Vertebral body tethering for Lenke 1A curves: the lumbar modifier predicts less optimal outcomes

INTRODUCTION

The addition of the L4 "AR" and "AL" lumbar modifier for Lenke 1A idiopathic scoliosis (IS) has been shown to direct treatment in posterior spinal fusion; however, its utility in vertebral body tethering (VBT) has yet to be evaluated.

METHODS

A review of a prospective, multicenter database for VBT in IS was performed for patients with Lenke 1A deformities and a minimum of 2 years follow-up. Patients were categorized by their lumbar modifier (AR vs AL). Less optimal VBT outcome (LOVO) was defined as a final coronal curve > 35°, lumbar adding-on, or revision surgery for deformity progression or adding-on.

RESULTS

Ninety-nine patients met inclusion criteria (81% female, mean 12.6 years), with 55.6% being AL curves. Overall, there were 23 instances of tether breakage (23.3%) and 20 instances of LOVO (20.2%). There was a higher rate of LOVO in AR curves (31.8% vs 10.9%, P = 0.01). Patients with LOVO had greater preoperative deformity, greater apical translation, larger coronal deformity on first erect radiographs, and less coronal deformity correction. Failure to correct the deformity < 30° on first erect was associated with LOVO, as was LIV selection short of the last touch vertebra (TV). Independent risk factors for LOVO included AR curves (OR 3.4; P = 0.04) and first erect curve magnitudes > 30 degrees (OR 6.0; P = 0.002).

DISCUSSION

There is a 20.2% rate of less optimal VBT following VBT for Lenke 1A curves. AR curves are independently predictive of less optimal outcomes following VBT and require close attention to LIV selection. Surgeons should consider achieving an initial coronal correction < 30 degrees and extending the LIV to at least the TV to minimize the risk of LOVO.

Consensus-Based Best Practice Guidelines for the Management of Spinal Deformity and Associated Tumors in Pediatric Neurofibromatosis Type 1: Screening and Surveillance, Surgical Intervention, and Medical Therapy

BACKGROUND

Spinal conditions, such as scoliosis and spinal tumors, are prevalent in neurofibromatosis type 1 (NF1). Despite the recognized importance of their early detection and treatment, there remain knowledge gaps in how to approach these manifestations. The purpose of this study was to utilize the experience of a multidisciplinary committee of experts to establish consensus-based best practice guidelines (BPGs) for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric patients with NF1.

METHODS

Using the results of a prior systematic review, 10 key questions that required further assessment were first identified. A committee of 20 experts across medical specialties was then chosen based on their clinical experience with spinal deformity and tumors in NF1. These were 9 orthopaedic surgeons, 4 neuro-oncologists/oncologists, 3 neurosurgeons, 2 neurologists, 1 pulmonologist, and 1 clinical geneticist. An initial online survey on current practices and opinions was conducted, followed by 2 additional surveys via a formal consensus-based modified Delphi method. The final survey involved voting on agreement or disagreement with 35 recommendations. Items reaching consensus (≥70% agreement or disagreement) were included in the final BPGs.

RESULTS

Consensus was reached for 30 total recommendations on the management of spinal deformity and tumors in NF1. These were 11 recommendations on screening and surveillance, 16 on surgical intervention, and 3 on medical therapy. Five recommendations did not achieve consensus and were excluded from the BPGs.

CONCLUSION

We present a set of consensus-based BPGs comprised of 30 recommendations for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric NF1.

Avoiding PICU admission following PSF for neuromuscular scoliosis in non-ambulatory cerebral palsy managed with ERAS protocol

PURPOSE

Children with neuromuscular scoliosis (NMS) undergoing posterior spinal fusion (PSF) have historically been managed post-operatively in the pediatric intensive care unit (PICU) due to institutional tendencies. This study sought to define risk factors for PICU admission when using an enhanced recovery after surgery (ERAS) pathway.

METHODS

A retrospective review of children with non-ambulatory (GMFCS 4 or 5) cerebral palsy undergoing PSF for NMS performed at two institutions by 5 surgeons. Both institutions have a pre-existing ERAS pathway for NMS patients consisting of post-surgical transfer to the hospital floor with early reinstitution of feeding and mobilization. PICU admission is used at the discretion of the surgeon and anesthesiologist rather than by institutional decree. Patient and surgical factors were assessed for risk factors of PICU admission.

RESULTS

A total of 103 children were included (84% GMFCS 5, mean 14.52 years (± 3.4 years)). Forty children (38.8%) required postoperative PICU admission. PICU admission was associated with seizure disorder (P = 0.09), pre-existing feeding tube (P = 0.003), tracheostomy (P = 0.03), and modified GMFCS-5 subclassification (P = 0.003). Independent predictors of PICU admission include pre-existing feeding (Odd's ratio = 2.9, P = 0.02) and length of surgery (Odd's ratio = 2.6, P < 0.001), with surgery lasting ≥ 5.0 h having an 82.5% sensitivity and 63.5% specificity (AUC 0.8, P < 0.001) for post-operative PICU admission.

CONCLUSION

The majority of children with non-ambulatory cerebral palsy can be successfully managed on the hospital floor following PSF. The extent of central neuromotor impairment is significantly associated with PICU admission along with surgery lasting longer than 5 h.

To tether or fuse? Significant equipoise remains in treatment recommendations for idiopathic scoliosis

PURPOSE

Vertebral body tethering (VBT) continues to grow in interest from both a patient and surgeon perspective for the treatment of scoliosis. However, the data are limited when it comes to surgeon selection of both procedure type and instrumented levels. This study sought to assess surgeon variability in treatment recommendation and level selection for VBT versus posterior spinal fusion (PSF) for the management of scoliosis.

METHODS

Surgeon members of the Pediatric Spine Study Group and Harms Study Group were queried for treatment recommendations and proposed upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV) selection for PSF and VBT based on 17 detailed clinical vignettes. Responses were subdivided in each clinical vignette according to surgeon experience and treatment recommendations with assessment of intra-rater reliability. Binomial distribution tests were used to establish equipoise, selecting p < 0.10 to indicate the presence of a treatment choice with consensus set > 70% agreement. For treatment choice, responses were assessed first for consensus on the decision to proceed with PSF or VBT.

