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Study design A prospective clinical data analysis. Objective To determine the long-term clinical success of 2-level total disc replacement (TDR) in patients with degenerative disc disease. Summary of background data Early successful clinical results of 2-level TDR have been reported. Few studies exist that have described this procedure's durability in the long term. Methods Fifteen patients underwent 2-level lumbar TDR with the ProDisc-L as part of a randomized trial, 13 of whom were available for follow-up. The patients were assessed preoperatively and at 2 years, 5 years, and more than 9 years postoperatively using visual Oswestry Disability Index. At the last follow-up visit, 2 additional questions were asked: satisfaction with surgery and willingness to undergo the same treatment. Finally, clinical success was assessed using a previously described definition. Results Mean follow-up time was 9.6 years (range, 9.2-10.3 yr). Postoperatively there was a significant improvement in Oswestry Disability Index score from baseline (70.0 vs. 15.7 at 2 yr, P = 0.002) that remained unchanged during the period of follow-up (19.8 at 5 yr, P = 0.003 and 12.9 at 9-10 yr, P = 0.002). Ninety-two percent of patients were "satisfied" or "somewhat satisfied" with treatment and the same number would undergo treatment again. Eighty-five percent of patients achieved clinical success. Conclusion This prospective study demonstrates the durable clinical success of 2-level lumbar TDR as assessed at more than 9 years postoperatively. Level of evidence 4.

BACKGROUND CONTEXT: Vertebral end plate support is necessary for successful lumbar total disc replacement (TDR) surgery. Failure to achieve anterior column support as a result of lumbar TDR device undersizing could lead to implant subsidence and fracture. PURPOSE: The purpose of the study was to examine the compressive biomechanical behavior of the vertebral end plate with varying sizes of disc replacement implants. STUDY DESIGN: The study design comprises a biomechanical investigation using a human cadaveric lumbar spine model. METHODS: Fifty-six vertebrae with intact posterior elements were prepared from 13 fresh frozen lumbar spines. Peripheral quantitative computed tomography was performed to assess regional bone density. Vertebrae were potted and subjected to nondestructive compression testing with a small, medium, and large custom-made implants with the footplate geometry of the ProDisc-LTDR (Synthes Spine, West Chester, PA, USA) system and having no keel. Failure testing was performed using the ProDisc-L implant with an intact keel. Pressure sensor film was used to assess contact pressure and distribution. RESULTS: Therewasalinearcorrelationbetweenpercentcoverageoftheendplateandimplant-end plate stiffness (p5.0001) and an inverse correlation with displacement (p5.01). The difference in implant-end plate stiffness between small-medium, medium-large, and small-large implants was 10.5% (p5.03), 10.2% (p5.02), and 19.6% (p!.0001), respectively. Failure analysis revealed similartrendsforimplantsizing,butonlybonedensitywasfoundtosignificantlycorrelatewithfailure properties (r50.76, p!.0001).Therewas a significant reduction in implant-end plate stiffness of 18% whenthekeelwasintactcomparedtowithoutthekeel(range6‐27%,p5.0008).Pressurefilmanalysis revealed that the implant was loaded peripherally and did not have central contact during nondestructiveloading.Therewasatrendtowardgreatercontactpressurewiththesmallimplantwhencompared with the medium implant (p5.06) and the large implant (p5.06). CONCLUSIONS: Although larger implants reduce end plate displacement, increase apparent implant-end plate stiffness, increase the implant-end plate contact area, and decrease the peak contact pressures, low bone density reduces failure properties. The keel introduces a reduction in stiffness to the implant-end plate interface, the clinical significance of which is currently

STUDY DESIGN Radiographic results of a multicenter, prospective randomized study comparing 1-level cervical total disc replacement (TDR-C) with anterior cervical discectomy and fusion (ACDF). OBJECTIVE To evaluate the effect on device-level lordosis, cranial and caudal adjacent level lordosis, and overall cervical sagittal alignment (C2-C6) after TDR-C or ACDF. SUMMARY OF BACKGROUND DATA Cervical total disc replacement (TDR-C) has emerged as a promising alternative to ACDF in a select group of patients. The maintenance and/or improvement of sagittal balance is essential in preserving functionality after reconstructive spinal procedures. Recent studies have documented changes in spinal alignment after TDR-C, however, no studies have compared these changes to those noted in matched group of patients that have undergone ACDF. METHODS Radiographic data were obtained from the randomized group of a multicenter, randomized, prospective, controlled study comparing TDR-C (ProDisc-C, Synthes Spine, West Chester, PA) with ACDF in the treatment of 1-level cervical disc disease. Complete radiographic data were available for 89 TDR-C patients (average age: 42.2 years) and 91 ACDF patients (average age: 41.7 years). Cervical lordosis at the device level, cranial and caudal adjacent levels, and total cervical lordosis (C2-C6) were independently measured before surgery and 2 years after surgery using custom image stabilization software (Quantitative Motion Analysis, Medical Metrics, Inc, Houston, TX). RESULTS C5-C6 was the most common operative level (TDR-C: 54%; ACDF: 55%). At 2 years after surgery, the TDR-C group experienced statistically significant changes in lordosis of 3.0 degrees (P < 0.001), 0.90 degrees (P = 0.006), and -1.9 degrees (P < 0.001) at the operative, cranial, and caudal adj-acent levels, respectively. ACDF experienced changes in lordosis of 4.2 degrees (P < 0.001), 1.0 degrees (P = 0.001), and -1.5 degrees (P = 0.001), respectively. The between-group differences were significant at the operative level (P = 0.03) and the caudal adjacent level (P = 0.05). Total cervical lordosis increased in both TDR-C and ACDF by 3.1 degrees and 3.8 degrees , respectively (P = 0.49). CONCLUSION In both TDR-C and ACDF, lordosis increased at the device-level, cranial adjacent level, and in total cervical lordosis, while lordosis decreased at the caudal adjacent level. Although ACDF facilitated a greater increase in device level lordosis (+1.25 degrees ) and less loss of lordosis at the caudal adjacent level compared with TDR-C (-0.39 degrees ), the clinical relevance of the small differences remain unknown.

