Objective. To analyze the short-term outcome after medial open-wedge high tibial osteotomy with a 3D-printing technology in early medial keen osteoarthritis and varus malalignment. Design and Method. 32 knees(28 cases) of mOWHTO (fixation with an angular-stable TomoFix implant(Synthes)) with a 3D-printing technology combined with arhtroscopy were prospectively surveyed with regard to functional outcome(Hospital for special knee score [HSS] score). Pre- and postoperative tibial bone varus angle (TBVA), mechanical medial proximal tibial angle (MPTA), and alignment were analyzed with regard to the result. Results. 32 knees were included (28 patients; mean age 46.5±9.3 years). The follow-up rate was 100% at 1.7±0.6 years (range, 1.2–3.2 years). Pre- and postoperative mechanical tibiofemoral axis were 6.8°±2°of varus and 1.2°± 3.4° of valgus, respectively. HSS score significantly improved from 46.0±18.3 preoperatively to 84±12 at one, 80±7 at two years (P<0.01). Conclusions. Medial open-wedge high tibial osteotomy with a 3D-printing technology combined with arthroscopy in medial keen osteoarthritis and varus malalignment is an accurate and good treatment option. High preoperative TBVA and appropriate corrected angle(0–3° of valgus)) was associated with better functional outcome at final follow-up

Aims. The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants. Methods. We compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method. Results. The two groups were matched for patient sex, age (61 and 63 years), time to revision (30 and 41 months), implant size (54 mm and 52 mm), and porosity (72% and 60%) (p > 0.152). There was no difference in visual bony attachment (p = 0.209). Histological analysis showed greater bone ingrowth in 3D-printed implants (p < 0.001), with mean bone attachment of 63% (SD 28%) and 37% (SD 20%), respectively. This was observed for all the outcome measures. Conclusion. This was the first study to investigate osseointegration in retrieved 3D-printed acetabular implants. Greater bone ingrowth was found in 3D-printed implants, suggesting that better osseointegration can be achieved. However, the influence of specific surgeon, implant, and patient factors needs to be considered. Cite this article: Bone Joint Res 2021;10(7):388–400

Reconstructing mandibular and maxillary bone defects with free vascularized bone flaps requires to take into account the aesthetic and functional requirements to consider subsequent placement of dental implants. It implies a three-dimensional conformation of the bone fragment. This is usually done by making osteotomies on the bone harvested. The aim of our study was to evaluate the interest of virtual planning and 3D printing using free software and a consumer printer in this indication.

Invesalius® software (Technology of Information Renato Archer Center, Campinas, Brazil) was used to build virtual models from the patients' CT scan imaging data. The surgical procedure was planned using Meshmixer® (Autodesk, San Rafael, United States). Meshlab® software (Visual Computing Lab, Pisa, Italy) was used to design cutting guides for the flap harvest and modelling. 3D printing of these guides with a consumer printer (Ultimaker 2® Ultimaker B.V., Geldermalsen, the Netherlands) allowed the transfer of the planning to the operating room.

Three patients requiring mandibular reconstruction underwent an iliac crest free flap, a fibula free flap and a scapula free flap, and could benefit from this technique. In each case, the bone resection was performed virtually and the positioning of the bone available at the donor site was simulated on screen. This allowed to anticipate the position and orientation of the cutting planes on the bone flap. From the anatomy of the donor site and the cutting planes, harvest templates and cutting guides could be designed by computer. Planning the conformation of the bone flap to the recipient site has allowed an anatomical, aesthetic and functional reconstruction of the bone defect.

Surgeon-made virtual planning and “low cost” 3D printing helps harvest the bone flap and position and orient the osteotomies to adapt it to the defect. They provide, both the patient and the surgeon, reduced operative time and better anticipation of the result, particularly in the context of the maxillofacial reconstruction. Compared to commercially available custom-made devices, this technique allows the manufacture of the guides without delay and at a cheap price.

