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Technical Brief

A Comparison of the Contact Force Distributions on the Acetabular Surface Due to Orthopedic Treatments for Developmental Hip Dysplasia

[+] Author and Article Information
Kalenia M. Márquez-Flórez

Department of Mechanical and Mechatronics Engineering,
Numerical Methods and Modeling Research Group
(GNUM),
Universidad Nacional de Colombia,
Bogotá 111321142, Colombia
e-mail: kmmarquezf@unal.edu.co

Octavio Silva

Department of Physical Medicine and Rehabilitation,
Universidad Nacional de Colombia,
Bogotá 111321142, Colombia
e-mail: osilvac@unal.edu.co

Carlos A. Narváez-Tovar

Department of Mechanical and Mechatronics Engineering,
Numerical Methods and Modeling Research Group
(GNUM),
Universidad Nacional de Colombia,
Bogotá 111321142, Colombia
e-mail: canarvaezt@unal.edu.co

Diego A. Garzón-Alvarado

Department of Mechanical and Mechatronics Engineering,
Numerical Methods and Modeling Research Group
(GNUM),
Universidad Nacional de Colombia, Bogotá 111321142, Colombia
e-mail: dagarzona@unal.edu.co

1Corresponding author.

Manuscript received November 14, 2015; final manuscript received April 28, 2016; published online June 7, 2016. Assoc. Editor: David Corr.

J Biomech Eng 138(7), 074501 (Jun 07, 2016) (7 pages) Paper No: BIO-15-1589; doi: 10.1115/1.4033547 History: Received November 14, 2015; Revised April 28, 2016

We used a three-dimensional rigid body spring model (RBSM) to compare the contact force distributions on the acetabular surface of the infant hip joint that are produced by three orthopedic treatments for developmental dysplasia of the hip (DDH). We analyzed treatments using a Pavlik harness, a generic rigid splint, and a spica cast. The joint geometry was modeled from tomography images of a 1-year-old female. The articular cartilage was modeled as linear springs connecting the surfaces of the acetabulum and the femoral head, whereas the femur and the hip bone were considered as rigid bodies. The hip muscles were modeled as tensile-only preloaded springs. The treatments with the Pavlik harness and the generic rigid splint were modeled for an infant in supine position with a hip flexion angle of 90 deg. Also, since rigid splints are often recommended when children are initiating their gait phase, we modeled the treatment with the infant in standing position. For the spica cast, we only considered the infant in standing position with a flexion angle of 0 deg, and the fixation bar at two heights: at the ankle and at the knee. In order to analyze the effect of the hip abduction angle over the contact force distribution, different abduction angles were used for all the treatments modeled. We have found that the treatments with the infant in supine position, with a flexion angle of 90 deg and abduction angles between 60 deg and 80 deg, produce a more homogenous contact force distribution compared to those obtained for the treatments with the infant in standing position.

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References

Figures

Grahic Jump Location
Fig. 3

Support conditions for each treatment. (a) Infant in supine position using a Pavlik harness: the distal part of the leg can rotate and move on its own longitudinal axis, the foot sole can move along a plane transversal to the body, and the pelvis is fixed; (b) infant in supine position using a rigid splint: the pelvis is fixed and the leg can only move along the femoral longitudinal axis; (c) infant in standing position using a rigid splint: the pelvis can only move on the longitudinal axis of the body, the leg in the longitudinal femoral direction, and the foot sole has a planar restriction simulating the normal force exerted by the floor; (d) infant in standing position using a spica cast with the fixation bar at knee height: the pelvis can only move on the longitudinal axis of the body, the leg has been restricted to move only on a sagittal plane at knee height, and the foot sole has a planar restriction simulating the normal force of the floor; (e) infant in standing position using a spica cast with the fixation bar at ankle height: the pelvis can only move on the longitudinal axis of the body, the leg has been restricted to move only on a sagittal plane at ankle height, and the foot sole has a planar restriction simulating the normal force of the floor; and (f) infant with no orthopedic treatment: the pelvis can only move on the longitudinal axis of the body and the foot sole has a planar restriction simulating the normal force of the floor.

Grahic Jump Location
Fig. 2

Positions for the infant leg using a Pavlik harness, a rigid splint, a spica cast, and with no treatment at all, and schemes used to calculate the CG for any abduction angle (r) in supine position, (s) in standing position (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, (e) 60 deg, (f) 80 deg, (g) 0 deg, (h) 20 deg, (i) 40 deg, (j) 45 deg, (k) 60 deg, (l) 80 deg, (m) 0 deg, (n) 20 deg, (o) 40 deg, (p) 45 deg, (q) 60 deg

Grahic Jump Location
Fig. 1

Treatment cases modeled: (a) infant in supine position using a Pavlik harness, (b) infant using a rigid splint in supine and standing positions, (c) infant using a spica cast in standing position, (d) infant in standing position with no treatment

Grahic Jump Location
Fig. 4

Contact force distribution when the infant is using a Pavlik harness in supine position with leg flexed 90 deg and abduction angles of: (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, (e) 60 deg, and (f) 80 deg

Grahic Jump Location
Fig. 5

Contact force distribution when the infant is using a rigid splint in supine position with leg flexed 90 and abduction angles of (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, (e) 60 deg, and (f) 80 deg

Grahic Jump Location
Fig. 6

Contact force distribution when the infant is using a Milgram splint standing upright with leg flexed 90 deg and abduction angles of: (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, (e) 60 deg, and (f) 80 deg

Grahic Jump Location
Fig. 7

Contact force distribution when the infant is using a spica cast standing upright with the fixation bar at knee height and abduction angles of: (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, and (e) 60 deg

Grahic Jump Location
Fig. 8

Contact force distribution when the infant is using a spica cast standing upright with the fixation bar at ankle height and abduction angles of: (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, and (e) 60 deg

Grahic Jump Location
Fig. 9

Contact force distribution when the infant is standing upright with no treatment for abduction angles of: (a) 0 deg, (b) 20 deg, (c) 40 deg, (d) 45 deg, and (e) 60 deg

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