Anatomical and Clinical Concepts in Distal Radius Volar Ulnar Corner fractures

Abstract

Background  Volar ulnar corner fractures are a subset of distal radius fractures that can have disastrous complications if not appreciated, recognized, and appropriately managed. The volar ulnar corner of the distal radius is the “critical corner” between the radial calcar, distal ulna, and carpus and is responsible for maintaining stability while transferring force from the carpus.

Description  Force transmitted from the carpus to the radial diaphysis is via the radial calcar. A breach in this area of thickened cortex may result in the collapse of the critical corner. The watershed ridge (line) is clinically important in these injuries and must be appreciated during planning and fixation. Fractures distal to the watershed ridge create an added level of complexity and associated injuries must be managed. An osteoligamentous unit comprises bone–ligament–bone construct. Volar ulnar corner fractures represent a spectrum of osteoligamentous injuries each with their own associated injuries and management techniques. The force from the initial volar ulnar corner fracture can propagate along the volar rim resulting in an occult volar ligament injury, which is a larger zone of injury than appreciated on radiographs and computerized tomography scan. These lesions are often underestimated at the time of fixation, and for this reason, we refer to them as sleeper lesions. Unfortunately, they may become unmasked once the wrist is mobilized or loaded.

Conclusions  Management requires careful planning due to a relatively high rate of complications after fixation. A systematic approach to plate positioning, utilizing several fixation techniques beyond the standard volar rim plate, and utilizing fluoroscopy and/or arthroscopy is the key strategy to assist with management. In this article, we take a different view of the volar ulnar corner anatomy, applied anatomy of the region, associated injuries, and management options.

Volar ulnar corner injuries of the distal radius account for 4 to 11% of distal radius fractures. ^{1 2} They can range from a large isolated stable fragment to a small fragment that is part of an unstable volar rim injury. The volar rim of the distal radius is crucial to the stability of the carpus due to the ligamentous attachments, as fractures in this area are associated with other concomitant wrist instabilities. ^{3 4} Due to their inherent instability, these injuries are usually managed operatively. The fixation is often challenging due to the local anatomy, size, and vascularity of the fragments, associated injuries, obtaining stability, and avoiding tendon irritation. Despite surgical intervention, there is an increased risk of loss of fixation, persistent instability, and need for revision surgery. ³ A good functional outcome can be obtained if these challenges are understood and addressed.

Anatomy

Bony Architecture

Sagittal images of the lunate facet demonstrate that the primary load-bearing area involves the lunate facet that has thick volar trabecular columns and is in line with the thick volar cortex ( Fig. 1A, B ). ⁵ This emphasizes that with these high loads on the volar rim, we require very stable, rigid fixation to avoid failure. As Wolf's law states, the regions of greater loading produce higher densities of bone. In the proximal humerus, the high-density region of cortical bone is known as the calcar. ⁶ It is similar to the calcar femorale that bears a compressive load from the femoral head to the proximal femur. ⁷ In contrast, the calcar femorale is internal but we believe this is due to the load bypassing the lesser trochanter. A microcomputed tomography slice of a cadaveric distal radius shows thickened trabeculae immediately distal to the thickened volar cortex ( Fig. 1B ). We believe the radial calcar comprises both the curved volar cortex and the internal thickened trabeculae.

Fig. 1.

Anatomy of the distal radius. ( A ) Cadaveric wrist with an oblique osteotomy through the radiocarpal joint. The osteotomy was performed obliquely from the volar ulnar corner across the scaphoid and lunate fossa. The volar cortex is a thick concave calcar that transmits the load to the diaphysis. C, capitate; L, lunate; S, scaphoid. The arrows show the transmission of load. ( B ) An oblique micro-CT image of a cadaveric distal radius demonstrating the thickened trabecular columns that transmit load to the thick volar cortex ( blue dotted arrow ). CT, computerized tomography. Image copyright: Gregory I. Bain.

The volar ulnar corner of the distal radius is the critical corner between the distal radius, ulna, and carpus. It consists of the overhanging radius with its lunate facet and sigmoid notch articulations. It includes the important volar ligament attachments, short radiolunate ligament (SRLL) and volar radioulnar ligament (VRUL). This “critical corner” has the unenviable responsibility of transmitting the load to the radial calcar and maintaining stability between the distal radius, ulna, and carpus.

