Regional shear wave elastography of Achilles tendinopathy in symptomatic versus contralateral Achilles tendons.

OBJECTIVES: Ultrasound often corroborates clinical diagnosis of Achilles tendinopathy (AT). Traditional measures assess macromorphological features or use qualitative grading scales, primarily focused within the free tendon. Shear wave imaging can non-invasively quantify tendon elasticity, yet it is unknown if proximal structures are affected by tendon pathology. The purpose of the study was to determine the characteristics of both traditional sonographic measures and regional shear wave speed (SWS) between limbs in patients with AT. METHODS: Twenty patients with chronic AT were recruited. Traditional sonographic measures of tendon structure were measured. Regional SWS was collected in a resting ankle position along the entire length of the tendon bilaterally. SWS measures were extracted and interpolated across evenly distributed points corresponding to the free tendon (FT), soleus aponeurosis (SA), and gastrocnemius aponeurosis (GA). Comparisons were made between limbs in both traditional sonographic measures and regional SWS. RESULTS: Symptomatic tendons were thicker (10.2 (1.9) vs. 6.8 (1.8) mm; p < 0.001) and had more hyperemia (p = 0.001) and hypoechogenicity (p = 0.002) than the contralateral tendon. Regional SWS in the FT was lower in the symptomatic limb compared to the contralateral limb (11.53 [10.99, 12.07] vs. 10.97 [10.43, 11.51]; p = 0.03). No differences between limbs were found for the SA (p = 0.13) or GA (p = 0.99). CONCLUSIONS: Lower SWS was only observed in the FT in AT patients, indicating that alterations in tendon elasticity associated with AT were localized to the FT and did not involve the proximal passive tendon structures. KEY POINTS: • Baseline characteristics of a pilot sample of 20 subjects suffering from chronic Achilles tendinopathy showed differences in conventional sonographic measures of tendon thickness, qualitatively assessed hypoechogenicity, hyperemia, and quantitative measures of shear wave speed. • Regional shear wave speeds were lower in the free tendon but not in the proximal regions of the soleus or gastrocnemius aponeuroses in Achilles tendinopathy patients. • Using shear wave imaging to estimate tendon stiffness may prove beneficial for clinical validation studies to address important topics such as return to activity and the effectiveness of rehabilitation protocols.

Influence of ultrasound machine settings on quantitative measures derived from spatial frequency analysis of muscle tissue.

BACKGROUND: Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle. METHODS: Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter. RESULTS: PSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values. CONCLUSIONS: Frequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method.

Spatial frequency analysis detects altered tissue organization following hamstring strain injury at time of injury but not return to sport.

BACKGROUND: Hamstring strain injury (HSI) diagnosis is often corroborated using ultrasound. Spatial frequency analysis (SFA) is a quantitative ultrasound method that has proven useful in characterizing altered tissue organization. The purpose of this study was to determine changes in muscular tissue organization using SFA following HSI. METHODS: Ultrasound B-mode images were captured at time of injury (TOI) and return to sport (RTS) in collegiate athletes who sustained an HSI. Spatial frequency parameters extracted from two-dimensional Fourier Transforms in user-defined regions of interest (ROI) were analyzed. Separate ROIs encompassed injured and adjacent tissue within the same image of the injured limb and mirrored locations in the contralateral limb at TOI. The ROIs for RTS images were drawn to correspond to the injury-matched location determined from TOI imaging. Peak spatial frequency radius (PSFR) and the fascicular banded pattern relative to image background (Mmax%) were compared between injured and adjacent portions within the same image with separate paired t-tests. Within-image differences of SFA parameters in the injured limb were calculated and compared between TOI and RTS with Wilcoxon rank sum tests. RESULTS: Within the injured limb at TOI, PSFR differences in injured and healthy regions did not strictly meet statistical significance (p = 0.06), while Mmax% was different between regions (p < 0.001). No differences were observed between regions in the contralateral limb at TOI (PSFR, p = 0.16; Mmax%, p = 0.30). Significant within-image differences in PSFR (p = 0.03) and Mmax% (p = 0.04) at RTS were detected relative to TOI. CONCLUSIONS: These findings are a first step in determining the usefulness of SFA in muscle injury characterization and provide quantitative assessment of both fascicular disruption and edema presence in acute HSI.

Spatial-frequency Analysis of the Anatomical Differences in Hamstring Muscles.

