Fine structural alterations in chronic Achilles paratenonitis in athletes

Ultrasound-guided injection of the achilles paratenon: A cadaveric investigation

BACKGROUND

Injections around the Achilles tendon (AT) are commonly performed in clinical practice to manage non-insertional Achilles tendinopathy, but the presence/distribution of the injectate with relation to its sheath has not been assessed specifically. Accordingly, the aim of this cadaveric investigation was to demonstrate the feasibility of Achilles paratenon injection under ultrasound guidance - by confirming the exact needle positioning as well as the dye distribution inside the paratenon lumen.

METHODS

A descriptive laboratory study with three human cadaveric specimens (one fresh cadaver and two cadavers embalmed using the Fix for Life (F4L) method) was performed in a tertiary-care academic institution. The interventional technique and the related anatomical findings were illustrated. During the injection, the needle was advanced inside the Achilles paratenon under ultrasound guidance i.e. in-plane medial-to-lateral approach. With the objective to confirm its correct placement, the needle was kept in situ on the right AT of the fresh cadaver. Likewise, to demonstrate the location of the dye inside the lumen of Achilles paratenon, the other five ATs - four on the embalmed cadavers and one on the fresh cadaver - were injected with 5 mL of green color dye. After removal of the needle, a layer-by-layer anatomical dissection was performed on all three cadavers.

RESULTS

On the right AT of the fresh cadaver, the position of the needle's tip within the Achilles paratenon was confirmed. Accurate placement of the dye inside the paratenon lumen was confirmed in four (80%) ATs, one of the fresh and three of the embalmed cadavers. No spread inside the crural fascia compartment or between the AT and the Kager's fat pad was observed. Herewith, unintentional spilling of the dye within the superficial soft tissues of the posterior leg was reported in the left AT of one of the two embalmed cadavers (20%).

CONCLUSIONS

Ultrasound-guided injection using the in-plane, medial-to-lateral approach can accurately target the lumen of Achilles paratenon.

Different clinical presentations of Achilles tendinopathy: a cross-sectional study

Achilles tendinopathy (AT) is a common debilitating tendon disorder in the lower extremity. Clinical presentation of AT might differ from place to place, depending on different variables including cultural factors. This study was conducted to determine the clinical picture of AT in a group of clients referring to an outpatient orthopedics clinic in Shiraz, southern Iran. In this cross-sectional study, a convenient sample of 61 (46 female and 15 male) patients attending to a referral outpatient clinic affiliated to Shiraz University of Medical Sciences with a definite diagnosis of AT was studied. Patients with partial- or full-thickness tear of Achilles tendon, history of radicular pain or lower extremity injury, previous history of surgery on their lower extremity, and pregnant women were excluded from the study. We used Maffulli et al. (Foot Ankle Surg 26:240-9, 2020) criteria for the diagnosis of AT in our patients. The patients had a mean age of 47.7 (SD 11.1) years and mean BMI of 28.7 (4.2) kg/m2. There was no significant correlation between the age and body mass index of the participants (Pearson's r = -0.028, p = 0.832). The prevalence of insertional AT among 58 patients with only one site affected, was 84% (95% CI 72-92%), significantly (p < 0.001) higher than that of midportional AT (16%). Women were more frequently affected than men (p < 0.001). The clinical presentation of AT in southern Iran is somewhat different from those reported in other parts of the world. Further studies on larger groups of patients should be done to determine the causes of the observed differences.

Neutralization of excessive levels of active TGF-β1 reduces MSC recruitment and differentiation to mitigate peritendinous adhesion

Peritendinous adhesion formation (PAF) can substantially limit the range of motion of digits. However, the origin of myofibroblasts in PAF tissues is still unclear. In this study, we found that the concentration of active TGF-β1 and the numbers of macrophages, mesenchymal stromal cells (MSCs), and myofibroblasts in human and mouse adhesion tissues were increased. Furthermore, knockout of TGF-β1 in macrophages or TGF-β1R2 in MSCs inhibited PAF by reducing MSC and myofibroblast infiltration and collagen I and III deposition, respectively. Moreover, we found that MSCs differentiated into myofibroblasts to form adhesion tissues. Systemic injection of the TGF-β-neutralizing antibody 1D11 during the granulation formation stage of PAF significantly reduced the infiltration of MSCs and myofibroblasts and, subsequently, PAF. These results suggest that macrophage-derived TGF-β1 recruits MSCs to form myofibroblasts in peritendinous adhesions. An improved understanding of PAF mechanisms could help identify a potential therapeutic strategy.

Assessing the functional properties of tenogenic primed mesenchymal stem cells in ex vivo equine tendon and ligament explants: A preliminary study

Injuries to equine tendons and ligaments are career-compromising, causing reduced performance and premature retirement. Promising treatment alternatives have been investigated in the field of mesenchymal stem cells (MSCs). In this study, the tissue adherence and protein expression of tenogenic primed mesenchymal stem cells (tpMSCs) after administration to ex vivo tendon and ligament explants is investigated. First, collagen type I (COL I) and smooth muscle actin (SMA) expression was assessed in cytospins prepared from native MSCs and tpMSCs. Second, equine superficial digital flexor tendon and suspensory ligament explants were cultivated, and a lesion was treated with both cell types. Subsequently, cell adhesion to the explants and the amount of COL I and SMA positive cells was evaluated. The cytospins revealed a significantly higher COL I and lower SMA expression in tpMSCs compared to native MSCs. In the explants, tpMSCs showed a significantly higher tendon and ligament adherence. Furthermore, a significantly higher percentage of COL I positive and a lower percentage of SMA positive cells were observed in the lesions treated with tpMSCs. The results of these explant co-cultures may demonstrate at least a part of the mechanism of action and functional properties of tpMSCs in restoring function to tendons and ligaments.