Study Design. A validated nonlinear three-dimensional finite element (FE) model of a single lumbar motion segment (L3-L4) was used to evaluate the effects of total disc replacement (TDR). The model was implanted with a fixed-bearing TDR (ProDisc-L) at 2 surgically relevant positions and exercised about the 3 anatomic axes. Facet forces, range of motion (RoM), and vertebral body strains were evaluated. Objective. The objective of the current study was to evaluate how TDR implantation and positioning affects facet joint forces and vertebral body strains. We hypothesized that facet contact forces (FCFs) would increase with TDR to compensate for the loss of periprosthetic load-bearing structures, and that vertebral body strains would increase in the region around the metallic foot-plates. Summary of Background Data. TDR has the potential to replace fusion as the gold standard for the treatment of painful degenerative disc disease. However, complications after TDR include index level facet arthrosis and implant subsidence. Alterations in facet and vertebral body loading after TDR and their dependence on implant positioning are not fully understood. Methods. An FEM of L3-L4 was created and validated using RoM, disc pressure, and bony strains from previously published data. A TDR was incorporated into the L3-L4 spine model. All models were subjected to a compressive follower load of 500 N and moments of 7.5 Nm about the 3 anatomic axes. Results. Overall RoM and FCFs tended to increase with TDR. FCFs increased by an order of magnitude during flexion. Posterior placement of the device resulted in an unloading of the facets during extension. Areas of strain maxima were observed in the anterior portion of the vertebral body during flexion after TDR. The area of initial bone resorption signal under the metal footplate was greater when the device was anteriorly placed. Conclusion. The current study predicted a decrease in segmental rotational stiffness resulting from TDR. This resulted from the removal of load bearing soft tissue structures, and caused increased loading in the facets. Additionally, vertebral body strains were generally higher after TDR, and tended to increase with decreased rotational stiffness. Posterior placement of the device provided a more physiologic load transfer to the vertebral body.

Background Range of motion (ROM) has been shown to influence clinical outcomes of total disc replacement (TDR). While the parallax effect in image acquisition has been shown in the literature to influence the accuracy of a variety of measurements, this concept has not been investigated in the assessment of ROM analysis following TDR. We performed an evaluation of the influence of radiograph beam angle on “by hand” and on “gold standard” flexion-extension ROM measurements in lumbar total disc replacement. The purpose of this study is to determine (1) the influence of X-ray beam angle on index level angle (ILA) measurements in lumbar TDR using the keel method, and (2) whether the out-of-plane radiographic beam effects cause a difference between true and calculated range of motion. Methods Eight blinded orthopaedic surgeons used the keel method to calculate ROM measurements from radiographs of a flexible Sawbones model (Pacific Research Laboratories, Inc., Vashon, Washington) implanted with a ProDisc-L device (Synthes Spine, West Chester, Pennsylvania). Radiographs were obtained at beam angles of 0°, 5°, 10°, and 15° in the sagittal plane from the device center. Calculations were compared to measurements obtained by a validated digitized software method (Quantitative Motion Analysis, QMA, Medical Metrics, Inc., Houston, Texas). Inter- and intraobserver precision and accuracy were determined. Results Compared with QMA, the radiographic keel method had an average error of 3.7°. No significant effect of variation in beam angle on interobserver precision (N = 16, P = .92) or accuracy (N = 16, P = 0.86) or intraobserver precision (N = 8, P = .09) or accuracy (N = 8, P = 0.07) of ROM measurements was identified. Repeat testing with QMA also revealed no effect of parallax and resulted in nearly identical ROM measurements. Conclusions Accuracy and precision of the keel method to determine ROM from index level angle measurements after TDR was not affected by increases in X-ray beam angles up to 15 from the device center. Clinical Relevance Our study demonstrates that range of motion measurements are not influenced by parallax effect when using the keel method to determine index level angle measurements in lumbar total disc replacement.

The impetus for motion preservation in the treatment of degenerative conditions of the lumbar spine is to protect the adjacent levels from accelerated or de novo degeneration. Our ability to reliably and precisely measure, analyze, and understand resultant lumbar motion following implantation of a motion-preserving device is therefore indispensable to the proper interpretation of results from clinical studies. The first section of this article highlights current imaging techniques and strategies utilized in the preoperative evaluation of a potential candidate for lumbar total disc replacement. In the second section of this article, we describe current and novel imaging techniques that are used to evaluate range of motion and the lumbar kinematic profile that results following implantation of a lumbar total disc replacement.

The intervertebral disc is characterized by a tension-resisting annulus fibrosus and a compression-resisting nucleus pulposus composed largely of proteoglycan. Both the annulus and the nucleus function in concert to provide the disc with mechanical stability. Early disc degeneration begins in the nucleus with proteoglycan depletion. Quantitative magnetic resonance imaging techniques have been developed to noninvasively quantify the earliest degenerative changes that occur within the disc. Our ability to identify and quantify these early biochemical changes will provide a better understanding of the pathophysiology of disc degeneration and facilitate the study of interventions that aim to halt or reverse the degenerative process.

Diagnostic methods and biomarkers of early disc degeneration are needed as emerging treatment technologies develop (e.g., nucleus replacement, total disc arthroplasty, cell therapy, growth factor therapy) to serve as an alternative to lumbar spine fusion in treatment of low back pain. We have recently demonstrated in cadaveric human discs an MR imaging and analysis technique, spin-lock T(1rho)-weighted MRI, which may provide a quantitative, objective, and non-invasive assessment of disc degeneration. The goal of the present study was to assess the feasibility of using T(1rho) MRI in vivo to detect intervertebral disc degeneration. We evaluated ten asymptomatic 40-60-year-old subjects. Each subject was imaged on a 1.5 T whole-body clinical MR scanner. Mean T(1rho) values from a circular region of interest in the center of the nucleus pulposus were calculated from maps generated from a series of T(1rho)-weighted images. The degenerative grade of each lumbar disc was assessed from conventional T(2)-weighted images according to the Pfirmann classification system. The T(1rho) relaxation correlated significantly with disc degeneration (r=-0.51, P0.01) and the values were consistent with our previous cadaveric study, in which we demonstrated correlation between T(1rho) and proteoglycan content. The technique allows for spatial measurements on a continuous rather than an integer-based scale, minimizes the potential for observer bias, has a greater dynamic range than T(2)-weighted imaging, and can be implemented on a 1.5 T clinical scanner without significant hardware modifications. Thus, there is a strong potential to use T(1rho) in vivo as a non-invasive biomarker of proteoglycan loss and early disc degeneration.

