Tethered Cord Research Articles

P11. Clinically applicable tension through vertebral body tethering cord preserves thoracolumbar motion

P11. Clinically applicable tension through vertebral body tethering cord preserves thoracolumbar motion

Clinically applicable tension through vertebral body tethering cord preserves thoracolumbar motion

Clinically applicable tension through vertebral body tethering cord preserves thoracolumbar motion

Determination of tibial somatosensory evoked potentials predicts detrusor sphincter dyssynergia in children with neurogenic bladder dysfunction.

Tibial somatosensory evoked potentials (SEP) are used to identify the neurological status and tethered cord (TC) in patients with spina bifida (SB). Its significance in contributing to the interpretation of urodynamics to determine bladder status is unknown. This study aimed to determine the correlation between SEP and urodynamics in children with SB. SEP and urodynamic results, for differential diagnosis of TC, were evaluated. SEP scores were correlated with urodynamic findings. SEP results were scored from 1 to 6, with 1, denoting a favorable score and 6, an unfavorable score. Age, gender, detrusor, and sphincter activities in urodynamics were noted. Results were analyzed using the χ2 test and logistic regression analysis. Receiver operating characteristic (ROC) curve was formed to get a valid threshold for the SEP score to predict the urodynamic condition. There were 44 SB patients for whom SEP was done for differential diagnosis of TC. Fifteen patients who did not meet the inclusion criteria were excluded from the study. SB aperta was present in 17 patients and occulta in 12, respectively. The patients had a mean age of 6.6 ± 3.2 years. There were 13 boys and 16 girls. A strong correlation was found between high SEP scores and detrusor sphincter dyssynergia (p < 0.001). A SEP score over 3.5 was found to be 93% sensitive and 73% specific to predict this correlation. There was no relationship between detrusor activity and SEP scores (p = 0.18). Tibial SEP is an important noninvasive adjunct tool for the diagnosis of TC in patients with SB. Urodynamic studies are the gold standard in the evaluation of bladder status in neurogenic bladder dysfunction due to SB. Detrusor sphincter dyssynergia may be regarded as a sign of severe spinal cord injury in these patients. Our findings suggest that in children with neurogenic bladder, high SEP scores may predict the presence of detrusor sphincter dyssynergia but not the status of detrusor function while providing pathophysiological evidence for neural injury.

Detection and Management of Tethered Cord in Anorectal Malformation: A Survey of Pediatric Neurosurgeons in the United States

Introduction: The reported prevalence of tethered spinal cord in patients with anorectal malformations (ARMs) ranges from 9% to 64%. Practice patterns surrounding the diagnosis and management of tethered cord (TC) are suspected to vary, with consideration to the type of spine imaging, adjunct imaging modalities, what patients are offered surgical intervention, and how patients are followed after detethering. We sought to determine what consensus, if any, exists among pediatric neurosurgeons in the USA in terms of diagnosis and management of TC and, specifically, patients with TC and ARM. Methods: A survey was sent to members of the American Society of Pediatric Neurosurgeons (ASPN). Members of the ASPN received an email with a link to an anonymous REDCap survey that asked about their experience with detethering procedures, indications for surgery, diagnostic tools used, and follow-up protocols. Results: The survey was completed by 93 of the 192 ASPN members (48%). When respondents were asked about the total number of all simple filum detetherings they performed annually, 61% (N = 57) indicated they perform less than 10 for all TC patients. Ninety-three percent (N = 87) of neurosurgeons performed these procedures in patients with simple filum TC and ARM patients (TC + ARM) specifically. When asked about prophylactic detethering in those with a confirmed diagnosis of low-lying conus and with a filum fatty terminale, 59.1% (N = 55) indicated they would offer this to TC + ARM patients regardless of their age. Regarding preoperative workup for simple filum detethering, all respondents indicated they would order an MRI in both TC and TC + ARM patients, with a minority also requiring additional testing such as urodynamics, neurodevelopmental assessments, and anorectal manometry for both groups. When following patients postoperatively, almost all respondents indicated they would require clinical neurosurgical follow-up with a clinic visit (100% in all simple filum TC patients, 98.9% in fatty filum/low-lying conus TC + ARM patients), but there was wide variation in the use of other tools such as urological testing, neurodevelopmental assessment, and anorectal manometry. Discussion/Conclusions: A wide variety of diagnostic criteria and indication for procedural intervention exists for management of TC patients with and without ARM. Further studies are needed to determine outcomes. Prospective protocols need to be developed and evaluated to standardize care for this patient population and determine best practices.

