Introduction Letters of recommendation are considered an important factor in the holistic ranking of orthopaedic residency applications. The standardized letter of recommendation (SLOR) was introduced in 2017 in response to the inherent bias and limited comparative value of traditional LORs. It includes standardized questions about an applicant's orthopaedic qualifications, designed to enable fair comparisons among candidates. However, disparate and inconsistent findings have made it difficult to draw meaningful conclusions from individual studies on the SLOR and narrative letter of recommendation. Question/purposes In this systematic review we asked: (1) What is the distribution of applicant SLOR rating among nine domains and summative scores? (2) Are there applicant characteristics associated with SLOR ratings? (3) Is there gender and racial bias in the SLOR and narrative letter of recommendation? Methods PubMed, EBSCO, and Google Scholar electronic databases were queried on March 20, 2023, to identify all studies evaluating SLOR and narrative letter of recommendations between January 1, 2017, and March 20, 2023. Articles that evaluated orthopaedic SLOR or narrative LORs were included. Systematic reviews, case reports, duplicate studies between databases, and grey literature such as abstracts and articles on preprint servers were excluded. Eight studies including 6179 applicants and 18,987 letters of recommendation were included in the final analysis. The applicant classes ranged from years 2014 to 2020. Two reviewers independently evaluated the quality of the included studies using the Joanna Briggs Institute (JBI) tool for cross-sectional studies. The mean JBI score of included studies was 7.4 out of a maximum of 8, with higher scores indicating better quality. The primary outcome was to determine the distribution of applicant SLOR rankings in their summative score. Summative scores were separated into ranked to match, top one-third, middle one-third, lower one-third, and not a fit. Four studies reported the summative SLOR scores of applicants. Our secondary study goal was to assess applicant characteristics associated with SLOR summative scores and assess any bias present in the SLOR or narrative recommendation. Five studies compared SLOR ratings across applicant characteristics including gender, race, USMLE Step 1 score, USMLE Step 2 score, Alpha Omega Alpha (A Omega A) membership, clerkship grades, and publications. Gender and racial bias were also assessed across five studies. Four studies utilized a linguistic analysis software to search letters of recommendation for differences in word category use by gender and race. Results Studies consistently found that a higher percentage of candidates were identified in the top percentile blocks than is mathematically possible. For example, the two studies that tallied the proportion of candidates ranking in the top 10% of applicants found that 36% and 42% were rated as being in the top 10%. Similarly, articles found more than 87% of applicants scored in the top one-third. Studies had mixed results, but in general, they suggested that A Omega A status, higher Step 1 scores, and more research publications have a slightly positive association with increased SLOR scores. We found no evidence of gender bias against women, and in fact, most studies evaluating word choices found word choices for women candidates generally were stronger. Similarly, no consistent disparities were identified in word categories utilized in SLORs based on applicant race. Conclusion Most notably, a mathematically impossible proportion of applicants were counted in the top percentiles in letters of recommendation. This compromises readers' abilities to differentiate candidates. Factors like AOA status and research publications displayed a modest positive correlation with SLOR scores. Gender bias against women or candidates from racial minority groups was not evident.
