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Attempts to alleviate the pain attributed to degeneration of the nucleus pulposus using replacement or reinforcement techniques dating back to the 1950s are reviewed. The various materials and their insertion techniques are discussed as are results available from early clinical experiences. These techniques are in evolution and clinical outcomes will be necessary to establish the efficacy of these approaches.

(R.B. Winter, MD) Background content: This is a synopsis of a symposium presented to the North American Spine Society Annual Meeting in Seattle, WA, 2001. Purpose: To bring to the reader who may not have attended the symposium a distillation of the material presented on this frontier of spinal surgery. Methods: Panel presentation. Results: The proposed indication for artificial disc replacement is a degenerated but contained disc, painful to the point of major life-style interruption, refractory to at least 1 year of nonoperative treatment, preferably at a single lumbar level and without infection, listhesis or major facet joint disease or spinal stenosis. Total disc replacements have been developed and used mostly in Europe. Disc nucleus replacements have also been developed. No disc replacement has been approved for general use in North America as yet. The US Food and Drug Administration is conducting investigational device exemption studies at this time. Conclusions: Artificial disc replacement is not a new concept, the first attempts having been done in the early 1950s. During the past 15 years, considerable advance has been made with large numbers of patients, mostly in Europe, having surgery with either total disc prostheses or disc nucleus replacements. Only with truly scientific studies using patient randomization, pre- and postsurgery outcome analyses by unbiased independent observers and statistical analysis by independent experts will the real value of these devices be realized.

This study evaluates the residual biomechanical stability of the spine following multilevel anterior diskectomies and anterior longitudinal ligament release using video-assisted thoracoscopic surgery (VATS). Eighteen domestic pigs were randomly divided into three groups of six pigs. Group 1 underwent thoracic anterior release from T4-T9 using a left-sided VATS approach, group 2 underwent thoracic anterior release from T4-T9 via a traditional left thoracotomy (open), and group 3 did not undergo surgery and served as a control. After surgery, the animals were euthanized, and the thoracic spinal columns were harvested for biomechanical testing. Nondestructive testing was performed on all specimens in pure compression, flexion, extension, right lateral bending, and torsion. Specimens from group 1 had significantly lower stiffness values (P

The adequate reduction of vertebral burst fractures is dependent on successful application of distractive forces in combination with the restoration of normal spinal lordosis. However, the optimal sequence of distraction in comparison to distraction plus lordosis in the anatomic restoration of the f

Spinal burst fractures are produced by rapid compressive loading, and may result in spinal cord injury from bone fragments forced from the vertebral body into the spinal canal. This fracture is one of the most difficult injuries of the spine to successfully treat, in part because the biomechanics of reduction and the exact mechanism by which the distraction forces are transmitted to the intracanal fragments of the burst fracture have not been adequately investigated. The authors developed a reproducible technique for creating these fractures in vitro. The fractures produced were identical to those observed in clinical practice, and were used for investigating the mechanics of this fracture and its reduction. This work describes the pathologic anatomy of the burst fracture both on the gross structure and also on microtome sections of the vertebrae, and examines the biomechanics of fracture reduction. The margins of the vertebral bone fragment, which was forced posteriorly into the spinal canal during fracture, were noted to extend far laterally beyond the pedicles. The authors also found extensive damage not only to the disc above the injured level, but also to that below, explaining the clinical observation that disc degeneration frequently occurs at both levels. Examination of anatomic data provided by microtome section supported the hypothesis that the fibers that actually reduce the intracanal fragment originate in the anulus of the superior vertebra in the midportion of the endplate and insert into the lateral margins of the intracanal fragment. Investigations using magnetic resonance imaging confirmed that these obliquely directed fibers account for the indirect reduction of the fragment. The authors' studies demonstrate that the posterior longitudinal ligament provides only a minor contribution in the reduction of the fracture in comparison to the attachments of the posterior portion of the anulus fibrosus. The forces required to reduce this fragment were studied. Distraction was found to be the predominant force required for indirect posterior reduction. This was confirmed by a series of tests using devices that provided segmental fixation. The application of uniform distraction forces was most effective in the posterior reduction of the intracanal fragment.

