Pediatric Wrist Injuries

INTRODUCTION

∗ I dedicate this chapter to my deceased father, Arthur M. Simmons, MD, who was my role model as a physician and as a parent

Pediatric wrist injuries were once thought to encompass only self-limited sprains and infrequent carpal fractures. However, over the past decade, the scope of these injuries has widened significantly. This is primarily due to a blossoming of the intensity of athletics and recreational activities and to the vastly improved visualization of the anatomy through advances in arthroscopy and imaging. This chapter highlights two of the more common soft tissue injuries in the pediatric wrist: triangular fibrocartilage complex (TFCC) injuries and scapholunate tears.

PEDIATRIC TRIANGULAR FIBROCARTILAGE COMPLEX TEARS

Since the 1980s, there has been widespread interest in TFCC injuries in adults. Only recently have these injuries been identified as a source of ulnar-sided wrist pain in children. Several theories exist for this lack of reporting of these injuries, including the increase in emphasis placed on high-level sports participation at younger ages and a lack of awareness by health care professionals. Furthermore, it is possible that recent advances in magnetic resonance imaging (MRI) technology have improved the diagnostic sensitivity of these injuries. A detailed understanding of this injury and the differences seen in the pediatric population is essential in the management of patients with these injuries.

Anatomy

Palmer and Werner described the TFCC as a complex of structures that includes the triangular fibrocartilage, the dorsal and volar radioulnar ligaments, the meniscal homolog, the ulnolunate and ulnotriquetral ligaments, and the subsheath of the extensor carpi ulnaris (ECU) tendon. The TFCC arises from the ulnar aspect of the lunate fossa and courses ulnarly and distally to insert at the base of the ulnar styloid, triquetrum, hamate, and the base of the fifth metacarpal. The TFCC has many functions. First, it acts as a smooth articular surface and a durable connection between the distal aspect of the radius and ulna. This connection allows for controlled forearm pronation and supination. Second, it transmits and absorbs axial load across the ulnocarpal articulation. Studies have shown that approximately 20% of the axial load through the forearm is absorbed through the ulnocarpal articulation and TFCC with neutral ulnar variance. In addition, the TFCC is the primary stabilizer of the distal radioulnar joint.

Classification

The Palmer classification is the most commonly used to describe lesions of the TFCC. This classification separates TFCC injuries into traumatic (class I) and degenerative (class II). Each class of lesion is then further broken down by location of the injury on the TFCC. Although degenerative lesions are far more common in the adult population, most TFCC lesions in children are traumatic. Furthermore, studies by Terry and Waters showed that nearly 80% of these injuries in children and adolescents were subtype IB or tears off the ulnar attachment of the TFCC. Tears off the radial attachment, subtype ID, are the second most common and are frequently misdiagnosed and mistreated, leading to persistent pain and disability.

Clinical Presentation

Clinical presentation may be subtle, but patients with TFCC injuries typically present with ulnar-sided wrist pain. Classically, patients report an increase in symptoms with activities that stress the ulnar side of the wrist such as forceful grip or forearm rotation. Most children report antecedent trauma to the wrist. The trauma is usually reported as a fall onto an extended and pronated wrist.

On physical examination, pain may be experienced to direct palpation of the TFCC in the foveal region, which is located between the flexor carpi ulnaris (FCU), triquetrum, and ulnar styloid. Furthermore, loading of the TFCC with the wrist in ulnar deviation and rotation may provoke symptoms. It is also critical to assess the stability of the distal radioulnar joint (DRUJ) when an injury to the TFCC is suspected. This can be performed by testing anterior and posterior translation of the ulnar head. Testing should be done with the forearm in different positions of pronation and supination and compared with the contralateral side.

Wrist radiographs are essential in the evaluation of a child with suspected injury to the TFCC. Radiographs should be scrutinized for coexisting pathology of the wrist, which has been found to be present in 86% of patients. This pathology included ulnar styloid nonunion, DRUJ instability, ulnocarpal impaction, and distal radius deformity or fracture. Furthermore, ulnar variance should be measured, making sure that radiographs are obtained with the wrist in neutral position, and compared with the opposite wrist.

