Biological augmentation of graft healing in anterior cruciate ligament reconstruction: a systematic review

Application and optimization of bioengineering strategies in facilitating tendon-bone healing

Tendon-bone insertion trauma is prevalent in both rotator cuff and anterior cruciate ligament injuries, which are frequently encountered conditions in the field of sports medicine. The main treatment for such injuries is reconstructive surgery. The primary determinant impacting this process is the graft's capacity to integrate with the bone tunnel. In recent years, researchers have attempted to use a variety of methods to facilitate tendon-bone healing after reconstructive surgery. Such as the implantation of biological materials, cytokines and the local application of permanently differentiated cells from various sources. However, there are limitations to the efficacy of one therapy alone in facilitating tendon-bone healing. Therefore, researchers are trying to combine strategies to overcome this conundrum. At present, most studies are based on biomaterial combined with other therapeutic strategies for tissue repair and regeneration. Biomaterials mainly include the application of bioengineering scaffolds, hydrogels and bioabsorbable interference screws. By conducting a thorough review of relevant literature, this study provides a comprehensive overview of the present research progress in enhancing tendon-bone healing using biomaterials. Additionally, it explores the potential benefits of combining biomaterials with other approaches to promote tendon-bone healing. The ultimate goal is to offer insights for future basic research endeavors and establish a solid groundwork for advancing clinical applications in the near future.

Use of extracorporeal shockwave therapy combined with standard rehabilitation following anterior cruciate ligament reconstruction: a systematic review with meta-analysis

BACKGROUND

Anterior cruciate ligament (ACL) injuries are one of the most common sports injuries, accounting for approximately 50% of knee-related injuries. Extracorporeal shockwave therapy (ESWT), in the form of the radial (R-SWT) or focused shockwave (F-SWT), has been shown effective in treating various orthopaedic conditions. Recently, studies have investigated whether ESWT combined with standard rehabilitation may improve outcomes following anterior cruciate ligament reconstruction (ACLR). Therefore, this study aimed to determine whether ESWT can improve clinical outcomes following ACLR.

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We searched PubMed, Embase, and Web of Science and included studies involving ESWT treatment following ACLR, which consisted of randomized controlled trials (RCTs) and cohort studies. Two authors independently extracted the outcome measurements and used a revised Cochrane risk-of-bias tool (RoB 2) for RCTs and the Risk of Bias in Non-randomised Studies of Interventions (ROBINS-I) for a cohort study to assess the risk of bias. A random effects pairwise meta-analysis was used to compare patient-reported outcomes between ESWT and controlled treatments.

RESULTS

Five studies (Level I: 4; Level II: 1) with 242 participants (male: 167; female: 75) were included. Regarding the patient-reported outcomes, the risk of bias for all RCTs was 'high' and 'serious' for a non-randomized study. The meta-analysis demonstrated that the Lysholm scores were significantly higher in ESWT groups than those of controls at 12 months (Weighted mean difference [WMD]: 7.037, 95% confidence interval [CI]: 6.172-7.902, I2: 0%) and 24 months (WMD: 5.463, 95% CI: 2.870-8.056, I2: 0%). Furthermore, the International Knee Documentation Committee (IKDC) scores were also significantly higher in the ESWT group than that of the control at 12 months (WMD: 6.371, 95% CI: 3.397-9.344, I2: 68.8%). However, the WMDs for these outcomes between the two groups did not exceed the minimal clinically important difference (MCID).

CONCLUSION

Based on the meta-analyses performed with a few studies, ESWT combined with standard rehabilitation may potentially lead to better patient-reported outcomes. However, these differences may not be clinically significant. Further high-quality studies are needed to confirm our review's findings.

Biological augmentation of anterior cruciate ligament reconstruction with bone marrow aspirate concentrate: a systematic review and meta-analysis of randomised controlled trials

PURPOSE

Biological augmentation of anterior cruciate ligament (ACL) reconstruction with bone marrow aspirate concentrate (BMAC) is gaining attention for its theoretical potential to enhance postoperative healing and recovery. However, its clinical benefits remain uncertain, and its high cost raises questions about efficacy. Hence, we systematically reviewed randomised controlled trials (RCTs) to evaluate the effectiveness of BMAC in ACL reconstruction.

METHODS

Our search included Cochrane, EMBASE, OVID, PubMed, and Scopus databases for RCTs evaluating the use of BMAC in ACL reconstruction. Primary outcomes focused on International Knee Documentation Committee (IKDC) scores and Lysholm scores. Secondary outcomes included MRI-related outcomes and postoperative complications. Statistical analysis was conducted using Review Manager 5.4 (Cochrane Collaboration), with heterogeneity assessed using Cochrane's Q test and I2 statistics.

RESULTS

221 patients from five RCTs were included, with 109 (49.3%) receiving BMAC augmentation. Follow-up ranged from 11.05 to 24 months. No significant differences were found in postoperative IKDC scores between the BMAC and control groups at, three, six and 12 months. The BMAC group had significantly higher IKDC scores at 24 months; however, this difference was unlikely to be clinically significant. No significant differences were observed in postoperative Lysholm scores at 12 or 24 months. MRI-related outcomes suggested potential graft recovery improvement with BMAC, and complication rates were comparable between groups.

CONCLUSION

In summary, biological augmentation with BMAC in ACL reconstruction does not significantly improve early patient-reported outcomes but offers potential benefits in graft recovery without increasing complication rates.

Preparation of Bone Patellar Tendon Bone Allograft With Biocomposite Scaffold Augmentation

Anterior cruciate ligament (ACL) injuries and subsequent surgical reconstruction are exceedingly common orthopaedic procedures. Surgical technique and graft preparation techniques continue to evolve as surgeons seek to increase surgical outcomes and decrease recovery time. As such, there is significant interest in identifying tools and techniques that may enhance the surgical process for patients undergoing an ACL reconstruction. Recently, there has been significant interest in evaluating biologic scaffolds that may augment graft healing. This Technical Note describes our technique for the preparation of a bone-patellar tendon-bone ACL graft with a BioBrace biocomposite scaffold augmentation.

Biologic Impact of Anterior Cruciate Ligament Injury and Reconstruction

Surgical intervention after anterior cruciate ligament (ACL) tears is typically required because of the limited healing capacity of the ACL. However, mechanical factors and the inflammatory response triggered by the injury and surgery can impact patient outcomes. This review explores key aspects of ACL injury and reconstruction biology, including the inflammatory response, limited spontaneous healing, secondary inflammation after reconstruction, and graft healing processes. Understanding these biologic mechanisms is crucial for developing new treatment strategies and enhancing patient well-being. By shedding light on these aspects, clinicians and researchers can work toward improving quality of life for individuals affected by ACL tears.

Repair potential of self-assembling peptide hydrogel in a mouse model of anterior cruciate ligament reconstruction

PURPOSE

Establishing zonal tendon-to-bone attachment could accelerate the anterior cruciate ligament reconstruction (ACLR) rehabilitation schedule and facilitate an earlier return to sports. KI24RGDS is a self-assembling peptide hydrogel scaffold (SAPS) with the RGDS amino acid sequence. This study aimed to elucidate the therapeutic potential of KI24RGDS in facilitating zonal tendon-to-bone attachment after ACLR.

METHODS

Sixty-four C57BL/6 mice were divided into the ACLR + SAPS and ACLR groups. ACLR was performed using the tail tendon. To assess the maturation of tendon-to-bone attachment, we quantified the area of mineralized fibrocartilage (MFC) in the tendon graft with demeclocycline. Immunofluorescence staining of α-smooth muscle actin (α-SMA) was performed to evaluate progenitor cell proliferation. The strength of tendon-to-bone attachment was evaluated using a pull-out test.

RESULTS

The MFC and maximum failure load in the ACLR + SAPS group were remarkably higher than in the ACLR group on Day 14. However, no significant difference was observed between the two groups on Day 28. The number of α-SMA-positive cells in the tendon graft was highest on Day 7 after ACLR in both the groups and was significantly higher in the ACLR + SAPS group than in the ACLR group.

CONCLUSION

This study highlighted the latent healing potential of KI24RGDS in facilitating early-stage zonal attachment of tendon grafts and bone tunnels post-ACLR. These findings may expedite rehabilitation protocols and shorten the timeline for returning to sports.

LEVEL OF EVIDENCE

Not applicable.

Intra-Articular Platelet-Rich Plasma Injection After Anterior Cruciate Ligament Reconstruction: A Randomized Clinical Trial

Importance

Platelet-rich plasma (PRP) has been considered a promising treatment for musculoskeletal disorders. The effects of PRP on clinical outcomes of anterior cruciate ligament reconstruction (ACLR) are controversial.

Objective

To compare subjective outcomes and graft maturity in patients undergoing ACLR with and without postoperative intra-articular PRP injection.

Design, Setting, and Participants

This surgeon- and investigator-masked randomized clinical trial included patients treated at a national medical center in China who were aged 16 to 45 years and scheduled to undergo ACLR. Participants were enrolled between March 21, 2021, and August 18, 2022, and followed up for 12 months, with the last participant completing follow-up on August 28, 2023.

Interventions

Participants were randomized 1:1 to the PRP group (n = 60), which received 3 doses of postoperative intra-articular PRP injection at monthly intervals, or to the control group (n = 60), which did not receive postoperative PRP injection. Both groups had the same follow-up schedule.

