Abstract
OBJECTIVE OF THE STUDY
The objective of this study is to establish the short-term and medium-term clinical and radiological results with the cementless three-dimensional Vektor-Titan stem (Figure 1). This three-dimensional tapered stem has been given to evaluate the extent to which the implant design achieves an optimal proximal anchoring property, thus reducing bone atrophy and avoiding stress shielding in the proximal femur.
MATERIAL AND METHODS
From July, 2004, to May, 2010, 80 Vektor-Titan stems were implanted in 75 patients in the Shinonoi General Hospital. Forty two patients (42 hips) with femoral neck fracture (FNF) and one patients (2 hips) with aseptic necrosis of the femoral head (ANF) were died or impossible to come outpatient clinic for postoperative follow-up due to serious illness not related to the surgery. Of 32 patients (36 hips) with a minimum two-year follow-up, 23 patients (23 hips) with FNF and 9 patients (13 hips) with ANF were analyzed in the study. Demographics and clinical outcomes of the patients were shown in Table 1. The results were evaluated clinically using Japanese Orthopedic Association (JOA) Scores and radiologically within the scope of a retrospective cohort study.
RESULTS
One patient had intraoperative femoral shaft fracture and healed by conservative treatment. There was no radiolucent zones around stems evaluated by Gruen's zonal analyses. There was no cases of loosening or postoperative infection. Although signs of bone atrophy were found in the proximal femur and the trochanters in 13 hips (FNF group) and 11 hips (ANF group) (66.7âζŠ% of all cases), bone structure was radiologically normal without stress shielding. On the contrary, there was evidence of an even denser bone structure, such as trabeculae, at the tip of the stem and the lateral implant fixation within the greater trochanter. These findings remained unchanged over observation periods. Clinically, JOA Scores were improved significantly in the ANF group (Table 1).
DISCUSSION AND CONCLUSIONS
The cementless Vektor-Titan stem is made of Ti6AI7Nb, has got the shape of a straight three-dimensional cone. It has a high proximal volume in the form of a three-dimensional taper with longitudinal ribs. This design achieves strong primary fixation in the proximal metaphysis. Radiologically, newly formed trabeculae toward to the stem were indicative of direct biological fixation at the bone-implant interface. Short-term and medium-term results with the cementless Vektor-Titan stem show no implant loosening with stable metaphyseal fixation and preservation of bone structure in the proximal femur and the absence of radiolucent zones around the stem.
