Shinji Kashiwaguchi

Quantitative Analysis of Human Cruciate Ligament Insertions

The objective of this study was to provide quantitative data on the insertion sites of the cruciate ligaments. In the first part of the study, we determined the shapes and sizes of the insertions of the anterior and posterior cruciate ligaments (ACL and PCL), and further compared these data with the midsubstance cross-sectional areas of the ligaments. The cross-sectional area of the ACL and PCL midsubstance of 5 human knees was measured using a laser micrometer system. The insertion sites of each ligament were then digitized and the 2-dimensional insertion site areas were determined. Relative to the ligament midsubstance, the PCL tibial and femoral insertions were approximately 3 times larger, whereas those of the ACL were over 3.5 times larger. In the second part of the study, the ACLs and PCLs of 10 knees were each divided into their 2 components and the areas of each insertion were determined. Each component was approximately 50% of the total ligament insertion area and no significant difference between the 2 could be shown.

The Human Posterior Cruciate Ligament Complex: An Interdisciplinary Study Ligament Morphology and Biomechanical Evaluation

To study the structural and functional properties of the human posterior cruciate ligament complex, we meas ured the cross-sectional shape and area of the anterior cruciate, posterior cruciate, and meniscofemoral liga ments in eight cadaveric knees. The posterior cruciate ligament increased in cross-sectional area from tibia to femur, and the anterior cruciate ligament area de creased from tibia to femur. The meniscofemoral liga ments did not change shape in their course from the lateral meniscus to their femoral insertions. The pos terior cruciate ligament cross-sectional area was ap proximately 50% and 20% greater than that of the an terior cruciate ligament at the femur and tibia, respectively. The meniscofemoral ligaments averaged approximately 22% of the entire cross-sectional area of the posterior cruciate ligament. The insertion sites of the anterior and posterior cruciate ligaments were evalu ated. The insertion sites of the anterior and posterior cruciate ligaments were 300% to 500% larger than the cross-section of their respective midsubstances. We determined, through transmission electron microscopy, fibril size within the anterior and posterior cruciate liga ment complex from the femur to the tibia. The posterior cruciate ligament becomes increasingly larger from the tibial to the femoral insertions, and the anterior cruciate ligament becomes smaller toward the femoral insertion. We evaluated the biomechanical properties of the femur-posterior cruciate ligament-tibia complex using 14 additional human cadaveric knees. The posterior cruciate ligament was divided into two functional com ponents : the anterolateral, which is taut in knee flexion, and the posteromedial, which is taut in knee extension. The anterolateral component had a significantly greater linear stiffness and ultimate load than both the postero medial component and meniscofemoral ligaments. The anterolateral component and the meniscofemoral liga ments displayed similar elastic moduli, which were both significantly greater than that of the posteromedial com ponent.

The use of a universal force-moment sensor to determine in-situ forces in ligaments: a new methodology

Determination of ligament forces is an integral part of understanding their contribution during motion and external loading of an intact joint. While almost all previous investigations have reported only the magnitude of tension, this alone cannot adequately describe the function of a particular ligament. An alternative approach to determine the in-situ forces in ligaments has been developed which utilizes a universal force-moment sensor in conjunction with a force transformation scheme. In addition to providing the magnitude of ligament force, the direction and point of application of this in-situ force can also be determined. Further, the approach does not require mechanical contact with the ligament. Application of this new methodology is demonstrated for the human anterior cruciate ligament in the present study (n = 7) although it may be similarly applied to other ligaments at the knee or in other synovial joints of the human body.

Determination of the in situ forces and force distribution within the human anterior cruciate ligament.

Thein situ forces and their distribution within the human anterior cruciate ligament (ACL) can clarify this ligaments role in the knee and help to resolve controversies regarding surgical treatment of ACL deficiency. We used a universal force-moment sensor (UFS) to determine the magnitude, direction, and point of application of thein situ forces in the ACL in intact human cadaveric knees. Unlike previous studies, this approach does not require surgical intervention, the attachment of mechanical devices to or near the ACL, ora priori assumptions about the direction ofin situ force. Anterior tibial loads were applied to intact knees, which were limited to 1 degree of freedom at 30o flexion. Thein situ forces developed in the ACL were lower than the applied force for loads under 80 N, but larger for applied loads of more than 80 N. The direction of the force vector corresponded to that of the anteromedial (AM) portion of the ACL insertion on the tibial plateau. The point of force application was located in the posterior section of the anteromedial portion of the tibial insertion site. The anterior and posterior aspects of the anteromedial portion of the ACL supported 25% and 70% of thein situ force, respectively, with the remainder carried by the posterolateral portion. We believe that the data obtained with this new UFS methodology improves our understanding of the role of the ACL in knee function, and that this methodology can be easily extended to study the function of other ligaments.

