BKA / Below Knee Amputation / Transtibial
Best results
- long posterior musculocutaneous flap
- well cushioned mobile muscle mass
- full thickness skin
- very anterior scar
Contraindication
- non-ambulator
- get FFD
- better with through knee amputation
Advantages over AKA
1. Good Healing
- > 90% in DM with BKA
2. Higher prosthesis wearing rates
- 74% vs 26% for AKA
3. Reduced energy required for walking
- 74% BKA < 45 year old walk > 1 mile
4. Reduced mortality
- 10% vs 30%
Technique
Tourniquet
- no tourniquet if PVD
- tourniquet in trauma (patients can bleed to death)
Posterior flap
- mark long posterior flap
- avoid suture line over anterior aspect of tibia / problems frequent here
Anterior flap
- short anterior flap at level of tibia cut
- want to extend posterior flap over distal tibia
Anterior Dissection
- find anterior NV bundle between T anterior and EHL
- deep peroneal nerve on interossesous bundle
- divide anterolateral muscles at tibial level to avoid bulbous stump
Tibial resection
- 15cm stump from joint
- no advantage in > 15cm as skinny poor stump
- < 3cm stump worse than through knee
- sharp dissect periosteum 2 cm above
- leave periosteal flap so can suture muscle flap to it
- bevel sharp edges
Fibula resection
- divide fibula 2cm above this
- need to ensure is stable (well connected to tibia via interosseous membrane)
- if not may need to create arthrodesis in young active patient
Fibular arthrodesis / unstabile fibula
- create wedge in tibia
- elevate periosteal sleeve to place over top of graft
- use 1 cm of fibula
- can get pain for 6-9 months as the graft unites
Posterior dissection
- find posterior tibial artery and tibial nerve
- on tibialis posterior between FDL and FHL
- divide deep muscles and allow to retract
- remove soleus leaving only gastrocnemius flap
- ensure vascularity flap
Myodesis gastrocnemius
- through drill holes in tibia and to periosteum of tibia
- fascial repair over muscle bellies
Closure
- over drain
- DPC if trauma or infection
- careful pressure dressings with tape to ensure good shaping
Through Knee
Indications
1. Non ambulators
- aids sitting balance
- avoids FFD and subsequent problems
2. < 3-5 cm tibia
3. ST tissue loss means BKA not possible
Advantage over AKA
- improved socket suspension
- longer lever arm
- muscle balanced amputation
- end-bearing potential
- less volume changes
Disadvantage
- asymmetrical knee joint
- bulky prosthesis
- overcome by newer prosthetic techniques
Technique
Tourniquet
- patients can bleed to death
Flaps
- equal anterior / posterior flaps
- 5cm distal to knee joint
- fish mouth
- can make posterior flap slightly longer
Patella
- depends on technique
- original method is to retain patella
- Mazet & Hennessy excise patella from tendon
Knee dissection
- divide PT off tibial tuberosity
- cruciates and collaterals divided at level of below meniscus
- aim to keep them long
- this preserves the rich proprioceptive function of the capsule
Deep dissection
- divide posterior capsule
- find and ligate popliteal artery and vein
- finding tibial nerve, tension, sharp divide, diathermy
Myodesis
- PT sutured to cruciate stumps
- biceps tendon sutured to PT
- gastrocnemius to anterior capsule
Above Knee Amputation / Transfemoral
Vumedi video
https://www.vumedi.com/video/above-knee-amputation-aka/
Indications
Trauma
Failed / septic TKR
Issues
- energy expenditure increased by 65%
- residual abduction as Adductor Magnus released from adductor tubercle
- myodesis in 10o adduction maintains abductor strength and prevents abductor lurch
- residual flexion due to quads / hamstring inbalance
Technique
Position
- sandbag under buttock
- avoid having leg in flexed position
Flaps
- actually want scar slightly posterior, with larger anterior muscle flap
- fish mouth
- larger anterior flap skin and muscle
Dissection
- cut quadriceps tendon above patella
- detach sartorius / gracilis / hamstrings 2 cm longer for myodesis
- detach Adductor Magnus
Vessels
- femoral artery below vas medialis in Hunter's canal / subsartorial canal
- profunda femoris posterior to femur
- can cut femur first to give access to NV bundles
Femoral transection
- save all possible femoral length
- increasing length increases muscle strength
- minimum 12 cm above knee to fit in prosthetic knee joint
- has to be >18 cm from GT or fixation difficult
- if stump < 5 cm below lesser trochanter then fitted as hip disarticulation
- smooth anterior edge of distal femur to avoid stump issues
Adductor myodesis
- maintain stump in 10° adduction
- anatomical position
- suture through drill holes in lateral femoral cortex
Anterior musculature
- myodesis of quadriceps to posterior femur avoids FFD
- through anterior drill holes
Posterior musculature
- myoplasty to A Magnus or quads
Soft spica
- suspend dressing from waist
- support medial thigh
Post-op
- positioning important to prevent contractures
- stump flat on bed
- intermittent prone positioning