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INTRODUCTION
The treatment of distal radius fractures has evolved substantially over recent years. Most authors still agree that anatomic reconstruction of both the radiocarpal and radioulnar joints is required to restore normal wrist kinematics and achieve optimal outcomes in both the short and long term. More controversial is the question of how to achieve anatomic reconstruction of the distal radius. Stable extra-articular fractures may be treated with manipulation and casting. Intra-articular, unstable, and irreducible fractures, especially in the younger patient, require more invasive treatment.
The options for internal fixation have greatly increased over the past 10 years. Dorsal plating was popular for some time, but concerns lingered over the lack of recovery of wrist flexion, which is believed to result from a combination of an extensive dorsal exposure and capsulotomy, in addition to the space-occupying plate, which leads to thick scar formation and capsular contracture.
Two prospective, randomized controlled trials, published in 2005, compared the results of predominantly dorsal internal fixation with percutaneous fixation and external fixation, including mini-open reduction if required. Kreder and colleagues found that when displaced intra-articular fractures can be treated by indirect reduction and percutaneous fixation, a more rapid return to function and a superior functional outcome will be obtained than by open reduction and internal fixation, provided that the intra-articular step and gap formation is minimized. Grewal and colleagues terminated enrollment half-way through their study, since the dorsal plating group showed significantly higher complication rates, as well as significantly higher pain levels, weaker grip, and longer surgical and tourniquet times. A meta-analysis of outcomes of external fixation versus plate osteosynthesis for unstable distal radius fractures was published later in the same year. The review included 917 patients in the external fixation group and 603 in the plating group, of which only 55 were treated with a volar fixed-angle device. The authors did not detect any significant differences in grip strength, range of motion, radiographic alignment, pain, or physician-rated outcomes. Patients had higher rates of infection, hardware failures, and neuritis with external fixation and higher rates of tendon complications and early hardware removal with internal fixation. The authors concluded that the literature offered no evidence to support the use of internal fixation over external fixation for these injuries.
The disappointing results of open reduction and internal fixation have to be revisited in light of the development of volar fixed-angle plate technology and fragment-specific low-profile fixation techniques.
Robert Medoff and colleagues described a specific fragmentation pattern of the distal radius and derived his fragment-specific approach from this. They described five main articular fragments and developed the TriMed Wrist Fixation System (TriMed, Inc, Valencia, California), fragment-specific fixation implants for these fragments. This system enables the surgeon to reliably stabilize fracture fragments through limited volar and dorsal approaches and to institute immediate mobilization in the majority of cases.
The early experience in our department with this system showed a restoration of articular congruity to less than 2 mm in 20 of 21 patients with AO type C2 and C3 fractures, with no loss of reduction at a minimum 6-months’ follow-up. The mean range of motion was 50 degrees flexion, 63 degrees extension, and a pronation-supination arc of 149 degrees.
Before the advent of locking technology, volar plating was mainly indicated for volar rim shearing fractures. New angle stable plate designs have expanded the indications for volar plating to include dorsally displaced unstable fractures. A variety of designs (DVR, Hand Innovations; volar subchondral support systems, Avanta; and the LCP Distal Radius Plate, Synthes North America) were developed, and clinical results were presented. These confirmed the safety and efficacy of these devices. In a comparison with external fixation, the restoration of intra-articular congruity, radial length, and volar tilt was significantly improved with volar plating. Moreover, successful maintenance of reduction, with minor settling of the fracture in only 3 of 23 patients, was noted in an osteopenic patient population over 75 years.
The subsequent development of variable-angle volar locking plates offers the potential to combine the advantages of volar plating with the deliberate placement of fixation screws and pegs to achieve some degree of fragment-specific fixation.
