Comparison of the 5-Year Outcomes Between Standard and Short Fit-and-Fill Stems in Japanese Populations.

BACKGROUND

Fit-and-fill stems are known to have excellent outcomes; however, severe stress shielding has been reported in Japanese populations. Short fit-and-fill stems were modified for Asians; however, there have been no previous reports of its outcome. In this study, we compared the 5-year (mean 68-month) outcomes of 2 fit-and-fill stems with different lengths (standard or short).

MATERIAL AND METHODS

We reviewed 100 total hip arthroplasties in each standard- or short-stem group. Radiographs were evaluated for femoral morphology, stress shielding, bone remodeling, and fixation. Clinical evaluation was performed using the Japanese Orthopaedic Association (JOA) scores.

RESULTS

There was no difference in the degree of stress shielding between the 2 groups. Significant differences were observed in radiolucent lines in zone 4 ( = .005) and cortical hypertrophy in zone 3 ( < .0001) and 5 ( = .048) between the 2 groups. The canal flare index ( < .0003), cortical index ( < .0003), height ( < .0345), and stem size ( < .0081) individually affected stress shielding in the standard-stem group. In contrast, the cortical index ( < .0107) was the only relative factor in the short-stem group. All stems were judged to have bone ingrowth. The JOA score improved significantly ( < .0001); however, there were no significant differences between the 2 groups.

CONCLUSION

The outcomes of both standard and short fit-and-fill stems were favorable. There were no significant differences in the stress shielding or JOA scores. Although there were a few differences in bone remodeling and factors affecting stress shielding, stem length reduction has been achieved without adverse effects with the Japanese femur.