A 3D finite element model for geometrical and mechanical comparison of different supraspinatus repair techniques

Design and Mechanical Evaluation of Sutureless Implants for the Surgery Treatment of Rotator Cuff Tears

Rotator cuff (RC) tears cause pain and functional disability of the shoulder. Despite advances in suture anchors, there are still reports about the incidence of surgical-related injuries to RC mainly associated with sutures. The purpose of this study was to design and evaluate the mechanical behavior of sutureless implants to repair RC tears. We hypothesized that the implants present mechanical characteristics suitable for the surgical treatment of RC tears as suture anchors. Three different implants (T1, T2, T3) were designed and fabricated with titanium: T1 has two rods and rectangular head; T2 has two rods with a small opening and enlarged rectangular head; and T3 has three rods and a circular head. The implants were fixed in rigid polyurethane foam blocks by a series of blows, and the applied mechanical loads along with the number of blows were quantified. Pullout tests using tapes fixed between the implant head and testing machine grip were conducted until implant failure. The maximum pullout strength and displacement of the implant relative to the rigid foam block were computed. Statistical significance was set at p < 0.05. Owing to its geometric configuration, implant T2 presented the best characteristics related to stability, strength, and ease of insertion. Implant T2 confirms our hypothesis that its mechanical behavior is compatible with that of suture anchors, which could lead to the reduction of RC repair failures and simplify the arthroscopic procedure.

Joining soft tissues to bone: Insights from modeling and simulations

Entheses are complex multi-tissue regions of the musculoskeletal system serving the challenging task of connecting highly dissimilar materials such as the compliant tendon to the much stiffer bone, over a very small region. The first aim of this review is to highlight mathematical and computational models that have been developed to investigate the many attachment strategies present at entheses at different length scales. Entheses are also relevant in the medical context due to the high prevalence of orthopedic injuries requiring the reattachment of tendons or ligaments to bone, which are associated with a rather poor long-term clinical outcome. The second aim of the review is to report on the computational works analyzing the whole tendon to bone complex as well as targeting orthopedic relevant issues. Modeling approaches have provided important insights on anchoring mechanisms and surgical repair strategies, that would not have been revealed with experiments alone. We intend to demonstrate the necessity of including, in future models, an enriched description of enthesis biomechanical behavior in order to unravel additional mechanical cues underlying the development, the functioning and the maintaining of such a complex biological interface as well as to enhance the development of novel biomimetic adhesive, attachment procedures or tissue engineered implants.

Comparison between single and double suture passing techniques in the suture bridge rotator cuff repair with a 2-mm tape: A simulation study using a three-dimensional finite element method

BACKGROUND

Suture bridge repair has been widely used as one of the standard procedures in the arthroscopic rotator cuff repair. We compared the intratendinous stress distribution between single and double suture passing techniques in the suture bridge repair using a 2-mm tape and clarified the roles of tensioning in this procedure.

METHODS

A board-like model of the supraspinatus tendon and humeral head was used in order to standardize conditions and exclude the influence of anatomical variations between individuals. Reattachment of the supraspinatus tendon to the bone was simulated using both single and double suture passing techniques for the suture bridge repair using a 2-mm tape. A tensile load was applied to the medial end of the tendon, and the stress distribution pattern was observed. Elastic analysis enabled comparison of the von Mises equivalent and maximum principal stresses between the single and double suture passing techniques. The tape configuration was subsequently translated 1 mm toward the insertion points of lateral anchors to simulate the tensioning maneuver.

RESULTS

Although the distribution pattern of both the equivalent and the maximum principal stresses was similar for both models, areas with a high stress concentration were smaller in the single suture passing model than those in the double suture passing model. The equivalent stress concentrated within the tendon beneath the tapes as well as in the area between the crossing tapes and the lateral end of the tendon, whereas the maximum principal stress concentrated medial to the sites of suture penetration.

CONCLUSIONS

Single suture passing technique can reduce the extent of intratendinous stress concentration compared with double suture passing technique, which might be beneficial to reduce the incidence of type 2 retear after suture bridge repair of rotator cuff tendon using a 2-mm tape.

Comparison of 3 supraspinatus tendon repair techniques - a 3D computational finite element analysis

Considering that optimal contact area and pressure at the tendon-bone interface are associated with better footprint repair and outcomes, the aim of this study was to compare the performance of standard double-row, transosseous equivalent (TOE), and partial articular supraspinatus tendon avulsion (PASTA) techniques for the treatment of full-thickness tears of the supraspinatus tendon using 3D finite element models. Loading consisted, alternately, in a preloading of 10 N and 20 N of the sutures. The footprint coverage of the standard double-row, TOE, and PASTA techniques was estimated to represent 19%, 30%, and 35%, respectively, of the repair area. The average contact pressures followed an opposite trend, i.e., the largest was estimated for the standard double-row technique, whereas the lowest was estimated for the PASTA technique. Despite the present study advancing the computational modelling of rotator cuff repair, and the results being consistent with the literature, its findings must be evaluated cautiously, bearing in mind its limitations.

