Abstract
Background
Composite screws of uncalcined and unsintered hydroxyapatite (HA) particles and poly-l-lactide (PLLA) were developed as completely absorbable bone fixation devices. So far the durability of HA-PLLA composite screws is unclear when used for the fixation of acetabular bone graft in total hip arthroplasty under full-weight conditions. We have used this type of screw for the fixation of acetabular bone graft in cemented or reverse-hybrid total hip arthroplasty since 2003. Hence, we conducted a follow-up study to assess the safety and efficacy of these screws when used for cemented socket fixation.
Methods
During 2003–2009, HA-PLLA composite screws were used for fixation of acetabular bone graft in cemented or reverse-hybrid primary THA in 106 patients (114 cases). All the THAs were performed through direct lateral approaches, and postoperative gait exercise with full weight bearing usually started two days after surgery. One patient died of an unrelated disease and seven patients were lost to follow-up within 5 years. Finally, 98 patients (106 cases) were followed up for over 5 years and were reviewed retrospectively (follow-up rate, 93%). Radiographic loosening of the acetabular component was assessed according to the criteria of Hodgkinson et al., and the radiolucent line around the socket was evaluated in all zones, as described by DeLee and Charnley.
Results
The patient population comprised 10 men and 88 women with a mean age of 60.3 years (range, 41–81 years) at the time of surgery. The mean follow-up period was 7.6 years (range, 5–11 years). The original diagnosis for primary THA was secondary osteoarthritis in 97 cases and high hip dislocation in nine cases. No patient in this series required revision surgery, and no radiographical loosening occurred during the follow-up period. Grafted bone union was confirmed in all cases, and no apparent osteolysis around the cemented socket or composite screws was detected. Configurations of the HA-PLLA composite screws appeared obscure on radiographs at 5 years after surgery, and only osteosclerotic traces remained in the screw positions at the final follow-up. This finding was consistent in this series. The screw heads sometimes appeared to be broken with absorption within 3 years of surgery, and the remnants were identified in situ at the final follow up. Kaplan–Meier survival analyses with socket revision surgery for any reason, socket loosening, and appearance of a radiolucent line >1 mm in any zone as the endpoints yielded survival rates of 100%, 100%, and 86.8% at 5 years, and 100%, 100%, and 85.8% at 10 years, respectively.
Conclusion
This absorbable screw seems to have no negative effects on the mid-term clinical results of cemented socket fixation.
