Accuracy of leg length prediction in children younger than 10 years of age

Indications and Timing of Guided Growth Techniques for Pediatric Upper Extremity Deformities: A Literature Review

Osseous deformities in children arise due to progressive angular growth or complete physeal arrest. Clinical and radiological alignment measurements help to provide an impression of the deformity, which can be corrected using guided growth techniques. However, little is known about timing and techniques for the upper extremity. Treatment options for deformity correction include monitoring of the deformity, (hemi-)epiphysiodesis, physeal bar resection, and correction osteotomy. Treatment is dependent on the extent and location of the deformity, physeal involvement, presence of a physeal bar, patient age, and predicted length inequality at skeletal maturity. An accurate estimation of the projected limb or bone length inequality is crucial for optimal timing of the intervention. The Paley multiplier method remains the most accurate and simple method for calculating limb growth. While the multiplier method is accurate for calculating growth prior to the growth spurt, measuring peak height velocity (PHV) is superior to chronological age after the onset of the growth spurt. PHV is closely related to skeletal age in children. The Sauvegrain method of skeletal age assessment using elbow radiographs is possibly a simpler and more reliable method than the method by Greulich and Pyle using hand radiographs. PHV-derived multipliers need to be developed for the Sauvegrain method for a more accurate calculation of limb growth during the growth spurt. This paper provides a review of the current literature on the clinical and radiological evaluation of normal upper extremity alignment and aims to provide state-of-the-art directions on deformity evaluation, treatment options, and optimal timing of these options during growth.

Height and Extremity-Length Prediction for Healthy Children Using Age-Based Versus Peak Height Velocity Timing-Based Multipliers

BACKGROUND

The age-based multiplier method described by Paley et al. markedly simplifies height and limb length predictions but may not adequately accommodate children's maturational differences. Multipliers can be derived relative to any maturity measure. This study compares Paley age-based multipliers with those based on peak height velocity (PHV) timing.

METHODS

In a longitudinal cohort of healthy children (66 male and 70 female), actual adult heights and limb lengths were compared with the measurements predicted using the Paley multipliers and multipliers developed relative to PHV timing. The age-based multipliers (adult divided by current) in our series were compared with those reported by Paley et al. to ensure that there were no systematic differences between the series. Absolute differences between the actual and predicted adult heights and limb lengths and the standard deviations of those differences were compared between the 2 methods.

RESULTS

The average age-based multipliers in our series were nearly identical to those reported by Paley et al. The differences between the predicted and actual adult values showed wide ranges when either the Paley or the PHV multipliers were used during infancy. The Paley method performed better than the PHV method throughout pre-growth-spurt childhood. The PHV-timing-derived multipliers became superior as children entered their growth spurt, whereas the performance of the age-based multipliers worsened. In adolescence, the maximum standard deviation for adult-height-prediction errors with use of the Paley multipliers occurred at the age of 13.5 years for boys and 11.5 years for girls and was 7.0 cm for boys and 5.6 cm for girls. For limb lengths, the maximum standard deviations occurred 6 months earlier and were 3.9 cm for boys and 3.2 cm for girls. The maximum standard deviation for the height prediction error with the age-based method occurred at the average time of PHV for the population. The PHV method became better than the Paley method just before growth-spurt initiation, at age 8 in girls and 11 in boys.

CONCLUSIONS

The age-based multipliers described by Paley et al. are superior to PHV-timing-based multipliers prior to the adolescent growth spurt for predicting height. They become less predictive, with wide standard deviations, as children enter their growth spurts, and PHV-derived multipliers become superior. The Paley height multipliers should be used before the age of 8 years in girls and 11 years in boys. After this, PHV-derived multipliers are superior for height and limb length prediction. In practice, these predictions are currently made using skeletal maturity, which is closely related to PHV during adolescence.

Efficacy and late complications of percutaneous epiphysiodesis with transphyseal screws

Percutaneous epiphysiodesis using transphyseal screws (PETS) has been developed for the treatment of lower limb discrepancies with the aim of replacing traditional open procedures. The goal of this study was to evaluate its efficacy and safety at skeletal maturity. A total of 45 consecutive patients with a mean skeletal age of 12.7 years (8.5 to 15) were included and followed until maturity. The mean efficacy of the femoral epiphysiodesis was 35% (14% to 87%) at six months and 66% (21% to 100%) at maturity. The mean efficacy of the tibial epiphysiodesis was 46% (18% to 73%) at six months and 66% (25% to 100%) at maturity. In both groups of patients the under-correction was significantly reduced between six months post-operatively and skeletal maturity. The overall rate of revision was 18% (eight patients), and seven of these revisions (87.5%) involved the tibia. This series showed that use of the PETS technique in the femur was safe, but that its use in the tibia was associated with a significant rate of complications, including a valgus deformity in nine patients (20%), leading us to abandon it in the tibia. The arrest of growth was delayed and the final loss of growth at maturity was only 66% of that predicted pre-operatively. This should be taken into account in the pre-operative planning.

