Our aim was to evaluate accurate details by following-up of Chinese patients using Corail® stem, a full extensive HA-coated femoral stem. Our series showed a survival rate of 100% of Corail® stem at 10 years and an overall survival rate of 97.83%, equal to other published survival of HA-coated femoral components (Shetty et al. 2005; Vidalain 2011). J.A. Epinette reported that excellent results from the partially coated HA Ominifit stem with a survival rate of 99.20% at 17-year follow-up. Compared with porous alone femoral stems, HA stems demonstrated better result with less adverse effects (Epinette and Manley 2008). Sariali et al. (2012) reported that the survivalship of anatomic cementless stem (SPS) was 100% considering stem revision for aseptic loosening as the end point. Antonio Herrera et al. reported their surgical experience with more than 4000 cementless hydroxyapatite coated hip prostheses (the ABG I and ABG II prosthesis an anatomical HA-coated stem with press-fit metaphyseal fixation, Stryker) since 1990. The survival at 10-year follow-up was 97.1% in ABG I, while a mean of 11.3 years follow-up was 98.30% in ABG II (Herrera et al. 2015). All these results confirmed the long-term stability of HA-coated prostheses.
The Merle d’Aubigné and Postel score improved satisfactorily in all patients, and the mean total score was 6.8 ± 0.5 pre-operatively and 16.1 ± 1.4 at latest follow-up. Each part of the score showed improvement. The mean Harris hip score was 92.3 ± 5.6 (72–100) at last follow-up. To our opinion, the proximal flared design of Corail® stem increases three dimensional metaphyseal femoral fit and avoid stress-shielding. Macrotextural features (horizontal and vertical grooves) enhance primary mechanical stability. The stability was achieved primarily through mechanical fixation (tight press-fit into the bone) and then secondarily through biological fixation (biological anchoring in bone), which is needed for a long-term survival of the prosthesis (Engh et al. 1987). However, the ARTRO Group affirmed that secondary fixation cannot take place unless primary mechanical fixation has been achieved (Vidalain and ARTRO Group 1999). It demonstrates early stability was essential for better rehabilitation (Kärrholm et al. 1994). Early peri-operative rehabilitation is pivotal for accelerated recovery and reduced the hospital length of stay after THA (Minns Lowe et al. 2009). The patients can early return to normal activities with absence of pain.
There was no patient in our series complaining of anterior thigh pain, in contrast with reports of other cementless femoral components without HA-coating (McNally et al. 2000; Engh and Massin 1989). The cause of this thigh pain had been considered to be multifactorial. M. Rokkum et al. reported an excellent clinical result of 100 consecutive entirely hydroxyapatite-coated hip arthroplasties in 86 patients. All patients had no thigh pain. They believed that all components were bonded directly to bone, promoted by the reliable primary fixation and the osteoconductive effect of HA (Rokkum and Reigstad 1999). The extensive HA coating and proximal flared design has the same function. And the diaphyseal part of the Corail stem offers a press fit property, as comfortable transition between the metaphyseal and diaphyseal part. Osteoblastic reaction was observed around stem, particularly in the 2–6 zones in our series. The distal stem fix indicated a shift from proximal to distal loading and ensured fewer incidences of thigh pain, similar with the previous results (Faraj and Yousuf 2005).
HA brings a chemical fixation between bone and implants, which can be resorped and replaced by bone within 16 weeks after implantation (Søballe et al. 1993). This phenomenon is a continuous, reproducible and reliable integration process. That means HA generates ‘spot welding’ of bone to the prosthesis, and impedes the access of polyethylene debris to the interface to prevent imminent or potential failure (Donnelly et al. 1997). As resorption of the HA coating, the new formed bone will replaces with a higher percentage. Complete osseointegration isn’t requisite, biological anchoring in bone can supply a sufficient stable fixation (Tonino et al. 2009). Young and very active patients could be surgical indications also (Wangen et al. 2008). Loupasis et al. (1998), in a 6 year follow-up study of 45 patients under the age of 50, reported no revision for aseptic loosening or evidence of stem loosening. What’s more, all the stems were excellently stable with no evidence of pedestal formation or radiolucent line. Ulivi et al. (2013) demonstrated that HA-coated implants have a higher long-term survival even in elderly patients. That suggests that distal fixation does not lead to stress shielding proximally.
In present group, the revision was only found in two patients (34 and 47 years old) due to line wear, which implied the age at the time of surgery maybe a significant influence factor for prosthesis revision. The previous reports have shown that higher rate of THR failure was associated with a higher proportion of PE wear (Reikeras and Gunderson 2002). Ohnsorge et al. (2006) considered the reason of higher proportion of failure was not solely poor PE quality, but also poor PE congruency.
The clinical and radiographic results at this series provided a good evidence for long-term efficacy of Corail stem with full extensive HA coating, which prevented most adverse events. HA-coating of stem appears to offer a satisfactory solution to fixation. However, polyethylene wear maybe a concern, especially in young patients.