Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five L2-3, five L4-5) were tested. From each cadaver spine, one motion segment was fixed with a pair of cylindrical cages (BAK, Sulzer Medica) and the other with paired rectangular cages (Rotafix, Corin Spinal). Each specimen was tested in an unconstrained state, after cage introduction and after additional posterior translaminar screw fixation. The range of motion (ROM) in flexion-extension, lateral bending, and rotation was tested in a materials testing machine, with +/- 5 Nm cyclical load over 10 sec per cycle; data from the third cycle was captured for analysis. RESULTS: ROM in all directions was significantly reduced (p < 0.05) with both types of cages. There was no significant difference in reduction of ROM in flexion-extension (p = 0.6) and rotation (p = 0.92) between the two cage groups, but stability in lateral bending was marginally superior with the rectangular cages (p = 0.11). Additional posterior fixation further reduced the ROM significantly (p < 0.05) in most directions in both cage groups, but did not show any difference between the cage groups. CONCLUSIONS: There was no significant difference in immediate stability in any direction between the threaded cylindrical cage and the new design of the rectangular cage with endplate teeth

Pain drawings in the evaluation of lumbar disc-related pain

Pain drawings have been used in a variety of settings to investigate pain, including low back pain. The drawings allow a rapidly completed assessment that have several potential applications including psychological screening tool, documenting pain location, and evaluating pain quality. The purpose of this work was to investigate the use of pain drawings in low back pain populations with particular focus on patients suspected of having lumbar disc-related pain. More specifically, the primary objectives were to: determine the repeatability of low back pain patients in completing pain drawings, determine if the overall pain pattern indicated in the drawings was related to the pain provocation component of discography, determine if there was a relationship between the pattern of pain and/or the quality of sensation indicated by patients in pain drawings to symptomatic lumbar disc pathology identified by CT/discography, investigate the potential relationship between distal pain location and/or pain quality with respect to the severity of symptomatic lumbar disc disruption, and to determine if there was a relationship between the pattern of pain indicated in pain drawings and the specific disc level(s) identified by CT/discography to be symptomatic and disrupted. The populations studied were being evaluated and treated by spine specialists for suspected lumbar discrelated pain. All had failed to gain adequate pain relief from conservative care and were chronic pain patients. The primary population in the repeatability study included 45 males and 21 females with a mean age of 40.6 years. In the other studies the primary population included 187 patients (118 males and 69 females) with a mean age of 37.2 years, ranging from 18 to 62 years. All the pain drawings were scored by a single evaluator. In studies involving CT/discography, all the images were scored by a different single evaluator. Low back pain patients demonstrated an acceptable level of repeatability in completing the drawings, even over a period of several months. Patients whose drawings were classified as possibly being related to psychological disturbances did report pain more often during discographic injection; although such patients did not tend to have more discs that were classified as disrupted based on imaging methods. There was a significant relationship between the pattern of pain indicated in the drawings and the presence of symptomatic disc disruption. Also, it was found that the severity of disc disruption was not related to the distal extend of the pain indicated in the drawings. That is, patients with nonbulging or nonherniated discs were just as likely to indicate pain in the thigh and leg as were patients with more severe disc pathology resulting in deformation of the outer annular wall. However, patients with the less severe disc disruption reported more burning and aching sensations than did patients with more severe disruption. There was a significant relationship between the specific intervertebral disc level demonstrating symptomatic disc pathology and the location of the patient's pain. This work indicates that patients are repeatable in completing pain drawings, even over a period of several months and thus it appears to be a stable evaluation instrument in this population of chronic back pain patients. The drawings also provide an easily administered evaluation, which may help identify patients with symptomatic disc pathology in the lumbar spine. They also appear to be a useful instrument in studying various aspects of low back pain

Robotic-assisted pedicle screw placement: lessons learned from the first 102 patients. Eur Spine J 2013;22:661-6. Disclosures Xiaobang Hu received a travel support for lecturing from Mazor Robotics in 2011. Donna D. Ohnmeiss is employed by a foundation th

Abstract Introduction Surgeons&apos; interest in image and/or robotic guidance for spinal implant placement is increasing. This technology is continually improving and may be particularly useful in patients with challenging anatomy. Only through careful clinical evaluation can its successful applications, limitations, and areas for improvement be defined. This study evaluates the outcomes of robotic-assisted screw placement in a consecutive series of 102 patients. Methods Data were recorded from technical notes and operative records created immediately following each surgery case, in which the robotic system was used to guide pedicle screw placement. All cases were performed at the same hospital by a single surgeon. The majority of patients had spinal deformity and/or previous spine surgery. Each planned screw placement was classified as: (1) successful/ accurately placed screw using robotic guidance; (2) screw malpositioned using robot; (3) use of robot aborted and screw placed manually; (4) planned screw not placed as screw deemed non essential for construct stability. Data from each case were reviewed by two independent researchers to indentify the diagnosis, number of attempted robotic guided screw placements and the outcome of the attempted placement as well as complications or reasons for non-placement. Results Robotic-guided screw placement was successfully used in 95 out of 102 patients. In those 95 patients, 949 screws (87.5 % of 1,085 planned screws) were successfully implanted. Eleven screws (1.0 %) placed using the robotic system were misplaced (all presumably due to &apos;&apos;skiving&apos;&apos; of the drill bit or trocar off the side of the facet). Robotic guidance was aborted and 110 screws (10.1 %) were manually placed, generally due to poor registration and/or technical trajectory issues. Fifteen screws (1.4 %) were not placed after intraoperative determination that the screw was not essential for construct stability. The robot was not used as planned in seven patients, one due to severe deformity, one due to very high body mass index, one due to extremely poor bone quality, one due to registration difficulty caused by previously placed loosened hardware, one due to difficulty with platform mounting and two due to device technical issues. Conclusion Of the 960 screws that were implanted using the robot, 949 (98.9 %) were successfully and accurately implanted and 11 (1.1 %) were malpositioned, despite the fact that the majority of patients had significant spinal deformities and/or previous spine surgeries. &apos;&apos;Tool skiving&apos;&apos; was thought to be the inciting issue with the misplaced screws. Intraoperative anteroposterior and oblique fluoroscopic imaging for registration is critical and was the limiting issue in four of the seven aborted cases

