Spinous process hypertrophy associated with implanted devices in the external link model.

OBJECTIVE: Recent development of a chiropractic subluxation mimic, the external link model, uses titanium implants on lumbar vertebrae in the rat. The objective of this study was to evaluate potential correlations in the model between linking history, bone resorption, exudate formation, and experimentally induced intervertebral hypomobility. METHODS: Serial lateral radiographs of 73 male Sprague Dawley rats with implanted devices were reviewed. A baseline radiograph was obtained after a 6-week surgical recovery period, and a second radiograph was exposed after an 8-week hypomobility induction period. Spinous hypertrophy at the implant sites (L4, L5, and L6) was measured on the radiographs with a vernier caliper. Bone resorption and exudate build-up were assessed and compared with intervertebral hypomobility data previously collected. Data trends were described using cross-tabulated counts, analysis of variance, and regression analysis. RESULTS: Cross-tabulation suggested differences between hypomobility-induced rats and control rats. However, correlation analysis showed no predictive role for spinous hypertrophy relative to intervertebral mobility. Similarly, exudate level did not predict spinous hypertrophy. However, implant presence and vertebral level had a significant interaction, with moderate and severe hypertrophy occurring more frequently at L4 and L6 in hypomobility-induced rats. Age did not materially influence spinous hypertrophy. CONCLUSIONS: Mechanical stresses produced at the implant bone interface in rats with induced hypomobility contribute to spinous hypertrophy beyond that simply due to the presence of the implants. However, spinous hypertrophy does not contribute significantly to intervertebral hypomobility in the external link model.

Coping strategies and chiropractic student perceived stress.

OBJECTIVE: To investigate coping strategies adopted by chiropractic college students and how these strategies affect student-perceived stress levels. METHODS: Four hundred seven (407) 1st-quarter students were recruited during 2014 and 2015. The validated Brief COPE inventory was used to assess coping strategies during the 1st week of classes. Perceived Chiropractic College Stress (PCCS) was assessed via a modification of Vitaliano Perceived Medical School Stress survey instrument. The modified coping instrument was administered during the 1st quarter (PCCS1) and 6 months later during the 3rd quarter (PCCS2). RESULTS: Mean perceived stress levels were greater after 6 months. Although perceived stress increased more for females than for males over that period, it was not statistically significant. Male and female coping strategies differed only in the preferential use of emotional support by females. Students generally adopted active coping strategies (eg, active coping and planning) rather than avoidant strategies (eg, substance abuse). Regression analysis revealed a moderate positive relationship between avoidant-emotion coping and PCCS1 with a weaker positive correlation between problem-focused coping, sex, and PCCS1. Avoidant-emotion coping also demonstrated a moderate positive correlation with PCCS2. Neither sex nor the 3 coping strategies were predictors of PCCS change (PCCS2 - PCCS1). CONCLUSION: This study is a starting point for exploring the relationship between perceived stress and coping behaviors in a chiropractic training institution. Students generally used healthy adaptive coping strategies with minimal sex differences. Avoidant-emotion coping appears to be a reliable predictor of PCCS, with sex being a poor predictor.

Zygapophyseal joint adhesions after induced hypomobility.

OBJECTIVE: Adhesions (ADH) have been previously identified in many hypomobile joints, but not in the zygapophyseal (Z) joints of the spine. The objective of this study was to determine if connective tissue ADH developed in lumbar Z joints after induced intervertebral hypomobility (segmental fixation). METHODS: Using an established rat model, 3 contiguous segments (L4, L5, L6) were fixed with specially engineered, surgically implanted, vertebral fixation devices. Z joints of experimental rats (17 rats, 64 Z joints) with 4, 8, 12, or 16 weeks of induced hypomobility were compared with Z joints of age-matched control rats (23 rats, 86 Z joints). Tissue was prepared for brightfield microscopy, examined, and photomicrographed. A standardized grading system identified small, medium, and large ADH and the average numbers of each per joint were calculated. RESULTS: Connective tissue ADH were characterized and their location within Z joints described. Small and medium ADH were found in rats from all study groups. However, large ADH were found only in rats with 8, 12, or 16 weeks of experimentally induced intervertebral hypomobility. Significant differences among study groups were found for small (P < .003), medium (P < .000), and large (P < .000) ADH. The average number of medium and large ADH per joint increased with the length of experimentally induced hypomobility in rats with 8 and 16 weeks of induced hypomobility. CONCLUSIONS: We conclude that hypomobility results in time-dependent ADH development within the Z joints. Such ADH development may have relevance to spinal manipulation, which could theoretically break up Z joint intra-articular ADHs.

