Prospective study on serum metal levels in patients with metal-on-metal lumbar disc arthroplasty.

PURPOSE: Metal-on-metal total disc replacement is a recent alternative treatment for degenerative disc disease. Wear and corrosion of these implants can lead to local and systemic transport of metal debris. This prospective longitudinal study examined the serum chromium and cobalt levels in 24 patients with cobalt-chromium alloy metal-on-metal lumbar disc replacements. METHODS: Serum was assayed for chromium (Cr) and cobalt (Co) using high-resolution inductively-coupled plasma-mass spectrometry. Detection limits were 0.015 ng/mL for Cr and 0.04 ng/mL for Co. RESULTS: Median serum Co levels at pre-op, 3, 6, 12, 24, and 36-months post-op were 0.10, 1.03, 0.96, 0.98, 0.67, and 0.52 ng/mL, respectively. Median serum Cr levels were 0.06, 0.49, 0.65, 0.43, 0.52, and 0.50 ng/mL, respectively. CONCLUSION: In general, these results indicated that serum Co and Cr levels are elevated at all postoperative time points and are of the same order of magnitude as those observed in well-functioning metal-on-metal surface replacements of the hip and in metal-on-metal total hip replacements at similar postoperative time points.

Segmental instrumentation for thoracic and thoracolumbar fractures: prospective analysis of construct survival and five-year follow-up.

BACKGROUND CONTEXT: Segmental instrumentation systems have replaced nonsegmental systems in all areas of spine surgery. Construct patterns for fracture stabilization have been adapted from deformity experience and from biomechanical studies using nonsegmental systems. Few studies have been completed to validate the use of these implants in trauma or to assess their relative strengths and weaknesses. PURPOSE: To substantiate the safety and efficacy of segmental spinal instrumentation used to treat patients with unstable spinal fractures and to identify successful construct strategies and potential pitfalls. STUDY DESIGN: A prospective, longitudinal single cohort study of patients treated with segmental instrumentation for fractures of the spine. Minimum 2-year follow-up. PATIENT SAMPLE: Seventy-five consecutive patients with unstable fractures of the thoracic, thoracolumbar and lumbar vertebrae, admitted to a level 1 trauma center. All patients sustained high-energy injuries: fifty-five (79%) were injured in motor vehicle accidents, 27 (38%) sustained two or more major additional injuries and 39 (56%) had neurological injuries. OUTCOME MEASURES: Perioperative morbidity and mortality, blood loss, surgical time; postoperative recovery, neurological recovery, complications, thromboembolic and pulmonary disease; long-term outcome measures of fusion, sagittal spinal alignment, construct survival, patient pain and function measures, and return to work and activity. METHODS: A longitudinal, prospective study of surgical outcome after segmental spinal instrumentation. Multifactorial assessment was carried out at prescribed intervals to a mean follow-up of 5 years (range, 2 to 8 years) from the time of surgery. Seventy patients were included in the final analysis. There were 17 thoracic, 36 thoracolumbar and 17 lumbar fractures. RESULTS: At 52 months mean follow-up, 57 of 62 patients (92%) had solid fusion with acceptable spinal alignment. Perioperative complications and mortality were less than expected, based on historical controls matched for injury severity. Rod and hook constructs had 97% good to excellent functional results, with no hardware complications. Six of 11 (55%) patients with short-segment pedicle instrumentation (SSPI) with no anterior column reconstruction had greater than 10 degrees of sagittal collapse during the fracture healing period. Twenty six of 36 neurologically injured patients (72%) experienced (mean) 1.5 Frankel grades recovery after decompression and stabilization. Residual neurological deficit determined return to work: 43 patients (70%) returned to work, 33 without restrictions, 10 with limitations. Five other patients (8%) were fit but unemployed. Fifteen percent experienced some form of hardware failure, but only three (5%) required revision. Hardware complications and fair to poor outcomes occurred after pedicle instrumentation without anterior reconstruction. Patients with anterior reconstruction had 100% construct survival, no sagittal deformity, and less pain. CONCLUSION: Segmental instrumentation allowed immediate mobilization of these severely injured patients, eliminating thromboembolic and pulmonary complications, and reducing overall morbidity and mortality. Segmental instrumentation produced a high rate of fusion with no rod breakage or hook failure. Pedicle screw constructs had a high rate of screw complications associated with anterior column insufficiency, but revision was not always necessary. Eighty percent of these severely injured patients were capable of returning to full-time employment, and 70% did so.

Surgical Interbody Research Group--radiographic assessment of interbody fusion devices: fusion criteria for anterior lumbar interbody surgery.

