Relationship between neovascularization and clinical severity in Achilles tendinopathy in 556 paired measurements.

Neovascularization is frequently observed in tendinopathy. Previous studies have focused on the role of neovascularization in Achilles tendinopathy, but have been conducted in small series. It is still unclear whether the degree of neovascularization is related to severity of symptoms. The purpose was to study the relationship between ultrasonographic neovascularization and clinical severity in patients with Achilles tendinopathy. In this prospective cohort study, data on 127 patients (141 tendons) were assembled from databases of three clinical trials. All patients followed an eccentric exercise program. The Öhberg neovascularization score (0-4+) and Victorian Institute of Sports Assessment-Achilles (VISA-A) score (split into domains: pain, function and activity) were collected during baseline and follow-up. The relationship between neovascularization and VISA-A score was calculated. At baseline, 107 tendons (76%) showed some degree of neovascularization. In 556 coupled measurements, neovascularization was weakly related to the VISA-A score [Exp (B) 1.017, 95% confidence interval (CI), 1.007-1.026]. No significant relationship was found between neovascularization and the pain domain (P = 0.277) and the activity domain (P = 0.283), but there was between neovascularization and the function domain of the VISA-A score [Exp (B) = 1.067, 95% CI 1.018-1.119]. In conclusion, neovascularization in Achilles tendinopathy is weakly related to clinical severity, mainly based on the function domain of the VISA-A score.

Prediction of the elastic strain limit of tendons.

The elastic strain limit (ESL) of tendons is the point where maximum elastic modulus is reached, after which micro-damage starts. Study of damage progression in tendons under repetitive (fatigue) loading requires a priori knowledge about ESL. In this study, we propose three different approaches for predicting ESL. First, one single value is assumed to represent the ESL of all tendon specimens. Second, different extrapolation curves are used for extrapolating the initial part of the stress-strain curve. Third, a method based on comparing the shape of the initial part of the stress-strain curve of specimens with a database of stress-strain curves is used. A large number of porcine tendon explants (97) were tested to examine the above-mentioned approaches. The variants of the third approach yielded significantly (p<0.05) smaller error values as compared to the other approaches. The mean absolute percentage error of the best-performing variant of the shape-based comparison was between 8.14±6.44% and 9.96±9.99% depending on the size of the initial part of the stress-strain curves. Interspecies generalizability of the best performing method was also studied by applying it for prediction of the ESL of horse tendons. The ESL of horse tendons was predicted with mean absolute percentage errors ranging between 10.53±7.6% and 19.16±14.31% depending on the size of the initial part of the stress-strain curves and the type of normalization. The results of this study suggest that both ESL and the shape of stress-strain curves may be highly different between different individuals and different anatomical locations.

Further characterisation of an experimental model of tendinopathy in the horse.

REASONS FOR PERFORMING STUDY: Injuries in energy-storing tendons are common in both horses and man. The high prevalence of reinjury and the relatively poor prognosis for returning to preinjury performance levels warrant further research, for which well characterised models would be very helpful. OBJECTIVES: Given the clinical similarities in tendinopathy of energy-storing tendons, we hypothesised that a recently developed experimental model of equine tendon injury would display many of the characteristics of clinical tendinopathy and could therefore be of use for both species, thus providing comparative insight to the human condition and offering direct potential impact to equine medicine. STUDY DESIGN: In vivo experimental study. METHODS: Surgical lesions were created in the superficial digital flexor tendon (SDFT) of 6 horses. Clinical examination, as well as biochemistry, histology and immunohistochemistry were performed on the harvested samples at 6 weeks post surgery. RESULTS: Disrupted collagen fibres, increased glycosaminoglycan content, increased presence of tenocytes with plump nuclei, the scarcity of inflammatory cells, increased matrix metalloproteinase (MMP) activity and neovascularisation were observed and found to be consistent with clinical tendinopathy. CONCLUSION AND RELEVANCE: This model displays the key features of the most common human and equine degenerative tendon disorders and is therefore an appropriate, if still imperfect, model of tendinopathy.

Tendon structure changes after maximal exercise in the Thoroughbred horse: use of ultrasound tissue characterisation to detect in vivo tendon response.

