Anterior Cruciate Ligament Reconstruction with LARS Artificial Ligament-Clinical Results after a Long-Term Follow-Up

Application of Nondegradable Synthetic Materials for Tendon and Ligament Injury

Tendon and ligament injuries, prevalent requiring surgical intervention, significantly impact joint stability and function. Owing to excellent mechanical properties and biochemical stability, Nondegradable synthetic materials, including polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE), have demonstrated significant potential in the treatment of tendon and ligament injuries. These above materials offer substantial mechanical support, joint mobility, and tissue healing promotion of the shoulder, knee, and ankle joint. This review conclude the latest development and application of nondegradable materials such as artificial patches and ligaments in tendon and ligament injuries including rotator cuff tears (RCTs), anterior cruciate ligament (ACL) injuries, and Achilles tendon ruptures.

Foreign Body Reaction Following Achilles Tendon Reconstruction With the Ligament Advanced Reconstructive System: Patient Outcomes and Clinical Course

The Ligament Advanced Reinforcement System (LARS) is a common choice for ligament reconstruction in the lower limb due to its good functional and quality of life (QoL)-related outcomes. It is commonly used for Achilles tendon repair following a rupture. While it facilitates tissue ingrowth and boasts good biocompatibility, we report on multiple cases whereby foreign body reactions have led to the growth of granulomas requiring surgical excision and Flexor Hallucis Longus (FHL) transfer. Following these cases, patients have been shown to have excellent functional and QoL-related outcomes using the Manchester Oxford Foot Questionnaire (MOX-FQ) and Foot and Ankle Ability Measure (FAAM). Surgeons should consider FHL transfer as an alternative in patients undergoing Achilles tendon repair and be aware of the risk of foreign body reactions and the impact on ankle function and QoL post-operatively.

A new method of anterior talofibular ligament reconstruction: Arthroscopically artificial ligament reconstruction with tensional remnant-repair

PURPOSE

To investigate the clinical effects of arthroscopically artificial ligament reconstruction with tensional remnant-repair in patients who are obese, and/or with demand for highly intensive sports, and/or with poor-quality ligament remnants.

METHODS

A retrospective case series study was performed on patients treated by arthroscopically anterior talofibular ligament (ATFL) reconstruction with tensional remnant repair technique from January 2019 to August 2021. General data, including demographics, surgical time, and postoperative adverse events, were recorded. The American Orthopaedic Foot and Ankle Society score (AOFAS), foot and ankle ability measure (FAAM), visual analog scale (VAS), and anterior talar translation were measured preoperatively and at 6 weeks, 3 months, and 2 years postoperatively. Ultrasonography examination was performed preoperatively and 2 years postoperatively to evaluate the ATFL. Data were analyzed using SPSS 19.0. F test was used to analyze the pre- and postoperative VAS, FAAM, and AOFAS scores. The significance was set at p < 0.05.

RESULTS

There were 20 males and 10 females among the patients with a mean age of (30.71 ± 5.81) years. The average surgical time was (40.21 ± 8.59) min. No adverse events were observed after surgery. At 2 years postoperatively, the anterior talar translation test showed grade 0 laxity in all patients. VAS score significantly decreased from preoperatively to 6 weeks, 3 months, and 2 years postoperatively (p < 0.001). Improvement of FAAM score and the AOFAS score from preoperatively to 6 weeks, 3 months, and 2 years postoperatively was statistically significant (p < 0.001). At 3 months postoperatively, most patients (23/30) could return to their pre-injured activities of daily living status. At 2 years postoperatively, all patients were able to return to their pre-injured activities of daily living status, and almost every patient (18/19) who expected highly intensive sports returned to sports with only 1 obese patient failing to achieve the goal. The ultrasonography examination at 2 years postoperatively showed that there was a linear band structure of soft tissue on the tension-rich fiber tape image from the fibular to the talar attachment sits of ATFL.

CONCLUSION

The novel arthroscopically artificial ligament reconstruction with tensional remnant-repair technique for ATFL achieved satisfactory clinical outcomes in the short and medium term after operation, and allowed early return to pre-injured activities, which could be a reliable option for patients with chronic lateral ankle instability.

Rotator Cuff Repair and Overlay Augmentation by Direct Interlocking of a Nonwoven Polyethylene Terephthalate Patch Into the Tendon: Evaluation in an Ovine Model

BACKGROUND

Arthroscopic repair of large rotator cuff tendon tears is associated with high rates of retear. Construct failure often occurs at the suture-tendon interface. Patch augmentation can improve mechanical strength and healing at this interface.

PURPOSE

To introduce a novel technique for suture-free attachment of an overlaid patch and evaluate its biomechanical strength and biological performance.

STUDY DESIGN

Descriptive and controlled laboratory studies.

METHODS

An established ovine model of partial infraspinatus tendon resection and immediate repair was used. After a nonwoven polyethylene terephthalate patch was overlaid to the resected tendon, a barbed microblade was used to draw fibers of the patch directly into the underlying tissue. In vivo histological assessment of healing was performed at 6 and 13 weeks after implantation. Ex vivo models were used to characterize primary repair strength of the suture-free patch fixation to tendon. Additional ex vivo testing assessed the potential of the technique for patch overlay augmentation of suture-based repair.

