Changes in Functional Meniscal Morphology During Skeletal Growth and Maturation.

Background: Little is known on how meniscal morphology develops during skeletal growth and maturation and its subsequent relationship with the corresponding bony anatomy. Hypotheses: (1) Meniscal dimensions and morphology would change by age during skeletal growth and maturation in different ways in boys compared with girls. (2) Morphological features of the medial and lateral menisci would correlate to medial and lateral femoral condyle curvatures. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Anatomic features of the medial and lateral menisci were measured on magnetic resonance imaging scans from 269 unique knees (age, 3-18 years; 51% female) with no prior history of injury, congenital or growth-related skeletal disorders, or bony deformities. Morphological shape-based measurements were normalized to tibial plateau width or determined as ratios of meniscal dimensions. The association between age and anatomy was analyzed with linear regression. Two-way analysis of variance with the Holm-Sídák post hoc method was used to compare anatomy between sexes in different age groups. Linear regression was used to evaluate the relationship between femoral condyle curvature radius and meniscal morphology in each compartment after adjusting for age and sex. Results: Meniscal length, width, horn distance, mean cross-sectional area (CSA), and mean height increased with age in both sexes (R2 > 0.1; P < .001). Age-related changes in meniscal morphology were seen in normalized length, width, horn distance, and mean height; width-to-length ratio; horn distance-to-length ratio (lateral meniscus only); normalized mean CSA (except lateral meniscus in girls); and mean tip angle (R2 > 0.04; P < .02). Sex-based differences were also found, with some morphological differences (normalized length and height) throughout development (P < .03) and size differences (length, width, and mean CSA) in later development (P < .01). After adjusting for age and sex, there were significant correlations between medial condyle curvature radius and normalized width, width-to-length ratio, horn distance, horn distance-to-length ratio, mean CSA, and mean height of the medial meniscus (P≤ .041) and between lateral condyle curvature radius and normalized length, mean height, and mean tip angle of the lateral meniscus (P≤ .004). Conclusion: Age-related changes in meniscal dimensions and morphology, most notably a nonuniform growth pattern in meniscal geometry, occurred during skeletal growth and maturation, with different trends in boys than in girls.

High Levels of Satisfaction and Adequate Patient-Reported Outcomes After Operative Reconstruction of Multiligament Knee Injury With Allograft Among Patients Aged 40 Years and Older.

Purpose: To describe injury characteristics and patient-reported outcomes (PROs) among patients aged 40 years and older who underwent allograft reconstruction for multiligament knee injury (MLKI). Methods: Records of patients aged 40 years and older who underwent allograft multiligament knee reconstruction at a single institution between 2007 and 2017 with a minimum of 2 years of follow-up were retrospectively reviewed. Demographic information, concomitant injuries, patient satisfaction, and PROs including International Knee Documentation Committee and Marx activity scores were obtained. Results: Twelve patients were included with a minimum follow-up time of 2.3 years (mean, 6.1; range, 2.3-10.1 years) and a mean age at surgery of 49.8 years. Seven patients were male, and the most common mechanism of injury was sport-related. The most frequently reconstructed MLKIs were anterior cruciate ligament and medial collateral ligament (4), anterior cruciate ligament and posterolateral corner (2), and posterior cruciate ligament and posterolateral corner (2). The majority of patients reported satisfaction with their treatment (11). Median International Knee Documentation Committee and Marx scores were 73 (interquartile range, 45.5-88.0) and 3 (interquartile range 0-5), respectively. Conclusions: Patients aged 40 years and older can expect a high level of satisfaction and adequate PROs at 2-years follow-up after operative reconstruction for a MLKI with allograft. This demonstrates that allograft reconstruction for a MLKI in older patients may have clinical utility. Level of Evidence: IV, therapeutic case series.

Preoperative factors associated with failure to reach the patient acceptable symptom state after anterior cruciate ligament reconstruction in patients aged 40 and older.

