Does Obesity Impact Outcomes of Total Knee Arthroplasty When Treated by High-Volume Surgeons? A Propensity-Matched Analysis From a High-Volume Urban Center

Effects of Surgeon Volume on Outcomes Following Primary Total Knee Arthroplasty in the Morbidly Obese: An Analysis from the American Joint Replacement Registry

INTRODUCTION

The purpose of this study was to utilize the American Joint Replacement Registry (AJRR) to examine the effects of surgeon total knee arthroplasty (TKA) volume and surgeon obesity-specific TKA volume on rates of revision following primary TKA in patients who have morbid obesity.

METHODS

We identified 833,099 primary TKAs performed from 2017 to 2021 by 4,829 surgeons in the AJRR. Surgeon primary TKA volumes (includes primary TKAs in all patients, all body mass indices [BMIs]) and obesity-specific primary TKA volumes (includes only primary TKAs in patients who have a BMI ≥ 40) were calculated based on the median annual number of primary TKAs performed per surgeon. Multivariate logistic regression was used to evaluate the effects of surgeon volume and obesity-specific volume on the risk of all-cause revision and revision for periprosthetic joint infection (PJI).

RESULTS

Median surgeon TKA volume was 85 cases/year (range, one to 466), and median surgeon obesity-specific TKA volume was 11 cases/year (range, one to 242). Increasing surgeon TKA volume was not associated with a decreased risk of any revision or a decreased risk of revision for PJI (P > 0.05 for all) for patients who had morbid obesity. Similarly, there were no associations between surgeon obesity-specific primary TKA volume and risk of any revision or revision for PJI following TKA in patients who had morbid obesity (P > 0.05 for all).

CONCLUSIONS

Morbidly obese patients had a similar risk of any revision and PJI after undergoing primary TKA performed by low-volume or high-volume surgeons. Similarly, the surgeon's annual obesity-specific primary TKA volume was not associated with these endpoints in this patient population. Based on these data, surgeon volume does not appear to be a modifiable risk factor for optimization of outcomes in morbidly obese patients undergoing primary TKA.

[Influence of obesity on midterm outcome after primary hip and knee arthroplasty in Germany : Analysis from the EPRD]

OBJECTIVES

To determine the influence of obesity on revision rates and mortality after primary elective hip and knee arthroplasty in Germany.

MATERIALS AND METHODS

In the German Arthroplasty Registry (EPRD) there were 403,073 elective total hip arthroplasties (THA), 320,913 bicondylar total knee arthroplasties (TKA) and 48,480 unicondylar knee arthroplasties (UKA) with valid BMI available for analysis. Cumulative revision rates and 1‑year mortality was calculated for BMI groups.

RESULTS

There were increased revision rates with increasing BMI, most distinctive for septic revisions in THA during the first year after surgery (non-obese 0.7%, obesity grade 1 1.3%, grade 2 2.1%, grade 3 4.2%). In TKA and UKA this increase was generally less pronounced. Age- and gender-standardized mortality was lower than expected in most groups, but also increasing with increasing BMI.

CONCLUSION

The risk for revisions in obese patients is more distinctive in hip arthroplasty than in knee arthroplasty and is especially high in morbidly obese patients (BMI ≥ 40 kg/m2). Nonetheless, this risk may be acceptable for affected patients. Therefore, the possible benefits and risks of an arthroplasty should be weighed against each other and individually discussed with the patient.

Weighing the Impact: The Influence of Body Mass Index on Facility Costs in Total Joint Arthroplasty

BACKGROUND

Using time-driven activity-based costing (TDABC), a novel cost calculation method that more accurately reflects true resource utilization in health care, we sought to compare the total facility costs across different body mass index (BMI) groups following total joint arthroplasty (TJA).

METHODS

The study consisted of 13,806 TJAs (7,340 total knee arthroplasties [TKAs] and 6,466 total hip arthroplasties [THAs]) performed between 2019 and 2023. The TDABC data from an analytics platform was employed to depict total facility costs, comprising personnel and supply costs. For the analysis, patients were stratified into four BMI categories: <30, 30 to <35, 35 to <40, and ≥40. Multivariable regression was used to determine the independent effect of BMI on facility costs.

RESULTS

When indexed to patients who had BMI <30, elevated BMI categories (30 to <35, 35 to <40, and ≥40) were associated with higher total personnel costs (TKA 1.03x versus 1.07x versus 1.13x, P < .001; THA 1.00x versus 1.08x versus 1.08x, P < .001), and total supply costs (TKA 1.01x versus 1.04x versus 1.04x, P < .001; THA 1.01x versus 1.02x versus 1.03x, P = .007). Total facility costs in TJAs were significantly greater in higher BMI categories (TKA 1.02x versus 1.05x versus 1.08x, P < .001; THA 1.01x versus 1.05x versus 1.05x, P < .001). Notably, when incorporating adjustments for demographics and comorbidities, BMI values of 35, 40, and 45 relative to BMI of 25, exhibit a significant association with a 2, 3, and 5% increase in total facility cost for TKAs and a 3, 5, and 7% increase for THAs.

CONCLUSIONS

Using TDABC methodology, this study found that overall facility costs of TJAs increase with BMI. The present study provides patient-level cost insights, indicating the potential need for reassessment of physician compensation models in this population. Further studies may facilitate the development of risk-adjusted procedural codes and compensation models for public and private payors.

LEVEL OF EVIDENCE

Level IV, economic and decision analyses.

Should high-risk patients seek out care from high-volume surgeons?

