Page 97 - ASOP ROT Study Guide

practice fairly limited. In practical terms if we retain ten or fifteen degrees of extension and thirty to fifty
degrees of flexion with a few degrees of abduction and rotation, particularly in extension, then useful hip
function in daily living is maintained.

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In the case of the knee the functional range of movement is surprisingly small, although ideally ninety degrees
of flexion must be achieved in order to get up and down stairs. In the knee, stability in extension is essential so
that we can support the full weight of the body whilst standing on a single straight leg. To achieve this the
surgery must achieve an accurate soft tissue balance through dissection of the capsule and the ligaments. The
modern knee replacement consists of two new, smooth surfaces but this is only half the operation. The
surgeon must balance the collateral ligaments by cutting tight parts of the ligaments and then putting in
artificial surface replacements of sufficient thickness to re-tighten the ligaments so that the medial and lateral
collateral ligaments are under equal tension. This is best explained in the diagrams below.

3 . 4 Complications
Complications of arthroplasty may be divided into those which are common to any major surgery and those
which are specific to the operation.
3 . 4 . 1 General
Most patients undergoing surgery for arthritis are elderly. While being old is unlikely to be a risk, it is true to
say that older people are more likely to have medical conditions predisposing them to risk. If these are not
recognized then problems may arise.
Anyone undergoing major surgery is prone to problems such as chest infection and urinary tract infection. They
are also prone to developing pressure sores if they are not nursed carefully. There are also the risks of deep
vein thrombosis (a blood clot in the veins of the leg and pelvis). This is dangerous because the blood clot may
dislodge from the leg and become lodged in the lungs causing a pulmonary embolism (a blood clot in the lung),
which is frequently fatal. Those undergoing hip and knee surgery are especially at risk. This is true in general
for any surgery in and around the pelvis.