Anatomical studies of the distal insertion of the extensor pollicis longus

Abstracts

Registramos pelo presente estudo que o músculo (ELP) e seu tendão apresentaram poucas variações anatômicas. Não registramos a presença de tendões acessórios e nem a ausência desse músculo ou de seu tendão. Verificamos em todas as preparações a passagem do tendão pelo terceiro compartimento osteofibroso, cruzando sobre os extensor radial curto (ERCC) e longo (ERLC) do carpo e dirigindo-se ao polegar. A alteração no trajeto tendinoso, desviando-se no sentido radial foi verificada em uma das preparações (1,6%). A duplicação parcial do tendão proximal a articulação metacarpofalângica (AMFP) foi verificada em 3 observações (4,8%), sendo 1 bilateral, e distal à articulação em 5 (8,3%), 2 bilateralmente. A inserção óssea na base da falange distal (BFD) foi encontrada em todas as observações. Durante sua passagem pela articulação metacarpofalângica, registramos sua inserção na cápsula articular em 14 observações (23,3%), porém não registramos a inserção óssea nesse local. O padrão mais comum em relação ao músculo ELP foi a presença constante de 1 tendão, passando pelo terceiro compartimento osteofibroso dorsal do punho com inserção óssea na base da falange distal do polegar.

Tenossinovite; Antebraço; Polegar

UPDATE ARTICLE

Anatomical studies of the distal insertion of the extensor pollicis longus

Maurício Benedito Ferreira Caetano^I; Walter Manna Albertoni^II; Edie Benedito Caetano^III

^IDoctor Assistant of the Hand Surgery Service of PUC –SP, Master in Orthopedics and Traumatology of Unifesp – EPM

^IIChairman. Head of the Orthopedics and Traumatology Department of Unifesp- EPM

^IIIChairman – Head of the Orthopedics and Traumatology Discipline of PUC – SP

^{Correspondence}

SUMMARY

We recorded with this study that the EPL muscle and its tendon show a few anatomical variations. Any accessories tendons either the absence of this muscle or its tendon was found. In all preparation the passage of the tendon through the third osteofibroses compartment, crossing on the ERBC and ERLC going to the thumb was seen. The change of the tendinuous trajectory, deviating itself to the radial direction in one of the preparations was checked (1,6%). The partial duplication of the proximal tendon to the metacarpophalangeal joint (AMP) was seen in three observations (4,8%), one bilateral and distal to the articulation in five (8,3%), 2 bilaterally. The bone insertion at the base of distal (BFD) phalanx in all observations were found. During its passage through metacarpophalangeal joint we recorded its insertion in the joint capsule in 14 observations (23,3%), however the bone insertion there was not observed in this place..

The most common pattern about this (EPL) extensor pollicis longus muscle was the presence of a tendon, passing through the osteofibroses dorsal of wrist compartment with a bone insertion at the base of distal pollicis phalanx.

Key words: Extensor pollicis longus; Anatomical variations; Distal insertions.

INTRODUCTION

On the dorsal surface of the wrist, we found a thick part of the front forearm fasciae called extensor tendon of the retinaculum. It is responsible for the six compartments where the extensor tendons pass through. As the retinaculum runs obliquely, from the side edge of the radial to the medial edge of the styloid ulna process and pyramidal and piriformis bones, it sends septas which join the underlying bones making six compartments where the extensor tendons pass through⁽⁵⁾.

In each compartment the tendons are protected with synovial sheath which has the function of decreasing friction during the passage of the tendons through the osteofibroses tunnels.

A common anatomical variation occurs in the first compartment where the tendon of abductor longus and the tendon of extensor pollicis brevis normally pass through, can have the synovial sheath and compartments separated increasing, then the numbers of compartments from six to seven⁽⁶⁾.

We very often found in the literature^(3,5,6,8,13) studies about anatomical variations o f tendon of the first compartment which is a frequent interest in the occurrence of cumulative traumatism developed by repetitive efforts, as well as for several inflammatory process, being the De Quervain tenosynovitis the most common .

