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

Abstract

New data obtained from treating polymethylmethacrylate (PMMA) with a non-moving cw- 10 watt-CO2 laser-beam focused at 2.5'', 5'', 7.5'' and 15.75'' are presented. . The final equations R(tc) and Z(tc) 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 osteotomies or bone cement removal operations using a continuous-wave CO2 laser-beam 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 laser-beams 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 laser-beam 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.

Optical Absorption Coefficient, Time of Thermal Relaxation, Time of Surface Threshold, and Time of Heat Incubation for PMMA Samples at the CO2Laser-Beam Wavelength of 10.6 µm

“…Now, observing that both t0 and r contain the absorption coefficient ␣, we can write: (6) The incubation time is dependent on several laser set-up parameters, the most important of which is the power density in both CW and pulsed-wave (PW) beams.…”

“…This experimental set-up was used in the definition of the LCA algorithm published by the author several years ago, 6,7 and is still an essential tool for this study to determine the complete time-dependent coefficient and to validate the related LCA mathematical calculations.…”

“…One of these research applications is the study of thermodynamic models that describe heat transfer patterns across biological media, or the "source of heat" for any known process of heat generation and related devices, including medical lasers. Several mathematical aspects of this analysis have published previously, by isolating the LCA model 6,7 and numerically solving the Canestri-Langerholc equation. 8 Another interesting application is the quantification of crater and cut generation processes, which brings new insight into both thermodynamic and mechanical phenomena occurring during biopolymeric media treatments and classical surgical operations.…”

Advances in (Un)Conventional Engineering of Biomaterials and Nursing Care

“…The existing technological advances referred to decrease of the required effort of a surgeon in cutting and to increase osteotomy speed in time with respect to operating parameters. In many publications particular attention is continually devoted to the issue of enhancement of the bone tissue cutting by conventional method (Johansson et all, 1981), (Canestri, 1992), (Sugita et al, 2005), (Mitsuishi et al, 2003), (Taylor & Stoianovici, 2003), (Kwon et al, 2002), (Mitsuishi et al, 2002). Professor Udiljak (Udiljak et al, 2007) and Tomislav Staroveski (Goran et al, 2012) studied the problem of avoiding the occurrence of irreversible death of bone cells exposed to high temperature during drilling.…”

The use of water-jetting technology in prostheses revision surgery?First results of parameter studies on bone and bone cement

“…10,11 The excimer laser is rather slow. 12 The carbon dioxide laser showed the best effect, but clinically it is used rarely.…”