Amorphous calcium phosphate nanoparticles using adenosine triphosphate as an organic phosphorus source for promoting tendon-bone healing.

BACKGROUND: Rotator cuff tear (RCT) is a common problem of the musculoskeletal system. With the advantage of promoting bone formation, calcium phosphate materials have been widely used to augment tendon-bone healing. However, only enhancing bone regeneration may be not enough for improving tendon-bone healing. Angiogenesis is another fundamental factor required for tendon-bone healing. Therefore, it's necessary to develop a convenient and reliable method to promote osteogenesis and angiogenesis simultaneously, thereby effectively promoting tendon-bone healing. METHODS: The amorphous calcium phosphate (ACP) nanoparticles with dual biological activities of osteogenesis and angiogenesis were prepared by a simple low-temperature aqueous solution method using adenosine triphosphate (ATP) as an organic phosphorus source. The activities of osteogenesis and angiogenesis and the effect on the tendon-bone healing of ACP nanoparticles were tested in vitro and in a rat model of acute RCT. RESULTS: The ACP nanoparticles with a diameter of tens of nanometers were rich in bioactive adenosine. In vitro, we confirmed that ACP nanoparticles could enhance osteogenesis and angiogenesis. In vivo, radiological and histological evaluations demonstrated that ACP nanoparticles could enhance bone and blood vessels formation at the tendon-bone junction. Biomechanical testing showed that ACP nanoparticles improved the biomechanical strength of the tendon-bone junction and ultimately promoted tendon-bone healing of rotator cuff. CONCLUSIONS: We successfully confirmed that ACP nanoparticles could promote tendon-bone healing. ACP nanoparticles are a promising biological nanomaterial in augmenting tendon-bone healing.

Microcirculatory Responses to Muscle and Tendon Exercises in Individuals With and Without Type 2 Diabetes Mellitus and the Association Between Microcirculatory and Exercise Performance.

Background: This study aimed to measure and compare (1) the microcirculation and microcirculatory responses of the muscles and tendons at rest and during isometric muscle contractions in participants with and without diabetes mellitus (DM) and (2) to determine correlations between microcirculation and muscle strength. Methods: Sixty-three participants with type 2 DM and 42 physically matched controls were recruited. Baseline measurements of the microcirculation of the rectus femoris (RF) and medial gastrocnemius (MG) muscles and patellar (PT) and Achilles tendons (AT), as well as their microcirculatory changes during maximal isometric exercises, were performed and recorded by using near-infrared spectroscopy and a red laser. Data on various laboratory tests (including glycated hemoglobin, triglyceride, high-density cholesterol), the monofilament test, and the ankle-brachial index were also obtained. Results: The baseline measurements indicated that, compared with the controls, the diabetic participants had lower oxygen saturation (SpO2) in their RF and MG muscles (both P < 0.001), and the total hemoglobin in the diabetic PT and AT was higher (P = 0.001 and P = 0.01). The minimal SpO2 levels in the aforementioned muscles during isometric contractions were lower in the diabetes group than in the control group (P ≤ 0.001). Furthermore, there were correlations between the microcirculatory change of the RF muscle and the knee extension force. Conclusions: This study demonstrated the effects of diabetes on the microcirculation of skeletal muscles and tendons during baseline measurements and responses to maximal isometric exercises. The results support the need for preventive strategies for diabetic muscles to prevent adverse complications when performing resistance training.

Musculoskeletal ultrasound assessment in pediatric knee hypermobility: a case control study.

