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Dive into the research topics where William O. Shaffer is active.

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Featured researches published by William O. Shaffer.


Spine | 2009

Interventional therapies, surgery, and interdisciplinary rehabilitation for low back pain: an evidence-based clinical practice guideline from the American Pain Society.

Roger Chou; John D. Loeser; Douglas K Owens; Richard W. Rosenquist; Steven J. Atlas; Jamie L. Baisden; Eugene J. Carragee; Martin Grabois; Donald R. Murphy; Daniel K. Resnick; Steven P. Stanos; William O. Shaffer; Eric M. Wall

Study Design. Clinical practice guideline. Objective. To develop evidence-based recommendations on use of interventional diagnostic tests and therapies, surgeries, and interdisciplinary rehabilitation for low back pain of any duration, with or without leg pain. Summary of Background Data. Management of patients with persistent and disabling low back pain remains a clinical challenge. A number of interventional diagnostic tests and therapies and surgery are available and their use is increasing, but in some cases their utility remains uncertain or controversial. Interdisciplinary rehabilitation has also been proposed as a potentially effective noninvasive intervention for persistent and disabling low back pain. Methods. A multidisciplinary panel was convened by the American Pain Society. Its recommendations were based on a systematic review that focused on evidence from randomized controlled trials. Recommendations were graded using methods adapted from the US Preventive Services Task Force and the Grading of Recommendations, Assessment, Development, and Evaluation Working Group. Results. Investigators reviewed 3348 abstracts. A total of 161 randomized trials were deemed relevant to the recommendations in this guideline. The panel developed a total of 8 recommendations. Conclusion. Recommendations on use of interventional diagnostic tests and therapies, surgery, and interdisciplinary rehabilitation are presented. Due to important trade-offs between potential benefits, harms, costs, and burdens of alternative therapies, shared decision-making is an important component of a number of the recommendations.


Spine | 2009

Surgery for low back pain: A review of the evidence for an American pain society clinical practice guideline

Roger Chou; Jamie L. Baisden; Eugene J. Carragee; Daniel K. Resnick; William O. Shaffer; John D. Loeser

Study Design. Systematic review. Objective. To systematically assess benefits and harms of surgery for nonradicular back pain with common degenerative changes, radiculopathy with herniated lumbar disc, and symptomatic spinal stenosis. Summary of Background Data. Although back surgery rates continue to increase, there is uncertainty or controversy about utility of back surgery for various conditions. Methods. Electronic database searches on Ovid MEDLINE and the Cochrane databases were conducted through July 2008 to identify randomized controlled trials and systematic reviews of the above therapies. All relevant studies were methodologically assessed by 2 independent reviewers using criteria developed by the Cochrane Back Review Group (for trials) and Oxman (for systematic reviews). A qualitative synthesis of results was performed using methods adapted from the US Preventive Services Task Force. Results. For nonradicular low back pain with common degenerative changes, we found fair evidence that fusion is no better than intensive rehabilitation with a cognitive-behavioral emphasis for improvement in pain or function, but slightly to moderately superior to standard (nonintensive) nonsurgical therapy. Less than half of patients experience optimal outcomes (defined as no more than sporadic pain, slight restriction of function, and occasional analgesics) following fusion. Clinical benefits of instrumented versus noninstrumented fusion are unclear. For radiculopathy with herniated lumbar disc, we found good evidence that standard open discectomy and microdiscectomy are moderately superior to nonsurgical therapy for improvement in pain and function through 2 to 3 months. For symptomatic spinal stenosis with or without degenerative spondylolisthesis, we found good evidence that decompressive surgery is moderately superior to nonsurgical therapy through 1 to 2 years. For both conditions, patients on average experience improvement either with or without surgery, and benefits associated with surgery decrease with long-term follow-up in some trials. Although there is fair evidence that artificial disc replacement is similarly effective compared to fusion for single level degenerative disc disease and that an interspinous spacer device is superior to nonsurgical therapy for 1- or 2-level spinal stenosis with symptoms relieved with forward flexion, insufficient evidence exists to judge long-term benefits or harms. Conclusion. Surgery for radiculopathy with herniated lumbar disc and symptomatic spinal stenosis is associated with short-term benefits compared to nonsurgical therapy, though benefits diminish with long-term follow-up in some trials. For nonradicular back pain with common degenerative changes, fusion is no more effective than intensive rehabilitation, but associated with small to moderate benefits compared to standard nonsurgical therapy.


