Krauss, William E.

OBJECTIVE The purpose of this study was to identify risk factors for mechanical complications following complex spinal reconstruction for spondylectomy of primary spinal column tumors. METHODS A retrospective chart review identified patients treated with spondylectomy for primary spinal column tumors in the thoracic or lumbar spine followed by posterior instrumentation and anterior column reconstruction. Variables collected included basic demographics, smoking status, chronic steroid use, frailty (Charlson Comorbidity Index), extent of resection, Weinstein-Boriani-Biagini classification, tumor volume, Spine Instability Neoplastic Score, anterior column reconstruction and fixation techniques, rod characteristics, Hounsfield units (HUs), and neoadjuvant/adjuvant chemoradiation. RESULTS Twenty-five patients were included (14 men, 11 women) with an average (± SD) age of 45 ± 18 years, BMI of 28 ± 5.7, and follow-up of 6.0 ± 6.2 years. Primary spinal column tumor pathology included chordoma (40%), chondrosarcoma (16%), giant cell tumor (16%), osteosarcoma (16%), osteoblastoma (8%), and aneurysmal bone cyst (4%). Six patients (24%) experienced mechanical complications, including rod fractures (n = 5) and distal junctional failure (n = 1). Of the 6 patients with mechanical complications, 4 (67%) underwent reoperation. The length of follow-up was the only statistically significant risk factor for patients with mechanical complications (average 11 years) compared to those without complications (average 4.4 years, p = 0.047). Average HUs were 144 for mechanical complication patients versus 180 for those without (p = 0.08). Anterior column reconstruction materials included a titanium cage (13 patients, 3 failures), structural allograft (6 patients, 2 failures), vascularized fibular strut autograft (6 patients, no failures), nonvascularized structural autograft (5 patients, 1 failure), vascularized rib autograft (5 patients, 2 failures), and a polyetheretherketone cage (2 patients, no failures). The vascularized fibular strut autograft had a 0% mechanical failure rate, but this did not reach statistical significance (p = 0.28). Twelve patients (48%) had anterior fixation placed, with a 17% rate of mechanical complications (p = 0.65). Five patients (20%) had > 2-rod constructs, with a 20% mechanical complication rate (p = 0.99). CONCLUSIONS Reconstruction following primary spinal column tumor resection is a significant challenge, as evident by a high rate of mechanical complications and instrumentation failure. Future studies are needed with larger sample sizes to identify techniques that may mitigate the risk of failure.

OBJECTIVE Transforaminal lumbar interbody fusion (TLIF) offers both indirect decompression and segmental correction through restoration of disc height. However, stresses exerted on the vertebral endplates by the interbody device can result in implant subsidence and loss of correction. The present time-to-event analysis aimed to identify predictors of interbody subsidence. METHODS Patients who underwent 1- or 2-level TLIF were identified. Data on demographics, surgical details, preoperative bone quality using CT-based Hounsfield units (HU), and pre- and postoperative lumbopelvic parameters were collected. Univariable analyses were conducted to identify predictors of subsidence (≥ 2-mm intrusion of interbody into cranial or caudal vertebrae) and significant subsidence (≥ 4-mm intrusion). Multivariable Cox regression was performed to identify independent predictors of subsidence, expressed as hazard ratios with 95% confidence intervals. RESULTS A total of 198 patients treated at 241 levels were included (median age 66.6 years, IQR 59.5, 73.7 years; 56.6% were women). In 92 levels (38.2%) there was some subsidence and in 25 (10.4%) there was significant subsidence. Implanted levels demonstrating subsidence (≥ 2 mm) were associated with lower HU in cranial and caudal vertebrae; had interbodies positioned farther from the anterior apophyseal ring; were implanted with taller, more lordotic interbodies; and underwent greater disc height restoration. Those showing significant subsidence (≥ 4 mm) were similarly associated with lower HU in the cranial and caudal vertebrae; had interbodies positioned farther from the anterior apophyseal ring of the caudal vertebrae; and underwent greater disc height restoration. Multivariable Cox regression showed that time to subsidence was predicted by greater implant height (HR 1.20/mm, 95% CI 1.05–1.38; p = 0.009), greater postoperative disc height (HR 1.21/mm, 95% CI 1.09–1.34; p < 0.001), and greater disc height restoration (HR 1.11/mm, 95% CI 1.04–1.19; p = 0.002). The time-to-subsidence analysis for significant (≥ 4 mm) subsidence showed that it was predicted by lower HU in the cranial vertebrae (HR 0.98/unit, 95% CI 0.97–0.99; p = 0.001); increasing number of levels instrumented (HR 1.26, 95% CI 1.04–1.52; p = 0.016); and greater disc height restoration (HR 1.33/mm, 95% CI 1.18–1.51; p < 0.001). CONCLUSIONS This time-to-event analysis suggests that interbody subsidence following TLIF is best predicted by implantation of a taller interbody and aggressive disc height restoration. Significant subsidence is similarly predicted by aggressive disc height restoration along with poor baseline bone quality. The results suggest the need to balance aggressive correction at the time of surgery against the increased risk of subsequent interbody subsidence.