Disc degeneration that occurs at the level adjacent to a previous fusion is known as adjacent segment degeneration (ASD). Altered biomechanical forces at the adjacent level motion segments may predispose to subsequent degeneration and pain, which may require further surgery consisting of decompression with or without an extension of the fusion. The rapid rise in the rates of lumbar spinal fusion over recent years suggests that ASD may become even more prevalent with time. Adjacent segment degeneration has served as the impetus for the development of motion-preserving alternatives for the treatment of degenerative disc disease, most notably total disc replacement (TDR). This article will highlight the diagnosis, etiology, risk factors, and treatment for lumbar instability adjacent to a previous fusion and discusses the potential role for total disc replacement in the prevention of ASD.

Arthrodesis of the lumbar spine is associated with lack of pain relief, loss of motion, pseudoarthrosis, sagittal balance malalignment, and adjacent segment disease. Recently, total disc replacement (TDR) has become an alternative to spinal fusion, which may prevent these complications while providing equivalent or improved outcomes. We report the single-surgeon, single-site results from a multicenter, randomized, prospective study comparing lumbar TDR with ProDisc-L with circumferential fusion. Thirty-seven patients met strict inclusion criteria. There were 5 patients in the fusion group (average age 38) and 32 patients in the ProDisc-L group (average age 41). Multiple linear regression analysis revealed that TDR significantly reduced operating times (87 versus 141 minutes, P = 0.01) and length of hospital stay (4.1 versus 5.4 days, P = 0.02). TDR subjects demonstrated equivocal overall patient satisfaction and Oswestry scores throughout 2-year follow-up. VAS scores were significantly higher in fusion patients at 18 months ( P = 0.02), while TDR patients had significant improvement in SF-36 at 6 weeks following surgery compared with fusion patients ( P = 0.04). TDR patients exhibited significantly increased range of motion at the operative level at 18 months following surgery ( P = 0.03), whereas fusion patients demonstrated a trend toward increasing range of motion at the proximal adjacent level over time ( P = 0.06). TDR patients had significantly increased anterior disc heights compared with fusion patients at 24 months ( P

Study design A prospective, nonblinded, multicenter study of outcomes in patients undergoing single-level anterior lumbar discectomy and interbody fusion with InFUSE Bone Graft. Objective To determine the safety and effectiveness of InFUSE Bone Graft applied to an absorbable collagen sponge in anterior lumbar interbody fusion with threaded cortical allografts. Summary of background data In primates, InFUSE Bone Graft used with allograft dowels was shown to increase rates of interbody fusion by promoting osteoinduction and enhancing incorporation of the allograft. Recently, in a small series of human patients undergoing anterior lumbar interbody fusion with a tapered cylindrical metal fusion cage, InFUSE Bone Graft has been shown to promote osteoinduction and fusion. Methods Forty-six patients underwent a single-level anterior lumbar discectomy and interbody fusion at five investigational sites. They were randomly assigned to one of two groups, and the results in the investigational patients who received threaded cortical allograft dowels with InFUSE Bone Graft were compared with those in the control patients who received threaded allograft dowels with autogenous iliac crest bone graft. Patients' clinical outcomes were assessed using neurologic status, work status, and Oswestry Low Back Pain Disability, Short Form-36, and back and leg pain questionnaires. Anteroposterior, lateral, flexion-extension radiographs, and computed tomography scans were used to evaluate the progression of fusion at 6, 12, and 24 months after surgery. Results All patients who received InFUSE Bone Graft showed radiographic evidence of bony induction and early incorporation of the cortical allografts. All patients in this group had fusions at 12 months that remained fused at 24 months. At 12 and 24 months, the investigational group showed higher rates of fusion and improved neurologic status and back and leg pain when compared with the control group. There were no unanticipated adverse events related to the use of InFUSE Bone Graft. Conclusion The use of InFUSE Bone Graft is a promising method of facilitating anterior intervertebral spinal fusion, decreasing pain, and improving clinical outcomes in patients who have undergone anterior lumbar fusion surgery with structural threaded cortical allograft bone dowels.

