Recommendation of minimal distal tibial length for long axis coordinate system definitions.

Accurate anatomical coordinate systems for the foot and ankle are critical for interpreting their complex biomechanics. The tibial superior-inferior axis is crucial for analyzing joint kinematics, influencing bone motion analysis during gait using CT imaging and biplane fluoroscopy. However, the lack of consensus on how to define the tibial axis has led to variability in research, hindering generalizability. Even as advanced imaging techniques evolve, including biplane fluoroscopy and weightbearing CT, there exist limitations to imaging the entire foot together with the full length of the tibia. These limitations highlight the need to refine axis definitions. This study investigated various superior-inferior axes using multiple distal tibia lengths to determine the minimal field of view for representing the full tibia long-axis. Twenty human cadaver tibias were imaged and segmented to generate 3D bone models. Axes were calculated based on coordinate definitions that required user manual input, and a gold standard mean superior-inferior axis was calculated based on the population's principal component analysis axis. Four manually calculated superior-inferior tibial axes groups were established based on landmarks and geometric fittings. Statistical analysis revealed that geometrically fitting a cylinder 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond, yielded the smallest angular deviation from the gold standard. From these findings, we recommend a minimum field of view that includes 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond for tibial long-axis definitions. Implementing these findings will help improve foot and ankle research generalizability and impact clinical decisions.

Drop landing analysis of rotational osteotomies.

Pathomechanics resulting from rotational deformities of the long bones in an idiopathic population have not been extensively studied, and are chiefly limited to level over ground walking. Thirty-five adolescents with excessive idiopathic outward tibial torsion (TT), femoral rotation, or both (pan genu) were studied both before and after corrective surgery. Data collected included computational motion analysis of a drop jump and patient-reported outcomes consisting of PODCI and Goal Attainment Scores. Results were compared to an age-matched typically developing cohort (n = 25). Subjects with femoral anteversion (FA) exhibited compensatory hip rotations to normalize knee progression angles at landing. Subjects with only TT did not compensate at the hip, landing with typical knee progression but excessive outward foot progression. These strategies resulted in elevated frontal plane knee moments for FA (P = 0.008), and elevated lateral knee forces in all groups compared to typical, with the TT group reaching significance (P < 0.001). Rotational osteotomies successfully restored elevated kinematics and kinetics to within or below typically developing ranges. Patient-reported outcomes generally improved after surgery across all domains studied. Drop jump testing elucidated compensation strategies employed by these cohorts. Compensation did not fully alleviate elevated forces at the knees. Surgical intervention normalized pathokinematics and pathokinetics, reduced pain, and improved patients' perception of their functional abilities. Greater improvements were found in individuals in the two groups with FA compared to the group with TT only.

The long-term effects of aggressive spasticity reducing treatment, including selective dorsal rhizotomy, on joint kinematic outcomes of persons with cerebral palsy.

BACKGROUND: Selective dorsal rhizotomy (SDR) creates a large and permanent reduction of spasticity for children with cerebral palsy (CP). Previous SDR outcomes studies have generally lacked appropriate control groups, had limited sample sizes, or reported short-term follow-up, limiting evidence for improvement in long-term gait function. RESEARCH QUESTION: Does aggressive spasticity management for individuals with CP improve long-term gait kinematics (discrete joint kinematics) compared to a control group of individuals with CP with minimal spasticity management? METHODS: This study was a secondary analysis - focused on joint-level kinematics - of a previous study evaluating the long-term outcomes of SDR. Two groups of participants were recruited based on a retrospectively completed baseline clinical gait study. One group received aggressive spasticity treatment including a selective dorsal rhizotomy (Yes-SDR group), while the other group had minimal spasticity management (No-SDR group). Both groups had orthopedic surgery treatment. Groups were matched on baseline spasticity. All participants prospectively returned for a follow-up gait study in young adulthood (greater than 21 years of age and at least 10 years after baseline). Change scores in discrete kinematic variables from baseline to follow-up were assessed using a linear model that included treatment arm (Yes-SDR, No-SDR), baseline age, and baseline kinematic value. For treatment arm, 5° and 5 Gait Deviation Index points were selected as thresholds to be considered a meaningful difference between treatment groups. RESULTS: At follow-up, there were no meaningful differences in pelvis, hip, knee, or ankle kinematic variable changes between treatment arms. Max knee flexion - swing showed a moderate treatment effect for Yes-SDR, although it did not reach the defined threshold. SIGNIFICANCE: Aggressive spasticity treatment does not result in meaningful differences in gait kinematics for persons with cerebral palsy in young adulthood compared to minimal spasticity management with both groups having orthopedic surgery.

