1753 ORIGINAL ARTICLE Preliminary Development of a Clinical Prediction Rule for Determining Which Patients With Low Back Pain Will Respond to a Stabilization Exercise Program Gregory E. Hicks, PhD, PT, Julie M. Fritz, PhD, PT, ATC, Anthony Delitto, PhD, PT, Stuart M. McGill, PhD ABSTRACT. Hicks GE, Fritz JM, Delitto A, McGill SM. PATHOLOGY-BASED DIAGNOSTIC approach to low Preliminary development of a clinical prediction rule for de- Aback pain (LBP) sets forth the idea that LBP is defined by termining which patients with low back pain will respond to a a deviation of the lumbopelvic complex from its normative stabilization exercise program. Arch Phys Med Rehabil 2005; physiologic and anatomic state.1 On application of the pathol- 86:1753-62. ogy-based model to LBP, one must first identify a structural fault and then treatment can be directed at correction of the Objective: To develop a clinical prediction rule to predict fault. As a result of this treatment and subsequent correction, treatment response to a stabilization exercise program for pa- the signs and symptoms should dissipate.2 A pathology-based tients with low back pain (LBP). approach to diagnosis for LBP has proven difficult because of Design: A prospective, cohort study of patients with nonra- the inability to identify a structural pathology in the vast dicular LBP referred to physical therapy (PT). majority of patients with LBP.3 Setting: Outpatient PT clinics. Despite the difficulties in identifying structural pathology for Participants: Fifty-four patients with nonradicular LBP. most patients, many authors continue to suggest that patients Intervention: A standardized stabilization exercise program. with LBP are not a homogenous group, but rather should be Main Outcome Measure: Treatment response (success or classified into subgroups that share similar clinical character- failure) was categorized based on changes in the Oswestry istics (eg, age, symptom duration, distribution).4-6 This type of Disability Questionnaire scores after 8 weeks. classification system could guide diagnosis and treatment and Results: Eighteen subjects were categorized as treatment improve overall decision making in the management of LBP successes, 15 as treatment failures, and 21 as somewhat im- patients.7 It may also improve research by denoting homoge- proved. After using regression analyses to determine the asso- nous subgroups for treatment outcome studies.8 ciation between standardized examination variables and treat- Patients with lumbar segmental instability (LSI) have been ment response status, preliminary clinical prediction rules were proposed as a unique subgroup of patients with LBP.7,9-11 LSI developed for predicting success (positive likelihood ratio has been defined as a condition in which there is a loss of [LR], 4.0) and failure (negative LR, .18). The most important stiffness between spinal motion segments, such that normally variables were age, straight-leg raise, prone instability test, tolerated external loads result in pain or deformity or place aberrant motions, lumbar hypermobility, and fear-avoidance neurologic structures at risk.10 The diagnosis of LSI has tradi- beliefs. tionally relied on the use of lateral flexion and extension Conclusions: It appears that the response to a stabilization radiographs.12-14 Thresholds for defining LSI have been devel- exercise program in patients with LBP can be predicted from oped from studies that have examined the magnitude of rota- variables collected from the clinical examination. The predic- tional and translational movement normally available at each tion rules could be used to determine whether patients with spinal motion segment during flexion and extension of the LBP are likely to benefit from stabilization exercises. lumbar spine.14,15 However, the use of these criteria for defin- Key Words: Classification; Exercise; Low back pain; Re- ing LSI has proven unsatisfactory because of high false-posi- habilitation. tive rates.16,17 For example, Hayes et al17 found that 42% of © 2005 by the American Congress of Rehabilitation Medi- asymptomatic subjects had at least 1 segment exceeding the cine and the American Academy of Physical Medicine and instability thresholds. The inadequacies associated with the use Rehabilitation of imaging to diagnosis LSI have led to a greater emphasis on clinical characteristics that may be indicative of the condition. Historical variables, presence of an “instability catch,” or ex- cessive intervertebral mobility have been suggested as diag- From the Departments of Physical Therapy and Rehabilitation Science and Epide- 18-20 miology and Preventive Medicine, University of Maryland School of Medicine, nostic ; however, the validity