Hemi-epiphysiodesis (guided growth) for varus knee

Hemi-epiphysiodesis (guided growth) for varus knee is a minimally invasive and highly effective surgical procedure for the treatment of genu varum in children.

It involves the application of fixative devices (mostly plates) to the outer aspect of the knee to slow growth in this area. Growth continues on the inner aspect, gradually correcting the varus deformity.

Epiphysiodesis (guided growth): what does it mean?

Epiphysiodesis is a surgical procedure aimed at stopping or slowing the growth of a specific growth plate or part of it.

Growth plates (also called physes) are the typical structures in children’s bones that allow the various bone segments to grow in length. They can be imagined as cartilage discs located at either end of a long bone, in which cartilage cells reproduce longitudinally and progressively ossify, thus increasing the length of the segment.
These cartilages are active throughout the child’s growth and cease their activity with skeletal maturity, when the cartilage closes and is completely replaced by bone.

Hemi-epiphysiodesis (guided growth): what does it mean?

In Hemi-epiphysiodesis (guided growth), the physis is slowed on only one side , while the remaining portion of the cartilage continues to grow normally. This causes growth deviation, the direction of which depends on where growth is slowed (if the internal portion is slowed, only external growth will continue, and vice versa).
The most commonly used fixation method is the so-called guided-growht plate: there are several models that all have a figure-8 shape (8-plate). In genu varum, these plates are positioned over the lateral growth plate and secured to the bone with two screws.

Hemi-epiphysiodesis (guided growth) for varus knee: Is immobilization necessary?

Postoperative immobilization is not required. From the first day, gradual mobilization of the knee and initial weight-bearing are permitted, as tolerated.
When correctly applied, the plates progressively spread apart and correct the axis, at a rate proportional to the growth of the operated limb.

This is a procedure capable of significantly altering limb growth, which can yield remarkable results despite its minimally invasive nature. Clearly, this surgery is not possible in patients at the end of growth, and the only alternative to correcting genu varum remains osteotomy. This is why it is essential that patients be promptly referred to a pediatric orthopedic surgeon, in time for appropriate assessments.

The procedure described is temporary epiphysiodesis : once the desired goal (the correct axis) is achieved, the plates can be removed to restart cartilage growth. It is therefore theoretically a reversible procedure.

Hemi-epiphysiodesis (guided growth) for varus knee: risks

There are two risks to consider:

• the risk of lesions to the growth cartilage produced at the time of surgery and by the plate itself: once the plates have been removed, if there is still growth of the cartilage on the opposite side, the knee may continue to deviate in the direction of the correction, leading to overcorrection (genu valgum)
• the “rebound” effect: once the plates are removed, the area of cartilage that had been slowed down starts to grow excessively again, leading to a recurrence of the bow knee

For this reason, it is essential to perform the procedures with the correct technique, and it is often preferable (when possible) to perform the surgery toward the end of growth, so as to achieve axis correction and prevent further growth that risks causing overcorrection or recurrence.
In cases where genu varum is very severe and the patient is still small, as in cases of skeletal dysplasia , it is preferable to operate during full growth, remove the plates once the axis has been corrected, and monitor the behavior during residual growth. It may be possible to repeat the procedure if the condition recurs.

Hemi-epiphysiodesis (guided growth) for varus knee: preoperative evaluation

A proper preoperative assessment is essential.
Before treating genu varum with epiphysiodesis, clinical and radiographic findings must be considered. It has been demonstrated that relying solely on clinical measurements, ignoring radiographic findings, carries a significant risk of making unnecessary corrections. Furthermore, the indication should be limited to cases where the mechanical axis alteration is significant.

Another key aspect is calculating the procedure’s timing as precisely as possible. Among the parameters generally analyzed are:

• Height growth rate: patients are asked to bring all their latest height measurements to the visit
• pubertal development: possibly through auxological evaluation
  of bone age using, depending on the case, the age at the wrist, at the elbow and pelvic parameters

In our experience, calculations made roughly (for example, only evaluating whether the knee cartilages are more or less open) or without taking the aforementioned aspects into consideration (for example, based only on chronological age) often lead to missed corrections.

The final key aspect is postoperative follow-up.
A program of medical check-ups is established, initially to ensure proper recovery of knee function and then to assess the effectiveness of the surgery.
To monitor the progress of the correction, follow-ups rely not only on clinical measurements but also on radiographic examinations, both of the knee (to verify that the fixation devices are correctly positioned) and panoramic X-rays (see above) to assess the evolution of the mechanical axis.

Overall, as repeatedly emphasized, it is a non-invasive procedure for the patient and achieves excellent results.

OrthoChildren Center performs regularly this procedure.