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# Does double distal locking reduce non-union rates in intramedullary nailing for humeral shaft fracture?

Jules Levasseur, Pierre Bordure, Yvon Moui, Guillaume David, Louis Rony

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## To cite this version:

Jules Levasseur, Pierre Bordure, Yvon Moui, Guillaume David, Louis Rony. Does double distal locking reduce non-union rates in intramedullary nailing for humeral shaft fracture?. Orthopaedics & Traumatology: Surgery & Research, 2025, 111 (1), pp.103913. 10.1016/j.otsr.2024.103913. hal-04991663

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Original article

# Does double distal locking reduce non-union rates in intramedullary nailing for humeral shaft fracture?

Jules Levasseur<sup>a</sup>, Pierre Bordure<sup>b</sup>, Yvon Moui<sup>c</sup>, Guillaume David<sup>a</sup>, Louis Rony<sup>a,*</sup>

<figure><img src="image_5.png" /></figure>

## INFO ARTICLE

Historique de l'article :
Reçu le 17 mai 2023
Accepté le 21 mars 2024

## ABSTRACT

**Introduction.** – Intramedullary nailing is one of the surgical treatments for humeral shaft fracture. Non-union is a common complication, with rates of 10–20%. The objective of this study was to compare non-union in humeral shaft fractures treated by intramedullary nailing with double distal locking, single distal locking or no locking.

**Hypothesis.** – Nailing with double distal locking decreases non-union rates compared to single or no locking.

**Material and methods.** – This single-center retrospective comparative study included 87 patients with closed humeral shaft fracture without neurologic deficit treated by anterograde intramedullary nailing: group 1 (double locking): 15 fractures; group 2 (single locking): 63 fractures; group 3 (no locking): 9 fractures. Non-union was defined as absence of radiographic callus at 6 months without clinical pain. The primary endpoint was non-union rate per group. The secondary endpoints were Constant score at 6 months, and postoperative use of non-steroidal anti-inflammatory drugs (NSAIDs).

**Results.** – There were no significant differences in non-union rate: 20.0% in group 1, 20.3% in group 2, and 0% in group 3 (p = 0.32). Constant score at 6 months was significantly different between the 3 groups (p = 0.01). Group 2 used more NSAIDs than the other groups (39.1% vs. 20.0% in group 1 and 33.3% in group 3; p = 0.37).

**Discussion.** – Non-union rates were similar regardless of distal locking for closed humeral shaft fractures without neurologic deficit treated by intramedullary nailing. Nevertheless, patients in the double locking group had higher Constant scores at 6 months, probably related to greater stability of fixation, allowing more efficient rehabilitation.

**Level of evidence.** – III; retrospective comparative study.

© 2024 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY license ([http://creativecommons.org/licenses/by/4.0/](http://creativecommons.org/licenses/by/4.0/)).

## 1. Introduction

Humeral shaft fractures account for 5% of all fractures in adults [1]. Intramedullary nailing is a treatment of choice for long-bone shaft fractures, especially when oblique, comminuted or bifocal [2–5]. In the lower limb, axial compression promotes consolidation, whereas it is absent in the upper limb, incurring a risk of non-union. The rate of non-union in closed humeral shaft fracture is around 15%, depending on the series and the technique. Intramedullary nailing is a treatment of choice for transverse and short oblique humeral shaft fractures, while plate fixation is preferred in AO/OTA type A fracture.

Apart from problems of fracture site compression, assembly instability and notably absence of nail locking may lead to non-union. However, there is no evidence-based consensus on distal locking in intramedullary nailing for closed humeral shaft fracture. Several studies found it not to be necessary, reporting non-superiority of dynamic distal locking in terms of bone consolidation, at 6 months [6–8].

The aim of the present study was to compare non-union rates in humeral shaft fracture treated by intramedullary nailing with double, single or no distal locking, presuming distal locking to affect non-union after nailing. The study hypothesis was that double distal locking reduces the rate of non-union compared to single or no distal locking in fixation by intramedullary nailing.

<footnote><sup>a</sup> Département de chirurgie osseuse, CHU d'Angers, 4, Rue Larrey, 49933 Angers cedex 9, France</footnote>

<footnote><sup>b</sup> Service de chirurgie de l'épaule, clinique Saint-Léonard, 18, rue de Bellinière, 49800 Trélazé, France</footnote>

<footnote><sup>c</sup> Service de chirurgie orthopédique, centre hospitalier du Mans, 194, avenue Rubillard, 72037 Le Mans, France</footnote>

<footnote>* Corresponding author.
Adresse e-mail: Louis.rony@chu-angers.fr (L. Rony).</footnote>
<figure><img src="image_6.png" /><figcaption>Fig. 1. Flowchart.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 2. X-rays illustrating different locking methods. A. Double distal locking. B. Single distal locking. C. No distal locking.</figcaption></figure>

## 2. Material and method

This was a retrospective single-center multi-surgeon case-control study. It had local review board approval and was registered with the CNIL data protection commission under the n° REF-0045.

