In my opinion, complications that develop following management of fractures in small animal practice can be a humbling experience and clinical experience plays a major role in reducing the frequency of complications. No one wants complications to develop. Certainly not the pet owner. Dealing with disgruntled clients is stressful for veterinarians as there are often financial pressures, animal welfare concerns and the obvious issue of how to resolve the initial problem as well as the new one too. Exposure to a high volume of different fractures and styles of repair is invaluable in gaining the experience required to develop balanced judgment. There are many factors which impact decision-making and they all need to be considered before an approach is selected. I enjoy the ongoing challenge of fracture repair and attempt to learn from complications that develop and then to apply that knowledge to the benefit of future patients. Much of what I have learned has come from the past five years as a solo specialist in private practice in Australia seeing over 100 trauma cases annually.
In my opinion, poor judgment and technical error during surgery are the cause of the majority of complications. There are certainly some complications that you never considered would develop that surprise you but in general, the surgeon can improve and limit the number of problems through a better understanding of fracture biomechanics and experience with a wide variety of patients, fixation techniques and postoperative environments.
Complications of External Coaptation
Delayed union and non-union can result from a lack of adequate fracture stability. It is ideal to immobilize the joints above and below the fractured bone to reduce motion at the interface to a minimum. Clinicians should consider the patient's conformation as well as the location and bone fractured and think about how effective coaptation might be in effectively achieving bone splintage as apposed to limb splintage. In general, simple fracture configurations, with minimal displacement and located within the diaphysis in young patients can potentially be adequately splinted if they are distal to the elbow or stifle. I do not favor management of any humeral or femoral fractures with coaptation alone. Common fractures that can be confidently treated with coaptation include: isolated diaphyseal radial or ulnar fractures (not both), one, two or three metacarpal / tarsal fractures, minimally displaced tibial crest avulsions, greenstick fractures of the tibial diaphysis and some non-articular talus and tarsal bone fractures. Be aware that splints will not be as rigid as casting and used alone may not result in osseous union.
Pressure (rub sores) often develop at the level of prominent underlying structures such as bone. Patients may lick or start chewing at the dressing which may be a marker of underlying problems. I always encourage regular dressing changes to permit early detection of pressures sores--which in my opinion are always going to develop, it is just a matter of time. In some ways it's a race between fracture healing and the development of skin problems. There is an art involved in the application of dressings. Too much padding results in less stiffness and more interfragmentary motion; insufficient padding predisposes to the development of unwanted pressure between the stiff cast material and the underlying bone. Great care should be taken in certain areas: olecranon, accessory carpal bone and calcaneus. Continued bandaging is often required to achieve healing which presents problems when pressure sores become severe.
Interdigital dermatitis commonly develops associated with prolonged coaptation or after moisture permeates the dressing such as with urine seepage/ water immersion. I often apply a small amount of cotton wool between the digits (like a cigarette between the toes) to absorb interdigital moisture. If the ends of the length of cotton wool are long they can be incorporated in the dressing and this will limit the chances that they will prematurely dislodge. Simple patient management such as regular walks to encourage urination and use of water-proof outer layers can help.
Joint laxity and stiffness develop after prolonged coaptation esp. in higher motion joints that have been completely immobilized. Beware of the 'frozen' joint that is somewhat disastrous. I have seen a few acetabular fractures treated with internal fixation and an Ehmer sling develop marked periarticular fibrosis and dramatically reduced extension with a poor long term result. Excessive carpal extension is common in pups after coaptation but tends to be self-limiting with exercise. Toy breeds can quickly develop disuse osteoporosis.
Cast or splint breakage seems to correlate with extremely active patients and can result in inadequate fracture healing. I exclusively use fiberglass in several layers to achieve stiffness and prevent bending stress across the fracture interface. In my experience, few clients return to inform me that the fiberglass has in fact broken and to tell me that the splint is no longer effective! Regular checks are the best way to avoid prolonged periods of ineffective splint / cast application.
There are advantages of internal fixation or application of an external frame which eliminate the need for continued use of dressings. The limb can 'breathe' and many of the superficial problems can be avoided.
Poor Implant Selection
A fracture assessment score is a simple system that enables preoperative planning to consider both fracture biology as well as biomechanics. The concept is to systematically go through the steps of thinking about each of the variables associated with the case at hand so that the treatment plan is neither insufficient or excessive.
Patient factors include: breed, age, body condition score, level of activity, location and configuration of fracture/s, presence of concurrent injuries (polytrauma / osteoarthritis) and general health status.
Client factors include: ability to adequately confine their pet at home, presence of financial constraints, level of commitment to ongoing patient care (medications, physical therapy, hydrotherapy), presence of other pets in household, size of yard etc.
Surgeon factors include: training / experience in fracture repair, availability of instrumentation and implants, time constraints (Friday evening, too many consults) and level of support (inadequate / untrained support staff).
The fracture assessment score for a healthy 6mo old kitten living with two professional owners in a flat with a closed, transverse, minimally-displaced, diaphyseal tibial fracture is low meaning that the fracture is not of a high level of difficultly. Closed reduction and coaptation or use of an IM pin would likely suffice.
In contrast, the fracture assessment score for a diabetic, obese, 8 yo Newfoundland living with a single mother on a farm with two other active dogs and having an open, comminuted, articular distal femur fracture as well as a concurrent contralateral coxofemoral luxation is poor. This patient requires the best surgeon available to apply the most rigid yet minimally invasive construct to have a chance at acceptable fracture healing.