This investigation was conducted in two parts. In the first part, a morphometric analysis of critical cervical pedicle dimensions were measured to create guidelines for cervical pedicle screw fixation based on posterior cervical topography. In the second part of the study, a human cadaver model was used to assess the accuracy and safety of transpedicular screw placement in the subaxial spine using three different surgical techniques: 1) using surface landmarks established in the first part of the study, 2) using supplemental visual and tactile cues provided by performing laminoforaminotomies, and 3) using a computer-assisted surgical guidance system.To assess the accuracy of transpedicular screw placement in the cervical spine using three surgical techniques.A three-column fixation device implanted to secure an unstable cervical spine can be a valuable tool with a biomechanical advantage in the spine surgeon's armamentarium. Despite this advantage, concerns over surgical neurovascular complications have surfaced. Cadaver-based morphometric measurements used to guide the surgeon in the placement of a pedicle screw show significant variability, raising legitimate concerns as to whether transpedicular fixation can be applied safely.Precise measurements of 14 human cadaveric cervical spines were made by two independent examiners of pedicle dimensions, angulation, and offset relative to the lateral mass boundaries. On the basis of this analysis, guidelines for pedicle screw placement relative to posterior cervical topography were derived. In the second part of the study, 12 human cadaveric cervical spines were instrumented with 3.5-mm screws placed in the pedicles C3-C7 according to one of three techniques. Cortical integrity and neurovascular injury were then assessed by obtaining postoperative computed tomography scans (1-mm cuts) of each specimen. Cortical breaches were classified into critical or noncritical breaches.Linear measurements of pedicle dimensions had a wide range of values with only fair interobservercorrelation. Angular measurements showed similarangulation in the transverse plane (40 degrees ) at each level. With respect to the sagittal plane, both C3 and C4 pedicles were oriented superiorly relative to the axis of the lateral mass, whereas the C6 and C7 pedicles were oriented inferiorly. The dorsal entry point of the pedicle on the lateral mass defined by transverse and sagittal offset had similar mean values with wide ranges, although there often was excellent correlation between observers. There were no significant interlevel, right/left, or male/female differences noted with respect to offset. Using one of three techniques, 120 pedicles were instrumented. In group 1 (morphometric data): 12.5% of the screws were placed entirely within the pedicle; 21.9% had a noncritical breach; and 65. 5% had a critical breach. In group 2 (laminoforaminotomy), 45% of the screws were within the pedicle; 15.4% had a noncritical breach; and 39.6% had a critical breach. In group 3 (computer-assisted surgical guidance system), 76% of the screws were entirely within the pedicle; 13.4% had a noncritical breach; and 10.6% had a critical breach. Regardless of the technique used, the vertebral artery was the structure most likely to be injured.On the basis of the morphometric data, guidelines for cervical spine pedicle screw placement at each subaxial level were derived. Although a statistical analysis of cadaveric morphometric data obtained from the cervical spine could provide guidelines for transpedicular screw placement based on topographic landmarks, sufficient variation exists to preclude safe instrumentation without additional anatomic data. Insufficient correlation between different surgeons' assessments of surface landmarks attests to the inadequacy of screw insertion techniques in the cervical spine based on such specific topographic guide

Study design A prospective clinical study using magnetic resonance imaging of the cervical spine in a consecutive series of patients with cervical spine dislocations. Objectives To determine the incidence of intervertebral disc herniations and injury to the spinal ligaments before and after awake closed traction reduction of cervical spine dislocations. Summary of background data Prior series in which the prereduction imaging of disc herniations in the dislocated cervical spine are described have been anecdotal and have involved small numbers of patients. In addition, no uniform clinical criteria to define the presence of an intervertebral disc herniation in the dislocated cervical spine has been described. The incidence of disc herniations in the unreduced dislocated cervical spine is unknown. Methods Eleven consecutive patients with cervical spine dislocations who met the clinical criteria for an awake closed traction reduction had prereduction and postreduction magnetic resonance imaging. Using strict clinical criteria for the definition of an intervertebral disc herniation, the presence or absence of disc herniation, spinal ligament injury, and cord injury was determined. Neurologic status before, during, and after the closed reduction maneuver was documented. Results Disc herniations were identified in 2 of 11 patients before reduction. Awake closed traction reduction was successful in 9 of the 11 patients. Of the nine patients with a successful closed reduction, two had disc herniations before reduction, and five had disc herniations after reduction. No patient had neurologic worsening after attempted awake closed traction reduction. Conclusions The process of closed traction reduction appears to increase the incidence of intervertebral disc herniations. The relation of these findings, however, to the neurologic safety of awake closed traction reduction remain unclear.

Study design A prospective study to determine the long-term outcome of traumatically induced vertebral artery injuries. Magnetic resonance angiography was performed at the time of cervical injury and at a follow-up office visit. Objective To determine the long-term outcome in terms of arterial flow competency of traumatically induced vertebral artery injuries. Summary of background data Vertebral artery injury associated with cervical spine trauma has been well documented; however its healing or nonhealing potential has not been elucidated. Methods During the 7-month period from July 1993 to January 1994, all patients admitted to the authors' institution with cervical spine injuries underwent magnetic resonance imaging and magnetic resonance angiography of the cervical spine to determine the patency of their vertebral arteries. Magnetic resonance angiography was performed at the time of injury and at a follow-up office visit. Twelve of 61 patients were found to have a lack of signal flow within one of their vertebral vessels during this study period. Results Eighty-three percent of the patients (five of six) who were available for follow-up observation in this study did not manifest flow reconstitution of their vertebral arteries after an average 25.8-month follow-up period. Conclusions According to these data, most patients with vertebral artery injuries after nonpenetrating cervical spine trauma do not reconstitute flow in the injured vertebral arteries. This lack of flow must be considered if future surgery in this region of the cervical spine is contemplated.

Study design The authors of this prospective study examined the preoperative and 3-year postoperative magnetic resonance images of 14 patients undergoing anterior and posterior fusion and/or posterior fusion only for scoliosis. All magnetic resonance images were ready by two independent neuroradiologists, who were blinded to the purposes of the study, for the presence of disc narrowing, signal decrease on T2, or herniated nucleus pulposus before and after surgery. Particular attention was paid to the disc changes at the level directly below the end vertebral level of the fusion and two levels below the fusion in the lumbosacral spine existing before surgical intervention. Objectives To evaluate the potential for disc degeneration distal to long scoliosis fusions with end fusion levels in the mid to lower lumbar spine. Summary of background data The determination of end levels of fusion for contructs presently used to manage adult scoliotic deformity has been evaluated in terms of correction of curvature and late decompensation in coronal and sagittal plane balance after fusion. However, the natural history of the caudal, free-motion segments in terms of degeneration and/or correlation with pain has not yet been addressed. Methods Fourteen patients undergoing scoliosis fusion underwent magnetic resonance imaging before surgery and approximately 3 years after surgery. The scans were reviewed by two independent neuroradiologists who looked at three degenerative indices at the disc below the area of scoliosis fusion. The authors analyzed rates of change of the three degenerative indices in the pre- and postoperative magnetic resonance images and created associations between the observed changes on the magnetic resonance images and the clinical outcomes of pain, the presence or absence of solid fusion, and the need for repeat surgery. Results Estimates of the rates of change of the three degenerative indices one or two levels below the fusion were as follow: the chance of disc narrowing, .2-34%; the chance of a decreasing signal on T2, 5-54%, with a 23% incidence among this group; and the chance of herniated nucleus pulposus, 0-34%. There was a significant correlation between the presence of back and/or leg pain and the signal decrease one level below the fusion (P = .04). Conclusions If these results are corroborated in a larger sample size, surgeons who manage deformity may have to consider altering fusion levels at the time of fusion based on magnetic resonance imaging predictors. The present data may help to inform patients about the risk of developing junctional degenerative changes and potential symptoms from these changes below scoliosis fusions.