The Evaluation of Equine Allogeneic Tenogenic Primed Mesenchymal Stem Cells in a Surgically Induced Superficial Digital Flexor Tendon Lesion Model

Background: Tendon injuries are very common in horses and jeopardize the athletic performance, and due to the high risk of reinjury may lead to early retirement. The use of mesenchymal stem cells for the treatment of equine tendon disease is widely investigated because of their regenerative potential. The objective of this study is to investigate the safety and efficacy of equine allogeneic tenogenic primed mesenchymal stem cells (tpMSCs) for the management of tendinitis in horses.

Methods: A core lesion was surgically induced in the superficial digital flexor tendon of both forelimbs of eight horses. After 7 days, one forelimb was treated with tpMSCs, while the contralateral forelimb served as an intra-individual control and was treated with saline. A prescribed exercise program was started. All horses underwent a daily clinical evaluation throughout the entire study period of 112 days. Blood samples were taken at different time points for hematological and biochemical analysis. Tendon assessment, lameness examination, ultrasound assessment and ultrasound tissue characterization (UTC) were performed at regular time intervals. At the end of the study period, the superficial digital flexor tendons were evaluated macroscopically and histologically.

Results: No suspected or serious adverse events occurred during the entire study period. There was no difference in local effects including heat and pain to pressure between a single intralesional injection of allogeneic tpMSCs and a single intralesional injection with saline. A transient moderate local swelling was noted in the tpMSC treated limbs, which dissipated by day 11. Starting at a different time point depending on the parameter, a significant improvement was observed in the tpMSC treated limbs compared to the placebo for echogenicity score, fiber alignment score, anterior-posterior thickness of the tendon and echo type by UTC assessment. Immunohistochemistry 112 days post-injection revealed that the amount of collagen type I and Von Willebrand factor were significantly higher in the tendon tissue of the tpMSC group, while the amount of collagen type III and smooth muscle actin was significantly lower.

Conclusion: Equine allogeneic tenogenic primed mesenchymal stem cells were shown to be well-tolerated and may be effective for the management of tendon injuries.

Overuse injuries in sport: a comprehensive overview

BACKGROUND

The absence of a single, identifiable traumatic cause has been traditionally used as a definition for a causative factor of overuse injury. Excessive loading, insufficient recovery, and underpreparedness can increase injury risk by exposing athletes to relatively large changes in load. The musculoskeletal system, if subjected to excessive stress, can suffer from various types of overuse injuries which may affect the bone, muscles, tendons, and ligaments.

METHODS

We performed a search (up to March 2018) in the PubMed and Scopus electronic databases to identify the available scientific articles about the pathophysiology and the incidence of overuse sport injuries. For the purposes of our review, we used several combinations of the following keywords: overuse, injury, tendon, tendinopathy, stress fracture, stress reaction, and juvenile osteochondritis dissecans.

RESULTS

Overuse tendinopathy induces in the tendon pain and swelling with associated decreased tolerance to exercise and various types of tendon degeneration. Poor training technique and a variety of risk factors may predispose athletes to stress reactions that may be interpreted as possible precursors of stress fractures. A frequent cause of pain in adolescents is juvenile osteochondritis dissecans (JOCD), which is characterized by delamination and localized necrosis of the subchondral bone, with or without the involvement of articular cartilage. The purpose of this compressive review is to give an overview of overuse injuries in sport by describing the theoretical foundations of these conditions that may predispose to the development of tendinopathy, stress fractures, stress reactions, and juvenile osteochondritis dissecans and the implication that these pathologies may have in their management.

CONCLUSIONS

Further research is required to improve our knowledge on tendon and bone healing, enabling specific treatment strategies to be developed for the management of overuse injuries.

Achilles Tendinopathy

Achilles tendinopathy is a common cause of disability. Despite the economic and social relevance of the problem, the causes and mechanisms of Achilles tendinopathy remain unclear. Tendon vascularity, gastrocnemius-soleus dysfunction, age, sex, body weight and height, pes cavus, and lateral ankle instability are considered common intrinsic factors. The essence of Achilles tendinopathy is a failed healing response, with haphazard proliferation of tenocytes, some evidence of degeneration in tendon cells and disruption of collagen fibers, and subsequent increase in noncollagenous matrix. Tendinopathic tendons have an increased rate of matrix remodeling, leading to a mechanically less stable tendon which is more susceptible to damage. The diagnosis of Achilles tendinopathy is mainly based on a careful history and detailed clinical examination. The latter remains the best diagnostic tool. Over the past few years, various new therapeutic options have been proposed for the management of Achilles tendinopathy. Despite the morbidity associated with Achilles tendinopathy, many of the therapeutic options described and in common use are far from scientifically based. New minimally invasive techniques of stripping of neovessels from the Kager's triangle of the tendo Achillis have been described, and seem to allow faster recovery and accelerated return to sports, rather than open surgery. A genetic component has been implicated in tendinopathies of the Achilles tendon, but these studies are still at their infancy.

Mechanical Considerations for Electrospun Nanofibers in Tendon and Ligament Repair

Electrospun nanofibers possess unique qualities such as nanodiameter, high surface area to volume ratio, biomimetic architecture, and tunable chemical and electrical properties. Numerous studies have demonstrated the potential of nanofibrous architecture to direct cell morphology, migration, and more complex biological processes such as differentiation and extracellular matrix (ECM) deposition through topographical guidance cues. These advantages have created great interest in electrospun fibers for biomedical applications, including tendon and ligament repair. Electrospun nanofibers, despite their nanoscale size, generally exhibit poor mechanical properties compared to larger conventionally manufactured polymer fiber materials. This invites the question of what role electrospun polymer nanofibers can play in tendon and ligament repair applications that have both biological and mechanical requirements. At first glance, the strength and stiffness of electrospun nanofiber grafts appear to be too low to fill the rigorous loading conditions of these tissues. However, there are a number of strategies to enhance and tune the mechanical properties of electrospun nanofiber grafts. As researchers design the next-generation electrospun tendon and ligament grafts, it is critical to consider numerous physiologically relevant mechanical criteria and to evaluate graft mechanical performance in conditions and loading environments that reflect in vivo conditions and surgical fixation methods.