Other radiographic studies such as computed tomography (CT) scan and MRI can be appropriate in certain situations. MRI is often helpful in determining the integrity of the TFCC; however, the sensitivity and specificity of these scans for identifying TFCC pathology have varied widely. High-resolution pulsed sequences and dedicated MRI wrist coils have improved the sensitivity to almost 100% in some series. CT scan including coronal cuts is valuable in the assessment of osseous anatomy and is the standard method of evaluating the DRUJ for instability.

Management

Indications and Contraindications

The first-line treatment for management of TFCC injuries in children should always be nonoperative. Rest, activity modification, physical and occupational therapy, and, rarely, corticosteroid injections should precede discussions of surgical intervention. However, patients with ulnar-positive or ulnar-neutral wrists should be counseled that they are less likely to respond to conservative measures. Persistent pain, limitation in motion, and persistent DRUJ instability can be indications for surgical management.

The arthroscopic diagnosis and treatment of TFCC tears have evolved rapidly in recent years. Many surgeons currently advocate arthroscopic-assisted suture repair of the TFCC for injuries of both the radial and ulnar attachments, whereas open techniques are reserved for chronic injuries or those with ulnar styloid nonunions.

Contraindications to an arthroscopic TFCC repair include infection, unstable soft tissue envelope, and DRUJ instability that would require open techniques.

Surgical Technique: Arthroscopic-Assisted Repair

Diagnostic wrist arthroscopy is first performed in the usual fashion with a 2.7-mm arthroscope inserted in the 3-4 portal and the 4-5 or 6R portal used for working instruments. Arthroscopy has been shown to be highly sensitive for spotting TFCC tears ( Fig. 65-1 ). With tension on a probe introduced in the ulnar portal, the TFCC should be taut, similar to a trampoline. An absence of this “trampoline sign” is an indicator of TFCC pathology. Upon identifying a TFCC tear, debridement of synovium should be performed with an appropriate arthroscopic shaver such that a bleeding surface is created at the proposed repair site.

For IB tears (i.e., peripheral TFCC tears), many variations have been proposed for arthroscopic suturing of the TFCC including outside-in and inside-out techniques. All arthroscopic methods have been used with success. The authors advocate an outside-in technique popularized by Whipple and Geisler. Staying dorsal to the flexor carpi ulnaris tendon, two 18-gauge Tuohy needles are introduced through the capsule and across the undersurface of the TFCC and through the intact cartilage under arthroscopic guidance. A 2-0 PDS (polydioxanone suture, Ethicon, Inc, Somerville, New Jersey) suture is then introduced through one needle and a wire loop through the other. The suture is manipulated through the wire loop and through the second needle, completing a horizontal mattress stitch ( Fig. 65-2 ). A small dorsal wrist incision is made at the level of the exiting PDS sutures, and careful spreading down to the capsule is performed to prevent entrapment of the dorsoulnar sensory branches. The suture is then tied over the wrist capsule with the wrist in neutral position.

For ID tears, arthroscopic principles similar to those previously outlined are followed with regard to identification and preparation for repair. Next, two long straight Keith needles are introduced from the ulnar border of the wrist through the intact radial TFCC, across the tear and subsequently drilled through the radial metaphysis, exiting between the first and second dorsal compartments. A 2-0 PDS suture is passed through the Keith needles, tensioned, and tied over the radial metaphysis.

Previous studies have shown a high incidence of coexisting pathology with TFCC injuries in children. Ulnar styloid fracture and nonunion should be addressed at the time of TFCC repair with fixation, if amenable, or with excision. DRUJ instability is also frequently seen in children with TFCC tears. DRUJ stabilization can be performed concurrently with an ulnar-based flap of the extensor retinaculum. Furthermore, ulnar impaction and ulnar-positive variance need to be addressed at the time of repair. Ulnar-shortening osteotomy with compression plating and distal ulna epiphysiodesis is usually performed in this instance.