Paediatric musculoskeletal (MSK) disorders often produce severe limb deformities, that may require surgical correction. This may be challenging, especially in case of multiplanar, multifocal and/or multilevel deformities. The increasing implementation of novel technologies, such as virtual surgical planning (VSP), computer aided surgical simulation (CASS) and 3D-printing is rapidly gaining traction for a range of surgical applications in paediatric orthopaedics, allowing for extreme personalization and accuracy of the correction, by also reducing operative times and complications. However, prompt availability and accessible costs of this technology remain a concern. Here, we report our experience using an in-hospital low-cost desk workstation for VSP and rapid prototyping in the field of paediatric orthopaedic surgery. From April 2018 to September 2022 20 children presenting with congenital or post-traumatic deformities of the limbs requiring corrective osteotomies were included in the study. A conversion procedure was applied to transform the CT scan into a 3D model. The surgery was planned using the 3D generated model. The simulation consisted of a virtual process of correction of the alignment, rotation, lengthening of the bones and choosing the level, shape and direction of the osteotomies. We also simulated and calculated the size and position of hardware and customized massive allografts that were shaped in clean room at the hospital bone bank. Sterilizable 3D models and PSI were printed in high-temperature poly-lactic acid (HTPLA), using a low-cost 3D-printer. Twenty-three operations in twenty patients were performed by using VSP and CASS. The sites of correction were: leg (9 cases) hip (5 cases) elbow/forearm (5 cases) foot (5 cases) The 3D printed sterilizable models were used in 21 cases while HTPLA-PSI were used in five cases. customized massive bone allografts were implanted in 4 cases. No complications related to the use of 3D printed models or cutting guides within the surgical field were observed. Post-operative good or excellent radiographic correction was achieved in 21 cases. In conclusion, the application of VSP, CASS and 3D-printing technology can improve the surgical correction of complex limb deformities in children, helping the surgeon to identify the correct landmarks for the osteotomy, to achieve the desired degree of correction, accurately modelling and positioning hardware and bone grafts when required. The implementation of in-hospital low-cost desk workstations for VSP, CASS and 3D-Printing is an effective and cost-advantageous solution for facilitating the use of these technologies in daily clinical and surgical practice

Intervertebral disc degeneration can lead to physical disability and significant pain, while the present therapeutics still fail to biochemically and biomechanically restore the tissue. Stem cell-based therapy in treating intervertebral disc (IVD) degeneration is promising while transplanting cells alone might not be adequate for effective regeneration. Recently, gene modification and 3D-printing strategies represent promising strategies to enhanced therapeutic efficacy of MSC therapy. In this regard, we hypothesized that the combination of thermosensitive chitosan hydrogel and adipose derived stem cells (ADSCs) engineered with modRNA encoding Interleukin − 4 (IL-4) can inhibit inflammation and promote the regeneration of the degenerative IVD. Rat ADSCs were acquired from adipose tissue and transfected with modRNAs. First, the kinetics and efficacy of modRNA-mediated gene transfer in mouse ADSCs were analyzed in vitro. Next, we applied an indirect co-culture system to analyze the pro-anabolic potential of IL-4 modRNA engineered ADSCs (named as IL-4-ADSCs) on nucleus pulposus cells. ModRNA transfected mouse ADSCs with high efficiency and the IL-4 modRNA-transfected ADSCs facilitated burst-like production of bio-functional IL-4 protein. In vitro, IL-4-ADSCs induced increased anabolic markers expression of nucleus pulposus cells in inflammation environment compared to untreated ADSCs. These findings collectively supported the therapeutic potential of the combination of thermosensitive chitosan hydrogel and IL-4-ADSCs for intervertebral disc degeneration management. Histological and in vivo validation are now being conducted

