Effects of administration of exogenous growth factors on biomechanical properties of the elongation-type anterior cruciate ligament injury with partial laceration

Nanosurgical and Bioengineering Treatment of Human Anterior Cruciate Ligament Tears with Ultrasound-Guided Injection of Modified Platelet-Rich Plasma Using Human Cell Memory Based on Clinical, Ultrasound, MRI, and Nanoscope Analyses: A Double-Blind Randomized Trial

Background: Anterior cruciate ligament (ACL) tears account for 40% to 50% of all ligamentous knee injuries. Most patients with ACL ruptures undergo surgical treatment. There is currently no objective, well-documented, repeatable, and standardized nonsurgical method for ACL tear treatment. This study aimed to investigate ACL outcomes in patients who underwent a novel nanosurgery and bioengineering treatment (NSBT) for an ACL tear. Methods: This was a double-blind randomized trial including 44 patients with a history of traumatic knee injury and a confirmed ACL tear. The final sample comprised 40 patients who met all the eligibility criteria. The patients were divided into two groups: the treatment group (n = 30) and the control group (n = 10). The treatment group underwent nanosurgery with an ultrasound-guided injection of modified platelet-rich plasma (PRP) using human cell memory (RP-hCM). The control group was treated with an ultrasound-guided PRP injection into the joint capsule. At baseline and post-treatment, all patients underwent both ultrasonography and magnetic resonance imaging (MRI), and the following clinical variables were assessed: the WOMAC score, the Lysholm knee score, the visual analog scale score, and knee instability. In most patients, the clinical outcome was verified using nanoscopy. Results: The median WOMAC, VAS, and LKS scores, as well as knee instability, improved significantly 12 weeks after the procedure in the treatment group (p < 0.001). We found a significantly larger improvement in the assessed parameters in the treatment group compared to the control group (p < 0.001). In the treatment group, all the patients had good and very good clinical outcomes, while 90% of the patients had a normal ACL signal in a follow-up MRI scan. In the control group, a physical examination revealed no changes in knee stability after treatment. Conclusions: This study showed that there is a significant difference in patient experience and the duration of recovery for patients with ACL tears treated with NSBT. The novel nonsurgical method was shown to be repeatable, objective, well documented, standardized, and highly effective.

Advanced Gene Therapy Strategies for the Repair of ACL Injuries

The anterior cruciate ligament (ACL), the principal ligament for stabilization of the knee, is highly predisposed to injury in the human population. As a result of its poor intrinsic healing capacities, surgical intervention is generally necessary to repair ACL lesions, yet the outcomes are never fully satisfactory in terms of long-lasting, complete, and safe repair. Gene therapy, based on the transfer of therapeutic genetic sequences via a gene vector, is a potent tool to durably and adeptly enhance the processes of ACL repair and has been reported for its workability in various experimental models relevant to ACL injuries in vitro, in situ, and in vivo. As critical hurdles to the effective and safe translation of gene therapy for clinical applications still remain, including physiological barriers and host immune responses, biomaterial-guided gene therapy inspired by drug delivery systems has been further developed to protect and improve the classical procedures of gene transfer in the future treatment of ACL injuries in patients, as critically presented here.

Influences of Partial Anterior Cruciate Ligament Injury On Anterior Cruciate Ligament Tensional Force and Kinematic Stability During Walking

Injuries in the anterior cruciate ligament (ACL), including partial tear and lengthening of the ACL, change the dynamic function of the knee. However, there is a lack of information on the effect of ACL partial tear on knee kinematics during walking. This study aimed to investigate the effects of different levels of ACL injuries on the knee stability and ACL tensional force to identify the critical injury level. Motion data of five normal subjects were acquired along with the ground reaction force. A knee model with 14 ligaments was developed using cadaveric specimen data. The initial length and stiffness of the ACL were changed to develop ACL-injured knee models. Musculoskeletal simulations of the knee models were performed using the measured gait data. The average tibial anterior translation increased significantly by 2.6 ± 0.7 mm when the ACL stiffness decreased to 25% of its original stiffness. The average tibial anterior translation increased significantly by 2.6 ± 0.3 mm at an increase in initial length of 10%. The knee with partial ACL tear had a non-linear decrease in ACL forces owing to the increase in the level of ACL injury, while the knee with ACL lengthening had linear decreased ACL forces. The partial tear of the ACL caused translational instability, while the complete tear caused both rotational and translational instabilities during the musculoskeletal walking simulation. This study presents the effects of partial ACL injuries on joint kinematics and ACL tensional force during the dynamic motion of walking.