Introducing the external link model for studying spine fixation and misalignment: current procedures, costs, and failure rates.

OBJECTIVE: This is the last article in a series of 3 articles introducing a new animal model, the external link model (ELM), that permits reversible, nontraumatic control of the cardinal biomechanical features of the subluxation: fixation and misalignment. A detailed description of current ELM procedures is presented and practical issues are reviewed such as expense (dollars and time) and construct failure rates during and after the surgical implant procedure. METHOD: Descriptive report of current ELM procedures, refinements to the spinous attachment units (SAUs), and tabulation of costs and failure rates drawn from recent studies. RESULTS: In contrast to the older, 1-piece stainless steel SAUs, new 3-piece titanium SAUs may be reimplanted many times without failure. Consequently, the cost per ELM ranges from $579 to $69, depending on whether the SAUs, links, and screws must be purchased or are already available for implanting. The SAU implant procedure requires between 0.5 and 1.25 hours, depending on the experience of the surgeon. The total construct failure rate for the ELM is 24.2% (6.6% at surgery failure + 17.8% postsurgery failures). This rate is consistent with that reported in spine implant studies with other devices. To date, more than 500 male Sprague-Dawley rats (350-450 g) have been implanted with SAUs for ELM studies at the Palmer Center for Chiropractic Research and the National University of Health Sciences. CONCLUSION: It has been our experience that individuals with basic animal research training will become proficient at producing the ELM after observing 3 to 4 implant procedures and performing 4 to 6 procedures on their own.

Predicting stress and test anxiety among 1st-year chiropractic students.

OBJECTIVE: We evaluated perceived stress in 1st-year chiropractic students and the relationship between perceived stress and test anxiety. Moreover, we sought student-identified stressors that complicate chiropractic education. METHODS: We tested 3 hypotheses in a longitudinal descriptive study: (1) student-perceived stress would increase over 6 months of chiropractic training, (2) depression level and grade-point average (GPA) at matriculation would predict student-perceived stress 6 months into the program, and (3) perceived stress would correlate with cognitive and emotional test anxiety levels. Assessments used were prematriculation GPA, perceived chiropractic college stress (PCCS), the Center for Epidemiologic Studies Depression Scale, and the Test Anxiety Inventory. RESULTS: Four hundred and seven students participated during 2014 and 2015. PCCS increased 18% after 6 months (t(406) = 6.32, p < .001, d = .33). Prematriculation GPA was not a significant predictor of PCCS at 6 months, p = .082. By contrast, the Center for Epidemiologic Studies Depression Scale at the beginning of the chiropractic training program was a significant predictor p < .001, multiple R2 = 7.1%. PCCS correlated with test anxiety worry and emotionality (r = .37, p < .001 and r = .35, p < .001, respectively). The top 4 stressors identified by students were (by priority) finances, time for a life outside school, personal competence/endurance, and curriculum/environment. CONCLUSION: Our findings are consistent with perceived stress increases during medical school. Surprisingly, prematriculation GPA, a widely used academic performance predictor, was a poor predictor of PCCS, while depression level at matriculation was a moderate predictor. PCCS correlated with test anxiety worry and emotionality, known academic performance impediments.

Preliminary morphological evidence that vertebral hypomobility induces synaptic plasticity in the spinal cord.

