The Volar Midline Longitudinal Groove of the Middle Phalanx: An Anatomic Study and Clinical Implications

To investigate the volar anatomy of the middle phalanges of the hand; in particular, to define the presence and depth of a volar midline longitudinal groove.

Measurements were performed at 5 equidistant points along the shafts of 60 skeletonized middle phalanges from 15 cadaveric hands. The thickness at the midline of each phalanx was subtracted from the maximal dorsovolar thickness to indicate the presence or absence of a groove at each point. The phalanges were also evaluated by computed tomography to confirm the presence of a volar groove and to rule out morphological abnormalities.

A volar groove was confirmed in all 60 phalanges. The groove had an average depth of 0.4 mm and was found to be deepest at the mid-phalangeal shaft. The groove reached a depth of greater than 1 mm in 23% of the phalanges. The middle phalanges of the middle and ring digits consistently revealed deeper grooves than those found in the index and little fingers. Computed tomography confirmed the presence of a volar groove and showed no morphological abnormalities.

A midline volar longitudinal groove is present in the middle phalanges, is most pronounced in the mid-phalangeal shaft, and is the deepest in the middle and ring fingers.

Surgeons should be cognizant of the volar longitudinal groove when inserting screws from dorsal to volar during the fixation of middle phalangeal fractures. Lateral intraoperative fluoroscopy may not reveal excessive screw penetration because of the presence of ridges on either side of the groove. Particular care should be taken at the mid-phalangeal level of the middle phalanges of the middle and ring fingers.