RESULTS

Thirty-five surgeons with varied experience completed the survey with 26 surgeons (74%) completing the second follow-up survey. Overall, VBT was the recommended treatment by 47% of surgeons, ranging by clinical vignette. Consensus in treatment recommendation was present for 6 clinical vignettes including 3 for VBT and 3 for PSF, with equipoise present for the remaining 11. Of the 17 vignettes, 12 demonstrated moderate intra-observer reliability including the 3 consensus vignettes for VBT. Sanders stage ≤ 3 and smaller curve magnitude were related with VBT recommendation but neither age nor curve flexibility significantly influenced the decision to recommend VBT. Surgeons with high VBT volume, ≥ 11 VBT cases/year, were more likely to recommend VBT than those with low volumes (0-10 cases per year (p < 0.0001)). High VBT volume surgeons demonstrated consensus in VBT recommendation for Lenke 5/6 curves (75% mean recommendation). High VBT volume surgeons had a significantly higher VBT recommendation rate for Lenke 1A, 2A curves (71.8% vs 48.0%, p = 0.012), and Lenke 3 curves (62% vs 26.9%, p = 0.023). Equipoise was present for all vignettes in low volume surgeons. In addition, high VBT volume surgeons trended toward including more instrumented levels than low VBT volume surgeons (7.17 vs 6.69 levels).

CONCLUSION

Significant equipoise is present among pediatric spine surgeons for treatment recommendations regarding VBT and PSF. Surgeon-, patient-, and curve-specific variables were identified to influence treatment recommendations, including surgeon experience, curve subtype, deformity magnitude, and skeletal maturity. This study highlights the need for continued research in identifying the optimal indications for VBT and PSF in the treatment of pediatric spinal deformity.

Comparative cost-utility analysis of postoperative discharge pathways following posterior spinal fusion for scoliosis in non-ambulatory cerebral palsy patients

PURPOSE

Accelerated postoperative discharge (AD) pathways have demonstrated numerous benefits for patients with adolescent idiopathic scoliosis undergoing PSF. Although early evidence supports the application of AD pathways over more traditional discharge (TD) approaches for patients with neuromuscular scoliosis, the economic impact of these pathways has not been investigated.

METHODS

A decision-analysis model was constructed using a hypothetical 15-year-old male with non-ambulatory CP with a 65-degree thoracolumbar scoliosis and pelvic obliquity undergoing operative treatment with PSF from T2-pelvis with pedicle screw fixation. The literature was reviewed to estimate costs, probabilities, and quality-adjusted life years (QALYs)) for identified complication profiles for discharge pathways. QALYs were constructed using age-matched values for US population average, applying a CP diagnosis corrective value. A probabilistic sensitivity analysis was performed using a second-order Monte Carlo simulations. Incremental cost-utility ratio and incremental net monetary benefit (NMB) were calculated. One-way sensitivity analyses were performed by selective variable variation.

RESULTS

AD pathway resulted in an average cost and effectiveness of $67,069 and 15.4 QALYs compared with $81,312 and 15.4 QALYs for TD. AD resulted in a 2.1% greater NMB with a cost-effectiveness ratio of $4361/QALY compared with $5290/QALY in the TD. The cost-effectiveness of TD was inversely sensitive to implant cost variation while the AD maintained effectiveness despite cost variations.

CONCLUSION

This cost-utility analysis demonstrated that the implementation of an AD pathway following PSF for non-ambulatory CP scoliosis is economically more effective, providing a 17.5% cost reduction with enhanced value of care evidenced by a 2.1% greater NMB over a TD pathway. The cost-effectiveness of the AD was maintained despite implant cost variations.

Short term outcomes of an enhanced recovery after surgery (ERAS) pathway versus a traditional discharge pathway after posterior spinal fusion for adolescent idiopathic scoliosis

PURPOSE

Enhanced Recovery after Surgery (ERAS) pathways have been shown to decrease length of stay (LOS) after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). The aim of this study was to compare immediate post-operative outcomes following an ERAS pathway with a traditional pathway for AIS.

METHODS

A prospective dual-center study of patients treated using an ERAS pathway (203 patients) or a traditional discharge (TD) pathway (73 patients) was performed with focus on pain at discharge, quality of life at one month, and return to school/work.

RESULTS

LOS was 55% less in the ERAS group (4.8 days TD vs. 2.2 days ERAS, p < 0.001). Length of surgery (4.8 h TD vs. 2.8 h, p < 0.001) and EBL (500 cc vs. 240 cc, p < 0.001) were greater in the TD group, likely related to larger curve magnitudes ((62.0° TD vs. 54.0° ERAS, p < 0.001), a higher percentage of patients undergoing osteotomies (94% vs. 46%, p < 0.001) and more levels fused (11.4 ± 1.6 vs. 10.1 ± 2.6, p < 0.001) in the TD group. Regression analysis showed no difference in Visual Analog Score (VAS) score at discharge or quality of recovery using the QOR9 instrument between groups at follow up. There was no difference in return to school (p = 0.43) and parents' return to work (p = 0.61) between the groups.

CONCLUSION

Patients managed with an ERAS pathway had similar pain scores at discharge than those managed with a TD pathway. Both groups showed evidence of rapid return to normalcy by the first follow up visit.

In-hospital opioid usage following posterior spinal fusion for adolescent idiopathic scoliosis: Does methadone offer an advantage when used with an ERAS pathway?

PURPOSE

Intraoperative methadone has been shown to decrease opioid medication requirement following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). No study to date has investigated the effect of methadone on opioid medication requirement when used in conjunction with an enhanced recovery after surgery (ERAS) protocol following PSF.

METHODS

A retrospective cohort study was performed at a single, tertiary care pediatric hospital. Patients with AIS undergoing PSF were consecutively given a single intra-operative methadone dose and matched 1:2 to a AIS control group without methadone. Patients were matched for age, curve magnitude, levels fused, blood loss, and operating time. All children followed a standard ERAS protocol with methadone being the only change in the post-operative regimen. In-hospital data for opioid and non-opioid medication use, surgical, and patient variables were recorded and compared between cohorts.

RESULTS

Twenty-six patients received methadone (average 15.1 ± 1.9 years) and were matched with 52 control patients without methadone (average 14.7 ± 2.2 years). There were no significant differences in total opioid usage at any time-interval prior to hospital discharge or in cumulative opioid usage. Additionally, patients had a similar VAS pain level at discharge (methadone: 4.0 ± 2.3 vs control: 3.8 ± 1.9; P = 0.572). Total opioid usage was correlated with LOS. There were no opioid-related medication complications in either cohort.

CONCLUSION

There was no decrease of in-hospital opioid usage when methadone was used with an ERAS protocol. Total opioid usage is correlated with hospital LOS following PSF.

Flexible Intramedullary Nailing of Pediatric Femoral Fractures

Background

Flexible intramedullary nailing is performed for femoral fractures in pediatric patients who may be too large for spica cast immobilization but who have substantial growth remaining and who are not a candidate for rigid intramedullary nailing. Flexible nailing allows the surgeon to obtain correct alignment of the femur fracture so as to allow for healing without a lower extremity deformity.

