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Management of lower third humeral fractures in the adolescent age group using flexible intramedullary nailing through an antegrade proximal entry approach: A prospective interventional pilot study
*Corresponding author: Ahmed M. S. Masoud, Department of Orthopedics, Ain Shams University, Cairo, Egypt. sallam.ortho@hotmail.com
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Received: ,
Accepted: ,
How to cite this article: Masoud AM, Elhamady MG, Makeen TM. Management of lower third humeral fractures in the adolescent age group using flexible intramedullary nailing through an antegrade proximal entry approach: A prospective interventional pilot study. J Musculoskelet Surg Res. 2025;9:444-9. doi: 10.25259/JMSR_201_2025
Abstract
Objectives:
Lower third humeral fractures in adolescents present a unique surgical challenge due to proximity to the growth plate and anatomical complexity. Traditional fixation methods may be associated with complications such as growth disturbance or nerve injury. This study aimed to evaluate the safety and efficacy of antegrade flexible intramedullary nailing in adolescents.
Methods:
This prospective interventional single-arm study included 20 adolescents (mean age 13 ± 2 years) with recent (≤2 weeks), closed or Gustilo type I open lower third humeral fractures. Patients underwent flexible intramedullary nailing through an antegrade approach. Operative time, radiological union, functional outcomes (Stewart and Hundley score, disabilities of the arm, shoulder, and hand [DASH] score), and complications were evaluated over an 8-month follow-up period.
Results:
The mean operative time was 35 ± 8 min. Union was achieved in 85% of patients, with delayed union in 15%; no malunion or nonunion was observed. The median time to union was 1.5 months (range 1.5–5 months). At 6 months, excellent and good functional outcomes were recorded in 60% and 20% of patients, respectively; these improved to 90% and 10% at 8 months. Median DASH score at final follow-up was 0 (range 0–13). No patients experienced neurovascular injury or infection.
Conclusion:
Antegrade flexible intramedullary nailing appears to be a safe, efficient, and minimally invasive option for managing distal humeral fractures in adolescents, with promising union rates and excellent functional outcomes. However, these findings should be interpreted in light of the study’s small sample size and absence of a control group.
Keywords
Adolescent
Antegrade
Distal
Flexible intramedullary nailing
Fracture union
Humeral fractures
INTRODUCTION
Humeral shaft fractures account for approximately 1–5% of all fractures, with a bimodal age distribution. One peak occurs in adolescents aged 11–16 years, typically resulting from high-energy trauma such as falls or road traffic accidents, often leading to comminuted fractures and associated soft-tissue injuries.[1] The adolescent period is particularly critical due to ongoing skeletal growth and high functional demands. Fracture management strategies must maintain alignment and promote healing without compromising future bone development.[2]
While conservative methods such as functional bracing have been effective for many humeral shaft fractures, certain fracture patterns–particularly those in the distal third of the humerus–may require surgical intervention to ensure stability and facilitate early mobilization. Surgical options include plate osteosynthesis, external fixation, and intramedullary nailing.[3] Among these, flexible intramedullary nailing, elastic stable intramedullary nailing (ESIN) has gained popularity due to its minimally invasive nature, biological fixation principle, and favorable biomechanical profile. The technique offers load-sharing support, preserves periosteal blood supply, and reduces the risk of stress shielding and implant-related complications.[4,5]
Historically, retrograde insertion of flexible nails has been the common approach; however, it carries risks such as soft tissue irritation or iatrogenic injury. An antegrade entry through the proximal humerus may offer a safer and more efficient route, particularly in the adolescent population, by avoiding the distal physis and reducing the risk of nerve injury when executed correctly.[6,7]
We hypothesized that antegrade flexible intramedullary nailing would result in high union rates, excellent functional recovery, and minimal complications in adolescents with distal humeral fractures. Therefore, this study aimed to evaluate the clinical and radiological outcomes of using antegrade flexible intramedullary nailing in the management of distal humeral fractures in adolescents, focusing on union rates, complication profiles, and functional recovery.
MATERIALS AND METHODS
Study design and setting
This study was designed as a prospective, single-arm interventional pilot study conducted at the Department of Orthopedic Surgery and Traumatology, Ain Shams University Hospitals, from January to October 2024.
Eligibility criteria
Eligible patients were adolescents aged between 11 and 16 years who presented with recent lower third humeral fractures (injury duration <2 weeks). Both closed fractures and open fractures classified as Gustilo type I were included. Exclusion criteria included intra-articular extensions and any associated neurovascular injuries.
