Authors: Caitlin Wetzel, Matthew Rohl, Taylor Manes, Allen Kadado
Categories: Current Concept Review, Pediatric forearm fractures, Bowing fracture, Plastic deformation, Radius, Ulna, Pediatric bone biomechanics, Radiographic measurement, Closed reduction
Source: Journal of the Pediatric Orthopaedic Society of North America
Authors: Caitlin Wetzel, Matthew Rohl, Taylor Manes, Allen Kadado
Pediatric forearm bowing fractures, also known as plastic deformation fractures, are a clinically important but often underdiagnosed injury pattern. These fractures usually occur from longitudinal compressive forces such as falls on an outstretched hand, causing plastic deformation that exceeds the elastic limit of pediatric bone. Patients often present with nonspecific symptoms like pain, swelling, and limited pronation-supination, and these injuries can be subtle on radiographs. Using standardized measurement methods, such as the percentage of radial bowing relative to total bone length, can improve diagnosis; values over approximately 10% of radial length are considered suggestive of pathological bowing. Missing or delaying diagnosis can lead to persistent deformity, limited forearm rotation, malunion, and long-term functional impairments. The purpose of this review is to synthesize and critically evaluate the current literature on pediatric forearm bowing fractures, focusing on their pathophysiology, injury mechanisms, clinical presentation, diagnostic challenges, imaging options, measurement techniques, treatment strategies, and outcomes.
(1)Pediatric forearm bowing fractures are subtle plastic deformation injuries that are often underdiagnosed because of minimal radiographic evidence.(2)Unique biomechanical properties of pediatric bone allow deformation without cortical disruption, which can increase the risk of missed diagnoses.(3)Standardized radiographic measurements and awareness of normative bowing values enhance diagnostic accuracy.(4)Early identification and suitable management are essential to prevent long-term deformity and loss of forearm rotation.
Isolated plastic (bowing) deformation of the pediatric forearm is a distinct injury pattern characterized by lasting cortical bending without obvious cortical disruption. Unlike complete or greenstick fractures, plastic deformation occurs when forces exceed the elastic limit of immature bone but do not produce a visible fracture line on standard radiographs. This phenomenon reflects the unique biomechanical properties of pediatric cortical bone including increased elasticity, lower mineral density, and a thick, biologically active periosteum, which together allow deformation before structural failure [1].
Normal forearm rotation relies on maintaining the natural radial bow, a physiological lateral curve of the radius that aids pronation and supination. Radiographic studies of uninjured pediatric forearms have shown that the position of maximum radial bow generally stays consistent at about 60% of the total radial length from the proximal end, while the proportional depth averages 7-8% of radial length during childhood and adolescence [2]. Although the overall bow size increases with skeletal growth, its relative position remains stable. These normative data offer a vital reference for differentiating normal curvature from deformities caused by trauma.
Traumatic forearm bowing was first systematically described by Borden in 1974, who reported children presenting with persistent curvature of the radius and/or ulna following trauma in the absence of discrete fracture lines [3]. Subsequent radiographic analyses emphasized that plastic deformation may be subtle and easily overlooked on routine imaging [3,4]. Because cortical continuity is preserved, these injuries are often underrecognized or mistaken for normal bowing, especially in emergency settings [4,5].
Remodeling potential in diaphyseal forearm injuries depends on patient age, deformity size, bone involvement, and fracture location. Younger children show a greater ability for correction over time; however, remodeling is less predictable in mid-diaphyseal injuries compared with metaphyseal fractures [1,6]. Combined radial and ulnar bowing may cause more impairment of pronation and supination than deformities in a single bone, reflecting the interconnectedness of forearm rotational mechanics [7]. Experimental models have shown that angular deformities as small as 10°-15° can significantly reduce forearm rotation, with larger deficits at higher angles [7]. Proximal deformities may have greater rotational effects due to changes in radial bow mechanics and interosseous membrane tension.
Failure to recognize and properly manage clinically significant plastic deformation may lead to persistent deformity, altered biomechanics, and measurable loss of pronation and supination [8]. While children have substantial remodeling capacity, diaphyseal plastic deformation may not reliably straighten with growth alone, especially when deformity is severe or diagnosis is delayed [6,8]. Importantly, no validated age-dependent angular thresholds have been established to guide treatment.
