eEF2 improves dense connective tissue repair and healing outcome by regulating cellular death, autophagy, apoptosis, proliferation and migration.

Outcomes following human dense connective tissue (DCT) repair are often variable and suboptimal, resulting in compromised function and development of chronic painful degenerative diseases. Moreover, biomarkers and mechanisms that guide good clinical outcomes after DCT injuries are mostly unknown. Here, we characterize the proteomic landscape of DCT repair following human Achilles tendon rupture and its association with long-term patient-reported outcomes. Moreover, the potential regulatory mechanisms of relevant biomarkers were assessed partly by gene silencing experiments. A mass-spectrometry based proteomic approach quantified a large number (769) of proteins, including 51 differentially expressed proteins among 20 good versus 20 poor outcome patients. A novel biomarker, elongation factor-2 (eEF2) was identified as being strongly prognostic of the 1-year clinical outcome. Further bioinformatic and experimental investigation revealed that eEF2 positively regulated autophagy, cell proliferation and migration, as well as reduced cell death and apoptosis, leading to improved DCT repair and outcomes. Findings of eEF2 as novel prognostic biomarker could pave the way for new targeted treatments to improve healing outcomes after DCT injuries.Trial registration: NCT02318472 registered 17 December 2014 and NCT01317160 registered 17 March 2011, with URL http://clinicaltrials.gov/ct2/show/NCT02318472 and http://clinicaltrials.gov/ct2/show/study/NCT01317160 .

Long-term patient outcome is affected by deep venous thrombosis after Achilles tendon rupture repair.

PURPOSE: The aim of the study was to examine the impact of a deep venous thrombosis (DVT) on patient outcomes 3 years after Achilles tendon rupture (ATR) repair and if there were continued improvements between 1 and 3 years after surgery. A secondary aim was to determine risk factors associated with impaired patient outcomes in the long term. METHODS: This cohort study consisted of 181 ATR-repaired patients, from two large randomized clinical trials, who attended a 3-year follow-up evaluation. Patients were postoperatively randomized to two different weight-bearing interventions compared with immobilization in a below-knee plaster cast for 2 weeks. During immobilization, screening for DVT was performed with Doppler ultrasound. At 1 and 3 years postoperatively, functional- and patient-reported outcomes were evaluated by the validated heel-rise test and self-reported questionnaire, Achilles tendon Total Rupture Score (ATRS). RESULTS: In total, 76 out of 181 (42%) patients exhibited a DVT at the 2- or 6-week screening after ATR surgery. Suffering from a DVT during immobilization resulted at 3 years in a worse limb symmetry index (LSI) of heel-rise total work compared to patients without DVT, adjusted for age (DVT mean LSI 68% vs. no DVT 78%, p = 0.027). At 3 years, patients with a DVT during immobilization displayed lower ATRS (DVT median 88 vs. no DVT 93, p = 0.046), which was not significant after adjustment for age. However, patients with DVT exhibited an improvement in ATRS, LSI total work, and LSI maximum height between 1 and 3 years, which was not seen among patients without DVT. Independent risk factors for reduced patient functional outcomes at 3 years were older age, greater calf muscle hypotrophy, and suffering a DVT. CONCLUSIONS: DVT during immobilization affects patients' long-term functional outcomes 3 years after ATR repair. Clinicians should adequately address risk factors contributing to impaired patient outcomes in the long term, including calf muscle hypotrophy, DVT, and older age. LEVEL OF EVIDENCE: Level Ⅲ.

Complement factor D as a predictor of Achilles tendon healing and long-term patient outcomes.

Dense connective tissue healing, such as tendon, is protracted leading to highly variable and unsatisfactory patient outcomes. Biomarkers prognostic of long-term clinical outcomes is, however, unknown. The present study was designed to investigate the proteomic profile of healing, identify potential biomarkers, and assess their association with the patient's long-term outcomes after ATR. Quantitative mass spectrometry analysis demonstrated 1423 proteins in healing and contralateral healthy Achilles tendons of 28 ATR patients. Comparing healing at 2 weeks and healthy protein profiles, we identified 821 overlapping, 390 upregulated, and 17 downregulated proteins. Upregulated proteins are related mainly to extracellular matrix organization and metabolism, while downregulated pathways were associated with exocytosis in immune modulation and thrombosis formation. Further proteomic profiling in relation to validated patient outcomes revealed the downregulated pro-inflammatory complement factor D (CFD) as the most reliable predictive biomarker of successful tendon healing. Our finding showed a comprehensive proteomic landscape and bioinformatics on human connective tissue, indicating subtype-specific and shared biological processes and proteins in healing and healthy Achilles tendons, as well as in tendons related to good and poor patient outcomes. Inflammatory protein CFD and serpin family B member 1 were finally identified as potential predictive biomarkers of effective healing outcomes when combined the proteomic profiles with a validated clinical database. Following the future elucidation of the mechanisms associated with the identified biomarkers as predictors of good outcomes, our findings could lead to improved prognostic accuracy and development of targeted treatments, thus improving the long-term healing outcomes for all patients.

Motor point heatmap of the calf.

BACKGROUND: Contractions of muscles in the calf induced by neuromuscular electrical stimulation (NMES) may prevent venous thromboembolism, help rehabilitation and optimize strength training, among other uses. However, compliance to NMES-treatment is limited by the use of suboptimal stimulation points which may cause discomfort and less effectivity. Knowledge of where one is most likely to find muscle motor points (MP) could improve NMES comfort and compliance. AIMS: To anatomically map the MPs of the calf as well as to calculate the probability of finding a MP in different areas of the calf. MATERIAL AND METHODS: On 30 healthy participants (mean age 37 years) anatomical landmarks on the lower limbs were defined. The location of the four most responsive MPs on respectively the medial and lateral head of gastrocnemius were determined in relation to these anatomical landmarks using a MP search pen and a pre-set MP search program with 3 Hz continuous stimulation (Search range:4.0-17.5 mA). The anatomy of the calves was normalized and subdivided into a matrix of 48 (6 × 8) smaller areas (3 × 3 cm), from upper medial to lower lateral, in order to calculate the probability of finding a MP in one of these areas. The probability of finding a MP was then calculated for each area and presented with a 95% confidence interval. RESULTS: The MP heatmap displayed a higher concentration of MPs proximally and centrally on the calf. However, there were wide inter-individual differences in the location of the MPs. The highest probability of finding a MP was in area 4, located centrally and medially, and in area 29, located centrolaterally and around the maximum circumference, both with 50% probability (95% CI: 0.31-0.69). The second highest probability of finding MPs was in areas 9, 10, 16, proximally and medially, all with 47% probability (95% CI: 0.28-0.66). These areas 4, 9, 10, 16 and 29 exhibited significantly higher probability of finding motor points than all areas with a mean probability of 27% and lower (p < 0.05) The lateral and distal outskirts exhibited almost zero probability of finding MPs. CONCLUSIONS: This MP heatmap of the calf could be used to expedite electrode placement and to improve compliance in order to receive consistent and enhanced results of NMES treatments.

Higher pyruvate levels after Achilles tendon rupture surgery could be used as a prognostic biomarker of an improved patient outcome.

PURPOSE: The primary aim of this study was to assess the relationship between the metabolites lactate and pyruvate in the healing tendon after Achilles tendon rupture (ATR) and patient-reported outcome at 6 and 12 months. A secondary aim was to evaluate which underlying factors regulate lactate and pyruvate concentrations. METHODS: Lactate and pyruvate concentrations were measured two weeks post-operatively in both the healing- and healthy Achilles tendon in 109 patients (90 men, 19 women; mean age 40 ± 7.9 years). Patient demographics, degree of physical activity, timing of surgery, operation time, patient-reported loading and step counts were investigated in relation to metabolite concentrations. At 6 and 12 months, the Achilles tendon Total Rupture Score (ATRS) questionnaire was used to assess patient outcome. RESULTS: The mean number of steps taken during the post-operative days 1-10 was the only factor significantly related to the mean concentration of lactate (R2 = 0.34, p = 0.038), and pyruvate (R2 = 0.46, p = 0.006). Pyruvate was demonstrated as the only factor significantly associated with ATRS at both 6 months (R2 = 0.32, p = 0.003) and at 12 months (R2 = 0.37, p = 0.004) using multiple linear regression. CONCLUSION: The mean concentration of pyruvate during early ATR healing may predict patient outcome at 6 and 12 months post-operatively and possibly be used as a biomarker of healing. Early mobilization with an increased number of steps taken is an important clinical strategy to improve the metabolite concentrations during healing. LEVEL OF EVIDENCE: III.

