- Email: [email protected]
Biomechanical evaluation of femoral anteversion in developmental dysplasia of the hip and potential implications for closed reduction
Journal Pre-proof Biomechanical evaluation of femoral anteversion in developmental dysplasia of the hip and potential implications for closed reduction
Victor Huayamave, Blake Lozinski, Christopher Rose, Hessein Ali, Alain Kassab, Eduardo Divo, Faissal Moslehy, Charles Price PII:
S0268-0033(18)30929-X
DOI:
https://doi.org/10.1016/j.clinbiomech.2019.11.017
Reference:
JCLB 4909
To appear in:
Clinical Biomechanics
Received date:
11 February 2019
Accepted date:
26 November 2019
Please cite this article as: V. Huayamave, B. Lozinski, C. Rose, et al., Biomechanical evaluation of femoral anteversion in developmental dysplasia of the hip and potential implications for closed reduction, Clinical Biomechanics (2019), https://doi.org/10.1016/ j.clinbiomech.2019.11.017
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier.
Journal Pre-proof Biomechanical Evaluation of Femoral Anteversion in Developmental Dysplasia of the Hip and Potential Implications for Closed Reduction
Complete List of Authors: Huayamave, Victor1; Lozinski, Blake2; Rose, Christopher2; Ali, Hessein2; Kassab, Alain2; Divo, Eduardo1; Moslehy, Faissal2, Price, Charles3,4 1
Department of Mechanical Engineering, Embry-Riddle Aeronautical University, Daytona Beach, Florida, US 2
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Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida, US College of Medicine, University of Central Florida, Orlando, Florida, US
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Orlando Health, Pediatric Orthopaedics, Orlando, Florida, US
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Corresponding Author:
Assistant Professor Department of Mechanical Engineering
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155 Lehman Engineering Center
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Embry-Riddle Aeronautical University
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Victor Huayamave
600 S. Clyde Morris Blvd, Daytona Beach, Florida, US
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Email: [email protected]
Funding: This study was funded in part using internal funds and by the International Hip Dysplasia Institute
Conflict of Interest: Authors declare that they have no conflict of interest
Running Title: Femoral Anteversion Mechanics in Hip Dysplasia
Abstract words: 219
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Journal Pre-proof Main text words: 3207
Abstract Background: Earlier clinical reports have identified femoral anteversion as a factor associated with developmental dysplasia of the hip. This study investigates the biomechanical influence of femoral anteversion on severe dislocations and its effect on hip reduction using the Pavlik harness.
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Methods: A computational model of an infant lower-extremity, representing a ten-week old female was
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used to analyze the biomechanics of anteversion angles ranging from thirty to seventy degrees when severe dislocation was being treated with the Pavlik harness. Specifically, the effects and relationships
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between muscle passive response and femoral anteversion angle were investigated over a range of hip
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abduction and external rotation.
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Findings: Results of this study suggest that increased femoral anteversion may decrease the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. However,
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hip external rotation and decreased abduction in the harness may facilitate initial reduction in these
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cases.
Interpretation: This biomechanical study may help explain why dissections of newborn specimen with
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developmental dysplasia of the hip have shown normal distribution of femoral anteversion in contrast to studies of patients requiring surgery where greater frequency of increased femoral anteversion has been reported. This study also suggests that adjusting the Pavlik harness to increase external hip rotation and decrease hip abduction may facilitate initial reduction for severe dislocations with increased femoral anteversion.
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Introduction Developmental Dysplasia of the Hip (DDH) describes the dislocation, misalignment or instability of the hip joint. DDH is the most common abnormality in neonates and the reported prevalence of clinical hip
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instability ranges from 1.6 to 28.5 per 1000 [1]. Approximately 6 out of every 1000 infants will require
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treatment [2]. Additionally, DDH is responsible for 29% of primary hip replacements in people up to age 60 years [3]. The Pavlik harness (PH) provides a non-surgical alternative for treatment of infants from
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birth to six months of age and has become the gold standard to treat subtle and severe dislocations.
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However, clinical reports have found low success of the PH for severe grades of hip dislocation [4].
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Suzuki noted that the femoral head is located posterior to the acetabulum in the Pavlik harness in higher grades of dislocation and reduction may be prevented by the posterior wall of the acetabulum [5]. To
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address such cases, recent computational studies utilizing patient-derived anatomy have shown that
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failure of the PH for a severe dislocation can be successfully quantified and have corroborated the impediment to reduction presented by the posterior wall of the acetabulum [6-9]. Although these
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studies have provided a state-of-the-art procedure to investigate the biomechanics of subtle and severe dislocations, relevant femoral pathoanatomy was idealized. Specifically, these previous studies used an average femoral anteversion (FA) angle of 50° because older infants with dislocated hips have increased femoral anteversion compared to unaffected infants [10]. In infants without pathology, the average FA angle is 31° and every year it decreases roughly 1.5° until about 15 years of age [10, 11]. In contrast to older infants with DDH, Some anatomical specimen of newborn infants with DDH have demonstrated similar FA as unaffected newborns [12].
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Journal Pre-proof Older children with DDH who require surgery generally have greater than normal FA [13, 14]. This suggests that FA does not improve spontaneously when the hip is dislocated, or that greater amount of FA may be the cause of PH treatment failure requiring surgical intervention at an older age. Thus, it is possible that the amount of FA may be a factor in successful or unsuccessful reduction of a dislocated hip treated with the PH [14]. No previous studies have examined the mechanical relationship between the FA angle and reduction of severe dislocations in infants. The hypothesis of this study is that
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increased FA is detrimental to successful closed reduction with the PH. Therefore, excessive femoral
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anteversion may increase the risk of surgical intervention and explain the finding that increased femoral
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anteversion is more common in surgical cases. To investigate this hypothesis, we employed our previous biomechanical model [8] to investigate the effects of FA on severe dislocations and to
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understand its influence on hip reduction when the PH is in use.
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Methods
A patient-derived Rigid Body Dynamics computational model of the lower extremity of a ten-week old
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female infant previously developed [7-9] was modified to include a range of FA angles. The infant age
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was selected because it represents an age where the lower limb is sensitive to deformation due to a severe dislocation. To elucidate the biomechanics of DDH treatment with the PH on severe dislocations when femoral morphological changes are present, several steps were required: [1] reconstruction of femora using several FA angles, [2] reconstruction of three-dimensional anatomical lower extremity of ten-week old female infant and [3] calibration of passive muscle responses [7]. The steps and methods are described in detail in this section.
