Immobilisation of the upper limb is a fundamental component of managing fractures, soft tissue injuries, and post-operative recovery in Trauma and Orthopaedics. This article provides an overview of the common methods used in clinical practice, outlining their indications, benefits, and key principles to support safe and effective patient care.

Casts

Backslab and Full Plaster of Paris (POP) Casts

Both a backslab and a full cast are made of natural gypsum (calcium sulfate dihydrate), more commonly known as Plaster of Paris (POP). Once mixed with water, the compound hardens and is used to immobilise a limb.

A backslab is when the hardened POP is applied only to one side of the limb and secured with bandage. The limb is wrapped in wool beforehand to protect the skin. Backslabs are commonly used in acute injuries to allow for soft tissue swelling.

In contrast, a full Plaster of Paris cast encases the limb circumferentially, providing greater stability. It can be used in acute injuries if the fracture pattern requires more support than a backslab can provide; in these cases, the cast is usually split to accommodate soft tissue swelling.

Fig1: Diagram demonstrating above elbow backslab applied to limb covered in padding wool rolllayer and stockinet to protect skin. Image Source: https://surgeryreference.aofoundation.org/orthopedic-trauma/pediatric-trauma/forearm-shaft/22r-d-11/cast-or-splint-fixation-without-reduction#principles

Synthetic Lightweight Casts

A synthetic lightweight cast is an alternative to a full POP cast, made from modern materials such as fibreglass or polyester. These casts are lighter, stronger, and more durable. Patients with fractures managed non-operatively are often changed from a backslab or full POP cast to a synthetic cast at fracture clinic review 1–2 weeks after injury.

Fig 2: Synthetic Below Elbow Cast. Image Source – https://ntkmedical.com/en/products/synthetic-casting-tape-and-splints/synthetic-casting

Slings

Collar and Cuff

A collar and cuff sling is a simple form of upper limb support. It consists of a fabric loop that passes around the neck (the collar) and cradles the forearm and hand (the cuff), holding the arm close to the chest. It is commonly used for proximal humerus fractures. When fitted correctly, the hand sits slightly higher than the elbow, allowing some weight to transmit through the upper arm, which helps maintain fracture alignment and promotes healing.

Fig 3: Collar and Cuff. Image Source – https://www.afrimedics.co.za/product/collar-cuff/

Broad-Arm Sling / Polysling

A broad-arm sling is a wide supportive sling designed to hold the entire forearm securely against the chest. It provides comfort, support, and varying degrees of immobilisation for a range of shoulder and upper limb injuries. A polysling is a commercial padded version of a broad-arm sling, offering improved comfort and adjustability.

Fig 4: Broad Arm Sling. Image Source – https://www.physique.co.uk/Supports-Braces/Shoulder-Supports/Adjustable-Arm-Sling

Further Reading

Baylor R, Al-Migdad A, Obeidat N, Melhem M, Abu-Ashour S, Gamage JC, et al. Revolution in orthopedic immobilization materials: a comprehensive review. Heliyon. 2023;9:e13640. doi:10.1016/j.heliyon.2023.e13640.

Written by Mr Amar Sidhu (CT2 in Trauma and Orthopaedics)