Main Outcomes and Measures

The primary outcome was the mean score for 4 subscales of the Knee Injury and Osteoarthritis Outcome Score (KOOS4) (range, 0-100, with higher scores indicating better knee function and fewer symptoms) at 12 months postoperatively. Secondary outcomes were patient-reported outcomes, graft maturity (on magnetic resonance imaging), and physical examinations at 3, 6, and 12 months.

Results

Among the 120 randomized participants (mean [SD] age, 29.0 [8.0] years; 84 males [70%]), 114 (95%) were available for the primary outcome analysis. The mean KOOS4 scores at 12 months were 78.3 (SD, 12.0; 95% CI, 75.2-81.4) in the PRP group and 76.8 (SD, 11.9; 95% CI, 73.7-79.9) in the control group (adjusted mean between-group difference, 2.0; 95% CI, -2.3 to 6.3; P = .36). Secondary outcomes were not statistically significantly different between the 2 groups except for sports and recreation level and graft maturity at 6 months. Intervention-related adverse events included pain at the injection site and knee swelling after injection.

Conclusions and Relevance

In this randomized clinical trial among patients undergoing ACLR, the addition of postoperative intra-articular PRP injection did not result in superior improvement of knee symptoms and function at 12 months compared with no postoperative injection. Further studies are required to determine appropriate indications for PRP in musculoskeletal disorders.

Trial Registration

Chinese Clinical Trial Registry Identifier: ChiCTR2000040262.

Activation of CGRP receptor-mediated signaling promotes tendon-bone healing

Calcitonin gene-related peptide (CGRP), an osteopromotive neurotransmitter with a short half-life, shows increase while calcitonin receptor-like (CALCRL) level is decreased at the early stage in bone fractures. Therefore, the activation of CALCRL-mediated signaling may be more critical to promote the tendon-bone healing. We found CGRP enhanced osteogenic differentiation of BMSCs through PKA/CREB/JUNB pathway, contributing to improved sonic hedgehog (SHH) expression, which was verified at the tendon-bone interface (TBI) in the mice with Calcrl overexpression. The osteoblast-derived SHH and slit guidance ligand 3 were reported to favor nerve regeneration and type H (CD31hiEMCNhi) vessel formation, respectively. Encouragingly, the activation or inactivation of CALCRL-mediated signaling significantly increased or decreased intensity of type H vessel and nerve fiber at the TBI, respectively. Simultaneously, improved gait characteristics and biomechanical performance were observed in the Calcrl overexpression group. Together, the gene therapy targeting CGRP receptor may be a therapeutic strategy in sports medicine.

Cells Remain Viable When Collected With an In-Line-Suction Tissue Collector From Byproducts of Anterior Cruciate Ligament Reconstruction Surgery

Purpose

To investigate the viability of cells collected with an in-line-suction autologous tissue collector from the tissue byproducts of arthroscopic anterior cruciate ligament (ACL) reconstruction, to characterize cells from different tissue types, and to identify mesenchymal stem cells.

Methods

Patients aged 14 to 50 years with ACL injuries requiring arthroscopic reconstruction surgery were offered enrollment and screened for participation. In total, 12 patients were enrolled in the descriptive laboratory study. Arthroscopic byproduct tissue was collected with an in-line-suction autologous tissue collector from 4 intraoperative collection sites for each patient: ACL stump, ACL fat pad, notchplasty debris, and tunnel drilling debris. All tissue samples were digested using collagenase, and the derived cellular populations were analyzed in vitro, characterizing cellular viability, proliferative potential, qualitative multipotent differentiation capacity, and cell-surface marker presence.

Results

An equivalent mass of arthroscopic byproduct tissue was taken from each of the 4 intraoperative collection sites (1.12-1.61 g, P = .433), which all showed an average viability of at least 99.95% and high average total nucleated cells (≥1.37 × 107 cells/mL). No significant differences in collected mass (P = .433), cellular viability (P = .880), or total nucleated cells (P = .692) were observed between the 4 byproduct tissues. The byproduct tissues did exhibit significant differences in monocyte (P = .037) and red blood cell (P = .038) concentrations, specifically with greater values present in the ACL stump tissue. Cells from all byproduct tissues adhered to plastic cell culture flasks. Significant differences were found between colony-forming unit fibroblast counts of the 4 byproduct tissues when plated at 106 (P = .003) and 103 (P = .016) cells as the initial seeding density. There was a significant relationship found between both the starting concentration (χ2 = 32.7, P < .001) and the byproduct tissue type (χ2 = 30.4, P < .001) to the presence of ≥80% confluency status at 10 days. Cells obtained from all 4 byproduct tissues qualitatively showed positive tri-lineage (adipocyte, osteoblast, chondroblast) differentiation potential compared with negative controls under standardized in vitro differentiation conditions. Cells derived from all 4 byproduct tissues expressed cell-surface antigens CD105+, CD73+, CD90+, CD45-, CD14-, and CD19- (>75%), and did not express CD45 (<10%). There were no statistically significant differences in cell-surface antigens between the four byproduct tissues.

Conclusions

This descriptive laboratory study demonstrated that cells derived from arthroscopic byproduct tissues of ACL reconstruction remain viable when collected with an in-line-suction autologous tissue collector and these cells meet the ISCT criteria to qualify as mesenchymal stem cells.

Clinical Relevance

It is known that viable mesenchymal stem cells reside in byproduct tissue of anterior cruciate ligament reconstruction surgery (ACLR). Practical methods to harvest these cells at the point of care require further development. This study validates the use of an in-line-suction autologous tissue collector for the harvest of viable mesenchymal stem cells after ACLR.

An Update on Orthobiologics: Cautious Optimism

Orthobiologics are rapidly growing in use given their potential to augment healing for multiple musculoskeletal conditions. Orthobiologics consist of a variety of treatments including platelet-rich plasma and stem cells that provide conceptual appeal in providing local delivery of growth factors and inflammation modulation. The lack of standardization in nomenclature and applications within the literature has led to a paucity of high-quality evidence to support their frequent use. The purpose of this review was to describe the current landscape of orthobiologics and the most recent evidence regarding their use.

Influence of periostin on the development of fibrocartilage layers of anterior cruciate ligament insertion

BACKGROUND

Periostin (Postn) is thought to play a role in the formation of anterior cruciate ligament (ACL) insertion. However, the influence of Postn on the development of ACL insertion requires further understanding. This study aimed to clarify the influence of Postn on the development of fibrocartilage layers of ACL insertion.

HYPOTHESIS

We hypothesized that Postn would influence the development of fibrocartilage layers of ACL insertion.

MATERIALS AND METHODS

C57BL/6N wild-type (Postn+/+; n=54) and Postn knockout (Postn-/-; n=54) mice were used in this study. Six animals were euthanized at 1 d and 1, 2, 3, 4, 6, 8, 10, and 12 weeks of age in each group. The chondrocyte number, proliferation, apoptosis, safranin O-stained glycosaminoglycan (GAG) area, type II collagen staining area, tidemark length, and insertion width were evaluated.

RESULTS

Chondrocyte proliferation was high up to 2 weeks in Postn+/+, while low at age 1 d; it was, especially lower in Postn-/- than in Postn+/+ at age 1 d and 1 week. Chondrocyte apoptosis was high up to age 8 weeks in Postn+/+ and at 6 weeks in Postn-/-; it was especially higher in Postn-/- than in Postn+/+ at age 1 week. The GAG stained area was thickest for age 1 d to 4 weeks in Postn+/+ and for age 2 to 6 weeks in Postn-/-. The type II collagen staining area in Postn+/+ was thicker than that in Postn-/- at age 6 and 8 weeks. The tidemark length in Postn+/+ was longer than that in Postn-/- from age 8 to 12 weeks. The insertion width in Postn+/+ was longer than that in Postn-/- from age 1 to 3 weeks.

DISCUSSION

Postn decreased cell proliferation in the early postnatal phase and influenced the development of the fibrocartilage layer extracellular matrix of ACL insertion in mice. Postn may contribute to the development of methods for regeneration of the ACL insertion.

LEVEL OF EVIDENCE

V; controlled laboratory study.

Targeting the hedgehog signaling pathway to improve tendon-to-bone integration

OBJECTIVE

While the role of hedgehog (Hh) signaling in promoting zonal fibrocartilage production during development is well-established, whether this pathway can be leveraged to improve tendon-to-bone repair in adults is unknown. Our objective was to genetically and pharmacologically stimulate the Hh pathway in cells that give rise to zonal fibrocartilaginous attachments to promote tendon-to-bone integration.

DESIGN

Hh signaling was stimulated genetically via constitutive Smo (SmoM2 construct) activation of bone marrow stromal cells or pharmacologically via systemic agonist delivery to mice following anterior cruciate ligament reconstruction (ACLR). To assess tunnel integration, we measured mineralized fibrocartilage (MFC) formation in these mice 28 days post-surgery and performed tunnel pullout testing.

