Abstract
Background
Orthopaedic studies have reported the prevalence of injuries and outcomes after treatment in men and women patients, and although these differences have been recognized, few studies have evaluated for gender-specific injury patterns, disease progression, and treatment outcomes. A thorough understanding of gender-related differences is important to better individualize treatment and improve outcomes.
Questions/purposes
In this study, we sought (1) to determine the proportion of studies published in six orthopaedic journals that provided sex- or gender-specific analyses in 2016 and whether a difference was found in outcomes between men and women and (2) to evaluate whether this proportion varied across several orthopaedic subspecialty journals or between general orthopaedic journals and subspecialty journals.
Methods
Six leading orthopaedic surgery journals were selected for review, including two general orthopaedic journals (Journal of Bone and Joint Surgery and Clinical Orthopaedics and Related Research®) and four subspecialty journals (American Journal of Sports Medicine, Journal of Arthroplasty, Journal of Shoulder and Elbow Surgery, and Spine). Journal issues published in the even-numbered months of 2016 were reviewed for clinical randomized controlled, cohort, and case-control studies in which women were a part of the study population. A total of 712 studies evaluating 24,607,597 patients met the criteria and were included in our review of publications from 2016. The selected studies were stratified based on whether gender was a variable in a multifactorial statistical model. Outcomes of interest included the proportion of patients who were women and the presence or absence of a gender-specific analysis. These endpoints were compared between journals.
Results
Overall, 55% (13,565,773 of 24,607,597) of patients analyzed in these studies were women. Only 34% (241 of 712) of the studies published in 2016 included gender as variable in a multifactorial statistical model. Of these, 39% (93 of 241) demonstrated a difference in the outcomes between patients who were men and women. The Journal of Arthroplasty had the greatest percentage of patients who were women (60%, 9,251,068 of 15,557,187) and the American Journal of Sports Medicine had the lowest (44%, 1,027,857 of 2,357,139; p < 0.001). Orthopaedic subspecialty journals tended to include a greater percentage of women (54%) than did general orthopaedic journals (50%; p = 0.04).
Conclusion
Currently, it is unclear what percentage of published orthopaedic studies should include a gender-specific analysis. In the current study, more than one-third of publications that performed a gender-specific analysis demonstrated a difference in outcomes between men and women, thereby emphasizing the need to determine when such an analysis is warranted.
Clinical Relevance
Future studies should aim to determine when a gender-specific analysis is necessary to improve the management of orthopaedic injuries in men and women. It is important for investigators at the individual-study level to look for every opportunity to ensure that both men’s and women’s health needs are met by performing appropriate by-sex and by-gender analyses, but not to perform them when they are unnecessary or inappropriate.
Introduction
Differences in the incidence and prevalence of commonly diagnosed conditions, including osteoarthritis, osteoporosis, spinal disorders, and fractures, between men and women have been reported [5, 8, 21]. Although these differences have been recognized, few studies have evaluated gender-specific injury patterns, disease progression, and treatment outcomes [24]. A thorough understanding of gender-related differences is important to better individualize treatment and improve outcomes. Responses to surgery and rehabilitation may differ based on patient gender, and an adequate understanding of these differences has not been established [24]. Hettrich et al. [8] performed a study in 2015 to determine whether there was an increase in the proportion of gender-specific reporting in orthopaedic journals from 2000 to 2005 to 2010. The authors reported an increase in gender-specific analysis use from 2000 to 2010, but they noted that 70% of orthopaedic studies did not use a gender-specific analysis. Revisiting this topic by analyzing data reported in the literature 6 years later is important to determine whether there have been any changes since that publication.
In 2018, Sciomer et al. [22] examined current guidelines in the management of cardiovascular disease. The authors found evidence showing gender disparities in the diagnosis, treatment, and prognosis of cardiovascular disease, supporting the importance of establishing an up-to-date and gender-based revision of current guidelines. In the treatment of rheumatoid arthritis, there is strong evidence demonstrating differences in treatment responses to medical management, consisting of disease-modifying antirheumatic drugs [17]. These convincing data regarding the importance of gender-specific differences in other medical specialties highlights the importance of evaluating for these differences in orthopaedic surgery.
