Prevention of vertebral body-splitting fractures after multilevel ProDisc-L implantation.

BACKGROUND: Prior studies of multilevel ProDisc-L (PD-L) implants (Synthes Spine, Inc., West Chester, Pennsylvania) using the standard US technique have used conventional radiography postoperatively. We found vertebral body-splitting fractures (VB-SFs) in interposed vertebral bodies after 5 sequential multilevel PD-L device implantations using the standard US technique. These were identified with postoperative computed tomography (CT) but were not visible on plain radiographs. In an additional patient, we found that a stress-relieving, pilot holes-only technique did not prevent VB-SFs. The 5 patients operated on with the standard technique composed the background series against which we compared the incidence of VB-SFs in patients operated on with a modification of the standard US technique-a combination of stress-relieving pilot holes, removal of cortex in the chisel path, and a fenestrated chisel (PH/CR/FC)-intended to reduce the incidence of VB-SFs in multilevel PD-L constructs. METHODS: Patients receiving multilevel PD-L implants at 2 sites-1 in the United States and the other in Germany-were operated on with the PH/CR/FC technique and their postoperative CT scans evaluated for the presence of VB-SFs. The frequency of VB-SFs in these patients was compared with that of the 5 patients from the background series who were operated on by the standard US technique. The groups' mean sex, age, body mass index, and vertebral body height, as well as average spinal T score, were also compared. RESULTS: No fractures were found in 13 interposed vertebral bodies in 11 patients operated on with the PH/CR/FC technique, as compared with 4 VB-SFs and 1 anterior keel cut-to-anterior keel cut fracture in 5 interposed vertebral bodies in 5 patients operated on with the US technique (P ≤ .001). Although the sample sizes were small, this difference in fracture rate was not associated with sex, age, body mass index, or average spinal T score. At up to 13 months of follow-up of patients in the background series, we found that VB-SFs tend not to bridge with bone, instead forming sclerotic margins. CONCLUSIONS: The PH/CR/FC technique studied reduced the incidence of VB-SF in multilevel PD-L implants. Because previously published multilevel studies did not use postoperative CT scans and because VB-SFs are not visible on conventional radiography, the incidence of VB-SFs in multilevel PD-L applications may be higher than previously reported. Our findings may contribute to prevention of complications in total disc replacement.

ProDisc-C: an in vivo kinematic study.

STUDY DESIGN: A prospective study of 22 patients with single-level cervical spondylosis. OBJECTIVE: To quantify the changes in the biomechanics of the cervical spine after the insertion of a ProDisc-C (Synthes Spine, Paoli, PA) artificial disc. SUMMARY OF BACKGROUND DATA: Cervical arthroplasty is designed to maintain cervical motion of the functional spinal unit (FSU) after cervical discectomy. The impact of the ProDisc-C on in vivo kinematics and sagittal alignment requires further assessment. METHODS: Flexion/extension lateral radiographs of the cervical spine were prospectively collected and reviewed in 22 patients preoperatively and after the placement of ProDisc-C. Disc height (DH), FSU angle, range of motion (ROM), and center of rotation (COR) were calculated at each time point using validated, computer-assisted methods. Preoperative values were compared with the postoperative values using paired student t tests. RESULTS: Mean follow-up time was 11.0 months (SD, 2.4 mo). At the surgical level, the ProDisc-C produced increased segmental ROM (P = 0.03), an anterior shift of 1.1 mm in COR X (P = 0.004), and increased DH both anteriorly (P < 0.0001) and posteriorly (P < 0.0001). At the inferior adjacent level, anterior DH decreased (P < 0.05) and posterior DH increased (P = 0.02) after surgery. The FSU angle at the surgical level increased (P < 0.0001), but the inferior adjacent-level FSU angle decreased (P = 0.002). No significant changes were observed at the superior adjacent level. CONCLUSIONS: The ProDisc-C increased segmental ROM and shifted the COR anteriorly at the surgical level. DH increased at the surgical level. The surgical level became more lordotic, whereas the inferior adjacent level became more kyphotic after ProDisc-C implantation.

Augmentation improves human cadaveric vertebral body compression mechanics for lumbar total disc replacement.

