Functional anatomy of the Achilles tendon

Anatomy of the Achilles tendon-A pictorial review

The Achilles tendon (AT) is the strongest tendon of the human body. The knowledge of AT anatomy is a basic prerequisite for the successful treatment of acute and chronic lesions. The structure of the AT results from a complicated fusion of three parts: the tendons of the medial and lateral gastrocnemius and the soleus muscles. From proximal to distal, the tendon fibers twist in a long spiral into a roughly 90° internal rotation. The tendon is narrowest approximately 5-7 cm above its calcaneal insertion and from there it expands again. The topography of the footprints of the individual AT components reflects the tendon origins. The anterior (deep) AT fibers insert into the middle third of the posterior aspect of the calcaneal tuberosity, the posterior (superficial) fibers pass over the calcaneal tuberosity and fuse with the plantar aponeurosis. A deep calcaneal bursa is interposed between the calcaneal tuberosity and the AT anterior surface. The AT has no synovial sheath but is covered along its entire length with a sliding connective tissue, the paratenon which is, however, absent on its anterior surface. The AT is supplied by the posterior tibial artery (PTA) and the peroneal artery (PA). Motor innervation of the triceps surae muscle is provided by fibers of the tibial nerve which also gives off sensitive fibers for the AT. Sensitive innervation is also provided via the sural nerve. The sural nerve crosses the AT approximately 11 cm proximal to the calcaneal tuberosity. The forces acting on the AT during exercise may be up to 12 times the body weight. Physiological stretching of AT collagen fibers ranges between 2% and 4% of its length. Stretching of the tendon over 4% results in microscopic failure and stretching beyond 8% in macroscopic failure.

Females present larger deficit in heel-rise height at 3 months following an Achilles tendon rupture compared with males

PURPOSE

There is a lack of knowledge concerning differences between females and males in the early stages after an acute Achilles tendon rupture. This article aims to explore the different factors affecting early function after an Achilles tendon rupture with a validated test battery that includes functional tests, clinical measurements and patient-reported outcome at a 3-month follow-up analysis of a larger prospective study.

METHODS

This study was part of the DUSTAR-study (Diagnostic UltraSonography for the choice of Treatment of acute Achilles tendon Rupture) where the main aim was to evaluate if an acute ultrasonography could determine which patients, with an Achilles tendon rupture, should be treated surgically or nonsurgically. At the 3-month follow-up, the results between males and females were compared.

RESULTS

One hundred and twenty-seven patients were included at the 3-month follow-up; of these, 102 (80%) were males and 25 (20%) were females. Amongst the females, 11 (44%) were able to perform a single leg heel-rise compared to 48 (47%) of the males; however, the difference was not statistically significant. There was no difference between the sexes in the frequency of completing a single-leg heel-rise at 3 months after injury; however, there were statistically significant differences between the groups when comparing Limb Symmetry Index (LSI) of heel-rise height and heel-rise work. The females had a median heel-rise height LSI/median heel-rise work LSI of 45%/14% compared to males who reached a level of 57%/23% (p = 0.006/p = 0.010). At the 3-month follow-up, the median (range) Achilles tendon Total Rupture Score (ATRS) reported by females was 28.5 (8-51), which had a nonsignificant difference compared to males who reported a median (range) ATRS of 30 (1-86).

CONCLUSION

The risk of reduced heel-rise height and worse heel-rise work 3 months after an acute Achilles tendon rupture increases by being a female. Through this knowledge, we highlighted the importance of an individualised treatment for acute Achilles tendon ruptures with better outcome for both males and females.

LEVEL OF EVIDENCE

Level II.

Does lower extremity stiffness influence change of direction speed in badminton athletes after dynamic loaded warm-up?

This study investigated whether lower extremity stiffness plays a role in the enhancement of change of direction speed (CODS) and the duration of this enhancement after dynamic loaded warm-up (DLWU). Fifteen badminton athletes underwent DLWU, and CODS, individual muscle and tendon stiffness, and vertical stiffness were measured before DLWU and 6, 12, and 18 min after DLWU. The data were analyzed using ANOVA and covariance analysis. Significant improvements in CODS were found at 6, 12, and 18 min post-DLWU compared to pre-DLWU (p < 0.05). The Achilles tendon stiffness of the dominant leg increased at 6 min (p = 0.039) and 18 min (p = 0.024) post-DLWU compared to pre-DLWU. Achilles tendon stiffness of the dominant leg had a significant effect on improving CODS (p > 0.05). CODS improvement lasted up to 18 min after DLWU in badminton athletes, potentially related to increased Achilles tendon stiffness of the dominant leg.

Probing nanoscale structural response of collagen fibril in human Achilles tendon during loading using in situ SAXS

The specific viscoelastic mechanical properties of the human Achilles tendon are strongly dependent on the structural characteristics of collagen. Although research on the deformation mechanisms of the Achilles tendon in various animals is extensive, understanding of these mechanisms in the human Achilles tendon remains largely empirical and macroscopic. In this work, the evolution of D-space, orientation, and average length of voids between fibers are investigated during the stretching using SAXS techniques. Initially, the void length increases marginally, while the misorientation breadth decreased rapidly as the D-space steadily increased. In the second region, D-space and the void length increase sharply under rising stress, even though misorientation width decreased. During the third region, the increases in void length and D-space decelerate, but the misorientation width widens, suggesting the onset of irreversible microscopic fibril failure in the Achilles tendon. In the final region, the fibers undergo macroscopic failure, with D-space and void length returning to their initial states. The macroscopic alterations are elucidated by the nanoscale structural responses, providing a fundamental understanding of the mechanisms driving the complex biomechanics, tissue structural organization, and Achilles tendon regeneration.

Do the fasciae of the soleus have a role in plantar fasciitis?

Plantar fasciitis is a chronic, self-limiting, and painful disabling condition affecting the inferomedial aspect of the heel, usually extending toward the metatarsophalangeal joints. There is compelling evidence for a strong correlation between Achilles tendon (AT) loading and plantar aponeurosis (PA) tension. In line with this, tightness of the AT is found in almost 80% of patients affected by plantar fasciitis. A positive correlation has also been reported between gastrocnemius-soleus tightness and heel pain severity in this condition. Despite its high prevalence, the exact etiology and pathological mechanisms underlying plantar heel pain remain unclear. Therefore, the aim of the present paper is to discuss the anatomical and biomechanical substrates of plantar fasciitis with special emphasis on the emerging, though largely neglected, fascial system. In particular, the relationship between the fascia, triceps surae muscle, AT, and PA will be analyzed. We then proceed to discuss how structural and biomechanical alterations of the muscle-tendon-fascia complex due to muscle overuse or injury can create the conditions for the onset of PA pathology. A deeper knowledge of the possible molecular mechanisms underpinning changes in the mechanical properties of the fascial system in response to altered loading and/or muscle contraction could help healthcare professionals and clinicians refine nonoperative treatment strategies and rehabilitation protocols for plantar fasciitis.

The Use of Extracellular Vesicles in Achilles Tendon Repair: A Systematic Review

Achilles tendon (AT) pathologies are common musculoskeletal conditions that can significantly impair function. Despite various traditional treatments, recovery is often slow and may not restore full functionality. The use of extracellular vesicles (EVs) has emerged as a promising therapeutic option due to their role in cell signaling and tissue regeneration. This systematic review aims to consolidate current in vivo animal study findings on the therapeutic effects of EVs on AT injuries. An extensive literature search was conducted using the PubMed, Scopus, and Embase databases for in vivo animal studies examining the effects of EVs on AT pathologies. The extracted variables included but were not limited to the study design, type of EVs used, administration methods, efficacy of treatment, and proposed therapeutic mechanisms. After screening, 18 studies comprising 800 subjects were included. All but one study reported that EVs augmented wound healing processes in the AT. The most proposed mechanisms through which this occurred were gene regulation of the extracellular matrix (ECM), the enhancement of macrophage polarization, and the delivery of therapeutic microRNAs to the injury site. Further research is warranted to not only explore the therapeutic potential of EVs in the context of AT pathologies, but also to establish protocols for their clinical application.

Does Radial Extracorporeal Shockwave Therapy Applied to the Achilles Tendon Influence Ankle Functionality?

