Biomedical subjects

B D Beynnon

Publications and source records attributed to B D Beynnon.

At least 19 recordsLinked to original sources

PubMed2003

Precision and accuracy of joint space width measurements of the medial compartment of the knee using standardized MTP semi-flexed radiographs.

OBJECTIVE: To quantify the precision and accuracy of measurements of joint space width (JSW) and joint space narrowing (JSN) from the medial tibiofemoral compartment of knee radiographs using a simple and easily adaptable protocol. METHODS: Radiographs of a caliper (a surrogate for JSW) were obtained to determine the precision limits of the system under ideal conditions. Bilateral knee radiographs from 10 healthy volunteers were obtained at three different times using the metatarsophalangeal (MTP) semi-flexed view posterior-anterior position without fluoroscopy. A backlit digitizing tablet and three manual methods were used to measure JSW and analyses of precision were performed. The accuracy of measuring change in JSW (a measure of JSN) was estimated from radiographs of cadaver knees that were placed in a servo-hydraulic device that moved the femur relative to the tibia through known intervals. RESULTS: Radiographic measurements of the caliper inter-blade distance were comparable to the resolution limits of the backlit digitizing tablet (0.025 mm). Repeated radiography of healthy subject knees produced JSW standard deviation (SD) measurements of 0.08 mm by the median SD method, and 0.11 mm by repeated measures analysis. The accuracy of JSN measurements in the cadaver knees as a mean difference from the known reference value was 0.09 mm. CONCLUSION: The results indicate a high level of precision in measurements of JSW from MTP semi-flexed view knee radiographs of normal volunteers. Reproducibility was attained through careful subject positioning without fluoroscopy and the use of a backlit digitizing tablet. From the cadaver study we can predict that greater than 0.13 mm of measured JSN represents actual or true change in JSN. This radiographic technique can be used as a primary measure for early knee osteoarthritis (OA) when cartilage thickness is decreasing and limited bony remodeling has occurred.

Arthrography↗

PubMed2003

Risk factors for lower extremity injury: a review of the literature.

Prospective studies on risk factors for lower extremity injury are reviewed. Many intrinsic and extrinsic risk factors have been implicated; however, there is little agreement with respect to the findings. Future prospective studies are needed using sufficient sample sizes of males and females, including collection of exposure data, and using established methods for identifying and classifying injury severity to conclusively determine additional risk factors for lower extremity injury.

Age Factors↗

PubMed2001

The effect of weightbearing and external loading on anterior cruciate ligament strain.

A force balance between the ligaments, articular contact, muscles and body weight maintains knee joint stability. Thus, it is important to study anterior cruciate ligament (ACL) biomechanics, in vivo, under weightbearing conditions. Our objective was to compare the ACL strain response under weightbearing and non-weightbearing conditions and in combination with three externally applied loadings: (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varus-valgus moments. A strain transducer was implanted on the ACL of 11 subjects. All joint loadings were performed with the knee at 20 degrees of flexion. A significant increase in ACL strain was observed as the knee made the transition from non-weightbearing to weightbearing. During anterior shear loading, the strain values produced during weightbearing were greater than those of the non-weightbearing knee (shear loads <40N). At higher shear loads, the strain values became equal. During axial torsion, an internal torque of 10Nm strained the ACL when the knee was non-weightbearing while an equivalent external torque did not. Weightbearing significantly increased ACL strain values in comparison to non-weightbearing with the application of external torques and low internal torques (<3Nm). The strains became equal for higher internal torques. For V-V loading, the ACL was not strained in the non-weightbearing knee. However, weightbearing increased the ACL strain values over the range of moments tested. These data have important clinical ramifications in the development of rehabilitation protocols following ACL reconstruction since weightbearing has been previously thought to provide a protective mechanism to the healing graft.

Adult↗

PubMed2001

Accuracy and repeatability of Roentgen stereophotogrammetric analysis (RSA) for measuring knee laxity in longitudinal studies.

