Hiroaki Inui

Surgical treatment of distal clavicle fractures using the clavicular hook plate.

From 1999 to 2003, 34 patients with unstable distal clavicular fractures (Neer Type 2) had surgery using the acromioclavicular titanium hook plate. To investigate the reliability of clavicular hook plate fixation and the effects of hook plates in the subacromial space, we retrospectively reviewed clinical results for pain, shoulder function, range of motion, and radiographic results. The Japanese Orthopaedic Association scores for shoulder disorders indicated good clinical results (mean, 98.3 points). All patients had radiographic bony union. Complications included plate displacement in one patient, acromion fracture caused by widening of the hook hole in one patient, and a rotator cuff tear caused by hook subacromial impingement in one patient. This plate fixation method is useful for treating unstable distal clavicular fracture. However, careful operative planning and familiarity with the technique are necessary to prevent complications including subacromial impingement, rotator cuff damage, acromion fracture, and hook cut-out. Care must be used when establishing the position of the hook hole, and it is best to remove the plate after bony union.Level of Evidence: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Glenoid shape in atraumatic posterior instability of the shoulder

Glenoid shape is related closely to shoulder stability and its abnormality is thought to affect the humeral head position in shoulders with atraumatic instability. However, it is unclear how the glenoid shape in shoulders with atraumatic instability is different from the glenoid shape in normal shoulders. The current authors investigated glenoid shape of 45 healthy individuals (20 males and 25 females; average age, 22 years) and 20 patients with atraumatic posterior instability with multidirectional laxity (six males and 14 females; average age, 19 years) using three-dimensional magnetic resonance imaging. The tilting angles of the glenoid bone were measured in five consecutive planes perpendicular to the long axis of the glenoid and cross sections were divided into three types (concave, flat, convex). In healthy individuals, the average tilting angles from the bottom to the top of the glenoid bone were 3.0° ± 3.6°, 1.0° ± 3.2°, −1.0° ± 2.0°, −2.3° ± 3.9°, and −6.9° ± 3.7° anteriorly, and tilting angles of patients were −6.1° ± 4.0°, −4.0° ± 3.6°, −4.8° ± 3.2°, −5.5° ± 2.7°, and −7.5° ± 3.1°. The type of cross section also was different on the bottom plane where the concave shape accounted for 78% of healthy individuals whereas it accounted for 0% of patients. The loss of tilting angles and concavity of the inferior glenoid would correlate with the direction of the head translation in posterior instability.

Evaluation of three-dimensional glenoid structure using MRI

The tilting angle and the shape of the glenoid cavity are considered to relate closely to shoulder stability. They are also important when planning arthroplasty and developing new designs. This study examines the glenoid cavity using 3‐dimensional MRI. Forty volunteers (20 men, 20 women; average age 21.4; range 18–35 y) were enrolled in the study. The tilting angles of the glenoid bone were measured in 5 consecutive axial planes perpendicular to the glenoidal long axis. Cross sections were divided into 3 types (concave, flat, convex) according to the shape on each plane.

Scapulohumeral rhythm : relationship between motion velocity and rhythm

The relative contributions of scapulothoracic and glenohumeral motion at different rates of shoulder motion were studied through adduction to abduction in the scapular plane. Nineteen shoulders of 10 healthy individuals (all men, 24–30 years of age) were analyzed using an image intensifier and a high-resolution digital video system. High- and low-speed motion consisted of 2 and 4 seconds per one cycle, respectively, from abduction to adduction in the scapular plane. Glenohumeral and scapulothoracic ratios were fixed at low speed and these results agree with the finding of other researchers. Ratios at high speed were not fixed and differed significantly from those at low speed. Ratios were high at the beginning of abduction or adduction and at angles beyond 40° abduction, then decreased according to the arm movement. Glenohumeral motion at high speed was more dominant at the beginning of abduction or adduction beyond the setting phase, then became less dominant according to the arm movement, compared with the motion at low speed.

Activation of cartilage-derived morphogenetic protein-1 in torn rotator cuff.

Localization and expression of cartilage-derived morphogenetic protein-1 in tissues of torn rotator cuff tendons were examined by in situ hybridization and immunohistochemical analysis. Histologic findings of torn rotator cuff tendons showed that active cells synthesizing the alpha-1 chain of collagen Type I messenger ribonucleic acid were localized predominantly in the torn edge and in the bursa side rather than in the joint side, and scarcely localized in a site distant from the torn edge. Cartilage-derived morphogenetic protein-1 had a similar distribution as the alpha-1 chain of collagen Type I. The current findings provide the first observational evidence that cartilage-derived morphogenetic protein-1 was activated specifically at the site of the torn rotator cuff tendon. The current findings suggest that the cells in the torn rotator cuffs are capable of synthesizing cartilagederived morphogenetic protein-1, one of the known essential factors for tendon formation.

