High-Performance Artificial Ligament Made from Helical Polyester Fibers Wrapped with Aligned Carbon Nanotube Sheets.

Repairing high-load connective tissues, such as ligaments, by surgically implanting artificial grafts after injury is challenging because they lack biointegration with host bones for stable interfaces. Herein, a high-performance helical composite fiber (HCF) ligament by wrapping aligned carbon nanotube (CNT) sheets around polyester fibers is proposed. Anterior cruciate ligament (ACL) reconstruction surgery shows that HCF grafts could induce effective bone regeneration, thus allowing the narrowing of bone tunnel defects. Such repair of the bone tunnel is in strong contrast to the tunnel enlargement of more than 50% for commercial artificial ligaments made from bare polyester fibers. Rats reconstructed with this HCF ligament show normal jumping, walking, and running without limping. This work allows bone regeneration in vivo through a one-step surgery without seeding cells or transforming growth factors, thereby opening an avenue for high-performance artificial tissues.

BMP-2/TGF-ß1 gene insertion into ligament-derived stem cells sheet promotes tendon-bone healing in a mouse.

Bone morphogenetic protein-2 (BMP-2) and transforming growth factor-ß1 (TGF-ß1) reportedly induce the osteogenic and tenogenic differentiation of anterior cruciate ligament (ACL)-derived stem cells (LDSCs), respectively. However, few studies have investigated the effect of BMP-2/TGF-ß1 on the differentiation of LDSC. We developed a BMP-2/TGF-ß1 gene insertion into an LDSC cell sheet that promotes tendon-bone healing in a mouse ACL reconstruction (ACLR) model. CD34+ LDSCs were isolated from human ACL stump tissues, virally transduced to express BMP-2 or TGF-ß1, and then embedded within cell sheets. All mice underwent ACLR using an autograft wrapped with a cell sheet and were randomly divided into three groups: BMP-2-, TGF-ß1-, and BMP-2/TGF-ß1-transduced. At 4 and 8 weeks, tendon-bone healing was evaluated by micro-CT, biomechanical test, and histological analysis. BMP-2 and TGF-ß1 promoted the osteogenic and tenogenic differentiation of LDSC in vitro. BMP-2/TGF-ß1-transduced LDSC sheet application contributed to early improvement in mean failure load and graft stiffness, accelerated maturation of the tendon-bone junction, and inhibited bone tunnel widening. Furthermore, reduced M1 macrophage infiltration and a higher M2 macrophage percentage were observed in the BMP-2/TGF-ß1-transduced LDSC group. This work demonstrated that BMP-2 and TGF-ß1 promoted CD34+ LDSCs osteogenic and tenogenic differentiation in vitro and in vivo, which accelerated the tendon-bone healing after ACLR using autografts wrapped with cell sheets in a mouse model.

Editorial Commentary: Soaking Anterior Cruciate Ligament Grafts in Vancomycin Solution Lowers Infection Rates Without Lowering Functional Outcomes.

Soaking anterior cruciate ligament grafts in vancomycin solution is done by many surgeons. Research has indicated decreased infection rates and similar anterior cruciate ligament retear rates between grafts soaked in vancomycin solution before implantation versus those without. In addition, there has been basic science evidence for tenocyte survival and viability even when exposed to vancomycin solution. The next frontier, investigating the maturation of vancomycin-soaked grafts with advanced imaging, may cause some surgeons to reconsider the practice but should not stop it, based on the available literature.

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-ß, 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.

Anterior Cruciate Ligament Reconstruction Graft Preference Most Dependent on Patient Age: A Survey of United States Surgeons.

