What is the fate of the neck after a collum femoris preserving prosthesis? a nineteen years single center experience.

PURPOSE: The aim of our study is to evaluate long-term outcomes from a cohort of patients treated with collum femoris preserving (CFP) stem correlating neck resorption with comorbidities, clinical outcomes, and complications.

METHODS: One hundred seventy-six patients (194 hips) were retrospectively reviewed with a minimum follow-up (f.u.) of ten years. Demographic and surgical data were collected. Clinical and radiological evaluation was performed at the last follow up. We calculated a neck resorption ratio (NRR) for each patient. Main complications were recorded. A p-value of <0.05 was considered significant.

RESULTS: The mean Harris hip score (HHS) was 89.1 ± 5.7. The mean visual analogue scale (VAS) and Oxford hip score (OHS) values were 1.1 ± 1 and 41.3 ± 5.1, respectively. The mean leg length discrepancy was 1.5 mm ± 1.9. The mean NRR was 0.35. We observed six cases of aseptic loosening, two cases of infection, one implant revision for recurrent dislocation, and one stem revision after periprosthetic femoral fracture. The overall survival rate of the stem was 94.8%. Statistically significant associations were found between NRR and steroid therapy/stem malposition. Correlation between aseptic loosening and NRR was also statistically significant. Correlations between NRR and HHS/OHS were -0.34 and -0.28 respectively. Odds ratio for aseptic loosening were: 4.6 if NRR > 0.25; 16.9 if > 0.50 and 24.1 if > 0.75.

CONCLUSION: CFP hip stem provided excellent long-term outcomes. NRR is correlated to steroid therapy and stem malposition. The risk of stem aseptic loosening rises according to NRR increase. Patients with an NRR > 0.5, especially if under steroid therapy or with stem malposition, should be strictly monitored.