Functional outcome after cord detethering in fecally incontinent patients with anorectal malformations

Tethered cord (TC) occurs in 36% of patients with anorectal malformations (ARMs), for whom the benefit of detethering surgery remains unclear regarding bowel and/or bladder function. This study aimed to examine whether cord detethering could improve fecal and urinary incontinence in these patients. This was a retrospective study of TC patients (>3 years old) with fecal incontinence and ARMs, who underwent detethering surgery between 2016 and 2020 and were followed up for at least 6months. Of the 27 included patients, 55% had sacral ratios between 0.4 and 0.7, and in 37% it was < 0.4; the remaining 8% was over 0.7; 52% suffered from colonic hypermotility. After detethering surgery, partial fecal continence was achieved in five patients (18%); total fecal continence, in ten patients (37%); 12 (44%) remained fecally incontinent. Partial urinary continence was obtained in four cases (14%), and the number of patients with total urinary continence rose from 7 (25%) to 15 (55%). Lower extremity symptoms were also improved in 72% of the cases. Patients with colonic hypomotility were found to have a better functional outcome than those with colonic hypermotility (69% vs. 43%, respectively). Our study demonstrated that detethering surgery led to remarkably improved bowel and bladder control in ARM patients with fecal incontinence, which, surprisingly, was not associated with sacral ratio.

Triple Use of Autologous Amnion Graft in the Treatment of Meningomyelocele and Split Cord Malformation

Summary:This article describes the triple use of autologous amnion graft as a new procedure in the treatment of myelomeningocele and in myelomeningocele with split cord malformation. The first amnion graft was used as a physical and mechanical barrier to protect the myelomeningocele (MMC) from desiccation and mechanical stress directly after birth. A second graft was used as a dura substitute to close the cerebrospinal fluid compartment. Autologous amnion seems to be the ideal dural graft for closure of an MMC and for an MMC with split cord malformation. A tension-free and watertight closure was obtained. With the epithelium side placed to the spinal cord and due to its beneficial effect on scar formation, the risk for tethering cord syndrome is reduced when using autologous amnion as a dural graft. The regenerative properties of autologous amnion may contribute to repair neural damage. Finally, a third amnion graft was placed beneath the perforator flap used to close the skin defect to provide a watertight barrier and to stimulate flap survival.

In Vivo Evaluation of Novel PLA/PCL Polymeric Patch in Rats for Potential Spina Bifida Coverage

BackgroundCurrent therapeutic materials for spina bifida repair showed a limited number of options in the market, and none of them have all the requirements as the ideal patch. In fact, sometimes the surgical procedures pose substantial challenges using different patches to fully cover the spina bifida lesion. For this purpose, a tailored patch made of poly (L-lactic acid) and poly (ε-caprolactone) blend was designed and validated in vitro to accomplish all these requirements but was never tested in vivo. Material and methodsIn our present study, the designed patch was analyzed in terms of rejection from the animal when implanted subcutaneously and as a dural substitute in the spinal cord. Inflammatory reaction (Iba1), astrogliosis (GFAP), was analyzed and functional interaction with spinal cord tissue assessing the (%motor-evoked potentials /compound motor action potential) by electrophysiology. ResultsNo evidence of adverse or inflammatory reactions was observed in both models of subcutaneous implantation, neither in the neural tissue as a dural substitute. No signs of astrogliosis in the neural tissue were observed, and no functional alteration with improvement of the motor-evoked potential's amplitude was detected after 4 wk of implantation as a dural substitute in the rat spinal cord. ConclusionsDesigned patch used as a dural substitute will apparently not produce inflammation, scar formation, or tethering cord and not induce any adverse effect on regular functions of the spinal cord. Further studies are needed to evaluate potential improvements of this novel polymeric patch in the spinal cord regeneration using spina bifida models.

Tethered cord in children with anorectal malformations with emphasis on rectobladder neck fistula.