RESULTS

Hh pathway-related genes increased in cells forming the zonal attachments in wild-type mice. Both genetic and pharmacologic stimulation of the Hh pathway increased MFC formation and integration strength 28 days post-surgery. We next conducted studies to define the role of Hh in specific stages of the tunnel integration process. We found Hh agonist treatment increased the proliferation of the progenitor pool in the first week post-surgery. Additionally, genetic stimulation led to continued MFC production in the later stages of the integration process. These results indicate that Hh signaling plays an important biphasic role in cell proliferation and differentiation towards fibrochondrocytes following ACLR.

CONCLUSION

This study reveals a biphasic role for Hh signaling during the tendon-to-bone integration process after ACLR. In addition, the Hh pathway is a promising therapeutic target to improve tendon-to-bone repair outcomes.

Human Trials on the Prevention of Tunnel Widening by the Emdogain in Anterior Cruciate Ligament Reconstruction

Background Although anterior cruciate ligament reconstruction (ACLR) is an established procedure, some problems remain, such as bone tunnel widening after ACLR. In animal studies, Emdogain (EMD) prevented tunnel widening by promoting tendon-bone healing. This study aimed to evaluate the effects of EMD on the prevention of tunnel widening after anterior cruciate ligament (ACL) injury in humans. Methods Nineteen patients who underwent ACLR were included. Seven patients in the EMD group were administered EMDs into the femoral tunnel during ACLR, while 12 patients in the control group were not administered EMDs. After surgery, at two and four weeks and three, six, and 12 months, femoral and tibial tunnel widening were evaluated on computed tomography images. Anteroposterior laxity and clinical scores such as the Lysholm score, the International Knee Documentation Committee (IKDC) subjective form, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were assessed before surgery and 12 months postoperatively. Results Tunnel widening on the femoral side was significantly smaller in the EMD group than in the control group at two weeks. However, there was no significant difference between the two groups at 12 months. There were no significant differences in anteroposterior laxity and clinical scores between the groups before and 12 months after surgery. Conclusion EMD administration into the bone tunnel did not prevent tunnel widening at 12 months after ACLR, although tunnel widening of the femoral tunnel was reduced by EMD administration in the early phase.

Radial Extracorporeal Shock Wave Therapy Enhances Graft Maturation at 2-Year Follow-up After ACL Reconstruction: A Randomized Controlled Trial

Background

Graft maturation is an important prognostic factor for hamstring autograft anterior cruciate ligament reconstruction (ACLR). It remains unclear whether extracorporeal shock wave therapy (ESWT) can promote graft healing after ACLR.

Purpose

To evaluate the therapeutic and graft maturation effects of ESWT in hamstring autograft ACLR.

Study Design

Randomized controlled trial; Level of evidence, 1.

Methods

Between May 18, 2019, and September 20, 2019, we randomly assigned 30 patients who met study inclusion criteria to 2 groups. Patients in the control group followed a 5-week advanced rehabilitation training program (30 minutes/session, 5 times/week) starting at 3 months postoperatively. In the ESWT group, together with the 5-week advanced rehabilitation training, radial ESWT was applied once a week for 5 weeks. Functional scores (Lysholm, International Knee Documentation Committee, and Tegner scores), KT-1000 arthrometer knee laxity measurement, and magnetic resonance imaging scans were assessed at 3 months (baseline), 6 months, and 24 months postoperatively. To evaluate graft maturation, we assessed the graft signal-to-noise quotients (SNQs) of the tibial, intra-articular, and femoral sides on magnetic resonance imaging scans. Data were compared between the ESWT and control groups.

Results

In total, 26 patients (13 with ESWT, 13 controls) were assessed. There were no significant between-group differences on any assessment at baseline, and no significant within-group or between-group differences were found in knee laxity at any point. At 24-month follow-up, the ESWT group had significantly higher Lysholm and Tegner scores compared with the controls (P = .012 and .017, respectively). Regarding graft maturation, at 6-month follow-up, the SNQ of the tibial intraosseous graft was significantly lower in the ESWT group versus controls (P = .006), but no differences were detected at the femoral intraosseous graft (P = .321) or the intra-articular graft (P = .314). At 24-month follow-up, the SNQs of the femoral intraosseous graft and intra-articular graft were significantly lower in the ESWT group versus controls (P = .020 and .044, respectively) but no difference was found at the tibial intraosseous graft (P = .579).

Conclusion

Both enhanced graft maturation and improved functional scores at 24-month follow-up were seen in patients who received radial ESWT during rehabilitation after hamstring autograft ACLR.

Registration

ChiCTR1900022853 (Chinese Clinical Trial Registry).

Bioactive Decellularized Tendon-Derived Stem Cell Sheet for Promoting Graft Healing After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Stem cell sheets provide a scaffold-free option for the promotion of graft healing after anterior cruciate ligament reconstruction (ACLR). However, cell viability, stability, and potential uncontrolled actions create challenges for clinical translation. The decellularization of cell sheets may overcome these problems as studies have shown that the natural extracellular matrix of stem cells is bioactive and can promote tissue repair.

HYPOTHESIS

The decellularized tendon-derived stem cell (dTDSC) sheet can promote graft healing after ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

An optimized decellularization protocol was developed to decellularize the TDSC sheets. A total of 64 Sprague-Dawley rats underwent ACLR with or without the dTDSC sheet wrapping the tendon graft (n = 32/group). At 2 and 6 weeks after surgery, graft healing was assessed by micro-computed tomography, histology, and biomechanical testing. The accumulation of iNOS⁺ and CD206⁺ cells and the expression of metalloproteinase 1 (MMP-1), MMP-13, and tissue inhibitor of metalloprotease 1 (TIMP-1) were assessed by immunohistochemistry.

RESULTS

The decellularization was successful, with the removal of 98.4% nucleic acid while preserving the collagenous proteins and bioactive factors. The expression of bone morphogenetic protein 2 (BMP-2) and VEGF in the dTDSC sheet was comparable with the TDSC sheet (P > .05). Micro-computed tomography showed significantly more tunnel bone formation in the dTDSC sheet group. The dTDSC sheet group demonstrated better graft osteointegration and higher integrity of graft midsubstance with significantly higher ultimate failure load (16.58 ± 7.24 vs 8.93 ± 2.45 N; P = .002) and stiffness (11.97 ± 5.21 vs 6.73 ± 2.20 N/mm; P = .027). Significantly fewer iNOS⁺ cells but more CD206⁺ cells, as well as lower MMP-1 and MMP-13 but higher TIMP-1 expression, were detected at the tendon-bone interface and graft midsubstance in the dTDSC sheet group.

CONCLUSION

An optimized decellularization protocol for producing bioactive dTDSC sheets was developed. Wrapping tendon graft with a dTDSC sheet promoted graft healing after ACLR, likely via enhancing bone formation and angiogenesis by BMP-2 and VEGF, modulating macrophage polarization and MMP/TIMP expression, and physically protecting the tendon graft.

CLINICAL RELEVANCE

dTDSC sheets alleviate the quality control and safety concerns of cell transplantation and can be used as a cell-free alternative for the promotion of graft healing in ACLR.

Vitamin D Metabolic Pathway Components in Orthopedic Patientes-Systematic Review

Vitamin D takes part in the functioning of many processes that ensure the homeostasis of the body. In orthopedics, it is indicated as an inseparable element ensuring proper bone growth and functioning, and its deficiencies are indicated in various diseases, mainly in the proper structure and function of the skeleton. In this review, we focus on the most important components of the vitamin D metabolic pathway, in correlation with selected orthopedic conditions. Records were obtained from the PubMed database in a timeline of 2010-2022. The keywords were as follows: vitamin D/cholesterol/vitamin D binding protein/ VDBP/Cytochrome/CYP24A1/CYP 27B1/Vitamin D receptor/VDR/ + diseases (ACL reconstruction, rotator cuff, arthroplasty knee/hip/shoulder). The recent original studies were analyzed, discussed, and the most important data were shown. The vast majority of articles concern the metabolite of vitamin D (25(OH)D), which is measured as a standard in diagnostic laboratories. Even though there is a lot of valuable information in the literature, we believe that the other elements of the vitamin D pathway also deserve attention and suggest their research in correlation with orthopedic disorders to supplement the missing knowledge on this topic.

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.

Effectiveness of Platelet-Rich Plasma in Anterior Cruciate Ligament Reconstruction: A Systematic Review of Randomized Controlled Trials

This study aimed to identify the effectiveness of platelet-rich plasma (PRP) for patients operated with anterior cruciate ligament reconstruction (ACLR). Databases of PubMed, Embase, and CENTRAL were independently retrieved by two authors, for identifying the eligible randomized controlled trials (RCTs) comparing the clinical and imaging outcomes of ACL reconstructed patients augmented with or without PRP. The Cochrane Collaboration tool was utilized to assess the risk of bias of the included trials. We qualitatively synthesized the outcomes include the image evaluations on the healing of bone tunnels, graft remodeling, donor site healing and tunnel widening, and clinical evaluations on knee stability and function, pain symptom by visual analogue scale (VAS), inflammatory parameters and so on. A total of 16 RCTs, including 1025 patients, were included for eligibility. Generally, the included studies were of low risk of bias, but the conducting of allocation concealment was not clearly described in many studies. Three imaging techniques, including MRI, CT and ultrasound, were selected in these trials. Significant improvement on graft remodeling, bone tunnel healing, harvest site healing and bone tunnel diameters were demonstrated in one of five (20.0%), three of five (60.0%), two of four (50.0%) and one of five (20.0%) studies respectively, for PRP group. Various clinical outcomes, such as IKDC score, Lysholm score, Tegner score, knee anteroposterior and rotational laxity, range of motion and VAS, could not be improved with PRP application. The PRP is associated with very limited role in improving knee outcomes following ACLR, and there is no indication for PRP procedures in ACLR at this stage.

