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Journal of the Anatomical Society of India

Atypical Innervation Of Palmaris Longus - A Case Report

Author(s): Chauhan, R.

Vol. 52, No. 2 (2003-07 - 2003-12)

Department of Anatomy, All India Institute of Medical Sciences, New Delhi- INDIA

Abstract

Palmaris longus muscle is gaining popularity for its role in reconstructive, plastic and cosmetic surgeries. Lip augmentation and repair of congenital ptosis, collapsed lunate, acute thenar muscle injury and tendoachillis loss have been successfully dealt using palmaris longus graft in one form or the other. Therefore, all possible variations in the innervation of such an important muscle should be well known. In the present case median nerve innervated palmaris longus at the level of elbow (a usual site of innervation) and at the level of distal third of forearm. The latter branch innervated the distal part of the tendon of palmaris longus and its aponeurosis. Clinical importance of the knowledge of such kind of variation has been discussed in this paper.

Key words: Palmaris Longus, Innervation of Palmaris longus, median nerve, palmar aponeurosis.

Introduction:

A degenerate flexor muscle of the metacarpophalangeal joint is the Palmaris longus. Generally, it is innervated by a branch from the median nerve in the proximal third of the forearm usually near the elbow joint. Any variation in the innervation of the palmaris longus is gaining importance as it is becoming very popular amongst graft material for reconstructive surgeries. Palmaris longus muscle or its tendon have been used in various combinations to repair oncologic defects of head and neck, ptosis in children, arthritis of the thumb with trapezium resection and in Camitz opponensplasty for acute thenar muscle injury.

Complete knowledge of innervation of palmaris longus is required by the operating surgeon to avoid post operative complications in the donor hand and for maintaining the required actions in operations such as Camitz opponensplasty. Therefore, the need to express the variation in the innervation of palmaris longus in the left upper limb of the present subject was realised.

Material and Methods:

During a routine dissection in the dissection hall of Anatomy department of AIIMS, New Delhi, a variation in the innervation of palmaris longus of left upper limb of an adult male cadaver was noticed. The region of interest was finely dissected and photographed.

Observations and Results:

In the left forearm and hand of an adult male cadaver it was observed that the muscle belly of palmaris longus received a branch from the median nerve in the proximal third of the forearm near the elbow joint. With further progress of the dissection it was noticed that another branch emerged from the median nerve (arrow, fig.1) and ramified into a number of branches to innervate the distal most part of the tendon and the proximal part of the palmar aponeurosis from its dorsal aspect (fig.2). These branches further passed through the aponeurosis to become cutaneous. Palmar cutaneous branch of the median nerve emerged proximal to the branch for the palmaris longus tendon (fig.1).

Discussion:

Palmaris longus, a muscle with small belly and long thin tendon is becoming popular in reconstructive surgeries. Its presence in 70-85% population (Wehbe, 1992) and its superficial location (Lam, et, al 1998) makes it the most common donor material for tendon and joint reconstructive surgeries (Lee, 1987) Palmaris longus is completely developed at birth (Vastamaki, 1987), while fascia lata, which is also used for reconstructive surgeries, is not so well developed at that age. (Jordan and Anderson 1987). All these factors facilitate harvesting of palmaris longus as the donor material in all age groups.

Proximally, this muscle is attached to the medial epicondyle of the humerus along with other superficial flexors of the forearm. Distally its long thin tendon forms the superficial portion of the mid palmar fascia (Nigro, 2001). Skin and fascia of the palm and digital webs give attachment to the fibres of palmar fascia. The muscle is innervated by a branch of the median nerve. Linell (1921) ; Sunderland and Ray (1946) : Lazorthes (1955); Bonnel and Mansat (1989) ; Canovas et al, (1998); Gunther et al (1992) and Liu et al (1997) report that the distribution of median nerve is very variable. It is important to bear a good knowledge of the variations in innervation of the palmaris longus as it is preferred for cosmetic, plastic and reconstructive surgery. Lip augmentation is carried out using palmaris longus muscle and its tendon (Davidson 1995) Collapsed lunate is replaced by tendon ball implant made from the palmaris longus and plantaris which frequently calcifies and ossifies post operatively (Ueba 1999) Congenital ptosis is successfully corrected using palmaris longus to suspend frontalis (Lam et al, 1996). Autogenous tendon is also used for ruptured extensor tendons in the Rheumatoid hands (Mountney et al, 1998). In acute thenar muscle injury when immediate Camitz opponensplasty is performed by using palmaris longus tendon with its distal palmar fascial extension and suturing it to the insertion of the abductor pollicis brevis under tension, it is seen that 79.7 90.1% opposition of the thumb to the fingers (Kapandji test) is restored (Lin and Wei, 2000). For improving thumb function especially opponens in localized thenar muscle destruction, Cooney (1988); Foucher et al (1991) and Terrono et al (1993) have advocated palmaris longus transfer. Challenging reconstructive problems like repair of loss of tendoachillis with overlying skin has been successfully dealt with radial forrearm palmaris longus composite free flap (Isenberg and Fusi 1995). Postoperatively, according to these authors, an ulnar drift of the wrist and abdominal laxity are seen in donor for Flexor carpi radialis and External oblique graft respectively. These post operative complications in the donor can be avoided if palmaris longus is used as a graft as loss of this tendon results in no major abnormality of hand function. But Mc Grouther (1996) states that the main function of palmaris longus is to anchor the skin and fascia of hand and hence to prevent degloving of palmar skin from horizontal shearing forces. Therefore, variations in the innervation of such a clinically important muscle should be of interest both to the academicians and clinicians.