Postoperatively, patients are immobilized with the elbow at 90 degrees and the wrist in supination for approximately 4 weeks. This is then followed by 2 weeks of short-arm casting. Active participation in sporting activities is reserved until 3 months postoperative.

Results

Few published data are available regarding treatment of TFCC injuries in children. Terry and Waters published the largest series of 29 pediatric and adolescent patients with surgically documented TFCC tears. In this series, the average age was 13 years. Nearly 80% of the patients had type IB tears and, as mentioned previously, 86% had coexisting pathology of the wrist. With an average follow-up of 21 months, 89% had good to excellent results as graded by the modified Mayo wrist score. The authors recommended repair for all TFCC tears. They also stressed the importance of identifying and treating coexisting pathology. Arthroscopic-assisted repair is preferable, but coexisting pathology may necessitate open treatment.

Conclusions

TFCC injuries are a source of ulnar-sided wrist pain in children and adolescents. Treatment of these injuries is predominantly nonsurgical. However, persistent pain, limitation in motion, and persistent instability can be indications for surgical management. TFCC tears in children are predominantly off its ulnar attachment and frequently occur with coexisting pathology. Arthroscopic repair is the mainstay of treatment for isolated lesions. Excellent results can be expected with repair of these lesions as long as coexisting pathology is addressed appropriately.

PEDIATRIC SCAPHOLUNATE LIGAMENT INJURIES

Scapholunate ligament injuries are the most common ligamentous injuries in the wrist in adults. However, they are relatively uncommon in the skeletally immature. With the speed and competitiveness of adolescent sports on the rise, it is likely that the incidence of ligamentous wrist injuries will similarly increase.

Anatomy

Not just a single ligament, the scapholunate ligament is actually a complex of ligamentous structures, anchored by the scapholunate interosseous ligament (SLIL). The SLIL is a C-shaped structure when viewed from the lateral plane. It traverses from the dorsal distal aspect of the lunate, follows the proximal curve of the lunate, and terminates at the volar distal lip. The SLIL is thickest dorsally (approximately 2 to 3 mm thick). The proximal membranous portion of the ligament is fibrocartilaginous and is easily seen arthroscopically. The volar SLIL is thinner (approximately 1 mm thick). Other supporting structures augment the scapholunate interval volarly, including the extrinsic radioscaphocapitate ligament and the long and short radiolunate ligaments.

The most structurally important aspect of this complex is the thick dorsal intrinsic component. This dorsal segment is not only the thickest but also the strongest, with an ultimate load to failure of 240N, whereas the proximal and volar segments fail at 60N and 120N, respectively. According to Mayfield’s progression, the volar portion fails first, then the proximal membranous portion, and then the stout dorsal ligament. When the scapholunate ligament is torn completely, the scaphoid flexes volarly, since it is still attached to the distal carpal row. The lunate, once unlinked from the scaphoid but tethered to the triquetrum, extends dorsally. Conceptually, this mimics the twisting motion of a dish towel when wrung dry. Once this dissociation occurs, a dorsal intercalated segment instability (DISI) results, and carpal kinematics are significantly altered.

Classification

As with all injuries, the degree of injury is related to the energy imparted to the wrist at the time of injury. These injuries can range from mild sprains to complete tears and associated carpal fracture-dislocations. In fact, a scapholunate ligament disruption is the first stage of Mayfield’s classification. Geissler and colleagues developed a classification system for SLIL tears ( Table 65-1 ). Adolescents often injure their wrists in recreational and organized sports, whereas adults tend to suffer such injuries in falls and in work or vehicular accidents. Patients in whom SLIL tears should be suspected are those who have fallen on an extended and ulnarly deviated wrist, worsened by a supinating force. Another group of patients to be mindful of are children with normal radiographs and wrist tenderness who have been diagnosed with a Salter-Harris I fracture. Children with persistent pain in this region after a sufficient period of immobilization should be investigated for SLIL tears.

TABLE 65-1

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