Intrinsic Hand Deformity Clinical Presentation

Updated: Feb 16, 2022
  • Author: Dimitrios Danikas, MD, FACS; Chief Editor: Harris Gellman, MD  more...
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The patient may present with a history of trauma, inflammation, tumor, leprosy disease, compartment syndrome, or rheumatoid disease.


Physical Examination

The first dorsal interosseous muscle is tested by having the patient place the ulnar side of the hand on the examination table. The radial side of the index finger is facing up. The patient is asked to raise the index finger toward the ceiling. The examiner applies resistance and observes the patient's strength. Muscle strength testing is likely to be more sensitive if the right and left sides are tested simultaneously rather than one after the other. [14]

The second, third, and fourth dorsal interosseous muscles are tested by having the patient place the palm on the examination table. The patient spreads all of the fingers against resistance (see the image below).

Ulnar-innervated intrinsic muscles can be checked Ulnar-innervated intrinsic muscles can be checked by resisting abduction of index (first dorsal interosseous muscle) and small fingers (abductor digiti minimi).

The palmar (volar) interosseous muscles are examined by placing a piece of paper between the digits and having the patient hold his or her fingers tightly together as the examiner tries to withdraw the paper. The test is repeated between each of the adjacent fingers.

Adhesions and contractures of the intrinsic and extrinsic extensor muscles can limit flexion of the digits. The intrinsic tightness test can be used to differentiate extrinsic pathology from intrinsic pathology.

During a test for intrinsic tightness, the examiner usually attempts to fully flex the proximal interphalangeal (PIP) joint of an examined finger while the metacarpophalangeal (MCP) joint is kept in full extension and in full flexion. In the case of intrinsic tightness, (passive) flexion of the PIP joint is more restricted when the MCP joint is in extension than when the MCP joint is in flexion (see the image below).

Gloved examiner checks for intrinsic tightness. Wi Gloved examiner checks for intrinsic tightness. With metacarpophalangeal (MCP) joint hyperextended, proximal interphalangeal (PIP) joint is passively flexed. Intrinsic muscles are volar to axis of rotation of MCP joint and dorsal to axis of PIP joint. MCP joint hyperextension tightens intrinsics. Results of this test are compared with those in contralatera, normal hand. Note intrinsic atrophy in first dorsal web space.

If the intrinsic muscles are scarred, passive MCP joint extension increases PIP joint extension and makes passive PIP joint flexion more difficult (see the images below).

Image from patient with partial ulnar nerve paraly Image from patient with partial ulnar nerve paralysis who is asked to extend digits. Hyperextension of metacarpophalangeal (MCP) joints of ring and small fingers occurs with loss of intrinsic ulnar-innervated MCP flexors. Index and middle fingers have median-innervated intrinsics (lumbricals) that allow extrinsics to extend interphalangeal (IP) joints.
When examiner prevents metacarpophalangeal (MCP) h When examiner prevents metacarpophalangeal (MCP) hyperextension of ring and fifth fingers, patient can completely extend interphalangeal (IP) joints with extrinsic tendons.

The abductor pollicis brevis (APB) is tested as the patient pushes against resistance while the thumb is in the abducted position. The opponens pollicis is similarly tested with the thumb more circumducted. The adductor pollicis is evaluated as the patient pinches a piece of paper between the thumb and index finger while the examiner pulls on the paper. The flexor pollicis brevis (FPB) is assessed with the thumb MCP joint in flexion and with resistance applied volarly.

The abductor digiti minimi (ADM) is tested by having the patient place the back of the hand on the examining table while the little finger is abducted against resistance. The flexor digiti minimi brevis (FDMB) is examined by flexing the MCP joint while the finger is adducted. The interphalangeal (IP) joints must be kept in extension. To test the opponens digiti minimi (ODM), the patient performs a pulp-to-pulp pinch by moving the little finger to the thumb.

Intrinsic tightness can result in a swan-neck deformity, which is characterized by PIP joint hyperextension and distal IP (DIP) joint flexion. The tight intrinsic muscles pull the PIP joints into extension, which allows passive DIP joint flexion. Over time, the PIP joint volar plate stretches as the extensor mechanism pulls the proximal phalanx into hyperextension. As PIP joint hyperextension increases, DIP joint flexion increases.

Intrinsic contracture disturbs fine hand-muscle balance. The fingers become stiff, function deteriorates, and the hand becomes disabled.

Boutonniere (buttonhole) deformity

The boutonniere deformity involves PIP joint flexion and hyperextension of DIP and MCP joints. Attenuation of the central slip with separation from the transverse retinacular ligaments causes migration of the lateral bands volar to the PIP joint rotational axis. Thus, the lateral bands act as flexors of the PIP joint. As a result, the flexor digitorum superficialis (FDS) meets less resistance and flexes the PIP joint.

Contraction of the lateral bands and oblique retinacular ligaments prevents extension of the PIP joint. The lateral bands extend the DIP joint. The MCP joint hyperextends as the sagittal band applies traction on the extensor tendon. [15, 16]

Physical examination involves evaluation of the range of motion (ROM), both active and passive, of both DIP and PIP joints. The examiner tries to passively flex the DIP joint while passively extending the PIP joint. In the presence of boutonniere deformity, both lateral bands and oblique retinacular ligaments are contracted, and the DIP joint will not flex. The examiner flexes the PIP joint, and the DIP joint can then actively and passively flex because both the lateral bands and the oblique retinacular ligaments are now relaxed.