Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength.

Background: In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. Methods: Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. Results: The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). Conclusion: In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Coccydynia: A Review of Anatomy, Causes, Diagnosis, and Treatment.

¼ Coccydynia is a painful condition affecting many patients at the terminal caudal end of the spine.¼ An understanding of coccyx anatomy and variations of morphology is necessary for proper diagnosis. A multifactorial etiology for pain may be responsible for this clinical entity.¼ Several treatment options exist. Successful outcomes for patients depend on individual patient characteristics and the etiology of pain.

Comparison of ChatGPT-3.5, ChatGPT-4, and Orthopaedic Resident Performance on Orthopaedic Assessment Examinations.

INTRODUCTION: Artificial intelligence (AI) programs have the ability to answer complex queries including medical profession examination questions. The purpose of this study was to compare the performance of orthopaedic residents (ortho residents) against Chat Generative Pretrained Transformer (ChatGPT)-3.5 and GPT-4 on orthopaedic assessment examinations. A secondary objective was to perform a subgroup analysis comparing the performance of each group on questions that included image interpretation versus text-only questions. METHODS: The ResStudy orthopaedic examination question bank was used as the primary source of questions. One hundred eighty questions and answer choices from nine different orthopaedic subspecialties were directly input into ChatGPT-3.5 and then GPT-4. ChatGPT did not have consistently available image interpretation, so no images were directly provided to either AI format. Answers were recorded as correct versus incorrect by the chatbot, and resident performance was recorded based on user data provided by ResStudy. RESULTS: Overall, ChatGPT-3.5, GPT-4, and ortho residents scored 29.4%, 47.2%, and 74.2%, respectively. There was a difference among the three groups in testing success, with ortho residents scoring higher than ChatGPT-3.5 and GPT-4 ( P < 0.001 and P < 0.001). GPT-4 scored higher than ChatGPT-3.5 ( P = 0.002). A subgroup analysis was performed by dividing questions into question stems without images and question stems with images. ChatGPT-3.5 was more correct (37.8% vs. 22.4%, respectively, OR = 2.1, P = 0.033) and ChatGPT-4 was also more correct (61.0% vs. 35.7%, OR = 2.8, P < 0.001), when comparing text-only questions versus questions with images. Residents were 72.6% versus 75.5% correct with text-only questions versus questions with images, with no significant difference ( P = 0.302). CONCLUSION: Orthopaedic residents were able to answer more questions accurately than ChatGPT-3.5 and GPT-4 on orthopaedic assessment examinations. GPT-4 is superior to ChatGPT-3.5 for answering orthopaedic resident assessment examination questions. Both ChatGPT-3.5 and GPT-4 performed better on text-only questions than questions with images. It is unlikely that GPT-4 or ChatGPT-3.5 would pass the American Board of Orthopaedic Surgery written examination.

Longitudinal Assessment of Modern Spine Surgery Training: 10-Year Follow-up of a Nationwide Survey of Residency and Spine Fellowship Program Directors.

Spine surgeons complete training through residency in orthopaedic surgery (ORTH) or neurosurgery (NSGY). A survey was conducted in 2013 to evaluate spine surgery training. Over the past decade, advances in surgical techniques and the changing dynamics in fellowship training may have affected training and program director (PD) perceptions may have shifted. Methods: This study is a cross-sectional survey distributed to all PDs of ORTH and NSGY residencies and spine fellowships in the United States. Participants were queried regarding characteristics of their program, ideal characteristics of residency training, and opinions regarding the current training environment. χ2 tests were used to compare answers over the years. Results: In total, 241 PDs completed the survey. From 2013 to 2023, NSGY increased the proportion of residents with >300 spine cases (86%-100%) while ORTH remained with >90% of residents with < 225 cases (p < 0.05). A greater number of NSGY PDs encouraged spine fellowship even for community spine surgery practice (0% in 2013 vs. 14% in 2023, p < 0.05), which continued to be significantly different from ORTH PDs (∼88% agreed, p > 0.05). 100% of NSGY PDs remained confident in their residents performing spine surgery, whereas ORTH confidence significantly decreased from 43% in 2013 to 25% in 2023 (p < 0.05). For spinal deformity, orthopaedic PDs (92%), NSGY PDs (96%), and fellowship directors (95%), all agreed that a spine fellowship should be pursued (p = 0.99). In both 2013 and 2023, approximately 44% were satisfied with the spine training model in the United States. In 2013, 24% of all PDs believed we should have a dedicated spine residency, which increased to 39% in 2023 (fellowship: 57%, ORTH: 38%, NSGY: 21%) (p < 0.05). Conclusion: Spine surgery training continues to evolve, yet ORTH and neurological surgery training remains significantly different in case volumes and educational strengths. In both 2013 and 2023, less than 50% of PDs were satisfied with the current spine surgery training model, and a growing minority believe that spine surgery should have its own residency training pathway. Level of Evidence: IV.

