Knee Osteotomies

Introduction

Osteotomies around the knee play a pivotal role in the treatment and prevention of osteoarthritis. They are also used as concomitant procedures to other joint preservation techniques, such as meniscal transplantation and articular cartilage restoration, and in the treatment of ligamentous instability. As such, realignment procedures in both the proximal tibia, distal femur, and tibial tubercle are regularly performed using a variety of techniques, all of which have potential specific complications.

The choice of the most appropriate surgical procedure is key to addressing the underlying pathology and associated deformity. Classically, valgus osteotomies were performed in the proximal tibia using a lateral proximal tibial closing wedge technique; however, the trend has more recently shifted toward medial opening wedge techniques, as respective outcomes prove to be equal, but with a technically less demanding procedure. ^{, , , , ,} Varus osteotomies are most commonly performed in the distal femur before idiopathic genu valgum is often caused by lateral femoral condyle hypoplasia. Therefore to restore a parallel joint line or to avoid producing joint line obliquity, either medial closing or lateral opening wedge distal femoral osteotomies (DFOs) are the procedures of choice in these cases. ^{, ,} Tibial tubercle osteotomies (TTOs) are most often performed in isolation, but may also be used in conjunction with tibial or femoral osteotomies. They are used to address several forms of patella malalignment in cases of recurrent patellofemoral instability. Their main aim is to unload the patellofemoral joint secondary to chondrosis or other secondary changes associated with increased contact pressures or abnormal patella tracking. Less commonly, they are combined with tibial osteotomies to maintain physiological patella height in cases where a large coronal plane correction is required to unload the affected tibiofemoral compartment. ^, Surgeon preference and intrinsic patient factors, along with an individual assessment of perioperative risk, all play a substantial role in determining which type of osteotomy will be selected for treatment.

Because each method has its particular hazards and pitfalls, an individualized approach to each case is needed to improve overall outcomes and decrease the risk of failure. Evaluation of preoperative risk factors can help decrease complications. Moreover, understanding the potential intraoperative, as well as postoperative, complications can aid in preventing them and enables the surgeon to master the procedure.

This chapter will outline the different complications associated with osteotomies around the knee, identifying specific areas where complication risk may be mitigated, using case examples where appropriate.

Medical Complications

The incidence of medical complications following osteotomy around the knee varies. Complications include, but are not limited to, cardiopulmonary issues, deep infection (1.7%), chronic regional pain syndrome (CRPS) (1.3%), and deep venous thromboembolism (1.3%). Preoperative patient assessment including a detailed history, physical examination, and investigational diagnostic workup is essential for successful patient selection before osteotomy procedures. Proper preoperative medical assessment helps to identify and optimize medical comorbidities, or to appropriately counsel those patients at high risk of complications, such as smokers or diabetics. ^{, ,} Thorough practice and cautious indications can potentially eliminate unnecessary operative risks. In those cases, where the specific risk be deemed to be too high, a nonoperative approach may be selected or an alternative procedure chosen.

Failure to Achieve Desired Coronal Plane Correction

Under- or overcorrection have been shown to lead to early failure. However, proper preoperative planning of every osteotomy procedure can reduce the impact of these potential complications. ^{, , ,} There is an ongoing discussion about the optimal postoperative coronal plane alignment for specific deformities and conditions. In cases of osteoarthritis, current consensus suggests that the weight bearing mechanical axis should pass through the knee between 50% to 62.5% of the medial to lateral tibial width, resulting in 3 to 5 degrees of mechanical valgus. The latter 62.5% position on the tibial joint line has come to be known as the Fujisawa point in recognition of the original work that suggested optimal outcomes with correction to this position. Anything beyond this point can be described as overcorrection and should be avoided because it can be associated with inferior cosmetic appearance and an unfavorable clinical functional outcome ( Fig. 23.1 ). Undercorrection, on the other hand, has also been discussed as problematic. However, a recent study demonstrated that, in those cases, a positive effect can still be achieved, based on the subsequent change in adductor moment following correction. It is yet to be determined if the long-term outcome is compromised by such undercorrection. Current consensus with regard to ligament and joint preservation procedures suggests not to correct into valgus, but opt for a more neutral limb alignment instead. In the varus knee, correction should have the achieved mechanical axis run through the lateral tibial spine. However, in the valgus knee, it is accepted that correction into a neutral position is optimal to avoid overloading of the medial compartment.