Convex Hemiepiphysiodesis

In a young, growing spine, a curve worsens partly because the two sides grow at different rates — the longer, convex (outer) side keeps growing and pushing the curve further. The idea behind convex growth arrest is to turn that growth to advantage. By deliberately stopping growth on the convex side, while leaving the concave (inner) side free to grow, the spine can gradually straighten itself, or at least stop getting worse, as the child grows. The rationale is to guide the shape of the spine over years using biology rather than to force an immediate mechanical correction. Because the effect depends entirely on there being plenty of growth left, the operation is generally considered only in young children — usually under about five years of age — with a short, flexible, reasonably balanced curve of only a few segments and good remaining growth potential on the concave side. It is a gentler, less immediately corrective approach than removing a hemivertebra.

This is what is generally done, although techniques vary between surgeons and centres. The classic method combines an anterior and a posterior step on the convex side of the curve: at the front, the growth plates (the cartilage where the vertebrae grow) on the convex side of several segments are removed or destroyed, and at the back the small joints and growth areas on the convex side are fused — together this is called convex hemiepiphysiodesis and hemiarthrodesis. A more modern variation reaches the front growth plates through the pedicle from the back (a transpedicular technique), sometimes combined with a small amount of posterior instrumentation to add a little immediate correction. In some contemporary approaches, the convex growth arrest is paired with a growing rod on the concave side to gently distract and encourage correction. Bone graft is used where fusion is intended. Because it acts slowly, the operation itself is smaller than a resection, but its benefit unfolds over the following years of growth.

The evidence for convex hemiepiphysiodesis is mixed, and it is honest to say so. In carefully selected young children with short, flexible curves, published series report that it can halt progression in most patients and produce modest gradual correction — coronal correction often in the region of a third to a half in those who respond — with the best results when it is done early and the curve is small and flexible. However, the response is unpredictable: some curves improve, some simply stop worsening, and some continue to progress despite the operation, requiring further surgery. Because of this unpredictability, the need for an anterior approach in the classic technique, and a relatively high rate of incomplete correction, convex growth arrest has in many centres been largely superseded by hemivertebra resection, which gives a more reliable and immediate correction. Contemporary reviews note that it still has a place as a growth-modulating option in the right young child, and can be combined with concave growing-rod techniques.

Because this is a growth-guiding operation, the most important thing to understand is that the correction happens slowly, over years, not straight away. After the operation a young child is helped to recover comfortably, and a protective brace or cast is commonly worn for a period while the fused areas heal. The immediate change in the curve on X-ray may be small; the intended benefit appears gradually as the child grows and the concave side lengthens while the convex side does not. For this reason, careful long-term follow-up with regular reviews and X-rays is central to the treatment, to watch how the curve behaves over time and to step in with further treatment if it does not respond as hoped. Families should expect a long horizon of monitoring rather than a single, dramatic correction.

As with any spinal operation, this surgery carries risks that the team discusses fully beforehand, including bleeding, infection and — where an anterior approach is used — the risks associated with reaching the front of the spine. A consideration particular to this operation is that its effect is unpredictable: the main "risk" is that the curve does not correct or continues to progress, which can require further surgery such as a resection or growing-rod treatment. This is why patient selection — a young child, a short and flexible curve, and plenty of growth remaining — is so important. This page is educational and does not recommend or advise for or against surgery in any individual case.

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