Advertisement

Impact of gender on outcomes following single-level anterior lumbar interbody fusion

Published:September 10, 2022DOI:https://doi.org/10.1016/j.jcot.2022.102019

      Abstract

      Background

      There have been a multitude of studies attempting to identify the relationship between gender and postoperative outcomes; however, few studies have examined how this relationship may affect outcomes after anterior lumbar interbody fusion (ALIF) surgery. We aim to better characterize the impact that self-reported gender may have on patient reported outcome measures (PROMs) and achievement rates of minimum clinically important difference (MCID) after ALIF.

      Methods

      A retrospective database of a single spine surgeon was searched for patients who had undergone single-level ALIF. Indications for surgery including acute trauma, infection, or malignancy were excluded. The population was separated into cohorts by self-reported gender, female or male. PROMs were recorded and compared within groups to their preoperative baselines and between groups. MCID achievement rate was compared between groups.

      Results

      140 patients were identified for this study, with 68 patients self-identifying as female gender. The male gender cohort was found to have a significantly greater prevalence of hypertension (p = 0.018). Both cohorts showed significant improvement during at least one or more postoperative time points for each evaluated outcome measure (p ≤ 0.048, all). No significant difference in mean PROM scores was noted between cohorts at any time point for any measured outcome. The female gender cohort had significantly greater MCID achievement rates for visual acuity scale (VAS) back pain overall and at the 6-month time point (p ≤ 0.043, both). The female gender cohort also had significantly greater achievement of MCID at the 1-year time point for VAS leg pain (p = 0.017).

      Conclusion

      Both female and male gender cohorts demonstrated significant improvement in all outcomes measured at one or more postoperative time points. Postoperative outcomes did not differ by gender. MCID achievement was more common in female patients. Female patients may experience more tangible clinical improvement after ALIF compared to male patients.

      Keywords

      Abbreviations:

      ALIF (anterior lumbar interbody fusion), MCID (minimum clinically important difference)

      1. Introduction

      Sociodemographic characteristics, especially sex, have been demonstrated to influence outcomes following surgical intervention across an array of fields. In search of better understanding as to how sex plays a role in outcomes following surgery, a multitude of literature comparing differences between male and female sex has been reported with contrasting results. These studies, including specialties ranging from pancreatic to orthopaedic surgery, have posited varying outcomes with several studies finding women to have inferior results or higher complication rates compared to men,
      • Sattartabar B.
      • Ajam A.
      • Pashang M.
      • et al.
      Sex and age difference in risk factor distribution, trend, and long-term outcome of patients undergoing isolated coronary artery bypass graft surgery.
      • Dixon L.K.
      • Di Tommaso E.
      • Dimagli A.
      • et al.
      Impact of sex on outcomes after cardiac surgery: a systematic review and meta-analysis.
      • Enumah Z.O.
      • Canner J.K.
      • Alejo D.
      • et al.
      Persistent racial and sex disparities in outcomes after coronary artery bypass surgery: a retrospective clinical registry review in the drug-eluting stent era.
      several reporting equivalent outcomes between the sexes,
      • MacDonald S.J.
      • Charron K.D.
      • Bourne R.B.
      • Naudie D.D.
      • McCalden R.W.
      • Rorabeck C.H.
      The John Insall Award: gender-specific total knee replacement: prospectively collected clinical outcomes.
      • Rucker D.
      • Warkentin L.M.
      • Huynh H.
      • Khadaroo R.G.
      Sex differences in the treatment and outcome of emergency general surgery.
      • Mousapour P.
      • Tasdighi E.
      • Khalaj A.
      • et al.
      Sex disparity in laparoscopic bariatric surgery outcomes: a matched-pair cohort analysis.
      • Mendolia-Loffredo S.
      • Laud P.W.
      • Sparapani R.
      • Loehrl T.A.
      • Smith T.L.
      Sex differences in outcomes of sinus surgery.
      • Filardo G.
      • Kon E.
      • Andriolo L.
      • et al.
      Does patient sex influence cartilage surgery outcome? Analysis of results at 5-year follow-up in a large cohort of patients treated with Matrix-assisted autologous chondrocyte transplantation.
      and others demonstrating superior outcomes for women.
      • Mocanu V.
      • Dang J.T.
      • Switzer N.
      • Madsen K.
      • Birch D.W.
      • Karmali S.
      Sex and race predict adverse outcomes following bariatric surgery: an MBSAQIP analysis.
      • Glein R.M.
      • Jimenez A.E.
      • Miecznikowski K.B.
      • et al.
      Patient-reported outcome scores and rate of return to sport after hip arthroscopic surgery: a sex-based comparison in professional and collegiate athletes.
      • Oh E.S.
      • Sieber F.E.
      • Leoutsakos J.M.
      • Inouye S.K.
      • Lee H.B.
      Sex differences in hip fracture surgery: preoperative risk factors for delirium and postoperative outcomes.
      • Damanakis A.I.
      • Toader J.
      • Wahler I.
      • et al.
      Influence of patient sex on outcomes after pancreatic surgery: multicentre study.
      As a result, our understanding of the impact that sex has on surgical outcomes is nuanced and unable to be generalized to different surgical subspecialties. However, the impact that sex has on outcomes following surgery can be significant. In a randomized review of studies published by six prominent orthopaedic surgery journals over a one-year period, Gianakos et al. (2020) reported 39% of studies that included gender analysis in a multivariable analysis demonstrated differences in outcomes regarding sex.
      • Gianakos A.L.
      • George N.
      • Pinninti A.
      • Kwan S.
      • LaPorte D.
      • Mulcahey M.K.
      Sex- and gender-specific analysis in orthopaedic studies.
      As a result, Gianakos et al. (2020) argued for the need to better understand differences between outcomes as influenced by sex in orthopaedic surgery to promote equitable healthcare for male and female patients.
      • Gianakos A.L.
      • George N.
      • Pinninti A.
      • Kwan S.
      • LaPorte D.
      • Mulcahey M.K.
      Sex- and gender-specific analysis in orthopaedic studies.
      The current published studies regarding the effect of gender on outcomes following lumbar surgery utilizing homogenous populations and techniques are sparse. In order to better understand the effect that gender may have on patients undergoing lumbar spine surgery, this study seeks to evaluate the potential relationship between self-reported gender and outcomes following anterior lumbar interbody fusion (ALIF) (Fig. 1, Fig. 2).
      Fig. 1
      Fig. 140 year old male undergoing ALIF at L5/S1. A: Preoperative anterior-posterior (AP) [left] and lateral [right] films. B: 6-week postoperative AP [left] and lateral [right] films.
      Fig. 2
      Fig. 247 year old female undergoing ALIF with posterior instrumentation at L5/S1. A: Preoperative AP [left] and lateral [right] films. B: 6-week postoperative AP [left] and lateral [right] films.