BACKGROUND: While musculoskeletal ultrasound (MSUS) use in pediatric rheumatology is becoming more common, the majority of pediatric MSUS literature continues to focus on ultrasound findings in healthy children and juvenile idiopathic arthritis with little discussion of other musculoskeletal problems that may mimic arthritis such as joint hypermobility. Chronic joint pain related to hypermobility is a common referral to pediatric rheumatology clinics. Our aim is to describe the musculoskeletal ultrasound (MSUS) characteristics of the knee in a population with joint hypermobility and pain in comparison to control participants. METHODS: Participants were recruited into three groups for a case-control study. Case group participants had knee hypermobility and pain symptoms (H + P). Participants in one control group had knee hypermobility without pain symptoms (H-P), and participants in the other control group had no knee hypermobility or pain symptoms (NP). B-mode and Doppler MSUS images were obtained and scored for each knee. Descriptive statistics are used for demographic variables and MSUS findings. Regression analysis is used to evaluate risk of synovial effusion and higher synovial effusion/hypertrophy quantitative score. RESULTS: MSUS assessment was performed on 91 knees of 50 participants. H + P knees were more likely to have positive findings noted on MSUS (94% vs. 70% of H-P and 74% of NP knees, p = 0.043). Patellar tendon hyperemia was more common in H + P knees (52%, vs. 19% among H-P and 23% among NP, p = 0.025). Participants who reported taking scheduled non-steroidal anti-inflammatory drugs (NSAIDs) had an increased risk of synovial effusion (RR = 1.83, 95% CI = 1.07-2.30, p = 0.026) and a trend towards increased risk of a higher synovial effusion/hypertrophy quantitative score (RR = 1.77, 95% CI = 0.92-3.38, p = 0.086). CONCLUSIONS: While positive MSUS findings were frequent in all participants, patellar tendon hyperemia was more frequent in participants with knee hypermobility and pain symptoms. Additionally, reported use of NSAIDs was associated with an increased risk of synovial effusion and higher synovial effusion/hypertrophy quantitative score. Further study should assess correlation between tendon abnormalities and degree of pain symptoms as well as the effect of NSAIDs on MSUS findings.

Flexor Tendon Injury and Repair. The Influence of Synovial Environment on the Early Healing Response in a Canine Model.

BACKGROUND: Environmental conditions strongly influence the healing capacity of connective tissues. Well-vascularized extrasynovial tendons typically undergo a robust wound-healing process following transection and repair. In contrast, avascular intrasynovial tendons do not mount an effective repair response. The current study tests the hypothesis that flexor tendons, as a function of their synovial environment, exhibit unique inflammatory, angiogenic, and metabolic responses to injury and repair. METHODS: Flexor tendons present a distinct opportunity to test the study hypothesis, as they have proximal regions that are extrasynovial and distal regions that are intrasynovial. In an internally controlled study design, the second and fifth forepaw flexor tendons were transected and repaired in either the extrasynovial or the intrasynovial anatomical region. Histological, gene expression, and proteomics analyses were performed at 3 and 7 days to define the early biological events that drive synovial environment-dependent healing responses. RESULTS: Uninjured intrasynovial tendons were avascular, contained high levels of proteoglycans, and expressed inflammatory factors, complement proteins, and glycolytic enzymes. In contrast, extrasynovial tendons were well vascularized, contained low levels of proteoglycans, and were enriched in inflammation inhibitors and oxidative phosphorylation enzymes. The response to injury and repair was markedly different between the 2 tendon regions. Extrasynovial tendons displayed a robust and rapid neovascularization response, increased expression levels of complement proteins, and an acute shift in metabolism to glycolysis, whereas intrasynovial tendons showed minimal vascularity and muted inflammatory and metabolic responses. CONCLUSIONS: The regional molecular profiles of intact and healing flexor tendons revealed extensive early differences in innate immune response, metabolism, vascularization, and expression of extracellular matrix as a function of the synovial environment. These differences reveal mechanisms through which extrasynovial tendons heal more effectively than do intrasynovial tendons. CLINICAL RELEVANCE: To improve outcomes after operative repair, future treatment strategies should promote features of extrasynovial healing, such as enhanced vascularization and modulation of the complement system and/or glucose metabolism.

The vascularization of the peroneal tendons: An anatomic study.