Eighty-four consecutive patients with posterolateral cervical disk herniation treated by keyhole foraminotomy between 1980 and 1987 were reviewed. Radicular pain was the most common presenting complaint Weakness was present in 59 patients. Sixty patients were available for long-term follow up, averaging 6.1 years. Fifty-six patients' results were graded as excellent. Three patients had good results and one fair result was noted. There were no poor results. Preoperative pain symptoms were relieved in all patients. There were no significant complications. The posterolateral keyhole foraminotomy is an efficient means of decompressing lateral soft disk herniations, without the risk of an anterior approach or iliac crest bone harvest. Careful patient selection and use of an operative microscope are essential in obtaining consistent, excellent results.

Anterior cervical plate instrumentation is useful in the maintenance of cervical alignment, the prevention of graft extrusion, and the development of late deformity as well as potentially avoiding the need for a secondary posterior cervical procedure in the setting of cervical trauma. Its role in cervical reconstruction after decompression for cervical spondylosis is evolving. The definite risks of anterior cervical instrumentation should be considered, that is, screw and plate displacement or screw violation of neurologic structures, before the implementation of this form of fixation.

The technique of lumbar vertebral body screw insertion is described in detail. The exposure, starting point determination, and direction of insertion are all discussed. The specifics of the use of the joystick or gear shift followed by the nuances of the insertion of the screw itself are detailed.

This issue in Seminars in Spine Surgery focuses on lumbar instability and, in particular, spinal instability potentially amenable to treatment with disc arthroplasty. In this first section, we present the classic and most current definitions of lumbar instability and relate the clinical significance of this often misunderstood spinal disorder.

A detailed review of the TJUH experience and the published literature on gunshot and stab wounds to the spine has been presented. The following statements are supported. (1) Military (high-velocity) gunshot wounds are distinct entities, and the management of these injuries cannot be carried over to civilian (low-velocity) handgun wounds. (2) Gunshot wounds with a resultant neurologic deficit are much more common than stab wounds and carry a worse prognosis. (3) Spinal infections are rare following a penetrating wound of the spine and a high index of suspicion is needed to detect them. (4) Extraspinal infections (septic complications) are much more common than spinal infections following a gunshot or stab wound to the spine. (5) Steroids are of no use in gunshot wounds to the spine. In fact, there was an increased incidence of spinal and extraspinal infections without a difference in neurologic outcome compared with those who did not receive steroids. (6) Spinal surgery is rarely indicated in the management of penetrating wounds of the spine. The recommendations for treatment at TJUH of victims of gunshot or stab wounds with a resultant neurologic deficit are as follows. (1) Spine surgery is indicated for progressive neurologic deficits and persistent cerebrospinal fluid leaks (particularly if meningitis is present), although these situations rarely occur. (2) Consider spine surgery for incomplete neurologic deficits with radiographic evidence of neural compression. Particularly in the cauda equina region, these surgeries may be technically demanding because of frequent dural violations and nerve root injuries/extrusions. These cases must be evaluated in an individual case-by-case manner. The neurologic outcomes of patients with incomplete neurologic deficits at TJUH who underwent acute spine surgery (usually for neural compression secondary to a bullet) were worse than the outcomes for the patients who did not have spine surgery. A selection bias against the patients undergoing spine surgery was likely present as these patients had evidence of ongoing neural compression. (3) A high index of suspicion is necessary to detect spinal and extraspinal infections. (4) Do not use glucorticoid steroids for gunshot wound victims. (5) Conservative (nonoperative) treatment with intravenous broad spectrum antibiotics and tetanus prophylaxis is the sole therapy indicated in the majority of patients who sustain a penetrating wound to the thoracic or lumbar spines.

Study Design. This study retrospectively reviewed the outcomes of 11 patients treated for a cervical spine injury with a tracheostomy placed before anterior cervical spine surgery. Objectives. The primary goal was to show that anterior cervical spine surgery in the setting of spinal cord injury is a viable option in patients with previous tracheostomy. Summary of Background Data. Respiratory failure after cervical cord injury commonly requires tracheostomy, possibly increasing the risk of soft tissue or bony infection in patients at high risk for morbidity after surgery. Although numerous studies have explored the risk of infection after tracheostomy or anterior cervical spine surgery, no study has been performed to explore the risk of infection in patients with previous tracheostomy at the time of anterior cervical spine surgery. Methods. A retrospective review of the clinical data of 1800 spinal cord injury patients seen from 1979 to the present at the Regional Spinal Cord Injury Center of the Delaware Valley of Thomas Jefferson University with affiliated institutions of Thomas Jefferson University Hospital and Magee Rehabilitation Hospital was performed. Eleven patients were found who had existing tracheostomy at the time of anterior cervical spine surgery. Clinical follow-up period averaged 28 months with a range of 6-51 months, and radiographic analysis averaged 7 months with a range of 1-51 months. Autogenous iliac crest graft was used in all patients, consisting of an intervertebral graft after a discectomy or a strut graft after a complete corpectomy. Anterior instrumentation was used in more than 50% of the patients. Results. After all patient interviews and review of all radiographs for evidence of infection, no patient was noted to have evidence of a cervical soft tissue or bony infection after surgery. The tracheostomy complications were minor and resolved quickly. Conclusions. the authors concluded that in patients with cervical cord damage resulting from nonpenetrating trauma, tracheostomy was not found to increase the risk of infection in subsequent anterior cervical surgery. Cereful preparation of the skin and placement of the second surgical incision lateral to the tracheostomy site is recommended. Anterior cervical spin surgey remains a viable treatment option in this severely injured patient population.

