Acute cauda equina syndrome after total knee arthroplasty as a result of epidural anesthesia and spinal stenosis.

An unusual complication of epidural anesthesia performed for routine total knee arthroplasty is presented. Epidural catheter placement or removal resulted in an acute cauda equina syndrome in a patient with asymptomatic high-grade lumbar spinal stenosis at L3-4. The case is presented along with a literature review.

Subarachnoid drainage of an established or chronic pseudomeningocele.

Incidental dural tears are a common complication of lumbar spine surgery, but if unrecognized cerebrospinal fluid (CSF) leakage can lead to the formation of a fistula or pseudomeningocele. Traditionally, fistulae and pseudomeningoceles have been treated with open revision surgery, but acute fistulae with direct CSF leakage through the incision site have reportedly been treated by extracorporal drainage. This report presents a case in which an established or chronic pseudomeningocele was successfully managed without open surgical repair.

Delayed postoperative epidural hematoma formation after heparinization in lumbar spinal surgery.

Treatment of thromboembolic disease in the postoperative lumbar spine patient is controversial. This case report describes an epidural hematoma with neurologic sequelae in an elderly patient who received intravenous heparin therapy over 2 weeks after lumbar decompression. Implications for treatment of thromboembolic disease in the postoperative lumbar spine is reviewed.

Strength and fatigue resistance of thoracolumbar spine implants: an experimental study of selected clinical devices.

Results of strength and endurance tests of several screw/rod thoracolumbar spinal implants are presented. The devices tested were: AcroMed ISOLA, CD systems, Depuy systems, and Synergy systems. The AcroMed ISOLA devices had the greatest stiffness and strength. The Synergy and AcroMed systems had the greatest fatigue resistance. The predominant failure mode was screw bending, although several instances of rod fracture and screw fracture were observed. A number of design improvements are identified, including reducing the number of components, thereby reducing the number of failure mechanisms; avoiding notches and knurled surfaces to provide greater resistance to crack initiation; and strengthening attachments between components, particularly between pedicle screws and horizontal rods.

Lumbosacral instrumented fusion: analysis of 124 consecutive cases.

One hundred twenty-four cases of lumbosacral fusion receiving transpedicular screw fixation were divided into two groups and reviewed retrospectively. The conditions treated include spondylolisthesis, scoliosis, tumor, trauma, and degenerative disc disease. There were 83 males and 41 females in this consecutive series averaging a 45.2-month follow-up. The primary or first-time arthrodesis rate was 91.9%. A learning curve effect as it relates to operative time but not pedicular screw placement was shown. Instrumentation-related and general medical and surgical complications were low. Infection rates were also low; superficial 2.4%, deep 1.6%. Nonunion or delayed union was salvaged in 10 cases, improving the overall fusion rate to 97.6%. The results of this study support the use of lumbosacral transpedicular screw fixation in select spinal conditions.

Effects of cross-linkage on fatigue life and failure modes of stainless steel posterior spinal constructs.

This study tested the effects of cross-linkage on the fatigue performance of posterior spinal constructs (i.e., AcroMed stainless steel Isola systems). The failure modes encountered during fatigue were also examined. The results of this study confirmed earlier findings that the use of cross-linkage does not significantly affect the stability of posterior constructs during axial loading. Their influence in torsion loading is much more pronounced. During the fatigue tests, posterior stainless steel spinal implants instrumented without cross-linkage reached 1 million cycles at 500- and 750-N loads. When the load was increased to 1,000 N, the number of cycles to failure dropped by two-thirds. These findings demonstrate that the endurance limit was between 750 N and 1,000 N for spinal constructs without cross-linkage, with the limit being closer to 750 N. Devices equipped with one or two cross-linkages reached 1 million cycles at 500 N. The number of cycles to failure dropped dramatically as the load was increased to 750 and 1,000 N. It appears that the endurance limits for spinal devices using cross-linkage should be 500 and 750 N, with the limit closer to the 500-N load. All rod fractures occurred near the junction between the longitudinal and transverse rods. Stress concentration was greatly in the vicinity of that contact point. These results should provide a basis for future improvement in endurance limits of spinal implants equipped with cross-linkage. Higher endurance limits will reduce the toxic effects encountered during fracture modes. The implants will also be better able to withstand the high physiologic loads experienced by obese individuals.

