Normative Achilles and patellar tendon shear wave speeds and loading patterns during walking in typically developing children

BackgroundMotion analysis is commonly used to evaluate joint kinetics in children with cerebral palsy who exhibit gait disorders. However, one cannot readily infer muscle-tendon forces from joint kinetics. This study investigates the use of shear wave tensiometry to characterize Achilles and patellar tendon forces during gait.Research QuestionHow do Achilles and patellar tendon wave speed and loading modulate with walking speed in typically developing children?MethodsTwelve typically developing children (9–16 years old) walked on an instrumented treadmill with shear wave tensiometers over their Achilles (n = 11) and patellar (n = 9) tendons. Wave speeds were recorded at five leg length-normalized walking speeds (very slow to very fast). Achilles and patellar tendon moment arms were measured with synchronized ultrasound and motion capture. The tendon wave speed-load relationship was calibrated at the typical walking speed and used to estimate tendon loading at other walking speeds.ResultsCharacteristic Achilles and patellar tendon wave speed trajectories exhibited two peaks over a gait cycle. Peak Achilles tendon force closely aligned with peak ankle plantarflexor moment during pushoff, though force exhibited less modulation with walking speed. A second peak in late swing Achilles loading, which was not evident from the ankle moment, increased significantly with walking speed (p < 0.001). The two peaks in patellar tendon loading occurred at 12 ± 1% and 68 ± 6% of the gait cycle, matching the timing of peak knee extension moment in early stance and early swing. Both patellar tendon load peaks increased significantly with walking speed (p < 0.05).SignificanceThis is the first study to use shear wave tensiometry to characterize Achilles and patellar tendon loading during gait in children. These data could serve as a normative comparison when using tensiometry to identify abnormal tendon loading patterns in individuals who exhibit equinus and/or crouch gait.     

应用超声剪切波弹性成像技术定量评价兔深静脉血栓弹性研究

目的探讨应用超声剪切波弹性成像技术定量评价兔深静脉血栓(DVT)弹性的价值。方法建立DVT兔模型,应用超声剪切波弹性成像技术检测血栓形成后第1~14天及第21天血栓上、中、下三部分的杨氏模量值,取均值进行分析。结果前7 d连续检测的血栓杨氏模量值随时间而增大,增长趋势最明显,第1天、第4天、第7天之间差异有统计学意义(P<0.05);7 d后血栓杨氏模量值增长趋势减缓,第8、9天与第11天以后的杨氏模量值间差异有统计学意义(P<0.05);第10天以后杨氏模量值逐渐趋于稳定;第12、13、14天与第21天差异有统计学意义(P<0.05);两周后,杨氏模量值无明显变化。结论应用超声剪切波弹性成像技术定量评价兔DVT的杨氏模量值,可无创、客观地反映血栓弹性动态演变过程,可为评估DVT分期的定量检测提供依据。     

Quantitative magnetization transfer ultrashort echo time imaging of the Achilles tendon

Ultrashort echo time imaging allows the short T₂ Achilles tendon to be directly visualized with MRI. Radiofrequency saturation 1 kHz or less off‐resonance has been used previously to improve image contrast. In this study, magnetization transfer was investigated in the Achilles tendon of eight normal volunteers and one patient with psoriatic arthritis. 2D Ultrashort echo time images were acquired using saturation pulses 2–100 kHz off‐resonance at 4 pulse powers. On‐resonance saturation recovery images were also obtained to estimate T₁. The results were fitted to a two compartment quantitative magnetization transfer model. The estimated bound proton fraction for the eight healthy volunteers was 21.0 ± 1.2% (mean ± standard deviation) compared to 16.4% in the patient with psoriatic arthritis (P < 0.05). The T₂ of the bound protons was measured as 6.1 ± 0.3 μsec in the healthy volunteers and 6.0 μsec in the patient. This technique appears clinically feasible and may be useful for assessing the collagen and water changes which occur in Achilles tendinopathy. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Effect of ultrasound therapy on the repair of Achilles tendon injuries in rats

