Metacarpal (MC) and metatarsal (MT) fractures are reported to occur with an incidence of up to 5–12% of all fractures in dogs and 3% in cats [1,2,3,4,5,6]. They are usually a result of trauma, most frequently road traffic accidents and falls [5,6,7], and most commonly affect the mid- or distal diaphysis of MCs, and the proximal region of MTs [8,9,10].
Conservative management has been historically recommended for minimally displaced fractures and fractures where at least one major weight-bearing bone (MCs/MTs III or IV) is undamaged [6, 9, 10]. Surgery is recommended when more than two bones are fractured, if both main weight-bearing bones are affected, or there is a proximal fracture of MCs/MTs II or V. Additionally, surgery is advised for significantly displaced fractures, open fractures, infected fractures and those in large or working dogs [5, 6, 10,11,12].
Various surgical techniques have been described [3, 5, 6, 11,12,13,14,15,16,17]. Open techniques consist of intramedullary (IM) pin fixation, internal fixation with bone plates, tension-band wire fixation, and lag screws. Closed techniques include several configurations of External Skeletal Fixators (ESFs). [6, 18, 19]
ESFs are the preferred technique for comminuted and/or for open fractures, where “biological osteosynthesis” is desired for preservation of blood supply and reduction of contamination [20,21,22]. Closed reduction decreases tissue trauma and infection risk at the fracture site by eliminating the soft tissue incision and approach [17, 22, 23]. ESFs provide a less rigid fixation than internal fixation and may allow micromotion at the fracture site, which has been shown to be important in stimulating blood flow and callus formation [23]. However, any further increase in motion at the fracture site will exceed the strain limits of healing tissues, leading to fibrous tissue formation and an eventual non-union. [22, 23] Surgeons must find a balance between acceptable stability for fracture healing and adequate flexibility to allow stimulatory micromovement. Epoxy putty external skeletal fixation has been described as a successful technique for the management of multiple MC and MT fractures in 11 dogs and 11 cats when a good alignment is achieved [24].
Circular external skeletal fixation has also been described as an option to treat multiple MT and MC fractures in three dogs [25]. The main advantage of using a circular fixator construct is the small-diameter fixation wires. Despite local inflammation and drainage tract from the wires were seen in all cases, none of the dogs had residual lameness in the follow up period [25].
An external skeletal traction device for distal fractures has been described in eleven dogs as an option for closed treatment [26]. The majority of the fractures had an improvement in both alignment and apposition postoperatively. In multiple metatarsal or metacarpal fractures that are not amenable to internal fixation or external coaptation, the traction- ESF device can provide a valuable alternative in fracture management. This is especially beneficial if the wounds are infected and require frequent attention and dressing [26].
Open fixation methods can disrupt blood supply at the fracture sites to a greater extent than closed methods, [21] which could lead to increased risk of delayed healing, non-union and/or infection [7, 22]. For simple or mildly comminuted fractures, internal fixation generally provides better alignment, [25] and the surgeon must decide whether this advantage outweighs the detriment of disturbing the healing environment. Intramedullary pins can also achieve satisfactory stabilisation with or without additional stabilization [10, 12, 27]. Intramedullary pins can be applied in a normograde or retrograde (Dowel pinning) fashion. Normograde application of the k-wires/pins usually requires the creation of a dorsal slot in the distal aspect of the bone to allow the pin to slide into the medullary cavity and not getting driven into the opposite cortex. A “dowel” intramedullary pin technique has been described in cats and avoids both joint penetration and drilling of a slot in the dorsal MT or MC cortex [25].
The veterinary cuttable plate is a traditional implant for the open stabilization of metacarpal/tarsal fractures. Other commonly used implants are locking plates of appropriate size. A minimally invasive approach to the repair of meta-bone fractures represents a viable option with several benefits related to the preservation of the local biology. Fractures of the body of meta-bones III and IV can be approached by creating 1 or 2 small skin incisions proximally and distally to the fractured area [23].
ESFs can be used together with intramedullary pins, [7, 9] which allows more accurate anatomical alignment of fracture fragments than closed techniques alone. This is the case of the Spider external fixator. The surgical technique involves normograde or retrograde intramedullary pin placement into the fractured MT/MC bones and transverse pin placement at the base of the MT/MCs or tarsal/carpal bones. The distal pin ends are contoured dorsally in epoxy resin and implants maintained until fracture union. Pin penetration of MT-phalangeal or MC-phalangeal joints may cause morbidity and requires further study [9]. Distal application of the pin without open approach to the fracture site can limit damage to vascularity, thereby retaining more biological potential compared to other open repair techniques [7, 9].
There have been some studies comparing the efficacy of conservative versus surgical management of MC and MT fractures in dogs and cats, [10, 13] however, to the authors knowledge, there are no studies describing differences between outcomes of open versus closed surgical repair of metatarsal or metacarpal fractures.
The objective of this study was to gather data on healing and complications from patients with metatarsal or metacarpal fractures, and test the hypothesis that there is a difference in these parameters between those treated with an open surgical approach as opposed to a closed surgical approach.
