The proximal interphalangeal joint (PIPJ) is stabilized by bony articulations, collateral ligaments, a volar plate, and surrounding tendons. Dorsal dislocations of the PIPJ commonly result from hyperextension injuries and can be classified as Type I-III injuries of increasing severity. Treatment depends on the injury type and stability but generally involves reduction, splinting, and avoiding prolonged immobilization to prevent stiffness. Surgical options may be needed for open injuries or unstable fractures.

2. PIPJ Anatomy

3. 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

4. Anatomy
 PIPJ - Hinge joint
 Arc of motion up to 1100
 Stability:
 Articular contours
 Periarticular ligaments
 Secondary stabilization by adjacent tendon &
retinacular systems

5. 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)

7. 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

10. 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

11. 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

13. 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

14. 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

15. PIPJ - Secondary Stabilization
 Secondary
stabilization by
adjacent tendon &
retinacular systems

16. PIPJ dislocations

17. Dorsal PIPJ Dislocation

18. 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.

19. Dorsal PIPJ Dislocations
 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

20. Dorsal PIPJ Dislocations
 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

37. Dorsal PIPJ Dislocations
 Treatment depends on open vs closed, stable
vs unstable injuries
 Rx principles:
 Patient education
 Avoidance of prolonged immobilisation

38. Dorsal PIPJ Dislocations
 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)

39. Dorsal PIPJ Dislocations
 Complications of operative Mx:
 Redisplacement
 Angulation
 Flexion contracture
 DIPJ stiffness