Patellar tendon mechanical properties change with gender, body mass index and quadriceps femoris muscle strength

Patellar tendon repair restores extensor mechanism function with a low complication rate: A systematic review

Introduction

The patellar tendon plays a crucial role in knee extension and lower extremity mobility. Although PT ruptures are rare, they result in severe loss of function when untreated. The purpose of this study was to evaluate clinical and functional outcomes and complications following primary, acute patellar tendon (PT) repair.

Methods

In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, PubMed, Embase, and Cochrane Library databases were searched in August 2024 for studies published after 2004. Studies were included if they met these criteria: evaluated patients who underwent acute PT repair with any technique including for mid-substance tear or avulsion, were prospective or retrospective studies, and reported functional outcomes or complications. Studies not written in English were excluded.

Results

The initial screen identified 1737 studies, 9 of which were included in this systematic review. There were three retrospective cohort studies, three retrospective case series, one retrospective case control study, and two prospective case series. Each study had low risk of bias. A total of 970 patients (93.8 % males) were included. Mean age across studies ranged from 32.1 to 44.6 years. Five included studies reported on mean extension at follow-up, ranging from 0 to 6.4 degrees of extension. Five included studies reported on mean flexion at follow-up, ranging from 128.5 to 143.3 degrees of flexion. The range of re-rupture and re-operation were 0-21.4 % with an overall re-rupture rate of 3.9 % and an overall re-operation rate of 5.7 %. Only one study reported a significant difference in re-rupture rates with transosseous repair versus suture anchor repair (7.5 % versus 0 % respectively). Other complications identified were venous thromboembolism (VTE) (0-5.0 %), stiffness (0-35.0 %), hardware discomfort (0-5.0 %), and infection (0-5.0 %).

Conclusions

Patellar tendon repair with both transosseous and suture anchor technique restores range of motion in patients post-operatively with a low complication rate. Decisions regarding operative technique should be tailored to individual patient characteristics and surgeon preferences.

Level of evidence

Level IV, systematic review of level III-IV studies.

Shear wave elastography, as a feasible tool, can be used to reflect the lower limb dysfunction in patients with chronic obstructive pulmonary disease?

To explore the additional value of shear wave elastography (SWE) in chronic obstructive pulmonary disease (COPD) patients. Ultrasound elastography of the rectus femoris and patellar tendon was performed to determine the mean elasticity index (SWEmean) of the rectus femoris (SWERF) and patellar tendon (SWEPT) in 56 patients with COPD and 53 healthy controls. Clinical tests included the COPD Assessment Test (CAT), the dyspnea index score (modified British Medical Research Council (mMRC)score), the Five-Repetition Sit-to-Stand Test(5STS) and the Six-Minute Walk Test (6MWT). We compared differences in SWEmean between healthy controls and COPD patients while describing the correlation between SWEmean and clinical tests in COPD patients. Both the intra-observer and inter-observer repeatability of SWE performance were excellent (all correlation coefficients > 0.75; p < 0.05). There was a statistically significant difference between healthy controls and COPD patients in the SWERF and SWEPT between healthy controls and COPD patients (p < 0.001). The COPD patients had smaller SWERF and larger SWEPT than healthy controls. The SWERF was positively correlated with the 6MWT (r = 0.591, p < 0.001), and negatively related to the mMRC (r = - 0.794, p < 0.001), CAT (r = - 0.894, p < 0.001) and 5STS (r = - 0.928, p < 0.001). But the SWEPT was positively related to the 6MWT (r = 0.269, p < 0.05), mMRC (r = 0.398, p < 0.05), CAT (r = 0.377, p < 0.05) and 5STS (r = 0.332, p < 0.05). SWEmean of COPD patients was statisticant, different from that of healthy controls, and associated with clinical tests. SWE was a simple and feasible tool for reflecting the lower limb dysfunction in patients with COPD.

Effect of joint angle positioning on shearwave speed and variability with ultrasound shearwave elastography in asymptomatic Achilles and patellar tendons

This study investigated the impact of joint positioning on ultrasound shear wave elastography measurements in the Achilles and patellar tendons. Twenty-eight healthy adults underwent SWE assessment of shear wave speed (SWS) and coefficient of variation in SWS (CV-SWS) at three ankle positions (neutral, 10° plantar flexion, and 20° dorsiflexion) and two knee positions (90° flexion and full extension), at two academic sites. Participant positioning for ankle testing differed between sites (prone vs long-sitting)-while knee testing used consistent positioning. At the ankle, both joint and participant positioning significantly affected SWS. In the prone position, SWS was lower in neutral compared to dorsiflexed position (3.07 ± 1.13  m/s vs. 3.95 ± 1.03  m/s, p = 0.013). In long-sitting, SWS was lower in neutral compared to plantarflexed position (2.85 ± 0.53  m/s vs. 4.86 ± 1.92  m/s, p = 0.016); and SWS was higher in the plantarflexed position when participants were in long-sitting compared to prone (4.86 ± 1.92  m/s vs. 3.25 ± 1.13  m/s, p = 0.016). Participant positioning affected CV-SWS, with higher variability observed in prone compared to long-sitting in plantarflexed (29.3 ± 15.5 % vs 12.4 ± 9.12 %, p = 0.005) and neutral ankle angles (p = 0.03). At the knee, joint position significantly influenced SWS, with higher values in flexed versus extended positions (6.48 ± 3.1  m/s vs. 4.60 ± 2.3  m/s, p = 0.007). Extending the knee reduced CV-SWS compared to flexed position (14.5 ± 11.2 vs 19.2 ± 13.4, p = 0.044). In conclusion, joint position significantly affected SWS measurements in both the Achilles and patellar tendons, while participant positioning influenced measurement variability. Thus, standardizing joint and participant positioning is important to enhance the reliability of SWE assessments of tendon elasticity.

Study on the correlation between shear wave elastography and MRI grading of meniscal degeneration

BACKGROUND

Shear Wave Elastography (SWE) offers quantitative insights into the hardness and elasticity characteristics of tissues. The objective of this study is to investigate the correlation between SWE of the menisci and MRI-assessed degenerative changes in the menisci, with the aim of providing novel reference source for improving non-invasive evaluation of meniscal degenerative alterations.

METHODS

The participants in this study were selected from patients who underwent knee joint MRI scans at our hospital from February 2023 to February 2024. The anterior horns of both the medial and lateral menisci were evaluated using SWE technique. The differences in elastic values of meniscus among different MRI grades were compared. The correlation between elastic values and MRI grades, as well as various parameters, was analyzed. Using MRI Grade 3 as the gold standard, the optimal cutoff value for meniscal tear was determined. The intraclass correlation coefficient (ICC) was employed to evaluate the reliability of repeated measurements performed by the same observer.

RESULTS

A total of 104 female participants were enrolled in this study, with 152 lateral menisci (LM) and 144 medial menisci (MM) assessed. For the male group, 83 individuals were included, with 147 LM and 145 MM evaluated. The results demonstrated statistically significant differences in the elasticity values of the menisci at the same anatomical sites across different MRI grades (P < 0.001). Within the same grade, the MM had higher elasticity values than the LM, showing a statistically significant difference (P < 0.001). The elasticity values of the menisci were higher in males compared to females. There were statistically significant positive correlations between the elasticity values of the menisci and age, BMI, and MRI grade. The ICC for repeated measurements within the observer demonstrated good reliability (> 0.79).

CONCLUSIONS

The meniscal elasticity values measured by SWE exhibit a significant positive correlation with the grades of degeneration assessed by MRI. Furthermore, the elasticity values of the meniscus are found to increase with advancing age and elevated BMI.

Determination of differences in ultrasound parameters for patellar tendons in males with unilateral patellar tendinopathy-An ancillary analysis of data from two randomized controlled trials

PURPOSE

To investigate power Doppler (PD) activity and tendon structure (between the injured and contralateral limb) in patients with unilateral patellar tendinopathy (PT) using ultrasonography (US). Secondly, the aim was to determine the intra-rater reliability of the PD activity and tendon structure.

METHODS

This study analyzed US baseline data from 57 male participants with symptomatic unilateral PT who had been enrolled in one of two randomized clinical trials. Data were analyzed to examine if systematic differences existed between injured and contralateral limbs using Fiji ImageJ.

RESULTS

The PD activity of the symptomatic tendon was larger 25.6 (Q1 = 14.9; Q3 = 41.6) mm2 than the asymptomatic 0 (Q1 = 0.0; Q3 = 0.0) mm2 (p < 0.001). There was a significantly greater tendon thickness at the proximal (2.5 mm 95% CI [2.0; 3.0]), mid (0.8 mm 95% CI [0.5; 1.1]), and distal (0.2 mm 95% CI [0.1; 0.4]) part of the tendon for the symptomatic compared to the asymptomatic tendon. Intra-rater reliability for PD activity and tendon structure ranged from moderate-to-excellent (0.74; 0.99).

CONCLUSION

These results provide mean estimates for tendon thickness of symptomatic and asymptomatic tendons, that can be used for clinicians to reliably estimate pathological tendon thickness.

Maximal Lower Limb Strength in Patellar Tendinopathy: A Systematic Review With Meta-Analysis

OBJECTIVE

To investigate whether lower limb strength is reduced in people with patellar tendinopathy (PT) compared with asymptomatic control individuals or the asymptomatic contralateral limb.