Improved Outcomes After Reinforced Radial Meniscus Repair Augmented With Bone Marrow Aspirate Concentrate.

Purpose: To assess clinical outcomes of patients who have undergone surgical repair of radial meniscal tears with reinforced suture bar (rebar) technique augmented with bone marrow aspirate concentrate. Methods: This is a retrospective study of a single fellowship-trained sports medicine surgeon's experience on all patients who underwent a reinforced repair (rebar) of a radial meniscus tear from November 2016 to 2018, with a minimum of 12-month follow-up. Lysholm scores, IKDC (International Knee Documentation Committee) Subjective Knee Form scores, and Tegner scale were collected postoperatively at periods for at least 1 year and retrospectively studied. Results: Patients were followed for an average of 36.3 ± 25.0 months [range: 12.0-69.0 months]. Pain scores improved from 6.1 ± 2.1 to 0.4 ± 1.4 at 1 year (P < .001). IKDC Subjective Knee Form scores improved from 63 ± 26 to 90 ± 13 (P = .021). Lysholm scores improved from 64 ± 28 to 94 ± 9 (P = .025). Based on a calculated minimal clinical important difference (MCID) of 1.5, 100% of patients had improvement above the MCID. In addition, 88% of patients had a 1-year IKDC Subjective Knee Form score above the patient acceptable symptomatic state. Preoperative Tegner activity scale improved from 3 ± 1.5 to 8 ± 2.6 (P = .007). Patients returned to their preinjury activity with little difference in the Tegner activity scale when we compared preinjury and 1-year postoperative (8.1 ± 1.3 vs 8.0 ± 2.6 respectively, P = .317). Conclusions: The rebar repair technique for radial meniscus tears, with bone marrow aspirate concentrate augmentation, showed improved outcomes in both pain and function at minimum follow-up of 12 months. Patients were able to return to a high preinjury activity level by 1 year, and 100% of patients had improvement above the MCID and 88% met patient acceptable symptomatic state. Level of Evidence: Level IV, therapeutic case series.

Complications of Lateral Decubitus Positioning During Orthopaedic Surgery.

¼ Lateral decubitus positioning is a nonanatomical position used for multiple orthopaedic procedures to obtain adequate surgical exposure.¼ Unique ophthalmologic, musculoskeletal, neurovascular, and hemodynamic complications may arise inadvertently from positioning.¼ Orthopaedic surgeons should be aware of the possible complications that may manifest from placing patients in the lateral decubitus position to adequately prevent and to properly manage them.

Lumbar Disc Herniation: Diagnosis and Management.

Lumbar disc herniations are common causes of lower back pain, neurological dysfunction, and buttock/leg pain. Herniation refers to the displacement of the nucleus pulposus of the intervertebral disc through the annulus fibrosus, thereby causing pressure on the neural elements. The sequalae of lumbar disc herniations range in severity from mild low back and buttock pain to severe cases of inability to ambulate and cauda equina syndrome. Diagnosis is achieved with a thorough history and physical examination along with advanced imaging. Treatment plans are dictated by corresponding patient symptoms and examination findings with their imaging. Most patients can experience relief with nonsurgical measures. However, if symptoms persist or worsen, surgery may be appropriate.

Severe Hypersensitivity Reaction to Dermabond Prineo After Anterior Cervical Discectomy and Fusion: A Case Report.

CASE: A 68-year-old woman underwent an anterior cervical discectomy and fusion for cervical radiculopathy and subsequently developed a severe contact hypersensitivity reaction in response to Dermabond Prineo, beginning 10 days postoperatively. The Dermabond Prineo mesh was removed, and the patient was treated symptomatically with diphenhydramine, systemic steroids, and oral antibiotics, with complete resolution of her symptoms. CONCLUSION: This is the first reported contact hypersensitivity reaction to Dermabond Prineo in the context of spine surgery. Surgeons should be able to recognize this presentation and treat this appropriately.