The treatment of paediatric supracondylar humeral fractures is likely one of the first procedures involving X-ray guided wire insertion that trainee orthopaedic surgeons will encounter. Pinning is a skill that requires high levels of anatomical knowledge, spatial awareness, and hand-eye coordination. We developed a simulation model using silicone soft-tissue and 3D-printed bones to allow development and practice of this skill at no additional risk to patients. For this model, we have focused on reusability and lowering raw-material costs without compromising fidelity. To achieve this, the initial bone model was extracted from open-source computed tomography scans and modified from adult to paediatric size. Muscle of appropriate robustness was then sculpted around the bones using 3D modelling software. A cutaneous layer was developed to mimic oedema using clay sculpturing on a plaster-casted paediatric forearm. These models were then used for 3D-printing and silicone casting respectively. The bone models were printed with settings to imitate cortical and cancellous densities and give high-fidelity tactile feedback upon drilling. Each humerus costs NZD $0.30 in material to print and can be used 1–3 times. Silicone casting of the soft-tissue layers imitates differing relative densities between muscle and oedematous cutaneous tissue, thereby increasing skill necessary to accurately palpate landmarks. Each soft-tissue sleeve cost NZD $70 in material costs to produce and can be used 20+ times. The resulting model is modular, reusable, and replaceable, with each component standardised and easily reproduced. It can be used to practice land-mark palpation and Kirschner wire pinning and is especially valuable in smaller centres which may not be able to afford traditional Saw Bones models. This low-cost model thereby improves equity while maintaining quality of simulation training

In the field of tissue engineering (TE), mainly two approaches have been widely studied and utilised throughout the last two decades. Ovsianikov et al. proposed a third strategy for tissue engineering to combine the advantages of the scaffold-based and scaffold-free approach [1]. We utilise the third strategy for TE by fabrication of cell spheroids that are reinforced by microscaffolds, called tissue units (TUs). Aim of the presented study is to differentiate TUs towards a chondrogenic phenotype to show the self-assembly of a millimetre sized cartilage-like tissue in a bottom-up TE approach in vitro. Two-Photon polymerization (2PP) was utilised to fabricate highly porous microscaffolds with a diameter of 300 µm. The biocompatible and biodegradable, resin Degrad INX (supplied from Xpect INX, Ghent, Belgium) was used for 3D-printing. Each microscaffold was seeded with 4000 human adipose derived stem cells (hASCs) in low-adhesive 96-well plates to allow spheroid formation. TUs were differentiated towards the chondrogenic lineage by application of chondrogenic media, subsequently merged in a cylindrical agarose mold, to fuse into a connected tissue with a diameter of ~1.8 mm and a height of 8 mm. The characterization of TUs differentiated towards the chondrogenic phenotype included gene expression and protein analysis. Furthermore, immunohistochemically staining for Collagen II and Alcian blue staining were performed to investigate the matrix deposition and fusion of the self-assembled tissue. Our results suggest that the utilised method could be a promising approach for a variety of tissue engineering approaches, due to the good applicability to a defect side combined with the self-assembly properties of the TUs. Furthermore, the differentiation potential of hASCs is not limited to chondrogenic lineages only, which could pave the way to further TE applications in the future. Acknowledgements:. This research work was financially supported by the European Research Council (Consolidator Grant 772464 A.O.)

To design slow resorption patient-specific bone graft whose properties of bone regeneration are increased by its geometry and composition and to assess it in in-vitro and in-vivo models. A graft composed by hydroxyapatite (HA) and β-TCP was designed as a cylinder with 3D gyroid porosities and 7 mm medullary space based on swine's anatomy. It was produced using a stereolithography 3D-printing machine (V6000, Prodways). Sterile bone grafts impregnated with or without a 10µg/mL porcine BMP-2 (pBMP-2) solution were implanted into porcine femurs in a bone loss model. Bone defect was bi-weekly evaluated by X-ray during 3 months. After sacrifice, microscanner and non-decalcified histology analysis were conducted on biopsies. Finally, osteoblasts were cultured inside the bone graft or in monolayer underneath the bone graft. Cell viability, proliferation, and gene expression were assessed after 7 and 14 days of cell culture (n=3 patients). 3D scaffolds were successfully manufactured with a composition of 80% HA and 20% β-TCP ±5% with indentation compressive strength of 4.14 MPa and bending strength of 11.8MPa. In vivo study showed that bone regeneration was highly improved in presence of pBMP-2. Micro-CT shows a filling of the gyroid sinuses of the implant (Figure 1). In vitro, the presence of BMP2 did not influence the viability of the osteoblasts and the mortality remained below 3%. After 7 days, the presence of BMP2 in the scaffold significantly increased by 85 and 65% the COL1A1 expression and by 8 and 33-fold the TNAP expression by osteoblasts in the monolayer or in the scaffold, respectively. This BMP2 effect was transient in monolayer and did not modify gene expression at day 14. BMP2-impregnated bone graft is a promising patient-personalized 3D-printed solution for bone defect regeneration, by promoting neighboring host cells recruitment and solid new bone formation. For any figures and tables, please contact the authors directly

