Quality Assurance
to various patient needs, procedural demands, and anatomical challenges. However, we considered that the significant number of new instruments needing replacement due to sizing issues would delay instruments entering clinical service and have a potential negative impact on surgical tray resilience. Following the audit, we took a pragmatic view to develop our own tolerance levels to enable a higher number of instruments to enter clinical service, while maintaining the high standards of the QA process. When compared to the in-house developed
tolerance levels (table 2), it was observed that 2.6% of the instruments would be rejected and returned to the manufacturer or supplier. This included: 12.2% of scissors, 1.5% of clamps and 0% of forceps. Incorrect sizing of surgical instruments may
feel like a minor infringement, but it affects everything from the precision and control a surgeon has, to patient safety and comfort, to the overall efficiency and effectiveness of the operation. Instruments that are too large or too small may result in unintended tissue damage. For example, a large retractor may overstretch tissues, while a small retractor may not provide an adequate support and restrict surgeons access to the treatment site. This may increase the risk of cuts, tears and tissue damage to
Permissible deviations in mm for ranges in the nominal lengths
0.5 up to 3
Over 3 up to 6 Over 6 up to 30 Over 30 up to 120 Over 120 up to 400 Over 400 up to 1000 Over 1000 6 up to 2000 Over 2000 6 up to 4000
Fine
±0.05 ±0.05 ±0.1
±0.15 ±0.2 ±0.3 ±0.5 -
Medium ±0.1
±0.1 ±0.2 ±0.3 ±0.5 ±0.8 ±1.2 ±2.0
Table 1: General tolerances for linear dimensions (for fine, medium, coarse and very coarse tolerance levels) from ISO 2768.
0 to 74 mm 75 to 149 mm
±2.5 ±4.0
150 to 225 mm ±6.0 226 to 300 mm ±8.0
Table 2: In-house tolerance mm level.
the patient. Incorrect sized instruments may make it difficult to perform delicate procedures, that may result in unnecessary trauma to surrounding tissues. We have taken a pragmatic approach to quality assurance acceptance testing for sizing surgical instruments. This audit has
Instrument sizing: comparison against ISO 2768 tolerance ('very course')
150 225 300
75 0 Clamp Forceps Needle holder Instrument type
Figure 1: Results of the new instruments entering Barts Health NHS Trust when compared to the very coarse tolerances of ISO 2768.
Figure 1a: Results of the new instruments entering Barts Health NHS Trust when compared to the very coarse tolerances of ISO 2768.
Instrument sizing: comparison against in-house tolerance level
150 225 300
75 0 Clamp Forceps Needle holder Instrument type
Figure 2: Results of the new instruments entering Barts Health NHS Trust when compared to our own in-house tolerance levels.
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www.clinicalservicesjournal.com I April 2025
Figure 2: Results of the new instruments entering Barts Health NHS Trust when compared to our own in-house tolerance levels.
Retractors Osteotomes Series3
Pass Fail
Retractors Osteotomes
Pass Fail
demonstrated that a significant number of instruments (19.8%) that entered our QA process did not meet the ‘very coarse’ tolerance standards as set out in ISO 2768. This ISO is a general standard for tolerances on dimensions and geometry in engineering, used to define permissible variations for parts that are manufactured without specific tolerance requirements. While ISO 2768 is not specifically tailored to surgical instruments, it does play a role in their manufacturing by establishing baseline tolerances for certain dimensions. It is essential to ensure that instruments are safe, functional, and ergonomic, while keeping testing processes efficient. By focusing on critical dimensions, real-world functionality, and regulatory compliance, this approach streamlines testing, while maintaining the highest standards. Ultimately, it leads to surgical instruments that meet clinical needs, support patient safety, and provide value through efficient and targeted quality assurance. It would be helpful if manufacturers informed their customers on how they measure and label their products, to make it easier for users to order correctly sized new or replacement instruments. Additionally, manufacturers should take a standardised approach to measuring dimensions. For example, we are aware that some manufacturers measure the length of micro scissors in a closed position, while others are measured in an open position. This will help provide clarity to the clinical users. With a consistent approach to sizing, this would enable QA to be undertaken against the stringent requirements of ISO 2768, rather than our in-house tolerance levels to prevent blockages or delays in getting instruments into service. This will allow every instrument entering service to match their intended design and performance requirements. This consistency is crucial for maintaining high standards in surgical outcomes and ensuring reliability across all instruments.
CSJ
Coarse ±0.2
±0.3 ±0.5 ±0.8 ±1.2 ±2.0 ±3.0 ±4.0
Very coarse -
±0.5 ±1.0 ±1.5 ±2.5 ±4.0 ±6.0 ±8.0
Number of instruments
Number of instruments
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