Demographic Analysis of Pedicle Diameter, and Estimated Pedicle Screw Length of the Lumbar Spine in a Diverse Population

BACKGROUND

Recent literature confirms the importance of understanding the variability in pedicle morphology among races. These studies suggest that more detailed and reliable measurements of pedicles should be undertaken. However, there is limited data on average pedicle diameters (PDs) or estimated pedicle screw lengths (EPSLs) between diverse racial populations. We sought to determine the differences in PD and EPSL in the lumbar spine between various races: "Asian," "Black," "White," and "Hispanic" to aid in perioperative planning during instrumented spinal fusion.

METHODS

Axial cuts of 404 patients were inspected to obtain their transverse outer cortical PD as measured through the isthmus, and EPSL by measuring the posterior entry point at the longest distance, which perpendicularly transected the measured isthmic diameter, to the anterior vertebral cortex from L1 to L5. We examined the average PD and PD range at each level for each race. To determine the significance, we used a mixed analysis of variance and a post hoc analysis.

RESULTS

In this retrospective chart review the races were found to be significantly different in PD and EPSL (P < .001). Post hoc analysis using Dunn-Bonferroni correction showed that Asians had significantly smaller PDs than Blacks and Whites (P < .002 and P < .014, respectively). The White and Hispanic population had significantly longer EPSLs when compared to Blacks and Asians from L1 to L5 (P < .01).

CONCLUSIONS

This study demonstrates that there are significant differences in pedicle morphology among races that must be taken into consideration when inserting pedicle screws during lumbar spinal fusion. Knowledge of these differences is of the utmost importance in order to limit complications while improving fixation.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

Pedicle morphology is variable between races and understanding these differences is important for the safe placement of pedicle screws.

A comparison of lumbar transverse pedicle angles between ethnic groups: a retrospective review

BACKGROUND

Spinal surgery requires an intimate understanding of pedicle morphology to provide safe and effective outcomes. Although current research has attempted to identify morphological vertebral pedicle trends, no study has utilized computed tomography (CT) scans to compare the lumbar transverse pedicle angle (TPA) with patient demographics factors in a diverse population throughout multiple hospital centers.

METHODS

Analysis of randomly selected CT scans from L1-L5 of 97 individuals who underwent imaging over a two-week period for non-back pain related complaints was conducted. Measuring 970 TPAs in total allowed for comparison of each patients' pedicle angle with important patient specific demographics including ethnicity, age, gender, height and weight. Statistical analysis utilized multiple comparisons of demographics at each level with post-hoc Bonferroni correction analysis to compare demographics at each level.

RESULTS

With relation to gender, age, height or weight, no statistically significant differences were identified for TPAs at any vertebral level. However, when stratified by ethnicity, the differences in transverse pedicle angles averages (TPA -Avg) at L2 and L3 were found to be statistically significant (p < 0.05).

CONCLUSION

We have identified a previously unknown and significant relationship between ethnicity and TPA at lumbar vertebral levels. These findings provide critical information that may be added to the operating surgeons' knowledge of pedicle morphology. We hope this novel information can assist in preoperative planning of pedicle screw placement and potentially help improve surgical outcomes.

Demographic Analysis of Lumbar Pedicle Diameters in a Diverse Population

Study Design

Retrospective chart review.

Purpose

We sought to determine the differences in pedicle diameter (PD) in the lumbar spine between various races: ‘Asian,’ ‘Black,’ ‘White,’ and ‘Other.’ These data could aid in perioperative planning during instrumented spinal fusion.

Overview of Literature

Recent literature underscores the importance of understanding diverse pedicle isthmus morphology to perform successful transpedicular procedures. These studies suggest that more detailed and reliable measurements of pedicles should be undertaken. However, none of the current literature comprehensively compares average PDs between diverse racial populations with a standardized study design.

Methods

Coronal cuts of 5,060 lumbar spine pedicles were inspected to obtain their transverse outer cortical PD as measured through the isthmus at L1–L5. Data were collected and categorized on the basis of patient-reported race. We examined average PD and PD range at each level for each race. To determine the significance, we used a mixed analysis of variance and a post hoc analysis.

