Guided growth for correction of axial deformities of the knee in children: a literature review

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Abstract


Literature review was performed for axial deformities of the knee in children and possible correction by guided growth, which aims to restore the mechanical axis of the lower limbs by targeting the growth plate. In 2004, P. Stevens proposed temporarily blocking the bone growth plate with metal plate and two screws. The method includes the extraperiosteal placement of the metal plate at a certain segment of the growth plate (i.e., at the top of or in plane with the deformity). Its advantages are minimal invasiveness, higher accuracy and reliability, and ease and efficiency of use. In addition, there is a negligible risk of possible complications. The method of guided growth is a preferable alternative to osteotomy for the correction of the axial deformity of the knee joint in children and should be more widely used in the everyday practice of pediatric orthopedic surgeons.

Axial deformity of the knee joints is a common problem in children and a frequent cause of visits to orthopedists [1]. Although most such deformities are physiological, some deformities are pathological and therefore require timely diagnosis and treatment. The etiologies, indications, time courses, and treatment methods for these types of deformities remain unresolved topical issues.

This study aims to provide a literature analysis and overview of the modern concepts of pediatric axial deformities of the knee joint as well as possibilities for the correction of these deformities using the guided growth method.

Lower limb axis formation occurs during a number of phases and is thus exposed to regular changes in the growth process. In most cases, deformities in the lower limb are of a physiological nature and do not require correction. For instance, varus diversion of the mechanical axis at the knee joint level (anatomical femoral–tibial angle: 10°–15°) can be observed in a newborn child. According to some authors, this type of diversion is related to the pre-natal position of the fetus. The pre-natal position may cause contraction not only of the medial segment of the capsule but also of the posterior oblique ligament of the knee joint. This contraction leads to rotation of the whole lower limb and formation of varus deformities of the knee joints in newborns. During the first year of the child’s life, this contraction is gradually reduced, and the remaining extent when the child begins to walk independently will define the intensity of varus deformity in the lower limbs. By 18–22 months of age, contraction of the medial capsule segment will disappear completely and hypercorrection will occur; in other words, the varus deformity transforms to a valgus deformity (8°–10°) [2]. Within the next several years, the mechanical axis is restored [3]. However, axial deformities at the knee joint level are not always physiological and not always can be corrected without intervention. Unlike physiological deformities, pathological deformities underlie the main disease, which influences the growth and formation of the child’s skeleton, leading to a gradual deviation of the mechanical axes of the lower limbs. This deviation causes an uneven load distribution on different segments of the knee joint, which may cause osteoarthritis in the future [4, 5]. Brouwer et al. conducted a study wherein the objective was to reveal an association between the presence of axial deformities of the lower limb in patients and the development of knee joint osteoarthritis. The study included 1501 subjects (2664 knee joints), of which 38% (1012 knee joints) had no deviation of the lower limb mechanical axes, 26% (693 knee joints) exhibited varus deviation, and 36% (959 knee joints) exhibited valgus deviation. On average, subjects were observed for 6.6 years. Based on the obtained results, the risk of osteoarthritis occurrence in patients with a valgus deviation of axis by 1.64% was found to be higher than that among patients with no deviation of the mechanical axis of lower limbs. Simultaneously, the study found that in the presence of varus deviations, the risk of osteoarthritis occurrence was increased by approximately two-fold and accounts for 2.06% of all osteoarthritis cases [6].

The described disorders may be related to deformities in the femoral bone, shin bones, or both. Regardless of the etiology of these axial deformities, the main objective of treatment is restoration of the mechanical axis of the lower limbs. To define the size and summit of the deformity as well as the required level of correction, different calculation methods are used. Currently, the most commonly used method involves defining the center of rotation of angulation, as suggested by Paley. Using this method, it is possible to distinguish reference lines and angles on X-ray photographs, and deviation is calculated both for the anatomic axes of femoral and tibial bones and the general mechanical axis of the lower limbs. The most informative parameters used to characterize varus and valgus deformities of the knee joints are mechanical axis deviations, mechanical lateral distal femoral angle (mLDFA), and medial proximal tibial angle (MPTA). Localization of the deformity summit and determination of the reference angle values allow to plan the level and value of mechanical axis deviation correction.

