Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed.

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The image-free robotic sculpting tool achieved accurate implementation of the surgical plan with small errors in implant placement. The next step will be to determine whether accurate implant placement translates into a clinical and functional benefit for the patient.

The potential to bioprint and study 3D bacterial biofilm constructs could have great clinical significance at a time when antimicrobial resistance is rising to dangerously high levels worldwide. In this study, clinically relevant bacterial species including Escherichia coli, Staphylococcus aureus (MSSA), Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa were 3D bioprinted using a double-crosslinked alginate bioink to form mature bacteria biofilms, characterized by confocal laser scanning microscopy (CLSM) and fluorescent staining. Solid and porous bacteria-laden constructs were reproducibly bioprinted with thicknesses ranging from 0.25 to 4 mm. We demonstrated 3D bioprinting of thicker biofilms (>4 mm) than found in currently available in vitro models. Bacterial viability was excellent in the bioprinted constructs, with CLSM observation of bacterial biofilm production and maturation possible for at least 28 d in culture. Importantly, we observed the complete five-step biofilm life cycle in vitro following 3D bioprinting for the first time, suggesting the formation of mature 3D bioprinted biofilms. Bacterial growth was faster in thinner, more porous constructs whilst constructs crosslinked with BaCl2 concentrations of above 10 mM had denser biofilm formation. 3D MRSA and MSSA biofilm constructs were found to show greater resistance to antimicrobials than corresponding two-dimensional (2D) cultures. Thicker 3D E. coli biofilms had greater resistance to tetracycline than thinner constructs over 7 d of treatment. Our methodology allowed for the precise 3D bioprinting of self-supporting 3D bacterial biofilm structures that developed biofilms during extended culture. 3D biofilm constructs containing bacterial biofilms produce a model with much greater clinical relevance compared to 2D culture models and we have demonstrated their use in antimicrobial testing.

T he passive stability of the knee is primarily provided by a complex system of intra-and extra-articular ligaments that resist anterior and posterior translation, abnormal tibial rotation, and varus and valgus rotation. Functionally, the medial collateral ligament complex (MCL) acts as the primary restraint to valgus rotation of the tibia, providing as much as 80% of the restraining force to valgus loads. 11 The lateral collateral T T STUDY DESIGN: Controlled laboratory study. T T BACKGROUND:Varus knee instability arising from lateral collateral ligament (LCL) injury increases stress on cruciate ligament grafts, potentially leading to failure of reconstructed ligaments. In contrast to the medial collateral ligament (MCL), little is known about the structural properties of the LCL. T T OBJECTIVES:To compare the tensile properties of the LCL and MCL complex of the human knee joint. T T METHODS:Ten fresh-frozen cadaveric knees (mean  SD age, 81  11 years), free of gross musculoskeletal pathology, were obtained. Following dissection, the length, width, and thickness of the ligaments were measured using calipers, and bone-ligament-bone preparations were mounted in a uniaxial load frame. After preconditioning, specimens were extended to failure at a rate of 500 mm/min (approximately 20%/s). Force and crosshead displacement were used to calculate structural properties, including stiffness, yield strength, ultimate tensile strength, and failure energy. T T RESULTS:The fan-shaped MCL was significantly longer (60%; P<.001), wider (680%; P<.001), and thinner (19%; P = .009) than the cord-like LCL.The LCL failed at either the fibular attachment (n = 6) or midsubstance (n = 4), while failure of the MCL primarily occurred at the femoral attachment (n = 7). Although the ultimate tensile strength of the MCL (mean  SD, 799  209 N) was twice that of the LCL (392  104 N; P<.001), there was no significant difference in stiffness of the ligaments (MCL, 63  14 N/mm; LCL, 59  12 N/ mm). 30 During normal gait, the LCL is the primary passive structure resisting the knee adduction (varus) moment, which has been implicated in the progression of knee osteoarthritis. T T CONCLUSIONS: 31While isolated ligamentous injury of the knee often involves the MCL, traumatic sports injuries can affect multiple knee ligaments.1 Concomitant injury to the posterolateral structures is often unrecognized in patients with multiple ligament or combined ligament disruptions.12,22 Abnormal varus laxity arising subsequent to injuries of the LCL and other posterolateral structures has been shown to increase stress on cruciate ligament grafts, and has been implicated as one of the causes of failed cruciate ligament reconstructions. 12,19 Unlike the MCL, animal models have demonstrated that the LCL heals poorly when torn, 20 and, consequently, surgical repair or reconstruction of the LCL is often advocated with acute grade III injuries, particularly when multiple posterolateral structures are involved.14 Although sparse data are available concerning the c...