Rescue plan for Achilles: Therapeutics steering the fate and functions of stem cells in tendon wound healing

Due to the increasing age of our society and a rise in engagement of young people in extreme and/or competitive sports, both tendinopathies and tendon ruptures present a clinical and financial challenge. Tendon has limited natural healing capacity and often responds poorly to treatments, hence it requires prolonged rehabilitation in most cases. Till today, none of the therapeutic options has provided successful long-term solutions, meaning that repaired tendons do not recover their complete strength and functionality. Our understanding of tendon biology and healing increases only slowly and the development of new treatment options is insufficient. In this review, following discussion on tendon structure, healing and the clinical relevance of tendon injury, we aim to elucidate the role of stem cells in tendon healing and discuss new possibilities to enhance stem cell treatment of injured tendon. To date, studies mainly apply stem cells, often in combination with scaffolds or growth factors, to surgically created tendon defects. Deeper understanding of how stem cells and vasculature in the healing tendon react to growth factors, common drugs used to treat injured tendons and promising cellular boosters could help to develop new and more efficient ways to manage tendon injuries.

Deletion of EP4 in S100a4-lineage cells reduces scar tissue formation during early but not later stages of tendon healing

Tendon injuries heal via scar tissue rather than regeneration. This healing response forms adhesions between the flexor tendons in the hand and surrounding tissues, resulting in impaired range of motion and hand function. Mechanistically, inflammation has been strongly linked to adhesion formation, and Prostaglandin E2 (PGE2) is associated with both adhesion formation and tendinopathy. In the present study we tested the hypothesis that deletion of the PGE2 receptor EP4 in S100a4-lineage cells would decrease adhesion formation. S100a4-Cre; EP4 ^flox/flox (EP4cKO^S100a4) repairs healed with improved gliding function at day 14, followed by impaired gliding at day 28, relative to wild type. Interestingly, EP4cKO^S100a4 resulted in only transient deletion of EP4, suggesting up-regulation of EP4 in an alternative cell population in these mice. Loss of EP4 in Scleraxis-lineage cells did not alter gliding function, suggesting that Scx-lineage cells are not the predominant EP4 expressing population. In contrast, a dramatic increase in α-SMA⁺, EP4⁺ double-positive cells were observed in EP4cKO^S100a4 suggesting that EP4cKO^S100a4 repairs heal with increased infiltration of EP4 expressing α-SMA myofibroblasts, identifying a potential mechanism of late up-regulation of EP4 and impaired gliding function in EP4cKO^S100a4 tendon repairs.

Noninsertional Achilles Tendinopathy Pathologic Background and Clinical Examination

The term tendinopathy includes a series of pathologies, all of which have a combination of pain, swelling, and impaired performance. The terms tendinosis, tendinitis and peritendinitis are all within the main heading of tendinopathy; this terminology provides a more accurate understanding of the condition and highlights the uniformity of clinical findings while distinguishing the individual histopathological findings of each condition. Understanding the clinical features and the underlying histopathology leads to a more accurate clinical diagnosis and subsequent treatment selection. Misuse of the term tendinitis can lead to the underestimation of chronic degenerative nature of many tendinopathies, affecting the treatment selection.

Achilles tendinopathy

Achilles tendinopathy is a common clinical condition. The aetiology of Achilles tendinopathy remains unclear, but is probably multifactorial resulting from a combination of intrinsic and extrinsic factors. Excessive loading of the tendon during vigorous training activities is regarded as the main pathological stimulus. The Achilles tendon may respond to repetitive overload beyond physiological threshold by either inflammation of its sheath, degeneration of its body, or a combination of both. Conservative management, including relative rest, anti-inflammatory drugs, physiotherapy and orthoses may be beneficial. Surgery is generally recommended after exhausting conservative management, usually after at least three to six months. Long-standing Achilles tendinopathy is associated with poor postoperative results, with a greater rate of reoperation before reaching an acceptable outcome.

[Surgical treatment of chronic non-insertional Achilles tendinopathy in runners using bipolar radiofrequency]

OBJECTIVE

To present the surgical technique with release of peritendon and radiofrequency as an effective treatment for athletes with chronic tendinopathy of the Achilles tendon body.

MATERIALS AND METHODS

This is a retrospective case series descriptive type study. The series consists of 17 Achilles tendon surgeries in 13 patients, who habitually run. The study included patients with non-insertional Achilles tendinopathy refractory to conservative treatments. After a minimum follow-up of 12 months, clinical improvement of the athletes was assessed using the Nirschl pain scale, as well as athletic performance.

RESULTS

An improvement was obtained in 94% of symptoms and a return to the previous performance in of 70% of cases in the 12 months follow-up.

DISCUSSION

Peritendon release combined with bipolar radiofrequency is presented as an effective solution in this condition, for which there is currently no consensus on the best treatment. In patients in whom, after an appropriate conservative treatment for a sufficient period (at least 6 months) the non-insertional Achilles tendinopathy persists, open adhesiolysis combined with bipolar radiofrequency is a safe and with a high success rate clinical and functional intervention. In high performance athletes this technique allows a return to previous activity in a high percentage of cases.

