Wataru Sahara

In vivo three-dimensional evaluation of the functional length of glenohumeral ligaments

BACKGROUND Glenohumeral ligaments play an important role in stabilizing the shoulder. However, it is impossible to know how they function in vivo during shoulder motion. To help elucidate this stabilizing role, we studied the in vivo three-dimensional kinematics of the normal shoulder joint using a markerless bone-registration technique. METHODS Our technique utilized image registration to determine corresponding relations between several image volumes represented at different coordinates. Magnetic resonance images of 14 shoulder joints of seven healthy volunteers were acquired for seven isometric abduction orientations between 0 degrees and 180 degrees . We then calculated three-dimensional shortest path between the origin and insertion of each ligament based on anatomical study in each abduction orientation. FINDINGS At 0 degrees of abduction, the posterior band of the coracohumeral ligament displayed the maximum length. At 30 degrees of abduction, the superior glenohumeral ligament displayed the maximum length. At 60 degrees of abduction, the anterior band of the coracohumeral ligament and the middle glenohumeral ligament displayed the maximum length. At 120 degrees of abduction, the anterior band of the inferior glenohumeral ligament displayed the maximum length. INTERPRETATION Based on progressive abduction of the arm, each ligament had different pattern in change of length. At different arm orientation of abduction, each ligament displayed the maximum length. We think that each ligament might play an important role in stabilizing the shoulder at different arm orientation.

Influence of posterior capsular tightness on throwing shoulder injury

PurposeThe role of posterior capsular tightness in throwing shoulder injury has not yet been clarified. Accordingly, the influence of posterior capsular tightness on the occurrence of throwing shoulder injury was investigated.MethodsSixty-one shoulders with throwing injury were retrospectively reviewed, including 50 tight shoulders and 11 non-tight shoulders. Occurrence of long head of biceps (LHB) lesions, superior glenohumeral ligament (SGHL) and middle glenohumeral ligament (MGHL) injuries, type 2 SLAP lesions, and supraspinatus and subscapularis tendon injuries was compared between the tight and non-tight groups.ResultsThere were LHB lesions in 8 tight shoulders and 6 non-tight shoulders, SGHL injury in 14 and 8 shoulders, and subscapularis tendon injury in 6 and 5 shoulders, respectively, showing significant differences between tight and non-tight shoulders. In contrast, MGHL injury, type 2 SLAP lesions, and supraspinatus tendon injury showed no significant differences. The SLAP lesion was located anteriorly in 6 tight shoulders, posteriorly in 5, and combined in 4 versus 0, 3, and 0 for the non-tight shoulders, respectively, so anterior SLAP lesions only occurred in tight shoulders. Similarly, anterior supraspinatus tendon injuries had a higher incidence in tight shoulders than in non-tight shoulders (19 vs 3).ConclusionsRotator interval lesions were frequent in non-tight shoulders, while anterior SLAP lesions and anterior supraspinatus tendon injuries were predominant in tight shoulders. The significance of posterior capsular tightness should be reconsidered.Level of evidence Retrospective, Level IV.

Directional bias of soft-tissue artifacts on the acromion during recording of 3D scapular kinematics

Scapular kinematics during sports performances can be recorded using skin-mounted trackers attached to the skin overlying the acromion for continuous data collection without restricting natural motions of the subject relative to medical imaging analyses limiting its use for wide-range or high-speed motions. This study aimed to describe the existence of a directional bias in the translational and rotational errors of skin-mounted trackers using a 3D magnetic resonance imaging (3D-MRI) protocol. 3D-MRI scans of the healthy right shoulders of 19 males were acquired in 12 arm positions. The relative transformation of the scapular configuration determined to be the measurement error, as recorded by the configuration of the small cuboid imitating a skin-mounted tracker relative to the actual scapular configuration measured by the voxel-based registration. These measurement errors were expressed with either positive or negative values to describe the bias. Overall translational errors in the lateral, anterior, and superior directions were 3.7 ± 8.4 mm, 9.5 ± 6.4 mm, and 6.2 ± 4.6 mm, respectively. Overall rotational errors in protraction, upward rotation, and posterior tilt were 7.8 ± 8.4°, 0.2 ± 7.4°, and - 4.0 ± 7.5°, respectively. The skin-mounted tracker displayed a high probability of displacement in antero-superior (93% and 91%) directions and rotates in a protracting manner (82%) relative to the position of the underlying bone with the gradual nature of its change. The existence of the directional bias with its gradual change suggests a statistical predictability in measurement errors, which can be used to predict accurate scapular translation and rotation.

Kinematics and Motion Analysis

The shoulder girdle has a complex motion. Many researchers have taken interest in the complex motions of the shoulder and investigated it by various methodologies. We have recently been able to evaluate 3D kinematics of the shoulder with the aid of 3D motion analysis systems such as 3D motion capture system, 3D MRI, and 2D/3D registration technique. In this chapter, we summarize the advantage and disadvantage of each 3D motion analysis system and introduce the results of the shoulder kinematics previously reported.

Transosseous-Equivalent Arthroscopic Bankart Repair by Twin Anchor Footprint Fixation (TAFF) Technique Using JuggerKnot™ Soft Anchor

In 2004, we developed a new type of arthroscopic Bankart repair technique named the double anchor footprint fixation (DAFF), using two different suture anchors for the glenoid neck and glenoid surface anchors, to achieve a more anatomic and wider footprint fixation. As soon as the small, all-suture soft anchor was available in 2011, the twin anchor footprint fixation (TAFF) technique was developed using only the soft anchor for both the glenoid neck and glenoid surface anchors. This TAFF technique might be suitably indicated for patients with a significant ALPSA (anterior labro ligamentous periosteal sleeve avulsion) lesion or those who need capsular shift. Moreover, the specific indications of this technique are revision cases after conventional arthroscopic Bankart repair surgery, and a bony Bankart lesion with large thick bone fragments. The TAFF technique using the all-suture soft anchors is a step closer to a true transosseous suture technique, which is the conventional open procedure making a bone tunnel.