The authors present their radiographic criteria for assessing fusion of the lumbar spine after anterior interbody fusion with intradiscal implants. These criteria include the assessment of plain radiographs, dynamic motion radiographs, and thin-cut computerized tomography scans. Fusion within the instrumented spinal motion segment can be determined using radiographic evaluation to assess spinal alignment on sequential examinations, angular and translational changes on dynamic motion studies, and device-host interface, and to identify new bone formation and bone remodeling. Finally, to aid the clinician in assessing fusion, the authors describe the five zones of fusion within the intervertebral disc space.

The usefulness of electrical stimulation for assessing pedicle screw placements.

The purpose of this study was to further establish the efficacy of pedicle screw stimulation as a monitoring technique to avoid nerve root injury during screw placement. The study population consisted of 662 patients in whom 3,409 pedicle screws were placed and tested by electrical stimulation. If stimulation resulted in a myogenic response at a stimulation intensity of 10 mA or less, the placement of the screw was inspected. Inspection was necessary for 3.9% of the screw placements in 15.4% of the study population. None of the patients in the study experienced any new postoperative neurologic deficits. These findings provide guidelines for the interpretation of stimulation data and support the use of this technique as an easy, inexpensive, and quick method to reliably assess screw placements and protecting neurological function.

Spinally elicited peripheral nerve responses are sensory rather than motor.

OBJECTIVES: Spinally elicited peripheral nerve responses, commonly called neurogenic motor evoked potentials (NMEPs), are widely used to monitor spinal cord motor function during surgery. However, numerous evidence suggests that these responses are primarily sensory rather than motor. The collision technique was utilized to address this issue. METHODS: Collision studies were performed in 7 patients during surgery. An ascending volley of sensory (AS) and motor activity (AM) was elicited by posterior tibial nerve stimulation at the popliteal fossa. After a short time delay, high cervical spinal stimulation produced a descending volley of sensory (DS) and motor (DM) activity. The AM volley ascended only to the anterior horn cells whereas the AS and DS volleys collided in the spinal cord. The inter-stimulus delays were varied so as to affect the degree of spinal cord collision. The DS and DM activity which remained after collision was recorded from the posterior tibial nerves at the ankle. RESULTS: Inter-stimulus delays of 18 ms or less resulted in no apparent peripheral descending volleys. These findings were consistent for all the patients studied. CONCLUSIONS: Spinally elicited peripheral nerve responses are primarily sensory rather than motor and are mediated by the same neural pathways as SEPs.

Anterior exposure of the thoracic spine.

Spinal operation via an anterior thoracic approach is becoming increasingly common, and the thoracic surgeon is now being called upon to provide exposure for orthopedic and neurosurgical colleagues. We report experience with 126 such patients from 1982 through 1993. There were 61 male and 65 female patients (mean age, 39.0 years; range, 14 to 77 years). Indications were trauma in 45 patients (36%), spinal deformity in 42 (33%), cancer in 15 (12%), disc disease in 12 (10%), and infection in 12 (10%). Operative incisions included 22 (17%) right and 14 (11%) left thoracotomies, 33 (26%) right and 56 (44%) left thoracolumbar approaches, and one (1%) sternotomy. A prior spinal operation had been performed on 31 patients (25%), and 56 (44%) had a subsequent posterior spinal operation. Instrumentation was used in 38 (30%) and bone grafts in all but 6 patients. A neurologic deficit was present in 69 patients (55%) preoperatively and was improved in 67 patients postoperatively. Operative mortality was 3.2% (4 patients) due to myocardial infarction, stroke with pneumonia, adult respiratory distress syndrome, and malignant biliary obstruction. Univariate and multivariate risk analysis were performed. Only the diagnosis of osteomyelitis proved to be a significant (p = 0.0002) indicator of operative mortality, with 3 of 12 such patients dying (25%). These results suggest that anterior spinal exposure via thoracic approach is a major operation with considerable perioperative risk. Patients with osteomyelitis appear to be at increased risk for operative mortality.

Hyperextension injuries of the thoracic spine in diffuse idiopathic skeletal hyperostosis. Report of four cases.

