Grant E. Norte

Relationship between transcranial magnetic stimulation and percutaneous electrical stimulation in determining the quadriceps central activation ratio.

Norte GE, Pietrosimone BG, Hart JM, Hertel J, Ingersoll CD: Relationship between transcranial magnetic stimulation and percutaneous electrical stimulation in determining the quadriceps central activation ratio. Objective:To determine the relationship between quadriceps central activation ratios (CARs) derived from a percutaneous electrical stimulation (CARSIB) and a transcranial magnetic stimulation (CARTMS) in healthy participants. Design:Nineteen healthy participants (5 men, 14 women, 23.7 ± 4.8 yrs, 66.8 ± 10.0 kg, and 170.1 ± 7.0 cm) qualified for this descriptive study. Muscle activation, using both methods (CARSIB and CARTMS), was measured at days 1, 14, and 28. All participants performed both methods in a counterbalanced order. Correlation coefficients and Bland-Altman plots were used to assess relationships and agreement between the two methods. For both methods, reliability was assessed at 14 and 28 days using Bland-Altman plots and intraclass correlation coefficients. Results:CARTMS scores were higher than CARSIB scores for all three sessions, with mean differences between CAR scores of −0.06 (95% confidence interval, −0.19–0.07), −0.03 (95% confidence interval, −0.14–0.08), and −0.03 (95% confidence interval, −0.11–0.05). There was a significant moderate positive correlation between CARSIB and CARTMS at 14 days from baseline (&rgr; = 0.45, P = 0.05). Intersession reliability was strong for CARSIB at 14 and 28 days from baseline (intraclass correlation coefficients = 0.80 [P = 0.001] and 0.85 [P < 0.001], respectively). Intersession reliability for CARTMS was moderate from baseline to 14 days (intraclass correlation coefficients = 0.68 [P = 0.01]). Conclusions:It does not seem that the CARTMS and CARSIB methods are interchangeable measurements for evaluating volitional quadriceps activation; however, both measurements seem to have acceptable agreement at 14 and 28 days compared with day 1.

Reliability of the Superimposed-Burst Technique in Patients With Patellofemoral Pain: A Technical Report.

CONTEXT The superimposed-burst (SIB) technique is commonly used to quantify central activation failure after knee-joint injury, but its reliability has not been established in pathologic cohorts. OBJECTIVE To assess within-session and between-sessions reliability of the SIB technique in patients with patellofemoral pain. DESIGN Descriptive laboratory study. SETTING University laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 10 patients with self-reported patellofemoral pain (1 man, 9 women; age = 24.1 ± 3.8 years, height = 167.8 ± 15.2 cm, mass = 71.6 ± 17.5 kg) and 10 healthy control participants (3 men, 7 women; age = 27.4 ± 5.0 years, height = 173.5 ± 9.9 cm, mass = 78.2 ± 16.5 kg) volunteered. INTERVENTION(S) Participants were assessed at 6 intervals spanning 21 days. Intraclass correlation coefficients (ICCs [3,3]) were used to assess reliability. MAIN OUTCOME MEASURE(S) Quadriceps central activation ratio, knee-extension maximal voluntary isometric contraction force, and SIB force. RESULTS The quadriceps central activation ratio was highly reliable within session (ICC [3,3] = 0.97) and between sessions through day 21 (ICC [3,3] = 0.90-0.95). Acceptable reliability of knee extension (ICC [3,3] = 0.75-0.91) and SIB force (ICC [3,3] = 0.77-0.89) was observed through day 21. CONCLUSIONS The SIB technique was reliable for clinical research up to 21 days in patients with patellofemoral pain.

