Acute versus gradual correction of idiopathic tibia vara in children: a systematic review

Surgical approach to correction of severe knee malalignment in a pediatric population in Tanzania

AIM

Severe knee malalignment in children usually needs surgery with different options available in surgical approaches. The aim of this study was to report the results of the surgical correction of severe knee malalignment in children treated with femoral and tibial osteotomy, temporarily fixed with percutaneous Kirschner wires, in a low- and middle-income country (LMIC), with limited medical resources.

Recurrence and Complication Rates of Surgical Treatment for Blount's Disease in Children: A Systematic Review and Meta-Analysis

BACKGROUND

Blount's disease is a growth disorder of the proximal tibia that causes progressive genu varum in children. Surgical treatment is recommended if the deformity worsens, but which intervention is best remains controversial. This study aims to identify factors influencing outcomes and determine the most effective surgical approach.

METHODS

A systematic review was conducted of studies published before January 2022.

RESULTS

In total, 63 retrospective studies with CEBM IIIb/IV levels were included (1672 knees in 1234 patients). The most commonly reported treatment was acute correction via osteotomy (47%), followed by hemiepiphysiodesis (22%) and gradual correction (18%). Combined procedures were reported in 13% of cases. The overall recurrence rate was 18%, with a significant difference when comparing the recurrence rates after gradual correction with those after hemiepiphysiodesis (7% and 29%, respectively). Major complications beyond recurrence were observed in 5% of cases. A meta-analysis of the available raw data showed a significantly increased recurrence rate (39%) among treated children who were between 4.5 and 11.25 years of age and were followed for a minimum follow-up of 2.5 years.

CONCLUSIONS

Overall, poor evidence with which to establish an optimal treatment for Blount's disease was found. This study remarked on the need for early diagnosis, classification, and treatment of infantile tibia vara, since a significant rate of recurrence was found in neglected cases.

Single-Stage Tibial Osteotomy for Correction of Genu Varum Deformity in Children

Conservative and operative treatments with gradual or acute correction of severe varus deformities of the leg have been described. We evaluated whether the corrective osteotomy used within the NGO Mercy Ships is an effective treatment for genu varum deformity of different etiologies in children and which patient specific factors have an influence on the radiographic outcome. In total, 208 tibial valgisation osteotomies were performed in 124 patients between 2013 and 2017. The patients' mean age at the time of surgery was 8.4 (2.9 to 16.9 (min/max)) years. Seven radiographically measured angles were used to assess the deformity. Clinical photographs taken pre- and postoperatively were assessed. The mean time between the surgery and the end of physiotherapeutic treatment was 13.5 (7.3 to 28) weeks. Complications were monitored and classified according to the modified Clavien-Dindo-classification system. The mean preoperative mechanical tibiofemoral angle was 42.1° varus (range: 85°-12° varus). The mean postoperative mechanical tibiofemoral angle was 4.3° varus (range: 30° varus-13° valgus). The factors predicting a residual varus deformity were higher age, greater preoperative varus deformity and the diagnosis of Blount disease. The tibiofemoral angle measured on routine clinical photographs correlated well with the radiographic measurements. The single-stage tibial osteotomy described is a simple, safe and cost-effective technique to correct three-dimensional deformities of the tibia. Our study shows very good mean postoperative results, but with a higher variability than in other studies published. Nevertheless, considering the severity of preoperative deformities and the limited opportunities for aftercare, this method is excellent for the correction of varus deformities.

Acute correction of severe complex adolescent late-onset tibia vara by minimally invasive osteotomy and simple circular fixation: a case series with 2-year minimum follow-up

Background

Despite multiple published reviews, the optimum method of correction and stabilisation of Blount’s disease remains controversial. The purpose of this study is to evaluate the clinical and radiological outcomes of acute correction of late-onset tibial vara by percutaneous proximal tibial osteotomy with circular external fixation using two simple rings. Weighing up the pros and cons and to establish if this method would be the method of choice in similar severe cases especially in a context of limited resources.

Methods

This study was conducted between November 2016 and July 2020. We retrospectively reviewed the clinical notes and radiographs of 30 patients (32 tibiae) who had correction of severe late-onset tibia vara by proximal tibial osteotomy and Ilizarov external fixator. The mean age at the time of the operation was 16.6 (± 2.7) years (range 13–22).

