Deformity Correction by Femoral Supracondylar Dome Osteotomy with Retrograde Intramedullary Nailing in Varus Deformity of the Distal Femur after Pathologic Fracture of Giant Cell Tumor
A 46-year-old female patient visited our clinic with a complaint of persistent pain in the left knee that had lasted for one year. She had no history of trauma or infection. Physical examination revealed mild tenderness along the medial joint line and restricted range of motion in the affected knee (0-120 i) compared to the intact knee (0-140 pa). Although varus deformity of the knee was visible to the naked eye, joint instability was not present. Plain radiographs showed a varus deformity caused by malunion in the left distal femur, medial femorotibial joint space narrowing, and subchondral sclerosis (). The umbilicus malleolar distance (UMD) was 84.8 cm on the intact side and 83.2 cm on the affected side. The spina malleolar distance was 80.2 cm on the intact side and 79.1 cm on the affected side. The patient did not complain of discomfort related to the leg length discrepancy. The femorotibial angle was measured as 21.5° of varus, the mechanical lateral distal femoral angle (M-LDFA) was 104.3° and the anatomical lateral distal femoral angle (A-LDFA) was 109.5° in the left knee (). Her medical history showed that she had been diagnosed with giant cell tumor of the distal femur ten years ago, which was treated with curettage and cryotherapy with liquid nitrogen and allograft (), and then the same treatment was performed 9 and 8 years ago, respectively, due to recurrence. Thereafter, she sustained a pathologic fracture in the same region after a slip and fall, which was treated conservatively ().\nDeformity correction was determined necessary considering the patient's young age and radiographic findings of severe varus deformity combined with arthritis in the medial compartment. Although the UMD on the affected knee was shorter than that on the intact knee (83.2 cm vs. 84.8 cm), there was no significant side-to-side difference in the total anatomical length of the femur and the tibia (68.3 cm in the intact knee and 67.9 cm in the affected knee) and the patient did not complain of any discomfort. Thus, leg-length equalization was considered unnecessary. The correction angle was determined as 30° with the aim of achieving 5°-10° varus of the feromotibial angle postoperatively. It was estimated that the 30 correction for the femur with a diameter of 4 cm would result in 2.3 cm of leg lengthening with use of a medial open technique whereas 2.3 cm of leg shortening with use of a lateral closed technique. Thus, we determined to perform a corrective dome osteotomy that would have no significant influence on the leg length.\nAdhesiolysis around the anterior joint capsule and quadriceps lengthening were considered necessary due to limited flexion. For the osteotomy, we determined to use an anteromedial approach as in the previous surgery. After making a 15 cm skin incision on the anteromedial aspect, adhesiolysis around the anterior joint capsule and quadriceps lengthening using Z-plasty were performed. After verifying the recovery of complete range of motion, the rectus femoris and patellar bone were retracted laterally to expose the distal femur. Evidence of arthritis was observed across the medial articular surface of the distal femur, but specific findings that suggest a giant cell tumor were not noted. The center of rotation angulation (CORA) was located under fluoroscopy. After determining the dome osteotomy site from the femoral supracondylar with an interval of 10.0 mm using a 2.0 mm drill bit, the osteotomy was performed using a parallel saw blade (Synthes GmbH, Solothurn, Switzerland) (). The varus deformity was corrected and the mechanical and anatomical axes were assessed under the guidance of fluoroscopy. Without an additional incision, retrograde intramedullary nailing was performed through the distal femur for fixation. PolyBone (Kyungwon Medical Co., Seoul, Korea) containing polyphosphonate and bone morphogenetic protein was additionally inserted (). For six postoperative weeks, long leg cast immobilization was applied, and active joint exercises and partial weight-bearing were allowed. Full weight-bearing was permitted from the 12th postoperative week. At 24 weeks postoperatively, bone union and normal range of motion were achieved. The femorotibial angle was 6.3° of varus, the M-LDFA was 78.6, and the anatomical A-LDFA was 76.3 at 24 weeks postoperatively ().