Cruciate Ligament Replacement Research Articles

The effect of sterilization and storage on the viscoelastic properties of human tendon allografts – Continued: Storage for 0 to 4 months

The role of donor-derived tendons, also known as allografts, in anterior cruciate ligament replacement surgeries is steadily increasing. Before surgery, temporary storage and, in most cases, sterilization are essential. It is, thus, crucial to determine how these procedures alter the grafts’ biomechanical properties. The purpose of this research was to analyze the effect of different sterilization methods (native, frozen, frozen + 21 kGy gamma irradiation, frozen + 21 kGy electron beam irradiation) and storage durations (0 to 4 months) on the deformation and creep of two tendon types (tibialis anterior, peroneus longus). 80 tibialis anterior and 83 peroneus longus tendons from 51 human cadavers were included. The samples were removed, placed in a radio-cryoprotectant solution, then slowly cooled, sterilized and stored at −80 °C. All groups were subject to 60 s static creep test with 250 N load. Deformation during the loading phase, creep during static loading, and the ratio of these two were evaluated.Deformation at the end of the loading phase and creep consistently exhibited significantly smaller values in the tibialis anterior compared to the peroneus longus type, as well as in electron beam-sterilized grafts as opposed to gamma beam-sterilized ones. Prolonged storage periods (within 0 to 4 months) resulted in a notable increase in these values, particularly in deformation. Based on the experimental data, the tibialis anterior tendon type and sterilization by gamma beam irradiation are better choices for anterior cruciate ligament reconstruction than the peroneus longus and sterilization by electron beam. Increased storage time affects negatively the evaluated mechanical properties.

Hierarchical helical carbon nanotube fibre as a bone-integrating anterior cruciate ligament replacement.

High rates of ligament damage require replacements; however, current synthetic materials have issues with bone integration leading to implant failure. Here we introduce an artificial ligament that has the required mechanical properties and can integrate with the host bone and restore movement in animals. The ligament is assembled from aligned carbon nanotubes formed into hierarchical helical fibres bearing nanometre and micrometre channels. Osseointegration of the artificial ligament is observed in an anterior cruciate ligament replacement model where clinical polymer controls showed bone resorption. A higher pull-out force is found after a 13-week implantation in rabbit and ovine models, and animals can run and jump normally. The long-term safety of the artificial ligament is demonstrated, and the pathways involved in integration are studied.

Characterisation of native and decellularised porcine tendon under tension and compression: A closer look at glycosaminoglycan contribution to tendon mechanics

Decellularised porcine superflexor tendon (pSFT) has been characterised as a suitable scaffold for anterior cruciate ligament replacement, with dimensions similar to hamstring tendon autograft. However, decellularisation of tissues may reduce or damage extracellular matrix components, leading to undesirable biomechanical changes at a whole tissue scale. Although the role of collagen in tendons is well established, the mechanical contribution of glycosaminoglycans (GAGs) is less evident and could be altered by the decellularisation process. In this study, the contribution of GAGs to the tensile and compressive mechanical properties of pSFT was determined and whether decellularisation affected these properties by reducing GAG content or functionality.PSFTs were either enzymatically treated using chondroitinase ABC to remove GAGs or decellularised using previously established methods. Native, GAG-depleted and decellularised pSFT groups were then subjected to quantitative assays and biomechanical characterisation. In tension, specimens underwent stress relaxation and strength testing. In compression, specimens underwent confined compression testing.The GAG-depleted group was found to have circa 86% reduction of GAG content compared to native and decellularised groups. There was no significant difference in GAG content between native (3.75 ± 0.58 μg/mg) and decellularised (3.40 ± 0.37 μg/mg) groups. Stress relaxation testing discovered the time-independent and time-dependent relaxation moduli of the decellularised group were reduced ≥50% compared to native and GAG-depleted groups. However, viscoelastic behaviour of native and GAG-depleted groups resulted similar. Strength testing discovered no differences between native and GAG-depleted group's properties, albeit a reduction ∼20% for decellularised specimens' linear modulus and tensile strength compared to native tissue. In compression testing, the aggregate modulus was found to be circa 74% lower in the GAG-depleted group than the native and decellularised groups, while the zero-strain permeability was significantly higher in the GAG-depleted group (0.86 ± 0.65 mm4/N) than the decellularised group (0.03 ± 0.04 mm4/N).The results indicate that GAGs may significantly contribute to the mechanical properties of pSFT in compression, but not in tension. Furthermore, the content and function of GAGs in pSFTs are unaffected by decellularisation and the mechanical properties of the tissue remain comparable to native tissue.

