What is Knee Arthrodesis
Knee arthrodesis stands for surgical fusion of the knee joint. Arthrodesis is one of the last options available to obtain a stable, painless knee in a diseased or damaged knee joint which cannot be reconstructed or replaced. Indications of knee arthrodesis are mentioned below.
Today, there is reduction in number of arthrodesis surgeries are performed because of success of replacement arthroplasty.
Patient selection is very important in knee arthrodesis. For the carefully selected patient with realistic expectations, knee arthrodesis may relieve pain and removes the need for additional surgery or extensive postoperative rehabilitation.
Indications for Knee Arthrodesis
Common indications for knee arthrodesis
- Salvage for failed total knee arthroplasty [Most common indication in modern times]
- Posttraumatic arthritis
- Chronic infection
- Painful ankylosis after infection or trauma
- Neuropathic arthropathy
- loss of extensor mechanism of Knee [The joint becomes non functional]
Contraindications for Knee Arthrodesis
- Active infection
- Bilateral knee arthrodesis
- Contralateral limb amputation
- Ipsilateral hip arthrodesis
- Ipsilateral hip or ankle degenerative joint disease
Optimal Joint Position of Knee Arthrodesis
It is important to slightly shorten the limb and achieve slight flexion at the knee.
- 5-8° valgus
- 0-10° of external rotation depending on the rotation of other leg
- 0-15° of flexion
Some maount of limb shortening is done which eases self care and ground clearance while walking.
Patient Selection and Preoperative simulation
Except for the salvage situation where other options have exhausted, the patient should chose the arthrodesis, knowing that this would kill the movement at knee joint. Not only this, patient should also understand about the finality and irreversibility of the outcome. Patient would have to adjust to new kind of gait and lifestyle.
To make enable the patient to make better choice that suits him, a preoperative idea can be given to patient about the loss of movements and restrictions imposed by arthrodesis by application of above knee cast.
This restricts the knee motion and simulates the restrictions imposed by arthrodesis of the knee joint.
The plaster is applied for 3-6 weeks and in this period patient can very well chose if he wants to make the choice for knee arthrodesis.
Surgery for Knee Arthrodesis
There are many surgical procedures employed for knee arthrodesis. A variety of techniques has been described for surgical fusion and a range of implants is available.
Basic aim of the surgery is to remove cartilage and other tissues of the knee joint to expose the underlying bone on both sides [tibia and femur]. These exposed bones would fuse together in due course of time.
The techniques are
- External fixation
- Internal fixation by compression plates across the knee
- Intramedullary fixation with nail across the knee
In all procedures, bone grafting may be necessary to restore lost bone stock or to augment fusion.
The procedural details are to give an idea of the procedure only, so unnecessary details have not been included.
This is general approach to surgery. Depending upon surgeon and implant used, the technique may vary.
- The knee is approached under tourniquet, if the technique allows application of tourniquet. The patient may be positioned in supine position with a sandbag under the knee.
- An anterior curvilinear parapatellar incision is made starting from the suprapatellar pouch extending up to the tibial tubercle. The quadriceps expesion is cut in the same line leaving half to one cm of muscle attached to the patellar border.
- After erasing the capsule, the knee joint is gradually flexed, taking the patella and expansion to one side.
- Synovial membrane, the articular cartilage and subchondral bone is removed from the upper end of tibia and distal end of femur up to the cancellous bone. The apposing surfaces of tibia and femur are shaped and bought into contact to obtain maximal contact without rotation, gross displacement and angulation.
- The articular surface of patella is rawed and is apposed at the site of arthrodesis while closing.
- In case of infection, diseased bone, sequestra, cavities, caseous tissue and granulation tissue are removed. Resultant cavities are filled with bone grafts, allo or autograft. Autograft is usually taken from iliac crest. Allgrafts are commercially available.
- After achieving the desired position, the two bones are fixed with the selected implant.
Additional exposures may be necessitated by the technique of fixation. Postoperatively the limb is kept elevated on pillows. Blood loss may occur from the cut bones and blood transfusion may be necessary.
Complications of Knee Arthrodesis
Complications of knee arthrodesis can be due to infection, failure to unite or effects of altered gait biomechanics.
- Low back pain
- Ipsilateral hip degenerative changes
- Contralateral knee degenerative changes
- Stress fracture due to increased stress in the regions
- Supracondylar femur
- Proximal tibial metaphysis fractures
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