TENDON TRANSFER Flashcards
indications for a tendon transfer?
flexible deformities -PT dysfunction or spring ligament attenuation neuromuscular deficits -LMN disorders, drop foot, cavus foot pediatrics -polio, spina bifida
what are the considerations for a tendon transfer?
adequate motor power for tendon transfer
-foot should be at neutral and plantar grade position
tendon transfers do not correct the deformity
-only hold the corrected deformity
good passive ROM is desirable for better results
- no acute angulation
- adequate length of the donor tendon to be transferred
muscle function can recover up to how many years?
1 year
commonly injured in dropfoot?
common peroneal nerve
for the biomechanics of a tendon transfer, a tendon fixed at maximal elongation acts as?
tenodesis
- tendon fixed in relaxed state cannot generate adequate tension to pull effectively
- some stretching occurs
reverse phase tendon transfers usually lose how many grades of motor function?
one grade of motor function
- not always for tendon transfers in same phasic pattern
- muscle being considered for transfer optimally should have a grade 4/5 strength or better
what are the types of tendon transfers?
transfer underneath retinaculum
- act as pulley
- increases excursion
- decreases lever arm and strength
subcutaneous transfer
- decreases excursion
- increases motor strength
- greater distance from axes
- avoids angles
what is the incisional approach for a tendon transfer?
1st over tendon insertion
2nd approx at origin
3rd at change of muscle function
4th at new insertion
how does fixation occur with a tendon transfer?
tendon to ST interface
- sutured to ST
- minimal pull out strength of fixation vs force of tendon function
- type 3 collagen fibers were present and connected across the interface 6 weeks post op
tendon to bone interface
fixation technique
- new technique
- bioabsorbable interference screws
- although weaker than tendon to tendon suturing
- 3x stronger than minimally required pull out strength
principles of tendon transfer?
screw length determines pull out strength
-0.5-1 mm larger than tendon diameter
interference screw
-absorbable biotenodesis screw leads to concerns for osteoporotic bone
first 2 weeks leads to strength only from sutures, 3 weeks passive/active ROM, 4 weeks progressive muscle activity (avoid adhesions, amniotic membranes)
for fixation, this angle is the strongest for the tendon placed in when fixed to the bone
which angle is strongest, why?
dead mans angle
perpendicular is strongest, most pull out strength
-inserting FHL on posterior calcaneus is stronger than inserting on superior calcaneus
what are the stages of degradation for bioabsorbable screws in fixation for tendon transfer?
hydrolysis loss of molecular weight loss of functional strength loss of mass macrophage phagocytosis lactic acid pyruvate
what is an allograft useful for in fixation of a tendon transfer? why?
tenodesis because it doesn’t sacrifice normal anatomy
for fixation used in a tendon transfer what are the advantages of allograft?
does not sacrifice normal anatomy no motor function allows angular correction increase in creep -initial stretch with physiologic load -need to stretch before inserting because it will become elastic with use -3 days to 3 weeks
contraindications of tendon transfer?
recent loss of strength/function fixed deformities ST contractures weaker than 4/5 muscle strength be aware of osteoporosis
