1 Introduction

Climate change is of increasing global importance. Healthcare facilities are among the largest sectors in the United States and are responsible for an estimated 1,814,369,480 kg of waste annually. Operating rooms have been estimated to account for 20–70 % of hospital waste production.¹ In the United States and Europe, the healthcare industry is responsible for producing up to 10 % of greenhouse gas emissions.² Understanding the significant carbon footprint of operating rooms, surgeons, and hospital systems has allowed these systems to uniquely position themselves to help mitigate the environmental impact of healthcare. Table 1 demonstrates the mass and type of waste whereas Table 2 demonstrates the volume and type of waste.

Total joint arthroplasty is a major contributor to operating room waste production.³ Synthetic implants and prosthetics were estimated to account for over 15 % of the carbon footprint of the London Health Science Centre in 2006.⁴ Stall et al. showed the average surgical waste per total knee arthroplasty (TKA) was 13.3 kg, of which the majority (64.5 %) was solid waste followed by biohazard waste (19.2 %).⁴ Several factors have been highlighted as potential areas for improvement, including reusing equipment (external fixators, surgical gowns), limiting use of operating room materials, re-processing single use instruments, and properly selecting anesthetic techniques.⁵ Additionally, efficient segregation of waste can help reduce a procedure's carbon footprint.⁶ Recent studies have attempted to quantify waste differences between open and minimally invasive techniques.⁷ Furthermore, the volume of primary and revision TKAs is projected to grow 85 % to 1.26 million procedures by 2030.⁸

Much of the literature to date consists of waste audits and life cycle assessments (LCAs) to estimate the waste generated from a procedure or to compare different techniques (open vs. minimally invasive). However, little investigation has been done comparing the waste produced in various settings such as a hospital operating room and an ambulatory surgery center (ASC). ASCs’ waste production has become increasingly relevant given the drastic increase in outpatient total joint procedures following the COVID-19 pandemic. Powell et al. found an increase in TKAs and total hip arthroplasties performed at ASCs and hospital outpatient departments of 84 % and 125 %, respectively, between 2019 and 2020.⁹ This study aims to compare the types and amount of waste produced following manual non-cemented TKA at an ASC and hospital operating room.

2 Methods

A waste audit was performed on ten non-cemented primary TKAs performed by a single surgeon in both a single institution's operating room (OR) and an ASC OR. During each surgery, one member of the study team was present and sorted the waste into the appropriate streams. This study was approved as exempt by the local institutional review board.

The waste streams were categorized as normal landfill, sterile waste, laundered items, recyclable plastics, biohazard, and sharps. Sterile waste was defined as any waste that was either a sterile product (gloves or gowns) or used to cover sterile items (blue sterile wrapping). Items classified as recyclable plastics included but were not limited to implant packaging and fluid basins. Any item that was a recyclable plastic was included in this waste stream whether it was a sterile item or not. Laundered items included all items that were laundered and reused including towels, blankets, and bed linens. The biohazard waste stream encompassed all waste considered hazardous including items such as soiled sponges and bone fragments. Sharp waste was measured by weighing the sharps disposal box with and without the sharps following the surgery and calculating the difference. Normal landfill waste stream included all other waste that did not fit into another category including items such as implant boxes and other packaging items.

Following the conclusion of the surgery, all waste streams were weighed using a scale accurate to 0.1 pounds. The masses were later converted to kilograms. In order to measure the volume of each waste stream, a measuring stick accurate to 1 mm was used. Prior to measuring the volume of each waste stream, the bags of waste were compressed by hand in order to eliminate as much dead space as possible in each trash bag. Only mass was recorded for sharp waste as it is was deemed unsafe to measure the volumes of sharps.

Summary statistics were computed for all study variables. Mass and volume are summarized with measures of central tendency for each waste category and location (hospital and outpatient). Based on distribution and variance of the measures, either a t-test or the non-parametric Mann Whitney U test was used to compare both mass and volume in each waste category between the two location settings. P-values less than 0.05 were considered statistically significant.

3 Results

The median mass of waste for hospital based TKAs was 17.3 kg. The waste stream that was the largest contributor was the sterile waste at 9.57 kg followed by laundered linens at 3.49 kg. The normal landfill waste weighed 2.40 kg, the recyclable plastics contributed 0.82 kg, and the biohazard waste had a median mass of 0.32 kg. Sharps contributed the least weight at 0.18 kg. The median waste for ASC TKAs was 14.01 kg. Similar to hospital ORs, sterile waste was the largest contributor at 8.48 kg followed by laundered linens at 3.04 kg. Normal landfill waste contributed 1.81 kg, recyclable plastics 0.62 kg, and biohazard waste 0.30 kg. Sharps weighed 0.10 kg.

There was significantly more total mass for the hospital based TKAs as compared to the ASC cases (p-value = 0.0028). Hospital based TKAs produced significantly more sterile waste (p-value = 0.0199) and normal landfill waste (p-value = 0.0003) than the ASC TKAs. Additionally, there was significantly more sharps waste in hospital OR TKAs (p-value = 0.0422). There was no difference in the mass of waste in the recyclable plastic (p-value = 0.0593), biohazard (p-value = 0.4285), and laundered linen waste streams (p-value = 0.1402).

The median total volume of waste produced in the hospital OR TKAs was 305,866 cm³. The largest contributor was sterile waste followed by normal landfill waste with volumes of 165,368 cm³ and 71,505 cm³, respectively. Laundered linens had a median volume of 34,008 cm³, recyclable plastics 26,520 cm³, and biohazard 607 cm³. ASC TKAs produced a median total volume of waste of 260,052 cm³. As with hospital TKAs, sterile waste and normal landfill contributed the most volume at 138,957 cm³ and 59,302 cm³, respectively. Recyclable plastics contributed the next largest volume at 33,822 cm³ followed by laundered items at 28,932 cm³ and biohazard at 1215 cm³.