of these findings is mostly Baltimore, MD (Hicks); Division of Physical Therapy, University of Utah, Salt Lake unknown. Because of the current lack of a true reference City, UT (Fritz); Department of Physical Therapy, University of Pittsburgh, Pitts- standard for confirmation of LSI, it is not possible to accurately burgh, PA (Delitto); and Department of Kinesiology, University of Waterloo, Wa- diagnose LSI clinically; therefore, another approach should be terloo, ON, Canada (McGill). Supported by the Foundation for Physical Therapy Clinical Research Center. considered. The opinions and assertions contained herein are the private views of the author and If LSI could be accurately diagnosed, the conservative treat- are not to be construed as official or as reflecting the views of the U.S. Department ment of choice would be a lumbar stabilization program to of the Army or the Department of Defense. address the tissue damage and resultant loss of spinal stiffness No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any caused by mechanical overload to the spinal stabilizing system. organization with which the author(s) is/are associated. The goals of stabilization exercise are to train muscular motor Correspondence to Gregory E. Hicks, PhD, PT, Dept of Physical Therapy and patterns to increase spinal stability, restrain aberrant micromo- Rehabilitation Science, University of Maryland School of Medicine, 100 Penn St, tion, and reduce associated pain. Although several studies that Baltimore, MD 21201, e-mail: [email protected]. Reprints are not avail- observed muscle onset and electromyographic patterns have able from the author. 21 0003-9993/05/8609-9715$30.00/0 suggested that certain muscles are important stabilizers, mea- doi:10.1016/j.apmr.2005.03.033 surement of stability was not performed. In contrast, those Arch Phys Med Rehabil Vol 86, September 2005 1754 SUCCESS WITH STABILIZATION, Hicks studies that have quantified stability22,23 unanimously agree All subjects underwent a standardized history and physical that all muscles play a role in ensuring spine stability and that examination. History taking included questions proposed to the motor patterns of cocontraction between the full comple- indicate the presence of LSI,7,18,19 including mode of onset, ment of muscles are of utmost importance to ensure stability duration of symptoms, number of previous episodes of LBP, and minimize pain. Although the exercises used in this study and response to various interventions for previous episodes. are often described in the literature as targeting a specific Subjects were also asked about the distribution of symptoms muscle group, electromyography studies show that the exer- for the current episode and were asked to rank sitting versus cises will challenge groups of muscles in a way that enhances standing and walking and morning versus evening with respect overall spinal stability. 24-26 to their symptoms. Recent research has shown that exercise programs can Operational definitions for components of the physical ex- be designed to challenge the stabilizing muscles of the spine in amination are included in appendix 1. The physical examina- a way that appears to be effective for at least certain subgroups tion included lumbar spine range of motion (ROM) measured of patients with LBP. The development of a valid method for 32 identifying this subgroup of patients would help clinicians in with a single inclinometer. Waddell et al found these mea- determining which patients with LBP are most likely to benefit surements to be highly reliable (intraclass correlation coeffi- from this exercise program. The purpose of this study was to cient [ICC] range, .86–.95). Any aberrant motions believed to explore the value of various demographic, historic, and clin- be associated with LSI occurring during the performance of 33,34 ical examination variables for predicting outcome after par- lumbar ROM were noted, including an instability catch, ticipation in a program of spinal stabilization exercises. The painful arc of motion,35 “thigh climbing” (Gower’s sign), or a reference standard used to determine success was change in reversal of lumbopelvic rhythm.7 Subjects were categorized as disability. either having or not having aberrant motions present, a deter- mination found to be reliable in a previous study.36 Posterior- METHODS anterior lumbar mobility testing37 was performed at each spinal We conducted a prospective cohort study involving patients level. Although the reliability coefficients for these judgments referred to physical therapy (PT) with LBP. Subjects were generally have been shown to be only fair,38,39 percentage recruited from new patients referred for treatment of LBP to