Femoral anteversion anatomical model 4
Journal Pre-proof FA Angle defines the angular difference between the axis of the femoral neck and the transcondylar axis of the knee. To measure FA, we have adopted Murphy’s method [15]. Murphy defined the long femoral axis (FAx) using the center of the knee (K) and the base of the femoral neck (O); and the femoral neck axis (FNAx) using the center of the femoral head (H) and the center of the base of the femoral neck (O). For this method, the condylar axis (CAx) is defined as an axis that is intersected by the center of the knee (K) and is parallel to the axis formed by the posterior aspect of the medial condyle (M) and the posterior
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aspect of the lateral condyle (L). Subsequently, the condylar plane (CP) is defined by the intersection of
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condylar axis and the femoral axis. Then, the plane of anteversion (AP) is defined as the plane
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containing both the long femoral axis and the femoral neck axis. Finally, the angle of anteversion (θ) is the angle defined between the condylar plane and the plane of anteversion as seen in
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Fig 1.
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Fig 1. Femoral Anteversion Angle as defined by Murphy [15]. (a) The condylar axis (CAx) was defined as the axis that is intersected by the center of the knee (K) and is parallel to the axis formed by the
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posterior aspect of the medial condyle (M) and the posterior aspect of the lateral condyle (L), (b) The
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angle of anteversion (θ) was defined as the angle between the condylar plane (CP) and the plane of
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anteversion (AP). The CP was defined by the intersection of the CAx and the long femoral axis (FAx). The FAx was defined using the base of the femoral neck (O) and K. The AP was defined as the plane containing the FAx and the femoral neck axis (FNAx). The FNAx was defined using the center of the femoral head (H) and O. For the present analysis we have considered a range of moderately increased and severely increased FA as defined by Tönnis and Sankar [13, 16]. Consequently, the femur of the infant model was computationally altered using Mimics and 3-matic (Materialise Inc., Plymouth, MI) to emulate FA angles of 30, 40, 50, 60, and 70 degrees as seen in Fig 2.
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Journal Pre-proof Fig 2. Reconstructed ten-week old female infant femora of moderately and severely increased femoral anteversion (a) Femoral Anteversion angle (θ) defined as the angle between the condylar plane (CP) (green plane) and the plane of anteversion (AP) (orange plane), (b) 30 degrees anteversion, (c) 40 degrees anteversion, (d) 50 degrees anteversion, (e) 60 degrees anteversion, (f) 70 degrees anteversion.
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Three-dimensional lower extremity model of ten-week old female infant
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Our previous model included patient-specific anatomy derived from CT-scans and MRI which was
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anisotropically scaled to properly portray the lower extremity of the infant model. The anatomical
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model was composed of the hip, femur, tibia, fibula, and foot. The behavior of muscles that were identified clinically as mediating muscles during reduction with the PH is implemented in the complete
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lower extremity assembly [5, 6, 9]. As previously determined these muscles are: (1) Pectineus, (2)
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Adductor Brevis, (3) Adductor Longus, (4) Adductor Magnus, and (5) Gracilis as seen in Fig 3. The Iliopsoas, hamstrings, and abductors were excluded during this analysis. These muscles are relaxed and
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may not prevent reduction when the dislocated hip is flexed with the hip abducted in the Pavlik harness.
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A previous study analyzed the contributions of these muscles and confirmed negligible effects relative to the muscles included in the model [6, 9]. For this study, musculoskeletal tissue was modeled using a straight-line muscle path representation since lines of action do not intersect in the range of motion of interest and it allowed usage of classic methods of vector analysis [17]. Consistent with the literature, the Adductor Magnus was represented by three effective components: (a) Adductor Magnus Minimus, (b) Adductor Magnus Middle, and (c) Adductor Magnus Posterior [17]. Furthermore, calculations of the total body mass were based on a ten-week old female infant at the 50th length-for-age percentile [18] with an approximate lower extremity mass of 1.09 kg. Also, the femoral head had a diameter of 14mm, the acetabulum depth was approximately 7.9 mm, the acetabular depth-width ratio (ADR) was 45%, and 6
Journal Pre-proof the acetabulum diameter was approximately 17.5 mm [7]. In order to account for the muscle mass attached to each of the lower limbs, centers of mass of limbs were determined thus achieving physically representative load and moment distributions in the model [19]. Gravity acts as the sole external driving load in the dynamic model. Fig 3. Anterior view of the reconstructed infant lower limb with adductor muscles origin and insertion points.
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Passive muscle model and calibration
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Since hip reductions with the PH occur while resting [5] , the adductor muscles were modeled using a
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passive non-linear function commonly used in biological tissues as described in the following equation:
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𝐹 = 𝑃𝐶𝑆𝐴[𝑎(𝑒 𝑏(𝜆−1) − 1)]
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Where, F represents the passive muscle force as function of stretch (λ), PCSA is the physiological cross sectional area (scaled from the literature), and a and b are biological constants. These two constants are
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obtained by calibrating the model following the approach used on our previous model [7, 8]. Hence, six independent ten-week old female infant configurations were calibrated at a predetermined static
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equilibrium position with the hips flexed at 90° and abducted at 80°. Next, the hip was computationally
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severely dislocated for each configuration to display a Grade 4 dislocation as defined by the International Hip Dysplasia Institute classification [20]. Then, the leg was constrained to move in an envelope consistent with PH restraints. Finally, the dynamic response under passive muscle action and the effect of gravity was resolved using the ADAMS solver in Solidworks (Dassault Systemes, Concord, MA).
Anatomical dislocation configuration
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Journal Pre-proof Closed reduction failure is more common with higher grades of hip dislocation [21]. Therefore, the interest is to explore the unsuccessful reduction and explore alternatives for closed reduction. Hip dislocations have been defined by the International Hip Dysplasia Institute [20] and Grade 4 defines a severe dislocation where the femoral head is located on the posterior wall of the acetabulum. As such, the hip model was computationally dislocated to match a physiological dislocation according to a Grade 4 severe dislocation which represented the worst-case scenario based on clinical observations.
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Specifically, the center of the femoral head was placed at 𝑥 = −11.04 𝑚𝑚, 𝑦 = 13.31 𝑚𝑚, and
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𝑧 = 2.45 𝑚𝑚 relative to the origin located at the center of the acetabulum as seen in Fig 4.
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Fig 4. Dislocated femoral head initial position in a severe dislocation. Position and coordinates in the femoral head are defined in the center of the femoral head and the dislocated position is with respect
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to the center of the acetabulum.
