Michelle E. Aubin

Vertebral Artery Anatomy : A Review of Two Hundred Fifty Magnetic Resonance Imaging Scans

Study Design. The aim of this study is to characterize the anatomy of vertebral arteries using magnetic resonance imaging scans of 250 consecutive patients. Objectives. To document the prevalence of midline vertebral artery (VA) migration in a subgroup of patients presenting with neck pain, radiculopathy, or myelopathy and to identify the course of the VA through the TFs. Summary of Background Data. Knowledge of VA anomalies and their respective prevalence may help surgeons decrease the incidence of iatrogenic injury to this artery. Methods. In this retrospective review of 281 consecutive patients, who had an magnetic resonance imaging for axial neck pain, radiculopathy, or myelopathy, anatomic measurements were obtained from C2 to C7. Results. The observed VA anomalies can be classified into following 3 main groups: (1) intraforaminal anomalies-midline migration, (2) extraforaminal anomalies, and (3) arterial anomalies. Midline migration of the VA was identified in 7.6% (19/250) of patients. The etiology can be degenerative or traumatic. It is important to note that the pattern of medial migration was clockwise rotation from caudal to cephalad and was present in all of our patients with anomalous arteries. Additionally, at C6, only 92% (460/500) of VAs were located within their respective transverse foramens and hypoplastic VAs were identified in 10% (25/250) of patients. Conclusion. Anomalies that must be considered before surgery include interforamenal anomalies, extraforamenal anomalies, and arterial anomalies. The intraforaminal anomalies involve midline migration, which places the VA at direct risk during corpectomy. Extraforaminal anomalies are related to VAs entering the transverse foramen at a level other than C6, which can increase the risk of injury during the anterior approach to the cervical spine. Arterial anomalies can be fenestrated, hypoplastic, or absent. These raise concern with the ability to maintain cerebral perfusion in the setting of damage to one of the VAs with the presence of contralateral arterial abnormality.

The association between preoperative spinal cord rotation and postoperative C5 nerve palsy

BACKGROUND C5 nerve palsy is a known complication of cervical spine surgery. The development and etiology of this complication are not completely understood. The purpose of the present study was to determine whether rotation of the cervical spinal cord predicts the development of a C5 palsy. METHODS We performed a retrospective review of prospectively collected spine registry data as well as magnetic resonance images. We reviewed the records for 176 patients with degenerative disorders of the cervical spine who underwent anterior cervical decompression or corpectomy within the C4 to C6 levels. Our measurements included area for the spinal cord, space available for the cord, and rotation of the cord with respect to the vertebral body. RESULTS There was a 6.8% prevalence of postoperative C5 nerve palsy as defined by deltoid motor strength of ≤ 3 of 5. The average rotation of the spinal cord (and standard deviation) was 2.8° ± 3.0°. A significant association was detected between the degree of rotation (0° to 5° versus 6° to 10° versus ≥ 11°) and palsy (point-biserial correlation = 0.94; p < 0.001). A diagnostic criterion of 6° of rotation could identify patients who had a C5 palsy (sensitivity = 1.00 [95% confidence interval, 0.70 to 1.00], specificity = 0.97 [95% confidence interval, 0.93 to 0.99], positive predictive value = 0.71 [95% confidence interval, 0.44 to 0.89], negative predictive value = 1.00 [95% confidence interval, 0.97 to 1.00]). CONCLUSIONS Our evidence suggests that spinal cord rotation is a strong and significant predictor of C5 palsy postoperatively. Patients can be classified into three types, with Type 1 representing mild rotation (0° to 5°), Type 2 representing moderate rotation (6° to 10°), and Type 3 representing severe rotation (≥ 11°). The rate of C5 palsy was zero of 159 in the Type-1 group, eight of thirteen in the Type-2 group, and four of four in the Type-3 group. This information may be valuable for surgeons and patients considering anterior surgery in the C4 to C6 levels.

