Restoration of Native Leg Length After Opening-Wedge High Tibial Osteotomy: An Intraindividual Analysis.

Abstract

Background:Opening-wedge high tibial osteotomy (OWHTO) has been shown to significantly increase leg length, especially in patients with large varus deformity. Thus, the current literature recommends closing-wedge high tibial osteotomy to correct malalignment in these patients to prevent postoperative leg length discrepancy. However, potential preoperative leg length discrepancy has not been considered yet.Hypothesis:It was hypothesized that patients have a decreased preoperative length of the involved leg compared with the contralateral side and that OWHTO would subsequently restore native leg length.Study Design:Case series; Level of evidence, 4.Methods:Included were 67 patients who underwent OWHTO for unilateral medial compartment knee osteoarthritis and who received full leg length assessment pre- and postoperatively. Patients with varus or valgus deformity (>3°) of the contralateral side were excluded. A musculoskeletal radiologist assessed imaging for the mechanical axis, full leg length, and tibial length of the involved and contralateral lower extremity. Statistical analysis determined the pre- and postoperative leg length discrepancy and the influence of the mechanical axis.Results:Most patients (62.7%) had a decreased length of the involved leg, with a mean preoperative mechanical axis of 5.0° ± 2.9°. Length discrepancy averaged –2.2 ± 5.8 mm, indicating a shortened involved extremity (P = .003). OWHTO significantly increased the mean lengths of the tibia and lower limb by 3.6 ± 2.9 and 4.4 ± 4.7 mm (P < .001), leading to a postoperative tibial and full leg length discrepancy of 2.8 ± 4.3 mm and 2.2 ± 7.3 mm (P < .001 and P = .017, respectively). Preoperative leg length discrepancy was significantly correlated with the preoperative mechanical axis of the involved limb (r = 0.292; P = .016), and the amount of correction was significantly associated with leg lengthening after OWHTO (r = 0.319; P = .009). Patients with a varus deformity of ≥6.5° (n = 14) had a preoperative length discrepancy of –4.5 ± 1.6 mm (P < .001) that was reduced to 1.8 ± 3.5 mm (P = .08).Conclusion:Patients undergoing OWHTO have a preoperative leg length discrepancy that is directly associated with the varus deformity of the involved extremity. As OWHTO significantly increases leg length, restoration of native leg length can be achieved particularly in patients with large varus deformity.