Faculty Bibliography

BACKGROUND CONTEXT: The spine is a complex and vital structure. Its function includes not only structural support of the body as a whole, but it also serves as a conduit for safe passage of the neural elements while allowing proper interaction with the brain. Anatomically, a variety of tissue types are represented in the spine. Embryologically, a detailed cascade of events must occur to result in the proper formation of both the musculoskeletal and neural elements of the spine. Alterations in these embryologic steps can result in one or more congenital abnormalities of the spine. Other body systems forming at the same time embryologically can be affected as well, resulting in associated defects in the cardiopulmonary system and the gastrointestinal and genitourinary tracts. PURPOSE: This article is to serve as a review of the basic embryonic development of the spine. We will discuss the common congenital anomalies of the spine, including their clinical presentation, as examples of errors of this basic embryologic process. STUDY DESIGN/SETTING: Review of the current literature on the embryology of the spine and associated congenital abnormalities. METHODS: A literature search was performed on the embryology of the spine and associated congenital abnormalities. RESULTS: Development of the spine is a complex event involving genes, signaling pathways and numerous metabolic processes. Various abnormalities are associated with errors in this process. CONCLUSION: Physicians treating patients with congenital spinal deformities should have an understanding of normal embryologic development as well as common associated abnormalities

As life expectancies increase, the geriatric population will increase, and the treatment of spinal diseases in the elderly will become even more commonplace. Treatment of spinal disorders in the geriatric patient population is a difficult challenge and involves numerous surgical, medical, and social issues. This review will provide an overview of the various spinal disorders particular to the geriatric patient population and will highlight certain concepts critical in the treatment of the spine in the geriatric population. Multiple factors, including poor tolerance of immobilization, medical comorbidities, use of multiple chronic medications, poor nutritional status, inadequate bone stock, and poor bone quality limit rigorous adherence to one treatment algorithm. These issues should be taken into consideration when formulating an individualized treatment plan that emphasizes early mobilization and functional rehabilitation. Goals, expectations, and surgical indications should be realistic and often will differ from those for a younger, healthier population. The use of a multidisciplinary approach will increase the likelihood of a successful treatment outcome and decrease the likelihood of potential complications

BACKGROUND CONTEXT: Somatosensory evoked potentials (SSEP) are commonly used to monitor the spinal cord and nerve roots during operative procedures that put those structures at risk. The utility of SSEPs to evaluate cauda equina and nerve root function during posterior spinal arthrodesis with pedicular fixation for degenerative lumbar disease has been reported anecdotally and remains controversial. PURPOSE: An institution-wide review of the ability of SSEP readings to monitor nerve function during posterior lumbar spinal arthrodeses with transpedicular fixation for degenerative lumbar spinal disorders was undertaken. STUDY DESIGN/SETTING: A retrospective review was undertaken. Patient history, preoperative physical examination, intraoperative anesthesia, SSEP records and the postoperative course were reviewed. METHODS: A total of 186 consecutive arthrodeses as described above were reviewed. Patients who had anterior procedures, spondyloreduction or scoliosis correction were excluded from the study. There were 76 male and 110 female patients. Five fellowship-trained spine surgeons placed a total of 888 pedicle screws. Sixty-five percent of the patients had a principal preoperative diagnosis of spinal stenosis with degenerative spondylolisthesis. Other common diagnoses were isthmic spondylolisthesis and degenerative scoliosis. Ninety-three percent of the cases involved decompressive laminectomy. Eight percent had posterior interbody fusions. All pedicle screws were placed without the assistance of fluoroscopy or stereotactic computer-assisted guidance. Screw position was evaluated intraoperatively with standard posteroanterior and lateral radiographs.Anesthetic agents compatible with SSEP monitoring were used in all patients. SSEP baseline readings were obtained in all patients in the operating room soon after induction of general anesthesia. An acute and sustained loss of 50% of the SSEP amplitude and/or increase by 10% of latency from baseline was considered to be pathologic. RESULTS: None of the 186 patients had significant SSEP changes. There were, however, 5 patients with postoperative radiculopathies distinct from their preoperative presentations. Early postoperative plain radiographs and computed assisted tomography (CAT) scans revealed malpositioned pedicle screws. Consequently, eight pedicle screws were either revised or removed. All patients had partial or full recovery of their new deficits after revision surgery. CONCLUSION: We conclude that the use of SSEPs in evaluating pedicle screw placement during lumbar arthrodesis is limited. In this setting, if monitoring is required, alternative methods with greater sensitivity and efficacy should be explored

