Is early migration enough to explain late clinical loosening of hip prostheses?

Abstract

Prosthetic loosening has been debated for decades, both in terms of the timing and nature of the triggering events. Multiple radiostereometric studies of hip prostheses have now shown that early migration poses a risk of future clinical failure, but is this enough to explain late clinical loosening?To answer this question, the progression of loosening from initiation to radiographic detection is described; and the need for explanations other than early prosthetic loosening is analysed, such as stress-shielding, particle disease, and metal sensitivity.Much evidence indicates that prosthetic loosening has already been initiated during or shortly after the surgery, and that the subsequent progression of loosening is affected by biomechanical factors, fluid pressure fluctuations and inflammatory responses to necrotic cells and cell fragments, i.e. the concept of late loosening appears to be a misinterpretation of late-detected loosening.Clinical implications: atraumatic surgery and initial prosthetic stability are crucial in ensuring low risk of prosthetic loosening. Cite this article: EFORT Open Rev 2020;5:113-117. DOI: 10.1302/2058-5241.5.190014.

Keywords: periprosthetic osteolysis; prosthetic loosening; radiostereometric analysis.

Fig. 1

Cranial migration of a migrating acetabular component studied using RSA at close intervals during the first year following arthroplasty. Note. From Acta Orthop Scand with permission.

Fig. 2

Cranial migration of the acetabular component (above) and distal migration of the head of the femoral component (below) followed by RSA from six months postoperatively until the revision after 12 years. The acetabular component was found to be loose in an eroded cavity and surrounded by a thick layer of dense fibrous connective tissue. Note. From Arch Orthop Trauma Surg with permission.

Fig. 3

Drawing to show how prosthetic micromovements (arrows) pump joint fluid (dashed arrows) under high pressure from the gap between the stem and the cement through a defect in the cement mantle. The pressure waves may devitalize the adjacent bone tissue, which is resorbed, thereby causing focal femoral osteolysis. Note. From Acta Orthop with permission.