Background. Partial or nonweight bearing is a useful treatment prescribed by medical professionals (e.g., orthopedists, podiatrists) for patients rehabilitating from lower extremity injuries However, there is significant variability in patient conformance with the commonly used, but very imprecise “weight scale method.” Furthermore, the few commercially available load monitoring devices are rarely used because of their high cost. Method of Approach. As a simple and inexpensive alternative to current load monitoring methods and commercial products, a new medical device called a snap dome weight bearing indicator (WBI) has been developed to gently warn a patient when they have exceeded a limited percentage of their body weight on the recovering leg or foot. When installed in a patient’s shoe or medical appliance, the device does so by utilizing the reversible buckling phenomena of a snap dome to provide a tactile and audible feedback when the prescribed weight has been exceeded. To demonstrate the feasibility of this new device, the performance of (1) the snap dome by itself and (2) several WBI designs developed were tested. The most useful of the new designs include one incorporating a heel cup for loose fitting medical appliances and a podiatric off-loading indicator (POLI). In addition, a pilot study and manufacturing cost analysis of the POLI device were performed to investigate patient usability and affordability issues. Results. The particular four-leg snap domes used in device prototypes performed quite well with regards to buckling load consistency between domes, the linearity of buckling load by stacking domes in a parallel arrangement, and buckling load repeatability of a single dome. The performance of each WBI prototype was tested with regards to load transfer, tactile, and audible feedback to the patient, patient comfort, and ease of installation. Prototype performance was generally very good or excellent except for the POLI device, which does not provide sufficient tactile or audible feedback for many patients. A costing analysis of the POLI device suggests that it can be manufactured in the U.S. for around one dollar. Conclusions. The generally positive results from performance testing of commercially available snap domes and WBI prototypes suggest that this new medical device will indeed be an inexpensive, yet effective conformance tool for orthopedists and podiatrists to use in prescribing partial or no weight bearing for a patient.

1.
Jones
,
H. H.
,
Priest
,
J. D.
,
Hayes
,
W. C.
,
Tichenor
,
C. C.
, and
Nagel
,
D. A.
, 1977, “
Humeral Hypertrophy in Response to Exercise
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
59-A
, pp.
204
228
.
2.
Schmidt
,
A.
, and
Rorabeck
,
C. H.
, 1983, “
Fractures of the Tibia Treated by Flexible External Fixation
,”
Clin. Orthop. Relat. Res.
0009-921X,
178
, pp.
162
172
.
3.
DeBastiani
,
G.
,
Aldigheri
,
R.
, and Renzi
Brivio
,
L.
, 1984, “
The Treatment of Fractures With a Dynamic Axial Fixator
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
6613
, pp.
538
545
.
4.
Meadows
,
T. H.
,
Bronk
,
J. T.
,
Chao
,
E. Y. S.
, and
Kelly
,
P. J.
, 1984, “
Effect of Weight Bearing on Healing of Cortical Defects in the Canine Tibia
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
72-A
(
7
), pp.
1074
1080
.
5.
Rubin
,
C. T.
, and
Lanyon
,
L. E.
, 1984, “
Regulation of Bone Formation by Applied Dynamic Loads
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
66-A
(
3
), pp.
397
402
.
6.
Kenwright
,
J.
, and
Goodship
,
A.
, 1989, “
Controlled Mechanical Stimulation in the Treatment of Tibial Fractures
,”
Clin. Orthop. Relat. Res.
0009-921X,
241
, pp.
36
47
.
7.
Chao
,
E. Y. S.
,
Aro
,
H. T.
,
Lewallen
,
D.
, and
Kelly
,
P.
, 1989, “
Effect of Rigidity on Fracture Healing in External Fixation
,”
Clin. Orthop. Relat. Res.
0009-921X,
241
, pp.
24
35
.
8.
Rubin
,
C. T.
, and
McLeod
,
K.
, 1994, “
Promotion of Bony Ingrowth by Frequency-Specific, Low-Amplitude Mechanical Strain
,”
Clin. Orthop. Relat. Res.
0009-921X,
298
, pp.
165
174
.
9.
Mullender
,
M. G.
, and
Huiskes
,
R.
, 1995, “
Proposal for the Regulatory Mechanism of Wolff’s Law
,”
J. Orthop. Res.
0736-0266,
13
(
4
), pp.
503
512
.
10.
Rubin
,
C. T.
,
Gross
,
T. S.
,
McLeod
,
K.