The purpose was to determine the effects of selected regimens of ultrasound therapy on the rates of repair of injured Achilles tendons of rats. Specific dependent variables examined were tendon breaking strength and rate of collagen formation. A puncture technique was used to induce injuries to both Achilles tendons of rats. Continuous ultrasound was administered to the left tendon for 4 min per treatment session at an intensity of 1.5 W.cm-2. Rats were sacrificed 2, 5, 9, 15, and 21 d following injury for measurement of tendon breaking strength and 3 and 5 d postinjury for analysis of collagen synthesis. Breaking strength was defined as the minimum force required to completely rupture the tendon. Collagen synthesis was indicated by the conversion of labeled proline to hydroxyproline. The breaking strengths of the treated tendons were significantly greater than strengths of the untreated tendons 5, 9, 15, and 21 d postinjury. Collagen synthesis was increased in the treated tendons compared with the untreated tendons 5 d postinjury. The results indicate that ultrasound treatment increases the rate of repair of injured Achilles tendons of rats. The results are also consistent with an association between increased collagen synthesis and greater breaking strength during tendon repair.     

Quantitative MRI measurements of the Achilles tendon in spondyloarthritis using ultrashort echo times

Objectives

Tendon involvement is common in spondyloarthritis. The MRI signal from the Achilles tendon has been used to quantify mechanical tendinopathy; however, conventional MRI is limited by the short T₂ of normal tendon. Short and ultrashort echo time (UTE) MRI have the potential to better measure signal intensity reflecting changes in T₂ or gadolinium enhancement. Furthermore, UTE images could be used for normalisation to reduce variability. The aim of this work was to investigate such techniques in patients with spondyloarthritis (SpA).

Methods

The Achilles tendons of 14 healthy volunteers and 24 patients with symptomatic spondyloarthritis were studied. Combined UTE (TE=0.07 ms) and gradient echo (TE=4.9 ms) images were acquired before and after intravenous gadolinium together with pre-contrast gradient echo images (TE=2 ms). The signal intensity from a region of interest in the Achilles tendon above the calcaneus was measured. The relative enhancement at echo times of 0.07 ms (RE_0.1) and 4.9 ms (RE₅) were calculated. The ratios of the signal intensities from both 4.9 ms and 2 ms gradient echo images to the signal intensity from the UTE image were calculated (RTE₅ and RTE₂ respectively).

Results

Interobserver intraclass correlation coefficients were excellent (≥0.97). The contrast-to-noise ratio was higher for enhancement on UTE images than on gradient echo images. RE_0.1, RTE₅ and RTE₂ were significantly higher in SpA patients than controls.

Conclusion

Signal intensity ratios using UTE images allow quantitative measurements to be made which are sensitive to tendon T₂ or contrast enhancement and which are increased in spondyloarthritis. They therefore have the potential for use as measures of tendon disease in spondyloarthritis.A cardinal manifestation of seronegative spondyloarthritis (SpA) is inflammation at tendons or ligaments near their insertions, which is well described at many disease sites [1]; the Achilles tendon is the largest such structure in the body. SpA is associated with various MRI findings, including changes within and around the tendon near its insertion, and erosion and oedema of the adjacent bone [2].Conventional MRI has been used to study the Achilles tendon in patients with mechanical tendinopathy and scoring systems have been devised that correlate with surgical outcome [3]. Techniques for quantifying Achilles tendinopathy in these patients based on signal intensity have been shown to correlate with pain and functional impairment [4]. However, measurements of signal intensity from conventional MRI are limited by the short T₂ of the normal Achilles tendon (1–2 ms) [5-7], which limits the detection of subtle increases in T₂ or contrast enhancement [8]. Short echo time (STE) gradient echo images can detect small increases in T₂ which may occur in mild or early tendinopathy [9]. Ultrashort echo time (UTE) techniques reduce the time between excitation and acquisition still further, to under 100 μs, directly visualising the tendon and enabling the demonstration of contrast enhancement despite the short T₂ relaxation times of the normal tendon.Single measurements of signal intensity are prone to variation (e.g. due to radiofrequency coil inhomogeneities, coil loading and variation between patients). Unenhanced UTE images are insensitive to changes in T₂ due to their short effective echo times and can therefore be used to normalise contrast-enhanced or STE images to give a ratio that is strongly dependent on only contrast enhancement or T₂*.The aim of this work was to investigate such quantitative measurements from the Achilles tendon and to apply them in patients with symptomatic SpA.     

