Self-Retaining Surgical Retractors: Maximum Sustainable Force of Surgical Stays and Stay Hooks in Human Tissue, and the Usual Force Applied to Both During Surgery – An Original Article

Spang A. Self-Retaining Surgical Retractors: Maximum Sustainable Force of Surgical Stays and Stay Hooks in Human Tissue, and the Usual Force Applied to Both During Surgery – An Original Article. J Anaesth Surg Res. 2022;3(1):1-6. 

Surgical Retractor systems are used by surgeons every day and have been considered as useful tools in hospitals for decades. Modern versions consist of a sterile disposable retractor ring and sterile elastic stays, positioned with cam locks for easier one-handed adjustments. New innovations have recently seen a sliding frame and the addition of surgical light guides attached to the frame. Despite the frequency of use, no formal studies and data exist on tension load capabilities or tension impact on human tissue. This paper identifies the baseline requirement for retracting tissue during surgery, the common range of tension being used, and the upper maximum of load.


Surgical retractors; Self-retaining ring retractors; Cadaveric testing; Force load; Patient safety


The purpose of self-retaining retractors is to reduce the tension on the tissue, reduce clutter around the patient by removing one or more assistants, and allow the surgeon better access to the operative site. Modern retractors allow gentle but efficient adjustable tension of retraction throughout the surgical procedure. However, data on the maximum force that can be safely applied to stays are lacking. The important gap is addressed in the three investigations:

• Stay integrity

• Maximum sustainable pull force

• Tension normally applied by surgeons when using stays to retract tissue

This is fundamental work that has never been previously published, yet forms a baseline assessment for both product design as well as clinical use in every hospital across the globe. It directly impacts safety during surgery and patient post-operative comfort and recovery.

History of retractors

Surgical retractors probably originated from extremely basic tools used in the Stone Age. Branches or antlers of various shapes were used to dig and extract food from the ground. As the use of tools evolved, a variety of instruments came about to substitute for the use of hooked or grasping fingers in the butchering of meat or dissection of bodies.

The use of metals in toolmaking was of significant importance. A variety of Roman metal instruments of the hook and retractor family have been found by archeologists. These instruments would generally be called hooks if the end was as narrow as the handle of the instrument. If the end was broad, it would be called a retractor.Also arising from this group of tools were other related tools for displacing (elevators and spatulas) and scooping (spoons and curettes).

In the 4th century CE, Indian physician Susruta used surgical tools such as READ MORE

Summary of Findings

The minimum requirement for retracting tissue during surgery is a load ranging from 1N and up, depending on tissue and procedure, and number of hooks used. The common range of tension used in vaginal procedures is between 2.5N–7.5N. The upper maximum load was 10N when applied in vaginal tissue using sharp 5mm low profile hooks. Using sharp 5mm stay hooks in the vaginal wall, we found that this tissue started to come apart at 3–7N. Rectus fascia tissue, when pulled with blunt 5mm low profile hooks, started to come apart at 5–10N. Both sharp and blunt 5mm stay hooks were tested in the outer labia, which started to come apart at 5–15N.


Together, these investigations demonstrate that surgical hook stays can safely sustain a maximum force of up to 3 times the usual tension applied during surgical procedures, without visible changes in hook or product design. Impact on tissue is a balance between higher loads on fewer hooks, or more hooks with lower load (but more puncture sites).

Further investigations and research on other types of tissue, a combination of other hooks and a range of surgical specialties need to be conducted to ensure a safer use of tissue penetrating hooks for optimal patient recovery and minimal damage.


First and foremost, gratitude should go to human tissue donors[6] who generously and bravely donated their bodies to medical research and training. Thank you to leading surgeons Dr.Wael Agur for his support in the lab in Glasgow University, and Dr. Alex Digesu, for his support in cadaveric testing. Thank you also to Glasgow University for the use of equipment and location.


1. Retractor (medical)–Wikipedia

2. Steele PRC, Curran JF, MountainRE. Current and future practices in surgical retraction. Surgeon. 2013;11(6):330-7.

3. University of Glasgow – Schools, School of Life Sciences, Anatomy Facility.

4. Human Tissue Act. UK Public General. 2004.

5. UK-based Manufacturer June Medical encountered several occasions of copyright infringement of Galaxy II.

6. The Human Tissue Act 2004 (HT Act) and associated Regulations. Human Tissue (Quality and Safety for Human Application) Regulations 2007 (as amended). Quality and Safety of Organs Intended for Transplantation Regulations 2012. These laws ensure that human tissue is used safely and ethically, with proper consent.