Introduction: Bone health optimization is a key component of the preoperative management of spine surgery patients, as poor bone quality increases the odds of mechanical complications. The present study aimed to achieve the following: (1) compare the relative efficacy of current osteoporosis medications in improving bone quality; (2) identify factors influencing treatment response in preoperative spine surgery patients. Methods: Patients treated at a single, multisite institution who received osteoporosis treatment were identified. Data were gathered on pre- and post-treatment lumbar spine Hounsfield Unit (HU) measurements, patient demographics, frailty scores (modified Frailty Index/mFI, risk analysis index/RAI), and pharmacologic treatment details. The primary outcome was a ≥7 point improvement in lumbar HU, and baseline and logistic regression models were utilized to identify factors associated with this improvement. Medications were grouped as anabolic (teriparatide, romosozumab) and antiresorptive (denosumab, alendronate) therapies. Results: A total of 267 patients were included (median age: 74 years; IQR [66–81]; 67.3% female), with 127 (47.6%) improving by ≥7 HU. The treatment agents used were alendronate (95), denosumab (113), romosozumab (31), and teriparatide (28). Univariable comparisons revealed significant differences across medication groups in age (p < 0.001), sex (p < 0.001), mFI (p < 0.001), RAI (p = 0.004), BMI (p < 0.001), pre-treatment HU (p = 0.022), and treatment duration (p < 0.001). The highest HU improvement rates (ΔHU ≥ 7) were observed in patients receiving the anabolic medications romosozumab (67.7%) and teriparatide (60.7%). Univariable logistic regression identified male sex (OR 0.54, p = 0.019), higher pre-treatment HU (OR 0.99, p = 0.006), and longer treatment duration (OR 0.97, p = 0.003) as factors associated with lower odds of HU improvement. Only romosozumab was associated with significantly higher odds of HU improvement relative to alendronate (OR 3.02, p = 0.012). In our multivariable analysis, male sex (OR 0.53, p = 0.028) and higher pre-treatment HU (OR 0.99, p = 0.002) remained significant predictors of HU improvement. However, medication type was not significant in the multivariable analysis. Conclusions: Our study highlights that male sex and higher pre-treatment HU were independently associated with lower odds of HU improvement, while medication type was not a significant predictor. Additionally, anabolic agents offered superior improvement relative to antiresorptive therapies.

