Peter J. Barrance

Mechanisms underlying quadriceps weakness in knee osteoarthritis.

PURPOSE To identify determinants of quadriceps weakness among persons with end-stage knee osteoarthritis (OA). METHODS One-hundred twenty-three individuals (mean age 64.9 +/- 8.5 yr) with Kellgren/Lawrence grade IV knee OA participated. Quadriceps strength (MVIC) and volitional muscle activation (CAR) were measured using a burst superimposition test. Muscle composition (lean muscle cross-sectional area (LMCSA) and fat CSA (FCSA)) were quantified using magnetic resonance imaging. Specific strength (MVIC/LMCSA) was computed. Interlimb differences were analyzed using paired-sample t-tests. Regression analysis was applied to identify determinants of MVIC. An alpha level of 0.05 was adopted. RESULTS The OA limb was significantly weaker, had lower CAR, and had smaller LMCSA than the contralateral limb. CAR explained 17% of the variance in the contralateral limbs MVIC compared with 40% in the OA limb. LMCSA explained 41% of the variance in the contralateral limbs MVIC compared with 27% in the OA limb. CONCLUSION Both reduced CAR and LMCSA contribute to muscle weakness in persons with knee OA. Similar to healthy elders, the best predictor of strength in the contralateral, nondiseased limb was largely determined by LMCSA, whereas CAR was found to be the primary determinant of strength in the OA limb. Deficits in CAR may undermine the effectiveness of volitional strengthening programs in targeting quadriceps weakness in the OA population.

Quadriceps Weakness, Atrophy, and Activation Failure in Predicted Noncopers After Anterior Cruciate Ligament Injury

Background Quadriceps weakness is common after anterior cruciate ligament injury, especially in those who do not compensate well for the injury (“noncopers”). Both atrophy and activation failure have been demonstrated in this population but have not been directly related to quadriceps weakness. Hypotheses (1) Quadriceps strength, volumes, and cross-sectional areas of the noncopers would be smaller than those of the contralateral muscles, whereas other muscles would not demonstrate atrophy. (2) Quadriceps muscle activation deficits would be observed. (3) Atrophy and activation failure would account for the quadriceps weakness in these patients. Study Design Cross-sectional study, Level of evidence, 3. Methods Seventeen noncopers with isolated anterior cruciate ligament injury underwent burst-superimposition strength and activation testing of the quadriceps and magnetic resonance imaging of 12 muscles an average of 2 months after injury. Morphological characteristics was described by digitally reconstructing each muscle from the axial images and calculating muscle volume and peak cross-sectional area. Results The quadriceps muscles of the anterior cruciate ligament-deficient limb were significantly weaker (average 25%) than those of the uninjured side; activation failure (8%-10%) was observed for the quadriceps muscles of both limbs. The total quadriceps, vastus lateralis, and vastus intermedius volume and cross-sectional area were significantly smaller in the anterior cruciate ligament-deficient limb. There was no significant atrophy of any other muscle or muscle group. Atrophy and activation failure explained more than 60% of the variance in quadriceps weakness (P =. 004). Conclusion The quadriceps femoris weakens soon after acute anterior cruciate ligament injury. Activation deficits and atrophy occur and affect quadriceps strength. Rehabilitation techniques that address activation deficits as well as atrophy may be necessary to restore quadriceps strength.

Muscle and Tendon Morphology After Reconstruction of the Anterior Cruciate Ligament with Autologous Semitendinosus-Gracilis Graft

BACKGROUND The autologous semitendinosus-gracilis graft is the first choice of many orthopaedic surgeons when reconstructing the anterior cruciate ligament. The effect that graft harvest has on muscle and tendon morphology remains unclear. The purpose of this study was to describe these effects more completely. METHODS Magnetic resonance images were acquired from eight patients before the anterior cruciate ligament reconstruction with semitendinosus-gracilis autograft and then again postoperatively after they had returned to sports. Muscle and tendon morphology was described by determining the volume and peak cross-sectional area of each structure on digitally reconstructed images. The effects that the procedure had on muscle and tendon length were evaluated separately and then together as a muscle-tendon complex. RESULTS Anterior cruciate ligament reconstruction with semitendinosus-gracilis autograft resulted in a marked decrease in volume, cross-sectional area, and length of the semitendinosus and gracilis muscles. Tendon regeneration occurred in varying degrees in nearly all subjects. The morphology of the biceps femoris and semimembranosus muscles suggested that they had been compensating for the reduced semitendinosus and gracilis muscle function. Although semitendinosus and gracilis muscle retraction occurred following tendon stripping, nearly all of the subjects displayed evidence of at least partial tendon regeneration. CONCLUSIONS Anterior cruciate ligament reconstruction with semitendinosus-gracilis autograft had a marked impact on semitendinosus and gracilis muscle morphology. However, this altered muscle morphology did not appear to have a clinically important impact on short-term outcomes. The biceps femoris and semimembranosus muscles appear to compensate for reduced semitendinosus and gracilis function. Tendon regeneration is observed in most people, but it is often incomplete at six months.