Study protocol for double-blind, randomised placebo-controlled trial evaluating semitendinosus function and morbidity following tendon harvesting for anterior cruciate ligament reconstruction augmented by platelet-rich plasma

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is debilitating, often requiring surgical reconstruction. An ACL reconstruction (ACLR) using a tendon autograft harvested from the semitendinosus results in substantial injury to the donor muscle. Following ACLR, patients rarely return to their preinjury level of physical activity, are at elevated risk of secondary lower limb injuries and early onset knee osteoarthritis. To date, no randomised controlled trial has evaluated the efficacy of platelet-rich plasma (PRP) in aiding knee function and semitendinosus morphology of following ALCR.

METHODS AND ANALYSIS

This is a multicentre double-blind randomised placebo-controlled trial. Fifty-four ACLR patients aged 18-50 years will be randomised to receive either a single application of PRP (ACLR+) or placebo saline (ACLR) into the semitendinosus harvest zone at the time of surgery. All patients will undergo normal postoperative rehabilitation recommended by the attending orthopaedic surgeon or physiotherapist. The primary outcome measure is between-limb difference (ACLR compared with intact contralateral) in isometric knee flexor strength at 60o knee flexion, collected 10-12 months postsurgery. This primary outcome measure will be statistically compared between groups (ACLR+ and standard ACLR). Secondary outcome measures include bilateral assessments of hamstring muscle morphology via MRI, biomechanical and electromyographic parameters during an anticipated 45° running side-step cut and multidirectional hopping task and patient-reported outcomes questionaries. Additionally, patient-reported outcomes questionaries will be collected before (baseline) as well as immediately after surgery, and at 2-6 weeks, 3-4 months, 10-12 months and 22-24 months postsurgery 10-12 months following surgery.

ETHICS AND DISSEMINATION

Ethics approval has been granted by Griffith University Human Research Ethics Committee, Greenslopes Research and Ethics Committee, and Royal Brisbane & Women's Hospital Human Research Ethics Committee. Results will be submitted for publication in a peer-reviewed medical journal.

TRIAL REGISTRATION NUMBER

ACTRN12618000762257p.

Exosomes derived from magnetically actuated bone mesenchymal stem cells promote tendon-bone healing through the miR-21-5p/SMAD7 pathway

Graft healing after anterior cruciate ligament reconstruction (ACLR) involves slow biological processes, and various types of biological modulations have been explored to promote tendon-to-bone integration. Exosomes have been extensively studied as a promising new cell-free strategy for tissue regeneration, but few studies have reported their potential in tendon-to-bone healing. In this study, a novel type of exosome derived from magnetically actuated (iron oxide nanoparticles (IONPs) combined with a magnetic field) bone mesenchymal stem cells (BMSCs) (IONP-Exos) was developed, and the primary purpose of this study was to determine whether IONP-Exos exert more significant effects on tendon-to-bone healing than normal BMSC-derived exosomes (BMSC-Exos). Here, we isolated and characterized the two types of exosomes, conducted in vitro experiments to measure their effects on fibroblasts (NIH3T3), and performed in vivo experiments to compare the effects on tendon-to-bone integration. Moreover, functional exploration of exosomal miRNAs was further performed by utilizing a series of gain- and loss-of-function experiments. Experimental results showed that both BMSC-Exos and IONP-Exos could be shuttled intercellularly into NIH3T3 fibroblasts and enhanced fibroblast activity, including proliferation, migration, and fibrogenesis. In vivo, we found that IONP-Exos significantly prevented peri-tunnel bone loss, promoted more osseous ingrowth into the tendon graft, increased fibrocartilage formation at the tendon-bone tunnel interface, and induced a higher maximum load to failure than BMSC-Exos. Furthermore, overexpression of miR-21-5p remarkably enhanced fibrogenesis in vitro, and SMAD7 was shown to be involved in the promotive effect of IONP-Exos on tendon-to-bone healing. Our findings may provide new insights into the regulatory roles of IONPs in IONP-Exos communication via stimulating exosomal miR-21-5p secretion and the SMAD7 signaling pathway in the fibrogenic process of tendon-to-bone integration. This work could provide a new strategy to promote tendon-to-bone healing for tissue engineering in the future.

Cellular Augmentation of Anterior Cruciate Ligament Surgery Is Not Currently Evidence Based: A Systematic Review of Clinical Studies

PURPOSE

To perform a systematic review of clinical outcome studies exploring cellular augmentation of anterior cruciate ligament (ACL) surgery, including stem cell techniques.

METHODS

A systematic search was performed according to the Preferred Reporting Items of Systematic Reviews and Meta-analyses (PRISMA) guidelines using the Cochrane, PubMed, MEDLINE, SPORTDiscus, and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases from 2000 to 2019. The inclusion criteria were clinical studies that reported on ACL surgery augmented with stem cells or cellular therapy and patient-reported outcome measures or graft healing. Risk of bias was assessed using the Cochrane risk-of-bias tool for randomized clinical trials, and nonrandomized trials were assessed using the Methodological Items for Non-randomized Studies (MINORS) tool. Methodologic assessment was performed according to the Modified Coleman Methodology Score.

RESULTS

Four studies were found: 2 randomized clinical trials, 1 cohort study with a matched historical control group, and 1 case series. The mean Modified Coleman Methodology Score in these studies was 59, and there was a low risk of bias in 1 study. One study reported outcomes of augmented ACL repair, and 3 studies reported the results of augmented ACL reconstruction. Cellular therapies varied and included concentrated bone marrow aspirate, collagenase/centrifuge processed adipose, and marrow stimulation combined with platelet-rich plasma, as well as cells cultured from allograft bone marrow aspirate. The concentrated bone marrow aspirate and adipose tissue study results did not support their use. The marrow stimulation technique combined with repair led to promising clinical results. The use of allograft cultured cells improved patient-reported outcomes and postoperative radiographic findings.

CONCLUSIONS

Augmentation of ACL surgery with cellular therapy is not supported by clinical evidence at this time.

LEVEL OF EVIDENCE

Level IV.

Biomechanical Comparison of Modified Adams-Berger and DX technique in DRUJ Reconstruction

Background  Adams-Berger ligamentoplasty is a widely accepted reconstruction for unrepairable triangular fibrocartilage complex (TFCC) injuries with instability. Failure of the reconstruction and recurrent instability is still a clinical problem. Internal brace augmentation of tendon grafts is gaining more popularity, but use in the distal radioulnar joint (DRUJ) is not yet published. Questions/Purposes  The purpose of this study was to compare a novel anatomical DRUJ reconstruction with a modified Adams-Berger reconstruction to answer which technique stabilize better the DRUJ and which has enough stabilizing effect to allow early mobilization. Methods  Nine matched pairs of cadaveric upper extremities were used. The dorsopalmar translations in the DRUJ that occurred with 50 N load were measured before and after detachment of the TFCC from the ulna and after ligament reconstruction with either modified Adams-Berger procedure or DX Swivelock technique. Internal brace augmented palmaris longus tendon grafts were used in all reconstruction. Results  In the Adams-Berger group, the injured and the reconstructed displacements were significantly higher than the native, while in the DX group both the native and the reconstructed displacements were significantly lower than the injured. The mean (standard deviation) change of translations was 0.46 (1.94) mm after Adams-Berger and 2.51 (1.31) mm after DX reconstruction, implying significant better stabilizing effect of the latter. Conclusions  DX Swivelock reconstruction showed better time zero stabilizing effect compared with Adams-Berger procedure, regaining almost normal stability of the DRUJ.

Anterior Cruciate Ligament Reconstruction: Is Biological Augmentation Beneficial?

Surgical reconstruction in anterior cruciate ligament (ACL) ruptures has proven to be a highly effective technique that usually provides satisfactory results. However, despite the majority of patients recovering their function after this procedure, ACL reconstruction (ACLR) is still imperfect. To improve these results, various biological augmentation (BA) techniques have been employed mostly in animal models. They include: (1) growth factors (bone morphogenetic protein, epidermal growth factor, granulocyte colony-stimulating factor, basic fibroblast growth factor, transforming growth factor-β, hepatocyte growth factor, vascular endothelial growth factor, and platelet concentrates such as platelet-rich plasma, fibrin clot, and autologous conditioned serum), (2) mesenchymal stem cells, (3) autologous tissue, (4) various pharmaceuticals (matrix metalloproteinase-inhibitor alpha-2-macroglobulin bisphosphonates), (5) biophysical/environmental methods (hyperbaric oxygen, low-intensity pulsed ultrasound, extracorporeal shockwave therapy), (6) biomaterials (fixation methods, biological coatings, biosynthetic bone substitutes, osteoconductive materials), and (7) gene therapy. All of them have shown good results in experimental studies; however, the clinical studies on BA published so far are highly heterogeneous and have a low degree of evidence. The most widely used technique to date is platelet-rich plasma. My position is that orthopedic surgeons must be very cautious when considering using PRP or other BA methods in ACLR.