Spine | 2005

Variation in Surgical Decision Making For Degenerative Spinal Disorders. Part Ii: Cervical Spine

Zareth N. Irwin; Alan S. Hilibrand; Michael Gustavel; Robert F. McLain; William O. Shaffer; Mark A. Myers; John Glaser; Robert A. Hart

Study Design. Survey-based descriptive study. Objective. To study relationships between surgeon-specific factors and surgical approach to degenerative diseases of the cervical spine. Summary of Background Data. Geographic variations in the rates of cervical spine surgery are significant within the United States. Although surgeon density correlates with the rates of spinal surgery, other reasons for variation such as surgeon-specific factors are poorly understood. Methods. A total of 22 orthopedic surgeons and 8 neurosurgeons of varied ages and geographic regions answered questions regarding the need for surgery, surgical approach, and use of fusion and instrumentation for 5 simulated cases. Cases included: (1) single-level disc herniation with osteophyte and radiculopathy, (2) single-level pseudarthrosis with axial neck pain, (3) multilevel stenosis with radiculopathy and neutral lordosis, (4) multilevel stenosis with myelopathy and neutral lordosis, and (5) multilevel stenosis with myelopathy and marked kyphosis. The effects of surgeon age and training background on surgical decision making were analyzed using an independent samples t test and Fisher exact test, respectively. Results. The greatest agreement occurred for the single-level disc herniation, with all surgeons choosing an anterior discectomy, and 28 of the 29 respondents recommending fusion. Younger surgeons recommended instrumentation more often for all cases, reaching significance for the case of multilevel stenosis with myelopathy and neutral lordosis (Fisher exact test P = 0.02). Differences in recommendation for fusion, instrumentation, and the use of a posterior approach between orthopedic and neurosurgeons were limited. Conclusions. Variations in surgical procedures for cervical degenerative disease may depend on the clinical condition. Although this study found strong agreement in treatment approach to single-level disc herniation, significant variation was seen for the other degenerative conditions of the cervical spine. While differences in recommendation for fusion were not clearly associated with surgeon age, there was a trend toward the higher use of instrumentation by younger surgeons. Previously documented geographic variation may result in part from a lack of consensus regarding appropriate treatment techniques for certain degenerative conditions of the cervical spine, as well as surgeon-specific factors.


The Spine Journal | 2013

An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis (update)

D. Scott Kreiner; William O. Shaffer; Jamie L. Baisden; Thomas R. Gilbert; Jeffrey T. Summers; John F. Toton; Steven W. Hwang; Richard C. Mendel; Charles A. Reitman

BACKGROUND CONTEXT The evidence-based clinical guideline on the diagnosis and treatment of degenerative lumbar spinal stenosis by the North American Spine Society (NASS) provides evidence-based recommendations to address key clinical questions surrounding the diagnosis and treatment of degenerative lumbar spinal stenosis. The guideline is intended to reflect contemporary treatment concepts for symptomatic degenerative lumbar spinal stenosis as reflected in the highest quality clinical literature available on this subject as of July 2010. The goals of the guideline recommendations are to assist in delivering optimum efficacious treatment and functional recovery from this spinal disorder. PURPOSE Provide an evidence-based educational tool to assist spine care providers in improving quality and efficiency of care delivered to patients with degenerative lumbar spinal stenosis. STUDY DESIGN Systematic review and evidence-based clinical guideline. METHODS This report is from the Degenerative Lumbar Spinal Stenosis Work Group of the NASSs Evidence-Based Clinical Guideline Development Committee. The work group consisted of multidisciplinary spine care specialists trained in the principles of evidence-based analysis. The original guideline, published in 2006, was carefully reviewed. A literature search addressing each question and using a specific search protocol was performed on English language references found in MEDLINE, EMBASE (Drugs and Pharmacology), and four additional, evidence-based, databases to identify articles published since the search performed for the original guideline. The relevant literature was then independently rated by a minimum of three physician reviewers using the NASS-adopted standardized levels of evidence. An evidentiary table was created for each of the questions. Final recommendations to answer each clinical question were arrived at via work group discussion, and grades were assigned to the recommendations using standardized grades of recommendation. In the absence of Levels I to IV evidence, work group consensus statements have been developed using a modified nominal group technique, and these statements are clearly identified as such in the guideline. RESULTS Sixteen key clinical questions were assessed, addressing issues of natural history, diagnosis, and treatment of degenerative lumbar spinal stenosis. The answers are summarized in this document. The respective recommendations were graded by the strength of the supporting literature that was stratified by levels of evidence. CONCLUSIONS A clinical guideline for degenerative lumbar spinal stenosis has been updated using the techniques of evidence-based medicine and using the best available clinical evidence to aid both practitioners and patients involved with the care of this condition. The entire guideline document, including the evidentiary tables, suggestions for future research, and all references, will be available electronically at the NASS Web site (www.spine.org) and will remain updated on a timely schedule.


