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Yoshihisa Kotani, Kuniyoshi Abumi, Yasuo Shikinami, Masahiko Takahata, Ken Kadoya, Tsuyoshi Kadosawa, Akio Minami and Kiyoshi Kaneda

R ecent treatments for spinal disorders have rapidly progressed, and new motion preservation technologies such as AID replacement or flexible spinal stabilization have evolved. 3–5, 7, 8, 10, 13–21, 24, 37, 38, 41 The AID technology includes several different designs and surgery-related concepts. To date, some devices are undergoing multicenter clinical trials for clinical approval; 17, 19 however, a paucity of information exists regarding appropriate design concepts of unconstrained or constrained interface material and its modification, and their in vivo

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Evaluation and treatment of adult spinal deformity

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004

Robert F. Heary

°. Significant variations are found in healthy patients without spinal deformities. In the lumbar spine, 67% of the total lumbar lordosis occurs at L4–5 and L5—S1. 2 Recognition of this has led numerous surgeons to attempt to limit the caudal extent of surgical correction to L-4. In so doing, preservation of motion at the two inferior-most segments allows for compensatory mechanisms that are advantageous in preventing sagittal-plane imbalance. An overreliance on L4–5 and L5—S1 motion preservation may lead to accelerated degeneration of the discs and facet joints at these

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Denis J. DiAngelo and Kevin T. Foley

Object

An experimental study was performed to determine the biomechanical end-mounting configurations that replicate in vivo physiological motion of the cervical spine in a multiple-level human cadaveric model. The vertebral motion response for the modified testing protocol was compared to in vivo motion data and traditional pure-moment testing methods.

Methods

Biomechanical tests were performed on fresh human cadaveric cervical spines (C2–T1) mounted in a programmable testing apparatus. Three different end-mounting conditions were studied: pinned–pinned, pinned–fixed, and translational/pinned–fixed. The motion response of the individual segmental vertebral rotations was statistically compared using one-way analysis of variance and Student-Newman-Keuls tests (p < 0.05 unless otherwise stated) to determine differences in the motion responses for different testing methods.

Conclusions

A translational/pinned–fixed mounting configuration induced a bending-moment distribution across the cervical spine, resulting in a motion response that closely matched the in vivo case. In contrast, application of pure-moment loading did not reproduce the physiological response and is less suitable for studying disc arthroplasty and nonfusion devices.

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. Smith David W. Wimberley Alexander R. Vaccaro 9 2004 17 3 1 21 10.3171/foc.2004.17.3.3 FOC.2004.17.3.3 An improved biomechanical testing protocol for evaluating spinal arthroplasty and motion preservation devices in a multilevel human cadaveric cervical model Denis J. DiAngelo Kevin T. Foley 9 2004 17 3 1 29 10.3171/foc.2004.17.3.4 FOC.2004.17.3.4 Effects of a cervical disc prosthesis on segmental and cervical spine alignment Gwynedd E. Pickett Demytra K. Mitsis Lali H. Sekhon William R. Sears Neil Duggal 9 2004 17 3 1 35 10.3171/foc.2004.17.3.5 FOC.2004

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Yoshihisa Kotani, Bryan W. Cunningham, Kuniyoshi Abumi, Anton E. Dmitriev, Manabu Ito, Niabin Hu, Yasuo Shikinami, Paul C. McAfee and Akio Minami

device design of the biomimetic structure of the 3D FD disc, the initial mobility can be set at a relatively hypermobile setting, and it may approach the normal mobility over the long term. The control of in vivo motion preservation is the future problem to be solved in this field. Adjacent-segment biomechanics is another matter of concern in artificial intervertebral disc reconstruction. The lower adjacent segment ROM of the 3D FD was statistically equivalent to that of the intact segment in all loading modes. The upper adjacent segment ROM of the 3D FD was

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Rudolf Bertagnoli, James J. Yue, Frank Pfeiffer, Andrea Fenk-Mayer, James P. Lawrence, Trace Kershaw and Regina Nanieva

fixed axis of rotation ( Fig. 4 ). The surgical technique is relatively atraumatic because of the limited exposure required for the locked-pin intervertebral distractor and the use of a table-based circular self-retaining soft-tissue retractor system. The keel cutting chisel can be safely used with this pin distractor/stabilizer in addition to a safety block mechanism ( Fig. 5 ). Whether this semiconstrained device will afford a more optimal balance between motion preservation, ease and consistency of implantation, and neurological fitness has yet to be defined

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Chris J. Neal, Michael K. Rosner and Timothy R. Kuklo

pilot study, it appears that sagittal MR imaging can be conducted to evaluate adjacent segments after disc arthroplasty. Although it does not provide 100% visualization, MR imaging should be considered as a component of the radiographic/neuroimaging follow-up examination of patients undergoing disc arthroplasty. Only with long-term clinical and radiographic evaluation of the adjacent segments can the theoretical benefits of motion preservation be discerned. Disclaimer The opinions or assertions contained herein are the private views of the authors and are

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Prospective randomized controlled study of the Bryan Cervical Disc: early clinical results from a single investigational site

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005

Domagoj Coric, Frederick Finger and Peggy Boltes

whether arthroplasty can maintain its clinical success and provide protection to adjacent levels. Long-term follow-up examination is especially crucial in establishing the optimal indications for cervical arthroplasty. Theoretically, younger patients would benefit from preserved motion over a longer period. Intuitively, patients with proven, symptomatic adjacent-level degeneration and diffuse spondylosis could benefit from decompression, motion preservation, and decreased adjacent-level stresses ( Fig. 4 ). The long-term wear characteristics of artificial discs