DATA SOURCES

MEDLINE, PubMed, Scopus, and Web of Science.

STUDY SELECTION

To be included in the systematic review and meta-analysis, studies were required to be peer reviewed, published in the English language, and case control investigations; include participants with a clinical diagnosis of PT and an asymptomatic control or contralateral limb group; and include an objective measure of lower limb maximal strength.

DATA EXTRACTION

We extracted descriptive statistics for maximal strength for the symptomatic and asymptomatic limbs of individuals with PT and the limb(s) of the asymptomatic control group, inferential statistics for between-groups differences, participant characteristics, and details of the strength-testing protocol. The risk of bias was assessed using the Joanna Briggs Institute critical appraisal tool for analytical cross-sectional studies.

DATA SYNTHESIS

Of the 23 included studies, 21 reported knee strength, 3 reported hip strength, and 1 reported ankle strength. Random-effects models (Hedges g) were used to calculate the pooled effect sizes (ESs) of muscle strength according to the direction of joint movement and type of contraction. The pooled ESs (95% CI) for maximal voluntary isometric contraction knee-extension strength, concentric knee-extension strength, and concentric knee-flexion strength were 0.54 (0.27, 0.80), 0.78 (0.30, 1.33), and 0.41 (0.04, 0.78), respectively, with all favoring greater strength in the asymptomatic control group. Researchers of 2 studies described maximal eccentric knee-extensor strength with no differences between the PT and asymptomatic control groups. In 3 studies, researchers measured maximal hip strength (abduction, extension, and external rotation), and all within-study ESs favored greater strength in the asymptomatic control group.

CONCLUSIONS

Isometric and concentric knee-extensor strength are reduced in people with PT compared with asymptomatic control individuals. In contrast, evidence for reduced eccentric knee-extension strength in people with PT compared with asymptomatic control individuals is limited and inconsistent. Although evidence is emerging that both knee-flexion and hip strength may be reduced in people with PT, more examination is needed to confirm this observation.

Clinical and Ultrasonographic Characteristics of the Achilles Tendon in Hemodialysis Patients

Background and Objectives: The early recognition of tendon alterations in chronic hemodialysis (HD) patients, an awareness of the factors that influence the condition, and active intervention have considerable clinical relevance. The aim of this study was to investigate the musculoskeletal ultrasound (MSUS) features of the Achilles tendon in chronic HD patients and determine the factors associated with tendon abnormalities. Materials and Methods: This study was conducted on 46 HD patients and 24 sex- and age-matched controls. All participants were evaluated clinically for any signs of Achilles tendon abnormalities. Then, the Achilles tendon was scanned bilaterally using MSUS. Results: Among the 92 Achilles tendons in the HD patients, there was tenderness and swelling of only two (2.2%). Regarding MSUS features, there were statistically significant higher thicknesses in the proximal end (p < 0.001), midpoint (p < 0.001), and distal end (p < 0.001) of the Achilles tendons in the HD patients when compared with the healthy controls. Tendinosis was found in 12 (13%) of the HD patients' Achilles tendons, which was statistically significant in comparison to the healthy controls (p = 0.008). There were statistically significant higher scores of structural abnormalities (p = 0.005), bone erosions (p = 0.017), and calcifications (p = 0.015) in the HD patients when compared to the healthy controls. According to the results of a univariate regression analysis, age and male gender were predictive for US abnormalities in HD patients (p = 0.002 and 0.025, respectively). Conclusions: The Achilles tendon in subjects on chronic HD showed frequent US abnormalities. These abnormalities in HD patients appear to be more related to age and gender and may be asymptomatic.

Assessment of Knee Menisci in Healthy Adults Using Shear Wave Elastography

OBJECTIVES

The aim of this study was to explore the application value of shear wave elastography in healthy adults with knee meniscus.

METHODS

One hundred adult subjects who underwent health checkups at our hospital from December 2022 to February 2023 were selected as research participants. Shear wave elastography was used to evaluate the periphery of the lateral and medial meniscus in both knees. To assess the mean differences in Young's modulus values between male and female groups, a one-way analysis of variance (ANOVA) and independent samples t-test were conducted. In addition, a Pearson correlation coefficient test was used to analyze the correlation between the elastic values of the meniscus and age, height, weight, and body mass index (BMI).

RESULTS

There were no significant differences in elastic values between the lateral meniscus of the left and right sides or between the medial meniscus of the left and right sides within the same gender group (P > .05). Stiffness values of the medial meniscus were higher in each gender group than those of the lateral meniscus (P < .01). Additionally, males demonstrated higher stiffness values than females (P < .01). As age increased, the Young's modulus of the meniscus increased significantly (r > .75, P < .01).

CONCLUSION

Shear wave elastography can serve as an adjunctive tool to aid in the assessment of knee meniscal elasticity.

Post-Operative Greater Tuberosity Resorption or Malreduction Is Associated with Poor Prognostic Outcomes in Patients with Proximal Humeral Fractures Treated Operatively-A Single-Center Retrospective Cohort Study

(1) Background: Proximal humerus fractures can be a debilitating condition if not properly treated. These fracture patterns are varied and differ in every patient. Functional outcomes may be determined by the integrity of the shoulder girdle involving the rotator cuff insertion. The post-operative resorption or malreduction of the greater tuberosity (GT) is an important factor contributing to the poor functional outcome of a patient. Thus, we intend to evaluate the cause-and-effect relationship between GT complications and clinical prognosis and outcomes. (2) Methods: A single-center retrospective comparative study was performed to evaluate the functional outcomes of patients undergoing operative fixation for this injury. A total of 387 consecutive cases treated operatively from 2019-2021 were included for analysis. (3) Results: 94 cases fulfilled our criteria for analysis. A matched-group comparison of 19 patients each was performed to compare demographics, post-operative fracture characteristics and clinical outcomes. (4) Conclusions: The resorption or malreduction of the GT contributes greatly to the prognostic outcome in patients treated with open reduction and internal fixation (ORIF) surgery. In our demographic study, obesity is another contributing factor affecting the parameters of post-operative reduction in proximal humerus fractures. Appropriate surgical planning and post-operative multidisciplinary care must be taken into consideration to attain a satisfactory prognostic outcome.

Effect of Anthropometric Parameters on Achilles Tendon Stiffness of Professional Athletes Measured by Shear Wave Elastography

BACKGROUND

Shear wave elastography (SWE) is currently used to detect tissue pathologies and, in the setting of preventive medicine, may have the potential to reveal structural changes before they lead to functional impairment. Hence, it would be desirable to determine the sensitivity of SWE and to investigate how Achilles tendon stiffness is affected by anthropometric variables and sport-specific locomotion.

METHODS

To investigate the influence of anthropometric parameters on Achilles tendon stiffness using SWE and examine different types of sports to develop approaches in preventive medicine for professional athletes, standardized SWE of Achilles tendon stiffness was performed in 65 healthy professional athletes (33 female, 32 male) in the longitudinal plane and relaxed tendon position. Descriptive analysis and linear regression were performed. Furthermore, subgroup analysis was performed for different sports (soccer, handball, sprint, volleyball, hammer throw).

RESULTS

In the total study population (n = 65), Achilles tendon stiffness was significantly higher in male professional athletes (p < 0.001) than in female professional athletes (10.98 m/s (10.15-11.65) vs. 12.19 m/s (11.25-14.74)). Multiple linear regression for AT stiffness did not reveal a significant impact of age or body mass index (BMI) (p > 0.05). Subgroup analysis for type of sport showed the highest AT stiffness values in sprinters (14.02 m/s (13.50-14.63)).

CONCLUSION

There are significant gender differences in AT stiffness across different types of professional athletes. The highest AT stiffness values were found in sprinters, which needs to be considered when diagnosing tendon pathologies. Future studies are needed to investigate the benefit of pre- and post-season musculoskeletal SWE examinations of professional athletes and a possible benefit of rehabilitation or preventive medicine.

A discrete shear lag model of the mechanics of hitchhiker plants, and its prospective application to tendon-to-bone repair

Tendon-to-bone repairs often fail when sutures pull through tendon, like a wire through cheese. Repair strength is maximized when loads are balanced equally among all sutures, relative to the pullout resistance of the tendon and the strength of the sutures. This problem of balancing loads across multiple, discrete attachment sites has been solved in nature by hitchhiker plants that proliferate by adhering relatively stiff fruit to relatively soft fur and fabrics through arrays of hooks. We, therefore, studied the fruits of such a plant, Harpagonella palmeri , and developed a discrete shear lag analysis of the force distributions in H. palmeri 's linear arrays of long, slender hooks of varied lengths and spacing. Results suggested that strategies were used by the plant to distribute loads, including variations in the spacing and stiffnesses of hooks that serve to equalize forces over attachment sites. When applying these models to suturing schemes for surgical reattachment of tendon to bone, results suggested that strategies exhibited by H. palmeri show promise for balancing forces over sutures, potentially doubling repair strength relative to what could be achieved with a uniform suture distribution. Results suggest a potential pathway for strengthening surgical repairs, and more broadly for optimizing fasteners for bi-material attachment.

