Loss of Cement-bone Interlock in Retrieved Tibial Components from Total Knee Arthroplasties

Abstract

Background Aseptic loosening continues to be a shortand long-term complication for patients with cemented TKAs. Most studies to this point have evaluated tibial component fixation via radiographic changes at the implant-bone interface and quantification of component migration; direct assessment of morphologic features of the interface from functioning TKAs may provide new information regarding how TKAs function and are fixed to bone. Questions/purposes In a postmortem retrieval study, we asked: (1) What are the morphologic features at the cement-trabecular bone interface in retrieved tibial components? (2) Do constructs with greater time in service have less cement-trabecular bone interlock? (3) Do constructs with more estimated initial interlock sustain more interlock with in vivo service? Methods Fourteen postmortem retrieved tibial components with time in service from 0 to 20 years were sectioned and imaged at high resolution, and the current contact fraction, estimated initial interdigitation depth, current interdigitation depth, and loss of interdigitation depth were quantified at the cement-bone interface. Estimated initial interdigitation depth was calculated from the initial mold shape of the cement mantle that forms around the individual trabeculae at the time of surgery. Loss of interdigitation depth was the difference between the initial and current interdigitation depth. Results There was resorption of trabeculae that initially interlocked with the cement in the postmortem retrievals as evidenced by the differences between current interdigitation and the estimated original interdigitation. The current contact fraction (r 2 = 0.54; p = 0.0027) and current interdigitation depth (r 2 = 0.33; p = 0.033) were less for constructs with longer time in service. The current contact fraction for implants with 10 or more years in service (6.2%; 95% CI, 4.7%-7.7%) was much less than implants with less than 10 years in service (22.9%; 95% CI, 8.9%-37%). Similarly, the current interdigitation depth for implants with 10 or more years in service (0.4 mm; 95% CI, 0.27-0.53 mm) was much less than implants with less

Microdamage assessment of bone-cement interfaces under monotonic and cyclic compression

“…Bone-cement interface integrity has been identified as the critical element in the success and longevity of both hip and knee cemented replacements (Gardiner & Hozack, 1994;Stocks et al, 1995;Thanner et al, 1999;Zant et al, 2008;Wang et al, 2009;Tozzi et al, 2012;Goodheart et al, 2014;Howard et al, 2014;Miller et al, 2014Miller et al, , 2014b. Principal concerns regarding the performance of cemented fixation in the hip were related to fatigue damage accumulation in the cement mantle in femoral (Cristofolini et al, 2007;Race et al, 2003Race et al, , 2011 and acetabular (Heaton-Adegbile et al, 2006;Zant et al, 2007;Tong et al, 2008) components.…”

“…On the acetabular side the cracking in the cement mantle seems to be limited compared to the femoral counterpart and other failure mechanisms, such as debonding at the bone-cement interface, are mainly responsible for the implant loosening Wang et al, 2009;Tozzi et al, 2012). With regards to bone-cement fixation in the knee, a number of recent studies reported how the loss of interlock between bone and cement following in vivo service may eventually jeopardise the performance of both tibial Miller et al, 2014Miller et al, , 2014b and femoral (Howard et al, 2014) components over time. Goodheart et al (2014) also showed how such ex vivo loss of interlock resulted in a reduced strength of the bone-cement fixation in total knee arthroplasty (TKA).…”

The Distribution of Implant Fixation for Femoral Components of TKA: A Postmortem Retrieval Study

“…The initial interdigitation depth (inID) was used to estimate the initial extent of interlock between cement and bone at the completion of surgery [12]. A line was drawn at the furthest initial extent of bone into cement, as documented by the cement mold (Line 1, Figure 2C).…”

“…The percent difference between inID and curID (inID-curID/inID) defined the loss of interdigitation depth (lossID) and represented an estimate of how much trabecular bone was resorbed during in vivo service. The estimated error in determining the inID has been reported to be 0.06mm [12] using lab-prepared constructs where there was no bony resorption.…”

“…Enbloc postmortem retrievals, obtained from functioning TKAs, could be used to assess the fixation morphology and the changes that occur due to in vivo service. Our group recently assessed the fixation between trabecular bone and cement in tibial components with time in service ranging from 0–20 years [12]. We quantified the amount of bone in contact with the cement layer, as well as the loss of interdigitation, due to in vivo service.…”