Augmented tendon Achilles repair using a tissue reinforcement scaffold: a biomechanical study

Native anterior talo-fibular ligament tensile characteristics compared to allograft, suture tape, and copolymer augmentation elements: A biomechanical study

Surgical augmentation methods have been introduced to the Modified Broström (MB) technique to support native anterior talo-fibular ligament (ATFL) healing and function. This study aimed to investigate the isolated biomechanical performance of common MB augmentation elements, including allograft, suture tape, and copolymer, compared to native ATFL. Six cadaveric feet were dissected, isolating the ATFL from all surrounding soft tissue. The fibula and talus were clamped on the testing frame so that the ligament was in line with the load cell. Six samples per augment group were fixed on a test frame with a gauge length of 20 mm to replicate ATFL length. All samples were pulled to failure at 305 mm/min. Biomechanical outcomes included stiffness, elongation, and ultimate load. Mean ± standard deviation was reported. Stiffness was highest for suture tape (246.4 ± 52.1N/mm), followed by allograft (114.2 ± 26.2 N/mm), native ATFL (78.6 ± 31.8 N/mm), and copolymer (9.4 ± 2.9 N/mm). Significant differences in stiffness were observed between all groups except when comparing ATFL stiffness to allograft (P = 0.086). Copolymer resulted in significantly larger elongation at ultimate load compared to native ATFL, suture tape, and allograft (P < 0.001). Elongation at ultimate failure was highest for copolymer (30.0 ± 8.7 mm) and significantly greater than all other groups (P < 0.001). Ultimate load was highest for suture tape (544.1 ± 59.7 N), followed by native ATFL (338.5 ± 63.7 N), allograft (308.3 ± 98.5 N) and copolymer (146.7 ± 8.9 N). Suture tape ultimate load was significantly greater than copolymer (P < 0.001). Isolated biomechanical data of augment materials can be utilized by foot and ankle surgeons when considering appropriate ligament augmentation options. Level of clinical evidence 5, controlled laboratory study.

Safety Profile of Synthetic Elastic Degradable Matrix for Soft Tissue Reconstruction in Foot & Ankle Surgery

BACKGROUND

Augmentation of soft tissue repairs has been helpful in protecting surgically repaired tissues as they heal. FlexBand (Artelon, Marietta, Georgia) is a synthetic, degradable, polycaprolactone-based polyurethane urea (PUUR) matrix that has been investigated and used for soft tissue repair in a variety of settings. The purpose of this study was to evaluate the safety profile of a PUUR matrix in a large cohort of patients undergoing soft tissue repairs about the foot and ankle.

METHODS

A retrospective chart review of consecutive patients who underwent surgery using FlexBand to augment a soft tissue repair was performed to evaluate for major and minor complications related to the PUUR matrix. Results. A total of 105 patients with an average >6 months follow-up were included. The most common procedures were spring ligament repair, Achilles tendon repair, and Brostrom. There were 12 complications. Four major complications occurred with only 1 requiring PUUR matrix removal. Patients with wound complications had a higher body mass index (BMI) and rate of smoking.

CONCLUSION

Complication rates involving PUUR matrix in soft tissue foot and ankle reconstruction procedures are low and comparable with historical complication rates. The PUUR matrix is safe for use in a variety of soft tissue procedures about the foot and ankle.Level of Evidence: Level 4, Retrospective case-series.

Treatment of Insertional Achilles Tendinosis With Polyurethane Urea-Based Matrix Augmentation

INTRODUCTION

Surgical treatment for insertional Achilles tendinosis (IAT) sometimes requires tendon repair augmentation. The purpose of this study is to evaluate the efficacy of polycaprolactone-based polyurethane urea (PUUR) matrix augmentation in the treatment of IAT.

METHODS

A retrospective review was performed in surgically treated IAT. Repairs were augmented with a PUUR matrix. Factors evaluated included date of full weightbearing, patient satisfaction, Visual Analog Scale (VAS) pain score, strength, and ankle motion. The Wilcoxon signed-rank test was used to compare baseline and final follow-up VAS scores.

