Factors influencing correction rate following hemiepiphysiodesis using tension band plates for deformities around the knee: a multivariate analysis study.

PURPOSE: The aim of this study was to appraise various factors influencing the correction rate in temporary hemiepiphysiodesis (THE) around the knee joint. Specifically, the study analysed the relationship of correction rate with age, gender, aetiology, type and location of deformity. METHODS: The retrospective study included children who underwent THE for a coronal plane deformity (genu valgus or varum) around the knee joint (distal femur or proximal tibia) over a ten year period (2010-2020). The primary outcome of interest was the correction rate of the deformity. RESULTS: Thirty-three children (27 females and 6 males) with a mean age of 8.1 years involving 86 plates were included in the study. The mean correction achieved was 12.2° over a treatment period of 13.3 months. Subgroup analysis showed significant differences between the type (varus (0.8° per month), valgus (1.1° per month)) and the location of deformity femur (1.2° per month) and tibia (0.7° per month)]. On multivariate analysis, the location and the duration of treatment showed significant associations with the correction rate. CONCLUSION: The correction of coronal deformities following temporary hemiepiphysiodesis is influenced by several factors. Valgus, femoral and deformities in younger children correct at a faster rate. Location of deformity and duration of treatment emerged as potential factors affecting the correction rate.

Temporary hemiepiphysiodesis using eight-plates for angular deformities of the lower extremities in children with X-linked hypophosphataemic rickets.

PURPOSES: Temporary hemiepiphysiodesis (TH) using eight-plates is one of the most frequently performed surgeries for correcting angular deformities of the lower extremities in adolescents. Rarely have studies examined children with X-linked hypophosphataemic rickets (X-LHPR) treated with TH using eight-plates. This study was conducted to investigate the efficacy, the endpoint, and the complications of TH using eight-plates to correct angular deformities of the lower extremities in skeletally immature children. METHODS: We reviewed a total of 26 children (86 physes, 52 knees) with X-LHPR (mean age of 6.2 years, range from 2 to 13 years) who underwent TH using eight-plate to correct angular deformities of the lower extremities. Radiographs and clinical records of these patients were evaluated for demographic data and related clinical factors. RESULTS: The average correction of the mechanical lateral distal femoral angle (mLDFA) was 11.7 ± 8.7° (range from 1.0 to 29.7°), and the average correction of the mechanical medial proximal tibial angle (mMPTA) was 8.4 ± 5.0° (range from 0.3 to 16.7°). The mean deformity correction time was 22.7 months (range from 7 to 60 months), and the mean follow-up after eight-plate removal was 43.9 months (range from 24 to 101 months). Overall, 76.9% (20/26 patients) of the angular deformities of the knee were completely corrected and 15.4% (4/26) of the patients received osteotomy surgery. The femoral correction velocity (0.9° per month) was significantly higher than the proximal tibial (0.6° per month) (p = 0.02). The correction velocity of the mLDFA and mMPTA with the TH procedure was faster than that in the absence of intervention (0.9° vs. 0.2°, 0.7° vs. 0.4° per month, p < 0.05). The correction velocity of the mLDFA (1.2° vs. 0.5° per month, [Formula: see text]) and mMPTA (0.7° vs. 0.5° per month, p = 0.04) of patients whose age ≤ five years old was faster than that of patients whose age > five years old. A total of 69.2% (18/26) patients experienced one TH procedure using eight-plates only. Two patients had screw loosening (2/26, 7.7%). One patient (1/26, 3.8%) had a rebound phenomenon after the removal of eight-plate and had the TH procedure again. There was no breakage, infection, physis preclosure, or limited range of movement found in the follow-up. CONCLUSION: TH using eight-plates is a safe and effective procedure with a relatively low incidence of complication and rebound, and it could be used as part of a streamlined treatment for younger X-LHPR patients with resistant or progressive lower limb deformity despite optimal medical treatment. Early intervention can achieve better results.

Temporary hemiepiphysiodesis using an eight-plate implant for coronal angular deformity around the knee in children aged less than 10 years: efficacy, complications, occurrence of rebound and risk factors.