Assessment of the wrist reveals a “Shenton's line” from the radius and ulna ( Fig. 2 ), a concept described for the hip by Shenton in 1902. Interestingly, the shape of the line created by the radius and ulna is similar to that of a Gothic arch ( Fig. 2 ), which has stood for centuries, due to the fact that mechanically it transmits the compressive forces from the building, bridge, or carpus. This concave parabolic arch does not experience the tensile stresses that lead to the failure of stone, concrete, and bone. The interosseous ligament spans the interval between the radius and the ulna. When there is a fracture of the radial calcar, the radial shaft translates in an ulnar direction, therefore closing the space, disrupting “Shenton's line,” and causing the collapse of the arch.

Fig. 2.

The radial and ulnar calcar. Cadaveric dissection illustrating the calcar (C) of the distal radius. The radial calcar is comprised of both the curved volar cortex and the internal thickened trabeculae. The yellow arrow illustrates the interosseous membrane between the radius and ulna. The dotted line along the distal radius and ulna is “Shenton's line.” This arch is parabolic in shape ( dotted lines ), similar to that of a Gothic arch, which mechanically minimizes tensile stresses. Image copyright: Amit Gupta.

Ligament Attachments

The carpal ligaments provide the stability to the carpus, proprioception to the wrist joint, and vascularity to the carpal bones. ^{8 9} They restrain the motion of the adjacent bone in the direction of its fibers. Disruption of the ligaments allows for subluxation of the joint under load.

Berger described the volar aspect of the distal radius to be completely spanned by a series of capsular ligaments. ¹⁰ He described the SRLL as one of the most important ligaments in the wrist. The SRLL attaches to the volar margin of the lunate facet and along with the bony morphology of the lunate fossa restrains volar translation of the carpus. ^{11 12}

The VRUL attaches at the volar limit of the sigmoid notch. The ligament extends ulnarly, with most of the ligament attached to the fovea of the ulna. It stabilizes the distal radioulnar joint (DRUJ), restraining subluxation of the ulna.

The long radiolunate ligament (LRLL) and the radioscaphocapitate ligament (RSCL) do not attach to the volar ulnar corner; they, instead, attach to the scaphoid facet. They are large capsular ligaments and are positioned to restrain the lunate and carpus against ulnar translocation. They can be involved in cases where there is further radial involvement of a fracture beyond the volar ulnar corner ( Fig. 3 ).

Fig. 3.

A “sleeper lesion” is a significant injury to a stabilizing structure that can be unmasked following loading or mobilization. By their nature, they are often missed due to the occult radiological changes. The ligamentous injuries can lead to carpal instability including ulnar translocation. The illustration shows the injury zone of the volar ulnar corner fracture, long radiolunate ligament ( black arrow ) and the distal radioulnar joint ( gray arrow ) with minimal bony involvement ( dotted lines ). DRUL, dorsal radioulnar ligament; LRLL, long radiolunate ligament; RSCL, radioscaphocapitate ligament; SRLL, short radiolunate ligament; VRUL, volar radioulnar ligament. Image copyright: Gregory I. Bain.

Applied Anatomy

Watershed Ridge

The watershed line is a term that is still being defined and debated in the literature. ^{13 14} The term has a geographical origin and relates to the topographic ridge, which spans between mountains, dividing the area into two rainfall catchment areas. The analog is that the dry bone radius is lying on the table, and the rain proximal to the ridge drains into the pronator fossa and the rain distal to the ridge drains toward the wrist joint ( Fig. 4A ).

Fig. 4.

The watershed ridge. ( A ) Cadaveric sagittal section highlighting the watershed ridge. Akin to the geographical definition of “watershed” describing a topographic ridge that divides two rainfall catchment areas, rain proximal to the ridge drains into the pronator fossa and the rain distal to the ridge drains toward the wrist joint. The watershed ridge is the most volar aspect of the distal radius ( black arrow ). The blue dotted arrows represent the water and water catchment separated by the ridge. White star = volar ligaments. L, lunate; PQ, pronator quadratus. (Image copyright: Gregory I. Bain). ( B ) Cadaveric anatomical specimen. The watershed ridge is the most volar aspect of the distal radius. The watershed ridge is identified by the dotted line. The thick volar capsule and volar carpal ligaments can make it difficult to palpate the osseous ridge during surgery. LRLL, long radiolunate ligament; RSCL, radioscaphocapitate ligament; SRLL, short radiolunate ligament; PQ, pronator quadratus fossa (Image courtesy: Amit Gupta).

