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Perilunate Dislocations

- See:
       - Carpal Instability
       - Ligaments of the Wrist

- Discussion:
    - perilunate dislocation pattern provides a whole spectrum of wrist sprains, fractures, dislocations;
    - types of perilunate dislocations (in order of frequency):
            - transscaphoid-perilunate
            - perilunar
            - transscaphoid-trans-capitate-perilunar
            - transradial-styloid

- Mechanism:
    - carpal dislocations result from hyperdorsiflexion;
    - severe ligament injury is necessary to tear the distal row from the lunate to produce perilunate dislocation;
    - sequence of injury:
            - this injury pattern usually begins radially & destabilizes thru body of scaphoid (w/ frx) or thru scapholunate interval (w/ dissociation);
                   - scaphoid bridges the proximal and distal carpal rows;
                   - w/ dislocation between these rows, the scaphoid must either rotate or fracture
                   - this produces a perilunate dislocation, which may cause: trans-sccaphoid perilunate dislocation:
                   - distal half of scaphoid & remaining carpus dislocate around lunate;
            - force is transmitted ulnarly thru the space of Poirier (between lunate and capitate);
            - next force transmission disrupts the luno-triquetral articulation;
            - as a manifestation of the most severe form of the injury, the lunate may be dislocated into the carpal tunnel;
    - transradial styloid perilunate dislocation:
            - frx of radial styloid w/ dislocation of it & remaining carpus around lunate;
            - further destabilization passes distal to lunate, either thru space of Poirier or thru capitate (transcapitate frx), & then ulnar to lunate, either through hamate & triquetrum or thru lunotriquetral interval;

- Radiographs:
    - lateral radiographs will reveal loss of co-linearity between the capitate, lunate, and radius;
    - typically the captitate is located dorsal to the lunate and is aligned with the radius;


- Components of Perilunate Dislocation:
    - includes dorsal dislocation of distal row, scaphoid, and triquetrum;
    - lunate:
           - vascularity of the lunate
           - lunate is usually subluxated and angulated palmarly but still is located in the lunate fossa of the radius;
           - w/ more severe injury lunate may be dislocated into the carpal canal, or if strong, short radiolunate and ulnolunate ligamens are torn, it may be displaced free fragment;
           - lunate dislocation is considered the last stage of perilunate dislocation;
           - example of lunate dislocation: 


    - capitate:
           - capitate fragment is frequently turned 180 deg so that its articular surface faces cancellous surface of major capitate fragment;
           - scaphoid & capitate fragments are devascularized by displacement;
           - space of poirier:
           - disruption occurs at scapholunate area & progresses into space of Poirier and then thru the lunotriquetral space;
           - rent develops during dorsal dislocations, and it is thru Space of Poirier interval that the lunate displaces into the carpal canal;
    - misc:
           - DISI:
                  - DISI collapse pattern, occurs because stabilizing influence of scaphoid is inital component of dislocation;
           - VISI:
                  - destabilization may begin ulnarly w/ a lunotriquetral dissociation;
                  - if lunate remains attached to scaphoid VISI will develop;

- Surgical Treatment:
    - delineate between those dislocations which easily reduce w/ close reduction & those that are irreducible or unstable;
           - in the later group, interposed capsule may be preventing the reduction;
    - palmar approach is typically needed to repair the rent in the volar capsule at the lunocapitate joint as well as carpal tunnel release;
    - dorsal approach is required for scaphoid fracture fixation or repair the torn scapholunate interosseous ligament;
    - note that one of the essential goals of treatment is to reduce the scapholunate gap (inaddition of volar ligament repair);
    - volar approach:
           - not all surgeons use a volar approach (unless a scaphoid fracture is present);
                   - in the case of a scaphoid fracture, the volar approach is devoted to fixing the fracture;
           - if there are neurovascular problems, a volar approach allows release of carpal tunnel;
           - combined w/ dorsal approach, this allows both intra articular & extra-articular damage to be assessed and treated adequately;
           - volar approach allows better reduction of the lunate and repair of the volar capsule;
           - may be opened, either along its attachments to radial rim or thru the constant rent in the space of poirier;
           - reference:
                   - The palmar radiocarpal ligaments:  A study of adult and fetal human wrist ligaments