BACKGROUND: Temporary hemiepiphysiodesis (TH) using an eight-Plate implant is one of the most common surgeries used for the correction of coronal angular deformities around the knee in adolescents. However, few studies have focused on children aged less than 10 years treated with TH using an eight-Plate implant. The purpose of this study was to investigate the efficacy, correction velocity, and complications of TH with an eight-Plate implant as well as the occurrence of rebound and risk factors in this population. METHODS: This retrospective study included a total of 135 physes (101 knees) from 66 children (mean age of 4.69 years old, range from 1 to 10 years old) who underwent TH with an eight-Plate implant to correct coronal genu angular deformities in our hospital. Related clinical factors were recorded and analysed by multivariable linear and logistic regression models. RESULTS: The mean deformity correction period was 13.26 months, and the mean follow-up after eight-Plate removal was 12.71 months. In all, 94.06% (95/101 knees) of the genu angular deformities were completely corrected. Non-idiopathic genu angular deformity was found to be an independent risk factor for deformity correction failure (odds ratio (OR) = 2.47). The femoral correction velocity was significantly higher than the tibial correction velocity (1.28° vs. 0.83° per month, p < 0.001). After adjustment for other factors, younger children had higher correction velocities in the distal femur; however, genu valgum and idiopathic deformities were associated with higher correction velocities in the proximal tibia. In addition, we found three (3/101, 2.97%) knees with genu valgum that experienced rebound after removal of the eight-Plate, while five (5/101, 4.95%) knees with non-idiopathic genu angular deformity experienced screw loosening. No other complications were found, and non-idiopathic deformity was the only risk factor for complications (OR = 3.96). No risk factor was found for rebound in our study. CONCLUSIONS: TH using an eight-Plate implant is an effective procedure for coronal genu angular deformities with a low incidence of complications and rebound in patients younger than 10 years old. For this population, TH using an eight-Plate should be considered as soon as the deformity stops responding to conservative treatments. The parents of children younger than 10 years of age with non-idiopathic deformities should be informed preoperatively that the deformity may be prone to correction failure or screw loosening after eight-Plate implantation.

Relevance of instrumented gait analysis in the prediction of the rebound phenomenon after guided growth intervention.

Predictors of rebound after correction of coronal plane deformities using temporary hemiepiphysiodesis (TH) are not well defined. The following research questions were tested: (1) Is the dynamic knee joint load useful to improve rebound prediction accuracy? (2) Does a large initial deformity play a critical role in rebound development? (3) Are BMI and a young age risk factors for rebound? Fifty children and adolescents with idiopathic knee valgus malalignment were included. A deviation of the mechanical femorotibial angle (MFA) of ≥ 3° into valgus between explantation and the one-year follow-up period was chosen to classify a rebound. A rebound was detected in 22 of the 50 patients (44%). Two predictors of rebound were identified: 1. reduced peak lateral knee joint contact force in the first half of the stance phase at the time of explantation (72.7% prediction); 2. minor initial deformity according to the MFA (70.5% prediction). The best prediction (75%) was obtained by including both parameters in the binary logistic regression method. A TH should not be advised in patients with a minor initial deformity of the leg axis. Dynamic knee joint loading using gait analysis and musculoskeletal modeling can be used to determine the optimum time to remove the plates.

Antegrade Intramedullary Femoral Lengthening and Distal Temporary Hemiepiphysiodesis for Combined Correction of Leg Length Discrepancy and Coronal Angular Deformity in Skeletally Immature Patients.