, and
Bain
,
S. D.
, 1995, “
Morphologic Stages in Lamellar Bone Formation Stimulated by a Potent Mechanical Stimulus
,”
J. Bone Miner. Res.
0884-0431,
10
(
3
), pp.
488
495
.
11.
Rubin
,
C. T.
,
Gross
,
T.
,
Qin
,
Y.-X.
,
Fritton
,
S.
,
Gublak
,
F.
, and
McLeod
,
K.
, 1996, “
Differentiation of the Bone-Tiossue Remodeling Response to Axial and Torsional Loading in the Turkey Ulna
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
78-A
(
10
), pp.
1523
1533
.
12.
McLeod
,
K. J.
,
Rubin
,
C. T.
,
Otter
,
M. W.
, and
Qin
,
Y.-X.
, 1998, “
Skeletal Cell Stresses and Bone Adaptation
,”
Am. J. Med. Sci.
0002-9629,
316
(
3
), pp.
176
183
.
13.
National Osteoporosis Foundation, 2005, “
Fast Facts on Osteoporosis
,” http://www.nof.org/osteoporosis/diseasefacts.htmhttp://www.nof.org/osteoporosis/diseasefacts.htm.
14.
Duscha
,
B. D.
,
Cipriani
,
D. J.
, and
Roberts
,
C. P.
, 1999, “
A Review of Open vs. Closed Kinematic Chain Exercise for Lower Extremity Rehabilitation
,”
Clin. Physiol.
0144-5979,
1
(
2
), pp.
57
63
.
15.
Banks
,
A. S.
, and
McGlamry
,
E. D.
, 1989, “
Charcot Foot
,”
J. Am. Podiatry Assoc.
0003-0538,
79
(
5
), pp.
213
234
.
16.
Armstrong
,
D. G.
,
Todd
,
W. F.
,
Lavery
,
L. A.
,
Harkless
,
L. B.
, and
Bushman
,
T. R.
, 1997, “
The Natural History of Acute Charcot’s Arthropathy in a Diabetic Foot Specialty Clinic
,”
J. Am. Podiatry Assoc.
0003-0538,
87
(
6
), pp.
272
278
.
17.
Sommer
,
T. C.
, and
Lee
,
T. H.
, 2001, “
Charcot Foot: The Diagnostic Dilemma
,”
Am. Fam. Physician
0002-838X,
64
(
9
), pp.
1591
1598
.
18.
Frykberg
,
R. G.
, 2002, “
Diabetic Foot Ulcers: Pathogenesis and Management
,”
Am. Fam. Physician
0002-838X,
66
(
9
), pp.
1655
1662
.
19.
Walczyk
,
D. F.
, and
Kerdok
,
A. E.
, 2002 “
Mechanical Weight Bearing Indicator for the Foot
,” U.S. Patent No. 6,405,606.
20.
Baxter
,
M. L.
,
Allington
,
R. O.
, and
Koepke
,
G. H.
, 1969, “
Weight-distribution Variables in the Use of Crutches and Canes
,”
Phys. Ther.
0031-9023,
49
(
4
), pp.
360
365
.
21.
Winstein
,
C. J.
,
Christensen
,
S.
, and
Fitch
,
N.
, 1993, “
Effects of Summary Knowledge of Results on the Acquisition and Retention of Partial Weight Bearing During Gait
,”
Phys. Ther.
0031-9023,
2
(
4
), pp.
40
51
.
22.
Winstein
,
C. J.
,
Pohl
,
P. S.
,
Cardinale
,
C.
,
Green
,
A.
,
Scholtz
,
L.
, and
Waters
,
C. S.
, 1996, “
Learning a Partial-Weight-Bearing Skill, Effectiveness of Two Forms of Feedback
,”
Phys. Ther.
0031-9023,
76
(
9
), pp.
985
993
.
23.
Gray
,
F. B.
,
Gray
,
C.
, and
McClanahan
,
J. W.
, 1998, “
Assessing the Accuracy of Partial Weight-Bearing Instruction
,”
Am. J. Orthop.
0065-9002,
27
(
8
), pp.
558
60
.
24.
Tveit
,
M.
, and
Kärrholm
,
J.
, 2001, “
Low Effectiveness of Prescribed Partial Weight Bearing, Continuous Recording of Vertical Loads Using a New Pressure-Sensitive Insole
,”
J. Rehabil.
0022-4154,
33
, pp.