Histological evaluation of cellular response to a multifilament electrospun suture for tendon repair

BACKGROUND

Rotator cuff tendon repair in humans is a commonly performed procedure aimed at restoring the tendon-bone interface. Despite significant innovation of surgical techniques and suture anchor implants, only 60% of repairs heal successfully. One strategy to enhance repair is the use of bioactive sutures that provide the native tendon with biophysical cues for healing. We investigated the tissue response to a multifilament electrospun polydioxanone (PDO) suture in a sheep tendon injury model characterised by a natural history of failure of healing.

METHODOLOGY AND RESULTS

Eight skeletally mature English Mule sheep underwent repair with electrospun sutures. Monofilament sutures were used as a control. Three months after surgery, all tendon repairs healed, without systemic features of inflammation, signs of tumour or infection at necropsy. A mild local inflammatory reaction was seen. On histology the electrospun sutures were densely infiltrated with predominantly tendon fibroblast-like cells. In comparison, no cellular infiltration was observed in the control suture. Neovascularisation was observed within the electrospun suture, whilst none was seen in the control. Foreign body giant cells were rarely seen with either sutures.

CONCLUSION

This study demonstrates that a tissue response can be induced in tendon with a multifilament electrospun suture with no safety concerns.

Finite element analysis of the rotator cuff: A systematic review

BACKGROUND

Finite element modeling serves as a promising tool for investigating underlying rotator cuff biomechanics and pathology. However, there are currently no concrete guidelines for reporting in finite element model studies. This has compromised the reliability, validity, and reproducibility of literature due to omission of pertinent items within publications. Recently a Finite Element Model Grading Procedure has been proposed as a reporting guideline for model developers. The aim of this study was to conduct a systematic review of rotator cuff focused finite element models and characterize the reporting quality of those articles.

METHODS

A comprehensive literature search was performed in PubMed, Web of Science, and Embase to find relevant articles. Each article was graded and given a reporting quality ranking based on a score generated from the Finite Element Model Grading Procedure.

FINDINGS

We found that only 5/22 articles had scores of 75% or higher and fell within the "exceptional" reporting quality range. Most of the articles (16/22) fell within the "good" reporting quality range with scores between 50% and 75%. However, 9/16 articles within the "good" reporting quality range had scores below 60%.

INTERPRETATION

This study indicates that improved guidelines and standards for good reporting practices must be made in the field of finite element modeling. Furthermore, it supports the use of the Finite Element Model Grading Procedure as an objective method for evaluating the quality of finite element model reporting in the literature.

A Prospective Randomized Trial Comparing Suture Bridge and Medially Based Single-Row Rotator Cuff Repair in Medium-Sized Supraspinatus Tears

PURPOSE

To compare the clinical and imaging outcomes between the suture bridge technique (SB) and the medially based single-row technique (medSR) in patients with 1- to 3-cm tear sizes.

METHODS

All patients were evaluated preoperatively and postoperatively (at 12 and 24 months) using the modified University of California, Los Angeles scoring system; active range of motion (flexion and external rotation); and a visual analog scale for pain. Healing status was examined by postoperative magnetic resonance imaging.

RESULTS

Clinical and imaging evaluations were completed by 92 patients at 1-year follow-up and by 74 patients at 2 years. No significant differences were found between the 2 groups across all measures at final follow-up: The University of California, Los Angeles scores were 33.4 points in SB patients and 33.0 points in medSR patients (P = .58); the visual analog scale scores were 6 mm and 7 mm, respectively (P = .38); the active flexion angles were 161° and 159°, respectively (P = .34); and the external rotation angles were 49° and 52°, respectively (P = .37). Retears were observed in 6.5% of SB patients and 2.1% of medSR patients (P = .31). Medial cuff failure was observed only in SB patients (4.3%, 2 cases), whereas incomplete healing (deep-layer retraction pattern) was observed only in medSR patients (8.7%, 4 cases). Neo-tendon regeneration in the medSR group was observed in 93% of patients.

CONCLUSIONS

This study did not show any significant differences in the clinical outcomes and cuff integrity between the 2 treatment groups at final follow-up; however, medial cuff failure was observed only in the SB group, and incomplete healing was more frequent in the medSR group. One should consider the risk of medial cuff failure and incomplete healing of the repaired cuff before choosing the repair technique for medium-sized supraspinatus tears.

LEVEL OF EVIDENCE

Level I, therapeutic, prospective, randomized trial.

