Morphology and morphometry of the fundiform and suspensory ligaments of the penis in Thai population

Abstract

The fundiform ligament and penile suspensory ligament (PSL) are essential for maintaining prepubic curvature and stabilizing erections. PSL dissection is a key step in penile lengthening surgery for micropenis; however, the precise origin and insertion of the fundiform ligament, as well as the insertion of the PSL, remain subjects to debate. In this study, 34 embalmed male cadavers without pathology or prior pelvic or perineal surgery were dissected layer by layer from the lower abdominal wall to the penile base. The fundiform and PSL were identified, and their origin, insertion, morphology, length, and vascular associations were documented. Four distinct shapes of the fundiform ligament were identified: double, triangular, Y-shaped, and irregular type, with the double type being most common. The majority originated from the linea alba, while some arose from Scarpa’s fascia or both, inserting distally into the superficial penile fascia. The external pudendal artery was observed near its insertion in 56% of cases. The PSL consistently exhibited a triangular configuration, with an average depth of 27.4±5.7 mm along the pubic symphysis. The angle between the pubic margin and penile shaft margin measured 58.6°±9.7°. The deep dorsal vein of the penis was identified at the deep margin of the PSL in 53% of specimens. These findings provide detailed anatomical insights into the penile suspensory apparatus, highlighting structural variations, origins, and relationships with adjacent vascular structures. Further surgical validation is required to establish their clinical implications in penile lengthening procedures.

Introduction

The penile suspensory apparatus comprises three groups of ligaments arranged from superficial to deep, the fundiform ligament, penile suspensory ligament (PSL), and arcuate subpubic ligament [1]. The fundiform ligament is superficial and unattached to the tunica albuginea, while the suspensory ligament properly extends from the pubic symphysis to the tunica albuginea, enclosing the dorsal vein. The arcuate subpubic ligament runs a similar but more posterior course and is slightly denser. Functionally, the suspensory ligament proper supports the penis against the pubis and stabilizes erection [1]. Both the fundiform and suspensory ligaments are important in maintaining the normal prepubic curvature of the penis [2]. They serve to connect the penile body to the pelvis, ensuring midline alignment of the penis, and positioning it at a 30-degree angle from the anterior abdominal wall during sexual intercourse, facilitating coitus [3]. The clinical significance of the PSL lies in its vulnerability to trauma during sexual intercourse, particularly with forced downward pressure. Such trauma can result in penile instability, deformity, and varying degrees of erectile dysfunction [4-6]. Congenital absence of the PSL can lead to congenital penile instability and deformity, including penile curvature and rotation [6-9]. According to Liu et al. [9], PSL repair using permanent sutures or a fascial graft effectively re-establishes penile support, stabilizes erection, and maintains sexual function. Penile elongation surgery is indicated for congenital or acquired micropenis to restore functional length, facilitate normal voiding and intercourse, and enhance quality of life [10]. Surgical release of the PSL changes the acute angle of the penis to the pubic symphysis to an obtuse angle which allows the penis to lie in a more dependent position and therefore gives the perception of lengthening [10-16]. Despite its significance, there exists considerable variability and controversy regarding its anatomical details and terminology.

The fundiform ligament, located superficially within the penile suspensory apparatus, is characterized by a loose fibrofatty fascial consistency [1, 17-19]. Its precise origin and insertion points have sparked debate within the literature. The origin of the fundiform ligament remains debated, with reports describing attachment to the linea alba, Scarpa’s fascia, or both [1, 17, 20]. Its insertion is likewise contentious, with fibers reported in either the superficial or deep (Buck’s) fascia [1, 20].

Deeper to the fundiform ligament lies the PSL, which is characterized as a tough, dense, and discrete fibrous structure [1, 17-21]. Its origin remains debated: some studies describe a connection to the pubic symphysis, including continuation with the perichondrium of the symphysis [1, 17-19], whereas others report an origin from the linea alba [21, 22]. The ligament extends toward the base of the penis, but its insertion site is likewise controversial. Certain authors describe insertion into the deep fascia of the penis (Buck’s fascia) [17], while others propose a firm attachment to the tunica albuginea [1, 18, 19]. Functionally, the PSL serves as a stabilizing structure with a major role in maintaining penile erection [18, 19].

Morphologically, PSL has been described as triangular in shape [1, 19, 20, 22]. Mariani et al. [17] reported its dimensions as approximately 5.08 cm in length and 2.6 cm in width. Neurovascular relationships include the PSL inserting between the superficial and deep dorsal veins of the penis [1, 17, 20]. Deep to the PSL lies the arcuate subpubic ligament, a dense fibrous structure that stabilizes the fixed portion of the penis, specifically anchoring the crura of the corpora cavernosa to the inferior pubic rami [1, 18-20].

