Taku Hatta

Feasibility assessment of shear wave elastography to rotator cuff muscle.

Pre‐surgical measurement of supraspinatus muscle extensibility is important for rotator cuff repair. The purpose of the present study was to explore the potential feasibility of a shear wave ultrasound elastography (SWE)‐based method, combined with B‐mode ultrasound, to measure the in vivo stiffness of the supraspinatus muscle non‐invasively and thus obtain key information about supraspinatus muscle extensibility. Our investigation comprised two steps. First, we determined the orientation of the supraspinatus muscle fibers in cadaveric shoulders without rotator cuff tear in order to optimize the ultrasound probe positions for SWE imaging. Second, we investigated the feasibility of quantifying the stiffness of the normal supraspinatus muscle by SWE in vivo. The supraspinatus muscle was divided into four anatomical regions: anterior superficial (AS), posterior superficial (PS), anterior deep (AD), and posterior deep (PD). Each region was examined by SWE. The SWE stiffnesses of AD, AS, PD, and PS were 40.0 ± 12.4, 34.0 ± 9.9, 32.7 ± 12.7, 39.1 ± 15.7 kPa, respectively. SWE combined with B‐Mode ultrasound imaging could be a feasible method for quantifying the local stiffness of the rotator cuff muscles. Clin. Anat. 28:213–218, 2015.

Quantitative assessment of rotator cuff muscle elasticity: Reliability and feasibility of shear wave elastography

Ultrasound imaging has been used to evaluate various shoulder pathologies, whereas, quantification of the rotator cuff muscle stiffness using shear wave elastography (SWE) has not been verified. The purpose of this study was to investigate the reliability and feasibility of SWE measurements for the quantification of supraspinatus (SSP) muscle elasticity. Thirty cadaveric shoulders (18 intact and 12 with torn rotator cuff) were used. Intra- and inter-observer reliability was evaluated on an established SWE technique for measuring the SSP muscle elasticity. To assess the effect of overlying soft tissues above the SSP muscle, SWE values were measured with the transducer placed on the skin, on the subcutaneous fat after removing the skin, on the trapezius muscle after removing the subcutaneous fat, and directly on the SSP muscle. In addition, SWE measurements on 4 shoulder positions (0°, 30°, 60°, and 90° abduction) were compared in those with/without rotator cuff tears. Intra- and inter-observer reliability of SWE measurements were excellent for all regions in SSP muscle. Also, removing the overlying soft tissue showed no significant difference on SWE values measured in the SSP muscle. The SSP muscle with 0° abduction showed large SWE values, whereas, shoulders with large-massive tear showed smaller variation throughout the adduction-abduction positions. SWE is a reliable and feasible tool for quantitatively assessing the SSP muscle elasticity. This study also presented SWE measurements on the SSP muscle under various shoulder abduction positions which might help characterize patterns in accordance to the size of rotator cuff tears.

Stress Distribution Within Rotator Cuff Tendons With a Crescent-Shaped and an L-Shaped Tear

Background: There are 2 representative shapes of full-thickness rotator cuff tears commonly observed: crescent-shaped and L-shaped tears. To date, the exact process of tear propagation in each shape remains unknown. Purpose: To determine the stress distribution pattern in rotator cuff tendons with a crescent-shaped tear and an L-shaped tear. Study Design: Descriptive laboratory study. Methods: The computed tomography (CT) data of a normal cadaveric shoulder from a 69-year-old man were used to develop a 3-dimensional finite element model of the rotator cuff tendons. Three different sizes (1.0-, 2.0-, and 3.0-cm widths) of crescent-shaped and L-shaped tears were created. Tensile load was applied to each cuff tendon that simulated shoulder abduction and external rotation in the hanging-arm position. Elastic analysis was performed, and distribution of the von Mises equivalent stress was calculated. Then, the stress distribution pattern was compared between the 2 tear shapes and among the 3 different tear sizes. Results: In the crescent-shaped tear models, stress concentration was seen in both the anterior and the posterior edges of the torn tendon stump. In the L-shaped tear models, stress concentration was seen in the posterior torn tendon edge as well as the bottom of the longitudinal tear. The areas with high stress concentration increased with increasing tear size. At the posterior torn tendon edge, a common site of delamination, the articular half represented a higher equivalent stress than the bursal half in all models. The highest equivalent stress increased with an increase in tear size for both the abduction and the external rotation loads. Conclusion: A high stress concentration was seen in both the anterior and the posterior tendon edge in crescent-shaped tears and in both the posterior tendon edge and the bottom of the longitudinal tear in L-shaped tears. Stress concentration inside the tendon increased with increasing tear size. Clinical relevance: Crescent-shaped tears may propagate in the anterior and posterior directions, whereas L-shaped tears may propagate in the posterior and medial directions. Tear propagation may accelerate with an increase in tear size.