BACKGROUND: Arterial vascularization is intimately related to the peroneal tendon ruptures. Our purpose is to describe the vascular anatomy of peroneal tendons and assess differences in the vascularization patterns between peroneus brevis tendon (PBT) and peroneus longus tendon (PLT). METHODS: Anatomical study of 22 cadaveric lower extremities. We exposed tendons' vascularization by injecting latex. To systematize the vascular description, we considered four anatomical regions in the PBT and six in the PLT. RESULTS: Vascularization was supplied by the peroneal, anterior tibial and lateral plantar arteries and from the deep plantar arch through the vincula connecting the tendons. No avascular areas were found in the PLT. 22.7% of specimens had avascular areas in the PBT. Two visual vascularization patterns were found (arcuate and weblike). Increasing age and a web-like vascularization were associated with a lower number of blood vessels at the tendons' post malleolus area. CONCLUSION: Peroneal tendons are well vascularized throughout their course, running through a common vincula, with vascularization provided by various arteries. Avascular areas were observed in the PBT, but none at the PLT.

Effects of type II SLAP lesion repair techniques on the vascular supply of the long head of the biceps tendon: a cadaveric injection study.

BACKGROUND: One option for the treatment of type 2 superior labral anterior to posterior (SLAP) lesions is arthroscopic repair. However, the fact that the vascular supply of the proximal long head of the biceps tendon (LHBT) arises from the soft tissue near the SLAP repair site must also be considered. The aims of this study were to evaluate the vascular channel of the proximal long head biceps tendon and to compare potential damage to the vascular supply with alternative SLAP techniques. METHODS: Forty-five fresh cadaveric shoulders were divided into 3 groups: 9 shoulders each for the normal group and the created SLAP group, and 27 shoulders for the repaired SLAP group. SLAP group shoulders were repaired using one of 3 techniques: 2 anchors with simple sutures, 1 anchor with double sutures, or 1 anchor with a horizontal mattress suture. India ink was then injected into the acromial branch of the thoracoacromial artery. The proximal LHBT was resected for a histologic cross-sectional study. The intratendinous vascular distance was measured and compared among the groups. RESULTS: The vascular supply of the proximal LHBT arises from soft tissue lying anterior and dorsal to the tendon origin. In the normal shoulders, the average intratendinous vascular distance was 16.9 ± 1.5 mm (95% confidence interval: 15.8-18.1). A comparison of nonrepaired SLAPs with each of the repair techniques found that using 2 anchors with simple sutures showed no significant difference in vascular distance (P = .716), whereas the other techniques showed a significant disruption of the blood supply. The differences in vascular distance among the 3 repair techniques were statistically significant (P = .0001). CONCLUSIONS: The main vascular supply of the proximal LHBT comes from the anterior-dorsal direction. Some SLAP repair techniques can disrupt vascularization; however, the technique using 2 anchors with simple sutures, 1 anchor 3 mm anterior to the anterior border and 1 at the posterior border of the tendon, can preserve the vascularization of the LHBT.

A pilot study of blood supply of the coracoid process and the coracoid bone graft after Latarjet osteotomy.

Latarjet osteotomy is still one of the most reliable and commonly used surgeries in treating recurrent anterior shoulder dislocation. The coracoid process (CP) is the main structure of this surgery. However, the blood supply of CP is not fully understood, and the extent of destruction of blood supply of coracoid bone graft after Latarjet osteotomy procedure is still controversial. Five embalmed cadaveric upper limbs specimens were employed for macro observation of the blood supply of CP. The conjoint tendon (CT) and CP interface were dissected for histology. Sixteen fresh frozen shoulder specimens were used for perfusion and micro CT scanning. Eight specimens were used to present the whole vessel structure of CP. The other eight underwent Latarjet osteotomy procedure. The coracoid bone grafts in both groups were scanned to clarify the remnant blood supply. It was found that the CP was nourished by supra-scapular artery (SSA), thoracic-acromial artery and branch from second portion of the axillary artery (AA). After Latarjet osteotomy procedure, no artery from CT was detected to penetrate the CP at its attachment. Only in one specimen the blood vessel that originated from the CT penetrated the bone graft at the inferior side. Therefore, most of the blood supply was destroyed although there is a subtle possibility that the vessels derived from the CT nourished the inferior side of the CP. In a nutshell, CP is a structure with rich blood supply. The traditional Latarjet osteotomy procedure would inevitably cut off the blood supply of the coracoid bone graft.

