Abstract
Introduction:
In fields outside of orthopaedics, patient-physician sex concordance has been linked to improved rapport, better quality of care, and decreased mortality. However, the effects of sex concordance have yet to be evaluated in orthopaedic surgery. This study examined whether patient-surgeon sex concordance was associated with outcomes following total joint arthroplasty (TJA).
Methods:
This retrospective cohort study used data from a US integrated healthcare system’s TJA registry (2009-2020). Patients 18 years and older with hip or knee osteoarthritis who underwent primary total hip or knee arthroplasty were included. The primary outcome was all-cause revision, analyzed using accelerated failure time regression adjusted for potentially confounding variables, with patient-surgeon sex concordance as the exposure. Secondary outcomes included 90-day emergency department (ED) visits and readmissions, analyzed using logistic regression models also adjusted for confounders.
Results:
A total of 213,540 patients (median age 67.0 years, 59.9% female, 69.8% White) and 319 surgeons (18 female, 301 male) met the inclusion criteria. There were 70,883 total hip arthroplasty cases and 142,657 total knee arthroplasty cases. Sex concordance was not associated with all-cause revision for male patients (time ratio [TR] 1.18, 95% confidence interval (CI) 0.80-1.75, p = 0.40) or for female patients (TR 0.98, 95% CI 0.72-1.34, p = 0.92). Sex concordance was also not associated with 90-day readmission for male patients (odds ratio [OR] 0.99, 95% CI 0.84-1.16, p = 0.88) or for female patients (OR 0.99, 95% CI 0.86-1.14, p = 0.87). Both male and female patients had a lower likelihood of 90-day ED visit when treated by a female surgeon (OR 0.80, 95% CI 0.71-0.89, p < 0.001 and OR 0.86, 95% CI 0.79-0.94, p < 0.001, respectively).
Conclusions:
In this study of 213,540 TJA procedures performed within an integrated healthcare system, surgeon-patient sex concordance was not associated with all-cause revision or 90-day readmission. Ninety-day ED visits were less common among patients treated by female surgeons. Further research is required to determine if there are other aspects of TJA care, such as patient satisfaction or utilization, that could be more affected by patient-surgeon sex concordance.
Level of Evidence:
Therapeutic Level III, prognostic. See Instructions for Authors for a complete description of levels of evidence.
Introduction
Total joint arthroplasty (TJA) is highly effective in helping patients with end-stage osteoarthritis (OA) regain or improve their functional status1,2. However, prior research has demonstrated various disparities based on sex and gender for both total hip arthroplasty (THA) and total knee arthroplasty (TKA)3. For example, women are less likely to undergo TJA4,5, even though OA is more prevalent among women4.
It is interesting to consider sex-based disparities in TJA in relation to the demographics of orthopaedic surgeons. Specifically, orthopaedic surgery is one of the least diverse specialties with regard to sex6-8. Women were found to account for just 6.5% of practicing orthopaedic surgeons in a census conducted by the American Academy of Orthopaedic Surgeons in 2018, with a more recent study reporting this figure to have increased to 7.5% as of 20239-11.
In other fields of medicine—including general surgery12-14, emergency medicine15, and primary care16—patient-physician sex concordance has been associated with improved physician-patient rapport, better quality of care, and decreased mortality rates. To date, however, the effects of patient-surgeon sex concordance have not been examined in orthopaedic surgery. The purpose of this study was to determine whether patient-surgeon sex concordance is associated with outcomes following TJA.
Methods
To conduct this retrospective cohort study, data were obtained from Kaiser Permanente, a US integrated healthcare system covering over 12 million individuals across 8 different geographic regions in the United States (i.e., Southern California, Northern California, Colorado, the Northwest, Hawaii, Washington, Mid-Atlantic, and Georgia). Data were obtained from the Kaiser Permanente Total Joint Replacement Registry (TJRR), which was established in 2001 and consistently maintains a voluntary participation rate of over 90%17-19. The registry collects information on TJA procedures performed within the Kaiser Permanente healthcare system via electronic intraoperative forms completed voluntarily at the point of care by the primary surgeon. Detailed information regarding the data collection protocols and participation rates for the TJRR has been published previously17-19.
Our study included Kaiser Permanente patients aged 18 years and older who underwent primary THA or TKA between 2009 and 2020 in the Southern California and Northern California regions of Kaiser Permanente, along with their corresponding surgeons. Exclusion criteria included revision TJA, non-OA indications for surgery, and prior surgery on the affected hip or knee. In addition, patients whose procedure was performed by a non-Kaiser Permanente surgeon, patients with American Society of Anesthesiologists (ASA) classification 5 or 6, and patients with missing race/ethnicity data were excluded. We received approval from the Kaiser Permanente Institutional Review Board before the commencement of the study.
