ANATOMICAL LARGE FEMORAL HEADS: EARLY COMPLICATIONS AND MID TERM RESULTS

Abstract

Purpose: mechanical complications such as malrestoration of hip anatomy still impede surgical results and patient satisfaction after THA. Anatomical femoral «mega-heads» are a novel approach which enables a surgeon to use a large diameter metal on metal implant to restore hip anatomy. Ability to place femoral head eccentrically on the femoral taper results in possible anteversion, retroversion, offset and lengthening. Our hypothesis is that use of this device will result in more accurate anatomical restoration and clinical results. Methods: 64 anatomical mega-head arthroplasties were evaluated. Preoperative planning was done in order to determine the desired position of the head, restore the anatomy and avoid leg lengthening. Patients were observed at an average of 50-months for both subjective and objective outcomes. Radiograph analysis assessed anatomical restoration. Results: 51 of the 64 hips were available for follow up. In 35 the head was placed eccentrically. In 20 the positioning was inferior, 6 — posterior, 3 — anterior, 1 — superior, and 4 inferior and posterior. Harris Hip and SF-36 scores improved significantly (P < 0.001). Mean radiographic limb and offset discrepancy were 0.1 and 0.01mm respectively. Six patients (11.7 %) underwent revision surgery; elevated metal ion levels and pseudotumor (3), acetabular component loosening (2), and unexplained hip pain (1). Conclusions: The novel anatomical femoral mega-head allows versatility in restoration of normal hip anatomy. Mid-term follow-up showed a higher than anticipated rate of complications for this cup design and reduced longevity of the implant. Novel ways need to be explored to allow such versatility in restoring hip anatomy.