Dedicated Early Morning Orthopaedic Trauma Operating Room Is Associated With Shorter Time to Surgery and Decreased Length of Hospital Stay for Children Undergoing Surgical Treatment of Supracondylar Humerus Fractures: A Retrospective Cohort Study

INTRODUCTION

The purpose of this study was to investigate whether the use of a dedicated early morning orthopaedic trauma operating room (OR) resulted in shorter wait times, decreased surgical times, decreased length of stay (LOS), and decreased complications in children treated with urgent surgical intervention for supracondylar humerus fractures.

METHODS

This retrospective comparative cohort study at a level I pediatric trauma center included patients younger than 12 years with supracondylar humerus fractures urgently treated with closed or open reduction and percutaneous pinning. Index surgical cases from April 28, 2013, to February 26, 2020, were included. Patients with prior humerus fracture, concomitant injuries, open fracture, pulseless supracondylar fracture, or missing data were excluded. Patients were analyzed based on the type of OR: dedicated early morning orthopaedic trauma OR or typical daytime orthopaedic OR. The primary outcome was time from presentation to surgery. Secondary outcomes included surgical time, complications, and LOS.

RESULTS

A total of 401 patients with a mean age of 5 ± 2 (range: 1 to 11) years and a mean follow-up of 2.0 ± 2.1 (range: 0.5 to 25.0) months were included, of whom 137 patients (34%) underwent surgery in the early morning dedicated orthopaedic trauma OR. The dedicated early morning orthopaedic OR group had significantly less time from presentation to surgery (7.5 versus 9.4 hours; P = 0.0002) and shorter LOS (21.0 versus 24.0 hours; P = 0.004) compared with children treated in the typical daytime orthopaedic OR. Surgical time (31.1 versus 32.6 minutes; P = 0.40) and complication rates (5.8% versus 4.9%; P = 0.65) were similar between the groups. No revision surgery was required in either group.

DISCUSSION

Surgical wait times were diminished with use of the dedicated early morning OR, as was LOS. Surgical times and complication rates were similar between groups. Institutions may consider adopting a dedicated early morning orthopaedic trauma OR to improve surgical wait times and decrease LOS.

LEVEL OF EVIDENCE

III.

Tranexamic acid use decreases transfusion rate in children with cerebral palsy undergoing proximal femoral varus derotational osteotomy

Previous studies demonstrated the safety of tranexamic acid (TXA) use in cerebral palsy (CP) patients undergoing proximal femoral varus derotational osteotomy (VDRO), but were underpowered to determine if TXA alters transfusion rates or estimated blood loss (EBL). The purpose of this study was to investigate if intraoperative TXA administration alters transfusion rates or EBL in patients with CP undergoing VDRO surgery.We conducted a retrospective review of 390 patients with CP who underwent VDRO surgery between January 2004 and August 2019 at a single institution. Patients without sufficient clinical data and patients with preexisting bleeding or coagulation disorders were excluded. Patients were divided into 2 groups: those who received intraoperative TXA and those who did not.Out of 390 patients (mean age 9.4 ± 3.8 years), 80 received intravenous TXA (TXA group) and 310 did not (No-TXA group). There was no difference in mean weight at surgery (P = .25), Gross Motor Function Classification System level (P = .99), American Society of Anesthesiologist classification (P = .50), preoperative feeding status (P = .16), operative time (P = .91), or number of procedures performed (P = .12) between the groups. The overall transfusion rate was lower in the TXA group (13.8%; 11/80) than the No-TXA group (25.2%; 78/310) (P = .04), as was the postoperative transfusion rate (7.5%; 6/80 in the TXA group vs 18.4%; 57/310 in the No-TXA group) (P = .02). The intraoperative transfusion rate was similar for the 2 groups (TXA: 7.5%; 6/80 vs No-TXA: 10.3%; 32/310; P = .53). The EBL was slightly lower in the TXA group, although this was not significant (TXA: 142.9 ± 113.1 mL vs No-TXA: 177.4 ± 169.1 mL; P = .09). The standard deviation for EBL was greater in the No-TXA group due to more high EBL outliers. The percentage of blood loss based on weight was similar between the groups (TXA: 9.2% vs No-TXA: 10.1%; P = .40). The number needed to treat (NNT) with TXA to avoid one peri-operative blood transfusion in this series was 9.The use of intraoperative TXA in patients with CP undergoing VDRO surgery lowers overall and postoperative transfusion rates.Level of evidence: III, Retrospective Comparative Study.