Outcomes of Interest
The primary outcome of interest was revision for any reason following the index unilateral TJA. Revisions included any reoperation following the index procedure that involved the removal or replacement of the original implant. All patients in the TJRR were continuously monitored for revision by trained clinical content experts via chart review until membership termination, death, or the study end point (12/31/2022). Secondary outcome measures included emergency department (ED) visits and readmission within 90 days. Information regarding ED visits and readmission encounters was obtained through documentation found in the electronic health record.
Exposures of Interest
In the primary analysis, the exposure of interest was patient-surgeon sex concordance. Patient sex data were obtained from the electronic health record and classified as male or female based on sex assigned at birth. Surgeon sex data were obtained from the Permanente Medical Groups and classified as male or female. Pairings in which the patient and the surgeon were of the same sex (e.g., male-male or female-female) were categorized as concordant, while pairings in which the patient and the surgeon were of different sexes (e.g., male-female or female-male) were considered discordant. In a secondary analysis, surgeon sex served as the exposure of interest.
Covariates
Patient-specific covariates included age (categorized as 18-44, 45-64, 65-74, 75-84, 85+ years), race/ethnicity (Asian, Black, Hispanic or White, as self-classified by patients in the electronic health record), body mass index (BMI, classified as <18.5; 18.5-24.9; 25-29.9; 30-34.9; 35+), educational attainment, annual household income, ASA classification, smoking status (current, former, or never), operative site (hip or knee), diabetes status, operative year, and surgeon average annual TJA volume. The highest educational attainment and annual household income for each patient were estimated using the Geographically Enriched Member Sociodemographics data mart20. Prior studies have demonstrated the validity of using geocoding to assess the educational attainment and socioeconomic status of members within a healthcare system21. The reference groups were set at the national averages of high school graduate for educational attainment and $50,000 to $74,999 for annual household income.
Statistical Analysis
Patient characteristics were stratified by patient and treating surgeon sex and summarized using means (SD) for continuous data and n (%) for categorical data. Crude rates were calculated by dividing the number of patients who experienced each outcome (i.e., all-cause revision, ED visits within 90 days, and readmissions within 90 days) by the total number of patients. Given that the proportional hazards assumption was not met, accelerated failure time (AFT) regression was used for the analysis of all-cause revision while logistic regression was performed for the 90-day outcome measures. All models were controlled for age, race/ethnicity, BMI, ASA classification, smoking status, operative site (hip or knee), diabetes status, operative year, and surgeon average annual TJA volume. Patients were censored at the time of membership termination, death, or study end point (December 31, 2022). Mortality information was obtained from the Social Security Administration to capture all patients, regardless of insurance status at the time of death. In addition, time ratios (TR; AFT regression) and odds ratios (OR; logistic regression), 95% confidence intervals (CIs) and p-values are reported. The primary analysis considered all patients, with sex concordance as the exposure. Secondary analyses considered surgeon sex as the exposure, as well as hip and knee arthroplasty patients separately. This study used p < 0.05 as the statistical significance threshold. Coding was performed in R version 4.3.1 (2023-06-16).
Results
The study population included 213,540 procedures (70,883 THA and 142,657 TKA) (Fig. 1). The median patient age was 67.0 years, and women accounted for 59.9% (Table I). Demographic information for the THA and TKA cohorts separately is presented in Supplemental Tables 1a and 1b (Appendix). With regard to the operating surgeons, 301 were male and 18 were female (5.6%). The median follow-up time was 6.7 years.
Fig. 1.
Inclusion and exclusion criteria. THA = total hip arthroplasty, and TKA, total knee arthroplasty.
Table I.
