|SYMPOSIUM - DISTAL RADIAL FRACTURES
|Year : 2020 | Volume
| Issue : 2 | Page : 30-35
Surgical anatomy of distal radius and surgical approaches for distal radius fractures
Shilp Verma, Alok Chandra Agrawal, Buddhdev Nayak, Bikram Kar, Harshal Sakale, Sandeep K Yadav
Department of Orthopaedics, All India Institute of Medical Sciences, Raipur, Chhattisgarh, India
|Date of Submission||28-Jun-2020|
|Date of Decision||18-Jul-2020|
|Date of Acceptance||25-Jul-2020|
|Date of Web Publication||10-Sep-2020|
Department of Orthopaedics, All India Institute of Medical Sciences, Raipur Chhattisgarh
Source of Support: None, Conflict of Interest: None
Distal radius fractures are increasingly managed by operative means now. Hence the anatomy and surgical approaches are of utmost importance. Distal end of radius articulates with carpal bones forming radiocarpal joint and distal ulna forming distal radio ulnar joint. Presence of multiple tendons and neurovascular structure makes the dissection of this area difficult. Authors have reviewed the anatomy and surgical approaches of this area.
Keywords: Anatomy, distal radius, surgical approach
|How to cite this article:|
Verma S, Agrawal AC, Nayak B, Kar B, Sakale H, Yadav SK. Surgical anatomy of distal radius and surgical approaches for distal radius fractures. J Orthop Dis Traumatol 2020;3:30-5
|How to cite this URL:|
Verma S, Agrawal AC, Nayak B, Kar B, Sakale H, Yadav SK. Surgical anatomy of distal radius and surgical approaches for distal radius fractures. J Orthop Dis Traumatol [serial online] 2020 [cited 2020 Sep 22];3:30-5. Available from: http://www.jodt.org/text.asp?2020/3/2/30/294734
| Introduction|| |
Fractures of the distal radius are one among the most common fractures seen., As our population ages, the prevalence of these injuries is expected to increase. Similarly, over the past several years, we have observed increase in the surgical management of distal radius fractures. Only few studies on the anatomy of the radial epiphysis have been published in the past 10 years. Published studies on distal radius anatomy in recent years have focused on three aspects: distal limit and watershed line, dorsal tubercle, and wrist columns. This information should be taken into account during volar plating of distal radius fractures. Henceforth, in this article, we review the regional anatomy of the distal radius and the various relevant surgical approaches.
| Anatomy|| |
Exposure of the distal radius and its fracture fragments is complicated by proximity to the surrounding muscle, ligaments, tendons, and neurovascular structures. The individual alignment of various articular fracture fragments of the distal radius is affected by these soft tissue attachments. When studying the distal radius, it is helpful to consider its five “surfaces:” (1) the volar surface, (2) the radial surface, (3) the dorsal surface, (4) the distal radiocarpal articular surface, and (5) the distal radioulnar articular surface.
The anterior surface is concave, angled anteriorly, and covered by the pronator quadratus [Figure 1]. Its rough surface provides an attachment point for the palmar radiocarpal ligaments. The anterior surface extends radially from the radial styloid ulnarly to the triangular fibrocartilage complex (TFCC). It extends distally and ulnarly to the capitate (radiocapitate), lunate (radiolunate), and triquetrum (radiotriquetral) surface [Figure 2]. Superficially, the volar anatomy of the wrist includes, from radial to ulnar: radial artery, flexor carpi radialis (FCR) tendon, palmaris longus tendon, and flexor carpi ulnaris tendon. Deep to the palmaris longus tendon lies the median nerve and the finger flexor tendons. The flexor pollicis longus tendon lies deep to the FCR tendon. The deepest volar soft tissue structure is the pronator quadratus as it completely covers the flat volar surface of the distal radius.
|Figure 1: The four surfaces (anterior, medial, posterior, and lateral) of the distal radius are shown from left to right along with the styloid process and dorsal tubercle|
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|Figure 2: Volar view of the distal radius showing in dotted line, the anatomical region of interest|
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The lateral surface extends along the lateral margin to form the styloid process [Figure 1]. The styloid process is conical and projects 10–12 mm beyond the articular surface for the proximal scaphoid and lunate. The distal part of the styloid provides an attachment for the articular capsule and for the capsular thickening of the collateral ligament. A more proximal area at the base of the styloid provides the brachioradialis attachment [Figure 3]. The radial sensory nerve emerges from below the brachioradialis tendon approximately 8–9 cm proximal to the radial styloid and on average divides into four branches., The dorsal cutaneous branch of the ulnar nerve provides sensation to the ulnar aspect of the wrist. It arises approximately 3–5 cm proximal to the ulnar styloid, and it typically crosses volar to the head of the ulna before traveling dorsally to the ulnar hand.
