Circular external fixation frames with divergent half pins: a pilot biomechanical study.
The use of hexapod circular external fixators has simplified the ability to correct complex limb deformities without cumbersome frame reconfigurations. These frames are applied primarily using half pin mountings and may be difficult to utilize given the constraints of traditional half pin constructs. We compared the biomechanical performance of simplified divergent half pin frames to mountings currently being utilized for application of hexapod frames. Three 6-mm half pins per limb segment were placed into sawbones at 60 degree divergent angles in both the sagittal and coronal planes in a 2-cm diaphyseal fracture gap model. Pin mountings were attached to a standardized four-ring construct. This was compared to similar four-ring frames with two differing pin/wire configurations: (1) two tensioned wires per ring placed at 90 degree angles, a total eight wires; and (2) two 5-mm half pins per ring placed at 90 degree angles, a total eight half pins. The divergent 6-mm half pin frames demonstrated similar performance compared the standardized tensioned wire and 5-mm half pin frames in terms of axial micromotion and angular deflection. Based on the mechanical performance of these divergent half pin frames we believe they can be used clinically without detrimental consequences.
Lenarz
Christopher
C
Department of Orthopaedic Surgery and Biomechanics, St. Louis University, St. Louis, MO 63110 USA.
Bledsoe
Gary
G
Watson
J Tracy
JT
D001696:Biomechanical Phenomena; D001852:Bone Lengthening / Q000295:instrumentation*; D001858:Bone Nails; D004867:Equipment Design; D016267:External Fixators; D006801:Humans; D013978:Tibial Fractures / Q000601:surgery*
J Orthop Trauma. 2003 Jul;17(6):415-20
12843726
J Bone Joint Surg Am. 2006 Dec;88 Suppl 4:156-74
17142445
Clin Orthop Relat Res. 1983 Sep;(178):103-10
6883844
Clin Orthop Relat Res. 1983 Sep;(178):111-20
6883845
Clin Orthop Relat Res. 1983 Nov;(180):50-62
6627797
Clin Orthop Relat Res. 1989 Apr;(241):15-23
2647333
Clin Orthop Relat Res. 1989 Apr;(241):24-35
2647334
Clin Orthop Relat Res. 1989 Apr;(241):36-47
2924478
Clin Orthop Relat Res. 1989 Apr;(241):48-56
2924479
Clin Orthop Relat Res. 1989 Apr;(241):5-14
2924480
J Biomech Eng. 1990 Feb;112(1):15-21
2308299
Orthop Clin North Am. 1991 Oct;22(4):677-88
1945345
Clin Orthop Relat Res. 1992 Jul;(280):104-16
1611729
Clin Orthop Relat Res. 1992 Jul;(280):11-4
1611730
Clin Orthop Relat Res. 1992 Jul;(280):15-22
1611735
Clin Orthop Relat Res. 1993 Aug;(293):28-36
8339493
Clin Orthop Relat Res. 1993 Aug;(293):61-70
8339510
J Appl Biomater. 1995 Summer;6(2):99-104
7640445
J Orthop Trauma. 1999 Jan;13(1):20-6
9892121
J Orthop Trauma. 1999 Aug;13(6):418-25
10459601
J Bone Joint Surg Br. 2005 Jun;87(6):868-72
15911676
J Trauma. 2005 Jun;58(6):1213-22
15995473
Am J Sports Med. 2005 Nov;33(11):1735-41
16093544
J Am Acad Orthop Surg. 2006;14(10 Spec No.):S168-74
17003192
J Orthop Res. 2003 Nov;21(6):1011-7
14554213