Fragment Displacement in Fractures

Correction of length displacement

Displacement of bone fragments along the length is a serious biomechanical problem. The main difficulty in performing closed reduction is the need to apply significant force. This is due to the fact that trauma triggers a pronounced reflex contraction of the surrounding muscles. This problem is particularly prominent in femoral fractures, where the muscle mass possesses enormous traction force.

The basic technique for correcting this type of displacement involves two simultaneous and oppositely directed force vectors:

• Longitudinal traction (traction of the distal fragment along the axis of the limb).
• Counter-traction applied to the central (proximal) end of the limb.

The adequacy of the manipulation and the completeness of longitudinal displacement correction must be monitored by carefully measuring the length of the injured limb.

Mean physiological position

To maximize relaxation of reflexively contracted muscles and facilitate the reduction process (both in length and width), the injured limb must be placed in the mean physiological position. These are strictly calibrated angles of flexion and abduction at which the tension of antagonistic muscles is balanced.

The parameters of the physiological position differ significantly for various segments of the musculoskeletal system:

1. Lower limb (in femoral fractures):
2. It is necessary to ensure simultaneous flexion in both the hip and knee joints.
3. The flexion angle in both joints should be exactly 140°.

1. Upper limb (in humeral fractures):
2. Abduction of the shoulder by 60° is required.
3. Additionally, anterior abduction of the shoulder by 30° is performed.
4. The arm is flexed at the elbow joint at a right angle (90°).
5. The forearm is fixed in the neutral (mid) position, exactly halfway between pronation and supination.

Correction of width displacement

Displacement of fragments in width (lateral displacement) is officially recognized as the most difficult type of reduction in trauma practice. As with longitudinal displacement, the basic technique involves traction and counter-traction maneuvers, which are strictly performed while the limb is in the mean physiological position.

However, the surgeon often encounters insurmountable mechanical obstacles on the path to successful closed fragment apposition:

• Soft tissue interposition — entrapment of muscles, fascia, or neurovascular bundles between bone fragments. This complication is most commonly observed in transverse diaphyseal fractures.
• Bone spikes and projections — sharp irregularities on the edges of the fragments that cause them to firmly hook onto each other, blocking their movement.

If attempts at closed apposition fail due to soft tissue interposition or engagement of bone spikes, this is regarded as a relative indication for surgical treatment (open reduction of bone fragments).

Class and exam questions

What else to study on this topic

• Biomechanics of reflex muscle contraction in fractures
• Methodology for measuring lower and upper limb length
• Soft tissue interposition: risks and consequences
• Technique of open reduction in transverse diaphyseal fractures
• Features of traction in fractures of the leg and forearm bones

Other topics in "CHAPTER 10. GENERAL ISSUES IN TRAUMATOLOGY"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.