This study aimed to determine the effectiveness of radial extracorporeal shockwave therapy (rESWT) in enhancing ankle function in patients with Achilles tendon injuries. The choice of rESWT was based on previous success in the treatment of musculoskeletal conditions. The study involved an intervention group that received rESWT, and a control group that received sham therapy. The results revealed that rESWT led to significant improvements in single-leg vertical jump (d = 0.55, p < 0.05), indicating enhanced power generation and ankle functionality that were not observed in the control group. Additionally, the therapy resulted in increased ankle mobility, as observed by improvements in plantar flexion and heel-rise tests. Interestingly, these functional gains were not accompanied by changes in the Achilles tendon stiffness, suggesting that the benefits of rESWT may be more functional than structural. This study highlights rESWT as a promising tool for rehabilitation, particularly following Achilles tendon injuries. The study concluded that, although rESWT appears to improve certain aspects of ankle function, further studies with a larger and more diverse population over a longer period are necessary to confirm these findings and establish comprehensive treatment protocols.

The Heel Complex: Anatomy, Imaging, Pathologic Conditions, and Treatment

The differential diagnosis for heel pain is broad but primarily involves abnormalities of the Achilles tendon, calcaneus, and plantar fascia. Achilles tendon disorders include tendinosis, tendinitis, and partial or complete tears. Tendinosis refers to tendon degeneration, while tendinitis is inflammation after acute overload. Untreated tendinosis can progress to partial or complete tears. Tendon disorders can be accompanied by paratenonitis or inflammation of the loose sheath enclosing the tendon. Initial management involves rehabilitation and image-guided procedures. Operative management is reserved for tendon tears and includes direct repair, tendon transfer, and graft reconstruction. The calcaneus is the most commonly fractured tarsal bone. The majority of fractures are intra-articular; extra-articular fractures, stress or insufficiency fractures, medial process avulsion, and neuropathic avulsion can also occur. Posterosuperior calcaneal exostosis or Haglund deformity, retrocalcaneal bursitis, and insertional Achilles tendinosis form the characteristic triad of Haglund syndrome. It is initially managed with orthotics and physiotherapy. Operative management aims to correct osseous or soft-tissue derangements. The plantar fascia is a strong fibrous tissue that invests the sole of the foot and contributes to midfoot stability. Inflammation or plantar fasciitis is the most common cause of heel pain and can be related to overuse or mechanical causes. Acute rupture is less common but can occur in preexisting plantar fasciitis. Conservative treatment includes footwear modification, calf stretches, and percutaneous procedures. The main operative treatment is plantar fasciotomy. Plantar fibromatosis is a benign fibroblastic proliferation within the fascia that can be locally aggressive and is prone to recurrence. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Sex differences in biomechanical properties of the Achilles tendon may predispose men to higher risk of injury: A systematic review

IMPORTANCE

Men have a higher risk of Achilles tendon (AT) injury, and the impact of morphological and mechanical sex differences may play a role.

AIM

The aim of this study is to systematically review the literature to determine whether there are sex-specific differences in AT morphological and mechanical properties and analyze how these differences may impact AT injury in both men and women.

EVIDENCE REVIEW

A systematic literature search of articles published between 2001 and 2021, in the MEDLINE, EMBASE, and Cochrane databases was performed during May 2022 according to PRISMA. The primary outcome measures included sex-related differences in the mechanical and morphological properties of the Achilles tendon. Secondary outcomes included impact of sex on Achilles tendon properties and adaptation.

FINDINGS

Nineteen studies with a total of 1,143 participants (613 men and 530 women) were included in this systematic review. Men had increased measurements when compared with women in the following: AT length, thickness, cross-sectional area (CSA), stiffness, peak force, loading rate, and voluntary muscle contraction. Women had an increase in CSA deformation, strain, and compliance.

CONCLUSIONS AND RELEVANCE

Our study demonstrates that men have an increased AT length, thickness, and CSA, indicating that men may be subjected biomechanically to higher loads in their day-to-day activities. In addition, men have lower deformation and compliance properties, along with increased AT stiffness, reducing their capacity to adapt during loading, potentially increasing their risk of injury.

LEVEL OF EVIDENCE

IV.

Effect of platelet-rich plasma in Achilles tendon allograft in rabbits

BACKGROUND

Achilles tendon is composed of dense connective tissue and is one of the largest tendons in the body. In veterinary medicine, acute ruptures are associated with impact injury or sharp trauma. Healing of the ruptured tendon is challenging because of poor blood and nerve supply as well as the residual cell population. Platelet-rich plasma (PRP) contains numerous bioactive agents and growth factors and has been utilized to promote healing in bone, soft tissue, and tendons.

OBJECTIVE

The purpose of this study was to evaluate the healing effect of PRP injected into the surrounding fascia of the Achilles tendon after allograft in rabbits.

METHODS

Donor rabbits (n = 8) were anesthetized and 16 lateral gastrocnemius tendons were fully transected bilaterally. Transected tendons were decellularized and stored at -80°C prior to allograft. The allograft was placed on the partially transected medial gastrocnemius tendon in the left hindlimb of 16 rabbits. The allograft PRP group (n = 8) had 0.3 mL of PRP administered in the tendon and the allograft control group (n = 8) did not receive any treatment. After 8 weeks, rabbits were euthanatized and allograft tendons were transected for macroscopic, biomechanical, and histological assessment.

RESULTS

The allograft PRP group exhibited superior macroscopic assessment scores, greater tensile strength, and a histologically enhanced healing process compared to those in the allograft control group.

CONCLUSIONS

Our results suggest administration of PRP on an allograft tendon has a positive effect on the healing process in a ruptured Achilles tendon.

Tendon Elongation and Function After Delayed or Standard Loading of Surgically Repaired Achilles Tendon Ruptures: A Randomized Controlled Trial

BACKGROUND

Achilles tendon ruptures often result in long-term functional deficits despite accelerated (standard) rehabilitation.

PURPOSE/HYPOTHESIS

The purpose of this study was to investigate if delayed loading would influence functional, clinical, and structural outcomes of the muscles and tendon 1 year after a surgical repair. It was hypothesized that delaying the loading would reduce the heel-rise height deficit 1 year after Achilles tendon rupture.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

In total, 48 patients with a surgically repaired Achilles tendon rupture were randomized to 2 groups: the standard group received the currently accepted rehabilitation, and the delayed group received the same rehabilitation except that initial loading was delayed by 6 weeks. The primary outcome was the heel-rise height difference between the injured and uninjured sides at 1 year. The secondary outcomes were (1) tendon length measured with magnetic resonance imaging, (2) muscle fascicle length and pennation angle of the gastrocnemius medialis muscle, (3) Doppler activity measured with ultrasonography, (4) Achilles tendon Total Rupture Score (ATRS), and (5) isometric muscle strength.

RESULTS

The mean heel-rise height deficits for the standard and delayed groups were -2.2 cm and -2.1 cm, respectively (P = .719). The soleus part of the tendon was already elongated 1 week after surgery in both groups without a between-group difference (side-to-side difference: standard, 16.3 mm; delayed, 17.5 mm; P = .997) and did not change over 52 weeks. The gastrocnemius tendon length was unchanged at 1 week but elongated over time without a between-group difference (side-to-side difference at 52 weeks: standard, 10.5 mm; delayed, 13.0 mm; P = .899). The delayed group had less Doppler activity at 12 weeks (P = .006) and a better ATRS (standard, 60 points; delayed, 72 points; P = .032) at 52 weeks.

CONCLUSION

Delayed loading was not superior to standard loading in reducing the heel-rise height difference at 1 year. The data indirectly suggested reduced inflammation in the initial months and a better patient-reported outcome at 1 year in the delayed group. The soleus part of the tendon was already markedly elongated (35%) 1 week after surgery, while the length of the gastrocnemius tendon was unchanged at 1 week but was 6% elongated at 1 year. Together, these data indirectly suggest that the delayed group fared better, although this finding needs to be confirmed in future investigations.

REGISTRATION

NCT04263493 (ClinicalTrials.gov identifier).

From Trauma to Recovery: A Comprehensive Management of Achilles Tendon Injury in a Young Female

The incidence of the Achilles tendon getting injured has recently increased by 18 in 100,000. Compared to non-surgical treatment, surgical results are superior. The Achilles tendon repaired with surgery has a re-rupture rate of only 5%, while if treated non-operatively, it has a rupture rate of 40%. This case report analyses the traumatic Achilles tendon rupture and subsequent surgical repair in a young woman. In this case study, a 19-year-old female patient's severe Achilles tendon injury was successfully managed by integrating prompt surgical intervention and structure. After rehabilitation, the patient's range of motion (ROM), muscle strength, and gait patterns all significantly improved. Scores on the Lower Extremity Functional Scale (LEFS) and the Dynamic Gait Index (DGI) both significantly improved. This case study reiterates the significance of an integrated healthcare strategy for Achilles tendon injuries. An immediate surgical procedure followed by a specific rehabilitation programme accelerates healing and the return to optimal function. The results emphasize the critical role of physical therapy in assisting surgical interventions and underline the necessity of comprehensive patient care in the treatment of complex orthopaedic problems.