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Anatomical ranges of motion
For this study, several anatomical positions were considered. Two main cases were developed: 1)
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Constant hip flexion and constant hip external rotation with varying hip abduction and 2) Constant hip
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flexion and constant hip abduction with varying hip external rotation. Hip external rotation (β) and hip abduction (α) were measured as shown in Fig 5. Fig 5. a) Lateral view of the abducted hip showing the hip external rotation angle (β). β is the defined as the angle between the tibia anatomical axis and a plane which is parallel to the sagittal plane and intersects the center of the knee, (b) Inferior view of the lower extremity showing the hip abduction angle (α). α is defined as the angle between the long femoral axis (FAx) and a plane which is parallel to the sagittal plane and intersects the center of the acetabulum.
Constant hip flexion and external rotation with varying abduction
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Journal Pre-proof For this anatomical configuration hip abduction was varied to emulate angles of 40, 50, 60, 70, and 80 degrees while hip flexion was kept constant at 90 degrees, hip external rotation was kept at 40 degrees, and the knee was kept flexed at 90 degrees. A 40 degrees angle for hip external rotation was used since this angle represented an average of hip external rotation of the model.
Constant hip flexion and abduction with varying external rotation For this anatomical configuration hip external rotation was varied to emulate angles of 30, 40, and 55
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degrees while hip flexion was kept constant at 90 degrees, hip abduction was kept constant at 80
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degrees, and the knee was kept flexed at 90 degrees. For hip external rotation, increments of 10 degrees
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were proposed starting at 30 degrees. However, preliminary results at 40 hip external rotation and 50
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hip external rotation were similar and therefore results at 55 degrees were reported. For all configurations the five femora samples previously described were used. In addition, an external
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force parallel to the femoral neck axis was applied to the center of the femoral head to achieve
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reduction on fully dislocated hip described by a Grade 4 as seen in Fig 6a. This external force is applied to overcome the reduction obstacle presented by the area between the ischial spine and border of the
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acetabulum in the transverse plane on the lateral aspect of the ischium as shown in Fig 6b. As
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previously explained, Grade 4 reductions are frequently unsuccessful but our previous work has shown that using external forces in conjunction with hip external rotation aids reduction of Grade 4 dislocation. Fig 6. (a) Lower extremity model showing the external force (single headed arrow) applied to the center of the femoral head and parallel to the femoral neck axis on a Grade 4 dislocation needed to achieve closed reduction. (b) Ridge identified as anatomical obstacle to reduction located in the posterior wall of the acetabulum.
Results 9
Journal Pre-proof The results of this study demonstrate that increased force is required for reduction of high-grade hip dislocations when anteversion is 70 degrees as shown in Fig 7 and Fig 8. This additional force is minimal when abduction is 50 degrees or less. However, force required for reduction increases noticeably when abduction is 60 degrees or greater and anteversion is 60 degrees or greater. Preliminary results also suggest that hip external rotation and hip abduction were prime factors influencing successful reduction in severe dislocations.
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Results of varying hip abduction with constant hip flexion and
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external rotation
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Table 1 and Fig 7 show the values and plots of external forces needed to successfully reduce Grade 4
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dislocations as a function of femoral anteversion (FA) angle and hip abduction (HA) angle. These results
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reveal that the external force required for hip reduction monotonically increases with both the HA angle and the FA angle. For HA angles of 60 degrees or less, the effect of changing the FA angle on the external
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force required for reduction is almost negligible except at FA angles above 60 degrees when this force
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significantly increases with the FA angle. For HA angles above 60 degrees, the external force required for reduction increases significantly with the FA angle, particularly at FA angles of 50 degrees or less. These
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results suggest that decrease in hip abduction allows for a lower external force needed for initial reduction in Grade 4 hip dislocations. When full abduction has been achieved without reduction, then femoral anteversion may contribute additionally to failure of the Pavlik harness. In addition, these values may provide physicians insight for new practices to consider when adjusting the straps in the Pavlik Harness. For example, increased hip external rotation along with decreased abduction may facilitate initial reduction for severe hip dislocations when using the Pavlik harness for infants with increased FA.
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Journal Pre-proof Table 1. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip external rotation with varying hip abduction.
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Femoral 80o hip 70o hip 60o hip 50o hip 40o hip Anteversion abduction abduction abduction abduction abduction (degrees) Force (N) Force (N) Force (N) Force (N) Force (N) 30 64 59 53 19 10 40 68 64 54 20 11 50 80 72 54 20 11 60 83 74 54 20 11 70 84 75 55 22 14 Fig 7. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip
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external rotation with varying hip abduction. These results suggest that greater forces are needed for
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reduction when increased anteversion is accompanied by greater degrees of abduction.
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Results of varying hip external rotation with constant hip flexion and
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abduction
Results suggest that external forces needed for successful reduction are lower as hip external rotation
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increases. Table 2 and Fig 8 show the values of external forces needed to successfully reduce Grade 4
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dislocation. Fig 8 addresses the influence of external rotation on the additional force needed to
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overcome the obstacle to reduction in Grade 4 dislocation presented by the area between the ischial spine and border of the acetabulum in the transverse plane on the lateral aspect of the ischium. Table 2. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip abduction with varying hip external rotation. Femoral Anteversion (degrees) 30 40 50 60 70
30o external rotation Force (N) 68 77 90 93 95
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40o external rotation Force (N) 64 68 80 83 84
55o external rotation Force (N) 45 48 53 55 59
Journal Pre-proof Fig 8. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip abduction with varying hip external rotation. These results suggest that forces needed for reduction are lower when external rotation is increased.
Discussion
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Our model suggests that decreased femoral anteversion may increase the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. In lesser degrees of
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abduction, the influence of femoral anteversion appears to be minimal until the anteversion angle
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approaches 70°. This is consistent with clinical experience that manual reduction of dislocated hips is
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performed with the hip in minimal abduction even though this position is known to be unstable
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following reduction.
For infants in the Pavlik harness, gradual elongation of the adductors without achieving reduction
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may further impede reduction when femoral anteversion is greater than 40. In these circumstances, external rotation may alleviate some of the resistance to reduction for hips that remain dislocated in the
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Pavlik harness. These results suggest the potential for new adjustments to consider when using the
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Pavlik harness to treat developmental dysplasia of the hip. In recalcitrant cases this may include greater external rotation or decreased abduction until the hip is reduced. This study did not evaluate the effects of increased flexion greater than 90 degrees. However, increased flexion has been reported as a method to improve reduction of high-grade dislocations [20]. The effects of increased flexion may be worthwhile in future studies since increased flexion may also facilitate reduction in cases with increased femoral anteversion. This biomechanical study may also help explain why dissections of newborn specimen with developmental dysplasia of the hip have shown normal distribution of femoral anteversion in contrast to
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Journal Pre-proof studies of patients requiring surgery where greater frequency of increased femoral anteversion has been reported. The adverse effects of increased femoral anteversion are further supported by the observation that redislocation following open reduction is more likely to occur when excessive femoral anteversion remains uncorrected [22]. Sankar found significant individual variation in femoral anteversion for patients undergoing open reduction surgery, and only recommended derotational femoral osteotomy for those patients with increased anteversion [13].
