Four Tendinous Slips of Flexor Hallucis Longus Tendon: A Case Report.

Interindividual variability presents a rich field of study in medical sciences. During a cadaveric dissection at Louisiana State University Health Sciences Center, a rare anatomical variation was discovered in the pedal anatomy of a female cadaver. Medical students, while dissecting the sole of the foot, identified a variant tendinous structure. This aberrant tendinous slip from the flexor hallucis longus (FHL) extended to the lateral four tendons of flexor digitorum longus (FDL) along the plantar aspect of the foot. The discovery suggested that the FHL shares a functional relationship with the FDL. Application of tension to the FHL was found to result in simultaneous flexion motion in the lesser toes, from the second to the fifth digit. The presence of this anatomical variant holds considerable importance for surgical interventions, especially as a potential graft source in tendon reconstructions, warranting its documentation in this report.

Hindlimb and pelvic anatomy of Caiman yacare (Archosauria, Pseudosuchia): Myology and osteological correlates with emphasis on lower leg and autopodial musculature.

The anatomy of the archosaurian pelvis and hindlimb has adopted a diversity of successful configurations allowing a wide range of postures during the evolution of the group (e.g., erect, sprawling). For this reason, thorough studies of the structure and function of the pelvic and hindlimb musculature of crocodylians are required and provide the possibility to expand their implications for the evolution of archosaurian locomotion, as well as to identify potential new characters based on muscles and their bony correlates. In this study, we give a detailed description of the pelvic and hindlimb musculature of the South American alligator Caiman yacare, providing comprehensive novel information regarding lower limb and autopodial muscles. Particularly for the pedal muscles, we propose a new classification for the dorsal and ventral muscles of the autopodium based on the organisation of these muscles in successive layers. We have studied the myology in a global background in which we have compared the Caiman yacare musculature with other crocodylians. In this sense, differences in the arrangement of m. flexor tibialis internus 1, m. flexor tibialis externus, m. iliofibularis, mm. puboischiofemorales internii 1 and 2, between Ca. yacare and other crocodylians were found. We also discuss the muscle attachments that have different bony correlates among the crocodylian species and their morphological variation. Most of the correlates did not exhibit great variation among the species compared. The majority of the recognised correlates were identified in the pelvic girdle; additionally, some bony correlates associated with the pedal muscles are highlighted here for the first time. This research provides a wide framework for future studies on comparative anatomy and functional morphology, which could contribute to improving the character definition used in phylogenetic analyses and to understand the patterns of musculoskeletal hindlimb evolution.

Treatment of Dynamic Claw Toe Deformity Through Lengthening of the Flexor Tendons of the Hallux and Toes at the Midfoot Level.

The claw toe deformity is characterized by the flexion of interphalangeal joints (IPJs) with hyperextension of the metatarsophalangeal (MTP) joint. It can be flexible and reducible or rigid and irreducible, or dynamic. The most common cause of dynamic claw toes is a neurological disorder, like sequelae of an ischemic contracture of the muscle belly after a compartment syndrome. Most of the surgical techniques require multiple procedures and may be associated with complications such as toe stiffness, persisting metatarsalgia, and toe malalignment. The aim of this study is to present an option for the surgical treatment of the dynamic claw toe deformity, by simultaneous tenodesis and lengthening of the flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons at Henry's knot through a single midfoot incision.Levels of Evidence: V; Therapeutic Study; Expert Opinion.

Morphological variability of the leg muscles: potential traps on ultrasound that await clinicians.

BACKGROUND: Although muscles and their tendons are not considered the most morphologically variable structures, they still manifest a substantial diversity of variants. The aim of this study is to increase awareness of some of the many possible variants found during ultrasound imaging of one lower limb compartment, the leg, that could potentially mislead clinicians and lead to misdiagnosis. MATERIALS AND METHODS: PubMed was used for a comprehensive literature search for morphological variations. Relevant papers were included, and citation tracking was used to identify further publications. RESULTS: Several morphological variants of muscles of the leg have been described over many years, but this study shows that the occurrence of further variations in ultrasound imaging requires further investigations. CONCLUSIONS: The incidence of additional structures including muscles and tendons during ultrasound examination can cause confusion and lead to misinterpretation of images, misdiagnosis, and the introduction of unnecessary and inappropriate treatments.

Severe pure open dislocation of the ankle and flexor digitorum longus tendon tear a case report.