We believe the best definition is that it is a ridge and is the most volar aspect of the distal radius ( Fig. 4A ). It is not a single point, and during surgery, we cannot physically see the line. We can palpate the raised volar tubercule of the radius and appreciate the landmark in that manner. Proximal to the watershed ridge is the pronator fossa, with the pronator quadratus. ¹⁵ Distal to the watershed ridge is the attachment of the strong volar ligaments ( Fig. 4B ). The thickness of the adjacent pronator quadratus and fibrous transition zone may make it more difficult to interpret.

The watershed ridge usually serves as the distal limit for the placement of a volar plate. ¹⁵ Most volar fractures are depressed and/or impacted, extending proximal to the watershed ridge. The standard volar plate proximal to the watershed ridge provides a buttress for the fracture, while minimizing tendon irritation. ^{16 17}

The raised volar tubercule provides the offset mechanical advantage for the volar ligaments. So, by definition, any fracture distal to the watershed ridge involves the attachments of the volar ligaments. These fractures that are distal to the watershed ridge are much more difficult to manage, as they are small ligament avulsion fractures. This highlights the anatomical reason why these injuries are associated with carpal instability. ¹⁸ In addition, the fracture is too distal to allow a buttress plate to be used, so other fixation methods are required.

Fragment Vascularity

Following a fracture of the distal radius, there are regional hyperemia and edema that develop to assist with fracture healing. The hyperemia causes regional osteoporosis making the fragment softer, structurally weaker, and prone to collapse or displacement ¹⁹ ( Fig. 5 ). Iatrogenic ischemia may occur following open surgical reduction if there is extensive stripping of the soft tissues from the fragments. Poor quality fixation that allows interfragmentary motion will also compromise vascularity of articular fragments ¹⁹

Fig. 5.

Coronal T2 MRI of a 17-year-old female 3 weeks following a distal radius fracture. The causes of the posttraumatic high-signal changes surrounding the fracture include osseous edema, hyperemia, and regional osteopenia. The result is soft metaphyseal bone, which is prone to secondary collapse in the first few weeks. MRI, magnetic resonance imaging. Image copyright: Gregory I. Bain.

Fracture Characteristics

The pathogenesis of intra-articular fractures of the distal radius involves ligament tension, bony compression, and shearing forces between the articular fragments. ¹⁸ There is a strong association between fracture location and known ligament attachments. ¹¹

Physiological extension of the wrist creates tension on the volar radiocarpal ligaments and acts as a tension band, increasing contact pressure on the lunate facet. Following impact on an outstretched hand, forced hyperextension and axial compression cause a fracture of the subchondral bone plate and avulsion of the lunate facet with the attached SRLL ( Fig. 6 ). The wrist settles with volar subluxation of the carpus, with its attached SRLL and lunate facet. With ulnar deviation and carpal supination, the force propagates radially to include the scaphoid facet with the LRLL and RSCL, leading to ulnar translocation. ²⁰ The pattern of injury depends on the quality of the bone, the position of the wrist, and the velocity of impact. With most low-energy injuries, there is lunate impaction into the lunate fossa. When there is a higher energy injury, there may be extension further into the metaphyseal aspect of the radius. We have observed cases where there is a pronation rotatory component, where the axial computerized tomography (CT) scan images demonstrate that the volar fragment and the carpus have rotated around the VRUL. There must be an associated volar capsular disruption with this pattern of injury ( Fig. 7A–C ).

Fig. 6.

Fracture characteristics. With forced wrist extension the ligaments become taut, creating a compressive force. ( A ) Axial forces ( red arrows ) can result in the lunate impacting against the volar ulnar corner (Image copyright: Crespi for Gregory I. Bain). ( B ) Following the fracture, the SRLL remains intact, leading to the displacement of the osteoligamentous unit and volar subluxation of the carpus. SRLL, short radiolunate ligament (Image copyright: Bain Chiri).

Fig. 7.

