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.

Aims

The mid-term results of kinematic alignment (KA) for total knee arthroplasty (TKA) using image derived instrumentation (IDI) have not been reported in detail, and questions remain regarding ligamentous stability and revisions. This paper aims to address the following: 1) what is the distribution of alignment of KA TKAs using IDI; 2) is a TKA alignment category associated with increased risk of failure or poor patient outcomes; 3) does extending limb alignment lead to changes in soft-tissue laxity; and 4) what is the five-year survivorship and outcomes of KA TKA using IDI?