EVOLUTION OF VOLAR ANGLE STABLE PLATE DESIGN
First-Generation Volar Plates
The first-generation volar angle stable plates were somewhat analogous to blade plate implants. They were a one-piece design with no capacity to adjust the angle or length of the blade components. An example of this design was the Tine plate (Avanta). These implants were at the forefront of the development of angle stable volar plating; however, they were technically challenging to use and limited in application to diverse fracture patterns.
Second-Generation Volar Plates
The second generation of volar plates may be divided into two categories. The first category had a distal screw angulation that was symmetrical from the radial to the ulnar side of the plate. The only variability was in terms of the length of the distal pegs or screws. One of the first plates of this design was the volar plate of the AO Pi Plate set; however, this was more frequently used in combination with a dorsal implant.
The second category of second-generation volar plates had fixed variation of screw angulation from the radial through to the ulnar side of the plate so that the natural anatomic slope of the radius could be more closely paralleled, resulting in more widespread subchondral support of the articular surface.
Third-Generation Volar Plates
The most recent development in volar implants for distal radius fracture fixation involves variable-angle screws, which maintain angular stability. The ability to vary the angle of screws imparts multiple benefits in dealing with radial fractures.
Goals in the deployment of a volar implant include the accurate and safe subchondral placement of screws or pegs, combined with the achievement of true radial column support. In using a fixed-angle plate, this may be difficult to achieve because of variations in the size of the radius as well as variations in the location of the fracture lines, particularly the volar fracture lines. In addition, variation in size and distribution of fracture fragments can present challenges in fixed-angle implants.
Variable-angle screws allow adaptation of the plate position to volar fracture lines in both a proximal-to-distal plane and a radial-to-ulnar plane. This adaptation in position can be achieved while still minimizing the risk of screw perforation of either the distal radioulnar joint or the radiocarpal joint by directing screws away from the joint. In addition, the screw direction can be adapted to specific fracture fragments. Furthermore, there is an enormous variability in the arc of screw coverage that can be achieved ( Fig. 10-1 ).
DESIGNS FOR VARIABLE ANGULAR STABILITY
Currently, three major groups of plate design facilitate the combination of variable-angle and angular stability.
Material Hardness Mismatch
The most common design in this group uses higher grade 5 titanium screws or pegs, which achieve purchase by tapping into a softer grade 2 titanium within the plate. An example of this type of plate is the VariAx Distal Radius Locking Plate System (Stryker, Kalamazoo, MI). These screws may be inserted or re-inserted at an angle of plus or minus 15 degrees up to three times.
Other material mismatch plates have included titanium plates with zones of polyetheretherketone (PEEK) in the distal portion of the plate through which titanium screws may be inserted.
Mobile Expansion Bearings
This design is a variation on the expansion bolt concept frequently used in construction. In this setting, a mobile spherical expandable bearing rests within the plate; when the conical screw head engages the bearing, it expands the bearing such that the bearing achieves an interference fit within its corresponding spherical portion of the plate and thus achieves angular stability. The bearing mechanism may be disengaged and then re-engaged with alteration in the angulation of the screw on several occasions. An example of this style of implant is the Bearing Plate (TriMed, Inc).
Interference Fit
The third group of plates uses an interference fit between the screw head and the plate. An example of this type of plate is the Aptus Distal Radius Plate (Medartis, Switzerland).
INDICATIONS FOR VOLAR PLATING
Volar plating is currently our preferred choice of fixation when a decision has been made to perform internal fixation of distal radius fractures and it is technically feasible to employ this type of implant (see Contraindications, following).
