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Overview & Historical Context
The Thomas splint is one of the most historically significant devices in orthopaedic surgery. Designed by Hugh Owen Thomas in Liverpool in the 1860s, it was originally intended for the conservative management of tuberculosis of the hip and knee joints by providing continuous traction and rest. Its most dramatic impact came during the First World War, when its widespread use for femoral shaft fractures reduced the mortality rate from approximately 80% to under 20% — one of the most remarkable improvements in trauma outcomes in military history. Today, the Thomas splint`s primary role has shifted to emergency transport immobilisation of femoral shaft fractures, where it remains indispensable.
Mechanism of action: the Thomas splint works by providing fixed traction; a padded ring (the `Thomas ring`) is sized to fit snugly around the upper thigh in the groin, with the ring resting against the ischial tuberosity and the inner thigh; two metal rods (the `irons`) extend from the ring distally, past the foot; skin or skeletal traction strapping applied to the lower leg attaches to the distal end of the irons (or a cross bar); as the traction pulls the leg distally, the ischial ring provides countertraction, effectively pulling the fractured femoral shaft toward alignment; the leg is supported by canvas slings threaded through the irons; the principle is `fixed traction` — traction force is resisted by the ring rather than by the patient`s body weight
Traction vs countertraction in the Thomas splint: unlike balanced traction (where the patient`s body weight on a tilted bed provides countertraction), the Thomas splint is self-contained — the ring provides the countertraction within the splint itself; this makes it portable and suitable for field use and transport
Indications
Primary indication — transport immobilisation of femoral shaft fractures: the Thomas splint is used by paramedics, military medics, and emergency teams to immobilise femoral shaft fractures before and during transport to hospital; it dramatically reduces: (1) pain (by immobilising the fracture and reducing muscle spasm); (2) haemorrhage (by immobilising the fracture — the thigh can expand to accommodate 1–1.5 litres of blood with an unstabilised fracture; immobilisation reduces this ongoing blood loss); (3) further soft tissue injury (by preventing fracture ends from moving against surrounding tissue); (4) fat embolism risk (unstabilised fractures release more marrow fat into the circulation); the `before hospital` application is the Thomas splint`s most important modern role
Secondary indication — inpatient traction for femoral fractures (historical/adjunct): in children awaiting definitive surgery; as a temporary measure before intramedullary nailing; in resource-limited settings where surgical fixation is not immediately available; in a modified form as balanced traction (traction through skin or skeletal traction attached to the distal end of the Thomas splint with the proximal end elevated on a Böhler-Braun frame)
Other historical indications: tuberculosis of the hip (now managed medically); knee joint infections requiring rest; not appropriate for subtrochanteric fractures (the ring may be painful and ineffective if the fracture is too proximal)
Sizing & Application Technique
Step
Action
Key Points
1. Ring sizing
Measure the circumference of the uninjured upper thigh at the groin; add 2–3 cm to allow for swelling; select the Thomas ring accordingly; the ring must be snug but not tight enough to cause neurovascular compromise; the ring should sit in the groin contacting the ischial tuberosity posteriorly and the pubic ramus anteriorly
If the ring is too small = constriction, neurovascular compromise of the proximal thigh; if too large = inadequate countertraction; standard sizes are available; pad the ring generously
2. Splint length
The distal end of the splint (the cross bar or the tips of the irons) should extend approximately 25–30 cm (10 inches) beyond the heel of the injured leg; this allows traction strapping to be attached and pulled distally without bunching at the foot
Too short = insufficient room for traction attachment; too long = cumbersome and the ring shifts; the splint is slightly longer on the lateral side than the medial to maintain alignment
3. Canvas slings
Thread the canvas slings through the medial and lateral irons to support the posterior aspect of the leg and thigh; the slings should be tensioned to support the limb without creating pressure points; ensure the heel is clear of the most distal sling (heel pad or sling-free zone at the heel to prevent pressure sores)
Check the heel is not resting on the sling — heel pressure sores are a common complication; the heel should hang free or be supported on a separate padded heel support
4. Traction application
Apply skin traction strapping to the lower leg (foam strapping from ankle to mid-thigh); attach the traction cord to the spreader bar (which maintains separation of the two straps and prevents ankle constriction); thread the cord through the cross bar at the distal end of the irons; apply approximately 3–5 kg of traction force (twisting the cord over the cross bar or using a traction bow with weights over a pulley if in hospital)
In the field, traction can be applied manually then fixed by tying the cord over the distal cross bar; in hospital, weights on a cord over a pulley provide measured traction; re-assess the traction force at regular intervals — the leg relaxes as muscle spasm decreases