Background Facet arthroplasty is a motion restoring procedure. It is normally suggested as an alternative to rigid fixation after destabilizing decompression procedures in the posterior lumbar spine. While previous studies have reported successful results in reproducing normal spine kinematics after facet replacement at L4-5 and L3-4, there are no data on the viability of facet replacement at the lumbosacral joint. The anatomy of posterior elements and the resulting kinematics at L5-S1 are distinctly different from those at superior levels, making the task of facet replacement at the lumbosacral level challenging. This study evaluated the kinematics of facet replacement at L5-S1. Methods Six human cadaveric lumbar spines (L1-S1, 46.7 ± 13.0 years) were tested in the following sequence: (1) intact (L1-S1), (2) complete laminectomy and bilateral facetectomy at L5-S1, and (3) implantation of TFAS-LS (Lumbosacral Total Facet Arthroplasty System, Archus Orthopedics, Redmond, Washington) at L5-S1 using pedicle screws. Specimens were tested in flexion (8Nm), extension (6Nm), lateral bending (LB, ± 6Nm), and axial rotation (AR, ± 5Nm). The level of significance was α = .017 after Bonferroni correction for three comparisons: (1) intact vs. destabilized, (2) destabilized vs. reconstructed, and (3) intact vs. reconstructed. Results Laminectomy-facetectomy at L5-S1 increased the L5-S1 angular range of motion (ROM) in all directions. Flexion-extension (F-E) ROM increased from 15.3 ± 2.9 to 18.7 ± 3.5 degrees (P < .017), LB from 8.2 ± 1.8 to 9.3 ± 1.6 degrees (P < .017), and AR from 3.7 ± 2.0 to 5.9 ± 1.8 degrees (P < .017). The facet arthroplasty system decreased ROM compared to the laminectomy-facetectomy condition in all tested directions (P < .017). The facet arthroplasty system restored the L5-S1 ROM to its intact levels in LB and AR (P > .017). F-E ROM after the facet arthroplasty system implantation was smaller than the intact value (10.1 ± 2.2 vs. 15.3 ± 2.9 degrees, P < .017). The load-displacement curves after the facet arthroplasty system implantation at L5-S1 were sigmoidal, and quality of motion measures were similar to intact, demonstrating graded resistance to angular motion in F-E, LB and AR. Conclusions The facet arthroplasty system was able to restore stability to the lumbosacral segment after complete laminectomy and bilateral facetectomy, while also allowing near-normal kinematics in all planes. While F-E ROM after the facet arthroplasty system implantation was smaller than the intact value, it was within the physiologic norms for L5-S1. These results are consistent with previous studies of facet arthroplasty at L3-L4 and L4-L5 and demonstrate that TFAS technology can be adapted to the lumbosacral joint with functionality comparable to its application in superior lumbar levels.

A prospective, randomized, multicenter, Food and Drug Administration-regulated Investigational Device Exemption clinical trial.To evaluate the safety and effectiveness of the ProDisc-L (Synthes Spine, West Chester, PA) lumbar total disc replacement compared to circumferential spinal fusion for the treatment of discogenic pain at 1 vertebral level between L3 and S1.As part of the Investigational Device Exemption clinical trial, favorable single center results of lumbar total disc replacement with the ProDisc-L have been reported previously.Two hundred eighty-six (286) patients were treated on protocol. Patients were evaluated before and after surgery, at 6 weeks, 3, 6, 12, 18, and 24 months. Evaluation at each visit included patient self-assessments, physical and neurologic examinations, and radiographic evaluation.Safety of ProDisc-L implantation was demonstrated with 0% major complications. At 24 months, 91.8% of investigational and 84.5% of control patients reported improvement in the Oswestry Low Back Pain Disability Questionnaire (Oswestry Disability Index [ODI]) from preoperative levels, and 77.2% of investigational and 64.8% of control patients met theor =15% Oswestry Disability Index improvement criteria. Overall neurologic success in the investigational group was superior to the control group (91.2% investigational and 81.4% control; P = 0.0341). At 6 weeks and 3 months follow-up time points, the ProDisc-L patients recorded SF-36 Health Survey scores significantly higher than the control group (P = 0.018, P = 0.0036, respectively). The visual analog scale pain assessment showed statistically significant improvement from preoperative levels regardless of treatment (P0.0001). Visual analog scale patient satisfaction at 24 months showed a statistically significant difference favoring investigational patients over the control group (P = 0.015). Radiographic range of motion was maintained within a normal functional range in 93.7% of investigational patients and averaged 7.7 degrees.ProDisc-L has been found to be safe and efficacious. In properly chosen patients, ProDisc-L has been shown to be superior to circumferential fusion by multiple clinical criteria.

