Over time the treatment of both-bone forearm shaft fractures in children has become increasingly surgical in nature1,17–19,29,30
. However, before closed reduction and casting should be supplanted as the preferred method of treatment for these injuries, clinicians must understand the circumstances in which surgery may be more advantageous29
. To our knowledge this is the largest shaft-specific complete both-bone forearm fracture study to characterize the early radiographic outcomes of non-operatively treated children. This is also the first known study to use a multivariate statistical analysis to model failure probability. Identifying those injuries most likely to fail non-operative treatment could provide key decision making information both for parents and the clinicians caring for children with these injuries.
Evaluation of 282 complete both-bone forearm shaft fractures treated by closed reduction and casting revealed that 51% of participants failed to meet angulation criteria with non-operative treatment within four weeks of follow-up. Our findings are consistent with previous studies. Kay et al. determined that 64% of their patients older than age 10 failed closed reduction and casting using an angulation criterion of 10 degrees4
. Thomas et al. found that 39% of their patients with mid-shaft fractures had unsatisfactory results due to an angulation of >10 degrees, loss of range of motion, or a cosmetic deformity3
. The results of our multivariate analysis indicate that those at highest risk of failure following closed reduction and casting are patients 10 years or older (OR= 2.79, CI95
1.47 to 5.29), those with proximal radius fractures (OR= 6.81, CI95
3.28 to 14.14), and those with initial ulna angulations <15 degrees (OR= 2.94, CI95
1.49 to 5.83). While the findings for age and level of fracture are intuitive, it is initially perplexing that a lesser initial angle of the ulna predicts failure, though the association was strong and consistent. We suggest that this is due to the relatively intact ulna allowing uneven static and dynamic forces to negatively influence the position of the radius. Re-angulation occurs as swelling decreases and the tensions afforded by the interosseous membrane and attaching muscles change. The location of attachment and relative strength of these structures will affect the position of the healing bones22
Over half of participants who failed angulation criteria at follow-up had their first radiographic evidence of failure during the first week, with 95% failing within three weeks. Voto et al. made a similar observation, stating that the majority of fractures that re-angulated in their study did so by two weeks8
. Our results also showed that 84% of participants who had post-reduction angulations exceeding the acceptable angulation criteria failed to meet the criteria at follow-up, illustrating that residual angulation generally does not improve within the first month following reduction. This suggests that anatomic reduction is imperative. Patients should also be monitored weekly within the first month in order to properly monitor closed fracture care. We note that bayonet apposition with shortening, leading to severe compromise of the interosseous space, was present in all 12 of our participants who underwent surgery though they did not fail the angulation criteria. This shows that clinicians base decisions on factors other than angulation alone. Based on limits of agreement, we found the maximum deviation between any two measurements was 4.3 degrees, which is consistent with previous estimates of variation in radiographic fracture angulation measurements of ±5 degrees27,28
The anatomy of the forearm dictates its function. In 1959, Sage described the bow of the radius to be 9.3 degrees31
. His approximation used the entire bone to estimate the bow of the radius, which averaged over the subtle curvatures of each segment. Clinically however, forearm shaft fractures are analyzed by thirds. After we evaluated 30 normal forearms and found a mean angulation of 6.0 degrees apex radial in the middle-third, we felt it appropriate to account for the natural bow of the radius using a population based correction factor. Since the mean angulation value for the distal and proximal thirds were within the range of error for our measurements, we chose to not correct these segments. In 1986, Roberts employed a similar technique and found a mean angulation of 3.7 degrees in the middle third of the radius32
. Other methods of approximating the natural bow of the radius using axis deviation have been described and applied, although the calculations can be cumbersome in practice9
. Our hope is that future studies of forearm shaft fractures will apply methods similar to ours to account for the anatomy of the radius.
