Effect of lead vest on back and shoulder muscle fatigue development
TimeThursday, April 152:00pm - 3:00pm EDT
DescriptionThe use of radiation protection equipment (rPPE or lead vest) in image-guided fluoroscopic minimally invasive surgery has been associated with the development of work-related low back problems (WRLBP). However, the evidence supporting this claim is inconclusive and contradictory. In support of the association between the use of rPPE and WRLBP development, a survey on 263 surgeons from the Society for Clinical Vascular Surgery showed that 48% of survey respondents wore rPPE each day and 54% of the rPPE users reported physical discomfort which could hinder their surgical performance (Davila et al., 2019). Another survey on 775 surgeons from the Society of Vascular Surgery found that after a full day of endovascular procedures, surgeons experienced moderate pain (3.9 ± 2.4 out of a max 10) and the most severe pain was found in the low back (Wohlauer et al., 2019). Alarmingly, 39 respondents left their careers as practicing surgeons, and 26% said they retired because of work-related pain. While these studies pointed to a relation between rPPE usage and WRLBP development, the postures assumed by these surgeons were not reported. Furthermore, subjective measures vary across respondents, warranting the need for objective studies to isolate the effect of using rPPEs.
Objective/experimental studies on the role that rPPE usage plays in WRLBP development is not clear and conclusive. For instance (Johnson et al., 2011), reported no significant impact of using rPPE using time-domain electromyography analyses. Conversely, another study used thermography to investigate the difference in the heat emitted by back muscles in the operating room with and without the rPPE. This study reported significant heat emission from using the rPPE; however, such results could be confounded by the extra heat accumulation as rPPEs prevent heat from dissipating from the body surface.
With contradictory and inconclusive evidence in the literature, the current study was designed to quantify the effect of rPPE utilization on EMG-based measures (time and frequency domain) of localized muscle fatigue (both frequency and time domain) of the trapezius muscles and multiple levels of the trunk extensor muscles of the lumbar and thoracic regions of the torso. It was hypothesized that the extra moment required to hold the weight of the rPPE would result in EMG responses indicative of muscle fatigue over time.
Sixteen participants (eight men and eight women) were recruited to participate in a simulated surgical task requiring a 30-degree trunk flexion for a total of 15 minutes, with and without donning a lead vest. Muscle activity was sampled via electromyography (EMG) electrodes attached bilaterally at three levels of the trunk extensor muscles. Furthermore, a subjective fatigue assessment was conducted before and after the simulation task.
Frequency domain analysis of the muscle activation data showed a significant difference in the shift of median frequency in the left lumbar erector spinae LLES (p=0.024, CI = 1.5-17.9), and left lower thoracic erector spinae (p=0.0006, CI = 4.0-11.8) between the lead vest and no lead vest condition. The lead vest condition demonstrated higher muscle activation in these two muscles. Analysis of the ARV variables did not show a statistically significant effect of the rPPE for any of the muscles sampled. Trends from the subjective fatigue assessment showed that both conditions induced back muscle fatigue however, results from the statistical analysis showed that the rPPE condition caused a significant amount of back muscle fatigue compared to the no rPPE condition (p-value = 0.040, CI =0.060-2.217).
Results from the time-domain EMG analysis from the current study appears to agree with the findings from Johnson et al., (2011) in that while there was an increase in muscle activation over time, this increment was not statistically significant in both studies despite the perceived rise in muscle fatigue/activation. Thus, the real difference in the effect of wearing rPPE on fatigue development was revealed by the frequency domain analysis via the median frequency. This finding highlights the importance of using both time and frequency domain analysis in assessing muscle fatigue in EMG studies as described by (Cifrek et.al. 2009).
The U.S. Clinical Vascular Surgeons (SCVS) reported wearing rPPE, with 91% wearing it at least one time per week and 97% of that same group reported pain at the end of their surgical day with 6% of those survey having to stop operating owing to work-related pain (Davila et al., 2019). In the Wohlauer et al. (2019) survey, 44% of the respondents performing the cases wearing lead had low back pain, with 4% of the survey respondents overall not currently operating due to physical pain. In both surveys, more than 50% of the surgeons who routinely wear rPPE for their work tasks were concerned about their career longevity due to work-related pain. There are many causes of this concern, including long-duration surgeries where they are in awkward postures and wear lead.
As compared to the duration of actual surgeries, the time spent performing this procedure in our study was relatively modest; however, even under these short-duration conditions, low back fatigue was evident through the downward shift of the median frequency response of the extensor musculature, and the rPPE accelerated this fatigue response. To enhance the comfort and effectiveness of the surgeons performing these procedures, ergonomic interventions are needed. Several promising directions for intervention are being explored. Suspended Personal Radiation Protection Systems (SPRPS) are overhead-mounted systems fitted with radiation protection materials such as lead shields etc. They are designed to move with the operator while maintaining an optimized spatial distance from the operator’s body. This eliminates the load on the musculoskeletal system and has been shown to provide effective radiation protection in a prospective case-control study (Haussen et al., 2016). Another intervention approach is to adjust the work-rest cycles of the surgical procedure to provide intermittent relief through the use of micro-breaks. This technique was shown to delay pain sensation in the shoulder and neck region in addition to reducing overall muscle activation via EMG (Vijendren et al., 2018) or by self-reported pain reduction (Park et al., 2017). This approach has the benefit of being appropriate for both rPPE and non-rPPE procedures.
In conclusion, this study provided empirical evidence of accelerated lower back muscle fatigue development when wearing rPPE while performing surgical tasks. Furthermore, this accelerated muscle fatigue development seems to be logically linked to the level of muscle force required by the task with the contra-lateral trunk extensors experiencing a more significant impact of the rPPE than their right-side counterparts. This finding supports recent surveys that associate low back pain to performing these types of surgical procedures while wearing rPPE. Finding ways to relieve the biomechanical loading associated with rPPE can be a future line of engineering control development to reduce the surgeons' pain and fatigue and potentially reduce occupational illnesses and prolong careers.