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.

Communications between the tendons of flexor hallucis longus and flexor digitorum longus: a cadaveric study.

INTRODUCTION: Tibialis posterior tendon insufficiency in adult acquired flat foot deformity (AAFFD) is treated by reinforcing the posterior tibial tendon (PTT) using grafts from flexor hallucis longus (FHL) and flexor digitorum longus (FDL). The communication between FHL and FDL will influence the length of the graft that can be harvested from FHL and FDL. In this study, we aim to study the patterns of communications between FHL and FDL tendons and the location of Master Knot of Henry (MKH) and point of division of FDL tendons in Indian population. MATERIALS AND METHODS: In this observational descriptive study, 36 formalin-fixed cadavers were sourced from Subbaiah Institute of Medical Sciences, Shimoga, Karnataka, India, and JIPMER, Puducherry, India, during the period of 2017-19. Various parameters of the foot to locate the MKH and point of division of FDL tendons and various types of communications between FHL and FDL were observed. RESULTS: Among the various types of communications between FHL and FDL tendons, type I was present in 61.76% of cases, type II in 2.94% of cases, type III in 7.35% of cases, type IV in 14.70% of cases, type V in 8.82% of cases, type VI in 0% of cases, type VII in 1.47% of cases and an unusual type in 2.94% of cases. CONCLUSION: In the present study done in Indian population, we found that type I variety is present more commonly followed by type IV. FHL and FDL tendon grafts can be lengthened based on the communications between them. In type I variety, the communication can be severed at the FDL end to lengthen the tendon graft for harvest.

The retromalleolar compression test: a useful exploratory maneuver in the clinical evaluation of flexor hallucis longus rupture.

The clinical examination of ruptures of the flexor hallucis longus can be difficult, especially spontaneous defects that arise without a definitive history of trauma. Advanced imaging, in particular, magnetic resonance imaging, can be a useful adjunct to the clinical examination. However, we believe that a simple clinical maneuver can be used to reliably ascertain the presence of a rupture of the flexor hallucis longus.

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.

Surface localisation of master knot of Henry, in situ and ex vivo length of flexor hallucis longus tendon: pertinent data for tendon harvesting and transfer.

BACKGROUND: Length of flexor hallucis longus (FHL), localisation of master knot of Henry (MKH) and relationship between MKH and neurovascular bundle are essential for the achievement of FHL tendon transfer. The purpose of this study is to define the localisation of MKH in reference to bony landmarks of the foot, its relationship to plantar neurovascular bundle and to investigate in situ and ex vivo length of FHL tendon in single incision, double incision and minimally invasive techniques. MATERIALS AND METHODS: Foot length was examined in 62 feet of 31 soft cadavers (9 males, 22 females). Various parameters including the relationship between MKH and neurovascular bundle, the distances from MKH to medial malleolus (MM), navicular tuberosity (NT) and the first interphalangeal joint of great toe (IP) were measured. Surface localisation of MKH in relation to a line joining the medial end of plantar flexion crease at the base of great toes (MC) to NT (MC-NT line) was determined. Lengths of FHL tendon graft from three surgical techniques were examined. In situ length was measured in the plantar surface of foot and ex vivo length was measured after tendon was cut from its insertion. RESULTS: The mean length of foot was 230.98 ± 15.35 mm with a statistically significant difference between genders in both sides (p < 0.05). No distance was found between medial plantar neurovascular bundle (MPNVB) and MKH. Mean distance of 17.13 ± 3.55 mm was found between lateral plantar neurovascular bundle (LPNVB) and MKH. MKH was located at a mean distance of 117.11 ± 1.00 mm proximal to IP, 26.28 ± 4.75 mm under NT and 59.58 ± 7.51 mm distal to MM with a statistically significant difference of MKH-IP distance between genders in both sides and MKH-NT in right side. MKH was located anterior to NT (66.1%), at NT (27.4%) and posterior to NT (6.5%) on the MC-NT line. Surface localisation of MKH was 94.75 ± 8.43% of MC-NT line from MC with a perpendicular distance of 25.11 ± 5.37 mm below MC-NT line. The in situ and ex vivo tendon lengths from MTJ to ST, to MKH and to IP were 39.05 ± 10.88 mm and 34.43 ± 10.23 mm, 73.45 ± 9.91 mm and 68.63 ± 9.43 mm, 197.98 ± 13.89 and 191.79 ± 14.00 mm, respectively. A statistically significant difference between genders was found in MTJ-IP of in situ and ex vivo length of both sides (p < 0.05). The mean length of tendon between in situ and ex vivo was significantly different in all techniques (p < 0.05). A moderate positive correlation between foot length and tendon length was found in MTJ-IP of both in situ and ex vivo tendon length. CONCLUSIONS: A statistically significant difference between in situ and ex vivo tendon length was shown in all harvesting techniques. Surface location of MKH was approximately at 95% of MC-NT line from MC with a perpendicular distance of 25 mm from MC-NT line.

