Ottawa Ankle & Foot Rules
Ankle Zone
Foot Zone
詳細ガイド 近日公開
Ottawa Ankle Rulesの包括的な教育ガイドを準備中です。ステップバイステップの解説、数式、実例、専門家のヒントをお届けしますので、もうしばらくお待ちください。
The Ottawa Ankle Rules are a set of clinical decision guidelines developed by Ian Stiell and colleagues at the Ottawa Civic Hospital in 1992, designed to safely reduce unnecessary X-ray imaging in patients presenting with acute ankle and foot injuries. Before the Ottawa Rules, ankle injuries were routinely X-rayed in most emergency departments despite a fracture rate of only 15–20%, meaning over 80% of X-rays were negative and therefore unnecessary. The Ottawa Rules use a combination of specific bony tenderness locations and the ability to bear weight to identify which patients have a sufficiently low risk of fracture that imaging can be safely omitted. The rules consist of two components: the Ottawa Ankle Rules (for ankle fractures) and the Ottawa Foot Rules (for midfoot fractures). For the ankle, an X-ray is required if there is pain in the malleolar zone AND one of: bony tenderness at the posterior edge or tip of the lateral malleolus, OR bony tenderness at the posterior edge or tip of the medial malleolus, OR inability to bear weight both immediately after injury and in the emergency department (four steps). For the midfoot (foot rules), an X-ray is required if there is pain in the midfoot zone AND one of: bony tenderness at the base of the fifth metatarsal, OR bony tenderness over the navicular, OR inability to bear weight. The Ottawa Ankle Rules have a sensitivity of 97–99% for clinically significant fractures, with a specificity of approximately 30–40%, meaning they successfully identify almost all true fractures while still reducing unnecessary X-rays by 30–40%. They have been validated in over 15 prospective studies and are recommended by NICE as the standard clinical decision tool for ankle trauma.
Ankle X-ray if: pain in malleolar zone AND (posterior lateral malleolus OR posterior medial malleolus OR unable to weight-bear x4 steps); Foot X-ray if: midfoot pain AND (navicular OR 5th metatarsal base tenderness OR unable to weight-bear)
- 1Step 1 — Establish mechanism: Determine it is an acute ankle/foot injury (rule applies within 10 days of injury and for blunt trauma; not for open fractures, isolated skin trauma, or pregnancy without other concerns).
- 2Step 2 — Identify malleolar zone: The malleolar zone is the distal 6 cm of the fibula (lateral) and tibia (medial). Any pain in this zone triggers assessment of the next criterion.
- 3Step 3 — Assess lateral malleolus tenderness: Palpate the posterior aspect and tip of the lateral malleolus. If bony tenderness at the posterior edge or tip → ankle X-ray indicated.
- 4Step 4 — Assess medial malleolus tenderness: Palpate the posterior aspect and tip of the medial malleolus. If bony tenderness here → ankle X-ray indicated.
- 5Step 5 — Weight-bearing test: Ask patient to take 4 steps (limping counts as bearing weight). If unable to bear weight immediately after injury AND in the emergency department → X-ray indicated.
- 6Step 6 — Midfoot zone assessment: If pain is in the midfoot, palpate the base of the 5th metatarsal and the navicular bone. Tenderness at either → foot X-ray indicated.
- 7Step 7 — Apply result: If none of the above criteria are met, fracture probability is <1% and X-ray can be safely omitted. Manage with RICE (rest, ice, compression, elevation), analgesia, and follow-up.
Likely lateral ligament sprain; RICE protocol, NSAIDs, follow up in 5–7 days
Pain in malleolar zone (yes) but no posterior malleolar tenderness and able to weight-bear → rules negative → X-ray not indicated. This avoids unnecessary radiation and wait time.
X-ray to rule out lateral or medial malleolus fracture
Pain in malleolar zone + inability to weight-bear = Ottawa positive. X-ray may reveal fibular fracture, bimalleolar fracture, or Maisonneuve injury.
Rule positive due to 5th metatarsal base tenderness — Jones fracture or styloid avulsion must be excluded
Even though weight-bearing is possible, specific tenderness at the base of the 5th metatarsal (a common fracture site) triggers X-ray under the Ottawa Foot Rules.
