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Biomedical subjects

Paul A Anderson

Publications and source records attributed to Paul A Anderson.

At least 19 recordsLinked to original sources
PubMed2006

Work status as a predictor of surgical outcome of discogenic low back pain.

STUDY DESIGN: Prospective observational study. OBJECTIVES: To evaluate the role of work status as a predictor of outcome from anterior lumbar fusion. SUMMARY OF BACKGROUND DATA: Many psychosocial factors have been identified as predictors of chronic disability and of outcomes of surgery. Workers' Compensation and job satisfaction are two of the strongest and most evaluated factors. Work status at the time of intervention may also be relevant but has rarely been studied independently in patients having lumbar fusion. METHODS: A total of 106 patients with discogenic low back pain were treated by anterior lumbar interbody fusion. Patients were prospectively monitored by VAS, Roland Morris score, and work status. The influence of preoperative work status on outcome variables was assessed using odds ratios. A multivariate analysis was performed to assess influence of other confounding variables. Follow-up was a mean 29.7 months with 95% greater than 1 year. RESULTS: Patients working at the time of surgery had a 10.5 times greater likelihood of working at follow-up. Overall, only 43% of nonworkers were working at follow-up compared with 90% of patients who were working before surgery. This association was independent of Workers' Compensation, number of levels treated, and other demographic variables. A greater degree of pain relief was seen in patients working before surgery but not in function as measured by the Roland Morris score. CONCLUSION: These results show that patients with chronic low back pain should be encouraged to continue working up until surgery.

Adult↗
PubMed2006

Biomechanical and clinical evaluation of a novel technique for surgical repair of spondylolysis in adolescents.

STUDY DESIGN: A biomechanical comparison of a novel spondylolysis repair technique method to established spondylolysis repair constructs accompanied by a case series of 5 adolescent patients with spondylolysis treated with this technique. OBJECTIVES: To provide retrospective data on these patients treated with an intralaminar link construct, as well as present comparative biomechanical data on this construct and that of an intact spine, lytic spine, and known methods of repair. SUMMARY OF BACKGROUND DATA: Spondylolysis is a unilateral or bilateral defect in the pars interarticularis, and most commonly occurs at L5 and less frequently at L4. Surgical treatment may be indicated in patients with persistent pain and impairment despite conservative treatment. Unlike posterolateral fusion, direct pars repairs may benefit adolescents by sparing motion segments. METHODS: Biomechanical testing of 5 cadaver lumbar spines was completed to provide comparative biomechanical data on this intralaminar link construct, and that of an intact spine, destabilized spondylolytic spine, Scott wiring technique, pedicle screw-cable system, and the pedicle screw-rod-hook constructs. There were 5 adolescent patients with spondylolysis treated with multiaxial pedicle screws, with a modular linkage that passes beneath the spinous process of the same segment. RESULTS: Biomechanical evaluation of the intralaminar link construct showed the least displacement (across pars defect) followed by the pedicle screw-rod-hook system, Scott wiring, and, finally, the pedicle screw-cable system. Interbody flexion and extension stiffness was highest for pedicle screw-rod-hook followed by normal, intralaminar link construct, Scott wiring, pedicle screw-cable system, and, finally, the destabilized spine. Interbody torsional stiffness was highest for pedicle screw-rod-hook followed by intralaminar link construct, normal, pedicle screw-cable system, Scott wiring, and lytic spine. Retrospective follow-up (average 4.6 years) of patients showed complete radiographic healing or pain relief in all 5 patients. There was 1 patient with solid healing of L3 spondylolysis who later had onset pain despite evidence of solid fusion on computerized tomographic images. In this patient, pain resolved after implant removal. CONCLUSIONS: Biomechanical evaluation of the intralaminar link construct showed excellent stability of a spondylolytic defect in comparison to established methods. Clinical follow-up of this method reflects the results of biomechanical testing with excellent clinical results.

Adolescent↗
PubMed2006

Assessment of injury to the posterior ligamentous complex in thoracolumbar spine trauma.

