Purpose Popliteal artery injury is a rare but devastating complication of open-wedge high tibial osteotomy (OWHTO). The objectives of this study were: to document the location of the artery in the virtual osteotomy plane (VOP), to measure the minimal distance between the popliteal artery and three virtual saw-progression lines (VSLs), and to present a safe sawing technique for OWHTO. Method In total, 45 computed tomography angiographies were reconstructed and virtual osteotomy was simulated using 3D image-processing software. The VOP was defined as an inclined plane commencing 3.5 cm below the articular plane towards the fibular head. VSLs were defined as saw-progression guidelines that lie on the VOP: "VSL-mid" runs from the midpoint of the tibial medial cortex towards the fibular head; "VSL-ant" starts from the same point as VSL-mid, but runs 10° anterior to the fibular head; and "VSL-post" runs 10° posterior to the fibular head. The distances between the popliteal artery and the three VSLs were measured, and the risk of injury was assessed. ResultsThe popliteal artery was located 20.7° posterior to VSL-mid and 51 mm from the starting point. The minimum distance between the popliteal artery and VSL-mid was 18 mm (99% confidence interval 9-27 mm). When the saw was moved along VSL-mid, 42% of the arteries were susceptible to injury. However, when it followed VSL-ant, there was no risk of injury. Conclusions Sawing toward the fibular head carries a risk of popliteal artery injury and should not be performed. When sawing in OWHTO, the recommended target should be 10° anterior to the fibular head. This technique eliminates the risk of popliteal artery injury.

Study Design: Retrospective case series. Purpose: We reviewed the cases that showed significant improvement of intraoperative neurophysiological monitoring (IONM) signals during spine surgery to assess whether there is a correlation with signal improvement and postoperative clinical status and its clinical significance. Overview of Literature: To reduce the risk of neural injury, many spine surgeons are using multimodality IONM. Although many studies attempted to identify valid alarm criteria for predicting postoperative neurologic deterioration, studies concerning the improvement of IONM signals are rare. Methods: We reviewed all spine surgery cases with IONM data treated at our department between January 2013 and May 2017. We found cases showing significant IONM signal improvements. We prospectively analyzed the neurological and clinical outcomes of these patients and compared outcomes pre-and postoperatively. Results: Among 317 cases with the IONM data, we found 29 cases that showed IONM signal improvement compared with baseline. There were 27 cases of compressive myelopathy: 22 had a degenerative cause at the cervical spine, and five, at the thoracic spine. There were two cases of huge neurogenic tumor each at the craniovertebral junction and at the lumbar spine. Both motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs) signals were improved in six cases, only the MEPs signal improved in 10, and only SSEP signal improved in 13 cases. All cases showed the IONM signal improvement consistently after the decompression procedure during surgery. All patients had a significant improvement in neurological function and subjective symptoms, and none had neurologic deterioration postoperatively. Conclusions: Improvement of IONM signals during surgery may indicate that no unrecognized neural injury occurred during surgery and a favorable postoperative neurological outcome can be expected.

PurposeThis study presents the clinical and radiological outcomes of cementless total hip arthroplasty using the COREN hip system after a minimum duration of follow-up of 5 years.Materials and MethodsWe evaluated the results of a consecutive series of the first 200 primary total hip arthroplasties that had been performed in our hospital in 169 patients between February 2007 and April 2011. Six patients (6 hips) had died within 5 years, and 12 patients (13 hips) had been lost to follow-up, leaving a total of 151 patients (181 hips) available for the study. All patients were evaluated clinically and radiologically with special attention to thigh pain, implant fixation, radiolucent line and osteolysis around implants.ResultsThe mean Harris hip score improved from 59.4 preoperatively to 97.2 postoperatively. No patient complained of thigh pain. All implants demonstrated radiographic evidence of stable fixation by bone ingrowth without any change in position. No implant was loose radiographically or was revised. Eleven hips (7.7%) had a radiolucent line around the femoral stem. Focal osteolytic area was detected in 3 cases (2.1%). An osteolytic lesion was stabilized in 1 case and further observation was needed in 2 cases in which the lesions were detected several years after surgery. Stress shielding was observed in 80.3% of cases (first degree, 35.9%; second degree, 44.4%); there were no cases of third or fourth degree stress shielding. One case was complicated by bacterial infection and repeated dislocation.ConclusionMid-term results of total hip arthroplasty using the COREN hip system are very encouraging clinically and radiologically.

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Primary central nervous system (CNS) sarcomas are exceedingly rare, and, to the best of our knowledge, there has not yet been a report of intramedullary sarcoma. Here, we report a primary intradural intramedullary sarcoma of the spinal cord in a four-year-old boy who presented with low back pain and a radiculopathy involving both lower extremities. The tumor showed significant enhancement on magnetic resonance (MR) images due to its extreme vascularity. Gross total tumor removal was performed with microelectrical pulse recording, and the patient also received adjuvant radiotherapy and chemotherapy. After the operation, the patient's sensory deficits were improved. Because CNS dissemination is common, entire neuraxis evaluation is essential, although there was no evidence of dissemination in this case. The prognosis of primary CNS sarcoma is poor due to infiltrative nature and early CNS dissemination is common, and the treatment of choice is radical surgical resection. Adjuvant therapy is also beneficial with radiotherapy and chemotherapy.