In Vivo Ultrasound Shear Wave Elastography Assessment of Acute Compartment Syndrome in a Turkey Model.

OBJECTIVE: The aim of the work described here was to evaluate the objectivity and reproducibility of non-invasive intra-compartment pressure (ICP) measurement using ultrasound shear wave elastography (SWE) in a turkey model in vivo and to determine the biological and histologic changes in acute compartment syndrome (ACS). METHODS: Twenty-four turkeys were randomly divided into four groups based on the duration and fasciotomy of ACS created by infusion of up to 50 mm Hg in the tibialis muscle: group 1, ACS 2 h; group 2, ACS 4 h; group 3, ACS 2 h + fasciotomy 2 h; group 4, ACS 4 h + fasciotomy 2 h. For each turkey, the contralateral limb was considered the control. Time-synchronized measures of SWE and ICP from each leg were collected. Then turkeys were euthanized for histology and quantitative reverse transcription polymerase chain reaction (qRT-PCR) examination. RESULTS: All models created reproducible increases in ICP and SWE, which had a strong linear relationship (r = 0.802, p < 0.0001) during phase 1. SWE remained stable (50.86 ± 9.64 kPa) when ICP remained at 50.28 ± 2.17 mm Hg in phase 2. After fasciotomy, SWE declined stepwise and then normalized (r = 0.737, p < 0.0001). Histologically, the myofiber diameter of group 2 (82.31 ± 22.92 µm) and group 4 (90.90 ± 20.48 µm) decreased significantly (p < 0.01) compared with that of the control group (103.1 ± 20.39 µm); the interstitial space of all groups increased significantly (p < 0.01). Multifocal muscle damage revealed neutrophilic infiltration, degeneration, hemorrhage and necrosis, especially in group 4. Quantitative RT-PCR verified that interleukin-6 and heparin-binding EGF-like growth factor were significantly increased in group 4. CONCLUSION: SWE provided sensitive measurements correlating to ICP in a clinically relevant ACS animal model. Once ACS time was exceeded, progression to irreversible necrosis continued spontaneously, even after fasciotomy. SWE may help surgeons in the early detection, monitoring, prognosis and decision making on fasciotomy for ACS.

Rotator cuff repair with a novel mesh suture: An ex vivo assessment of mechanical properties.

Surgical repair is a common treatment for rotator cuff tear; however, the retear rate is high. A high degree of suture repair strength is important to ensure rotator cuff integrity for healing. The purpose of this study was to compare the mechanical performance of rotator cuffs repaired with a mesh suture versus traditional polydioxanone suture II and FiberWire sutures in a canine in vitro model. Seventy-two canine shoulders were harvested. An infraspinatus tendon tear was created in each shoulder. Two suture techniques-simple interrupted sutures and two-row suture bridge-were used to reconnect the infraspinatus tendon to the greater tuberosity, using three different suture types: Mesh suture, polydioxanone suture II, or FiberWire. Shoulders were loaded to failure under displacement control at a rate of 20 mm/min. Failure load was compared between suture types and techniques. Ultimate failure load was significantly higher in the specimens repaired with mesh suture than with polydioxanone suture II or FiberWire, regardless of suture technique. There was no significant difference in stiffness among the six groups, with the exception that FiberWire repairs were stiffer than polydioxanone suture II repairs with the simple interrupted technique. All specimens failed by suture pull-out from the tendon. Based on our biomechanical findings, rotator cuff repair with the mesh suture might provide superior initial strength against failure compared with the traditional polydioxanone suture II or FiberWire sutures. Use of the mesh suture may provide increased initial fixation strength and decrease gap formation, which could result in improved healing and lower re-tear rates following rotator cuff repair. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:987-992, 2018.

Biomechanical Effect of Margin Convergence Techniques: Quantitative Assessment of Supraspinatus Muscle Stiffness.

