Electron beam sterilization does not have a detrimental effect on the ability of extracellular matrix scaffolds to support in vivo ligament healing

Early MRI-based quantitative outcomes are associated with a positive functional performance trajectory from 6 to 24 months post-ACL surgery

PURPOSE

Quantitative magnetic resonance imaging (qMRI) has been used to determine the failure properties of ACL grafts and native ACL repairs and/or restorations. How these properties relate to future clinical, functional, and patient-reported outcomes remain unknown. The study objective was to investigate the relationship between non-contemporaneous qMRI measures and traditional outcome measures following Bridge-Enhanced ACL Restoration (BEAR). It was hypothesized that qMRI parameters at 6 months would be associated with clinical, functional, and/or patient-reported outcomes at 6 months, 24 months, and changes from 6 to 24 months post-surgery.

METHODS

Data of BEAR patients (n = 65) from a randomized control trial of BEAR versus ACL reconstruction (BEAR II Trial; NCT02664545) were utilized retrospectively for the present analysis. Images were acquired using the Constructive Interference in Steady State (CISS) sequence at 6 months post-surgery. Single-leg hop test ratios, arthrometric knee laxity values, and International Knee Documentation Committee (IKDC) subjective scores were determined at 6 and 24 months post-surgery. The associations between traditional outcomes and MRI measures of normalized signal intensity, mean cross-sectional area (CSA), volume, and estimated failure load of the healing ACL were evaluated based on bivariate correlations and multivariable regression analyses, which considered the potential effects of age, sex, and body mass index.

RESULTS

CSA (r = 0.44, p = 0.01), volume (r = 0.44, p = 0.01), and estimated failure load (r = 0.48, p = 0.01) at 6 months were predictive of the change in single-leg hop ratio from 6 to 24 months in bivariate analysis. CSA (βstandardized = 0.42, p = 0.01), volume (βstandardized = 0.42, p = 0.01), and estimated failure load (βstandardized = 0.48, p = 0.01) remained significant predictors when considering the demographic variables. No significant associations were observed between MRI variables and either knee laxity or IKDC when adjusting for demographic variables. Signal intensity was also not significant at any timepoint.

CONCLUSION

The qMRI-based measures of CSA, volume, and estimated failure load were predictive of a positive functional outcome trajectory from 6 to 24 months post-surgery. These variables measured using qMRI at 6 months post-surgery could serve as prospective markers of the functional outcome trajectory from 6 to 24 months post-surgery, aiding in rehabilitation programming and return-to-sport decisions to improve surgical outcomes and reduce the risk of reinjury.

LEVEL OF EVIDENCE

Level II.

Natural, synthetic and commercially-available biopolymers used to regenerate tendons and ligaments

Tendon and ligament (TL) injuries affect millions of people annually. Biopolymers play a significant role in TL tissue repair, whether the treatment relies on tissue engineering strategies or using artificial tendon grafts. The biopolymer governs the mechanical properties, biocompatibility, degradation, and fabrication method of the TL scaffold. Many natural, synthetic and hybrid biopolymers have been studied in TL regeneration, often combined with therapeutic agents and minerals to engineer novel scaffold systems. However, most of the advanced biopolymers have not advanced to clinical use yet. Here, we aim to review recent biopolymers and discuss their features for TL tissue engineering. After introducing the properties of the native tissue, we discuss different types of natural, synthetic and hybrid biopolymers used in TL tissue engineering. Then, we review biopolymers used in commercial absorbable and non-absorbable TL grafts. Finally, we explain the challenges and future directions for the development of novel biopolymers in TL regenerative treatment.

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Both natural and synthetic biopolymers are reviewed for regeneration of TL and their interface tissues.

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Advances on hybrid-composite biopolymers to fabricate TL scaffolds were reviewed.

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The current biopolymers used in commercial TL grafts are discussed.

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The challenges and emerging strategies for biopolymer development are presented.

