A new method for evaluating ankle foot orthosis characteristics: BRUCE.

The mechanical characteristics of ankle foot orthoses (AFOs), such as the stiffness and neutral angle around the ankle and metatarsal-phalangeal (MTP) joints, are rarely quantified. Paradoxically, it is expected that these characteristics determine the function of the AFO in pathological gait. Therefore a device to determine these AFO characteristics named BRUCE was designed based on multidisciplinary consensus. The design is based on a replicated human leg that is manually driven and continuously registers joint configuration and force exerted by the AFO onto the device. From this information, neutral angles and stiffnesses around the ankle and MTP joints are determined using a linear fit. The reliability of the stiffnesses and neutral angles was studied by repeatedly measuring the mechanical characteristics of four different AFOs, and evaluating the inter-session, intra-session, and inter-observer errors. The reliability study revealed that ankle and MTP stiffness could be measured with very high reliability (ICC=0.98-1.00). Ankle and MTP neutral angles showed reasonable reliability (ICC=0.79-0.92). Measurement error in the neutral angles could mainly be attributed to the difference in testers. With a fixed tester excellent reliability was obtained (ICC=0.99-0.99). The results derived using BRUCE can help to gain insight into the role of the mechanical characteristics of AFOs in correcting pathological gait. Objective information of AFO characteristics is expected to lead to a better founded prescription of AFOs, resulting in optimal functional benefit for the patient.

[1]  Joseph M. Mansour,et al.  Design Changes in Ankle-Foot Orthosis Intended to Alter Stiffness Also Alter Orthosis Kinematics , 1999 .

[2]  J. Geertzen,et al.  Development of Clinical Guidelines for the Prescription of Orthoses in Patients with Neurological Disorders in The Netherlands , 2006, Prosthetics and orthotics international.

[3]  S. Miyazaki,et al.  Effect of ankle-foot orthosis on active ankle moment in patients with hemiparesis , 1997, Medical and Biological Engineering and Computing.

[4]  External tibial torsion and the effectiveness of the solid ankle-foot orthoses. , 2000, Journal of pediatric orthopedics.

[5]  Derick T Wade,et al.  Relative contribution of footwear to the efficacy of ankle-foot orthoses , 2003, Clinical rehabilitation.

[6]  Kaat Desloovere,et al.  How can push-off be preserved during use of an ankle foot orthosis in children with hemiplegia? A prospective controlled study. , 2006, Gait & posture.

[7]  Richard J. Shavelson,et al.  Generalizability Theory: A Primer , 1991 .

[8]  Elena M Gutierrez-Farewik,et al.  Effects of carbon fibre spring orthoses on gait in ambulatory children with motor disorders and plantarflexor weakness , 2007, Developmental medicine and child neurology.

[9]  P Cappa,et al.  A novel device to evaluate the stiffness of ankle-foot orthosis devices. , 2003, Journal of biomechanical engineering.

[10]  P. Cappa,et al.  A continuous loading apparatus for measuring three-dimensional stiffness of ankle-foot orthoses. , 2005, Journal of biomechanical engineering.

[11]  R. Major,et al.  A new structural concept in moulded fixed ankle foot orthoses and comparison of the bending stiffness of four constructions , 2004, Prosthetics and orthotics international.

[12]  A. Danielsson,et al.  Energy expenditure in stroke subjects walking with a carbon composite ankle foot orthosis. , 2004, Journal of rehabilitation medicine.

[13]  Elena M Gutierrez-Farewik,et al.  A new carbon fibre spring orthosis for children with plantarflexor weakness. , 2007, Gait & posture.

[14]  Y Suzuki,et al.  Stiffness control in posterior-type plastic ankle-foot orthoses: Effect of ankle trimline Part 2: Orthosis characteristics and orthosis/patient matching , 1996, Prosthetics and orthotics international.

[15]  Y Suzuki,et al.  Stiffness control in posterior-type plastic ankle-foot orthoses: Effect of ankle trimline Part 1: A device for measuring ankle moment , 1996, Prosthetics and orthotics international.

[16]  A Leardini,et al.  Position and orientation in space of bones during movement: anatomical frame definition and determination. , 1995, Clinical biomechanics.

[17]  Development of a Testing Apparatus for Structural Stiffness Evaluation of Ankle-Foot Orthoses , 2001 .

[18]  A. Verbeek,et al.  Walking ability of stroke patients: efficacy of tibial nerve blocking and a polypropylene ankle-foot orthosis. , 1996, Archives of physical medicine and rehabilitation.

[19]  Adam Rozumalski,et al.  Quantifying the Spring-Like Properties of Ankle-Foot Orthoses (AFOs) , 2007 .

[20]  Maarten J. IJzerman,et al.  The effect of an ankle-foot orthosis on walking ability in chronic stroke patients: a randomized controlled trial , 2004, Clinical rehabilitation.

[21]  Sumiko Yamamoto,et al.  Comparative Study of Mechanical Characteristics of Plastic AFOs , 1993 .

[22]  R. Brand,et al.  The biomechanics and motor control of human gait: Normal, elderly, and pathological , 1992 .

[23]  J. Harlaar,et al.  The application of generalizability theory to reliability assessment: an illustration using isometric force measurements. , 1993, Physical therapy.