Comparison of fetal and maternal tissue elasticity between euploid and aneuploid pregnancies by shear wave elastography

AIM

B-mode ultrasonography utilized for fetal screening of common trisomies is referred to as a genetic sonogram and includes determining major abnormalities and soft markers such as hypoplastic nasal bone and increased thickness of the nuchal fold. Elastography is a novel ultrasound technique giving information about tissue stiffness used for diagnosing cancer, transplant rejection, and organ fibrosis. This study aimed to determine via shear wave elastography (SWE) whether euploid and aneuploid fetal soft marker tissues vary in stiffness.

METHODS

The participants were all singleton pregnancies between 19 and 23 weeks of gestation; 35 euploid and 14 aneuploid fetus pregnancies were enrolled. Fetal bowel, kidney, liver, nasal bone, nuchal fold, placenta, and myometrium were investigated with SWE using acoustic radiation impulse force. Images were analyzed with a novel software calibrated and written by us using MATLAB. Statistical analysis was completed with the SPSS Program. Shapiro-Wilk normality distribution analysis, Student's t-test, and Mann-Whitney U methods were used.

RESULTS

The mean shear wave speed of fetal nasal bone was significantly lower in aneuploid fetuses. There was no difference between other tissues in mean shear wave velocity.

CONCLUSIONS

Euploid and aneuploid fetuses have different elastic properties of the nasal bone and this may have a role in differentiating aneuploid fetuses noninvasively.

Achilles Tendon, Patellar Tendon, and Femoral Cartilage Thickness in Control vs Asymptomatic Flatfoot Young Adults

BACKGROUND

Changes in lower extremity alignment in individuals with flatfoot may be associated with differences in morphology of the tendons or cartilage in lower extremities. The purpose of the present study was to investigate the potential association of flatfoot with the morphology of the Achilles tendon, patellar tendon, and femoral cartilage.

METHODS

This study was conducted with 40 participants with flatfoot (28 females, 12 males) and 40 participants with a normal foot posture (28 females, 12 males). The thickness of the Achilles tendon (at points 2 and 3 cm proximal to the superior aspect of the calcaneus), patellar tendon (at the inferior pole of the patella and 1 cm proximal of the inferior pole of the patella), and femoral cartilage (at the intercondylar area, medial condyle, and lateral condyle) was measured by an ultrasonography device.

RESULTS

The Achilles tendon thickness at 2 cm (P = .009) and 3 cm (P = .010) proximal of the superior aspect of the calcaneus was on average 4% to 6% lower in individuals with flatfoot compared with controls. The cartilage thickness at the intercondylar area (P = .005) and medial condyle (P = .018) was on average 8% to 12% greater in individuals with flatfoot; however, the cartilage thickness at the lateral condyle and patellar tendon thickness was similar in both groups.

CONCLUSION

The results obtained suggest that foot posture is associated with the morphology of the Achilles tendon and femoral cartilage.

LEVEL OF EVIDENCE

Level III, diagnostic comparative study.

Investigation of the relationship between tensile viscoelasticity and unloaded ultrasound shear wave measurements in ex vivo tendon

Mechanical properties of biological tissues are of key importance for proper function and in situ methods for mechanical characterization are sought after in the context of both medical diagnosis as well as understanding of pathophysiological processes. Shear wave elastography (SWE) and accompanying physical modelling methods provide valid estimates of stiffness in quasi-linear viscoelastic, isotropic tissue but suffer from limitations in assessing non-linear viscoelastic or anisotropic material, such as tendon. Indeed, mathematical modelling predicts the longitudinal shear wave velocity to be unaffected by the tensile but rather the shear viscoelasticity. Here, we employ a heuristic experimental testing approach to the problem to assess the most important potential confounders, namely tendon mass density and diameter, and to investigate associations between tendon tensile viscoelasticity with shear wave descriptors. Small oscillatory testing of animal flexor tendons at two baseline stress levels over a large frequency range comprehensively characterized tensile viscoelastic behavior. A broad set of shear wave descriptors was retrieved on the unloaded tendon based on high frame-rate plane wave ultrasound after applying an acoustic deformation impulse. Tensile modulus and strain energy dissipation increased logarithmically and linearly, respectively, with the frequency of the applied strain. Shear wave descriptors were mostly unaffected by tendon diameter but were highly sensitive to tendon mass density. Shear wave group and phase velocity showed no association with tensile elasticity or strain rate-stiffening but did show an association with tensile strain energy dissipation. The longitudinal shear wave velocity may not characterize tensile elasticity but rather tensile viscous properties of transversely isotropic collagenous tissues.

Investigation of the Tissue Degenerative Impact of Increased BMI in Achilles Tendon via Strain Elastography and Finite Element Analysis

BACKGROUND

This study is focused on establishing a relationship between poor muscle activity faced by obese individuals due to the change in stiffness of the intramuscular mass of the lower limb. This issue is also common among athletes and physically active teenagers.

OBJECTIVE

The study is aimed at a subject assessment diagnosis technique named as Strain Elastography (SE) to measure muscle strain. Further, Finite Element Modelling (FEM) technique is used to investigate the strain and/or deformations generated in the Achilles Tendon (AT) models, which were categorized according to their Body Mass Index (BMI) through computationally applied loadings.

METHODS

Total 54 volunteers with an average age of 21.85 ± 1.28 years were categorized into three groups according to their BMI (kg/m2); under BMI < 18.5 (n=14), normal BMI = 18.5-24.9 (n=20) and over BMI/obese > 25.0 (n=20). Additionally, multiple correlational analyses were performed between full range of BMI values and SE outcome.

RESULTS

The presence of significant difference (p<0.05) was measured between different categories for BMI, BFMI, FFMI, DLFC, tendon length, tendon thickness and SR. Moreover, multiple correlational analyses and scatter plot strengthen the results. For FEM simulations, the maximum deformation was observed at the proximal end of the tendon in all three groups.

CONCLUSION

It can be concluded that change in tendon stiffness and the resulting change in tendon structure was visualized with increased BMI. Moreover, obese individuals are more prone to tendon injury due to the increment in tendon thickness which causes bulging of the AT due to higher loads.

Ex vivo study correlating the stiffness of the ovine patellar tendon to age and weight

Tendons play a crucial role in the musculoskeletal system. In humans, tendon injuries, especially chronic tendinopathy, are very common and the patellar tendon is a frequent location for tendinopathy or injuries. The biomechanical characteristics of the patellar tendon, such as elasticity and stiffness, are of paramount importance and constitute major outcome measures in research studies. We aimed to assess whether the stiffness of the healthy ovine patellar tendon changes with age and weight in a population of normal animals. Sixty-eight 'patella-patellar tendon-tibial tuberosity' units from thirty-four Ile-de-France ewes of body mass 65 to 95 kg, euthanized for reasons other than musculoskeletal diseases, underwent a tensile test providing a measure of the tendon stiffness. Animals were sorted into three categories of age (1-2 yo, 3-5 yo, 6-10 yo). We found a positive but not significant correlation between age category and stiffness (r = 0.22, p = 0.27). There was a significantly positive correlation between weight and stiffness (r = 0.39, p = 0.04). In conclusion, the study characterized biomechanical properties of healthy tendons, provided useful reference values, and established the basis for future biomechanical tests on healing tendons in sheep. The most appropriate sheep population for those future studies would be non-overweight young adults presenting with no lameness.

Relationships between tendon structure and clinical impairments in patients with patellar tendinopathy

The clinical relevance of altered tendon structure in patellar tendinopathy is contested since structural change persists after symptom resolution. The purpose of this study was to explore the relationships between tendon structure and clinical impairments in patellar tendinopathy. In this retrospective, secondary analysis of individuals with patellar tendinopathy (n = 41), tendon structure (thickness, cross-sectional area [CSA], shear modulus, and viscosity), symptom severity, lower extremity function (counter-movement jump [CMJ] height), and quadriceps muscle performance (knee extension force and central activation ratio [CAR]) were recorded for the symptomatic limb. Relationships among structure, symptom severity, lower extremity function, and quadriceps muscle performance were examined using sequential regression models. Adjusting for age, sex, body mass index, and pain levels, there were significant positive relationships for thickness (p < 0.001, β = 0.718) and viscosity (p = 0.006, β = 0.496) with CMJ height. There were significant negative relationships between CSA with both CMJ height (p = 0.001, β = -0.538) and CAR (p = 0.04, β = -0.517). This is the first study to demonstrate relationships between tendon structure and lower extremity function or quadriceps muscle performance in patients with patellar tendinopathy. Clinical significance: Since structural changes persist after symptom resolution, addressing these changes may assist in restoring lower extremity function and quadriceps muscle performance.

Quantification of the in vivo stiffness and natural length of the human plantar aponeurosis during quiet standing using ultrasound elastography

This study aimed to identify the stiffness and natural length of the human plantar aponeurosis (PA) during quiet standing using ultrasound shear wave elastography. The shear wave velocity (SWV) of the PA in young healthy males and females (10 participants each) was measured by placing a probe in a hole in the floor plate. The change in the SWV with the passive dorsiflexion of the metatarsophalangeal (MP) joint was measured. The Young's modulus of the PA was estimated to be 64.7 ± 9.4 kPa, which exponentially increased with MP joint dorsiflexion. The PA was estimated to have the natural length when the MP joint was plantarflexed by 13.8°, indicating that the PA is stretched by arch compression during standing. However, the present study demonstrated that the estimated stiffness for the natural length in quiet standing was significantly larger than that in the unloaded condition, revealing that the PA during standing is stiffened by elongation and through the possible activation of intrinsic muscles. Such quantitative information possibly contributes to the detailed biomechanical modeling of the human foot, facilitating an improved understanding of the mechanical functions and pathogenetic mechanisms of the PA during movements.