To find the incidence of tethered cord (TC) in patients with anorectal malformations (ARM) and to determine the relationship between bowel/urinary control and TC in a subset of patients with rectobladder neck fistula (RBNF). The database of a tertiary medical center was retrospectively collected for all patients treated for ARM from 1980 to 2012. All patients with TC and RBNF were identified. Among 790 patients, who underwent screening for TC, 285(36%) were diagnosed with TC. Eleven of 37 screened patients with RBNF were diagnosed with TC. The median follow-up period was 49 months (range 2-222 months). TC was diagnosed in 3/18(16.6%) patients with sacral ratio (SR) ≥ 0.7; 4/12(33.3%) with SR 0.41-0.69; and 4/7(57.1%) patients with SR 0-0.4. The association of TC in RBNF patients had a negative influence in the prognosis for bowel and urinary control. The incidence of TC among patients with ARM is 36%. Incidence of TC among patients with RBNF correlates with SR value and is higher with lower SR. Patients with RBNF and TC have dismal prognosis for bowel control, unrelated to their SR status. Many unresolved questions related to the management of ARM patients with asymptomatic TC still remain.

Can sacral development as a marker for caudal regression help identify associated urologic anomalies in patients with anorectal malformation?

Background and aimThe sacral ratio (SR) is a well-established tool to quantify sacral development in patients with anorectal malformations (ARM) and can be used as a predictor of fecal continence. We hypothesized that a lower SR correlated with the presence of urologic and renal malformations. MethodsWe retrospectively reviewed the medical records of patients with ARM treated at our center from 2014 to 2016. We measured the lateral SR as a marker for sacral development and assessed the spine for the presence of tethered cord (TC). Urological and renal anomalies, including single kidney, hydronephrosis, hypospadias, vesicoureteral reflux (VUR), ectopic ureter, and penoscrotal transposition were assessed. Analysis of variance (ANOVA), t-tests, and multivariable linear regression were used to test for differences in SR with consideration of associated urologic malformations and tethered cord. Results283 patients with ARM were included for analysis (156 females). The median age was 39months (10–90). Among these, 178 (55.6%) had 1 or more urologic malformations, and 81 (25.3%) had a TC. Hydronephrosis, high-grade VUR (3–5), solitary kidney, and tethered cord were significantly associated with lower SR (p<0.01). In multivariable regression models, the presence of urologic abnormalities remained significantly associated with lower a SR despite the presence or absence of TC (p<0.001). ConclusionSR is a potentially useful indicator of certain urologic anomalies including hydronephrosis, high grade VUR, and solitary kidney in patients with ARM. This association is independent of the presence of TC. A sacral ratio as a part of the VACTERL screening can help the surgeon identify which patients need closer urologic follow up. Level of evidenceIV

Incidence of symptomatic tethered spinal cord in pediatric patients presenting with neurofibromatosis types 1 and 2.

OBJECTIVE The relationship between a tethered cord (TC) and neurofibromatosis type 1 (NF1) and NF2 is not known. The purpose of this study was to define the incidence of TC in pediatric neurosurgical patients who present with NF. METHODS The authors performed a single-institution (tertiary care pediatric hospital) 10-year retrospective analysis of patients who were diagnosed with or who underwent surgery for a TC and/or NF. Clinical and radiological characteristics were analyzed, as was histopathology. RESULTS A total of 424 patients underwent surgery for a TC during the study period, and 67 patients with NF were seen in the pediatric neurosurgery clinic. Of these 67 patients, 9 (13%) were diagnosed with a TC, and filum lysis surgery was recommended. Among the 9 patients with NF recommended for TC-release surgery, 4 (44%) were female, the mean age was 8 years (range 4-14 years), the conus position ranged from L1-2 to L-3, and 3 (33%) had a filum lipoma, defined as high signal intensity on T1-weighted MR images. All 9 of these patients presented with neuromotor, skeletal, voiding, and/or pain-related symptoms. Histopathological examination consistently revealed dense fibroconnective tissue and blood vessels. CONCLUSIONS Despite the lack of any known pathophysiological relationship between NF and TC, the incidence of a symptomatic TC in patients with NF1 and NF2 who presented for any reason to this tertiary care pediatric neurosurgery clinic was 13%. Counseling patients and families regarding TC symptomatology might be indicated in this patient population.

Ipsilateral hip dysplasia in patients with sacral hemiagenesis: a report of two cases.

