Ankle Splinting

Anatomy and Physiology

The ankle's anatomy can be broken down into osteology, musculature, and neurovascular structures.

The ankle joint is made up of the distal tibia, the distal fibula, and the talus. The distal tibia articulates with the distal fibula to form the distal tibiofibular articulation and the talus, forming the tibiotalar joint. This is an important anatomical distinction as this is the true “ankle” joint. Oftentimes the subtalar joint, which is the articulation between the talus and the calcaneus, is included when discussing the ankle joint; however, this is, technically, not a part of the ankle but, rather, the hindfoot.[4] The different acute conditions associated with the tibiotalar and subtalar joint make this clinically important.

The distal tibia has three distinct portions: the plafond, the lateral distal tibia, and the medial malleolus. The plafond is the actual weight-bearing portion that articulates with the talus below. The distal physis ossifies around the age of one year and typically fuses around the age of 18 to 20 years. The physis closes in a predictable manner, first centrally, followed by medially, and finally laterally. As a result of this phased closure, there are unique adolescent ankle fractures such as the tillaux fracture and the triplane fracture.[5] The distal tibia has a concave shape and therefore is congruent with the talar body/dome. The lateral distal tibia serves as an important attachment site for two of the syndesmotic ligaments: the anterior-inferior tibiofibular ligament (AITFL) and posterior-inferior tibiofibular ligament (PITFL). The AITFL attaches to the tillaux-Chaput tubercle, and the PITFL attaches to the posterior malleolus.[6] The lateral distal tibia also contains a groove for the fibula called the incisura. The medial malleolus serves as the attachment site for the deltoid ligament, which is composed of a superficial and deep portion. In addition to this, the medial malleolus serves as a bony restraint to the medial translation of the talus within the tibiotalar joint.

The distal fibula, commonly referred to as the lateral malleolus at the level of the ankle joint, ossifies around the age of 4 years and fuses around the age of 18 to 20 years. As previously mentioned, it serves as an important attachment site for the two syndesmotic ligaments (AITFL and PITFL). It also serves as an attachment site for the anterior talofibular ligament (ATFL), the posterior talofibular ligament (PTFL), and the calcaneofibular ligament. Avulsion fractures are common due to the multiple ligamentous attachments to the lateral malleolus. The lateral malleolus serves as a bony restraint to lateral translation of the talus within the tibiotalar joint and is important in the stability of the ankle joint.

The talus ossifies around the age of 7 months and fuses around the age of 13 to 15 years. It is composed of a head, neck, body/dome, posterior process, and lateral process. The talus articulates with the navicular, the calcaneus, and the distal tibia. The body is mostly covered with articular cartilage, and the majority of the body weight is transmitted through the dome upon weight-bearing.[7]

The musculature at the level of the ankle joint tends to be more tendinous, as the bulk of the muscle bellies are more proximal in the leg. As the muscles travel distally, their tendons cross the ankle joint and insert on the bones of the foot. The four compartments in the leg each have their own set of muscles. 

Four Leg Compartments

Anterior Compartment

• Tibialis anterior
• Extensor hallucis longus
• Extensor digitorum longus
• Peroneus tertius

Lateral Compartment

• Peroneus longus
• Peroneus brevis

Superficial Posterior Compartment

• Gastrocnemius
• Soleus
• Plantaris

Deep Posterior Compartment

• Popliteus
• Flexor hallucis longus
• Flexor digitorum longus
• Tibialis posterior

The nervous structures surrounding the ankle joint include the saphenous, tibial, sural, superficial peroneal, and deep peroneal nerves. The saphenous nerve, the terminal branch of the femoral nerve, descends in the superficial medial leg and anterior to the medial malleolus. It provides sensation to the medial ankle and has no motor function. The tibial nerve originates from the anterior division of the sacral plexus and descends posterior to the medial malleolus into the tarsal tunnel. It provides sensation to the medial heel and provides a motor function to the superficial and deep posterior compartment muscles. The sural nerve is formed from the medial sural cutaneous nerve, a branch of the tibial nerve, and the lateral sural cutaneous nerve, a branch of the peroneal nerve. It runs subcutaneously in the posterolateral leg to provide sensation in the posterolateral distal leg. It does not provide any motor function. The superficial peroneal nerve is a branch off of the common peroneal nerve. It runs in the lateral compartment of the leg and crosses anteriorly 10 centimeters above the lateral malleolus. It provides sensation to the anterolateral leg and ankle and provides a motor function to the lateral compartment muscles. The deep peroneal nerve branches off of the common peroneal nerve. It runs in the anterior compartment of the leg with the anterior tibial artery. It does not provide any sensation in the leg or around the ankle joint and provides a motor function to the anterior compartment muscles.