PURPOSE: The purpose of this study was to define the anterior cruciate ligament (ACL) reconstruction (ACLR) graft preference of surgeons and to explore factors associated with their predilection. METHODS: A 15-question survey regarding ACLR graft preference in various situations was completed by 514 American Orthopaedic Society for Sports Medicine and Arthroscopy Association of North America surgeons. Surgeon and practice demographics, along with various patient factors, were evaluated with bivariate and multivariable models for association with surgeon preference. Surgeons were also queried about their preference for their own ACLR. For surgeons who personally sustained an ACL, an additional 6 questions inquired about their experience. RESULTS: Surgeons reported the 5 most important factors in patient graft choice, in order: patient age, graft failure in literature and practice, pivot sport, and patient preference. Autograft patellar and quadriceps tendon were strongly preferred for younger, pivoting athletes (P < .001), among those with fellowship training (47% vs 33%, P = .006), in academic practices (52% vs 44%, P = .003), and in more sports medicine-specific practices, with a higher number of ACLRs performed per year (P < .001). Northeast, Southeast, Midwest, and Southwest surgeons had lower hamstring autograft preference (P < .001). Non-fellowship-trained surgeons preferred hamstring autograft (P = .010). Allograft was preferred for older patients (P < .001). Nonsignificant predictors included highest level of athlete for whom an ACLR had been performed, level of athlete serving as team physician, and years in practice. No factors were associated with surgeon preference for their own ACLR despite deeming these factors important for patients. ACL tears were reported by 13% of respondents, with 86% stating it influenced their decision to enter orthopaedics. CONCLUSIONS: Patient age was the most important factor in graft choice, with patellar and quadriceps tendon autograft the preferred graft for ACLR for younger, pivoting athletes. Fellowship training and practice demographics were also correlated with graft choice for patients. CLINICAL RELEVANCE: Graft preference for ACLR varies among surgeons and is associated with surgeon experience and patient characteristics, including patient age, type of sport, and patient preference.

A Biomechanical Study of Pivot-Shift and Lachman Translations in Anterior Cruciate Ligament-Sectioned Knees, Anterior Cruciate Ligament-Reconstructed Knees, and Knees With Partial Anterior Cruciate Ligament Graft Slackening: Instrumented Lachman Tests Statistically Correlate and Supplement Subjective Pivot-Shift Tests.

PURPOSE: To determine the statistical and predictive correlation between instrumented Lachman and pivot-shift tests with progressive loss of anterior cruciate ligament (ACL) function. METHODS: The kinematic correlations between pivot-shift and Lachman anterior tibial translations (ATTs) in ACL-deficient and ACL-reconstructed states and in partially lax ACL grafts were determined with precise robotic testing in cadaveric knees. The Lachman test (100-N anteroposterior) and 2 pivot-shift loadings were conducted: anterior tibial loading (100 N), valgus rotation (7 Nm), and internal rotation (5 Nm and 1 Nm). The tibia was digitized to study the resulting medial, central, and lateral tibiofemoral compartment translations. In group 1 knees, 15 bone-patellar tendon-bone reconstructions were first tested, followed by ACL graft loosening with 3- and 5-mm increases in Lachman ATT. In group 2, 43 knees underwent robotic testing before and after ACL sectioning and underwent analysis of the effect of 3- and 5-mm increases in Lachman ATT and complete ACL sectioning on pivot-shift compartment translations. RESULTS: In group 1 knees, ACL graft loosening allowing a 3-mm increase in Lachman ATT resulted in increases in pivot-shift lateral compartment translation (lateral compartment ATT) of only 1.6 ± 0.3 mm and 2.2 ± 1.0 mm (internal rotation of 5 Nm and 1 Nm, respectively) that were one-half of those required for a positive pivot-shift test finding. In group 2, for a 3-mm increased Lachman test, there were no positive pivot-shift values. In both groups, a Lachman test with an increase in ATT of 3 mm or less (100 N) had a 100% predictive value for a negative pivot-shift test finding. With ACL graft loosening and a 5-mm increase in the Lachman ATT, group 1 still had no positive pivot-shift values, and in group 2, a positive pivot-shift test finding occurred in 3 of 43 knees (7%, pivot shift 1-Nm internal rotation). After ACL sectioning, a highly predictive correlation was found between abnormal increases in Lachman and pivot-shift translations (P < .001). CONCLUSIONS: ACL graft slackening and an instrumented Lachman test with an increase in ATT of 3 mm or less were 100% predictive of a negative pivot-shift subluxation finding and retained ACL stability. Further graft slackening and a 5-mm increase in the Lachman ATT produced pivot-shift lateral compartment ATT increases still less than the values in the ACL-deficient state; however, 7% of the knees (3 of 43) were converted to a positive pivot-shift test finding indicative of ACL graft failure. CLINICAL RELEVANCE: Instrumented Lachman tests provide objective data on ACL function and graft failure to supplement subjective pivot-shift tests and are highly recommended for single-center and multicenter ACL studies. In the past decade, a near majority of published ACL studies no longer reported on instrumented Lachman tests, relying solely on highly subjective pivot-shift grading by multiple examiners.