      2. Methods

      2.1 Patient population

      Following acquisition of patient consent and Institutional Review Board approval (ORA #14051301), patients who had undergone single-level ALIF were retrospectively searched in a prospectively maintained registry from a single academic spine surgeon. Patients missing information regarding gender or with surgical indication including infection, trauma, or malignancy were excluded. Patients were divided into two cohorts by gender: female or male.

      2.2 Data collection

      Demographics and perioperative characteristics were collected for both cohorts. Demographics collected included age, body mass index (BMI), ethnicity, presence of diabetes, active smoking, and hypertension, American Society of Anesthesiologists (ASA) score, Charlson Comorbidity Index (CCI) score, and insurance provider variant (Medicare/Medicaid versus Workers’ Compensation versus Private). Perioperative characteristics included spinal pathology, level of fusion, operative time, estimated blood loss, length of stay, acute postoperative visual analog scale (VAS) pain, postoperative narcotic consumption, and postoperative day of discharge. Patient-reported Outcome Measures (PROMs) were collected preoperatively and at 6 weeks, 12 weeks, 6 months, and 1 year postoperatively. PROMs collected included Patient-reported Outcomes Measurement Information System Physical Function (PROMIS PF), 12-item Short Form Physical Component Score (SF-12 PCS), VAS back, VAS leg, and Oswestry Disability Index (ODI).

      2.3 Statistical analysis

      All statistical analysis was performed utilizing Stata 16.0 (StataCorp LP, College Station, TX) with a p-value <0.050 used to determine significance. Continuous variables were compared between cohorts via independent t-tests. Chi-square tests were utilized to compare categorical variables between cohorts. Differences in mean PROM scores between the preoperative period and each postoperative period were compared within groups via paired sample t-tests. Absolute arithmetic differences in PROM scores between the preoperative stage and each postoperative period were calculated and compared to literal values for to assess for achievement of minimal clinically important differences (MCID) for each PROM. The literature values used to assess MCID achievement are as follows: 4.5 for PROMIS PF, 2.5 for SF-12 PCS, 2.1 for VAS back, 2.8 for VAS leg, and 14.9 for ODI.
      • Hung M.
      • Saltzman C.L.
      • Kendall R.
      • et al.
      What are the MCIDs for PROMIS, NDI, and ODI instruments among patients with spinal conditions?.
      • Parker S.L.
      • Adogwa O.
      • Paul A.R.
      • et al.
      Utility of minimum clinically important difference in assessing pain, disability, and health state after transforaminal lumbar interbody fusion for degenerative lumbar spondylolisthesis.
      • Parker S.L.
      • Mendenhall S.K.
      • Shau D.N.
      • et al.
      Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance.