Immediate Effects of Therapeutic Ultrasound on Quadriceps Spinal Reflex Excitability in Patients With Knee Injury

OBJECTIVE To investigate the effects of nonthermal therapeutic ultrasound on quadriceps spinal reflex excitability in patients with knee joint injury. DESIGN Double-blind, randomized controlled laboratory study with a pretest posttest design. SETTING University laboratory. PARTICIPANTS Recreationally active volunteers with a self-reported history of diagnosed intra-articular knee joint injury and documented quadriceps dysfunction (N=30). INTERVENTIONS A nonthermal ultrasound, or sham, treatment was applied to the anteromedial knee. MAIN OUTCOME MEASURES Hoffmann reflex measurements were recorded at baseline, immediately postintervention, and 20 minutes post-intervention. The peak Hoffmann reflex amplitude was normalized by the peak motor response (H/M ratio) measured from the vastus medialis using surface electromyography as an estimate of quadriceps motorneuron pool excitability. A repeated-measures analysis of variance was used for comparisons. RESULTS A significant group-by-time interaction was observed for mean (P=.016) and change (P=.044) in H/M ratio. The ultrasound group demonstrated significantly higher mean (P=.015) and change (P=.028) in H/M ratio 20 minutes postintervention than did the sham ultrasound group. CONCLUSIONS Quadriceps motoneuron pool excitability was facilitated 20 minutes after a nonthermal therapeutic ultrasound treatment, and not a sham treatment. These data provide supporting evidence of the contribution of peripheral receptors in modulation of the arthrogenic response in patients with persistent quadriceps dysfunction. Future research in this area should attempt to identify optimal treatment parameters and translate them to clinical outcomes.

Surface electromyography of the forearm musculature during an overhead throwing rehabilitation progression program

OBJECTIVE The flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) provide dynamic stabilization to the medial elbow. It remains unclear how these muscles function during progressive throwing exercises. Our objective was to compare FCU and FDS surface electromyography (sEMG) during a throwing progression. DESIGN Crossover. SETTING Laboratory. PARTICIPANTS Sixteen healthy males. MAIN OUTCOME MEASURES Participants completed a plyometric throw (PLYO), long-toss 50% (LT50), long-toss 75% (LT75), and pitch (PITCH). sEMG was synchronized with three-dimensional kinematics to assess the acceleration phase of each exercise. Peak sEMG amplitude (%MVIC) and percentage change between progressive exercises was measured. Continuous sEMG data were assessed to determine when peak activation occurred during acceleration. RESULTS FCU activity was greater during PITCH than LT50, and during LT75 than LT50. Percentage change was greater from LT50-to-LT75 than PLYO-to-LT50 for both muscles. PLYO and PITCH increased most during late acceleration, whereas LT50 and LT75 increased most during mid-acceleration. CONCLUSIONS FCU activity did not increase in a stepwise manner, and FDS remained unchanged. Each muscle demonstrated a disproportionate increase in activation during the second exercise progression (LT50-to-LT75) compared to the first (PLYO-to-LT50), suggesting that additional exercises may be required to achieve a stepwise progression relative to forearm muscle activation.

Quadriceps Neuromuscular Function in Patients With Anterior Cruciate Ligament Reconstruction With or Without Knee Osteoarthritis: A Cross-Sectional Study

