Introduction
Carpal dislocations constitute a small group of injuries to the wrist. Compared to distal radius fractures and the less common scaphoid fractures, they are rare injuries. This is probably also because these are high-energy traumas resulting from motorbike accidents or falls from a great height. Such high-energy traumas are naturally less common than a simple fall on the outstretched hand.
Despite the rarity of carpal dislocations, their clinical significance should not be underestimated. Due to their complexity, a thorough evaluation of the instabilities with appropriate treatment of all injured structures is necessary to achieve an acceptable result. Complete restoration of function is not a given in these cases.
The clinically relevant carpal dislocations are perilunate dislocation and perilunate fracture-dislocation, radiocarpal dislocations, axial dislocations, and isolated carpal bone dislocations.
Carpal dislocations belong to the groups of carpal nondissociative instability and complex intercarpal instabilities in the Mayo classification. It distinguishes carpal instability dissociative, where only intercarpal ligaments such as scapholunate (SL) or lunotraquetral (LT) ligaments are injured, from carpal instability nondissociative, where intercarpal ligaments are not torn but the ligaments that stabilize the whole proximal and distal row of the wrist are disrupted and unstable. This includes radiocarpal dislocation. If both the ligaments within a carpal row and the ligaments between the carpal rows are torn, a carpal instability complex is present. Apart from radiocarpal dislocations, all the clinical manifestations mentioned above are carpal instability complex injuries.
Perilunate dislocations and perilunate fracture-dislocations are the most common carpal dislocations. Radiocarpal dislocations are most often associated with distal radius fractures because the radiocarpal ligaments are strong and often tear loose with a bony fragment ( Fig. 13.1 ). Compared to the fist mentioned groups, axial instabilities and isolated carpal dislocations other than in the lunate are rare.
Perilunate dislocations
Basics and classifications
Of the carpal luxations, the perilunate ones are the best known and most common. Perilunate luxations can be divided into subgroups.
One criterion for differentiation is the direction of dislocation. A dorsal dislocation is when the proximal capitate pole is dorsally positioned in relation to the lunate bone. This is the predominant direction of dislocation and is much more common than palmar dislocation, where which the head of the capitate is anterior to the lunate. The position of the lunate in relation to the radius does not play a role in differentiating between dorsal and palmar luxations. Thus a perilunate dislocation with dislocation of the lunate in the palmar direction into the paronal space is still a dorsal dislocation if the capitatum lies dorsal to the lunate ( Fig. 13.2 ). The distinction between palmar and dorsal dislocations applies to pure lunate dislocations as well as to combined fracture-dislocations.
The term perilunate dislocations (PLD ) describes pure ligament injuries, whereas combined fracture-dislocations are called perilunate fracture-dislocation (PLFD) .
Mayfield et al described progressive perilunate instability in four stages by studying 32 cadaveric wrists. The force was applied with increasing wrist extension, ulnar deviation, and supination of the carpus. The first stage was rupture of the SL ligament (stage 1), followed by dislocation in the midcarpal joint due to rupture of the extrinsic radial ligaments (stage 2), and then rupture of the LT ligament (stage 3). Stage 4 represents the complete dislocation of the lunate. The direction of injury was always from radial, around the lunate, to ulnar and never vice versa ( Fig. 13.3 ).
Compared to PLD, the force vectors run partly through the other carpal bones in PLFD. Because the course of injury in PLD is around the lunate, Mayfield called this a lesser arc injury, whereas he called PLFD, where the force vector passes through the carpus and/or radius, a greater arc injury . Bain added to this the translunar dislocation in which fractures of the lunate (usually edge fractures with perilunate dislocation) occur. , He then referred to this line of injury as lunar arc injury ( Fig. 13.4 ).
The most common type of PLFD is the transscaphoid perilunate fracture-dislocation, where the line of injury passes through the scaphoid and around the lunate, with rupture of the LT ligament. For this injury, the term De Quervain’s fracture-dislocation is also commonly used ( Fig. 13.5 ). A radial styloid fracture may also occur, and this injury is a transstyloid-transcaphoid PLFD. The combination of radial styloid avulsion with perilunate luxation is possible as well. The proportion of a radius fracture can extend far beyond a styloid injury ( Fig. 13.6 ). Similarly, a fracture of the triquetrum indicates that the injury line does not run through the LT ligament but through the triquetrum. Another special form of the greater arc injury is the scapho-capitate syndrome, also known as Fenton syndrome, in which the injury line runs through the proximal pole of the capitate, resulting in 180 degrees rotation of the pole (see Chapter 14 Other Carpal Fractures and Carpal Disorders).
