N. Peter Reeves

Deficits in Neuromuscular Control of the Trunk Predict Knee Injury Risk A Prospective Biomechanical-Epidemiologic Study

Background Female athletes are at significantly greater risk of anterior cruciate ligament (ACL) injury than male athletes in the same high-risk sports. Decreased trunk (core) neuromuscular control may compromise dynamic knee stability. Hypotheses (1) Increased trunk displacement after sudden force release would be associated with increased knee injury risk; (2) coronal (lateral), not sagittal, plane displacement would be the strongest predictor of knee ligament injury; (3) logistic regression of factors related to core stability would accurately predict knee, ligament, and ACL injury risk; and (4) the predictive value of these models would differ between genders. Study Design Cohort study (prognosis); Level of evidence, 2. Methods In this study, 277 collegiate athletes (140 female and 137 male) were prospectively tested for trunk displacement after a sudden force release. Analysis of variance and multivariate logistic regression identified predictors of risk in athletes who sustained knee injury. Results Twenty-five athletes (11 female and 14 male) sustained knee injuries over a 3-year period. Trunk displacement was greater in athletes with knee, ligament, and ACL injuries than in uninjured athletes (P < .05). Lateral displacement was the strongest predictor of ligament injury (P = .009). A logistic regression model, consisting of trunk displacements, proprioception, and history of low back pain, predicted knee ligament injury with 91% sensitivity and 68% specificity (P = .001). This model predicted knee, ligament, and ACL injury risk in female athletes with 84%, 89%, and 91% accuracy, but only history of low back pain was a significant predictor of knee ligament injury risk in male athletes. Conclusions Factors related to core stability predicted risk of athletic knee, ligament, and ACL injuries with high sensitivity and moderate specificity in female, but not male, athletes.

The Effects of Core Proprioception on Knee Injury A Prospective Biomechanical-Epidemiological Study

Background In sports involving pivoting and landing, female athletes suffer knee injury at a greater rate than male athletes. Hypotheses Proprioceptive deficits in control of the bodys core may affect dynamic stability of the knee. Female, but not male, athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes. Study Design Cohort study (prognosis); Level of evidence, 2. Methods Study subjects were 277 collegiate athletes (140 female, 137 male) who were prospectively tested for core proprioception by active and passive proprioceptive repositioning. Athletes were monitored for injury for 3 years. An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes. Results Twenty-five athletes sustained knee injuries (11 women, 14 men). Deficits in active proprioceptive repositioning were observed in women with knee injuries (2.2°) and ligament/meniscal injuries (2.4°) compared with uninjured women (1.5°, P ≤ .05). There were no differences in average active proprioceptive repositioning error between injured men and uninjured men (P ≥ .05). Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men (1.5° vs 1.7°, P ≤ .05). For each degree increase in average active proprioceptive repositioning error, a 2.9-fold increase in the odds ratio of knee injury was observed, and a 3.3-fold increase in odds ratio of ligament/meniscal injury was observed (P ≤ .01). Active proprioceptive repositioning predicted knee injury status with 90% sensitivity and 56% specificity in female athletes. Conclusions Impaired core proprioception, measured by active proprioceptive repositioning of the trunk, predicted knee injury risk in female, but not male, athletes.

Delayed trunk muscle reflex responses increase the risk of low back injuries

Study Design. Prospective observational study with a 2- to 3-year follow-up. Objectives. To determine whether delayed muscle reflex response to sudden trunk loading is a result of or a risk factor for sustaining a low back injury (LBI). Summary of Background Data. Differences in motor control have been identified in individuals with chronic low back pain and in athletes with a history of LBI when compared with controls. However, it is not known whether these changes are a risk for or a result of LBI. Methods. Muscle reflex latencies in response to a quick force release in trunk flexion, extension, and lateral bending were measured in 303 college athletes. Information was also obtained regarding their personal data, athletic experience, and history of LBI. The data were entered into a binary logistic regression model to identify the predictors of future LBI. Results. A total of 292 athletes were used for the final analysis (148 females and 144 males). During the follow-up period, 31 (11%) athletes sustained an LBI. The regression model, consisting of history of LBI, body weight, and the latency of muscles shutting off during flexion and lateral bending load releases, predicted correctly 74% of LBI outcomes. The odds of sustaining LBI increased 2.8-fold when a history of LBI was present and increased by 3% with each millisecond of abdominal muscle shut-off latency. On average, this latency was 14 milliseconds longer for athletes who sustained LBI in comparison to athletes who did not sustain LBI (77 [36] vs. 63 [31]). There were no significant changes in any of the muscle response latencies on retest following the injury. Conclusions. The delayed muscle reflex response significantly increases the odds of sustaining an LBI. These delayed latencies appear to be a preexisting risk factor and not the effect of an LBI.

