Ankle Splinting for 3mm Lateral Ankle Avulsion Fracture
A rigid immobilization splint is required for a 3mm lateral ankle avulsion fracture, with a sugar-tong or posterior splint applied in neutral (90-degree) position being the optimal choice to prevent displacement and allow ligamentous healing. 1, 2
Rationale for Immobilization
Small avulsion fractures at the lateral ankle represent ligamentous injury with bony attachment and require immobilization because the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) remain attached to these fragments, preventing spontaneous healing if motion occurs between the fragment and fibula 3
66% of patients requiring lateral ankle ligament reconstruction had osseous pathology (accessory ossicles or avulsion fractures), suggesting these injuries represent significant ligamentous damage that warrants more aggressive initial treatment than simple sprains 4
Motion between the avulsion fragment and fibula prevents healing and can lead to chronic instability, making primary immobilization critical 3
Optimal Splint Type
Sugar-tong splint provides superior immobilization compared to standard posterior, ridged posterior, or figure-of-eight designs, generating significantly more resistance to plantar flexion and maintaining better fracture stability 2
Three-way ankle splint is an alternative for severe injuries with significant edema when immediate casting is not possible, providing excellent interim immobilization 5
Posterior splints are commonly used but less durable in the outpatient setting and allow more motion than sugar-tong designs 2
Splinting Position
Neutral position (90 degrees) is mandatory as it minimizes tension on neurovascular structures, prevents equinus contracture, and maintains anatomic relationships 1
Avoid plantarflexion as it increases posterior displacement of the talus and can worsen fragment displacement 1
Avoid dorsiflexion as it creates excessive tension on anterior neurovascular structures and increases soft tissue swelling 1
If significant deformity is present, splint in the position found to avoid neurovascular injury, but neutral is preferred when achievable without resistance 1
Critical Assessment Before Splinting
Document neurovascular status including pulses, capillary refill, and sensation before and after splint application 1
Check for vascular compromise immediately - if the extremity is blue, purple, or pale, activate emergency services as this indicates limb-threatening injury 1
Obtain weight-bearing radiographs if possible to assess stability, as a medial clear space <4mm confirms stability 6
Cover any open wounds with clean dressing before splinting to reduce contamination risk 1
Common Pitfalls to Avoid
Do not force the ankle into position if significant resistance or deformity is present 1
Avoid excessive padding that could mask developing compartment syndrome, which is a risk with these injuries 1
Do not treat as a simple ankle sprain - avulsion fractures require immobilization unlike isolated ligamentous injuries, which benefit from early functional treatment 6
Monitor for compartment syndrome as these injuries involve significant soft tissue trauma 1
Follow-up Considerations
Primary fixation may be indicated for displaced fragments, as screw fixation has shown excellent outcomes with restoration of stability and function at 2-4 year follow-up 3
Displacement increases under varus stress, so reassessment after initial swelling subsides is important 3
Fragment size averaging 6.3mm width × 5.2mm length typically involves both ATFL and CFL attachments, making anatomic reduction important 3