STUDY DESIGN: Cadaveric biomechanical study. OBJECTIVE: To quantify the effects of vertebral body augmentation on biomechanics under axial compression by a total disc replacement (TDR) implant. SUMMARY OF BACKGROUND DATA: TDR is a surgical alternative to lumbar spinal fusion to treat degenerative disc disease. Osteoporosis in the adjacent vertebrae to the interposed TDR may lead to implant subsidence or vertebral body fracture. Vertebral augmentation is used to treat osteoporotic compression fracture. This study sought to evaluate whether vertebral augmentation improves biomechanics under TDR axial loading. METHODS: Forty-five L1-L5 lumbar vertebral body segments with intact posterior elements were used. Peripheral quantitative computed tomography scans were performed to determine bone density, and specimens were block-randomized by bone density into augmentation and control groups. A semiconstrained keeled lumbar disc replacement device was implanted, providing 50% endplate coverage. Vertebral augmentation of 17.6% +/- 0.9% vertebral volume fill with Cortoss was performed on the augmentation group. All segments underwent axial compression at a rate of 0.2 mm/s to 6 mm. RESULTS: The load-displacement response for all specimens was nonlinear. Subfailure mechanical properties with augmentation were significantly different from control; in all cases, the augmented group was 2 times higher than control. At failure, the maximum load and stiffness with augmentation was not significantly different from control. The maximum apparent stress and modulus with augmentation were 2 times and 1.3 times greater than control, respectively. The subfailure stress and apparent modulus with augmentation were moderately correlated with bone density whereas the control subfailure properties were not. The augmented maximum stress was not correlated with bone density, whereas the control was weakly correlated. The maximum apparent modulus was moderately correlated with bone density for both the augmented and the control groups. CONCLUSION: Augmentation improved the mechanical properties of the lumbar vertebral body for compression by a TDR implant.

Sagittal balance influences range of motion: an in vivo study with the ProDisc-C.

BACKGROUND CONTEXT: Cervical arthroplasty is designed to maintain cervical motion of the functional spinal unit after cervical discectomy. The impact of the ProDisc-C (Synthes Spine, Paoli, PA) on in vivo kinematics and sagittal alignment requires further assessment. PURPOSE: The purpose of this study is to test the hypothesis that the ProDisc-C increases range of motion (ROM) in flexion and extension at the surgical level, and assess its impact on cervical alignment. STUDY DESIGN: Clinical study. PATIENT SAMPLE: Fifteen patients with a mean age of 49 years were included in this study. Each patient had a single-level arthroplasty. Patients with multilevel arthroplasty, previous cervical spine surgery, and length of follow-up less than 6 months were excluded from this study. OUTCOME MEASURE: Lateral dynamic radiographs of the cervical spine were analyzed using quantitative measurement analysis (QMA) preoperatively and postoperatively. QMA software was also used to determine the ROM and sagittal translation at the surgical level. METHODS: Flexion/extension lateral radiographs of the cervical spine were prospectively collected and reviewed in 15 patients preoperatively and at early (1-3 months) and late (6-14 months) follow-up after placement of the ProDisc-C. Shell angle (SA) and C2-C7 Cobb angles were measured. Sagittal translation and ROM were calculated at each time point. Preoperative values were compared with early and late follow-up values using paired Student t tests and Pearson's correlation. RESULTS: The C2-C7 Cobb angle did not change significantly after surgery. Segmental ROM increased significantly from neutral to flexion (p=.02) and neutral to extension (p=.002) at late follow-up. SA correlated significantly with ROM from neutral to extension (Pearson's r=-0.55; p=.02) and translation from neutral to extension (Pearson's r=-0.58; p=.02). CONCLUSIONS: The ProDisc-C increased overall segmental ROM. A lordotic SA may be associated with restricted segmental ROM and translation in extension. This study did not detect any change in overall cervical spinal alignment after insertion of the device.

Does vertebral endplate morphology influence outcomes in lumbar disc arthroplasty? Part I: an initial assessment of a novel classification system of lumbar endplate morphology.