|Figure 3: One oblique and one anterior view of the distal radius showing the more proximal pronator quadratus (solid line) and the watershed line (dashed line)|
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The medial surface of the distal radius consists of the ulnar notch and the articular surface for the ulnar head [Figure 1]. The distal radius rotates about the ulnar head by means of the sigmoid notch, which is concave with well-defined dorsal, palmar, and distal margins. Its depth varies according to the articulation with the ulnar head. Ulnar length varies with radial length and changes with pronation and supination. Between the distal radioulnar joint and the radiocarpal joint, there is a ridge, located in the ulnar notch; this ridge provides the radial attachment point for the TFCC. The TFCC arises from the ulnar aspect of the lunate facet of the radius, above the sigmoid notch, and extends on to the base of the ulnar styloid process. It functions as an additional stabilizer of the distal radioulnar joint and increases the relative articulating area of the wrist [Figure 4]. A large fracture of the ulnar styloid or peripheral tear of the TFCC can theoretically destabilize the distal radioulnar joint.
The dorsal surface and radial surface are otherwise covered by the six traversing extrinsic dorsal extensor compartments of the wrist. The radial surface is covered by the first dorsal compartment and its abductor pollicis longus and extensor pollicis brevis tendons. The second dorsal compartment is separated by the third dorsal compartment by Lister's tubercle, which acts as a pulley for the extensor pollicis longus (EPL) tendon running within the third dorsal compartment [Figure 5].
|Figure 5: Diagram showing extensor compartment of wrist, with star mark indicating surgical plane|
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| Osseous Anatomy|| |
The distal end of the radius should be viewed as the anatomic foundation of the wrist joint. Beginning 2–3 cm proximal to the radiocarpal joint at the metaphyseal flare, the distal end of the radius is uniquely designed to maintain the capacity to transmit axial load and provide mobility. In the coronal plane, the distal radius assumes an inclination of 22°–23°. In the sagittal plane, the distal radius assumes a tilt angled volarly approximately 11°–12° [Figure 6].
|Figure 6: Radial and volar column representing volar tilt, radial inclination, and watershed line|
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The distal radiocarpal articular surface is both biconcave and triangular in shape. The apex of the triangle points toward the radial styloid process, and the base of the triangle forms the sigmoid notch which articulates with the distal end of the ulna. Viewed from the lateral side, the radial styloid sits volar to the mid-axis of the radius. The articular surface is separated into two distinct concave facets known as the scaphoid and lunate facets, with the latter having a larger radius and extending volarly into the lunate facet. Standard compressive articular fracture lines commonly propagate between these facets. Additional compressive force will split the fragments in the coronal plane or cause central fragmentation and impaction. In addition, there is often an associated intercarpal ligament injury with radial styloid fractures that exit at the level of the scapholunate ligament.
The volar aspect of the lunate facet is approximately 5 mm thick and projects approximately 3 mm anteriorly to the flat volar surface of the distal radius, making it relatively vulnerable to injury and difficult to fix internally.
| Surgical Approach|| |
The volar approach can be accomplished through three different intervals: (1) the Henry approach, (2) the trans-FCR approach, and (3) the volar-extensile approach. Both the Henry and trans-FCR approaches provide excellent exposure to the volar surface of the distal radius for the reduction and internal fixation of distal radius fractures.
The Henry and transflexor carpi radialis approach
Although similar in the location of the incision and the deep surgical dissection, the Henry approach and trans-FCR approach utilize different superficial intervals before exposure of the deep volar compartment or the space of Parona. The classic Henry interval describes the volar forearm approach to the radius but did not specifically describe exposure of the wrist.