      3. Results

      3.1 Descriptive analysis

      One-hundred and forty patients were identified for the study, with 68 female patients and 72 male patients included. Cohort demographics did not significantly differ with the exception of hypertension, which was more prevalent among male patients (38.9% versus 20.6%, p = 0.018) (Table 1). A large majority of patients underwent fusion at L5-S1 (82.9%) (Table 2). There were no significant differences between cohorts regarding spinal pathology, fusion level, operative time, estimated blood loss, length of stay, or acute postoperative pain or narcotic consumption (Table 2).
      Table 1Patient demographics.
      CharacteristicTotal (n = 140)Female Gender (n = 68)Male Gender (n = 72)∗p-value
      Age (mean ± SD, years)50.2 ± 12.149.7 ± 12.250.6 ± 12.10.639
      BMI (mean ± SD, kg/m2)30.9 ± 6.531.2 ± 6.930.5 ± 6.20.530
      Ethnicity0.991
       African-American12.9% (18)11.8% (8)13.9% (10)
       Asian2.9% (4)2.9% (2)2.8% (2)
       Hispanic7.9% (11)8.8% (6)6.9% (5)
       White75.0% (105)75.0% (51)75.0% (54)
       Other1.4% (2)1.5% (1)1.4% (1)
      Diabetic Status0.166
       Non-Diabetic87.1% (122)91.2% (62)83.3% (60)
       Diabetic12.9% (18)8.8% (6)16.7% (12)
      Smoking Status0.754
       Non-Smoker81.3% (113)82.4% (56)80.3% (57)
       Smoker18.7% (26)17.7% (12)19.7% (14)
      Blood Pressure0.018
       Normotensive70.0% (98)79.4% (54)61.1% (44)
       Hypertensive30.0% (42)20.6% (14)38.9% (28)
      ASA score0.745
       ≤212.7% (17)13.6% (9)11.8% (8)
       >287.3% (117)86.4% (57)88.2% (60)
      CCI Score (mean ± SD)1.73 ± 1.61.5 ± 1.31.9 ± 1.80.934
      Insurance Type0.837
       Medicare/Medicaid7.2% (10)6.0% (4)8.3% (6)
       Workers' Comp23.0% (32)22.4% (15)23.6% (17)
       Private69.8% (97)71.6% (48)68.1% (49)
      BMI = Body Mass Index; ASA = American Society of Anesthesiologists; CCI = Charlson Comorbidity Index; SD = Standard Deviations; Workers' Comp = workers' compensation.
      ∗p-value calculated using Chi-square analysis for categorical variables or Student's t-test for continuous variables.
      Boldface indicates significance.
      Table 2Perioperative characteristics.
      CharacteristicTotal (n = 140)Female Gender (n = 68)Male Gender (n = 72)∗p-value
      Spinal Pathology
       Degenerative Spondylolisthesis15.0% (21)16.2% (11)13.9% (10)0.705
       Isthmic Spondylolisthesis50.0% (70)48.5% (33)51.4% (37)0.735
       Degenerative Scoliosis7.1% (10)7.4% (5)6.9% (5)0.925
       Herniated Nucleus Pulposus7.1% (10)7.4% (5)6.9% (5)0.925
       Central Stenosis77.9% (109)77.9% (53)77.8% (56)0.981
       Foraminal Stenosis51.4% (72)45.6% (31)56.9% (41)0.179
      Fusion Level0.289
       L1-L20.7% (1)1.5% (1)0.0% (0)
       L2-L30.0% (0)0.0% (0)0.0% (0)
       L3-L42.9% (4)1.5% (1)4.2% (3)
       L4-L513.6% (19)17.7% (12)9.7% (7)
       L5-S182.9% (116)79.4% (54)86.1% (62)
      Operative Time (min)
       Mean ± SD156.7 ± 69.1148.6 ± 60.0164.5 ± 76.40.177
      Estimated Blood Loss (mL)
       Mean ± SD83.8 ± 77.589.1 ± 81.578.9 ± 74.00.451
      Length of Stay (hours)
       Mean ± SD46.7 ± 24.948.4 ± 26.945.0 ± 22.90.441
      Acute Postoperative VAS Pain
       POD 05.2 ± 1.55.1 ± 1.25.3 ± 1.80.681
       POD 14.7 ± 1.64.5 ± 1.44.9 ± 1.70.267
      Postoperative Narcotic Consumption
       POD 070.1 ± 69.973.1 ± 84.367.2 ± 53.40.621
       POD 153.0 ± 71.449.8 ± 43.856.0 ± 90.30.614
      Day of Discharge0.464
       POD 04.6% (6)4.6% (3)4.6% (3)
       POD 140.0% (52)40.0% (26)40.0% (26)
       POD 233.1% (43)33.9% (22)32.3% (21)
       POD 313.9% (18)9.2% (6)18.5% (12)
       POD 47.7% (10)10.8% (7)4.6% (3)
       POD 50.8% (1)1.5% (1)0.0% (0)
      POD = postoperative day; SD = standard deviation; VAS = Visual analog scale.
      ∗p-value calculated using Chi-square analysis for categorical variables or Student's t-test for continuous variables.