Biomechanical comparison of shoelace suture technique for repairing calcaneal tendon

BACKGROUND

The biomechanical assessment of tendon repair is essential for the evaluation of different tendon suturing techniques. The shoelace suture technique with absorbable Vicryl® is a modified technique of Achilles tendon repair that may have biomechanical advantages depending on the number of threads used and the direction of the suture.

PURPOSE

To evaluate the creep under constant pre-load, the stiffness, the maximum strength, and the failure mode for three different configurations of the shoelace suture in a bovine tendon biomechanical model.

STUDY DESIGN

Controlled Laboratory Study.

METHODS

36 bovine Achilles tendon specimens were acquired and divided into three test groups of 12 Achilles tendons each. A model of the calcaneal tendon rupture was created through a transverse cut with a scalpel, performed 5 centimeters proximal to the calcaneal bone insertion. Group 1 was repaired using the simple shoelace technique with just one suture. Group 2 was repaired using the shoelace technique with three sutures individually sutured from distal to proximal at the site of rupture. Group 3 was repaired using the shoelace technique with three sutures individually sutured from proximal to distal at the site of rupture.

RESULTS

System creep after constant pre-load was 5.9 ± 2.5 mm, 3.0 ± 0.4 mm and 2.9 ± 0.4 mm for groups 1, 2 and 3, respectively. The system's stiffness was 23.2 ± 2.8 N/mm, 30.3 ± 1.1 N/mm and 29.8 ± 2.3 N/mm for groups 1, 2 and 3, respectively. In the final load-to-failure test, the ultimate load force (ULF) was 158.2 ± 27.5 N, 346.5 ± 47.6 N and 358.1 ± 41.6 N for groups 1, 2 and 3, respectively. There was statistical significance in the comparative tests between groups 1-2 and 1-3 in terms of means of creep, system stiffness and maximum system strength. No statistically significant difference was found between groups 2 and 3 when analyzing creep, system stiffness and ULF. Suture breakage was the prevalent mode of failure for all tested groups.

CONCLUSION

The shoelace with three sutures significantly reduced creep in the preloading phase and increased the stiffness and ultimate load force. The biomechanical results demonstrate better overall mechanical performance of the technique than the simple shoelace technique. The better mechanical performance indicates that the shoelace with three sutures could result in early postoperative rehabilitation.

CLINICAL RELEVANCE

This study indicates that the shoelace suture technique with three sutures is biomechanically strong and stiff, being a possible therapeutic option to be used.

Surgical treatment of chronic achilles tendon rupture: An anatomical consideration of various autograft options

Background

Acute Achilles tendon rupture is a common injury and when missed leads to the development of a chronic Achilles tendon rupture. Studies suggest surgical treatment (either repair or reconstruction) for most patients with a chronic Achilles rupture due to the functional deficit caused by the lack of an intact Achilles tendon. Numerous autograft options such as the flexor hallucis longus, hamstrings, peroneal and quadriceps tendon have been used to reconstruct the Achilles tendon, either as a tendon transfer or as an interposition graft. The choice of autograft used usually depends on the size of the defect left after debridement of the Achilles tendon edges, but is often dictated by surgeon preference and tissue availability. Currently, there is no consensus as to the best autograft option.

Aims and methodology

The aim of this study was to evaluate the various autograft options used to reconstruct the Achilles tendon, and the advantages and disadvantages of using each tendon, focussing specifically on the harvesting technique, anatomical and biomechanical properties. This was done by reviewing the current published literature, supplemented by carrying out anatomical dissection in the cadaveric lab.

Results

The flexor hallucis longus is synergistically related to the Achilles tendon and biomechanically strong, however harvesting can result in weakness in big toe flexion. The peroneus brevis whilst being biomechanically strong is a much shorter tendon compared to the other autograft options. Similarly, the quadriceps tendon is also a strong tendon option, but may not be appropriate for larger chronic Achilles tendon rupture gaps. The semitendinosus tendon can be tripled/quadrupled to resemble the Achilles tendon, but is associated with higher risks of patient morbidity when harvesting the tendon.

Conclusion

Treatment of chronic Achilles tendon ruptures remains a challenge. Each autograft option has its own unique advantages and disadvantages which should be considered on a case-specific basis. Further work is required to analyse the biomechanical properties of the autograft options to determine if one option is superior.

Growth factors in the treatment of Achilles tendon injury

Achilles tendon (AT) injury is one of the most common tendon injuries, especially in athletes, the elderly, and working-age people. In AT injury, the biomechanical properties of the tendon are severely affected, leading to abnormal function. In recent years, many efforts have been underway to develop effective treatments for AT injuries to enable patients to return to sports faster. For instance, several new techniques for tissue-engineered biological augmentation for tendon healing, growth factors (GFs), gene therapy, and mesenchymal stem cells were introduced. Increasing evidence has suggested that GFs can reduce inflammation, promote extracellular matrix production, and accelerate AT repair. In this review, we highlighted some recent investigations regarding the role of GFs, such as transforming GF-β(TGF-β), bone morphogenetic proteins (BMP), fibroblast GF (FGF), vascular endothelial GF (VEGF), platelet-derived GF (PDGF), and insulin-like GF (IGF), in tendon healing. In addition, we summarized the clinical trials and animal experiments on the efficacy of GFs in AT repair. We also highlighted the advantages and disadvantages of the different isoforms of TGF-β and BMPs, including GFs combined with stem cells, scaffolds, or other GFs. The strategies discussed in this review are currently in the early stages of development. It is noteworthy that although these emerging technologies may potentially develop into substantial clinical treatment options for AT injury, definitive conclusions on the use of these techniques for routine management of tendon ailments could not be drawn due to the lack of data.

Wearable High-Density MXene-Bioelectronics for Neuromuscular Diagnostics, Rehabilitation, and Assistive Technologies

High-density surface electromyography (HDsEMG) allows noninvasive muscle monitoring and disease diagnosis. Clinical translation of current HDsEMG technologies is hampered by cost, limited scalability, low usability, and minimal spatial coverage. Here, this study presents, validates, and demonstrates the broad clinical applicability of dry wearable MXene HDsEMG arrays (MXtrodes) fabricated from safe and scalable liquid-phase processing of Ti3 C2 Tx . The fabrication scheme allows easy customization of array geometry to match subject anatomy, while the gel-free and minimal skin preparation enhance usability and comfort. The low impedance and high conductivity of the MXtrode arrays allow detection of the activity of large muscle groups at higher quality and spatial resolution than state-of-the-art wireless electromyography  sensors, and in realistic clinical scenarios. To demonstrate the clinical applicability of MXtrodes in the context of neuromuscular diagnostics and rehabilitation, simultaneous HDsEMG and biomechanical mapping of muscle groups across the whole calf during various tasks, ranging from controlled contractions to walking is shown. Finally, the integration of HDsEMG acquired with MXtrodes with a machine learning pipeline and the accurate prediction of the phases of human gait are shown. The results underscore the advantages and translatability of MXene-based wearable bioelectronics for studying neuromuscular function and disease, as well as for precision rehabilitation.

Effectiveness of platelet-rich plasma in the treatment of Achilles tendon disease

BACKGROUND

The effectiveness of Platelet-Rich Plasma (PRP) in the treatment of patients with Achilles tendon rupture (ATR) and Achilles tendinopathy (AT) has been controversial.

AIM

To assess PRP injections’ effectiveness in treating ATR and AT.

METHODS

A comprehensive review of relevant literature was conducted utilizing multiple databases such as Cochrane Library, PubMed, Web of Science, Chinese Science and Technology Journal, EMBASE, and China Biomedical CD-ROM. The present investigation integrated randomized controlled trials that assessed the effectiveness of platelet-rich plasma injections in managing individuals with Achilles tendon rupture and tendinopathy. The eligibility criteria for the trials encompassed publications that were published within the timeframe of January 1, 1966 to December 2022. The statistical analysis was performed utilizing the Review Manager 5.4.1, the visual analogue scale (VAS), Victorian Institute Ankle Function Scale (VISA-A), and Achilles Tendon Thickness were used to assess outcomes.

