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Design Innovation Paper

New Adjustable Unloader Knee Brace and Its Effectiveness

[+] Author and Article Information
Gajendra Hangalur, Ryan Bakker, Naveen Chandrashekar

Mechanical and Mechatronics Engineering,
University of Waterloo,
Waterloo, ON N2 L 3G1, Canada
e-mail: nchandra@uwaterloo.ca

Sebastian Tomescu

Sunnybrook Health Sciences Centre,
University of Toronto,
43 Wellesley Street East,
Toronto, ON M4Y 1H1, Canada

Manuscript received November 8, 2016; final manuscript received October 16, 2017; published online November 22, 2017. Assoc. Editor: Elizabeth Hsiao-Wecksler.

J. Med. Devices 12(1), 015001 (Nov 22, 2017) (5 pages) Paper No: MED-16-1357; doi: 10.1115/1.4038439 History: Received November 08, 2016; Revised October 16, 2017

Unloader knee braces are prescribed for patients with unicompartmental osteoarthritis of the knee. These braces aim to reduce pain in patients by applying a coronal moment to the knee to unload the symptomatic knee compartment. However, existing unloading mechanisms use straps that go directly behind the knee joint, to apply the needed moment. This can impinge on the popliteal artery and peroneal nerves thereby causing discomfort to the patient. Hence, these braces cannot be worn for prolonged periods of time. This research focused on developing a new knee brace to improve comfort while unloading the osteoarthritic knee. A new knee brace was developed that uses a four-point bending approach to unload the knee. In this brace, unloading can be adjusted, and the unloading mechanism is away from the joint. The new brace was tested on a cadaver specimen to quantify its capability to unload the knee compartment. The brace was also worn by a patient with osteoarthritis who subjectively compared it to his existing unloader brace. During cadaver testing, the new brace design could reduce the force exerted on the medial condyle by 25%. Radiographic images of the patient's knee confirmed that the brace unloaded the medial condyle successfully. The patient reported that the new brace reduced pain, was significantly comfortable to wear and could be used for a longer duration in comparison to his existing brace.

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References

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Figures

Grahic Jump Location
Fig. 1

The new adjustable unloader brace. “U” are the uprights, P is the polycentric joint, and “T” are the thermoplastic cases for thigh and shank.

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Fig. 2

New adjustable knee brace upright link. Assembly components: (1) thermoplastic case, (2) outer upright, (3) spring plate, (4) floating hinge, (5) lever arm, (6) set screw, (7) inner upright, and (8) polycentric joint

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Fig. 3

Additional views of the assembly: (a) medial, (b) sagittal, and (c) lateral views. All dimensions are in millimeter.

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Fig. 4

Unloader mechanism: (a) straight position and (b) unloaded position

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Fig. 5

(a) Frontal, (b) sagittal, and (c) backside view of the newly designed brace. The arrows in (a) show the direction of the forces applied by the rigid case on the leg. “S” are the straps.

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Fig. 6

Cyclic testing machine: (1) brace linkage, (2) and (3) slider crank mechanism, and (4) tester frame

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Fig. 7

Tekscan pressure distribution plot of cadaver knee with 580 N compressive load: (a) without brace, indicating 480 N force in the medial condyle and (b) with brace, showing 360 N through the medial condyle. P, posterior; L, lateral. Each sensel is 1.29 mm2.

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Fig. 8

X-rays of unbraced (a) and braced (b) knee under nonweight bearing condition. The dark lines show the change in angle between the condylar surfaces.

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