The treatment of critical-sized bone defects still remains today a challenge, especially when the surrounding soft, vascularized and innervated tissues have been damaged - a lack of revascularization within the injured site leading to physiological disorders, from delayed healing to osteonecrosis. The axial insertion of a vascular bundle (e.g. arterio-venous loop, AVL) within a synthetic bone filler to initiate and promote its revascularization has been foreseen as a promising alternative to the current strategies (e.g., vascularized free flaps) for the regeneration of large bone defects. In a previous work, we showed that the insertion of a vein in a 3D-printed monetite scaffold induced its higher revascularization than AVL, thus a possible simplification of the surgical procedures (no microsurgery required). Going further, we investigate in this study whether or not the presence of a vein could stimulate the formation of mineralized tissue insides a synthetic scaffold filled with bone marrow and implanted in ectopic site. Monetite scaffolds were produced by additive manufacturing according to a reactive 3D-printing technique co-developed by the authors then thoroughly characterized. Animal study was performed on 14 male Wistar rats. After anesthesia and analgesia, a skin medial incision in rat thigh allowed the site on implantation to be exposed. Bone marrow was collected on the opposite femur through a minimally invasive procedure and the implant was soaked with it. For the control group (N=7), the implant was inserted in the incision and the wound was closed whereas the femoral bundle was dissected and the vein inserted in the implant for the experimental group (N=7). After 8 weeks animals were sacrificed, the implant collected and fixed in a 4% paraformaldehyde solution. Explants were characterized by µCT then embedded in poly-methyl methacrylate prior SEM, histology and immunohistochemistry. Images were analyzed with CT-Analyzer (Bruker) and ImageJ (NIH) and statistical analyses were carried out using SPSS (IBM). Implants were successfully 3D-printed with a +150 µm deviation from the initial CAD. As expected, implants were composed of 63%wt monetite and 37%wt unreacted TCP, with a total porosity of 44%. Data suggested that scaffold biodegradation was significantly higher when perfused by a vein. Moreover, the latter allowed for the development of a dense vascular network within the implant, which is far more advanced than for the control group. Finally, although mineralized tissues were observed both inside and outside the implant for both groups, bone formation appeared to be much more important in the experimental one. The ectopic formation of a new mineralized tissue within a monetite implant soaked with bone marrow seems to be highly stimulated by the simple presence of a vein alone. Although AVL have been studied extensively, little is known about the couple angiogenesis/osteogenesis which appears to be a key factor for the regeneration of critical-sized bone defects. Even less is known about the mechanisms that lead to the formation of a new bone tissue, induced by the presence of a vein only. With this in mind, this study could be considered as a proof of concept for further investigations

