Cervical disc replacement-porous coated motion prosthesis: a comparative biomechanical analysis showing the key role of the posterior longitudinal ligament

• Published in: Spine (Philadelphia, Pa. 1976) Pa. 1976), 2003-10, Vol.28 (20), p.S176-S185
• Main Authors: McAfee, Paul C, Cunningham, Bryan, Dmitriev, Anton, Hu, Niabin, Woo Kim, Seok, Cappuccino, Andy, Pimenta, Luiz
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Animals; Arthroplasty, Replacement - methods; Biomechanical Phenomena; Cadaver; Cervical Vertebrae - surgery; Goats; Humans; Intervertebral Disc - surgery; Longitudinal Ligaments - physiology; Longitudinal Ligaments - surgery; Middle Aged; Models, Animal; Range of Motion, Articular; Rotation
• ISSN: 0362-2436; 1528-1159
• DOI: 10.1097/01.brs.0000092219.28382.0c

Benchtop cadaveric biomechanical comparative testing and caprine animal model in vivo implantation. To evaluate the role of the posterior longitudinal ligament in cervical arthroplasty and to understand the relative contribution of this ligament in nonfusion applications. Rauschning refers to the posterior longitudinal ligament as "The Kleenex Ligament" due to its apparent anatomic insignificance. White and Panjabi found the posterior longitudinal ligament ranked only fourth in importance in tensile load-to-failure biomechanical testing. In the postoperative situation following anterior cervical diskectomy fusion, posterior longitudinal ligament integrity is overlooked by physicians because the entire disc space usually fuses into a homogeneous block of bone. This biomechanical study was undertaken to determine the relative importance of the posterior longitudinal ligament following two different degrees of anterior decompression, anterior disc replacement, and anterior arthrodesis procedures. A total of seven fresh frozen human cadaveric cervical spines (C3-C7) (mean age 68 +/- 19 years) were used for biomechanical testing. Each vertebra was equipped with three non-colinear light emitting diodes designed for detection by an optoelectronic motion measurement system (3020 Optotract System). To determine the multidirectional flexibility, six pure moments (flexion, extension, right + left lateral bending, right + left axial rotation) and axial compression were applied using a servohydraulic 858 Bionix testing device configured with a six-degree-of-freedom spine simulator. Range of motion was defined as the peak displacement from the initial neutral position to the maximum load, whereas the neutral zone represents the motion from the initial neutral position to the unloaded position at the beginning of the third cycle. Seven groups of (N = 7 each) constructs at C5-C6 were: 1) intact "native" C5-C6 level; 2) anterior diskectomy (posterior longitudinal ligament intact); 3) a Low Profile Porous Coated Motion cervical disc replacement; 4) posterior longitudinal ligament resected; 5) Porous Coated Motion cervical disc replacement fixed with anterior flanges and screws; 6) tricortical structural allograft; and 7) an anterior cervical translational plate + allograft. The caprine model was evaluated for suitability as an animal model with 12 goats undergoing C3-C4 anterior cervical Porous Coated Motion disc replacement. Group 2 (anterior diskectomy alone) was signific