The vasculature and its role in the damaged and healing tendon

Tendon pathology has many manifestations, from spontaneous rupture to chronic tendinitis or tendinosis; the etiology and pathology of each are very different, and poorly understood. Tendon is a comparatively poorly vascularised tissue that relies heavily upon synovial fluid diffusion to provide nutrition. During tendon injury, as with damage to any tissue, there is a requirement for cell infiltration from the blood system to provide the necessary reparative factors for tissue healing. We describe in this review the response of the vasculature to tendon damage in a number of forms, and how and when the revascularisation or neovascularisation process occurs. We also include a section on the revascularisation of tendon during its use as a tendon graft in both ligament reconstruction and tendon–tendon grafting

The Regulation of Aggrecanase ADAMTS-4 Expression in Human Achilles Tendon and tendon-Derived Cells

Several members of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin motifs) family have been identified as aggrecanases, whose substrates include versican, the principal large proteoglycan in the tendon extracellular matrix. We have characterized the expression of ADAMTS-4 in human Achilles tendon and tendon-derived cells. ADAMTS-4 mRNA levels were higher in ruptured tendon compared with normal tendon or chronic painful tendinopathy. In tissue extracts probed by Western blotting, mature ADAMTS-4 (68 kDa) was detected only in ruptured tendons, while processed ADAMTS-4 (53 kDa) was detected also in chronic painful tendinopathy and in normal tendon. In cultured Achilles tendon cells, transforming growth factor-ß (TGF-ß) stimulated ADAMTS-4 mRNA expression (typically 20-fold after 24 h), while interleukin-1 induced a smaller, shorter-term stimulation which synergised markedly with that induced by TGF-ß. Increased levels of immunoreactive proteins consistent with mature and processed forms of ADAMTS-4 were detected in TGF-ß-stimulated cells. ADAMTS-4 mRNA was expressed at higher levels by tendon cells in collagen gels than in monolayer cultures. In contrast, the expression of ADAMTS-1 and -5 mRNA was lower in collagen gels compared with monolayers, and these mRNA showed smaller or opposite responses to growth factors and cytokines compared with that of ADAMTS-4 mRNA. We conclude that both ADAMTS-4 mRNA and ADAMTS-4 protein processing may be differentially regulated in normal and damaged tendons and that both the matrix environment and growth factors such as TGF-ß are potentially important factors controlling ADAMTS aggrecanase activities in tendon pathology

Effect of front and back squat techniques on peak loads experienced by the Achilles tendon

Background A primary technique in the discipline of strength and conditioning the squat has two principal ‘back and front’ variants. Despite the physiological and strength benefits of the squat, the propensity for musculoskeletal injury is high. The current investigation examined the influence of the front and back squat variations on the load experienced by the Achilles tendon. Material/Methods Achilles tendon loads were obtained from eighteen experienced male participants as they completed both back and front squats. Differences between squat conditions were examined using Bonferroni adjusted (p = 0.0125) paired t-tests. Results The results showed that the peak Achilles tendon load was significantly greater in the back squat (2.67 ±0.74 B.W) condition compared to the front squat (2.37 ±0.69 B.W). Conclusions Given the proposed relationship between the magnitude of the load experienced by the Achilles tendon and tendon pathology, the back squat appears to place lifters at greater risk from Achilles tendon injury. Therefore, it may be prudent for lifters who are predisposed to Achilles tendon pathology to utilize the front squat in their training

L-configuration re-attachment of distal biceps tendon rupture

In distal biceps tendon ruptures, re-attachment to the radial tuberosity should ensure adequate tendon to bone contact for optimal healing

Do Outcomes of Arthroscopic Subscapularis Tendon Repairs Depend on Rotator Cuff Fatty Infiltration?