Pronation of the volar ulnar corner fragment. ( A ) Axial CT image of the wrist at the level of the DRUJ. The volar ulnar corner fragment pronates around the intact volar radioulnar ligament attached to the fovea. The fracture fragment is then superimposed and reduced to calculate the angle of rotation. The yellow lines represent the degree of rotation (14°). ( B ) A three-dimensional CT reconstruction showing rotation of the fragment. The arrow shows the pronation of the fragment. Note the volarly subluxated scaphoid (S) and lunate (L). ( C ) Axial CT image with the radius and carpus superimposed and two sagittal CT slices through the lunate fossa and scaphoid fossa. The lunate and scaphoid both subluxate volarly with the fragment. The scaphoid is not contained; therefore, the radioscaphocapitate ligament must be disrupted. L, lunate; S, scaphoid, F, fragment. CT, computerized tomography; DRUJ, distal radioulnar joint. Image copyright: Gregory I. Bain.

The injuries we have found most concerning are the volar rim avulsion fractures. Radiological findings maybe subtle, with small avulsions and carpal subluxation. The main ligament injuries are usually obvious, but injuries to adjacent secondary stabilizers may be more subtle. However, the extensive soft swelling should ring alarm bells, highlighting the extensive soft tissue injury that is not apparent on plain radiographs. There can be a further or secondary carpal subluxation , as the swelling subsides and the secondary restraints are loaded.

Associated Injuries

A retrospective review recognized that along with volar subluxation of the carpus, the volar ulnar corner fractures can be associated with scapholunate instability, DRUJ instability, and ulnar translocation of the carpus. ²¹ They are complex injuries that can result in many different forms of instability if not recognized and managed appropriately. We will explore some of the reasons for them.

The Osteoligamentous Unit

The concept of an osteoligamentous unit is important to appreciate as it allows us to understand the fracture characteristics and plan fixation according to these units. We have identified that distal radius fractures typically occur between the ligament attachments, and the ligaments remain attached to the fragments. ^{11 21} The ligament attachments determine the settling position and the deformity of the fracture. The lunate facet when fractured displaces in a volar and proximal direction and continues to articulate with the lunate ( Fig. 6 ). This is an important observation as it indicates that the strong SRLL remains attached to the lunate and lunate facet of the radius. Thus, the osteoligamentous unit is a functional bone–ligament–bone construct, and assessment and fixation must take into account the integrity of the osteoligamentous unit(s) involved in an injury ( Fig. 8A, B ). In addition, care is required during the surgical exposure to ensure that the individual units remain intact.

Fig. 8.

Osteoligamentous concept. ( A ) Volar Ulnar Corner osteoligamentous unit involving the short radiolunate ligament (SRLL). The unit includes the volar ulnar corner fragment (bone), short radiolunate ligament (ligament) and the lunate (bone). These units must not be disrupted during surgery as this may result in delayed carpal instability. ( B ) Radial styloid osteoligamentous unit involving the radioscaphocapitate ligament (RSCL). The bone–ligament–bone unit is highlighted and involves the radial styloid (bone), radioscaphocapitate ligament (ligament) and the capitate (bone). Image copyright: Crespi for Gregory I. Bain.

Carpal Instability

Carpal instability is commonly associated with volar lunate facet fractures and, unfortunately, often persists after surgical stabilization. ³

Radiocarpal Instability

Volar subluxation of the carpus is well known to be associated with volar rim fractures. Clarnette et al identified that the volar fragment and the lunate maintain their association, which implies that the SRLL remains intact ( Fig. 6 ). ⁴ The lunate facet also has the VRUL attachment of the triangular fibrocartilage complex (TFCC), which attaches to the fovea and ulnar styloid. With the smaller fragment fractures, there is increasing volar and proximal translation of the lunate facet fragment. We postulate that the carpus pronates around the fovea of the distal ulna ( Fig. 7A, B )

Scapholunate Instability

Clarnette et al identified that the volar scapholunate interval increased with a greater displacement of the lunate fossa fragment. Sun et al replicated these findings without reaching statistical significance along with identifying an increased volar scapholunate interval in the volar coronal fracture subtype ( Fig. 9 ). ¹⁸ This is likely due to the compromise of secondary stabilizers of the scapholunate joint and displacement of the lunate osteoligamentous unit (SRLL).

Fig. 9.