BACKGROUND: The influence of lumbar endplate morphology on the clinical and radiographic outcomes of lumbar disc arthroplasty has not been evaluated to the best of our knowledge. STUDY DESIGN AND OBJECTIVE: In this observational study of 80 patients, the objective was to formulate a reproducible and valid lumbar endplate classification system to be used in evaluating lumbar total disc replacement patients. METHODS: A novel vertebral endplate morphology classification system was formulated after review of data related to 80 patients enrolled in a prospective, randomized clinical trial in conjunction with an application for a US Food and Drug Administration investigational device exemption. Intraobserver and interobserver analyses of the classification system were performed on the same 80 patients utilizing the classification system. RESULTS: The initial review of the radiographs revealed 5 types of endplates: Type I (n = 82) flat endplates; Type II (n = 26) posterior lip; Type III (n = 5) central concavity; Type IV (n = 4) anterior sloping endplate; and Type V (n = 2) combination of Types I-IV. The intraobserver kappa was 0.66 and the interobserver kappa was 0.51. These kappa values indicate "substantial" to "moderate" reproducibility, respectively. CONCLUSIONS: In this study, we propose a lumbar endplate classification system to be used in the preoperative assessment of patients undergoing lumbar disc arthroplasty. The classification can function as a basis for comparison and discussion among arthroplasty clinicians, and serve as a possible exclusionary screening tool for disc arthroplasty. Special consideration should be given to Type II endplates to optimize proper positioning and functioning of a total disc replacement (TDR) implant. Further outcome studies are warranted to assess the clinical significance of this classification system. The key points of our study are: (1) We present a novel lumbar vertebral endplate classification system; (2) Five types of endplates were identified and classified; (3) Intraobserver and interobserver reliability were classified as substantial and moderate, respectively; and (4) The classification system used may assist in the preoperative evaluation of patients for total disc replacement. LEVEL OF EVIDENCE: A systematic review of cohort studies (level 2a).

Does Vertebral Endplate Morphology Influence Outcomes in Lumbar Total Disc Arthroplasty? Part II: Clinical and Radiographic Results as Evaluated Utilizing the Vertebral Endplate Yue-Bertagnoli (VEYBR) Classification.

STUDY DESIGN: This study was a prospective study with a minimum patient follow-up of 2 years. Objective The purpose of this study was to evaluate the clinical usefulness of a vertebral endplate classification system (VEYBR) in predicting outcomes following lumbar arthroplasty. BACKGROUND: In the present study, our previously described endplate classification system was evaluated to determine its clinical usefulness in patients undergoing lumbar arthroplasty. METHODS: The patient cohort in this study consisted of 80 patients who had been enrolled in the US FDA ProDisc clinical trial. Radiographs were classified using the VEYBR classification. The preoperative categories (Types I to V) were then correlated with the patients' visual analogue scores (VAS) and Oswestry Disability Index (ODI) scores and radiographic outcomes at an average follow-up point of 28 months. RESULTS: The rank order of total change in VAS based on preoperative VEYBR classification was Type IV, III, I II, and V, with Type IV having the greatest improvement in VAS and Type V having the least improvement. The rank order of total change in ODI was Type IV, II, III, I, and V. We found no differences in clinical outcomes among the 5 vertebral endplate types. Type II endplates had least optimal sagittal positioning. CONCLUSIONS: Although not statistically significant, there was a strong trend for Type V endplates to have the least improvements in VAS and Oswestry clinical outcome scores. Knowledge and use of the endplate classification system did lead to consistent implant placement across endplate classes which may indicate the usefulness of this classification system in preoperative planning, especially for physicians in the "learning curve" phase of this procedure. LEVEL OF EVIDENCE: Case series (Level IV).

Lumbar total disc arthroplasty utilizing the ProDisc prosthesis in smokers versus nonsmokers: a prospective study with 2-year minimum follow-up.

STUDY DESIGN: Prospective nonrandomized clinical series. OBJECTIVES: To evaluate the efficacy of ProDisc lumbar artificial disc replacement (ADR) in smokers versus nonsmokers. SUMMARY OF BACKGROUND DATA: Smoking is a negative predictor in fusion surgery. To date, a prospective study of the treatment of incapacitating discogenic low back pain using ADR in smokers versus nonsmokers has not been described. METHODS: A prospective analysis was performed on 104 patients with disabling discogenic low back pain treated with single-level lumbar ProDisc total disc arthroplasty. Smokers and nonsmokers were assessed before surgery and after surgery using patient satisfaction, Oswestry, and Visual Analog Scores. Additionally, preoperative and postoperative neurologic, radiographic, and pain medication assessments were performed at similar postoperative intervals. RESULTS: Oswestry, Visual Analog Scores, and patient satisfaction scores revealed statistical improvement beginning 3 months after surgery and were maintained at minimum 2-year follow-up. Patient satisfaction scores were higher in smokers (94%) than in nonsmokers (87%) at 2-year follow-up (P = 0.07). Radiographic analysis revealed an affected disc height increase from 4 mm to 13 mm (P < 0.05) and an affected disc motion from 3 degrees to 7 degrees (P < 0.05). No cases of loosening, dislodgment, mechanical failure, infection, or fusion of the affected segment occurred. CONCLUSIONS: The results of our study indicate that smokers do equally well compared with nonsmokers when ProDisc ADR is used in the treatment of debilitating lumbar spondylosis. Patient outcome and radiographic scores showed significant improvement compared with preoperative levels. Although not evident in our series, additional surveillance for intraoperative and postoperative vascular spasm and occlusion may be warranted in smokers.

