Role of Arthroscopy in the Treatment of Carpal Fractures and Nonunion

8 Role of Arthroscopy in the Treatment of Carpal Fractures and Nonunion

Peter Jørgsholm

Abstract

Arthroscopy has resulted in a new three-dimensional (3D) and dynamic understanding of the wrist joint and carpal joints and a better comprehension of the pathomechanism of carpal fractures and ligament injuries. MRI and CT scans have added better diagnosis of carpal fractures and injuries and combined with arthroscopy a possibility of a tailored treatment plan for these often complex injuries. This new knowledge can benefit the patients and give them a faster return of wrist function.

Keywords: arthroscopy, scaphoid fracture, carpal fracture, scapholunate (SL) ligament injury, lunotriquetral (LT) ligament injury, scaphoid nonunion, cannulated screw fixation, bone grafting

8.1 Introduction

The most common carpal fracture is scaphoid fracture followed by capitate and triquetral fracture 1,2 ( Fig. 8.1). Combined carpal fractures are not uncommon (12%) and often seen after high-energy trauma—probably as part of a greater arc injury presenting as a perilunate injury nondislocated (PLIND).³ The most frequent carpal fracture combination is that of a scaphoid and capitate fracture (8% of scaphoid fractures). The sensitivity of radiography is low in diagnosing carpal fractures especially in children and MRI or CT is often necessary to get the diagnosis and should always be considered when adequate trauma is involved.^1,2

After the introduction of wrist arthroscopy in the 1980s, the technical advances of scopes, cameras, instruments, and traction devices as well as fluoroscopes and cannulated screws have made arthroscopic reduction and internal fixation (ARIF) possible. The stability of fractures and ligament injuries is visualized in a live 3D fashion and the surgeon can tailor a treatment and postoperative mobilization for each individual injury. In the case of late presentation and bone deficit, techniques for percutaneous bone grafting are increasingly used particularly in scaphoid nonunions.

8.2 Indications

It is generally accepted that proximal pole fractures of the scaphoid have a poor prognosis when treated conservatively with one-third going into nonunion.4 Many therefore offer surgery to patients with fracture in the proximal third of the scaphoid. Proximal pole fractures are easily approached from dorsal when using a traction tower and often quite stable and nondisplaced.

Fig. 8.1 Two hundred and sixty-two carpal fractures diagnosed by MRI in 403 patients presenting with posttraumatic radial-sided wrist pain: 75% scaphoid fractures, 10% capitate fractures, 8% triquetral fractures, and 3% hamate fractures.

Displaced (> 1 mm) fractures have a nonunion rate of 27% and require twice as long to unite as nondisplaced (13 weeks).5 Comminuted fractures have a nonunion rate of 11% with 60% longer time to union (10 weeks).⁵ Displaced and comminuted scaphoid fractures are more difficult to treat by ARIF as the reduction can be challenging. Greater arc injuries need reduction and stability to unite⁶ and several reports on arthroscopic approach to these injuries are reported in recent years.^7,8

The current recommendations for surgical treatment of scaphoid fractures are listed in Table 8.1.

Other carpal fractures and intercarpal ligament injuries will reveal during MRI, CT, and the arthroscopic procedure. At arthroscopy, the carpal and fracture stability can be tested by probing carpal bones and fractures fragments, respectively. A tailored treatment can then be implemented accordingly. In some cases, multiple fractures are diagnosed by MRI ( Fig. 8.2) and found stable at arthroscopy and consequently treated with a cast. These patients are checked at 6 weeks and union estimated by CT scans. In other instances, both unstable scaphoid fractures and capitate fractures need ARIF ( Fig. 8.3). In some cases, a combination of ARIF and percutaneous pinning is necessary, for example, in the simultaneous scaphoid waist fracture and complete SL ligament injury which is seen in 24%¹⁰ ( Fig. 8.4). Even carpal fractures other than scaphoid are sometimes found unstable and therefor suitable for ARIF ( Fig. 8.5).

Table 8.1 Indication for surgical treatment of scaphoid fractures (ORIF or ARIF)

1. Displaced fractures (> 1 mm/15-degree palmar)^a

2. Comminuted fractures^a

3. Proximal pole fractures (proximal third)^b

4. Transscaphoid perilunate dislocation

5. More than one fracture (PLIND?)

6. Late diagnosed fractures (> 4 weeks)^b

7. Bilateral fractures

8. Multitrauma

Abbreviations: ARIF, arthroscopic reduction and internal fixation; ORIF, open reduction internal fixation; PLIND, perilunate injury nondislocated.

^aSignificant higher risk of nonunion (Grewal 2013 5).

^bSignificant higher risk of delayed union (Grewal 2013,5 2016⁹).

Fig. 8.2 STIR coronal of an ice hockey player’s wrist after a high-energy trauma. Nondisplaced scaphoid fracture found on CT. MRI reveals further nondisplaced fractures in radius, capitate, and triquetrum as indicated by arrows.

Fig. 8.3 Posteroanterior radiograph of ARIF with cannulated screws of simultaneous scaphoid and capitate fracture by dorsal approach.