Sacral agenesis (SA) is a rare condition consisting of the imperfect development of any part of the sacrum. This paper describes two cases of the rare cooccurrence of ipsilateral SA and developmental dysplasia of the hip (DDH) and analyzes possible contributory factors for SA and DDH. Each of a 16-year-old female and 13-year-old female visited our hospital for left hip pain and limping. The findings of physical examinations showed a lower limb length discrepancy (left side) in both cases, as well as left hip pain without limitations of the range of motion or neurological deficits. Initial radiographs demonstrated left subluxation of the left hip with associated acetabular dysplasia and partial left sacral agenesis. MRI revealed a tethering cord with a fatty filum terminale, and periacetabular osteotomy combined with allogeneic bone grafting was performed. After the surgery, the patients experienced no further pain, with no leg length discrepancy and were able to walk without a limp, being neurologically normal with a normal left hip range of motion. The cooccurrence of SA and DDH suggests a plausible hypothesis to explain the embryogenic relationship between malformation of the sacrum and hip.

Putative height acceleration following tethered cord release in children.

Tethered cord (TC) is a neurological disorder caused by tissue attachments that limit the normal movement of the spinal cord. A TC can be unmasked by a cutaneous abnormality or manifest clinically in myriad neurological, urological, and orthopedic symptoms. The relationship between TC and height is previously unknown. This study investigates the association between TC release and changes in height profiles in the pediatric population. Fifty-two children undergoing first-time TC release at a single institution were examined retrospectively. Clinical symptoms, radiographic findings, pre- and postoperative height, and height-for-age percentiles were recorded and analyzed. Children with TC experienced a statistically significant increase in age-adjusted height percentiles after TC release (p = 0.0028), with a mean increase of 7 percentile points (from 48.1st to 54.9th percentile). When stratified by age, children 5 years or older (5-18 years) demonstrated a mean percentile increase of 10 percentile points (from 46.7th to 56.4th percentile) (p = 0.0001). Among the same age group, this effect scaled significantly with age (p = 0.02, beta coefficient -1.3). There was no significant difference in height-for-age after detethering surgery in children younger than 5 years. There was no significant association between the presence of clinical symptoms or specific radiographic findings and height outcomes after surgery. Overall, 56% of TC-related clinical symptoms improved after detethering (mean follow-up 4.6 months). Among children younger than 5 years, 82% of TC-related clinical symptoms improved after detethering (average follow-up 4.5 months); in children 5-18 years, 47% of symptoms improved after detethering (average follow-up 4.8 months). The authors observed a statistically significant gain in height-for-age percentiles in children undergoing surgical release of TC. The authors' data suggest that such gains may be more significant in older children (≥ 5 years) and the increase appears to scale positively with youth in the older cohort. In this study, postoperative height gains did not appear to correlate with the presence of TC-related clinical symptoms or radiographic findings. Further investigation is necessary to elucidate any potential correlation between release of TC and height changes in children postoperatively.

Neurocutaneous melanosis is associated with tethered spinal cord.

Neurocutaneous melanosis (NCM) is a rare congenital disorder occurring in children born with multiple or large congenital melanocytic nevi (CMN) in association with melanocytic deposits in the leptomeninges. Multiple associations between NCM and other syndromes or neurologic abnormalities have been reported. Of note, there exists a possible association between NCM and tethered cord (TC). We retrospectively reviewed charts and films of all patients with the diagnosis of NCM at the Children's Hospital of Pittsburgh (CHP) from August 2002 to present. Five children met the criteria for NCM at our institution over a 12-year period. Apart from the melanocytic deposits, one or more additional spinal abnormalities were identified in all children. Three children had radiographic evidence of a low-lying conus medullaris, two of which also demonstrated lipomatous infiltration of the filum terminale, consistent with a tethered cord (TC). Clinical features of NCM include dermatologic and neurologic manifestations. To date, this is the first series to note an association between NCM and TC. While nearly all recent series of NCM patients advocate early MRI of the neuroaxis, we recommend screening imaging of the spine on children with possible NCM regardless of the locations of CMN.

Congenital midline cervical cleft.

Congenital midline cervical cleft.

