Hesham Mostafa Zakaria

Morphometrics as a predictor of perioperative morbidity after lumbar spine surgery

OBJECT Improved objective assessments of perioperative risk after spine surgery are necessary to decrease postoperative morbidity and mortality rates. Morphometric analysis has proven utility in predicting postoperative morbidity and mortality in surgical disciplines. The aim of the present study was to evaluate whether morphometrics can be applied to the cases of patients undergoing lumbar spine surgery. METHODS The authors performed a retrospective review of the perioperative course of 395 patients who underwent lumbar surgery at their institution from 2013 to 2014. Preoperative risk factors such as age, diabetes, smoking, coronary artery disease, and body mass index (BMI) were recorded. Preoperative MRI was used to measure the psoas muscle area at the L-4 vertebra and paraspinal muscle area at the T-12 vertebra. Primary outcomes included unplanned return to the operating room, 30- and 90-day readmissions, surgical site infection, wound dehiscence, new neurological deficit, deep vein thrombosis, pulmonary embolism, myocardial infarction, urinary tract infection, urinary retention, hospital-acquired pneumonia, stroke, and prolonged stay in the intensive care unit. RESULTS The overall rate of adverse events was 30%, the most common event being urinary retention (12%). Greater age (p = 0.015) and tobacco usage (p = 0.026) were both significantly associated with complications for all patients, while diabetes, coronary artery disease, and high BMI were not. No surgery-related characteristics were associated with postoperative morbidity, including whether surgery required instrumentation, whether it was a revision, or the number of vertebral levels treated. Using multivariate regression analysis, male and female patients with the lowest psoas tertile had an OR of 1.70 (95% CI 1.04-2.79, p = 0.035) for having postoperative complications. Male patients in the lowest psoas tertile had an OR of 2.42 (95% CI 1.17-5.01, p = 0.016) for having a postoperative complication. The paraspinal muscle groups did not provide any significant data for postoperative morbidity, even after multivariate analysis. CONCLUSIONS The morphometric measurement of psoas muscle size may be a sensitive predictive tool compared with other risk factors for perioperative morbidity in male patients undergoing lumbar surgery.

Application of morphometric analysis to patients with lung cancer metastasis to the spine: a clinical study.

OBJECTIVE Predicting the survival rate for patients with cancer is currently performed using the TNM Classification of Malignant Tumors (TNM). Identifying accurate prognostic markers of survival would allow better treatment stratification between more aggressive treatment strategies or palliation. This is especially relevant for patients with spinal metastases, who all have identical TNM staging and whose surgical decision-making is potentially complex. Analytical morphometrics quantifies patient frailty by measuring lean muscle mass and can predict risk for postoperative morbidity after lumbar spine surgery. This study evaluates whether morphometrics can be predictive of survival in patients with spinal metastases. METHODS Utilizing a retrospective registry of patients with spinal metastases who had undergone stereotactic body radiation therapy, the authors identified patients with primary lung cancer. Morphometric measurements were taken of the psoas muscle using CT of the lumbar spine. Additional morphometrics were taken of the L-4 vertebral body. Patients were stratified into tertiles based on psoas muscle area. The primary outcome measure was overall survival, which was measured from the date of the patients CT scan to date of death. RESULTS A total of 168 patients were identified, with 54% male and 54% having multiple-level metastases. The median survival for all patients was 185.5 days (95% confidence interval [CI] 146-228 days). Survival was not associated with age, sex, or the number of levels of metastasis. Patients in the smallest tertile for the left psoas area had significantly shorter survival compared with a combination of the other two tertiles: 139 days versus 222 days, respectively, hazard ratio (HR) 1.47, 95% CI 1.06-2.04, p = 0.007. Total psoas tertiles were not predictive of mortality, but patients whose total psoas size was below the median size had significantly shorter survival compared with those greater than the median size: 146 days versus 253.5 days, respectively, HR 1.43, 95% CI 1.05-1.94, p = 0.025. To try to differentiate small body habitus from frailty, the ratio of psoas muscle area to vertebral body area was calculated. Total psoas size became predictive of mortality when normalized to vertebral body ratio, with patients in the lowest tertile having significantly shorter survival (p = 0.017). Left psoas to vertebral body ratio was also predictive of mortality in patients within the lowest tertile (p = 0.021). Right psoas size was not predictive of mortality in any calculations. CONCLUSIONS In patients with lung cancer metastases to the spine, morphometric analysis of psoas muscle and vertebral body size can be used to identify patients who are at risk for shorter survival. This information should be used to select patients who are appropriate candidates for surgery and for the tailoring of oncological treatment regimens.