However, we found in the classical anatomy dissertation and specialized magazines a few articles about the variation of the tendon of the muscle (EPL), especially about its distal insertions.

The tendon of EPL crosses the third osteofibroses compartment passing by a sulcus on the radialis medially to the tubercle of Lister, then crosses the extensors carpis longus and brevis from the ulnar to the radialis side, forming a medial limit of the Anatomical shape⁽¹³⁾.

About pathological situations such as, rheumatoid arthritis , the tendon loses its protection for the synovial seath, which is accessed by the sickness, besides, without this protection the constant friction due to its passage to the osteofibroses canal cause the broke of the tendon and also loses an important function of the hand. The same can occur in the distal radialis broke where the irregularities of the bones caused at the level of the Tubercle of Lister can lead to the broken tendon.

The objective of this writing was to analyze the anatomical variations of the tendon (EPL) during its trajectory to the third compartment as well as the anatomical place where the distal insertion happens.

MATERIAL AND METHOD

The study material of this work is made of 60 anatomical pieces corresponding to 30 pairs of upper and lower extremities from human cadavers, from which distal forearm , wrist and hand were dissected.

This research was done in the Laboratory of Anatomy of the Medical and Biological Science College of Potifícia Católica University of São Paulo - Campus Sorocaba.

From the 60 pieces, 20 corresponds to 10 fresh human cadavers kept in the refrigerator, and 40 pieces corresponds to 20 human cadavers which were prepared with formaldehyde injection at 10% (4 liters) and glycerin having 1 liter amount. in the femoral artery.

The dissected upper limbs belonged to individuals whose age ranging from 23 to 67. Homogenous material was chosen to make this work, all the human cadavers were from the white race and all were male.

The human cadavers were put on a table for dissection , in dorsiduct position with the upper limb resting on a wooden board in position of medium prone supination of the forearm.

The dissection followed these steps:

It started with distal transverse incision to the interphalangeal. thumb Another transverse incision was made at the transition level of medium and distal thirds of the forearm, above the joint of the myotendinous of the muscles to be dissected.

The center of these two transverse incisions were bound with a longitudinal incision that passed through the medium point between the Tubercle of Lister and the styloid radialis process. Thus, two pieces were suspended undercut, one in a ventral direction and the other in a dorsal direction. The sensitive branches of the radialis nerve and the cephalic artery with its branches dissected and removed.

We start the identification of the muscles with the first osteofibroses tunnel. The EPB, APL and EPL muscles were dissected from the myotendinuous to their insertion compartments.

The anatomic variation presence such as the presence of the tendons accessories, absence of tendons, duplification of the tendons, alterations in their trajectory were observed and taken note. The distal tendon insertion was precisely verified and many times with the help of a magnifying made it twice bigger, because in some situations it was difficult to know exactly where the tendon insertion was.

RESULTS

The muscular fibers of the EPL converge to a flatted tendon, which crosses the third osteofibroses canal, formed by the extensor of the retinaculum and the sulcus on the radialis medially to the tubercle of Lister, crossing long and short radialis of carpum from the ulnar to the radial side, forming a medial limit of the anatomical shape.

In the 60 upper and lower limbs dissected any anatomical variation in relation to the passage of this tendon through the third osteofibroses compartment was not found, nor the extension of muscular body of this tendon till the level of the third canal. The presence of accessory tendon of the EPL passing through the third or any other extensor compartment were found, neither its absence during the dissection.

About the variation of the thickness of this tendon a few variations were found, however with no great importance from the anatomical or clinical view . About the trajectory of the tendon was found only in a lateral observation ( right side), that the tendon after passing through the third osteofibroses canal bent towards the radialis following the tendons of the APL and EPD muscles in order not to make in a usual way to the anatomical shape. (figure 1 and 2).

The tendon duplication in a passage on the dorsal of the first metacarpals was observed. The tendon duplicated some distal centimeters to its passage by the third osteofibroses compartment and joined again before reaching the metacarpophalangeal joint This fact was detected in three pieces (4.8%), and one bilateral case (fig.3).