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The results of this biomechanical study and other reports suggest that variations in femoral
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anteversion may be insignificant in the etiology of DDH, but the presence of excessive femoral
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anteversion may interfere with successful reduction by closed or open methods. The authors recognize that the elements of this study cannot be carried out by clinical studies since
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it will be nearly impossible to assemble a population of infant cadaveric femora exhibiting different
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femoral anteversion for in vitro testing. The values presented were obtained using morphology of 50th percentile ten-week old female infant and therefore should not be assumed to be similar among an
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infant population. Therefore, this computational approach proposes a novel solution when clinical
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studies are a limitation. Understanding the biomechanical effect of this pathology may be relevant to
remedies.
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identify possible causes of treatment failure for severe dislocation and may help explore alternative
Conclusion We used our biomechanical model to test the hypothesis that increased femoral anteversion is detrimental to successful closed reduction with the Pavlik harness. Our model suggest that decreased femoral anteversion may increase the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. In lesser degrees of abduction, the influence of femoral
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Journal Pre-proof anteversion appears to be minimal until the anteversion angle approaches 70°. This is consistent with clinical experience that manual reduction of dislocated hips is performed with the hip in minimal abduction even though this position is known to be unstable following reduction. The results of this study may validate clinical reports that initial closed reduction of some hips can be facilitated by
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increasing external rotation using hyperflexion.
References
5. 6. 7.
8.
9.
10.
11. 12. 13.
ro
-p
re
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4.
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3.
ur
2.
Dezateux, C. and K. Rosendahl, Developmental dysplasia of the hip. The Lancet, 2007. 369(9572): p. 1541-1552. Bialik, V., et al., Developmental Dysplasia of the Hip: A New Approach to Incidence. Pediatrics, 1999. 103(1): p. 93-99. Furnes, O., et al., Hip disease and the prognosis of total hip replacements: a review of 53 698 primary total hip replacements reported to the Norwegian Arthroplasty Register 1987-99. Journal of Bone & Joint Surgery, British Volume, 2001. 83B(4): p. 579-586. Atalar, H., et al., Indicators of successful use of the Pavlik harness in infants with developmental dysplasia of the hip. International Orthopaedics, 2007. 31(2): p. 145-150. Suzuki, S., Reduction of CDH by the Pavlik harness. Spontaneous reduction observed by ultrasound. Journal of Bone and Joint Surgery, British Volume, 1994. 76-B(3): p. 460-462. Ardila, O.J., et al., Mechanics of hip dysplasia reductions in infants using the Pavlik harness: A physics-based computational model. Journal of Biomechanics, 2013. 46(9): p. 1501-1507. Huayamave, V., et al., A patient-specific model of the biomechanics of hip reduction for neonatal Developmental Dysplasia of the Hip: Investigation of strategies for low to severe grades of Developmental Dysplasia of the Hip. Journal of Biomechanics, 2015. 48(10): p. 2026-2033. Huayamave, V., Biomechanics of developmental dysplasia of the hip - an engineering study of closed reduction utilizing the pavlik harness for a range of subtle to severe dislocations in infants. [electronic resource]. 2015: Orlando, Fla. : PhD Dissertation, University of Central Florida, 2015. Zwawi, M.A., et al., Developmental dysplasia of the hip: A computational biomechanical model of the path of least energy for closed reduction. Journal of Orthopaedic Research, 2016. 35(8): p. 1799-1805. Fabry, G.U.Y., G.D. Macewen, and A.R. Shandsjr, Torsion of the Femur A follow-up study in normal and abnormal conditions. The Journal of Bone & Joint Surgery, 1973. 55(8): p. 17261738. Cibulka, M.T., Determination and significance of femoral neck anteversion. Physical therapy, 2004. 84(6): p. 550-558. Edelson, J., et al., Congenital dislocation of the hip and computerised axial tomography. The Journal of bone and joint surgery. British volume, 1984. 66(4): p. 472-478. Sankar, W.N., C.O. Neubuerger, and C.F. Moseley, Femoral anteversion in developmental dysplasia of the hip. Journal of Pediatric Orthopaedics, 2009. 29(8): p. 885-888.
Jo
1.
14
Journal Pre-proof
21.
22.
of
ro
20.
-p
19.
re
18.
lP
17.
na
16.
ur
15.
Mootha, A.K., et al., MRI evaluation of femoral and acetabular anteversion in developmental dysplasia of the hip. A study in an early walking age group. Acta Orthop Belg, 2010. 76(2): p. 174-180. Murphy, S.B., et al., Femoral anteversion. The Journal of Bone & Joint Surgery, 1987. 69(8): p. 1169-1176. Tönnis, D. and A. Heinecke, Current Concepts Review-Acetabular and Femoral Anteversion: Relationship with Osteoarthritis of the Hip. The Journal of Bone & Joint Surgery, 1999. 81(12): p. 1747-70. Dostal, W.F. and J.G. Andrews, A three-dimensional biomechanical model of hip musculature. Journal of Biomechanics, 1981. 14(11): p. 803-812. CDC, Centers for Disease and Prevention, "Birth to 24 months: Girls Length-for-age percentiles and Weight-for-age percentiles," http://www.cdc.gov/growthcharts/who_charts.htm 2009. Drillis, R. and R. Contini, Body Segment Parameters. 1966, New York University School of Engineering and Science: New York. Narayanan, U., et al., Reliability of a New Radiographic Classification for Developmental Dysplasia of the Hip. Journal of Pediatric Orthopaedics, 2015. 35(5): p. 478. Grill, F., et al., The Pavlik Harness in the Treatment of Congenital Dislocating Hip: Report on a Multicenter Study of the European Paediatric Orthopaedic Society. Journal of Pediatric Orthopaedics, 1988. 8(1): p. 1-8. Tuhanioğlu, Ü., et al., Evaluation of Late Redislocation in Patients who Underwent Open Reduction and Pelvic Osteotomy as Treament for Developmental Dysplasia of the Hip. HIP International. 0(0): p. hipint.5000571.