Study Design. This was a prospective multicenter clinical trial of a lumbar interbody fusion cage with a minimum of 4 years'follow-up. Objectives. To determine whether the early positive clinical results in fusions with lumbar cages, such as the Bagby and Kuslich (BAK) cage, are maintained beyond 2 years. Summary of Background Data. Threaded cages have been used increasingly for the treatment of symptomatic degenerative intervertebral disc disease. Concerns about the long-term clinical outcomes of this procedure have been posed, particularly regarding bony fusion viability, revision rates, potential adjacent level disease, and late complications. Methods. The study cohort was a 196-patient subset from a prospective investigational device exemption. In addition to early postoperative examinations, these patients were examined biannually with a minimum of 4 years' follow-up. Patient outcome was assessed by a 6-point scale that evaluated pain relief, and functional improvement was determined by changes in activities of daily living. Fusion rates and return to work were determined. Complications and secondary operations were reported and categorized as non-device related or device related. Results. The patient cohort with 4-year follow-up represented 25.6% of the original study population eligible at that time. Overall, the largest percentage of pain relief and functional improvements occurred by 3 months, and these improvements were maintained at each follow-up. Overall fusion rate was 91.7% and 95.1% at 2 and 4 years, respectively. In this cohort, 39.5% of patients were working or were able to work within 3 months of surgery. After 4 years, 62.7% of patients were gainfully employed or able to work. The late-occurring complication rate in this cohort was 13.8% (27/196). Complications necessitating a second operation occurred in 8.7% (17/196), whereas re-operations that were deemed device related were performed in 3.1% (6/196). Conclusions. This study indicates that the early positive benefits of interbody fusion cage procedures are maintained through 4 years with acceptably low morbidity.

The optimal timing of surgical intervention in cervical spinal cord injuries has not been defined. The goals of the study were to investigate changes in neurologic status, length of hospitalization, and acute complications associated with surgery within 3 days of injury versus surgery more than 3 days after the injury. All patients undergoing surgical treatment for an acute cervical spinal injury with neurologic deficit at two institutions between March 1989 and May 1991 were reviewed retrospectively. Forty-three patients initially were evaluated. At one institution, patients with neurologic spinal injuries had surgical intervention within 72 hours of injury. At the other institution, patients underwent immediate closed reduction with subsequent observation of neurologic status for 10 to 14 days before undergoing surgical stabilization. This study indicates that patients who sustain acute traumatic injuries of the cervical spine with associated neurologic deficit may benefit from surgical decompression and stabilization within 72 hours of injury. Surgery within 72 hours of injury in patients sustaining acute cervical spinal injuries with neurologic involvement is not associated with a higher complication rate. Early surgery may improve neurologic recovery and decrease hospitalization time in patients with cervical spinal cord injuries.

Study design Two hundred-forty consecutive patients underwent laparoscopic instrumented interbody fusion using custom-designed instrumentation and BAK (Sulzer Spine Tech, Minneapolis, MN) fusion cages. The surgeries were performed at eight spine centers during U.S. Food and Drug Administration investigational device evaluation clinical trials. This cohort was compared with 591 consecutive patients undergoing open anterior fusion with the same device. Objectives To investigate the feasibility and safety of the laparoscopic approach compared with that of open procedures. Summary of background data In other areas of medicine, advances in laparoscopic surgical procedures have resulted in reduced morbidity, expense, and pain when compared with results of the open counterpart. Methods The open anterior procedure was performed using a retroperitoneal approach. The laparoscopic procedure was performed transperitoneally with carbon dioxide insufflation to provide visualization using a 10-mm endoscope. Two hollow, titanium, threaded interbody implants packed with autologous bone were inserted into the diseased interspace. Results The laparoscopy group had a shorter hospital stay and reduced blood loss but had increased operative time. Operative time improved in the laparoscopy group as surgeons' experience increased. Operative complications were comparable in both groups, with an occurrence of 4.2% in the open approach and 4.9% in the laparoscopic approach. Overall, the device-related reoperation rate was higher in the laparoscopy group (4.7% vs. 2.3%), primarily as a result of intraoperative disc herniation. Conversion to open procedure in the laparoscopy group was 10%, with most cases predictable and preventable. Conclusions The laparoscopic procedure is associated with a learning curve, but once mastered, it is effective and safe when compared with open techniques of fusion.

