Arjan J. Knulst

Indicating shortcomings in surgical lighting systems

Abstract Ergonomic problems of surgical lighting systems have been indicated by surgeons; however, the underlying causes are not clear. The aim of this study is to assess the problems in detail. Luminaire use during 46 hours of surgery was observed and quantified. Furthermore, a questionnaire on perceived illumination of and usability problems with surgical luminaires was issued among OR-staff in 13 hospitals. The results showed that every 7.5 minutes a luminaire action (LA) takes place, intended to reposition the luminaire. Of these LAs, 74% were performed by surgeons and residents. For 64% of these LAs the surgical tasks of the OR-staff were interrupted. The amount of LAs to obtain a well-lit wound, the illumination level, shadows, and the illumination of deep wounds were most frequently indicated lighting aspects needing improvement. Different kinematic aspects of the pendant system of the lights that influence usability were also mentioned: High forces for repositioning, ease of focusing and aiming, ease of moving, collisions of the luminaire, entangling of pendant arms, and maneuverability. Based on these results conclusions regarding the improvement of surgical lighting systems are formulated. Focus for improvements should be on minimizing the need for repositioning the luminaire, and on minimizing the effort for repositioning.

Standards and Performance Indicators for Surgical Luminaires

Abstract The illumination performance of surgical luminaires is quantified by performance indicators defined in an international standard (IEC 2000). The remaining maximum illuminance in relevant situations, the light-field size, and the spectral characteristics are performance indicators used by hospitals as input for luminaire opting processes. Industry however focuses on illuminance when communicating with health care professionals. The aim of this study is to evaluate whether these standards are sufficient to describe luminaire performance, especially for modern LED lighting technology. Illuminance distribution and spectrum measurements were performed on 5 different state-of-the-art (LED) surgical luminaires. The results showed that changing situations not only changed the maximum illuminance but also changed the light-field sizes and shapes, introducing substantial differences between luminaires. Moreover, colored cast shadows and light color variations across the light-field were observed for 3 luminaires using differently colored light emitting diodes (LEDs). Both the changing light-field sizes and shapes, and the cast shadows and light color variations for LED luminaires are not covered by the current standard. The standard should therefore be extended to incorporate these aspects, especially for such a high-end application as surgical lighting.

Threshold Amplitude and Frequency for Ocular Tissue Release from a Vibrating Instrument:An Experimental Study

PURPOSE During retinal pigment epithelium (RPE) and choroid graft translocation in the treatment of patients with exudative age-related macular degeneration, the adhesion of the graft to the translocation instrument complicated its submacular release. Vibration of the instrument improved the release of the graft. This study was conducted to validate the effectiveness of the principle of vibration and to determine the threshold amplitude and frequency required for development of an optimized instrument. METHODS An experimental in vitro model with fresh porcine RPE-choroid grafts was used. Release of the graft was studied by a masked observer for amplitudes in the range of 0.05 to 1.2 mm and frequencies in the range of 25 to 200 Hz in the horizontal plane. RESULTS The minimum threshold amplitude required to release the graft was approximately 0.15 mm from a frequency of 100 Hz and higher. CONCLUSIONS This study confirmed the clinical experience that vibration of an instrument induces the release of the RPE-choroid graft. The minimum threshold amplitude and frequency needed for optimum tissue release were estimated.

Micro-scale thermal tissue gripper.

During eye surgery translocating a graft of retinal tissue without damaging the vulnerable top layer is highly problematic using the currently available instruments. This study presents indirect Heat Induced Attachment and Detachment (HIAD) as a new concept for single side attachment of tissue to, and detachment from a heated metal wire. A small-scale prototype was built, having a 50 μm molybdenum wire that could be heated via an electric current. Tests (n = 60) were performed on submerged chicken meat to study the attachment and detachment properties of the prototype at different electric signal lengths. A 9V signal was applied to the prototype, with amplifier input signal lengths varying from 0.6–1.5 ms. Voltages and currents were sampled at 250 kHz to obtain energies. Both attachment and detachment occurred with 98% and 90% certainty, respectively, supplying 41 and 110 mJ of energy to the prototype in 0.7 and 1.5 ms. The attachment strength was estimated at 0.2 mN. Visible damage appeared to be approximately 0.005 mm2. The concept of indirect heating of the instrument-tissue interface proved to be effective as the prototype could induce attachment and detachment of tissue. Indirect HIAD may be applicable in many different surgical applications.