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Journal Pre-proof Highlights:
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Increased femoral anteversion may decrease success of Pavlik harness treatment Hip external rotation and decreased abduction facilitates Pavlik harness treatment Femoral anteversion influence is minimal until anteversion approaches 70 degrees Increased external rotation using hyperflexion could facilitate closed reduction
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Victor Huayamave, Blake Lozinski, Christopher Rose, Hessein Ali, Alain Kassab, Eduardo Divo, Faissal Moslehy, Charles Price PII:
S0268-0033(18)30929-X
DOI:
https://doi.org/10.1016/j.clinbiomech.2019.11.017
Reference:
JCLB 4909
To appear in:
Clinical Biomechanics
Received date:
11 February 2019
Accepted date:
26 November 2019
Please cite this article as: V. Huayamave, B. Lozinski, C. Rose, et al., Biomechanical evaluation of femoral anteversion in developmental dysplasia of the hip and potential implications for closed reduction, Clinical Biomechanics (2019), https://doi.org/10.1016/ j.clinbiomech.2019.11.017
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier.
Journal Pre-proof Biomechanical Evaluation of Femoral Anteversion in Developmental Dysplasia of the Hip and Potential Implications for Closed Reduction
Complete List of Authors: Huayamave, Victor1; Lozinski, Blake2; Rose, Christopher2; Ali, Hessein2; Kassab, Alain2; Divo, Eduardo1; Moslehy, Faissal2, Price, Charles3,4 1
Department of Mechanical Engineering, Embry-Riddle Aeronautical University, Daytona Beach, Florida, US 2
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Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida, US College of Medicine, University of Central Florida, Orlando, Florida, US
4
Orlando Health, Pediatric Orthopaedics, Orlando, Florida, US
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3
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Corresponding Author:
Assistant Professor Department of Mechanical Engineering
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155 Lehman Engineering Center
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Embry-Riddle Aeronautical University
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Victor Huayamave
600 S. Clyde Morris Blvd, Daytona Beach, Florida, US
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Email: [email protected]
Funding: This study was funded in part using internal funds and by the International Hip Dysplasia Institute
Conflict of Interest: Authors declare that they have no conflict of interest
Running Title: Femoral Anteversion Mechanics in Hip Dysplasia
Abstract words: 219
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Journal Pre-proof Main text words: 3207
Abstract Background: Earlier clinical reports have identified femoral anteversion as a factor associated with developmental dysplasia of the hip. This study investigates the biomechanical influence of femoral anteversion on severe dislocations and its effect on hip reduction using the Pavlik harness.
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Methods: A computational model of an infant lower-extremity, representing a ten-week old female was
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used to analyze the biomechanics of anteversion angles ranging from thirty to seventy degrees when severe dislocation was being treated with the Pavlik harness. Specifically, the effects and relationships
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between muscle passive response and femoral anteversion angle were investigated over a range of hip
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abduction and external rotation.
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Findings: Results of this study suggest that increased femoral anteversion may decrease the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. However,
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hip external rotation and decreased abduction in the harness may facilitate initial reduction in these
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cases.
Interpretation: This biomechanical study may help explain why dissections of newborn specimen with
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developmental dysplasia of the hip have shown normal distribution of femoral anteversion in contrast to studies of patients requiring surgery where greater frequency of increased femoral anteversion has been reported. This study also suggests that adjusting the Pavlik harness to increase external hip rotation and decrease hip abduction may facilitate initial reduction for severe dislocations with increased femoral anteversion.
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Introduction Developmental Dysplasia of the Hip (DDH) describes the dislocation, misalignment or instability of the hip joint. DDH is the most common abnormality in neonates and the reported prevalence of clinical hip
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instability ranges from 1.6 to 28.5 per 1000 [1]. Approximately 6 out of every 1000 infants will require
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treatment [2]. Additionally, DDH is responsible for 29% of primary hip replacements in people up to age 60 years [3]. The Pavlik harness (PH) provides a non-surgical alternative for treatment of infants from
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birth to six months of age and has become the gold standard to treat subtle and severe dislocations.
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However, clinical reports have found low success of the PH for severe grades of hip dislocation [4].
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Suzuki noted that the femoral head is located posterior to the acetabulum in the Pavlik harness in higher grades of dislocation and reduction may be prevented by the posterior wall of the acetabulum [5]. To
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address such cases, recent computational studies utilizing patient-derived anatomy have shown that
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failure of the PH for a severe dislocation can be successfully quantified and have corroborated the impediment to reduction presented by the posterior wall of the acetabulum [6-9]. Although these
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studies have provided a state-of-the-art procedure to investigate the biomechanics of subtle and severe dislocations, relevant femoral pathoanatomy was idealized. Specifically, these previous studies used an average femoral anteversion (FA) angle of 50° because older infants with dislocated hips have increased femoral anteversion compared to unaffected infants [10]. In infants without pathology, the average FA angle is 31° and every year it decreases roughly 1.5° until about 15 years of age [10, 11]. In contrast to older infants with DDH, Some anatomical specimen of newborn infants with DDH have demonstrated similar FA as unaffected newborns [12].
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Journal Pre-proof Older children with DDH who require surgery generally have greater than normal FA [13, 14]. This suggests that FA does not improve spontaneously when the hip is dislocated, or that greater amount of FA may be the cause of PH treatment failure requiring surgical intervention at an older age. Thus, it is possible that the amount of FA may be a factor in successful or unsuccessful reduction of a dislocated hip treated with the PH [14]. No previous studies have examined the mechanical relationship between the FA angle and reduction of severe dislocations in infants. The hypothesis of this study is that
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increased FA is detrimental to successful closed reduction with the PH. Therefore, excessive femoral
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anteversion may increase the risk of surgical intervention and explain the finding that increased femoral
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anteversion is more common in surgical cases. To investigate this hypothesis, we employed our previous biomechanical model [8] to investigate the effects of FA on severe dislocations and to
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understand its influence on hip reduction when the PH is in use.
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Methods
A patient-derived Rigid Body Dynamics computational model of the lower extremity of a ten-week old
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female infant previously developed [7-9] was modified to include a range of FA angles. The infant age
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was selected because it represents an age where the lower limb is sensitive to deformation due to a severe dislocation. To elucidate the biomechanics of DDH treatment with the PH on severe dislocations when femoral morphological changes are present, several steps were required: [1] reconstruction of femora using several FA angles, [2] reconstruction of three-dimensional anatomical lower extremity of ten-week old female infant and [3] calibration of passive muscle responses [7]. The steps and methods are described in detail in this section.
