When the astragalus is luxated from the navicular or calcaneum, but remains in its normal relation with the bones of the leg, it's known as Subastragalar and Medio-tarsal Dislocations. When dislocated from tibia and fibula but attached to tarsal bones, it’s an ankle dislocation. Complete luxations are considered under this heading. These may be forward or forward and outward.
Surgical Anatomy: The astragalus is covered by compact tissue with articular surfaces forming calcaneo-astragalar, astragalo-navicular, and tibio-tarsal joints. It articulates with the tibia above and two malleoli below form a firm mortise joint allowing motion in one plane.
In falls on the foot, the astragalus may be crushed between tibia and calcaneum, often associated with calcaneum fractures. Fractures of the body are transverse, longitudinal, or stellate; neck fractures are common from extreme dorsal flexion.
Luxations of the astragalus are often compound due to limited space within skin accommodating displaced bone. Ligamentous damage is extensive and deformity depends on position occupied by astragalus. Fracture and dislocation may coexist, usually with fracture of neck and luxation of head or body.
Symptoms: Pain, swelling, loss of function, local tenderness are pronounced in fractures; crepitus may be present. Luxations have extreme deformity, pain, swelling, and the displaced bone can be felt as a prominent mass in ankle bend.
Diagnosis: Based on symptoms and X-ray for confirmation. Deformity is usually sufficient to recognize luxation.
Treatment: Traumatic reaction is severe initially; pillow splint, elevation, ice cap are used. When swelling subsides, foot and ankle may be fixed in short plaster stirrup or posterior splint if other fractures exist. Reduction should be immediate unless compound; manipulations depend on bone position. Open incision under proper surgical surroundings is needed for anterior luxations to prevent sloughing.
Operative Treatment: Simple uncomplicated fractures rarely require operation, but compound cases do. No reduction attempt until in operating room; wound irrigated with sterile salt solution and closed with sutures. Excision of bone was common earlier but now only necessary in extreme cases.
After-Treatment: Proper union time for fragments is essential to prevent deformity. Foot protected from weight bearing until two months post-injury, then gradual resumption of function. Massage and early passive motion are crucial to prevent joint adhesions.
Prognosis: Simple luxations with prompt reduction have good restoration of function; fractures recovery slower with some restriction in motion possible. Complete removal of bone surprisingly results in good function.
Subastragalar Luxations: Astragalus articulates with calcaneum by two facets divided by deep groove for interosseous ligament attachment. Calcaneo-astragaloid and internal, external lateral ankle-joint ligaments bind them together. Subastragalar luxation is common in forcible inversion or eversion of foot.
Symptoms: Outward luxations show downward and outward sole displacement; inward shows downward and inward sole with prominent inner malleolus. Backward displacements have heel prominence and dorsum shortening.
Key Takeaways
- Complete luxations of the astragalus are considered under this heading, often involving forward or outward displacement.
- Symptoms include pain, swelling, and deformity; diagnosis is confirmed with X-ray.
- Immediate reduction is crucial for compound cases to prevent tissue damage.
Practical Tips
- Use a pillow splint initially for severe traumatic reactions in fractures.
- Apply short plaster stirrup after swelling subsides to fix the foot and ankle.
- Promptly seek surgical intervention if luxations are not reducible by manipulation.
Warnings & Risks
- Failure to reduce compound cases promptly can lead to tissue sloughing and infection.
- Ignoring symptoms of fractures or mistaking them for sprains can delay proper treatment.
Modern Application
While the surgical techniques described here are outdated, understanding the anatomy and recognizing symptoms of astragalus injuries remains crucial. Modern imaging technology like MRI and CT scans provide clearer diagnoses, but initial first aid principles remain relevant.
Frequently Asked Questions
Q: What is the most common type of fracture in the astragalus?
The most common type of fracture in the astragalus is a transverse fracture of the neck, often resulting from extreme dorsal flexion of the foot.
Q: Why are luxations of the astragalus often compound?
Luxations of the astragalus are often compound due to limited space within the skin accommodating the bulk of the displaced bone, leading to potential tissue damage and sloughing if left unreduced.
Q: What is the significance of X-ray confirmation in diagnosing fractures or dislocations?
X-ray confirmation is crucial for accurate diagnosis as symptoms can be similar between fractures and sprains. It helps identify any complicating lesions that might otherwise go unnoticed.