Development of shock-dynamics study with synchrotron-based time-resolved X-ray diffraction using an Nd:glass laser system.

The combination of high-power laser and synchrotron X-ray pulses allows us to observe material responses under shock compression and release states at the crystal structure on a nanosecond time scale. A higher-power Nd:glass laser system for laser shock experiments was installed as a shock driving source at the NW14A beamline of PF-AR, KEK, Japan. It had a maximum pulse energy of 16 J, a pulse duration of 12 ns and a flat-top intensity profile on the target position. The shock-induced deformation dynamics of polycrystalline aluminium was investigated using synchrotron-based time-resolved X-ray diffraction (XRD) under laser-induced shock. The shock pressure reached up to about 17 GPa with a strain rate of at least 4.6 × 107 s-1 and remained there for nanoseconds. The plastic deformation caused by the shock-wave loading led to crystallite fragmentation. The preferred orientation of the polycrystalline aluminium remained essentially unchanged during the shock compression and release processes in this strain rate. The newly established time-resolved XRD experimental system can provide useful information for understanding the complex dynamic compression and release behaviors.

Correlations of coracohumeral ligament and range of motion restriction in patients with recurrent anterior glenohumeral instability evaluated by magnetic resonance arthrography.

BACKGROUND: Evaluation of range of motion (ROM) restriction before treatment of shoulder disorders is important for predicting the final functional outcomes. The purpose of this study was to investigate correlations of thickness of the coracohumeral ligament (CHL) and ROM restriction in patients with recurrent anterior glenohumeral instability. METHODS: Between January 2005 and March 2015, 181 shoulders (137 male and 44 female patients; mean age, 29.3 years) with recurrent anterior glenohumeral instability treated with an arthroscopic Bankart repair were enrolled in this study. We evaluated preoperative ROM, thickness of the CHL, and obliteration of the subcoracoid fat triangle on magnetic resonance arthrography. ROM measurements, including forward flexion (FF), external rotation with the arm at the side (ER), and hand behind the back (HBB), were made in a standing position. RESULTS: There were significant negative correlations between FF and age (P < .001) and between HBB and age (P < .001) but not between ER and age (P = .11). The thickness of the CHL significantly increased with age (P < .001). FF, ER, and HBB were significantly restricted in patients with obliteration compared with those without obliteration (P < .001, P = .004, P < .001, respectively). CONCLUSIONS: Obliteration of the subcoracoid fat triangle and the thickness of the CHL positively correlated with ROM restrictions, and these changes were greater with age in patients with recurrent anterior glenohumeral instability.

Progression of degenerative changes of the biceps tendon after successful rotator cuff repair.

BACKGROUND: This study investigated the morphologic changes in the biceps tendon using ultrasonography before and after successful arthroscopic posterosuperior rotator cuff repair. METHODS: Forty-four patients (44 shoulders) underwent arthroscopic posterosuperior rotator cuff repair with 1-year postoperative magnetic resonance imaging (MRI) follow-up. The patients comprised 22 men and 22 women with an average age of 61 years. The cross-sectional area (CSA) of the biceps tendon in the bicipital groove was measured, and the vascularity in the bicipital groove was graded as 0 to 3, based on the signal density of the anterior circumflex artery, using power Doppler ultrasonography. The preoperative and postoperative CSA and vascularity grades were compared. The pain score on the University of California, Los Angeles Shoulder Rating Scale was used to analyze the correlation between vascularity and postoperative pain. RESULTS: The average preoperative and postoperative CSA of the biceps tendon was 15.4 ± 6.5 and 17.9 ± 7.5 mm2, respectively. The postoperative CSA was significantly larger than the preoperative CSA (P < .01). Although no significant difference in the vascularity of the bicipital groove was observed between preoperative and postoperative grading, a negative correlation was observed between the vascularity and postoperative pain score on the University of California, Los Angeles scale (r = -0.369). CONCLUSIONS: The biceps tendon in the bicipital groove becomes thicker over time, even after successful posterosuperior rotator cuff repair. In addition, an increase in the vascularity around the biceps tendon in the groove is correlated with pain symptoms after successful repair.