In 1994, the NIH developed the NIH Revitalization Act which required NIH-supported research to include women [15]. In 2001, the Institute of Medicine (IOM) reported a policy that gender must be included in all aspects of biomedical research [10]; despite this, a 2012 IOM report demonstrated that gender-related differences are still under-reported [2]. This report recommended an assumption that gender differences exist, so that adequate power for a subgroup analysis is inherent in a study’s design. In 2014, Clinical Orthopaedics and Related Research® published an editorial highlighting the under-representation of women in orthopaedic research [13]. The editorial recommended that investigators design sufficiently powered studies to answer questions for both men and women, provide gender-specific data where relevant, analyze the influence of gender on the results of the study, and indicate that their analysis may be underpowered and that results should be interpreted cautiously.
As an important note on language, we consider that the terms sex, male, and female refer to biological (anatomical or physiological) parameters, and the terms gender, men, and women refer to endpoints that have or may have a social component. Since our study evaluates research pertaining both to sex and gender, we have in general opted throughout to use the term gender, and the more-humanizing terms men and women, rather than males and females.
We proposed to accomplish the following in our study: (1) To determine the proportion of studies published in six orthopaedic journals that provided sex- or gender-specific analyses in 2016 and whether a difference was found in outcomes between men and women and (2) to evaluate whether this proportion varied across several orthopaedic subspecialty journals or between general orthopaedic journals and subspecialty journals.
Materials and Methods
Article Selection
We selected six leading orthopaedic surgery journals for review, including two general orthopaedic journals (Journal of Bone and Joint Surgery and Clinical Orthopaedics and Related Research®) and four subspecialty journals (American Journal of Sports Medicine, Journal of Arthroplasty, Journal of Shoulder and Elbow Surgery, and Spine). Journal issues published during even-numbered months in 2016 were assessed for the use of a gender-specific analysis by two independent reviewers (AP, SK). We considered for inclusion only randomized controlled trials, prospective or retrospective studies with control groups, and case-control studies. We excluded case reports and case series, review articles, cadaveric studies, biomechanical studies, and animal studies.
We screened the abstract of each article for the inclusion of men and women, and we excluded from the analysis studies that did not include women. If the abstract indicated that women were part of the study population, or if this information could not be determined based on the abstract alone, we reviewed the methods and results sections. Then, we classified studies based on whether they reported gender as a demographic factor or included this factor in their statistical analysis. For the present study, gender-specific analysis was defined as the use of sex as a variable in a multifactorial statistical model. A total of 712 studies evaluating 24,607,597 patients met the criteria and were included in this review (Table 1).
Table 1.
Descriptive analysis of articles published in leading orthopaedic journals in 2016
Data Collection
We then collected and recorded further information from all articles that met the inclusion criteria. Variables of interest included journal and article information, total number of patients, total number of women, whether a gender-specific analysis was performed, and results of the gender-specific analysis (if applicable). The percentage of studies that reported a significant finding within gender-specific analysis was also recorded.
Statistical Analysis
All studies were stratified into two groups: those that reported using gender-specific analysis and those that either solely reported gender as a demographic characteristic or those that used gender-matched cohorts without further analysis. The primary outcome of this study was to determine the proportion of publications from six orthopaedic journals that performed gender-specific analysis in 2016. Secondary outcomes included whether performance of gender-specific analysis differed between individual journals or between journal categories (that is, general versus subspecialty orthopaedics), whether the proportion of female study subjects differed between journals, and whether gender-related differences in outcome varied between journals.
We used a chi-square analysis to evaluate categorical variables (such as the presence or absence of gender-specific analysis, categorization as a general or subspecialty orthopaedic journal, or whether a difference in outcomes was found between men and women). Specifically, we investigated whether the performance of gender-specific analysis differed between general and subspecialty orthopaedic journals and whether it differed between each individual journal. We also investigated whether the reporting of gender-related differences in study outcomes varied between journals or subcategories. We used the Student's t-test and ANOVA to evaluate continuous variables (that is, total number of subjects evaluated, total number of women included in study population, and proportion of women comprising study population). Specifically, we analyzed whether the proportion of women in each study varied between individual journals and whether it varied between general and subspecialty journals. We used Games-Howell post-hoc testing to identify the specific journals with statistically significant differences in the proportion of women. All statistical analyses were performed using SPSS version 25 (IBM Corp, Armonk, NY, USA). A p value of less than 0.05 was designated as the threshold for statistical significance.
