Fractures at the Base of the Proximal Phalanx

16 Fractures at the Base of the Proximal Phalanx

Lars S. Vadstrup

Abstract

Treatment of base fractures in the proximal phalanx depends on the fracture type, the degree of displacement, and whether fracture reduction is stable or not. In this chapter, intervention options are reviewed focusing on restoration of finger function and to a lesser extent on exact reposition of the fractured digit. Conservative treatment and immediate mobilization are first choice for undisplaced fractures. If osteosynthesis are required to maintain an acceptable position of the fracture after closed reduction, K-wire fixation should be considered, with respect for the anatomy of the extensor apparatus. Open reposition and internal plate fixation is a specialist procedure, where absolute stability is needed, so that immediate mobilization of the finger can be initiated soon after surgery.

Keywords: conservative treatment, Buddy Loops, early mobilization

16.1 Trauma Mechanism

Hyperextension and abduction of one of the fingers tend to cause a base fracture of the proximal phalanges, most frequently to the fourth or fifth finger. An extra-articular transverse or oblique fracture is often the outcome of the described trauma, whereas torsion injuries might cause an oblique or spiral fracture of the shaft. A direct blow creating an axial load to the finger may result in a comminuted, intra-articular base fracture. If coronal forces are applied to a finger, intra-articular avulsion fractures of the base of the proximal phalanx are a consequence of ligament strength superior to bone strength. This type of fracture results in evident joint instability ( Fig. 16.1).

A phalangeal fracture is the most common injury to the skeletal system and accounts for approximately 10% of all fractures. The trauma is most likely related to sports activities in the 10-to 30-year-olds, work related in the 30- to 70-year-olds, and due to fall from a standing position in people above 70 years of age.^1–3 The fracture often results in a dorsal angulation at the fracture site in the base of the proximal phalanx. This deformity tends to be maintained by the intrinsic muscle insertion on the base of the proximal phalanx (dorsal interossei) and the extension force of the central slip across the proximal interphalangeal (PIP) joint (palmar interossei and lumbricals insertion into lateral bands of the extensor hood). Unlike diaphyseal fractures, these do not tend to cause appreciable rotational deformity.

16.2 Classification

The AO Foundation divides the base fractures of the proximal phalanx into proximal metaphyseal and proximal articular. The proximal metaphyseal fractures are extra-articular and segmented into transverse and oblique types. The proximal articular fractures are subdivided into avulsion, shearing, and multifragmentary fractures. Upon consideration of the subsequent treatment of the fractured phalanx, stability, angulation, and possible rotation of the fracture should be observed.

16.3 Clinical Signs and Tests

When evaluating a proximal phalanx fracture, it is important to pay attention to the tendon function of the involved digit, as the bottom of the flexor tendon sheath is constituted of the palmar aspect of the phalangeal bone. Test of ligament stability is performed on the metacarpophalangeal (MP), PIP, and distal interphalangeal (DIP) joints taking a possible intra-articular base fracture of the proximal phalanx into account. If any doubt about the function of the flexor tendons or ligament stability of the finger, the finger should be examined under local anesthesia (finger block anesthesia). With the finger anesthetized, the examiner also gets the best possible evaluation of a possible rotation deformity of the finger, comparing the plane of the digits nails, as the patient actively flexes and extends the affected finger. Rotational deformity is a clinical diagnosis, not assessed on radiographs, and no rotational deformity can be accepted.

Fig. 16.1 An intra-articular avulsion fracture of the base of the proximal phalanx is a consequent of ligament stability superior to bone strength.

16.4 Investigatory Examinations

Plain radiographs (posteroanterior [PA] and lateral views) of the injured finger should always be performed when a fracture is suspected. Proper assessment of the injured hand should also include radiographs of the entire hand, to rule out associated fractures.

In adults a dorsal fracture angulation, up to 25 degrees is acceptable in an extra-articular fracture, but no more than 10 degrees of lateral of volar angulation should be accepted. Malunion causes impairment of digital function, and causes loss of equilibrium between flexor and extensor tendons. Clinically, the shortening of the proximal phalanx leads to loss of full extension at the PIP joint due to laxity of the extensor mechanism, and the dorsal angulation to hyperextension at the fracture site and MP joint. Sonography of the flexor tendons can be used in case of doubt concerning tendon lesions. Computed tomography (CT) scan is rarely needed.

16.5 Possible Concurrent Lesions of Bone and Soft Tissue

Evaluation of the soft tissues, nerves, and tendons of the injured finger is mandatory when the treatment method is to be determined. Reduced motion of the injured finger(s) may be the result of tendon adhesions (either flexor or extensor) or capsular contracture. Associated joint injury and soft tissue injury are contributing factors to reduced mobility of the fractured finger.4 When treating a combined fracture and tendon lesion, it is necessary to achieve absolute stability in the fixation of the fracture, to enable early active mobilization of the tendon injury. Nerve lesions are usually associated to open injuries.

16.6 Evidence

Fractures of the metaphysis of the proximal phalanx can be transverse, oblique, or comminuted. Reduction is achieved by traction and digital manipulation. When the fracture is undisplaced and stable or displaced, and stable after closed reduction, it can be treated nonoperatively with “buddy taping” and immediate active mobilization for 5 weeks.5 Reduced fractures are prone to displace and radiographical monitoring after 1 and 2 weeks treatment is advised.

Displaced fractures, that are unstable after closed reduction, require stable pin or percutaneous screw fixation. Pins or screws should be placed in the plane that crosses the fracture plane and at least two pin/screw diameters from the fracture line. When using lag screws, maximal fracture compression is obtained. Nerve and tendon anatomy should be taken into consideration when planning pin or screw placement. Postoperatively, a plaster of Paris in intrinsic-plus position is applied for 1 to 2 weeks followed by “buddy taping” and active mobilization for 5 weeks. Pin removal is done after 3 to 4 weeks.

Comminuted fractures are treated with either closed reduction and external fixation, or open reduction and internal fixation (ORIF). When addressing a comminuted fracture, one must consider whether the soft tissues tolerate further mobilizing or not. Closed reduction and external fixation provides stabilization with minimal risk of worsening the soft tissue lesion caused by the trauma. The use of plates and screws requires that a rigid osteosynthesis is obtained during surgery, as immediate mobilization is needed after open surgery to secure an acceptable function by avoiding adhesion of the soft tissues to the bone.^6–8

16.7 Author’s Favored Treatment Option

Treatment of base fractures at the proximal phalanx is a compromise between fixation and mobilization in retrieval of full range of motion (ROM) of the finger.3,9–12 Surgical fixation tends to cause a substantial loss of motion when percutaneous K-wire fixation or open reduction and internal fixation is performed.^13–15 Standard treatment strategy for base fractures of the proximal phalanx should focus on function and to a lesser extent exact reposition of the fractured digit. In my practice “buddy taping” is always used if the fracture is non-displaced and stable, or displaced and stable after closed reduction allowing immediate mobilization ( Fig. 16.2).

Displaced (> 2 mm) radial/ulnar avulsion or shearing fractures of the proximal metaphysis needs closed or open reduction and internal fixation, as joint stability may be compromised. The fracture can be addressed with K-wires (1–1.25 mm) with a percutaneous technique. If open surgery is required for fracture reposition, a volar approach is recommended.16 Brunner incisions are used at the level of the MP joint. The digital nerves and arteries are identified and the A1 and proximal part of A2 pulley are divided to expose the fracture as the flexor tendons are kept aside. A rigid osteosynthesis should be obtained, as early mobilization after 1 to 2 weeks is necessary to secure a satisfactory functional outcome ( Fig. 16.3).