Complete mid-portion rupture of the rat achilles tendon leads to remote and time-mismatched changes in uninjured regions.

PURPOSE: To examine healing adaptations over 17 weeks post Achilles tendon (AT) rupture in the injured region (IR) compared to an uninjured region (UIR) of the AT. METHODS: Twenty-four rats were subjected to a complete right-sided AT rupture, while the left side served as a control. ATs were harvested at 1, 2, 8 and 17 weeks post-rupture and stained with antibodies specific to Collagen type I (Col I) and II (Col II) as well as Alcian Blue and Picrosirius Red staining techniques. Histopathological changes, proteoglycan content, collagen alignment and immunoexpression were assessed. RESULTS: Both regions examined, IR and UIR, exhibited over weeks 1-17 similar healing adaptations of increasing collagen alignment, decreasing Col I immunoexpression, as well as increasing proteoglycan content and Col II occurrence. Increased proteoglycan content was found already at week 2 in the UIR, while it first increased at week 8 in the IR. The area positive to Col II was increased compared to controls at week 8 in the UIR, whereas it first raised at week 17 in the IR. Collagen disorganization successively declined to reach control levels at week 17 in the UIR, but was still higher in the IR. CONCLUSION: This study demonstrated that uninjured areas of the AT remote from the rupture site also undergo pronounced remodeling, although with time-span differences relative to injured AT portions. These changes including the pathologic heterotopic mineralization and chondrogenic differentiation observed in both regions may have implications in the choice of rehabilitation regimes in order to prevent secondary rupture.

Deep venous thrombosis after Achilles tendon rupture is associated with poor patient-reported outcome.

PURPOSE: The aim of this study was to investigate whether patient subjective and functional outcomes after Achilles tendon rupture (ATR) are related to deep venous thrombosis (DVT) during leg immobilization. METHODS: A cohort study with prospectively collected randomized data was conducted between 2010 and 2017. Two-hundred and fifty-one Patients with an Achilles tendon rupture (mean age = 41 ± 8), treated with uniform surgical techniques, were retrospectively analyzed. DVT incidence at 2 and 6 weeks was assessed using compression duplex ultrasound. At 12 months patient-reported outcomes were assessed using the Achilles tendon Total Rupture Score (ATRS), Foot- and Ankle Outcome Score (FAOS), Physical Activity Scale (PAS) and functional outcome with the calf-muscle endurance test. ANOVA analyses were used and adjusted for assumed confounding factors (patient age, sex, BMI and rehabilitation). RESULTS: The total DVT incidence was 122 out of 251 (49%). Patients suffering a DVT exhibited significantly lower ATRS at 1 year compared to patients without DVT (mean 76 vs 83, 95% CI 71-79 vs 80-87; p < 0.01). Sixty-seven percent (95% CI 57-77%) of the patients devoid of DVT reported a good outcome (ATRS > 80) compared to 51% (95% CI 41-61%) of the patients sustaining a DVT (p < 0.05). Quality of life displayed significantly better outcome in the non-DVT versus DVT patients (mean = 75 (95% CI 71-79) vs. mean = 68 (95% CI 64-72); p < 0.05). A significant difference in total concentric work was observed between non-DVT and DVT patients (median = 1.9 kJ (IQR = 0.9 kJ) vs. median = 1.6 kJ (IQR = 1.0 kJ); p < 0.01). CONCLUSION: Sustaining a DVT during leg immobilization significantly impairs patient-reported outcome at 1 year after surgical repair of ATR. LEVEL OF EVIDENCE: III.

Early mobilization does not reduce the risk of deep venous thrombosis after Achilles tendon rupture: a randomized controlled trial.

