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Concept: Achilles tendon


BackgroundLess invasive percutaneous acute Achilles tendon rupture repair techniques gain popularity because of lower risk of surgical wound complications. But these approaches have an increased risk of sural nerve iatrogenic injury as this sensory nerve is usually not visualized during minimally invasive operative procedures. We compared standard percutaneous Bunnell type and our proposed modified-medialized percutaneous technique in a cadaver study to evaluate potential advantages. Methods10 pairs of fresh frozen specimens were divided into two groups for comparative anatomical study. Tenotomies of Achilles tendons were made and wounds sutured. 10 standard and 10 modified-medialized repairs were applied for artificially performed ruptures. All sutured tendons were dissected meticulously. We carefully looked at repaired Achilles tendon end-to-end contact and adaptation, distance from Achilles insertion in calcaneal tubercle to place where sural nerve crosses lateral border of the Achilles tendon and possible sural nerve and vein entrapment. Groups were compared using Fisher’s exact and Student-T tests.ResultsAll ends of sharply dissected tendons in both groups were in sufficient contact. No measurable diastasis between tendon ends was found in all cases. No entrapment of sural nerve or vein was found in modified percutaneous Bunnell suture technique group. Whereas 7 of 10 sural nerves and 9 small saphenous veins were entrapped when using standard percutaneous Bunnell type technique. Average distance from Achilles tendon insertion in tuber calcanei to sural nerve crossing the lateral border of Achilles was 93 mm.ConclusionMedialization of percutaneous suture in acute Achilles tendon rupture repair show clear advantages compared to standard non medialized technique ensuring a possible lower incidence of sural nerve entrapment injury. Our modified percutaneous Bunnell type technique allows sufficient adaptation of ruptured Achilles tendon.

Concepts: Muscle, Wound, Tendon, Achilles tendon, Tendons, Small saphenous vein, Sural nerve, Achilles tendon rupture


Tendons are often injured and heal poorly. Whether this is caused by a slow tissue turnover is unknown, since existing data provide diverging estimates of tendon protein half-life that range from 2 mo to 200 yr. With the purpose of determining life-long turnover of human tendon tissue, we used the (14)C bomb-pulse method. This method takes advantage of the dramatic increase in atmospheric levels of (14)C, produced by nuclear bomb tests in 1955-1963, which is reflected in all living organisms. Levels of (14)C were measured in 28 forensic samples of Achilles tendon core and 4 skeletal muscle samples (donor birth years 1945-1983) with accelerator mass spectrometry (AMS) and compared to known atmospheric levels to estimate tissue turnover. We found that Achilles tendon tissue retained levels of (14)C corresponding to atmospheric levels several decades before tissue sampling, demonstrating a very limited tissue turnover. The tendon concentrations of (14)C approximately reflected the atmospheric levels present during the first 17 yr of life, indicating that the tendon core is formed during height growth and is essentially not renewed thereafter. In contrast, (14)C levels in muscle indicated continuous turnover. Our observation provides a fundamental premise for understanding tendon function and pathology, and likely explains the poor regenerative capacity of tendon tissue.-Heinemeier, K. M., Schjerling, P., Heinemeier, J., Magnusson, S. P., Kjaer, M. Lack of tissue renewal in human adult Achilles tendon is revealed by nuclear bomb (14)C.

Concepts: Mass spectrometry, Biology, Tendon, Achilles tendon, Nuclear weapon, Tendons, Carbon-14, Accelerator mass spectrometry