Treatment of symptomatic adjacent-segment degeneration after lumbar fusion with total disc arthroplasty by using the prodisc prosthesis: a prospective study with 2-year minimum follow up.

OBJECT: The authors conducted a prospective longitudinal study to assess the efficacy of ProDisc arthroplasty in patients in whom symptomatic adjacent-segment degeneration has developed after remote lumbar fusion. The follow-up period was a minimum of 2 years. METHODS: The 20 patients in this study ranged in age from 18 to 67 years. They presented with disabling adjacent-level discogenic low-back pain with or without L1-S1 radicular pain. Patients with radiographic evidence of circumferential spinal stenosis or facet joint degeneration had been excluded. Patients were assessed preoperatively and postoperatively at 3, 6, 12, and 24 months. Eighteen patients (90%) fulfilled all follow-up criteria. The median age of all patients was 50 years. Statistical improvements in visual analog scale, Oswestry Disability Index, and patient satisfaction scores were documented 3 months after arthroplasty. These improvements remained at the 24-month follow-up examinations. Patient satisfaction rates were 86% at 24 months. Radicular pain was also significantly decreased. No additional surgeries were necessary at affected or unaffected levels. CONCLUSIONS: Analysis of early results indicates that ProDisc lumbar total disc arthroplasty is an efficacious treatment for symptomatic adjacent-segment lumbar discogenic low-back pain following remote fusion. Significant improvements in patient satisfaction and disability scores were observed by 3 months postoperatively and were maintained at the 2-year follow-up examination. No device-related complications occurred. Patients should be screened carefully for evidence of facet joint impingement/degeneration, hardware-induced pain, and/or nonunion at prior fusion levels before undergoing disc replacement surgery.

Lumbar total disc arthroplasty in patients older than 60 years of age: a prospective study of the ProDisc prosthesis with 2-year minimum follow-up period.

OBJECT: The authors conducted a prospective longitudinal study to obtain outcome (minimum follow-up period 2 years) regarding the safety and efficacy of single-level lumbar disc (ProDisc prosthesis) replacement in patients 60 years of age or older. METHODS: This prospective analysis involved 22 patients treated in whom the lumbar ProDisc prosthesis was used for total disc arthroplasty. All patients presented with disabling discogenic low-back pain (LBP) with or without radicular pain. The involved segments ranged from L-2 to S-1. Patients in whom there was no evidence of radiographic circumferential spinal stenosis and with minimal or no facet joint degeneration were included. Patients were assessed preoperatively and outcome was evaluated postoperatively at 3, 6, 12, and 24 months by administration of standardized tests (the visual analog scale [VAS], Oswestry Disability Index [ODI], and patient satisfaction). Secondary parameters included analysis of pre- and postoperative radiographic results of disc height at the affected level, adjacent-level disc height and motion, and complications. Twenty-two (100%) fulfilled all follow-up criteria. The median age of all patients was 63 years (range 61-71 years). There were 17 single-level cases, four two-level cases, and one three-level case. Statistical improvements in VAS, ODI, and patient satisfaction scores were observed at 3 months postoperatively. These improvements were maintained at 24-month follow-up examination. Patient satisfaction rates were 94% at 24 months (compared with 95% reported in a previously reported ProDisc study). Radicular pain also decreased significantly. Patients in whom bone mineral density was decreased underwent same-session vertebroplasty following implantation of the ProDisc device(s). There were two cases involving neurological deterioration: unilateral foot drop and loss of proprioception and vibration in one patient and unilateral foot drop in another patient. Both deficits occurred in patients in whom there was evidence preoperatively of circumferential spinal stenosis. There were two cases of implant subsidence and no thromboembolic phenomena. CONCLUSIONS: Significant improvements in patient satisfaction and ODI scores were observed by 3 months postoperatively and these improvements were maintained at the 2-year follow-up examination. Although the authors' early results indicate that the use of ProDisc lumbar total disc arthroplasty in patients older than 60 years of age reduces chronic LBP and improves clinical functional outcomes, they recommend the judicious use of artificial disc replacement in this age group. Until further findings are reported, the authors cautiously recommend the use of artificial disc replacement in the treatment of chronic discogenic LBP in patients older than age 60 years in whom bone quality is adequate in the absence of circumferential spinal stenosis.