An Artificial Intelligence Approach to Predicting Unplanned Intubation Following Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Level III retrospective database study. OBJECTIVES: The purpose of this study is to determine if machine learning algorithms are effective in predicting unplanned intubation following anterior cervical discectomy and fusion (ACDF). METHODS: The National Surgical Quality Initiative Program (NSQIP) was queried to select patients who had undergone ACDF. Machine learning analysis was conducted in Python and multivariate regression analysis was conducted in R. C-Statistics area under the curve (AUC) and prediction accuracy were used to measure the classifier's effectiveness in distinguishing cases. RESULTS: In total, 54 502 patients met the study criteria. Of these patients, .51% underwent an unplanned re-intubation. Machine learning algorithms accurately classified between 72%-100% of the test cases with AUC values of between .52-.77. Multivariable regression indicated that the number of levels fused, male sex, COPD, American Society of Anesthesiologists (ASA) > 2, increased operating time, Age > 65, pre-operative weight loss, dialysis, and disseminated cancer were associated with increased risk of unplanned intubation. CONCLUSIONS: The models presented here achieved high accuracy in predicting risk factors for re-intubation following ACDF surgery. Machine learning analysis may be useful in identifying patients who are at a higher risk of unplanned post-operative re-intubation and their treatment plans can be modified to prophylactically prevent respiratory compromise and consequently unplanned re-intubation.

Medical optimization of osteoporosis for adult spinal deformity surgery: a state-of-the-art evidence-based review of current pharmacotherapy.

PURPOSE: Osteoporosis is a common, but challenging phenomenon to overcome in adult spinal deformity (ASD) surgery. Several pharmacological agents are at the surgeon's disposal to optimize the osteoporotic patient prior to undergoing extensive reconstruction. Familiarity with these medications will allow the surgeon to make informed decisions on selecting the most appropriate adjuncts for each individual patient. METHODS: A comprehensive literature review was conducted in PubMed from September 2021 to April 2022. Studies were selected that contained combinations of various terms including osteoporosis, specific medications, spine surgery, fusion, cage subsidence, screw loosening, pull-out, junctional kyphosis/failure. RESULTS: Bisphosphonates, denosumab, selective estrogen receptor modulators, teriparatide, abaloparatide and romosozumab are all pharmacological agents currently available for adjunctive use. While these medications have been shown to have beneficial effects on improving bone mineral density in the osteoporotic patient, varying evidence is available on their specific effects in the context of extensive spine surgery. There is still a lack of human studies with use of the newer agents. CONCLUSION: Bisphosphonates are first-line agents due to their low cost and robust evidence behind their utility. However, in the absence of contraindications, optimizing bone quality with anabolic medications should be strongly considered in preparation for spinal deformity surgeries due to their beneficial and favorable effects on fusion and hardware compared to the anti-resorptive medications.

Phantom limb syndrome: Assessment of psychiatric and medical comorbidities associated with Phantom pain in 44,028 below knee amputees.

INTRODUCTION: Phantom limb syndrome is a debilitating complication after extremity amputation that poses significant challenges to recovery. This study aims to examine the relationship between phantom limb syndrome and mental and physical comorbidities, including a comparison between phantom limb pain and phantom limb syndrome without pain in below knee amputees. METHODS: This is a retrospective cohort study of patients who underwent below knee amputation of the lower extremity in the PearlDiver database, as identified using CPT codes. Analysis was carried out to evaluate the absence or presence of phantom limb syndrome. Matched bivariate analysis accounting for age, sex, Charlson Comorbidity Index score, and region was used to assess whether the presence of pain in phantom limb syndrome patients was associated with increased comorbidity. RESULTS: In total, 44,028 patients with below knee amputation were examined: 95% (42,493 patients) did not develop phantom limb syndrome while 4.8% (1,535 patients) of patients did develop phantom limb syndrome. Phantom limb syndrome was significantly associated with increased odds of coexistent major depressive disorder (OR = 1.86, p <0.0001), generalized anxiety disorder (OR = 2.14, p = 0.04), posttraumatic stress disorder (OR = 1.7, p <0.0001), suicidal ideation (OR = 1.62, p <0.0001), obesity (OR = 1.28, p = 0.0007), osteoarthritis (OR = 1.53, p <0.0001), osteoporosis (OR = 1.64, p <0.0001), and low back pain (OR = 2.31, p <0.0001). Analysis of patient cohorts of phantom limb syndrome with pain and those without pain did not reveal a statistically significant relationship between the presence of pain and any dependent variable. CONCLUSIONS: This investigation of over 44,000 patients with below knee amputation revealed that patients with phantom limb syndrome exhibit significantly higher rate of psychiatric comorbidities compared to those without documented phantom limb pain. Suicidal ideation, major depressive disorder, generalized anxiety disorder, and post-traumatic stress disorder were especially common, and consequently a multi-disciplinary approach to management is essential.

