Newly proposed classification of plantaris tendon insertion based on branching patterns: a morphological study
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Abstract
Background: Although the plantaris muscle (PM) is considered vestigial in humans, it plays a significant clinical role in procedures like grafting. Recent reports have suggested its potential involvement in mid-portion Achilles tendon tendinopathy. Therefore, this study aims to evaluate the morphological variations of the PM, focusing on its branching patterns at the level of insertion. Materials and methods: Dissections were performed on 58 lower limbs obtained from 29 adult cadavers preserved in a 10% formalin solution. The morphology of the PM was assessed concerning its branching patterns at the insertion level and its relationship with the calcaneal tendon. Results: The PM was present in 52 out of 58 cases (89.65%). In majority of these cases (37 limbs, 63.79%), there was no splitting of the plantaris tendon (PT) at the level of the extensor expansion (ExP). Bifurcation occurred in 10 cases (19.23%), trifurcation in 4 cases (7.69%), and in one instance, the tendon divided into four slips. In 11 cases (22.4%), the insertion blended with the Achilles tendon (Type VII), which may increase the risk of Achilles tendinopathy. Conclusions: The study indicates the existence of new types of PM tendon insertions that could potentially influence the development of Achilles tendinopathy. Variations in the anatomical morphology of the PM tendon may lead to potential conflicts with the Achilles tendon and the tibialis posterior tendon, thereby increasing the risk of tendinopathy.
Keywords: plantaris muscletendon insertionbranching patternsmorphological classificationanatomical variations
References
- Alfredson H, Spang C. Clinical presentation and surgical management of chronic Achilles tendon disorders. Foot Ankle Surg. 2018; 24(6): 490–494.
- Aragão JA, Reis F, Guerra D, et al. The occurrence of the plantaris muscle and its muscle-tendon relationship in adult human cadavers. Int J Morphol. 2010; 28(1): 255–258.
- Asplund CA, Best TM, et al. Achilles tendon disorders. BMJ. 2013; 346(15): f1262.
- Bergman RA, Afifi AK, Miyauchi R. Illustrated encyclopedia of human anatomic variation: Opera. Anatomy Atlases, Iowa City 2006.
- Daseler EH, Anson BJ. The plantaris muscle: an anatomical study of 750 specimens. J Bone Joint Surg Am. 1943; 25(4): 822–827.
- de Jonge S, van den Berg C, de Vos RJ, et al. Incidence of midportion Achilles tendinopathy in the general population. Br J Sports Med. 2011; 45(13): 1026–1028.
- D'Souza J, Goldie IF. The plantaris muscle. J Anat. 1964; 98(Pt 4): 569–573.
- Harvey FJ, Chu G, Harvey PM. Surgical availability of the plantaris tendon. J Hand Surg Am. 1983; 8(3): 243–247.
- Järvinen TA, Kannus P, Paavola M, et al. Achilles tendon injuries. Curr Opin Rheumatol. 2001; 13(2): 150–155.
- Karauda P, Podgórski M, Paulsen F, et al. Anatomical variations of the tibialis anterior tendon. Clin Anat. 2021; 34(3): 397–404.
- Karauda P, Shane Tubbs R, Polguj M, et al. Morphological variability of the extensor hallucis longus in human fetuses. Ann Anat. 2021; 234: 151627.
- Kvist M. Achilles tendon injuries in athletes. Sports Med. 1994; 18(3): 173–201.
- Kwinter DM, Lagopoulos M. Variations of the plantaris muscle and tendon. Clin Anat. 2011; 24(8): 915–922.
- Merenda L, Carnett J, Horton W. Graft selection in ligament reconstruction surgery: role of plantaris tendon. Orthop Rev (Pavia). 2010; 2(2): e24.
- Mobin N. Anatomical variations of plantaris muscle: a cadaveric study. Int J Anat Res. 2016; 4(2): 2196–2199.
- Möller M, Movin T, Granhed H, et al. Acute rupture of tendon Achillis. A prospective randomised study of comparison between surgical and non-surgical treatment. J Bone Joint Surg Br. 2001; 83(6): 843–848.
