CSM 2017 Orthopaedic Section Platform Presentations (Abstracts OPL1–OPL64)

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Previous article Next article Full AccessAPTA Combined Sections MeetingOrthopaedic Section Platform Presentations (Abstracts OPL1–OPL64)AuthorsJournal of Orthopaedic & Sports Physical TherapyPublished Online:December 31, 2016Volume47Issue1PagesA1-A29https://www.jospt.org/doi/10.2519/jospt.2017.47.1.A1SectionsPDFPDF PLUSAbstract ToolsAdd to FavoritesDownload CitationsTrack CitationsPermissions ShareShare onFacebookTwitterLinkedInRedditEmail AboutAbstractThese abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, OPL designates an Orthopaedic Section platform presentation.J Orthop Sports Phys Ther 2017;47(1):A1–A29. doi:10.2519/jospt.2017.47.1.A1CSM AbstractsThe Journal of Orthopaedic & Sports Physical Therapy is pleased to publish abstracts of the 2017 Combined Sections Meeting (CSM), which will take place in San Antonio, TX, February 15–18, 2017. This collection of abstracts provides a glimpse into the research presented as part of the scientific programming of the Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association. The number and variety of the presentations scheduled for CSM are testimony to the exciting and far-reaching research activities taking place in the field of physical therapy.The abstracts presented in the following pages are reviewed and selected by members of the research committee for each Section. The abstracts are not, however, reviewed by the Associate Editors or the Editor-in-Chief of the Journal of Orthopaedic & Sports Physical Therapy. By design, each abstract presents only a brief summary of a research project—and thus does not permit full assessment of the scientific rigor with which the work was conducted. Publication and presentation of these abstracts serves the purpose of sharing new research ideas, and, in many cases, the abstract presented offers only preliminary results that may require further refinement and future validation. Nonetheless, presenting this, often preliminary, type of research information at meetings such as CSM plays an important role in encouraging dialog among researchers, clinicians, and educators that contributes to advancing the research process and, where appropriate, translation into clinical practice.The CSM provides a valuable forum for learning from clinical and research experts in physical therapy and related fields. Moreover, unlike reading a manuscript in a journal, attending a professional conference presents us the opportunity to interact with the authors—our colleagues—by asking questions and exchanging ideas. Dive in, and engage.I look forward to seeing you all in San Antonio!Sincerely,Download FigureDownload PowerPointJ. Haxby Abbott, DPT, PhD, FNZCPEditor-in-ChiefOPL1Timing of Supervised Physical Therapy After Hindfoot Fractures: A Randomized Controlled TrialStephanie Albin, Shane Koppenhaver, Julie Fritz, Thomas G. McPoil, Drew Van BoerumPhysical Therapy, Intermountain Healthcare, Salt Lake City, Utah; Physical Therapy, US Army-Baylor, San Antonio, Texas; Physical Therapy, University of Utah, Salt Lake City, Utah; Physical Therapy, Regis University, Denver, ColoradoPURPOSE/HYPOTHESIS: Fractures to the hindfoot, including the talus and calcaneus, have devastating long-term functional outcomes. To date, no randomized trials have been done assessing when is the best time to initiate physical therapy after surgical fixation. The purpose of this study is to assess whether initiating a supervised physical therapy program including therapeutic exercise and manual therapy 2 to 3 weeks postoperatively (EARLY) versus 7 to 8 weeks postoperatively (LATE) in patients following surgery for talus or calcaneus fractures results in differences in clinical outcomes. The secondary purpose of this study is to assess what factors predict outcomes after these hindfoot fractures.NUMBER OF SUBJECTS: Fifty patients between the ages of 18 and 70 years having undergone an open reduction internal fixation (ORIF) of the calcaneus or talus were recruited to participate from 2 foot and ankle fellowship-trained orthopaedic surgeons.MATERIALS/METHODS: Subjects were randomly assigned to initiate formal physical therapy