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.

Though the perceived advantages of computer assisted orthopaedic systems (CAOS) have been claimed incessantly over the years, these systems are far from commonplace in most orthopaedic theatres. Here, we present a summary of those very reasons.

Health Technology Assessment report elicited no proof of clinical benefits of the Robodoc over conventional procedures. Mazoochian et al were unable to confirm the same accuracy of implant position while using the Caspar. Honl et al found a higher revision and dislocation rate accompanied with longer surgery durations when robotic assisted technology was used.

Shortcomings identified in the CT-based navigation systems included an additional CT scan, which represents extra costs for the acquisition as well as additional radiation to the patient. Sistan et al claims that image-free navigational systems in knee arthroplasty do not provide a more reliable means for rotational alignment as compared to traditional techniques. Computer assisted pedicle screw insertion in the spine has also not demonstrated any significant clinical advantages.

To date, long term results of computer-guided or robot-assisted implantation of endoprosthetic devices are still lacking. With the unproven long-term clinical and functional results of patients who had computer aided surgery and given the multi-factorial complexities of patient outcome, it is difficult to claim via small scale short term studies that these systems present a significant benefit to the patient or the healthcare providers. Potential benefits of long-term outcome, better implant survival and functional improvement require further investigation and until that information is available this technology must be further developed before its widespread usage can be justified.

Aims: Dynamic hip screw (DHS) is a common implant used for extracapsular fracture neck of femur. Accurate placement of the guide wires for the DHS insertion is the most important surgical step. In order to improve precision and accuracy of the guide wire placement, Computer Assisted Orthopaedic Surgery System (CAOSS) was used which was developed at the University of Hull. Early clinical experience in 14 cases is presented. Methods: CAOSS helps in surgical planning and aid surgeons for accurate guide wire placement into femoral neck. After fracture reduction, intraoperative computer based surgical planning was performed using one ßuoroscopic image in two planes each. A trajectory obtained thus helped surgeon to place a guide wire along with the required course under the computer guidance. Results: CAOSS system was used on 11 patients for guide wire placement. Intraoperative ßuoroscopic images of all the patients showed accurate position of the guide wire both in AP and lateral planes. Only 4 ßuoroscopic images were required during the surgical procedure in total, both pre and post guide wire insertion. Conclusions: The computer aided surgery used in guide wire placement for dynamic hip screw insertion proves to be accurate and reliable. It also reduces ionisation radiation exposure to the surgeon, patients and theatre personnel.

Aims: Dynamic hip screw (DHS) is a common implant used for extracapsular fracture neck of femur. Accurate placement of the guide wires for the DHS insertion is the most important surgical step. In order to improve precision and accuracy of the guide wire placement, Computer Assisted Orthopaedic Surgery System (CAOSS) was used , which was developed at the University of Hull.

Methods: CAOSS helps in surgical planning and aid surgeons for accurate guide wire placement into femoral neck. After fracture reduction, intra-operative computer based surgical planning was performed using one fluoroscopic image in two planes each. A trajectory obtained thus helped surgeon to place a guide wire along with the required course under the computer guidance.

Results: CAOSS system was used on 11 patients for guide wire placement. Intra-operative fluoroscopic images of all the patients showed accurate position of the guide wire both in AP and lateral planes. In theory only 4 fluoroscopic images are required during this surgical procedure in total. But in practice, more than 4 were required depending upon the experience of the radiographer. None of the patient had any intra-operative complication. Conclusions: The computer aided surgery was found to be safe, accurate and reliable for guide wire placement for dynamic hip screw insertion.

Hull Medical Engineering (HULMEC) group was established in 1992 as a collaboration of orthopaedic surgeons and various research groups from the University of Hull to promote multidisciplinary research especially the application of computers to aid in surgery. With the joint effort of researchers and surgeons CAOSS was developed.

The key aim of the CAOSS has been to use intra-operative surgical planning using fluoroscopic based images, hence this system aids in performing those procedure which requires fluoroscopy namely dynamic hip screw guide wire insertion, distal locking of the screw and placement of cannulated hip screw. The major steps of CAOSS are the precision calibration of the fluoroscopic images, use of these images for accurate intra operative surgical planning, innovative planning algorithms, and a safe, rapid and accurate approach to trajectory execution. CAOSS has been used on the plastic bones in the laboratory setting and was found to be accurate. Presently CAOSS has been used in an ethically approved clinical trial for guide wire insertion for the DHS placement.

Perceived Advantages of CAOSS

Safe

Passive system

Non-invasive

Surgeon maintains decision making

Decreasing radiation exposure

Reducing complexity of the procedure

Reducing technical failures

Reducing operating time

Improving accuracy of implant placement

Reducing bone damage (by reducing repeated guide wire insertion)

Improving Patient outcome

Cost Effective

Easy to use