OBJECTIVE: A widely accepted theoretical model suggests that vertebral hypomobility can cause pain and abnormal spinal mechanics because of changes in sensory input from spinal and paraspinal tissues. The purpose of this pilot study was 3-fold: (1) to make a preliminary determination if chronic vertebral hypomobility at L4 through L6 in the rat would affect synaptic density and/or morphology in the superficial dorsal horn of the L2 spinal cord level, (2) to identify relevant outcome variables for future studies, and (3) to obtain preliminary data that would permit estimating an appropriate sample size for future studies. METHODS: Using an established rat model, we fixed 3 contiguous lumbar segments (L4-L6) for 8 weeks with a specially engineered vertebral fixation device. Electron micrographs were obtained from 2 animals from the experimental (fixed) group and each of 3 control groups (no surgery, surgery but no devices implanted, and devices implanted but not fixed). Synapses were randomly selected using a stereological approach and were analyzed for symmetry, curvature, type of postsynaptic profile, and perforations. The synaptic density was also estimated. RESULTS: There was increased synaptic density and percentage of positively curved synapses in the dorsal horn of experimental animals as compared with controls. Experimental animals had a lower percentage of axospinous synapses, with a concomitant increase in the percentage of synapses on dendritic shafts. CONCLUSIONS: These preliminary data suggest for the first time that chronic vertebral hypomobility at L4 through L6 in the rat affects synaptic density and morphology in the superficial dorsal horn of the L2 spinal cord level. More definitive studies are warranted, and the biologic significance of these finding should be investigated.

Introducing the external link model for studying spine fixation and misalignment: part 2, Biomechanical features.

OBJECTIVES: The purpose of this study was to characterize intervertebral stiffness and alignment changes in the external link model and evaluate it as an experimental mimic for studying the chiropractic subluxation. METHOD: A controlled test-retest design was used to evaluate rats with spine segments linked in 3 alignment configurations and controls that were never linked. Dorsal-to-ventral spine stiffness was measured with a load platform, and flexion/extension misalignment was assessed on lateral radiographs obtained with a spine extension jig. Descriptive statistics were computed for study groups, and multiple linear regression models were used to examine all potential explanatory variables for the response variables "stiffness" and "joint position." RESULTS: Rats tested with links in place had significantly higher dorsal-to-ventral stiffness in the neutral configuration than rats in the flexed configuration. This difference remained after the links were removed. Stiffness after link removal was greater for longer linked periods. Surprisingly, stiffness after link removal was also greater with longer unlinked periods. Longer linked periods also produced greater misalignments during forced spine extension testing. Although link configuration was not a statistically significant predictor of misalignments, longer times after link removal did produce greater misalignments. CONCLUSIONS: This study suggests that the external link model can be a valuable tool for studying the effects of spine fixation and misalignment, 2 cardinal features of what has been historically described as the chiropractic subluxation. Significant residual stiffness and misalignment remained after the links were removed. The progressive course of this lesion is consistent with subluxation theory and clinical chiropractic experience.

Introducing the external link model for studying spine fixation and misalignment: part 1--need, rationale, and applications.

This is the first article in a series introducing a new animal model, the External Link Model that we propose will allow researchers to produce and study spine lesions with the cardinal biomechanical features of the chiropractic subluxation: fixation (hypomobility) and misalignment.

Requiring students to justify answer changes during collaborative testing may be necessary for improved academic performance.

OBJECTIVE: Three hypotheses were tested in a chiropractic education program: (1) Collaborative topic-specific exams during a course would enhance student performance on a noncollaborative final exam administered at the end-of-term, compared to students given traditional (noncollaborative) topic-specific exams during the course. (2) Requiring reasons for answer changes during collaborative topical exams would further enhance final-exam performance. (3) There would be a differential question-type effect on the cumulative final exam, with greater improvement in comprehension question scores compared to simple recall question scores. METHODS: A total of 223 students participated in the study. Students were assigned to 1 of 2 study cohorts: (1) control - a traditional, noncollaborative, exam format; (2) collaborative exam only (CEO) - a collaborative format, not requiring answer change justification; and (3) collaborative exam with justification (CEJ) - a collaborative exam format, but requiring justification for answer changes. RESULTS: Contrary to expectation (hypothesis 1), there was no significant difference between control and CEO final exam scores (p = .566). However, CEJ final exam scores were statistically greater (hypothesis 2) than the control (p = .010) and CEO (p = .011) scores. There was greater collaboration benefit when answering comprehension than recall questions during topic-specific exams (p = .000), but this did not differentially influence study cohort final exam scores (p = .571, hypothesis 3). CONCLUSION: We conclude that test collaboration with the requirement that students explain the reason for making answer changes is a more effective learning tool than simple collaboration that does not require answer change justification.