Results

The mean proximal tibial angle was 65.7° (± 7.8) preoperatively and 89.8° (± 1.7) postoperatively (p < 0.001). The mean mechanical axis deviation improved from 56.2 (± 8.3) preoperatively to 2.8 (± 1.6) mm postoperatively (p < 0.001). The mean femoral-tibial shaft angle was changed from –34.3° (± 6.7) preoperatively to 5.7° (± 2.8) after correction, with degree of correction ranging from 25° to 45°. Complications included overcorrection (three cases 9%) and pin tract infection (eight cases 25%). The mean Hospital for Special Surgery knee scoring system (HSS) improved from 51.03 (± 11.24) preoperatively to 94.2 (± 6.8) postoperatively (p < 0.001). The mean length of follow up period 33.22 (± 6.77) months, (rang: 25–46 months). At final follow up, all patients had full knee range of motion and normal function. All cases progressed to union and there were no cases of recurrence of deformity.

Conclusion

This simple procedure provides secure fixation allowing early weight bearing and early return to function. It can be used in the context of health care systems with limited resources. It has a relatively low complication rate. Our results suggest that acute correction and simple circular frame fixation is an excellent treatment choice for cases of late-onset tibia vara, especially in severe deformities.

The Medial Elevation Osteotomy for Late-presenting and Recurrent Infantile Blount Disease

BACKGROUND

Late-presenting or recurrent infantile Blount disease (IBD) is characterized by knee instability because of medial tibial plateau depression, multiplanar proximal tibial deformity, and potential distal femoral deformity. The surgical treatment strategy includes medial elevation osteotomy to stabilize the knee, together with proximal tibial osteotomy to correct alignment, and lateral epiphysiodesis to prevent a recurrence. This study's primary aim was to describe the clinical outcomes of medial elevation osteotomy for the management of late-presenting and recurrent IBD.

METHODS

The authors reviewed the records of 48 children (64 limbs) who had medial elevation osteotomies and lateral epiphysiodesis, combined with proximal tibial realignment in 78% (50/64) of cases in the same setting. IBD was bilateral in 33% (16/48), 77% (37/48) were female individuals, and 42% (20/48) were obese.

RESULTS

The mean age at surgery was 8.6 years (SD, 1.6; range, 5.8 to 12.8). The mean preoperative tibiofemoral angle (TFA) was 28±11 degrees (8 to 55 degrees), and the mean angle of depression of the medial plateau (ADMP) was 49±8 degrees (26 to 65 degrees). Distal femoral valgus was present in 27% (17/62) and varus in 10% (6/62) children. At a median follow-up of 3.2 years (range, 1 to 6.2 y), the median TFA was 1-degree valgus (interquartile range, 7-degree varus to 5-degree valgus), whereas the ADMP was corrected to 25±8 degrees (8 to 45 degrees). Obesity was associated with more severe deformity as measured by TFA (P<0.001) but did not affect the extent of medial plateau depression (P=0.113). The good or excellent alignment was achieved in 75% (47/63) limbs. Obesity was associated with an increased risk of recurrence [odds ratio (OR), 5.21; 95% CI, 1.26-21.63; P=0.023]. Age at the surgery or previous surgery was not associated with recurrence (OR, 1.29; 95% CI, 0.88-1.88; P=0.195 and OR, 1.22; 95% CI, 0.36-4.17; P=0.746). Obesity and residual instability were associated with an increased risk of poor alignment at the latest follow-up (OR, 3.24; 95% CI, 1.02-10.31; P=0.047 and OR, 1.21; 95% CI, 1.05-1.40; P=0.008).

CONCLUSION

Late-presenting or recurrent IBD is a surgical challenge. Obesity is associated with more severe deformity. Medial elevation osteotomy combined with lateral proximal tibial epiphysiodesis and metaphyseal tibial realignment osteotomy will result in restoration of lower limb alignment in a high proportion of cases. The recurrent deformity may be the result of failed epiphysiodesis. Obesity and residual instability are associated with an increased risk of poor alignment. Although complications are rare, surgical measures to decrease risk should be followed.

LEVEL OF EVIDENCE

Level IV.

A retrospective comparative study of corrective osteotomy for tibial deformities with the multiaxial correction fixator and the circular fixator

PURPOSE

A multiaxial correction (MAC) fixator is a monolateral type of fixator that can correct multi-planer deformities. The purpose of this study is to compare the clinical outcome of correction for tibial deformities with the MAC fixator and the circular external fixators.

METHODS

We retrospectively reviewed consecutive patients reconstructed with the MAC fixator (MAC group) or circular external fixators (Ring group) due to the congenital diseases or residual conditions after treatment of trauma, infection, tumor, or limb lengthening between 2003 and 2016.

