Surgical Risk Assessment and Prevention in Elderly Spinal Deformity Patients

Clinical Outcomes and Complication Profile of Spine Surgery in Septuagenarians and Octogenarians: Case Series

OBJECTIVE

The aging global population presents an increasing challenge for spine surgeons. Advancements in spine surgery, including minimally invasive techniques, have broadened treatment options, potentially benefiting older patients. This study aims to explore the clinical outcomes of spine surgery in septuagenarians and octogenarians.

METHODS

This retrospective analysis, conducted at a US tertiary center, included patients aged 70 and older who underwent elective spine surgery for degenerative conditions. Data included the Charlson Comorbidity Index (CCI), ASA classification, surgical procedures, intraoperative and postoperative complications, and reoperation rates. The objective of this study was to describe the outcomes of our cohort of older patients and discern whether differences existed between septuagenarians and octogenarians.

RESULTS

Among the 120 patients meeting the inclusion criteria, there were no significant differences in preoperative factors between the age groups (P > 0.05). Notably, the septuagenarian group had a higher average number of fused levels (2.36 vs. 0.38, P = 0.001), while the octogenarian group underwent a higher proportion of minimally invasive procedures (P = 0.012), resulting in lower overall bleeding in the oldest group(P < 0.001). Mobility outcomes were more favorable in septuagenarians, whereas octogenarians tended to maintain or experience a decline in mobility(P = 0.012). A total of 6 (5%) intraoperative complications and 12 (10%) postoperative complications were documented, with no statistically significant differences observed between the groups.

CONCLUSIONS

This case series demonstrates that septuagenarians and octogenarians can achieve favorable clinical outcomes with elective spine surgery. Spine surgeons should be well-versed in the clinical and surgical care of older adults, providing optimal management that considers their increased comorbidity burden and heightened fragility.

Assessing performance of Geriatric Surgery Verification Program preoperative communication standards in spine surgery

BACKGROUND

To assess performance of the American College of Surgeons Geriatric Surgery Verification (GSV) Program preoperative communication standards in older patients undergoing high risk spine surgery.

METHODS

We performed an external validation of a natural language processing (NLP) method for identifying documentation meeting GSV communication standards. We then applied this method to a retrospective cohort of patients aged 65 and older who underwent spinal fusion procedures between January 2018-December 2020 in a large healthcare system in Massachusetts. Our primary outcome of interest was fulfillment of GSV communication domains: overall health goals, treatment goals, and patient-centered outcomes. Factors associated with the fulfillment of at least one domain were assessed using Poisson regression to adjust for confounding.

RESULTS

External validation of the NLP method had a sensitivity of 88.6% and specificity of 99.0%. Our study population included 1294 patients, of whom only 0.8% (n = 10) patients contained documentation of all three GSV domains, and 33.7% (n = 436) had documentation fulfilling at least one GSV domain. The GSV domain with lowest frequency of documentation was overall health goals, with only 35 (2.7%) of patients meeting this requirement. Adjusted analysis suggested that patients with a Charlson comorbidity score of one or more had higher fulfillment of GSV criteria (CCI 1-3: prevalence rate ratio (PRR) 1.8, 95% confidence interval (CI) 1.5-2.1; CCI >3: PRR 1.5, 95% CI 1.2-1.9).

CONCLUSION

A paucity of geriatric patients undergoing spine surgery had preoperative documentation consistent with GSV standards. Given that spine surgery is one of the highest risk surgeries in older adults and GSV standards are relevant to all surgical specialties, wider promulgation of these standards is warranted.

Bone Mineral Density T-Score is an Independent Predictor of Major Blood Loss in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVE

The purpose of this study was to determine the effect of low bone mineral density (BMD), as assessed by preoperative Dual-energy X-ray Absorptiometry (DEXA) scans, on intraoperative blood loss following adult spinal deformity (ASD) surgery.

