Longitudinal Resilience and Risk Factors in Pediatric Postoperative Pain (LORRIS): Protocol for a Prospective Longitudinal Swiss University Children's Hospitals-Based Study.

INTRODUCTION: Chronic postsurgical pain (CPSP) is defined as pain that persists after a surgical procedure and has a significant impact on quality of life. Previous studies show the importance of psychological factors in CPSP, yet the majority of studies focused solely on negative emotions. This longitudinal observational study aims to broaden this knowledge base by examining the role of emotional state, emotion variability, emotion regulation and emotion differentiation on the child and the parent level for the development CPSP, and to describe pain and emotion-related trajectories following surgery. METHODS AND ANALYSIS: We intend to include 280 children and adolescents aged 8-18 years with a planned orthopaedic surgery and their parents. A total of five assessment time points is planned: 3 weeks before surgery (baseline), 2 weeks after surgery (post) and 3 months (follow-up (FU) 1), 6 months and 12 months after surgery. At baseline and post only, children and parents are asked to complete a daily diary thrice a day for a week where they rate their current emotional state and their pain severity (children only). Emotional state ratings will be used to calculate indices of emotion variability, emotion regulation and emotion differentiation. Children and parents will complete questionnaires at each time point, including measures on quality of life, social support, sleep, and symptoms of anxiety and depression.To predict development of CPSP, generalised linear regression models will be used, resulting in ORs and 95% CIs. Pearson product-moment correlations between predictors and outcomes will be evaluated at each time point. The primary outcome of the prediction model is CPSP at FU1. For the trajectory analysis, the classification method K-means for longitudinal data will be used to determine clusters in the data. ETHICS AND DISSEMINATION: The Ethics Committee of the Canton of Zurich, Switzerland, has approved the study (ID: 2023-01475). Participants will be compensated, and a dissemination workshop will be held. TRIAL REGISTRATION NUMBER: NCT05816174.

The Variable Influence of Orthotic Management on Hip and Pelvic Rotation in Children with Unilateral Neurogenic Equinus Deformity.

BACKGROUND: Equinus deformity with or without concomitant drop foot is a common finding in children with unilateral spastic cerebral palsy and spastic hemiplegia of other causes. Hypothetically, these deformities may lead to pelvic retraction and hip internal rotation during gait. Orthoses are used to reduce pes equinus during gait and to restore hindfoot first contact. OBJECTIVE: We aimed to investigate whether the use of orthotic equinus correction reduces rotational hip and pelvic asymmetries. METHODS: In a retrospective study, 34 children with unilateral spastic cerebral palsy or spastic hemiplegia of other causes underwent standardized instrumented 3D gait analysis with and without orthotic equinus management. We analyzed the differences in the torsional profile during barefoot walking and while wearing orthoses, as well as investigated the influence of ankle dorsiflexion and femoral anteversion on pelvic and hip kinematics and hip kinetics. RESULTS: Wearing orthoses corrected pes equinus and pelvic internal rotation at the end of the stance phase and in the swing phase compared to barefoot walking. Hip rotation and the rotational moment did not significantly change with orthoses. Orthotic management or femoral anteversion did not correlate to pelvic and hip asymmetry. CONCLUSION: The findings indicate that the correction of the equinus by using orthoses had a variable effect on the asymmetry of the hip and pelvis and internal rotation; both appear to have a multifactorial cause that is not primarily driven by the equinus component.

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.

Distal femoral extension osteotomy and patellar tendon advancement or shortening in ambulatory children with cerebral palsy: A modified Delphi consensus study and literature review.