PURPOSE: To perform a predictive analysis to identify preoperative patient factors associated with failure to achieve a newly defined patient acceptable symptom state (PASS) for the International Knee Documentation Committee (IKDC) Score after anterior cruciate ligament reconstruction (ACLR) in patients aged ≥ 40 years with a minimum of 2-year follow-up. METHODS: This was a secondary analysis of a retrospective review of all patients aged 40 years or older receiving a primary allograft ACLR at a single institution between the years of 2005 and 2016, with 2-year minimum follow-up. Using an updated PASS threshold of 66.7 for the International Knee Documentation Committee (IKDC) score previously established for this patient cohort, a univariate and multivariate analysis was performed to identify preoperative patient characteristics predictive of failure to achieve PASS. RESULTS: A total of 197 patients with a mean follow-up of 6.2 ± 2.1 years (range 2.7 - 11.2) were included in the analysis (48.5 ± 5.6 years, 51.8% female, Body Mass Index (BMI) 25.9 ± 4.4). PASS was achieved by 162 patients (82.2%). Patients who failed to achieve PASS more often had lateral compartment cartilage defects (P = 0.001) and lateral meniscus tears (P = 0.004), higher BMIs (P = 0.004), and Workers' Compensation status (P = 0.043) on univariable analysis. Factors predictive of failure to achieve PASS on multivariable analysis included BMI and lateral compartment cartilage defect (OR 1.12 [1.03-1.23], P = 0.013; OR 5.1 [1.87-13.9], P = 0.001). CONCLUSION: Among patients ≥ 40 years who receive a primary allograft ACLR, patients who fail to achieve PASS more often had lateral compartment cartilage defects and higher BMIs. LEVEL OF EVIDENCE: Level IV.

Revision Soft-Tissue Allograft Anterior Cruciate Ligament Reconstruction Is Associated With Lower Patient-Reported Outcomes Compared With Primary Anterior Cruciate Ligament Reconstruction in Patients Aged 40 and Older.

PURPOSE: To evaluate patient-reported outcomes (PROs) and graft failure rates in revision allograft anterior cruciate ligament reconstruction (ACLR) in patients aged 40 and older and compare them with primary ACLRs. METHODS: Patients aged 40 and older who underwent arthroscopic soft-tissue allograft ACLR between 2005 and 2016 with a minimum 2-year follow-up were retrospectively reviewed. Patients were grouped based on revision versus primary ACLR. The rate of achieving an International Knee Documentation Committee (IKDC) patient acceptable symptom state (PASS) score was recorded. Patient satisfaction, PROs, and graft failure were compared between groups using the χ2 test, Fisher exact test, and Mann-Whitney U test. RESULTS: We identified 32 patients who underwent revision ACLR and 201 patients who underwent primary ACLR aged 40 and older who met inclusion criteria with a mean follow-up of 6.2 and 6.9 years, respectively (P = .042). There was a lower rate of concomitant meniscal repair in the primary ACLR group (6% vs 21.9%, P = .007) There were no other differences in chondral injuries, mechanism of injury, or meniscal injuries between groups. The median IKDC score was greater in the primary ACLR group as compared with the revision ACLR group (83.9 vs 70.6, P < .001). Patients who underwent revision ACLR were less likely to achieve the IKDC PASS threshold (82.5% vs 56.3%, P = .001) and were less likely to report satisfaction as compared with patients who underwent primary ACLR (90.5% vs 78.1%, P =.038). No difference in graft failure rates was identified between groups (8% vs 15.6%, P = .180). CONCLUSIONS: Revision allograft ACLR in patients aged 40 and older was associated with lower PROs compared with primary ACLR. Patients who underwent revision ACLR failed to meet the IKDC PASS threshold more often and were dissatisfied with procedure results more than twice as often as patients that underwent primary ACLR. LEVEL OF EVIDENCE: III, retrospective cohort study.

Changes in Anatomic Risk Factors for Patellar Instability During Skeletal Growth and Maturation.

