Greater sigmoid notch of the olecranon disruption in a minimally displaced pediatric olecranon fracture: A case report

INTRODUCTION

Olecranon fractures in children are uncommon, accounting for approximately 4% of elbow injuries.^[1] Although no definitive treatment guidelines exist, nonoperative management is generally recommended for olecranon fractures with displacement of <2–5 mm. In contrast, operative treatment is advised for those with greater displacement or an articular step-off.^[1-4] However, this threshold has inherent limitations, as plain radiographs offer limited reliability due to the thick articular cartilage, varying ossification stages, and difficulty in assessing the overall contour of the articular surface.^[1,5]

Here, we report a 14-year-old boy with an olecranon fracture showing displacement of <2 mm on radiography and computed tomography (CT) but disruption of the greater sigmoid notch (GSN), which required surgical management.

CASE REPORT

A 14-year-old male sustained a hyperextension injury to the left elbow after a bicycle fall. Initial radiographs and CT scans obtained at a local clinic demonstrated an olecranon fracture with <2 mm of displacement and an articular step-off, consistent with findings of conservative treatment [Figure 1a-c]. However, the GSN, normally forming a continuous circular arc that articulates congruently with the trochlea^[6] demonstrated flattening on CT, raising concern for disruption of its native morphology [Figure 1d and e]. In pediatric patients, a substantial portion of the articular surface remains cartilaginous, limiting CT’s ability to evaluate the true articular contour of the GSN accurately. Therefore, magnetic resonance imaging (MRI) was performed to precisely assess the cartilaginous component, which confirmed flattening of the GSN arc and loss of its normal curvature due to the fracture [Figure 2].

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Figure 1:

Preoperative elbow radiographs and computed tomography (CT) scan. (a-c) Anteroposterior, oblique, and lateral radiographs of the left elbow demonstrate an olecranon fracture. (d) Sagittal CT image showing <2 mm of fracture displacement. (e) Lateral radiograph of the contralateral elbow for reference.

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Figure 2:

Magnetic resonance imaging findings of the injured elbow. Sagittal T2-weighted turbo spin-echo sequence (sagittal plane) demonstrates flattening and disruption of the normal greater sigmoid notch contour despite minimal fracture displacement. The fracture line at the olecranon is indicated by the yellow arrow.

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We were unable to identify any reference describing this fracture pattern. Evaluation of the contralateral elbow on anteroposterior and lateral radiographs using the Sauvegrain method demonstrated a skeletal maturity corresponding to approximately 13 years of age.^[7] Given that the olecranon physis fuses at approximately 14–16 years of age,^[1,8] we considered restoration of the GSN contour to be necessary.

Because incomplete ossification made direct assessment of the articular surface difficult, intraoperative arthrography with contrast injection was performed [Figure 3a], which confirmed the GSN contour disruption observed on MRI. Subsequently, surgery was performed using a posterior approach with minimal dissection to preserve the muscle and periosteum. Gradual compression with a reduction clamp restored the GSN arc [Figure 3b]. To avoid physeal violation caused by the implant and to prevent recurrence of the restored GSN deformity, we applied an anatomical olecranon plate commonly used in adults for fixation. Insertion of a distal dynamic compression screw drew the plate against the olecranon fragment, generating stable compression (red arrow) to maintain reduction [Figure 3c], while additional distal locking screws provided supplementary stability [Figure 3d].

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Figure 3:

Intraoperative fluoroscopic images observed under arthrography. (a) Arthrography confirms greater sigmoid notch (GSN) contour disruption consistent with preoperative magnetic resonance imaging findings (yellow arrow). (b) Gradual compression with a reduction clamp restores the native GSN arc. (c and d) An anatomical olecranon plate is applied to avoid physeal violation caused by the intramedullary implant. A distal dynamic compression screw (yellow circle) generates compression across the fractured olecranon fragment (red arrow), and an additional unicortical distal locking screw provides supplementary stability. Arthrography confirms congruent restoration of the GSN contour.

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Postoperatively, the patient was immobilized in a long-arm splint for 3 weeks, after which elbow range-of-motion exercises were initiated. Radiographic union and full range of motion were achieved by 6 weeks [Figure 4a], allowing him to return to daily activities. Return to sports activities was achieved at 3 months. The implant was removed at 6 months. By 1 year, physeal closure was observed bilaterally [Figure 4b and c]. No postoperative complications, including wound-related issues, implant prominence, infection, or heterotopic ossification, were identified during follow-up. Two years later, the patient demonstrated full, painless elbow motion with an arc of 0°–140°, without radiographic abnormalities or differences in olecranon morphology between the elbows [Figure 5].

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Figure 4:

Radiographic evaluation at mid-term follow-up. (a) Six-week follow-up radiograph demonstrating osseous union with a congruent greater sigmoid notch contour. (b) One-year follow-up radiograph of the operated elbow demonstrating a congruent greater sigmoid notch with earlier physeal closure than the contralateral side. (c) One-year follow-up radiograph of the contralateral elbow demonstrating near-complete physeal closure, suggesting that no substantial long-term difference in ossification is expected between the sides.

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Figure 5:

Two-year follow-up evaluation. (a) Operated and (b) contralateral sides. Both elbows demonstrate well-preserved morphology and a congruent greater sigmoid notch, with no abnormalities or apparent differences between the sides. (c) Clinical photograph demonstrating full elbow flexion and (d) full elbow extension at the final follow-up, confirming a painless arc of motion from 0° to 140°.

