Question

Fracture base of 5th metatarsal, below knee cast should be worn for

• A. 6-8 weeks
• B. 2-3 weeks
• C. 16-20 weeks
• D. 3-5 weeks

Hint:

An avulsion fracture of cancellous bone with good blood supply heals in the standard fracture-union window, not weeks longer.

Answer 1

The Correct Option is A

Step 1: Understand the injury. An avulsion fracture of the base of the fifth metatarsal (a "pseudo-Jones" or tuberosity avulsion injury) is the commonest metatarsal fracture, usually caused by sudden inversion of the foot which pulls the bone via the peroneus brevis tendon and lateral band of the plantar aponeurosis.

Step 2: Decide on management duration. Most undisplaced base-of-fifth-metatarsal fractures are treated with immobilisation in a below-knee walking cast or boot. The standard period of cast immobilisation to allow bony union is approximately 6-8 weeks.

Step 3: Why option A (6-8 weeks) is correct. Six to eight weeks gives adequate time for callus formation and clinical/radiological union of a cancellous metaphyseal fracture at this site, after which the cast is removed and weight-bearing/mobilisation progressed.

Step 4: Why the other options are wrong. 2-3 weeks (option B) and 3-5 weeks (option D) are too short for reliable union and risk re-displacement or non-union. 16-20 weeks (option C) is far longer than required and would cause unnecessary stiffness and disuse atrophy.

Final answer: A (6-8 weeks).