Does intraoperative neurophysiological monitoring have predictive value for functional recovery following spinal cord injury? A case report.

To present a case report of a patient with an ASIA B spinal cord injury with partially intact baseline IONM who made a complete functional recovery postoperatively. A thirty-three year old male presented after a motor vehicle accident. Imaging studies revealed a C4-C5 bilateral facet dislocation. On presentation the patient had 4/5 strength in bilateral biceps and wrist extensors, 3/5 strength in bilateral triceps, and 0/5 strength in the finger flexors, intrinsics and all lower extremity muscles. Motor level was C7. Sensation was grossly intact to light touch throughout all extremities, intact to pinprick from C2 to T7, and absent to pinprick caudal to T7. Rectal tone and contraction were absent. After attempts at closed reduction failed the patient underwent an open reduction and posterior C4-C5 fusion. Intraoperative neurophysiologic monitoring (IONM) revealed the presence of baseline responses to the posterior tibial nerve using somatosensory evoked potentials and to the right abductor hallucis using transcranial motor evoked potentials. At the 6 weeks postoperative visit the patient had full 5/5 motor strength to all muscles except the left deltoid that was 4/5 due to a rotator cuff injury. This case illustrates a potential prognostic value of IONM. Despite lack of clinical motor function at the time of surgery, IONM was able to illicit a motor response in the right lower extremity. Further prospective studies are needed for further investigation.

Estimating the effective radiation dose imparted to patients by intraoperative cone-beam computed tomography in thoracolumbar spinal surgery.

STUDY DESIGN: Observational. OBJECTIVE: To estimate the radiation dose imparted to patients during typical thoracolumbar spinal surgical scenarios. SUMMARY OF BACKGROUND DATA: Minimally invasive techniques continue to become more common in spine surgery. Computer-assisted navigation systems coupled with intraoperative cone-beam computed tomography (CT) represent one such method used to aid in instrumented spinal procedures. Some studies indicate that cone-beam CT technology delivers a relatively low dose of radiation to patients compared with other x-ray-based imaging modalities. The goal of this study was to estimate the radiation exposure to the patient imparted during typical posterior thoracolumbar instrumented spinal procedures, using intraoperative cone-beam CT and to place these values in the context of standard CT doses. METHODS: Cone-beam CT scans were obtained using Medtronic O-arm (Medtronic, Minneapolis, MN). Thermoluminescence dosimeters were placed in a linear array on a foam-plastic thoracolumbar spine model centered above the radiation source for O-arm presets of lumbar scans for small or large patients. In-air dosimeter measurements were converted to skin surface measurements, using published conversion factors. Dose-length product was calculated from these values. Effective dose was estimated using published effective dose to dose-length product conversion factors. RESULTS: Calculated dosages for many full-length procedures using the small-patient setting fell within the range of published effective doses of abdominal CT scans (1-31 mSv). Calculated dosages for many full-length procedures using the large-patient setting fell within the range of published effective doses of abdominal CT scans when the number of scans did not exceed 3. CONCLUSION: We have demonstrated that single cone-beam CT scans and most full-length posterior instrumented spinal procedures using O-arm in standard mode would likely impart a radiation dose within the range of those imparted by a single standard CT scan of the abdomen. Radiation dose increases with patient size, and the radiation dose received by larger patients as a result of more than 3 O-arm scans in standard mode may exceed the dose received during standard CT of the abdomen. Understanding radiation imparted to patients by cone-beam CT is important for assessing risks and benefits of this technology, especially when spinal surgical procedures require multiple intraoperative scans.

Accuracy of intraoperative computed tomography-based navigation for placement of percutaneous pedicle screws.