Is peak hamstrings muscle-tendon length criterion a sufficient indicator to recommend against surgical lengthening of hamstrings?

BACKGROUND: Excessive knee flexion during stance in children with cerebral palsy is often treated by surgical hamstrings lengthening. Pre-operative hamstrings muscle-tendon length can be estimated from kinematics and often used for decision making to rule out surgical lengthening if peak hamstrings muscle-tendon length is 'Not Short'. RESEARCH QUESTION: If peak hamstrings muscle-tendon length is within two standard deviations of typical, is that a sufficient indicator to rule out surgical hamstrings lengthening? METHODS: Three motion analysis centers retrospectively identified children with cerebral palsy, age 6-17 years, who had consecutive gait analyses with knee flexion at initial contact > 20° and popliteal angle > 35° at initial study. Three groups were considered: Medial Hamstrings Lengthening (MHL), Medial and Lateral Hamstrings Lengthening (MLHL), no surgical intervention (Control). Peak hamstrings muscle-tendon length at initial gait study was computed and categorized as 'Short' or 'Not Short'. Two outcomes variables were considered: change in peak knee extension (PKE) and change in pelvic tilt. Univariate comparisons of all variables were assessed along with a multivariate stepwise regression analysis to identify pre-operative characteristics that may predict post-operative improvement. RESULTS: 440 individuals met inclusion criteria. Percentage of individuals with improved PKE by grouping were- MHL-'Short': 60%, MHL-'Not Short': 65%, MLHL-'Short': 74%, MLHL-'Not Short': 74%, Control 'Short': 20%, Control 'Not Short': 19%. Percentage of individuals with worsened pelvic tilt were- MHL-'Short': 25%, MHL-'Not Short': 11%, MLHL-'Short': 42%, MLHL-'Not Short': 21% with significantly more individuals in MHL-'Short' subgroup compared to MHL-'Not Short'. Multivariate analysis suggested that pre-operative pelvic tilt and weak hip extensor strength have the largest effect on predicting post-operative increase in APT. Peak muscle-tendon length was not a significant predictor of post-operative knee kinematics or increase in APT. SIGNIFICANCE: This study suggests that hamstrings muscle-tendon length criteria by itself is not a sufficient indicator to recommend against hamstrings lengthening.

Highly selective motor nerve block and movement analysis for preoperative evaluation of complex spastic gait.

BACKGROUND: Lower-extremity spasticity and impaired gait control after central nervous system injury are challenging to improve, because spasticity limits residual motor control while providing mechanical support. Highly selective partial neurectomies (HSPNs) can substantially reduce spasticity but may have greater risks in patients with complex lower-extremity spastic gait. OBJECTIVE: To examine the potential of ultrasound- and stimulation-guided highly selective motor nerve blocks (HSMNBs) to assess the potential impact of reduced spasticity on gait. METHODS: In this retrospective series, six patients underwent HSMNBs with movement assessment before and after the block. Range of motion, strength, position angles, surface electromyography, lower limb kinematics, and patient satisfaction were assessed. RESULTS: Pre- and post-HSMNB movement analysis yielded dichotomous gait kinematics, which facilitated surgical decisions. Of the 59 metrics evaluated, 82% demonstrated a positive improvement post-block (62% improved more than one standard deviation (SD) of typically developing means, 49% improved > 2 SD) and 16% demonstrated a negative change (2% worsened > 1 SD). CONCLUSION: HSMNB provided clear efficacy in changing clinical, surface electromyography, and gait parameters. Movement analysis provided clear and robust objective and patient-centered evidence for surgical guidance. This protocol may provide utility in evaluation of patients being considered for HSPNs for complex spastic gait patterns.