The classification of PLDs and PLFDs is difficult because although recurrent injury patterns occur, such as the frequent De Quervain’s fracture dislocation, a large number of combined injuries are possible and unique, which make the overall group heterogenous and not easily comparable. Herzberg et al confirmed this with their multicenter analysis of 166 cases.
Simultaneous complete scapholunate ligament injuries have also been described in PLFD in combination with scaphoid fractures , ( Fig. 13.7 ). When only the scaphoid fracture was treated, more SL instabilities developed than when the fracture and ligament injury were treated together. These results indicate that the forces on the carpus can also be more complex than covered in the concepts of greater and lesser arc injuries.
Diagnosis
As PLDs and PLFDs are usually high-energy injuries, pain at the wrist and limitation of movement are obvious. Nevertheless, the simpler injuries in this group, such as dorsal PLDs, are sometimes overlooked. In the series of Herzberg et al, only 61% of the patients were definitively treated within the first week, and in Minami et al only 2 of 32 patents were found to be treated within the first 4 weeks. The main problem is surely that the injuries are uncommon and are not considered when analyzing the radiographs. The injury can easily be overlooked on superficial examination of the anterior-posterior view. Close examination of the lateral radiograph usually yields the diagnosis. Anatomical knowledge of the carpus is a prerequisite. Early diagnosis should be made carefully to ensure timely treatment. Paresthesia in the median nerve area is often present because carpal dislocation may compress the median nerve.
X-rays of the wrist should be performed in two planes. If the situation is unclear, two oblique radiographs are also helpful in establishing the diagnosis. On the AP view, the interruption of the Gilula arches is an indication of an injury, as well as the triangular presentation of the lunate due to its rotation. In greater arc injuries, the fractures are usually obvious and lead to the diagnosis. The most important x-ray view is the lateral one, where the interruption of the straight alignment of the metacarpal-capitate-lunate radius is clearly interrupted. Observing and evaluating this line usually leads to the correct diagnosis ( Fig. 13.8 ). CT scans may be used. Their 3D reconstructions provide further information about the exact injury pattern and injured bones. The MRI does not play a role in acute diagnostics.
Treatment
Treatment of PLD and PLFD should be considered an emergency because the malposition can lead to damage of the articular cartilage. A delay of weeks not only damages the joint surfaces but often leads to a retraction of both the injured and intact ligaments. Delay makes reduction of the carpus and repair or reconstruction of the ruptured ligaments difficult or impossible. Treatment after 6 weeks leads to poorer results. , Treatment on the day of injury is ideal. If there is not a specialist available, it preferably should be done the next day.
If competent and sufficient surgical treatment of the disrupted ligaments and any fractures is not possible shortly after injury, at least the carpus should be reduced immediately. Analgesia and/or sedation is required for this, as traction and countertraction must be exerted on the wrist. Continuous traction for about 10 minutes is recommended. This is followed by an attempt of reduction using the Tavernier method. Under traction, the wrist is first extended and then brought into flexion with palmar stabilization of the lunate to reduce the capitate against the distal articular surface of the lunate. Fluoroscopy confirms successful reduction. The definitive treatment, such as ligament repair and treatment of fractures, should be carried out as soon as possible.
Definitive treatment can be performed by open surgery from the dorsal side, from both the dorsal and palmar sides, or by arthroscopy. Conservative treatment of the reduced dislocation is not recommended, as the results are clearly worse than with surgical repair. , , Open surgery has the most options for treatment. The individual injuries tears can be seen directly and treated.
In PLD, the first step is realignment of the carpal bones. Due to the combination of SL instability, LT instability, and extrinsic ligament ruptures in the midcarpal joint, reduction and Kirschner (K) wire fixation of the intercarpal joints are often difficult and need to be done step by step. To secure the sutures of the ruptured ligaments, K-wire fixation between scaphoid and lunate, scaphoid and capitate, and triquetrum and lunate is mandatory to achieve a stable result ( Fig. 13.9 ).
