The Chimeric Antero-Lateral Thigh Flap and Vastus Lateralis Muscle Flap for the Infratemporal Fossa Reconstruction in Oral Cancer Defects

Abstract

Objectives

To evaluate the effectiveness of the chimeric Free Anterolateral Thigh (FALT) and vastus lateralis muscle (VLM) flap for reconstructing extensive defects in advanced oral squamous cell carcinoma (OSCC), particularly those involving the infratemporal fossa (ITF) and masticator space.

Methods

A retrospective study was conducted at Sri Shankara Cancer Hospital, Bangalore, from January 2023 to June 2024. It included 22 patients with T4a and T4b OSCC who underwent curative ablative surgery, ITF clearance, and reconstruction using the chimeric FALT-VLM flap. The surgical technique involved harvesting a skin paddle based on a single perforator and a separate vastus lateralis muscle from the same donor site. The reconstruction aimed to provide oral cavity lining, oro-cervical separation, and ITF obliteration.

Results

Patient age ranged from 38 to 76 years (mean 53.6). The majority had buccal mucosa (54.5%) and retromolar trigone (36.3%) cancers. The FALT skin paddle size varied from 94.2 to 408.2 cm², with muscle bulk between 201.0 and 391.9 cm³. Complications included seroma and hematoma in 9.1% of cases, with 81.8% showing no complications. No donor site morbidity was noted. Post-operative mouth opening ranged between 2.5 and 3.5 cm. Most patients (72.7%) received adjuvant radiotherapy. All maintained local-regional control status.

Conclusion

The chimeric FALT-VLM flap is a robust technique for reconstructing complex oral cancer defects, effectively addressing both functional and aesthetic needs. This approach, combining skin and muscle components with independent vascular supplies, represents a significant advancement in reconstructive surgery for advanced OSCC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-024-05286-3.

Introduction

Head and neck cancer constitutes a significant global cancer burden, with approximately 30% of new cancer cases in India being head and neck cancers [1]. A majority of these patients present with locally advanced disease, with over 50% classified as such [2].

In oral squamous cell carcinoma (OSCC), involvement of the skin and bone categorizes patients as T4a, while involvement of the masticator space, pterygoid plates, skull base, and internal carotid artery leads to a T4b classification [3]. The close proximity of the buccal mucosa to bone, skin, and muscles of mastication results in the early involvement of these structures in buccal mucosa cancers, leading to a large proportion of buccal tumours being classified as either T4a or T4b [4].

Traditionally, T4b advanced oral cavity cancers were considered inoperable, with treatment limited to palliative radiation and chemotherapy, either alone or in combination. Recently, surgery is the primary curative modality for such T4b (due to masticator space involvement) cases. A recent meta-analysis by the International Head and Neck Scientific Group suggests that curative intent ablative surgery for infra-mandibular notch T4b oral cancers can achieve survival rates similar to those of T4a cancers [5].

When planning such extensive ablative procedures, reconstruction of the oral cavity becomes essential. The goals of reconstruction include providing a lining for the buccal mucosa, ensuring oro-cervical separation, obliterating the infratemporal space cavity to prevent complications, and reconstructing the contour defects of the cheek caused by the removal of infratemporal space tissue [6].

The flaps traditionally used for reconstructing these defects include the Free Anterolateral Thigh (FALT) flap [7], Thoracodorsal Artery Perforator (TDAP) flap [8], Latissimus Dorsi (LD) flap [9], Vertical Rectus Abdominis Muscle (VRAM) flap [10], and Pectoralis Major Myocutaneous (PMMC) flap [11].

Our work aims to discuss the surgical technique, favourable outcomes, and our experience in reconstructing such large defects using the FALT and vastus lateralis muscle (VLM) in a chimeric fashion. This study represents the first effort to describe this specific reconstruction technique.