Lower material stiffness in rupture-repaired Achilles tendon during walking: transmission-mode ultrasound for post-surgical tendon evaluation

Purpose

This cross-sectional study used transmission-mode ultrasound to evaluate dynamic tendon properties during walking in surgically repaired and contralateral Achilles tendon (AT), with a median (range) post-operative period of 22 (4–58) months. It was hypothesised that the axial transmission speed of ultrasound (TSOU) during walking would be slower, indicating lower material stiffness in repaired compared with contralateral AT.

Methods

Ten patients [median (range) age 47 (37–69) years; height 180 (170–189) cm; weight 93 (62–119) kg], who had undergone open surgical repair of the AT and were clinically recovered according to their treating clinicians, walked barefoot on a treadmill at self-selected speed (1.0 ± 0.2 m/s). Synchronous measures of TSOU, sagittal ankle motion, vertical ground reaction force (GRF), and spatiotemporal gait parameters were recorded during 20 s of steady-state walking. Paired t tests were used to evaluate potential between-limb differences in TSOU, GRF, ankle motion, and spatiotemporal gait parameters.

Results

TSOU was significantly lower (≈175 m/s) in the repaired than in the contralateral AT over the entire gait cycle (P < 0.05). Sagittal ankle motion was significantly greater (≈3°) in the repaired than in the contralateral limb (P = 0.036). There were no significant differences in GRF or spatiotemporal parameters between limbs.

Conclusions

Repaired AT was characterised by a lower TSOU, reflecting a lower material stiffness in the repaired tendon than in the contralateral tendon. A lower material stiffness may underpin greater ankle joint motion of the repaired limb during walking and long-term deficits in the muscle-tendon unit reported with AT repair. Treatment and rehabilitation approaches that focus on increasing the material stiffness of the repaired AT may be clinically beneficial. Transmission-mode ultrasound would seem useful for quantifying tendon properties post AT rupture repair and may have the potential to individually guide rehabilitation programmes, thereby aiding safer return to physical activity.

Level of evidence

II.

     

Ultrasound and color Doppler ultrasound of acute and subacute Achilles tendon ruptures

Acute rupture of the Achilles tendon is one of many foot and ankle injuries that may present to the emergency department. Using ultrasound and color Doppler ultrasound, the radiologist can determine which acutely injured patients require operative management and which can be treated nonoperatively. Nonoperative management can be used in those patients with closely apposed tendon ends. This article reviews the use of gray-scale ultrasound in evaluating the appearance of the torn Achilles tendon. The use of color Doppler ultrasound for distinguishing torn tendon ends from hematoma and granulation tissue is discussed.     

Partial rupture of the proximal Achilles tendon: a differential diagnostic problem in ultrasound imaging

Objectives: The aim of this study was to determine whether ultrasound can correctly visualise partial ruptures of the proximal Achilles tendon. Method: This was a prospective study in which all chronic Achilles tendon injury patients seen at three centres in Germany from 1998 to 2003 were screened. All patients with clinical and/or sonographic signs of abnormalities in the region of the proximal third of the Achilles tendon and tendomuscular junction were included in the analysis. Each of these cases was evaluated by ultrasound following an assessment protocol. Patients with ambiguous ultrasound findings and/or clinical signs were additionally assessed by magnetic resonance imaging (MRI). Results: Sonomorphologic changes suggestive of an abnormality in the proximal third of the Achilles tendon were detected in 13 out of 320 patients (4.2%) with recurring Achilles tendon complaints. Thirteen patients had clinical signs but no sonographic changes in the tendon. The sonographic diagnosis was correct in 19 cases. In six of the 26 cases studied, MRI was needed to establish the correct diagnosis of partial intratendinous rupture of the proximal Achilles tendon. Sensitivity was 0.5, specificity was 0.81, and the overall agreement of the ultrasound examination was 61.5%. All patients were asymptomatic at follow up at a mean of 14 months (range 12–17 months) after surgery. Conclusions: Ultrasound is a useful tool for evaluation of proximal Achilles tendon complaints. However, ultrasound is not sufficiently reliable for diagnosis of all pathologies, especially partial ruptures of the Achilles tendon. Thus, the definitive diagnosis must be established by MRI.     

