Proposal of a computerized algorithm for continuous wave CO2 laser on-line control during orthopaedic surgery. Phase I: Theoretical introduction and firstin vitro trials

New data obtained from treating polymethylmethacrylate (PMMA) with a non-moving cw- 10 watt-CO₂ laserbeam focused at 2.5, 5, 7.5 and 15.75 are presented. The final equations R(t_c) and Z(t_c) for each focal length are proposed. A very interesting correlation between the focal lengths in use and the integrated values of R and Z between 0 and 2 sec has been identified and discussed. This result has been used as basis to define a convenient operative protocol to follow during the planning phase of critical osteotomier or bone cement removal operations using a continuous-wave CO₂ laserbeam set to any output power and focused by a set of most common, moving or non-moving focal lengths placed on the operating area. With a simple equation, it is possible to compare craters obtained with moving and non-moving laserbeams at different operative conditions between 0 and 2 sec, time interval which covers the majority of cases. A value of 2.3±0.1 between ablated volumes of PMMA and bone tissue has been identified. Several case studies regarding orthopaedic procedures from Literature are here reported and compared to the present LCA^* model. The computerized on-line flow of information for the laserbeam optimization and safety control is also described. Finally, a method for the simultaneous data collection from several operating rooms via a Local Area Network (LAN-Industry Standard IEEE) onto a central data base for later consultation is proposed in its general design.