Manual skills

Attainment of neuromicrosurgical skills is a challenge in teaching hospitals throughout training. Models that mimic the workflow, as well as haptics, are time-consuming, expensive, unsuitable to serve as a routine platform.

Presenting a model and a set of tasks, based upon a hard-boiled egg, microscope and a cavitron ultrasonic aspirator (CUSA), which is cheap, easy to set up, and can be used for training microsurgery and CUSA skills, required for removal of deep-seated tumors.

The goal was to remove the egg yolk from within a hard-boiled egg, representing an intrinsic brain tumor, surrounded by the egg's white, representing adjacent brain tissue while preserving it. The assessment was based on the yolk's exposure, completeness of removal and collateral damage, and task completion duration, with repeated trials (N=4), for validation purposes, for 6 operators with different experience levels.

Improvement in overall score (mean of 47.5±19 in the 1st trial vs 80.0±12 in the 4th trial, p<0.01), and task duration completion (mean initial duration of 21:25±4:52 minutes to 15:30±5:17 minutes, p<0.01) was observed. Parameters gradually improved on repeated attempts and the experience level of the operators correlated with scores.

The egg model is an easy-to-handle, cheap model that enables the acquisition of basic micro-neurosurgical skills and basic workflow required for removing intrinsic brain tumors. The study of Doron et al. has validated and defined reproducible tasks that can be scored, correlated with performance. This model can be incorporated into a resident's routine and potentially provide an accessible training platform for neurosurgical trainees 1).

Technical skills can refer to the ability to perform tasks that require the use of certain tools, whether tangible or intangible, and technology to complete them. In this regard, the knowledge in a technical skills area is seen as practical in nature as it allows a person to complete a designated task in a real, not theoretical, way. Given the growth of technology within the economy, the need for technical skills is likely to continue to grow.

Although technical skills are fundamental in neurosurgery, there is little agreement on how to describe, measure, or compare skills among surgeons.

Volovici V, Dindelegan G. Studies of Microsurgical Skill-The Key Lies in the Design. JAMA Ophthalmol. 2020 Nov 5. doi: 10.1001/jamaophthalmol.2020.4755. Epub ahead of print. PMID: 33151277. 2).

Microsurgical interposition of vein grafts is an extraordinarily filigree surgical technique, which requires both sound theoretical knowledge and solid manual skills. Although there are a large number of training models, the majority of these are either relatively expensive, technically complex, or employ synthetic materials with poor resemblance to human tissue. The authors' model allows training of ex vivo vein graft interposition on gradually thawed cryopreserved vessels and it, therefore, is cost-efficient and readily available when needed. Furthermore, it respects the 3R-principle (Reduce-Refine-Replace), as it is based on rat cadaveric vessels.

Three trainees with basic microsurgical experience, but without prior performance of vein graft interpositioning, were chosen to perform 20 femoral vein graft (5 mm) interpositions into femoral artery defects. The patency and leakage rate served as qualitative variable and operation time as a quantitative variable for efficiency control.

For the first half of trials, the trainees had a patency failure rate of 50% and for the second half a rate of 13.3%. The leakage rate noticeably decreased from 44.4% in the first half of trials to 10% in the second half. Although the trainees needed 60 minutes on average for their first 10 trials, they improved to 51 minutes for their last 10 anastomoses.

Safis et al., microsurgical model offers a simple, low-cost simulation training, specifically designed for learning of vein graft interposition into arterial defects. The model is associated with a high learning curve, based on an objective control of the anastomoses by assessment of the patency, leakage, and operation time 3).

The primary goal of a study was to develop a quantitative grading scale for technical surgical performance that distinguishes operator skill when graded by domain experts (residents, attendings, and non-surgeons). Scores provided by raters should be highly reliable with respect to scores from other observers.

Neurosurgery residents were fitted with a head-mounted video camera while performing craniotomies under attending supervision. Seven videos, one from each PGY level (1-7), were anonymized and scored by 16 attendings, 8 residents, and 7 non-surgeons using a grading scale. Seven skills were graded; these were incision, efficiency of instrument use, cauterization, tissue handling, drilling/craniotomy, confidence, and training level.

A strong correlation was found between skills score and PGY year (p< .001, ANOVA). Junior residents (PGY 1-3) had significantly lower scores than senior residents (PGY 4-7, p< .001, t-test). Significant variation among junior residents was observed, while senior residents' scores were not significantly different from one another. Inter-rater reliability, measured against other observers, was high (r= 0.581 ± 0.245, Spearman) as was assessment of resident training level (r= 0.583 ± 0.278, Spearman). Both variables were strongly correlated (r = 0.90, Pearson). Attendings, residents, and non-surgeons did not score differently (p=0.46, ANOVA).

Technical skills of neurosurgery residents recorded during craniotomy can be measured with high inter-rater reliability. Surgeons and non-surgeons alike readily distinguish different skill levels. This type of assessment could be used to coach residents, to track performance over time, and potentially to compare skill levels. Developing an objective tool to evaluate surgical performance would be useful in several areas of neurosurgery education 4).

Neurosurgery requires manual dexterity. But should tests be devised to assess manual skills as part of a selection process for training or used as a means of determining surgical competence? Neil-Dwyer and Lang debated this fundamental question and proposed that manual skills for neurosurgical tasks need to be defined within the overall context of a recognised and fully assessed training programme. The importance of training as a means of transferring competence, part of which is manual skills, is emphasised. In conclusion the paper points out the inadequacy of solely measuring manual skills, were it possible, in assessing neurosurgical competence 5).

Manual skills reflect the intellectual ability for analysis of different situations during surgery. Samii doesn’t believe that a very skillful artist who is able to perform a very complicated piece repeatedly would necessarily become a skilled neurosurgeon 6).


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Doron O, Langer DJ, Paldor I. Acquisition of Basic Micro Neurosurgical Skills Using Cavitron Ultrasonic Aspirator in Low Cost Readily Available Models: The Egg Model. World Neurosurg. 2021 May 12:S1878-8750(21)00708-7. doi: 10.1016/j.wneu.2021.05.013. Epub ahead of print. PMID: 33991732.
Volovici V, Dindelegan G. Studies of Microsurgical Skill-The Key Lies in the Design. JAMA Ophthalmol. 2020 Nov 5. doi: 10.1001/jamaophthalmol.2020.4755. Epub ahead of print. PMID: 33151277.
Safi AF, Safi S, Tayeh M, Gojowy D, Timmer M, Goldbrunner R, Kauke M. Vein Graft Interposition: A Training Model Using Gradually Thawed Cryopreserved Vessels. J Craniofac Surg. 2019 Feb 9. doi: 10.1097/SCS.0000000000005197. [Epub ahead of print] PubMed PMID: 30845093.
Sarkiss CA, Philemond S, Lee J, Sobotka S, Holloway TD, Moore M, Costa AB, Gordon EL, Bederson JB. Neurosurgical Skills Assessment: Measuring Technical Proficiency in Neurosurgery Residents through Intraoperative Video Evaluations. World Neurosurg. 2015 Dec 24. pii: S1878-8750(15)01756-8. doi: 10.1016/j.wneu.2015.12.052. [Epub ahead of print] PubMed PMID: 26724633.
Neil-Dwyer G, Lang DA. Can we define or measure manual skills in surgical training? Acta Neurochir Suppl. 1997;69:27-9. PubMed PMID: 9253434.
Samii M. The making of a great neurosurgeon, introduction. In: Kalangu K, KatoY, Dechambenoit G, eds. Essentials of Neurosurgery. 2nd ed. Nagoya, Japan: Access Publishing Co., Ltd; 2010:2-3
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