Good results of circumferential spine fusion in smokers, using autograft and allograft.

We have examined the rates of anterior interbody fusion of lumbar spine segments following fusion with a fresh frozen femoral head allograft in 25 heavy smoking patients. They were all stabilized both anteriorly and posteriorly. The indications for surgery were: degenerative disc disease, degenerative spondylolisthesis and nonunion following previous posterolateral fusion of lumbar spine segments. Only patients who had fusion of one or two lumbar segments were included. They all were stabilized posteriorly with pedicle screws and autogenic iliac bone graft. The fusion was assessed at least one year after surgery according to plan X-rays as "Solid", "Questionable" or "Failure". One patient was found at follow up not fused, in another one the fusion was "questionable" and all the other 23 patients had an anterior solid fusion. Clinically, 84% of the patients had the same or improved work status as before surgery and 68% acknowledged that they were satisfied with the surgical results. No major complications were recorded and the average length of hospitalization was 10.3 days.

Comparison between the outer table and intracortical methods of obtaining autogenous bone graft from the iliac crest.

STUDY DESIGN: A prospective study in two groups of patients selected randomly. OBJECTIVES: To determine whether keeping the outer and inner cortices of the ilium intact, while obtaining bone graft, would result in reduced postoperative bleeding and less postoperative pain. SUMMARY OF BACKGROUND DATA: Donor site complications after harvesting bone from the iliac crest are frequent. They comprise pain and bleeding related to the large bone exposed, injuries to the cluneal nerve, and sacroiliac instability. METHOD: Sixty patients who were admitted for elective fusion of lumbar segments were included in the study. In half of them, the iliac bone graft was taken in the outer Table method (group A), which included the outer cortex and the cancellous bone beneath, and in the remaining 30 patients only the cancellous bone from between the cortices was collected (group B). The amount of bone harvested, and the time taken to obtain it, were measured, as was the blood volume in the drains. At fixed intervals after surgery and up to 2 years thereafter, the patients were asked to grade the severity of pain in their back and at the donor site. RESULTS: Two years after surgery, 22% of the patients in group A and 17% of the patients in group B reported to have significant pain at the donor site. This difference was not found to be statistically significant, nor was the postoperative bleeding. The average amount of bone harvested in group A was 36 grams compared with 25.7 grams in group B, taking 14 minutes and 20.3 minutes, respectively, to harvest it. These differences were found to be statistically significant. CONCLUSIONS: Preserving the iliac cortices, while obtaining bone graft, does not reduce the postoperative bleeding or the severity of pain at the donor site. In the intraosseous method, less bone is harvested and longer duration of surgery is required, compared with that of the outer Table method.

Use of the anterior interbody fresh-frozen femoral head allograft in circumferential lumbar fusions.

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.

An algorithm for selection of instrumentation levels in scoliosis.

Appropriate levels for instrumentation and fusion in scoliosis have been a matter of debate among surgeons since the introduction of operative management of this deformity. We set out to examine the hypothesis that the amount of correction achieved in all planes during surgical instrumentation of a curve should be less than, or comparable to, the degree of correction attainable at any non-instrumented adjacent curve. An algorithm was designed to facilitate preoperative planning and intraoperative performance of spinal fusion procedures in the management of scoliosis. To test the validity of the hypothesis and the proposed algorithm, measurements were taken from the preoperative radiographs of 200 patients. The dimensions of the curves were obtained from an initial set of four X-ray films: (1) standing anteroposterior film of the whole spine, (2) standing lateral film of the whole spine, (3) two properly performed side-bending films including each curve of the spine. With this data, a plan was designed using the algorithm. The results of this plan were compared with the actual results of the surgery, which were revealed only at this stage. All patients in whom actual instrumentation levels fell within those predicted by the proposed algorithm had no imbalance at follow-up. All patients whose actual instrumentation levels were short of those recommended by the algorithm showed obvious imbalance on final postoperative standing radiograph.