A detailed discussion of the indications for fixation is beyond the scope of this chapter; however, it is important to recognize certain principles. Although discussion of the unstable fracture is common, a radiographic or morphologic definition of what constitutes an unstable fracture requiring fixation has not been possible. In addition, simple numeric indices may give some guidance but need to be adjusted for factors such as physiologic age and functional demands. Shortening that is not acceptable in a 20-year-old patient may often be acceptable in a functionally less demanding, 70-year-old patient. Furthermore, the improved efficacy and potentially decreased complication profile of internal fixation with these implants mean that there is also an expansion of relative indications including ease and speed of rehabilitation. Within these qualifications there are still parameters that require careful consideration before fixation:
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Articular stepoff or gap of 1 to 2 mm
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Dorsal tilt greater than 5 degrees (young patient) to 20 degrees (elderly patient)
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Radial shortening of more than 2 to 5 mm
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Radial translation of distal fragment with visible widening of distal radioulnar joint (DRUJ)
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Worsening position on serial radiographs, particularly after initial closed reduction
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Patient with poor supination in cast at 1- to 2-week clinical follow-up
It is important to appreciate that with extremely careful attention to cast changes, it might be possible to control recurrence of angulation with cast treatment, but shortening is almost certain to recur or worsen by the time of union.
CONTRAINDICATIONS TO VOLAR PLATING
Although variable-angle stable implants have broadened the indications for volar plating, there remain certain circumstances in which it is inadvisable to use volar plates. These include:
Very small radial column fragments . In addition to indicating a highly comminuted fracture, very small radial column fragments pose a considerable challenge because even with appropriately directed screws, adequate support of the radial column is difficult to achieve.
Very distal volar fracture line or absent volar fracture line. If the volar fracture line is too distal, it is difficult and potentially hazardous to position the plate far enough distally to stabilize the fracture. When there is no volar fracture line present at all, there are significant biomechanical concerns in using a volar implant to stabilize a dorsal shear fracture.
Highly comminuted articular surface . There remain articular fractures in which the number and distribution of articular fragments are such that even with modern implants, volar plating is inadvisable. Frequently, these types of fractures present a challenge in achieving, as well as maintaining, adequate articular reduction.
Fracture dislocations . Clearly these are more in the realm of radiocarpal dislocations. Although fracture dislocations may often have a reasonably significant radial column fragment, the volar fragments are usually just small ligamentous avulsions and there is significant dorsal instability associated with the shearing nature of the injury. Volar plating is not appropriate for these injuries, and excellent reconstructions may be achieved with fragment-specific fixation.
SURGICAL TECHNIQUE
The surgical approach is through the bed of the flexor carpi radialis (FCR) tendon. This approach is actually ulnar to the classic Henry’s approach, which uses the interval between the superficial branch of the radial nerve and the radial artery. After opening the sheath of the FCR tendon, the tendon should be retracted in an ulnar direction. This reduces the possibility of injury to the palmar cutaneous branch of the median nerve that lies between the FCR tendon and the palmaris longus tendon. The deep portion of the FCR sheath is incised to enter a plane that is defined by the distal aspect of the flexor digitorum sublimis (FDS) muscle and the flexor pollicis longus (FPL) muscle and tendon on the ulnar aspect and by the radial artery on the radial aspect. The plane between the flexor tendons and the pronator quadratus tendon is easily developed.
In our experience, it is almost never necessary to develop the volar incision distal to the palmar wrist flexion crease using the classical Z-shaped extension as described by Orbay and Fernandez.
In the deeper aspect of the approach, the brachioradialis tendon is identified inserting onto the distal radius, frequently distal to most common fracture line locations. The brachioradialis forms part of the floor of the first dorsal extensor compartment.
In most surgical cases, significant benefit lies in releasing the brachioradialis distal to the fracture line. The brachioradialis is usually a deforming force, and in all but the most acute fractures that are operated on within the first 72 hours, it tends to resist correction of radial height and inclination. The brachioradialis may be safely released from its bony insertion onto the radius without risk of significant proximal retraction due to its extensive fascial insertions in the region. We have not found it necessary to perform a complex Z-type release of the brachioradialis because we do not specifically reattach the brachioradialis tendon at the end of surgery.
Careful attention should be given to the elevation of the pronator quadratus muscle. The pronator quadratus is usually elevated in an L-shaped fashion with the longitudinal limb elevating the muscular part of the pronator off the radial border of the radius. The transverse incision in the pronator should be through the well-defined tendinous portion, leaving good-quality tendinous tissue on both sides of the incision to facilitate subsequent repair.