      3.2 Primary outcome measures

      Regarding function, female patients reported significant improvement in PROMIS PF at 6 months and 1 year (p ≤ 0.007, all) (Table 3). Male patients reported significant improvement in PROMIS PF at 12 weeks, 6 months, and 1 year time points (p ≤ 0.048, all) (Table 3). There was no significant difference in PROMIS PF score between cohorts at any period (Table 3). SF-12 PCS scores significantly improved from preoperative baseline in female patients at 12 weeks, 6 months, and 1 year periods (p ≤ 0.017, all) (Table 3). Male patients reported improved SF-12 PCS scores at 6 week, 12 week, and 6 month time points (p ≤ 0.043, all) (Table 3). SF-12 PCS did not significantly differ between groups at any period (Table 3). Regarding pain, mean VAS back scores improved for both female and male cohorts at all postoperative periods with the exception of the male cohort at 1 year (p < 0.001, all) (Table 3). VAS leg scores were significantly improved at 12 weeks and 1 year in the female cohort (p ≤ 0.014, all) (Table 3). VAS leg scores were significantly improved in the male cohort at 6 months (p = 0.011) (Table 3). There were no significant differences between cohorts at any period in mean VAS back or VAS leg scores (Table 3). ODI significantly improved from preoperative baseline for both female and male cohorts at the 12 week, 6 month, and 1 year periods (p ≤ 0.008, all) (Table 3). There was no significant difference demonstrated between cohorts in ODI at any period (Table 3). Female patients more frequently achieved MCID in VAS back at 6 months and overall (p ≤ 0.043, both) (Table 4). Female patients also more frequently achieved MCID in VAS leg at 1 year (p = 0.017) (Table 4).
      Table 3Mean patient reported outcome measures.
      PROMFemale Gender (mean ± SD)∗p-valueMale Gender (mean ± SD)∗p-value†p-value
      PROMIS PF
       Preoperative37.2 ± 5.636.0 ± 5.90.516
       6-week38.7 ± 5.30.95239.3 ± 6.00.1160.778
       12-week42.2 ± 7.60.12043.1 ± 9.10.0480.757
       6-month46.7 ± 8.10.00746.4 ± 10.10.0020.927
       1-year42.2 ± 8.6<0.00150.7 ± 9.90.0170.054
      SF-12 PCS
       Preoperative30.3 ± 9.630.6 ± 8.70.888
       6-week32.6 ± 6.50.60534.8 ± 10.70.0430.452
       12-week36.9 ± 8.20.01738.9 ± 10.10.0010.497
       6-month39.1 ± 10.20.00138.8 ± 11.00.0020.944
       1-year43.9 ± 10.90.00939.9 ± 10.50.4000.434
      VAS back
       Preoperative7.1 ± 2.16.5 ± 2.50.141
       6-week4.0 ± 2.6<0.0014.1 ± 2.7<0.0010.903
       12-week3.4 ± 2.7<0.0013.7 ± 2.6<0.0010.545
       6-month3.0 ± 2.7<0.0013.4 ± 2.6<0.0010.424
       1-year2.8 ± 3.4<0.0013.5 ± 3.70.6040.702
      VAS leg
       Preoperative5.2 ± 2.94.2 ± 3.20.185
       6-week3.7 ± 2.70.0503.6 ± 3.30.8950.926
       12-week2.8 ± 2.60.0142.8 ± 2.90.1300.993
       6-month3.3 ± 3.20.0892.1 ± 2.70.0110.227
       1-year1.9 ± 2.70.0033.0 ± 3.40.3220.390
      ODI
       Preoperative40.3 ± 13.638.8 ± 20.50.722
       6-week35.2 ± 18.60.28034.3 ± 25.50.5780.880
       12-week24.3 ± 17.5<0.00121.5 ± 13.5<0.0010.493
       6-month23.5 ± 18.3<0.00118.1 ± 17.00.0080.300
       1-year26.3 ± 25.20.00520.7 ± 21.00.0040.582
      SD = standard deviation.
      p-values calculated using paired samples t-test to determine improvement in PROMs.
      †p-values calculated using Student's t-test for independent samples to compare PROMs between groups.
      Boldface indicates significance.
      Table 4MCID achievement.
      PROMFemale Gender

      %, (n)
      Male Gender

      %, (n)
      ∗p-value
      PROMIS-PF
       6-weeks33.3% (4)39.1% (9)0.736
       12-weeks40.0% (4)42.1% (8)0.913
       6-months71.4% (5)64.7% (11)0.751
       1-year66.7% (6)66.7% (6)1.000
       Overall76.9% (10)64.3% (18)0.418
      SF-12 PCS
       6-weeks56.3% (9)50.0% (11)0.703
       12-weeks71.4% (10)79.0% (15)0.618
       6-months81.8% (9)76.5% (13)0.736
       1-year75.0% (9)66.7% (4)0.710
       Overall85.7% (18)75.9% (22)0.390
      VAS back
       6-weeks56.9% (29)50.9% (27)0.545
       12-weeks60.4% (29)52.9% (27)0.453
       6-months70.0% (28)47.6% (20)0.040
       1-year83.3% (10)42.9% (3)0.067
       Overall80.7% (46)63.8% (37)0.043
      VAS leg
       6-weeks28.0% (7)23.1% (6)0.687
       12-weeks43.5% (10)20.8% (5)0.096
       6-months36.8% (7)31.3% (5)0.728
       1-year66.7% (8)12.5% (1)0.017
       Overall56.7% (17)37.9% (11)0.150
      ODI
       6-weeks24.0% (6)29.6% (8)0.647
       12-weeks34.8% (8)40.0% (10)0.709
       6-months50.0% (10)35.3% (6)0.368
       1-year66.7% (8)75.0% (6)0.690
       Overall58.1% (18)46.7% (14)0.373
      p-values calculated using chi-square analysis.
      Boldface indicates significance.

