EXAMINER: What do these radiographs (Figures 13.1a and 13.1b) show?

CANDIDATE: These are PA and lateral radiographs of a wrist showing a lunate dislocation.

EXAMINER: What signs are there on the radiographs which point to this diagnosis?

CANDIDATE: There is disruption of Gilula’s lines on both views. The lunate can be seen sitting palmarly in the carpal tunnel.

EXAMINER: What do you suppose was the mechanism of injury?

CANDIDATE: This is usually caused by high-energy trauma such as a road traffic collision or a fall from a height.

EXAMINER: Why do you infer that?

CANDIDATE: This is a hyperextension injury in ulnar deviation: a Mayfield stage 4. Lower-energy hyperextension injuries might result in scapholunate ligament injury. In order to dislocate the lunate, this patient must have torn the scapholunate ligament, dislocated the lunocapitate joint, torn the lunotriquetral ligament and the dorsal radiolunate ligament. The only remaining ligamentous attachments are the strong volar radiocarpal ligaments.

EXAMINER: How will you manage this injury?

CANDIDATE: This patient has sustained high-energy trauma, so first I would treat any life-threatening injuries. As regards the wrist, this is an emergency as the median nerve is likely stretched over the dislocated lunate. This needs an emergent reduction in A&E.

EXAMINER: How will you reduce it?

CANDIDATE: Before reduction I would assess and document the neurovascular status of the hand with particular attention to the median nerve. The patient needs to be relaxed and sedated. I would apply traction to the limb to stretch the soft tissues; this is best achieved using gravity and finger traps. I would then hyperextend the wrist and push the lunate back onto the radius with my thumb. Then, leaving my thumb on the lunate to prevent displacement, I would distract and flex the wrist to lift the capitate back onto the lunate. I would then reassess and document the neurovascular status, apply a below-elbow plaster backslab and obtain plain radiographs to confirm reduction.

EXAMINER: What if you can’t reduce it?

CANDIDATE: If I cannot reduce this in A&E then the patient will need to go to theatre for reduction. Ideally this should be done by someone who can proceed to definitive fixation, but reduction should not be delayed for this as it is imperative that the dislocation is reduced to protect the neurovascular structures. I would attempt a closed reduction under general anaesthetic in theatre with an image intensifier, then proceed to open the wrist if I cannot achieve reduction.

EXAMINER: How will you open the wrist?

CANDIDATE: Palmarly first. I would do an extended carpal tunnel release which should relieve pressure on the median nerve and should enable me to reduce the dislocation, which is my main objective. If I still cannot reduce the dislocation, I will open the dorsum of the wrist. This is done with a midline longitudinal incision centred on Lister’s tubercle. I would incise the third extensor compartment, lift EPL from its bed, then dissect into compartments 2 and 4 to reveal the dorsal carpal ligaments. I would then use a Berger flap to open the wrist joint.

EXAMINER: Can you describe the Berger flap?

CANDIDATE: This is a ligament-preserving technique for opening the dorsum of the wrist. The incision splits the dorsal intercarpal ligament and radiotriquetral ligament in line with the fibres to form a radial-based triangular flap. When elevating the flap, it is important to protect the intrinsic carpal ligaments, particularly the scapholunate ligament which is most significant dorsally, although in this case I expect it to be torn.

EXAMINER: OK, so let’s assume you are a hand surgeon and are prepared to manage this definitively. How will you proceed?

CANDIDATE: I would first reduce the carpus, by direct means if necessary, and assess the damage. I expect the scapholunate ligament and lunotriquetral ligaments to be torn. I would need to stabilize the carpal bones in their normal orientation using K-wires as joysticks and further K-wires to transfix the carpus. Once the bony anatomy is restored, I would repair the scapholunate ligament, with a bone anchor if necessary, then return to the volar wrist wound where I would pull the contents of the carpal tunnel to the radial side to protect the recurrent motor branch of the median nerve. I would anticipate a rent in the volar capsule in conjunction with a volar lunotriquetral ligament tear which I would repair directly with sutures. I would apply a backslab postoperatively and emphasize the importance of elevation as these injuries tend to swell a lot.

EXAMINER: What are the long-term outcomes of this injury?

CANDIDATE: This is a severe injury and the wrist will never be normal. As long as it was treated promptly, I would expect the median nerve to make a full recovery, although this is not guaranteed and depends on the degree of primary injury. Further surgery is required to remove the K-wires at 8 weeks, then intensive physiotherapy will be required to optimize function. The wrist will likely be quite stiff (about 50% normal movement) but should be stable and strong enough to return to most kinds of work. As the joint has been injured, there is a risk of degenerative change in the long term which may require salvage surgery.