Leg length discrepancies (LLD) are frequently associated with coronal malalignment. Temporary hemiepiphysiodesis (HED) is a well-established procedure for the correction of limb malalignment in skeletally immature patients. For treatment of LLD > 2 cm, lengthening with intramedullary devices gains increasing popularity. However, no studies have investigated the combined application of HED and intramedullary lengthening in skeletally immature patients. This retrospective single-center study evaluated the clinical and radiological outcomes of femoral lengthening with an antegrade intramedullary lengthening nail combined with temporary HED performed in 25 patients (14 females) between 2014 and 2019. Temporary HED through the implantation of flexible staples of the distal femur and/or proximal tibia was either performed prior (n = 11), simultaneously (n = 10) or subsequently (n = 4) to femoral lengthening. The mean follow-up period was 3.7 years (±1.4). The median initial LLD was 39.0 mm (35.0-45.0). Twenty-one patients (84%) presented valgus and four (16%) showed varus malalignment. Leg length equalization was achieved in 13 of the skeletally mature patients (62%). The median LLD of the eight patients with residual LLD > 10 mm at skeletal maturity was 15.5 mm (12.8-21.8). Limb realignment was observed in nine of seventeen skeletally mature patients (53%) in the valgus group, and in one of four patients (25%) in the varus group. Combining antegrade femoral lengthening and temporary HED is a viable option to correct LLD and coronal limb malalignment in skeletally immature patients; however, achieving limb length equalization and realignment may be difficult in cases of severe LLD and angular deformity, in particular.

Outcomes of Temporary Hemi-Epiphysiodesis Using a New Device for The Treatment of Pediatric Valgus Knee Deformity: a Preliminary Report.

BACKGROUND: This study aimed to evaluate the efficacy of hemi-epiphysiodesis using a new device (X-plate) for the correction of genu valgum. METHODS: In total, 22 children with a total of 34 pathologic knee valgus deformities underwent the procedure and were followed up 25.3 months on average. RESULTS: The mean time to clinical correction of genu valgum was 10.9±2.2 months. Furthermore, the mean preoperative anatomic Lateral Distal Femoral Angle (aLDFA) and mechanical Tibia Femoral angle (mTFA) were obtained at 75.1±3.8 and 6±2.8 degrees, respectively. When clinical correction of the deformity was achieved, the mean of aLDFA and mTFA corrections were determined at 8.9±5.3 and 6.5±3.2 degrees, respectively. The mean speed of aLDFA and mTFA corrections were estimated at 0.8±0.45 and 0.6±0.3 degrees per month, respectively. The postoperative aLDFA and mTFA were measured at 84±4.2 and -0.8±2.9 on average. With a mean of 25.3±14.5 months at final follow-up, there were 6 (17.6%) mild valgus knees, 26 (75.5%) normal alignment knees, and only 2 (5.9%) mild varus knee within an acceptable clinical limit. CONCLUSION: Hemi-epiphysiodesis using X-plate at the distal physis of the femur is an effective and safe method for the treatment of valgus knee deformity in children.

Growth modulation of angular deformities with a novel constant force implant concept-preclinical results.

PURPOSE: Varus-valgus deformities in children and adolescents are often corrected by temporary hemi-epiphysiodesis, in which the physis is bridged by an implant to inhibit growth. With standard implant solutions, the acting forces cannot be regulated, rendering the correction difficult to control. Furthermore, the implant load steadily increases with ongoing growth potentially leading to implant-related failures. A novel implant concept was developed applying a controlled constant force to the physis, which carries the potential to avoid these complications. The study aim was to proof the concept in vivo by analyzing the effect of three distinct force levels on the creation of varus deformities. METHODS: The proposed implant is made of a conventional cerclage wire and features a twisted coil that unwinds with growth resulting in an implant-specific constant force level. The proximal medial tibial physes of 18 lambs were treated with the implant and assigned to three groups distinct by the force level of the implant (200 N, 120 N, 60 N). RESULTS: The treatment appeared safe without implant-related failures. Deformity creation was statistically different between the groups and yielded on average 10.6° (200 N), 4.8° (120 N) and 0.4° (60 N) over the treatment period. Modulation rates were 0.51°/mm (200 N), 0.23°/mm (120 N) and 0.05°/mm (60 N) and were constant throughout the treatment. CONCLUSION: By means of the constant force concept, controlled growth modulation appeared feasible in this preclinical experiment. However, clinical trials are necessary to confirm whether the results are translatable to the human pathological situation.

Guided growth for the Treatment of Infantile Blount's disease: Is it a viable option?

