Aims

The increased in vivo resistance to wear of highly crosslinked polyethylene (HXLPE) in total hip arthroplasty (THA) has led to an increased use of larger articulations which have been shown to reduce the incidence of early dislocation. To date, there are few reports of the wear of larger articulations using second generation HXLPE liners. Our prospective cohort study measured the bedding-in and early wear of large (36 mm and 40 mm diameter) articulations involving a second generation X3 HXLPE liner and compared our findings with previous clinical and in vitro studies of the same material.

The evolution of bone plate design has been with a view to reducing the interface contact between the plate and the underlying bone thereby limiting the perfusion deþciency that developes. Little consequence however, has been attributed to the drilling of holes in the steps prior to bone plate application; the work present herein attempts to deþne the vascular response of bone to the trauma of drilling holes.

Anaesthetized sheep underwent the creation of drill holes in both tibiae and metatarsi. Animals were then heparinized and euthanatized. Utilizing femoral cannula, perfusion of the vasculature ensued; Spalteholz (India ink), Disulphine blue and radiocontrast material (Barium sulfate). Decalciþed histology was performed and correlated with the perfusion studies.

Regions of perfusion deþciency were observed immediately adjacent to, and removed from, the drill hole site. Radiographic images showed substantial haematoma formation and vascular disruption in the vicinity of the drill hole site. Histologically, blood vessels immediately adjacent and distal to the drill hole site, contained a proteinaceous/ cellular material occluding the vascular space.

Our þndings support the proposal of a short-term obstruction in cortical blood ßow which may contribute to later adaptational osteopaenia following bone plate application. We have observed an acute vascular insufþciency in cortical bone directly related to the trauma of drilling screw holes.