Roentgen stereophotogrammetric analysis (RSA) can be used to assess temporal changes in anterior-posterior (A-P) knee laxity. However, the accuracy and precision of RSA is dependent on many factors and should be independently evaluated for a particular application. The objective of this study was to evaluate the use of RSA for measuring A-P knee laxity. The specific aims were to assess the variation or "noise" inherent to RSA, to determine the reproducibility of RSA for repeated A-P laxity testing, and to assess the accuracy of these measurements. Two experiments were performed. The first experiment utilized three rigid models of the tibiofemoral joint to assess the noise and to compare digitization errors of two independent examiners. No differences were found in the kinematic outputs of the RSA due to examiner, repeated trials, or the model used. In a second experiment, A-P laxity values between the A-P shear load limits of +/-60 N of five cadaver goat knees were measured to assess the error associated with repeated testing. The RSA laxity values were also compared to those obtained from a custom designed linkage system. The mean A-P laxity values with the knee 30 degrees, 60 degrees, and 90 degrees of flexion for the ACL-intact goat knee (+/-95% confidence interval) were 0.8 (+/-0.25), 0.9 (+/-0.29), and 0.4 (+/-0.22) mm, respectively. In the ACL-deficient knee, the A-P laxity values increased by an order of magnitude to 8.8 (+/-1.39), 7.6 (+/-1.32), and 3.1 (+/-1.20)mm, respectively. No significant differences were found between the A-P laxity values measured by RSA and the independent measurement technique. A highly significant linear relationship (r(2)=0.83) was also found between these techniques. This study suggests that the RSA method is an accurate and precise means to measure A-P knee laxity for repeated testing over time.

Animals↗

PubMed2001

A numerical solution to calculate internal-external rotation at the glenohumeral joint.

OBJECTIVE: To validate the approach of using angular velocity vectors to quantify internal-external rotation of the humerus. DESIGN: An experimental approach was used to compare predictions of internal-external rotation of the humerus based on angular velocity vectors, and known measurements of internal-external rotation. BACKGROUND: A primary concern associated with description of glenohumeral biomechanics is measurement of internal-external rotation of the humerus. Euler angles are often used, yet they do not address problems such as Codman's paradox and 'gimbal lock'. Previous work has presented a technique that uses angular velocity vectors to quantify internal-external rotation instead of Euler angles. This approach is promising with regard to providing an independent measure of internal-external rotation of the humerus, and requires validation for subsequent use on humans. METHODS: A gimbal with three axes of rotation that simulated the rotational d.o.f. of the humerus relative to the glenoid was developed and used to validate the use of angular velocity vectors to quantify internal-external rotation of the humeral shaft portion of the gimbal. RESULTS: Correlations between calculated and measured rotation values revealed R(2) values of 0.99, slopes at diagonal (1.0), and y-intercepts near zero (-0.6 degrees ).Conclusions. The expression developed here is a valid and useful method for measuring motion of the humerus relative to the glenoid. RELEVANCE: Angular velocity vectors can be used to accurately determine internal-external rotation of the humerus relative to the glenoid, and this may be useful for the development of arthrometers to characterize the glenohumeral joint.

Biomechanical Phenomena↗

PubMed2001

Ankle ligament injury risk factors: a prospective study of college athletes.

Over two million individuals suffer ankle ligament trauma each year in the United States, more than half of these injuries are severe ligament sprains; however, very little is known about the factors that predispose individuals to these injuries. The purpose of this study was to determine the risk factors associated with ankle injury. We performed a prospective study of 118 Division I collegiate athletes who participated in soccer, lacrosse, or field hockey. Prior to the start of the athletic season, potential ankle injury risk factors were measured, subjects were monitored during the athletic season, and injuries documented. The number of ankle injuries per 1,000 person-days of exposure to sports was 1.6 for the men and 2.2 for the women. There were 13 injuries among the 68 women (19%) and seven injuries among the 50 men (13%), but these proportions were not significantly different. Women who played soccer had a higher incidence of ankle injury than those who played field hockey or lacrosse. Among men, there was no relationship between type of sport and incidence of injury. Factors associated with ankle ligament injury differ for men relative to women. Women with increased tibial varum and calcaneal eversion range of motion are at greater risk of suffering ankle ligament trauma, while men with increased talar tilt are at greater risk. Generalized joint laxity, strength, postural stability, and muscle reaction time were unrelated to injury.

Adult↗

PubMed2001

The relationship between graft tensioning and the anterior-posterior laxity in the anterior cruciate ligament reconstructed goat knee.

