The Effect of Soft-Tissue Restraints After Type II Odontoid Fractures in the Elderly: A Biomechanical Study

• Published in: Spine (Philadelphia, Pa. 1976) Vol. 37; no. 12; pp. 1030 - 1035
• Main Authors: MCCABE, C. Maxwell J, MCLACHLIN, Stewart D, BAILEY, Stewart I, GURR, Kevin R, BAILEY, Christopher S, DUNNING, Cynthia E
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 20-05-2012
• Subjects: Age Factors; Aged; Aged, 80 and over; Biological and medical sciences; Biomechanical Phenomena; Cadaver; Cerebrospinal fluid. Meninges. Spinal cord; Cervical Vertebrae - injuries; Fractures, Bone - complications; Humans; Ligaments - injuries; Medical sciences; Nervous system (semeiology, syndromes); Neurology; Neuropharmacology; Neuroprotective agent; Odontoid Process - injuries; Pharmacology. Drug treatments; Restraint, Physical; Rotation; Soft Tissue Injuries - etiology; Soft Tissue Injuries - prevention & control; Human; Nervous system diseases; Vertebral canal; spine biomechanics; Diseases of the osteoarticular system; odontoid fracture; Fracture; Trauma; facet capsules; Biomechanics; cervical spine injuries; Central nervous system disease; Instability; Soft tissue; Spinal cord disease; Elderly; Cervical spine; Facet; Anterior longitudinal ligament
• ISSN: 0362-2436; 1528-1159
• DOI: 10.1097/BRS.0b013e31823b4ed0

A biomechanical analysis of soft-tissue restraints to passive motion in odontoid fractures.
To quantify the role of the C1-C2 facet joint capsules and anterior longitudinal ligaments (ALLs) in the setting of a type II odontoid fracture in the elderly.
The odontoid process itself is the primary stabilizer at the C1-C2 level; however, little is known about the role of the soft-tissue structures that remain intact in the setting of an odontoid fracture after a low-energy mechanism.
Ten cadaveric C0-C2 spinal segments were studied. Specimens were tested under simulated axial rotation with an applied moment of ±1 Nm and with an application of a 10 N anteriorly directed force to the body of C2 to induce sagittal translation. Optical motion data were initially collected for the intact state and after a simulated dens fracture. The specimens were then divided into 2 groups, where 1 group underwent unilateral and then bilateral C1-C2 facet capsular injuries followed by an ALL injury. The second group underwent the ALL injury before the same capsular injuries. Changes in axial range of motion and C1-C2 translation were analyzed using 2-way repeated measures analyses of variance and post hoc Student-Newman-Keuls tests (α = 0.05).
In axial rotation, there was an increase in range of motion by approximately 13%, with the fracture of the dens compared with the intact state (P < 0.05). An increase was also present for each subsequent soft-tissue injury state compared with the previous (P < 0.05); however, there was no difference found between the 2 sectioning protocols. For sagittal translation testing, it was found that the odontoid fracture alone showed an increase of 3 mm of C1-C2 translation compared with intact (P < 0.05). Further soft-tissue injuries did not show an increase until the complete injury state.
This study identifies that type II odontoid fractures without associated soft-tissue injury may be stable under certain loading modes.