Wilderness Medical Series — Module 08

How to Use a SAM® Splint for Ankle Injuries in the Field

How to use a SAM® splint for ankle injuries in the field — ankle stirrup technique, improvised wool blanket splint, and CMS assessment protocol.

By Joshua Enyart · Founder & Head Instructor, Gray Bearded Green Beret

Former Army Ranger, Green Beret, and full-time survival instructor · three decades of professional instructor experience

Ankle injuries are among the most common backcountry mechanical injuries. Uneven terrain, loaded packs, fatigue in the lower legs, and the cumulative stress of miles on difficult ground all contribute to a high rate of ankle sprains and fractures in wilderness settings.

The consequence of an ankle injury that goes unsplinted is not just pain — it is lost mobility. A person who cannot walk under their own power in a remote location needs to be carried or evacuated by external means. In most wilderness settings, neither option is fast or simple. Splinting a manageable ankle injury correctly can mean the difference between walking out and waiting for a rescue team.

This article covers the splinting techniques specific to ankle injuries: the Ankle Stirrup using a SAM® splint, and the Wool Blanket improvised splint for situations where a moldable splint is unavailable. Both techniques are built on the same splinting principles and the same assessment protocol.

Ankle Injuries in the Backcountry: Sprains vs. Fractures

The first clinical distinction to make with an ankle injury is whether you are dealing with a sprain, a fracture, or a combination. In the field, this distinction is important because it affects the urgency of evacuation and the degree of immobilization required — but it does not change the core field treatment significantly.

A sprain is a stretching or tearing of the ligaments that connect the bones of the ankle joint. Common causes include lateral rolls (the foot rolling outward) and inversion injuries. Sprains produce tenderness on the lateral (outside) or medial (inside) ankle, swelling, bruising, and pain with movement or weight-bearing.

A fracture is a break in one or more of the ankle bones. The distal fibula and tibia are most commonly involved. Fractures tend to produce more immediate and severe swelling, may produce a visible deformity or abnormal position of the joint, and are often accompanied by crepitus — a grating, cracking, or popping sensation when the joint is gently palpated. A fracture that has broken the skin is an open fracture and carries significantly higher infection risk.

Without imaging, a field determination of sprain versus fracture is educated assessment, not diagnosis. What matters for field management is whether the ankle can bear weight safely enough to allow evacuation and how stable the injury is for the distance and terrain involved. If there is any question, splint and evacuate.

RICES: The Protocol for Ankle Sprains

For a suspected ankle sprain without significant deformity or inability to bear any weight, the RICES protocol guides field management.

• Rest: Take weight off the injured ankle. Even a brief period of rest immediately after injury — ten to fifteen minutes — reduces the initial inflammatory response and allows a better assessment of the injury severity.
• Ice: If snow or cold water is available, apply cold to the ankle to reduce swelling and pain. Apply early — within the first thirty minutes after injury, cold is most effective. Apply for fifteen to twenty minutes at a time, with breaks to prevent frostbite on skin.
• Compression: An elastic bandage wrapped from the foot up through the lower leg provides compression that limits swelling and provides some stability. Compression should be firm but not tight enough to compromise circulation.
• Elevation: Elevate the ankle above the heart when resting to assist in reducing swelling.
• Stabilize: Tape, splint, or brace the ankle to prevent further injury. For a field-ready splint, this is where the SAM® splint ankle stirrup or improvised splint comes in.

Some of these steps are harder to execute in a remote setting where you have other priorities. Focus on compression and stabilization — the two RICES components most directly tied to field function and the ability to move.

Principles of Splinting Before You Apply

Every splinting application — ankle, knee, forearm, shoulder — follows the same seven principles. Checking these before and after application is the standard protocol.

