Jae Taek Hong

Analysis of anatomical variations of bone and vascular structures around the posterior atlantal arch using three- dimensional computed tomography angiography

OBJECT The current study evaluates the incidence of anatomical variations of the V(3) segment of the vertebral artery (VA) and the posterior arch of the atlas (C-1). Failure to appreciate these types of anatomical variations can cause catastrophic injury to the VA during posterior approaches to the upper cervical spine. METHODS In the present study, the authors analyzed the records of 1013 Korean patients who underwent computed tomography (CT) angiography to evaluate the incidence of anomalous variations in the third segment of the VA and to determine the incidence and morphometric characteristics of any detected posterior ponticuli. The authors also hoped to determine any specific imaging features that might indicate a VA anomaly around the craniovertebral junction. RESULTS The mean age of the patients was approximately 55.7 years and the prevalence of a posterior ponticulus was 15.6%. The incidence rate of a posterior ponticulus in the male population was 19.3%, whereas in the female population it was 12.8%. The incomplete type of posterior ponticulus was more common than the complete type. The mean age of the patients with an incomplete posterior ponticulus (55.7 years) was significantly younger (p = 0.018) than the mean age of patients with a complete posterior ponticulus (57.6 years). The incidence rate of a persistent first inter-segmental artery was 4.7% and the incidence rate of a fenestrated VA was 0.6%. The area of the C-1 transverse foramen on the abnormal side was significantly smaller than that of the contralateral normal side. CONCLUSIONS The shape of the C-1 posterior arch and the third segment of the VA are heterogeneous. Therefore, preoperative radiological studies should be performed to identify any anatomical variations. Using preoperative 3D CT angiography, we can precisely identify an anomalous VA and significantly reduce the risk of VA injury.

Anatomical variations of the vertebral artery segment in the lower cervical spine: analysis by three-dimensional computed tomography angiography.

Study Design. Observational study with retrospective computerized tomography (CT) angiography analysis. Objective. The purpose of this study is to examine the vertebral artery’s course in the V2 segment and define the anatomic variations in the adult population using CT angiography. Summary of Background Data. The V2 segment of the vertebral artery (VA) usually extends from the transverse processes of C6–C2; however, the presence of abnormal VA course has been reported. These variations may predispose a patient to higher risk of iatrogenic vascular injury during anterior cervical surgery. Methods. Retrospectively, 700 vertebral arteries on 350 three-dimensional CT angiographies were analyzed. Measurements were taken describing the relationship between the extraosseous portions of the VA to surgical landmarks. In addition, the diameter of the transverse foramen was measured on axial CT images. Results. The VA entered the C6 transverse process in 94.9% of the specimens (664 out of 700 VA courses). Abnormal VA entrance was observed in 5.1% of the specimens (36 VA courses), with entrance into the C4, C5, or C7 transverse foramen 1.6%, 3.3%, and 0.3%, respectively. In 2 of 36 cases (5.6%) of abnormal VA entrance, the extraosseous VA formed an unusual medial loop, and the center of VA was positioned medial to the longus colli muscle. Furthermore, transverse foramens filled with VA were significantly larger than unfilled foramens (P < 0.01), but there was no significant difference between the C7 unfilled foraminal area and unfilled foraminal area above C7 (P = 0.768). Conclusion. The present study confirms the presence of anomalous VA routes in the V2 segment. A preoperativethree-dimensional computerized tomography (CT) angiography with axial images may be useful to identify the presence of an anomalous V2 route when suspected on magnetic resonance imaging or CT. Delineation of this anomaly may reduce the risk of intraoperative VA injury.

Significance of laminar screw fixation in the subaxial cervical spine.

