Fine motor and sensory proficiency: implications for simulator-based surgical assessments

Abstract

Purpose

Simulation technologies have advanced surgical education by enhancing motor skills, hand-eye coordination, and sensory acuity. This study examines correlations between sensory-motor skills and surgical simulator performance.

Methods

The cross-sectional and observational study included fifty medical doctors without surgical experience. Assessments included the McKinnon two-point discrimination test, the Semmes-Weinstein monofilament test, and the Nine-Hole Peg test. Performance scores for forceps, anti-tremor, and bimanual training modules were recorded using the Eyesi Surgical Simulator (VRmagic^®, Mannheim, Germany).

Results

The mean age was 28.6 ± 4.4 years, with 28 females and 22 males. The mean value of McKinnon's two-point static discrimination test was 3.08 ± 0.72 mm, the Semmes-Weinstein Monofilament test was 2.42 ± 0.29 inches, and the Nine-Hole Peg Test mean completion time was 19.04 ± 2.60 seconds. Two-point discrimination test showed a significant negative correlation with bimanual training module scores within the 95% confidence interval (r =-0.41, p = 0.0027) but weak, non-significant correlations with forceps module (r = -0.23, p = 0.101) and anti-tremor modules (r = -0.10; p = 0.505). Monofilament test scores showed no significant correlations with simulator modules. The Nine-Hole Peg test correlated significantly with bimanual performance (r =-0.42, p = 0.002 and weakly with forceps scores (r =-0.24, p = 0.090).

Conclusion

Simulation devices enhance surgical training by identifying sensory-motor deficits and adapting training. Motor skill and sensory acuity are associated with better bimanual performance and emphasize individualized approaches for optimal outcomes.

Introduction

Cataract surgery is the most common surgery in ophthalmology. Despite being performed so frequently, some problems may occur during the learning process of the surgery. These problems can seriously affect the visual prognosis of patients [1]. Recent advancements in simulation technologies have led to revolutionary developments in ophthalmology. Cataract surgery, vitreoretinal surgery, and ROP diagnosis and treatment simulator devices, which contribute greatly to surgical training, offer trainees a safe space where they can improve their surgical skills without compromising safety of patients [2, 3]. These devices can separately evaluate participants’ precision, dexterity, and decision-making skills [4].

Fine motor skills and hand-eye coordination are important parameters for mastering the surgical procedure. In addition, sensory acuity, which includes sensory sensitivity, contributes to the perception and correct guidance of tiny surgical instruments [5]. Both of these concepts are necessary skills for the surgeon in real life. However, simultaneous evaluation with virtual reality (VR) devices and comparison with device performance is an unexplored area of research.

Understanding the relationship between fine motor skills and sensory acuity scores on simulator devices may be useful for surgical training strategies. Educators can tailor training programs to individual needs by identifying strengths and weaknesses. In this way, they can accelerate the learning curve and contribute to better final surgical performance. They can also help identify trainees who need further motor and sensory development.

The present study aimed to examine the impact of intrinsic sensorimotor skills on microsurgical simulation performance. To this end, standardized tests were employed to assess tactile perception and fine motor control. It is hypothesized that these abilities play a critical role in tasks requiring high precision, such as tremor suppression, depth perception, and bimanual coordination. Accordingly, the central hypothesis posits that individuals with stronger baseline sensorimotor skills would demonstrate superior performance on simulator modules specifically designed to assess these domains.

In this study, we aimed to evaluate the correlation of motor skills and sensory sensitivity with simulator device performance. By analyzing the effect of these intrinsic factors on the performance score of the surgical simulation device, we hope to contribute to surgical training optimization and provide a basis for further research.

