Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly. These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening

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 cm³. 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.

Anatomically specific fixation devices have become mainstream, yet there are anatomical regions and clinical conditions where no pre-contoured plates are available, such as for glenohumeral arthrodesis. In a case series of 4 glenohumeral arthrodesis patients, a consultant orthopaedic surgeon at GCUH implemented 3D printing technology to create reconstructions of each patient's shoulder girdle to pre-contour arthrodesis plates. Our aim was to quantify the cost-benefit & intra-operative time savings of this technique in glenohumeral arthrodesis. We hypothesized that the use of 3D printing for creating patient specific implants through pre-operative contouring of plates will lead to intra-operative time and cost savings by minimising time spent bending plates during surgery. This study analysed 4 patients who underwent shoulder arthrodesis by a single consultant orthopaedic surgeon at GCUH between 2017-2021. A CT-based life-size model of each patient's shoulder girdle was 3D printed using freely available computer software programs: 3D Slicer, Blender, Mesh Mixer & Cura. Once the patient's 3D model was created, plate benders were used to contour the plate pre-op, which was then sterilised prior to surgery. Arthrodesis was performed according to AO principles of fixation. The time spent pre-bending the plate using the 3D model was calculated to analyse the intra-op time and cost-saving benefits. For the 4 cases, the plate pre-bending times were 45, 40, 45 & 20 minutes (average 38.8 mins). The intra-op correction time to make small adjustments to the plate was 2 min/ case. 3 plates needed minor (3 degree) adjustment to fine-tune scapula spine contouring. 1 plate needed a 5 degree correction to fine-tune hand position. On average, the pre-bending of the plate saved approximately 38.8 mins intra-op/ case. These shorter anaesthetic and operating times equate to approximately $2586 saving/ case, given an estimate of $4000/hour of theatre costs. We conclude that pre-bending plates around 3D-printed life-size models of an individual's shoulder girdle prior to surgery results in approximately 38.8 mins time saving intra-op when used in shoulder arthrodesis. This is a viable and effective technique that will ultimately result in significant operative time and financial savings

Lower limb fractures in children are common. These fractures can be managed in a variety of ways, and the method chosen depends on a number of factors including:. Age of the child. Site of fracture. Whether the fracture is open or closed. Associated injuries. Surgeon’s expertise and experience. Parental wishes. Femur: Immediate or early hip spica gives good results withminimal shortening particularly in the younger child. Flexible IM nails have been widely reported and give good results. It is important to appreciate the mechanics of how the nails function to stabilise the bone and to recognise that pre-bending the nails is a vital step in the operation. As surgeons become more confident in using the nails, the range of indications can be extended to include proximal or distal fractures, comminuted, open and pathological fractures. Tibia: Skeletal stabilisation of open tibial fractures can be provided by application of an external fixator. The use of flexible IM nails in the tibia is more controversial. Introduction of these nails into the proximal tibia can be difficult and even with pre-bending of the wires, additional cast protection may be required

Introduction: Compression staples are becoming increasingly popular for osteotomies and arthrodesis. Their design can be divided into “Mechanical Compression” or “Shape Memory”. However, there are no publications investigating the actual compressive forces achieved or the ideal limb-length to staple width ratio. Methods and Materials: Compression was compared using a load cell mounted within a previously validated simulated fusion site. Two designs each of “mechanical compression” and “shape memory” staples were tested and filmed. The effect of altering limb length on compression was noted. Results: Both designs of “mechanical compression” staple splayed open causing either no net compression or even distraction. Distractive forces of up to 23N were recorded. The “shape memory” staples all achieved compression at the fusion site of between 5 and 25N. Limb length did not appear to alter the compression force achieved. The outcome was not affected by the material used. Discussion: “Mechanical compression” staples act in a similar manner to the AO principle of a 2-hole compression plate used without a lag screw or pre-bending. Although there is compression of the cis-cortex, the limbs of the staple splay open with a fulcrum around the bridge-limb intersection resulting in distraction of the trans-cortex. “Shape memory” staples compress both the cis-and trans-cortices along the length of the limb leading to adequate stability and compression forces across the fusion site. Conclusion: “Mechanical compression” staples cause a distractive force rather than a compressive force and we therefore recommend that they are not relied upon for fusion and the manufacturers need to modify the product or it’s indications for use. The “shape memory” staples do provide compression and the length-to-width ratio of the staple does not appear to be important