• Manually stabilize: Hold the injury steady with your hands before applying any splint material. Prevent further injury during the construction process.
• Position of function: Splint the ankle in a neutral position — 90 degrees between the foot and the lower leg. Do not force the ankle into any position that causes additional pain.
• Accessible for CMS reassessment: The splint must be constructed in a way that allows CMS — circulation, motor function, sensation — to be checked at the toes both before and after application.
• Padded at pressure points: Pad anywhere the rigid splint material contacts a bony prominence — the ankle bones, the heel, the shin. Unpadded pressure points cause tissue injury over time.
• Rigid: The splint material must be rigid enough to prevent the injury from moving in the direction that causes harm. The SAM® splint achieves rigidity through its aluminum core combined with the C-curve and U-shape formations.
• Adjustable: Use knots or fasteners that can be released quickly. CMS changes after application require immediate splint adjustment.
• Secure above and below the injury: The splint must immobilize the joint above and below the injured site.

The Ankle Stirrup: SAM® Splint Application

The SAM® splint ankle stirrup is a commercial moldable splint technique that provides both rigidity and some compression. The SAM® splint's aluminum core takes and holds any shape it is formed into, making it ideal for forming around the ankle contour.

Ankle Stirrup application procedure:

• Check CMS before application. Note the baseline: what is the capillary refill time at the toes? Can the patient wiggle their toes? Do they have normal sensation in the foot and toes?
• Form the splint using the uninjured foot as a model. Hold the splint against the uninjured foot and ankle to create the U-shape that will fit the injured side. This is faster and more accurate than forming blind.
• Apply a C-curve to the upper third of both sides of the U-shaped splint. The C-curve creates a channel that adds rigidity along the length of the splint — without it, the splint can collapse under axial load.
• Mold the formed splint to the injured ankle. Position the U-shape under the heel with the sides coming up along the inner and outer ankle.
• Secure with an elastic bandage wrapped from the foot upward to the lower shin, bottom to top. The bandage should be snug but not tight enough to restrict circulation.
• Recheck CMS after application. Capillary refill, toe wiggle, sensation. Any change from baseline indicates the splint needs adjustment.

The Wool Blanket Improvised Ankle Splint

When a SAM® splint is unavailable, a tightly rolled wool blanket provides a functional improvised ankle splint. Wool maintains some rigidity when rolled tightly and has enough bulk to provide padding simultaneously.

Wool blanket splint procedure:

• Roll the blanket tightly along its length to produce as much rigidity as possible. The tighter the roll, the more effective it is as a rigid component.
• Position the rolled blanket in a U-shape under the foot, with the foot in a position of function — 90 degrees, heel seated in the curve of the U.
• Bring both sides of the U up along the inner and outer ankle, securing them against the leg.
• Secure the splint above the ankle and below the ankle (at the foot) using cravats or available fabric strips. Use knots that can be released quickly for CMS reassessment.
• As always, check CMS before and after application.

The wool blanket splint is less rigid than the SAM® splint ankle stirrup, but it is a functional field expedient when the purpose-built option is unavailable. The principles are identical: position of function, padded at pressure points, secured above and below, accessible for CMS.

CMS Assessment: What You Are Checking and Why

CMS — circulation, motor function, sensation — is the three-part assessment that brackets every splinting application. Check before applying the splint to establish baseline. Check after applying to confirm the splint has not compromised anything.

Circulation: Check capillary refill at the toenails. Press on the nail and release — color should return within two seconds. Also check the skin temperature and color at the toes. Cold, pale toes after splint application indicate compromised circulation. Loosen the splint immediately.

Motor function: Ask the patient to wiggle their toes. Any inability that was not present before splinting indicates the splint may be compressing a nerve or blood vessel.

Sensation: Ask the patient if they have normal feeling in the toes and foot. Numbness or tingling that developed after splinting indicates nerve compression. Adjust the splint.

Reassess CMS at regular intervals — every thirty minutes during the initial period after application, and at every rest stop if the patient is being moved. CMS can change as swelling develops, especially in the first two to four hours after injury.

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