### 2.1. Patients

All patients operated on by intramedullary nailing for closed humeral shaft fracture without neurologic deficit between January 2010 and January 2021 were included. Exclusion criteria comprised age < 18 years, history of non-union, pathologic fracture, fixation by plate or stable elastic intramedullary nailing, and lack of 6-month follow-up. There were 110 closed humeral shaft fractures without neurologic deficit; 23 were excluded: 6 patients aged < 18 years, 5 pathologic fractures, 7 with other fixation, 6 deceased within 6 months, and 2 nailings for non-union (Fig. 1). Fractures were classified on the AO/OTA system [9]. Group 1 (double locking) (Fig. 2A) comprised 15 patients: 5 males, 10 females, mean age 61.3 years, mean body mass index (BMI) 26.5 kg/m², 7 smokers. AO types are shown in Table 1. Group 2 (single locking) (Fig. 2B) comprised 63 patients (1 bilateral case): 30 males, 34 females, mean age 59.0 years, mean BMI 25.9 kg/m², 11 smokers. AO types are shown in Table 1. Group 3 (no locking) comprised 9 patients: 2 males, 7

females, mean age 68.6 years, mean BMI 27.7 kg/m², 2 smokers. AO types are shown in Table 1. Table 1 shows all demographic data.

### 2.2. Surgical technique

Two types of nail were used: Multiloc® (Johnson & Johnson, Warsaw, Indiana) and Telegraph® (FH Industrie, Quimper, France) (Fig. 2). Patients were positioned semi-seated, under general anesthesia. Via a 5-cm superolateral approach, the deltoid muscle and the supraspinatus tendon were opened along their fibers [10]. The entry point was located under fluoroscopic control. Reaming on guide was performed according to the operator's judgment, and the nail was inserted under fluoroscopic control. Proximal locking used the dedicated instrumentation; distal locking, if any, was performed freehand with 1 or 2 anterolateral screws placed medially to limit iatrogenesis. The rotator cuff was systematically sutured.

Postoperative immobilization was comparable between groups, using an orthopedic vest for 6 weeks. Sub-threshold physical therapy was initiated during the first postoperative week.

### 2.3. Assessment

The primary endpoint was humeral shaft non-union at 6 months in 3 groups differing only in terms of locking. Non-union was defined by absence of callus at 6 months on standard AP and lateral
<table><caption>**Table 1**
Population characteristics.</caption><thead><tr><th></th><th>Total</th><th>Group 1</th><th>Group 2</th><th>Group 3</th><th>p</th></tr></thead><tbody><tr><td>Number of fractures</td><td>88</td><td>15</td><td>64</td><td>9</td><td></td></tr><tr><td>Mean age at surgery (years)</td><td>60.3</td><td>61.3</td><td>59.0</td><td>68.6</td><td>> 0.05</td></tr><tr><td>Gender, n (%)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Male</td><td>37 (42)</td><td>5 (33)</td><td>30 (47)</td><td>2 (22)</td><td>> 0.05</td></tr><tr><td>Female</td><td>51 (58)</td><td>10 (67)</td><td>34 (53)</td><td>7 (78)</td><td>> 0.05</td></tr><tr><td>BMI, n (%)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>&lt;18.5</td><td>2 (2)</td><td>1 (7)</td><td>1 (2)</td><td>0 (0)</td><td>> 0.05</td></tr><tr><td>18.5-24.9</td><td>41 (47)</td><td>6 (40)</td><td>32 (50)</td><td>3 (33)</td><td>> 0.05</td></tr><tr><td>25-29.9</td><td>21 (24)</td><td>3 (20)</td><td>14 (22)</td><td>4 (45)</td><td>> 0.05</td></tr><tr><td>30-34.9</td><td>18 (20)</td><td>4 (26)</td><td>13 (20)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>35-39.9</td><td>4 (5)</td><td>0 (0)</td><td>3 (5)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>> 40</td><td>2 (2)</td><td>1 (7)</td><td>1 (1)</td><td>0 (0)</td><td>> 0.05</td></tr><tr><td>Comorbidities, n (%)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Smoking</td><td>20 (23)</td><td>7 (47)</td><td>11 (17)</td><td>2 (22)</td><td>> 0.05</td></tr><tr><td>NSAIDs</td><td>30 (34)</td><td>3 (20)</td><td>25 (39)</td><td>3 (33)</td><td>> 0.05</td></tr><tr><td>Alcohol</td><td>19 (22)</td><td>6 (40)</td><td>12 (19)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>Diabetes</td><td>12 (14)</td><td>2 (13)</td><td>8 (12)</td><td>2 (22)</td><td>> 0.05</td></tr><tr><td>Start of rehabilitation, n (%)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>D0-D6</td><td>61 (69)</td><td>9 (60%)</td><td>48 (75)</td><td>4 (45)</td><td>> 0.05</td></tr><tr><td>D7-D20</td><td>4 (5)</td><td>1 (7%)</td><td>2 (3)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>D21-D45</td><td>17 (19)</td><td>3 (20%)</td><td>11 (17)</td><td>3 (33)</td><td>> 0.05</td></tr><tr><td>> D45</td><td>6 (7)</td><td>2 (13%)</td><td>3 (5)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>AO classification, n (%)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>A1</td><td>26 (30)</td><td>3 (20)</td><td>19 (29)</td><td>4 (45)</td><td>> 0.05</td></tr><tr><td>A2</td><td>12 (14)</td><td>4 (26)</td><td>7 (11)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>A3</td><td>30 (34)</td><td>4 (26)</td><td>23 (36)</td><td>3 (33)</td><td>> 0.05</td></tr><tr><td>B2</td><td>15 (17)</td><td>3 (20)</td><td>11 (17)</td><td>1 (11)</td><td>> 0.05</td></tr><tr><td>B3</td><td>1 (1)</td><td>1 (7)</td><td>0 (0)</td><td>0 (0)</td><td>> 0.05</td></tr><tr><td>C2</td><td>1 (1)</td><td>0 (0)</td><td>1 (2)</td><td>0 (0)</td><td>> 0.05</td></tr><tr><td>C3</td><td>3 (3)</td><td>0 (0)</td><td>3 (5)</td><td>0 (0)</td><td>> 0.05</td></tr></tbody></table>