Aims

Patients with a high comorbidity burden (HCB) can achieve similar improvements in quality of life compared with low-risk patients, but greater morbidity may deter surgeons from operating on these patients. Whether surgeon volume influences total hip arthroplasty (THA) outcomes in HCB patients has not been investigated. This study aimed to compare complication rates and implant survivorship in HCB patients operated on by high-volume (HV) and non-HV THA surgeons.

Methods

Patients with Charlson Comorbidity Index ≥ 5 and American Society of Anesthesiologists grade of III or IV, undergoing primary elective THA between January 2013 and December 2021, were retrospectively reviewed. Patients were separated into groups based on whether they were operated on by a HV surgeon (defined as the top 25% of surgeons at our institution by number of primary THAs per year) or a non-HV surgeon. Groups were propensity-matched 1:1 to control for demographic variables. A total of 1,134 patients were included in the matched analysis. Between groups, 90-day readmissions and revisions were compared, and Kaplan-Meier analysis was used to evaluate implant survivorship within the follow-up period.

Results

Years of experience were comparable between non-HV and HV surgeons (p = 0.733). The HV group had significantly shorter surgical times (p < 0.001) and shorter length of stay (p = 0.009) than the non-HV group. The HV group also had significantly fewer 90-day readmissions (p = 0.030), all-cause revisions (p = 0.023), and septic revisions (p = 0.020) compared with the non-HV group at latest follow-up. The HV group had significantly greater freedom from all-cause (p = 0.023) and septic revision (p = 0.020) than the non-HV group.

Conclusion

The HCB THA patients have fewer 90-day readmissions, all-cause revisions, and septic revisions, as well as shorter length of stay when treated by HV surgeons. THA candidates with a HCB may benefit from referral to HV surgeons to reduce procedural risk and improve postoperative outcomes.

The Impact of Obesity on Total Hip Arthroplasty Outcomes When Performed by High-Volume Surgeons-A Propensity Matched Analysis From a High-Volume Urban Center

BACKGROUND

Previous data suggest that obesity does not impact surgical outcomes following total knee arthroplasty performed by high-volume (HV) surgeons. However, this effect has yet to be studied in total hip arthroplasty (THA) patients. This study aimed to evaluate the impact of patient obesity on THA outcomes when surgery is performed by HV surgeons.

METHODS

A retrospective analysis of patients who underwent primary, elective THA between January 2012 and December 2022 with a HV surgeon (top 25% of surgeons by number of annual primary THA) was performed. Patients were stratified by their body mass index (BMI) into 3 cohorts: BMI ≥ 40 (morbidly obese [MO]), 30 ≤ BMI < 40 (obese), and BMI < 30 (nonobese); and 1:1:1 propensity matched based on baseline characteristics. A total of 13,223 patients were evaluated, of which 669 patients were included in the final matched analysis (223 patients per group). The average number of annual THAs performed for HV surgeons was 171 cases.

RESULTS

The MO patients had significantly longer surgical times (P < .001) and hospital lengths of stay (P < .001). Rates of 90-day readmissions (P = .211) and all-cause, septic, and aseptic revisions at the latest follow-up (P = .268, P = .903, and P = .168, respectively) were comparable between groups. In a subanalysis for non-HV surgeons, MO patients had a significantly greater risk of revision (P = .021) and trended toward significantly greater readmissions (P = .056).

CONCLUSIONS

Clinical outcomes and complication rates after THA performed by a HV surgeon are similar regardless of patient obesity status. Patients who have MO may experience improved outcomes and reduced procedural risks if they are referred to HV surgeons.

LEVEL OF EVIDENCE

III.

Does experience with total knee arthroplasty in morbidly obese patients effect surgical outcomes

INTRODUCTION

Literature examining the risks, benefits, and potential complications of TKA in morbidly obese patients is conflicting. Surgeons with more experience performing TKA on morbidly obese patients may generate superior outcomes. This study sought to assess whether complication rates and implant survivorship in morbidly obese TKA patients varies between high (HV) and low (LV) volume surgeons.

METHODS

A retrospective review was performed to include all morbidly obese (BMI ≥ 40) patients that underwent primary TKA between January 2016 and July 2021 at our high-volume center. Demographics and clinical outcomes were collected and compared between surgeons with a higher morbidly obese TKA volume (> 10 annual cases) and surgeons with a lower morbidly obese TKA volume.

RESULTS

A total of 964 patients (HV 91 [9.4%], LV 873 [90.6%]) were identified. The HV surgeon and LV surgeons had an average annual volume of 15.3 and 5.2 cases, respectively. The average BMI for the HV and LV cohorts were 44.5 ± 3.7 and 44.0 ± 3.6, respectively (p = 0.160). The HV surgeon had significantly lower operative times (105.7 ± 17.4 vs. 110.7 ± 29.6 min, p = 0.018), and a lower 90-day minor complication rate (0.0% vs. 4.7%, p = 0.035). For patients with at least 2-year follow-up, all-cause revision (3.4% vs. 12.5%, p = 0.149) and revision due to PJI (0.0% vs. 5.8%, 0.193) rates were numerically lower in the HV cohort. Improvements in KOOS, JR and VR-12 scores were similar at 3-month and 1-year follow-up. Freedom from all-cause revision (HV: 96.6% vs. LV: 80.4%, p = 0.175) and revision due to PJI (HV: 100.0% vs. LV: 93.6%, p = 0.190, p = 0.190) at latest follow-up did not statistically differ between groups.

CONCLUSION

The HV surgeon had significantly lower operative time and 90-day minor complication rates and numerically lower all-cause revision and revision due to PJI rates when performing TKA in morbidly obese patients. Surgeon's experience may affect surgical outcomes after TKA in morbidly obese patients.

LEVEL OF EVIDENCE

III.