BACKGROUND. Total hip revision surgery in cases with previous multiple reconstructive procedures is a challenging treatment due to difficulties in treatment huge bone defects with standard revision prosthetic combinations. A new specially made production system in Electron-Beam Melting (EBM) technology based on a precise analysis of patients' preoperative CT scans has been developed. METHODS. Objectives of design customization in difficult cases are to correctly evaluate patient's anatomy, to plan a surgical procedure and to obtain an optimal fixation to a poor bone stock. The 3D Printing (EBM) technology permits to create an extremely flexible patient matching implant and instrument, with material performances not viable with standard manufacturing process. Dedicated visual 3D tools and instrumentations improve implants congruency according to preoperative plan. Primary stability is enhanced and tailored on patient's anatomy by means of press-fit, iliac stems and the high friction performances of Trabecular Titanium matrix. The use of bone screws and their position is designed to enhance primary stability, even in critical bone conditions, avoiding implant stress shielding and allowing bone integration. 4 cases (2 men and 2 women) of acetabular customized implants were performed. Mean age at surgery was 51.5 years (range 25–72). Patients were reviewed clinically and radiographically at follow-up. RESULTS. No signs of miss-match between intraoperative bone conditions and pre-operative planning were observed. No additional bone grafts or further native bone removal were needed. Biomechanical parameters were restored by using internal modularity (i.e. face-changers / angled spacers). Face-changers allow to correct coverage and anteversion of the acetabular system. Incompatibility or impingement between the stems and new acetabular component was not observed and stem revision was performed in one case. On-table stability proved excellent and no intraoperative complications were observed. All patients underwent an immediate mobilization with full weight-bearing. Mean Harris Hip Score increased significantly from 13.9 (range 6.9–20.6) preoperatively to 75.8 (range 53.9–94) at last follow-up (mean 17.5, range: 10–33), showing an improvement in terms of both pain relief, function and joint mobility. Radiographically neither signs of instability, migration nor tilting were observed. No case of dislocation nor infection were recorded. CONCLUSION. A detailed anatomical reconstruction, in-depth preoperative planning, custom-implant design, high performance of the 3D-printing technology, system modularity and patient-specific surgical tools permitted an effective restoration of the biomechanical joint parameters in these complex revision cases. The optimal primary stability of the implants promoted an early osseointegration with the remaining bone stock. Further studies shall be necessary to assess the performance of these Implants at long-term follow-up

Since the development of biomimetic and ceramic bone reconstructive in the early 1970, these specialised bioreactors intended for bone or cartilage regeneration have come a long way in trying to design an alternative procedure other than autogenous bone grafting. However, all known biomaterials still fall short of inducing substantial bone formation in vitro or in vivo, especially when treating large bony defects. As such there is a necessity to develop novel bone-reconstructive biomaterials that can more appropriately be utilised and can induce substantial more bone formation than current scaffolds. Using the rapid prototyping technique (Friedrich-Baur BioMed Center, Bayreuth, Germany) to develop new and improved hydroxyapatite/β-tricalcium phosphate devices, which can be predesigned to any outer shape with controlled pore structure and exhibit a unique intrinsic porosity <150µm due to the 3D-printing process to fit any skeletal bone loss site, the aim of our laboratories was to test the osteoinductive capacity of these new bioreactors in an in vitro culture system utilising adipose-derived stem cells (ADSCs). Immunofluorescent staining revealed that beside the standard surface protein expression patterns typical for ADSCs, the cells also produced osteoblast specific proteins, specifically osteocalcin, osteopontin and dentin matrix acidic phosphoprotein 1. ADSCs seeded on the surface of the biomimetic scaffolds showed constant proliferation, maintained viability and differentiation throughout the scaffold, including the small intrinsic pores. Subsequent, qRT-PCR also revealed that alkaline phosphatase and osteocalcin expression was significantly increased upon addition of osteogenic medium but even more so when human recombinant morphogenetic protein 2 (hBMP-2) was included. Immunofluorescent data of protein expression was consistent with qRT-PCR data. Taken into account with previous results by our laboratories in respect to adipose tissue as a viable inductive medium that can form substantial new bone formation in vivo the present results demonstrated that the investigated bioceramic devices possess the necessary capacity that could, together with adipose tissue, provide the next leap necessary to finally and decisively induce substantial or total new bone formation in clinical bone defects of humans