In a anatomical piece (1,6%) corresponds to the right hand of a human cadavers, the tendon of EPL muscles duplicated into 3 centimeters proximal to the pollicis metacarpophalangeal, the same happening to the tendon of EPB muscle. The components and expansion of the two tendons drove themselves to the center of the articulation binding and inserting each other at the level of metacarpophalangeal joint. The two components and the expansions crossed the metacarpophalangeal joint and drove in order to insert themselves to the base of the distal phalanx (figure 4).

At the level of metacarpophalangeal joint. The aponeurotic fibers of the muscles of the abductor pollicis brevis (APB) laterally and the abductor pollicis (AP) medially insert them to the tendon of (EPL) and (EPB), maintaining the tendons extensors centered on the metacarpophalangeal joint (fig. 5).

About the insertions of the tendon (EPL) muscle at the base of proximal pollicis phalanx, we found it in joint capsule in 14 cases (23,3%), however we did not check the bone insertion of the long extensor at the base of the proximal phalanx (fig 6).

When passing through the metacarpophalangeal joint the tendon stretched and reached the insertion at the base of the distal phalanx. In all pieces we noticed the bone insertion of the (EPL) along the base of the distal phalanx (fig 7).

Among 5 observations (8,3%), two bilaterally, we found the tendon of the EPL muscle duplicated distally to the metacarpophalangeal articulation and inserting itself separately at the base of distal phalanx (figure 8).

Among other three dissected pieces (4,8%) all unilaterally, one at the left side and the two others at the right side., we found a tendinous bound joining the of the tendons pollicis abductor to the (EPL) next to the insertion of the distal phalanx (figure 9).

At most observations we found the tendon of the EPL muscle thicker than the tendon of the EPB , however in some observations, the thickness between them was exaggeratedly disproportional (figure 10). In some cases they had the same thickness, however in any of the preparations was note the dominance of the thickness of the tendon EPB in relation to EPL. The asymmetric among the antimeres was recorded in 13 cases (21,6%).

DISCUSSION

Differently from what was found in relation to the EPB muscle, we did not see in any of the preparations the absence of the muscle or tendon of the EPL. Zadek⁽¹⁵⁾ found a case where there was the bilateral congenital absence of the EPL, he reported he did not find any similar description in the literature. However, previously, Pearson & Robinson⁽¹⁰⁾ while dissecting 131 upper and lower limbs had already checked them twice (1,5%) the absence of the EPL muscle. Later, some authors^(7,9,14) also noted the absence of this tendon, however without referring the frequency of this occurrence .

About the duplication of the tendon the EPL muscle reported by some authors^(8,11,13), we found among 3 of our observations (4,8%), one bilateral, in these cases the tendon duplicated after passing through the third osteofibrosesr compartment, joining again some centimeters proximally to the metacarpophalangeal joint.

The existence of the EPL accessory muscle described at the beginning by Kaplan⁽⁶⁾, was recently reported by other authors^(1,2,4,13), however the description about the way and insertion of the accessory muscle differ from the authors. Kaplan describes that this accessory muscle is located between the EPL and the extensor of the index finger originating a double tendon one which goes to the thumb and the other to the index finger. Abu-Huleh⁽¹⁾ states that accessory muscle, which he found in a male human cadaver dissection , originated from the ulna passing through the fourth osteofibroses compartment together with the common extensors of the fingers and the own index finger, going to the thumb and insert itself at the base of the proximal phalanx Cohen & Haber⁽⁴⁾ reported they found a muscle having accessory tendon also passing through the fourth extensor canal, however with a different insertion at the base of distal phalanx of thumb.

Beatty et al.⁽²⁾ found an accessory tendon of the EPL while making a surgery , however they refer that it was not possible to identify the local of this tendon insertion, but they noticed that after the removing of this accessory tendon relieved the severe pains the patient had. During the surgery, however in 1998, made by our staff, was found an accessory tendon placed between the EPL and the extensors of the index fingers, which originated a double tendon, and this corresponds to the description made by Kaplan⁽⁶⁾. In this case, the double tendon also drove itself to the thumb and index finger; nevertheless it joined each other to the tendon of the EPL muscle and to the tendon of the common extensors fingers muscles which drove to the index finger.