Spatial frequency analysis (SFA) is a quantitative ultrasound method that characterizes tissue organization. SFA has been used for research involving tendon injury, but may prove useful in similar research involving skeletal muscle. As a first step, we investigated if SFA could detect known architectural differences within hamstring muscles. Ultrasound B-mode images were collected bilaterally at locations corresponding to proximal, mid-belly, and distal thirds along the hamstrings from 10 healthy participants. Images were analyzed in the spatial frequency domain by applying a two-dimensional Fourier Transform in all 6.5 × 6.5 mm kernels in a region of interest corresponding to the central portion of the muscle. SFA parameters (peak spatial frequency radius [PSFR], maximum frequency amplitude [Mmax], sum of frequencies [Sum], and ratio of Mmax to Sum [Mmax%]) were extracted from each muscle location and analyzed by separate linear mixed effects models. Significant differences were observed proximo-distally in PSFR (p = .039), Mmax (p < .0001), and Sum (p < .0001), consistent with architectural descriptions of the hamstring muscles. These results suggest that SFA can detect regional differences of healthy tissue structure within the hamstrings-an important finding for future research in regional muscle structure and mechanics.

Transverse forces in skeletal muscle with massage-like loading in a rabbit model.

BACKGROUND: The objective of this study was to quantify the transverse forces in skeletal muscle subjected to constant compressive massage-like loading (MLL) following eccentric exercise (ECC). METHODS: Twenty-eight New Zealand White rabbits were used for this two-part study. For all testing, a customized electromechanical device was utilized to apply a constant compressive force MLL to the tibialis anterior (TA) muscle and the resultant transverse forces were quantified. The device consisted of two stepper motors that were positioned orthogonally to each other and connected to separate sliding tracks. A stainless steel cylindrical massage tip was mounted to a customized two-axis sensor consisting of two strain gauges with which forces along the two axes were measured. First, we determined the effects of tissue loading frequency and compression magnitude on transverse forces in the TA. Following a bout of ECC, sixteen rabbits were randomly assigned to a protocol with MLL frequency of 0.25 Hz or 0.5 Hz at a constant compressive force of 5 N or 10 N. Secondly, we utilized a protocol of 0.5 Hz, 10 N, 15 min MLL that was performed on 4 consecutive days commencing immediately post ECC (n = 6 animals) or 48 hours following ECC (n = 6 animals). Transverse forces were measured during all 4 MLL sessions for the entire 15 min duration for both the immediate and the delayed groups. RESULTS: Both frequency and magnitude of compressive force due to MLL showed an effect on the magnitude of transverse force (p < 0.05 for each parameter). Furthermore, MLL beginning immediately following ECC produced higher transverse forces than MLL delayed by 48 hours with an average 20% difference between the two MLL groups over the four day protocol. Forces were higher in the middle 5 minutes compared to the first 5 minutes for all MLL bouts in both groups. CONCLUSIONS: Frequency and magnitude of MLL and timing for delivery of MLL following ECC affect resultant transverse force values for exercised muscle. The application of our findings to humans receiving massage following exercise remains unknown at this time.

Ultrasound shear wave seeds reduced following hamstring strain injury but not after returning to sport.

OBJECTIVES: The purpose of the study was to investigate differences in ultrasound shear wave speed (SWS) between uninjured and injured limbs following hamstring strain injury (HSI) at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks). METHODS: This observational, prospective, cross-sectional design included male and female collegiate athletes who sustained an HSI. SWS imaging was performed at TOI, RTS, and 12wks with magnetic resonance imaging. SWS maps were acquired by a musculoskeletal-trained sonographer at the injury location of the injured limb and location-matched on the contralateral limb. The average SWS from three 5 mm diameter Q-boxes on each limb were used for analysis. A linear mixed effects model was performed to determine differences in SWS between limbs across the study time points. RESULTS: SWS was lower in the injured limb compared to the contralateral limb at TOI (uninjured - injured limb difference: 0.23 [0.05, 0.41] m/s, p = 0.006). No between-limb differences in SWS were observed at RTS (0.15 [-0.05, 0.36] m/s, p = 0.23) or 12wks (-0.11 [-0.41, 0.18] m/s, p = 0.84). CONCLUSIONS: The SWS in the injured limb of collegiate athletes after HSI was lower compared to the uninjured limb at TOI but not at RTS or 12 weeks after RTS. CRITICAL RELEVANCE STATEMENT: Hamstring strain injury with structural disruption can be detected by lower injured limb shear wave speed compared to the uninjured limb. Lack of between-limb differences at return to sport may demonstrate changes consistent with healing. Shear wave speed may complement traditional ultrasound or MRI for monitoring muscle injury. KEY POINTS: • Ultrasound shear wave speed can non-invasively measure tissue elasticity in muscle injury locations. • Injured limb time of injury shear wave speeds were lower versus uninjured limb but not thereafter. • Null return to sport shear wave speed differences may correspond to structural changes associated with healing. • Shear wave speed may provide quantitative measures for monitoring muscle elasticity during recovery.

