[Transoral atlanto-axial plate fixation in the treatment of a malunited dens fracture and secondary atlanto-axial instability]

Novel posterior artificial atlanto-odontoid joint for atlantoaxial instability: a biomechanical study

OBJECTIVE

Atlantoaxial instability is usually corrected by anterior and/or posterior C1–2 fusion. However, fusion can lead to considerable loss of movement at the C1–2 level, which can adversely impact a patient’s quality of life. In this study, the authors investigated the stability and function of a novel posterior artificial atlanto-odontoid joint (NPAAJ) by using cadaveric cervical spines.

METHODS

The Oc–C7 regions from 10 cadaveric spines were used for anteroposterior (AP) translation and range of motion (ROM) tests while intact and after destabilization, NPAAJ implantation, and double-rod fixation.

RESULTS

The mean AP C1–2 translational distances in the intact, destabilization, and double-rod groups were 6.53 ± 1.07 mm, 11.54 ± 1.59 mm, and 3.24 ± 0.99 mm, respectively, and the AP translational distance in the NPAAJ group was significantly different from that in the intact group (p < 0.05). The AP translational distance in the NPAAJ group was not significantly different from that in the double-rod group (p = 0.24). The mean flexion, extension, and axial rotation ROM values of the NPAAJ group were 9.87° ± 0.91°, 8.75° ± 0.99°, and 61.93° ± 2.93°, respectively, and these were lower than the corresponding values in the intact group (p < 0.05). The mean lateral bending ROM in the NPAAJ group (9.26° ± 0.86°) was not significantly different from that in the intact group (p = 0.23), and the flexion, extension, and rotation ranges in the NPAAJ group were 79.5%, 85.2%, and 82.3%, respectively, of those in the intact group.

CONCLUSIONS

Use of NPAAJ for correction of atlantoaxial instability disorders caused by congenital odontoid dysplasia, odontoid fracture nonunion, and C-1 transverse ligament disruption (IA, IB, and IIB) may restore the stability and preserve most of the ROM of C1–2. Additionally, the NPAAJ may prevent soft tissue from embedding within the joint. However, additional studies should be performed before the NPAAJ is used clinically.

Corrective surgery for deformity of the upper cervical spine due to ankylosing spondylitis

Rotational and flexion deformity of C1-C2 due to ankylosing spondylitis is rare. We did surgical correction in one such case by lateral release, resection of the posterior arch of C1 and mobilization of the vertebral arteries, wedge osteotomy of the lateral masses of C1 and internal fixation under general anesthesia. There were no vascular and neurological complications during the surgery. After operation the atlantoaxial rotational deformity was corrected and the normal cervical lordosis was restored. At 1 year followup his visual field and feeding became normal and internal fixation was stable.

C2-fractures: part I. Quantitative morphology of the C2 vertebra is a prerequisite for the radiographic assessment of posttraumatic C2-alignment and the investigation of clinical outcomes

Pertinent literature exists concerning indications, techniques, complications of treatment, and risk factors for nonunion in axis and odontoid fractures; however, there are scarce data regarding the incidence and definition of malunion in these fractures. As a prerequisite for the study of anatomical alignment following surgical and nonsurgical treatment of C2-fractures, an understanding of normal C2 anatomy is essential. Therefore, the authors intended to evaluate morphometrical dimensions of the C2 vertebra. The purpose was to provide normalized quantitative data to enable assessment of malalignment following the treatment of C2-fractures within a classification system. Using digitized cervical spine lateral and transoral odontoid radiographs of 100 consecutive patients without any evidence of traumatic or neoplastic disorders, the authors performed measurements on distinct anatomical structures and investigated morphometrical dimensions of the normal axis vertebra. The incidence of atlantoaxial arthritis was also evaluated. In addition, with the assessment of twenty arbitrarily chosen sets of radiographs by three different observers we calculated the interobserver reliability in terms of intraclass correlation coefficients for each parameter. With calculation of SD and 95% confidence limits, pathological cut-offs were reconstructed from measurements performed resembling non-physiological and pathological limits. Distinct parameters were selected to form a new classification system for radiographical follow-up that focuses on the quantitative C1-2 vertebral alignment. The measurement process resulted in 2,400 data points. Distinct morphometrical parameters, such as a quantitative characterization of the sagittal atlantoaxial congruency, the lateral mass inclination and the type of degenerative changes at the atlantoaxial joint could be demonstrated to be valuable and reliably used within a proposed classification for C2-malunions following C2-fractures. The current study offers a template including recommended radiological measurements for further research on the study of clinical outcome and posttraumatic alignment following C2-fractures.