Objective—To provide a quantitative description of the
architecture of superficial digital flexor (SDF) and deep
digital flexor (DDF) muscles in adult horses to predict
muscle-tendon behavior and estimate muscle forces.
Sample Population—7 forelimb specimens from 7
Procedure—Muscle and tendon lengths and volumes
were measured from 6 fixed forelimbs. After processing,
fiber bundle and sarcomere lengths were
measured. Optimal fascicle lengths and muscle
length-to-fascicle length, muscle length-to-free tendon
length, and fascicle length-to-tendon length ratios
were calculated, as were tendon and muscle physiologic
cross-sectional areas (PCSAs). Pennation angles
were measured in 1 embalmed specimen.
Results—The SDF optimal fascicle lengths were uniformly
short (mean ± SD, 0.8 ± 0.1 cm), whereas DDF
lengths ranged from 0.9 ± 0.2 cm to 10.8 ± 1.6 cm.
The DDF humeral head had 3 architectural subunits,
each receiving a separate median nerve branch, suggestive
of neuromuscular compartmentalization.
Pennation angles were small (10o to 25o). The PCSAs
of the SDF and DDF muscle were 234 ± 51 cm2 and
259 ± 30 cm2, with estimated forces of 4,982 ± 1148
N and 5,520 ± 544 N, respectively.
Conclusions and Clinical Relevance—The SDF
muscle appears to provide strong tendinous support
with little muscle fascicular shortening and fatigueresistance
properties. The DDF muscle combines
passive and dynamic functions with larger tension
development and higher shortening velocities during
digital motion. Architectural parameters are useful for
estimation of forces and have implications for analysis
of muscle-tendon function, surgical procedures
involving muscle-tendon lengthening, and biomechanical
modeling. (Am J Vet Res 2004;65:819–828)
Objective—To determine effects of incremental radial
shortening and subsequent ulnar ostectomies on joint
surface contact patterns in a canine elbow joint model.
Sample Population—Paired forelimbs from 9 adult
Procedure—Joint casting was performed by placement
of colored polymethylmethacrylate in the elbow
joint cavity and loading in a materials testing system
at physiologic angle and load. Joint casting was performed
in unaltered specimens, after radial shortening,
and after subsequent distal ulnar ostectomy,
proximal ulnar ostectomy, and proximal ulnar ostectomy
with intramedullary pinning. Computer-aided
analysis of photographs of proximal radial and ulnar
articular surfaces without joint casts was performed
before and after each casting procedure.
Results—All increments of radial shortening changed
the size and location of radial and ulnar contact areas.
The radial contact area became smaller, the anconeal
contact area disappeared, the medial coronoid contact
area migrated craniolaterally, and the lateral projection
of the coronoid process became a contact area. A proximal
ulnar ostectomy stabilized with an intramedullary
pin restored normal contact area size and location and
restored continuity of the radial and coronoid contact
areas across the radioulnar articulation in 6 of 10 specimens.
A midshaft ulnar ostectomy, distal to the level of
the radioulnar ligament, had no effect on contact patterns.
A proximal ulnar ostectomy without stabilization
resulted in varus deformity during loading.
Conclusion and Clinical Relevance—Proximal radial
shortening, which creates articular step incongruity,
changes the location and size of the radioulnar contact
areas. Dynamically stabilized ulnar ostectomies
proximal to the radioulnar ligament restore contact
patterns in vitro . (Am J Vet Res 2001;62:1548–1556)
Objective—To compare in vitro mechanical properties
of toggle pins and toggle rods used as suture
anchors and of 3 suture materials (50-lb monofilament
polybutester, No. 5 braided polyester, and 5-mm
woven polyester) commonly used as prosthetic ligaments
in the repair of hip joint luxation in dogs.
Sample Population—Femoropelvic specimens from
the cadavers of 18 dogs.
Procedure—Suture anchors were compared by use
of pullout tests. Suture materials were compared by
use of monotonic and cyclic tensile tests; cyclic tensile
tests were performed with the suture placed over
the edge of an aluminum bar to simulate the edge of
the femoral bone tunnel. In vitro mechanical properties
of the ligament of the femoral head were determined
by use of monotonic tensile tests, using boneligament-bone cadaveric specimens. The in vitro
mechanical properties of the acetabulum-ligamentfemur
complex and of this complex following rupture
of the ligament and stabilization with a toggle rod and
5-mm woven polyester were determined by use of
compression tests that simulated weight-bearing.
Results—Mechanical properties of the toggle rod
were not significantly different from those of the toggle
pin. Woven polyester had the longest fatigue life
in cyclic testing. Hip joints stabilized with a toggle rod
and woven polyester had less than half the strength
in vitro of intact joints.
Conclusions and Clinical Relevance—Results suggested
that a toggle rod or toggle pin can be used for
stabilization of hip joint luxations in dogs. Of the
materials tested, braided polyester had the best in
vitro mechanical properties. (Am J Vet Res 2001;62: