Anomalous origin of the lumbrical muscles: a study on South Indian cadavers

New insights into the origin of the lumbrical muscles of the foot: tendinous slip of the flexor hallucis longus muscle

PURPOSE

The aim of this study was to clarify the origins of the lumbricals of the foot toward a better understanding of its precise action in the gait.

METHODS

The lumbricals in the foot were investigated in 66 specimens of embalmed Korean adult cadavers.

RESULTS

The first lumbrical arose as two muscle bellies from both the tendon of the FDL and the tendinous slip of the FHL in 83.3 %, and as one muscle belly from the tendon of the FDL or the tendinous slip of the FHL in 16.7 %. These two muscle bellies subsequently merged to form the muscle belly of the first lumbrical. The second lumbrical arose from the tendinous slips of the FHL for the second and third toes as well as the tendon of the FDL in all specimens. The third lumbrical arose from the tendinous slips of the FHL for the third and fourth toes in 69.7 %, and the fourth lumbrical arose from the tendinous slip of the FHL for the fourth toe in 18.2 %. Some deep muscle fibers of the fourth lumbrical arose from the tendinous slip of the FHL for the second toe in 4.5 %, for the third toe in 28.8 %, and for the fourth toe in 15.2 %.

CONCLUSIONS

The results of this study constitute new anatomical knowledge regarding the origin of the lumbricals, and provide insight into their specific role in production of gait. These findings will be useful for various types of surgery, biomechanics research, and rehabilitation programs.

Carpal tunnel syndrome caused by supernumerous lumbrical muscle in hemihyperplasia of the upper extremity

INTRODUCTION

Hemihyperplasia of the upper extremity is a rare pathology that occurs in 1/86,000 births. Carpal tunnel syndrome may be associated with this disease.

CLINICAL PRESENTATION

We describe the case of a 74-year-old male who has hemihyperplasia of both upper extremities since birth. At the age of 73, he started experiencing continuous, progressive and high intensity pain that occurred more frequently at night and was localized in the right hand. It was associated with paresthesia and hypoesthesia predominantly of the thumb, index finger and middle finger. Clinical examination and electrodiagnosis led to diagnosis of carpal tunnel syndrome.

RESULTS

The patient underwent surgical carpal tunnel release to treat the disease. The enlarged nerve was compressed by a supernumerous lumbrical muscle, which was resected intraoperatively. After six months of follow-up the patient has normal sensitivity and grip strength in the right hand.

CONCLUSION

Hemihyperplasia should be clearly distinguished from other complex pathologies that may also entail CTS. Since significant variation in the anatomy of the hemihyperplasic extremities is the rule rather than the exception, a conventional open approach should be taken to localize and treat the compression.

An additional muscle belly of the first lumbrical muscle

Introduction

Lumbrical muscles play a vital role in the precision movements of the hand, along with the thenar, hypothenar and interossei muscles. The variation in the lumbrical muscle is clinically significant.

Case presentation

During routine dissection of an adult male cadaver, we observed an additional muscle belly of the first lumbrical muscle took origin from the tendon of the flexor digitorum superficialis (FDS) to the index finger, close to the proximal margin of the flexor retinaculum.

Conclusion

The presence of such an additional muscle in the carpal tunnel should be considered in the aetiology of carpal tunnel syndrome (CTS).