Adipose-Derived Stem Cell Sheets Improve Early Biomechanical Graft Strength in Rabbits After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Although various reconstruction techniques are available for anterior cruciate ligament (ACL) injuries, a long recovery time is required before patients return to sports activities, as the reconstructed ACL requires time to regain strength. To date, several studies have reported use of mesenchymal stem cells in orthopaedic surgery; however, no studies have used adipose-derived stem cell (ADSC) sheets in ACL reconstruction (ACLR).

HYPOTHESIS

ADSC sheet transplantation can improve biomechanical strength of the autograft used in ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 68 healthy Japanese white rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into a control group (no sheet; n = 34) and a sheet group (ADSC sheet; n = 34). At 2, 4, 8, 16, and 24 weeks after surgery, rabbits in each group were sacrificed to evaluate tendon-bone healing using histological staining, micro-computed tomography, and biomechanical testing. At 24 weeks, scanning transmission electron microscopy of the graft midsubstance was performed.

RESULTS

The ultimate failure load for the control and sheet groups, respectively, was as follows: 17.2 ± 5.5 versus 37.3 ± 10.3 (P = .01) at 2 weeks, 28.6 ± 1.9 versus 47.4 ± 10.4 (P = .003) at 4 weeks, 53.0 ± 14.3 versus 48.1 ± 9.3 (P = .59) at 8 weeks, 66.2 ± 9.3 versus 95.2 ± 43.1 (P = .24) at 16 weeks, and 66.7 ± 27.3 versus 85.3 ± 29.5 (P = .39) at 24 weeks. The histological score was also significantly higher in the sheet group compared with the control group at early stages up to 8 weeks. On micro-computed tomography, relative to the control group, the bone tunnel area was significantly narrower in the sheet group at 4 weeks, and the bone volume/tissue volume of the tendon-bone interface was significantly greater at 24 weeks. Scanning transmission electron microscopy at 24 weeks indicated that the mean collagen fiber diameter in the midsubstance was significantly greater, as was the occupation ratio of collagen fibers per field of view, in the sheet group.

CONCLUSION

ADSC sheets improved biomechanical strength, prevented bone tunnel enlargement, and promoted tendon-bone interface healing and graft midsubstance healing in an in vivo rabbit model.

CLINICAL RELEVANCE

ADSC sheets may be useful for early tendon-bone healing and graft maturation in ACLR.

Efficacy of Surgical Tenodesis for Treatment of Distal Semitendinosus Hamstring Tendon Injuries

Background:

Understanding the optimal management of distal semitendinosus hamstring injuries is critical for reducing pain, restoring preinjury function, maintaining knee stability, improving hamstring muscle strength, and minimizing the risk of complications and recurrence. To our knowledge, the outcomes of surgical tenodesis for distal semitendinosus hamstring injuries have not been previously reported.

Hypothesis:

Surgical tenodesis for injuries of the semitendinosus would enable return to preinjury level of sport with low risk of recurrence.

Study Design:

Case series; Level of evidence, 4.

Methods:

This prospective single-surgeon study included 13 professional athletes (12 men, 1 woman; mean age, 32 ± 8.2 years; mean body mass index, 26.7 ± 3.9 kg/m²) undergoing treatment for distal semitendinosus hamstring injuries with primary tenodesis to the distal semimembranosus. Indications for surgical tenodesis included distal semitendinosus tendon avulsion injury (n = 8) or residual tendon instability and hamstring weakness after semitendinosus graft harvest for anterior cruciate ligament reconstruction (n = 5). All study patients underwent a standardized postoperative rehabilitation program. The primary outcome was defined as time for return to sporting activity. Secondary outcomes were patient satisfaction, injury recurrence, and complications. The mean follow-up time was 17 months (range, 12-24 months) from date of surgery.

Results:

All study patients returned to their preinjury level of sporting activity. The mean time from the surgical intervention to return to full sporting activity was 15 ± 4.6 weeks. At 1-year follow-up, all study patients were still participating at their preinjury level of sporting activity, and 12 patients (92%) were very satisfied and 1 patient (8%) was satisfied about the outcomes of their surgery. No study patients had recurrence of the primary injury. No surgical complications, injury recurrence, or reoperations were observed within the follow-up period.

Conclusion:

Early return to sporting activity was seen after surgical tenodesis for distal semitendinosus hamstring injuries after acute trauma or residual symptoms following previous hamstring graft harvest, with high levels of patient satisfaction and low risk of recurrence at short-term follow-up.

Citrate-based mussel-inspired magnesium whitlockite composite adhesives augmented bone-to-tendon healing

Citrate-based mussel-inspired whitlockite composite adhesives (CMWAs) were developed and administered to the bone-tendon interface in anterior cruciate ligament (ACL) reconstruction. CMWAs could improve the initial bone-tendon bonding strength, promote the bony inward growth from the bone tunnel and enhance the chondrogenesis and osteogenesis of the bone-tendon interface, thus augmenting bone-to-tendon healing.

The efficacy of platelet rich plasma on anterior cruciate ligament reconstruction: a systematic review and meta-analysis

Anterior cruciate ligament (ACL) rupture is a common musculoskeletal injury, most frequently affecting young and physically active patients. Platelet-rich plasma (PRP) has been widely used in ACL reconstruction to augment the graft healing. However, high-level studies addressing its clinical efficacy could not reach a consensus. In this study, we assess the efficacy of PRP on pain relief, functional improvement along with radiological changes in patients who underwent ACL reconstruction. We performed comprehensive literature search and included 17 RCTs containing 970 participants who underwent ACL reconstruction. The combined data showed significant difference between PRP and control with regard to VAS score (MD: -1.12, 95% CI -1.92, -0.31; P = .007), subjective IKDC score (MD: 6.08, 95% CI 4.39, 7.77; P < .00001) and Lysholm score (MD: 8.49, 95% CI 1.63, 15.36; P = .02) by postoperative 6 months, but only pain reduction was deemed clinically important. At the end of one year's follow-up, no clinically meaningful improvement in VAS (MD: -0.47, P = .04), subjective IKDC score (MD: 3.99, P = .03), Lysholm score (MD: 2.30, P = .32), objective IKDC score (RR: 1.03, P = .09) and knee joint laxity (MD: 0.17, P = .28) was seen. In terms of radiological findings, about one-third of the studies favored PRP to facilitate the graft healing, improve the harvest site morbidity and prevent tunnel widening. In summary, moderate quality of evidence suggested that PRP could provide short-term but not long-term clinically important pain reduction.

Treatment of Partial Posterior Cruciate Ligament Injuries with Platelet-Rich Plasma in Growth Factors (PRGF) Intraligamentous Infiltration and a Specific Knee Brace

Posterior cruciate ligament (PCL) injuries are not as common as other knee ligament injuries, but may present a challenging scenario for even skilled knee surgeons. Complete PCL tears are typically encountered in the setting of multiligament knee injuries and require surgical treatment. Isolated complete PCL injuries are uncommon and the best treatment is debated, and likely depends on the degree of symptoms and objective instability. However, many PCL injuries will be partial tears (grade I or II). The purpose of this chapter is to describe our treatment of choice for partial PCL injuries through a conservative approach.

Level of evidence  Level IV.

Mesenchymal stromal cells and platelet-rich plasma promote tendon allograft healing in ovine anterior cruciate ligament reconstruction

PURPOSE

The effect of bone marrow mesenchymal stromal cells (BMSCs) and platelet-rich plasma (PRP) on tendon allograft maturation in a large animal anterior cruciate ligament (ACL) reconstruction model was reported for the first time. It was hypothesised that compared with non-augmented ACL reconstruction, BMSCs and PRP would enhance graft maturation after 12 weeks and this would be detected using magnetic resonance imaging (MRI).

METHODS

Fifteen sheep underwent unilateral tendon allograft ACL reconstruction using aperture fixation and were randomised into three groups (n = 5). Group 1 received 10 million allogeneic BMSCs in 2 ml fibrin sealant; Group 2 received 12 ml PRP in a plasma clot injected into the graft and bone tunnels; and Group 3 (control) received no adjunctive treatment. At autopsy at 12 weeks, a graft maturation score was determined by the sum for graft integrity, synovial coverage and vascularisation, graft thickness and apparent tension, and synovial sealing at tunnel apertures. MRI analysis (n = 2 animals per group) of the signal-noise quotient (SNQ) and fibrous interzone (FIZ) was used to evaluate intra-articular graft maturation and tendon-bone healing, respectively. Spearman's rank correlation coefficient (r) of SNQ, autopsy graft maturation score and bone tunnel diameter were analysed.

RESULTS

The BMSC group (p = 0.01) and PRP group (p = 0.03) had a significantly higher graft maturation score compared with the control group. The BMSC group scored significantly higher for synovial sealing at tunnel apertures (p = 0.03) compared with the control group. The graft maturation score at autopsy significantly correlated with the SNQ (r = - 0.83, p < 0.01). The tunnel diameter of the femoral tunnel at the aperture (r = 0.883, p = 0.03) and mid-portion (r = 0.941, p = 0.02) positively correlated with the SNQ.

