Valgus arthritic knees can be classified into nine phenotypes

Abstract

Purpose It is not shown whether anatomical variations exist in valgus arthritic limbs as to support individualized component and limb alignment. The null hypothesis was that there was no phenotypic variation of coronal femoro-tibial morphology in valgus knees. The aim was to determine whether distinct phenotypes of valgus knees could be identiied to help surgical planning and classifying valgus knees for outcome studies. Methods Full-leg weight-bearing radiographs of 233 knees (182 preoperative; 51 of contralateral arthritic knee) were measured for HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TBA (tibial bowing angle). Results Nine phenotypes were identiied encompassing all 233 knees which could be clubbed into 4 broad types. Type 1 Neutral knees (12.5%) had almost normal values (mean VCA 5.3°, mLDFA 86.9°, aLDFA 81.1°). Type 2 'Intra-articular valgus' (22.7%) showed lateral compartment bone loss (mean mLDFA 83.9°; MPTA 90.2°). Type 3 'Extra-articular valgus' (35.2%) had extra-articular deformity: 3a showed valgus femoral bowing (mean VCA 2.7°); 3b valgus tibial bowing; 3c showed valgus tibial bowing with lateral femoral condyle wear (mean mLDFA 84.3°). Type 4 'Varus' type (29.6%) had features of varus knees: 4a had varus femoral bowing (VCA 8.3°); distal femur in 4b was akin to varus knees (mean mLDFA 89.3°) with lateral tibial bone loss (mean MPTA 91.2°). 4c had varus tibial bowing and deicient lateral femoral condyle (mLDFA 83.7°). 4d had varus tibial bowing and lateral tibial bone loss (mean MPTA 89.8°). ConclusionsThe study identiied four broad groups of valgus arthritic knees with nine phenotypes based on coronal plane variations in femoro-tibial morphology. This study may be of value in planning and performing corrective osteotomies, and planning the optimal position of femoral and tibial components in unicompartmental and total knee arthroplasty. The classiication presented in this study may aid in categorizing valgus knees for outcome studies. Level of evidence IV.

Functional Alignment Philosophy in Total Knee Arthroplasty—Rationale and Technique for the Valgus Morphotype Using an Image Based Robotic Platform and Individualized Planning

“…As the concept of alignment morphotypes has evolved [ 5 , 25 ], the understanding that varus and valgus limbs behave differently and thus may require alternate strategies in TKA has also emerged [ 22 ]. Recently, the valgus morphotype was described as having nine discrete entities depending on the origin of the deformity (intra-articular and/or extra-articular, femur and/or tibia) [ 26 ]. Such variation demands a more individualized approach to TKA.…”

“…The implications being that following the PCA for rotational alignment, as is the case in KA, will lead to an excessively internally rotated femoral component. This is particularly relevant in the valgus morphotype where lateral condyle bone deficiency is encountered in at least 25% of cases [ 26 ], making the PCA an unreliable landmark. Recently it was demonstrated that using the PCA as reference for femoral component position, as is the case in KA, led to more than 20% of TKA’s having a femoral component that was more than 3° internally rotated relative to the TEA [ 24 ].…”

“…As the concept of alignment morphotypes has evolved [ 5 , 25 ], so too has the understanding that varus and valgus limbs behave differently and thus require different strategies in TKA [ 22 ]. Recently, the valgus morphotype was described as having nine discrete entities based on coronal plane variations in femoro-tibial morphology [ 26 ]. TKA for the valgus morphotype has traditionally been considered more demanding [ 27 , 28 , 29 , 30 ] due to factors such as extra articular deformity in the tibia [ 31 , 32 ], external tibial rotation (which is coupled with lateral soft tissue contractures that predispose to patellofemoral joint (PFJ) balancing difficulties), medial collateral ligament (MCL) attenuation [ 31 , 33 ], and a significant variability in the morphology of the distal femur [ 34 ].…”

Total Knee Arthroplasty in Valgus Knee

“…Based on full-leg weight-bearing radiographs of 233 knees, the study of Mulaji et al [9] identified four broad groups of valgus arthritic knees with nine phenotypes based on coronal plane variations in femoral and tibial morphology. Type 1 Neutral knees (12.5%) had almost normal values.…”

Varus morphology and its surgical implication in osteoarthritic knee and total knee arthroplasty

“…Moreover, there is great interest to understand and classify knee deformity not only based on HKA but also on the coronal joint line orientation. As demonstrated in different studies [ 14 – 16 ], the joint line obliquity can be determined by different combination of femoral and tibial phenotypes, both in varus and in valgus knees. The knowledge of the individual role of these patterns could be the key to personalize the reconstructive procedures in the future.…”