Ch 70 Muscle and tendon Flashcards
What is the most common general location for a muscle strain?
What are the three stages of muscle strain?
Most common at musculotendinous junction, muscles which cross two or more joints appear predisposed
Three stages:
- Stage I: Myositis and brusing, architecture intact
- Stage II: Myositis and some tearing of the fascial sheath
- Stage III: Tearing of the fascial sheath, muscle fiber disruption and haematoma formation
What are the two processes of muscle healing?
- Direct regeneration of myofibrils
- Production of fibrous scar tissue
Myofibrils regenerate rapidly, provided the sarcolemmal nuclei have survived, complete repair if the endomysium is intact
muscle healing
- Hematoma formation > inflammatory response, cellular infiltration and phagocytosis occurring 6 to 12 hours after injury.
- 48 hours > invasion of capillaries and myoblast proliferation, followed by myofiber formation.
- Fibroblast proliferation and collagen scar formation 4 to 6 days
- filling the damaged area with a new collagen network by day 10.
- Tissue strength increases rapidly up to day 14, when the entire process slows down.
Stage I and II injuries are more likely in the power group of muscles (6)
- triceps brachii,
- biceps femoris,
- quadriceps femoris,
- tensor fascia lata,
- semitendinosus,
- semimembranosus
Stage III injuries
- long head of triceps brachii,
- gracilis,
- gastrocnemius,
- tensor fasciae latae
What are the general principles of muscle treatment?
- Maximise direct myofibril repair while minimising scar formation (excessive scar can reduce a muscles ability to produce tension by 50%)
- 24 to 48hr > cold compresses and nsaid ( minimize the early disruptive effects of inflammation, edema, and swelling)
- Early mobilisation essential for proper myofibril orientation and can be considered after day 5-10
- Stage III injuries > surgery to eliminate any gaps and reduce scar, 2 to 3 days following injury
Stage I +/- stage II, good healing can be expected with direct growth of new muscle tissue
What are some common muscle injuries of the thoracic limb? (3)
- Rupture of long head of triceps brachii (racing Greyhounds). Causes depression caudal and distal to scapula. Reattachment recommended
- Avulsion of triceps brachii tendon of insertion. Primary reattachment to olecranon with immobilisation with transarticular ESF or olecranon- humeral screw
- Rupture of serratus ventralis causing dramatic dorsal replacement of scapula (conservative vs tether the scapula to the thoracic wall via bone tunnels)
What are some common muscle injuries of the pelvic limb? (2)
- Rupture of gracilis (Greyhounds, GSD, Foxhounds). Surgical repair or reattachment
- Iliopsoas and pectineus muscle strain. Most common! Conservative management usually successful
What are the most common forms of muscle contracture in dogs? (5)
dt injury vs localized compartment syndrome???
- Infraspinatus contracture (circumbuction and carpal flip with abduction of shoulder, adduction of elbow, lower limb abducted and externally rotated). Tendonectomy with release of surrounding fibrous tissue
- Quadriceps contracture Neither the stifle nor the hock joint can be flexed, physiotherapy if early, sx usually unsuccessful > amputation
- Gracilis and semitendinosus contracture (limb riase in jerk-like fashion with hyperflexion of the tarsocrural joint and internal rotation of metatarsus)
- GSD 3- 7 years
- condition becomes static
- Conservative recommended dt recurrence after surgical intervention
- Flexor carpi ulnaris muscle of puppies
- Myositis ossificans (heterotrophic bone formation in muscles after trauma, most common at hip)
non painful, fibrotic replacement of the muscle fibers
What cells do tendon healing rely on?
Influx of fibroblasts to produce new collagen
How does tendon healing differ between paratenon-lined tendons and sheathed tendons?
Paratenon-lined:
- Can recieve vascular buds and an influx of undifferentiated cells from the paratenon and surrounding soft tissues.
- Better capacity for rapid healing
- Tendons of insertion of gastroc and triceps
Sheathed:
- Depend much more on intrinsic blood supply
- Digital flexor tendons
Tendon Healing
- characteristically slow
depends on if:
1. paratenon lined or not
2. if Gap formation > When a gap is present, a scar is formed
- first 4 to 5 days after repair > tendon ends lose holding power and then gradually increase in strength again during the next 2 weeks (fibroplasia and collagenization take place)
- strength and resistance to gap> entirely achieved by the suture during the first 3 weeks
- New tendon collagen requires strain or load for development of correct alignment > should be exposed at 3 weeks post repair.
What percentage strength does a tendon have at 6 weeks and 1 year after repair?
What percentage of normal capacity strain in placed on a tendon during normal muscle contraction?
6 weeks: 56%
1 year: 79%
Normal contraction places 25-33% of normal full capacity of strain. Thus, strength at 6 weeks should be sufficient to withstand limited exercise
How long must the suture material primarily maintain strength and resist gap formation during tendon healing?
What are the three main forms of suture patterns for tendon apposition?
Initial three weeks
Suture patterns:
- Locking loop
- Krakow
- Three-loop pulley
Surgery aims/principles (2)
- produce healing without gap formation
- allows early loading to ensure correct collagen formation and alignment.
