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 [8]. 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 [9] (Table 14.1 edited from Brinkman et al. [10]).

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 [11]. 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 [11]. 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 [12]. 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 [13] (Fig. 14.3).

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 [14], the old [15], smokers [16] and those with a raised BMI [16]. 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.

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.