Influence of Anaesthesia on Harvesting the Semitendinosus Tendon for Anterior Cruciate Ligament Replacement.

Aim The aim of the study was to investigate if the mode of anesthesia is a relevant factor influencing the length of the semitendinosus tendon harvested for anterior cruciate ligament (ACL) replacement. Methods Patients undergoing ACL replacement were given the choice between spinal and general anesthesia. If general anesthesia was chosen, a short relaxation period was applied while harvesting the Semitendinosus (ST) tendon. The data for tendon length, the folding factor, and the diameter of the graft were collected. Except for redo procedures and ACL replacement with allograft all patients undergoing an ACL replacement were enrolled. Results Thirty-one patients with general anesthesia (GA) and 14 patients with spinal anesthesia (SA) were examined. The ST tendon length was 29.03 cm ± 2.6 cm in the GA group and 25.4 cm ± 2.70 in the SA group(t value 4.245, p=0.0001). The ST tendon could be quadrupled in 23 patients in the GA and 6 patients in the SA group (χ2=4.13, p=0.04). The graft diameter obtained was 8.53 mm ± 0.62 mm in the GA group and 7.71 mm ± 0.47 mm in the SA group (t value 4.885, p<0.0001). Conclusion General anesthesia with short-time relaxation while harvesting the ST tendon for ACL grafting allows to harvestlonger ST tendons and consequently yields better results regarding the graft dimensions and should be offered to patients as a first-choice procedure. There is no other paper published yet, analyzing this relationship and if validated on a larger cohort, this might change clinical practice.

Outcome of cranial cruciate ligament replacement with an enhanced polyethylene terephthalate implant in the dog: A pilot clinical trial.

To assess the 6-month outcome and survival of enhanced polyethylene terephthalate (PET) implants as a replacement for the cranial cruciate ligament (CCL) in dogs with spontaneous CCL disease (CCLD). Pilot, prospective case series. Ten client-owned large breed dogs with unilateral spontaneous CCLD. Dogs were evaluated before and 6months after intra-articular placement of a PET implant with the Liverpool Osteoarthritis in Dogs questionnaire and force platform gait analysis. Arthroscopy was performed 6months after surgery to visually assess implant integrity. Scores on owner questionnaires and limb asymmetry improved in all dogs that reached the 6-month time point, by 51.7% (p=.008) and 86% (p=.002), respectively. The PET implant appeared intact and functioning in two stifles, partially intact and functioning in four stifles and completely torn in three stifles. One dog had an implant infection and was removed from the study. Evidence of deterioration and tearing occurred in the midbody of the implant. Although function improved over the course of this study, only 2/10 implants appeared intact 6months after placement. Implant survivability prohibits further clinical investigation using this implant.

Bioinspired Silk Fibroin-Based Composite Grafts as Bone Tunnel Fillers for Anterior Cruciate Ligament Reconstruction.

Anterior cruciate ligament (ACL) replacement is still a big challenge in orthopedics due to the need to develop bioinspired implants that can mimic the complexity of bone-ligament interface. In this study, we propose biomimetic composite tubular grafts (CTGs) made of horseradish peroxidase (HRP)-cross-linked silk fibroin (SF) hydrogels containing ZnSr-doped β-tricalcium phosphate (ZnSr-β-TCP) particles, as promising bone tunnel fillers to be used in ACL grafts (ACLGs) implantation. For comparative purposes, plain HRP-cross-linked SF hydrogels (PTGs) were fabricated. Sonication and freeze-drying methodologies capable of inducing crystalline β-sheet conformation were carried out to produce both the CTGs and PTGs. A homogeneous microstructure was achieved from microporous to nanoporous scales. The mechanical properties were dependent on the inorganic powder’s incorporation, with a superior tensile modulus observed on the CTGs (12.05 ± 1.03 MPa) as compared to the PTGs (5.30 ± 0.93 MPa). The CTGs presented adequate swelling properties to fill the space in the bone structure after bone tunnel enlargement and provide a stable degradation profile under low concentration of protease XIV. The in vitro studies revealed that SaOs-2 cells adhered, proliferated and remained viable when cultured into the CTGs. In addition, the bioactive CTGs supported the osteogenic activity of cells in terms of alkaline phosphatase (ALP) production, activity, and relative gene expression of osteogenic-related markers. Therefore, this study is the first evidence that the developed CTGs hold adequate structural, chemical, and biological properties to be used as bone tunnel fillers capable of connecting to the ACL tissue while stimulating bone tissue regeneration for a faster osteointegration.