Outcomes of Operatively Managed Lumbar and Sacral Facet Fractures in Pediatric Athletes: A Case Series

BACKGROUND

Facet fractures have been reported in a total of 6 young athletes in 4 previous publications. These injuries were not diagnosed on magnetic resonance imaging (MRI) or radiographs, and were identified on computed tomography (CT). Our purpose was to report a series of athletes with operatively managed facet fractures. This may be an under-recognized diagnosis.

METHODS

Retrospective review of pediatric patients with operatively managed isolated lumbar or sacral facet fractures from 3 tertiary pediatric hospitals from 2014 to 2019. Clinical records and imaging studies were reviewed.

RESULTS

Ten patients with symptomatic lumbar or sacral facet fractures met inclusion criteria (mean age at presentation; 13.3±2.1 years, 70% Female). All patients reported competitive participation in sports. On physical examination, 10/10 (100%) of patients had lower back pain that was exacerbated with lumbar spine extension. Limited CT scans demonstrated facet fractures in 10/10 (100%) patients not detected on plain film or MRI. All patients experienced significant relief of pain following excision of the facet fracture fragment. At time of first postoperative visit, 9/10 (90%) patients were pain free while one had generalized back pain thought to be related to fibromyalgia and not facet pathology. At time of last follow-up, 2/10 (20%) of patients reported nonspecific back pain that was not localized in the area of the facet fracture, while 80% (8/10) remained pain free. All patients 100% (10/10) returned to full participation to sports. There were no complications noted in this series. Average follow-up was 27 months (range: 1 to 68 mo).

CONCLUSIONS

Athletes with localized back pain exacerbated by spine extension may have a facet fracture. As facet fractures are usually not identified with radiographs or MRI, a limited CT scan should be considered in the evaluation of pediatric athletes with localized back pain exacerbated by extension. In this series, surgical excision of facet fracture fragments was safe and provided predictable pain relief.

Obesity as a Predictor of Outcomes in Type III and Type IV Supracondylar Humerus Fractures

OBJECTIVES

To investigate the association of obesity with fracture characteristics and outcomes of operatively treated pediatric supracondylar humerus fractures.

DESIGN

Retrospective multicenter.

SETTING

Two Level I pediatric hospitals.

PATIENTS

Patients (age <18 years) with operatively treated Gartland type III and type IV fractures 2010-2014.

INTERVENTION

Closed or open reduction and percutaneous pinning of supracondylar humerus fractures.

MAIN OUTCOME MEASURE

Incidence of Gartland IV fracture, preoperative nerve palsy, open reduction and complication rates.

RESULTS

Patients in the obese group had a significantly higher likelihood of having a Gartland IV fracture (not obese: 17%; obese: 35%; P = 0.007). There was a significantly higher incidence of nerve palsy on presentation in the obese group (not obese: 20%; obese: 33%; P = 0.03). No significant differences were found between groups regarding incidence of open reduction, compartment syndrome, and rates of reoperation.

CONCLUSIONS

The present study demonstrates that obese children with a completely displaced supracondylar humerus fractures have an increased risk of Gartland type IV and preoperative nerve palsy compared with normal weight children.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Traumatic Posterior Hip Dislocation and Epiphysiolysis in a High School Football Player with Successful Outcome at 4 Years Follow-up: A Case Report

CASE

We describe a case of posterior hip dislocation in a 13-year-old boy after a contact football injury with attempted closed reduction resulting in complete separation of the epiphysis from the femoral neck metaphysis with associated femoral head fracture and posterior dislocation of the femoral head. Treatment was emergently performed with a greater trochanteric osteotomy, open reduction internal fixation using cannulated screws, and additional small diameter drill holes in the femoral head to promote blood flow. The patient did well postoperatively and at over 4 years follow-up had no evidence of avascular necrosis and returned to full athletics participation.