42
46
.
25.
Dabke
,
H. V.
,
Gupta
,
S. K.
,
Holt
,
C. A.
,
O’Callaghan
,
P.
, and
Dent
,
C. M.
, 2004, “
How Accurate is Partial Weightbearing?
,”
Clin. Orthop. Relat. Res.
0009-921X,
421
, pp.
282
286
.
26.
Warren
,
C. G.
, and
Lehmann
,
J. F.
, 1975, “
Training Procedures and Biofeedback Methods to Achieve Controlled Partial Weight Bearing: An Assessment
,”
Arch. Phys. Med. Rehabil.
0003-9993,
56
, pp.
449
455
.
27.
Batavia
,
M.
,
Gianutsos
,
J. G.
,
Vaccaro
,
A.
, and
Gold
,
J. T.
, 2001, “
A Do-It-Yourself Membrane-Activated Auditory Feedback Device for Weight Bearing and Gait Training, A Case Report
,”
Arch. Phys. Med. Rehabil.
0003-9993,
82
, pp.
541
545
.
28.
Gradisar
,
I. A.
, 1972, “
Partial Weight Bearing Warning Device
,” U.S. Patent No. 3,702,999.
29.
Pfeiffer
,
E. A.
, 1974, “
Device for Sensing and Warning of Excessive Ambulation Force
,” U.S. Patent No. 3,791,375.
30.
Sipe
,
J. J.
, 1974, “
Load Signaling Device for a Patient’s Foot
,” U.S. Patent No. 3,974,491.
31.
Goforth
,
W. P.
, 1987, “
Multi-event Notification System for Monitoring Critical Pressure Points on Persons With Diminished Sensation of the Foot
,” U.S. Patent No. 4,647,918.
32.
Confer
,
R. G.
, 1988, “
Force Sensing Insole for Electro-Goniometer
,” U.S. Patent No. 4,745,930.
33.
Ratzlaff
,
M. H.
,
Grant
,
B. D.
, and
Frame
,
J. M.
, 1989, “
Systems for Measurement and Analysis of Forces Exerted During Human Locomotion
,” U.S. Patent No. 4,814,661.
34.
Sugarman
,
E. D.
,
D’Antonio
,
N. F.
, and
D’Antonio
,
N. J.
, 1989, “
Warning System for Excessive Orthopedic Pressures
,” U.S. Patent No. 4,858,620.
35.
Gray
,
F. B.
, 1993, “
Force Monitoring Shoe
,” U.S. Patent No. 5,269,081.
36.
Thomas
,
B. R.
,
Steinman
,
H.
, and
Alley
,
S. D.
, 1993, “
Orthopedic Weight Monitor
,” U.S. Patent No. 5,253,654.
37.
Fullen
,
G.
, and
Fullen
,
J. G.
, 1994, “
System for Continuously Measuring Forces Applied to the Foot
,” U.S. Patent No. 5,323,650.
38.
Gray
,
F. B.
, and
Parris
,
J. L.
, 1994, “
Device for Measuring Force Applied to a Wearer’s Foot
,” U.S. Patent No. 5,357,696.
39.
Schmidt
,
R. N.
,
Chizeck
,
H. J.
, and
Diefes
,
R. S.
, 1995, “
Foot Force Sensor
,” U.S. Patent No. 5,408,873.
40.
Schmidt
,
R. N.
, and
Diefes
,
R. S.
, 1997, “
Foot Weight Alarm
,” U.S. Patent No. 5,619,186.
41.
Bechmann
,
P.
, 2000, “
Load Signaling Device for a Patient’s Foot
,” U.S. Patent No. 6,031,463.
42.
Gray
,
F. B.
,
Parris
,
J. L.
,
Gray
,
D. H.
, and
Riffert
,
R. G.
, 2000, “
Force Monitoring Shoe
,” U.S. Patent No. 6,122,846.
45.
Kinsler
,
L. E.
, 1982,
Fundamentals of Acoustics
,
3rd ed.
,
Wiley
,
New York
.
46.
Bartlet
,
J. P.
, 2006, “
Design and Development of a Weight Bearing Indicator
,” MS thesis, Department of Mechanical, Aerospace, & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY.
49.
Planet Products, 1996, “PedAlert™ 100 & PedAlert™ 120 Operator’s Manual,” Planet Products, LLC, Madison, WI.
You do not currently have access to this content.