Differences between the cell populations from the peritenon and the tendon core with regard to their potential implication in tendon repair

The role of intrinsic and extrinsic healing in injured tendons is still debated. In this study, we characterized cell plasticity, proliferative capacity, and migration characteristics as proxy measures of healing potential in cells derived from the peritenon (extrinsic healing) and compared these to cells from the tendon core (intrinsic healing). Both cell populations were extracted from horse superficial digital flexor tendon and characterized for tenogenic and matrix remodeling markers as well as for rates of migration and replication. Furthermore, colony-forming unit assays, multipotency assays, and real-time quantitative polymerase chain reaction analyses of markers of osteogenic and adipogenic differentiation after culture in induction media were performed. Finally, cellular capacity for differentiation towards a myofibroblastic phenotype was assessed. Our results demonstrate that both tendon- and peritenon-derived cell populations are capable of adipogenic and osteogenic differentiation, with higher expression of progenitor cell markers in peritenon cells. Cells from the peritenon also migrated faster, replicate more quickly, and show higher differentiation potential toward a myofibroblastic phenotype when compared to cells from the tendon core. Based on these data, we suggest that cells from the peritenon have substantial potential to influence tendon-healing outcome, warranting further scrutiny of their role.

The paratendineous tissues: an anatomical study of their role in the pathogenesis of tendinopathy

The aim of this paper was to examine the macroscopic and microscopic characteristics of the paratendineous tissues (paratenon, epitenon and endotenon) of the calcaneal tendon to better understand their role in the pathogenesis of "tendinopathy". Ten non-embalmed legs from cadavers were used. Histological and immunohistochemical studies were done at the middle third of the tendon. Magnetic resonance images of the hind foot were made in 60 living subjects to analyze the morphological alterations of tendon and paratenon. The paratenon is a thick fibrous layer with few elastic fibers, continuous with the crural fascia, well vascularized and innervated. It forms a sheath around the tendon similar to a synovial layer, but less organized. Indeed, it has no complete epithelium, but only some cells producing hyaluronan, called fasciacytes. Crural fascia and paratenon can be clearly observed by MRI, appearing as homogeneous, low signal intensity bands, sharply defined in the context of subcutaneous tissue in T1-weighted sequences. The mean thickness of the crural fascia was 1.11 mm in healthy subjects and 1.30 mm in patients (p < 0.005). The mean value of paratenon thickness in patients was 1.34 mm, 0.85 in healthy (p < 0.0001). The paratenon is more highly vascularized and innervated than the tendon, supporting the hypothesis that it is the origin of pain in tendinopathy. The imaging study suggests that, an increase in the thickness of the paratenon more than 1.35 mm is predictive of paratendinopathy, even before tendon damage.

An overview of the management of flexor tendon injuries

Flexor tendon injuries still remain a challenging condition to manage to ensure optimal outcome for the patient. Since the first flexor tendon repair was described by Kirchmayr in 1917, several approaches to flexor tendon injury have enabled successful repairs rates of 70-90%. Primary surgical repair results in better functional outcome compared to secondary repair or tendon graft surgery. Flexor tendon injury repair has been extensively researched and the literature demonstrates successful repair requires minimal gapping at the repair site or interference with tendon vascularity, secure suture knots, smooth junction of tendon end and having sufficient strength for healing. However, the exact surgical approach to achieve success being currently used among surgeons is still controversial. Therefore, this review aims to discuss the results of studies demonstrating the current knowledge regarding the optimal approach for flexor tendon repair. Post-operative rehabilitation for flexor tendon surgery is another area, which has caused extensive debate in hand surgery. The trend to more active mobilisation protocols seems to be favoured but further study in this area is needed to find the protocol, which achieves function and gliding but avoids rupture of the tendons. Lastly despite success following surgery complications commonly still occur post surgery, including adhesion formation, tendon rupture and stiffness of the joints. Therefore, this review aims to discuss the appropriate management of these difficulties post surgery. New techniques in management of flexor tendon will also be discussed including external laser devices, addition of growth factors and cytokines.

Histopathology of rotator cuff tears

The pathogenesis of rotator cuff tears is multifactorial. Tendon abnormalities of the rotator cuff include alteration of collagen fiber structure, tenocytes, cellularity, and vascularity. Ruptured tendons show marked collagen degeneration and disordered arrangement of collagen fibers. Fibroblast population decreases as the size of the tear in the rotator cuff increases. The larger fibroblast population seen in the smaller tears is also actively proliferating and is part of an active reparative process. Inflammatory cell infiltrate correlates inversely to rotator cuff tear size in the torn supraspinatus tendon samples, with larger tears showing a marked reduction in all cell types. As tear size increase, there is also a progressive decrease in the number of blood vessels. Whether rotator cuff tear heals spontaneously is an important pathologic and clinical question. Histologic changes indicative of repair and inflammation lead to consider biological options in addition to biomechanical treatment of the rotator cuff tears.

Mid-portion Achilles tendinopathy: why painful? An evidence-based philosophy

Chronic mid-portion Achilles tendinopathy is generally difficult to treat as the background to the pain mechanisms has not yet been clarified. A wide range of conservative and surgical treatment options are available. Most address intratendinous degenerative changes when present, as it is believed that these changes are responsible for the symptoms. Since up to 34% of asymptomatic tendons show histopathological changes, we believe that the tendon proper is not the cause of pain in the majority of patients. Chronic painful tendons show the ingrowth of sensory and sympathetic nerves from the paratenon with release of nociceptive substances. Denervating the Achilles tendon by release of the paratenon is sufficient to cause pain relief in the majority of patients. This type of treatment has the additional advantage that it is associated with a shorter recovery time when compared with treatment options that address the tendon itself. An evidence-based philosophy on the cause of pain in chronic mid-portion Achilles tendinopathy is presented. Level of evidence V.