starting within 2 weeks postoperatively (EARLY) (n = 26) or 8 weeks postoperatively (LATE) (n = 24). Treatment for both groups consisted of impairment based manual therapy and therapeutic exercise. The Lower Extremity Functional Scale (LEFS), the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot scale, range of motion, pain and girth measurements were the outcome measures for this study. Subjects in both groups were seen for a total of 10 visits. All subjects underwent follow-up assessments at 3 months, 6 months, and 12 months postoperatively. Between-group differences were analyzed using ANCOVAs with baseline scores as covariates.RESULTS: Results indicated no significant differences between the groups at any time point for the LEFS (P = .637) or the AOFAS (P = .634). Baseline anxiety (as measured by the Beck Anxiety Questionnaire) significantly predicted LEFS scores at both the 6-month and 12-month follow-up periods (r = −0.55, P = .0015 and r = −0.53, P = .007).CONCLUSIONS: The timing of supervised physical therapy does not change clinical outcomes after surgical fixation of a hindfoot fracture as assessed by the LEFS or the AOFAS hindfoot scores, or clinical outcomes compared to patients initiating a formal physical therapy program 7 to 8 weeks after surgery. Although these patients typically have poor clinical outcomes, it is possible that addressing other factors such as psychosocial issues such as anxiety may help improve long-term outcomes.CLINICAL RELEVANCE: The timing of initiating formal physical therapy on long-term outcomes does not change outcomes for patients undergoing ORIF for hindfoot fractures. However, addressing psychosocial factors, such as anxiety, may improve long-term outcomes.OPL2Osteoarthritic Pain Intensity and Locations in People with and without Diabetes Using a Clinical Data Repository SystemAqeel M. Alenazi, Mohammed Alshehri, Shaima Alothman, Lemuel R. Waitman, Patricia KludingPhysical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Missouri; Department of Medical Informatics; Department of Internal Medicine, University of Kansas Medical Center, Kansas City, MissouriPURPOSE/HYPOTHESIS: Osteoarthritis (OA) and diabetes mellitus (DM) are common chronic diseases with a significant effect on function and quality of life. It is known that hyperglycemia may affect cellular functions in the musculoskeletal system. Hyperglycemia leads to increased production of advanced glycation end products that is associated with pro-inflammatory markers, and these harmfully affect joint mechanical properties, increase the stiffness and fragility of bone and cartilage. These molecular changes may affect pain intensity and locations of OA. The aim of this retrospective analysis was to examine pain intensity and pain locations among patients with both OA and DM (OA+DM), compared to patients who have OA but do not have DM (OA only).NUMBER OF SUBJECTS: Data from 870 OA+DM patients (53.6% female; mean ± SD age, 64.29 ± 11.10 years) and 2505 OA-only patients (53.5% female; age, 59.39 ± 15.10 years) were analyzed.MATERIALS/METHODS: Retrospective electronic review of de-identified data for patients who were seen in a large academic medical system were selected using a clinical data repository system (i2b2) [7]. A query was built by selecting 2 groups: patients who had the diagnoses codes of both localized OA and type 2 diabetes (OA+DM) and patients who had diagnoses codes of localized OA without DM (OA only). These diagnoses code queries were conducted with a search of documented pain intensity ratings using a numeric scale (0–10) and pain locations such as knee, hip, shoulder and other joints that were selected as the variables of interest. The query linked pain intensity to pain locations using the same date to minimize nonmusculoskeletal pain complaints such as headache. Pain intensity scores were averaged for each patient. A 2-way ANOVA was used at a .05 alpha level.RESULTS: There was a statistically significant difference in average total pain intensity between the OA+DM group (5.87 ± 1.56) and the OA only group (5.48 ± 1.56; P = .005). Also, average pain intensity was statistically different between locations (P<.001). OA+DM group showed higher pain intensity than OA only group