Proximal avulsion rupture of the flexor digitorum longus (FDL) tendon associated with an ankle dislocation is extremely rare. We report a case of a 29 years old patient presenting a severe open ankle dislocation with flexor digitorum longus tendon tear after a motorcycle accident. We performed wound debridement, ankle reduction, tendon repair and stabilization with external fixation. At our last follow-up 17 months after the operation, the patient had good functional outcome and returned to work. This report is noticeable as it is, to the best of our knowledge, the third study reporting a case with simultaneous open ankle dislocation and proximal avulsion rupture of the FDL tendon.

Navicular Tuberosity: A Surface Landmark for the Masterknot of Henry.

Background: Medial aspect of foot is unexplored due to its complex anatomy. Masterknot of Henry is an important landmark in this region, which plays a key role during tendon transfer procedures especially in those involving the flexor hallucis longus and flexor digitorum longus. We aim to determine the exact anatomical location of masterknot of Henry with respect to the bony prominences of the medial aspect of the foot and compare these measurements to the length of the foot. Methods: Twenty cadaveric below-knee specimens were dissected. Structures on the medial side of the foot were exposed. Distance of the masterknot of Henry from surrounding bony landmarks was measured. Depth of the masterknot from skin of the plantar aspect was also measured. Means of all parameters were calculated. Relation between measurements and the foot length was determined using correlation and regression analysis. P value of less than 0.05 was considered significant. Results: Distance of masterknot of Henry from navicular tuberosity was found to be fairly constant of 19.965 mm. Foot length was found to be correlating with the distance between masterknot of Henry and medial malleolus, navicular tuberosity and its depth from the skin. Conclusions: Navicular tuberosity can be considered an important surface landmark for the location of masterknot of Henry. Correlation of length of the feet with various measurements helps to find the masterknot considering the foot length to be an important variable. Good knowledge of surface anatomy leads to shorter operating time and less morbidity during procedures involving the flexor hallucis longus and flexor digitorum longus.

Camptodactyly: From Embryological Basis to Surgical Treatment.

Camptodactyly is a relatively rare hand deformity presenting as the proximal interphalangeal joint's nontraumatic and progressive flexion contracture. Most cases are limited to the fifth finger. The severity and type of camptodactyly should be considered to optimize treatment. Since many structures at the finger base can be involved in the pathogenesis of the deformity, surgical treatment for this particular type of deformity is challenging. This paper aims to bring insight into camptodactyly's pathogenesis and treatment options. We discuss the indication and pitfalls of surgical treatment options for particular camptodactyly types and present a case of a fourteen-year-old boy who was admitted to our department with proximal interphalangeal joint flexion contracture of the left fifth digit.

Anatomical variation of quadratus plantae in relation to flexor hallucis longus and flexor digitorum longus: a rare case.

The quadratus plantae (QP) is considered as a part of the plantar intrinsic foot muscles. This muscle has two lateral and medial heads of origin, both of which arise from the plantar surface of calcaneus, and insert into the tendon of flexor digitorum longus (FDL). Various functions have been attributed to the QP muscle, which includes assisting the plantar flexion of the lateral four toes, straightening the oblique pull of FDL and etc. Several anatomical variations of the QP muscle have been reported in the literature. During a routine dissection in the Department of Anatomy at Kerman University of Medical Sciences, a variant plantar muscle was observed in a 40-year-old male cadaver. In the present case, we report a rare variation associated with the insertion pattern of this muscle, which is reported for the first time in Iran. The tendinous end of the QP muscle was divided into three tendons and were then inserted to the inferior surface of 2nd, 3rd and 4th tendons of FDL. Also, a slim tendinous interconnection was also observed between the QP and flexor hallucis longus (FHL). The lack of connection between the FDL and FHL tendons was the other rare variation of this case. Exact knowledge of the possible variations of the QP muscle is of utmost importance to foot surgeons, clinicians and also anatomists.

Effects of Flexor Digitorum Longus Muscle Anatomical Structure on the Response to Botulinum Toxin Treatment in Patients with Post-Stroke Claw Foot Deformity.