Investigations into the response of the superficial digital flexor tendon (SDFT) of the Thoroughbred horse to mechanical stimuli have been limited to in vitro cell culture studies focused primarily on gene expression of critical matrix proteins. It is uncertain how well in vitro outcomes translate to the tendon of the horse during exercise. The current study examined changes in tendon structure in response to maximal exercise using ultrasound tissue characterisation (UTC) to scan the SDFT prior to and after competitive racing. UTC uses contiguous transverse ultrasound images to assess the dynamics of the echopattern, which has a close relationship with changes in the 3-D ultra-structure of the tendon. Using UTC, it was possible to detect subtle changes in the dynamics of the echopattern, with a reduction in pixels that represent aligned and integer collagen tendon bundles on days 1 and 2 post-race when compared to pre-race (P<0.05). The echopattern of these tendons returned to baseline on day 3. This change in echopattern was not seen in control horses. It was concluded that short-term changes in the SDFT following maximal exercise could be detected using UTC.

The effect of platelet-rich plasma on the neovascularization of surgically created equine superficial digital flexor tendon lesions.

The repair process of tendon injuries, which are common in both human and equine athletes, is slow and the quality of the repair tissue is often inferior to the original tendon tissue, which frequently leads to re-injury. The relatively poor vascularization of tendons is considered to be one of the reasons for their limited healing potential. Recently, platelet-rich plasma (PRP), an autologous concentrate of platelets, rich in growth factors, has been shown to enhance the repair process of injured tendons. This effect has been ascribed to the high levels of growth factors in PRP, several of which are known to be involved in tendon repair. Among many other growth factors, the vascular endothelial growth factor, a powerful stimulator of angiogenesis, is abundantly present in PRP, suggesting that enhancement of neovascularization might be one of the working mechanisms. In this study, the effect of PRP on neovascularization was studied in experimentally induced tendon injuries using color Doppler ultrasonography and immunological staining of Factor VIII. PRP induced significantly more neovascularization than the placebo treatment until at least 23 weeks after treatment, as detected by both Doppler ultrasonography and Factor VIII staining. Neovascularization might be one of the explanations for the long-lasting effect of a single intratendinous treatment with PRP.

No effects of PRP on ultrasonographic tendon structure and neovascularisation in chronic midportion Achilles tendinopathy.

OBJECTIVE: To assess whether a platelet-rich plasma (PRP) injection leads to an enhanced tendon structure and neovascularisation, measured with ultrasonographic techniques, in chronic midportion Achilles tendinopathy. DESIGN: Double-blind, randomised, placebo-controlled clinical trial. SETTING: Sports medical department of The Hague medical centre. PATIENTS: 54 patients with chronic midportion Achilles tendinopathy were included. INTERVENTIONS: Patients were randomised to eccentric exercise therapy with either a PRP injection (PRP group) or a saline injection (placebo group). MAIN OUTCOME MEASUREMENTS: Tendon structure was evaluated by ultrasonographic tissue characterisation, a novel technique which quantifies tendon structure into four echo-types: echo-types I+II represent organised tendon bundles, whereas echo-types III+IV represent a disorganised tendon structure. Colour Doppler ultrasonography was used to measure the degree of neovascularisation. Follow-up was at 6, 12 and 24 weeks. RESULTS: A significant improvement in echo-types I+II was found after 24 weeks within both the PRP group (n=27) and the placebo group (n=27), but there was no significant between-group difference (95% CI -1.6 to 7.8, p=0.169). After 6 weeks, the neovascularisation score increased within the PRP group (p=0.001) and the placebo group (p=0.002), but there was no significant between-group difference in change in neovascularisation score at any point in time. CONCLUSION: Injecting PRP for the treatment of chronic midportion Achilles tendinopathy does not contribute to an increased tendon structure or alter the degree of neovascularisation, compared with placebo. FUNDING: Biomet Biologics LLC, Warsaw, Indiana.

Regional differences in biochemical, biomechanical and histomorphological characteristics of the equine suspensory ligament.

