Clinical implication of sagittal translation in lengthening over nail of tibia

Purpose: During the surgery of lengthening over nail (LON), we sometimes observe sagittal translation of proximal tibia (STPT) when the nail is inserted into the canal. We investigated the factors that lead to STPT and its clinical significance.

Methods: We reviewed 35 consecutive patients who underwent bilateral tibial lengthening with LON. The following parameters were assessed to evaluate the factors that can lead to STPT; the level of tibia osteotomy (OT) in sagittal plane, the type of the nail, the nail entry point in sagittal/coronal planes, and the type of the OT. Then, the followings are analyzed to find any possible clinical significance of this phenomenon: the change of posterior proximal tibial angle (PPTA), the cortical healing index, and the translation of the sagittal mechanical axis (SMA) of the lower extremity.

Results: The postoperative STPT was 3.04 ± 2.73 mm, and proximal location of the OT in relation to the nail bending point was found to increase STPT. The nail entry point in sagittal/coronal planes and the type of tibia OT had no significant correlations with STPT. It had no significant relations with the PPTA or cortical healing index. It pushed the SMA posteriorly, but the SMA was always anterior to the center of rotation of the knee joint.

Conclusions: Proximal location of the OT in relation to the nail bending point is related to STPT. However, it does not negatively influence cortical healing, posterior tibial slope, or SMA of the lower extremity.