Despite their clinical importance, the literature on isolated pediatric forearm plastic deformation remains sparse, mainly consisting of case reports and small retrospective series [3,6,9]. Diagnostic criteria, standardized measurement methods, and management thresholds are not consistently defined across studies. Although plastic deformation may occur in association with other injury patterns such as Monteggia lesions, the present review focuses on isolated traumatic plastic deformation to better define its diagnostic features, radiographic assessment, and management considerations. Percentage-based measurement strategies, which describe the maximal radial bow relative to total bone length, have enhanced objective radiographic assessment [2,10]. However, these approaches have not been linked to validated intervention thresholds, and variability continues in their clinical use.
The purpose of this review is to synthesize the existing literature specifically addressing isolated traumatic plastic deformation of the pediatric forearm, with emphasis on biomechanical mechanisms, radiographic recognition, and standardized measurement, as well as natural history, remodeling considerations, management strategies, and functional outcomes. By isolating this injury entity from broader pediatric forearm fracture patterns, this review aims to clarify the current evidence, address gaps in clinical guidance, and identify areas requiring further investigation.
This review was conducted following current-concepts review methodology and did not include a meta-analysis due to significant clinical and methodological heterogeneity. A structured literature search was performed using PubMed/MEDLINE and Scopus from database inception through February 1, 2026. Search terms included combinations of “plastic deformation,” “plastic bowing,” “bowing fracture,” “traumatic bowing,” “forearm,” “radius,” “ulna,” “pediatric/paediatric,” and “child/children.” Reference lists of included articles were manually reviewed to identify additional relevant publications. Duplicate records found across databases were removed before screening.
Studies were included if they reported traumatic plastic (bowing) deformation of the forearm (radius, ulna, or both) in skeletally immature patients and described isolated plastic deformation without overt cortical disruption on plain radiographs. Eligible studies needed to provide forearm-specific clinical data including presentation, diagnostic evaluation, management strategy, and/or outcomes. Original reports, such as case reports, case series, and cohort studies, were included. Diagnostic imaging-focused studies were retained if they specifically addressed acute plastic deformation of the pediatric forearm (eg radiographic recognition or magnetic resonance imaging [MRI] evaluation).
Study identification and selection are illustrated in Fig. 1. Titles and abstracts were screened for relevance, followed by a full-text review to confirm eligibility. For included studies, extracted data included patient demographics, mechanism of injury, bones involved, diagnostic method, measurement technique when reported, treatment strategy, follow-up duration, and clinical outcomes.Figure 1Flow diagram illustrating literature identification, screening, and inclusion of studies evaluating isolated traumatic plastic deformation of the pediatric forearm.Figure 1
Given the predominance of case reports and small case series, findings were synthesized qualitatively.
A total of 19 studies met the inclusion criteria after database search and reference mining (Fig. 1, Table 1). The literature mainly consisted of case-based reports including individual case reports and small case series, as well as additional diagnostic imaging-focused studies and one narrative review with extractable clinical data. Publication years ranged from 1974 to 2025.Table 1Reported degree of bowing and corresponding management in published cases of pediatric forearm plastic deformation.Table 1StudyPopulationStudy designBone(s) involvedPrimary focusBorden (1974)PediatricCase reportRadius ± ulnaRadiographic recognition of acute plastic bowingBorden (1975)PediatricCase seriesRadius ± ulnaTraumatic bowing in childrenCrowe & Swischuk (1977)PediatricCase seriesRadius and ulnaFrequently missed acute bowing injuriesKöteles & Szigetváry (1982)Pediatric extremity cohortCase seriesForearm cases included (bowing degree not isolated)Pediatric bowing patternsNaga & Broadrick (1977)PediatricCase reportRadius and ulnaTraumatic bowing with associated instabilitySanders & Heckman (1984)PediatricCase seriesRadius and ulnaClosed reduction technique for plastic deformationRydholm & Nilsson (1979)PediatricCase reportRadius and ulnaTraumatic forearm bowingDemos (1980)PediatricCase reportUlnaIsolated ulnar plastic bowingMizutani et al.PediatricImaging studyRadiusMRI evaluation of acute plastic deformationMiller & OsterkampPediatricImaging studyForearmScintigraphy in acute plastic bowingNimityongskul et al.PediatricReview + case reportsForearmDiagnosis and management of plastic deformationScheuer & PotPediatricCase reportRadius and ulnaAcute traumatic bowing fractureVervaeke et al.PediatricCase reportForearmImportance of adequate diagnosisZhou et al.PediatricDiagnostic modeling studyForearmComputer-assisted detection (CADx)Blankstein et al.PediatricBiomechanics-focused studyForearmBiomechanical aspects of traumatic bowingKomara et al.PediatricCase reportRadius and ulnaAcute plastic bowing fracturesVorlat & De BoeckPediatricCase series (LTFU)Radius and ulnaLong-term outcomes of bowing fracturesWorrallPediatricCase reportRadius and ulnaPathophysiology, diagnosis, and managementAttia & GlasstetterPediatricCase reportForearmPlastic bowing type fracture in childrenMRI, magnetic resonance imaging.