Mechanical testing of a novel hydrogel nucleus replacement implant.

BACKGROUND CONTEXT: Both total disc and nucleus replacement arthroplastic approaches are emerging as viable treatment modalities for discogenic pain resulting from degenerative disc disease. The results of the testing in this investigation show that this novel nucleus replacement implant exhibits physical and mechanical properties which make it uniquely suitable as a replacement to the degenerated nucleus pulposus. PURPOSE: The purpose of this investigation was to evaluate key performance characteristics of a novel nucleus replacement device. STUDY DESIGN: Mechanical tests were performed to evaluate essential properties of the implant. Of key importance was the ability of the implant to withstand fatigue testing and resist extrusion in cadaveric motion segments. Resistance of the implant to radial deformation is also relevant to the ability of the implant to resist extrusion and maintain disc height. METHODS: Resistance to radial bulging was demonstrated by applying axial compressive loads while examining the "footprint" of the implant through a clear plexiglass lower platen. A NeuDisc implant was compared with an isotropic implant produced from the same hydrolyzed polyacrylonitrile hydrogel. Confined compression tests were used to determine "lifting force" when implants were loaded within stainless steel cylinders submerged in Hanks' balanced salt solution. Fatigue tests involved loading for 10 million cycles. Implants were then examined for physical damage, retention of mechanical properties, and for the ability of the device to return to a complete level of hydration. The final evaluation was extrusion testing in a cadaveric model. Implanted specimens were either tested in compression, lateral bending, or flexion until catastrophic failure was apparent. RESULTS: The NeuDisc implant showed considerably less "bulging" when compared with the identically sized isotropic device. Confined compression testing revealed a lifting force of 400 N at 70% hydration for these hydrogel implants. After fatigue testing, all implants were physically intact and possessed similar swelling characteristics to control samples. In cadaver testing, mean force to failure in compression was 3581.3+/-1558.5 N. Mean moment to failure in lateral bending was 25.6+/-11.1 Nm. In flexion tests, the mean moment to failure was 52.2+/-18.3 Nm. End plate fracture and ligament failure were the most commonly observed failure modes. CONCLUSIONS: These initial results suggest that this novel implant may prove to be a suitable nucleus pulposus substitute.

The treatment of disabling multilevel lumbar discogenic low back pain with total disc arthroplasty utilizing the ProDisc prosthesis: a prospective study with 2-year minimum follow-up.

STUDY DESIGN: Prospective, longitudinal minimum 2-year follow-up. OBJECTIVE: To assess the efficacy and safety of the Prodisc implant in patients with disabling multilevel discogenic low back pain (LBP). SUMMARY OF BACKGROUND DATA: Few, if any, alternatives have been proposed to treat recalcitrant and debilitating multilevel lumbar discogenic low back pain. To date, a prospective study specifically examining the use of multilevel Prodisc total disc arthroplasty has not been described. METHODS: A prospective analysis was performed on 25 patients (63 prostheses) treated with multilevel lumbar ProDisc total disc arthroplasty. Minimum follow-up was 2 years. Patients 18 to 60 years of age with disabling discogenic low back pain and minimal radicular pain secondary to multiple level lumbar spondylosis from L1 to S1 were included. Preoperative and postoperative disability and pain scores were measured using Oswestry and visual analog scores. Preoperative and postoperative neurologic, radiographic, and pain medication assessments were also performed at similar postoperative intervals. RESULTS: A total of 29 patients (72 prostheses) were enrolled in the prospective analysis. Twenty-five patients (63 prostheses) fulfilled all follow-up criteria and are included for final analysis. Fifteen bisegmental and 10 trisegmental level cases were performed. Visual analog pain, Oswestry, and patient satisfaction scores were significantly reduced at the 3-month as well as at 48-month follow-up. Radiographic analysis revealed an affected disc height increases from 5 mm to 12 mm (P < 0.05) and affected disc motions from 3 degrees to 7 degrees (P < 0.05). No change in adjacent level disc heights was seen. Complications included a single case of subsidence of the inferior endplate of the L4-L5 segment in a bisegmental L4-L5/L5-S1 case. We also report a delayed case of anterior extrusion of a polyethylene component in a patient who had sustained a fall of a bicycle. CONCLUSIONS: Our preliminary data on multisegmental ProDisc lumbar total disc arthroplasty appear to be a safe and efficacious treatment method for debilitating lumbar spondylosis without significant facet arthropathy. In our select (non-Workers Compensation and/or medical legal) cohort of patients, we demonstrate a patient satisfaction rate of 93%. Careful and appropriate patient selection is essential in ensuring optimal surgical outcomes.

