|Year : 2021 | Volume
| Issue : 2 | Page : 152-154
A combined anomaly comprising triple muscular variations - An aberrant flexor indicis profundus lateralis associated with gantzer's muscle and flexor indicis profundus
Deepa Somanath1, Sudha Ramalingam1, S Jayanthi2
1 Department of Anatomy, Sri Manakula Vinayagar Medical College and Hospital, Puducherry, India
2 Department of Anatomy, Mahatma Gandhi Medical College and Research Institute, Puducherry, India
|Date of Submission||09-Jun-2020|
|Date of Acceptance||11-Apr-2021|
|Date of Web Publication||27-Dec-2021|
Dr. Sudha Ramalingam
Department of Anatomy, Sri Manakula Vinayagar Medical College and Hospital, Puducherry - 605 107
Source of Support: None, Conflict of Interest: None
Aberrations in the deep wrist flexors are frequently documented. These varied muscles might account for anterior interosseous nerve compression syndrome. The present study describes a case with three variations in the deep flexor of wrist comprising two separate small muscle bellies with their tendons and a higher level cleavage of the lateral tendon of flexor digitorum profundus muscle. Such a triple anomaly is a rare occurrence that has to be borne in mind by hand surgeons in case of nerve entrapment syndromes.
Keywords: Accessory flexors of the forearm, additional belly, anterior interosseous nerve, flexor digitorum profundus, flexor pollicis longus
|How to cite this article:|
Somanath D, Ramalingam S, Jayanthi S. A combined anomaly comprising triple muscular variations - An aberrant flexor indicis profundus lateralis associated with gantzer's muscle and flexor indicis profundus. J Orthop Traumatol Rehabil 2021;13:152-4
|How to cite this URL:|
Somanath D, Ramalingam S, Jayanthi S. A combined anomaly comprising triple muscular variations - An aberrant flexor indicis profundus lateralis associated with gantzer's muscle and flexor indicis profundus. J Orthop Traumatol Rehabil [serial online] 2021 [cited 2022 Jan 26];13:152-4. Available from: https://www.jotr.in/text.asp?2021/13/2/152/333563
| Introduction|| |
Variations in the deep flexors of the forearm are not uncommon since the superficial and deep flexors are embryologically derived from a common muscle mass by the appearance of the cleavage. Any variation in the cleavage of the deep flexor muscle mass can lead to the formation of an additional muscle in the forearm. Gantzer's muscle is an additional belly of flexor pollicis longus muscle (FPL) and is the most common muscle variation in the flexors of the wrist. This kind of aberration has been documented by many authors.,,,,,
Jones and Abrahams observed an additional muscle of the deep flexors of the forearm (Gantzer's muscle) which arose from the deeper surface of the flexor digitorum superficialis (FDS) muscle and was inserted into FPL and/or flexor digitorum profundus (FDP) muscle. This muscle belly was located in front of the anterior interosseous nerve and ulnar artery which supplied the muscle.
The separation of the index finger tendon from the other tendons of FDP is a uniquely human characteristic corresponding with the special features of the index finger, and this type of discrepancy is also evidenced by few authors. These anomalous bellies usually pass in front of the anterior interosseous nerve. Hence, there are possibilities of compression of this nerve, leading to palsy. The present case discusses a unique combination of three muscle variations in the deep flexors of the wrist.
| Case Report|| |
The following variations were observed in a routine dissection of the right upper limb in a male cadaver of 55 years of age, for undergraduate students in the department of anatomy. The forearm was dissected using I-shaped incision extending from elbow to wrist, after the reflection of skin and fasciae; two additional muscles (medial Jones and Abrahams observed an additional muscle (AM)/flexor profundus indicis lateralis, lateral AM/Gantzer's muscle) were noted under the cover of pronator teres, flexor carpi radialis, and FDS muscles. Once these muscles were reflected, the origin of the additional muscles was seen from the medial epicondyle of the humerus with short and narrow bellies of 6 and 7 cm length, respectively [Figure 1]a. At its origin point, they merged with the common origin of the FDS muscle. The tendon of medial AM was measuring 17 cm which ran from medial to the lateral direction, crossing the anterior aspect of the lower part of the radius. On the lateral side of the lower part of the tendon, it was joined by fleshy fibers of the FPL muscle at about 16 cm proximal to the wrist line since they were adjacent. It was found traveling through the carpal tunnel in front of the first tendon of FDP muscle for the index finger in a common synovial sheath. On tracing its course in hand, it was found attached to the palmar aspect of the base of the distal phalanx of the index finger on the lateral side, while the original tendon of FDP muscle was attached to the medial side of the above-mentioned part of the finger [Figure 1]b. The tendon of FDS muscle as usual split into two tendons to allow the passage of the original tendon of FDP muscle and the tendon of medial AM to the index finger. Both of these tendons gave origin to the first lumbrical muscle measuring about 7 cm in length and 0.8 cm in breadth within the carpal tunnel at the level of the proximal border of the flexor retinaculum and got inserted into the dorsal digital expansion of the index finger as usual.