Our motivation for repairing the pronator quadratus is solely for the purpose of soft tissue coverage of the distal aspect of the plate. Early in our experience with volar plating when we were using fixed-angle implants, the nature of the fixed-angle implants meant that the plate was never positioned in a particularly distal fashion. As such, the risk of flexor tendon irritation or attrition was very low. In these cases, we did not repair the pronator quadratus and we observed no significant functional limitations. Variable-angle plates can be placed more distally to deal with more complex and more distal fracture patterns, which brings the plate into the zone of the distal radius, where there is close contact between the flexor tendons and the volar ridge of the distal radius. As a consequence, the more distally the plate is positioned, the more important it is to achieve some degree of soft tissue coverage over the plate to afford some protection to the flexor tendons.
Although other authors have suggested suturing the pronator quadratus in a radial fashion to the brachioradialis tendon, we have found that this is not reliable in achieving coverage of the most distal aspect of a distally placed implant. As a consequence, our priority is achieving distal reattachment of the pronator tendon to its original anatomic tendinous insertion ( Fig. 10-2 A and B ). We do not restrict postoperative motion to protect this repair.
It is worth noting that in the small percentage of cases in which we have removed implants after fracture union, the pronator repair has appeared intact with good soft tissue coverage of the plate. With a careful anatomic distal reattachment of the pronator quadratus muscle, we have observed almost no instances of flexor tendon erosion on the distal aspect of the plate.
FRACTURE REDUCTION
Fracture reduction is generally undertaken through a combination of strategies including indirect fracture reduction through the classic techniques of traction and manipulation. This may be combined with direct fragment manipulation, which can be achieved to a large extent through the volar incision. In addition, fracture fragments may be manipulated through the fracture lines. This is undertaken most commonly through the volar approach. After elevation of the brachioradialis tendon, there is very frequently a soft area of the fracture line on the radial border immediately deep to the brachioradialis insertion through which access to the fracture line can be achieved, even if volar cortical apposition has not been disrupted. Through this fracture line, intra-articular fragments often can be elevated using a fine bone punch or other device. This so-called soft spot is also useful for the insertion of bone graft or bone graft substitute without the necessity for resorting to a separate dorsal incision.
We have found that it is uncommon to have to use the more extensive approach described by Orbay and Fernandez involving release of the radial septum and pronation of the proximal diaphyseal portion of the radius to achieve access to the fracture line, including dorsal fragments. The most problematic dorsal fragments are the dorsoulnar fragments, which may be associated with a coronal plane split in the distal radioulnar joint. These fragments are extremely important because their stabilization is essential for the achievement of an early pain-free restoration of supination and pronation. We have actually found it to be more beneficial to undertake a small strategically placed incision over the dorsoulnar aspect of the radius to facilitate reduction of these fragments when there is difficulty in achieving satisfactory reduction and fixation through a volar approach. Usually, this can be achieved through a small 1.5- to 2.5-cm incision made directly over the interval between the fourth and fifth extensor compartments. This incision can allow reduction of this important fragment after the remainder of the fracture complex has been reduced. Temporary fixation with a Kirschner (K) wire may be used with direct visualization even of quite small fragments.
With variable-angle stable implants, a useful technique is to pass a fine K wire centrally through the ulnar-most hole of the plate within the fracture fragment under direct vision through the small dorsal incision. When the optimal K wire direction has been ascertained, the drill guide can be locked into position on the volar aspect of the plate. The K wire is then withdrawn, and the drill is passed down the drill guide ensuring that the drill will go in the exact location required to stabilize the critical dorsoulnar fragment. In addition, direct inspection over the fragment allows an optimal estimation of screw length with satisfactory engagement and stabilization of the fragment without the risk of excessive dorsal penetration and consequent extensor tendon irritation or damage. A small incision of this nature used primarily for temporary fixation followed by optimal positioning of volar angle stable screws does not seem to be associated with a compromise of flexion range, as is seen when positioning dorsal implants through dorsal incisions.