Fibular Collateral Ligament Reconstruction Graft Options: Clinical and Radiographic Outcomes of Autograft Versus Allograft.

PURPOSE: To compare varus knee stability and clinical outcomes between patients who underwent fibular collateral ligament reconstruction (FCLR) or lateral collateral ligament (LCL) reconstruction with autografts versus allografts when undergoing concomitant anterior cruciate ligament reconstruction (ACLR). METHODS: All patients who underwent primary ACLR and concomitant FCLR from 2010 to 2017 performed by a single surgeon (R.F.L.) were retrospectively identified. Clinical characteristics and graft choices for FCLR were collected. Patients with a minimum 2-year follow-up for clinical outcome scores and 6-month stress radiographs were included. Patients with any other ligamentous procedure or revision ACLR were excluded. RESULTS: We identified 69 primary ACLR with concomitant FCLR patients who met the inclusion criteria. Fifty patients underwent FCLR with semitendinosus autografts, and 19 with allografts. There were no significant side-to-side differences (SSDs) in lateral compartment gapping on varus stress x-rays between the 2 cohorts (allograft, 0.49 mm; autograft, 0.15 mm, P = .22), and no FCLR failures. There were no significant differences between autograft and allograft groups at minimum 2-year outcomes for 12-Item Short Form mental or physical composite score (SF12 MCS, P = .134; SF12 PCS, P = .642), WOMAC total (P = .158), pain (P = .116), stiffness (P = .061), or activity (P = .252); International Knee Documentation Committee (IKDC) (P = .337), Tegner (P = .601), Lysholm (P = .622), or patient satisfaction (P = .218). There were no significant differences in clinical knee stability between groups at an average follow-up of 3.6 years (P = 1.0). CONCLUSION: There were no differences in varus stress laxity 6 months postoperatively or clinical outcome scores at ≥2 years postoperatively between patients having FCL reconstructions with either autograft or allograft. This study demonstrates that both hamstring autografts and allografts for FCL reconstructions offer reliable and similar radiographic and clinical results at short-term follow-up. LEVEL OF EVIDENCE: III, retrospective comparative trial.

Significantly Lower Infection Risk for Anterior Cruciate Ligament Grafts Presoaked in Vancomycin Compared With Unsoaked Grafts: A Systematic Review and Meta-analysis.

PURPOSE: To compare postoperative infection rates following ACL reconstruction performed with grafts presoaked in vancomycin versus those without vancomycin. METHODS: A systematic review was performed using PRISMA guidelines. PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials were searched for therapeutic level I to III studies that compared outcomes of presoaking ACL grafts with vancomycin versus without vancomycin in human patients. Included graft types were tendon autografts or allografts, and included studies documented infection with a minimum follow-up of 30 days. Postoperative infection rates and knee-specific patient-reported outcome scores were extracted from each study and compared between groups. Study methodological quality was analyzed using the Methodological Index for Non-Randomized Studies (MINORS) and Modified Coleman Methodology Score (MCMS). Infection rates and retear rates were pooled and weighted for meta-analysis using a random-effects model. All P values were reported with an α level of 0.05 set as significant. RESULTS: The initial search yielded 144 articles (44 duplicates, 100 screened, 29 full-text review). Ten articles (21,368 subjects [7,507 vancomycin and 13,861 no vancomycin], 67% males, mean ± standard deviation age 29.5 ± 1.5 years) were included and analyzed. Eight of the 10 studies included only autografts, with 94.5% of grafts being hamstring autografts. Soaking grafts in vancomycin resulted in significantly fewer infections (0.013% versus 0.77%; odds ratio 0.07; 95% confidence interval 0.03, 0.18; P < .001). Only 2 studies included patient-reported outcomes, and both demonstrated no difference in International Knee Documentation Committee scores 1 year after surgery for patients with grafts presoaked in vancomycin versus without vancomycin. CONCLUSIONS: Soaking ACL tendon grafts with vancomycin before implantation is associated with a nearly 15 times decrease in odds of infection compared with grafts not soaked in vancomycin. Few studies investigated patient-reported outcomes and retear rates after soaking ACL grafts in vancomycin. LEVEL OF EVIDENCE: III, systematic review of level III studies.