Patient-reported Outcomes of Adolescents Treated With Guided Growth to Correct Idiopathic Genu Valgum.

BACKGROUND: Guided growth is commonly used to treat frontal plane alignment deformities in skeletally immature individuals. Treatment aims are to correct the biomechanical loading of the knee and to avoid more invasive surgery that would be required after skeletal maturity. There is little published evidence of pain perception or functional limitations in this population. In addition, the intervention has the potential to worsen pain and function with hardware implantation, and symptoms may not fully resolve after removal. Understanding of pain and function limitations in this population is important to guide the clinical expectations. METHODS: Individuals with idiopathic knee genu valgum who underwent hemiepiphysiodesis with tension plate constructs were identified through a medical records database search. Patient-reported outcomes measurement information system Physical Function/Mobility and Pain Interference domain scores were assessed before hemiepiphysiodesis, immediately before hardware removal, and after hardware removal. Radiographs were also assessed at these times to record the zones and angles of deformity and correction. RESULTS: Twenty-eight subjects (53 operative limbs) contributed to the analysis. Mobility and pain interference as measured by the patient-reported outcomes measurement information system were below typical values in a small percentage of the population studied, only 3.6% scored in the moderate and none in the severe categories for both domains. Valgus by radiographic zone was corrected in all patients without significant rebound at follow-up. Compared with preoperative levels, mobility scores improved before hardware removal. Pain Interference scores improved both before hardware removal and at the final follow-up. CONCLUSIONS: Frontal plane knee deformities in the idiopathic population do not cause pain or limit mobility in most subjects. This is critical information, emphasizing that surgical decisions may be made based on the deformity alone, presence of symptoms, and possible future morbidity secondary to valgus deformity. If surgery is postponed because an individual is asymptomatic, the window for correction with guided growth may be lost. Individuals undergoing hemiepiphysiodesis can expect that their pain and function will not be worse during the time that hardware is in place and that surgery is likely to improve any pain they may be experiencing. LEVEL OF EVIDENCE: Level III; retrospective comparative study.

A model for understanding the causes and consequences of walking impairments.

Walking is an important skill with positive impacts on health, function, and well-being. Many disorders impair walking and its positive impacts through a variety of complex and interrelated mechanisms. Any attempt to understand walking impairments, or the effects of interventions intended to treat these impairments, must respect this complexity. Therefore, our main objectives in conducting this study were to (1) propose a comprehensive model for quantifying the causes and consequences of walking impairments and (2) demonstrate the potential utility of the model for supporting clinical care and addressing basic scientific questions related to walking. To achieve these goals, we introduced a model, described by a directed acyclic graph, consisting of 10 nodes and 23 primary causal paths. We gave detailed descriptions of each node and path based on domain knowledge. We then demonstrated the model's utility using a large sample of gait data (N = 9504) acquired as part of routine care at a regional referral center. We analyzed five relevant examples that involved many of the model's nodes and paths. We computed causal effect magnitudes as Shapley values and displayed the overall importance of variables (mean absolute Shapley value), the variation of Shapley values with respect to underlying variables, and Shapley values for individual observations (case studies). We showed that the model was plausible, captured some well-known cause-effect relationships, provided new insights into others, and generated novel hypotheses requiring further testing through simulation or experiment. To aid in transparency, reproducibility, and future enhancements we have included an extensively commented Rmarkdown file and a deidentified data set.

Age-Stratified Outcomes of Mehta Casting in Idiopathic Early-Onset Scoliosis: A Multicenter Review.

