(a) Physiological alignment measurements in the coronal plane from a long leg weight bearing radiograph measurement. (b) Enlarged image shows the weight-bearing axis in the medial compartment. Also shown are the medial proximal tibial angle (MPTA) and the mechanical lateral distal femoral angle (mLDFA) (All measurements taken using MediCAD© Classic Version 220.127.116.11)
A high tibial osteotomy (HTO) is the most widely recognised and widely practiced osteotomy for the treatment of medial compartment OA in the varus knee. Broadly speaking, there are three methods that can be employed to achieve the desired correction. These include a closing wedge, an opening wedge and a dome osteotomy (Fig. 14.2). Traditionally, the objective of surgery is to push the patient into valgus alignment and transfer load into the disease-free lateral compartment. The objective is to reduce pain and slow the progression of disease.
Illustration of the three broad categories of high tibial ostetomy for medial compartment osteoarthritis associated with metaphyseal tibia vara (a). Opening wedge (b), closing wedge (c) and dome osteotomy (d)
The lateral closing-wedge HTO (CWHTO) was popularised by Coventry through his work at the Mayo clinic . He took the original technique described by Gariepy and secured his closed wedge with a staple. He achieved good outcomes with 75 % survival rates reported at 10 years . Subsequently, this has been the most widely reported and practiced surgical technique. More recently, a medial opening-wedge HTO (OWHTO) has gained in popularity. This is in part due to advances in plate technology that enable stable fixation and high rates of union . The relative merits of these opposing techniques will be discussed later in this chapter.
Lateral compartment OA with valgus deformity is a less common phenotype and consequently there are fewer studies supporting the use of osteotomy in this patient group. A distal femoral varus osteotomy (DFVO) is typically achieved using a medial closing wedge technique . Outcomes for this type of surgery will also be discussed later in the chapter.
The popularity of osteotomy surgery has certainly been in decline since the introduction of arthroplasty surgery. For many surgeons, the latter offers consistent outcomes and is their treatment of choice for patients with established osteoarthritis. However, there is evidence that arthroplasty surgery has less satisfactory outcomes in high demand, young patients. It is our belief that modern osteotomy surgery offers a viable alternative for these patients and others, offering good outcomes and low complication rates.
14.1.1 Patient Selection
As with any orthopaedic procedure, careful patient selection is key to a successful outcome. Patients should be made aware from the outset that osteotomy surgery is a major undertaking with significant risks and requires considerable application and commitment with post-operative rehabilitation. As a result, it should only be considered when all other conservative measures have been exhausted.
A thorough clinical history and examination is essential. Important considerations include the patient’s age, body mass index (BMI), smoking status, medical co-morbidities and any history of prior trauma or surgery. In addition to current activity level, it is valuable to gain an understanding of the patient’s expected activity level following osteotomy. Patients should be made aware that although a return to sport is expected they will typically not recover their pre-pathology level of activity . Clinical examination should include an evaluation of alignment, soft tissue integrity, ligamentous stability and neurovascular status. In addition, the range of movement and the presence of any fixed flexion deformity should be documented. The presence of any active infection locally or systemically should preclude surgery.
Traditionally, osteotomy surgery was reserved for end-stage ‘bone on bone’ unicompartmental osteoarthritis. However, in line with developments in surgical technique, the indications for this procedure are evolving. An expert panel from ISAKOS defined the criteria for a patient undergoing HTO for medial compartment osteoarthritis  (Table 14.1 edited from Brinkman et al. ).
Selection criteria for high tibial osteotomy as defined by ISAKOS, 2005 
Possible but not ideal
Isolated medial joint line pain
Flexion contracture <15°
Bi-compartmental (medial and lateral) OA
Age (40–60 year)
Fixed flexion contracture >15°
Age 60–70 year or <40 year
High-demand activity but no running or jumping
ACL, PCL or PLC insufficiency
Meniscectomy in the compartment to be loaded by the osteotomy
Moderate patellofemoral OA
Metaphyseal varus TBVA >5°
Wish to continue all sports
Full range of movement
Normal lateral and patellofemoral components
Ahlback grade I to IV
Normal ligament balance
Some level of pain tolerance
An important consideration is not only the underlying deformity but the cause of that deformity. Bonnin and Chambat reported superior clinical outcomes for patients undergoing osteotomy for medial OA for patients with a constitutional varus deformity of the proximal tibia . They proposed using the Tibia Bone Varus Angle (TBVA) to differentiate those patients with a congenital varus deformity from those with an acquired varus deformity (Fig. 14.1). Osteotomy in patients with a TBVA >5° was described as a curative procedure compared to those with a TBVA <5° in whom such surgery was felt to be a palliative measure . The anatomy of the distal femur may also play a part in outcome for HTO surgery. An overly varus distal femur has been associated with recurrence of varus deformity following surgery . However, a recent study has challenged these findings determining that neither varus inclination of the proximal tibia or distal femur influenced long-term survival of HTO over 10 years  (Fig. 14.3).
Figure illustrating the tibia bone varus angle (TBVA). This angle is formed between a line that links the midpoint of the tibial spines and the midpoint of the physis and a line that represents the mechanical axis of the tibia. TBVA >5° was associated with improved outcomes for high tibial osteotomy surgery 
Advances in the technical aspects of osteotomy are challenging the traditional concepts of an ‘ideal’ osteotomy patient. Favourable outcomes have been demonstrated in the young , the old , smokers  and those with a raised BMI . As research progresses it is likely that the ideal osteotomy patient will continue to be re-defined. As such it is important for surgeons to keep an open mind when considering patients who might be suitable for such a procedure.
14.2 Pre-operative Planning
Careful pre-operative assessment should be undertaken for all patients undergoing osteotomy surgery. Radiological assessment is necessary to establish both the extent of disease and the presence of a correctable deformity.
14.2.1 Radiological Assessment
Pre-operative assessment should include antero-posterior, lateral and skyline radiographs to enable the pattern of disease to be established. Weight-bearing views may assist with defining the severity of osteoarthritis and stress views can be used to identify the stability of the collateral ligaments. Where there is doubt about the underlying pathology or concerns that the disease process may not be confined to a single compartment, an MRI of the knee may be of use.
A weight-bearing radiograph of the lower limb is necessary to assess the site of the deformity and the correction required in the coronal plane. Institutions should make efforts to standardise the methods by which such radiographs are taken to ensure that the images obtained are both accurate and reproducible. The presence of malrotation or flexion deformity will significantly alter the perceived alignment .
Computed tomography (CT) may be required in cases associated with traumatic defects or where a significant torsional element to the deformity is suspected.
14.2.2 Coronal Alignment
The most frequent deformity associated with unicompartmental OA of the knee is varus or valgus malalignment. The long leg weight-bearing radiograph is considered by many to be the gold standard investigation for both the assessment of the underlying deformity and the planning of its correction.