Bone shape variability within a specific population has been seldom investigated and used to optimize implant design. There is insufficient anatomical fitting of the existing prebend periarticular plates for the distal fibula. We developed a methodology for design of orthopaedic implants that fit a maximum percentage of the target population, both in terms of geometry and biomechanical stability. In co-operation with an implant manufacturer and different academic institutions, a virtual bone database has been developed that contains anatomical data of more than 1000 CT datasets with the implemented possibility to generate idealized implant fits for different anatomical sites. This program (Stryker Virtual Bone Database (VBD) is able to generate statistical anatomical shapes for different populations like age groups or ethnical groups. Based on this, an implant for the distal fibula has been developed (VariAx Distal Lateral Fibula Locking Plate) for distal fibula fracture treatment. Aim of this study was to develop and validate an implant that is optimized for the specific anatomical area. It should be precontoured and still fit to the majority of patients sustaining a distal fibular fracture. Another objective was to create a distally tapered design as there is less soft tissue cover in that anatomic area. Materials & Methods. ProE CAD system was used in combination with the Bone Database (VBDB) to evaluate the bone shape of the target population plate shape. Several bones (from CT scans) have been used in a first validation process in comparison with an implant already available on the market (SPS Fibula Plate). Additionally, the results have been verified with a bone fitting study which was conducted in collaboration with the Maurice E. Müller Institute (MEM) in Bern/Switzerland. In a second step, the finished implant design was validated against statistical bone shapes of populations of different ethical origin. Results. The comparison of the new Plate's shape with real bone data confirmed that the neutral form does cope with the anatomic situation laterally which means that no systematic pre-bending of the plate is required. Comparing with a conventional implant, the new implant could have been implanted unbend in 6 of 7 cases of virtual matching with real patient datasets compared to none with the conventional implant. The validation of statistical datasets of different ethnical origin (Caucasian, Asian) showed no statistical difference of implant mismatch. Conclusion. Based on these results, the new Plate can be considered an efficient solution to treat distal fibula fractures without or only limited time consuming intra-operative bending. Although technically now possible, different plate designs for Caucasians and Asians are not required

Introduction: Compression staples are indicated for use in forefoot osteotomies and midfoot and forefoot fusions. The staple design can be divided into “Mechanical Compression” or “Shape Memory”. Although they are becoming increasingly popular because of their ease of use, there is little data published on the effectiveness of the true compression achieved across bony surfaces. There is no data on the optimal limb-length to staple width ratio required for compression. We aimed to compare four commercially available types of compression staple and measure the compression force achieved. Methods and Materials: Compression in porcine tibia, cancellous bone substitute and perspex was compared using a load cell mounted within a simulated fusion site between two test blocks. The amplified output was continuously recorded using a datalogger and the data analysed. Two designs of “mechanical” compression staple and two designs of “shape memory” staple were tested. The effect of altering limb length on compression was also noted. Results: The “mechanical” compression staples splayed open with the limbs of both designs causing either no compression or even distraction at simulated fusion site. Distractive forces of up to 23N were recorded. By contrast, the “shape memory” staples all achieved compression at the fusion site of between 5–25N. Limb length did not appear to alter the compression force achieved. Discussion: “Mechanical” compression staples act in a similar way to basic AO principles of a 2-hole compression plate used without a lag screw technique or pre-bending. Although there is compression of the cis-cortex, the limbs of the staple splay open with a fulcrum around the bridge-limb intersection resulting in distraction of the trans-cortex. “Shape memory” staples compress both the cis- and trans-cortices along the length of the limb leading to adequate stability and compression forces across the fusion site. Conclusion: This study demonstrates that “mechanical” compression staples cause a distractive force rather than a compressive force and manufacturers should be aware that further design modifications are required to prevent this. We recommend that “shape memory” staples, standard staples or lag screws are used instead. The limb-length to staple width ratio does not appear to be important