METHODS

Patients who received spinal fusion for ASD (>5 levels fused) at a single academic center from 2010-2018 were included in this study. The lowest preoperative T-score was recorded for patients who had preoperative DEXA scans within a year of surgery. Patients with liver/kidney disease or on prescription anticoagulant medication were excluded. Major blood loss was a binary variable defined as above or below the 90th percentile of our cohort. Binomial regression was performed controlling for age, number of vertebrae fused, 3-column osteotomy, primary vs. revision surgery, preoperative platelet count, and if the patient was taking medication for osteoporosis.

RESULTS

91 patients were identified in the cohort. Mean age was 63 ± 11.6 years, 81% female. 56 (62%) of cases included revision of previous instrumentation. Patients had a mean SVA of 9.6 ± 8.6 cm and median of 9 vertebrae fused (range 5-22). The average T-score was -1.2 ± 1.0. Each point lower T-score was associated with significantly higher odds of major blood loss (OR 2.5, 95% CI 1.0 - 5.9) when controlling for age, number of vertebrae fused, 3-column osteotomy, preoperative platelet count and primary vs. revision surgery.

CONCLUSIONS

Preoperative T-score is independently associated with increased odds of major blood loss in ASD surgery.

Risk Stratification of Elderly Patients Undergoing Spinal Surgery Using the Modified Frailty Index

STUDY DESIGN

Retrospective cohort.

OBJECTIVES

To validate the 11-item modified Frailty Index (mFI) as a perioperative risk stratification tool in elderly patients undergoing spine surgery.

METHODS

All consecutive cases of spine surgery in patients aged 65 years or older between July 2016 and June 2018 at a state-wide trauma center were retrospectively reviewed. The primary outcome was post-operative major complication rate (Clavien-Dindo Classification ≥ III). Secondary outcome measures included the rate of all complications, 6-month mortality and surgical site infection.

RESULTS

A total of 348 cases were identified. The major complication rate was significantly lower in patients with an mFI of 0 compared to ≥ 0.45 (18.3% versus 42.5%, P = .049). As the mFI increased from 0 to ≥ 0.45 there was a stepwise increase in risk of major complications (P < .001). Additionally, 6-month mortality rate was considerably lower when the mFI was 0 rather than ≥ 0.27 (4.2% versus 20.4%, P = .007). Multivariate analysis demonstrated an mFI ≥ 0.27 was significantly associated with an increased incidence of major complication (OR 2.80, 95% CI 1.46-5.35, P = .002), all complication (OR 2.93, 95% CI 1.70-15.11, P < .001), 6-month mortality (OR 7.39, 95% CI 2.55-21.43, P < .001) and surgical site infection (OR 4.43, 95% CI 1.71-11.51, P = .002). The American Society of Anesthesiologists' (ASA) index did not share a stepwise relationship with any outcome.

CONCLUSION

The mFI is significantly associated in a gradated fashion with increased morbidity and mortality. Patients with an mFI ≥ 0.27 are at greater risk of major complications, all-complications, 6-monthy mortality, and surgical site infection.

The Impact of Cognitive Impairment on Postoperative Complications After Spinal Surgery: A Matched Analysis

OBJECTIVE

The coprevalence of age-related comorbidities such as cognitive impairment and spinal disorders is increasing. No studies to date have assessed the postoperative spine surgery outcomes of patients with mild cognitive impairment (MCI) or severe cognitive impairment (dementia) compared with those without preexisting cognitive impairment.

METHODS

Using all-payer claims database, 235,123 persons undergoing either cervical or lumbar spine procedures between January 2010 and October 2020 were identified. Exact 1:1:1 matching based on baseline patient demographics and comorbidities was used to create a dementia group, MCI group, and control group without MCI/dementia (n = 3636). The primary outcome was the rate of any 30-day major postoperative complications. Secondary outcomes included the rates of revision surgery, readmission rates within 30 days, and health care costs within 1 year postoperatively.

RESULTS

Compared with the control group, patients with dementia had an 8-fold and 5.4-fold increase in all-cause 30-day complications after undergoing cervical and lumbar spine procedures, respectively. Similarly, patients with MCI had a 3.1-fold and 2.2-fold increase in all-cause 30-day complications, respectively. Patients with either MCI or dementia had increased rates of pneumonia and urinary tract infection after either spine procedure compared with control (P < 0.01). Odds of revision surgery were increased in the lumbar surgery cohort for dementia (3.43; 95% confidence interval, 1.69-6.95) and for MCI (2.41; 95% confidence interval, 1.14-5.05).