RESULTS

The in vivo study revealed no macroscopic evidence of adverse tissue reactions to the interlocked patch fibers. Histological testing indicated a normal host healing response with minimal fibrosis. Uniform and aligned tissue ingrowth to the core of the patch was observed from both the tendon and the bone interfaces to the patch. There was no evident retraction of the infraspinatus muscle, lengthening of the tendon, or tendon gap formation over 13 weeks. Ex vivo testing revealed that direct patch interlocking yielded tendon purchase equivalent to a Mason-Allen suture (150 ± 58 vs 154 ± 49 N, respectively; P = .25). In an overlay configuration, fiber interlocked patch augmentation increased Mason-Allen suture retention strength by 88% (from 221 ± 43 N to 417 ± 86 N; P < .01) with no detectable difference in repair stiffness.

CONCLUSION

Testing in an ovine model of rotator cuff tendon repair suggested that surgical interlocking of a nonwoven medical textile can provide effective biomechanical performance, support functional tissue ingrowth, and help avoid musculotendinous retraction after surgical tendon repair.

CLINICAL RELEVANCE

The novel technique may facilitate patch augmentation of rotator cuff repairs.

Hierarchical helical carbon nanotube fibre as a bone-integrating anterior cruciate ligament replacement

High rates of ligament damage require replacements; however, current synthetic materials have issues with bone integration leading to implant failure. Here we introduce an artificial ligament that has the required mechanical properties and can integrate with the host bone and restore movement in animals. The ligament is assembled from aligned carbon nanotubes formed into hierarchical helical fibres bearing nanometre and micrometre channels. Osseointegration of the artificial ligament is observed in an anterior cruciate ligament replacement model where clinical polymer controls showed bone resorption. A higher pull-out force is found after a 13-week implantation in rabbit and ovine models, and animals can run and jump normally. The long-term safety of the artificial ligament is demonstrated, and the pathways involved in integration are studied.

Anterior Cruciate Ligament Reconstruction with Quadrupled Semitendinosus Graft or Synthetic Ligament: Knee Stability and Clinical Outcomes at Three Years Follow-Up

The incidence of anterior cruciate ligament reconstruction (ACLR) surgeries is increasing and graft choice is important for a rapid return to activity, especially in patients older than 30 years. The aim of this study is to compare in term of quality of life and knee stability of patients who undergone ACLR using quadrupled semitendinosus (ST4) graft against patients who undergone ACLR with synthetic ligaments. Thirty-nine patients undergoing ACLR were enrolled in the study and were divided into two groups: ACLR with synthetic ligaments-LARS (group A) and ACLR with quadrupled semitendinosus graft ST4 (group B). They underwent surgery at Policlinico di Bari Orthopedic Unit between January 2017 and January 2020. Group A was composed by nineteen patients (36.16 ± 4.41 mean age-years, 22.47 ± 2.63 mean BMI-kg/m², 39.37 ± 10.05 mean time evaluation after surgery-months) and group B was composed by twenty patients (34.95 ± 3.59 mean age-years, 21.1 ± 2.88 mean BMI-kg/m², 36.75 ± 8.69 mean time evaluation after surgery-months). For each patient, the following data were recorded: age; side of injury, BMI, date of surgery, anterior knee laxity with the arthrometer, and Lysholm knee scoring scale. Mean value of anterior tibial translation (ATT) in group A was 3.09 mm ± 0.65 and in group B was 2.66 mm ± 1.61 (pvalue of 0.1139). Mann--Whitney U test used to compare the Lysholm means values between groups showed a pvalue of 0.9307. LARS has comparable clinical and functional outcomes compared with hamstring autografts at short-term of 3 years follow-up. Level of Evidence: IV.

Synthetic grafts for anterior cruciate ligament reconstructive surgery

The quest for a good and durable substitute to anterior cruciate ligament (ACL) is driving scientists to explore new promising areas of research. Autologous and allogenic ligament reconstruction bring satisfactory results in managing ACL surgery although their use is associated with significant drawbacks. To overcome the limitations of biologic grafts, many artificial devices have been developed and implanted as a substitute to the native ACL over the past decades. Although many synthetic grafts used in the past have been withdrawn from the market due to early mechanical failures ultimately leading to synovitis and osteoarthritis, there is recently a resurgence of interest in the use of synthetic ligaments for ACL reconstruction. However, this new generation of artificial ligaments, despite promising initial results, have shown to produce serious side effects such as high rupture rates, insufficient tendon-bone healing and loosening. For these reasons, recent advancements in biomedical engineering are focusing on improving technical features of artificial ligaments combining mechanical properties to biocompatibility. Bioactive coatings and surface modification methods have been proposed to enhance synthetic ligament biocompatibility and promote osseointegration. The path to the development of a safe and effective artificial ligament is still full of challenges, however recent advancements are leading the way towards a tissue-engineered substitute to the native ACL.