Characteristics of Patients Who Underwent Total Hip or Knee Arthroplasty
| Male Surgeon With Male Patient, N = 82,453* | Female Surgeon With Female Patient, N = 5,344* | Male Surgeon With Female Patient, N = 122,608* | Female Surgeon With Male Patient, N = 3,135* | Overall, N = 213,540 | |
|---|---|---|---|---|---|
| Age group | |||||
| 18-44 | 800 (1.0%) | 20 (0.4%) | 770 (0.6%) | 35 (1.1%) | 1,625 |
| 45-64 | 33,437 (41%) | 1,971 (37%) | 43,580 (36%) | 1,208 (39%) | 80,196 |
| 65-74 | 31,059 (38%) | 2,203 (41%) | 48,897 (40%) | 1,230 (39%) | 83,389 |
| 75-84 | 15,230 (18%) | 1,011 (19%) | 25,743 (21%) | 581 (19%) | 42,565 |
| 85+ | 1,927 (2.3%) | 139 (2.6%) | 3,618 (3.0%) | 81 (2.6%) | 5,765 |
| BMI† | 30.5 (5.0) | 30.5 (5.7) | 30.5 (6.0) | 30.7 (4.6) | 30.5 (5.6) |
| Race/ethnicity | |||||
| Asian | 4,126 (5.0%) | 364 (6.8%) | 8,462 (6.9%) | 180 (5.7%) | 13,132 |
| Black | 6,140 (7.4%) | 411 (7.7%) | 11,525 (9.4%) | 205 (6.5%) | 18,281 |
| Hispanic | 12,526 (15%) | 579 (11%) | 18,247 (15%) | 330 (11%) | 31,682 |
| Native American | 513 (0.6%) | 36 (0.7%) | 732 (0.6%) | 26 (0.8%) | 1,307 |
| White | 59,148 (72%) | 3,954 (74%) | 83,642 (68%) | 2,394 (76%) | 149,138 |
| BMI | |||||
| Underweight (<18.5) | 153 (0.2%) | 33 (0.6%) | 836 (0.7%) | 1 (<0.1%) | 1,023 |
| Healthy (18.5-25) | 9,804 (12%) | 938 (18%) | 22,841 (19%) | 328 (10%) | 33,911 |
| Overweight (25-30) | 32,267 (39%) | 1,627 (30%) | 37,669 (31%) | 1,184 (38%) | 72,747 |
| Class I Obesity (30-35) | 25,866 (31%) | 1,587 (30%) | 34,128 (28%) | 1,068 (34%) | 62,649 |
| Class II + Obesity (>35) | 14,363 (17%) | 1,159 (22%) | 27,134 (22%) | 554 (18%) | 43,210 |
| Smoking status | |||||
| Never | 40,370 (49%) | 3,313 (62%) | 76,532 (62%) | 1,564 (50%) | 121,779 |
| Current | 4,243 (5.1%) | 143 (2.7%) | 3,964 (3.2%) | 109 (3.5%) | 8,459 |
| Quit | 37,840 (46%) | 1,888 (35%) | 42,112 (34%) | 1,462 (47%) | 83,302 |
| Diabetes | 25,193 (31%) | 1,323 (25%) | 31,838 (26%) | 954 (30%) | 59,308 |
| ASA category | |||||
| 1-2 | 51,777 (63%) | 3,338 (62%) | 81,435 (66%) | 1,825 (58%) | 138,375 |
| 3-4 | 30,676 (37%) | 2,006 (38%) | 41,173 (34%) | 1,310 (42%) | 75,165 |
| Operation site | |||||
| Hip | 29,139 (35%) | 1,486 (28%) | 39,292 (32%) | 966 (31%) | 70,883 |
| Knee | 53,314 (65%) | 3,858 (72%) | 83,316 (68%) | 2,169 (69%) | 142,657 |
| Operation side | |||||
| Left | 40,252 (49%) | 2,466 (46%) | 56,581 (46%) | 1,535 (49%) | 100,834 |
| Right | 42,201 (51%) | 2,878 (54%) | 66,027 (54%) | 1,600 (51%) | 112,706 |
| Educational attainment | |||||
| No High School Degree | 13% | 12% | 14% | 12% | 13% |
| High School Graduate | 20% | 21% | 21% | 20% | 21% |
| Some College | 31% | 32% | 31% | 32% | 31% |
| Bachelor Degree or Higher | 36% | 35% | 35% | 36% | 35% |
| Annual household income | |||||
| Income < $35k | 21% | 22% | 22% | 21% | 22% |
| Income $35k-$50k | 11% | 11% | 11% | 11% | 11% |
| Income $50k-$75k | 16% | 17% | 17% | 17% | 17% |
| Income $75k-$100k | 13% | 14% | 13% | 14% | 13% |
| Income $100k-$150k | 18% | 18% | 18% | 19% | 18% |
| Income of $150k or more | 20% | 18% | 19% | 19% | 19% |
| Unknown | 144 | 3 | 193 | 4 | 344 |
ASA = American Society of Anesthesiologists, and BMI = body mass index.
n (%) unless otherwise noted.
Mean (SD).