The importance of the normal curvature of the radius is recognized for its role in the normal rotation of the radius about the ulna6,33–35
. Normal range of forearm motion is approximately 71 degrees pronation and 84 degrees supination36
. Schemitsch and Richards, who examined both-bone fracture malunions in adults, claimed that loss of forearm rotation and grip strength could be expected if the normal radial bow magnitude and location were not restored relative to the non-injured extremity within 4–5%35
. Clinical studies of both-bone forearm shaft fractures in children show that range of motion is significantly affected by residual angulation of fractures. Daruwalla et al. found that 53% of patients had limited range of motion, and 13% had greater than 40 degrees of loss10
. Carey et al. revealed that 60% of their patients 11–15 years had residual loss of motion, up to 30 degrees11
. Cadaveric studies described the loss of rotation expected with varying degrees of angulation. Matthews et al. found that approximately 30%, or 60 degrees, loss of pronation-supination resulted with an angulation of 20 degrees5
. Tarr et al. described angulations of 15 degrees causing greater than 27% loss in range of motion, with middle-third deformities causing the greatest loss6
. Sarmiento et al. confirmed these findings and showed greater supination losses in middle-third forearm shaft fractures and greater pronation losses in distal-third forearm shaft fractures7
The criteria for failure that we used changed based on age and level of fracture, an approach based on biological phenomena and well supported in the literature9,13,19,22–26
. Though paradoxical outcomes occur (poor alignment with no loss of motion and anatomic alignment with significant loss of motion), there is a direct relationship between increasing radial shaft angulation and loss of forearm rotation5–7
. However, the remarkable remodeling potential that the radius and ulna posses in children is an important confounding factor of this relationship26
. Clinicians account for remodeling in their treatment decisions, allowing post-reduction angulations of greater than 10 degrees in younger children. Most clinicians agree that prognosis changes as the fracture level progresses from distal to proximal due to a greater capacity for remodeling at the distal end4,15,32,37
. The distal forearm in younger children is particularly adept at correcting non-anatomic alignments because 75% of the radial growth occurs at the distal physis16
. Remodeling capacity declines with age, and is greatly diminished as females reach 8 years and males 10 years of age16,26
. Since remodeling capacity decreases with age and more proximal level shaft fractures, residual angulation of middle and proximal shaft fractures is more problematic in older children2,15,26
. The angulation criteria used in our study account for likely remodeling capacity.
One may argue as to what amount of loss of motion is clinically relevant. Morrey et al. found that most activities of daily living could be performed with only 100 degrees of rotation, 50 degrees of both pronation and supination36
. Others have found that patients are often unaware of their deficits of 35 up to 60 degrees loss of forearm motion due to compensation with shoulder abduction, and that cosmesis is often the patient’s main concern2,10–13
. However, even if a child is unaware of a moderate loss of forearm rotation or daily activities are not impaired, it seems inappropriate to place a child at this disadvantage when better options exist. Certainly, informed decision makers would choose normal range-of-motion.
The imperfect correlation between residual angulation and loss of forearm rotation fuels the debate over the proper management of both-bone forearm fractures, particularly in older pediatric populations11,13
. Several studies show non-operative treatment to have low rates of re-angulation8,37
. However, high numbers of distal forearm fractures near the metaphysis skew these results due to their more forgiving nature compared to mid-shaft fractures38
. Fracture re-manipulation with closed reduction and casting is another viable option if initial reduction is insufficient. Operative techniques, including ESIN, have been shown to effectively prevent re-angulation17–21
. However, surgery carries its own risk of complications, and it is wise to remember Sarmiento’s advice that closed fracture treatment must not be abandoned for newer, less proven, surgical techniques, and that surgical intervention does not always restore a normal range of forearm motion7,39
. The current treatment protocol used at our institution implements the same criteria for acceptable shaft angles as indicated in our study and mimics the criteria proposed by Price et al.13
. Bayonet apposition is considered acceptable, unless the interosseous space is significantly compromised, and malrotation of less than 45 degrees is accepted. Our audit of surgical decision making at our institution revealed that only 40 of the 144 participants who did not meet radiographic angulation standards actually underwent surgery. Barriers to demanding optimal radiographic outcomes include limited operating room access, patient choice, lack of adequate follow-up, perceived potential for remodeling, lack of noticeable range of motion loss despite angulation, and differing opinions among surgeons in our practice.
Our work must be interpreted within the context of the study design. Our predictive model was derived from a retrospective cohort, and future prospective validation is required. Another limitation of our study is that we used angular data from only two planes. Concurrent angulation in both the radioulnar and dorsoventral planes indicates a maximum angle that is out of the plane of either view, whereby the actual magnitude and direction can be approximated using geometry9
. We also note that a cohort of our both-bone shaft fractures went immediately to surgery, suggesting that our prediction of failure may in fact be underestimated due to removal of the potentially more severe cases. We acknowledge that re-angulation may occur beyond one month of follow-up, though our results indicate it is more likely early in treatment. Finally, although the most accurate comparison for the normal bow of the radius would be personalized, based on comparison to an individual’s “normal” forearm, the retrospective nature of our data prohibited this evaluation.
Closed reduction and casting plays an essential role in fracture care. However, clinicians must recognize when patients are at risk for suboptimal outcomes. We do not propose abandonment of closed reduction and casting for forearm shaft fractures. On the contrary, we support a prudent approach that evaluates a patient’s likelihood of failing angulation criteria with closed reduction and casting, to appropriately balance the risk and potential benefits. According to this study, those at highest risk are patients 10 years or older, those with proximal-third radius fractures, and ulna fracture angles less than 15 degrees. These patients should be considered for surgery. Inadequate initial reduction and bayonet apposition with shortening, if the interosseous space is severely compromised, may also be important factors in surgical decision making. It appears that the greatest chance of failure occurs early in non-operative treatment, and generally speaking, residual angulation does not improve in the first month. Proper management of complete forearm fractures in children is challenging, however, clinicians can use predictors of age, level of fracture, initial angulation, and sufficiency of initial reduction to guide treatment and attempt to achieve the best possible outcome for the patient.