STUDY DESIGN Prospective radiographic evaluation of patients that underwent cervical total disc replacement (TDR-C) or anterior cervical discectomy and fusion (ACDF) for one-level cervical disc disease. OBJECTIVE To evaluate the following: (1) total cervical range of motion (ROM) from C2 to C7, and (2) the relative contribution to total cervical ROM from the operative level and each adjacent level after one-level TDR-C or ACDF. SUMMARY OF BACKGROUND DATA The development of symptomatic adjacent segment disease after ACDF has served as the impetus for the development of motion-preserving alternatives, most notably cervical disc arthroplasty. While previous reports have evaluated device-level and total cervical motion, no study has comprehensively quantified the relative contribution made from each of the adjacent levels to total cervical ROM in TDR-C and ACDF. METHODS Radiographic review of 187 randomized patients from a multicenter, prospective, randomized trial comparing TDR-C with ACDF for one-level cervical disc disease. There were 93 TDR-C and 94 ACDF patients included. ROM measurements were performed independently using quantitative motion analysis, a custom digitized image stabilization software program, to evaluate total cervical ROM and relative contribution to total ROM from each level from C2 to C7 preoperatively and at 24 months. RESULTS The most common operative level was C5/C6 (57%) followed by C6/C7 (34%). At 2 years, the TDR-C group underwent a statistically greater improvement in total cervical ROM (+5.9°) compared with ACDF (-0.8°, P = 0.001). In TDR-C, the relative contributions to total cervical ROM from the operative level and each caudal and cranial adjacent level were statistically equivalent from baseline to 24 months. In contrast, ACDF patients had significantly reduced contribution to total cervical ROM from the operative level (by 15%, P < 0.001), and significantly elevated contribution from the caudal adjacent level (by 5.9%, P < 0.001), first cranial adjacent level (by 3.3%, P < 0.001), second cranial adjacent level (by 5.3%, P < 0.001), and third cranial adjacent level (by 3.0%, P < 0.001). CONCLUSION Compensation for the loss of motion at the operative level in ACDF is seen throughout the unfused cervical spine. Cervical disc arthroplasty, however, increases total cervical ROM compared with ACDF and maintains a physiologic distribution of ROM throughout the cervical spine at 2 years, potentially lowering the risk for adjacent segment breakdown.

Background: Disc replacement arthroplasty previously has been shown to be an effective alternative to spine fusion for the treatment of single-level lumbar degenerative disc disease. The purpose of the present study was to determine the twenty-four-month results of a clinical trial of the ProDisc-L total disc replacement as compared with spinal fusion for the treatment of degenerative disc disease at two contiguous vertebral levels from L3 to S1. Methods: A total of 237 patients were treated in a randomized controlled trial designed as a non-inferiority study for regulatory application purposes. Blocked randomization was performed with use of a 2:1 ratio of total disc arthroplasty to circumferential arthrodesis. Evaluations, including patient self-assessments, physical and neurological examinations, and radiographic examinations, were performed preoperatively, six weeks postoperatively, and three, six, twelve, eighteen, and twenty-four months postoperatively. Results: At twenty-four months, 58.8% (eighty-seven) of 148 patients in the total disc replacement group were classified as a statistical success, compared with 47.8% (thirty-two) of sixty-seven patients in the arthrodesis group; non-inferiority was demonstrated. The mean Oswestry Disability Index in both groups significantly improved from baseline (p < 0.0001); the mean percentage improvement for the total disc replacement group was significantly better than that for the arthrodesis group (p = 0.0282). An established clinical criterion for success, a ≥15-point improvement in the Oswestry Disability Index from baseline, occurred in 73.2% (109) of 149 patients in the total disc replacement group and 59.7% (thirty-seven) of sixty-two patients in the arthrodesis group. The Short Form-36 physical component scores were significantly better for the total disc replacement group as compared with the arthrodesis group (p = 0.0141 at twenty-four months). Visual analog scale scores for satisfaction significantly favored total disc replacement from three to twenty-four months. At twenty-four months, 78.2% (111) of 142 patients in the total disc replacement group and 62.1% (thirty-six) of fifty-eight patients in the arthrodesis group responded “yes” when asked if they would have the same surgery again. Lumbar spine range of motion on radiographs averaged 7.8° at the superior disc and 6.2° at the inferior disc in patients with total disc replacement. Reduction in narcotics usage significantly favored the total disc replacement group at twenty-four months after surgery (p = 0.0020). Conclusions: Despite the relatively short duration of follow-up and design limitations, the present study suggests that two-level lumbar disc arthroplasty is an alternative to and offers clinical advantages in terms of pain relief and functional recovery in comparison with arthrodesis. Longer-term follow-up is needed to determine the risks for implant wear and/or degenerative segment changes. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