Description

The patient is positioned on a radiolucent table, flexible nails are chosen according to the diameter of the medullary canal, medial and lateral incisions are made along the distal aspect of the thigh, and access to the canal is obtained with use of a drill-bit of the appropriate size. Flexible nails are contoured to place the apex at the location of the fracture site and then passed 1 at a time up to the fracture through the medial and lateral corticotomies. Fracture reduction is obtained, and the nails are passed across the fracture 1 at a time. Leave a small amount of nail prominent at the entry site; the nails are then cut and advanced with a tamp.

Alternatives

Spica cast immobilization, rigid intramedullary nailing, external fixation, and submuscular plating.

Rationale

Flexible nailing provides relative stability of a femoral fracture similar to external fixation, submuscular plating, and rigid nailing; however, external fixators come with pin-track complications and infections, as well as a bulky device external to the thigh. Submuscular plating is beneficial for length-unstable fractures but is a longer procedure and implant removal is more difficult. In an older child with growth remaining, a rigid femoral nail is an option with similar outcomes to flexible nailing; however, the implant is harder to remove. Flexible nailing provides a cosmetic incision with reliable relative fixation in length-stable fractures, and easy removal of implants with equal or even improved outcomes compared with other surgical techniques.

Expected Outcomes

The outcomes of this procedure are excellent. Most pediatric femoral fractures treated with flexible nailing heal well with few complications. Angulation at the fracture site is the most common complication and is more common in fractures of the proximal or distal third of the femur¹. Worse outcomes occur in older children and children who are heavier¹. Outcomes are improved when flexible nailing is done in length-stable fractures; however, postoperative immobilization in a single-leg spica cast or knee immobilizer can augment fixation in fractures that are not stable. Implant irritation can occur at the insertion site; however, the implants are easy to remove once the fracture has healed. There is a substantially lower rate of malunion when stainless-steel nails (6%) are utilized compared with titanium nails (23%). Consideration should therefore be given to the use of stainless-steel nails for pediatric femoral fractures².

Important Tips

Use a radiolucent table with either a post or a sheet for counter-traction aids during reductionUse stainless-steel nailsPass the easier nail firstAdvance into the femoral neck or trochanteric apophysisDo not wrap rods around each otherCut off the machined tip of the nail and custom-contour the nail in patients with poor bone quality.

Application of a Halo Fixator for the Treatment of Pediatric Spinal Deformity

Background

In spine surgery, the halo fixator was initially utilized to stabilize cervical fusions in patients with poliomyelitis. More recently, the indications for halo fixation have evolved to include stabilization and definitive treatment for upper cervical spine injuries (Jefferson fractures, atlanto-occipital dissociations, odontoid fractures, etc.), treatment of atlantoaxial rotatory subluxation, stabilization of long cervical fusions, and preoperative traction. In the realm of pediatric spinal deformity, halo fixation has proved to be a valuable resource for severe or neglected spinal deformities. In this video article, we demonstrate the application of a halo fixator in a pediatric patient with severe scoliosis.

Description

The procedure includes appropriate pin placement in the safe zones of the skull performed under either general anesthesia or local anesthesia. Pins are secured to a halo frame that is sized to be 2 cm larger than the circumference of the skull and are tightened according to age-specific torque guidelines.

Alternatives

Alternative treatments vary from cervical spine immobilization to definitive surgical treatment in the spine, or even spinal osteotomies, depending on the underlying spinal pathology.

Rationale

The halo fixator works by limiting motion of the cervical spine in flexion, extension, and axial rotation. The halo is also able to control and correct translational injuries of the cervical spine. In the setting of spinal deformity, the halo fixator can also be utilized to overcome the effects of gravity and lengthen the spine.

Expected Outcomes

For spinal deformities, the halo fixator can be expected to lengthen the spine and increase deformity flexibility prior to definitive surgical treatment in the spine or growth-friendly spinal instrumentation.

Important Tips

Correct identification of safe zones for pin placement is vital to correct pin placement.For pediatric patients, it is important to obtain fixation with a minimum of 6 to 8 pins.Pins should be tightened with use of a torque-limiting wrench, up to no more than 1 in/lb (55.9 mm/kg) per year of age, up to a maximum of 8 in/lb (447.9 mm/kg).Applied traction should be a maximum of 50% of the body weight of the patient.Neurovascular examination is vital following application of weight.

Postoperative Dexamethasone Following Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

BACKGROUND

Surgeons have hesitated to use steroids in patients undergoing posterior spinal fusion because of the risk of wound complications. The literature has supported the use of postoperative steroids in other areas of orthopaedics on the basis of more rapid recovery and improved postoperative pain control. We hypothesized that a short course of postoperative dexamethasone following posterior spinal fusion for the treatment of adolescent idiopathic scoliosis (AIS) would decrease opioid usage without increasing wound-healing problems.

METHODS

Consecutive patients undergoing posterior spinal fusion for the treatment of AIS from 2015 to 2018 at a single hospital were included. A review of demographic characteristics, curve characteristics, surgical data, and postoperative clinic notes was performed. Opioid usage was determined by converting all postoperative opioids given into morphine milligram equivalents (MME).

RESULTS

Sixty-five patients underwent posterior spinal fusion for the treatment of AIS without postoperative steroids (the NS group), and 48 patients were managed with 3 doses of postoperative steroids (the WS group) (median, 8.0 mg/dose). There was no difference between the groups in terms of curve magnitude, number of vertebrae fused, or estimated blood loss. There was a 39.6% decrease in total MME used and a 29.5% decrease in weight-based MME used in the group receiving postoperative steroids (82.0 mg [1.29 mg/kg] in the NS group versus 49.5 mg [0.91 mg/kg] in the WS group]; p < 0.001). This difference persisted after accounting for gabapentin, ketorolac, and diazepam usage; surgical time; curve size; levels fused; and number of osteotomies (median decrease, 0.756 mg/kg [95% CI, 0.307 to 1.205 mg/kg]; p = 0.001). Three patients in the NS group (4.6%) and 4 patients in the WS group (8.3%) developed wound dehiscence requiring wound care (p = 0.53). One patient in the NS group required surgical debridement for the treatment of an infection. Patients in the WS group were more likely to walk at the time of the initial physical therapy evaluation (60.4% versus 35.4%; p = 0.013).

CONCLUSIONS

A short course of postoperative steroids after posterior spinal fusion was associated with a 40% decrease in the use of opioids, with no increase in wound complications. Surgeons may consider the use of perioperative steroids in an effort to decrease the use of postoperative opioids following posterior spinal fusion for the treatment of AIS.

LEVEL OF EVIDENCE

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

Are precontoured cobalt-chromium spinal rods mechanically superior to manually contoured rods?

STUDY DESIGN

Laboratory based study.