Effects of intra-articular steroid injection before pan-capsular release in patients with refractory frozen shoulder.

PURPOSE: The purpose of the study was to retrospectively determine the effects of intra-articular steroid injection on the clinical outcome of patients who underwent arthroscopic pan-capsular release for refractory frozen shoulder. METHODS: Between 2000 and 2010, 34 patients (20 males, 14 females) who underwent an arthroscopic pan-capsular release for frozen shoulder were included. Intra-articular steroid injections were administered from April 2006, and just before surgery and at the final follow-up, ranges of motion (ROM) and scores of the Shoulder Rating Scale of the University of California, Los Angeles (UCLA) scoring system were evaluated. RESULTS: Intra-articular steroid injection significantly improved the UCLA scores of pain just before surgery and at the final follow-up (1.7 ± 0.5 vs. 6 ± 2, p < 0.0001). We subdivided the patients into those with and without diabetes mellitus. Steroid injection had a significant effect on the ROM in forward flexion (166.6 ± 8.6 vs. 140 ± 36.1, p = 0.026) and the scores of pain (10 vs. 9.3 ± 1.2, p = 0.046) at the final follow-up in the group without diabetes mellitus compared with those with it. CONCLUSION: Intra-articular steroid injection improves pain just before an arthroscopic pan-capsular release and at the final follow-up in all the patients with refractory frozen shoulder. However, it improves the ROM in forward flexion and the UCLA scores of pain at the final follow-up only in those without diabetes mellitus. LEVEL OF EVIDENCE: Therapeutic studies, Level IV.

Arthroscopic management of selective loss of external rotation after surgical stabilization of traumatic anterior glenohumeral instability: arthroscopic restoration of anterior transverse sliding procedure.

PURPOSE: The purpose of this study was to clarify the effectiveness of an arthroscopic procedure for restoration of anterior transverse sliding (RATS) mechanism of the subscapularis tendon in patients with loss of external rotation after surgical stabilization of anterior glenohumeral instability. METHODS: Seven patients who underwent an arthroscopic RATS procedure for loss of external rotation after surgical stabilization of anterior glenohumeral instability were retrospectively reviewed. There were 4 male and 3 female patients with a mean age of 30.7 years. The original procedure was arthroscopic Bankart repair and rotator interval closure in 5 patients, open Bankart repair in 1, and an open Bristow procedure in 1. The arthroscopic RATS procedure was performed as follows: (1) removal of the fibrous tissue in the rotator interval; (2) release of the subscapularis tendon from the glenoid neck; and (3) incision of the superior part of the inferior glenohumeral ligament until a sufficient external rotation angle was obtained without causing anterior instability. We evaluated the mean forward flexion and external and internal rotation angles, Constant score, and University of California, Los Angeles score before the arthroscopic RATS procedure and at final follow-up (mean, 24 months). RESULTS: The mean forward flexion and external and internal rotation angles improved from 162.1° ± 9.5° to 171.4° ± 3.8° (P < .05), from 2.9° ± 4.9° to 47.9° ± 9.1° (P < .005), and from T10 to T8 (P < .05), respectively. The mean Constant and University of California, Los Angeles scores improved from 81.0 ± 13.6 points to 95.1 ± 4.0 points and from 24.0 ± 3.7 points to 33.9 ± 2.0 points, respectively (P < .005). CONCLUSIONS: The arthroscopic RATS mechanism procedure is a useful treatment option with minimum morbidity in patients with loss of external rotation after surgical stabilization of traumatic anterior glenohumeral instability. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Preoperative Pain Control in Arthroscopic Rotator Cuff Repair: Does It Matter?