Results
The total study population was comprised of 55% (13,565,773 of 24,607,597) women, with Journal of Arthroplasty studies including a greater percentage of women (60%, 9,251,068 of 15,557,187) and American Journal of Sports Medicine including a smaller percentage of women (44%, 1,027,857 of 2,357,139) than studies in the other four journals (p < 0.001) (Table 1). In addition, orthopaedic subspecialty journals tended to include a greater percentage of women (54%) than did general orthopaedic journals (50%; p = 0.04). Overall, 34% (241 of 712) of studies included gender as a variable in a multifactorial statistical model. Thirty-nine percent (93 of 241) of studies demonstrated a difference in outcomes between men and women (Table 2).
Table 2.
Topics of articles that reported a difference in outcomes using gender-specific analysis in orthopaedic specialty journals in 2016
Gender-related differences were most commonly reported in the hip and knee arthroplasty journal (Journal of Arthroplasty), with 32% (67 of 208) performing a gender-specific analysis. Thirty-nine percent (41 of 105) in the American Journal of Sports Medicine reported using a gender-specific analysis. The orthopaedic spine journal (Spine) demonstrated the highest percentage of studies (40%; 65 of 162 studies) reporting gender-specific analysis compared with journals in the other subspecialty areas. However, there was no difference between the six journals with regard to the percentage of studies using gender-specific analysis (Table 3). Furthermore, there were no differences in the reporting of gender-specific analysis between general and subspecialty journals (Table 4).
Table 3.
Comparison of orthopaedic journal articles using gender-specific analysis in 2016 (n = 712)
Table 4.
Comparison of orthopaedic journal articles using gender-specific analysis in 2016, stratified by journal type (n = 253)
Discussion
Recognizing that there are gender-related differences in injury patterns and disease progression is important when treating and managing orthopaedic conditions in both men and women. Treatment outcomes may differ based on patient gender, and an adequate understanding of these differences has not been established. Only 34% (241 of 712) of the studies published in 2016 in the six orthopaedic journals evaluated in this study included gender as a variable in a multifactorial statistical model. Of these studies, 39% demonstrated a difference in the outcomes between men and women patients. There were no differences in the reporting of gender-specific analysis between general and subspecialty journals.
There are several limitations to this study. Gender-specific analysis may not be practical or even necessary for all studies; therefore, it is difficult to determine what percentage of studies should report gender-specific analysis because doing so requires possessing information that may be available at the individual-study level (such as whether analyzing by gender or sex was clinically or scientifically appropriate, possible, or even practical). Using gender-specific analysis when not indicated may lead to important errors of interpretation. Specifically, performing analyses by gender or sex when not appropriate (for example, when there were insufficient numbers of women or men in the population because the conditions in question do not affect both men and women in comparable proportions) can result in underpowered analyses and incorrect inferences regarding the absence of between-gender (or between-sex) differences. Conversely, performing sex- or gender-analyses in every study or in every analysis may result in a large number of unnecessary or inappropriate statistical comparisons, risking spurious statistical significance and incorrect conclusions of between-group differences when in fact, there were no such differences. Thus, it is important for investigators at the individual-study level to look for every opportunity to ensure that both men’s and women’s health needs are met by performing appropriate by-sex and by-gender analyses, but not to perform them when they are unnecessary or inappropriate. Studies should typically perform an initial analysis assessing for confounding variables including sex/gender. If this analysis demonstrates that sex/gender are in fact confounding variables that will affect statistical analysis, then at this point, gender-specific analysis should be considered within the final analysis. Lastly, our study only evaluated publications from the even-numbered months of 2016 for six journals because this was the last year with a full 12 months of articles available at the time we collected data for the study.
