Growth arrest: leg length correction through temporary epiphysiodesis with a novel rigid staple (RigidTack)

Abstract

Aims: Temporary epiphysiodesis (ED) is commonly applied in children and adolescents to treat leg length discrepancies (LLDs) and tall stature. Traditional Blount staples or modern two-hole plates are used in clinical practice. However, they require accurate planning, precise surgical techniques, and attentive follow-up to achieve the desired outcome without complications. This study reports the results of ED using a novel rigid staple (RigidTack) incorporating safety, as well as technical and procedural success according to the idea, development, evaluation, assessment, long-term (IDEAL) study framework.

Methods: A cohort of 56 patients, including 45 unilateral EDs for LLD and 11 bilateral EDs for tall stature, were prospectively analyzed. ED was performed with 222 rigid staples with a mean follow-up of 24.4 months (8 to 49). Patients with a predicted LLD of ≥ 2 cm at skeletal maturity were included. Mean age at surgery was 12.1 years (8 to 14). Correction and complication rates including implant-associated problems, and secondary deformities as well as perioperative parameters, were recorded (IDEAL stage 2a). These results were compared to historical cohorts treated for correction of LLD with two-hole plates or Blount staples.

Results: The mean LLD was reduced from 25.2 mm (15 to 45) before surgery to 9.3 mm (6 to 25) at skeletal maturity. Implant-associated complications occurred in 4/56 treatments (7%), and secondary frontal plane deformities were detected in 5/45 legs (11%) of the LLD cohort. Including tall stature patients, the rate increased to 12/67 legs (18%). Sagittal plane deformities were observed during 1/45 LLD treatments (2%). Compared to two-hole plates and Blount staples, similar correction rates were observed in all devices. Lower rates of frontal and sagittal plane deformities were observed using rigid staples.

Conclusion: Treatment of LLD using novel rigid staples appears a feasible and promising strategy. Secondary frontal and sagittal plane deformities remain a potential complication, although the rate seems to be lower in patients treated with rigid staples. Further comparative studies are needed to investigate this issue. Cite this article: Bone Joint J 2021;103-B(8):1428-1437.

Keywords: Adolescents; Children; Growth arrest; Leg length discrepancy; Tall stature; Temporary epiphysiodesis.

Fig. 1

Implantation of rigid staples. a) Incision was followed by manual insertion of a first Kirschner wire, to guide the staple, and b) a second wire is inserted through the vacant, cannulated prong. c) Then, the crossbar is impacted until each staple was d) fully immersed in bone.

Fig. 2

Explantation of a rigid staple (same patient shown in Figure 7). a) Kirschner wire threaded into the staple prongs after exposure followed by b) chisel insertion to clear the interface and c) extraction with sliding hammer to d) fully remove the staple without residual bone.

Fig. 3

Zones of the mechanical axis. The neutral mechanical axis (white line) divides the central knee joint area in the frontal plane into zones 1 and -1. Zones 2 and 3 are the more medial (varus), and zones -2 and -3 are the more lateral (valgus) zones, their boarders are tangent to the medial and lateral femoral condlyes.

Fig. 4

Treatment outcome of leg length discrepancy (LLD) and tall stature. a) Differences in LLD before and after treatment (shaded), b) treatment durations in months, and c) LLD correction speed rates in mm/month. d) Mean body height of tall stature patients before and after treatment with rigid staples are compared to predicted body height.

Fig. 5

Secondary deformities. a) Absolute shift of the mechanical axis after treatment per treated leg between rigid staples, two-hole plates, and Blount staples including tall stature patients and b) secondary frontal plane deformities with mechanical axis shifts ≥ 1 cm into varus and valgus (shaded) in leg length discrepancy (LLD) patients. c) Zone changes in treated LLD patients with a share of biomechanically relevant zone changes away from zone 1/-1 (shaded) and d) secondary sagittal deformities in LLD patients per treated leg are presented.

Fig. 6

Secondary deformity complication management. a) Parallel guidewires during implantation of rigid staples may reduce iatrogenic deformities due to precise placement in the frontal and the sagittal plane. b) Iatrogenic deformities such as this varus deformity of the proximal tibia of the right knee (b1) can be corrected through premature removal of the concave-sided implant (b2) achieving correction at the end of growth arrest (b3).

Fig. 7

Radiographs before and after treatment with rigid staples (same patient shown in Figure 2). Left: 4.2 cm leg length discrepancy in a male patient at 11 years and one month. Right: Corrected leg length after three years and seven months at 14 years and eight months of age.