Correlation between Hypervascularization of the First Annular Pulley on Color Doppler Imaging of Trigger Finger and Patients' Backgrounds.

OBJECTIVES: The aim of this study was to investigate the correlation between hypervascularization of the first annular (A1) pulley on color Doppler imaging of trigger finger and patients' backgrounds. METHODS: A total of 148 trigger digits from 144 patients were studied with ultrasound at the time of initial diagnosis. We observed the A1 pulley at the level of the metacarpophalangeal joint in a transverse image and noted the presence or absence of a signal in the A1 pulley on color Doppler imaging. Patients' ages, sexes, clinical grades, symptom durations, prevalence of interphalangeal joint contracture, and visual analog scale pain scores were compared between the groups with positive and negative Doppler findings. RESULTS: The 144 patients included 45 men and 99 women. Sixty-one of 148 digits (41%) showed positive Doppler findings in the A1 pulley. Patients' ages and visual analog scale scores in the Doppler-positive group were slightly greater than those in the Doppler-negative group (P = .03; P < .01, respectively). The digit with positive Doppler findings tended to be categorized into a severer grade and into the group with a shorter symptom duration (P < .01 for both). CONCLUSIONS: Hypervascularization of the A1 pulley tended to appear in an earlier period after the patients had become aware of symptoms, as frequently as their symptoms became severe, in conjunction with higher pain scores. Doppler imaging of the A1 pulley might help in better understanding patients' conditions.

The Potential Roles of Tendon Stem/Progenitor Cells in Tendon Aging.

Aging is a key dangerous factor for the occurrence and severity of tendon injury, but the exact cognition of the relationship is elusive at present. More previous studies suggest age-related changes occur at tendon mechanical properties, structure and composition, but the pathological alternations may be overlooked, which might be a cause for the structure and function variations, and even speed up the progress of age-related disorders. Recently, the presence of tendon stem/progenitor cells (TSPCs) would provide new insights for the pathogenesis of tendon aging. In this review, the tendon mechanical properties, structure and composition are presented in brief, then, the pathological changes of the aging tendon are described firstly, and the latest researches on alterations of TSPCs in the pathogenesis of tendon aging have also been analyzed. At a cellular level, the hypothetical model of altered TSPCs fate for tendon aging is also proposed. Moreover, the regulation of TSPCs as a potential way of the therapies for age-related tendon diseases is discussed. Therefore, reversing the impaired function of TSPCs and promoting the tenogenic differentiation of TSPCs could become hot spots for further study and give the opportunity to establish new treatment strategies for age-related tendon injuries.

Relationship between ultrasound detected tendon abnormalities, and sensory and clinical characteristics in people with chronic lateral epicondylalgia.