Currently, the methods used to correct these deformities are versatile, and the efficiency and safety of these methods are disputable. Conservative methods of treatment, according to some authors, are inefficient in most pathological cases, given the level of intensity of the deformity [7]. Operative methods mainly include single-stage correction, such as osteotomy correction with subsequent fixation of osseous fragments in the correct position using different metal constructions (e.g., spokes, external fixation devices, and plates with screws), as well as gradual correction using compressing-distracting devices [4, 7]. Azizov published the treatment results of conservative and operative methods (i.e., mounting of an external fixation device) used to treat knee joint axial deformities in children. That study included 55 patients. Conservative and operative treatments were administered to 18 and 37 patients, respectively. Distraction began on the third or fourth day after the operation and before hypercorrection of the deformity had reached 4°–5°. The rate of distraction was 1 mm per day over a fixation period of 4–6 weeks. According to the author, 16 patients responded positively to conservative treatment, whereas two patients developed recurrences of their deformities that later required operative treatment. Regarding the operative method, treatment outcomes were evaluated in 24 children; of them, 21 patients exhibited positive outcomes with limb axis correction and full amplitude of movement in the lower limb joints, whereas three patients developed complications during treatment, such as soft tissue inflammation around the spokes that required prescribed antibiotic therapy. Based on the obtained results, the author concluded that axial deformities of the lower limbs in children often required operative treatment, among which apparatus–surgical treatment was found to be less traumatic and more efficient even in very young children [7]. However, the author did not indicate the etiologies or levels of intensity of the lower limb axial deformities observed in the enrolled children; thus, one cannot estimate in detail the efficiencies of the indicated methods.

Certainly, surgical treatment methods allow the correction of axial deformities, and thus restore the mechanical axis of lower limbs; however, as the child grows, recurrent deformities may occur, leading to a requirement for repeated osteotomy. Notably, osteotomy is a fairly extensive intervention method and is associated with a particular risk of complications related both to the operation itself and to disorders of consolidation.

For a long time, doctors attempted to use the natural bone growth potential to correct axial deformities of lower limbs in children without resorting to osteotomies. The possibility of intentional influence on the growth plate served as a basis for this guided growth concept. As the focus of interest in modern orthopedics has shifted toward the direction of minimally invasive manipulations, guided growth methods have recently become more relevant [8–15].

In 1933, Phemister first conducted operations on the growth plate to correct axial deformities [16]. These operations consisted of the excision of an osteochondrous fragment in the region of metaepiphysial cartilage, with subsequent rotation so that the growth plate was overlapped by the bone fragment site [17]. This procedure enabled the creation of a stable synostosis between the bone epiphysis and metaphysis; however, this manipulation was irreversible and accompanied by the risk of excessive correction of the deformity, which limited its application.

To allow reversal of the effect on the growth plate, in 1949 Blount suggested the use of metal staples for epiphysiodesis to correct the mechanical axis of the lower limbs. In this procedure, two or three staples were placed such that they could overlap the metaepiphysial cartilage and thus temporarily block a part of the bone growth plate at the summit of the deformity. After the deformity was completely corrected during growth, the staples were removed [18, 19].

Courvoisier et al. published results of their study, which investigated the use of Blount staples for the correction of idiopathic valgus deformities of the knee joint. The authors of that study reported treatment outcomes for nine children aged 9–16 years. The average initial intermalleolar distance (IMD) was 8.7 cm (range: 7–11 cm), with mLDFA and MPTA values of 84° and 88°, respectively. For correction, temporary epiphysiodesis of the medial segment of the tibial proximal growth plate was performed using Blount staples. Patients were observed for 1–3 years. In this study, eight patients exhibited satisfactory correction results (average IMD, 2.5 cm; average mLDFA and MPTA, 86° and 88°, respectively); however, one patient was estimated to have a negative outcome (mLDFA angle, 84°; MPTA angle, 83°). No new deformities were observed after the implants were removed. Based on the obtained results, the authors considered Blount staples to be a reliable and safe correction method for valgus deformity in children [8].

Other authors reported similarly positive outcomes following the application of Blount staples in children with valgus deformities of the lower limbs. Deqreef et al. reported the treatment outcomes of 44 patients with valgus deformities of the knee joints who underwent temporary epiphysiodesis of the medial segments of the distal femoral and proximal tibial bones. The average correction period was 7 months (range: 3–18 months). Satisfactory outcomes were observed in 40 patients, whereas four had recurrent deformities. Based on the study findings, the authors concluded that Blount staples were a reliable method of valgus deformity treatment in children and were associated with few complications [20].

Similar results were obtained by Zueqe, who described the treatment outcomes of 56 patients with axial deformities at the knee joint level. These patients were treated using Blount staples. The rate of deformity correction was 87% [11].

Despite the reported positive results with Blount staples, this method has not yet been widely applied in practice. This lack of usage is mainly associated with the high risk of possible complications during application. Metaepiphysial cartilage is a dynamic structure, and its influence may cause staples to change their shape, break down, or migrate during growth, possibly causing damage and premature closure of the growth plate [21]. Moreover, this method has age limitations. Blount staples are associated with an increased risk of complications (e.g., staple migration) and are therefore undesirable for epiphysiodesis in girls younger than 9 years and boys younger than 11 years [22].

To avoid the adverse effects of the application of Blount staples, Metaizeau introduced transphyseal screws for deformity correction [23]. Although the author achieved positive results with respect to correction, it remained uncertain whether this type of epiphysiodesis would be reversible [24].

