6  Plate and Screw Fixation of Hand and Carpal Fractures

6.1 Introduction and Historical Perspective

Open reduction with plate and screws fixation has become a standard technique in the management of hand and carpal fractures. It requires a good knowledge of bone healing biology, implants, indications and surgical technique, as well as potential complications. This chapter exposes the general principles of osteosynthesis, as coined by Lambotte in 19071 and their clinical applications.

The natural healing of a fractured bone occurs through the formation of a callus secondary to interfragmentary movements, the so-called indirect bone healing. Lucas-Championnière in 1895 advised movements rather than immobilization for fracture healing and functional recovery.²

When the fracture is absolutely stable, for example, by screw and plate fixation, the consolidation of the bone takes place without any external callus formation but, instead, by direct osteonal remodelling.^3,4

Hansmann in Germany is credited of the first fracture treatment with a plate in 1886. After he had advocated conservative treatment, Perkins from England in 1940 also started to fix the fractures to allow early mobilization.² In 1949, Robert Danis from Belgium, exposed his theory of osteosynthesis: the fracture should be rigidly stabilized to allow early motion and rehabilitation.⁵ He called the healing of the bone without external callus formation, “soudure autogène” (autogenous welding).⁵

Further development of internal fixation was subsequently based on experimental and clinical studies conducted by the AO foundation (Arbeitsgemeinschaft für Osteosynthesefragen), created in 1958 by Swiss surgeons Maurice Müller, Martin Allgöwer, Robert Schneider, and Hans Willenegger.²

6.2 Implants and Technical Principles

Compression at the fracture site increases the rigidity of fixation and allows direct bone healing. The dynamic compression plate (DCP) has eccentric holes with a sloping surface on the side away from the fracture. When the screw is tightened, its head moves down the slope and shifts the plate in relation to bone resulting in compression at the fracture site.2 The plates currently available for metacarpal and phalangeal fixation have oval holes without any sloping inner surface. The compression is achieved by first drilling a hole close to the fracture line and inserting a screw engaging the far cortex but without tightening it. The plate is then pulled toward the other fragment. The first screw then occupies an eccentric load position. The second screw is then inserted as a load screw at the distalmost edge of the hole in relation to the fracture. The screws are then tightened alternately to produce the interfragmentary axial compression ( Fig. 6.1).

To decrease the pressure on the bone surface that causes necrosis, the plates are carved on their undersurface to decrease the areas of pressure on the underlying bone without decreasing the amount of metal at any transverse section of the plate. These plates are referred as limited-contact dynamic compression plate (LC-DCP).²

In single-plane fracture, any strain or movement will concentrate on that plane with a risk of failure. Therefore, if it is only supported with a plate in axial compression, a gap may open at the opposite cortex due to the elasticity of the plate. This pitfall may be prevented by inserting a lag screw through the fracture plane or by prestressing the plate with an overbending, the natural tendency of the plate to return to its original shape resisting the opening of the other cortex.²

When the fracture is multiplanar, one must not try to achieve absolute rigid fixation that might jeopardize the blood supply. The rule is never to sacrifice the biology of the fracture site to achieve a reduction and fixation.⁶ The multiple fragments are aligned and the minor residual instability between them will result in motion of relatively low amplitude, evenly distributed between fracture planes. A biological osteosynthesis is done with a plate bridging the fracture, restoring the length, the axis, the rotation, respecting the biology.^2,6 Bony fragments without bony attachment, too small or missing, can be replaced in hand fracture by bone graft and plate bridging.^6,7

Fig. 6.1 Principle of compression plate for metacarpal and phalangeal fractures. (a) The first screw is inserted in the hole close to the fracture line, engaging the far cortex, without tightening it. The plate is pulled toward the other fragment, to bring the first screw to an eccentric load position. (b) The second screw is inserted at the distalmost edge of the hole in relation to the fracture and the screws are tightened alternatively, producing the interfragmentary axial compression. (c) The remaining screws are inserted in neutral position, or, in the locking technique in the threaded holes (black arrows).