Screw omission and the stability of posterior pedicle screw constructs for short-segment stabilization.

To determine the net contribution of a spinal construct to stability, and whether extending the construct to another level in situations in which a defective pedicle cannot have a screw inserted, we performed biomechanical tests in which we evaluated three-, four-, and five-level synthetic spinal constructs in which the location and number of pedicle screws were varied above and below a vertebrectomy defect. We subjected all constructs to axial, compression, lateral bending, flexion, extension, and torsional forces with the use of an Instron biaxial machine. Left-right symmetrical constructs were more stable than asymmetrical ones. Three-level constructs were statistically stiffer than the longer ones in compression, left bending, and flexion. Torsional stability, however, was greater in the longer constructs. Five-level constructs with both end screws in place had greater torsional stiffness than when they were missing a screw. In vertebrectomy defects, if four screws cannot be placed across it, then the engagement of two screws is indicated. The stability provided by a single screw at a spinal level is minimal. Additional screws augment the purchase of the construct in the bone; however, they do not afford further protection to the defect.

The mechanical role of laminar hook protection of pedicle screws at the caudal end vertebra.

Biomechanical studies have shown hooks to be superior to pedicle screws in pull-out, especially in osteoporosis. This study evaluates the possible increase in stiffness of pedicle screws provided by laminar hooks while applying non-destructive forces to a vertebrectomy model assembled with Compact Cotrel Dubousset (CCD) instrumentation. Synthetic vertebrae were employed in a three-level vertebrectomy model. CCD screw-based three-level constructs with and without sublaminar hooks in the caudal element were tested in flexion, extension, compression, lateral bending, and torsion. There was no statistically significant advantage in adding inferior laminar hooks to a caudal end vertebra that had bilateral pedicle screws in any of the testing modes. Torsional stability, however, was augmented, but not significantly. Torsional instability and osteoporotic bone may be the clinical justifications for adding laminar hooks below screws in the caudal end vertebra.

An anatomic evaluation of L5 nerve stretch in spondylolisthesis reduction.

STUDY DESIGN: Lumbosacral spondylolisthesis was simulated using four embalmed human spines, and the path of the L5 nerve was studied. OBJECTIVES: To quantify the change in length of the L5 nerve root associated with reduction of spondylolisthesis, correction of slip angle, and changing disc height. SUMMARY OF BACKGROUND DATA: Stretch injury to the lumbar nerves remains a complication of spondylolisthesis reduction. To date, no anatomic studies have been performed to quantify this effect of reduction on the lumbar nerves. METHODS: The L5 vertebral body and the sacrum of four embalmed human spines were constrained in an adjustable jig, and the length of a simulated nerve was determined for various position variables--sagittal translation (0-100% slip), slip angle (-40 degrees to +20 degrees), and disc height (5 or 10 mm). Two standard points of reference were chosen to represent fixed points along the path of the L5 nerve. An inelastic cord was used to measure the path length between these points as L5 was reduced from 100% to 0% slip. Testing was performed using a 5-mm and a 10-mm disc height. The effect of varying slip angle alone was also studied. RESULTS: The effect of spondylolisthesis reduction and slip angle correction on nerve length varied depending on the location of L5 with respect to the sacrum. There was an increasing effect of partial reduction on nerve length as L5 approached full reduction. Initially, little strain was produced in the L5 nerve as L5 was reduced in higher grade slips. However, as L5 approached full reduction, the strain per increment of reduction increased rapidly. On average, the mean nerve strain was 4.0% for the first 50% of reduction and 10.0% for the second half of reduction. Increasing lordosis relaxed the nerve in high-grade slips and stretched the nerve in fully reduced slips. At 100% slip, the mean nerve excursion decreased 5.1 mm (nerve slackening) when L5 was rotated from +20 degrees to -40 degrees. At 0% slip, the mean nerve excursion increased 3.1 mm (nerve stretch). Increasing disc height directly stretched the L5 nerve. However, given a larger disc height, the strain on the nerve per increment of reduction was less than for the smaller height. CONCLUSION: The findings suggest that the risk of stretch injury to the L5 nerve with reduction of a high-grade spondylolisthesis is not linear; with 71% of the total L5 nerve strain occurring during the second half of reduction, partial reduction may be a significantly safer treatment approach for high-grade spondylolisthesis than complete reduction. Correction of lumbosacral kyphosis in high-grade spondylolisthesis may be protective of the L5 nerve.