Purpose: In children with cerebral palsy, flexion deformities of the knee can be treated with a distal femoral extension osteotomy combined with either patellar tendon advancement or patellar tendon shortening. The purpose of this study was to establish a consensus through expert orthopedic opinion, using a modified Delphi process to describe the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. A literature review was also conducted to summarize the recent literature on distal femoral extension osteotomy and patellar tendon shortening/patellar tendon advancement. Method: A group of 16 pediatric orthopedic surgeons, with more than 10 years of experience in the surgical management of children with cerebral palsy, was established. The group used a 5-level Likert-type scale to record agreement or disagreement with statements regarding distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening. Consensus for the surgical indications for distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening was achieved through a modified Delphi process. The literature review, summarized studies of clinical outcomes of distal femoral extension osteotomy/patellar tendon shortening/patellar tendon advancement, published between 2008 and 2022. Results: There was a high level of agreement with consensus for 31 out of 44 (70%) statements on distal femoral extension osteotomy. Agreement was lower for patellar tendon advancement/patellar tendon shortening with consensus reached for 8 of 21 (38%) of statements. The literature review included 25 studies which revealed variation in operative technique for distal femoral extension osteotomy, patellar tendon advancement, and patellar tendon shortening. Distal femoral extension osteotomy and patellar tendon advancement/patellar tendon shortening were generally effective in correcting knee flexion deformities and extensor lag, but there was marked variation in outcomes and complication rates. Conclusion: The results from this study will provide guidelines for surgeons who care for children with cerebral palsy and point to unresolved questions for further research. Level of evidence: level V.

Outcome Prognostic Factors in MRI during Spica Cast Therapy Treating Developmental Hip Dysplasia with Midterm Follow-Up.

Closed reduction followed by spica casting is a conservative treatment for developmental dysplasia of the hip (DDH). Magnetic resonance imaging (MRI) can verify proper closed reduction of the dysplastic hip. Our aim was to find prognostic factors in the first MRI to predict the possible outcome of the initial treatment success by means of ultrasound monitoring according to Graf and the further development of the hip dysplasia or risk of recurrence in the radiological follow-up examinations. A total of 48 patients (96 hips) with DDH on at least one side, and who were treated with closed reduction and spica cast were included in this retrospective cohort study. Treatment began at a mean age of 9.9 weeks. The children were followed for 47.4 months on average. We performed closed reduction and spica casting under general balanced anaesthesia. This was directly followed by MRI to control the position/reduction of the femoral head without anaesthesia. The following parameters were measured in the MRI: hip abduction angle, coronal, anterior and posterior bony axial acetabular angles and pelvic width. A Graf alpha angle of at least 60° was considered successful. In the radiological follow-up controls, we evaluated for residual dysplasia or recurrence. In our cohort, we only found the abduction angle to be an influencing factor for improvement of the DDH. No other prognostic factors in MRI measurements, such as gender, age at time of the first spica cast, or treatment involving overhead extension were found to be predictive of mid-term outcomes. This may, however, be due to the relatively small number of treatment failures.

Assessment of foot alignment and function for ambulatory children with cerebral palsy: Results of a modified Delphi technique consensus study.

Purpose: The purpose of this study was to establish consensus for the assessment of foot alignment and function in ambulatory children with cerebral palsy, using expert surgeon's opinion through a modified Delphi technique. Methods: The panel used a five-level Likert-type scale to record agreement or disagreement with 33 statements regarding the assessment of foot alignment and function. Consensus was defined as at least 80% of responses being in the highest or lowest of two of the five Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest two ratings. There was no agreement if neither threshold was reached. Results: Consensus was achieved for 25 (76%) statements, general agreement for 4 (12%) statements, and lack of consensus for 4 (12%) of the statements. There was consensus that the functional anatomy of the foot is best understood by dividing the foot into three segments and two columns. Consensus was achieved concerning descriptors of foot segmental alignment for both static and dynamic assessment. There was consensus that radiographs of the foot should be weight-bearing. There was general agreement that foot deformity in children with cerebral palsy can be classified into three levels based on soft tissue imbalance and skeletal malalignment. Conclusion: The practices identified in this study can be used to establish best care guidelines, and the format used will be a template for future Delphi technique studies on clinical decision-making for the management of specific foot segmental malalignment patterns commonly seen in children with cerebral palsy. Level of Evidence: V.

Effects of artificially induced bilateral internal rotation gait on gait kinematics and kinetics.

