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Journal of the Anatomical Society of India

Applied Significance Of Variations Of The First Extensor Compartment Of Wrist

Author(s): Joshi, S.S. & Joshi, S.D.

Vol. 51, No. 2 (2002-07 - 2002-12)

Department of Anatomy, Rural Medial College, Loni (Dist. Ahmednagar) - INDIA

Abstract

The applied significance of the first extensor compartment of wrist lies in the fact that this is involved in de Quervain's disease. In this condition there is pain at radial styloid process caused by stensoing tenosynovitis of abductor pollicis longus and extensor pollicis brevis muscles. When conservative treatment and physiotherapy fail then surgical decompression of this compartment is carried out to relieve the symptoms. Failure of this operation is due to overlooking the variations of tendons or septation of this compartment. The text books of anatomy do not lay emphasis on these variations. Although these are well documented in the clinical literature no such study has been done amongst Indians.

A detailed study has been carried out in 50 upper limbs. It was observed that in more than 80% cases the tendon of abductor pollicis longus is double or multiple. Besides base of first metacarpal, it also sends slips of insertion to trapezium, thenar fascia, opponens pollicis and abductor pollicis brevis muscles. Extensor pollicis brevis was found to be absent in 2% cases. In 18%, it gets inserted on the distal phalanx along with extensor pollicis longus. In about 40% cases, the first extensor compartment is divided completely or incompletely into two by a septum.

Key words: Abductor pollicis longus, extensor policis brevis,muscle variations, assessory tendons, de Quervain's disease, first extensor compartment.

Introduction :

In the year 1895 de Quervain described the disease (that goes by his name) in which there is pain at the radial styloid process caused by stenosing tenosynovitis of abductor pollicis longus and extensor pollicis brevis tendons as they run in the first extensor compartment of wrist. This fibroosseous tunnel is fairly constricting normally and is frequently divided by a vertical septum that separates the two tendons. With addition of tenosynovitis this restriction becomes constriction and the pain syndome develops (Mcfarland, 1983). Stenosing tenosynovitis occurs more often in hand and wrist than elsewhere in the body. Women are affected 10 times more, usually between the ages of 30 and 50 years. This could be because of overuse of hand at home or at work (Mc Farland, 1983). To confirm the diagnosis Finkelstein test is carried out : in this the thumb is passively flexed at the matacarpophalangeal joint and then with the thumb flexed passively forcing the hand into ulnar deviation results in pain at the radial styloid process (McFarland, 1983; Campbell, 1998).

When routine methods like splinting, injection of steroids, use of anti-inflammatory drugs and physiotherapy fail to relieve pain then surgical decompression of this compartment is done. Failure of operation is related to the anatomical variations of abductor pollicis longus and extensor pollicis brevis muscles or their lying in separate compartments (Baba, 1954; Giles, 1960).

Most of the anatomical text book descriptions are an exception rather than the rule (Baba, 1954). The clinical literature is replete with descriptions of detailed anatomy of this region obtained from both operative findings as well as cadaveric dissections. As no work of this nature has been done on Indian subjects we planned to carry out a detailed study of the first extensor compartment of wrist.

Material and Methods:

A total of 50 upper limbs from 25 cadavers were utilized for the present work. The muscles of the extensor compartment were dissected ; extensor retinaculum was defined and the structures on the lateral part of dorsum of hand and thumb were displayed. The extensor retinaculum covering the first extensor compartment was split vertically and the underlying tendons of abductor pollicis longus and extensor pollicis brevis were exposed carefully to note the complete or partial septation of the compartment and the presence of variations of these two tendons. The tendons were traced to their insertion and the findings noted.

Observations:

The first extensor compartment showed septation in 40% cases [complete septations in 16% (Fig. 2); incomplete (Fig.3) in 24%- (being present only in the distal part)]. The thin tendon of extensor pollicis brevis occupied the separate compartment.