Subjects and Methods

This retrospective study was carried out in the Department of Head and Neck Surgical Oncology at Sri Shankara Cancer Hospital, Bangalore. It involved patients with oral squamous cell carcinoma who underwent curative ablative surgery, including ITF clearance, neck dissection, and reconstruction using the free chimeric ALT-VLM flap, between January 2023 and June 2024. The parameters such as age, gender, tumour sub-site, extent of primary resection, presence of cutaneous defect, FALT skin paddle area, VLM volume, post-operative events, pathological T and N staging, neck and flap site drain removal time, duration of hospital stay, adjuvant therapy, post-operative mouth opening and current oncological status. All procedures performed in the study were conducted by the ethical standards in the 1964 Declaration of Helsinki, as revised in 2013.

Ablative Technique

A standard “bite excision” was performed, where the specimen included the inferior and superior alveolus in continuity with the intervening buccal mucosa, retromolar trigone mucosa, and the medial pterygoid and masseter muscles (Suppl. Fig) [10]. ITF clearance was carried out for all cases (Fig. 1). A standard technique was used for neck dissection [12].

Fig. 1.

Panel A to E– Infratemporal fossa (ITF) defects; a (in panel A to E) - ITF and skull base, b (in panel E)– condylar fossa, c (in panel E) - palate, d (in panel E)– parotid, e (in panel E)– temporal fossa

Reconstruction Technique

Our technique describes the harvest of FALT-VLM flaps in a chimeric fashion, where the skin paddle is based on a single perforator, and the VLM is taken from the distal runoff of the flap pedicle, independent of the skin paddle (Fig. 2). The harvest begins with an exploratory incision 2 cm anterior to the septum, marked by the anterosuperior iliac spine (ASIS) and superolateral patella. After identifying the rectus femoris muscle, the plane between the rectus femoris and VLM is opened to expose the flap pedicle, the descending branch of the lateral circumflex femoral artery (LCFA). A perforator that pierces the fascia and connects proximally to the pedicle is selected and dissected along with the entire perforator and pedicle.

Fig. 2.

Panel A to D– showing the harvested (pre-inset) chimeric free anterolateral thigh (FALT) flap with vastus lateralis muscle (VLM); Panel C and D showing the separate pedicle for FALT and VLM, joining to form a single pedicle

In the conventional ALT flap harvest, the distal runoff of the pedicle, which typically branches into the muscle, is clipped. However, in this modified approach, instead of clipping the distal runoff, a portion of the VLM is harvested on the distal runoff of the pedicle, remaining independent of the skin paddle [13, 14]. The VLM, taken on the distal runoff of the LCFA and fully mobile from the skin paddle, is positioned in the infratemporal space, while the skin paddle, based on the perforator, is used to reconstruct the oral cavity lining and, if necessary, the outer skin cover. Facial artery, external jugular vein or common facial vein was used for microvascular anastomosis.

Inset: The mucosal inset was done first by suturing the cutaneous portion of the flap to the residual oral mucosa. Afterward, the microvascular anastomosis was completed. The muscular component was gently tucked into the ITF defect (Suppl. Video), which is feasible because the ITF defect is only open inferiorly. The required volume of the VLM muscle was calculated intraoperatively based on the size of the ITF defect. The outer skin defect was closed using the remaining cutaneous component of the ALT flap. If there was no outer skin defect, the cheek flap was repositioned, and closed suction drains were placed.

Postoperative Care

Delayed extubation was performed for all cases, and patients were observed in the ICU for 2 days. Flap monitoring was conducted every 4 h using skin prick tests and Doppler to assess blood flow in the anastomosed vessel [15]. If any adverse events occurred, such as flap colour changes, venous blood on prick testing, or neck hematoma, the patient was taken for re-exploration.

Patients were transferred to the ward on postoperative day 2 with intravenous antibiotics. Enhanced Recovery After Surgery (ERAS) protocols were stringently followed. Regular aseptic dressings were applied daily, and drains were removed when output fell below 25 ml. Dry swallows were initiated, followed by a methylene blue saline swallow test to check for leaks. The nasogastric tube (NGT) was removed between postoperative days 7 and 10. Patients were discharged on days 8 to 12 once the wounds were healed and they were able to consume adequate food orally.