based on specific locations including arm (6.28 ± 1.56 versus 5.70 ± 1.51), back (5.92 ± 1.47 versus 5.63 ± 1.57), hip (5.65 ± 1.62 versus 5.32 ± 1.54), knee (5.66 ± 1.56 versus 5.18 ± 1.43), and leg (5.99 ± 1.45 versus 5.69 ± 1.66).CONCLUSIONS: Patients with OA+DM may experience higher pain intensity compared to patients with OA only. Limitations in this study include not accounting for other associated risk factors such as pain medications, surgical interventions, neuropathy and obesity.CLINICAL RELEVANCE: It is known that pain can negatively impact function and quality of life in people with OA. The results of this study indicate that a coexisting diagnosis of DM may increase the intensity of pain in this population, and is an important area for future study.OPL3Association Between Low Back Pain and Gluteus Maximus Cross-sectional Area in WomenAmy H. Amabile, John H. Bolte, Saskia D. RichterDivision of Anatomy, The Ohio State University, Columbus, OhioPURPOSE/HYPOTHESIS: Decreased trunk and hip muscle strength and endurance have been identified in persons with low back pain (LBP) [1,2,3,4], yet it is unknown if these deficits are a cause or an effect of LBP. Although multifidus and other trunk muscles have been extensively studied vis-à-vis LBP [5,6,7,8,9], only 1 prior study [10] has been identified which examines the relationship between gluteus maximus (GM) size and LBP. The purpose of this study was to compare GM cross-sectional area (CSA) in individuals with chronic LBP, with GM CSA in a control group of individuals without LBP. Our hypothesis was that participants with LBP would have greater atrophy in their GM muscles than control participants.NUMBER OF SUBJECTS: Subjects were 36 women with chronic LBP, aged 40 to 69 years, and 32 women in the same age range and without any known history of LBP. Subjects and controls had all received a minimum of 1 year of medical care as inpatients or outpatients within the Ohio State University Wexner Medical Center care system. Each experimental participant had at least 2 back pain-related medical visits, with a history of back pain lasting at least 3 months, in order to comply with the most commonly used definition of chronic LBP.MATERIALS/METHODS: Muscle CSA was measured using computed tomography and magnetic resonance imaging scans of GM. Measurement of CSA was performed using OsiriX MD software on an Apple iMac computer. Anthropometric variables and past medical history information were obtained from subject electronic medical records in order to normalize CSA measurements, apply exclusionary criteria, and perform correlations with muscle CSA.RESULTS: Mean normalized CSA was compared, showing a significantly smaller CSA for the LBP group than for the control group, with U = 383, at the P<.05 level. The number of back pain-related visits was correlated with normalized CSA and were found to be significantly correlated with a Spearman's rho of −0.339 at the P<.005 level. Age was shown to not be a covariate in this sample.CONCLUSIONS: This research demonstrated a previously only minimally explored relationship between GM CSA and LBP in women. The possible role of GM in the genesis of LBP has been virtually unstudied. GM has a well-established role in the lifting of loads from a fully flexed position [11,12,13] and lifting has been identified as an important cause of LBP [14,15,16]. Weak GM may lead to an improper lifting technique at the beginning of extension from full flexion, just when intervertebral discs are most vulnerable to herniation [13,17]. Further research is indicated on GM CSA in individuals with varying age, sex and LBP diagnoses.CLINICAL RELEVANCE: This research supports the use of conservatively applied physical therapy interventions targeting GM in those LBP patients where such exercises are not contraindicated. Targeted strengthening of GM in healthy adults may also be useful as 1 component of a comprehensive program designed to prevent LBP.OPL4Fear of Movement and Pain Self-Efficacy Mediate Outcomes Following a Targeted Rehabilitation Intervention After Spine SurgeryKristin Archer, Rogelio A. Coronado, Dawn Ehde, Susan Vanston, Tatsuki Koyama, Sharon Phillips, Matthew J. McGirt, Dan Spengler, Oran S. Aaronson, Joseph S. Cheng, Clinton