Pin loosening is a frequent complication associated with the use of halo orthoses. Efforts to reduce pin loosening incidence include increasing the number of halo pins, increasing the torque specification, and proactively retightening the halo pins. Although these approaches lower pin loosening incidence rates, none addresses the cause of pin loosening, which is the inability of current halo ring designs to accommodate changes in geometry of the skull. A novel four-pin adaptive halo ring is introduced that can accommodate changes in geometry of the skull and provide a nearly constant pin force. To quantify pin loosening in a halo ring, tests were performed using a fixture that was capable of simulating the changes in skull geometry that are responsible for pin loosening. Both the four-pin adaptive halo and a conventional halo were tested. After 1.1mm of radial recession of the skull at the pin site, the average halo pin force in the conventional halo decreased by 78% while the average halo pin force in the four-pin adaptive halo decreased by 12%. In addition, the four-pin adaptive halo had significantly less variation in initial halo pin force (p-value <0.0001) than that of the four-pin adaptive halo.

1.
Perry
,
J.
, and
Nickel
,
V. L.
, 1959, “
Total Cervical-Spine Fusion for Neck Paralysis
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
41-A
, pp.
37
59
.
2.
Botte
,
M. J.
,
Garfin
,
S. R.
,
Byrne
,
T. P.
,
et al.
, 1989, “
The Halo Skeletal Fixator, Principles of Application and Maintenance
,”
Clin. Orthop. Relat. Res.
0009-921X,
239
, pp.
12
17
.
3.
Garfin
,
S. R.
,
Botte
,
M. J.
,
Waters
,
R. L.
, and
Nickel
,
V. L.
, 1986, “
Complications in the Use of the Halo Fixation Device
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
68-A
, pp.
320
325
.
4.
Botte
,
M. J.
,
Byrne
,
T. P.
, and
Garfin
,
S. R.
, 1987, “
Application of the Halo Device for Immobilization of the Cervical Spine Utilizing an Increase Torque Pressure
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
69-A
, pp.
750
52
.
5.
Botte
,
M. J.
,
Byrne
,
T. P.
,
Abrams
,
R. A.
, and
Garfin
,
S. R.
, 1995, “
The Halo Skeletal Fixator: Current Concepts of Application and Maintenance
,”
Orthopedics
0147-7447,
18
, pp.
463
71
.
6.
Fleming
,
B. C.
,
Huston
,
D. R.
,
Krag
,
M. H.
, and
Shigeaki
,
S.
, 1998, “
Pin Force Measurement in a Halo-Vest Orthosis, In Vivo
,”
J. Biomech.
0021-9290,
31
, pp.
647
651
.
7.
Voor
,
M.
, and
Khalily
,
C.
, 1998, “
Halo Pin Loosening: A Biomedical Comparison of Experimental and Conventional Designs
,”
J. Biomech.
0021-9290,
31
, pp.
397
400
.
8.
Letts
,
M.
,
Girourard
,
L.
, and
Yeadon
,
A.
, 1997, “
Mechanical Evaluation of Four—Versus Eight-Pin Halo Fixation
,”
J. Pediatr. Orthop.
0271-6798,
17
, pp.
121
124
.
9.
Vertullo
,
C.
,
Duke
,
P.
, and
Askin
,
G.
, 1997, “
Pin-Site Complications of the Halo Thoracic Brace With Routine Pin Re-Tightening
,”
Spine
0362-2436,
22
, pp.
2514
2516
.
10.
Nemeth
,
J. A.
, and
Mattingly
,
L. G.
, 2001, “
Six-Pin Halo Fixation and the Resulting Prevalence of Pin-Site Complications
,”
J. Bone Jt. Surg., Am. Vol.
0021-9355,
83-A
, pp.
377
382
.
11.
Kuester
,
W. M.
, 2002, “
An Investigation of Skull Constraint During Treatment With a Four-Pin Halo Orthosis
,” thesis, Rose-Hulman Institute of Technology.
12.
Voor
,
M. J.
,
Anderson
,
R. C.
, and
Hart
,
R. T.
, 1997, “
Stress Analysis of Halo Pin Insertion by Non-Linear Finite Element Modeling
,”
J. Biomech.
0021-9290,
30
, pp.
903
909
.
13.
Stamper
,
R. E.
,
Kuester
,
W. M.
, and
Meek
,
M. P.
, 2002, “
Design and Testing of a Halo Orthosis to Reduce Pin Loosening Using Constraint Analysis
,”
ASME Design Engineering Technical Conferences
,
Montreal, QC, Canada
, Sept.
14.
Whitesides
,
T. E.
,
Mehserle
,
W. L.
, and
Hutton
,
W. C.
, 1992, “
The Force Exerted by the Halo Pin, a Study Comparing Different Halo Systems
,”
Spine
0362-2436,
17
, pp.
413
417
.
You do not currently have access to this content.