RESULTS

A total of 18 cases were included in the study. The mean patient age was 54.61 ± 8.25 (40-75) years with a mean follow-up of 163.61 ± 57.81 (92-314) days. Patient satisfaction was obtained on 15 of 18 patients, with 14 patients satisfied with their outcome. Mean VAS for pain significantly decreased from 6.19 ± 1.97 (2.5-9) to 0.83 ± 1.54 (0-5) postoperatively, which was statistically significant (P < .01).

CONCLUSION

Achilles tendon augmentation with the PUUR matrix is a viable option in the treatment of IAT. Its use in this condition has minimal morbidity and can be an alternative to other forms of augmentation.

LEVELS OF EVIDENCE

Level IV: Retrospective case series.

Biomechanical Comparison of Tape Versus Suture in Simulated Achilles Tendon Midsubstance Rupture

As sutures have progressed in strength, increasing evidence supports the suture tendon interface as the site where most tendon repairs fail. We hypothesized that suture tape would have a higher load to failure versus polyblend suture due to its larger surface area. Eleven matched pairs of cadaveric Achilles tendons were sutured with 2 mm wide braided ultrahigh molecular weight polyethylene tape (Tape) or 2 mm wide braided ultrahigh molecular weight polyethylene suture (Suture) using a Krackow repair method. All Achilles repair constructs were cyclically loaded, after which they were loaded to failure. Change in suture footprint height, clinical and ultimate load to failure, and location of failure was recorded. Clinical loads to failure for Tape and Suture were 290.4 ± 74.8 and 231.7 ± 70.4 Newtons, respectively (p= .01). Ultimate loads to failure for Tape and Suture were 352.9 ± 108.1 and 289.8 ± 53.7 Newtons, respectively (p = .11). Cyclic testing resulted in significant changes in footprint height for both Tape and Suture, but the 2 sutures did not differ in terms of the magnitude of change in footprint height (p = .52). The suture tendon interface was the most common site of failure for both Tape and Suture. Our results suggest that Tape may provide added repair strength in vivo for Achilles midsubstance rupture.

Repair of Tendon Disruption Using a Novel Synthetic Fiber Implant in Dogs and Cats: The Surgical Procedure and Three Case Reports

Surgical management of tendon rupture is challenging. One concern is to provide adequate tensile strength to prevent distraction during weight-bearing and gap formation following repair, associated with an increased risk of repair failure. Additional challenges may arise from the nature or the chronicity of the lesion. In the event of avulsion, when the tendon is torn off at the bone insertion, its reinsertion on the bone is generally difficult and may even be impossible in the presence of an avulsion fracture, especially when the bone fragment is too small or fragmented. Repair management is also complicated in chronic cases, as degeneration of the tendon may lead to excessive scar tissue formation, tendon retraction, and muscle atrophy, resulting in a large gap and inadequate tissue for reconstruction. The authors describe the surgical procedure for implanting a novel implant, illustrated by three characteristic clinical cases: (1) an acute Achilles tendon avulsion; (2) a chronic patellar tendon rupture; and (3) a chronic avulsion fracture of the triceps tendon. In these three cases, complete recovery of the function was observed at the last clinical evaluation (6 or 8 months), and no complication was noted. A splinted dressing (6 to 8 weeks) was used successfully in two cases. A resin cast (8 weeks) was preferred in case 1, a very active dog. In conclusion, this novel implant represents a simple procedure for the effective repair of chronic tendon rupture, as well as an effective tendon reinsertion on the bone and adequate support for bone tendon healing in the treatment of tendon avulsion, even in cases of fragmented bone fracture. The thinness of the implant facilitates its insertion into the native tendon, while the bone-screw-implant interface provides immediate and lasting mechanical support. This may facilitate the healing process and potentially shorten the period of immobilization.

