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Severely obese patients slated for total knee replacement had generally better outcomes when they lost substantial weight beforehand through bariatric surgery, compared with usual treatment in a randomized trial.

Not only did the group undergoing laparoscopic gastric banding have a lower rate of complications -- 14.6% versus 36.6% in the control group (P=0.02) -- but nearly one-third of the group ended up declining knee surgery because of symptom improvement compared with 5% of controls, reported Michelle M. Dowsey, BHealthSci, MEpi, PhD, of the University of Melbourne in Australia, and colleagues .

They attributed much of the difference in complication rates to the latter result. Among the patients in the lap-band group who actually underwent knee replacement, duration of hospital stay and need for inpatient rehabilitation were similar to patients in the usual-care group, as were the number of reoperations and readmissions.

Overall complication rates did still favor the lap-band group, however. Six of the 29 (20.6%) who underwent knee replacement experienced one or more of the researchers' prespecified complications, versus 15 of 39 (38.5%) in the control group. Wound complications accounted for a big chunk of the difference: there were eight among controls versus just one in the lap-band group. On the other hand, these figures don't include the three infections that occurred in connection with the lap-banding, leading the authors to note that bariatric surgery has risks, too.

These findings should help settle the question of whether bariatric surgery is a good idea for patients with severe obesity and advanced osteoarthritis of the knee. Dowsey and colleagues concluded that "for a substantial portion of patients with severe obesity and knee [osteoarthritis], symptoms may be effectively managed with weight-loss strategies alone."

The researchers didn't anticipate this outcome. They conceived the trial to address what they saw as "equivocal" results from earlier uncontrolled studies of knee-replacement outcomes after bariatric surgery, with complication rates as the primary endpoint -- specifically, a composite of the following:

• All-cause mortality
• Any complication leading to delay in discharge ("e.g., fracture, neurapraxia, sepsis, nosocomial infection, myocardial infarction, bowel obstruction, venous thromboembolism, cerebrovascular event, and renal failure")
• Surgical wound complications
• Implant-related infection
• Unplanned procedures
• Readmission

For this study, 82 patients with BMI values of 35 or greater were recruited from an academic orthopedic clinic in Melbourne from 2012 to 2016; those enrolled were followed for at least 12 months after arthroplasty (range up to 80 months). Participants were randomized 1:1 to receive an adjustable laparoscopic gastric band or usual care that included "general weight management advice."

Mean patient age was about 58, and about 80% were women. BMI at baseline averaged 43.6 in the usual-care group and 43.8 for those assigned to the bariatric procedure. Median time to undergo lap-banding after assignment was 64 days (interquartile range [IQR] 48-90). Those participants were given time for maximum weight loss to occur before undergoing knee replacement, such that a median 522 days elapsed from randomization to arthroplasty (IQR 341-824). In the control group, knee replacement was performed a median of 118 days after randomization (IQR 52-213).

Patients in the lap-band group lost a mean 19.5 kg from baseline to month 12, versus 2.5 kg among controls. BMI values reflected this trend, with a between-group difference of -6.32 (95% CI -7.90 to -4.50).

Dowsey and colleagues also found weak trends favoring bariatric surgery for joint-related outcomes after knee replacement, including general function and knee stiffness. Pain, however, was similar in the two groups.

Limitations to the study included the protocol's requirement to cap participant age at 65 and the use of one type of bariatric surgery.

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