BACKGROUND: This study provides age-stratified outcomes of cast treatment for idiopathic early-onset scoliosis. METHODS: This is a multicenter, retrospective review of patients with idiopathic early-onset scoliosis treated with Mehta casting at 4 tertiary children's hospitals between 2001 and 2016. The inclusion criteria were idiopathic early-onset scoliosis and a minimum follow-up of 2 years after casting ended. The exclusion criteria were <2 casts, >3 casts at an outside facility, and a major curve of <20° pre-treatment. Subjects were grouped by age at first cast: <18 months, 18 to <24 months, 2 to <3 years, 3 to <4 years, and ≥4 years. RESULTS: There were 134 patients with a mean follow-up of 5.2 years (95% confidence interval [CI], 4.8 to 5.5 years) after casting. Prior to treatment, the major curve was not significantly different between the various age groups and was a mean of 50.4° (95% CI, 48.0° to 52.8° [range, 22° to 109°]). Of the <18-month group (n = 59), at the final follow-up at a mean of 7.4 years (95% CI, 6.8 to 8.1 years) of age, 75% had scoliosis of <15°, and 6.8% had undergone a surgical procedure or had a major curve of ≥50°. The results declined in the 18 to <24-month group (n = 30), with a major curve of <15° at the final follow-up at 8.5 years (95% CI, 7.3 to 9.7 years) of age in 33% (p < 0.001), and 17% having undergone a surgical procedure or had a major curve of ≥50°, with results nearly identical in the 2 to <3-year group (n = 21). The results continued to decline with increasing age; 23% of the 3 to <4-year group had a major curve of <15° at the final follow-up, and 31% had undergone a surgical procedure or had scoliosis of ≥50°. Of the ≥4-year group, just 9.1% had scoliosis of <15° (p < 0.0001 compared with the <18-month group), and 64% had undergone a surgical procedure or had scoliosis of ≥50°. CONCLUSIONS: Children who underwent casting prior to 18 months of age were more likely to have a major curve of <15° at a minimum 2-year follow-up after casting. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Discrimination between hereditary spastic paraplegia and cerebral palsy based on gait analysis data: A machine learning approach.

BACKGROUND: There is no current consensus on how to differentiate between hereditary spastic paraplegia and spastic cerebral palsy on the basis of clinical presentation. Several previous studies have investigated differences in kinematic parameters obtained from clinical gait analysis. None have attempted to combine multiple gait and physical exam measures to discriminate between these two diagnoses. This study aims to investigate the ability of a machine learning approach using data from clinical gait analysis to differentiate these cohorts. METHODS: A retrospective analysis of a gait database compiled a dataset of 179 gait and physical exam variables from 28 individuals (62 analyses) diagnosed with hereditary spastic paraplegia and 678 (1504 analyses) with bilateral spastic cerebral palsy. This data was used in a Bayesian additive regression tree (BART) analysis classified by medical record diagnosis. A 10-fold cross validation generated probabilistic distribution that each analysis was from an individual carrying the hereditary spastic paraplegia diagnosis. A diagnostic probability cutoff threshold balanced type I and type II errors. Predicted versus actual diagnoses were classified into a contingency table. RESULTS: The algorithm was able to correctly classify the two diagnoses with 91% specificity and 90% sensitivity. CONCLUSIONS: A machine learning approach using data from clinical gait analysis was able to distinguish participants with hereditary spastic paraplegia from those with bilateral spastic cerebral palsy with high specificity and sensitivity. This algorithm can be used to assess if individuals seen for gait disorders who do not yet have a definitive diagnosis have characteristics associated with hereditary spastic paraplegia. The results of the model inform the decision to suggest genetic testing to either confirm or refute the diagnosis of hereditary spastic paraplegia.

Causal factors affecting gross motor function in children diagnosed with cerebral palsy.

BACKGROUND: Cerebral palsy (CP) is a complex neuromuscular condition that may negatively influence gross motor function. Children diagnosed with CP often exhibit spasticity, weakness, reduced motor control, contracture, and bony malalignment. Despite many previous association studies, the causal impact of these impairments on motor function is unknown. AIM: In this study, we proposed a causal model which estimated the effects of common impairments on motor function in children with spastic CP as measured by the 66-item Gross Motor Function Measure (GMFM-66). We estimated both direct and total effect sizes of all included variables using linear regression based on covariate adjustment sets implied by the minimally sufficient adjustment sets. In addition, we estimated bivariate effect sizes of all measures for comparison. METHOD: We retrospectively evaluated 300 consecutive subjects with spastic cerebral palsy who underwent routine clinical gait analysis. Model data included standard information collected during this analysis. RESULTS: The largest causal effect sizes, as measured by standardized regression coefficients, were found for selective voluntary motor control and dynamic motor control, followed by strength, then gait deviations. In contrast, common treatment targets, such as spasticity and orthopedic deformity, had relatively small effects. Effect sizes estimated from bivariate models, which cannot appropriately adjust for other causal factors, substantially overestimated the total effect of spasticity, strength, and orthopedic deformity. INTERPRETATION: Understanding the effects of impairments on gross motor function will allow clinicians to direct treatments at those impairments with the greatest potential to influence gross motor function and provide realistic expectations of the anticipated changes.