A simulation model that predicts handling forces required to reposition surgical lights

Introduction: High handling forces of surgical lighting systems limit their usability. To make improvements to the mechanical design of the system the behaviour of the system should be understood. Therefore, this study presents a model that predicts handling forces of surgical lighting systems. Methods: Geometry and joint friction torques of a real lighting system were measured and implemented in a validated force model. Mean, standard deviation within the spatial region, minimum force and maximum force were computed for three different regions of the working area. Results: The mean (standard deviation within the spatial region) forces were 129 (106) N in the centre region, and 61 (14) N and 60 (17) N in more off-centre regions. Conclusion: The simulation results showed high handling forces in the central region, explaining the observed repositioning patterns of the surgical light during surgery. The model can also be used to compare different lighting systems, or to evaluate the effect of design changes.

Single-sided and small-scaled grasping of delicate tissues: effectiveness of indirect heat-induced attachment and detachment.

Abstract Introduction: Indirect heat-induced attachment and detachment (iHIAD) is a promising concept for gripping delicate tissues in microsurgery. However, the optimal settings of iHIAD are unknown. This study evaluates the effects of the instrument heating properties and initial contact force on the adhesion force, detachment success and thermal damage. Material and methods: An instrument prototype was developed to test attachment and detachment for different combinations of generated energy (3.5–20.0 mJ) and pulse length (0.25–2.50 ms). The tissues tested on were kidney and eye from the pig. Thermal tissue damage was estimated with a histological analysis. Results: The adhesion force Fa depended strongly on the amount of generated energy (Fa = 0.03–2.5 mN) and contact force (Fa = 0.25–1.0 mN). Pulse length played a minor role. Detachment success (0–100%) was determined by generated energy (3–16 mJ). Histological analysis showed minimal damage. Conclusion: Adhesion forces increased with increasing contact forces. iHIAD proved sensitive to heating characteristics. Detachment success increased with generated energy. Thermal damage was minimal. iHIAD creates a potential to build better performing tissue manipulators.

Evaluation of a New Surgical Light Source for Difficult Visibility Procedures

A new lighting device for open surgery of difficult access wounds was designed: the Extender add-on. The performance of the Extender is evaluated and compared with the conventional solutions used in the operating room (OR) on illumination quality. A cylindrical setup was built to measure the distribution of light in a simulated pelvic wound. The light was provided by a head-mounted light, an OR light, and a pair of Extender prototypes. The results showed that the Extender prototypes provided 12.2 lumens inside the wound, whereas the head-mounted light gave 5.7 lumens. The Extenders provided smoothly angular distributed light from 0° to 180°, whereas the head-mounted light and OR light only provided light from 115° to 180°. The Extender prototypes had a promising performance in terms of light distribution. It is expected that a more accurately produced Extender will increase performance in terms of illumination quantity and illumination distribution smoothness even further.

Indicating Shortcomings in Surgical Lighting Systems

Ergonomic problems of surgical lighting systems have been indicated by surgeons. However, the underlying causes are not clear. The aim of this study is to assess the problems in detail. Luminaire use during 46 h of surgery was observed and quantified. Furthermore, a questionnaire on perceived illumination of and usability problems with surgical luminaires was issued among OR-staff in 13 hospitals. The results showed that every 7.5 min a luminaire action (LA) takes place, intended to reposition the luminaire. Of these LAs, 74% was performed by surgeons and residents. For 64% of these LAs the surgical tasks of OR-staff were interrupted. The amount of LAs to obtain a well-lit wound, illumination level, shadows, and illumination of deep wounds were most frequently indicated lighting aspects needing improvement. Different kinematic aspects of the pendant system of the lights that influence usability were also mentioned: high forces for repositioning, ease of focusing and aiming, ease of moving, collisions of the luminaire, entangling of pendant arms, and maneuverability. Based on these results, conclusions regarding to improvement of surgical lighting systems are formulated. Focus for improvements should be on minimizing the need for repositioning the luminaire, and on minimizing the effort for repositioning.