3D printed patient-specific fixation plates for the treatment of slipped capital femoral epiphysis: Topology optimization vs. conventional design.

Orthopedic plates are commonly used after osteotomies for temporary fixation of bones. Patient-specific plates have recently emerged as a promising fixation device. However, it is unclear how various strategies used for the design of such plates perform in comparison with each other. Here, we compare the biomechanical performance of 3D printed patient-specific bone plates designed using conventional computer-aided design (CAD) techniques with those designed with the help of topology optimization (TO) algorithms, focusing on cases involving slipped capital femoral epiphysis (SCFE). We established a biomechanical testing protocol to experimentally assess the performance of the designed plates while measuring the full-field strain using digital image correlation. We also created an experimentally validated finite element model to analyze the performance of the plates under physiologically relevant loading conditions. The results indicated that the TO construct exhibited higher ultimate load and biomechanical performance as compared to the CAD construct, suggesting that TO is a viable approach for the design of such patient-specific bone plates. The TO plate also distributed stress more evenly over the screws, likely resulting in more durable constructs and improved anatomical conformity while reducing the risk of screw and plate failure during cyclic loading. Although differences existed between finite element analysis and experimental testing, this study demonstrated that finite element modelling can be used as a reliable method for evaluating and optimizing plates for SCFE patients. In addition to enhancing the mechanical performance of patient-specific fixation plates, the utilization of TO in plate design may also improve the surgical outcome and decrease the recovery time by reducing the plate and incision sizes.

Design considerations for patient-specific bone fixation plates: a literature review.

In orthopedic surgery, patient-specific bone plates are used for fixation when conventional bone plates do not fit the specific anatomy of a patient. However, plate failure can occur due to a lack of properly established design parameters that support optimal biomechanical properties of the plate.This review provides an overview of design parameters and biomechanical properties of patient-specific bone plates, which can assist in the design of the optimal plate.A literature search was conducted through PubMed and Embase, resulting in the inclusion of 78 studies, comprising clinical studies using patient-specific bone plates for fracture fixation or experimental studies that evaluated biomechanical properties or design parameters of bone plates. Biomechanical properties of the plates, including elastic stiffness, yield strength, tensile strength, and Poisson's ratio are influenced by various factors, such as material properties, geometry, interface distance, fixation mechanism, screw pattern, working length and manufacturing techniques.Although variations within studies challenge direct translation of experimental results into clinical practice, this review serves as a useful reference guide to determine which parameters must be carefully considered during the design and manufacturing process to achieve the desired biomechanical properties of a plate for fixation of a specific type of fracture.

Assessment of foot deformities in individuals with cerebral palsy using weight-bearing CT.

OBJECTIVE: The aims of this study were to visualize and quantify relative bone positions in the feet of individuals with cerebral palsy (CP) with a foot deformity and compare bone positions with those of typically developed (TD) controls. MATERIALS AND METHODS: Weight-bearing CT images of 14 individuals with CP scheduled for tendon transfer and/or bony surgery and of 20 TD controls were acquired on a Planmed Verity WBCT scanner. Centroids of the navicular and calcaneus with respect to the talus were used to quantify foot deformities. All taluses were aligned and the size and dimensions of the individuals' talus were scaled to correct for differences in bone sizes. In order to visualize and quantify variations in relative bone positions, 95% CI ellipsoids and standard deviations in its principle X-, Y-, and Z-directions were determined. RESULTS: In individuals with CP (age 11-17), a large variation in centroid positions was observed compared to data of TD controls. Radiuses of the ellipsoids, representing the standard deviations of the 95% CI in the principle X-, Y-, and Z-directions, were larger in individuals with CP compared to TD controls for both the calcaneus (3.16 vs 1.86 mm, 4.26 vs 2.60 mm, 9.19 vs 3.60 mm) and navicular (4.63 vs 1.55 mm, 5.18 vs 2.10 mm, 16.07 vs 4.16 mm). CONCLUSION: By determining centroids of the calcaneus and navicular with respect to the talus on WBCT images, normal and abnormal relative bone positions can be visualized and quantified in individuals with CP with various foot deformities.

Abduction treatment in stable hip dysplasia does not alter the acetabular growth: results of a randomized clinical trial.

