Anthony S. Kulas

Intratester and Intertester Reliability of Clinical Measures of Lower Extremity Anatomic Characteristics: Implications for Multicenter Studies

ObjectiveTo determine whether multiple examiners could be trained to measure lower extremity anatomic characteristics with acceptable reliability and precision, both within (intratester) and between (intertester) testers. We also determined whether testers trained 18 months apart could perform these measurements with good agreement. SettingUniversitys Applied Neuromechanics Research Laboratory. ParticipantsSixteen, healthy participants (7 men, 9 women). Assessment of Risk FactorsSix investigators measured 12 anatomic characteristics on the right lower extremity in the Fall of 2004. Four testers underwent training immediately preceding the study, and measured subjects on 2 separate days to examine intratester reliability. Two testers trained 18 months before the study (Spring 2002) measured each subject on day 1 to examine the consistency of intertester reliability when testers are trained at different times. Main Outcome MeasurementsKnee laxity, genu recurvatum, quadriceps angle, tibial torsion, tibiofemoral angle, hamstring extensibility, pelvic angle, navicular drop, femur length, tibial length, and hip anteversion. ResultsWith few exceptions, all testers consistently measured each variable between test days (intraclass correlation coefficient≥0.80). Intraclass correlation coefficient values were lower for intertester reliability (0.48 to 0.97), and improved from day 1 to day 2. Intertester reliability was similar when comparing testers trained 18 months before those trained immediately before the study. Absolute measurement error varied considerably across individual testers. ConclusionsMultiple investigators can be trained at different times to measure anatomic characteristics with good to excellent intratester reliability. Intratester reliability did not always ensure acceptable intertester reliability or measurement precision, suggesting more training (or more experience) may be required to achieve acceptable measurement reliability and precision between multiple testers.

The Interaction of Trunk-Load and Trunk-Position Adaptations on Knee Anterior Shear and Hamstrings Muscle Forces During Landing

CONTEXT Because anterior cruciate ligament (ACL) injuries can occur during deceleration maneuvers, biomechanics research has been focused on the lower extremity kinetic chain. Trunk mass and changes in trunk position affect lower extremity joint torques and work during gait and landing, but how the trunk affects knee joint and muscle forces is not well understood. OBJECTIVE To evaluate the effects of added trunk load and adaptations to trunk position on knee anterior shear and knee muscle forces in landing. DESIGN Crossover study. SETTING Controlled laboratory environment. PATIENTS OR OTHER PARTICIPANTS Twenty-one participants (10 men: age = 20.3 +/- 1.15 years, height = 1.82 +/- 0.04 m, mass = 78.2 +/- 7.3 kg; 11 women: age = 20.0 +/- 1.10 years, height = 1.72 +/- 0.06 m, mass = 62.3 +/- 6.4 kg). INTERVENTION(S) Participants performed 2 sets of 8 double-leg landings under 2 conditions: no load and trunk load (10% body mass). Participants were categorized into one of 2 groups based on the kinematic trunk adaptation to the load: trunk flexor or trunk extensor. MAIN OUTCOME MEASURE(S) We estimated peak and average knee anterior shear, quadriceps, hamstrings, and gastrocnemius forces with a biomechanical model. RESULTS We found condition-by-group interactions showing that adding a trunk load increased peak (17%) and average (35%) knee anterior shear forces in the trunk-extensor group but did not increase them in the trunk-flexor group (peak: F(1,19) = 10.56, P = .004; average: F(1,19) = 9.56, P = .006). We also found a main effect for condition for quadriceps and gastrocnemius forces. When trunk load was added, peak (6%; F(1,19) = 5.52, P = .030) and average (8%; F(1,19) = 8.83, P = .008) quadriceps forces increased and average (4%; F(1,19) = 4.94, P = .039) gastrocnemius forces increased, regardless of group. We found a condition-by-group interaction for peak (F(1,19) = 5.16, P = .035) and average (F(1,19) = 12.35, P = .002) hamstrings forces. When trunk load was added, average hamstrings forces decreased by 16% in the trunk-extensor group but increased by 13% in the trunk-flexor group. CONCLUSIONS Added trunk loads increased knee anterior shear and knee muscle forces, depending on trunk adaptation strategy. The trunk-extensor adaptation to the load resulted in a quadriceps-dominant strategy that increased knee anterior shear forces. Trunk-flexor adaptations may serve as a protective strategy against the added load. These findings should be interpreted with caution, as only the face validity of the biomechanical model was assessed.

