Younger THA patients show activity levels similar to their older counterparts

Patients with a higher BMI demonstrated decreased walking activity, suggesting the negative relationship between BMI and activity is also valid for patients aged 50 years and younger.

Younger patients may not be as active as previously believed after undergoing total hip arthroplasty, and may actually exhibit activity levels similar to more elderly hip replacement patients, according to a study by Minnesota researchers.

"In our study of patients with a mean age of 42 years at the time of surgery and a mean age of 50 years at the time of follow-up, the average number of gait cycles per year was 1.2 million. Interestingly, this value is consistent with what has been reported in studies of older patients after THA (total hip arthroplasty)," the authors said in the study.

V. Franklin Sechriest II, MD, and colleagues evaluated postoperative activity levels among patients aged 50 years and younger who underwent primary THA. The researchers used digital pedometers and pedometer-based activity logs provided to patients to document their average number of gait cycles per day and estimate annual cycles. They also contacted patients by telephone for updates on medical histories and to complete follow-up Harris Hip questionnaires, according to the study, published in the Journal of Arthroplasty.

The study included 41 primary THAs in 34 patients (17 men and 17 women). In all cases, surgeons implanted a porous-coated acetabular component (Reflection, Smith & Nephew) with its modular Reflection Microstable polyethylene liner. All cases also received cementless femoral stem components — either the Anatomic or Anatomic Bias Revision (Zimmer) — and either a cobalt chrome or alumina ceramic femoral head with a 22-mm or 28-mm diameter.

At 6.3 years mean follow-up, the researchers found that Harris Hip scores had significantly improved from a preoperative mean of 55 to average 81 at follow-up (P<.001).

Also at follow-up, 17 patients (50%) reported having undergone surgery on their contralateral hip and 17 patients (50%) reported having another artificial hip or knee joint, according to the study.

Patients had a mean self-reported UCLA activity score of 6.3. "Patients with a history of contralateral hip surgery perceived themselves as less active and thus had significantly lower UCLA scores. Likewise, patients with more than one artificial joint rated themselves lower on the UCLA 10-point scale," the authors said, noting that UCLA scores positively correlated with Harris Hip scores.

However, UCLA scores did not correlate with the number of index hip surgeries, age, body mass index, weight or gait cycles per year, according to the study.

Annual gait cycles averaged 1.2 million, and increased BMI negatively correlated with the number of cycles (P=.002). Advanced age also negatively correlated with fewer cycles, but the correlation did not reach statistical significance. In addition, the researchers found no correlation between the number of gait cycles and presence of other artificial joints, the number of contralateral hip surgeries or UCLA scores, according to the study.

"It has been previously shown in older populations after arthroplasty that those with a higher BMI demonstrate a decreased level of walking activity. Our study suggests this relationship remains valid for patients in their 30s, 40s and 50s as well," the authors said.

For more information:
Sechriest VF, Kyle RF, Marek DJ, et al. Activity level in young patients with primary total hip arthroplasty. A 5-year minimum follow-up. J Arthroplasty. 2007;22:39-47.