Introduction: Operating theatres generate a lot of waste and as such are a major contributor to the rise of negative environmental impact of hospitals. Thus reducing operating room waste is an essential strategy for hospitals to reduce their environmental impact and contribute to a healthier environment. This study aims to quantify waste from six common orthopaedic procedures and identify potential strategies for reduction. Methods: The Healthcare Sustainability Mode and Effect Analysis (HSMEA) is a method to assess the environmental impact of waste. It is a systematic approach to analyse waste, calculate the environmental impact and identify strategies to reduce this impact. In this study an HSMEA of operating room waste of 18 orthopaedic procedures was performed: open and percutaneous spinal fusion (n = 6), unicompartmental and total knee arthroplasty (n = 6), reverse shoulder arthroplasty (n = 3) and total hip arthroplasty (n = 3). For each type of waste, the strategies of the 6R methodology were considered to reduce the environmental impact of the operating theatre department. Results: The weight of the waste of orthopaedic procedures ranged between 6.35 and 8.30 kg. About 70% of the total waste was plastic. The environmental impact of measured orthopaedic procedures ranged between 19.14 and 23.96 kg CO₂-eq. The impact of the six orthopaedic procedures could be reduced with 10.3 to 13.9 kg CO₂-eq. using the 6R methodology. Conclusion: The environmental impact of waste from orthopaedic procedures is substantial and can be reduced up to 63%. Applying the HSMEA method to all procedures in the operating theatres can lead to a significant reduction of the carbon footprint of hospitals.

Objectives
Shoulder arthroplasty has a large environmental impact. Part of the environmental impact is caused by the sterilisation of surgical instruments. This study examines the effect of optimising surgical instrument trays for reverse shoulder arthroplasty (RSA), to reduce the environmental impact.

Methods
An adjusted LEAN 5s method was used to optimise the number of instruments of shoulder arthroplasty specific trays. A Life Cycle Assessment was performed to calculate the CO2-eq.

Results
After careful selection, 139 of the 254 (55%) instruments were removed from the original RSA trays. Out of the 139 removed instruments, 19 were placed in a supplemental tray. The number of base trays was reduced with 3 trays. The estimated impact by reducing these trays from the standard pre-operative setup is a reduction of 28% of the environmental impact annually (524 kg CO2 equivalent).

Discussion
This study confirms the feasibility of optimising instrument trays for RSA, offering a straightforward method to reduce the environmental impact of shoulder arthroplasty. Our results show that strategic instrument selection can contribute to lowering the environmental impact of orthopaedic surgery.