Deep vein thrombosis after major reconstructive spinal surgery.

STUDY DESIGN: A prospective study was performed. OBJECTIVES: The goals of the study were to determine the incidence of deep vein thrombosis after major adult spinal surgery and the optimal mode of prophylaxis in this surgical population. SUMMARY OF BACKGROUND DATA: Few studies have evaluated deep vein thrombosis incidence and prophylaxis after major adult spinal surgery. Incidence rates have ranged from 0.9-14%. METHODS: Three hundred twenty-nine patients were evaluated. One hundred ten patients were randomized to 3 different deep vein thrombosis prophylaxis groups. These patients had duplex doppler scans between the fifth and seventh postoperative days. The remaining 219 patients formed a nonrandomized group and received either thrombosis embolic deterrent stockings alone or thrombosis embolic deterrent stockings and pneumatic compression boots for deep vein thrombosis prophylaxis. The type of deep vein thrombosis prophylaxis in this group was based on surgeon preference. All 329 patients were followed for clinical signs and symptoms of thromboembolic disease. Patients were followed clinically for a minimum of 1 year. RESULTS: All 110 prophylaxis study group patients were clinically asymptomatic and 109 duplex scans were normal. One scan was indeterminate and a follow-up venogram was negative. Two patients in the coumadin group (5.7%) experienced excessive blood loss. One of the 219 patients from the nonrandomized group developed a clinically detectable proximal deep vein thrombosis which was confirmed by duplex ultra-sonography. The overall clinical incidence of deep vein thrombosis was 0.3% (1 in 329 patients). CONCLUSIONS: This low 0.3% rate is in agreement with recent studies that focus on thromboembolic disease. Given the low incidence, routine screening for asymptomatic thrombi appears unwarranted. In addition, mechanical prophylaxis with graduated compression stockings and pneumatic compression boots is preferable to anticoagulation therapy.

The relationship between degenerative changes and osteoporosis in the lumbar spine.

Degenerative changes in the spine, specifically disc degeneration and facet arthrosis, and osteoporosis are conditions that primarily affect the elderly and may significantly impact the quality of life. The relationship between osteoporosis and degenerative changes in the hip joint has been studied, but their correlation in the spine is not entirely clear. Two hundred ninety-four subjects older than 50 years of age were retrospectively studied for the existence of lumbar spinal degeneration and osteoporosis through radiologic examination for 3 clinical manifestations: (1) disc degeneration, (2) facet joint arthrosis, and (3) lumbar osteoporosis. Peripheral osteoporosis in the distal radius of the nondominant hand was measured using a single-photon bone absorptiometer. Results indicated that subjects with severe osteoporosis in the distal radius also had severe degenerative changes in the discs and the facets; those with mild osteoporosis in the distal radius showed a tendency to have a lesser degree of degenerative changes than the subjects without osteoporosis.

Cotrel Dubousset and Wisconsin segmental spine instrumentation: comparison of results in adolescents with idiopathic scoliosis King Type II.