J. Devin, Stephen WegenerVanderbilt University Medical Center, Nashville, Tennessee; University of Washington School of Medicine, Seattle, Washington; Carolina Neurosurgery and Spine Associates, Charlotte, North Carolina; Johns Hopkins Medical Center, Baltimore, MarylandPURPOSE/HYPOTHESIS: Cognitive-behavioral therapy is an effective strategy for improving pain and disability in patients with chronic pain. Recently, a cognitive-behavioral based physical therapy program (Changing Behavior through Physical Therapy [CBPT]) has been shown to improve outcomes after lumbar spine surgery compared to education. The purpose of this study was to determine the mediators underlying the efficacy of the CBPT program. The hypothesis was that decreases in fear of movement and pain catastrophizing and increases in pain self-efficacy would be associated with reductions in pain and disability and improvement in general health and physical performance at 6 months after lumbar spine surgery.NUMBER OF SUBJECTS: Eighty-six participants (mean ± SD age, 57.6 ± 12.2 years; 55.8% female) who underwent spine surgery for a degenerative lumbar condition.MATERIALS/METHODS: Participants were enrolled into a randomized trial comparing CBPT (n = 43) and an education program (n = 43). Participants completed a battery of validated questionnaires and performance-based tests prior to surgery and at 6 weeks (pretreatment) and 3 and 6 months following surgery to measure pain (Brief Pain Inventory), disability (Oswestry Disability Index), general health (SF-12), physical performance (5-chair stand; timed up-and-go; 10-meter walk), fear of movement (Tampa Scale of Kinesiophobia), pain catastrophizing (Pain Catastrophizing Scale), and pain self-efficacy (Pain Self-Efficacy Questionnaire). Mediation analyses were conducted using the approach by Baron and Kenny to test whether 3- and 6-month changes in fear of movement, pain catastrophizing, and pain self-efficacy mediate treatment effects on outcomes at 6 months.RESULTS: There were no between-group differences in baseline characteristics, treatment session completion, or follow-up rates. At 6 months, CBPT compared to education participants demonstrated greater improvement in pain, disability, physical and mental health, and the 5-chair stand test (P<.05). Six month changes, but not 3-month changes, in fear of movement and pain self-efficacy were found to mediate postoperative outcomes at 6 months (P<.05). Specifically, changes in fear-avoidance mediated the effects of CBPT treatment on all outcomes (P<.05), while changes in self-efficacy mediated the effects of CBPT treatment on pain interference and physical health (P<.05). Pain catastrophizing was not found to be a mediator of treatment outcomes.CONCLUSIONS: This study advances evidence on the mechanisms underlying cognitive-behavioral strategies and supports targeting fear of movement and self-efficacy for improving recovery after spine surgery.CLINICAL RELEVANCE: Fear of movement and self-efficacy are modifiable targets that could improve the effectiveness of the CBPT program. Robust postoperative rehabilitation effects may occur by an increased focus on well-established strategies, such as graded activity, pacing, goal setting, and problem-solving, that target these specific psychosocial constructs.OPL5Cost-Effectiveness of Cognitive-Behavioral-Based Physical Therapy After Lumbar Spine SurgeryKristin Archer, Stephen Wegener, Clinton J. Devin, Susan Vanston, Matthew J. McGirt, Dan Spengler, Oran S. Aaronson, Joseph S. Cheng, Kenneth J. SmithVanderbilt University Medical Center, Nashville, Tennessee; Johns Hopkins Medicine, Baltimore, Maryland; Carolina Neurosurgery and Spine Associates, Charlotte, North Carolina; University of Pittsburgh, Pittsburgh, PennsylvaniaPURPOSE/HYPOTHESIS: Biopsychosocial approaches to rehabilitation are becoming more common for patients following spine surgery. However, economic evaluation data are limited. The purpose of this study was to determine the cost-effectiveness of a telephone-based cognitive-behavioral based physical therapy (CBPT) program using Markov decision-analysis. The hypothesis was that CBPT would be less expensive and more effective than an Education program.NUMBER OF SUBJECTS: