Rapidly acquired valgus deformity of the knee after osteochondroma resection in multiple hereditary exostoses pediatric patients: A report of two cases

Abstract

Patients with multiple hereditary exostoses (MHE) often develop leg length discrepancies and limb alignment deformity around the knee as part of the natural course of the disease. Limb alignment deformity occurring post-resection of an osteochondroma has been described in one case report and only pertaining to the proximal medial tibia location. Here we describe the case of 2 patients with MHE, a 7-year-old female who underwent resection of distal femur and proximal tibia osteochondromas and a 9-year-old female who had a distal femur osteochondroma resected. Both patients developed rapidly progressive valgus knee deformity requiring surgical intervention. Excision of osteochondromas near the physis of a skeletally immature patient can cause overgrowth from the involved side of the growth plate resulting in a rapidly progressing unilateral coronal plane deformity. Surgeons should be aware of this potential complication and closely follow growing patients with serial alignment radiographs and counsel the family regarding the potential of acquired limb deformity and subsequent surgeries.

Keywords: Femur; Hemiepiphysiodesis; Knee; MHE; Multiple hereditary exostosis; Tibia.

Fig. 1

Case 1: Preoperative standing hip-to-ankle radiograph displaying normal limb alignment and large exostoses on the left medial distal femur and proximal tibia. Left leg mechanical lateral distal femoral angle (mLDFA) measured 81º and mechanical medial proximal tibial angle (mMPTA) measured 90º.

Fig. 2

Case 1: Red circles indicate the left limb medial distal femoral and proximal tibial osteochondromas prior to excision (left) and intraoperatively after excision (right) (Color version of the figure is available online.)

Fig. 3

Case 1: Standing hip-to-ankle radiographs showing progressive left valgus deformity 2 months (A), 8 months (B) and 24 months (C) post medial distal femoral and proximal tibial osteochondroma excision. Left leg mLDFA measured 85, 81, and 82º respectively and mMPTA measured 91, 92, and 94° respectively.

Fig. 4

Case 1: Standing hip-to-ankle radiographs showing progressive correction of left valgus deformity 8 months (A) and 12 months (B) after implant mediated guided growth procedure. (C) Standing hip-to-ankle radiographs showing satisfactory left limb alignment 5 months post removal of implant mediated guided growth hardware on the left limb. Left leg mLDFA measured 88, 93, and 88º respectively and mMPTA measured 91, 86, and 90º respectively.

Fig. 5

Case 2: Preoperative standing hip-to-ankle radiograph displaying left leg with valgus alignment, and right leg with normal alignment and a large exostosis on the right medial distal femur. Right leg mLDFA measured 89º and mMPTA measured 95º.

Fig. 6

Case 2: Red circles indicate the right medial distal femoral osteochondroma prior to excision (A) and intraoperatively after excision (B) (Color version of the figure is available online.)

Fig. 7

Case 2: Standing hip-to-ankle radiographs showing progressive right valgus deformity 2 months (A) and 4 months (B) post medial distal femoral osteochondroma excision. Right leg mLDFA measured 89 and 87º respectively and mMPTA measured 96º at both time points.

Fig. 8

Case 2: Standing hip-to-ankle radiographs showing progressive correction of right valgus deformity 4 months (A) and 6 months (B) after implant mediated guided growth procedure. (C) Standing hip-to-ankle radiographs showing satisfactory right limb alignment 4 months post removal of metaphyseal screws. Right leg mLDFA measured 89, 93, and 91º respectively and mMPTA measured 93, 92, and 90º respectively.