Inconsistencies in the existing literature underscore a major limitation of prior studies, which were often based on small sample sizes—10 and 7 cadavers [1, 20] or a single patient in a three-dimensional virtual model [2]. Such limited material is inadequate for delineating the fine morphology of these ligaments and their precise attachments. Moreover, the absence of standardized terminology and detailed morphometric data has hindered a comprehensive understanding of their true anatomy. The primary objective of this study was to define and quantify their origins, insertions, and dimensions, thereby offering a more definitive anatomical characterization. A secondary objective was to identify anatomical variations in a Thai cadaveric population and correlate our findings with previous reports to address existing controversies. Embalmed cadaveric studies remain invaluable for clearly delineating ligamentous structures from adjacent soft tissues and visualizing their attachments; however, they do not preserve the native consistency of the ligaments as in the living state. This study aims to address the following research questions:

1. What are the precise and most common origins, insertions, and dimensions of the penile suspensory and fundiform ligaments?

2. To what extent do these ligaments exhibit anatomical variation within a Thai cadaveric population?

Materials and Methods

Thirty-four male pelvic and perineal regions of embalmed cadavers from the Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand, were evaluated. Specimens with any pathology or history of previous surgery involving the pelvic or perineal regions were excluded from the study. Cadaveric demographic data were obtained from the registry of the Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.

Ethical consideration

The Institutional Review Board of the Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand, has exempted this study in compliance with the International guidelines for human research protection as Declaration of Helsinki, The Belmont Report, CIOMS Guideline, International Conference on Harmonization in Good Clinical Practice (ICH-GCP) and 45CFR 46.101(b). The certificate of exempt number is 138/2024.

Dissection

A superior horizontal incision was made along the pubic region, approximately 8 cm above the pubic symphysis. A vertical incision was then made perpendicular to the horizontal incision, extending inferiorly to the dorsal surface of the penis. The skin was reflected laterally on both sides, followed by the removal of subcutaneous fat to expose the fundiform ligament. The region containing the fundiform ligament was carefully dissected to delineate its shape, the presence of bundles, and its proximal attachments—whether to the linea alba or Scarpa’s fascia. The penile skin was also reflected to expose the superficial fascia of the penis. Meticulous dissection was performed to expose the distal attachment of the fundiform ligament to the penis, during which the external pudendal artery was identified.

In the subpubic region, the PSL was dissected to delineate its three margins—free, penile shaft, and pubic—and its attachment to the penile fascia. The deep dorsal vein of the penis was also identified. All dissected specimens were photographed and analyzed accordingly.

Measurements

Measurements of the fundiform ligament were obtained using a measuring tape, while those of the PSL were taken with a digital vernier caliper (Mitutoyo^®; Mitutoyo Co.; range: 0–150 mm, resolution: 0.01 mm). Angles were measured using a standard protractor. Each measurement was performed twice by a single investigator to ensure accuracy, and the average of the two measurements was recorded. Intraobserver reliability was assessed to determine the accuracy of the measurements. The various measurements of the penile ligaments were taken as described below.

The fundiform ligament

The lengths of the fundiform ligament of both sides, including any accessory bundles were measured. The superior landmark for measurement was defined by the fundiform ligament’s attachment to its origin—either Scarpa’s fascia or the linea alba. The inferior border was marked where the fundiform ligament attached to either side of the penile base. These anatomical landmarks were pinned to facilitate accurate measurements (Fig. 1).

Fig. 1.

Photograph of the fundiform ligament. Fixed reference points were marked at the origin (blue star) and insertions (red stars) of the ligament to ensure accurate measurement. Black star, penile suspensory ligament.

The penile suspensory ligament

The PSL is composed of three distinct margins; the free margin of the penile suspensory ligament (PSLF), penile shaft margin of the penile suspensory ligament (PSLS), and pubic margin of the penile suspensory ligament (PSLP), as illustrated in Fig. 2A.

Fig. 2.

(A) Diagram showing all measurement points of the penile suspensory ligament (PSL). (B) Photograph of the PSL. The dotted triangle represents its three margins. PSLF, free margin of the penile suspensory ligament; PSLP, pubic margin of the penile suspensory ligament; PSLS, penile shaft margin of the penile suspensory ligament; Angle θ, angle between PSLP and PSLS.

• PSLF (free margin): this represents the distance from the highest point of origin of the PSL on the pubic symphysis to the most anterior point of its insertion on the dorsum of the penis.

