A case of excessive femoral anteversion which caused instability of the medial collateral ligament of the knee joint

Abstract

Introduction: The most cases of excessive femoral anteversion may be asymptomatic, because the he hip joint is a ball joint. However, when the hip, knee, or ankle joint is in a pathological state, excessive femoral anteversion may not be compensated for and induce symptoms.

Case report: A 16-year-old female with achondroplasia. Medullary compression by the odontoid process caused right hemiplegia at 10 months after birth and equinus foot concomitantly developed. At 14 years old, right knee pain developed during walking. For treatment, firstly, tenodesis of medial collateral ligament of the knee joint (MCL) was performed. Oblique osteotomy was applied to the proximal MCL attachment site over the distal tibial tuberosity, followed by simple limb lengthening, which improved knee instability. To prevent recurrence of knee instability, varus and derotationosteotomy of the femur and Vulpius procedure (triceps surae muscle lengthening) were additionally performed, and gait stabilized after surgery.

Discussion: Regarding the pathogenesis, her gait was originally in-toeing because of excessive femoral anteversion, but the lower leg did not internally rotate during walking because of equinus foot, and the foot grounded in an externally rotated position, loading burdens on the MCL. This condition may have gradually caused instability of the knee over the years.

Conclusion: We surgically treated the patient with knee joint valgus instability caused by excessive femoral anteversion and equinus foot and achieved a favorable outcome.

Keywords: Derotation osteotomy of femur; Equinus foot; Excessive femoral anteversion; Laxity of medial collateral ligament; Limb lengthening; case report.

Fig. 1

a: Internal rotations of the right and left hip joints were 80 and 30°, respectively. b: In the sitting position, the right and left hip joints were internally and externally rotated, respectively. c: Marked instability of the right knee was noted in the presence of valgus stress.

Fig. 2

a: The entire lower limb was externally rotated to improve clearance disturbed by the presence of equinus foot in the swing phase. b: On one-leg standing in the stance phase, the foot and crus were fixed in an externally rotated position on the ground, but the proximal region above the knee joint showed knee-in gait.

Fig. 3

Frontal radiology in the long standing position.

Fig. 4

Marked right knee joint instability was noted on valgus stress radiography.

Fig. 5

On coronal MRI, loosening of MCL was observed at the femoral attachment site.

Fig. 6

Right and left femoral anteversion were 71 and -3°, respectively, on CT.

Fig. 7

Osteotomy was applied to the proximal MCL attachment site to the distal patellar tendon attachment site, followed by 35 mm lengthening.

Fig. 8

Frontal radiology in the long standing position on the final follow-up.

Fig. 9

Knee instability was resolved on valgus stress radiography.

Fig. 10

Knee-in gait on one-leg standing in the stance phase of walking was resolved.

Fig. 11

Loosening of MCL was resolved on coronal MRI.