Strain sonoelastography in asymptomatic individuals and individuals with knee osteoarthritis: an evaluation of quadriceps and patellar tendon

An advanced ultrasound imaging technique, sonoelastography (SE) is used to evaluate tissue elasticity. To determine SE potential to detect pathological-related changes, and characteristics related to tendon pathology we aimed to (1) compare quadriceps and patellar tendon findings in individuals with knee osteoarthritis (KOA) and asymptomatic older adults (AC), and (2) explore associations between SE, participant characteristics (age, BMI, and leg circumference) and KOA status. 84 participants (47; KOA and 37; asymptomatic older adults) underwent SE examination of quadriceps (distal) and patellar (distal, proximal) tendon in a supine position with the knee bent at 30°. Colour score (CS) and Elasticity Ratio (ER) analysis were performed by a blinded experienced operator using Esaote Mylab 70 XVG Ultrasound equipment. Significantly reduced elasticity in the distal quadriceps (median (IQR) 2(2), 3(1), p = 0.033 for KOA and AC, respectively) and proximal patellar (3(1), 3(0), p = 0.001) tendons and more elastic distal patellar (1.50 (0.55), 1.87 (0.72), p = 0.034) tendons were observed in the KOA group. Significant associations) were identified between SE and participant BMI (Rs = − 0.249–0.750, p < 0.05) and leg circumference (Rs = − 0.260–0.903, p < 0.05). Age, BMI and KOA status, were independent explanatory variables of SE CS findings at the distal quadriceps tendon patellar tendon, proximal patellar tendon and distal patellar tendon, explaining 66%, 81% and 64% of variance, respectively. Age, BMI and KOA status were independent explanatory variables of SE ER findings at the distal patellar tendon explaining 19% of variance. Potentially clinically relevant altered tendon stiffness were observed between individuals with KOA and asymptomatic controls. Key KOA risk factors and participant characteristics explained variance in tendon stiffness. Findings provide context for future studies to investigate the potential for targeted SE detected early clinical management based on associated participant characteristics.

Patellar Tendon Shear Wave Velocity Is Higher and has Different Regional Patterns in Elite Competitive Alpine Skiers than in Healthy Controls

Competitive alpine skiers are exposed to enormous forces acting on their bodies–particularly on the knee joint and hence the patellar tendon - during both the off-season preparation and in-season competition phases. However, factors influencing patellar tendon adaptation and regional pattern differences between alpine skiers and healthy controls are not yet fully understood, but are essential for deriving effective screening approaches and preventative countermeasures. Thirty elite competitive alpine skiers, all members of the Swiss Alpine Ski Team, and 38 healthy age-matched controls were recruited. A set of two-dimensional shear wave elastography measurements of the PT was acquired and projected into three-dimensional space yielding a volumetric representation of the shear wave velocity profile of the patellar tendon. Multivariate linear models served to quantify differences between the two cohorts and effects of other confounding variables with respect to regional shear wave velocity. A significant (p < 0.001) intergroup difference was found between skiers (mean ± SD = 10.4 ± 1.32 m/s) and controls (mean ± SD = 8.9 ± 1.59 m/s). A significant sex difference was found within skiers (p = 0.024), but no such difference was found in the control group (p = 0.842). Regional SWV pattern alterations between skiers and controls were found for the distal region when compared to the mid-portion (p = 0.023). Competitive alpine skiers exhibit higher SWV in all PT regions than healthy controls, potentially caused by long-term adaptations to heavy tendon loading. The presence of sex-specific differences in PT SWV in skiers but not in controls indicates that sex effects have load-dependent dimensions. Alterations in regional SWV patterns between skiers and controls suggest that patellar tendon adaptation is region specific. In addition to the implementation of 3D SWE, deeper insights into long-term tendon adaptation and normative values for the purpose of preventative screening are provided.

Sex-related differences and effects of short and long trail running races on resting muscle-tendon mechanical properties

The purpose of the study was to assess sex-related differences in resting mechanical properties and adaptations of skeletal muscles and tendons in response to trail running races of different distances using multi-site shear wave elastography assessments of the lower limb, force capacity and blood analyses. Sex differences in resting mechanical properties of knee extensor and plantar flexor muscles and tendons were characterized by shear wave velocity measurements in healthy males (N=42) and females (N=25) trained in long distance running. Effects of running distance on muscle and tendon properties were assessed in short (<60km, N=23) vs. long (>100km, N=26) distance races. Changes in isometric maximal voluntary contraction torque, serum C-reactive protein and creatine kinase activity were also quantified after running races. Higher shear wave velocity of relaxed triceps surae muscle was detected in females as compared to males before running races (+4.8%, p=0.006), but the significant increases in triceps surae muscle group (+7.0%, p=0.001) and patellar tendon shear wave velocity (+15.4%, p=0.001) after short-distance races were independent of sex. A significant decrease in triceps surae muscle shear wave velocity was found after long-distance races in the whole experimental population (-3.1%, p=0.049). Post-races increase in C-reactive protein and creatine kinase activity were significantly correlated to the relative decreases in triceps surae and quadriceps femoris skeletal muscle shear wave velocity (ρ=-0.56, p=0.001 and ρ=-0.51, p=0.001, respectively). Resting mechanical properties of muscles and tendons are affected by sex, and that adaptations to trail races are related to running distance. Exercise-induced changes in resting skeletal muscle mechanical properties are associated with enhanced indirect markers of inflammation and muscle damage.

An Examination of Two Resistance Training Frequency Techniques in Morphological and Functional Adaptations of the Patellar Tendon

The aim of the present study was to investigate the effects of distinct resistance training frequencies with equated-volume conditions in morphological and functional adaptations of the patellar tendon. Twenty-seven recreationally resistance-trained subjects (men [n=17] and women [n=10]) (age: 20.8 ± 1.9 years [range 18 to 25 years]; height: 1.73 ± 9.8 cm; total body mass = 73.2 ± 11.7 kg; previous RT experience = 3.3 ± 1.6 years) volunteered to participate in this study. A total of 16 training sessions were performed during the study period. Each subject's leg was randomly allocated to one of the following training protocols: 2 training sessions/week (2x) or 4 training sessions/week (4x). Measurements of tendon cross sectional area (CSA) and length were performed through ultrasound imaging. One repetition maximum test was performed to assess patellar tendon force (PTF) unilaterally. For CSA (2x: Δ= -1.3%; 4x: Δ= -0.9%), and length (2x: Δ= -0.4%; 4x: Δ= 1.2%), no significant differences were observed within or between conditions (all p > 0.05). For PTF, a significant difference was observed between conditions (mean difference = 0.05 [-125 to 224] p= 0.001). In conclusion, the leg extension exercise performed 2 vs 4x/week induces similar patellar tendon morphological responses. However, the increase in force seems to be enhanced by a lower weekly training frequency associated with a longer intervention period.

Effects of β-Hydroxy β-Methylbutyric Supplementation in Combination with Conservative Non-Invasive Treatments in Athletes with Patellar Tendinopathy: A Pilot Study

The aim of the present study was to analyze the effect of conservative non-invasive treatments based on eccentric training, stretching and extracorporeal shock wave therapy (ESWT) supplemented with β-Hydroxy β-methylbutyric (HMB) or placebo (PLAC) on body composition, pain and muscular function (jump ability, muscular power and muscular strength) in athletes with patellar tendinopathy (PT). In a double-blind randomized trial, 8 athletes (4 males and 4 females) performed a physical rehabilitation for 4 weeks. They were randomly divided into two experimental groups (two males and two females in each one) that ingested HMB (HMBG) or PLAC (PLACG). In pre- and post-intervention were assessed body composition, pain, countermovement jump (CMJ), back-squat (BS) for analyzing peak power (W) (PPPP), load (kg) associated to PPPP (PPKG) and mean velocity (m/s) (PPMV) in addition to a 5-RM leg extension tests. An interaction intervention·supplementation (p = 0.049; Ƞ2p = 0.774) was observed in the height reached in the CMJ as an intervention effect in PPPP detected for the HMBG (p = 0.049). In addition, an enhancement in PPKG (p = 0.028; Ƞ2p = 0.842) was detected in the intervention, but not in PPMV, as an increase in the intervention in the 5-RM test (p = 0.001; Ƞ2p = 0.981) was observed. No changes were noted on body composition or pain (p > 0.05). The combination of eccentric training with stretching and ESWT increased concentric muscular power and strength after 4 weeks without changes in body lean mass or pain. In addition, HMB supplementation could enhance the power muscular performance in athletes with PT, optimizing the intervention adaptions.

Recovery of gait and function during the first six months after tibial shaft fractures

BACKGROUND

Tibial shaft fractures require surgical stabilization preferably by intramedullary nailing. Recovery is often unsatisfactory due to limited knee function and pain, resulting in reduced quality of life. The extent of these functional limitations with respect to gait deficits has not been sufficiently recognized.

