Hydroxyapatite in total hip arthroplasty. Our experience with a plasma spray porous titanium alloy/hydroxyapatite double-coated cementless stem

Survival and performance of a dual tapered-wedge fully HA-coated press fit femoral stem

INTRODUCTION

Fully hydroxyapatite-coated titanium alloy double-tapered stems have been successful implant designs for THA. The Novation Element Stem (Exactech, Gainesville, FL) is one of several of these implants following a modified Corail design philosophy. Although a great deal is known about the results of the Corail stem, little is known about the more recent Corail-inspired implants. The authors evaluated the clinical outcomes, radiographic findings and survival statistics of the collarless version of the Element Stem when used routinely in a diverse patient population.

METHODS

A retrospective review was performed for all primary THR cases from 2010 to 2018. Patient demographics and HHS/OHS/patient satisfaction scores were obtained. Radiographs were evaluated for stem subsidence, radiolucencies, and bone responses to the implant.

RESULTS

One hundred and fifty seven Element Stems were implanted with greater than 2 years of radiographic follow-up, while 105 Element Stems implanted during the study period had a survival of 5 years or more. Average HHS was 91.7 and average OHS was 44.0. 54 of 157 hips had radiolucencies, all of which included a proximal zonal radiolucency. Average subsidence was 3.33 mm; 18 hips had subsidence > 4 mm. There were 8 revisions for: aseptic loosening (4), trauma-related peri-prosthetic fractures, and early proximal-medial fractures. At 5 years, the all-cause survival rate is 92.4%, 96.2% based only on aseptic loosening and 98.1% based only on proximal medial fractures.

CONCLUSION

Clinical outcomes using the collarless Novation Element Stem are good, but early proximal medial fracture is still a factor in patients with poor-quality bone. Proximal radiolucencies progressing to aseptic loosening post-operatively are also a concern. The 11.5% rate of subsidence is comparable to other fully HA-coated collarless stems. This study provides a thorough critical analysis of outcomes and midterm survival data of this dual tapered-wedge fully HA-coated collarless stem used routinely in a diverse patient population.

Use of a Plasma-Sprayed Titanium-Hydroxyapatite Femoral Stem in Hip Arthroplasty in Patients Older than 70 Years. Is Cementless Fixation a Reliable Option in the Elderly?

Background: Although cementless implants are increasing in popularity, the use of cementless femoral stems for total hip arthroplasty (THA) and hip hemiarthroplasty (HH) in elderly patients remains controversial. The aim of this study was to report the outcomes of a cementless stem used in a large multicentric cohort of elderly patients receiving elective THA and HH for displaced femoral neck fracture. Methods: A total of 293 patients (301 hips) aged 70 years or older (mean age, 78 years; range, 70–93) who received the same cementless plasma-sprayed porous titanium–hydroxyapatite stem were retrospectively evaluated after primary THA and HH to investigate stem survival, complications, and clinical and radiographic results. Results: Cumulative stem survival was 98.5% (95% CI, 96.4–99.4%; 91 hips at risks) with revision due to any reason as the end-point at 10-year follow-up (mean 8.6 years, range 4–12). No stem was revised due to aseptic loosening. The mean Forgotten Joint Score was 98.7. Radiographically, the implants showed complete osseointegration, with slight stress-shieling signs in less than 10% of the hips. Conclusion: The use of cementless stems was proven to be a reliable and versatile option even in elderly patients for elective THA and HH for femoral neck fracture.

Long-term results of an anatomically implanted hip arthroplasty with a short stem prosthesis (MiniHipTM)

AIM

To evaluate the clinical and radiological outcome nine and ten years after short-stemmed, bone preserving and anatomical hip arthroplasty with the MiniHip^TM system.

METHODS

In a prospective study, 186 patients underwent hip arthroplasty with a partial neck preserving short stem (MiniHip^TM, Corin). Elderly patients were not excluded from this study, thus the mean age at the time of surgery was 59.3 years (range 32 to 82 years). Surgery and the follow-up assessments were performed at two Centers. Up until now, the mean follow-up was 112.5 ± 8.2 mo. The Oxford Hip Score (OHS) and the Hip Dysfunction Osteoarthritis and Outcome Score (HOOS) was assessed pre- and each year after surgery. The clinical follow-up was accompanied by standardized a.p. and axial radiological examinations. Periprosthetic lucencies, hypertrophies within the Gruen zones one to fourteen were assessed. A subsidence of the stem was investigated according to Morray and heterotopic ossifications were assessed according to Brooker.

RESULTS

The OHS and HOOS improved from 18 ± 3.3 to 46 ± 2.0 and from 30 ± 8.3 to 95 ± 4.6 points, P < 0.001 respectively. There were no differences regarding age, etiology, friction pairings, etc., (P > 0.05). Two stems were revised due to a symptomatic subsidence four and twelve months postoperatively. Thus, the survivorship for aseptic loosening at nine to ten years was 98.66%. Including one stem revision due to a symptomatic exostosis, bursitis and thigh pain as well as one revision because of a septic stem loosening, the overall survival for the stem with revision for any reason was 97.32%. Besides one asymptomatic patient, radiological signs of a proximal stress-shielding, such as bone resorptions within the proximal Gruen zones, were not noticed. Findings suggesting a distal loading, e.g., bony hypertrophies or bone appositions of more than 2 mm, were also not detected.

CONCLUSION

Regarding these first long-term results on the MiniHip^TM, the implant performed exceedingly well with a high rate of survivorship for aseptic loosening. Our radiological results within the Gruen zones support the design rationale of the Minihip to provide a reliable metaphyseal anchoring with the expected proximal, more physiological load transfer. This might minimize or exclude a stress shielding which might be associated with thigh pain, proximal bone loss and an increased risk of aseptic loosening. The MiniHip^TM is a reliable partial-neck retaining prosthesis with good a clinical long-term outcome in younger as well as elderly patients.