Massive foreign body reaction and osteolysis following primary anterior cruciate ligament reconstruction with the ligament augmentation and reconstruction system (LARS): a case report with histopathological and physicochemical analysis

BACKGROUND

Autologous hamstrings and patellar tendon have historically been considered the gold standard grafts for anterior cruciate ligament reconstruction (ACLR). In the last decades, the utilization of synthetic grafts has re-emerged due to advantageous lack of donor site morbidity and more rapid return to sport. The Ligament Augmentation and Reconstruction System (LARS) has demonstrated to be a valid and safe option for ACLR in the short term. However, recent studies have pointed out the notable frequency of associated complications, including synovitis, mechanical failure, and even chondrolysis requiring joint replacement.

CASE PRESENTATION

We report the case of a 23-year-old male who developed a serious foreign body reaction with wide osteolysis of both femoral and tibial tunnels following ACLR with LARS. During first-stage arthroscopy, we performed a debridement of the pseudocystic mass incorporating the anterior cruciate ligament (ACL) and extending towards the tunnels, which were filled with autologous anterior iliac crest bone graft chips. Histological analysis revealed the presence of chronic inflammation, fibrosis, and foreign body giant cells with synthetic fiber inclusions. Furthermore, physicochemical analysis showed signs of fiber depolymerization, increased crystallinity and formation of lipid peroxidation-derived aldehydes, which indicate mechanical aging and instability of the graft. After 8 months, revision surgery was performed and ACL revision surgery with autologous hamstrings was successfully carried out.

CONCLUSIONS

The use of the LARS grafts for ACLR should be cautiously contemplated considering the high risk of complications and early failure.

Current strategies for enhancement of the bioactivity of artificial ligaments: A mini-review

Background and objective

Anterior cruciate ligament (ACL) reconstruction calls for artificial ligaments with better bioactivity, however systematic reviews regarding bioactivity enhancement strategies, technologies, and perspectives of artificial ligaments have been rarely found.

Methods

Research papers, reviews, and clinical reports related to artificial ligaments were searched and summarized the current status and research trends of artificial ligaments through a systematic analysis.

Results

Having experienced ups and downs since the very first record of clinical application, artificial ligaments differing in material, and fabrication methods have been reported with different clinical performances. Various manufacturing technologies have developed and realized scaffold- and cell-based strategies. Despite encouraging in-vivo and in-vitro test results, the clinical results of such new designs need further clinical examinations.

Conclusion

As the demand for ACL reconstruction dramatically increases, novel artificial ligaments with better osteoinductivity and mechanical performance are promising.

The translational potential of this article

To develop novel artificial ligaments simultaneously possessing excellent osteoinductivity and satisfactory mechanical performance, it is important to grab a glance at recent research advances. This systematic analysis provides researchers and clinicians with comprehensive and comparable information on artificial ligaments, thus being of clinical translational significance.

An off-the-shelf decellularized and sterilized human bone-ACL-bone allograft for anterior cruciate ligament reconstruction

Approximately 1% of active individuals participating in sports rupture their anterior cruciate ligaments (ACL) every year, which is currently reconstructed using tendon autografts. Upon reconstruction, clinical issues of concern are ACL graft rupture, persistent knee instability, limited return to sports, and early onset of osteoarthritis (OA). This happens because tendon autografts do not have the same compositional, structural, and mechanical properties as a native ACL. To overcome these problems, we propose to use decellularized bone-ACL-bone allografts in ACL reconstruction (ACLR) as a mechanically robust, biocompatible, and immunologically safe alternative to autografts. Here, a decellularization protocol combined with sterilization using supercritical carbon dioxide (scCO₂) was used to thoroughly decellularize porcine and human ACLs attached to tibial and femoral bone blocks. The specimens were named ultrACLean and their compositional, structural, and mechanical properties were determined. Our results indicate that: 1) decellularization of ultrACLean allografts leads to the removal of nearly 97% of donor cells, 2) ultrACLean has mechanical properties which are not different to native ACL, 3) ultrACLean maintained similar collagen content and decreased GAG content compared to native ACL, and 4) ultrACLean is not cytotoxic to seeded tendon-derived cells in vitro. Results from an in vivo pilot experiment showed that ultrACLean is biocompatible and elicits a moderate immunological response. In summary, ultrACLean has proven to be a mechanically competent and biocompatible graft with the potential to be used in ACLR surgery.

[Core techniques and adverse events in anterior cruciate ligament reconstruction using a new generation of artificial ligaments: the consensus of Chinese specialists based on a modified Delphi method (Part 2)]

OBJECTIVE

Anterior cruciate ligament (ACL) reconstruction using a new generation of artificial ligaments (NGAL) gained popularity in China owing to its good effectiveness and early functional recovery, but iatrogenic surgical failures and preconceived misconceptions have seriously affected its standardized clinical application. A specialist consensus is now developed to provide guidance and reference for orthopaedic sports medicine doctors when adopting or considering the NGAL for ACL reconstruction.

METHODS

The consensus on the core techniques and adverse events in ACL reconstruction using the NGAL was developed by a modified Delphi method, referring exclusively to the NGAL for ACL reconstruction approved by the National Medical Products Administration (NMPA). Consensus specialists were selected from the members of the Chinese Association of Orthopaedic Surgeons (CAOS) and the Chinese Society of Sports Medicine (CSSM). The drafting team summarized the draft consensus terms based on medical evidence and organized rounds of investigation: two rounds of online questionnaire investigation and the final round of face-to-face meeting. After discussion, revision, and voting, a consensus on the draft consensus term was reached when the agreement rate exceeded 85%. The consensus terms were categorized as "strong" (agreement rate: 95.0%-100%), "moderate" (agreement rate: 90.0%-94.9%), and "basic" (agreement rate: 85.0%-89.9%).

