17 Management of complications after high-tibial open-wedge osteotomy
Performing open-wedge osteotomies around the knee the surgeon must be aware of complications that might occur and must be able to manage these.
Overcorrection in medial open-wedge osteotomy of the proximal tibia leads to a severe valgus deformity of the leg. Besides being cosmetically unacceptable, this overcorrection results in overload of the lateral joint compartment.
If overcorrection is noticed intraoperatively, the osteotomy gap can be corrected by adjusting the arthrodesis spreader before inserting the angular locking head screws (“fine tuning” see chapter 9 “High-tibial open-wedge valgization osteotomy with plate fixator”, subchapter 5 “Surgical technique”, and Fig 9-12 ).
If the overcorrected axis is observed during the early postoperative phase (week 1–12), it is sufficient to remove the distal locking bolts and to readjust the osteotomy opening. In some cases it might be necessary to remove the granulation tissue in the osteotomy gap (see chapter 12 “Radiological examination of bone healing after open-wedge tibial osteotomy”, subchapter 2 “Evaluation of magnetic resonance imaging”) and to weaken the lateral hinge with a 2.0 mm drill to close the osteotomy. After achieving the correct alignment the distal fixation of the TomoFix implant should be performed with bicortical locking head screws. The authors would like to stress that in primary high-tibial open-wedge osteotomy (HTO) procedures monocortical locking head screws should be used in holes 2–4 of the plate fixator. If a revision is necessary, the opposite cortex is intact and secure fixation can be achieved using bicortical locking head screws ( Fig 17-1 ).
During the late postoperative phase (after 3 months) bone healing of the osteotomy has advanced. In order to achieve correction the implant must be removed completely and a medial closed-wedge osteotomy of the proximal tibia is necessary. The result is stabilized by reapplying the TomoFix fixator with bicortical locking head screws ( Fig 17-2 ).
Valgus overcorrection can be prevented by correct preoperative planning. Projection errors on the long-leg weight-bearing x-ray must be detected, eg, the patella must be located exactly anteriorly on the AP view, the knee must be completely extended and both legs should be loaded symmetrically. Before planning the osteotomy on the radiographic workstation, a calibration must be performed. The problem of asymmetric joint line opening must be addressed either by graphic or mathematical correction (see chapter 5 “Detailed planning algorithm for high-tibial osteotomy”). To assess the mechanical axis during surgery, the entire leg should be draped including the iliac crest. Before stabilizing the osteotomy the corrected axis must be checked using a metal rod (see chapter 9 “High-tibial open-wedge valgization osteotomy with plate fixator”, Fig 9-14) which is more reliable than an electrocautery cable. Correct positioning in full extension of the knee joint and exact rotation is mandatory in this step. Weight bearing should be simulated to balance asymmetric joint opening by applying dosed axial pressure to the foot sole.
Drape entire leg and iliac crest.
Be aware of projection errors.
Correct asymmetric joint opening during preoperative radiographic planning.
Check corrected mechanical axis intraoperatively.
Simulate weight bearing and balance asymmetric joint opening.
3 Joint-line obliquity
When correcting the leg axis of the lower limb, the osteotomy must be performed at the site of the deformity. Frontal plane correction can result in a pathological alteration of the joint line if the correction is not performed at the site of the bone deformity (Fig 17-3), therefore leading to subsequent loading on an incorrectly aligned plane (see chapter 14 “Double osteotomies of the femur and the tibia”, Fig 14-2a-c). Studies have proven that only 31% of patients with varus degeneration of the knee have osseous deformity at the tibia, whereas in 59% the varus deformity is located at the femur and in 10% both femur and tibia are affected . This means that in 69% of patients with varus deformity a valgization osteotomy at the tibia will result in an unphysiological joint line. Joint-line divergence more than 8° from normal will definitively lead to significant pain under loading [2, 3] and must be avoided under all circumstances.
All axes and angles must be analyzed preoperatively (see chapter 1 “Physiological axes of the lower limb”, Fig 1-1a-b ) and the level of the deformity must be identified (see chapter 1 “Physiological axes of the lower limb”, Fig 1-5a-b ). In case of a pathological mechanical lateral distal femoral angle (mLDFA > 87 ± 3°) and a normal mechanical medial proximal tibial angle (mMPTA = 87 ± 3°) the correction must be performed at the femoral side as a lateral closed-wedge osteotomy.
Analyze all axes and angles preoperatively. Identify level of deformity.