Posterior instrumentation for thoracolumbar trauma.

The majority of thoracolumbar spine fractures and fracture dislocations may be considered acute sagittal plane deformities. Unstable thoracolumbar spine injuries require stabilization to (1) allow mobilization of the patient to prevent pulmonary and venous complications; (2) to relieve pain; (3) to realign the spine and spinal canal, and (4) to decompress directly or indirectly the neural elements. Posterior spinal instrumentation is a safe, available, familiar, and effective method to achieve these goals. Posterior spinal instrumentation techniques used rod hook systems or screw rod and screw plate systems. Most of these unstable injuries can be managed using these well established techniques without the need for additional combined or staged anterior spinal surgery.

Biomechanical assessment of titanium and stainless steel posterior spinal constructs: effects of absolute/relative loading and frequency on fatigue life and determination of failure modes.

The goal of this study was to examine the effects of absolute/relative loads and frequency on the fatigue life of titanium and stainless steel posterior spinal constructs, and to determine the failure fracture modes. The stainless steel constructs had higher stiffness and yield strength than the titanium constructs, but the ultimate static strength was almost equal for both types of constructs. Titanium constructs, however, exhibited higher variability than the stainless steel constructs. In fatigue tests, the stainless steel constructs were significantly affected by the external load and were frequency independent. It appears from fatigue curves that 500 N can be approximated as the endurance limit for the stainless steel constructs. Titanium constructs were load-frequency dependent, and their endurance limit was somewhere between the 500 and 750 N load levels. There were no differences in performance between the stainless steel and titanium constructs at 16 Hz. At 4 Hz, titanium constructs performed as well or better than stainless steel constructs. Also, the titanium constructs resulted in better performance than the stainless steel constructs in the elastic region, and with smaller differences in the plastic region. Most of the failure modes for stainless steel constructs were in screw bending at 16 Hz with a smaller percentage of rod fractures at high loads, with a higher percentage of rod fractures observed for the stainless steel constructs at 4 Hz. Most of the failure modes for titanium constructs occurred in screw bending or fracture.

Lumbar disk herniation: an analysis of 175 surgically treated cases.

This is a retrospective review of 175 consecutive open lumbar diskectomies with a minimum 1-year follow-up (average follow-up, 54 months). Results of the diskectomies were: 91.0% good-to-excellent result, 3.4% fair, and 1.1% poor. Complications were few, and the overall recurrence rate was 4.6%. By multiple linear regression analysis, no one factor could predict the relief of leg pain.

Frankel A paraplegia: a comparison of two spinal instrumentation systems.

Seventeen patients with unstable thoracolumbar fracture dislocations and Frankel A (complete) paraplegia had posterior spinal fusion and instrumentation--nine with Cotrel-Dubousset instrumentation and eight with Luque rod instrumentation (LRI). Both systems maintained fracture reduction, and fusion occurred in all cases within a mean of 42 months (range, 30 to 66 months). Operative time and associated blood loss was less in the LRI group. One patient with LRI had fracture of the sublaminar wires that did not lead to loss of reduction or nonunion. Both instrumentation systems provided long-term posterior spinal stabilization in these patients.

Cotrel-Dubousset instrumentation and thoracolumbar spine trauma: a review of 55 cases.

A series of 55 patients treated with posterior Cotrel-Dubousset instrumentation and osteosynthesis for unstable thoracolumbar spine fractures were reviewed. Follow-up averaged 48.3 months. The fractures were all unstable, with 27 classified as fracture-dislocations (FD) and 28 classified as flexion compression injuries or unstable burst fractures (FC/B). The study population was composed of 29 men and 26 women with an average age of 31 (range 20-45) years. Mechanisms of injuries included 35 motor vehicle accidents, 19 falls, and one blunt trauma. No case worsened as a result of surgery, and 31% of the cases improved an average of 0.5 Frankel grade (range 0-2). Sixty percent of patients were braced with a custom molded thoracolumbosacral orthosis (TLSO) fitted after surgical stabilization. Minor complications occurred in 45% of the cases (urinary tract infection most common). There was a singular deep wound infection and another iliac crest donor site infection. There were no instrument failures or pseudarthroses. Radiographic analysis showed the following improvements in fracture angle, vertebral body compression, and fracture displacement. The pattern of radiographic improvement in the FD and FC/B subgroups showed significant improvement in each parameter when comparing preoperative to immediate postoperative values. Of importance, the radiographic findings comparing 1 month to the final follow-up showed little to no deterioration. Cotrel-Dubousset instrumentation proved to be a highly effective device for immediate restabilization of unstable thoracolumbar injuries.