RESULTS

Thirty-one specialists completed the questionnaire investigation. They all practiced in university teaching hospitals (Grade-A tertiary hospitals) from 16 provinces, autonomous regions, and municipalities in China. Among them, 28 were chief physicians and 3 were associate chief physicians; 22 were professors and 7 were associate professors; the average seniority in orthopedic sports medicine was 25.2 years (range, 12-40 years); the average seniority in performing ACL reconstruction procedures was 13.2 years (range, 7-23 years); in terms of the number of ACL reconstruction using the NGAL, 18 completed more than 100 cases, of which 6 had more than 300 cases; in terms of research, 28 had published more than 1 related paper in the past 5 years, of which 13 had published more than 3 related papers. Twenty-six specialists attended the face-to-face meeting and reached a consensus on 9 terms, including 8 strong terms and 1 moderate term.

CONCLUSION

ACL reconstruction using the NGAL must deploy "isometric" or "near-isometric" reconstruction and should preserve the natural ACL remnants as much as possible. Bone tunnel positioning can be performed using intraoperative radiographic measurements or the lateral femoral intercondylar ridge as reference marks. Incorrect positioning of the bone tunnel is the main reason of surgical failure, and there is a lack of consensus on handling interference screws during revision. Bone tunnel enlargement exists after reconstruction but rarely causes related symptoms. Synovitis and infection are uncommon complications. The aging effect of polyethylene terephthalate fiber on the long-term clinical outcomes is unknown and deserves attention.

Optimal Graft Choice in Athletic Patients with Anterior Cruciate Ligament Injuries: Review and Clinical Insights

Anterior cruciate ligament (ACL) rupture is a common sporting-related knee injury with a potentially detrimental impact on the athlete’s career, yet there is no formal consensus on the optimal graft choice for reconstructing the ruptured ACL in this specific population. Options for reconstruction include autograft, allograft, and artificial grafts. However, each has associated failure risk and donor site morbidity. Our operational definition of the athlete is a skeletally mature individual participating in high level activity with the expectation to return to pre-injury level of activity. The athlete has unique injury characteristics, post-operative expectations, and graft demands that differ to the general population. Long-term outcomes are of particular importance given on-going mechanical demands on the reconstructed knee. Therefore, the purpose of this review is to consolidate current literature on the various ACL reconstruction graft options, with a focus on the optimal graft for returning the athlete to activity with the lowest rate of re-injury.

Long-term outcomes of surgery using the Ligament Advanced Reinforcement System as treatment for anterior cruciate ligament tears

AIMS

The aim of this prospective study was to assess the long-term clinical, radiological, functional, and quality of life (QoL)-related outcome of patients treated with the synthetic Ligament Advanced Reinforcement System (LARS) device for anterior cruciate ligament (ACL) rupture.

METHODS

A total of 41 patients who underwent ACL reconstruction with the LARS device (mean age 39.8 years (SD 12.1 ); 32% females (n = 13)) were prospectively included between August 2001 and March 2005. MRI scans and radiographs were performed at a median follow-up of 2.0 years (interquartile range (IQR) 1.3 to 3.0; n = 40) and 12.8 years (IQR 12.1 to 13.8; n = 22). Functional and QoL-related outcome was assessed in 29 patients at a median follow-up of 12.8 years (IQR 12.0 to 14.0) and clinically reconfirmed at latest median follow-up of 16.5 years (IQR 15.5 to 17.9). International Knee Documentation Committee (IKDC) and Tegner scores were obtained pre- and postoperatively, and Lysholm score postoperatively only. At latest follow-up, range of motion, knee stability tests, 36-Item Short Form Health Survey (SF-36), and IKDC scores were ascertained. Complications and reoperations during follow-up were documented.

RESULTS

Cumulative complication rate was 66% (n = 27), with 11 developing within one year from surgery and 16 after one year (including five patients with both early and late complications). Ten graft failures (24%) and eight cases of reactive synovitis were observed (20%). All 11 patients with early complications and ten with late complications underwent reoperation (including five with another surgical procedure for early complications), amounting to a cumulative reoperation rate of 51% (n = 21). Revision ACL reconstruction was performed in one patient (2.4%). Median IKDC at latest follow-up was 89.7 (IQR 78.2 to 93.1), being significantly worse in the event of previous complications. Lachman test was positive in 56% (n = 15) of reconstructed knees. All norm-based SF-36 items were at or above median at latest follow-up, and did not differ depending on development of complications.

CONCLUSION

Despite good functional and QoL-related results in the long term, the cumulative complication rate of 66%, including graft failures and reactive synovitis, has to be viewed with great concern. Cite this article: Bone Joint J 2022;104-B(2):242-248.

