Clinical outcomes after cervical spine fusion

Magnetic resonance imaging artifact following anterior cervical discectomy and fusion with a trabecular metal cage

OBJECT

This study was undertaken to evaluate the impact of postoperative MRI artifact on the assessment of ongoing spinal cord or nerve root compression after anterior cervical discectomy and fusion (ACDF) using a trabecular tantalum cage or bone autograft or allograft.

METHODS

The authors conducted a retrospective review of postoperative MRI studies of patients treated surgically for cervical disc degenerative disease or cervical instability secondary to trauma. Standard ACDF with either a trabecular tantalum cage or interbody bone graft had been performed. Postoperative MR images were shown twice in random order to each of 3 assessors (2 spine surgeons, 1 neuroradiologist) to determine whether the presence of a tantalum interbody cage and/or anterior cervical fixation plate or screws imparted MRI artifact significant enough to prevent reliable postoperative assessment of ongoing spinal cord or nerve root compression.

RESULTS

A total of 63 patients were identified. One group of 29 patients received a tantalum interbody cage, with 13 patients (45%) undergoing anterior plate fixation. A second group of 34 patients received bone auto- or allograft, with 23 (68%) undergoing anterior plate fixation. The paramagnetic implant construct artifact had minimal impact on visualization of postoperative surgical level spinal cord compression. In the cage group, 98% (171/174) of the cases were rated as assessable versus 99% in the bone graft group (201/204), with high intraobserver reliability. In contrast, for the assessment of ongoing surgical level nerve root compression, the presence of a tantalum cage significantly decreased visualization of nerve roots to 70% (121/174) in comparison with 85% (173/204) in the bone graft group (p < 0.001). When sequences using turbo spin echo (TSE), a T2-weighted axial sequence, were acquired, nerve roots were rated as assessable in 88% (69/78) of cases; when only axial T2-weighted sequences were available, the nerve roots were rated as assessable in 54% (52/96) of cases (p < 0.01). The presence of anterior plate fixation had minimal impact on visualization of the spinal cord (99% [213/216] for plated cases vs 98% [159/162] for nonplated cases; p = 1.0) or nerve roots (79% [170/216] for plated cases vs 77% [124/162] for nonplated cases; p = 0.62).

CONCLUSIONS

Interbody fusion with tantalum cage following anterior cervical discectomy imparts significant paramagnetic artifact, which significantly decreases visualization and assessment of ongoing surgical level nerve root, but not spinal cord, compression. Anterior plate constructs do not affect visualization of these structures. TSE T2-weighted sequences significantly improve nerve root visualization and should be performed as part of a standard postoperative protocol when imaging the cervical spine following interbody implantation of materials with potential for paramagnetic artifact.

Active cervical and lumbar range of motion during performance of activities of daily living in healthy young adults

STUDY DESIGN

Observational cohort design.

OBJECTIVE

The purpose of this investigation was to characterize the maximum, cumulative, and average cervical and lumbar spine motion required to perform common activities of daily living (ADLs).

SUMMARY OF BACKGROUND DATA

Previous studies have measured the maximum cervical and lumbar excursions during ADLs, but none have used a motion capture system to allow for noninvasive continuous motion monitoring.

METHODS

Ten healthy, young adults performed 16 ADLs while 3-dimensional kinematics were recorded. Cervical and lumbar rigid body kinematic models were created and scaled to each subject to calculate angular motion. Cervical and lumbar mean active range of motion (ROM) and total excursion for flexion-extension, lateral bending, and axial rotation were calculated.

RESULTS

The majority of activities used 20% to 40% of maximum available cervical ROM and 40% to 60% of maximum available lumbar ROM. Activities that required concurrent cervical and lumbar spine motion, such as washing in the shower, picking an object up from the floor, and clearing the table, had the greatest motion totals. These activities typically required rates of excursion greater than 10° per second.

CONCLUSION

This is the first investigation to report cumulative spine motion totals associated with the performance of common ADLs. These results provide a preliminary cervical and lumbar spine motion profile in healthy, young adults. The relationship between traditional end ROM measurements and function is not well defined. In agreement with previous research, this investigation concludes that only a small percentage of available ROM is used in performing most activities. Thus, determining the total wear related to common activities may help us to better understand and address spine-related impairments.

LEVEL OF EVIDENCE

N/A.

Anterior cervical fusion with tantalum implant: a prospective randomized controlled study

STUDY DESIGN

A prospective randomized controlled study was carried out.

OBJECTIVE

To determine the effectiveness and safety of a tantalum implant in achieving anterior cervical fusion following 1-level discectomy as treatment of degenerative cervical disc disease with radiculopathy.

SUMMARY OF BACKGROUND DATA

The gold standard for the treatment of degenerative cervical disc disease could not be already identified. The morbidity of autologous graft and plating, and the doubt about the mechanical efficacy of plate fixation and the clinical benefits in 1-level fusion have promoted the use of other constructs.

METHODS

Sixty-one patients were randomized to anterior cervical discectomy and fusion with interbody implant of tantalum (n = 28) or by means of autologous iliac bone graft and plating (n = 33). Fusion rate and segmental height and alignment were blind assessed by radiographs by 2 independent reviewers. Clinical status was evaluated using pain visual analogue scale, the Neck Disability Index, and the Zung Depression Scale. Patient's subjective satisfaction was recorded. Complications and operative parameters were also taken into account.

RESULTS

With an endpoint of 24 months, radiologic and clinical outcomes were similar for both treatments without significant difference. The safety of fusion with tantalum implant was obvious, based on the analysis of complications. Complication rate was considerably higher for the autologous graft plus plating procedure than for implant tantalum (P < 0.005).

CONCLUSION

The efficacy to achieve fusion after 1-level anterior cervical discectomy, with a good radiologic and clinical outcome, using tantalum implant is equivalent to that of autologous graft and anterior plate, being safer as avoids donor-site graft harvesting and plating complications.

Cervical plates: comparison of physical characteristics and in vitro pushout strength

BACKGROUND CONTEXT

There are many cervical plates available to the spine surgeon today. A single plate design may not be appropriate for every clinical situation. It is important for the surgeon to understand the differences of these plating systems. Plate systems are known to fail by screw pullout from the bone, screw and plate breakage and a less frequent but clinically observed screw pushout from the plate. Pushout testing of the screws from the plate have not previously been subjected to study.

PURPOSE

This compares the features of cervical plating systems and the strength of the locking mechanisms to allow the surgeon to make a knowledgeable choice of plating system.

STUDY DESIGN

This is a review of descriptive geometric characteristics of cervical plate systems and a biomechanical evaluation of locking mechanism screw pushout strength.

METHODS

Physical characteristics of each plate were determined. Features of plates and screws were cataloged. Each of the test plate systems had a different locking mechanism. Biomechanical testing of the locking mechanism-screw-plate constructs was performed to determine the pushout strength of the fixation screw from the plate-locking mechanism.

RESULTS

Physical characteristics of the plating systems, including lengths, widths, shortest screw lengths and distance from edge of plate to nearest screw, were determined. Biomechanical testing showed significant differences in pushout strength, in part explained by the type of locking mechanism.

CONCLUSIONS

Biomechanical screw pushout data demonstrate that a significant range of pushout strengths exist across the available cervical plate systems today. Knowing the physical characteristics of the cervical plating systems available may allow the selection of a plate best suited for a given clinical situation.