Quantitative Assessment of In Vivo Human Anterior Cruciate Ligament Autograft Remodeling: A 3-Dimensional UTE-T2* Imaging Study.

BACKGROUND: The timing of return to play after anterior cruciate ligament (ACL) reconstruction is still controversial due to uncertainty of true ACL graft state at the time of RTP. Recent work utilizing ultra-short echo T2* (UTE-T2*) magnetic resonance imaging (MRI) as a scanner-independent method to objectively and non-invasively assess the status of in vivo ACL graft remodeling has produced promising results. PURPOSE/HYPOTHESIS: The purpose of this study was to prospectively and noninvasively investigate longitudinal changes in T2* within ACL autografts at incremental time points up to 12 months after primary ACL reconstruction in human patients. We hypothesized that (1) T2* would increase from baseline and initially exceed that of the intact contralateral ACL, followed by a gradual decline as the graft undergoes remodeling, and (2) remodeling would occur in a region-dependent manner. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Twelve patients (age range, 14-45 years) who underwent primary ACL reconstruction with semitendinosus tendon or bone-patellar tendon-bone autograft (with or without meniscal repair) were enrolled. Patients with a history of previous injury or surgery to either knee were excluded. Patients returned for UTE MRI at 1, 3, 6, 9, and 12 months after ACL reconstruction. Imaging at 1 month included the contralateral knee. MRI pulse sequences included high-resolution 3-dimensional gradient echo sequence and a 4-echo T2-UTE sequence (slice thickness, 1 mm; repetition time, 20 ms; echo time, 0.3, 3.3, 6.3, and 9.3 ms). All slices containing the intra-articular ACL were segmented from high-resolution sequences to generate volumetric regions of interest (ROIs). ROIs were divided into proximal/distal and core/peripheral sub-ROIs using standardized methods, followed by voxel-to-voxel registration to generate T2* maps at each time point. This process was repeated by a second reviewer for interobserver reliability. Statistical differences in mean T2* values and mean ratios of T2*inj/T2*intact (ie, injured knee to intact knee) among the ROIs and sub-ROIs were assessed using repeated measures and one-way analyses of variance. P < .05 represented statistical significance. RESULTS: Twelve patients enrolled in this prospective study, 2 withdrew, and ultimately 10 patients were included in the analysis (n = 7, semitendinosus tendon; n = 3, bone-patellar tendon-bone). Interobserver reliability for T2* values was good to excellent (intraclass correlation coefficient, 0.84; 95% CI, 0.59-0.94; P < .001). T2* values increased from 5.5 ± 2.1 ms (mean ± SD) at 1 month to 10.0 ± 2.9 ms at 6 months (P = .001), followed by a decline to 8.1 ± 2.0 ms at 12 months (P = .129, vs 1 month; P = .094, vs 6 months). Similarly, mean T2*inj/T2*intact ratios increased from 62.8% ± 22.9% at 1 month to 111.1% ± 23.9% at 6 months (P = .001), followed by a decline to 92.8% ± 29.8% at 12 months (P = .110, vs 1 month; P = .086, vs 6 months). Sub-ROIs exhibited similar increases in T2* until reaching a peak at 6 months, followed by a gradual decline until the 12-month time point. There were no statistically significant differences among the sub-ROIs (P > .05). CONCLUSION: In this preliminary study, T2* values for ACL autografts exhibited a statistically significant increase of 82% between 1 and 6 months, followed by an approximate 19% decline in T2* values between 6 and 12 months. In the future, UTE-T2* MRI may provide unique insights into the condition of remodeling ACL grafts and may improve our ability to noninvasively assess graft maturity before return to play.