OA foundations - experimental models of osteoarthritis

Osteoarthritis (OA) is increasingly recognised as a disease of diverse phenotypes with variable clinical presentation, progression, and response to therapeutic intervention. This same diversity is readily apparent in the many animal models of OA. However, model selection, study design, and interpretation of resultant findings, are not routinely done in the context of the target human (or veterinary) patient OA sub-population or phenotype. This review discusses the selection and use of animal models of OA in discovery and therapeutic-development research. Beyond evaluation of the different animal models on offer, this review suggests focussing the approach to OA-animal model selection on study objective(s), alignment of available models with OA-patient sub-types, and the resources available to achieve valid and translatable results. How this approach impacts model selection is discussed and an experimental design checklist for selecting the optimal model(s) is proposed. This approach should act as a guide to new researchers and a reminder to those already in the field, as to issues that need to be considered before embarking on in vivo pre-clinical research. The ultimate purpose of using an OA animal model is to provide the best possible evidence if, how, when and where a molecule, pathway, cell or process is important in clinical disease. By definition this requires both model and study outcomes to align with and be predictive of outcomes in patients. Keeping this at the forefront of research using pre-clinical OA models, will go a long way to improving the quality of evidence and its translational value.

Fibrin-Based Biomaterial Systems to Enhance Anterior Cruciate Ligament Healing

Anterior cruciate ligament (ACL) tears are a common and potentially career-ending injury, particularly for athletes and soldiers. Partial and complete ruptures of this ligament cause instability in the knee, and the ACL does not have the capacity for healing due, in part, to its position within the highly thrombolytic synovial fluid environment of the knee joint. Traditional methods of ACL reconstruction, such as graft replacement with attached bone anchors for bone integration, restore stability, but do not prevent the development of post-traumatic osteoarthritis. To enhance therapeutic treatment options, novel fibrin-based technologies and repair techniques have been recently explored and show promise for improved patient outcomes. Through modification of existing surgical methods, such as the use of fibrin glues incorporating growth factors and cells and the implementation of scaffolds containing platelet-rich plasma, platelet-rich fibrin, and other blood derivatives, surgeons are attempting to overcome the shortcomings of traditional treatments. This mini-review will detail current efforts using fibrin-based treatments and discuss opportunities to further enhance ACL healing.

The effect of thermosensitive hydrogel platelet-rich-plasma complex in the treatment of partial tear of anterior cruciate ligament in rat model

Background/Objective

The treatment of anterior cruciate ligament (ACL) partial tear is controversial. The reconstructive surgery is invasive while the prevalence of subsequent insufficiency after conservative treatment has been reported to range from 11% to 62%. Therefore, a new method that promotes tissue regeneration is needed. The aim of this study was to observe the healing of ACL partial tear biomechanically and histologically after the administration of a thermosensitive hydrogel platelet-rich-plasma (PRP) complex.

Methods

The complex was prepared according to a previously published protocol. One hundred and fifty 12-week-old male Sprague-Dawley rats were included and they were allocated into 4 groups. Lesion control group (Group 1), treatment group (Group 2), gel-only group (Group 3) and intact group (Group 4). Biomechanical testing, histological analysis (H&E and immunohistochemical staining) and scoring was performed.

Results

On gross observation, the treatment group showed a continuous ACL with slightly thickened synovium or a partially healed ACL at 6-week follow up. In the biomechanical testing at 6 weeks after surgery, the failure load of the treatment group was significantly superior when compared with the lesion control group (52.7±10.8N vs. 41.6±7.8N, p<0.01), but the failure load was not restored to level of the intact group (52.7±10.8N vs. 61.5±9.1N, p=0.037). The maturity index of wound sites showed no significant inter-group differences at any timepoints. However, an increased expression of vascular endothelial growth factor (VEGF) and pro-collagen I was detected.

Conclusion

The thermosensitive hydrogel-PRP was shown to be effective in enhancing the healing of ACL partial tear in the rat model, and potentially this complex can be used as a treatment for patients with ACL partial tear.

The translational potential of this article

The thermosensitive hydrogel-PRP is potentially translated to clinical use to treat patients with ACL partial tear by injection under arthroscopy or ultrasound guiding.

Exploring new genetic variants within COL5A1 intron 4-exon 5 region and TGF-β family with risk of anterior cruciate ligament ruptures

Variants within genes encoding structural and regulatory elements of ligaments have been associated with musculoskeletal soft tissue injury risk. The role of intron 4-exon 5 variants within the α1 chain of type V collagen (COL5A1) gene and genes of the transforming growth factor-β (TGF-β) family, TGFBR3 and TGFBI, was investigated on the risk of anterior cruciate ligament (ACL) ruptures. A case-control genetic association study was performed on 210 control (CON) and 249 participants with surgically diagnosed ruptures (ACL), of which 147 reported a noncontact mechanism of injury (NON). Whole-exome sequencing data were used to prioritize variants of potential functional relevance. Genotyping for COL5A1 (rs3922912 G>A, rs4841926 C>T, and rs3124299 C>T), TGFBR3 (rs1805113 G>A and rs1805117 T>C), and TGFBI (rs1442 G>C) was performed using Taqman SNP genotyping assays. Significant overrepresentation of the G allele of TGFBR3 rs1805113 was observed in CON vs ACL (P = .014) and NON groups (P = .021). Similar results were obtained in a female with the G allele (CON vs ACL: P = .029; CON vs NON: P = .016). The TGFBI rs1442 CC genotype was overrepresented in the female ACL vs CON (P = .013). Associations of inferred allele combinations were observed in line with the above results. COL5A1 intron 4-exon 5 genomic interval was not associated with the risk of ACL ruptures. Instead, this novel study is the first to use this approach to identify variants within the TGF-β signaling pathway to be implicated in the risk of ACL ruptures. A genetic susceptibility interval was identified to be explored in the context of extracellular matrix remodeling.