Adjuvant radiotherapy (RT) or chemoradiotherapy (CRT) was administered based on histopathology reports, with standard intensity-modulated radiotherapy (IMRT) protocols used for adjuvant radiation and weekly cisplatin was used was adjuvant chemotherapy. Pre-IMRT planning CT scans assessed the baseline viability of the muscular component of the chimeric flap (Suppl. Fig). the patients were followed up as per the National comprehensive cancer network (NCCN) guidelines (Fig. 3). Four to six weeks post-radiation, a guide bite prosthesis was used to correct mandibular deviation. A positron emission computerised tomography (PETCT) scan was performed 6 months post-treatment to evaluate the response to therapy.

Fig. 3.

Panel A to D– Post-operative follow up photographs; Panel A and B– shows the intra oral appearance of the chimeric free anterolateral thigh (FALT) flap; Panel C– shows good mucosalisation of flap; Panel C and D– shows good external contour

Results

The patient cohort consisted of 22 individuals, with ages ranging from 38 to 76 years. The mean age of the group was 53.6 years. In terms of gender distribution, 13 of the patients were male (59.1%), and 9 were female (40.9%). Regarding the subsites of the cancer, the buccal mucosa was 12 patients (54.5%), the retromolar trigone was involved in 8 patients (36.3%), while 2 patients (9.1%) had lesions located on the palate.

The primary surgical procedures included bite composite resections in 16 patients (72.7%), which included various combinations such as posterior segmental mandibulectomy (PSM), infrastructure maxillectomy (ISM), upper alveolectomy (UA), and skin excision (SE). Of these, 9 patients (40.9%) underwent BCR combined with PSM, ISM, and ITF clearance (ITFC). Posterior segmental mandibulectomy (PSM) with ITFC in 2 patients (9.1%), and Total maxillectomy (TM) and orbital plate preserving maxillectomy (OPPM) each in one patient (4.5%). Eight patients (36.4%) had a skin defect, while the remaining 14 patients (63.6%) did not have a skin defect. Seventeen patients (67.3%) underwent selective neck dissection (SND) and Modified neck dissection (MND) was performed in 5 patients (22.7%).

The FALT skin paddle size ranged from 94.2 cm² to 408.2 cm², with a mean size of around 226.1 cm². Chimeric FALT-VLM muscle bulk volume varied between 201.0 cm³ and 391.9 cm³, with larger muscle volumes often associated with larger skin paddle sizes and larger defects.

Post-operative events, such as seroma and hematoma in the neck, were observed in 9.1% of the cases respectively, with the majority (81.8%) experiencing no complications.

The time for neck drain removal varied from 5 to 8 days, with an average of around 6 days. The time for thigh drain removal varied from 5 to 7 days with a mean of 5.6 days. None of the patients had flap donor site morbidity. The duration of hospital stay ranged from 9 to 12 days, with longer stays often associated with post-operative events.

In the dataset (Table 1), T3 stages account for 2 cases (8%), with T3N0 representing 1 case (4%) and T3N1 also at 1 case (4%). T4a is the most common T stage, with 18 cases (72%); among these, N0 is present in 6 cases (24%), N1 in 9 cases (36%), N2a in 1 case (4%), and N3b in 2 cases (8%). T4b stages make up 7 cases (28%), with N0 occurring in 3 cases (12%), N1 in 1 case (4%), N2a and N2b each in 2 cases (8%), and N3b in 1 case (4%).

Table 1.