Study Design. We retrospectively reviewed 11 patients who underwent laminar screw fixation in the subaxial cervical spine. In 4 patients, laminar screws were inserted for posterior cervical arthrodesis, and in 7 patients it was used for fixation of the open laminae during laminoplasty. Objective. In this study, the author describes the technique and surgical results of translaminar screw placement in the subaxial cervical spine. Summary of Background Data. The use of laminar screws for fixation of the second cervical vertebra and upper thoracic vertebrae has been introduced as an important technique in spinal surgery because they can avoid injury to adjacent neurovascular structures. However, there have been no reports of translaminar screw use in the subaxial spine including C7. In this study, we describe the use of translaminar screws for fixation of the subaxial cervical spine in cases of degenerative or traumatic spine disease. Methods. Between June 2006 and March 2007, 34 translaminar screws were placed in 11 patients to treat trauma or degenerative disease: 6 at C7, 6 at C6, 7 at C5, 7 at C4, 7 at C3, and 1 at T1. There were 6 women and 5 men. The ages ranged from 23 to 87 years with a mean age of 61.3 years. All patients were evaluated at 6 weeks, as well as at 3 and 6 months using flexion and extension lateral radiographs. Patients requiring fusion were also evaluated with computed tomography at 3 and 6 months to verify arthrodesis. Results. The mean follow-up period was 5.7 months, at which time there was no significant complications from laminar screw placement, except for 2 asymptomatic breaches of the dorsal lamina cortex. Sound bone fusion was identified in cases where arthrodesis was the goal. No screw pullout or avulsion was identified in the laminoplasty cases. Conclusion. The translaminar screw method avoided damaging vascular structures, especially when the vertebral artery courses in the C7 transverse foramen, and it maintains solid stabilization of the subaxial cervical spine. This technique has 2 important advantages to currently used techniques: it is simpler and is not limited by the position of vascular structures. Therefore, it may be applicable to a wider number of patients, especially as it may be used in the subaxial cervical spine.

Clinical and radiologic outcome of laminar screw at C2 and C7 for posterior instrumentation--review of 25 cases and comparison of C2 and C7 intralaminar screw fixation.

BACKGROUND The aim of this study is 2-fold: to analyze a clinical case series in which we used laminar screws for cervical posterior instrumentation and to describe the difference between C2 and C7 laminar screws in terms of technique and anatomy. METHODS Data were obtained from 25 patients who underwent cervical posterior fixation with intralaminar screws at C2 or C7. C2 intralaminar screw instrumentation was used for 7 patients requiring occipitocervical fixation (basilar invagination [3 patients], C1 unstable bursting fracture [1 patient], C1-C2 instability with occipital assimilation [2 patients], and dystopic os odontoideum [1 patient]), 13 patients with C1-C2 instability, 1 patient with C2-C3 subluxation, and 4 patients undergoing C7 fixation due to pseudoarthrosis or cervical instability after trauma. A total of 34 laminar screws were placed including 1 thoracic laminar screw, and the patients were assessed both clinically and radiographically. RESULTS There were no instances where a screw violated the spinal canal nor any hardware fractures noted during the follow-up period. As for perioperative complications, there were 2 cases of postoperative wound infection, 1 case of dural laceration during dissection, and 2 cases of partial dorsal laminar breach. However, there was no neurologic compromise in any of the cases. The fusion success rate was 100%. CONCLUSION These preliminary results support the use of intralaminar screws for posterior instrumentation at C2 and C7.

Motor cortex stimulation for central pain following a traumatic brain injury

Abstract Central pain can occur in any lesions along the central nervous system affecting the spinothalamocortical pathway. Although diverse etiologies have been reported to cause central pain, there are few reports on the occurrence and surgical treatment of central pain following a traumatic brain injury (TBI). This paper describes the occurrence of central pain following a severe TBI, in which the diagnosis of central pain was typically delayed due to the patient’s decreased ability to express his pain for severe aphasia as a neurological sequela. The severe burning pain, deep pressure‐like pain, and deep mechanical allodynia, which presented over the contralateral side to the TBI, were successfully relieved with motor cortex stimulation (MCS). The analgesic effect of stimulation was found to be long lasting and was still present at the 12‐month follow up. As shown in this patient, the occurrence of central pain syndrome should be considered by physicians caring for TBI patients, and a comprehensive, systematic study will be needed to determine the prevalence of central pain after a TBI.