Familial Currarino syndrome associated with Hirschsprung disease: Two cases of a mother and daughter

Currarino syndrome with Hirschsprung disease (CS-HD) is extremely rare. We present the first family with CS-HD. Case 1: A 28-year-old woman was admitted with severe abdominal distension and dyspnea. She was diagnosed with anal stenosis, hemisacrum, anterior sacral meningocele (ASM), tethered cord (TC), and short-segment aganglionosis. She underwent the modified Duhamel operation after meningocele repair and cord detethering. A bicornuate uterus, bilateral ovarian dermoid cysts, and small rectal duplication were also noted intraoperatively. Case 2: The daughter of case 1 was admitted for abdominal distension and anal stenosis at the age of 17days. Studies revealed a hemisacrum, ASM, TC, presacral mass, atrial septal defect, polyp in the right nasal cavity, right vesicoureteral reflux, and short-segment aganglionosis. She underwent the modified Soave operation at the age of 1year and 4months after meningocele repair, cord detethering, and resection of the presacral mass (epidermoid cyst). In both cases, the aganglionic segments were confirmed by preoperative rectal suction biopsy and postoperative pathological examination on full-thickness rectal specimens. Some causal genes for Currarino syndrome (CS) and Hirschsprung disease (HD) are currently investigated. Thus far, 10 CS-HD cases have been reported, including 6 cases of familial CS. However, all the patients had sporadic HD. Recent reports suggest that anomalies of the enteric nerve system contribute to postoperative constipation in CS cases.

The value of postoperative MR in tethered cord: a review of 140 cases

This study aimed to determine the justification for routine postoperative MRI (POMR) following surgical release of tethered cord (TC) given that an MR, in this situation, mostly serves as a baseline and rarely has immediate clinical implications. Furthermore, later in the course of the disease, the presence of retethering is mostly assessed by clinical parameters, rather than imaging. A single-center retrospective review of patients who underwent tethered cord release surgery between the years 1997 and 2009 at the Department of Pediatric Neurosurgery, Tel Aviv Medical Center, Israel was performed. Collected data including basis for diagnosis, pathology, associated clinical and radiologic findings, surgical procedure and outcome, postoperative follow-up and morbidities, and postoperative MRI findings were recorded and analyzed. One hundred forty patients operated upon between 1997 and 2009 for tethered cord syndrome were reviewed. Routine postoperative MR was performed in all cases 6-18months after surgery. All cases were fully untethered. MR revealed relevant information in eight cases, two with residual dermoid, and six with significant terminal syrinx. None of these findings led to repeat surgery or special treatment. Retethering operations were performed in two cases in which retethering was diagnosed based on clinical evaluation. Based on analysis of our series of 140 consecutive patients who all underwent POMR 6-18months after TC release, we suggest that POMR as routine clinical practice is not justified for uncomplicated cases of TC release. In cases of high risk for retethering, or significant preoperative syrinx or dermoid, POMR is recommended to establish a baseline for future clinical follow-up.

The value of intraoperative neurophysiological monitoring in tethered cord surgery

PurposeThe value of intraoperative neurophysiological monitoring (IONM) with surgical detethering in dysraphic patients has been questioned. A retrospective analysis of our series of 65 patients is presented with special focus on technical set-up and outcome.MethodsAll patients were diagnosed with a tethered cord (TC) due to spinal dysraphism. A high-risk group (HRG) was determined consisting of 40 patients with a lipomyelomeningocele and/or a split cord malformation sometimes in combination with a tight filum terminale. The surgical procedure was a detethering operation in all cases performed by a single surgeon during a 9-year period (1999–2008). A standard set-up of IONM was used in all patients consisting of motor-evoked potentials (MEP) evoked by transcranial electrical stimulation (TES) and electrical nerve root stimulation. In young patients, conditioning stimulation was applied in order to improve absent or weak MEPs.ResultsIONM responses could be obtained in all patients. Postoperative deterioration of symptoms was found in two patients of whom one patient belonged to the HRG. Mean maximal follow-up of all 65 patients was 4.6 years (median 4.1 years). Long-term deterioration of symptoms was found in 6 of 65 patients with a mean follow-up of 5 years (median 5.3 years).ConclusionThe use of IONM is feasible in all TC patients. The identification of functional nervous structures and continuous guarding of the integrity of sacral motor roots by IONM may contribute to the safety of surgical detethering.

Congenital myelomeningocele - do we have to change our management?

