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Courtney E. Sherman, Peter S. Rose, Lori L. Pierce, Michael J. Yaszemski, and Franklin H. Sim

Object

Sacrectomy positioning must balance surgical exposure, localization, associated operative procedures, and patient safety. Poor positioning may increase hemorrhage, risk of blindness, and skin breakdown.

Methods

The authors prospectively identified positioning-related morbidity in 17 patients undergoing 19 prone sacral procedures from September 2008 to August 2009 following institution of a standardized positioning protocol. Key elements include skull traction/head suspension, an open radiolucent frame, and wide draping for associated closure and reconstructive procedures.

Results

Tumors included 5 chordomas, 4 high-grade sarcomas, 1 chondrosarcoma, 2 presacral extradural myxopapillary ependymomas, and 5 others. Mean patient age was 49.9 years (range 17–74 years); mean body mass index was 27.6 kg/m2 (range 19.3–43.9 kg/m2). Mean preoperative Braden skin integrity score was 21.1 (range 17–23). Average operative time was 501 minutes (range 158–1136 minutes). Prone surgery was a part of staged anterior/posterior resections in 8 patients. Localization was conducted using fluoroscopy in 13 patients and intraoperative CT in 4 patients. All imaging studies were successful. One patient developed a transient ulnar nerve palsy attributed to positioning. Three patients (two of whom were morbidly obese) developed Stage I pressure injuries to the chest and another developed Stage II pressure injury following a 1136-minute procedure. Morbidity was only observed in patients with morbid obesity or with procedures lasting in excess of 10 hours.

Conclusions

A positioning protocol using head suspension on an open radiolucent frame facilitates oncological sacral surgery with reasonable patient morbidity. Morbid obesity and procedure times in excess of 10 hours are risk factors for positioning-related complications. To the authors' knowledge, this is the first report of surgical positioning morbidity in this patient population.

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Godard C. W. de Ruiter, Martijn J. A. Malessy, Michael J. Yaszemski, Anthony J. Windebank, and Robert J. Spinner

Nerve tubes, guides, or conduits are a promising alternative for autologous nerve graft repair. The first biodegradable empty single lumen or hollow nerve tubes are currently available for clinical use and are being used mostly in the repair of small-diameter nerves with nerve defects of < 3 cm. These nerve tubes are made of different biomaterials using various fabrication techniques. As a result these tubes also differ in physical properties. In addition, several modifications to the common hollow nerve tube (for example, the addition of Schwann cells, growth factors, and internal frameworks) are being investigated that may increase the gap that can be bridged. This combination of chemical, physical, and biological factors has made the design of a nerve conduit into a complex process that demands close collaboration of bioengineers, neuroscientists, and peripheral nerve surgeons. In this article the authors discuss the different steps that are involved in the process of the design of an ideal nerve conduit for peripheral nerve repair.

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Konstantinos A. Starantzis, Vasileios I. Sakellariou, Peter S. Rose, Michael J. Yaszemski, and Panayiotis J. Papagelopoulos

This is a technical note of pelvic reconstruction performed by an advanced multidisciplinary team. The authors report a new 3-stage reconstruction of the hemipelvis after Type 3 sacrectomy involving instrumented spinoiliac arthrodesis and pedicled fibula grafting in 2 patients.

The anterior stage of the procedure begins with a transabdominal approach to mobilize the viscera and to free up the tumor from the vessels. The posterior divisions of internal iliac vessels, the middle sacral vessels, and the lateral sacral vessels are then ligated. An anterior vertebrectomy is done at the appropriate level, followed by an anterior osteotomy through the lateral planed surgical margin of the sacrum close to the salvaged sacroiliac joint. The second stage includes a major sacral resection with lower-extremity amputation from the pubic symphysis through the intact side of the sacrum, ipsilateral pedicled fibula harvesting, and closure with an ipsilateral pedicled quadriceps flap. The final stage involves reconstruction with lumboiliac instrumentation. The pedicled fibular graft left from the second stage is then placed distally within the previously created iliopectineal docking site and proximally within the L-5 docking site.

The authors believe that this is a feasible and reproducible technique with theoretical advantages that have to be proved in the long-term follow-up.

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Kari Hanson, Carly Isder, Kristen Shogren, Anthony L. Mikula, Lichun Lu, Michael J. Yaszemski, and Benjamin D. Elder

OBJECTIVE

The use of intrawound vancomycin powder in spine surgery has been shown to decrease the rate of surgical site infections; however, the optimal dose is unknown. High-dose vancomycin inhibits osteoblast proliferation in vitro and may decrease the rate of solid arthrodesis. Bone marrow–derived mesenchymal stem cells (BMSCs) are multipotent cells that are a source of osteogenesis in spine fusions. The purpose of this study was to determine the effects of vancomycin on rat BMSC viability and differentiation in vitro.

