Does screw position matter for guided growth in cerebral palsy hips?

Abstract

Aims Guided growth has been used to treat coxa valga for cerebral palsy (CP) children. However, there has been no study on the optimal position of screw application. In this paper we have investigated the influence of screw position on the outcomes of guided growth. Methods We retrospectively analyzed 61 hips in 32 CP children who underwent proximal femoral hemi epiphysiodesis between July 2012 and September 2017. The hips were divided into two groups according to the transphyseal position of the screw in the coronal plane: across medial quarter (Group 1) or middle quarter (Group 2) of the medial half of the physis. We compared pre- and postoperative radiographs in head-shaft angle (HSA), Reimer’s migration percentage (MP), acetabular index (AI), and femoral anteversion angle (FAVA), as well as incidences of the physis growing-off the screw within two years. Linear and Cox regression analysis were conducted to identify factors related to HSA correction and risk of the physis growing-off the screw. Results A total of 37 hips in Group 1 and 24 hips in Group 2 were compared. Group 1 showed a more substantial decrease in the HSA (p = 0.003) and the MP (p = 0.032). Both groups had significant and similar improvements in the AI (p = 0.809) and the FAVA (p = 0.304). Group 1 presented a higher incidence of the physis growing-off the screw (p = 0.038). Results of the regression analysis indicated that the eccentricity of screw position correlated with HSA correction and increases the risk of the physis growing-off the screw. Conclusion Guided growth is effective in improving coxa valga and excessive femoral anteversion in CP children. For younger children, despite compromised efficacy of varus correction, we recommend a more centered screw position, at least across the middle quarter of the medial physis, to avoid early revision. Cite this article: Bone Joint J 2020;102-B(9):1242–1247.

Guided growth versus varus osteotomy for type II avascular necrosis following surgery for developmental dysplasia of the hip

“…The physis growing off the screw remains a disadvantage of guided growth because of the need for another operation to advance the screw. Hsu et al 25 showed that the transphyseal location of the screw can influence the revision rate in guided growth of the proximal femur. Future studies are needed to clarify whether the screw position plays a role in the context of Kalamchi type II AVN in children with DDH.…”

Proximal Femur Guided Growth for the Management of Hip Dysplasia in Children with Cerebral Palsy

“…In children with CP, proximal femoral guided growth (PFGG) with medial screw hemiepiphysiodesis has been shown to decrease the head shaft angle and Reimer's migration percentage (RMP); and decrease the need for subsequent skeletal hip reconstructive surgery. [8][9][10][11] The indications, surgical technique, postoperative management, and potential pitfalls of this relatively new procedure are considered below.…”

“…There is no consensus in the literature regarding optimal screw diameter, with reported screw sizes ranging from 4.0 to 7.3 mm. [8][9][10][11] In most cases, a 4.5 mm screw is ideal, given the size of the femoral neck and head in children with CP who are appropriate candidates for PFGG. A fully threaded cannulated screw is preferred to facilitate screw exchange/removal if indicated.…”

“…The primary radiographic measurement is the RMP; secondary measurements may include the neck shaft and head shaft angles. 3,4,9 Late guided growth of the proximal femur occurs at the time of hardware removal, and postoperative immobilization is driven by the latter. A hip abduction orthosis is used for comfort for 2 weeks following surgery.…”

“…The primary radiographic measurement is the RMP; secondary measurements may include the neck shaft angle, head shaft angle, and acetabular index. 3,4,9,13 Complications/Salvage Growing off of the screw following early guided growth of the proximal femur has been reported to occur in between 15 and 50% of cases. 8,10,11 The RMP should be followed carefully in these cases.…”