The non-reconstructive treatment of complete ACL tear with biological enhancement in clinical and preclinical studies: A systematic review

Introduction

There is still controversy regarding the bio-enhanced non-reconstructive ACL treatment.

Materials and methods

A search for articles in databases was performed in February 2017. The objective and subjective evaluations of clinical studies and biomechanical and histological data of preclinical studies were extracted.

Results

Eighteen articles were included for analysis. In clinical studies, although subjective scores were significantly improved, the rate of re-operation rate was high. In preclinical studies, bio-enhancing techniques demonstrated promotion of the healing of ACL.

Conclusions

The efficacy of biological enhancement cannot be validated in clinical studies. Preclinical studies showed improved biomechanical and healing potential.

Biologic Approaches for the Treatment of Partial Tears of the Anterior Cruciate Ligament: A Current Concepts Review

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) has been established as the gold standard for treatment of complete ruptures of the anterior cruciate ligament (ACL) in active, symptomatic individuals. In contrast, treatment of partial tears of the ACL remains controversial. Biologically augmented ACL-repair techniques are expanding in an attempt to regenerate and improve healing and outcomes of both the native ACL and the reconstructed graft tissue.

PURPOSE

To review the biologic treatment options for partial tears of the ACL.

STUDY DESIGN

Review.

METHODS

A literature review was performed that included searches of PubMed, Medline, and Cochrane databases using the following keywords: partial tear of the ACL, ACL repair, bone marrow concentrate, growth factors/healing enhancement, platelet-rich plasma (PRP), stem cell therapy.

RESULTS

The use of novel biologic ACL repair techniques, including growth factors, PRP, stem cells, and bioscaffolds, have been reported to result in promising preclinical and short-term clinical outcomes.

CONCLUSION

The potential benefits of these biological augmentation approaches for partial ACL tears are improved healing, better proprioception, and a faster return to sport and activities of daily living when compared with standard reconstruction procedures. However, long-term studies with larger cohorts of patients and with technique validation are necessary to assess the real effect of these approaches.

A Novel Silk Fiber-Based Scaffold for Regeneration of the Anterior Cruciate Ligament: Histological Results From a Study in Sheep

BACKGROUND

Because of ongoing problems with anterior cruciate ligament (ACL) reconstruction, new approaches in the treatment of ACL injuries, particularly strategies based on tissue engineering, have gained increasing research interest. To allow for ACL regeneration, a structured scaffold that provides a mechanical basis, has cells from different sources, and comprises mechanical as well as biological factors is needed. Biological materials, biodegradable polymers, and composite materials are being used and tested as scaffolds. The optimal scaffold for ACL regeneration should be biocompatible and biodegradable to allow tissue ingrowth but also needs to have the right mechanical properties to provide immediate mechanical stability.

HYPOTHESES

The study hypotheses were that (1) a novel degradable silk fiber-based scaffold with mechanical properties similar to the native ACL will be able to initiate ligament regeneration after ACL resection and reconstruction under in vivo conditions and (2) additional cell seeding of the scaffold with autologous stromal vascular fraction-containing adipose-derived stem cells will increase regenerative activity.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 33 mountain sheep underwent ACL resection and randomization to 2 experimental groups: (1) ACL reconstruction with a scaffold alone and (2) ACL reconstruction with a cell-seeded scaffold. Histological evaluation of the intra-articular portion of the reconstructed/regenerated ligament was performed after 6 and 12 months.

RESULTS

After 6 months, connective tissue surrounded the silk scaffold with ingrowth in some areas. The cell-seeded scaffolds had a significant lower silk content compared with the unseeded scaffolds and demonstrated a higher content of newly formed tissue. After 12 months, the density of the silk fibers decreased significantly, and the ingrowth of newly formed tissue increased in both groups. No differences between the 2 groups regarding silk fiber degradation and regenerated tissue were detected at 12 months.

CONCLUSION

The novel silk fiber-based scaffold was able to stimulate ACL regeneration under in vivo conditions. Additional cell seeding led to increased tissue regeneration and decreased silk fiber content at 6 months, whereas these differences were not present at 12 months.

CLINICAL RELEVANCE

ACL regeneration using a silk fiber-based scaffold with and without additional cell seeding may provide a new treatment option after joint injuries.