Since 1993, we have been developing preoperative planning system based on CAT scan data. In early period it was used to decide cup diameter and orientation for Total Hip Arthroplasty (THA). It was done using hemisphere object locating proper position and orientation. According to our progress, we have started using it for custom stem designing, stem selection and stem size planning too since 1995. Since 2001, we have been using it for almost all THA cases. We also have started use it for any case we have question about 3D geometries. Since 2005 we started computer planed 2 staged THA after leg elongation for high riding hips and reported at ISTA 2007 too. Now our policy became that every tiny question we have, we shall analyze and plan preoperatively. In our population, the incidence of the developmental dysplastic hips is higher. The necks often have bigger anteversion, and less acetabular coverage. So we often use screws for cup fixation. The screw direction allowed in thin shell thickness is limited and less bone coverage makes good cup fixation difficult. With highly defected cases and with revision cases the situation is more difficult. In the present study, we have developed acetabular 3D preoperative planning method with screw direction, length, and for the cases with defect, cup supporter pre-shaping with models and prediction of the allograft volume. For the less defect cases, geometries of cup with screw holes were requested to the maker and were provided for us. Screws were attached perpendicular to each screw hole. Screw geometries have marks at every 5mm to plan proper length. The cup was located as much as closer to the original acetabular edge, keeping in the limit to avoid dislocation. Small space above the cup was accepted if anterior and posterior cup edge could be supported by original bone. Then the cup was rotated until we can obtain proper screw fixation. For the cases with severe defects, we use cup supporters and allografts. Cup supporters are designed to be bent and fit to the pelvis during the surgery. But to shape it a properly; for good coverage and strong support; is very difficult and takes long through the limited window with fatty gloves. And mean while we get more bleeding. The geometries were obtained by CAT scan of the devices. Then proper size was determined as cup size. Chemiwood model was made and proper size supporter was opened and bent preoperatively using the model. It was scanned again and compared to the pelvic geometry again. Using cluster cups, no dangerous screw was found as long as normal cup orientation was decided and screws were less than 30mm. Posterior screws were often too short then rotated anterior and found to have good fixation. Pre-bending could reduce surgical time remarkably. As long as we could know, no navigation system can control the cup rotation. But acetabular preoperative planning was very useful and could reduce operative invasion. It could be done easily without using navigation system

End caps are intended to prevent nail migration (push-out) in elastic stable intramedullary nailing. The aim of this study was to investigate the force at failure with and without end caps, and whether different insertion angles of nails and end caps would alter that force at failure.

Simulated oblique fractures of the diaphysis were created in 15 artificial paediatric femurs. Titanium Elastic Nails with end caps were inserted at angles of 45°, 55° and 65° in five specimens for each angle to create three study groups. Biomechanical testing was performed with axial compression until failure. An identical fracture was created in four small adult cadaveric femurs harvested from two donors (both female, aged 81 and 85 years, height 149 cm and 156 cm, respectively). All femurs were tested without and subsequently with end caps inserted at 45°.

In the artificial femurs, maximum force was not significantly different between the three groups (p = 0.613). Push-out force was significantly higher in the cadaveric specimens with the use of end caps by an up to sixfold load increase (830 N, standard deviation (SD) 280 vs 150 N, SD 120, respectively; p = 0.007).

These results indicate that the nail and end cap insertion angle can be varied within 20° without altering construct stability and that the risk of elastic stable intramedullary nailing push–out can be effectively reduced by the use of end caps.

Cite this article: Bone Joint J 2015;97-B:558–63.

Objectives

Small animal models of fracture repair primarily investigate indirect fracture healing via external callus formation. We present the first described rat model of direct fracture healing.