CONTEXT   Central and peripheral neural adaptations have been identified after anterior cruciate ligament (ACL) injury and reconstruction (ACLR) and are hypothesized to contribute to posttraumatic muscle dysfunction. Limited evidence exists about the temporal nature of neuromuscular adaptations during early and late-term phases of recovery after ACLR, and no researchers have studied patients with posttraumatic osteoarthritis. OBJECTIVE   To compare quadriceps neuromuscular function less than 2 years ( early) and more than 2 years ( late) after ACLR, including in patients who experienced posttraumatic knee osteoarthritis. DESIGN   Cross-sectional study. SETTING   Laboratory. PATIENTS OR OTHER PARTICIPANTS   A total of 72 patients after ACLR, consisting of 34 early (9.0 ± 4.3 months postsurgery), 30 late (70.5 ± 41.6 months postsurgery), and 8 with osteoarthritis (115.9 ± 110.0 months postsurgery), and 30 healthy control volunteers. MAIN OUTCOME MEASURE(S)   Quadriceps function was measured bilaterally during a single visit to determine normalized Hoffmann reflex (H : M ratio), knee-extension maximal voluntary isometric contraction torque (Nm/kg), central activation ratio (%), fatigue index (% decline), and active motor threshold (%). Comparisons were made using 2-way analyses of variance to identify the effect of limb and group on each outcome measure. We calculated Cohen d effect sizes to assess the magnitude of difference between ACLR and matched control limbs for each group. RESULTS   Compared with healthy control limbs, involved-limb maximal voluntary isometric contraction was lower among all patients after ACLR ( P < .001, Cohen d values = -1.00 to -1.75). The central activation ratio ( P < .001, Cohen d = -1.74) and fatigue index ( P = .003, Cohen d = -0.95) were lower among patients only early after ACLR. The active motor threshold was higher among all patients after ACLR ( P < .001, Cohen d values = -0.42 to -1.56). CONCLUSIONS   Neuromuscular impairments were present in patients early and late after ACLR, regardless of osteoarthritis status. Quadriceps strength and corticospinal excitability were impaired at each time point compared with values in healthy control individuals, suggesting the need to address cortical function early after ACLR.

Quadriceps Function and Patient-Reported Outcomes After Anterior Cruciate Ligament Reconstruction in Patients With or Without Knee Osteoarthritis

CONTEXT Relationships between quadriceps function and patient-reported outcomes after anterior cruciate ligament reconstruction (ACLR) are variable and may be confounded by including patients at widely different time points after surgery. Understanding these relationships during the clinically relevant phases of recovery may improve our knowledge of specific factors that influence clinical outcomes. OBJECTIVE To identify the relationships between quadriceps function and patient-reported outcomes in patients <2 years (early) and >2 years (late) after ACLR, including those with posttraumatic knee osteoarthritis. DESIGN Cross-sectional study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 72 patients after ACLR: early (n = 34, time from surgery = 9.0 ± 4.3 months), late (n = 30, time from surgery = 70.5 ± 41.6 months), or osteoarthritis (n = 8, time from surgery = 115.9 ± 110.0 months). MAIN OUTCOME MEASURE(S) The total Knee Injury and Osteoarthritis Outcome Score (KOOS) and Veterans RAND 12-Item Health Survey (VR-12) were used to quantify knee function and global health. Predictors of patient-reported outcomes were involved-limb and symmetry indices of quadriceps function (isokinetic strength [peak torque, total work, average power], maximum voluntary isometric contraction torque, fatigue index, central activation ratio, Hoffmann reflex, active motor threshold) and demographics (age, activity level, pain, kinesiophobia, time since surgery). Multiple linear regression analyses were used to predict KOOS and VR-12 scores in each group. RESULTS In the early patients, knee-extensor work, active motor threshold symmetry, pain, and activity level explained 67.8% of the variance in the KOOS score ( P < .001); knee-extensor work, activity level, and pain explained 53.0% of the variance in the VR-12 score ( P < .001). In the late patients, age and isokinetic torque symmetry explained 28.9% of the variance in the KOOS score ( P = .004). In the osteoarthritis patients, kinesiophobia and isokinetic torque explained 77.8% of the variance in the KOOS score ( P = .010); activity level explained 86.4% of the variance in the VR-12 score ( P = .001). CONCLUSIONS Factors of muscle function and demographics that explain patient-reported outcomes were different in patients early and late after ACLR and in those with knee osteoarthritis.

