Knee arthrodesis as primary surgery is very rare now a days because of success of knee arthroplasty. It usually is reserved for patients who are not candidates for total knee replacement or where arthrodesis is be more appropriate than arthroplasty due to age , occupation, weight or activity.
Apart from this following patients can undergo arthrodesis are
- Painful stiffness of knee after infection, tuberculosis or injury
- Severe deformity in paralytic conditions
- Neuropathic arthropathy [Charcot joint]
- Malignancy around the knee.
The most frequent indication for knee arthrodesis at present is salvage of a failed total knee arthroplasty.
- 0 to 15 degrees of flexion
- 5 to 8 degrees of valgus
- 10 degrees of external rotation
Techniques in literature for this surgery and mainly classified on the basis of type of fixation
- External Fixation
- Internal Fixation
The amount and quality of bone, patient demands, quality of bone and surgeon’s experience are important factors for seleting a particular techinqe.
Compression Arthrodesis with External Fixation
It is done in knees with minimal bone loss and broad cancellous surfaces with adequate cortical bone to allow good bony apposition and compression.
Advantages of compression arthrodesis
- Good, stable compression across the fusion site
- Placecement of fixation proximal and distal to an infected or neuropathic joint.
Pin track problems, poor patient compliance, and the frequent need for early removal and cast immobilization are the usual disadvantages.
Arthrodesis with Iinternal fixation
Internal fixation could be by
- Intramedullary rod
- Plate fixation
Intramedullary Rod Fixation
Most appropriate when extensive bone loss does not allow compression. Examples are after tumor resection or failed total knee arthroplasty.
Advantages of intramedullary nailing are
- Immediate weight bearing
- Easier rehabilitation
- No pin track problem
- High fusion rate
Significant blood loss, more frequent major complications, and difficulty in obtaining correct alignment are the problem faced with ineral fixation arthrodesis with intrameduallry rod.
Two long plates placed at right angles to each other have also been used in knee arthrodesis offering same benefits of internal fixation but require extensive surgical exposure and are contraindicated in infection.
Reported success rates of knee arthrodesis are 80% to 98% of patients.
Properly selected patients are satisfied especially with the decrease in pain.
Usual concerns of patients after successful aoutcome are
- Awkwardness of gait my cause public attention
- Difficulty riding public transportation
- Difficulty sitting in theaters and stadiums
- Difficulty getting up after a fall.
A proper preoperative conselling would reduce the anxiety faced in postoperative period.
A trial of preoperative long-leg immobilization can be done to make the patient assess himself if he could manage after a fused knee.