(1) Background: The purpose of this retrospective case-control study was to determine the relationship between the control of toe movements by flexor hallucis longus (FHL) and flexor digitorum longus (FDL) muscles and the response to treatment with botulinum toxin (BoNT) in post-stroke patients with claw toe. (2) Methods: Subjects with stroke-related leg paralysis/spasticity and claw toes received multiple injections of BoNT (onabotulinumtoxin A) into the FHL or FDL muscles. We investigated the relationship between the mode of transmission of FHL and FDL muscle tension to each toe (MCT) and treatment outcome using the data of 53 patients who received 124 injections with clinically recorded treatment outcome. We also dissected the potential variables that could determine the treatment outcome. (3) Results: The effectiveness of BoNT treatment was significantly altered by FDL-MCT (OR = 0.400, 95% CI = 0.162-0.987, p = 0.047). Analysis of the response to the first BoNT injection showed an odds ratio of FDL-MCT of approximately 6.0 times (OR = 0.168, 95% CI = 0.033-0.857, p = 0.032). The more tibial the influence of the FDL muscle on each toe, the better the treatment outcome on the claw toe. (4) Conclusions: The anatomic relation between FDL muscle and each toe seems to affect the response to treatment with BoNT in post-stroke patients with claw toes.

Pigmented Villonodular Synovitis of Flexor Hallusis Longus, Flexor Digitorum Longus, Tibialis Posterior: A Rare Case Report.

Pigmented villonodular synovitis (PVNS) is a locally aggressive benign tumour of the synovial membrane and tendon sheath. The unique presentation of this tumour is hemosiderin deposition with synovial proliferation. Depending on the situation, surgical excision is always the first line of treatment with adjuvant radiotherapy. Arthroscopic excision is preferred in some intraarticular nodular PVNS cases. This is a rare pigmented villonodular synovitis involving flexor hallusis longus, flexor digitorum longus, and tibialis posterior (TP). The tumour was entirely extra-articular without any joint involvement. The tumour was the diffuse type of PVNS and was treated by excision followed by radiotherapy. There is no recurrence till nine months of follow-up.

A Unique Variation of Quadratus Plantae in Relation to the Tendons of the Midfoot.

A novel combination of variations involving the quadratus plantae muscle (QP) and its relationship to the flexor hallucis longus (FHL) tendon was observed unilaterally in the right foot of an 88-year-old female cadaver during routine dissection. The medial head of QP was observed inserting onto the tendon of FHL rather than the tendon of flexor digitorum longus (FDL), while also contributing to an anomalous tendinous slip to the second digit in conjunction with the tendon of FHL. The tendon of FHL also gave off a slip to the third digit. Both tendinous slips attached distally to the digital tendons of FDL. Lastly, the lateral head of QP inserted onto the tendinous slip from FHL to the third digit. Ninety-five additional feet were assessed for these variations, but none were observed. This combination of variations expands upon the proposed actions of QP in the literature. Furthermore, connections between the tendons of the midfoot are of clinical significance for harvesting tendon grafts.

A Simple Method to Locate the Master Knot of Henry Using the Correlation between the Flexor Tendon Length Parameter and the Foot Length.

The precise location of the Master Knot of Henry (MKH) has important clinical significance, but its anatomical definition has not been agreed upon. The purpose of this study is to present a linear regression equation for predicting length variables based on foot length, by evaluating the correlation of length variables related to flexor hallucis longus (FHL) and flexor digitorum longus (FDL), with respect to the location of the MKH. A total of 95 limbs were dissected from 48 adult cadavers, and were fixed in formalin. Measurements were made for the length parameter, with reference to the landmark. The relevance between length variables was analyzed through simple correlation analysis and linear regression analysis. The foot length was 213.69 ± 17.53 mm, MKH-great toe distal phalanx was 140.16 ± 14.69 mm, MKH-FHL insertion was 124.55 ± 13.46 mm, MKH-little toe distal phalanx was 121.79 ± 13.41 mm, MKH-FDL little toe insertion was 109.07 ± 14.16 mm, and the FHL-FDL angle was 33.15 ± 5.39. The correlation coefficient between all the length variables for foot length showed a high positive correlation. We derived a regression equation that can predict the length of each variable. This regression formula is considered to be highly useful because it can estimate the positional relationship of the MKH relatively simply.