INTRODUCTION: Guided growth with temporary hemiepiphysiodesis has gained interest as a less invasive means for the treatment of coronal plane lower extremity deformities as well as leg length discrepancies. Its application to infantile Blount's disease has been less reported. The object of this study was to identify predictive factors of guided growth for treatment of infantile Blount's. METHODS: A retrospective review was performed of children undergoing guided growth for the treatment of infantile Blount's disease over an eight-year period. Inclusion criteria included treatment with THE for infantile Blount's disease. Clinical information, preoperative Langenskiold classification, and intra-operative and post-operative data. Preoperative variables were used to identify risk factors for speed of correction and the need for subsequent surgery. RESULTS: A total of 11 patients, 17 extremities, meeting inclusionary criteria. Preoperatively, 7 extremities were classified as Langenskiold stage ≥3, with 12 being classified as stage ≤2. Overall, the Drennan's angle improved from 18.3° to 0.3° by final follow-up at an average of 4.31 years. Eight extremities demonstrated deformity recurrence/persistence (stage ≤2:33% vs stage ≥3: 100%), requiring 24 reoperations. Children with Langenskiold stage ≥3 demonstrated a significantly higher rate of reoperation. CONCLUSION: Guided growth is a viable treatment option for Infantile Blount's disease presenting with Langenskiold stage ≤2 disease at treatment initiation. The treatment course can expect a 33% rate of recurrent deformity, treated successfully with repeat THE. No child stage ≤2 required corrective osteotomy. Caution should be used when considering guided growth for children presenting with Langenskiold stage ≥3.

Effect of guided growth intervention on static leg alignment and dynamic knee contact forces during gait.

BACKGROUND: Lower limb malalignment in the frontal plane is one of the major causes of developing knee osteoarthritis. Growing children can be treated by temporary hemiepiphysiodesis when diagnosed with lower limb malalignment. RESEARCH QUESTION: Is there a difference between medial or lateral knee contact force (KCF) before (PRE) and after (POST) hemiepiphysiodesis in patients with valgus malalignment and compared to a typically developed control group (TD)? Does a linear relationship exist between the static radiographic mechanical axis angle and dynamic medial/lateral KCF? METHODS: In this prospective study, an OpenSim full body model with an adapted knee joint was used to calculate KCFs in the stance phase of 16 children with diagnosed genu valgum and 16 age- and sex-matched TDs. SPM was applied to compare KCFs before and after guided growth and to test a linear relationship between the mechanical axis angle and KCFs. RESULTS: After the intervention, POST revealed a significantly increased medial KCF (p < 0.001, 4-97 % of stance) and decreased lateral KCF (p < 0.001, 6-98 %) compared to PRE. Comparing POST with TD, short phases with a significant difference were found (medial: p = 0.039, 84-88 %; lateral: p = 0.019, 3-11 %). The static mechanical axis angle showed a longer phase of a significant relation to KCFs for POST compared to PRE. SIGNIFICANCE: This study showed that temporary hemiepiphysiodesis in patients with valgus malalignment reduces the loading in the lateral compartment of the knee and thus the risk of developing osteoarthritis in this compartment. The determination of dynamic KCFs can be clinically relevant for the treatment of lower limb malalignment, especially for decision making before surgery, when compensatory mechanisms may play an important role. Additionally, the static radiographic mechanical axis angle does not necessarily represent the dynamic loading of the lateral knee compartment.

Finite element and biomechanical analysis of risk factors for implant failure during tension band plating.

OBJECTIVE: Tension band plating has recently gained widespread acceptance as a method of correcting angular limb deformities in skeletally immature patients. We examined the role of biomechanics in procedural failure and devised a new method of reducing the rate of implant failure. METHODS: In the biomechanical model, afterload (static or cyclic) was applied to each specimen. The residual stress of the screw combined with different screw sizes and configurations were measured and compared by X-ray diffraction. With regard to static load and similar conditions, the stress distribution was analyzed according to a three-dimensional finite element model. RESULTS: The residual stress was close to zero in the static tension group, whereas it was very high in the cyclic load group. The residual stress of screws was significantly lower in the convergent group and parallel group than in the divergent group. The finite element model showed similar results. CONCLUSIONS: In both the finite element analysis and biomechanical tests, the maximum stress of the screw was concentrated at the position where the screws enter the cortex. Cyclic loading is the primary cause of implant failure.