Immunohistochemical analysis of sensory corpuscles in human transplants of the anterior cruciate ligament.

BACKGROUND: Sensory nerve endings in ligaments play an important role for the proprioceptive function. Clinical trials show that the sense of body position does not fully recover in the knee joint after reconstructive surgery of the ruptured anterior cruciate ligament. The aim of this study is to identify sensory corpuscles in autogenous and allogenous transplants of the ligament and to compare their quantity between the used allografts and autografts. METHODS: Thirty-three patients were included in this study. Three patellar tendon allografts, 14 patellar tendon autografts and 12 semitendinosus autografts were harvested during revision surgery after traumatic rerupture of the graft. The control consisted of 4 healthy anterior cruciate ligaments after fresh rupture. After haematoxylin staining, immunohistochemical analysis was performed using antibodies against S100, p75 and PGP9.5. Microscopical examination was carried out, and the number of mechanoreceptors was counted. Statistical analysis was performed using the Mann-Whitney U test. RESULTS: Two types of mechanoreceptors were identified in each graft: Ruffini corpuscles and free nerve endings. The number of Ruffini corpuscles per square centimeter was the highest in the control. Comparing the grafts, the highest number of receptors could be detected in the semitendinosus autograft. The amount of free nerve endings was higher in the semitendinosus and patellar tendon autografts than in the control; the allografts showed the lowest number of receptors. With increasing time after reconstruction, the number of both types of receptors showed a decrease in the semitendinosus graft, whereas it increased in the patellar tendon graft and allograft. The number of mechanoreceptors in the semitendinosus and patellar tendon graft decreased over time after graft-failure, whereas it increased slightly in the allograft. CONCLUSION: This study was the first to identify mechanoreceptors in human transplants of the anterior cruciate ligament. The partial increase in the number of receptors over time after reconstruction could indicate a reinnervation of the grafts.

Long-term arthroscopic assessment of intra-articular allografts for treatment of spontaneous cranial cruciate ligament rupture in the dog.

OBJECTIVE: To assess the 12-month survival of intra-articular, decellularized allografts for the treatment of cranial cruciate ligament disease (CCLD) in dogs. STUDY DESIGN: Prospective case series. ANIMALS: Twenty client-owned dogs with spontaneous CCL rupture. METHODS: Affected stifles were treated solely by implantation of an intra-articular, decellularized, deep digital flexor tendon allograft. Functional outcome was evaluated at baseline and at 6 and 12 months after surgery with the Liverpool Osteoarthritis for Dogs questionnaire and force platform gait analysis. At 12 months after surgery, dogs underwent arthroscopy to visually assess the allografts. RESULTS: Scores on owner questionnaires (improved 62.5%; P = .005) and ground reaction forces (improved 34.4%; P = .017) were improved in all dogs 12 months after surgery. Dogs with an intact graft (IG) were more likely to have a successful outcome compared with dogs with a torn graft (P = .011). According to arthroscopy, 45% of grafts seemed to survive at 12 months after surgery. CONCLUSION: About half of intra-articular allografts survived 12 months after implantation in CCL-deficient stifles. Dogs with IG had successful outcomes at 12 months after surgery according to assessment by force platform gait analysis. CLINICAL SIGNIFICANCE: These results preclude immediate clinical application but provide evidence to justify further investigation of intra-articular grafts as a repair option for CLLD.

Pediatric Anterior Cruciate Ligament Reconstruction.

The increasing incidence of anterior cruciate ligament injuries in skeletally immature children demands careful attention by orthopedic surgeons. Assessing skeletal age is essential to selecting the appropriate reconstruction technique. Males with a bone age of 15 years or older and females of 13 years and older are ideal candidates for a transphyseal anterior cruciate ligament reconstruction because there is minimal risk of growth disturbance. Children with substantial growth remaining (skeletal age males ≤12 years and females ≤10 years) seem to be at risk for more significant growth disturbance, so we generally recommend physeal-sparing techniques for these younger patients.

