M. Jakopec

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.

Active-Constraint Robotics for Surgery

The concepts and benefits of hands-on robotic surgery and active-constraint robotics are introduced. The argument is made for systems to be cost effective and simple in order that they can be justified for a large range of surgical procedures. The case is made for robotic systems to have a clear justification, with benefits compared to those from cheaper navigation systems. The need to have robust systems, that require little surgical training and no technical presence in the operating room, is also discussed. An active constraint medical robot, the Acrobot System, is described together with its use in a prospective randomized controlled trial of unicondylar knee arthroplasty (UKA), comparing the performance of the Acrobot System with conventional surgery. Twenty-eight patients awaiting UKA were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. 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 having to wait for a number of years before long-term clinical improvements can be demonstrated

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.

Intra-operative Application of a Robotic Knee Surgery System

A robotic system is described with associated components for registration and fixation capable of performing total knee replacement (TKR) surgery. The robot uses an active constraint concept allowing it to work with the surgeon, allowing him to cut flat planes required for a standard TKR prosthesis in the tibia and femur. The human-computer interface for this co-operative scheme is described. Experiments are described that test the robot’s basic accuracy. Trials with plastic bone phantoms have been used to calibrate the system, after which tests on cadaveric legs have shown a good fit between the bone and prosthesis.

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.

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

Abstract 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.

The Acrobot® system for total knee replacement

A “hands‐on” robotic system for total knee replacement (TKR) surgery is presented. Computed tomography (CT) based software is used to accurately plan the procedure pre‐operatively. Intra‐operatively, the surgeon guides a small, special‐purpose robot, called Acrobot®, which is mounted on a gross positioning device. The Acrobot uses active constraint control, which constrains the motion to a pre‐defined region, and thus allows the surgeon to safely cut the knee bones to fit a TKR prosthesis with high precision. A non‐invasive anatomical registration method is used. The system has undergone early clinical trials with very promising outcomes.

Interactive Pre-Operative Selection of Cutting Constraints, and Interactive Force Controlled Knee Surgery by a Surgical Robot

This paper describes a low-cost computer system that takes CT images of the knee, and with three-dimensional models of knee prostheses allows a surgeon to position the prosthesis correctly pre-operatively in an interactive manner. Once in position the computer can process bone and prosthesis geometry to derive a set of constraint boundaries that constitute a safe cutting area for a force controlled robot (i.e. that avoids soft tissue such as ligaments), and provides the correct cutting planes for good prosthesis/bone alignment. This boundary information is used to program the robot, allowing a surgeon to move the robot within predefined regions to machine away bone accurately whilst preventing damage to soft tissue.

Hands-On Robotic Surgery: Is This the Future?

An introduction to robotic surgery is given, together with a classification of the range of systems available with their problems and benefits. The potential for a new class of robot system, called a hands-on robot is then discussed. The hands-on robotic system, which is called Acrobot®, is then presented for total knee replacement (TKR) surgery and for uni-condylar knee replacement (UKR) surgery. CT-based software is used to accurately plan the procedure pre-operatively. Intra-operatively, the surgeon guides a small, special-purpose robot, which is mounted on a gross positioning device. The Acrobot® uses active constraint control, which constrains the motion to a predefined region, and thus allows the surgeon to safely cut the knee bones to fit a TKR or a UKR prosthesis with high precision. A non-invasive anatomical registration method is used. The system has undergone early clinical trials of a TKR surgery and, more recently a blind randomised clinical trial of UKR surgery. Preliminary results of the UKR study are presented in which the pre-operative CT based plan is contrasted with a post operative CT scan of the result, in an attempt to gain an objective assessment of the efficacy of the procedure. Finally, proposals for future requirements of robotic surgery systems are given.

A mechatronic based robotic system for knee surgery

The paper describes experiments using a new concept in mechatronic robot surgery: that of a robot with a force control handle moved by the surgeon. The surgeon back-drives the robot under servo-assistance, whilst feeling the force from a rotating cutter during surgery, for example, in total knee replacement. Thus, when machining the knee bones to take a prosthetic metal replacement, the surgeon can use his inherent sensing to slow down, or take a lighter cut, when cutting hard bone. The robot however, can be provided with regions of force constraint so that, say, a flat or curved plane can be cut accurately into the bone to allow the prosthetic implant to be subsequently fitted. At the same time the robot can also be programmed to prevent entry to adjacent regions, thus avoiding damage to features such as ligaments. An experimental system using this active constraint robot (or ACROBOT) for knee surgery is described.