Paretic muscle atrophy and non-contractile tissue content in individual muscles of the post-stroke lower extremity

Muscle atrophy is one of many factors contributing to post-stroke hemiparetic weakness. Since muscle force is a function of muscle size, the amount of muscle atrophy an individual muscle undergoes has implications for its overall force-generating capability post-stroke. In this study, post-stroke atrophy was determined bilaterally in fifteen leg muscles with volumes quantified using magnetic resonance imaging (MRI). All muscle volumes were adjusted to exclude non-contractile tissue content, and muscle atrophy was quantified by comparing the volumes between paretic and non-paretic sides. Non-contractile tissue or intramuscular fat was calculated by determining the amount of tissue excluded from the muscle volume measurement. With the exception of the gracilis, all individual paretic muscles examined had smaller volumes in the non-paretic side. The average decrease in volume for these paretic muscles was 23%. The gracilis volume, on the other hand, was approximately 11% larger on the paretic side. The amount of non-contractile tissue was higher in all paretic muscles except the gracilis, where no difference was observed between sides. To compensate for paretic plantar flexor weakness, one idea might be that use of the paretic gracilis actually causes the muscle to increase in size and not develop intramuscular fat. By eliminating non-contractile tissue from our volume calculations, we have presented volume data that more appropriately represents force-generating muscle tissue. Non-uniform muscle atrophy was observed across muscles and may provide important clues when assessing the effect of muscle atrophy on post-stroke gait.

A Method for Measurement of Joint Kinematics in Vivo by Registration of 3-D Geometric Models With Cine Phase Contrast Magnetic Resonance Imaging Data

A new method is presented for measuring joint kinematics by optimally matching modeled trajectories of geometric surface models of bones with cine phase contrast (cine-PC) magnetic resonance imaging data. The incorporation of the geometric bone models (GBMs) allows computation of kinematics based on coordinate systems placed relative to full 3-D anatomy, as well as quantification of changes in articular contact locations and relative velocities during dynamic motion. These capabilities are additional to those of cine-PC based techniques that have been used previously to measure joint kinematics during activity. Cine-PC magnitude and velocity data are collected on a fixed image plane prescribed through a repetitively moved skeletal joint. The intersection of each GBM with a simulated image plane is calculated as the model moves along a computed trajectory, and cine-PC velocity data are sampled from the regions of the velocity images within the area of this intersection. From the sampled velocity data, the instantaneous linear and angular velocities of a coordinate system fixed to the GBM are estimated, and integration of the linear and angular velocities is used to predict updated trajectories. A moving validation phantom that produces motions and velocity data similar to those observed in an experiment on human knee kinematics was designed. This phantom was used to assess cine-PC rigid body tracking performance by comparing the kinematics of the phantom measured by this method to similar measurements made using a magnetic tracking system. Average differences between the two methods were measured as 2.82 mm rms for anterior/posterior tibial position, and 2.63 deg rms for axial rotation. An intertrial repeatability study of human knee kinematics using the new method produced rms differences in anterior/posterior tibial position and axial rotation of 1.44 mm and 2.35 deg. The performance of the method is concluded to be sufficient for the effective study of kinematic changes caused to knees by soft tissue injuries.

Time Course of Quad Strength, Area and Activation after Knee Arthroplasty and Strength Training

INTRODUCTION changes in strength, activation, and morphology of the quadriceps femoris muscle group were assessed in 61 individuals that underwent unilateral total knee arthroplasty, with progressive postoperative strength training, for primary knee osteoarthritis. METHODS assessments of these three parameters were made at four time points (preoperatively and 4, 12, and 52 wk postoperatively). Maximal voluntary knee extension strength was recorded using an electromechanical dynamometer, and voluntary muscle activation was measured using a burst superimposition technique. Lean muscle cross-sectional area (CSA) was determined using magnetic resonance imaging. RESULTS preoperatively, the surgical limb was significantly weaker and smaller than the nonsurgical limb. Strength, voluntary muscle activation, and CSA of the quadriceps femoris significantly improved over the study period. At 52 wk, the surgical limb was still significantly smaller than the nonsurgical limb but had greater levels of voluntary muscle activation. In the nonsurgical limb, CSA was the primary determinant of strength across all time points, with voluntary muscle activation progressively contributing more from the preoperative assessment (R = 0.11) to the assessment 52 wk postoperatively (R = 0.26). In the surgical limb, voluntary muscle activation was the primary determinant of strength preoperatively and 4 wk postoperatively (R = 0.38 and 0.41, respectively), whereas CSA was the primary determinant of quadriceps strength 12 and 52 wk postoperatively (R = 0.44). CONCLUSION resolving the impairments in voluntary muscle activation after total knee arthroplasty may be necessary before visible gains in strength and muscle hypertrophy are evident.

