Question

why would it be more difficult to replace an ankle than a knee, or ,hip, or even an elbow or shoulder?

Answer 1

Ankle replacement surgery is the replacement of a damaged ankle joint with an artificial implant.The ankle joint (tibiotalar joint) is where your shinbone (tibia) rests on top of a bone of your foot, the talus.Arthritis can affect this joint as well as other joints in the foot. Over time, the smooth cartilage on the surface of the bones wears away. This can result in pain, inflammation, and swelling of your joint.Ankle replacement surgery is a procedure to replace this damaged joint to eliminate this pain and swelling. Typically, the procedure takes place under general anesthesia. Your surgeon will make an incision in your ankle to access the affected joint. Next, your surgeon will remove the damaged parts of your tibia and talus bones. Your surgeon will attach artificial metal joints to the remaining bone surfaces, with a piece of plastic inserted between them.

Total ankle arthroplasty was largely abandoned due to poor survivorship most often caused by loss of bone support. High complication rates were also reported. Despite this, there is renewed interest in ankle arthroplasty and encouraging results are seen in survivorship with midterm follow-up. The procedure, however, remains more challenging than total hip or total knee arthroplasty. With the limited soft tissue envelope, wound problems are not uncommon. Forces at the ankle are very large and yet the surface area for prosthetic support is small. Therefore, fixation can be more difficult. The strongest bone can be eccentric at the distal tibia. The tibial prosthesis can, therefore, tend to settle into the softer bone often laterally. Polyethylene needs to be sufficiently thick to maintain its integrity but that requires a larger bone resection, which weakens bone support. Polyethylene failure or wear leads to the majority of failures in hip and knee arthroplasty. There is a need for further basic science research in total ankle arthroplasty. The lessons learned from other arthroplasty should be considered in ankle arthroplasty design.

Complications after total knee replacement surgery

Total knee replacement has become an effective method of treating severe arthritis of the knee. A range of early complications can occur after knee replacement.Such complications include problems with wound healing, infection, bleeding, deep venous thrombosis, swelling, stiffness and persistent pain.

Fig : Knee is inflamed and infected after total knee replacement surgery

• Wound healing problems

Wound healing problems occur because of the thin soft tissue covering the knee, especially over the anterior aspect.Healing problems can be associated with haematoma, especially in the elderly, patients on steroids, and rheumatoid arthritis and psoriasis patients.Wound healing problems require urgent diagnosis and management to avoid more serious complications such as skin loss, infection and possible loss of the prosthesis. An unhealthy looking wound should be referred back to the surgeon as soon as possible.

• Infection

Infection is a serious complication of total knee arthroplasty. The incidence of infection has been reported to be less than 1-2% with primary arthroplasty, 3-5% of revision knee arthroplasty 3 and as high as 16% with hinged implants. Patients with rheumatoid arthritis, diabetes mellitus, poor nutrition, old age, and obesity are at higher risk of both superficial and deep infection.Surgical wound infections are often pain free with redness around the wound, discharging fluid, but with no joint effusion, joint stiffness, or restriction of movement.Early deep infections are often due to relatively virulent pathogens such as Staph aureus and present with an acute onset of symptoms, including joint pain, joint effusion, induration, erythema, wound oozing and fever.Early orthopaedic referral is paramount for the timely management of possible prosthetic joint infections, rather than immediately starting antibiotics.Prompt aspiration and tissue culture is essential to start appropriate antibiotics. The treatment for deep infection in a joint includes intravenous antibiotic therapy, debridement, polyethylene liner exchange and revision surgery.

• Deep vein thrombosis

DVT is one of the most feared complications of total knee replacement surgery and potentially can be fatal if the thrombosis embolises to the lungs.4 A DVT may be silent, presenting as a pulmonary embolism with shortness of breath, chest pain, and cyanosis, without limb symptoms. Alternatively, it may present with a painful calf or thigh usually 5-7 days postoperatively or earlier. A low threshold for lower limb ultrasound, chest X-rays and spiral CT chest may help to establish early diagnosis. Physical examination may reveal a unilateral swollen calf or thigh, erythema, tenderness, warmth, and a difference in calf diameters.Prompt diagnosis and initiation of treatment can prevent further clot extension and pulmonary embolism. Anticoagulation therapy is indicated for patients with DVT and prompt referral to the orthopaedic department or A&E should be organised for further investigations.

• Neurological injury

Peroneal nerve palsy is the most common neurological complication after total knee replacement. It presents with numbness, paraesthesia and foot drop. The surgical dressings should be removed, and the patient should be referred back to the orthopaedic surgeon. Depending upon the symptoms a conservative approach may be followed or the nerve explored.

• Restriction of movements

Patients may present with postoperative limitation of motion that results in functional impairment of the joint. Many factors can be responsible including malrotation of the prosthesis and poor preoperative range of movement. Treatment may comprise physiotherapy or manipulation under anesthesia.

• Persistent pain and dissatisfaction

Although outcomes after total knee replacement are good, many patients continue to report pain and dissatisfaction.Clinically significant persistent pain and dissatisfaction has been reported in 20% of patients.5 Night pain is quite common after knee replacement. Possible explanations for such pain include unrealistic expectations, technical flaws of the procedure and pain from other sites. If the pain is persistent without a known cause then referral to the pain management team should be made.