OBJECTIVE: To investigate the relationship between tendon structural changes determined by static ultrasound images (US) and sensory changes using quantitative sensory testing (QST), and clinical measures in lateral epicondylalgia. MATERIALS AND METHODS: Both elbows of 66 adult participants with a clinical diagnosis of lateral epicondylalgia were investigated. Using a standardised ultrasound image rating scale, common extensor hypoechogenicity, heterogenicity, neovascularity, and bony abnormalities at the enthesis were scored, and tendon thickness (longitudinal and transverse plane) was measured by a trained assessor. Sensory measures of pressure, heat and cold pain thresholds and vibration detection threshold were recorded. Pain and function were assessed using the patient-rated tennis elbow (PRTEE), pain-free grip strength, pain visual analog scale (PVAS) and quality of life (EuroQoL EQ -5D). Univariate and multivariate linear regression analyses were used to explore the association between tendon structural, sensory and clinical variables which were adjusted for age, gender and duration of symptoms. RESULTS: A negative correlation was identified between the presence of neovascularity and cold pain threshold (P = 0.015). Multiple regression analyses revealed that a combination of female gender (P = 0.044) and transverse tendon thickness (P = 0.010) were significantly associated with vibration detection threshold in affected elbows, while gender (P = 0.012) and total ultrasound scale score (P = 0.024) were significantly associated with heat pain threshold and vibration detection threshold in unaffected elbows. Heat pain threshold and gender were significantly associated with pain and disability (PRTEE; P < 0.001), and pain-free grip strength (P < 0.001) respectively, in the affected elbows. CONCLUSION: Generally, structural and sensory measures were weakly correlated. However, neovascularity and transverse tendon thickness may be related to sensory system changes in LE.

Anatomic Limitations of the Transmetatarsal Amputation With Consideration of the Deep Plantar Perforating Branch of the Dorsalis Pedis Artery.

The transmetatarsal amputation is considered a durable procedure with respect to limb salvage when managing the consequences of diabetic foot disease. The success of the procedure is, in part, determined by the preoperative appreciation of arterial and functional status. The objectives of the present investigation were to determine the length of the remaining first metatarsal required during transmetatarsal amputation to preserve the anastomotic connection of the deep plantar perforating artery and subsequent "vascular arch" of the foot and the insertion of the tibialis anterior tendon. The primary outcome measure of our investigation was a measurement of the distance between the first metatarsal-medial cuneiform articulation and the distal extent of the deep plantar perforating artery in 85 embalmed lower limbs. As a secondary outcome measure, the insertion of the tibialis anterior tendon was evaluated relative to the deep plantar perforating artery. The most distal extent of the deep plantar perforating artery was observed at a mean ± standard deviation of 15.62 ± 3.74 (range 6.0 to 28.28) mm from the first metatarsal-medial cuneiform articulation. Most (89.41%) of the arteries were found within 20 mm of the first metatarsal-medial cuneiform articulation. The insertion of the tibialis anterior tendon was found to be proximal to the deep plantar perforating artery in all specimens (100.0%). In conclusion, 2.0 cm of remnant first metatarsal might represent an anatomic definition of how "short" a transmetatarsal amputation can safely be performed in most patients when considering the vascular and biomechanical anatomy.

Peroneal perforator-based peroneus longus tendon and sural neurofasciocutaneous composite flap transfer for a large soft-tissue defect of the forearm: A case report.

We describe the use of a composite flap composed of a sural neurofasciocutaneous flap and a vascularized peroneus longus tendon for the reconstruction of severe composite forearm tissue defects in a patient. A 43-year-old man had his left arm caught in a conveyor belt resulting in a large soft-tissue defect of 18 × 11 cm over the dorsum forearm. The extensor carpi radialis, superficial radial nerve, and radial artery were severely damaged. A free neurofasciocutaneous composite flap measuring 16 × 11 cm was outlined on the patient's left lower leg to allow simultaneous skin, tendon, nerve, and artery reconstruction. The flap, which included the peroneus longus tendon, was elevated on the subfascial plane. After the flap was transferred to the recipient site, the peroneal artery was anastomosed to the radial artery in a flow-through manner. The vascularized tendon graft with 15 cm in length was used to reconstruct the extensor carpi radialis longus tendon defect using an interlacing suture technique. As the skin paddle of the sural neurofasciocutaneous flap and the vascularized peroneus longus tendon graft were linked by the perforator and minimal fascial tissue, the skin paddle was able to rotate and slide with comparative ease. The flap survived completely without any complications. The length of follow-up was 12 months and was uneventful. Range of motion of his left wrist joint was slightly limited to 75 degrees. This novel composite flap may be useful for reconstructing long tendon defects associated with extensive forearm soft tissue defects.