CONCLUSIONS

This is the first study to characterize the postoperative complications profile of patients with preexisting dementia or MCI undergoing cervical and lumbar spine surgery. Both dementia and MCI are associated with increased postoperative complications within 30 days.

Modified Frailty Index Does Not Provide Additional Value in Predicting Outcomes in Patients Undergoing Elective Transforaminal Lumbar Interbody Fusion

OBJECTIVE

To determine the predictive value of the modified Frailty Index (mFI) in evaluating sarcopenia and clinical outcomes in patients undergoing 1-level or 2-level transforaminal lumbar interbody fusion (TLIF).

METHODS

Patients who underwent a 1-level or 2-level TLIF between 2012 and 2020 were retrospectively identified. Frailty was compared among groups using mFI, and sarcopenia was classified by the psoas muscle cross-sectional area. Bivariate statistics compared demographics, comorbidities, and clinical outcomes. A linear regression model was developed using the Charlson Comorbidity Index (CCI) or mFI as independent variables to determine potential predictors for improvement in 1-year patient-reported outcomes.

RESULTS

Of 488 included patients, 60 were severely frail and 60 patients had sarcopenia, but sarcopenia was not associated with patient frailty (P = 0.469). Severely frail patients had worse baseline Oswestry Disability Index (ODI) (P < 0.001), Mental Component Score-12 (P = 0.001), and Physical Component Score-12 (P < 0.001), and worse improvement in ODI (P = 0.037), Physical Component Score-12 (P < 0.001), and visual analog scale (VAS) back (P = 0.007). mFI was an independent predictor of poorer improvement in VAS back and ODI, whereas age + CCI in addition predicted poorer improvement in VAS leg. Patients with higher mFI experienced longer length of stay, less frequent home discharge, and higher rates of complications, but similar readmission and reoperation rates.

CONCLUSIONS

Frailer patients experience poorer improvement in back pain, physical functioning, and disability after TLIF. mFI and the combination of age and CCI comparably predict patient-reported outcomes but do not correlate to baseline sarcopenia. Frailty increased the risk of complications, length of hospital stay, and risk of nonhome discharge.

The importance of thoracolumbar junctional orientation, change in thoracolumbar angle, and overcorrection of lumbar lordosis in development of proximal junctional kyphosis in adult spinal deformity surgery

OBJECTIVE

Changes in the thoracolumbar angle (TLA) would play a pivotal role in the reciprocal changes following spine realignment surgery, thereby leading to the development of proximal junctional kyphosis (PJK). This study aimed to investigate the association between TLA and the development of PJK following adult spinal deformity surgery.

METHODS

A total of 107 patients were divided into PJK+ and PJK- groups according to the development of PJK within 12 months after surgery. The TLA and spinopelvic radiological parameters were compared between the PJK+ and PJK- groups. A multivariate logistic regression model was used to identify the risk factors for PJK. The receiver operating characteristic curves of the regression models were used to investigate the cutoff values of significant parameters needed so that PJK would not occur.

RESULTS

The change in TLA (ΔTLA) in the PJK+ group was significantly larger than in the PJK- group (6.7° ± 7.9° and 2.2° ± 8.1°, respectively; p = 0.006). Multivariate logistic regression analysis demonstrated that age, postoperative pelvic incidence-lumbar lordosis, and ΔTLA were significant risk factors for PJK. The risk of developing PJK was higher when the postoperative pelvic incidence-lumbar lordosis was < 5.2 and the ΔTLA was > 3.58°.

CONCLUSIONS

The present study highlights the thinking that extensive correction of TLA and lumbar lordosis should be avoided in patients with adult spinal deformity. Overcorrection of TLA of > 3.58° could result in higher odds of PJK.

5-Year Revision Rates After Elective Multilevel Lumbar/Thoracolumbar Instrumented Fusions in Older Patients: An Analysis of State Databases

OBJECTIVE

The purpose of this study wasto evaluate cause-specific 5-year revision rates and risk factors for revision after elective multilevel lumbar instrumented fusion in older patients.