Achilles and patellar tendinopathy: current understanding of pathophysiology and management

PURPOSE

Achilles and patellar tendinopathy cause significant morbidity in professional and recreational athletes. Both the Achilles and patellar tendons are weight-bearing tendons that lack a true tendon sheath but are surrounded by paratenon.

METHOD

A review of the literature to outline the characteristics of tendinopathy in these two tendons, and to discuss current concepts of pathophysiology, use of imaging in the diagnosis and aid to clinical management strategies in tendinopathy.

RESULTS

Achilles and patellar tendinopathy share common histopathology such as intratendinous failed healing response and neoangiogenesis.

CONCLUSION

Achilles and patellar tendinopathy cause much morbidity in the athletic and non athletic population attending sports medicine and rheumatology clinics. Tendinopathy is essentially an 'overuse', degenerative condition. Neovascularisation evident on Doppler ultrasound correlates well with pain and poor function. Peritendinous injections and eccentric training decrease neovascularity, relieve pain and improve outcome. Although surgery is the last resort in those patients failing conservative management, it is still unclear how the removal of adhesions and excision of affected tendinopathic areas affects healing and vascularity, or resolves pain.

Basic biology of tendon injury and healing

Tendon disorders are commonly seen in clinical practice. Their successful treatment is difficult and patients often experience symptoms for prolonged periods of time. At present the aetiology of tendon disorders remains unclear, with several factors having been implicated. An improved understanding of tendon injury and healing is essential to enable focused treatment strategies to be devised.

Paratendinopathy

Because most Achilles tendon injuries take place in sports and there has been a general increase in the popularity of sporting activities, the number and incidence of Achilles tendon overuse injuries have increased in the industrialized countries during the last few decades. The term "Achilles paratendinopathy" is used in clinical practice to describe activity-related Achilles pain combined with tenderness on palpation, providing that there is no suspicion of intratendinous pathology on the basis of patient history, clinical examination, or imaging examinations. This article discusses Achilles paratendinopathy.

Tendinopathies in the upper extremity: a paradigm shift

Epicondylitis and de Quervain's tenosynovitis are two common diagnoses seen by hand therapists in clinical practice. Traditionally, these conditions have been viewed as being due to an inflammatory process and treated as such. New research shows that tendons exhibit areas of degeneration and a distinct lack of inflammatory cells. Tendinosis is degeneration of the collagen tissue due to aging, microtrauma, or vascular compromise. This article reviews key literature related to tendinopathies in the lower extremity and comments on the dearth of similar articles for the elbow and forearm. Hand therapists are encouraged to embrace this new terminology and to engage in research in this difficult area to improve treatment regimens and outcome measures.

Tendon injury and tendinopathy: healing and repair

Tendon disorders are frequent and are responsible for substantial morbidity both in sports and in the workplace. Tendinopathy, as opposed to tendinitis or tendinosis, is the best generic descriptive term for the clinical conditions in and around tendons arising from overuse. Tendinopathy is a difficult problem requiring lengthy management, and patients often respond poorly to treatment. Preexisting degeneration has been implicated as a risk factor for acute tendon rupture. Several physical modalities have been developed to treat tendinopathy. There is limited and mixed high-level evidence to support the, albeit common, clinical use of these modalities. Further research and scientific evaluation are required before biological solutions become realistic options.

Role of extracellular matrix in adaptation of tendon and skeletal muscle to mechanical loading

The extracellular matrix (ECM), and especially the connective tissue with its collagen, links tissues of the body together and plays an important role in the force transmission and tissue structure maintenance especially in tendons, ligaments, bone, and muscle. The ECM turnover is influenced by physical activity, and both collagen synthesis and degrading metalloprotease enzymes increase with mechanical loading. Both transcription and posttranslational modifications, as well as local and systemic release of growth factors, are enhanced following exercise. For tendons, metabolic activity, circulatory responses, and collagen turnover are demonstrated to be more pronounced in humans than hitherto thought. Conversely, inactivity markedly decreases collagen turnover in both tendon and muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as, dependent on the type of collagen in question, some degree of net collagen synthesis. These changes will modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress, and likely make it more load resistant. Cross-linking in connective tissue involves an intimate, enzymatical interplay between collagen synthesis and ECM proteoglycan components during growth and maturation and influences the collagen-derived functional properties of the tissue. With aging, glycation contributes to additional cross-linking which modifies tissue stiffness. Physiological signaling pathways from mechanical loading to changes in ECM most likely involve feedback signaling that results in rapid alterations in the mechanical properties of the ECM. In developing skeletal muscle, an important interplay between muscle cells and the ECM is present, and some evidence from adult human muscle suggests common signaling pathways to stimulate contractile and ECM components. Unaccostumed overloading responses suggest an important role of ECM in the adaptation of myofibrillar structures in adult muscle. Development of overuse injury in tendons involve morphological and biochemical changes including altered collagen typing and fibril size, hypervascularization zones, accumulation of nociceptive substances, and impaired collagen degradation activity. Counteracting these phenomena requires adjusted loading rather than absence of loading in the form of immobilization. Full understanding of these physiological processes will provide the physiological basis for understanding of tissue overloading and injury seen in both tendons and muscle with repetitive work and leisure time physical activity.

