Computer-assisted hip resurfacing surgery using the acrobot navigation system.

The authors have previously reported on the laboratory development of the Acrobot Navigation System for accurate computer-assisted hip resurfacing surgery. This paper describes the findings of using the system in the clinical setting and including the improvements that have been made to expedite the procedure. The aim of the present system is to allow accurate planning of the procedure and precise placement of the prosthesis in accordance with the plan, with a zero intraoperative time penalty in comparison to the standard non-navigated technique. At present the navigation system is undergoing final clinical evaluation prior to a clinical study designed to demonstrate the accuracy of outcome compared with the conventional technique. While full results are not yet available, this paper describes the techniques that will be used to evaluate accuracy by comparing pre-operative computed tomography (CT)-based plans with post-operative CT scans. Example qualitative clinical results are included based on visual comparison of the plan with post-operative X-rays.

Robotic control in knee joint replacement surgery.

A brief history of robotic systems in knee arthroplasty is provided. The place of autonomous robots is then discussed and compared to more recent 'hands-on' robotic systems that can be more cost effective. The case is made for robotic systems to have a clear justification, with improved benefits compared to those from cheaper navigation systems. A number of more recent, smaller, robot systems for knee arthroplasty are also described. A specific example is given of an active constraint medical robot, the ACROBOT system, used in a prospective randomized controlled trial of unicondylar robotic knee arthroplasty in which the robot was compared to conventional surgery. The results of the trial are presented together with a discussion of the need for measures of accuracy to be introduced so that the efficacy of the robotic surgery can be immediately identified, rather than have to wait for a number of years before long-term clinical improvements can be demonstrated.

Very low-dose computed tomography for planning and outcome measurement in knee replacement. The imperial knee protocol.

Surgeons need to be able to measure angles and distances in three dimensions in the planning and assessment of knee replacement. Computed tomography (CT) offers the accuracy needed but involves greater radiation exposure to patients than traditional long-leg standing radiographs, which give very little information outside the plane of the image. There is considerable variation in CT radiation doses between research centres, scanning protocols and individual scanners, and ethics committees are rightly demanding more consistency in this area. By refining the CT scanning protocol we have reduced the effective radiation dose received by the patient down to the equivalent of one long-leg standing radiograph. Because of this, it will be more acceptable to obtain the three-dimensional data set produced by CT scanning. Surgeons will be able to document the impact of implant position on outcome with greater precision.

Preoperative planning and intraoperative guidance for accurate computer-assisted minimally invasive hip resurfacing surgery.

Hip resurfacing is an alternative to total hip replacement (THR) and is particularly suitable for the younger, more active patient. However, it is a more demanding procedure. This paper describes a system that enables the surgeon to plan the surgery preoperatively with optimally sized and placed components, and then transfer this plan to an intraoperative system that registers computer models to the real patient and tracks surgical tools, allowing the surgeon to ensure that the bone is resected correctly and that the components are fitted in accordance with the plan. The paper describes a series of instruments used with the system which are locked to the bone. These instruments serve the dual purpose of soft tissue retraction and bone immobilization. The system will shortly be the subject of laboratory and clinical evaluation. Registration, a cornerstone of the tracked instrument system, has been tested, and accuracy measures are provided. Experimental results for the remainder of the system will be provided after clinical trials.