Regenerative treatments to enhance orthopedic surgical outcome

In orthopedic surgery there has been a never-ending quest to improve surgical outcome and the patient's experience. Progression has been marked by the refinement of surgical techniques and instruments and later by enhanced diagnostic imaging capability, specifically magnetic resonance. Over time implant optimization was achieved, along with the development of innovative minimally invasive arthroscopic technical skills to leverage new versions of classic procedures and implants to improve short-term patient morbidity and initial, mid-term, and long-term patient outcomes. The use of regenerative and/or biological adjuncts to aid the healing process has followed in the drive for continual improvement, and major breakthroughs in basic science have significantly unraveled the mechanisms of key healing and regenerative pathways. A wide spectrum of primary and complementary regenerative treatments is becoming increasingly available, including blood-derived preparations, growth factors, bone marrow preparations, and stem cells. This is a new era in the application of biologically active material, and it is transforming clinical practice by providing effective supportive treatments either at the time of the index procedure or during the postoperative period. Regenerative treatments are currently in active use to enhance many areas of orthopedic surgery in an attempt to improve success and outcome. In this review we provide a comprehensive overview of the peer-reviewed evidence-based literature, highlighting the clinical outcomes in humans both with preclinical data and human clinical trials involving regenerative preparations within the areas of rotator cuff, meniscus, ligament, and articular cartilage surgical repair.

Central defect type partial ACL injury model on goat knees: the effect of infrapatellar fat pad excision

Background

The mid-substance central defect injury has been used to investigate the primary healing capacity of the anterior cruciate ligament (ACL) in a goat model. The sagittal plane stability on this model has not been confirmed, and possible effects of fat pad excision on healing have not been evaluated. We hypothesize that excising the fat pad tissue results in poorer ligament healing as assessed histologically and decreased tensile strength of the healing ligament. We further hypothesize that the creation of a central defect does not affect sagittal plane knee stability.

Methods

A mid-substance central defect was created with a 4-mm arthroscopic punch in the ACLs of right knees of all the subjects through a medial mini-arthrotomy. Goats were assigned to groups based on whether the fat pad was preserved (group 1, n = 5) or excised completely (group 2, n = 5). The left knees served as controls in each goat. Histopathology of the defect area along with measurement of type I collagen in one goat from each group were performed at 10th week postoperatively. The remaining knees were evaluated biomechanically at the 12th week, by measuring anterior tibial translation (ATT) of the knee joints at 90° of flexion and testing tensile properties (ultimate tensile load (UTL), ultimate elongation (UE), stiffness (S), failure mode (FM)) of the femur-ACL-tibia complex.

Results and discussion

Histopathology analysis revealed that the central defect area was fully filled macroscopically and microscopically. However, myxoid degeneration and fibrosis were observed in group 2 and increased collagen type I content was noted in group 2. There were no significant differences within and between groups in terms of ATT values (p = 0.715 and p = 0.149, respectively). There were no significance between or within groups in terms of ultimate tensile load and ultimate elongation; however, group 2 demonstrated greater stiffness than group 1 that was correlated with the fibrotic changes detected microscopically (p = 0.043).

Conclusions

The central defect type injury model was confirmed to be biomechanically stable in a goat model. Resection of the fat pad was noted to negatively affect defect healing and increase ligament stiffness in the central defect injury model.

rhPDGF-BB promotes early healing in a rat rotator cuff repair model

BACKGROUND

Tendon-bone healing after rotator cuff repair occurs by fibrovascular scar tissue formation, which is weaker than a normal tendon-bone insertion site. Growth factors play a role in tissue formation and have the potential to augment soft tissue healing in the perioperative period.

QUESTIONS/PURPOSES

Our study aim was to determine if rhPDGF-BB delivery on a collagen scaffold can improve tendon-to-bone healing after supraspinatus tendon repair compared with no growth factor in rats as measured by (1) gross observations; (2) histologic analysis; and (3) biomechanical testing.

METHODS

Ninety-five male Sprague-Dawley rats underwent acute repair of the supraspinatus tendon. Rats were randomized into one of five groups: control (ie, repair only), scaffold only, and three different platelet-derived growth factor (PDGF) doses on the collagen scaffold. Animals were euthanized 5 days after surgery to assess cellular proliferation and angiogenesis. The remaining animals were analyzed at 4 weeks to assess repair site integrity by gross visualization, fibrocartilage formation with safranin-O staining, and collagen fiber organization with picrosirius red staining, and to determine the biomechanical properties (ie, load-to-failure testing) of the supraspinatus tendon-bone construct.

