Abstract. Background. Distal femoral osteotomy is an established successful procedure which can delay the progression of arthritis and the need for knee arthroplasty. The surgery, however, is complex and lengthy and consequently it is generally the preserve of highly experienced specialists and thus not widely offered. Patient specific instrumentation is known to reduce procedural complexity, time, and surgeons’ anxiety levels. 1. in proximal tibial osteotomy procedures. This study evaluated a novel patient specific distal femoral osteotomy procedure (Orthoscape, Bath, UK) which aimed to use custom-made implants and instrumentation to provide a precision correction while also simplifying the procedure so that more surgeons would be comfortable offering the procedure. Presenting problem. Three patients (n=3) with early-stage knee arthritis presented with valgus malalignment, the source of which was predominantly located within the distal femur, rather than intraarticular. Using conventional techniques and instrumentation, distal femoral knee osteotomy cases typically require 1.5–2 hours surgery time. The use of bi-planar osteotomy cuts have been shown to improve intraoperative stability as well as bone healing times. 2. This normally also increases surgical complexity; however, multiple cutting slots can be easily incorporated into patient specific instrumentation. Clinical management. All three cases were treated at a high-volume tertiary referral centre (Istituto Ortopedico Rizzoli, Bologna) using medial closing wedge distal femoral knee osteotomies by a team experienced in using patient specific osteotomy systems. 3. Virtual surgical planning was conducted using CT-scans and long-leg weight-bearing x-rays (Orthoscape, Bath, UK). Patient specific surgical guides and custom-made locking plates were design for each case. The guides were designed to allow temporary positioning, drilling and bi-planar saw-cutting. The drills were positioned such that the drills above and below the osteotomy became parallel on closing following osteotomy wedge removal. This gave reassurance of the achieved correction allowed the plate to be located precisely over the drills. All screw lengths were pre-measured. Discussion. The surgical time reduced to approximately 30 minutes by the third procedure. It was evident that surgical time was saved because no intraoperative screw length measurements were required, relatively few x-rays were used to confirm the position of the surgical guide, and the use of custom instrumentation significantly reduced the surgical inventory. The reduced invasiveness and ease of surgery may contribute to faster patient recovery compared to conventional techniques. The final post-operative alignment was within 1° of the planned alignment in all cases. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Summary Statement. This is the first report of a new technique for unicompartmental to total knee arthroplasty revision surgery in which patient specific guides are formed based on preoperative CT imaging. This technique can help to make revision surgery less technically demanding. Introduction. Unicompartmental to total knee arthroplasty revision surgery can be a technically demanding procedure. Joint line restoration, rotation and augmentations can cause difficulties. This study describes a new technique in which single way fitting guides serve to position knee system cutting blocks. Methods. Preoperatively an image of the distal femur and proximal tibia are formed using CT-scanning. This image is used to create patient specific guides that fit in one single position on the contours of the bone and prosthesis in situ. These guides are fixed with pins and thereafter removed. The pins determine the position of the cutting blocks. Ten consecutive revisions were performed using this technique. Results. All guides fitted well. All femoral prostheses were properly inserted using this technique. One proximal tibia however did not have not enough bonestock so that conversion to intramedular referencing was performed. This was to be expected after the preoperative planning. Postoperative position of the prosthesis was good in all cases. Discussion. This new technique can help to make unicompartmental to total knee arthroplasty less demanding. Problems such as the need for augmentations can be predicted in the preoperative planning. Radiation issues due to CT scanning are limited. The instrumentation needs to be redesigned in order to make this technique work in cases with minimal bonestock present