5. Neurovascular check
After application, check circulation, sensation, and movement of the foot and toes; check that the ring is not compressing the groin vasculature (femoral artery/vein) or the lateral femoral cutaneous nerve; re-check at 30–60 minute intervals
Ring pressure complications: femoral nerve compression (anterior ring too tight); lateral femoral cutaneous nerve compression (`meralgia paraesthetica` — anterolateral thigh numbness); peroneal nerve palsy from sling/strap pressure at the fibular neck
Complications & Contraindications
Ring complications: the groin ring can cause pressure necrosis if it is too tight, incorrectly positioned, or left in situ for prolonged periods without reassessment; the ring must sit against the ischial tuberosity (posteriorly) and pubic ramus (anteriorly) — if it slips anteriorly or proximally, it can compress the femoral neurovascular bundle; in a patient with a proximal femoral fracture (neck of femur), the ring may be too painful and ineffective — the Thomas splint is primarily for shaft fractures; neurovascular checks are mandatory at regular intervals
Heel pressure sores: the heel is particularly vulnerable to pressure necrosis in any traction setup; the posterior heel skin over the calcaneum has very little subcutaneous padding; the heel must be either hanging freely between slings or supported on a specifically padded `heel raise` away from the slings; heel checks are included in the standard neurovascular assessment
Contraindications: fractures proximal to the lesser trochanter (subtrochanteric/intertrochanteric fractures — the ring cannot provide effective countertraction and may be extremely painful); open fractures with extensive groin wounds; vascular injuries to the femoral vessels where ring pressure would be dangerous; patients requiring immediate surgical intervention (proceed directly to theatre rather than applying traction)
Modern Alternatives — Sager Splint & Kendrick Traction Device
Sager Emergency Traction Splint: a lightweight, compact unilateral traction device; the proximal end is positioned at the perineum (ischial pad against the ischial tuberosity) rather than a full ring around the thigh; ankle straps provide distal attachment; a calibrated scale shows the traction force applied; advantages over the Thomas splint: lighter, applies to one leg only (easier in field conditions), packable in an ambulance bag, can be applied by a single responder, allows bilateral application if needed; widely used by paramedics in the UK and USA
Kendrick Traction Device (KTD): a flexible pole and strapping system; similar principle to the Sager; designed for rapid field application; less rigid than the Thomas splint but more compact and portable; both the Sager and KTD are preferred by most paramedic services over the full Thomas splint for prehospital use due to their portability and single-operator application
Exam Pearls
Thomas splint: fixed traction device; ring at ischial tuberosity provides countertraction; skin/skeletal traction at distal end pulls the fracture; designed by Hugh Owen Thomas (Liverpool, 1860s); WWI mortality for femoral fractures fell from ~80% to <20% with its introduction
Primary modern use: transport immobilisation of femoral shaft fractures by paramedics; reduces pain, haemorrhage, soft tissue injury, and fat embolism; NOT a definitive treatment in modern orthopaedics
Ring sizing: circumference of uninjured thigh + 2–3 cm; ring at groin resting against ischial tuberosity (posterior) and pubic ramus (anterior); too small = vascular/nerve compression; ring at trochanter level NOT the groin = ineffective countertraction
Splint length: extends 25–30 cm (10 inches) beyond the heel; allows traction attachment without bunching; canvas slings support the posterior leg; heel must hang FREE from slings (heel pressure sores)
Complications: ring pressure (femoral nerve, lateral femoral cutaneous nerve, femoral vessels); heel pressure sores; peroneal nerve palsy at fibular neck; overtraction (too much weight); loss of reduction; do neurovascular checks every 30–60 minutes
Contraindicated for: subtrochanteric/intertrochanteric fractures (ring cannot provide effective countertraction; painful); proximal femoral fractures (NOF); open fractures with groin wounds; immediate operative cases
Sager splint: modern lightweight alternative; ischial pad (unilateral — no ring); calibrated traction scale; single-operator application; preferred by paramedics over the full Thomas splint for prehospital use due to portability
Fixed vs balanced traction: Thomas splint = fixed traction (ring provides countertraction within the splint — portable); balanced traction (Hamilton-Russell, Böhler-Braun) = body weight on tilted bed provides countertraction — hospital use only
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References
Thomas HO. Diseases of the Hip, Knee, and Ankle Joints. Liverpool. 1875.
Hey Groves EW. The treatment of fractures of the femur. Lancet. 1918.
Cooper GJ, Clasper JC. The Thomas splint in World War I — a historical reappraisal. Ann R Coll Surg Engl. 1997.
Alton TB, Gee AO. The Thomas splint: still a mainstay. Injury. 2014.
Dick W. Thomas splint: current status and comparison with Sager traction splint. Emerg Med J. 1997.
Bledsoe BE. Traction splints — what the evidence says. JEMS. 2008.
Campbells Operative Orthopaedics. 14th Edition. Elsevier.
PHTLS — Prehospital Trauma Life Support Manual. 9th Edition. Jones & Bartlett.
Orthobullets — Thomas Splint; Femoral Shaft Traction; Prehospital Fracture Management.
