Complications of Fractures and Immobilization

Fractures and their treatment can be followed by complications that arise either from the injury itself or from the consequences of immobilizing an injured limb. These range from disturbances of healing, such as delayed union and nonunion, to acute limb-threatening problems such as compartment syndrome, and to the systemic and local effects of prolonged immobility.

Definition

Complications of fractures and immobilization are the adverse outcomes that follow skeletal injury or its management, including impaired or failed bone union, acute compartment syndrome, infection, and the local and systemic effects of prolonged immobility.

Scope

This entry surveys the principal complications associated with fractures and immobilization as reference concepts: disturbances of union (delayed union, nonunion, malunion), acute compartment syndrome, infection of open or operated fractures, and the consequences of immobility. Stress fractures, the MeSH anchor for this entry, are included as an injury arising from repetitive loading. The entry does not provide diagnostic thresholds or treatment instructions for any individual.

Core questions

• How do delayed union, nonunion, and malunion differ?
• What is acute compartment syndrome and why is it time-critical?
• What complications arise specifically from prolonged immobilization?
• How does repetitive loading produce a stress fracture?

Key concepts

• Delayed union
• Nonunion (atrophic and hypertrophic)
• Malunion
• Acute compartment syndrome
• Fracture-related infection
• Stress (fatigue and insufficiency) fracture
• Complications of immobility
• Avascular necrosis

Mechanisms

Disturbed healing reflects an inadequate biological or mechanical environment: insufficient blood supply or biology produces atrophic nonunion, while excessive motion at the fracture produces hypertrophic nonunion with abundant but non-bridging callus; Einhorn and Gerstenfeld (2014) frame these as failures of the normal repair sequence. Acute compartment syndrome occurs when rising pressure within an enclosed fascial compartment compromises tissue perfusion; McQueen and Court-Brown (1996) defined a perfusion-based (differential) pressure threshold for decompression, and McQueen et al. (2013) characterized the diagnostic performance of continuous pressure monitoring. Compartment syndrome can itself impair healing, as Court-Brown and McQueen (1987) showed for tibial fractures. A stress fracture, the MeSH anchor here, arises when repetitive submaximal loading exceeds the bone's capacity to remodel, producing a fatigue fracture in normal bone or an insufficiency fracture in weakened bone. Prolonged immobilization adds its own burden through muscle wasting, joint stiffness, bone loss, and thromboembolic and other systemic risks.

Clinical relevance

Recognizing the spectrum of fracture and immobilization complications is central to interpreting outcomes after injury and to evidence appraisal in orthopedics. As reference knowledge it explains why some fractures fail to heal and why certain complications are emergencies; it describes these processes and is not a source of diagnostic thresholds or treatment decisions for any individual.

Epidemiology

Compartment syndrome is most often associated with tibial diaphyseal fractures and with younger patients, as documented in the tibial-fracture cohorts of McQueen and colleagues. The frequency of nonunion varies markedly by bone, fracture pattern, and host factors, and stress fractures cluster in weight-bearing bones of physically active populations.

History

Awareness of fracture complications evolved alongside fixation surgery: as operative treatment expanded, infection, nonunion, and malunion became defined endpoints, and compartment syndrome was increasingly recognized as a time-critical emergency. Work in tibial fractures established perfusion-based pressure thresholds and quantified the limits of pressure monitoring, refining how the syndrome is conceptualized.

Debates

How should acute compartment syndrome be diagnosed?

Reliance on intracompartmental pressure measurement versus serial clinical assessment is contested, because continuous monitoring can over-diagnose the syndrome; the balance between sensitivity and specificity of pressure thresholds remains unresolved.

Key figures

• Margaret McQueen
• Charles Court-Brown
• Thomas Einhorn

Seminal works

• mcqueen-court-brown-1996
• mcqueen-2013
• einhorn-gerstenfeld-2014

Frequently asked questions

What is the difference between delayed union and nonunion?

Delayed union means a fracture is taking longer than expected to heal but is still progressing, whereas nonunion means the healing process has stopped without achieving bony union; the distinction is one of trajectory rather than a single fixed time point.

Why is acute compartment syndrome considered an emergency?

Because rising pressure within a closed fascial compartment can cut off perfusion to muscle and nerve, prolonged unrelieved pressure leads to irreversible tissue damage, which is why it is treated as time-critical.