RESEARCH QUESTION

Are there functional limitations during gait and squat performance during the first six months after surgically treated tibial shaft fractures?

METHODS

Twenty-three patients (BMI: 24 ± 3, Age:39 ± 15) with tibial shaft fractures and 23 healthy, matched controls (BMI: 24 ± 3, Age: 40 ± 14) were assessed using instrumented motion analysis two, three and six months after surgery. Kinematic and kinetic data of the lower extremities were collected during level walking and squat performance. Data were compared among follow-up time intervals and between groups.

RESULTS

Significant improvements were found for all spatiotemporal parameters and most kinetic parameters. Even six months after surgery functional deficits persisted when compared to healthy controls. There were only slight improvements in sagittal knee and ankle kinematics as well as knee moments and power within the follow-up period. A significant difference compared to the healthy controls can still be observed in these parameters.

SIGNIFICANCE

Although patients with tibia fractures demonstrated functional improvements over the early course of healing, some residual deficits in lower extremity movement biomechanics were identified at six months post surgery. In particular knee kinematics in squatting as well as knee kinematics and kinetics during walking only recovered incompletely. This result can help explain the often-reported functional limitations.

CLINICAL TRIAL REGISTRATION NUMBER

German register for clinical trials (DRKS00023790).

Shear Wave Elastography Evaluation of Meniscus Degeneration with Magnetic Resonance Imaging Correlation

RATIONALE AND OBJECTIVES

The objective of the study was to assess the diagnostic efficiency of shear wave elastography in the grading of meniscal degeneration compared to magnetic resonance imaging (MRI) as a reference standard.

MATERIALS AND METHODS

Fifty patients were included in the study (who had bilateral knee MRI). Tissue elasticity was measured in the coronal plane from the meniscus body in kilopascal. Nonparametric testing (Mann-Whitney U) was utilized to assess the differences between mean elasticity of the meniscus tissue, gender. The inter-intraobserver agreement was determined by the intraclass correlation coefficient. The correlations between the mean elasticity of the meniscus versus age, height, and body mass index were calculated via the "Pearson Correlation Coefficient Test." The relationship between MRI meniscal degeneration grading and elastography elasticity module was determined via the "Spearman Correlation Test." A p value less than 0.05 was considered statistically significant.

RESULTS

İnter-intraobserver intraclass correlation coefficient of the lateral and medial meniscus mean stiffness values were good or excellent (>0.8). A statistically significant increase in stiffness of meniscus tissue was observed with an increase in age (p = 0.003 for medial menisci, 0.006 for lateral menisci). Tissue stiffness was higher in the medial meniscus than the lateral meniscus (p < 0.001). A positive correlation was observed between the MRI meniscal degeneration grade and tissue stiffness (p < 0.05). Additionally, mean stiffness values from lateral and medial menisci were higher in the group with degeneration (p < 0.0001).

CONCLUSION

Meniscus stiffness is increased with aging. There was a statistically significant positive correlation between meniscal stiffness and degeneration grading in MRI.

Immediate Effect of Whole Body Vibration on Knee Extensor Tendon Stiffness in Hemiparetic Stroke Patients

Background and Objectives: Whole body vibration is widely used to enhance muscle performance, but evidence of its effects on the tendon stiffness of the knee extensor tendon in stroke remains inconclusive. Our study was aimed to determine the difference in patellar and quadriceps tendon stiffness between hemiparetic and unaffected limbs in stroke patients and to investigate the immediate effect of whole body vibration on tendon stiffness. Materials and Methods: The patellar and quadriceps tendon stiffness of first-ever hemiplegic stroke patients was evaluated with elastography to compare the differences between hemiparetic and unaffected limbs. After one 20 min session of whole body vibration exercise in the standing position, tendon stiffness was again measured to evaluate the immediate effects of whole body vibration on tendon stiffness. Results: The results showed no significant differences in the tendon stiffness of the patellar and quadriceps tendons between hemiparetic and unaffected limbs. However, significant associations were found between the tendon stiffness of the patellar and quadriceps tendons and knee extensor spasticity on the hemiparetic side (ρ = 0.62; p = 0.044). There were no significant changes in tendon stiffness after a single session of whole body vibration. Conclusions: In conclusion, knee extensor tendon stiffness in hemiparetic limbs is positively correlated to the degree of knee extensor spasticity in stroke patients. However, a single session of whole body vibration does not alter tendon stiffness.

Influence of Bias in the Assessment of Patellar Tendon Stiffness: A Systematic Review and Meta-analysis

The aim of the present study was to provide a systematic review and meta-analysis of the main biases in practical applications of the different types of elastography in assessment of the stiffness of healthy patellar tendons. A literature search on four databases (Scopus, Web of Science, Pubmed and SportDiscus) was conducted on March 25, 2020. After analysis of 1,052 resultant articles, studies were included if they met two inclusion criteria: (1) studies were observational or randomized controlled trials; (2) studies included outcomes of patellar tendon stiffness. Twenty-one studies met the inclusion criteria and were included in this meta-analysis. Four meta-analyses were performed with respect to assessment procedure and participant characteristics. This meta-analysis found a low effect of examined portion of patellar tendon (standardized mean difference [SMD] = 0.27, 95% confidence interval [CI]: 0.01-0.54, n = 379, Z = 2.01, p = 0.04) and a high effect of knee flexion angle during assessment (SMD = -2.12; 95% CI: -2.67 to -1.58, n = 97, Z = 7.68, p < 0.01) in stiffness outcomes. The risk of bias was generally low, but the heterogenicity of the results downgraded the level of evidence. There is evidence in the elastography assessment of patellar tendon suggesting that the knee position and patellar tendon portion evaluated influence stiffness outcomes for patellar tendon in healthy volunteers.

Three-Dimensional Mapping of Shear Wave Velocity in Human Tendon: A Proof of Concept Study

Ultrasound-based shear wave elastography (SWE) provides the means to quantify tissue mechanical properties in vivo and has proven valuable in detecting degenerative processes in tendons. Its current mode of use is for two-dimensional rendering measurements, which are highly position-dependent. We therefore propose an approach to create a volumetric reconstruction of the mechano-acoustic properties of a structure of interest based on optically tracking the ultrasound probe during free-hand measurement sweeps. In the current work, we aimed (1) to assess the technical feasibility of the three-dimensional mapping of unidirectional shear wave velocity (SWV), (2) to evaluate the possible artefacts associated with hand-held image acquisition, (3) to investigate the reproducibility of the proposed technique, and (4) to study the potential of this method in detecting local adaptations in a longitudinal study setting. Operative and technical feasibility as well as potential artefacts associated with hand-held image acquisition were studied on a synthetic phantom containing discrete targets of known mechanical properties. Measurement reproducibility was assessed based on inter-day and inter-reader scans of the patellar, Achilles, and supraspinatus tendon of ten healthy volunteers and was compared to traditional two-dimensional image acquisition. The potential of this method in detecting local adaptations was studied by testing the effect of short-term voluntary isometric loading history on SWV along the tendon long axis. The suggested approach was technically feasible and reproducible, with a moderate to very good reliability and a standard error of measurement in the range of 0.300-0.591 m/s for the three assessed tendons at the two test-retest modalities. We found a consistent variation in SWV along the longitudinal axis of each tendon, and isometric loading resulted in regional increases in SWV in the patellar and Achilles tendons. The proposed method outperforms traditional two-dimensional measurement with regards to reproducibility and may prove valuable in the objective assessment of pathological tendon changes.

Foot Posture, Muscle Strength, Range of Motion, and Plantar Sensation in Overweight and Obese

The purpose of the study was to investigate the foot posture, ankle muscle strength, range of motion (ROM), and plantar sensation differences among normal weight, overweight, and obese individuals. One hundred and twenty-three individuals (42 normal weight, 40 overweight, and 41 obese) aged between 18 and 50 years participated in the study. Foot posture, ankle muscle strength, ROM, plantar sensation, and foot-related disabilities were evaluated. The relative muscle strength of left plantar flexors and invertors and light touch sensation of the left heel were significantly lower in obese individuals compared with overweight and normal weight (P < .016) individuals. Obese individuals had significantly reduced relative muscle strength of plantar flexors, dorsiflexor, and invertors, plantar flexion and inversion ROM in the left foot; and light touch sensation of the right heel compared with normal weight (P < .016) individuals. Foot Posture Index scores were significantly higher in obese individuals compared with overweight (P < .016) individuals. There were no significant differences in absolute muscle strength, vibration sensation, and foot-related disability scores among the 3 groups (P > .05). Obesity was found to have adverse effects on ankle muscle strength, ROM, and plantar light touch sensation. Vibration sensation was not affected by body mass index, and foot-related disability was not observed in obese adults.

Influence of body mass index and weight lifting on bicep brachii muscle and distal bicep tendon stiffness evaluated using ultrasound elastography

BACKGROUND

This study aimed to investigate the relationship between stiffness of the bicep brachii muscle (BBM) and distal bicep tendon (DBT) and effects of weight lifting (pre- to post-workout changes) among groups with different body mass indexes (BMI).