STUDY DESIGN Prospective magnetic resonance imaging (MRI) study of patients low back pain (LBP) requiring discography as part of their routine clinical diagnoses and asymptomatic age-matched volunteers. OBJECTIVE To determine whether T1ρ MRI and discography opening pressure (OP) are quantitative biomarkers of disc degeneration in LBP patients and in asymptomatic volunteers. SUMMARY OF BACKGROUND DATA Disc degenerative disease, a common cause of LBP, is related to the patient's prognosis and serves as a target for therapeutic interventions. However, there are few quantitative measures in the clinical setting. Discography OP and T1ρ MRI are potential biomarkers of disc degenerative disease related to biochemical composition of the intervertebral disc. METHODS The institutional review board approved all experiments, and informed consent was provided by each subject. Patients being treated for LBP (n = 17; 68 levels; mean age, 44 ± 6 years; and range, 30-53) and control subjects (n = 11; 44 levels; mean age, 43 ± 17 years; and range, 22-76) underwent T1ρ and T2 MRI on a Siemens 3T Tim Trio clinical scanner (Siemens Medical Solutions, Malvern, PA). The LBP patients also received multilevel provocative discography before their MRI. OP was recorded as the pressure when fluid first enters the nucleus of the intervertebral disc. RESULTS T1ρ was significantly lower in the painful discs (55.3 ± 3.0 ms, mean ± SE) from control (92.0 ± 4.9 ms, P < 0.001) and nonpainful discs (83.6 ± 3.2 ms, P < 0.001). Mean OP for the painful discs (11.8 ± 1.0 psi, mean ± SE) was significantly lower than that for nonpainful discs (19.1 ± 0.7 psi, P < 0.001). Both T1ρ and OP correlated moderately with Pfirrmann degenerative grade. Receiver-operating-characteristic area under the curve was 0.91 for T1ρ MRI and 0.84 for OP for predicting painful discs. CONCLUSION T1ρ and OP are quantitative measures of degeneration that are consistent across both control subjects and LBP patients. A significant and strong correlation exists between T1ρ values and in vivo OP measurements obtained by discography in LBP patients.

A consecutive series of 23 thoracic disc herniations in 21 patients treated between 1980 and 1988 were reviewed. All patients were decompressed through a posterolateral approach (costotransversectomy or transpedicular). Pain and weakness were the most common presenting symptoms. Twenty-one thoracic disc herniations in 19 patients were available for long-term follow-up, averaging 58.1 months. Sixteen patients had an excellent or good result. Three patients had a fair result. There were no poor results. All six patients with significant preoperative lower extremity weakness improved. Pain was relieved in 16 patients and reduced in three. There were no significant neurologic complications associated with the procedure. Posterolateral decompression for thoracic disc herniation remains a viable alternative without the inherent risk and morbidity of the transthoracic approach.

Seventeen patients were identified with concomitant thoracolumbar and sacral fractures representing 26% of sacral fractures and 7.7% of pelvic fractures. The thirteen men and four women exhibited a bimodal age distribution. There were thirteen vertical compression thoracolumbar fractures, three transverse process fractures, and one traumatic herniated nucleus pulposus. There were seven Zone I, seven Zone II, and three Zone III sacral fractures using the Denis classification. Five of the sacral fractures were missed on initial presentation. Four of the patients had neurogenic bowel or bladder symptoms. Seven of the thoracolumbar fractures and three of the sacral fractures were treated operatively. Results were generally good or excellent unless significant neurologic injury was present at initial presentation. The authors recommend aggressive computed tomographic evaluation of the sacrum in any suspicious pelvic trauma or when the neurologic lesion does not match the more proximal bony lesion. They hypothesize that decompression of both sacral and thoracolumbar lesions may be necessary if either lesion could be responsible for neurogenic bowel or bladder symptoms.

The transthoracic approach to the vertebral bodies offers the widest exposure of the anterior thoracic spine for decompression and strut graft reconstruction. The standard approach exposes T4 to T12 and modifications extend the exposure to the extreme upper thoracic and thoracolumbar junctions. Surgeons unfamiliar with this relatively uncommon approach must be thoroughly aware of its indications, preoperative evaluation, surgical technique, and potential complications before attempting it. This review details the methods we believe best limit the complications associated with transthoracic corpectomy and strut fusion.

During a 5 1/2-year period from January 1984 to July 1989, 736 patients between the ages of 50 and 75 with a diagnosis of osteoarthritis had either cemented or uncemented primary total hip arthroplasty. Patients were treated with low-dose sodium warfarin for prophylaxis against pulmonary embolism and had preoperative and postoperative serial lung scanning. The overall incidence of pulmonary embolism was not statistically different between the cemented and uncemented groups (3.87% and 6.19%, respectively; P>.05). Eighty-one percent of the pulmonary emboli were asymptomatic. The incidence of pulmonary embolism was higher in men than in women (7.3% and 2.93%, respectively; P .55). These data indicate that the use of uncemented total hip arthroplasty does not offer any additional protective value against pulmonary embolism when using low-dose sodium warfarin prophylaxis.

STUDY DESIGN Radiographic results from a prospective, randomized, multicenter trial assessing patients who underwent lumbar total disc replacement (TDR) or circumferential arthrodesis for 1-level degenerative disc disease. OBJECTIVE To quantify the relative segmental contribution to total lumbar range of motion (ROM) at the operative level at each adjacent level in lumbar TDR and arthrodesis. SUMMARY OF BACKGROUND DATA Although previous studies have evaluated ROM in TDR and fusion, no study has quantified or compared the relative segmental contribution to total lumbar ROM. Further, no study to the best of our knowledge has evaluated the kinematic profile of the more cranial adjacent segments (i.e., the second or third adjacent levels) following implantation of either TDR or fusion. METHODS Radiographic data collected from all randomized 1-level degenerative disc disease patients operated at L4/5 or L5/S1 that participated in the multicenter, prospective, randomized IDE study comparing ProDisc-L with circumferential lumbar arthrodesis were evaluated before surgery and at 24 months. Radiographic measurements were performed independently using custom digitized image stabilization software to generate ROM at the operative level, and at each cranial and caudal adjacent level. RESULTS There were 200 total patients included (155 ProDisc-L, average age 39 years; 45 arthrodesis, average age 40 years). At 24 months, the L4/5 TDR group experienced a significant improvement in total lumbar ROM from baseline (+6.3 degrees ), whereas there was no change seen with L5/S1 TDR or any fusion group. Between-group comparisons from baseline to 24 months postoperatively revealed: (1) significantly more contribution from the operative level towards total lumbar range in TDR at operative level L4/5 (TDR: -2.5%, fusion: -16.8%, P = 0.006), and operative level L5/S1 (TDR: -5.1%, fusion: -15.9%, P < 0.001), and (2) the relative contribution towards total lumbar range of motion from the first cranial adjacent segment to fusion at L5/S1 increased by 12.1%, compared with -1.2% seen in TDR (P = 0.03). There were elevated contributions from the more cranial adjacent levels to a fusion when compared with TDR, however, these differences were not statistically significant. At operative level L4/5, there was significantly increased ROM from the first caudal segment below TDR (6%, P = 0.03), but not below fusion (3.1%, P = 0.59). CONCLUSION In conclusion, patients with TDR lost slight relative contribution to total lumbar motion from the operative level which was mostly compensated for by the caudal adjacent level (if operated at L4/5). In contrast, the significant loss of relative range of motion contribution from the operative level in fusions was redistributed among multiple cranial adjacent levels, most notably at the first cranial adjacent level.