Biomechanical Analysis of Bilateral Facet Joint Stabilization Using Bioderived Tendon for Posterior Cervical Spine Motion Reservation in Goats.

OBJECTIVES: To investigate the biomechanical properties of a novel stabilization method for posterior cervical motion preservation using bioderived freeze-dried tendon. METHODS: Experiments were conducted both in vitro and in vivo. For the in vitro group, 15 fresh-frozen goat spines (C1-C7) were randomly divided into 3 subgroups: intact (INT-vitro, n = 5), injury model (IM-vitro, n = 5), and bilateral facet joint stabilization (BFJS-vitro, n = 5) subgroups. For the in vivo group, 15 adult goats were randomly divided into 3 experimental subgroups: INT-vivo subgroup (n = 5), IM-vivo subgroup (n = 5), and BFJS-vivo subgroup (n = 5). Goats in the in vivo group were euthanized 12 weeks after surgery. Biomechanical tests were performed to evaluate range of motion. Histologic analysis was conducted to evaluate survival and reactions associated with the bioderived tendon. RESULTS: Compared with the INT-vitro and INT-vivo subgroups, the flexion of IM-vitro and IM-vivo subgroups increased significantly, respectively (P < 0.05). The flexion of the BFJS-vitro and BFJS-vivo subgroups was significantly smaller than in the IM-vitro and IM-vivo subgroups, respectively (P < 0.05). Significant differences between the BFJS-vitro and BFJS-vivo subgroups were observed in flexion, lateral bending, and rotation (P < 0.05). Histologic evaluation demonstrated that fibers arranged regularly and stained homogeneously. New vessels in growth indicated that the bioderived tendon was survival and processed good regeneration. CONCLUSIONS: Bilateral facet joint stabilization can significantly limit excessive flexion motion and maintain adequate stability. Furthermore, the preservation of extension motions without limiting lateral bending and rotation ideally simulates the features of the posterior ligamentous complex. This preserves the dynamic stability of the lower cervical spine.

Anatomy, pathophysiology and classification of posterior tibial tendon dysfunction.

OBJECTIVE: Adult acquired flatfoot deformity is generally associated with a collapsing medial longitudinal arch and a progressive loss of strength of the posterior tibial tendon (PTT). This condition is commonly associated with PTT dysfunction or rupture, which can have an arthritic or a traumatic etiology. Several causes have been proposed to explain the clinical evidence of tendon degeneration observed at the time of surgery including trauma, anatomical, mechanical, inflammatory and ischemic factors. MATERIALS AND METHODS: In this review, we analyzed anatomy, pathophysiology and existing classifications of posterior tibial tendon dysfunction. RESULTS: Anatomical features, and in particular vascularization, expose PTT to major degenerative disorders until rupture. A literature overview showed that a low blood supply of the gliding part of the tendon is linked to a dysfunction and/or a rupture of the PTT in the region located behind the medial malleolus. CONCLUSIONS: PTT low blood supply causes a dysfunction resulting in an abnormal loading of the foot's medial structures. This may be the reason why PTT dysfunction leads to an acquired flatfoot deformity. Conversely, flatfoot deformity may be a predisposing factor for the onset of PTT dysfunction.

Progression of degenerative changes of the biceps tendon after successful rotator cuff repair.