Overview of included cases

CN	Age	Sex	Subsite	Primary surgery	Skin defect	Neck Dissection	Skin Paddle size (cm2)	Vastus lateralis muscle Volume (cm3)	Post operative events	pTN stage	Drain removal (Neck)	Drain removal (Thigh)	Duration of hospital stay	Adjuvant therapy	Mouth opening	Status
1	39	M	RMT	R BCR (PSM + BM + ISM) + ITFC	Yes	MND	345.4	316.6	None	T4aN1	6	5	12	ADJ CTRT	2.5-3.5CM	LRC
2	51	M	RMT	R BCR (PSM + BM + ISM) + ITFC	No	MND	188.4	254.4	None	T4bN3b	7	6	10	ADJ CTRT	2.5-3.5CM	LRC
3	76	M	BM	R BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	226.1	261.7	Hematoma	T3N0	8	7	12	ADJ CTRT	> 3.5 cm	LRC
4	57	F	BM	R BCR (PSM + BM + OPPM) + ITFC	No	SND(I-IV)	201.0	376.8	None	T4aN0	6	5	11	ADJ RT	2.5-3.5CM	LRC
5	59	F	BM	L BCR (PSM + BM + ISM) + ITFC	No	SND(I-IIV)	175.8	237.4	None	T4aN1	5	5	10	ADJ RT	2.5-3.5CM	LRC
6	41	F	RMT	L BCR (PSM  + BM + UA) + ITFC	No	SND(I-IV)	188.4	234.5	None	T4aN2a	6	6	10	ADJ RT	> 3.5 cm	LRC
7	45	M	Palate	L TM + ITFC	No	SND(I-IV)	94.2	376.8	None	T4bN0	5	5	9	ADJ CTRT	2.5-3.5CM	LRC
8	39	F	RMT	L BCR (PSM + BM + ISM) + SE + ITFC	Yes	MND	381.5	376.8	Seroma	T4aN3b	7	6	12	ADJ CTRT	2.5-3.5CM	LRC
9	38	M	RMT	R BCR (PSM + BM + ISM) + SE + ITFC	Yes	SND(I-IV)	339.1	381.0	None	T4aN0	7	5	10	ADJ CTRT	2.5-3.5CM	LRC
10	64	M	BM	R BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	213.5	316.6	None	T4aN1	6	6	9	ADJ RT	2.5-3.5CM	LRC
11	69	M	BM	L BCR (PSM  + BM + UA) + ITFC	No	SND(I-IV)	201.0	261.7	None	T4bN0	6	5	9	ADJ RT	> 3.5 cm	LRC
12	53	F	BM	L BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	175.8	201.0	None	T4aN1	5	5	10	ADJ RT	2.5-3.5CM	LRC
13	52	M	BM	L PSM + ITFC	No	SND(I-IV)	164.9	212.0	None	T4bN2b	6	5	10	ADJ RT	2.5-3.5CM	LRC
14	54	M	Palate	L OPPM + ITFC	No	SND(I-IV)	109.9	316.5	None	T4aN1	5	5	12	ADJ RT	1.5-2.5CM	LRC
15	39	F	BM	R BCR (PSM + BM + ISM) + SE + ITFC	Yes	SND(I-IV)	395.6	391.9	Seroma	T4aN1	6	7	12	ADJ RT	> 3.5 cm	LRC
16	58	M	RMT	L PSM + ITFC	No	SND(I-IV)	197.8	261.7	Hematoma	T4aN1	8	7	12	ADJ CTRT	2.5-3.5CM	LRC
17	54	M	RMT	L BCR (PSM + BM + ISM) + SE + ITFC	Yes	MND	188.4	237.4	None	T4bN2a	6	6	11	ADJ RT	2.5-3.5CM	LRC
18	56	M	RMT	R BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	197.8	209.4	None	T4aN1	7	6	10	ADJ CTRT	> 3.5 cm	LRC
19	65	M	BM	L BCR (PSM  + BM + UA) + SE + ITFC	Yes	SND(I-IV)	408.2	376.8	None	T4aN0	8	6	9	ADJ RT	2.5-3.5CM	LRC
20	40	F	RMT	L BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	226.1	230.3	None	T3N1	7	5	9	ADJ RT	2.5-3.5CM	LRC
21	41	F	RMT	L BCR (PSM + BM + ISM) + SE + ITFC	Yes	SND(I-IV)	351.7	376.8	Seroma	T4bN2a	7	7	12	ADJ RT	2.5-3.5CM	LRC
22	69	F	RMT	L BCR (PSM + BM + ISM) + ITFC	No	SND(I-IV)	226.1	245.9	None	T4aN0	6	5	10	ADJ RT	2.5-3.5CM	LRC

