Outcome of realignment for genu varum with tibial bone defect managed with antegrade bone transport / 中华骨科杂志

ABSTRACT

Objective:To study the outcome of realignment for genu varum with tibial bone defect managed with antegrade bone transport.Methods:To retrospectively study 11 patients with tibial bone defect and genu varum treated with antegrade bone transport from January 2012 to December 2020. All the patients were males, aged 42±16 years, left in 8 cases and right in 3. The segmental bone defect was secondary to fractures with amount of 7.9±2.1 cm. 10 cases were congenital genu varus, and 1 case was genu varus caused by malunion of proximal tibial fracture. The anatomical lateral tibio-femoral angle (aLTFA) was 179°(178°, 180°), the anatomical lateral distal femoral angle (aLDFA) was 82°(81°, 83°), joint line convergence angle (JLCA) was 0°(0°, 1°) and the anatomical medial proximal tibial angle (aMPTA) was 83.1°±3.9° before treatment. 7 cases were treated with unilateral external fixators, 3 cases with circular external fixators, and 1 case with hybrid external fixator. Antegrade bone transport surgeries were performed to treat bone defects and varus deformities. Among them, 3 cases using unilateral external fixators were additionally corrected for varus using swinging clamps, while 1 case using a circular external fixator was corrected for varus by installing hinges on the lateral side of the proximal tibia and distracting the medial-positioned threaded rod. The data including the angles between proximal pins in monorail fixators or proximal ring orientation in ring fixators and knee joint line, post-operative mechanic axis deviation (MAD) of lower extremity, the position of the mechanical axis relative to the width of the tibial plateau, mechanic medial proximal tibial angle (mMPTA), the amount of deformity correction in radiographic AP view, bone healing time, bone healing index (BHI), functional score and complications according to Paley's criteria were studied.Results:All 11 patients were followed up, and the follow-up time after removing the external fixators was 11(3, 25) months. The angles between pins in proximal clamp in monorail frame of 7 cases and hybrid frame of 1 case and joint line were 0° (-1°, 1°), while those between proximal ring orientation in circular fixators of 3 cases and joint line were 0°, 0° and 2° respectively. The MAD were -6±6 mm, mMPTA was 90°(89°, 92°), the amount of correction was 7.2°±3.9° in the last follow-up. The final mechanic axis passed through the lateral plateau at 58%±9% of its width (counting from medial knee edge). Well consolidation was achieved for all patients with 12±4 months (range, 7-20 months) of bone healing time. BHI was 1.6±0.6 months/cm (range, 1.2-2.9 months/cm). Functional score according to Paley's criteria was excellent in 7 cases and good in 4. Complications were 5 problems (3 of pin site infections and 2 of soft tissue infections) and 1 obstacle (soft tissue invagination). All the cases with problems were resolved with oral antibiotics. In the one with the obstacle of soft tissue invagination, the skin and docking site bone healing were noticed after invaginated tissue resection and refreshment procedure.Conclusion:It is advisable for genu varum with tibial bone defect to be realigned while managed with antegrade bone transport.