The standard approach of diagnosing and monitoring scoliosis involves using the Cobb angle from posteroanterior (PA) radiograph. This approach has two key limitations: 1) It involves exposing the patients to ionising radiation during a period of heightened radiosensitivity. 2) The 2D x-ray image is a projection image of a 3D deformity and the Cobb angle represents only lateral rotation. 3DUS would overcome both these limitations. We developed a 3DUS system by combining motion capture technology, a conventional 2D ultrasound scanner and bespoke software. An ex vivo experiment and a pilot clinical study were carried out to demonstrate the system's ability in identifying vertebrae landmarks and quantifying the curvature. For the ex vivo validation, a spine phantom was created by 3D-printing a segmented abdo-pelvis CT scan. The spine phantom was then scanned using 3DUS and the level of agreement in the dimensions measured using 3DUS and CT was assessed. An 11 year old female with adolescent idiopathic scoliosis (AIS) was scanned with 3DUS. The SP co-ordinates were projected on a plane of best-fit to compare the curvature angle from 3DUS with the Cobb angle from the x-ray image. The spinous (SP), transverse processes and the laminae demonstrated high echogenicity and were easily identifiable. The difference between the spine phantom inter-SP dimension measurements made in 3DUS and CT was <2.5%. The PA x-ray of the AIS patient revealed 47° (L4-T11) and 52° (T6-T11) curves. 3DUS was able to represent the deformity in 3D revealing complex curvatures in all planes. The curvature angle from derived from 3DUS for the L4-T11 and T6-T11 curves were 132° (48°) and 125° (55°) respectively. The results of this pilot study demonstrate 3DUS as a promising tool for imaging spine curvature

Total ankle replacement (TAR) is the main surgical option in case of severe joint osteoarthritis. The high failure rate of current TAR is often associated to inappropriate prosthetic articulating surfaces designed according to old biomechanical concepts such the fixed axis of rotation, thus resulting in non-physiological joint motion. A recent image-based 3D morphological study of the normal ankle (Siegler et al. 2014) has demonstrated that the ankle joint surfaces can be approximated by a saddle-shaped cone with its apex located laterally (SSCL). We aimed at comparing the kinematic effects of this original solution both with the intact joint and with the traditional prosthetic articulating surfaces via in-silico models and in-vitro measurements. Native 3D morphology of ten normal cadaver ankle specimens was reconstructed via MRI and CT images. Three custom-fit ankle joint models were then developed, according to the most common TAR designs: cylindrical, symmetrically-truncated medial apex cone (as in Inman's pioneering measures), and the novel lateral apex cone, i.e. SSCL. Bone-to-bone motion, surface-to-surface distance maps, and ligament forces and deformations were evaluated via computer simulation. Prototypes of corresponding prosthesis components were designed and manufactured via 3D-printing, both in polymer-like-carbon and in cobalt-chromium-molybdenum powders, for in-vitro tests on the cadaver specimens. A custom testing rig was used for application of external moments to the ankle joint in the three anatomical planes; a motion tracking system with trackers pinned into the bone was used to measure tibial, talar and calcaneal motion (Franci et al. 2009), represented then as tibiotalar, subtalar and ankle complex 3D joint rotations. Each ankle specimen was tested in the intact joint configuration and after replacement of the articulating surfaces according with the three joint models: cylindrical, medial apex cone and SSCL. Results. Small intra-specimen data variability in cycle-to-cycle joint kinematics was found in all cadaver ankles, the maximum standard deviation of all rotation patterns being smaller than 2.0 deg. In-silico ligament strain/stress analysis and in-vitro joint kinematic and load transfer measurements revealed that the novel SSCL surfaces reproduce more natural joint patterns than those with the most common surfaces used in current TAR. TAR based on a saddle-shaped skewed truncated cone with lateral apex is expected to restore more normal joint function. Additional tests are undergoing for further biomechanical validation. The present study has also demonstrated the feasibility and the quality of the full process of custom TAR design and production for any specific subject. This implies a thorough procedure, from medical imaging to the production of artificial surfaces via 3D printing, which is allowing for personalised implants to become the future standard in total joint replacement