OBJECTIVE

To compare reduction force and plastic deformation of cobalt-chromium (Co-Cr) spinal rods using a rigid, thoracolumbar spinal deformity model. Pre-contoured spinal rods are growing in their utilization for spinal deformity. Although there are theoretical advantages to pre-contouring rods, no previous studies have compared pre-contoured and manually contoured rods for their ability to maintain sagittal contour and resist mechanical load.

METHODS

A spinal deformity model was utilized, simulating a rigid, thoracolumbar spinal deformity fixated with pedicle screws. Roll-formed pre-contoured and manually contoured 5.5 mm and 6.0 mm Co-Cr rods were reduced to the model with a load cell attached to the apical screw to measure corrective force. Rods remained reduced in the model for 20 min and change in contour was assessed to characterize plastic deformation.

RESULTS

Twenty-four rods were tested with six rods per group (Table 1). The load to reduction was significantly lower in the 5.5 mm rods compared to the 6.0 mm rods (95% CI -254.0 to -61.42; p = 0.008). Although there was no difference in the corrective forces for manual and pre-contoured 5.5 mm rods (p = 0.722), the 6.0 mm rod produced significantly less corrective force compared to the manually contoured 6.0 mm rods (95% CI -134.42 to -5.317; p = 0.039). Additionally, rod contour for the manual group showed significantly less plastic deformation than the pre-contoured group in both 5.5 mm and 6.0 mm rods (5.5 mm: 57.1% vs. 61.6%, p = 0.006; 6.0 mm: 54.3% vs. 62.28%, p = 0.003).

CONCLUSIONS

Roll formed, pre-contoured Co-Cr rods demonstrated significantly greater plastic deformation when compared with manually contoured rods of the same diameter. Furthermore, 6.0 mm pre-contoured rods required significantly lower load for rod reduction, the equivalent of 15 lb-force. Post-manufacturing, roll-formed pre-contouring of larger diameter Co-Cr may impair the rods mechanical properties.

Diagnosis and Management of Common Conditions of the Pediatric Spine

Back pain and spinal deformity in the pediatric and adolescent patient population are common reasons for presentation to the orthopaedic surgeon, and although most conditions are benign and self-limiting, a standardized approach to the history and physical examination can identify concerning signs and symptoms as well as aid in determining the final diagnosis and a recommended treatment plan. The most common and concerning etiologies of back pain and spinal deformity will be reviewed, along with nonsurgical and surgical management of these conditions.

Magnetically controlled growing instrumentation for early onset scoliosis: Caution needed when interpreting the literature

BACKGROUND

Magnetically controlled growing rods (MCGR) are a novel treatment option for early onset scoliosis (EOS). Although the complication profile with MCGR use has been reviewed, these reviews do not take into account important implants modifications, termed iterations, that were made due to early on postoperative complications is not well reported or understood.

AIM

To assess the effect of MCGR implant iterations on post-operative complications in EOS.

METHODS

A systematic review was performed to identify studies investigating MCGR specifically for the treatment of EOS, refined to those reporting the implant iteration, specifically the incorporation of the keeper plate to the implant design. Articles with mixed implant iteration usage were excluded. Complications following surgery were recorded as well as potential risk factors and compared between implant cohorts.

RESULTS

Although 20 articles were identified for inclusion, 5 included mixed implant iteration leaving a total of 271 patients identified through 15 clinical studies that met inclusion criteria. The average follow-up was 25.4-mo. Pre-keeper plate implants were utilized in 3 studies with a total of 49 patients. Overall, 115 (42.4%) post-operative complications were identified, with 87% defined as major. The addition of the keeper plate significantly decreased the rate of post-operative complications per study (35.7% vs 80.6%, P = 0.036), and the rate of distraction failure (8.1% vs 40.8%, P = 0.02). Unplanned reoperation occurred in 69 (26.7%) patients but was not different between implant iteration cohorts (25.5% without keeper plate vs 27.1% with keeper plate, P = 0.92).

CONCLUSION

MCGR for EOS has a cumulative complication rate of 42.4% but this is significantly reduced to 35.7% when reviewing only keeper-plate enabled implants. However, 25% of published articles included mixed implant iterations. Future studies should discern between implants iterations when reporting on the usage of MCGR for EOS.

Nighttime bracing with the Providence thoracolumbosacral orthosis for treatment of adolescent idiopathic scoliosis: A retrospective consecutive clinical series

BACKGROUND:

Orthotic treatment for adolescent idiopathic scoliosis is a mainstay in nonoperative treatment to prevent progressive spinal deformity.

OBJECTIVE:

To determine the effectiveness of the Providence orthosis in the treatment of adolescent idiopathic scoliosis.

STUDY DESIGN:

Retrospective review.

METHODS:

Patients treated with a Providence orthosis for adolescent idiopathic scoliosis were reviewed. Inclusion criteria included the following: age of 10-18 years; curve magnitude of 25°-40°; Risser stage of 0-2; and, if female, <1 year post menarche at the time of brace initiation. Failure was defined as curve magnitudes progressing >5° or to >45° or surgery. Radiographs and clinical information were recorded and compared between treatment success and failure cohorts.

RESULTS:

56 patients (51 female and 5 male; average of 12.26 years) were identified with average of 2.21-year follow-up and a 57.1% success rate for preventing curve progression. Factors associated with successful treatment included curve apex T10 and caudal and Risser sign ⩾ 1. Multivariate analysis identified Risser ⩾ 1 and curve apex T10 and caudal as independent predictors of successful treatment.

CONCLUSION:

The Providence nighttime orthosis can be an effective treatment for adolescent idiopathic scoliosis. Curve Apex at T10 or caudal was an independent predictors of treatment success.

CLINICAL RELEVANCE

This study identifies variables associated with treatment success using the Providence nighttime orthosis in a consecutive series of adolescent idiopathic scoliosis patients. This information provides the foundation for identifying ideal patients for nighttime bracing to guide clinical treatment.

Perioperative Complications After Spinal Fusion in Pediatric Patients With Congenital Heart Disease

BACKGROUND

Children with congenital heart disease (CHD) have been reported to be at increased risk of developing scoliosis following cardiac surgery. Previous sample studies have reported that these patients may safely undergo posterior spinal fusion (PSF) with low complication rates. The goal of this study is to provide an updated analysis of the perioperative complication profile for posterior spinal fusion in a large cohort of pediatric patients with CHD, using a nationwide database.

METHODS

A retrospective cohort study was conducted using 30-day perioperative outcomes data from the NSQIP-P database. Our inclusion criteria were all pediatric patients who underwent posterior spinal fusion by CPT code. Patients were subdivided into two groups: those with a history of cardiac surgery for CHD and those without. Postoperative complications were classified according to the Clavien-Dindo system. Risk factors were assessed in univariate and multivariate logistic regression analyses, with significance set at p < .05.

