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Biomedical subjects

B D Beynnon

Publications and source records attributed to B D Beynnon.

At least 37 records · Page 2Linked to original sources
PubMed1999

Calibration and application of an intra-articular force transducer for the measurement of patellar tendon graft forces: an in situ evaluation.

The objective of this study was to evaluate two calibration methods for the "Arthroscopically Implantable Force Probe" (AIFP) that are potentially suitable for in vivo use: (1) a direct, experimentally based method performed by applying a tensile load directly to the graft after it is harvested but prior to implantation (the "pre-implantation" technique), and (2) an indirect method that utilizes cadaver-based analytical expressions to transform the AIFP output versus anterior shear load relationship, which may be established in vivo, to resultant graft load (the "post-implantation" technique). The AIFP outputs during anterior shear loading of the knee joint using these two calibration methods were compared directly to graft force measurements using a ligament cutting protocol and a 6 DOF load cell. The mean percent error (actual-measured)/(actual)* 100) associated with the pre-implantation calibration ranged between 85 and 175 percent, and was dependent on the knee flexion angle tested. The percent error associated with the post-implantation technique was evaluated in two load ranges: loads less than 40 N, and loads greater than 40 N. For graft force values greater than 40 N, the mean percent errors inherent to the post-implantation calibration method ranged between 20 and 29 percent, depending on the knee flexion angle tested. Below 40 N, these errors were substantially greater. Of the two calibration methods evaluated, the post-implantation approach provided a better estimate of the ACL graft force than the pre-implantation technique. However, the errors for the post-implantation approach were still high and suggested that caution should be employed when using implantable force probes for in vivo measurement of ACL graft forces.

Aged↗
PubMed1999

Alpine ski bindings and injuries. Current findings.

In spite of the fact that the overall incidence of alpine ski injuries has decreased during the last 25 years, the incidence of serious knee sprains usually involving the anterior cruciate ligament (ACL) has risen dramatically since the late 1970s. This trend runs counter to a dramatic reduction in lower leg injuries that began in the early 1970s and to date has lowered the risk of injury below the knee by almost 90%. One of the primary design objectives of modern ski boots and bindings has been to protect the skier from tibia and ankle fractures. So, in that sense, they have done an excellent job. However, despite advances in equipment design, modern ski bindings have not protected the knee from serious ligament trauma. At the present time, we are unaware of any binding design, settings or function that can protect both the knee and lower extremities from serious ligament sprains. No innovative change in binding design appears to be on the horizon that has the potential to reduce the risk of these severe knee injuries. Indeed, only 1 study has demonstrated a means to help reduce this risk of serious knee sprains, and this study involved education of skiers, not ski equipment. Despite the inability of bindings to reduce the risk of severe knee injuries there can be no doubt that improvement in ski bindings has been the most important factor in the marked reduction in incidence of lower leg and ankle injuries during the last 25 years. The authors strongly endorse the application of present International Standards Organisation (ISO) and American Society for Testing and Materials (ASTM) standards concerning mounting, setting and maintaining modern 'state of the art' bindings.

Athletic Injuries↗
PubMed1999

Joint position sense is not changed after acute disruption of the anterior cruciate ligament.

We evaluated the impact of acute, isolated ACL disruption on knee joint proprioception by means of passive-active and active-active joint position sense (JPS) measurement techniques. 18 subjects with acute, isolated and unilateral ACL disruption were tested for JPS in a standing position. The test protocol included 6 trials for each leg. In each trial, the lower leg was passively positioned to an index angle approximating either 30 degrees or 70 degrees, followed by 5 active repetitions of the index angle where the subjects attempted to reproduce the index angle to the best of their ability. The errors from the exact index angle reproduction were calculated as both real (showing both magnitude and direction) and absolute values (only magnitude). All subjects had a tendency to reproduce the index angle with both the injured and normal knees in a more flexed position (overestimation). Only the absolute error produced by the active-active test at flexion angles greater than 45 degrees produced a significant difference with a larger error for the normal knee. In all other comparisons between the injured and the normal knee no differences were found. We conclude that the afferent signals which are compromised by an acute tear of the ACL are insignificant compared to afferent signals from the other joint and muscle receptors.

