External Minifixation

Frédéric Schuind, Fabian Moungondo, Wissam El Kazzi

Abstract

External minifixation allows stable bone fixation of hand fractures, allowing early active mobilization, the best way to prevent stiffness and complex regional pain syndrome (CRPS). The problems of internal fixation (infection, local discomfort, tendon impingement) are avoided. External minifixation can be applied in a wide variety of clinical situations, not only to treat open and infected fractures and nonunions, but also to stabilize closed unstable metacarpal and phalangeal fractures, or to perform a corrective osteotomy. Other excellent indications are lengthening and arthrodesis. The main drawbacks are the bone and skin reactions to the pins, not uncommon at the metacarpal level, and the cost of the implant.

Keywords: external fixation, external minifixation, hand fracture, osteotomy, lengthening—arthrodesis, finger stiffness

7.1 Introduction

Stiffness was the rule rather than the exception after nonoperative treatment of hand fractures: after 4 weeks of immobilization of stable hand fractures, only 25% of the 809 patients in the series of Wright regained full active motion, and only 10%, in case of unstable fractures.1 Similarly, poor fixation using Kirschner’s wires, imposing subsequent plaster cast immobilization, leads to stiffness, but, to our surprise, this form of treatment is still widely accepted as standard care of hand fractures. As F. Burny once said, “la Nature a horreur du plâtre” (“Nature abhors plaster”), or, according to L. De Smet, “plaster is disaster.” The best way to improve the functional results of hand fractures is to allow early or, better, immediate post-traumatic active motion. This is true for stable fractures, which should be managed using minimal functional splints and early remobilization, for example, in buddy taping; a short duration of immobilization in the protective position² is, however, sometimes necessary. Unstable fractures should be converted to a stable situation using modern osteosynthesis techniques, allowing early unprotected active mobilization. This principle stands, whether the fracture is isolated, simple, and closed, and also in the case of a severe hand traumatism. Indeed, fracture opening, the presence of multiple fractures, the existence of a segmental bone loss, and/or of associated soft tissue lesions, including tendon lesions, are no reasons to delay postoperative remobilization; on the contrary, the benefits of early active mobilization are especially obvious in complex traumatic situations.

Stable bone fixation can sometimes be achieved by elastic endomedullary nailing, for example, the “bouquet” osteosynthesis of metacarpal neck fractures (see also Chapter 22). Another form of stable osteosynthesis is represented by isolated screws fixing reduced articular fractures; or by miniplates, opposed to bone by conventional or better by locked screws (see also Chapter 6). The latter internal fixation techniques are especially indicated in articular and periarticular fractures and osteotomies, although they can also be used to treat diaphyseal fractures. The use of apposition methods of osteosynthesis imposes, however, an open approach of and around the fracture, a possible cause of adherences and stiffness. Although modern plates are quite thin to prevent soft tissue impingement, these implants may still limit tendon gliding, in particular, of the extensor apparatus. In addition, the use of an internal implant is contraindicated in open, contaminated fractures, particularly in case of poor posttraumatic finger vascularization and/or skin coverage.

Another form of stable osteosynthesis is external mini-fixation, especially indicated in open, contaminated fractures ( Fig. 7.1), and also an excellent technique to treat closed diaphyseal metacarpal and phalangeal fractures ( Fig. 7.2). External minifixation is not a new idea, and several authors have already long time ago proposed the use of various small external devices for the osteosynthesis at the hand, foot, and mandible, and for fractures occurring in children.^3–5 These fixators did not gain popularity, because of lack of stability and difficulties in application. Henri Jaquet developed the first modern external minifixator in the years 1975–1976.^6–8 The Brussels school has been using this implant since 1977 and has published a book in 1990 presenting the results of a prospective study of 516 cases.⁹ Other publications from our group have followed.^10–13 Since 2004, we use the “Micro Hoffman II Fixator” developed by Stryker following the concept of the Hoffman II.^12,13 The external minifixator is relatively expensive, limiting its widespread use in hand surgery. Recently, various new models of small external fixators have appeared on the market, initiating a regain of interest of the hand surgery community for this method of treatment of hand fractures.

7.2 Surgical Technique

The implantation of an external minifixator, which requires the same rules of sterility as any other form of osteoarticular surgery, is usually performed before the repair of other lesions, allowing the surgeon to perform the soft tissue repairs on a stable skeleton. Rarely, the implantation of a minifixator renders microsurgical repairs difficult, especially in replantation surgery, thus, despite its disadvantages, the use of Kirschner wires in this particular form of open fracture may sometimes be more appropriate.

A C-arm is necessary to check the length of the pins and the quality of fracture reduction. We recommend the use of two 2-mm threaded half-pins, strongly fixed into both cortices of intact parts of the bone on each side of the fracture, as close as possible to the fracture. The pins should not protrude more than 2 mm on the opposite site of insertion, to avoid soft tissue lesions, particularly of the flexor tendons and neurovascular bundles (in some rare cases we have used only one pin on either side of the fracture, relying on the good hold of this isolated pin in cortical bone, Fig. 7.3). One incision of 6 to 10 mm is used for the insertion of each group of parallel half-pins. The tendons and neurovascular structures are protected and the bone must be clearly visualized. Pilot holes of 1.5 mm are created with a power drill. The pins are then manually inserted. In the metacarpal bones of the long fingers, the pins are implanted in a 45-degree posteromedial or posterolateral direction, avoiding the extensor tendons and the superficial terminal sensory branches of the radial or ulnar nerves. In the first metacarpal, the pins should be implanted in the posteroradial aspect of the bone, radial to the extensor pollicis brevis tendon. In the proximal phalanx of the long bones, the pins are implanted on either side of the finger, in a posterolateral or posteromedial direction, through a small incision in the extensor apparatus. In the middle phalanx of the long bones or in the proximal phalanx of the thumb, the pins are implanted in the lateromedial or laterolateral aspect of the bone, if necessary through the oblique retinacular ligament, palmar to the extensor apparatus. In the distal phalanx, the pins must be inserted in the lateral or medial aspect of the bone, to avoid injury to the finger pulp or to the nail matrix. In the distal phalanx, the use of transfixing pins with a triangular frame is another choice.