- Nawoczenski DA, Ludewig PM. Plantaris-related variations and their implications in tendinopathy. Sports Med Rehabil J. 1999; 28(3): 191–199.
- Nayak SR, Krishnamurthy A, Ramanathan L, et al. Anatomy of plantaris muscle: a study in adult Indians. Clin Ter. 2010; 161(3): 249–252.
- Olewnik Ł, Kurtys K, Gonera B, et al. Proposal for a new classification of plantaris muscle origin and its potential effect on the knee joint. Ann Anat. 2020; 231: 151506.
- Olewnik Ł, Wysiadecki G, Polguj M, et al. The report on the co-occurrence of two different rare anatomic variations of the plantaris muscle tendon on both sides of an individual. Folia Morphol. 2017; 76(2): 331–333.
- Olewnik Ł, Wysiadecki G, Polguj M, et al. Anatomic study suggests that the morphology of the plantaris tendon may be related to Achilles tendonitis. Surg Radiol Anat. 2017; 39(1): 69–75.
- Olewnik Ł, Wysiadecki G, Podgórski M, et al. The plantaris muscle tendon and its relationship with the Achilles tendinopathy. Biomed Res Int. 2018; 2018: 9623579.
- Olewnik Ł, Waśniewska A, Polguj M, et al. Morphological variability of the palmaris longus muscle in human fetuses. Surg Radiol Anat. 2018; 40(11): 1283–1291.
- Olewnik Ł, Wysiadecki G, Polguj M, et al. Anatomic study of the morphology and morphometry of the plantaris tendon and its various insertion patterns. Clin Anat. 2017; 30(4): 522–531.
- Prakash S, Ojha P. Morphological study of plantaris muscle in cadavers and its clinical significance. Indian J Clin Anat Physiol. 2020; 5(1): 17–19.
- Schiaffino S, Mammucari C. Regulation of skeletal muscle growth by the IGF1-Akt/PKB pathway: insights from genetic models. Skelet Muscle. 2011; 1(1): 4.
- Simpson SL, Hertzog MS, Barja RH. The plantaris tendon graft: an ultrasound study. J Hand Surg Am. 1991; 16(4): 708–711.
- Spang C, Alfredson H, Ferguson M, et al. The plantaris tendon in association with midportion Achilles tendinosis. Histol Histopathol. 2013; 28(5): 623–632.
- Spina AA. The plantaris muscle: anatomy, injury, imaging, and treatment. J Can Chiropr Assoc. 2007; 51(3): 158–165.
- Suydam SM, Buchanan TS, Manal K. Plantaris tendon: a biomechanical comparison of cadaveric specimens and clinical implications. J Biomech. 2015; 48(9): 1775–81.
- Szaro P, Witkowski G, Ciszek B. The twisted structure of the fetal calcaneal tendon is already visible in the second trimester. Surg Radiol Anat. 2021; 43(7): 1075–1082.
- Theobalt K, Turk M, Kalu G, et al. Morphological variation of the soleus muscle: Determining general patterns and characteristics of the connective tissue architecture. Transl Res Anat. 2024; 37: 100331.
- Triantafyllou G, Zielinska N, Piagkou M, et al. A three-headed plantaris muscle with a bipartite insertion of its two accessory heads. Anat Sci Int. 2025; 100(1): 133–137.
- van Sterkenburg MN, Kerkhoffs GM, Kleipool RP, et al. The plantaris tendon and a potential role in mid-portion Achilles tendinopathy: an observational anatomical study. J Anat. 2011; 218(3): 336–341.
- Waśniewska-Włodarczyk A, Paulsen F, Olewnik Ł, et al. Morphological variability of the plantaris tendon in the human fetus. Sci Rep. 2021; 11(1): 16871.
- Wysiadecki G, Varga I, Klejbor I, et al. Reporting anatomical variations: should unified standards and protocol (checklist) for anatomical studies and case reports be established? Transl Res Anat. 2024; 35: 100284.
- Zielinska N, Maślanka K, Węgiel A, et al. Never undescribed four–headed plantaris muscle. Folia Morphol. 2024 [Epub ahead of print].
