Background: Nonunion is a rare complication of a fracture of the
clavicle, but its occurrence can compromise shoulder function. The aim of this
study was to evaluate the prevalence of and risk factors for nonunion in a
cohort of patients who were treated nonoperatively after a clavicular
fracture.
Methods: Over a fifty-one-month period, we performed a prospective,
observational cohort study of a consecutive series of 868 patients (638 men
and 230 women with a median age of 29.5 years; interquartile range, 19.25 to
46.75 years) with a radiographically confirmed fracture of the clavicle, which
was treated nonoperatively. Eight patients were excluded from the study, as
they received immediate surgery. Patients were evaluated clinically and
radiographically at six, twelve, and twenty-four weeks after the injury. There
were 581 fractures in the diaphysis, 263 fractures in the lateral fifth of the
clavicle, and twenty-four fractures in the medial fifth.
Results: On survivorship analysis, the overall prevalence of
nonunion at twenty-four weeks after the fracture was 6.2%, with 8.3% of the
medial end fractures, 4.5% of the diaphyseal fractures, and 11.5% of the
lateral end fractures remaining ununited. Following a diaphyseal fracture, the
risk of nonunion was significantly increased by advancing age, female gender,
displacement of the fracture, and the presence of comminution (p < 0.05 for
all). On multivariate analysis, all of these factors remained independently
predictive of nonunion, and, in the final model, the risk of nonunion was
increased by lack of cortical apposition (relative risk = 0.43; 95% confidence
interval = 0.34 to 0.54), female gender (relative risk = 0.70; 95% confidence
interval = 0.55 to 0.89), the presence of comminution (relative risk = 0.69;
95% confidence interval = 0.52 to 0.91), and advancing age (relative risk =
0.99; 95% confidence interval = 0.99 to 1.00). Following a lateral end
fracture, the risk of nonunion was significantly increased only by advancing
age and displacement of the fracture (p < 0.05 for both). On multivariate
analysis, both of these factors remained independently predictive of nonunion
(p < 0.05), and, in the final model, the risk of nonunion was increased by
a lack of cortical apposition (relative risk = 0.38; 95% confidence interval =
0.25 to 0.57) and advancing age (relative risk = 0.98; 95% confidence interval
= 0.97 to 0.99).
Conclusions: Nonunion at twenty-four weeks after a clavicular
fracture is an uncommon occurrence, although the prevalence is higher than
previously reported. There are subgroups of individuals who appear to be
predisposed to the development of this complication, either from intrinsic
factors, such as age or gender, or from the type of injury sustained. The
predictive models that we developed may be used clinically to counsel patients
about the risk for the development of this complication immediately after the
injury.
Level of Evidence: Prognostic study, Level I-1
(prospective study). See Instructions to Authors for a complete description of
levels of evidence.