Head repositioning errors in normal student volunteers: a possible tool to assess the neck's neuromuscular system.

BACKGROUND: A challenge for practitioners using spinal manipulation is identifying when an intervention is required. It has been recognized that joint pain can interfere with the ability to position body parts accurately and that the recent history of muscle contraction can play a part in that interference. In this study, we tested whether repositioning errors could be induced in a normal population by contraction or shortening of the neck muscles. METHODS: In the experimental protocol, volunteers free of neck problems first found a comfortable neutral head posture with eyes closed. They deconditioned their cervical muscles by moving their heads 5 times in either flexion/extension or lateral flexion and then attempted to return to the same starting position. Two conditioning sequences were interspersed within the task: hold the head in an extended or laterally flexed position for 10 seconds; or hold a 70% maximum voluntary contraction in the same position for 10 seconds. A computer-interfaced electrogoniometer was used to measure head position while a force transducer coupled to an auditory alarm signaled the force of isometric contraction. The difference between the initial and final head orientation was calculated in 3 orthogonal planes. Analysis of variance (1-way ANOVA) with a blocking factor (participants) was used to detect differences in proprioceptive error among the conditioning sequences while controlling for variation between participants. RESULTS: Forty-eight chiropractic students participated: 36 males and 12 females, aged 28.2 +/- 4.8 yrs. During the neck extension test, actively contracting the posterior neck muscles evoked an undershoot of the target position by 2.1 degrees (p <0.001). No differences in repositioning were found during the lateral flexion test. CONCLUSION: The results suggest that the recent history of cervical paraspinal muscle contraction can influence head repositioning in flexion/extension. To our knowledge this is the first time that muscle mechanical history has been shown to influence proprioceptive accuracy in the necks of humans. This finding may be used to elucidate the mechanism behind repositioning errors seen in people with neck pain and could guide development of a clinical test for involvement of paraspinal muscles in cervical pain and dysfunction.

Brief, cooperative peer-instruction sessions during lectures enhance student recall and comprehension.

OBJECTIVE: The objective of this study was to evaluate the academic impact of cooperative peer instruction during lecture pauses in an immunology/endocrinology course. METHODS: Third-quarter students participated across iterations of the course. Each class offered 20 lectures of 50 minutes each. Classes were divided into a peer-instruction group incorporating cooperative peer instruction and a control group receiving traditional lectures. Peer-instruction group lectures were divided into 2-3 short presentations followed by a multiple-choice question (MCQ). Students recorded an initial answer and then had 1 minute to discuss answers with group peers. Following this, students could submit a revised answer. The control group received the same lecture material, but without MCQs or peer discussions. Final-exam scores were compared across study groups. A mixed-design analysis of covariance was used to analyze the data. RESULTS: There was a statistically significant main effect for the peer-instruction activity (F(1, 93) = 6.573, p = .012, r = .257), with recall scores higher for MCQs asked after peer-instruction activities than for those asked before peer instruction. Final-exam scores at the end of term were greater in the peer-instruction group than the control group (F(1, 193) = 9.264, p = .003, r = .214; question type, F(1, 193) = 26.671, p = .000, r = .348). CONCLUSION: Lectures with peer-instruction pauses increase student recall and comprehension compared with traditional lectures.

Can formative quizzes predict or improve summative exam performance?

OBJECTIVE: Despite wide use, the value of formative exams remains unclear. We evaluated the possible benefits of formative assessments in a physical examination course at our chiropractic college. METHODS: Three hypotheses were examined: (1) Receiving formative quizzes (FQs) will increase summative exam (SX) scores, (2) writing FQ questions will further increase SE scores, and (3) FQs can predict SX scores. Hypotheses were tested across three separate iterations of the class. RESULTS: The SX scores for the control group (Class 3) were significantly less than those of Classes 1 and 2, but writing quiz questions and taking FQs (Class 1) did not produce significantly higher SX scores than only taking FQs (Class 2). The FQ scores were significant predictors of SX scores, accounting for 52% of the SX score. Sex, age, academic degrees, and ethnicity were not significant copredictors. CONCLUSION: Our results support the assertion that FQs can improve written SX performance, but students producing quiz questions didn't further increase SX scores. We concluded that nonthreatening FQs may be used to enhance student learning and suggest that they also may serve to identify students who, without additional remediation, will perform poorly on subsequent summative written exams.