BACKGROUND CONTEXT: Posterior ligamentous complex (PLC), consisting of supraspinous ligament (SSL), interspinous ligament (ISL), ligamentum flavum (LF), and the facet joint capsules is thought to contribute significantly to the stability of thoracolumbar spine. Currently, no consensus exists on radiographic imaging parameters that may indicate injury to the posterior ligamentous complex. PURPOSE: To identify imaging parameters that may suggest a disruption of the PLC of the thoracolumbar spine. STUDY DESIGN/SETTING: A survey analysis of members of the Spine Trauma Study Group. PATIENT SAMPLE: None. OUTCOMES MEASURES: Compilation of survey results. METHODS: An extensive review of the literature from 1949 to the present was performed to identify key radiographic elements that have been suggested as indicators of PLC injury. Twelve items identified as such were placed on a survey and sent to the members of the Spine Trauma Study Group. They were asked to rank the items from most important to least important, and the results were compiled for analysis. RESULTS: Twenty-eight surveys were returned for final analysis. Fifty-percent (14/28) of the members ranked "vertebral body translation" on plain radiographs as the most important factor in determining disruption of PLC. Plain radiographic signs were ranked higher than computed tomography or magnetic resonance imaging indicators, and history of the mechanism ranked lowest. The members were also given freedom to add other criteria that they felt were important in determining PLC integrity. "Interspinous spacing 7 mm greater than that of level above or below on antero posterior plain X-rays" was the only new category that was suggested. CONCLUSION: Plain radiographic findings were felt to be most helpful in determining PLC injury by the members of the Spine Trauma Study Group. Physical examination findings and history of the mechanism of injury were ranked lower than imaging studies. Future analysis should focus on indicators of PLC injury when plain radiographic findings are either subtle or not present.

Consensus↗
PubMed2006

Classification of lower cervical spine injuries.

STUDY DESIGN: Blinded assessment by multiple observers of consecutive case series. OBJECTIVES: Measure the reliability of a new system of determining stability in subaxial cervical spine injuries. SUMMARY OF BACKGROUND DATA: Classification is fundamental to allow communication, determine prognosis, and direct treatment. Current systems have many limitations, including difficultly of use, lack of proven reliability and validity, and no assessment of stability. A new system to assess instability is proposed. METHODS: A literature review of the most commonly described classification systems is reported. The Cervical Spine Injury Severity Score was tested for reliability by 10 examiners who graded 35 consecutive cases of cervical trauma. Plain radiographs and CT were saved as read using Efilm Lite in random order. Each was scored and intraobserver and interobserver agreement was measured using intraclass correlation coefficients (ICC). RESULTS: Intraobserver agreement was excellent with ICC ranging from 0.97 to 0.99. Interobserver agreement was also excellent with mean 0.80 ranging from 0.75 to 0.98. CONCLUSION: A new cervical spine classification system of injury is paramount to treatment and outcomes. A new system may increase reliability and therefore allow more accurate determination of stability and dictate treatment.

Cervical Vertebrae↗
PubMed2006

Radiographic measurement techniques for sacral fractures consensus statement of the Spine Trauma Study Group.

STUDY DESIGN: Literature review. OBJECTIVES: Members of the Spine Trauma Study Group evaluated various imaging methods and compiled standardized approaches to making radiographic measurements for the assessment of sacral fractures. SUMMARY OF BACKGROUND DATA: The diagnosis of sacral fractures is frequently missed or delayed, and the treatment is controversial, with significant variations in recommendations regarding nonoperative treatment, neural decompression, and internal fixation. A paucity of specific radiographic measurements and criteria exist to aid the clinician in making sound treatment decisions. This may obligate surgeons to base clinical decisions on nonstandardized, nonvalidated recommendations and measures and, in some cases, anecdotal evidence. We think that a critical first step toward valid and optimal clinical decision-making requires an accurate and clear definition of imaging measurement parameters used to evaluate sacral injuries and gather data for future studies. METHODS: A review of the English-speaking literature was performed to assess cited radiographic measurement techniques of sacral fractures currently in use. This allowed the formulation of detailed radiographic assessments designed to more reliably describe sacral fracture morphometry. RESULTS: These measurements include: anterior-posterior sacral fracture displacement (axial computed tomography [CT] of the pelvis), vertical sacral fracture displacement (coronal CT reconstruction), anterior-posterior translation and kyphotic angulation (sagittal CT reconstructions), and degree of central canal involvement and foraminal encroachment (axial CT with fine cuts and coronal and sagittal reconstructions). Other radiographic factors that should be considered that may impact treatment outcomes include the level and type of sacral fracture, lumbosacral junction and sacroiliac joint involvement, and associated pelvic ring injury. CONCLUSIONS: With adoption of these radiographic guidelines, future studies will have a uniform method in which to describe sacral injuries and therefore allow study of the efficacy of various recommended treatment protocols.

Consensus↗
PubMed2006

Biomechanics of occipitocervical fixation.