METHODS

Older patients (>60 years) who underwent elective multilevel (3+) lumbar instrumented fusions were identified in Healthcare Cost and Utilization Project state inpatient databases and followed for 5 years for revision operations because of mechanical failure, degenerative disease (DD), infection, postlaminectomy syndrome, and stenosis. Cox proportional hazards multivariate analyses were conducted to determine risk factors associated with revision for each diagnostic cause.

RESULTS

The cohort included 5,636 patients (female-3,285; average age-71.6 years). Most of the operations were 3 to 7 levels (97.4%), and the mean length of stay was 5.4 days. The overall 5-year revision rate was 16.5% with predominant etiologies of DD (50.7%), mechanical failure (32.2%), and stenosis (8.0%). The revision procedure at the index operation was associated with an increased revision risk for DD (hazards ratio [HR] = 1.59, 95% confidence interval [CI], 1.29 to 1.98, P < 0.001) and mechanical failure (HR = 1.56, 95% CI, 1.19 to 2.04, P = 0.020). Male sex was associated with a significantly reduced revision risk for DD (HR = 0.75, 95% CI, 0.62 to 0.91, P = 0.04). Age, race, and number of comorbidities had no notable effect on the overall or cause-specific risk of revision.

DISCUSSION

In this large database analysis, DD and mechanical failure were the most common etiologies comprising a 5-year revision rate of 16.5% after elective multilevel lumbar instrumented fusion in older patients. Revision operations and female patients carried the strongest risks for revision.

Preoperative Polypharmacy in Geriatric Patients is Associated with Increased 90-Day All-Cause Hospital Readmission After Surgery for Adult Spinal Deformity Patients

OBJECTIVE

To investigate the effect of preoperative polypharmacy (PP) on 90-day all-cause readmission rate in older adults undergoing corrective surgery for ASD.

METHODS

Older adults with a diagnosis of ASD undergoing spinal surgery at a quaternary medical center from January 2016 to March 2019 were enrolled in this study. Patients were dichotomized into two groups stratified by the number of preoperative prescription medications; with PP defined as 5 or more prescription medications. The primary outcome measure was 90-day all-cause readmission rate. Secondary outcomes included postoperative changes in health-related quality of life measures.

RESULTS

Among 161 patients (mean [SD], 69.59[8.79] years), 97 patients were included in PP cohort and 64 in non-polypharmacy (non-PP) cohort. Both groups were balanced at baseline. The duration of hospital (5.82[1.93] vs. 6.50[4.00] days), mean number of fusion levels, and duration of surgery was statistically similar between both groups (p>0.05). There was no difference in the proportion of patients discharged directly home (31.25% vs. 40.42%, p=0.36). 90-day all-cause readmission rate was 3-fold higher in the PP cohort compared with the non-PP cohort. After adjusting for preoperative patient optimization, ASA grade, surgical invasiveness, smoking, depression and baseline functional disability, older adults with PP had a 9.79 increased odds of 90-day all-cause hospital readmission (p=0.04). Change in HRQOL measures were similar between both groups.

CONCLUSION

This study's findings indicate that despite preoperative optimization, older adults exposed to polypharmacy are at a significantly increased risk of hospital readmission within 90-days of surgery.

Diagnostic Roots Radiofrequency Sensory Stimulation Looking for Symptomatic Injured Roots in Multiple Lumbar Stenosis

Objective

We present how to perform radiofrequency sensory stimulation (RFSS) and whether RFSS could be helpful in identifying symptomatic injured roots in multilevel lumbar stenosis.

Methods

Consecutive patients who underwent RFSS from 2010 to 2012 were enrolled. To identify pathologic lesions, RFSS was performed for suspicious roots, as determined using lumbar magnetic resonance imaging (MRI). The RFSS procedure resembled transforaminal root block. During RFSS of the suspicious root, patients could indicate whether stimulation induced their usual pain and/or sensory changes and could indicate whether the same leg area was affected. The number of possible symptomatic roots on MRI was evaluated before and after RFSS. Based on the RFSS results, we confirmed the presence of symptomatic nerve root(s) and performed surgical decompression. Surgical results, such as numeric rating scale (NRS) scores for low back pain (LBP) and leg pain (LP), and Oswestry disability index (ODI), were evaluated.