Although the margin convergence (MC) technique has been recognized as an option for rotator cuff repair, little is known about the biomechanical effect on repaired rotator cuff muscle, especially after supplemented footprint repair. The purpose of this study was to assess the passive stiffness changes of the supraspinatus (SSP) muscle after MC techniques using shear wave elastography (SWE). A 30 × 40-mm U-shaped rotator cuff tear was created in 8 cadaveric shoulders. Each specimen was repaired with 6 types of MC technique (1-, 2-, 3-suture MC with/without footprint repair, in a random order) at 30° glenohumeral abduction. Passive stiffness of four anatomical regions in the SSP muscle was measured based on an established SWE method. Data were obtained from the SSP muscle at 0° abduction under 8 different conditions: intact (before making a tear), torn, and postoperative conditions with 6 techniques. MC techniques using 1-, or 2-suture combined with footprint repair showed significantly higher stiffness values than the intact condition. Passive stiffness of the SSP muscle was highest after a 1-suture MC with footprint repair for all regions when compared among all repair procedures. There was no significant difference between the intact condition and a 3-suture MC with footprint repair. MC techniques with single stitch and subsequent footprint repair may have adverse effects on muscle properties and tensile loading on repair, increasing the risk of retear of repairs. Adding more MC stitches could reverse these adverse effects.

Transverse ultrasound assessment of median nerve deformation and displacement in the human carpal tunnel during wrist movements.

The symptoms of carpal tunnel syndrome, a compression neuropathy of the median nerve at the wrist, are aggravated by wrist motion, but the effect of these motions on median nerve motion are unknown. To better understand the biomechanics of the abnormal nerve, it is first necessary to understand normal nerve movement. The purpose of this study was to evaluate the deformation and displacement of the normal median nerve at the proximal carpal tunnel level on transverse ultrasound images during different wrist movements, to have a baseline for comparison with abnormal movements. Dynamic ultrasound images of both wrists of 10 asymptomatic volunteers were obtained during wrist maximal flexion, extension and ulnar deviation. To simplify the analysis, the initial and final shape and position of the median nerve were measured and analyzed. The circularity of the median nerve was significantly increased and the aspect ratio and perimeter were significantly decreased in the final image compared with the first image during wrist flexion with finger extension, wrist flexion with finger flexion and wrist ulnar deviation with finger extension (p < 0.01). There were significant differences in median nerve displacement vector between finger flexion, wrist flexion with finger extension and wrist ulnar deviation with finger extension (all p's < 0.001). The mean amplitudes of median nerve motion in wrist flexion with finger extension (2.36 ± 0.79 normalized units [NU]), wrist flexion with finger flexion (2.46 ± 0.84 NU) and wrist ulnar deviation with finger extension (2.86 ± 0.51 NU) were higher than those in finger flexion (0.82 ± 0.33 NU), wrist extension with finger extension (0.77 ± 0.46 NU) and wrist extension with finger flexion (0.81 ± 0.58 NU) (p < 0.0001). In the normal carpal tunnel, wrist flexion and ulnar deviation could induce significant transverse displacement and deformation of the median nerve.

Ultrasound assessment of the motion patterns of human flexor digitorum superficialis and profundus tendons with speckle tracking.

The purposes of our study were to correlate ultrasonographically measured and joint angle estimated excursions of the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons of the hand and to estimate the relative motion of FDS and FDP while gripping cylinders of standard diameter in normal human subjects. Thirty wrists from 15 human subjects were imaged with an ultrasound scanner. Speckle tracking was used to measure the excursion of the FDS and FDP tendons. The tendon excursions necessary to grip three differently sized acrylic tubes were measured and correlated with the corresponding finger joint angles. The FDP/FDS excursion ratio was calculated. The Pearson's correlation coefficient between the FDS excursion and MP + PIP joint angle was 0.61. The Pearson's correlation coefficient between the FDP + FDS excursion and the DIP + PIP + MP joint angle was 0.67. The FDP/FDS excursion ratio was smaller for larger excursions (gripping a smaller diameter tube) and larger for small excursions (gripping a larger diameter tube, P < 0.01). These data suggest that speckle tracking may be a useful method to discriminate the relative motion of flexor tendons, which in turn may be relevant in evaluating tendon function, for example after tendon injury.

Ultrasound assessment of the displacement and deformation of the median nerve in the human carpal tunnel with active finger motion.

