Biomechanical effects of interbody cage height on cervical spine / 医用生物力学

Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.

Biomechanical effects of interbody cage height on cervical spine / 医用生物力学

Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.

Biomechanical effects of interbody cage height on cervical spine / 医用生物力学

Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery, so as to provide references for selection of interbody cage. Methods The finite element model of normal cervical spine (C2-7) was built and validated, and the cages with different height (5, 6, 7, 8 mm) were implanted into C5-6 disc (cage5, 6, 7, 8 model). All the models were loaded with pure moment of 1.5 N•m to produce flexion, extension, blending and axial torsion motions on the cervical spine, and the effects of cage height on range of motion (ROM), facet joint stress, intervertebral pressure in cervical spine were investigated. Results The intervertebral angle at the fusion segment increased by 0.68°with per 1 mm-increase of height. The ROM at C5-6 after cage implantation was less than 0.44°. The influence of cage height on ROM in C4-5 was greater than that in C6-7, and the changes of ROM in non-fusion segments were less than 7.3%. The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure. The stresses in the capsular ligament, cage and screw-plate system increased gradually with the increase of cage height, and these stresses in the cage6, 7, 8 models were much higher than those in the cage5 model. Conclusions For patients who need implanting fusion cage, the cage height should be 0-1 mm greater than the original intervertebral space height.

Cervical disc arthroplasty with ProDisc-C artificial disc: 5-year radiographic follow-up results / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cervical disc arthroplasty is an alternative surgery to standard cervical decompression and fusion for disc degeneration. Different types of cervical disc prosthesis are used in China. The aim of this study was to evaluate the radiographic outcomes of cervical arthroplasty using the ProDisc-C prosthesis.</p><p><b>METHODS</b>Radiographic evaluation, including static and dynamic flexion-extension lateral images, was performed at baseline and at final follow-up.</p><p><b>RESULTS</b>Twenty six patients who had single-level ProDisc-C arthroplasty were followed up for a mean period of 63 months (56-76 months). The range of motion at the operated level was 9.3°±3.7° at baseline and 7.3°±3.5° at final follow-up, with a significant difference (P < 0.05). Seventeen of 26 levels (65.4%) developed heterotopic ossification: three were classified as grade II, 13 were classified as grade III, and 1 as grade IV, according to McAfee's classification. Forty nine adjacent segments were evaluated by lateral X-ray and 18 (36.7%) segments developed adjacent segment degenerations.</p><p><b>CONCLUSIONS</b>ProDisc-C arthroplasty had acceptable radiographic results at 5-year follow-up. The range of motion was preserved. However, more than 60% of the patients developed heterotopic ossification.</p>

Comparison of adjacent segment degeneration five years after single level cervical fusion and cervical arthroplasty: a retrospective controlled study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cervical arthroplasty is indicated to preserve cervical motion and prevent accelerated adjacent segment degeneration. Whether accelerated adjacent segment degeneration is prevented in the long term is unclear. This trial compared adjacent segment degeneration in Bryan disc arthroplasty with that in anterior cervical decompression and fusion five years after the surgery.</p><p><b>METHODS</b>We studied patients with single level degenerative cervical disc disease. The extent of adjacent segment degeneration was estimated from lateral X-rays.</p><p><b>RESULTS</b>Twenty-six patients underwent single level Bryan disc arthroplasty and twenty-four patients underwent single level anterior cervical decompression and fusion. All patients were followed up for an average of sixty months. In the Bryan arthroplasty group, nine (17.6%) segments developed adjacent segment degeneration, which was significantly lower than that (60.4%) in the anterior cervical decompression and fusion group. Eleven segments in the Bryan arthroplasty group developed heterotopic ossification according to McAfee's classification and two segments had range of motion less than 2°. In the heterotopic ossification group, four (19.5%) segments developed adjacent segment degeneration, similar to the number in the non-heterotopic ossification group (16.7%). Adjacent segment degeneration rate was 50% in grade IV group but 11.8% in grade II to III.</p><p><b>CONCLUSIONS</b>Adjacent segment degeneration was accelerated after anterior cervical decompression and fusion. However, Bryan disc arthroplasty avoided accelerated adjacent segment degeneration by preserving motion. Patients with grade IV heterotopic ossification lost motion, and the rate of adjacent segment degeneration was higher than that in patients without heterotopic ossification.</p>