Results

Ten patients were enrolled in the study. Their mean age was 70.1±9.7 years. Clinically, NRS-LBP, NRS-LP, and ODI before surgery were 5.1%, 7.5%, and 53.2%, respectively. The mean number of suspicious roots was 2.6±0.8. After RFSS, the mean number of symptomatic roots was 1.6±1.0. On average, 1.4 lumbar segments were decompressed. The follow-up period was 35.3±12.8 months. At the last follow-up, NRS-LBP, NRS-LP, and ODI were 3.1%, 1.5%, and 35.3%, respectively. There was no recurrence or need for further surgical treatment for lumbar stenosis.

Conclusion

RFSS is a potentially helpful diagnostic tool for verifying and localizing symptomatic injured root lesions, particularly in patients with multilevel spinal stenosis.

A Self-Contained 3D Biomechanical Analysis Lab for Complete Automatic Spine and Full Skeleton Assessment of Posture, Gait and Run

Quantitative functional assessment of Posture and Motion Analysis of the entire skeleton and spine is highly desirable. Nonetheless, in most studies focused on posture and movement biomechanics, the spine is only grossly depicted because of its required level of complexity. Approaches integrating pressure measurement devices with stereophotogrammetric systems have been presented in the literature, but spine biomechanics studies have rarely been linked to baropodometry. A new multi-sensor system called GOALS-E.G.G. (Global Opto-electronic Approach for Locomotion and Spine-Expert Gait Guru), integrating a fully genlock-synched baropodometric treadmill with a stereophotogrammetric device, is introduced to overcome the above-described limitations. The GOALS-EGG extends the features of a complete 3D parametric biomechanical skeleton model, developed in an original way for static 3D posture analysis, to kinematic and kinetic analysis of movement, gait and run. By integrating baropodometric data, the model allows the estimation of lower limb net-joint forces, torques and muscle power. Net forces and torques are also assessed at intervertebral levels. All the elaborations are completely automatised up to the mean behaviour extraction for both posture and cyclic-repetitive tasks, allowing the clinician/researcher to perform, per each patient, multiple postural/movement tests and compare them in a unified statistically reliable framework.

Consensus statement for perioperative care in lumbar spinal fusion: Enhanced Recovery After Surgery (ERAS®) Society recommendations

BACKGROUND

Enhanced Recovery After Surgery (ERAS) evidence-based protocols for perioperative care have led to improvements in outcomes in numerous surgical areas, through multimodal optimization of patient pathway, reduction of complications, improved patient experience and reduction in the length of stay. ERAS represent a relatively new paradigm in spine surgery.

PURPOSE

This multidisciplinary consensus review summarizes the literature and proposes recommendations for the perioperative care of patients undergoing lumbar fusion surgery with an ERAS program.

STUDY DESIGN

This is a review article.

METHODS

Under the impetus of the ERAS® society, a multidisciplinary guideline development group was constituted by bringing together international experts involved in the practice of ERAS and spine surgery. This group identified 22 ERAS items for lumbar fusion. A systematic search in the English language was performed in MEDLINE, Embase, and Cochrane Central Register of Controlled Trials. Systematic reviews, randomized controlled trials, and cohort studies were included, and the evidence was graded according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Consensus recommendation was reached by the group after a critical appraisal of the literature.

RESULTS

Two hundred fifty-six articles were included to develop the consensus statements for 22 ERAS items; one ERAS item (prehabilitation) was excluded from the final summary due to very poor quality and conflicting evidence in lumbar spinal fusion. From these remaining 21 ERAS items, 28 recommendations were included. All recommendations on ERAS protocol items are based on the best available evidence. These included nine preoperative, eleven intraoperative, and six postoperative recommendations. They span topics from preoperative patient education and nutritional evaluation, intraoperative anesthetic and surgical techniques, and postoperative multimodal analgesic strategies. The level of evidence for the use of each recommendation is presented.