Trunk position modulates anterior cruciate ligament forces and strains during a single-leg squat

BACKGROUND Although the squat exercise and its variations are commonly prescribed for anterior cruciate ligament rehabilitation, whether trunk position affects these ligament forces and strains during the squat is unclear. Our purpose was to evaluate the effects of trunk position on anterior cruciate ligament forces and strains during a single-leg squat. METHODS While instrumented for biomechanical analysis, twelve recreationally active subjects performed single-leg squats with minimal and moderate amounts of forward trunk lean. A combination of inverse dynamics, Hill-type muscle modeling, and mathematical computations estimated anterior cruciate ligament forces, strains and quadriceps, hamstrings, and gastrocnemius forces. FINDINGS The moderate forward trunk lean condition vs. minimal forward trunk lean condition had lower peak anterior cruciate ligament forces (↓24%), strains (↓16%), and average anterior cruciate ligament forces and strains during knee flexion ranges of motion of 25-55°(descent) and 35-55°(ascent). A moderate vs. minimal forward trunk lean also produced 35% higher hamstring forces throughout the majority of the squat, but lower quadriceps forces only at knee flexion angles greater than 65°. INTERPRETATION Single-leg squats performed with a moderate forward trunk lean (~40°) can minimize anterior cruciate ligament loads. Mechanistically, trunk lean reduced anterior cruciate ligament forces and strains through concomitant modulations in hip flexion angle and biarticular thigh muscle forces. These findings are clinically relevant for anterior cruciate ligament rehabilitation as a common goal is to minimize anterior cruciate ligament forces and strains through enhancing hamstring and quadriceps co-contractions.

Reliability and Precision of Stress Sonography of the Ulnar Collateral Ligament

Musculoskeletal sonography has emerged as an additional diagnostic tool that can be used to assess medial elbow pain and laxity in overhead throwers. It provides a dynamic, rapid, and noninvasive modality in the evaluation of ligamentous structural integrity. Many studies have demonstrated the utility of dynamic sonography for medial elbow and ulnar collateral ligament (UCL) integrity. However, evaluating the reliabilityand precision of these measurements is critical if sonography is ultimately used as a clinical diagnostic tool. The purpose of this study was to evaluate the reliability and precision of stress sonography applied to the medial elbow.

Heterogeneous fascicle behavior within the biceps femoris long head at different muscle activation levels

Magnetic resonance and ultrasound imaging have shown hamstring strain injuries occur most often in the biceps femoris long head (BFLH), and particularly in the proximal vs. distal region of this muscle. Animal research and musculoskeletal modeling (MSK) have detected heterogeneous fascicle behavior within muscle regions, and within fascicles. Understanding architectural behavior differences during muscle contractions may help to discern possible mechanisms behind proximal BFLH injuries. The purpose of our study was to assess the magnitude of shortening of the proximal and distal fascicles of the BFLH under a range of muscle activation levels under isometric conditions using ultrasound imaging (US). Thirteen healthy adults performed targeted sustained isometric contractions while US were taken of the entire BFLH. Measurements of fascicle lengths in both muscle regions were compared at 20%, 30%, 50%, and 67% MVIC. The results showed that while both regions shortened significantly with activation, the proximal fascicles were significantly longer, regardless of activation level (~38%), and shortened significantly more than the distal fascicles overall (~40%), and cumulatively at higher activation levels (30% and above). No significant strain differences were found between the two regions. These data suggest heterogeneous fascicle behavior exists in an absolute sense; however, differences in behavior are eliminated when normalized (strain). Coupled with MSK literature, the absence of regional fascicle strain differences in this study may indicate strain heterogeneity is not detectable at the whole fascicle level. Further knowledge of this commonly strained muscles regional behavior during dynamic movements could provide evidence of proximal hamstring strain predisposition.

Relationships of hamstring muscle volumes to lateral tibial slope.