E-cadherin as a predictive marker of brain metastasis in non-small-cell lung cancer, and its regulation by pioglitazone in a preclinical model

It remains unclear whether patients with non-small-cell lung cancer (NSCLC) develop brain metastasis during or after standard therapy. We attempted to identify biological markers that predict brain metastasis, and investigated how to modulate expression of such markers. A case–control study of patients who were newly diagnosed with NSCLC and who had developed brain metastasis during follow-up was conducted between 2004 and 2009. These patients were compared with a control group of patients who had NSCLC but no evidence of brain metastasis. Immunohistochemical analysis of expression of Ki-67, p53, Bcl-2, Bax, vascular endothelial growth factor, epidermal growth factor receptor, caspase-3, and E-cadherin was conducted. The methylation status of the genes for O6-methylguanine-DNA-methyltransferase, tissue inhibitor of matrix metalloproteinase (TIMP)-2, TIMP-3, and death-associated protein-kinase was also determined, by use of a methylation-specific polymerase chain reaction. A significantly increased risk of developing brain metastasis was associated with the presence of primary tumors with low E-cadherin expression in patients with NSCLC. We also investigated the effects of pioglitazone, a peroxisome proliferator-activated receptor γ-activating drug, in tumor-bearing mouse models. We found that E-cadherin expression was proportional to pioglitazone exposure time. Interestingly, pioglitazone pretreatment before cancer cell inoculation prevented loss of E-cadherin expression and reduced expression of MMP9 and fibronectin, compared with the control group. E-cadherin expression could be a predictor of brain metastasis in patients with NSCLC. Preventive treatment with pioglitazone may be useful for modulating E-cadherin expression.

Biomechanical comparison of three different types of C7 fixation techniques: Lateral mass screw, transpedicular screw, and intralaminar screw

Study Design. In vitro biomechanical comparison of 3 C7 posterior fixation methods. Objective. To investigate the posterior cervical construct stability afforded by this novel C7 intralaminar screw with lateral mass and transpedicular screw. Summary of Background Data. The intralaminar screw method is recently introduced and used in C7 fixation. However, no biomechanical comparisons of the C7 intralaminar screw with lateral mass screw or transpedicular screw technique have been performed. Methods. Ten fresh frozen human cadaveric C6-C7 motion segments were tested before and after 3 different types of C7 screw fixation (lateral mass screw, intralaminar screw and pedicle screw). After the kinematic study was completed, the pull out strength test for each type of C7 screw was performed. Results. To compare 3 C7 fixation techniques, normalized range of motion (ROM) of each type of screw was analyzed relative to the intact state. There were no significant differences between 3 types of C7 screws in terms of mean ROM in flexion/extension. The mean lateral bending ROM of C7 intralaminar screw construct (30.5% ± 9.2%) was significantly larger than C7 pedicle screw construct (19.2% ± 6.9%, P < 0.05). The mean axial rotation of C7 lateral mass construct (52.0% ± 27.1 %) was significantly larger than C7 pedicle screw construct (38.7% ± 23.8%, P < 0.05). The pull-out strength of lateral mass screw was significantly weaker than other 2 types of C7 screw (intralaminar and pedicle screw). However, there was no significant pull-out strength difference between the C7 intralaminar and C7 pedicle screw techniques. Conclusion. This study demonstrates that the pedicle screw fixation is the strongest instrumentation method for C7 fixation. However, if C7 pedicle fixation is unfavorable, in case that vertebral artery course through the C7 transverse foramen or C7 pedicle is not large enough to insert screw, the C7 laminar screw can be an alternative fixation point with similar limitation of motion except in lateral bending.