Supernumerary muscles in the posterior leg compartment: a case report / Músculos supernumerarios en el compartimento posterior de la pierna: reporte de un caso

SUMMARY: The leg muscles are organized in anterior, lateral and posterior compartments. The posterior compartment is usually divided in two layers: superficial and deep. The deep muscles of the posterior compartment of the leg are known to mainly plantar flexion and toes flexion. In comparison to the other leg compartments, variations of the posterior one are rare. These variants often involve the presence or absence of one or more muscles, and they have differences among origin and insertion, which leads to confusion between anatomists. We aim to describe a case of a male cadaver that possessed three supernumerary muscles in the lateral and posterior compartments of both legs: the peroneus quartus muscle and two accessory bellies of the flexor digitorum longus. This presentation seems to be very rare and scarcely reported in the literature. These variants have the potential of causing nervous or vascular compression, thus leading to tarsal tunnel syndrome or a symptomatic peroneus quartus. The clinical and surgical implications of this abnormal presentation is discussed.

RESUMEN: Los músculos de la pierna están organizados en compartimentos anterior, lateral y posterior. El compartimento posterior por lo general es dividido en dos capas: superficial y profunda. Se sabe que los músculos profundos del compartimento posterior de la pierna se caracterizan principalmente por participar de la flexión plantar y la flexión de los dedos de los pies. En comparación con los otros compartimentos de la pierna, las variaciones musculares en el compartimiento posterior son raras. Estas variantes suelen implicar la presencia o ausencia de uno o más músculos y presentan diferencias en el origen y en la inserción, lo que conduce a confusión entre los anatomistas. Nuestro objetivo fue describir el caso de un cadáver masculino que poseía tres músculos supernumerarios en los compartimentos lateral y posterior de ambas piernas: el músculo fibular cuarto y dos vientres accesorios del músculo flexor largo de los dedos. Esta presentación parece ser muy rara y escasamente reportada en la literatura. Estas variantes musculares tienen el potencial de causar compresión nerviosa o vascular, lo que conduce al síndrome del túnel del tarso o un cuarto músculo fibular sintomático. Se discuten las implicaciones clínicas y quirúrgicas de esta presentación anormal.

Arnold Kirkpatrick Henry (1886-1962) and his eponym (Master Knot of Henry): a narrative review.

PURPOSE: The aims of this review were to form a more precise description for Master Knot of Henry (MKH), and to modify classifications related to interconnections between flexor hallucis longus (FHL) and flexor digitorum longus (FDL) for showing all configurations in the literature. METHODS: A literature search was performed in main databases to obtain information related to anatomical definitions and variations of MKH. The search was carried out using the following keywords: "Master Knot of Henry", "Chiasma plantare", "Flexor hallucis longus" and "Flexor digitorum longus". Information extracted from the studies was: sample size, numerical values, classifications, variation types, incidence of types, anatomical definitions of MKH, year of publication, and type of study. RESULTS: This study proposes that MKH should be defined as the intersection territory where FDL crosses over FHL in the plantar foot. The postchiasmatic plantar area located at distal to MKH (the narrow space between MKH and the division of FDL) should be termed as the triangle of Henry. Moreover, the classification systems showing different configurations related to interconnections situated at Henry's triangle were updated as eight types to present all forms in the literature. CONCLUSION: Our definitions may assist in determining the precise anatomical boundaries of MKH, and thus facilitate the use of MKH as a surgical landmark. In addition, our modified classification systems covering all variations in the current literature may be helpful for surgeons and anatomists to understand formations of the triangle of Henry, and the long flexor tendons of the lesser toes.

Claw Toe: Anatomic Guide for Injection of Botulinum Toxin into Foot Muscles.

BACKGROUND: Poor response to injection of botulinum toxin (BoNT) into the flexor digitorum longus (FDL) muscle has been reported especially in patients with claw foot deformity. We previously advocated BoNT injection into the flexor hallucis longus (FHL) muscle in such patients. Here, we determined the functional and anatomical relationships between FHL and FDL. METHODS: Toe flexion pattern was observed during electrical stimulation of FHL and FDL muscles in 31 post-stroke patients with claw-foot deformity treated with BoNT. The FHL and FDL tendon arrangement was also studied in five limbs of three cadavers. RESULTS: Electrical stimulation of the FHL muscle elicited big toe flexion in all 28 cases examined and second toe in 25, but the response was limited to the big toe in 3. FDL muscle stimulation in 29 patients elicited weak big toe flexion in 1 and flexion of four toes (2nd to 5th) in 16 patients. Cadaver studies showed division of the FHL tendon with branches fusing with the FDL tendon in all five limbs examined; none of the tendons was inserted only in the first toe. No branches of the FDL tendon merged with the FHL tendon. CONCLUSION: Our results showed coupling of FHL and FDL tendons in most subjects. Movements of the second and third toes are controlled by both the FDL and FHL muscles. The findings highlight the need for BoNT injection in both the FDL and FHL muscles for the treatment of claw-toe deformity.