Eighty-six participants (43 in CBPT group and 43 in Education group) who underwent lumbar spine surgery for a degenerative condition.MATERIALS/METHODS: A Markov state-transition model was constructed, based on data from a randomized clinical trial, and a health system perspective was taken for cost-effectiveness. A $20 000 quality-adjusted life-year (QALY) criterion was used, which is considered to represent strong evidence favoring adoption of an intervention. All parameters were varied individually in 1-way sensitivity analyses. Participants could be in 1 of 3 health states after spine surgery based on a change in the Oswestry Disability Index (ODI) score (better, not better, better then get worse). Initial placement and transitions between states were based on an improvement or worsening of the ODI score beyond the published minimal clinically important difference (MCID) of 12.8 points. Direct health care costs from hospital discharge to 1 year postoperatively were derived from registry data and adjusted based on Medicare national-allowable payment amounts. Postoperative QALYs were calculated from a validated questionnaire (EQ-5D) that was completed by patients at 3-month and 1-year follow-up.RESULTS: At 1 year after surgery, 89% were better, 2% were not better, and 8% were better then get worse in the CBPT group, while the Education group had 68% in the better, 8% in the not better, and 25% in the better then get worse health states. The total per person postoperative management and follow-up cost for the CBPT group was $2493 and for the Education group was $2595. The CBPT group cost $102 less per person and gained 0.09 more QALYs compared with the Education group in base-case analysis, which indicated that CBPT was the dominant (less expensive, more effective) strategy. In sensitivity analyses, CBPT remained the favored strategy at a $20 000 QALY threshold when all values were individually varied over plausible ranges.CONCLUSIONS: Using Markov modeling, the CBPT program was less costly and more effective than an Education program when used after surgery for patients with degenerative lumbar spine conditions.CLINICAL RELEVANCE: The CBPT program, delivered by physical therapists over the telephone, is a low-cost, evidence-based program to improve outcomes in patients with chronic pain undergoing lumbar spine surgery. Results support a biopsychosocial approach to postoperative spine management and the integration of cognitive-behavioral strategies into physical therapy care, with CBPT being an economically reasonable, and perhaps cost saving, intervention.OPL6The Effect of Movement Training on 2-D Kinematics during an Untrained Task in Females with Patellofemoral Pain: Relationship to Hip Muscle StrengthElanna Arhos, Angela Reitenbach, Barb Yemm, Gretchen B. SalsichPhysical Therapy, Saint Louis University, St Louis, MissouriPURPOSE/HYPOTHESIS: Patellofemoral pain (PFP) may develop from a faulty movement pattern (dynamic knee valgus) that occurs during weight-bearing activities. Movement pattern training is a proposed intervention aimed to optimize movement during weight-bearing tasks. Such interventions typically use a multimodal approach which isolates hip strengthening. However, movement training by itself may be effective. Further, focused practice of daily tasks emphasizing optimal limb alignment may yield carry over to untrained tasks. We used a clinically available method (2-D video) of quantifying dynamic knee valgus (DKV) to determine (1) if 2-D hip and knee frontal plane projection angles (FPPA) obtained during an untrained task improve after a movement pattern focused intervention, and (2) if improved FPPAs are associated with increased hip muscle strength.NUMBER OF SUBJECTS: Twenty-three females with PFP of approximately 2 months in duration who demonstrated observable DKV during single limb squat (mean ± SD age, 21.8 ± 3.7 years; BMI, 22.2 ± 2.0 kg/m2; pain duration, 4.1 ± 3.4 years; average pain [past week], 3.7 ± 1.0 [numeric pain rating, 0–10]).MATERIALS/METHODS: Physical therapy intervention was delivered 2 times per week for 6 weeks and focused solely on maintaining optimal limb alignment during daily tasks. At pre and postintervention assessments, digital video captured subjects