Kirschner wires through the body of the tendon away from ends, Monofilament synthetic long-term absorbable or nonabsorbable, holding suture patterns are required to resist pull-out, ends of the tendon are carefully debrided> apposition to ensure that the gap has been eliminated
Immobolise ESF, CAST, TA screw practically for 6 weeks
What are some common tendon injuries in small animals? (4)
-
Superficial and deep digital flexor tendon laceration
above or below the metacarpal or metatarsal foot pad (if below may need to repiar 8 x tendons)
common mistake is to fail to identify the deep digital tendons > present with flattened digits (dropped foot) or with a painful sore on the metatarsal pad - Common calcaneal tendon injury (most common)
- tendon of origin of biceps brachii (Partial or full avulsion, Medial displacement in greyhounds, miniature Poodle and a Border Collie)
- long digital extensor tendon (avulsion or displacement) immature large-breed dogs, joint effusion and lameness, Surgical exploration with reattachment of the tendon
Effect of calcanean bone-tunnel orientation
for teno-osseous repair in a canine common calcanean
tendon avulsion model
Beamon 2022
duffy
Results: The only difference detected consisted of TT constructs yielding at
loads 25% higher than MT constructs (P = .027).
Conclusion: Although yield loads were lower in MT constructs than other
groups, the bone-tunnel anchoring techniques tested here did not appear to
influence the biomechanical properties or gapping characteristics of tenoosseous repairs in this canine CCT avulsion model.
Rupture of the gastrocnemius muscle at its
distal musculotendinous junction: conservative
treatment and outcomes in 11 dogs
Boyd 2023
NZVJ
diagnosis was confirmed with ultrasound or MRI in six dogs
All dogs were managed conservatively, either with complete confinement alone (n = 10; median 9 weeks), external coaptation alone (n = 1), or a combination of both (n = 4).
A good (persistently increased tibiotarsal standing angle > partial plantigrade) to excellent outcome was achieved for all cases in this cohort
Currently,
there is no consensus on the treatment of
DGMJR in dogs.
All sporting dogs had an
excellent outcome. In contrast, all companion dogs
had a shorter duration of complete confinement and
some form of coaptation (Table 2) and achieved a
good outcome.
in humans: almost uniformly non-surgical
regeneration of functional tissue or by
the proliferation of fibrous tissue to span the defect;
a combination of both occurs in high-grade muscle
injuries
The predominance
of one form of healing over the other can be
influenced by the load, or lack thereof, placed
through the healing tissues in
Calcaneotibial screws for immobilisation of the
tarsocrural joint of dogs in extension: effect of the
angle of screw placement on the force to failure in
a canine cadaveric model
S Devereux 2021
NZVJ
Twelve pairs of cadaveric hindlimbs
A calcaneotibial screw placed at an angle approximately perpendicular to the
long axis of the calcaneus, has a higher force to failure under axial loading than a
calcaneotibial screw that is placed at an angle approximately perpendicular to the tibia, in a
canine cadaveric model.
constructs were tested for load to failure rather
than cyclic loading.
likey due to increased Surface area
no bending or breakage of screws during
the force testing suggesting that the screws pulled out
of the tibia before a high enough force was achieved to
bend or break the screw between
Biomechanical Comparison of a 3-Loop Pulley
and a 4-Loop Pulley Suture for Tenorrhaphy in
the Canine Gastrocnemius Tendon
Kadie L. O’Byrne 2022
Randomized, cadaveric, biomechanical study of 30 canine gastrocnemius tendons. 2–0 polypropylene
A 4LP pattern was biomechanically superior to a 3LP pattern, as
demonstrated by a greater load required to form both a 1 and 3mm gap and a greater
load for failure
Ideally, gap formation should be less than 1mmto reduce the occurrence of scar formation
a gap greater than 3mm did not change
with time, indicating that a gap of 3mm or more prevents accrual of strength and stiffness,
The 3LP has been compared with both a double Krackow, self-locking suture and two locking loops.9,10,12,13 and the 3LP wasmore resistant to gap
formation.12
While the 3LP
better resisted gap formation than the double locking loop,
when compared with the double Krackow, the load required
to form a 3mm gap was 21.37N greater compared with the
3LP
The addition of an epitendinous suture resulted in a twofold greater resistance to gap formation, greater load required before failure and also resulted in suture breakage becoming a source of construct failure, rather than suture pull through alone.
This supports previous findings that the suture tissue
interaction is the weakest part of the repair, rather than
the suture itself
negative affect on perfusion and vascularity needs to also be considered.
Duffy
Effect of partial vs complete circumferential epitendinous
suture placement on the biomechanical properties and gap
formation of canine cadaveric tendons
Daniel J. Duffy 2020
Study design: Ex vivo, biomechanical study.
Sample population: Thirty-six
Addition of a complete circumferential ES with a single or double
knotting technique increased the biomechanical strength of normal tendon
repairs while reducing gap formation compared with partial ES placement alone
more even force distribution and higher strength vs partial
Effect of a continuous epitendinous suture as adjunct to
three-loop pulley and locking-loop patterns for flexor tendon
repair in a canine model
Putterman 2019
Study design: Ex vivo biomechanical study.
Sample population: Seventy-two cadaveric SDFT
3LP → better gap prevention than locking loop
- overall yield force increased significantly by epitendinous suture
- LL subjectively → better approximation
Clinical outcomes after common calcanean tendon rupture repair
in dogs with a loop-suture tenorrhaphy technique and autogenous
leukoreduced platelet-rich plasma
Kurt S. Schulz 2019
fiberloop
FiberWire has greater stiffness and strength than comparably sized monofilament nonabsorbable suture.21 Braided multifilament suture
Two dogs had major complications that
were successfully revised. Follow-up was available in 11 of 12 dogs, with a median
time of 12 months
Owners scored function (COI) as 96.4% (range, 93.3%–97.8%) and quality of life as 94.6%
(range, 92%–98.2%).
