Periprosthetic Fracture Torque for Short Versus Standard Cemented Hip Stems: An Experimental In Vitro Study

Abstract

In an attempt to preserve proximal femoral bone stock and achieve a better fit in smaller femora, especially in the Asian population, several new shorter stem designs have become available. We investigated the torque to periprosthetic femoral fracture of the Exeter short stem compared with the conventional length Exeter stem in a Sawbone model. Forty-two stems; 21 shorter and 21 conventional stems both with three different offsets were cemented in a composite Sawbone model and torqued to fracture. Results showed that Sawbone femurs break at a statistically significantly lower torque to failure with a shorter compared to conventional-length Exeter stem of the same offset. Both standard and short-stem designs are safe to use as the torque to failure is 7-10 times that seen in activities of daily living.

High risk of early periprosthetic fractures after primary hip arthroplasty in elderly patients using a cemented, tapered, polished stem

“…The collared Lubinus SP2 stem also shows extremely low distal migration, as measured by radiostereometry ( Wierer et al 2013 ), and all of these contributory factors may reduce the risk of PPF—especially in FNF patients. Longer cemented stems anchored distally in harder diaphyseal bone might conceivably reduce this risk further, which is supported by biomechanical studies showing that shorter stems have reduced resistance to torque forces ( Bishop et al 2010 , Morishima et al 2014 ). The standard length (150 mm) of the Exeter and CPT stems is the same as for the Lubinus SP2 stem, which alone might explain the previous registry-based results where stem length was not taken into account either.…”

Current Concepts, Classification, and Results in Short Stem Hip Arthroplasty

“…A suggestive field of application of short stems may be, in the near future, the development of cemented short designs. A shortened version of the Exeter stem (Stryker) is already under in vitro investigation, 50 after the encouraging results achieved with a special series of Exeter stems implanted in Asia, shorter than conventional, with reduced offset and different taper angles to match the smaller femora in that specific population. 51,52 It may seem that short stems and cemented stems are clashing terms, but perhaps it is possible that the shortness of the component will reduce the complexity of cemented stem revision and that the long-term follow-up of cemented prostheses will increase potential survivorship of short stems.…”

Reduced periprosthetic fracture rate when changing from a tapered polished stem to an anatomical stem for cemented hip arthroplasty: an observational prospective cohort study with a follow-up of 2 years

“…2010, Morishima et al. 2014). However, the shorter 130 mm Lubinus SP2 stem has shown a good long-term outcome without any increased risk for PPF, in a younger population treated mainly for osteoarthritis (Prins et al.…”