Reducing the Risk and Management of Early and Late Tibial Component Failure After Calipered Kinematically Aligned Total Knee Arthroplasty

Outline

The discussion and videos in this chapter assist the surgeon in (1) reducing the risk of aseptic loosening of the tibial component and (2) managing both early and late tibial component failure from insert wear after calipered kinematically aligned (KA) total knee arthroplasty (TKA). The chapter draws from the author's experience treating of over 5300 primary KA TKAs from 2006 to 2020 without restrictions on preoperative alignment, without limits on the postoperative correction to the patient’s pre-arthritic femoral and tibial joint lines, and with the use of posterior cruciate ligament–retaining implants (CR), to provide the background. The first section discusses the incidence and early and late causes of tibial component failure. The second describes the use of verification checks that restore the native posterior slope and native laxities (except anterior laxity) of the trapezoidal flexion space, which reduces the risk of early failure from posterior subsidence or rim wear of the insert. The third section proposes the use of a medial stabilized ball-in-socket implant with a flat lateral compartment as a strategy for reducing the risk of late posterior rim wear of the insert (>9 years). The case studies in the final section showcase options for managing early tibial component failure, which is a revision of the tibial component and restoration of the native posterior slope. For late failure, management includes an exchange with a thicker insert or one with a medial constraint when available. The objective is to encourage those surgeons who perform calipered KA TKA to restore the native posterior slope when using the CR insert and consider the use of a medial stabilized implant with a flat lateral compartment.

Incidence and Causes of Early and Late Tibial Component Failure After Calipered Kinematically Aligned Total Knee Arthroplasty With Posterior Cruciate Ligament–Retaining Implants

Video 18.1 discusses the incidence, time of onset, and early and late causes of tibial component failure.

A case-match study from 2006 to 2015, clinical observations, and results from in vivo contact kinematic studies provide information for understanding the early and late causes of tibial component failure after calipered KA TKA. Early tibial component failure in this series presented at an average of 28 months, following surgery for an incidence of 0.3%. The cohort consisted of 8 patients out of 2725 consecutive primary KA TKAs. The setting of the slope of the tibial component was more posterior than native in seven patients. Not restoring the native posterior slope caused early posterior subsidence of the tibial baseplate or posterior rim wear of the insert within the first 2 to 5 years of the index surgery. In those patients with early tibial component failure, the mean posterior slope was 11 degrees, whereas the mean in the control cohort was 7 degrees ( Fig. 18.1 ). Posterior slope greater than the native slope slackened the flexion space. Laxity in the flexion space that is more slack than native promotes excessive anterior tibial component translation and excessive posterior rollback of the femoral component on the tibial component that causes posterior overload. This combination of abnormal motions manifested as posterior and not varus subsidence of the baseplate or wear of posterior rim of the polyethylene insert. Hence a strategy for reducing the risk of early failure with a CR insert is to restore the native posterior slope.

In 2016, we introduced the use of three verification checks to restore the native posterior slope, soft tissue laxities, and tibiofemoral compartment forces of the trapezoidal flexion space when using a CR insert. The verification checks were designed to reduce the risk of both early and late failure from posterior tibial component subsidence and rim wear. Following the introduction of the verification checks (2017–2020), we noted that late tibial component failure (>9 years) was no longer related to subsidence of the tibial base plate but rather to wear of the posterior rim of the insert. We concluded that a KA TKA with a low-constraint CR and posterior stabilized (PS) implant design has anterior tibial instability similar to a partial meniscal and anterior cruciate ligament (ACL)–deficient knee ( Fig. 18.1 ). ^, The ACL-deficient functioning insert representative of nearly all modern TKA CR and PS designs enables excessive anterior translation of the tibial component and excessive posterior rollback of the femoral component during flexion. This abnormal motion increases the risk of overload of the posterior rim of the insert in mid-flexion during activities of daily living, leading to wear.