Foundational descriptions of traumatic forearm bowing were published in the 1970s [3,11], with additional early radiographic case reports emphasizing diagnostic subtlety [12], and subsequent case-based reports continuing intermittently through the modern era [4,6,8,9,[13], [14], [15], [16], [17]].
Most studies described isolated plastic deformation of the radius or ulna, or both, without obvious cortical disruption on plain radiographs (Figure 2A, Figure 2B, Figure 2CA-2C). Several publications focused specifically on diagnostic recognition including radiographic identification [4], scintigraphic evaluation [18], MRI-based assessment [19], and, more recently, computer-assisted detection approaches [20]. Despite advances in imaging modalities, plain radiography remained the main diagnostic tool across all eras (Table 2).Figure 2AIsolated radial plastic deformation. Anteroposterior (AP) and lateral radiographs demonstrating isolated plastic (bowing) deformation of the radius following trauma. Subtle diaphyseal curvature is present without overt cortical disruption. Arrows indicate the region of maximal bowing. No contralateral comparison radiographs were available [21].Figure 2AFigure 2BIsolated ulnar plastic deformation. AP and lateral radiographs demonstrating isolated traumatic plastic deformation of the ulna. The diaphyseal bowing is appreciable on both projections without a visible fracture line. The arrow indicates the region of maximal ulnar curvature. No contralateral comparison views were available [22]. *AP, anteroposterior.*Figure 2BFigure 2CCombined volar bowing of the radius and ulna. AP and lateral radiographs demonstrating combined plastic deformation of both the radius and ulna with dorsally directed diaphyseal curvature. Arrows highlight maximal bowing. No discrete cortical disruption is identified. Contralateral radiographs were not available for comparison [23]. AP, anteroposterior.Figure 2CTable 2Radiographic measurement techniques and quantitative parameters used to assess forearm bowing.Table 2StudyMeasurement methodQuantitative Bow ReportedContralateral comparisonIntervention threshold reportedBorden (1974, 1975)Visual radiographic assessmentNoYes (recommended)NoCrowe & Swischuk (1977)Visual + radiographic scrutinyNoYesNoSanders & Heckman (1984)Radiographic angulation assessmentLimited qualitative descriptionNot consistently reportedNoRydholm & Nilsson (1979)Radiographic curvature assessmentNoNot specifiedNoDemos (1980)Visual radiographic recognitionNoNot specifiedNoMizutani et al.MRI confirmation of bowingNo angular thresholdNot primary focusNoMiller & OsterkampScintigraphy + radiographsNo quantitative angleNot primary focusNoZhou et al.Computer-assisted detection modelAlgorithm-derived curvatureNo clinical thresholdNoVorlat & De BoeckRadiographic bowing assessmentYes (descriptive magnitude)Not standardizedNoKass et al. (normative reference)Percentage radial bow (location + depth)Yes (location ∼60%, depth ∼7-8%)Not applicableNo validated cutoffAll other case reportsQualitative radiographic evaluationNo standardized measurementOccasionally usedNoMRI, magnetic resonance imaging.
