The axis of deformity correction lies on the convex cortex. The overall length of the limb increases following deformity correction. The final length achieved will be equal to the sum of the lengths of the convex border of the deformity (Fig. 6.3a). If the combined total correction exceeds 2.5–3 cm of lengthening, shortening may be required as a cautionary measure since significant lengthening could compromise the neurovascular status. The nerve stretch in certain circumstances may be further influenced by the direction of rotation such as the risk of iatrogenic injury being somewhat less in external than internal rotation when performing a proximal tibial osteotomy because of tethering of the peroneal nerve at the proximal fibula [23]. When the axis of correction lies away from the osteotomy site further lengthening is achieved; for instance in calcaneal lengthening osteotomy the axis of correction lies away from the calcaneum, i.e. at the talar head [24] (Fig. 6.4).

The axis of deformity correction lies on the concave side of the deformity. The overall length of the limb increases following deformity correction and is equal to the sum of the concave borders of the deformity as shown in Fig. 6.3b. Generally, a closed wedge osteotomy in a straight bone reduces the limb length whereas the bone length increases or remains the same with an open wedge osteotomy, for instance with compensatory osteotomies for the proximal femur in Perthes disease and non-union of the neck of femur (Fig. 6.3c).

Dome osteotomy is ideal for deformities with CORA close to the joint line such as in physeal or metaphyseal injuries near the knee or ankle. The displacement of the osteotomy is directly proportional to the radius of correction. Dome osteotomy causes minimal length alteration as the CORA is usually at or near the site of deformity in the metaphysis. The advantage of such an osteotomy is good bony contact and intrinsic stability. However this technique is limited by its inability to correct rotational malalignment.

An angular osteotomy involves shifting of mechanical axis in the direction of correction of the deformity; that is, the mechanical axis shifts medially in varus and laterally in valgus osteotomy. Hence translation of the distal fragment has been advised in order to restore the mechanical axis [23]. A valgus proximal femoral osteotomy requires lateralisation of the distal fragment. However when doing an angular correction below the knee the direction of translation is opposite, i.e. lateral translation for varus and medial translation for a valgus osteotomy. Glard et al. showed that proximal femoral varus osteotomy with medial translation in Perthes disease did not affect the mechanical axis deviation at the knee [25]. There are a number of studies which show remodelling of the femoral neck-shaft angle following varus osteotomy with or without translation [25–30]. In a child, do we need to translate the distal fragment when performing angular correction to optimise the mechanical axis? Sanghavi et al. found that after varus de-rotation osteotomy, the neck-shaft angle tends to revert to normal depending on the age at which the operation was undertaken [26]. Tercier et al. showed that following proximal femoral osteotomy in Perthes, the resulting mechanical axis deviation is usually subtle and clinically insignificant in children [27]. Following varus osteotomy of the proximal femur in cerebral palsy 60 % of the correction is lost after 8 years by remodelling [28]. In pelvic support osteotomy it has been shown that up to 30° of valgus angulation at the osteotomy site does not cause any significant change in mechanical axis [31]. Therefore it is our assumption that translation of the distal fragment during angular correction of proximal femoral deformities is not mandatory in younger children unless the magnitude of correction is outsized, such as greater than 30°. This observation is also supported by the acceptability of overriding/bayoneting fracture reduction in younger children where after a few years complete restoration of the anatomy occurs [32]. The advantages of not translating are that the periosteal hinge medial or lateral stays intact and the final lengthening achieved is greater than with translation (Fig. 6.5).

An oblique osteotomy corrects multi-planar deformities at the same time. A meticulous preoperative planning is essential as it involves correction of the deformity in various planes through a single osteotomy. Lesser the obliquity of the plane, lesser is the bony contact after angular correction but easier and greater is the rotational correction such as in Rab’s osteotomy (Fig. 6.6).

