Purpose: Intramedullary lengthening nails are an accepted alternative to external fixators but are limited by anatomical preconditions. Therefore, to date the use of external fixators is sometimes inevitable. We report on a new technique for correction of combined limb length discrepancies and complex axis deformities using solely internal devices - a lengthening nail and a locking plate.
Methods: Between October 2008 and November 2011 five patients (two femora, three tibias) with a mean leg length discrepancy of 36 mm (25 to 50) and a complex angular deformity were treated with a fully implantable motorized lengthening nail (Fitbone) and a locking plate. All patients were evaluated with regards to the pre- and postoperative leg length as well as axis alignment, functional outcome, lengthening indices and complications.
Results: A successful leg length equalization was achieved in all cases and physiological joint orientation angles in all but one case. The mean distraction index was 1.2 mm/day, the maturation index 24 days/cm and the consolidation index 35 days/cm. The functional outcome was very encouraging in all cases with bilateral free range of movement. In total, two complications were observed, one nonunion and one loss of leg length after an early locking bolt removal in a peripheral hospital.
Conclusion: The combination of a fully implantable motorized lengthening nail and a locking plate is a valuable alternative option for treating selected cases with limb length discrepancies in combination with a complex deformity of the lower leg. However, the reported technique puts high demands on the preoperative planning, operative technique as well as surgeon's skills.
Level of evidence: IV (retrospective series).
Keywords: axis deformity; fitbone; intramedullary nailing; leg lengthening; mechanical axis.