The management of maxillofacial injuries requires restoring the contours of the facial skeleton to achieve an aesthetic outcome. When fractures are simple, open reduction and rigid fixation with stock titanium osteosynthesis plates is usually sufficient. However, when the damage is more substantial (when the fracture is comminuted or in case of a bone defect) anatomical landmarks are lost and the reconstruction requires the use of titanium meshes. These meshes are usually modelled intraoperatively to restore the contours of the bone. This can be a tough and time consuming task in case of minimal invasive approach and intraoperative edema. When the injury is unilateral, printing a 3D anatomical model of the mirrored unaffected side is an easy way to accurately pre-bend the mesh preoperatively. With the emergence of “low cost” consumer 3D printers, the aim of our study was to evaluate the cost of this technique in a department of maxillofacial surgery. The first part of the study was to evaluate free software solutions available online to determine which of these could be used to create 3D virtual models from the patients' volume imaging data, mirror the model and export an STL file suitable for 3D-printing with a consumer 3D-printer. The second part was to identify the desktop 3D-printers commercially available according to the different technology used, their prices and that of consumables required. Five free software solutions were identified to create STL meshes of the patient's anatomy from thin slice CT scan DICOM data. Two more were available to repair, segment and mirror them to provide a clean STL file suitable for 3D printing with a desktop 3D printer. The prices of 2 different printers were then listed for each of the 3 additive manufacturing technologies available to date. Prices ranged from 2,299 € for the Ultimaker 2+© (Fuse Deposition Modeling, FDM), to 4,999 € for the Sintratec© printer (Selective Laser Sintering, SLS), the Formlabs 2© (stereolithography) being at an intermediate price of 3,299 €. Finally, the cost of the manufacture of a model was calculated for each of these printers. Considering a model of a supraorbital ridge printed to restore the anterior wall of the frontal sinus, the volume of the mesh is around 20 cm. 3. This represents a cost of less than 1 € with the FDM technology, 4.70 € with stereolithography and 1.50 € with the SLS printer. Since patents of additive manufacturing have become part of the public domain, the cost of 3D printing technology has fallen drastically. Desktop printers are now an investment accessible to a surgery department and the cost of the material is low. This allows the surgeons, by the mean of free software, to directly create 3D models of their patients' anatomy, mirror them if needed and manufacture a template to pre-bend titanium meshes that will be subsequently sterilized for the surgery. Having the printer in the department reduces manufacturing lead times and makes this technique possible even for urgent cases

Aims

The aim of this study was to investigate the safety and efficacy of 3D-printed modular prostheses in patients who underwent joint-sparing limb salvage surgery (JSLSS) for malignant femoral diaphyseal bone tumours.