The tension applied to the anterior cruciate ligament (ACL) graft at time of fixation is thought to influence graft healing, knee kinematics, and joint contact forces; however, the optimal tensioning procedure remains unclear. An animal model provides a means by which the effect of graft tensioning on healing can be studied. Prior to using the model, the relationship between graft tensioning and knee kinematics at time of surgery should be established. Our objective was to explore the relationship between graft tensioning and anterior-posterior (A-P) laxity of the reconstructed goat knee. Eight cadaver knees were tested. The A-P laxity values of the intact knee were measured with the knee at 30 degrees, 60 degrees. and 90 degrees flexion. The ACL was then severed and the laxity measurements were repeated. The ACL was reconstructed using a bone-patellar tendon-bone autograft. The laxity measurements were repeated for nine different tensioning conditions; three tension magnitudes (30, 60, and 90 N), each applied with the knee at three angles (30 degrees, 60 degrees and 90 degrees). Both graft tension and the knee angle at which it was applied produced significant changes on A-P laxity values. An increase in tension reduced laxity values. A tension level of 60 N applied with the knee flexed to 30 degrees was the best combination for restoring normal A-P laxity values at all knee angles tested.

Animals↗

PubMed2001

A new device to measure knee laxity during weightbearing and non-weightbearing conditions.

The Vermont knee laxity device (VKLD) was developed to evaluate anterior-posterior (A-P) displacement of the tibia relative to the femur (A-P laxity) during weightbearing and non-weightbearing conditions. The purposes of this study were to determine the repeatability and reliability of the VKLD measurements of A-P laxity and to compare them with two devices currently in clinical use: the KT-1000 knee arthrometer and planar stress radiography. Two independent examiners tested six subjects with no history of knee injury. A-P laxity was measured on three separate days with the KT-1000 and the VKLD. With the VKLD, A-P laxity was measured in the weightbearing and non-weightbearing conditions. In addition, one examiner measured A P laxity in each subject on each day using a planar stress radiography technique. Similar A-P laxity values were obtained with the KT-1000 and the VKLD; however, the planar stress radiography technique measured less A-P laxity compared to the VKLD (9.2+/-2.2 mm versus 13.3+/-2.9 mm, P = 0.0004). None of the three devices showed significant differences in measuring A-P laxity between days. During weightbearing, A-P laxity was reduced by 65-70% compared to the non-weightbearing condition (P = 0.0001). Future investigations will use the VKLD to study subjects that have suffered injury to the anterior and posterior cruciate ligaments.

Adolescent↗

PubMed2001

The gastrocnemius muscle is an antagonist of the anterior cruciate ligament.

Since the proximal tendon of the gastrocnemius muscle wraps around the posterior aspect of the tibia, its contraction could potentially strain the anterior cruciate ligament (ACL) by pushing the tibia anteriorly. However, the relationship between contraction of the gastrocnemius muscle and ACL strain has not been studied in vivo. The objectives of this study were to evaluate the ACL strain response due to isolated contractions of the gastrocnemius muscle and to determine how these strains are affected by cocontraction with the hamstrings and quadriceps muscles. Six subjects with normal ACLs participated in the study; they underwent spinal anesthesia to ensure that their leg musculature was relaxed. Transcutaneous electrical muscle stimulation (TEMS) was used to induce contractions of the gastrocnemius, quadriceps and hamstrings muscles while the strains in the anteromedial bundle of the ACL were measured using a differential variable reluctance transducer. The ACL strain values produced by contraction of the gastrocnemius muscle were dependent on the magnitude of the ankle torque and knee flexion angle. Strains of 2.8% and 3.5% were produced at 5 degrees and 15 degrees of knee flexion, respectively. The ACL was not strained at 30 degrees and 45 degrees. Changes in ankle angle did not significantly affect these strain values. Co-contraction of the gastrocnemius and quadriceps muscles produced ACL strain values that were greater than those produced by isolated activation of either muscle group when the knee was at 15 degrees and 30 degrees. Co-contraction of the gastrocnemius and hamstrings muscles produced strains that were higher than those produced by the isolated contraction of the hamstrings muscles. At 15 degrees and 30 degrees of knee flexion. the co-contraction strain values were less than those produced by stimulation of the gastrocnemius muscle alone. This study verified that the gastrocnemius muscle is an antagonist of the ACL. Since the gastrocnemius is a flexor of the knee, this finding may have important clinical ramifications in ACL rehabilitation since flexor torques are generally thought to be protective of a healing ACL graft.