PURPOSE: The hypothesis was that early functional mobilization would reduce the incidence of deep venous thrombosis (DVT) during leg immobilization after Achilles tendon rupture surgery. A secondary aim was to evaluate if the amount of weightbearing and daily steps influenced the risk of sustaining a DVT. METHODS: One-hundred and fifty patients with Achilles tendon rupture repair were randomized to treatment with early functional mobilization, encouraging full weightbearing and ankle motion in orthosis, or treatment-as-usual, i.e., 2 weeks of unloading in plaster cast followed by 4 weeks weightbearing in orthosis. At 2 and 6 weeks postoperatively, all patients were screened for DVT using compression duplex ultrasound. During the first 2 weeks postoperatively, patient-reported loading, pain and step counts were assessed. RESULTS: At 2 weeks, 28/96 (29%) of the patients in early functional mobilization group and 15/49 (31%) in the control group (n.s) had sustained a DVT. At 6 weeks, the DVT rate was 35/94 (37%) in the early functional mobilization and 14/49 (29%) in the control group (n.s). During the first postoperative week, the early functional mobilization group reported low loading and higher experience of pain vs. the control group (p = 0.001). Low patient-reported loading ≤ 50% (OR = 4.3; 95% CI 1.28-14.3) was found to be an independent risk factor for DVT, in addition to high BMI and higher age. CONCLUSIONS: Early functional mobilization does not prevent the high incidence of DVT during leg immobilization in patients with Achilles tendon rupture as compared to treatment-as-usual. The low efficacy of early functional mobilization is mainly explained by postoperative pain and subsequent low weightbearing. To minimize the risk of DVT, patients should be encouraged to load at least 50% of body weight on the injured leg 1 week after surgery. LEVEL OF EVIDENCE: Therapeutic, level 1.

Pyruvate and lactate as local prognostic biomarkers of patient outcome after achilles tendon rupture.

BACKGROUND: Acute Achilles tendon rupture (ATR) is a frequently disabling injury, which exhibits unclear variability in long-term functional and patient-reported outcomes. Biomarkers from early healing, which have been shown to be prognostic of long-term outcome would facilitate the development of improved treatment methods. HYPOTHESIS/PURPOSE: The aim of this study was to assess essential metabolites pyruvate and its product lactate, as early biomarkers in relation to long-term functional- and patient-reported outcome after ATR. STUDY DESIGN: Prospective cohort study. METHODS: A total of 124 patients (103 men, 21 women; mean age 40 ± 7 years) with ATR, treated with uniform anesthetic and surgical technique, were prospectively assessed. At two weeks post-injury pyruvate and lactate concentrations were assessed in both the injured and uninjured limbs using microdialysis followed by enzymatic quantification. The ratios of the concentration in the injured versus uninjured limb of pyruvate (pyruvate-r) and lactate (lactate-r) were calculated as well as the lactate/pyruvate ratios (L/P-r). At 12 months, patient-reported outcome was examined using self-reported questionnaires; Achilles tendon Total Rupture Score (ATRS), Foot and Ankle Outcome Score (FAOS), and physical activity score. At 12 months, functional outcome was studied using the validated heel-rise test. RESULTS: Elevated pyruvate-r, at two weeks, was significantly associated with total ATRS (R = 0.254, P = 0.028), less loss in physical activity (R = 0.241, P = 0.039), less experience of pain in FAOS (R = 0.275, P = 0.032), and a higher number of heel-rise repetitions on injured side (R = 0.230, P = 0.040) at 12 months. Increased lactate-r was related with less strength limitations in the calf (R = 0.283, P = 0.011), while the elevated lactate-pyruvate ratio, notably, was related to more limitations in walking on uneven surface (R = -0,243, P = 0.027). The findings were verified by multiple linear regression taking confounding factors into consideration. CONCLUSION: This study established that the metabolite pyruvate is a good potential biomarker, prognostic of patient outcome at the one-year follow-up after ATR surgery. These novel findings suggest that local biomarkers could be developed at an early-stage screen for new ATR treatments.

Achilles tendon rupture healing is enhanced by intermittent pneumatic compression upregulating collagen type I synthesis.

