European Journal of Cardiovascular Medicine

Alignment of the femoral and tibial components is a major independent indicator of implant survival. Ideal coronal alignment of 2.4° to 7.2° valgus is related to the highest knee implant survival rate. Malalignment, particularly in the varus, can result in a number of problems, including poor clinical results, excessive polyethylene wear, patellar issues, implant loosening, medium- to long-term failure, and early revision of the arthroplasty.^[1]

Lateral tibial bending causes varus placement of the tibial component in varus knees during total knee replacement. The placement of a lateralized tibial jig can increase the precision of the tibial cut.^[2] Tibial varus was related to higher medial compartment wear and overall wear, hence impacting osteolysis and local deterioration of the bearing surface. Varus malalignment of as little as 3° can accelerate wear, even if limb alignment is virtually ideal.^[3-4] The aim of this study was to investigate whether lateralization of the lateral tibial plateau reference point influences proper coronal plane alignment of the complete knee prosthesis after surgery, based on the degree of tibia vara. We anticipated that using an extramedullary jig for tibial component alignment in TKA for patients with tibia vara and lateralizing the reference point 8 might achieve an acceptable level of precision.

This was a prospective observational study carried out at the Department of Orthopaedics, Mahavir Institute of Medical Sciences, Vikarabad, Telangana,, between January 2022 to May 2023. The current study comprised 19 patients, ages 18 to 80, who were receiving primary TKA for osteoarthritis of the knee with tibia vara. The study excluded patients with revision knee arthroplasties, post-traumatic arthritis, and tibia abnormalities from prior fractures.

Using a marking pen, the tibial reference point was measured from the intercondylar eminence center. The extramedullary jig was positioned so that the lateral tibial plateau's reference line and the jig's reference marking corresponded. The main outcomes were the tibia vara, the postoperative tibiofemoral angle, and the amount of lateralization of the tibial plateau reference point (and its relationship to the magnitude of the tibia vara). Knee function and clinical results were secondary factors. The association between tibia vara and lateralization of the proximal tibia reference point from the center of intercondylar eminence was evaluated using linear regression analysis. We computed the p-value and the R2 value. The American Knee Society Score was used to measure postoperative outcomes. A p-value of less than 0.05 was deemed significant. The Student t-test was utilized to examine the significance of the difference between the pre- and postoperative outcome ratings (pain score and function score).

Age of the patients ranged between 51-72 years. A majority (63%) belonged to 60–70 years. The mean (SD) of the age (years) was 62.58 ± 5.46. Out of 19 patients (30 knee joints), the majority of the patients were female (84.2%).

The majority of the patients, 57.9%, underwent bilateral knee replacement. 21% each underwent right or left knee replacement. The preoperative tibio-femoral angle mean (SD) in degree was 17.13 ± 6.04. The postoperative tibio-femoral angle mean (SD) in degree was 5.6 ± 1.38 .The difference was statistically significant (p<0.001).

The preoperative tibia vara mean (SD) in degree was 9.89 ± 5.335. The postoperative tibia vara mean (SD) in degree was 0 ± 0. The difference was statistically significant (p<0.001).

AKSS

There was a significant, progressive improvement in the AKSS scores during the followups compared to the preoperative scores (Table 4 and Figure 1).

Linear regression analysis showed a very high degree of positive correlation between the amount of lateralization of the tibial reference point and the magnitude of the tibia vara (R2 = 0.526, p = 0.003) as well as the tibio femoral angle (R2 = -.440, p = 0.015), as shown in Table 5 and Figure 2.

Most surgeons choose to use extramedullary tibial guides to position the tibial component during TKA. The intercondylar eminence center has traditionally been used as the proximal reference point for the tibial plateau when utilizing an extramedullary guide. In the event that the proximal tibia vara is preexisting, it has been noted that the tibial incision made with reference to the center of the intercondylar eminence causes a varus malalignment.^[5-7] The goal of this study was to determine if lateralization of the lateral tibial plateau reference point-which is dependent on the proximal tibia vara's magnitude-contributes to the complete knee prosthesis's ideal postoperative coronal plane alignment. Literature about the utility of lateralization is very sparse. The following discussion is based on a similar study conducted by Thippana RK et al.^[8]

In the present study, we observed that out of a total of 19 patients with 30 knees, 3 were male patients and 16 were female patients. In a study conducted by Thippana RK et al.^[8] there were also more females afflicted. In their study, 33 patients (66 knees) underwent bilateral surgery, and 29 patients (29 knees) underwent unilateral surgery. In our study, there were a total of 19 patients, of which 11 had bilateral knee surgeries, 4 had right knee surgeries, and 4 had left knee surgeries. 91% of patients were diagnosed with KL with grade 4, and 9% of patients had KL with grade 3 osteoarthritis. In our study, all the patients were diagnosed with osteoarthritis of the knee with a KL grade of 4 in both sexes.

In the study by Thippana RK et al.^[8] the mean preoperative AKSS was 27.4 (SD, 8.7) and the postoperative mean knee pain score was 96.3 (SD, 6.6), and the difference was significant (p < 0.001) in AKSS. In our study, pre-operative and post-operative AKSS scores were calculated on the 7^th day, 4^th week, and 3rd month. In all patients AKSS score was increased progressively from pre-operative mean (SD) 61.76 (33.76) to post-operative at 3rd month mean (SD) 142.95 (37.16).