CONCLUSIONS

BMSCs and PRP significantly enhanced graft maturation, which indicates that orthobiologics can accelerate the biologic events in tendon allograft incorporation. Femoral tunnel expansion significantly correlated with inferior maturation of the intra-articular graft. The clinical relevance of this study is that BMSCs and PRP enhance allograft healing in a translational model, and biological modulation of graft healing can be evaluated non-invasively using MRI.

Revascularization to the bone tunnel wall after anterior cruciate ligament reconstruction may relate to the distance from the vessels

Purpose

We use magnetic resonance angiography to evaluate the difference of vascular ingrowth to the bone tunnel on the anterior and posterior walls quantitatively after anterior cruciate ligament reconstruction.

Materials and methods

One hundred patients underwent anterior cruciate ligament reconstruction with multi-stranded semitendinosus tendons. They were retrospectively divided into those who underwent magnetic resonance angiography 2, 3, 4 to 6, and ≥ 7 months after surgery. The mean signal-to-noise ratios of the bone tunnel walls in the femur and tibia from the digital data were measured and compared for the anterior and posterior walls.

Results

The signal-to-noise ratio of the posterior wall of the femoral bone tunnel was significantly higher than that of the anterior wall in each group. On the tibial side, the signal-to-noise ratio of the anterior wall was significantly higher than that of the posterior wall at ≥4 months after surgery.

Conclusions

This study showed that the blood flow after anterior cruciate ligament reconstruction to the femoral bone tunnel is maintained from the posterior wall, and is maintained to the tibial side from the anterior wall 4 months postoperatively. Revascularization to the bone tunnel wall after anterior cruciate ligament reconstruction may relate to the distance from the vessels.

Extracorporeal shock wave promotes activation of anterior cruciate ligament remnant cells and their paracrine regulation of bone marrow stromal cells' proliferation, migration, collagen synthesis, and differentiation

Aims

Proliferation, migration, and differentiation of anterior cruciate ligament (ACL) remnant and surrounding cells are fundamental processes for ACL reconstruction; however, the interaction between ACL remnant and surrounding cells is unclear. We hypothesized that ACL remnant cells preserve the capability to regulate the surrounding cells' activity, collagen gene expression, and tenogenic differentiation. Moreover, extracorporeal shock wave (ESW) would not only promote activity of ACL remnant cells, but also enhance their paracrine regulation of surrounding cells.

Methods

Cell viability, proliferation, migration, and expression levels of Collagen-I (COL-I) A1, transforming growth factor beta (TGF-β), and vascular endothelial growth factor (VEGF) were compared between ACL remnant cells untreated and treated with ESW (0.15 mJ/mm², 1,000 impulses, 4 Hz). To evaluate the subsequent effects on the surrounding cells, bone marrow stromal cells (BMSCs)' viability, proliferation, migration, and levels of Type I Collagen, Type III Collagen, and tenogenic gene (Scx, TNC) expression were investigated using coculture system.

Results

ESW-treated ACL remnant cells presented higher cell viability, proliferation, migration, and increased expression of COL-I A1, TGF-β, and VEGF. BMSC proliferation and migration rate significantly increased after coculture with ACL remnant cells with and without ESW stimulation compared to the BMSCs alone group. Furthermore, ESW significantly enhanced ACL remnant cells' capability to upregulate the collagen gene expression and tenogenic differentiation of BMSCs, without affecting cell viability, TGF-β, and VEGF expression.

Conclusion

ACL remnant cells modulated activity and differentiation of surrounding cells. The results indicated that ESW enhanced ACL remnant cells viability, proliferation, migration, and expression of collagen, TGF-β, VEGF, and paracrine regulation of BMSC proliferation, migration, collagen expression, and tenogenesis.Cite this article: Bone Joint Res 2020;9(8):458-468.

Characterisation of the tensile properties of Demineralised Cortical Bone when used as an anterior cruciate ligament allograft

BACKGROUND

Graft choice in anterior cruciate ligament (ACL) reconstruction remains controversial and some grafts fail due to inadequate osteointegration. Demineralised cortical bone (DCB) is an osteoinductive collagen-based scaffold. The aim of this study was to measure the tensile properties of DCB from different locations and from different ages, and determine its compatibility with current ACL fixation systems.

METHODS

The tensile properties of DCB manufactured from femur and tibia of young (9 month) and old (2-3 years) sheep was measured to determine the most appropriate graft choice. The ultimate load and stiffness of DCB allograft using two fixation systems, interference screws and sutures tied around screw posts, was measured ex vivo in an ovine ACL reconstruction model. Comparison was made with superficial digital flexor tendon (SDFT) and ovine ACL.

RESULTS

DCB derived from young tibia had the highest ultimate load and stiffness of 67.7 ± 10.6 N and 130.2 ± 64.3 N/mm respectively. No DCB fixation system reached the published peak in vivo force through the ovine ACL of 150 N. SDFT fixation with interference screws (308.2 ± 87.3 N) did reach the in vivo threshold but was significantly weaker than ovine ACL (871.0 ± 64.2 N).

CONCLUSION

The tensile properties of DCB were influenced by the donor age and bone. Owing to inferior tensile properties and incompatibility with suspensory fixation devices, this study indicates DCB is inferior to current tendon grafts options for ACL reconstruction.

The development of a novel autologous blood glue aiming to improve osseointegration in the bone-implant interface

Aims

For cementless implants, stability is initially attained by an interference fit into the bone and osteo-integration may be encouraged by coating the implant with bioactive substances. Blood based autologous glue provides an easy, cost-effective way of obtaining high concentrations of growth factors for tissue healing and regeneration with the intention of spraying it onto the implant surface during surgery. The aim of this study was to incorporate nucleated cells from autologous bone marrow (BM) aspirate into gels made from the patient’s own blood, and to investigate the effects of incorporating three different concentrations of platelet rich plasma (PRP) on the proliferation and viability of the cells in the gel.

Methods

The autologous blood glue (ABG) that constituted 1.25, 2.5, and 5 times concentration PRP were made with and without equal volumes of BM nucleated cells. Proliferation, morphology, and viability of the cells in the glue was measured at days 7 and 14 and compared to cells seeded in fibrin glue.

Results

Overall, 2.5 times concentration of PRP in ABG was capable of supporting the maximum growth of cells isolated from the BM aspirate and maintain their characteristics. Irrespective of PRP concentration, cells in ABG had statistically significantly higher viability compared to cells in fibrin glue.

Conclusion

In vitro this novel autologous gel is more capable of supporting the growth of cells in its structure for up to 14 days, compared to commercially available fibrin-based sealants, and this difference was statistically significant.

Cite this article: Bone Joint Res 2020;9(7):402–411.

Decellularized porcine xenograft for anterior cruciate ligament reconstruction: A histological study in sheep comparing cross-pin and cortical suspensory femoral fixation

Aims

To evaluate graft healing of decellularized porcine superflexor tendon (pSFT) xenograft in an ovine anterior cruciate ligament (ACL) reconstruction model using two femoral fixation devices. Also, to determine if pSFT allows functional recovery of gait as compared with the preoperative measurements.

Methods

A total of 12 sheep underwent unilateral single-bundle ACL reconstruction using pSFT. Two femoral fixation devices were investigated: Group 1 (n = 6) used cortical suspensory fixation (Endobutton CL) and Group 2 (n = 6) used cross-pin fixation (Stratis ST). A soft screw was used for tibial fixation. Functional recovery was quantified using force plate analysis at weeks 5, 8, and 11. The sheep were euthanized after 12 weeks and comprehensive histological analysis characterized graft healing at the graft-bone interface and the intra-articular graft (ligamentization).

Results

The pSFT remodelled into a ligament-like structure and no adverse inflammatory reaction was seen. The ground reaction force in the operated leg of the Endobutton group was higher at 11 weeks (p < 0.05). An indirect insertion was seen at the graft-bone interface characterized by Sharpey-like fibres. Qualitative differences in tendon remodelling were seen between the two groups, with greater crimp-like organization and more aligned collagen fibres seen with Endobutton fixation. One graft rupture occurred in the cross-pin group, which histologically showed low collagen organization.

Conclusion

Decellularized pSFT xenograft remodels into a ligament-like structure after 12 weeks and regenerates an indirect-type insertion with Sharpey-like fibres. No adverse inflammatory reaction was observed. Cortical suspensory femoral fixation was associated with more enhanced graft remodelling and earlier functional recovery when compared with the stiffer cross-pin fixation.

Effects of autologous adipose-derived regenerative stem cells administered at the time of anterior cruciate ligament reconstruction on knee function and graft healing

PURPOSE

To compare the healing and clinical outcomes of anterior cruciate ligament (ACL) reconstruction between patients with or without intraoperative administration of adipose-derived regenerative stem cells (ADRC).

METHODS

Between 2013 and 2014, the outcomes of 20 soccer players undergoing ACL reconstruction using bone-patellar tendon-bone autograft infiltrated with ADRC at the end of the procedure were compared to a historical, matched cohort of 19 soccer players undergoing the same procedure without ADRC. Outcomes were obtained at baseline, and 6 and 12 months postop for IKDC (International Knee Documentation Committee), Lysholm, and Lequesne, and at 2, 4, 6, and 12 months postop for VAS (visual analogue scale) for pain and graft maturation to evaluate the ligamentization process (magnetic resonance imaging (MRI)-based).