Osteochondritis dissecans of the femoral condyle in the growth stage

The site of lesion, spontaneous healing, onset mechanism, and magnetic resonance imaging findings of 51 knees in 38 patients with osteochondritis dissecans involving the femoral condyle in the growth stage were investigated. Half of the lesions were found in the center of the lateral condyle, 1/4 were in the medial in tercondylar site, and the remaining 1/4 were in other sites. Compared with those in the other sites, the lesions in a medial intercondylar site had a lower healing rate and required a longer time to heal. T2 weighted images of the lesions showed a progression from low signal areas to the appearance of a high signal line at the fragment to parent to bone interface, to a high signal double line at the interface and parentbone surface, or to disappearance of the line. Magnetic resonance imaging often revealed discoid menisci or meniscal tears in patients with lesions in the lateral condyle, suggesting that endogenous forces play an important role in the onset of osteochondritis dissecans.

The Most Effective Exercise for Strengthening the Supraspinatus Muscle Evaluation by Magnetic Resonance Imaging

Background Electromyography has been used to determine the best exercise for strengthening the supraspinatus muscle, but conflicting results have been reported. Magnetic resonance imaging T2 relaxation time appears to be more accurate in determining muscle activation. Purpose To determine the best exercises for strengthening the supraspinatus muscle. Study Design Criterion standard. Methods Six male volunteers performed three exercises: the empty can, the full can, and horizontal abduction. Immediately before and after each exercise, magnetic resonance imaging examinations were performed and changes in relaxation time for the subscapularis, supraspinatus, infraspinatus, teres minor, and deltoid muscles were recorded. Results The supraspinatus muscle had the greatest change among the studied muscles in relaxation time for the empty can (10.5 ms) and full can (10.5 ms) exercises. After the horizontal abduction exercise the change in relaxation time for the supraspinatus muscle (3.6 ms) was significantly smaller than that for the posterior deltoid muscle (11.5 ms) and not significantly different from that of the other muscles studied. Conclusion The empty can and full can exercises were most effective in activating the supraspinatus muscle.

Conservative Treatment for Osteochondrosis of the Humeral Capitellum

Background Conservative treatment is recommended for the early stage of osteochondrosis of the humeral capitellum. However, the outcome of conservative treatment has not been well documented. Hypothesis Osteochondrosis of the humeral capitellum detected at an early stage responds well to conservative treatment. Study Design Cohort study; Level of evidence, 3. Methods We retrospectively reviewed 176 patients with osteochondrosis of the humeral capitellum. There were 134 lesions that were stage I (radiolucent area) in patients with a mean age of 11.5 years and 42 lesions that were stage II (nondisplaced fragments) in patients with a mean age of 13.9 years based on anteroposterior radiographs of the elbow in 45° of flexion. Conservative treatment was performed on 101 patients. The remaining 75 patients did not follow the authors’ advice. Conservative treatment consisted of discontinuation of heavy use of the elbow for at least 6 months. Follow-up radiographs were taken at 1 -month intervals. At a mean follow-up of 24 months, all patients were evaluated clinically and radiographically. Results Conservative management produced healing in 90.5% of stage I lesions and 52.9% of stage II lesions. The mean period required for healing was 14.9 months in stage I and 12.3 months in stage II. Sixty-six of 84 (78.6%) stage I patients and 9 of 17 (52.9%) stage II patients returned to competitive-level baseball. Of the 75 patients who did not follow our advice, healing was observed in 17 (22.7%). The healing rate was higher for the 101 patients who followed our advice as opposed to the 75 patients who did not. Conclusion Osteochondrosis of the humeral capitellum can be successfully treated conservatively if treatment is begun in an early stage of the disease.

