Procollagen markers in microdialysate can predict patient outcome after Achilles tendon rupture

Systematic Review of Relevant Biomarkers for Human Connective Tissue Repair and Healing Outcome: Implications for Understanding Healing Processes and Design of Healing Interventions

Objective: The healing process following connective tissue (CT) injuries is complex, resulting in variable and often suboptimal outcomes. Patients undergoing CT repair frequently experience healing failures, compromised function, and chronic degenerative diseases. The identification of biomarkers to guide improved clinical outcomes after CT injuries remains an emerging but promising field. [Figure: see text] [Figure: see text] Design: Systematic review. Data sources: Databases, including PubMed, MEDLINE Ovid, Web of Science, and Google Scholar, were searched up to August 2024. Eligibility criteria: To achieve the research objective, randomized control trials, cohort studies, and case-control studies on biomarkers associated with CT repair and healing outcomes were selected. The present analysis was confined to clinical and preclinical models, excluding imaging studies. The entire process of this systematic review adhered strictly to the guidelines outlined in the Preferred Reporting Items for Systematic Review and Meta-Analyses protocol checklist. Results: A total of 1,815 studies on biomarkers of CT repair were initially identified, with 75 studies meeting eligibility criteria and 55 passing quality assessments. For biomarkers associated with CT healing outcomes, 281 studies were considered, with 30 studies meeting eligibility criteria and 24 passing quality assessments. Twenty-one overlapping studies investigated the effects of biomarkers on both CT repair and healing outcomes. Specific biomarkers identified, and ranked from highest to lowest quality, include complement factor D, eukaryotic elongation factor-2, procollagen type I N-terminal propetide, procollagen type III N-terminal propetide, lactate, pyruvate, platelet-derived growth factor-BB, tissue inhibitor of metalloproteinase-3 (TIMP-3), cysteine-rich protein-1, plastin-3, periostin, protein S100-A11, vimentin, matrix metalloproteinases (MMP-2, MMP-7, and MMP-9), hepatocyte growth factor, interferon-γ, interleukins (IL-6, IL-8, and IL-10), MMP-1, MMP-3, tumor necrosis factor-α, fibroblast growth factor-2, IL-1α, chondroitin-6-sulfate, inter-alpha-trypsin inhibitor heavy chain-4, transforming growth factor-beta 1, vascular endothelial growth factor, C-C chemokine receptor 7, C-C chemokine ligand 19, IL-1β, IL-1Ra, IL-12p40, granulocyte-macrophage colony-stimulating factor (GM-CSF), and TIMP-1. Conclusions: All of the 37 identified potential biomarkers demonstrated regulatory effects on CT repair and mediated healing outcomes. Notably, the identified biomarkers from human studies can potentially play an essential role in the development of targeted treatment protocols to counteract compromised healing and can also serve as predictors for detecting CT healing processes and long-term outcomes.

Novel application of in vivo microdialysis in a rat Achilles tendon acute injury model

Tendon injury and healing involve intricate changes to tissue metabolism, biology, and inflammation. Current techniques often require animal euthanasia or tissue destruction, limiting assessment of dynamic changes in tendon, including treatment response, disease development, rupture risk, and healing progression. Microdialysis, a minimally invasive technique, offers potential for longitudinal assessment, yet it has not been applied to rat tendon models. Therefore, the objective of this study is to adapt a novel application of an in vivo assay, microdialysis, using acute injury as a model for extreme disruption of the tendon homeostasis. We hypothesize that microdialysis will be able to detect measurable differences in the healing responses of acute injury with high specificity and sensitivity. Overall results suggest that microdialysis is a promising in vivo technique for longitudinal assessment for this system with strong correlations between extracellular fluid (ECF) and dialysate concentrations and reasonable recovery rates considering the limitations of this model. Strong positive correlations were found between dialysate and extracellular fluid (ECF) concentration for each target molecule of interest including metabolites, inflammatory mediators, and collagen synthesis and degradation byproducts. These results suggest that microdialysis is capable of detecting changes in tendon healing following acute tendon injury with high specificity and sensitivity. In summary, this is the first study to apply microdialysis to a rat tendon model and assess its efficacy as a direct measurement of tendon metabolism, biology, and inflammation.NEW & NOTEWORTHY This study adapts a novel application of microdialysis to rat tendon models, offering a minimally invasive avenue for longitudinal tendon assessment. Successfully detecting changes in tendon healing after acute injury, it showcases strong correlations between extracellular fluid and dialysate concentrations. The results highlight the potential of microdialysis as a direct measure of tendon metabolism, biology, and inflammation, bypassing the need for animal euthanasia and tissue destruction.