Acute Disease↗
PubMed1998

Kinematics of the glenohumeral joint with Bankart lesion and repair.

A Bankart repair is performed to reduce abnormal translations of the humeral head on the glenoid due to a Bankart lesion, a separation of the capsulolabral complex from the glenoid rim. However, this is often accompanied by a loss of rotational range of motion that may lead to decreased function and osteoarthritis. This loss of rotation, coupled to the goal of reducing humeral translations, may be a result of the amount of imbrication of the capsule during repair. To determine the effects of capsular imbrication, we investigated how two Bankart repairs (2.5 and 5.0 mm of capsular imbrication) and a Bankart lesion altered the translations and rotations of the human glenohumeral joint in vitro. Coupled moments were applied to the unconstrained humerus in abduction-adduction, in flexion-extension, and to simulate the cocked phase of throwing. Motion was measured with an electromagnetic system. There were no differences in the kinematics between the intact specimens and those with a Bankart lesion or between normal specimens and the first (2.5 mm) Bankart repair. The first repair significantly reduced external rotation for the cocked phase of throwing compared with the Bankart lesion: from 46.8 +/- 23.6 degrees to 32.4 +/- 14.2 degrees (+/-SD). The second (5.0 mm) Bankart repair produced significantly different posterior translation (-4.7 +/- 3.9 mm) of the humeral head relative to the glenoid compared with normal (5.1 +/- 4.7 mm anterior) and the first repair (6.1 +/- 8.3 mm anterior), as the humerus moved from full flexion to full extension. Differences were also found for all rotations in the cocked phase of throwing. For the second repair, the humerus extended 24.3 degrees and externally rotated 18.6 degrees less than normal and was abducted 15.4 degrees more. These results indicate that both Bankart repairs do little to affect humeral translations with unconstrained moment loading but that rotations are affected during the cocked phase of throwing, with significant losses of external and extension rotations.

Biomechanical Phenomena↗
PubMed1998

In vitro testing protocols for the cruciate ligaments and ligament reconstructions.

The techniques that have been used to characterize the biomechanical behavior of the knee, cruciate ligaments, and cruciate ligament replacements differ, making comparisons between studies difficult or, at times, impossible. Therefore, it is important to standardize the testing protocols and techniques that describe the biomechanical behavior of the knee and cruciate ligaments. This will allow investigators to express opinions with respect to the interpretation of data, rather than based on differences between testing techniques. Standardized techniques are proposed to locate the origins of the tibial and femoral coordinate systems, and thus, allow comparisons of knee kinematics (e.g., displacements and rotations) between investigations. Standard techniques that can be used to measure the load-displacement behavior of the knee are described, and important considerations that should be appreciated with respect to preparing and testing of the joint are summarized. It is important to evaluate the single cycle load-to-failure characteristics and the cyclic loading response of an anterior cruciate ligament graft, and techniques to evaluate cruciate ligament graft fixation are proposed. The strengths of different models to characterize the biomechanical behavior of the knee are reviewed.

Anterior Cruciate Ligament↗
PubMed1998

Anterior cruciate ligament strain in-vivo: a review of previous work.

Disruption of the anterior cruciate ligament (ACL), a primary stabilizer of the knee, can produce disability. The purpose of our work has been to study the normal ACL in humans, in the presence of normal muscle function and body weight, and develop clinical criteria for reconstruction, establish a basis for rehabilitation programs, and evaluate how knee braces protect this important ligament. The strain behavior of the ACL has been measured by arthroscopic implantation of the Differential Variable Reluctance Transducer while subjects are under local anesthesia. Movement of the knee from a flexed to an extended position, either passively or through contraction of the leg muscles, produces an increase in ACL strain values. Isolated contraction of the dominant quadriceps with the knee between 50 degrees and extension creates substantial increases in strain. In contrast, isolated contraction of the hamstrings at any knee position does not increase strain. With the knee un-weighted, the protective strain shielding effect of a functional knee brace decreases as the magnitude of anterior shear load applied to the tibia increases. A different behavior occurs during weight bearing, the strain shielding effect of the brace remains constant as the magnitude of anterior load increases. Our approach is novel in that it can be used to measure on important portion of the ACLs strain distribution while clinically relevant loads are applied to the knee, subjects perform rehabilitation exercises, or in the presence of different orthoses such as functional knee braces.

