General Descriptors and Background for the Terms

1. The use of the word digit versus finger and toe is problematic. Finger is usually specific to digits 2-5 of the hand and toe to digits 2-5 of the foot whereas digit is a more general term that can be used to describe any finger or toe. We generally use the word finger to be distinct from thumb (pollex, although this latter term is used rarely in English) and toe is distinct from hallux (which, oddly enough, is more commonly used in English than is great toe). It is important for the user to read the definition to understand the context in which the term finger or toe is used. We recognize that some languages do not use a term equivalent to finger and toe and instead use a modifier of digit (e.g., dita della mano). The term ray is a yet more general term that can refer to a finger, toe, thumb, or hallux, but it also includes metacarpals/tarsals, whereas digit, thumb, hallux, finger, and toe only refers to the phalangeal segments of the ray. The term ray is little used in this terminology.
2. The proximo-distal axis of the digits is specified according to the name of the underlying bones, for examples, the portion of the finger overlying the distal phalangeal bone is the distal phalanx of the finger.
3. The digits are numbered 1-5 (or 6 or more in patients with polydactyly) from the radial/tibial side of the limb, starting with thumb/pollex (great toe/hallux) to little finger/toe; F denotes that they are fingers, T denotes toes. It is acknowledged that identifying the thumb as F1 contradicts the notion that this digit is designated as thumb instead of first finger, but for simplicity this has been used. In the case of polydactyly, if one can determine the origin of the duplicated digit (e.g., for a partially duplicated thumb where a relatively small digit emanates from the distal first metacarpal, and it is clearly a partially duplicated thumb and not an index finger, the duplicated digit is sub-labeled A and B, with A used for the more anterior (radial/tibial) sub-digit. In this case, the six digits are numbered F1A, F1B, F2, F3, F4, and F5. If the origin of the supernumerary hand digit cannot be clearly ascertained, the digits are labeled F1, F2, ..., F6. We recognize that the latter scheme leads to issues comparing pre- and postoperative digit identifiers.
4. Joint specification: interphalangeal joints = IPJ (which is a general term for fingers and toes but is a specific term for the normal thumb and hallux, as they have only a single IPJ) with use of the more specific terms distal IPJ (DIPJ) for the joint between the middle and distal phalanges and proximal IPJ (PIPJ) for the joint between the middle and proximal phalanges of any triphalangeal digit. The metacarpal-phalangeal joint is abbreviated as the MCPJ and MTPJ is used for the metatarsal-phalangeal joint.
5. Fingertip. The distal segment of the digit overlying the distal phalanx of the finger and including the nail, and dorsal and ventral surfaces.
6. Descriptions should specify bilateral vs. right or left for laterally paired structures. We do not specify terms for findings of asymmetry. Instead, we endorse the approach of defining a body part as small or large, which is less ambiguous and reduces the number of terms that must be defined.
7. The axes of the limb are specified as per embryological terminology. Anterior-Posterior (A/P) (from the thumb/great toe to the little finger/small toe), Dorsal-Ventral (D/V) (from the back of the hand/top of the foot to the palm/sole), and Proximo-Distal (P/D) (from the shoulder/hip to the fingers/toes). Note that common medical usage often substitutes the terms preaxial for anterior and postaxial for posterior.
8. There are some definitions where one term applies only to the feet and a similar second term applies to the hands. For others, a single term for all limbs may be used with a modifier for feet or hands, as appropriate. The terms were set out this way primarily for convenience, as some of the terms, definitions, and comments are cumbersome or awkward if one tries to define them in terms of both hand and foot features. In some cases, the definitions were substantially different owing to distinct anatomic features of the hand or foot.
9. For a few of the features, the position of the patient is important (e.g., pes planus). In those cases, the positioning of the patient is discussed in the comments for the term.
10. Note that radiographs are not used in this terminology. See Allanson et al. [2009b] for a discussion of this issue.
11. The terms are organized alphabetically in three sections (Hands and Feet, Creases, and Nails). We use the singular form as the default for all terms. For some terms, the singular form cannot exist (e.g., Cutaneous syndactyly of the toes). In such cases, the singular and plural forms of a word are mixed (e.g., Toe and Toes), alphabetized by the next word of the term. No attempt was made to hierarchically organize the terms. The primary or preferred form of each term appears in the paper in bold and italic font, except within the comments section for that term.