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Mini knee procedure

Mr Fares Haddad and Mr Nicholas Wardle advise on the use of minimally invasive total knee replacement

Mr Fares Haddad and Mr Nicholas Wardle advise on the use of minimally invasive total knee replacement

Case history

A 60-year-old woman describes a five-year history of worsening left knee pain. She can no longer use public transport to get to and from work, requires the use of one walking stick for everyday mobility, and finds stairs difficult. Her pain is constant, worse after activity and is located primarily on the medial aspect of her knee, though she has anterior knee pain when climbing stairs or standing up after sitting for a long period. She is woken at night by pain despite regular analgesics.

On examination she has an uneven gait, and is unable to squat without holding on to her surroundings ­ even then only managing halfway. The knee is swollen and has 5° of correctable varus deformity. She is tender around the medial joint line where osteophytes are palpable, and displays patello-femoral irritation with obvious crepitus on movement. She has a reasonable range of motion from 0°-100°. Her right knee is normally aligned and flexes to 125°. Her back and hips have a pain-free full range of motion.

Diagnosis and management

Arthritis affecting the knee joint is a very common condition, but it is important to differentiate it from other diagnoses causing pain around the knee joint such as referred pain from lumbo-sacral arthritis, nerve entrapment and hip arthritis.

It is also important to ensure that the pain is not a result of meniscal pathology, though the history is usually different (shorter duration of symptoms, rapid onset, mechanical symptoms such as locking). The vast majority of knee arthropathies are secondary to osteoarthritis. However rheumatoid arthritis, post-traumatic arthritis and mal-tracking leading to accelerated wear can also be responsible. In this case, arthritis was confirmed.

Assessment should always include an examination of both knees as well as an assessment of the back and hip on the affected side.

If non-operative management ­ analgesia, glucosamine, walking aids, physiotherapy ­ fails to keep symptoms controlled, or the joint deformity progresses rapidly, then it is reasonable to recommend knee replacement surgery. It is better to perform a knee replacement before the knee gets very stiff and before the patient's mobility deteriorates dramatically, as earlier intervention leads to better functional outcomes.

The procedure

Advantages of minimally invasive surgery

  • smaller and less noticeable scar (9-13cm vs 20-30cm)
  • minimal interruption and dissection of neurovascular tissues, tendons, ligaments and muscles, including quadriceps
  • shorter hospital stay for patient ­ discharge at four days post-operative, but dependent on patient and availability of occupational therapy, physiotherapy, social services
  • greater flexion earlier than with standard incision ­ difference maintained at later assessment
  • theoretically less blood loss ­ not demonstrated in all studies
  • return to function more quickly
  • less pain
  • use of assistive devices for shorter periods of time

Current patient selection criteria

  • patient in good medical health ­ procedure can last two hours
  • knee deformity no more than: 10° anatomic varus15° anatomic valgus10° flexion contracture

Nicholas Wardle is specialist registrar in trauma and orthopaedics at The Royal London Hospital. His special interest is joint arthroplasty and reconstruction Competing interests None declaredFares Haddad is consultant orthopaedic surgeon specialising in knee and hip arthroscopy, reconstruction, joint replacement and revision ­ he is clinical director at University College London Hospitals. Competing interests None declared

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