RESULTS

Our results included 3,426 pediatric patients (68.2% female, 31.8% male) with a median age at spinal fusion of 13.7 ± 2.87 years. A CHD diagnosis was present in 312 patients, with 128 having had prior cardiac surgery. The overall complication rate was 6.68%, with a 10.9% rate in the prior cardiac surgery cohort (p = .068). The most common overall perioperative complications were unplanned readmission (3.5%), reoperation (2.6%), and superficial wound dehiscence (2.5%). Patients with a history of cardiac surgery were not at increased risk for postoperative complications; however, blood transfusion (p < .001), bronchopulmonary dysplasia (p < .001), combined bronchopulmonary dysplasia and previous cardiac surgery (p = .004), and a neuromuscular diagnosis (p < .001) were all risk factors for major postoperative complications in this cohort.

CONCLUSIONS

Children with scoliosis who have undergone cardiac surgery to address CHD are not at an increased risk of perioperative complications within 30 days of undergoing a posterior spinal fusion. However, patients who underwent cardiac surgery for CHD who also had bronchopulmonary dysplasia or an associated neuromuscular diagnosis are at increased risk for perioperative complications. It is important for pediatric orthopedic spine surgeons to be familiar with an updated profile of potential perioperative obstacles they may face when treating these patients, as seen in a large and representative cohort.

LEVEL OF EVIDENCE

Level III.

Ulnar Nerve Injury in Pediatric Midshaft Forearm Fractures: A Case Series

OBJECTIVES

To describe a midshaft forearm fracture pattern that places the ulnar nerve at risk in the pediatric population and provide 7 clinical case examples describing the injury pattern and treatment methods.

DESIGN

Retrospective observational case series, review of literature, cadaver dissection, and treatment recommendations.

SETTING

Multi-institutional, Southeast United States.

PATIENTS

Seven pediatric patients (5 male and 2 female) with mean age of 8.7 years (range, 3-14) who sustained a significantly displaced closed, or grade I open, middle to distal one-third both-bone forearm fracture with subsequent ulnar nerve dysfunction.

INTERVENTIONS

Manual reduction and casting of both-bone forearm shaft fractures, operative debridement, fracture fixation, nerve exploration, neurolysis, nerve repair, and nerve grafting.

MAIN OUTCOME MEASUREMENTS

Radiographic fracture union, clinical ulnar nerve motor and sensory function testing, along with selective electric nerve testing and advanced imaging were monitored throughout follow-up postinjury.

RESULTS

Five of 7 patients underwent surgical treatment and 2 others were treated with conservative measures. The ulnar nerve was entrapped within the fracture site of one patient with an open fracture along with partial nerve transection, and 4 patients were found to have the nerve encased in hypertrophic scar tissue or bony callus upon surgical exploration at 3-12 months postinjury.

CONCLUSIONS

The ulnar nerve lies in a precarious position in the middle to distal one-third forearm and is bound by anatomic constraints that place the nerve at risk of injury. This article offers a treatment algorithm that includes conservative treatment, acute exploration, early exploration (≤3 months), and late exploration (>3 months).

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Accuracy of robot-assisted pedicle screw insertion in adolescent idiopathic scoliosis: is triggered electromyographic pedicle screw stimulation necessary?

Background

Screw malpositioning is an identifiable cause of intraoperative neurophysiologic changes. Although triggered screw electromyography (t-EMG) has been found to exhibit high sensitivity for identifying malpositioned screws, no previous study has assessed the utility of combining t-EMG with robotic-assisted pedicle screw placement for identifying malpositioned screws. We sought to evaluate the utility of t-EMG used in combination with robotic-assisted pedicle screw placement for identifying malpositioned screws in patients with adolescent idiopathic scoliosis (AIS).

Methods

Patients undergoing robotic-assisted posterior spinal fusion with pedicle screw fixation for AIS underwent retrospective review from a single surgeons prospectively collected database. Preoperative demographic data and curve characteristics were recorded. Computed tomography (CT) scans were reviewed, measuring pedicle width and classifying pedicle morphology using the channel classification system. Pedicle data was compared against intra-operative t-EMG data, with a minimal threshold of 8 mA used for screw removal and screw path examination and the rate of screw re-direction recorded. All pedicle screws were verified using image intensification.

Results

Forty-nine patients (11 males, 38 females, average age 14.49 years) with an average curve magnitude of 51 degrees and placement of 844 pedicle screws to attain an average curve correction of 67.7%. The incidence of an absent pedicle (type C or D morphology) was 2%. Overall, 24 screws (2.8%) were identified with an abnormal t-EMG threshold. All screws were found to have an intact medial wall upon probing and were reinserted without re-direction. No patient or curve characteristic was predictive of abnormal t-EMG amplitude but smaller pedicles correlated with smaller amplitudes.

Conclusions

With precise pre-operative planning, robotic-assisted pedicle screw placement has shown to be a safe and effective method in treating AIS patients as shown by the lack of medial pedicle breach and malpositioned screws. We found no evidence to support combined use of t-EMG for identifying medially malpositioned screws.

Complications following lengthening of spinal growing implants: is postoperative admission necessary?

OBJECTIVE The aim of this study was to evaluate the effect of postoperative admission status on 30-day perioperative complications in patients with growing spinal instrumentation undergoing surgical lengthening. METHODS This retrospective case-control study of records from the 2014-2015 National Surgical Quality Improvement Program-Pediatric database was performed to identify surgical lengthening procedures of spinal implants in patients with growing instrumentation by Current Procedural Terminology code. The 30-day postoperative complications were classified according to the Clavien-Dindo system. Patients were subdivided according to their postsurgical admission status. Admission status, American Society of Anesthesiologists (ASA) Physical Status classification, tracheostomy, neuromuscular diagnosis, ventilator dependence, and nutritional support were considered as possible risk factors in univariate and multivariate logistic regression analyses. RESULTS A total of 796 patients were identified (mean age 9.09 ± 3.44 years; 54% of patients were female), of whom 73% underwent lengthening on an inpatient basis. Patients with a tracheostomy or ventilator dependence were more likely to be admitted postoperatively. The overall rate of major complications was 3.5% and did not differ based on admission status (2.8% inpatient vs 3.8% outpatient, p = 0.517). On univariate analysis, ventilator dependence (9.5% vs 2.7%, p = 0.002), need for nutritional support (7.1% vs 2.5%, p = 0.006), and ASA class > II (4.8% vs 1.3%, p = 0.04) placed patients at a higher risk for any postoperative complications. Multivariate analysis identified only ventilator dependence as an independent risk factor for any perioperative complication. CONCLUSIONS Postoperative admission status did not affect the rate of 30-day perioperative complications, readmission, or rate of unplanned operations following lengthening of growing spinal instrumentation. Outpatient lengthening appears to be safe; however, consideration for postoperative admission should be given for those who are ventilator dependent.