Henry approach is taken distally to the level of the wrist; the interval will lie between the FCR tendon and the radial artery. In contrast, the trans-FCR approach involves opening the tendon sheath of the FCR tendon and through its floor entry into the deep volar compartment is achieved [Figure 7]. Both provide reliable approaches to the volar surface of the distal radius, but the trans-FCR approach affords the benefit of not requiring direct radial artery dissection and isolation. The palmar cutaneous branch of the median nerve is potentially at risk for injury but can be prevented by avoiding any dissection ulnar to the FCR tendon.
|Figure 7: Henry approach, volar extensile approach, and transflexor carpi radialis approach|
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The incision is placed longitudinally in line with the FCR tendon. For volar plate insertion, the incision should measure approximately 7–8 cm but can be extended proximally as needed. If necessary, the wrist crease should be crossed obliquely. Superficially, either the Henry approach can be utilized or the trans-FCR approach [Figure 7]. If the latter is used, the FCR tendon should be fully mobilized and retracted ulnarly to maximize release and entry through its tendon sheath floor. Using blunt dissection, the flexor pollicis longus tendon and the flexor digitorum superficialis and profundus tendons are swept ulnarly. Avoid radial retraction of the flexor pollicis longus to avoid potential denervation of the muscle. Retraction is best held with reverse or right angle retractors. Self-retaining retractors should be used with caution. The pronator quadratus is released along its radial border of the distal radius and raised ulnarly. To facilitate repair of the pronator quadratus upon closure, the release is performed as far radial as possible and should be raised in a subperiosteal fashion.
If the carpal tunnel requires release connecting the original incision with the carpal tunnel, incision should be avoided due to high risk of injury to branches of the palmar cutaneous branch of the median nerve. Similarly, identification and protection of the branches can avoid inadvertent traction or injury.
The volar-extensile approach
The volar-extensile approach requires placement of an incision further ulnar in a longitudinal fashion between the palmaris longus and flexor carpi ulnaris tendons. The incision is brought obliquely across the wrist into the palm for the carpal tunnel release [Figure 7]. The fascia is released between the flexor carpi ulnaris and the palmaris longus, and the interval between the ulnar neurovascular structures deeps to the flexor carpi ulnaris ulnarly and the flexor digitorum superficialis/profundus tendons radially developed. As the dissection is taken distally, the ulnar neurovascular structures are allowed to traverse ulnarly as they travel toward Guyon's canal and the finger flexor tendons are retracted radially, thereby exposing the volar ulnar corner of the distal radius and the floor of the carpal tunnel.
Lattmann et al. compared the direct volar approach with a concomitant carpal tunnel release versus the standard Henry approach for volar plate fixation of distal radius fractures and found a significant increase in median nerve irritation both early and late, following fracture fixation.
The radial approach
Place the incision along the radial side of the wrist in a longitudinal or oblique fashion. Identify the branches of the radial sensory nerve that will be located immediately in the subcutaneous tissue. Gently mobilize and retract these nerves. The first dorsal compartment will be crossing along the volar border of the radial styloid [Figure 8]. The second dorsal compartment will be crossing along the dorsal border of the radial styloid. The brachioradialis inserts onto the radial styloid deep into the first dorsal compartment at its base. There will be a bare area between the first and second dorsal compartments at the distal aspect of the radial styloid. To expose the styloid, raise the first compartment in a subperiosteal fashion volarly. Alternatively, the first compartment's tendon sheath can be released in its entirety and both the abductor pollicis longus and extensor pollicis brevis tendons can be retracted and the styloid exposed through the compartment floor. Proximally, the brachioradialis can be released in its entirety as needed both for exposure or to eliminate its deforming force.
|Figure 8: Diagram showing dorsal approach, transextensor pollicis longus, and dorsal ulnar approach through extensor retinaculum|
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The dorsal approach
The dorsal approach to the distal radius can be used for dorsal plate and fragment-specific fixation of fractures. Approaching the distal radius along its dorsal surface requires identification and navigation between the dorsal compartments of the wrist [Figure 8]. Multiple intervals may be utilized between the various dorsal extensor compartments to approach the distal radius dorsally. Two will be emphasized for their versatility and commonality. The trans-EPL approach, also referred to the “universal dorsal approach,” provides extensile exposure to much of the dorsal aspect of the distal radius. The dorsal–ulnar approach provides direct visualization of the dorsal–ulnar corner of the distal radius as well as the distal radioulnar joint.