Introduction and Objective. After anterior cruciate ligament reconstruction one of the risk factors for graft (re-)rupture is an increased posterior tibial slope (PTS). The current treatment for PTS is a high tibial osteotomy (HTO). This is a free-hand method, with 1 degree of tibial slope correction considered to be equal to 1 or even 1.67 mm of the anterior wedge resection. Error rates in the frontal plane reported in literature vary from 1 – 8.6 degrees, and in the sagittal plane outcomes in a range of 2 – 8 degrees are reported when planned on PTSs of 3 – 5 degrees. Therefore, the free-hand method is considered to have limited accuracy. It is expected that HTO becomes more accurate with patient specific saw guides (PSGs), with an accuracy margin reported in literature of 2 degrees. This proof of concept porcine cadaver case study aimed to investigate whether the use of PSGs improves the accuracy of HTO to less than 2 degrees. Secondly, the reproducibility of tibial slope measurement was evaluated. Materials and Methods. Preoperative MRI images of porcine cadaver knees (n = 3) were used to create 3D anatomical bone models (Mimics, Materialise, Belgium). These 3D models were subsequently used to develop PSGs (3-Matic, Materialise, Belgium) to correct all tibias for 3 degrees PTS and 4 degrees varus. The PSG mediated HTOs were performed by an experienced orthopaedic surgeon, after which postoperative MRI images were obtained. 3D anatomical models of postoperative tibias were created, and tibial slopes were assessed on both pre- and postoperative tibias. The tibial slope was defined as the angle between the mechanical axis and 3D tibial reference plane in the frontal and sagittal plane. The accuracy of the PSG mediated HTO (median and range) was defined as the difference in all possible combinations of the preoperatively planned and postoperatively obtained tibial slopes. To ensure reproducibility, the pre- and postoperative tibial slopes were measured thrice by one observer. The intra-class correlation coefficients (ICCs) were subsequently calculated to assess the intra-rater reliability (SPSS, IBM Corp., Armonk, N.Y., USA). Results. An accuracy within 2 degrees was achieved in all three cases. The median and range in accuracy for each specimen were +0.46 (−0.57 – 1.45), +0.60 (−1.07 – 1.00), and +0.45 (−0.16 – 0.71) degrees in the frontal plane, and −0.45 (−1.97 – 1.22), −0.80 (−2.42 – 1.77), and 0.00 (−2.19 – 1.93) degrees in the sagittal plane. The pre- and postoperatively planned tibial slopes in the frontal and sagittal plane were measured with a good up to excellent reproducibility. The ICCs of the preoperative planned tibial slopes were 0.82 (95% CI, 0.11 – 1.0), and 0.77 (95% CI, 0.17 – 1.0) for the frontal and sagittal plane, respectively. Postoperative, the ICC for the frontal plane was 0.92 (95% CI, 0.43 – 1.0), and 0.67 (95% CI, −0.06 – 0.99) for the sagittal plane. Conclusions. This proof of concept porcine case study showed an accuracy for the PSG mediated HTO within 2 degrees for each specimen. Moreover, the tibial slopes were measured with a good up to excellent reproducibility. Therefore, the PSG mediated HTO seems to be accurate and might be better than the current used free-hand HTO method. These results offer perspective for implementation of PSG mediated HTO to correct PTS and metaphyseal varus

3D printing and rapid prototyping in surgery is an expanding technology. It is often used for preoperative planning, procedure rehearsal and patient education. There have been recent advances in orthopaedic surgery for the development of patient specific guides and jigs. The logical next step as the technology advances is the production of custom orthopaedic implants. I aimed to use freely available open source software and online cloud 3D printing services to produce a patient specific orthopaedic implant without requiring the input of a university department, specialised equipment or implant companies. Using standard CT scan DICOM data, a 3D surface reconstruction was made of a patient's uninjured radial head using open source DICOM viewer OsiriX. This was then manipulated in other open source software packages called Meshlabs and Netfabb to create a mirror image 3D model of the radial head with a stem to produce a prosthesis suitable to replace the contralateral fractured radial head. This was then uploaded and printed in stainless steel via cloud printing service . Shapeways.com. . The model produced was an exact replication of the patient's original anatomy, except a mirror image suitable for replacement of the contralateral side. The process did not involve any specialist equipment or input from an academic department or implant company. It took a total of 10 days to produce and cost less than £40. From this study I was able to show that production of patient specific orthopaedic implants is possible. It also highlights that the technology is accessible to all, and does not require any special equipment or large investment. It can be achieved quickly and for a very small financial outlay. As a proof of concept it has been very successful

Summary Statement. We are taking very expensive cutting edge technology, usually reserved for industry, and using it with the help of open source free software and a cloud 3D printing services to produce custom and anatomically unique patient individual implants for only £32. This is approx. 1/100. th. of the traditional cost of implant production. Introduction. 