In the study by Thippana RK et al.^[8] tibia vara were noted in 62 (95 knees). In our study, 19 patients (30 knees) had tibia vara. We measured the radiographic tibia vara preoperatively and postoperatively. The preoperative value was 9.89 ±5.335 degrees, which was corrected to zero postoperatively. This shows that none of the patients had tibia vara postoperatively due to lateralization of the tibial plateau reference point for tibial resection.

Lateralization of the proximal tibial reference point in the Thippana RK et al.^[8] study was 7 ± 2.2 mm. In our study, we measured lateralization preoperatively (4.30 ± 2.41 mm), and the same measurement was used in lateralization during the placement of the extramedullary tibial zig intraoperatively.

The majority of individuals who meet the criteria for TKA have proximal tibial varus deformities. A varus tibial cut is likely to occur in such circumstances when an extramedullary guide is positioned in the middle of the intercondylar eminence. By shifting the tibial jig's center to the lateral eminence of the tibia, which was in the extension of the tibial shaft axis, we were able to perform more valgus tibial cuts in our study than we could have with the traditional methods. This allowed us to achieve more stable alignment without endangering the mechanical axis.

While it may be tempting to remove more lateral tibial plateau in order to properly align the TKA, doing so might cause the implant to subside. The center of the tibial plateau is frequently medial to the anatomic axis (center of the tibial shaft) in Asian individuals with varus osteoarthritis. As a result, it is not the best spot to insert the tibial component. Previous research has suggested that the lateral border of intercondylar eminence be used as the reference point rather than the center of intercondylar eminence. The lateral intercondylar eminence has not been utilized as a permanent reference point in our investigation. The reference point might extend even farther lateral to the lateral intercondylar eminence and was customized based on the degree of metaphyseal tibial deformity.^[6]

When the radiographic evaluation was done after surgery, the angles between the mechanical/shaft axis and the prosthesis' perpendicular line fell within a normal range. In our study, there was a significant improvement in coronal alignment, knee society score, and functional outcome postoperatively after lateralisation of the tibial plateau reference point from center of intercondylar eminence for tibial resection.

Zones were used to depict the point of junction of the distal tibial diaphyseal line at the tibial plateau delineated on long films in a research by Palanisami D. et al.^[2] Only 28% of knees had a femoral bending greater than 5°. The proximal tibia's tibial jig placement was lateralized based on the zones. In varus knees with tibial bending, lateralized tibial jig placement enhanced tibial component placement and postoperative limb alignment during total knee arthroplasty. Our research has demonstrated that correct coronal alignment and improved functional outcomes are the outcomes of lateralizing the tibial jig in the tibia vara.

The mean tibia vara in the RK Thippana et al.^[8] research was 7.1° (standard deviation [SD], 2.3°). The reference point's mean lateral displacement was 7 mm. In 94% of patients, the postoperative tibiofemoral angle was 6° to 10° valgus. The degree of lateralization of the tibial reference point and the size of the tibia vara showed a high association, in line with our results. The authors came to the conclusion that by lateralizing the proximal tibial reference point, patients undergoing total knee arthroplasty who have proximal tibia vara can achieve satisfactory precision when using the extramedullary jig for tibial component alignment.

By lateralizing the proximal tibial reference point in patients with tibia vara, the extramedullary jig may be used to achieve reasonable precision for tibial component alignment. This is demonstrated by improvements in post-operative AKSS scores and deformity repair.

• Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM. Insall Award paper. Why are total knee arthroplasties failing today? Clin Orthop Relat Res 2002;(404):7-13.
• Palanisami D, Jagdishbhai CP, Manohar M, Ramesh P, Natesan R, Shanmuganathan R. Improving the accuracy of tibial component placement during total knee replacement in varus knees with tibial bowing: a prospective randomised controlled study. Knee 2019;26(5):1088-95.
• Srivastava A, Lee GY, Steklov N, Colwell CW, Ezzet KA, D'Lima DD. Effect of tibial component varus on wear in total knee arthroplasty. Knee 2012;19(5):560-3.
• Green GV, Berend KR, Berend ME, Glisson RR, Vail TP. The effects of varus tibial alignment on proximal tibial surface strain in total knee arthroplasty: the posteromedial hot spot. J Arthroplasty 2002;17(8):1033-9.
• Green GV, Berend KR, Berend ME, Glisson RR, Vail TP. The effects of varus tibial alignment on proximal tibial surface strain in total knee arthroplasty: the posteromedial hot spot. J Arthroplasty 2002;17(8):1033-9.
• Thippana RK, Kumar MN. Lateralization of tibial plateau reference point improves accuracy of tibial resection in total knee arthroplasty in patients with proximal tibia vara. Clin Orthop Surg 2017;9(4):458-64.
• Mullaji A. Registration of proximal tibial centre may need to be selectively lateralized to avoid coronal malalignment in digitally-assisted knee arthroplasty. Indian J Orthop 2022;56(5):902-7.
• Thippana RK, Kumar MN. Lateralization of tibial plateau reference point improves accuracy of tibial resection in total knee arthroplasty in patients with proximal tibia vara. Clin Orthop Surg 2017;9(4):458-64.