Legg-Calvé-Perthes disease (LCPD)

Legg-Calvé-Perthes disease (LCPD) is a common developmental orthopedic disease that affects almost exclusively young small breed dogs. Some of the overrepresented breeds that are prone to this condition are Yorkshire Terriers, WHWT, Miniature Pinschers, and Miniature Poodles. 
Legg-Calvé-Perthes disease (LCPD) is condition where the blood supply to the femoral head is interrupted leading to bone death (also described as an ischemic necrosis of the femoral head) resulting in an incongruous and malformed coxo-femoral joint.
It is a non-inflammatory local ischemia that leads to slow necrosis (over weeks and even months), with subsequent deformation of the femoral head and neck.
The following synonyms are sometimes used to describe Legg Calvé Perthes disease: Perthes’ disease, avascular necrosis of the femoral, aseptic necrosis of the femoral head, osteochondritis of the femoral head, coxa plana and idiopathic osteosis.

Etiology
A specific etiology remains unknown. Some of the cited causes are vascular origin, anatomic conformation, increased capsular pressure and hereditary factors. Breed susceptibility may suggest a genetic component in the disease etiology. no sexual predisposition has been observed. Some studies suggest that the peculiarities of the vascularization of proximal femoral epiphysis in puppies may clarify the frequency observed in young dogs.

Clinical signs
The disease is progressive, and symptoms usually get worse over time. Common signs vary from mild & intermittent to non-weightbearing lameness, pain on palpation and manipulation in the hip joint, muscle atrophy and reduced movement in the affected leg.  Symptoms usually start at an early stage of the disease, before radiological signs are evident.

Diagnosis
Diagnosis is made by signalment (young small and toy breeds), physical examination, radiographs, and possibly other imaging techniques (CT scan for example). Since radiographic signs appear at a later stage, the more the disease progresses, the easier is the diagnosis on x-ray.
Radiographic findings depend on the disease stage and include decreased bone density  close to the epiphyseal line, femoral head flattening, osteophytes and eventually fragmentation of the femoral head.

Treatment
Treatment can be conservative or surgical.
Conservative treatment may include weight management, rest, balanced diet and pain medication for at least 4-8 weeks. Some studies suggest intra-articular injections of autologous platelet concentrate as treatment for LCPD. The effectiveness of the conservative treatment ranges from 18 to 25%.
Surgical treatment is the most common option and consist in excisional arthroplasty of the head and femoral neck, also known as FHNO. In other cases, total hip replacement surgery can be taken into consideration.

Prognosis
LCPD generally has good prognosis, even though surgery is the treatment of choice and requires physical rehabilitation in the post-operative period. The prognosis depends on the severity of the condition and the effectiveness of treatment. There are generally a satisfactory functional results in toy breed dogs. Slow recovery is frequent in chronic cases and is related to muscle hypomiotrophy.

Sources:

Aguado E, Goyenvalle E. Legg Calvé Perthes disease in the dog. Morphologie. 2021 Jun;105(349):143-147.
Parra E, Vergara A, Silva RF. Autologous Platelet Concentrates as Treatment for Avascular Necrosis of Femoral Head in a Dog. Top Companion Anim Med. 2017 Mar;32(1):31-35
Launder WJ, Hungerford DS, Jones LH. Hemodynamics of the femoral head. J Bone Joint Surg Am. 1981 Mar;63(3):442-8.