Background:Rotator cuff fatty infiltration has been correlated with poorer radiographic and clinical outcomes in supraspinatus and infraspinatus tendon repairs, but this has not been well-studied in subscapularis tendon repairs. Purpose:To evaluate the influence of preoperative rotator cuff fatty infiltration on postoperative outcomes for patients undergoing arthroscopic subscapularis tendon repair. Study Design:Cohort study; Level of evidence, 3. Methods:Patients who underwent arthroscopic subscapularis repair between 2010 and 2016 were retrospectively identified, and demographic data and surgical findings were recorded. The extent of fatty infiltration was determined on preoperative magnetic resonance imaging by the Fuchs modification of the Goutallier classification. At the most recent follow-up, patients completed the Patient-Reported Outcomes Measurement Information System for Upper Extremity (PROMIS-UE) computer adaptive test and a postoperative visual analog scale for pain. The distribution of fatty infiltration was compared between patients undergoing subscapularis tendon repair versus subscapularis tendon repair combined with a posterior cuff repair. Outcomes were compared for patients using Goutallier grade 0-1 versus grade ≥2 changes in each rotator cuff muscle. Multivariate linear regression analysis was performed to evaluate the influence of muscle quality, as well as demographic factors, on PROMIS-UE scores. Significance was defined as P < .05. Results:There were 140 shoulders included (mean age, 61.8 years; 42.1% female; mean follow-up, 51.7 months). The prevalence of Goutallier grade 2 changes or higher was significantly greater in patients with multitendon repair relative to isolated subscapularis tendon repair. For the overall group of all patients undergoing subscapularis tendon repair, whether in isolation or as part of a multitendon repair, PROMIS-UE scores were significantly lower for patients with infraspinatus muscle grade 2 or higher Goutallier changes relative to grade 0 or 1. After adjustment for age, body mass index, patient sex, and fatty infiltration in other rotator cuff muscles, poor infraspinatus muscle quality remained the only significant predictor for lower PROMIS-UE scores. Conclusion:Patients undergoing arthroscopic subscapularis tendon repair with poor infraspinatus muscle quality had worse patient-reported outcomes. This was true whether subscapularis tendon repair was isolated or was performed in conjunction with supraspinatus and infraspinatus tendon repairs

How does a cadaver model work for testing ultrasound diagnostic capability for rheumatic-like tendon damage?

To establish whether a cadaver model can serve as an effective surrogate for the detection of tendon damage characteristic of rheumatoid arthritis (RA). In addition, we evaluated intraobserver and interobserver agreement in the grading of RA-like tendon tears shown by US, as well as the concordance between the US findings and the surgically induced lesions in the cadaver model. RA-like tendon damage was surgically induced in the tibialis anterior tendon (TAT) and tibialis posterior tendon (TPT) of ten ankle/foot fresh-frozen cadaveric specimens. Of the 20 tendons examined, six were randomly assigned a surgically induced partial tear; six a complete tear; and eight left undamaged. Three rheumatologists, experts in musculoskeletal US, assessed from 1 to 5 the quality of US imaging of the cadaveric models on a Likert scale. Tendons were then categorized as having either no damage, (0); partial tear, (1); or complete tear (2). All 20 tendons were blindly and independently evaluated twice, over two rounds, by each of the three observers. Overall, technical performance was satisfactory for all items in the two rounds (all values over 2.9 in a Likert scale 1-5). Intraobserver and interobserver agreement for US grading of tendon damage was good (mean κ values 0.62 and 0.71, respectively), with greater reliability found in the TAT than the TPT. Concordance between US findings and experimental tendon lesions was acceptable (70-100 %), again greater for the TAT than for the TPT. A cadaver model with surgically created tendon damage can be useful in evaluating US metric properties of RA tendon lesions

Sex variation in patellar tendon kinetics during running

Purpose. The aim of the current investigation was to determine whether female recreational runners exhibit distinct patellar tendon loading patterns in relation to their male counterparts. Methods. Twelve male (age 26.55 ± 4.11 years, height 1.78 ± 0.11 m, mass 77.11 ± 5.06 kg) and twelve female (age 26.67 ± 5.34 years, height 1.67 ± 0.12 m, mass 63.28 ± 9.75 kg) runners ran over a force platform at 4.0 m · s –1. Lower limb kinematics were collected using an eight-camera optoelectric motion capture system which operated at 250 Hz. Patellar tendon loads were examined using a predictive algorithm. Sex differences in limb, knee and ankle joint stiffness were examined statistically using independent samples t tests. Results. The results indicate that patellar tendon force (male = 6.49 ± 2.28, female = 7.03 ± 1.35) and patelllar tendon loading rate (male = 92.41 ± 32.51, female = 111.05 ± 48.58) were significantly higher in female runners. Conclusions. Excessive tendon loading in female runners indicates that female runners may be at increased risk of patellar tendon pathologies