In the multivariable analysis controlling for potential confounders, sex concordance was not associated with all-cause revision for either male (TR 1.18, 95% CI 0.80-1.75, p = 0.40) or female (TR 0.98, 95% CI 0.72-1.34, p = 0.92) patients (Table II and Fig. 2). Similarly, sex concordance was not associated with 90-day readmission for either male (OR 0.99, 95% CI 0.84-1.16, p = 0.88) or female (OR 0.99, 95% CI 0.86-1.14, p = 0.87) patients (Table II). Surgery by a female surgeon was associated with a lower odds of 90-day ED visit for both male (OR 0.80, 95% CI 0.71-0.89, p < 0.001) and female (OR 0.86, 95% CI 0.79-0.94, p < 0.001) patients (Table II).
Fig. 2.
Graph showing rates of total hip arthroplasty or total knee arthroplasty revision over time, by surgeon-patient sex pairing. There were no differences in revision rate by surgeon-patient sex concordance at any time point.
Table II.
Association Between Sex Concordance and Postoperative Outcomes Among Patients Who Underwent Total Hip or Knee Arthroplasty
| 90-day ED Visits | 90-day Readmission | All-Cause Revision | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Crude Rate | OR (95% CI) | p | Crude Rate | OR (95% CI) | p | Crude Rate | TR (95% CI) | p | |
| Among male patients | |||||||||
| Male patient with female surgeon (discordant) | 10.0% | 1 (reference) | NA | 5.1% | 1 (reference) | NA | 3.7% | 1 (reference) | NA |
| Male patient with male surgeon (concordant) | 12.4% | 1.25 (1.12, 1.41) | <0.001 | 5.1% | 0.99 (0.84, 1.16) | 0.88 | 3.2% | 1.18 (0.80, 1.75) | 0.40 |
| Among female patients | |||||||||
| Female patient with male surgeon (discordant) | 12.8% | 1 (reference) | NA | 4.4% | 1 (reference) | NA | 2.9% | 1 (reference) | NA |
| Female patient with female surgeon (concordant) | 11.0% | 0.86 (0.79, 0.94) | <0.001 | 4.3% | 0.99 (0.86, 1.14) | 0.87 | 3.1% | 0.98 (0.72, 1.34) | 0.92 |
ED = emergency department, OR = odds ratio, and TR = time ratio.
Overall, surgery by a female surgeon was associated with a lower rate of postoperative ED visit (OR 0.84, 95% CI 0.78-0.90, p < 0.001). There were no differences in all-cause revision or readmission on the basis of surgeon sex (Table III). Similar patterns were observed when considering THA and TKA separately (Supplemental Tables 2A, 2B, 3A and 3B and Supplemental Figures 1 and 2; see Appendix).
Table III.
Association Between Surgeon Sex and Postoperative Outcomes Among Patients Who Underwent Total Hip or Knee Arthroplasty
| 90-day ED Visits | 90-day Readmission | All-Cause Revision | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Crude Rate | OR (95% CI) | p | Crude Rate | OR (95% CI) | p | Crude Rate | TR (95% CI) | p | |
| Male surgeon | 12.60% | 1 (reference) | NA | 4.70% | 1 (reference) | NA | 2.90% | 1 (reference) | NA |
| Female surgeon | 10.60% | 0.84 (0.78,0.90) | <0.001 | 4.60% | 1.00 (0.90, 1.11) | 0.96 | 3.20% | 0.92 (0.72, 1.18) | 0.52 |
ED = emergency department, OR = odds ratio, and TR = time ratio.
Discussion
In this study of 213,540 TJA procedures, sex concordance was not found to be associated with all-cause revision or 90-day readmission. Both male and female patients had a lower odds of 90-day ED visit after undergoing TJA by a female surgeon. There were no differences in all-cause revision or 90-day readmission on the basis of surgeon sex.
Prior studies in other fields have shown patient-physician sex concordance to be associated with improved patient satisfaction, greater patient-physician communication, and lower mortality rates. In emergency medicine, for example, female patient/female physician pairings were found to be associated with a significantly higher patient satisfaction score22. In the fields of family practice and internal medicine, sex-concordant dyads were found to be associated with a higher component score of “understanding the whole person,” a measure of patient-centered communication23. A subsequent study from the same medical center also found that female physician/female patient dyads demonstrated significantly higher patient-centered care (a healthcare approach focusing on patient preferences, needs, and values, aiming to support shared clinical decision making and improve health outcomes). With regard to mortality rates, a study based on a census of Florida patients admitted for myocardial infarction found sex concordance to be associated with a 5.4% lower probability of death22.
