Clinical Trial and Cost/Benefit Analysis of Spinal CAD/CAM Software

Allan Heaver, C.O.


ABSTRACT

A clinical trial examining the cost effectiveness of CAD/CAM Technology in the design and manufacture of spinal orthoses was carried out in Vancouver, B.C. In all, 18 TLSO'S were produced for 9 volunteers (eight female, one male). Each volunteer was fitted with one TLSO made using the conventional methods and one TLSO made using the CAD/CAM technique. The results of the trial showed that by using CAD/CAM technology a clinical orthotist can reduce the amount of time required to provide a patient with a TLSO. Material costs were higher using CAD/CAM system, though it is expected that these costs will drop as the use of CAD/CAM technology becomes more widespread.

INTRODUCTION

With the development of CAD/CAM software moving from a focus on prosthetics to orthotics, one of the first areas targeted for development was that of spinal orthotics (2,3). The size and weight of spinal casts makes them unwise to modify and long term storage of casts is impractical. It was expected the CAD/CAM technology could be used to simplify and speed up the process of designing and manufacturing well fitting orthoses, as well as making long term storage of the resulting shapes practical if so desired.

DESCRIPTION

The purpose of the trial was to compare the CAD/CAM to the conventional method for the following criteria:

1) fit.

2) time and materials costs.

Fit was assessed only insofar as answering the question, 'Can an orthosis that fits each volunteer be produced via both the methods?' The orthoses were fitted to the volunteer and the volunteer was sent home to wear each of the orthoses for a period of eight hours before the final assessment. The fit of the orthoses was carried out by an independent orthotist who was unaware of which of the orthoses had been produced using the conventional method and which had been produced using CAD/CAM. It was decided that standard TLSO design would be produced, regardless of what orthosis design the volunteer was wearing for the treatment of their curve. This avoided any difference in overall costs caused by the differences in time and materials required for the different orthosis design. This, however, meant that it was not possible for the volunteers to wear the orthosis for a period of longer than eight hours for ethical reasons. Also for ethical reasons, the degree of correction obtained by both the conventional and CAD/CAM orthoses was not checked by X-ray. The purpose of the study was not to research the degree of correction that could be obtained by either method, but simply to determine the time and material costs required to produce an orthosis that 'fits' according to the standard spinal check out procedure used in Vancouver. Time and materials data was collected using standardized time and material forms that the clinical study's uses for accounting purposes.

The overall CAD/CAM set-up used in the study consisted of the CANFIT-PLUS tm P&O Software, the M+IND digitizer and the IPOS CASCD.

The volunteers who agreed to participate in the study were restricted to patients who were already being treated for a spinal curve with an orthosis prior to their involvement in the study. They were therefore familiar with the casting and fitting procedures. The volunteers were not told which was the conventional or the computer-assisted-designed-orthosis. At the beginning of the study a standing cast was taken of the volunteers. The cast taken was digitized and the shape put into the CANFIT-PLUS tm P&O Software System. Next, the data was modified. Then, since the cast had not been affected by digitization in any way, the cast was filled with plaster of pans and modified in the conventional manner.

From the plaster of paris cast a conventional TLSO was produced and from the digitized data a CAD/CAM TLSO was produced. Once each of the orthoses had been manufactured and fitted, the TLSO's were both assessed for fit and for time and material costs. Each of the orthoses had to be deemed to fit before the time and manufacturing procedure would be considered to have been completed.

RESULTS

With respect to the question of fit, the CANFIT-PLUS tm designed TLSO's did not require any more revision time than the conventionally modified/ produced TLSO's. All of the 18 TLSOs produced did fit well and the independent orthotist doing the assessments felt the fit was appropriate. With respect to material costs, the material costs of using a CAD/CAM system were slightly higher (by approximately $50.00 (Canadian), because of the use of polyurethane, rather than POP foam blanks in the carving procedure.

Time costs were broken down into technical time and clinical time. The average technical time spent in producing one TLSO using the conventional method was 113 minutes. Using the CAD/CAM method it was 109 minutes, a slight decrease of 4 minutes. With respect to clinical time spent, the conventional method took 118 minutes while the CAD/CAM method used 70 minutes. This is a 40% reduction in time spent by using CAD/CAM.

DISCUSSION

Though the material costs were higher using the CAD/CAM methodology, it can be expected for this cost to fall somewhat over time. The difference in cost was primarily due to the fact that in the initial stage of the study the more expensive polyurethane blanks had to be imported from Germany to Canada. With an increase in use of CAD/CAM for prosthetics and orthotics it can be expected that the demand for blanks will increase and their costs will decrease. As well, in Canada, the costs could be likely reduced by finding a local supplier for the blanks.

It is in the area of time spent that the results of the trial become interesting. Though technical time involved reduced only slightly, a 40% savings in clinical time occurred using the CANFIT-PLUS tm P&O systems to do the modification of the TLSOs. When one considers the cost of the clinician's time, this can be considered to be significant. A clinical orthotist is under constant pressure to optimize his or her time so that he or she spends enough time with each patient to do a full and careful assessment, while not wasting time. Any technology which reduces workload for the clinical orthotist will make an impact on the orthotisfs practice, freeing him for other tasks. A further spin-off would be the formation of data bases, allowing more quantified research to be done on the topic of orthotic design, a neglected area when compared, for example, to prosthetic socket design. (1,4). This can only have a positive effect on the practice of orthotics.

Acknowledgements

This study was funded by the Science Council of British Columbia and with the generous help and co-operation of J A. Pentland Ltd.,Vancouver, B.C.

Assistant Clinical Instructor, 95/96 British Columbia Institute of Technology, Burnaby, B.C.,Canada. Chief Orthotist, J. A. Pentland Ltd.,Vancouver, B.C.

References:
1. Klasson, B.,(1985) Computer aided design, computer aided manufacture and other computer aides in prosthetics, Prosthetics and Orthotics International Vol 9,pp3-l1
2. Raschke, S.U., Bannon, M.A., et al (1990); CAD/CAM application for spinal orthotics-a preliminary investigation, Journal of Prosthetics and Orthotics, Vol.2,ppl 15-118
3. Raschke, S.U., Saunders, C.G.,(1991); Rumpforthetic-Neuentwicklungen auf dem CAD/CAM Secktor, Orthopaedic Technik, Vol. 8/91,pp572-576
4. Sauders, C.G., Bannon M.A.,et al (1989); The CANFIT System, Shape Management Technology for Prosthetic and Orthotic Application, Journal of Prosthetics and Orthotics, Vol.1 .ppl22-130.