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.

The triangular fibrocartilage complex (TFCC) is a known stabiliser of the distal radioulnar joint (DRUJ). An injury to these structures can result in significant disability including pain, weakness and joint stiffness. The contribution each of its components makes to the stability of the TFCC is not well understood. This study was undertaken to investigate the role of the individual ligaments of the TFCC and their contribution to joint stability.

The study was undertaken in two parts. 30 cadaveric forearms were studied in each group. The ligaments of the TFCC were progressively sectioned and the resulting effect on the stability of the DRUJ was measured. A custom jig was created to apply a 20N force through the distal radius, with the ulna fixed.

Experiment one measured the effect on DRUJ translation after TFCC sectioning. Experiment two added the measurement of rotational instability.

Part one of the study showed that complete sectioning of the TFCC caused a mean increase in translation of 6.09(±3) mm. Sectioning the palmar radioulnar ligament of the TFCC caused the most translation.

Part two demonstrated a change in rotation with a mean of 18 (± 6) degrees following sectioning of the TFCC. There was a progressive increase in rotational instability until the palmar radioulnar ligament was also sectioned.

Linear translation consistently increased after sectioning all of the TFCC ligaments, confirming its importance for DRUJ stability. Sectioning of the palmar radioulnar ligament most commonly caused the greatest degree of translation. This suggests injury to this ligament would more likely result in a greater degree of translational instability. The increase in rotation also suggests that this type of instability would be symptomatic in a TFCC injury.

Augmented reality simulators offer opportunities for practice of orthopaedic procedures outside of theatre environments. We developed an augmented reality simulator that allows trainees to practice pinning of paediatric supracondylar humeral fractures (SCHF) in a radiation-free environment at no extra risk to patients. The simulator is composed of a tangible child's elbow model, and simulated fluoroscopy on a tablet device. The treatment of these fractures is likely one of the first procedures involving X-ray guided wire insertion that trainee orthopaedic surgeons will encounter. This study aims to examine the extent of improvement simulator training provides to real-world operating theatre performance.

This multi-centre study will involve four cohorts of New Zealand orthopaedic trainees in their SET1 year. Trainees with no simulator exposure in 2019 - 2021 will form the comparator cohort. Trainees in 2022 will receive additional, regular simulator training as the intervention cohort. The comparator cohort's performance in paediatric SCHF surgery will be retrospectively audited using routinely collected operative outcomes and parameters over a six-month period. The performance of the intervention cohorts will be collected in the same way over a comparable period. The data collected for both groups will be used to examine whether additional training with an augmented reality simulator shows improved real-world surgical outcomes compared to traditional surgical training. This protocol has been approved by the University of Otago Health Ethics committee, and the study is due for completion in 2024.

This study is the first nation-wide transfer validity study of a surgical simulator in New Zealand. As of September 2022, all trainees in the intervention cohort have been recruited along with eight retrospective trainees via email. We present this protocol to maintain transparency of the prespecified research plans and ensure robust scientific methods. This protocol may also assist other researchers conducting similar studies within small populations.

Unrecognized pin penetrance in the treatment of SCFE by percutaneous pinning has been shown to be under-reported with serious long-term sequelae. The purpose of this study was to use post-operative CT to determine the true position of the screw tip when compared to intra-operative x-rays.

Twenty-four patients were offered post operative CT scans in the acute and clinic setting. Intra-operative plain films (AP and lateral) were compared to post operative CT scans (coronal and axial) to determine

the distance of the screw tip from the particular surface of the hip joint,

The positions of a total of 38 screws were measured. Plain x-rays where shown to consistently underestimate the distance to the articular surface. There were significant differences in the distance to the articular surface in the AP (5.5 mm) vs. coronal (3.4 mm) and lateral (4.7 mm) and vs. axial CT (4.1 mm) planes (p < 0.01). The average number of screw threads across the articular surface on the lateral x-ray was 6.7 vs. 8.1 in the coronal CT (p< 0.05). Four of the screws were shown to penetrate the joint surface in CT not shown on plain film.

This study has found that CT scans show screws are closer to the joint surface in the axial and coronal plane on CT when compared to plain x-ray in the AP and lateral plane. CT scans also show that there are more screw threads across the epiphysis than shown on plain x-ray. Placement of the screw within specific quadrants of the femoral head was found to be similar on CT and x-ray. CT scans identified pin penetrance not seen on intra-operative images.

Correct sizing of knee arthroplasty implants avoids problems such as stiffness from too large an implant, or periprosthetic fractures from undersizing. Currently most implants are based on a generic unisex population. Femoral component sizing is therefore based solely on the AP measurement after the distal femoral cut. In order to investigate the differences between the New Zealand population and other populations with reported anthropometrics we studied the anthropometrics of the male and female distal femur.

The distal femur of 26 cadaveric knees was resected using standard cutting guides. Using a sizing guide the AP dimension was measured from the posterior condyle to the anterior cortex just proximal to the trochlea (posterior referencing). The ML dimension was measured at the cut surface in the coronal plane of the epicondylar axis.

Overall AP measurement had a mean(standard deviation) of 62(±6.7) mm, the ML measurements had a mean (sd.) of 72(±6.6)mm yielding an ML/AP(100) ratio of 117(±11). The male AP mean was 67(±4.5) mm and female AP 57 (±4.4)mm. The male ML was 77 (±4.7)mm and female ML 68 (±4.5)mm. The ML/AP ratio for male was 111(±12) and female was 120 (±10).