Lengthening osteotomy in a single stage is best achieved either by a step cut/long oblique osteotomy to maintain adequate contact while lengthening at the same time such as in distal fibula, metatarsals or proximal ulna. Acute lengthening of 1.7 cm and 3.2 cm for the tibia and femur, respectively, has been performed with minimal complications in adults [33]. Opening wedge angular correction can some time offset the shortening caused by varus angulation and gain in length to some extent, for instance in Perthes disease (see Fig. 6.4a). It is important to keep in mind the change in length ratio as compared to the companion bones in case of osteotomies of leg and foot [34]. Acute shortening of up to 3 cm can be performed safely in young adults with open tibial fractures with bone loss [35]. Further shortening should be gauged based on the clinical assessment of limb vascularity. Fibular shortening osteotomy can be combined with proximal tibia corrective osteotomy in achondroplasia to correct the lateral collateral laxity and fibular overriding [36]. The major disadvantage of lengthening/shortening osteotomy with acute correction is that the amount of correction safely gained is limited. If the magnitude of angular deformity correction is considerable, either a shortening osteotomy or distraction osteogenesis is preferred to avoid significant risk to the neurovascular structures and soft-tissue tightness (Fig. 6.7).

Angular deformity secondary to physeal insult is usually progressive until skeletal maturity. The following strategies can be adopted for such corrections:

In the Indian subcontinent, raw mango slice, a savoury seasonal snack for children, is split into multiple radial cuts for better seasoning. This makes a good illustration for osteotomy with multiple open wedges for diaphyseal deformity as seen following rickets and other metabolic disorders. The concept and execution are explained in the following illustration. Small corrections at two or more CORAs allow lengthening and deformity correction spread over the length of bone (Fig. 6.8).

Paediatric congenital and developmental conditions such as developmental coxa vara, fibular hemimelia and posteromedial bowing of tibia have a memory because of associated soft-tissue contractures. Following an osteotomy, either the deformity can recur by bending the callus or slow relapse occurs due to abnormal forces on the growing physis [Heuter-Volkmann]. In these situations the osteotomies should be combined with soft-tissue lengthening or shortening of the bone (Fig. 6.9).

Certain fractures of the proximal tibia in a growing child are associated with a proximal tibial valgus deformity. These deformities may correct spontaneously over a few years, and thus an acute corrective surgery for the tibial valgus should be deferred for at least 3–4 years following the fracture [37, 38] (Fig. 6.10).

Sometimes acute correction of the deformity can be combined with another procedure. This can be unifocal such as physeal bar excision with corrective osteotomy in hemi-physeal arrests around the knee (see Fig. 6.2). Alternatively it could be bifocal, where it is not optimal to do the angular correction at the same site as that of lengthening, for instance pelvic support osteotomy with distal femoral lengthening [47, 48]. Guided growth procedures can also be performed along with acute osteotomy, e.g. lateral proximal tibial guided growth along with ipsilateral Rab’s osteotomy for a child with Blount’s disease [49]. To counter the muscle imbalance brought about by cerebral palsy or meningomyelocele and other neuromuscular disorders, corrective osteotomy is combined with a muscle-balancing procedure, thereby avoiding relapse. For example, patellar tendon reefing is done following supracondylar extension osteotomy for fixed flexion deformity of the knee in cerebral palsy, and tibialis anterior transfer to the heel is combined with a calcaneal osteotomy in a child with excessive ankle dorsiflexion and weak plantarflexors.

In certain conditions like osteogenesis imperfecta, when the child is non-ambulatory, the indication for a corrective osteotomy is to aid seating on a wheelchair, better hygiene and prevent further deformities rather than aligning mechanical axis. A long-standing dislocated or destroyed painful hip in a child can be managed by a pelvic support osteotomy combined with excision of the femoral head.

Growth considerations have to be kept in mind when planning deformity correction. Hence osteotomy planning in children is somewhat different from that of adults where accurate line diagrams and metaphyseal angles are drawn with a view to achieve precise alignment of the knee mechanical axis. While restoring the mechanical axis is important in children, the deformity correction involves aligning the proximal and distal physes parallel to each other and perpendicular to the ground rather than merely achieving exact anatomical alignment. However in older children nearing skeletal maturity, the principles of restoring the mechanical axis used for adults are more applicable. While there are several methods for preoperative planning, we will illustrate our preferred planning methods for acute correction of the tibial and femoral deformities in children.