When introduced, the Wisconsin segmental spine instrumentation (WSSI) and the Cotrel Dubousset instrumentation (CDI) were promoted as technical advances for the correction of spinal deformities. Both systems provide acceptable correction and greatly reduce the need for postoperative immobilization. A retrospective study of a homogeneous group of 53 adolescent patients with idiopathic scoliosis with King Type II curves who had reached skeletal maturity at follow-up was conducted to compare and analyze the results of these two systems. Thirty-six of these patients had been operated on using WSSI and 17 had been operated on using CDI. CDI and WSSI were found to be equally effective in treating King Type II curves. No difference was found between the two groups in the fusion rates, spinal balance, time required for surgery, or amount of curve correction. The answer to the question of which system is "better" depends on the surgeon's experience and familiarity with the equipment.

Fracture of the iliac crest following bone grafting: a case report and literature review.

Fracture of the anterior iliac crest following bone grafting is an extremely rare occurrence. Five cases have been reported in the literature, none of which were internally stabilized. We are reporting a sixth case. Of the six cases, our harvest site is the furthest posterior from the anterior superior iliac spine. The fracture resulted in a large displaced anterior fragment that required open reduction and internal fixation with plates and screws. Osteoporosis increases the risk of anterior iliac crest fractures following bone grafting, but preventive procedures can be performed.

Hydroxyapatite enhancement of posterior spinal instrumentation fixation.

STUDY DESIGN: The ability of hydroxyapatite (HA) materials to enhance the fixation strength of posterior spinal instrumentation was examined in 19 adult mongrel dogs. METHODS: Sixteen dogs underwent bilateral placement of lumbar transpedicular screws from L1 to L6, sacral alar screws, and posterior iliac rods. The six transpedicular screw test groups included standard and plasma-sprayed HA-coated screws with the recommended insertion technique, standard and HA-coated screws with a poor initial fit insertion technique using an oversized pilot hole, and HA-grout augmentation of standard and HA-coated screws with a poor initial fit. The sacral alar screws and posterior iliac rods were either uncoated or HA-coated. Six dogs were killed immediately; ten dogs were killed at 6 weeks, and the fixation elements were mechanically tested or histologically examined. Three additional dogs and synthetic bone material were used for additional baseline mechanical testing. RESULTS: The strength of standard screws with recommended insertion did not change after 6 weeks in vivo. HA-coated screws were initially 13% less resistant to pull out than standard screws, but this difference was not significant at 6 weeks. Screws inserted with a poor initial fit technique were significantly weaker initially; at 6 weeks, pull-out strength was similar to the standard screws properly inserted. The HA-grout material significantly enhanced pull-out strength for both screw types at 6 weeks. Sacral alar screw pull-out strength was not significantly different between standard and HA-coated screws initially or at 6 weeks. HA-coated rods were initially twice as resistant to pull out than standard rods and became stronger after 6 weeks in vivo, whereas standard rods became significantly weaker. Histologically, the quantity and morphology of bone around all implants was similar, with HA-coated rods and screws demonstrating regions of direct attachment to bone. An osteoconductive response and new bone formation was observed within the HA-grout material. Scanning electron microscopic observation of mechanically tested implants revealed a shear failure of surrounding bone (and HA if present) at the screw outer thread margin or at the bone-metal or HA-metal interfaces for the posterior iliac rods. CONCLUSIONS: The strength of poorly inserted transpedicular screws was significantly enhanced in vivo by the resorbable HA-grout material. The lower strength of HA-coated screws was attributed to screw geometry changes resulting from the coating process, and modifications of screw coating are recommended.

Automated percutaneous discectomy for reherniations of lumbar discs.

Ten patients with lumbar disc reherniation at the same level as the one previously openly operated on were treated by automated percutaneous discectomy (APD). The results after follow-up for 2.5 years, on the average, showed 70% with complete or significant pain relief, 60% with motor deficit improvement, and 22% with improvement of sensory deficit. Included among the patients who had pain relief were two of three in whom discography had produced only a small amount of pain, but only one of two in whom the contrast material showed contained epidural leak. To reduce the unsuccessful results, patients with segmental instability or spinal stenosis after open surgery should not be treated by APD.

The perioperative course of combined anterior and posterior spinal fusion.