MISS techniques have gained recent popularity. The proposed benefits of these techniques include reduced tissue trauma, reduced blood loss, less perioperative pain, and a quicker recovery and return to normal activities. The purpose of this study was to evaluate the accuracy of intraoperative computed tomography (CT)-based navigation for placement of percutaneous pedicle screws in a cadaveric model. Outcome measures included accuracy of screw placement. Two cadaveric specimens were utilized. CT images were obtained using an O-Arm (Medtronic, Memphis, Tennessee, United States) and were coupled to the Stealth navigation system (Medtronic). Computer navigation was used for placement of percutaneous pedicle screws. Screws were placed bilaterally from T5 to S1. Postinsertion CT scans were obtained. Pedicle breach was assessed and classified (I: none, II: < 2 mm, III: 2 to 4 mm, or IV: > 4 mm) with direction of breach. Thirty thoracic screws were placed with 3 (10%) medial breaches and 17 (56.7%) lateral breaches (grade III). Of 20 lumbar screws there were 0 medial breaches and 2 (10%) lateral breaches (1 grade III, 1 grade IV). Four sacral screws were placed without breaches. The real-time computer-aided navigation tool ("simulated screw") was limited in identifying a breach. Manipulation of the surgeon's hand or driver could change the orientation of the navigation tool without changing the screw trajectory. CT-based navigation for percutaneous pedicle screw placement appears safe for the lumbar spine. Lateral thoracic breaches appeared commonly but were not felt to be clinically significant. The 10% rate of medial thoracic breach was concerning, but definitive conclusions could not be made due to the small sample size.

Is there a difference between simultaneous or staged decompressions for combined cervical and lumbar stenosis?

STUDY DESIGN: We evaluated 43 patients diagnosed with tandem spinal stenosis (TSS) from 1999 to 2005 in an academic hospital. OBJECTIVE: The purpose of this study is to compare outcomes after simultaneous decompression of the cervical and lumbar spine versus staged operations. SUMMARY OF BACKGROUND DATA: TSS is a rare degenerative disease affecting multiple spinal levels with limited research describing operative management. METHODS: Of our patients, 21 underwent simultaneous decompression of both the cervical and lumbar spine and 22 underwent staged decompression of the cervical spine followed by the lumbar spine at a later date. Medical records were reviewed for patient demographics, type and duration of symptoms, operative time, combined blood loss, cervical myelopathy modified Japan Orthopaedic Association Score, Oswestry Disability Index (ODI), major and minor complications, and average length of follow up. Each category was evaluated by Pearson correlations and unpaired Student t tests. RESULTS: With a mean follow-up of 7 years, both groups improved in JOA and ODI without a significant difference between the 2 operative groups in terms of major or minor complications, JOA, or ODI. Independent of the surgical algorithm, age above 68 years, estimated blood loss ≥400 mL, and operative time ≥150 minutes significantly increased the number of complications. CONCLUSIONS: These results indicate that TSS can be effectively managed by either surgical intervention, simultaneous, or staged decompressions. However, patient age, blood loss, and operative time do significantly impact outcomes. Therefore, operative management should be tailored to the patient's age and the option which will limit blood loss and operative time, whether that is by simultaneous or staged procedures.

Revision strategy for posterior extrusion of the CHARITÉ polyethylene core.

STUDY DESIGN: This is a case report of a posterior extrusion of the polyethylene core from a CHARITÉ arthroplasty. This is the first reported case of posterior dislocation of the polyethylene and the revision strategies used to correct this problem. OBJECTIVE: To report a novel failure mechanism and revision strategy for CHARITÉ total disc arthroplasty (TDA). SUMMARY OF BACKGROUND DATA: Case report at a Level 1 tertiary care referral center in the northeastern United States. METHODS: This is a case report and review of the literature of a patient who sustained posterior dislocation of the polyethylene core from a CHARITÉ TDA several months after the index procedure. RESULTS: Core dislocation is a known complication of TDA. However, of the known reported dislocations all have been anterior. This case describes the first known occurrence of posterior core dislocation and the revision strategy for this problem. CONCLUSION: This case report highlights the first known case of a posterior dislocation of a CHARITÉ core. It is likely that altered biomechanical forces generated over time attributed to device failure. An instrumented posterior fusion with removal of the core is what ultimately led to a stable revision construct.