Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator.

A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 74 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prosthesis over the study period. A p-value <0.05 was considered statistically significant.

Demographics, Dorr types and blood serum markers were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years.

When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking.

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator.

A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 70 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prostheses over the study period. A p-value <0.05 was considered statistically significant.

Demographics and Dorr types were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years.

When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking.

There are several different ways of preparing the femoral canal prior to cementing a hip prosthesis. This study investigated the mechanical strength of the cement-bone interface of four different types of preparation determined by the maximum tensile force required to separate a cemented prosthesis from its cancellous bone origin.

Forty-eight fresh-frozen ox femora were prepared for hip arthroplasty, In a four-way comparison, groups of eleven femora were prepared by irrigation using

syringe injected normal saline;

Specimens were secured to a Material-test System (MTS), and the femoral implant pulled from the femur uni-axially at a rate of 5mm/min. The ‘pull-out strength’ was defined as the maximum tension recorded by the MTS during separation. Cement interdigitation was also inspected for each technique by microscopy of eight bone-implant transverse sections taken from prepared specimens.

Following an analysis of variance and pair-wise Fisher comparison, the average pull-out strength of the cemented prosthesis was significantly higher (P< 0.001) using pulse-lavage brushing (mean 8049.2 N), and pulse-lavage brushing in combination with hydrogen-peroxide soaked gauze (mean 8489.1 N), than with normal saline irrigation (mean 947.1 N) or hydrogen-peroxide soaked gauze preparation (mean 1832.6 N). Prosthesis pull-out strength following pulse-lavage brushing in combination with hydrogen-peroxide soaked gauze was not significantly different (P> 0.05) than preparing with pulse-lavage brushing alone. Low and high power microscopy of specimen transverse sections revealed the greatest levels of cement penetration in specimens prepared using pulse-lavage brushing.

This study demonstrated that one of the most effective preparations of the femoral canal for optimal mechanical fixation between cement and cancellous bone is pulse- lavage brushing. The use of hydrogen-peroxide soaked gauze in femoral canal preparation, either alone or in combination with pulse-lavage brushing, may not significantly improve prosthesis fixation.