Anterior Cruciate Ligament↗
PubMed1998

The transepicondylar axis approximates the optimal flexion axis of the knee.

The traditional understanding of knee kinematics holds that no single fixed axis of rotation exists in the knee. In contrast, a recent hypothesis suggests that knee kinematics are better described simply as two simultaneous rotations occurring about fixed axes. Knee flexion and extension occurs about an optimal flexion axis fixed in the femur, whereas tibial internal and external rotations occur about a longitudinal rotation axis fixed in the tibia. No other translations or rotations exist. This hypothesis has been tested. Tibiofemoral kinematics were measured for 15 cadaveric knees undergoing a realistic loadbearing activity (simulated squatting). An optimization technique was used to identify the locations of the optimal flexion and longitudinal rotation axes such that simultaneous rotations about them could best represent the measured kinematics. The optimal flexion axis was compared with the transepicondylar axis defined by bony landmarks. The longitudinal rotation axis was found to pass through the medial joint compartment. The optimal flexion axis passed through the centers of the posterior femoral condyles. No significant difference was found between the optimal flexion and transepicondylar axes. To an average accuracy of better than 3.4 mm in translation, and 2.9 degrees in orientation, knee kinematics were represented successfully by simple rotations about the optimal flexion and longitudinal rotation axes. The optimal flexion axis is fixed in the femur and can be considered the true flexion axis of the knee. The transepicondylar axis axis, which is identified easily by palpation, closely approximates the optimal flexion axis.

Adult↗
PubMed1998

Knee Injury and Osteoarthritis Outcome Score (KOOS)--development of a self-administered outcome measure.

There is broad consensus that good outcome measures are needed to distinguish interventions that are effective from those that are not. This task requires standardized, patient-centered measures that can be administered at a low cost. We developed a questionnaire to assess short- and long-term patient-relevant outcomes following knee injury, based on the WOMAC Osteoarthritis Index, a literature review, an expert panel, and a pilot study. The Knee injury and Osteoarthritis Outcome Score (KOOS) is self-administered and assesses five outcomes: pain, symptoms, activities of daily living, sport and recreation function, and knee-related quality of life. In this clinical study, the KOOS proved reliable, responsive to surgery and physical therapy, and valid for patients undergoing anterior cruciate ligament reconstruction. The KOOS meets basic criteria of outcome measures and can be used to evaluate the course of knee injury and treatment outcome.

Activities of Daily Living↗
PubMed1997

Laxity and flexibility of the ankle following reconstruction with the Chrisman-Snook procedure.

The effect of reconstruction of the anterior talofibular ligament with the Chrisman-Snook procedure on neutral zone laxity (anterior-posterior displacement at low loads) and flexibility (a measure of the nonlinear load-displacement response) of the ankle was investigated in vitro during the anterior drawer test. Neutral zone laxity was defined as the magnitude of anterior-posterior displacement of the ankle joint at +/- 2.5 N of applied load. The flexibility parameter was defined as the slope of a line between the natural logarithm of the anterior load applied to the ankle and the resulting displacement. After reconstruction with the Chrisman-Snook procedure, the values for neutral zone laxity of the ankle were significantly less than normal at 0 degree of plantar flexion, whereas the flexibility values were significantly greater than normal. This study revealed that, after the Chrisman-Snook procedure, values for ankle flexibility are not restored to normal even if those for neutral zone laxity are reduced to less than normal. The findings suggest that this nonanatomical reconstruction procedure does not reproduce normal kinematics of the ankle joint. This may help explain some of the adverse clinical reports associated with the Chrisman-Snook reconstruction procedure.

