The membrane present at the bone-cement interface was retrieved from
twenty patients with a loose, non-septic failed total hip replacement at a
site clearly remote from the pseudocapsule that reformed postoperatively.
The orientation of the membrane was carefully marked to identify the
surface in contact with cement. The membrane was studied histologically,
histochemically, by cell culture, by organ culture, and by assessment of
its ability to synthesize prostaglandin E2 and collagenase. This membrane,
rather than being a nondescript so-called fibrous membrane, has the
histological and histochemical characteristics of a synovial-like lining.
The synovial-like cells are adjacent to the cement layer. Deep to them
macrophages predominate. Inflammatory cells are absent. Cell cultures of
this membrane contain stellate cells similar to those found in cell
cultures of normal and rheumatoid synovial tissue. This membrane has the
capacity to produce large amounts of prostaglandin E2 and collagenase.
Clinical Relevance: This transformation of tissue at the bone-cement
interface in patients with a non-septic, loose total hip component to a
synovial-like tissue with the capacity to generate prostaglandin E2 and
collagenase may explain the progressive lysis of bone that is seen in some
patients with loose cemented total joint implants. Loosening of the
component may be a stimulus to the synthetic activity of this tissue, which
leads to further resorption of bone. Understanding and the possibility of
pharmacological control of this membrane may contribute to improved
duration of total joint implants.