- Chronic Injury:
- flexion deformity of PIP & an extension deformity at DIP joint;
- MCP hyperextension deformity;
- after the central slip has been disrupted for some time, there will be volar
migration of
lateral bands, and contracture of
oblique retaincular lig.
- after the lateral bands have become contracted in a volar position, there
will be limited flexion of the DIP joint when the finger is placed in
MCP hyperextension and PIP hyperflexion (which puts lateral bands on
maximum stretch);
- Acute Injury:
- at initial presentation, PIP may appear to be a swollen & painful;
- w/ time, manifestations of deformity (PIP flexion, DIP extension) appear;
-
w/ disrupted triangular ligament:
- patients will not be able to actively extend PIP joint, but will be able
to actively hold the PIP in extension, if it is first passively extended;
- this occurs because the
lateral bands will relocate into their native
position w/ PIP extension, allowing pt to hold finger in extension;
- if it is unclear whether the central slip is disrupted, then test PIP joint
extension w/ the wrist and MP joints held in flexion;
- this should relax the lateral bands;
-
w/ intact triangular ligament:
- PIP joint may initially be capable of weak finger extension if the triangular
ligament is intact;
- active extension is possible because the triangular ligament holds the
lateral bands in their native posiiton;
-
rupture of central slip must be differentiated from
collateral ligament sprain;
- pt will note tenderness on dorsum of finger rather than sides of joint;
- loss of active PIP extension when MP is in extension and PIP is placed
in 90 deg flexion;
- weak extension against resistance = central slip injury;
- extravasation of intra-articular dye dorsal and distal to PIP joint;
- >15-20 deg loss of active extension at PIP joint w/ wrist & MCP flexed;
- w/ acute injury the patient should at least be able to passively extend the PIP joint;
- inability to passively extend the PIP joint, may indicated that the lateral
bands have become trapped under the proximal phalanx condyles;
