P. Gomes

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

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.

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.

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.