Comparison of the Paley method using chronological age with use of skeletal maturity for predicting mature limb length in children

BACKGROUND

Treating patients with congenital or acquired limb-length inequality requires accurate estimations of limb length at skeletal maturity. There is controversy over the best indicator of maturity to be used for limb-length calculations. Paley popularized the multiplier method, in which chronological age is used, which has the virtue of simplicity but does not account for the wide variance in timing of the adolescent growth spurt. The purpose of this study was to determine whether the use of chronological age or the level of skeletal maturity provides more accurate limb-length predictions.

METHODS

We identified patients with limb-length inequality, for whom scanograms had been obtained before and at maturity, and who had had no surgical procedures on their normal lower limb. Skeletal maturity was determined with use of the Greulich and Pyle atlas, Tanner-Whitehouse-3 method, and simplified stages described by Sanders et al. The length of the lower extremity was compared with the ultimate limb length and the actual multiplier (final limb length divided by current limb length) for each point in time. A linear model was used to determine the log-transformed multipliers for the level of skeletal maturity, and Paley's multipliers were used for chronological age. Residual standard errors were determined to compare the results of the methods. We also conducted piecewise linear regression on each of the methods and used the residual standard errors to rank their performance and cross-validated the results.

RESULTS

We identified twenty-four patients (twelve girls and twelve boys) who met the study criteria. Most subjects had had multiple scanograms along with skeletal age radiographs (average, 4.5) at different ages. When all ages are considered, the Paley method had the best overall performance, with residual standard errors that were typically =5 cm. However, the Paley method did not perform best for subjects at stage-2 skeletal maturity or above; in those cases, skeletal-maturity-based predictions had residual standard errors of <2 cm.

CONCLUSIONS

While the Paley method, which is based on chronological age, provides reasonable estimates of ultimate limb length for most patients, use of skeletal-maturity determinations appears to provide better predictions of mature limb length during adolescence.

Possible mistakes in prediction of bone maturation in fibular hemimelia by Moseley chart

The purpose of this study was to establish a nomogram in order to predict limb length discrepancies in children with unilateral fibular hemimelia more accurately. In 31 children with unilateral fibular hemimelia the femoral-tibial length and skeletal age were determined an average of seven times per case by sequential radiographs during growth. From the data, a skeletal age nomogram was developed which shows a steeply declining mean skeletal age pattern in unilateral fibular hemimelia (the slope in girls was -0.59 and in boys -0.64). This nomogram crosses the normal mean skeletal age line of the Moseley straight-line graph at 10.5 years in girls and at 12 years in boys, and continues to decline until maturity. The results demonstrate an abnormal skeletal maturation process in patients with unilateral fibular hemimelia. The consistently declining steep skeletal age nomogram in unilateral fibular hemimelia makes prediction of skeletal maturity and limb length discrepancy inaccurate by the standard predictive methods particularly when using early skeletal ages. The skeletal age nomogram from our data determines skeletal maturation in children with unilateral fibular hemimelia more accurately, and allows a correct prediction of limb length discrepancy.

Lower-limb growth: how predictable are predictions?

PURPOSE

The purpose of this review is to clarify the different methods of predictions for growth of the lower limb and to propose a simplified method to calculate the final limb deficit and the correct timing of epiphysiodesis.

BACKGROUND

Lower-limb growth is characterized by four different periods: antenatal growth (exponential); birth to 5 years (rapid growth); 5 years to puberty (stable growth); and puberty, which is the final growth spurt characterized by a rapid acceleration phase lasting 1 year followed by a more gradual deceleration phase lasting 1.5 years. The younger the child, the less precise is the prediction. Repeating measurements can increase the accuracy of predictions and those calculated at the beginning of puberty are the most accurate. The challenge is to reduce the margin of uncertainty. Confrontation of the different parameters-bone age, Tanner signs, annual growth velocity of the standing height, sub-ischial length and sitting height-is the most accurate method. Charts and diagrams are only models and templates. There are many mathematical equations in the literature; we must be able to step back from these rigid calculations because they are a false guarantee. The dynamic of growth needs a flexible approach. There are, however, some rules of thumb that may be helpful for different clinical scenarios.

CALCULATION OF LIMB LENGTH DISCREPANCY

For congenital malformations, at birth the limb length discrepancy must be multiplied by 5 to give the final limb length discrepancy. Multiple by 3 at 1 year of age; by 2 at 3 years in girls and 4 years in boys; by 1.5 at 7 years in girls and boys, by 1.2 at 9 years in girls and 11 years in boys and by 1.1 at the onset of puberty (11 years bone age for girls and 13 years bone age for boys).

