Porous tantalum rod implantation is associated with low survival rates in patients with type C2 osteonecrosis of the femoral head but has no effect on the clinical outcome of conversion total hip arthroplasty: a retrospective study with an average 8-year follow-up.

BACKGROUND

Our study aimed to investigate the clinical outcomes and survival rates following porous tantalum rod surgery (PTRS) and conversion total hip arthroplasty (THA) subsequent to failed PTRS.

METHODS

A total of 38 subjects (40 hips) with osteonecrosis of the femoral head (ONFH) were included in this retrospective study between January 2008 and December 2011. All subjects were evaluated before surgery by using the Association Research Circulation Osseous (ARCO) classification system, the Japan Investigation Committee (JIC) classification and the Harris hip score (HHS). The endpoint of this study was set as final follow-up (including the survival time of PTRS and conversion THA). The rates of radiological progression were also evaluated. Patients who received conversion THA were further followed and compared to a control group of 58 patients with ONFH who underwent primary THA.

RESULTS

The mean follow-up time was 120.7 ± 9.2 (range, 104-143) months, and the overall survival rate was 75% at 96 months (ARCO stage II: 81.5%; stage III: 38.5%; JIC type C1: 83.3%; C2: 30%). The HHS before surgery was 59 (55-61), in contrast to 94 (91-96) at 96 months follow-up (P < 0.01). HHS in stage III show a significant poorer result compared to stage II at 24 months. HHS in Type C2 group show no significant difference compared to HHS before surgery at 24 and 60 months follow up (P = 0.91, P = 0.30). Twelve hips requiring secondary THA were followed for 66.9 ± 31.7 months, and control hips that underwent primary THA was followed for 75.4 ± 14.9 months. The HHS in the conversion group was 89 (86-93) and that in the primary THA group was 92 (79-95, P = 0.09) at the 5-year follow-up.

CONCLUSION

In the mid-term follow-up, porous tantalum implants showed an encouraging survival rate in symptomatic patients in early stages (ARCO stage II) or with limited necrotic lesions (JIC type C1). In addition, our results did not demonstrated any difference between primary THA and conversion THA.