Knee Disarticulation Surgical Procedure
Knee disarticulation is an atraumatic amputation procedure that preserves all thigh muscles, maintains hip joint range of motion, and creates a bulbous stump capable of full end-bearing weight, offering superior outcomes compared to transfemoral amputation. 1
Indications
- Alternative to transfemoral amputation for various etiologies
- Infected/loosened total knee replacements
- Trauma, tumors, chronic osteomyelitis
- Contraindicated in Buerger-Winiwarter's disease
Preoperative Considerations
- Evaluate vascular status with ankle-brachial index (normal >0.9)
- Assess for critical limb ischemia (chronic rest pain, ulcers, gangrene)
- Consider revascularization if anatomically possible before amputation 2
- Determine if limb salvage is possible in hemodynamically stable patients 2
Surgical Technique
Step 1: Incision and Flap Design
- Apply tourniquet for hemostasis
- Create longer ventral flap (10 cm distal from joint line) and shorter dorsal flap (5 cm distal from joint line) 3
- Alternative: Consider dorsomyocutaneous flap technique which has shown better primary wound healing rates compared to sagittal flaps 4
Step 2: Soft Tissue Dissection
- Incise ligamentum patellae at tibial attachments
- Cut through articular capsule
- Detach the following muscles at their distal attachments:
- Sartorius
- Gracilis
- Semitendinosus
- Semimembranosus
- Biceps femoris
- Tractus iliotibialis
Step 3: Joint Disarticulation
- Incise collateral and cruciate ligaments at their femoral attachments
- Dissect the neurovascular bundle carefully
- Double ligate vessels after proper identification
- Infiltrate tibial and peroneal nerves with local anesthetic before transection
- Cut through popliteus muscle, popliteum arcuatum ligament, and both heads of gastrocnemius muscle
- Separate and remove the lower leg 3
Step 4: Condylar Modification (Optional)
- Standard technique: Preserve femoral condyles and patella intact
- Modified technique: Moderate trimming of femoral condylar prominences with patellofemoral arthrodesis in intercondylar notch to create a more conical stump 5
- Beveling of femoral cartilage only if osteoarthritis is present 1
Step 5: Closure
- After tourniquet release, achieve meticulous hemostasis
- Suture ligamentum patellae to the tendons of semimembranosus, semitendinosus, and biceps femoris
- Attach sartorius and tractus iliotibialis to the extensor apparatus
- Perform layered closure with individual sutures
- Place two suction drains below the fascia
- Ensure skin closure without tension, avoiding weight-bearing areas 1, 3
Postoperative Management
- Proper bandaging is critical to prevent decubital ulcers
- Prosthetic fitting possible 3-6 weeks after surgery
- Prosthesis type depends on patient's activity level 1
Outcomes and Advantages
- Wound healing rates of approximately 91% (57% primary healing, 33% delayed healing) 4
- Only 10% require conversion to transfemoral amputation 4
- 62% of patients can be fitted with prosthesis; 91% of those with preoperative intention to ambulate receive prosthesis 4
- Superior stump characteristics:
Potential Complications
- Stump ulceration (rare)
- Fistula formation
- Delayed wound healing
- Risk of decubital ulcers if improper bandaging 5
Special Considerations
- Dorsomyocutaneous flap technique is preferred when feasible due to better wound healing outcomes 4
- Patients who undergo reamputation at transfemoral level show significantly reduced ambulation compared to those who maintain knee disarticulation level 4
- Bilateral knee disarticulation patients can walk "barefoot" 1
This procedure offers significant advantages over transfemoral amputation while maintaining excellent functional outcomes and quality of life for appropriate candidates.