Sample size and recruitment
A total of 20 patients meeting the inclusion criteria were recruited consecutively for this pilot study. The selected patients underwent a thorough clinical evaluation, radiographic assessment (including anteroposterior and lateral radiographs), and a pre-operative laboratory workup. Analgesics, along with anti-edematous agents (such as chemotrypsin and paracetamol), were administered until the time of surgery.
Surgical technique
All patients underwent surgery under general anesthesia in the supine position, with the affected limb placed on an arm board. A 2 cm skin incision was made over the anterolateral aspect of the proximal humerus, approximately 1–2 cm below the greater tuberosity.
Care was taken to identify and confirm the location of the proximal humeral physis radiologically. The entry point was intentionally placed 1–2 cm distal to the proximal growth plate within the metaphyseal region to avoid any risk of physeal injury, thereby minimizing the potential for growth disturbances.
No axillary nerve injury occurred, as the nerve lies about 3.5 cm distal to the greater tuberosity, making the 1–2 cm level a safe position. The deltoid muscle was split longitudinally to expose the entry site while preserving the surrounding neurovascular structures. Two oval-shaped entry holes were drilled into the anterolateral metaphyseal region of the proximal humerus, approximately 1–2 cm below the greater tuberosity and spaced about 1 cm apart. These holes were then widened using a bone awl to accommodate the nails [Figure 1].
- (a) 2 cm incision in the metaphyseal region of the proximal humerus, (b) an entry by awl, (c) 1st nail insertion, (d) final nail alignment.
Flexible intramedullary nails of appropriate diameter (40% of the narrowest canal width) were manually prebent to a 30° curvature. The first nail was introduced through the lateral entry point, and the second through a more medial anterolateral entry, ensuring parallel placement. Nails were advanced into the medullary canal under fluoroscopic guidance using controlled rotational and axial movements. Fracture reduction and implant positioning were confirmed intraoperatively, and wounds were closed in layers [Figure 1].
Post-operative management and follow-up
Postoperatively, all patients underwent assessment of neurovascular integrity and underwent radiographic imaging to evaluate fracture alignment and implant positioning. Elbow mobilization exercises were initiated on the first post-operative day. Follow-up visits were scheduled at 2, 6, and 12 weeks, and then monthly until radiological union was confirmed. Suture removal was performed 2 weeks after the procedure. At each visit, functional assessment was conducted using the Stewart and Hundley scoring system and the disabilities of the arm, shoulder, and hand (DASH) questionnaire. The mean follow-up duration was 32 weeks [Figure 2].
- Pre-operative anteroposterior and radiographs demonstrating (a) a markedly displaced and angulated mid-shaft humeral fracture, (b) post-operative intramedullary fixation with a humeral nail, with the fracture reduced and stabilized.
Statistical methods
Data management and statistical analysis were done using Statistical Package for the Social Sciences version 27 (IBM, Armonk, New York, United States). Quantitative data were assessed for normality using the Shapiro–Wilk test and direct data visualization methods. According to normality, quantitative data were summarized as means and standard deviations or medians and ranges. Categorical data were summarized as numbers and percentages. Kaplan–Meier analysis was performed to estimate the union time of the studied patients.
RESULTS
Demographic and fracture characteristics
The studied patients had a mean age of 13 ± 2 years. There was a clear male predominance, with 16 (80%) being males and only 4 (20%) females. Regarding hand dominance, the majority, 19 (95%), were right-handed, whereas only 1 (5%) was left-handed. Regarding the side affected, 12 (60%) fractures occurred on the left side, while 8 (40%) were on the right [Table 1].
| Demographic and fracture characteristics | ||
|---|---|---|
| Age (years) | Mean±SD | 13±2 |
| Sex | ||
| Males | n(%) | 16 (80) |
| Females | n(%) | 4 (20) |
| Dominance | ||
| Right hand | n(%) | 19 (95) |
| Left hand | n(%) | 1 (5) |
| Side affected | ||
| Right | n(%) | 8 (40) |
| Left | n(%) | 12 (60) |
| Mechanism of injury | ||
| Fall from height | n(%) | 6 (30) |
| Direct trauma | n(%) | 11 (55) |
| Road traffic accident | n(%) | 2 (10) |
| Fall on an outstretched hand | n(%) | 1 (5) |
| Fracture type | ||
| Transverse | n(%) | 4 (20) |
| Oblique | n(%) | 1 (5) |
| Spiral | n(%) | 10 (50) |
| Comminuted | n(%) | 5 (25) |
n: Number, SD: Standard deviation.
