Lunate and Perilunate Dislocations

Mayfield's classification describes the sequential failure of the perilunate structures from the radial side to the ulnar as the wrist is loaded in hyperextension, ulnar deviation and intercarpal supination.

Stage I, scapholunate dissociation. The scapholunate interosseous ligament is disrupted. The scaphoid flexes and the lunate extends, the beginning of a DISI pattern, and the PA radiograph shows a widened scapholunate interval of over 3mm, the Terry Thomas sign.

Stage II, capitolunate dissociation. The space of Poirier disrupts and the capitate dislocates dorsally relative to the lunate. The lunate still articulates with the radius as the ligament failure continues.

Stage III, perilunate dislocation. The lunotriquetral ligament fails and the entire carpus dislocates dorsally around the lunate. The lunate remains in the lunate fossa of the radius, which is the key point, and no longer articulates with the capitate; the lateral radiograph shows the capitate displaced dorsally.

Stage IV, lunate dislocation. The dorsal radiocarpal ligament, the final ligament, fails. The lunate rotates and tips volarly out of the fossa into the carpal tunnel, the spilled teacup, and a Stage IV injury with nerve symptoms is a surgical emergency.

The injury reaches the lunate by one of two routes. The lesser arc passes through ligament only: the scapholunate ligament, the capitolunate space (the space of Poirier) and the lunotriquetral ligament, with no fracture. The greater arc passes through bone, and the fracture names the injury: trans-scaphoid, trans-radial styloid, trans-capitate or trans-triquetral. The trans-scaphoid perilunate fracture-dislocation is the most common pattern, 61% of Herzberg's whole series.

Why the distinction matters. A greater arc injury needs fracture fixation as well as ligament repair, but bone heals more reliably than ligament. The lesser arc injury, with nothing but ligament to heal, is the more challenging reconstruction and the one that may need ligament reconstruction later. The pooled data in the evidence section point the same way: the pure dislocation is the injury that loses reduction after fixation, and the one that fares worse when chronic.

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Time since injury decides what is still possible: whether the carpus will reduce closed, whether the ligaments can be repaired or must be reconstructed, and how good the result can be.

Initial assessment. Before anything else:

• Neurovascular status immediately, the median nerve above all
• Mechanism of injury
• Skin integrity and tension
• PA, lateral and oblique radiographs
• Splint in the position of comfort initially

When to reduce emergently. Any of these means the wrist is reduced now:

• Acute carpal tunnel syndrome (Stage IV lunate dislocation)
• Skin compromise or threatened skin
• Open injury
• Vascular compromise

Closed reduction. Under a regional block or procedural sedation, the manoeuvre reverses the injury: longitudinal traction through the fingers first, then the wrist extended to disengage the carpus and recreate the deformity, thumbs over the dorsal carpus applying pressure, and the carpus pushed volarly while the wrist is flexed. Take immediate post-reduction films to verify the reduction.

After reduction. Splint in neutral, repeat the neurovascular examination, confirm the reduction on radiographs, and arrange definitive surgery within 24-72 hours. Closed reduction is temporising only: every perilunate and lunate dislocation requires definitive surgical treatment, because closed treatment alone results in unacceptable rates of instability and arthritis.

If closed reduction fails, interposed tissue is preventing it, and the answer is emergent open reduction in theatre.

Timing. Emergent if closed reduction has failed or acute carpal tunnel syndrome is not relieved; urgent, within 24-72 hours, for most closed injuries after a successful closed reduction. The best outcomes are reported with surgery within 7-14 days, the acute window of the timing classification. Note that van der Oest's review in the evidence section draws its acute line at 7 days and finds outcomes inferior with any delay and worst beyond 6 weeks, so within the window, earlier is better.

Approach. The combined volar and dorsal approach is the one widely taught, and each half has a job: the volar approach, performed first, for carpal tunnel release and direct visualisation of the lunate; the dorsal for ligament repair and definitive fixation. It is not a rule for every wrist. Liechti's pooled data in the evidence section found more complications after a combined dorsopalmar approach than after an isolated dorsal one (17.4% versus 8.4%); that comparison is observational and almost certainly confounded, the bigger operation being chosen for the worse wrist, but it means the combined exposure is chosen for its indications, a lunate in the tunnel and a nerve to decompress, rather than because it is always superior.

Carpal tunnel release. Emergency decompression is mandatory when the lunate lies in the tunnel and is considered for a perilunate dislocation with nerve symptoms. At the definitive operation the carpal tunnel is released in every case, symptoms or not. Routine versus selective release remains a point of practice variation, and Wickramasinghe's series, which established how common the neuropathy is, does not report whether release improved recovery.

Fixation strategy. The arc decides the operation. A lesser arc injury is a ligament repair with K-wire protection; a trans-scaphoid greater arc injury is fixed fracture first, and because the intact proximal scaphoid fragment preserves the scapholunate ligament, the ligament that still needs repair is the lunotriquetral. The steps are set out under Surgical Technique.

Two to six weeks. Open reduction is required, and the combined approach is mandatory. Primary ligament repair is still possible but technically challenging, and the patient should know that outcomes are worse than after acute treatment.

Over six weeks. The dislocation is chronic. Ligament reconstruction rather than primary repair may be required, a staged reconstruction should be considered, and counselling covers the significantly worse outcomes.