RESULTS

The 30 patients who had angular tibial deformity were included. In patients with tibia vara or lateral bowing, the average pre-operative mechanical medial proximal tibial angle (mMPTA) of the MAC group and the Ring group was significantly increased to 86.9 ± 3.5° in the MAC group and 88.0 ± 3.6° in the Ring group postoperatively. Medial bowing was also successfully corrected in both groups. Regarding the sagittal alignment, post-operative anatomical posterior proximal tibial angle (aPPTA) of the MAC group was deteriorated after coronal correction. The operative time was significantly shorter in the MAC group than the Ring group (p < 0.05).

CONCLUSION

The MAC fixator successfully corrected coronal deformities of the tibia with shorter operative time, but it has a risk of occurrence of the procurvatum deformity compared with circular external fixators. Paying attention to the sagittal alignment, the MAC fixator can be one of the treatment options for correction of the coronal tibial deformities.

Gradual Deformity Correction in Blount Disease

BACKGROUND

Blount disease is a disorder of the posteromedial proximal tibial physis which causes a progressive varus, procurvatum, and internal rotation deformity of the tibia. Untreated, it can cause significant limb malalignment. The goal of this study is to evaluate the results of correction of Blount disease using types of external fixation.

METHODS

We conducted a retrospective review of 41 patients (51 limbs) who underwent correction of Blount disease with an Ilizarov external fixator or a Taylor spatial frame (TSF) by a single surgeon. The medial proximal tibial angle (MPTA), mean axis deviation (MAD), posterior proximal tibial angle, and joint line congruence angle (JLCA) were measured on radiographs preoperatively, at frame removal and at final follow-up.

RESULTS

The average age at treatment was 9.6 years old, with a mean follow-up time of 34 months. Mean preoperative MPTA, MAD, and JLCA were significantly improved at the time of frame removal as well as at final follow-up with no significant changes in correction between the time of frame removal and final follow-up. There was no difference in MPTA and MAD in patients treated with an Ilizarov frame versus a TSF. MPTA, MAD, and JLCA all significantly improved regardless of the underlying diagnosis (infantile vs. adolescent Blount disease) or history of prior surgical intervention. The most common complication was superficial pin-site infection.

CONCLUSIONS

Both Iliazarov and TSF are viable treatment options for infantile and adolescent Blount disease, with the ability to significantly improve both the limb mechanical axis and the mechanical axis of the affected tibia. Correction can be attained regardless of whether patients have previously failed surgical intervention.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Step cut "V" osteotomy for acute correction in Blount's disease treatment: A case series

•

Severe Blount’s disease results in progressive multiplanar deformity of the lower limb.

•

Blount’s disease management should be tailored individually.

•

Step Cut “V” Osteotomy developed by our institution in order to have more predictable result.

•

Step Cut “V” Osteotomy provide accurate and safe correction even in severe deformity.

Introduction

Severe Blount’s disease results in progressive multiplanar deformity of the lower limb. There are varus, procurvatum, and internal tibia rotational deformity. Treatment varies for each patient, depending on age, magnitude of deformity, discrepancy, psychosocial factor, and surgeon’s experience. The aim of treatment is to acutely correct deformity and realign the mechanical axis. We proposed a technique of step cut “V” Osteotomy which could achieve the aim of treatment safely and effectively.

Methods

Twenty-seven legs from eighteen patients were underwent Step Cut “V” Osteotomy technique in our institution from 2015 to 2017 to produce overvalgus correction. Eleven patients had bilateral deformities, and seven patients had unilateral deformity. All patients had mechanical axis deviation (MAD) away medially to the center of the knee, increase of tibiofemoral angle, and Drennan angle. Outcomes were recorded postoperatively such as infection, compartment syndrome, nerve palsy, range of motion, stability of knee ligaments, union time, early weight bearing and recurrence.

Results

From this Step Cut “V” Osteotomy, we can accurately measure the angle of correction we want to achieve preoperatively. Drennan angle and Tibiofemoral angle (TFA) of the patients improved with subsequent correction of interbal tibia rotation and procurvatum. No complication of compartment syndrome and nerve palsy were found. Patient could perform early mobilization, and weight bearing on second month after surgery because of strong fixation and good ligament stability. No significant postoperative infection occurred. Union time achieved in two to three months, but four legs from patients over 4 years old who underwent surgery experienced a recurrence.

Conclusion

Step Cut "V" Osteotomy is a simple, safe and effective technique for acute correction of severe Blount’s disease. And can produce an accurate correction, high union rate and early weight bearing with no complication as a result that would be achieved at the end of treatment.

