Progression of cortical hypertrophy, subsidence and thigh pain after short curved fitmore femoral hip stem over 10 years.

backgroundShort femoral stems were introduced for total hip arthroplasty (THA) to preserve bone stock, increase proximal load transfer, and enable minimal invasive approaches. However, after implanting the short curved Fitmore hip stem, an increased occurrence of cortical hypertrophy (CH), cortical thinning (CT) and radiolucency (RL) was observed. There are few long-term data on the progression of CH with the Fitmore hip stem, and no data on other radiological parameters. Furthermore, the clinical relevance of these radiological parameters (e.g. for thigh pain) has not yet been investigated.

methods80 Fitmore hip stems were evaluated prospectively over 10-years. The main radiographic parameters were CH, CT, RL and subsidence. The clinical parameters were thigh pain, Oxford Hip Score and Harris Hip Score.

resultsThe rate of CH was 69% after 1 year, and 74% after 10 years. CH mainly appeared in Gruen Zones 2, 3, 5, and 6. CT was 65% after 1 year, and 80% after 10 years, mainly in Gruen Zones 6, 7, 8, 9, 12, and 13. RL was found in 58% of cases after 1 year and in 18% of cases after 10 years, primarily in Gruen Zones 1 and 8. Subsidence was 1.6 ± 1.6 mm after 1 year and 5.0 ± 3.1 mm after 10 years. The Oxford Hip Score increased from 22 to 43, the Harris Hip Score from 59 to 94. The prevalence of preoperative of thigh pain was 96%, dropping to 16% after 10 years. Over 10 years, the radiological parameters did not correlate with any of the clinical parameters.

conclusionsOver 10 years, the short curved Fitmore hip stem did not prevent proximal stress shielding and exhibited CH and CT. However, this had no clinical consequences and was not correlated with symptoms. Despite its primary press-fit fixation, we observed that, unlike other stems, the Fitmore hip stem did not settle to its final position after one year, but continued to subside over 10 years by a maximum of 5 mm.