Materials and methods

The study was designed as a cross-sectional study, approved by the Clinical Research Ethics Committee of Selçuk University Faculty of Medicine (No:2024/459), and conducted by the principles of the Declaration of Helsinki. The study included volunteer medical doctors who had never performed surgery. Age, gender, dominant eye, dominant hand, and comorbidities were recorded. The participants were residents with no surgical experience. It is noteworthy that none of the participants had prior experience in ophthalmology or surgical procedures. The selection of this inclusion criterion was driven by eliminating the influence of surgical specialty training and ensuring that intrinsic fine motor and sensory skills were assessed at the initial baseline. Participants with hobbies requiring microsurgical skills (building ships in bottles, etc.) or diabetes that may cause sensory changes were excluded from the study.

The participants’ performance was recorded with the Eyesi Surgical Simulator (VRmagic, Mannheim, Germany) during an interval when they slept, were full, and felt rested. The Eyesi Surgical Simulator is a high-fidelity virtual reality platform designed for ophthalmic surgical training. The environment is characterized by its risk-free nature, thereby facilitating the development and evaluation of surgical skills. These skills include, but are not limited to, hand–eye coordination, instrument handling, and depth perception. The simulator encompasses a series of task-specific modules meticulously engineered to evaluate fine motor control and stability. These modules encompass forceps training, anti-tremor exercises, and bimanual coordination tasks, among others. These modules offer two types of outputs: total and sub-score. These outputs reflect the user’s performance: precision, efficiency, and consistency. The simulation comprised modules meticulously designed to assess diverse aspects of surgical microskills. A select group of three training modules was identified as the primary components:

1. 1.

Forceps Training Module: The instrument assesses precision and control during fine grasp and release tasks. The participant manipulates virtual objects using simulated forceps under magnified, three-dimensional visual guidance.

2. 2.

The Anti-Tremor Training Module: The Anti-Tremor Training Module is a specialized program designed to address the issue of tremors by offering a series of exercises and activities aimed at reducing and preventing the occurrence of tremors. The objective of the present study is to measure, balance, and control micromotors. It is imperative that the participant maintains a stable instrument position and completes tasks with minimal hand tremor.

3. 3.

Bimanual Training Module: The test is designed to evaluate the individual's ability to coordinate both hands and to perform dual-handed tasks with precision and efficiency. The tasks entail the synchronized movement of instruments across different spatial planes, thereby simulating real-life cataract surgery.

Each module furnishes a composite score and submetrics, encompassing target accuracy, efficiency, and movement stability. The same researcher recorded the simulator performance scores to avoid bias (G.G.C.). First, the task was introduced and shown to the participant. The participant’s performance was then observed. Total and sub-heading evaluation scores were noted in the forceps, anti-tremor, and bimanual training modules, respectively.

The same investigator (S.U.) performed McKinnon’s two-point static discrimination test, the Semmes-Weinstein monofilament test, and the Nine-Hole Peg test [6].

1. 1.

McKinnon's Two-Point Static Discrimination Test: This evaluation method assesses tactile spatial resolution, which is defined as the ability of the skin to discern between two proximate stimuli. The procedure was repeated on the index fingertips twice, with the initial distance between the points being measured at a narrow setting. The distance was then gradually increased until the participant could no longer discern two discrete points [5, 6]. The minimum perceivable distance (in millimeters) is indicative of the level of tactile acuity, which is pertinent to the successful execution of fine instrument control during microsurgical procedures (Figure 1a).

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2. 2.

Semmes-Weinstein Monofilament Test: The Semmes-Weinstein monofilament test was applied twice to each participant's index fingertips using six monofilaments ranging in diameter from 1.65 to 4.31 inches. This test quantifies pressure sensitivity by applying nylon monofilaments of varying thicknesses to the index fingertips. The thinnest monofilament that bends upon contact and is perceived by the participant indicates the threshold for tactile pressure detection. The utilization of this scale is pervasive within the domains of neurology and diabetic screening [5, 6]. In the present study, it functions as a proxy for sensory input modulation during instrument handling (Figure 1b).

3. 3.