Risk of Dysphagia and Dysphonia in Patients With Prior Thyroidectomy Undergoing Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Retrospective cohort study using PearlDiver database. OBJECTIVES: To evaluate the effect of prior thyroidectomy on complications of Anterior Cervical Discectomy and Fusion (ACDF) surgery. METHODS: PearlDiver was used to identify patients without prior dysphagia or dysphonia undergoing ACDF between the years 2010-2020Q1. Patients with and without prior thyroidectomy were matched by levels of fusion, alcohol use, and gastroesophageal reflux disease in a 1:5 ratio. Postoperative outcomes were assessed for each cohort with multivariable logistic regression, controlling for age, sex, and Elixhauser Comorbidity Index. RESULTS: Between 2010 and 2019, matched cohorts of 792 ACDF patients with prior thyroidectomy and 3960 ACDF only patients were included in the study. Of patients with previous thyroidectomy undergoing ACDF, 16.3% experienced dysphagia at 1-year compared with 10.6% for patients undergoing ACDF only (aOR=1.39, P=.004). Patients with previous thyroidectomy also had higher odds of dysphonia at 1-year following ACDF, as compared to patients with ACDF alone (2.7% vs 1.2%, aOR=1.74, P= .048). Patients undergoing ACDF with prior thyroidectomy did not have increased risk of revision at 1 year (aOR=1.10, P=.698), 2 years (aOR=1.16, P=.457), or 5 years (aOR=1.20, P=.255) following surgery. There were no differences in postoperative opioid utilization rates at 1 month (aOR=2.07, P=.138), 3 months (aOR=2.45, P=.095), 6 months (aOR=1.34, P=.520), and 12 months (aOR=1.69, P=.202). Prior thyroidectomy was not associated with reintubation following ACDF (P=.995). CONCLUSIONS: Patients with prior thyroidectomy undergoing ACDF surgery experience increased odds of dysphagia and dysphonia at 1-year follow-up compared to those without prior thyroidectomy.

Antibiotic Cement Utilization for the Prophylaxis and Treatment of Infections in Spine Surgery: Basic Science Principles and Rationale for Clinical Use.

Antibiotic bone cement (ABC) is an effective tool for the prophylaxis and treatment of osteomyelitis due to the controlled, sustained release of local antibiotics. ABC has been proven to be effective in the orthopedic fields of arthroplasty and extremity trauma, but the adoption of ABC in spine surgery is limited. The characteristics of ABC make it an optimal solution for treating vertebral osteomyelitis (VO), a serious complication following spine surgery, typically caused by bacterial and sometimes fungal and parasitic pathogens. VO can be devastating, as infection can result in pathogenic biofilms on instrumentation that is dangerous to remove. New techniques, such as kyphoplasty and novel vertebroplasty methods, could amplify the potential of ABC in spine surgery. However, caution should be exercised when using ABC as there is some evidence of toxicity to patients and surgeons, antibiotic allergies, bone cement structural impairment, and possible development of antibiotic resistance. The purpose of this article is to describe the basic science of antibiotic cement utilization and review its usage in spine surgery.

Kyphoplasty and Vertebroplasty Performed by Surgeons versus Nonsurgeons: Trends in Procedure Rates, Complications, and Revisions.