ACL reconstructed individuals do not demonstrate deficits in postural control as measured by single-leg balance

BACKGROUND Following anterior cruciate ligament reconstruction (ACLR), patients undergo a battery of performance assessments to determine progression of return to sport activity. Rates of reinjury following ACLR are high, indicating that current assessments may not accurately identify deficits at the time point of return to sport progression. RESEARCH QUESTION To assess single-leg postural control in ACLR patients around the time point of return to sport progression and their relationships to subjective function. STUDY DESIGN Descriptive Laboratory Study. METHODS 198 individuals (108 ACLR, 90 healthy) participated. All ACLR participants were at the time point of return to play progression. Postural stability was quantified by center of pressure (COP) average velocity measured through a straight-knee single-leg balance assessment for 10-seconds with the participants eyes closed. Subjective knee function was measured from the International Knee Documentation Committee (IKDC) Subjective Knee Form and the Knee Osteoarthritis Outcome Score (KOOS) subscales. RESULTS No significant differences existed between COP average velocity between limbs (uninvolved, involved) or groups (ACLR, Healthy). As a secondary aim, no significant relationships existed between measures of subjective knee function and postural stability. SIGNIFICANCE Individuals following ACLR demonstrate similar patterns of postural stability as healthy individuals in a straight knee single leg balance task. Single-leg balance in a straight knee position may not be sensitive enough to detect impairments and does not predict subjective function in ACLR patients at the time of return to sport progression.

A Comparison of Cervical Spine Motion After Immobilization With a Traditional Spine Board and Full-Body Vacuum-Mattress Splint:

Background: The National Athletic Trainers’ Association (NATA) advocates for cervical spine immobilization on a rigid board or vacuum splint and for removal of athletic equipment before transfer to an emergency medical facility. Purpose: To (1) compare triplanar cervical spine motion using motion capture between a traditional rigid spine board and a full-body vacuum splint in equipped and unequipped athletes, (2) assess cervical spine motion during the removal of a football helmet and shoulder pads, and (3) evaluate the effect of body mass on cervical spine motion. Study Design: Controlled laboratory study. Methods: Twenty healthy male participants volunteered for this study to examine the influence of immobilization type and presence of equipment on triplanar angular cervical spine motion. Three-dimensional cervical spine kinematics was measured using an electromagnetic motion analysis system. Independent variables included testing condition (static lift and hold, 30° tilt, transfer, equipment removal), immobilization type (rigid, vacuum-mattress), and equipment (on, off). Peak sagittal-, frontal-, and transverse-plane angular motions were the primary outcome measures of interest. Results: Subjective ratings of comfort and security did not differ between immobilization types (P > .05). Motion between the rigid board and vacuum splint did not differ by more than 2° under any testing condition, either with or without equipment. In removing equipment, the mean peak motion ranged from 12.5° to 14.0° for the rigid spine board and from 11.4° to 15.4° for the vacuum-mattress splint, and more transverse-plane motion occurred when using the vacuum-mattress splint compared with the rigid spine board (mean difference, 0.14 deg/s [95% CI, 0.05-0.23 deg/s]; P = .002). In patients weighing more than 250 lb, the rigid board provided less motion in the frontal plane (P = .027) and sagittal plane (P = .030) during the tilt condition and transfer condition, respectively. Conclusion: The current study confirms similar motion in the vacuum-mattress splint compared with the rigid backboard in varying sized equipped or nonequipped athletes. Cervical spine motion occurs when removing a football helmet and shoulder pads, at an unknown risk to the injured athlete. In athletes who weighed more than 250 lb, immobilization with the rigid board helped to reduce cervical spine motion. Clinical Relevance: Athletic trainers and team physicians should consider immobilization of athletes who weigh more than 250 lb with a rigid board.