Results

The Asian cohort consistently had a significantly smaller PD at L1–L5 than Blacks or Whites (p<0.001), as did the ‘Other’ group compared with Blacks (p<0.001) and Whites (p=0.032). At L1–L2, the ‘Other’ group showed the least variability in PD. At L3–L5, the Asian population showed the smallest range, and the Black population had the largest variability in PD except at L5. There was a significant difference in PD between the various races.

Conclusions

The Asian population consistently has significantly smaller pedicles in the lumbar spine than the Black or White populations. This information could prove useful for surgical planning. We suggest using preoperative computed tomography for pedicle screw templating as a safe method for pedicle screw instrumentation with the highest pullout strength given the wide range of PD in the Black population and the variability of PD between races.

Pattern reversal visual evoked potentials as a measure of visual pathway pathology in multiple sclerosis

BACKGROUND

Pattern reversal visual evoked potentials (PRVEPs) have a well-documented role in diagnosis of multiple sclerosis (MS), but their value as a visual function surrogate remains controversial.

METHODS

We evaluated PRVEP in 37 patients with MS who were participating in a long-term follow-up study following a phase III trial of interferon beta-1a (Avonex). Patients were examined to determine the Kurtzke Extended Disability Status Score (EDSS), multiple sclerosis functional composite (MSFC), contrast letter acuity (CLA), and had cranial MRI scans to determine whole brain atrophy (BPF). PRVEP was evaluated for P100 latency, amplitude, and waveform morphology. Two summary scores were created: for Score A, abnormal latencies, morphologies, and amplitudes of each individual eye were added; for Score B, abnormal latencies, morphologies, and amplitude ratio between eyes was determined. Sixteen patients in this group also had PRVEP at the time they enrolled in the clinical trial, eight years previously.

RESULTS

At the follow-up exam, over 75% of patients had abnormal PVEP parameters while visual acuity (VA) was abnormal only in 59%. Increased PRVEP latency over the eight-year period correlated with deterioration assessed by EDSS (P = 0.006), BPF (P = 0.0001), and MSFC (P = 0.0041). Score A was significantly correlated with EDSS, BPF, CLA, cognitive function, and quality of life assessed with the Sickness Impact profile. No correlation was seen with the MSFC.

CONCLUSIONS

The results indicate that PRVEP measures MS-related pathology, and can provide not only diagnostic but also prognostic information during evaluation of MS patients.

The spectrum of cardiac rate and rhythm in normal newborns

The distribution and variation of cardiac rate and rhythm in normal neonates has previously received little attention. This has made clinical assessment of dysrhythmia in newborns difficult. We therefore performed continuous 24-hour electrocardiography in 29 normal newborn subjects (age range, 1 to 6 days; mean, 3.5 days). The ECG tapes were then analysed in detail to define the normal range of cardiac rate, conduction intervals, and rhythm during waking and sleeping periods. Maximum sinus rate (awake) ranged from 150 to 222 beats per minute (mean, 192 +/- 16 [SD]), and minimum rate (awake) from 78 to 140 beats per minute (mean, 107 +/- 15). During sleep, the maximum rate ranged from 125 to 210 (mean, 168 +/- 23) and the minimum from 72 to 120 beats per minute (mean, 92 +/- 11). The maximum variation in rate for any individual during the 24-hour period ranged from 73 to 134 beats per minute (mean, 100 +/- 17). Sinus rhythm predominated with mild irregularity occurring episodically in 24 and moderate irregularity in 4 infants. An isolated atrial premature beat was present in 2 subjects, and an atrioventricular (AV) junctional escape rhythm occurred in one other after a sinus pause of 840 msec. Ventricular premature beats or AV conduction abnormalities were not observed. The corrected QT interval (QTc) ranged from 0.298 to 0.514 sec (mean, 0.390 +/- 0.026). The maximum variation in QTc over 24 hours ranged from 0.052 to 0.160 sec (mean, 0.097 +/- 0.028). We conclude that cardiac rhythm and conduction appear more stable in normal newborns than in older normal subjects and that bradycardia, conduction defects, and ventricular ectopy of the type recently reported in young normal adults seem to be more uncommon in the neonatal period.