Introduction

The objective of fracture repair is twofold: firstly to achieve clinical union of the fractured bone and secondly to achieve normal limb function. Any outcome that compromises either fracture healing or limb function is by definition a complication of the fracture repair.

Complications of fracture repair may be divided into two groups: those that directly affect bone healing and those that affect limb function. Fracture diseases are those complications that result in compromised function after the fracture has healed (e.g., muscle contracture). Complications that have a direct effect on bone healing include delayed union, malunion, nonunion, osteomyelitis, premature implant loosening, and implant failure.

All fracture repair surgery may be viewed as a race between fracture healing and implant failure. Surgery is successful when healing takes place before implant failure.

Fracture complications may occur for a variety of reasons:

 Violation of surgical principles

 Poor client compliance

 Poor patient compliance

 Compromised health status of the patient

 Defective implants

 Poor choice of implants/# stabilization method

Many complications of fracture repair are directly related to the surgery performed. It is critical to assess complications in order to resolve them but also to reduce the incidence of complications in future patients.

Surgical Principles

As with all surgery, basic principles are crucial. Halstead's surgical principles of atraumatic tissue handling, haemostasis, elimination of dead space, and asepsis must be adhered to. Failure to do this will result in unacceptably high complications rates.

Factors specific to fracture repair surgery include assessment of the biomechanical factors acting on the fracture, forces to be neutralized, implant selection and application, implant size, load sharing vs. non-load sharing, biological osteosynthesis, use of bone graft, etc.

All fractures and fracture patients need to be assessed and classified in order to make correct decisions regarding management of the fracture. A mechanical fracture assessment, biological fracture assessment, and a clinical fracture assessment should be performed in order to decide on the appropriate fracture repair method for that particular patient and fracture.

Mechanical fracture assessment includes factors such as fracture configuration (simple transverse vs. comminuted), multiple limb #s vs. single limb #s, weight and size of the patient etc. Biological assessment includes age, overall health status, soft-tissue trauma, cortical vs. cancellous bone, required surgical approach (open/extensive vs. closed/minimally invasive), etc. Clinical assessment takes into account patient and client compliance and requirements.

Fracture Complications

Fracture complications commonly seen in small animal orthopaedics include:

 Fracture disease (muscle contracture, muscle atrophy, reduced ROM, osteoporosis, and growth disturbances)

 Implant failure

 Osteomyelitis

 Complications of fracture healing (malunion, delayed union, and nonunion)

Fracture Disease

Immobilisation of a limb and its joints results in progressive structural, metabolic, and biomechanical changes. These include atrophy of muscle, bone, ligament, articular cartilage, and synovium. Atrophy of articular cartilage is particularly problematic as it may become progressive and irreversible. Risk factors for fracture disease include delayed union, nonunion, osteomyelitis, articular and periarticular fractures, extensive soft-tissue trauma, and prolonged immobilization and non-weight bearing.

Clinical signs of fracture disease include muscle atrophy, reduced ROM, pain on flexion and extension, joint laxity (especially young animals), reduced weight bearing or non-weight bearing, osteoporosis, and muscle contracture (e.g., quadriceps tie-down/contracture).

Muscle atrophy will start to occur within 3–5 days of non-weight bearing. Recovery will take 2–4 times as long as the atrophy took to occur. Disuse osteoporosis occurs secondary to non-weight bearing, reduced muscular activity, and prolonged immobilization. Young animals and those immobilized for greater than 3 months may have irreversible changes. Joint health and nutrition of the articular cartilage is dependent on weight bearing and motion. Prolonged immobilisation and non-weight bearing will result in degenerative changes within the joint as well as periarticular fibrosis and adhesions. Immobilisation for longer than 7 weeks will result in permanent changes. Immobilisation of joints in extension results in more damage than immobilization in flexion or normal anatomical angles.

Quadriceps contracture is a debilitating condition which results in hyperextension of the stifle. This condition is most likely in young animals with distal femur fractures, especially if there is extensive soft-tissue trauma and immobilization in extension. The prognosis for these animals is generally poor.