Plastic deformation was reported most frequently in skeletally immature children, typically under 10 years of age, although age reporting was inconsistent across studies [3,6,8,24].
Mechanisms of injury were most commonly low-to moderate-energy trauma including falls onto an outstretched hand, playground injuries, sports-related incidents, and bicycle accidents [3,4,15].
Both-bone involvement of the radius and ulna was described in the majority of cases [6,8]. Isolated single-bone bowing, most commonly involving the ulna, was reported in several studies [14,16,25].
The underlying pathophysiology was consistently attributed to the viscoelastic properties of pediatric cortical bone, which permit deformation when forces exceed the elastic limit but remain below the threshold for cortical fracture [1]. Several reports noted that unrecognized plastic deformation may predispose to secondary complications including radial head instability [8,13].
Delayed or missed diagnosis was reported in multiple studies, particularly when deformity was subtle and cortical continuity appeared preserved [[3], [4], [5],11].
Early descriptions by Borden emphasized careful radiographic scrutiny and, when available, contralateral comparison to detect abnormal bowing patterns [3,13]. Crowe and Swischuk similarly characterized acute bowing as a frequently overlooked injury due to the absence of visible fracture lines [4].
Advanced diagnostic approaches were described in selected publications including scintigraphy [18], MRI [19], and computer-assisted detection modeling [20]. Nevertheless, standardized diagnostic criteria remain lacking, and plain radiography remains the cornerstone of evaluation (Table 2).
Radiographic measurement techniques were inconsistently applied across the available literature (Table 2). Early reports relied primarily on qualitative assessment or contralateral comparison to detect abnormal curvature [3,4]. Although these approaches improved clinical recognition, they lacked standardized, reproducible metrics.
Subsequent radiographic analyses introduced percentage-based measurement of radial bow relative to total bone length, providing a more objective framework for assessment [2,10]. Normative pediatric studies demonstrate that maximal radial bow occurs approximately 60% of the radial shaft length and averages 7-8% of the total radial length across childhood [2,10]. Values of approximately 10% of radial length have been described as suggestive of pathologic bowing.
Importantly, the 10% value indicates extrapolation beyond typical developmental variation rather than a validated outcome-based threshold. No study to date has established a percentage-based magnitude that reliably predicts functional deficit or requires operative intervention [7,8]. Therefore, percentage-based measurements should be viewed as diagnostic tools that suggest abnormal curvature rather than definitive treatment thresholds. Notably, no included study proposed or validated a specific angular or percentage cutoff for operative intervention in cases of isolated plastic deformation.
Despite increased use of objective measurement methods, quantitative documentation of deformity severity remains scarce. Only a small number of studies reported numerical bow depth or angular values using standardized techniques [2,10], and even fewer correlated these measurements with objective pronation-supination outcomes [8]. Most publications relied on qualitative descriptions of curvature and functional recovery [3,4,9]. This variability in measurement and outcome reporting prevents the development of validated angular or percentage-based treatment criteria.
Management approaches varied based on patient age, deformity severity, timing of presentation, bone involvement, and level of functional limitation (Table 3).Table 3Clinical presentation, management, and functional outcomes.Table 3StudyTiming of diagnosisManagementFunctional outcomeComplicationsBorden (1974, 1975)AcuteClosed reduction + castingRestoration of alignment reportedNone reportedCrowe & Swischuk (1977)Often delayedVariableRisk of persistent deformity if missedMissed injurySanders & Heckman (1984)AcuteClosed reduction under anesthesiaFavorable rotation when treated earlyNone significantRydholm & Nilsson (1979)AcuteClosed managementGenerally favorableNot reportedDemos (1980)AcuteClosed reductionGood outcomeNone reportedMizutani et al.AcuteConservative managementResolution reportedNoneMiller & OsterkampAcuteConservativeFavorable outcomeNoneVorlat & De BoeckDelayed in some casesOsteotomy in persistent deformityResidual ROM deficits in delayed casesSecondary osteotomyKomara et al.AcuteClosed reductionRestoration of pronation-supinationNoneScheuer & PotAcuteClosed reductionGood functional recoveryNoneNaga & BroadrickDelayedSurgical interventionImproved after correctionRadial head instabilityZhou et al.Not clinical outcome studyDiagnostic modeling onlyNot applicableNot applicableOther isolated reportsAcute vs delayedIndividualized managementEarly treatment favorablePersistent rotational deficit if untreatedROM, range of motion.