BACKGROUND: This study investigated the morphologic changes in the biceps tendon using ultrasonography before and after successful arthroscopic posterosuperior rotator cuff repair. METHODS: Forty-four patients (44 shoulders) underwent arthroscopic posterosuperior rotator cuff repair with 1-year postoperative magnetic resonance imaging (MRI) follow-up. The patients comprised 22 men and 22 women with an average age of 61 years. The cross-sectional area (CSA) of the biceps tendon in the bicipital groove was measured, and the vascularity in the bicipital groove was graded as 0 to 3, based on the signal density of the anterior circumflex artery, using power Doppler ultrasonography. The preoperative and postoperative CSA and vascularity grades were compared. The pain score on the University of California, Los Angeles Shoulder Rating Scale was used to analyze the correlation between vascularity and postoperative pain. RESULTS: The average preoperative and postoperative CSA of the biceps tendon was 15.4 ± 6.5 and 17.9 ± 7.5 mm2, respectively. The postoperative CSA was significantly larger than the preoperative CSA (P < .01). Although no significant difference in the vascularity of the bicipital groove was observed between preoperative and postoperative grading, a negative correlation was observed between the vascularity and postoperative pain score on the University of California, Los Angeles scale (r = -0.369). CONCLUSIONS: The biceps tendon in the bicipital groove becomes thicker over time, even after successful posterosuperior rotator cuff repair. In addition, an increase in the vascularity around the biceps tendon in the groove is correlated with pain symptoms after successful repair.

Management of Open Distal Lower Extremity Wounds With Exposed Tendons Using Porcine Urinary Bladder Matrix.

Open wounds of the distal third of the leg and foot with an exposed tendon present a challenge in wound management and in attaining stable, durable coverage. The mobility of the tendon often leads to chronic inflammation that impedes wound closure, while the desiccation of the exposed tendon leads to progressive tendon necrosis. For the authors' cases, the ability of extracellular matrix (ECM) products to modulate wound bed inflammation and facilitate constructive remodeling of a wound seemed a reasonable approach in treating these wounds, especially in patients who are often poor surgical candidates for more advanced reconstructive procedures. METHODS: The authors reviewed 13 patients who had open wounds of the distal third of the leg and/or foot that had associated tendon involvement in the wound (Achilles, 6; tibialis anterior, 6; and peroneal, 1). Patients' wounds were treated to total closure. The clinical course and patient management is reviewed herein. RESULTS: The authors found newer ECM products can provide a more optimal method of management of patients with exposed tendons, as compared to prolonged negative pressure wound therapy. CONCLUSION: Furthermore, the authors conclude the use of newer ECM products yields a more stable, less scarred, reconstructed wound that more closely resembles normal foot and ankle appearance compared to other more complex reconstructive operative procedures.

Low Concentration of Sodium Butyrate from Ultrabraid+NaBu suture, Promotes Angiogenesis and Tissue Remodelling in Tendon-bones Injury.

Sodium butyrate (NaBu), a form of short-chain fatty acid (SCFA), acts classically as a potent anti-angiogenic agent in tumour angiogenesis models, some authors demonstrated that low concentrations of NaBu may contribute to healing of tendon-bone injury in part at least through promotion of tissue remodelling. Here, we investigated the effects of low-range concentrations of NaBu using in vitro and in vivo assays using angiogenesis as the primary outcome measure and the mechanisms through which it acts. We demonstrated that NaBu, alone or perfused from the UltraBraid+NaBu suture was pro-angiogenic at very low-range doses promoting migration, tube formation and cell invasion in bovine aortic endothelial cells (BAECs). Furthermore, cell exposure to low NaBu concentrations increased expression of proteins involved in angiogenic cell signalling, including p-PKCß1, p-FAK, p-ERK1/2, p-NFκß, p-PLCγ1 and p-VEGFR2. In addition, inhibitors of both VEGFR2 and PKCß1 blocked the angiogenic response. In in vivo assays, low concentrations of NaBu induced neovascularization in sponge implants in mice, evidenced by increased numbers of vessels and haemoglobin content in these implants. The findings in this study indicate that low concentrations of NaBu could be an important compound to stimulate angiogenesis at a site where vasculature is deficient and healing is compromised.

Revascularisation pattern of ruptured flexor tendon grafts in anterior cruciate ligament reconstruction: A histological study. / Patrón de revascularización de injertos de tendones flexores rotos en reconstrucción de ligamento cruzado anterior: un estudio histológico.