Comparison of Trunk Proprioception Between Patients With Low Back Pain and Healthy Controls

OBJECTIVE To determine whether proprioceptive impairments exist in patients with low back pain (LBP). We hypothesized that patients with LBP would exhibit larger trunk proprioception errors than healthy controls. DESIGN Case-control study. SETTING University laboratory. PARTICIPANTS 24 patients with nonspecific LBP and 24 age-matched healthy controls. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES We measured trunk proprioception in all 3 anatomical planes using motion perception threshold, active repositioning, and passive repositioning tests. RESULTS LBP patients had significantly greater motion perception threshold than controls (P<.001) (1.3+/-0.9 degrees vs 0.8+/-0.6 degrees ). Furthermore, all subjects had the largest motion perception threshold in the transverse plane (P<.001) (1.2+/-0.7 degrees vs 1.0+/-0.8 degrees for all other planes averaged). There was no significant difference between LBP and healthy control groups in the repositioning tasks. Errors in the active repositioning test were significantly smaller than in the passive repositioning test (P=.032) (1.9+/-1.2 degrees vs 2.3+/-1.4 degrees ). CONCLUSIONS These findings suggest that impairments in proprioception may be detected in patients with LBP when assessed with a motion perception threshold measure.

Lumbar position sense and the risk of low back injuries in college athletes: a prospective cohort study.

BackgroundImpaired proprioception in the lumbar spine has often been reported in people with low back pain. However, no prospective studies exist to assert the cause and effect of this association. We hypothesized that athletes with a history of low back injury (LBI) would demonstrate poorer lumbar position sense (PS) than athletes without a history of LBI, and that this deficit would be a risk factor for future LBI.MethodsThis was a prospective cohort study with 2–3 year follow-up. Lumbar spine PS in the transverse plane was evaluated in 292 athletes using three tests: 1) passive and 2) active trunk repositioning, and 3) motion perception threshold. Mean absolute (accuracy) and variable (precision) errors were computed.ResultsThere were no significant differences in the repositioning errors or motion perception threshold between athletes with and without a history of LBI or between those who did and did not get injured during the follow-up. Active trunk repositioning resulted in smaller errors than passive repositioning (1.6°± 0.8°) versus 2.1°± 1.0°) and 1.7°± 0.8°) versus 2.3°± 1.1°) for the absolute and relative errors, respectively).ConclusionPoor trunk PS in transverse plane is not associated with LBI in athletes, nor does it appear that poor trunk PS predisposes athletes to LBI.

Spine stability: Lessons from balancing a stick

This paper introduces control concepts that are important for ensuring stability. To clarify these concepts, a series of experiments using a simple task of stick balancing will be performed. The lessons from these experiments will be applied to the spine system and illustrated with clinical examples. Insight into the following will be gained: what information is used to stabilize the spine, how does noise in control affect spine performance, how has the spine evolved to allow it to be stabilized and controlled in a metabolically efficient way, how do delays in control affect spine performance, and how do different goals (i.e., maximizing performance versus minimizing fatigue) affect the logic for controlling the spine?

The effects of stochastic resonance stimulation on spine proprioception and postural control in chronic low back pain patients.

Study Design. Spine proprioception and postural control in unstable sitting were compared in 18 chronic low back pain patients using a repeated measures design. Objective. The study objective was to determine if stochastic resonance (SR) stimulation of the paraspinal muscles improves spine proprioception and trunk postural control. Summary of Background Data. Decreased spine proprioception and larger postural sway have been found in low back pain patients, although several studies have also shown no differences in spine proprioception. Methods. Spine proprioception, measuring subjects’ sensitivity to change in position, was assessed in 3 orthopaedic planes. Postural control was assessed using an unstable seat with a hemisphere attached to the bottom. Subjects balanced with eyes closed on the most challenging size hemisphere they could manage while center-of-pressure was recorded with a force plate beneath the seat. Both tasks were performed with SR stimulation randomized at 0%, 25%, 50%, and 90% intensity levels. Results. No significant differences in spine proprioception were observed between SR stimulation levels for any of the 3 orthopaedic planes. SR stimulation significantly improved postural control, but only in the lateral plane. No differences in postural control were observed between stimulation levels 25%, 50%, and 90% in the lateral plane. There was no correlation between spine proprioception and postural control. Conclusion. Results suggest that SR stimulation to the paraspinal muscles can improve postural control; however, this improvement cannot be attributed to improved spine proprioception based on the current study. People with compromised neuromuscular control or those exposed to unstable environments may benefit from SR stimulation.