Melt-Spun, Cross-Section Modified Polycaprolactone Fibers for Use in Tendon and Ligament Tissue Engineering

Tissue Engineering is considered a promising route to address existing deficits of autografts and permanent synthetic prostheses for tendons and ligaments. However, the requirements placed on the scaffold material are manifold and include mechanical, biological and degradation-related aspects. In addition, scalable processes and FDA-approved materials should be applied to ensure the transfer into clinical practice. To accommodate these aspects, this work focuses on the high-scale fabrication of high-strength and highly oriented polycaprolactone (PCL) fibers with adjustable cross-sectional geometry and degradation kinetics applying melt spinning technology. Four different fiber cross-sections were investigated to account for potential functionalization and cell growth guidance. Mechanical properties and crystallinity were studied for a 24-week exposure to phosphate-buffered saline (PBS) at 37 °C. PCL fibers were further processed into scaffolds using multistage circular braiding with three different hierarchical structures. One structure was selected based on its morphology and scaled up in thickness to match the requirements for a human anterior cruciate ligament (ACL) replacement. Applying a broad range of draw ratios (up to DR9.25), high-strength PCL fibers with excellent tensile strength (up to 69 cN/tex) could be readily fabricated. The strength retention after 24 weeks in PBS at 37 °C was 83–93%. The following braiding procedure did not affect the scaffolds’ mechanical properties as long as the number of filaments and the braiding angle remained constant. Up-scaled PCL scaffolds resisted loads of up to 4353.88 ± 37.30 N, whilst matching the stiffness of the human ACL (111–396 N/mm). In conclusion, this work demonstrates the fabrication of highly oriented PCL fibers with excellent mechanical properties. The created fibers represent a promising building block that can be further processed into versatile textile implants for tissue engineering and regenerative medicine.

Role of Anthropometric Data in Assessing Hamstring Graft Size in Anterior Cruciate Ligament Reconstruction

Background and Objective: Preoperative information of hamstring graft size for anterior cruciate ligament reconstruction (ACL) is critical for making optimal graft selections. The aim of the present study was to view whether anthropometric parameters including height, weight, BMI and thigh circumference have any bearing on the size of hamstring tendon grafts used in anterior cruciate ligament replacement.&#x0D; Methods: Pre-operative anthropometric measurements were taken on 72 patients undergoing primary ACL reconstruction, including age, gender, height, weight, BMI, and thigh circumference. The Person correlation coefficient was used to assess the correlation of these anthropometric variables and simple logistic regression was used to evaluate the correlation of these anthropometric variables on the size of the graft that was acquired.&#x0D; Results: Gracilis tendon [GT] length correlates with height (r 1/4 0,432), and semitendinosus [ST] length correlates with thigh circumference (r 1/4 0,255). Women's graft diameter (7.16 ± 0.82 mm) smaller than that of men (7.39 ± 0.63 mm) (p &gt; 0.05), although not statistically significant. The diameter of the autograft was shown to be strongly linked with parameters.&#x0D; Conclusion: As a consequence, our findings suggest that anthropometric measures can be used in the preoperative planning and prediction of hamstring graft length and diameter in anterior cruciate ligament reconstruction.

Assessment of sheep knee joint after ACL replacement with Achilles tendon autograft and PLA-based implant

