Kaddour Bouazza-Marouf

Robotic-Assisted Internal Fixation of Femoral Fractures

Closed surgical techniques for the internal fixation of femoral fractures require orthopaedic surgeons to work in close proximity to X-rays. In addition to the occupational health risk this imposes, inexperienced surgeons often encounter great difficulty in achieving optimal positioning of fracture repair fixtures. A vision-guided robotic system has been proposed as a possible solution to these problems and an initial investigation involving two exemplar orthopaedic procedures has been undertaken Robotic surgery assistance imposes rigorous safety-related design constraints, since the orthopaedic robot must operate in close proximity to the patient and operating staff. The design and implementation of a purpose-built robotic system for orthopaedic surgery assistance is described in this paper.

The detection of drill bit break-through for the enhancement of safety in mechatronic assisted orthopaedic drilling

The present surgical drilling processes, which are performed manually, can greatly benefit from mechatronic assistance. Measurement of bone drilling force can contribute significantly towards the enhancement of safety through the detection of drill bit break-through in order to prevent excessive protrusion of the drill bit. This paper describes a reliable and repeatable method of break-through detection based on a modified Kalman filter when drilling into long bones. A control strategy for the break-through detection is also provided. By applying the modified Kalman filter to force difference between successive samples (FDSS), the imminent drill bit break-through can be detected using different threshold levels of Kalman filtered FDSS (K-FDSS) in the presence of system compliance and inherent drilling force fluctuation. In addition, the method of break-through detection can be applied to different drill bit types over a range of drilling conditions.

Robot-assisted invasive orthopaedic surgery

Changes in orthopaedic practice have led to an increased reliance upon fluoroscopic image guidance during internal fracture fixation (osteosynthesis) procedures. The resulting complexity of surgical techniques, and concerns over X-ray radiation exposure levels to orthopaedic surgeons, has prompted the introduction of new technologies into the operating room with the aim of improving the precision, repeatability and radiation safety of existing surgical procedures. The generic vision-guided robotic system for orthopaedic applications described in this paper is typical of this trend. In order to satisfy the stringent safety requirements of robotic-assisted surgery, the mechatronics design philosophy has been applied to the system. A purpose built manipulator has therefore been manufactured, which when interfaced to an existing C-arm unit allows a drill-bit guide to be automatically aligned with an intra-operatively planned drilling trajectory. Manual completion of the drilling stage can then be performed by the surgeon. The preliminary findings of an ongoing study into the potential for an invasive application of such a system, through the use of an actuated drilling unit incorporating a novel use of force feedback, are also presented. Initial results indicate that force feedback could play a major role in the safety protocol of such an invasive system.

Drilling in cortical bone: a finite element model and experimental investigations.

Bone drilling is an essential part of many orthopaedic surgery procedures, including those for internal fixation and for attaching prosthetics. Estimation and control of bone drilling forces are critical to prevent drill-bit breakthrough, excessive heat generation, and mechanical damage to the bone. An experimental and computational study of drilling in cortical bone has been conducted. A 3D finite element (FE) model for prediction of thrust forces experienced during bone drilling has been developed. The model incorporates the dynamic characteristics involved in the process along with geometrical considerations. An elastic-plastic material model is used to predict the behaviour of cortical bone during drilling. The average critical thrust forces and torques obtained using FE analysis are found to be in good agreement with the experimental results.

Practical control enhancement via mechatronics design

Mechatronics is concerned with designing machines with enhanced capabilities using advanced control methods. Here we describe how some of these advanced control methods have evolved and how they can be applied effectively. The resulting performance enhancement is explained by the use of a number of example case studies. It is shown that using these methods greatly improves the operational capabilities of mechatronics products and can, in many cases, lead to considerable increases in performance specifications. The paper represents a survey of research work undertaken into mechatronics control methods by the authors and their colleagues. The following control issues are discussed: kinematics control; dynamic control; deadbeat robotics control; active force control; adaptive control; and an active suspension system.

Automated surgical screwdriver: automated screw placement.