Guided growth for angular correction in children: a comparison of two tension band plate designs

This retrospective cohort study examined 20 patients (48 physes), 11 boys and nine girls, who were treated with hinge-plate or eight-plate. The mean age of the patients at surgery was 11.9±2.6 years. The mean follow-up duration was 13±2.7 months. The radiographic measurement of both distal femoral and proximal tibial deformity showed significant correction, with no difference between the hinge-plate and the eight-plate. Both screw divergence angle and the hinge angle showed significant changes at the last follow-up. The deformity correction of the distal femoral physis was quicker than the proximal tibial physis. The rate of mechanical femoral-tibial angle correction was 0.97°/month if both femoral and tibial physes were treated.

LEVEL OF EVIDENCE

III.

Treatment of Infantile Blount Disease: An Update

Although the core principles of managing infantile Blount disease generally remain unchanged, treatment modalities have evolved over the years. Consensus has yet to be reached regarding the efficacy of bracing. Children with Blount disease commonly have advanced bone age, which may impact the timing and magnitude of (over) correction of angular deformity. Techniques of growth modulation, based on the tension band principle, continue to gain popularity. Although there are limited reports in the last decade on proximal tibial osteotomy for this developmental disorder, both acute and gradual correction remain viable treatment options in the appropriate setting. In certain older children (>7 y old) with advanced stages of the disease, a medial hemiplateau elevation combined with lateral proximal tibial hemiepiphysiodesis may be needed to address the epiphyseal deformity. Given the possibility of unpredictable proximal tibial physeal activity, all children with Blount disease should be followed at regular intervals till skeletal maturity. To provide sufficient granularity for pooled analyses and help establish evidence-based clinical guidelines, standardization of reporting clinical outcomes among children with Blount disease is encouraged.

Solid screw insertion for tension band plates: a surgical technique tip

PURPOSE

Growth modulation with tension band plates (TBPs) and cannulated screws is the current mainstay of treatment for pediatric lower extremity angular deformities. Solid screws have been used as an alternative to cannulated screws to decrease the risk of screw failure, particularly in obese children. The downside of solid screws is the decrease in precision of placement. This study describes a surgical technique to insert solid TBP screws accurately.

METHODS

TBP insertion starts with the same conventional steps by inserting the guidewires into the epiphysis and metaphysis, straddling the physis. After fluoroscopic confirmation of the position of the guidewires, the cannulated drill bit is used to broach the cortex to a depth of 5 mm in the bone. A standard 4.5-mm cannulated screw from the TBP set is used to tap the screw tract over the guidewires for approximately three-quarters of the planned screw length. After removing the guidewires, the solid screws are then inserted in each hole to follow the tapped tracts.

RESULTS

This technique was used in five patients including four with Blount disease and one with bilateral genu varum.

CONCLUSION

It is recommended to use solid screws with TBPs in patients with a high body mass index to avoid screw fracture. Our technique describes using a cannulated screw as a tap to create a tract to ease accurate insertion of the solid screws, and prevent the solid screw from deviating outside the desired path.

A modified Puddu technique for the treatment of adolescent mild to moderate tibia vara

The aim of this work was to evaluate the results of a modified 'subphyseal' Puddu technique for the treatment of selected cases of the adolescent tibia vara. Twenty-five legs in 18 patients with adolescent tibia vara between January 2008 and February 2012 were included. The mean value of angular correction was 22.24° (range, 18°-25°, SD 2.0°). All of the osteotomies in this series healed by 8 weeks. There were no postoperative neurologic or vascular complications. At the end of follow-up, no iatrogenic disturbance to the proximal tibial physis was observed, but recurrence was reported in three cases (12%). The modified 'subphyseal' Puddu technique is a reproducible, easy, and convenient technique for the treatment of adolescent tibia vara, provided there is proper case selection.

Treatment of Adolescent Blount Disease Using Taylor Spatial Frame With and Without Fibular Osteotomy: Is There any Difference?

BACKGROUND

In adolescents, Tibia Vara (Blount disease) patients usually present with combination of marked genu varum, procurvatum, and internal tibial torsion. When no growth remaining, standard treatment protocol for correction is osteotomy of the proximal tibia and fibula. In our study we compared 2 groups of patients: group A was treated with fibular osteotomy and group B was treated without fibular osteotomy.