We did not find the presence of the accessory tendons during our dissections, neither found tendinuous expansion from the common extensor fingers which acted with effort to the EPL, according to Poirier & Charpy ⁽¹¹⁾ e Testut & Latarjet⁽¹³⁾.

Kaplan⁽⁶⁾ also states in some situations the EPL muscle may have shorter caliber than the EPB. During the dissection this fact was not checked, because we normally found the EPL with a normal calibre or most of the time having bigger calibre than the EPB. The results showed that in some cases the difference of size can be disproportional, as it can be seen in the figure10. It was found in our laboratory⁽³⁾ bilaterally in a human cadaver, a variation in the trajectory of the tendon of EPB that after passing through a osteofibroses tunnel, drove towards the radial direction almost in a straight angle in relation to its trajectory of the forearm, following together with the tendons APL and EPB in order to form the anatomical shape; it means that in this case the tendon of the EPB was absent. We found similar variation in one of the dissections, and in this case the tendon EPB muscle was there.

In an anatomical piece corresponding to the left hand of a human cadaver, the tendon EPL muscle duplicated 3 centimeters proximal to the metacarpophalangeal joint, the same happening with the tendon EPB. The components of the two tendons which drove to the center of the joint and inserted themselves till the level of the metacarpophalangeal joint, the two lateral components crossed the metacarpophalangeal joint and drove in order to insert in the base of distal phalanx. We state we did not find reports about anatomical arrangements similar to these ones in the researched literature. The figure4 shows the anatomical variation. The insertion of the tendon EPL in the joint capsule of the metacarpophalangeal joint verified in 14 cases, however we did not check the bone insertion at the base of proximal phalanx in any of the cases. In five hands (two bilateral) we found the duplication of the EPL, distally to the metacarpophalangeal joint, and the two components insert themselves into the base of distal phalanx, recorded at figure 8. among three anatomical pieces , all unilaterally we found the existence of a tendinuous bound joining the tendons of abductor pollicis to the tendon EPL next to its insertion at the base of distal phalanx, showed in figure 9. Kaplan ⁽⁶⁾ states that the insertion of the abductor and APB in the extensor device may happen in a variable way. Therefore we can consider these bindings as making part of these variations.

Ledouble⁽⁸⁾ described a case that the tendon EPL muscle, in addition of inserting itself in the first and second phalanx, it also inserted itself in the scaphoid. We did not report a similar case in the dissection work.

Stein⁽¹²⁾ found asymmetry between the right and left antimeres in three of 42 human cadavers (7,1%) e Caetano⁽³⁾ only once among 30 dissected human cadavers (3,2%). We verified asymmetry in 12 among 30 cadavers (35,2%) This disagreement can be explained differently from the authors cited above, the most important objective of this study was the distal tendon insertion, therefore any variation of insertion between the antimeres was classified as asymmetric.

CONCLUSION

The tendon bone insertion of the tendon EPL at the base of distal phalanx was recorded in all observations (100%). While passing through the metacarpophalangeal joint an insertion in the capsule of this joint was seen in 14 hands (23,3%), however any bone insertion in this area was seen.

The anatomical pattern in relation to the tendon EPL insertion we suggest it to be considered as normal, it was the presence of an unique tendon insert itself through a bone insertion at the base of distal pollicis phalanx .

REFERÊNCIAS BIBLIOGRÁFICAS

Work performed in the Laboratory of Anatomy of the Medical and Biological Science College of Potifícia Católica University of São Paulo - Campus Sorocaba.

• 1 - Abu-Higleh MF. Extensor pollicis tertius: an additional extensor muscle of the thumb. Plast Reconst Surg 92:340-343, 1993.
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Publication Dates

• Publication in this collection
  16 June 2004
• Date of issue
  June 2004

History

• Accepted
  09 Apr 2004
• Received
  28 July 2003