Introduction: Surgical training is being greatly affected by the challenges of reduced training opportunities, shortened working hours, and financial pressures. There is thus an increased need for training systems to aid development of psychomotor skills of the surgical trainee. Furthermore, simulation environments can provide a friendlier and less hazardous environment for learning surgical skills. Such simulations may be used to augment training in the operating room (OR) so that trainees acquire key skills in a non-threatening and unhurried environment. Trajectory planning and implementation forms a substantial part of current and future orthopaedic practice. This type of surgery is governed by a basic orthopaedic principle where the placement of a surgical tool at a specific site within a region via a trajectory that is planned from X-ray based 2D images and is governed by 3D anatomical constraints. The accuracy and safety of procedures utilising the basic orthopaedic principle depends on the surgeon’s judgement, experience, ability to integrate images, utilisation of intra-operative X-ray, knowledge of anatomical-biomechanical constraints and eye hand dexterity. With the decrease in training opportunities in OR for the surgical trainee, these skills are developing at a much later stage in training. Several studies have shown a reduction in the number of operations undertaken and a reduction in the level of competence achieved by surgical trainees. Purpose of the study: This study develops our existing surgical CAOSS (Computer Assisted Orthopaedic Surgical System) [4, 5] for fracture fixation into a training tool for skill acquisition of the basic orthopaedic principle, namely, 3D navigation using 2D X-ray images. Material and Methods: Orthopaedic trainees who are presently working in Hull and East Yorkshire NHS Trust are recruited in this study. The study is divided into two parts. The initial part of the study involves the use of the conventional CAOSS to train the orthopaedic trainees with no prior exposure of distal locking of femoral nails and the dynamic hip screw. The second part of the study involves the use of modified CAOSS to assess whether the initial training has helped in developing mental navigation skills of using a 2-D image and navigating the drill bit in 3-D space. The scoring system is based on a combination of parameters which include the time taken for centring of the interlocking screw, total exposures taken and the improvement in the position of the tip of the drill bit with each exposure. Results: The presentation will discuss the theories, methodology and scoring criteria to produce a training tool for training of the basic orthopaedic principle and how the training tool was validated. Discussion: The ability to quantify precisely three-dimensional navigation and processing of virtual information to help in hand eye co-ordination has not previously been used as a formal orthopaedic training tool. Clearly the assessment of such skills demands a scoring system that is both reproducible as well as being able to validate it that it predicts skill acquisition correctly. Currently, there is no known scoring system which can accurately assess the ability to navigate instruments in 3-D space using a C-arm image. We therefore propose that using CAOSS as a training tool for the surgical trainees in a relaxing less hurried environment is beneficial to training and we also propose for this tool a reproducible scoring system.

The Phantom based Computer assisted orthopaedic surgical system (CAOSS) has been developed collaboratively by the University of Hull and the Hull Royal Infirmary, to assist in operations like dynamic hip screw fixation. Here we present summary of our system. CAOSS comprises a personal computer based computer system, a frame grabber with video feed from a C-arm image intensifier, an optical tracking system and a radiolucent registration phantom which consists of an H arrangement of 21 metal balls. The phantom is held in position by the optically tracked end-effector. Knowing the optical position of the phantom, a registration algorithm calculates the position of C-arm in coordinate space of the optical tracking system. Computer based planning uses an anteroposterior (AP) and lateral image of the fracture. Marks are placed on the 2D projections of femoral shaft, neck and head on the computer screen, which are then used to create 3D surgical plan. The computer then plans a trajectory for the guide wire of DHS. The depth of the drill hole is also calculated. The trajectory is then shown on both AP and lateral images on the screen. CAOSS meets all the requisite of electrical and electromagnetic radiation standards for medical equipment. There has been extensive validation using software simulation, performance evaluation of system components, extensive laboratory trials on plastic bones. The positional accuracy was shown to be within 0.7mm and angular accuracy to be within 0.2°. The system was also validated using Coordinate Measurement Machine. Our system has the unique feature of the registration phantom which provides accurate registration of the fluoroscopic image.

The use of the C-arm fluoroscope for surgical navigation in various Computer Assisted Orthopaedic Surgery Systems (CAOS) has been an important success of research into CAOS technology. To use the fluoroscope for quantitative surgical navigation involves calibrating its 2D images and tracking the spatial position of the fluoroscope's image beam. This allows 3D reconstruction of anatomy from a series of 2D fluoroscopic images. This paper presents a new technique for determining the C-arm position and calibrating the image beam. This technique is based on a small imaging phantom that is placed close to the patient. This paper also briefly describes the CAOS system developed at Hull that uses this imaging phantom and reports on in vivo and in vitro studies.

The difficult part of the intramedullary (IM) nailing operation of long bone is to insert the distal locking screws. The current technique to insert these screws uses numerous fluoroscopic images and depends on skills and expertise of the surgeon. A Computer-Assisted Orthopaedic Surgical System (CAOSS) has been developed collaboratively by the University of Hull and the East Yorkshire Hospitals NHS Trust to assist the orthopaedic surgeons in these operations. The laboratory based test results for insertion of distal locking screws in intramedullary nailing procedure are presented and discussed in terms of accuracy and as part of the validation process to introduce new CAOS procedures into clinical use. This study shows that CAOSS in IM nails is robust and reliable. The positional accuracy in planning the trajectory for insertion of the distal locking screws was shown to be within 0.3 mm and angular accuracy within 0.2°.