TIMING OF EPIPHYSIODESIS

For the timing of epiphysiodesis, several simple principles must be observed to reduce the margin of error; strict and repeated measurements, rigorous analysis of the data obtained, perfect evaluation of bone age with elbow plus hand radiographs and confirmation with Tanner signs. The decision should always be taken at the beginning of puberty. A simple rule is that, at the beginning of puberty, there is an average of 5 cm growth remaining at the knee. There are four common different scenarios: (1) A 5-cm discrepancy-epiphysiodesis of both femur and tibia at the beginning of puberty (11 years bone age girls and 13 years in boys). (2) A 4-cm discrepancy-epiphysiodesis of femur and tibia 6 months after the onset of puberty (11 years 6 months bone age girls, 13 years 6 months bone age boys, tri-radiate cartilage open). (3) A 3-cm discrepancy-epiphysiodesis of femur only at the start of puberty, (skeletal age of 11 years in girls and 13 years in boys). (4) A 2-cm discrepancy-epiphysiodesis of femur only, 1 year after the start of puberty (12 years bone age girls and 14 years in boys).

Measurement variance in limb length discrepancy: clinical and radiographic assessment of interobserver and intraobserver variability

The purpose of this study was to assess interobserver and intraobserver variability in the assessment of clinical and radiographic measurement of lower limb length discrepancy. Clinical measurements included direct measurement with a tape measure from anterior superior iliac spine (ASIS) to lateral malleolus and ASIS to medial malleolus as well as block measurement. Slit scanogram radiographic measurement was also evaluated. All three clinical measurements had excellent reliability, but the relatively large mean differences and the large 95% confidence intervals for clinical measurements limit the usefulness of these techniques. Slit scanogram measurement was the most reliable measurement technique. The intraobserver variance of direct slit scanogram measurement included intraclass correlation coefficient of 0.99, mean difference of 0.1 cm, and 95% confidence interval of 0.4 cm. Results were not influenced by patient age or body mass index. Slit scanogram measurement is the preferred method for assessment of limb length discrepancy. The direct slit scanogram measurement described in the text follows the mechanical axis line of the leg in the "at ease" standing position described by Paley. Direct measurement using a measuring tape on a full-length slit scanogram is more reliable than indirect measurement using horizontal lines drawn to a radiolucent ruler that is positioned by a technician, since direct measurement avoids errors due to nonparallel positioning of the limb relative to the ruler, and direct measurement also avoids errors due to non-horizontal lines drawn from standard bony landmarks to the ruler. The ideal radiographic measurement technique would have high reliability and accuracy and would minimize or eliminate radiation.

Clinical validation of the multiplier method for predicting limb length discrepancy and outcome of epiphysiodesis, part II

To validate the accuracy of the multiplier method in predicting limb length discrepancy (LLD) and outcome of epiphysiodesis, radiographs of 60 patients treated for LLD were measured. Data generated were used to predict maturity lengths of epiphysiodesed limbs, bone length discrepancies at maturity, and LLD at maturity after epiphysiodesis (residual discrepancy) using the multiplier and Moseley methods. The multiplier method mean error for bone length discrepancies predictions was 0.6 cm (SD = 0.6). Mean error for predicting lengths of epiphysiodesed limbs was 1.6 cm (SD = 1.2) for both methods. Mean errors for predicting residual discrepancies were 0.9 cm for the multiplier method using chronologic age, 1 cm for the multiplier method using skeletal age, and 1.3 cm for the Moseley method. Mean error difference between the methods was significant (P = 0.0008). The multiplier method accurately predicts LLD and outcome of epiphysiodesis and is more accurate than the Moseley method in predicting LLD at maturity after epiphysiodesis.

Clinical validation of the multiplier method for predicting limb length at maturity, part I

To validate the accuracy of the multiplier method in predicting bone and limb maturity lengths, radiographs of 60 patients treated for lower limb length discrepancy were measured. Longitudinal limb length data were used to predict maturity lengths of non-epiphysiodesed normal bones and short bones. Mean errors for predictions were 1.1 cm (SD = 0.9) and 1.5 cm (SD = 1.3) for the multiplier method using chronologic age and skeletal age, respectively. Regression correlation values between multiplier method predictions and actual measurements were 0.93 using chronologic age and 0.90 using skeletal age. The multiplier method was more accurate than prediction using the Anderson et al growth charts. Mean error for limb length predictions was 2.5 cm for the multiplier method using chronologic age and 2.6 cm for the Moseley method. Although as accurate as the Moseley method, the multiplier method seems to be quicker and simpler to use and requires only one data point for predicting limb length at maturity.

Residual shortening after Legg-Calve-Perthes disease, focusing on the response of the ipsilateral tibia

Residual shortening of the affected limb was measured at skeletal maturity by teleoroentgenograms in 68 patients with Legg-Calve-Perthes disease (LCPD); special attention was paid to the length of the ipsilateral tibia. Of these 68 patients, 38 were treated by abduction orthosis (AO) and 30 by femoral varus osteotomy (FVO). Residual shortening in AO group was significantly greater than that in FVO group. The femoral lengths in both of these groups were similar (12.5 mm in the AO group and 10.1 mm in the FVO group), but the tibial lengths were significantly different (2.5 mm shortening in the AO group and 0.9 mm lengthening in the FVO group). Residual shortening in the patients treated by FVO was less than that in patients treated by AO. The difference is speculated to be caused by the overgrowth of the ipsilateral tibia.