Do ACL-injured copers exhibit differences in knee kinematics?: An MRI study.

Kinematic changes after anterior cruciate ligament (ACL) injury may play a role in the long-term development of osteoarthritis (OA). Some ACL-injured patients (copers) successfully return to demanding activities without the reconstructive surgery usually recommended for functionally unstable patients (noncopers). We determined whether copers exhibit less disruption to kinematics than noncopers, perhaps because of lower impairment of muscular control as observed in earlier studies. We used dynamic magnetic resonance imaging and model-based tracking to investigate anteroposterior (AP) and internal-external tibial positioning in copers, presurgical noncopers, and uninjured control subjects during dynamic nonloaded knee extension. Copers and control subjects showed similar levels of side-to-side differences in AP tibial positioning (1.1 ± 4.9 mm and 1.4 ± 2.7 mm, respectively), whereas noncopers exhibited anterior tibial positioning in their injured knees (2.6 ± 3 mm) that differed from control subjects. Copers were the most variable of the three groups, and contrary to our hypothesis, tibial positioning in copers was not different from that of noncopers. Differences in tibial positioning did not correlate with side-to-side differences in AP laxity in any of the groups, and we identified no changes to tibial axial rotation patterns associated with ACL deficiency.

Comparison of MRI-Based Estimates of Articular Cartilage Contact Area in the Tibiofemoral Joint

Knee osteoarthritis (OA) detrimentally impacts the lives of millions of older Americans through pain and decreased functional ability. Unfortunately, the pathomechanics and associated deviations from joint homeostasis that OA patients experience are not well understood. Alterations in mechanical stress in the knee joint may play an essential role in OA; however, existing literature in this area is limited. The purpose of this study was to evaluate the ability of an existing magnetic resonance imaging (MRI)-based modeling method to estimate articular cartilage contact area in vivo. Imaging data of both knees were collected on a single subject with no history of knee pathology at three knee flexion angles. Intra-observer reliability and sensitivity studies were also performed to determine the role of operator-influenced elements of the data processing on the results. The methods articular cartilage contact area estimates were compared with existing contact area estimates in the literature. The method demonstrated an intra-observer reliability of 0.95 when assessed using Pearsons correlation coefficient and was found to be most sensitive to changes in the cartilage tracings on the peripheries of the compartment. The articular cartilage contact area estimates at full extension were similar to those reported in the literature. The relationships between tibiofemoral articular cartilage contact area and knee flexion were also qualitatively and quantitatively similar to those previously reported. The MRI-based knee modeling method was found to have high intra-observer reliability, sensitivity to peripheral articular cartilage tracings, and agreeability with previous investigations when using data from a single healthy adult. Future studies will implement this modeling method to investigate the role that mechanical stress may play in progression of knee OA through estimation of articular cartilage contact area.

Validation of an MRI-Based Method to Measure Tibiofemoral Joint Cartilage Contact Area

Osteoarthritis is a progressive and debilitating joint disease that is the leading cause of physical disability in industrial nations around the world [1]. It not only negatively affects the comfort and functional activity of individuals, but as a result also taxes the health care system of these countries.Copyright

Investigating the Ability of Knee OA Patients to Maintain Targeted Knee Flexion Angles for Weight Bearing MRI

Knee osteoarthritis (OA) is the most common clinical presentation of osteoarthritis, and has been estimated to affect 12–16% of the population older than 60 years in the US [1]. A biomechanical risk factor that has been linked to knee OA is the changes in the local loading and the contact area between the cartilage surfaces [2]. Investigation of such factors requires precise measurement tools to determine knee joint positioning and contact areas. Clinically, MR images of the knee are most frequently acquired in the supine position; such images are not representative of the loading conditions experienced functionally in the weight bearing knee joint. With the advent of vertically open MRI (e.g. Upright MRI, Fonar Corporation, Melville, NY), it is now possible to scan the knee in fully upright weight bearing conditions representing truly functional positions. To measure sensitive variables such as joint positioning and cartilage contact, it is important to minimize subject movement in order to obtain high quality images. In MRI, increased scan times allow for data of improved signal to noise ratio and resolution; however, long scanning durations without subject movement are not feasible, particularly in individuals with symptomatic knee OA.Copyright