To the Editor:
We have read with great interest the article Unicompartmental Knee Arthroplasty Compares Favorably to Total Knee Arthroplasty in the Same Patient (http://www.orthosupersite.com/view.asp?rID=38057), in the April 2009 issue of ORTHOPEDICS. We agree that unicompartmental knee arthroplasty (UKA) is a successful option for patients with osteoarthritis, in accordance with appropriate patient selection. Based on our experience with UKA, the main factor influencing outcome is surgical approach. Von Langenbecks traditional medial parapatellar approach should be used, with the knee flexed 110° and the patella everted, instead of a mini-incision on the affected compartment.
Through the traditional approach, a panoramic view can be achieved, which is optimal for precise bone resections, knee balancing (Figure 1), correct cement pressurization, and accurate prosthetic components positioning (Figure 2). This approach also decreases the risk of malalignment. The complete view given by the traditional approach allows the surgeon to correctly check the patellar tracking in a similar way to the total knee arthroplasty (Figure 3). Moreover, meniscal fragments, osteophytes, and bone particulate can be visualized and removed with ease, therefore avoiding possible sources of intra-articular scratches and catching. The most difficult problem with minimally invasive technique is to access the posterior compartment of the articulation to take away the meniscus and posterior osteophytes that, if retained, may lead to impingement of the meniscal bearing, loosening, and dislocation.1 Moreover, limited surgical access causes skin, capsular, and perhaps bone surfaces higher stresses due to the retraction required,2 increasing the risks for condylar fractures and patellar tendon rupture, as well as prolonging the tourniquet time,3 leading to an increase in the rate of technical error and early failure.1 We recommend a standard medial parapatellar approach to UKA, rather than a minimally invasive approach, since the surgical act would become complex when operating through a keyhole.2
Andrea Emilio Salvi, MD
Iseo (Brescia), Italy
Tonin Alia, MD
- Luscombe KL, Lim J, Jones PW, White SH Minimally invasive Oxford medial unicompartmental knee arthroplasty. A note of caution! Int Orthop. 2007; 31(3):321-324.
- Aglietti P, Baldini A, Giron F, Sensi L Minimally invasive total knee arthroplasty: is it for everybody? HSS J. 2006; 2(1):22-26.
- Boerger TO, Aglietti P, Mondanelli N, Sensi L Mini-subvastus versus medial parapatellar approach in total knee arthroplasty. Clin Orthop Relat Res. 2005; (440):82-87.
We appreciate the comments made by Drs Salvi and Alia regarding our article comparing unicompartmental knee arthroplasty (UKA) with total knee arthroplasty. They raise many good points. There is no question that a larger incision is advantageous for visualization of the entire knee and removal of retained bone and cement fragments. However, several authors have demonstrated that, when carefully performed, an incision that does not evert the patella and keeps the patella-femoral orientation in place during a UKA can be safely performed. In some respects, this improves the implant-to-implant alignment, an important determinant in long-term survivorship of UKA.
Ultimately, we agree with Drs Salvi and Alia that a surgeon needs to be able to assess the joint adequately, and we concur that a smaller incision should never compromise the outcome of UKA.
David F. Dalury, MD