INTRODUCTION: Achilles and patellar tendinopathy are overuse injuries that are common among athletes. Isolated eccentric muscle training has become the dominant conservative management strategy for Achilles and patellar tendinopathy but, in some cases, up to 45 % of patients may not respond. Eccentric-concentric progressing to eccentric (Silbernagel combined) and eccentric-concentric isotonic (heavy-slow resistance; HSR) loading have also been investigated. In order for clinicians to make informed decisions, they need to be aware of the loading options and comparative evidence. The mechanisms of loading also need to be elucidated in order to focus treatment to patient deficits and refine loading programmes in future studies. OBJECTIVES: The objectives of this review are to evaluate the evidence in studies that compare two or more loading programmes in Achilles and patellar tendinopathy, and to review the non-clinical outcomes (potential mechanisms), such as improved imaging outcomes, associated with clinical outcomes. METHODS: Comprehensive searching (MEDLINE, EMBASE, CINAHL, Current Contents and SPORTDiscus(™)) identified 403 studies. Two authors independently reviewed studies for inclusion and quality. The final yield included 32 studies; ten compared loading programmes and 28 investigated at least one potential mechanism (six studies compared loading programmes and investigated potential mechanisms). RESULTS: This review has identified limited (Achilles) and conflicting (patellar) evidence that clinical outcomes are superior with eccentric loading compared with other loading programmes, questioning the currently entrenched clinical approach to these injuries. There is equivalent evidence for Silbernagel combined (Achilles) and greater evidence for HSR loading (patellar). The only potential mechanism that was consistently associated with improved clinical outcomes in both Achilles and patellar tendon rehabilitation was improved neuromuscular performance (e.g. torque, work, endurance), and Silbernagel-combined (Achilles) HSR loading (patellar) had an equivalent or higher level of evidence than isolated eccentric loading. In the Achilles tendon, a majority of studies did not find an association between improved imaging (e.g. reduced anteroposterior diameter, proportion of tendons with Doppler signal) and clinical outcomes, including all high-quality studies. In contrast, HSR loading in the patellar tendon was associated with reduced Doppler area and anteroposterior diameter, as well as greater evidence of collagen turnover, and this was not seen following eccentric loading. HSR seems more likely to lead to tendon adaptation and warrants further investigation. Improved jump performance was associated with Achilles but not patellar tendon clinical outcomes. The mechanisms associated with clinical benefit may vary between loading interventions and tendons. CONCLUSION: There is little clinical or mechanistic evidence for isolating the eccentric component, although it should be made clear that there is a paucity of good quality evidence and several potential mechanisms have not been investigated, such as neural adaptation and central nervous system changes (e.g. cortical reorganization). Clinicians should consider eccentric-concentric loading alongside or instead of eccentric loading in Achilles and patellar tendinopathy. Good-quality studies comparing loading programmes and evaluating clinical and mechanistic outcomes are needed in both Achilles and patellar tendinopathy rehabilitation.

Concepts: Central nervous system, Nervous system, Collagen, Evidence-based medicine, Tendon, Achilles tendon, Tendinopathy, Tendons


Achilles tendon rupture is a frequent injury with an increasing incidence. Until now, there is no consensus regarding optimal treatment. The aim of this review was to illuminate and summarize randomized controlled trials comparing surgical and non-surgical treatment of Achilles tendon ruptures during the last 10 years. Seven articles were found and they were all acceptable according to international quality assessment guidelines. Primary outcomes were re-ruptures, other complications, and functional outcomes. There was no significant difference in re-ruptures between the two treatments, but a tendency to favoring surgical treatment. Further, one study found an increased risk of soft-tissue-related complications after surgery. Patient satisfaction and time to return to work were significantly different in favor of surgery in one study, and there was also better functional outcome after surgery in some studies. These seven studies indicate that surgical patients have a faster rehabilitation. However, the differences between surgical and non-surgical treatment appear to be subtle and it could mean that rehabilitation is more important, rather than the actual initial treatment. Therefore, further studies will be needed in regard to understanding the interplay between acute surgical or non-surgical treatment, and the rehabilitation regimen for the overall outcome after Achilles tendon ruptures.