Abbreviated quantitative UTE imaging in anterior cruciate ligament reconstruction.

BACKGROUND: Existing ultrashort echo time magnetic resonance imaging (UTE MRI) methods require prohibitively long acquisition times (~ 20-40 min) to quantitatively assess the clinically relevant fast decay T2* component in ligaments and tendons. The purpose of this study was to evaluate the feasibility and clinical translatability of a novel abbreviated quantitative UTE MRI paradigm for monitoring graft remodeling after anterior cruciate ligament (ACL) reconstruction. METHODS: Eight patients who had Graftlink™ hamstring autograft reconstruction were recruited for this prospective study. A 3D double-echo UTE sequence at 3.0 Tesla was performed at 3- and 6-months post-surgery. An abbreviated UTE MRI paradigm was established based on numerical simulations and in vivo validation from healthy knees. This proposed approach was used to assess the T2* for fast decay component ([Formula: see text]) and bound water signal fraction (fbw) of ACL graft in regions of interest drawn by a radiologist. RESULTS: Compared to the conventional bi-exponential model, the abbreviated UTE MRI paradigm achieved low relative estimation bias for [Formula: see text] and fbw over a range of clinically relevant values for ACL grafts. A decrease in [Formula: see text] of the intra-articular graft was observed in 7 of the 8 ACL reconstruction patients from 3- to 6-months (- 0.11 ± 0.16 ms, P = 0.10). Increases in [Formula: see text] and fbw from 3- to 6-months were observed in the tibial intra-bone graft ([Formula: see text]: 0.19 ± 0.18 ms, P < 0.05; Δfbw: 4% ± 4%, P < 0.05). Lower [Formula: see text] (- 0.09 ± 0.11 ms, P < 0.05) was observed at 3-months when comparing the intra-bone graft to the graft/bone interface in the femoral tunnel. The same comparisons at the 6-months also yielded relatively lower [Formula: see text] (- 0.09 ± 0.12 ms, P < 0.05). CONCLUSION: The proposed abbreviated 3D UTE MRI paradigm is capable of assessing the ACL graft remodeling process in a clinically translatable acquisition time. Longitudinal changes in [Formula: see text] and fbw of the ACL graft were observed.

The effect of cyclic knee motion on the elongation of four-strand hamstring autograft in anterior cruciate ligament reconstruction: an in-situ pilot study.

BACKGROUND: Pretension of the viscoelastic graft by cyclic knee motion has been confirmed to decrease the graft creep and improve the outcome of anterior cruciate ligament (ACL) reconstruction. The purpose of the present study was to investigate the effect of cyclic knee motion on the elongation of the four-strand hamstring tendon autograft in situ and to explore the stable level cycle, in which the tendon length achieved a stable level. METHODS: The study was performed with 53 consecutive patients undergoing transtibial ACL reconstruction with four strand hamstring tendon from Aug 2013 to Apr 2015. 43 males and 10 females were included with mean age of 29 ± 10 years. The pretension of the tendons was operated by cyclical knee motion ranging from 0 to 110°after the femoral fixation with Endo-button. The tendon length after 10, 20, 30 and 40 cycles was measured respectively and compared by repeated measure ANOVA. Then multivariate logistic regression was used to investigate the effect of the patients' parameters (age, gender, height, body weight, tendon length, etc.) on the elongation of the graft and the stable level cycle. RESULTS: The mean lengthening of the graft at 10, 20, 30 and 40 times was 3.0 ± 1.4 mm, 4.3 ± 1.5 mm, 4.8 ± 1.7 mm and 4.8 ± 1.8 mm respectively. No significant correlation was found between the elongation and the patients' parameters. There was significant difference of the tendon length from 0 to 30 cycles (F = 264.8, df = 1.95, p<0.001). However, the tendon length achieved a stable level after 30 cycles and the median elongation from 30 cycles to 40 cycles was 0 (0-1) mm with no significant difference (F = 2.039, p = 0.159). The male and female tendon length achieved to a stable level at 20 cycles and 30 cycles respectively but with no significant difference (p = 0.074). CONCLUSIONS: The four-strand hamstring tendon was elongated after cyclic knee motion and the elongation achieved a stable level after 30 cycles for the transtibial technique. Both of the tendon elongation and the stable level cycle were not correlated with patients' gender, age, preoperative duration, graft diameter and length.

