The decision about whether or not to correct a given deformity can be quite individual for each patient and there are no absolute rules. Relative indications for surgical correction of a deformity include the presence of pain or a deformity with a natural history of substantial progression (Table 3.2). In general, current or anticipated limb length discrepancies greater than 2 cm should be addressed.

Angulatory deformities about the knee should generally be corrected if the mechanical axis falls within zone 2 and the patient is symptomatic and should be corrected if the mechanical axis is beyond zone 2 (Fig. 3.1) even if the patient is asymptomatic. When the deformity about the knee requires correction, the joint orientation angles such as the lateral distal femur angle (LDFA), the medial proximal tibial angle (MPTA), and the joint line congruency angle (JLCA) should be measured. If the JLCA is more than 5° in conjunction with a bony deformity, we prefer to address the ligamentous laxity as well. If the deformity about the knee involves only the femur or the tibia and the other bone is normal, correction should nearly always occur within the affected bone. If both bones are abnormal but the majority of the deformity is within one of the bones, there may be some consideration to correcting only the bone with the majority of the deformity if less than 5° of abnormality is present in either the LDFA or MPTA. If greater than 5° of abnormality is noted in both the LDFA and MPTA, we prefer to address the deformity at both sites.

For sagittal plane deformities about the knee, one must consider both the bony deformity within the distal femur and proximal tibia as well as the soft-tissue constraints about the knee joint. The goal of treatment of sagittal deformity about the knee is functional range of motion in both extension and flexion. My preference is to develop a surgical plan that achieves knee extension within 5° of full extension and without hyperextension of greater than 5° as well as knee flexion of at least 90°. For patients with limited extension, one must consider concomitant hamstring, iliotibial band, or posterior capsule releases while correcting the bony sagittal deformity. Likewise, one can consider quadriceps lengthening to augment a deformity correction in a patient with limited knee flexion.

The decision to correct ankle alignment must be made in conjunction with a careful examination of the hindfoot. Patients with substantial deformity of the ankle may be clinically well aligned with a compensatory hindfoot deformity (Fig. 3.2). Patients with such well-compensated deformity and with limited subtalar motion may not be well served by a decision to correct the ankle and thus “create” a more visible deformity by uncovering the fixed hindfoot abnormality.

Contraindications to surgery are necessarily somewhat vague and include a number of patient-related factors including unrealistic expectations on the part of the patient and caretakers, their inability to follow through with the necessary outpatient components of a treatment program, as well as situations where the risks of surgical intervention outweigh the potential benefits to the patient (Table 3.3). For instance, patients with severe mental illness or with limited ability to comprehend the treatment plan may not have the ability to comply with more complex treatment protocols including gradual correction using external fixation. Although more complex treatment protocols may be contraindicated in these patients, simplified alternatives may represent better choices. For example, for some patients the difficulties involved in complying with instructions and a physical therapy program associated with a limb lengthening may be able to comply easily with the less strenuous instructions and therapy associated with a closed femoral shortening (Fig. 3.3).

The plan for each deformity may comprise any of a number of different techniques that might be applicable in a given situation (Table 3.4). There is no compelling reason to avoid combining techniques when clinically applicable. General categories that should be considered include soft-tissue surgery, physeal bar resection, growth modulation, acute correction with internal or external fixation, or gradual correction with external fixation. A brief description of the techniques follows with a general description of indications and contraindications.