INTRODUCTION: For successful anterior cruciate ligament (ACL) reconstruction, revascularisation and histological maturation are necessary, as their failure can cause graft rupture. PURPOSE: The purpose of this study was to describe differences in the histological maturation of early failed plasty (less than 12 months after surgery) and late failed plasty (more than 12 months after surgery) in patients with re-rupture after ACL reconstruction with hamstring tendons. MATERIAL AND METHODS: A descriptive observational study was conducted on a consecutive series of 20 patients whose ACL reconstruction had failed. Graft biopsy samples were obtained during the revision surgery from the proximal, medial, and distal graft remnants. The samples were evaluated by light microscopy, and the vascularity and maturation of the samples were established by histological scoring. RESULTS: The most common aetiology of reconstruction failure (86.6%) was a specific event with non-contact mechanism. The patients with re-rupture of their ACL plasty less than 12 months after surgery had substance vessels that were less deep. The distal segment of the graft in those patients showed a delay in histological maturation with fewer collagen fibres. CONCLUSION: In patients whose ACL grafts failed less than 12 months after surgery, a lower distribution of blood vessels and collagen fibres was found that were less ordered in the distal graft. These results indicate a delay in maturation, which leads to a higher risk of graft failure.

Blood Supply.

It has been suggested that blood circulation within the tendons contributes to repair of the tendon after the exercises. Recently, blood circulation of human tendons could be measured using red laser lights (Kubo et al. 2008b). Using this technique, we were able to measure changes in blood volume and oxygen saturation of human tendons by various treatments. During a 60-min heating, the blood volume and oxygen saturation of the tendon increased significantly from the resting level, and continued to increase by 35 min. These changes in blood circulation of tendon were considerably different from the temperatures of muscle and skin. Furthermore, when the needle tip was moved up and down from the targeted depth (up-and-down manipulation) at approximately 1 mm amplitude, the blood volume and oxygen saturation of the treated tendon increased significantly. After the removal of the acupuncture needle, the blood volume and oxygen saturation of the tendon increased gradually for the non-treated side. These results suggested that the change in blood circulation of the tendon during acupuncture with up-and-down manipulation was caused by axon reflex, and increase in blood flow in the tendons after the needle removal might be caused through the central nervous system. It is well known that heating and acupuncture treatments were quite effective in the management of tendon injuries. Therefore, these phenomena would be related to the changes in blood circulation of tendons due to heating and acupuncture treatments.

The blood-tendon barrier: identification and characterisation of a novel tissue barrier in tendon blood vessels.

Tissue barriers function as "gate keepers" between different compartments (usually blood and tissue) and are formed by specialised membrane-associated proteins, localising to the apicolateral plasma membrane domain of epithelial and endothelial cells. By sealing the paracellular space, the free diffusion of solutes and molecules across epithelia and endothelia is impeded. Thereby, tissue barriers contribute to the establishment and maintenance of a distinct internal and external environment, which is crucial during organ development and allows maintenance of an organ-specific homeostatic milieu. So far, various epithelial and endothelial tissue barriers have been described, including the blood-brain barrier, the blood-retina barrier, the blood-testis barrier, the blood-placenta barrier, and the cerebrospinal fluid (CSF)-brain barrier, which are vital for physiological function and any disturbance of these barriers can result in severe organ damage or even death. Here, we describe the identification of a novel barrier, located in the vascular bed of tendons, which we term the blood-tendon barrier (BTB). By using immunohistochemistry, transmission electron microscopy, and tracer studies we demonstrate the presence of a functional endothelial barrier within tendons restricting the passage of large blood-borne molecules into the surrounding tendon tissue. We further provide in vitro evidence that the BTB potentially contributes to the creation of a distinct internal tissue environment impacting upon the proliferation and differentiation of tendon-resident cells, effects which might be fundamental for the onset of tendon pathologies.