Bimalleolar fracture or Maisonneuve fracture (check entire fibula); orthopaedic review required
Bilateral posterior malleolar tenderness + inability to weight-bear = very high suspicion for bimalleolar fracture or unstable ankle. Full ankle series plus proximal fibula palpation.
Emergency department triage of ankle and foot injuries to determine need for X-ray imaging, representing an important application area for the Ottawa Ankle Rule in professional and analytical contexts where accurate ottawa ankle rule calculations directly support informed decision-making, strategic planning, and performance optimization
Minor injury unit (MIU) and urgent treatment centre (UTC) safe discharge of sprain patients without X-ray, representing an important application area for the Ottawa Ankle Rule in professional and analytical contexts where accurate ottawa ankle rule calculations directly support informed decision-making, strategic planning, and performance optimization
Pre-hospital assessment by paramedics to guide hospital destination and resource allocation, representing an important application area for the Ottawa Ankle Rule in professional and analytical contexts where accurate ottawa ankle rule calculations directly support informed decision-making, strategic planning, and performance optimization
Sports medicine and physiotherapy field assessment to guide return-to-play versus imaging decisions, representing an important application area for the Ottawa Ankle Rule in professional and analytical contexts where accurate ottawa ankle rule calculations directly support informed decision-making, strategic planning, and performance optimization
Quality improvement audits in emergency departments measuring compliance with Ottawa Rule-guided imaging rates, representing an important application area for the Ottawa Ankle Rule in professional and analytical contexts where accurate ottawa ankle rule calculations directly support informed decision-making, strategic planning, and performance optimization
Children Under 18 Years
{'title': 'Children Under 18 Years', 'body': 'Children have open growth plates at the distal fibula and tibia (Salter-Harris fractures) and at the base of the 5th metatarsal. These injuries can be subtle on X-ray and may require comparison views. The Ottawa Ankle Rules in their original form are not validated in children under 18. Consider X-raying all children under 12 with significant ankle injury, and use clinical judgement for older adolescents.'}
Syndesmotic (High Ankle) Sprain
A positive squeeze test (squeezing fibula and tibia together at mid-leg reproduces ankle pain) and external rotation stress test suggest syndesmotic injury. These patients may be Ottawa-negative but have significant instability requiring immobilisation and orthopaedic follow-up. Always assess syndesmosis in mechanism injuries.'}
Lisfranc (Tarsometatarsal) Injuries
{'title': 'Lisfranc (Tarsometatarsal) Injuries', 'body': 'Lisfranc injuries involve the tarsometatarsal joint complex and are frequently missed on plain X-ray. Weight-bearing AP views of the foot show subtle diastasis of the 1st and 2nd metatarsal bases. The Ottawa Foot Rules do not specifically detect Lisfranc injury. High clinical suspicion based on mechanism (forced plantar flexion, equestrian injury) warrants imaging even if Ottawa-negative.'}
Elderly Patients with Osteoporosis
{'title': 'Elderly Patients with Osteoporosis', 'body': 'Osteoporotic elderly patients can sustain insufficiency fractures with minimal mechanism. The Ottawa Rules apply but clinical judgement should favour X-raying in elderly patients with significant osteoporosis risk, even with borderline examination findings. Additionally, confusion or pain insensitivity (diabetic neuropathy) may make weight-bearing assessment unreliable.'}
| Rule | Criteria | X-ray Required? |
|---|---|---|
| Ankle Rule | Pain in malleolar zone + posterior lateral malleolus tender | Yes |
| Ankle Rule | Pain in malleolar zone + posterior medial malleolus tender | Yes |
| Ankle Rule | Pain in malleolar zone + cannot weight-bear (4 steps) | Yes |
| Ankle Rule | Pain in malleolar zone only — none of above positive | No |
| Foot Rule | Midfoot pain + navicular tenderness | Yes |
| Foot Rule | Midfoot pain + base of 5th metatarsal tenderness | Yes |
| Foot Rule | Midfoot pain + cannot weight-bear (4 steps) | Yes |
| Foot Rule | Midfoot pain only — none of above positive | No |
What is the sensitivity and specificity of the Ottawa Ankle Rules?
The Ottawa Ankle Rules have a sensitivity of 97–99% for clinically significant ankle fractures, meaning they miss fewer than 1–3% of fractures. Specificity is 30–40%, meaning 60–70% of Ottawa-positive patients will not have a fracture on X-ray. This is acceptable given the high sensitivity — the rules are designed to maximise safe fracture exclusion, not to eliminate all unnecessary X-rays.