Obviously these two scenarios are extremes and all of the cases that present to us are somewhere in between. There are no right or wrong answers and many repair techniques can work for each fracture. Often you are better using an implant system that you are familiar and comfortable with rather than trying to use a ring fixator or interlocking nail because you knows it's the future of veterinary medicine. In my opinion, in most cases where there has been a loss of internal fixation and catastrophic failure, there has been an obvious error in the choice of size or application of an implant system. The most common mistakes include:
1. Solitary use of an IM pin
2. Use of cerclage wire that is too small in diameter
3. Use of an insufficient number of cerclage wires
4. Use of a bone plate without filling the central holes
5. Excessive plate size due to a lack of inventory
6. Use of a short plate with too few screws
7. Use of a plate that is too short relative to the length of the bone
The era of specialized implants in small animal orthopaedics has arrived. There are many companies that produce and advertise a wide range of fracture specific plates (pancarpal arthrodesis, tibiotarsal arthrodesis, acetabular plate, 'T' plates for distal radial fractures, supracondylar femoral fracture plates etc.). It can be hard to justify having a comprehensive range of implants available unless your practice services a high volume of trauma cases.
Delayed Union and Non-union
Vascular injury to the major fracture fragments or excessive removal of key periosteal attachments can lead to compromised bone healing across a fracture interface. In addition poor reduction or the presence of a bone defect at the fracture site allow fibrous tissue to develop in the place of osteoid. It can be impossible to measure the degree of vascular compromise or to know exactly how much soft tissue dissection will negatively influence fracture healing. In recent times, the orthopaedic fraternity has explored more 'biologic' approaches to fracture fixation utilizing closed repairs and intraoperative fluoroscopic assistance. The goal is to be mindful of the importance of periosteal blood supply and favor its preservation over achieving perfect anatomic fracture reconstruction. In some situations however, it is appropriate to open the fracture completely to allow accurate reconstruction of the bone column and achieve 'load-sharing' with the advantage of a reduced the risk of premature implant failure.
Cancellous autografting is available to aid fracture healing if there are concerns about bone defects or relatively avascular bone segments. The most common oversight is to not anticipate the possibility that a bone graft would be useful and not have a surgically prepared donor site available in higher complexity cases. I routinely clip the proximal humerus in geriatric patients with comminuted longbone fractures.
Successful management of non-unions requires a correct understanding of the cause of the non-union in order to rectify it. Simply replacing a broken plate or pin is not ideal. Often, the bone-implant construct has insufficient rigidity to enable a bridging callus to form and revision surgery is required to improve construct stiffness. The ends of the major fracture fragments can be debrided of fibrous tissue (which may involve a transverse osteotomy of the bone ends), the medullary canal opened with a reaming instrument, rigid fixation applied and a large volume of cancellous bone applied.
Rotational, angular and bowing deformities can result if the major fracture fragments heal with non-anatomic alignment. Minor deformities are well tolerated in pets, esp. discrepancies in length. Bowing deformities are tolerated best in the sagittal plane. Bowing in the mediolateral plane can predispose to non-uniform load distribution across joints and the development of degenerative changes.
The most common causes of rotational malunion are solitary use of smooth, poorly positioned or undersized intramedullary pins. The most significant longbone rotational malunion involves diaphyseal femoral fractures where the pull of the external hip rotator muscle group results in relative external rotation of the proximal fragment and excessive femoral neck anteversion. This leads to coxofemoral osteoarthritis. Malunion of articular fractures results in osteoarthritis. Careful articular reduction is best assessed with adequate exposure and visualization.
Muscle atrophy, cartilage degeneration, periarticular fibrosis and loss of joint mobility are the consequences of poor limb use or prolonged immobilization of a joint or limb. These problems can be avoided by allowing an early return to function. If fractures are treated early and with rigidity, patients have limited discomfort and have a higher chance of using the limb which maintains joint and muscular health. The most dramatic example of fracture disease involves the development of irreversible adhesions between the vastus intermedius and the exuberant fracture callus produced in comminuted distal femoral fractures in juvenile patients. This complication can lead to loss of limb use and require amputation. Prevention involves identification of 'at risk' patients and use of aggressive early stifle flexion exercises. Pin migration into a joint (e.g., trocar of IM pin passing into the stifle) causes pain and morbidity. This leads to direct cartilage injury but also limits limb use as well.
Wound Infection and Osteomyelitis
Prophylactic systemic antibiotics are effective in reducing the risks of postoperative infection. Use of protective dressings and restrictive head collars will help reduce the incidence of self-trauma. Elimination of dead space/seroma formation will also reduce the risks of wound infection.
Gross wound contamination may best be treated with open wound management prior to delayed primary closure. External skeletal fixation allows treatment of open wounds.
Deep infection of the soft tissue and /or bone may require surgical debridement and placement of drains. Implants can be removed once the bone has adequately healed.
Clinicians should be aware that the typical radiographic findings of infected bone are irregular, reactive periosteal proliferation and lysis. Avascular segments of cortical bone can persist and are termed sequestra. They appear static on serial radiographic evaluations with sharp well defined edges that indicate limited remodeling and a lack of incorporation. Often a draining tract can be seen to extend towards a sequestrum. These bone segments should be surgically removed and the adjacent fibrous tissue debrided using a curette.
Accurate assessment of distal limb and tail sensation prior to offering surgical repair is important to enable an accurate prognosis to be issued to pet owners. Displaced ileal, acetabular, sacral and caudal fractures have the highest incidence of sciatic nerve injury. These cases carry a poor prognosis if there is concurrent anal atony and limb flaccidity.
Iatrogenic radial nerve injury during humeral fracture repair is best avoided by early nerve identification and careful retraction. Injury to the median and ulnar nerve is not catastrophic. Protrusion of an IM pin from the proximal femur due to migration can result in transaction of the proximal sciatic nerve branches. Pins should be either countersunk or left long enough to protrude through the skin proximally.