Comparison of trunk stiffness provided by different design characteristics of lumbosacral orthoses

BACKGROUND Lumbosacral orthoses (LSOs) are class I medical devices that are used in conservative and postoperative management of low back pain. The effectiveness of LSOs depends on their design aimed at enhancing trunk stiffness. Therefore, the purpose of this study was to compare two lumbar supports: extensible (made of neoprene and lycra) and non-extensible (made of polyester and nylon). METHODS Trunk stiffness and damping was estimated from trunk displacement data in response to a quick force release in trunk flexion, extension, and lateral bending. Fourteen male and 6 female subjects performed five trials at each experimental condition: (1) No LSO, (2) extensible LSO, (3) non-extensible LSO, (4) non-extensible LSO with a small rigid front panel, and (5) non-extensible LSO with a large rigid front panel. Testing order was randomized and the LSOs were cinched to a pressure of 70 mmHg (9.4 kPa) measured between posterior aspect of the iliac crest and the orthosis. FINDINGS The non-extensible LSO reduced trunk displacement by 14% and increased trunk stiffness by 14% (P<0.001). The extensible LSO did not result in any significant change in trunk displacement or stiffness. The addition of rigid front panels to the non-extensible LSO did not improve its effectiveness. The trunk damping did not differ between the LSO conditions. INTERPRETATION A non-extensible LSO is more effective in augmenting trunk stiffness and limiting trunk motion following a perturbation than an extensible LSO. The rigid front panels do not provide any additional trunk stiffness most likely due to incongruence created between the body and a brace.

Reliability of assessing trunk motor control using position and force tracking and stabilization tasks

System-based methods have been applied to assess trunk motor control in people with and without back pain, although the reliability of these methods has yet to be established. Therefore, the goal of this study was to quantify within- and between-day reliability using systems-based methods involving position and force tracking and stabilization tasks. Ten healthy subjects performed six tasks, involving tracking and stabilizing of trunk angular position in the sagittal plane, and trunk flexion and extension force. Tracking tasks involved following a one-dimensional, time-varying input signal displayed on a screen by changing trunk position (position tracking) or trunk force (force tracking). Stabilization tasks involved maintaining a constant trunk position (position stabilization) or constant trunk force (force stabilization) while a sagittal plane disturbance input was applied to the pelvis using a robotic platform. Time and frequency domain assessments of error (root mean square and H2 norm, respectively) were computed for each task on two separate days. Intra-class correlation coefficients (ICC) for error and coefficients of multiple correlations (CMC) for frequency response curves were used to quantify reliability of each task. Reliability for all tasks was excellent (between-day ICC≥0.8 and CMC>0.75, within-day CMC>0.85). Therefore, position and force control tasks used to assess trunk motor control can be deemed reliable.

Frequency domain mediolateral balance assessment using a center of pressure tracking task

Since impaired mediolateral balance can increase fall risk, especially in the elderly, its quantification and training might be a powerful preventive tool. We propose a visual tracking task (VTT) with increasing frequencies (.3-2.0Hz) and with center of pressure as visual feedback as an assessment method. This mediolateral balance assessment (MELBA) consists of two tasks, tracking a predictable target signal to determine physical capacity and tracking an unpredictable target signal to determine sensorimotor integration limitations. Within and between sessions learning effects and reliability in balance performance descriptors in both tasks were studied in 20 young adults. Balance performance was expressed as the phase-shift (PS) and gain (G) between the target and CoP in the frequency domain and cut-off frequencies at which the performance dropped. Results showed significant differences between the MELBA tasks in PS and G indicating a lower delay and higher accuracy in tracking the predictable target. Significant within and between sessions learning effects for the same measures were found only for the unpredictable task. Reliability of the cut-off frequencies at which PS and G performance declined and the average values within cut-off frequencies was fair to good (ICC .46-.66) for the unpredictable task and fair to excellent for the predictable task (ICC .68-.87). In conclusion, MELBA can reliably quantify balance performance using a predictable VTT. Additionally, the unpredictable tasks can give insight into the visuomotor integration mechanisms controlling balance and highlights MELBAs potential as a training tool.