Four patients who had multisegmental ankylosis of the thoracic and lumbar spine due to diffuse idiopathic skeletal hyperostosis sustained a hyperextension fracture-dislocation. The patients had a mean age of sixty-four years (range, fifty-eight to sixty-nine years); all four patients were men. All injuries occurred between the seventh and eleventh thoracic vertebrae. All patients had intact neurological function at the time of admission to the hospital. Three patients were managed with posterior spinal arthrodesis with Cotrel-Dubousset segmental instrumentation; one patient was managed non-operatively with a molded thoracolumbosacral orthosis. At a minimum duration of follow-up of twenty-two months (mean, twenty-seven months), the three patients who had been managed operatively had healing of the fracture with anatomical alignment of the spine and without postoperative complications. The one patient who had been managed non-operatively with a brace had severe neurological deterioration and non-anatomical alignment of the spine.

Development of the cartilage canals and the secondary center of ossification in the distal chondroepiphysis of the prenatal human femur.

The cartilaginous epiphysis of the distal femur is vascularized by a network of cartilage canals during prenatal development. The vascular invasion of the epiphysis begins at approximately eight to ten weeks of gestation with the initiation of cartilage canal formation. A complex vascular system develops within the canals and is well defined by fourteen weeks of gestation. The vascular system is fully developed several months prior to the development of the secondary center of ossification. The formation of the secondary center of ossification within the distal femoral epiphysis is preceded by changes that occur simultaneously within both the chondrocytes in the central portion of the epiphysis and the vascular and perivascular elements contained within the cartilage canals in the central portion of the epiphysis. These concurrent changes in the cellular morphology of the central chondrocytes and in the cellular structure of the central cartilage canals appear to be linked with the initiation of the process of osteogenesis.

Unstable thoracolumbar and lumbar burst fractures treated with the AO fixateur interne.

Twenty-five consecutive patients with unstable thoracolumbar and lumbar burst fractures were surgically treated with the AO Fixateur Interne (Synthes USA, 1690 Russell Rd., Paoli, PA). Indications for surgery included a progressive neurologic deficit, spinal canal compromise greater than 50%, vertebral body collapse greater than 50%, or sagittal angulation greater than 20 degrees. Twenty males and five females ranging in age from 16 to 60 years (average 31) were treated surgically and prospectively followed. Twenty-one fractures occurred at the thoracolumbar junction (T10-L2) and 4 in the lumbar spine (L3-5). Twenty-four patients were followed for a minimum of 12 months, ranging from 12 to 38 months (average 22); one patient was lost to follow-up after 1 month postoperatively. Preoperatively, 12 patients had partial neurologic deficits; postoperatively, 11 improved at least 1 Frankel grade. Preoperatively, the 12 patients with partial neurologic deficits averaged 45 points (range 24-49) on the lower extremity motor index scale. After surgery, these patients improved an average of five points (range 1-23) on the motor index scale. Both patients with complete spinal cord injuries remained unchanged neurologically postoperatively; no patients deteriorated neurologically after surgery. The average preoperative sagittal kyphosis at the fracture site was +16 degrees (range +10 degrees to +31 degrees); the immediate postoperative sagittal angular correction averaged -4 degrees (lordosis) and ranged from +12 degrees (kyphosis) to -26 degrees (lordosis). At last follow-up, the sagittal angular correction remained unchanged in three patients and decreased in 21 patients to an average of +5 degrees (range +37 degrees to -14 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)

Neurologic recovery associated with anterior decompression of spine fractures at the thoracolumbar junction (T12-L1).

Between 1981 and 1990, twenty-two patients with incomplete neurologic deficits after thoracolumbar junction fractures were treated by anterior decompression and stabilization. Two patients were unavailable for follow-up examination, eleven underwent spinal canal decompression within 48 hours of injury (Group A); and nine patients underwent surgical decompression in an average of 61 days after injury (Group B). Neurologic recovery was analyzed by a modified Frankel grading system, the ASIA motor point scale and conus medullaris function. Patients were followed for an average of 3.5 years (range, 6-92 months). No patients had any deterioration in neurologic function after surgery. Patients in Group A had a modified Frankel grade improvement with a median of two grades and a mean American Spine Injury Association motor point improvement of 21.1 +/- 4.1. Four of nine patients with conus medullaris deficits demonstrated complete functional bladder and bowel return postoperatively. Those patients in Group B had a modified Frankel grade improvement with a median of one grade and a mean ASIA motor point improvement of 7.6 +/- 1.7. None of the six patients with conus medullaris injuries showed complete improvement in bladder or bowel function postoperatively. The modified Frankel grade and ASIA motor point score improvements were significant when the two groups were compared (P less than 0.04 and P less than 0.01, respectively). In this series of patients, early anterior decompression for traumatic injuries at the thoracolumbar junction was associated with improved rates of neurologic recovery when compared to late decompression.

