APPENDIX A: Principles of percutaneous pinning of hand fractures
1. Typically 1.1 mm or similar (e.g. 1.0 – 1.3 mm) K wires suffice for almost all hand fractures. For children 0.9 mm may on occasions be more appropriate but they are significantly less stiff which may make them unsuitable.
2. A clear surgical plan with good pre-operative radiographs and peri-operative image intensification/fluoroscan is essential.
3. The fracture reduction should be confirmed on the operating table. Often this will not be prefect due to plastic deformation at the fracture lines. If the fracture is extra-articular the aim is to hold the joints at either end of the bone out to length and correctly aligned. Although perfect reduction of the fracture is the ideal some there is some tolerance: shortening of up to 3mm in the phalanges and 5mm in the metacarpals; angular deformity of 200; but rotational deformity is least well accepted and should be <50. If the fracture is intra-articular then accurate reduction of the joint surface is even more important and a step of a maximum 1 mm should be the aim but sometimes a step of 2mm has to be accepted. Thus the reduction of intra-articular fractures often needs to be performed open to be accurate enough (this is not inevitable).
4. The patient needs to be fully consented and prepared ideally under local anaesthetic (we use 0.5% Bupivicaine as it gives prolonged post-operative anaesthesia. Although it acts slower than Lignocaine this is not a problem provided the patient is anaesthetised before painting and draping). They must be given peri-operative antibiotics to minimise the risks of infection. We typically give 1.5 gm of Cefuroxime. Patients are rarely allergic to it. Post-operative antibiotics are not required except as part of treatment of significantly contaminated fractures. The image intensifier/fluoroscan needs to be in the operating theatre at the beginning of the operation especially if the fracture is to be treated closed.
5. DO NOT TRY TO REDUCE THE FRACTURE AND INSERT THE FIRST K WIRE AS THE FIRST STEP. THIS RARELY WORKS AND WILL SIMPLY RESULT IN UNNECESSARY PASSAGES OF THE K WIRE WITH BONE AND SOFT TISSUE DAMAGE.
6. Rather the steps are: insertion of one K wire in one fragment; reduce the fracture; further advance the K wire into the second fragment; insert further K wires. In detail:
7. The position of the first (and most important) K wire is planned in advance and then identified on the patient’s finger using the image intensifier (this can be helped by marking the skin with a sterile marker pen). The K wire should aim to cross the fracture perpendicular to the fracture line. It should also allow for placement of at least one and preferably two other K wires. The first K wire is then drilled into the first fracture fragment with no need to hold the fracture reduced at this point. (It is essential to plan how the wire will cross the fracture and how the other wires will lie).
8. Advance the wire slowly and check the position regularly on the image intensifier. This avoids repeat drilling. (the more experienced we have become the more we often we use the image intensifier and then use it less overall). The first wire is advanced to the fracture line. This is confirmed on the image intensifier.
9. The fracture is reduced. This is the most important step, so the more experienced/skilled surgeon should do this. This should be confirmed in the image intensifier before advancing the first K wire. It can be difficult to do and avoid irradiation of the surgeons fingers. Passing a transverse K wire distallly e.g. through the middle phalanx gives a good purchase for traction with a pair of needle holders. An alternative is to use pointed tissue/towel holders or bone reduction forceps passed through the skin. In theory this should work well but in practice is difficult and often gives an imperfect reduction. When the pointed forceps is used in conjunction with traction through a distal wire then it can help hold the reduction and provide some compression at the fracture site. With the fracture reduced the K wire can be advance by a more junior surgeon or a nursing assistant. They must be advised how far to advance the wire. By holding the end of the K wire driver a set distance from the skin the assistant can advance only that distance and thus minimise the risk of advancing the wire too far. The wire should ideally bite into but not pass fully across the far cortex i.e. the point of the wire should pass through the far cortex but part of the angled tip should stay in the cortex. This provides enough hold and minimises the risk of wire migration. The position is confirmed on the image intensifier.
10. Further wires can be introduced. Ideally at least 3 wires should cross the fracture if possible. 2 wires may be insufficient to hold the fracture except for small peri-articular fractures.
11. As each wire is introduced it should be felt to pass through each cortex. Ideally the far cortex should not be completely breached rather embedding the tip of the wire in the cortex. This will minimise wire migration, which is associated with loss of position and pin track infection.
12. Sometimes it may be preferable to pass the wires across the finger and out the other side. This may allow the wires to lie more conveniently for the patient. The best indication for this is where there has been soft tissue contusion on one side of a narrow fragment of bone. If the wire is passed through to lie outside the skin on the other side then if a pin track infection occurs it must travel through good skin and a substantial piece of bone before reaching the fracture. This should minimise the risk of infection. Ideally the wires should be inserted from that side to start with, but that is not always easy.
13. The wires should only be used once in one direction of rotation, as they do not have cutting tips and easily become blunt. This will increase the likelihood of thermal damage. Likewise use of a tourniquet should be avoided to allow for local blood to dissipate the bone heat. (Nonetheless we usually apply one but do not inflate it. It is in reserve but rarely used)
14. Rotation can be very difficult to assess in the fingers. It is best assessed in flexion with the patient awake and under local anaesthesia.
15. Surgery under local anaesthetic has several other advantages: If the patient is numb peri-operatively they will be numb for some of the postoperative period helping ensure they remain pain free; the patient will see what has happened (they typically look at the image intensifier) and this helps them to understand the process and the post-operative rehabilitation; and you can talk to the patient emphasising the key steps in their recovery.
16. Almost all K wires need to be protected postoperatively with POP or a splint. This should be for the duration of time they remain in although towards the end of that i.e. for the last week, partial use of a splint allows earlier increased movement but is only suitable for a minority of cases, such as very reliable patients with very stable fracture/fixation configurations. The POP or splint should be as small as possible i.e. only protecting the fracture/wire complex and leaving as many joints free as possible. The free joints must be mobilised starting early in the post-operative period This allows some tendon gliding to minimise adhesions.
17. Often the POP in the operating theatre is quite bulky to allow for swelling but should not be too big immobilising joints unnecessarily.. This needs to be changed in the first week or so and a smaller POP/splint fitted and movement encouraged of the free joints. Physiotherapy supervision and support can be very useful to ensure compliance.
18. Patients also need advice on pin-track care if they are not buried under the skin or not covered by a POP. Patients are instructed to leave the pins alone if they remain dry. If they start to discharge they should be cleaned with sterile (boiled) water three times a day. If they do not settle within 24 hours antibiotics should be given and surgical advice sought. Typically the infection is Staphylococcus Aureus, which settles on Flucloxacillin 500 mg q.d.s. We typically also give Amoxycillin 500 mg t.d.s to maximise the chance of settling the infection. Most wires do not become infected before 4 weeks. We typically remove wires in clinic at 4.5 – 5 weeks by which time most fractures have united. Wires through the end of the finger e.g. for DIP joint dislocations or distal phalanx fractures seem to be the most prone to infection and need the closest attention. Some surgeons bury all K wires. We rarely bury them as it makes their removal so much more difficult. We bury wires likely to remain in for more than 6 weeks e.g. for stabilisation of carpal ligament injuries .
19. The principles are illustrated below in a PowerPoint presentation that using nails and a stick to simulate K wires and bone