      4. Discussion

      Anterior lumbar interbody fusion is a common technique for management of chronic, refractory back pain as a result of degenerative spine disease.
      • Upadhyayula P.S.
      • Curtis E.I.
      • Yue J.K.
      • Sidhu N.
      • Ciacci J.D.
      Anterior versus transforaminal lumbar interbody fusion: perioperative risk factors and 30-day outcomes.
      ,
      • Wert Jr., W.G.
      • Sellers W.
      • Mariner D.
      • et al.
      Identifying risk factors for complications during exposure for anterior lumbar interbody fusion.
      ALIF has demonstrated safety and efficacy when compared to other approaches, even in the ambulatory setting.
      • Upadhyayula P.S.
      • Curtis E.I.
      • Yue J.K.
      • Sidhu N.
      • Ciacci J.D.
      Anterior versus transforaminal lumbar interbody fusion: perioperative risk factors and 30-day outcomes.
      ,
      • Vieli M.
      • Staartjes V.E.
      • Eversdjik H.A.J.
      • De Wispelaere M.P.
      • Oosterhuis J.W.A.
      • Schröder M.L.
      Safety and efficacy of anterior lumbar interbody fusion for discogenic chronic low back pain in a short-stay setting: data from a prospective registry.
      ,
      • Kamalapathy P.N.
      • Bell J.
      • Chen D.
      • Raso J.
      • Hassanzadeh H.
      Propensity scored analysis of outpatient Anterior lumbar interbody fusion: No increased complications.
      However, there is little-to-no published data regarding the influence of gender on outcomes following ALIF. As Gianakos et al. (2020) posited, it is necessary to have a better understanding of the influence gender has on spine surgery to provide equitable healthcare to both female and male patients alike.
      • Gianakos A.L.
      • George N.
      • Pinninti A.
      • Kwan S.
      • LaPorte D.
      • Mulcahey M.K.
      Sex- and gender-specific analysis in orthopaedic studies.
      Prior studies of lumbar spine surgery outcomes have reported contrasting findings. Additionally, none of these studies reported on isolated ALIF patients. Ekman et al. (2009) reported male gender to be an independent predictor for superior outcomes following lumbar fusion for isthmic spondylolisthesis.
      • Ekman P.
      • Möller H.
      • Hedlund R.
      Predictive factors for the outcome of fusion in adult isthmic spondylolisthesis.
      Similarly, Elsamadicy et al. (2017) reported significantly fewer female patients to report satisfaction following elective lumbar spine surgery along with significantly greater pain and disability present in the female cohort when compared to male patients.
      • Elsamadicy A.A.
      • Reddy G.B.
      • Nayar G.
      • et al.
      Impact of gender disparities on short-term and long-term patient reported outcomes and satisfaction measures after elective lumbar spine surgery: a single institutional study of 384 patients.
      Strömqvist et al. (2008) additionally reported an increased rate of analgesic utilization in female patients at 1-year follow-up after lumbar disc herniation surgery.
      • Strömqvist F.
      • Ahmad M.
      • Hildingsson C.
      • Jönsson B.
      • Strömqvist B.
      Gender differences in lumbar disc herniation surgery.
      However, Strömqvist et al. (2008) also noted that there was no statistical significance between relative improvement or surgical satisfaction between male and female patients.
      • Strömqvist F.
      • Ahmad M.
      • Hildingsson C.
      • Jönsson B.
      • Strömqvist B.
      Gender differences in lumbar disc herniation surgery.
      In a later epidemiological study of 15,631 lumbar disc herniation operations, this same group reported that female patients reported inferior pain scores when compared to male patients at time of surgery scheduling.
      • Strömqvist F.
      • Strömqvist B.
      • Jönsson B.
      • Karlsson M.K.
      Gender differences in patients scheduled for lumbar disc herniation surgery: a National Register Study including 15,631 operations.
      Strömqvist et al. (2016) postulated that this discrepancy may be due to differences in selection timing on a surgeon or patient level.
      • Strömqvist F.
      • Strömqvist B.
      • Jönsson B.
      • Karlsson M.K.
      Gender differences in patients scheduled for lumbar disc herniation surgery: a National Register Study including 15,631 operations.
      Several studies demonstrated female patients to present with inferior pain and disability scores, but reported females to improve more dramatically than male patients after lumbar spine surgery.
      • Triebel J.
      • Snellman G.
      • Sandén B.
      • Strömqvist F.
      • Robinson Y.
      Women do not fare worse than men after lumbar fusion surgery: two-year follow-up results from 4,780 prospectively collected patients in the Swedish National Spine Register with lumbar degenerative disc disease and chronic low back pain.
      ,
      • MacLean M.A.
      • Touchette C.J.
      • Han J.H.
      • Christie S.D.
      • Pickett G.E.
      Gender differences in the surgical management of lumbar degenerative disease: a scoping review.
      Finally, a large collection of studies reported that female patients presented with inferior baseline outcome measure scores, but noted that these differences between genders were not significant in the postoperative periods.
      • Siccoli A.
      • Staartjes V.E.
      • de Wispelaere M.P.
      • Schröder M.L.
      Gender differences in degenerative spine surgery: do female patients really fare worse?.
      • Khechen B.
      • Haws B.E.
      • Patel D.V.
      • Cardinal K.L.
      • Guntin J.A.
      • Singh K.
      Does gender influence postoperative outcomes in minimally invasive transforaminal lumbar interbody fusion?.
      • Pochon L.
      • Kleinstück F.S.
      • Porchet F.
      • Mannion A.F.
      Influence of gender on patient-oriented outcomes in spine surgery.
      • Kanaan S.F.
      • Melton B.L.
      • Waitman L.R.
      • Simpson M.H.
      • Sharma N.K.
      The effect of age and gender on acute postoperative pain and function following lumbar spine surgeries.
      • Nolte M.T.
      • Jenkins N.W.
      • Parrish J.M.
      • et al.
      The influence of sex on clinical outcomes in minimally invasive lumbar decompression.
      • Gautschi O.P.
      • Smoll N.R.
      • Corniola M.V.
      • et al.
      Sex differences in lumbar degenerative disc disease.