BACKGROUND: The purpose of this study was to clarify the importance of preoperative pain control using corticosteroid injections in patients with persistent rest pain (RP) before arthroscopic rotator cuff repair (ARCR). METHODS: A total of 360 patients (374 shoulders) who underwent primary ARCR and were followed up for at least 2 years were enrolled. After one-to-one propensity score matching, 266 patients (145 men and 128 women, 273 shoulders) were included in the study. Their mean age was 65.2 ± 7.7 years (range, 42 to 88 years) at the time of surgery. The patients were divided into three groups: those who required several intra-articular or subacromial bursa corticosteroid injections preoperatively for refractory RP (group A+), those in whom RP was resolved preoperatively (group A-), and those who had no RP and did not require any injections (group B). The incidence of postoperative RP and preoperative and final follow-up American Shoulder and Elbow Surgeons (ASES) scores were compared among the three groups. RESULTS: The incidence of postoperative RP was significantly higher in group A+ (35/91 cases, 38.5%) than in group A- (10/91, 11.0%) and group B (7/91, 7.7%, p < 0.001 for both). The preoperative ASES score was significantly lower in group A+ (33.2 ± 14.2) than in group A- (53.9 ± 11.9) and group B (62.3 ± 11.2, p < 0.001 for both), and it was significantly lower in group A- than in group B (p = 0.000). The final follow-up ASES score was significantly lower in group A+ (92.1 ± 8.4) than in group A- (97.6 ± 5.4) and group B (99.0 ± 2.5, p < 0.001 for both). There was no significant difference in the final follow-up ASES score between group A- and group B (p = 0.242). CONCLUSIONS: Patients in whom preoperative RP could be resolved before surgery achieved postoperative outcomes comparable to those in patients who had no RP before surgery, whereas the outcomes in patients with refractory preoperative RP were inferior. The results suggest that preoperative pain control is important in patients undergoing ARCR.

Supraspinatus muscle location changes after arthroscopic rotator cuff repair: a potential source of preoperatively predicting tear patterns.

PURPOSE: When repairing retracted rotator cuff tears, the tear pattern (eg, crescent-shaped, L-shaped) is best determined intraoperatively by evaluating the mobility of the tendon in multiple directions. The purpose of our study was to evaluate the location of the supraspinatus (SSP) muscle belly on magnetic resonance imaging (MRI) in patients undergoing arthroscopic repair of retracted rotator cuff tears. We hypothesized that the location of the rotator cuff muscle would move after tendon repair, and that the perioperative change in muscle position would correlate with the tear pattern. METHODS: A series of primary arthroscopic repairs for rotator cuff tears with >3 cm of medial retraction from 2015 to 2016 was reviewed. MRIs were performed preoperatively and within 10 days postoperatively. The SSP muscle was assessed on sagittal MRI and evaluated for the "occupation ratio", "tangent sign", and the "location index" proposed in this study. Pre and postoperative MRIs were compared, and correlated with intraoperatively determined tear patterns. Fifty shoulders without rotator cuff pathology were also assessed for the "location index" as control. RESULTS: Fifty-nine shoulders (mean age 65.0 years) were included, among which five reverse L-shaped tears were identified. The occupation ratio and tangent sign improved postoperatively. Preoperatively, in the majority of tears, the SSP muscle was located more posteriorly in the SSP fossa, compared to the control group, and shifted anteriorly after repair. However, in reverse L-shaped tears the SSP muscle was located more centrally in the fossa, and shifted posteriorly following repair. CONCLUSION: Rotator cuff tearing and arthroscopic rotator cuff repair change the location of the SSP muscle. Although repair usually results in shifting of the muscle belly from posterior to anterior, reverse L-shaped tears demonstrated an opposite pattern. The location of the SSP muscle belly may be useful in predicting tear patterns of retracted rotator cuff tears. LEVEL OF EVIDENCE: Level IV (case series).

Microstructural deformation process of shock-compressed polycrystalline aluminum.