There was a similar total volume of waste in both the hospital OR and ASC TKAs (p-value = 0.2494). No differences existed in the amount of sterile waste (p-value = 0.3578), recyclable plastics (p-value = 0.7490), laundered linens (p-value = 0.7031), and biohazard waste (p-value = 0.7321). There was significantly more volume of normal landfill waste produced from hospital TKAs compared with ASC TKAs (p-value = 0.0328).

4 Discussion

The total number of TKAs continues to increase in the United States. In a recent study, Shichman et al. projected the total number of TKAs to increase 139 % by 2040 and 469 % by 2060.¹⁰ Likewise, the removal of elective TKAs from the Medicare inpatient-only list compounded by COVID-19 resulted in increases in elective arthroplasty procedures being performed at ambulatory centers.¹¹ As climate change becomes a reality, it falls at least partially on the surgeon to responsibly utilize resources and minimize waste to ensure the sustainability of orthopaedics. This study suggests that ASC ORs are more sustainable when performing non-cemented manual TKAs compared to hospital ORs as they generate less mass of waste per procedure.

In this study, the largest waste stream was the sterile waste from drapes and gowns. As a teaching institution, the centers included in the study have a large volume of fellows, residents, and medical students participating in each case. The high number of participants scrubbed into each case will predictably lead to more sterile gowns and gloves. However, this was consistent between both settings. Another factor that could be contributing to the difference in the mass of sterile waste is the tendency of scrub techs in the hospital ORs to be relieved for lunch breaks. In addition, in the hospital setting, scrub techs frequently break scrub and rescrub multiple times prior to the procedure beginning. This causes additional gowns, gloves, and hoods to be wasted. Both of these practices were noticeably much less common at the ASC setting. In the hospital setting, there are entire separate sterile trays that are opened for each procedure and include implant trials of various sizes. This differs at the ASC where only a single wrapped individual component is opened after measuring sizes intraoperatively. For example, in the hospital setting 5 total knee trays are opened while in the ASC setting only two trays are opened with an additional 3–4 peel packs being opened per case specific for the size and side of the procedure. The large sterile trays likely contribute to more waste than the small individually wrapped trial implants. To decrease waste further, sterile cubes which contain multiple sterilized instrument trays with minimal wrapping, could be used in both settings to decrease the amount of individual packaging, although further research is needed to measure their impact on operating room waste. Reusable gowns may also be a consideration to help decrease waste further. It has been predicted that up to 30,000 pounds of solid waste may be averted in a tertiary center be transitioning to reusable sterile gowns.¹²

Similar to sterile waste, the hospital OR had increased normal landfill waste compared to that of the ASC. One possibility is the hospital ORs could have more items opened at baseline than the ASC. This would lead to higher amounts of waste and could be leading to higher costs at the hospital. There also proved to be more sharps used in the hospital than the ASC. This small but statistically significant difference could have arisen from the hospital having more sharp items opened for each case than at the ASC. This may be a result of opening sutures as needed at the ASC at the end of the case instead of pulling the sutures at the beginning of the case in the hospital OR. Also, the suture at the hospital may be smaller in length requiring more suture packages to be open.

The overall volumes of waste produced between the two centers were similar. The only waste stream that showed a significant difference was the normal landfill stream with more volume in the hospital ORs. This was predictable as the normal landfill mass was also greater at the hospital. Interestingly, even though the mass of sterile waste was greater, there was no difference observed in the volume of this waste stream. This could have arisen from the manner in which items were compressed before being measured and the inherent variability in doing so. Measuring the volume of the waste streams was difficult and subject to error and significant variability as it was compressed and measured with a yard stick, and our data may reflect this difficulty.

Performing TKAs in an ASC setting helps lower the ecological footprint of the procedure, and it can also lower the costs to the healthcare system. According to a prior study, the cost of waste disposal at healthcare facilities was $2.36 for each kilogram of waste produced.¹³ Thus, each case performed at an ASC offers a cost savings of $7.55. Each year there are approximately 480,000 TKAs performed in the United States.¹⁰ If half of these procedures were performed in ASCs, this would yield an annual cost savings to the healthcare system of $1,812,000 from waste disposal costs alone.

One of the limitations of this project is the limited sample size. If more cases had been studied, the difference might have become non-significant. Additionally, inherent inaccuracies exist when measuring and comparing the volumes of waste created. However, efforts were taken to collect this information similarly for all cases.

In conclusion, the results of this study show that performing TKAs in an ASC as opposed to a hospital could lower the environmental footprint of the case. Increased mass of waste in the hospital could have both long term ecological and financial consequences on the healthcare ecosystem. Future multi-center studies with more cases will help to correctly define the waste produced during such procedures.

Guardian/Patient Consent

No consent was obtained as local IRB deemed this non-human subject research.

CRediT authorship contribution statement

Christopher E. Bejcek: Conceptualization, Methodology, Writing – review & editing. Jeffrey R. Baker: Investigation, Writing – original draft, Writing – review & editing. Anthony G. Sleiman: Conceptualization, Investigation, Writing – review & editing. Sowmyanarayanan V. Thuppal: Conceptualization, Methodology, Data curation, Writing – review & editing. Kristin Delfino: Formal analysis, Data curation, Writing – review & editing. D. Gordon Allan: Conceptualization, Methodology, Supervision, Writing – review & editing.

Ethical statement

This research was conducted in accordance with all relevant ethical guidelines, maintaining confidentiality of data, and minimizing potential harm. Ethical approval was obtained from SIU IRB. The study was granted exempt status as no patient data was collected.

Funding source

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.