Concerning the mechanism of injury, direct trauma predominated, accounting for 11 (55%) cases. This was followed by falls from a height (6; 30%), road traffic accidents (2; 10%), and falls on outstretched hands (1; 5%) [Table 1].
In terms of fracture morphology, spiral fractures were the most common, comprising 50% (10 cases), followed by comminuted fractures (25%), transverse fractures (20%), and oblique fractures (5%) [Table 1].
Operative data and union results
The mean operative time was 35 ± 8 min. Regarding radiological outcomes, union was achieved in the majority of cases (17; 85%). Delayed union occurred in 3 (15%), whereas no cases of malunion or nonunion were observed. The median time to union was 1.5 months, with a range of 1.5–5 months [Table 2].
| Operative data and union results | ||
|---|---|---|
| Operative time (minutes) | Mean±SD | 35±8 |
| Radiological result | ||
| Union | n(%) | 17 (85) |
| Delayed union | n(%) | 3 (15) |
| Malunion | n(%) | 0 (0) |
| Nonunion | n(%) | 0 (0) |
| Time of union (months) | Median (range) | 1.5 (1.5–5) |
n: Number, SD: Standard deviation.
Complications
No early or late complications were reported among the studied patients, as none experienced radial or axillary nerve injury, infection, malunion, or nonunion.
Functional outcomes
At the 6-month Stewart and Hundley assessment, 5 (25%) patients reported pain, elbow limitation, and shoulder limitation, while angulation was noted in 1 (5%) of the cases. Functionally, 60% (12) of patients achieved excellent scores, 20% (4) had good outcomes, 15% (3) had fair outcomes, and 5% (1) had poor outcomes [Table 3].
| Functional outcomes | ||
|---|---|---|
| 6-month Stewart and Hundley scoring | ||
| Pain | n(%) | 5 (25) |
| Limitations of the elbow | n(%) | 5 (25) |
| Limitations of the shoulder | n(%) | 5 (25) |
| Angulation | n(%) | 1 (5) |
| Score | ||
| Poor | n(%) | 1 (5) |
| Fair | n(%) | 3 (15) |
| Good | n(%) | 4 (20) |
| Excellent | n(%) | 12 (60) |
| 8-month Stewart and Hundley scoring | ||
| Pain | n(%) | 1 (5) |
| Limitations of the elbow | n(%) | 0 (0) |
| Limitations of the shoulder | n(%) | 0 (0) |
| Angulation | n(%) | 1 (5) |
| Score | ||
| Good | n(%) | 2 (10) |
| Excellent | n(%) | 18 (90) |
| 8-Month DASH score | Median (range) | 0 (0–13) |
n: Number, DASH: Disabilities of the arm, shoulder, and hand.
At the 6-month follow-up, all patients demonstrated full and symmetrical active shoulder range of motion compared to the contralateral side, with normal strength during resisted flexion, abduction, and external rotation. No patient reported shoulder pain, stiffness, or weakness, indicating preservation of rotator cuff and deltoid function.
At the 8-month follow-up, clinical improvement was observed. Only 5% (1) reported pain and angulation, with no cases of elbow or shoulder limitation. Functionally, the majority (90%) (18) achieved excellent scores, and 10% were classified as good [Table 3].
The median 8-month DASH score was 0, ranging from 0 to 13, indicating minimal disability [Table 3].
Kaplan-Meier analysis for union time
A Kaplan–Meier analysis was performed to estimate the time to radiological union in the studied patients. The cumulative incidence of the union steadily increased throughout the follow-up period, with 60% achieving union at 1.5 months, 85% at 2 months, 95% at 4 months, and 100% at 5 months. The median time to union was 2 months [Figure 3].
- Kaplan–Meier analysis for union time in the studied patients.
DISCUSSION
In this prospective study, using antegrade flexible intramedullary nailing in adolescents with distal humeral fractures demonstrated excellent clinical and radiological outcomes. Union was achieved in 85% of cases within a median time of 1.5 months, with no cases of nonunion or malunion. Functional recovery was excellent or good in 90% of patients by 8 months, with minimal complications and no reported neurovascular injuries.
The antegrade approach used in this study offered several advantages. It avoided the distal physis, thereby minimizing the risk of growth disturbances. In addition, the use of pre-bent flexible intramedullary nails provided stable fixation with minimal soft-tissue disruption. Early mobilization was possible in all patients, contributing to faster functional recovery.