Adult↗

PubMed2001

The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty.

Increasing femoral rollback in flexion is thought to reduce patellofemoral contact load in total knee arthroplasty (TKA). The objectives of this study were to quantify the dependence of patellar load on rollback and to assess the effectiveness of posterior cruciate ligament (PCL)-retaining, PCL-sacrificing, and PCL-substituting TKA types in generating rollback. Nine cadaver knees were tested in simulated squatting. Six TKAs that were expected to produce varying amounts of femoral rollback were evaluated: PCL-retaining TKA, PCL-sacrificing TKA, a commercially available PCL-substituting TKA, and 3 modified PCL-substituting TKAs in which the anteroposterior position of the tibial post was varied. Kinematics, quadriceps loads, and patellofemoral contact loads were recorded. Significant differences in rollback were observed in the 30 degrees to 90 degrees flexion range. PCL-sacrificing TKAs generated the least rollback. PCL-retaining TKAs produced greater rollback but had the most variability. PCL-substituting TKAs produced the greatest and most reproducible rollback. Moving the tibial post posteriorly further increased rollback. Increased rollback correlated with reduced patellar load (-2.2%/mm). Reductions in patellar load of 17.6% were observed. Quadriceps loads were reduced by increasing rollback but to a smaller degree (-0.9%/mm). Rollback primarily affects patellar load rather than quadriceps load or efficiency.

Adult↗

PubMed2001

Femoral stem insertion generates high bone cement pressurization.

Adequate bone cement pressurization is critical in obtaining optimal femoral cement mantles during total hip arthroplasty. Pressurization can be generated during insertion of the femoral stem into the cement-filled canal. This may be clinically useful in augmenting conventional cement gun pressurization. Two factors, which were expected to influence the amount of insertion-induced pressurization, are the cement's cure state (viscosity) at the time of insertion and the femoral stem profile. This study evaluated the effect of these factors on cement pressurization during stem insertion. Femoral stems were inserted at a controlled rate into a reusable, simulated femoral canal. Intramedullary pressures were monitored at four locations along the canal's medial midline. The intrusion factor quantity, which accounts for pressure magnitude, duration of pressurization, and cement viscosity, was developed to quantify pressurization. Stem insertion into late cure stage (high viscosity) cement resulted in significantly higher intramedullary pressures (as much as 187% higher) and intrusion factors (as much as 43% higher) as compared with early stage (low viscosity) cement. The highest pressures and intrusion factors were found in the distal canal. A tapered stem profile resulted in significantly higher pressures (as much as 65%) and higher intrusion factors (as much as 63%) than a straight stem.

Arthroplasty, Replacement, Hip↗

PubMed2001

Bending stiffness, torsional stability, and insertion force of cementless femoral stems.

In cementless total hip arthroplasty, increased femoral stem flexibility and decreased fracture propensity are desirable characteristics. The slotting and tapering of the stem have been introduced to achieve this. These features should not, however, be allowed to interfere with the ability of the distal stem to provide initial mechanical stability, especially under rotation. This study was done to investigate the ability of slotted and tapered stem designs to reduce stiffness and insertion force while still maintaining adequate torsional strength. The torsional strength, maximum insertion force, and insertional work of straight, slotted, and taper stems were measured by inserting each type into rigid polyurethane foam and torque testing to failure. Bending stiffness of each stem design was calculated using numerical methods. When compared to a straight stem, a unislot stem has similar torsional strength, maximum insertional force, and work of insertion. The bending stiffness is decreased by 19% to 82% depending on the bending direction. A trislot design decreased torque strength by 29%, maximal insertion force by 36%, and work by 11%. Bending stiffness was decreased by 74% and was not dependent on bending direction. A 0.5-mm taper decreased torque strength by 11% and insertional work by 14%. No difference was seen in maximum insertional force. We conclude that the design features studied (slots and taper) are effective in decreasing stem stiffness and reducing fracture propensity.

Analysis of Variance↗

PubMed2000

In vivo technique to quantify the internal-external rotation kinematics of the human glenohumeral joint.