Factors Affecting Slip Progression After In Situ Screw Fixation of Stable Slipped Capital Femoral Epiphysis.

BACKGROUND: Slip progression after in situ fixation of slipped capital femoral epiphysis (SCFE) has been reported as occurring in up to 20% of patients. We review SCFE treated with in situ single screw fixation performed at 2 hospitals over a 15-year period to determine the factors associated with slip progression. METHODS: This case-control study reviews SCFE treated with in situ single cannulated screw fixation with minimum follow up of 1 year and full closure of the affected physis. Slip progression (failure) was defined as worsening of the Southwick slip angle of 10 or more degrees or revision surgery for symptomatic slip progression. Univariate and multivariate analyses were performed comparing success and failure groups for patient characteristics, screw type and position, and radiographic measurements. RESULTS: Ninety three patients with 108 slips met all criteria, with 15 hips (14%) classified as having slip progression (failure). All failures had 3 threads or fewer across the physis. Five hips had 2 threads across the physis, and 4 of the 5 were classified as failures. Lower modified Oxford bone scores were found in the failure group, though the difference was small (0.9, P=0.013). Failure was also associated with partially threaded screws (P=0.001). Failed hips were associated with lower initial Southwick angles (32.8 degrees) than successful hips (40.4 degrees) (P=0.047). In the stepwise model for multivariate regression, 4 factors were identified as significant, with lower initial number of threads (P<0.0001), mild initial Southwick category (P=0.0050), male sex (P=0.0061), and partially threaded screw type (P=0.0116) predicting failure. CONCLUSION: This study is the largest to date evaluating risk factors for slip progression after SCFE fixation, and the first to consider revision surgery for symptomatic slip progression. For stable SCFE, we demonstrate that 4 threads across the physis with a fully threaded screw of 6.5 mm diameter or greater was sufficient to avoid slip progression. We provide a risk stratification for progression of slip showing that in some cases 3 threads across the physis may be sufficient. LEVEL OF EVIDENCE: Level III-case-control study.

Long-term effects of spasticity treatment, including selective dorsal rhizotomy, for individuals with cerebral palsy.

AIM: To understand the long-term effects of comprehensive spasticity treatment, including selective dorsal rhizotomy (SDR), on individuals with spastic cerebral palsy. METHOD: This was a pre-registered, multicenter, retrospectively matched cohort study. Children were matched on age range and spasticity at baseline. Children at one center underwent spasticity treatment including SDR (Yes-SDR, n=35) and antispastic injections. Children at two other centers had no SDR (No-SDR, n=40 total) and limited antispastic injections. All underwent subsequent orthopedic treatment. Participants returned for comprehensive long-term assessment (age ≥21y, follow-up ≥10y). Assessment included spasticity, contracture, bony alignment, strength, gait, walking energy, function, pain, stiffness, participation, and quality of life. RESULTS: Spasticity was effectively reduced at long-term assessment in the Yes-SDR group and was unchanged in the No-SDR group. There were no meaningful differences between the groups in any measure except the Gait Deviation Index (Yes-SDR + 11 vs No-SDR + 5) and walking speed (Yes-SDR unchanged, No-SDR declined 25%). The Yes-SDR group underwent more subsequent orthopedic surgery (11.9 vs 9.7 per individual) and antispastic injections to the lower limbs (14.4 vs <3, by design). INTERPRETATION: Untreated spasticity does not cause meaningful impairments in young adulthood at the level of pathophysiology, function, or quality of life.

Outcome of Gastrocnemius Soleus Facial Lengthening in Ambulatory Patients With Cerebral Palsy.

