Efficacy of Hydroxyapatite Cementless Femoral Stem in Primary Hip Arthroplasty in Elderly Patients
Authors: Asal Mohamed Kamal Mohamed , Mounir Ayman Fathy , Mohasseb Ahmed Mohamed , Elshabrawy Waleed Elsayd , Ahmed Mohamed Yasser Reda 
Published: November 2024

Abstract

Background
Total Hip Arthroplasty (THA) significantly improves the lives of patients with hip issues, achieving a 78% survival rate after 35 years. Challenges such as distal stem migration impact longevity, but innovations like tapered femoral stems and hydroxyapatite (HA) coatings enhance stability and osteointegration, thus promoting implant durability and avoiding the need for bone cement. Continuous advancements in surgical methods and materials promise even better future outcomes for THA patients.

Objective
To assess the efficacy of different hydroxyapatite stem designs in different Dorr index and to decrease complications of bone cement implantation syndrome in elderly patients. To assess the subsidence of cementless femoral stem in 65 years old and above patients. To measure the functional outcomes, complications, morbidity, and mortality after cementless femoral stem in 65 years old and above patients.

Patients and Methods
This was a prospective, interventional study. 34 patients were included in the study between 2022-2024. All patients were 65 years old and above, and all of them were planned to undergo HA-coated cementless femoral surgery after preoperative assessment of the Dorr index. Subsidence and functional outcomes (HHS, HOOS) were assessed at three time points (6 months, 1year and 2 years). In addition, subgroup analysis was performed to assess anti-osteoporotic agents and smoking, and their correlation with subsidence and functional outcomes.

Results
This study included 34 patients with a female-to-male ratio of 20:14 who underwent different primary hip arthroplasties. Our study employed a per-protocol approach for postoperative functional analysis, necessitating the exclusion of two patients (5.88%) due to inadequate filling fixation of the cementless stem, and we had to use a cemented stem. One patient (2.9%) had a dislocation three weeks post-surgery, which required revision due to stem instability, and another patient was excluded due to a periprosthetic infection (2.9%), necessitating implant removal in the 2nd session of debridement four weeks after surgery. Thirty patients were subjected to the final analysis using a per-protocol approach, and the mean subsidence was quantified at three time points (6 months, 1 year, and 2 years). The data demonstrated a temporal increase in mean subsidence, which peaked at 1.92 ± 0.34 mm at the conclusion of the 2-year period. The mean of Subsidence 1.92 ± 0.34 mm were statistically non-significant to the functional outcomes which showing statistically significant of the HA coating cementless femoral stem by time P-value of 0.001. Subgroup analysis of the anti-osteoporotic agents had a statistically significant effect on lowering the subsidence (P &lt; 0.001) but did not affect the functional outcomes. Smoking showed a statistically significant decrease in subsidence (P = 0.007) compared with the non-smoking group.

Conclusion
The employment of cementless hydroxyapatite femoral stems in geriatric patients aged 65 years and above, presenting with hip pathologies such as osteoarthritis or fractures, constitutes a viable surgical strategy. This approach mitigates the risk associated with cement usage, while ensuring favorable functional outcomes with early unrestricted weight bearing and a low rate of complications. Additionally, our results indicate a reduction in stem subsidence among patients receiving anti-osteoporotic treatments and those who do not smoke when a hydroxyapatite cementless femoral stem is used; however, these variations did not demonstrate a correlation with functional outcomes. Consequently, we advocate for additional research to elucidate the influence of anti-osteoporotic treatment on femoral stem osteointegration in such a high-risk cohort.