The purpose of this randomized, prospective study was to compare accuracy in tunnel placement as performed with a traditional arthroscopic anterior cruciate ligament (ACL) reconstruction technique and with KneeNavTM ACL, a computer-assisted surgical navigation technique. Two surgeons experienced in ACL reconstruction, but inexperienced in computer-assisted surgical navigation technique, each randomly used traditional arthroscopic guides or KneeNavTM ACL to drill a tunnel in twenty identical foam knees. Placement of the resulting tibial and femoral tunnels was measured with a computer-assisted digitizing method and compared to traditional biplanar radiographs. Statistical analysis with Student's t-test was used to compare the distance from the ideal tunnel placement to the femoral and tibial tunnels. Accuracy of tunnel placement with KneeNavTM ACL was significantly better than that obtained with the traditional arthroscopic technique. Distances from the ideal tunnel placement to the femoral and tibial tunnels were 4.2 +/- 1.8 mm (mean +/- SD) and 4.9 +/- 2.3 mm, respectively, for the traditional arthroscopic technique, and 2.7 +/- 1.9 mm (femur) and 3.4 +/- 2.3 mm (tibia) for KneeNavTM ACL. These differences were statistically different. Tunnel placement for ACL reconstruction with KneeNavTM ACL, an image-based, computer-assisted surgical navigation device with a simple and intuitive interface, was more accurate than with the traditional arthroscopic technique.

The quantification of knee alignment is a routine part of orthopaedic practice and is important for monitoring disease progression, planning interventional strategies, and follow-up of patients. Currently available technologies such as radiographic measurements have a number of drawbacks. The aim of this study was to validate a potentially improved technique for measuring knee alignment under different conditions. An image-free navigation system was adapted for non-invasive use through the development of external infrared tracker mountings. Stability was assessed by comparing the variance (F-test) of repeated mechanical femoro-tibial (MFT) angle measurements for a volunteer and a leg model. MFT angles were then measured supine, standing and with varus-valgus stress in asymptomatic volunteers who each underwent two separate registrations and repeated measurements for each condition. The mean difference and 95% limits of agreement were used to assess intra-registration and inter-registration repeatability. For multiple registrations the range of measurements for the external mountings was 1 larger than for the rigid model with statistically similar variance ( p ¼ 0.34). Thirty volunteers were assessed (19 males, 11 females) with a mean age of 41 years (range: 20-65) and a mean BMI of 26 (range: 19-34). For intra-registration repeatability, consecutive coronal alignment readings agreed to almost AE1, with up to AE0.5 loss of repeatability for coronal alignment measured before and after stress maneuvers, and a AE0.2 loss following stance trials. Sagittal alignment measurements were less repeatable overall by an approximate factor of two. Inter-registration agreement limits for coronal and sagittal supine MFT angles were AE1.6 and AE2.3 , respectively. Varus and valgus stress measurements agreed to within AE1.3 and AE1.1 , respectively. Agreement limits for standing MFT angles were AE2.9(coronal) and AE5.0 (sagittal), which may have reflected a variation in stance between measurements. The system provided repeatable, real-time measurements of coronal and sagittal knee alignment under a number of dynamic, real-time conditions, offering a potential alternative to radiographs.