In the first long-term follow-up study of its kind, Shane J. Nho, MD, MS, and his team found that patients with higher BMIs tend to have worse outcomes 10 years after hip arthroscopy, compared with normal weight patients.
Effects of Body Mass Index on Hip Arthroscopy Outcomes in Femoroacetabular Impingement Syndrome
Research Profile
Nearly half of patients undergoing hip arthroscopy (HA) are overweight or obese. To date, studies on the effects of body mass index (BMI) on outcomes post-HA in patients with femoroacetabular impingement syndrome (FAIS) have shown mixed results and have been limited to two- and five-year follow-up.
Shane J. Nho, MD, MS, an orthopedic surgeon focused on sports medicine and arthroscopic treatment of the hip, shoulder and knee at Rush University Medical Center, and his research team sought to investigate how patients with greater BMIs fare over the long term following HA, using outcomes data they have collected for a more than a decade.
The study’s aim and methodology
Dr. Nho and his co-authors — including Thomas E. Moran, MD, and Eric Y. Hu and Jesus E. Cervantes from Rush — compared patient-reported outcomes (PROs), achievement of clinically significant outcomes (CSOs) and reoperation rates between different BMI groups.
They identified patients in a prospective surgery repository who had undergone HA for FAIS between January 2012 through June 2014 with 10-year follow-up. The team stratified patients based on BMI at the time of surgery using established definitions of normal weight, overweight and obesity. Patients with normal BMI (n = 256) were propensity matched 1:1:1 to overweight (n = 118), and obese (n = 61) patients based on age and sex. Ultimately, 56 patients were matched in each group.
The team collected PROs preoperatively and at two-, five- and 10-year follow-up. PROs compared included Hip Outcome Score–Activities of Daily Living (HOS-ADL), Hip Outcome Score–Sports Subscale (HOS-SS), modified Harris Hip Score (mHHS), 12-item International Hip Outcome Tool (iHOT-12) and Visual Analog System (VAS) for pain and satisfaction.
Results
Mean BMIs were as follows: normal weight (22.2 ± 2.1 kg/m²), overweight (27.1 ± 1.5 kg/m²) and obese (34.4 ± 4.0 kg/m²) (p < 0.001). All three patient groups reported significant improvements of all outcome scores from preoperative baseline to 10-year follow-up, although obese patients tended to have worse functional PRO scores.
“Patients with higher BMIs started at a lower pre-op baseline and had a lower final outcomes score, but the magnitude of improvement was similar to that of the normal BMI patients,” Dr. Nho explains. “While these patients do show improvement, they fare slightly worse than normal BMI patients because they start at a lower baseline score.”
The team also found that a larger share of patients with higher BMIs had pre-operative radiographic features and intra-operative findings suggesting a greater burden of chondromalacia and early signs of arthritis. “A greater proportion of patients in the higher BMI groups had acetabular cartilage grade 3 and 4 or Tönnis grade 1,” Dr. Nho says. “Patients with these factors at baseline may not have as predictable results as those without them at 10 years.”
Dr. Nho’s team also noted a sizable difference in the incidence of total hip replacement (THA) over a 10-year period following HA, with 19.6% of obese patients, 14.3% of overweight patients and 3.6% of normal weight patients requiring a conversion to THA. These results suggest continuity of previously reported trends linking higher BMI to greater risk of conversion to THA seen at two-year follow-up by Gupta, et al, and at five-year follow-up by Perets, et al.
Overall, the findings from the Rush team suggest that HA remains a durable treatment option for overweight and obese patients with FAIS. “BMI is not necessarily a reason to contraindicate a patient for surgery,” Dr. Nho says. “It is one factor amongst many factors that influence their outcomes.”
Next steps
Based on this report, orthopedic surgeons should inform patients with FAIS with higher BMIs that they may have a higher risk of conversion to hip replacement in the 10 years following HA, Dr. Nho says.
Besides setting expectations with higher-BMI patients, surgeons should also consider preoperative interventions to help these patients lose weight prior to HA. “Pharmacological or behavioral treatments could optimize their weight and improve their baseline status prior to undergoing surgery, so their outcomes may mirror a patient in the normal BMI category,” he says.
For future research, Dr. Nho and his team plan to study the impact of weight-reduction interventions on patients with FAIS, both with and without HA.