Although we have utilized the above-mentioned technique described by Orbay and Fernandez with pronation of the proximal ray or fragment to access and reduce dorsal and intra-articular fragments, we have certainly been satisfied with the safety and efficacy afforded by the use of a small supplementary dorsal incision. Access to the dorsoulnar fragment can usually be achieved through the interval between the fourth and fifth extensor compartments with the majority of the exposure occurring proximal to the main part of the extensor retinaculum.
In most cases, we have been able to achieve satisfactory reduction utilizing these techniques. We have tried to avoid arthrotomy when performing dorsal incisions. Our belief is that dorsal arthrotomy increases the risk of stiffness, particularly with regard to loss of flexion. Improvements in image intensification technology have led to the availability of high-quality intraoperative images. In addition, an understanding of appropriate positioning of the arm for intraoperative imaging has allowed a very satisfactory assessment of articular reduction without the need for arthrotomy in the majority of cases. Certainly, the use of the 15-degree inclined lateral to bring the articular surface of the lunate fossa into relief has been extremely valuable in indirect assessment of reduction.
The major area with a risk of malreduction through indirect assessment relates to malrotation of the radial column and scaphoid facet in the sagittal plane. This is considerably more difficult to assess using image intensification. Although it is rare to see rotational malalignment of a portion of the scaphoid facet, an index of suspicion needs to be maintained. This frequently occurs when a fracture line that involves the radial column passes between the radial origins of the radioscaphocapitate ligament and the long and short radiolunate ligaments within the region of the ligament of Testut. In this circumstance, care should be given to intraoperative screening to assess the reduction of the radial column in both the posteroanterior (pronated) view as well as the anteroposterior (supinated) view. The reduction may appear satisfactory in one of these views, but a clue to unsatisfactory reduction due to malrotation may be obtained in the alternate view. In addition, we have found that frequently this fracture pattern, which occurs between the above-mentioned ligamentous attachments, is often associated with a volar capsular rent within the same interligamentous plane. This is a rare circumstance in which we may choose to minimally extend this capsular rent with elevation of a small portion of capsule between the two major ligamentous structures, thereby affording a direct intra-articular view through a small arthrotomy. We have not seen any significant adverse sequelae in terms of stability, extension range, or pathologic ulnar translation of the carpus when we have used this minor arthrotomy, although we have been careful to respect the integrity of the radioscaphocapitate and radiolunate ligaments.
INTRAOPERATIVE TECHNIQUES WITH VARIABLE-ANGLE PLATES
These techniques and benefits may be achieved with all three classes of variable-angle stable plates previously described.
Accommodating Volar Fracture Line Variation
Distal Volar Fracture Line
When the volar fracture line is quite distal, the risk of joint perforation by screws exists if the plate is positioned in the optimal location covering the distal fragment. If the plate is positioned more proximally to ensure an appropriate relation between the distal screws and the distal articular surface, there is a risk that the volar fracture line may not be covered by the plate. This can lead to a biomechanically inferior construct.
With a variable-angle plate, the plate may be positioned more distally to cover the volar fracture line. The more ulnar screws may be directed perpendicular or even angled slightly proximal relative to the plate to ensure that articular perforation does not occur, but at the same time the angulation of the more radial screws may be adjusted so that radial column support is still achieved.
Volar Ulnar Fracture Line
When a sagittal plane fracture line exits on the more ulnar aspect of the distal radius, there is a similar risk of perforation of the distal radioulnar joint by fixed-angle screws when the plate is positioned to cover the volar fracture line and fragment ( Fig. 10-3 ). The sequelae of failing to stabilize the volar ulnar corner fragment with the risk of secondary loss of position and possible carpal subluxation is well described.
