Kevin P. Sherman

Image guided orthopaedic surgery design and analysis

Within the next few years it is envisaged that a number of computer assisted surgery products will become available. For many surgical procedures, outcome of surgery,, will rely on the accuracy and repeatability with which a computer assisted surgical toolperforms its task. This paper presents a Computer Assisted Orthopaedic System (CAOS) which takes an image guided approach to planning and implementing a trajectory, to assist an orthopaedic surgeon. Accurate delivery of this trajectory is achieved via an intelligent guide. This paper details the design issues and identifies the registration and calibration techniques used by the CAOS intelligent guide. The paper also enumerates, and where possible quantifies, thefactors that influence the accuracy performance of the system. Accuracy trees are used to show the root source of inaccuracies and how they propagate and combine in a system.

Quantification of T2 relaxation changes in articular cartilage with in situ mechanical loading of the knee

To devise a method for producing in vivo MRI images of the knee under physiologically significant loading, and to compare and evaluate the changes in cartilage characteristics before and during in situ compression of the knee.

Haptic feedback can provide an objective assessment of arthroscopic skills.

AbstractThe outcome of arthroscopic procedures is related to the surgeon’s skills in arthroscopy. Currently, evaluation of such skills relies on direct observation by a surgeon trainer. This type of assessment, by its nature, is subjective and time-consuming. The aim of our study was to identify whether haptic information generated from arthroscopic tools could distinguish between skilled and less skilled surgeons. A standard arthroscopic probe was fitted with a force/torque sensor. The probe was used by five surgeons with different levels of experience in knee arthroscopy performing 11 different tasks in 10 standard knee arthroscopies. The force/torque data from the hand and tool interface were recorded and synchronized with a video recording of the procedure. The torque magnitude and patterns generated were analyzed and compared. A computerized system was used to analyze the force/torque signature based on general principles for quality of performance using such measures as economy in movement, time efficiency, and consistency in performance. The results showed a considerable correlation between three haptic parameters and the surgeon’s experience, which could be used in an automated objective assessment system for arthroscopic surgery. Level of Evidence: Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Timing of antibiotic prophylaxis in surgery for adult hip fracture.

BACKGROUND Antibiotic prophylaxis is widely used in surgery for hip fractures. METHODS AND RESULTS In a retrospective study of case notes of 100 patients, frequent inaccuracies in dose administration were observed. This was applicable to both the pre-operative and the postoperative doses. Longer time intervals between the doses, failure to administer the prescribed doses, and failure of proper documentation were observed. CONCLUSIONS Improvement in the awareness of staff and timely administration of prophylactic antibiotic has resulted from this study.

Cadaveric analysis of capsular attachments of the distal femur related to pin and wire placement

OBJECTIVES Septic arthritis following intra-capsular penetration of the knee by external fixation devices is a complication of traction/fixation devices inserted in the lower extremity [1,2]. The authors were unable to find reference to or exact measurements of the capsular attachments relating to the distal femur documented in the current literature. This study aimed to demonstrate the capsular attachments and reflections of the distal femur to determine safe placements of wires or traction devices. METHODS The attachments of the capsule to the distal femur were measured in 10 unembalmed cadaveric knees. Capsular attachments were measured anteriorly at the maximal extension of the supra-patella pouch. Medially and laterally measurements were expressed as percentages related to the maximal AP diameter of the distal femur. RESULTS Mean distance from the centre of the anterior part of the notch to the superior fold was 79.5mm (Range 48.1-120.7 mm). The medial capsular reflections measured in a plane from the adductor tubercle to the anterior edge of the medial femoral condyle demonstrated the capsular reflection was attached an average of 57% back from the anterior edge (Range 41-74%). Laterally the capsular reflections on a line drawn from the maximal diameter in the sagittal plane were attached an average of 48% from the anterior reference point (Range 33-57%). Measuring the reflections at 45 degrees to the long axis of the femur in the sagittal plane the attachment was an average of 51% from the anterior reference point. CONCLUSIONS Capsular reflections varied among specimens. Medially the capsule attachment was up to 74% of diameter of distal femur at the level of the adductor tubercle. Therefore, the insertion of distal femoral traction pins or similar should be placed proximal to the adductor tubercle and no further than 25% of the distance to the anterior cortex. Care is also needed to ensure pins do not travel to exit too anteriorly on the lateral side as capsular attachments were found to be up to a distance 48% of the diameter of the femur from anterior reference point. Distal condylar extra-articular fixation with Schanz screws is feasible if orientated in the oblique plane.

End user issues for computer assisted surgical systems

Orthopaedic implants are manufactured to the highest degree of precision by some of the most precise machines known to man and inserted into patients by some of the most imprecise methods known. Computer assisted systems aim to overcome this dichotomy by improving the planning and implementation of orthopaedic surgery. This can be achieved by providing the surgeon with better information for planning and a more precise means of implementing the surgery. This surgical advancement will change current orthopaedic practice significantly if the appropriate surgical issues are considered during their development. Safety is obviously paramount and is being addressed, as is registration between the real (patient) and the virtual computer world. The more subtle, but nevertheless important, surgical issues have as yet not been fully identified or addressed satisfactorily. The following questions serve to highlight them. Is there an optimal system size, shape, reach, control and positioning in surgery? What are the salient environmental and functional requirements ? Can there be intra-operative computer processing time? How important and what does timelessness, universality, communality and simplicity of the system mean? Should there be a relationship between training, surgical feedback and simplicity? What is partial or total sterilisation ? Can capital outlay and running costs for the system be reduced or avoided by the hospitals? Are computer assisted orthopaedic surgical systems cost effective, necessary, desirable or indeed indicated in current cost containment in the NHS? The above questions are answered in this paper and points which are conducive to a positive response from the end user (surgeons, and hospital management) are discussed.

Concerns: Article of J.F. Quinlan, D. McCarthy and W.R. Quinlan

We read with interest the case report by Quinlan et al. [3] concerning intramedullary nailing of long bones in all four limbs in a patient with multiple myeloma. It has been our experience that in patients with disseminated skeletal malignancy undergoing multiple nailing procedures, both staged or in one sitting, there can be a high rate of mortality. Given the successful surgical outcome in this patient we would be grateful if the authors could clarify three queries: 1. What was the time interval between the four procedures? 2. Were the humeral nails inserted reamed or unreamed? 3. Given that venting of femora prior to nailing has been shown to reduce complications [1, 2], with the prophylactic use of the reconstruction nails, did the surgeon vent the femora either directly or by using the (cannulated) Russell-Taylor reconstruction nail without a guidewire? Whilst we concur with the authors’ assertion that patients with malignant bone disease of the humeri and femora should be referred early for consideration of prophylactic intramedullary nailing, we would expand this to cover all long bones (especially the tibia). We do, however, feel that the authors’ final conclusion that multiple intramedullary nailing should be considered in these patients – based on a single case – is somewhat aggressive. The prognosis of the patients needs to be considered, and close liaison with the haematologists prior to embarking on such a surgical approach is mandatory.