated surgeries have played a bigger role in orthopedic surgery. These surgical modalities offer the advantages of high accuracy and reproducibility, which may lead to accurate leg length and offset, as well as improved bone stock preservation. Improved accuracy may also reduce rates of dislocations and early wear. The present study included patients who all had computer-navigated surgery and did not compare outcomes to surgeries performed without navigation. Other comparative studies have shown significant improvement in accuracy with robotics and navigation, and future long-term studies may demonstrate the clinical implications of these improvements.