Complement factor D regulates collagen type I expression and fibroblast migration to enhance human tendon repair and healing outcomes

Introduction

Dense connective tissues (DCTs) such as tendon, ligament, and cartilage are important stabilizers and force transmitters in the musculoskeletal system. The healing processes after DCT injuries are highly variable, often leading to degenerative changes and poor clinical outcome. Biomarkers in relation to repair quality for human DCTs, especially tendon are lacking. This study expands our previous findings and aimed to characterize the mechanisms by which a potential biomarker of good outcomes, complement factor D (CFD), regulates tendon healing.

Methods

Quantitative mass spectrometry (QMS) profiling of tissue biopsies from the inflammatory phase of healing (n = 40 patients) and microdialysates from the proliferative phase of healing (n = 28 patients) were used to identify specific biomarkers for tendon healing. Further bioinformatic and experimental investigations based on primary fibroblasts and fibroblast cell line were used to confirm the identified biomarkers.

Results

The QMS profiling of tissue biopsies from the inflammatory phase of healing identified 769 unique proteins, and microdialysates from the proliferative phase of healing identified 1423 unique proteins in Achilles tendon rupture patients. QMS-profiling showed that CFD expression was higher during the inflammatory- and lower during the proliferative healing phase in the good outcome patients. Further bioinformatic and experimental explorations based on both inflammatory and proliferative fibroblast models demonstrated that CFD potentially improved repair by regulating cell migration and modulating collagen type I (Col1a1) expression. Moreover, it was shown that the enhanced Col1a1 expression, through increased fibroblast migration, was correlated with the validated clinical outcome.

Discussion

The results of the current studies characterized underlying inflammatory- and proliferative healing mechanisms by which CFD potentially improved tendon repair. These findings may lead to improved individualized treatment options, as well the development of effective therapies to promote good long-term clinical outcomes after tendon and other DCT injuries.

Trial registration

http://clinicaltrials.gov, identifiers NCT02318472, NCT01317160.

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 .

Outcomes of early versus late functional weight-bearing after the acute Achilles tendon rupture repair with minimally invasive surgery: a randomized controlled trial

INTRODUCTION

Optimal postoperative rehabilitation regimen for acute Achilles tendon rupture (AATR) remains unclear. It is important to evaluate whether early functional weight-bearing rehabilitation program after minimally invasive repair results in an earlier return to pre-injury activity but increases the risk of re-rupture.

MATERIALS AND METHODS

This was a prospective randomized controlled trial involving 68 AATR patients undergoing minimally invasive surgery. 34 patients were enrolled in early weight‑bearing mobilization accelerated rehabilitation group (AR group); 34 patients were enrolled in the traditional rehabilitation (TR) group. Outcomes measures included American Orthopaedic Foot and Ankle Society Score (AOFAS) score and Achilles Tendon Total Rupture Score (ATRS) score before surgery and 3, 6, and 12 months after surgery, incidence rate of Achilles tendon re-rupture and total complications, length of hospital stay, time return to work and sports.

RESULTS

There was no significant difference in preoperative basic data between the two groups. However, AOFAS score and ATRS score were better in AR group than TR group at 3 months postoperatively (92.4 ± 3.5 vs 88.3 ± 4.5, P < 0.01; 91.1 ± 4.4 vs 88.9 ± 3.4, P = 0.03, respectively), the mean length of hospital stay (4.7 ± 1.5 vs 7.6 ± 2.0 days, P < 0.01) and time return to work (4.5 ± 1.0 vs 7.5 ± 1.6 weeks, P < 0.01) were shorter in AR group than in TR group. No statistical significance was calculated in patient-reported outcomes during the rest of the follow-up time and complications.