Systemic vanadate ingestion modulates rat tendon repair

The chronic ingestion of vanadate prevents the appearance of myofibroblasts within granulation tissue of full excision wounds in rats, yet these wounds close at an optimal rate. Myofibroblasts are reported in the repair of transected tendons. Here we investigate tendon repair in the absence of myofibroblasts. Vanadate in saline drinking water was given to rats in the experimental group, while rats in the control group received saline alone. The Achilles tendon of the left leg of each rat was transected and suture repaired. On day 10, both repaired tendons and uninjured tendons from the right leg were harvested and processed for histology. By immunohistology the repaired tendons of control rats had myofibroblasts (fibroblasts with alpha smooth muscle actin positive stress fibers), while myofibroblasts were absent in healing tendons from vanadate-treated rats. By transmission electron microscopy and polarized light optics, repaired tendons of control rats demonstrated thin, loosely packed, immature collagen fiber bundles. Collagen fiber bundles from healing tendons of the vanadate-treated group were thicker, uniformly packed, and more mature. The chronic ingestion of vanadate promotes the more rapid organization of collagen fiber bundles of healing transected tendons in the absence of myofibroblasts.

Achilles tendinopathy: some aspects of basic science and clinical management

Achilles tendinopathy is prevalent and potentially incapacitating in athletes involved in running sports. It is a degenerative, not an inflammatory, condition. Most patients respond to conservative measures if the condition is recognised early. Surgery usually involves removal of adhesions and degenerated areas and decompression of the tendon by tenotomy or measures that influence the local circulation.

Safe relief of rest pain that eases with activity in achillodynia by intrabursal or peritendinous steroid injection: the rupture rate was not increased by these steroid injections

A history of morning and rest pain that eases with activity was found to improve after anti-inflammatory injections around the paratenon or within the Achilles bursae. The reduction in pain morbidity was significant, and the peritendinous steroid injections did not increase the rupture rate.

Partial rupture in chronic achilles tendinopathy. A retrospective analysis of 342 cases

342 achilles tendons in 298 patients were operated on for painful chronic achilles tendinopathy (81% men; mean age 35 (18-82) years; 79% athletes). A partial rupture was found in 23%, tendinosis (degeneration) in 49% and no macroscopic pathology in 28% of the tendons. In partial ruptures, as compared with non-ruptured tendons, the lesion was commoner in the distal part of the tendon and more frequent in physically active men slightly below middle age who had received local steroid injections before surgery. In a logistic regression analyzing age, gender, physical activity and preoperative steroid injections, only preoperative steroid injections and male gender predicted a partial rupture.

Histopathological findings in chronic tendon disorders

Tendon injuries and other tendon disorders represent a common diagnostic and therapeutic challenge in sports medicine, resulting in chronic and long-lasting problems. Tissue degeneration is a common finding in many sports-related tendon complaints. In the great majority of spontaneous tendon ruptures, chronic degenerative changes are seen at the rupture site of the tendon (1). Systemic diseases and diseases specifically deteriorating the normal structure of the tendon (i.e. foreign bodies, and metabolic, inherited and infectious tendon diseases) are only rarely the cause of tendon pathology. Inherited diseases, such as various hereditary diseases with disturbed collagen metabolism and characteristic pathological structural alterations (Ehlers-Danlos syndrome, Marfani syndrome, homocystinuria (ochronosis)), represent approximately 1% of the causes of chronic tendon complaints (2), whereas foreign bodies are somewhat more common and are found in less than 10% of all chronic tendon problems (1). Rheumatoid arthritis and sarcoidosis are typical systemic diseases that cause chronic inflammation in tendon and peritendinous tissues. Altogether, these 'specific' disorders represented less than 2% of the pathological alterations found in the histological analysis of more than 1000 spontaneously ruptured tendons (1, 3, 4). In this material, degenerative changes were seen in a great majority of the tendons, indicating that a spontaneous tendon rupture is a typical clinical end-state manifestation of a degenerative process in the tendon tissue. The role of overuse in the pathogenesis of chronic tendon injuries and disorders is not completely understood. It has been speculated that when tendon is overused it becomes fatigued and loses its basal reparative ability, the repetitive microtraumatic processes thus overwhelming the ability of the tendon cells to repair the fiber damage. The intensive repetitive activity, which often is eccentric by nature, may lead to cumulative microtrauma which further weakens the collagen cross-linking, non-collagenous matrix, and vascular elements of the tendon. Overuse has also been speculated to cause chronic tendon problems, by disturbing the micro- and macrovasculature of the tendon and resulting in insufficiency in the local blood circulation. Decreased blood flow simultaneous with an increased activity may result in local tissue hypoxia, impaired nutrition and energy metabolism, and together these factors are likely to play an important role in the sequence of events leading to tendon degeneration (4). A sedentary lifestyle has been proposed as a main reason for poor basal circulation of the tendon, and presumably is at least partly responsible for the high number of tendon problems in people with a sedentary lifestyle who occasionally take part in high physical activity sports events.

Tendon pathology in long-standing achillodynia. Biopsy findings in 40 patients

We evaluated biopsy specimens from the Achilles tendon in 40 patients with long-standing achillodynia and an ultrasonographic widened tendon with hypoechogenic areas. We used a standardized protocol to assess the general tendon pathology score of paraffin-embedded specimens stained with HE. Stereologic measurement of the volume density of glycosaminoglycan (GAG)-rich areas, stained with the Alcian blue (pH 2.5)/periodic acid Schiff method (AB/PAS) was performed. 14 specimens obtained at autopsy served as reference material. Abnormal fiber structure and arrangement, focal variations in cellularity, rounded nuclei, decreased collagen stainability and increased non-collagenous extracellular matrix were seen in all biopsy specimens. Slight histopathological changes were noted in half of the controls. Increased vascularity was present in two thirds of the patient specimens and in one third of the controls, and signs of perivascular hemorrhage, as evidenced by hemosiderin deposition in 6/40 of the patients, but in none of the controls. The volume density of GAG-rich areas was higher in the patients 0.47 (0-0.86) than in the controls 0 (0-0.07). Changes in the fiber structure and arrangement, as well as increased amounts of interfibrillar GAG, appear to be characteristic morphological features in Achilles tendons with long-standing achillodynia and ultrasonographic widening. These findings may indicate that achillodynia is due to local disturbances in connective tissue metabolism or circulation or to both.