METHODS

Twenty-three patients (25 tibias), 21 males and 2 females, mean age of 14.7 years (range, 13 to 21 y) were included in our study. All patients underwent correction with Taylor spatial frame. Group A (with fibular osteotomy) included 11 tibias and group B (no fibular osteotomy) included 14 tibias. Group A underwent correction by proximal tibial and fibular osteotomies (fibula was fixed distally by 2 ilizarov wires to the distal ring). Group B was treated by proximal tibial osteotomy only (fibula was not osteotomized and was not fixed to the tibia).

RESULTS

Correction goal was achieved in 9 cases in group A and 12 in group B. Mean time in frame was 15.9 weeks in group A and 14.14 in group B. Mean lengthening was 16.5 mm in group A and 12.8 mm in group B. Mean proximal tibia-fibula distance was 21.1 mm (group A) and 14.9 mm (group B). Mean distal tibia-fibula distance was 9.8 mm (group A) and 9.6 mm (group B). There was no ankle malalignment in both the groups. Complications included pin-tract infection in 11 patients and delayed union in 2 patients (1 in each group).

CONCLUSION

We believe that in patients with minimal lengthening as needed in patients with adolescent Tibia Vara correction might be performed safely without osteotomy and fixation of the fibula.

LEVEL OF EVIDENCE

Level III.

Evaluation of complications of treatment of severe Blount's disease by circular external fixation using a novel classification scheme

Corrective osteotomy for recalcitrant varus deformity secondary to adolescent and infantile Blount's disease can be challenging because of a combination of severity of deformity, complexity of deformity, and frequent association with patient obesity. We present here the outcome of treatment by osteotomy and gradual deformity correction by circular external fixation in 31 patients with either infantile or adolescent Blount's disease. We used a unique classification scheme to quantify and qualify complications in this patient group: category I, complications not requiring an alteration in the treatment plan, not involving unplanned return to surgery, and not influencing outcome; category II, complications requiring an alteration in the treatment plan, including unplanned returns to surgery, but that did not influence outcome; category IIIA, complications that resulted in a failure to achieve treatment goals; and category IIIB, complications that resulted in a failure to achieve treatment goals and the development of a new pathology or worsening of patient condition. All but one patient in this group incurred at least one complication. However, despite the complex nature of this patient population, 88% achieved satisfactory correction without developing category IIIA or IIIB complications. Careful selection of patients and vigilant postoperative management can result in excellent outcomes with circular external fixation and gradual correction in this challenging patient population.

Blount disease: an update

Blount disease is a developmental disorder associated with childhood obesity. Based on whether the deformity is first noted before or after 4 years of age, early-onset and late-onset forms of Blount disease have been described. Besides physeal abnormalities of the proximal tibia, compensatory changes in the intra-articular morphology of the medial compartment of the affected knee are often noted on MRI scan. Both guided growth and acute and gradual correction via a proximal tibial osteotomy have roles in the surgical management of these patients. In order to optimize clinical outcome, frequent follow-up until skeletal maturity is recommended.

Proximal tibial osteotomy and Taylor Spatial Frame application for correction of tibia vara in morbidly obese adolescents

BACKGROUND

Four percent of children and adolescents in the United States are morbidly obese. Treatment for tibia vara includes proximal tibial osteotomy and correction with a Taylor Spatial Frame (TSF). There are no reports that specifically examine the success of this technique in morbidly obese adolescents.

METHODS

A retrospective review was conducted of patients between 12 and 18 years of age with a body mass index for age at or above the 99th percentile who had undergone gradual correction of tibia vara with proximal tibial osteotomy and application of a TSF at our institution between 2005 and 2009. Deformity analysis was performed on full-length standing anteroposterior radiographs of both lower extremities and lateral radiographs of the involved tibia obtained preoperatively and at latest follow-up. All complications were recorded.

RESULTS

Fourteen patients met the inclusion criteria. The mean age was 13 years. The average body mass index was 45 kg/m. Preoperative deformity analysis demonstrated a mean mechanical axis deviation of 90 mm, mean mechanical medial proximal tibial angle of 66 degrees, and mean posterior proximal tibial angle of 80 degrees. Analysis at an average follow-up of 14 months demonstrated a mean mechanical axis deviation of 10 mm, mean mechanical medial proximal tibial angle of 88 degrees, and mean posterior proximal tibial angle of 81 degrees. Complications specifically related to the TSF occurred in 2 patients. Both experienced strut disengagement and loss of osteotomy position. This was treated with refastening of the strut and a new program of deformity correction. Complications related to the deformity correction occurred in 3 patients. One had premature fibular consolidation requiring repeat osteotomy, 1 developed a transient partial deep peroneal nerve palsy, and 1 experienced thigh soft tissue irritation from the proximal ring necessitating early TSF removal. One patient had a residual leg-length discrepancy that required tibial lengthening.