Is there a difference between simultaneous or staged decompressions for combined cervical and lumbar stenosis

Study Design We evaluated 43 patients diagnosed with tandem spinal stenosis (TSS) from 1999 to 2005 in an academic hospital. Objective The purpose of this study is to compare outcomes after simultaneous decompression of the cervical and lumbar spine versus staged operations. Summary of Background Data TSS is a rare degenerative disease affecting multiple spinal levels with limited research describing operative management. Methods Of our patients, 21 underwent simultaneous decompression of both the cervical and lumbar spine and 22 underwent staged decompression of the cervical spine followed by the lumbar spine at a later date. Medical records were reviewed for patient demographics, type and duration of symptoms, operative time, combined blood loss, cervical myelopathy modified Japan Orthopaedic Association Score, Oswestry Disability Index (ODI), major and minor complications, and average length of follow up. Each category was evaluated by Pearson correlations and unpaired Student t tests. Results With a mean follow-up of 7 years, both groups improved in JOA and ODI without a significant difference between the 2 operative groups in terms of major or minor complications, JOA, or ODI. Independent of the surgical algorithm, age above 68 years, estimated blood loss ≥400 mL, and operative time ≥150 minutes significantly increased the number of complications. Conclusions These results indicate that TSS can be effectively managed by either surgical intervention, simultaneous, or staged decompressions. However, patient age, blood loss, and operative time do significantly impact outcomes. Therefore, operative management should be tailored to the patients age and the option which will limit blood loss and operative time, whether that is by simultaneous or staged procedures.

Radiostereometric Analysis Study of Tantalum Compared with Titanium Acetabular Cups and Highly Cross-Linked Compared with Conventional Liners in Young Patients Undergoing Total Hip Replacement

BACKGROUND Radiostereometric analysis provides highly precise measurements of component micromotion relative to the bone that is otherwise undetectable by routine radiographs. This study compared, at a minimum of five years following surgery, the micromotion of tantalum and titanium acetabular cups and femoral head penetration in highly cross-linked polyethylene liners and conventional (ultra-high molecular weight polyethylene) liners in active patients who had undergone total hip replacement. METHODS This institutional review board-approved prospective, randomized, blinded study involved forty-six patients. Patients were randomized into one of four cohorts according to both acetabular cup and polyethylene liner. Patients received either a cementless cup with a titanium mesh surface or a tantalum trabecular surface and either a highly cross-linked polyethylene liner or an ultra-high molecular weight polyethylene liner. Radiostereometric analysis examinations and Short Form-36 Physical Component Summary, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), University of California Los Angeles (UCLA) activity, and Harris hip scores were obtained preoperatively, postoperatively, at six months, and annually thereafter. RESULTS All patients had significant improvement (p < 0.05) in Short Form-36 Physical Component Summary, WOMAC, UCLA activity, and Harris hip scores postoperatively. On radiostereometric analysis examination, highly cross-linked polyethylene liners showed significantly less median femoral head penetration at five years (p < 0.05). Steady-state wear rates from one year to five years were 0.04 mm per year for ultra-high molecular weight polyethylene liners and 0.004 mm per year for highly cross-linked polyethylene liners. At the five-year follow-up, the median migration (and standard error) was 0.05 ± 0.20 mm proximally for titanium cups and 0.21 ± 0.05 mm for tantalum cups. CONCLUSIONS In this young population who had undergone total hip replacement, radiostereometric analysis showed significantly less femoral head penetration in the highly cross-linked polyethylene liners compared with that in the conventional ultra-high molecular weight polyethylene liners. Penetration rates were one order of magnitude less in highly cross-linked polyethylene liners compared with ultra-high molecular weight polyethylene liners. There was no significant difference in proximal migration between the tantalum and titanium acetabular cups through the five-year follow-up (p > 0.19).

Identification of type 1: interforaminal vertebral artery anomalies in cervical spine MRIs.

Study Design. This is a prospective study. Objective. The aim of our study is to identify whether vertebral arteries (VA), normal or aberrant, are routinely described in cervical spine magnetic resonance imaging (MRI) interpretations. Summary of Background Data. VA injury is a serious complication of anterior cervical spine surgery. Aberrant VA anatomy is a potential cause of such complications. Therefore, VA anatomy should be evaluated in cervical MRIs. Methods. Six neuroradiologists were blinded to the study design and were asked to interpret 79 cervical MRIs. Of these, 39 had aberrant VAs, whereas 40 had normal VAs. Initially, the indications for the study included only a description of patients symptoms. The radiologists were then given the same MRIs with different indications. This time, the indications included the patients symptoms, a request for annotations on the VA, and a definition of VA anomaly. All of the MRI interpretations were then evaluated for the frequency and accuracy of VA description. Results. When the indications for the study did not specifically request a comment on VAs, the VA was never described (0%). When the indications included the specific request and definition, all 6 commented on the VA (100%). Three of the 6 radiologists were 100% accurate in identifying all 40 normal and 39 aberrant VAs, whereas the other 3 identified all 40 normal and 38 of 39 aberrant VAs. Conclusion. This study demonstrates that the VA is not a standard component of cervical spine MRI interpretations. Because of the significant complications related to its injury, VA anatomy, whether normal or variant, needs to be evaluated in cervical MRIs. When ordering a cervical MRI, surgeons should request a description of the VA and any anomalies.