CONCLUSION

Particular attention should be taken when reducing hip dislocations in the adolescent population who may be predisposed to epiphysiolysis. Preservation of periosteal soft-tissue attachments and the use of small diameter drill holes to promote femoral head blood flow may have contributed to the excellent outcome.

Hip Dysplasia Is Not More Common in W-Sitters

Parents are frequently cautioned by therapists, teachers, physicians, and online resources about potential negative effects of w-sitting in children (including hip dysplasia), despite lack of evidence. To examine relationships between w-sitting and hip dysplasia, a prospective cohort study was conducted of 104 patients (196 hips), aged 9.9 (standard deviation = 5.7) years, who underwent hip/pelvis radiography at a pediatric tertiary care center. Measures of hip dysplasia were taken from radiographs. Parents/patients completed a questionnaire regarding the patients' sitting habits. Associations between hip dysplasia and w-sitting were analyzed statistically. About 48/104 parents/patients (46%) reported current or past w-sitting: 11/104 (11%) current, preferred position; 23/104 (22%) current, nonpreferred position, 14/104 (13%) w-sat in past, and 56/104 (54%) never w-sat. There was no difference in measures of hip dysplasia (P > .12) or hip dysplasia frequency between w-sitters (9%) and non-w-sitters (10%; P = .81), or among w-sitting persistence groups (P = .26). W-sitting in children is not associated with hip dysplasia.

Pre-operative methicillin resistant Staphylococcus aureus results do not predict surgical site infections in children undergoing varus derotational osteotomy

Literature regarding the value of pre-operative nasal methicillin resistant Staphylococcus aureus (MRSA) swabs to predict surgical site infections (SSIs) in children undergoing lower extremity surgery is limited. The purpose of our study was to determine if pre-operative nasal MRSA swab results were predictive of SSI development in children undergoing a femoral varus derotational osteotomy (VDRO).Patients who underwent VDRO between 2004-2016 were reviewed to determine pre-operative MRSA colonization rates and SSI devolvement rates. Patients with less than 1 year of follow-up, previous history of infections, or absent pre-operative MRSA swab were excluded. SSI rates of patients with negative MRSA and positive MRSA swab result were compared using the Fisher exact test. Aside from contact isolation precautions, no other changes in treatment were made during inpatient hospital course based on positive pre-operative nasal MRSA swab results.247 patients met the inclusion criteria (mean age: 9.3 ± 3.6 years, 62% male). There were 242 (98%) patients with a negative MRSA swab and 5 (2%) patients with a positive MRSA swab. Out of the 242 patients with a negative MRSA swab, 4 developed an SSI. Of the patients with positive MRSA swab results, 0% (0/5) developed an SSI compared to 1.7% (4/242) of negative MRSA swab results who developed an SSI. Results indicated no significant difference in SSI development rates between the groups (P = 1.00).In this series of children undergoing VDRO surgery, the results of a pre-operative MRSA nasal swab had no relationship to SSI incidence and no impact on clinical patient care. Pre-operative MRSA nasal swabs appear to be of limited benefit for routine pre-operative screening in this patient population.Level III, retrospective comparative.

Growth guidance constructs with apical fusion and sliding pedicle screws (SHILLA) results in approximately 1/3rd of normal T1-S1 growth

STUDY DESIGN

Retrospective, multicenter.

OBJECTIVE

To investigate clinical outcomes in particular T1-S1 growth in patients with SHILLA instrumentation independent of inventor's reports. Guided growth with apical fusion and sliding pedicle screws (GGC/SHILLA) is an alternative to distraction-based growing rods for the treatment of EOS. A recent report of patients treated with GGC primarily at the center where the procedure was invented reported surprisingly good spinal growth similar to normal growth.

METHODS

Retrospective review of EOS patients treated with GGC between 2007 and 2013 was performed from a multicenter database prior to final fusion. Inclusion criteria were < 10 years at index surgery and minimum 2-year follow-up. Patients with GGC performed at the inventor's institution or prior spinal instrumentation were excluded. Predicted normal T1-S1 change during the growth period was calculated for each patient based on Dimeglio's growth rates.

