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PIPJ Anatomy

Proximal Interphalangial Joint

Anatomical & functional locus of finger function Site of most common ligament injury in the hand Most ligament injury are incomplete with

maintenance of joint congruity & stability In certain injuries (eg. Lateral dislocations &

hyperextension injuries) --> complete rupture of one or more supporting structures

Treatment based on accurate diagnosis of pathological lesions & degree of clinical dysfunction

Anatomy

PIPJ - Hinge joint Arc of motion up to 1100

Stability: Articular contours Periarticular ligaments Secondary stabilization by adjacent tendon &

retinacular systems

Anatomy - Bony Factors

Head of PP - 2x concentric condyles seperated by an intercondylar notch

Condyles (PP) articulate with 2x concave fossa in the broad, flattened base of MP separated by a median ridge

Tongue-and-groove contour & breadth of congruence add stability by resisting lateral & rotatory stress (esp. when PIPJ is fully extended)

Anatomy - Ligamentous factors

Radial & ulnar collateral ligaments Primary restraints to radial & ulnar deviation force Proper & accessory component Both arise from the concave fossae on lateral aspects

of each condyle & pass obliquely & volary to their insertions

Anatomically confluent but distinguished by their points of insertion

Proper collateral lig. --> volar 1/3 base of MP Accessory collateral lig. --> volar plate

Anatomy - Volar Plate Floor of joint Suspended laterally by collateral

ligs. Distal portion inserts across volar

base of MP (only densely attached at its lateral margins - col. lig. insertion)

Thinner centrally & blends with MP volar periosteum

Central portion tapers proximally into an areolar sheet & laterally thickens to form a pair of check ligaments

Secondary stabilizer against lateral deviation esp when PIPJ extended but only when collaterals torn

Check ligaments: +Originate from periosteum of PP1 just inside walls of A2 pulley at its distal margin and are confluent with proximal origins of C1 pulley

+prevent hyperextension while permitting full flexion thereby providing maximum stability with minimum bulk

PIPJ Stability

Key: strong conjoined attachment of the paired collateral lig. & the volar plate into the volar 1/3 of the MP

Ligament-box configuration produces a 3D strength that strongly resists PIPJ displacement

For MP displacement to occur, the ligament-box complex must be disrupted in at least 2 planes

PIPJ Stability

Based on load to failure cadeveric studies & clinical observation, collateral ligs. fail proximally about 85% of the time while the volar plate avulses distally up to 80% of the time

At lower angular velocities of side-to-side deformation, the collateral ligs. tend to fail in their midsubstance

PIPJ - Secondary Stabilization

Secondary stabilization by adjacent tendon & retinacular systems

PIPJ dislocations

Dorsal PIPJ Dislocation

Dorsal PIPJ Dislocations

Mechanism: PIPJ hyperextension combined with some degree of longitudinal compression

Frequently occurs in ball-handling sports Usually produces soft tissue or bone injury to the

distal insertions of the 3D ligament-box complex. The greater the longitudinal force, the more

likelihood for fracture dislocation Rarely, VP ruptures volarly & become interposed

within the PIPJ causing irreducible dislocation Volar fracture may even become trapped within the

flexor sheath and inhibit motion.


Type I (hyperextension): VP avulsed; incomplete longitudinal split in col. ligs.; articular surfaces remain congruous.

Type II (dorsal dislocation): complete rupture VP; complete split in col. ligs.; MP resting on dorsum of PP.

Type III (fracture-dislocation): disruption at the volar base of MP where VP is inserted; stable vs unstable injuries


Stable Type III: fracture < 40% of volar

base MP; significant portion of col. ligs. still attached; possible congruous reduction

Unstable Type III: fracture > 40% of volar

base MP; little or no col. ligs. attached; congruous reduction unlikely; depressed volar articular defect


Treatment depends on open vs closed, stable vs unstable injuries

Rx principles: Patient education Avoidance of prolonged immobilisation


Operative Mx: Debridement & joint washout for open injuries Dorsal block splinting ? Role of primary VP repair Other specific techniques for unstable PIPJ injuries:

Dynamic skeletal traction Extension block pinning Trans-articular pinning ORIF Volar plate arthroplasty FDS tenodesis (for chronic hyperextension deformity of PIPJ)


Complications of operative Mx: Redisplacement Angulation Flexion contracture DIPJ stiffness

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