|Figure 1: (A) The triple muscular variations after the reflection of superficial flexors of forearm. a: Flexor indicis profundus lateralis, b: Gantzer's muscle, c: Flexor indicis profundus, d: Tendons of flexor digitorum profundus, e: Tendon of flexor pollicis longus, f: Anterior interosseous nerve. (B) The relations of tendons in the index finger. a: Tendon of flexor digitorum superficialis, b: Carpal tunnel, c. First lumbrical muscle, d: Tendon of flexor indicis profundus lateralis, e: Tendon of flexor digitorum profundus for the index finger|
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The lateral AM (Gantzer's muscle) took its origin like the medial AM, ran from medial to lateral side, and its tendon merged with the tendon of FPL 15 cm proximal to the wrist line.
The higher level cleavage of the first tendon of FDP muscle with its muscle belly was observed at about 21 cm above the wrist crease, which proceeded downward accompanying the tendon of medial AM through the carpal tunnel and hand till its destination.
Regarding the relations, both the AMs were superficially related to the median nerve and nerve branches to flexor carpi radialis and FDS muscles. Deep to the AM, the course of the anterior interosseous nerve was seen along with the ulnar artery. Direct branches from the median nerve were seen supplying both the AMs, 3 cm distal to the elbow. There were no other variations in the same limb and no such variations in the left limb.
| Discussion|| |
The variations in the deep flexors of the forearm are reported extensively in the literature. In this case, it is hypothesized that the two AMs were formed due to the appearance of extra grooves in the deep muscle lump. The references opine that these AMs conventionally either fuse with FPL or the index tendon of FDP muscle. However, here, a complete medial AM was observed without fusing with the FDP tendon. Kumar et al. reported a case of flexor indicis profundus as a separate muscle with a tendon cleaved from the rest of the tendons of FDP muscle. This tendon was located between FDP and FPL, which then inserted into the distal phalanx of the index finger at its palmar aspect of the base.
It was reported that a separate muscle was arising from the medial epicondyle under the FDS muscle and its tendon merged with the tendon of FDP to the little finger but another variation showed the tendon of AM joining the indicial part of profundus with the FPL. The above said variations were similar to the present case report. In this case, the tendon of medial AM coursed absolutely free, neither attached to FPL nor FDP, but received few fleshy fibers from the FPL and inserted to the lateral side of the base of the distal phalanx of the index finger. Kopuz et al. described a similar case where the tendon of AM formed a conjoint tendon after fusing with the index finger tendon of FDP.
Ballesteros et al. reported that the additional head of the FPL muscle was noted in 32.1% of the 106 forearms. It took its origin from the FDS muscle or medial epicondyle of the humerus or the coronoid process of the ulna, and the insertion was on the medial border of the FPL muscle. Maximal insertion was to the proximal third and the middle third of the FPL muscle.
In a study by Al-Qattan, it was revealed that 52% of the cases showed this variation with similar attachments. The Gantzer's muscle was seen in 68% of the forearms and is called the accessory muscle of the FDS since they share common features. Gunnal et al. observed 51.11% cases with an accessory head of the FPL muscle, in which four cases exhibited its origin both from the medial epicondyle of humerus and coronoid process of ulna. Jones and Abrahams discovered an additional belly that came from the posterior surface of the FDS muscle dividing into three tendinous slips, namely lateral, intermediate, and medial. The lateral slip divided into two and inserted into the proximal and middle-third of FPL, respectively, and the medial slip attached to the tendon of FDP muscle to the middle finger. Nayak et al. noted two additional bellies on the anterior aspect of proximal forearm among which one belly joined the FPL and the other with the tendon of FDP of the middle finger within the carpal tunnel and contributed to the origin of the second lumbrical muscle.
Singla et al. identified an extra muscular slip from the common flexor origin of the forearm and the FDS muscle passing distally and attached to the tendon of FDP. Meanwhile, another additional belly was attached to the ulnar side of the tendon of FPL. Degreef and Smet presented a case of anterior interosseous nerve syndrome accompanied by a Gantzer's muscle with fibrous edge arising from the coronoid process of ulna to the FPL muscle compressing the nerve. The present case showed the tendon of the lateral AM (Gantzer's muscle), after crossing superficial to the anterior interosseous nerve, fused with the FPL tendon which might be a cause for the compression of the nerve. Lee et al. added that the presence of multiple Gantzer's muscles may reduce the contraction of wrist flexors and result in a painful lower forearm and they added that this muscle can be utilized for local transfer in case of peripheral neuropathy.
| Conclusion|| |
The knowledge of such varied forearm flexor muscle anatomy should be clearly understood by surgeons since their relations with the anterior interosseous nerve can result in compression during muscular contraction. The higher level cleavage of the first tendon of FDP muscle indicates the significance of the movements of the index finger in humans.
The authors would like to thank Sri Manakula Vinayagar Medical College and Hospital for their kind consent to utilize the department facilities.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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