RESULTS

This meta-analysis included 13 randomized controlled trials, 8 of which were randomized controlled trials of PRP for AT and 5 of which were randomized controlled trials of PRP for ATR. PRP for AT at 6 wk [weighted mean difference (WMD) = 1.92, 95%CI: -0.54 to 4.38, I² = 34%], at 3 mo [WMD = 0.20, 95%CI: -2.65 to 3.05, I² = 60%], and 6 mo [WMD = 2.75, 95%CI: -2.76 to 8.26, I² = 87%) after which there was no significant difference in VISA-A scores between the PRP and control groups. There was no significant difference in VAS scores between the PRP group and the control group after 6 wk [WMD = 6.75, 95%CI: -6.12 to 19.62, I² = 69%] and 6 mo [WMD = 10.46, 95%CI: -2.44 to 23.37, I² = 69%] of treatment, and at mid-treatment at 3 mo [WMD = 11.30, 95%CI: 7.33 to 15.27, I² = 0%] after mid-treatment, the PRP group demonstrated better outcomes than the control group. Post-treatment patient satisfaction [WMD = 1.07, 95%CI: 0.84 to 1.35, I² = 0%], Achilles tendon thickness [WMD = 0.34, 95%CI: -0.04 to 0.71, I² = 61%] and return to sport [WMD = 1.11, 95%CI: 0.87 to 1.42, I² = 0%] were not significantly different between the PRP and control groups. The study did not find any statistically significant distinction between the groups that received PRP treatment and those that did not, regarding the Victorian Institute of Sport Assessment - Achilles scores at 3 mo [WMD = -1.49, 95%CI: -5.24 to 2.25, I² = 0%], 6 mo [WMD = -0.24, 95%CI: -3.80 to 3.32, I² = 0%], and 12 mo [WMD = -2.02, 95%CI: -5.34 to 1.29, I² = 87%] for ATR patients. Additionally, no significant difference was observed between the PRP and the control groups in improving Heel lift height respectively at 6 mo [WMD = -3.96, 95%CI: -8.61 to 0.69, I² = 0%] and 12 mo [WMD = -1.66, 95%CI: -11.15 to 7.83, I² = 0%] for ATR patients. There was no significant difference in calf circumference between the PRP group and the control group after 6 mo [WMD = 1.01, 95%CI: -0.78 to 2.80, I² = 54%] and 12 mo [WMD = -0.55, 95%CI: -2.2 to 1.09, I² = 0%] of treatment. There was no significant difference in ankle mobility between the PRP and control groups at 6 mo of treatment [WMD = -0.38, 95%CI: -2.34 to 1.58, I² = 82%] and after 12 mo of treatment [WMD = -0.98, 95%CI: -1.41 to -0.56, I² = 10%] there was a significant improvement in ankle mobility between the PRP and control groups. There was no significant difference in the rate of return to exercise after treatment [WMD = 1.20, 95%CI: 0.77 to 1.87, I² = 0%] and the rate of adverse events [WMD = 0.85, 95%CI: 0.50 to 1.45, I² = 0%] between the PRP group and the control group.

CONCLUSION

The use of PRP for AT improved the patient’s immediate VAS scores but not VISA-A scores, changes in Achilles tendon thickness, patient satisfaction, or return to sport. Treatment of ATR with PRP injections alone improved long-term ankle mobility but had no significant effect on VISA-A scores, single heel lift height, calf circumference or return to sport. Additional research employing more extensive sampling sizes, more strict experimental methods, and standard methodologies may be necessary to yield more dependable and precise findings.

The tendon unit: biochemical, biomechanical, hormonal influences

The current literature has mainly focused on the biology of tendons and on the characterization of the biological properties of tenocytes and tenoblasts. It is still not understood how these cells can work together in homeostatic equilibrium. We put forward the concept of the "tendon unit" as a morpho-functional unit that can be influenced by a variety of external stimuli such as mechanical stimuli, hormonal influence, or pathological states. We describe how this unit can modify itself to respond to such stimuli. We evidence the capability of the tendon unit of healing itself through the production of collagen following different mechanical stimuli and hypothesize that restoration of the homeostatic balance of the tendon unit should be a therapeutic target.

Model of calf muscle tear during a simulated eccentric contraction, comparison between ex-vivo experiments and discrete element model

The tearing of the muscle-tendon complex (MTC) is one of the common sports-related injuries. A better understanding of the mechanisms of rupture and its location could help clinicians improve the way they manage the rehabilitation period of patients. A new numerical approach using the discrete element method (DEM) may be an appropriate approach, as it considers the architecture and the complex behavior of the MTC. The aims of this study were therefore: first, to model and investigate the mechanical elongation response of the MTC until rupture with muscular activation. Secondly, to compare results with experimental data, ex vivo tensile tests until rupture were done on human cadavers {triceps surae muscle + Achilles tendon}. Force/displacement curves and patterns of rupture were analyzed. A numerical model of the MTC was completed in DEM. In both numerical and experimental data, rupture appeared at the myotendinous junction (MTJ). Moreover, force/displacement curves and global rupture strain were in agreement between both studies. The order of magnitude of rupture force was close between numerical (858 N for passive rupture and 996 N-1032 N for rupture with muscular activation) and experimental tests (622 N ± 273 N) as for the displacement of the beginning of rupture (numerical: 28-29 mm, experimental: 31.9 mm ± 3.6 mm). These differences could be explained by choices of DEM model and mechanical properties of MTC's components or their rupture strain values. Here we show that he MTC was broken by fibers' delamination at the distal MTJ and by tendon disinsertion at the proximal MTJ in agreement with experimental data and literature.

Avulsion fracture of the calcaneal tuberosity treated with novel surgical technique using the combination of the side-locking loop suture technique and ring pins: a case report

A 78-year-old woman complained of right heel pain when tripping during walking. Radiographs revealed an avulsion fracture of the calcaneal tuberosity. Because the bone fragment was displaced, a novel osteosynthesis using the side-locking loop suture (SLLS) and ring pins was performed. At 3 months after the surgery, non-contrast computed tomography revealed complete bone union. At 2 years postoperatively, she had no symptoms and dysfunctions. Here, we describe a case of avulsion fracture of the calcaneal tuberosity in a 79-year-old female who treated with a novel surgical technique using combination the SLLS technique and ring pins. This surgical technique may be a useful option in the treatment for avulsion fractures of the calcaneal tuberosity.

Local displacement within the Achilles tendon induced by electrical stimulation of the single gastrocnemius muscles

BACKGROUND

The Achilles tendon consists of three subtendons, but their functional meaning is still unknown. There are several approaches for the examination in-vivo using sonographic imaging, however, there is no approach for in-vivo examination with respect to the single subtendons of the m. triceps surae. The study's aim was to reveal the single subtendons of the m. triceps surae.

METHODS

The Achilles tendon of 17 subjects was analysed. The muscles (m. gastrocnemius lateralis and medialis) were stimulated separately using neuromuscular electrical stimulation. The intensity of muscle contraction was controlled using electromyographic data. Sonographic videos of the Achilles tendon were recorded during muscle contraction. A speckle tracking algorithm was used to analyse the moving areas within the Achilles tendon during the initial phase of contraction.

FINDINGS

The muscles were activated at 10-20% of the maximal M-wave. Isolated contraction of m. gastrocnemius lateralis led to local displacement in the lateral part of the Achilles tendon's cross-section whereas isolated contraction of m. gastrocnemius medialis led to displacement in the medial part and to a larger size of the area where initial displacement took place (m. gastrocnemius lateralis to medialis approximately 1:2).

INTERPRETATION

The results demonstrate that isolated contractions of m. gastrocnemius lateralis and medialis lead to individual displacements which significantly differ. The differences in position and size of the area of the local displacement indicate an independent individual function. Unlike other studies generally investigating the AT in-vivo using muscle stimulation and ultrasonic imaging, this study investigated the AT's cross-section which had never been investigated before.

