Abstract
INTRODUCTION
Cementless femoral component designs supplemented with hydroxyapatite (HA) coating have been hypothesised to enhance osseointegration, thereby improving stability and clinical outcomes. We herein offer interim results at 5 years from a prospective, multi-centre study of a femoral stem (SL-PLUS™ Hip Stem Prosthesis), forged from titanium alloy (Ti6Al7Nb) and consisting of a titanium plasma sprayed coating (0.3mm) with an additional 0.05mm layer of HA.
METHODS
Investigators at 2 centres enrolled patients between 18–75 years of age who underwent primary total hip arthroplasty (THA) with this HA-coated stem. The study's primary outcome was the clinical efficacy of the stem, as measured by the Harris Hip Score (HHS), Western Ontario & McMaster Universities Osteoarthritis (WOMAC) Score calculated out of Hip Disability and Osteoarthritis Outcome Score (HOOS), and the EuroQol EQ-5D-3L index score and visual analogue scale (VAS). Its secondary outcomes included a radiographic assessment of implant position and fixation, and overall safety, as measured by intraoperative/early postoperative complications and survivorship calculated using Kaplan-Meier estimates.
RESULTS
Ninety-three patients (94 hips) were enrolled in the study. At the time of surgery, the study population had a mean age of 60.1 years (standard deviation [SD], 8.4), a mean body mass index of 27.9 kg/m2 (SD, 4.75), and 54.8% were female. Indications for surgery include primary osteoarthritis (74.5%), dysplasia (17.5%), femoral head necrosis (6.4%), and other (2.1%). Patients were followed up through 5 years in the ongoing safety and performance analysis. Between preoperative baseline and final follow up, there were notable improvements in the mean scores for all primary clinical outcomes: HHS (51.6 to 91.4, respectively), WOMAC from HOOS (42.6 to 91.0, respectively), mean EQ-5D-3L index score (0.7 to 0.9, respectively), and EQ-5D-3L VAS (54.7 to 80.2, respectively). The majority of patients rated their satisfaction as excellent (84.2% of treated hips), with an additional 14.5% of treated hips being mostly satisfied. Five years after surgery, radiographic findings showed an overall stability of the device, with 100% unchanged stem positions (no movement in varus/valgus or subsidence) and no stem was classified as loose. Intraoperative complications were observed in 3 patients (3.2%), consisting of 2 cases of trochanteric fracture and 1 case of leg lengthening. There were no general early postoperative complications reported in any patient. Two revision surgeries of the study device were reported, both due to infection, resulting in a survivorship of 97.5% (95% confidence interval: 90.3% – 99.4%) at 5 years.
CONCLUSION
These results confirm the safety and efficacy of this HA-coated femoral stem at 5 years. All clinical outcomes showed significant improvement between baseline and midterm follow up, with mean HHS in particular meeting the 90-point range considered “excellent.” Additionally, revision rates met the accepted benchmarks for a successful THA device.
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