The Spine Journal | 2011

An evidence-based clinical guideline for the diagnosis and treatment of cervical radiculopathy from degenerative disorders

Christopher M. Bono; Gary Ghiselli; Thomas J. Gilbert; D. Scott Kreiner; Charles A. Reitman; Jeffrey T. Summers; Jamie L. Baisden; John E. Easa; Robert Fernand; Tim J. Lamer; Paul G. Matz; Daniel J. Mazanec; Daniel K. Resnick; William O. Shaffer; Anil K. Sharma; Reuben B. Timmons; John F. Toton

Abstract Background context The North American Spine Society (NASS) Evidence-Based Clinical Guideline on the Diagnosis and Treatment of Cervical Radiculopathy from Degenerative Disorders provides evidence-based recommendations on key clinical questions concerning the diagnosis and treatment of cervical radiculopathy from degenerative disorders. The guideline addresses these questions based on the highest quality clinical literature available on this subject as of May 2009. The guideline’s recommendations assist the practitioner in delivering optimum efficacious treatment of and functional recovery from this common disorder. Purpose Provide an evidence-based educational tool to assist spine care providers in improving quality and efficiency of care delivered to patients with cervical radiculopathy from degenerative disorders. Study design Systematic review and evidence-based clinical guideline. Methods This report is from the Cervical Radiculopathy from Degenerative Disorders Work Group of the NASS’ Evidence-Based Clinical Guideline Development Committee. The work group consisted of multidisciplinary spine care specialists trained in the principles of evidence-based analysis. Each member of the group formatted a series of clinical questions to be addressed by the group. The final questions agreed on by the group are the subjects of this report. A literature search addressing each question using a specific search protocol was performed on English language references found in MEDLINE, EMBASE (Drugs and Pharmacology), and four additional evidence-based databases. The relevant literature was then independently rated by a minimum of three reviewers using the NASS-adopted standardized levels of evidence. An evidentiary table was created for each of the questions. Final recommendations to answer each clinical question were arrived at via work group discussion, and grades were assigned to the recommendations using standardized grades of recommendation. In the absence of Levels I to IV evidence, work group consensus statements have been developed using a modified nominal group technique, and these statements are clearly identified as such in the guideline. Results Eighteen clinical questions were formulated, addressing issues of natural history, diagnosis, and treatment of cervical radiculopathy from degenerative disorders. The answers are summarized in this article. The respective recommendations were graded by the strength of the supporting literature, which was stratified by levels of evidence. Conclusions A clinical guideline for cervical radiculopathy from degenerative disorders has been created using the techniques of evidence-based medicine and best available evidence to aid both practitioners and patients involved with the care of this condition. The entire guideline document, including the evidentiary tables, suggestions for future research, and all references, is available electronically at the NASS Web site ( www.spine.org ) and will remain updated on a timely schedule.


The Spine Journal | 2009

An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spondylolisthesis†

William C. Watters; Christopher M. Bono; Thomas J. Gilbert; D. Scott Kreiner; Daniel J. Mazanec; William O. Shaffer; Jamie L. Baisden; John E. Easa; Robert Fernand; Gary Ghiselli; Michael H. Heggeness; Richard C. Mendel; Conor O'Neill; Charles A. Reitman; Daniel K. Resnick; Jeffrey T. Summers; Reuben B. Timmons; John F. Toton