BACKGROUND: Treatment of equinus contractures in children with cerebral palsy (CP) varies across centers. Existing literature utilizes mixed study populations with a variety of procedures. As such, there is limited knowledge regarding recurrence rates and efficacy of a single procedure performed on a homogenous cohort. Here we retrospectively evaluate outcomes from gastroc soleus fascial lengthenings (GSFL) performed at 2 centers with consistent approaches in both patient selection and operative technique. METHODS: Subjects meeting inclusion criteria including CP diagnosis, ambulation status, and minimum follow-up criteria were identified. Revision rate was reported based on need for additional calf lengthening procedures. Functional outcomes were evaluated using physical exam measures and selected variables from computational gait analysis. Outcomes factors were identified by comparing revised subjects to unrevised. Longitudinal outcomes of index surgeries were assessed by comparing preoperative functional data to short-term, mid-term, and long-term data. RESULTS: A total of 64 subjects with 87 limbs met inclusion criteria. In all, 25% of subjects and 21% of limbs went on to revision. Factors influencing revision were age at index surgery and gross motor function classification system (GMFCS) level. More than half of revised limbs had index surgery before age 7. Revision rates for subjects less than 7 were 44% compared with a 17% revision rate for ages 7 to 12, and a 4% revision rate on children older than 12. GMFCSIII subjects had significantly higher revision rates (43%) compared with GMFCSII (18%) and GMFCSI (11%) subjects. Ankle range of motion measures improved significantly with GSFL and most maintained improvements at all time periods. GSFL did not lead to significant calcaneal gait or crouch. CONCLUSIONS: This study evaluates long term efficacy of GSFL to address equinus in ambulatory children with CP. Overall revision rates are similar to previous reports for GSFL and other calf lengthening procedures. This information may be useful in setting expectations and counselling families. Younger subjects and those with more severe involvement are more likely to need revision surgery, with these factors compounding the likelihood in the younger GMFCSIII child. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Assignment of local coordinate systems and methods to calculate tibiotalar and subtalar kinematics: A systematic review.

The introduction of biplane fluoroscopy has created the ability to evaluate in vivo motion, enabling six degree-of-freedom measurement of the tibiotalar and subtalar joints. Although the International Society of Biomechanics defines a standard method of assigning local coordinate systems for the ankle joint complex, standards for the tibiotalar and subtalar joints are lacking. The objective of this systematic review was to summarize and appraise the existing literature that (1) defined coordinate systems for the tibia, talus, and/or calcaneus or (2) assigned kinematic definitions for the tibiotalar and/or subtalar joints. A systematic literature search was developed with search results limited to English Language from 2006 through 2020. Articles were screened by two independent reviewers based on title and abstract. Methodological quality was evaluated using a modified assessment tool. Following screening, 52 articles were identified as having met inclusion criteria. Methodological assessment of these articles varied in quality from 61 to 97. Included articles adopted primary methods for defining coordinate systems that included: (1) anatomical coordinate system (ACS) based on individual bone landmarks and/or geometric shapes, (2) orthogonal principal axes, and (3) interactive closest point (ICP) registration. Common methods for calculating kinematics included: (1) joint coordinate system (JCS) to calculate rotation and translation, (2) Cardan/Euler sequences, and (3) inclination and deviation angles for helical angles. The methods each have strengths and weaknesses. This summarized knowledge should provide the basis for the foot and ankle biomechanics community to create an accepted standard for calculating and reporting tibiotalar and subtalar kinematics.

Synergies analysis produces consistent results between motion analysis laboratories.

AIM: The dynamic motor control index during walking (walk-DMC) is a scaled measure of motor control derived from electromyographic analysis of the lower extremity during gait. Walk-DMC has been shown to be related to patient outcomes and there has been an increasing interest from motion analysis centers regarding using this metric in their own practice. However, the methods for computing the index reported in the literature are not consistent. Here we propose a standardized method and investigate if this leads to results that are consistent between laboratories. METHOD: Comparisons between three sets of typically developing controls contributed by three independent motion analysis centers are made. Comparisons are also made between the proposed and previously published methods. A program script to compute the walk-DMC was used for this study and is made freely available with this manuscript. RESULTS: Using this script, results are highly consistent between three participating centers. The currently proposed method results in a wider distribution of walk-DMC values than those previously reported. INTERPRETATION: Using consistent processing methods, synergy measures are equivalent between centers. The major differences between current and published data are attributed to the use of concatenation of several walking trials.