CONCLUSION

Early accelerated rehabilitation with weight-bearing in patients with AATR after minimally invasive surgery results in better early functional outcomes and shows similar security and feasibility.

REGISTRATION NO

ChiCTR2100043398.

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.

STOP leg clots-Swedish multicentre trial of outpatient prevention of leg clots: study protocol for a randomised controlled trial on the efficacy of intermittent pneumatic compression on venous thromboembolism in lower leg immobilised patients

INTRODUCTION

Leg immobilisation in a cast or an orthosis after lower limb injuries is associated with a high risk of complications of venous thromboembolism (VTE) and hampered healing. Current pharmacoprophylaxes of VTE are inefficient and associated with adverse events. Intermittent pneumatic compression (IPC) could represent a novel, efficient and safe VTE-prophylactic alternative that may enhance injury healing. The aim of STOP leg clots is to assess the efficacy of adjuvant IPC-therapy on reduction of VTE incidence and improvement of healing in lower leg immobilised outpatients.

METHODS AND ANALYSIS

STOP leg clots is a multicentre randomised controlled superiority trial. Eligible patients (700 patients/arm) with either an acute ankle fracture or Achilles tendon rupture will be randomised to either addition of IPC during lower-leg immobilisation or to treatment-as-usual. The primary outcome will be the total VTE incidence, that is, symptomatic and asymptomatic deep venous thrombosis (DVT) or symptomatic pulmonary embolism (PE), during the leg immobilisation period, approximately 6-8 weeks. DVT incidence will be assessed by screening whole leg compression duplex ultrasound at removal of leg immobilisation and/or clinically diagnosed within the time of immobilisation. Symptomatic PE will be verified by CT.Secondary outcomes will include patient-reported outcome using validated questionnaires, healing evaluated by measurements of tendon callus production and changes in VTE-prophylactic mechanisms assessed by blood flow and fibrinolysis. Data analyses will be blinded and based on the intention-to-treat.

ETHICS AND DISSEMINATION

Ethical approval was obtained by the ethical review board in Stockholm, Sweden, Dnr 2016/1573-31. The study will be conducted in accordance with the Helsinki declaration. The results of the study will be disseminated in peer-reviewed international journals.

TRIAL REGISTRATION

NCT03259204.

TIME SCHEDULE

1 September 2018 to 31 December 2022.

FGF gene expression in injured tendons as a prognostic biomarker of 1-year patient outcome after Achilles tendon repair

PURPOSE

Healing outcome after Achilles Tendon Rupture (ATR) is variable and unsatisfactory. Many ATR patients still exhibit pain, functional deficits and limitations in walking one-year post-surgery. The present study was designed to investigate the association between the expression of healing biomarkers and patient outcome after ATR.

METHODS

Tendon biopsies were collected from 25 ATR patients during surgery. At 1-year post surgery, all patients completed questionnaires; Achilles tendon Total Rupture Score (ATRS) and Foot and Ankle Outcome Score (FAOS), and were tested for functional outcomes by heel-rise test. In biopsies, FGF, COL III, FN, COL I and MMP-9 mRNA levels were assessed by quantitative RT-PCR while protein expression was studied by immunohistochemistry (IHC).

RESULTS

Our analysis confirmed the presence of FGF, COL III, FN, COL I and MMP-9 at mRNA and protein levels in tendon biopsies. FGF gene expression associated positively with improved total ATRS and better functional outcomes. Additionally, FGF mRNA levels were associated with less pain, less running limitations and less loss in physical activity. In addition, higher COL III mRNA expression was associated with more tendon strength.