Femoral anteversion anatomical model 4
Journal Pre-proof FA Angle defines the angular difference between the axis of the femoral neck and the transcondylar axis of the knee. To measure FA, we have adopted Murphy’s method [15]. Murphy defined the long femoral axis (FAx) using the center of the knee (K) and the base of the femoral neck (O); and the femoral neck axis (FNAx) using the center of the femoral head (H) and the center of the base of the femoral neck (O). For this method, the condylar axis (CAx) is defined as an axis that is intersected by the center of the knee (K) and is parallel to the axis formed by the posterior aspect of the medial condyle (M) and the posterior
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aspect of the lateral condyle (L). Subsequently, the condylar plane (CP) is defined by the intersection of
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condylar axis and the femoral axis. Then, the plane of anteversion (AP) is defined as the plane
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containing both the long femoral axis and the femoral neck axis. Finally, the angle of anteversion (θ) is the angle defined between the condylar plane and the plane of anteversion as seen in
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Fig 1.
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Fig 1. Femoral Anteversion Angle as defined by Murphy [15]. (a) The condylar axis (CAx) was defined as the axis that is intersected by the center of the knee (K) and is parallel to the axis formed by the
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posterior aspect of the medial condyle (M) and the posterior aspect of the lateral condyle (L), (b) The
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angle of anteversion (θ) was defined as the angle between the condylar plane (CP) and the plane of
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anteversion (AP). The CP was defined by the intersection of the CAx and the long femoral axis (FAx). The FAx was defined using the base of the femoral neck (O) and K. The AP was defined as the plane containing the FAx and the femoral neck axis (FNAx). The FNAx was defined using the center of the femoral head (H) and O. For the present analysis we have considered a range of moderately increased and severely increased FA as defined by Tönnis and Sankar [13, 16]. Consequently, the femur of the infant model was computationally altered using Mimics and 3-matic (Materialise Inc., Plymouth, MI) to emulate FA angles of 30, 40, 50, 60, and 70 degrees as seen in Fig 2.
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Journal Pre-proof Fig 2. Reconstructed ten-week old female infant femora of moderately and severely increased femoral anteversion (a) Femoral Anteversion angle (θ) defined as the angle between the condylar plane (CP) (green plane) and the plane of anteversion (AP) (orange plane), (b) 30 degrees anteversion, (c) 40 degrees anteversion, (d) 50 degrees anteversion, (e) 60 degrees anteversion, (f) 70 degrees anteversion.
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Three-dimensional lower extremity model of ten-week old female infant
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Our previous model included patient-specific anatomy derived from CT-scans and MRI which was
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anisotropically scaled to properly portray the lower extremity of the infant model. The anatomical
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model was composed of the hip, femur, tibia, fibula, and foot. The behavior of muscles that were identified clinically as mediating muscles during reduction with the PH is implemented in the complete
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lower extremity assembly [5, 6, 9]. As previously determined these muscles are: (1) Pectineus, (2)
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Adductor Brevis, (3) Adductor Longus, (4) Adductor Magnus, and (5) Gracilis as seen in Fig 3. The Iliopsoas, hamstrings, and abductors were excluded during this analysis. These muscles are relaxed and
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may not prevent reduction when the dislocated hip is flexed with the hip abducted in the Pavlik harness.
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A previous study analyzed the contributions of these muscles and confirmed negligible effects relative to the muscles included in the model [6, 9]. For this study, musculoskeletal tissue was modeled using a straight-line muscle path representation since lines of action do not intersect in the range of motion of interest and it allowed usage of classic methods of vector analysis [17]. Consistent with the literature, the Adductor Magnus was represented by three effective components: (a) Adductor Magnus Minimus, (b) Adductor Magnus Middle, and (c) Adductor Magnus Posterior [17]. Furthermore, calculations of the total body mass were based on a ten-week old female infant at the 50th length-for-age percentile [18] with an approximate lower extremity mass of 1.09 kg. Also, the femoral head had a diameter of 14mm, the acetabulum depth was approximately 7.9 mm, the acetabular depth-width ratio (ADR) was 45%, and 6
Journal Pre-proof the acetabulum diameter was approximately 17.5 mm [7]. In order to account for the muscle mass attached to each of the lower limbs, centers of mass of limbs were determined thus achieving physically representative load and moment distributions in the model [19]. Gravity acts as the sole external driving load in the dynamic model. Fig 3. Anterior view of the reconstructed infant lower limb with adductor muscles origin and insertion points.
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Passive muscle model and calibration
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Since hip reductions with the PH occur while resting [5] , the adductor muscles were modeled using a
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passive non-linear function commonly used in biological tissues as described in the following equation:
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𝐹 = 𝑃𝐶𝑆𝐴[𝑎(𝑒 𝑏(𝜆−1) − 1)]
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Where, F represents the passive muscle force as function of stretch (λ), PCSA is the physiological cross sectional area (scaled from the literature), and a and b are biological constants. These two constants are
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obtained by calibrating the model following the approach used on our previous model [7, 8]. Hence, six independent ten-week old female infant configurations were calibrated at a predetermined static
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equilibrium position with the hips flexed at 90° and abducted at 80°. Next, the hip was computationally
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severely dislocated for each configuration to display a Grade 4 dislocation as defined by the International Hip Dysplasia Institute classification [20]. Then, the leg was constrained to move in an envelope consistent with PH restraints. Finally, the dynamic response under passive muscle action and the effect of gravity was resolved using the ADAMS solver in Solidworks (Dassault Systemes, Concord, MA).
Anatomical dislocation configuration
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Journal Pre-proof Closed reduction failure is more common with higher grades of hip dislocation [21]. Therefore, the interest is to explore the unsuccessful reduction and explore alternatives for closed reduction. Hip dislocations have been defined by the International Hip Dysplasia Institute [20] and Grade 4 defines a severe dislocation where the femoral head is located on the posterior wall of the acetabulum. As such, the hip model was computationally dislocated to match a physiological dislocation according to a Grade 4 severe dislocation which represented the worst-case scenario based on clinical observations.
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Specifically, the center of the femoral head was placed at 𝑥 = −11.04 𝑚𝑚, 𝑦 = 13.31 𝑚𝑚, and
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𝑧 = 2.45 𝑚𝑚 relative to the origin located at the center of the acetabulum as seen in Fig 4.
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Fig 4. Dislocated femoral head initial position in a severe dislocation. Position and coordinates in the femoral head are defined in the center of the femoral head and the dislocated position is with respect
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to the center of the acetabulum.
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Anatomical ranges of motion
For this study, several anatomical positions were considered. Two main cases were developed: 1)
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Constant hip flexion and constant hip external rotation with varying hip abduction and 2) Constant hip
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flexion and constant hip abduction with varying hip external rotation. Hip external rotation (β) and hip abduction (α) were measured as shown in Fig 5. Fig 5. a) Lateral view of the abducted hip showing the hip external rotation angle (β). β is the defined as the angle between the tibia anatomical axis and a plane which is parallel to the sagittal plane and intersects the center of the knee, (b) Inferior view of the lower extremity showing the hip abduction angle (α). α is defined as the angle between the long femoral axis (FAx) and a plane which is parallel to the sagittal plane and intersects the center of the acetabulum.