RESULTS

20 patients (mean age at surgery: 5.7 years) with the following diagnoses met inclusion criteria: syndromic (N = 9), neuromuscular (N = 5), idiopathic (N = 3) and congenital (N = 3). Preoperative mean Cobb was 77° (range 33°-111°). Mean increase in T1-S1 length from preoperative to postoperative was 51.5 mm, and change from postoperative to final follow-up was 21.8 mm (4.2 mm/year) which was 36% of predicted growth. 15/20 (75%) patients underwent 21 revision surgeries most commonly for implant complications (N = 26) and 8/20 (40%) underwent definitive fusion at a mean of 5.1 ± 1.2 years after guided growth surgery.

CONCLUSION

This study constitutes the largest case series of patients with EOS treated with GGC outside of the inventor's institution. The change in T1-S1 observed through the follow-up period in EOS patients treated with GGC was approximately 1/3rd of predicted normal growth, and less than 1/3rd of growth reported in previous reports. Similar curve correction and complication rates but less T1-S1 growth during the growth period were found compared to prior GGC (SHILLA) series.

Bilateral Congenital Posterior Hemivertebrae and Lumbar Spinal Stenosis Treated With Posterior Spinal Fusion and Instrumentation

Posterior hemivertebrae are wedge shaped deformities that can result in progressive kyphosis. Surgical intervention at an early age may be required, however choice of surgical technique is controversial. The aim of this report was to describe a case of progressive congenital lumbar kyphosis and bilateral posterior hemivertebra with retropulsion of tissue into the spinal canal treated successfully by posterior spinal fusion and instrumentation without anterior hemivertebra resection or decompression. We report on a patient with bilateral lumbar posterior hemivertebra at L1-L2 treated with posterior spinal fusion and instrumentation at less than 1 year of age. At 10 mo of age, the patient underwent posterior spinal fusion and instrumentation with resection of L1 and L2 posterior elements. No resection of the anterior aspect of the bilateral hemivertebrae was performed. Correction of the kyphotic deformity was maintained at last radiographic follow-up at five years post-operatively and there is no evidence of spinal stenosis. Early intervention with resection of posterior elements and fusion with instrumentation for bilateral congenital lumbar hemivertebrae provided adequate deformity correction and maintenance of the spinal canal width without anterior resection. Despite his young age, instrumentation was both feasible and beneficial in maintaining alignment.

Rectus Femoris Transfer Surgery Worsens Crouch Gait in Children With Cerebral Palsy at GMFCS Levels III and IV

BACKGROUND

Previous study has shown that children with cerebral palsy (CP) functioning at Gross Motor Function Classification System (GMFCS) levels III and IV do not benefit from distal rectus femoris transfer (DRFT) due to lack of improvement in stance knee extension. The fate of knees in such subjects who do not undergo DRFT is unknown. The purpose of this study was to compare knee kinematic outcomes in patients with CP and stiff knee gait who underwent single-event multilevel surgery with and without DRFT.

METHODS

Preoperative and postoperative gait analysis data were retrospectively reviewed for ambulatory (GMFCS levels I to IV) patients with CP with crouch and stiff knee gait whom underwent single-event multilevel surgery, including hamstring lengthening either with DRFT (N=34) or without DRFT (N=40). Statistical analyses included t tests and χ tests, and multiple regression analysis was performed to adjust for covariates. Data were stratified by GMFCS level groups I/II and III/IV.

RESULTS

Improved maximum knee extension in stance was seen for both the DRFT (P=0.0002) and no DRFT groups (P≤0.0006) at GMFCS levels I/II, and the no DRFT group at GMFCS levels III/IV (P=0.02). Excessive stance knee flexion persisted for those at GMFCS level III/IV after DRFT. Maximum knee flexion in swing was maintained after DRFT, but significantly decreased in the no DRFT group (P<0.002) for both GMFCS groups. Change in total knee range of motion improved after DRFT only in the GMFCS I/II group subjects with unilateral involvement (P=0.01). Timing of maximum knee flexion in swing improved for all patients regardless of DRFT or GMFCS level group (P<0.0001).