Concepts: Randomized controlled trial, Tendon, Achilles tendon, Tendinosis, Achilles tendon rupture


INTRODUCTION: Understanding the mechanical and morphological adaptation of the Achilles tendon in response to acute exercise could have important implications for athletic performance, injury prevention and rehabilitation. The purpose of this study was to conduct a systematic review and critical evaluation of the literature to determine the immediate effect of a single bout of exercise on the mechanical and morphological properties of the Achilles tendon in vivo. METHODS: Five electronic research databases were systematically searched for intervention based studies reporting mechanical and morphological properties of the AT following a single bout exercise bout. RESULTS: Searches revealed 3292 possible articles, 21 met the inclusion criteria. There is evidence that maximal isometric contractions and prolonged static stretching (> 5 min) of the triceps surae complex cause an immediate decrease in Achilles tendon stiffness, while prolonged running and hopping have minimal effect. Limited, but consistent evidence exists indicating that Achilles tendon hysteresis is reduced following prolonged static stretching. Consistent evidence supports a reduction in free Achilles tendon diameter (anterior-posterior) following dynamic ankle exercise and this change appears most pronounced in the healthy tendon and following eccentric exercise. CONCLUSIONS: The mechanical and morphological properties of the Achilles tendon in vivo are affected by acute exercise in a mode and dose dependent manner. Transient changes in Achilles tendon stiffness, hysteresis and diameter following unaccustomed exercise modes and doses may expose the tendon to increased risk of strain injury and impact on the mechanical function of the triceps surae muscle-tendon unit.

Concepts: Critical thinking, Exercise, Dose, Meta-analysis, Tendon, Achilles tendon, Stretching, Adaptation


The standard approach to reconstruction after resection of a diffuse-type tenosynovial giant cell tumor is a local patch with free flaps. However, in cases in which the Achilles tendon involvement is extensive, and the entire tendon must be removed, an autologous flap graft might not be adequate to allow a return to function. We report a case of a 52-year-old female patient who developed bilateral tumors of the Achilles tendon, with a 10-year duration. By the time, she sought medical help, both Achilles tendons required removal. We chose to use Achilles tendon allografts to replace the Achilles tendons. Postoperatively, the patient did well. The allograft shortened the recovery time, and the patient regained full ankle range of motion.

Concepts: Human anatomy, Tendon, Achilles tendon, Tendons, Achilles' heel, Achilles tendon rupture


PURPOSE: Ideally, a classification should have some prognostic value, and should therefore include precise information upon extent and location of the Achilles tendon disorders. We propose a new imaging and anatomical system to classify Achilles tendon disorders at imaging using US and MRI. APPROACH: We consider the non-insertional region as the tendon mid-portion, and distinguish the insertional component into a pre-insertion site, located about two centimetres above the calcaneum, and a calcaneal insertion, where the tendon is attached to the bone. On sagittal scans, we introduced a new classification which considers two main portions: “musculotendinous” and “insertional”. In the context of the muscolotendinous portion, it is possible to find muscle fibres proximally, and the free tendon distally. This latter is made up of proximal, middle and distal portions. We also propose a 5 grade Doppler classification system to quantify blood flow, in which Grades I and II are respectively characterised by the presence of one and two vessels within the tendon; in Grades III, IV and V, the neovascularisation respectively involves less than 50 %, from 50 to 90 %, and more than 90 % of the tendon tissue. These proposed systems will require validation and possible modification to be applied to different tendons.

Concepts: Muscle, Anatomy, Anatomical terms of location, Tendon, Achilles tendon, Calcaneus


The Achilles tendon has a high incidence of rupture, and the healing process leads to a disorganized extracellular matrix (ECM) with a high rate of injury recurrence. To evaluate the effects of different conditions of low-level laser (LLL) application on partially tenotomized tendons, adult male rats were divided into the following groups: G1, intact; G2, injured; G3, injured + LLL therapy (LLLT; 4 J/cm(2) continuous); G4, injured + LLLT (4 J/cm(2), 20 Hz); G5, injured; G6, injured + LLLT (4 J/cm(2) continuous); and G7, injured + LLLT (4 J/cm(2), 20 Hz until the 7th day and 2 kHz from 8 to 14 days). G2, G3, and G4 were euthanized 8 days after injury, and G5, G6, and G7 were euthanized on the 15th day. The quantification of hydroxyproline (HOPro) and non-collagenous protein (NCP), zymography for matrix metalloproteinase (MMP)-2 and MMP-9, and Western blotting (WB) for collagen types I and III were performed. HOPro levels showed a significant decrease in all groups (except G7) when compared with G1. The NCP level increased in all transected groups. WB for collagen type I showed an increase in G4 and G7. For collagen type III, G4 presented a higher value than G2. Zymography for MMP-2 indicated high values in G4 and G7. MMP-9 increased in both treatment groups euthanized at 8 days, especially in G4. Our results indicate that the pulsed LLLT improved the remodeling of the ECM during the healing process in tendons through activation of MMP-2 and stimulation of collagen synthesis.

