Early clinical experience with a metaphyseal loading implant: Why have a stem?

This is a prospective cohort study of patients undergoing total hip replacement using an uncemented, proximally coated stem with a short tapered distal stem. Patients with a minimum of 24 months of clinical and radiological follow-up were included in this study. There were 18 males and 34 females. Average age at surgery was 40 years. The diagnoses included developmental dysplasia of the hip in 20 patients, osteoarthritis in 15, avascular necrosis of the femoral head in nine, and inflammatory arthritis in three. Average follow-up was 46 months (range 25-78). There was no evidence of subsidence of any stem at the final follow-up. Interface buttressing was observed in 52 patients on the AP view and in 32 on the lateral view. This was seen in Gruen zones 1, 7, 8 and 14. Heterotopic ossification was seen in 15 patients. Distal cortical hypertrophy was seen in three patients. Three patients had one episode of dislocation and two patients had superficial wound infection. None of the hips has been revised and there was no radiological evidence of aseptic loosening. The high percentage of patients exhibiting condensation of the bone and interface buttressing at the lower reaches of the metaphysis suggest the objective of proximal loading is being achieved. We believe that early stability and durable biological fixation can be achieved by this cementless implant, in which the stem is designed to avoid any contact with the diaphyseal cortex.