Lumbrical Muscles Neural Branching Patterns: A Cadaveric Study With Potential Clinical Implications

Background Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles’ absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles. Materials Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted. Results The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified. Conclusion The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations.

Morton Neuroma Surgery: Relation Clinical Results to Excised Sample Length

Background:Morton’s neuroma (MN) is mechanical neuropathy of plantar interdigital nerve. It is one of the most common causes of forefoot pain. One of the most undesirable complications of MN surgery is recurrent neuroma. Excision level of MN is important to prevent recurrence. In this study, we aimed to find the relation resection lenght of MN to clinical results of MN surgery cases. Methods:76 samples sent with the diagnosis of Morton neuroma to the pathology department of our hospital between years 2010-2019. 66 patients whose clinical results were available were included in the study. Mean age was 41,5 (between 21 to 70). All of 66 patients were primary diagnosed 22 of them was left foot and the other 170 were right foot. 50 of them were female, and 16 were male. Recurrent neuromas, pathological sample more than one piece from one surgical site were excluded from the study. 72 of them were evaluated as a clinically and compare the sample lenght.Results:76 pathological specimens were prepared and examined by the same pathologist. Gross pathological appearance and histopathology findings were recorded. Mean sample length was 2,05 cm (between 0,7cm and 3,5 cm). 68 samples was smaller (89.5%) than 3 cm and only 8 sample (10.5%) was bigger than 3 cm. Average interdigital neuroma score improved from 20 to 62 points following the surgery (p<0.05).Conclusion:We recommend that, the common digital nerve should be cut from the proximal as much as possible to bury the proximal stump into the lumbrical muscles regardless of the sample size and using loupe magnification, careful and sharp dissection can be prevent injury to the PDNB.Level of Evidence: 2

Revisiting the Morphological Variations in Lumbricals of Hand

Introduction: The lumbrical muscles are unique in their functions in being only intrinsic muscles which bridges between the palmar and dorsal surface. This unique property endows them in performing fast, alternating movements and fine tuning digit motion. The aim of this study was to evaluate the anatomical variations in the morphology and architecture of lumbricals and to discuss its clinical implications. Subjects and Methods: This study was conducted on 74 disarticulated upper limbs during routine dissection of cadavers in the Department of Anatomy of MVJMC & RH. The dissection was carried out based on the steps as per the Cunningham’s manual. Results: Variations in lumbricals were observed in 12 specimens (8 in right side & 4 in left side). The variation encountered were the proximal origin of lumbricals in 4 specimens (5.41%), Split insertion in one specimen (1.35%), bipennate second lumbrical in two specimens (2.70%), accessory belly of first lumbrical in 4 specimens (5.41%) and hypertrophied lumbrical in one specimen (1.35%). Conclusion: Variations of the lumbrical can present with wide range of clinical presentations like compression of neurovascular structures as in hypertrophy, carpal tunnel syndrome as in proximal origin and accessory belly of lumbrical.

Caffeine attenuates contraction-induced diminutions of the intracellular calcium transient in mouse lumbrical muscle ex vivo

The amount of calcium released from the sarcoplasmic reticulum in skeletal muscle rapidly declines during repeated twitch contractions. In this study, we test the hypothesis that caffeine can mitigate these contraction-induced declines in calcium release. Lumbrical muscles were isolated from male C57BL/6 mice and loaded with the calcium-sensitive indicator, AM-furaptra. Muscles were then stimulated at 8 Hz for 2.0 s in the presence or absence of 0.5 mM caffeine, at either 30 °C or 37 °C. The amplitude and area of the furaptra-based intracellular calcium transients and force produced during twitch contractions were calculated. For each of these measures, the values for twitch 16 relative to twitch 1 were higher in the presence of caffeine than in the absence of caffeine at both temperatures. We conclude that caffeine can attenuate contraction-induced diminutions of calcium release during repeated twitch contractions, thereby contributing to the inotropic effects of caffeine.