Prospective, Randomized Comparison of One-level Mobi-C Cervical Total Disc Replacement vs. Anterior Cervical Discectomy and Fusion: Results at 5-year Follow-up

INTRODUCTION: There is increasing interest in the role of cervical total disc replacement (TDR) as an alternative to anterior cervical discectomy and fusion (ACDF). Multiple prospective randomized studies with minimum 2 year follow-up have shown TDR to be at least as safe and effective as ACDF in treating symptomatic degenerative disc disease at a single level. The purpose of this study was to compare outcomes of cervical TDR using the Mobi-C(®) with ACDF at 5-year follow-up. METHODS: This prospective, randomized, controlled trial was conducted as a Food and Drug Administration regulated Investigational Device Exemption trial across 23 centers with 245 patients randomized (2:1) to receive TDR with Mobi-C(®) Cervical Disc Prosthesis or ACDF with anterior plate and allograft. Outcome assessments included a composite overall success score, Neck Disability Index (NDI), visual analog scales (VAS) assessing neck and arm pain, Short Form-12 (SF-12) health survey, patient satisfaction, major complications, subsequent surgery, segmental range of motion, and adjacent segment degeneration. RESULTS: The 60-month follow-up rate was 85.5% for the TDR group and 78.9% for the ACDF group. The composite overall success was 61.9% with TDR vs. 52.2% with ACDF, demonstrating statistical non-inferiority. Improvements in NDI, VAS neck and arm pain, and SF-12 scores were similar between groups and were maintained from earlier follow-up through 60 months. There was no significant difference between TDR and ACDF in adverse events or major complications. Range of motion was maintained with TDR through 60 months. Device-related subsequent surgeries (TDR: 3.0%, ACDF: 11.1%, p<0.02) and adjacent segment degeneration at the superior level (TDR: 37.1%, ACDF: 54.7%, p<0.03) were significantly lower for TDR patients. CONCLUSIONS: Five-year results demonstrate the safety and efficacy of TDR with the Mobi-C as a viable alternative to ACDF with the potential advantage of lower rates of reoperation and adjacent segment degeneration, in the treatment of one-level symptomatic cervical degenerative disc disease. CLINICAL RELEVANCE: This prospective, randomized study with 5-year follow-up adds to the existing literature indicating that cervical TDR is a viable alternative to ACDF in appropriately selected patients. LEVEL OF EVIDENCE: This is a Level I study

Prospective, Randomized Comparison of One-level Mobi-C Cervical Total Disc Replacement vs. Anterior Cervical Discectomy and Fusion: Results at 5-year Follow-up.

IntroductionThere is increasing interest in the role of cervical total disc replacement (TDR) as an alternative to anterior cervical discectomy and fusion (ACDF). Multiple prospective randomized studies with minimum 2 year follow-up have shown TDR to be at least as safe and effective as ACDF in treating symptomatic degenerative disc disease at a single level. The purpose of this study was to compare outcomes of cervical TDR using the Mobi-C(®) with ACDF at 5-year follow-up.MethodsThis prospective, randomized, controlled trial was conducted as a Food and Drug Administration regulated Investigational Device Exemption trial across 23 centers with 245 patients randomized (2:1) to receive TDR with Mobi-C(®) Cervical Disc Prosthesis or ACDF with anterior plate and allograft. Outcome assessments included a composite overall success score, Neck Disability Index (NDI), visual analog scales (VAS) assessing neck and arm pain, Short Form-12 (SF-12) health survey, patient satisfaction, major complications, subsequent surgery, segmental range of motion, and adjacent segment degeneration.ResultsThe 60-month follow-up rate was 85.5% for the TDR group and 78.9% for the ACDF group. The composite overall success was 61.9% with TDR vs. 52.2% with ACDF, demonstrating statistical non-inferiority. Improvements in NDI, VAS neck and arm pain, and SF-12 scores were similar between groups and were maintained from earlier follow-up through 60 months. There was no significant difference between TDR and ACDF in adverse events or major complications. Range of motion was maintained with TDR through 60 months. Device-related subsequent surgeries (TDR: 3.0%, ACDF: 11.1%, p&lt;0.02) and adjacent segment degeneration at the superior level (TDR: 37.1%, ACDF: 54.7%, p&lt;0.03) were significantly lower for TDR patients.ConclusionsFive-year results demonstrate the safety and efficacy of TDR with the Mobi-C as a viable alternative to ACDF with the potential advantage of lower rates of reoperation and adjacent segment degeneration, in the treatment of one-level symptomatic cervical degenerative disc disease.Clinical relevanceThis prospective, randomized study with 5-year follow-up adds to the existing literature indicating that cervical TDR is a viable alternative to ACDF in appropriately selected patients.Level of evidenceThis is a Level I study