Femoral fracture

What it is

A break in the continuity of the femur. The usual cause is high-energy trauma (road traffic accident, fall from a height, gunshot), although pathological fractures also occur in bone weakened by a tumour or metabolic disease. The femur is completely surrounded by muscle, which has two consequences: the fracture comes with a large haematoma and displacement from muscle pull, and it cannot be immobilised from outside with bandages or splints.

Who it affects

Any dog can suffer one, but young animals predominate, being more active and more often outdoors. In puppies with open physes the weakest zone is not the shaft but the growth cartilage, which is why physeal fractures are typical in them.

Classification by location

• Proximal: capital physeal fracture (slipping of the epiphysis of the head), femoral neck, trochanteric and subtrochanteric fractures.
• Diaphyseal: the most numerous. They are described by third (proximal, middle, distal) and by configuration: transverse, oblique, spiral or comminuted; closed or open.
• Distal: supracondylar, condylar and distal physeal fractures, the most frequent physeal fracture site in the dog.

Physeal fractures (Salter-Harris)

In the growing dog the Salter-Harris classification is used: type I through the physis; type II through the physis with a metaphyseal fragment (the most common in the distal femur); type III extending into the epiphysis; type IV through epiphysis, physis and metaphysis; type V by crushing of the physis. Capital physeal fractures are usually type I. Any of them can cause premature physeal closure, with shortening or angular deformity of the limb.

Clinical signs and diagnosis

Non-weight-bearing lameness, thigh swelling, pain, crepitus and apparent shortening of the limb. Before focusing on the fracture the patient must be stabilised and thoracic, abdominal and urinary tract injuries ruled out, as they are common in the same accident. Two orthogonal radiographic views including the hip and the stifle are needed; in puppies a capital physeal fracture can be missed on the standard ventrodorsal view and is better seen on the frog-leg view.

Treatment

Treatment is almost always surgical. The options depend on location, configuration, patient size and age:

• Shaft: intramedullary pin with cerclage wires in long oblique fractures; intramedullary pin combined with a plate ("plate-rod") or plate alone in comminuted fractures; interlocking nail; external fixator in configurations limited by the muscle mass.
• Distal physis: crossed pins or Rush pins, crossing the physis as little as possible.
• Capital physis and neck: parallel pins or a compression screw; when reconstruction is not feasible, femoral head and neck excision or hip replacement.

Notable complications are quadriceps contracture in puppies with distal fractures immobilised for too long, sciatic nerve injury when pins are introduced through the trochanteric fossa, and malunion or non-union.

In the cat

The femur is one of the long bones cats fracture most often, mainly in road traffic accidents and, to a lesser extent, in falls from height. Concurrent injuries of the pelvis, thorax and bladder are common.

• Anatomy: the feline femur is relatively straight and has a medullary canal of fairly uniform diameter, which makes intramedullary pins, interlocking nails and pin–plate combinations easier to use; small plates and screws suited to its bone are available.
• Capital physeal fractures: besides traumatic fractures, young, neutered, overweight male cats develop spontaneous slipping of the capital epiphysis without trauma (femoral capital physeal dysplasia).
• Irreparable proximal fractures: femoral head and neck excision arthroplasty gives very good functional results in cats because of their low body weight.

Healing is usually good, although non-union is possible in poorly stabilised fractures. Quadriceps contracture after distal fractures in immobilised kittens has also been described, so prolonged external immobilisation is avoided.

Key studies in the cat

• Könning et al. (2013), 106 feline diaphyseal femoral fractures repaired with an external fixator (30), a plate (20) or a plate-rod construct (56). All methods achieved healing with no difference in time to union. The external fixator had the most complications overall but the fewest major ones, and the plate-rod construct had the fewest complications overall. It is retrospective and the method was not randomised.
• Marturello et al. (2021), a prospective study of 30 fractures in 29 cats (53.3% femoral) treated with an angle-stable interlocking nail. Mean time to clinical union was 7.2 weeks, all cats regained full limb function and there were no major complications. There is no control group.
• Mund et al. (2023), 67 cats (48 femurs) treated with a 3.5 mm titanium interlocking nail. Complications occurred in 11 of 67 fractures, major in 8 (mostly screw or nail breakage), and were associated with fracture type.
• Bondonny et al. (2024), 31 cats with Salter-Harris type I and II distal femoral physeal fractures treated with an intramedullary pin and an antirotational pin. All healed within 6 to 8 weeks, 30 of 31 regained full function and there was a single complication.
• Rubinos and Meeson (2022), 36 traumatic physeal fractures in 34 cats, excluding the proximal femoral physis. The distal femur was the most common site (17), and some cats were adults with delayed physeal closure. After repair, physeal closure was recorded in 23 fractures, premature in 15, without apparent consequence, and the outcome was good in 28 fractures.