Fractures of the Metacarpus and Metatarsus
World Small Animal Veterinary Association Congress Proceedings, 2017
N. Fitzpatrick
Fitzpatrick Referrals, Eashing, Surrey, UK

Metatarsal and metacarpal injuries account for 8.1% and 3.3% of fractures in dogs and cats respectively. Various management techniques are reported (including plates, screws, pins, wires, dowel pins, and external fixation devices) but selection guidelines, pre-operative planning and validated outcome measures are lacking. Restriction of physical exercise or external coaptation may be adequate for minimally displaced and solitary metacarpal or metatarsal injuries, particularly of digits 2 and 5, but in the majority of clinical circumstances surgical intervention is indicated.

Secured Pin Intramedullary Dorsal Epoxy Resin, SPIDER, ESF Frame

A novel, inexpensive ESF (Secured Pin Intramedullary Dorsal Epoxy Resin, SPIDER) frame has been designed for stabilisation of metacarpal and metatarsal fractures and subsequently adapted to allow for management of metacarpo- or metatarso-phalangeal luxations and for tarsometatarsal arthrodesis. The SPIDER technique is sufficiently robust to avoid the requirement for post­operative external coaptation, which has been implicated as a significant cause of morbidity. Lack of requirement for coaptation also facilitates management of concomitant soft tissue injuries which are common with fractures and luxations in this location. Implant removal is straightforward and can be performed under sedation without an additional sterile surgical procedure.

Surgical technique entails a single midline dorsal incision directly over the site of fracture or luxation. Where arthrodesis is required (e.g., of a tarso-metatarsal joint), articular cartilage should be removed if the joints are luxated. Bone graft is rarely required. K-wires (50–75% medullary diameter) are directed retrograde through the fractures or luxations to exit the metatarsal or metacarpal bones at the dorsal aspects of the distal articular surfaces. Fractures or luxations are then manually reduced and the K-wires driven proximally into the proximal metacarpal or metatarsal bones (and through the tarso-metatarsal joints or carpo-metacarpal joints where arthrodesis at this level is indicated). There is an argument to create small approach holes on the dorsal aspect of the heads of the metacarpal or metatarsal bones and drive the pins normograde to avoid joint penetration, but this can be difficult in cats and small dogs with small diameter medullary canals that are difficult to access.

One or two K-wires are then placed transversely across the bases of the metatarsal/metacarpal bones or distal row of tarsal bones and calcaneal base or carpal bones. All exposed pin ends are finally bent dorsally such that they converge over the dorsal aspect of the pes or manus. The surgical site can be closed routinely prior to application of epoxy resin which is compressed over the ends of the K-wires (additional contouring of the K-wires at this site may improve stability of the epoxy resin bolus). Wooden spatulas (to a thickness of 4–10 mm) are placed between the epoxy resin bolus and the patient skin surface to avoid thermal injury during resin curing, and to allow for postoperative swelling.

Cage confinement or equivalent is routinely enforced for 4–6 weeks depending on predicted rate of healing (based on injury and patient factors). Frame removal can be performed upon documentation of radiographic union.

The SPIDER technique has been shown to provide reliable and durable stabilisation for T-MT and C-MC luxations, MT and MC fractures and MC-P and MT-P luxations and has been quicker and simpler to perform than many conventional techniques in the author’s experience, particularly where multiple fractures or luxations are present and in extremely proximal or distal metacarpal or metatarsal fractures where bone stock is limited. External coaptation is unnecessary with proper application of the technique. SPIDER has been successfully applied in both juvenile and mature patients and the surgical approach required is consistent with biologic fixation principles. The author routinely employs this technique in cats and small dogs but is more cautious with larger dogs where other fixation systems may be superior. Whilst weight-bearing may be limited during frame application, we have not experienced arthrosis of meta-phalangeal discomfort as a clinically significant issue in joints that had not been affected by precedent trauma.

Pedal Arch Wire Scaffold (PAWS)

The author has encountered a number of cases of multiple MC- or MT-phalangeal fracture luxation, in conjunction with either infectious arthritis or severe soft tissue injury. In this circumstance, skewer wires can be used to facilitate stability or phalangeal arthrodesis and if protection from weight-bearing is required for healing, a customized wire-arch hybrid frame can be constructed which allows ambulation on metal arches whilst providing a “tent” for healing, dressing of pad or palmar/plantar lesions or abscess-drainage. This technique has also been applied for management of trophic ulceration of bilateral pelvic limb pads secondary to spinal disease, and for management of severe acid burns of all paw pads of three feet. The walking external fixation frame, transmits load bearing forces directly to the appendicular skeleton, by-passing the pads and other soft tissues of the paw.

A similar but distinct type of walking frame involves bridging the tarsus or carpus using an external bilateral linear frame. The side-bars of the frame are bent distally to provide a platform on which the patient can walk. Within the frame, distal tibial or radial physeal fractures in juveniles or metacarpal/metatarsal or phalangeal fractures in small dogs or cats can be re-aligned by tensioning a length of plastic drip tube which is looped over the distal walking bars and sutured proximally to the skin of the antebrachium.

Distraction-Compression Osteo-Integration (DCOI)

Non-union following fracture repair or primary loss of significant MT or MC bone stock due to trauma is uncommon but may be associated with infection, inadequate blood supply and shearing injuries. Revision surgical procedures can compound the underlying reason for suboptimal bone healing by further compromising the biologic envelope. The author has operated a number of cases of fracture non-union or massive traumatic bone loss of the canine manus/pes using a biologic stimulation technique featuring sequential distraction and compression in order to stimulate incorporation of large cortico-cancellous autogenous bone graft blocks. This technique was developed from reports of cyclical distraction and compression in humans for successful treatment of non-unions of femoral fractures. The technique is termed distraction-compression osteo-integration (DCOI).

The bone blocks used are generally autogenous coccygeal vertebrae (or less commonly blocks from the iliac crest and wing). These are incorporated into the defect by being “skewered” onto Kirschner wires which themselves are placed as intramedullary pins across the fracture defect. The fractures and bone defects are stabilized using modified hybrid circular pin-arch external skeletal fixator constructs. Dynamic phases of distraction and compression are performed daily for several weeks to enhance bone regeneration and to promote incorporation of the autogenous cortical bone blocks into the defects. The majority of the cases that we have treated had undergone multiple previous surgical procedures, with many associated complications prior to presentation and the DCOI technique was employed as a last resort before considering amputation.


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N. Fitzpatrick
Fitzpatrick Referrals
Eashing, Surrey, UK

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