Adhesion of the subacromial bursa may cause subacromial impingement in patients with rotator cuff tears: Pressure measurements in 18 patients

In order to determine whether adhesion of the subacromial bursa leads to impingement, we measured the subacromial contact pressures before and after release of adhesion of this bursa. 18 shoulders with cuff tears and adhesion of the subacromial bursa were evaluated in 8 male and 10 female patients, of mean age 62 (53–71) years and who had no particular limitation of shoulder motion. We recorded subacromial pressures using a very sensitive film inserted under the acromion during surgery. In passive scapular plane elevation (scaption) at 100°, the mean subacromial contact pressure and area declined from 1.43 (SD 0.23) MPa before release to 1.14 (SD 0.35) MPa after release (p < 0.001), and from 163 (SD 81) mm2before release to 80 (SD 46) mm2after release (p < 0.001), respectively. We suggest that adhesion of the subacromial bursa increases impingement between the acromion and the insertion of rotator cuff tendons.

External rotation during elevation of the arm

Background Knowledge about the pattern of rotation during arm elevation is necessary for a full understanding of shoulder function, and it is also useful for planning of rehabilitation protocols to restore range of motion in shoulders in disorder. However, there are insufficient in vivo data available. Methods We investigated dynamic arm rotation during elevation in different planes using 30 shoulders in 15 healthy men (age range 21–33 years). Both arms were moved from neutral dependent position to maximum elevated position in 4 planes from laterally to anteriorly, and each dynamic course of motion was traced using a 3-dimensional motion capture system. Results Patterns of rotation were categorized as being one of 2 types, depending on whether or not external rotation peaked before the arm reached the maximum elevated position. External rotation peaked at 122˚ (SD14) of abduction, then decreased according to the arm movement in the lateral planes, but increased gradually to maximum elevated position in the anterior planes. Mean maximal angles of external rotation (in degrees) during elevation were 27 (SD11), 13 (SD13), 3 (SD9), and 3 (SD5), from laterally to anteriorly. Interpretation There were differences in rotational patterns, and more external rotation was needed to reach maximum elevation in lateral planes than in anterior planes.

Influence of Combinations of Shoulder, Elbow and Trunk Orientation on Elbow Joint Loads in Youth Baseball Pitchers:

Objectives: Shoulder and elbow pain in youth baseball pitchers is a well-recognized phenomenon. Common problems in pitching mechanics that can lead to injury begin with stride foot contact. The purpose of this study was to address the relationships between the combinations of shoulder, elbow and trunk orientation at the instant of stride foot contact and elbow joint loads in youth baseball pitchers. Methods: A total of 143 Japanese male youth baseball pitchers participated in this study after providing written informed consents approved by the hospital’s institutional review board. The procedures to be performed were also explained to their parent(s) or legal guardian(s). Each participant was not currently injured or recovering from an injury at time of testing. For data collection of baseball pitching, a set of 14-mm spherical reflective markers was placed on the skin overlying 34 anatomical landmarks determined. Subsequently, a motion capture three-dimensional automatic digitizing system was used to collect 500-Hz from 7 charge-coupled-device synchronized cameras was set up around the regulation pitching mound in an indoor laboratory. After performing a preparation routine of stretching and warm-up pitching, each player pitch to 5 fastball pitches off the pitching mound to a catcher at the regulation distance of 16 m for youth pitchers. The best pitch thrown for a strike was chosen for kinematic and kinetic analysis. The local coordinate systems were used to calculate 3-dimesional rotation at the trunk, shoulder and elbow using the typical Eulerian sequence. Afterward, the standard inverse dynamic equation was used to estimate resultant joint forces and torques at throwing shoulder and elbow. In order to normalize data between subjects, forces and torques were expressed as percent using body weight and height. A multiple regression analysis was carried out to assess the combined effects of shoulder (external rotation, abduction and horizontal adduction), elbow (pronation and extension) and trunk (extension, contralateral tilt, rotation) orientation at SFC and the onset time of trunk rotation on elbow joint loads at SFC. The onset time of trunk rotation was defined as the event in which the magnitude of trunk rotation begins to decrease from tis maximum value. Results: The peak medial force of the elbow was significant correlated with the peak internal rotation torque of the shoulder and the peak varus torque of the elbow (Figure 1). The medial force of the elbow at SFC was significantly correlated with the peak medial force of the elbow (r = .41, p < .001). The adjusted multiple R2 value was 0.45, indicating that over 45% of the variance in the medial force of the elbow at SFC was explained by the regression equation. The standard error of estimate was 4.34. All 3 of the regression variables were significant and are shown in Table 1. Conclusion: The combinations of the greater external rotation of the shoulder, contralateral trunk tilt and elbow extension at SFC may have an indirect influence on the peak medial force on the elbow (Table 1). Then the peak elbow varus torque and shoulder internal rotation torque lead to increase as a result of these. These biomechanical data provide a scientific basis for clinicians, athletes, and coaches to establish methods to prevent pitching-related injuries and improve pitching mechanics.