BACKGROUND CONTEXT The objective of the North American Spine Society (NASS) evidence-based clinical guideline on the diagnosis and treatment of degenerative lumbar spondylolisthesis is to provide evidence-based recommendations on key clinical questions concerning the diagnosis and treatment of degenerative lumbar spondylolisthesis. The guideline is intended to address these questions based on the highest quality clinical literature available on this subject as of January 2007. The goal of the guideline recommendations is to assist the practitioner in delivering optimum, efficacious treatment of and functional recovery from this common disorder. PURPOSE To provide an evidence-based, educational tool to assist spine care providers in improving the quality and efficiency of care delivered to patients with degenerative lumbar spondylolisthesis. STUDY DESIGN Systematic review and evidence-based clinical guideline. METHODS This report is from the Degenerative Lumbar Spondylolisthesis Work Group of the NASS Evidence-Based Clinical Guideline Development Committee. The work group was comprised of multidisciplinary spine care specialists, all of whom were trained in the principles of evidence-based analysis. Each member participated in the development of a series of clinical questions to be addressed by the group. The final questions agreed on by the group are the subject of this report. A literature search addressing each question and using a specific search protocol was performed on English language references found in MEDLINE, EMBASE (Drugs and Pharmacology) and four additional, evidence-based, databases. The relevant literature was then independently rated by at least three reviewers using the NASS-adopted standardized levels of evidence. An evidentiary table was created for each of the questions. Final grades of recommendation for the answer to each clinical question were arrived at via face-to-face meetings among members of the work group using standardized grades of recommendation. When Level I-IV evidence was insufficient to support a recommendation to answer a specific clinical question, expert consensus was arrived at by the work group through the modified nominal group technique and is clearly identified as such in the guideline. RESULTS Nineteen clinical questions were formulated, addressing issues of prognosis, diagnosis, and treatment of degenerative lumbar spondylolisthesis. The answers to these 19 clinical questions are summarized in this document. The respective recommendations were graded by the strength of the supporting literature that was stratified by levels of evidence. CONCLUSIONS A clinical guideline for degenerative lumbar spondylolisthesis has been created using the techniques of evidence-based medicine and using the best available evidence as a tool to aid practitioners involved with the care of this condition. The entire guideline document, including the evidentiary tables, suggestions for future research, and all references, is available electronically at the NASS Web site (www.spine.org) and will remain updated on a timely schedule.


The Spine Journal | 2009

Antibiotic prophylaxis in spine surgery: an evidence-based clinical guideline for the use of prophylactic antibiotics in spine surgery

William C. Watters; Jamie L. Baisden; Christopher M. Bono; Michael H. Heggeness; Daniel K. Resnick; William O. Shaffer; John F. Toton

BACKGROUND CONTEXT The objective of the North American Spine Societys (NASS) Evidence-Based Clinical Guideline on Antibiotic Prophylaxis in Spine Surgery is to provide evidence-based recommendations on key clinical questions concerning the use of prophylactic antibiotics in spine surgery. The guideline is intended to address these questions based on the highest quality clinical literature available on this subject as of December 2006. The goal of the guideline recommendations is to assist in delivering optimum, efficacious treatment to prevent surgical site infection. PURPOSE To provide an evidence-based, educational tool to assist spine surgeons in preventing surgical site infections. STUDY DESIGN Evidence-based Clinical Guideline. METHODS This report is from the Antibiotic Prophylaxis Work Group of the NASSs Evidence-Based Clinical Guideline Development Committee. The work group comprised multidisciplinary surgical spine care specialists, who were trained in the principles of evidence-based analysis. Each member of the group formatted a series of clinical questions to be addressed by the group. The final questions agreed upon by the group are the subjects of this report. A literature search addressing each question and using a specific search protocol was performed on English language references found in MEDLINE, EMBASE (Drugs and Pharmacology), and four additional, evidence-based, databases. The relevant literature was then independently rated by at least three reviewers using the NASS-adopted standardized levels of evidence. An evidentiary table was created for each of the questions. Final grades of recommendation for the answer to each clinical question were arrived at via Webcast meetings among members of the work group using standardized grades of recommendation. When Level I to Level IV evidence was insufficient to support a recommendation to answer a specific clinical question, expert consensus was arrived at by the work group through the modified nominal group technique and is clearly identified in the guideline. RESULTS Eleven clinical questions addressed the efficacy and appropriateness of antibiotic prophylaxis protocols, repeat dosing, discontinuation, wound drains, and special considerations related to the potential impact of comorbidities on antibiotic prophylaxis. The responses to these 11 clinical questions are summarized in this document. The respective recommendations were graded by the strength of the supported literature which was stratified by levels of evidence. CONCLUSIONS A clinical guideline addressing the use of antibiotic prophylaxis in spine surgery has been created using the techniques of evidence-based medicine and the best available evidence. This educational tool will assist spine surgeons in preventing surgical site infections. The entire guideline document, including the evidentiary tables, suggestions for future research, and references, is available electronically at the NASS Web site (www.spine.org) and will remain updated on a timely schedule.