A retrospective study was undertaken to characterize and compare the perioperative course of 91 cases of one- and two-stage combined anterior and posterior spinal fusions over a 7-year period. The two patient populations were similar regarding preoperative characteristics and the number of levels fused. Significantly decreased operative and anesthesia time, operative blood loss, and postoperative hospital days were seen in the one-stage population compared to the two-stage cases (P < 0.05). For the spinal deformity subgroup, a longer chest-tube duration, decreased anesthesia time, and decreased postoperative hospital stay in the one-stage group were the only significant differences. Surgical treatment delays were noted in 8% of one-stage cases and in 23% of two-stage cases. Complications occurred in 53% of all cases, with a significantly higher major complication rate in patients with preoperative medical comorbidities who underwent two-stage combined fusion versus one-stage reconstruction. Higher complication rates were also associated with an age greater than 40 years, the presence of medical comorbidities, and cases treated with a thoracoabdominal anterior approach.

Osteoporosis management and hospital strategy.

As the patient population grows, strategies for preventing osteoporosis and for improving its management are urgently needed. Coordinating the efforts of existing hospital programs may help to meet these goals.

Results of interspinous segmental instrumentation in the sagittal plane.

There is concern that distraction instrumentation with segmental interspinous wiring (ISSI) might flatten the sagittal curves. We studied 110 cases of idiopathic scoliosis treated with ISSI with an average follow-up of > 2 years. The coronal deformity averaged 53 degrees preoperatively with a 58% average correction. For the entire group, the average preoperative thoracic kyphosis was 34 degrees and 32 degrees at follow-up. Children, however, gained an average of 4 degrees of thoracic kyphosis. Children wired to both rods gained 10 degrees in thoracic kyphosis. Preoperative lumbar lordosis was 45 degrees and 42.5 degrees at follow-up. There were five wire breakages in four patients, without loss of correction. There was one deep and one superficial infection and one dysesthesia that resolved. There were no cases of rod failure or pseudarthrosis. ISSI with careful rod contouring can maintain sagittal curves. In children, small improvements in the hypokyphotic spinal deformity can be achieved.

The logic of imaging in spine surgery.

Spinal imaging has rapidly evolved into a complex diagnostic field requiring specialized expertise. While many imaging modalities reveal portions of a topographic map of the spine necessary for surgery, only magnetic resonance imaging emerges as the imaging modality of widest and most efficacious first choice. With the increasing high-technology sophistication of modern imaging modalities, the spine surgeon must become completely conversant with the radiologic data produced by these imaging techniques. The authors present a logical approach to spinal imaging--an algorithm--based on etiologic classification and aimed at conserving medical resources and developing an optimal diagnostic pathway for spine injury and disease. Spine surgeons are urged to incorporate the interpretative insights of radiologists into the diagnostic process.

Pseudomonas aeruginosa as a causative agent of cervical osteomyelitis. Case report and review of the literature.

Pseudomonas aeruginosa osteomyelitis and epidural abscess of the cervical spine developed in a previously healthy, 73-year-old man who was not an intravenous drug abuser. In the recent literature, Pseudomonas cervical osteomyelitis has been reported only in intravenous drug abusers or in otherwise healthy individuals after a tooth extraction. In the literature of the past 30 years, isolated cases of cervical osteomyelitis were associated with urinary tract infections. The majority of these cases involved urinary tract instrumentation. The pathogenesis remains controversial. It appears that spontaneous cervical osteomyelitis in a non-intravenous drug abuser has not been previously reported.

Segmental spinal instrumentation. A historic review and current concepts.

Current methods of segmental fixation used to treat nonidiopathic scoliosis are reviewed in terms of their applicability to the treatment of idiopathic scoliosis. L-rod instrumentation, Harrington rod and segmental wires, and Wisconsin segmental instrumentation are the three techniques discussed. Each is illustrated with a case report.