Functional anatomy of the Achilles tendon

The Achilles tendon is the strongest and thickest tendon in the human body. It is also the commonest tendon to rupture. It begins near the middle of the calf and is the conjoint tendon of the gastrocnemius and soleus muscles. The relative contribution of the two muscles to the tendon varies. Spiralisation of the fibres of the tendon produces an area of concentrated stress and confers a mechanical advantage. The calcaneal insertion is specialised and designed to aid the dissipation of stress from the tendon to the calcaneum. The insertion is crescent shaped and has significant medial and lateral projections. The blood supply of the tendon is from the musculotendinous junction, vessels in surrounding connective tissue and the osteotendinous junction. The vascular territories can be classified simply in three, with the midsection supplied by the peroneal artery, and the proximal and distal sections supplied by the posterior tibial artery. This leaves a relatively hypovascular area in the mid-portion of the tendon where most problems occur. The Achilles tendon derives its innervation from the sural nerve with a smaller supply from the tibial nerve. Tenocytes produce type I collagen and form 90% of the cellular component of the normal tendon. Evidence suggests ruptured or pathological tendon produce more type III collagen, which may affect the tensile strength of the tendon. Direct measurements of forces reveal loading in the Achilles tendon as high as 9 KN during running, which is up to 12.5 times body weight.     

Evaluation of sonoelastography in Achilles tendon of healthy volunteers and patients with symptomatic Achilles tendon

Aim and objectives: To assess the role of SEL in evaluation of Achilles tendon. Methodology: This study included 40 healthy volunteers and 40 patients with symptomatic Achilles tendon. All patients were examined by conventional B-mode ultrasound, sonoelastography and MRI. Results: Achilles tendons of the volunteers were characterized by hard texture with higher strain ratios than those of the patients with Achilles tendinopathy. No significant differences could be detected between SR of male and female volunteers yet significant differences could be detected in the volunteer group above and below forty being lower with softer tendon properties in the group above forty with a cut-off value of ≤1.84 between healthy and diseased group. Sonoelastography had the sensitivity of 89.1% and specificity of 96.1% for diagnosis of tendinopathy with results superior to those of conventional B-mode ultrasonography. Conclusion: SEL is a reliable tool in the evaluation of Achilles tendinopathy with sensitivity and specificity superior to B-mode US. Strain ratio provides excellent non-invasive diagnostic data adds strongly in more objective evaluation of Achilles tendon properties.     

Muscle transplant in the rabbit's Achilles tendon

Achilles tendinopathy (AT) is a degenerative disorder resulting from functional overload, especially during running and jumping, with some inflammatory features at the insertions, bursae, and paratenon. The Achilles tendon is poorly vascularized, especially in the middle third, and the consequent slow metabolic rate allows it to work at very low oxygen tensions but prevents on the other hand a rapid healing. PURPOSE: To create an animal model to study a novel surgical technique employed in AT: transplanting some fibers of the soleus muscle into the tendon in order to improve its vascularization and healing and to study the histological appearance of the soleus graft incorporated in the tendon. METHODS: We operated on 10 white New Zealand rabbits (eight rabbits underwent the procedure, two rabbits the sham operation with incision of the tendon without graft). Two animals were euthanized at 1 wk, 1, 2, and 3 months. RESULTS: Histology showed that after 3 months the muscle fibers were still viable within the tendons, interspersed within connective tissue fibers. Tendon and muscle tissues were intimately fused. CONCLUSIONS: The persistence of the soleus muscle pedicle graft within the Achilles tendon tissue is an index of sound blood supply. This surgical model is suitable for application in further studies on tendon healing.     

Microcirculatory effects of topical glyceryl trinitrate on the Achilles tendon microcirculation in patients with previous Achilles tendon rupture

