A rhombus is classically defined as an oblique-angled equilateral parallelogram, whereas a rhomboid differs in that it has uneven adjacent sides. The term rhomboid is frequently used in facial reconstruction literature to mean either rhombuslike or to describe one of the popular transposition flaps used to repair rhombus-shaped defects.
History of the Procedure
In 1946, Limberg first described a technique for closing a 60° rhombus-shaped defect with a transposition flap. Dufourmentel modified this technique in 1962 to close defects with any acute angle. Webster published a third significant modification in 1978.  The Webster, or 30° flap, uses a 30° angulation of the distal flap end along with an M-plasty closure at the defect base.
Transposition flaps are useful when the size or shape of a lesion does not permit direct closure using a standard fusiform incision. For example, attempting to close a wide defect primarily requires an ellipse with either long limbs or blunt angles. Lengthy limbs create long scars and remove healthy tissue unnecessarily, whereas blunt ends often create an unpleasant standing-cone or dog-ear appearance.
Considerations when designing any local flap are lesion diameter, amount of normal skin that needs to be discarded, scar orientation with respect to relaxed skin tension lines, arc of skin rotation, and the vector of maximal tension after closure. Rhomboid flaps have been used in reconstruction of the cheek, temple, lips, ears, nose, chin, eyelids, and neck. The aesthetic and mechanical properties of these flaps, however, make them especially useful for reconstruction of small defects in the lower cheek, mid-cheek, and upper lip. 
A study by Rashidian et al of 60 patients indicated that in the repair of sacrococcygeal pilonidal sinuses, treatment with either simple primary closure or a rhomboid flap leads to faster complete wound healing and a lower frequency of postoperative infection and hemorrhage than does management in which the wound is left open. 
Rhomboid flaps are full-thickness local flaps with a random blood supply. Rather than depend on an axial blood vessel for nourishment, rhomboid flaps rely upon the dermal-subdermal plexus of blood vessels.
Pedicle width controls the amount of circulation within the dermal-subdermal plexus to some extent. The blood supply to the head and neck is so vigorous that this variable is frequently considered to be of minor importance. Generally, the accepted safe maximum length-to-width ratio of the pedicle in the head and neck is 2-4:1, whereas in some other parts of the body with poorer circulation this ratio might fall to 1:1.
The surgeon must not violate the dermis when undermining this or any other random flap because the chances for partial or complete flap necrosis increases.
Heavy smokers or patients with insulin-dependent diabetes mellitus have a higher complication rate with all flaps.
If a carcinoma has been excised, use frozen sections to confirm that the margins are free of disease before any local flap is used to cover the area.
Rhomboid flaps rotate neighboring tissue to close the primary surgical defect, whereas the donor site is closed by primary closure. Do not consider these flaps for extremely large lesions or in instances where the resulting vector of tension distorts neighboring fixed landmarks such as the nasal ala, eyelid margin, or the lip.
The natural, parallel, horizontal wrinkles of the central forehead prevent good aesthetic result with this closure; therefore, rhomboid flaps are generally avoided in this area.