BACKGROUND: Vertebral compression fractures are the most common fragility fractures affecting osteoporotic patients. This study evaluated volume trends and outcomes across specialties performing cement augmentation procedures. METHODS: Patients were identified using Current Procedural Terminology codes for vertebroplasty or kyphoplasty from 2010 to 2019. Patients were grouped by surgical providers (orthopedic surgery and neurological surgery) or nonsurgical providers (anesthesia, pain medicine, radiology, and physical medicine and rehabilitation). Outcomes recorded included reoperation rates and postoperative complications occurring within 30 days. Logistic regression was employed to account for potential confounding variables, and odds ratios were obtained. RESULTS: Inclusion criteria were met by 80,864 patients who received cement augmentation. Surgeon specialists performed 51.7% of all procedures. Of procedures carried out by nonsurgeon specialists, radiologists performed the most. Despite a stable number of procedures performed over the period, the percentage of procedures performed by surgeons decreased from 58.8% to 49.9% (P < 0.001). Patients with procedures performed by surgeons experienced lower odds of reoperation at 30 days (P < 0.001) and 1 year (P < 0.001), but 5-year and overall rates were not significant (P > 0.05). Surgical patients had lower odds of acute kidney injury (P < 0.004) and pulmonary embolism (odds ratio = 0.62, P < 0.001), yet increased odds of surgical site infection (P < 0.001). CONCLUSIONS: Kyphoplasties and vertebroplasties are increasingly performed by nonsurgeon specialists. Although early reoperation rates are higher for nonsurgeon specialists, 5-year and overall reoperation rates were similar. Differing complication rates may relate to patient selection rather than operative technique and can be investigated with future studies.

Cervical Laminoplasty Versus Posterior Laminectomy and Fusion: Trends in Utilization and Evaluation of Complication and Revision Surgery Rates.

INTRODUCTION: Cervical laminoplasty (LP) and laminectomy with fusion (LF) are common operations used to treat cervical spondylotic myelopathy. Conflicting data exist regarding which operation provides superior patient outcomes while minimizing the risk of complications. This study evaluates the trends of LP compared with LF over the past decade in patients with cervical myelopathy and examines long-term revision rates and complications between the two procedures. METHODS: Patients aged 18 years or older who underwent LP or LF for cervical myelopathy from 2010 to 2019 were identified in the PearlDiver Mariner Database. Patients were grouped independently (LP versus fusion) and assessed for association with common medical and surgical complications. The primary outcome was the incidence of LP versus LF for cervical myelopathy over time. Secondary outcomes were revision rates up to 5 years postoperatively and the development of complications attributable to either surgery. RESULTS: In total, 1,420 patients underwent LP and 10,440 patients underwent LF. Rates of LP (10.5% to 13.7%) and LF (86.3% to 89.5%) remained stable, although the number of procedures nearly doubled from 865 in 2010 to 1,525 in 2019. On matched analysis, LP exhibited lower rates of wound complications, surgical site infections, spinal cord injury, dysphagia, cervical kyphosis, limb paralysis, incision and drainage/exploration, implant removal, respiratory failure, renal failure, and sepsis. Revision rates for both procedures at were not different at any time point. CONCLUSION: From 2010 to 2019, rates of LP have not increased and represent less than 15% of posterior-based myelopathy operations. Up to 5 years of follow-up, there were no differences in revision rates for LP compared with LF; however, LP was associated with fewer postoperative complications than LF. LEVEL OF EVIDENCE: Level III retrospective cohort study.

Indolent Infection After Lumbar Interbody Fusion: An Under-recognized Cause of Pseudarthrosis, Which Can Be Successfully Treated With Anterior Revision Fusion.

INTRODUCTION: Bacterial infection is a common etiology for pseudarthrosis after transforaminal lumbar interbody fusion, although it is often difficult to identify because of a delayed presentation and normal laboratory values. The primary goal of this study was to present a series of cases demonstrating patients with infection-related pseudarthrosis successfully managed with anterior revision. METHODS: We retrospectively reviewed patients presenting to a single academic spine center who were found to have evidence of Cutibacterium acnes or coagulase-negative Staphylococcus infection on routine culturing of lumbar interbody fusion revisions from July 2019 to January 2021. All patients underwent salvage of a transforaminal lumbar interbody fusion pseudarthrosis through an anterior lumbar approach. RESULTS: A total of six patients managed for pseudarthrosis secondary to suspected infection were eligible for this study (mean age 64.8 years, range 54-70 years; mean body mass index, range 24.5-39.1). Persistent radiculopathy was the primary presenting symptom in all patients with a mean time to revision of 17 months. Coagulase-negative Staphylococcus was the primary pathogen, identified from intraoperative samples in 50% of the cases. All patients demonstrated a resolution of symptoms after placement of an anterior lumbar interbody cage, without intraoperative complications, and a subsequent antibiotic regimen. DISCUSSION: Indolent infection is an under-recognized cause of pseudarthrosis of the lumbar spine. Revision surgery through an anterior lumbar approach, which promotes ease of cage removal and optimized alignment and surface area available for revision fusion, is sufficient to manage pseudarthrosis due to infection.

