Cervical Spine Osteoradionecrosis.

Osteoradionecrosis (ORN), a well-known complication of radiotherapy in the mandibular bone, is very rare in the cervical spine. The authors report the result of a 3-year follow-up of a 63-year-old female patient with ORN of the cervical spine. The patient had a history of laryngeal carcinoma and was treated with chemotherapy and radiation therapy with a total of 120 Gy. Eight years later, she developed acute, severe neck pain due to cervical spine necrosis. The authors performed vascularized fibular bone graft and posterior pedicle screw fixation to reconstruct her cervical spine. The patient was successfully treated with surgery, and cervical alignment was preserved. She had neither neurological deficits nor severe neck pain at her final follow-up 3 years later. Delaying treatment of ORN may be life threatening, so the early diagnosis of this condition is important for patients who receive radiotherapy. Otolaryngologists and spine surgeons should understand this potential complication to speed diagnosis and treatment as early as possible.

Development of dysphagia and trismus developed after c1-2 posterior fusion in extended position.

Cervical misalignment after upper cervical fusion including the occipital bone may cause trismus or dysphagia, because the occipito-atlanto joint is associated with most of the flex and extended motion of the cervical spine. There are no reports of dysphagia and trismus after C1-2 fusion. The purpose of this paper is to demonstrate the potential risk of dysphagia and trismus even after upper cervical short fusion without the occipital bone. The patient was a 69-year-old man with myelopathy caused by os odontoideum and Klippel-Feil syndrome, who developed dysphagia and trismus immediately after C1-2 fusion and C3-6 laminoplasty. Radiographs and CT revealed that his neck posture was extended, but his symptoms still existed a week after surgery. The fixation angle was hyperextended 12 days after the first surgery. His symptoms disappeared immediately after revision surgery. The fixation in the neck-flexed position is thought to be the main cause of the patient's post-operative dysphagia and trismus. Dysphagia and trismus may occur even after short upper cervical fusion without the occipital bone or cervical fusion in the neck-extended position. The pre-operative cervical alignment and range of motion of each segment should be thoroughly evaluated.

Clinical application of a pedicle nail system with polymethylmethacrylate for osteoporotic vertebral fracture.

The instrumentation of the osteoporotic spine may sometimes result in failure due to the loosening or pullout of the conventional pedicle screw. Moreover, augmentation of screws with polymethylmethacrylate (PMMA) has risks of complications. We developed a new and original pedicle nail system with PMMA for osteoporotic vertebral fractures. A clinical evaluation of this novel pedicle nail system utilized in patients with an osteoporotic vertebral collapse was performed to determine the effectiveness and safety of this technique. Thirty-four elderly patients who suffered from osteoporotic compression fractures were treated by posterolateral fusion using the pedicle nail system. The mean follow-up period was 37 months. Of the 25 patients with neurological symptoms, two patients improved two stages at the Frankel level. Fifteen patients improved one stage at the Frankel level, and eight other patients improved, however, their improvement did not exceed a Frankel level. Nine cases with neuralgia symptoms improved from 4.4 to 2.2 points on average on the Denis pain scale (p < 0.01). The fusion rate was 94% as determined by X-rays of flexion and extension, and the correction of the compression fracture site was maintained well. A pedicle nail system stabilizes the spinal column with osteoporosis and reduces the instrumentation failure. The technique for the insertion of the pedicle nail reduces complication from cement augmentation. The authors speculate that the strategy using the pedicle nail system for osteoporotic spine may be effective and safe when the surgery is performed through a posterior approach.

Clinical accuracy of 3D fluoroscopy-assisted cervical pedicle screw insertion.

OBJECT: Cervical pedicle screw (PS) misplacement leads to injury of the spinal cord, nerve root, and vertebral artery. Recently, several investigators reported on the usefulness of a spinal navigation system that improves the accuracy of PS insertion. In this study, the authors assessed the accuracy of cervical pedicle, lateral mass, and odontoid screw insertions placed using a 3D fluoroscopy navigation system, the Iso-C3D unit. METHODS: In this prospective analysis of the authors' initial 50 cases of 3D fluoroscopy-assisted cervical screw insertion, the authors inserted 176 PSs, 58 lateral mass screws, and 5 odontoid screws into the C1-7 vertebrae. They placed screws using intraoperative acquisition of data by the isocentric C-arm fluoroscope and a computer navigation system. They obtained postoperative fine-cut CT scans in all patients and assessed the accuracy of screw insertion. RESULTS: A PS (>or= 3.5 mm) could be inserted into 24 (63%) of 38 pedicles at the level of C-3, 18 (53%) of 34 pedicles at C-4, 30 (65%) of 46 at C-5, 33 (80%) of 41 at C-6, and 43 (100%) of 43 at C-7. Of 176 PSs inserted into vertebrae between C-2 and C-7, 171 screws (97.2%) were classified as Grade 1 (no pedicle perforation), and 5 screws (2.8%) were classified as Grade 2 (screw perforation of the cortex by up to 2 mm). Clinically significant screw deviation in the present study was considered Grade 3 (screw perforation of the cortex by > 2 mm), and this occurred in 0% of the placements. CONCLUSIONS: In this study, the authors were able to correctly insert cervical PSs using the 3D fluoroscopy and navigation system.