Nine-Hole Peg Test: The Nine-Hole Peg Test was performed using a 10x10x1 cm wooden box and nine wooden nails with a diameter of 7 mm and a length of 3.2 cm. The test is a standardized measure of fine motor dexterity and hand–eye coordination [5, 6]. Participants are instructed to place and subsequently remove nine pegs from a wooden board as expeditiously as possible, with the duration of this endeavor recorded in seconds. It provides a quantitative measure of motor precision and speed, which are considered fundamental competencies in surgical training (Figure 1c).

Statistical analysis

Study data were analyzed using the SPSS (Statistical Package for Social Sciences) version 18.0 software. The Shapiro-Wilk test evaluated whether the study data were normally distributed. Parametric tests were used for normally distributed data, and non-parametric tests were used for non-normally distributed data. For independent data, t-test or Mann-Whitney U test was used to analyze group differences. Pearson correlation analysis evaluated the relationships between fine motor skills, sensory sensitivity, and simulator performance. Results were considered statistically significant if the p-value was less than 0.05 and calculated at 95% confidence intervals.

Results

Twenty-eight (56%) participants were female, and 22 were male (44%), with a mean age of 28.6 ± 4.4 years. The dominant hand of 46 (92%) of the participants was the right hand, and the dominant eye of 43 (86%) was the right eye. The total score and sub-heading scores of the participants in forceps training, anti-tremor training, and bimanual training modules are summarized in Table 1. Total scores in these modules did not differ between the genders of the participants (p = 0.252, p = 0.326, p = 0.354). Forceps training and anti-tremor training module scores did not differ significantly with age, while bimanual training module scores decreased with increasing age (p = 0.197, p = 0.928 p = 0.016).

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Analysis of the three tests performed reveals different characteristics. The mean value of McKinnon’s two-point static discrimination test was 3.08 ± 0.72 mm, the Semmes-Weinstein Monofilament test was 2.42 ± 0.29 inches, and the Nine-Hole Peg Test mean completion time was 19.04 ± 2.60 s. Test results did not show a significant difference according to gender (p = 0.211, p = 0.951, p = 0.651, respectively). Similarly, there was no significant statistical relationship between age and test results (p = 0.704, p = 0.601, p = 0.251, respectively).

The correlation of McKinnon’s two-point static discrimination test with forceps training, anti-tremor training, and bimanual training module scores was analyzed. Correlation between the two-point discrimination test and forceps training module and anti-tremor training module scores was weak (r =−0.23 and r = −0.10, respectively) and not statistically significant (p = 0.101; 95% CI: −0.49 to 0.05 and p = 0.505; 95% CI: −0.37 to 0.19 respectively). However, there was a moderate and statistically significant negative correlation between the two-point discrimination test and the bimanual training module scores (r =−0.41, p = 0.0027; 95% CI: −0.63 to −0.15), suggesting that the higher accuracy in two-point discrimination, the better performance in bimanual practice.

Correlation between the Semmes-Weinstein Monofilament test results and forceps training, anti-tremor training, and bimanual training module scores was weak (r =−0.11, r = 0.03, r = 0.04, respectively) and not statistically significant (p = 0.438; 95% CI: −0.39 to 0.18, p = 0.832; 95% CI: −0.40 to 0.16, p = 0.755; 95% CI: −0.24 to 0.33, respectively).

The Nine-Hole Peg test duration and forceps training module scores show a weak negative correlation (r=−0.24, p = 0.090; 95% CI: −0.49 to 0.05). The correlation was insignificant in anti-tremor training module score (r = 0.06, p = 0.691; 95% CI: −0.33 to 0.24). However, a moderate and statistically significant negative correlation was found in bimanual training module score (r=−0.42, p = 0.002; 95% CI: −0.63 to −0.16).

Discussion

The use of simulator devices in ophthalmologic surgical training is a very important development [7, 8]. Simulator-guided training has a critical role in patient safety, reduction of intra- and postoperative complications, and shortening of surgical time [9, 10].