The main vascular structures surrounding the ankle include the anterior and posterior tibial arteries. The anterior tibial artery branches off of the popliteal artery and courses beneath the tibialis anterior and extensor hallucis longus tendons anterior to the ankle joint where it forms the dorsalis pedis artery in the foot. The posterior tibial artery is also a branch off of the popliteal artery. It runs with the tibial nerve in the deep posterior compartment and lies between the flexor digitorum longus and flexor hallucis longus tendons posterior to the medial malleolus where its pulse is palpable.

Indications

The main goal of ankle splinting is to immobilize the ankle joint. There are a variety of reasons as to when ankle splinting would be appropriate; however, these also include the injuries to the entire distal leg and foot. In general, the ankle should be immobilized for fractures and dislocations. Ankle fractures include lateral malleolus, medial malleolus, posterior malleolus, any combination of malleoli fractures, and talus fractures. Dislocation of the tibiotalar joint is common with malleoli fractures, as the malleoli serve as bony restraints to keep the talus centered within the ankle mortise. In the setting of tibiotalar dislocation or subluxation following reduction, the splint serves to keep the tibiotalar joint reduced and prevent re-dislocation or persistent subluxation until definitive treatment.[8][9][10]

Indications for Ankle Splinting

• Lateral malleolus fracture
• Medial malleolus fracture
• Posterior malleolus fracture
• Bimalleolar fracture
• Trimalleolar fracture
• Tibiotalar dislocation or subluxation
• Ankle fracture-dislocation

Contraindications

While there are no absolute contraindications to splinting, there needs to be appropriate clinical decision-making before 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 before splinting. In the setting of open fractures and/or grossly contaminated wounds, quick irrigation and gross debridement followed by a wet-to-dry dressing should be placed over the open wound before application of the splint. Furthermore, splinting is preferred over casting in the setting of significant soft tissue swelling, as the splint is not circumferential or constricting and may be easily loosened or removed. The stability conferred by the splint prevents continued trauma in the setting of ankle fracture or dislocation which also helps reduce swelling.

Ankle splinting is not indicated in the setting of ankle sprains; rather, a simple elastic wrap is sufficient as the goal should be to minimize swelling. Early mobilization results in better recovery in ankle sprains.[11] Should a brief period of immobilization be necessary, a controlled ankle motion boot is ideal as it allows for weight-bearing immobilization. A splint is not appropriate for weight-bearing.

Equipment

• Stockinette
• Cast padding
• Plaster splinting material
• Water; cold water maximizes molding time, warmer water facilitates hardening
• Elastic bandages

Personnel

Depending on the application, ankle splinting may be done alone or may require an assistant. If the patient can follow directions and there is no dislocation or subluxation of the ankle joint, an assistant may not be necessary. If the ankle requires a reduction, an assistant will be necessary to hold the ankle during splint application. Furthermore, if the patient is not cooperative or is sedated, an assistant will be required to hold the leg.

Preparation

There are three main splinting options for the ankle. The most stable splint is the stirrup plus posterior slap splint. This is the most ideal splint for bimalleolar, trimalleolar, or ankle fracture-dislocations. The other options include a stirrup splint or a posterior slab splint. These two splints do not provide sufficient stability for anything other than an isolated medial, lateral, or posterior malleolar fracture. The posterior slab provides stability in the antero-posterior direction as well as preventing ankle dorsiflexion and plantarflexion. The stirrup wraps around the medial and lateral malleoli providing medial-lateral stability.

It is important to determine the length of the plaster required for splinting before beginning. For patient comfort, the uninjured leg may be used as a substitute to measure length. The length of the posterior slab should begin just distal to the metatarsal heads and end below the popliteal fossa. It is important that the posterior slab is not too long as this can cause skin irritation and breakdown in the popliteal fossa especially as the knee is flexed. The stirrup portion wraps from the medial aspect of the leg, around the heel, and up the lateral aspect of the leg. It should begin around the proximal third of the tibia medially and below the fibular head laterally. Plaster needs to be at least eight 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.

