Several anterior and posterior methods are today available for stabilization of the cervical spine. Factors such as level and degree of instability, method of decompression, bone quality, length of fixation and safety factors influence the choice of method for a particular patient. The use of laminar hooks in the cervical spine has been restricted by fear of cord compression with the potential of tetraplegia. The aim of the present study was to assess the safety and determine the anatomical relation between hooks inserted in the cervical spinal canal and the dura and spinal cord. Thirteen cadavers from seven women and six men with no evidence of cervical spine disorder were included. The mean age was 81.3 years (range 65-101 years). The cervical spine was instrumented with cervical Compact Cotrel Dubousset hooks and rods. The effect of the hook on the dura was studied by myelography in nine cadavers. The deformation of the dural sac was quantified by measurement of the maximal width of the indentation of the contrast column at each level. A CT myelography scan was obtained in three cadavers. The ratio between the distance of maximal hook intrusion into the spinal canal and the canal diameter in the direction of the hook was calculated. The relation between inserted hooks and the spinal cord and dura was documented in a fresh cadaver studied with CT myelography. A hemilaminectomy was performed at all levels in three cadavers with direct visual inspection and photography of the hook sites before and after excision of the dura. A dural deformation of 2 mm or less, as observed by myelography, was found at four out of 77 (5%) hook sites. The deformation was caused by a supralaminar hook at C3, C6 and C7 and by an infralaminar hook at C6. The mean hook intrusion in the spinal canal, as observed on CT, was 27% (range 8-43) of the canal diameter. On visual inspection, 14 out of 18 hooks were in contact with the dura. After removal of the dura, two out of the 18 hooks in the same cadaver were in contact with the spinal cord. However, no deformation of the cord was observed. To our knowledge this is the first study systematically documenting the relation between hooks and the spinal cord in cadavers. In 95% of the hooks no deformation of the dural sac was observed and there was no evidence of spinal cord deformation. From an anatomical point of view, laminar hook instrumentation can be considered a safe procedure. The study shows, however, that hooks inserted in the cervical spine have a close anatomical relationship with the neuraxis, and at stenotic levels the use of other techniques is therefore recommended.
IntroductionSince Hadra first described the time-honored technique of cervical wiring, several alternative fixation techniques have been developed, all with inherent limitations and risks.In atlanto-axial surgical stabilization, the Gallie wiring technique is still the gold standard, but it has several limitations [15,26]. Its mechanical stabilizing potential is limited, it does not result in rotational or translational sagittal stability and additional external fixation is needed, which is a great disadvantage, particularly in rheumatoid arthritis (RA) and metastatic disease. Transarticular C2-1 screws with additional Gallie type wire fixation is biomechanically attractive, offering rotational and translational stability, but is technically demanding, with a risk of vertebral artery injury [8,29,40].Wiring is also a traditional method of subaxial spine fixation [33]. Techniques based on wires through the Abstract There are today several techniques available for cervical fixation -all with inherent limitations and risks. In view of the drawbacks of wiring and screw fixation, which both presuppose good bone quality for stabilization, there is a need for a stable and safe fixation system that can also be used in osteoporotic bone. The objective of the present retrospective study was to assess the usefulness and safety of Cervical Cotrel Dubousset Instrumentation (CCDI), based on sublaminar hooks. The material comprises 60 consecutive patients, 28 men and 32 women, with a mean age of 57.3 years (range 17-84 years), operated on with CCDI. The diagnosis was trauma in 17 patients, rheumatoid arthritis in 16 patients, tumor in 20 patients and miscellaneous diagnoses in 7 patients. The material was dominated by severe pathologies, with neurological impairment in 17 patients (28%). Complications, subjective outcome and Frankel classification of neurological status pre-and postoperatively was documented. The patient outcome evaluation was excellent in 46%, good in 34%, fair in 10%, and poor in 10%. The physician's assessment was similar: 56% excellent, 27% good, 10% fair and 7% poor. Two patients improved by two Frankel grades, 7 by one and 47 patients had the same Frankel grade as preoperatively. Two patients deteriorated by one Frankel grade, one by three grades and one patient by four Frankel grades. Except for a 10% deep wound infection rate, there were few complications, with no evidence of neurological injury from the hooks in the spinal canal. The results of this study show that the cervical CDI system can be safely used for stable cervical fixation without need for external support in severe pathologies of the cervical spine.
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