*CN– case number, M– male, F– female, BM– buccal mucosa, RMT– retromolar trigone, L– left, R- right, BCR– bite composite resection, PSM– posterior segmental mandibulectomy, ISM– infrastructure maxillectomy, SE– skin excision, ITFC– infratemporal fossa clearance, UA– upper alveolectomy, OPPM– orbital plate preserving maxillectomy, TM– total maxillectomy, MND– modified radical neck dissection, SND– selective neck dissection, ADJ– adjuvant, RT– radiation therapy, CRT– chemoradiation therapy, LRC– loco-regional control, CM - centimeter

Most patients (72.7%) received adjuvant radiotherapy (ADJ RT), while the rest received chemoradiotherapy (ADJ CTRT). Post-operative mouth opening measurements generally fell between 2.5 and 3.5 cm, with a small percentage showing mouth openings greater than 3.5 cm or between 1.5 and 2.5 cm. Despite the variations in these factors, all patients maintained local-regional control (LRC) status post-surgery.

Discussion

Locally advanced gingivobuccal cancers (cT4a-b) represent a significant portion of oral cancers in the Indian subcontinent, largely due to the high prevalence of tobacco chewing [16]. These cancers are complex in their spread, and the placement of tobacco quid in the gingivobuccal sulcus contributes to a propensity for early mandibular involvement and extensive soft tissue invasion. This often includes involvement of the masticator space or infratemporal fossa, which are classified as cT4b.

The cheek is composed of various elements including skin, fat pads, facial muscles, ligaments, and periosteum. Unlike early-stage T1 and T2 tumours that are confined to limited structures, advanced cases can involve medullary bone, deep muscle of the tongue, maxillary sinus, and skin in T4a disease. T4b disease can extend to the masticator space, pterygoid plates, skull base, or encase the internal carotid artery [5].

Resections for infra-mandibular notch cT4b cases require infratemporal fossa clearance. This anatomical region, located beneath the base of the skull, is an inverted pyramidal-shaped depression between the styloid process of the temporal bone and the posterior surface of the maxillary sinus.

Reconstructing these extensive defects involves addressing multiple components, including providing skin and mucosal lining, adequate soft tissue bulk, and obliteration of the dead space to prevent issues such as salivary collections, seromas, or hemorrhage. Inadequate reconstruction can lead to long-term deformities and functional impairments such as trismus, lip incompetence, cheek hollowness, and food lodgement in the floor of the mouth.

A morphometric analysis by Huseyin Erdem et al. using three-dimensional (3D) digital models revealed that the infratemporal fossa can measure up to 61.1 ± 4.4 mm in length, 60.1 ± 4.4 mm in depth, and 28.2 ± 4.0 mm in width. These dimensions highlight the complexity of reconstructing such defects [17].

In a 2014 study by Kekatpure et al., tumours from the posterior hard palate or maxilla extending into the infratemporal fossa were resected, creating defects reconstructed with adipofascial anterolateral thigh flaps. This case series of four patients showed successful reconstruction with no donor-site complications, smooth mucosalisation within six weeks, and functional recovery, including adequate mouth opening [7].

In a 2014 study by Diwan et al., 56 patients with superior gingivobuccal sulcus tumors underwent ITF clearance, with PMMC flap reconstruction. Over 11 years, the 10-year overall survival was 40% with ITF clearance and 36% without, while disease-free survival was 58% with ITF clearance and 49% without [18].