performing a single limb squat balance task (Y Balance test, posteromedial) which was not practiced during the intervention. DKV was quantified using hip and knee FPPAs, measured at the deepest point in the squat. Isometric hip muscle strength of the lateral rotators, abductors, and extensors was quantified using a handheld dynamometer. Paired Student's t tests compared FPPAs and strength preintervention and postintervention. Pearson correlation coefficients quantified the relationship between the change in FPPA and change in strength after intervention.RESULTS: Hip FPPA and knee FPPA decreased from pre to postintervention (hip: 23.2° ± 5.8° versus 18.5° ± 5.8°, P = .003; knee: 19.9° ± 10.7° versus 8.2° ± 9.8°, P<.001). Hip muscle strength improved postintervention (lateral rotators: 23.5 ± 4.2 kg versus 25.0 ± 3.7 kg, P = .006; hip abductors: 19.6 ± 5.0 kg versus 21.7 ± 4.9 kg, P = .010; hip extensors: 36.0 ± 8.8 kg versus 39.1 ± 8.7 kg, P = .033). There was no correlation between changes in hip and knee FPPA and changes in strength (P>.05).CONCLUSIONS: Hip and knee angles improved following a physical therapy intervention focused on movement pattern training. Hip muscle strength improved, despite the intervention having no focused muscle strengthening component. No correlation between strength and movement was observed, suggesting the improvements in movement were due more to improved motor control and neuromuscular training than increased strength in hip musculature.CLINICAL RELEVANCE: A physical therapy intervention comprised solely of movement pattern training may yield improved DKV, even in novel tasks that are not addressed in the intervention. Improved movement patterns may be detected using clinically applicable methods.OPL7Bilateral MRI Findings in Individuals with Unilateral Shoulder PainRodrigo P. Barreto, Paula M. Ludewig, Paula CamargoPhysical Therapy Post Graduation Program, University of São Carlos, São Carlos, Brazil; Program in Physical Therapy, University of Minnesota, Minneapolis, MinnesotaPURPOSE/HYPOTHESIS: Shoulder pain is a frequent musculoskeletal condition. Bilateral deficits in different outcome measures have previously been reported in individuals with unilateral shoulder pain. Previous studies have shown that scapular motion, humeral translation, abductor and scapular muscles performance are not different between symptomatic and asymptomatic shoulders in some unilaterally involved patient samples. In this context, it is also interesting to know if soft tissue or bony pathologies are present in these shoulders for understanding the deficits already described in the literature. Therefore, the purpose of this study was to describe magnetic resonance imaging (MRI) findings in both shoulders in individuals presenting with unilateral shoulder pain.NUMBER OF SUBJECTS: Thirty-six (20 male; average ± SD age, 41.2 ± 15.5 years; range, 21–73 years).MATERIALS/METHODS: Thirty-six individuals with unilateral shoulder pain participated in this study. All had to have pain for at least 4 weeks. Individuals with bilateral complaints, history of previous fractures, or surgeries in the upper limbs, recurrent shoulder dislocations, or neck pain were excluded based on history and clinical examination by a physical therapist. The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire was completed by all participants. MRI (Magnetom Essenza, Siemens) with a field strength of 1.5 T was performed for both symptomatic and asymptomatic shoulders in all participants. Sequences in T1, T2, and proton density with slices in sagittal, coronal and axial planes were performed for both shoulders. A specialized musculoskeletal radiologist read all the exams.RESULTS: Nineteen (52.8%) of individuals assessed were involved in recreational overhead sports 1.5 ± 1.8 times per week; 10 having pain on the dominant side. The symptomatic side was the dominant side for 19 (52.8%) of individuals overall (18 right-handed). The mean DASH was 26.4 ± 18.56 out of 100 (range, 1.7–79). MRIs revealed pathoanatomic alterations in all asymptomatic and symptomatic shoulders. The most prevalent condition of tendinopathy was observed in at least 2 tendons (supraspinatus [SS] and infraspinatus [IS]) or 3 (SS, IS, and