Recurrent same-level, ipsilateral lumbar disc herniation.

An operative technique for the surgical management of the recurrent lumbar disc herniation is illustrated and presented. Five cases of ipsilateral, same-level, recurrent disc herniations are reviewed and discussed in light of the available literature. All patients presented with severe recurrent sciatica at variable times from the incident surgery. The treatment and possible factors favoring recurrence are discussed.

Critical analysis of strut grafts in anterior spinal fusions.

Fifty patients undergoing anterior spinal decompression with partial or complete corpectomy and fusion with strut grafting were reviewed. The etiology of the spinal lesions included pathologic fracture (9 patients), trauma (22 patients), congenital/developmental lesions (6 patients), failed fusion (6 patients), and degenerative lesions (7 patients). Vertebral body reconstruction of the cervical, thoracic, or lumbar spine used iliac crest (20 cases), rib (12 cases), and fibular autografts (9 cases). Additionally, in 10 cases fibular allografts were used. There were four deaths, all secondary to systemic disease. Of the remaining 46 patients, 2 required revisions and all subsequently progressed to a solid anterior arthrodesis with an average follow-up of 30.4 months (range 12-62 months). Posterior spinal fusion was staged in 38 patients. Twenty of 29 patients with neurologic lesions improved after corpectomy. Eleven cases treated for a progressive, painful kyphosis averaged correction of 11.4 degrees (26%), which was maintained on long-term follow-up. Complications were primarily pulmonary and/or genitourinary. Others included a pseudarthrosis, an early fractured strut, and a late allograft infection. On the basis of this review, it appears that spinal arthrodesis with anterior decompression and strut grafting is an effective method of treating anterior compressive syndromes of the spine and painful progressive kyphoses.

Latissimus dorsi rupture: an unusual complication of anterior spine surgery.

Anterior spinal surgery is a common part of the treatment for spinal trauma and deformity. Two cases of an unusual postoperative complication of the surgical exposure for anterior spinal fusion with rib strut grafts are herein reviewed. In each case, the patient presented 3-6 months postoperatively with a large, painful mass along the posterior axillary line near the surgical incision. The mass was diagnosed as a rupture of the latissimus dorsi. The cause of this disruption is unclear, but it appears to be a complication of the surgical approach; therefore, surgeons performing transthoracic and thoracoabdominal approaches should be aware of it.

Postoperative wound infections complicating adult spine surgery.

A review of 19 consecutive patients treated for deep wound infections after spinal surgery was performed. Patients were analyzed for preoperative risk factors, original diagnosis requiring surgery, onset of infection, presentation, treatment, and outcome. These patients (10 men, nine women), with a mean age of 44 years (range 18-74) were treated for 13 deep and six subcutaneous infections: 16 spine infections and nine graft site infections (six with both). All 19 presented with draining wounds on an average of 17 days after surgery (range 4-86). Staphylococcus aureus was cultured in 14. Patients were treated with i.v. antibiotics for an average of 3 weeks (range 0-14) followed by oral antibiotics for an average of 6 weeks (range 2-12). Surgical treatment included an average of 1.8 debridements (range 0-5), primary closure in two, delayed primary closure in seven, and healing by secondary intent in 10. All but three patients were noted to be malnourished at the onset of their infection, with a total lymphocyte count of less than 2,000. Three patients required removal of their hardware. Eighteen of 19 healed or their infections were stabilized, 17 of 18 arthrodeses fused, and no patient had neurological deterioration secondary to the infection. The treatment outlined produced satisfactory results in all but one patient. We conclude that postoperative spine infections are frequently associated with poor nutrition. Although definitive diagnosis is determined by the culture, clinical exam is helpful in establishing a presumptive diagnosis and, thus, earlier institution of surgical and antibiotic treatment.

Central retinal artery occlusion: a complication of the knee-chest position.

A rare complication of the knee-chest position used for lumbar disk surgery is reported. Central retinal artery occlusion resulted in permanent loss of vision secondary to direct ocular pressure. Prevention is the only rational treatment for this unfortunate condition.