Internal and external rotation of the humerus are often related to instability, injury mechanisms, and surgical and rehabilitation outcomes at the glenohumeral joint. The goal of this study was to develop a technique to quantify the internal-external rotation kinematics of the glenohumeral joint in human subjects, including the rotational range of motion, neutral-zone laxity, and flexibility. For both arms of 10 normal subjects, the rotational range of motion of the humerus was assessed at 45 degrees of abduction with 4 Nm of applied moment to produce internal and external rotations about the long axis. The neutral zone was defined as the portion of the rotational range of motion that occurred between +1 and -1 Nm of applied internal-external rotation torque. The flexibility was determined from the slope of the moment-rotation curve from 1 to 4 Nm of applied moment. The repeatability of the device during two trials on the same day and two trials 1 week apart was determined. There were no significant differences between the two same-day and two across-day trials for each outcome measure. The internal-external rotational range of motion was 139.4 degrees (SD 40.5 degrees). The neutral-zone laxity was 77.8 degrees (SD 46.0 degrees). With a linear approximation, the external rotation flexibility (20.1 degrees/Nm [SD 13.7 degrees/Nm]) was four times greater than the internal rotation flexibility (5.8 degrees/Nm [SD 5.1 degrees/Nm]). The changes in the magnitude of the laxity, the ratio between the laxity and the range of motion, or the values for flexibility determined with this technique could be used to describe joint laxity, surgical outcome, and rehabilitation progress.

Adult↗

PubMed2000

Factors influencing the output of an implantable force transducer.

The objective of this study was to evaluate the performance of the Arthroscopically Implantable Force Probe (AIFP; MicroStrain, Burlington VT) for measuring force in a patellar tendon graft. Transducer drift, reproducibility of output due to the number of loading cycles and device location, and sensitivity to the tendon cross-sectional area were investigated. The AIFP was initialized, and then implanted into five human patellar tendon grafts three times; twice within the same location and once in a different location. The tendons were cyclically loaded in uniaxial tension for 500 cycles in each insertion site. The AIFP was then removed from the tendon and the baseline output was remeasured. It was determined that transducer drift was negligible. The relationship between the tensile load applied to the graft and AIFP output was quadratic and specimen dependent. The cyclic load response of the tendon-AIFP interface demonstrated a 24.9% decrease over the first 20 loading cycles, and subsequent cycling yielded relatively reproducible output. The output of the transducer varied when it was removed from the tendon and then reimplanted in the same location (range 3.7-109. 4% error), as well as in the second location (range 1.5-202.8% error). No correlation was observed between the cross-sectional area of the tendon and transducer output. This study concludes that implantable force probes should be used with caution and calibrated without removing the transducer from the graft.

Aged↗

PubMed2000

Modeling the stability of the human glenohumeral joint during external rotation.

An analytical model of the human glenohumeral joint was developed to predict glenohumeral kinematics and investigate how the glenohumeral capsule and articular contact between the humeral head and the glenoid stabilize the joint. This was performed during a simulation of an apprehension clinical exam or the cocked phase of throwing, when the humerus is susceptible to anterior instability or dislocation. Contact between the joint surfaces was modeled using a deformable articular contact method and the capsule was modeled as five elements with the ability to wrap around the surface of the humeral head. Experimental measurements (Novotny et al., Journal of Shoulder and Elbow surgery, 1998, 7, 629-639) provided geometric data from four in vitro specimens and kinematic results to validate model predictions. Material properties were taken from the literature. An equilibrium approach was used with the forces and moments produced by the ligaments and surface contact balanced against those applied externally to the humerus during external rotation of the abducted and extended humerus. The six equilibrium equations were solved for the position and orientation of the humerus. The center of the humeral head translated posteriorly and superiorly with external rotation. Model predictions for translational and rotational ranges of motion were not significantly different from experimental findings; however, at individual moment increments, the model underestimated the external rotation and overestimated the superior-inferior position of the humerus relative to the glenoid. The anterior band of the inferior glenohumeral ligament increased in tension with external rotation, while the axillary pouch and posterior band decreased in tension. Contact area, stress and force increased with external rotation and the contact area moved posteriorly and inferiorly around the rim of the glenoid. The model results provide information on how the relationship between the ligament element tensions and contact forces may act to avoid glenohumeral instability.