BACKGROUND: Several anatomic risk factors have been identified in the pathogenesis of patellofemoral instability. The literature is sparce regarding how these anatomic risk factors change during skeletal growth and development. HYPOTHESIS: The anatomic risk factors associated with patellar instability change significantly during skeletal growth and maturation with different patterns in male versus female patients. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Magnetic resonance imaging data from 240 unique, asymptomatic knees (7-18 years of age; 50% female) were used to measure patellar height (Caton-Deschamps index), lateral patellar tilt angle, trochlear height, trochlear groove depth, trochlear sulcus angle, and tibial tubercle-trochlear groove (TT-TG) distance. Linear regression was used to test the associations between age and anatomic findings. Two-way analysis of variance with Holm-Sídák post hoc test was used to compare anatomic characteristics between sexes in 3 age groups: prepubertal school-aged children (7-10 years old), early adolescents (11-14 years old), and late adolescents (15-18 years old). RESULTS: Patellar height (female sex), lateral patellar tilt angle (male sex), and trochlear sulcus angle (both sexes) decreased with age (P < .001). Trochlear height, depth, and TT-TG distance increased with age in both male and female participants (P < .02). Male participants had a larger sulcus angle (by 5.3°± 1.6° at age 11-14 years) and greater trochlear height (by >5 mm across medial, central, and lateral regions at age 15-18 years) than age-matched female participants (P < .01). We found no other sex-related differences in quantified anatomic features (P > .1). CONCLUSION: The findings partially support our hypothesis indicating significant age-related changes in all quantified features, which were not different between male and female participants except for trochlear sulcus angle in early adolescence and trochlear height in late adolescence. In general, the majority of anatomic risk factors for patellar instability change with maturity in a direction that assists in reducing the risk of patellar instability and/or dislocation. The only outlier is the TT-TG distance, which increased by age, and in our oldest cohort of patients, the mean fell below the normal adult range. The current observations highlight the importance of age in the interpretation of risk for injury as well as the need for further studies to identify intrinsic and extrinsic factors that may result in abnormal development of these anatomic features during skeletal growth and maturation.

The Majority of Patients Aged 40 and Older Having Allograft Anterior Cruciate Ligament Reconstruction Achieve a Patient Acceptable Symptomatic State.

PURPOSE: To evaluate patient satisfaction, retear rates, and patient-reported outcomes (PROs) in patients aged 40 and older undergoing allograft anterior cruciate ligament reconstruction (ACLR). The secondary goal was to compare these parameters between groups of patients with intact versus failed grafts, and to evaluate these in relation to a historically reported International Knee Documentation Committee (IKDC) patient-acceptable symptoms state (PASS) score. METHODS: Records of patients aged 40 and older who underwent ACLR between 2005 and 2016 at a single institution with a minimum 2-year follow-up were retrospectively reviewed. Patient-reported satisfaction, outcome scores, and failure rates were analyzed. The rate of achieving a previously defined IKDC PASS score based on younger cohorts was reported, and an updated PASS threshold for older patients was calculated. RESULTS: 201 patients were included with a mean age of 48.6 years (range: 40-68) and mean follow-up of 6.2 years (range: 2.8-11.2). 182 (90.5%) patients reported satisfaction following surgery. 16 (8.0%) patients experienced failure of their ACLR, 10 of which underwent revision ACLR. The median IKDC score in the intact ACLR group was 86.2, compared to 66.7 in the failure group (P < .001). In total, 134 (72.4%) patients in the intact group achieved the historical PASS score of 75.9 on IKDC compared to only 4 (25%) in the failure group (χ2 = 15.396, P < .001). An updated IKDC PASS threshold for older cohorts was calculated to be 66.7. CONCLUSION: Patients aged 40 and older who underwent allograft ACLR had an 8.0% failure rate at a mean follow-up of 6 years. Graft failure in patients aged 40 and older was associated with worse PROs. The majority of patients achieved the historically reported IKDC PASS threshold. Additionally, an updated age-appropriate IKDC PASS score of 66.7 was calculated to aid in future ACLR studies assessing older patients. STUDY DESIGN: Level IV.

Risk of Secondary ACL Injury in Adolescents Prescribed Functional Bracing After ACL Reconstruction.

