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

Abstract

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.

Keywords: derotational distal femoral osteotomy; genu valgus; lateral opening wedge distal femoral osteotomy; medial patellofemoral ligament; patellar instability.

FIGURE 1

Preoperative photographs and fluoroscopy. (A) The preoperative standing X‐ray of the lower limbs. (B) The preoperative X‐ray of the knee in anteroposterior position. (C) The preoperative X‐ray of the knee in lateral position. (D) The preoperative X‐ray of the knee in 90° axial position. (E) The preoperative 3D‐CT revealed genu valgus of the left lower limb. (F) The preoperative 3D‐CT showed that the femoral anteversion angle was 37.4°. (G) The preoperative 3D‐CT showed that the tibial tuberosity‐trochlear groove distance was 16.8 mm. (H) The preoperative MRI revealed the injury of the MPFL. (I) Preoperative appearance revealed genu valgus of the left lower limb. (J) Preoperative appearance suggested that the left hip internal rotation angle was 70°.

FIGURE 2

The 3D model reconstruction and simulated surgery. (A) CT images of the lower limbs. (B) Design of iliac crest osteotomy guide. (C) Design of femoral crest osteotomy guide. On the guide plate, we designed the symmetry point of MPFL femoral stop. The opposite side of this point is the femoral stop for MPFL reconstruction. (D) Determination of the osteotomy plane. (E) The end of the osteotomy is stretched 14.8°, that is, 14.76 mm. (F, G) Design of plate and screws. (H) Simulated surgery showed that the lower limb alignment returned to normal. (I) Simulated surgery indicated that the internal fixation position was satisfactory and the plate was attached well. (J–L) 3D printing guides, plates, and limb models.

FIGURE 3

Intraoperative photographs and fluoroscopy. (A) Lateral compartment under arthroscopy. (B) Medial compartment under arthroscopy. (C) Patellofemoral joint under arthroscopy. (D) Expose ilium. (E) The iliac crest osteotomy guide was placed. (F) Two trapezoidal iliac bone fragments were removed completely. (G) Expose the distal femur. (H) The femoral osteotomy guide was placed. (I) The position of the femoral osteotomy guide was observed under fluoroscopy. (J) Distal femoral osteotomy was performed with a swinging saw. (K) A bone chisel was used to open the distal femur and a plate was placed. (L) The distal femur was derotated and laterally opened with a distractor. (M)The plate was fixed and the iliac bone was implanted into the osteotomy. (N) Intraoperative X‐ray of the knee in anteroposterior position. (O) Intraoperative X‐ray of the knee in lateral position.

FIGURE 4

Postoperative photographs and fluoroscopy. (A) The postoperative standing X‐ray of the lower limbs. (B) The postoperative X‐ray of the knee in anteroposterior position. (C) The postoperative X‐ray of the knee in lateral position. (D) The postoperative X‐ray of the knee in 90° axial position. (E) The postoperative 3D‐CT showed that the lower limb alignment returned to normal. (F) The postoperative 3D‐CT showed that the femoral anteversion angle was 15°. (G) The postoperative 3D‐CT showed that the patellofemoral relationship returned to normal. (H) The postoperative 3D‐CT indicated that the femoral stop position of reconstructed MPFL was satisfactory. (I) Good function while standing. (J) Good function while knee extension. (K) Good function while knee flexion.