Plastic deformation of polycrystalline materials under shock wave loading is a critical characteristic in material science and engineering. However, owing to the nanosecond time scale of the shock-induced deformation process, we currently have a poor mechanistic understanding of the structural changes from atomic scale to mesoscale. Here, we observed the dynamic grain refinement of polycrystalline aluminum foil under laser-driven shock wave loading using time-resolved X-ray diffraction. Diffraction spots on the Debye-Scherrer ring from micrometer-sized aluminum grains appeared and disappeared irregularly, and were shifted and broadened as a result of laser-induced shock wave loading. Behind the front of shock wave, large grains in aluminum foil were deformed, and subsequently exhibited grain rotation and a reduction in size. The width distribution of the diffraction spots broadened because of shock-induced grain refinement and microstrain in each grain. We performed quantitative analysis of the inhomogeneous lattice strain and grain size in the shocked polycrysalline aluminum using the Williamson-Hall method and determined the dislocation density under shock wave loading.

Diagnostic system to measure spatial and temporal profiles of shock front using compact two-stage light-gas gun and line reflection method.

A diagnostic system has been developed to obtain spatial and temporal profiles of shock front. A two-stage light-gas gun is used to accelerate impactors in velocity range with 4-9 km/s. The system consists of the Faraday-type electromagnetic sensors to measure impactor velocity, optical system with high-speed streak camera to measure shock-wave velocities, and the delay trigger system with self-adjustable pre-event pulse generator. We describe the specifications and performance of this system and data-analysis technique on the tilt and distortion of the shock front. Finally, we obtained the Hugoniot data of copper for system demonstration.

Target range of motion at 3 months after arthroscopic rotator cuff repair and its effect on the final outcome.

PURPOSE: The postoperative protocol after arthroscopic rotator cuff repair (ARCR) is still controversial. Some surgeons recommend slower rehabilitation in order to improve the integrity of the repair, while others prefer early range-of-motion (ROM) exercise to avoid postoperative stiffness. The purpose of this study was to determine target ROM (T-ROM) measurements at 3 months after ARCR that are predictive of eventual full recovery without structural failure. METHODS: The cases consisted of 374 shoulders in 360 patients who underwent primary ARCR and were followed up for at least 2 years. Forward flexion (FF) and side-lying external rotation (ER) were measured preoperatively at 3, 6, 9, 12, and 24 months after surgery, and the patients were divided into six subgroups according to the values for each type of ROM at 3 months (ROM-3M). In each subgroup, the final ROM at 24 months after surgery was compared to determine the T-ROM. The average ROMs with time and re-tear rate were then compared between the under-T-ROM and over-T-ROM groups. RESULTS: The only significant difference in FF was between the 120-129° and 110-119° ROM-3M groups. Therefore, the T-ROM for FF was determined to be 120°. Similarly, the T-ROM for ER was determined to be 20°. Each ROM in the over-T-ROM group was significantly better than that in the under-T-ROM group at all assessments. There was no significant difference in the re-tear rate between the groups. CONCLUSION: To acquire sufficient ROM in 2 years without high re-tear rate, a target FF of 120° and ER of 20° should be achieved within 3 months after surgery.

Osteochondritis Dissecans of the Humeral Capitellum in Young Athletes: Comparison Between Baseball Players and Gymnasts.