BACKGROUND: There is a high incidence of a secondary anterior cruciate ligament (ACL) injury in unbraced adolescent athletes. Little is known about the effect of functional bracing with regard to the risk of secondary ACL injuries among adolescents. HYPOTHESIS: Our primary hypothesis was that adolescents would have a high rate of secondary ACL injury even with brace use. A secondary hypothesis was that the reinjury rate with brace use would be lower than that of a historical control group of unbraced patients. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A group of 219 patients (age <20 years at surgery) who underwent ACL reconstruction and were prescribed postoperative functional bracing during cutting and pivoting sports for 2 years after surgery completed a survey regarding reinjury to either knee. Rates of knee injuries following ACL reconstruction were calculated and compared with those reported in a similar unbraced cohort. The effect of demographic and anatomic factors on risk of secondary ACL injuries was also investigated. RESULTS: The overall follow-up rate was 65% (142/219) at a mean 5.6 years after surgery. In the braced cohort, the overall graft retear rate was 10%, with the highest retear rates observed in male patients 17 years of age and younger (18%). The overall contralateral ACL injury and combined (graft or contralateral ACL) secondary injury rates were 13% and 23%, respectively, with female patients younger than 18 years having the highest contralateral and combined injury rates (17% and 26%, respectively). Younger age (odds ratio [OR], 0.70; P = .021), family history of ACL injury (OR, 2.81; P = .015), and higher lateral tibial slope (OR, 1.25; P = .016) were associated with increased risk of secondary knee injury in the braced cohort. Compared with the unbraced cohort, the braced cohort had a lower overall graft retear rate (P = .028), a lower graft retear rate in patients younger than 18 years (P = .012), lower early graft retear rate (within the first year after surgery) (P = .011), and lower early graft retear rate in subjects younger than 18 years (P = .003). CONCLUSION: Postoperative use of functional bracing can result in reduced risk of graft retear and no change in contralateral injury rates. Clinicians may want to consider the use of postoperative functional bracing in adolescent patients.

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.

Delayed ACL Reconstruction in Patients ≥40 Years of Age Is Associated With Increased Risk of Medial Meniscal Injury at 1 Year.

BACKGROUND: Anterior cruciate ligament (ACL) tears in the pediatric and young adult ACL-deficient knee are often associated with meniscal or chondral injury with delayed time to surgery. The incidence of ACL reconstruction performed in patients aged ≥40 years is rising, and it is unclear if delayed surgery in this cohort similarly affects the health of the meniscus and cartilage. PURPOSE: To evaluate whether delayed reconstruction in a cohort of patients aged ≥40 years is associated with an increased risk of meniscal or chondral injury. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Records of patients aged ≥40 years who underwent primary arthroscopic ACL reconstruction between 2012 and 2016 at an academic hospital were retrospectively reviewed. Patient characteristic data and time to surgery were recorded. Operative reports were analyzed for meniscal and chondral injuries as well as treatment. Patients were grouped according to time to surgery, defined as early (<90 days) or delayed (≥90 days). Logistic regression modeling was used to form associations between elapsed time to surgery and patient characteristics to meniscal and chondral damage. Additionally, risks for meniscal and chondral injury were analyzed at time points of 180 days and 1 year from injury to surgery. RESULTS: A total of 227 patients met the study criteria: 106 patients underwent early surgery, and 121 underwent delayed surgery. The authors identified 127 medial meniscal tears and 106 lateral meniscal tears. Medial, lateral, and patellofemoral compartment chondral injury was reported in 127, 82, and 130 patients, respectively. Delayed surgery (≥90 days) was not associated with increased risk of medial or lateral meniscal tears or any chondral injury at 90 days. Each year of increased age was associated with an increased odds ratio: 1.09 ( P = .001) for medial meniscal tears, 1.06 ( P = .014) for lateral meniscal tears, 1.10 ( P = .001) for medial compartment chondral injuries, and 1.07 ( P = .007) for patellofemoral compartment chondral injuries. Additionally, each unit of increased body mass index was associated with an increased odds ratio: 1.09 ( P = .039) for medial meniscal tears and 1.14 ( P = .003) for medial compartment cartilage injury. Analysis of 180-day and 1-year time points revealed an increased risk (odds ratio, 3.47; 95% CI, 1.55-7.77; P = .002) for medial meniscal injury when surgery was delayed for >1 year. CONCLUSION: Delayed ACL reconstruction (≥90 days) among patients aged ≥40 years was not associated with an increased risk of meniscal or chondral injury. Increasing age and body mass index were associated with higher risks of meniscal and chondral injuries in this cohort. Delay in surgery for >1 year was associated with increased risk of medial meniscal tear.

Transcriptional profiling of synovium in a porcine model of early post-traumatic osteoarthritis.