Before splint application, any fracture-dislocation should be reduced. Stockinette is cut to cover the leg so that there is extra past the toes and past the knee.  The extra stockinette will be folded down over the plaster which allows the creation of padded cuffs at the ends of the splint for patient comfort. Cast padding is used to wrap directly over the stockinette, beginning from the metatarsal heads and continuing all of the way up to the tibial tubercle. Care must be taken to sufficiently pad the medial and lateral malleoli and heel to prevent pressure ulcers from developing in the splint. The plaster splinting material for the posterior mold is wet, wrung, bonded, and placed on the plantar aspect of the foot, extending up to below the popliteal fossa. Cast padding may be used to wrap over the plaster to hold it in place while the remainder of the plaster is applied. The plaster splinting material for the stirrup is wet, wrung, bonded, and placed starting on the medial aspect of the leg, wrapping around the plantar aspect of the heel and up the lateral aspect of the leg. Cast padding may be used to wrap over the plaster splinting material once more, and the excess stockinette at the ends of the splint may be folded down to produce a cuff. An elastic bandage is used to wrap over the splint. Once wrapped with the elastic bandage, molding may begin. Molding is necessary for ankle dislocations or subluxations to produce a buttress to keep the ankle joint reduced. It is also important to ensure that the ankle joint is in neutral dorsiflexion. Splinting the ankle in a plantarflexed position will result in an equinus contracture of the heel cord.

Technique or Treatment

1. Measure the appropriate length of plaster, 8 to 12 sheets thick for posterior slab and stirrup.
2. Measure and cut stockinet for the leg.
3. Perform reduction of the ankle, if necessary. Have assistant hold leg and ankle to maintain reduction during splinting.
4. Place stockinette on the leg.
5. Wrap leg with cotton rap beginning at the metatarsal heads and ending at the tibial tubercle, ensuring 50% overlap of padding with a minimum of two layers. Ensure that the medial and lateral malleoli and heel are well padded. Attempt to avoid bunching or wrinkles in padding.
6. Dip plaster into the water to thoroughly wet.
7. Wring wet plaster and bond together between fingers.
8. Apply posterior slab over cotton wrap on the leg, ensuring that the plaster begins at the plantar aspect of the metatarsal heads and ends below the popliteal fossa.
9. Apply stirrup over cotton rap on the leg, ensuring that the plaster begins around the proximal third of the tibia medially, wrapping around the heel, and up the lateral aspect of the leg ending below the fibular head.
10. Overwrap plaster with one layer of cotton wrap to keep the plaster from sticking to the elastic bandage.
11. Fold excess stockinette over plaster and wrap so that there is a cuff at each end of the splint.
12. Loosely wrap the entire splint with an elastic bandage.
13. Apply appropriate mold while the plaster is hardening. Ensure that the ankle is in neutral dorsiflexion.
14. Avoid placing the splint on pillows or a blanket as this has an insulating effect.
15. Once the splint is hard, re-assess the neurovascular status of the foot and toes.

Complications

• Pressure necrosis – can begin as soon as 2 hours after splint application, resulting from inadequate padding of bony prominences
• Compartment syndrome – if splint wrapped too tightly
• Thermal injury – if plaster too thick or if inadequate padding
• Equinus contracture – if splint applied with the ankle in plantarflexion

Clinical Significance

Ankle splinting is an excellent way to immobilize and stabilize the ankle joint in the acute setting of fractures or dislocations. It serves to prevent further damage to the bones, cartilage, and surrounding neurovascular structures. Splinting allows for soft tissue swelling due to the non-circumferential nature of the splint and can be easily removed by the clinician to evaluate any wounds beneath. It is an excellent way to temporize ankle injuries until definitive treatment can be performed.[12][13][14]

After placement of the 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 beneath the splint, 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 dislocation. Removal in this instance can cause re-dislocation or persistent subluxation of the joint. Most importantly, should the patient develop new-onset numbness or tingling of the foot or toes he or she first should elevate the leg and, if it does not resolve, return to the place of splint application or emergency department for further evaluation.

Enhancing Healthcare Team Outcomes

Healthcare workers including the primary care provider, emergency department clinician, orthopedic surgeon, nurse practitioner, and sports physician should be familiar with ankle splinting. 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, and fractures. In the chronic setting, splinting is useful mainly for inflammatory or degenerative conditions. The main goal of ankle splinting is to prevent dorsiflexion and plantar flexion as well as inversion and eversion of the ankle joint. Specific conditions that call for ankle splinting include injuries to the distal tibia or fibula, ankle joint, or hindfoot.