Kinematic Magnetic Resonance Imaging Assessment of the Degenerative Cervical Spine: Changes after Anterior Decompression and Cage Fusion

Stretching the Limits of MRI-Stretchable and Modular Coil Array Using Conductive Thread Technology

Objective

We propose a modular stretchable coil design using conductive threads and commercially available embroidery machines. The coil design increases customizability of coil arrays for individual patients and each body part.

Methods

Eight rectangular coils were constructed with custom-fabricated stretchable tinsel copper threads incorporated onto textile. Tune, match, and detune circuits were incorporated on the coil. A hook-and-loop mechanism was used to attach and decouple the modular coils. Phantom and in vivo scans at various anatomical flexion angles were acquired to highlight performance, and a temperature test was performed to verify safety.

Results

In vivo MRI experiments demonstrate high sensitivity and coverage of each anatomy. As the coils are stretched, the sensitive volume increases at a rate of 10.93 mL/cm2. The SNR reduction of a single coil was greater during compression than when stretched, but this did not affect image quality for the array. The modularity of the array allows for adaptability for any anatomy with simple on-demand adjustment to the number and position of coil elements.

Conclusion

The images demonstrated high sensitivity and coverage of the stretchable array for various anatomies and flexion angles. Stretching the coils increases the sensitive volume, allowing for a larger region to be effectively imaged. The resonance shift and SNR decrease during stretch and compression support further investigation of methods to reduce frequency shift in stretchable coils.

Significance

The proposed array design allows for highly stretchable, flexible, modular, and conformal patient-centered coils that allow for increased imaging quality, greater comfort, and rapid production.

Influence of cervical spine sagittal alignment on range of motion after corpectomy: a finite element study

BACKGROUND

Sagittal alignment of the cervical spine might influence the development of radiological adjacent segment pathology (RASP) after central corpectomy (CC). Range of motion (ROM) of the adjacent segments is closely linked to the development of RASP.

METHODS

To investigate the ROM of the adjacent segments after CC, we developed a C2-T1 finite element (FE) model. The model with a lordotic sagittal alignment served as the baseline model. Models with straight and kyphotic alignment were generated using mesh morphing methods. Single-level corpectomy at C5 was done on these models. Segmental ROMs of intact and corpectomized spines were compared for physiologic flexion-extension loads.

RESULTS

The flexion ROM decreased by an average of 13% with the change in sagittal alignment from lordosis to kyphosis; however, a consistent decrease was not observed in extension. After CC, the ROM increased by an average of 95% and 31% in the superior and inferior adjacent segments. With kyphotic change in the sagittal alignment, the postoperative increase in flexion ROM exhibited a decreasing trend, while this was not seen in extension.

CONCLUSIONS

Kyphotic changes of the intact spine resulted in segmental stiffening, and after corpectomy, it resulted in inconsistent variations of segmental extension ROMs.

Risk factor analysis of axial symptoms after single-segment anterior cervical discectomy and fusion: A retrospective study of 113 patients

Objective

This retrospective study was performed to investigate the risk factors for axial symptoms (AS) after single-segment anterior cervical discectomy and fusion (ACDF).

Methods

One hundred thirteen patients with cervical spondylosis who had undergone single-segment ACDF from January 2012 to December 2015 were divided into those with and without AS (n = 34 and n = 79, respectively). Clinical data and radiological evaluation results were recorded.

Results

The occurrence rate of AS was 30.1% (34/113), and the average visual analog scale score was 4.5 points. Bony fusion was achieved in all cases during follow-up. There were no differences in age, sex, disease duration, diagnostic categories, operative segment, Japanese Orthopaedic Association score, or adjacent segment degeneration. However, cervical range of motion (CROM), cervical curvature, and disc space enlargement significantly differed between the groups. Logistic regression analysis revealed that CROM, cervical curvature, and disc space enlargement were independently associated with AS.

Conclusions

AS after single-segment ACDF is not rare. Disc space enlargement is a risk factor for AS, while higher CROM and lordotic cervical curvature are protective factors. Excessive or insufficient disc space enlargement could increase the incidence of AS. Maintaining CROM within the normal range and restoring cervical lordosis might help to prevent AS.