In 2004, Stevens suggested the use of two-screw plates to temporarily block the bone growth plate. This method involves the placement of an extra-periosteal plate at the level of the particular growth plate segment, either at the summit or in the plane of the deformity. This method was prospectively described as the “eight-plate guided growth method.” According to most authors who have applied this method, its advantages relative to staples and transphyseal screws include minimal invasiveness, higher accuracy, greater comfort, better reliability, and improved efficiency as well as an insignificant risk of complications [25–29].

Regarding evidence of the efficiency and reliability of this method, Stevens conducted a study with the intent to compare the rate of valgus and varus knee joint deformity correction in children treated with staples and eight-plates. This study included 34 patients aged 20 months to 17 years. Plates were removed after a deformity correction period of 11 months. Based on the results, the author concluded that the eight-plate method was associated with a 30% higher rate of deformity correction than that achieved with Blount staples, and no premature growth plate closure was observed in the enrolled children [4].

At the same time, some authors have reported identical rates of knee joint valgus and varus deformity correction in children when using Blount staples or the eight-plate method. Regardless, the eight-plate method has a number of incontestable advantages. In particular, the setting and removal of these plates requires less time than the similar interventions required with Blount staples [28].

Niethard, when estimating his study outcomes, concluded that the eight-plate method for temporary epiphysiodesis was the safest and most reliable method. The technique used to set this metal construction is easy to apply, and frequency of complications is minimal when compared with the use of Blount staples. The study conducted by Niethard included 13 patients with an average age of 9.5 years (range: 2.3–13.7 years). Axial deformities of the lower limbs were observed in all patients. The correction period ranged from 6 to 34 months. No complications were observed [30].

Kanellopoulos et al. conducted a porcine study to compare the rates of axial deformity correction following the use of eight-plates and Blount staples. Accordingly, each animal underwent temporary epiphysiodesis under the control of an image converter tube with eight-plates on the right shin and Blount staples on the left shin. X-ray images were taken every 4 weeks for control purposes. Animal studies of lower limb axial deformity correction have found that the eight-plate method is more efficient than Blount staples. Furthermore, complications such as migration or metal construction deformities are less frequent with eight-plates than with Blount staples [31].

Initially, the guided growth method was used only to correct lower limb deformities in the frontal plane. Subsequently, the prospective indications for the application of this method were significantly expanded; currently, the guided growth method is widely used to correct deformities in both the frontal and sagittal planes; these deformities include post-traumatic deformities, changes in the epimetaphyseal cartilage consequent to systemic diseases, and deformities at the ankle joint and hip joint levels [32].

Therefore, the bone guided growth method proved to be effective for the treatment of axial deformities of the lower limbs in children who have not yet completed the osseous growth process. However, despite the wide application of this method, a number of unsolved issues remain. For instance, the age range in which patients are indicated to undergo the eight-plate method is still disputable. In his work, Stevens used this method in children aged 20 months to 17 years. Niethard applied eight-plates to correct knee joint axial deformities in children with an average age of 9.5 years (range: 2.3–13.7 years). Burghardt studied patients with ages ranging from 4.9 to 13.7 years [33]. No growth plate complications were observed in these studies.

Whether epiphysiodesis of the splint bone proximal growth plate is necessary for the correction of varus deformities of the knee joints also remains open for debate. The literature does not contain data to support or refute the necessity of hyper-correction during the correction of knee joint axial deformities in children. In addition, most scientific work has been devoted to idiopathic valgus and varus knee joint deformities; accordingly, issues related to the correction of deformities resulting from primary growth plate pathologies are insufficiently represented, particularly for children with systemic skeletal dysplasias. Moreover, prognostic methods to determine the potential for deformity correction have not yet been developed. Although the eight-plate method is easy to use and relatively versatile, the optimization of the tools and implants used in the guided growth method remains topical. Nevertheless, the guided growth method is a better alternative to osteotomy for the correction of knee joint deformities in children and may be widely applied in the daily practices of pediatric orthopedists.

Ekaterina S Morenko

The Turner Scientific and Research Institute for Children’s Orthopedics

Author for correspondence.
Email: emorenko@gmail.com

Russian Federation MD, PhD student of the department of foot pathology, neuroorthopedics and systemic diseases. The Turner Scientific and Research Institute for Children’s Orthopedics

Vladimir M Kenis

The Turner Scientific and Research Institute for Children’s Orthopedics

Email: kenis@mail.ru

Russian Federation MD, PhD, professor, Deputy Director of Development and International Relations, head of the department of foot pathology, neuroorthopedics and systemic diseases. The Turner Scientific and Research Institute for Children’s Orthopedic

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  • Kenis VM, Morenko ES, Korshunov AV, Kleimanov RV. NUMERICAL SIMULATION OF STRAIN WITHIN THE CONSTRUCTIONS FOR TEMPORARY HEMIEPIPHYSEODESIS IN PATIENTS WITH SYSTEMIC SKELETAL DYSPLASIAS. Vestnik travmatologii i ortopedii imeni N.N. Priorova. 2018;(1):30. doi: 10.32414/0869-8678-2018-1-30-35

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