Lip carcinoma is the most prevalent form of malignancy in the head and neck region, representing roughly 25% to 30% of all oral cancers. Importantly, around 90% of these cancers of the lip develop on the lower lip [1]. The fundamental principle of surgical management of lip cancer is the complete excision of the tumor with a safe margin, typically 0.5–1 cm of surrounding tissue [2]. Following resection, the resulting defect and loss of lip substance necessitate reconstructive surgery. The goals of lip reconstruction are multifaceted, encompassing both the restoration of oral function and the achievement of an acceptable aesthetic outcome [3]. The size and location of the defect primarily determine the choice of an appropriate reconstructive technique. If a full-thickness lower lip defect involves less than one-third of the total lower lip length, primary closure can often be performed without significant functional compromise. However, defects involving more than one-third of the lip length preclude direct closure and require more complex reconstructive procedures to replace the missing tissue [4].

Several surgical options are available for reconstructing such lower lip defects, including the nasolabial flap (NLF), Karapandzic flap, Abbe-Estlander flap, Gillies fan flap, Bernard-Webster flap, and the Fujimori gate flap, among others [5]. The NLF is a widely used and reliable technique for lower lip reconstruction. However, it has several recognized drawbacks. A primary functional limitation is its inability to reconstruct the native orbicularis oris muscle complex. As a non-sphincteric replacement, it fails to restore dynamic circumoral function, a key factor theorized to contribute to postoperative complications such as oral incompetence and drooling [6,7]. Additional concerns include a conspicuous facial scar, which can be a significant cosmetic issue for younger patients, and potential asymmetry in cases of unilateral reconstruction [8]. The modified neurovascular cheek flap (MNCF), described by Chowchuen et al. [9-12], offers an alternative approach. This technique is an adaptation of the method reported by Vatanasapt et al. in 1987, as cited in Chowchuen et al. [9]. The MNCF is versatile and can be employed to reconstruct both upper and lower lip defects, ranging from those larger than one-third of the lip length to subtotal or total lip defects, unilaterally or bilaterally [10-12]. While it aims to provide a more anatomical reconstruction, it is not without its own limitations. The incision creates a scar across the natural skin lines of the cheek, and similar to the NLF, it does not fully reconstitute the complete, functional orbicularis oris sphincter.

Theoretically, both the NLF and MNCF, by virtue of not fully restoring the muscular sphincter, carry a risk of impairing oral competence and leading to drooling. At our institution, these two techniques collectively account for over 90% of major lower lip reconstructions. Despite their prevalent use, a direct comparative analysis of their functional outcomes, particularly the incidence of drooling, is lacking in the literature. This study aims to fill this critical knowledge gap. The primary objective is to directly compare the functional outcomes of the NLF and MNCF techniques, specifically focusing on the rate of postoperative drooling. The secondary aim is to compare overall wound complication rates, including dehiscence, infection, and flap necrosis, between the two techniques.

This retrospective cohort study provides the first direct comparison of functional and surgical outcomes between the MNCF and the NLF for lower lip reconstruction following oncologic resection. Despite being applied to significantly larger defects and more frequently in bilateral configurations, the MNCF demonstrated lower postoperative drooling and wound complication rates.

The overall drooling rate in this cohort was 14.4%, comparable to previously published data [7]. Although univariate analysis did not reveal a statistically significant difference, multivariate analysis demonstrated a strong protective effect of the MNCF (aOR, 0.18; p=0.026). This finding highlights the critical importance of adjusting for confounders, particularly flap laterality, to reveal the true functional advantage of the technique masked by clinical practice patterns.

The favorable continence observed with the MNCF, despite significantly larger reconstructed defects (median 75.0% vs. 60.0%; p=0.007), warrants further attention. Several anatomical characteristics may explain this outcome. First, bilateral advancement provides symmetrical tissue bulk and preserves lip height and commissure position, facilitating passive lip seal [11,12]. Second, preservation of sensory innervation through the buccal nerve branches enhances saliva detection and compensatory swallowing responses [11,12,14]. Third, cheek tissue more closely approximates the biomechanical properties of native lip tissue than nasolabial skin [14,15]. Because neither technique restores circumferential orbicularis oris contraction [7,8,11,12], postoperative continence depends largely on tissue bulk, lip eversion, and sensory feedback rather than active sphincteric function [12]. The three-month assessment period may therefore reflect the stage at which sensory recovery and adaptive swallowing mechanisms become functionally evident [16,17].