CONCLUSION

Based on the best evidence available for each ERAS item within the multidisciplinary perioperative care pathways, the ERAS® Society presents this comprehensive consensus review for perioperative care in lumbar fusion.

Complications After Adult Spinal Deformity Surgeries: All Are Not Created Equal

BACKGROUND

Data on timing of complications are important for accurate quality assessments. We sought to better define pre- and postdischarge complications occurring within 90 days of adult spinal deformity (ASD) surgery and quantify the effect of multiple complications on recovery.

METHODS

We performed a review of 1040 patients who underwent ASD surgery (age: 46 ± 23; body mass index: 25 ± 7, American Society of Anesthesiologists [ASA] score: 2.5 ± 0.6, levels: 10 ± 4, revision: 9%, 3-column osteotomy: 13%). We assessed pre- and postdischarge complications and risk factors for isolated versus multiple complications, as well as the impact of multiple complications.

RESULTS

The 90-day complication rate was 17.7%. 85 patients (8.2%) developed a predischarge complication, most commonly ileus (12%), and pulmonary embolism (PE; 7.1%). The most common causes of predischarge unplanned reoperation were neurologic injury (12.9%) and surgical site drainage (8.2%). Predictors of a predischarge complication included smoking (odds ratio [OR]: 2.2, P = .02), higher ASA (OR: 1.8, P = .008), hypertension (HTN; OR: 2.0, P = .004), and iliac fixation (OR: 4.3, P < .001). Ninety-nine patients (9.5%) developed a postdischarge complication, most commonly infection (34%), instrumentation failure (13.4%), and proximal junctional failure (10.4%). Predictors of postdischarge complications included chronic obstructive pulmonary disease (OR: 3.6, P < .0001), congestive heart failure (OR: 4.4, P = .016), HTN (OR: 2.3, P < .0001), and multiple rod construct (OR: 1.8, P = .02). Patients who developed multiple complications (9.3%) had a longer length of stay, and increased risk for readmission and unplanned reoperation.

CONCLUSIONS

Knowledge regarding timing of postoperative complications in relation to discharge may better inform quality improvement measures. PE and implant-related complications play a prominent role in perioperative complications and need for readmission, with several modifiable risk factors identified.

LEVEL OF EVIDENCE

Level 3.

CLINICAL RELEVANCE

Advances in surgical techniques and instrumentation have improved postoperative radiographic and clinical outcomes after ASD surgery. The rate of complications after complex ASD surgery remains high, both at early postoperative and long term follow-up. This study reviews complications within 90 days of surgery, with an assessment of patient and surgical risk factors. We found that modifiable risk factors for early complications after ASD surgery include COPD, and current smoking. The data presented in this study also provide surgeons with knowledge of the most common complications encountered after ASD surgery, to aid in preoperative patient discussion.

Spinal Cord Stimulation: A Reasonable Alternative Treatment in Patients With Symptomatic Adult Scoliosis for Whom Surgical Therapy Is Not Suitable? A Pilot Study

INTRODUCTION

In adult scoliosis, dorsal instrumentation and fusion can provide significant improvement of pain and disability scores (Owestry Index); however, complication rates of up to 39% have been reported. As such, recent attempts have been made at expanding the surgical spectrum to include less invasive techniques in patients such as neuromodulation, specifically spinal cord stimulation (SCS). We therefore aimed to evaluate its use in a larger cohort of adult scoliosis patients in the form of a pilot study.

MATERIALS AND METHODS

We analyzed prospectively collected data from 18 adult scoliosis patients receiving SCS treatment in our institution between February 2019 and May 2020. Clinical follow-up was performed at 3, 6, and 12 months following implantation of an epidural SCS System. Patients reported numeric rating scale (NRS) values for the categories of lower back pain (LBP) and regional pain (RP) both at rest and in motion. Further, SF-36, ADS-K, PSQI, and ODI forms were completed. The study was approved by the institutional Ethics Committee (EA2/093/13).

