Knee Joint Line Obliquity Causes Tibiofemoral Subluxation That Alters Contact Areas and Meniscal Loading

Abstract

Background: Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO) before and after coronal realignment osteotomy. Hypotheses: Higher JLO would lead to abnormal relative position of the femur on the tibia, a shift of the joint contact areas, and elevated joint contact pressures. Study Design: Descriptive laboratory study. Methods: 10 fresh-frozen human cadaveric knees (age, 59 ± 5 years) were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0°, 4°, 8°, and 12° varus (“downhill” medially) and valgus, at 0° and 20° of knee flexion. The mechanical compression axis was aligned to the center of the tibial plateau. Contact pressure and contact area were recorded by pressure sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system. Results: Both medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to subluxate medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes ( P < .01), giving a 6-mm range of subluxation. The areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the downhill meniscus and the “uphill” tibial spine. Changes in JLO had only small effects on maximum contact pressures. Conclusion: A 4° change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. This caused large movements of the tibiofemoral contact pressures across each compartment. Clinical Relevance: These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO. This information provides guidance regarding the choice of single- or double-level osteotomy. Excessive JLO alteration may cause abnormal tibiofemoral joint articulation and chondral or meniscal loading.

Clinical Effect of Isolated Lateral Closing Wedge Distal Femoral Osteotomy Compared to Medial Opening Wedge High Tibial Osteotomy for the Correction of Varus Malalignment: A Propensity Score–Matched Analysis

“…When a mowHTO is performed in a predominantly femoral varus malalignment, this may result in the creation of an oblique KJL, 30 which emphasizes the paradigm that the corrective osteotomy should be performed at the location of the deformity to sustain a physiologic KJL postoperatively. 10 , 30 Biomechanical consequences of an oblique KJL created during mowHTO include increased tibial contact pressure, 43 increased shear stress to the articular cartilage, 28 translational knee instability, 15 tibiofemoral subluxation, 43 and progressive degeneration of the joint space. 38 Clinically, this may translate into inferior PROs 38 and lateral compartment pain.…”

“…Recent investigations increasingly focus on the role of knee joint line (KJL) orientation in the context of alignment-corrective osteotomy, 15 , 19 , 28 , 38 , 43 which is horizontal in the coronal plane during gait under physiologic conditions. 30 To maintain a leveled KJL postoperatively, the osteotomy should be performed at the location of the varus deformity, 30 as an oblique KJL has been associated with nonphysiologic biomechanical pressure distribution 28 and inferior clinical outcomes.…”

“…2,3,6,13,27,35,36,39,45 Although traditionally an ''all-intibia'' approach to varus deformity correction via medial opening wedge high tibial osteotomy (mowHTO) has been advocated, 6,13,39,45 the dogma of an isolated tibial-based deformity has recently been reevaluated. 10,28 Recent investigations increasingly focus on the role of knee joint line (KJL) orientation in the context of alignment-corrective osteotomy, 15,19,28,38,43 which is horizontal in the coronal plane during gait under physiologic conditions. 30 To maintain a leveled KJL postoperatively, the osteotomy should be performed at the location of the varus deformity, 30 as an oblique KJL has been associated with nonphysiologic biomechanical pressure distribution 28 and inferior clinical outcomes.…”

Conceptos actuales en osteotomías en doble nivel alrededor de la rodilla

“…La oblicuidad de la interlínea articular (OIA) se define como el ángulo que forman la intersección de una línea paralela al suelo y una tangente a la superficie articular proximal de la tibia. Su valor normal se ha calculado, mediante estudios clínicos 33 34 35 36 y biomecánicos, 37 38 en 0° ± 4°. Su inclinación lateral (valgo) genera un valor positivo, mientras que una inclinación medial (varo), un valor negativo.…”

“…The JLO is the angle between a line parallel to the ground and a line tangent to the proximal tibial articular surface. Its normal value has been calculated in clinical 33 34 35 36 and biomechanical 37 38 studies as 0° ± 4°. Its lateral tilt (valgum) generates a positive value, and a medial tilt (varum) results in a negative value.…”