STUDY DESIGN: A human cadaveric biomechanical study comparing occipital fixation techniques. OBJECTIVES: To compare ranges of motion between midline and lateral occipital fixation and between rigid and nonrigid occipital fixation of an unstable craniocervical spine. SUMMARY OF BACKGROUND DATA: New fixation techniques using rods and screws increase surgical choice on where fixation is placed onto the occiput. Lateral fixation theoretically gives improved resistance to deformation because of its increased effective moment arm and bilateral purchase. Midline fixation allows significantly longer screw purchase. This study compares these two fixation location. METHODS: Cadaveric occipital cervical spine specimens were tested biomechanically intact and under six different fixation techniques. Range of motion between the skull and C2 at 1.5 N-m and 2 N-m bending moments was measured in flexion-extension, lateral bending, and axial rotation. Mechanical testing of different rod diameters and a reconstruction plate was performed and compared with biomechanical testing. Results were compared between the intact condition and all fixations, between the medial and lateral fixations, and between the rigid and nonrigid fixations by analysis of variance. RESULTS: The range of motion of all constructs was significantly reduced compared with intact. Significant differences between groups were only seen in lateral bending in fixation placed laterally. Mechanical testing demonstrated that construct stiffness was predicted by area moment of inertia of the rod and plate to a greater degree than variation in placement of occipital screws or locking of the implant. CONCLUSION: The choice of location of occipital fixation should be based more on the ease of use and instability pattern. The decreased stiffness of the newer small rod systems should be considered.

Biomechanical Phenomena↗
PubMed2006

Synthesis and crystal structure of Li4BH4(NH2)3.

The solid solution, (LiNH2)x(LiBH4)(1-x), formed through the reaction of the two potential hydrogen storage materials, LiNH2 and LiBH4, is dominated by a compound that has an ideal stoichiometry of Li4BN3H10 and forms a body-centred cubic structure with a lattice constant of ca. 10.66 A.

Journal Article↗
PubMed2006

The diagnostic and predictive value of hip anesthetic arthrograms in selected patients before total hip arthroplasty.

Concurrent osteoarthritis of the hip and lumbar spine occurs frequently. Our study tests the hypothesis that hip anesthetic arthrograms can be used as predictive diagnostic tool before total hip arthroplasty when standard evaluation techniques fail to provide convincing evidence of the source of pain. Thirty-four consecutive hip anesthetic arthrograms were reviewed retrospectively. Quantified outcome measures included Visual Analog Pain Score, Harris Hip Score, and patient satisfaction. The pain relief after hip anesthetic arthrogram accurately predicted pain relief after hip arthroplasty (positive predictive value = 95.23%, negative predictive value = 87.5%). Our study supports the selected use of hip anesthetic arthrograms in the preoperative assessment of patients with concurrent hip and lumbar spine osteoarthritis associated with nondiagnostic history and physical examinations.

Aged↗
PubMed2006

Biomechanical comparison of four C1 to C2 rigid fixative techniques: anterior transarticular, posterior transarticular, C1 to C2 pedicle, and C1 to C2 intralaminar screws.

OBJECTIVE: We performed a biomechanical comparison of several C1 to C2 fixation techniques including crossed laminar (intralaminar) screw fixation, anterior C1 to C2 transarticular screw fixation, C1 to 2 pedicle screw fixation, and posterior C1 to C2 transarticular screw fixation. METHODS: Eight cadaveric cervical spines were tested intact and after dens fracture. Four different C1 to C2 screw fixation techniques were tested. Posterior transarticular and pedicle screw constructs were tested twice, once with supplemental sublaminar cables and once without cables. The specimens were tested in three modes of loading: flexion-extension, lateral bending, and axial rotation. All tests were performed in load and torque control. Pure bending moments of 2 nm were applied in flexion-extension and lateral bending, whereas a 1 nm moment was applied in axial rotation. Linear displacements were recorded from extensometers rigidly affixed to the C1 and C2 vertebrae. Linear displacements were reduced to angular displacements using trigonometry. RESULTS: Adding cable fixation results in a stiffer construct for posterior transarticular screws. The addition of cables did not affect the stiffness of C1 to C2 pedicle screw constructs. There were no significant differences in stiffness between anterior and posterior transarticular screw techniques, unless cable fixation was added to the posterior construct. All three posterior screw constructs with supplemental cable fixation provide equal stiffness with regard to flexion-extension and axial rotation. C1 lateral mass-C2 intralaminar screw fixation restored resistance to lateral bending but not to the same degree as the other screw fixation techniques. CONCLUSION: All four screw fixation techniques limit motion at the C1 to 2 articulation. The addition of cable fixation improves resistance to flexion and extension for posterior transarticular screw fixation.