Polydopamine Coating-Mediated Immobilization of BMP-2 on Polyethylene Terephthalate-Based Artificial Ligaments for Enhanced Bioactivity

Background/objectives: Polyethylene terephthalate (PET)-based artificial ligaments are one of the most commonly used grafts in anterior cruciate ligament (ACL) reconstruction surgery. However, the lack of favorable hydrophilicity and cell attachment for PET highly impeded its widespread application in clinical practice. Studies found that surface modification on PET materials could enhance the biocompatibility and bioactivity of PET ligaments. In this study, we immobilized bone morphogenetic protein-2 (BMP-2) on the surface of PET ligaments mediated by polydopamine (PDA) coating and investigated the bioactivation and graft-to-bone healing effect of the modified grafts in vivo and in vitro.

Methods: In this study, we prepared the PDA coating and subsequent BMP-2-immobilized PET artificial ligaments. Scanning electron microscopy (SEM) was used to analyze the morphological changes of the modified grafts. In addition, the surface wettability properties of the modified ligaments, amount of immobilized BMP 2, and the release of BMP-2 during a dynamic period up to 28 days were tested. Then, the attachment and proliferation of rat bone mesenchymal stem cells (rBMSCs) on grafts were examined by SEM and Cell Counting Kit-8 (CCK-8) assay, respectively. Alkaline phosphatase (ALP) assay, RT-PCR, and Alizarin Red S staining were performed to test the osteoinduction property. For in vivo experiments, an extra-articular graft-to-bone healing model in rabbits was established. At 8 weeks after surgery, biomechanical tests, micro-CT, and histological staining were performed on harvested samples.

Results: A surface morphological analysis verified the success of the PDA coating. The wettability of the PET artificial ligaments was improved, and more than 80% of BMP-2 stably remained on the graft surface for 28 days. The modified grafts could significantly enhance the proliferation, attachment, as well as expression of ALP and osteogenic-related genes, which demonstrated the favorable bioactivity of the grafts immobilized with BMP-2 in vitro. Moreover, the grafts immobilized with BMP-2 at a concentration of 138.4 ± 10.6 ng/cm² could highly improve the biomechanical properties, bone regeneration, and healing between grafts and host bone after the implantation into the rabbits compared with the PDA-PET group or the PET group.

Conclusion: The immobilization of BMP-2 mediated by polydopamine coating on PET artificial ligament surface could enhance the compatibility and bioactivity of the scaffolds and the graft-to-bone healing in vivo.

Patellar tendon versus artificial grafts in anterior cruciate ligament reconstruction: a systematic review and meta-analysis

Background

The aim of anterior cruciate ligament reconstruction (ACLR) is to restore the function of the knee joint, protect the cartilage, and reduce the occurrence of osteoarthritis. However, due to the structural limitations of the human body, it is not possible to perform ACLR with conventional sutures. To restore normal functioning of the anterior cruciate ligament (ACL), a new ligament must be reconstructed in the position of the previous ACL.

Objective

To compare autografts and synthetic grafts in terms of postoperative knee stability and function

Search methods

The protocol for this study was registered with PROSPERO (CRD42021243451). Two reviewers independently searched the PubMed, Embase, and the Cochrane Library databases from database inception though February 10, 2021. The following search method was used: ((Autograft) OR (Autologous) OR (Autotransplant)) OR Artificial Ligament AND (Anterior Cruciate Ligament Injury [MeSH Terms]) AND (Randomized controlled trial [MeSH Terms]). Methodological quality was assessed by the Cochrane risk of bias tool.

Selection criteria

We only included randomized controlled trials (level I) that compared autograft and synthetic graft interventions in participants with ACL injury. We included trials that evaluated ACLR using at least one outcome (Lachman test, pivot shift test, IKDC grades, or complications).

Results

A total of 748 studies were identified in the initial literature search, and seven studies that examined only bone-patellar tendon-bone (BPTB) grafts compared with artificial grafts met the predetermined inclusion criteria. The results showed that BPTB grafts were associated with significantly better pivot shift test and Lachman test results and better IKDC grades and lower complication rates than synthetic grafts.

Conclusions

This review indicates that for adults, BPTB grafts perform more favorably than synthetic grafts in ACLR in terms of knee stability, function, and complication. More research is needed to compare autologous tendons and allogeneic tendons with artificial ligaments, especially in elderly individuals.

Level of evidence

Level I, systematic review and meta-analysis

Establishment of near and non isometric anterior cruciate ligament reconstruction with artificial ligament in a rabbit model

Background

Tunnel position deicide the isometry of graft attachment in synthetic anterior cruciate ligament (ACL) reconstruction. Near-isometric tunnel position may have advantage in graft integration and knee function in ACL reconstruction (ACLR) with polyethylene terephthalate (PET) ligament. Few studies focused on tunnel position isometry when conduct ACLR with an animal model. This study aimed to establish a preclinical rabbit model of near and non isometric ACLR with PET ligament and investigate the advantage of near-isometric ACLR compared to non-isometric ACLR.

Methods

Nine hind limbs of rabbit were used in tunnel position study. Two femoral(anatomic, nonanatomic) tunnels and three tibial(anterior, middle, posterior) tunnels were used to measure tunnel position isometry during knee full range of motion. The tunnel position combination with minimal isometry was considered as near-isometric tunnel position. Then, 48 rabbits divided into two groups were conducted near or non isometric ACLR with PET ligament with graft fixation angle of 30° and constant tension of 5N. PET ligament isometry, range of motion(ROM) restriction, knee laxity were recorded after operation and followed up with macroscopic observation, microcomputed tomography (micro-CT) analysis, histology assessment and biomechanical test at 4 and 8 weeks postoperatively.