The MNCF was also associated with substantially lower complication rates (1.3% vs. 14.9%: aOR, 0.06; p=0.030) despite being used for larger defects and more frequent bilateral reconstructions— factors typically associated with increased risk [14,18]. This advantage likely reflects both anatomical and technical aspects. The multilayered composition of the MNCF, incorporating skin, subcutaneous tissue, muscle, and mucosa, provides robust neurovascular pedicles and vascular redundancy [11,12]. In contrast, the thinner NLF relies primarily on a narrower subdermal plexus [7,19]. In addition, direct advancement with the MNCF avoids mechanical vulnerabilities inherent to flap rotation, such as pedicle torsion and venous congestion [7,8,19,20]. Bilateral MNCF reconstruction may more evenly distribute tension across the defect [11,12]. Consistent with this, our analysis confirmed that flap laterality itself was not an independent risk factor (p=0.753). In contrast, the trend toward increased complications with MRND (p=0.057) likely reflects greater operative magnitude rather than flap choice [21].

Beyond nasolabial and cheek-based advancement flaps, rotation-advancement techniques such as Karapandzic and Gillies fan flaps represent another major option for lower lip defects exceeding one-third of the lip length [4,5]. These techniques preserve the orbicularis oris muscle and neurovascular supply, theoretically restoring dynamic sphincteric function [5,16]. However, the Karapandzic flap carries a high risk of microstomia and commissure distortion, particularly in larger defects, which can compromise denture usage and oral hygiene [5]. Similarly, the standard Gillies fan flap may cause commissure blunting and is typically insensate unless modified [15,16].

Within this reconstructive landscape, the MNCF offers complementary advantages. Unlike rotation flaps, which prioritize sphincter restitution at the potential expense of the oral aperture, the MNCF’s lateral advancement preserves the oral aperture and minimizes microstomia [11,12]. Compared with the insensate NLF or standard Gillies flap, the MNCF reliably preserves sensory function via buccal nerve branches, facilitating passive oral competence [12,14]. Bilateral advancement extends its applicability to near-total defects [11,12]. Although the MNCF does not restore active circumferential sphincter contraction, the combined preservation of sensation, tissue bulk, and lip height provides acceptable functional outcomes, particularly in significant, central, or bilateral defects where rotation-advancement flaps may be less suitable. These techniques should be viewed as complementary rather than competing, with flap selection guided by defect characteristics, oncologic considerations, and surgical expertise.

This study holds several clinical implications. The emergence of the MNCF’s protective effect only after multivariate adjustment underscores the importance of accounting for defect size and flap laterality in reconstructive outcome analysis. These findings support the feasibility of wider oncologic resections when adequate MNCF expertise is available, without compromising functional outcomes. Strengths of this study include the first direct comparison of postoperative drooling between these techniques, a sufficient sample size, and comprehensive adjustment for confounders.

Several limitations should be acknowledged. First, the retrospective design introduces potential selection bias and residual confounding despite multivariate adjustment. Second, postoperative drooling was assessed as a dichotomous clinical variable (present/absent) rather than using a validated quantitative scale [17]. This limitation lacks sensitivity for severity grading and potentially underrepresents subtle functional deficits. Finally, this single-center experience reflects substantial institutional familiarity with the MNCF technique [11,12]. The superior outcomes observed may reflect learning curve effects, which may limit generalizability to centers less experienced with this specific flap. Future prospective studies incorporating validated quality-of-life instruments are warranted to validate these findings.

In conclusion, after adjustment for confounders, including flap laterality, the MNCF demonstrated significantly lower rates of postoperative drooling and wound complications compared with the NLF, despite reconstructing larger defects. These findings support the MNCF as a preferred reconstructive option for extensive lower lip defects when appropriate surgical expertise is available.