CONCLUSIONS

In patients with CP functioning at GMFCS levels III and IV, DRFT results in persistent crouch postoperatively. Given the importance of maintaining upright posture in these patients, we do not recommend DRFT in patients functioning at GMFCS levels III and IV.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Percutaneous Hamstring Lengthening Surgery is as Effective as Open Lengthening in Children With Cerebral Palsy

BACKGROUND

Surgical lengthening of the hamstrings is often performed to correct crouch gait in children with cerebral palsy (CP). Previous studies have demonstrated the effectiveness of open hamstring lengthening (oHSL) in improving knee extension static and dynamic range of motion; however, literature regarding percutaneous hamstring lengthening (pHSL) is limited. The purpose of this study was to investigate the effect of open versus pHSL for improving crouch gait and knee function in children with CP.

METHODS

This retrospective cohort study included 87 ambulatory children with CP who underwent HLS surgery with both preoperative and postoperative gait analysis (mean time, 29.4±19.9 mo after surgery) testing between 1997 and 2015. In total, 65 patients underwent oHLS surgery (mean age, 8.5±2.5 y) and 22 patients underwent pHSL surgery (mean age, 8.3±2.3 y). Lower extremity three-dimensional kinematic data were collected while subjects walked at a self-selected speed. Outcome variables for operative limbs were compared within and between groups using t tests, χ tests, and multiple regression analysis.

RESULTS

Significant postoperative decreases in knee flexion at initial contact were seen for both open (Δ12.7±13.4 degrees; P<0.001) and percutaneous (Δ19.1±13.1 degrees; P<0.001) groups. Increased postoperative maximum knee extension in stance was found for both open (Δ8.2±16.8 degrees; P=0.001) and percutaneous (Δ14.4±16.5 degrees; P=0.001) groups. No significant differences between open and percutaneous groups were found when comparing postoperative changes in kinematic variables between groups after adjusting for covariates. Postoperative changes in static range of motion were similar between lengthening groups.

CONCLUSIONS

pHSL is as effective as open lengthening in improving stance phase knee kinematics during gait in children with CP. This is the first study to compare the kinematic effects of open versus pHSL in the pediatric population. Percutaneous lengthening is tolerated well by patients, and as it allows for rapid rehabilitation it may be preferable to the open procedure.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Risk Factors for Postoperative Venous Thromboembolic Events in Patients Undergoing Lumbar Spine Surgery

STUDY DESIGN

Retrospective, database study.

OBJECTIVES

The aim of this study was to investigate incidence and risk factors associated with venous thromboembolic events (VTEs) after lumbar spine surgery.

METHODS

Patients who underwent lumbar surgery between 2007 and 2014 were identified using the Humana within PearlDiver database. ICD-9 (International Classification of Diseases Ninth Revision) diagnosis codes were used to search for the incidence of VTEs among surgery types, patient demographics and comorbidities. Complications including DVT and PE were queried each day from the day of surgery to postoperative day 7 and for periods 0 to 1 week, 0 to 1 month, 0 to 2 months, and 0 to 3 months postoperatively.

RESULTS

A total of 64 892 patients within the Humana insurance database received lumbar surgery between 2007 and 2014. Overall VTE rate was 0.9% at 1 week, 1.8% at 1 month, and 2.6% at 3 months postoperatively. Among patients that developed a VTE within 1 week postoperatively, 45.3% had a VTE on the day of surgery. Patients with 1 or more identified risk factors had a VTE incidence of 2.73%, compared with 0.95% for patients without risk factors (P < .001). Risk factors associated with the highest VTE incidence and odds ratios (ORs) were primary coagulation disorder (10.01%, OR 4.33), extremity paralysis (7.49%, OR 2.96), central venous line (6.70%, OR 2.87), and varicose veins (6.51%, OR 2.58).

CONCLUSIONS

This study identified several patient comorbidities that were independent predictors of postoperative VTE occurrence after lumbar surgery. Clinical VTE risk assessment may improve with increased focus toward patient comorbidities rather than surgery type or patient demographics.

