In our series, guided growth was used in patients with a mean age of 5.5±2.5 years (range, 2-9 years) and classified at most Catonne 3, and we considered it appropriate to combine it with medial distal femoral hemiphysiodesis in 4 patients who had a distal femoral valgus greater than 100°. This technique enabled us to restore the mechanical axis of the limb in 8/14 knees (60%) with significant correction of the HKA angle and distal femoral valgus and normalization of the MMPTA angle despite our small follow-up. However, the effect on MDA is less pronounced, but our follow-up remains small. Danino et al. after a review of the literature on the effect of GG in BD found a significant reduction in MMPTA angle and mechanical axis deviation in patients treated with this technique .
Helfing et al. retrospectively analyzed the efficacy of hemiphysiodesis on 27 knees treated with this technique. All patients in their series were skeletally immature and were treated without regard to age or weight until medial superior tibial epiphysiodesis was available. Results were generally good with 78% correction without any major complications . All subjects under 4 years of age had total correction with spontaneous correction of tibial torsion, except for one case of recurrence. Among subjects over 12 years of age, the correction was close to normal or complete in only 62% of cases. These patients would have required osteotomies if they had not been treated with hemiepiphysiodesis. Therefore, they believe that it is a relatively safe and effective first-line treatment in this age group, considering the potential complications associated with an osteotomy. Several other studies report good results from this technique [9,10,11,12]. The rate of angular correction found by Danino et al. was 1° per month .
A few complications have been reported, in particular the removal or breakage of the screw within an average period of 13.6 months, much more observed in obeses patients . The biomechanical study by Stitgen et al. found that the stainless steel screws we use in most of our patients are superior to titanium screws. The failure rate involving the use of osteotomy after GG varies between 11 and 44% and mainly concerns children close to skeletal maturity [7,8,10,15]. The explanation we could use is that children reach skeletal maturity before total correction. Recently a systematic review by Fan et al. found no correlation between age at surgery or implant type and hemiphysiodesis failure, but their database was heterogeneous . Another complication related to growth rebound with recurrence of the deformity suggests waiting for valgus hypercorrection before removing the material. In our patients, we remove the plaque after obtaining physiological valgus. All patients will be followed up until bone maturity. The procedure can be repeated even if there is a rebound effect as long as there is no medial upper tibial epiphysiodesis. Furthermore, the progressive nature of the correction guarantees a better adaptation of the anatomical elements of the knee, all the more so as the children are growing. The staple’s removals in our series only concerned children with advanced angular deformity and treated with a makeshift staple made by ourselves. In fact, staples are known to be poorly resistant, especially in advanced deformities and in cases of obesity, but we had no choice because of the financial limitations of these patients .
When we compare patients treated by growth modulation and those treated by RRO, we realize that although they belong to the same age group and have a TV of similar stages, the results appear to be better in cases of GG, especially in terms of axis correction, despite the small follow-up in patients treated by this technique.
In fact, Rab's osteotomy was published in 1988 by Rab, who stated that because all clinical deformities of Blount desease (varus and internal rotation) must be corrected, the osteotomy should have transverse and frontal components, which he obtains by performing an osteotomy oblique by 45° to the vertical through the anterior tibial tuberosity, directed from antero distal to postero proximal [6, 17]. The different degrees of liberty offered by the two sides of the osteotomy allow the surgeon to correct the deformities in the best possible way. The results were good, but the follow-up was only 15 months. In our series with a greater follow-up, we realized that despite perfect postoperative correction, there was a progressive loss of axis correction obtained with a recurrence rate of 60%. In fact, like all the other osteotomies described in this pathology, Rab's osteotomy is performed under and behind the anterior tibial tuberosity [17,18,19]. No gesture is performed on the growth plate, which is the site of the pathology. Moreover, the children are young and growing. The disease therefore evolves on its own account, thus making the correction obtained transitory, which explains the progressive loss of correction and justified recurrences. In our series, all the patients in our series had to be treated with external fixator, which is nevertheless more invasive, as they developed a medial proximal tibial epiphysiodesis after osteotomy. Helfing et al. treated patients who had a recurrence after Rab's osteotomy by GG with good results, but these patients were still skeletally immature and had no epiphysiodesis . Osteotomy in early stage of BD thus appears to be a transitory treatment making growth modulation the best means of correcting deformities at this stage.
LIMITATIONS OF THE STUDY
The main limitation is the relatively small follow-up of patients treated by GG. The size of the study population also appears to be small, but the pathology is not so frequent. However, our results are valid in accordance with data available in the literature.