Study Design. A biomechanical study of graft loading characteristics for anterior cervical discectomy and fusion comparing the amount and location of transmitted forces. Objectives. To evaluate the difference between traditional iliac grafting and reverse iliac grafting used for anterior cervical discectomy and fusion in the amount and location of forces applied to the grafts. of Background Data. Traditional fusion after anterior cervical discectomy involves placing a tricortical iliac crest strut into the disc space with the cortical portion facing anteriorly and the cancellous portion posteriorly. Recently, reverse iliac grafting has been introduced in which the cortical portion is placed in the posterior disc space and the cancellous portion in the anterior disc space. There is no biomechanical or clinical study showing an advantage of using one technique over the other. This study is the first to produce data supporting one technique as biomechanically superior. Methods. Five fresh cadaveric cervical spines were tested using pressure-sensitive film placed between the bone graft and the vertebral endplate after an anterior discectomy was performed. A 10-pound load was applied to the cervical spine at predetermined sagittal positions. Recordings were made at neutral, 10° of flexion, and 10° and 20° of extension after traditional and reverse iliac grafting. Results. Graft forces were identical in both traditional and reverse grafting in the location and amount of force applied. Total force increased to the maximum in flexion and gradually decreased in more extended positions. The location of the forces was completely anterior with flexion, moving to the posterior portion of the graft with positions of extension. With 10° of flexion, the load applied to the grafts was 20.4 N. In the neutral position, the load was 12 N. The loads decreased further with extension with forces of 11 N in 10° extension, and 4 N in 20° of extension. Conclusions. The optimal position of the tricortical iliac graft for an anterior cervical fusion is with the stronger cortical portion placed in the anterior disc space and the weaker cancellous ponion placed in the posterior disc space. In this traditional position, the graft will best resist the loads applied to the cervical spine, preventing graft collapse.

A retrospective evaluation of 138 patients requiring operative decompression, reduction and fixation of spinal injuries between January 1986 and April 1989 was conducted. The variables of timing and method of operative intervention, level and classification of fracture, associated injuries, injury severity score (ISS), associated neurologic deficits, length of intensive care unit and hospital stays, and projected costs were analyzed for correlation with postoperative complications (pulmonary, skin, urinary, other). Four subgroups were identified: group IA patients underwent surgery within 72 h of injury and had an ISS of18; group IB patients underwent surgery after 72 h and had an ISS of18; group IIA patients underwent surgery within 72 h and had an ISS ofor = 18; and group IIB underwent surgery after 72 h and had an ISS ofor = 18. There was no statistically significant difference in the incidence of medical complications in patients comparing groups IA and IB. Group IIB patients had a statistically significant higher rate of morbidity than did group IIA. A separate group of patients with cervical spine injuries with neurologic deficit was analyzed by the same statistical analysis. Irrespective of associated injuries, all had fewer complications if they underwent surgery within 72 h. Morbidity was higher in patients with a neurological deficit compared with neurologically intact patients. Surgical decompression, reduction, and/or fixation of spinal fractures within the first 72 h is indicated in patients with multiple trauma (ISSor = 18) and cervical injuries with a neurological deficit.

