What is the proper procedure for performing a disarticulation at the knee?

Knee Disarticulation Procedure: Surgical Technique and Considerations

Knee disarticulation is an atraumatic amputation procedure that preserves the entire femur and thigh musculature, providing superior outcomes compared to transfemoral amputation through better weight-bearing capacity, muscle balance, and prosthetic fitting. 1

Surgical Technique

Patient Positioning and Preparation

• Position patient supine with a tourniquet applied to the proximal thigh
• Prepare and drape the limb in standard sterile fashion
• Mark flaps before incision, planning for adequate soft tissue coverage

Flap Design Options

1. Dorsal-myocutaneous flap technique (preferred method) 2

   • Creates a longer posterior flap with good vascularity
   • Associated with better primary wound healing rates
   • Provides robust soft tissue coverage for end-bearing

2. Modified Rogers procedure 3

   • Create a 10 cm ventral incision from the articular fissure distally
   • Create a 5 cm dorsal incision distal to the articular fissure
   • Results in a longer anterior flap and shorter posterior flap

Step-by-Step Surgical Procedure

1. Skin Incision and Initial Dissection

   • Make skin incisions according to chosen flap design
   • Elevate skin flaps to the level of the joint line
   • Identify and protect neurovascular structures

2. Soft Tissue Dissection

   • Incise the patellar ligament at its tibial attachment
   • Divide the joint capsule circumferentially
   • Transect hamstring tendons (semitendinosus, semimembranosus, biceps femoris) at their distal attachments
   • Divide the iliotibial band

3. Joint Disarticulation

   • Cut the collateral and cruciate ligaments at their femoral attachments
   • Identify and carefully dissect the popliteal neurovascular bundle
   • Double ligate and divide the popliteal vessels
   • Infiltrate the tibial and peroneal nerves with local anesthetic before transection
   • Divide the popliteus muscle and gastrocnemius heads
   • Complete the disarticulation by separating the tibia from the femur

4. Femoral Condyle Management

   • Option 1: Preserve the femoral condyles intact for optimal end-bearing 1
   • Option 2: Moderately trim femoral condylar prominences if needed for prosthetic fitting 4
   • The patella should be preserved in its anatomical position

5. Patellofemoral Management Options

   • Standard approach: Maintain the patella in position held by retinacula 1
   • Enhanced stability: Consider patellofemoral arthrodesis in the intercondylar notch for improved stump contouring 4

6. Myodesis and Closure

   • Suture the patellar ligament to the hamstring tendons
   • Attach sartorius and iliotibial band to the extensor mechanism
   • Close fascia with interrupted sutures
   • Place suction drains beneath the fascia
   • Close skin without tension, avoiding suture lines in weight-bearing areas

7. Post-Procedure Management

   • Apply compressive dressing
   • Elevate the limb
   • Monitor for hematoma formation

Clinical Advantages and Outcomes

Advantages Over Transfemoral Amputation

• Preserves all thigh muscles with undisturbed muscle balance
• Maintains full hip joint range of motion
• Provides end-bearing capability due to bulbous stump shape
• Allows for easier prosthetic fitting
• Enables bilateral amputees to "walk barefoot"
• More atraumatic procedure (no bone or muscle transection)

Wound Healing and Complications

• Primary wound healing occurs in approximately 57% of cases
• Delayed healing may occur in about 33% of patients
• Conversion to transfemoral amputation is necessary in approximately 10% of cases
• Dorsal-myocutaneous flap technique shows significantly better primary wound healing compared to sagittal flaps 2

Functional Outcomes

• About 62% of patients can be fitted with a prosthesis
• Of patients with preoperative intention to ambulate with prosthesis, 91% receive one
• Approximately 35% of prosthesis users can walk independently
• Patients requiring subsequent transfemoral amputation show significantly reduced ambulation 2

Special Considerations

Prosthetic Fitting

• Prosthetic fitting typically possible 3-6 weeks after surgery
• Four-bar linkage prosthetic knee joint provides intrinsic stability during walking 5
• Modern prostheses offer excellent functional outcomes

Pitfalls and Caveats

• Risk of decubital ulcers is relatively high; proper bandaging is essential
• Skin closure must be performed without tension and away from weight-bearing areas
• Consider transcondylar amputation only when insufficient soft tissue is available for knee disarticulation
• Careful patient selection is critical for optimal outcomes

Knee disarticulation represents an excellent alternative to transfemoral amputation when more distal preservation is not possible, offering superior functional outcomes and quality of life for appropriate candidates.