METHODS

Participants were divided into four groups according to BMI: A, underweight (< 18.5 kg/m²); B, normal (18.5-24.9 kg/m²); C, overweight (25.0-29.9 kg/m²); and D, obese (> 30.0 kg/m²). All participants were males who were untrained and had sedentary lifestyle without involvement in sports activities for the past 12 months. Ultrasonographic measurements to determine muscle and tendon stiffness was performed on the dominant side (i.e., right side) of the upper extremities in all participants.

RESULTS

Twenty-one healthy and untrained males volunteered to participate in this study; 14 were nonsmokers and 7 were smokers. The mean age and BMI were 22.5 ± 1.5 years and 23.8 ± 6.3 kg/m², respectively. Groups A, B, C, and D had four, ten, four, and three participants, respectively. The BBM thickness did not increase with increase in BMI and was not significantly different (P > .05) between groups. The BBM stiffness was significantly different (all P < .05) from pre- to post-workout values in all groups, whereas DBT stiffness did not follow the same trend.

CONCLUSIONS

Our study revealed that the BBM thickness is independent of BMI. After weight lifting, BBM stiffness in groups A and B increased for BBM compared to those in groups C and D. A similar trend was also recorded for DBT. Weight lifting in concentric and eccentric motions affects the stiffness of the BBM and DBT, thus weight lifting plays a role in adjusting the stiffness of the BBM and DBT. Trial registration The study was approved by ethics committee of the College of Applied Medical Sciences (CAMS 080-3839; March 14, 2018).

Age and sex-related decline of muscle strength across the adult lifespan: a scoping review of aggregated data

Muscle strength is sex-related and declines with advancing age; yet, a comprehensive comparative evaluation of age-related strength loss in human females and males has not been undertaken. To do so, segmented piecewise regression analysis was performed on aggregated data from studies published from 1990 to 2018 and are available in CINAHL, EMBASE, MEDLINE, and PsycINFO databases. The search identified 5613 articles that were reviewed for physical assessment results stratified by sex and age. Maximal isometric and isokinetic 60°·s-1 knee extension (KE) and knee flexion (KF) contractions from 57 studies and 15 283 subjects (N = 7918 females) had sufficient data reported on females and males for meaningful statistical evaluation to be undertaken. The analysis revealed that isometric KE and KF strength undergo similar rapid declines in both sexes late in the sixth decade of life. Yet, there is an abrupt age-related decline in KE 60°·s-1 peak torque earlier in females (aged 41.8 years) than males (aged 66.7 years). In the assessment of KF peak torque, an age-related acceleration in strength loss was only identified in males (aged 49.3 years). The results suggest that age-related isometric strength loss is similar between sexes while the characteristics of KE and KF peak torque decline are sex-related, which likely explains the differential rate of age-related functional decline. Novelty Inclusion of muscle strength and torque of KE and KF data from >15 000 subjects. Isometric KE and KF strength loss are similar between sexes. Isokinetic 60°·s-1 KE torque decline accelerates 25 years earlier in females and female age-related KF peak torque decline does not accelerate with age.

Effect of Stifle Flexion Angle on the Repeatability of Real-Time Elastosonography of the Patellar Ligament in Medium- to Large-Breed Dogs

OBJECTIVE

 The aims of this study were to describe the elastosonographic findings of the patellar ligament in healthy dogs >15 kg in different positions and determine the most appropriate stifle angle to perform elastosonography of the patellar ligament.

STUDY DESIGN

 Eighteen clinically healthy dogs, weighing >15 kg, were prospectively recruited. B-mode ultrasound and real-time elastosonography of both patellar ligaments were performed on days 0 and 14. Elastosonography examinations were performed with the stifle in four positions: standing position, lateral recumbency with the stifle positioned at 135 degrees extension and in full passive flexion and extension.

RESULTS

 The percentage hardness of the patellar ligament was significantly lower when the elastosonographic examination was performed with the dog standing, compared with the other positions (p < 0.005). The variability in the elastosonography readings for each stifle position was lowest when the dog was standing (89.32%).

CONCLUSION

 Elastosonography is a feasible technique for evaluating the elasticity of the normal canine patellar ligament in dogs >15 kg and would be a useful technique for investigating the mechanical changes within the patellar ligament following stifle surgery. Elastosonography of the patellar ligament should be performed with the dog standing to provide the most accurate elastosonograms with lowest variability between readings.

Obesity Increases the Risk of Tendinopathy, Tendon Tear and Rupture, and Postoperative Complications: A Systematic Review of Clinical Studies

BACKGROUND

Inflammation and mechanical demands play a role in the development of tendon conditions and the dysregulation of tendon healing. In patients with obesity, high levels of pro-inflammatory cytokines and a high mechanical demand promote chronic low-grade inflammation. Although controversial results have been reported, we aimed to summarize current evidence while highlighting the role of obesity in tendinopathy.

QUESTIONS/PURPOSES

(1) Do patients with obesity have a greater risk of tendinopathy, stratified by upper and lower extremity sites, than patients who do not have obesity? (2) Is obesity associated with a higher risk of upper and lower extremity tendon tear and ruptures? (3) Is obesity associated with an increased risk of complications after upper and lower extremity tendon surgery?

METHODS

We performed a systematic review by searching the PubMed, Embase, and Cochrane Library databases, combining the term "tendon" with common terms for tendinopathy and rupture such as "tendon injury OR tendinopathy OR tendon rupture" and "obese" OR "obesity." We included studies with any level of evidence published from January 2000 to July 10, 2019 in peer-reviewed journals reporting clinical results. After we removed the duplicates, there were 365 records. Two independent authors screened these records and excluded 320 based on abstract and title screening. Of the remaining 45 studies, 23 were excluded because the topic did not address the research questions (n = 19), the article was outdated (n = 3), or because there was a serious risk of bias (n = 1). Finally, we included 22 studies with 49,914 participants (5984 with obesity), 31,100 (1884 with obesity) of whom had upper-extremity tendinopathy, while 18,814 (4010 with obesity) had lower-extremity tendinopathy. Obesity was defined as a BMI ≥ 30 kg/m according to the WHO's criteria. Data were extracted and analyzed critically. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were applied, and the risk of bias (ROBINS tool) of the studies was assessed, as was the methodological quality (Coleman score). The assessment was performed independently by two authors. Inter-rater agreement for the assessments of the risk of bias and methodological quality were 89% and 94%, respectively. All studies were observational, and most were retrospective case-control studies. Any discrepancy was discussed and solved by consensus. The articles had a moderate risk of bias (eight articles) or a low risk of bias (fourteen articles). We excluded one article because of a serious risk of bias. The mean (range) Coleman score was 53.5 (42-74).

RESULTS

Obesity was associated with a greater risk of upper extremity tendinopathy (rotator cuff: odds ratio 1.25 [95% confidence interval 1.12 to 1.40]; p < 0.001; medial epicondylitis: OR 1.9 [95% CI 1.0 to 3.7]; p < 0.05) and lower-extremity tendinopathy (Achilles tendon: OR 3.81 [95% CI 2.57 to 5.63]; OR 3.77 [95% CI 2.24 to 6.34]; OR 6.56 [95% CI 3.18 to 13.55], for obesity Classes I, II and III, respectively; patellar tendon: OR 1.10 [95% CI 1.05 to 1.90]; p = 0.001; plantar fascia: OR 2.97 [95% CI 1.64 to 5.37]; p = 0.004). Obesity was associated with a greater risk of upper extremity tendon tear (rotator cuff: OR 2.35 [95% CI 1.62 to 3.40]; p < 0.001) and rupture leading to tendon surgery (rotator cuff in men: OR 3.13 [95% CI 1.29 to 7.61]; p < 0.001 and women: OR 3.51 [95% CI 1.80 to 6.85]; p < 0.001). However, no association was found between BMI and lower extremity rupture (Achilles mean BMI: 27.77 kg/m [95% CI 26.94 to 28.49] versus control: 26.66 kg/m [95% CI 26.06 to 27.27]; p = 0.047). Upper extremity complications (n = 359) after tendon repair surgery had a weighted incidence of 13.27% and 8.13% for rotator cuff surgery in patients with and without obesity, respectively. In the lower extremity (n = 21,152), the weighted incidence for Achilles tendon surgery was 11.28% and 8.6% in patients with and without obesity, respectively.

CONCLUSIONS

Obesity is associated with a higher risk of tendinopathy, tendon tear and rupture, and complications after tendon surgery than non-obesity. However, the high heterogeneity and observational nature of the studies highlight the need to be cautious about the results of our study. We encourage researchers to perform clinical and preclinical studies to explore pathways related to the metabolic state of this population.

LEVEL OF EVIDENCE

Level IV, prognostic study.

Use of Shear Wave Elastography to Quantify Abdominal Wall Muscular Properties in Patients With Incisional Hernia

Shear wave elastography (SWE) is a potential modality that quantitatively measures the elasticity (shear wave speed [SWS]) of musculoskeletal structure. This SWS was bilaterally measured in the rectus abdominis (RA), external oblique (EO) muscle, internal oblique (IO) muscle and transversus abdominis (TrA) using SWE in 28 patients with incisional hernia and 14 healthy controls. The differences in muscle thickness for IO and TrA were significant between the two groups (p < 0.05). The SWS of RA, EO, IO and TrA was significantly higher in the incisional hernia patient group than in the healthy controls (p < 0.05). Significant differences were also observed between the upper and lower points in both groups (p < 0.05). The measurements of SWS help in evaluating the elastic properties of abdominal wall muscles, which could further aid in preparing treatment plans to improve muscle strength.

