Conservative Treatment and External Coaptation for Fractures
World Small Animal Veterinary Association World Congress Proceedings, 2015
S. Langley-Hobbs
School of Veterinary Sciences, University of Bristol, Langford, Bristol, UK

The presentation and accompanying notes aim to cover the principles of both conservative management and external coaptation of fractures and when such methods of fracture management are indicated or contraindicated. Overviews are included in the literature.1,2

When considering which stabilisation technique is the optimal one to use for management of a specific fracture the options to consider include conservative management, external coaptation, external skeletal fixation, with or without open fracture reduction, and repair by internal fixation using pins and wires, bone plates and screws, interlocking nails etc. The main objective when managing a fracture is to try and return the patient to normal function as soon as possible. Circumstances must be created which allow bone healing to be optimal and the outcome is related to the decision as to how to best manage that fracture.

The decision as to how best manage a fracture should be made primarily according to the nature of the fracture and age of the patient. Other influencing factors will include available equipment, expertise of the veterinary surgeon and financial restraints. Unfortunately, decisions made due to financial restraints may not result in the optimal management strategy being used and therefore a poor outcome for the patient. Usually the cheapest treatment option is the one that works first time. If a decision is made to use conservative management or external coaptation on financial grounds and that results in a fracture that does not heal the dog or cat will then require surgical stabilisation or amputation, which will necessitate additional expenditure and probably result in a poorer outcome than if this option had been chosen in the first place.

There are some fractures that will heal very well with nonsurgical management, such as conservative management or external coaptation, and the art is being able to select those cases and manage them appropriately to achieve optimal outcomes for all patients.

Non-surgical management includes conservative management (cage rest or lead exercise only) and external coaptation (splint, bandage, cast of sling). Non-surgical management has the potential advantages of reducing the need for anaesthesia, avoiding the need for an open surgical approach and the potential risks associate with that, potentially using cheaper materials for fracture stabilisation and therefore this approach may be more economic overall. Non-surgical management has the potential disadvantages of resulting in fracture disease (complications that occur as a result of limb immobilisation), providing insufficient instability resulting in a delayed union or non-union, cast sores and insufficient fracture reduction resulting in a malunion.

Conservative Management

The aim with conservative treatment is that the surrounding soft tissues (muscle, fascia and periosteum) and adjacent bones will provide enough stability to keep the bones in reasonable alignment whilst healing occurs.

Fractures suitable for conservative treatment include stable undisplaced fractures, greenstick fractures and selected fractures of flat bones or the axial skeleton such as the pelvis, scapula, skull or vertebrae where strong muscular forces act to immobilise the fracture fragments. If the anatomical displacement is acceptable then this is a reasonable option in some of these cases. Management usually involves a period of restricted activity with confinement to a cage or room. Restriction time varies according to the severity of the fracture and age of the patient and the anticipated time for healing. It is usually 4–6 weeks for most fractures. Prevention of weight bearing may be useful for certain fractures such as scapula fractures, by using a bandage to prevent weight bearing such as a carpal flexion bandage or Velpeau sling.

External Coaptation

The aim of external coaptation is that compressive forces are transmitted from the bandage or splint to the bones by means of the interposed soft tissues. Pressure must be evenly distributed throughout the cast or splint to avoid circulatory stasis. For successful external coaptation at least the joint above and below the fracture should be immobilised. To reduce complications in clinical cases the external coaptation should actually extend to include all the joints (not just the one joint) distal to the fracture (to prevent foot swelling). So for a tibial fracture the cast is extended from the foot to proximal to the stifle, for antebrachial fractures the cast extends from the foot to proximal to the elbow. Fractures suitable for external coaptation include stable fractures distal to the elbow or shoulder, with at least 50% overlap of fracture fragments on orthogonal radiographs. Fractures of just the radius with an intact ulna or similarly fractures of the tibia with an intact fibula can also be suitable for external coaptation. When 2 or fewer metacarpal or metatarsal bones are fractured external coaptation can be considered.

Consideration should also be taken of the following variables

 Age - immature animals (< 6 months) are often suitable candidates given their rapid healing times.

 Breed of dog - it may be easier to keep a cast on a long legged dog than a brachiocephalic breed. However, toy breed dogs are renowned to develop non-union fractures of the radius and ulna if these are treated with external coaptation.3

 Function of the dog - conservative treatment may be suitable for certain fractures in pet dogs; however, for racing or working dogs internal fixation may be advisable (e.g., caudal acetabular fractures).

External coaptation is one of the most widely used and abused fracture stabilisation techniques. There are a high number of complications seen with external coaptation and as with any other form of fracture fixation a successful outcome is more likely with careful case selection and meticulous attention to the process and the post-operative care.

External coaptation can be achieved by casts, splints, slings of bandages, although the strict definition of coapt means to approximate so probably is more accurately applied to casts and splints. Splints are available in two main types: preformed splints - available in several types and sizes such as Mason-Meta splints or Green Gutter splints, tibial splints, and custom made splints - formed to the individual patient's limb using casting tape or moldable plastics. Preformed splints are readily available and convenient but frequently don't provide a good enough fit and they are really only appropriate for temporary immobilization (e.g., while transporting the dog for surgery). Molding several layers of casting tape to the limb for the entire length that is needed produces a more comfortable splint for the animal; and therefore, its usage is less likely to result in pressure sores.