OBJECTIVE The aim of this study was to determine independent risk factors for vertebral compression fracture (VCF) following stereotactic body radiation therapy (SBRT) in metastatic spine disease. METHODS Patients treated with SBRT for spinal metastasis at a single tertiary care center between 2008 and 2019 were retrospectively identified. Patients with CT scans obtained within 1 year of SBRT completion were included. Variables collected included demographics, Spine Instability Neoplastic Score (SINS), primary tumor pathology, Weinstein-Boriani-Biagini (WBB) classification, chemoradiation treatment details, and bone quality as assessed by Hounsfield units (HUs) on CT. HUs were measured for the medullary bone of the metastatic level, the tumor, and the vertebral bodies cephalad and caudal to the metastasis. Multivariable logistic regression was used to identify predictors of post-SBRT pathological fracture. RESULTS A total of 292 patients (mean age 66 years) with 392 unique lesions were included. The most common pathologies were prostate (n = 193), kidney/renal cell (n = 46), and lung (n = 33). The most common tumor levels were thoracic (n = 206 lesions) and lumbar (n = 128 lesions). SBRT was generally delivered in 1–3 fractions with doses ranging from 16 to 24 Gy in 1 fraction and 24–36 Gy in 3 fractions. Of the 392 lesions, 73 suffered VCF: 21 (29%) with < 25% height loss, 15 (21%) with 25%–40% height loss, and 37 (51%) with > 40% height loss. On univariate analysis, patients with VCF had lower average HUs (156 ± 52 vs 202 ± 89, p < 0.001), more WBB sectors involved (3 ± 2 vs 3 ± 1, p < 0.001), higher SINSs (8 ± 3 vs 6 ± 2, p < 0.001), were more commonly female (33% vs 22%, p = 0.05), and more commonly had nonprostate pathology (67% vs 47%, p = 0.003). VCF rates were similar between moderate (< 20 Gy in 1 fraction, < 30 Gy in 3 or 5 fractions) and high-dose (> 20 Gy in 1 fraction, > 30 Gy in 3 or 5 fractions) radiation schema (15% VCF vs 16% no VCF, respectively; p = 0.99). On multivariable logistic regression, independently significant predictors of VCF were HUs ≤ 229 (OR 6, p < 0.001), affected levels ≥ 3 WBB segments (OR 3, p < 0.001), and an SINS ≥ 8 (OR 2, p = 0.02). CONCLUSIONS Low pre-radiation HUs, involvement of more WBB sectors, and a higher SINS were independent predictors of VCF following SBRT for metastatic spine disease.

BACKGROUND AND OBJECTIVES: Transforaminal lumbar interbody fusion (TLIF) allows for direct and indirect decompression and segmental lordosis in sagittal plane correction. This study compares the effectiveness of “Bullet” type and “Banana” type devices for sagittal plane correction. METHODS: Patients who underwent 1-level or 2-level TLIF for degenerative pathology at a single tertiary care center were identified. Details were extracted on demographics, interbody dimensions, and preoperative and postoperative lumbopelvic parameters from upright radiographs. Cages were categorized as “Bullet” or “Banana” type based on morphology and manufacturer description of optimal position. Univariable comparisons between levels treated with “Bullet” and “Banana” type interbodies were performed. Multivariable linear regression was performed to identify independent predictors of postoperative segmental lordosis and change in segmental lordosis. RESULTS: One hundred and ninety eight unique patients (median 66.6 years; [IQR 59.5, 73.7]; 56.6% female) were included with 241 levels treated, of which 114 (52.7%) were treated with “Banana” type interbodies and 127 (47.3%) with “Bullet” type. “Banana” type interbodies afforded both greater postoperative segmental lordosis (8.1 [6.2, 10.7] vs 7.5 [5.2, 9.6]; P = .048) and greater increase in segmental lordosis (3.3 [0.7, 7.0] vs 2.3 [0.1, 4.2]; P = .015). On multivariable linear regression, only preoperative segmental lordosis (β = 0.322 per degree; [0.244, 0.399]; P < .001), implant listed lordosis (β = 0.146 per degree; 95% CI [0.048, 0.244]; P = .004), preoperative pelvic incidence (0.072 per degree; [0.034, 0.111]; P < .001), and use of bilateral TLIF windows (β = 3.133; [1.213, 5.053]; P = .001) were predictive of postoperative segmental lordosis. CONCLUSION: The present analysis suggests that baseline lumbopelvic anatomy, interbody lordosis, and the use of bilateral TLIF windows are the most important predictors of postoperative segmental lordosis. Use of “Banana” vs “Bullet” type interbodies was not predictive of segmental lordosis achieved on immediate postoperative upright radiographs. Further work is merited to determine whether the 2 interbody types demonstrate differences regarding subsidence risk or maintenance of correction.