Long-term evaluation of adolescents treated operatively for spondylolisthesis. A comparison of in situ arthrodesis only with in situ arthrodesis and reduction followed by immobilization in a cast.

The medical records and radiographs of forty-two adolescents (twenty-three male and nineteen female) who had had a posterolateral spinal arthrodesis for spondylolisthesis between 1950 and 1986 were reviewed to assess the long-term outcome of this form of treatment. The average age of the patients at the time of the operation was fourteen years (range, seven years and nine months to seventeen years and eleven months). The duration of the clinical and radiographic follow-up ranged from two years to twenty-seven years and seven months. All patients had an in situ arthrodesis of the involved vertebrae. Eighteen patients had no additional intervention, and twenty-four patients had reduction and application of a cast. Use of the cast led to a decrease in sagittal translation of more than 5 per cent in eighteen patients and a decrease in lumbosacral kyphosis (the slip angle) of more than 5 degrees in fourteen patients. Of the patients who did not have a cast, eight had an increase in sagittal translation of more than 5 per cent and ten had an increase in lumbosacral kyphosis of more than 5 degrees. There were no neurological problems at the time of the initial operation or after the reduction maneuver. At the most recent clinical follow-up examination, thirty-eight patients had no complaints of low-back pain or any restriction of work-related or recreational activities. Persistent low-back pain and pain in the lower extremities limited the activities of the remaining four patients, two of whom had another operation to alleviate these symptoms.

Shear fracture-dislocations of the thoracic and lumbar spine associated with forceful hyperextension (lumberjack paraplegia).

Twelve patients sustained a shear fracture-dislocation of their thoracic or lumbar spines by a hyperextension mechanism of injury. Ten male and two female patients were injured; their average age was 29 years (range, 22 months to 56 years). Ten fracture-dislocations occurred in the thoracic spine, one at the thoracolumbar junction, and one in the lumbar spine. Eleven patients had complete paraplegia, and one had incomplete paraplegia at the time of injury. Dural tears were found in six of the patients. Eleven patients were treated by posterior spinal fusion with instrumentation, and one was treated with a brace. Three patients were treated with Harrington distraction rods alone, six had Harrington distraction rods supplemented with a midline Harrington compression rod or interspinous wiring, and two were treated with Cotrel-Dubousset instrumentation. No patient was lost to follow-up. The average length of follow-up was 3.5 years (range, 1-9 years). Six of the patients treated with Cotrel-Dubousset instrumentation or Harrington distraction rods supplemented with either a midline compression rod or interspinous wiring healed anatomically; two patients developed pseudarthroses. None of the patients treated with Harrington distraction rods alone healed in an anatomic position. The use of Harrington distraction rods alone was associated with overdistraction and nonanatomic alignment of the spine. The disruption of the anterior stabilizing structures of the spine associated with hyperextension injuries necessitates the use of instrumentation that can stabilize the spine and prevent overdistraction. This injury can be successfully treated with Cotrel-Dubousset or Harrington distraction rods supplemented with either a midline compression rod or interspinous wiring.

Lateral distraction injuries to the thoracic and lumbar spine. A report of three cases.

Three patients sustained a lateral distraction injury to the thoracic or lumbar spine. These injuries were associated with multiple fractures of the ribs and extremities as well as with thoracic and abdominal visceral injuries. No patient had an injury to the spinal cord or cauda equina. The injuries to the spine were successfully treated with open reduction of the unilateral subluxation of the facet joint and with internal fixation with Harrington instrumentation. Fusion was achieved with the spine in anatomical alignment, without any complications, in all three patients.

Diagnosis and treatment of cauda equina entrapment in the vertical lamina fracture of lumbar burst fractures.

Posterior dural lacerations associated with lumbar burst fractures are caused by impaction of the dural sac into the vertical lamina fracture. Neural elements may be extruded outside of the dura and become entrapped in the lamina fracture. This diagnosis must be made before surgery and is based on the patient's clinical presentation, the fracture pattern, and the radiographic findings. Entrapped neural elements can be successfully extracted from the lamina fracture by an opening laminoplasty of the posterior neural arch. Patients with lumbar burst fractures and radiographic evidence of posterior displacement of the neural elements in the lamina fracture should undergo posterior exploration of the spinal canal, extraction of cauda equina neural elements, and repair of the dural laceration before any spinal reduction maneuver.

Spinal canal decompression in traumatic thoracolumbar burst fractures: posterior distraction rods versus transpedicular screw fixation.