Hamstring muscle function after tendon harvest for anterior cruciate ligament reconstruction: evaluation with T2 relaxation time of magnetic resonance imaging.

Background Regeneration of the semitendinosus and gracilis tendons after harvesting for anterior cruciate ligament reconstruction has been reported; however, muscle belly function after tendon regeneration has not been well documented. Hypothesis The semitendinosus and gracilis muscles are highly activated during knee flexion if their tendons are well regenerated after anterior cruciate ligament reconstruction. Study Design Descriptive laboratory study. Methods Hamstring muscle activation in 11 patients who had undergone anterior cruciate ligament reconstruction with semitendinosus and gracilis tendons was evaluated by measuring the increase of T2 relaxation time measured via magnetic resonance imaging after knee flexion exercise. Tendon regeneration was evaluated via magnetic resonance imaging. Results Both muscles increased T2 relaxation time after knee flexion exercise in the operated legs, and there was no significant difference in those values between the operated and nonoperated legs. All the semitendinosus tendons were regenerated at or below the joint line, but no gracilis tendons were observed beyond the joint line. The results indicated that both muscles were highly recruited during knee flexion, regardless of the degree of their tendon regeneration. Conclusion The semitendinosus and gracilis muscles are able to restore or maintain their contractile capability after harvest of their tendons for anterior cruciate ligament reconstruction, regardless of the degree of regeneration.

The Value of Using Radiographic Criteria for the Treatment of Persistent Symptomatic Olecranon Physis in Adolescent Throwing Athletes

Background Previously published reports present a variety of nonoperative and operative treatments for a persistent olecranon physis. However, the radiographic indication for the operative treatment is not clear. Hypothesis Our radiographic classification of persistent olecranon physis is helpful in formulating treatment decisions. Study Design: Cohort study; Level of evidence, 3. Methods Sixteen male baseball players with persistent olecranon physis were retrospectively evaluated. The mean age at first presentation was 14.7 years (range, 12-17 years). The lesion was classified into 2 stages based on radiographic appearance. Stage I demonstrated widening of the olecranon epiphyseal plate when compared with the contralateral elbow on the lateral view. Sclerotic change indicated stage II. All patients underwent nonoperative treatment for at least 3 months. Follow-up radiographs were taken at 1-month intervals. Operative treatment was provided to the patients whose condition had failed to improve after nonoperative treatment. Results Of the 16 patients, 12 had stage I lesions and 4 had stage II lesions. Nonoperative management produced healing in 91.7% of patients with stage I lesions and none of the patients with stage II lesions. Conclusion Our radiographic classification of persistent olecranon physis is useful for treatment decision making. In addition, our results demonstrated that sclerotic change is a high predictive indicator of the need for operative treatment.

Elbow Injuries in Youth Baseball Players Without Prior Elbow Pain: A 1-Year Prospective Study

Background: Many risk factors for throwing injuries have been proposed. However, little is known about the risk factors for elbow injuries, particularly on physeal injuries in youth baseball players without prior elbow pain. Purpose: To investigate the risk factors for elbow injuries with a focus on physeal injuries that could predispose youth baseball players without elbow pain to elbow injuries. Study Design: A prospective epidemiology study. Methods: In 2006, 449 players without prior elbow pain were observed prospectively for 1 season to study injury incidence in relation to specific risk factors. The average age was 10.1 years (range, 7-11 years). One year later, all players were examined by administering a questionnaire, physical examination, and radiographic examination. Data for the groups with and without elbow pain were analyzed using multivariate logistic regression models. Results: Among the 449 participants, 30.5% reported episodes of elbow pain during the season. Of the players who reported elbow pain, 72.3% presented abnormal findings on physical examination, and of those players, 81.4% had radiographic abnormalities. Multivariate analysis showed that the age of 12 years (at 1-year examination), pitcher and catcher positions, and playing more than 100 games per year were risk factors for elbow pain. Conclusion: It is expected that 30% of youth baseball players have elbow pain each year, and nearly 60% of players with elbow pain exhibit radiographic abnormalities. The age of 12 years, pitcher and catcher positions, and playing more than 100 games per year are risk factors for elbow pain.