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Early Weight Bearing Does Not Appear to Increase Risk of Loosening in Uncemented Cementless Hip Replacement

For patients who have undergone an uncemented total hip arthroplasty (replacement), rehabilitation includes limited/partial weight bearing on the affected hip for a period of six to 12 weeks to reduce the risk of the stem of the implant moving, resulting in the bone not being able to settle and to solidly hold the implant.

This approach has not been backed up through studies. The authors of this study wanted to see if it was possible for patients to begin earlier weight bearing without affecting the implants' stability. To do this, the researchers enrolled 43 patients who received an uncemented CLS hip stem arthroplasty; however, one patient died two weeks after surgery due to a pulmonary embolism (clot to the lung), so results were based on 42 patients.

The researchers evaluated the patients' bone density in most of the patients; two patients could not be measured. All patients, average age 54.5 years, had osteoarthritis of the hip and weighed no more than 100 kg. After surgery, the patients were randomized, 21 per group, to unrestricted weight bearing (UWB) or partial weight bearing (PWB). Although patients were allowed to have paracetamol and morphine for pain, as needed, nonsteroidal anti-inflammatory drugs (NSAIDs) were not given for the first week after surgery. Patients also received heparin, to reduce the risk of blood clots, and antibiotics to reduce the risk of postoperative infections.

The patients in the UWB group underwent intensive physiotherapy for the first three months after surgery, which included full weight bearing in addition to flexion and strength exercises. They also trained in the water for the first four to six weeks, and cycling on an ergometer bicycle was added at seven weeks.

The patients in the PWB group began with crutches, limiting their weigh bearing on the affected hip, while the UWB group patients only used crutches if they felt they needed them. The PWB group followed instructions that "focused on cautious training," allowing full weight bearing only after three months.

For evaluation, the weight bearing was evaluated before surgery at 1 week after surgery, and again at three, six, and 12 months after surgery. Clinical evaluations were done before surgery and at one week, and then again at one, three, 12, and 24 months. The findings were based on the 42 patients, two of whom had surgery on the other hip during the study period. One patient in the UWB group had revision surgery due to loosening, at 1.5 years after the initial surgery. The researchers found no significant differences between the two groups of patients and the ability of the implant to become fixed. The authors wrote, "We combined early full weight bearing with a vigorous physiotherapy program including loaded exercises and ergometer cycling. However, this very active regimen did not significantly affect the measured parameters, compared with our current rehabilitation program with PWD for three months."

References: Hakan Strom, MD, et al. The Effect of Early Weight Bearing on Migration Pattern of the Uncemented CLS Stem in Total Hip Arthroplasty. In The Journal of Arthroplasty. December 2007. Vol. 22. No. 8. Pp. 1122-1129.

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