Application of cervical arthroplasty with Bryan cervical disc: long-term X-ray and magnetic resonance imaging follow-up results / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cervical disc arthroplasty is a new technique for treating degenerative cervical disease. Its goal is to avoid the degeneration of adjacent levels by preserving motion at the treated level. The aims of this study were to evaluate the radiologic outcomes of Bryan cervical disc replacement and the degenerative status of adjacent segments.</p><p><b>METHODS</b>Twenty-two patients at a single center underwent discectomy and implantation of Bryan cervical disc. The mean follow-up period was 60 months (57 - 69 months). Twenty patients underwent single-level arthroplasty and two underwent arthroplasty at two levels. The levels of surgery included C3/4 (3 levels), C4/5 (2 levels), C5/6 (18 levels) and C6/7 (1 level). Radiographic evaluation included dynamic X-ray examination and magnetic resonance imaging (MRI) at baseline and at final follow-up.</p><p><b>RESULTS</b>On X-ray examination, the range of motion (ROM) at the operated level was 7.2° (2.5° - 13.0°) at baseline and 7.8° (1.0° - 15.0°) at final follow-up (P > 0.05). Heterotopic ossification around the prosthesis was observed in eight levels, and two levels showed loss of motion (ROM < 2°). MRI showed worsening by a grade at the upper level in 2/22 patients, and worsening by a grade at the lower level in 3/22, according to Miyazaki's classification. No further impingement of the ligamentum flavum into the spinal canal was observed at adjacent levels, though the disc bulge was slightly increased at both the adjacent upper and lower levels at final follow-up.</p><p><b>CONCLUSIONS</b>Arthroplasty using Bryan cervical disc prosthesis resulted in favorable radiologic outcomes in this study. Disc degeneration at adjacent levels may be postponed by this technique.</p>

The application of cervical spine arthroplasty with Bryan disc and mid-term clinical and radiological follow-up results / 中华外科杂志

<p><b>OBJECTIVE</b>To study the clinical and radiological outcome of Bryan cervical disc replacement and the degenerative status on adjacent segments.</p><p><b>METHODS</b>The data of 26 cases of single level disc replacement with minimal 2 years follow-up were reviewed. CLINICAL OUTCOME was assessed with the JOA 17 score scale and Odom's score. Radiological assessment including range of motion and heterotopic ossification of operated level were recorded. Adjacent level degeneration on X-ray and MRI scan at baseline and at follow-up were compared.</p><p><b>RESULTS</b>(1) CLINICAL OUTCOME: the average JOA score was 16 with 84% improvement ratio at final follow-up in 18 cases of cervical myelopathy. Eight cases of radiculopathy were fully recovered. According to the Odom's criteria 15 cases had an excellent outcome, 7 good, 4 fair, and no case of poor result. (2) On X-ray: The range of motion (ROM) at operated level was 6.9 degrees (2 degrees-12 degrees) at baseline and 7.8 degrees (1 degree-14 degrees) at final follow-up. The heterotopic ossification around the prosthesis was observed in 7 cases and only 1 case lost movement. The average ROM was 5.3 degree in other 6 cases. There was no obvious change of disc height at adjacent levels. (3) On MRI: There was no deterioration of disc degeneration at adjacent levels at final follow-up according to Pfirrmann's classification. There was no further ligamentum flavum impingement into spinal canal observed at adjacent levels but the disc movement slightly increased at both upper and lower adjacent level at final follow-up.</p><p><b>CONCLUSIONS</b>The motion at operated level is preserved after minimal 2 years Bryan disc replacement with satisfied clinical outcome. The deterioration of disc degeneration at adjacent levels may be postponed.</p>