Osteotomies for lateral compartment knee osteoarthritis

Abstract

Lateral compartment osteoarthritis (LCOA) is often associated with valgus deformity of the knee. The concept of correcting the alignment by performing distal femoral varus osteotomy (DFVO) to unload the lateral compartment is well accepted and it is viewed as the preferred option for young active patients due to dissatisfaction from arthroplasty under 55 years of age or if they wish to remain active. Beyond this there is no consensus on patient selection, preoperative assessment, techniques to achieve correction, end point of correction, return to work or sports post-surgery, and survivorship of osteotomy with conversion to a total knee replacement as the end point due to heterogenous, retrospective studies. Here, we review relevant literature to help patient selection, preoperative work up, techniques, and outcomes.

Keywords: Distal femoral osteotomy; Genu Valgum; Lateral compartment; Osteoarthritis; Osteotomy around the knee; Valgus deformity.

Fig. 1a

Analysis of long leg xray to calculate the desired correction angle.

Fig. 1b

Open and Close Wedge Distal Femoral Varus Osteotomies. Use of External Fixator – it is removed once the plate is fixed.

Fig. 2

56 yr male presented with lateral compartment OA from recurrent lateral meniscal tear. Also known to have knock knees from very young age. Malalignment and Malorientation tests show that the valgus is from the proximal tibia – mLDFA (mechanical Lateral Distal Femoral Angle) is normal (86 and 85° - normal 85–90) and mMPTA (mechanical Medial Proximal Tibial Angle) is abnormal (93 and 96° - normal 85–90°). Cartilage loss in lateral compartment is also contributing (JLCA – Joint Line Congruence Angle – is 4° compared to 0 on right side).

Fig. 3

Surgical technique illustrates the use of femoral distractor (or an external fixator) to aid control of correction. A. Femoral distractor with two pins inserted outside the plate location. Distal pin is applied parallel to the articular surface of femur to mimic the valgus alignment. B. Image intensifier picture illustrating the distal pin position and removal of measure medial wedge with apex ending approximately 5 mm from the lateral cortex. C. Wedge should include anterior and posterior cortices. Often it doesn't come out as clean wedge. Curette and small osteotome are used to extract all of the wedge – leaving bit at the apex often makes it difficult to close the wedge and also risks fracture. D. Note the position of distal screw after correction – it is now in neutral position from valgus before correction. E. Always use a rod or diathermy cable to assess alignment (from hip to ankle) before completing plate fixation. F. Care is taken to avoid flexion or extension of distal femur – distractor assists in preventing this. G. Pre and Post correction long leg views after medial colosing wedge.