BACKGROUND CONTEXT: Lumbar radiculopathy is commonly caused by degenerative conditions such as a herniated disc or lumbar spinal stenosis. Less common etiologies include intraspinal extradural masses such as synovial cysts and gas-containing ganglion cysts. Intraspinal extradural cysts that communicate with the intervertebral disc are a rare entity and thus, an uncommon cause of lumbar radiculopathy. There are only ten cases of an intervertebral disc cyst reported in the literature. PURPOSE: To document the first reported case of an intervertebral disc cyst in North America. Two series of Japanese patients with intervertebral disc cyst confirmed radiographically and intraoperatively have recently been reported. STUDY DESIGN: A case report of an intervertebral disc cyst at L4-5 causing an L5 radiculopathy. OUTCOME MEASURES: Japanese Orthopaedic Association score for low back pain. METHODS: The patient and the authors involved in the patient's management were interviewed. All medical records, radiographic imaging studies, intraoperative findings, and pertinent literature were also reviewed. RESULTS: Preoperative magnetic resonance imaging (MRI) scan demonstrated a well-localized cyst compressing the ventral aspect of the thecal sac at L4-L5. Discography and subsequent computed tomographic (CT) scanning demonstrated the cyst communicating with an intervertebral disc herniation via an annular rupture. Decompressive discectomy and surgical excision of the disc cyst from the spinal canal resulted in complete recovery and resolution of the preoperative radiculopathy. Clinical improvement was documented using the JOA scoring system. Patient's preoperative score was 4/15, and postoperative score was 15/15. CONCLUSION: Although exceedingly rare, an intervertebral disc cyst should remain in the differential diagnosis of any extradural intraspinal mass ventral to the thecal sac. Diagnosis of an intervertebral disc cyst requires recognition of this uncommon entity and a high index of suspicion. Discography and post-discography computerized tomography (CT) scan confirm the diagnosis. Operative treatment includes decompression, and excision of the cyst and is reserved only for cases in which the cyst results in clinical symptoms unresponsive to nonoperative management

Degenerative spondylolisthesis in the lumbar spine is due to long-standing segmental instability. A standing plain radiograph is commonly the only imaging study needed to establish the diagnosis. Translatory motion in spondylolisthesis is traditionally assessed with lateral flexion and extension radiographs. These dynamic studies often demonstrate a decrease in the slip percentage between the vertebral segments with extension and an increase with forward flexion. Some low-grade spondylolisthetic deformities reduce anatomically on the operating table after the administration of an anesthetic. We encountered one case in which there was complete reduction of an L4-5 grade I degenerative spondylolisthesis with positioning of a non-anesthetized patient in the supine position during a lumbosacral magnetic resonance imaging (MRI) scan. The patient's condition was originally misdiagnosed, as the spondylolisthesis was not identified on recumbent plain radiographs or on lumbosacral MRI. This case stresses the importance of correlating static and dynamic imaging studies in developing a treatment plan for patients with degenerative spondylolisthesis