Type and location of flexor hallucis longus musculotendinous junctions and its tendinous interconnections with flexor digitorum longus tendon: pertinent data for tendon harvesting and transfer.

BACKGROUND: Anatomy of flexor hallucis longus (FHL) is essential for the achievement of tendon transfer and several procedures performed in the foot and ankle. The aim of this study was to evaluate the anatomical knowledge of FHL including the type and location of musculotendinous junction (MTJ), tendinous interconnections (TIC) morphology, its location related to Master Knot of Henry (MKH), and the pattern of TIC distribution. MATERIALS AND METHODS: One hundred and sixty-six legs from 52 embalmed and 31 soft cadavers were assessed. The medial (MB) and lateral (LB) bellies of FHL were identified and traced until the end of the most distal muscle fibre to determine the medial and lateral MTJs. MTJ was classified into four types based on the existence and length of MB and LB: type 1, long LB and shorter MB; type 2, equal length of both bellies; type 3, only LB and no MB; type 4, long MB and shorter LB. Low lying muscle belly was defined as muscle extending beyond the zero point (the point of intersection between distal osseous part of tibia and FHL tendon). The distance between MTJ and zero point was measured. TIC was classified into seven types based on the direction and number of slip: type I, one slip from FHL to flexor digitorum longus (FDL); type II, crossed connection: type III, one slip from FDL to FHL; type IV, no connection; type V, two slip from FHL to FDL; type VI, two slip from FHL to FDL and one slip from FDL to FHL; type VII, two slips from FDL to FHL and one slip from FHL to FDL. The distance between the TIC and MKH was measured. TIC distribution was defined into four types based on slip distribution to lesser toes: type a, distributed to second toe; type b, distributed to second and third toes; type c, distributed to second to fourth toes, and type d, distributed to second to fifth toes. RESULTS: Type 1 and type 3 of MTJ morphology were found in 87.3% and 12.7%, respectively. Low lying LB was detected in 66.13% of cases with a mean distance of 13.10 ± 4.51 mm. All MBs ended proximal to the zero point with a mean distance of -21.99 ± 13.21 mm. Three types of TIC (I, II, V) were identified. The highest frequency was type I (82.93%). In addition, a new type of TIC was depicted in 8.53% of cases. Part of the FHL tendon in this type fused with FDL tendon and the rest extended directly to the first toe. TIC could be located either proximal, distal or at the MKH. The highest prevalence was distal to MKH in 51.67% of cases with a mean distance of 11.23 ± 5.13 mm and 8.73 ± 4.2 mm in low lying and non-low-lying groups, respectively. Four types of slip distribution to lesser toes were defined, mostly in type b. No statistically significant differences were detected among all parameters including genders, sides, and groups. CONCLUSIONS: Knowledge of this investigation might enhance the clinical efficacy of tendon harvesting and transfer in foot and ankle surgery.

Impact of intertendinous connections between the flexor digitorum brevis and longus on percutaneous tenotomy for the treatment of claw toes: an anatomic and ultrasound study.

PURPOSE: Selective percutaneous tenotomy of the flexor digitorum longus (FDL) is a treatment for claw toes that gives astonishingly good functional results despite tendon sacrifice. However, the involution of the FDL tendon stump after tenotomy is unknown. The aim of our study was to assess the involution of the tendon stump after selective percutaneous tenotomy of the FDL. METHODS: The study included two parts. In the clinical part, an ultrasound analysis of 15 FDL tenotomies in 7 patients was carried out 3 months post-surgery. In the anatomic part, the feet of 10 bodies donated to science were dissected and examined anatomically. RESULTS: The proximal stump of the FDL was located near the base of the proximal phalanx and moved synchronously with the flexor digitorum brevis (FDB).Separating the FDB and FDL revealed a large tissue connection between the plantar surface of the tendinous chiasm of the FDB and the dorsal part of the FDL. These connections had significant resistance ranging from 2 to 9 Newtons depending on the toe. Tenotomy of the FDL followed by proximal traction of it led to retraction of the stump up to the base of the proximal phalanx and transfer of its action to the FDB by tensioning the intertendinous structure. Histologically, these structures were mostly comprised of tendon connective tissue. Their vascular component was small. CONCLUSION: The presence of this intertendinous connection leads, in the case of isolated tenotomy of the FDL, to equivalent transfer of the latter to the FDB.