RESULTS

The repaired supraspinatus tendon was in continuity with the bone in all animals. At 5 days, rhPDGF-BB delivery on a scaffold demonstrated a dose-dependent response in cellular proliferation and angiogenesis compared with the control and scaffold groups. At 28 days, with the numbers available, rhPDGF-BB had no effect on increasing fibrocartilage formation or improving collagen fiber maturity at the tendon-bone insertion site compared with controls. The control group had higher tensile loads to failure and stiffness (35.5 ± 8.8 N and 20.3 ± 4.5 N/mm) than all the groups receiving the scaffold, including the PDGF groups (scaffold: 27 ± 6.4 N, p = 0.021 and 13 ± 5.7 N/mm, p = 0.01; 30 µg/mL PDGF: 26.5 ± 7.5 N, p = 0.014 and 13.3 ± 3.2 N/mm, p = 0.01; 100 µg/mL PDGF: 25.7 ± 6.1 N, p = 0.005 and 11.6 ± 3.3 N/mm, p = 0.01; 300 µg/mL PDGF: 27 ± 6.9 N, p = 0.014 and 12.7 ± 4.1 N/mm, p = 0.01).

CONCLUSIONS

rhPDGF-BB delivery on a collagen scaffold enhanced cellular proliferation and angiogenesis during the early phase of healing, but this did not result in either a more structurally organized or stronger attachment site at later stages of healing. The collagen scaffold had a detrimental effect on healing strength at 28 days, and its relatively larger size compared with the rat tendon may have caused mechanical impingement and extrinsic compression of the healing tendon. Future studies should be performed in larger animal models where healing occurs more slowly.

CLINICAL RELEVANCE

Augmenting the healing environment to improve the structural integrity and to reduce the retear rate after rotator cuff repair may be realized with continued understanding and optimization of growth factor delivery systems.

Healing of donor site in bone-tendon-bone ACL reconstruction accelerated with plasma rich in growth factors: a randomized clinical trial

PURPOSE

To determine whether the use of plasma rich in growth factors accelerates healing of the donor site in bone-tendon-bone anterior cruciate ligament (ACL) reconstruction (patellar graft). The use of the patellar graft presents post-operative problems such as anterior knee pain, which limits its use and leads to preference being taken for alternative grafts.

METHODS

A double-blind, randomized, clinical trial was performed comparing two groups of patients who underwent ACL reconstruction using patellar tendon graft and comparing the use of plasma rich in growth factors at the donor site after graft harvest in terms of local regeneration by ultrasound assessment.

RESULTS

The plasma rich in growth factors group shows earlier donor site regeneration in comparison with the control group (2 months earlier), with significant differences in the first 4 months of the follow-up.

CONCLUSION

The application of plasma rich in growth factors shows accelerated tissue regeneration processes with respect to the control group. This fact, together with the previously published with similar conclusions, can create a knowledge basis in order to set out new recovery guidelines following ACL reconstruction.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Sonographically Guided Anterior Cruciate Ligament Injection: Technique and Validation

OBJECTIVE

To describe and validate a practical technique for sonographically guided anterior cruciate ligament (ACL) injections.

DESIGN

Prospective, cadaveric laboratory investigation.

SETTING

Procedural skills laboratory in a tertiary medical center.

SUBJECTS

Ten unembalmed, cadaveric mid-thigh-knee-ankle foot specimens (5 left knees and 5 right knees; 5 male and 5 female) from 10 donors aged 76 to 93 years (mean 85.6 years) with body mass indices of 17.6 to 42.2 kg/m(2) (mean 28.8 kg/m(2)).

METHODS

A single, experienced operator used a 22-gauge, 63.5-mm stainless steel needle and a 12-3-MHz linear transducer to inject 1.5 mL of diluted colored latex into the ACLs of 10 unembalmed cadaveric specimens via an in-plane, caudad-to-cephalad approach, long axis to the ACL. At a minimum of 24 hours postinjection, specimens were dissected, and the presence and distribution of latex within the ACL assessed by a study co-investigator.

MAIN OUTCOME

Presence and distribution of latex within the ACL.

RESULTS

All 10 injections accurately delivered latex into the proximal (femoral), midsubstance, and distal (tibial) portions of the ACL. No specimens exhibited evidence of needle injury or latex infiltration with respect to the menisci, hyaline cartilage, or posterior cruciate ligament.

CONCLUSIONS

Sonographically guided intra-ligamentous ACL injections are technically feasible and can be performed with a high degree of accuracy. Sonographically guided ACL injections could be considered for research and clinical purposes to directly deliver injectable agents into the healing ACL postinjury or postreconstruction.

Systematic Review of Biological Modulation of Healing in Anterior Cruciate Ligament Reconstruction

Background:

Whether biological modulation is effective to promote healing in anterior cruciate ligament (ACL) reconstruction remains unclear.

Purpose:

To perform a systematic review of both clinical and experimental evidence of preclinical animal studies on biological modulation to promote healing in ACL reconstruction.

Study Design:

Systematic review; Level of evidence, 2.

Methods:

A systematic search was performed using the PubMed, Ovid, and Scopus search engines. Inclusion criteria were clinical and animal studies involving subjects with ACL injury with the use of biological modulation to promote healing outcomes. Methodological quality of clinical studies was evaluated using the Critical Appraisal Skill Programme (CASP) appraisal tool, and animal studies were evaluated by a scoring system based on a published checklist of good animal studies.