RESULTS

Initial preoperative NRS of LBP at rest was significantly reduced following SCS at three (45% reduction, p = 0.005) and six (43% reduction, p = 0.009) months follow-up. LBP in motion was also reduced at three (27% reduction, p = 0.002) and six (33% reduction vs. preoperative, p = 0.005) months. RP at rest was reduced at three (38% reduction, p = 0.003) and six (37% reduction, p = 0.007) and in movement at three (29% reduction, 0.006) and six (32% reduction, p = 0.011). Loss of thoracic kyphosis and increased pelvic incidence were associated with worse NRS response to SCS stimulation at six months follow-up.

DISCUSSION

In overweight, older adults for whom the risks of corrective surgery must be carefully considered, neuromodulation can significantly reduce LBP as well as regional pain in the first six months following implantation. These findings may provide a reasonable alternative in patients not willing or eligible to undergo extensive corrective surgery.

Validity of the global alignment proportion (GAP) score in predicting mechanical complications after adult spinal deformity surgery in elderly patients

PURPOSE

This study aimed to validate the usefulness of the global alignment proportion (GAP) score to predict postoperative mechanical failure in the elderly (mean age, 70.5 years) individuals with severe sagittal imbalance.

METHODS

A total of 84 patients were enrolled: mechanical complications (MC), minor mechanical complications (mMC), proximal junctional failure (PJF), and revision surgery occurred in 61% (51/84), 58% (49/84), 44% (37/84), and 13% (11/84) of the patients, respectively. The GAP score was calculated using the X-ray obtained in the early postoperative period. The validity of the GAP score's predictive ability was evaluated by calculating the area under the curve (AUC) of the receiver operating characteristics curve. Univariate logistic regression analysis and Cochran-Armitage test of trend were performed to determine the association between mechanical complications and GAP score.

RESULTS

The discriminatory power of GAP score to predict MC, mMC, and PJF was "moderately accurate," with an AUC of 0.839 (confidence interval [CI] 0.755-0.824, p < 0.001), 0.836 (CI 0.749-0.923, p < 0.001), and 0.702 (CI 0.588-0.851, p < 0.001), respectively. The GAP score showed a statistically significant association with MC, mMC, and PJF in univariate logistic regression analysis and Cochran-Armitage test for trend. However, it was not significantly associated with revision surgery.

CONCLUSION

This study showed promising results regarding the GAP score's predictive power for MC, mMC, and PJF in the elderly population with degenerative kyphoscoliosis. Using the GAP score, we can determine the patient's specific correction goal preoperatively to prevent mechanical failure based on individual patient's characteristics such as pelvic incidence.

Drivers of Prolonged Hospitalization Following Spine Surgery: A Game-Theory-Based Approach to Explaining Machine Learning Models

BACKGROUND

Understanding the interactions between variables that predict prolonged hospital length of stay (LOS) following spine surgery can help uncover drivers of this risk in patients. This study utilized a novel game-theory-based approach to develop explainable machine learning models to understand such interactions in a large cohort of patients treated with spine surgery.

METHODS

Of 11,150 patients who underwent surgery for degenerative spine conditions at a single institution, 3,310 (29.7%) were characterized as having prolonged LOS. Machine learning models predicting LOS were built for each patient. Shapley additive explanation (SHAP) values were calculated for each patient model to quantify the importance of features and variable interaction effects.

RESULTS

Models using features identified by SHAP values were highly predictive of prolonged LOS risk (mean C-statistic = 0.87). Feature importance analysis revealed that prolonged LOS risk is multifactorial. Non-elective admission produced elevated SHAP values, indicating a clear, strong risk of prolonged LOS. In contrast, intraoperative and sociodemographic factors displayed bidirectional influences on risk, suggesting potential protective effects with optimization of factors such as estimated blood loss, surgical duration, and comorbidity burden.

CONCLUSIONS

Meticulous management of patients with high comorbidity burdens or Medicaid insurance who are admitted non-electively or spend clinically indicated time in the intensive care unit (ICU) during their hospitalization course may be warranted to reduce their risk of unanticipated prolonged LOS following spine surgery.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.