The clinical strategies for tendon repair with biomaterials: A review on rotator cuff and Achilles tendons

Tendon repair is a complex process due to the low tenocyte density, metabolism, and vascularization. Tears of rotator cuff (RCT) and Achilles tendons ruptures have a major impact on healthcare costs and quality of life of patients. Scaffolds are used to improve the healing rate after surgery and long-term results. A systematic search was carried out to identify the different types of scaffolds used during RCT and Achilles tendon repair surgery in the last 10 years. A higher number of clinical studies were reported on RCT ruptures. Biological scaffolds were used more than synthetic ones, for both rotator cuff and Achilles tendons. Moreover, platelet-rich plasma (PRP)-based scaffolds were the most widely used in RCT. A different type of synthetic scaffold was used in each of the five studies found. Biological scaffolds either provide variable results, in particular PRP-based ones, or poor results, such as bovine equine pericardium. All the synthetic scaffolds demonstrated a significant increase in clinical and functional scores in biomechanics, and a significant decrease in pain and re-tear rate in comparison to conventional surgery. Despite the limited number of studies, further investigation in the clinical use of synthetic scaffolds should be carried out.

Chronic Achilles Ruptures: Reconstructive Options

Achilles tendon ruptures, if neglected or identified late, lead to impairments in function and gait. Surgical reconstruction is typically required to restore the resting length and tension to the gastrocnemius-soleus complex. A variety of reconstructive options have been described, depending on several factors, including chronicity, residual gap size, remaining tissue quality and vascularity, location of tendon rupture or deficiency, and patient-specific factors. Despite the many surgical options described from local soft-tissue rearrangements and tendon transfers, to the use of allograft tissue and synthetic material augmentation, there is understandably a paucity of evidence-based guidelines available to direct surgeons in the optimal procedure for each patient-specific situation. Reconstructive options for the patient with a chronic Achilles rupture are detailed and reviewed here, to serve as a framework for the treating surgeon in these complex cases.

Soft Tissue Reconstruction with Artelon for Multiple Foot and Ankle Applications

Surgical repair of tendons of the foot and ankle is performed utilizing various methods, including autografts, allografts, and synthetic grafts. Artelon is a synthetic biomaterial that is fabricated from wet-spun fibers of PCL-based polyurethane urea, and has, optimal mechanical properties compared with other grafting options. Because of excellent results of Artelon in ACL reconstruction, its use was explored in 3 foot and ankle cases: repair of Achilles, posterior tibial, and peroneal tendons. Artelon has proven to be a successful alternative for tendon repairs, with all 3 cases returning to full function within 8 to 16 weeks and with no complications related to the graft.

Reconstruction of chronic triceps tendon avulsion using synthetic mesh graft in a dog

Avulsion of the triceps tendon insertion was diagnosed in a two-year-old Poodle mixed breed dog 10 weeks after traumatic injury. Diagnosis was confirmed with clinical examination and magnetic resonance imaging (MRI). The tendon was reconstructed using tension-relieving sutures augmented with a synthetic degradable porous polyurethane urea onlay mesh graft. The repair was immobilized using a transarticular external skeletal fixator with staged increases in elbow flexion. Treatment was successful, with signs of healing confirmed by MRI and normal clinical function one year after surgery. The successful outcome in this case suggests that surgical repair of a chronic triceps tendon injury using a synthetic mesh augmentation may be successful in similar cases.

Failed synthetic graft after acute Achilles tendon repair

Background

The present case report aimed to determine the results of Flexor Hallucis Longus (FHL) transfer as a second surgery after synthetic tissue reinforcement graft (Artelon^®) implanted to a primary repaired Achilles tendon (AT), that was undertaken by another orthopedic. One year post-operative the patient was referred to us with retrocalcaneal pain and difficulty in walking, associated with stiffness and significant impairment of daily living activities.

Methods

MRI and full clinical examination were the outcome measures applied before and 1 year after surgery. Removal of the synthetic graft and subsequent FHL autologous transfer was undertaken and the graft was sent for histology examination. After removing the below knee leg cast, patient started rehabilitation program supervised by a trained physiotherapist.