Results:

Ten clinical studies and 50 animal studies were included. Twenty-five included studies were regarded as good quality, with a methodological score ≥5. These studies suggested that transforming growth factor–beta (TGF-β), mesenchymal stem cells, osteogenic factors, and modalities that reduce local inflammation may be beneficial to promote graft healing in ACL reconstruction.

Conclusion:

This systematic review suggests that biological modulation is able to promote healing on top of surgical treatment for ACL injuries. This treatment strategy chiefly works through promotion of healing at the tunnel-graft interface, but the integrity of the intra-articular midsubstance of the graft would be another target for biological modulation.

Basic science of anterior cruciate ligament injury and repair

Injury to the anterior cruciate ligament (ACL) is one of the most devastating and frequent injuries of the knee. Surgical reconstruction is the current standard of care for treatment of ACL injuries in active patients. The widespread adoption of ACL reconstruction over primary repair was based on early perception of the limited healing capacity of the ACL. Although the majority of ACL reconstruction surgeries successfully restore gross joint stability, post-traumatic osteoarthritis is commonplace following these injuries, even with ACL reconstruction. The development of new techniques to limit the long-term clinical sequelae associated with ACL reconstruction has been the main focus of research over the past decades. The improved knowledge of healing, along with recent advances in tissue engineering and regenerative medicine, has resulted in the discovery of novel biologically augmented ACL-repair techniques that have satisfactory outcomes in preclinical studies. This instructional review provides a summary of the latest advances made in ACL repair. Cite this article: Bone Joint Res 2014;3:20-31.

Magnetic resonance imaging evaluation of patellar tendon graft remodelling after anterior cruciate ligament reconstruction with or without platelet-rich plasma

PURPOSE

To evaluate the stages of patellar tendon graft remodelling using magnetic resonance imaging (MRI) after anterior cruciate ligament (ACL) reconstruction with or without platelet-rich plasma (PRP) injection.

METHODS

98 patients aged 18 to 65 years with complete rupture of the ACL were randomised to undergo reconstruction with the autologous patellar tendon grafts with or without PRP injection. For the PRP group, 8 ml of PRP was obtained in the surgery room and was percutaneously injected into the suprapatellar joint after portal suture. MRI was obtained at months 4, 6, and 12. Remodelling stages of the grafts were classified as hypointense, mildly hyperintense, moderately hyperintense, severely hyperintense, and diffusely hyperintense by a radiologist blinded to treatment allocation.

RESULTS

More patients in the PRP group than controls attained higher stages of remodelling at month 4 (p=0.003), month 6 (p=0.0001), and month 12 (p=0.354).

CONCLUSION

PRP enabled faster remodelling of patellar tendon grafts.

The effect of intra-articular autogenous bone marrow injection on healing of an acute posterior cruciate ligament injury in rabbits

PURPOSE

The purpose was to identify the effect of intra-articular autogenous bone marrow injection on the healing of an acute posterior cruciate ligament (PCL) rupture in a rabbit model. The effect of autogenous bone marrow on the healing process was assessed serially by gross inspection, histologic examination, and immunohistochemical study of growth factors.

METHODS

In both knee joints, the PCL was completely transected surgically near the femoral attachment site in 24 rabbits. Autogenous bone marrow was obtained from both tibias and delivered only to the right knee joint by direct intra-articular injection. Gross inspection, histologic examination, and immunohistochemical study of growth factors were performed at 8, 12, and 16 weeks after severing of the posterior cruciate ligament (PCL) among 8 randomly chosen specimens. The degree of healing in both marrow-stimulated and untreated control ligaments was evaluated by gross inspection using an ordinal scale consisting of 5 grades. The degree of fibroblast and vessel proliferation and alignment of collagen fibers were evaluated by histologic examination. The degree of expression of transforming growth factor β1, epidermal growth factor receptor, and vascular endothelial growth factor was evaluated by immunohistochemical study. Statistical analysis was performed with the Mann-Whitney U test.

RESULTS

In the group with marrow-stimulated ligaments, the degree of healing was higher at 8 and 12 weeks by gross examination, whereas there was no significant difference at 16 weeks between the 2 groups. According to histologic examination, the healing process was faster in the bone marrow injection group than in the control group at 8 and 12 weeks because the degree of fibroblast and vessel proliferation significantly declined and collagen fibers were arranged more regularly compared with the control group. Similar to the results of histologic examination, the results of immunohistochemical studies showed that the healing process was faster in the bone marrow injection group. However, the recovery of the PCL was completed at 16 weeks after PCL resection in both the bone marrow injection group and the control group.

CONCLUSIONS

Intra-articular autogenous bone marrow injection appeared to promote the initiation of healing response in acutely injured PCLs in rabbits.

CLINICAL RELEVANCE

Intra-articular autogenous bone marrow injection can be a viable option for treating acutely injured PCLs.

Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally.