      4.1 Physical function

      In this current study, both female and male cohorts reported significant improvement at multiple postoperative time points in both PROMIS PF and SF-12 PCS scores when compared to preoperative baseline scores. There was no significant difference in physical function outcome scores found between cohorts at any period, including the preoperative stage. Additionally, there was no significant difference in MCID achievement between cohorts. These findings most closely replicate those found by Gautschi et al. (2016) who reported similar preoperative and postoperative levels of function between male and female patients undergoing intervention for lumbar degenerative disc disease.
      • Gautschi O.P.
      • Smoll N.R.
      • Corniola M.V.
      • et al.
      Sex differences in lumbar degenerative disc disease.
      Gautschi et al. (2016) utilized objective functional impairment (OFI) scores and subjective functional impairment (SFI) scores to compare outcomes between genders, finding the OFI scores to be similar prior to and following intervention for both cohorts.
      • Gautschi O.P.
      • Smoll N.R.
      • Corniola M.V.
      • et al.
      Sex differences in lumbar degenerative disc disease.
      Gautschi et al. (2016) recommended use of more objective measurements of function and disability, such as the timed-up-and-go test, to protect against reporting bias regarding these outcomes.
      • Gautschi O.P.
      • Smoll N.R.
      • Corniola M.V.
      • et al.
      Sex differences in lumbar degenerative disc disease.
      Further, since all patients were evaluated and operated on by a single spine surgeon, discrepancies in preoperative patient reported scores between male and female patients may be lacking as surgical selection timing may be more consistent, limiting the concern posed by Strömqvist et al. (2008).
      • Strömqvist F.
      • Ahmad M.
      • Hildingsson C.
      • Jönsson B.
      • Strömqvist B.
      Gender differences in lumbar disc herniation surgery.

      4.2 Pain

      With regard to pain, both VAS back and VAS leg scores significantly improved in the postoperative period regardless of gender. Mean scores did not significantly differ between male and female cohorts at any time period. However, female patients were more likely to achieve MCID in both VAS back and VAS leg scores. These results are most similar to those of MacLean et al. (2020) and Triebel et al. (2016), both finding female patients to improve at a greater relative increment following intervention.
      • Triebel J.
      • Snellman G.
      • Sandén B.
      • Strömqvist F.
      • Robinson Y.
      Women do not fare worse than men after lumbar fusion surgery: two-year follow-up results from 4,780 prospectively collected patients in the Swedish National Spine Register with lumbar degenerative disc disease and chronic low back pain.
      ,
      • MacLean M.A.
      • Touchette C.J.
      • Han J.H.
      • Christie S.D.
      • Pickett G.E.
      Gender differences in the surgical management of lumbar degenerative disease: a scoping review.
      One potential explanation for the variation in MCID achievement rates between cohorts may be due to variation in pain scores at presentation. While not significantly different, female patients did present with higher mean VAS back (7.1 versus 6.5 in male patients) and higher mean VAS leg (5.2 versus 4.2 in male patients), which may account for the difference in MCID achievement between the two groups.

      4.3 Disability

      Both female and male cohorts reported significant improvement in mean ODI scores at the 12-week mark and all following time points when compared to preoperative baseline. Significant differences between cohorts were not observed at any period. Similarly, MCID achievement rate did not significantly vary between cohorts. As discussed in relation to our findings regarding physical function, these results are most similar to those found by Gautschi et al. (2016).
      • Gautschi O.P.
      • Smoll N.R.
      • Corniola M.V.
      • et al.
      Sex differences in lumbar degenerative disc disease.

      4.4 Limitations

      This current study has several limitations. Use of single-surgeon data, while lending strength due to homogeneity of technique, patient population, and surgical timing, limits generalizability of these findings. In similar manner, only single-level fusions were included to prevent potential confounding, yet this limits generalizability to multi-level procedures. Further, this study utilized PROMs which are collected via survey and are subject to reporting bias. An additional limitation for relying on patient surveys was selection bias, as some patients were lost to follow-up. Further, some patients may have not reached the 1-year postoperative time point, as all data were analyzed through a prospectively maintained database. This limitation may be noted as the loss of significance at the 1-year time point for SF-12 PCS, VAS back, and VAS leg in male patients. Inclusion of a variety of spinal pathologies allows for greater generalization of our conclusions; however, this limits specificity in application to a particular diagnosis. Additionally, univariate analysis can be susceptible to confounding variables that may be more accurately accounted for by multivariable analysis. Unfortunately, multivariable analysis of this data was limited due to the large collection of preoperative variables in relation to the sample size at later follow-up times, preventing fit of a reliable predictive model. With the exception of prevalence of hypertension, which is known to vary between genders,
      • Everett B.
      • Zajacova A.
      Gender differences in hypertension and hypertension awareness among young adults.
      there were no significant demographic or perioperative differences between groups save the experimental question of gender, which lends strength to the univariate analysis. Finally, more patients in the male cohort suffered from hypertension; however, this reflects the well-known increased prevalence of hypertension in males and as such may not detract significantly from our conclusions.
      • Tostes R.C.
      • Fortes Z.B.
      • Callera G.E.
      • et al.
      Endothelin, sex and hypertension.

