Behavior of Injured Lamina in Lumbar Burst Fractures during Reduction Maneuvers: A Biomechanical Study

STUDY DESIGN: An experimental biomechanical study. PURPOSE: This study aims to investigate the behavior of a lamina injury in lumbar burst fractures during reduction maneuvers. OVERVIEW OF LITERATURE: Lumbar burst fractures are frequently accompanied by a lamina fracture. Many researchers concluded that any reduction maneuver will close the fractured lamina edges and possibly crush the entrapped neural elements. This conclusion did not rely on solid biomechanical trials and was based primarily on clinical experience. METHODS: Eighteen fresh-frozen lamb spines were randomly divided into three groups. Using the preinjury and the dropped-mass technique, a burst fracture model was developed. A central laminectomy of 5 mm of the L3 lumbar spine was created to mimic a complete type of lamina fracture. To measure the movement of the fractured laminar edges, two holes were drilled on both sides of the upper and lower regions of the lamina to allow for optic marker placement. A single specific spine movement was applied to each group: traction, flexion, and extension. Gap changes were measured by camera extensometers. RESULTS: After traction, the average values of the upper and lower aspects of the lamina interval showed narrowing of 1.65±0.82 mm and 1.97±1.14 mm, respectively. No statistical significance was detected between the two aspects. The upper and lower regions of the lamina gap behaved differently during extension. At 10°, 20°, and 30°, the upper part of the lamina interval was widened by an average of 0.016±0.024, 0.29±0.32, and 1.73±1.45 mm, respectively, whereas the lower part was narrowed by an average of 0.023±0.012, 0.47±0.038, and 1.94±1.46 mm, respectively. CONCLUSIONS: Neural element crushing may take place, particularly at the lower aspect of the fractured lamina gap during extension and throughout the whole lamina gap during traction. The lamina gap widens during flexion. Reduction maneuvers should be attempted after exploring the fractured lamina to prevent further neurological compromise.

Predictable Imaging Signs of Cauda Equina Entrapment in Thoracolumbar and Lumbar Burst Fractures with Greenstick Lamina Fractures

STUDY DESIGN: A retrospective study. PURPOSE: The aim of present study was to investigate imaging findings suggestive of cauda equina entrapment in thoracolumbar and lumbar burst fractures. OVERVIEW OF LITERATURE: Burst fractures with cauda equina entrapment can cause neurologic deterioration during surgery. However, dural tears and cauda equina entrapment are very difficult to diagnose clinically or radiographically before surgery. METHODS: Twenty-three patients who underwent spinal surgery for thoracolumbar or lumbar burst fractures were enrolled in this study. In magnetic resonance imaging T2-weighted images of the transverse plane, we defined cauda equina notch sign (CENS) as a v-shaped image that entrapped cauda equina gathers between lamina fractures. We evaluated the fractured spine by using CENS and lamina fractures and the rate of available space for the spinal canal at the narrowest portion of the burst fracture level. We classified patients into entrapment group or non-entrapment group, based on whether cauda equina entrapment existed. RESULTS: Lamina fractures were detected in 18 (78.3%) and CENS were detected in 6 (26.1%) of 23 burst-fracture patients. Cauda equina entrapment existed in all the patients with CENS. In addition, the rate of available space for the spinal canal increased according to logistic regression. The size of the retropulsed fragment in the spinal canal was the most reliable of all the factors, suggesting cauda equina entrapment. CONCLUSIONS: CENS was the most predictable sign of cauda equina entrapment associated with burst fractures.

Relationship between Lamina Fractures and Dural Tear in Low Lumbar Burst Fractures

PURPOSE: To investigate the relationship between the greenstick laminar fractures and the dural tear in low lumbar burst fractures and their optimal treatment. MATERIALS AND METHODS: We enrolled 51 patients (52 cases) who had been diagnosed with low lumbar burst fracture from June 2003 to May 2007. The average age was 39 years (range, 22 to 58), 30 male patients (58.8%), and 21 female patients (41.2%). Average follow-up periods was 19 months (range, 11 to 45). Lumbar CT scan were taken 1 mm slices in precision for all patients. We judged it incomplete fracture if lumbar CT scans show loss of cortical continuity over 3 slices if there is an aggrement of two among one radiologist and two orthopaedic surgeons reached a consensus. Dural tear and entrapment of nerve root were confirmed intraoperatively by the senior surgeon. RESULTS: In 52 burst fractures, complete lamina fractures occurred in 21 cases and there were green stick laminar fractures in 14 cases. Neurologic defect has been found in 12 cases, 5 (63%) from complete laminar fractures and 3 (37%) from green stick laminar fractures. Dural tears has been detected in 9 cases (26%), 4 (19%) from complete laminar fractures and 5 (36%) from green stick laminar fractures. CONCLUSION: Dural tear and nerve root entrapment can be accompanied in patients with green stick fracture. There is necessary to consider the possibility of dural tear and nerve root entrapment before operation and to indentify carefully to the presence of nerve root entrapment during operation.