Do Dynamic Cement-on-Cement Knee Spacers Provide Better Function and Activity During Two-stage Exchange?

Abstract

Background Implantation of an antibiotic bone cement spacer is used to treat infection of a TKA. Dynamic spacers fashioned with cement-on-cement articulating surfaces potentially facilitate patient mobility and reduce bone loss as compared with their static counterparts, while consisting of a biomaterial not traditionally used for load-bearing articulations. However, their direct impact on patient mobility and wear damage while implanted remains poorly understood. Questions/purposes We characterized patient activity, surface damage, and porous structure of dynamic cementon-cement spacers. Methods We collected 22 dynamic and 14 static knee antibiotic cement spacers at revision surgeries at times ranging from 0.5 to 13 months from implantation. For these patients, we obtained demographic data and UCLA activity levels. We characterized surface damage using the Hood damage scoring method and used micro-CT analysis to observe the internal structure, cracking, and porosity of the cement. Results The average UCLA score was higher for patients with dynamic spacers than for patients with static spacers, with no differences in BMI or age. Burnishing was the only prevalent damage mode on all the bearing surfaces. Micro-CT analysis revealed the internal structure of the spacers was porous and highly inhomogeneous, including heterogeneous dispersion of radiopaque material and cavity defects. The average porosity was 8% (range, 1%-29%) and more than 1 . 2 of the spacers had pores greater than 1 mm in diameter. Conclusions Our observations suggest dynamic, cementon-cement spacers allow for increased patient activity without catastrophic failure. Despite the antibiotic loading and internal structural inhomogeneity, burnishing was the only prevalent damage mode that could be consistently classified with no evidence of fracture or delamination. The porous structure of the spacers varied highly across the surfaces without influencing the material failure.

A systematic review of the evidence for single stage and two stage revision of infected knee replacement

“…Cement spacers that allow the patient to move the knee whilst undergoing antibiotic therapy were introduced to prevent bone loss and soft tissue contraction associated with static spacer use and ultimately patient function [83]. …”

Nano-carrier based drug delivery systems for sustained antimicrobial agent release from orthopaedic cementous material

“…The use of a temporary spacer in two-stage surgery in knee replacement gives the patient the ability to move, also provides good alignment of the knee between the two stages [94,95]. Success rates with the use of antibiotic impregnated PMMA interim spacer/prosthesis are reported to be higher than 90% [96]. The advantage offered by such spacer is delivering high level of antibiotic locally, while maintaining joint mobility [97].…”

Low-grade periprosthetic knee infection: diagnosis and management

“…Infection continues to be a rare but devastating complication of total knee arthroplasty (TKA), occurring in 1–3 % of cases [ 1 – 5 ]. Despite the low incidence, infection is associated with patient morbidity, increased healthcare costs, and recurrence and is also challenging to control [ 6 ]. TKA infections are often attributable to staphylococci and streptococci, whereas aerobic gram-negative bacteria cause 10–20 % of all infections and anaerobic bacteria are responsible for another 10 % [ 7 ].…”