Preoperative external tissue expansion for complex cranial reconstructions

OBJECTIVE Reconstruction of large solitary cranial defects after multiple craniotomies is challenging because scalp contraction generally requires more than simple subcutaneous undermining to ensure effective and cosmetically appealing closure. In plastic and reconstructive surgery, soft tissue expansion is considered the gold standard for reconstructing scalp defects; however, these techniques are not well known nor are they routinely practiced among neurosurgeons. The authors here describe a simple external tissue expansion technique that is associated with low morbidity and results in high cosmetic satisfaction among patients. METHODS The authors reviewed the medical records of patients with large cranial defects (> 5 cm) following multiple complicated craniotomies who had undergone reconstructive cranioplasty with preoperative tissue expansion using the DermaClose RC device. In addition to gathering data on patient age, sex, primary pathology, number of craniotomies and/or craniectomies, history of radiation therapy, and duration of external scalp tissue expansion, the authors screened patient charts for cerebrospinal fluid (CSF) leak, meningitis, intracranial abscess formation, dermatitis, and patient satisfaction rates. RESULTS The 6 identified patients (5 female, 1 male) had an age range from 36 to 70 years. All patients had complicating factors such as recalcitrant scalp infections after multiple craniotomies or cranial radiation, which led to secondary scalp tissue scarring and retraction. All patients were deemed to be potential candidates for rotational flaps with or without skin grafts. All patients underwent the same preoperative tissue expansion followed by standard cranial bone reconstruction. None of the patients developed CSF leak, meningitis, intracranial abscess, dermatitis, or permanent cosmetic defects. None of the patients required a reoperation. Mean follow-up was 117 days. CONCLUSIONS Preoperative scalp tissue expansion with the DermaClose RC device allows for simple and reliable completion of complicated cranial reconstruction with low morbidity rates and high cosmetic satisfaction among patients.

Mechanomyography for Intraoperative Assessment of Cortical Breach During Instrumented Spine Surgery

OBJECTIVE We sought to determine the utility of mechanomyography (MMG) in detecting and preventing pedicle breach in instrumented lumbar spine surgery. METHODS In a prospective nonrandomized trial without controls, we selected consecutive patients to undergo intraoperative MMG during instrumented lumbar spine surgery. MMG testing was performed at the original pilot hole, after tapping, and after screw placement, with the minimum current to elicit a recorded MMG response. All patients underwent a postoperative computed tomography scan, and a single radiologist interpreted each pedicle to identify breach. Chi-square test was used to compare patients with and without breaches. Two sample Students t-tests were used to compare changes in functional outcomes. Sensitivity and specificity of MMG were computed using receiver operating characteristic curve analysis. RESULTS There were 122 consecutive instrumented lumbar surgery patients enrolled, with a total of 890 lumbar pedicle screws tested with MMG. The medial or inferior breach rate was 2.25%, with no statistically significant difference in Oswestry Disability Index or visual analog scale between patients who breached and who did not. For the MMG measurement from the original pilot hole, the area under the receiver operating characteristic was 0.835; the maximum combination of sensitivity (80.42%) and specificity (80.6%) was found using MMG current ≤12 mA. We found that an MMG cutoff of >12 mA resulted in a 99.5% likelihood of no medial or inferior breach. CONCLUSIONS MMG can be safely used during instrumented lumbar spine surgery. A cutoff value of >12 mA for MMG can accurately predict and prevent medial and inferior pedicle screw breach.

