Obesity and Hip Replacements

Overweight and obesity are well-established risk factors for osteoarthritis and a major factor in driving the increasing demand for hip and knee replacements.

How does being overweight or obese affect functional outcomes of hip surgery?

This question was addressed by André Busato and colleagues from the Institute for Evaluative Research in Orthopaedic Surgery, University of Berne, Switzerland in a paper just out in Obesity Surgery.

Busato and colleagues quantified the role of high preoperative BMI on long-term pain status and functional outcome after total hip replacements in a multi-center cohort of 20,553 primary hip replacements (18,968 patients) and 43,562 postoperative clinical examinations for a follow-up period of up to 15 years.

Despite equal pain relief in obese and lean patients, there was an almost perfect dose-effect relationship between preoperative BMI and decreased ambulation during the follow-up period.

This means that despite improvement in pain, patients with higher BMIs tend to regain less mobility following the hip replacement.

While the authors suggest that lifestyle management and pre- or post-surgical weight loss will improve outcomes, this has yet to be demonstrated in a large randomized trial.

It may well be that other factors unrelated to pain may be affecting mobility in heavier patients. In fact many factors that may have led to the weight gain in the first place may not be resolved simply by having a hip replacement.

This observation is not different from that of a previous study that I recently blogged on which reported that back surgery for pain relief in patients with spinal stenosis does not automatically result in increased mobility or weight loss.

Obesity is a multifactorial chronic disease and the long-term impact of educational and behavioural interventions is modest at best.

When present, obesity has to be addressed with the same interdisciplinary acumen and persistence as any other chronic disease.

AMS
Edmonton, Alberta

Back Surgery Does Not Cure Obesity

Immobility, due to pain or otherwise, is certainly a major contributor to weight gain. Pain is indeed often presented by overweight and obese patients as a factor limiting their ability to lose weight.

Given the widely-held (but false!) belief that exercise is the most effective way to lose weight, the general expectation of both patients and health professionals is probably that restoring mobility by relieving pain will enable patients to be more physically active and thereby lose weight.

But is this actually the case?

This issue was recently addressed by Ryan Garcia and colleagues from the Department of Orthopaedic Surgery, Case Western Reserve University, Cleveland, OH in a study just out in the Journal of Bone and Joint Surgery.

Garcia and colleagues examined weight changes in 63 overweight and obese patients with neurogenic claudication who experienced substantial pain relief after lumbar decompression surgery for spinal stenosis. Although Zurich Claudication Questionnaire (ZCQ) Symptom Severity and Physical Function scores significantly improved by a mean of 56.4% and 53.0%, respectively, body weight and BMI significantly increased by 2.48 kg and 0.83 kg/m(2), respectively.

Overall, an average 34 months after surgery, 35% of the patients had actually gained at least 5% of their preoperative body weight while only 6% of the patients weighed at least 5% less than before their operation. The vast majority (59%) remained within 5% of their preoperative body weight.

This study, consistent with several previous studies on joint surgery, nicely documents that increased mobility after pain-alleviating surgery does not necessarily translate into weight loss - in fact, most people will either continue to gain weight or simply stay the same.

Obviously, this should not be an argument against alleviating pain in obese patients - no one deserves to live with pain. It just goes to show that increased mobility alone is not likely to substantially lower body weight - at best, it may prevent further weight gain (difficult enough even at the best of times).

This is probably something patients should be counseled about to not raise any false expectations.

On the other hand, it is important to note that this was not a weight-loss study. This means, that patients were not expressly counseled for weight loss or offered obesity treatments.

The question therefore remains whether or not improving mobility in patients by alleviating pain would improve efficacy of obesity management strategies (which I believe it would).

That is obviously a study that remains to be done.

AMS
Edmonton, Alberta