Lesions of the Achilles tendon. A sonographic, biomechanical and histological study

Thirty-four Achilles tendons were explanted post-mortem. The explanation took place less than 24 h after death. The tendons were examined by means of ultrasonography and after explanation assessed histologically and biomechanically. In the sonograms 19 changes in echogenicity were noted. Changes in form with an increase in the diameter of the tendon of up to 10 mm (compared with the contralateral side) were found in 6 tendons. The changes in echogenicity and form were found most frequently 2-4 cm from the insertion of the tendon at the os calcis. At a speed of 5 mm/min, the average force needed until rupture occurred was calculated as 27.6 N/mm2. The tear was located on average 29.7 mm from the bony insertion of the tendon at the calcaneus. Histologically, necroses could be found most frequently in all regions of the tendon, followed by scars and fissures. When there were differences of more than 25% in tensile strength between the right and left sides, there was a histological change in the weaker tendon at the site of the tear. Sonographic changes in form pointed to histological lesions in this region. Changes in the echogenicity led to the detection of degenerative changes of the tendon, but they have to be analysed carefully, as they are prone to artefacts. There was not statistically relevant correlation either with regard to tensile strength or to the site of the rupture for sonographically proven changes in the area of the rupture. However, when there was a sonographically abnormal finding in the course of a tendon, the tendon tore at an earlier point than those exhibiting no abnormality. Sonography proved to be a useful method in the detection of degenerative lesions of tendons. A direct influence on the biomechanics of the tendon could not be found.

Achilles tendon injuries in athletes

Two-thirds of Achilles tendon injuries in competitive athletes are paratenonitis and one-fifth are insertional complaints (bursitis and insertion tendinitis). The remaining afflictions consist of pain syndromes of the myotendineal junction and tendinopathies. The majority of Achilles tendon injuries from sport occur in males, mainly because of their higher rates of participation in sport, but also with tendinopathies a gender difference is probably indicated. Athletes in running sports have a high incidence of Achilles tendon overuse injuries. About 75% of total and the majority of partial tendon ruptures are related to sports activities usually involving abrupt repetitive jumping and sprinting movements. Mechanical factors and a sedentary lifestyle play a role in the pathology of these injuries. Achilles tendon overuse injuries occur at a higher rate in older athletes than most other typical overuse injuries. Recreational athletes with a complete Achilles tendon rupture are about 15 years younger than those with other spontaneous tendon ruptures. Following surgery, about 70 to 90% of athletes have a successful comeback after Achilles tendon injury. Surgery is required in about 25% of athletes with Achilles tendon overuse injuries and the frequency of surgery increases with patient age and duration of symptoms as well as occurrence of tendinopathic changes. However, about 20% of injured athletes require a re-operation for Achilles tendon overuse injuries, and about 3 to 5% are compelled to abandon their sports career because of these injuries. Myotendineal junction pain should be treated conservatively. Partial Achilles tendon ruptures are primarily treated conservatively, although the best treatment method of chronic partial rupture seems to be surgery. Complete Achilles tendon ruptures of athletes are treated surgically, because this increases the likelihood of athletes reaching preinjury activity levels and minimises the risk of re-ruptures. Marked forefoot varus is found in athletes with Achilles tendon overuse injuries, reflecting the predisposing role of ankle joint overpronation. Athletes with the major stress in lower extremities have often a limited range of motion in the passive dorsiflexion of the ankle joint and total subtalar joint mobility, which seems to be predisposing factor for these injuries. Various predisposing transient factors are found in about one-third of athletes with Achilles tendon overuse injuries; of these, traumatic factors (mostly minor injuries) predominate. The typical histological features of chronically inflamed paratendineal tissue of the Achilles tendon are profound proliferation of loose, immature connective tissue and marked obliterative and degenerative alterations in the blood vessels. These changes cause continuing leakage of plasma proteins, which may have an important role in the pathophysiology of these injuries. The chronically inflamed paratendineal tissues of the Achilles tendon do not seem to have enough capacity to form mature connective tissue.

Achilles tendon lesions in sport

Achillodynia (Achilles tendon pain) is a significant source of disability to many people taking part in sports. Papers in the English language published since 1986 are reviewed here, grouped into specific subject areas including biomechanics, pathology, general clinical presentations, experimental treatments, steroids, podiatry and surgery. While there has been no dramatic breakthrough in the field, there have been various interesting advances with particular reference to imaging and conservative management, which will hopefully stimulate further studies. Many problems of Achilles tendon lesions in athletes remain unsolved, however, and much is yet to be done to provide adequate and generally effective methods of prevention and conservative treatment.

Amianthoid fibres in ruptured human tendons

So-called amianthoid fibres were identified in 17 of 460 tendons (3.7%) after spontaneous rupture. These tendons belonged to 10 men and 7 women with an age-range from 18 to 67 years. In 445 postmortem control tendons taken of accidentally killed previously healthy persons amianthoid fibres were not found. Ultrastructurally the tendineal amianthoid fibres differ from normal tendon collagen fibrils in many respects. Their diameter (600-1400 nm) is many times larger than that of native collagen fibrils (20-120 nm). The fibre profile is often irregular and the cross-sectioned fibres have a homogeneous granular appearance. In longitudinal sections, the amianthoid fibres are frequently disintegrated and outspread, and some of the fibres have lost their periodicity. In addition, some of the fibres are angulated and show nonparallel organization. Occasionally the amianthoid fibres are calcified.

