Study finds no significant increase in the risk of malunion or refracture
Historically, an above-knee cast (AKC) has been the gold standard for isolated fractures of the tibia in children. Although these fractures routinely heal, they have a tendency to displace into varus angulation. Researchers from the University of Utah hypothesized that when treated in a well-molded below-knee cast (BKC) with early weight bearing, pediatric fractures of the tibia with an intact fibula do not have a significant rate of displacement or complication.
The researchers retrospectively reviewed 269 pediatric patients ranging in age from 6 months to 16 years with isolated diaphyseal tibia fractures (closed or open) treated nonsurgically over a 4-year period in a high-volume fracture clinic with two attending staff surgeons. After being treated in splints at the time of injury, 44 patients (82 percent male; average age 8.3 years) were transitioned to an AKC; 225 patients (64 percent male; average age 3.2 years) were transitioned to a BKC and allowed weight bearing as tolerated at the time of casting.
Although the fractures were generally mid-diaphyseal and spiral in both groups, the frequency of the type of fracture treated in each group was different.
“Based on the significant differences in age, fracture pattern, and location, we did not compare the two groups directly. Rather, we drew our conclusions from analysis of the outcome of the BKC patients as a group,” explained Joshua W.B. Klatt, MD, the study’s lead author.
Changes in angulation
Initial fracture angulation in the BKC was less than one degree, on average, in each plane. All fractures healed with no delayed unions and the average healing time was 5.2 weeks. Because patients with minimal residual deformity were discharged from the fracture clinic when the cast was removed, the average follow-up was 7.5 weeks.
Average residual coronal angulation was 2.1 degrees (range: 10 degrees varus to 10 degrees valgus). Although 47 patients (21 percent) showed residual coronal angulation of 5 degrees to 9 degrees, and 2 patients (0.8 percent) had residual coronal angulation of 10 degrees, the researchers believed these ranges to be within the remodeling potential of each child. None of the patients had an unacceptable deformity of greater than 10 degrees of coronal angulation.
Average residual sagittal angulation was 0.3 degrees (range: 6 degrees recurvatum to 12 degrees procurvatum). Six patients (3 percent) had residual sagittal angulation of 5 degrees to 9 degrees, and one 15-year-old patient had residual sagittal angulation of 12 degrees. Examination of this patient at 6 months follow-up, however, showed a residual deformity of less than 10 degrees, with no symptoms, and the patient was discharged from the clinic.
The researchers looked for differences in angulation that could be attributed to various descriptive variables, including age, gender, fracture location, and pattern.
“We found no global, significant difference when comparing age to a tendency to angulate in the cast,” Dr. Klatt said. “There was also no difference when looking at those patients with a deformity greater than 10 degrees, and specifically, such deformities did not seem to occur in older children. We found similar findings in terms of gender.”
The researchers also found no significant difference based on fracture pattern.
Fracture type, however, did seem to correlate with change in angulation (Table 1), with oblique fractures having a greater tendency to change than spiral fractures. Transverse fractures had a similar tendency, but it was not statistically significant, noted Dr. Klatt.
The researchers found very few complications in the BKC group, none of which were determined to be directly related to the casting, although two patients did request that their BKC be changed to an AKC due to pain felt to be related to torsional instability in a short cast. None of the patients in the BKC had the cast wedged. Two patients sustained refractures at an average of 7 weeks after cast removal and were treated with a BKC for an additional 4 to 6 weeks.
The researchers concluded that when treating isolated fractures of the tibia with a BKC without specific weight-bearing restrictions, the risk of change in alignment greater than 5 degrees and the risk of residual malalignment greater than 10 degrees appear to be minimal.
“In our experience, a BKC with early weight bearing for isolated tibial shaft fractures in children adequately controls coronal and sagittal alignment,” said Dr. Klatt. “Based on these data, we routinely treat children up to the age of 15 years with an isolated tibia fracture in a well-molded below-knee fiberglass cast at 5 to 10 days post-injury.”
Dr. Klatt’s coauthors of “Isolated Pediatric Tibial Shaft Fractures Do Not Need to be Treated in Above-Knee Cast” were Alan K. Stotts, MD, and John T. Smith, MD.
Disclosures: The authors report no conflicts.
- This was a retrospective study conducted at a single high-volume fracture clinic.
- Traditionally, conservative treatment of isolated pediatric tibial shaft fractures has been an above-knee cast, transitioning to a below-knee cast after 2 to 4 weeks.
- Among pediatric patients (younger than age 15) whose isolated tibial shaft fractures were treated with a well-molded, fiberglass below-knee cast and no limitations on weight bearing, researchers found few complications and minimal residual malalignment.
- Oblique and transverse fractures were more likely to result in residual deformity than other fracture types.
Maureen Leahy is assistant managing editor for AAOS Now. She can be reached at firstname.lastname@example.org