BACKGROUND: Osteochondritis dissecans (OCD) lesions are often observed in the humeral capitellum both in young baseball players and gymnasts. It is generally believed that capitellar OCD in baseball players can be seen on an anteroposterior (AP) radiograph with the elbow in 45° of flexion. However, the mechanism of injury seems to be different in baseball players and gymnasts. Repetitive valgus overload with the elbow in flexion is believed to be the cause of capitellar OCD lesions in baseball players, whereas weightbearing with the elbow in extension may be the cause of OCD in gymnasts. PURPOSE: To determine the difference in capitellar OCD location between baseball players and gymnasts and to propose the optimal AP radiographic angle of the elbow for visualization of early-stage OCD lesions in adolescent gymnasts. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Subjects consisted of 95 baseball players (95 elbows) and 21 gymnasts (24 elbows) with a mean age of 13.7 years (range, 11-18 years). To localize the lesion, inclination of the affected area in the humeral capitellum against the humeral axis was investigated using sagittal computed tomography images of the elbow. The inclination angle was defined as the angle between the long axis of the humerus and the line perpendicular to a line that connected the anterior and posterior margin of the lesion. The inclination angle in each group was compared and statistically analyzed. RESULTS: The mean inclination angle was 57.6° ± 10.7° in baseball players and 28.0° ± 10.7° in gymnasts. Capitellar OCD lesions were located more anterior in baseball players when compared with gymnasts (P < .01). CONCLUSION: Due to differences in applied stress, capitellar OCD lesions in baseball players were located more anteriorly compared with those seen in gymnasts. Therefore, although AP radiographs with the elbow in 45° of flexion are optimal for detecting OCD lesions in baseball players, radiographs with less elbow flexion or full extension are more useful in gymnasts, especially in early-stage OCD.

Radiological analysis of the medial epicondyle in the adolescent throwing athlete.

INTRODUCTION: Injuries to the medial structures of the elbow due to overhead throwing games are well documented. However, variations of medial epicondyles are not well described, especially in athletes with fused medial epicondyles. In this study, we evaluated variations in the medial epicondyle of baseball players who were aged 15-17 years and had fused epicondyles. METHODS: In this cross-sectional observational study, 155 skeletally mature baseball players with unilateral medial elbow pain and 310 elbow radiographs were reviewed by two independent reviewers. The medial epicondyles were categorised into three groups: normal, elongated or separated. RESULTS: Among the 155 patients, 65 (41.9%) had normal epicondyles, 41 (26.5%) had elongated epicondyles and 49 (31.6%) had separated epicondyles. The medial epicondyle was larger on the dominant arm for 125 (80.6%) patients; the mean surface area on the dominant arm was 222.50 ± 45.77 mm2, while that of the non-dominant arm was 189.14 ± 39.56 mm2 (p < 0.01). Among the three categories of medial epicondyles, separated epicondyles had the largest surface area, followed by elongated and normal epicondyles. CONCLUSION: Medial epicondyles in adolescent throwing athletes can be categorised into three different groups according to their shape (normal, elongated and separated). We observed a correlation between the shape and the surface area of the medial epicondyle in adolescent throwing athletes, with separated medial epicondyles having the largest surface area. Further studies and follow-up are needed to determine the prognostic value and clinical significance of these morphological variations.

Rotator Cuff Lesions in Patients with Stiff Shoulders: A Prospective Analysis of 379 Shoulders.

BACKGROUND: Idiopathic adhesive capsulitis is defined as a frozen shoulder with severe and global range-of-motion loss of unknown etiology. The purpose of our study was to clarify the prevalence of rotator cuff lesions according to patterns and severity of range-of-motion loss in a large cohort of patients with stiff shoulders. METHODS: Rotator cuff pathology was prospectively investigated with use of magnetic resonance imaging (MRI) or ultrasonography in a series of 379 stiff shoulders; patients with traumatic etiology, diabetes, or radiographic abnormalities were excluded. Eighty-nine shoulders demonstrated severe and global loss of passive motion (≤100° of forward flexion, ≤10° of external rotation with the arm at the side, and internal rotation not more cephalad than the L5 level) and were classified as having severe and global loss of motion (Group 1). The remaining 290 shoulders were divided into two groups: those with severe but not global loss (Group 2; 111 shoulders) and mild to moderate limitation (Group 3; 179 shoulders). RESULTS: Among all shoulders, imaging demonstrated an intact rotator cuff in 51%, a full-thickness tear in 35%, and a partial-thickness tear in 15%. In Group 1, 91% had an intact rotator cuff and 9% had a partial-thickness rotator cuff tear. No patient in this group demonstrated a full-thickness tear. In Group 2 and Group 3, respectively, 44% and 35% of the shoulders were intact, 17% and 16% had a partial-thickness tear, and 39% and 50% had a full-thickness tear. CONCLUSIONS: Shoulder stiffness with severe and global loss of passive range of motion is not associated with full-thickness rotator cuff tears, although some patients may have a partial-thickness tear. Shoulders with severe and global loss of range of motion at a first visit are likely to be cases of idiopathic adhesive capsulitis and may not require further imaging studies.