Adolescent↗
PubMed1997

Knee kinematics in genesis total knee arthroplasty. A comparison of different tibial designs with and without posterior cruciate substitution in cadaveric specimens.

Knee joint kinematics after total knee arthroplasty (TKA) are not well understood. This study measured knee kinematics before and after TKA in six cadaveric specimens. Different tibial surface contours (standard, flat, and dished) and slopes (10 degrees and 15 degrees) with the posterior cruciate ligament (PCL) intact as well as a posterior-stabilized design were studied. The anteroposterior and proximal-distal displacements of the tibia relative to the femur were measured during active knee extension. For the standard design, it was possible to restore the normal position of the tibia relative to the femur at 90 degrees of flexion to within 2 mm; however, restoration of the tibiofemoral position was not achieved with the knee in the extended position. At 90 degrees of flexion, all of the TKA components resulted in a posteriorly positioned tibia compared with the normal knee. The standard, flat, and dished components shifted the tibia into a proximal position compared with the normal knee, while the 15 degrees and posterior-stabilized components shifted the tibia distally. With the knee in the extended position, the standard, flat, dished, and posterior-stabilized designs placed the tibia posteriorly and proximally compared with the normal position of the tibia relative to the femur. The 10 degrees and 15 degrees sloped components placed the tibia in a more anterior position. Of the PCL-retaining designs tested, the 10 degrees sloped tibial component produced the closest to normal knee kinematics. Overall, normal kinematic behavior of the knee was not restored after TKA.

Aged↗
PubMed1996

Anterior cruciate ligament injury rehabilitation in athletes. Biomechanical considerations.

Postoperative rehabilitation is a major factor in the success of an anterior cruciate ligament (ACL) reconstruction procedure. Clinical investigations of patients after ACL reconstruction have shown that immobilisation of the knee, or restricted motion without muscle contraction, leads to undesired outcomes for the articular, ligamentous, and musculature structures that surround the knee. Early joint motion is beneficial for; reducing pain, capsular contractions, articular cartilage, and for minimising scar formation that limit joint motion. These findings, combined with graft materials that have biomechanical properties similar to the normal ACL, and adequate fixation strength, have led many to recommend aggressive rehabilitation programmes that involve contraction of the dominant quadriceps muscles. Recently, a prospective, randomised study of rehabilitation following ACL reconstruction has presented evidence that a closed kinetic chain exercise programme (foot fixed against a resistance) results in anterior-posterior knee laxity values that are similar to the contralateral normal knee. Also, open kinetic chain exercises (foot not fixed against a resistance) result in increased anterior-posterior knee laxity compared with the normal knee. Criteria must be observed because the relationship between rehabilitation exercises and the healing response of an ACL graft is unknown at present. Biomechanical studies of healing ACL grafts performed in animals have shown that the graft requires a long time to revascularise and heal, and that the biomechanical behaviour of the graft never returns to normal. Functional knee braces provide a protective strain-shielding effect on the ACL when anterior shear loads and internal torques are applied to the knee in the non-weight-bearing condition. However, the strain shielding effect of functional braces decrease as the magnitude of anterior shear and internal torque applied to the knee increase. Future studies should strive to determine the actual loads transmitted across the knee and ACL graft strain during various rehabilitation exercises and relate these to the healing response of the knee and graft.

Anterior Cruciate Ligament Injuries↗
PubMed1995

Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries.

