Osteotomy to correct lower-limb deformity may be necessary when residual growth precludes asymmetric epiphysiodesis. Interlocking intramedullary nailing (IMN) provides minimally invasive stable fixation, spanning fragile segments, and compatible with bone lengthening, but requires precise preoperative planning and meticulous operative technique, as the room for postoperative adjustment is very limited. Our aim here is to present practical indications, planning principles, instrumentation, operative steps and postoperative management for safe and effective correction of femoral and tibial deformities using IMN.

This is a narrative technique-focused synthesis drawing on the authors’ surgical experience and current operative principles to guide patient selection, imaging, osteotomy level, implant selection and intraoperative strategy. Five main questions are addressed:

Preoperative clinical examination includes assessment of the stability and range of motion of the joints adjacent to the deformed bone segment. A scaled full-length standing radiograph with patellae facing forward is necessary for preoperative planning, along with a true lateral view. Intraoperatively, the patient is placed supine on a standard table fitted with an alignment grid. Contraindications include very severe or complex deformities and current or recent bone infection. IMN is suitable for correction of most cases of valgus/varus, pro-/re-curvatum and rotational deformities, and intramedullary motorized lengthening nails can also be applied in case of limb length discrepancy. Diaphyseal and metaphyseal deformities around the knee are the best indications. Straight reamers are recommended for metaphyseal deformities. Reference Schanz screws are placed above and below the planned osteotomy level for rotation control. A tube system, introduced like a working portal into the bone, seals the joint completely and maintains the reamer at the entry point in a constant trajectory according to the preoperative plan.

Holes are drilled at the osteotomy site and serve as venting holes to decrease the risk of fat embolism during reaming and to enhance bone healing, like autologous bone grafting. Blocking screws can be used to increase stability in case of a wide medullary canal and/or to allow large corrections.

IMN typically allows at least partial immediate weight-bearing and free range of motion without immobilization. Patients undergoing limb lengthening should be followed up regularly in the outpatient clinic by a multidisciplinary team assessing bone formation, implant-related complications and joint contractures.

Interlocking IMN is a versatile option for acute correction of most femoral and tibial diaphyseal and metaphyseal deformities, and for simultaneous length restoration using motorized nails when indicated. Success hinges on careful patient selection, planning based on the center of rotation and angulation (CORA), precise osteotomy placement and staged reaming, frequent use of blocking screws, Schanz-pin rotation control, and adjunct fixation when necessary, with regular follow-up. When complexity or juxta-articular epiphyseal involvement precludes IMN, hexapod external fixation is an alternative.

V, expert opinion.