RESULTS

Both groups significantly improved the IKDC (p < 0.001 in both groups), Lysholm (p < 0.001 in both groups), Lequesne index (p < 0.001 in both groups), VAS for pain (p = 0.002 for the ADRC and p < 0.001 for the control group), and MRI scores (p < 0.001 in both groups) in the 12 months postop compared to baseline scores. However, there were no significant differences in the improvement of the outcomes between groups across time (p > 0.05). All patients returned to sports after surgery, but 8 (40%) patients in the ADRC and 13 (68.4%) patients in the control group had lower Tegner activity score at 12 months postop.

CONCLUSIONS

Patients receiving ADRC at the time of ACL reconstruction significantly improved knee function and healing/maturation of the graft at 12 months. However, this improvement was not statistically significant compared to a control group undergoing ACL reconstruction alone.

Bioaugmentation in the surgical treatment of anterior cruciate ligament injuries: A review of current concepts and emerging techniques

Injuries involving the anterior cruciate ligament are among the most common athletic injuries, and are the most common involving the knee. The anterior cruciate ligament is a key translational and rotational stabilizer of the knee joint during pivoting and cutting activities. Traditionally, surgical intervention in the form of anterior cruciate ligament reconstruction has been recommended for those who sustain an anterior cruciate ligament rupture and wish to remain active and return to sport. The intra-articular environment of the anterior cruciate ligament makes achieving successful healing following repair challenging. Historically, results following repair were poor, and anterior cruciate ligament reconstruction emerged as the gold-standard for treatment. While earlier literature reported high rates of return to play, the results of more recent studies with longer follow-up have suggested that anterior cruciate ligament reconstruction may not be as successful as once thought: fewer athletes are able to return to sport at their preinjury level, and many still go on to develop osteoarthritis of the knee at a relatively younger age. The four principles of tissue engineering (cells, growth factors, scaffolds, and mechanical stimuli) combined in various methods of bioaugmentation have been increasingly explored in an effort to improve outcomes following surgical treatment of anterior cruciate ligament injuries. Newer technologies have also led to the re-emergence of anterior cruciate ligament repair as an option for select patients. The different biological challenges associated with anterior cruciate ligament repair and reconstruction each present unique opportunities for targeted bioaugmentation strategies that may eventually lead to better outcomes with better return-to-play rates and fewer revisions.

The role of anterolateral augmentation in primary ACL reconstruction

The anterolateral soft tissue envelope of the knee has long been recognised as a key stabilising structure. Once the mainstay of operative management of anterior cruciate ligament (ACL) rupture, interest in the area fell away with the advent of intraarticular arthroscopic reconstruction. Renewed interest in these structures together with cadaveric data evidencing the potential for restoration of near normal knee biomechanics following ACL and anterolateral soft tissue reconstruction has driven current concepts and development of operative techniques. Options for current anterolateral augmentation techniques in primary ACL reconstruction plus patient selection considerations are reviewed, together with an outlook at future research key to development of this area.

Anterior Cruciate Ligament Reconstruction with Platelet-Rich Plasma: A Systematic Review of Randomized Control Trials

PURPOSE

To perform a systematic review of the randomized controlled trials (RCTs) evaluating the efficacy of platelet-rich plasma (PRP) to augment anterior cruciate ligament (ACL) reconstruction.

METHODS

Two independent reviewers screened the MEDLINE, The Cochrane Library, and EMBASE databases using Preferred Reporting for Systematic Reviews and Meta-Analyses guidelines for applicable RCTs evaluating the efficacy of PRP in ACL reconstruction. A meta-analysis was performed on the papers involving bone-patellar tendon-bone (BPTB) grafting.

RESULTS

Thirteen RCTs fulfilled the inclusion criteria involving 765 patients. There was no clinical improvement (Tegner, Lysholm, Knee Injury and Osteoarthritis Outcome Score, or International Knee Documentation Committee scores) in any of the 7 studies evaluating PRP alongside the hamstring tendon autograft ACL reconstructions versus the control. Two studies evaluating PRP for hamstring tendon autograft demonstrated significantly improved magnetic resonance imaging findings. Two studies analyzed the use of PRP with allograft ACL reconstruction showed no clinical, biochemical, or radiologic improvements in postoperative follow-up. No functional improvements were found when PRP was used alongside BPTB in 4 studies. There was no significant difference in visual analog scale score in the BPTB group (1.1 vs 1.5, P = .18), or tibial filling defects (P = .30).

CONCLUSIONS

This study found that the current level I evidence does not support the use of PRP to improve graft healing, improve donor-site morbidity, reduce postoperative pain levels, or improve functional outcomes following ACL reconstruction.

LEVEL OF EVIDENCE

Level I; systematic review of level I evidence.

Satisfactory functional and MRI outcomes at the foot and ankle following harvesting of full thickness peroneus longus tendon graft

AIMS

To evaluate the donor site morbidity and tendon morphology after harvesting whole length, full-thickness peroneus longus tendon (PLT) proximal to the lateral malleolus for ligament reconstructions or tendon transfer.

METHODS

A total of 21 eligible patients (mean age 34.0 years (standard deviation (SD) 11.2); mean follow-up period 31.8 months (SD 7.7), and 12 healthy controls (mean age, 26.8 years (SD 5.9) were included. For patients, clinical evaluation of the donor ankle was performed preoperatively and postoperatively. Square hop test, ankle strength assessment, and MRI of distal calf were assessed bilaterally in the final follow-up. The morphological symmetry of peroneal tendons bilaterally was evaluated by MRI in healthy controls.

RESULTS

Among the patients, the mean pre- and postoperative American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score and Karlsson-Peterson score were 98.7 (SD 2.5; p = 0.480) and 98.5 (SD 2.4; p = 0.480), and 98.3 (SD 2.4; p = 0.162) and 97.9 (SD 2.5; p = 0.162), respectively. There was no significant difference between square hop test bilaterally (p = 0.109) and plantar flexion peak force bilaterally (p = 0.371). The harvested limb had significantly less eversion peak force compared to the contralateral limb (p < 0.001). Evidence of probable tendon regeneration was observed in all the patients by MRI and the total bilateral peroneal tendon index (mean ratio of harvested side cross-sectional area of peroneal tendon compared with the contralateral side) was 82.9% (SD 17.4). In 12 healthy controls, peroneal tendons (mean 99.4% (SD 4.3) were found to be morphologically symmetrical between the two sides.

CONCLUSION

The current study showed satisfactory clinical foot and ankle outcomes after full-thickness PLT harvesting and indicated the regenerative potential of PLT after its removal. Level of Evidence: Level IV, therapeutic retrospective case series. Cite this article: Bone Joint J 2020;102-B(2):205-211.

Paediatric and adolescent anterior cruciate ligament reconstruction surgery

Aims

Anterior cruciate ligament (ACL) surgery in children and the adolescent population has increased steadily over recent years. We used a national database to look at trends in ACL reconstruction and rates of serious complications, growth disturbance, and revision surgery, over 20 years.

Methods

All hospital episodes for patients undergoing ACL reconstruction, under the age of 20 years, between 1 April 1997 and 31 March 2017, were extracted by procedure code from the national Hospital Episode Statistics (HES). Population standardized rates of intervention were determined by age group and year of treatment. Subsequent rates of serious complications including reoperation for infection, growth disturbance (osteotomy, epiphysiodesis), revision reconstruction, and/or contralateral ACL reconstruction rates were determined.

Results

Over the 20 year period, 16,125 ACL reconstructions were included. The mean age of patients was 16.9 years (SD 2.0; 27.1% female, n = 4,374/16,125). The majority of procedures were observed in the 15 to 19 years age group. The rate of ACL reconstruction increased 29-fold from 1997 to 1998, to 2016 to 2017. Within 90 days of ACL reconstruction, the rate of reoperation for infection was 0.31% (95% confidence interval (CI) 0.23 to 0.41, n = 50/16,125) and the rate of pulmonary embolism was 0.037% (95%.CI 0.014 to 0.081, n = 6/16,125). Of those with minimum five-year follow-up following ACL reconstruction (n = 7,585), 1.00% of patients subsequently underwent an osteotomy (95% CI 0.79 to 1.25, n = 76/7,585), 0.09% an epiphysiodesis (95% CI 0.04 to 0.19, n = 7/7,585), 7.46% revision ACL reconstruction (95% CI 6.88 to 8.08, n = 566/7,585), and 6.37% contralateral ACL reconstruction (95% CI 5.83 to 6.94, n = 483/7,585).

Conclusion

Rates of paediatric and adolescent ACL reconstruction have increased 29-fold over the last 20 years. Despite the increasing rate in the younger population, the risk of serious complications, including further surgery for growth disturbance is very low. The results of our study provide a point of reference for shared decision making in the management of ACL injury in the paediatric and adolescent population. Cite this article: Bone Joint J 2020;102-B(2):239–245.