PURPOSE AND HYPOTHESIS: Adjuvant intermittent pneumatic compression (IPC) during leg immobilization following Achilles tendon rupture (ATR) has been shown to reduce the risk of deep venous thrombosis. The purpose of this study was to investigate whether IPC can also promote tendon healing. METHODS: One hundred and fifty patients with surgical repair of acute ATR were post-operatively leg immobilized and prospectively randomized. Patients were allocated for 2 weeks of either adjuvant IPC treatment (n = 74) or treatment-as-usual (n = 74) in a plaster cast without IPC. The IPC group received 6 h daily bilateral calf IPC applied under an orthosis on the injured side. At 2 weeks post-operatively, tendon healing was assessed using microdialysis followed by enzymatic quantification of tendon callus production, procollagen type I (PINP) and type III (PIIINP) N-terminal propeptide, and total protein content. 14 IPC and 19 cast patients (control group) consented to undergo microdialysis. During weeks 3-6, all subjects were leg-immobilized in an orthosis without IPC. At 3 and 12 months, patient-reported outcome was assessed using reliable questionnaires (ATRS and EQ-5D). At 12 months, functional outcome was measured using the validated heel-rise test. RESULTS: At 2 weeks post-rupture, the IPC-treated patients exhibited 69% higher levels of PINP in the ruptured Achilles tendon (AT) compared to the control group (p = 0.001). Interestingly, the IPC-treated contralateral, intact AT also demonstrated 49% higher concentrations of PINP compared to the non-treated intact AT of the plaster cast group (p = 0.002). There were no adverse events observed associated with IPC. At 3 and 12 months, no significant (n.s.) differences between the two treatments were observed using patient-reported and functional outcome measures. CONCLUSIONS: Adjuvant IPC during limb immobilization in patients with ATR seems to effectively enhance the early healing response by upregulation of collagen type I synthesis, without any adverse effects. Whether prolonged IPC application during the whole immobilization period can also lead to improved long-term clinical healing response should be further investigated. The healing process during leg immobilization in patients with Achilles tendon rupture can be improved through adjuvant IPC therapy, which additionally prevents deep venous thrombosis. LEVEL OF EVIDENCE: Randomized controlled trial, Level I.

Longer duration of operative time enhances healing metabolites and improves patient outcome after Achilles tendon rupture surgery.

PURPOSE: The relationship between the duration of operative time (DOT), healing response and patient outcome has not been previously investigated. An enhanced healing response related to DOT may potentiate repair processes, especially in hypovascular and sparsely metabolized musculoskeletal tissues such as tendons. This study aimed to investigate the association between DOT and the metabolic healing response, patient-reported outcome and the rate of post-operative complications after acute Achilles tendon injury. METHODS: Observational cohort, cross-sectional study with observers blinded to patient grouping. A total of two-hundred and fifty-six prospectively randomized patients (210 men, 46 women; mean age 41 years) with an acute total Achilles tendon rupture all operated on with uniform anaesthetic and surgical technique were retrospectively assessed. At 2 weeks post-operatively, six metabolites were quantified using microdialysis. At 3, 6 and 12 months, patient-reported pain, walking ability and physical activity were examined using self-reported questionnaires, Achilles tendon total rupture score, foot and ankle outcome score and physical activity scale. At 12 months, functional outcome was assessed using the heel-rise test. Complications, such as deep venous thrombosis, infections and re-operations, were recorded throughout the study. RESULTS: Patients who underwent longer DOT exhibited higher levels of glutamate (p = 0.026) and glycerol (p = 0.023) at 2 weeks. At the 1-year follow-up, longer DOT was associated with significantly less loss in physical activity (p = 0.003), less pain (p = 0.009), less walking limitations (p = 0.022) and better functional outcome (p = 0.014). DOT did not significantly correlate with the rate of adverse events, such as deep venous thrombosis, infections or re-ruptures. Higher glutamate levels were associated with less loss in physical activity (p = 0.017). All correlations were confirmed by multiple linear regressions taking confounding factors into consideration. CONCLUSION: The results from this study suggest a previously unknown mechanism, increased metabolic response associated with longer DOT, which may improve patient outcome after Achilles tendon rupture surgery. Allowing for a higher amount of traumatized tissue, as reflected by up-regulation of glycerol in patients with longer DOT, may prove to be an important surgical tip for stimulation of repair of hypometabolic soft tissue injuries, such as Achilles tendon ruptures. LEVEL OF EVIDENCE: II.

Increased mast cell degranulation and co-localization of mast cells with the NMDA receptor-1 during healing after Achilles tendon rupture.

The role of inflammation and the mechanism of tendon healing after rupture has historically been a matter of controversy. The purpose of the present study is to investigate the role of mast cells and their relation to the NMDA receptor-1 (a glutamate receptor) during healing after Achilles tendon rupture. Eight female Sprague Dawley rats had their right Achilles tendon transected. Three weeks after rupture, histological quantification of mast cell numbers and their state of degranulation was assessed by histochemistry. Co-localization of mast cell tryptase (a mast cell marker) and NMDA receptor-1 was determined by immunofluorescence. The intact left Achilles tendon was used as control. An increased number of mast cells and a higher proportion of degranulated mast cells were found in the healing Achilles tendon compared to the intact. In addition, increased co-localization of mast cell tryptase and NMDA receptor-1 was seen in the areas of myotendinous junction, mid-tendon proper and bone tendon junction of the healing versus the intact tendon. These findings introduce a possible role for mast cells in the healing phase after Achilles tendon rupture.