The traditional technique of plate fixation to the bone surface by screws engaging both cortices create frictional forces between the plate and the bone that neutralize the destabilizing forces.2 They are indicated when compression at the fracture site is required, in multiple ipsilateral metacarpal fractures, for nonunions that require absolute stability, in marked comminution, and for periarticular fractures.^8,9 A screw purchase decreased by poor bone quality (osteoporosis, high comminution, bone loss, metaphyseal or pathological bone) yields a risk of screw anchorage loosening and implant failure.^2,10,11 Attempts at increasing the plate-bone friction may jeopardize the fracture site and periosteal biology.¹⁰ New concepts have therefore been developed where the screws, locked in threaded holes in the plate, create a frame with angular stability that acts as an internal–external fixator.^2,10 The plate is then no longer compressed against the bone, but “hovers” over it with a slight space between the plate and the bone that preserve periosteal blood supply.^2,4,10 The stability achieved in a locked plate system do not rely on the fixation strength of a single screw but on the sum of the strength of all screw-bone interfaces.^8,10 This locking compression plate (LCP) seems to provide more stable fixation than conventional nonlocking plates as it has been shown in multiple laboratory and clinical studies, although data are sometimes confusing.^10,11 Its use is, however, recommended for indirect fracture reduction, periarticular metacarpal and phalangeal fractures, in particular with comminution, for diaphyseal fractures with bone loss or poor quality bone, for nonunion or corrective osteotomy fixation, in severe fracture to prevent fragment devitalization, for plating where anatomical constraints prevent insertion on the tension side of the bone and for small joints fusion.^8–10 Experimentally, metacarpal fracture dorsal plate fixation with four bicortical locking screws has equivalent biomechanical properties as a plate with six bicortical nonlocking screws, thus decreasing the dissection and allowing stable plate fixation in very proximal and distal fractures.¹² It has been assumed that unicortical plate fixation could be strong enough with the advantage of decreasing the risks of damage to the volar structure such as flexor tendons, compared to the traditional bicortical fixation.^13,14 Other biomechanical studies have shown, however, that bicortical was superior in metacarpals and phalanges.^15,16 The modern locking plates can be used either with locking or conventional screws with the compression effect, owing to the double circular holes, one with a thread, the other eccentric and smooth ( Fig. 6.2).

In addition to straight plates, a wide range of shapes are proposed to adapt to the various patterns of fractures that can be encountered. The plates can be T- or Y-shape, with a double row or a perpendicular blade for bone anchoring.

6.2.2 Screws

The screws that are used for metacarpal and phalangeal fixation are of self-tapping cortical type. They are used either to anchor the plate or for direct bone fixation. A screw can be defined as a device composed of a central core surrounded by an helicoidal thread, that converts rotational force into linear motion causing the screw to move along the longitudinal axis of its shaft.17 The effective thread depth of the helix purchases in the bone to promote this motion. The pitch is the height travelled by the screw with each 360-degree turn of the helix. Therefore, the shorter the distance, the finer the pitch, the longer the distance, the coarser the pitch. With a finer pitch, more turns engage in the cortex ( Fig. 6.3a).

When a screw is fully inserted, its head contacts the bone and resists further longitudinal motion. Therefore, more drive will create a tensile force in the core, balanced by an equal compression force at the screw head/bone interface. Countersink of the cortex beneath the screw head will increase the area of compression, decreasing the local pressure, thus the risk of bone failure. If the screw is inserted across a fracture plane with purchase in both cortices, the compression does not pass across the fracture plane, unless the reduced bone fragments are held under compression by a reduction clamp, before inserting the screw, as shown by Roth et al.18 The technique of lag screw is, however, commonly used in order to allow compression forces to pass across the fracture plane. Owing to the small size of metacarpal and phalangeal bones, the technique of lag screw insertion may slightly differ in hand than in larger bones. After fracture reduction, the pilot hole, at a diameter slightly bigger than the core, is drilled in both cortices. To drill first, both cortices prevent the risk of axial deviation, but require a good inspection of the fragments prior to reduction to aim correctly when the fracture is reduced. A gliding hole is then drilled in the proximal cortex at a diameter greater than the outer diameter of the screw. The hole in the near cortex is countersunk and the screw inserted with its tip protruding slightly beyond the outer cortex, in order to have a maximum of purchase in the bone. In this manner, the screw glides through the inner cortex and purchases in the outer cortex. When its head abuts against the proximal cortex, it creates a compressive force through the fracture line ( Fig. 6.4).

Fig. 6.2 Locking plate. (a) The threaded hole for the locking screw (blue arrow). The screw locked in place (black arrow). The plate and the screws act as a functional frame that increases the stability (red frame). (b) The plate lies on the bone with a slight interval to preserve the periosteal blood supply (red arrows).

A lag screw inserted perpendicularly to the long axis of the bone will give a maximum resistance to shearing forces generated by axial loading. If the screw is inserted perpendicularly to the fracture plane, it produces a maximal interfragmentary compression. Therefore, to meet both types of stability, different options can be used: either insert two screws, one perpendicular to the bone long axis and one perpendicular to the fracture plane. Another option is to insert one or more lag screws perpendicular to the fracture plane, yielding interfragmentary compression, and neutralize the shear forces by a so-called neutralizing or protection plate.2,6,19

Two more important points must be observed in screw insertion: First, the holes in both fragments must be coaxial, otherwise the reduction will be lost. Secondly, the interfragmentary screw should pass perpendicularly to the fracture plane and the holes should seat in the center of each fragment, which is sometimes difficult to achieve in the small bones of the hand.