Three-dimensional kinematic analysis of throwing motion focusing on pelvic rotation at stride foot contact

Background Because the throwing motion can be considered a kinetic chain, pelvic and trunk motion should be included in the analysis. Early pelvic rotation during the throwing sequence has been reported to be a factor leading to overloading of the shoulder and the elbow. A large pelvic rotation angle at the stride foot contact (SFC) was thought to indicate early pelvic opening. This study examined the kinematic features in each motion segment associated with increased pelvic rotation at SFC in pitchers of various ages and competition levels. Materials and methods The study included 324 pitchers with various age/competition levels. Throwing motion was analyzed using an infrared-type motion capture system. In the assessment, pelvic rotation angle at SFC was adopted as a parameter for the timing of pelvic opening. Statistical analyses were performed for correlation between pelvic rotation and kinematic variables of other motion segments at the instant of SFC as well as the difference in kinematics between the groups of different levels. Results Most of the kinematic results were not significantly different among the 4 groups with different levels. The increase in the pelvic opening angle at SFC was significantly correlated with increased trunk bend to the nonthrowing arm side and decreased hip flexion angle on the throwing arm side. Discussion and Conclusion Early pelvic rotation in the throwing motion sequence, as manifested by increased pelvic rotation at SFC, was correlated with changes in kinematic parameters at other motion segments such as increased trunk tilt and decreased hip flexion.

Estimation of Shoulder Behavior From the Viewpoint of Minimized Shoulder Joint Load Among Adolescent Baseball Pitchers

Background: During pitching, an overloaded joint reaction force exerted on the shoulder and excessive shoulder horizontal abduction at ball release are considered risk factors causing anterior shoulder pain for young baseball pitchers. Hypothesis/Purpose: The first aim was to examine the relationship between shoulder horizontal abduction position and force on the shoulder at ball release. The second was to identify the relative rotational position of the shoulder and the range of shoulder motion at ball release that minimize force on the shoulder. It was hypothesized that the amount of force on the shoulder would be exacerbated by excessive shoulder horizontal abduction. Study Design: Descriptive laboratory study. Methods: Participants were 183 adolescent baseball pitchers (mean ± SD age, 15.5 ± 1.2 years) without shoulder/elbow problems. Each pitcher threw 5 fastballs to a catcher behind a home plate. The kinematics and kinetics of the throwing shoulder during fastball pitching were calculated with 3-dimensional measurements from 36 reflective markers. In data analysis, the correlations were calculated between the relative rotational positions of the shoulder (abduction, horizontal adduction-abduction) and the forces on the shoulder (anterior-posterior, proximal, and superior-inferior) at ball release. Subsequently, the specific rotational position and range of motion of the shoulder at ball release that minimized forces on the shoulder were determined. Results: Statistically significant correlations were identified between the magnitude of superior-inferior force on the shoulder and shoulder abduction position (R2 = 0.44, P < .001) as well as between the magnitude of anterior-posterior force on the shoulder and shoulder horizontal adduction-abduction position (R2 = 0.72, P < .001). Minimal anterior-posterior and superior-inferior forces were obtained with a combination of 80.6° of shoulder abduction and 10.7° of shoulder horizontal adduction. Any deviation >5° from this position significantly increased the anterior-posterior and superior-inferior forces on the shoulder. Conclusion: Increasing shoulder horizontal abduction position significantly increased the magnitude of anterior force on the shoulder at ball release. The combination of 80.6° of shoulder abduction and 10.7° of horizontal shoulder adduction minimized the shear forces on the shoulder at this point. Clinical Relevance: The present data can be useful for screening pitching technique to prevent shoulder pain and injury with motion capture assessment.