Paget’s disease of the hip

14 Oct
2011

Paget's disease of the hip

Introduction

First described by Sir James Paget in 1876, the exact etiolo­gy of the disease remains unknown today. Genetic predispo­sition, slow virus or bacterial infection has been postulated as possible causes. Although its incidence may be declining, Paget’s disease may affect up to 3.5 per cent of persons older than forty-five years. The pelvis and the femur are the areas of the skeleton most commonly involved and may be affected in up to eighty per cent of patients with Paget’s disease. Paget’s disease is a localized disorder of the bone marked by increased bone resorption, bone formation and remodeling, which may lead to major deformity and al­tered joint mechanics. These deformities, alterations in bone quality, and the older age of the pagetoid patients may all contribute to the development of severe degenerative joint disease of the hip.

Pathophysiology

The metabolic hyperactivity is the main feature of Paget’s dis­ease. Excessive activity of osteoclasts results in resorption of the bone, leading to creation of voids and cavities in the bone. The physiological compensatory mechanism for repair results in lying down of fibrotic tissue in theses cavities and even new bone by osteoblasts. There is a high degree of vascularity in the pagetoid bone due to the increased metabolic activity. The disruption of the architecture of the bone occurring as a result of excessive osteoclast activity leads to mechanical weakening of the cortex and creation of microfractures. The increased bone resorption and the excessive metabolic activity as well as microfractures are all thought to be the cause of pain in pa­tients with underlying Paget’s disease of the bone. The newly formed bone matrix remains non-organized and lacks the mechanical strength of normal bone. The continued process of excessive activity and creation of microfractures re­sult in deformities with resultant change in the biomechanical milieu of the adjacent joints. The latter combined with the old age predispose these patients to arthritis. Femur is one of the most commonly affected bones. The deformities observed around the hip in patients with Paget’s disease includes coxa vara, femoral bowing with enlargement of the intramedullary canal, and protrusio acetabuli.

Diagnosis

The radiographs of affected pagetoid bone have a classical ap­pearance (Figure 1). There is combination of sclerosis and radiolucencies of the affected cortex. Disruption of the normal ar­chitecture is apparent with loss of tension bands in the proxi­mal femur and the periacetabular region. The pagetoid bone appears capacious and disorganized on cross sectional studies such as CT scan and MRI. Bone scan shows area of dense up­take in pagetoid bone because of the underlying high metabolic activity.

Figure 1 - Anteroposterior radiograph of a patient with Paget’s diseaseFigure 1 – Anteroposterior radiograph of a patient with Paget’s disease. The loss of normal trabecular pattern of the bone, widening of the canal, and the ensuing deformity is all apparent (A). Intraoperative osteotomy had to be performed to allow insertion of femoral prosthesis (B).

Serological markers can also be helpful in diagnosis of Paget’s disease. The bone specific alkaline phosphatase is elevated. The level of bone breakdown products such as pyrindolines and hydroxyproline are also high. Source your medication needs online. cialis professional

Patients with Paget’s disease usually present with severe pain and may exhibit gross deformities of the long bones. The flat bones particularly that of skull may also be affected resulting in frontal bossing. The vertebra, when affected, becomes disrupt­ed with narrowing of the spinal canal. Symptoms of spinal stenosis are not uncommon in these patients. In addition loss of hearing, affected inner ear bones, and high output cardiac failure may be seen.

 

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