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Takahisa Hishiya, Tetsuhiro Ishikawa, and Mitsutoshi Ota

OBJECTIVE

Diffuse idiopathic skeletal hyperostosis (DISH)–related vertebral fractures essentially require operative treatment due to severe fracture site instability and high potential risk of posttraumatic neurological deficit. However, the optimal surgical procedure remains unclear. The purpose of this study was to assess the efficacy of posterior spinal fixation with penetrating endplate screws (PESs) for DISH-related thoracolumbar fractures.

METHODS

The authors conducted a retrospective, single-center, observational study. They included data from 26 consecutive patients with DISH-related thoracolumbar fractures who were treated with posterior spinal fixation using either conventional pedicle screws (PS group, n = 8) or a combined PES technique (PES group, n = 18) between 2013 and 2019. Age, sex, BMI, bone mineral density, fracture level, use of antithrombotic drug, blood loss, operation time, fixation range, perioperative American Spinal Injury Association Impairment Scale score, implant failure, revision surgery, complications, and mortality were compared. The authors also evaluated screw loosening and bone healing on radiographs and CT scans.

RESULTS

More patients had vertebral fractures in the lumbar spine in the PS group than in the PES group (3 vs 0; p = 0.019). Patients in the PES group had less blood loss (63 vs 173 ml; p = 0.048) and shorter range of fixation (5 vs 5.5 levels; p = 0.041). The screw loosening rate was significantly lower in the PES group than in the PS group (3% vs 49%; p < 0.001).

CONCLUSIONS

Posterior spinal fixation using a PES technique may be an ideal surgical procedure for thoracolumbar fractures with DISH, providing more rigid and less invasive fixation than PS.

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Satoshi Maki, Masaaki Aramomi, Yusuke Matsuura, Takeo Furuya, Mitsutoshi Ota, Yasushi Iijima, Junya Saito, Takane Suzuki, Chikato Mannoji, Kazuhisa Takahashi, Masashi Yamazaki, and Masao Koda

OBJECTIVE

Fusion surgery with instrumentation is a widely accepted treatment for cervical spine pathologies. The authors propose a novel technique for subaxial cervical fusion surgery using paravertebral foramen screws (PVFS). The authors consider that PVFS have equal or greater biomechanical strength than lateral mass screws (LMS). The authors’ goals of this study were to conduct a biomechanical study of PVFS, to investigate the suitability of PVFS as salvage fixation for failed LMS, and to describe this novel technique.

METHODS

The authors harvested 24 human cervical spine vertebrae (C3–6) from 6 fresh-frozen cadaver specimens from donors whose mean age was 84.3 ± 10.4 years at death. For each vertebra, one side was chosen randomly for PVFS and the other for LMS. For PVFS, a 3.2-mm drill with a stopper was advanced under lateral fluoroscopic imaging. The drill stopper was set to 12 mm, which was considered sufficiently short not to breach the transverse foramen. The drill was directed from 20° to 25° medially so that the screw could purchase the relatively hard cancellous bone around the entry zone of the pedicle. The hole was tapped and a 4.5-mm-diameter × 12-mm screw was inserted. For LMS, 3.5-mm-diameter × 14-mm screws were inserted into the lateral mass of C3–6. The pullout strength of each screw was measured. After pullout testing of LMS, a drill was inserted into the screw hole and the superior cortex of the lateral mass was pried to cause a fracture through the screw hole, simulating intraoperative fracture of the lateral mass. After the procedure, PVFS for salvage (sPVFS) were inserted on the same side and pullout strength was measured.

RESULTS

The CT scans obtained after screw insertion revealed no sign of pedicle breaching, violation of the transverse foramen, or fracture of the lateral mass. A total of 69 screws were tested (23 PVFS, 23 LMS, and 23 sPVFS). One vertebra was not used because of a fracture that occurred while the specimen was prepared. The mean bone mineral density of the specimens was 0.29 ± 0.10 g/cm3. The mean pullout strength was 234 ± 114 N for PVFS, 158 ± 91 N for LMS, and 195 ± 125 N for sPVFS. The pullout strength for PVFS tended to be greater than that for LMS. However, the difference was not quite significant (p = 0.06).

CONCLUSIONS

The authors introduce a novel fixation technique for the subaxial cervical spine. This study suggests that PVFS tend to provide stronger fixation than LMS for initial applications and fixation equal to LMS for salvage applications. If placement of LMS fails, PVFS can serve as a salvage fixation technique.