Constant hip flexion and external rotation with varying abduction
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Journal Pre-proof For this anatomical configuration hip abduction was varied to emulate angles of 40, 50, 60, 70, and 80 degrees while hip flexion was kept constant at 90 degrees, hip external rotation was kept at 40 degrees, and the knee was kept flexed at 90 degrees. A 40 degrees angle for hip external rotation was used since this angle represented an average of hip external rotation of the model.
Constant hip flexion and abduction with varying external rotation For this anatomical configuration hip external rotation was varied to emulate angles of 30, 40, and 55
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degrees while hip flexion was kept constant at 90 degrees, hip abduction was kept constant at 80
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degrees, and the knee was kept flexed at 90 degrees. For hip external rotation, increments of 10 degrees
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were proposed starting at 30 degrees. However, preliminary results at 40 hip external rotation and 50
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hip external rotation were similar and therefore results at 55 degrees were reported. For all configurations the five femora samples previously described were used. In addition, an external
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force parallel to the femoral neck axis was applied to the center of the femoral head to achieve
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reduction on fully dislocated hip described by a Grade 4 as seen in Fig 6a. This external force is applied to overcome the reduction obstacle presented by the area between the ischial spine and border of the
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acetabulum in the transverse plane on the lateral aspect of the ischium as shown in Fig 6b. As
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previously explained, Grade 4 reductions are frequently unsuccessful but our previous work has shown that using external forces in conjunction with hip external rotation aids reduction of Grade 4 dislocation. Fig 6. (a) Lower extremity model showing the external force (single headed arrow) applied to the center of the femoral head and parallel to the femoral neck axis on a Grade 4 dislocation needed to achieve closed reduction. (b) Ridge identified as anatomical obstacle to reduction located in the posterior wall of the acetabulum.
Results 9
Journal Pre-proof The results of this study demonstrate that increased force is required for reduction of high-grade hip dislocations when anteversion is 70 degrees as shown in Fig 7 and Fig 8. This additional force is minimal when abduction is 50 degrees or less. However, force required for reduction increases noticeably when abduction is 60 degrees or greater and anteversion is 60 degrees or greater. Preliminary results also suggest that hip external rotation and hip abduction were prime factors influencing successful reduction in severe dislocations.
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Results of varying hip abduction with constant hip flexion and
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external rotation
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Table 1 and Fig 7 show the values and plots of external forces needed to successfully reduce Grade 4
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dislocations as a function of femoral anteversion (FA) angle and hip abduction (HA) angle. These results
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reveal that the external force required for hip reduction monotonically increases with both the HA angle and the FA angle. For HA angles of 60 degrees or less, the effect of changing the FA angle on the external
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force required for reduction is almost negligible except at FA angles above 60 degrees when this force
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significantly increases with the FA angle. For HA angles above 60 degrees, the external force required for reduction increases significantly with the FA angle, particularly at FA angles of 50 degrees or less. These
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results suggest that decrease in hip abduction allows for a lower external force needed for initial reduction in Grade 4 hip dislocations. When full abduction has been achieved without reduction, then femoral anteversion may contribute additionally to failure of the Pavlik harness. In addition, these values may provide physicians insight for new practices to consider when adjusting the straps in the Pavlik Harness. For example, increased hip external rotation along with decreased abduction may facilitate initial reduction for severe hip dislocations when using the Pavlik harness for infants with increased FA.
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Journal Pre-proof Table 1. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip external rotation with varying hip abduction.
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Femoral 80o hip 70o hip 60o hip 50o hip 40o hip Anteversion abduction abduction abduction abduction abduction (degrees) Force (N) Force (N) Force (N) Force (N) Force (N) 30 64 59 53 19 10 40 68 64 54 20 11 50 80 72 54 20 11 60 83 74 54 20 11 70 84 75 55 22 14 Fig 7. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip
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external rotation with varying hip abduction. These results suggest that greater forces are needed for
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reduction when increased anteversion is accompanied by greater degrees of abduction.
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Results of varying hip external rotation with constant hip flexion and
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abduction
Results suggest that external forces needed for successful reduction are lower as hip external rotation
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increases. Table 2 and Fig 8 show the values of external forces needed to successfully reduce Grade 4
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dislocation. Fig 8 addresses the influence of external rotation on the additional force needed to
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overcome the obstacle to reduction in Grade 4 dislocation presented by the area between the ischial spine and border of the acetabulum in the transverse plane on the lateral aspect of the ischium. Table 2. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip abduction with varying hip external rotation. Femoral Anteversion (degrees) 30 40 50 60 70
30o external rotation Force (N) 68 77 90 93 95
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40o external rotation Force (N) 64 68 80 83 84
55o external rotation Force (N) 45 48 53 55 59
Journal Pre-proof Fig 8. External forces required to reduce Grade 4 dislocation using constant hip flexion and hip abduction with varying hip external rotation. These results suggest that forces needed for reduction are lower when external rotation is increased.
Discussion
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Our model suggests that decreased femoral anteversion may increase the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. In lesser degrees of
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abduction, the influence of femoral anteversion appears to be minimal until the anteversion angle
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approaches 70°. This is consistent with clinical experience that manual reduction of dislocated hips is
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performed with the hip in minimal abduction even though this position is known to be unstable
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following reduction.
For infants in the Pavlik harness, gradual elongation of the adductors without achieving reduction
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may further impede reduction when femoral anteversion is greater than 40. In these circumstances, external rotation may alleviate some of the resistance to reduction for hips that remain dislocated in the
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Pavlik harness. These results suggest the potential for new adjustments to consider when using the
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Pavlik harness to treat developmental dysplasia of the hip. In recalcitrant cases this may include greater external rotation or decreased abduction until the hip is reduced. This study did not evaluate the effects of increased flexion greater than 90 degrees. However, increased flexion has been reported as a method to improve reduction of high-grade dislocations [20]. The effects of increased flexion may be worthwhile in future studies since increased flexion may also facilitate reduction in cases with increased femoral anteversion. This biomechanical study may also help explain why dissections of newborn specimen with developmental dysplasia of the hip have shown normal distribution of femoral anteversion in contrast to
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Journal Pre-proof studies of patients requiring surgery where greater frequency of increased femoral anteversion has been reported. The adverse effects of increased femoral anteversion are further supported by the observation that redislocation following open reduction is more likely to occur when excessive femoral anteversion remains uncorrected [22]. Sankar found significant individual variation in femoral anteversion for patients undergoing open reduction surgery, and only recommended derotational femoral osteotomy for those patients with increased anteversion [13].