Scaphoid and lunate orientation for volar ulnar corner (VUC) fractures. Both the scaphoid and lunate translate in a volar ulnar direction, 1.0 and 1.6 mm, respectively. There is pronation of 4.4° and 5.3°, respectively. The SL interval was increased compared with the control wrists. Image modified from Sun et al. ¹⁸

Ulnar Translocation

We have seen cases of ulnar translocation of the carpus, both before and after stabilization of the volar ulnar corner injuries ^{3 18} ( Fig. 10 ). As mentioned, this is most likely due to the propagation of the force associated with the fracture radially to involve the LRLL and RSCL. It can also be caused by iatrogenic injury to the volar capsule/ligaments during surgery and also due to subtle osseous collapse following fixation.

Fig. 10.

Ulnar translocation of the carpus. Preoperative three-dimensional CT reconstruction and radiographs of a 42-year-old male patient following fixation (Synthes Volar Rim Plate) of a very distal volar ulnar corner fracture via an extended FCR approach. The white dotted lines mark the ulnar border of the radius to assess ulnar translocation of the lunate. The majority of ulnar translocation of the carpus occurred between day 14 and 30. We believe this maybe caused by either an iatrogenic volar capsular release used to expose the joint surface, prior to application of the plate or due to subtle osseous collapse following fixation. The associated ligamentous injuries predispose to the further collapse which need to be identified and stabilized. CT, computerized tomography; FCR, flexor carpi radialis. Image copyright: Gregory I. Bain.

Distal Radioulnar Joint Instability

We have found that the DRUJ widening and instability can be associated with volar ulnar corner injuries. ³ The fracture is typically into the sigmoid notch, with it rotating around the VRUL.

Secondary Collapse

We have witnessed cases with a volar ulnar corner fracture with minimal displacement that appears to be innocuous. However, some of these fractures have had secondary collapse or subluxation of the carpus. It does beg the question as to why this occurs. We believe there are several factors that contribute to the secondary displacement. The force from the initial volar ulnar corner fracture can propagate along the volar rim resulting in an occult volar ligament injury, which is a larger zone of injury than appreciated on radiographs and CT scans ( Fig. 3 ). These lesions are often underestimated at the time of fixation, and for this reason, we refer to them as sleeper lesions. Unfortunately, they may become unmasked once the wrist is mobilized or loaded. The cases in which the sleeper lesions should be considered are the higher energy injuries, with significant bruising/swelling, and those cases with associated dislocation which is now reduced. The clinician needs a high index of suspicion to unmask these lesions and should consider magnetic resonance imaging (MRI), stress fluoroscopy, and arthroscopy. It is important to point out that these sleeper lesions were not part of the original osteoligamentous unit concept yet they are now an integral extension to that understanding.

The body's response to a fracture includes edema and hyperemia followed by regional osteopenia surrounding the fracture site. This is typically in the first few weeks and makes the bone soft and at risk of further collapse. The combination of the load on the lunate fossa fragment and mobilization creating tension on the ligaments before the fracture has united may lead to secondary fracture collapse and subluxation of the carpus. This MRI example demonstrates these physiological aspects of fracture healing ( Fig. 11 ). Obviously, these same physiological factors occur following internal fixation.

Fig. 11.

Posttraumatic osseous resorption. 63-year-old female with a volar Barton's fracture. Sagittal CT scan images demonstrate: ( A ) At day 0 of the injury, there is a volar distal radius fracture with no obvious dorsal fracture. Volar tilt is 19°. ( B ) At day 14, there is considerable resorption of the underlying metaphyseal bone. Now the distal radius articular surface is only stabilized by the cantilever of the thin dorsal cortex. The loading point of the lunate facet has slipped volarly, down the articular slope (22°), to be volar to the radial shaft ( dotted white line ). There is now sclerosis of the dorsal metaphyseal bone, which could be from impaction or new bone formation. Any greater force or volar translation, and the dorsal radial cortex would fracture, leading to a volar fracture dislocation. ( C ) At day 35, there is minimal further collapse and the radial volar tilt has stabilized at 22°. Image copyright: Gregory I. Bain.

Surgical Management

It is important to define the surgical approach that will allow the fracture to be exposed, reduced, and stabilized. The options are follows.