Cervical Myelopathy: Diagnosis, Contemporary Treatment, and Outcomes.

Cervical myelopathy is a clinical syndrome caused by compression of the spinal cord between the levels of the C1 and T1 vertebrae. Its clinical presentation can mimic other degenerative and neurological pathologies, making diagnosis challenging. Diagnosis is confirmed with appropriate imaging studies carefully correlated with history and physical examination. Treatment options are focused on decompression of the spinal canal from an anterior, posterior, or combined anterior and posterior surgical approach depending on the location of compression and patient factors. Outcomes are favorable if treatment is performed prior to severe symptom onset.

Transforaminal 360° lumbar endoscopic foraminotomy in postfusion patients: technical note and case series.

OBJECTIVE: This report describes a minimally invasive lumbar foraminotomy technique that can be applied in patients who underwent complex spine decompression procedures or in patients with severe foraminal stenosis. METHODS: Awake, endoscopic decompression surgery was performed in 538 patients over a 5-year period between 2014 and 2019. Transforaminal endoscopic foraminal decompression surgery using a high-speed endoscopic drill was performed in 34 patients who had previously undergone fusions at the treated level. RESULTS: At 2-year follow-up, the mean (± SD) preoperative visual analog scale score for leg pain and the Oswestry Disability Index improved from 7.1 (± 1.5) and 40.1% (± 12.1%) to 2.1 (± 1.9) and 13.6% (± 11.1%). CONCLUSIONS: A minimally invasive, awake procedure is presented for the treatment of severe lumbar foraminal stenosis in patients with lumbar radiculopathy after lumbar fusion.

Supervised Machine Learning for Predicting Length of Stay After Lumbar Arthrodesis: A Comprehensive Artificial Intelligence Approach.

INTRODUCTION: Few studies have evaluated the utility of machine learning techniques to predict and classify outcomes, such as length of stay (LOS), for lumbar fusion patients. Six supervised machine learning algorithms may be able to predict and classify whether a patient will experience a short or long hospital LOS after lumbar fusion surgery with a high degree of accuracy. METHODS: Data were obtained from the National Surgical Quality Improvement Program between 2009 and 2018. Demographic and comorbidity information was collected for patients who underwent anterior, anterolateral, or lateral transverse process technique arthrodesis procedure; anterior lumbar interbody fusion (ALIF); posterior, posterolateral, or lateral transverse process technique arthrodesis procedure; posterior lumbar interbody fusion/transforaminal lumbar interbody fusion (PLIF/TLIF); and posterior fusion procedure posterior spine fusion (PSF). Machine learning algorithmic analyses were done with the scikit-learn package in Python on a high-performance computing cluster. In the total sample, 85% of patients were used for training the models, whereas the remaining patients were used for testing the models. C-statistic area under the curve and prediction accuracy (PA) were calculated for each of the models to determine their accuracy in correctly classifying the test cases. RESULTS: In total, 12,915 ALIF patients, 27,212 PLIF/TLIF patients, and 23,406 PSF patients were included in the algorithmic analyses. The patient factors most strongly associated with LOS were sex, ethnicity, dialysis, and disseminated cancer. The machine learning algorithms yielded area under the curve values of between 0.673 and 0.752 (PA: 69.6% to 80.1%) for ALIF, 0.673 and 0.729 (PA: 66.0% to 81.3%) for PLIF/TLIF, and 0.698 and 0.749 (PA: 69.9% to 80.4%) for PSF. CONCLUSION: Machine learning classification algorithms were able to accurately predict long LOS for ALIF, PLIF/TLIF, and PSF patients. Supervised machine learning algorithms may be useful in clinical and administrative settings. These data may additionally help inform predictive analytic models and assist in setting patient expectations. LEVEL III: Diagnostic study, retrospective cohort study.