Studies emphasize the simulator device’s predictive feature in addition to increasing surgical skills [11, 12]. The scores that the surgeon trainee receives at the beginning are useful for creating a reliable prediction of surgical skills and for individualizing the training to the point where it is needed [13, 14].

When evaluating performances on the simulator device, experienced and inexperienced surgeon scores are usually compared [15]. In our study, the participants had no previous surgical experience. When we compared the scores with the age of the participants, it was observed that the score decreased statistically significantly with increasing age in the bimanual training module.

A substantial body of research has demonstrated that experienced surgeons consistently outperform novice trainees on surgical simulators, particularly in modules that require tremor suppression, depth judgment, and bimanual dexterity [11, 15]. These findings lend credence to the validity of simulator metrics in reflecting real-world surgical competence. In the present study, although the participants were novices, their mean performance scores in the bimanual and forceps modules appear to align with the lower range of scores reported in the literature for beginner-level residents. Including participants with varying experience levels in future studies may facilitate the determination of whether baseline motor and sensory proficiency can predict differential learning trajectories across surgeon training levels.

McKinnon’s two-point static discrimination test is widely used to assess tactile acuity and central somatosensory function in neurology patients [16]. The literature suggests that in microsurgery, tactile acuity may develop more over time through neuroplasticity pathways [5]. Our study observed that individuals with better two-point discrimination performed better in bimanual training module. To confirm the views on neuroplasticity, studies can be designed to monitor changes in patients’ long-term performance scores and sensory acuity.

Clinicians use the Semmes-Weinstein Monofilament test to assess sensory sensitivity, especially in patients with diabetic peripheral neuropathy [17, 18]. In the context of the present study, however, our participant group consisted exclusively of young and healthy individuals, which likely resulted in a relatively narrow range of sensory values. This limited variability may have contributed to the absence of statistically significant differences in sensory test scores across participants.

Although the Nine-Hole Peg test is widely used in neurologic patients, it is also used in the normal population and is considered the gold standard in manual dexterity [19]. As it varies with factors such as age, gender, and dominant hand, it is a tool that shows how much it affects motor skills in neurological diseases and helps in planning rehabilitation processes [20]. In our study, it was observed that forceps training and bimanual scanning scores decreased as the duration of the Nine-Hole Peg test increased. Still, the change was statistically significant only in the bimanual training score. Motor skills and simulation performance can be evaluated more accurately in future studies with more participants.

A notable strength of this study was the implementation of rigorous exclusion criteria, which was intended to minimize potential confounders that could independently affect fine motor or sensory performance. Participants with preexisting conditions, including diabetes, or those engaged in hobbies that necessitate microsurgical skills, were excluded to ensure a baseline that is as uniform as possible. However, we acknowledge that including such individuals could provide additional insight into the role of prior experience or altered sensory processing in simulator-based performance. Subsequent studies may concentrate on these subgroups to ascertain whether targeted training can enhance sensorimotor function and to further evaluate the role of such characteristics in predicting intrinsic aptitude for surgical performance.

The literature emphasizes the contribution of fine motor skills to surgery using simulator devices and the effect of non-dominant hand exercises on surgical success [12, 21]. However, we did not observe a study in which sensory sensitivity and motor skills were quantitatively determined and simulator device performance was compared.

One of the limiting factors of the study is the relatively limited number of participants. In future studies, the number of participants can be increased, and temporal changes can be evaluated in the same participants.

In conclusion, simulator devices are generally accepted to facilitate surgical training in terms of the safety of patients, shortening operation times, and decreasing complications. However, device costs and trainer problems are still controversial issues. The detection of deficiencies in individualizing surgical training increases the desirability of simulator devices in training clinics. Predicting the intrinsic factors of the individual may make it possible to save time and efficiency for surgical training. Measurement of sensory acuity and motor skills can also be part of personalized surgical training to identify intrinsic factors.

Data availability

Data are available upon reasonable request.

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