Modified Henry's Approach

Traditionally, the volar aspect of the distal radius is approached through the classic Henry approach between the radial artery and flexor carpi radialis (FCR) tendon or modified FCR approach through the bed of the FCR sheath. Despite surgeons being most comfortable with this approach, the difficulty is inadequately visualizing the volar ulnar corner due to the overlying flexor muscle mass. A fracture with a large volar ulnar corner fragment or a volar Bartons fracture will be suitable for this approach due to the larger and more proximal fragment sizes. These types are also comparatively more stable.

Extended Flexor Carpi Radialis Approach

This approach requires the FCR tendon and its sheath to be released to the trapezium that exposes the ulnar corner when FCR is retracted ulnarly. It also involves the release of the “radial septum” that exposes the distal radius metaphysis and dorsal fragments. Orbay et al recommended this approach for complex distal radius fractures as it provided improved access and facilitated the reduction of volar ulnar corner fragments. ²² An extended FCR approach is preferred if a volar ulnar corner fracture is one component of the distal radius injury or there is more radial extension of a marginal volar rim fracture.

Dual-Window Approach

The dual-window approach utilizes the retraction of the flexor tendon mass in a radial or ulnar direction to visualize the volar aspect of the distal radius. It is a combination of the modified Henry approach and an anteromedial approach between the flexor mass/median nerve and the ulnar pedicle. ²³ The incision is extended in a distal and ulnar direction, which allows the flexor tendon mass to be retracted radially, to enable visualization of the volar ulnar corner through the more ulnar sided window. An advantage of this approach is that while the wrist is in traction and the flexor mass is taught, the exposure is not compromised and visualization of the volar ulnar side is achievable through the ulnar-sided window.

Volar Ulnar Approach

This approach utilizes a curved ulnar-based incision, along the interval between the ulnar neurovascular bundle and the flexor tendon mass ( Fig. 12 ). The flexor retinaculum is released to allow the flexor tendons to be retracted radially. ²⁴ This is a safe and extensile approach that results in excellent exposure of the entire volar distal radius and carpus. This approach is useful for the isolated volar ulnar corner fragment (type 1). The senior author has found this approach to be a good option to manage the acute VUC fractures and for the revision cases. ²⁵ This extended version provides exposure of the distal radius, DRUJ, and carpus. A more limited version includes the proximal aspect of the above incision ceasing at the wrist crease without releasing the flexor retinaculum. This allows exposure of the volar distal ulna and the ulnar aspect of the distal radius including the volar ulnar corner.

Fig. 12.

Volar ulnar approach. ( A ) The skin incision proximally is radial to FCU tendon then passes the wrist crease obliquely. It then passes across the transverse carpal ligament along the line of the ring finger and enters the palm just ulnar to the thenar crease. It is a safe, extensile approach and allows excellent exposure of the volar ulnar corner (Image copyright: Crespi for Gregory I. Bain). ( B ) The interval is between the ulnar neurovascular bundle and the flexor mass. Pronator quadratus is then reflected from the radius subperiosteally (Image copyright: Crespi for Gregory I. Bain). ( C ) With the transverse carpal ligament divided, flexion of the wrist and retraction of the flexor tendons with Hohmann retractors along the radial border allow for excellent exposure of the volar aspect of the carpus, wrist capsule, pronator quadratus and the distal radius (Image copyright: Gregory I. Bain). FCU, flexor carpi ulnaris, FM, flexor tendon mass, PQ, pronator quadratus, UN, ulnar neurovascular bundle; VC, volar capsule.

Assessment of Reduction

Achieving articular congruency and accurately assessing carpal ligament integrity are both important aspects of treating volar ulnar corner fractures. A valuable adjunct to this is the use of arthroscopy and fluoroscopy. ²⁶ Burnier et al reported that the addition of arthroscopy provided a more accurate reduction of intra-articular distal radius fractures than fluoroscopy alone. ²⁷ Both assessment modalities allow dynamic assessment as well as careful visualization of subtle changes associated with fixation and carpal instability. A stress examination under arthroscopic ²⁶ and/or fluoroscopic assessment ³ can be performed by applying a posterior–anterior force to elicit volar subluxation and a radial–ulnar force to assess for ulnar translocation.

