Page 24 - ISAKOS 2018 Newsletter Volume 2

CURRENT CONCEPTS
Trends in Total Knee Arthroplasty in South America
David Figueroa, MD
Santiago, CHILE
Francisco Figueroa, MD, Prof.
Santiago, CHILE
Orthopaedics Department, Knee Section Facultad de Medicina Clínica Alemana-Universidad del Desarrollo Santiago, CHILE
In the present article, we will discuss common controversies related to total knee arthroplasty (TKA), review different trends in our region (as indicated by a recent survey of 316 South American surgeons), compare these trends with those in other regions, and propose our preferred management.
Stabilization Method
Retention or sacrifice of the posterior cruciate ligament (PCL) remains controversial. Both strategies provide advantages and disadvantages, but there is no consensus regarding which approach provides superior outcomes. The PCL plays a crucial role in femoral rollback, allowing adequate flexion and granting efficiency to the extensor mechanism, and therefore efforts to preserve this structure during prosthetic surgery have been attempted. However, the current evidence is ambiguous: some studies have shown higher success rates in association with PCL sacrifice, whereas others have demonstrated proprioceptive and biomechanical benefits in association with PCL retention. Moreover, PCL retention is associated with lower cost (cheaper implants) and less bone loss, allowing future revision surgery with posterior- stabilized designs.
Our survey indicated that posterior-sacrificing (PS) implants are the most commonly used design in South America, with 73% of surgeons preferring them over cruciate-retaining (CR) implants (17.87%) and Medial Pivot implants (9.13%). This trend is contrary to those in other regions. For example, 7 of the top 10 most commonly used TKA prostheses in the Australian registry and almost 70% of those in the New Zealand joint registry are CR implants.
In the United Kingdom, the National Joint Registry (covering England, Wales, Northern Ireland, and the Isle of Man) shows the same tendency, with about two-thirds of primary TKAs being performed with CR implants. Is important to note that in all of these registries, CR implants perform better than PS implants in terms of the rate of revision.
Given the successful outcomes that have been reported in association with both techniques, and on the basis of expert recommendations, we reserve PCL-retention surgery for patients without substantial varus or valgus misalignment or flexion contracture. Consequently, we perform PCL-sacrificing surgery in patients with substantial malalignment or flexion contracture of the knee, as well as in those with inflammatory diseases, previous osteotomies, or patellectomy, because PCL sacrifice has been associated with better results in these groups.
Fixation Method
For the last 20 years, cement fixation has been the standard practice, with excellent implant survival rates (90% to 95% at 15 years of follow-up). Although cement fixation provides an immediate stable interface between the bone and the implant, it is well known that this method compromises bone stock. In the 1980s, manufacturers developed cementless implants, which hypothetically helped to preserve bone stock, for use in high-demand patients who were potential candidates for revision surgery in the future. However, studies revealed that cementless fixation was associated with increased micro-movement of the tibial component and early aseptic loosening of the implant. These findings led to a rapid decrease in the popularity of cementless implants and the development of hybrid implants (featuring cemented tibial and patellar components and uncemented femoral components), which demonstrated good intermediate-term results.
In our region, cemented fixation of the femoral and tibial components was preferred by 97.72% of the surgeons surveyed. This rate was similar to those in the New Zealand and United Kingdom registries, which indicate that cemented implants are used in approximately 100% and 85% of cases, respectively. On the other hand, the Australian registry shows that about one-third of procedures are performed with hybrid fixation (i.e., an uncemented femoral implant and a cemented tibial implant) and 20% are performed with cementless implants. It is important to note that, in the Australian registry, hybrid implants are associated a lower rate of revision compared with cemented and cementless implants, whereas in the New Zealand and United Kingdom registries, cemented implants perform better.
Our standard practice today is to insert all components with cement as there are no substantial data to support changing this practice. However, we recognize that some series have demonstrated promising results in association with hybrid fixation and are expecting more evidence-based studies on this topic.
22 ISAKOS NEWSLETTER 2018: VOLUME II