Continuous periprosthetic bone loss but preserved stability for a collum femoris-preserving stem: follow-up of a prospective cohort study of 21 patients with dualenergy X-ray absorptiometry and radiostereometric analysis with minimum 8 years of follow-up

Abstract

Background and purpose — We previously described a decrease in bone mineral density (BMD) in the calcar region 2 years after insertion of the collum femoris-preserving (CFP) stem, but the implants were stable. Now we have examined the long-term changes in periprosthetic BMD and stability of the CFP stem. Patients and methods — We conducted a minimum 8-year follow-up of 21 patients from our original investigation. We examined periprosthetic BMD by dual-energy X-ray absorptiometry (DEXA) and implant stability by radiostereometric analysis (RSA). Results — Between 2 and 8 years 1 stem was revised due to aseptic loosening. Between 2 and 8 years we found a 14% (95% confidence interval [CI] 9–19) reduction in BMD in Gruen zone 6 and 17% (CI 6–28) in Gruen zone 7. From baseline the reduction in BMD was 30% (CI 23–36) in Gruen zone 6, 39% (CI 31–47) in Gruen zone 7, and 19% (CI 14–23) in Gruen zone 2. Between 2 and 8 years, RSA (n = 17) showed a mean translation along the stem axis of 0.02mm (CI –0.02 to 0.06) and a mean rotation around the stem axis of 0.08° (CI –0.26 to 0.41). From baseline mean subsidence was 0.07 mm (CI –0.16 to 0.03) and mean rotation around the stem axis was 0.23° (CI –0.23 to 0.68) at 8 years. Interpretation — There was continuous loss of proximomedial BMD at 8 years while the CFP stem remained stable. Proximal periprosthetic bone loss cannot be prevented by this stem.

Short versus conventional straight stem in uncemented total hip arthroplasty: functional outcomes up to 5 years and survival up to 12 years: secondary results of a randomized controlled trial

“…The HOOS is a disease-specific PROM for patients undergoing THA but is not extensively used in the literature. Another commonly used PROM is the HHS, for which similar results were founded in our trial [12][13][14][15]. The MCII and PASS for the EQ5D are both achieved by patients in our trial [24].…”

“…No strong conclusions can be drawn on implant survival because this trial was not statistically powered for survival analysis. When looking at observational studies, we also see higher revision rates for the CFP than for the Zweymüller stem [11][12][13][27][28][29][30]. Although not statistically significant, our RCT supports these findings.…”

“…We previously reported that functional outcomes of the CFP were not superior to the conventional uncemented Zweymüller stem up to 2 years after surgery [9]. Other studies investigating the CFP were mostly cohort studies [10][11][12][13][14]. Available RCTs have small sample sizes and a relatively short follow-up [15,16].…”

Biomechanical Properties of Bionic Collum Femoris Preserving Hip Prosthesis: A Finite Element Analysis

“…In the rectangular CFP prosthesis, the average stress shielding rate is 5.6% (4.1%–6.7%), while in the circular CFP prosthesis, the average stress shielding rate is as high as 35% (5.2%–66%) 19–25 . In the latest prospective cohort study, 21 patients who underwent THA with CFP prosthesis were followed up for at least 8 years, and the results of the 2‐year follow‐up showed that the bone loss at the top of the femur continued for 8 years 26 . The authors believed that the CFP prosthesis could not prevent bone absorption around the prosthesis.…”

“…[19][20][21][22][23][24][25] In the latest prospective cohort study, 21 patients who underwent THA with CFP prosthesis were followed up for at least 8 years, and the results of the 2-year follow-up showed that the bone loss at the top of the femur continued for 8 years. 26 The authors believed that the CFP prosthesis could not prevent bone absorption around the prosthesis.…”