Factors Influencing Outcomes of the Dysplastic Hip in Nonambulatory Children With Cerebral Palsy.

BACKGROUND: Hip dysplasia in the nonambulatory child with spastic cerebral palsy (CP) is a common condition not always effectively treated with conservative measures even when recognized early. Optimal surgical intervention strategies and timing are not clear from previous studies. Contralateral hips with less severe subluxation in these patients also often undergo surgery and little is known of outcomes of these less severe hips. This study aims to clarify treatment factors related to long term success following hip surgery for subluxation in nonambulatory children with CP. METHODS: A total of 183 nonambulatory subjects with CP and a minimum of 2-year follow-up were included. All subjects underwent varus rotational osteotomy of the femur; other surgical factors considered were addition of pelvic osteotomy (PO), capsulorrhaphy, and soft tissue releases. Additional factors studied were age at index surgery, sex, and unilateral versus bilateral surgery. Severely subluxated (SS) hips, defined as having >50% migration, were studied separately from contralateral nonsevere hips. Surgeries were deemed successful if final follow-up indicated a migration of <25%; patients with any revision surgeries or >25% migration were categorized as failures. RESULTS: A 60% success rate was found in SS hips and a 68% success rate in nonsevere hips. Age at index surgery did not influence success rates in SS hips. In the nonsevere hips, success was associated with index surgery at older age. The addition of a PO was the only concomitant procedure demonstrated to improve outcomes. In SS hips, those with a successful outcome were 2.5 times more likely to have had a PO. The addition of capsulorrhaphy had a negative effect on the entire group, reducing odds of success to 0.8. No other factors were significant. CONCLUSIONS: The findings from this multicenter retrospective study suggest that PO be added to varus rotational osteotomies in patients with severe hip subluxation. Surgery should be undertaken for severe dysplasia without concern for age. The addition of capsulorrhaphy does not improve rate of success. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

The modified Shriners Hospitals for Children Greenville (mSHCG) multi-segment foot model provides clinically acceptable measurements of ankle and midfoot angles: A dual fluoroscopy study.

BACKGROUND: Several multi-segment foot models have been developed to evaluate foot and ankle motion using skin-marker motion analysis. However, few multi-segment models have been evaluated against a reference standard to establish kinematic accuracy. RESEARCH QUESTION: How accurately do skin-markers estimate foot and ankle motion for the modified Shriners Hospitals for Children Greenville (mSHCG) multi-segment foot model when compared against the reference standard, dual fluoroscopy (DF), during gait, in asymptomatic participants? METHODS: Five participants walked overground as full-body skin-marker trajectory data and DF images of the foot and shank were simultaneously acquired. Using the mSHCG model, ankle and midfoot angles were calculated throughout stance for both motion analysis techniques. Statistical parametric mapping assessed differences in joint angles and marker positions between skin-marker and DF motion analysis techniques. Paired t tests, and linear regression models were used to compare joint angles and range of motion (ROM) calculated from the two techniques. RESULTS: In the coronal plane, the skin-marker model significantly overestimated ROM (p = 0.028). Further, the DF model midfoot ROM was significantly positively related to differences between DF and skin-marker midfoot angles (p = 0.035, adjusted R2 = 0.76). In the sagittal plane, skin-markers underestimated ankle angles by as much as 7.26°, while midfoot angles were overestimated by as much as 9.01°. However, DF and skin-marker joint angles were not significantly different over stance. Skin-markers on the tibia, calcaneus, and fifth metatarsal had significantly different positions than the DF markers along the direction of walking for isolated portions that were less than 10 % of stance. Euclidean distances between DF and skin-markers positions were less than 9.36 mm. SIGNIFICANCE: As the accuracy of the mSHCG model was formerly unknown, the results of this study provide ranges of confidence for key angles calculated by this model.