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The results of this biomechanical study and other reports suggest that variations in femoral
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anteversion may be insignificant in the etiology of DDH, but the presence of excessive femoral
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anteversion may interfere with successful reduction by closed or open methods. The authors recognize that the elements of this study cannot be carried out by clinical studies since
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it will be nearly impossible to assemble a population of infant cadaveric femora exhibiting different
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femoral anteversion for in vitro testing. The values presented were obtained using morphology of 50th percentile ten-week old female infant and therefore should not be assumed to be similar among an
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infant population. Therefore, this computational approach proposes a novel solution when clinical
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studies are a limitation. Understanding the biomechanical effect of this pathology may be relevant to
remedies.
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identify possible causes of treatment failure for severe dislocation and may help explore alternative
Conclusion We used our biomechanical model to test the hypothesis that increased femoral anteversion is detrimental to successful closed reduction with the Pavlik harness. Our model suggest that decreased femoral anteversion may increase the success rate for treatment of high-grade developmental dysplasia of the hip when using the Pavlik harness. In lesser degrees of abduction, the influence of femoral
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Journal Pre-proof anteversion appears to be minimal until the anteversion angle approaches 70°. This is consistent with clinical experience that manual reduction of dislocated hips is performed with the hip in minimal abduction even though this position is known to be unstable following reduction. The results of this study may validate clinical reports that initial closed reduction of some hips can be facilitated by
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increasing external rotation using hyperflexion.
References
5. 6. 7.
8.
9.
10.
11. 12. 13.
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-p
re
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4.
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3.
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2.
Dezateux, C. and K. Rosendahl, Developmental dysplasia of the hip. The Lancet, 2007. 369(9572): p. 1541-1552. Bialik, V., et al., Developmental Dysplasia of the Hip: A New Approach to Incidence. Pediatrics, 1999. 103(1): p. 93-99. Furnes, O., et al., Hip disease and the prognosis of total hip replacements: a review of 53 698 primary total hip replacements reported to the Norwegian Arthroplasty Register 1987-99. Journal of Bone & Joint Surgery, British Volume, 2001. 83B(4): p. 579-586. Atalar, H., et al., Indicators of successful use of the Pavlik harness in infants with developmental dysplasia of the hip. International Orthopaedics, 2007. 31(2): p. 145-150. Suzuki, S., Reduction of CDH by the Pavlik harness. Spontaneous reduction observed by ultrasound. Journal of Bone and Joint Surgery, British Volume, 1994. 76-B(3): p. 460-462. Ardila, O.J., et al., Mechanics of hip dysplasia reductions in infants using the Pavlik harness: A physics-based computational model. Journal of Biomechanics, 2013. 46(9): p. 1501-1507. Huayamave, V., et al., A patient-specific model of the biomechanics of hip reduction for neonatal Developmental Dysplasia of the Hip: Investigation of strategies for low to severe grades of Developmental Dysplasia of the Hip. Journal of Biomechanics, 2015. 48(10): p. 2026-2033. Huayamave, V., Biomechanics of developmental dysplasia of the hip - an engineering study of closed reduction utilizing the pavlik harness for a range of subtle to severe dislocations in infants. [electronic resource]. 2015: Orlando, Fla. : PhD Dissertation, University of Central Florida, 2015. Zwawi, M.A., et al., Developmental dysplasia of the hip: A computational biomechanical model of the path of least energy for closed reduction. Journal of Orthopaedic Research, 2016. 35(8): p. 1799-1805. Fabry, G.U.Y., G.D. Macewen, and A.R. Shandsjr, Torsion of the Femur A follow-up study in normal and abnormal conditions. The Journal of Bone & Joint Surgery, 1973. 55(8): p. 17261738. Cibulka, M.T., Determination and significance of femoral neck anteversion. Physical therapy, 2004. 84(6): p. 550-558. Edelson, J., et al., Congenital dislocation of the hip and computerised axial tomography. The Journal of bone and joint surgery. British volume, 1984. 66(4): p. 472-478. Sankar, W.N., C.O. Neubuerger, and C.F. Moseley, Femoral anteversion in developmental dysplasia of the hip. Journal of Pediatric Orthopaedics, 2009. 29(8): p. 885-888.
Jo
1.
14
Journal Pre-proof
21.
22.
of
ro
20.
-p
19.
re
18.
lP
17.
na
16.
ur
15.
Mootha, A.K., et al., MRI evaluation of femoral and acetabular anteversion in developmental dysplasia of the hip. A study in an early walking age group. Acta Orthop Belg, 2010. 76(2): p. 174-180. Murphy, S.B., et al., Femoral anteversion. The Journal of Bone & Joint Surgery, 1987. 69(8): p. 1169-1176. Tönnis, D. and A. Heinecke, Current Concepts Review-Acetabular and Femoral Anteversion: Relationship with Osteoarthritis of the Hip. The Journal of Bone & Joint Surgery, 1999. 81(12): p. 1747-70. Dostal, W.F. and J.G. Andrews, A three-dimensional biomechanical model of hip musculature. Journal of Biomechanics, 1981. 14(11): p. 803-812. CDC, Centers for Disease and Prevention, "Birth to 24 months: Girls Length-for-age percentiles and Weight-for-age percentiles," http://www.cdc.gov/growthcharts/who_charts.htm 2009. Drillis, R. and R. Contini, Body Segment Parameters. 1966, New York University School of Engineering and Science: New York. Narayanan, U., et al., Reliability of a New Radiographic Classification for Developmental Dysplasia of the Hip. Journal of Pediatric Orthopaedics, 2015. 35(5): p. 478. Grill, F., et al., The Pavlik Harness in the Treatment of Congenital Dislocating Hip: Report on a Multicenter Study of the European Paediatric Orthopaedic Society. Journal of Pediatric Orthopaedics, 1988. 8(1): p. 1-8. Tuhanioğlu, Ü., et al., Evaluation of Late Redislocation in Patients who Underwent Open Reduction and Pelvic Osteotomy as Treament for Developmental Dysplasia of the Hip. HIP International. 0(0): p. hipint.5000571.
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Journal Pre-proof Highlights:
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Increased femoral anteversion may decrease success of Pavlik harness treatment Hip external rotation and decreased abduction facilitates Pavlik harness treatment Femoral anteversion influence is minimal until anteversion approaches 70 degrees Increased external rotation using hyperflexion could facilitate closed reduction
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