PMC7700959_01
(A) External rotation of the right lower extremity was observed. (B) The patient could sit straight but her posture was like a 'mermaid'.
gr1.jpg
PMC7700959_01_gr1.jpg
fig0005
A physical examination at our hospital revealed a thigh-foot angles of 30 degrees on the right and 10 degrees on the left, and this 20 degree difference resulted in sitting with her legs out to one side when she attempted to sit straight (Fig. 1A, B).
(A) Rosenberg view. The right knee had an Ahlback classification of a 3rd degree valgus knee OA.(B) A long leg standing X-ray revealed that the weight bearing line passed laterally through to the medial tibial plateau.(C) Anterior hip rotation and tibial external torsion were evident.(D) MRI (proton density-enhanced imaging) scan indicating that the lateral cartilage was severely worn.
gr2.jpg
PMC7700959_01_gr2.jpg
fig0010
Ahlback classification of grade 3 in the lateral compartment of the knee. According to the deformity analysis, her % mechanical axis (%MA) was 69 %, the femoro-tibial angle (FTA) was 168 degrees, the hip-knee-ankle angle (HKA) was 4 degrees, the mechanical lateral distal femoral angle (mLDFA) was 87 degrees, and the medial proximal tibial angle (MPTA) was 88 degrees (Fig. 2A, B). Computed tomography (CT) further revealed a femoral neck anteversion of 27 degrees on the right and 29 degrees on the left, and a tibial external torsion of 52 degrees on the right and 23 degrees on the left (Fig. 2C). Magnetic resonance imaging (MRI) indicated moderate to severe cartilage wear of the lateral femoral tibial joint (Fig. 2D).
(A) The cartilage of the lateral compartment with the lateral meniscus was absent and the subchondral bone could be observed. (B) K-wires were inserted both proximal and distal to the tibia as references.(C) A distal tibial osteotomy was performed through a longitudinal skin incision.(D) A 30 degree rotational correction was performed and with subsequent fixation achieved using a TomoFix plate which was placed upside down.
gr3.jpg
PMC7700959_01_gr3.jpg
fig0015
From an arthroscopy assessment, we found that the cartilage in the lateral compartment was absent and that the subchondral bone could be observed (Fig. 3A). During the DTDO, K-wires were first inserted proximal and distal to the tibia as references to control the tibial rotation (Fig. 3B). We then performed an osteotomy perpendicular to the longitudinal axis of the tibia using a bone saw (Precision  Oscillating Tip Saw; Stryker, Kalamazoo, MI) at 3 cm from the distal tibial plafond after exposing the tibia between the extensor hallucis longus and tibialis anterior tendon (Fig. 3C, D).
(A, B) Frontal and lateral views of a postoperative X-ray.(C) A postoperative long leg standing X-ray revealed that the weight bearing line passed medially through to the medial tibial plateau.(D, E) The postoperative right tibial external torsion angle was 22 degrees (23 degrees on the healthy side).
gr4.jpg
PMC7700959_01_gr4.jpg
fig0020
At the final postoperative evaluation (28 months), the %MA was 20 %, the FTA was 179 degrees, the valgus alignment was improved, the external torsion was 22 degrees, and the side-to-side difference was 1 degree, respectively (Fig. 4A-E, respectively).
(A, B) Following surgery the patient could attain a normal straight sitting position.
gr5.jpg
PMC7700959_01_gr5.jpg
fig0025
At 28 months after surgery, this patient had no knee pain during walking, could run, and could sit straight (Fig. 5A, B), although careful follow-up continued to be needed.