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ABSTRACT

The Peroneus longus muscle plays an important role in ankle stability and is increasingly utilized as a tendon graft in reconstructive surgeries, including anterior cruciate ligament (ACL) reconstruction and ankle stabilization surgeries. Despite its clinical significance, morphometric data comparing right and left limbs and sex-based variations remain limited. This study aims to evaluate the morphometry of the Peroneus longus muscle and tendon in cadavers and its relationship with anthropometric parameters. Methods: A total of 38 independent human cadaveric lower limbs (22 Male, 16 Female; 18 Right, 20 left) were dissected. Measurements recorded included length of lower limb, length of thigh, length of leg, total muscle length, tendon length, and tendon width. Descriptive statistics were calculated. Comparisons were made between sexes and sides using independent sample t-tests. Correlations with anthropometric measures were assessed using Pearson’s correlation and linear regression where the regression models were adjusted for gender and side. Significance was set at p <

0.05. Results: The mean length of the Peroneus longus muscle was 36.44 ± 2.66 cm, tendon length was 9.83 ± 2.48 cm, and tendon width was 6.19 ± 0.87 mm. Male cadavers demonstrated significantly greater tendon width compared to female cadavers (p < 0.05). No significant difference was found between right and left limbs for most parameters, although minor asymmetry was observed in tendon length. The Peroneus longus muscle was significantly longer in males than females (p < 0.05). No significant side-to-side differences were observed. Multivariable regression analyses were performed with adjustment for sex and side. Peroneus longus muscle length showed a strong positive relationship with leg length (β = 0.670, 95% CI: 0.341–0.998, p < 0.001) and thigh length (β = 0.382, 95% CI: 0.054–0.710, p = 0.024) when examined separately. In the mutually adjusted model, leg length remained the only significant predictor of Peroneus Longus muscle length (β = 0.563, 95% CI: 0.138–0.988, p = 0.011).For tendon outcomes, thigh length was positively associated with Peroneus Longus tendon thickness, both in univariable analysis (β = 0.133, 95% CI: 0.017–0.248, p = 0.026) and in the multivariable model. Conclusion: This study provides baseline morphometric data for the Peroneus longus muscle and its tendon, highlighting sexual dimorphism and anthropometric predictors of its morphometry, reinforcing its reliability as a tendon graft. Leg length predicts muscle length, while thigh length predicts tendon thickness, providing clinically useful preoperative markers. Keywords: Peroneus longus, Peroneus longus tendon, ACL, Tendon graft

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INTRODUCTION

The Peroneus Longus (PL) muscle also known as Fibularis Longus muscle is located in the lateral compartment of the leg, superficial to Peroneus Brevis muscle. It arises from the head and proximal two-thirds of the lateral surface of the fibula, deep surface of the deep fascia, the anterior and posterior crural intermuscular septa, and occasionally few fibres from the lateral condyle of the tibia. The muscle belly ends in a long tendon that runs distally behind the lateralmalleolus. The tendon runs obliquely on the lateral side of the calcaneus, deep to inferior fibular retinaculum; crosses the sole of the foot obliquely and is attached by two slips, one to the lateral side of the base of the first metatarsal bone and another to the lateral aspect of the medial cuneiform; occasionally a third slip attached to the base of second metatarsal bone. It contributes to eversion and plantar flexion of the ankle and plays an essential role in maintaining the medial and transverse arches and the concavity of the foot during toe-off and tip-toeing [1]. Anatomical studies have shown that the PL has distinct neuromuscular compartments, reflecting its complex functional contribution to ankle stability [2].

PL tendon has emerged as an important autograft option in reconstructive procedures, like anterior cruciate ligament (ACL) reconstruction and ankle stabilization surgeries. Its adequate length, favorable diameter, and high tensile strength make it a promising alternative to commonly used grafts such as the hamstrings and patellar tendon [3]. It has been successfully applied in both anterior and posterior cruciate ligament reconstructions, consistently achieving graft diameters ≥8 mm [4.5]. Despite this clinical importance, comprehensive morphometric data on the PL muscle and tendon remain limited, with respect to bilateral variations and sex-based differences. Understanding these parameters is crucial for both anatomists and surgeons to optimize tendon harvesting and to minimize donor-site morbidity. Several cadaveric and imaging studies have examined the morphometry of the Peroneus longus tendon, particularly its suitability as a graft. Clinical outcomes are comparable to hamstring autografts, with studies suggesting larger graft diameters and reduced donor- site morbidity [6, 7]. However, donor ankle morbidity, including mild reduction in eversion torque, has been reported [8].Studies has demonstrated that the PL tendon provides sufficient length and graft diameter for use in ACL reconstruction, with minimal donor- site morbidity. Anthropometric predictors, such as height, weight, and lower limb length, have been correlated with PL graft dimensions [9, 10]. Anatomical studies also describe variations in tendon insertion into the medial cuneiform and first metatarsal, which may influence surgical harvest [11, 12]. It has been reported that patients undergoing ACL reconstruction with PL autografts achieve comparable stability and functional recovery to those with hamstring grafts, while avoiding complications such as anterior knee pain or hamstring weakness

The majority of available data focus on graft feasibility, with relatively limited data on sex-based and bilateral variations and the relationship of PL morphometry to anthropometric parameters. The increasing trend towards the use of PL tendon grafts, a more comprehensive morphometric database is required to guide surgeons in graft selection and to anticipate variation

AIM AND OBJECTIVES

1. Estimate the length of lower limb, length of thigh, length of leg, length of muscle belly, tendon length, and tendon width in human cadaveric specimens.
2. Comparing morphometric parameters between male and female cadavers.
3. Analyzing right–left side differences in morphometric measurements.