Our study demonstrated similar percentages of gender-specific analysis reporting in 2016 compared with data reported by Hettrich et al. [8] (30.2% to 34.5% from 2010 to 2016; p < 0.001). Most studies had populations consisting of approximately 50% women and 50% men. The decision to include a gender-specific analysis within a study may be related to the clinical or scientific topic being evaluated and is often a judgment call determined by the investigators. Cochrane is an organization of international researchers, patients, and health professionals who work together to develop systematic reviews of healthcare interventions [19]. They are combating issues of under-representation by endorsing Sex and Gender Equity in Research (SAGER) guidelines, which encourage the reporting of gender data. These guidelines offer a tool for researchers to standardize gender reporting in scientific publications [7]. This tool may be able to guide decision making for authors and help diminish exclusion of gender-specific data. It is also important that journal editors and reviewers consider this during the manuscript review process to help determine when gender as a variable is necessary in analyzing data. Consistency in the use of gender-specific analysis may result in a better understanding of whether differences exist when men and women are compared.
Gender-related differences were most commonly reported in hip and knee arthroplasty studies (Journal of Arthroplasty), with 32% (67 of 208) of studies performing a gender-specific analysis. Sixty-eight percent (46 of 68) of all included arthroplasty studies demonstrated a difference, including higher postoperative pain scores with higher rates of reduced postoperative ROM after TKA in women than in men [23]. Ong et al. [18] reported that being a woman was a risk factor for longer duration of symptoms before undergoing TKA, and Bawa et al. [5] reported that women were more likely than men to undergo various nonsurgical treatments before TKA. A greater number of studies reported longer lengths of hospital stay, higher levels of opioid requirements, and a higher rate of non-home discharge after TKA in women than in men [9, 11, 20, 26]. In the articles reporting THA outcomes, two studies demonstrated anatomic, radiographic differences that may be beneficial during preoperative planning and intraoperative assessment [12, 16]. Thirty-nine percent (41 of 105) of studies in an orthopaedic sports medicine journal (American Journal of Sports Medicine) reported using a gender-specific analysis. These articles demonstrated differences in the incidence of ACL injury and risk factors for knee ligamentous injuries [21, 25]. In addition, two studies reported differences in anatomic parameters contributing to femoroacetabular impingement and labral tears as well as anatomic differences leading to shoulder instability and variable treatment outcomes [3, 4]. In the current study, 41% (17 of 41) sports medicine studies in 2016 reported differences in outcomes between men and women. An orthopaedic spine journal (Spine) demonstrated the highest percentage (40%; 65 of 162 studies) of studies reporting gender-specific analysis compared with the other subspecialty journals. Twenty studies (31%) demonstrated a difference in gender-related outcomes. Several studies [6, 14] reported on anatomic differences and variations in sagittal, occipitocervical, and cervicothoracic alignment parameters. In addition, the identified studies demonstrated that there was a higher risk of complications including prolonged intubation and hospitalization in women after either cervical or lumbar fusion [6, 14]. Aldebeyan et al. [1] reported that being a woman was a major risk factor associated with discharging patients to a facility other than home after lumbar fusion surgery.
In summary, our study demonstrated that although most of the evaluated studies published in six leading orthopaedic journals in 2016 included approximately 50% women and 50% men, statistical analyses differentiating the two subsets were not routinely performed. Only 36% of studies performed gender-specific analysis, 39% of which demonstrated a difference in outcomes between men and women. Future orthopaedic studies should aim to determine when a gender-specific analysis is warranted to improve the management of orthopaedic injuries in men and women. It is important for investigators at the individual-study level to look for every opportunity to ensure that both men’s and women’s health needs are met by performing appropriate by-sex and by-gender analyses when necessary.
Acknowledgments
None.
Footnotes
Each author certifies that she has no commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.
Each author certifies that her institution waived approval for the reporting of this investigation and that all investigations were conducted in conformity with ethical principles of research.
This work was performed at Robert Wood Johnson Barnabas Health – Jersey City Medical Center, Jersey City, NJ, USA.
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