Results

The patient was allowed to return to his normal activities at the sixth post-operative month, 1 year post-surgery MRI showed correct position of the autograft in the calcaneous bone and in the centre of the native AT plus reduced oedema of the AT body, with clinical improvement of the patient who reported no pain and was able to walk on tiptoes.

Conclusion

Synthetic patch augmentation to enhance tendon healing should be subjected to proper investigation before using it in routine parctice, as it may act as a barrier against proper tendon healing.

Level of evidence

V.

Noninsertional Tendinopathy of the Achilles

Noninsertional Achilles tendinosis is differentiated from insertional Achilles tendinosis based on anatomic location. Tendinosis, as opposed to tendonitis, is primarily a degenerative process and the role of inflammation is believed limited. The etiology of Achilles tendinopathy may include overuse leading to repetitive microtrauma, poor vascularity of the tissue, mechanical imbalances of the extremity, or combination of these elements. There is evidence to support eccentric exercise nonoperative management for patients with noninsertional Achilles tendinopathy. Operative treatment options include percutaneous longitudinal tenotomies, minimally invasive tendon scraping, open débridement and tubularization, and tendon augmentation with flexor hallucis longus.

Is Dual Semitendinosus Allograft Stronger Than Turndown for Achilles Tendon Reconstruction? An In Vitro Analysis

BACKGROUND

Large Achilles tendon defects pose a treatment challenge. The standard treatment with a turndown flap requires a large extensile incision, puts the sural nerve at risk, and demands slow, careful rehabilitation. Dual allograft semitendinosus reconstruction is a new clinical alternative that has the theoretical advantages of a smaller incision, less dissection, and a stronger construct that may allow for faster rehabilitation.

QUESTIONS/PURPOSES

In a cadaver biomechanical model, we compared the dual allograft semitendinosus reconstruction with the myofascial turndown in terms of (1) mechanical strength and resistance to deformation and (2) failure mechanisms in reconstruction of large segmental Achilles defects.

METHODS

An 8-cm segmental Achilles defect was created in 18 cadaveric lower extremities, nine matched pairs without defect or previous surgery (mean age, 78.4 years; range, 60-97 years; three female and six male pairs). Femoral neck densitometry to determine bone mineral density found that all specimens except two were osteopenic or osteoporotic. Specimens in each pair were assigned to allograft or turndown reconstruction. The constructs were mounted on a load frame and differential variable reluctance transducers were applied to measure deformation. Specimens were preconditioned and then loaded axially. Tensile force and proximal and distal construct deformation were measured at clinical failure, defined as 10 mm of displacement, and at ultimate failure, defined as failure of the reconstruction. Failure mechanism was recorded.

RESULTS

Tensile strength at time zero was higher in the allograft versus the turndown construct at clinical failure (156.9 ± 29.7 N versus 107.2 ± 20.0 N, respectively; mean difference, -49.7 N; 95% CI, -66.3 to -33.0 N; p < 0.001) and at ultimate failure (290.9 ± 83.2 N versus 140.7 ± 43.5 N, respectively; mean difference, -150.2 N; 95% CI, -202.9 to -97.6 N; p < 0.001). Distal construct deformation was lower in the turndown versus the allograft construct at clinical failure (1.6 ± 1.0 mm versus 4.7 ± 0.7 mm medially and 2.2 ± 1.0 mm versus 4.8 ± 1.1 mm laterally; p < 0.001). Semitendinosus allograft failure occurred via calcaneal bone bridge fracture in eight of nine specimens. All myofascial turndowns failed via suture pullout through the fascial tissue at its insertion.

CONCLUSION

In this comparative biomechanical study, dual semitendinosus allograft reconstruction showed greater tensile strength and construct deformation compared with myofascial turndown in a cadaveric model of large Achilles tendon defects.

CLINICAL RELEVANCE

Further study of dual semitendinosus allograft for treatment of severe Achilles tendon defects with cyclic loading and investigation of clinical results will better elucidate the clinical utility and indications for this technique.