The effects of hip- vs. knee-dominant hamstring exercise on biceps femoris morphology, strength, and sprint performance: a randomized intervention trial protocol.

BACKGROUND: The hamstrings are an important muscle group that contribute to horizontal force during sprint acceleration and are also the most injured muscle group in running-based sports. Given the significant time loss associated with hamstrings injury and impaired sprinting performance following return to sport, identifying exercises that drive adaptations that are both protective of strain injury and beneficial to sprint performance is important for the strength and conditioning professional. This paper describes the study protocol investigating the effects of a 6-week training program using either the hip-dominant Romanian deadlift (RDL) or the knee-dominant Nordic hamstring exercise (NHE) on hamstring strain injury risk factors and sprint performance. METHODS: A permuted block randomized (1:1 allocation) intervention trial will be conducted involving young, physically-active men and women. A target sample size of 32 will be recruited and enrolled participants will undergo baseline testing involving extended-field-of-view ultrasound imaging and shear wave elastography of the biceps femoris long head muscle, maximal hamstrings strength testing in both the RDL and NHE, and on-field sprint performance and biomechanics. Participants will complete the 6-week training intervention using either the RDL or NHE, according to group allocation. Baseline testing will be repeated at the end of the 6-week intervention followed by 2 weeks of detraining and a final testing session. The primary outcome will be regional changes in fascicle length with secondary outcomes including pennation angle, muscle cross sectional area, hamstring strength, and maximal sprint performance and biomechanics. An exploratory aim will determine changes in shear wave velocity. DISCUSSION: Despite extensive research showing the benefits of the NHE on reducing hamstring strain injury risk, alternative exercises, such as the RDL, may offer similar or potentially even greater benefits. The findings of this study will aim to inform future researchers and practitioners investigating alternatives to the NHE, such as the RDL, in terms of their effectiveness in reducing rates of hamstring strain injury in larger scale prospective intervention studies. TRIAL REGISTRATION: The trial is prospectively registered on ClinicalTrials.gov (NCT05455346; July 15, 2022).

Longitudinal Quantitative Ultrasonic Analysis of Patellar Tendon in a Collegiate Athlete After Bilateral Debridement: A Case Report.

CONTEXT: A National Collegiate Athletic Association Division I female basketball athlete (age = 20 years, height = 190.5 cm, mass = 87 kg) had chronic patellar tendinopathy. INTERVENTION(S): After undergoing unsuccessful conservative treatments, the athlete underwent bilateral open patellar debridement surgery. Pain and dysfunction were assessed via the Victorian Institute of Sport-P (VISA-P) score with concurrently collected B-mode ultrasound images of the patellar tendon throughout a 12-month rehabilitation. RESULTS: Peak spatial frequency radius (PSFR), a quantitative ultrasound measure previously shown to be correlated with collagen organization, was compared with changes in VISA-P scores. Overall increases in PSFR values across 0°, 30°, 60°, and 90° of knee flexion were observed throughout recovery. Despite increased PSFR values and returning to sport, the athlete reported substantial pain. CONCLUSIONS: In this level 3 exploration case report, we provide novel insight into ultrasonically measured structural changes of the patellar tendon after surgery and during rehabilitation of an athlete with chronic tendinopathy. Perceived pain measurements were not necessarily related to structural adaptations.

Intra-session and inter-rater reliability of spatial frequency analysis methods in skeletal muscle.