Intermachine Variation of Ultrasound Strain Elastographic Measures of the Quadriceps and Patellar Tendons in Healthy Participants: Implications for Clinical Practice

OBJECTIVES

To evaluate intermachine variation and compare intraoperator and interoperator agreement and repeatability characteristics of 2 ultrasound (US) systems for measurements of quadriceps and patellar tendons by strain elastography (SE).

METHODS

Forty tendons from 20 healthy participants were investigated by operators with different experience (operator 1, 12 years of US experience and >50 SE examinations; operator 2, no US experience and 1 day of SE training). Repeated measures were performed on GE Healthcare (Waukesha, WI) and Esaote (Genoa, Italy) US systems. The percentage of agreement, Cohen κ, intraclass correlation coefficient, and correlation tests assessed agreement, repeatability, and associations of SE measures. A paired t test and Wilcoxon signed rank test assessed differences in SE measures.

RESULTS

The study participants included 5 male and 15 female volunteers (mean [range] age, 29.3 [21-39] years). Better agreement and repeatability characteristics were observed for the patellar compared to the quadriceps tendon and the color score (CS) method over the elasticity ratio (ER). Intraoperator agreement was better for the experienced operator. Intraoperator repeatability was achieved in 55% of ER (intraclass correlation coefficient, 0.40-0.91; P < .05) and 77% to 85% (κ = -0.25-1) of CS measures. Interoperator repeatability was achieved in 35% (t/z, -2.93-7.94; P < .001-.048) of all ER measures. No significant differences in proximal (z, -0.13- -0.78) and distal patellar (z, -1.52-2.26; P > .5) patellar ER measures were observed. Seventy-four percent to 75% mean agreement (κ = 0-0.5) for CS measures comparable across both US systems was observed. Intermachine ER associations were poor (r = -0.39-0.13; P > .05), whereas greater than 70% agreement (κ = -0.87-0.53) for the CS was achieved.

CONCLUSIONS

The reproducibility of knee tendon SE measurements is influenced by the operator experience, US system, and tendon site.

The Effect of Strength Training on Vastus Lateralis' Stiffness: An Ultrasound Quasi-Static Elastography Study

Ultrasound imaging allows the evaluation of musculoskeletal morphology and function. Ultrasound elastography can also offer semi-quantitative and/or quantitative assessment of tissue stiffness providing relevant information about adaptations of skeletal muscle mechanical properties. In this study we aimed to explore the feasibility of elastography ultrasound imaging in assessing the effect of strength training on vastus lateralis stiffness. Twenty-eight young male adults were separated in a control (n = 9) and strength-training (n = 20) groups. The strength-training group completed 15 weeks of either concentric (n = 10) or eccentric (n = 10) isokinetic training of the knee extensors. Ultrasound scans of the vastus lateralis for quasi-static elastography were collected. All image acquisitions and measurements were done by the same experienced sonographer. After 15 weeks, knee maximal extension isometric torque increased in the strength-training groups. After strength training, there was a decrease in the amount of red pixels in vastus lateralis region of interest [F_(1,18) = 25.490; p < 0.001; η² = 0.586], whereas the amount of green and blue pixels increased F_(1,18) = 17.179; p < 0.01; η² = 0.488; F_(1,18) = 6.522; p < 0.05; η² = 0.266], suggesting higher vastus lateralis stiffness. We conclude that concentric and eccentric strength training increases skeletal muscle stiffness, which can be evaluated by quasi-static elastography. Ultrasound elastography is suitable for non-invasive evaluation of skeletal muscle functional adaptations, which can be of importance for sports medicine and in designing optimal training and rehabilitation programs.

The association between patellar tendon stiffness measured with shear-wave elastography and patellar tendinopathy-a case-control study

OBJECTIVES

(1) To determine the association between patellar tendon stiffness and the presence of patellar tendinopathy (PT). (2) To evaluate the reliability of shear-wave elastography (SWE).

METHODS

Participants were consecutively enrolled between January 2017 and June 2019. PT was diagnosed clinically and confirmed by either grayscale US or power Doppler US, or both. Controls had no history of anterior knee pain and no clinical signs of PT. Patellar tendon stiffness (kilopascal, kPa) was assessed using SWE. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). Reliability analyses included coefficients-of-variation (CV), coefficients-of-repeatability (CR), intraclass correlation coefficient (ICC) for intraobserver and interobserver reliability, and Bland-Altman analysis.

RESULTS

In total, 76 participants with PT (58 men, mean age 24.4 ± 3.8 years) and 35 asymptomatic controls (16 men, mean age 21.5 ± 3.8 years) were included. Univariate analyses (OR 1.094, 95% CI 1.061-1.128, p < .001) and adjusted multivariate analyses (OR 1.294, 95% CI 1.044-1.605, p = .018) showed that athletes with PT had significantly increased patellar tendon stiffness. ICC for intraobserver reliability was 0.95 (95% CI 0.92-0.97), CR (CV) 12 kPa (10%) and 0.79 (95% CI 0.65-0.88), CR (CV) 18 kPa (21%) for interobserver reliability. Mean differences from Bland-Altman analysis were 5.6 kPa (95% CI 3.1-8.1, p < .001) for intraobserver reliability and 4.6 kPa (95% CI 1.9-7.2, p < .001) for interobserver reliability.

CONCLUSIONS

PT is associated with significantly higher patellar tendon stiffness. SWE measurements demonstrate excellent intraobserver reliability and good interobserver reliability. Therefore, SWE is a promising tool to implement in longitudinal studies and future studies should evaluate its prognostic value and utility as a monitoring tool in athletes with PT.

KEY POINTS

• Patellar tendon stiffness measured with shear-wave elastography (SWE) is higher in athletes with patellar tendinopathy than in healthy controls, also after adjusting for potential confounders. • Excellent intraobserver reliability and good interobserver reliability were found for the quantitative assessment of patellar tendon stiffness using SWE.

Effects of hyperlipidemia on patellar tendon stiffness: A shear wave elastography study

BACKGROUND

Recent studies presented that increased adiposity and hyperlipidemia may cause tendon pathology. The aim of this study was to evaluate the effect of hyperlipidemia on the patellar tendon stiffness by shear wave elastography.

METHODS

A total of 51 participants (19 female, 32 male) were included. Participants were divided into two groups, according to their low-density lipoprotein levels, as the study group (hyperlipidemia, n = 24) and the control group (non-hyperlipidemia, n = 27). The patellar tendon and rectus femoris muscle shear wave velocities were measured by shear wave elastography.

FINDINGS

Patellar tendon shear wave velocities was 5.02 (SD: 0.78) m/s in the control group and 5.98 (SD: 1.19) m/s in the hyperlipidemia group (ES = 0.95, P = .001). There was a positive moderate statistically significant correlation between patellar tendon shear wave velocity and low-density lipoprotein (r = 0.432, p < .002). In the multiple linear regression analysis, only low-density lipoprotein was found as a significant predictor of patellar tendon shear wave velocity (CI: 0.005-0.028, P = .007).

INTERPRETATION

We evaluated the effects of hyperlipidemia and body mass index on patellar tendon mechanical properties with shear wave elastography. We found that the blood low-density lipoprotein level had an impact on patellar tendon stiffness independently of body mass index. Accordingly, it is important to evaluate individuals' low-density lipoprotein levels when examining risk factors for tendon pathology.

Relationship between infrared skin radiation and muscular strength tests in patients affected by Emery-Dreifuss muscular dystrophy

Considering that infrared thermography is presented as a diagnostic technique for non-invasive, non-ionizing, fast and easy to use imaging and Emery-Dreifuss muscular dystrophy is a clinical condition that seems to be related to changes in the emission of infrared radiation at the skin level due to its neurodegenerative character, we have conducted an investigation by infrared thermography and the use of functional strength tests in the lower limbs in a family of 4 affected members of Emery-Dreifuss muscular dystrophy to try to establish a relationship between the evolution of the disease and the emission of infrared radiation in this pathology at the lower limb level and provide a more general view of this disease for a better evaluation and monitoring of the disease.

An investigation of the sex-related differences in the stiffness of the Achilles tendon and gastrocnemius muscle: Inter-observer reliability and inter-day repeatability and the effect of ankle joint motion

PURPOSE

The purpose of the present study was to investigate sex-related differences in the stiffness of the Achilles tendon and gastrocnemius muscle at rest and tensioned state. Another purpose of the study was to investigate the inter-observer reliability and inter-day repeatability of MyotonPRO, a portable myotonometer, in measuring tendon and muscle stiffness.

METHODS

The study included 73 healthy participants (19 males for the reliability and repeatability study; 24 males and 30 females for the experimental study) with an age range of 19-27 years. The stiffness of the Achilles tendon and medial gastrocnemius muscle was measured with a portable myotonometer (MyotonPRO). The stiffness measurements of the Achilles tendon and medial gastrocnemius muscle were performed at 0° and 10° of ankle joint dorsiflexion. The stiffness measurements were performed by two physiotherapists to determine the inter-observer reliability of the device. For the inter-day repeatability (or between-day precision), the same individuals were reassessed by the same examiner after a 3-day interval.

