Yon-Sik Yoo

A Biomechanical Analysis of the Native Coracoclavicular Ligaments and Their Influence on a New Reconstruction Using a Coracoid Tunnel and Free Tendon Graft

PURPOSE To understand and characterize the kinematic properties of the 2 coracoclavicular ligaments and to evaluate the biomechanical performance of a new 3-tunnel reconstruction of the coracoclavicular ligaments by use of a free tendon graft. METHODS Ten fresh-frozen cadaveric shoulders were tested. The kinematics and in situ forces of the coracoclavicular ligaments were tested with a robotic testing system. Kinematics of the shoulder in the intact state, in the sectioned state, and finally, after a coracoclavicular reconstruction and a coracoclavicular sling reconstruction were evaluated. RESULTS The conoid had higher in situ forces during anterior and superior loading of the clavicle when compared with the trapezoid ligament, whereas the trapezoid ligament had higher in situ forces during posterior loading. Sectioning the trapezoid ligament significantly increased translation of the clavicle in the posterior direction, whereas sectioning the conoid ligament significantly increased superior translation. When we compared the 2 reconstruction techniques, the coracoid tunnel reconstruction was superior in controlling anterior translation whereas the coracoclavicular sling reconstruction was inferior because of anterior displacement of the graft. There was no significant difference in posterior or superior translation between either reconstruction technique. CONCLUSIONS The trapezoid and conoid ligaments have unique functions in normal shoulder kinematics because of their anatomic attachments. By more faithfully restoring these insertion sites on the clavicle and controlling motion of the graft on the coracoid, the 3-tunnel reconstruction technique more closely restores native shoulder kinematics than the coracoclavicular sling technique. CLINICAL RELEVANCE Understanding the unique roles of the conoid and trapezoid bundles of the coracoclavicular ligament may improve surgical techniques in the management of acromioclavicular joint injuries. The reconstructive technique presented more faithfully restores normal kinematics and forces across the acromioclavicular joint than the coracoclavicular sling technique.

An Analysis of the Posterior Cruciate Ligament Isometric Position Using an In Vivo 3-Dimensional Computed Tomography–Based Knee Joint Model

PURPOSE This study aimed to review the isometric point of the posterior cruciate ligament (PCL) based on insertional locations identified in recent anatomic studies by use of a 3-dimensional knee model. METHODS Ten living subjects with healthy knees were evaluated. High-resolution computed tomography scans were performed at 3 positions of 0°, 90°, and 135°, and 3-dimensional knee images were constructed. Customized software was used to define tibial and femoral insertion points of the PCL, based on recently described anatomy. The femoral attachment site of the PCL was divided into 4 sectors (labeled A through D), and the tibial attachment site was divided into 6 sectors (labeled 1 through 6). Twenty-four virtual PCL bundles were created between these sectors, and their length was measured in the 3 knee flexion positions. RESULTS In 0° and 90° of knee flexion, the virtual bundle showing the least amount of length change (1.10 ± 0.66 mm) was at sector D-6, that is, a posteromedial bundle inserting into the most posterior femoral sector (sector D) and the most distal tibial sector (sector 6). This change was not significantly different compared with all other virtual bundles with tibial points connected to femoral sector D (P > .05). An isometric position for the PCL (length change <2 mm) could not be found in 135° of knee flexion because of lengthening of all virtual bundles. CONCLUSIONS Our data suggest that the femoral attachment point is more important than the tibial attachment point: any of the 6 tibial bundles attached to the most posterior femoral sector had similar isometric properties. CLINICAL RELEVANCE Reproducing normal tibial and femoral anatomy underpins PCL surgical reconstruction. These findings suggest that to perform an isometrically accurate PCL reconstruction, particular attention should be paid to the location of the femoral attachment site, once the tibial footprint has been established. There were no isometric points in any virtual PCL bundle in the fully flexed knee because of excessive lengthening. Therefore, to avoid lengthening of the reconstructed graft, we recommend that fixation is performed at knee flexion angles between 0° and 90° and that patients avoid high flexion during postoperative rehabilitation.