Electron-Beam Irradiated Recombinant Human Collagen-Phosphorylcholine Corneal Implants Retain Pro-Regeneration Capacity

Sterilization of biodegradable, collagen-based implants is challenging as irradiation sterilization methods can alter their mechanical properties. Electron beam (EB) irradiation is a terminal sterilization method that has been used for biologically-derived implants. Here, recombinant human collagen type III-phosphorylcholine (RHCIII-MPC) hydrogels were irradiated with EB doses of 17, 19, or 21 kGy and their subsequent biocompatibility and ability to promote regeneration in rabbit corneas was evaluated. Unirradiated hydrogels stored in 1% chloroform in phosphate-buffered saline (C-PBS) were the controls. There were no significant differences between irradiated and non-irradiated samples in optical or physical properties (tensile strength, modulus, elasticity), or the ability to support cell growth. However, irradiated implants were more sensitive to high levels of collagenase than unirradiated controls and the C-PBS implants had increased cell growth compared to EB and controls at 72 h. Corneal implants e-beamed at 17 kGy or e-beamed and subsequently frozen (EB-F) to increase shelf-life showed no adverse biological effects of the irradiation. EB, EB-F, and C-PBS implanted corneas all rapidly re-epithelialized but showed mild neovascularization that resolved over 6 months. The regenerated neo-corneas were transparent at 6 months post-operation. In vivo confocal microscopy confirmed normal morphology for the epithelium, stroma, sub-basal nerves and unoperated endothelium. Histology showed that all the regenerated corneas were morphologically similar to the normal. Immunohistochemistry indicated the presence of a differentiated corneal epithelium and functional tear film. In conclusion, the e-beamed corneal implants performed as well as non-irradiated control implants, resulting in fully regenerated neo-corneas with new nerves and without blood vessels or inflammation that may impede vision or corneal function. Therefore, a complete validation study to establish EB irradiation as an effective means for corneal implant sterilization prior to clinical application is necessary as a next step.

Terminal sterilization influences the efficacy of an extracellular matrix-blood composite for treating posttraumatic osteoarthritis in the rat model

The objective was to determine if an intra-articular injection of an extracellular matrix (ECM) powder and blood composite (ECM-B) after anterior cruciate ligament (ACL) injury would have a mitigating effect on posttraumatic osteoarthritis and if that effect would be different with terminal sterilization of the ECM powder before use. Eighty Lewis rats underwent ACL transection and were divided into four groups: (1) intra-articular injection with phosphate-buffered saline (PBS; n = 20), (2) intra-articular injection of ECM-B using aseptically processed ECM (ASEPTIC; n = 20), (3) intra-articular injection of the ECM-busing ECM powder sterilized with 15 kGy electron beam irradiation (EBEAM; n = 20), and (4) intra-articular injection of the ECM-B using ECM powder sterilized with ethylene oxide (EO; n = 20). Twenty additional animals received capsulotomy only (SHAM). The animals were followed for 6 weeks and evaluations of gait, radiographs, and joint cartilage histology were performed. At 6 weeks, when compared to the SHAM group, the group treated with PBS had significantly worse gait and histologic changes, while the ASEPTIC group was not different from SHAM for either of these outcomes. When compared to the SHAM group, the EO group had similar gait outcomes, but greater histologic damage, and the EBEAM group had significantly worse gait and histological outcomes. The ECM-B composite produced using aseptically processed ECM powder mitigated the gait and histologic changes associated with osteoarthritis after ACL transection in the rat; however, care must be taken when selecting a terminal sterilization method as this may affect the effectiveness of treatment.

Effects of radiation dose and nitrogen purge on collagen scaffold properties

Sterilization of medical devices is commonly performed using radiation methods. However, collagen materials can be damaged when using standard radiation doses (25 kGy). Small increases of radiation dose can allow for increases in the acceptable initial bioburden load of aseptically manufactured devices while maintaining required sterility assurance levels, which is often critical in early stage translational settings. In this study, we hypothesized that small increases in radiation dose from 15 to 20 kGy would result in significant changes to several key characteristics of collagen scaffolds. Scaffolds were manufactured by lyophilizing the pepsin digest of dense bovine connective tissue in cylindrical molds and were irradiated at either 0, 15, 17.5, or 20 kGy with an additional group packaged in nitrogen and irradiated at 17.5 kGy. Groups were evaluated for changes to the soluble collagen and glycosaminoglycan mass fractions, protein banding patterns in electrophoresis, a collagen fragmentation assay, and resistance to enzymatic degradation. All parameters were statistically analyzed using one-way analysis of variance with Tukey's correction for multiple comparisons. The soluble collagen mass fraction was significantly decreased in the 20 kGy group; however, there was no significant effect of radiation dose or a nitrogen-rich environment on the other measured parameters, including protein banding patterns, fragmented collagen content, and resistance to enzymatic degradation.Statement of Clinical Significance: Collagen scaffolds have proven useful in clinical applications but can be damaged by standard radiation doses. Low-dose sterilization may be a viable alternative that minimally impacts key properties of these scaffolds.