What Is the Cost of a "Cast Holiday" in Treating Children With Early Onset Scoliosis (EOS) With Elongation Derotation Flexion (EDF, "Mehta") Casting?

INTRODUCTION: Serial casting of children with early onset scoliosis (EOS) is an established treatment option. A break from cast treatment often called a "cast holiday," (CH) is often allowed by some centers, particularly over the summer months. The impact of CHs on treatment duration or outcome has not been examined. METHODS: Institution review board approved retrospective review of children treated for EOS with elongation derotation flexion ("Mehta") casting at a children's hospital between 2001 and 2016 with a minimum of 2 years' follow-up. A CH was defined as a minimum of 4 weeks out of the cast, braced, or unbraced.The analysis was performed to determine the impact of a CH within the first 18 months of treatment. Separate analyses were performed for the entire cohort of children castedduring the study period, and then separately looking at idiopathic EOS in isolation. The impact of a CH was assessed in terms of the likelihood of achieving scoliosis <15 degrees at the final follow-up ("success"). Odds ratios were used to assess group differences between "success" ratios, and Student t tests assessed group differences for parametric data. RESULTS: Ninety children met inclusion and exclusion criteria, 31 of whom took a CH during the first 18 months of treatment (34%). This included 59 patients with idiopathic EOS (66%), 18 with syndromic EOS, 5 congenital, and 1 neuromuscular. There were no statistically significant differences between CH and no CH groups.Forty-four percent of the no CH group achieved scoliosis <15 degrees at final follow-up, as opposed to 13% of the CH group, an odds ratio of 5.3 for success without a CH. When limited to children with idiopathic EOS, 56% achieved success in the no CH, versus only 22% in the group that took a CH, an odds ratio of 4.4 for success with no CH. CONCLUSION: This study demonstrates that children treated for EOS with serial casting who take a CH within the first 18 months of treatment are less likely to achieve scoliosis <15 degrees than those who persist with treatment. LEVEL OF EVIDENCE: Level III.

Minimum 5-Year Follow-up of Mehta Casting to Treat Idiopathic Early-Onset Scoliosis.

BACKGROUND: With the exception of Mehta's 2005 report on her experience treating early-onset scoliosis with serial casting, all subsequent studies have had limited follow-up. This current study sought to assess the results of serial casting at a minimum 5-year follow-up and to identify the predictors of the sustained resolution of scoliosis. METHODS: This study is a retrospective review of children treated for idiopathic early-onset scoliosis with serial casting at a children's hospital between 2001 and 2013 with a minimum 5-year follow-up. A Cobb angle of ≤15° and a decrease in the Cobb angle of >20° at the most recent follow-up were separately assessed. The differences between groups based on these criteria were tested with Student t tests with alpha = 0.05. RESULTS: Fifty-four children were treated during the study period; of these, 38 had at least 5 years of follow-up and comprised the study sample. The mean follow-up (and standard deviation) was 8 ± 2 years (range, 5 to 13 years). The mean patient age at the time of the first cast was 24 ± 15.1 months (range, 9 to 63 months), with a mean Cobb angle of 56.2° ± 20.1° (range, 22° to 109°). Forty-nine percent of children had scoliosis of ≤15° at the time of the most recent follow-up, and 73% of children were improved by at least 20°. Children with ≤15° scoliosis, compared with children with >15° scoliosis, had significantly lower initial Cobb angle (48.2° compared with 63.7°; p = 0.016), supine traction Cobb angle (22.5° compared with 33.2°; p = 0.048), first-in-cast Cobb angle (24.1° compared with 37.6°; p = 0.01), and first-in-cast rib-vertebral angle difference (12.8° compared with 26.2°; p < 0.01). Age at the time of the first cast, initial rib-vertebral angle difference, flexibility, and body mass index were not significantly different (p > 0.05) between the groups. Three children who initially achieved scoliosis of ≤15° after casting substantially relapsed. CONCLUSIONS: At a minimum follow-up of 5 years, the initial Cobb angle, first-cast Cobb angle, rib-vertebral angle difference, and traction Cobb angle were all predictive of sustained scoliosis of ≤15°. However, with continued growth, relapse of scoliosis was seen in 3 patients. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.