Objective
To compare the pull-out strength of polyaxial general screws and rescue screws when inserted into the lateral mass through cadaveric biomechanical experiment
Materials and Methods
Twenty three segments of the human cervical spine (from C3 to C7) were prepared. Two biomechanical studies were progressed. In the first experiment (13 segments), each segment was instrumented with 3.5×12 mm polyaxial screws on both sides. In one side, the inserted screw was removed and then the rescue screw was inserted to the same screw hole. In the second experiment (10 segments), all segments were instrumented with 3.5×12 mm polyaxial screws on both sides and all screws were removed. In one side, removed same screw was reinserted and in the other side, the rescue screw was inserted without change of the screw trajectory. All specimens were fixed to the specially designed frame with the cement. Universal Material Test Machine (Mini Bionix 858) was used to assess the pull-out strength of the screws. All data were compared with non-parametric paired test (Wilcoxon’s signed rank test).
Results
There was no crack or fracture around the screw hole. No significant difference was noted between the original screws (not reinserted) and the rescue screws in the first experiment (p=0.753). There is no significant difference between the same screw reinsertion and the conversion to the rescue screw (p=0.646).
Conclusions
The overall results of this study showed the conversion to the rescue screw with the same screw trajectory could offer no biomechanical advantage over reinsertion of the same screw. In case of secure screw hole after removal of the screw, the reinsertion of the same screw could be recommended.

Purpose
To evaluate long term efficacy of percutaneous balloon kyphoplasty for osteoporotic compressive vertebral fracture.
Materials and Methods
Percutaneous balloon kyphoplasty was performed to 52 vertebral bodies, for 42 patients with compression fracture from March 2003 to October 2007. During observation, 32 patients (39 vertebral bodies) were followed over 5 years except 8 patients (19.0%) who have expired. Pre operational, post operational and final observational radiologic evaluation (vertebral height, compression ratio, kyphotic angle) and clinic evaluation(VAS score) were checked. And correlation with bone cement leakage, fracture of adjacent vertebral body, gender, age, bone mineral density and medication was analyzed.
Result
Average age was 71.3 years old and average observation period was 74.3 months. Average interval from injury to operation was 24.1 days. Vertebral compression ratio recovered 29.7% to 17.4% (12.3%), kyphotic angle improved 11.6 degree to 9.0 degree (2.6 degree) and there was no significant change until final observation. VAS score got better 7.60 to 3.57 (4.03) after operation. Bone cement leakage occurred in 5 cases (12.8%) and fracture of adjacent vertebral body occurred in 10 cases (25.6%), there was no correlation between two groups (p=1.000). Fracture of adjacent vertebral body showed meaningful correlation with bone mineral density only.
Conclusion
Percutaneous balloon kyphoplasty relieve the pain after compression fracture of vertebral body and is safe and efficient procedure to correct sagittal deformity. After 5 year follow up, the effect of procedure was maintained clinically. Bone cement leakage did not increase risk of fracture of adjacent vertebral body which occurred frequently in low bone mineral density.

Minimally invasive TLIF has been reported to be a useful treatment option for the patients with various degenerative lumbar diseases. Many studies have reported the favorable clinical results of MIS TLIF. However it remains technically demanding, leading to higher complication rates and longer operative times during the early period of the learning curve. It showed some potential complications due to small working space and visual field. In this study, authors tried to find out various possible complications and some tips avoiding these complications through the review of various articles and authors’ clinical experiences. In many studies, the general complication fusion rates of MIS TLIF have been reported to be similar to that of open fusion. The technical difficulty of the procedure, combined with inadequate training, is evident in initial studies of MIS TLIF. A difficult learning curve of MIS TLIF demands that surgeons have sufficient preclinical training, and education is obtained before the application of MIS TLIF in clinical practice.

Percutaneous vertebroplasty and balloon kyphoplasty are both safe and effective procedures in case of patients with osteoporotic vertebral compression fractures. The authors have already reported a new technique called lordoplasty using polymethylmethacrylate to manage vertebral osteoporotic compression fractures. The purpose and indication of lordoplasty do not differ from that of percutaneous vertebroplasty or balloon kyphoplasty. However, there are advantages of lordoplasty in terms of restoration of the wedge and kyphotic angle and cost-effectiveness compared with the other procedures mentioned above. For the advantages of lordoplasty, authors thereby introduce the detailed procedure of lordoplasty.

Thirty-four-year old female patient visited our clinic for posterior neck pain for 3 days. She had no medical history or traumatic injury. On physical examination, posterior neck pain aggravating with neck motion was seen, there was no neurologic symptom. WBC, ESR and CRP were slightly increased. There was no specific finding on simple cervical radiologic study but, on cervical CT, calcified lesion was seen on the right lateral side of dens. The symptom got better after medication with NSAIDs, oral and intra venous steroid drugs for 2 days, disappeared after 4 days with NSAIDs and intra venous steroid drug. In following lab study, inflammatory marker decreased. Crowned Dens Syndrome could be misdiagnosed with meningitis, so cervical CT study is essential for differential diagnosis. Symptoms can be treated with NSAIDs and steroid drug.