Immobilizing performances, comfort, and user-friendliness of the shoulder abduction-external rotation braces.

Abstract Background. Shoulder external rotation braces used for patients with a first-time shoulder dislocation are designed with a variety of arm positions in abduction as well as external rotation. However, few studies have focused on their immobilizing performance, comfort, or user-friendliness. Especially, there have been no robust data of shoulder abduction-external rotation (A-ER) braces in comparison to those of external rotation (ER) braces. Methods. Four types of commercially available shoulder braces (two ER and two A-ER braces) were tested in 30 healthy participants. The angles of external rotation and abduction were measured for each brace at initial application, after simulated daily activities, and after reapplication. Then, subjects were asked to assess the discomfort of bracing and difficulty of reapplication using a visual analogue scale. Data were compared between the two ER braces and two A-ER braces as well as among the four braces. Results. For both external rotation angle and subjective assessment, there were no significant differences between the ER and A-ER braces. Among the four braces, the measurement of arm position demonstrated no significant differences, except the external rotation angles between the two ER braces. The A-ER braces were assessed to be significantly less comfortable than the ER braces in the subjective assessment. Conclusions. Immobilization using the A-ER braces could maintain the arm position in abduction-external rotation with comparable user-friendliness, although they tended to be less comfortable during daily activities compared to the ER braces.

Arm Abduction Provides a Better Reduction of the Bankart Lesion During Immobilization in External Rotation After an Initial Shoulder Dislocation

Background: Shoulder dislocation often recurs, especially in the younger population. Immobilization in external rotation, in which a Bankart lesion is displaced in the anterior, medial, and inferior directions, was introduced as a new method of nonoperative treatment, but its clinical efficiency is controversial. In terms of reducing the lesion, it is reasonable to incorporate not only external rotation, which makes the anterior soft tissues tight to push the lesion posteriorly and laterally, but also abduction, which makes the inferior soft tissues tight to push the lesion superiorly. Hypothesis: Abducting the arm during immobilization in external rotation will improve the reduction of a Bankart lesion. Study Design: Controlled laboratory study. Methods: There were 37 patients with initial shoulder dislocation enrolled in this study. After reduction, MRI was taken in 4 positions of the shoulder: adduction and internal rotation (Add-IR), adduction and external rotation (Add-ER), 30° of abduction and 30° of external rotation (Abd-30ER), and 30° of abduction and 60° of external rotation (Abd-60ER). On radial slices, the separation, displacement of the labrum, and opening angle of the capsule were measured. Results: Add-ER improved the reduction of the anterior labrum but not the inferior labrum when compared with Add-IR. Both Abd-30ER and Abd-60ER improved the reduction of the inferior labrum as compared with Add-IR. Furthermore, Abd-60ER improved the reduction more than Add-ER. Conclusion: Among the 4 positions tested, Abd-60ER is the best position in terms of reducing the Bankart lesion. Clinical Relevance: Abducting the shoulder during immobilization in external rotation is demonstrated to improve the reduction of the Bankart lesion. Therefore, this position is expected to reduce the recurrence rate after initial dislocation of the shoulder. Future clinical trials are necessary.

In vivo measurement of rotator cuff tendon strain with ultrasound elastography: an investigation using a porcine model.

To clarify the relationship between the strain ratio measured by ultrasound elastography and the mechanical properties of the tendon measured by a universal testing machine. We also attempted to determine the effect of the type and depth of soft tissue overlying the tendon on the elastographic measurement.

Comparative study of treatment for distal radius fractures with two different palmar locking plates

Few randomized trials have shown how the placement of a palmar locking plate affects outcomes. The purpose of this study was to compare clinical and radiological outcomes of fixation using locking plates with different concepts for placement relative to the watershed line in a prospective randomized trial. Sixty-four patients with a displaced distal radius fracture were divided into two groups according to the plates used for fixation: distal-type (AcuLocTM, Group A) and proximal-type (VariAxTM, Group V). Wrist function including the range of motion and grip strength was compared at 1, 2, 3 and 6 months postoperatively. Loss of reduction was assessed radiologically. Both groups demonstrated overall satisfactory function at 6 months with no significant difference found between the groups. Minimal loss of reduction was demonstrated in both groups. Internal fixation using the palmar locking plates with two different placements provided satisfactory outcomes at 6-month follow-up, but our results indicate that plates placed distal to the watershed line may delay recovery of wrist motion.