• PSLS (penile shaft margin): this is the measured distance of the ligament from its most posterior insertion point to its most anterior insertion point on the dorsum of the penis.

• PSLP (pubic margin): this is the distance from the highest point of origin of the PSL on the pubic symphysis to the most posterior point of its insertion on the dorsum of the penis.

All three margins were measured accurately during dissection. Additionally, the angle between PSLP and PSLS was measured, as depicted in Fig. 2.

Data analysis and statistics

Statistical analysis was performed using IBM SPSS Statistics, Version 29.0 (IBM Co.). The mean±SD was calculated for each parameter. A paired t-test was applied to assess mean differences between sides. Results were considered statistically significant at P<0.05.

Results

Demographic data

The average age of death of the donors was 80.1±11.0 years (ranging between 56–104 years).

The fundiform ligament

Among the 34 observed cases, the majority of fundiform ligaments originated from the linea alba in 23 cases (68%), while 11 cases (32%) were derived from the Scarpa’s fascia and attached distally on either side of the superficial fascia of penis in all cases. The shape of the fundiform ligament was observed as triangular, with its apex at the linea alba, or as consisting of two bundles originating from the linea alba or Scarpa’s fascia. Accessory bundles were also present in two cases (6%). A broad attachment of the superior border was identified in one case (3%). Based on these morphological variations, the fundiform ligament was classified into four types (Figs. 3, 4). Considering the reliability of the classification system, two researchers (PW and VC) were assigned to independently determine the type, and a consensus was reached afterward. The prevalence and origin of each type are summarized in Table 1. A detailed description of each type is provided below:

Fig. 3.

Photographs showing variations in the shape of the fundiform ligament (dotted line). (A) Double structure. (B) Double structure with a median bundle. (C) Double structure with an accessory bundle on each side. Arrowhead, penile suspensory ligament; a, accessory bundle; M, median bundle.

Fig. 4.

Additional variations in fundiform ligament morphology (dotted line). (A) Triangular shape. (B) Y shape. (C) Irregular shape.

Table 1.

Prevalence and origin of each type of fundiform ligament

Type	Total	Origin
		Linea alba	Scarpa’s fascia
Type 1: double structure	19 (56)	12 (35)	7 (20)
Double structure with median ligament	1 (3)	1 (3)	0
Double structure with accessory bundle	1 (3)	1 (3)	0
Type 2: triangular shape	9 (26)	9 (26)	0
Type 3: Y shape	3 (9)	0	3 (9)
Type 4: irregular shape	1 (3)	0	1 (3)
Total	34 (100)	23 (68)	11 (32)

Values are presented as number (%).

Type 1 double structure: the double-structured fundiform ligament consists of two bundles that originate superiorly from the midpoint of the suprapubic area. These bundles descend and diverge into left and right components that attach to the superficial fascia of the penis at the penile base (Fig. 3A). Inferior to the penile base, the left and right bundles join to form a loop supporting the penile base (Fig. 5). This type was found in 19 cases (56%). Among the double-structured fundiform ligaments, 63% originated from the linea alba and 37% from the more superficial Scarpa’s fascia. The mean length of the right bundle was 8.9±1.6 cm (range 6.3–12.2 cm), and the left bundle was 8.8±1.6 cm (range 6.0–12.5 cm). Two variants of the double-bundle type were noted; (1) a double structure with a median bundle (Fig. 3B) in one case and (2) a double structure with an accessory bundle on each side (Fig. 3C) in another one case. In the first variant, the right bundle measured 13.6 cm, the left bundle 13.7 cm, and the median bundle 11.8 cm. In the second variant, the right bundle measured 11.3 cm, the left bundle 11.2 cm, the right accessory bundle 9.9 cm, and the left accessory bundle 10.1 cm.

Fig. 5.

Photograph showing the fundiform ligament (dotted line) attaching to the superficial fascia of the penis and encircling the penile base. f, fundiform ligament.

Type 2 triangular shape: the triangular shape fundiform ligament originates from the midpoint of the suprapubic area and fans out as a single triangular structure, attaching to the dorsal part of the superficial fascia of the penis at the penile base (Fig. 4A). All triangular-shaped fundiform ligaments originated from the linea alba. This type was found in 9 cases (26%). The mean length of the right and left borders of the triangular fundiform ligament was 9.3±1.5 cm (range 7.0–11.8 cm for the right and 6.9–11.8 cm for the left side).