Amplifying Bone Marrow Progenitors Expressing α-Smooth Muscle Actin Produce Zonal Insertion Sites During Tendon-to-Bone Repair

Traditional tendon-to-bone repair where the tendon is reattached to bone via suture anchors often results in disorganized scar production rather than the formation of a zonal insertion. In contrast, ligament reconstructions where tendon grafts are passed through bone tunnels can yield zonal tendon-to-bone attachments between the graft and adjacent bone. Therefore, ligament reconstructions can be used to study mechanisms that regulate zonal tendon-to-bone repair in the adult. Anterior cruciate ligament (ACL) reconstructions are one of the most common reconstruction procedures and while we know that cells from outside the graft produce the attachments, we have not yet established specific cell populations that give rise to this tissue. To address this knowledge gap, we performed ACL reconstructions in lineage tracing mice where α-smooth muscle actin (αSMACreERT2) was used to label αSMA-expressing progenitors within the bone marrow that produced zonal attachments. Expression of αSMA was increased during early stages of the repair process such that the contribution of SMA-labeled cells to the tunnel integration was highest when tamoxifen was delivered in the first week post-surgery. The zonal attachments shared features with normal entheses, including tidemarks oriented perpendicularly to collagen fibers, Col1a1-expressing cells, alkaline phosphatase activity, and proteoglycan-rich staining. Finally, the integration strength increased with time, requiring 112% greater force to remove the graft from the tunnel at 28 days compared with 14 days post-surgery. Future studies will target these progenitor cells to define the pathways that regulate zonal tendon-to-bone repair in the adult. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:105-116, 2020.

Posterior cruciate ligament reconstruction implemented by the Ligament Advanced Reinforcement System over a minimum follow-up of 10 years

PURPOSE

This study evaluated the long-term clinical follow-up results of patients who underwent double-bundle posterior cruciate ligament (PCL) reconstruction using the Ligament Advanced Reinforcement System (LARS).

METHODS

Patients were assessed using clinical scores that included the Tegner activity level scale, the Lysholm score, and the International Knee Documentation Committee (IKDC) score. KT-1000 was adopted to assess stability. Radiographs and magnetic resonance imaging (MRI) were used to evaluate osteoarthritis and LARS condition.

RESULTS

This study examined 38 patients, of which follow-up procedures were completed for 33 patients, resulting in a follow-up rate of 86.8%. The average follow-up period was 11.9 ± 1.2 years (range: 10.3-14.2 years). The median scores of the clinical scales were as follows: Tegner activity score, 6 (range: five to seven); Lysholm score, 90 (range: 67-100); and IKDC score, 89.7 (range: 46-100). The median of the side-to-side difference (SSD) was four millimeters (range: 0-10 mm). In radiographs, the moderate OA rate was 6.9%. MRI results revealed that 26 patients exhibited ingrowth and 11 patients exhibited partial rupture of the LARS. With SSD ≤ 3 mm set as the standard for successful knee stabilization, the optimal cutoff point of LARS midsubstance thickness in the receiver operating characteristic (ROC) curve analysis was 14.3 mm.

CONCLUSIONS

Long-term follow-up of the studied patients demonstrated the durability of LARS. However, clinical outcomes showed no enhancement using LARS, so it is not recommended for routine use in PCL reconstruction.

LEVEL OF EVIDENCE

IV.

Stratifying the mechanical performance of a decellularized xenogeneic tendon graft for anterior cruciate ligament reconstruction as a function of graft diameter: An animal study

Objectives

This study investigated the biomechanical performance of decellularized porcine superflexor tendon (pSFT) grafts of varying diameters when utilized in conjunction with contemporary ACL graft fixation systems. This aimed to produce a range of ‘off-the-shelf’ products with predictable mechanical performance, depending on the individual requirements of the patient.

Methods

Decellularized pSFTs were prepared to create double-bundle grafts of 7 mm, 8 mm, and 9 mm diameter. Femoral and tibial fixation systems were simulated utilizing Arthrex suspension devices and interference screws in bovine bone, respectively. Dynamic stiffness and creep were measured, followed by ramp to failure from which linear stiffness and load at failure were measured. The mechanisms of failure were also recorded.

Results

Dynamic stiffness was found to increase with greater graft diameter, with significant differences between all groups. Conversely, dynamic creep reduced with increasing graft diameter with significant differences between the 7 mm and 9 mm groups and the 8 mm and 9 mm groups. Significant differences were also found between the 7 mm, 8 mm, and 9 mm groups for linear stiffness, but no significant differences were found between groups for load at failure. The distribution of failure mechanisms was found to change with graft diameter.

Conclusion

This study showed that decellularized pSFTs demonstrate comparable biomechanical properties to other ACL graft options and are a potentially viable option for ACL reconstruction. Although grafts can be stratified by their diameter to provide varying biomechanical properties, it may be more appropriate to alter the fixation technique to stratify for a greater diversity of biomechanical requirements.

Cite this article: Bone Joint Res 2019;8:518–525.

BIOLOGICAL ENHANCEMENTS FOR ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

The anterior cruciate ligament (ACL) is mostly responsible for providing knee stability. ACL injury has a marked effect on daily activities, causing pain, dysfunction, and elevated healthcare costs. ACL reconstruction (ACLR) is the standard treatment for this injury. However, despite good results, ACLR is associated with a significant rate of failure. In this context, the mechanical and biological causes must be considered. From a biological perspective, the ACLR depends on the osseointegration of the graft in the adjacent bone and the process of intra-articular ligamentization for good results. Here, we discuss the mechanisms underlying the normal graft healing process after ACLR and its biological modulation, thus, presenting novel strategies for biological enhancements of the ACL graft. Level of evidence III, Systematic review of level III studies.

In vivo assessment of high-molecular-weight polyethylene core suture tape for intra-articular ligament reconstruction: an animal study

AIMS

Options for the treatment of intra-articular ligament injuries are limited, and insufficient ligament reconstruction can cause painful joint instability, loss of function, and progressive development of degenerative arthritis. This study aimed to assess the capability of a biologically enhanced matrix material for ligament reconstruction to withstand tensile forces within the joint and enhance ligament regeneration needed to regain joint function.

MATERIALS AND METHODS

A total of 18 New Zealand rabbits underwent bilateral anterior cruciate ligament reconstruction by autograft, FiberTape, or FiberTape-augmented autograft. Primary outcomes were biomechanical assessment (n = 17), microCT (µCT) assessment (n = 12), histological evaluation (n = 12), and quantitative polymerase chain reaction (qPCR) analysis (n = 6).

RESULTS

At eight weeks, FiberTape alone or FiberTape-augmented autograft demonstrated increased biomechanical stability compared with autograft regarding ultimate load to failure (p = 0.035), elongation (p = 0.006), and energy absorption (p = 0.022). FiberTape-grafted samples also demonstrated increased bone mineral density in the bone tunnel (p = 0.039). Histological evaluation showed integration of all grafts in the bone tunnels by new bone formation, and limited signs of inflammation overall. A lack of prolonged inflammation in all samples was confirmed by quantification of inflammation biomarkers. However, no regeneration of ligament-like tissue was observed along the suture tape materials. Except for one autograft failure, no adverse events were detected.

CONCLUSION

Our results indicate that FiberTape increases the biomechanical performance of intra-articular ligament reconstructions in a verified rabbit model at eight weeks. Within this period, FiberTape did not adversely affect bone tunnel healing or invoke a prolonged elevation in inflammation. Cite this article: Bone Joint J 2019;101-B:1238-1247.

Tendon-to-Bone Healing in a Rat Extra-articular Bone Tunnel Model: A Comparison of Fresh Autologous Bone Marrow and Bone Marrow-Derived Mesenchymal Stem Cells

BACKGROUND

Despite widespread acceptance of fresh autologous bone marrow (BM) for use in clinical practice, limited information exists to analyze if tendon-to-bone healing could be accelerated with local use of fresh autologous BM.

PURPOSE

To investigate the effect of fresh autologous BM on tendon-to-bone healing with a novel rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

An extra-articular bone tunnel was created and filled with an autologous tendon graft in skeletally mature Sprague-Dawley rats (N = 60). They were then randomly divided into 3 groups: BM group (injection of fresh autologous BM into the tendon-bone interface, n = 20), BM-derived mesenchymal stem cell (BMSC) group (injection of allogenic cultured BMSCs, n = 20), and the control group (tendon-bone interface without injection of BM or BMSCs, n = 20). Biomechanical, histological, and immunohistochemical analyses were performed at 2 and 6 weeks after surgery.

RESULTS

The BM group showed a relatively well-organized and dense connective tissue interface with better orientation of collagen fibers as compared with the BMSC group. At 2 weeks, the tendon-bone interface tissue thickness of the BMSC group was 140 ± 25 μm (mean ± SEM), which was significantly greater than the BM group (58 ± 15 μm). The BM group showed fewer M1 macrophages at the tendon-bone interface at 2 and 6 weeks (P < .001). In contrast, there were more M2 macrophages at the interface in the BM group 2 and 6 weeks postoperatively when compared with controls and the BMSC group (P < .001). Biomechanical tests revealed significantly higher stiffness in the BM group versus the control and BMSC groups at 2 and 6 weeks after surgery (P < .05). Load to failure showed similar trends to stiffness.

CONCLUSION

These findings indicate that local delivery of fresh autologous BM enhances tendon-to-bone healing better than the alternative treatments in this study. This effect may be partially due to the observed modulation of inflammatory processes, especially in M2 macrophage polarization.

CLINICAL RELEVANCE

Fresh autologous BM could be a treatment option for this disorder.