Another way to achieve fragment compression is the headless compression screw designed by Timothy Herbert to achieve compression by use of a differential thread pitch between its proximal and distal ends, the proximal one being narrower than the distal. Therefore, by inserting the screw, the distal thread progresses quicker than the proximal, compressing the fragments as would a lag screw do^20–22 ( Fig. 6.3b). Further development with a central cannulation simplify the insertion over a guiding K-wire and another design with a conical shape with a progressively shorter thread has also been proposed ( Fig. 6.3c). Although designed initially for the scaphoid fracture and nonunion, increasing the fusion rate and allowing early mobilization, it can also be used for fracture of other carpal bones as capitate or uncinated process of the hamate, as well as hand fractures as more recently described^23–26 ( Fig. 6.5).

Fig. 6.3 Various types of screws for carpal, metacarpal, and phalangeal fractures. (a) Cortical screw. 1. Head; 2. Core diameter; 3. Outside diameter or thread; 4. Pitch: distance the screw advances for each 360-degree turn; 5. Effective thread depth. (b) Headless compression screw with double thread with different pitch. The distal thread with a coarse pitch progresses more quickly than the proximal, finer, pitch, creating interfragmentary compression. (c) The same principle of compression with the conical screw with progressively finer pitch from distal to proximal.

Fig. 6.4 Principles of lag screw insertion. (a) After fracture reduction, the pilot hole, slightly larger than the core diameter, is drilled perpendicular to the fracture plane. (b) After screw length measurement with a depth gauge, the gliding hole is drilled in proximal cortex at a diameter greater than the screw’s outer diameter. (c) The screw is inserted after countersinking of proximal cortex (yellow arrow showing the bevel of the hole).

Fig. 6.5 Examples of headless screw use. (a) Retrograde scaphoid fixation (waist fracture). (b) Bone graft (white arrows) and anterograde scaphoid fixation for nonunion. (c) Uncinate process of the hamate fixation. (d) Trapezium fracture. (e) Phalangeal fracture fixation.

6.3 General Considerations and Indications

This part is based on the literature, but also and foremost on the author’s clinical experience through years of good results and disappointing failures. Evidence-based guidelines would be in theory beneficial, but are lacking (see also Chapter 2).²⁷ Moreover, even if the strategy is evidence based, the outcome is not surely good, depending on the technique, the patient’s healing biology, the quality of the rehabilitation, and patient’s ability to cooperate. Indications to use plate and screw fixation are summarized in Table 6.1.

This chapter focuses mostly on fracture treatment with plate and screws. The technique of osteosynthesis, however, is also used in nonunion, malunion, or bone reconstruction following excision for tumor or other pathological bony conditions. As the general principles of fixation follow the same rules as in fracture treatment, these other indications are not developed here, as they are exposed in other,¹ more specific, chapters.

Table 6.1 Indications to internal fixation with plate and/or screw

General indications for metacarpal or phalangeal fractures’ operative treatment are unstable or unreducible fractures, displaced or unstable comminuted, multiple fractures, fractures associated with polytrauma or open fractures, fractures with bone loss.6,28–31

In carpal trauma, the main indication for screw fixation is the scaphoid fracture. Although a conservative treatment with cast is possible, multiple series has shown that long immobilization is no longer necessary and that percutaneous fixation of scaphoid may be the routine treatment to decrease the out of work time and increase the union rate.³² Uncinate process of hamate fracture, although less common, or less frequently diagnosed, is also a good indication for percutaneous screw fixation, as are other carpal bone, capitate, trapezium, as well as combined carpal fractures.

Arthritis of the carpus secondary to scaphoid nonunion advanced collapse (SNAC wrist) may require either partial of complete fusion. Although fixation may be achieved by K-wires or specially designed plates, headless compression screws are also an option for intracarpal fusions. If the degenerative changes are too extensive, a total wrist fusion may be required, when prosthetic arthroplasty is contraindicated. A specially designed plate either dorsally bent or straight is generally used.