Clinical Outcome and Glenoid Morphology After Arthroscopic Repair of Chronic Osseous Bankart Lesions: A Five to Eight-Year Follow-up Study.

BACKGROUND: Arthroscopic osseous Bankart repair for shoulders with chronic recurrent anterior instability has been reported as an effective procedure with promising short-term outcomes. However, to date, we know of no report describing longer-term outcomes and glenoid morphologic change. The purpose of the present study was to report intermediate to long-term outcomes and glenoid morphologic change after arthroscopic osseous Bankart repair in patients with substantial glenoid bone loss. METHODS: A consecutive series of eighty-five patients with traumatic anterior glenohumeral instability associated with a chronic osseous Bankart lesion underwent arthroscopic repair from January 2005 through December 2006. Forty-six patients with bone loss of >15% of the inferior glenoid diameter relative to the assumed inferior circle regardless of the fragment size were selected as candidates for this study. Thirty-eight patients (83%), including thirty-four male and four female patients, with a mean age of 23.4 years (range, fifteen to thirty-six years) at the time of surgery, were available for final follow-up at a mean of 6.2 years (range, 5.0 to 8.1 years) after surgery. RESULTS: One patient had a redislocation during a traffic accident five months after surgery before obtaining an osseous union. The mean Rowe score and the mean Western Ontario Shoulder Instability Index improved significantly from 30.7 points preoperatively to 95.4 points postoperatively and from 26.5% to 81.5%, respectively. Although the mean preoperative fragment size was measured as only 4.7%, the mean glenoid bone loss improved from 20.4% preoperatively to -1.1% postoperatively. CONCLUSIONS: Arthroscopic osseous Bankart repair is an effective primary treatment for shoulders with substantial glenoid bone loss as it provides successful outcomes without recurrence of instability once osseous union is obtained. Glenoid morphology can be normalized during the intermediate to long-term postoperative period, even in shoulders with a smaller fragment.

Management of calcium and bone abnormalities in hemodialysis patients.

In chronic renal failure, hyperphosphatemia, hypocalcemia, hyperparathyroidism, reduced activation of vitamin D, decreased level of calcium-sensing receptor, osteitis fibrosa, and osteomalacia are features related to calcium abnormalities. Hyperparathyroidism is a risk factor for survival of hemodialysis patients as well as hypoparathyroidism, which is another feature in hemodialysis patients. Treatment of these abnormalities includes control of parathyroid hormone (PTH) secretion, counteracting hyperphosphatemia, correction of hypocalcemia, and others. Various kinds of vitamin D analogs have been introduced recently in addition to calcitriol and alfacalcidol, which have a rather long history (eg, maxacalcitol and falecalcitriol). Sevelamer is a newly developed phosphate binder to treat soft-tissue calcification.

Single microparticle launching method using two-stage light-gas gun for simulating hypervelocity impacts of micrometeoroids and space debris.

A single microparticle launching method is described to simulate the hypervelocity impacts of micrometeoroids and microdebris on space structures at the Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency. A microparticle placed in a sabot with slits is accelerated using a rifled two-stage light-gas gun. The centrifugal force provided by the rifling in the launch tube separates the sabot. The sabot-separation distance and the impact-point deviation are strongly affected by the combination of the sabot diameter and the bore diameter, and by the projectile diameter. Using this method, spherical projectiles of 1.0-0.1 mm diameter were launched at up to 7 km/s.