Spatial frequency analysis (SFA) is a quantitative ultrasound (US) method originally developed to assess intratendinous tissue structure. This method may also be advantageous in assessing other musculoskeletal tissues. Although SFA has been shown to be a reliable assessment strategy in tendon tissue, its reliability in muscle has not been investigated. The purpose of this study was to examine the reliability of spatial frequency parameter measurement for a large muscle group within a healthy population. Ten participants with no history of lower extremity surgery or hamstring strain injury volunteered. Longitudinal B-mode images were collected in three different locations across the hamstring muscles. Following a short rest, the entire imaging procedure was repeated. B-mode images were processed by manually drawing a region of interest (ROI) about the entire muscle thickness. Four spatial frequency parameters of interest were extracted from the image ROIs. Intra- and inter-rater reliabilities of extracted SFA parameters were performed. Test-retest reliability of the image acquisition procedure was assessed between repeat trials. Intraclass correlation coefficients showed high intra- and inter-rater reliability (ICC(3,1) > 0.9 for all parameters) and good to moderate test-retest reliability (ICC(3,1) > 0.50) between trials. No differences in parameter values were observed between trials across all muscles and locations (p > 0.05). The high reliability metrics suggest that SFA will be useful for future studies assessing muscle tissue structure, and may have value in assessing muscular adaptations following injury and during recovery.

Effect of manual compressive therapy on latent myofascial trigger point pressure pain thresholds.

OBJECTIVE: This study compared the effects of 90 s of manual compressive therapy (MCT) on latent myofascial trigger points (LTPs) for 3 sessions per week for 4 weeks to determine changes in individual pressure pain threshold (PPT). A total of 30 (15 males, 15 females; age = 22 ±â€¯4 y/o, height = 175 ±â€¯18 cm, weight = 162.5 ±â€¯57.5 kg) symptomatic subjects with LTPs volunteered for the study. METHODS: PPT was measured at baseline and pre- and post-treatment for all 12 sessions with a pressure algometer across the 4-week treatment time frame. The MCT was applied to the control group on their LTP at pressure intended to provide a sham condition (1/10 on verbalized analog scale (VAS)). Two experimental groups had MCT applied either directly on the LTP (d-TP) or in close-proximity to their LTP (cp-TP) at moderate pressure (7/10 on VAS). RESULTS: There was a significant increase in PPT from the first through twelfth treatment sessions (p < 0.001, partial η2 = 0.914). A significant increase in PPTs between treatment groups was acutely observed from pre- to post-therapy tests (p = 0.001, partial η2 = 0.146). The differences between pre- versus post-treatment PPT measures indicated significant differences (d-TP vs. control, p < 0.001; cp-TP vs. control, p = 0.007). No differences were observed between experimental groups (p = 0.215). CONCLUSIONS: PPT continued to increase after several weeks of MCT when applied directly on or within 2.5 cm of an identified LTP compared to control.

Effects of immediate vs. delayed massage-like loading on skeletal muscle viscoelastic properties following eccentric exercise.

BACKGROUND: This study compared immediate versus delayed massage-like compressive loading on skeletal muscle viscoelastic properties following eccentric exercise. METHODS: Eighteen rabbits were surgically instrumented with peroneal nerve cuffs for stimulation of the tibialis anterior muscle. Rabbits were randomly assigned to a massage loading protocol applied immediately post exercise (n=6), commencing 48h post exercise (n=6), or exercised no-massage control (n=6). Viscoelastic properties were evaluated in vivo by performing a stress-relaxation test pre- and post-exercise and daily pre- and post-massage for four consecutive days of massage loading. A quasi-linear viscoelastic approach modeled the instantaneous elastic response (AG0), fast (g1(p)) and slow (g2(p)) relaxation coefficients, and the corresponding relaxation time constants τ1 and τ2. FINDINGS: Exercise increased AG0 in all groups (P<0.05). After adjusting for the three multiple comparisons, recovery of AG0 was not significant in the immediate (P=0.021) or delayed (P=0.048) group compared to the control group following four days of massage. However, within-day (pre- to post-massage) analysis revealed a decrease in AG0 in both massage groups. Following exercise, g1(p) increased and g2(p) and τ1 decreased for all groups (P<0.05). Exercise had no effect on τ2 (P>0.05). After four days of massage, there was no significant recovery of the relaxation parameters for either massage loading group compared to the control group. INTERPRETATION: Our findings suggest that massage loading following eccentric exercise has a greater effect on reducing muscle stiffness, estimated by AG0, within-day rather than affecting recovery over multiple days. Massage loading also has little effect on the relaxation response.