REASONS FOR PERFORMING STUDY: Desmopathies of the suspensory ligament are relatively frequent and vary in prevalence over different anatomical regions. This variation may be because of regional differences in tissue characteristics. OBJECTIVE: To characterise different regions of healthy forelimb suspensory ligaments (SLs) by means of biochemical, biomechanical and histomorphological techniques. HYPOTHESIS: There is substantial topographical heterogeneity in the SL with respect to structural, compositional and functional characteristics. METHODS: SLs were harvested from 38 limbs and used for biochemical (n = 20), biomechanical (n = 14) and histomorphological (n = 4) evaluation. Sulphated glycosaminoglycan (S-GAG), DNA and collagen content, degree of lysyl hydroxylation and numbers of enzymatic and nonenzymatic cross-links were determined in 7 regions of the SL: lateral and medial part of the origin (OM, OL), mid-body (MB), axial and abaxial parts of the lateral and medial branches (ILAX, ILAB, IMAX and IMAB, respectively). Passive resistance to tensile loading was measured in 5 regions of the SL (all except OL and OM). RESULTS: DNA content was lower in OL and OM than in all other parts. GAG content was also lower in OL and OM and highest in ILAB and IMAB. Collagen content was lower in OL/OM and highest in ILAX/IMAX. Pentosidine levels were highest in OL and significantly lower in the lateral insertion (ILAX/ILAB). There were no differences in hydroxylysylpyridinoline (HP) cross-links or lysyl hydroxylation. Stiffness (P<0.01) and modulus of elasticity (P<0.01) were substantially higher in the MB region than in all other regions except for IMAB. Strain at failure was lower in the MB region (P<0.0001), resulting in a comparable force at rupture as in the other regions. CONCLUSIONS: Matrix composition differs to a relatively limited extent between different regions of the SL. The mid-body of the ligament is stiffer than the branches, which have similar properties and relevance and mechanical differences between mid-body and branches/origin may explain some use-related differences in the prevalence of lesions.

Ultrasonographic tissue characterisation of human Achilles tendons: quantification of tendon structure through a novel non-invasive approach.

OBJECTIVE: To assess whether three-dimensional imaging of the Achilles tendon by ultrasonographic tissue characterisation (UTC) can differentiate between symptomatic and asymptomatic tendons. DESIGN: Case-control study. SETTING: Sports Medical Department of the Hague Medical Centre. PATIENTS: Twenty-six tendons from patients with chronic midportion Achilles tendinopathy were included. The "matched" control group consisted of 26 asymptomatic tendons. INTERVENTIONS: Symptomatic and asymptomatic tendons were scanned using the UTC procedure. One researcher performed the ultrasonographic data collection. These blinded data were randomised, and outcome measures were determined by two independent observers. MAIN OUTCOME MEASUREMENTS: The raw ultrasonographic images were analysed with a custom-designed algorithm that quantifies the three-dimensional stability of echo patterns, qua intensity and distribution over contiguous transverse images. This three-dimensional stability was related to tendon structure in previous studies. UTC categorises four different echotypes that represent (I) highly stable; (II) medium stable; (III) highly variable and (IV) constantly low intensity and variable distribution. The percentages of echo-types were calculated, and the maximum tendon thickness was measured. Finally, the inter-observer reliability of UTC was determined. RESULTS: Symptomatic tendons showed less pixels in echo-types I and II than asymptomatic tendons (51.5% vs 76.6%, p<0.001), thus less three-dimensional stability of the echo pattern. The mean maximum tendon thickness was 9.2 mm in the symptomatic group and 6.8 mm in the asymptomatic group (p<0.001). The Intraclass Correlation Coefficient (ICC) for the interobserver reliability of determining the echo-types I+II was 0.95. The ICC for tendon thickness was 0.84. CONCLUSION: UTC can quantitatively evaluate tendon structure and thereby discriminate symptomatic and asymptomatic tendons. As such, UTC might be useful to monitor treatment protocols.

One-year follow-up of a randomised controlled trial on added splinting to eccentric exercises in chronic midportion Achilles tendinopathy.

OBJECTIVE: The study examined whether the addition of a night splint to eccentric exercises is beneficial for functional outcome in chronic midportion Achilles tendinopathy. DESIGN: One-year follow-up of a randomised controlled single blinded clinical trial. SETTING: Sports medicine department in a general hospital. PATIENTS: 58 patients (70 tendons) were included. INTERVENTIONS: All patients completed a 12-week heavy load eccentric training programme. One group received a night splint in addition to eccentric exercises. MAIN OUTCOME MEASUREMENTS: Outcome scores were: Victorian Institute of Sport Assessment-Achilles (VISAA) score, subjective patient satisfaction and neovascularisation score measured with power Doppler ultrasonography (PDU). RESULTS: For both groups the VISA-A score increased significantly (from 50 to 76 (p<0.01) in the eccentric group and from 49 to 78 (p<0.01) in the night splint group). No significant differences in the VISA-A score were found between the groups from baseline to one year (p = 0.32). The presence of neovessels at baseline did not predict a change in the VISA-A score after one year in the whole group (p = 0.71). CONCLUSION: Eccentric exercises with or without a night splint improved functional outcome at one year follow-up. At follow-up there was no significant difference in clinical outcome when a night splint was used in addition to an eccentric exercise programme. Between 3 months and one year follow-up, a continuing increase in the VISA-A score was found. Assessment of the neovascularisation score with PDU at baseline has no prognostic value on long-term clinical outcome.