When considering an operative fixation, some rules have to be followed: do not treat X-rays, but a patient according to his or her needs; choose plate and screws fixation because it is indicated not because it is a nice operation to perform. The technique must be tailored to the patient and not the patient to a preoperatively planned operation. This must be kept in mind when deciding to go to the operation theater. A less invasive method of fixation may create less soft tissue damage than a formal open approach. It is nowadays sometimes possible to use mini-invasive technique to fix a fracture with percutaneous screw, be cannulated or not. Once again, conservative treatment must always be considered if possible.

In situation where plate and screws’ fixation is indicated, it must be used only when a complete ancillary set is available, the operating theater conditions good, and the surgeon is well trained in this technique. Failure to observe these prerequisites could do more damage to the patient’s hand than a conservative treatment.

The principles of hand fracture operative management, anatomical reposition of the fracture, stable fixation preserving soft tissues, and institution of early motion have to be followed.²⁷

As the size of the screws varies greatly between the manufacturers, it is not specified in the text. The screw of diameters between 1 and 2.5 mm are currently available. The screw diameter depends on the size of the fracture fragments, as well as the size of the plate, if any.

6.4 Specific Indications and Procedures

This chapter is based on various textbooks and articles6,19,33–36 that are not systematically referenced through the text.

6.4.1 Phalangeal Fractures

The distal phalanx fractures are commonly either comminuted or transverse and better treated with K-wires. The intra-articular fracture of the phalangeal basis with a displaced dorsal fragment can, however, be fixed by two or three mini-screws after open reduction. In certain cases, when close reduction is still possible, percutaneous screw insertion may be tried. To prevent breakage of the displaced fragment, the holes are not made with a drill but with an 0.8-mm K-wire instead. A mini dorsal plate with proximal hooks may also be used.37

A volar avulsion fracture, as in jersey finger, as well as oblique fracture, may be indications to lag screw fixation, if the fragment is large enough.

Fractures of the Proximal and Middle Phalanges

Owing to the delicate extensor tendon mechanism running on the dorsum of the phalanges, the use of plate involves a risk of scar adhesions leading to stiffness, above all on the basal phalanx of the fifth finger. Therefore, alternative methods of fixation should be encouraged, whenever possible. The approach of the proximal and middle phalanges may be dorsal or lateral. The former requires the longitudinal split of the extensor on both phalanges, or elevating an interval between central and lateral bands on the proximal phalanx or elevation of the lateral band on the middle phalanx. It gives a better exposure of the fracture and is the preferred method of the author. The lateral approach is less damaging for the extensor apparatus, produces less adhesions, is more cosmetic, but may give a less good fracture exposure.³⁸ Plates, when needed, may be inserted dorsally or laterally. It depends on fracture anatomy and personal preference. Biomechanical studies seem to show that dorsally applied plates yield better stability, but results are, however, dependent on the quality of the implants that greatly differ from one manufacturer to another.^39,40 Clinical analysis seems to confirm that there is no difference in outcome, be the plate lateral or dorsal.⁴¹

Transverse Fracture of the Proximal and Middle Phalanges

If an alternative method is not chosen (intramedullary pin or compression screw), the fixation is achieved by a compression plate. Approach can be lateral or dorsal. In order to prevent opening of the fracture at the opposite cortex, the plate is slightly overbent. A 5-hole plate is used leaving the central hole empty at the level of the fracture site. Care must be taken to center the plate on the long axis of the diaphysis laterally. A laterally placed plate is favored by the AO group.¹⁷ However, dorsally placed plate is also possible following the same rules.

Short Oblique Fracture of the Proximal and Middle Phalanges

Obliquity of the fracture may be either in frontal or sagittal plane. The plate can be applied either dorsally or laterally on the phalanx, depending on the fracture plane. Fixation is achieved by a lag screw and a neutralizing plate. If the fracture is seen in the anteroposterior (AP) view, the plate is placed laterally with the lag screw inserted through the plate perpendicular to the fracture line. If the obliquity is visible in the lateral view, the plate should be applied dorsally for the same reason. The lag screw can also be inserted separately from the plate that will seat either laterally or dorsally according to the fracture plane. The use of a double row neutralization plate is a good option, but this type of facture may sometimes be treated by lag screws without plate, if the fragments are large enough ( Fig. 6.6).

Long Oblique Fracture of the Proximal and Middle Phalanges

This type of fracture is perfectly suitable for multiple lag screws. It is important to determine correctly the geometry of the fracture in order to place the lag screws in the middle of the fragments, otherwise the risk of displacement exists. A minimum of two screws is required for stability. A comparison of two versus three lag screws to fix this type of fracture did not show any difference in stability.⁴² Screws are evenly distributed along the fracture line and their direction vary according to the need to be perpendicular to the fracture line. This technique is less invasive than plate fixation and yields good functional results.43

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