Surgical repair of symptomatic chronic achilles tendon rupture using synthetic graft augmentation

BACKGROUND

Surgical repair of symptomatic chronic Achilles tendon (TA) rupture is a challenging problem due to the presence of a large defect between tendon edges. We report the results of surgical repair of symptomatic chronic TA rupture by synthetic graft augmentation.

METHODS

Seven consecutive patients with a symptomatic chronic TA rupture underwent surgical repair by VY plasty and augmentation with bio-absorbable synthetic graft (Artelon^®). In all patients, the intraoperative tendon gap after debridement was more than 5cm (Myerson Grade 3). The total duration of plaster immobilization was 10 weeks. The complications were recorded prospectively and functional outcome was assessed by AOFAS score and Achilles tendon Total Rupture Score (ATRS).

RESULTS

At a mean follow up of 29 months there was no re-rupture or deep infection. All patients reported good functional outcome as shown by AOFAS and ATRS scores. There were no graft related complications. At final follow up, six patients were able to do single stance heel raise however, calf wasting was noted in all patients.

CONCLUSIONS

Tendon repair augmented by absorbable synthetic graft is an acceptable technique in Myerson Grade 3 chronic symptomatic TA ruptures.

LEVEL OF EVIDENCE

Level IV, Case series.

Enhancement of tendon-bone healing via the combination of biodegradable collagen-loaded nanofibrous membranes and a three-dimensional printed bone-anchoring bolt

A composite biodegradable polymeric model was developed to enhance tendon graft healing. This model included a biodegradable polylactide (PLA) bolt as the bone anchor and a poly(D,L-lactide-co-glycolide) (PLGA) nanofibrous membrane embedded with collagen as a biomimic patch to promote tendon–bone interface integration. Degradation rate and compressive strength of the PLA bolt were measured after immersion in a buffer solution for 3 months. In vitro biochemical characteristics and the nanofibrous matrix were assessed using a water contact angle analyzer, pH meter, and tetrazolium reduction assay. In vivo efficacies of PLGA/collagen nanofibers and PLA bolts for tendon–bone healing were investigated on a rabbit bone tunnel model with histological and tendon pullout tests. The PLGA/collagen-blended nanofibrous membrane was a hydrophilic, stable, and biocompatible scaffold. The PLA bolt was durable for tendon–bone anchoring. Histology showed adequate biocompatibility of the PLA bolt on a medial cortex with progressive bone ingrowth and without tissue overreaction. PLGA nanofibers within the bone tunnel also decreased the tunnel enlargement phenomenon and enhanced tendon–bone integration. Composite polymers of the PLA bolt and PLGA/collagen nanofibrous membrane can effectively promote outcomes of tendon reconstruction in a rabbit model. The composite biodegradable polymeric system may be useful in humans for tendon reconstruction.

Collagen ribbon augmentation of Achilles tendon tears: a biomechanical evaluation

Early motion of a repaired Achilles tendon has been accepted to improve both clinical and biomechanical outcomes. It has been postulated that augmenting a primary Achilles tendon repair with a collagen ribbon will improve the repair construct's initial strength, thereby facilitating early motion. The purpose of the present study was to compare the failure load of Achilles tendon defects repaired with suture, with or without augmentation with a collagen ribbon. Ten matched pairs of cadaveric feet and tibiae underwent simulated Achilles tendon tear in the watershed area and were then repaired with 4-strand Krackow sutures only or were sutured and augmented with a box weave collagen ribbon xenograft. The specimens were prepared for testing by keeping the insertion of the Achilles to the calcaneus intact and dissecting the gastrocnemius at its origin, leaving the repair undisturbed. The mean load at failure for the augmented (suture plus collagen ribbon) specimens was 392.4 ± 74.9 N. In contrast, the mean load at failure for the suture-only (control) construct was 98.0 ± 17.6 N (p < .001). The augmented specimens demonstrated a greater mean strength of 4.1 ± 0.9 N (range 3.2 to 5.6). After cyclic loading, the mean gap across the Achilles repair was significantly smaller in the augmented group than in the control group (p = .006). We have concluded that box weave collagen ribbon augmentation of the primary suture Achilles tendon repairs can provide enhanced gap resistance and strength under cyclic loading and ramped tensile testing.

