The technique of splinting can be found throughout multiple fields of medicine including emergency medicine, orthopedics, primary care, and podiatry. It is primarily used to immobilize a joint or limb to allow for pain control, injury stabilization, and ultimately tissue healing. In the acute setting, splinting is useful as a temporizing treatment for sprains, strains, joint dislocations, fractures, and soft tissue lacerations. In the chronic setting, splinting is useful mainly for inflammatory conditions. The main goal of forearm splinting is to prevent rotation about the entire forearm. Specific conditions in which forearm splinting would be useful include injuries to any part of the radius and/or ulna or soft tissue structures located within the forearm.
The anatomy of the forearm can be broken down into osteology, musculature, and neurovascular structures.
The osteology of the forearm is composed of the radius and ulna. The radius is a cylindrical long bone which has a bow within the shaft, whereas the ulna is purely a straight bone with a triangular cross-section. This bow in the radius allows for rotation of the radius around a stationary ulna bone thus allowing for pronation and supination of the forearm. There 4 main articulations with regard to the radius. These include the radiocapitellar joint, proximal radial-ulnar joint, distal radial-ulnar joint, and radial-carpal joint. The ulna shares the same articulations, save for the radiocapitellar joint, and instead has an ulno-humeral articulation proximally. The radius has a tuberosity proximally where the biceps inserts and a styloid distally where the brachioradialis inserts. The ulna also has a tuberosity proximally where the brachialis inserts and a styloid distally.
The musculature of the forearm can be broken down into the anterior and posterior compartment. The anterior compartment is composed of the flexor muscles. The superficial flexors include the pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis and flexor carpi ulnaris. The deep flexors include the flexor digitorum profundus, flexor pollicis longus and pronator quadratus. The posterior compartment is composed of the extensor muscles. The superficial extensors include the anconeus, extensor digitorum communis, extensor digit minimi and extensor carpi ulnaris. There is a subdivision within the superficial extensors called the "mobile wad" which is composed of the brachioradialis, extensor carpi radialis longus and extensor carpi radialis brevis. The deep extensors include supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis proprius.
The nervous structures located within the forearm include the median, radial, ulnar and musculocutaneous nerves. The median nerve comes from the medial and lateral cords of the brachial plexus and provides an only motor function in the forearm. The anterior interosseous nerve is a continuation of the median nerve and provides a motor function in the forearm and volar wrist capsule sensation. The radial nerve comes from the posterior cord of the brachial plexus and provides motor function and sensation to the posterior forearm via the posterior cutaneous nerve of the forearm. The posterior interosseous nerve is a continuation of the radial nerve and provides motor function and dorsal wrist capsular sensation. The ulnar nerve comes from the medial cord of the brachial plexus and provides purely motor function in the forearm. The musculocutaneous nerve comes from the lateral cord of the brachial plexus and provides the only sensation to the radial aspect of the forearm via the lateral antebrachial cutaneous nerve.
The vascular structures in the forearm include the radial and ulnar arteries, which are a continuation of the brachial artery. Both the radial and ulnar artery continue throughout the forearm and ultimately form the deep and superficial palmar arch, respectively, in the hand.
The main goal of forearm splinting is to prevent pronation and supination about the entire forearm. There are a variety of reasons as to when forearm splinting would be appropriate, including soft tissue strains or sprains, fractures, joint dislocations, tendon lacerations, and compression neuropathies. In any case, the main objectives are to decrease pain and debility, prevent further injury and facilitate the healing process. Common reasons encountered which would necessitate forearm splinting in the acute setting include distal radius and/or ulna fractures, radial and/or ulnar shaft fractures, flexor tendon lacerations within the forearm and a radial nerve palsy which manifests clinically as a wrist drop. In the chronic setting, common reasons include De Quervain’s tenosynovitis, medial and lateral epicondylitis and any compressive neuropathies affecting the nerves in the forearm.
While there are no absolute contraindications to splinting, there needs to be appropriate clinical decision making prior to splinting, especially in the acute setting. Situations in which caution must be exercised include the presence of thermal or electrical burns, open fractures, grossly contaminated wounds and significant soft tissue swelling. In general, splinting may be performed so long as any concomitant injury is addressed prior to splinting. Furthermore, splinting in the setting of significant soft tissue swelling is preferred over casting as the splint is not circumferential or constricting and may be easily loosened or removed.
Depending on the application, forearm splinting may be done alone or may require an assistant. If the patient can follow direction, an assistant may not be necessary. If the patient is not cooperative or is sedated, an assistant will be required to hold the forearm.
Preparation begins first with identifying the injury being treated. Once this is identified, the type of splint may be determined. The most common forearm splint is the sugar-tong splint. Other forearm splints include a sugar tong with a posterior mold and a volar-forearm splint. It is necessary to determine the splint being used as the required length of the splinting materials differs. For the sugar-tong splint, the forearm needs to be in the neutral rotation, and the elbow flexed to 90 degrees. The splint should begin at the distal palmar crease, wrap around the flexed elbow, and stop at the dorsal metacarpal heads. If necessary, to add a posterior slab to the sugar tong, it should begin distal to the wrist on the ulnar aspect of the forearm and stop proximal to the elbow, which prevents elbow flexion and extension. The volar forearm splint also begins at the distal palmar crease and stops proximal to the antecubital fossa, thus allowing for elbow flexion and some pronation and supination. Whether using plaster or prefabricated splinting material, the required length may be measured directly on the patient using a sheet of cotton cast padding (Webril) as a proxy. The splinting material can then be cut to the length of the measured cotton cast padding. Plaster needs to be at least 8 sheets thick to provide adequate strength but no more than 12 sheets thick to avoid thermal injury. Plaster produces heat as it hardens and care must be taken to prevent thermal injury. Stockinet is cut so that there is extra on both ends. The extra stockinet will be folded down over the plaster which allows the creation of padded cuffs at the ends of the splint for patient comfort. Cotton cast padding is used to wrap the forearm directly over the stockinet. The plaster splinting material is wet, wrung and bonded and placed on the forearm. Webril may be used to wrap over the splinting material once more before overwrapping with an elastic bandage. If necessary, appropriate molding of the splint may commence.
Complications of forearm splinting include pressure necrosis, which can begin as soon as 2 hours after application, compartment syndrome if wrapped too tightly, thermal injury from plaster if too thick, and joint stiffness, specifically the metacarpophalangeal joints if the splint extends past the distal palmar crease.
Forearm splinting is an excellent way to immobilize the forearm to help alleviate pain, stabilize injuries, prevent further damage to bones, muscles, nerves and/or arteries, and prevents a closed fracture from becoming an open one. Furthermore, due to the non-circumferential nature of the splint, as opposed to a cast, it can allow for soft tissue swelling and can be easily removed by the clinician to evaluate any wounds beneath. In the acute setting, it is an excellent way to temporize forearm injuries.
After placement of the forearm splint, it is important to educate the patient on proper splint care. The splint needs to remain clean and dry. If the splint gets wet, the plaster loses its strength and the padding beneath will not dry. This can lead to maceration and breakdown of intact skin. Furthermore, if there is an open wound already beneath, it can lead to infection. In instances where the splint becomes wet, the patient should return to the place where the splint was placed. The patient should be instructed to avoid removing the splint, especially if the splint was applied for a fracture or dislocation. Removal in this instance can cause re-displacement of the fracture or re-dislocation. Most importantly, should the patient develop new-onset numbness or tingling of the hand or fingers they should first elevate the forearm and if it does not resolve, return to the place of splint application or emergency department for further evaluation.