A combination of omega-3 and exercise reduces experimental Achilles tendinopathy induced with a type-1 collagenase in rats

This study aimed to evaluate the effectiveness of omega-3 supplementation with exercise in a collagenase-induced Achilles tendinopathy (AT) rat model. Experimental groups (healthy control (HC), AT, exercise (Ex), omega-3 (W), and Ex+W) were randomly allocated. After a week of adaptation, oral omega-3 was initiated for 8 weeks (5 days/week). The exercise groups performed treadmill running for 30 min/day (5 days/week, 20 m/min, 8 weeks) following one week of adaptation (10 m/min, 15 min/day). Matrix metalloproteinase-13 (MMP-13), interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and total antioxidant-oxidant status (TAS) levels were determined in serum samples. Tendon samples were obtained for biomechanical, histopathological, and immunohistochemical assessments. Ultimate tensile force, yield force, stiffness values, collagen type-I alpha 1 expression, and serum TAS significantly decreased (P < 0.05) in AT vs. HC. These values and expression significantly increased in the Ex+W group vs. AT. Serum MMP-13, IL-1β, and TNF-α levels decreased in all treatment groups vs. AT. The most significant decrease was found in the Ex+W group (P < 0.01). Histopathologically, the improvement in degeneration was statistically significant in the Ex+W group (P < 0.05). Immunohistochemically, MMP-13, IL-1β, TNF-α, and nitric oxide synthase-2 expression was decreased in all treatment groups vs. AT. In conclusion, omega-3 and exercise might be recommended in AT patients.

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.

Tendon-Specific Activation of Tenogenic Transcription Factors Enables Keeping Tenocytes' Identity In Vitro

We generated a novel tetracycline-inducible transgenic mouse line with the tendon-specific expression of a series of tendon-critical transcription factors. Primary tenocytes derived from this mouse line consistently expressed green fluorescent protein reporter transcription factors in response to doxycycline. The tenocytes maintained their tendon cell properties for a longer time after the transient induction in the absence of growth factors and mechanical stress. Four key transcription factors for tendon development and the green fluorescent protein reporter were linked with different viral 2A self-cleaving peptides. They were expressed under the control of the tet-responsive element. In combination with the expression of BFP, which reports on the tendon-specific collagen I, and mScarlet, which reports on the tendon-specific transcription factor Scleraxis (Scx), we observed the more extended maintenance of the tendon cell identity of in vitro cultured tendon cells and Achilles tendon explants. This means that the Scleraxis bHLH transcription factor (Scx), mohawk homeobox (Mkx), early growth response 1 (Egr1) and early growth response 2 (Egr2) contributed to the maintenance of tenocytes' identity in vitro, providing a new model for studying extracellular matrix alterations and identifying alternative biomaterials in vitro.

[Reconstruction of Soft Tissue Defects of the Achilles Tendon Region: a Literature Review]

BACKGROUND

Soft tissue defects in the achilles tendon region occur after trauma, but also as a complication after open recon- struction of the tendon with subsequent infection.

OBJECTIVES

Recommendations for the treatment of soft tissue injuries involving the Achilles tendon are presented.

MATERIALS AND METHODS

A search of the German, French and English literature on reconstruction of soft tissue defects of the Achilles tendon region was performed, which were differentiated into singular and combined tendocutaneous defects. Combined defects were further subdivided into three reconstructive principles: a simple soft tissue reconstruction without tendon repair or a combined reconstruction of the soft tissue as well as the tendon using either a vascularized tendon transplant or an avascular tendon graft.

RESULTS

Local and distally-based pedicled flaps include a relatively high risk or perioperative morbidity, whereas free flaps are described with significantly lower complications rates. Therefore, the authors prefer free flaps for reconstruction. Potential donor sites are the Medial Sural Artery (MSAP-) flap for smaller defects or free fasciocutaneous or muscle flaps in patients with large defects. The standard for tendocutaneousreconstructions is the free anterolateral thigh flap including vascularized fascia. Non-vascularized tendon grafts are frequently applied from the flexor hallucis longus- or peroneus brevis tendon.

CONCLUSIONS

Reconstructions over the Achilles tendon require thin and stable reconstructions that additionally allow slippage of soft tissues. Moreover, the use of normal shoes should be possible. The postoperative strength and range of motion of the ankle joint show comparable functional results after vascularized and non-vascularized tendon reconstruction.

Stem Cells from Healthy and Tendinopathic Human Tendons: Morphology, Collagen and Cytokines Expression and Their Response to T3 Thyroid Hormone

The aim of this study was to investigate the effect of triiodothyronine (T3) on tendon specific markers and cytokines expression of stem cells extracted from human tendons. Indeed, thyroid hormones have been reported to be protective factors, maintaining tendons' homeostasis, whereas tendinopathy is believed to be related to a failed healing response. Healthy and tendinopathic human tendons were harvested to isolate tendon stem/progenitor cells (TSPCs). TSPCs obtained from pathological samples showed gene expression and morphological modifications at baseline in comparison with cells harvested from healthy tissues. When cells were maintained in a medium supplemented with T3 (10-6 M), only pathological populations showed a significant upregulation of tenogenic markers (DCN, TNC, COL1A1, COL3A1). Immunostaining revealed that healthy cells constantly released type I collagen, typical of tendon matrix, whereas pathological ones overexpressed and secreted type III collagen, typical of scarred and impaired tissue. Pathological cells also overexpressed pro- and anti-inflammatory cytokines, suggesting an impaired balance in the presence of T3, without STAT3 activation. Moreover, DKK-1 was significantly high in the culture medium of pathological cell cultures and was reversed by T3. This study opens perspectives on the complex biochemical alteration of cells from pathological tendons, which may lead to the chronic disease context with an impaired extracellular matrix.

Tendon healing: a concise review on cellular and molecular mechanisms with a particular focus on the Achilles tendon

Tendon is a bradytrophic and hypovascular tissue, hence, healing remains a major challenge. The molecular key events involved in successful repair have to be unravelled to develop novel strategies that reduce the risk of unfavourable outcomes such as non-healing, adhesion formation, and scarring. This review will consider the diverse pathophysiological features of tendon-derived cells that lead to failed healing, including misrouted differentiation (e.g. de- or transdifferentiation) and premature cell senescence, as well as the loss of functional progenitors. Many of these features can be attributed to disturbed cell-extracellular matrix (ECM) or unbalanced soluble mediators involving not only resident tendon cells, but also the cross-talk with immigrating immune cell populations. Unrestrained post-traumatic inflammation could hinder successful healing. Pro-angiogenic mediators trigger hypervascularization and lead to persistence of an immature repair tissue, which does not provide sufficient mechano-competence. Tendon repair tissue needs to achieve an ECM composition, structure, strength, and stiffness that resembles the undamaged highly hierarchically ordered tendon ECM. Adequate mechano-sensation and -transduction by tendon cells orchestrate ECM synthesis, stabilization by cross-linking, and remodelling as a prerequisite for the adaptation to the increased mechanical challenges during healing. Lastly, this review will discuss, from the cell biological point of view, possible optimization strategies for augmenting Achilles tendon (AT) healing outcomes, including adapted mechanostimulation and novel approaches by restraining neoangiogenesis, modifying stem cell niche parameters, tissue engineering, the modulation of the inflammatory cells, and the application of stimulatory factors.Cite this article: Bone Joint Res 2022;11(8):561-574.

Does the Achilles Tendon Influence Foot Strike Patterns During an Exhaustive Run?

The study purpose was to investigate whether there is a relationship between the Achilles tendon (AT) length, moment arm length, and the foot strike pattern (FP) change during an exhaustive run (EXR) in nonrearfoot FP runners. Twenty-eight runners were recruited and divided into 2 groups (highly trained/moderately trained) according to their weekly training volume. Participants underwent the graded exercise test, the EXR with biomechanical analysis at the beginning, and at the end, and the magnetic resonance imaging scan of the AT. Correlations were used to assess associations between FP change (value of the difference between end and beginning) and the selected performance and AT variables. AT length significantly correlated with the FP change according to foot strike angle (r = -.265, P = .049). The AT moment arm length significantly correlated with the FP change according to strike index during EXR (r = -.536, P = .003). Multiple regression showed that AT length was a significant predictor for the FP change according to foot strike angle if the second predictor was the graded exercise test duration and the third predictor was training group association. These results suggest that a runner's training volume, along with a longer AT and AT moment arm appear to be associated with the ability to maintain a consistent FP during EXR by nonrearfoot FP runners.

Evaluation of cytokines in protective effect of docosahexaenoic acid in experimental achilles tendinopathy rat model induced with type-1 collagenase

BACKGROUND

We aimed to investigate the effectiveness of docosahexaenoic acid (DHA) as a treatment for Achilles tendinopathy (AT) induced with type-I collagenase in rats and compare it with collagen.

