Mitigating spinal cord distraction injuries: the effect of durotomy in decreasing cord interstitial pressure in vitro.

STUDY DESIGN: The present study involved an in vitro examination of spinal cord interstitial pressure (CIP) during distraction before and after durotomy in three spinal cord segments obtained from five pigs. OBJECTIVES: To determine whether durotomy can be used to decrease the elevated CIP associated with spinal cord distraction. SUMMARY OF BACKGROUND DATA: Spinal cord distraction is a known cause of spinal cord injury. Several articles describing the pathophysiology of cord distraction injuries suggest that the underlying mechanism of injury is a microvascular ischemic event. The authors have previously described an increase in CIP with spinal cord distraction, with average pressures of 23 mmHg at loads of 1,000 g. To date, there are no published studies that have evaluated the efficacy of intentional durotomies as a treatment for elevated CIP. METHODS: A total of 15 spinal cord sections were harvested from pigs and distracted while immersed in saline, using a fixed 1,000 g distraction force. The CIP decay was then measured at 30-s intervals for 10 min. The distraction/relaxation maneuver was performed six times with continuous CIP monitoring and was subsequently followed by durotomy. RESULTS: The pressure-decay curves were similar for each specimen, but varied according to individual pigs and anatomical levels. CIP decayed over the first 4 min of distraction and remained constant for the final 6 min. Longitudinal durotomy led to a dramatic drop in CIP toward baseline and appeared to be as effective as transverse durotomy with regard to the normalization of pressure. CONCLUSION: Spinal cord distraction causes elevations in CIP. Durotomy lowers elevated CIP in vitro and may be effective at lowering CIP in vivo. Further study is required to evaluate the usefulness of durotomy in vivo.

How Do Pelvic Parameters Correlate With Postoperative Outcomes When the Parameters Are Not Measured Preoperatively in Patients Undergoing Instrumented Lumbar Fusion?

OBJECTIVE: A normal age-adjusted sagittal alignment is an important factor in achieving long-term functional results after lumbar spinal fusion. We aim to determine if the changes in spino-pelvic alignment (SPA) correlate with post-operative functional outcomes in patients who underwent instrumented lumbar spine surgery when the parameters were not measured before. METHOD: A retrospective review of medical records from 2012 to 2016, and radiographs of the patients who underwent instrumented fusion of the lumbar spine. The X-rays of the available preoperative lumbar spine were reviewed for SPA and compared with the last follow-up postoperative images. The patients were contacted by telephone to complete the EuroQoL 5 Dimensions 5-level questionnaire and visual analog scale for evaluation of their functional outcomes during 2017. Correlation studies were performed using Pearson's coefficient. RESULTS: Forty-six patients were included with a mean age of 53 years and a follow-up of 47 months. There was a significant improvement in the functional outcomes and pain in the whole group. All the patients showed improvement in their SPA, and those who underwent more than two levels of fusion showed a significant improvement (P<0.05). Lumbar lordosis and sacral slope had a significant correlation with postoperative clinical improvement (R=0.8). CONCLUSION: The study showed that single or double fusion has significant improvement in pain and functional outcome with a significant change in SPA.

Spontaneous Spinal Epidural Hematoma: Correlation of Timing of Surgical Decompression and MRI Findings with Functional Neurological Outcome.

OBJECTIVE: Spontaneous spinal epidural hematoma (SSEH) is a rare and morbid entity, with the prognosis affected by delayed diagnosis and surgical intervention. The correlation between the timing of the intervention and neurological recovery has not been clearly reported. We present a retrospective study of SSEH to determine the correlation between the timing of surgical intervention and changes in the spinal cord signal on magnetic resonance imaging (MRI) with the neurological outcome. METHODS: The records of 14 patients who had undergone surgical decompression of SSEHs during a 10-year duration were reviewed. The diagnosis was established from the MRI, intraoperative, and histopathological examination findings. RESULTS: We identified 14 patients from both centers, 6 of whom were male. Their mean age was 54.1 years. The onset was spontaneous, and 2 patients were receiving anticoagulant therapy. The most common presentation was paraplegia (n = 8), followed by paraparesis (n = 3) and quadriparesis (n = 2). Spinal cord signal changes were demonstrated on all T2-weighted MRI studies. The response to surgery was favorable for 13 of our patients at the 6-month follow-up examination. The spinal cord changes had persisted in 5 patients on the 6-month postoperative MRI scan. All 14 patients, except for 1, had a favorable neurological outcome at the last follow-up examination. CONCLUSIONS: Significant neurological recovery after surgical decompression of SSEHs can be achieved, despite the significant preoperative neurological deficits, spinal cord changes on MRI, and delayed timing of intervention.

