Kinematics of progressive circumferential ligament resection (decompression) in conjunction with cervical disc arthroplasty in a spondylotic spine model.
METHODS
Benchtop biomechanics study examining kinematic effects of progressive resection in a human cadaveric spine model.


OBJECTIVE
To determine the effects of posterior longitudinal ligament (PLL) resection, unilateral and bilateral foraminotomy, and laminectomy on cervical intervertebral rotation and translation after cervical disc arthroplasty (CDA).


BACKGROUND
Although the clinical results after CDA have been studied, there remain unanswered questions regarding the surgical techniques used at the time of device insertion. For example, it is unclear whether a surgeon should retain or resect the PLL and uncinate processes at the time of primary surgical intervention. Further, the effect of a subsequent posterior decompression (foraminotomy or laminectomy) on the stability of a motion segment containing a disc arthroplasty is unknown.


METHODS
Three-dimensional intervertebral motion was measured by biplanar videography in human cadaveric spines at C4-C5 or at C5-C6 subjected to a 1.5-Nm moment applied to induce motion in the sagittal plane. Coupled motions were not constrained. After measuring intact spine motion, disc arthroplasty with bilateral ventral foraminotomy was performed without PLL resection. Sequentially, rotations and translations were measured after PLL resection, unilateral foraminotomy, bilateral foraminotomy, and laminectomy.


RESULTS
CDA with bilateral ventral foraminotomy increased sagittal rotation by 0.4 degrees (16%) compared with the intact spine. The addition of PLL resection increased rotation by 0.5 degrees (14% increase). Unilateral and bilateral foraminotomy had negligible effects on sagittal rotation or anteroposterior (AP) translation. Laminectomy resulted in an additional sagittal plane rotation of 2 degrees. The sagittal-plane interverterbal rotation resultant after all interventions was 6 degrees , with 1.5 mm of AP translation occurring only.


CONCLUSIONS
Given that a greater degree of motion was seen with PLL resection combined with ventral foraminotomy, we recommend that PLL resection be performed when performing CDA. In our benchtop model, unilateral and bilateral posterior foraminotomies were not associated with the creation of significant sagittal rotational or AP translational instability.
Department of Orthopaedic Surgery, University of California, Davis, Medical Center, Sacramento, CA 95817, USA. Rolando.Roberto@ucdmc.ucdavis.edu
Rolando F
RF
Roberto
Thomas
T
McDonald
Shane
S
Curtiss
Corey P
CP
Neu
Kee
K
Kim
Fritz
F
Pennings
D000368:Aged; D000369:Aged, 80 and over; D001178:Arthroplasty / Q000009:adverse effects* / Q000379:methods / Q000592:standards; D001696:Biomechanical Phenomena / Q000502:physiology; D002574:Cervical Vertebrae / Q000502:physiology / Q000601:surgery*; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D017846:Longitudinal Ligaments / Q000502:physiology / Q000601:surgery*; D008875:Middle Aged; D008953:Models, Anatomic; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D055009:Spondylosis / Q000601:surgery*