RESULTS

It was found that MyotonPRO has excellent inter-observer reliability and inter-day repeatability in measuring the stiffness of the Achilles tendon and medial gastrocnemius muscle (ICC=0.83-0.98). The stiffness of the Achilles tendon and gastrocnemius muscle at neutral and 10° joint dorsiflexion was higher in males compared to females (p<0.05); however, the stiffness value of difference between neutral and 10° joint dorsiflexion for the Achilles tendon and gastrocnemius muscle was similar in both groups (p>0.05).

DISCUSSION

The obtained results suggest that MyotonPRO is a reliable and repeatable device in measuring the stiffness of the Achilles tendon and gastrocnemius muscle. Furthermore, males have stiffer Achilles tendon and gastrocnemius muscle, compared to females; however, the change in the stiffness of the assessed tissues caused by joint motion was similar in both sexes.

Thickness, cross-sectional area, and stiffness of intrinsic foot muscles affect performance in single-leg stance balance tests in healthy sedentary young females

The purpose of this study was to investigate the effect of thickness, cross-sectional area and stiffness of intrinsic foot muscles on performance in single-leg stance balance tasks in healthy sedentary young females. This study included a total of 40 healthy sedentary young females between the ages of 19 and 35 years. Single-leg stance balance assessments were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). Performance in the single-leg stance balance tests was assessed using the overall stability index (OSI), mediolateral stability index (MLSI) and the anteroposterior stability index (APSI). Lower scores indicated better postural stability. Stiffness, thickness and cross-sectional area measurements of the abductor hallucis (AbH), flexor digitorum brevis (FDB) and flexor hallucis brevis (FHB) muscles were performed using an ultrasonography device. Larger AbH and FHB muscles were correlated with higher OSI, APSI, and MLSI (r = 0.31-0.46, p < 0.05), whereas larger FDB muscle was correlated with higher OSI and MLSI (r = 0.28-0.38, p < 0.05). Higher stiffness of the AbH and FHB muscles were correlated with lower OSI, APSI, and MLSI (r = -0.32 to 0.58, p < 0.05), but stiffness of the FDB muscle was not significantly correlated with OSI, APSI, and MLSI (r = 0.03-0.22, p ˃ 0.05). These results suggest that larger AbH, FDB and FHB muscles are related to reduced performance in single-leg stance balance tests, whereas higher AbH and FHB stiffness are related to better performance in single-leg stance balance tests in healthy sedentary young females.

Patellar tendon morphology in trans-tibial amputees utilizing a prosthesis with a patellar-tendon-bearing feature

A patellar-tendon-bearing (PTB) bar is a common design feature used in the socket of trans-tibial prostheses to place load on the pressure-tolerant tissue. As the patellar tendon in the residual limb is subjected to the perpendicular compressive force not commonly experienced in normal tendons, it is possible for tendon degeneration to occur over time. The purpose of this study was to compare patellar tendon morphology and neovascularity between the residual and intact limbs in trans-tibial amputees and healthy controls. Fifteen unilateral trans-tibial amputees who utilized a prosthesis with a PTB feature and 15 age- and sex- matched controls participated. Sonography was performed at the proximal, mid-, and distal portions of each patellar tendon. One-way ANOVAs were conducted to compare thickness and collagen fiber organization and a chi-square analysis was used to compare the presence of neovascularity between the three tendon groups. Compared to healthy controls, both tendons in the amputees exhibited increased thickness at the mid- and distal portions and a higher degree of collagen fiber disorganization. Furthermore, neovascularity was more common in the tendon of the residual limb. Our results suggest that the use of a prosthesis with a PTB feature contributes to morphological changes in bilateral patellar tendons.

Body Mass Index and Segmental Mass Correlation With Elastographic Strain Ratios of the Quadriceps Tendon

OBJECTIVES

The aim of this study was to establish a relationship between quadriceps tendon stiffness and its properties and variations in the body mass index (BMI) and segmental mass.

METHODS

This study was conducted in 3 groups according to their BMI (A, low [<18.5 kg/m² ]; B, normal [18.5-25.0 kg/m² ]; and C, high [>25.0 kg/m² ]). All of the participants included had a sedentary lifestyle and did not do any weightlifting or any kind of sports activity in the previous 6 months. Ultrasound measurements were performed on the participants' lower right extremities, since it was the dominant side for all of the participants.

RESULTS

A total of 40 healthy untrained men participated in the study. The mean age of the participants ± SD was 22.1 ± 1.3 years; the age ranges for groups A (n = 6), B (n = 18), and C (n = 16) were 19-23, 19-25, and 20-25 years, respectively; 28 of the participants were nonsmokers, and 12 of were smokers. A strong statistical difference (all P < .05) was witnessed for most of the parameters (BMI, body fat mass, dominant leg body fat content, fat-free mass index, tendon thickness, and strain ratio) among the groups.

CONCLUSIONS

The length of the tendon did not show a significant increase with an increase in the BMI, body fat mass, dominant leg body fat content, and fat-free mass index. However, a greater intensification was observed for the thickness of the tendon with a significant increase in tendon stiffness (with the use of external reference material).

An 8-week resistance training protocol is effective in adapting quadriceps but not patellar tendon shear modulus measured by Shear Wave Elastography

Habitual loading and resistance training (RT) can lead to changes in muscle and tendon morphology as well as in its mechanical properties which can be measured by Shear Wave Elastography (SWE) technique. The objective of this study was to analyze the Vastus Lateralis (VL) and patellar tendon (PT) mechanical properties adaptations to an 8-week RT protocol using SWE. We submitted 15 untrained health young men to an 8-week RT directed for knee extensor mechanism. VL and PT shear modulus (μ) were assessed pre and post intervention with SWE. PT thickness (PTT), VL muscle thickness (VL MT) and knee extension torque (KT) were also measure pre and post intervention to ensure the RT efficiency. Significant increases were observed in VL MT and KT (pre = 2.40 ± 0.40 cm and post = 2.63 ± 0.35 cm, p = 0.0111, and pre = 294.66 ± 73.98 Nm and post = 338.93 ± 76.39 Nm, p = 0.005, respectively). The 8-week RT was also effective in promoting VL μ adaptations (pre = 4.87 ± 1.38 kPa and post = 9.08.12 ± 1.86 kPa, p = 0.0105), but not in significantly affecting PT μ (pre = 78.85 ± 7.37 kPa and post = 66.41 ± 7.25 kPa, p = 0.1287) nor PTT (baseline = 0.364 ± 0.053 cm and post = 0.368 ± 0.046 cm, p = 0.71). The present study showed that an 8-week resistance training protocol was effective in adapting VL μ but not PT μ. Further investigation should be conducted with special attention to longer interventions, to possible PT differential individual responsiveness and to the muscle-tendon resting state tension environment.

Ultrasound Characteristics of Foot and Ankle Structures in Healthy, Coper, and Chronically Unstable Ankles

OBJECTIVE

Ankle sprains constitute approximately 85% of all ankle injuries, and up to 70% of people experience residual symptoms. While the injury to ligaments is well understood, the potential role of other foot and ankle structures has not been explored. The objective was to characterize and compare selected ankle structures in participants with and without a history of lateral ankle sprain.

METHODS

A total of 71 participants were divided into 31 healthy, 20 coper, and 20 chronic ankle instability groups. Ultrasound images of the anterior talofibular and calcaneofibular ligaments, fibularis tendons and muscles, tibialis posterior, and Achilles tendon were obtained. Thickness, length, and cross-sectional areas were measured and compared among groups.

RESULTS

When under tension, the anterior talofibular ligament (ATFL) was longer in copers and chronic ankle instability groups compared to healthy participants (P < .001 and P = .001, respectively). The chronic ankle instability group had the thickest ATFL and calcaneofibular ligament among the 3 groups (p < 0.001). No significant differences (P > .05) in tendons and muscles were observed among the 3 groups.

CONCLUSIONS

The ultrasound protocol proved reliable and was used to evaluate the length, thickness, and cross-sectional areas of selected ankle structures. The length of the ATFL and the thickness of the ATFL and calcaneofibular ligament were longer and thicker in injured groups compared to healthy.

A simple method for determining ligament stiffness during total knee arthroplasty in vivo

A key requirement in both native knee joints and total knee arthroplasty is a stable capsular ligament complex. However, knee stability is highly individual and ranges from clinically loose to tight. So far, hardly any in vivo data on the intrinsic mechanical of the knee are available. This study investigated if stiffness of the native ligament complex may be determined in vivo using a standard knee balancer. Measurements were obtained with a commercially available knee balancer, which was initially calibrated in vitro. 5 patients underwent reconstruction of the force-displacement curves of the ligament complex. Stiffness of the medial and lateral compartments were calculated to measure the stability of the capsular ligament complex. All force-displacement curves consisted of a non-linear section at the beginning and of a linear section from about 80 N onwards. The medial compartment showed values of 28.4 ± 1.2 N/mm for minimum stiffness and of 39.9 ± 1.1 N/mm for maximum stiffness; the respective values for the lateral compartment were 19.9 ± 0.9 N/mm and 46.6 ± 0.8 N/mm. A commercially available knee balancer may be calibrated for measuring stiffness of knee ligament complex in vivo, which may contribute to a better understanding of the intrinsic mechanical behaviour of knee joints.