Tendon-to-bone multi-tissue transition exhibits a hierarchical and continuous gradient of matrix composition and alignment, allowing for efficient transmission of mechanical loading between tendon and bone. Upon injury, main problems associated with tendon-to-bone regeneration include disorganized matrix deposition, with a gradual loss of mineral content resulting in poor mechanical properties, limiting tissue integration and the formation of a graded interface. Therefore, we propose to assembly two types of continuous microfibres with distinct topological and compositional features tailored to guide cell alignment and matrix deposition while matching the mechanical requirements of the native tissue.

Wet-spinning was used to produce textured composite microfibres using different flow rates and two polymer blends to replicate the anisotropic architecture of tendon (PCL/Gelatin, 22/9%, w/v) and the isotropic organization together with mineral composition of bone (PCL/Gelatin/Hydroxyapatite, 22/9% w/v and 7.7% w/w HAp). Obtained microfibres morphology, chemical and mechanical properties were evaluated. Biological performance was studied using human adipose-derived stem cells (hASCs). Cytoskeleton alignment, nuclei elongation and matrix mineralization were evaluated. Textile techniques were used to create a 3D fibrous scaffold. Morphological features were analyzed by micro-CT.

PCL/Gelatin fibers produced at 1 mL/h extrusion rate exhibited the highest anisotropic alignment, in opposition to PCL/Gelatin/HAp fibers produced under the same condition. Micro-CT analysis of PCL/Gelatin/HAp fibers demonstrated variations within pore diameter and particles size between the different flow rates. Herein, PCL/Gelatin fibers induced a higher cytoskeleton alignment and nuclei elongation (p < 0.0001) in seeded hASCs. In contrast, significantly higher mineralization was found in PCL/Gelatin/HAp fibres (day 7, p < 0.04; day 14, p < 0.0001) as observed by alizarin red staining and quantification, suggesting the induction of an osteogenic-like phenotype. As proof of concept, textile techniques were used to assemble the two types of fibers and create a 3D scaffold presenting a continuous gradient in HAp content, as well as topological cues. After 14 days of culture with hASCs, a gradient of collagen deposition and matrix mineralization was found (p < 0.014, p < 0.0001). Higher deposition of collagen type II was observed in the tendon and interface parts of the fibrous scaffold and collagen type X in the interface.

Overall, the wet-spinning method was efficiently used to engineer continuous textured composite microfibers. PCL/Gelatin fibers supported cell alignment mimicking tendon one, while PCL/Gelatin/HAp fibers induced mineral deposition and a possible phenotypic change without additional medium supplementation. Textile techniques allowed fibres assemblage and 3D scaffolds fabrication envisioning tendon-to-bone applications.

Tendon injuries constitute a major healthcare burden owing to the limited healing ability of these tissues and the poor clinical outcomes of surgical repair treatments. Recent advances in tendon tissue engineering (TTE) strategies, particularly through the use of biotextile technologies, hold great promise toward the generation of artificial living tendon constructs. We have previously developed a braided construct based on suture threads coated with gelMA:alginate hydrogel encapsulating human tendon cells. These cell-laden composite fibers enabled the replication of cell and tissue-level properties simultaneously. Based on this concept, in this study we explored the use of platelet lysate (PL), a pool of supra-physiological concentrations of growth factors (GFs), to generate a hydrogel layer, which is envisioned to act as a depot of therapeutic factors to induce tenogenic differentiation of encapsulated human adipose stem cells (hASCs). For this purpose, commercially available suture threads were first embedded in a thrombin solution and then incubated in PL containing hASCs. Herein, thrombin induces the gelation of PL and consequent hydrogel formation. After coating suture threads with the mixture of PL-ASCs, cells were found to be viable and homogeneously distributed along the fibers. Strikingly, hASCs encapsulated within the PL hydrogel layer around the suture thread were able to sense chemotactic factors present in PL and to establish connections between adjacent independent fibers, suggesting a tremendous potential of PL cell-laden hydrogel fibers as building blocks in the development of living constructs aimed at tendon repair applications.

Tendon detachment from its bony insertion is one of the most frequent injuries occurring in the musculoskeletal interface, constituting an unmet challenge in orthopaedics. Tendon-to-bone integration occurs at the enthesis, which is characterized by a complex structure organized in a gradient of cells and microenvironments. Hence, the maintenance of a heterotypic cellular niche is critical for tissue functionality and homeostasis. Replicating this unique complexity constitutes a challenge when addressing tendon-to-bone regeneration and interfacial tissue engineering strategies. Currently, mechanisms presiding to tendon-to-bone interface healing are not yet fully understood, particularly the interactions between tendon and bone cells in the orchestration of interfacial repair versus regeneration. Therefore, this study focused on the hypothesis that interactions between human tendon-derived cells (hTDCs) and pre-osteoblasts (pre-OB) can initiate a cascade of events, potentially leading to interfacial regeneration. Thus, hTDCs and pre-OB (pre-differentiated human adipose-derived stem cells) were used. Herein, five different ratios between basal and osteogenic media (100:0,75:25,50:50,25:75,0:100) were assessed to estimate their influence on cell behaviour and identify the ideal parameters for simultaneously supporting tenogenic and osteogenic differentiation before establishing a co-culture. Tenogenic and osteogenic differentiation were assessed through the expression of tendon and bone markers, mineralization (alizarin red, AZ) and alkaline phosphatase (ALP) quantification. Results showed that hTDCs exhibited osteogenic differentiation potential when cultured in the presence of osteogenic media, as demonstrated by an increase in ALP activity and mineralization. Pre-OB expressed osteogenic markers (OCN, OPN) in all media conditions confirming osteogenic commitment, which was simultaneously confirmed by ALP levels and AZ staining. Thus, three different conditions (100:0, 50:50, 0:100) were chosen for further studies in a direct contact co-culture system. Similarly to single cultures, a significant proliferation was observed in all conditions and mineralization was increased as soon as 7 days of culture. Additionally, osteogenic, tenogenic and interface-relevant markers will be assessed to study the effect of co-culture on phenotype maintenance. In summary, the present work addresses major limitations to clinical translation of cell-based therapies aiming at promoting interfacial regeneration. Particularly, we explored the influence of culture media on the maintenance of tenogenic and osteogenic niches, taking a basic and critical step towards the establishment of more complex cell-based systems.