Background The effect of bracing over natural history of stable dysplastic hips is not well known. This multicenter randomized trial aimed at objectifying the effect of abduction treatment versus active surveillance in infants of 3 to 4 months of age. Methods Patients were randomized to either Pavlik harness or active surveillance group. Ultrasound was repeated at 6 and 12 weeks post randomization. The primary outcome was the degree of dysplasia using the Graf α-angle at 6 months of age. The measurement of the acetabular index (AI) on plain pelvis X-rays was used to identify persistent dysplasia after 9 months and walking age (after 18 months). Findings The Pavlik harness group (n = 55) and active surveillance group (n = 49) were comparable for predictors of outcome. At 12 weeks follow-up the mean α-angle was 60.5° ± 3.8° in the Pavlik harness group and 60.0° ± 5.6° in the active surveillance group. (p = 0.30). Analysis of secondary outcomes (standard of care) showed no treatment differences for acetabular index at age 10 months (p = 0.82) and walking age (p = 0.35). Interpretation Pavlik harness treatment of stable but sonographic dysplastic hips has no effect on acetabular development. Eighty percent of the patients will have a normal development of the hip after twelve weeks. Therefore, we recommend observation rather than treatment for stable dysplastic hips.

The head-shaft angle of the hip in early childhood: a comparison of reference values for children with cerebral palsy and normally developing hips.

The recognition of hips at risk of displacement in children with cerebral palsy (CP) is a difficult problem for the orthopaedic surgeon. The Gross Motor Function Classification System (GMFCS) and head-shaft angle (HSA) are prognostic factors for hip displacement. However, reference values for HSA are lacking. This study describes and compares the development of HSA in normal hips and children with CP. We selected 33 children from a retrospective cohort with unilateral developmental dysplasia of the hip (DDH) (five boys, 28 girls) and 50 children (35 boys, 15 girls) with CP with GMFCS levels II to V. HSA of normal developing hips was measured at the contralateral hip of unilateral DDH children (33 hips) and HSA of CP children was measured in both hips (100 hips). Measurements were taken from the radiographs of the children at age two, four and seven years. The normal hip HSA decreased by 2° per year (p < 0.001). In children with CP with GMFCS levels II and III HSA decreased by 0.6° (p = 0.046) and 0.9° (p = 0.049) per year, respectively. The HSA did not alter significantly in GMFCS levels IV and V. Between the ages of two and eight years, the HSA decreases in normal hips and CP children with GMFCS level, II to III but does not change in GMFCS levels IV to V. As HSA has a prognostic value for hip displacement, these reference values may help the orthopaedic surgeon to predict future hip displacement in children with CP.

The prognostic value of the head-shaft angle on hip displacement in children with cerebral palsy.

BACKGROUND: Hip displacement is the second most common deformity in cerebral palsy (CP). The risk for hip displacement is related to the Gross Motor Function Classification System (GMFCS). Recently, the head-shaft angle (HSA) has been identified as a predictor for hip displacement and the aim of this study is to assess the predictive value of the HSA for hip displacement in CP. METHODS: In this retrospective cohort, we performed radiological measurements in 50 children on both hips. In children with GMFCS level II (30 hips), III (30 hips), IV (20 hips) and V (20 hips), we measured the HSA and migration percentage (MP) in three age intervals: age two years (T1), age four years (T2) and age seven years (T3). RESULTS: At T1, the HSA was larger (more valgus) in hips that will displace than in hips that will not displace (174° vs. 166°; p = 0.001) and was also larger in higher GMFCS levels (IV-V vs. II-III) (172° vs. 165°; p < 0.001). At T1, GMFCS [odds ratio (OR) 14.7; p = 0.001] and HSA (OR 1.102; p = 0.043) were predictors for hip displacement at T3, but at T2, MP (OR 1.071; p = 0.010) was the only predictor for hip displacement at T3. CONCLUSIONS: The HSA at two years is larger in hips that will displace and larger in children with higher GMFCS levels (IV-V). At age two years, GMFCS and HSA are valuable predictors for hip displacement, but at the age of four years, only MP should be used in the prediction of hip displacement. LEVEL OF EVIDENCE: Prognostic study, level II.

Incidence and gender differences of slipped capital femoral epiphysis in the Netherlands from 1998-2010 combined with a review of the literature on the epidemiology of SCFE.

PURPOSE: The incidence of slipped capital femoral epiphysis (SCFE) among children living in the Netherlands has never been published. METHODS: The national hospitalization registration system of the Netherlands was searched for the incidence of surgical procedures for SCFE in the Netherlands among different pediatric age groups between 1998 and 2010. International Classification of Diseases, 9th Revision codes were used. RESULTS AND CONCLUSION: The incidence of surgical procedures for SCFE during the last decade was 11.6 per 100,000 children aged 5 to 19 years. No statistical difference in the incidence of SCFE was found between boys and girls, although the incidence of SCFE did significantly increase in girls during the study period. Based on our analysis, the Netherlands appears to be the first country in which no difference in the incidence of SCFE among boys and girls has been reported. However, during the study period there has been a concomitant increase in the number of girls with SCFE.

Slipped capital femoral epiphysis and its association with endocrine, metabolic and chronic diseases: a systematic review of the literature.