      5. Conclusion

      Independent of gender, male and female patients report significant improvement in physical function, pain, and disability outcomes following ALIF. Significant differences between cohorts regarding function, pain, or disability were not present preoperatively or at any postoperative period. Female patients were more likely to achieve MCID in VAS back and VAS leg measures. Female patients may more frequently see clinically meaningful differences in both back and leg pain following ALIF.

      IRB approval

      ORA #14051301.

      CRediT authorship contribution statement

      Timothy J. Hartman: Conceptualization, Methodology, Visualization, Formal analysis, Software, Investigation, Writing – original draft, Writing – review & editing. James W. Nie: Conceptualization, Methodology, Visualization, Formal analysis, Software, Investigation, Writing – original draft, Writing – review & editing. Keith R. MacGregor: Project administration, Data curation, Investigation, Writing – review & editing. Omolabake O. Oyetayo: Project administration, Data curation, Investigation, Writing – review & editing. Eileen Zheng: Project administration, Data curation, Investigation, Writing – review & editing. Kern Singh: Conceptualization, Methodology, Supervision, Resources, Investigation, Writing – review & editing.

      Declaration of competing interest

      None.

      References

        • Sattartabar B.
        • Ajam A.
        • Pashang M.
        • et al.
        Sex and age difference in risk factor distribution, trend, and long-term outcome of patients undergoing isolated coronary artery bypass graft surgery.
        BMC Cardiovasc Disord. 2021; 21: 460
        • Dixon L.K.
        • Di Tommaso E.
        • Dimagli A.
        • et al.
        Impact of sex on outcomes after cardiac surgery: a systematic review and meta-analysis.
        Int J Cardiol. 2021; 343: 27-34
        • Enumah Z.O.
        • Canner J.K.
        • Alejo D.
        • et al.
        Persistent racial and sex disparities in outcomes after coronary artery bypass surgery: a retrospective clinical registry review in the drug-eluting stent era.
        Ann Surg. 2020; 272: 660-667
        • MacDonald S.J.
        • Charron K.D.
        • Bourne R.B.
        • Naudie D.D.
        • McCalden R.W.
        • Rorabeck C.H.
        The John Insall Award: gender-specific total knee replacement: prospectively collected clinical outcomes.
        Clin Orthop Relat Res. 2008; 466: 2612-2616
        • Rucker D.
        • Warkentin L.M.
        • Huynh H.
        • Khadaroo R.G.
        Sex differences in the treatment and outcome of emergency general surgery.
        PLoS One. 2019; 14e0224278
        • Mousapour P.
        • Tasdighi E.
        • Khalaj A.
        • et al.
        Sex disparity in laparoscopic bariatric surgery outcomes: a matched-pair cohort analysis.
        Sci Rep. 2021; 1112809
        • Mendolia-Loffredo S.
        • Laud P.W.
        • Sparapani R.
        • Loehrl T.A.
        • Smith T.L.
        Sex differences in outcomes of sinus surgery.
        Laryngoscope. 2006; 116: 1199-1203
        • Filardo G.
        • Kon E.
        • Andriolo L.
        • et al.
        Does patient sex influence cartilage surgery outcome? Analysis of results at 5-year follow-up in a large cohort of patients treated with Matrix-assisted autologous chondrocyte transplantation.
        Am J Sports Med. 2013; 41: 1827-1834
        • Mocanu V.
        • Dang J.T.
        • Switzer N.
        • Madsen K.
        • Birch D.W.
        • Karmali S.
        Sex and race predict adverse outcomes following bariatric surgery: an MBSAQIP analysis.
        Obes Surg. 2020; 30: 1093-1101
        • Glein R.M.
        • Jimenez A.E.
        • Miecznikowski K.B.
        • et al.
        Patient-reported outcome scores and rate of return to sport after hip arthroscopic surgery: a sex-based comparison in professional and collegiate athletes.
        Am J Sports Med. 2021; 49: 3242-3249
        • Oh E.S.
        • Sieber F.E.
        • Leoutsakos J.M.
        • Inouye S.K.
        • Lee H.B.
        Sex differences in hip fracture surgery: preoperative risk factors for delirium and postoperative outcomes.
        J Am Geriatr Soc. 2016; 64: 1616-1621
        • Damanakis A.I.
        • Toader J.
        • Wahler I.
        • et al.
        Influence of patient sex on outcomes after pancreatic surgery: multicentre study.
        Br J Surg. 2022; (Published online May 16)https://doi.org/10.1093/bjs/znac128
        • Gianakos A.L.
        • George N.
        • Pinninti A.
        • Kwan S.
        • LaPorte D.
        • Mulcahey M.K.
        Sex- and gender-specific analysis in orthopaedic studies.
        Clin Orthop Relat Res. 2020; 478: 1482-1488
        • Hung M.
        • Saltzman C.L.
        • Kendall R.
        • et al.
        What are the MCIDs for PROMIS, NDI, and ODI instruments among patients with spinal conditions?.
        Clin Orthop Relat Res. 2018; 476: 2027-2036
        • Parker S.L.
        • Adogwa O.
        • Paul A.R.
        • et al.