subscapularis [SB]) for both shoulders in 97% of subjects. Partial tears were observed with slightly higher prevalence on the symptomatic side (39% versus 31%) in isolation in the SS tendon or extending to a second tendon. Bursitis was observed more frequently on the asymptomatic side (75% versus 61%). Fatty infiltration was observed more frequently in 3 tendons (SS, IS and SB) than associated full thickness rotator cuff tears. Acromioclavicular arthritis or edema was present in 83% and 86% of symptomatic and asymptomatic shoulders, respectively.CONCLUSIONS: Tissue alterations in the asymptomatic side of individuals with unilateral shoulder pain were as highly prevalent as in the symptomatic shoulders.CLINICAL RELEVANCE: These results suggest that MRI findings are not representing the pain generator in many cases, and deserve less attention in the clinical decision-making process.OPL8Effect of Manipulation on Lumbar Multifidus ActivationScott Biely, Michael Hmara, Jonathan Raymond, Richard Winters, Erin Whalen, Brannon CatherinePhysical Therapy, Neumann University, Aston, PennsylvaniaPURPOSE/HYPOTHESIS: The effectiveness of lumbar spine manipulation in decreasing pain has been well supported in the literature. Flynn et al identified 5 criteria in patients with low back pain that were used as indications for manipulation. Flynn attributed the pain relief to a “resetting” of the musculoskeletal system suggesting that the manipulation caused a relaxation of muscles around the spine. Studies of the effects of knee joint effusion on quadriceps activity indicate that capsular distension has an inhibitory effect on muscles that control that joint. A similar mechanism appears to occur with manipulation. The capsular distension caused by stretching the joint leads to inhibition of surrounding muscles. The immediate decrease in muscle guarding leads to a pain decrease. However, current research is equivocal concerning the effect of manipulation on the lumbar multifidus (LM), a key stabilizing muscle of the lumbar spine [1–6]. Thus, the purpose of this study was to study changes in lumbar multifidus thickness and activation not only after 1 lumbar spine manipulation but also after 6 manipulations performed over 2 weeks.NUMBER OF SUBJECTS: Twenty-eight subjects (14 male, 14 female; age, 21–54 years) with no current low back pain were recruited to participate in the study.MATERIALS/METHODS: Left LM thickness at L3–4 was measured in a relaxed state and in a contracted state (prone contralateral straight leg raise) using real time ultrasound (RTUS) (Biosound Esaote Aquilla). LM activation was calculated as LM thickness at rest subtracted from LM thickness when contracting. Subjects then underwent a lumbar facet gap manipulation of the left L3–4 facet. RTUS measures were repeated immediately following the manipulation. Subjects underwent 4 more manipulations over the next 2 weeks. The RTUS measures, a sixth manipulation, and follow-up measures were repeated during a final data collection session.RESULTS: Intra and interrater reliability for LM thickness measured at rest was strong (ICC>0.70); and in a contracted state excellent (ICC>0.80). LM thickness at rest, with subsequent manipulations, showed a trend toward increasing, although the increases did not exceed the minimal detectable change (MDC). LM thickness in the contracted state showed a progressive decrease that exceeded the MDC. There was a significant decrease in LM activation, F3,106 = 2.845, P = .041, comparing the first RTUS measure (prior to any manipulations) with the last RTUS measure (after the sixth manipulation).CONCLUSIONS: Frequent manipulation has been associated with lumbar instability, but this association was thought to be related to overstretching the passive stabilization subsystem. This research suggests that the instability may occur not only because of changes in the passive subsystem, but also because of weakening of key spinal stabilizing muscles (changes in the active stabilizing subsystem).CLINICAL RELEVANCE: This study suggests that manipulation should be accompanied by LM exercises to prevent inhibition of this key stabilizing muscle. Furthermore, excessive use of manipulation may lead to LM atrophy, lumbar instability, and chronic