The effect of temporary hemiepiphysiodesis in the treatment of skeleton immature posttraumatic genu angular deformity: a retrospective study of 27 cases.

BACKGROUND: The purpose of this study was to evaluate the effect, rate of angular correction, and complications of temporary hemiepiphysiodesis (TH) in the treatment of skeleton immature posttraumatic genu angular deformity. METHODS: We retrospectively reviewed the records of 27 patients undergoing temporary hemiepiphysiodesis for the management of posttraumatic genu angular deformity. Based on the data from these patients, the rate of correction, effect of correction, length of the lower limbs, and complications were used as the outcome measures. RESULTS: Outcome measurements were obtained from a chart review of medical records that included information about clinical evaluations. Fifteen boys and 12 girls, with an average age of 6.3 years, were included in the study. The average follow-up was 3.8 years (range, 1.9 to 5.9 years) after surgery. Complete correction was obtained in 24 patients, while partial correction was obtained in 3 patients. The mean rate of angular correction was 8.41°/year in distal femur and 15.19°/year in proximal tibia. One patient had recurrence of genu valgum. No leg length discrepancy was found in our patients. CONCLUSION: Temporary hemiepiphysiodesis is a simple, effective, reliable, and reproducible method for the treatment of posttraumatic genu angular deformity, with fewer complications than osteotomy. Nevertheless, it is important to follow the rebound patient closely until skeletal maturity in our future work.

Multiplier method may be unreliable to predict the timing of temporary hemiepiphysiodesis for coronal angular deformity.

BACKGROUND AND PURPOSES: The multiplier method was introduced by Paley to calculate the timing for temporary hemiepiphysiodesis. However, this method has not been verified in terms of clinical outcome measure. We aimed to (1) predict the rate of angular correction per year (ACPY) at the various corresponding ages by means of multiplier method and verify the reliability based on the data from the published studies and (2) screen out risk factors for deviation of prediction. METHODS: A comprehensive search was performed in the following electronic databases: Cochrane, PubMed, and EMBASE™. A total of 22 studies met the inclusion criteria. If the actual value of ACPY from the collected date was located out of the range of the predicted value based on the multiplier method, it was considered as the deviation of prediction (DOP). The associations of patient characteristics with DOP were assessed with the use of univariate logistic regression. RESULTS: Only one article was evaluated as moderate evidence; the remaining articles were evaluated as poor quality. The rate of DOP was 31.82%. In the detailed individual data of included studies, the rate of DOP was 55.44%. CONCLUSION: The multiplier method is not reliable in predicting the timing for temporary hemiepiphysiodesis, even though it is prone to be more reliable for the younger patients with idiopathic genu coronal deformity.

A technical note on improved instrumentation for Blount staple insertion.

PURPOSE: Temporary hemiepiphysiodesis has gained increasing popularity after the introduction of the eight-Plate Guided Growth System. Since its introduction, the eight-Plate has largely supplanted the traditional Blount staple. The eight-Plate offers better purchase in the bone and a more precise insertion technique. However, the Blount staple is less expensive than the various guided growth plates. Further, some surgeons feel that the Blount staple may work faster, making it more appropriate for children who are approaching skeletal maturity. Unfortunately, the original instrumentation and technique for inserting the Blount staple is over 50 years old and has not been updated. METHODS: The purpose of this study was to develop new instrumentation to make Blount staple insertion as accurate and minimally invasive as eight-Plate insertion. We developed wire/drill guides to accommodate all three sizes of the Blount staple. Two wires are inserted through the wire guide under image intensifier control. After confirming the accurate position of the guidewires, a 3.2-mm cannulated step drill is used to drill over the wires to a depth of 5 mm. This creates two pilot holes for the two tines of the Blount staple. The final insertion is guided under an anteroposterior image intensifier view. We also developed a small staple holder that permits insertion through a small incision. RESULTS: We developed a working prototype of the new instrumentation and used it in three clinical cases. CONCLUSIONS: With the new staple inserter and instrumentation, Blount staples can now be inserted through a smaller incision with similar accuracy as eight-Plate insertion.