        Utility of minimum clinically important difference in assessing pain, disability, and health state after transforaminal lumbar interbody fusion for degenerative lumbar spondylolisthesis.
        J Neurosurg Spine. 2011; 14: 598-604
        • Parker S.L.
        • Mendenhall S.K.
        • Shau D.N.
        • et al.
        Minimum clinically important difference in pain, disability, and quality of life after neural decompression and fusion for same-level recurrent lumbar stenosis: understanding clinical versus statistical significance.
        J Neurosurg Spine. 2012; 16: 471-478
        • Upadhyayula P.S.
        • Curtis E.I.
        • Yue J.K.
        • Sidhu N.
        • Ciacci J.D.
        Anterior versus transforaminal lumbar interbody fusion: perioperative risk factors and 30-day outcomes.
        Internet J Spine Surg. 2018; 12: 533-542
        • Wert Jr., W.G.
        • Sellers W.
        • Mariner D.
        • et al.
        Identifying risk factors for complications during exposure for anterior lumbar interbody fusion.
        Cureus. 2021; 13e16792
        • Vieli M.
        • Staartjes V.E.
        • Eversdjik H.A.J.
        • De Wispelaere M.P.
        • Oosterhuis J.W.A.
        • Schröder M.L.
        Safety and efficacy of anterior lumbar interbody fusion for discogenic chronic low back pain in a short-stay setting: data from a prospective registry.
        Cureus. 2019; 11e5332
        • Kamalapathy P.N.
        • Bell J.
        • Chen D.
        • Raso J.
        • Hassanzadeh H.
        Propensity scored analysis of outpatient Anterior lumbar interbody fusion: No increased complications.
        Clin Spine Surg. 2022; 35: E320-E326
        • Ekman P.
        • Möller H.
        • Hedlund R.
        Predictive factors for the outcome of fusion in adult isthmic spondylolisthesis.
        Spine. 2009; 34: 1204-1210
        • Elsamadicy A.A.
        • Reddy G.B.
        • Nayar G.
        • et al.
        Impact of gender disparities on short-term and long-term patient reported outcomes and satisfaction measures after elective lumbar spine surgery: a single institutional study of 384 patients.
        World Neurosurg. 2017; 107: 952-958
        • Strömqvist F.
        • Ahmad M.
        • Hildingsson C.
        • Jönsson B.
        • Strömqvist B.
        Gender differences in lumbar disc herniation surgery.
        Acta Orthop. 2008; 79: 643-649
        • Strömqvist F.
        • Strömqvist B.
        • Jönsson B.
        • Karlsson M.K.
        Gender differences in patients scheduled for lumbar disc herniation surgery: a National Register Study including 15,631 operations.
        Eur Spine J. 2016; 25: 162-167
        • Triebel J.
        • Snellman G.
        • Sandén B.
        • Strömqvist F.
        • Robinson Y.
        Women do not fare worse than men after lumbar fusion surgery: two-year follow-up results from 4,780 prospectively collected patients in the Swedish National Spine Register with lumbar degenerative disc disease and chronic low back pain.
        Spine J. 2017; 17: 656-662
        • MacLean M.A.
        • Touchette C.J.
        • Han J.H.
        • Christie S.D.
        • Pickett G.E.
        Gender differences in the surgical management of lumbar degenerative disease: a scoping review.
        J Neurosurg Spine. Published online January. 2020; 31: 1-18
        • Siccoli A.
        • Staartjes V.E.
        • de Wispelaere M.P.
        • Schröder M.L.
        Gender differences in degenerative spine surgery: do female patients really fare worse?.
        Eur Spine J. 2018; 27: 2427-2435
        • Khechen B.
        • Haws B.E.
        • Patel D.V.
        • Cardinal K.L.
        • Guntin J.A.
        • Singh K.
        Does gender influence postoperative outcomes in minimally invasive transforaminal lumbar interbody fusion?.
        Clin Spine Surg. 2019; 32: E107-E111
        • Pochon L.
        • Kleinstück F.S.
        • Porchet F.
        • Mannion A.F.
        Influence of gender on patient-oriented outcomes in spine surgery.
        Eur Spine J. 2016; 25: 235-246
        • Kanaan S.F.
        • Melton B.L.
        • Waitman L.R.
        • Simpson M.H.
        • Sharma N.K.
        The effect of age and gender on acute postoperative pain and function following lumbar spine surgeries.
        Physiother Res Int. 2021; 26e1888
        • Nolte M.T.
        • Jenkins N.W.
        • Parrish J.M.
        • et al.
        The influence of sex on clinical outcomes in minimally invasive lumbar decompression.
        Internet J Spine Surg. 2021; 15: 763-769
        • Gautschi O.P.
        • Smoll N.R.
        • Corniola M.V.
        • et al.
        Sex differences in lumbar degenerative disc disease.
        Clin Neurol Neurosurg. 2016; 145: 52-57
        • Tostes R.C.
        • Fortes Z.B.
        • Callera G.E.
        • et al.
        Endothelin, sex and hypertension.
        Clin Sci. 2008; 114: 85-97
        • Everett B.
        • Zajacova A.
        Gender differences in hypertension and hypertension awareness among young adults.
        Biodemogr Soc Biol. 2015; 61: 1-17