CONCLUSIONS

Correction of tibia vara with proximal tibial osteotomy and application of a TSF is an effective treatment option in morbidly obese adolescents. Associated complications are minimal.

LEVEL OF EVIDENCE

Level IV-therapeutic study.

Gradual correction of idiopathic genu varum deformity using the Ilizarov technique

PURPOSE

Proximal tibial osteotomy is an effective treatment option for genu varum deformity among the many other described techniques. The purpose of this study is to evaluate the clinical and radiological outcomes and the complications in gradual correction of idiopathic genu varum deformity using Ilizarov frame.

METHODS

Proximal tibial medial opening wedge osteotomy was performed in 21 lower limbs of 11 patients, with whom the Ilizarov external fixator was used for gradual correction of the varus deformity. The mean age of the patients was 24.8 years (SD, 5.3). Deformity measurements of conventional mechanical axis deviation, mechanical medial proximal tibial angle, mechanical lateral distal femoral angle, posterior proximal tibial angle, joint conversion angle, tibio-femoral angle and tibial slope were compared.

RESULTS

The mean time for removal of the Ilizarov fixator was 24.7 weeks. At the last follow-up, the mean of Hospital for Special Surgery knee score increased, and the mean mechanical medial proximal tibial angle, tibio-femoral angle and conventional mechanical axis deviation improved. The differences between preoperative and postoperative posterior proximal tibial angle, mechanical lateral distal femoral angle, joint conversion angle and tibial slope were not significant. Ten complications were observed, of which 8 were minor complications and 2 were minor complications.

CONCLUSION

With a few complications, normal alignment and orientation of lower extremity can be established in patients with idiopathic genu varum deformity through gradual correction using a Ilizarov fixator.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Combined distal tibial rotational osteotomy and proximal growth plate modulation for treatment of infantile Blount’s disease

Infantile Blount’s disease is a condition that causes genu varum and internal tibial torsion. Treatment options include observation, orthotics, corrective osteotomy, elevation of the medial tibial plateau, resection of a physeal bar, lateral hemi-epiphysiodesis, and guided growth of the proximal tibial physis. Each of these treatment options has its disadvantages. Treating the coronal deformity alone (genu varum) will result in persistence of the internal tibial torsion (the axial deformity). In this report, we describe the combination of lateral growth modulation and distal tibial external rotation osteotomy to correct all the elements of the disease. This has not been described before for treatment of Blount’s disease. Both coronal and axial deformities were corrected in this patient. We propose this combination (rather than the lateral growth modulation alone) as the method of treatment for early stages of Blount’s disease as it corrects both elements of the disease and in the same time avoids the complications of proximal tibial osteotomy.

Limb angular deformity correction using Dyna-ATC: surgical technique, calculation method, and clinical outcome

PURPOSE

Dyna-ATC is a unilateral external fixator with angulator, lengthener, and translator, which allows for angular correction and compensation of the secondary displacement during angular correction. The purpose of this study is to introduce surgical technique and calculation methods and to evaluate the clinical outcome of angular deformity correction using Dyna-ATC.

MATERIALS AND METHODS

The amounts of secondary displacement were calculated with the distances between axis of correction of angulation, Center of Rotational Angulation, and osteotomy and the amount of angular deformity. The rate of angular correction was determined to distract the corticotomy at 1 mm/day. Clinical and radiographic evaluation was performed on 13 patients who underwent deformity correction using Dyna-ATC. There were 8 proximal tibia vara, 1 tibia valga, 2 varus and 4 valgus deformities on distal femur. One patient underwent pelvic support femoral reconstruction. Concomitant lengthening was combined in all femur cases. Mean age at surgery was 17.5 years (7 to 64).

RESULTS

All but one achieved bony healing and normal alignment with the index procedure. Mean mechanical axis deviation improved from 31.9 mm to 3.0 mm. The average amount of angular correction was 11.0° on tibiae and 10.0° on femora. The average length gain on femora was 6.4 cm, and the healing index averaged to 1.1 mo/cm. One patient underwent quadricepsplasty and one patient had three augmentation surgeries due to poor new bone formation.

CONCLUSION

We believe that Dyna-ATC is a useful alternative to bulky ring fixators for selective patients with angular deformity less than 30 degrees in the coronal plane around the knee joint.