Optimizing outcomes of ACL surgery-Is autograft reconstruction the only reasonable option?

Anterior cruciate ligament (ACL) injuries occur at a high frequency in the United States with approximately 400,000 ACL reconstructions being performed each year. While ACL reconstruction is our current gold standard of treatment, it does not restore joint motion, or prevent the premature development of posttraumatic osteoarthritis (PTOA) in many patients. Thus, new treatments for an ACL injury, which are less invasive and minimize patient morbidity, including cartilage damage, are highly desirable. We have used a tissue-engineered approach to stimulate ligament healing, to improve upon current treatment options. In this review, we describe and discuss our work moving a tissue engineering strategy from the concept to bench, preclinical, clinical trials and ultimately FDA 510(k) de Novo approval, providing clinicians and patients with a viable alternative to ACL reconstruction.

Electron beam induced modification of ZIF-8 membrane permeation properties

Modification of the gas permeation properties of ZIF-8 membranes using electron beam irradiation is reported. 3.8 and 3.2 fold enhancements in ideal selectivity for CO2/N2 and CO2/CH4 can be achieved with less than 1 min exposure time.

Meditation Monologue can Reduce Clinical Injection-Related Anxiety: Randomized Controlled Trial

Background.

Strategies to reduce anxiety prior to injection procedures are not well understood. The purpose is to determine the effect of a meditation monologue intervention delivered via phone/mobile application on pre-injection anxiety levels among patients undergoing a clinical injection. The following hypothesis was tested: patients who listened to a meditation monologue via phone/mobile application prior to clinical injection would experience less anxiety compared to those who did not.

Methods.

A prospective, randomized controlled trial was performed at an orthopedics and sports medicine clinic of a tertiary level medical center in the New England region, USA. Thirty patients scheduled for intra- or peri-articular injections were randomly allocated to intervention (meditation monologue) or placebo (nature sounds) group. Main outcome variables were state and trait anxiety inventory (STAI) scores and blood pressure (BP), heart rate, and respiratory rate.

Results.

There were 16 participants who were allocated to intervention (meditation monologue) while 14 participants were assigned to placebo (nature sounds). There was no interaction effect. However, a main time effect was found. Both state anxiety (STAI-S) and trait anxiety (STAI-T) scores were significantly reduced post-intervention compared to pre-intervention (STAI-S: p = 0.04, STAI-T: p = 0.04). Also, a statistically significant main group effect was detected. The pre- and post- STAI-S score reduction was greater in the intervention group (p = 0.028). Also, a significant diastolic BP increase between pre- and post-intervention was recorded in the intervention group (p = 0.028), but not in the placebo group (p = 0.999).

Conclusion.

Listening to a meditation monologue via phone/mobile application prior to clinical injection can reduce anxiety in adult patients receiving intra- and peri-articular injections. Registration:ClinicalTrials.gov NCT02690194

Bridge-Enhanced Anterior Cruciate Ligament Repair Leads to Greater Limb Asymmetry and Less Cartilage Damage Than Untreated ACL Transection or ACL Reconstruction in the Porcine Model

BACKGROUND

The extent of posttraumatic osteoarthritis (PTOA) in the porcine anterior cruciate ligament (ACL) transection model is dependent on the surgical treatment selected. In a previous study, animals treated with bridge-enhanced ACL repair using a tissue-engineered implant developed less PTOA than those treated with ACL reconstruction (ACLR). Alterations in gait, including asymmetric weightbearing and shorter stance times, have been noted in clinical studies of subjects with osteoarthritis.

HYPOTHESIS

Animals receiving a surgical treatment that results in less PTOA (ie, bridge-enhanced ACL repair) would exhibit fewer longitudinal postoperative gait asymmetries over a 1-year period when compared with treatments that result in greater PTOA (ie, ACLR and ACL transection).

