Orthopaedic

CASE 72: aSSeSSment oF an anKle injury

history

A 17-year-old boy is brought to the emergency department by his father, having fallen off his skateboard earlier on in the afternoon. He is complaining of ankle swelling and pain, and has been unable to fully weight-bear on his right leg. He is otherwise fit and healthy. He last ate a sandwich 7 h ago.

examination

He has been assessed by the casualty officer, who reports that he warranted an x-ray based on the Ottawa rules.

INVESTIGATIONS

X-rays taken, and are shown in Figure 72.1.

Figure 72.1 plain x-rays of the ankle.

Questions

•What are the Ottawa rules?

•What do the x-rays show?

•What is the initial management?

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100 Cases in Surgery

ANSWER 72

The Ottawa rules were developed to help clinicians make a decision as to whether an ankle (or mid-foot) injury warrants radiographic assessment:

•Bone tenderness at the posterior edge or distal 6 cm or tip of the medial or lateral malleolus

•Bone tenderness at the base of the fifth metatarsal (for foot injuries)

•Bone tenderness at the navicular bone (for foot injuries)

•Unable both to weight-bear immediately after injury and walk four steps in the emergency department

All suspected bony injuries should have x-rays taken in at least two different planes (normally AP and lateral), to show whether there is a fracture. For the assessment of ankle injuries, mortise

Figure 72.2 Fractured medial malleolus.

and lateral view (and sometimes AP gravity stress) x-rays are taken. In this case, the patient has sustained a fracture of the medial malleolus (arrows in Figure 72.2).

The initial principles of management of any closed fracture are the same. Having made the diagnosis of an ankle fracture, the fracture should be stabilized. Usually this involves applying a ‘backslab’ (a plaster of Paris cast that is a half-completed cylinder, which will mean that any resultant swelling is not restricted). It is important that the patient is provided with adequate analgesia; the act of stabilizing the fracture will reduce the fracture movement and so help with pain control. Stabilization will also allow the ankle and leg to be elevated to reduce the swelling. The next stages in the management are reduction of the fracture, and fixation. In this case the ankle will need operative fixation; this can potentially be performed quickly as the patient has fasted for over 6 h. However, if the ankle is too swollen and there is concern that the soft tissues will be compromised by the operation, then this will mean a delay by a matter of days.

KEY POINT

•the ottawa rules can be used to determine if radiographical assessment of the ankle injury is required.

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Orthopaedic

CASE 73: a painFul anD SWollen Knee

history

A 63-year-old man with insulin-dependent diabetes mellitus attends the emergency department complaining of pain affecting his right knee. There is no history of significant trauma. On further questioning he had noticed that while gardening a few days previously, he sustained a small graze to the skin in that area.

examination

On examination, he is febrile (temperature 37.8°C), his blood pressure is 160/86 mmHg and his pulse rate is 96/min. Examination of his right knee reveals a red swollen joint that is tender. Attempting to move his knee both actively and passively results in severe pain. There is no abnormality to be found on examining his right ankle or hip.

INVESTIGATIONS

Questions

•What is the likely diagnosis?

•What should the initial management involve?

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100 Cases in Surgery

ANSWER 73

This man has a septic arthritis of the right knee. The localized redness and swelling can be associated with any inflammatory monoarthritis, but a septic arthritis is an important differential diagnosis suggested here by the history, examination findings and blood tests.

Septic arthritis can affect any joint. The most commonly affected joint is the knee (50 per cent of cases), followed by the hip (20 per cent), shoulder (8 per cent), ankle (7 per cent) and wrist (7 per cent). Staphylococcus aureus is the cause in the vast majority of cases of acute bacterial arthritis in adults. Streptococcal species, such as Streptococcus viridans, Streptococcus pneumoniae, and group B streptococci, account for 20 per cent of cases. Aerobic Gram-negative rods are involved in 20–25 per cent of cases. Organisms may invade the joint by direct inoculation, spread from adjacent infected tissue, or via the bloodstream, which is the most common route. Following the initial stabilization of the patient (they may be unwell with signs of septic shock), the joint should be aspirated. The aspirated fluid should be sent to the laboratory for microscopy to look for pus cells and evidence of bacterial infection. The fluid should also be examined with polarizing microscopy to look for the presence of crystals. This is to exclude the differential diagnosis of crystal arthropathy (gout or pseudo-gout). Blood tests can be useful as they suggest the presence of infection (raised WCC and inflammatory markers). In addition, blood cultures should be sent as they may isolate a causative organism. Treatment of a septic joint should be prompt and effective. The joint should undergo a thorough washout followed by immobilization. High-dose empirical antibiotics such as flucloxacillin or a third-generation cephalosporin should be administered intravenously until cultures and sensitivities are available. The major consequence of bacterial infection is damage to articular cartilage. This may be the result of the infective organism’s pathological properties or the host’s own immune response. Delay in the diagnosis and treatment will result in a poorly functioning joint.

KEY POINTS

•Staphylococcus aureus is the most common causative organism.

•prompt treatment is required to prevent permanent damage to the joint.

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