Ultrasonographic test for detecting the chiasma plantare formation between the flexor hallucis longus and flexor digitorum longus.

PURPOSE: Flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are frequently used in surgery. Therefore, it is necessary to evaluate the chiasma plantare formation preoperatively. The development of ultrasonography (US) may help the chiasma plantare formation evaluation. The purpose of this study is to prove the usefulness of the US method using cadavers. METHODS: Eleven cases (twenty-two ankles) were obtained from Asian adult cadavers. At first, we evaluated and compared the chiasma plantare formation using US. Later, we evaluated that using the findings after dissection as type A (connection from FHL to FDL of the second toe), type B (connection from FHL to the second and third toes), type C (connection from FHL to the second through fourth toes), or type D (connection from FHL to all lesser toes). RESULTS: Chiasma plantare formation was classified as types A and B in fifteen and seven ankles, respectively. After dissection, chiasma plantare formation was classified as types A, B, and C in fourteen, six, and two ankles, respectively. Therefore, there was an 86% similarity between the two methods. CONCLUSIONS: Chiasma plantare formation can be reliably and noninvasively evaluated using US. This may be useful for preoperative rehabilitation or surgical procedure planning.

A histological study on the tendons at chiasma plantare in pes cavus.

INTRODUCTION: In the dysfunction of large muscles of the leg, tendon transfer surgery is found to be very helpful in restoring the normal function of these muscles. The tendons involved in the chiasma plantare play a major role in this regard. OBJECTIVE: The present cadaveric study has been carried out in cadavers presenting pes cavus. MATERIAL AND METHODS: Cadaveric feet presenting pes cavus were identified based on their foot prints. All these tendons and their interconnections were subjected to histological procedures. The sections of the tendons were stained with hematoxylin and eosin in order to identify the underlying pathologies in the tendons. RESULTS: Various types of tendinous interconnections between the tendons of flexor digitorum longus and flexor hallucis longus were noted. The histological findings showed infiltration of lymphocytes in the tendon sheath indicating tenosynovitis and tendinitis. This could be attributed to the compression of the tendons. A few tendons were also stretched due to the skeletal framework of the foot in pes cavus. The bones along the medial longitudinal arch in pes cavus feet could tend to develop spurs or elongated tuberosity that could impinge on the tendons causing the tendons to stretch and elongate. CONCLUSION: In harvesting the tendons for grafting, the surgeons must be aware about the pathologies involved, such as tendinitis or tenosynovitis, in order to reduce the time taken for the healing of the graft post-surgery. These variations and histological findings can sub-serve as an efficient guide for the restoration of non-functioning muscles of the lower limb.

Development and growth of the foot lumbricalis muscle: a histological study using human foetuses.

BACKGROUND: Our group has shown early development of the hand lumbricalis and hypothesized that, at midterm, the lumbricalis (LU) bundles flexor tendons to provide a configuration of "one tendon per one finger" (Cho K.H. Folia Morphol. 2012; 71, 3: 154-163). However, the study concentrated on the hand and contained no sections of near-term foetuses. MATERIALS AND METHODS: The present examination of paraffin-embedded tangential sections along the planta from 25 embryos and foetuses at 6-40 weeks (15-320 mm crown-rump length) demonstrated that, at 8 weeks, the initial foot LU appeared in the proximal side of the common tendinous plate of all five deep tendons. RESULTS: After midterm, a drastic three-phase change occurred at the muscle origin: 1) the LU originated from each of the flexor digitorum longus tendon (FDLT), but abundant tenocyte candidates separated the muscle fibre from the tendon collagen bundle; 2) the LU arose from the covering fascia depending on increased thickness of the muscle; and 3) the LU muscle fibres intermingled with tendon collagen bundles and partly surrounded the tendon. Simultaneously, a dividing site of the FDLT migrated distally to accelerate the changes at the LU origin. These phases did not always correspond to the size of foetus after 30 weeks. CONCLUSIONS: Consequently, in contrast to the hand LU, the delayed changes in the foot were characterised by involvement of the LU origin into a single common part of the FDLT. The quadratus plantae muscle fibres did not attach to the LU at any phase, and connected with the fourth and fifth toe tendons.