Tension Changes Within the Bundles of Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction at Different Knee Flexion Angles: A Study Using a 3-Dimensional Finite Element Model

PURPOSE The aim of this study was to determine the change in length and tension of the reconstructed anterior cruciate ligament (ACL) double bundles at different knee flexion angles by use of a 3-dimensional finite element model. METHODS The right knees of 12 living subjects were scanned with a high-resolution computed tomography scanner at 0°, 45°, 90°, and 135° of knee flexion. Several modeling programs were used to simulate double-bundle ACL reconstruction. A finite element model of each bundle with a tension of 20 N was put into each tunnel followed by fixation of the bundles. The tension and length changes of each bundle at different knee flexion angles were assessed. RESULTS For the anteromedial bundle, the length decreased gradually between 45° and 90° of knee flexion and then reached a plateau, whereas the length of the posterolateral bundle significantly decreased at 45° and 90° of flexion but then increased at full flexion. The reaction force of the anteromedial graft slightly decreased at 45° and then remained constant between 90° and 135° of knee flexion. The reaction force of the posterolateral bundle at full extension slightly decreased at 45° and 90° of flexion, followed by a rebound increase at 135°. CONCLUSIONS We found that both bundles functioned throughout the arc of flexion with consistency in tension, although their lengths decreased. The 2 ACL grafts did not function in a reciprocal manner, unlike previous descriptions. CLINICAL RELEVANCE The data obtained for length and tension versus flexion angle have the potential to suggest the appropriate knee position for graft fixation and tensioning to be near extension in clinical situations.

In vivo analysis of acromioclavicular joint motion after hook plate fixation using three-dimensional computed tomography

BACKGROUND The clavicle hook plate can be used to treat acromioclavicular and coracoclavicular ligament injury or distal clavicular fracture with comminution. However, the hook plate can induce subacromial impingement, resulting in discomfort from the hardware. METHODS Our inclusion criteria were (1) men and women aged older than 20 years and (2) the presence of comminuted distal clavicular fractures (Neer type IIB) fixed with a hook plate (Synthes, Oberdorf, Switzerland). Three-dimensional computed tomography was obtained before removal of the hook plate. Seven patients were enrolled prospectively. The mean age was 42 years (range, 24-60 years). Zero degree images and abduction images were obtained. The sagittal cut surface was obtained 5 mm medial from the distal clavicle. The equator of the cut surface of the clavicle was compared with the full abduction model to analyze rotation. The center of the cut surface of the clavicle was compared with the full abduction model to analyze translation. RESULTS The average difference in rotation of the distal clavicle between both shoulders was 16° (range, 3°-22°; P = .001). The mean difference in anterior translation of the distal clavicle was 2.2 mm (range, -0.7 to 5.6 mm; P = .030). CONCLUSION Hook plate fixation at the acromioclavicular joint causes decreased internal rotation and increased anterior translation of the distal clavicle with respect to the medial acromion, indicating that the scapula relative to the thorax has decreased posterior tilting and increased external rotation in shoulders fixed using a hook plate.

Dynamic Function of Coracoclavicular Ligament at Different Shoulder Abduction Angles: A Study Using a 3-Dimensional Finite Element Model

PURPOSE The aim of this study was to determine the acromioclavicular (AC) motion and change in length and tension of the coracoclavicular ligament during different positions of shoulder abduction using a 3-dimensional finite element model based on computed tomography images from normal human shoulders. METHODS The right shoulders of 10 living subjects were scanned with a high-resolution computed tomography scanner at 0°, 60°, 120°, and 180° of shoulder abduction. Several modeling programs were used to simulate AC motion. Finite element models of the conoid and trapezoid ligaments were constructed based on each footprint. The tension and length changes of each ligament during shoulder abduction were assessed. RESULTS The distal clavicle exhibited internal rotation with respect to the medial acromion at 0°, 60°, 120°, and full abduction (3.2° ± 2.9°, 23.2° ± 10.8°, 20.6° ± 3.7°, and 37.1° ± 3.4°, respectively). With horizontal motion, the clavicle translated posteriorly at 60° of abduction (4.4 ± 3.4 mm) and then translated anteriorly at 120° and full abduction (0.4 ± 1.6 mm and 1.9 ± 0.4 mm, respectively). The lengths of the conoid ligament gradually increased at 60° to 180° of shoulder abduction whereas those of the trapezoid ligament remained relatively consistent at 60° to 120° of abduction compared with 0° of abduction. CONCLUSIONS The distal clavicle had a wide range of motion during shoulder abduction, which did not support the concept of synchronous motion with the scapula. The conoid and trapezoid ligaments functioned reciprocally during shoulder abduction. With increasing shoulder abduction, the length of the conoid ligament gradually increased; meanwhile, the trapezoid ligament was relatively consistent and then lax at full abduction. In particular, the conoid ligament may act as a key restraint to prevent excessive retraction of the scapula during shoulder abduction. CLINICAL RELEVANCE The data in this study have the potential to suggest that conoid and trapezoid ligaments should be reconstructed separately, and rigid AC fixation in patients with AC separation is not recommended based on the findings of this study.

Arthroscopic percutaneous repair of anterosuperior rotator cuff tear including biceps long head: a 2-year follow-up.