The Utility of Objective Strength and Functional Performance to Predict Subjective Outcomes After Anterior Cruciate Ligament Reconstruction

Background: Many clinicians release patients to return to activity after anterior cruciate ligament reconstruction (ACLR) based on time from surgery despite deficits in muscle strength and function. It is unclear whether symmetry or unilateral performance is the best predictor of subjective outcomes after ACLR. Purpose: To determine physical performance predictors of patient-reported outcomes after reconstruction. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 88 participants (49 males, 39 females; mean ± SD height, 174.0 ± 9.6 cm; weight, 76.1 ± 18.5 kg; age, 19.4 ± 3.7 years) who underwent primary, unilateral ACLR volunteered for this study. Participants had undergone reconstruction a mean of 6.9 ± 1.8 months (range, 5.0-14.1 months) before the study. All participants underwent strength testing as well as hop testing and then completed the International Knee Documentation Committee (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaires. Stepwise linear regression models were used for symmetry and unilateral performance to identify the proportion of variance explained in the IKDC score, KOOS total score, KOOS-sport subscale, and time from surgery, as well as receiver operating characteristic (ROC) curve analyses on those variables that explained the most variance in patient-reported outcomes to determine cutoff thresholds. Results: No significant correlations were found between time from surgery and objective performance. The only significant predictors of IKDC score were single-hop limb symmetry index (LSI) and age (R 2 = 0.177) and unilateral triple-hop performance and age (R 2 = 0.228). The cutoff for single-hop symmetry was 0.92 (area under the curve [AUC], 0.703; P = .012), and the cutoff for normalized triple-hop distance was 3.93 (AUC, 0.726; P = .005). When stratified by age, the cutoff for single-hop symmetry was 0.81 (AUC, 0.721; P = .051) for younger patients (age <19.1 years) and was not significant for older patients (age ≥19.1 years). The cutoff for normalized triple-hop distance was 3.85 (AUC, 0.832; P = .005) in older patients and was not significant for younger patients. The only significant predictors of KOOS-sport subscale were single-hop LSI (R 2 = 0.140) and normalized knee extensor power at 180 deg/s (R 2 = 0.096). When subjective outcomes were predicted based on KOOS-sport subscale, the cutoff for single-hop symmetry was 0.85 (AUC, 0.692; P = .018). Conclusion: Hopping performance is the most predictive functional variable of subjective outcomes after reconstruction. Single-hop symmetry was most important for younger patients and unilateral triple-hop distance was most important for older patients. Clinicians should consider hopping performance when making return-to-activity decisions after ACLR.

Peroneal Nerve Dysfunction due to Multiligament Knee Injury: Patient Characteristics and Comparative Outcomes After Posterior Tibial Tendon Transfer.

Objective: To objectively compare outcomes of nonoperative management and posterior tibial tendon (PTT) transfer for peroneal nerve injury due to multiligament knee injury (MLI). Design: Retrospective cohort study with prospective follow-up. Setting: Tertiary care institution. Patients: Ten patients with peroneal nerve injury due to MLI (5 managed nonoperatively, 5 with PTT transfer) were evaluated and a control group of 4 patients without peroneal nerve injury. Interventions: Clinical examination, subjective questionnaires, and 3-D motion capture gait analysis during flat-ground walking and stair descent. Main Outcome Measures: The primary outcome measure was the result of gait analysis. The results of subjective questionnaires were a secondary outcome measure. Results: Dorsiflexion was significantly reduced at initial contact and mid–late swing phase in the nonoperative cohort. The PTT transfer cohort demonstrated increased dorsiflexion at each of these time intervals compared with patients managed nonoperatively, restoring symmetry between limbs. The PTT transfer cohort demonstrated similar gait patterns to controls but tended to be more everted. Ground reaction force was increased in the uninvolved limb in the PTT transfer group during gait and step down. There were no statistically significant differences in AOFAS, FAAM, IKDC, or Lysholm results. Conclusions: Posterior tibial tendon transfer is an option to restore dorsiflexion and eliminate the need for an orthosis in patients with foot drop due to MLI. Gait analysis demonstrates a significant improvement in sagittal plane ankle kinematics after PTT transfer. The trade-off is subtle instability, highlighting the dynamic stability that the PTT provides.