Noise-induced hearing loss in orthopaedic surgery: Are we at risk?

Jerry Sam and Hiro Tanaka

Noise-induced hearing loss (NIHL) is an increasingly recognised occupational health risk across many industries, but its presence in healthcare, specifically in orthopaedic surgery, remains underappreciated. The orthopaedic operating theatre can be a high noise environment with the sound of specific tools and devices reaching levels of 90-140 dB. Prolonged exposure over the course of a career presents a significant risk to surgeons and theatre staff. In this article, we move forward in our series towards creating the safest possible work environment. We will explore the impact of noise on healthcare workers, the Health and Safety Regulations, the various factors contributing to noise levels in orthopaedic surgery, and potential preventive strategies to mitigate risk.

Why is it important?

The National Institute on Deafness and Other Communication Disorders (NIDOCD) estimates that approximately 15% of Americans between the ages of 20 and 69 experience hearing loss that may have been caused by exposure to noise at work or leisure activities. The risk of NIHL among senior orthopaedic surgeons neared 50% in a study conducted by Willetts and appeared to be dose related [1].

Professional and personal impact of NIHL

1. Impaired communication: One of the most immediate consequences of hearing loss is difficulty in communication. The first symptom of NIHL may be difficulty hearing a conversation against a noisy background. This occurs due to a perceived reduction in volume as well as loss of clarity due to high frequency loss. In the operating room, where clear, precise, and timely communication is essential for patient safety, even minor hearing impairment can lead to misunderstandings or delays in responding to critical situations.

2. Increased stress and fatigue: Noise exposure, even without hearing loss, is associated with increased cognitive load, stress and fatigue. Healthcare professionals working in noisy environments may experience reduced concentration, leading to errors or inefficiencies during surgery.

3. Quality of life: Outside the professional environment, NIHL can significantly affect quality of life due to impaired social interactions leading to feelings of isolation. Tinnitus, for example can lead to difficulty sleeping, anxiety and depression.

Key terminologies

Noise is typically measured on the logarithmic Decibel (dB) scale, which means that a noise level of 100 dB has 10 times as much sound energy as one of 90 dB. A 10 dB increase makes the sound twice as loud. In order to improve the sensitivity of the sound perceived by the human ear, modern measurement devices incorporate an A-weighting dB(A) which decreases sensitivity to low and high frequencies. Typical levels of noise from daily activities can be seen in Table 1. It is important to note that a single loud noise above 120 dB may cause immediate and permanent hearing loss.

The Time Weighted Average (TWA) shows a worker’s daily exposure to occupational noise normalised to an eight-hour day and takes into account the duration and amplitude of sound exposure. It can also be calculated from the dose percentage detected by a dosimeter.

The Occupational Safety and Health Administration (OSHA) states that an eight-hour time-weighted average exposure of 85 dB(A) or a peak exposure of 140 dB represents the threshold for safe exposure.

A 40 year exposure to 85 dB(A) per eighthour working day carries a 35% risk of NIHL amongst exposed workers. This increases to 51% with a 90 dB(A) exposure [2].

Health and Safety Regulations

The European Commission Directive 2003 on noise at work and the current Control of Noise at Work Regulations 2005 define threshold levels for noise exposure and aims to reduce the risk to staff to as low a level as reasonably practicable [3]. Action should be taken where noise exposure is likely to be at, or above any of the three action levels given in Table 2.

Should any work, following a risk assessment or noise survey breach the above levels then the following actions should be undertaken:

LEAV: Employees will be notified and advised of the risk from noise.

UEAV: These areas will be designated as Hearing Protection Zones and only authorised staff, equipped with the appropriate hearing protection may work in those areas.

ELV: Immediate action must be undertaken to reduce exposure to noise.

What is the current evidence?

Several studies have demonstrated that a number of orthopaedic instruments would exceed the threshold for sensorineural damage with prolonged exposure. A systemic review of 14 papers by Mistry et al. concluded that 61% of orthopaedic operations and 70% of instruments exceeded the A-weighted noise regulations and 22% of operations exceeded the peak C-weighted acceptable noise levels [4] Kwan et al., identified that the highest risk procedure was microdiscectomy followed by hip and knee arthroplasty [5].