Effect of smoking on complications following primary shoulder arthroplasty

BACKGROUND The purpose of this study was to examine the effect of smoking on the incidence of complications after primary anatomic total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA). METHODS All patients who underwent primary TSA or RSA at our institution between 2002 and 2011 and had a minimum 2-year follow-up were included. Smoking status was assessed at the time of surgery. Current smokers, former smokers, and nonsmokers were compared for periprosthetic infection, fractures (intraoperative and postoperative), and loosening after surgery. RESULTS The cohort included 1834 shoulders in 1614 patients (814 in smokers and 1020 in nonsmokers). Complications occurred in 73 patients (75 shoulders; 44 in smokers and 31 in nonsmokers). There were 20 periprosthetic infections (16 in smokers and 4 in nonsmokers), 27 periprosthetic fractures (14 in smokers and 13 in nonsmokers), and 28 loosenings (14 in smokers and 14 in nonsmokers). Smokers had lower periprosthetic infection-free survival rates (95.3%-99.4% at 10 years; P = .001) and overall complication-free survival rates (78.4%-90.2%; P = .012) than nonsmokers. Multivariable analyses showed that both current and former smokers had significantly higher risk of periprosthetic infection in comparison with nonsmokers (hazard ratio [HR], 7.27 and 4.56, respectively). In addition, current smokers showed a higher risk of postoperative fractures than both former smokers (HR, 3.63) and nonsmokers (HR, 6.99). CONCLUSIONS This study demonstrates that smoking is a significant risk factor of complications after TSA and RSA. These findings emphasize the need for preoperative collaborative interventions, including smoking cessation programs.

Nicotine reduced MMP-9 expression in the primary porcine tenocytes exposed to cyclic stretch†

Nicotine is one of the major chemical components of the cigarette smoke, which has been known as a risk factor for tendon ruptures including rotator cuff tears. This study investigated the effect of nicotine on tenocytes under cyclic‐stretched condition. Particularly, we focused on the morphologic changes of tenocytes and their expression of MMPs. Primary porcine tenocytes were obtained from the infraspinatus tendon. The cells were cultured on elastic chambers under static or cyclic‐stretched condition for 24 h in the existence of nicotine (0, 1, 10, and 100 µM). Cell shape, gene expression of collagen type I and III, MMPs (‐1, ‐2, ‐3, ‐9, and ‐13) and TIMPs (‐1, ‐2, and ‐3) and enzyme activity of MMP‐9 were analyzed using immunohistochemistry, RT‐PCR, and zymography. Tenocytes exposed to nicotine represented significantly decreased gene expressions in MMP‐9 (p < 0.001) and TIMP‐3 (p < 0.05) under the cyclic stretch. Enzymatic activity of MMP‐9 was also reduced by nicotine exposure in a dose‐dependent manner (p < 0.001). The down‐regulation of MMP and TIMP expression by nicotine shown in our in vitro experiment might deteriorate normal metabolism of the tendon. These mechanisms might affect the mechanical properties of the extracellular matrix of the rotator cuff tendon.

Is previous nonarthroplasty surgery a risk factor for periprosthetic infection in primary shoulder arthroplasty

BACKGROUND The purpose of this study was to determine the risk of periprosthetic infection after primary shoulder arthroplasty (SA) in patients undergoing previous nonarthroplasty shoulder surgery compared with those without previous surgery. MATERIALS AND METHODS All patients undergoing primary SA at our institution between 1970 and 2012 were included in this study. The cohort consisted of 4577 patients treated with 2890 total SAs, 1233 hemiarthroplasties, and 454 reverse SAs; 813 (18%) patients had undergone prior nonarthroplasty shoulder surgery on the operative side. Patients with and without previous surgery were compared for postoperative periprosthetic infection. Univariate and multivariable analyses were used. RESULTS Deep postoperative infection of the shoulder was diagnosed in 68 patients (1.49%). Of the 813 patients who had undergone previous surgery, 20 (2.46%) developed a deep postoperative infection. However, of the 3764 patients who did not have previous shoulder surgery, 48 patients (1.28%) sustained deep shoulder infection. This difference was significant in both the univariate (P = .0094) and multivariate analyses (P = .0390). In addition, older age and female gender were significantly associated with a lower risk of deep postoperative infection (P = .0150 and P = .0074, respectively). A higher number of previous surgeries was also significantly associated with an increased risk of deep postoperative infection (P = .0272). CONCLUSIONS The risk of infection after primary SA is significantly higher in patients with a history of prior non-arthroplasty-related surgery. This finding should be discussed with the patients before their surgery, and potential preoperative and intraoperative workup should be undertaken to identify at-risk patients.