A Validated, Subject-Specific Finite Element Model for Predictions of Rotator Cuff Tear Propagation

Rotator cuff tears are a significant clinical problem previously investigated by unvalidated computational models that either use simplified geometry or isotropic elastic material properties to represent the tendon. The objective of this study was to develop an experimentally validated, finite element model of supraspinatus tendon using specimen-specific geometry and inhomogeneous material properties to predict strains in intact supraspinatus tendon. Three-dimensional tendon surface strains were determined at 60°, 70°, and 90° of glenohumeral abduction for articular and bursal surfaces of supraspinatus tendon during cyclic loading to serve as validation data. A finite element model was developed using the tendon geometry and inhomogeneous material properties to predict surface strains for loading conditions mimicking experimental loading conditions. Experimental strains were directly compared with computational model predictions to validate the model. Overall, the model successfully predicted magnitudes of strains that were within the experimental repeatability of 3% strain of experimental measures on both surfaces of the tendon. Model predictions and experiments showed the largest strains to be located on the articular surface (~8% strain) between the middle and anterior edge of the tendon. Importantly, the reference configuration chosen to calculate strains had a significant effect on strain calculations, and therefore must be defined with an innovative optimization algorithm. This study establishes a rigorously validated, specimen-specific computational model using novel surface strain measurements for use in investigating the function of the supraspinatus tendon and to ultimately predict the propagation of supraspinatus tendon tears based on the tendon's mechanical environment.

Nanotopographical cues of electrospun PLLA efficiently modulate non-coding RNA network to osteogenic differentiation of mesenchymal stem cells during BMP signaling pathway

Application of stem cells in combination with nanofibrous substrates is an interesting biomimetic approach for enhanced regeneration of damaged tissues such as bone and cartilage. The investigation of the complex interplay between nanotopographical cues of niche and noncoding RNAs in stem cells fate is an effective tool to find a new strategy for enhancing the induction of osteogenesis. In this study, we investigated the effects of aligned and random orientations of nanofibers as a natural ECM-mimicking environment on the network of noncoding RNA in mesenchymal stem cells. Aligned and randomly oriented Ploy (L-lactide) PLLA scaffolds were fabricated via electrospinning. Human Adipose Tissue-Derived Mesenchymal Stem Cells (hASCs) were isolated from adipose tissue and were cultured on surfaces of these scaffolds. Their capacity to support hMSCs proliferation was also investigated by MTT assay and the expression of c-Myc gene. Then, after 7, 14 and 21 days, the osteogenic commitment of hMSCs and the miRNA regulatory network in BMP signaling pathway were evaluated by measuring alkaline phosphatase (ALP) activity, extracellular calcium deposition, and bone-related gene activation by Real-Time PCR. Furthermore, osteogenic differentiation was evaluated with regard to their noncoding RNA network. Our results for the first time showed an interaction between nanotopographical cues and miRNA activity in hMSCs. We found that the nanotopographical cues could be used to influence the osteogenic differentiation process of hMSCs through the modulation of lncRNAs and miR-125b as negative regulators of osteogenesis as well as the H19 modulator BMP signaling pathway that acts as a miRNA sponge. Moreover, we also demonstrated for the first time that MEG3 as a long noncoding RNA is controlled by miR-125b and microRNA-triggered lncRNA decay mechanism. This strategy seems to be an important tool for controlling stem cell fate in engineered tissues and provide new insights into most biocompatible scaffolds for bone-graft substitutes.

Arthroscopic trans-osseous rotator cuff repair

BACKGROUND

Mechanical factors are at the basis of any tendon healing process, being pressure an aspect able to positively influence it. For this reason transosseous rotator cuff repair represents the gold standard procedure for patients affected by a cuff tear, maximizing the tendon footprint contact area and reducing motion at the tendon to bone interface.

METHODS

The Authors present an all arthroscopic suture bridge-like transosseous repair with the preparation of a single transosseous tunnel perfor med thanks to a precise dedicated instrument (Compasso®) and one implant (Elite-SPK®) with the use of only 3 suture wires. In addition this technique permits to accurately prepare the bony side of the lesion without any risk or complication, such as anchor pull-out and greater tuberosity bone osteolysis.

CONCLUSIONS

However, even if this technique seems less demanding, the arthroscopic transosseous repair is still an advanced procedure, and should be performed only by well prepared arthroscopic shoulder surgeons.

LEVEL OF EVIDENCE

V.

Tight medial knot tying may increase retearing risk after transosseous equivalent repair of rotator cuff tendon

BACKGROUND

Retearing mechanism after transosseous equivalent (TOE) rotator cuff repair has not been fully clarified yet.

OBJECTIVE

The purposes of this study were to compare the stress distribution pattern in the tendon stump between knotted and knotless TOE repair and to investigate the role of suture tension applied during medial knot tying using a 3-dimensional finite element (3D-FE) method.

METHODS

Both knotted and knotless TOE repairs were simulated on the 3D-FE human rotator cuff tear model. Elastic analysis was performed to compare the stress distribution pattern inside the tendon between the two models. The amount of compressive load applied to the medial-row sutures was then changed as 0, 20, 40, 60, 80, and 100 N in the knotted model.

RESULTS

Knotted model demonstrated more distinct stress concentration inside the tendon around medial-row sutures than the knotless model. Mean von Mises equivalent stress in this area in the 0, 20, 40, 60, 80, and 100 N models was 0.26, 0.35, 0.50, 0.70, 1.11, and 1.14 MPa, respectively.

CONCLUSIONS

In the knotted TOE repair, tight medial knot tying might cause a high stress concentration around medial knots, which may constitute one of the pathogenetic factors of postoperative retearing at this site.