BACKGROUND: Bilateral internal rotation gait is a common gait abnormality in children with bilateral cerebral palsy, but still not fully understood. RESEARCH QUESTION: The aim of this clinical study was to analyze the effects of artificially induced bilateral internal rotation gait on kinematics and kinetics. Our hypothesis was, that the internal rotation gait defined as increased dynamic internal hip rotation itself causes significant alterations in gait kinematics and kinetics. METHODS: 30 typically developing children with a mean age of 12 (SD 3) years (range 8 - 16) performed three-dimensional gait analysis in two different conditions: with unaffected gait and with artificially induced bilateral internal rotation gait with two rotation bandages worn in order to internally rotate the hips. Kinematic and kinetic changes between these two conditions were calculated and compared using a mixed linear model with "gait condition" as fixed effect and both "limb" and "patient" as random effects. RESULTS: The rotation bandages induced a significant increase in internal hip rotation and foot progression angle towards internal without affecting pelvic rotation. The peak hip internal rotator moment during loading response and the peak hip external rotator moment during the first half of stance phase increased significantly and the peak hip internal rotator moment during the second half of stance phase decreased significantly. Anterior pelvic tilt, hip flexion, knee flexion and ankle dorsiflexion increased significantly. The first peak of the frontal hip moment decreased, and the second increased significantly. The second peak of the frontal knee moment decreased significantly, while the first didn't change significantly. SIGNIFICANCE: The data suggest, that the bilaterally increased dynamic internal hip rotation itself has a relevant impact on frontal hip moments. The increased anterior pelvic tilt, hip and knee flexion may be either induced by the pull of the rotation bandage or a secondary gait deviation.

Finding consensus for hamstring surgery in ambulatory children with cerebral palsy using the Delphi method.

Purpose: There is marked variation in indications and techniques for hamstring surgery in children with cerebral palsy. There is particular uncertainty regarding the indications for hamstring transfer compared to traditional hamstring lengthening. The purpose of this study was for an international panel of experts to use the Delphi method to establish consensus indications for hamstring surgery in ambulatory children with cerebral palsy. Methods: The panel used a five-level Likert-type scale to record agreement or disagreement with statements regarding hamstring surgery, including surgical indications and techniques, post-operative care, and outcome measures. Consensus was defined as at least 80% of responses being in the highest or lowest two of the five Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest two ratings. There was no agreement if neither of these thresholds was reached. Results: The panel reached consensus or general agreement for 38 (84%) of 45 statements regarding hamstring surgery. The panel noted the importance of assessing pelvic tilt during gait when considering hamstring surgery, and also that lateral hamstring lengthening is rarely needed, particularly at the index surgery. They noted that repeat hamstring lengthening often has poor outcomes. The panel was divided regarding hamstring transfer surgery, with only half performing such surgery. Conclusion: The results of this study can help pediatric orthopedic surgeons optimize decision-making in their choice and practice of hamstring surgery for ambulatory children with cerebral palsy. This has the potential to reduce practice variation and significantly improve outcomes for ambulatory children with cerebral palsy. Level of evidence: level V.

Anterior distal femoral hemiepiphysiodesis in children with cerebral palsy: Establishing surgical indications and techniques using the modified Delphi method and literature review.

Purpose: The purpose of this study was to develop consensus for the surgical indications of anterior distal femur hemiepiphysiodesis in children with cerebral palsy using expert surgeon opinion through a modified Delphi technique. Methods: The panel used a 5-level Likert-type scale to record agreement or disagreement with 27 statements regarding anterior distal femur hemiepiphysiodesis. Consensus was defined as at least 80% of responses being in the highest or lowest 2 of the Likert-type ratings. General agreement was defined as 60%-79% falling into the highest or lowest 2 ratings. Results: For anterior distal femur hemiepiphysiodesis, 27 statements were surveyed: consensus or general agreement among the panelists was achieved for 22 of 27 statements (22/27, 82%) and 5 statements had no agreement (5/27, 18%). There was general consensus that anterior distal femur hemiepiphysiodesis is indicated for ambulatory children with cerebral palsy, with at least 2 years growth remaining, and smaller (<30 degrees) knee flexion contractures and for minimally ambulatory children to aid in standing/transfers. Consensus was achieved regarding the importance of close radiographic follow-up after screw insertion to identify or prevent secondary deformity. There was general agreement that percutaneous screws are preferred over anterior plates due to the pain and irritation associated with plates. Finally, it was agreed that anterior distal femur hemiepiphysiodesis was not indicated in the absence of a knee flexion contracture. Conclusion: Anterior distal femur hemiepiphysiodesis can be used to treat fixed knee flexion contractures in the setting of crouch gait, but other associated lever arm dysfunctions must be addressed by single-event multilevel surgery. Level of evidence: V.

