Although metacarpal and metatarsal fractures are fairly common injuries in cats and dogs, the best way to treat is somewhat controversial. Incomplete or complete fractures of one or two metacarpal/metatarsal bones can be treated with external coaptation. The splint should immobilize the carpus/tarsus completely to be effective. Generally, external coaptation requires six to 12 weeks to achieve bony union. Splints should be changed at least weekly to decrease the risk of pressure sores in an at-risk area because of the lack of soft tissue coverage. If three or four metacarpal/tarsal bones are fractured and displacement is present, external coaptation may be a poor choice. When multiple bones are fractured, the splint cannot maintain reduction properly, and while union may occur, the recovery will be prolonged and deformity is likely. Surgery is considered a better choice in such cases. Indications for surgery Internal fixation is used for simple or comminuted metacarpal/metatarsal bone fractures or in patients with three or four fractured bones. In multiple bone fractures, the fixation can be used for all fractured bones or for metacarpal/metatarsal bones 3 and 4 only, i.e. weight-bearing toes. Options for fixation include plating or wiring (rarely performed), traditional IM pinning, IM pinning by distraction and the most recent technique, the SPIDER external fixator. Let’s describe the three pinning techniques. 1. Traditional intramedullary pinning In this technique, the pins are placed in a retrograde fashion. Pins are first placed into the distal bone segment. The pins exit at the metacarpophalangeal or metatarsophalangeal joint. Then the pins are driven into the proximal segment of the fractured bone. Once proper placement has been achieved, the pins are bent and cut short near the knuckles. Benefits * Simple technique Disadvantages * Articular cartilage damage * Often need a second surgery to remove the pins * Flimsy repair * Needs splinting, with weekly bandage changes for six to eight weeks, which is costly and time consuming * Bandages and splints can lead to complications (e.g. if too little padding is used) 2. IM pinning by distraction This older technique has been recently revived by Degasperi et al.* The two bone fragments are distracted and “impaled” onto a short pin. This is easier to do in cats than in dogs, presumably because of increased flexibility of the feline paw. The distraction or “dowel” technique is next to impossible in some dogs. Care should be taken not to break or crush the bone during distraction, especially in young patients. Benefits * Protection of the articular cartilage * No need for pin removal Disadvantages * Flimsy repair (probably even more so than above because the pins are much shorter) * Need for a splint, with weekly bandage changes for six to eight weeks, which is costly and time-consuming * Bandages and splints can lead to complications (e.g. if too little padding is used) 3. SPIDER external fixator A new technique has been recently described by a British surgeon, Dr. Noel Fitzpatrick. Nicknamed a SPIDER (for secured pin intramedullary dorsal epoxy resin), the device combines IM pins with an external skeletal fixator, which means that we do not need a splint. In the case of fractures of all four toes (metacarpals or metatarsals), four IM pins are placed as in the traditional IM technique described above. The pins are bent dorsally but not cut short. One or two additional pins are placed transversally across the carpus or the tarsus, and bent dorsally. The ends of all converging pins are encased in bone cement (polymethyl methacrylate) or acrylic. Benefits * A really cool concept * A fun surgery * A stronger repair * No need for external coaptation (cheaper and fewer complications) * Quick weight-bearing (within a week in most cases) Disadvantages * Articular cartilage damage * Need a second anesthetic event to remove the device * Managing of pin tracts by the owner Conclusion Although the SPIDER external fixator is the cool new kid on the block, each technique has its place. Which to use depends on client and patient factors. For example, some patients simply will not allow their owners to clean the pin tracts. Some owners are mentally incapable of looking at the SPIDER external fixator, let alone clean the pin tracts. As in all surgical endeavors, the “ideal” technique is a matter of indications, not dogma. All factors need to be taken into consideration before the “ideal” technique is chosen. Dr. Phil Zeltzman is a mobile board-certified surgeon in Allentown, Pa. His website is www.DrPhilZeltzman.com. He is the co-author of “Walk a Hound, Lose a Pound” (www.WalkaHound.com). REFERENCES * B. Degasperi et al. “Intramedullary pinning of metacarpal fractures in cats using simple a distraction technique. Vet Surgery 2007, Vol 36, N 4, p. 382-388 * N. Fitzpatrick et al. “Combined intrameduillary and external skeletal fixation of metatarsal and metacarpal fractures in 12 dogs and 19 cats. Vet. Surgery 2011, Vol 40, N 8, p. 1015-1022.”