Aged↗
PubMed2006

Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis.

OBJECT: Interspinous process decompression (IPD) theoretically relieves narrowing of the spinal canal and neural foramen in extension and thus reduces the symptoms of neurogenic intermittent claudication (NIC). The purpose of this study was to compare the efficacy of IPD with nonoperative treatment in patients with NIC secondary to degenerative spondylolisthesis. METHODS: The authors conducted a randomized controlled study in patients with NIC; they compared the results obtained in patients treated with the X STOP IPD device with those acquired in patients treated nonoperatively. The X STOP implant is a titanium alloy device that is placed between the spinous processes to reduce the canal and foraminal narrowing that occurs in extension. In a cohort of 75 patients with degenerative spondylolisthesis, 42 underwent surgical treatment in which the X STOP IPD device was placed and 33 control individuals were treated nonoperatively. Patients underwent serial follow-up evaluations. The Zurich Claudication Questionnaire (ZCQ), 36-Item Short Form Health Survey (SF-36), and radiographic assessment were used to determine outcomes. Two-year follow-up data were obtained in 70 of 75 patients. Statistically significant improvement in ZCQ and SF-36 scores was seen in X STOP device-treated patients but not in the nonoperative control patients at all postoperative intervals. Overall clinical success occurred in 63.4% of X STOP device-treated patients and only 12.9% of controls. Spondylolisthesis and kyphosis were unaltered. CONCLUSIONS: The X STOP device was more effective than nonoperative treatment in the management of NIC secondary to degenerative lumbar spondylolisthesis.

Aged↗
PubMed2005

Bone ingrowth in retrieved Bryan Cervical Disc prostheses.

STUDY DESIGN: Explant analysis for bone ingrowth of retrieved cervical disc prosthesis in chimpanzees and humans. OBJECTIVES: To assess the bone ingrowth into retrieved Bryan Cervical Discs. SUMMARY OF BACKGROUND DATA: Bone ingrowth in cervical disc prosthesis has not been documented in the literature. METHODS: Chimpanzee: Two chimpanzees underwent placement of the Bryan disc at C3-C4 and 3 months later had explantation and interbody fusion. Human: Two patients had removal of their Bryan disc and interbody fusion for failure to resolve symptoms at 8 and 10 months. The explants were analyzed for bone ingrowth. RESULTS: Chimpanzee: Histologic analysis showed bony ingrowth through the interstices of the porous coating and apposition ranging from 10% to 50% of toluidine blue-stained sections. New ingrowth, rather than bony impaction, was confirmed with fluorochrome-labeled sections Human: Bone ingrowth was a mean of 30.1% (12% SD). No difference was observed between peripheral, intermediate, or central locations. CONCLUSIONS: Adequate bony apposition was found in all primate device-to-vertebral body interfaces. Human retrievals also demonstrated significant ingrowth in all four surfaces. This compares with hip and knee arthroplasty percent ingrowth rates of 10% to 30%. All implants had stable fixation judged by radiographs and at the time of implant removal.

Animals↗
PubMed2005

A new classification of thoracolumbar injuries: the importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status.

STUDY DESIGN: A new proposed classification system for thoracolumbar (TL) spine injuries, including injury severity assessment, designed to assist in clinical management. OBJECTIVE: To devise a practical, yet comprehensive, classification system for TL injuries that assists in clinical decision-making in terms of the need for operative versus nonoperative care and surgical treatment approach in unstable injury patterns. SUMMARY OF BACKGROUND DATA: The most appropriate classification of traumatic TL spine injuries remains controversial. Systems currently in use can be cumbersome and difficult to apply. None of the published classification schemata is constructed to aid with decisions in clinical management. METHODS: Clinical spine trauma specialists from a variety of institutions around the world were canvassed with respect to information they deemed pivotal in the communication of TL spine trauma and the clinical decision-making process. Traditional injury patterns were reviewed and reconsidered in light of these essential characteristics. An initial validation process to determine the reliability and validity of an earlier version of this system was also undertaken. RESULTS: A new classification system called the Thoracolumbar Injury Classification and Severity Score (TLICS) was devised based on three injury characteristics: 1) morphology of injury determined by radiographic appearance, 2) integrity of the posterior ligamentous complex, and 3) neurologic status of the patient. A composite injury severity score was calculated from these characteristics stratifying patients into surgical and nonsurgical treatment groups. Finally, a methodology was developed to determine the optimum operative approach for surgical injury patterns. CONCLUSIONS: Although there will always be limitations to any cataloging system, the TLICS reflects accepted features cited in the literature important in predicting spinal stability, future deformity, and progressive neurologic compromise. This classification system is intended to be easy to apply and to facilitate clinical decision-making as a practical alternative to cumbersome classification systems already in use. The TLICS may improve communication between spine trauma physicians and the education of residents and fellows. Further studies are underway to determine the reliability and validity of this tool.