Early weight-bearing after anterior cruciate ligament reconstruction with hamstring grafts induce femoral bone tunnel enlargement: a prospective clinical and radiographic study.

BACKGROUND: Bone tunnel enlargement following primary anterior cruciate ligament (ACL) reconstruction with soft tissue graft might be a severe disadvantage for revision surgery. The postoperative rehabilitation protocol including the non-weight-bearing periods were different depending on the surgeon or institute. To determine the relationship between femoral bone tunnel enlargement and the postoperative non-weight-bearing period after double-bundle ACL reconstruction with hamstring grafts. METHODS: Forty-two patients who underwent primary double-bundle ACL reconstruction with hamstring grafts were divided into two postoperative non-weight-bearing protocol groups: 1-week non-weight-bearing postoperatively (group A, n = 19); and 2-week non-weight-bearing (group B, n = 18). Five cases were excluded due to additional knee injury, pregnancy, and lost to follow-up. Bone tunnel enlargement was evaluated by computed digital radiographs (anteroposterior (A-P) and lateral views) taken on the first postoperative day and at 12 months. Each tunnel diameter was shown as a percentage to the maximum joint width of the proximal tibia in the A-P view, or a percentage of the maximum diameter of the patella in the lateral view. To determine the incidence of tunnel enlargement, percentage diameter changes of more than 10% were defined as an enlarged tunnel. The magnitude of tunnel enlargement and the standard clinical evaluation were also evaluated. RESULTS: There were no significant differences between groups in the incidences of anteromedial and posterolateral bone tunnel enlargement, both in the A-P and lateral views (2 × 2 Chi-squared test). The magnitude of femoral posterolateral bone tunnel enlargement was significantly greater in group A in the A-P view (p = 0.01) and lateral view (p = 0.03) (Mann Whitney U-test). Twelve months after surgery, the Lysholm score and Tegner activity level scale were not significantly different between the groups. CONCLUSIONS: This prospective, clinical and radiographical study showed that early weight-bearing protocol after double-bundle ACL reconstruction with hamstring grafts might have the potential risk of significant postoperative femoral bone tunnel enlargement of the posterolateral bundle. There was no significant difference in clinical outcomes by postoperative non-weight-bearing period. To reduce and prevent the femoral bone tunnel enlargement, the comprehensive management could be considered and required to establish the suitable early stage rehabilitation protocol after surgery. TRIAL REGISTRATION: Trial registration number; UMIN000036212 . Scientific title: Prospective comparisons of femoral tunnel enlargement with two different postoperative non weight bearing periods after double-bundle anterior cruciate ligament reconstruction with hamstring grafts. Registered date: 15 Mar 2019 (retrospectively registered).

The Stability study: a protocol for a multicenter randomized clinical trial comparing anterior cruciate ligament reconstruction with and without Lateral Extra-articular Tenodesis in individuals who are at high risk of graft failure.