In this study, we propose a new approach in the anterior cruciate ligament (ACL) replacement to provide stability and integration with bone tunnel. A polylactide (PLA)-based tubular implant was used to support the graft stabilization in femoral and tibial bones and to stimulate the healing process after (ACL) replacement on a sheep model. The ACL was replaced with an autologous Achilles tendon split graft. The tendon-to-bone healing in the model was analyzed after 6 and 12 weeks. Two groups of animals were compared, i.e. the group with the PLA-based implant used in the ACL replacement and the control group without the implant. The knee joints were mechanically and clinically evaluated, including the histopathology tests, to determine their stability and integrity. The results indicated that the bioresorbable PLA-based tubular implant may facilitate integration of the tendon graft with bone. Remodeling the allograft inside the implant improves the joint mobility from the first week of healing: no pathological changes were observed at the surgery site and in the animals’ mobility. After 6 and 12 weeks of healing no significant changes in the mechanical parameters of the knee joint were observed, regarding the joint failure force, knee displacement, angular mobility range and joint stiffness. Relatively small values of the non-destructive tests in the knee displacement, already 6 weeks after surgery, indicated the early stabilization of the knee joint. The studies showed that the failure forces of knee joints after the ACL replacement with the PLA-based implant are lower than those of an intact joint, although their biomechanical features, including strain-at- failure, are similar.The biomechanical parameters of the knee joint were significantly improved due to the selected method of attaching the autograft ends to the femoral and tibial bone surfaces. After 12 weeks the intra-tunnel tendon-bone site with the PLA implant revealed the better tibia-femur joint mechanical stability, linear force-strain function and the decreasing strain-to-failure value, as compared to the control group.

The effect of sterilization and storage on the viscoelastic properties of human tendon allografts

Allografts have become increasingly preferred for anterior cruciate ligament replacement purposes. The risk of infections necessitates thorough sterilization procedures, and the allografts usually need to be stored prior to surgery. Classical mechanical tests have been performed with various types of tendons, however, tibialis anterior and peroneus longus tend to suffer the least biomechanical changes after irradiation. Only few results are available of the strain and creep behaviour of tendons, even though this information is necessary to provide suitable allografts. The aim of the present study is to analyze the effect of different tendon types (T-tibialis anterior, P-peroneus longus), sterilization methods (G-gamma irradiation of 21 kGy, E-electron beam irradiation of 21 kGy) and storage times (5 and 6 months) on the creep behavior, which is characterized by the strain at the end of the loading phase and creep deformation after static loading. Static creep tests were performed with 250 N load during 60 s. Deformation at the end of the loading phase of both tendons was significantly smaller after 5 months long storage than that after 6 months long storage. TE5 showed significantly less creep than group TE6, and TE6 significantly greater than PE6. The creep of TE5 was significantly lower than that of TG5. Based on the data, the peroneus longus sterilized by electron beam and stored deep frozen for 5 months is a better choice for anterior cruciate ligament reconstruction than tibialis anterior sterilized by gamma irradiation stored for 6 months.

Synthesis of silver @hydroxyapatite nanoparticles based biocomposite and their assessment for viability of Osseointegration for rabbit knee joint anterior cruciate ligament rehabilitation

In this examination, chitosan-silk fibroin/polyethylene terephthalate (CTS-SF/PET), chitosan-silk fibroin/polyethylene terephthalate/hydroxyapatite (CTS-SF/PET/HAP) and chitosan-silk fibroin/polyethylene terephthalate/Silver @hydroxyapatite (CTS-SF/PET/Ag@HAP) scaffolds were prepared by utilizing the plasma splashing procedure. Field emission scanning electron microscopy (FESEM) results demonstrated that the outside of the PET covered with HAP nanoparticles. The cell viability results demonstrated that the number of Mesenchymal stem cells (MSCs) primarily spread out on CTS-SF/PET/Ag@HAP. RT-PCR results demonstrated that there was an upregulated mRNA articulation of osseous development-related properties in the CTS-SF/PET/Ag@HAP composite. The in vivo rabbit animal assessment scores of the CTS-SF/PET/Ag@HAP composite were significantly better than those of the CTS-SF/PET at 1 to 3 months. Both in-vivo and in-vitro results exhibited in this investigation recommend that the cytocompatibility and osseointegration of CTS-SF/PET/Ag@HAP tendon were fundamentally improved by expanding the multiplication of cells and up-regulating the outflow of tendon development-related properties. In conclusion, the CTS-SF/PET/Ag@HAP tendon is a promising candidate for Anterior Cruciate Ligament (ACL) replacement in the future.