The effect of sectioning the anterior talofibular ligament on the load-displacement behavior of the ankle was evaluated in vitro during the anterior drawer test using the flexibility approach. Controlled forces were applied across the ankle joint in the anterior-posterior direction, and the resulting displacements were measured at four flexion angles (10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion). The anterior talofibular ligament then was sectioned, and the anterior-posterior loadings were repeated at the four flexion angles. Two parameters were developed to describe the nonlinear load-displacement response of the ankle joint: neutral zone laxity (joint displacement between +/- 2.5 N) and flexibility (a measure of the nonlinear load-displacement response of the ankle between 10 and 50 N of anterior drawer loading). After sectioning the anterior talofibular ligament, significant increases in neutral zone laxity were observed at all angles of ankle flexion. The largest increases in neutral zone laxity were found with the ankle in 10 degrees of plantar flexion (76.3% increase) and 20 degrees of plantar flexion (89.7% increase). After sectioning the ligament, a significant increase (19.3%) in flexibility of the ankle was observed at 10 degrees of dorsiflexion, but no change in flexibility was observed with the ankle in the neutral and plantar flexed positions. These findings indicate that anterior drawer testing of the anterior talofibular ligament-deficient ankle between 10 degrees and 20 degrees of plantar flexion results in the largest increase in neutral zone laxity compared with the normal ankle with intact ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament.

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30 degrees. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30 degrees of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).

Adult↗
PubMed1994

An in vivo comparison between intraoperative isometric measurement and local elongation of the graft after reconstruction of the anterior cruciate ligament.

This study was designed to determine if isometric measurement can be used to predict the pattern of elongation (the change in length) of a bone-patellar ligament-bone graft during passive flexion-extension of the knee at the time of reconstruction of the anterior cruciate ligament in vivo. A standard operative reconstruction technique was performed on nine patients. The tunnel sites for the grafts were selected, and the change in the distance between these sites was measured, with use of a CA-5000 drill-guide isometer as the knee was subjected to passive flexion-extension. After the reconstruction was completed, a Hall-effect transducer was implanted in the graft to measure the local displacement in the mid-substance of the graft that was produced by passive flexion-extension of the knee. For comparison, the isometric measurements and the values for local displacement of the graft were normalized by calculation of the percentage change in the length. With the knee in 10 to 30 degrees of flexion, the average isometric measurements and the measurements of local displacement demonstrated a decrease in length; however, the two techniques of measurement deviated at angles of flexion of 40 degrees and more. On the average, the isometric measurement of elongation between the trial insertion sites predicted that the graft would increase in length in flexion relative to extension, in contrast to the response of the graft after fixation. There was no significant correlation between the isometric measurements and the local elongation of the graft (r2 = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

The measurement of elongation of anterior cruciate-ligament grafts in vivo.

Many investigators who have studied the mechanical behavior of anterior cruciate-ligament grafts have attributed the increase in anterior translation of the tibia relative to the femur (an increase in the anterior laxity of the knee joint) to the temporal changes in the material behavior (strength and elastic properties) of the graft that occur throughout the process of remodeling. However, with the onset of motion of the joint, it is unclear whether the repeatable mechanical behavior of the graft remains unchanged immediately after fixation, if the fixation slips, or if the length of the graft changes and produces an increase in anterior translation of the tibia relative to the femur. It is also unknown if procedures performed by different surgeons, using similar graft material and similar operative techniques, can produce similar mechanical behavior of the graft, or if the behavior of the graft is similar to that of the normal anterior cruciate ligament. In an effort to address these questions, two surgeons performed a reconstruction of the anterior cruciate ligament on ten patients each (groups 1 and 2) with use of a bone-patellar ligament-bone graft. Immediately after fixation of the graft, a Hall-effect transducer was implanted to measure the changes in the length of the mid-substance of the graft while the knee was moved through twenty cycles of passive flexion-extension. Unlike the length pattern of the normal anterior cruciate ligament, the length pattern of the graft changed during the initial cycles of passive motion of the knee. We defined this phenomenon as the cyclic response of the graft and characterized it by calculation of the changes in the length of the graft at fixed positions of the knee across the multiple cycles of passive motion. In some patients, the length of the graft increased through the initial passive-motion cycles, while in others, it decreased. With the knee nearly extended, the predicted increase in anterior translation of the tibia relative to the femur, resulting from the increase in the length of the graft, was a maximum of 1.0 millimeter. This indicates that increases in anterior translation of the tibia relative to the femur can occur immediately after reconstruction of the anterior cruciate ligament and that changes in the length of the graft occur after fixation at loads that are less than the ultimate failure load of the graft or of the fixation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