The clinical frailty scale predicts 1-year mortality in emergency department patients aged 65 years and older.

OBJECTIVE: To validate the Clinical Frailty Scale (CFS) for prediction of 1-year all-cause mortality in the emergency department (ED) and compare its performance to the Emergency Severity Index (ESI). METHODS: Prospective cohort study at the ED of a tertiary care center in Northwestern Switzerland. All patients aged ≥65 years were included from March 18 to May 20, 2019, after informed consent. Frailty status was assessed using CFS, excluding level 9 (palliative). Acuity level was assessed using ESI. Both CFS and ESI were adjusted for age, sex and presenting condition in multivariable logistic regression. Prognostic performance was assessed for discrimination and calibration separately. Estimates were internally validated by Bootstrapping. Restricted mean survival time (RMST) was determined for all levels of CFS. RESULTS: In the final study population of 2191 patients, 1-year all-cause mortality was 17% (n = 372). RMST values ranged from 219 days for CFS 8 to 365 days for CFS 1. The adjusted CFS model had an area under receiver operating characteristic of 0.767 (95% confidence interval [CI]: 0.741-0.793), compared to 0.703 (95% CI: 0.673-0.732) for the adjusted ESI model. CONCLUSION: The CFS predicts 1-year all-cause mortality for older ED patients and predicts survival time in a graded manner. The CFS is superior to the ESI when adjusted for age, sex, and presenting condition.

Pain in Adults With Cerebral Palsy After Single-Event Multilevel Surgery.

OBJECTIVE: The aim of the investigation was to assess the contribution of pain to functional, social, and health-related quality-of-life outcomes in adults with cerebral palsy. DESIGN: This monocentric, prospective study included long-term data for ambulant adults with cerebral palsy and at levels I-III in the Gross Motor Function Classification System who had received orthopedic multilevel surgery in adulthood and in whom preoperative and postoperative three-dimensional gait analysis was conducted, including the Gait Profile Score. A questionnaire including the Visual Analog Scale, Oswestry Disability Index, and European Quality of Life 5 Dimensions 3 Level was analyzed. RESULTS: Twenty-four adults at a mean age of 38.0 yrs were included. Sixteen patients (66.7%) indicated that they experienced pain and 10 patients (41.7%) had pain for more than 6 mos. Overall, 13 patients (54%) experienced both pain and anxiety. There was no correlation of the Gait Profile Score with pain, Gross Motor Function Classification System, and Oswestry Disability Index. The Oswestry Disability Index showed a positive correlation with the Gross Motor Function Classification System (r = 0.39, P = 0.05) and pain (r = 0.57, P = 0.004). CONCLUSIONS: Pain and anxiety represent relevant comorbidities in adults with cerebral palsy. The occurrence of pain correlates with the Oswestry Disability Index and is higher than in children with cerebral palsy.

Femoral derotation osteotomy-Does intraoperative electromagnetic tracking reflect the dynamic outcome?