Although the benefit of spinal canal decompression of traumatic thoracolumbar burst fractures is controversial, it remains a desirable procedure, as many reports describe improved neurologic outcome with spinal canal reconstruction. The optimal type of posterior instrumentation for reconstructing the spinal canal is unclear. This study focused on the efficacy of posterior distraction rods versus transpedicular screw fixation implants in decompressing the spinal canal and on the relationship between the amount of canal decompression and subsequent neurologic recovery. A medical records review was conducted to identify all patients surgically treated for traumatic burst fractures of the thoracolumbar spine from January 1, 1987 to June 30, 1989. Sixty-seven patients were selected by this review, and, of these, 30 had had both preoperative and postoperative CT scans. We could find no bias among patients who received both preoperative and postoperative CT scans as compared to those who did not, therefore the 30 patients were considered to be a random sample of the total population of 67. A retrospective study was then conducted on the 30 patients with surgically treated burst fractures--15 treated with posterior distraction rods and 15 treated with AO Fixator Interne transpedicular screw fixation implants. Preoperative and postoperative spinal canal cross-sectional areas were measured directly from the scaled CT scans. The area of most severe compromise was compared with an internal standard defined as the next, caudal, uncompromised spinal level, and the percentage of preoperative and postoperative canal compromise was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Unilateral spondylolysis associated with spina bifida occulta and nerve root compression.

Three patients with unilateral spondylolysis and spina bifida occulta were treated with hemilaminectomy, pseudarthrosis excision, and bilateral posterolateral fusion. All patients had persistent radiating leg pain, a positive sciatic tension sign, an objective neurologic deficit, and neuroradiographic studies that confirmed isolated L5 nerve root entrapment at the pars defect. Postoperatively, all patients noted complete relief of their radicular symptoms.

Surgical discectomy in an active-duty military population: a report of 66 consecutive cases.

Sixty-six consecutive active duty military personnel with herniated lumbar intervertebral discs were treated by open surgical discectomy. Of these patients, 54 (82%) had relief of their radiating leg pain and were able to return to full duty status. The other 12 patients (18%) were unable to return to full duty because of either persistent postoperative radiating leg pain or low back pain. Open surgical discectomy is an effective treatment modality for lumbar disc herniations in a military population with a vigorous life-style mandated by their active duty status.

Chymopapain chemonucleolysis versus surgical discectomy in a military population.

From 1983 to 1987, 100 consecutive patients with lumbar herniated nucleus pulposus were treated with either chymopapain chemonucleolysis (51 patients) or surgical discectomy (49 patients). The chymopapain-treated group was followed for an average of 16 months and the surgically treated group was followed for an average of 12 months. All patients had to be candidates for both procedures and were grouped for therapy based on their preference. The groups were similar in military duty status, history, age, gender, duration and character of symptoms, physical findings, and computed tomography/myelogram results. Satisfactory outcomes were achieved in 40 of 51 (78%) chymopapain-treated patients and in 39 of 49 (80%) surgically treated patients. Seventy-eight percent of the chymopapain group and 79% of the surgery group ultimately returned to full military duty. Of the nine initial chymopapain failures, eight were successfully treated with surgical discectomy. There were fewer complications, 4% versus 10%, in the chymopapain group. The authors now consider chemonucleolysis as the final conservative measure prior to surgery, rather than an alternative to surgical discectomy.

Malignant neuroepithelioma (peripheral neuroblastoma). A case report.

Malignant neuroepithelioma is a rare neoplasm arising within the peripheral nervous system. It usually occurs in the lower extremities and may involve patients in any age group. In children younger than the age of five years, the tumor must be differentiated from a metastatic neuroblastoma; in adolescents and adults the tumor must be distinguished from other malignant round-cell tumors. The poor prognosis and the need for aggressive, combined surgical and chemotherapeutic modalities in treating this tumor necessitate a prompt and accurate diagnosis.

Long-term follow-up of Syme amputations for peripheral vascular disease associated with diabetes mellitus.

Ten patients underwent Syme amputation for diabetic peripheral vascular disease between 1980 and 1986 and were observed postoperatively for an average of 5 years. Surgical wounds healed in only five of the 10 patients; they were then fitted for a permanent Syme's prosthesis. All failures resulted from the inability to heal the surgical incisions primarily. The clinical records of these patients were retrospectively analyzed for predictors of successful clinical outcome. The ischemic index, grade of the lesion, initial wound treatment, and presence of the infection at the time of amputation were not found to be reliable predictors of a successful level of amputation. Clinical assessment of both the vascular and nutritional status of the patient was necessary to predict a successful result at this level of amputation.