GRAFT CHOICE FOR ADOLESCENT ATHLETES RETURNING TO HIGH-RISK SPORTS: A MATCHED COHORT ANALYSIS OF PATELLAR TENDON AND HAMSTRING AUTOGRAFTS

Background: Graft selection for skeletally mature adolescents undergoing anterior cruciate ligament (ACL) reconstruction is guided by surgeon and patient preference. In young patients returning to high-risk cutting and pivoting sports, graft rupture is the most feared complication of ACL reconstruction. Some studies have demonstrated slightly lower rates of graft failure and decreased laxity in the short term associated with patellar tendon (BTB) autografts as compared to hamstring (HS) autografts, but these studies are limited by their heterogeneity of ages and activity level1-3. The purpose of this study is to compare the rates of graft failure between BTB and HS ACL reconstruction cohorts matched by age, sex, and sport. Methods: A single-institution retrospective review was performed of consecutive patients less than 19 years of age treated with ACL reconstructions using either patellar tendon (BTB) or hamstring (HS) autograft performed by a single surgeon. Skeletally mature or nearly mature patients in “high-risk” ACL injury sports (basketball, football, soccer, lacrosse, and gymnastics) were initially treated with hamstring autografts but the graft preference transitioned to BTB autografts as the preferred graft choice during the study period. This transition in graft preference for adolescents participating in “high risk” sports allows for a comparison of outcomes based on graft types. Inclusion criteria were ages 13 – 18 years, participation in a “high risk” sport, and minimum 6-month follow-up. The two cohorts of patients were matched by age, gender, and sport. The primary outcome measure was graft rupture. Results: One hundred fifty-two patients with an average age of 16 years (range 13 – 18 years) underwent ACL reconstruction during the study period. There were 71 BTB reconstructions and 81 HS reconstructions. There were 64 females and 88 males. There was no difference in age, sex, BMI, or laterality between groups. There were more patients who played soccer in the BTB cohort (44%) vs HS cohort (20%) and fewer who played basketball in the BTB cohort (24%) vs HS cohort (41%), p = 0.005. There were no differences between the BTB and HS cohorts in terms of meniscus tears (61% v 72%, p = 0.15), meniscus repair (21% v 32%, p = 0.13), or partial meniscectomy (32% v 33%, p = 0.90). Mean duration of follow-up was 28 months (range 7-57 months). There was no difference in follow-up between cohorts (BTB 28 months and HS 29 months, p = 0.19). There were a total of 16 graft ruptures (10.5%). There was no difference in the rate of graft rupture between cohorts (BTB 8.5% vs HS 12.3%, p = 0.60). Mean time to graft rupture was 21 months (range 8 – 35 months) and Kaplan-Meier survival curves demonstrated no difference between cohorts. Conclusions: ACL reconstruction in adolescents returning to high-risk sports can be performed utilizing BTB or HS autografts with similar rates of graft rupture. There is a trend toward lower rates of graft rupture associated with BTB autografts, but additional patients will be necessary to determine if this trend will become a statistically significant difference. Beynnon BD, Johnson RJ, Fleming BC, et al. Anterior cruciate ligament replacement: comparison of bone-patellar tendon bone grafts with two-strand hamstring grafts. A prospective, randomized study. J Bone Joint Surg Am 2002;84(9):1503-1513. Ho B, Edmonds EW, Chambers HG et al. Risk factors for early ACL reconstruction failure in pediatric and adolescent patients: a review of 561 cases. J Pediatr Orthop 2016. Samuelsen BT, Webster KE, Johnson NR, et al. Hamstring autograft versus patellar tendon autograft for ACL reconstruction: is there a difference in graft failure rate? A meta-analysis of 47,613 patients. Clin Orthop Relat Res 2017;475(10):2459-2468.

Decellularisation affects the strain rate dependent and dynamic mechanical properties of a xenogeneic tendon intended for anterior cruciate ligament replacement