Closed reduction followed by immobilization was described in the majority of acutely recognized cases [6,[14], [15], [16]]. Reduction was typically performed under sedation or anesthesia due to the sustained corrective force required for diaphyseal plastic deformation.
Early recognition in younger children was linked to positive outcomes including the restoration of radial bow and forearm rotation [6,15]. Several reports highlighted that spontaneous remodeling alone may be inadequate when deformity is severe.
Open surgical correction was most frequently reported in cases of delayed diagnosis, persistent deformity after failed closed management, or associated complications, such as radial head instability [8,13].
Surgical management in delayed or persistent cases most commonly involves corrective diaphyseal osteotomy to restore radial bow alignment [8,13]. Reports describing delayed recognition note increased technical difficulty and a higher likelihood of persistent rotational limitation compared with acutely treated cases [8].
Importantly, treatment decisions across studies were individualized rather than algorithmic. No validated radiographic magnitude consistently dictated operative versus nonoperative management (Table 3).
When recognized early and properly managed, outcomes were generally positive, with restoration of pronation and supination reported in most acute cases [6,15]. Complications described in the literature included persistent rotational deficits, radial head subluxation or dislocation [8,13], malunion following incomplete correction, and the need for secondary osteotomy in delayed cases [8].
Long-term follow-up data are still limited, with case reports and small series making up most of the evidence. However, untreated or poorly corrected bowing deformities are consistently relate to altered forearm biomechanics and measurable loss of rotational function [7,8].
Plastic deformation reflects the viscoelastic behavior of immature cortical bone. Increased collagen content, reduced mineralization, and enhanced energy-absorption capacity permit sustained bending loads to exceed the elastic limit without fracture-line propagation [1]. Early biomechanical investigations demonstrated that pediatric cortical bone can undergo permanent deformation under sustained loading, demonstrating permanent deformation without cortical failure when stress exceeds the elastic threshold [26]. This mechanism explains the radiographic subtlety of bowing injuries. Because cortical continuity is preserved, diagnosis depends on recognition of abnormal curvature rather than fracture visualization [3,11].
Delayed or missed diagnosis remains a recurring theme across decades of literature. Borden first emphasized careful radiographic evaluation and contralateral comparison to detect subtle curvature abnormalities [3,11]. Crowe and Swischuk characterized acute bowing as a frequently overlooked injury because it lacks visible fracture lines [4]. Several reports associate delayed recognition with persistent deformity or secondary instability including radial head subluxation or Monteggia-type injury patterns [8,13]. In some cases, plastic deformation of the ulna may contribute to instability of the proximal radioulnar joint, producing a Monteggia-type injury pattern. Subtle ulnar bowing may prevent spontaneous reduction of the radial head, and correction of the ulnar deformity may therefore be required to restore alignment. An illustrative case demonstrates persistent radial head dislocation associated with ulnar plastic deformation requiring corrective osteotomy to achieve reduction (Figure 3A, Figure 3B, Figure 3CA-3C). These findings highlight the need for heightened suspicion in children presenting with restricted pronation-supination despite apparently normal radiographs.Figure 3AForearm radiograph demonstrating ulnar plastic deformation without a discrete fracture line. The arrow indicates the apex of ulnar bowing. The dashed line represents the radiocapitellar line**,** which fails to intersect the capitellum, indicating radial head dislocation. The distal arrow highlights the radiocapitellar region.Figure 3AFigure 3BIntraoperative fluoroscopic lateral elbow image demonstrating radial head dislocation associated with ulnar plastic deformation. The arrow indicates the displaced radial head**,** which is not aligned with the capitellum.Figure 3BFigure 3CIntraoperative fluoroscopic image demonstrating corrective ulnar osteotomies performed to restore alignment of the ulna and allow reduction of the radial head. Arrows indicate the osteotomy sites.Figure 3C
To improve diagnostic consistency, quantitative measurement of radial bow has been increasingly utilized (Fig. 4). Analyses of uninjured pediatric forearms demonstrate that maximal radial bow is consistently located at approximately 60% of total radial length from the proximal end, with proportional depth averaging 7-8% across childhood and adolescence [2,10]. While absolute bow magnitude increases with skeletal growth, its relative position remains stable. These normative values provide an essential reference for distinguishing physiologic curvature from pathologic deformity following trauma.Figure 4Standardized radiographic assessment of pediatric radial bow on anteroposterior forearm imaging. Measurements include total radial length (a), maximal bow depth (b), location of maximal radial bow expressed as a percentage of total length (c), and segmental bow measurements at the distal, middle, and proximal thirds of the radius. Normative pediatric studies demonstrate that the maximal radial bow is typically located at approximately 60% of the total radial length, with a proportional depth of 7-8% [2,10].Figure 4
Advanced imaging modalities have been reported in specific cases where radiographic findings are uncertain. The MRI has been documented in isolated cases showing diaphyseal bone marrow edema without cortical disruption, supporting the diagnosis of plastic deformation when no visible fracture line is present [19].
