Cozen's deformity: resolved by guided growth

Abstract

Proximal tibial metaphyseal fractures in children can lead to progressive and symptomatic tibial valgus. Corrective osteotomy has been abandoned, due to frequent complications, including recurrent valgus deformity. While spontaneous remodelling has been reported, this is not predictable. For children with persistent deformities, we have resorted to guided growth of the tibia. We present 19 patients who were successfully treated with guided growth, tethering the proximal medial physis. There were ten boys and nine girls, ranging in age from two to 13.6 years at the time of intervention. The mean follow-up from injury was 7.3 years. We documented the intermalleolar distance, mechanical axis deviation (by zone), medial proximal tibial angle (MPTA), and leg length discrepancy. Removal of the plate, or more recently, the metaphyseal screw, was undertaken upon normalization of the mechanical axis. Including the four patients who have undergone repeat tethering for recurrent valgus (one patient-twice), we are effectively reviewing 24 Cozen's phenomena, making this the largest series reported in the literature. Correction of the mechanical axis and the proximal medial tibial angle was achieved in all but one patient. Limb length inequality at follow-up ranged from 0.1 to 1.5 cm, with a mean of 0.5 cm. There have been five recurrences in four patients to date; four corrected with repeat tethering and one is pending. Two patients developed significant over correction because of parental failure to pursue timely follow-up. Both have corrected to neutral with lateral tibial physeal tethering. Ten patients have attained skeletal maturity and required no further treatment. The remaining nine patients will be followed until maturity. Guided growth is an excellent choice for the management of post-traumatic tibial valgus. Our rationale for restricting medial overgrowth is twofold: (1) to restore the MPTA and (2) to reduce the length discrepancy due to tibial overgrowth caused by the fracture. Recognizing the potential for recurrent deformity following implant removal, our standard practice now includes removal of just the metaphyseal screw and subsequent reinsertion, in the event of rebound valgus deformity.Level of evidence Therapeutic IV, retrospective series/no control cohort.

Keywords: Cozen’s phenomenon; Guided growth; Tibial valgus.

Fig. 1

a Clinical measurements included the relative limb lengths and the intermalleolar distance (IMD). b The radiographic measurements comprised of the mechanical axis zone (by quadrants), the limb lengths, and the anatomic angles, including the lateral distal femoral angle (LDFA) and the medial proximal tibial angle (MPTA)

Fig. 2

a Toddler who is 3 months status post-undisplaced proximal tibial fracture (intact fibula), treated in a cast. The proximal medial tibial angle PMTA is 96 degrees. b At follow-up, one year later, he has knee pain with activities. The PMTA has increased to 102 degrees, and the tibia is 9 mm longer. The mechanical axis is lateral zone +3. c 18 months following guided growth, his mechanical axis is intentionally overcorrected into medial zone -1 and the PMTA is 84 degrees. The implant was removed. d At age 10, he has mild and fairly symmetrical genu valgum (femoral). The mechanical axis is in lateral zone +1 bilaterally. His PMTA is 90 degrees (normal), and his tibial lengths are equal

Fig. 3

a This 3-year-old child presented 18 months following a proximal fracture of her left tibia. The mechanical axis was in lateral zone +3, and she had become symptomatic. b Two and a half years following guided growth of the tibia, her mechanical axis is neutral and the metaphyseal screw was removed. c At age seven, 18 months following screw removal, there is moderate recurrence of genu valgum and the mechanical axis is in lateral zone +2. d 6 months later, she remains asymptomatic, with slight improvement in tibial valgus. Note the distal femoral contribution to valgus. She will be monitored biannually, and the screw may be reinserted as indicated ± a femoral plate may be added for increasing valgus