Seventy-two joint arthroplasties undergoing total hip or total knee surgery were studied prospectively with plain radiographs, three-phase bone imaging (3PBI), erythrocyte sedimentation rate (ESR), aspiration of the joint for culture, and multiple intraoperative cultures at the time of revision. Intraoperative cultures and the operative appearance were used to form a diagnosis of definite infection (unequivocal microbiology and gross sepsis), possible infection (positive microbiology or gross sepsis), or no infection (neither positive microbiology nor gross sepsis). For the preoperative diagnosis of infection, as opposed to aseptic loosening, 3PBI alone had a sensitivity of 33% and a specificity of 86%. In conjunction with plain radiographs, minimal improvement in accuracy was seen. A preoperative ESR greater than 30 had low sensitivity (60%) and a specificity of (65%). However, the ESR was statistically significantly higher in the joints with definite infection as compared to those joints without infection. The preoperative joint aspiration had a sensitivity of 67% and a specificity of 96% and, therefore, appears to be the most useful single test in the workup of a painful total joint arthroplasty.

Femoral neuropathy is an uncommon yet debilitating complication of total hip arthroplasty (THA). Over a 1-year period, in 440 consecutive THAs performed at Pennsylvania Hospital, 10 (2.3%) femoral neuropathies occurred. Among primary arthroplasties, all neuropathies were associated with the Hardinge anterolateral approach. A retrospective case review as well as a detailed anatomic cadaveric study highlighted the characteristics of the femoral nerve that make it susceptible to injury. In addition, a review of the existing literature on this subject was performed. Placement and management of acetabular retractors were the factors most commonly associated with injury of the femoral nerve. All affected patients had significant initial disability. However, full femoral nerve. All affected patients had significant initial disability. However, full functional recovery occurred within 1 postoperative year. Clear understanding and awareness of the anatomy of the femoral triangle as well as accurate placement of anterior acetabular retractors can minimize the incidence of this complication.

Survivorship analysis of 1,041 cemented Charnley total hip arthroplasties performed as a primary procedure revealed a probability of component survival at 10 years of 92%; the probability of acetabular cup survival was 99% and of femoral component survival was 96%. Three-zone acetabular demarcation was present in 16% of cases, as was migration of the cup greater than 5 mm. However, the acetabular revision rate was 1.65%, confirming the long-term clinical durability of the 22-mm internal diameter cup. Radiographic evidence of definite femoral component loosening was present in 9.6% and high-grade femoral bone-cement demarcation was present in 3.5%. The isolated femoral revision rate was 1.8%. Based on detailed survivorship analysis, a high-risk group of patients was identified for component failure and for femoral component loosening (radiographic). These patients were male, young (less than 50 years), heavy (greater than 170 pounds), and active (not Charnley class C). Given these findings, it is difficult to justify the widespread use of noncemented total hip systems, except in identifiable high-risk patients.

Endplate subsidence and vertebral body (VB) fracture are potential complications following lumbar total disc replacement (TDR) [1]. Early clinical evidence suggests that these events can be ameliorated in patients with osteopenia and osteoporosis by vertebral augmentation performed at the time of TDR [2]. However, the biomechanical basis to support vertebral augmentation of TDR has not been established. The objective of this study was to quantify the effects of vertebral augmentation with Cortoss on VB mechanics under compression by a TDR implant. We hypothesize that augmentation with Cortoss will improve the mechanical behavior in compression.Copyright © 2007 by ASME

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.

Fourteen consecutive patients with a diagnosis of isthmic spondylolisthesis (grade I and II) underwent provocative lumbar diskography (L2-S1) to evaluate the disk adjacent to the spondylolisthesis. Seven (50%) of 1 4 patients had concordant pain at the disk above the slip and 2 patients had no pain at the slip level. Surgical treatment included anteroposterior fusion of the slip level and any adjacent concordant levels. Clinical results included 3 excellent, 7 good, 2 fair, and 1 poor outcome. This data supports the hypothesis that the disk adjacent to an isthmic slip is predisposed to symptomatic degeneration 1 in the adult patient with axial pain. It does not prove that a fusion is indicated or that clinical outcomes would be improved with this approach.

The incidence of acute herniated nucleus pulposus was determined in 55 patients with cervical spine trauma. A standardized protocol and a 1.5-T magnetic resonance image scanner was used to document a 42% incidence of acute herniated nucleus pulposus in patients studied within 72 hours of injury. The incidence of herniated nucleus pulposus was correlated with the patients' presenting neurologic status and mechanism of injury. The incidence of herniated nucleus pulposus was highest in patients with bilateral facet dislocations (80%) and anterior cord syndromes (100%). There was no statistically significant correlation between the incidence of herniated nucleus pulposus and patients' age or sex.

Between 1983 and 1988, 182 total hip arthroplastics were inserted using modern cement techniques including metal-backed acetabular components. Femoral head size was 32 mm in 84, 22 mm in 98. Radiographic analysis revealed three-zone demarcation of acetabular bone-cement interface in 56% of the 32 mm group as compared to 5% of the 22 mm group at 19 and 24 months mean follow-up period, respectively. When a subgroup of women under 60 years of age was created to control variables, the high-grade demarcation rates were 67% and 18%, respectively. Although Charnley hip scores remain similar between the two groups, these results emphasize the adverse effects of large femoral head prostheses on cement-bone interface and underline the need for alternative methods of fixation