humerus X-ray, read 3 times by a single observer. Secondary end-points comprised active and passive ipsilateral shoulder motion on Constant score at 6-month consultation [11]. Postoperative consumption of non-steroidal anti-inflammatory drugs (NSAIDs) was assessed; if NSAIDs were prescribed, the patient was presumed to have taken them.

## 2.4. Statistics

Statistical analysis used JASP software, version 0.16.1 (Department of Psychological Methods, University of Amsterdam, Nieuwe Achtergracht 129B, Amsterdam, The Netherlands). Categorical variables were reported as number and percentage, and continuous variables as mean with standard deviation. Intergroup differences were assessed on ANOVA for quantitative data, and on Chi² test for qualitative data. All tests were 2-tailed. The significance threshold was set at 5%. Ninety-five percent confidence intervals were calculated.

## 3. Results

For the main endpoint, there were no significant intergroup differences in non-union rate at 6 months: 20.0% in group 1, 20.3% in group 2, and 0% in group 3 (p = 0.32) (Table 2).

Mean Constant score differed significantly between groups: group 1, 90.2; group 2, 73.6; and group 3, 74.6 (p = 0.01) (Table 3).

NSAID consumption did not significantly differ between groups (p = 0.37) (Table 4), but did significantly differ between patients with and without non-union (p = 0.01) (Table 5).

Four patients (2 in group 1 and 2 in group 2) had postoperative radial nerve deficit, with full recovery.

## 4. Discussion

Double distal locking in humeral intramedullary nailing did not prove superior to single or no locking in terms of non-union.

The question of distal locking of intramedullary nails for humeral shaft fracture remains open, as seen in several studies [12] including one French study [13]. Biomechanically, distal locking enhances rotational stability according to Mazirt [8]. Some authors found that distal locking was not a prerequisite for good functional results [13], while others reported that dynamic distal locking was associated with less non-union than other types of locking [14], and that locking improved function [15]. The present results confirmed this, with improvement in Constant score at 6 months in case of double locking, although without lower incidence of non-union. Colombi, in a recent cohort comparable to ours, found no difference between uni- and bi-polar locking in 106 patients: 89% consolidation without distal locking and 83% with [6]. The originality of the present study was to compare 3 types of fixation. The rate of iatrogenic radial palsy was very low, and comparable to other reports; anteroposterior locking may be implicated, but reaming and reduction maneuvers could also explain the cases of palsy [16].