Femoral version: Comparison among advanced imaging methods

Accurate assessment of femoral version is essential to the surgical treatment of lower extremity deformities, yet the ideal modality and technique to measure femoral version is controversial. This study explored two hypotheses: First, there is no difference in the accuracy of femoral version measurement from 2D CT, 2D MRI, and 3D biplanar radiography reconstructions compared to a 3D model created from CT. Second, there is a difference between the measured version from traditional axial sections of the proximal femur compared to femoral neck oblique sections for CT and MRI. Eight adult cadaver lower extremities underwent CT, MRI, and biplanar radiography. Femoral version measurements from the CT and MRI axial and oblique sections, as well as biplanar radiography reconstructions, were compared to 3D reconstructed models from CT. All five techniques underestimated femoral version compared to the 3D model, but none were statistically significantly different. Regarding the first hypothesis, all five techniques had excellent correlation (r > 0.81, p ≤ 0.01) with the 3D model. Concerning the second hypothesis, the CT and MRI version measurements in femoral neck oblique sections were greater by 5.4° and 1.4°compared to traditional axial sections, respectively. All five techniques across three modalities provided accurate assessment of femoral version, suggesting that the treating physician's choice of modality can be determined per individual patient, not on measurement accuracy.

CLINICAL SIGNIFICANCE

In choosing a modality to determine femoral version, consider the advantages and disadvantages of each modality for the individual patient, using femoral neck oblique slices for CT and MRI when available. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1536-1542, 2018.

Predictors of Distal Adding-on in Thoracic Major Curves With AR Lumbar Modifiers

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

To determine whether the last substantially touched vertebra (LSTV) is a valid lowest instrumented vertebra (LIV) for both Lenke 1 and 2 curve patterns with AR lumbar modifiers, and to identify preoperative risk factors of distal adding-on.

SUMMARY OF BACKGROUND DATA

Previous studies have recommended selecting the LSTV as the LIV for Lenke 1AR curves (main thoracic curve with A lumbar modifier and L4 tilt to the right (thoracic overhang/King type IV curve).

METHODS

One-hundred sixty patients with a Lenke 1 or 2 curve pattern and AR lumbar modifier who underwent posterior spinal fusion between 2008 and 2012 were reviewed. All patients had minimum 2-year follow up. Patients were identified with distal adding-on between first erect radiographs and 2-year follow up based on previously defined parameters. Factors predictive of the adding-on phenomenon were identified in a multivariate binary logistic regression model.

RESULTS

Twenty-seven patients (17%) were identified as having distal adding-on of their primary thoracic curve; however, only 8 of 89 patients (9%) fused to the LSTV developed adding-on (P = 0.005). Three variables were found to be significant predictors of adding-on: LIV proximal to LSTV (odds ratio, OR 3.63; P = 0.01), Risser zero (OR 4.93; P = 0.02), and C7-CSVL distance <2 cm (OR 3.97; P = 0.01). The risk of adding-on increased as the number of predictors increased from 16% with one risk factor to 80% when all three preoperative risk factors were present (P < 0.001).

CONCLUSION

Choosing the LSTV as the LIV in Lenke 1 and 2 curve patterns with an AR lumbar modifier significantly decreases the risk of distal adding-on. Skeletally immature patients, those fused short of LSTV, and those with relative coronal balance preoperatively are at increased risk of distal adding-on between the initial postoperative visit and 2-year follow up.

LEVEL OF EVIDENCE

4.

Purification of B. megatherium Phage G and Evidence for a Muralytic Enzyme as an Integral Part of the Phage

The Purification Of B. megatherium G phage is described and it is shown that DEAE cellulose chromatography combined with conventional methods gave a phage preparation which was at least 95 per cent pure, and contained 2.16 µg nitrogen/10¹¹ infective particles. The phage particle weight in molecular weight units was 91 x 10⁶. The small amount of contaminating material appeared to represent phage "ghosts." An essentially 1:1 ratio of particles to infective units was found when data from electron microscopic counts or data from chemical analysis were related to phage infectivity. Comparison, by several methods, of the G phage and coliphage T2 shows that T2 is 2.6 times larger than G phage. The specific activity of the muralytic component obtained by disintegration of phage preparations with urea was unchanged by the purification indicating that the phage-"bound" muralytic activity is an integral part of the phage structure.

Assessment of relative tumor burden in patients with clinical T1c prostate cancer treated with either external beam or radical prostatectomy

The choice between external beam radiation therapy (EBRT) or retropubic radical prostatectomy (RPX) as potentially curative treatment for localized carcinoma of the prostate gland (CaP) has not been delineated in randomized studies. Both treatments are more effective if tumor burden is low. We sought to compare these two treatments in patients who had clinical stage T1c (cT1c) lesions and who were thought to have limited tumor burdens pretreatment. Sixty cT1c patients referred to the Department of Radiation Oncology received 66 Gy in 33 sessions of EBRT to localized prostate ports and 59 cT1c patients had RPX. No neoadjuvant nor early adjuvant therapies were prescribed. Radiotherapy success was defined biochemically as a nonrising prostate-specific antigen (PSA) of +/- 1.5 ng/ml. RPX success required a postoperative PSA that was undetectable (PSA <0.2 ng/ml by the Hybritech or Abbott IMx technics). Analysis for nonrising posttreatment PSA levels was performed using Kaplan-Meier and Cox regression methods. Mantel-Haenszel methods were used to determine odds ratios for treatment groups adjusting for potential confounders. We ultimately assessed the relative tumor burden by histologic examination of the RPX specimens. The two treatment groups, although not randomized, were statistically similar in biopsy Gleason Scores, transrectal ultrasonography calculated gland volumes, number of positive biopsy cores, and estimated amount of cancer identified on initial biopsies. Pathologic stage T3 was identified in 25% of RPX patients. Fifty to 60% of RPX specimens histologically had substantial tumor burden and by inference also the EBRT patients. At a median follow-up (F/U) of 36 months, 76% of RPX patients maintained an undetectable PSA, whereas 62% of EBRT patients had a PSA < 1.5 ng/ml at a median F/U of 29 months. The pretreatment PSA values significantly affected EBRT patients' risk of a rising posttreatment PSA level. Twenty-four months after treatment, RPX patients were 3.7 times more likely to maintain a nonrising PSA level (RPX patients posttreatment PSA < 0.2 ng/ml), than EBRT patients (posttreatment PSA < or = 1.5 ng/ml) (p = 0.006). Sixty-six gray in 33 sessions to localized EBRT ports is not sufficiently aggressive therapy for one third or more of patients with cT1c CaP. RPX alone is insufficient therapy for one fourth of cT1c patients. Analysis of the RPX specimens showed that many cT1c tumors have a significant tumor burden. Selection methodologies to separate out patients who require more than conventional dose or type of radiotherapy or more than RPX as monotherapy are needed. Pretreatment PSA and number of positive biopsies may assist this selection process.