METHODS

The AT model was induced with type I collagenase, and animals were randomly assigned to groups. Group 1:AT, Group 2: Collagen (7.2 mg/kg/day), Group 3:DHA (300 mg/kg/day), and Group 4:DHA (100 mg/kg/day). Right tendons of Group1 were used as a healthy control (HC). Oral treatments were applied for eight weeks. Serum tumor necrosis factor-alpha(TNF-α), matrix metalloproteinase-13 (MMP-13), and interleukin-1 beta(IL-1β) concentrations were determined by ELISA. Tendon samples were taken for histopathological evaluation and examined immunohistochemically with antibodies specific for Col1A1, TNF-α, MMP-13, IL-1β, and nitric oxide synthase-2(NOS-2). The ultimate tensile force (UTF) yield force(YF) and stiffness were measured by biomechanical assessments.

RESULTS

UTF,YF and stiffness values were increased in all treatment groups compared to the AT control, a significant increase was found in Group 2 (p < 0.05). There was severe degeneration of tendon cells in the AT control. The tendon cells in samples from Groups 2-3 were less degraded, and this was statistically significant (p < 0.05). TNF-α, MMP-13, IL-1β, and NOS-2 expressions were significantly higher in the AT control compared to the HC. In all treatment groups, their concentrations were lower than in the AT control. Serum TNF-α, MMP-13, and IL-1β levels were lower in all treatment groups (Especially in Group3 (p < 0.001)) compared to Group1.

CONCLUSION

The efficacy of high-dose DHA as a treatment for AT was investigated from biochemical, histopathological, and biomechanical perspectives. The results showed that DHA could be an alternative treatment compound to collagen.

A Critical Biomechanical Evaluation of Foot and Ankle Soft Tissue Repair

The objective of this article is to review the biomechanical stresses that occur during normal physiologic function of lower extremity soft tissue anatomic structures and to use this as a baseline for a critical analysis of the medical literature because it relates to surgical reconstruction following injury. The Achilles tendon, anterior talofibular ligament, plantar plate, and spring ligament are specifically evaluated.

The Influence of Ankle Position on Radiographic Diagnosis of Acute Achilles Tendon Rupture

No previous study has demonstrated the relationship between the ankle position and radiographic diagnosis of acute Achilles tendon rupture. The purpose of this study was to investigate the influence of ankle position in the presence of diagnostic radiographic signs in acute Achilles tendon rupture. A retrospective review of 154 ankle lateral radiographs of acute Achilles tendon rupture was performed. Ankle position was classified as dorsiflexion, neutral, or plantar flexion by measurement of the tibiotalar angle. Kager's triangle, Toygar's angle, Arner's sign, and thickening of the Achilles tendon were assessed as diagnostic radiographic signs, and their relations to ankle position were analyzed. Interobserver reliabilities of radiographic signs were moderate to substantial (kappa value, range 0.41-0.68). All 4 signs were significantly more visible in ankle plantar flexion than dorsiflexion. The presence of Toygar's angle and positive Arner's sign were significantly increased in ankle plantar flexion compared to neutral, while the presence of Kager's triangle, and thickening of the Achilles tendon did not differ according to ankle position. The diagnostic radiographic signs of acute Achilles tendon rupture were better presented in ankle plantar flexion position than neutral and dorsiflexion positions. Neutral and dorsiflexion ankle positions should be avoided when performing lateral radiographs of patients with suspected acute Achilles tendon rupture.

Failed Surgery for Achilles Tendinopathy

Treatments of Achilles tendinopathy continue to evolve. The body of literature is inadequate to provide a comprehensive guide to evaluation and treat failed surgeries. Issues related to failed surgical treatment may be divided into infection/wound issue, mechanical failure, and persistent pain. Awareness of the potential problems described in this article will allow surgeons to have a foundation in clinical assessment and making accurate diagnoses. Various surgical treatment options are available and should be executed carefully to treat individualized patient conditions.

Quantifying the ossification and fusion of the calcaneal apophysis using computed tomography

Knowledge of the anatomical development of the calcaneal apophysis is essential in clinical assessment and management of both paediatric and sub‐adult patients presenting with heel pain. Despite this, the current understanding of calcaneal apophyseal development is constrained by the limitations of the imaging modalities used to examine the apophysis, with no current literature reporting the development of the medial and lateral processes. This study aimed to overcome these limitations by investigating the ossification and fusion of the calcaneal apophysis using three‐dimensional computed tomography analysis, and statistically predicting the apophyseal developmental stage in contemporary Australian children. The development and fusion status of the apophysis was scored using a novel 11‐stage scoring system on 568 multi‐slice computed tomography scans (295 females; 274 males) and 266 lateral radiographic scans (119 females; 147 males) from the Queensland Children's Hospital. Multinomial logistic regression along with classification tables and predictive probabilities were then utilised to assess developmental stage likelihood from known age and sex. The apophysis commenced ossification at a mean age of 5.2 years for females and 7.2 years for males, and then elongated to form the apophyseal cap around 10 years for females and 12.4 years for males. Fusion of the apophysis commenced at a mean age of 11.18 years for females and 13.3 years for males, with the earliest age of complete fusion observed at 10 years for females and 14 years for males. The results demonstrate significant sexual dimorphism in ossification and fusion with females developing and fusing significantly earlier. Furthermore, the use of computed tomography in this study allowed for the first time evaluation of the ossification and fusion of the medial and lateral processes of the calcaneus. The medial process formed at a mean age of 9.5 years for females and 10.9 years for males while the lateral process formed at around 9.8 years for females and 11.7 years for males. The medial process demonstrated slower rates of fusion compared to the lateral process. The present study provides Queensland specific standards for assessing the calcaneal apophyseal developmental stage as well as novel predictive regression models for apophyseal stage estimation using known age and sex to aid in the diagnosis of heel pain conditions such as apophysitis or screen for developmental delays in children and subadults.

Age-related changes to triceps surae muscle-subtendon interaction dynamics during walking

Push-off intensity is largely governed by the forces generated by the triceps surae (TS) muscles (gastrocnemius-GAS, soleus-SOL). During walking, the TS muscles undergo different fascicle kinematics and contribute differently to biomechanical subtasks. These differences may be facilitated by the Achilles tendon (AT), which is comprised of subtendons that originate from the TS muscles. We and others have revealed non-uniform displacement patterns within the AT—evidence for sliding between subtendons that may facilitate independent muscle actuation. However, in older adults, we have observed more uniform AT tissue displacements that correlate with reduced push-off intensity. Here, we employed dual-probe ultrasound imaging to investigate TS muscle length change heterogeneity (GAS–SOL) as a determinant of reduced push-off intensity in older adults. Compared to young, older adults walked with more uniform AT tissue displacements and reduced TS muscle length change heterogeneity. These muscle-level differences appeared to negatively impact push-off intensity—evidenced by between-group differences in the extent to which TS muscle length change heterogeneity correlates with mechanical output across walking tasks. Our findings suggest that the capacity for sliding between subtendons may facilitate independent TS muscle actuation in young adults but may restrict that actuation in older adults, likely contributing to reduced push-off intensity.

The Surgical Care Practitioner role in Achilles tendon re-rupture: A case study

The value of a Surgical Care Practitioner to an orthopaedic team is demonstrated in this case study of a patient who presented with a re-ruptured Achilles tendon. It highlights the role the practitioner plays in the patient journey and illustrates it's value throughout the clinical course from consultation through to discharge. The Surgical Care Practitioner, as a member of the extended surgical team can help to explain the diagnosis and associated treatment options, facilitate informed consent and provide expert procedural assistance to the surgeon. A Surgical Care Practitioner is ideally placed to answer patient queries and aid in rehabilitation.

Sex Differences in the Morphological and Mechanical Properties of the Achilles Tendon

Background: Patients with Achilles tendon (AT) injuries are often engaged in sedentary work because of decreasing tendon vascularisation. Furthermore, men are more likely to be exposed to AT tendinosis or ruptures. These conditions are related to the morphological and mechanical properties of AT, but the mechanism remains unclear. This study aimed to investigate the effects of sex on the morphological and mechanical properties of the AT in inactive individuals. Methods: In total, 30 inactive healthy participants (15 male participants and 15 female participants) were recruited. The AT morphological properties (cross-sectional area, thickness, and length) were captured by using an ultrasound device. The AT force–elongation characteristics were determined during isometric plantarflexion with the ultrasonic videos. The AT stiffness was determined at 50%–100% maximum voluntary contraction force. The AT strain, stress, and hysteresis were calculated. Results: Male participants had 15% longer AT length, 31% larger AT cross-sectional area and 21% thicker AT than female participants (p < 0.05). The plantarflexion torque, peak AT force, peak AT stress, and AT stiffness were significantly greater in male participants than in female participants (p < 0.05). However, no significant sex-specific differences were observed in peak AT strain and hysteresis (p > 0.05). Conclusions: In physically inactive adults, the morphological properties of AT were superior in men but were exposed to higher stress conditions. Moreover, no significant sex-specific differences were observed in peak AT strain and hysteresis, indicating that the AT of males did not store and return elastic energy more efficiently than that of females. Thus, the mechanical properties of the AT should be maintained and/or improved through physical exercise.