In a 2024 study by Jaiswal et al., chimeric ALT + anteromedial thigh (AMT) flaps were used to reconstruct complex head and neck defects following cancer surgery in 13 patients. The study highlights the effectiveness of these flaps, based on the lateral circumflex femoral artery, in addressing large, multidimensional defects with a single donor site and microvascular anastomosis. Despite one AMT flap loss and the need for skin grafting at all donor sites, the technique proved valuable for managing extensive defects [8].

In a study by Katna et al. involving 54 patients with T4b oral cavity carcinoma, ITF clearance was evaluated for its clinical outcomes. The median follow-up was 29 months, with 2-year loco-regional control, disease-free survival, and overall survival rates of 52%, 54%, and 54%, respectively. ALT flaps were used for microvascular reconstruction in all patients, providing sufficient bulk and lining for buccal mucosa and palate, though the method was not described in detail [19].

Kumar et al. in 2023, described the surgical technique and oncological outcomes of en bloc resection for OSCC involving ITF were evaluated. Among 32 patients with cT4b OSCC, 30 underwent surgery with a systematic “out to in and top to bottom” approach. Reconstruction included PMMC flaps in 15 patients, bipaddled PMMC in 10, and additional cervicodeltopectoral (CDP) flaps in 3 patients. FALT flaps were used in 2 patients. There were no significant intraoperative or postoperative complications [20].

The chimeric ALT flap described here is distinctive because it incorporates multiple tissue components from a single donor site while avoiding the need for multiple vascular anastomoses. The distal part of the VLM is independent of the skin paddle and can be easily positioned in the infratemporal space without affecting the microvascular anastomosis. In contrast, a conventional fascio-cutaneous ALT flap does not compeletely address the hollowness of the infratemporal space effectively. The proximal part of this flap, when de-epithelized and used in the infratemporal space, tends to atrophy and lose vascularity compared to the muscle component, which maintains an independent blood supply in the chimeric ALT flap. If the skin paddle is not de-epithelized adequately, there is a risk of dermoid inclusion formation within the ITF and potential cavity infection due to residual squamous epithelium. Additionally, the vascularized muscle used in the reconstruction mimics the normal soft tissue environment of the ITF. This not only helps in accurately assessing the ITF cavity for any recurrence but also maintains the structural integrity of the reconstructed area.

Chimeric flaps consist of multiple spatially independent flaps, each with its own vascular supply, joined to a larger common vessel [8]. This technique allows for reconstruction of various components of the defect, such as the skin paddle for buccal mucosa lining and outer skin cover, and the VLM for obliterating the dead space. Each component operates independently, catering effectively to the reconstructive needs of resected tissue, especially in the challenging infratemporal space. Additionally, this flap approach helps restore the defect third dimension, correcting facial contour deformities.

Limitations

The study has a few limitations, including the small sample size of 22 patients and the relatively short study duration, which may not capture long-term outcomes or variations in the effectiveness of the reconstruction. The lack of direct comparative data limits the ability to evaluate the chimeric FALT-VLM flap technique relative to other reconstruction methods. Due to the retrospective design of the study, specific measurements for anteroposterior, mediolateral, or depth vectors of the ITF defect were not explicitly recorded. Additionally, the technique complexity might limit its reproducibility in different settings or by other practitioners. The direct monitoring of the VLM component of the flap is not possible, so its viability is assessed indirectly through the monitoring of the FALT component. Overall, more extensive studies with larger sample sizes and longer follow-up would be helpful to better understand the long-term outcomes and effectiveness of this reconstruction technique.

Conclusion

The chimeric FALT-VLM flap technique provides an effective solution for reconstructing extensive defects involving the ITF in advanced OSCC. This approach combines skin and muscle components with independent vascular supplies, addressing both structural and aesthetic aspects. This method represents a valuable advancement in surgical reconstruction for complex oral cancer cases.

Electronic Supplementary Material

Below is the link to the electronic supplementary material.

Funding

No funding received.

Data Availability

Data is available with the corresponding author and shall be made available with considerable request.

Declarations

Provenance and Peer Review

Not commissioned, externally peer-reviewed.

Competing Interests

No competing interests.