The treatment of disabling single-level lumbar discogenic low back pain with total disc arthroplasty utilizing the Prodisc prosthesis: a prospective study with 2-year minimum follow-up.

STUDY DESIGN: Prospective, longitudinal minimum 2-year follow-up. OBJECTIVE: To assess the efficacy and safety of the Prodisc implant in patients with disabling single-level discogenic low back pain (LBP). SUMMARY OF BACKGROUND DATA: The treatment of debilitating discogenic LBP has been controversial and varied. To date, a longitudinal prospective study of the treatment of single-level incapacitating discogenic LBP using the Prodisc total disc arthroplasty technique has not been described. METHODS: A prospective analysis was performed on 118 patients treated with single-level lumbar Prodisc total disc arthroplasty. Patients 18 to 60 years of age with disabling and recalcitrant discogenic LBP with or without radicular pain secondary to single-level discogenic LBP from L3 to S1 were included. Patients were assessed before surgery, and outcome measurements were after surgery administered at 3, 6, 12, and 24 months. RESULTS: A total of 104 patients (88%) fulfilled all follow-up criteria. The median age of all patients was 47 years (range, 36-60 years). Statistical improvements in VAS, Oswestry, and patient satisfaction scores occurred 3 months postoperatively. These improvements were maintained at the 24-month follow-up. Radicular pain also decreased significantly. Full-time and part-time work rates increased from 10% to 35% and 3% to 24%, respectively. No additional fusion surgeries were necessary either at the affected or unaffected levels. Radiographic analysis revealed an affected disc height increase from 4 mm to 13 mm (P < 0.001) and an affected disc motion from 3 degrees to 7 degrees (P < 0.004). CONCLUSIONS: Single-level Prodisc lumbar total disc arthroplasty is a safe and efficacious treatment method for debilitating lumbar discogenic LBP. Significant improvements in patient satisfaction and disability scores occurred after surgery by 3 months and were maintained at the 2-year follow-up. No device-related complications occurred. Patients with severe to moderate disc height loss as well as those with symptomatic posterior anular defects with minimal disc height loss achieve functional gains and significant pain relief. Careful and appropriate patient selection is essential in ensuring optimal surgical outcomes.

Clinical results of an open prospective study of a bis-GMA composite in percutaneous vertebral augmentation.

In this open prospective trial, 53 patients with acute pain from osteoporotic vertebral fracture related to osteoporosis or malignancy underwent vertebral augmentation with a new bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss, Orthovita, Malvern, Pa, USA). Treatment consisted of up to 8 ml of Cortoss injected into a given vertebra. The procedure encompassed single and multiple injections (including the contralateral hemivertebra, to a maximum of 3 vertebral levels). Follow-up was at 4 and 8 days and at 1, 3, and 6 months. The primary efficacy end point was patient-rated pain using a 100-point visual analog scale (VAS, with 100 as severest pain) on day 4 following treatment; secondary end points were analgesic use and quality-of-life and disability scores from the Oswestry Disability Index (ODI) and a short-form 12-item questionnaire (SF-12). The present report contains interim results collected up to the 1-month post-treatment time point. At baseline, the group's mean VAS score was 69, indicating moderate to severe pain; at day 4, 32 of 53 patients (60.4%) reported a 30% or greater reduction in baseline pain accompanied by a VAS pain score less than 50 (mean 38.1). Pain reduction was maintained at 1 month (mean VAS 31.3). The average ODI score at baseline was 55, suggesting significant disability among participants prior to Cortoss treatment. Following treatment, the ODI scores were significantly reduced from these baseline levels (day 8, 47.4; 1 month, 33.6). Further, SF-12 physical and mental component scores at 1 month after treatment increased from baseline by 26% and 11%, respectively; while analgesic use decreased concomitantly, primarily among patients with underlying osteoporosis. A total of 20 adverse events were deemed to be device-related. The most frequent clinically significant adverse events attributed to Cortoss were leakage of Cortoss from within the vertebral body at placement (12%), back pain (7%), and unspecified pain (7%). These results indicate that vertebral augmentation with Cortoss rapidly reduces pain, decreases disability, and improves physical functioning in patients with painful vertebral compression fractures.

