Affecting Factors and Correction Ratio in Genu Valgum or Varum Treated with Percutaneous Epiphysiodesis Using Transphyseal Screws

Factors Affecting Postoperative Courses After Removal of Transphyseal Screws Inserted for Correction of Genu Valgum

BACKGROUND

The aim of this study was to investigate factors determining the final outcomes of hemipercutaneous epiphysiodesis using transphyseal screw (PETS) for the genu valgum, especially focusing on postoperative courses after screw removal.

METHODS

Fifty-five patients with idiopathic genu valgum treated with hemi-PETS were included. The mechanical lateral distal femoral angle (mLDFA) and medial proximal tibial angle (MPTA) were measured to calculate the degree of correction and rebound. Regarding factors related to surgical techniques, the number of screw threads beyond the physis, the moment arm of the screw, and screw insertion angles were measured.

RESULTS

In 54 femoral segments (randomly selected in bilateral cases), hemi-PETS was performed with a growth remaining of 2.0±0.6 years. The screw was removed after 6.5±2.1 months, and the degree of correction was 5.0±1.5 degrees. The mean rebound angle was -0.4±2.4 (the negative value means further correction after screw removal). A late time of surgery and an extreme peripheral position of a screw were associated with the growth inhibition. In 50 tibial segments (also randomly selected in bilateral cases), a screw was inserted with a growth remaining of 2.0±0.6 years and removed after 6.3±1.9 months. The degree of correction was 2.9±1.7 degrees during the interval, and the rebound angle was 0.8±1.7 degrees. An earlier time of surgery and a greater correction angle before screw removal were associated with the rebound phenomenon.

CONCLUSIONS

Growth inhibition of >1.6 degrees was observed in about one-fourth of femoral segments. An extreme peripheral position of a screw should be avoided when performing hemi-PETS at the distal femur. We also recommend not performing hemi-PETS at distal femur with too short a period of growth remaining.

LEVEL OF EVIDENCE

Level III-retrospective comparative series.

Factors Affecting Rebound Phenomenon After Temporary Hemiepiphysiodesis and Implant Removal for Idiopathic Genu Valgum in Adolescent Patients

BACKGROUND

The aim of this study was to investigate factors determining postoperative courses, especially focusing on the rebound phenomenon, in adolescent patients with idiopathic genu valgum who underwent temporary hemiepiphysiodesis and implant removal.

METHODS

We identified and reviewed patients with idiopathic genu valgum treated with temporary hemiepiphysiodesis [using tension-band plates (plate group, PG) or transphyseal screws (screw group, SG)] and followed-up to skeletal maturity.

RESULTS

In our cohort [68 patients and their 68 limbs (randomly selected in bilateral cases)], the mean hip-knee-ankle alignment was -5.4±1.8 degrees at the time of temporary hemiepiphysiodesis (negative means valgus), 2.6±2.1 degrees at the time of implant removal, and 0.7±2.6 degrees at the last follow-up, respectively. Regarding the implants, the correction speed was not significantly different (P=0.192-0.315) between the PG (total 1.29±0.37 degrees/mo, 0.71±0.23 degrees/mo at distal femur, 0.59±0.16 degrees/mo at proximal tibia, n=19) and the SG (total 1.22±0.49 degrees/mo, 0.65±0.25 degrees/mo at distal femur, 0.57±0.23 degrees/mo at proximal tibia, n=49). The magnitude of rebound phenomenon in the PG (4.1±1.9 degrees) was greater (P<0.001) than that in the SG (1.1±3.1 degrees). The use of plates and faster correction speed, rather than more severe preoperative deformity or greater correction angle, were positively associated with the rebound phenomenon in regression analyses. Among the 68 knees, 1 showed valgus alignment ≥5 degrees and 5 showed varus alignment ≥5 degrees at the last follow-up. All the 6 cases were observed in the SG. Surgical wound dehiscence was observed in 1 patient in the PG.

CONCLUSIONS

The use of plates and faster correction speed were positively associated with the rebound phenomenon. Careful attention will be needed with the corresponding conditions for optimal results. Progressive genu varum after transphyseal screw removal, which was observed in this study, should be explored in future research.

LEVEL OF EVIDENCE

Level III-retrospective comparative series.