The two numbers that you’ll want to remember from the computer model-based cost-effectiveness study by McLawhorn et al. in the January 20, 2016 Journal of Bone & Joint Surgery are $13,910 and $100,000. The first number is an incremental cost-effectiveness ratio (ICER). Here, it’s the estimated added cost per quality-adjusted life year (QALY) for morbidly obese patients (BMI ≥35 kg/m2) with end-stage knee osteoarthritis who undergo bariatric surgery two years prior to total knee arthroplasty (TKA), compared with similar patients who undergo immediate TKA.
The $100,000 is the threshold “willingness to pay” (WTP) that the authors used in their evaluation. Willingness to pay reflects the amount society and healthcare payers such as Medicare and private insurers are willing to pay for a patient to accrue one year lived in perfect health.
Here’s another way to view these findings: Morbidly obese patients who undergo TKA are at increased risk for wound-healing problems, superficial and deep infections, early revision, and poor function. The authors estimated that if bariatric surgery reduces the TKA risks in these patients by at least 16%, on average, the combination of bariatric surgery followed by TKA is more cost-effective than immediate TKA alone.
Because the ICER was much less than the WTP in this model, the authors conclude that “bariatric surgery prior to total knee arthroplasty may be a cost-effective option for improving outcomes in motivated patients with a BMI of ≥35 kg/m2 with end-stage knee osteoarthritis.” However, they are quick to add that “decision modeling cannot simulate reality for every clinical situation.” While this rigorously developed model may provide a decision-making framework for surgeons and policymakers, the authors say, “this approach may be impractical for an individual patient…desiring immediate symptomatic relief from knee osteoarthritis.”
Researchers at Vanderbilt University Medical Center have concluded that fibrin, a protein involved in blood clotting and found abundantly around the site of new bone fractures, impedes rather than supports fracture healing.
Their recent study in The Journal of Clinical Investigation looked at mice that had experimentally induced deficits in either fibrin production or fibrin clearance. Researchers found normal fracture repair in mice without fibrin and impaired vascularization and fracture healing in mice with inhibited fibrin clearance. They also saw increased heterotopic ossification in the mice unable to remove fibrin.
In a Vanderbilt press release, study coauthor Jonathan Schoenecker, MD, commented that “any condition associated with vascular disease and thrombosis will impair fracture healing.” These findings, he suggested, may explain why obesity, diabetes, smoking, and old age—all of which are associated with impaired fibrin clearance—are also associated with impaired fracture healing. Dr. Schoenecker went on to speculate that anti-clotting drugs commonly used to treat cardiovascular conditions may find new applications in enhancing fracture repair.
The relationships between body weight and joint replacement are debated often in the orthopaedic community. Some surgeons are so concerned about perioperative complications related to obesity that they recommend delaying arthroplasty in obese patients until weight loss is achieved.
But what are the likelihood and implications of weight changes after joint replacement? For those answers, in the June 3, 2015 edition of JBJS, Ast et al. tracked differences in body mass index (BMI) among nearly 7,000 patients for two years after total hip arthroplasty (THA) or total knee arthroplasty (TKA). Establishing a 5% BMI change as “clinically meaningful,” the researchers found that:
- Most patients (73% of those undergoing THA and 69% of those undergoing TKA) experienced no weight change.
- Female patients, patients with a higher preoperative BMI, and those undergoing TKA were most likely to lose weight after surgery.
- Weight loss was associated with improved clinical outcomes after THA, but not after TKA. However, weight gain in general was associated with inferior clinical outcomes.
- Those with better preoperative functional status were less likely to gain weight after THA or TKA.
Countering conventional wisdom that weight loss after total joint arthroplasty is unlikely, Ast. Et al. emphasize that “obese patients who undergo total joint arthroplasty are more likely than non-obese patients to lose weight after surgery.”
The latest market report from Transparency Market Research predicts that the global orthobiologics market will grow at a compound annual rate of nearly 6% over the next 5 years. In 2012, the orthobiologics market was worth $3.7 billion, and it is expected to hit $5.5 billion by the end of 2019. What will drive the growth? The 50+ population is expected to almost double by 2020, and increases in obesity and sports injuries will spur market growth. Technical improvements and a trend away from the use of autografts and allografts will also drive interest in orthobiologics.