Most dogs adapt well to amputation of a limb and return to normal levels of activity within a month after surgical removal of a limb1; however, the biomechanical impact of limb amputation on the remaining musculoskeletal system is not known. Pelvic limb amputation is thought to impair balance and locomotor function as a result of increased weight bearing on the RPL and increased vertebral range of motion attributable to asymmetric support and propulsion of the pelvic limb.2,3 Investigators in 1 study2 found that peak vertical forces and impulses across all limbs are comparable between pelvic limb amputees and quadruped dogs. However, the stance duration is decreased in amputees, which indicates that the same force is still applied to the limbs but over a shortened time period.2 In quadruped dogs, decreased stance duration is typically associated with increased velocity2; however, in pelvic limb amputees, the decreased stance duration is a result of an increase in limb cadence and not because of an increase in overall velocity.2 Consequently, examining the adaptations made by amputees during trotting is of importance. Additionally, it has been proposed that as velocity increases, the rigor of the test also increases,4 such that amputee dogs may have different adaptations during trotting than those observed for amputee dogs at a walking velocity.
Pelvic limb amputation also causes a redistribution of weight bearing in the limbs in that 74% of body weight is supported by the 2 thoracic limbs and 26% is supported by the RPL during walking.2 Analysis of gait kinetics indicates that a typical quadruped dog supports 60% of its body weight on the thoracic limbs and 40% on the pelvic limbs during walking.2 To fully understand the effects of altered limb loading after amputation on the entire musculoskeletal system, additional alterations in limb and vertebral kinematics need to be examined. A study3 on balance in trotting dogs reveals that rotational forces about the transverse and sagittal axes of the trunk are countered by placement of the diagonal limb pair during the stance phase. Pelvic limb amputation removes the contralateral limb support for one of the thoracic limbs; thus, there must be substantial limb or vertebral compensation to maintain balance and trunk support or core stability.
The purpose of the study reported here was to objectively characterize differences in the gait during trotting for client-owned pelvic limb–amputee dogs and a cohort of client-owned quadruped dogs that had orthopedic, neurologic, or other related comorbidities similar to those of the amputee dogs, thus reflecting patient conditions in a clinical environment. We hypothesized that limb loading and joint motion would be significantly increased in pelvic limb–amputee dogs, with an increased range of motion in the joints of the remaining limbs and increased GRFs in all limbs.
Contralateral thoracic limb
Cervicothoracic vertebral region
Ground reaction force
Ipsilateral thoracic limb
Lumbosacral vertebral region
Remaining pelvic limb
Thoracolumbar vertebral region
Roberts indoor/outdoor double-sided carpet tape, QEP, Boca Raton, Fla.
Model BP400600-1000 force platforms, AMTI Inc, Watertown, Mass.
Model OR6-5-1000 force platforms, AMTI Inc, Watertown, Mass.
Motus, version 9.0, Vicon Motion Systems Inc, Centennial, Colo.
Dinion, Bosch Security Systems Inc, Fairport, NY.
MEK-92-PAD, Mekontrol, Richardson, Tex.
G*Power 3, version 20, release 3.1.5, Heinrich Heine Universität Düsseldorf, Düsseldorf, Germany. Available at: www.psycho.uni-duesseldorf.de/abteilungen/aap/gpower3/. Accessed Jan 8, 2013.
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