In the present case a separate branch of median nerve distal to the palmar cutaneous branch of median nerve (fig.1) was given off which ramified and then innervated the distal part of the tendon of palmaris longus and the palmar aponeurosis from their dorsal aspect. The ramifications further seemed to pierce the palmar aponeurosis, in which case it is likely to innervate the palmar skin to a variable extent. Very fine dissection of the nerve to palmaris longus tendon and palmar aponeurosis was not possible as the branches of the nerve were very delicate and fragile and broke whenever microdissection was attempted under dissecting microscope.

Surgeons handling palmaris longus graft should be aware of this kind of variation so as to preserve the function of the palmar aponeurosis in the donor hand. Accidental damage of this nerve if present may result in degloving of the palmar skin in the donor limb along with post operative tenderness and dysaesthesia or occasional pain in the thenar and hypothenar eminence. Accidental damage or ignorance of the presence of this type of branch of median nerve to the tendon and palmar aponeurosis may lead to ineffective opponensplasty using palmaris longus graft in thenar muscle damage. Although occasional passage of palmar cutaneous branch of the median nerve through the substance of palmaris longus tendon has been reported (Kleinert, et al 1991) but the variation noted in the present case has no mention in the literature.

References:

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  3. Cooney, W. R. (1988) : Tendon transfer for median nerve palsy. Hand Clinic. 4 : 155 - 165.
  4. Davidson, B. A. (1995) : Lip Augmentation using the Palmaris Longus tendon Plastic and Reconstructive Surgery. 95 (6) : 1108 - 1110.
  5. Foucher, G., Malizon, C. Sammut, D., Braun, F.M. (1991) : Primary Palmaris longus transfer as an opponensplasty in carpal tunnel syndrome. Journal of Hand Surgery 16B : 56 60.
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  9. Kleinert, H.E. Smith D., J., Pulvertaft, R.G.: Flynn's hand surgery. 4th Edn. Williams and Wilkins. Baltimore. p 285. (1991).
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  11. Lam, D.S.C., NG, J.S.K. Cheng, G.P.M., Li, R.T.H. (1998) : Autogenous Palmaris Longus Tendon as Frontalis Suspension material for Ptosis Correction in children. American Journal of Ophthalmology. 126 (1) : 109-115
  12. Lazorthes, G. : Le systeme nerveux peripherique. Masson, Paris, pp 233. (1955).
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  21. Terrono, A.L., Rose, J.H., Mulory, J., Millender, L.H. (1993) : Camitz palmaris longus abductorplasty for severe thenar atrophy secondary to carpal tunnel syndrome. Journal of Hand Surgery. 18A : 204-206.
  22. Uba, Y., Nosaka, K. Seto, Y., lkeda, N., Nakamura, T. (1999) : An operative procedure for advanced Kienbock's disease. excision of lunate and subsequent replacement with a tendon ball implant. Journal of Orthopaedic Science . 4 (3) : 207- 215.
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FIG-1

Missing Image

Photograph of the dissected left lower forearm, wrist and hand showing a branch (arrow) of the median nerve (M) innervating tendon (T) of palmaris longus muscle.

C : Palmar cutaneous branch of median nerve, P : Palmar aponeurosis

FIG-2

Missing Image

Dissected left lower forearm, wrist and hand showing the branch (arrow) of the median nerve (M) innervating tendon (T) of palmaris longus muscle and palmar aponeurosis (P) from its dorsal aspect.

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