Results

The tunnel combination with minimal isometry was femoral anatomic position and tibial posterior position(5.19 ​± ​1.78%) and considered as near-isometric tunnel position. ROM restriction were observed in non-isometric group (22.50 ​± ​14.14°) while none in near-isometric group. However, no ROM restriction observed at 8 weeks in both group. Knee laxity compared to contralateral knee were better in near-isometric group than non-isometric group (stable/slack/total 10/2/12 VS 3/9/12, p ​= ​0.012) at 8 weeks postoperatively. Supeiror PET ligament integration were also observed in near-isometric group through macroscopic observation, micro-CT analysis, histology assessment at both 4 and 8 weeks. The failure load in the Near-Isometric group at 8 weeks were higher than timezero reconstruction with statistical difference (156.8N ​± ​25.98N vs.102.6 ​± ​22.96N, p ​= ​0.02).

Conclusion

A rabbit model of ACLR based on tunnel position isometry was successfully established in this study. The near-isometric tunnel position in rabbit model was femoral anatomic position and tibial posterior position. A near-isometric ACLR with PET ligament did not cause ROM restriction and had a better graft integration and follow-up stability than non-isometric ACLR with ROM restriction.

The Translational Potential of this Article

The study demonstrate the establishmentof near-isometric tunnel position and non-isometric tunnel position with significant difference of ROM restriction and graft-bone integration. The described tunnel positions with differential isometry in a rabbit ACLR provides a reproducible and translational small animal model and enables preclinical research between tunnel position isometry and its affection on variable grafts, graft integration and knee function.

Biofabrication and Signaling Strategies for Tendon/Ligament Interfacial Tissue Engineering

Tendons and ligaments (TL) have poor healing capability, and for serious injuries like tears or ruptures, surgical intervention employing autografts or allografts is usually required. Current tissue replacements are nonideal and can lead to future problems such as high retear rates, poor tissue integration, or heterotopic ossification. Alternatively, tissue engineering strategies are being pursued using biodegradable scaffolds. As tendons connect muscle and bone and ligaments attach bones, the interface of TL with other tissues represent complex structures, and this intricacy must be considered in tissue engineered approaches. In this paper, we review recent biofabrication and signaling strategies for biodegradable polymeric scaffolds for TL interfacial tissue engineering. First, we discuss biodegradable polymeric scaffolds based on the fabrication techniques as well as the target tissue application. Next, we consider the effect of signaling factors, including cell culture, growth factors, and biophysical stimulation. Then, we discuss human clinical studies on TL tissue healing using commercial synthetic scaffolds that have occurred over the past decade. Finally, we highlight the challenges and future directions for biodegradable scaffolds in the field of TL and interface tissue engineering.

A case report of traumatic osteoarthritis associated with LARS artificial ligament use in anterior cruciate ligament reconstruction

Background

A ligament advanced reinforcement system (LARS) artificial ligament has been proposed for use in anterior cruciate ligament (ACL) reconstruction, and many reports have shown its success in ACL reconstruction. However, there are great concerns about the potential risk of complications, which might prevent its extensive use. Late failure may occur due to serious complications.

Case presentation

We report a rare case of serious osteoarthritis that occurred 2 years postoperatively in a 51-year-old man who underwent reconstruction with an LARS artificial ligament. In X-rays, the tibial tunnel was placed too posteriorly. MRI showed that the tibial tunnel was enlarged, and there was a large effusion in the knee joint. The LARS device was rough and worn. Histologically, a large number of fibroblasts and a few multinucleated giant cells infiltrated the graft fibres.

Conclusion

Our findings remind surgeons that an LARS device should be with great caution in ACL reconstruction.

Which role for synthetic ligaments in the reconstruction of patellar tendon chronic rupture after TKA? Mid-term outcomes using LARS ligament

BACKGROUND AND AIM OF THE WORK

Patellar tendon rupture is a rare complication after Total Knee Arthroplasty (TKA) which often requires surgical treatment. Patients with chronic lesions or tendon degenerations showed good results when treated using autografts or allografts, but these techniques showed poor outcomes at long-term follow-up (FU). Moreover, allografts have high costs and limited availability, not to mention the increased risk of immune reactions and infections. Recently, the use of synthetic ligaments for patellar tendon reconstruction has taken hold with encouraging results. We report our experience in the treatment of patellar tendon ruptures after TKA using the Ligament Advanced Reinforcement System-LARS®.

METHODS

Clinical evaluation was performed using the Knee Society Score and recording extensor lag. Instrumental evaluation was performed using ultrasound imaging to assess patellar tendon thickness and using conventional x-rays to assess prosthesis' mobilization signs and patella's height.

RESULTS

At the final FU, 6 knees were included in our study. Patient's mean age was 66.7. Patellar tendon reconstruction occurred after a mean time of 4 months from the previous surgery. The mean FU was 44,2 months. The mean Knee Score was 63.3 and the mean Function Score was 35. In 4 knees the extensor lag was < 10° while in 2 knees it was > 20°. The mean ISI was 1.16, while the average increment in tendon thickness was 127.12%.