Topical glyceryl trinitrate treatment has demonstrated short- to mid-term efficacy in chronic noninsertional Achilles tendinopathy. However, the underlying mechanisms are far from being understood. We hypothetized that Achilles tendon capillary blood flow changes immediately after topical glyceryl trinitrate treatment. Fifteen patients (55 ± 15 years, VAS 5.8 ± 2.3) with current mid-portion Achilles tendon pain 36 months after open surgical Achilles tendon repair for tendon rupture were included. On the Achilles mid-portion, 1.2 mg topical glyceryl trinitrate was sprayed. Microcirculatory monitoring included capillary blood flow, tendon oxygen saturation and postcapillary venous filling pressures at the insertion and 2, 4 and 6 cm above the insertion using a combined laser Doppler and spectrophotometry system. Baseline capillary blood-flows of the painful versus the uninjured tendon were increased [108 ± 46 vs. 81 ± 20 (2 cm above the insertion), 104 ± 40 vs. 76 ± 20 (4 cm above the insertion), 111 ± 53 vs. 90 ± 21 (6 cm above the insertion, P < 0.05)]. However, topical glyceryl trinitrate did not change capillary blood-flow at 2 and 8-mm tissue depths at the painful Achilles tendon or the healthy tendon. Tendon oxygenation was not changed at the painful or the healthy Achilles tendon. Postcapillary venous filling pressure was reduced at 8 mm at the mid-portion in the painful Achilles tendon only (113 ± 37 vs. 95 ± 31, P = 0.030). Acute topical glyceryl trinitrate facilitates capillary venous outflow in painful Achilles tendons. However, capillary blood-flow and tendon oxygenation remain unchanged following acute topical glyceryl trinitrate application. Elevated capillary blood-flow at the entire mid-portion is encountered at baseline in previously ruptured painful Achilles tendons even 3 years after surgical repair of the Achilles tendon indicating an altered microcirculatory flow pattern.     

Role of MRI in the study of the Achilles tendon and patellar tendon

The possibilities of MRI and radiography with mammogram to diagnose mechanical tendinitis have been prospectively evaluated in thirty sportsmen. Sixteen had Achilles tendon lesion, fourteen had patellar ligament lesion. Each patient included in the study was programmed for radiography with mammogram and MRI of the pathologic tendon and the controlateral tendon. These examinations were separately interpreted by two reviewers who had no knowledge of pain location. The number of tendinitis diagnosis based on X-ray and MRI was approximatively the same. But the microtearings were more often diagnosed on MRI data than on X-ray data (10/1). Eight patients underwent an operation. The surgery findings always confirmed the MRI diagnoses. MRI seems to be the examination of choice to evaluate the tendon injuries and particularly microtearings before surgery.     

Biomechanical properties of the calcaneal tendon in vivo assessed by transient shear wave elastography

Objective

The purpose of this study is to assess the elastic and anisotropic properties of normal calcaneal tendon in vivo by transient shear wave elastography (SWE).

Materials and methods

This study was approved by our institutional ethics committee. Eighty healthy subjects over 18 years of age were prospectively included. Data on the patients’ height, weight, sporting activities, and take-off foot were assessed. The thickness, width, and cross-sectional area of the calcaneal tendons were measured. The shear wave propagation velocity (V_mean) was measured by three radiologists on axial and sagittal SWE images at four different degrees of ankle flexion, enabling to calculate elasticity modulus (E_mean), and relative anisotropy coefficient (A) values.

Results

In complete plantar flexion, V_mean was 6.8?±?1.4 m.s^?1 and 5.1?±?0.8 m.s^?1, respectively, on the sagittal and axial SWE image, resulting in an elastographic anisotropy A of 0.24?±?0.16. The best interobserver correlation coefficient of E_mean and V_mean was 0.43 and 0.46, respectively, in the sagittal SWE for complete plantar flexion. V_mean and E_mean significantly increase when the tendon is stretched by ankle dorsiflexion. The maximal values in sagittal SWE were V_mean?=?16.1?±?0.7 m.s^?1, E_mean?=?779.5?±?57.1kPa and A = 0.63?±?0.07.

Conclusions

SWE allows the elastic properties of the calcaneal tendon to be evaluated quantitatively in vivo, but interobserver reproducibility is questionable. It confirms the tendinous elastographic anisotropy and stiffness augmentation of stretched tendon.     

Reconstruction of neglected Achilles tendon rupture using the flexor hallucis tendon

Neglected ruptures of the Achilles tendon (AT) are not common and have a greater tendency to cause complications and to produce poorer functional results than fresh ruptures. Numerous surgical procedures have been described for the reconstruction of neglected AT ruptures. However, no report has been issued about an AT rupture neglected for more than 2 years. The authors reported about three patients (four tendons) with a neglected AT rupture of mean duration of 5 years, who were treated by interposed scar tissue repair combined with flexor hallucis longus tendon transfer. All patients experienced good clinical results and were satisfied with surgery. None of the authors received financial support for this study.