The effect of focused extracorporeal shock wave therapy on collagen matrix and gene expression in normal tendons and ligaments.

REASONS FOR PERFORMING STUDY: Extracorporeal shock wave therapy (ESWT) is frequently used in equine practice, but little is known about its biological action. OBJECTIVES: To study the effects of ESWT on matrix structure and gene expression levels in normal, physiologically loaded tendinous structures in ponies. METHODS: Six Shetland ponies, free of lameness and with ultrasonographically normal flexor and extensor tendons and suspensory ligaments (SL), were used. ESWT was applied at the origin of the suspensory ligament and the mid-metacarpal region of the superficial digital flexor tendon (SDFT) 6 weeks prior to sample taking, and at the mid-metacarpal region (ET) and the insertion on the extensor process of the distal phalanx (EP) of the common digital extensor tendon 3 h prior to tendon sampling. In all animals one forelimb was treated and the other limb was used as control. After euthanasia, tendon tissue was harvested for real-time PCR to determine gene expression levels and additional samples were taken for histological evaluation and biochemical analyses RESULTS: Histologically a disorganisation of the normal collagen structure was observed 3 h after ESWT, remnants of which were still visible after 6 weeks. While degraded collagen levels showed an increase at 3 h post treatment (P= 0.012) they were reduced at 6 weeks post ESWT (P = 0.039). Gene expression for both COL1 (P = 0.004) and MMP14 (P = 0.020) was upregulated at 6 weeks after treatment. CONCLUSIONS: Exposure of normal tendinous tissue to ESWT is not uneventful; it leads to a disorganisation of matrix structure and changes in degraded collagen levels. The upregulation of COL1 expression 6 weeks after ESWT may be indicative for repair. POTENTIAL RELEVANCE: The observed disorganisation of the collagen network warrants caution when using ESWT. Exposing noninjured tissue to ESWT should be avoided and it may be advisable to restrict exercise in recently treated patients. However, the induced tissue disorganisation might also be a trigger for repair in chronic tendinopathies.

Effect of extracorporeal shock wave therapy on the biochemical composition and metabolic activity of tenocytes in normal tendinous structures in ponies.

REASONS FOR PERFORMING STUDY: Extracorporeal shockwave therapy (ESWT) has recently been introduced as a new therapy for tendon injuries in horses, but little is known about the basic mechanism of action of this therapy. OBJECTIVES: To study the effect of ESWT on biochemical parameters and tenocyte metabolism of normal tendinous structures in ponies. METHODS: Six Shetland ponies, free of lameness and with ultrasonographically normal flexor and extensor tendons and suspensory ligaments (SL), were used. ESWT was applied at the origin of the suspensory ligament and the mid-metacarpal region of the superficial digital flexor tendon (SDFT) 6 weeks prior to sample taking, and at the mid-metacarpal region (ET) and the insertion on the extensor process of the distal phalanx (EP) of the common digital extensor tendon 3 h prior to tendon sampling. In all animals one front leg was treated and the other front leg was used as control. After euthanasia, tendon explants were harvested aseptically for in vitro cell culture experiments and additional samples were taken for biochemical analyses. RESULTS: In the explants harvested 3 h after treatment, glycosaminoglycan (GAG) and protein syntheses were increased (P<0.05). The synthesis of all measured parameters was decreased 6 weeks after ESWT treatment. Biochemically, the level of degraded collagen was increased 3 h after treatment (P<0.05). Six weeks after treatment, there was a decrease of degraded collagen and GAG contents. DNA content had not changed in either tendon samples or explants after culturing. CONCLUSIONS: ESWT causes a transient stimulation of metabolism in tendinous structures of ponies shortly after treatment. After 6 weeks metabolism has decreased significantly and GAG levels are lower than in untreated control limbs. POTENTIAL RELEVANCE: The stimulating short-term effect of ESWT might accelerate the initiation of the healing process in injured tendons. The long-term effect seems less beneficial. Further research should aim at determining the duration of this effect and at assessing its relevance for end-stage tendon quality.