The Spine Journal | 2009

An evidence-based clinical guideline for the use of antithrombotic therapies in spine surgery

Christopher M. Bono; William C. Watters; Michael H. Heggeness; Daniel K. Resnick; William O. Shaffer; Jamie L. Baisden; Peleg Ben-Galim; John E. Easa; Robert Fernand; Tim J. Lamer; Paul G. Matz; Richard C. Mendel; Rajeev K. Patel; Charles A. Reitman; John F. Toton

BACKGROUND CONTEXT The objective of the North American Spine Society (NASS) Evidence-Based Clinical Guideline on antithrombotic therapies in spine surgery was to provide evidence-based recommendations to address key clinical questions surrounding the use of antithrombotic therapies in spine surgery. The guideline is intended to address these questions based on the highest quality clinical literature available on this subject as of February 2008. The goal of the guideline recommendations was to assist in delivering optimum, efficacious treatment with the goal of preventing thromboembolic events. PURPOSE To provide an evidence-based, educational tool to assist spine surgeons in minimizing the risk of deep venous thrombosis (DVT) and pulmonary embolism (PE). STUDY DESIGN Systematic review and evidence-based clinical guideline. METHODS This report is from the Antithrombotic Therapies Work Group of the NASS Evidence-Based Guideline Development Committee. The work group was composed of multidisciplinary spine care specialists, all of whom were trained in the principles of evidence-based analysis. Each member of the group was involved in formatting a series of clinical questions to be addressed by the group. The final questions agreed on by the group are the subject of this report. A literature search addressing each question and using a specific search protocol was performed on English language references found in MEDLINE, EMBASE (Drugs and Pharmacology), and four additional, evidence-based databases. The relevant literature was then independently rated by at least three reviewers using the NASS-adopted standardized levels of evidence. An evidentiary table was created for each of the questions. Final grades of recommendation for the answers to each clinical question were arrived at via Web casts among members of the work group using standardized grades of recommendation. When Level I to IV evidence was insufficient to support a recommendation to answer a specific clinical question, expert consensus was arrived at by the work group through the modified nominal group technique and is clearly identified as such in the guideline. RESULTS Fourteen clinical questions were formulated, addressing issues of incidence of DVT and PE in spine surgery and recommendations regarding utilization of mechanical prophylaxis and chemoprophylaxis in spine surgery. The answers to these 14 clinical questions are summarized in this article. The respective recommendations were graded by the strength of the supporting literature that was stratified by levels of evidence. CONCLUSIONS A clinical guideline addressing the use of antithrombotic therapies in spine surgery has been created using the techniques of evidence-based medicine and using the best available evidence as a tool to assist spine surgeons in minimizing the risk of DVT and PE. The entire guideline document, including the evidentiary tables, suggestions for future research, and all references, is available electronically at the NASS Web site (www.spine.org) and will remain updated on a timely schedule.


Spine | 1990

The consistency and accuracy of roentgenograms for measuring sagittal translation in the lumbar vertebral motion segment : an experimental model

William O. Shaffer; Kevin F. Spratt; James N. Weinstein; Thomas R. Lehmann; Vijay K. Goel