Stability studies and high-performance liquid chromatographic procedures for L-648,548 and its major degradates in an animal health formulation

L-648,548 is a new avermectin which was evaluated for the development of an animal health formulation. A stability-indicating method for the essay of 5% (w/v) L-648,548 in an animal health formulation has been developed using reversed-phase high-performance liquid chromatography (HPLC) with UV detection (245 nm). The procedure to determine L-648,548 is linear and accurate over the range 80-120% of the target concentration with a limit of quantitation of 0.2%. Validation data are presented. Also two related degradates of this compound were observed during the stability studies of the L-648,548 formulation. These degradates were determined to be the 2-epimer formed in the presence of base and the 8a-oxo degradate formed by oxidation. Identification of these compounds following direct chemical synthesis was based on mass, UV and NMR spectroscopy. The mechanistic pathways for the formation of these degradates are discussed. The 8a-oxo degradate has a modified chromophore, thus requiring a second HPLC method with detection at 280 nm that was also validated.

Identification of the secondary degradates of L-648,548 in an animal health formulation

L-648,548 is a semisynthetic analog of avermectin. During stability investigations of this compound in an animal health formulation, two new degradates were discovered. These degradates (L-648,548 phenol and its 8,9-Z isomer) were identified as the reaction products of 5-oxo-L-648,548 formed by oxidation of L-648,548. Addition of base to the reaction medium containing 5-oxo-L-648,548 was found to catalyze the formation of L-648,548 phenol via a postulated dehydration by an E1cb elimination followed by the rapid tautomerization of the C5 carbonyl. Photolysis of L-648,548 phenol with visible light (including ambient laboratory lighting) was found to readily produce 8,9-Z-L-648,548 phenol. This transformation was confirmed to be exclusively a photoinduced process.

Dissociation between early loss of actin fibres and subsequent cell death in serum-deprived quiescent Balb/c-3T3 cells

Serum withdrawal from either growing or quiescent Balb/c-3T3 murine fibroblasts causes a loss of F-actin fibres and focal adhesions within 30 min. Cells that are growing survive serum deprivation, whereas the great majority of density-arrested quiescent cells die during a period of up to 5 h from serum withdrawal. During this time an approximately constant fraction of the quiescent cell population dies per unit time. The population half-life is 60-70 min during this time. Addition of an appropriate cell growth factor or second messenger agonist at the time of serum withdrawal or within 2 h after serum withdrawal protects a similar fraction of viable cells. These findings suggest a model according to which withdrawal of serum (i.e. growth factors) initiates the death process in cells of the population with kinetics that approximate first-order kinetics. We postulate that appropriate growth factors or second messenger agonists block the initiating event that starts the cell death process.

Total joint replacement: implication of cancelled operations for hospital costs and waiting list management

OBJECTIVE

To identify aspects of provision of total joint replacements which could be improved.

DESIGN

10 month prospective study of hospital admissions and hospital costs for patients whose total joint replacement was cancelled.

SETTING

Information and Waiting List Unit, Musgrave Park Regional Orthopaedic Service, Belfast.

PATIENTS

284 consecutive patients called for admission for total joint replacement.

MAIN MEASURES

Costs of cancellation of operation after admission in terms of hotel and opportunity costs.

RESULTS

28(10%) planned operations were cancelled, 27 of which were avoidable cancellations. Five replacement patients were substituted on the theatre list, leaving 22(8%) of 232 operating theatre opportunities unused. Patients seen at assessment clinics within two months before admission had a significantly higher operation rate than those admitted from a routine waiting list (224/232(97%) v 32/52(62%), x2 = 58.6, df = 1; p < 0.005). Mean duration of hospital stay in 28 patients with cancelled operations was 1.92 days. Operating theatre opportunity costs were 73% of the total costs of cancelled total joint replacements.

CONCLUSION

Patients on long waiting lists for surgery should be reassessed before admission to avoid wasting theatre opportunities, whose cost is the largest component of the total costs of cancelled operations.

Decreased adherence of interleukin 6-treated breast carcinoma cells can lead to separation from neighbors after mitosis

Interleukin 6 (IL-6) has been shown to inhibit the proliferation, but increase the motility, of wild-type ZR-75-1 human ductal breast carcinoma cells, a line of cells that resemble closely the malignant cells cultured from the ascitic effusion. IL-6-treated cells lose their epithelial character, become stellate or fusiform in shape, and migrate away from neighbors. In the wild-type ZR-75-1 cells, IL-6 causes cell-cell separation in preformed colonies as well as postmitotically. We have now investigated the action of IL-6 in clone B ZR-75-1 cells, which are morphologically distinct from wild-type ZR-75-1 cells. In the more polygonal rather than cuboidal clone B cells, IL-6 did not cause early inhibition of DNA synthesis and it caused little cell-cell separation in preformed colonies. However, IL-6 treatment markedly prolonged the interval between mitosis and readherence of daughter cells to their neighbors and the substratum. Supernatants from IL-6-treated cultures contained detached viable cells in increased numbers. Intermitotic intervals were prolonged in IL-6-treated cultures. IL-6-treated dividing breast carcinoma cells are characterized by an increased probability of separation from neighbors and the substratum.

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Effects of interferon-beta on the translocation rate and stationary time in human fibroblasts in culture

The rate of translocation and the percent of the time that cells are stationary have been measured by computer-assisted time-lapse cinemicrography in over 1,000 freshly planted human foreskin fibroblasts (FS-4 cell strain) for periods of up to a week and the effects of interferon-beta (IFN-beta) on these parameters have been determined. Cells were planted at 2.5 X 10(3) cells/cm2 in Eagle's minimal essential medium (MEM) with 10% fetal bovine serum (FBS). Frames were taken every 2 or 4 minutes and data were collected on both cell location and cell division as a function of time. After planting FS-4 cells require approximately 48 hr to reach maximum motility both with respect to the translocation rate when moving and percent time cells are moving. Recombinant human INF-beta (800 mu/ml) caused a marked increase in the fraction of time cells were stationary and a decrease of lesser magnitude in the translocation rate, as quantitated during the period during which the stationary fraction for control cells was at a minimum. IFN-beta also decreased the rate of cell proliferation, without any evidence of degeneration or death of cells. Our results contribute new evidence that the fraction of time cells spend moving directionally is an important determinant of their locomotory behavior and that this determinant is responsive to modulation by cytokines.

Structure and activity of hydrogenated derivatives of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801)

Several hydrogenated derivatives of the potent NMDA antagonist 1 have been prepared and evaluated as competitive inhibitors of [3H]-1 binding. These compounds were also tested for their ability to act as noncompetitive antagonists of NMDA in vitro. These studies indicate that two aromatic rings are not strictly required for high-affinity binding or NMDA antagonism.