In PLFD, the strategy is to achieve a preliminary reduction, fix the fractures, and then reduce the carpus and secure the bones in their reduced positions with K-wires. When the alignment is correct, the ends of the ligaments are close together and can easily be sutured. Often, the carpus is highly unstable, and it is helpful to use initially a Lindscheid-wire (wire from distal radius to lunate) to fix the lunate in a correct position, especially in the lateral view using fluoroscopy. Then, the other carpal bones can be aligned with the lunate.
For transscaphoid perilunate instability the scaphoid should be treated with either a compression screw or with two K-wires to maintain reduction. The lunate should be transfixed with K-wires to the adjacent carpals to maintain reduction. The volar and dorsal ligaments can be sutured.
In the case of a radius fracture, the distal radius should be stabilized by an osteosynthesis (plates, screws, or K-wires) to align the carpal bones ( Fig. 13.10 ). A double (palmar and dorsal) or a single approach can be used. Trumble reported good results using a double approach for treating perilunate dislocations. This is easier than trying to repair everything through a single approach. In cases with multiple injured structures, a single dorsal approach usually is sufficient if the surgeon can achieve a closed reduction and address the radius fracture, scaphoid fracture, and SL ligament repair with K-wire fixation of the reduced carpal bones ( Fig. 13.7 B). Only when the lunate is dislocated into the Parona space, closed reduction is often not successful, and these patients need an additional palmar approach.
The treatment can also be performed arthroscopically. Kim reported 20 arthroscopic treatments of PLD and PLFD. For closed reduction, K-wires were used as joysticks to reduce the bones, which were then fixed by K-wires under arthroscopic and fluoroscopic control. Scaphoid fractures were also reduced, and 10 were fixed with a cannulated headless compression screw. The results showed 79% excellent and good results and four poor results. Other publications by Oh et al and Chow and Ho demonstrated that the arthroscopic treatment is feasible. , The meticulous reduction of the carpal bones leads to reduction of the ruptured ligaments, so that healing in the correct anatomical position is possible.
Aftercare
Follow-up treatment corresponds to the time the ligaments need to heal. Recommended wrist immobilization is for at least 8 to 10 weeks with the left in place. As the forces within the carpus are large, stable ligament healing is not guaranteed earlier. The fingers, including the metacarpophalangeal joints, should be exercised from day one. The disadvantage of the necessary long period of immobilization of the wrist is stiffening, which after removal of the K-wires must be treated diligently with therapy, usually for at least 3 months.
Prognosis
Recovery of full function is not to be expected with these complex severe injuries. With correct treatment, i.e., surgical treatment of all injured structures with reduction of the normal carpal alignment, quite acceptable results can be achieved. Herzberg and Forressier published in 14 cases with 8-year follow-up having a Mayo wrist score of 79. Trumble found recovery of 80% range of motion and 77% strength compared to the opposite side. ,
Delayed treatment has poorer results due to cartilage damage in the dislocated position and shrinkage of the ruptured ligaments. In a follow-up of 73 patients with a follow-up of at least 15 years, the extension flexion of the wrist was 8% of the opposite side. However, the range was large, 35 to 140 degrees. Predicting the functional outcome is therefore impossible in individual cases and should not be too positive. Up to 70% of patients develop osteoarthritis. However, the radiological situation does not generally correlate with function and pain.
Radiocarpal dislocation
Dislocation of the proximal row from the articular surface of the radius accounts for 0.2% of all dislocations. Radiocarpal dislocation represent a high-energy trauma from falls and motor vehicle and industrial accidents, which can occur with or without fractures of the wrist. The concomitant disruptions of strong ligaments support of the carpus produce a radiocarpal dislocation. Poor outcomes are often due to radiocarpal instability and secondary ulnar translation.
Classifications
Radiocarpal dislocations are classified based on the ligamentous instabilities in the proximal row in 1985 by Moneim et al. Type I injuries have an intact proximal row, and type II injuries have an associated tear of either the SL or LT ligament.
Dumontier and colleagues proposed a classification system based on the status of the radial styloid in 2005. Type I has either no radial styloid fracture or only a small avulsion fracture. Type I is exceedingly uncommon and is usually associated with ulnar translation of the carpus. Type I injuries usually are the result of severe shear and rotational forces in young subjects. Type II has an associated radial styloid avulsion fracture greater than one-third width of the scaphoid fossa. Type II injuries are seen more frequently than type I, and usually the reduction of the carpus after radial styloid fixation is maintained due to an intact radioscaphocapitate ligament ( Fig. 13.11 ).