Study Design. This study quantified changes in the size of the stenotic neuroformen in degenerative lumbar spines. The volume and area of the neuroforamen were measured before and after the application of anterior distraction using the BAK interbody fusion system. Objective. To quantitatively assess the neuroforaminal area and volume when the BAK interbody fusion system is applied to lumbar spines with neuroforaminal stenosis. Summary of Background Data. The spatial relationship between the nerve root and the osseous and nonosseous elements of the neuroforamen is clinically important. Few studies have focused on changes in neuroforaminal size in the lumbar spine after anterior interbody distraction. No previous study has assessed the neuroforaminal volume. Methods. The BAK instrumentation system was applied anteriorly at L4-L5 and L5-S1 intervertebral discs in nine degenerative cadaver lumbar spines. The neuroforaminal volumes of L4-L5 and L5-S1 were measured from silicon molds taken of the neuroforamen. In addition, computed tomography and circular blunt probes were used to determine the neuroforaminal areas. The disc height was recorded from lateral radiographs. Results. After the BAK instrumentation, the volume of the neuroforamen increased significantly-by 22.9% for L4-L5 and 21.5% for L5-S1. The posterior disc height increased by 37.1% at L4-L5 and 45.1% at L5-S1. The neuroforaminal areas significantly increased-by 29.0% at L4-L5 and 33.8% at L5-S1. There was good correlation between the volume and the posterior disc height (R 2 =0.50) and the volume and the area of the narrowest portion of neuroforamen (R 2 =0.56). Conclusions. The result indicated that anterio systems such as the BAK system, which increase disc heights, can significantly increase neuroforaminal volume and area, providing neuroforaminal volume and ara, providing adequate space for the nerve root and improving neuroforaminal stenosis

The dislodgement of anterior bone graft in the cervical spine is a frequent complication of attempted fusion following discectomy or corpectomy. It has been hypothesized that fixation augmented with interference screws may increase the pull-out strength of the construct and decrease the rate of these complications. Mechanical tests were conducted to compare interference screw fixation methods for enhancing the fixation between the bone graft and the adjacent vertebra. The anterior pull-out strengths of cervical bone grafts were compared using fixation with and without the addition of interference screws. Both discectomy and corpectomy graft models were examined in vitro. The mean pull-out force for a Smith-Robinson type bone graft alone was 58.1 N (SD +/- 11.4 N); for the graft augmented with two 3.5 mm cancellous bone screws, 153.9 N (+/- 58.9 N); for the graft with four 3.5 mm screws, 217.1 N (SD +/- 69.9 N). The pull-out strengths of the two and four 3.5 mm screw constructs were significantly greater than the strength of the graft alone (p less than 0.05). Similarly placed 2.7 mm cortical screws of the same length provided increased pull-out strength (123.7 N +/- 38.6 N and 142.5 N +/- 38.2 N for two and four screws, respectively); however, in comparison to the graft alone, these differences were not statistically significant. For both screw types, the four screw fixations were stronger than the two-screw fixations, although these differences were not statistically different.(ABSTRACT TRUNCATED AT 250 WORDS)

This textbook, which comprises thirty-five chapters by more than sixty-five authors (several of whom are very well known), covers anatomy, biomechanics, epidemiology, neuroradiology, psychology, nonoperative care, and operative intervention. Although whiplash injury is a very common occurrence, not much is known about it. Whiplash is a very broad term. The manifestations of this injury …

The purpose of this study is to evaluate the technique of video-assisted thoracic surgery (VATS) to perform corpectomy and spinal reconstruction with the Harrington rod and polymethylmethacrylate construct, and to compare the biomechanical stability of the constructs created with both open thoracotomy and VATS technique. Fourteen farm-raised pigs were divided into two groups. Group I underwent thoracic corpectomy using a VATS approach and group II had the same procedure performed through a traditional thoracotomy. The stiffness (newtons per millimeter) for the non-destructive tests for each loading mode are flexion-compression (open 124.4 +/- 124.9; VAT 75.8 + 29.9); extension-compression (open 165.8 + 41.8: VATS 96.5 + 31.2); pure compression (open 231.4 + 126.4; VATS 264.6 + 184.3). The difference between group I (VATS) and group II (open) in extension compression is statistically significant. Although not statistically significant, the results also show the group II (open) specimens to be stiffer in flexion-compression and the group I (VATS) specimens to be stiffer in pure compression. Although corpectomy and spinal reconstruction can be performed with the VATS technique, the constructs obtained endoscopically may not have the same strength as those constructs obtained via an open procedure.

A rational program of diagnosis and therapy can be recommended on the basis of the results in a series of 34 cases of pyogenic vertebral osteomyelitis. The diagnosis can be made on history, physical examination, sedimentation rate, bone scan and X-ray. Blood and urine cultures should be done and may be of value. Biopsy of the area confirms the diagnosis and establishes adequate and specific antibiotic therapy. Bed rest is needed to relieve the patient's initial discomfort and to prevent deformity. Immobilization is most important in those patients with greater than 50% vertebral destruction for the first 3 months in order to prevent deformity.