A long term histological analysis of effect of interposed hydroxyapatite between bone and bone cement in THA and TKA

The standard cementing technique for total hip and knee arthroplasty (THA, TKA) was modified by interposing osteoconductive porous polycrystalline hydroxyapatite (HA) granules at the cement-bone interface to augment cement-bone bonding. Twenty-one specimens from the acetabulum and two specimens from the femur containing well-fixed bone-cement interface were retrieved five months to twenty-two years after THA and TKA with an interface bioactive bone cement technique. Histological findings were evaluated in terms of the retrieved sites, the interval between index operation and revision, patient age at retrieval and bone pathology. Dense bone ingrowth was observed in all specimens retrieved from the superior wall of the acetabulum. Cancellous bone ingrowth was observed in specimens retrieved from the infero-medial wall of the acetabulum. Connective tissue interposition and osteolysis were observed at the sites where hydroxyapatite granules were absent. Findings of bone ingrowth for the HA interposed retrievals were similar regardless of the interval between index operation and revision, patient age at retrieval, and bone pathology. Longer survivability of the bone-cement bonding was attributed more to the interposed HA granules. In spite of various degrees of aging, postmenopausal osteoporosis, and pathological bone condition the histological findings were not affected by the bone pathology. There was long-term direct contact between the bone and hydroxyapatite granules. Thus, the interface bioactive bone cement technique can ensure longevity of bone-cement bonding even after the onset of osteoporosis and for pathological bone conditions.