CONCLUSIONS

In our opinion, synthetic ligaments can be successfully employed for the reconstruction of patellar tendon breakage after TKA and rTKA in selected patients, in order to quickly return them to their activity of daily living.

Stiffness and shape of the ACL graft affects tunnel enlargement and graft wear

PURPOSE

Tunnel enlargement and graft rupture are common complications associated with ACL reconstruction (ACLR). This study aims to explore how variations in graft stiffness and shape affect the strain energy density (SED) around bone tunnel entrances and stress on the graft and subsequently influencing the level of tunnel enlargement and graft wear.

METHODS

Finite element ACLR models were developed using different graft stiffnesses (323 N/mm, 545 N/mm and 776 N/mm) and shapes (circular and elliptical). The models were subjected to a combined loading of 103 N anterior tibial load, 7.5 Nm internal tibial moment, and 6.9 Nm valgus tibial moment at joint flexion of 30°. SED at tunnel entrances and stresses on the graft was recorded and compared among the different models.

RESULTS

Increasing the graft stiffness resulted in greater stress on the graft (17.2, 24.4 and 31.7 MPa for graft stiffnesses of 323 N/mm, 545 N/mm and 776 N/mm), but had little effect on the SED reduction around the tunnel entrances. Changing the cross section of the graft from circular to elliptical caused an additional reduction in SED (56.8 vs 2.8 kJ/m³) at the posterior zone of the femoral tunnel entrance and increased the stress on the graft (31.7 MPa vs 38.9 MPa).

CONCLUSIONS

This study recommends using ACL grafts with lower stiffness and a circular cross section to reduce tunnel enlargement and graft wear following ACLR.

A novel protection liner to improve graft-tunnel interaction following anterior cruciate ligament reconstruction: a finite element analysis

Background

Deteriorated bone-graft interaction at the tunnel entrance following ACL reconstruction (ACLR) is considered one of the primary causes of long-term tunnel enlargement and graft wear. Methods have been introduced to improve the long-term outcome, such as novel graft materials or alternative fixation methods, but have been met with varying degrees of success. This study aims to design a protection liner to improve the bone-graft interaction at the tunnel entrances.

Methods

A finite element model of a human cadaveric knee was used to simulate traditional ACLR and ACLR using the protection liner. Stress distribution around the tunnel entrances and on the ACL graft were calculated under a combined loading of 103 N anterior tibial load, 7.5 Nm internal tibial moment, and 6.9 Nm valgus tibial moment at a joint flexion angle of 20°. Results were compared between the traditional ACLR and ACLR using a double liner (femoral and tibial) setup, as well as between the ACLR using a double liner setup and a single liner (femoral side) setup. Different materials (PEEK, Ti-6Al-4V, CoCrMo) for the liner were also evaluated.

Results

The traditional ACLR resulted in concentrated stress on the graft where it contacted the tunnel entrance. Correspondingly, there were stress concentrations at the distal posterior zone of the femoral tunnel entrance and medial posterior zone of the tibial tunnel entrance, while the other zones suffered from a stress reduction. Use of the protection liner reduced the stress concentration around the tunnel entrances by up to 89% and increased the stress at the unloaded zones by up to 106%. Also, stress concentration on the graft was slightly decreased (15.4 vs 15.1 MPa) after using the liner. The single liner setup increased the stress concentration around the tibial tunnel entrance. Stiffer materials improved the stress distribution around tunnel entrances but had little effect on the stress on the graft.

Conclusions

The novel protection liner can improve the stress distribution on the graft and at the tunnel entrances, which may be beneficial for improving the clinical outcome of ACLR.

Histological analysis of ACL reconstruction failures due to synthetic-ACL (LARS) ruptures

INTRODUCTION

Anterior Cruciate Ligament (ACL) reconstruction is an established surgical procedure. Synthetic ligaments represent an option for ACL reconstruction. Their popularity declined for the raising concerns due to re-ruptures, knee synovitis and early arthritis related to I and II generation artificial ligaments. The introduction of a III generation synthetic ligament (Ligament Advanced Reinforcement System-LARS) permitted renewed interest in the adoption of this kind of graft. Main purpose of our study was to describe the histological findings on samples obtained from a consecutive series of ACL revision surgeries due to LARS ACL reconstruction failures. Secondary aim was to determine the reason for LARS rupture.

METHODS

In a period between 2016 and 2018 eleven patients underwent ACL revision surgery due to LARS ACL reconstruction failure. At the time of the arthroscopic procedure, samples of synovial membrane and remnants of the torn LARS were sent to the Pathological-Anatomy Institute of our Hospital for a histological analysis.

RESULTS

Histological analysis of the synovial tissues confirmed the arthroscopic evidence of synovitis mainly characterized by chronic inflammation with predominance of multinucleated giant cells. The adoption of polarized light microscopy revealed the presence of brightly bi-refractive material (LARS wear particles) in the synovial tissue; at higher magnification wear debris were detected inside the cytoplasma of multi nucleated cells. The histological analysis of the removed LARS revealed a surrounding typical foreign body reaction with poor signs of fibrovascular ingrowth of the synthetic ligament.

