A.R.W. Barrett

Hands-on robotic unicompartmental knee replacement - A prospective, randomised controlled study of the Acrobot system

We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported. All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2 degrees of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages.

Robotic control in knee joint replacement surgery.

Abstract 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.

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

Abstract 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.

A computer-assisted training/monitoring system for TURP structure and design

A generic framework for a computer-assisted system for both soft tissue endoscopic surgery and surgical training is being researched and developed. The concept demonstrator is a specific system for transurethral prostatic resection (TURF). The main novelty of the research is that it is not confined to an in vitro trainer system. An in vivo monitoring version of the system, for use in the operating theater, is also being researched. This paper presents the frameworks structure and design using the Unified Modeling Language. It also discusses and justifies the underlying information technologies chosen to implement this approach. Object-oriented concepts and well-proven mathematical tools have been adopted as the foundation of this research and development. The rationale for having chosen such tools is presented. The objectives are to arrive at a system which is modular, general, and reusable.

Computer-Assisted Soft-Tissue Surgery Training and Monitoring

Last year at MICCAI, a computer-assisted surgical training system (CASTS) for Transurethral Resection of the Prostate (TURP), was presented [1]. Unpredictable deformation of the prostate phantom caused unacceptable inaccuracies. Solutions have now been investigated which are descnbed in this paper, namely constraining the phantom, using a different phantom, and tracking the phantoms deformation and movement with ultrasound. Ethics Committee approval was obtained to assess the feasibility of using CASTS as an in vivo system for surgical monitoring (CASMS). Pre-operative ultrasound of the patient forms the basis of the computer-generated prostates model. Peroperative ultrasound is employed to detect and compensate for prostate movement. An optically tracked ultrasound probe is used to relate the images to the optically tracked resectoscopes coordinate system. The CASMS in vivo system will help in the assessment of completeness of resection, the provision of information of resection both distal to the verumontanum and near to the capsule. Tests of the CASMS system in the operating room are described.

THE ACROBOT® SYSTEM FOR ROBOTIC MIS TOTAL KNEE AND UNI-CONDYLAR ARTHROPLASTY

The concept of the Acrobot® system is described. The technical details of the complete system are then outlined, including the pre-operative planner which incorporates 3D CT models together with CAD models of prostheses that can be used to plan the leg alignment, position the prostheses, plan the shape of the cuts required and generate the regions within which cuts must be constrained. The robotic system is also described, together with the methods for locating and clamping the patient. An outline is given of the means by which the preoperative model is registered or aligned to the intra-operative position of the patient and of the robot, without the need for fiducial markers. Post-operative results are given, for both total knee replacement and also for the more recent clinical trials using a minimally invasive robotic procedure for uni-condylar arthroplasty.