Another question in suspense is the use of nailing for humeral shaft fracture, where non-operative treatment can play a large role [1], as well as locking or non-locking plate fixation [17]. With plate fixation, compression is an advantage; nailing provides better stability, but plate fixation does not involve the rotator cuff [18]. However, the present study found no iatrogenesis relating to the rotator cuff, and Constant scores were significantly better with double locking, which allowed earlier pain-free rehabilitation, with less functional limitation at 6 months [19-21]. To avoid any such risk, some authors advocate a nail entry point in the humeral pallet, although this incurs a non-negligible risk of pallet fracture [22]. Given the variety of techniques, comparison between them cannot establish any superiority in terms of consolidation [17,23,24].

One limitation of the present study was the 6-week postoperative immobilization, whatever the locking technique, whereas distal locking should allow early rehabilitation [25]. Moreover, group sizes precluded subgroup analysis of non-union risk according to fracture type; this would be useful to investigate in a larger series.
<table><caption>**Table 2**
Results for the primary endpoint (comparison of non-union rates).</caption><thead><tr><th></th><th>Total</th><th>Group 1</th><th>Group 2</th><th>Group 3</th><th>p</th></tr></thead><tbody><tr><td>Number of fractures</td><td>88</td><td>15</td><td>64</td><td>9</td><td></td></tr><tr><td>Radiologic consolidation at 6 months, n (%)</td><td>72 (81.8)</td><td>12 (80.0)</td><td>51 (79.9)</td><td>9 (100)</td><td>0.32</td></tr></tbody></table>

<table><caption>**Table 3**
Comparison of Constant score at 6 months postoperatively between group 1, group 2, and group 3.</caption><thead><tr><th></th><th>Total</th><th>Group 1</th><th>Group 2</th><th>Group 3</th><th>p</th></tr></thead><tbody><tr><td>Mean Constant score</td><td>76.5</td><td>90.2</td><td>73.7</td><td>74.6</td><td>0.01</td></tr></tbody></table>

<table><caption>**Table 4**
Comparison of perioperative non-steroidal anti-inflammatory drug use between groups 1, 2, and 3.</caption><thead><tr><th></th><th>Total</th><th>Group 1</th><th>Group 2</th><th>Group 3</th><th>p</th></tr></thead><tbody><tr><td>Number of fractures</td><td>88</td><td>15</td><td>25</td><td>9</td><td></td></tr><tr><td>NSAIDs, n (%)</td><td>31 (35.2)</td><td>3 (20.0)</td><td>25 (39.1)</td><td>3 (33.3)</td><td>0.37</td></tr></tbody></table>

<table><caption>**Table 5**
Comparison of perioperative non-steroidal anti-inflammatory drug use between patients with and without non-union.</caption><thead><tr><th></th><th>Total</th><th>Non-union</th><th>No non-union</th><th>p</th></tr></thead><tbody><tr><td>Number of patients</td><td>88</td><td>16</td><td>72</td><td></td></tr><tr><td>NSAIDs, n (%)</td><td>31 (35.2)</td><td>10 (62.5)</td><td>21 (29.2)</td><td>0.01</td></tr></tbody></table>

Apart from the type of fixation, other factors for non-union include smoking status, alcohol use, initial open skin wound, diabetes, and anti-inflammatory drugs [26–29]. There are also other limitations to the present study. We considered that differences in proximal locking between the two nails that we used would not affect stabilization of the humeral shaft fracture site. Also, we did not record whether reaming was systematic or was itself a factor for consolidation. And we did not analyze inter-fragment diastasis. On the other hand, the groups were comparable demographically and it is unlikely that failure to analyze inter-fragment diastasis could introduce selection bias. And the study revealed a correlation between NSAIDs and non-union, as confirmed by a recent meta-analysis [30].

The present study included a large enough cohort for our statistical findings to be valid, but the retrospective design could entail an analysis bias related to the method of data collection. A recent study suggested not using distal locking for humeral shaft fracture [31], challenging received wisdom and highlighting the need for standardized, prospectively assessed practice. This is especially important in traumatology, where practices vary more.

## 5. Conclusion

Double distal locking in humeral shaft fracture did not provide a lower rate of non-union than single or no distal locking. However, it enables earlier rehabilitation and faster shoulder recovery despite trans-tendon passage in the rotator cuff. The contribution of locking may thus not concern consolidation but rather functional recovery.

## Disclosure of interest

L. Rony is a consultant for Newclip Technics.
The other authors have no competing interest.

## Funding

None.

## Authors' contributions

J. Levasseur: data collection, article writing.

P. Bordure: study design, manuscript review and correction.

Y. Moui: manuscript correction.

G. David: manuscript review and iconography.

L. Rony: manuscript review, iconography, patient inclusion.

## Declaration on artificial intelligence

No artificial intelligence was used in writing the article.

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