Humans↗
PubMed2005

A blinded assessment of radiographic criteria for atlanto-occipital dislocation.

STUDY DESIGN: Blinded comparison of 5 methods to diagnose atlanto-occipital dislocation (AOD) on plain radiographs and computerized tomography (CT) of the cervical spine. OBJECTIVE: To determine the best method to diagnose AOD. SUMMARY OF BACKGROUND DATA: Several methods are proposed for the diagnosis of AOD, including the Power's ratio, X-line method, basion-dens interval, condylar gap, and Harris method. No blinded comparison of the results of these methods has been compared to patient outcome, and there is no information available regarding the accuracy of these methods applied to CT scans. METHODS: Plain lateral radiographs and CTs of the cervical spine were reviewed in 104 patients, including 6 with AOD. Images underwent a blinded review by a board certified neurosurgeon (D.K.R.), orthopedist (P.A.A.), radiologist (J.C.), and emergency physician (D.B.B.). Each diagnostic method for AOD was applied for determination of sensitivity, specificity, and positive and negative predictive values. The ability to identify relevant anatomic landmarks was also tabulated. RESULTS: Average values for sensitivities, specificities, positive and negative predictive values for each method applied to plain radiographs are: 0.4625-1.0, 0.8933-0.9725, 0.2775-0.45, and 0.975-1.0, respectively. These values for each method applied to CT scans are: 0.7075-1.0, 0.8725-0.9775, 0.3175-1, and 0.98-1.0, respectively. Identification of relevant anatomic landmarks occurred 99.75% of the time when these methods were applied to CT scans compared to 39% to 84% of the time on plain radiographs. CONCLUSIONS: Sensitivity, specificity, positive and negative predictive values of these methods improve when applied to CT scans because of better visualization of anatomic landmarks. This result suggests CT scans of the cervical spine may be warranted in all trauma patients suspected of having cervical spine injury.

Atlanto-Occipital Joint↗
PubMed2005

Thoracolumbar injury classification and severity score: a new paradigm for the treatment of thoracolumbar spine trauma.

BACKGROUND: Contemporary understanding of the biomechanics, natural history, and methods of treating thoracolumbar spine injuries continues to evolve. Current classification schemes of these injuries, however, can be either too simplified or overly complex for clinical use. METHODS: The Spine Trauma Group was given a survey to identify similarities in treatment algorithms for common thoracolumbar injuries, as well as to identify characteristics of injury that played a key role in the decision-making process. RESULTS: Based on the survey, the Spine Trauma Group has developed a classification system and an injury severity score (thoracolumbar injury classification and severity score, or TLICS), which may facilitate communication between physicians and serve as a guideline for treating these injuries. The classification system is based on the morphology of the injury, integrity of the posterior ligamentous complex, and neurological status of the patient. Points are assigned for each category, and the final total points suggest a possible treatment option. CONCLUSIONS: The usefulness of this new system will have to be proven in future studies investigating inter- and intraobserver reliability, as well as long-term outcome studies for operative and nonoperative treatment methods.

Algorithms↗
PubMed2005

The ponticulus posticus: implications for screw insertion into the first cervical lateral mass.

BACKGROUND: The arcuate foramen is an important osseous anomaly of the first cervical vertebra (the atlas) that must be taken into consideration during placement of lateral mass screws into the atlas. METHODS: The prevalence of this anomaly in our patient population was determined through a retrospective review of 464 lateral radiographs of the neck. The anatomy of the arcuate foramen was identified in a study of cadavers. RESULTS: Seventy-two arcuate foramina, complete or incomplete, were identified on the 464 lateral radiographs of the neck; thus, the prevalence was 15.5% in our patient population. CONCLUSIONS: Although the arcuate foramen is a common anomaly, it is often not recognized. Proper identification of this anomaly on preoperative lateral radiographs should alert the surgeon to avoid using the ponticulus posticus as a starting point for a lateral mass screw in order to not injure the vertebral artery.

Bone Screws↗