    - dorsal approach:
           - some surgeons rely on the dorsal approach alone for surgical fixation of perilunate dislocations;
                  - in the study by Cooney, et al (1987), 18 of 21 patients who underwent a dorsal approach had a satisfactory outcome;
           - patient is supine w/ wrist slightly flexed & placed on arm board;
           - perform a provisional reduction before the incision is made;
           - incision:
                  - Z or S shaped incision from base of second metacarpal over wrist to distal forearm is suggested for good healthy skin;
                  - alternatively, make a straight midline longitudinal one in line w/ third metacarpal and into the distal forearm;
                        - the incision will be made thru the 3rd compartment;
                        - this passes safely between the dorsal sensory branches of the ulnar nerve medially, and ofthe radial nerve laterally; 
                  - ref: Difficult wrist fractures. Perilunate fracture-dislocations of the wrist
           - extensor retinaculum:
                 - extensor retinaculum between the 3rd and 4th extensor compartments is reflected off of wrist capsule w/ care to avoid any damage to capsule itself;
                 - EPL is mobilized out of its sheath and is reflected radially;
                 - subperiosteally elevate the fourth compartment, w/o violating the tendon sheath;
                 - place Homan retractors on either side of the radius;
           - capsular incision:
                 - longitudinally incise thru the dorsal capsule in line w/ Lister's tubercle, and then elevate the wrist capsule off of the dorsal rim of the distal radius including the dorsal radiotriquetral ligament;
                        - preserve radiotriquetral ligament;
           - need to remove loose fragments
           - dorsal capsule is usually opened along its origins from dorsal rim, & longitudianlly in space between 2nd & 4th extensor compartments;
           - it is easier to examine cartilage surfaces & intra articular fragments thru the dorsal approach;
           - note that some surgeons elect to fix the scaphoid fracture (if one is present) through the dorsal incision;
    - K wire fixation:
           - following either open or closed reduction, K wire fixation will be required;
           - the usual statedgy includes:
                   - ORIF of scaphoid fracture, if one is present (see trans-scaphoid perilunate dislocation);
                   - temporary lunate fixation to the radius (w/ care to take the lunate out of dorsiflexion);
                         - alternatively insert a K wire into the lunate which then can be used as a joystick;
                   - capitolunate angle should be held at neutral or slight flexion;
                   - scapholunate fixation;
                         - before the scapho-lunate joint is pinned, pass the ligamentous repair sutures, but do not tie them together until all of the pins have been inserted and the reduction is optimal;
                         - once K wire fixation has been achieved, consider repairing the scapholunate interosseous ligament with a bone anchor, and then augmenting the repair with a dorsal capsulodesis;
                   - scapho-capitate fixation;
                         - w/ an optimal reduction, the lunate should cover the head of the capitate;
                   - triquetral-lunate fixation;


- Post Op:
    - patients should understand clinical improvement takes upto one year;

- Complications:
    - secondary carpal collapse;
    - scapholunate dissociation;
    - lunotriquetral dissociation;

- Case Example:
    - 50-year-old male who was assaulted, sustaining a lunate dislocation; 


Problem Fractures of the Hand and Wrist--Symposium: Difficult Wrist Fractures: Perilunate Fracture-Dislocations of the Wrist.

Late Treatment of a Dorsal Transscaphoid, Transtriquetral Perilunate Wrist Dislocation With Avascular Changes of the Lunate.

Current Concepts Review. Carpal Instability.

Chronic capitolunate instability

Dislocations of the lunate with and without fracture of the scaphoid.

Carpometacarpal dislocations. Long-term follow-up.

Open reduction of carpal dislocations: indications and operative techniques.

Transient vascular compromise of the lunate after fracture-dislocation or dislocation of the carpus.

Difficult wrist fractures. Perilunate fracture-dislocations of the wrist.

Late treatment of a dorsal transscaphoid, transtriquetral perilunate wrist dislocation with avascular changes of the lunate.

Median-nerve neuropathy associated with chronic anterior dislocation of the lunate.

Posttraumatic ulnar translation of the carpus.  

Repair and/or reconstruction of scapholunate interosseous ligament in lunate and perilunate dislocations.

Correlation between clinical results and carpal instabilities in patients after reduction of lunate and perilunate dislocations

Perilunate dislocations and fracture-dislocations: a multicenter study
Perilunate dislocation and fracture dislocation: a critical analysis of the volar dorsal approach

Radiocarpal Dislocations: Classification and Proposal for Treatment. A Review of Twenty-seven Cases 

Treatment of isolated perilunate and lunate dislocations with combined dorsal and volar approach and intraosseous cerclage wire.

Perilunate Fracture–Dislocations of the Wrist: Comparison of Temporary Screw Versus K-Wire Fixation. 

The Mechanism of Ulnar-sided Perilunate Instability of the Wrist: A Cadaveric Study and 6 Clinical Cases