Using Platelet-Rich Plasma to Reverse the Effects of Tendinopathy and Prevent Tendon Re-rupture after Surgery in Athletes: The Search for a Standardized Protocol

30-50% of all lesions amateur and professional sports players will experience during activity are related to the tendon. Moreover, the incidence of tendinopathy, a precursor to tendon rupture, is much higher in both of these groups due to excessive loading of tendons during physical activity, insufficient rest afterwards and certain antibiotic use. The tendon anatomically has both a low blood supply and a low cell turnover rate, which contribute to the relative ease by which an athlete can develop tendinopathy. Chronic tendinopathy has very few high-success treatments but in recent years, platelet-rich plasma (PRP), a treatment in which platelets are isolated from the patient’s blood and injected back into the diseased tendon, has seen promising results. Prior research has focused on assessing the viability of PRP as a treatment but failed to come up with a standard and procedure protocol for its administration. In this study, PRP is evaluated in terms of success rate, concentration of cells other than platelets, concentration of growth factors, life of growth factors, and size and cross section of the tendon to develop a formulation standard, injection plan, and procedure protocol for different tendinopathies. Furthermore, a rehabilitation program that takes into account both the treatment and natural healing process of the tendon to shorten the time the athlete spends off the field is outlined

Exposure of a tendon extracellular matrix to synovial fluid triggers endogenous and engrafted cell death: A mechanism for failed healing of intrathecal tendon injuries

Aim: The purpose of this study was to investigate the effect of normal synovial fluid (SF) on exposed endogenous tendon-derived cells (TDC) and engrafted mesenchymal stem cells (MSCs) within the tendon extracellular matrix. Methods: Explants from equine superficial digital flexor (extra-synovial) and deep digital flexor tendons (DDFT) from the compressed, intra-synovial and the tensile, extra-synovial regions were cultured in allogeneic or autologous SF-media. Human hamstring explants were cultured in allogeneic SF. Explant viability was assessed by staining. Proliferation of equine monolayer MSCs and TDCs in SF-media and co-culture with DDFT explants was determined by alamarblue®. Non-viable Native Tendon matrices (NNTs) were re-populated with MSCs or TDCs and cultured in SF-media. Immunohistochemical staining of tendon sections for the apoptotic proteins caspase-3, -8 and -9 was performed. Results: Contact with autologous or allogeneic SF resulted in rapid death of resident tenocytes in equine and human tendon. SF did not affect the viability of equine epitenon cells, or of MSCs and TDCs in monolayer or indirect explant co-culture. MSCs and TDCs, engrafted into NNTs, died when cultured in SF. Caspase-3, -8 and -9 expression was greatest in SDFT explants exposed to allogeneic SF. Conclusions: The efficacy of cells administered intra-synovially for tendon lesion repair is likely to be limited, since once incorporated into the matrix, cells become vulnerable to the adverse effects of SF. These observations could account for the poor success rate of intra-synovial tendon healing following damage to the epitenon and contact with SF, common with most soft tissue intra-synovial pathologies

Patellar Tendon Morphology in Trans-tibial Amputees Utilizing a Prosthesis with a Patellar-tendon- Bearing Feature

A patellar-tendon-bearing (PTB) bar is a common design feature used in the socket of trans-tibial prostheses to place load on the pressure-tolerant tissue. As the patellar tendon in the residual limb is subjected to the perpendicular compressive force not commonly experienced in normal tendons, it is possible for tendon degeneration to occur over time. The purpose of this study was to compare patellar tendon morphology and neovascularity between the residual and intact limbs in trans-tibial amputees and healthy controls. Fifteen unilateral trans-tibial amputees who utilized a prosthesis with a PTB feature and 15 age- and sex- matched controls participated. Sonography was performed at the proximal, mid-, and distal portions of each patellar tendon. One-way ANOVAs were conducted to compare thickness and collagen fber organization and a chi-square analysis was used to compare the presence of neovascularity between the three tendon groups. Compared to healthy controls, both tendons in the amputees exhibited increased thickness at the mid- and distal portions and a higher degree of collagen fber disorganization. Furthermore, neovascularity was more common in the tendon of the residual limb. Our results suggest that the use of a prosthesis with a PTB feature contributes to morphological changes in bilateral patellar tendons