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-six Yucatan minipigs underwent ACL transection and were randomized to receive (1) no further treatment, (2) ACLR, or (3) bridge-enhanced ACL repair. Gait analyses were performed preoperatively, and at 4, 12, 26, and 52 weeks postoperatively. Macroscopic cartilage assessments were performed at 52 weeks.

RESULTS

Knees treated with bridge-enhanced ACL repair had less macroscopic damage in the medial tibial plateau than those treated with ACLR or ACL transection (adjusted P = .03 for both comparisons). The knees treated with bridge-enhanced ACL repair had greater asymmetry in hindlimb maximum force and impulse loading at 52 weeks than the knees treated with ACL transection (adjusted P < .05 for both comparisons). Although not significant, there was a trend that knees treated with bridge-enhanced ACL repair had greater asymmetry in hindlimb maximum force and impulse loading (adjusted P < .10 for both comparisons) compared with ACLR.

CONCLUSION

Contrary to our hypothesis, the surgical treatment resulting in less macroscopic cartilage damage (ie, bridge-enhanced ACL repair) exhibited greater asymmetry in load-related gait parameters than the other surgical groups. This finding suggests that increased offloading of the surgical knee may be associated with a slower rate of PTOA development.

CLINICAL RELEVANCE

Less cartilage damage at 52 weeks was found in the surgical group that continued to protect the limb from full body weight during gait. This finding suggests that protection of the knee from maximum stresses may be important in minimizing the development of PTOA in the ACL-injured knee within 1 year.

Resolution of Pain and Predictors of Postoperative Opioid use after Bridge-Enhanced Anterior Cruciate Ligament Repair and Anterior Cruciate Ligament Reconstruction

Purpose

To compare postoperative pain scores and opioid use between patients undergoing a standard arthroscopic anterior cruciate ligament reconstruction (ACLR) using hamstring autograft with those undergoing a suture repair augmented with an extracellular matrix scaffold (bridge-enhanced ACL repair) performed through an arthrotomy and to determine factors predictive of postoperative opioid use and levels of overprescription.

Methods

A nonrandomized controlled trial was conducted with 20 patients (10 ACLR, 10 bridge-enhanced ACL repair), aged 18 to 35 years. All surgeries were performed by a single surgeon. A pain medication log was provided to patients on discharge. No regional anesthesia was performed. Pain scores via a visual analog pain scale were recorded at each visit. Correlations between preoperative and intraoperative characteristics and postoperative opioid use were determined.

Results

The total morphine-equivalent dose ranged from 30 to 309 mg (4-42 pills oxycodone) for the ACLR group and 75 to 254 mg (10-34 pills oxycodone) for the bridge-enhanced ACL repair group. The average opioid use per day was 35.8 mg for the patients undergoing bridge-enhanced ACL repair and 44.2 mg for patients undergoing ACLR (P = .29). Pain scores at time points up to 2 years postoperatively were not significantly different between the 2 groups. Across both groups, the average oversupply of oxycodone was 46 pills per patient, a greater than 70% unused opiate rate. Preoperative body mass index and preoperative Knee Injury and Osteoarthritis Outcome Scores pain score were predictive of greater postoperative opioid use per day, whereas age, concurrent meniscal repair, and operative time were not.

Conclusions

Total overall opiate intake was not different between the patients undergoing bridge-enhanced ACL repair through an arthrotomy and those undergoing arthroscopic ACLR. Both groups had similar pain scores from 2 weeks to 2 years postoperatively. Greater body mass index and greater preoperative pain (lower Knee Injury and Osteoarthritis Outcome Scores pain score) correlated with greater postoperative opioid use per day. There was an overprescription of opioids across all patients.

Level of Evidence

Level III, case control study (therapeutic).

Bridge-Enhanced Anterior Cruciate Ligament Repair: Two-Year Results of a First-in-Human Study

Background

Bridge-enhanced anterior cruciate ligament repair (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with a specific extracellular matrix scaffold (the BEAR scaffold) that is placed in the gap between the torn ends of the ACL to facilitate ligament healing.

Purpose/Hypothesis

The purpose of this study was to report the 12- and 24-month outcomes of patients who underwent the BEAR procedure compared with a nonrandomized concurrent control group who underwent ACL reconstruction (ACLR) with an autograft. We hypothesized that the BEAR group would have physical examination findings, patient-reported outcomes, and adverse events that were similar to those of the ACLR group.

Study Design

Cohort study; Level of evidence, 2.