Humans↗

PubMed1999

Sensitivity to changes over time for the IKDC form, the Lysholm score, and the Cincinnati knee score. A prospective study of 120 ACL reconstructed patients with a 2-year follow-up.

The purpose of this study was to determine: (1) the sensitivity to changes over time for the IKDC form, the Lysholm score, and the Cincinnati knee score, (2) the relationship between the IKDC form, the Lysholm score and the Cincinnati knee score, (3) the criterion validity of each graded variable included in the IKDC form, and (4) if a functional knee test should be included as a graded variable and part of the final result of the IKDC form. We included in this prospective study 120 subjects who underwent ACL reconstruction with follow-up times of 3 and 6 months, and 1 and 2 years after surgery. Outcome measurements were the graded variables of the IKDC form (IKDC1-4 and IKDC-final), the Lysholm score, the Cincinnati knee score, a visual analogue scale for patient's satisfaction, knee joint laxity measurement (KT-1000 knee arthrometer), and two functional knee tests (the triple jump and stairs hopple tests). The IKDC1, IKDC2, IKDC-final, and the Lysholm score were not sensitive to changes over time. The Cincinnati knee score was highly sensitive to changes over time and showed significantly improved outcome between each follow-up. IKDC1-4 showed high criterion validity, indicating that the IKDC1-4 is a good means of documenting clinical examination at one follow-up, but not of detecting changes over time. The functional knee tests were significant outcome measurements after ACL reconstruction, and should be reported separately.

Adolescent↗

PubMed1999

Proprioception after anterior cruciate ligament reconstruction with and without bracing.

In this investigation we evaluated the effect of ACL reconstruction and functional knee bracing on knee proprioception. Twenty subjects who experienced acute ACL disruption and underwent reconstruction with a bone-patellar tendon-bone graft participated in a controlled rehabilitation program and were studied at a mean follow-up of 2 years. A control group of ten subjects were also studied. In both groups proprioception was evaluated by measuring the threshold to detection of passive motion (TDPM) with the knee at 15 degrees of flexion with and without a functional knee brace applied. The Knee Osteoarthritis Outcome Score, Cincinnati knee score, and two functional knee tests were also used as outcome measurements. Anterior-posterior displacement of the tibia relative to the femur was evaluated with the KT-1000 arthrometer. There were no significant differences in TDPM between the ACL-reconstructed and contralateral knees, or between the ACL reconstructed group and the healthy control group. Bracing did not produce a significant change in the TDPM for the ACL-reconstructed group or for the control group. There were low to moderate correlations between TDPM and the other outcome measurements. This study indicates that there is no significant differences in proprioception between the ACL-reconstructed knee and the contralateral uninvolved knee 1 year or more after surgery. Functional knee bracing does not seem to improve proprioception in patients who have undergone ACL reconstruction and been followed up on average 2 years after surgery.

Adult↗

PubMed1999

The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study.

Stair climbing is a closed kinetic chain exercise that is thought to be useful for knee rehabilitation following anterior cruciate ligament (ACL) reconstruction while protecting the graft from excessive strain. The objectives of this study were to measure the strain produced in the anteromedial band (AMB) of the normal ACL during stair climbing in vivo. We have previously shown that the normal AMB strain pattern during knee passive flexion-extension motion is similar to that of an ACL graft immediately after graft fixation. We successfully tested five subjects with normal ACLs, who were candidates for arthroscopic meniscectomy under local anesthesia. AMB strain was measured in vivo using the Differential Variable Reluctance Transducer (MicroStrain, Burlington, VT). The stair climbing activities were performed on a StairMaster 4000PT (Randall Sports Medicine, Kirkland, WA). Two different climbing cadences were evaluated; 80 and 112 steps per minute. Consistent with our previous studies of ACL biomechanics, strain values increased as the knee was moved from a flexed to an extended position. The mean peak AMB strain values for the 80 and 112 steps per minute conditions were 2.69% (+/-2.89&) and 2.76% (+/-2.68%), respectively. These values were not significantly different. Compared with other rehabilitation activities previously tested in the same manner, the AMB strain values produced during stair climbing were highly variable across subjects. High strain values were observed in some patients but not in others.

Anterior Cruciate Ligament↗