Anatomy of Neurovascular Structures Around the Carpal Tunnel During Dynamic Wrist Motion for Endoscopic Carpal Tunnel Release

OBJECTIVE: The purpose of this study is to investigate the anatomic relationship between neurovascular structures and the transverse carpal ligament (TCL) so as to avoid complications during an endoscopic carpal tunnel release procedure. METHODS: Fresh cadaver hands from seven men and 12 women (age range, 48–74 yr) were used. The neurovascular structures just over and under the TCL were meticulously dissected under loupe magnification. Several anatomic landmarks were calculated (average length of the TCL; average distance between the TCL distal margin and the neurovascular structures; and average lengths of the superficial palmar arch, ramus communicantes, recurrent motor branch, and palmar cutaneous branch of the median nerve). The ulnar neurovascular structure was studied with the wrist positioned in neutral, ulnar flexion, and radial flexion. RESULTS: The anatomic relationships between the TCL and vascular and neural structures were measured. The ulnar neurovascular structures usually passed just over ulnar to the superior portion of the hook of the hamate. However, in 11 hands, a looped ulnar artery coursed 1 to 4 mm radial to the hook of the hamate and continued to the superficial palmar arch. The looped ulnar artery migrates on the ulnar side of Guyons canal (-2–2 mm radial to the hook of the hamate) with the wrist in radial flexion (of the wrist). During ulnar flexion of the wrist, the ulnar artery shifts more radially beyond the hook of the hamate (2–7 mm). CONCLUSION: It is appropriate to transect the ligament over 4 mm apart from the lateral margin of the hook of the hamate without placing the edge of the scalpel toward the ulnar side. We would also recommend not transecting the TCL in the ulnar flexed wrist position to protect the ulnar neurovascular structure. The proximal portal could be made just ulnar to the palmaris longus tendon to spare the neurovascular structures in the proximal portion of the TCL.

Intraoperative Monitoring of Motor-Evoked Potentials for Supratentorial Tumor Surgery

Objective The purpose of this study was to assess the feasibility and clinical efficacy of motor evoked potential (MEP) monitoring for supratentorial tumor surgery. Methods Between 2010 and 2012, to prevent postoperative motor deterioration, MEP recording after transcranial stimulation was performed in 84 patients with supratentorial brain tumors (45 males, 39 females; age range, 24-80 years; median age, 58 years). MEP monitoring results were correlated with postoperative motor outcome compared to preoperative motor status. Results MEP recordings were stable in amplitude (<50% reduction in amplitude) during surgery in 77 patients (91.7%). No postoperative motor deficit was found in 66 out of 77 patients with stable MEP amplitudes. However, postoperative paresis developed in 11 patients. False negative findings were associated with edema in peri-resectional regions and postoperative bleeding in the tumor bed. MEP decrease in amplitude (>50%) occurred in seven patients (8.3%). However, no deficit occurred postoperatively in four patients following preventive management during the operation. Three patients had permanent paresis, which could have been associated with vascular injury during tumor resection. Conclusions MEP monitoring during supratentorial tumor surgery is feasible and safe. However, false negative MEP results associated with postoperative events may occur in some patients. To achieve successful monitoring, collaboration between surgeon, anesthesiologist and an experienced technician is mandatory.

Analysis of accuracy of kyphotic angle measurement for vertebral osteoporotic compression fractures

A reliable and reproducible measurement technique for the sagittal contour in vertebral fractures is paramount to clinical decision-making. This study was designed to determine the most reliable measurement technique in osteoporotic vertebral compression fracture. Fifteen lateral radiographs of thoracic and lumbar fractures were selected and measured on two separate occasions by three spine surgeons using six different measurement techniques (centroid, Harrison posterior tangent method and 4 different types of modified Cobb method). The radiograph quality was assessed and the center beam location was determined. The inter- and intraobserver variance of the Cobb method 4 and the Harrison posterior tangent method were significantly lower than for the other four methods. The intraobserver correlation coefficients were the most consistent using the Cobb method 4 (0.982), followed by the Harrison posterior tangent method (0.953) and Cobb method 1 (0.874). The intraobserver agreement (% of repeated measures within 5 degrees of the original measurement) ranged from 42% to 98% for each technique for all three observers, with the Cobb method 4 showing the best agreement (97.8%) followed by the Harrison posterior tangent method (93.7%). The Cobb method 4 and Harrison posterior tangent method, when applied to measuring the kyphosis, were reliable and had a similar small error range. The Cobb method 4 showed the best overall reliability. The centroid method and the other Cobb methods using a fractured endplate did not produce an accurate result due to inter- and intraobserver differences in determining the baseline.