Identifying achilles tendon structure differences by ultrasound tissue characterization in asymptomatic individuals

Ultrasound Tissue Characterization (UTC) is a modality that can be utilized to characterize tendon tissue structure using ultrasonographic imaging paired with a computer algorithm to distinguish echo-types. Several studies have demonstrated UTCs ability to distinguish Achilles tendon morphology changes, but no study has established normative data of the Achilles tendon in the general population. The aim of this study was to determine UTC echo-type distribution in the Achilles tendon in an asymptomatic population. UTC scans were completed and analyzed on 508 participants without Achilles tendinopathy. Dedicated UTC-algorithms were used to distinguish and calculate echo-type percentages and the fiber type distribution was compared. The overall sample echo-type percentages demonstrated greater levels of Type I and II echo-types, 65.73% and 32.00%, respectively, and lower levels of Type III and IV echo-types, 1.74% and 0.57%, respectively. In addition, females had lower levels of Echo-type I compared to men and greater levels of echo-type II (p < 0.001). We also found that African-Americans had significantly greater amounts of echo-type I and lesser amounts of echo-type II when compared to Caucasians (p < 0.05). The results of this study create a normative data set for future UTC studies to utilize as a baseline for the evaluation of Achilles tendons. In addition, it demonstrated tendon type differences between sexes and races that need to be accounted for in future studies.

US-guided high-volume injection for Achilles tendinopathy

Achilles tendinopathy is a common overuse condition affecting the adult population. The incidence is on the rise because of greater participation of people in recreational or competitive sporting activities. Chronic Achilles tendinopathy occurs most commonly in the tendon’s mid-portion, and it is challenging to manage, leading to significant patient morbidity. Despite conservative management many patients still require surgical intervention. The mechanism underlying pain is not entirely understood; however, high-resolution color Doppler ultrasound has shown that neovascularisation could be involved. Minimally-invasive treatments for chronic Achilles tendinopathy may prevent the need for surgery when conservative methods have failed. Ultrasound provides an option to guide therapeutic interventions accurately, so that treatment is delivered to the desired site of pathology. High-volume image-guided injection is a relatively new technique where a high volume of liquid is injected between the anterior aspect of the Achilles tendon and the Kager’s fat pad, used to strip away the neovascularity and disrupt the nerve ingrowth seen in chronic cases of Achilles tendinopathy. High-volume image-guided injection has shown promising results in terms of reducing pain and improving function in patients where conservative measures have failed. This review aims to describe the fundamental technical factors, and investigate the efficacy of high-volume image-guided injection with reference to the available literature.

Arthroscopic, Single-Incision, and Double-Incision Approaches to Flexor Hallucis Longus Tendon Transfer Following Achilles Tendon Rupture: A Literature Review

Achilles tendon rupture is a common athletic injury that results in a painful and antalgic gait. Flexor hallucis longus tendon transfer through arthroscopic, single-incision, or double-incision techniques is used as a treatment approach to address this rupture; however, no studies have compared postoperative complications between these three techniques. A systematic search of published articles was conducted using keywords "Achilles rupture," "flexor hallucis tendon," "transfer," and "recovery." Articles were then selected based on their title, abstract, and content following full-text review. From each article's reported surgical outcomes, a comparison was made between arthroscopic and single- and double-incision postoperative complications using a χ2 test with significance set at a value of P < .05 followed by post hoc analysis. The arthroscopic approach maintained the lowest rate of postoperative complications, followed by the single- and double-incision techniques. A significant difference in the number of postoperative complications was found between all incisional approaches. The pairwise comparisons, however, could not identify which incisional approaches significantly differed between each other. A reduction in postoperative complications places arthroscopy and the single-incision techniques as the preferred approaches for flexor hallucis longus tendon transfer following an Achilles tendon rupture. Although current literature shows arthroscopy to be superior to single- and double-incision methods, this review demonstrates the need for a greater number of published cases using arthroscopy to establish significance regarding postoperative complications.

Thermographic assessment of the immediate and short term-effects of blood flow restriction exercise on Achilles tendon skin temperature

OBJECTIVES

To determine the thermal patterning of the Achilles tendon following bodyweight resistance exercise with and without blood-flow restriction (BFR).

DESIGN

Cross-sectional.

SETTING

Research laboratory.

PARTICIPANTS

Twelve asymptomatic recreational runners (Age: 37 ± 10, Height: 169 ± 20, Mass: 73.8 ± 13.4).

MAIN OUTCOME MEASURES

Thermograms were taken pre and post exercise with and without a BFR cuff on separate legs. BFR cuff pressure was set at 80% maximal arterial occlusion pressure determined using doppler via the tibial artery. Linear mixed-effects models were used to assess the effect of BFR and time post-exercise on skin-temperature (Tskin).

RESULTS

A lower Tskin was seen following BFR exercise at the tendon insertion (P = 0.002), but not at the free tendon (P = 0.234), or the musculotendinous junction (P = 0.933). A significant effect of time upon changes in Tskin was observed in both BFR and non-BFR groups (P = 0.002). No interaction of time and BFR were observed on changes in Tskin (P = 0.726).

CONCLUSION

Region specific changes in Tskin were found, with greater and longer reductions observed at the insertion of the Achilles following BFR exercise before returning to baseline. These findings could have implications for the programming of BFR exercise on tendon health. Future research should observe for differences between symptomatic and healthy tendons.

Surface Shape of the Calcaneal Tuberosity and the Occurrence of Retrocalcaneal Bursitis among Runners

Purpose: The aim of the study was to establish the relationship between the shape of the calcaneal tuberosity (flat, stepped, rounded, normal) and the probability that retrocalcaneal bursitis among people who train running regularly. Methods: The study included a group of 30 runners who suffered from retrocalcaneal bursitis in the past, and 30 people who never had symptoms of this disease. The study was based on a diagnostic survey, as well as on clinical examination. The surface of the calcaneal tuberosity and the slope of the calcaneus were assessed using X-rays. The mobility of the bursa, its surface size, the thickness of the Achilles tendon and its attachment rate were established during an ultrasound examination. Results: Flat surface of the calcaneal tuberosity increases fourfold the risk of suffering from retrocalcaneal bursitis (OR = 4.3). The people whose calcaneus slope is above 25° are at increased risk of suffering from such an inflammation compared with the people whose calcaneus bone is more horizontal (OR = 2.8). The analysis shows that the thickness of the Achilles tendon (p = 0.001), the surface size of the bursa (p = 0.009), as well as the flat surface of the calcaneal tuberosity (p = 0.008) are strongly associated with the occurrence of retrocalcaneal bursitis. Conclusions: The flat shape of the calcaneal tuberosity increases the risk of bursitis. The risk of inflammation is higher when the Achilles tendon is thicker and the surface of the bursa is smaller than normal.

Posttraumatic Perfusion Analysis of Quadriceps, Patellar, and Achilles Tendon Regeneration With Dynamic Contrast-Enhanced Ultrasound and Dynamic Contrast-Enhanced Magnetic Resonance Imaging: Preliminary Results

OBJECTIVES

The healing process of tendons after surgical treatment of tendon ruptures mainly depends on the perfusion of the tendon and its surrounding tissue. Dynamic contrast-enhanced ultrasound (DCE-US) and dynamic contrast-enhanced MRI (DCE-MRI) can provide additional information about the local microperfusion. In this pilot study, the feasibility of these techniques to assess the vascularization during tendon regeneration was evaluated.

METHODS

Between 2013 and 2015, 23 patients with surgical treatment of traumatic rupture of quadriceps, patellar, and Achilles tendons were involved. All patients received clinical follow-up examinations at 6, 12, and at least 52 weeks postoperatively. Dynamic contrast-enhanced US and DCE-MRI examinations were performed 6 and 12 weeks postoperatively. Dynamic contrast-enhanced US perfusion was quantified by the parameters peak enhancement, wash-in area under the curve, rise time, and initial area under the curve. Correlations between these parameters were examined via the Spearman rank correlation. The clinical and functional outcomes were assessed via the Lysholm Knee Score and Knee and Osteoarthritis Outcome Score at 12 and 52 weeks postoperatively.

