Executive Editor: Steve Krikler

Authors: Paulo Barbosa, Felix Bonnaire, Kodi Kojima, Paul Demmer

Malleoli 44-B2.2 Circular cast

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Glossary

1 General considerations top


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Preliminary remarks

Nonoperative treatment of 44-B ankle injuries is usually only indicated for undisplaced, stable fractures. However, if the facilities and the skill for safe operative treatment are not available, nonoperative treatment is safer, and if performed correctly and skilfully, it can lead to acceptable results.

In any situation, a displaced ankle fracture should be reduced as soon as possible, even if surgery is planned for the near future.


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In the case of severe swelling, the reduced ankle fracture should be immobilized temporarily with a plaster of Paris (POP) back-slab, and elevated on several pillows.


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Anesthesia

In the absence of the facility for general anaesthesia, reduction can be achieved under sedation (e.g., Pethidine plus Diazepam), and/or intraarticular local anaesthesia (Lignocaine 2% 15ml).


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The intraarticular injection of local anaesthetic is introduced  anteromedially, between the tendons of tibialis anterior and extensor hallucis longus, medial to the anterior tibial neurovascular bundle.


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Typical displacement

The mechanism of injury in 44-B fractures is of external rotation of the talus in the ankle mortise, producing first a transsyndesmotic, oblique fibular fracture, often a posterior tibial fracture (Volkmann’s fragment) and finally a medial failure (either a deltoid rupture or a medial malleolar fracture).


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The typical clinical displacement in 44-B fractures is posterior and lateral, usually with the foot lying externally rotated.

Careful review of the x-ray images is essential for a full understanding of the injury.

Regard the injury as a two-part fracture between the lower leg (tibia and fibula) proximally, and the foot distally. The task will be to get the foot into correct alignment with the leg.

If x-rays are not available, it is safer to correct the deformity clinically, rather than to leave it unreduced.

2 Reduction top

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Treatment of patients presenting early

The aim of any reduction (early or late) is to correct the displacement.

Treat the patient on the day of injury, when the deformity is typical, late swelling has not yet appeared and adequate anaesthesia can be administered.

Use gravity to help to reduce the fracture.

The patient lies supine on the table, with the lower leg hanging over the end of the table. Hold the heel of the injured foot as shown and lift the externally rotated leg. In this procedure the weight of the leg will, in many cases, reduce the posterior and the lateral displacement automatically. Further pressure against lateral malleolus is usually unnecessary.


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Treatment of patients presenting late

If the patient presents late and there is no possibility to administer general anaesthesia, so that the patient is not fully relaxed, but merely sedated, or has only local intraarticular analgesia, reduction will not be achieved by gravity alone. Manual reduction is performed on the hanging leg, with the knee flexed to reduce the pull of the Achilles tendon.


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Correct alignment

The aim is to bring the foot into correct alignment with the lower leg.
Without x-rays, this is the only alignment reference available.


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Patterns of fracture morphology

In some 44-B fractures there will be a medial shoulder.
Either the fracture of the medial malleolus has left a shoulder (or beak) on the tibia...


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..., or the medial failure is a deltoid ligament rupture.


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In some patterns of 44-B fractures the medial fracture is flush with the joint level, not leaving any medial bony shoulder against which to reduce the talus.

In 44-B injuries, there is rarely a lateral (fibular) shoulder.


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Reduction of fracture with a medial shoulder present

Firstly, the posterior displacement is corrected.

A plantigrade position of the foot is important, but needs to be achieved by manipulation of the hindfoot downwards, forwards and correcting any external rotation, rather than pushing upwards on the forefoot.


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Avoid pushing the forefoot into dorsiflexion, as this tends to displace the talus posteriorly in the mortise. This is especially important when the fracture complex includes a posterior tibial marginal fracture (Volkmann’s fragment).


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After the AP correction, the talus can be pressed against the medial shoulder by pushing the mid - and hindfoot (heel) from lateral to medial against the counterpressure of the other hand on the lower end of the tibia as shown. At the same time any external rotation deformity is corrected.


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By exploiting the resistance of the medial shoulder, over-reduction should be avoided.


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Reduction of fracture without medial or lateral shoulder

There is a danger of overcorrection of the ankle medially, although the reduced distal fibula will tend to minimize this risk. In such cases, the AP displacement is corrected and the foot orientated in alignment with the lower leg, avoiding any undue medial pressure, and correcting any malrotation.

3 Holding the reduced position top

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With an assistant:

The assistant stands on the medial side of the injured leg and maintains some flexion of the knee and the right angle position of the ankle, pressing gently on the knee and holding the big toe forwards in line with the patella.

This usually holds the reduction that has been achieved and allows the operator to apply the padding and the plaster cast.