Femoral derotation osteotomy (FDO) is a well-established procedure for the correction of internal rotation gait in children with cerebral palsy. Various studies have demonstrated good results for FDO both in short-term and long-term evaluation with some describing recurrence and over- or under-corrections. The present study evaluates the use of an objective intraoperative derotation measurement through electromagnetic tracking. We report the static and dynamic results of 11 cases with internal rotation gait (8 male, 3 female, mean age 22.2 years), that underwent FDO with intraoperative electromagnetic tracking and conventional goniometric measurement of the correction. The dynamic and static changes were assessed through three-dimensional gait analysis after a mean of 12 months after surgery and rotational imaging preoperative and after a mean of eleven days postoperatively. Mean hip rotation in stance significantly decreased from 20.9° (SD 5.9) to 5.8° (SD 4.7°) after FDO. The mean amount of derotation quantified by electromagnetic tracking was 23.2° (16.5°-28.8°) and 25.1° (20.0°-33.0°) for goniometric measurement. Both measurement modalities showed small differences to rotational imaging (electromagnetic bone tracking [EMT]: 0.72°; goniometer: 1.19°) but a large deviation when compared to three-dimensional gait analysis (EMT: 8.5°, goniometer: 9.1°). In comparison to the static changes and EMT measurement, the dynamic changes measured during 3-D-gait analysis reflected only 66% of the actual derotation performed during surgery. Although electromagnetic tracking allows a precise intraoperative assessment of the derotation during FDO, the amount of intraoperative correction is not reflected in the improvements in three-dimensional gait analysis.

Distal rectus femoris surgery in children with cerebral palsy: results of a Delphi consensus project.

PURPOSE: The purpose of this study was for an international panel of experts to establish consensus indications for distal rectus femoris surgery in children with cerebral palsy (CP) using a modified Delphi method. METHODS: The panel used a five-level Likert scale to record agreement or disagreement with 33 statements regarding distal rectus femoris surgery. The panel responded to statements regarding general characteristics, clinical indications, computerized gait data, intraoperative techniques and outcome measures. Consensus was defined as at least 80% of responses being in the highest or lowest two of the five Likert ratings, and general agreement as 60% to 79% falling into the highest or lowest two ratings. There was no agreement if neither threshold was reached. RESULTS: Consensus or general agreement was reached for 17 of 33 statements (52%). There was general consensus that distal rectus femoris surgery is better for stiff knee gait than is proximal rectus femoris release. There was no consensus about whether the results of distal rectus femoris release were comparable to those following distal rectus femoris transfer. Gross Motor Function Classification System (GMFCS) level was an important factor for the panel, with the best outcomes expected in children functioning at GMFCS levels I and II. The panel also reached consensus that they do distal rectus femoris surgery less frequently than earlier in their careers, in large part reflecting the narrowing of indications for this surgery over the last decade. CONCLUSION: This study can help paediatric orthopaedic surgeons optimize decision-making for, and outcomes of, distal rectus femoris surgery in children with CP. LEVEL OF EVIDENCE: V.

Simplified digital balance assessment in typically developing school children.

BACKGROUND: Postural balance can be considered a conjoined parameter of gross motor performance. It is acquired in early childhood and honed until adolescence, but may also be influenced by various conditions. A simplified clinical assessment of balance and posture could be helpful in monitoring motor development or therapy particularly in pediatric patients. While analogue scales are considered unprecise and lab-based force-plate posturography lacks accessibility, we propose a novel kinematic balance assessment based on markerless 3D sensor technology. RESEARCH QUESTION: Can balance and posture be assessed by tracking kinematic data using a single 3D motion tracking camera and are the results representative of normal motor development in a healthy pediatric cohort? METHODS: A proprietary algorithm was developed and tested that uses skeletal data from the Microsoft Kinect™ V2 3D motion capture camera to calculate and track the center of mass in real time during a set of balance tasks. The algorithm tracks the distance of the COM traveled over time to calculate a balance score (COM speed). For this study, 432 school children aged 4-18 years performed 5 balance tasks and the resulting balance scores were analyzed and correlated with demographic data. RESULTS: Preliminary experiments demonstrated that the system was able to reliably detect differences in COM speed during different balance tasks. The method showed moderate correlation with age and sex. Athletic activity positively correlated with balance skill in the age group < 8 years, but not in older children. Body mass appeared not to be correlated with balance ability. SIGNIFICANCE: This study demonstrates that markerless 3D motion analysis can be used for the clinical assessment of coordination and balance and could potentially be used to monitor gross motor performance at the point-of-care.