PURPOSE: Puberty, obesity, endocrine and chronic systemic diseases are known to be associated with slipped capital femoral epiphysis (SCFE). The mechanical insufficiency of the physis in SCFE is thought to be the result of an abnormal weakening of the physis. However, the mechanism at the cellular level has not been unravelled up to now. METHODS: To understand the pathophysiology of endocrine and metabolic factors acting on the physis, we performed a systematic review focussing on published studies reporting on hormonal, morphological and cellular abnormalities of the physis in children with SCFE. In addition, we looked for studies of the effects of endocrinopathies on the human physis which can lead to cause SCFE and focussed in detail on hormonal signalling, hormone receptor expression and extracellular matrix (ECM) composition of the physis. We searched in the PubMed, EMBASE.com and The Cochrane Library (via Wiley) databases from inception to 11th September 2012. The search generated a total of 689 references: 382 in PubMed, 232 in EMBASE.com and 75 in The Cochrane Library. After removing duplicate papers, 525 papers remained. Of these, 119 were selected based on titles and abstracts. After excluding 63 papers not related to the human physis, 56 papers were included in this review. RESULTS: Activation of the gonadal axis and the subsequent augmentation of the activity of the growth hormone-insulin-like growth factor 1 (GH-IGF-1) axis are important for the pubertal growth spurt, as well as for cessation of the physis at the end of puberty. The effects of leptin, thyroid hormone and corticosteroids on linear growth and on the physis are also discussed. Children with chronic diseases suffer from inflammation, acidosis and malnutrition. These consequences of chronic diseases affect the GH-IGF-1 axis, thereby, increasing the risk of the development of SCFE. The risk of SCFE and avascular necrosis in children with chronic renal insufficiency, growth hormone treatment and renal osteodystrophy remains equivocal. CONCLUSIONS: SCFE is most likely the result of a multi-factorial event during adolescence when height and weight increase dramatically and the delicate balance between the various hormonal equilibria can be disturbed. Up to now, there are no screening or diagnostic tests available to predict patients at risk.

Diagnosis and treatment of developmental dysplasia of the hip in the Netherlands: national questionnaire of paediatric orthopaedic surgeons on current practice in children less than 1 year old.

PURPOSE: There is no consensus in the literature regarding the diagnosis and treatment of developmental dysplasia of the hip (DDH). We designed a national questionnaire to assess the various opinions and current practice of paediatric orthopaedic surgeons in the Netherlands regarding the diagnosis and treatment of DDH in children less than 1 year old. METHODS: The questionnaire was sent to all members of the Dutch Paediatric Orthopaedic Society (DPOS). It discusses different methods and criteria used in the diagnosis of DDH, the use of different therapies and the use of different imaging techniques to evaluate the result of treatment. RESULTS: With 38 responders, the overall response rate to the survey was 67%. Most surgeons use clinical, radiographic and/or ultrasound examination for the diagnosis. The starting point of treatment is usually on the mild part of the DDH spectrum. The Pavlik harness is most popular in the treatment of dislocated hips, whereas in dysplastic hips, most surgeons use a rigid splint. The duration of treatment has a wide range and evaluation of the effect of treatment is predominantly done by radiography. CONCLUSIONS: The diagnosis and treatment of DDH in the Netherlands has as much diversity as the literature has recommendations about this subject. The lack of consensus on many aspects of DDH diagnosis and treatment should form the basis for a discussion among Dutch paediatric orthopaedic surgeons. Using the available evidence, it should be possible to formulate a more uniform protocol for the diagnosis and treatment of DDH.

Prolonged treatment with the Pavlik harness in infants with developmental dysplasia of the hip.

We prospectively studied the benefits and risks of prolonged treatment with the Pavlik harness in infants with idiopathic developmental dysplasia of the hip. Bracing was continued as long as abduction improved. It was started at a mean age of four months (1 to 6.9). Outcome measures were the number of successful reductions, the time to reduction, the acetabular index and evidence of avascular necrosis at follow-up at one year. In 50 infants with 62 subluxated and dislocated hips (42 Graf type III and 20 type IV), 37 were reduced successfully with a mean time to reduction of 13.4 weeks (sd 6.8). Bracing was successful in 31 type-III (73.8%) and in only six type-IV hips (20%, p = 0.002). Avascular necrosis was seen in ten hips. Prolonged treatment with the Pavlik harness for developmental dysplasia of the hip over the age of one month can be beneficial in type-III hips, but it is unclear as to whether this is the optimal treatment, since it may postpone the need for closed or open reduction to a more unfavourable age. The use of the Pavlik harness in type-IV hips in this age group is questionable, but if used, prolonged bracing is not advised.