Tip: Avoid strong dorsiflexion of the foot as this can cause posterior displacement of the talus, as previously discussed under reduction of 44-B fractures.


Without an assistant:

Apply the plaster padding.

Then, apply around the ankle one roll of POP (dipped in cold water to give more time until hardening), reduce the fracture and maintain it reduced until the POP skim is hard enough to hold the reduction.

Then complete the below knee portion of the cast.

4 Preparation for cast application top

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Two person team

  • Operator and assistant


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Materials (prepared before the procedure)

  • 3-4 rolls 100 mm padding
  • 8 - 9 plaster of Paris rolls, 100 mm wide
  • Bucket with cold, or lukewarm, water
  • Low stool
  • Examination couch, or table
  • Aprons to protect team members and patient
  • Paper to cover the floor

5 Application of cast top

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Positioning in undisplaced fractures

44-B2/3 fractures are unstable in rotation and the reduction can only be controlled by an above-knee cast.

In undisplaced 44-B1 fractures, reduction is not necessary, and a below-knee cast will suffice.

The below knee portion of the plaster cast will be applied on the hanging leg (knee flexed to 90 degrees and ankle held at 90 degrees).


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Application of the padding

First, apply the padding above and below the knee. This needs to be thicker over the malleoli and around the fibular head.


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The cast should reach from the MTP joints of the toes to the upper thigh.


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Handling of plaster bandages

It is important to hold the plaster rolls correctly during application, so that they can be rolled on, rather than pulled on.


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Application of plaster bandages

The below-knee portion of the cast is applied first.

It is easier to start proximally, overlapping by half the width of the roll and moving down the lower leg to around the ankle and foot.


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After the application of the second roll, whilst the plaster is still soft, final manipulation, with appropriate molding, is done and the reduction held until the plaster hardens. This may take 4 to 5 minutes, depending on the temperature of the water – colder water gives you more time.

A further two rolls are then applied below the knee and further molding is performed to achieve the desired 3-point fixation.


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Moulding of the cast: 3-point cast fixation

When molding the cast, the same action as for reduction is repeated and held until the plaster is firm.

The principle of 3-point fixation within the cast needs to be applied. The two main molding points are created by gentle pressure over the lateral hindfoot and above over the medial supramalleolar part of the lower leg.


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The third point is created later by molding the upper end of the cast firmly around the lateral aspect of the leg.


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Application of the above-knee portion of the cast

The above-knee portion of the cast is then added.

6 Evaporation period top

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The patient should be warned that the leg in the plaster will feel cool and moist. This is due to the evaporation of water from the plaster. Once the cast is dry, the moist, cold feeling will disappear.

During the evaporation period, the casted limb should remain exposed and not fully covered by blankets.

Tip: Remember that the plaster requires over 24 hours to gain full strength.


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Compartment syndrome

Any plaster, especially one without adequate padding, carries a risk of causing obstruction of circulation and compartment syndrome.

In case of inappropriate pain, especially on passive dorsiflexion or plantarflexion of the toes, the plaster and padding should be split immediately down to skin, over its whole length, and the leg watched carefully for rapid recovery. It is better to lose the reduction than to risk muscle necrosis.

If the slightest suspicion of compartment syndrome remains, the plaster needs to be removed and urgent dermatofasciotomy considered.

7 Aftercare top

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General guidelines

Elevate the lower leg on 2-3 pillows for 3-5 days.

X-ray control after reduction confirms the position, but must be repeated after 3-5 days. Redisplacement usually occurs during the early days, as the swelling subsides, and if diagnosed early enough, can often still be corrected non-operatively.

Analgesics and anti-inflammatory drugs should be prescribed, as necessary, during the first few weeks. If analgesia consumption is unexpectedly high, suspect redisplacement, or cast pressure on the skin.

If a cast becomes loose, it should be removed and replaced with a new one. If possible, wait until the fracture has become sticky (+/- 4 weeks) so that the reduction is not lost during the replacement procedure, but check regularly for redisplacement.

Non weight bearing should be maintained for 4-6 weeks. The above-knee cast is maintained for the first 4-6 weeks.


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Thereafter, a below-knee cast can be applied for the remaining period of casting, as determined by the surgical decision-maker. Knee mobilisation can be started.

Graduated weight bearing can begin, reaching full weight bearing by 8-9 weeks.

In fractures that required reduction, the plaster cast should not be removed before 9-12 weeks, or before the patient manages to walk pain-free with the cast. In fractures that did not require reduction, the period in the cast can be reduced at the discretion of the surgical decision-maker.

After removal of the cast, rehabilitation should involve dedicated ankle and foot mobilization for a prolonged period. At this stage, it is also advisable to give a non-steroidal anti-inflammatory preparation for several weeks.

v1.0 2016-11-15