Type 3 Y shape: the Y-shaped fundiform ligament originates as left and right bundles at the suprapubic area. These bundles travel downward and merge into a single bundle, forming a Y-shaped structure that inserts into the dorsal part of the superficial fascia of the penile base (Fig. 4B). This type was found in 3 cases (9%). All Y-shaped fundiform ligaments originated from the Scarpa’s fascia. The mean length of the right and left bundles was 10.1±2.5 cm (range 7.2–11.8 cm) and 10.1±2.4 cm (range 7.3–11.6 cm), respectively.

Type 4 irregular shape: this variant of the fundiform ligament has a broad origin at the midline of the suprapubic area and extends downward to the penile base, forming an irregular shape (Fig. 4C). This type was found in one case (3%). This type consistently originated from the Scarpa’s fascia. The measured length of the right border of the irregular-shaped ligament was 8.4 cm, and the left border measured 8.1 cm.

All types of the fundiform ligament were inserted into the superficial fascia of the penis at the penile base, where they split into two bands that encircled the penis to form a sling (Fig. 5). The mean length of the left bundle was 9.2±1.8 cm (range 6.0–13.6 cm), while the right bundle measured 9.3±1.8 cm (range 6.3–13.6 cm). A paired-samples t-test demonstrated no significant difference between the two sides (P=0.262). The external pudendal artery was present near the insertion site in 19 subjects (56%).

The penile suspensory ligament

The PSL consistently exhibited a triangular structure, composed of three distinct sides; the pubic side (PSLP), the penile shaft side (PSLS), and the free margin (PSLF) (Fig. 2). Descriptive statistics for these measurements, based on a sample of 34 ligaments, are as follows:

• Mean PSLF (free margin)=25.8±5.1 mm (range 17.1–35.5 mm)

• Mean PSLS (penile shaft)=22.4±5.7 mm (range 9.7–40.0 mm)

• Mean PSLP (pubic side)=27.4±5.7 mm (range 18.6–40.1 mm)

• Mean angle between PSLP and PSLS=58.6°±9.7° (range 40.5°–85.0°)

The PSL originated from the pubic symphysis and inserted into the deep fascia of the penis in all cases. The deep dorsal vein was present in 18 subjects (53%).

Intra-observer reliability was assessed using a two-way mixed-effects model with a consistency definition. The analysis demonstrated excellent reliability, with ICC (3, 1)=0.997 (95% confidence interval [CI], 0.997–0.998; P<0.001) for single measures and ICC (3, k)=0.999 (95% CI, 0.998–0.999; P<0.001) for average measures.

Discussion

The fundiform ligament

The fundiform ligament is the most superficial component of the penile suspensory apparatus, yet its classification remains unclear. Earlier studies did not attempt to categorize its morphology. Hoznek et al. [1] described it as a lax fibrous layer originating from the subpubic cutaneous layer, with deeper fibers connected to the linea alba. Its bundles separate and pass on either side of the penile base, converging at the midline at the lower border to form the upper and anterior portion of the scrotal septum [1]. This description closely corresponds to the Type 1 double-structure fundiform ligament identified in our study.

Chen et al. [19] also described the fundiform ligament as consisting of two bundles forming a loop-shaped structure, with a narrow superior portion and a wider inferior portion that envelops the corpora cavernosa and corpus spongiosum. However, they reported its origin from Scarpa’s fascia, with no connection to the linea alba—contrasting with our findings, in which most double-structure fundiform ligaments originated from the linea alba and, secondarily, from Scarpa’s fascia. Furthermore, Chen et al. [19] noted insertion into the deep fascia of the penis, whereas our results demonstrated insertion into the superficial fascia. The mean length of the double-structure fundiform ligament in our study was 8.9 cm in the right bundle and 8.8 cm in the left bundle, reflecting bilateral symmetry.

Filipoiu et al. [20] classified the fundiform ligament into three shapes, with the triangular type being the most common. This triangular configuration corresponded to the second most frequent form in our study. They reported ligament lengths of 5–7 cm with a base width of 2–3 cm, notably shorter than the Type 2 triangular ligament observed in our series (mean length 9.3 cm). Filipoiu et al. [20] also described a complex double structure with accessory fascicles, consisting of two fibrous bundles separated at their base and converging superiorly at the linea alba. Additional fascicles extended laterally from the aponeurosis of the external oblique muscle and inserted into the superficial fascia of the penis, anterior to the main ligament. This type accounted for 3% of cases in our series (a variant of Type 1). Notably, they also reported an irregular ligament type, which may correspond to the residual morphologies observed in our analysis. Their study, however, was limited by the small sample size (7 cadavers).