Abductor pollicis longus tendon was single in only 16% and in the remaining cases two or multiple tendons (Fig,2,3) were present (Two tendons in 56% and multiple in 28%). In all the cases the tendon was getting inserted on to the base of first metacarpal bone (in 40%, on the lateral surface and in 60%, on the anterolateral surface). The accessory tendons were found to be inserted on to trapezium (30%), abductor pollicis brevis (44%), (Fig.3) and opponens pollicis, (16%) or merging with thenar fascia (20%)

Extensor pollicis brevis was absent in 2% and double in 2% cases (Fig.1). In one case it was found to arise as a slip from abductor pollicis longus tendon. The tendon was inserted on the dorsum of the base of proximal phalanx of thumb in 76% and on the proximal and distal phalanx, both,in 2%. In 18% cases it joined the extensor pollicis longus and thus was inserted on to the distal phalanx of thumb. Occassionally it was seen to be lost on the dorsal surface of first metacarpal (4%).In majority of cases the tendon was very thin but in 8% it was moderately thick and in one case it was thicker than extensor pollicis longus tendon.

Discussion:

Phylogenetically abductor pollicis longus and extensor pollicis brevis are differentiated from a common muscle mass. Extensor pollicis brevis separates completely only in man and gorilla and is much smaller in size (Giles, 1960). It may sometimes be absent or united with extensor pollicis longus (Schafer et al., 1923). In chimpanzee it has a double insertion-on to the dorsal surface of the base of the proximal phalanx and lateral aspect of base of first metacarpal. Abductor pollicis longus is attached to the radial side of shaft of first metacarpal but in gorilla it is also attached to trapezium. In old world monkeys the insertion resembles that in man. Thus there is a gradation in the extent of differentiation of common muscle mass in different species-phylogenetically the process is still in infancy and therefore it is not surprising that anomalies are found in man which have great relevance to the surgery in de Quervain's disease (Giles, 1960). In the present series the tendon of abductor pollicis longus was seen to split into two or multiple tendons in 84% cases. Earlier Stein (1951), Giles (1960) and Jackson et al. (1986)-have demonstrated this splitting in 68% dissections while Baba (1954) found it in 98% of his specimens.

Various workers (Schafer et al., 1923; Stein, 1951; Jackson et al., 1986; Williams et al., 1995; Campbell, 1998) have reported that the tendon of insertion of abductor pollicis longus may, besides the base of first metacarpal, send slips to trapezium, abductor pollicis brevis, opponens pollicis, thenar fascia or capsule of carpometacarpal joint of thumb. Baba (1954) has shown a slip going to trapezium in 34%; to thenar fascia in 39% and abductor pollicis brevis in 25%. The values in the present series going to these sites are 30%, 44% and 20% respectively. We have also found slips going to opponens pollicis in 16% cases.

Extensor pollicis brevis was found to be absent in 2% cases in the present series which is similar to that reported by Jackson et al. (1986). Campbell (1998) reported it in 5% and Stein (1951) in 7.14%. The tendon was found to be double in 2% cases, whereas Giles (1960) found this in 1% and Stein (1951) in 8.3%. In the present series the tendon of extensor pollicis brevis was found to be attached to the proximal phalanx of thumb in 76%; into the distal phalanx with extensor pollicis longus in 18%; into both the proximal and distal phalanx in 2% and on the shaft of first metacarpal bone in 4%. This incidence of precise insertion has not been reported by earlier workers. Williams et al. (1995) have described that the tendon may reach distal phalanx by joining extensor pollicis longus or may be absent or fuse completely with abductor pollicis longus or extensor pollicis longus muscle.

The first extensor compartment was completely divided by a septa in 16% of our cases; other workers have reported this as follows : Stein (1951) in 10.7%; Giles (1960) in 33%; Jackson et al. (1986) in 30%; and Campbell (1998) in 21%.The compartment was divided only in its distal part in 24% of our cases; Giles (1960) has described it in 34% and Jackson et al (1986) in 11.3%.