Experimental study on pressure response to graded spinal canal compromise in an in vitro burst fracture mode.

BACKGROUND: Spinal cord compression is a known cause of spinal cord injury. The purpose of this study is to measure pressure response during graded spinal cord compression. This information will be important in evaluating the amount of canal compromise that can be tolerated before risking neurological injury secondary to cord compression. To date, there is no published study that has evaluated pressure response to graded canal compromise in the thoracic and lumbar spine. MATERIALS AND METHODS: A comparative biomechanical investigation using an in vitro burst fracture model of graded spinal canal compromise was performed. Four porcine spines, sectioned into four thoracics and four lumbar segments, were harvested from 30 kg pigs. Graded spinal canal compromise (0.75 mm/30 s) was achieved using a modified 12.7 mm dynamic hip screw. The real-time ventral epidural pressure was measured at each 0.75 mm of canal compromise. RESULTS: A significant increase in spinal cord pressure was recorded during graded spinal cord compression (P < 0.0001), and there were no statistical differences between the increase in pressure measured in the thoracic and lumbar spinal segments (P = 0.83). The pressure to degree of canal compromise curve exhibited an initial rapid rise in pressure followed by incrementally smaller increases in pressure as canal compromise increased. CONCLUSIONS: Spinal cord pressure increased with any degree of canal compromise, the most important rise occurring with initial compression. Future studies will evaluate the usefulness of laminectomy in vivo to completely restore ventral epidural pressure in the thoracic and lumbar spine.

An in vitro study on the effects of freezing, spine segment, repeat measurement, and individual cord properties on cord interstitial pressure.

STUDY DESIGN: In vitro study of the spinal cord tension and pressure relationships before and after thawing in 6 different spinal cord segment from 2 individual pigs. OBJECTIVES: To determine if frozen and thawed spinal cord segments had different tension/cord interstitial pressure(CIP) relationships to fresh spinal cord segments. In addition, we will determine if the cord level, individual cord properties, and repeated CIP measurements affect the tension/CIP relationships. SUMMARY OF BACKGROUND DATA: Spinal cord distraction is a known cause of spinal cord injury. Several articles published on the pathophysiology of the cord distraction injury suggest that the underlying mechanism of injury is a microvascular ischemic event. We have previously described an increase in CIP with spinal cord distraction, pressures average 23 mmHg at 1 kg loads. METHODS: Six cord segments harvested from 2 pigs contained cervical, thoracic, and lumbar segments, and underwent distraction using a series of 7 calibrated weights from 0 to 1000 g weight. The cords were measured at each level of distraction. The cords were then frozen at -20 degrees C for a period of 2 weeks, and then thawed and retested. Multiple linear regression was then performed. RESULTS: There was no difference between the fresh and the frozen-thawed cords; there was statistical difference between the 2 pigs (18 mmHg) (P < 0.001). There are differences between the cervical and the thoracic cord segments (P < 0.001), and between cervical and lumbar cord segments (P = 0.056). There is a significant relation between the tension applied and CIP. Repeated trials showed no drift with repeated measures. CONCLUSION: Freezing and thawing spinal cords has no effect on the CIP/tension curves. Cord interstitial pressure developed is dependant on cord tension, cord level, individual cord properties, but not on the number of repetitions carried out while testing the spinal cord.