Valgus Considered: Redefining Total Knee Arthroplasty Alignment for Optimal Patient Outcomes

Background: Valgus knees are common deformities induced by osteoarthritis (OA), which is usually characterized by a hip–knee angle (HKA)>3° valgus or a femoral-tibial angle (FTA)<170°. Total knee arthroplasty (TKA) is a pivotal treatment for valgus knee deformity in end-stage knee OA; however, the optimal alignment strategy remains a subject of debate. Traditionally, TKA aims for a neutral mechanical alignment (-3°< HKA <3°); however, the impact of retaining slight valgus (HKA>3°) alignment post-TKA has not been extensively studied. Methods: This retrospective study included patients with knee valgus who underwent TKA from September 2011 to September 2021. Patients were divided into two groups on the basis of postoperative HKA: neutral alignment (NA group) (-3°<HKA<3°) and undercorrection alignment (UA group) (HKA>3°). The clinical outcomes were assessed by the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), KSS, Hospital for Special Surgery (HSS) knee score, range of motion (ROM) and visual analog scale (VAS). Patient satisfaction and radiographic outcomes were also compared between the two groups. Results: A follow-up of 3–10 years was conducted on 99 patients, with an average age of 5.9 years, with no significant demographic differences between the NA and UA groups. Surgical outcomes, including hospital stay, operation duration, and total blood loss, were not obviously different. Pain scores were also measured by the WOMAC and were not significantly different between the two groups, nor were visual analog scale (VAS) scores or pain during movement. The clinical scores (KSS, HSS, and WOMAC function, stiffness, and total scores) and range of motion (ROM) were also comparable, as was patient satisfaction. The radiographic results demonstrated that the preoperative HKA was similar, but the postoperative HKA was significantly greater (p<0.0001, ****) in the UA group due to the study design. Other radiographic results, including the medial and posterior tibial slopes (PTS), mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA), showed no significant differences preoperatively, but the postoperative mLDFA was significantly lower in the UA group (p<0.0001, ^**** ). The incidence of complications and survival did not markedly differ between the groups. Conclusion: This study revealed no significant differences in postoperative outcomes between TKA patients with neutral alignment and those with slight valgus retention. This suggests that retaining slight valgus of an average of 6.3° may not compromise the success of TKA and could offer an alternative standard for surgical planning.