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DISCUSSION

This case represents an atypical scenario in which displacement and articular step-off were minimal, a condition that would ordinarily favor conservative management^[1,4,8] yet, advanced imaging revealed flattening of the GSN and loss of its normal arc. This finding indicates a limitation of relying only on displacement or articular step-off as operative criteria, as these parameters may not fully reflect the actual GSN contour. Our case shows that assessment of the integrity of the GSN contour should also be considered when evaluating pediatric olecranon fractures.

The GSN forms a continuous arc,^[6] and restoration of this native contour, as well as reduction of displacement or articular step-off, is considered the goal of surgical treatment for olecranon fractures.^[9,10] However, in children, the olecranon is incompletely ossified; thus, the presence of thick articular cartilage makes it difficult to assess the true contour of the GSN on plain radiographs.^[1,5] Consequently, disruption of the GSN arc may be overlooked if attention is directed only to fracture displacement or articular step-off, without recognizing that the contour itself can also be compromised.

Previous studies^[10,11] described an objective method for evaluating GSN deformity based on its geometric contour. In healthy anatomy, the GSN forms the arc of a single circle in the sagittal plane [Figure 6a]; when this contour is disrupted, the arc can be divided into two nonconcentric circular segments corresponding to the olecranon and coronoid components [Figure 6b]. In the present case, GSN disruption was characterized not by fragment separation but by flattening of the arc itself, resulting in loss of normal circular geometry despite minimal fracture displacement or an articular step-off [Figure 6c].

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Figure 6:

Schematic illustration of greater sigmoid notch (GSN) contour assessment based on geometric arc analysis. (a) In normal anatomy, the GSN forms the arc of a single circle in the sagittal plane (green circle). (b) In displaced olecranon fractures, disruption of the GSN contour can be represented by separation of the arc into two nonconcentric circular segments corresponding to the olecranon and coronoid components (blue and yellow circles). (c) In the present case, GSN disruption occurred through flattening of the arc itself rather than fragment separation, resulting in loss of normal circular geometry despite minimal fracture displacement or articular step-off (blue and yellow circles). The red dashed line indicates the fracture line.

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Several classification systems for pediatric olecranon fractures have been proposed, focusing on fracture location, orientation, relationship to the physis, articular involvement, and associated injuries.^[4,8,12] However, no universally accepted system exists, and treatment decisions are based on the degree of displacement and articular step-off.^[1,8] Thresholds for operative intervention vary among reports, with some recommending surgery for displacement of >2 mm, others for >3, 4, or 5 mm.^[1,4] Evans and Graham^[8] suggested that fractures with <2 mm of displacement should be managed nonoperatively, those with 2–4 mm of displacement represent a gray zone in which fracture stability determines the need for surgery, and those with >4 mm of displacement or any step-off should be treated operatively. More recently, Kalbitz et al.^[4] proposed that surgical treatment should be considered in cases of displacement of ≥5 mm, intra-articular involvement, unstable fracture patterns, or apophyseal involvement. However, we could not find prior reports addressing classification or treatment guidelines based on the GSN contour.

In our patient, displacement and step-off were <2 mm, but MRI and intraoperative arthrography clearly demonstrated flattening of the GSN arc and loss of its native curvature. Because olecranon ossification is usually completed between ages 14 and 16,^[8] relying solely on remodeling potential was considered insufficient. Although the long-term consequences of uncorrected GSN flattening in pediatric patients are not well defined, residual GSN incongruity has been associated with unfavorable radiographic outcomes in adult patients.^[9,13] We were concerned that if the fracture was allowed to ossify in its disrupted configuration, it could result in long-term incongruity of the ulnohumeral joint. Therefore, anatomical reduction and stable fixation were performed to restore the GSN arc. The observation that ossification of the contralateral olecranon in this patient was complete at approximately 15 years of age further supported the decision to proceed with surgical treatment [Figure 5b].

In pediatric olecranon fractures, surgical fixation is commonly performed with tension-band wiring or sutures.^[1,14] However, in the present case, we chose plate fixation, which is rarely used in children. Although this choice may be debated, our rationale was two-fold. First, we sought to avoid physeal injury associated with intramedullary implants traversing the olecranon physis. Second, because the GSN was elongated and flattened, we considered that maintaining its restored contour would be more reliably achieved with an anatomical plate.

Although the plate fixation technique requires a larger skin incision than the tension-band technique, we minimized soft-tissue dissection by positioning the plate over the periosteum without stripping muscle attachments. While the plate construct may appear to function as a bridging device, controlled compression across the olecranon fragment was achieved through a distal dynamic compression screw, as illustrated in Figure 3. This configuration allowed maintenance of the restored GSN contour while avoiding transphyseal fixation and excessive focal compression.

Despite efforts to protect the physis, premature physeal closure was observed on the operated side compared with the contralateral elbow, likely reflecting the combined effects of the initial injury and unavoidable physeal insult during clamp-assisted reduction. Because the patient had limited remaining growth potential at the time of injury, this premature closure did not result in a clinically meaningful difference at the final follow-up.

CONCLUSION

This case demonstrates that, even when displacement is <2 mm and the articular step-off is minimal, disruption of the GSN contour may occur, warranting surgical treatment. Careful evaluation of the GSN contour should be considered in treatment planning, as its disruption may be overlooked by displacement or step-off criteria alone.