Locking Plate System For The Management Of Unstable Diaphyseal, Metaphyseal Fractures Of Femur, Humerus And Radius In Dogs
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Date
2011
Journal Title
Journal ISSN
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Publisher
Tamil Nadu Veterinary and Animal Sciences University
Abstract
The study was carried out in 22 dogs of different breeds, sex and body weight
ranging from 10 to 30 kgs presented to the Small Animal Orthopaedic Unit of the
Madras Veterinary College Teaching Hospital with history of lameness and clinical
symptoms suggestive of unstable diaphyseal or metaphyseal fractures involving the
humerus, radius and femur. Thirteen cases of unstable diaphyseal long bone fractures
and nine cases of unstable metaphyseal long bone fractures were treated with locking
plate system under C-arm guidance. In the present study, Road Traffic Accident
(40.8%) was the primary cause for the fracture in dogs followed by fall from height
(18.3%), unknown cause (18.3%), slipped on the floor (13.5%), falling down when
playing (9.1%).
A cranio-lateral approach to the fracture of humerus and femur and medial and dorsal
approach to the diaphysis and metaphysis of radius were surgical approaches
undertaken in this study. Diaphyseal fractures were stabilized by open reduction and
internal fixation using linear 2.7mm and 3.5mm locking compression plates, distal
radial fractures were stabilized by open reduction and internal fixation using 3.5mm
locking ‘T’ plates and one case of condylar fracture was stabilized by open reduction
and internal fixation using 3.5mm locking condylar plate. Plates were applied as abuttress in comminuted fractures and as a compression in transverse fractures.
Locking ‘T’ plates and locking condylar plates were developed for the study.
The functional outcome was graded excellent, good, fair and poor based
on post operative assessment. One case was lost at follow up. Radiographic
evaluation of clinical cases indicated either primary healing with no callus formation
in cases subjected to compression plating or secondary healing in cases subjected to
buttress plating and was related to stability at the fracture site. Dependent oedema,
seroma formation, self mutilated wound, stress protection and exposure of plate was
the postoperative complications encountered during the study.
The fluorimetric reading of peak absorbance of pre and 45 th post operative day
serum showed increased intensity of BSAP at 45 th post operative day as compared to
values of pre operative samples indicating osteogenic activity and progressive fracture
healing.
Biomechanical studies were carried out on screw pullout strength, bending
strength of on bone, bone plate, bone plate construct and gap model. The mean screw
pull out strength on humeral diaphysis showed an yield load of 749.33±5.7019 N and
ultimate load of 813.83 ± 1.7401N whereas humeral metaphysis showed an yield load
of 501.50 ± 7.6365 N and an ultimate load of 540.67 ± 2.8245 N. Hence
comparatively, it is inferred that the screw pull out strength on diaphysis was stronger
when compared with metaphysis.
In the present study, it was observed that the mean bending load for
mechanical failure of femur, 3.5mm linear locking compression plate, linear locking
compression bone plate construct and linear locking compression plate construct with
gap model was 1520.33±5.34N, 1670.16±8.89N, 215.33±3.71N and 319.66±5.26N
respectively. In the present study, the yield load of linear locking compression plate
construct was 1670.16N (167 kgs) which was almost eight times greater than the
average body weight of a dog. Similarly, the bending strength of the linear locking
compression plate construct was significantly lower than the individual strength of
either bone or the linear locking compression plate.
In the present study, the locking compression plating technique provided
adequate apposition, stable fixation and promoted early weight bearing of traumatized
limb. The locking plate system had a unique combi hole design in a single implantand enabled to select the function best suited for the fracture configuration to achieve
the most stable fixation. The locking plate system acted as a single beam construct
which increased the stiffness of the implant and was effective in management of
unstable diaphyseal and metaphyseal simple and comminuted fractures of humerus,
radius and femur.