Unlike metaphyseal angulation, which often remodels predictably in skeletally immature patients, diaphyseal plastic deformation indicates permanent cortical bending without fracture propagation. This biomechanical difference is clinically significant; remodeling of diaphyseal bowing seems less reliable than that seen in metaphyseal fractures, especially in older children and when the deformity is severe [6,8]. Proximal deformities may cause greater rotational effects due to alterations in radial bow mechanics and tension in the interosseous membrane, while distal deformities may be partially counteracted by nearby joint movement. However, location-specific remodeling parameters remain undefined. When radial and ulnar bowing occur together, they further impair rotational movement compared to a deformity in only one bone [7].
Available follow-up data suggest that persistent deformity may cause a measurable loss of forearm rotation if not properly corrected [8]. Experimental biomechanical models further indicate that angular deformities as small as 10°-15° can significantly reduce pronation and supination, with even greater deficits at higher angles [7]. While these findings support intervention in certain cases, they do not establish pediatric-specific remodeling thresholds. No pediatric-specific angular or proportional threshold has been validated to predict persistent functional deficits or determine when intervention is necessary in cases of isolated plastic deformation. Long-term outcome data are still limited, and few studies correlate the magnitude of bowing with objective rotational measurements. As a result, clinically meaningful functional thresholds and evidence-based intervention criteria remain undefined.
Acute cases were most often treated with closed reduction and immobilization, with rotation restored in most early-diagnosed cases [6,15]. Younger patients tend to respond better to closed treatment, likely due to greater remodeling ability. Surgical intervention was usually reserved for delayed diagnosis, ongoing deformity, or functional issues. Techniques reported include corrective osteotomy and intramedullary fixation [8]. These cases show that untreated significant bowing can lead to complex reconstructive procedures to realign rotation.
Isolated traumatic plastic deformation of the pediatric forearm is a distinct and often underrecognized injury pattern characterized by permanent cortical bending without an obvious fracture. Although the existing literature mainly consists of case reports and small series, consistent themes emerge across decades of early recognition is essential, subtle radiographic signs require careful examination, and delayed diagnosis can lead to persistent functional limitations requiring surgical correction. Despite advances in imaging techniques and radiographic measurement, there is currently no validated angular threshold to guide treatment, highlighting the need for standardized reporting and prospective outcome data. Until such evidence is available, management should focus on restoring forearm rotation and depend on individual clinical judgment. Recognizing plastic deformation as a unique biomechanical failure mode, rather than a variation of incomplete fracture, is crucial for optimizing outcomes in this rare but clinically significant pediatric injury.
Caitlin Wetzel: Writing – review & editing, Writing – original draft, Visualization, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Matthew Rohl: Writing – review & editing, Writing – original draft, Formal analysis, Data curation. Taylor Manes: Writing – review & editing, Writing – original draft, Supervision, Conceptualization. Allen Kadado: Writing – review & editing, Writing – original draft, Supervision.
The authors declare that no patient consent was necessary as no images or identifying information are included in the article.
The authors received no financial support for the research, authorship, and/or publication of this article.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.