Concepts: Collagen, Extracellular matrix, Cartilage, Matrix metalloproteinase, Tendon, Achilles tendon, Tendons, Type-I collagen


Children demonstrate lower force production capacities compared to adults, whichhas often been attributed to ‘neuromuscular immaturity’. However, tendon stiffness, which influences both the electro-mechanical delay (EMD) and rate of force development (RFD) in adults, is lower in children and may influence rapid force production. PURPOSE: The aims of this study were to: 1) document EMD and RFD variation as a function of age, 2) determine the relationships between tendon stiffness and parameters relating to rapid force production in children and adults, and 3) estimate the relative neural and mechanical contributions to age-related changes in force production by examining the effects of tendon stiffness and muscle activation rate (rate of EMG increase; REI) on RFD. METHODS: Achilles tendon stiffness, EMD, RFD and REI were measured duringplantar flexion contractions in 47prepubertal children (5-12 yrs) and 19 adults. Relationships were determined between: 1) stiffness and EMD, 2) stiffness and RFD, and 3) REI and RFD. The relative contributions of age, stiffness and REI on RFD were determined using a multiple regression analysis. Age-related differences in tendon stiffness, EMD, RFD and REI were also examined according to chronological age (5-6, 7-8 and 9-10 years) and compared to adults. RESULTS: Increases in tendon stiffness with age were negatively correlated with EMD (r<-0.83). Stiffness and REI could account for up to 35% and 30% of RFD variability in children, respectively, which increased to 58% when these variables were combined. CONCLUSIONS: Both neural and mechanical factors influence rapid force production in prepubertal children. Children's longer EMD and slower RFD indicate a less effective development and transfer of muscular forces, which may have implications for complex movement performance.

Concepts: Regression analysis, Linear regression, Muscle, Childhood, Classical mechanics, Variable, Tendon, Achilles tendon


Tendinopathy is a widespread and disabling condition characterized by collagen fiber disruption and accumulation of a glycosaminoglycan-rich chondroid matrix. Recent clinical reports have illustrated the potential of mechanical loading (exercise) therapies to successfully treat chronic tendinopathies. We have developed a new murine tendinopathy model which requires a single injection of TGF-β1 into the Achilles tendon midsubstance followed by normal cage activity for 2 weeks. At this time, tendon maximum stress showed a dramatic (66%) reduction relative to that of normal controls and this persisted at four weeks. Loss of material properties was accompanied by abundant chondroid cells within the tendon (closely resembling the changes observed in human samples obtained intra-operatively) and increased expression of Acan, Col1a1, Col2a1, Col3a1, Fn1 and Mmp3. Mice subjected to two weeks of daily treadmill exercise following TGF-β1 injection showed a similar reduction in tendon material properties as the caged group. However, in mice subjected to 4 weeks of treadmill exercise, tendon maximum stress values were similar to those of naive controls. Tendons from the mice exercised for 4 weeks showed essentially no chondroid cells and the expression of Acan, Col1a1, Col2a1, Col3a1, and Mmp3 was significantly reduced relative to the 4-week cage group. This technically simple murine tendinopathy model is highly amenable to detailed mechanistic and translational studies of the biomechanical and cell biological pathways, that could be targeted to enhance healing of tendinopathy.

Concepts: Gene, Collagen, Extracellular matrix, Muscle, Tendon, Achilles tendon, Tendinopathy, Tendons