An experimental model of the L4-L5 lumbar motion segment was developed that allowed precise manipulation of sagittal translation, rotation of L5 relative to L4, tilt of L4 on L5, and control of roentgenogram quality (image clarity) by placing a water bath between the tube and the vertebral body. A series of experiments were designed to systematically assess the consistency and accuracy of sagittal translation measurements from roentgenograms of varying quality, using different measurement protocols and various rater combinations on models with varying degrees of concomitant motions (rotations and tilts). Study 1 assessed the effects of roentgenogram quality, raters, and seven measurement methods on the consistency and accuracy of evaluating translations in the sagittal plane. Results indicated very high reliabilities across roentgenogram quality, raters, and measurement. As expected, high-quality roentgenograms were more accurately evaluated than lower-quality roentgenograms. However, closer inspection of the consequences of errors in measured translations indicated surprisingly high false-positive and false-negative rates, with significant differences observed between measurement methods. Study 2 assessed the effects of concomitant motions and measurement methods on the consistency and accuracy of evaluations. Within-rater consistency and accuracy indices were remarkably high and similar across measurement methods and degrees of concomitant motions. However, important differences in the false-positive and false-negative rates were again observed. Method 2, described by Morgan and King, demonstrated the overall best performance and the least interference due to concomitant motions. Study 3 assessed the effects of raters and measurement methods on the consistency of measuring translation in clinical roentgenograms, where concomitant motion factors may be present, but not explicitly considered. Results indicated substantially lower within- and between-rater consistency estimates relative to consistencies obtained from the model, although these magnitudes were similar to those reported by others evaluating clinical roentgenograms. The implications of lower consistency estimates relative to increased false- positive and false-negative rates must be more closely examined. These studies present evidence suggesting that high consistency and accuracy indices do not ensure acceptable false-positive and false-negative rates and, thus, provide empirical evidence supporting the view that using roentgenograms as a basis for diagnosing instability often can lead to errors in classification. This is less so when observed translations are relatively large (± 5 + mm) on roentgenograms that are relatively clear, with little obliquity, and when concomitant motions are minimal. However, when roentgenogram quality is lower, obliquity problems are apparent, and concomitant motions are involved, even relatively large measured translations of ±6 mm or more may occur when actual translations are substantially less. In these settings, using roentgenograms to classify patients as haying excessive translation may result in large false-positive rates.


Spine | 1990

1990 Volvo Award in Clinical Sciences: The Consistency and Accuracy of Roentgenograms for Measuring Sagittal Translation in the Lumbar Vertebral Motion Segment

William O. Shaffer; Kevin F. Spratt; James N. Weinstein; Thomas R. Lehmann; Vijay K. Goel

An experimental model of the L4–L5 lumbar motion segment was developed that allowed precise manipulation of sagittal translation, rotation of L5 relative to L4, tilt of L4 on L5, and control of roentgenogram quality (image clarity) by placing a water bath between the tube and the vertebral body. A series of experiments were designed to systematically assess the consistency and accuracy of sagittal translation measurements from roentgenograms of varying quality, using different measurement protocols and various rater combinations on models with varying degrees of concomitant motions (rotations and tilts). Study 1 assessed the effects of roentgenogram quality, raters, and seven measurement methods on the consistency and accuracy of evaluating translations in the sagittal plane. Results indicated very high reliabilities across roentgenogram quality, raters, and measurement. As expected, high-quality roentgenograms were more accurately evaluated than lower-quality roentgenograms. However, closer inspection of the consequences of errors in measured translations indicated surprisingly high false-positive and false-negative rates, with significant differences observed between measurement methods. Study 2 assessed the effects of concomitant motions and measurement methods on the consistency and accuracy of evaluations. Within-rater consistency and accuracy indices were remarkably high and similar across measurement methods and degrees of concomitant motions. However, important differences in the false-positive and false-negative rates were again observed. Method 2, described by Morgan and King, demonstrated the overall best performance and the least interference due to concomitant motions. Study 3 assessed the effects of raters and measurement methods on the consistency of measuring translation in clinical roentgenograms, where concomitant motion factors may be present, but not explicitly considered. Results indicated substantially lower within-and between-rater consistency estimates relative to consistencies obtained from the model, although these magnitudes were similar to those reported by others evaluating clinical roentgenograms. The implications of lower consistency estimates relative to increased false-positive and false-negative rates must be more closely examined. These studies present evidence suggesting that high consistency and accuracy indices do not ensure acceptable false-positive and false-negative rates and, thus, provide empirical evidence supporting the view that using roentgenograms as a basis for diagnosing instability often can lead to errors in classification. This is less so when observed translations are relatively large ( ± 5+ mm) on roentgenograms that are relatively clear, with little obliquity, and when concomitant motions are minimal. However, when roentgenogram quality is lower, obliquity problems are apparent, and concomitant motions are involved, even relatively large measured translations of ±6 mm or more may occur when actual translations are substantially less. In these settings, using roentgenograms to classify patients as having excessive translation may result in large false-positive rates.

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Jamie L. Baisden

Medical College of Wisconsin

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Daniel K. Resnick

University of Wisconsin-Madison

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Christopher M. Bono

Brigham and Women's Hospital

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Gary Ghiselli

University of California

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John E. Easa

Michigan State University

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