Arthroscopic-assisted reduction and internal fixation is a recognized technique, which has been recently revised to ensure adequate access to the ulnar column of the distal radius. ²³ This can all be done while the wrist is in the traction tower that may aid with reduction. With the addition of more distal plating options, intra-articular screw penetration is a risk. If there is any doubt, the arthroscope can easily be introduced through the volar capsule, which is already exposed. ²⁶ As previously discussed, the rate of associated carpal injuries is high, and arthroscopy allows for meticulous assessment and/or treatment of the scapholunate ligament and TFCC.

Fixation

It is important to appreciate the spectrum of these injuries and the associated ligament injuries and the possible types of instability. There are various types of fixation methods that have been successful in treating volar ulnar corner fractures. The goal is to stabilize the fracture and the carpus.

Buttress Plating

Buttress plates have traditionally been the mainstay of fixation of volar distal radius fractures. However, buttress plates are only effective for the main large volar fragments, proximal to the watershed ridge. As these fractures often have other aspects that are distal to the watershed ridge, other fixation options often need to be considered.

There are also anatomic and task-specific plates that can be used to stabilize the distal fragments and, in this context, often used as buttress devices. The most important aspect to buttress plating is to ensure the correct position of the plate. If the plate is not in its appropriate position, the fragment can escape either distal or ulnar to the plate. ³ Fig. 13A shows our recommended technique in ensuring that the plate is properly positioned. Medoff developed the “volar buttress wire forms,” which include wires that are advanced into the distal fragment, which is then stabilized to the metaphyseal radius more proximally. ²⁸

Fig. 13.

Our recommended method for plate positioning for distal radius fracture. ( A ) Buttress plate. Perform an anatomic reduction of the distal radius and provide provisional fixation with K-wires. Insert a hypodermic needle into the Radiocarpal (RC) joint (1) and the DRUJ (2). Identify the point 8 mm proximal to the RC needle and 6 mm radial to the DRUJ needle. Insert a K-wire parallel to the radiocarpal joint surface (3). ( B ) Advance the ulnar corner hole of the plate over the K-wire (4). Center the proximal aspect of the plate on the diaphysis and insert the second K-wire into the most proximal aspect of the plate (5). Bend the K-wires away from each other which will provisionally stabilize the plate to the radius (6). ( C ) Containment plate. A similar method can be performed for the volar rim plate. Note, however, the K-wire requires to be placed further distal. DRUJ, distal radioulnar joint; K-wire, Kirschner wire. Image copyright: Bain Chiri.

Containment Plating

There are some plates that are designed to do more than buttress the fragments but extend more distally to contain the entire metaphysis and volar rim of the distal radius ²⁹ ( Fig. 13B ). These plates stabilize the fracture proximal and distal to the watershed ridge. As the “volar rim plate” extends past the watershed ridge, it places the flexor tendons at risk. It is critical to ensure that none of the screw heads are prominent, as they will quickly compromise the tendons. We usually pass the gloved finger over the plate and screws, to see if any aspect of the screws catches the glove. If this is the case, the screw is advanced or removed. We usually plan to remove these plates at 3 months.

Compression Fixation

Interfragmentary screws can be used to stabilize some of the fragments via compression. They are particularly good for the radial styloid fragments and in this context as an independent screw into the smaller volar ulnar corner fragment. Additionally, Kirschner wire (K-wires) can be inserted, bent, and compressed under a buttress plate. This can be useful when the volar ulnar corner fracture is one component of a comminuted metaphyseal distal radius fracture requiring a standard volar locking plate. This containment construct is then held rigidly under the plate.

Capture Fixation

New generation hook plates grasp and capture the avulsed fragment, with its associated ligaments. The hook will only be effective if it captures the distal fragment and its associated ligaments, and then pulls it down onto the metaphysis. This is usually achieved by placing an eccentric dynamic compression screw into the proximal hole. ³⁰ The capture plates often need to be removed at 3 months, as they are often very distal, and can encroach upon the flexor tendons.

Tension Devices

Tension-type fixation devices pull down the fragments and convert tensile forces into compression. ³¹ Examples include wire-loop sutures and suture anchors. ³² Volar rim fractures will often have propagation injuries of the adjacent ligaments. To augment fracture fixation, it is often necessary to repair the adjacent capsular avulsion using transosseous sutures or small suture anchors. Care is required to ensure that metallic suture anchors will not impinge on the joint, especially if there is fracture collapse.