A key concern with antegrade nailing has historically been the risk of damaging the rotator cuff or the deltoid insertion, which can lead to shoulder dysfunction.[8] However, our technique involved a small anterolateral metaphyseal entry point distal to the rotator cuff insertion, and all patients regained full shoulder motion and strength by 6 months, supporting the safety of this approach in adolescents.
Our study revealed a higher union rate and more favorable healing profile compared to previous studies using ESIN in humeral shaft fractures. Verma et al.[9] reported a union rate of 80% from a total of 20 adult patients aged 19–57 years, with a nonunion rate of 20%, particularly among patients with spiral and oblique fracture patterns. Most cases united between 10 and 16 weeks. Similarly, Manjunath et al.[10] showed an 80% union rate in 20 cases, with an average healing time of 7.2 weeks and 4 cases of nonunion. Kumar and Kaushik[11] revealed a comparable nonunion rate of 20% in 20 cases in middle-aged patients, along with implant failure in one case.
In contrast, our adolescent cohort demonstrated a higher union rate of 85%, a notably shorter median time to union of 1.5 months, and no cases of nonunion, malunion, or implant-related complications. It is important to note that many of the studies cited involved adult patients whose lower bone healing potential and higher rates of comorbidities could contribute to increased nonunion or complications compared to adolescents. This age-related difference may partly explain the superior outcomes observed in our cohort.
Our results compare favorably with existing literature on distal humeral fractures managed with flexible intramedullary nailing. Kornah et al.[12] reported a union rate of 92.8% in 28 patients treated with antegrade flexible nails for distal third humeral fractures, with a mean union time of 13.1 weeks. However, they reported complications such as nail migration and superficial infections, which were entirely absent in our cohort. In contrast, our study showed a slightly lower union rate (85%) but with a significantly shorter median time to union (1.5 months), no infections, and no implant-related issues.
Mahmoud et al.[13] evaluated elastic intramedullary nailing in 30 adult patients with humeral shaft fractures, including six with distal third fractures. Among these distal cases, excellent outcomes were achieved in 100%, with no reported nonunion or malunion. However, complications such as shoulder stiffness (10%), loss of elbow extension (20%), and nail-related skin irritation (3.3%) were observed in the broader cohort.
A study by Karim et al.[14] on 30 cases reported a lower union rate of 76.7% and a high nonunion rate of 23.3% among adult patients treated with intramedullary nailing, along with a 30% incidence of surgical site infection and notable joint stiffness; these less favorable outcomes may be attributed to the older age group, higher comorbidity burden, and greater risk of soft-tissue complications compared to our younger, healthier adolescent cohort with better bone healing capacity and no reported infections or joint dysfunction.
This study has some limitations, including the small sample size and the absence of a control group, which may limit the generalizability of the findings. In addition, the short follow-up period may not fully capture long-term complications or functional outcomes, particularly in relation to growth disturbances. Therefore, further multicenter studies with larger cohorts and longer follow-up are recommended to validate these results.
In addition, the absence of a control group treated with alternative methods, such as conservative management or plate osteosynthesis, limits the ability to draw comparative conclusions about the relative efficacy and safety of antegrade flexible nailing. Future studies incorporating a comparative design are essential to establish evidence-based guidelines for optimal management of distal humeral fractures in adolescents.
Future multicenter research incorporating control groups with alternative management strategies will be vital to confirm these preliminary findings and better define the most effective treatment protocols for adolescent distal humeral fractures.
Patients’ consent to use their data and images
Written informed consent was obtained from all patients or their legal guardians for the use of their clinical data and images in this research and publication, with measures taken to ensure confidentiality and anonymity.
CONCLUSION
Antegrade flexible intramedullary nailing appears to be a safe, efficient, and minimally invasive option for managing distal humeral fractures in adolescents, with promising union rates and functional outcomes; however, larger comparative studies are needed to confirm these findings.
Authors’ contributions:
AMS: Conceived and designed the study, conducted research, and collected and organized data. MGE: Analyzed and interpreted the data. TMM: Wrote the initial and final draft of the manuscript and provided logistical support. All authors have critically reviewed and approved the final draft and are responsible for the manuscript’s content and similarity index.
Ethical approval:
This research was approved by the institutional ethics committee (Approval code: FMASU MS 755/2024, Date: November 26, 2024).
Declaration of patient’s consent:
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of AI-assisted technology for assisting in the writing or editing of the manuscript, and no images were manipulated using AI.
Conflicts of interest:
There are no conflicting relationships or activities.
Financial support and sponsorship: This study did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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