BACKGROUND Greater posterior-inferior directed slope of the lateral tibial plateau (LTS) has been demonstrated to be a prospective ACL injury risk factor. Trainable measures to overcome a greater LTS need to be identified for optimizing injury prevention protocols. It was hypothesized that Healthy individuals with greater LTS who have not sustained an ACL injury would have a larger lateral hamstring volume. METHODS Eleven healthy females (mean +/- standard deviation) (1.63±0.07m, 62.0±8.9kg, 22.6±2.9years) & 10 healthy males (1.80±0.08m, 82.3±12.0kg, 23.2±3.4years) underwent magnetic resonance imaging of the left knee and thigh. LTS, semitendinosus muscle volume, and biceps femoris long head muscle volume were obtained from imaging data. RESULTS After controlling for potential sex confounds (R2=.00; P=.862), lesser semitendinosus volume and greater biceps femoris-long head volume were indicative of greater LTS (R2∆=.30, P=.008). CONCLUSIONS Healthy individuals with greater LTS have a muscular morphologic profile that includes a larger biceps femoris-long head volume. This may be indicative of a biomechanical strategy that relies more heavily on force generation of the lateral hamstring and is less reliant on force generation of the medial hamstring. LEVEL OF EVIDENCE Level IV.

Applying the socio-ecological model to barriers to implementation of ACL injury prevention programs: a systematic review

Background Preventing anterior cruciate ligament (ACL) injuries is important to avoid long-term adverse health consequences. Identifying barriers to implementation of these prevention programs is crucial to reducing the incidence of these injuries. Our purpose was to identify barriers of implementation for ACL injury prevention programs and suggest mechanisms for reducing the barriers through application of a Socio-Ecological Model (SEM). Methods Studies investigating ACL prevention program effectiveness were searched in Medline via PubMed and the Cochrane Library, and a subsequent review of the references of the identified articles, yielded 15 articles total. Inclusion criteria encompassed prospective controlled trials, published in English, with ACL injuries as the primary outcome. Studies were independently appraised by 2 reviewers for methodological quality using the PEDro scale. Barriers to implementation were identified when reported in at least 2 separate studies. A SEM was used to suggest ways to reduce the identified barriers. Results Five barriers were identified: motivation, time requirements, skill requirements for program facilitators, compliance, and cost. The SEM suggested ways to minimize the barriers at all levels of the model from the individual through policy levels. Conclusion Identification of barriers to program implementation and suggesting how to reduce them through the SEM is a critical first step toward enabling ACL prevention programs to be more effective and ultimately reducing the incidence of these injuries.

Bilateral quadriceps and hamstrings muscle volume asymmetries in healthy individuals

Determining the magnitude of quadriceps and hamstring muscle volume asymmetries in healthy individuals is a critical first step toward interpreting asymmetries as compensatory or abnormal in pathological populations. The purpose of this study was to determine the magnitude of whole and individual muscle volume asymmetries, quantified as right–left volume differences, for the quadriceps and hamstring muscles in a young and healthy population. Twenty‐one healthy individuals participated: Eleven females age = 22.6 ± 2.9 years and 10 males age = 23.2 ± 3.4 years. Whole muscle group and individual muscle volume asymmetries were quantified within the context of absolute measurement error using a 95% Limits of Agreement approach. Mean muscle asymmetries ranged from −3.0 to 6.0% for all individual and whole muscle groups. Whole muscle group 95% limits of agreements represented ±11.4% and ±8.8% volume asymmetries for the hamstrings and quadriceps, respectively. Individual muscle asymmetry 95% limits of agreements ranged from ∼ ± 11–13% for the vastii muscles while the biceps femoris short‐head (±33.5%), long‐head (±20.9%), and the rectus femoris (±21.4%) displayed the highest relative individual asymmetries. Individual muscle asymmetries exceeded absolute measurement error in 70% of all cases, with 26% of all cases exceeding 10% asymmetry. Although whole muscle group asymmetries appear to be near the 10% assumed clinical threshold of normality, the greater magnitude of individual muscle asymmetries highlights the subject‐ and muscle‐specific variability in volume asymmetry. Future research is warranted to determine if volume asymmetry thresholds exist that discriminate between healthy and pathological populations. Statement of Clinical Significance: Muscle volume asymmetries displayed in healthy individuals provide a reference for interpreting asymmetries in pathological populations.