METHODS

BMSCs were isolated from the femurs of immature female rats, cultured, and then split into two equal groups; half were treated to stimulate osteoblastic differentiation and half were not. Osteogenesis was stimulated by the addition of 50 µg/mL l-ascorbic acid, 10 mM β-glycerol phosphate, and 0.1 µM dexamethasone. Vancomycin was added to cell culture medium at concentrations of 0, 0.04, 0.4, or 4 mg/mL. Early differentiation was determined by alkaline phosphatase activity (4 days posttreatment) and late differentiation by alizarin red staining for mineralization (9 days posttreatment). Cell viability was determined at both the early and late time points by measurement of formazan colorimetric product.

RESULTS

Viability within the first 4 days decreased with high-dose vancomycin treatment, with cells receiving 4 mg/mL vancomycin having 40%–60% viability compared to the control. A gradual decrease in alizarin red staining and nodule formation was observed with increasing vancomycin doses. In the presence of the osteogenic factors, vancomycin did not have deleterious effects on alkaline phosphatase activity, whereas a trend toward reduced activity was seen in the absence of osteogenic factors when compared to osteogenically treated cells.

CONCLUSIONS

Vancomycin reduced BMSC viability and impaired late osteogenic differentiation with high-dose treatment. Therefore, the inhibitory effects of high-dose vancomycin on spinal fusion may result from both reduced BMSC viability and some impairment of osteogenic differentiation.

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Gemma E. Rooney, Toshiki Endo, Syed Ameenuddin, Bingkun Chen, Sandeep Vaishya, LouAnn Gross, Terry K. Schiefer, Bradford L. Currier, Robert J. Spinner, Michael J. Yaszemski, and Anthony J. Windebank

Object

Glial scar and cystic formation greatly contribute to the inhibition of axonal regeneration after spinal cord injury (SCI). Attempts to promote axonal regeneration are extremely challenging in this type of hostile environment. The objective of this study was to examine the surgical methods that may be used to assess the factors that influence the level of scar and cystic formation in SCI.

Methods

In the first part of this study, a complete transection was performed at vertebral level T9–10 in adult female Sprague-Dawley rats. The dura mater was either left open (control group) or was closed using sutures or hyaluronic acid. In the second part of the study, complete or subpial transection was performed, with the same dural closure technique applied to both groups. Histological analysis of longitudinal sections of the spinal cord was performed, and the percentage of scar and cyst formation was determined.

Results

Dural closure using sutures resulted in significantly less glial scar formation (p = 0.0248), while incorporation of the subpial transection surgical technique was then shown to significantly decrease cyst formation (p < 0.0001).

Conclusions

In this study, the authors demonstrated the importance of the vasculature in cyst formation after spinal cord trauma and confirmed the importance of dural closure in reducing glial scar formation.

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Teriparatide treatment increases Hounsfield units in the lumbar spine out of proportion to DEXA changes

Presented at the 2019 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves

Anthony L. Mikula, Ross C. Puffer, Jeffery D. St. Jeor, James T. Bernatz, Jeremy L. Fogelson, A. Noelle Larson, Ahmad Nassr, Arjun S. Sebastian, Brett A. Freedman, Bradford L. Currier, Mohamad Bydon, Michael J. Yaszemski, Paul A. Anderson, and Benjamin D. Elder

OBJECTIVE

The authors sought to assess whether Hounsfield units (HU) increase following teriparatide treatment and to compare HU increases with changes in bone mineral density (BMD) as measured by dual-energy x-ray absorptiometry (DEXA).

METHODS

A retrospective chart review was performed from 1997 to 2018 across all campuses at our institution. The authors identified patients who had been treated with at least 6 months of teriparatide and compared HU and BMD as measured on DEXA scans before and after treatment.

RESULTS

Fifty-two patients were identified for analysis (46 women and 6 men, average age 67 years) who underwent an average of 20.9 ± 6.5 months of teriparatide therapy. The mean ± standard deviation HU increase throughout the lumbar spine (L1–4) was from 109.8 ± 53 to 133.9 ± 61 HU (+22%, 95% CI 1.2–46, p value = 0.039). Based on DEXA results, lumbar spine BMD increased from 0.85 to 0.93 g/cm2 (+9%, p value = 0.044). Lumbar spine T-scores improved from −2.4 ± 1.5 to −1.7 ± 1.5 (p value = 0.03). Average femoral neck T-scores improved from −2.5 ± 1.1 to −2.3 ± 1.0 (p value = 0.31).

CONCLUSIONS

Teriparatide treatment increased both HU and BMD on DEXA in the lumbar spine, without a change in femoral BMD. The 22% improvement in HU surpassed the 9% improvement determined with DEXA. These results support some surgeons’ subjective sense that intraoperative bone quality following teriparatide treatment is better than indicated by DEXA results. To the authors’ knowledge, this is the first study demonstrating an increase in HU with teriparatide treatment.