Biotransformation of lovastatin. I. Structure elucidation of in vitro and in vivo metabolites in the rat and mouse

Structures of in vitro microsomal and in vivo metabolites of lovastatin, a new cholesterol-lowering drug, were elucidated with the combined application of HPLC, UV, fast atom bombardment-MS, and NMR spectroscopy. Liver microsomes from rats and mice catalyzed the biotransformation of lovastatin, primarily at the 6'-position of the molecule, to form 6'-hydroxy-lovastatin and a novel 6'-exomethylene derivative. Hydroxylation at the 6'-position occurred stereoselectively, giving 6'-beta-hydroxy-lovastatin. Stereoselective hydroxylation at the 3"-position of the methylbutyryl side chain and hydrolysis of the lactone group to the corresponding hydroxy acid were the other two pathways of microsomal metabolism. 3'-Hydroxy-iso-delta 4',5'-lovastatin was isolated, but is not believed to be a direct metabolite since 6'-beta-hydroxy-lovastatin rearranges to this compound under mildly acidic conditions. The major metabolites excreted in bile of rats treated with the hydroxy acid form of the drug were identified as the 3'-hydroxy analog and a taurine conjugate of a beta-oxidation product of lovastatin. The pentanoic acid derivative of lovastatin, formed by beta-oxidation of the heptanoic acid moiety, was a major metabolite in livers of mice dosed with the hydroxy acid form of lovastatin. The microsomal metabolites, in their hydroxy acid forms, were active inhibitors of HMG-CoA reductase. The relative enzyme inhibitory activities of hydroxy acid forms of lovastatin, 6'-beta-hydroxy-, 6'-exomethylene-, and 3"-hydroxy-lovastatin were 1, 0.6, 0.5, and 0.15, respectively.

Development of the Belfast orthopaedic information system

A team from Musgrave Park Hospital, Belfast, describe their success in reducing the hip waiting list and introducing an information system to manage the orthopaedic waiting list.

Interleukin 6 decreases cell-cell association and increases motility of ductal breast carcinoma cells

Treatment of transformed breast duct epithelial cells with IL-6 produces a unique cellular phenotype characterized by diminished proliferation and increased motility. Human ductal carcinoma cells (T-47D and ZR-75-1 lines) are typically epithelioid in shape and form compact colonies in culture. Time-lapse cinemicrography shows that some untreated cells can transiently become fusiform or stellate in shape and separate from each other within a colony, but they usually rejoin their neighbors. While IL-6 suppresses the proliferation of these carcinoma cells, the IL-6-treated cells generally become stellate or fusiform and show increased motility. These changes persist as long as the cells are exposed to IL-6. This results in the dispersal of cells within colonies. The effects on cell growth, shape, and motility are reversible upon removal of IL-6. IL-6-treated T-47D cells display diminished adherens-type cell junctions, as indicated by markedly decreased vinculin-containing adhesions and intercellular desmosomal attachments. The effects on ZR-75-1 cell shape, colony number, and DNA synthesis are dependent on IL-6 concentration in the range from 0.15 to 15 ng/ml. Higher concentrations are required in T-47D cells for equivalent effects. Anti-IL-6 immune serum blocks IL-6 action. IL-6 represents a well-characterized molecule that regulates both the proliferation and junction-forming ability of breast ductal carcinoma cells.

Occurrence of cell division is not exponentially distributed: differences in the generation times of sister cells can be derived from the theory of survival of populations

The Eyring-Stover survival theory has been applied to the kinetics of the distribution of intermitotic intervals of mammalian cells and by inference to the transition from the G1 phase into DNA synthesis (S phase). The theory faithfully fits experimental data acquired by time-lapse cinemicrography of cloned HeLa cells in tissue culture and also suggests the existence of a labile initiator substance which mediates the G1-S phase transition. This theory provides an alternative to the transition probability model proposed by Smith and Martin [Smith J. A. & Martin, L. (1973) Proc. Natl. Acad. Sci. USA 70, 1263-1267; see also Shields, R. & Smith, J. A. (1977) J. Cell Physiol. 91, 345-355 and Brooks, R. F., Bennett, D. C. & Smith, J. A. (1980) Cell 19, 493-504].

Pleiotropic effect of Tabby gene on epidermal growth factor-containing cells of mouse submandibular gland

The influence of the Tabby gene on the submandibular gland of the mouse was assessed by comparing the mass of the gland, and its content of granular convoluted tubules, in prepubertal, pubertal, and adult Tabby mice and their wild type brother controls. The Tabby mice showed reduction in mass of the adult submandibular gland, delayed development of the granular convoluted tubules, and reduction in relative content of granular convoluted tubules. Epidermal growth factor (EGF) is released from the granular convoluted tubules of the mouse submandibular gland, and it is known to experimentally influence the development of at least some of the structures that are affected by the Tabby gene. Accordingly, the question of a relationship between the Tabby gene and EGF is raised.

Serum enhances the cycling and survival of HeLa cells treated with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole

We have defined the growth kinetics of HeLa cell populations by determining the frequencies of mitoses and deaths and the lengths of intermitotic intervals. This was done by time-lapse cinemicrography. Untreated control cells proliferated at closely similar rates in medium enriched with 5% or 15% fetal calf serum, with an average of 4% dividing and less than 0.1% dying per hr. The mean intermitotic interval was 16 hr during exponential growth of the control populations. In contrast, in cultures treated with 40 or 60 microM 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), a selective inhibitor of heterogeneous nuclear RNA synthesis, the frequency of mitoses was markedly and directly dependent on serum concentration, whereas the frequency of deaths was inversely dependent. DRB prolonged the intermitotic interval in cells cycling in the presence of the drug, but the effect was less in 15% than in 5% serum. After prolonged treatment of HeLa cells with DRB, the inhibition of heterogeneous nuclear RNA synthesis by DRB appeared to be reduced, which was not due to inactivation of DRB in the culture medium.

Kinetics of desynchronization and distribution of generation times in synchronized cell populations

The kinetics of the distribution of generation times in synchronized cells can be analyzed by using Fourier transform analysis. Deviations of the experimental data from the curve of completely asynchronous growth reflect the degree of synchrony at a particular time. Fourier transform analysis of these deviations yields the average generation time as well as information on the distribution of generation times characterizing a synchronized culture. A detailed analysis of synchronized cell cultures does not provide any evidence for the existence of a subcycle or a polymodal distribution in generation times. The data do indicate that cell-cell interaction occurs at cell densities as low as 2.5 X 10(3)/cm2. It is also shown that the Eyring-Stover formalism for the dynamics of survival can correctly describe the distribution of the first round of cell divisions in a synchronized culture.