Lower leg overuse injuries in athletes

Achilles paratenonitis and medial tibial syndrome are the most common specific overuse injuries among athletes in Finland, and they are a problem especially in endurance sports, such as long-distance running and jogging. Conservative treatment is often successful, but if it fails operative treatment is necessary. The surgical methods developed in Finland, which are widely used in the treatment of Achilles paratenonitis and medial tibial syndrome, are presented with clinical follow-up results in this paper. The patients operated on for Achilles paratenonitis were some years older than the patients operated on for retrocalcaneal bursitis (mean 38.4 versus 32.3 years). Results after operation were excellent or good in 92.4% of 291 patients operated on for Achilles paratenonitis, 84.2% of the 63 operated on for retrocalcaneal bursitis and 79% of the 47 operated on for medial tibial syndrome. All the patients treated operatively were patients in whom conservative treatment had failed. In conclusion, operative treatment of Achilles paratenonitis or medial tibial syndrome in athletes is indicated when these complaints do not respond to any type of conservative treatment.

Range of motion, muscle torque and training habits in runners with and without Achilles tendon problems

Achilles tendon injuries are common in runners. The aim of the present study was to analyse the training programme, any Achilles tendon problems, muscle tightness and range of motion of the ankle joint, and concentric and eccentric muscle torques of the calf muscles in middle-distance runners with and without Achilles tendon problems. Eighty-three middle-distance runners answered a questionnaire on their sports background, training habits and any injuries. Thirty-four percent had suffered from some type of problem relating to the Achilles tendon. Ten of the athletes who had suffered from Achilles tendon problems and ten who had never had any Achilles tendon trouble were randomly selected. These 20 runners underwent a clinical examination. The range of motion of the ankle joint was recorded objectively by a hydraulic and computerised isokinetic dynamometer by measuring resistance to passive motion. Concentric and eccentric muscle torques of the gastrocnemius-soleus complex were recorded. The runners with Achilles tendon problems had trained for significantly more years and covered significantly longer distances per week than runners without Achilles tendon problems. There were no significant differences in other training methods or in best results over 800 m and 1500 m. Runners with Achilles tendon problems had a significantly lower range of motion of the ankle joint. They also had significantly lower eccentric torques of the gastrocnemius-soleus complex, but no differences in concentric torques were found between the groups.

Achilles tendinitis

Achilles tendinitis is a problem encountered frequently. There are certain anatomical and biomechanical principles that help explain the etiology of this entity. We prefer to separate our thinking into "insertional" and "noninsertional" Achilles tendinitis. This is helpful because it allows nonoperative and operative treatment to be problem specific and systematic.

Chronic achilles peritendinitis: etiology, pathophysiology, and treatment

Overuse injuries represent a significant percentage of injuries seen in a sports medicine setting. Sports medicine health professionals evaluate and treat patients with the overuse injury of chronic Achilles peritendinitis. This paper reviews the anatomy of the Achilles tendon and presents recent literature concerning the etiology, pathophysiology, and rehabilitation of chronic Achilles peritendinitis. A rehabilitation program is outlined addressing the specific demands of the chronically injured Achilles tendon. J Orthop Sports Phys Ther 1991;13(4):171-176.

Chronic achilles paratenonitis. An immunohistologic study of fibronectin and fibrinogen

Pathological alterations in chronic Achilles paratenonitis were studied histologically and using immunofluorescence techniques for fibronectin and fibrinogen in tissue samples obtained operatively from 11 athletes with this complaint and from 4 male cadavers serving as controls. The average duration of the paratenonitis was 20.4 months. The paratendineal fatty areolar tissue was clearly thickened and edematous, showing widespread fat necrosis and considerable connective tissue proliferation. The blood vessels were often obliterated and degenerated. Fibronectin and fibrinogen were commonly found in the proliferating connective tissue areas and in the vascular walls. Exudates rich in fibrinogen and fibronectin were seen in the inflamed paratendineal tissues, but not in the controls. The results indicate that increased vascular permeability and fibrin formation still persist in chronic Achilles paratenonitis and that marked obliterative and degenerative alterations of the blood vessels are frequent. The presence of fibronectin and fibrinogen points to an immature nature of scar tissue in chronic paratenonitis.

Chronic Achilles paratenonitis in athletes: a histological and histochemical study

Pathological alterations of chronic Achilles paratenonitis were studied histologically and histochemically in tissue samples obtained operatively from 16 athletes with this complaint and from 3 control patients. The activities of 11 different enzymes--lactate, succinate, malate, glucose-6-phosphate and glutamate dehydrogenases, lipoamide dehydrogenase and glutathione reductase (NADH2- and NADPH2-diaphorases), acid and alkaline phosphatases, phosphorylase and leucylaminopeptidase--were studied. Pathological findings were located diffusely around the tendon. A slight inflammatory cell reaction was found in all cases. The fatty areolar tissue was clearly thickened and edematous, and showed fibrinous exudations, widespread fat necrosis, considerable connective tissue proliferation and adhesion formation. The blood vessels showed profound degenerative and necrotizing changes. The thin membranes of the paratenon were clearly hypertrophied. Increased enzyme activities were mainly found in the fibroblasts, inflammatory cells and vascular walls. A moderate activity of lysosomal enzymes, an increased activity of enzymes of electron transport, anaerobic glycolysis, pentose phosphate shunt and decreased activity of those of aerobic energy metabolism were found. Simultaneously an increased amount of both neutral and acid mucopolysaccharides and a locally increased amount of elastic fibres were found in the inflamed paratenon. These results indicate that marked metabolic changes occur in paratenonitis, i.e. an increased catabolism and decreased oxygenation of the inflamed areas. The morphological alterations suggest that the gliding function of the paratenon may be impaired.