RESULTS

Fourteen patients with quadriceps (n = 8), patellar (n = 4) and Achilles (n = 2) tendon ruptures with complete follow-up were available. The microperfusion could be successful assessed. We could detect a strong correlation of DCE-US (peak enhancement) parameters with DCE-MRI (initial area under the curve) parameters after 6 and 12 weeks.

CONCLUSIONS

In this pilot study, DCE-US was able to visualize the microperfusion of healing tendons with a strong correlation with DCE-MRI. Our initial results are in favor of DCE-US as a potential quantitative imaging tool for evaluating the vascularization in tendon regeneration as a complementary method.

Achilles tendinopathy: Exploring injury characteristics and current treatment modalities

Achilles tendinopathy is a prevalent overuse injury to the Achilles tendon causing prominent pain and reduction in quality of life. Several biomechanical and anatomical properties govern the pathology of the Achilles tendinopathy, and as a result, choosing the optimal treatment option is challenging. The aim of this review is to study the anatomical and biomechanical characteristics of this injury and explore the available treatment options in order to extrapolate the most suitable option with the best prognosis. Treatment modalities for Achilles tendinopathy vary and include non-operative and operative options. Non-operative treatment modalities include physical therapy, extracorporeal shockwave therapy, injectable agents, and bracing and taping. Operative treatment modalities include surgical procedures, both percutaneous and open. Treatment should be catered to the individual patient. Further research is required in order to confirm the efficacy of the available treatment options, test the viability of novel techniques and approaches, and discover possible new therapeutic modalities.

Spider Silk-Augmented Scaffolds and Adipose-Derived Stromal Cells Loaded with Uniaxial Cyclic Strain: First Investigations of a Novel Approach for Tendon-Like Constructs

Tendon injuries still pose a challenge to reconstructive surgeons. Tendon tissue is a bradytrophic tissue and has a poor tendency to heal. Autologous tendon grafts are, therefore, still the gold standard in restorative operations but are associated with significant donor side morbidity. The experimental approach of the present study focused on the use of the biomaterial spider silk as a biocompatible and very stable carrier matrix in combination with a collagen type I hydrogel and adipose-derived stromal cells. The constructs were differentiated by axial strain to tendon-like tissue using a custom-made bioreactor. Macroscopically, tendon-like tissue could be detected which histologically showed high cell vitality even in long-term cultivation. In addition, cell morphology comparable to tenocytes could be detected in the bioreactor-stimulated tendon-like constructs compared to the controls. Immunohistochemically, tendon tissue-specific markers could be detected. Therefore, the developed tendon-like construct represents a promising approach towards patient specific tendon reconstruction, but further studies are needed.

Characterization of the structure, vascularity, and stem/progenitor cell populations in porcine Achilles tendon (PAT)

This study aimed to characterize porcine Achilles tendon (PAT) in terms of its structural components, vascularity, and resident tendon cells. We found that PAT is composed of a paratenon sheath, a core of fascicles, and an endotenon/interfascicular matrix (IFM) that encases the fascicle bundles. We analyzed each of these three tendon components structurally using tissue sections and by isolating cells from each component and analyzing in vitro. Many blood vessel-like tissues were present in the paratenon and IFM but not in fascicles, and the vessels in the paratenon and IFM appeared to be inter-connected. Cells isolated from the paratenon and IFM displayed characteristics of vascular stem/progenitor cells expressing the markers CD105, CD31, with α-smooth muscle actin (α-SMA) localized surrounding blood vessels. The isolated cells from paratenon and IFM also harbored abundant stem/progenitor cells as evidenced by their ability to form colonies and express stem cell markers including CD73 and CD146. Furthermore, we demonstrate that both paratenon and IFM-isolated cells were capable of undergoing multi-differentiation. In addition, both paratenon and IFM cells expressed elastin, osteocalcin, tubulin polymerization promoting protein (TPPP), and collagen IV, whereas fascicle cells expressed none of these markers, except collagen I. The neurotransmitter substance P (SP) was also found in the paratenon and IFM-localized surrounding blood vessels. The findings of this study will help us to better understand the vascular and cellular mechanisms of tendon homeostasis, injury, healing, and regeneration.

Three-dimensional ultrastructure reconstruction of tendinous components at the bifurcation of the bovine superficial digital flexor tendon using array and STEM tomographies

Tendons transmit force from muscle to bone for joint movement. Tenocytes are a specialized type of fibroblast that produces collagen fibrils in tendons. Their cytoplasmic processes form a network surrounding collagen fibrils to define a collagen fibre. Glycosaminoglycan (GAG) chains link collagen fibrils and adhere at the D-band of the collagen fibril. In this study, we used array and scanning transmission electron microscope (STEM) tomographies to reconstruct the three-dimensional ultrastructure of tenocytes, collagen fibres, collagen fibrils and GAG chains at the bifurcation of the bovine hindlimb superficial digital flexor tendon (SDFT). Collagen fibrils comprising a collagen fibre were not aligned uniformly and had at least two running directions. Spindle-shaped tenocytes were arranged along the long axis of a plurality of collagen fibres, where two groups of collagen fibrils with oblique directions to each other exhibited an oblique overlap of the two collagen fibril layers. Collagen fibrils with different running directions were observed in separating layers of about 300 nm in thickness and had diameters of 0-200 nm. About 40% of all collagen fibrils had a peak in the range of 20-40 nm. STEM analysis of the same site where the crossing of collagen fibres was observed by transmission electron microscopy demonstrated the outline of collagen fibrils with a clear D-banding pattern at a regular interval. Collagen fibrils were reconstructed three-dimensionally using continuous images acquired by STEM tomography, which confirmed that the collagen fibrils at the crossing sites did not orientate in layers, but were woven one by one. Higher magnification observation of GAG chains attached between the crossing collagen fibrils revealed numerous GAG chains arranged either vertically or obliquely on collagen fibrils. Furthermore, GAG chains at the cross of collagen fibrils connected the closest D-bands. GAG chains are thought to be universally present between collagen fibrils of the tendon. These observations by array and STEM tomographies increase our knowledge of the anatomy in the bifurcation of the bovine hindlimb SDFT and demonstrate the utility of these new imaging technologies.

Achilles Tendon Lesions - Part 2: Ruptures

The increasing incidence of calcaneal tendon ruptures has substantially impacted orthopedic care and costs related to its treatment and prevention. Primarily motivated by the increasing of life expectancy, the growing use of tenotoxic drugs and erratic access to physical activity, this injury accounts for considerable morbidity regardless of its outcome. In recent years, the evolution of surgical and rehabilitation techniques gave orthopedists better conditions to decide the most appropriate conduct in acute tendon rupture. Although still frequent due to their high neglect rate, Achilles chronic ruptures currently find simpler and more biological surgical options, being supported by a new specialty-focused paradigm.

Stiffness of the Gastrocnemius-Achilles Tendon Complex Between Amateur Basketball Players and the Non-athletic General Population

Muscle and tendon stiffness are related to sports performance, tendinopathy, and tendon degeneration. However, the effects of habitual loading on muscle and tendon mechanical properties are unclear. Using amateur basketball players as examples, we investigated the effects of mechanical loading on the stiffness of the gastrocnemius–Achilles tendon (AT) complex in non-dominant and dominant lower limbs. Then, we evaluated the correlation between gastrocnemius and AT stiffness. Forty participants (20 amateur basketball players; 20 normal non-athletic persons) were recruited for this study. Stiffness of the gastrocnemius–AT complex was assessed using MyotonPRO at neutral position and 10° dorsiflexion of the ankle joint in participants from amateur basketball players and the non-athletic general population. Our results showed a greater stiffness of the gastrocnemius–AT complex in amateur basketball players than that in healthy non-athletic subjects at neutral position and 10° dorsiflexion of the ankle joint (P < 0.05). No significant difference in stiffness was found between the non-dominant and dominant lower limbs either in amateur basketball players or in generally healthy subjects (P > 0.05). A significant positive correlation was obtained between stiffness of the AT and medial gastrocnemius (MG) in amateur basketball players (neutral position: r = 0.726 and P = 0.001; dorsiflexion 10°: r = 0.687 and P = 0.001). The amateur basketball players exhibit significantly higher stiffness value in Achilles and gastrocnemius. This is possibly caused by repeated training effects. The symmetric stiffness of the AT and gastrocnemius exists both in amateur basketball players and generally healthy subjects. A significant correlation between the AT and the MG was found in amateur basketball players.