Established malunion, over three months. Salvage options only:

• Proximal row carpectomy, if the capitate articular surface is intact
• Four-corner fusion (scaphoid excision with capitate-lunate-hamate-triquetrum fusion)
• Total wrist fusion, as the last resort
• Wrist denervation, for pain without fusion

Every chronic case has a CT for detailed assessment; MRI may help assess ligament quality and plan reconstruction. Extensive preoperative counselling about the limited outcomes is essential.

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Positioning. Supine, arm on a hand table, upper-arm tourniquet, and exsanguination by elevation rather than an Esmarch bandage where there is concern that a bandage would displace a fracture. The volar approach is performed first and the dorsal second.

Incision. An extended carpal tunnel incision from the distal palm to the proximal forearm, curving radially at the wrist crease to avoid a neuroma.

Dissection. In order:

• Identify and protect the palmar cutaneous branch of the median nerve
• Open the transverse carpal ligament completely, distal to proximal
• Release the volar forearm fascia proximally if needed
• Decompress the median nerve completely and inspect it for damage
• Visualise the volar wrist capsule

What the volar side gives you. The volar ligaments, usually disrupted in these injuries, can be assessed here. A lunate that is grossly displaced volarly can be reduced from this side, and any interposed tendon or capsule blocking reduction is identified and removed.

Incision. Longitudinal, centred over Lister's tubercle, from the mid-metacarpal level to the distal radius. Identify and elevate extensor pollicis longus from the third compartment and retract it radially out of harm's way, then perform a ligament-sparing capsulotomy between the third and fourth compartments, the preferred option, or raise a distally based capsular flap for later repair.

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Reduction. Clear the haematoma and debris from the joint and identify the lunate, which may be rotated 90-180 degrees. In a Stage IV injury reduce the lunate into its fossa first, then reduce the capitate onto the lunate with gentle dorsal-to-volar pressure. Assess the scapholunate interval for widening and the lunotriquetral interval for disruption.

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Lesser arc. A pure perilunate injury is repaired ligament by ligament and protected with wires:

1. Repair the scapholunate ligament with suture anchors, 2-3 anchors placed in the scaphoid and lunate
2. Place 2 K-wires across the SL interval, scaphoid to lunate
3. Repair the lunotriquetral ligament with suture anchors in the same way
4. Place 1-2 K-wires across the LT interval, lunate to triquetrum
5. Consider an additional scaphocapitate K-wire for stability
6. Consider a dorsal capsulodesis to augment the repair

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Trans-scaphoid greater arc. The fracture comes first:

1. Reduce and fix the scaphoid fracture with a headless compression screw, by a volar or dorsal approach
2. The scapholunate ligament is preserved by the intact proximal scaphoid fragment
3. Repair the lunotriquetral ligament, which is still disrupted despite the scaphoid fracture
4. K-wire the LT interval, lunate to triquetrum
5. Add a scaphocapitate K-wire if needed for additional stability

Wires. All K-wires are at least 1.6mm in diameter, left prominent outside the skin, cut and bent, and covered with a sterile dressing, so that removal in clinic is easy.

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Dorsal wound. Repair the dorsal capsule if a capsular flap was raised, close the extensor retinaculum layer, then the subcutaneous layer and the skin with nylon sutures.

Volar wound. Leave it open or close it very loosely. The carpal tunnel release site is never closed tightly, to avoid compressing the median nerve.

Immobilisation. A well-padded volar splint with the wrist in neutral, including the metacarpophalangeal joints and leaving the fingers free for range of motion exercises, with strict elevation postoperatively.

Global Epidemiology

Perilunate injuries are rare but consistently under-recognised. They constitute roughly 7% of all carpal traumas in a pooled systematic review (van der Oest 2022), and pure carpal-bone dislocations are far less common than the much more frequent scaphoid fracture in population series: in a Singapore cohort of 149 patients with 162 carpal fractures the scaphoid accounted for 99, and only 10 patients had multiple carpal fractures, of which 4 were perilunate fracture-dislocations (Hey 2011, PMID 21276891). Across the literature the demographic is strikingly uniform worldwide: young men injured by high-energy mechanisms (falls from height, road trauma, sport), reflecting the force required to fail the perilunate ligamentous ring. Hey's cohort matches that picture - 132 of 149 were male and 116 were under 40 - and found high-energy mechanism the only parameter associated with multiple carpal fractures (p=0.009).

Guideline & Consensus Landscape

No major society publishes a disease-specific clinical practice guideline dedicated to perilunate/lunate dislocations; management rests on body-of-evidence consensus rather than formal AAOS/NICE guidance. The points of broad international agreement are summarised below.

Registries

There is no dedicated international perilunate-injury registry, and arthroplasty registries (AOANJRR, the UK NJR, the American AJRR) do not capture these soft-tissue/carpal injuries because they are not arthroplasty procedures. The best population-level data therefore come from trauma databases and pooled systematic reviews (Liechti 2023; van der Oest 2022) rather than from a formal registry.

Practice Variation & Service Delivery

Internationally, the dominant modifiable factor is timely recognition and referral rather than choice of implant. Practice variation centres on approach (combined dorsal-volar versus dorsal-only versus arthroscopic-assisted reduction and fixation) and on routine versus selective carpal tunnel release; pooled data favour less invasive techniques where the injury pattern allows (Liechti 2023). High-income trauma systems with 24/7 hand-surgery cover and ready CT access achieve earlier definitive fixation, whereas in many settings inter-hospital transfer from regional centres is the rate-limiting step to surgery within the optimal window. Beyond operative fixation, structured hand-therapy rehabilitation drives final outcome, yet its availability is uneven, with rural and remote regions most affected by limited access.