Comparison of magnetic resonance imaging findings in anterior cruciate ligament grafts with and without autologous platelet-derived growth factors

PURPOSE

To determine whether the use of platelet-rich plasma gel (PRPG) affects magnetic resonance imaging (MRI) findings in the anterior cruciate ligament (ACL) graft during the first year after reconstruction.

METHODS

A prospective single-blinded study of 50 ACL reconstructions in 50 patients was performed. In group A (study group) PRPG was added to the graft with a standardized technique, and in group B (control group) no PRPG was added. An MRI study was performed postoperatively between 3 and 9 months in group A and between 3 and 12 months in group B. The imaging analysis was performed in a blind protocol by the same radiologist.

RESULTS

The mean heterogeneity score value at the time of MRI, assigned by the radiologist, was 1.14 in group A and 3.25 in group B. Both groups were comparable in terms of sex and age (P < .05). The mean time to obtain a completely homogeneous intra-articular segment in group A (PRPG added) was 177 days after surgery, and it was 369 days in group B. Using the quadratic predictive model, these findings show that group A (PRPG added) needed only 48% of the time group B required to achieve the same MRI image (P < .001).

CONCLUSIONS

ACL reconstruction with the use of PRPG achieves complete homogeneous grafts assessed by MRI, in 179 days compared with 369 days for ACL reconstruction without PRPG. This represents a time shortening of 48% with respect to ACL reconstruction without PRPG.

Effect of bone morphogenetic protein-12 gene transfer on posterior cruciate ligament healing in a rabbit model

BACKGROUND

The posterior cruciate ligament heals to some extent after injury. However, results after conservative treatment may diminish with long-term follow-up. Bone morphogenetic protein-12 can induce formation of ligament tissues.

HYPOTHESIS

Bone morphogenetic protein-12 gene transfer can improve the histologic and biomechanical properties of healing posterior cruciate ligaments.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bilateral posterior cruciate ligaments of 32 rabbits were injured. The cut ends in 1 limb received an injection containing 3 x 10(7) pfu recombinant bone morphogenetic protein-12 adenovirus, and the posterior cruciate ligament in the contralateral limb served as an untreated control. Eight rabbits were sacrificed at each time point of 3, 6, 12, and 26 weeks after the operation. In addition, 6 rabbits receiving a sham operation were used to obtain normal control data. The posterior cruciate ligament specimens were evaluated biomechanically and histologically.

RESULTS

The repair tissue of the treatment group at 26 weeks was similar to the normal posterior cruciate ligament in collagen arrangement, collagen formation, and mechanical properties. At weeks 6, 12, and 26, the ultimate load, stiffness, and energy absorbed at failure of the treatment group were significantly greater than those of the untreated group.

CONCLUSION

Adenovirus-mediated bone morphogenetic protein-12 gene transfer in a partial posterior cruciate ligament laceration rabbit model resulted in an obvious improvement of histologic properties, tensile strength, and stiffness of the repaired ligaments, indicating improved posterior cruciate ligament healing.

CLINICAL RELEVANCE

Bone morphogenetic protein-12 gene transfer is a potential future strategy to improve the repair of injured posterior cruciate ligaments.

Effects of platelet concentrate and a bone plug on the healing of hamstring tendons in a bone tunnel

PURPOSE

The purpose of this study was to determine if the use of platelet concentrate (PC) and bone plug (BP) does accelerate the healing process in anterior cruciate ligament (ACL) reconstruction.

METHODS

One hundred and eight patients requiring ACL reconstruction were prospectively randomized into 4 groups: control (27 patients), PC (26 patients), BP (28 patients), and a combination of PC and BP (27 patients). Magnetic resonance imaging (MRI) studies were carried out at both 3 and 6 months postsurgery. Maturation of the graft was evaluated at the femoral tunnel using MRI maturation criteria defined by a low-intensity signal, absence of osteoligamentous interface, and no widening of the femoral tunnel.

RESULTS

Three months after surgery, no differences were found among the groups regarding MRI maturation criteria. Six months postsurgery, 78% of the patients in the control group had a low-intensity signal, while in the PC group the low-intensity signal was present in 100% of the patients (P = .036). No statistical differences were observed regarding the osteoligamentous interface between the various groups. Finally, tunnel widening was seen in 11% of the patients of the BP group versus 41% of the patients in the control group (P = .047), but no statistical difference was seen with the other groups.

CONCLUSIONS

The use of PC had an enhancing effect on the graft maturation process evaluated only by MRI signal intensity, without showing any significant effect in the osteoligamentous interface or tunnel widening evolution. The use of a BP effectively prevented tunnel widening. The BP and PC combination did not show a synergic effect as compared to PC or BP individually.

LEVEL OF EVIDENCE

Level II, lesser quality randomized controlled trial.