Functional weight-bearing mobilization after Achilles tendon rupture enhances early healing response: a single-blinded randomized controlled trial.

PURPOSE: Functional weight-bearing mobilization may improve repair of Achilles tendon rupture (ATR), but the underlying mechanisms and outcome were unknown. We hypothesized that functional weight-bearing mobilization by means of increased metabolism could improve both early and long-term healing. METHODS: In this prospective randomized controlled trial, patients with acute ATR were randomized to either direct post-operative functional weight-bearing mobilization (n = 27) in an orthosis or to non-weight-bearing (n = 29) plaster cast immobilization. During the first two post-operative weeks, 15°-30° of plantar flexion was allowed and encouraged in the functional weight-bearing mobilization group. At 2 weeks, patients in the non-weight-bearing cast immobilization group received a stiff orthosis, while the functional weight-bearing mobilization group continued with increased range of motion. At 6 weeks, all patients discontinued immobilization. At 2 weeks, healing metabolites and markers of procollagen type I (PINP) and III (PIIINP) were examined using microdialysis. At 6 and 12 months, functional outcome using heel-rise test was assessed. RESULTS: Healing tendons of both groups exhibited increased levels of metabolites glutamate, lactate, pyruvate, and of PIIINP (all p < 0.05). Patients in functional weight-bearing mobilization group demonstrated significantly higher concentrations of glutamate compared to the non-weight-bearing cast immobilization group (p = 0.045).The upregulated glutamate levels were significantly correlated with the concentrations of PINP (r = 0.5, p = 0.002) as well as with improved functional outcome at 6 months (r = 0.4; p = 0.014). Heel-rise tests at 6 and 12 months did not display any differences between the two groups. CONCLUSIONS: Functional weight-bearing mobilization enhanced the early healing response of ATR. In addition, early ankle range of motion was improved without the risk of Achilles tendon elongation and without altering long-term functional outcome. The relationship between functional weight-bearing mobilization-induced upregulation of glutamate and enhanced healing suggests novel opportunities to optimize post-operative rehabilitation.

Deep Venous Thrombosis and Tendon Healing.

Tendon metabolism after acute Achilles tendon rupture (ATR) is associated with major complications related to immobilization, which results in reduced circulation, high risk of deep venous thrombosis (DVT), impaired healing and functional deficits.DVT has been demonstrated to occur in up to 50 % of the patients with ATR. Suffering from a DVT during tendon healing has been demonstrated as an independent predictive factor for impaired patient outcome at 1 year after ATR, suggesting that specific interventions are warranted to prevent DVT. Since pharmacological DVT prophylaxis has low or no effect during lower leg immobilization it is speculated whether adjuvant treatment with intermittent pneumatic compression (IPC) applied during lower limb immobilization can reduce the incidence of DVT.IPC, which acts through mechanical, chemical and molecular mechanisms, has been demonstrated to enhance neuro-vascular ingrowth in a tendon repair model and stimulate collagen production leading to improved maximum force during healing.Recently, a prospective randomized trial compared adjuvant IPC applied under an orthosis versus plaster cast only in ATR patients. The study found at 2 weeks post-operatively 21 % DVTs in the IPC-group compared to 37 % in the control group. Patients that received no IPC treatment exhibited an almost threefold increased odds for DVT, independently of age. Furthermore, using microdialysis technique, adjuvant IPC treatment was shown to increase the metabolic healing activity at 2 weeks post-ATR.Tendon healing is impaired by reduced circulation and DVT. The demonstration that adjuvant IPC effectively reduced DVT incidence, and also is capable of enhancing the metabolic response suggests that IPC treatment may not only be a viable means of prophylaxis against DVT, but possibly also a method of promoting healing.

General Overview and Summary of Concepts Regarding Tendon Disease Topics Addressed Related to Metabolic Disorders.