Implant Failure of Titanium Versus Cobalt-Chromium Growing Rods in Early-onset Scoliosis.

STUDY DESIGN: Retrospective case series of one institute database. OBJECTIVE: To investigate the differences in the metallic strength of rods used for implant failure in the dual growing rod technique and evaluate clinical outcomes. SUMMARY OF BACKGROUND DATA: The dual growing rod technique in which implanted rods extend with the growth of the spine is a useful treatment for early onset scoliosis. However, many complications, particularly those associated with rods, exist. Especially, the implant failure of growing rod focused on metallic strength is unknown. METHODS: Thirteen patients (42 lengthening surgeries) who underwent surgery by this technique at our hospital from 2007 were divided into a titanium rod plus titanium connector group (T group, n = 4, 26 lengthening surgeries) and cobalt-chromium rod plus titanium connection group (C group, n = 9, 16 lengthening surgeries). The incidence of implant failure and the site of fracture were retrospectively investigated. RESULTS: Implant failure occurred in three patients in the T group, because of rod fracture in two patients and connector fracture in one. In the C group, implant failure occurred in six patients, because of rod fracture in one patient and connector fracture in seven. Fracture occurred twice in two patients. The rod fracture rate decreased with the use of cobalt-chromium rods but the rate of connector fracture increased. We performed a stress distribution analysis using the finite element method to clarify the mechanisms underlying implant failure in both groups. Regardless of the rod type, the greater load was placed on the distal rod. However, differences in the metallic strength caused the rod to fracture when titanium rods were used and connectors (weak metallic strength) to fracture when cobalt-chromium rods were used. CONCLUSION: Rod fractures occurred more commonly with titanium rods and connector fractures with cobalt-chromium rods.

Posterior spinal fusion using a pedicle nail system with polymethylmethacrylate in a paraplegic patient after vertebral collapse caused by osteoporosis.

BACKGROUND CONTEXT: Because posterior decompression and fusion for vertebral collapse in an osteoporotic spine sometimes results in a pullout of the pedicle screw. Several authors reported that fixation of pedicle screws in severely osteoporotic bone could be improved by inserting polymethylmethacrylate (PMMA) into the hole before inserting the screw. However, pedicle screws were not designed to be used with PMMA. PURPOSE: To report a patient with vertebral collapse who were treated using a novel-concept, pedicle nail using with PMMA. STUDY DESIGN: Case report. METHODS: The patient was a 74-year-old female who experienced back pain after some heavy lifting 3 months before. She was laid up for 2 months because of the back pain and weakness of her lower legs. Radiographs and magnetic resonance imaging showed vertebral collapse and neural severe compression from the posterior wall of vertebra T12. The pedicle nail consists of an outer sheath with evenly spaced holes and an internal, removable, threaded component. The outer sheath and the internal component were connected before insertion. The pedicle nail attaches to and is bound by the PMMA through the holes of the outer sheath. We performed a T11-L1 posterior fusion and laminectomy using the pedicle nail, and we used a hydroxyapatite block to perform a transpedicular vertebroplasty of T12. RESULTS: Bone union was observed on a lateral radiograph without pedicle nail loosening. CONCLUSIONS: The authors speculate that posterior spinal fusion and vertebroplasty using the pedicle nail will be a reasonable choice for delayed paraplegia after osteoporotic vertebral fracture.

Comparative biomechanical analysis of an improved novel pedicle screw with sheath and bone cement.

STUDY DESIGN: A human cadaveric biomechanical study of fixation strength of an improved novel pedicle screw (NPS) with cement and a conventional screw. OBJECTIVE: To clarify whether the NPS has adequate fixation strength without leakage in vertebrae with low bone quality. SUMMARY OF BACKGROUND DATA: The fixation strength of pedicle screws decreases in frail spines of elderly osteoporotic patients. Augmentation of screw fixation with bone cement must be balanced against increased difficulty of screw removal and risk of cement leakage. We developed the NPS consisting of an internal screw and an outer sheath to mitigate the disadvantages of cement augmentation. METHODS: The T12 and L1 vertebrae obtained from 18 formalin preserved cadavers (11 males and 7 females; mean age, 82.7 y) were used. The mean bone mineral density was 0.39 +/- 0.14 g/cm2. The NPS was inserted into one pedicle of each vertebra and the control screw, a Compact CD2 screw, was inserted into the contralateral pedicle. Both screws were 6mm in diameter and 40 mm in length. Pull-out tests were performed at a crosshead speed of 10 mm/min. Cyclic loading tests were performed with a maximum 250 N load at 2 Hz until 30,000 cycles. RESULTS: Cement leakage did not occur in any of the specimens tested. The mean maximum force at pull-out was 760 +/- 344 N for the NPS and 346 +/- 172N for the control screw (P < 0.01). Loosening of 50% of the screws was observed after 17,000 cycles of the NPS and after 30 cycles of the control screw. The hazard ratio of loosening was 19.6 (95% confidence interval 19.3-19.9) (P < 0.001). CONCLUSIONS: The NPS showed a significantly higher mechanical strength than the control screw in both pull-out tests and cyclic loading tests. The NPS showed more than adequate strength without cement leakage.