This pilot study has shown differences between genders in the NZ population even with this small sample size. As this data is important for designers of total knee implants, planning is currently underway to perform measurements intraoperatively from approximately 400 patients undergoing total knee replacement.

Cannulated screw fixation is currently the treatment of choice for slipped capital femoral epiphyses (SCFE). A SCFE module of the Bonedoc simulator was created in order to test the ability of advanced trainees to place the screw in the correct position, and the practicality of using the simulator within the orthopaedic surgery training curriculum.

Bonedoc (University of Auckland) is a virtual reality simulator of image guided orthopaedic operations1. This simulator runs in Internet Explorer (Microsoft, USA) using the Octaga (Octaga, Norway) plugin. The total download is around 4 MB. The SCFE module was created from a CT scan of a Grade 2 acute on chronic SCFE. DICOM images were imported into 3DView (www.rmrsystems.co.uk) and a mesh created. The generic femur from the DHS module was morphed within the CAD package Blender (Blender.org) to conform to this reconstructed SCFE mesh.

Forty two advanced trainees operated on the same virtual SCFE during a training weekend. The trainees had 25 minutes to become familiar with the simulator and complete the operative case. The trainees performed all tasks relevant to the operation. At the operation’s conclusion the trainees self-assessed their performance. Subsequently the simulator provided surgically relevant objective feedback on aspects such as exact position of the screw, misplaced attempts and the number of x-rays. The results were analysed using SAS (SAS Institute, USA) in subgroups based on year on the scheme, as well as correlated within each operation.

There was no difference in the accuracy with which the virtual slipped capital femoral epiphysis was pinned by trainees in different years in the training programme. However, 26 of the 39 of the virtual screws were placed in the superior direction. There was no correlation between number of X-ray images taken and final accuracy of screw placement. The number of misplaced drill holes was correlated both with number of X-ray images taken (p< 0.01) and operative time (p< 0.01) but not with final accuracy of the screw. An increase in misplaced attempts was correlated with angulation errors in the anterior plane (p< 0.01). There was no correlation between the trainees’ self assessment and any of the measured variables.

The Bonedoc simulator provides a means to test trainees on technical aspects of a surgical procedure. It provides objective results, which can mimic real world outcomes. In addition, the ability to test all trainees on the same virtual operative case allows standardisation of assessment. All trainees completed the task to a similar level of accuracy, which may reflect the overall skill level in advanced trainees within the New Zealand. However, many trainees placed the screw in the superior portion of the femoral head, which is thought to increase the risk of avascular necrosis2. Further work is required to evaluate how accurately performance on the simulator predicts performance in the operating theatre

There is increasing pressure to develop virtual reality surgical simulation that can be used in surgical training. However, little is known of the attitudes of the surgical community towards such simulation, and which aspects of simulation are most important.

A postal survey on attitudes to surgical simulation was sent to all New Zealand orthopaedic surgeons and advanced trainees. This comprised 44 questions in ten sections, using either a visual analogue scale (0 to 10) or free text box replies. Results were analysed for two sub-groups; surgeons qualified before 1990 and those qualified in or after 1990 or still in training.

Of 208 possible responses, 142 were received, a response rate of 68%. Only 4 respondents had tried a surgical based simulator. Earlier qualified surgeons were more likely to agree that simulation was an effective way to practice surgical procedures, median score 7.7 versus 5.6 (p=0.03). Both groups thought the most important task for simulation was practicing angulation/spatial orientation (median score 8.4/10), while a realistic view of the operation was the most important requirement (median score 9/10). Both groups were unconvinced that simulation would impact on their practice in the next five years, with this statement being scored lower by later qualified surgeons, median score 2.4 versus 4.1 (p=0.04).

Orthopaedic surgeons in New Zealand are supportive of surgical simulation but do not expect simulation to have an impact in the near future. Intriguingly, later qualified surgeons and trainees are more sceptical than their earlier qualified colleagues.

A procedure is presented which allows the efficient production of a patient specific computer model of the femur, for surgical planning. Similar models require long processing times and/or high performance computing.

The method uses 24 key landmark points to customise a generic femur to patient data, using a desktop computer. By using non-linear elements a smooth, curved surface is obtained. A finite element mesh of a generic femur consisting of 384 elements was created using the analysis software CMISS (Bioengineering Institute, University of Auckland). A rectangular shaped host mesh was defined to enclose the generic femur. Datasets of 5 human femurs were obtained using a hand-held laser scanner on dry bones and the visible human dataset. Key landmark data points were selected on the generic femur along with corresponding target points on each data set. The host mesh was then deformed using a least squares algorithm, causing customisation of the generic femur to the patient specific model. Each customised model was compared with its entire dataset. The fitting process took less than 100 seconds on a 180 MHz 02 computer (SGI, CA, USA). The algorithm yielded an average root mean square (RMS) of 3.09mm with a standard deviation of 0.15mm. Operator time for positioning the projection points was less than 5 minutes.

This paper presents a novel means for customisation of human femoral geometry with generation of patient specific models on a PC from scan data in under 10 minutes. Current work is focusing on stress analysis, surgical simulation and planning.