Development of new replacement grafts for anterior cruciate ligament (ACL) repair requires mechanical testing to ensure they can provide joint stability following implantation. A decellularised porcine superflexor tendon (pSFT) has been developed previously as an alternative to current reconstruction methods and subjected to biomechanical analysis. The application of varied strain rates to biological tissues is known to alter their biomechanical properties, however the effects of decellularisation on strain rate dependent and dynamic mechanical behaviour of tissues have not been explored. This study utilised tensile testing to investigate the material properties of native and decellularised pSFTs at three different strain rates (1%.s−1, 10%.s−1 and 100%.s−1). In addition, dynamic mechanical analysis (DMA) was used to ascertain the relative contributions of the solid and fluid phase components of the tissues.Ultimate tensile strength was significantly reduced in decellularised compared with native untreated pSFTs but was unaffected by strain rate. In contrast, toe region moduli increased with increasing strain rate for native tissues, but this effect was not observed in decellularised pSFTs. Linear region moduli were unaffected by strain rate, but were significantly reduced in decellularised pSFT compared with native tissue.Following DMA, significant reductions in dynamic modulus, storage modulus and loss modulus were seen in decellularised compared with native pSFT. Interestingly, the damping ability of the tendons was unaffected by decellularisation, suggesting that solid and fluid phases of the tissue were affected equally. These results, alongside previous studies, suggest that decellularisation affects collagen crimp, tissue swelling and collagen fibre sliding. However, despite these findings, the biomechanical properties of decellularised pSFT remain sufficient to act as an off-the-shelf solution for ACL reconstruction.

Feasibility Study of the Elaboration of a Biodegradable and Bioactive Ligament Made of Poly(ε-caprolactone)-pNaSS Grafted Fibers for the Reconstruction of Anterior Cruciate Ligament: In Vivo Experiment

BackgroundThe anterior cruciate ligament rupture is a common injury which mainly affects young and active population. Faced to this problem, the development of synthetic structures for ligament reconstruction is increasing. The most recent researches focused on the development of biodegradable structures that could be functionalized to enhance host integration. This work describes the elaboration of different poly(ε-caprolactone) prototypes for the rat anterior cruciate ligament replacement in order to found the best design for further in vivo assays. MethodsAccording to the literature, it was decided to elaborate two different poly(ε-caprolactone) prototypes: a braided one and a free-fibers one. A chemical grafting of a bioactive polymer–poly(sodium styrene sulfonate) – was performed on both prototypes and mechanical and biological testing were assessed. Based on these results, one rat was implanted with the best prototype. ResultsThe mechanical and biological results demonstrated that the best prototype to implant was the poly(sodium styrene sulfonate)-grafted braided prototype. After one-month implantation, no inflammation was observable around the scar. The rat demonstrated good flexion and extension of the lower limb without any anterior drawer. The prototype was highly anchored to the bone. ESEM images of the explanted prototype showed the presence of cells and tissue ingrowth along and around the fibers. ConclusionThis work demonstrates the feasibility to implant a bioactive and biodegradable synthetic ligament in the rat model without any inflammation and with a good tissue anchoring at a short-term time. This will lead to an extensive in vivo assay.

Biomechanical considerations are crucial for the success of tendon and meniscus allograft integration—a systematic review

This systematic review intends to give an overview of the current knowledge on how allografts used for the reconstruction of cruciate ligaments and menisci are integrated and specifically perform regarding their biomechanical function. Two reviewers reviewed the PubMed and Central Cochrane library with focus on the biomechanical integration of tendon ligament and meniscus allografts. The literature search was conducted in accordance with the PRISMA statement for reporting systematic reviews and meta-analyses. The analysed literature on tendon allografts shows that they are more vulnerable to overstretching in the phase of degradation compared to autografts as the revascularization process starts later and takes longer. Therefore, to avoid excessive graft loads, allografts for cruciate ligament replacement should be selected that exhibit much higher failure loads than the native ligaments to counteract the detrimental effect of degradation. Further, placement techniques should be considered that result in a minimum of strain differences during knee joint motion, which is best achieved by near-isometric placement. The most important biomechanical parameters for meniscus allograft transplantation are secure fixation and proper graft sizing. Allograft attachment by bone plugs or by a bone block is superior to circumferential suturing and enables the allograft to restore the chondroprotective biomechanical function. Graft sizing is also of major relevance, because too small grafts are not able to compensate the knee joint incongruity and too large grafts may fail due to extrusion. Only adequate sizing and fixation together can lead to a biomechanically functioning allograft. The objective assessment of the biomechanical quality of allografts in a clinical setting is challenging, but would be highly desirable for monitoring the remodelling and incorporation process. Currently, indicators like ap-stability after ACL reconstruction or meniscal extrusion represent only indirect measures for biomechanical graft integration. These parameters are at best clinical indicators of allograft function, but the overall integration properties comprising e.g. fixation and graft stiffness remain unknown. Therefore, future research should e.g. focus on advanced imaging techniques or other non-invasive methods allowing for in vivo assessment of biomechanical allograft properties.