Anatomy of Master Knot of Henry: A morphometric study on cadavers.

OBJECTIVE: The objective of this study was to evaluate the features of flexor hallucis longus (FHL), flexor digitorum longus (FDL) and flexor digitorum accessorius (FDA) muscles with relevance to the tendon grafts and to reveal the location of Master Knot of Henry (MKH). METHODS: Twenty feet from ten formalin fixed cadavers were dissected, which were in the inventory of Anatomy Department of Medicine Faculty, Mersin University. The location of MKH was identified. Interconnections of FHL and FDL were categorized. According to incision techniques, lengths of FHL and FDL tendon grafts were measured. Attachment sites of FDA were assessed. RESULTS: MKH was 12.61 ± 1.11 cm proximal to first interphalangeal joint, 1.75 ± 0.39 cm below to navicular tuberosity and 5.93 ± 0.74 cm distal to medial malleolus. The connections of FHL and FDL were classified in 7 types. Tendon graft lengths of FDL according to medial and plantar approaches were 6.14 ± 0.60 cm and 9.37 ± 0.77 cm, respectively. Tendon graft lengths of FHL according to single, double and minimal invasive incision techniques were 5.75 ± 0.63 cm, 7.03 ± 0.86 cm and 20.22 ± 1.32 cm, respectively. FDA was found to be inserting to FHL slips in all cases and it inserted to various surfaces of FDL. CONCLUSION: The exact location of MKH and slips was determined. Two new connections not recorded in literature were found. It was observed that the main attachment site of FDA was the FHL slips. The surgical awareness of connections between the FHL, FDL and FDA, which participated in the formation of long flexor tendons of toes, could be important for reducing possible loss of function after tendon transfers postoperatively.

The high variability of the chiasma plantare and the long flexor tendons: Anatomical aspects of tendon transfer in foot surgery.

As tendon transfer of the flexor hallucis longus (FHL) and the flexor digitorum longus (FDL) is an established procedure, exact knowledge of the formation of the chiasma plantare is of great interest. Although the quadratus plantae (QP) appears to play a major role, it has been rarely addressed in previous studies. The aim of the present study was to reinvestigate the formation of the chiasma plantare and the composition of the long flexor tendons in order to clarify the inexact and partly contradictory descriptions published from 1865 onward. The chiasma plantare and the long flexor tendons in both feet of 50 formalin-fixed specimens of body donors (25 men and women) were analyzed by gross anatomical dissection. It was composed of one (3%), two (69%) or three layers (28%) which were variably established by the tendinous and muscular fibers of the FHL, the FDL and the QP. In 61% the FHL gave one or more slips to the FDL, and in 39% there was a bidirectional interconnection between the two tendons. The slip from the FHL to the FDL largely reinforces the second (45%), or the second and third tendon (46%). Thus, the FHL is involved in the first tendon in all cases, in the second one in 97% of cases, and in the third tendon in about one half of cases (53%). In all instances, the FDL contributes to the third to fourth, in 98% the second, and in at least 39% to the first tendon. The QP reinforces the second to fourth tendon in nearly all cases, the fifth in about one half of cases, and even the first tendon in 14% of cases. In addition, the individual composition of the five long flexor tendons arising from the chiasma plantare was analyzed in detail. Special emphasis was placed on the evaluation of side and sex differences as well as individual symmetry. Furthermore, biomechanical, developmental and phylogenetic aspects were outlined. In terms of the outcome of this study, the FHL appears to be the better donor for tendon transfer to restore lost function, but harvesting the FDL seems to be more suitable to prevent long-term functional damage. The decision depends on the individual patient's needs and should be made with due care.