Mehmet Senoglu

The frequency and clinical significance of congenital defects of the posterior and anterior arch of the atlas

OBJECT In this study the authors investigated the anatomical, clinical, and imaging features as well as incidence of congenital defects of the C-1 arch. METHODS The records of 1104 patients who presented with various medical problems during the time between January 2006 and December 2006 were reviewed retrospectively. The craniocervical computed tomography (CT) scans obtained in these patients were evaluated to define the incidence of congenital defects of the posterior arch of C-1. In addition, 166 dried C-1 specimens and 84 fresh human cadaveric cervical spine segments were evaluated for anomalies of the C-1 arch. RESULTS Altogether, 40 anomalies (2.95%) were found in 1354 evaluated cases. Of the 1104 patients in whom CT scans were acquired, 37 (3.35%) had congenital defects of the posterior arch of the atlas. The incidence of each anomaly was as follows: Type A, 29 (2.6%); Type B, six (0.54%); and Type E, two (0.18%). There were no Type C or D defects. One patient (0.09%) had an anterior arch cleft. None of the reviewed patients had neurological deficits or required surgical intervention for their anomalies. Three cases of Type A posterior arch anomalies were present in the cadaveric specimens. CONCLUSIONS Most congenital anomalies of the atlantal arch are found incidentally in asymptomatic patients. Congenital defects of the posterior arch are more common than defects of the anterior arch.

Dynamic lumbar pedicle screw-rod stabilization: in vitro biomechanical comparison with standard rigid pedicle screw-rod stabilization

OBJECT It is unclear how the biomechanics of dynamic posterior lumbar stabilization systems and traditional rigid pedicle screw-rod systems differ. This study examined the biomechanical response of a hinged-dynamic pedicle screw compared with a standard rigid screw used in a 1-level pedicle screw-rod construct. METHODS Unembalmed human cadaveric L3-S1 segments were tested intact, after L4-5 discectomy, after rigid pedicle screw-rod fixation, and after dynamic pedicle screw-rod fixation. Specimens were loaded using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording motion optoelectronically. Specimens were then loaded in physiological flexion-extension while applying 400 N of compression. Moment and force across instrumentation were recorded from pairs of strain gauges mounted on the interconnecting rods. RESULTS The hinged-dynamic screws allowed an average of 160% greater range of motion during flexion, extension, lateral bending, and axial rotation than standard rigid screws (p < 0.03) but 30% less motion than normal. When using standard screws, bending moments and axial loads on the rods were greater than the bending moments and axial loads on the rods when using dynamic screws during most loading modes (p < 0.05). The axis of rotation shifted significantly posteriorly more than 10 mm from its normal position with both devices. CONCLUSIONS In a 1-level pedicle screw-rod construct, hinged-dynamic screws allowed a quantity of motion that was substantially closer to normal motion than that allowed by rigid pedicle screws. Both systems altered kinematics similarly. Less load was borne by the hinged screw construct, indicating that the hinged-dynamic screws allow less stress shielding than standard rigid screws.

Microsurgical management of spinal schwannomas: evaluation of 128 cases.

OBJECT The authors conducted a study to evaluate the clinical characteristics and surgical outcomes in patients with spinal schwannomas and without neurofibromatosis (NF). METHODS The data obtained in 128 patients who underwent resection of spinal schwannomas were analyzed. All cases with neurofibromas and those with a known diagnosis of NF Type 1 or 2 were excluded. Karnofsky Performance Scale (KPS) scores were used to compare patient outcomes when examining the anatomical location and spinal level of the tumor. The neurological outcome was further assessed using the Medical Research Council (MRC) muscle testing scale. RESULTS Altogether, 131 schwannomas were treated in 128 patients (76 males and 52 females; mean age 47.7 years). The peak prevalence is seen between the 3rd and 6th decades. Pain was the most common presenting symptom. Gross-total resection was achieved in 127 (97.0%) of the 131 lesions. The nerve root had to be sacrificed in 34 cases and resulted in minor sensory deficits in 16 patients (12.5%) and slight motor weakness (MRC Grade 3/5) in 3 (2.3%). The KPS scores and MRC grades were significantly higher at the time of last follow-up in all patient groups (p = 0.001 and p = 0.005, respectively). CONCLUSIONS Spinal schwannomas may occur at any level of the spinal axis and are most commonly intradural. The most frequent clinical presentation is pain. Most spinal schwannomas in non-NF cases can be resected totally without or with minor postoperative deficits. Preoperative autonomic dysfunction does not improve significantly after surgical management.

Nontraumatic scalp arteriovenous fistula in an adult: technical report on an illustrative case

BACKGROUND The treatment of sAVF is difficult, and many therapeutic approaches have been proposed. General approaches for the treatment of sAVF include ligation of the feeding arteries, surgical removal, electrothrombosis, embolization, and a combination of these approaches. CASE DESCRIPTION A 35-year-old man presented with occipital subcutaneous pulsatile thrill. We discussed and illustrated a rare sAVF, which was a high-flow sAVF fed by the occipital branch of the right ACE draining intraosseously into the SS. The case was treated by surgical origin ligation. CONCLUSION This case was unusual in the sense that it was apparently spontaneous, and the major venous drainage was through the bone into the SS. Arterial supply pattern of sAVF is very important in therapeutic decision-making. We suggest that surgical origin ligation for sAVF be considered if the case has 1 feeding artery.

Biomechanics of C-7 transfacet screw fixation: Laboratory investigation

OBJECT The small diameter of the pedicle can make C-7 pedicle screw insertion dangerous. Although transfacet screws have been studied biomechanically when used in pinning joints, they have not been well studied when used as part of a C7-T1 screw/rod construct. The authors therefore compared C7-T1 fixation using a C-7 transfacet screw/T-1 pedicle screw construct with a construct composed of pedicle screws at both levels. METHODS Each rigid posterior screw/rod construct was placed in 7 human cadaveric C6-T2 specimens (14 total). Specimens were tested in normal condition, after 2-column instability, and once fixated. Nondestructive, nonconstraining pure moments (maximum 1.5 Nm) were applied to induce flexion, extension, lateral bending, and axial rotation while recording 3D motion optoelectronically. The entire construct was then loaded to failure by dorsal linear force. RESULTS There was no significant difference in angular range of motion between the 2 instrumented groups during any loading mode (p > 0.11, nonpaired t-tests). Both constructs reduced motion to < 2 degrees in any direction and allowed significantly less motion than in the normal condition. The C-7 facet screw/T-1 pedicle screw construct allowed a small but significantly greater lax zone than the pedicle screw/rod construct during lateral bending, and it failed under significantly less load than the pedicle screw/rod construct (p < 0.001). CONCLUSIONS When C-7 transfacet screws are connected to T-1 pedicle screws, they provide equivalent stability of constructs formed by pedicle screws at both levels. Although less resistant to failure, the transfacet screw construct should be a viable alternative in patients with healthy bone.