The existence of diabetes mellitus has been postulated to have a deleterious effect on the outcome following lumbar spine surgery. We retrospectively examined the records and radiographs of 32 diabetic patients (mean age, 60 years) who underwent posterior lumbar fusions using transpedicular instrumentation and iliac crest autograft. Ten patients were insulin-dependent and 22 required oral hypoglycemic agents for at least 1 year prior to surgery. The minimum follow-up time was 2 years after surgery (mean, 2.5 years). Surgical indications included herniated lumbar disk, lumbar spinal stenosis, thoracolumbar trauma, and lumbar pseudarthrosis. Clinical results were evaluated by chart review and/or interview by using Odom's criteria. At follow-up, 75% of patients were graded as excellent or good, and 25% as fair or poor. Twenty-five of 32 patients (78%) had improvement of back pain. Twenty of 27 (74%) patients had improvement of leg pain. Eight of 15 (53%) patients had improvement in motor strength, and 6 of 11 (54%) had improvement in light-touch sensation. Insulin dependence and the presence of polyneuropathy were associated with a poorer outcome. The average time to radiographic fusion was 5 months. Twenty-nine of 32 patients (91%) developed solid fusion by strict radiographic criteria. The three patients with a pseudarthrosis had persistent back pain and a poor result. Ten of 32 (31%) of the patients experienced perioperative complications, including prolonged wound drainage (n = 5), deep wound infection (n = 1), superficial wound infection (n = 1), atrial fibrillation (n = 1), ruptured cerebral aneurysm (n = 1), and ulnar nerve neuropathy (n = 1). We conclude that posterolateral lumbar spinal fusion with internal fixation in diabetic patients yields clinical results comparable to those of nondiabetic patients, with similar risks of perioperative complications

STUDY DESIGN: A case report of iatrogenic spondylolysis as a complication of microdiscectomy leading to contralateral pedicular stress fracture and unstable spondylolisthesis. OBJECTIVE: To improve understanding of this condition by presenting a case history and roentgenographic findings of a patient that differ from those already reported and to propose an effective method of surgical management. METHODS: A 67-year-old woman with no history of spondylolysis or spondylolisthesis underwent an L4-L5 microdiscectomy for a left herniated nucleus pulposus 1 year before the current consultation. For the preceding 8 months, she had been experiencing low back and bilateral leg pain. Imaging studies revealed a left L4 spondylolytic defect and a right L4 pedicular stress fracture with an unstable Grade I spondylolisthesis. RESULTS: The patient was treated with posterior spinal fusion, which resulted in complete resolution of her clinical and neurologic symptoms. CONCLUSIONS: Iatrogenic spondylolysis after microdiscectomy is an uncommon entity. However, it can lead to contralateral pedicular stress fracture and spondylolisthesis, and thus can be a source of persistent back pain after disc surgery. Surgeons caring for these patients should be aware of this potential complication

Many studies in the literature have documented the outcome of circumferential lumbar fusions. However, no study has specifically evaluated the performance of the anterior fresh-frozen femoral head allograft as a structural interbody graft material. All office and hospital records, including charts and radiographs, were reviewed to obtain pertinent clinical and radiographic information. The cases included 23 single-level fusions, 22 two-level fusions, and 5 fusions of three or more levels. In all, 88 fusion levels were analyzed radiographically. The mean follow-up time was 28 months (range, 24 to 36 months). All procedures were performed in a single stage. At the latest follow-up, clinical outcome was graded good to excellent in 39 (78%) cases, fair in 8 (16%) cases, and poor in 3 (6%) cases. The average time to anterior radiographic fusion was 6 months (range, 4 to 8 months). The overall fusion rate was 98%. The average preoperative anterior disk space height was 10 mm, 14 mm immediately after operation, and 13 mm at follow-up. The posterior disk space height averaged 5 mm before operation, 7 mm immediately after operation, and 6 mm at follow-up. The average segmental lordosis was 7 degrees before operation, 10 degrees immediately after operation, and 10 degrees at follow-up. Late postoperative disk space collapse of 3 mm or more was noted in 17% of the fused disk spaces examined. Seventy-eight percent of the disk spaces maintained a disk space height greater than that of their preoperative value at the latest follow-up. Segmental lordosis did not change significantly at follow-up. The occurrence of collapse did not correlate with the clinical result, smoking history, or surgical indication (p < 0.05). Perioperative complications included one pleural effusion, two urinary tract infections, and one deep wound infection. Late complications included five painful graft sites and two patients with pseudarthrosis. Fresh-frozen femoral head allograft fulfills its desired function as an anterior structural graft in combination with rigid posterior transpedicular fixation, maintaining the disk space height achieved at surgery while reliably allowing remodeling and incorporation into a solid anterior fusion.