3D printing and rapid prototyping in surgery is an expanding technology. It is often used for preoperative planning, procedure rehearsal and patient education. There have been recent advances in orthopaedic surgery for the development of patient specific guides and jigs. The logical next step as the technology advances is the production of custom orthopaedic implants. Our aim was to use freely available open source software, a personal computer and consumer access online cloud 3D printing services to produce an accurate patient specific orthopaedic implant without utilising specialist expertise, capital expenditure on specialist equipment or the involvement of traditional implant manufacturing companies. This was all to be done quickly, cost effectively and in department. Methods & Materials. Using standard computed tomography (CT) scan and the standard file format of digital imaging and communications in medicine (DICOM) data, a 3D surface reconstruction was made of a cadaveric radial head using the software OsiriX (DICOM image processing software for Apple OS X). This data was then processed in Meshlabs (a system for the processing and editing of unstructured 3D triangular meshes) to create a mirror image 3D model of the radial head with a stem added to produce prosthesis suitable to replace the contra lateral radial head. Both packages are distributed under open-source licensing—Lesser General Public Licence (LGPL)—and are therefore free. This was then uploaded and 3D printed using a process of selective laser sintering (SLS) in stainless steel via the commercial cloud printing service . Shapeways.com. . Results & Conclusions. The model produced was an accurate mirror image replica of the patient's original anatomy (all measurements equal +/− 0.2mm using TS411212 Digital Vernier Expert Caliper 300mm P=0.001 Showing no significant statistical difference. Production from original CT scan took a total of 10 days and the total cost including shipping was £32. This was then re-implanted in to the contra lateral cadaveric radius. We achieved our aims and goals of quick, cost effective and accurate implant creation

Summary Statement. Our data suggest that postoperative component positioning in TKA with PSPG is not consistent with pre-operative software planning. More studies are needed to rule out possible learning curve in this study. Introduction. Patient specific positioning guides (PSPGs) in TKA are based on MRI or CT data. Preoperatively, knee component positions can be visualised in 3-dimensional reconstructed images. Software allows anticipation of component position. From software planning PSPGs are manufactured and those PSPGs represent intra-operative component alignment. To our knowledge, there are no studies comparing pre-operative software planning with post-operative alignment. Aim of this study is to investigate the correlation between pre-operative planning of component positioning and the post-operative achieved alignment with PSPG technique. Patients & Methods. The first 25 TKA (cemented Vanguard® Complete Knee System, Biomet) with PSPG (Signature™ Biomet) performed at Telemark Hospital in 2009–2010 and the first 17 TKA with PSPG performed at Oslo University Hospital in 2010–2011 were included. A postoperative CT scanning and measurement protocol was used (Perth protocol). CT measurements were performed by 2 independent observers and comparative with pre-operative software (Materialise) planning. Component position angles of femur and tibia were measured. Mechanical axis for both femoral and tibial component angles in all planes was defined as zero degrees. Target angle for femoral component in sagittal plane was set to 2,8 degrees flexion on average and for the tibial tray to 3 degrees of posterior slope. Tibial rotation was in most cases obtained by using extra-medullary guide and therefore not included in this study. Results. In respectively coronal, sagittal and axial plane the femoral component angle was on average 1.2° in varus, SD 1.6 (1.7° valgus −4.5° varus), 4.4° in flexion, SD 3.9 (17.3° flexion −1.6° extension) and 0.5° in external rotation, SD 0.1 (2.3° internal rotation −4.3° external rotation). For the tibial component angle the component was on average 0,5° in varus (3.5° valgus −7.3° varus) and 3.7° posterior slope, SD 2.3 (8.8° flexion −2.4° extension). Intra-class correlation (ICC) between the 2 independent observers was for femoral component in coronal, sagittal and axial plane 0.85, 0.93 and 0.63 and tibial component in coronal and sigittal plane 0.94 and 0.95. Discussion/Conclusion. We expected that our measurements would be close to the pre-operative values. Although the mean values of post-operative measurements are close to pre-operative software planning, we found a considerable spread. Possible explanation might be error levels in pre-operative wrong identification of landmarks from MRI and/or different identification of bony landmarks on CT and intra-operative errors. All measurements were performed from the first Signatures performed in both hospitals. An early learning curve might explain some of the outliers. Time between manufacturing date and performed operation was in most cases several months, but less than the advocated 6 months. This time gap can theoretically provide a less proper fit in some cases due to slight change of anatomy in a progressive osteoarthritis. Our data suggest that postoperative positioning is not consistent with preoperative planning. This may be caused by the an early learning curve. It is uncertain whether this inconsistency is of clinical relevance. More data is necessary to prove any benefit of PSPG compared to existing procedures for TKA