Methods

Ten patients underwent BEAR, and 10 underwent ACLR with a 4-stranded hamstring autograft. At 24 months, 9 of the 10 BEAR patients and 7 of the 10 ACLR patients completed a study visit. Outcomes reported included International Knee Documentation Committee (IKDC) subjective and objective results, knee anteroposterior (AP) laxity findings via an arthrometer, and functional outcomes.

Results

There were no graft or repair failures in the first 24 months after surgery. The IKDC subjective scores in both groups improved significantly from baseline (P < .0001) at 12 and 24 months, to 84.6 ± 17.2 in the ACLR group and to 91.7 ± 11.7 in the BEAR group. An IKDC objective grade of A (normal) was found in 44% of patients in the BEAR group and in 29% of patients in the ACLR group at 24 months; no patients in either group had C (abnormal) or D (severely abnormal) grades. Arthrometer testing demonstrated mean side-to-side differences in AP laxity that were similar in the 2 groups at 24 months (BEAR, 1.94 ± 2.08 mm; ACLR, 3.14 ± 2.66 mm). Functional hop testing results were similar in the 2 groups at 12 and 24 months after surgery. Hamstring strength indices were significantly higher in the BEAR group compared with the ACLR group (P = .0001).

Conclusion

In this small, first-in-human study, BEAR produced similar outcomes to ACLR with a hamstring autograft. BEAR may result in knee stability and patient-reported outcomes at 2 years sufficient to warrant longer term studies of efficacy in larger groups of patients.

Impact of chemical and physical treatments on the mechanical properties of poly(ε-caprolactone) fibers bundles for the anterior cruciate ligament reconstruction

The anterior cruciate ligament rupture is one of the most common sport injuries. Due to ligaments’ poor healing capacity, surgical intervention is often required. Nowadays, these injuries are managed using replacement autografts or to a lesser extent using artificial ligaments. With the expansion of tissue engineering, more recent researches focus on the development of biodegradable structures that could allow graft functioning while enhancing host integration. The main challenge is to develop a structure that gradually loses its mechanical properties when at the same time the neo-ligament gains in solidity. Mechanical behavior and reconstruction of natural tissue are the two key points for such a successful device. This article evaluates the mechanical consistency of poly(ε-caprolactone) fibers bundles grafted with sodium polystyrene sulfonate, as a candidate for ligament prosthesis. In order to be medically used, PCL fibers need to cope with multiple steps before implantation including extensive washings, knitting, grafting and sterilization processes. The evolution of mechanical properties at each step of the elaboration process has been investigated. The results show that PCL bundles have the same visco-elastic behavior than the native ACL. Nevertheless, when undergoing physical treatments such as ionizing radiations, like UV or β-rays, the material endures a hardening, increasing its stiffness but also its fragility. At this opposite, the thermal radical grafting acts like an annealing step, increasing significantly the elasticity of the PCL fibers. With this chemical treatment, the stiffness is decreasing, leading to higher energy dissipation. Added to the observation of the structure of the material, this demonstrates the possibility of the PCL to modulate it microstructure. In case of orthopedic prosthesis, the need of such a construct is strongly required to avoid distension of the future prosthesis and to restore good knee stabilization, showing the promising future of PCL ligament prosthesis.

A Narrative Review of Four Different New Techniques in Primary Anterior Cruciate Ligament Repair: "Back to the Future" or Another Trend?

Recently, four different operative techniques, referring to the primary anterior cruciate ligament (ACL) repair, were described. These are the dynamic intraligamentary stabilization (DIS) with Ligamys™, the Bridge-enhanced repair (BEAR), the use of internal brace, and the refixation with suture anchors. The purpose of this study was to assess the already-published, clinical, and pre-clinical results of those techniques. A literature review was conducted and implemented by three independent researchers. Inclusion criteria were clinical or cadaveric or animal studies about patients suffering from ACL rupture, who were treated with one of those four different arthroscopic techniques of primary ACL repair. There were 10 clinical trials dealing with the different techniques of primary ACL repair and 12 cadaveric or animal studies. The majority of the published clinical trials investigated the dynamic intraligamentary stabilization (DIS), while only four studies referred to the three other surgical techniques. Most of the clinical trials suggested that primary ACL repair should be done during the first 14–21 days after a proximal ACL rupture and not later. Further clinical evidence is needed for the techniques of bridge-enhanced ACL repair, internal brace, and suture anchors ACL refixation in order to support the animal and cadaveric biomechanical studies. Till now, the existing clinical trials were not enough to establish the use of those techniques in the ACL-ruptured patients. On the contrary, the Dynamic intraligamentary stabilization with Ligamys™ device demonstrated very promising results in different types of clinical studies.