Important points to remember in order to reduce the risk of fracture disease:

 Stable fixation

 Early return to function/weight bearing

 Reduce time of immobilization

 Flexion rather than extension

 Use casts, etc. with extreme caution (avoid if possible)

 Physiotherapy/passive range of motion exercises

Implant Failure

Fatigue failure is the most common type of implant failure seen in veterinary orthopaedics and is usually due to incorrect application of implants. One should always assess forces to be neutralized, load sharing vs. non-load sharing repair, transcortical defects, etc. Augmenting the fracture repair can be considered (e.g., combining a plate and intramedullary pin or a "tie-in" configuration with an intramedullary pin and external skeletal fixation). Bone graft should be considered in order to speed up fracture repair in high-risk cases.

Osteomyelitis

Infection during bone healing is a major complication that may be encountered in fracture repair. Osteomyelitis may be bacterial or fungal. Bacterial osteomyelitis is the most common cause of osteomyelitis in veterinary orthopaedics. Osteomyelitis may be posttraumatic (open fractures) or postsurgical (contamination at surgery). Haematogenous spread of infection is also a possible cause of osteomyelitis. Risk factors for the development of osteomyelitis include significant bacterial contamination, necrotic tissue (bone and soft tissue), extensive soft-tissue trauma, presence of implants, haematoma formation, poor vascular supply, and instability of the fracture site. Infection in the presence of implants results in a biofilm formation which perpetuates infection and protects the bacteria from the host's immune system. It is for this reason that long-term resolution of osteomyelitis often requires that all implants be removed.

Osteomyelitis may predispose the fracture to delayed union or nonunion as the infection results in cortical resorption (lysis) and implant loosening, which then causes fracture instability and therefore compromised healing.

Clinical signs of osteomyelitis:

 Acute osteomyelitis

 Pain, swelling, pyrexia, draining sinus tracts

 Chronic osteomyelitis

 Lameness, pain, draining sinus tracts, muscle atrophy

Diagnosis of osteomyelitis is based on radiological appearance and results of microbiology (culture & sensitivity).

Treatment for osteomyelitis involves elimination of infection (debridement, drainage, obliterate dead space, and long-term appropriate antibiotics) and stabilization of the fracture. Infected fractures will heal in the face of infection, provided they are stable. Intramedullary pins should be avoided, if possible, in osteomyelitis cases. External skeletal fixation is ideal for fracture management in the face of infection as stability can be achieved while implants can be kept away from the fracture site. Plate and screw fixation is acceptable as it provides rigid fracture fixation. All implants should be removed as soon as clinical union is achieved.

Delayed Union

Delayed union is when a fracture is taking longer to heal than would be expected for a fracture of that nature in that situation. It may be difficult at times to distinguish between a delayed union and a nonunion.

Nonunion

Nonunion is defined as a fracture that has not healed within the expected time and is unlikely to heal without intervention. It is important to distinguish viable (hypertrophic, oligotrophic) from non-viable nonunions (dystrophic, necrotic, defect, and atrophic). Potential causes of nonunions include movement at the fracture site, large fracture gap, high degree of comminution, poor vascular supply, excessive implants, poor surgical technique, and infection.

Treatment of nonunions involves rigid stabilization and compression if possible, cancellous bone grafting/BMP, elimination of infection, and opening of the medullary cavity.

Malunion

Malunion is fracture healing with poor anatomical alignment. The malunion may result in shortening, angular deformities, rotational deformities, or a combination of all three. Malunions may also be classified as functional or non-functional malunions. Generally speaking, only non-functional malunions require treatment. Treatment for malunions requires corrective osteotomies/ostectomies. Common causes of malunions include untreated fractures, closed reduction, inaccurate open reduction, and an inability to visualize the entire limb during surgery.

Conclusion

Complications of fracture repair can have major influence on patient well-being, recovery and quality of life. Careful fracture assessment, fracture planning, and good surgical technique and application of the fixation method will reduce the incidence of fracture complications. Unfortunately, a large percentage of complications are due to poor surgical technique, poor application of the fixation, or poor assessment of the original fracture.