Cast Application

Casts tend to be preferable to splints for anything that needs to stay on for more than a week. My tried and tested way to apply a cast is to place a double layer of stockinette followed by a layer or two of a water repellent compressible material (e.g., Softban [Smith & Nephew]). Care is taken not to apply too much padding over pressure points such as the point of the hock/os calcaneus, I find that use of a "doughnut" or underpadding over pressure points is preferable. Then I generally use a polyurethane fiberglass impregnated cast material such as Vetcast (Smith & Nephew) with a minimal of 6 layers (3 times up and down with a 50% overlap) or more in large, active dogs or where there is an acute angle in the cast (at the hock). Then the cast is bivalved (split in two halves by cutting longitudinally down the medial and lateral aspects of the cast.) and taped immediately back together with strips of non-extensible tape such as zinc oxide tape and the whole cast is then covered in a cohesive elasticated bandage (e.g., Vetrap [Smith & Nephew]). Bivalving allows the cast to be easily removed if swelling develops or underlying soft tissues need to be examined. In addition, the caudal half of the cast can be used as a splint in the later stages of fracture healing. The cast should extend from the foot distally to proximal to the elbow or stifle as appropriate. The middle two toenails and pads should be visible (but not protruding), so the cast can be checked for slippage, toe swelling etc. If the foot swells the toenails will tend to splay outwards.

Complications with External Coaptation

No discussion of external coaptation would be complete without consideration of the potential complications associated with these techniques. Complications are not infrequent; one report placed the rate of soft tissue complication with casting at 63%.4 Complications can arise because of the difficulties inherent in cast or bandage management and owner compliance with animal patients. They can arise because of less than ideal case selection, but they can also arise in situations where case selection and patient management are optimal.2 Complications with external coaptation take three forms.

Soft Tissue Injury

Soft tissue injury with external coaptation is frustratingly common. Ischaemic injuries after incorrect bandaging or splinting techniques were reported in eleven dogs, two dogs had limb amputation, three had toe amputation and five required skin grafts all as a result of the bandage related injuries.5 A recent publication found soft tissue injury in nearly 2/3 of 60 animals after cast application.4 The injuries ranged in severity from mild dermatitis to pressure sores and sepsis to avascular necrosis of soft tissues; in eight cases additional surgery was required. All sight hounds in this survey developed soft tissue injury and mixed breeds were at less risk.4 The investigators were not able to demonstrate any protective value in weekly cast changes, nor in owner education and monitoring. They concluded that even the most observant owners were unreliable in detecting soft tissue injury and that the only way to detect cast sores was to remove the cast. Their examination of the literature produced no conclusive data and thus no consensus on the matter of cast padding. Recommendations vary as to the amount of padding to use, if any at all, and how it should be applied with no indication that there is any "best method."4 Ultimately, management of soft tissue injury caused by casts resulted in an increase in costs from 4% to 121% of the original surgery cost for these owners.

Malunion, Delayed Union, or Non-Union

Complications related to fracture healing most often result from inappropriate case selection. For example, external coaptation of a distal, radius and ulna fracture in a toy breed dog would be expected to have a high probability of nonunion due to high interfragmentary strain at the fracture site and poor intra- and extra-osseous blood supply to the healing fracture.3

Fracture Disease

Fracture disease refers to the complications that occur as a direct result of immobilization of the limb or decreased weight bearing of the injured leg. They include joint stiffness, muscle atrophy, muscle contracture and fibrosis and disuse osteoporosis associated with prolonged casting of a limb.1,2 While some of these effects may be reversible, particularly with physiotherapy, some permanent disability may remain particularly if immobilization occurs for more than four weeks. Fracture disease can be minimised or avoided by aiming for a fast return to weight bearing and avoiding unnecessary immobilisation by external coaptation. Some fractures suitable for external coaptation may also be suitable for minimal surgical intervention and external skeletal fixation (ESF). ESF preserves joint mobility, avoids the need for replacing casts that have been outgrown, or that been damaged (e.g., by being chewed or getting wet). ESF will often provide better immobilisation of fragments, giving better pain reduction and therefore better use of the leg.

Conclusion

Conservative management and external coaptation can be used successfully for management of fractures in both dogs and cats. However, attention should be paid to case selection with meticulous attention to technique, post-operative care and owner information in order to achieve the best results. Fractures that are not suitable for conservative treatment or external coaptation include articular fractures, displaced diaphyseal fractures and many fractures in older animals. Finally the use of non-surgical management of fractures can be considered for every fracture and in some cases it will be the optimal fracture management option; however, in many cases there are better options that will return the animal to normal function more quickly and with fewer complications.

References

1.  Dyce J. Conservative management of fractures. In: Coughlan AR, Miller A, eds. BSAVA Manual of Small Animal Fracture Repair and Management. Cheltenham, UK: British Small Animal Veterinary Association; 1998.

2.  Harasen G. Orthopedic therapy under wraps: The pros and cons of external coaptation. Can Vet J. 2012;53:679–680.

3.  Hamilton MH, Langley-Hobbs SJ. Use of the AO veterinary mini 'T'-plate for stabilization of distal radius and ulna fractures in toy breed dogs. Vet Comp Orthop Traumatol. 2005;18(1):18–25.

4.  Anderson DM, White RA. Ischemic bandage injuries: a case series and review of the literature. Vet Surg. 2000;29:488–498.

5.  Meeson RL, Davidson C, Arthurs GI. Soft-tissue injuries associated with cast application for distal limb orthopedic conditions. A retrospective study of sixty dogs and cats. Vet Comp Orthop Traumatol. 2011;24:126–131.

  

Speaker Information
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S. Langley-Hobbs
School of Veterinary Sciences
University of Bristol
Langford, Bristol, UK


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