The Characteristics of Patients with Type 1: Intraforaminal Vertebral Artery Anomalies?

In a previous study, intraforaminal anomalies were found to occur at a rate of 7.6%. This increases the risk of injury to this vessel if the surgeon is unaware of such abnormalities preoperatively. The aim of our retrospective study was to identify patient factors that may predict anomalous intraforaminal vertebral arteries. Patient records were obtained from a previous study. In that study, the records of each consecutive patient who underwent cervical spine magnetic resonance imaging (MRI) for axial neck pain, radiculopathy, or myelopathy between January 2007 and January 2008 were reviewed. The social and medical histories of each patient were evaluated with respect to the presence or absence of an aberrant vertebral artery. We reviewed the medical records of the 250 patients whose MRIs were reviewed in the previous study. Seven patients were excluded for incomplete records. Chi-square and Fishers exact tests were performed to compare the normal vertebral artery anatomy patients to the aberrant patients. The medical records of 19 patients with aberrant vertebral arteries and 224 patients with normal vertebral arteries were reviewed. The aberrant group was significantly older than the normal group (P=.00015). The only diagnostic condition that represented a statistically significant difference between the 2 groups was incidence of cancer. A relationship may exist between patient age, cancer, and medialization of the vertebral artery. The mechanism of this possible relationship is unclear. Although aberrant vertebral arteries are rare, a surgeon should have raised suspicion of this possibility in patients with a history of cancer.

Self-measured wrist range of motion by wrist-injured and wrist-healthy study participants using a built-in iPhone feature as compared with a universal goniometer

STUDY DESIGN Cross-sectional cohort. INTRODUCTION Smartphone gyroscope and goniometer applications have been shown to be a reliable way to measure wrist ROM when used by researchers or trained staff. If wrist-injured patients could reliably measure their own ROM, rehabilitation efforts could be more effectively tailored. PURPOSE OF THE STUDY To assess agreement of self-measured ROM by wrist-injured and wrist-healthy study participants using a built-in iPhone 5 level feature as compared to researcher-measured ROM using a universal goniometer (UG). METHODS Thirty wrist-healthy and 30 wrist-injured subjects self-measured wrist flexion, extension, supination, and pronation ROM using the built-in preinstalled digital level feature on an iPhone 5. Simultaneously a researcher measured ROM with a UG. RESULTS Average absolute deviation between the self-measured iPhone 5 level feature and researcher-measured UG ROM was less than 2° for all 4 movements individually and combined was found to be 1.6° for both populations. Intraclass correlation coefficient showed high correlation with values over 0.94 and Bland-Altman plots showed very strong agreement. There was no statistical difference in the ability of wrist-injured and healthy patients to self-measure wrist ROM. DISCUSSION Both populations showed very high agreement between their self-measured ROM using the built-in level feature on an iPhone 5 and the researcher-measured ROM using the UG. Both populations were able to use the iPhone self-measurement equally well and the injury status of the subject did not affect the agreement results. CONCLUSION Wrist-healthy and wrist-injured subjects were able to reliably and independently measure ROM using a smartphone level feature.

Intradural and epidural abscess presenting as sepsis 2 weeks after uncomplicated lumbar microdiscectomy

P ostoperative infections and abscess formation in the lumbar spine are well-known complications; however, intradural abscesses are comparatively rare. Although there is a well-defined treatment guideline for the management of this condition, its pathogenesis may be unclear and its diagnosis can be difficult. This case examines a patient presenting with sepsis 2 weeks after uncomplicated lumbar decompression surgery who was found to have intradural and epidural abscesses. This case evaluates the mechanism of diagnosing intradural abscess, potential etiologies, and the appropriate treatment.