Mariani et al. [17] did not classify the ligament into distinct types but described it as comprising two superficial bundles (right, 15.0±1.7 cm; left, 14.3±1.3 cm) and a deep median bundle (8.5±1.8 cm). This description aligns with the Type 1 variant in our study (double structure with a median bundle). Our findings showed slightly shorter lengths for the right and left bundles (13.6 cm and 13.7 cm, respectively). Interestingly, more complex structures—such as the double structure with a median bundle or accessory bundles—were consistently longer than simpler morphologies, such as the basic double structure or triangular type. Based on this observation, we hypothesize that longer ligaments may require accessory fascicles to provide additional mechanical support to the penis. Further studies are needed to confirm this hypothesis.

In addition to these previously described types, our study identified a novel Y-shaped morphology, not reported in earlier literature. This configuration resembled the triangular form but featured a diverging upper portion attaching to Scarpa’s fascia. By contrast, the irregular form displayed a broader upper attachment to more superficial structures, also involving Scarpa’s fascia, compared with the triangular type. The wide variability in fundiform ligament morphology underscores the importance of individualized surgical planning. In penile lengthening or suspensory ligament release procedures, unrecognized variants may result in incomplete or asymmetric division of the ligament. Furthermore, the external pudendal artery was identified near the ligament’s insertion in 56% of cases, emphasizing the need for caution to avoid vascular injury during surgical intervention.

Penile suspensory ligament

Descriptions of the PSL vary across studies. Some characterize it as a single triangular-shaped band [17, 19] while others describe it as comprising two parts: median and lateral bundles [1, 20]. In a recent study, Danino et al. [18] identified the PSL as a loose, non-stabilizing structure and proposed a vertical dense ligament responsible for stabilizing the penis. Calopedos et al. [23] investigated the PSL in six specimens using epoxy sheet plastination and confocal microscopy. Their analysis revealed three components of the PSL; the prepubic, subpubic, and retropubic parts, which originated from Scarpa’s fascia, the pubic symphysis, and the musculotendinous fibers of the urogenital diaphragm, respectively [23]. Our study, consistent with Mariani et al. [17], demonstrated that the PSL is a single triangular structure originating from the pubic symphysis and inserting into the deep fascia of the penis. Notably, unlike the fundiform ligament, which exhibits multiple variations, the PSL consistently exhibits a triangular shape. Mariani et al. [17] measured the PSL’s total length and height as 5.08±1.1 cm and 2.6±0.8 cm, respectively. In our research, we provided a more detailed description by measuring all three sides of the ligament for the first time. The PSLS length is shorter than the total length reported by Mariani et al. [17], potentially reflecting ethnic differences. The PSLF length was closely aligned with Mariani et al.’s [17] height measurement and the PSLP length in this study has not been prior reported.

Additionally, we measured the angle between PSLP and PSLS, observing that it can increase significantly after PSL dissection, subsequently altering the penile prepubic curvature.

Clinical implications of PSLF, PSLP, and angle between PSLP and PSLS

The PSLF represents the most anterior border of the ligament and can be assessed during physical examination [6]. The findings of this study suggest that patients with a shorter PSLF and a smaller angle between the PSLP and PSLS may derive greater benefit from PSL dissection. Further research is warranted to investigate this potential correlation.

The PSLP plays a particularly critical role during dissection. In our study, the deep dorsal vein of the penis was identified at the deep margin of the PSLP in 53% of cases. This observation may hypothesize that complete dissection of the PSLP may increase the risk of vascular injury. Therefore, partial dissection—limited to the average PSLP length—should be considered to minimize vascular damage. Future studies are needed to clarify the relationship between the extent of partial dissection and the degree of penile length gain.

This study has several limitations. The sample was restricted to Asian (Thai) individuals, limiting generalizability. The relatively small number of cadavers resulted in only one Type 4 specimen and a few Type 1 variants, requiring confirmation in larger studies. The arcuate subpubic ligament was not examined due to its deeper location and lower perceived clinical relevance. Finally, while embalmed cadaveric dissections provide excellent visualization of ligamentous structures, tissue consistency differs from that in living subjects.

In conclusion, this study clarifies the anatomy of the fundiform and suspensory ligaments, addressing controversies in their origin, insertion, morphology, and vascular relationships. Four distinct shapes of the fundiform ligament were identified, while the suspensory ligament consistently presented as a triangular structure from the pubic symphysis to the deep penile fascia. These findings enhance anatomical understanding and may improve surgical outcomes by reducing complications. Further research is needed to confirm these observations and refine clinical applications.