Cast Making

Part of Surgery

Immobilizing fractures and injuries using splints and casts made from available materials.

Why This Matters

Fractures that are not properly immobilized heal poorly or do not heal at all. The bone ends move with each muscle contraction, preventing the formation of the callus (new bone) that bridges the fracture. Improperly healed fractures result in shortened limbs, permanent deformity, chronic pain, and loss of function. A survivable injury becomes a lifelong disability.

Immobilization also controls pain dramatically. A properly splinted fracture causes far less pain than an unsupported one, allowing the patient to sleep, eat, and begin gentle movement toward recovery. This pain control alone improves outcomes by reducing the physiological stress of injury.

Modern plaster casts and fiberglass casting tape are convenient but not essential. Pre-modern societies successfully immobilized fractures using wood, bamboo, clay, linen, and even honey-soaked bandages that hardened. The principle is universal: provide rigid external support that prevents the bone ends from moving while allowing circulation to continue.

Principles of Good Immobilization

Regardless of what materials are used, a good cast or splint must:

1. Immobilize one joint above and one joint below the fracture. A broken forearm bone must immobilize both the wrist and the elbow — if either joint moves, it transmits force through the fracture site.
2. Maintain correct alignment. The bone must be set (reduced) into correct position before casting — a cast around a misaligned fracture heals it in wrong alignment.
3. Allow circulation to continue. A cast that swells, constricts, or cuts off blood flow causes compartment syndrome — a serious limb-threatening complication.
4. Protect the skin. Direct rigid material against skin causes pressure sores. Padding beneath the cast is essential.
5. Be removable for monitoring. If the cast cannot be removed, you cannot assess the fracture’s healing or detect complications.

Assessing Before Casting

Before applying any immobilization:

Check neurovascular status (the “5 Ps”):

• Pain: is it out of proportion to the injury?
• Pallor: is the skin beyond the injury pale or dusky?
• Pulselessness: can you feel a pulse beyond (distal to) the injury?
• Paraesthesia: does the patient feel tingling or numbness?
• Paralysis: can the patient move the fingers or toes?

Any abnormal finding suggests the injury is compromising circulation or nerves. Attempt reduction first; if neurovascular status remains abnormal after reduction, this is a surgical emergency.

Check skin integrity: open skin over a fracture (open/compound fracture) requires wound care before casting. Do not cast over an open wound — this creates an anaerobic environment perfect for anaerobic bacteria including Clostridium (gas gangrene, tetanus).

Splinting vs. Casting

Splint: a partial cast — rigid material on one or two sides, wrapped in place but not encircling the limb. Allows some swelling without constricting. Used acutely (within first 48-72 hours when swelling is maximal) and for injuries that need to be regularly monitored.

Circumferential cast: fully surrounds the limb. More rigid, better protection, but cannot expand with swelling. Used after acute swelling has stabilized (typically 3-5 days post-injury).

Post-collapse recommendation: almost always use a splint first. Convert to circumferential cast only after swelling has subsided and you are confident of alignment.

Materials for Splints and Casts

Wood and Bamboo Splints

The simplest and most universally available material.

Construction:

1. Select straight-grained wood (no knots), split to 1-3 cm width
2. Smooth all edges to prevent skin injury
3. Cut to appropriate length (joint above to joint below fracture)
4. Pad with cloth, wool, or dry grass wrapped around the splint
5. Apply to the injured limb with cloth bandaging
6. Check that knots and tying do not compress circulation

Bamboo: ideal natural splint material. Hollow, light, rigid, easily split to any width, smooth-edged when properly prepared. Used in Asian medicine for thousands of years.

Clay Cast

Ancient Egyptian and Hippocratic method. Mixed clay is applied wet to a cloth-padded limb and hardens as it dries. Effective but heavy, brittle, and cannot get wet.

Preparation:

1. Find fine-grained clay without large stones or organic material
2. Mix with water to a paste consistency — not too wet (won’t dry hard) not too dry (won’t conform)
3. Pad the limb thoroughly with cloth strips
4. Apply clay 2-3 cm thick over and around the limb
5. Mold to the limb shape
6. Allow to dry for 24-48 hours in dry conditions
7. Protect from moisture — wrap finished cast with dry cloth binding

Plaster of Paris analogue: if calcium sulfate is available (from gypsum deposits — a common mineral), roasting gypsum at 150-180°C for several hours drives off water, creating hemihydrate (plaster of Paris). Mixed with water, this sets rigid within 15-20 minutes and is far superior to clay.

Linen or Cloth Hardened with Natural Starch

Traditional method using stiffened cloth. Multiple layers of cloth soaked in starch (from any grain) applied wet and molded. As the starch dries, it stiffens. Less rigid than clay or plaster but lighter, breathable, and safe for long-term wear.

Improvement: adding pine resin or beeswax to the starch solution increases rigidity after drying.

Honey-Soaked Bandage

Historical record from ancient Egypt and Hippocratic texts. Cloth bandages soaked in honey and allowed to crystallize produce a firm, mold-retaining wrap. Honey also has antimicrobial properties protecting the underlying skin.

Applying a Forearm Splint (Example)

1. Set fracture first (see reduction techniques)
2. Check neurovascular status — document baseline
3. Cut padding (wool, cotton, dry moss) and wrap limb smoothly from knuckles to 4 cm below elbow
4. Cut two wooden or bamboo splints to appropriate length
5. Pad the splints with cloth wrapping
6. Place one splint on the dorsal (back of hand) side, one on the volar (palm) side
7. Hold in position while assistant wraps with cloth bandaging
8. Wrap from distal (knuckles) to proximal (near elbow), overlapping each turn by half
9. Do not apply tightly — two fingers should slide under the binding
10. Recheck neurovascular status immediately after application

Position: wrist neutral or slightly extended (functional position), elbow at 90 degrees. The hand should look like it is holding a glass of water.

Monitoring and Removal

Check every 24 hours for the first week:

• Fingers pink and warm?
• Swelling of fingers (puffiness beyond the cast)?
• Patient can feel touch on fingertips?
• Patient can bend fingers slightly?

Remove immediately if:

• Fingers become pale, blue, or cold
• Patient reports increasing rather than decreasing pain
• Loss of sensation in fingers
• Fingers cannot be moved even slightly

Most fractures require immobilization for:

• Upper extremity (arm): 4-6 weeks
• Lower extremity (leg): 6-12 weeks depending on fracture location and severity
• Elderly patients: may require 25-50% longer

After cast removal: the limb will appear thinner (muscle wasting) and feel weak. Gradual rehabilitation — gentle movement exercises increasing over weeks — restores function. Full recovery takes 2-3x the immobilization period.