Application of morphometrics as a predictor for survival in female patients with breast cancer spinal metastasis, a retrospective cohort study

BACKGROUND CONTEXT The current standard of care for prediction of survival of cancer staging is based on TNM staging. However, for patients with spinal metastasis, who all have identical stage IV disease, identifying accurate prognostic markers of survival would allow better treatment stratification between more aggressive treatment strategies or palliation. Analytical morphometrics enables physicians to quantify patient frailty by measuring lean muscle mass. Morphometrics also predicts survival in patients with lung cancer metastases to the spine. PURPOSE Our study evaluates whether morphometrics is predictive of survival in patients with breast cancer spinal metastasis. DESIGN This is an observational retrospective cohort study. PATIENT SAMPLE This study includes female patients with breast cancer spinal metastases and patients who have undergone stereotactic body radiation therapy. OUTCOME MEASURES Overall survival was the primary outcome measure. METHODS Morphometric measurements of the psoas muscle were taken using computed tomography scans of the lumbar spine. We then stratified patients into tertiles based on the psoas muscle area. RESULTS We identified 118 patients, with a median survival of 104 days (95% confidence interval [CI]=73-157 days). Overall survival was not associated with age, chemotherapy, or number of levels radiated. Patients in the lowest tertile of psoas size had significantly shorter survival compared with the highest tertile (68 days versus 148 days, hazard ratio 1.76 [95% CI=1.08-2.89], p=.024). The shorter survival was also true for the lowest tertile versus the middle tertile (68 days versus 167 days, hazard ratio 1.95 [95% CI=1.19-3.19], p=.007). Kaplan-Meier survival curves were used to visually illustrate the differences in survival between different tertiles. CONCLUSIONS Morphometric analysis of the psoas muscle size in patients with breast cancer metastases to the spine was effective in identifying patients at risk of shorter survival. Further research is needed to validate these results, as well as to see if these methodologies can be applied to other cancer histologies.

The reliability of identifying the Omega sign using axial T2-weighted magnetic resonance imaging

Preoperative identification of the eloquent brain is important for neurosurgical planning. One common method of finding the motor cortex is by localizing “the Omega sign.” No studies have tested the reliability of imaging to identify the Omega sign. We identified 40 recent and consecutive patients who had undergone preoperative functional magnetic resonance imaging for identification of the hand motor area prior to tumor resection. We recruited 11 neurosurgical residents of various levels of training and one board-certified neurosurgeon to identify the hand motor cortex Omega. Testees were given axial images of T2-weighted MRI and placed marks where they expected to find the Omega. Two board-certified radiologists graded and quantified the localization attempts. Inter-rater reliability was assessed using the kappa statistic, and Rao–Scott chi-square tests were used to examine the relationship between clinical factors and testees’ experience with correct identification of the Omega sign. The overall correct identification rate was 69.9% (95% CI = 63.4–75.7), ranging from 36.6% to 92.7% among all raters for the tumor side and from 46.2% to 97.4% for the non-tumor side. Anatomic distortion greatly affected correct identification (p < 0.005). Senior residents had a significantly higher rate of identification of the Omega than junior residents (p < 0.001). Overall, inter-rater reliability for the Omega sign is poor, with a Fleiss kappa of 0.23. We concluded that correct identification of the Omega sign is affected by tumor distortion and experience but overall is not reliable. This underscores the limitations of anatomic landmarks and the importance of utilizing multiple scanning planes and preoperative fMRI for appropriate localization.

Assessment of radiographic and clinical outcomes of an articulating expandable interbody cage in minimally invasive transforaminal lumbar interbody fusion for spondylolisthesis