Impact of tranexamic acid use on blood loss and transfusion rates following femoral varus derotational osteotomy in children with cerebral palsy

PURPOSE

Previous studies have established the safety and efficacy of tranexamic acid (TXA) in reducing blood loss after total joint arthroplasty and spinal fusion surgery; however, literature regarding the effectiveness of intraoperative TXA in children with cerebral palsy (CP) is limited. The aim of this study was to investigate the safety and efficacy of intraoperative TXA in reducing blood loss and transfusion requirements for children with CP undergoing a proximal femoral varus derotational osteotomy (VDRO).

METHODS

This is a retrospective review of 258 children with CP who underwent VDRO performed at the author's institution between 2004 and 2017. In all, 36 subjects underwent VDRO surgery with administration of intravenous TXA and 222 subjects underwent VDRO without administration of TXA. Outcome measures including blood loss, transfusion requirements and venous thromboembolic events were compared between groups using t-tests and chi-squared tests.

RESULTS

No significant differences were seen in the rates of transfusion between groups for the entire hospitalization (TXA group: 11.1% versus No TXA group: 19.8%), intraoperatively (TXA: 2.8% versus No TXA: 9.0%) or postoperatively (TXA: 8.3% versus No TXA: 14.4%). Intraoperative estimated blood loss (TXA: 144.4 mL versus No TXA: 159.0 mL) and percentage blood loss (TXA: 8.9% versus No TXA: 9.2%) were similar between groups. No major thromboembolic complications events occurred in either group.

CONCLUSION

The use of TXA was not associated with thromboembolic complications in this series of children with CP undergoing VDRO surgery. Though there was a trend toward lower rates of intraoperative and postoperative blood transfusion with TXA use in these patients, the differences were not significant, possibly due to low estimated blood loss in both groups and sample size.

LEVEL OF EVIDENCE

III- retrospective comparative study.

Evaluation of foraminal cross-sectional area in lumbar spondylolisthesis using kinematic MRI

PURPOSE

To evaluate the kinematic change of cross-sectional area of lumbar intervertebral foramen in degenerative lumbar spondylolisthesis patients using multi-positional MRI.

METHODS

Multi-positional MRI was performed on 31 patients diagnosed with single or multilevel degenerative lumbar spondylolisthesis and 31 control patients without degenerative lumbar spondylolisthesis. Foraminal area (FA) was measured at the lumbar spondylolisthesis level in degenerative lumbar spondylolisthesis group and at L3-4, L4-5, and L5-S1 level in the control group. FA was measured bilaterally in neutral, flexion, and extension positions. The difference in FA between the groups was analyzed using Mann-Whitney U test, and the difference between positions within groups was analyzed using Wilcoxon signed-rank test.

RESULTS

Degenerative lumbar spondylolisthesis group showed significantly smaller FA on both sides and on average in all three positions compared to the control group (p < 0.05 all). From neutral to flexion position, the change in FA was significantly smaller in the degenerative lumbar spondylolisthesis group than in the control group on both sides and on average (p < 0.005 all). In degenerative lumbar spondylolisthesis group, the FA showed no significant change from neutral to flexion, but showed significant change from neutral to extension (p < 0.005 all).

CONCLUSIONS

FA in the degenerative lumbar spondylolisthesis group was smaller than in the control group. There was no difference in FA in degenerative lumbar spondylolisthesis group from neutral to flexion, only from neutral to extension. Patients with degenerative lumbar spondylolisthesis have a higher chance of developing foraminal stenosis.

Kinematic evaluation of cervical sagittal balance and thoracic inlet alignment in degenerative cervical spondylolisthesis using kinematic magnetic resonance imaging

BACKGROUND CONTEXT

T1 slope is a novel thoracic parameter used to assess cervical spine sagittal balance. Thoracic index (TI) parameters including T1 slope and cervical sagittal alignment parameters may play an important role in degenerative cervical spondylolisthesis (DCS). Current literature regarding the relationship between TI and cervical sagittal alignment parameters in patients with DCS is limited.

PURPOSE

(1) To evaluate the T1 slope, cervical sagittal alignment, and thoracic inlet parameter in patients with DCS using kinematic magnetic resonance imaging (kMRI), and (2) to find a correlation between the T1 slope, TI, and other cervical sagittal parameters in patients with DCS.