OBJECTIVE Spine metastases are commonly treated with radiotherapy for local tumor control; pathologic fracture is a potential complication of spinal radiotherapy. Both Hounsfield units (HUs) on CT and vertebral bone quality (VBQ) on MRI have been argued to predict stability as measured by odds of pathologic fracture, although it is unclear if there is a difference in the predictive power between the two methodologies. The objective of the present study was to examine whether one methodology is a better predictor of pathologic fracture following radiotherapy for mobile spine metastases. METHODS Patients who underwent radiotherapy (conventional external-beam radiation therapy, stereotactic body radiation therapy, or intensity-modulated radiation therapy) for mobile spine (C1–L5) metastases at a tertiary care center were retrospectively identified. Details regarding underlying pathology, patient demographics, and tumor morphology were collected. Vertebral involvement was assessed using the Weinstein-Boriani-Biagini (WBB) system. Bone quality of the non–tumor-involved bone was assessed on both pretreatment CT and MRI. Univariable analyses were conducted to identify independent predictors of fracture, and Kaplan-Meier analyses were used to identify significant predictors of time to pathologic fracture. Stepwise Cox regression analysis was used to determine independent predictors of time to fracture. RESULTS One hundred patients were included (mean age 62.7 ± 11.9 years; 61% male), of whom 35 experienced postradiotherapy pathologic fractures. The most common histologies were lung (22%), prostate (21%), breast (14%), and renal cell (13%). On univariable analysis, the mean HUs of the vertebrae adjacent to the fractured vertebra were significantly lower among those experiencing fracture; VBQ was not significantly associated with fracture odds. Survival analysis showed that average HUs ≤ 132, nonprostate pathology, involvement of ≥ 3 vertebral body segments on the WBB system, Spine Instability Neoplastic Score (SINS) ≥ 7, and the presence of axial pain all predicted increased odds of fracture (all p < 0.001). Cox regression found that HUs ≤ 132 (OR 2.533, 95% CI 1.257–5.103; p = 0.009), ≥ 3 WBB vertebral body segments involved (OR 2.376, 95% CI 1.132–4.987; p = 0.022), and axial pain (OR 2.036, 95% CI 0.916–4.526; p = 0.081) predicted increased fracture odds, while prostate pathology predicted decreased odds (OR 0.076, 95% CI 0.009–0.613; p = 0.016). Sensitivity analysis suggested that an HU threshold of ≤ 132 and a SINS of ≥ 7 identified patients at increased risk of fracture. CONCLUSIONS The present results suggest that bone density surrogates as measured on CT, but not MRI, can be used to predict the risk of pathologic fracture following radiotherapy for mobile spine metastases. More extensive vertebral body involvement and the presence of mechanical axial pain additionally predict increased fracture odds.