Few studies have assessed the effect of patient-physician sex concordance on patient outcomes following surgical intervention. In one study of common elective and emergent surgeries in multiple surgical subspecialties (including cardiothoracic, general, and orthopaedic), sex discordance was found to be associated with higher rates of death, complications, and readmission within 30 days, driven primarily by worse outcomes among female patients treated by male surgeons13. In our study, by contrast, patient-surgeon sex concordance was not found to be associated with any differences in all-cause revision or readmission. This suggests that, at least in the arthroplasty setting within our healthcare system, patient-surgeon sex concordance does not appear to influence objective measures of surgical quality, in contrast to prior reports in other surgical populations.
In orthopaedics, Jolbäck and colleagues conducted a registry study of 11,993 primary THAs performed in Sweden and found patient-surgeon sex concordance to be associated with an increased risk of 90-day adverse events24. However, the analyses conducted in that study did not stratify by patient sex (since most of the surgeons in the study were male, the patients in the “concordant” group were nearly 90% male while those in the “discordant” group were over 90% female, meaning that the study represented an analysis of THA outcomes by patient sex, not patient-surgeon sex concordance).
The finding of a difference in the odds of 90-day ED visits based on surgeon sex parallels other research relating to potential differences in practice patterns between male and female physicians. Prior research in the field of internal medicine found that hospitalized patients treated by female internists had lower readmission and mortality rates in comparison with those treated by male internists25. Similarly, a study of common elective and emergent surgeries (including appendectomy as well as hip and knee arthroplasties) performed in Canada found that patients treated by female surgeons had lower rates of 90-day and 1-year mortality rates26. Given that there is greater standardization in the TJA care performed within our integrated healthcare system27, this is an interesting finding that warrants further investigation. With regard to readmission rates, we did not detect any differences on the basis of surgeon sex, which is consistent with prior research conducted by Chapman et al.28
Our study benefits from its large sample size (n = 213,540) and the nature of the dataset (Kaiser Permanente electronic medical record and TJRR). However, our findings should also be interpreted in the context of certain limitations. Although the Kaiser Permanente TJRR is an extensive database that includes large numbers of patients and surgeons, our results may be affected by the fact there were only 18 female surgeons. While we would have preferred to conduct our study on the basis of patient gender29, our study considered biologic sex given that gender was infrequently recorded in the electronic health record of our integrated healthcare system. With regard to ED visits, those that took place outside the Kaiser Permanente system would not have been recorded. However, the frequency of this occurrence is expected to be low given that most patients return to Kaiser Permanente facilities for their care30 and, more importantly, there is no reason to believe that the rates of presentation to an outside ED would have differed on the basis of patient or surgeon sex. Although we controlled for a number of covariates, the possibility of residual confounding by unmeasured factors cannot be excluded. Similarly, the retrospective nature of our analysis implies that our results should be taken to represent association as opposed to causation. While patient satisfaction and patient-reported outcome measures would have provided meaningful data to complement our results, these metrics are not currently available in the Kaiser Permanente TJRR. Finally, as these results are drawn from the Kaiser Permanente system, additional research in other settings will be needed to determine whether these findings are generalizable.
Conclusions
Our study of elective TJA within an integrated healthcare system did not find sex concordance to be associated with outcomes following TJA. However, these findings should not diminish ongoing efforts to address sex-based disparities in orthopaedic surgery and promote diversity within the field. Instead, our findings underscore the need for further research exploring the role of sex concordance and other social factors on a broader set of measures—such as patient-reported outcomes and utilization—within the larger context of understanding and addressing sex-based disparities in orthopaedic surgery.
Appendix
Supporting material provided by the authors is posted with the online version of this article as a data supplement at jbjs.org (https://links.lww.com/JBJSOA/B317). This content was not copyedited or verified by JBJS.
Acknowledgments
Note: The authors gratefully acknowledge the Surgical Outcomes and Analysis Department staff, as well as all Kaiser Permanente orthopaedic surgeons who contribute to the Total Joint Replacement Registry.
Footnotes
Investigation performed at the Surgical Outcomes and Analysis Department, Kaiser Permanente, San Diego, California; Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, California; and the Hawaii Permanente Medical Group, Honolulu, Hawaii
Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (https://links.lww.com/JBJSOA/B316).
Contributor Information
Tanya Watarastaporn, Email: tanya.watarastaporn@kp.org.
Mark C. Duggan, Email: mark.c.duggan@kp.org.
Elizabeth W. Paxton, Email: liz.w.paxton@kp.org.
Ronald A. Navarro, Email: ronald.a.navarro@kp.org.
Christopher D. Grimsrud, Email: christopher.d.grimsrud@kp.org.
Ajinkya A. Rane, Email: ajinkya.a.rane@kp.org.
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