DESIGN/SETTING

Retrospective kMRI study, Level III.

PATIENT SAMPLE

Fifty-two patients with DCS from 1,128 patients from a cervical kMRI database.

OUTCOME MEASURES

T1 slope, C2-C7 angle, sagittal vertical axis C2-C7 (SVA C2-C7), cranial tilt, cervical tilt, neck tilt, and thoracic inlet angle (TIA).

METHODS

Cervical spine kMRIs of 52 patients with DCS (mean age 51.7±standard deviation) were analyzed in neutral, flexion, and extension positions. Patients with DCS were divided into two groups: anterolisthesis (N=33) and retrolisthesis (N=19). Each listhesis group was subclassified into grade 1 (slip 2-3 mm) and grade 2 (slip>3 mm).

RESULTS

Grade 2 retrolisthesis had the largest T1 slope followed by grade 1 retrolisthesis, grade 2 anterolisthesis, and grade 1 anterolisthesis. Significant differences were found between the anterolisthesis and the retrolisthesis groups in the neutral position (p=.025). The flexion position had the largest T1 slope and showed a significant difference with anterolisthesis in the neutral position (p=.041). Sagittal vertical axis C2-C7 showed strong correlation with cranial tilt in all DCS groups and all positions.

CONCLUSIONS

In our study, T1 slope was larger in grade 2 DCS, and the retrolisthesis group had larger T1 slope than the anterolisthesis group. Presence of larger T1 slope was significantly correlated with larger cervical lordosis curvature. Furthermore, cranial tilt was strongly correlated with SVA C2-C7.

Gas chromatography-mass spectrometry characteristics of methylated perfluoroacyl derivatives of cytosine and 5-methylcytosine

Pentafluorobenzoyl and heptafluorobutyryl derivatives of cytosine and pentafluorobenzoyl-5-methylcytosine have been examined by mass spectrometry following permethylation. Electron impact mass spectra were used to confirm the structures of the derivatives. The permethylated pentafluorobenzoyl derivatives of cytosine and 5-methylcytosine are sensitive for quantitative analysis by capillary gas chromatography-mass spectrometry. Under negative ion chemical ionization conditions 1 femtogram of each is detected.

Evidence for surface effects in an electron-capture detector

We have found surface effects in a conventional electron-capture detector that are significantly reduced in an experimental, more inert version of this detector, both by Varian. These surface effects generate unique patterns of solute response for both pesticides-herbicides, and derivatized cytosine strong electrophores. They also cause a minimum followed by a more pronounced maximum in the response factor with increasing solute concentration, demonstrated with lindane. Certain speculations are presented to account for these observations.

Electrophore-labeling and alkylation of standards of nucleic acid pyrimidine bases for analysis by gas chromatography with electron-capture detection

The pyrimidine bases cytosine, uracil and thymine, along with some analogues, are electrophore-labeled either with pentafluorobenzoyl chloride (PFBC), pentafluorophenylsulfonyl chloride (PPSC), or heptafluorobutyric anhydride. Subsequent alkylation is most successful for PFB-cytosine, PPS-uracil, and PPS-thymine. These same alkylated compounds also have the highest aqueous stability and respond most strongly by gas chromatography-electron-capture detection. One of these derivatives, determined to be N4-PFB-1,3-dimethylcytosine by authentic synthesis, and its 5-methyl analogue, can be detected with good precision down to the 100-fg level. Poor reproducibility is encountered at the 10-fg level.

Automated analysis of antiepileptic drugs in serum by column-switching high-performance liquid chromatography

An automated high-performance liquid chromatographic column-switching system is presented for the analysis of antiepileptic drugs in serum. Initial results show that a reversed-phase extraction column works best overall when fitted with screens versus frits, and when packed with porous 30-micron particles as opposed to a pellicular packing of similar size or with smaller porous particles. The continuous analysis of primidone for over 2000 serum samples is achieved at a rate of twelve samples per hour with a single analytical column. An analogous boxcar high-performance liquid chromatographic system is also assembled and used to analyze two of four injected antiepileptic drugs at a rate of 40 samples per hour. For 1000 of these analyses, the coefficient of variation is 1% without an internal standard.