Painful and non-healing musculoskeletal disorders, eg. tendinopathy, pose a tremendous burden on society and the quality of life for patients. New advances in the understanding of connective tissue disorders such as tendinopathy reveal that common health problems such as obesity, atherosclerosis, hormonal dysfunctions and diabetes mellitus are closely linked to the metabolism of components of the musculoskeletal system, particularly tendons. As tendons function as multi-component "organ systems" (Muscle-TMJ-Tendon-Enthesis to Bone), tendons can be influenced directly, or indirectly via, for instance, alterations to muscle. However, this volume/set of chapters focus mainly on the tendon.Emerging findings in musculoskeletal research have established important new links in our understanding of tendon metabolism. Thereby, the function of the neuroendocrine/-immune axis, as well as supply of neuro-vascular factors, can be directly linked to the quality of tendon metabolism.Since some conditions, eg. atherosclerosis and diabetes mellitus, are more common in individuals as they age, and aging can also affect pain and tissue repair, convergence of such complications will potentially exert an increasingly significant impact on tendons as the demographics of many societies change with expanding percentages of the populations >60-65 years of age.Comorbidities related to metabolic dysfunction have to be identified early in patients with musculoskeletal disorders, such as acute tendon injuries or chronic tendinopathy, for therapeutic considerations regarding both operative and non-operative treatment protocols. Necessary interactions between researchers and clinicians with different subspecialties have to be initiated in order to optimize tissue metabolism for improved healing potentials.

Tendon Innervation.

The regulation of tendon metabolism including the responses to loading is far from being well understood. During the last decade, however, accumulating data show that tendon innervation in addition to afferent functions, via efferent pathways has a regulatory role in tendon homeostasis via a wide range of neuromediators, which coordinate metabolic and neuro-inflammatory pathways.Innervation of intact healthy tendons is localized in the surrounding structures, i.e paratenon, endotenon and epitenon, whereas the tendon proper is practically devoid of neuronal supply. This anatomical finding reflects that the tendon metabolism is regulated from the tendon envelope, i.e. interfascicular matrix (see Chap. 1 ).Tendon innervation after injury and during repair, however, is found as extensive nerve ingrowth into the tendon proper, followed by a time-dependent emergence of different neuronal mediators, which amplify and fine-tune inflammatory and metabolic pathways in tendon regeneration. After healing nerve fibers retract to the tendon envelope.In tendinopathy innervation has been identified to consist of excessive and protracted nerve ingrowth in the tendon proper, suggesting pro-inflammatory, nociceptive and hypertrophic (degenerative) tissue responses.In metabolic disorders such as eg. diabetes impaired tendon healing has been established to be related to dysregulation of neuronal growth factors.Targeted approaches to the peripheral nervous system including neuronal mediators and their receptors may prove to be effective therapies for painful, degenerative and traumatic tendon disorders.

Meta-analysis and suggested guidelines for prevention of venous thromboembolism (VTE) in foot and ankle surgery.

PURPOSE: To perform a meta-analysis investigating venous thromboembolism (VTE) following isolated foot and ankle surgery and propose guidelines for VTE prevention in this group of patients. METHODS: Following a PRISMA compliant search, 372 papers were identified and meta-analysis performed on 22 papers using the Critical Appraisal Skills Programme and Centre for Evidence-Based Medicine level of evidence. RESULTS: 43,381 patients were clinically assessed for VTE and the incidence with and without chemoprophylaxis was 0.6% (95% CI 0.4-0.8%) and 1% (95% CI 0.2-1.7%), respectively. 1666 Patients were assessed radiologically and the incidence of VTE with and without chemoprophylaxis was 12.5% (95% CI 6.8-18.2%) and 10.5% (95% CI 5.0-15.9%), respectively. There was no significant difference in the rates of VTE with or without chemoprophylaxis whether assessed clinically or by radiological criteria. The risk of VTE in those patients with Achilles tendon rupture was greater with a clinical incidence of 7% (95% CI 5.5-8.5%) and radiological incidence of 35.3% (95% CI 26.4-44.3%). CONCLUSION: Isolated foot and ankle surgery has a lower incidence of clinically apparent VTE when compared to general lower limb procedures, and this rate is not significantly reduced using low molecular weight heparin. The incidence of VTE following Achilles tendon rupture is high whether treated surgically or conservatively. With the exception of those with Achilles tendon rupture, routine use of chemical VTE prophylaxis is not justified in those undergoing isolated foot and ankle surgery, but patient-specific risk factors for VTE should be used to assess patients individually. LEVEL OF EVIDENCE: II.

