Combined Distal Femoral Osteotomy and Medial Patellofemoral Ligament Reconstruction for Patellar Instability and Genu Valgus: A Case Report and Literature Review.

BACKGROUND: Medial patellofemoral ligament (MPFL) reconstruction alone is not effective for patellar instability associated with anatomic abnormalities of lower limbs. In this article, we report a case of complex lower limb malformations, including genu valgus, lower limb shortening, and increased femoral anteversion angle. In addition to MPFL reconstruction, we performed a rare osteotomy named combined distal femoral osteotomy (CDFO), which combined the characteristics of lateral opening wedge distal femoral osteotomy (LOWDFO) and derotational distal femoral osteotomy (DDFO).

CASE PRESENTATION: We report the case of a 52-year-old female with left knee pain, valgus, and instability who was diagnosed with patellar instability and valgus knee osteoarthritis. Considering the patient's relatively young age, a hip-knee-ankle angle (HKA) of 194°, a mechanical lateral distal femoral angle (mLDFA) of 77.5°, a shortened left lower limb of 7 mm, an increased femoral anteversion angle (FAA) of 37.4°, and a patellar instability, we performed MPFL reconstruction and CDFO treatment. In this procedure, computer-aided design (CAD) combined 3D-printed osteotomy guide-assisted CDFO and MPFL reconstruction were performed. At 6-month follow-up, the patient achieved satisfactory results, with an HKA of 180°, an mLDFA of 90°, an FAA of 15°, the same length of lower limbs, and patellar stability. There was significant improvement in her left knee pain, function, and patellar stability.

CONCLUSIONS: To our knowledge, this rare pattern of patellar instability has not been previously described. Careful analysis of anatomic abnormalities is of great clinical significance and can better guide clinical treatment. CDFO may be an acceptable treatment for patellar instability with genu valgus and increased femoral anteversion angle.