Above, Through and Below Knee Amputations - Alistair Jepson 13/5/2002

BACKGROUND

Most common indications currently:trauma, peripheral vascular disease (+/- diabetes) & malignancy

Lower limb 85% of all amputations

90% of BK amputees learn to walkwith prosthesis c.f. 25-60% for AK.

Ratio ~1AK:3BK currently

General principles:

• Tournquets recommended except for PVD
• Antibiotics: Benzyl Penicillin & Metronidazole
• Incision: incise through skin down to level of deep fascia & then reflect this as a layer
• Small vessels: bipolar or limited monopolar diathermy
• Medium vessels: Ligation
• Large vessels: individually transfix & ligate (or double ligate) arteries & veins at different levels to avoid a-v formation
• Nerves: avoid strong traction, otherwise r/o intra-neural neuroma
• Bone: cut with tenon saw & shield, gigli saw or power saw with saline. Exposed bone end should be covered with periosteum or muscle
• Muscle: myoplasty is the suturing of one muscle to another or to fascia over end of stump & myodesis is muscle sutured onto bone under physiological tension — c.i. in ischamemic limbs
• Dressings: gelonet, gauze, wool crepe (soft) OR plaster dressing (rigid) — removed at 5-7d with immediate prosthetic cast if wound healed

Below knee:

• 12.5-17.5cm suggested as ideal depending on body height — extra 2.5cm per 30cm height
• Long posterior flap amputation first designed by Kendrick in 1956
• Modified by Burgess & Romano ( Washington , USA ) in 1967, leading to — rate of healing in PVD (Ernest M. Burgess, Robert L Romano et al. Amputations of the Leg for Peripheral Vascular Insufficiency. J Bone Joint Surg July 1971; 53-A(5): 874-90)
• Problems however are: Wide in transverse direction, invariably with dog-ears, making fitting difficult; and scar across tibia may break down with prosthetic use
• Therefore other flaps designed:
• Persson (1974) described sagittal (lateral) flaps skewed by 15 — for BK amputation
• advantage of preserving long posterior flap but producing a hemispherical end to allow early casting and the provision of a PTB socket; and brings the terminal vertical scar away from the prominent anterior crest of the tibia
• Robinson (1982) modified this skew flap, rotated 20 — , by adding a myoplasty:
• To provide extra soft tissue cover & to cover medullary canal
• Allows some function of the calf muscle pump, as well as some knee flexion undefinedundefinedundefined
  

• Sagittal/lateral flaps confirmed as better for wound healing:
• McCollum PT, Spence VA , Walker WF. Circumferentialskin blood flow measurements in the ischaemic limb. Br J Surg April 1985: 72 :310-12

• Showed with Doppler pressure measurements and by radioisotope clearance that the dominant blood supply in an ischaemic leg was medial and posterior (respectivevly from saphenous nerve artery and sural nerve artery)

Wyss CR, Harrington R, Burgess EM etal. Transcutaenous Oxygen Tension as a Predictor of Success after anAmputation. J Bone J Surg Feb 1988; 70-A (2): 203-7

• Transcutaneous oxygen tension is the best predictor of success or failure of healing after an amputation of foot or distal to knee, than measurement of systolic b.p. at the ankle. Not predictive though of outcome after AK amputation

Value of trancutaneous oximetry canbe further enhanced by comparing value with & without inhaled oxygen — an — after O ₂ is +ve sign ofgood local tissue perfusion

Where amputation indicated fornon-ischaemic reasons equal anterior & posterior flaps may also beindicated ( Campbells )

BKA c.i. if dependent rubor or FFDknee affecting prosthetic function

Through-kneeamputation

• One of first reports - Velpeau (through-knee): 1830
• Newer socket designs have made this a better amputation than before
• Now there are prosthetic knee mechanisms that provide swing phase control
• Several techniques proposed — one reproduced is Kjoble (1970):
• Lateral flap at least — diameter of leg & medial flap 3cm longer. Apex 2cm below lower pole of patella
• Stump of patella tendon sutured to stump of ACL
• Most frequent healing of all techniques
• Others include: Mazet and Hennessy (J Bone Joint Surg 1966; 48-A: 126), Batch & Spittler (J Bone Joint Surg 1954; 36-A: 921) — all in Campbells

Supracondylaramputation (Gritti-Stokes)

Rocco Gritti (supracondylar): 1857 —later applied by William Stokes: 1837

Above-kneeamputation

• Ideal stump length is at the junction of middle & distal 1/3 femur (>5cm for lesser troch certainly)
• Conventional constant friction knee joint used in most AKA prostheses extends for 9-10cm distal to end prosthesis, so level of amputation impt to ensure good lever arm and equal joint line with other leg
• Muscles divided 6cm below bone level
• Myoplasty of quads to hamstrings or myodesis of all muscles to femur