Casting an injured limb requires the cast technician to apply a cast which must make mechanical sense. The applied cast, depicted in the images below, was applied for an oblique, displaced fracture of the shaft of the fourth metacarpal.
The volar aspect of this cast extends to the proximal interphalangeal joints. This limits the flexion of the fingers without any clear clinical need and it may well impact on the full recovery of function when this cast is removed. The height of the plaster cast between the thumb and the index finger is much too long. It should have been terminated around the level of the proximal palmar crease.
The raw edge of the cast had abraded a significant area of skin in the first web space, thereby creating pain and discomfort for the patient and provided a focus for a superficial skin infection to take hold. The cast did not extend far enough in the proximal direction to adequately support the fracture which occupied about one half of the shaft of the involved metacarpal. It would normally be expected to extend towards the antecubital fossa.
The cast boundary extended to the head of the first metacarpal and needlessly limited the movement of the thumb. The edge of the cast was not trapping the undercast stockinette and migration of the padding under the cast edge was likely. The cast edges created an angle of less than 90 degrees around the base of the thumb and a focus for the abrasion of the base of the thumb.
The lateral view shows all of the faults mentioned in the previous image description. There has been no attempt to cut the casting tape to fit between the web space between the thumb and the index finger. The casting tape has been used at its full width of five centimetres.
The casting technique was poor because it folded the penultimate layer around the web space and then concluded with a fold which was applied over the first metacarpal. The needless restriction on thumb movement is obvious and likely to provide a cast boundary edge which will injure the base of the thumb; as it did in this particular case.
The dorsal view demonstrates the poor cast application technique with the same faults which have been described for the other two images. Additionally the proximal cast edge shows the undercast padding through almost the entire width of the casting tape.
This denotes that only a single layer of casting material was applied. There was no dorsal support in the proximal five centimetres of the cast. The distal cast edge displayed the same issue to a width of about one centimetre.
The cast was applied by a cast technician who held the British Casting Certificate (BCC). When the BCC certification leads to the application of casts which do not support the bony injury, the training must be questioned. Normally, one would expect to apply a full below elbow cast to derive sufficient mechanical advantage from the cast.
The cast was applied in a manner which belies the BCC qualification. It was the wrong selection of cast for the pattern of injury to be treated and it was applied without due regard to the basic principles of orthopaedic treatment and patient safety. A final point is the visibility of nail polish and adornments. Cast instructions should explicitly detail that nail polish and its associated details should not be worn while wearing a cast.