Bench-to-bedside: Bridge-enhanced anterior cruciate ligament repair

Anterior cruciate ligament (ACL) injuries are one of the most well-known orthopaedic injuries and are treated with one of the most common orthopaedic procedures performed in the United States. This surgical procedure, ACL reconstruction, is successful at restoring the gross stability of the knee. However, the outcomes of ACL reconstruction can be limited by short and long-term complications, including muscle weakness, graft rupture, and premature osteoarthritis. Thus, new methods of treating this injury are being explored. This review details the pathway of how a tissue engineering strategy can be used to improve the healing of the ACL in preclinical studies and then translated to patients in an FDA-approved clinical study. This review paper will outline the clinical importance of ACL injuries, history of primary repair, the pathology behind failure of the ACL to heal, pre-clinical studies, the FDA approval process for a high risk medical device, and the preliminary results from a first-in-human study. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2606-2612, 2017.

Orthopedic Interface Repair Strategies Based on Native Structural and Mechanical Features of the Multiscale Enthesis

The enthesis is an organ that connects a soft, aligned tissue (tendon/ligament) to a hard, amorphous tissue (bone) via a fibrocartilage interface. Mechanically, the enthesis sustains a dynamic loading environment that includes tensile, compressive, and shear forces. The structural components of the enthesis act to minimize stress concentrations and control stretch at the interface. Current surgical repair of the enthesis, such as in rotator cuff repair and anterior cruciate ligament reconstruction, aim to bridge the gap between the injured ends via reattachment of soft-to-hard tissues or graft replacement. In this review, we discuss the multiscale, morphological, and mechanical characteristics of the fibrocartilage attachment. Additionally, we review historical and recent clinical approaches to treating enthesis injury. Lastly, we explore new technological advancements in tissue-engineered biomaterials that have shown promise in preclinical studies.

The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study

Background:

This study assessed the safety of the newly developed bridge-enhanced anterior cruciate ligament (ACL) repair (BEAR), which involves suture repair of the ligament combined with a bioactive scaffold to bridge the gap between the torn ligament ends. As the intra-articular environment is complex in its response to implanted materials, this study was designed to determine whether there would be a significant rate of adverse reaction to the implanted scaffold.

Hypothesis:

The primary hypothesis was that the implanted scaffold would not result in a deep joint infection (arthrocentesis with positive culture) or significant inflammation (clinical symptoms justifying arthrocentesis but negative culture). The secondary hypotheses were that patients treated with BEAR would have early postoperative outcomes that were similar to patients treated with ACL reconstruction with an autologous hamstring graft.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 20 patients were enrolled in this nonrandomized, first-in-human study. Ten patients received BEAR treatment and 10 received a hamstring autograft ACL reconstruction. The BEAR procedure was performed by augmenting a suture repair with a proprietary scaffold, the BEAR scaffold, placed in between the torn ends of the ACL at the time of suture repair. The BEAR scaffold is to our knowledge the only device that fills the gap between the torn ligament ends to have current Investigational Device Exemption approval from the Food and Drug Administration. Ten milliliters of autologous whole blood were added to the scaffold prior to wound closure. Outcomes were assessed at 3 months postoperatively. The outcomes measures included postoperative pain, muscle atrophy, loss of joint range of motion, and implant failure (designated by an International Knee Documentation Committee grade C or D Lachman test and/or an absence of continuous ACL tissue on magnetic resonance images).

Results:

There were no joint infections or signs of significant inflammation in either group. There were no differences between groups in effusion or pain, and no failures by Lachman examination criteria (BEAR, 8 grade A and 2 grade B; ACL reconstruction, 10 grade A). Magnetic resonance images from all of the BEAR and ACL-reconstructed patients demonstrated a continuous ACL or intact graft. In addition, hamstring strength at 3 months was significantly better in the BEAR group than in the hamstring autograft group (mean ± SD: 77.9% ± 14.6% vs 55.9% ± 7.8% of the contralateral side; P < .001).