OBJECTIVE The inability to significantly improve sagittal parameters has been a limitation of minimally invasive surgery for transforaminal lumbar interbody fusion (MIS TLIF). Traditional cages have a limited capacity to restore lordosis. This study evaluates the use of a crescent-shaped articulating expandable cage (Altera) for MIS TLIF. METHODS This is a retrospective review of 1- and 2-level MIS TLIF. Radiographic outcomes included differences in segmental and lumbar lordosis, disc height, evidence of fusion, and any endplate violations. Clinical outcomes included the numeric rating scale for leg and back pain and the Oswestry Disability Index (ODI) for low-back pain. RESULTS Thirty-nine patients underwent single-level MIS TLIF, and 5 underwent 2-level MIS TLIF. The mean age was 63.1 years, with 64% women. On average, spondylolisthesis was corrected by 4.3 mm (preoperative = 6.69 mm, postoperative = 2.39 mm, p < 0.001), the segmental angle was improved by 4.94° (preoperative = 5.63°, postoperative = 10.58°, p < 0.001), and segmental height increased by 3.1 mm (preoperative = 5.09 mm, postoperative = 8.19 mm, p < 0.001). At 90 days after surgery the authors observed the following: a smaller postoperative sagittal vertical axis was associated with larger changes in back pain at 90 days (r = -0.558, p = 0.013); a larger decrease in spondylolisthesis was associated with greater improvements in ODI and back pain scores (r = -0.425, p = 0.043, and r = -0.43, p = 0.031, respectively); and a larger decrease in pelvic tilt (PT) was associated with greater improvements in back pain (r = -0.548, p = 0.043). For the 1-year PROs, the relationship between the change in PT and changes in ODI and numeric rating scale back pain were significant (r = 0.612, p = 0.009, and r = -0.803, p = 0.001, respectively) with larger decreases in PT associated with larger improvements in ODI and back pain. Overall for this study there was a 96% fusion rate. Fourteen patients were noted to have endplate violation on intraoperative fluoroscopy during placement of the cage. Only 3 of these had progression of their subsidence, with an overall subsidence rate of 6% (3 of 49) visible on postoperative CT. CONCLUSIONS The use of this expandable, articulating, lordotic, or hyperlordotic interbody cage for MIS TLIF provides a significant restoration of segmental height and segmental lordosis, with associated improvements in sagittal balance parameters. Patients treated with this technique had acceptable levels of fusion and significant reductions in pain and disability.

Risk Factors Associated With 90-Day Readmissions After Degenerative Lumbar Fusion: An Examination of the Michigan Spine Surgery Improvement Collaborative (MSSIC) Registry

BACKGROUND Most studies have evaluated 30-d readmissions after lumbar fusion surgery. Evaluation of the 90-d period, however, allows a more comprehensive assessment of factors associated with readmission. OBJECTIVE To assess the reasons and risk factors for 90-d readmissions after lumbar fusion surgery. METHODS The Michigan Spine Surgery Improvement Collaborative (MSSIC) registry is a prospective, multicenter, and spine-specific database of patients surgically treated for degenerative disease. MSSIC data were retrospectively analyzed for causes of readmission, and independent risk factors impacting readmission were found by multivariate logistic regression. RESULTS Of 10 204 patients who underwent lumbar fusion, 915 (9.0%) were readmitted within 90 d, most commonly for pain (17%), surgical site infection (16%), and radicular symptoms (10%). Risk factors associated with increased likelihood of readmission were other race (odds ratio [OR] 1.81, confidence interval [CI] 1.22-2.69), coronary artery disease (OR 1.57, CI 1.25-1.96), ≥4 fused levels (OR 1.41, CI 1.06-1.88), diabetes (OR 1.34, CI 1.10-1.63), and surgery length (OR 1.09, CI 1.03-1.16). Factors associated with decreased risk were discharge to home (OR 0.63, CI 0.51-0.78), private insurance (OR 0.79, CI 0.65-0.97), ambulation same day of surgery (OR 0.81, CI 0.67-0.97), and spondylolisthesis diagnosis (OR 0.82, CI 0.68-0.97). Of those readmitted, 385 (42.1%) patients underwent another surgery. CONCLUSION Ninety-day readmission occurred in 9.0% of patients, mainly for pain, wound infection, and radicular symptoms. Increased focus on postoperative pain may decrease readmissions. Among factors impacting the likelihood of 90-d readmission, early postoperative ambulation may be most easily modifiable. Optimization of preexisting medical conditions could also potentially decrease readmission risk.

Motor-Based Monitoring During Minimally Invasive Lateral Spine Surgery

The minimally invasive lateral transpsoas approach to the spine requires navigation near important neurological bundles. Injury to these nerves can cause severe pain and neuropathy or permanent weakness along numerous myotomes. During the lateral dissection, motor monitoring is often used to ensure safe access to the spine. This chapter focuses on motor-based monitoring during this approach.

Open Anterior and Lateral Thoracic Interbody Approaches and Techniques

Due to their rarity and diversity, pathologies of the thoracic disc space can be challenging to manage surgically. The complexity of these cases is compounded by the increased risk of patient morbidity that is associated with any pathology in this area, including the potential for devastating neurological deficit, vascular injury, or CSF leak. Open and lateral approaches to the thoracic disc space are perhaps some of the more invasive techniques used in spine surgery to treat thoracic disc disease and subsequently require special attention. This chapter will focus on open and lateral approaches to the thoracic spine for the purpose of interbody placement.