The use of power screwdrivers and drills for tapping and screw insertion in surgery is becoming more common. It has been established from clinical observations that the use of a small air drill for inserting self-tapping screws provides improved coaxial alignment and precision, and that the drill should be stopped before the screw head is completely seated on the plate, presumably to reduce the risk of over-tightening. The risk of overrun and over-tightening during tapping and screw insertion is increased with the use of power tools. Prevention of over-tightening is dependent upon when the surgeon detects the onset of tightening, both visually and from the feel of the rapid increase in torque. If detection is too late, then over-tightening or stripping can occur. This study is concerned with using a mechatronic screwdriver to control the tapping depth and to prevent the over-tightening of screws. The effects of various parameters upon the torque profile during tapping and screw insertion have been investigated in synthetic bone and sheep tibia. An automated system is proposed for preventing over-tightening of pre-tapped and self-tapping screws when attaching a surgical plate to a sheep tibia in vitro. The system was used to attach a plate to a sheep tibia using self-tapping screws. The mean torque of the screws inserted using the automated system was 35 per cent of the stripping torque.

A methodology for design and appraisal of surgical robotic systems

Surgical robotics is a growing discipline, continuously expanding with an influx of new ideas and research. However, it is important that the development of new devices take account of past mistakes and successes. A structured approach is necessary, as with proliferation of such research, there is a danger that these lessons will be obscured, resulting in the repetition of mistakes and wasted effort and energy. There are several research paths for surgical robotics, each with different risks and opportunities and different methodologies to reach a profitable outcome. The main emphasis of this paper is on a methodology for ‘applied research’ in surgical robotics. The methodology sets out a hierarchy of criteria consisting of three tiers, with the most important being the bottom tier and the least being the top tier. It is argued that a robotic system must adhere to these criteria in order to achieve acceptability. Recent commercial systems are reviewed against these criteria, and are found to conform up to at least the bottom and intermediate tiers, the most important first two tiers, and thus gain some acceptability. However, the lack of conformity to the criteria in the top tier, and the inability to conclusively prove increased clinical benefit, is shown to be hampering their potential in gaining wide establishment.

Robotic-assisted internal fixation of hip fractures: A fluoroscopy-based intraoperative registration technique

Abstract The internal fixation of proximal femoral (hip) fractures is the most frequently performed orthopaedic surgery procedure. When using a sliding compression hip screw, a commonly used fixation device, accurate positioning of the device within the femoral neck-head is achieved by initially drilling a pilot hole. A cannulated component of the hip screw is then inserted over the guide wire (surgical drill bit), which is used to drill the pilot hole. However, in practice, this fluoroscopically controlled drilling process is severely complicated by a depth perception problem and, as such, a surgeon can require several attempts to achieve a satisfactory guide wire placement. A prototype robotic-assisted orthopaedic surgery system has therefore been developed, with a view to achieving accurate right-first-time guide wire insertions. This paper describes the non-invasive digital X-ray photogrammetry-based registration technique which supports the proposed robotic-assisted drilling scenario. Results from preliminary laboratory (in vitro) trials employing this registration technique indicate that the cumulative error associated with the entire X-ray guided robotic system is within acceptable limits for the guide wire insertion process.

Evaluation of bone strength: Correlation between measurements of bone mineral density and drilling force

Abstract Bone drilling is a major part of modern orthopaedic surgery which involves the internal fixation of fractured bones. The investigation of bone drilling described in this paper demonstrates the contribution of automation technology towards the study of bone strength. The aim of this preliminary investigation is to establish a relationship between bone drilling forces and measurements of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA). A linear relationship with a high coefficient of correlation has been found between average drilling forces and BMD measurements at both the greater trochanter and the femoral head of porcine femurs when drilling in the anterior-posterior (AP) direction (i.e. the direction of the DXA scan). It has also been found that in the normal drilling direction (i.e. in the cervical axis direction), which is orthogonal to the DXA scanning direction, there are similar trends between the drilling forces and BMD levels in regions where bone density is more consistent (e.g. the femoral head). The findings of this investigation indicate that analysis of bone drilling forces has the potential to provide useful information about the strength of bone.

Drilling of bone: a robust automatic method for the detection of drill bit break-through

Abstract The aim of this investigation is to devise a robust detection method for drill bit breakthrough when drilling into long bones using an automated drilling system that is associated with mechatronic assisted surgery. This investigation looks into the effects of system compliance and inherent drilling force fluctuation on the profiles of drilling force, drilling force difference between successive samples and drill bit rotational speed. It is shown that these effects have significant influences on the bone drilling related profiles and thus on the detection of drill bit break-through. A robust method, based on a Kalman filter, has been proposed. Using a modified Kalman filter, it is possible to convert the profiles of drilling force difference between successive samples and/or the drill bit rotational speed into easily recognizable and more consistent profiles, allowing a robust and repeatable detection of drill bit break-through.