What are the factors to affect outcome and healing of meniscus bucket handle tears?

The purpose of this study is to identify patient, meniscus rupture and surgical characteristics that influence the outcome and clinical healing following operative repair of bucket handle tears. Between 02/2006 and 10/2012, a total of 38 patients (14 women, 24 men) with bucket handle tears underwent surgical meniscus repair. There were 27 isolated repairs and 11 with concomitant anterior cruciate ligament (ACL) replacement. Patients were analyzed on an average of 44.4months (range 15-96months) after surgery by the use of standardized subjective scoring instruments [Lysholm, International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner Activity Scale (TAS)]. To identify factors affecting the outcome and suture survival, patient-specific, trauma-specific as well as meniscus- and surgery-specific factors were collected. Patients were divided in two groups with healed menisci (group 1) and re-rupture subjects (group 2). Meniscus re-rupture was defined as a clinical failure. There were 25 patients with healed menisci and 13 (34.2%) that sustained re-rupture and underwent either partial meniscectomy (n = 8) or re-suture (n = 5). Group 1 achieved slightly higher outcome compared to group 2 [Lysholm: 87.8 vs. 84.3 (p = 0.35), IKDC: 86.9 vs. 85.7 (p = 0.67), KOOS: 91.3 vs. 90.5 (p = 0.74)]. TAS was better for group 2 [5.9 vs. 6.8 (p = 0.36)]. Strong impact to result in a significantly increased outcome was identified for higher age, subjective knee joint stability, high preoperative Lysholm Score, short trauma-to-repair time, previous ACL reconstruction and a smaller number of sutures to fulfill meniscus repair. Lower patient age, male gender and higher activity level had the strongest impact to provoke re-rupture. Clinical outcome after meniscus bucket handle suture is satisfying. Re-rupture rate among this collective was 34.2%. Clear risk factors were identified for diminished clinical healing and outcome.

Transient Scleraxis Overexpression Combined with Cyclic Strain Enhances Ligament Cell Differentiation.

Efforts to generate tissue-engineered anterior cruciate ligament replacements are limited by a lack of methods to derive mature ligament cells. Viral overexpression of the tendon/ligament marker scleraxis (Scx) can drive cell differentiation; however, the use of viral vectors hampers translation to clinical use. In this study, C3H10T1/2 cells were transiently transfected with expression vectors containing the full-length murine Scx cDNA and cultured in three-dimensional collagen hydrogels under static or cyclic strain for up to 14 days. β-galactosidase (LacZ) transfected cells served as controls. Cell morphology and gene expression for ligament-related genes, in addition to contraction (hydrogel width), mechanical properties, and glycosaminoglycan (GAG) and DNA content of hydrogels, were quantified and compared over time, between Scx and LacZ groups, and between static and cyclically strained constructs. Increased Scx expression was maintained for the entire 14-day study in both static and cyclically strained constructs. In static culture, overexpression of Scx resulted in greater cell elongation and construct contraction compared to LacZ controls. There were no differences in gene expression, DNA, or GAG content between Scx and LacZ constructs cultured under static conditions and no differences in DNA content between Scx and LacZ constructs. When exposed to cyclic strain, Scx-overexpressing cells maintained the elongated phenotype exhibited in static constructs, increased GAG production compared to static culture, and increased expression of the ligament-related genes collagen type I, decorin, and tenascin-C compared to strained LacZ controls. Cyclically strained constructs containing Scx-overexpressing cells had increased maximum load and stiffness compared to LacZ controls. The maintenance of increased Scx expression throughout the 14 day study and subsequent increases in ligament marker gene expression and mechanical properties with cyclic, but not static strain, suggest that transient transfection may be a viable alternative to viral transduction of Scx for ligament engineering studies and support a synergistic effect of Scx and mechanical strain on driving early ligament cell differentiation.

