Intramedullary Screw Fixation of the Metacarpals and Phalanges of the Hand

5 Intramedullary Screw Fixation of the Metacarpals and Phalanges of the Hand

Maurizio Calcagni, Lisa Reissner, Christoph Erling, Thomas Giesen

Abstract

The development of headless compression screws in the 1980s opened new possibilities for the internal fixation of carpal bones, rapidly becoming the standard. In fingers and metacarpals, their use was limited for a long time to the arthrodesis of the distal interphalangeal (DIP) joint or for the treatment of phalanges nonunion. The first reports were published about the fixation of transverse fresh fractures treated with intramedullary headless screws only after 2010. The technique is therefore relatively recent and not refined enough to give absolute indications. Ideally, the fracture should be transversal and with minimal comminution, although in some cases the intramedullary screw can also be used as strut to restore axis and length of the bone. The procedure is based on a few steps that must be adapted to the different anatomical sites: closed reduction of the fracture, insertion of an axial guidewire, and fixation with a compression headless screw, with or without predrilling. In the published case series, the results are very good in terms of bone healing and range of motion. The area of damaged articular surface was calculated by several papers with different methods, with results varying between 4 and 20% depending on the involved joint and the size of the screw.

Intramedullary screw fixation of metacarpal and phalangeal fractures is a relatively new technique with good reproducible results and low complication rate.

Keywords: intramedullary screw, osteosynthesis, hand fractures, headless screws

5.1 Introduction

The treatment of hand fractures has been debated for a very long time, often with diverging opinions among surgeons about conservative treatment versus surgical fixation for the same pattern of hand fracture. The use of casts or splints might reduce hardware associated complications, but sometimes it does not allow for true early rehabilitation and can cause stiffness and therefore prolonged sick leave. In hand fractures, the use of osteosynthesis material applied on the outer surface of the bone or protruding through the skin is associated with a high rate of complications.1,2 Some of the described complications are those related to surgery such as infection, iatrogenic nerve lesions or malposition, but most complications are related to the fixation material itself: allergic reactions, pin tract infections, tendon adhesions, joint stiffness, and hardware intolerance are the most common.

The hand is very sensitive to the volume of the inserted hardware as the hand bones are in the vicinity of gliding structures; tendons, ligaments, intrinsic muscles, and nerves that during healing time can become tethered with surgical scars and/or plates and screws. The evolution of materials and manufacturing techniques contributed greatly to the reduction of those problems; modern plates are made of titanium with higher tissue compatibility, have a lower profile, and screws no longer have any sharp edges, reducing volume-associated complications. Nevertheless, hardware placed on the outer surface of the bones of the hand often needs to be removed and the aforementioned structures released from the scar, leading the patient to a second operation with the potential of new complications.

In the 1930s, the use of the intramedullary nail was popularized in Germany for the lower extremities with a high rate of success, starting the development of this kind of osteosynthesis. Kirschner wires (K-wires), percutaneous and not, were widely used intramedullary for finger and metacarpal fractures, but still had some complications and limitations.

Looking for a better intramedullary fixation, in 1977, Foucher³ presented the bilboquet technique which is probably the first example of a stable intramedullary fixation in the phalanx of the hand. For the bilboquet technique, special intramedullary pins were used, and sometimes they were also cemented. Later the wires were modified in different fashions: with or without a thread or with a small hole for locking, in the case of phalangeal fractures. Unfortunately, this new material was difficult to use and never had much success.

Later, the headless compression screw was introduced for the treatment of scaphoid fractures,⁴ adding the feature of compression to the intramedullary position of the hardware. Despite their rapid success for the carpal bones, this concept was only recently also extended to the treatment of metacarpals and phalanges.

The first use of headless compression screws in the fingers was limited to the arthrodesis of the DIP joint⁵ or for the treatment of phalanges nonunion.⁶ The limitation of the use of the first generation of headless screws was the need for an external jig for drilling and compression.

In the next generations, headless screws were cannulated for a guidewire, for much easier insertion. As a last evolution, the screws were manufactured by different brands as self-drilling and self-tapping, reducing the need for drilling before insertion of the screw and further simplifying the surgical procedure and reducing the needed exposure.

In 2010, the first case report of a transverse fresh fracture treated with an intramedullary cannulated headless screw was published.⁶ Ruchelsman et al⁷ presented the first clinical case series after a theoretical work on the volume needed by the screw head and on the area of damaged cartilage surface.⁸ This paper was followed by few others^9–11 presenting more cases, although with short follow-up.

5.2 Indications

The technique is relatively recent and not refined enough to give absolute indications. Ideally, the fracture should be transversal and with minimal comminution, even though in some cases the intramedullary screw can also be used as a strut to restore axis and length of the bone. In comminuted metacarpal fractures, the use of two converging screws in order to lock the compression has been proposed.9

There is no data about the maximal acceptable angle of the fracture line that is amenable to this type of osteosynthesis, but we do not recommend fixing true oblique or spiral fractures. As a rule of thumb, we switch to lag screw fixation when at least two can be safely placed.

Both bone fragments must be big enough to accommodate the threaded heads without impinging the fracture line and preventing compression.

5.3 Surgical Technique

The procedure is based on a few steps that are common among the different anatomical sites.

Before surgery, it is mandatory to measure the width of the medullary canal in the two planes to choose the appropriate screw size. The canal is not symmetrical and the lateral view is the one to consider for accurate measurements. Normally, the distal head of the screw will lie at the isthmus, the narrowest point of the medullary canal, and this value is the one to consider. The choice is usually between 2.2 and 3 mm, but it might be different according to the brand of screw being used by the surgeon. For distal phalanx fractures, some brands do not provide a screw small enough.

For metacarpals, they might sometimes have a diameter of 4 mm or more, and a larger screw might be necessary. Nevertheless in such cases of large intramedullary canal, a smaller screw will work as an elastic fixation ( Fig. 5.1).

The fracture is reduced under the fluoroscope and the skin is incised by 2 to 4 mm depending on the size of the planned screw, in a site that will allow for central placing in the medullary canal of the guidewire. The site of introduction varies between different bones as described below. The wire is then drilled across the fracture line. After controlling the proper position of the wire in both planes, the screw is advanced (in most cases without predrilling if the screw allows it) for optimal compression. The head must be accurately countersunk in the subchondral bone to avoid secondary joint damage.

The length of the screw is calculated on the X-rays before surgery in order to spare time during the procedure. Compression is achieved by advancing the screw, therefore, when treating short bones or fractures near to a joint, a few millimeters should be detracted from the length in order to avoid protrusion of the screw into the joint space.

There are no data about the superiority of one brand over the others, as long as the screws have particular characteristics. In our experience, the screw must be cannulated to allow percutaneous fixation and the different pitch of the threads should be enough to achieve good compression without the need for external devices like compression-jigs or broad-head screwdrivers. The diameter of the screwdriver itself is also very important, because it must be of the same size or even smaller than the screw itself to avoid greater damage to the bone and cartilage at the insertion site.