Fig. 8.4 PA radiograph of ARIF with cannulated screw and temporary K-wire fixation of simultaneous scaphoid and SL ligament injury.

In the case of late presentation, particularly scaphoid delayed union and nonunion, a CT scan will give a hint of whether cleaning of fracture area and bone grafting will be necessary. This can be done with cancellous bone from radius in case of smaller defects and/or cysts, but if a larger defect or deformity is encountered, cancellous bone graft from the iliac crest is needed ( Fig. 8.6). The union rate after arthroscopic scaphoid nonunion procedures are similar or better than with open procedures.^11–15

Fig. 8.5 PA radiograph of ARIF with cannulated screws in simultaneous capitate and triquetral fractures by dorsal approach.

8.3 Method

8.3.1 Diagnosis

At least four radiographic views of the wrist and the scaphoid are recommended as initial investigation. If no fracture is found but clinical suspicion persists, MRI is indicated. MRI with a low-field scanner (> 0.23 T) is sufficient for diagnosis of carpal fractures and has a high sensitivity.1,2 If a carpal fracture is found on radiographs, CT scans are indicated to evaluate if any displacement or comminution exist. If a fracture reveal on MRI and any displacement is suspected, CT scan is indicated. CT scanning with axial sections of less than 0.6 mm and reconstructions in the coronal and sagittal planes defined by the long axis of the scaphoid and a 3D reconstruction will give detailed information of comminution or any displacement such as translation (step-off), gapping (diastasis), or angulation (humpback deformity). All this information enables the treating surgeon to decide on operation and provide him/her with a better 3D understanding of the injury.

8.3.2 Surgical Procedures

For arthroscopic procedures in the radiocarpal and the midcarpal joint, a small arthroscope (< 3 mm) and small joint instruments are needed. A traction device will help the surgeon to keep a constant distraction for easy joint access and support from the tower will minimize the need for an assistant surgeon ( Fig. 8.7). For reduction, a steady probe is important and 1.25-mm K-wires as joysticks or for temporary arthrodesis in intercarpal ligament injuries are needed. For internal fixation, cannulated screws in different dimensions and length should be available ( Fig. 8.8). A fluoroscope is a must for viewing and documenting fracture reduction and hardware position ( Fig. 8.9).

A dorsal approach is possible for most of the carpal fractures ( Fig. 8.10). In scaphoid fractures, flexion of the wrist will present the proximal pole for insertion of a guidewire through portal 3–4 with the scope inserted in portal 4–5 or 5–6 ( Fig. 8.11). Cleaning of debris, blood, and synovitis gives a better view and facilitates correct placement of a guidewire as palmar as possible and just adjacent to the SL ligament ( Fig. 8.12). The guidewire is directed toward the thumb base blindly and then controlled on fluoroscope. By introducing the guidewire into the trapezium, the wire is secured during drilling ( Fig. 8.13). Reduction is often obtained by traction and controlled by midcarpal arthroscopy. If not reduced, the guidewire is retracted to the fracture gap and by manipulating fragments eventually using probe, the blunt trocar, or K-wires as joysticks, the fracture can gently be reduced. In smaller wrists a 1.9-mm scope can be used for the midcarpal arthroscopy. The SL and LT intervals are controlled for any instability. Most capitate, lunate, triquetral, and some hamate fractures are seen by midcarpal arthroscopy. SL and LT ligament injuries are visualized by both radiocarpal and midcarpal arthroscopy. The triangular fibrocartilage complex (TFCC) injuries are viewed from radiocarpal ulnar portals. All joint surfaces in radiocarpal and midcarpal joint are carefully inspected for any lesions and eventually loose bodies removed. In case of simultaneous fracture and ligament injury, it is advisable to start with the fracture as the screws are more bulky and difficult to insert if several K-wires cross the joints. The combination of an unstable scaphoid waist fracture and a complete SL ligament injury creates a floating proximal scaphoid pole ( Fig. 8.14).

When bone grafting is indicated, standard instrumentations can be used for arthroscopic bone grafting ( Fig. 8.15). The bone is taken from the distal radius or iliac crest depending on the amount needed for filling the defect. A minimal invasive motorized drill system for taking morselized bone facilitates this procedure (Acumed, Oregon, United States) ( Fig. 8.16). If a humpback deformity has been reduced, plenty of packed cancellous bone graft will be able to fill and support the reconstruction. Tissue glue is sometimes added to protect the graft. The fragments are stabilized with screw(s) and/or K-wires.

If the fractures, delayed unions, or nonunions are considered arthroscopically stable after screw fixation, the patient is mobilized. If the fracture is not stable, the patient is immobilized in a below-elbow cast until union is greater than 50% as seen by CT scan.¹⁶ When any temporary intercarpal fixation is used, a protective plaster is applied until removal of K-wires usually around 6 weeks. The patient is not allowed to take part in any heavy lifting, contact sport, or risky activity before at least 50% union is seen on CT scan and 80% of contralateral grip force is regained.