In vivo local administration of osteogenic protein-1 increases structural properties of the overstretched anterior cruciate ligament with partial midsubstance laceration

We report the effects of local administration of osteogenic protein-1 on the biomechanical properties of the overstretched anterior cruciate ligament in an animal model. An injury in the anterior cruciate ligament was created in 45 rabbits. They were divided into three equal groups. In group 1, no treatment was applied, in group II, phosphate-buffered saline was applied around the injured ligament, and in group III, 12.5 μg of osteogenic protein-1 mixed with phosphate-buffered saline was applied around the injured ligament. A control group of 15 rabbits was assembled from randomly-selected injured knees from among the first three groups. Each rabbit was killed at 12 weeks.

The maximum load and stiffness of the anterior cruciate ligament was found to be significantly greater in group III than either group 1 (p = 0.002, p = 0.014) or group II (p = 0.032, p = 0.025). The tensile strength and the tangent modulus of fascicles from the ligament were also significantly greater in group III than either group I (p = 0.002, p = 0.0174) or II (p = 0.005, p = 0.022).

The application of osteogenic protein-1 enhanced the healing in the injured anterior cruciate ligament, but compared with the control group the treated ligament remained lengthened. The administration of osteogenic protein-1 may have a therapeutic role in treating the overstretched anterior cruciate ligament.

The potential use of enamel matrix derivative for in situ anterior cruciate ligament tissue engineering: a translational in vitro investigation

Polyester scaffolds have been used as an alternative to autogenous tissues for the reconstruction of the anterior cruciate ligament (ACL). They are biocompatible and encourage tissue infiltration, leading to neoligament formation. However, rupture can occur, caused by abrasion of the scaffold against the bone tunnels through which it is implanted. Good early tissue induction is therefore considered essential to protect the scaffold from this abrasion. Enamel matrix derivative (EMD) is used clinically in the treatment of periodontal disease. It is a complex mix of proteins with growth factor-like activity, which enhances periodontal ligament fibroblast attachment, proliferation, and differentiation, leading to the regeneration of periodontal bone and ligament tissues. We hypothesized that EMD might, in a similar manner, enhance tissue induction around scaffolds used in ACL reconstruction. This preliminary investigation adopted a translational approach, modelling in vitro 3 possible clinical modes of EMD administration, to ascertain the suitability of each protocol for application in an animal model or clinically. Preliminary investigations in monolayer culture indicated that EMD had a significant dose-dependent stimulatory effect (p < 0.05, n = 6) on the proliferation of bovine primary synovial cells. However, pre-treating culture plates with EMD significantly inhibited cell attachment (p < 0.01, n = 6). EMD's effects on synovial cells, seeded onto ligament scaffolds, were then investigated in several in vitro experiments modelling 3 possible modes for clinical EMD administration (pre-, intra-, and post-operative). In the pre-operative model, EMD was adsorbed onto scaffolds before the addition of cells. In the intra-operative model, EMD and cells were added simultaneously to scaffolds in the culture medium. In the post-operative model, cells were pre-seeded onto scaffolds before EMD was administered. EMD significantly inhibited cell adhesion in the pre-operative model (p < 0.05, n = 6) and had no significant benefit in the intra-operative model. In the post-operative model, the addition of EMD to previously cell-seeded scaffolds significantly increased their total deoxyribonucleic acid content (p < 0.01, n = 5). EMD's stimulative effect on cell proliferation in vitro suggests that it may accelerate scaffold colonization by cells (and in turn tissue induction) in situ. However, its inhibitory effect on synovial cell attachment in vitro implies that it may only be suited to post-operative administration.

Monopolar radiofrequency energy application to the dorsal extensor tendon apparatus in a canine model of tendon injury

PURPOSE

To evaluate the use of monopolar radiofrequency energy (MRFE) to shorten stretched dorsal extensor tendon apparatus (DETA) tissues in a canine model.

METHODS

Eleven adult canine forelimbs were used in this in vitro investigation. The DETA tissue was isolated between the metacarpophalangeal and proximal interphalangeal joints in the third and fourth digits of each limb. Isolated tissue was stretched in all but 2 of the digits (control group). After tissue stretching, monopular radiofrequency energy (MRFE) was applied to 18 of the digits at 1 of 3 temperatures: 50 degrees C, 60 degrees C, or 70 degrees C (stretch-treatment group). Two digits were treated identically, but MRFE was not applied (stretch-only group). Tissue length was measured before and after stretching and after treatment. Percent stretch, percent shortening, and percent original length were compared among the 3 stretch-treatment groups. All DETA specimens were examined with light microscopy.

RESULTS

Histologic changes were apparent in the stretch-treatment and stretch-only specimens compared with controls. Percent stretch was not significantly different between groups. Percent shortening and percent original length were significantly lower and higher, respectively, in the 50 degrees C group than in the 60 degrees C and 70 degrees C stretch-treatment groups, which were not significantly different from each other. There was a significant linear correspondence between percent shortening and treatment temperature.

CONCLUSIONS

The application of MRFE at a temperature of 60 degrees C and a power of 10 W appears to shorten stretched DETA tissue to approximately the prestretched length in an in vitro canine model. Further investigation is necessary to determine the effect of treatment on the tissue's mechanical properties.