OBJECTIVE The purpose of this study was to analyze risk factors for sacral fracture following noninstrumented partial sacral amputation for en bloc chordoma resection. METHODS A multicenter retrospective chart review identified patients who underwent noninstrumented partial sacral amputation for en bloc chordoma resection with pre- and postoperative imaging. Hounsfield units (HU) were measured in the S1 level. Sacral amputation level nomenclature was based on the highest sacral level with bone removed (e.g., S1 foramen amputation at the S1–2 vestigial disc is an S2 sacral amputation). Variables collected included basic demographics, patient comorbidities, surgical approach, preoperative radiographic details, neoadjuvant and adjuvant radiation therapy, and postoperative sacral fracture data. RESULTS A total of 101 patients (60 men, 41 women) were included; they had an average age of 69 years, BMI of 29 kg/m2, and follow-up of 60 months. The sacral amputation level was S1 (2%), S2 (37%), S3 (44%), S4 (9%), and S5 (9%). Patients had a posterior-only approach (77%) or a combined anterior–posterior approach (23%), with 10 patients (10%) having partial sacroiliac (SI) joint resection. Twenty-seven patients (27%) suffered a postoperative sacral fracture, all occurring between 1 and 7 months after the index surgery. Multivariable logistic regression analysis demonstrated S1 or S2 sacral amputation level (p = 0.001), combined anterior–posterior approach (p = 0.0064), and low superior S1 HU (p = 0.027) to be independent predictors of sacral fracture. The fracture rate for patients with superior S1 HU < 225, 225–300, and > 300 was 38%, 15%, and 9%, respectively. An optimal superior S1 HU cutoff of 300 was found to maximize sensitivity (89%) and specificity (42%) in predicting postamputation sacral fracture. In addition, the fracture rate for patients who underwent partial SI joint resection was 100%. CONCLUSIONS Patients with S1 or S2 partial sacral amputations, a combined anterior–posterior surgical approach, low superior S1 HU, and partial SI joint resection are at higher risk for postoperative sacral fracture following en bloc chordoma resection and should be considered for spinopelvic instrumentation at the index procedure.

Abstract Introduction: Sacral and presacral schwannomas are rare and account for a minority of spinal schwannomas. We aim to present our institution’s experience surgically treating sacral schwannomas over twenty-one years. Additionally, we assess the literature for surgical cases of sacral schwannomas to compare tumor characteristics and outcomes following resection.Methods: Data on demographics, presenting symptoms, lesion characteristics, surgical management, and outcomes were collected for 27 patients treated surgically for sacral or presacral schwannoma between 1997 and 2018 at all Mayo Clinic locations and compared to those of patients found in the literature. Results: We identified 31 studies in the literature containing 93 patients with sacral schwannoma treated surgically. Our patients and those in the literature experienced similar symptoms, with the most common symptom being pain and the least common being sexual dysfunction, and age at diagnosis. Most of our patients (59.3%) reported full recovery from preoperative symptoms, while a minority reported a partial recovery (33.3%) and no recovery (11.1%). A smaller percentage of patients found in the literature experienced full recovery (31.9%) and partial recovery (29.8%) but also no recovery (1.1%). Our patients experienced fewer complications (14.8% versus 25.5%).Conclusion: Outcomes of patients with sacral or presacral schwannomas vary based on patient demographics, tumor characteristics, symptoms, and surgical treatment. Among the range of symptoms experienced by these patients, the most common is pain. Prognosis improves and overall survival rate is high when the surgical approach towards sacral schwannomas is prepared and executed appropriately.

Background: Myxopapillary ependymomas (MPE) are intradural spinal tumors with a predilection to the filum terminale. Damage to conus medullaris during surgery can result in sphincteric and sexual dysfunction. The purpose of this study is to determine how myxopapillary ependymoma proximity to the conus impacts patient presentation, extent of resection, and clinical outcomes. Methods: Fifty-one patients who underwent surgical resection of pathologically confirmed myxopapillary ependymoma with at least 1 year of follow-up were included in the study. We collected initial presenting symptoms, distance of the tumor from the conus, extent of resection, and postoperative clinical outcomes including bladder dysfunction. Results: Average age was 38 years (range 7–75 years) with a male to female ratio of 1.43:1. Patients most commonly presented with pain symptoms (88%), and 12 patients (23.5%) had urologic symptoms on presentation. The mean tumor distance from the tip of the conus was 1.60 cm (10 cm above to 21 cm below the tip of the conus). Patients with tumors in contact with the conus had a significantly higher rate of preoperative urinary symptoms and were more likely (32% vs. 14%) to suffer postoperative urinary sphincteric disturbances. Tumors with direct invasion of the conus medullaris were more likely to require intralesional resection and fail to achieve a gross total resection (GTR). Conclusion: Patients with MPE in close proximity to the conus were more likely to suffer from long-term morbidity related to urologic issues following surgical resection. Adjuvant radiotherapy may be a viable option for patients who fail to achieve GTR.