Expressional changes in growth and inflammatory mediators during Achilles tendon repair in diabetic rats: new insights into a possible basis for compromised healing.

Dysregulation of growth and inflammatory mediators might contribute to defective tissue homeostasis and healing, as commonly observed in sedentary lifestyles and in conditions such as diabetes mellitus type-2. The present study aims to assess expression changes in growth and inflammatory mediators in the intact and healing Achilles tendon of type-2 diabetic rats. The study utilized 11 male diabetic Goto-Kakizaki (GK) and 10 age- and sex-matched Wistar control rats. The right Achilles tendon was transected in all animals, whereas the left Achilles tendon remained intact. At 2 weeks post-injury, intact and injured tendons were assessed for gene expression for VEGF, Tß-4, TGF-ß1, IGF-1, COX-2, iNOS, HIF-1α, and IL-1ß by quantitative reverse transcription plus the polymerase chain reaction, and their protein distribution was studied by immunolocalization. In injured tendons of diabetic GK rats, VEGF and Tß-4 mRNA and corresponding protein levels were significantly down-regulated compared with those of injured Wistar controls. Compared with intact tendons of diabetic GK rats, TGF-ß1, IGF-1, and COX-2 RNA levels were higher, whereas iNOS mRNA levels were lower in injured tendons of diabetic GK rats. Within Wistar controls, healing at 2 weeks post-injury led to significantly down-regulated VEGF and iNOS mRNA levels in injured tendons, whereas TGF-ß1 and HIF-1α mRNA levels increased compared with intact tendons. Thus, dysregulation of inflammatory and growth mediators occurs in type-2 diabetes injured tendons. Our data suggest that therapeutic modulation of Tß-4 and VEGF represent a new regenerative approach in operated, injured, or degenerative tendon diseases in diabetes.

Optimizing tendon repair and regeneration: how does the in vivo environment shape outcomes following rupture of a tendon such as the Achilles tendon?

Risk for rupture of the Achilles tendon, and other tendons increases with age. Such injuries of tissues that function in high load environments generally are believed to heal with variable outcome. However, in many cases, the healing does not lead to a good outcome and the patient cannot return to the previous level of participation in active living activities, including sports. In the past few years, using proteomic approaches and other biological techniques, reports have appeared that identify biomarkers that are prognostic of good outcomes from healing, and others that are destined for poor outcomes using validated criteria at 1-year post injury. This review will discuss some of these recent findings and their potential implications for improving outcomes following connective tissue injuries, as well as implications for how clinical research and clinical trials may be conducted in the future where the goal is to assess the impact of specific interventions on the healing process, as well as focusing the emphasis on regeneration and not just repair.

Neuronal regulation of tendon homoeostasis.

The regulation of tendon homoeostasis, including adaptation to loading, is still not fully understood. Accumulating data, however, demonstrates that in addition to afferent (sensory) functions, the nervous system, via efferent pathways which are associated with through specific neuronal mediators plays an active role in regulating pain, inflammation and tendon homeostasis. This neuronal regulation of intact-, healing- and tendinopathic tendons has been shown to be mediated by three major groups of molecules including opioid, autonomic and excitatory glutamatergic neuroregulators. In intact healthy tendons the neuromediators are found in the surrounding structures: paratenon, endotenon and epitenon, whereas the proper tendon itself is practically devoid of neurovascular supply. This neuroanatomy reflects that normal tendon homoeostasis is regulated from the tendon surroundings. After injury and during tendon repair, however, there is extensive nerve ingrowth into the tendon proper, followed by a time-dependent emergence of sensory, autonomic and glutamatergic mediators, which amplify and fine-tune inflammation and regulate tendon regeneration. In tendinopathic condition, excessive and protracted presence of sensory and glutamatergic neuromediators has been identified, suggesting involvement in inflammatory, nociceptive and hypertrophic (degenerative) tissue responses. Under experimental and clinical conditions of impaired (e.g. diabetes) as well as excessive (e.g. tendinopathy) neuromediator release, dysfunctional tendon homoeostasis develops resulting in chronic pain and gradual degeneration. Thus there is a prospect that in the future pharmacotherapy and tissue engineering approaches targeting neuronal mediators and their receptors may prove to be effective therapies for painful, degenerative and traumatic tendon disorders.