Standard and minimally invasive approaches to the spine.

With the advent of minimally invasive surgical approaches to the spine, the ability to adequately expose the desired anatomic structures while minimizing the disadvantages of excessive soft tissue stripping, dissection, and prolonged retraction has become increasingly popular. A minimally invasive one- or two-level posterior exposure of the spine is now safely attainable with the latest minimal-access systems that exploit the biomechanics of an adjustable blade retractor. As the clinical use of these developing systems escalates, more outcomes data will become available to determine the safety and value of these minimally invasive procedures.

Lumbar partial disc replacement.

On the basis of the anatomy of the disc, the nucleus as pain generator and the resulting treatment possibility using nucleus replacement technologies are reviewed. Various devices are presented, from the first historical steps to treatment possibilities in the future. Clinical experiences of the widely-used PDN prosthetic device are analyzed.

Cervical total disc replacement, part two: clinical results.

This article focuses on the clinical results of three prostheses (the Bryan Cervical Disc, the Bristol Disc, and the ProDisc-C) for cervical total disc replacement. Background on the development, design, and biomechanical characteristics of each prosthesis is given and surgical indications and clinical results are summarized and analyzed.

Hybrid constructs.

Hybrid constructs can combine motion-preserving technologies with each other or motion-preserving technologies with fusion techniques. Hybrid constructs can be implanted in single-stage or multistage surgeries. Early results are promising. Further study under formal scientific conditions is necessary to explore the benefit of these combinations.

Complications and strategies for revision surgery in total disc replacement.

Spinal arthroplasty is an acceptable alternative to fusion in many cases of disabling degenerative disc disease. Although arthroplasty has been demonstrated to be a safe and efficacious surgical option, complications related to the approach or the device may occur in few cases. Revision strategies for failed total disc arthroplasty can be planned as a posterior fusion, leaving the total disc replacement device in place, or by way of anterior removal with subsequent anterior fusion or revision replacement of the prosthesis.

Early results after ProDisc-C cervical disc replacement.

OBJECT: Cervical anterior decompression and total-disc replacement is currently being investigated as an alternative treatment in patients with symptomatic intervertebral cervical spondylosis with and without radiculopathy. The authors prospectively investigated the safety and efficacy of using the ProDisc-C disc for cervical arthroplasty in the treatment of symptomatic cervical spondylosis. METHODS: Sixteen patients in whom a diagnosis of symptomatic cervical spondylosis had been established were prospectively treated with complete anterior cervical discectomy and ProDisc-C cervical disc arthroplasty. Overall 12 single- and four two-level procedures were performed (20 prostheses). Patients underwent pre- and multiple postoperative assessments (3 and 6 weeks and 3, 6, and 12 months). The median age of all patients was 50 years (range 32-60 years). Levels of surgery included seven C5-6, six C6-7, and three C4-5. Neck and arm pain as well as disability scores were significantly improved by 3 months and remained significantly improved at 1 year. No additional fusion surgeries were necessary at the affected or unaffected levels. Radiography revealed an affected disc motion from 4 to 12 degrees. No surgery- or device-related complications were documented. CONCLUSIONS: Analysis of preliminary results involving ProDisc-C arthroplasty indicates significant improvement in pain and functional outcome scores. No spontaneous fusions at the level of surgery or at adjacent levels were noted. Long-term follow-up studies will be necessary before more definitive treatment recommendations can be formulated.