Adhesion and collagen production of human tenocytes seeded on degradable poly(urethane urea)

PURPOSE

The aim of this study was to investigate whether human tenocytes taken from ruptured quadriceps tendon could be seeded on a biodegradable polycaprolactone-based polyurethanes (PU) urea scaffold. Scaffold colonization and collagen production after different culture periods were analyzed to understand whether tenocytes from ruptured tendons are able to colonize these biodegradable scaffolds.

METHODS

Human primary tenocyte cultures of ruptured quadriceps tendons were seeded on PU scaffolds. After 3, 10 and 15 days of incubation, the samples were stained with haematoxylin and eosin and were examined under white light microscopy. After 15 and 30 days of incubation, samples were examined under transmission electron microscope. Total collagen accumulation was also evaluated after 15, 30 and 45 days of culture.

RESULTS

After 15 and 30 days of culture, tenocyte-seeded scaffolds showed cell colonization and cell accumulation around interconnecting micropores. Tenocyte phenotype was variable. Collagen accumulation in seeded scaffolds demonstrated a progressive increase after 15, 30 and 45 days of culture, while control non-seeded scaffolds show no collagen accumulation.

CONCLUSION

These results showed that human tenocytes from ruptured quadriceps tendon can be seeded on polycaprolactone-based PU urea scaffolds and cultured for a long time period (45 days). This study also showed that human tenocytes from ruptured tendons seeded on PU scaffolds are able to penetrate the scaffold showing a progressively higher collagen accumulation after 15, 30 and 45 days of incubation. This study provides the basis to use this PU biodegradable scaffold in vivo as an augmentation for chronic tendon ruptures and in vitro as a scaffold for tissue engineering construct.

How smart do biomaterials need to be? A translational science and clinical point of view

Over the last 4 decades innovations in biomaterials and medical technology have had a sustainable impact on the development of biopolymers, titanium/stainless steel and ceramics utilized in medical devices and implants. This progress was primarily driven by issues of biocompatibility and demands for enhanced mechanical performance of permanent and non-permanent implants as well as medical devices and artificial organs. In the 21st century, the biomaterials community aims to develop advanced medical devices and implants, to establish techniques to meet these requirements, and to facilitate the treatment of older as well as younger patient cohorts. The major advances in the last 10 years from a cellular and molecular knowledge point of view provided the scientific foundation for the development of third-generation biomaterials. With the introduction of new concepts in molecular biology in the 2000s and specifically advances in genomics and proteomics, a differentiated understanding of biocompatibility slowly evolved. These cell biological discoveries significantly affected the way of biomaterials design and use. At the same time both clinical demands and patient expectations continued to grow. Therefore, the development of cutting-edge treatment strategies that alleviate or at least delay the need of implants could open up new vistas. This represents the main challenge for the biomaterials community in the 21st century. As a result, the present decade has seen the emergence of the fourth generation of biomaterials, the so-called smart or biomimetic materials. A key challenge in designing smart biomaterials is to capture the degree of complexity needed to mimic the extracellular matrix (ECM) of natural tissue. We are still a long way from recreating the molecular architecture of the ECM one to one and the dynamic mechanisms by which information is revealed in the ECM proteins in response to challenges within the host environment. This special issue on smart biomaterials lists a large number of excellent review articles which core is to present and discuss the basic sciences on the topic of smart biomaterials. On the other hand, the purpose of our review is to assess state of the art and future perspectives of the so called "smart biomaterials" from a translational science and specifically clinical point of view. Our aim is to filter out and discuss which biomedical advances and innovations help us to achieve the objective to translate smart biomaterials from bench to bedside. The authors predict that analyzing the field of smart biomaterials from a clinical point of view, looking back 50 years from now, it will show that this is our heritage in the 21st century.