EXAMINER: This 15-year-old boy noticed that he couldn’t flex the end of his ring finger after a rugby match. What does the radiograph (Figure 13.2) show?

CANDIDATE: This is a lateral radiograph of a finger with a small avulsed fragment of bone sitting volar to the proximal phalanx. This is consistent with an avulsion of the FDP from the distal phalanx known as jersey finger.

EXAMINER: What is the typical mechanism of injury?

CANDIDATE: An extension force is applied to the finger while in active flexion. This is typical of a hand that is grasping a rugby jersey which is jerked from the patient’s grip.

EXAMINER: What is the anatomy of the flexor mechanism to the ring finger?

CANDIDATE: There are two flexor tendons. The FDP originates from a common muscle belly on the ulna and interosseous membrane and inserts distally into a broad footprint at the base of the distal phalanx. The FDS has its origin from the medial elbow and the radius. Each tendon has its own muscle belly. The tendon splits into two and inserts into the base of the middle phalanx. The FDP passes from deep to superficial through the two slips of FDS at Camper’s chiasm.

EXAMINER: What is the innervation of these muscles?

CANDIDATE: In the ring finger, the FDP is ulnar innervated and the FDS is median innervated. The median nerve supplies all FDS and, via the AIN, the radial two FDPs. The ulnar nerve supplies the ulnar FDPs.

EXAMINER: How would you classify this injury?

CANDIDATE: According to Leddy and Packer this is a grade 2 injury. Grade 1 retracts to the palm, grade 2 to the PIPJ, grade 3 involves a large fragment which sticks at the DIPJ, and grade 4 involves an avulsed fragment of bone which dissociates from the tendon, a so-called ‘double avulsion’.

EXAMINER: In this grade 2 injury, what is preventing further proximal migration of the fragment?

CANDIDATE: The vinculae.

EXAMINER: How will you treat this young man?

CANDIDATE: I would recommend surgery to repair the avulsed tendon and restore active flexion. I would counsel him that there is a prolonged recovery period involving splintage and physiotherapy for around 3 months. Alternatively, he may opt for non-operative management and rehab the finger with physiotherapy, accepting that active flexion will remain absent at the DIPJ. If he later finds the DIPJ unstable, he could have this fused.

EXAMINER: What other possible sequel is there of treating this non-operatively?

CANDIDATE: He may develop a lumbrical plus finger.

EXAMINER: What does that mean?

CANDIDATE: The origin of the lumbrical is on the FDP tendon. The function of the lumbrical is to flex the MCP joint and extend the IP joints. If the origin of the lumbrical migrates proximally such as in FDP avulsion, this applies an extension moment at the IP joints. The patient cannot actively flex the DIP joint due to the avulsion, but also struggles to flex the PIP joint with FDS due to the intrinsic tightness.

EXAMINER: What technique would you use to repair his tendon?

CANDIDATE: After proper consent and a regional or general anaesthetic, I would open the finger with a Brunner incision. I would identify the avulsed tendon and deliver it through the pulley system back to the footprint. I expect I may need to vent the pulley system and would probably need to fully release A3 but would take care not to release all of either A2 or A4 as these are the key restraints to prevent bowstringing. I would ensure that the anatomy of the chiasm is correct and that the FDP is appropriately passing between the FDS slips. I would take care to handle the tendon as little as possible and would site my core Bunnell suture early and use this to deliver the tendon through the pulley system.

EXAMINER: How would you anchor the tendon to the bone?

CANDIDATE: The bony fragment is too small to fix directly, but I wouldn’t excise it as it may improve the healing potential at the insertion site. There are various techniques described for anchoring the tendon, but the one I use is to drive two hollow needles though the phalanx from volar to dorsal, distal to the lunula, and pass the sutures through them and tie them over a button on the nail plate.

EXAMINER: What is the quadregia effect?

CANDIDATE: The FDP tendons share a common muscle belly. If the FDP to the operated finger is repaired too tight, as the patient attempts to make a fist, the operated finger contacts the palm first. The other fingers are unable to achieve maximal flexion as they are prevented from contracting any further.

EXAMINER: How would you rehab the patient after his tendon repair?

CANDIDATE: He needs early hand therapy with an early active motion protocol. This is to protect the repair and prevent adhesions forming.

EXAMINER: Do you know of any evidence showing superiority of early active motion over static or passive protocols?

CANDIDATE: There was a systematic review by Star et al. published in the American Journal of Hand Surgery in 2013. They reported a higher risk of finger stiffness in the passive protocols and a higher risk of tendon rupture in early active motion protocols. Despite this, they suggested that modern improvements in surgical technique, materials, and rehabilitation now allow for early active motion rehabilitation that can provide better postoperative motion while maintaining low rupture rates.