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Paul McAfee, Larry T. Khoo, Luiz Pimenta, Andy Capuccino, Domagoj Coric, Robert Hes, Bart Conix, Farbod Asgarzadie, Azmi Hamzaoglu, Yigal Mirofsky and Yoram Anekstein

Object

Total disc replacement is an alternative to lumbar fusion, but patients with spinal stenosis, spondylolisthesis, and facet arthropathy are often excluded from this procedure because increased adjacent-segment motion can exacerbate dorsal spondylotic changes. In such cases of degenerative spondylolisthesis with stenosis, decompression and fusion remain the gold standard of treatment. To avoid attendant loss of motion at the treated segment, the TOPS system is a novel total posterior arthroplasty prosthesis that allows for an alternative dynamic, multiaxial, three-column stabilization and motion preservation. The purpose of this study is to report preliminary surgical data and clinical outcomes in patients treated with the TOPS lumbar total posterior arthroplasty system.

Methods

Twenty-nine patients were enrolled in a nonrandomized, multicenter, prospective pilot study outside the US. All patients had spinal stenosis and/or spondylolisthesis at L4–5 due to facet arthropathy. Radiographs and scores on outcome measures including the visual analog scale (VAS) for pain, Oswestry Disability Index (ODI), Short Form-36, and Zurich Claudication Questionnaire were prospectively recorded before surgery and at 6-week, 3-month, 6-month, and 1-year intervals after surgery. Prior to instrumentation, a bilateral total facetectomy and laminectomy at L4–5 or L3–4 was performed via a standard midline posterior approach. After decompression, the TOPS screws were inserted into four pedicles to achieve maximal purchase with triangulating bicortical trajectories. An appropriately sized TOPS arthroplasty implant was then applied.

The mean surgical time was 3.1 hours, and patients' clinical status improved significantly following treatment with the TOPS device. The mean ODI score decreased compared with baseline by 41% at 1 year, and the 100-mm VAS score declined by 76 mm over the same time period. Radiographic analysis showed that lumbar motion was maintained, disc height was preserved, and no evidence of screw loosening was found. No device malfunctions or migrations and no device-related adverse events were reported during the study.

Conclusions

The TOPS total posterior arthroplasty system represents a novel, dynamic, posterior arthroplasty device that provides multiaxial stability in flexion, extension, rotation, and lateral bending after total facetectomy and neural decompression. The surgical data indicate that it can be safely applied via a traditional approach with low surgical morbidity and excellent 1-year functional and radiographic outcomes in patients with degenerative spondylolisthesis accompanied by stenosis and back pain.

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Paul McAfee, Larry T. Khoo, Luiz Pimenta, Andy Capuccino, Domagoj Coric, Robert Hes, Bart Conix, Farbod Asgarzadie, Azmi Hamzaoglu, Yigal Mirofsky and Yoram Anekstein

Object

Total disc replacement is an alternative to lumbar fusion, but patients with spinal stenosis, spondylolisthesis, and facet arthropathy are often excluded from this procedure because increased adjacent-segment motion can exacerbate dorsal spondylotic changes. In such cases of degenerative spondylolisthesis with stenosis, decompression and fusion remain the gold standard of treatment. To avoid attendant loss of motion at the treated segment, the TOPS system is a novel total posterior arthroplasty prosthesis that allows for an alternative dynamic, multiaxial, three-column stabilization and motion preservation. The purpose of this study is to report preliminary surgical data and clinical outcomes in patients treated with the TOPS lumbar total posterior arthroplasty system.

Methods

Twenty-nine patients were enrolled in a nonrandomized, multicenter, prospective pilot study outside the US. All patients had spinal stenosis and/or spondylolisthesis at L4–5 due to facet arthropathy. Radiographs and scores on outcome measures including the visual analog scale (VAS) for pain, Oswestry Disability Index (ODI), Short Form-36, and Zurich Claudication Questionnaire were prospectively recorded before surgery and at 6-week, 3-month, 6-month, and 1-year intervals after surgery. Prior to instrumentation, a bilateral total facetectomy and laminectomy at L4–5 or L3–4 was performed via a standard midline posterior approach. After decompression, the TOPS screws were inserted into four pedicles to achieve maximal purchase with triangulating bicortical trajectories. An appropriately sized TOPS arthroplasty implant was then applied.

The mean surgical time was 3.1 hours, and patients' clinical status improved significantly following treatment with the TOPS device. The mean ODI score decreased compared with baseline by 41% at 1 year, and the 100-mm VAS score declined by 76 mm over the same time period. Radiographic analysis showed that lumbar motion was maintained, disc height was preserved, and no evidence of screw loosening was found. No device malfunctions or migrations and no device-related adverse events were reported during the study.

Conclusions

The TOPS total posterior arthroplasty system represents a novel, dynamic, posterior arthroplasty device that provides multiaxial stability in flexion, extension, rotation, and lateral bending after total facetectomy and neural decompression. The surgical data indicate that it can be safely applied via a traditional approach with low surgical morbidity and excellent 1-year functional and radiographic outcomes in patients with degenerative spondylolisthesis accompanied by stenosis and back pain.