Love et al. demonstrated that average noise levels could exceed 80 dB(A) in hip and knee arthroplasty with peak noise values of 140 dB6. There is significant variation in the noise levels emitted from different instruments with the reciprocating saw producing the highest average and peak levels [7].

Due to the variation in surgical practice and exposure to instruments, the precise risk to orthopaedic surgeons cannot be determined. However, the evidence is clear that the instruments commonly used in orthopaedic surgery frequently exceed safety levels and potentially poses a risk to health.

Siverdeen et al. recommended that all patients especially the elderly as well as theatre staff should take precautions in procedures involving high-powered tools [8].

Preventative strategies to reduce NIHL

Given the significant risk of NIHL in the orthopaedic theatre, preventative strategies are essential to protect the hearing of surgeons and staff. These strategies can be divided into engineering controls, administrative controls and personal protective equipment (PPE).

1. Engineering controls

• Noise-reducing tools. Modern electric drills and saws can be engineered with noisedampening features and produce less noise than old-fashioned pneumatic instruments.

• Soundproofing. Soundproofing materials, such as acoustic panels or noise absorbing flooring, can help dampen the reverberation of sound, reducing overall noise level.

2. Administrative controls

• Risk assessment and noise monitoring. Regular monitoring using dosimeters can help identify where and who is at risk. By understanding the noise profile of different operations, targeted interventions can be implemented to reduce noise exposure.

3. Personal protective equipment

• Hearing protection. Although earplugs or earmuffs are an effective way to reduce exposure, they pose problems with communication and are not a practical solution. Custom-fitted earplugs can however, filter out harmful noise frequencies while allowing for speech intelligibility.

• Distance. Willets demonstrated that 95-100 dB(A) from an oscillating saw at 45cm decreases to 88 dB(A) at 3m.

Conclusion and key learning points

• Noise-induced hearing loss is an under-recognised occupational hazard in orthopaedic surgery.

• High frequency hearing loss affects communication, which can affect professional performance and social interactions.

• The impact of hearing loss is cumulative over a career and surgeons should be aware of safe threshold limits.

• A significant proportion of power tools will generate noise levels, which may exceed safe limits depending upon time exposure.

• By taking proactive steps to reduce noise exposure, the healthcare industry can safeguard the hearing of its workers, ensuring a healthier and more sustainable working environment.

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References

1. Willett KM. Noise-induced hearing loss in orthopaedic staff. J Bone Joint Surg Br. 1991;73(1):113-5.

2. Gates GA, Cobb JL, Linn RT, et al. Central auditory dysfunction, cognitive dysfunction, and dementia in older people. Arch Otolaryngol Head Neck Surg. 1996;122(2):161-7.

3. The Control of Noise At Work Regulations 2005, Health and Safety Executive UK. Available at: www.legislation.gov.uk/ uksi/2005/1643/pdfs/uksi_20051643_ en.pdf

4. Mistry D, Ahmed U, Aujla R, et al. The relationship between exposure to noise and hearing loss in orthopaedics. Bone Joint J. 2023;105-B(6):602-9.

5. Kwan SA, Lynch JC, DeFrance M, et al. Risk of Noise-Induced Hearing Loss for Orthopaedic Surgeons. J Bone Joint Surg Am. 2022;104(23):2053-8.

6. Love H. Noise exposure in the orthopaedic operating theatre: a significant health hazard. ANZ J Surg. 2003;73(10):836-8.

7. Butt DA, Hadjipavlou M, Walcrak J. A noise at work assessment in the orthopaedic operating theatre. Bulletin of the Royal College of Surgeons of England. 2014;96(1):32-4.

8. S Siverdeen Z, Ali A, Lakdawala AS, McKay C. Exposure to noise in orthopaedic theatres--do we need protection? Int J Clin Pract. 2008;62(11):1720-2.