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Fig. 2 Strut allograft was contoured into area where blade plate was removed.
Courtesy of Anthony A. Stans, MD

AAOS Now

Published 7/1/2011
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Mary Ann Porucznik

Retained pediatric hardware increases difficulty of THA

Study finds longer surgical times and hospital stays, more complications

Leaving orthopaedic implants in children may have an impact on later total hip arthroplasty (THA) surgery, according to the results of a study presented at the 2011 annual meeting of the Pediatric Orthopaedic Society of North America.

“Retained pediatric hardware was associated with increased operative time, more intraoperative fractures, and longer hospital stays when compared to a gender- and age-matched control group,” reported Anthony A. Stans, MD, assistant professor of orthopaedics at the Mayo Clinic in Rochester, Minn.

Leave it in? Take it out?
In adults, implants are typically removed only if they become symptomatic. In children, however, the decision to remove an implant is controversial. Although removing an implant carries standard surgical risks, as well as the risk of subsequent fracture, a retained implant may eventually become intramedullary, as bone grows over it.

“The question of implant removal is particularly important in the proximal femur,” said Dr. Stans, “because children with hip problems may be at significant risk for later THA. We hypothesized that performing THA in patients with retained pediatric implants would be more difficult, compared to a matched control group without implants. We hoped to provide some insight on whether routine removal of pediatric implants in the proximal femur would be a reasonable practice standard.”

Study description
Using an arthroplasty registry, researchers found 31 patients with retained pediatric hardware who underwent THA between 1990 and 2007. More than half (17) of these patients had a diagnosis of a slipped capital femoral epiphysis (SCFE), while six patients had implants due to hip dysplasia and five had implants inserted due to trauma. The mean age at implant placement was 13.3 years (range, 3.8 years to 17 years), and the average time from implant placement to THA was 30.9 years (range: 5 years to 54 years).

The control group—patients without any implants in the proximal femur at the time of THA—was age-, BMI-, and gender-matched. The primary reason for THA in the control group was osteoarthritis. The average age at THA was 47.1 years in the control group and 44.2 years in the implant group. Both groups had just over 7 years of follow-up.

Takes longer, more complications
The mean surgical time was 230 minutes for patients with implants and 158 minutes for patients without implants (p < 0.0001). In addition, patients with implants had a longer hospital stay than those without implants (5.2 days versus 3.8 days).

Five patients with implants sustained an intraoperative fracture, three of which were directly related to the retained hardware (blade plates). In addition, one patient had markedly increased intraoperative bleeding, and one experienced immediate postoperative peroneal nerve palsy. No major complications were reported in the control group.

Based on surgical notes, the surgery itself was also more difficult in patients with implants. Nearly half (48 percent) of patients with implants required bone grafting, and revision femoral stems were required in 35 percent of patients with implants (to bypass the defect from hardware removal). Surgeons could not completely remove the hardware in five patients. All of the complications and adverse outcomes were in patients who had retained blade plates or multiple small diameter solid pins and not in patients treated with single, large diameter, stainless steel screws currently used to pin SCFE.

By final follow-up, four patients in the implant group—including two who had intraoperative fractures—and two patients in the control group had revision hip surgery. However, no differences in implant loosening were found.

Although this was a small patient series, the researcher reported that retained hardware does appear to affect the complexity of the case.

“We do not know what proportion of patients with implants placed in childhood will eventually require THAs,” said Dr. Stans. “And ideally, our control group would have been composed of patients who had a history of previous hardware removal at least one year prior to THA. But we now know that implant removal at the time of arthroplasty is associated with increased intraoperative complications. At our center, we now routinely remove proximal femoral blade plates in all skeletally immature patients.”

Coauthors for “The effects of pediatric hardware on total hip arthroplasty” include Jessica A. Woodcock, MD, and Annalise Noelle Larson, MD.

Disclosure information: The authors report no conflicts.

Bottom line

  • This small, retrospective case-control study found that patients with retained pediatric hardware at the time of THA had longer surgical times, more intraoperative fractures, and longer hospital stays than matched controls.
  • Although orthopaedic implants in children may be retained, retained implants in the proximal femur, particularly retained blade plates, increase the difficulty of later surgery for THA.
  • In skeletally immature patients, plates and small screws should be removed because these retained implants may increase the difficulty of THA.