What factors should be considered when selecting casters for an operating table?

When selecting casters for an operating table, the four core objectives of surgical safety, environmental adaptability, ease of use, and long-term durability should be considered. Considering the heavy-duty nature of the operating table (typically carrying 150-300 kg, including the patient, medical staff, and equipment) and the specific operating room requirements, the following seven key factors should be considered:

1. Load-bearing capacity: The load capacity must match the total load of the operating table, with a safety margin.
The load capacity of the operating table casters must cover the combined weight of the bed + the patient + the weight of medical staff performing the operation + the weight of the equipment. This is the primary prerequisite for ensuring safety.
Core requirement: Rated load capacity of a single caster ≥ (total load of the operating table / number of casters) × 1.3 (allowing a 30% safety margin). For example, if a surgical table has a total load of 200 kg (bed 50 kg + patient 120 kg + medical staff/equipment 30 kg), and is equipped with four casters, the rated load capacity of each wheel must be ≥ (200 kg ÷ 4) × 1.3 = 65 kg to avoid wheel deformation and bearing seizure caused by excessive weight.
Material considerations: Prefer a stainless steel frame and high-pressure-resistant wheels (such as polyurethane or nylon). The frame should be thickened (≥ 3 mm), and the wheels must pass a 100,000-cycle heavy-load rolling test to ensure they will not crack or collapse after prolonged use.

2. Braking System: Dual Braking + Strong Locking to Prevent Intraoperative Displacement
During surgery, the operating table must be absolutely stationary (e.g., during incisions and suturing). The caster braking system must provide "instant locking and resistance to external forces":
Braking Type: A dual-braking structure with "wheel brake + bracket rotation brake" is essential. The wheel brake locks the wheels from rolling, while the bracket brake locks the caster from turning, providing dual protection against "sliding" or "spinning" of the operating table.
Braking Performance: The brake pedal must provide clear feedback, and the locking force must be ≥ 1.5 times the rated load capacity of the caster (e.g., a 65kg load-bearing caster requires a brake locking force ≥ 97.5kg). This prevents movement even if medical staff accidentally bump the operating table.
Operational Ease: The brake pedal must be at a height compatible with surgical shoes (10-15cm from the floor) and have a non-slip surface to prevent slipping. Some high-end casters offer "linked braking" (locking all casters with a single pedal) to improve operating efficiency.

3. Material Corrosion Resistance: Suitable for High-Frequency Chemical Disinfection in Operating Rooms
Operating rooms require daily cleaning and disinfection with highly corrosive agents such as chlorine-containing disinfectants (e.g., 500mg/L chlorine-containing disinfectant), alcohol (75%), and peracetic acid. Therefore, caster materials must be chemically resistant.
Bracket Material: 316 medical-grade stainless steel (superior to 304 stainless steel) is preferred. It contains molybdenum, which resists chloride ion corrosion and eliminates the risk of rust or fracture after long-term disinfection. Avoid ordinary carbon steel (which is prone to rust) or electroplated brackets (the coating can easily peel and contaminate the sterile area).
Wheel Material: Choose medical-grade polyurethane (PU) or nylon. PU wheels are resistant to alcohol and chlorine-containing disinfectants and do not harden or crack after disinfection. Nylon wheels offer greater chemical resistance and are suitable for frequent disinfection. However, be careful to select a low-friction model to avoid scratching the epoxy floor in the operating room. Sealing Design: Caster bearings must be fully sealed (e.g., with rubber seals) to prevent disinfectants and accumulated fluids from seeping into the bearings, causing rust and seizure, and to prevent bearing lubricant leakage from contaminating the sterile area.

4. Quietness and Stability: Ensuring Surgical Environment and Patient Safety

A quiet environment must be maintained during surgery (to facilitate communication between doctors and nurses and monitor instrument sounds), and the operating table must be moved smoothly (to avoid patient discomfort or instrument slippage).

Quietness Requirements: Caster rolling noise must be ≤40 decibels (equivalent to a library environment). This is achieved through a combination of silent bearings and soft wheels. Medical-grade precision ball bearings (e.g., ABEC-5 or higher) are used for the bearings to reduce rotational friction noise. Soft materials such as PU are used for the wheels to prevent noise from hard wheels hitting the ground. Stability Requirements: The wheel body must be calibrated for concentricity (error ≤ 0.1mm) to prevent bouncing during rolling. Anti-vibration pads (such as silicone) must be used between the caster bracket and the bed to reduce vibration transmission during movement. This is particularly suitable for patients undergoing anesthesia or for delicate surgeries (such as ophthalmology and neurosurgery).

5. Floor Compatibility: Avoid scratches and adapt to different floor materials.
Operating room floors are often made of epoxy, PVC, or non-slip tiles. Casters must be compatible with these surfaces to avoid damage or slipping.

Wheel Hardness: The wheel body's Shore A hardness should be between 70-85 degrees (soft PU wheels). Lower hardness can easily deform, while higher hardness can easily scratch the epoxy floor. For tiled floors, slightly harder nylon wheels (Shore D 60-70 degrees) can be selected, but ensure the wheel surface is smooth and burr-free. Wheel Tread Design: Wide wheels (tread width ≥ 30mm) are preferred to increase the contact area with the floor and reduce floor pressure (avoiding indentations). A micro-textured design can be used to enhance slip resistance on wet floors (e.g., after disinfection), preventing slippage during table movement.

6. Sterile Compatibility: No blind spots, meeting operating room aseptic standards.
The operating room is the "sterile core area," and casters must avoid harboring dirt and facilitate quick cleaning and disinfection.

Structural No-Blind Spots: The caster bracket must be integrally molded to avoid weld gaps, screw holes, and other structures prone to dust accumulation. The connection between the wheel and bracket must be seamless to prevent fluid and dust accumulation.

No Leakage Contamination: All materials that come into contact with the outside world (wheel, bracket, and seals) must pass medical-grade biocompatibility testing to ensure they do not leach harmful substances such as plasticizers and heavy metals, potentially contaminating the surgical wound or the patient's skin. Cleanability: The surface must be smooth and flat, leaving no residue when wiped with disinfectant wipes. It must also withstand high-temperature disinfection (e.g., 80°C hot water) to meet the operating room's "instant cleanliness and immediate sterility" requirements.

7. Durability and Maintenance Cost: Suitable for long-term, high-frequency use
Operating table casters must withstand frequent movement, braking, and disinfection daily. Durability directly impacts maintenance costs and surgical safety:
Service Life: The wheel must pass a 50,000-cycle heavy-load rolling test (1.2 times the rated load) without noticeable wear; the bracket must pass a 10,000-cycle braking test without loss of braking performance.
Maintenance Ease: The caster must feature a quick-release mechanism for easy replacement (e.g., if the wheel wears, the caster can be replaced without disassembling the entire operating table). The bearings must be filled with a long-lasting medical grease (e.g., silicone-based grease) to avoid frequent relubrication. Brand and certification: Give priority to caster brands that have passed "medical device certification" (such as FDA, CE certification) to ensure that the material and performance meet medical safety standards and avoid surgical safety hazards caused by inferior casters.