The transextensor pollicis longus approach
Identify and mark Lister's tubercle. Place a 7–8-cm incision longitudinally in line with the third metacarpal just ulnar to Lister's tubercle. Dissect down to the extensor retinaculum and then raise full-thickness skin flaps [Figure 8]. By raising flaps off of the retinaculum, the branches of the radial sensory and dorsal ulnar sensory nerves, and any dorsal veins, will retract away with the flaps. Identify the EPL tendon exiting the extensor retinaculum just distal to Lister's tubercle. Place a full-thickness incision across the extensor retinaculum through the roof of the third dorsal compartment, thereby releasing the EPL tendon. Retract the tendon radially. Raise the second and fourth compartments in a subperiosteal fashion in opposite directions to thereby expose the dorsal surface of the distal radius.
At the proximal floor of the fourth dorsal compartment resides the posterior interosseous nerve. At this level, it provides sensation and proprioceptive function to the dorsal wrist capsule. To expose the nerve, the fourth compartment should be elevated off not subperiosteally, but rather off of the periosteum.
The dorsal–ulnar approach
Palpate the distal radioulnar joint and place a longitudinal incision above it. Identify and open the fifth dorsal compartment by visualizing the extensor digiti minimi exiting distally [Figure 8]. Through its floor, the distal radioulnar joint can be entered. Multiple components of the distal radioulnar joint, including the TFCC, the pronator quadratus volarly, and the radioulnar ligaments, all contribute to distal radioulnar joint stability. The dorsal capsule incorporates the dorsal radioulnar ligament and TFCC. Therefore, upon closure, the dorsal capsule should be meticulously closed to prevent distal radioulnar joint instability but not over-sewn so to avoid loss of forearm rotation.
Arthroscopy affords direct visualization of the radial styloid, scaphoid fossa, lunate fossa, TFCC, and the volar radiocarpal ligaments. Appropriate set-up is integral for efficient arthroscopy of the wrist. Traction of 5–10 lb provides for adequate visualization and fluid flow. A small joint arthroscope with a diameter of 2.7 mm or smaller and a 30° lens is necessary. Similarly, small joint arthroscopy instruments should be available. Please note that throughout the procedure, very little fluid is necessary to facilitate visualization of the joint.
Recognition of surface landmarks and understanding the anatomy of the dorsal extensor compartments of the wrist are paramount to facilitating efficient portal placement and joint visualization. Portals are designated by their relationship to the six dorsal compartments. Palpation between these compartments will identify the sites of joint entry. For example, the 3–4 portal occurs between the extensor pollicis tendon of the third compartment and the extensor digitorum comminis of the fourth compartment [Figure 9]. The 3–4 portal is the main viewing portal and is typically established first. It can be identified by palpating the soft spot just distal to Lister's tubercle. Place the insufflation needle through the planned portal site and inject 5–10 cc of saline. Insufflation should occur with little resistance. Place a 3–5-mm longitudinal incision over the soft spot with an 11-blade pointing distally. Holding the blade in this position will avoid injury to tendons and any cutaneous nerves since they fan away as they arborize distally. Spread the soft tissue down to the capsule with a hemostat. Enter the joint with a blunt tipped trocar and cannula. Avoid iatrogenic injury to the articular surfaces by not aggressively plunging. The normal volar tilt of the distal radius is 10° and this normally should be replicated in the direction of cannula entry.
|Figure 9: Diagram showing portals entry with relationship to the six dorsal compartments|
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Beginning from radial to dorsal, the 3–4 portal will afford excellent visualization of the radial styloid, scaphoid fossa, lunate fossa, and TFCC. In addition, the volar radiocarpal ligaments should be clearly visible as well as the base of the scaphoid and lunate and the intervening scapholunate ligament.
Additional outflow or working portals can be established including the 4–5, 6-R (radial to the extensor carpi ulnaris), and 6-U (ulnar to the extensor carpi ulnaris). The 6-U portal is close to the path of the dorsal ulnar sensory nerve and should be placed with caution. Finally, the 1–2 portal can be established as an additional viewing portal but is limited by the risk of injury to branches of the radial sensory nerve and limited visualization afforded by the steep radial inclination of the distal radius.
| Summary|| |
Surgical approaches to the distal radius can be broadly divided into volar, radial, and dorsal. In addition, visualization of the articular surface can be accomplished best arthroscopically, either with fluid or dry. Each approach requires thorough understanding of the local anatomy of the distal radius to safely navigate and expose fractures of the distal radius.
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