Defining the Lower Limit of a "Critical Bone Defect" in Open Diaphyseal Tibial Fractures.
OBJECTIVE
To determine healing outcomes of open diaphyseal tibial shaft fractures treated with reamed intramedullary nailing (IMN) with a bone gap of 10-50 mm on ≥50% of the cortical circumference and to better define a "critical bone defect" based on healing outcome.


METHODS
Retrospective cohort study.


METHODS
Forty patients, age 18-65, with open diaphyseal tibial fractures with a bone gap of 10-50 mm on ≥50% of the circumference as measured on standard anteroposterior and lateral postoperative radiographs treated with IMN.


METHODS
IMN of an open diaphyseal tibial fracture with a bone gap.


METHODS
Level-1 trauma center.


METHODS
Healing outcomes, union or nonunion.


RESULTS
Forty patients were analyzed. Twenty-one (52.5%) went on to nonunion and nineteen (47.5%) achieved union. Radiographic apparent bone gap (RABG) and infection were the only 2 covariates predicting nonunion outcome (P = 0.046 for infection). The RABG was determined by measuring the bone gap on each cortex and averaging over 4 cortices. Fractures achieving union had a RABG of 12 ± 1 mm versus 20 ± 2 mm in those going on to nonunion (P < 0.01). This remained significant when patients with infection were removed. Receiver operator characteristic analysis demonstrated that RABG was predictive of outcome (area under the curve of 0.79). A RABG of 25 mm was the statistically optimal threshold for prediction of healing outcome.


CONCLUSIONS
Patients with open diaphyseal tibial fractures treated with IMN and a <25 mm RABG have a reasonable probability of achieving union without additional intervention, whereas those with larger gaps have a higher probability of nonunion. Research investigating interventions for RABGs should use a predictive threshold for defining a critical bone defect that is associated with greater than 50% risk of nonunion without supplementary treatment.


METHODS
Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
*Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC; and †Department of Orthopaedic Surgery, Loyola University Medical Center, Chicago, IL.
Nikkole M
NM
Haines
William D
WD
Lack
Rachel B
RB
Seymour
Michael J
MJ
Bosse
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005594:Fracture Fixation, Intramedullary; D017102:Fracture Healing; D005597:Fractures, Open / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020127:Recovery of Function; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013978:Tibial Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D055815:Young Adult