Percutaneous Screw Fixation for Fractures of the Scaphoid
Scaphoid fractures occur most commonly in young adults after a fall onto an outstretched hand, often during sports. Patients present with wrist pain, sometimes with swelling, and often with tenderness in the ‘anatomical snuff-box’.
The treatment of this injury presents a number of challenges:
- The diagnosis of a fractured scaphoid can be difficult in the first few weeks, as scaphoid fractures are not always recognised using conventional X-rays. In this situation, the use of more sophisticated imaging techniques, in particular, MRI scans, is helpful.
- The scaphoid has a blood supply that favours the distal end of the bone, so some fractures are at significant risk of not healing (scaphoid non-union). This is particularly common if the fracture is within the proximal pole of the bone if the fracture is displaced by as little as I -2mm, or if the fracture is not detected and the wrist not immobilised within four weeks of the injury. Smoking has also been shown to prejudice the healing of these fractures.
- The operative treatment of scaphoid non-union is usually more complex and potentially less successful than that of acute fractures.
- The natural history of scaphoid non-union is the gradual development of osteoarthritis within the wrist, often within a few years. A predictable pattern of cartilage wear occurs (known as Scaphoid Nonunion Advanced Collapse or SNAC wrist).
Undisplaced fractures of the scaphoid wrist or distal pole are generally treated with cast immobilisation for a period of six to twelve weeks, depending on the progress of healing of the fracture. Usually, six to eight weeks is sufficient.
The indications for surgical fixation of isolated scaphoid fractures are:
- All proximal pole fractures.
- Displaced waist fractures.
- A fracture that has not been detected and therefore not appropriately immobilised for the first four weeks.
A relative indication for surgical fixation is an active patient who does not wish to have their wrist immobilised in a below-elbow cast for between six and twelve weeks.
Percutaneous screw fixation (i.e. using only a small incision of approximately 5mm in length, rather than the conventional open technique) can be used in the majority of these situations, and the patient’s wrist is only immobilised in a cast for one to two weeks after surgery. After this time, a removable splint is worn which allows an early range of motion exercises, and unprotected use of the wrist for low-demand daily activities (e.g. washing, dressing, writing).
Percutaneous screw fixation also has a role in the treatment of selected patients with delayed or non-union of the scaphoid — although this is not always possible because of bone resorption at the fracture site and the consequent need for bone grafting, or because of significant displacement. Pre-operative CT scans are invaluable for surgical decision-making in this context.
Percutaneous screw fixation of the scaphoid — technical aspects:
- Can be performed antegrade (i.e. from proximal to distal) or retrograde.
- The antegrade technique is used for proximal pole fractures.
- The retrograde technique is used for waist or more distal fractures.
- Can be carried out as day case surgery under regional or general anaesthesia.
- A guide wire is passed across the fracture under X-ray guidance, along with the central axis of the bone.
- A headless screw is then passed over the guide wire and buried within the bone.
- The screw has a differential pitch, meaning that when inserted it leads to compression at the site of the fracture, optimising the chance of healing.
It is unusual to need the screw to be removed in the medium to long-term.
A 22-year-old Masters student was pushed over during a game of five-a-side football and landed on his outstretched dominant left hand. His wrist gradually became more painful over the evening, so the following day he saw his GP who suspected be May have a scaphoid fracture. Radiographs were carried out which confirmed the diagnosis of an undisplaced scaphoid waist fracture, and he was referred to Mr Gidwani.
After a discussion of the pros and cons of cast treatment versus percutaneous fixation, the patient elected to be treated in a cast. He returned to the clinic within a week, however, having changed his mind – he was frustrated by the cast, and by the difficulties he experienced while trying to write and take notes during lectures.
A few days later, a percutaneous fixation was carried out. He was kept in a cast for two weeks, before being transferred into a removable splint. A CT scan carried out at 12 weeks postoperatively confirmed complete union of the fracture and at that stage, all restrictions were lifted on the use of the wrist for sports and leisure activities.
At four months post-op, he has recovered a full range of motion, is back to skiing and playing football, and hopes to be back on the basketball court soon.
This article was written by Mr Sam Gidwani. Find out more about his speciality as a hand and wrist surgeon here.