CONCLUSIONS

Our findings could not clearly advocate a unique mechanism of LARS-ACL reconstruction failure: biologic issues (poor tissue ingrowth) and mechanical issues (fibers properties and tunnel position) probably concur in a multi factorial manner. ACL reconstruction using artificial ligaments can not be considered a simple surgery. Artificial augments require some expertise and could therefore achieve better results if used by skilled sport surgeons other than trainees or low volume surgeons. The Authors believe that ACL reconstruction with synthetic devices still have restricted indications for selected patients (e.g. elderly patients who require a fast recovery, professional athlete, autologous tendons not available and/or refusing donor tendons). Our study arises additional suspicion on the unresponsiveness of synthetic fibers and claim some concern in the implantation of synthetic devices.

Role of Biomaterials and Controlled Architecture on Tendon/Ligament Repair and Regeneration

Engineering synthetic scaffolds to repair and regenerate ruptured native tendon and ligament (T/L) tissues is a significant engineering challenge due to the need to satisfy both the unique biological and biomechanical properties of these tissues. Long-term clinical outcomes of synthetic scaffolds relying solely on high uniaxial tensile strength are poor with high rates of implant rupture and synovitis. Ideal biomaterials for T/L repair and regeneration need to possess the appropriate biological and biomechanical properties necessary for the successful repair and regeneration of ruptured tendon and ligament tissues.

Ligament augmentation reconstruction system artificial ligaments in patellar tendon reconstruction - a chronic patellar tendon rupture after multiple operations: A case report

BACKGROUND

Patellar tendon rupture is a rare disease, and reports regarding patellar tendon reconstruction with ligament augmentation reconstruction system (LARS) ligaments are limited, with only three reports available in the literature. LARS ligaments are made of polyethylene terephthalate and have been certified as a more favorable option than other tendon transplants. To our knowledge, this is the first report of patellar tendon reconstruction with LARS for suture fixation due to poor quality of the tendon after multiple operations to enable early mobilization and quick rehabilitation.

CASE SUMMARY

A 65-year-old woman had limited ability in extending her leg and an inability to perform a straight leg raise after multiple operations due to patella fracture. The patient underwent patellar tendon reconstruction with LARS artificial ligaments. After 12 mo of follow-up, the patient was able to perform a straight leg raise, and the incision healed well without complications. The Lysholm score was 95 and the range of motion of the knee was 0-130°.

CONCLUSION

This study revealed that patellar tendon reconstruction with LARS artificial ligaments is possible in a patient with a patellar tendon rupture who required rapid postoperative recovery.

"Swiss roll"-like bioactive hybrid scaffolds for promoting bone tissue ingrowth and tendon-bone healing after anterior cruciate ligament reconstruction

The choice of grafts for anterior cruciate ligament (ACL) reconstruction is a critical issue in sports medicine. Previous studies have revealed that scaffolds prepared from a single material could not achieve complete integration between the graft and autogenous bone tunnel. To solve this problem, we hypothesize that combining degradable scaffolds with nondegradable scaffolds can produce a novel hybrid ligament with the advantages of both types of scaffolds. In this study, a bone morphogenetic protein 7 (BMP-7)-loaded polycaprolactone (PCL) nanofibrous membrane was first manufactured as the degradable part of the hybrid ligament by using layer-by-layer (LbL) self-assembly. Then, we fabricated a multifunctional novel hybrid ligament by rolling up this nanofibrous membrane and polyethylene terephthalate (PET) mesh fabric (nondegradable part) into a "swiss roll" structure. The in vitro experimental results showed that this hybrid ligament could significantly improve the biocompatibility of pure PET ligament and further promote cell mineralization. The in vivo experimental results showed that this unique structure significantly promoted the integration of hybrid ligaments and bone tunnels, thereby achieving real "ligamentization" after ACL reconstruction surgery. These results suggest that this novel hybrid biomimetic artificial ligament scaffold provides a new direction for graft selection for ACL reconstruction.

Current Progress in Tendon and Ligament Tissue Engineering

Background

Tendon and ligament injuries accounted for 30% of all musculoskeletal consultations with 4 million new incidences worldwide each year and thus imposed a significant burden to the society and the economy. Damaged tendon and ligament can severely affect the normal body movement and might lead to many complications if not treated promptly and adequately. Current conventional treatment through surgical repair and tissue graft are ineffective with a high rate of recurrence.

Methods

In this review, we first discussed the anatomy, physiology and pathophysiology of tendon and ligament injuries and its current treatment. Secondly, we explored the current role of tendon and ligament tissue engineering, describing its recent advances. After that, we also described stem cell and cell secreted product approaches in tendon and ligament injuries. Lastly, we examined the role of the bioreactor and mechanical loading in in vitro maturation of engineered tendon and ligament.

Results

Tissue engineering offers various alternative ways of treatment from biological tissue constructs to stem cell therapy and cell secreted products. Bioreactor with mechanical stimulation is instrumental in preparing mature engineered tendon and ligament substitutes in vitro.

Conclusions

Tissue engineering showed great promise in replacing the damaged tendon and ligament. However, more study is needed to develop ideal engineered tendon and ligament.