Background To report the results of an arthroscopic percutaneous repair technique for partial-thickness tears of the anterosuperior cuff combined with a biceps lesion. Methods The inclusion criteria were evidence of the upper subscapularis tendon tear and an articular side partial-thickness tear of the supraspinatus tendon, degeneration of the biceps long head or degenerative superior labrum anterior-posterior, above lesions treated by arthroscopic percutaneous repair, and follow-up duration > 24 months after the operation. American Shoulder and Elbow Surgeons (ASES) score, constant score, the pain level on a visual analogue scale, ranges of motion and strength were assessed. Results The mean (± standard deviation) age of the 20 enrolled patients was 56.0 ± 7.7 years. The forward flexion strength increased from 26.3 ± 6.7 Nm preoperatively to 38.9 ± 5.1 Nm at final follow-up. External and internal rotation strength was also significantly increased (14.2 ± 1.7 to 19.1 ± 3.03 Nm, 12.3 ± 3.2 to 18.1 ± 2.8 Nm, respectively). Significant improvement was observed in ASES and constant scores at 3 months, 1 year and the time of final follow-up when compared with preoperative scores (p < 0.001). The mean subjective shoulder value was 86% (range, 78% to 97%). Conclusions The implementation of complete rotator cuff repair with concomitant tenodesis of the biceps long head using arthroscopic percutaneous repair achieved full recovery of normal rotator cuff function, maximum therapeutic efficacy, and patient satisfaction.

The Effect of Notchplasty on Tunnel Widening in Anterior Cruciate Ligament Reconstruction

PURPOSE To investigate changes in femoral tunnel diameter, dimension, and volume after anterior cruciate ligament reconstruction with notchplasty. METHODS Porcine knee specimens were divided into 2 groups of 10 specimens each. Group A did not receive notchplasty. A 2-mm notchplasty was conducted in group B. Seven-millimeter-diameter femoral tunnels were drilled and a doubled flexor digitorum profundus tendon was inserted and fixed with an EndoButton (Smith & Nephew, Andover, MA) in each knee specimen. Samples were mounted on a materials testing machine. Each group was preloaded at 10 N and subjected to 20 loading cycles (between 0 and 40 N), followed by 1,000 loading cycles in the elastic region (between 10 and 150 N). High-resolution computed tomography with 1.0-mm slices was conducted with all samples before and after testing. A 3-dimensional model was constructed to evaluate the degree of the tunnel change. RESULTS In group B the mean longest diameter and dimension of the femoral tunnel significantly increased after the test (P = .005 and P = .001, respectively). The volumetric loss of bony structure after the test in group B was significantly greater than that in group A (P = .039). Meanwhile, no significant difference was found before and after the test in terms of tunnel diameter, dimension, and volumetric loss around the tunnel in group A. CONCLUSIONS The intra-articular orifice of the femoral tunnel was enlarged after the uniaxial cyclic loading test after notchplasty. An enlarged tunnel orifice may lead to a discrepancy between the tunnel and the graft at the tunnel aperture. CLINICAL RELEVANCE The data may have an implication that suspensory fixation with a notchplasty has a negative effect on the full graft accommodation at the tunnel aperture. Aperture widening may affect graft positioning, leading to subtle changes in graft biomechanics and laxity.

Intertunnel Relationships in Combined Anterior Cruciate Ligament and Posterolateral Corner Reconstruction An In Vivo 3-Dimensional Anatomic Study

Background: Combined anterior cruciate ligament (ACL) and posterolateral corner (PLC) injuries are relatively common, and tunnel convergence could occur in combined ACL and PLC reconstruction. Purpose: This study sought to elucidate the ranges of angles and distances of lateral collateral ligament (LCL) and popliteus tendon (PT) femoral tunnels that do not violate the intercondylar notch distally and ACL tunnels proximally during combined ACL and PLC reconstruction. Study Design: Descriptive laboratory study. Methods: Three-dimensional anatomic knee models were developed using customized software from computed tomography images of 14 patients at 0°, 90°, and 120° of flexion. Single-bundle (SB) and double-bundle (DB) ACL tunnels using the transtibial method for anteromedial bundles and the anteromedial portal method for posterolateral bundles were created. The ranges of safe angles and distances were measured at 10° and 20° posterior, neutral (0°), and 10° and 20° anterior on the horizontal plane relative to the transepicondylar axis from the isometric LCL and PT femoral insertions. The SB ACL reconstruction using the accessory medial portal and LCL reconstruction using the anatomic footprint were also analyzed. Results: Distal and proximal angles from insertions of the LCL and PT, not violating the intercondylar notch or the ACL tunnels, increased as the LCL or PT headed from a posterior to anterior direction. Safe distances from the LCL and PT femoral insertions were approximately over 35 mm distally and 30 mm proximally. For SB ACL reconstruction using the accessory medial portal, safe angles were larger proximally than those of SB ACL reconstruction using the transtibial technique. For LCL reconstruction using the anatomic footprint, proximal angles were significantly smaller than those of the isometric LCL. Conclusion: Considering the relationship between the LCL and PT tunnels and fixation strength, tunneling will be safe when the LCL and PT are positioned at an angle of approximately 20° anterior and 10° proximal to the transepicondylar axis. Clinical Relevance: These results will help to reduce the incidence of tunnel convergence in combined ACL and PLC reconstructions.