Neutralization Devices

Complex unstable injuries, such as a comminuted fracture-dislocation, often need to be protected with a wrist neutralization device, such as a dorsal bridge plate or external fixateur. This unloads the zone of injury and protects the fixation, therefore reducing the chance of fixation failure. When applying a dorsal bridging plate, it is important to be sure that any carpal subluxation is reduced. There will be a tendency for persistent volar subluxation and/or ulnar translocation and supplemental transarticular K-wires to stabilize the carpus maybe required ( Fig. 14A, B ). Finally, a K wire may be used as an interfragmentary fragment neutralization device.

Fig. 14.

( A ) Fluoroscopic Anterior Posterior (AP) image of a revision volar ulnar corner fracture in a 42-year-old male who initially had surgical fixation acutely and consequently collapsed and developed ulnar translocation. Revision surgery performed at 3 months included a volar ulnar approach, release of the volar ligaments, and distal radius osteotomy to reduce the inclination and to reduce the risk of recurrent ulnar translocation. The osteotomy was stabilized and the capsule and Triangular Fibrocartilage Complex (TFC) repaired. There was still a tendency for ulnar translocation, so this was reduced, and radiocarpal transarticular K-wires were inserted. Due to the complex situation, a neutralization dorsal bridging plate was applied. ( B ) Lateral radiograph of the same patient at 3 months postfixation. The correction of the ulnar translocation has been maintained with the aid of the K-wires, and the dorsal bridge plate has minimized collapse of the revision distal radius fixation. K-wires, Kirschner wire. Image copyright: Gregory I. Bain.

Bone Graft

Volar ulnar corner fractures tend to be associated with impaction that can leave a void following reduction of the articular fragment. Filling this void with a bone graft will improve fracture stability and reduce displacement or collapse.

Surgical Results of Fixation of Volar Lunate Facet Fractures

Eardley-Harris et al reported a significantly higher incidence of carpal instability, failure of fixation, and a requirement for revision surgery in volar marginal rim fractures when compared with a cohort of consecutive intra-articular fractures. ³ Interestingly, four of the six failures occurred within the first 2 weeks. Preoperative factors associated with failure include osteoporosis, medical co-morbidities, high-energy injuries, distal volar rim fractures, and associated DRUJ and carpal instability. An intra-operative factor included failure to capture the volar fragment with a standard buttress plate so that it escapes over the distal or ulnar edge of the plate ( Fig. 15 ). This is either due to the buttress plate being poorly positioned or failure to recognize that a containment plate was required. If persistent instability is evident, the use of a dorsal neutralizing bridge plate is recommended.

Fig. 15.

Fragment escape after surgical fixation of the volar rim. This is often due to the fragment not being adequately contained and/or captured by the fixation. A lateral X-ray of a distal radius fracture internally fixed with a volar distal radius plate. There is fragment escape of the volar ulnar corner fragment ( yellow arrow ) and associated volar translation of the lunate (L) and carpus ( white arrow ). Image copyright: Gregory I. Bain.

Inadequate fixation of the volar marginal rim fragment was evident in the failures and highlighted the importance of preoperative three-dimensional (3D) imaging and planning, gaining adequate exposure, and the use of a containment plate such as the volar rim plate. Supplemental fixation with interfragmentary screws or K-wires may also be necessary.

Postoperative Management

We recommend a detailed assessment of the fracture and the fixation to understand the stability and potential complications. Due to the reported higher rate of early failure, we will often perform a postoperative CT scan. In most cases, we can commence early mobilization. In complex cases, we may use a postoperative cast immobilization for a few weeks. Repeat plain radiographs may also be used weekly for the first few weeks.

Recommendations

Often the most difficult aspect of volar ulnar corner injuries is correctly identifying them to appreciate the potential for associated injuries and formulate a plan to stabilize and fix. We recommend that these injuries be managed by a dedicated upper limb specialist. Appropriate preoperative imaging includes plain films and 3D imaging to understand the fracture configuration and the associated carpal instabilities. The use of intraoperative fluoroscopy and arthroscopy allows the surgeon to identify subtle carpal instability and dynamic translocation of the carpus. Depending on the pattern of injury, an extended FCR approach or volar ulnar approach is recommended. The choice of fixation depends on the fracture configuration. Very distal fractures often require interfragmentary screws and containment plating. If there is an extensive injury, we have a low threshold to include a neutralizing dorsal bridge plate.