This study aims to provide baseline anatomical data to enhance the understanding of the Peroneus longus morphometry and to reinforce its surgical relevance as a potential graft source in reconstructive procedures.MATERIAL AND METHODS:

Study Design and Sample

It is a descriptive, cross-sectional cadaveric study, conducted in the Department of Anatomy, St John’s Medical College, Bengaluru. A total of 38 independent formalin-fixed human lower limbs (18right, 20left) were included. The specimens were obtained from adult cadavers of known sex (22 male, 16 female).

Limbs with evidence of trauma, deformity, or previous surgical intervention in the leg and ankle region were excluded from the study.

Dissection Procedure

Standard anatomical dissection techniques were used during student dissection, to expose the Peroneus longus muscle in the lateral compartment of the leg. Skin, superficial fascia were carefully reflected, and the peroneal compartment was opened to visualize the Peroneus longus muscle belly and tendon. Care was taken to preserve the muscle-tendon unit without damaging adjacent neurovascular structures.

Measurements:

The following parameters were recorded for each limb:

1. Length of lower limb(cms) – measured from anterior superior iliac spine to the tip lateral malleolus
2. Length of thigh(cms) – measured from anterior superior iliac spine to lateral condyle of femur
3. Length of leg (cms) – measured from the head of the fibula to the tip of the lateral malleolus.
4. Muscle belly length (cms) – measured from the fibular head origin to the musculo-tendinous junction.
5. Tendon length(cms) – measured from the musculo-tendinous junction to the point behind the lateral malleolus
6. Tendon width (mm) – measured at the midpoint of the tendon using a digital vernier caliper.

All measurements were taken using a measuring tape (to the nearest millimeter) and a digital vernier caliper (accuracy 0.01 mm). Each measurement was repeated twice, by two independent observers and the average was recorded to minimize intra-observer error.

Figure: 1 Peroneus Longus muscle in situ
 

Figure: 2 Measurement of Peroneus Longus Tendon width

Ethics

This study was conducted in accordance with the ethical principles of cadaveric research. Ethical clearance was obtained from the Institutional Ethics Committee of St John’s medical College (Approval No. 237/2024) prior to commencement of the study

STATISTICAL ANALYSIS

Continuous variables were summarized as mean (standard deviation) and categorical variables as frequency (percentage) (Table 1). Normality was evaluated using the rule of thumb (SD < mean/2).

Group-wise differences in anthropometric and morphometric measures by gender and side of the leg were assessed using independent sample t-tests.

Associations of tendon length and thickness of Peroneus Longus muscle with leg length, thigh length, and limb length were examined using Pearson’s correlation and linear regression, where the regression models were adjusted for gender and side.

All analyses were performed in R (version 4.4.1; R Foundation for Statistical Computing) at a 5% level of significance.

RESULTS

A total of 38 independent lower limbs 22 male (57.8%),  16  female  (42.11%);  18right (47.37%),

20left              (52.63%)               were               analyzed. The overall mean lower limb length: 86.97± 4.02cms; length of thigh: 47.43 ± 2.84(cms); length of leg:

40.58 ± 2.2cms; length of PL measured 36.44 ± 2.66 cm, while the tendon length and tendon width measured 9.83 ± 2.48 cm and 6.19 ± 0.87 mm, respectively.

Length of lower limb, length of thigh, length of leg and the Peroneus Longus muscle length differed significantly between males and females (Table 2),

however these measures didn’t differ significantly between right and left legs (Table 3).

All the significant correlations between anthropometric and morphometric measures are plotted as correlation plots (Figures 5-8).

From the multivariable regression analyses (all models adjusted for gender and side), Model 1 examined each limb dimension separately, while Model 2 included all relevant limb dimensions together. Peroneus Longus muscle length showed a significant relationship, with leg length (β = 0.670, 95% CI: 0.341 to 0.998, p < 0.001) and thigh length

(β = 0.382, 95% CI: 0.054 to 0.710, p = 0.024). These

associations largely persisted in the mutually adjusted model, where leg length remained a significant predictor of Peroneus Longus muscle length (β = 0.563, 95% CI: 0.138 to 0.988, p = 0.011). For tendon

outcomes, thigh length was positively associated with Peroneus Longus tendon thickness, both in the univariable (β = 0.133, 95% CI: 0.017 to 0.248, p =

0.026) and multivariable models (β = 0.154, 95% CI:

0.020 to 0.289, p = 0.026) (Table 4)

Descriptive statistics: PL muscle length 36.44 ± 2.66 cm; tendon length 9.83 ± 2.48 cm; tendon thickness

6.19 ± 0.87 mm.

Sex differences: PL muscle length was significantly longer in males than females (p < 0.05). Tendon length and thickness showed no sex difference.

Side differences: No significant differences between right and left limbs.

Correlations: PL muscle length correlated strongly with leg length. Tendon thickness correlated positively with thigh length (Table 4)

Table 1: Descriptive statistics of morphometric parameters of the Peroneus Longus muscle and tendon (n

= 38)

Table 2: Comparison of morphometric parameters between male and female limbs

Table 3: Comparison of morphometric parameters between right and left limbs

Table 4: Correlation between anthropometric and peroneus longus morphometric parameters

*all the models have been adjusted for gender and side

Figure 3: Bar chart comparing males and females for PL tendon length

Figure 4: Bar chart comparing males and females for PL tendon thickness