Short and long-arm fiberglass cast immobilization for displaced distal forearm fractures in children: a randomized controlled trial.

PURPOSE: The aim of this study was to investigate whether short-arm fiberglass cast (SAC) immobilization provides fracture stabilization comparable to that of long-arm cast (LAC) treatment of displaced distal forearm fractures after closed reduction in paediatric patients. METHODS: A prospective, randomized, controlled trial of children aged four to 16 years (mean 9.9 years) was designed with a sample of 120 children, whose size was set a priori, with 60 treated with SAC and 60 with LAC. The primary outcome was fracture stability and rate of loss of reduction. The secondary outcome analysis evaluated duration of analgesic therapy, restriction in activities of daily life, and the duration until patients regained normal range of motion in the elbow. RESULTS: No statistically significant differences were found between the two groups in loss of reduction or duration of analgesic therapy. In contrast, the duration until normal range of motion in the elbow was regained was significantly longer in the LAC group (median 4.5 days, P < 0.001). Restriction in activities of daily life did not differ significantly between the two groups except for the item "help needed with showering in the first days after trauma" (SAC 60%, LAC 87%, P = 0.001). CONCLUSION: Fracture immobilization with short-arm fiberglass cast in reduced distal forearm fractures is not inferior to long-arm casts in children four years and older, excluding completely displaced fractures. Furthermore, short-arm casting reduces the need for assistance during showering. TRIAL REGISTRATION: NCT03297047, September 29, 2017.

Indications for gastrocsoleus lengthening in ambulatory children with cerebral palsy: a Delphi consensus study.

PURPOSE: Equinus is the most common deformity in cerebral palsy (CP) and gastrocsoleus lengthening (GSL) is the most commonly performed surgery to improve gait and function in ambulatory children with CP. Substantial variation exists in the indications for GSL and surgical technique. The purpose of this study was to review surgical anatomy and biomechanics of the gastrocsoleus and to utilize expert orthopaedic opinion through a Delphi technique to establish consensus for surgical indications for GSL in ambulatory children with CP. METHODS: A 17-member panel, of Fellowship-trained paediatric orthopaedic surgeons, each with at least 9 years of clinical post-training experience in the surgical management of children with CP, was established. Consensus for the surgical indications for GSL was achieved through a standardized, iterative Delphi process. RESULTS: Consensus was reached to support conservative Zone 1 surgery in diplegia and Zone 3 surgery (lengthening of the Achilles tendon) was contraindicated. Zone 2 or Zone 3 surgery reached general agreement as a choice in hemiplegia and under-correction was preferred to any degree of overcorrection. Agreement was reached that the optimum age for GSL surgery was 6 years to 10 years and should be avoided in children aged under 4 years. Physical examination measures with the child awake and under anaesthesia were important in decision making. Gait analysis was supported both for decision making and for assessing outcomes, in combination with patient reported outcomes (PROMS). CONCLUSIONS: The results from this study may encourage informed practice evaluation, reduce practice variability, improve clinical outcomes and point to questions for further research. LEVEL OF EVIDENCE: V.

Estimation of ankle joint parameters in typically developed adults using functional calibration methods.

BACKGROUND: Despite of many attempts to determine or correct hip and knee joint parameters via non-invasive techniques such as regression or functional methods, in conventional gait models the position of the ankle joint center still is assumed at the center point between malleoli. RESEARCH QUESTION: The aim of this study was to estimate the ankle joint parameters using a functional approach. METHODS: To this aim, we used data of 23 typically developed adults performing two different calibration motions. Subsequently, we applied functional approaches to determine the functional joint center and axis. RESULTS: The results show significant differences for ankle joint parameters in all directions for both calibration motions applied with respect to the malleoli line. Most prominently, we find a shift of the ankle joint center of 7 % of the foot length anteriorly to the malleoli mid-point when applying functional calibration. CONCLUSION: These significant alterations of the ankle joint center and axis indicate the importance of accurate determination of ankle joint parameters and consequently their influence on the clinical outcome.