To determine the transcriptional profile of synovium during the molecular phase of post-traumatic osteoarthritis, anterior cruciate ligament transections (ACL) were performed in 36 Yucatan minipigs. Equal numbers were randomly assigned to no further treatment, ACL reconstruction or repair. Perimeniscal synovium for histopathology and RNA-sequencing was harvested at 1 and 4 weeks post-operatively and from six healthy control animals. Microscopic synovitis scores significantly worsened at 1 (p < 0.001) and 4 weeks (p = 0.003) post-surgery relative to controls, and were driven by intimal hyperplasia and increased stromal cellularity without inflammatory infiltrates. Synovitis scores were similar between no treatment, reconstruction, and repair groups (p ≥ 0.668). Relative to no treatment at 1 week, 88 and 367 genes were differentially expressed in the reconstruction and repair groups, respectively (227 and 277 at 4 weeks). Relative to controls and with the treatment groups pooled, 1,683 transcripts were concordantly differentially expressed throughout the post-surgery time-course. Affected pathways included, proteolysis_connective tissue degradation (including upregulations of protease-encoding MMP1, MMP13, and ADAMTS4), and development_cartilage development (including upregulations of ACAN, SOX9, and RUNX2), among others. Using linear regression, significant associations of post-surgery synovial expression levels of 20 genes with the articular cartilage glycosaminoglycan loss were identified. These genes were predominantly related to embryonic skeletal system development and included RUNX2. In conclusion, this study confirmed an increased synovial expression of genes that may serve as targets to prevent cartilage degradation, including MMP1, MMP13, and ADAMTS4, in knees with microscopic synovitis and cartilage proteoglycan loss. Attractive novel targets include regulators of embryonic developmental processes in synovium. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Transcriptional profiling of articular cartilage in a porcine model of early post-traumatic osteoarthritis.

To identify the molecular pathophysiology present in early post-traumatic osteoarthritis (PTOA), the transcriptional profile of articular cartilage and its response to surgical PTOA induction were determined. Thirty six Yucatan minipigs underwent anterior cruciate ligament (ACL) transection and were randomly assigned in equal numbers to no further treatment, reconstruction or ligament repair. Cartilage was harvested at 1 and 4 weeks post-operatively and histology and RNA-sequencing were performed and compared to controls. Microscopic cartilage scores significantly worsened at 1 (p = 0.028) and 4 weeks (p = 0.001) post-surgery relative to controls, but did not differ between untreated, reconstruction or repair groups. Gene expression after ACL reconstruction and ACL transection were similar, with only 0.03% (including SERPINB7 and CR2) and 0.2% of transcripts (including INHBA) differentially expressed at 1 and 4 weeks respectively. COL2A1, COMP, SPARC, CHAD, and EF1ALPHA were the most highly expressed non ribosomal, non mitochondrial genes in the controls and remained abundant after surgery. A total of 1,275 genes were differentially expressed between 1 and 4 weeks post-surgery. With the treatment groups pooled, 682 genes were differentially expressed at both time-points, with the most significant changes observed in MMP1, COCH, POSTN, CYTL1, and PTGFR. This study confirmed the development of a microscopic PTOA stage after ACL surgery in the porcine model. Upregulation of multiple proteases (including MMP1 and ADAMTS4) were found; however, the level of expression remained orders of magnitude below that of extracellular matrix protein-coding genes (including COL2A1 and ACAN). In summary, genes with established roles in PTOA as well as novel targets for specific intervention were identified. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:318-329, 2018.

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.

Extracellular matrix-blood composite injection reduces post-traumatic osteoarthritis after anterior cruciate ligament injury in the rat.

The objective of this study was to determine if an injection of a novel extracellular matrix scaffold and blood composite (EMBC) after anterior cruciate ligament (ACL) injury would have a mitigating effect on post-traumatic osteoarthritis (PTOA) development in rat knees. Lewis rats underwent unilateral ACL transection and were divided into three groups as follows: (1) no further treatment (ACLT; n = 10); (2) an intra-articular injection of EMBC on day 0 (INJ0; n = 11); and (3) an intra-articular injection of EMBC on day 14 (INJ14; n = 11). Ten additional animals received capsulotomy only (n = 10, SHAM group). The OARSI histology scoring of the tibial cartilage and micro-CT of the tibial epiphysis were performed after 35 days. The ratio of intact/treated hind limb forces during gait was determined using a variable resistor walkway. The OARSI cartilage degradation sum score and total degeneration width were significantly greater in the ACLT group when compared to the INJ0 (p = 0.031, and p = 0.005) and INJ14 (p = 0.022 and p = 0.04) group. Weight bearing on the operated limb only decreased significantly in the ACLT group (p = 0.048). In the rat ACL transection model, early or delayed injection of EMBC ameliorated the significant decrease in weight bearing and cartilage degradation seen in knees subjected to ACL transection without injection. The results indicate that the injection of EMBC may slow the process of PTOA following ACL injury and may provide a promising treatment for PTOA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:995-1003, 2016.