In vivo heterotopic culturing of prefabricated tendon grafts with mechanical stimulation in a sheep model

BackgroundThe goal of this study is to investigate the biomechanical and histological properties of in vivo heterotopically prefabricated cruciate ligament replacement grafts with and without mechanical stimulation. The clinical goal is to heterotopically prefabricate a bone–tendon–bone graft for anterior cruciate ligament reconstruction, which allows rapid ingrowth and early full weight bearing. MethodsIn a sheep model, eight quadriceps tendon grafts were harvested and introduced into culture chambers at their proximal and distal ends. In group S, four tendon-chamber constructs were mechanically stimulated by direct attachment to the quadriceps tendon and patella. In group NS, the same constructs were cultured without proximal attachment. All sheep were sacrificed six weeks postoperatively and the constructs were examined biomechanically and histologically. The healthy contralateral ACL and quadriceps tendon were used as controls. ResultsMacroscopically, no obvious ossification could be observed at the ends of the tendon-chamber constructs six weeks postoperatively. Histologically, the tendon tissue from the mechanically stimulated constructs revealed higher counts of cells and capillaries. However, there was less regular cell distribution and collagen fiber orientation compared to the control group. In addition, osteoblasts and osteogenesis were observed in the prefabricated constructs both with and without mechanical stimulation. Biomechanically, there were no significant differences in stiffness, elongation and ultimate failure load between the groups. ConclusionIn vivo heterotopic culture of prefabricated tendon grafts may have the potential to stimulate osteoblasts and induce osteogenesis. Future studies with longer follow-up and modifications of the surgical technique and culture conditions are desirable.

Therapiestrategie bei Gelenkinfektionen

Joint infections represent asevere complication that results in irreversible joint destruction when left untreated or treated inadequately. The reasons for joint infections include endogenous hematological and exogenous factors. In the patient cohort described here, the empyema was almost exclusively acquired through iatrogenic measures (e.g. arthroscopic operations, punctures and intra-articular infections) or as aresult of fractures close to the joint and penetrating injuries. Acute joint empyema is an orthopedic emergency, which must be immediately surgically treated because irreversible cartilage damage can rapidly occur due to the pathophysiological process. Acute joint empyema must be treated arthroscopically. Chronic empyema must be assumed when the clinical symptoms last for more than 7days. Chronic empyema should be treated by arthrotomy, synovectomy and removal of extraneous material including cruciate ligament replacement material.

The Impact of Osseous Malalignment and Realignment Procedures in Knee Ligament Surgery: A Systematic Review of the Clinical Evidence.

Background:Failure rates of knee ligament surgery may be high, and the impact of osseous alignment on surgical outcome remains controversial. Basic science studies have demonstrated that osseous malalignment can negatively affect ligament strain and that realignment procedures may improve knee joint stability.Hypothesis/Purpose:The purpose of this review was to summarize the clinical evidence concerning the impact of osseous malalignment and realignment procedures in knee ligament surgery. The hypotheses were that lower extremity malalignment would be an important contributor to knee ligament surgery failure and that realignment surgery would contribute to increased knee stability and improved outcome in select cases.Study Design:Systematic review; Level of evidence, 4.Methods:According to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic electronic search of the PubMed database was performed in November 2015 to identify clinical studies investigating (A) the influence of osseous alignment on postoperative stability and/or failure rates after knee ligament surgery and (B) the impact of osseous realignment procedures in unstable knees with or without additional knee ligament surgery on postoperative knee function and stability. Methodological quality of the studies was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence and the Coleman Methodological Score (CMS).Results:Of the 1466 potentially relevant articles, 28 studies fulfilled the inclusion and exclusion criteria. Average study quality was poor (CMS, 40). For part A, studies showed increased rerupture rate after anterior cruciate ligament (ACL) replacement in patients with increased tibial slope. Concerning the posterior cruciate ligament (PCL)/posterolateral corner (PLC)/lateral collateral ligament (LCL), varus malalignment was considered a significant risk factor for failure. For part B, studies showed decreased anterior tibial translation after slope-decreasing high tibial osteotomy in ACL-deficient knees. Correcting varus malalignment in PCL/PLC/LCL instability also showed increased stability and better outcomes.Conclusion:In cases of complex knee instability, the 3-dimensional osseous alignment of the knee should be considered (eg, mechanical weightbearing line and tibial slope). In cases of failed ACL reconstruction, the tibial slope should be considered, and slope-reducing osteotomies are often helpful in the patient revised multiple times. In cases of chronic PCL and/or PLC instability, osseous correction of the varus alignment may reduce the failure rate and is often the first step in treatment. Changes in the mechanical axis should be considered in all cases of instability accompanied by early unicompartmental osteoarthritis.