Aims: Dynamic hip screw for intertrochanteric fractures is one of the most common procedures performed by orthopaedic surgeons. The prerequisite for proper placement of the implant is accurate insertion of the guide wire. The Computer Assisted Orthopaedic Surgical System [CAOSS] is designed to assist the surgeon by planning the trajectory based on one intra-operative AP and Lateral image from a C-Arm. Methodology: After closed reduction on the fracture table, two near orthogonal x-ray images containing the proximal femur with the registration phantom are obtained using a standard C-Arm and then processed after distortion correction. The phantom is supported by an end effector, which is continuously tracked in 3D space. Features of interest are extracted and the image registered in space through the evaluation of the phantom’s projection in the x-ray image. The versatility of the CAOSS is increased by the provision allowing the adjustment of the planned trajectory to the surgeon’s satisfaction. Once the trajectory is accepted, the surgeon implements the plan by moving a passive manipulator arm, while receiving visual positional cues from the computer in the form of a targeting screen. When the targeting is complete; the arm is locked in position and the trajectory implemented. Results: We present the results of the pilot clinical study involving 10 patients using this device. The results obtained were compared with an equal number of patients randomly selected from the complete neck of femur database, who had undergone a conventional DHS placement, during the last one-year. Accuracy of placement of the implant was assessed by an independent observer and by a previously validated computer program that assesses the accuracy from scanned post operative X-rays. The average targeting time was 6 minutes and overall there was no significant difference between the two groups.

A total of 125 consecutive hip fracture patients were investigated regarding hip geometry. There were 33 men of mean age 76 ± 10 years, and 92 women of mean age 78 ± 9 years. Patients with previous hip surgery were excluded. Hip geometry (hip-axis length, width of collum femoris, and femoral shaft and neck-shaft angle) were registered on both plain radiographs and DEXA scans performed within 2 weeks after fracture. On the radiographs, the calcar femorale, the Singh index, and the femoral neck index (FNI) were also calculated and compared with earlier published values of bone mineral density hip in the hip fracture patients. The fracture cases were compared with controls, 192 DEXA scans and 163 radiographs, in patients without hip surgery or known hip disease. As measured on the DEXA scans we found a wider collum femoris and a wider femoral shaft in both the male and female fracture cases, compared to controls. Also, the fracture cases showed signs of osteoporosis as measured by the calcar femorale, the Singh index, and the femoral neck index. These measurements showed good correlation with bone mineral density of the hip as measured by the DEXA scans.

In intramedullary nail (IMN) surgical operations, one of the main efforts for surgeons is to find the axes of two distal holes. Two distal holes on an IMN, which are inside the intramedullary canal of a patient's femur, can only be seen in a lateral X-ray view. For the standard surgical procedure, the localization of the distal hole axes is a trial-and-error process which results in a long surgical time and large dose of X-ray exposure. In this paper, an algorithm to derive the three-dimensional position and orientation of the distal hole axis was developed. The algorithm first derives the nail axis through two X-ray images. Then the distal hole axis is calculated through projecting back the hole boundary on the X-ray image from a lateral view to three-dimensional space. A least-squares method is used to determine the centres of the front hole and the back hole through iteration. The algorithm has been tested with real data and it was robust.

The C-arm fluoroscope is an indispensable intraoperative 2D imaging device for orthopaedic surgery. However, its frequent use in an operation presents a significant radiation hazard to the. theatre staff and patient. A recent technique known as virtual fluoroscopy (VF) enhances the fluoroscope's capability for image guided surgery by tracking optically the position of the C-arm, surgical instruments and the patient. Virtuality is achieved by overlay of surgical instruments onto one or more previously captured fluoroscopic images. A key benefit of VF is that it reduces considerably the radiation hazard. This paper reports on a new VF technique for tracking and calibration of the fluoroscopic C-arm. Also reported is the use of our VF system to provide a new image guided technique for the accurate placement of the femoral component of unicompartmental knee prosthesis.

Trajectory planning and implementation forms a substantial part of current and future orthopaedic practice. This type of surgery is governed by a basic orthopaedic principle [1] which involves the placement of a surgical tool at a specific site within a region, via a trajectory which is planned from X-ray based 2D images and governed by 3D anatomical constraints. The accuracy and safety of procedures utilising the basic orthopaedic principle depends on the surgeon's judgement, experience, ability to integrate images, utilisation of intra-operative X-ray, knowledge of anatomical-biomechanical constraints and eye hand dexterity. The surgeon must remain as the responsible medical expert in charge of the overall system. At the same time the surgeon covets the accuracy offered by Computer Assisted Surgery including a manipulator.A summary of current inadequacies of manipulators indicates that the main drivers for future work are that accuracy is critical in close contact with the environment, safety concerns dictate manipulator geometry and technological limitations are many. In any effort to develop an optimal manipulator to guide surgical instruments and tools it is an obvious first step to review and categorise current manipulators..The aim of this paper is to review all aspects of manipulator design against the five main criteria of ergonomics; safety; accuracy; sterility and measurable benefits such as reduced operative time, reduced surgical trauma and improved clinical results.