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.

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

Extracellular matrix (ECM) scaffolds have been used to enhance anterior cruciate ligament (ACL) repair in large animal models. To translate this technology to clinical care, identifying a method which effectively sterilizes the material without significantly impairing in vivo function is desirable. Sixteen Yorkshire pigs underwent ACL transection and were randomly assigned to bridge-enhanced ACL repair-primary suture repair of the ACL with addition of autologous blood soaked ECM scaffold--with either (i) an aseptically processed ECM scaffold, or (ii) an electron beam irradiated ECM scaffold. Primary outcome measures included sterility of the scaffold and biomechanical properties of the scaffold itself and the repaired ligament at 8 weeks after surgery. Scaffolds treated with 15 kGy electron beam irradiation had no bacterial or fungal growth noted, while aseptically processed scaffolds had bacterial growth in all tested samples. The mean biomechanical properties of the scaffold and healing ligament were lower in the electron beam group; however, differences were not statistically significant. Electron beam irradiation was able to effectively sterilize the scaffolds. In addition, this technique had only a minimal impact on the in vivo function of the scaffolds when used for ligament healing in the porcine model.

Bridge-enhanced ACL repair: A review of the science and the pathway through FDA investigational device approval.

Injuries to the anterior cruciate ligament (ACL) are currently treated with replacement of the torn ligament with a graft of tendon harvested from elsewhere in the knee. This procedure, called "ACL reconstruction," is excellent for restoring gross stability to the knee; however, there are relatively high graft failure rates in adolescent patients (Barber et al. in Arthroscopy 30(4):483-491, (2014); Engelman et al. in Am J Sports Med, (2014); Webster et al. in Am J Sports Med 42(3):641-647, (2014)), and the ACL reconstruction procedure does not prevent the premature osteoarthritis seen in patients after an ACL injury (Ajuied et al. in Am J Sports Med, (2013); Song et al. in J Sports Med 41(10):2340-2346, (2013); Tourville et al. Am J Sports Med 41(4):769-778, (2013)) .Thus, new solutions are needed for ACL injuries. Researchers have been investigating the use of scaffolds, growth factors and cells to supplement a suture repair of the ACL (bridge-enhanced repair; also called bio-enhanced repair in prior publications). In this paper, we will review the varied approaches which have been investigated for stimulating ACL healing and repair in preclinical models and how one of these technologies was able to move from promising preclinical results to FDA acceptance of an investigational device exemption application for a first-in-human study.

Can platelet-rich plasma enhance anterior cruciate ligament and meniscal repair?

The use of platelet-rich plasma (PRP) to improve clinical outcome following a soft tissue injury, regeneration, and repair has been the subject of intense investigation and discussion. This article endeavors to relate clinical and basic science strategies focused on biological augmentation of the healing response in anterior cruciate ligament (ACL) and meniscus repair and replacement using PRP. Therein, a translational feedback loop is created in the literature and targeted towards the entire multidisciplinary team. Ultimately, it is hoped that the theoretical benefits of PRP on soft-tissue interfacial healing will emerge clinically following a careful, focused characterization at the benchtop, and prospective randomized controlled clinical study.

The use of silk-based devices for fracture fixation.

Metallic fixation systems are currently the gold standard for fracture fixation but have problems including stress shielding, palpability and temperature sensitivity. Recently, resorbable systems have gained interest because they avoid removal and may improve bone remodelling due to the lack of stress shielding. However, their use is limited to paediatric craniofacial procedures mainly due to the laborious implantation requirements. Here we prepare and characterize a new family of resorbable screws prepared from silk fibroin for craniofacial fracture repair. In vivo assessment in rat femurs shows the screws to be self-tapping, remain fixed in the bone for 4 and 8 weeks, exhibit biocompatibility and promote bone remodelling. The silk-based devices compare favourably with current poly-lactic-co-glycolic acid fixation systems, however, silk-based devices offer numerous advantages including ease of implantation, conformal fit to the repair site, sterilization by autoclaving and minimal inflammatory response.