Antibiotic delivery for Infected TKA

Rhidian Morgan-Jones

The use of local antibiotics in managing infected TKA is a standard concept. Antibiotics can be delivered by absorbable and non-absorbable means. We discuss the rationale for both options and discuss the authors personal experience with a Calcium Sulphate bioabsorbable delivery system.

The extensor mechanism is essential for a functioning primary and revision TKA. We list the potential extensor complications and discuss options for dealing with each. The author discusses his experience and philosophy in managing these potentially complex problems.

Most infected TKA are amenable to eradication of infection and functional restoration. However recurrent infection leads to a higher level of complex surgery with poorer outcomes. Further failure results in limb threatening infection requiring salvage techniques, such as knee arthrodesis and/or amputation. The available literature is reviewed along with published literature, and placed in the context of a high volume revision practice.

Qurashi S, Wang T, Chinnappa J, Pelletier MH, Walsh WR

Fixation between the femoral head and taper is fundamental in total hip arthroplasty. Surgical technique can influence the ability to impact a femoral head at the time of surgery. We evaluated static pull off after cyclical loading of a femoral head placed on the taper under conditions of dry and wet and with and without impaction.

The surface profiles of 16 CoCr tapers and femoral heads were characterized at four sites before and after testing. Four assembly conditions were examined: Dry or Wet Tapers; No impaction or Impaction (n=4 per group). An additional sample per group was assembled and sectioned to examine the taper and femoral heads. Impaction with a metal tip with one hammer blow was performed by a single surgeon. Samples were loaded for 500 cycles between 250 – 2500 N at 1Hz and pull-off at 0.008 mm/second. Peak loads were compared between groups and surface damage using surface roughness (Ra, Rz) and scanning electron microscopy (SEM).

Mean impaction force of 622 N was used in this study. No differences were detected under dry conditions. However, static impaction to a wet taper resulted in a greater pull-off force compared to a dry taper. Differences were detected in Ra of the tapers and Rz of the heads before and after testing. SEM revealed areas of focal damage at the contact surfaces

Pulling a head off a taper alters the surface of both. Cyclically load after assembly provided a robust taper-head interface irrespective of static impaction and wet taper conditions showed a higher pull of force requirement for disassembly.