Test anxiety and academic performance in chiropractic students.

Objective : We assessed the level of students' test anxiety, and the relationship between test anxiety and academic performance. Methods : We recruited 166 third-quarter students. The Test Anxiety Inventory (TAI) was administered to all participants. Total scores from written examinations and objective structured clinical examinations (OSCEs) were used as response variables. Results : Multiple regression analysis shows that there was a modest, but statistically significant negative correlation between TAI scores and written exam scores, but not OSCE scores. Worry and emotionality were the best predictive models for written exam scores. Mean total anxiety and emotionality scores for females were significantly higher than those for males, but not worry scores. Conclusion : Moderate-to-high test anxiety was observed in 85% of the chiropractic students examined. However, total test anxiety, as measured by the TAI score, was a very weak predictive model for written exam performance. Multiple regression analysis demonstrated that replacing total anxiety (TAI) with worry and emotionality (TAI subscales) produces a much more effective predictive model of written exam performance. Sex, age, highest current academic degree, and ethnicity contributed little additional predictive power in either regression model. Moreover, TAI scores were not found to be statistically significant predictors of physical exam skill performance, as measured by OSCEs.

The basis for spinal manipulation: chiropractic perspective of indications and theory.

It is reasonable to think that patients responding to spinal manipulation (SM), a mechanically based therapy, would have mechanical derangement of the spine as a critical causal component in the mechanism of their condition. Consequently, SM practitioners routinely assess intervertebral motion, and treat patients on the basis of those assessments. In chiropractic practice, the vertebral subluxation has been the historical raison d'etre for SM. Vertebral subluxation is a biomechanical spine derangement thought to produce clinically significant effects by disturbing neurological function. This paper reviews the putative mechanical features of the subluxation and three theories that form the foundation for much of chiropractic practice. It concludes with discussion of subluxation as an indicator for SM therapy, particularly from the perspective that subluxation may be one contributory cause of ill-health within a "web of causation".

Degenerative changes following spinal fixation in a small animal model.

OBJECTIVE: The objective of this study was to evaluate changes of the lumbar vertebral column following fixation. DESIGN: Using an established small animal (rat) model of spinal fixation (hypomobility), 3 contiguous lumbar segments (L4, L5, L6) were fixed with a specially engineered vertebral fixation device. Spinal segments of control rats were compared with those of animals with 1, 4, or 8 weeks of fixation. Subgroups of these fixation animals subsequently had the fixation device removed for 1, 2, 4, 8, or 12 weeks to evaluate the effects of attempting to reestablish normal forces to the vertebral segments following hypomobility. SETTING: This Institutional Animal Care and Use Committee (IACUC) approved study was conducted in a university animal facility. ANIMALS: Eighty-seven animals (23 controls animals and 64 fixation animals) were used in this study. Main Outcome Measures Outcome measures were degenerative changes of the vertebral bodies (VBs) and intervertebral disks (IVDs), zygapophysial (Z) joint osteophyte formation, and Z joint articular surface degeneration (ASD). Changes found in vertebral segments that were fixed (hypomobile) were compared with changes in adjacent nonfixed vertebral segments, and changes among fixation animals were compared with nonfixed controls. Main Results Very few degenerative changes were identified on the VBs and IVDs. Z joint changes were significant, both for osteophyte formation (analysis of variance [ANOVA], P <.0001) and ASD (ANOVA, P <.0001). Fixed segments had more degenerative changes than nonfixed segments for all Z joint parameters (ANOVA, P <.0001). Osteophyte formation and ASD were directly dependent on duration of fixation. CONCLUSIONS: These findings indicate that fixation (hypomobility) results in time-dependent degenerative changes of the Z joints.