BACKGROUND: Peripheral nerves are mobile structures, stretching and translating in response to changes in the position of adjuvant anatomic structures. The objective of this study was to develop a novel method to characterize the relative motion and deformation of the median nerve on cross-sectional ultrasound images of the carpal tunnel during active finger motion. METHODS: Fifteen volunteers without a history of carpal tunnel syndrome or wrist trauma were recruited. An ultrasound scanner and a linear array transducer were used to evaluate the motion of the median nerve and the flexor tendons within the carpal tunnel during motion from full extension to full flexion by the four fingers (fist motion) and by the long finger alone. The displacement of the median nerve relative to the long-finger flexor digitorum superficialis tendon as well as the perimeter, cross-sectional area, circularity, and aspect ratio of a minimum enclosing rectangle of the median nerve were measured. The data were compared between single-digit motion and fist motion and between extension and flexion positions. RESULTS: The distance between the long-finger flexor digitorum superficialis tendon and the median nerve with isolated long-finger flexion was decreased in the ulnar-radial direction and increased in the palmar-dorsal direction as compared with the distance with four-finger flexion (p < 0.01). Compared with the values with fist motion, the aspect ratio was decreased and the circularity was increased with long-finger motion (p < 0.01). CONCLUSIONS: This report presents a method with which to assess displacement and deformation of the median nerve on a cross-sectional ultrasound image during different finger motions. This method may be useful to assess pathological changes within the carpal tunnel, and we plan to perform a similar study of patients with carpal tunnel syndrome on the basis of these preliminary data.

Speckle tracking ultrasound for assessment of the relative motion of flexor tendon and subsynovial connective tissue in the human carpal tunnel.

The objective of this study was to compare tissue Doppler imaging and speckle tracking ultrasound to assess the relative motion of flexor tendon and surrounding subsynovial connective tissue (SSCT). Twenty normal human wrists were imaged with an ultrasound scanner. The two ultrasound methods measured the excursion and maximum velocity of the tendon and SSCT while subjects gripped three different sized acrylic tubes and these were correlated with tendon excursions estimated from finger joint angle changes. The maximum velocity ratio (=SSCT/tendon velocity) and the shear index (=[(Tendon excursion-SSCT excursion)/Tendon excursion]x100%) were calculated. The intraclass correlation coefficient was higher for joint angle/speckle tracking tendon excursion (0.642) than for joint angle/tissue Doppler excursion (0.377). The speckle tracking method could also discriminate differences in maximum velocity ratio and shear index for different tube sizes. We conclude that speckle tracking may be useful in assessing the relative motion of tendon and SSCT.

Short-term assessment of optimal timing for postoperative rehabilitation after flexor digitorum profundus tendon repair in a canine model.

Abstract The purpose of this study was to compare the short-term outcome following flexor tendon repair for postoperative rehabilitation commencing on day 1 (a common clinical choice) versus day 5 (the day on which, with postoperative immobilization, the initial gliding resistance is least in this model) in an in vivo canine model. Work of flexion (WOF) and tendon strength were evaluated following tendon laceration and repair in 24 dogs sacrificed 10 days postoperatively. Starting postoperative mobilization at day 5 resulted in no tendon ruptures compared with tendon ruptures in four of the dogs (33%) in the group subjected to mobilization starting at day 1. While there was no statistically significant difference in WOF between groups at day 10, there was a trend toward lower resistance favoring the day 5 start group, and the statistical power to detect a difference in WOF was diminished by the ruptures in the day 1 group. We conclude that starting rehabilitation on day 5, when initial gliding resistance is lower, may have an advantage over earlier starting times, when surgical edema and other factors increase the initial force requirements to initiate tendon gliding. We plan further studies to evaluate the longer-term benefits of this rehabilitation program.

Assessment of non-invasive intervertebral motion measurements in the lumbar spine.

This study compared the accuracy of new, FDA-approved, image-analysis software to conventional radiographic assessment techniques for the measurement of intervertebral motion. Six adult human cadaveric lumbar spines (L1-S1) were individually mounted in a custom Plexiglas device and electromagnetic sensors were rigidly mounted to the spinous processes of L3, L4, and L5. Lateral radiographs of the spines in neutral, full flexion, and full extension were digitized and analyzed both using the software and manually by three orthopedic surgeons. Compared to intervertebral rotations determined from the electromagnetic device, the errors in rotations reported by the software and surgeons were 0.47+/-0.24 degrees and 2.16+/-0.78 degrees , respectively. Rotations measured by the surgeons were significantly less accurate and more variable than that of the software (p<0.05).