Conclusion:

The results of this study suggest that the BEAR procedure may have a rate of adverse reactions low enough to warrant a study of efficacy in a larger group of patients.

Sterilization of collagen scaffolds designed for peripheral nerve regeneration: Effect on microstructure, degradation and cellular colonization

In this study we investigated the impact of three different sterilization methods, dry heat (DHS), ethylene oxide (EtO) and electron beam radiation (β), on the properties of cylindrical collagen scaffolds with longitudinally oriented pore channels, specifically designed for peripheral nerve regeneration. Scanning electron microscopy, mechanical testing, quantification of primary amines, differential scanning calorimetry and enzymatic degradation were performed to analyze possible structural and chemical changes induced by the sterilization. Moreover, in vitro proliferation and infiltration of the rat Schwann cell line RSC96 within the scaffolds was evaluated, up to 10days of culture. No major differences in morphology and compressive stiffness were observed among scaffolds sterilized by the different methods, as all samples showed approximately the same structure and stiffness as the unsterilized control. Proliferation, infiltration, distribution and morphology of RSC96 cells within the scaffolds were also comparable throughout the duration of the cell culture study, regardless of the sterilization treatment. However, we found a slight increase of chemical crosslinking upon sterilization (EtO<DHS<β), together with an enhanced resistance to denaturation of the EtO treated scaffolds and a significantly accelerated enzymatic degradation of the β sterilized scaffolds. The results demonstrated that β irradiation impaired the scaffold properties to a greater extent, whereas EtO exposure appeared as the most suitable method for the sterilization of the proposed scaffolds.

Single-leg postural stability deficits following anterior cruciate ligament reconstruction in pediatric and adolescent athletes

The objective of this study was to compare the postural stability of pediatric and adolescent athletes without anterior cruciate ligament injury with those who underwent anterior cruciate reconstruction (ACLR). Postural stability ratings derived from a video-force plate system during the three stances of the modified Balance Error Scoring System were collected from pediatric and adolescent athletes who underwent ACLR (N=24; mean 1.2 years after surgery) and from uninjured controls (N=479). The postural control rating was calculated as the mean of the displacement and variance of the torso and center of pressure data, normalized on a scale from 0 to 100. A higher rating indicates greater postural stability. Participants who underwent ACLR showed lower postural stability ratings during single-leg stance compared with uninjured controls (40.0 vs. 48.7; P=0.037). ACLR is associated with deficits in postural stability.

Effect of low-temperature ethylene oxide and electron beam sterilization on the in vitro and in vivo function of reconstituted extracellular matrix-derived scaffolds

Reconstituted extracellular matrix (ECM)-derived scaffolds are commonly utilized in preclinical tissue engineering studies as delivery vehicles for cells and growth factors. Translation into clinical use requires identifying a sterilization method that effectively removes bacteria but does not harm scaffold function. To determine effectiveness of sterilization and impact on ECM scaffold integrity and function, low-temperature ethylene oxide and 15 kGy electron beam irradiation techniques were evaluated. Scaffold sterility was assessed in accordance to United States Pharmacopeia Chapter 71. Scaffold matrix degradation was determined in vitro using enzymatic resistance tests and gel electrophoresis. Scaffold mechanics including elastic modulus, yield stress and collapse modulus were tested. Lastly, 14 Yorkshire pigs underwent ACL transection and bio-enhanced ACL repair using sterilized scaffolds. Histologic response of ligament, synovium, and lymph nodes was compared at 4, 6, and 8 weeks. Ethylene oxide as well as electron beam irradiation yielded sterile scaffolds. Scaffold resistance to enzymatic digestion and protein integrity slightly decreased after electron beam irradiation while ethylene oxide altered scaffold matrix. Scaffold elastic modulus and yield stress were increased after electron beam treatment, while collapse modulus was increased after ethylene oxide treatment. No significant changes in ACL dimensions, in vivo scaffold resorption rate, or histologic response of synovium, ligament, and lymph nodes with either terminal sterilization technique were detectable. In conclusion, this study identifies two methods to terminally sterilize an ECM scaffold. In vitro scaffold properties were slightly changed without significantly influencing the biologic responses of the surrounding tissues in vivo. This is a critical step toward translating new tissue engineering strategies to clinical trials.