BACKGROUND: The purpose of anterior cruciate ligament reconstruction (ACLR) is to restore stability to the knee. Persistent rotational laxity following ACLR has been correlated with poor outcome and graft failure. We hypothesize that anterolateral complex reconstruction by way of a Modified Lemaire Lateral Extra-articular Tenodesis (LET) in combination with single bundle ACLR would reduce the risk of persistent rotatory laxity in young individuals who are deemed as being at high risk of failure. We will conduct a pragmatic, multicenter, randomized clinical trial comparing standard single bundle hamstring ACLR with combined ACLR and LET. METHODS: Six-hundred patients (300 per group) aged 25 years or less with an ACL deficient knee that meet two of the following three criteria will be included: 1) Grade 2 pivot shift or greater; 2) Returning to high risk cutting or pivoting sports; 3) Generalized ligamentous laxity. Participants will be seen at 3-months, 6-months, 12-months and 24-months post-operatively. The primary outcome measure is graft failure requiring revision ACLR or symptomatic instability associated with a positive asymmetric pivot shift indicating persistent rotational laxity. Patients will complete secondary outcome measures at each follow-up visit including patient-reported outcome measures, functional and biomechanical testing, and magnetic resonance imaging. DISCUSSION: This protocol is the first adequately powered randomized clinical trial investigating the effects of augmenting ACLR with an LET in patients at high-risk of graft failure. The successful completion of this trial has the potential to change surgical practice and provide evidence for the role of the LET in ACLR. TRIAL REGISTRATION: The trial is registered at ClinicalTrials.gov: NCT02018354 , 23-12-2013.

Development of fibrocartilage layers in the anterior cruciate ligament insertion in rabbits.

BACKGROUND: A detailed evaluation focusing on the fibrocartilage layers in the anterior cruciate ligament (ACL) insertion is necessary to consider regeneration of the insertion. This study examined the development of the fibrocartilage layers in the ACL tibial insertion in rabbits by quantitative morphometric evaluations based on histological and immunohistochemical analyses. METHODS: Male Japanese white rabbits were used because of their history of use for histomorphometric analyses of the ACL insertion and to eliminate the influence of female hormones on the ACL. Six animals were euthanized at each age (1 day and 1, 2, 4, 6, 8, 12, and 24 weeks); in total, 48 animals were used. Proliferation rate, apoptosis rate, Sox9-positive rate, and chondrocyte number were evaluated. Safranin O-stained glycosaminoglycan (GAG) areas, tidemark length, ACL insertion width, and ACL length were also evaluated. All parameters were compared with those at age 24 weeks of age. RESULTS: High levels of chondrocyte proliferation and Sox9 expression continued until 4 and 8 weeks of age, respectively, and then gradually decreased. Chondrocyte apoptosis increased up to 8 weeks. The chondrocyte number, ACL insertion width, ACL length, safranin O-stained GAG areas, and tidemark length gradually increased up to 12 weeks. CONCLUSION: Chondrocytes that displayed chondrocyte proliferation and Sox9 expression increased until 12 weeks of age, in accordance with development of the ACL length and its insertion width. The GAG production and tidemark length also increased until 12 weeks of age. The development of fibrocartilage layers in the ACL insertion was complete at 12 weeks of age.

Identification and Characterization of Canine Ligament Progenitor Cells and Their Extracellular Matrix Niche.

Ligaments are prone to injury and degeneration in humans and animals, however the healing potential of ligament is poor and current treatment options ineffective. Stem cell-based therapies hold potential for treatment of ligament injuries. This study aimed to characterize a ligament progenitor cell (LPC) population and to identify specific niche components which could promote the survival and function of LPCs. LPCs were isolated from canine cranial cruciate ligament and characterized for clonogenicity, multipotency and marker expression. The extracellular matrix (ECM) composition was characterized by the novel application of a metabolic labeling and mass spectrometry technique. LPCs demonstrated clonogenicity, multipotency, and stem cell marker expression. A number of different collagens, glycoproteins, and proteoglycans were identified in the LPC niche using proteomics. Metabolic labeling of cells demonstrated unique turnover profiles for distinct ECM protein groups, indicating the importance of certain niche components for LPC survival and function. The newly synthesized niche components identified in this study could be exploited to aid identification of LPCs and to promote their survival and function for potential ligament repair strategies.

Anterior Cruciate Ligament Reconstruction.

The past 3+ decades have been a period of intense interest in the anterior cruciate ligament. Graft choices, techniques, and fixation devices have all evolved. Our understanding of the anatomy has improved. Our follow-up and criteria for success have also expanded. Over the next several years advanced repair techniques, extra-articular augmentation, and addressing elevated tibial slope will all have to have their indications defined.