Background
In two-stage revision knee replacement, insertion of a temporary cement spacer is followed by implantation of the definitive prosthesis 6–12 weeks later. Static spacers restrict knee movement, leading to soft tissue contracture and bone loss.1 Articulating spacers maintain range of movement and elute more antibiotics than metal equivalents.2 Commercially available products have their limitations. We therefore describe a novel technique for creating custom fitting articulating spacers, which can include any heat stable antibiotic.
Technique
Tibial and femoral spacers are made independently with two separate double mixes of antibiotic loaded cement. A trial tibial insert is sized on the proximal tibia, usually one size greater than the implant removed. Cement is moulded in the hollow insert to a thickness that matches the extension gap less 10mm; a tibial stem is created (Figs 1 and 2). A femoral spacer is made using a femoral trial, usually one size less than the one removed. Cement is moulded to the contours of the trial adding a femoral shaft stem. The distal cement should be 10mm thick. A ‘cobra hood’ extension covering the anterior femur prevents suprapatella pouch scarring (Fig 3). The cement is removed from each mould as it becomes firm. After final moulding and confirmation of fit in situ, they are removed and allowed to harden. They are then reinserted and checked for stability (Figs 4 and 5).
Figure 1.
Cement is inserted into a hollow tibial trial and a stem created.
Figure 2.
The tibial spacer is removed as the cement becomes firm.
Figure 3.
A femoral spacer is created laying a sheet of cement over the femoral trial/impactor.
Figure 4.
Both spacers are inserted after the cement has hardened.
Figure 5.
Radiography confirms placement of the spacers.
Discussion
In two-stage revision knee replacement, our technique permits easy creation of inexpensive custom fit spacers.
References
- 1.Voleti PB, Baldwin KD, Lee GC. Use of static or articulating spacers for infection following total knee arthroplasty: a systematic literature review. J Bone Joint Surg Am 2013; 95: 1,594–1,599. [DOI] [PubMed] [Google Scholar]
- 2.Evans RP. Successful treatment of total hip and knee infection with articulating antibiotic components: a modified treatment method. Clin Orthop Relat Res 2004; 427: 37–46. [DOI] [PubMed] [Google Scholar]