Acknowledgements

Authors thank Fundação para a Ciência e Tecnologia in the framework of FCT-POPH-FSE, SFRH/BD/96593/2013 (RCA) and IF/00593/2015 (MEG); and to FCT/MCTES and the FSE/POCH, PD/59/2013 for PD/BD/128088/2016 (IC).

Purpose: Surgical prosthetic treatment of excentred degeneration of the shoulder joint has long been limited to simple humeral prostheses. Inverted total shoulder arthroplasty (ITSA) using the Grammont system appears to provide real improvement. What is the comparative outcome? Does the Grammont prosthesis give constant results? Is the simple humeral prosthesis still indicated for selected cases? In order to respond to these questions, we reviewed 84 patients who had undergone surgery between 1986 and 2000 for implantation of 52 simple humeral prostheses (mean follow-up 7.1 years) and 32 ITSA (mean follow-up 4.3 years).

Material and methods: Between 1986 and 1995, all patients with excentred degeneration of the shoulder joint were treated with a simple humeral prosthesis (36 cases). Between 1995 and 2000, either ITSA or simple humeral prosthesis (16 cases) was used. For the ITSA, indications were limited to excentred degeneration in patients aged over 70 years with a painful pseudoparalytic shoulder or contraindication for a simple prosthesis (alteration of the acromiocorocoid vault or the subscapular area). Simple prostheses were used either when an ITSA could not be implanted (patient too young, overly deteriorated glenoid, deltoid insufficiency) or when there was a preferential indication (excentred degeneration in young patients < 65 years, preservation of active motion, Favard type 1 or 2 glenoid…).

Results: For the simple humeral prosthesis series (1986–1995): the Constant score improved from 16.4 preoperatively to 489.6 postoperatively; radiographically there were one humeral loosening, three superior migrations, and three glenoid degenerations; three revision procedures were required. For the ITSA: the Constant score improved from 14.2 preoperatively to 61.6 postoperatively; radiographically there was one humeral loosening; 32% glenoid alterations in Nérot grades 3 and 4; one revision procedure was required. For the later simple humeral protheses (1995–2000): the Constant score improved from 18.2 preoperatively to 56.4 postoperatively (60.2 excluding cases with a simple prosthesis due to contraindication of an ITSA); radiologically there were one superior migration and two glenoid deteriorations.

Discussion: For a given indication, the results with the ITSA were better than with the simple prosthesis (p < 0.001). However, excluding salvage procedures where the ITSA could not be used, simple prostheses inserted for precise indications provided results nearly equivalent to the ITSA (p < 0.05) with less uncertainty concerning the future. For us, the inverted total shoulder prosthesis and the simple humeral prosthesis share indications for surgical repair of excentred degeneration of the shoulder joint.

Purpose: The hand-to-forehead test is a new subjective and objective test for anterior shoulder instability. This test is performed preoperatively under general anaesthesia and involves a quantifiable patient-controlled apprehension test and an objective quantitative test of anterior stability.

Material and methods: Between January 1998 and April 2000, 135 patients (97 men and 38 women), mean age 25 years, age range 16–40 years, candidates for surgery for anterior instability of the shoulder (115 Latarget, 14 Bankart, 6 capsular shift) were tested. A control group of 300 candidates free of any shoulder disorder for other surgery were also tested.

Results: the Apprehension test was positive in 95 of the operated patients and negative in 40. Mean angle was 160° (90–180°). The test was always negative in patients with an underlying hyperlaxity (18 patients). The test was positive in 20 controls and negative in 270. Test sensitivity was 72%, specificity 92.5%, positive predictive value 42%, (prevalence 1.5%) and negative predictive value 86%. Reproducibility was 80%. The objective test was positive in 125 of the operated patients and negative in 10. The value was 2++ in 55% of the cases. In the control group, the objective test was positive in 28 and negative in 272. The sensitivity of the objective test was 95%, specificity 90%, positive predictive value 55% and negative predictive value 95%. Reproducibility was 92%.

Discussion: The purpose of the hand-to-forehead test is to express the instability as perceived by the patient and to exteriorise anterior laxity without reproducing true anterior displacement. Excepting cases with underlying hyperlaxity, this test does not appear to be inflenced by different injuries subsequent to recurrent anterior dislocation. (no significant difference between glenoid bone lesions, Broca lesions or Malgaigne notches).

Conclusion: This new test provides a reliable objective assessment of anterior instability of the shoulder using a quantifiable combination of classical apprehension and laxity tests. It is a supplementary diagnostic tool for difficult cases and a useful aid for pre- and postoperative evaluation of these patients.