Giles (1960) is of the view that the standard text book description of abductor pollicis longus is an exception rather than the rule. Jackson et al. (1986) have stated that no clear relationship has been established between any one anatomical pattern and de Quervain's disease. Further, that there was no significant difference between the patients with de Quervain's disease and the cadaveric dissections in having two or more tandons of abductor pollicis longus. Baba (1954) has emphasised that aberrant tendons are subject to greater stress with activities of thumb and are more vulnerable to trauma. Though women are affected 10 times more in de Quervain's disease there is no plausible explanation for this; as there is no race or sex difference in the anatomy of this region (Stein, 1951)

Summary and Conclusion:

The First extensor compartment of wrist may be divided completely by a septum in 16% of the hands & incompletely, (only in the distal part) in 24% cases.

Only in 16% cases there is a single tendon of abductor pollicis longus and in more than 80% it is either double or multiple.

Slips from this tendon may proceed for attachment to trapezium, thenar fascia, abductor pollicis brevis or opponens pollicis.

Extensor pollicis brevis may be absent (2%) or double (2%). Besides its usual insertion to the dorsal surfaace of the base of proximal phalanx, it may extend on to the distal phalanx with the extensor pollicis longus. Rarely it may be attached to the first metacarpal.

Appreciation of these facts are essential in the proper surgical decompression of the first extensor compartment in de Quervain's disease. Otherwise it will lead to failure, incomplete cure or recurrence of disease.

References:

  1. Baba. M. A. (1954) : The accessory tendons of abductor pollicis longus muscle. Anatomical Record, 119 : 541-547.
  2. Campbell's Operative Orthopaedics. 9th Edition; Edr. Canale, T. S. ; Vol. IV, Mosby, New York, Philadelphia, pp 3695-96. (1998).
  3. Giles, K. W. (1960) : Anatomical variations affecting the surgery of de Quervain's disease Journal of Bone & Joint Surgery 42B (2) : 353-355.
  4. Jackson, W.T. ; Viegas, S. F.; Coon, T. M.; Stimson, K. D.,; Frogamani, A.D.;Simpson, J. M. (1986) : Anatomical variations of the first extensor compartment of wrist-A clinical and anatomical study. Journal of Bone & Joint Surgery 68A, 923-926.
  5. McFarland,G. B. : In Evart's surgery of Musculoskeletal system. Vol. II, chapter 20 : Entrapment syndrome. pp 524 525. (1983).
  6. Schafer, E.S.; Symington, J; Bryce, T.H.: In Quain's Elements of Anatomy. In: Part II-Myology 11th Edn Longmans, Green and Co., London. pp 143, 149. (1923).
  7. Stein, A.H. (1951): Variations of the tendons of insertion of the abductor pollicis longus and the extensor pollicis brevis. Anatomical Record. 110: 49-55.
  8. Williams, P.L. ; Bannister, L.H.; Berry, M.M.; Collins, P.; Dyson, M.; Dussek, J.E.; Ferguson, M.W.J.: Gray's Anatomy-The anatomical basis of Medicine and surgery. In: Muscle. Churchill Livingstone, U.K., pp 851. (1995)

Missing Image

Fig. 1: Dissection of Left Hand - Showing:
A : Two tendons of extensor pollicis brevis (EPB).;
B: Incomplete septum dividing the first extensor compartment in the distal part lodging the tendon of EPB;
C : Tendon of abductor pollicis longus.

Missing Image

Fig. 2 Dissection of Right Hand. Showing:
A : Very thin tendon of EPB;
B : Septum completely dividing the first extensor compartment which is lodging the tendon of EPB;
C : Two tendons of abductor pollicis longus. (APL);
D : Abductor pollicis brevis receiving one tendon of APL.

Missing Image

Fig. 3 Dissection of Right Hand. Showing:
A : EPB lying in a separate compartment.;
B : Incomplete septum dividing first extensor compartment in the distal part.;
C : Three tendons of APL;
(i) superficial (bold arrow) going to APB :
(ii) Intermediate (dot) going to opponens pollicis brevis, and
(iii) deeper (small circle) going to base of first metacar pal.;
D : APB receiving a tendon of APL.

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