Tibial bowing and tibial component placement in primary total knee arthroplasty in valgus knees: Are we overlooking?

Abstract

Purpose: Tibial bowing in valgus knees with arthritis can lead to component malplacement during total knee arthroplasty (TKA). Incidence of valgus knees with medial tibial bowing, its effect on tibial component placement during primary TKA and methods to improve accuracy of the component placement were studied. Methods: Full-length weight-bearing alignment radiograph was taken in 117 patients (149 knees) with valgus deformity undergoing TKA. In these cases, the proximal tibial reference for extramedullary jig placement was planned preoperatively with reference to the tibial spines and classified as four zones. Results: The mean preoperative hip–knee–ankle (HKA) angle was 192.9° (180.3–234.5°). Bowing >3° was considered significant ( p < 0.001) and at this level of bowing, the proximal tibial reference was shifted from centre to medial. Tibial bowing <3° was considered straight and >3° as tibia valga. Tibia was bowed in 70 knees (46.97%). Severity of valgus deformity had strong positive correlation with the tibia valga ( p < 0.001). The post-operative medial proximal tibial angle (MPTA) and HKA angle were 91.63° (87.9–95.7°) and 182.6° (178.1–189.7°), respectively. The mean MPTA and post-operative HKA angle in bowed and straight tibiae were 90.35° versus 89.78° ( p = 0.547) and 181.5° versus 180.7° ( p = 0.5716), respectively, and the difference was not statistically significant. Conclusion: Medial tibial bowing is very common in valgus knees. Tibia valga has a strong positive correlation with the severity of valgus deformity. Accurate tibial component placement can be achieved with a medialized reference point for extramedullary tibial cutting jig in knees with significant tibia valga. The study has been registered in clinical trials registry – India (CTRI/2018/03/012283).

Prevalence of Extra-Articular Tibia Valga Morphology in Valgus Knees and its Implications for Primary Total Knee Arthroplasty

“…The results of our study are consistent with the only two other studies 13,14 which have radiographically analysed tibia valga morphology in valgus knees. Alghamdi et al's 14 (2014) retrospective review of 97 osteoarthritic valgus knees prior to TKA via full lower limb weightbearing x-rays demonstrated a similar prevalence of tibia valga to ours, with 53% of valgus knees illustrating a tibia valga.…”

“…Palanisami et al's 13 (2019) study rea rms this suggestion, demonstrating that excellent prosthetic component placement can be achieved in valgus knees with tibia valga using extramedullary cutting guides. Similarly, the identi cation of extra-articular tibia valga in the pre-operative planning of revision TKA is critical, as the use of a straight stem for the tibial component might abut the cortex, hence offset options need to be available intra-operatively.…”

“…On average in non-arthritic knees, the articular surface of the tibia is 3 o varus to its mechanical axis. 13 However studies have demonstrated that tibial component placement in TKA should be 90 o to the mechanical axis as this allows the prosthetic component to evenly distribute its weight across the tibia and therefore prolong the survivorship of the implant. 14,25,29 The literature has differing evidence regarding the use of intramedullary and extramedullary tibial cutting guides in TKA.…”

“…Utilisation of intramedullary jigs and tibial stems in valgus knees with such a morphology have been demonstrated to result in malpositioning and cortical impingement, and therefore increase the risk of an iatrogenic tibial fracture if pre-operative planning is inadequate. 13 To date, the literature on the subject is limited, with only two studies using full lower-limb weightbearing xrays examining this morphology in detail despite its potential implications on tibial component placement in TKA. 12,14 This study aims to describe the prevalence and characteristics of tibia valga morphology in osteoarthritic knees.…”

Personalizing Revision Tibial Baseplate Position and Stem Trajectory With Custom Implants Using 3D Modeling to Optimize Press-fit Stem Placement

“…In uncemented prostheses, the stems are often offset in order to accommodate the canal position relative to the tibial tray [ 12 ]. However, mismatch between the trajectory of the intramedullary canal and the center of the metaphysis can cause components to be malpositioned, even with the use of offset stems [ 13 ]. The current stem constructs remain at fixed angles with the baseplate and are confined by specific offset sizes.…”