CONCLUSION

Our findings indicate that FGF gene expression is associated with improved patient-reported outcome. FGF expression in surgical biopsies could potentially be used to assist the prognostic evaluation of patient outcome and may be used as a predictor for healing. However, further studies are needed to evaluate the role of FGF in Achilles tendon healing.

LEVEL OF EVIDENCE

II.

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.

Older Age Predicts Worse Function 1 Year After an Acute Achilles Tendon Rupture: A Prognostic Multicenter Study on 391 Patients

Background

There is limited evidence regarding the patient-related factors that influence treatment outcomes after an acute Achilles tendon rupture.

Purpose/Hypothesis

The purpose of this study was to determine the predictors of functional and patient-reported outcomes 1 year after an acute Achilles tendon rupture using a multicenter cohort and to determine patient characteristics for reporting within the top and bottom 10% of the Achilles tendon Total Rupture Score (ATRS) and heel-rise height outcomes. The hypothesis was that older age, greater body mass index (BMI), and female sex would lead to inferior outcomes.

Study Design

Cohort study; Level of evidence, 2.

Methods

Patients were selected by combining 5 randomized controlled trials from 2 different centers in Sweden. Functional outcomes were assessed using validated heel-rise tests (height, number of repetitions, total work, and concentric power) for muscular endurance and strength, and the relationship between injured and uninjured legs was calculated as the limb symmetry index (LSI). Patient-reported outcomes were measured using the ATRS. All outcomes were collected at the 1-year follow-up. Independent predictors included were patient sex, smoking, BMI, age, and surgical versus nonsurgical treatment.

Results

Of the 391 included patients, 307 (79%) were treated surgically. The LSI of heel-rise height at the 1-year follow-up decreased by approximately 4% for every 10-year increment in age (beta, -3.94 [95% CI, -6.19 to -1.69]; P = .0006). In addition, every 10-year increment in age resulted in a 1.79-fold increase in the odds of being in the lowest 10% of the LSI of heel-rise height. Moreover, a nonsignificant superior LSI of heel-rise height was found in patients treated surgically compared with nonsurgical treatment (beta, -4.49 [95% CI, -9.14 to 0.16]; P = .058). No significant predictor was related to the ATRS. Smoking, patient sex, and BMI did not significantly affect the 1-year results for the LSI of the heel-rise tests.

Conclusion

Older age at the time of injury negatively affected heel-rise height 1 year after an Achilles tendon rupture. Irrespective of age, a nonsignificant relationship toward the superior recovery of heel-rise height was seen in patients treated surgically. None of the factors studied affected patient-reported outcomes.

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.

Microcirculation after Achilles tendon rupture correlates with functional and patient-reported outcomes

Patients with acute Achilles tendon rupture (ATR) display an extended healing process with varying clinical outcome. Poor microcirculatory blood flow has been suggested to be a significant factor for the healing process. However, whether microcirculation may predict healing outcome has been mostly unknown. Therefore, we investigated whether blood flow in the Achilles tendon may be associated with patient-reported and functional outcomes after ATR. In vivo laser-Doppler flowmetry was used to assess microvascular blood flow bilateral in the Achilles tendons, during post-occlusive reactive hyperemia, of nine patients with acute total ATR at 2 weeks post-operatively. At 3 months post-operatively, patient-reported outcome was assessed using Achilles tendon Total Rupture Score (ATRS). At 1 year a uniform outcome score, Achilles Combined Outcome Score (ACOS), was obtained by combining validated, independent, patient-reported (ATRS), and functional outcome (heel-rise test) measures. An improved combined patient-reported and functional outcome, ACOS, at 1 year was significantly correlated with higher maximum blood flow (r=.777, P=.040) in the injured limb. Furthermore, enhanced patient-reported outcome, ATRS, at 3 months, was associated with an elevated ratio of maximum to resting blood flow (r=.809, P=.015) in the uninjured limb. Blood flow in early tendon healing is associated with long-term patient-reported and functional outcomes after ATR. The microcirculatory blood flow of both the healing and contralateral Achilles tendon seems to determine the healing potential after injury.

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.