Graft tension of the posterior cruciate ligament using a finite element model

PurposeThe aim of the study was to analyse the change in length and tension of the reconstructed single-bundle posterior cruciate ligament (PCL) with three different femoral tunnels at different knee flexion angles by use of three-dimensional finite element method.MethodsThe right knees of 12 male subjects were scanned with a high-resolution computed tomography scanner at four different knee flexion angles (0°, 45°, 90° and 135°). Three types of single-bundle PCL reconstruction were then conducted in a 90° flexion model: femoral tunnels were created in anterolateral (AL), central and posteromedial (PM) regions of the footprint. Length versus flexion curves and tension versus flexion curves were generated.ResultsBetween 0° and 90° of knee flexion, changes in length and tension in the PM grafts were not significant. Whereas the lengths and tension of the AL and central grafts significantly increased in the same flexion range. The length and tension of the PM grafts at 135° of knee flexion were significantly higher than those at 90° of knee flexion, whereas the AL and the central grafts showed only slight length changes beyond 90° of flexion. However, the tension of the AL graft increased significantly beyond 90° of flexion.ConclusionsChanges in the graft length, and tension were generally affected by different femoral tunnels and knee flexion angles. In groups with the AL and PM single-bundle reconstruction, the graft tension increased beyond 90° of knee flexion when the graft is tensioned at 90° of flexion. These data suggest that final fixation angle at 90° for the AL or PM graft would induce graft overtension in high knee flexion of 135°. Whereas central graft which is fixed in 90° of flexion is desirable in terms of prevention of graft overtension. Because the graft tension within it was relatively constant beyond 90° of flexion.

Stress Distribution in Superior Labral Complex and Rotator Cuff During In Vivo Shoulder Motion: A Finite Element Analysis

PURPOSE To quantitatively and qualitatively evaluate the impingement behavior between structures within the glenohumeral joint under simulated abduction-external rotation (ABER) motion using finite element analysis. METHODS Computed tomography (CT) scanning of 1 shoulder in a volunteer was performed at 0° and 120° of shoulder abduction with external rotation (ABER position), followed by magnetic resonance imaging at 0° of abduction. The CT and magnetic resonance images were then imported into a customized software program to undergo 3-dimensional reconstruction followed by finite element modeling of the bone and soft tissue including the upper part of the rotator cuff and glenohumeral labral complex. Glenohumeral motion from 0° to the ABER position was simulated by CT images in 2 different humeral positions. On the basis of simulated humeral motion with respect to the scapula, we measured the stress value on the biceps-labral complex and upper part of the rotator cuff as a consequence of their structural deformation. In addition, we intended to design 2 types of labra--a normal stable labrum and an unstable posterosuperior labrum--to evaluate the geometric alteration and resulting stress change on the posterosuperior labrum against a compressive force from the humeral head and rotator cuff. RESULTS In the ABER position, the posterosuperior labrum was deformed by the humeral head and interposed posterior part of the rotator cuff. When viewed from the rotator cuff, the posterior part of the rotator cuff came into contact with the posterosuperior labrum as external rotation increased. The measured peak contact stress values were 19.7 MPa and 23.5 MPa for the posterosuperior labrum and the upper rotator cuff, respectively. The stress values for both structures decreased to 5.8 MPa and 18.1 MPa, respectively, in the simulated SLAP model. The root of the long head of the biceps became compressed halfway through the range of motion by the humeral head, especially from the part involving horizontal extension and external rotation, resulting in a high stress of 22.4 MPa. CONCLUSIONS In this simulated SLAP model, the posterosuperior labrum was medially displaced by the humeral head and upper rotator cuff in the ABER position, causing a functional loss of the spacer effect. CLINICAL RELEVANCE In SLAP lesions, the posterosuperior labrum loses its ability to function as a spacer in certain positions (especially ABER) and may decrease the important spacer effect between the humerus and the rotator cuff; this may lead to posterosuperior subluxation of the humeral head or rotator cuff abnormalities and tears during repetitive ABER tasks.