INTRODUCTION. Bone tumour resection and subsequent reconstruction remains challenging for the surgeon. Obtaining adequate margins is mandatory to decrease the risk of local recurrence. Improving surgical margins quality without excessive resection, reducing surgical time and increasing the quality of the reconstruction are the main goals of today's research in bone tumour surgical management. With the outstanding improvements in imaging and computerised planning, it is now a standard. However, surgical accuracy is essential in orthopaedic oncologic surgery (Grimmer 2005). Patient specific instruments (PSI) may greatly improve the surgeon's ability to achieve the targeted resection. Thanks to its physical support, PSI can physically guide the blade yielding to a better control over the cutting process (Wong, 2014). Surgical time might significantly be reduced as well when compared to conventional method or navigated procedure. Finally, reconstruction may gain in rapidity and quality especially when allograft is the preferred solution as PSI can be designed as well for allograft cutting (Bellanova, 2013). Since 2011, PSI have systematically been used in our institution for bone tumour resection and when applicable allograft reconstruction. This paper reports the mid- to long-term medical outcomes on a large series. MATERIALS AND METHODS. Between 2011 and 2016, we systematically used PSI to remove bone tumours in 30 patients. The pre-operative planning involved the tumour delineation drawn on MRI by the surgeon. The MRI and obtained tumour volume were transferred to the CT-scan by image fusion (co- registration). Cutting planes were positioned around the tumour including a safe margin. The PSI were designed to ensure a sufficient stability but kept thin enough to limit the bone exposure. The PSI was manufactured by 3D-printing in a biocompatible and sterilisable material. PSI has been intraoperatively to cut the bone with predetermined margins. Medical files were reviewed for large data collection: type, size and site of the tumour, pre-and post-operative metastatic status, bone and soft tissues resection margins, local recurrence, use of an allograft and a PSI for graft adjustment or not for the reconstruction, the fusion of the allograft when applicable, the follow-up time and early/late complications. RESULTS. Over a period of 5 years, 30 patients were operated on with PSI (10 osteosarcomas, 4 chondrosarcomas, 10 Ewing sarcomas and 6 other types of bone tumours). Mean follow-up was 27±20 months. 18 cases out of 30 have more than 2 years follow-up and 13 out of 30 have more than 3 years of follow-up. Mean operating time was 6h02±3h44. Mean size of the tumours was 8,4±4,7cm and location was the upper limb in 5 cases, inferior limb in 15 cases and the pelvis in 10 occurrences. Metastatic disease developed postoperatively in 5 patients. Surgical margins in the bone were R0 in all cases but one case where a R1 surgery was planned to preserve a nerve root. We did not observe any local recurrence in the bone. Within soft tissues, margins were classified as R0 in 28 patients and R1 in 2 patients. In 26 cases, an allograft was used to reconstruct the bone defect. In 23 of those patients, the allograft was selected by CT scan and cut using a PSI. In the 3 allografts cut free-handily, only one demonstrated a fusion. Of the 23 cut with a guide, 12 fused completely, 2 demonstrated a partial fusion and 9 were not fused at the last follow-up. At the last follow-up, 2 patients were dead of disease, 5 were alive with metastatic disease and 23 were alive without disease. DISCUSSION. Oncology is probably the field where PSI can bring the largest advantage when compared to the conventional procedure. Several papers have reported the use of PSI for bone tumour resection. All of them have shown very promising results on in-vitro experiments (Cartiaux 2014), cadaver experiment (Wong 2012) or small clinical series (Bellanova 2013, Gouin, 2014). None of these papers report a large patient series associated with a clinically relevant follow-up. This series is the first mid- to long-term follow-up series involving PSI tumour surgery. These results are showing strong evidences of clinical improvements. It comes into contradiction with PSI for total knee arthroplasty where controversial results on the patient's outcome has been reported (Thienpont 2014). R0 margin has been systematically obtained for all bone cuttings, and local recurrence has been strongly decreased (3%) when compared to the usual recurrence rates published in the literature (from 15% to 35% according to the location). Allograft fusion seems improved as well thanks to the shape-matching of the selected allograft and a close contact between host and allograft at bony junctions. With a longer follow-up, these evidences should be stronger to definitely make PSI the best option for bone tumour resection

Cementless knee arthroplasty has seen a recent resurgence in popularity due to conceptual advantages, including improved osseointegration providing biological fixation, increased surgical efficiency, and reduced systemic complications associated with cement impaction and wear from cement debris. Increasingly younger and higher demand patients are requiring knee arthroplasty, and as such, there is optimism cementless fixation may improve implant survivorship and functional outcomes.

Compared to cemented implants, the National Joint Registry (NJR) currently reports higher revision rates in cementless total knee arthroplasty (TKA), but lower in unicompartmental knee arthroplasty (UKA). However, recent studies are beginning to show excellent outcomes with cementless implants, particularly with UKA which has shown superior performance to cemented varieties. Cementless TKA has yet to show long-term benefit, and currently performs equivalently to cemented in short- to medium-term cohort studies. However, with novel concepts including 3D-printed coatings, robotic-assisted surgery, radiostereometric analysis, and kinematic or functional knee alignment principles, it is hoped they may help improve the outcomes of cementless TKA in the long-term. In addition, though cementless implant costs remain higher due to novel implant coatings, it is speculated cost-effectiveness can be achieved through greater surgical efficiency and potential reduction in revision costs. There is paucity of level one data on long-term outcomes between fixation methods and the cost-effectiveness of modern cementless knee arthroplasty.

This review explores recent literature on cementless knee arthroplasty, with regards to clinical outcomes, implant survivorship, complications, and cost-effectiveness; providing a concise update to assist clinicians on implant choice.

Cite this article: Bone Jt Open 2021;2(1):48–57.