Review Question - QID 219509

Midterm functional outcomes and rates of blood loss among all commonly performed approaches to total knee arthroplasty (TKA) have been shown to be equivalent.

A total knee arthroplasty can be performed using a number of surgical approaches based on surgeon preference, degree of deformity, prior incisions, and patient habitus. A primary TKA is most often approached via the standard medial parapatellar incision (A), as this is a familiar approach that offers excellent surgical exposure with easy eversion of the patella. A midvastus approach (B), though similar to the standard medial parapatellar, spares the insertion of the VMO and has been theorized to lead to quicker recovery, though this has not been shown to be the case in the literature. A subvastus approach (C) elevates the muscle belly of the vastus medialis off the intermuscular septum and, in theory, preserves more of the medial patellar vascularity, but comes with the inherent disadvantage of being less extensile for exposure purposes. Finally, a lateral parapatellar approach (D) can be employed when significant lateral soft tissue contractures are present (i.e., a bad valgus knee), but is infrequently used and makes patellar eversion more difficult. Despite these differences, functional outcomes at the midterm have not been shown to be superior for any one given approach.

Bouché et al. performed a systematic review and meta-analysis to compare the efficacy of the different surgical approaches in total knee arthroplasty, including the standard medial parapatellar, "mini"-parapatellar, midvastus, subvastus, and quad snip approaches. The authors reviewed 60 randomized controlled trials (RCTs) involving 5042 patients and 5107 TKAs. They found no significant differences between different approaches for the KSS assessment or the WOMAC at 6 months. They concluded that no differences were found in functional outcomes over short or medium terms and that until future studies can demonstrate a long-term benefit, based on these results all studied surgical approaches to perform a TKA are equal.

Liu et al. performed a meta-analysis comparing the midvastus and subvastus approaches to the standard medial parapatellar approach to a TKA. The authors reviewed a total of 32 RCTs including 2451 TKAs in 2129 patients and found that, when compared with the medial parapatellar approach, the midvastus approach showed better outcomes in pain and knee range of motion at postoperative 1–2 weeks but also was associated with longer operative time; the subvastus approach showed better outcomes in knee range of motion at postoperative 1 week, straight leg raise and lateral retinacular release, but none of these differences were sustained at mid- to long-term. The authors concluded that there were no differences in KSS, lateral retinacular release, blood loss, hospital stay, and complications between both groups and that no differences exist in the long-term clinical outcomes between the midvastus and sub-vastus versus the medial parapatellar approach in TKA.

Figure A is an illustration depicting the standard approaches for performing a total knee arthroplasty: (A) Medial parapatellar, (B) Midvastus, (C) Subvastus, (D) Lateral parapatellar.

Incorrect Answers:
Answer 1: Approach A is the medial parapatellar approach and, though it is most commonly used, has not been shown to have an association with superior functional outcomes post-operatively.
Answer 2: Approach B is the midvastus approach, which spares rather than compromises the VMO insertion.
Answer 3: Approach C is the subvastus approach, which is less extensile and preserves more of the medial patellar blood supply.
Answer 4: Approach D is the lateral parapatellar approach, which can help release tight lateral contractures but comes with the disadvantage of making patellar eversion more difficult.