Treatment Experience of Femoral Head Necrosis in Poodles

Femoral head necrosis (FHN), also known as avascular necrosis of the femoral head or aseptic necrosis of the femoral head, is a debilitating condition primarily caused by impaired blood flow to the femoral head, leading to osteonecrosis. This condition exhibits a high incidence in small-breed dogs, with the Poodle being a particularly susceptible breed. This case report details the successful treatment of a typical case of FHN in a Standard Poodle.

I. Case Presentation

The patient was a Standard Poodle with a previously healthy history, exhibiting normal appetite and demeanor, and maintained on a commercial dog food diet. One month prior to presentation, the owner noted a decreased willingness to exercise; the dog would stop during walks after a short distance. Seven days prior to admission, the dog displayed lameness in the left hind leg, refusing to bear weight on it. The affected leg appeared visibly thinner than the right hind leg, indicative of mild muscle atrophy. (See Figure 1 & 2 – Note: Figures are not included in this text-based response. In a published article, these would be appropriately placed.)

II. Examination and Diagnosis

1. Clinical Examination: The dog presented with a temperature of 38.5°C, a heart rate of 75 bpm, and a respiratory rate of 30 bpm. Mucous membranes were moist, and the dog’s overall demeanor remained normal. The left hind leg was held up, showing lameness and significant pain upon palpation. Muscle atrophy was evident, being noticeably more pronounced on the affected side.

2. Laboratory Examination: Radiographic examination revealed an irregular surface of the left femoral head, inconsistent density at the distal epiphysis, and the disappearance of the growth plate structure. Asymmetry between the left and right femoral heads was also observed. Routine blood work (complete blood count and serum biochemistry profile) showed no abnormalities. Based on the clinical signs and radiographic findings, a diagnosis of avascular necrosis of the femoral head was made. (See Figure 3 – Note: Figures are not included in this text-based response. In a published article, these would be appropriately placed.)

III. Surgical Treatment

After consultation with the owner, surgical intervention was deemed necessary. The dog was placed in lateral recumbency with the affected limb positioned upward. Atropine was administered subcutaneously, followed by propofol induction anesthesia 15 minutes later. Endotracheal intubation was performed, and isoflurane inhalational anesthesia was maintained throughout the procedure. Standard surgical preparation, including hair removal, disinfection, and draping, was performed.

A surgical incision was made on the anterolateral aspect of the thigh, dissecting through the tensor fasciae latae and the intermuscular fascia between the biceps femoris. The vastus lateralis and rectus femoris muscles were bluntly dissected and retracted to expose the hip joint capsule. The hip joint capsule was incised, and the ligamentum teres was severed. The femoral head was carefully mobilized, and any surrounding tissue was meticulously separated. A hole was drilled into the femoral neck near the base of the femoral head. A Kirschner wire was inserted, and the femoral neck was osteotomized along the wire using an osteotome. The cut end was smoothed, and the joint capsule was closed. The muscles and subcutaneous tissues were sutured layer by layer, followed by skin closure. (See Figure 4 – Note: Figures are not included in this text-based response. In a published article, these would be appropriately placed.)

Post-operatively, the limb was immobilized using a suspension bandage for 7 days. Antibiotics and analgesics were administered. Weight-bearing on the affected limb was allowed on day 7, gradually increasing the frequency of use daily. The owner was instructed to perform regular muscle massage and passive range-of-motion exercises. Suture removal was performed on day 9, and the dog was discharged. A follow-up examination at two weeks post-surgery revealed significant improvement, with minimal lameness observed.

IV. Discussion

1. Etiology and Pathogenesis of Femoral Head Necrosis:

The blood supply to the femoral head is derived from the ligamentum teres artery, the capsular arteries, and the medullary nutrient arteries of the femoral neck. The anatomical characteristics of these vessels result in a relatively poor blood supply to the bone. Any factor that compromises these vessels can easily lead to interruption of blood flow, causing local circulatory disturbances and resulting in avascular necrosis of the femoral head.

Traumatic FHN can occur due to various injuries causing disruption of the femoral head blood supply. Given the limited collateral circulation in this area, vascular interruption readily leads to avascular necrosis. This is often seen in femoral neck fractures and hip dislocations. Even trauma insufficient to cause a fracture can still compromise blood supply and cause FHN.

Non-traumatic FHN has a multifactorial etiology, including long-term corticosteroid use, connective tissue diseases, hematologic disorders, and fat embolism. The exact pathogenesis of non-traumatic FHN remains incompletely understood.

2. Risk Factors and Epidemiology:

FHN has been linked to trauma, transient synovitis, abnormal growth and development, endocrine imbalances, immune deficiencies, genetics, and environmental factors. The precise etiology and pathogenesis remain unclear. Small breeds are disproportionately affected, with Poodles, Miniature Schnauzers, Cairn Terriers, West Highland White Terriers, Manchester Terriers, Yorkshire Terriers, and Chihuahuas being commonly reported. The incidence is similar in male and female dogs, typically presenting between 3 and 13 months of age, with a peak incidence at 6–7 months. Bilateral involvement occurs in 10–17% of cases. At presentation, the disease duration often exceeds two weeks, sometimes exceeding one month.

3. Treatment Options:

Femoral head and neck excision (FHO) is currently the most effective treatment for canine FHN, relieving pain and facilitating the formation of a pseudoarthrosis that allows for weight-bearing and functional recovery. Conservative treatment, while able to alleviate pain, offers limited functional improvement. Early surgical intervention is crucial to prevent muscle atrophy, which hinders post-operative rehabilitation. Early weight-bearing and aggressive physical therapy are essential for optimal outcomes. In cases of bilateral FHN, the procedures should be staggered, typically 30–45 days apart. (See Figure 5 – Note: Figures are not included in this text-based response. In a published article, these would be appropriately placed.) Conservative management with analgesics may be considered in mild cases or when surgery is contraindicated due to underlying health issues. However, this approach primarily provides temporary pain relief and does not address the underlying cause. Definitive treatment remains surgical removal of the affected femoral head.

This case highlights the successful surgical management of FHN in a Poodle. Early diagnosis, prompt surgical intervention, and dedicated post-operative rehabilitation are paramount for optimal patient outcome and return to a good quality of life. Further research into the etiology and pathogenesis of FHN is warranted to improve preventative strategies and refine treatment protocols.