When can the Ottawa Ankle Rules not be applied?
The rules are not valid in: children under 18 (modified criteria or X-ray all), pregnancy (higher caution), acute gross swelling obscuring palpation, intoxicated or uncooperative patients who cannot reliably report tenderness, injuries older than 10 days, isolated skin wounds, multiple trauma, or pre-existing ankle deformity or neurological deficits affecting sensation.
Why is posterior malleolar tenderness more specific than anterior?
The posterior 6 cm of the lateral and medial malleoli correspond to the site of bony cortex most commonly fractured in ankle injuries. The anterior tibia and fibula rarely fracture from ankle twisting injuries. Tenderness here indicates the cortical bone is stressed, while tenderness over the ligamentous insertion sites anteriorly is more commonly from sprain.
What is the Maisonneuve fracture and why is it important?
A Maisonneuve fracture is a spiral fracture of the proximal fibula caused by a twisting ankle injury, associated with medial malleolar or deltoid ligament injury and interosseous membrane disruption. The ankle X-ray may appear relatively normal but the injury is unstable. If medial ankle tenderness or widened mortise is noted, the entire fibula must be palpated and X-rayed.
Can the Ottawa Rules be used for children?
The original Ottawa Ankle Rules were validated in adults. Children under 18 have growth plates (Salter-Harris fractures) at the malleoli that can be injured by the same forces that cause ligament sprains in adults. Modified paediatric criteria and lower X-ray thresholds are recommended. Many paediatric emergency guidelines advise X-raying all ankle injuries in children under 12.
What is a Jones fracture?
A Jones fracture is a transverse fracture at the proximal diaphysis of the 5th metatarsal (the shaft, not the styloid process/tuberosity). It has a notoriously poor blood supply and high non-union rate, often requiring surgical fixation. It is commonly confused with a styloid avulsion fracture (pseudo-Jones), which generally heals with conservative management. The Ottawa Foot Rules detect both types.
How much radiation does an ankle X-ray deliver?
Standard ankle X-ray (2–3 views) delivers approximately 0.001–0.01 mSv of radiation — roughly equivalent to 1–2 hours of natural background radiation. While very low in absolute terms, the Ottawa Rules aim to eliminate unnecessary examinations in the majority of ankle injuries that are pure soft tissue sprains, reducing cost, wait times, and cumulative population exposure.
Should I trust the Ottawa Rules in an intoxicated patient?
No — the Ottawa Ankle Rules require reliable patient cooperation for bony tenderness assessment and weight-bearing evaluation. Intoxicated patients may be unable to localise tenderness accurately or may walk despite fracture due to altered pain perception. X-ray all intoxicated patients with ankle injuries, or reassess after the patient sobers. This is particularly important in the context of ottawa ankle rule calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise ottawa ankle rule computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
プロのヒント
Use the mnemonic PALS — Posterior edge, Apex (tip), Lateral malleolus, Steps (4) — for the ankle, and NABS — Navicular, Ability to weight-bear, Base of 5th metatarsal, Steps — for the foot. If any criterion is positive, X-ray. If all are negative, reassure and treat for sprain. Always document the examination findings explicitly in your notes.
ご存知でしたか？
The Ottawa Ankle Rules were originally published in the Annals of Emergency Medicine in 1992 and validated in a population of over 1,000 patients. Within the first decade, they were estimated to have prevented over 1 million unnecessary ankle X-rays per year in North America alone. They remain the most widely cited and implemented clinical decision rules in emergency medicine, surpassing even the Canadian C-Spine Rules and the PECARN paediatric head CT rules in adoption.
参考文献
- ›Stiell IG et al. — A Study to Develop Clinical Decision Rules for the Use of Radiography in Acute Ankle Injuries (Ann Emerg Med 1992)
- ›Stiell IG et al. — Prospective Validation of a Decision Rule for Use of Radiography in Acute Ankle Injuries (JAMA 1994)
- ›NICE — Fractures (Non-Complex): Assessment and Management (NG38 2023)
- ›Bachmann LM et al. — Accuracy of Ottawa Ankle Rules — Systematic Review (BMJ 2003)
- ›LITFL Ottawa Ankle Rules Reference