BackgroundEagerly awaiting the results of the Management of Myelomeningocele Study (MOMS) and with an increasing interest in setting up intrauterine myelomeningocele repair (IUMR), the optimal management of patients suffering from congenital myelomeningocele (MMC) has become a matter of debate again. We performed a cross-sectional study at our referral-center for MMC to determine the outcome for our expectantly managed patients.Materials and methodsA computed chart review at our institution revealed 70 patients suffering from MMC. Forty-three patients were eligible for the study and analyzed further. A retrospective analysis was performed only in patients that underwent MMC repair within the first two days of life and were seen at our outpatient clinic between 2008 and 2009 for a regular multidisciplinary follow-up. Data were collected on: gestational age (GA) and weight at birth, age at shunt placement and shunt status after the first year of life, radiological evidence for Arnold-Chiari malformation (ACM) and tethered cord (TC), need for surgery for TC, bladder function, lower leg function and educational level. Data were compared to published results for IUMR and to studies of historical controls.ResultsPatients were born with MMC between 1979 and 2009 and are now 13.3 ± 8.9 (mean ± SD) years of age. At birth, mean GA was 37.8 ± 2.3 weeks and mean weight was 2921.3 ± 760.3 g, both significantly higher than in IUMR patients. Shunt placement in our cohort was required in 69.8% at a mean age of 16.0 ± 10.7 days, which was less frequent than for historical controls. Amongst our cohort, radiological observations showed 57.1% had ACM II and 41.9% had TC. Only two of our patients underwent a surgical correction for TC. Clean intermittent catheterization was performed in 69.7% of our patients, 56.4% were (assisted) walkers and 64.1% attended regular classes, both comparable to historical controls.ConclusionsWith a close and interdisciplinary management by pediatric surgeons, neurologists and urologists, the long-term outcome of patients suffering from MMC can currently be considered satisfactory. With respect to the known drawbacks of fetal interventions for mother and child, especially preterm delivery, the results of the MOMS trial should be awaited with caution before proceeding with a complex intervention like IUMR.

Tethered cord in patients with anorectal malformation: preliminary results

A tethered cord (TC) has been reported in as much as 50% of the patients affected by anorectal malformation (ARM). No guidelines for timing and modality of diagnosis and treatment have been established. We present the preliminary results of a multidisciplinary protocol carried out at our center. Seventy-four ARM patients underwent spinal magnetic resonance imaging (MRI). All TC patients underwent videourodynamic (UD), somatosensory-evoked potentials (SEPs), and neurological examination at baseline and, if normal, at 5 and 10 years of age. Conversely, when UD or SEP abnormalities were detected the follow-up was individually tailored at shorter time. 25/74 patients had a neuroradiological TC (33.7%). Based on the results of UD, SEP, and neurological status, four patients were untethered, eight are possible candidates, nine are stable, and four were excluded because of incomplete data. Tethered cord is frequent in ARM patients. Because neurological deficits secondary to TC can contribute to neurological disability, we recommend routine MRI examination and a multidisciplinary program of follow-up in cases of TC. Preliminary results suggest the combined use of SEPs and UD could represent a useful adjunct to clinical examination in patients in whom a "wait and see" approach is preferred to the prophylactic surgery.

CLINICAL FEATURES AND TREATMENT OUTCOMES OF ADULT TETHERED CORD SYNDROME

You have accessJournal of Urology1 Apr 2008CLINICAL FEATURES AND TREATMENT OUTCOMES OF ADULT TETHERED CORD SYNDROME Wesley M White, Regula Doggweiler, Todd Abel, and Frederick A Klein Wesley M WhiteWesley M White More articles by this author , Regula DoggweilerRegula Doggweiler More articles by this author , Todd AbelTodd Abel More articles by this author , and Frederick A KleinFrederick A Klein More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(08)61301-4AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "CLINICAL FEATURES AND TREATMENT OUTCOMES OF ADULT TETHERED CORD SYNDROME." The Journal of Urology, 179(4S), pp. 443–444 © 2008 by American Urological AssociationFiguresReferencesRelatedDetails Volume 179Issue 4SApril 2008Page: 443-444 Advertisement Copyright & Permissions© 2008 by American Urological AssociationMetricsAuthor Information Wesley M White More articles by this author Regula Doggweiler More articles by this author Todd Abel More articles by this author Frederick A Klein More articles by this author Expand All Advertisement PDF downloadLoading ...