Distal radius attachments of the radiocarpal ligaments: an anatomical study

Influence of forearm rotation on the kinetic stabilizing efficiency of the muscles that control the scapholunate joint. Clinical application in proprioceptive and neuromuscular rehabilitation programs

BACKGROUND

This study focuses on the relationship between forearm muscles, carpal ligaments, and their impact on scapholunate joint stability across varying forearm rotations. This is crucial for optimizing pre and postoperative rehabilitation strategies for scapholunate joint dysfunction.

PURPOSE

Our study aims to understand the kinetic influence of forearm muscles on scapholunate joint instability. We emphasize the significance of forearm rotation to enhance treatment efficacy.

STUDY DESIGN

We conducted an experimental study to understand how forearm muscles contribute to the stability of the scapholunate joint during different degrees of forearm rotation and we focused on the joint effect of muscle groups rather than individual muscles for treatment protocols.

RESULTS

Our findings shed light on the conservative treatment of dynamic scapholunate instability and the postoperative rehabilitation of scapholunate ligament repair. We found that the effect of forearm muscles significantly contributes to preserve stability in the scapholunate joint across various forearm rotational positions. These insights have practical implications for hand therapists, offering innovative strategies to enhance clinical practice.

CONCLUSIONS

This research underscores the importance of considering forearm rotation when developing rehabilitation protocols for scapholunate joint instability and provides a valuable perspective in line with current rehabilitation principles.

Radiographic Outcomes for Comminuted, Intra-articular Distal Radius Fractures Treated with Primary Distraction Bridge Plate Fixation

Purpose

To determine if distraction bridge plate (DBP) fixation as the primary method of stabilization can effectively correct and maintain acceptable radiographic parameters in the treatment of comminuted, intra-articular distal radius fractures while allowing early load-bearing.

Methods

A retrospective review was performed of all consecutive intra-articular distal radius fractures that underwent DBP fixation with or without supplemental fixation methods (fragment-specific implants or K-wires). Patients treated with a volar locked plate in addition to DBP were excluded. Radiographic outcomes measures included volar tilt (°), radial height (mm), radial inclination (°), articular step-off (mm), lunate-lunate facet ratio (LLFR), and teardrop angle (°) measured on post-reduction, immediately post-operative, prior to and after DBP removal.

Results

Twenty-three comminuted, intra-articular distal radius fractures were treated with primary DBP fixation. Supplemental fixation was utilized in 10 fractures and included fragment-specific implants (n = 6) and/or K-wires (n = 5). Distraction bridge plates were removed after a mean of 13.6 weeks. At a mean radiographic follow-up of 11.4 weeks (range: 2-45 weeks) following DBP removal, all fractures had united with a mean volar tilt of 6.3° ± 5.8°, radial height of 11.3 ± 2.3 mm, radial inclination of 20.2° ± 4.5°, articular step-off of 0.6 mm ± 0.8, and LLFR of 1.05 ± 0.06. However, the teardrop angle could not be restored to a normal value with DBP fixation. Complications included 1 plate breakage and 1 peri-hardware radial shaft fracture.

Conclusion

Distraction bridge plate fixation is a reliable method to stabilize highly comminuted, intra-articular distal radius fractures in patients with a well-aligned volar rim fragment of the lunate facet.

Graphical Abstract

Volar Lunate Facet Fractures of the Distal Radius: Fracture Mapping Using 3D CT Scans

Background  Fractures of the distal radius involving the lunate facet at the volar articular surface are unstable injuries and are usually managed operatively. Management of these fractures is challenging as our understanding of the exact fracture characteristics and associated injuries to the carpus is poor. Purpose  This study aims to define the anatomy and associated injuries of lunate facet fractures using three-dimensional computed tomography (CT) scans and fracture mapping techniques. Methods  A consecutive series of CT wrists was analyzed to identify intra-articular fractures involving the lunate facet at the volar distal radius. Fractures were mapped onto standardized templates of the distal radius using previously described fracture mapping techniques. We also identified instabilities of the carpus including volar carpal translation, ulnar translocation, scapholunate diastasis, and distal radioulnar joint (DRUJ) instability. Results  We present 23 lunate facet fractures of the distal radius. The lunate facet fragment displaces in a volar and proximal direction and the lunate always articulates with the displaced fragment. The smaller fragments displace a greater amount, in a volar direction, with pronation. The fracture tends to occur between the origin of the short and long radiolunate ligaments. Conclusion  Lunate facet fractures are frequently comprised of osteoligamentous units of the distal radius involving the short and long radiolunate ligaments and the radioscaphocapitate ligament. Assessment and management of volar carpal subluxation, scapholunate instability, ulnar translocation, and DRUJ instability should be considered. Clinical relevance  Our mapping of these fractures contributes to our understanding of the anatomy and associated instabilities and will aid in surgical planning and decision making.

Anatomical and radiological description of ligament insertions on the radial aspect of the scaphoid bone

Anatomical studies on the radial side of the scaphoid mention inter-ligamentous connections, but without detailed description of their relations to one another. The purpose of this study was to provide an anatomical and radiological description of the ligamentous structure on the radial side of the scaphoid. High-field 3-Tesla 3D MRI scans of 7 cadaveric formaldehyde-fixed wrists were performed to assess the presence and location of each ligament. Dissection was performed in 10 wrists under microscopy on the radial side to assess the dimensions, anatomical variations and angles between ligaments in various wrist positions during in intracarpal pronation/supination, flexion/extension and ulnar/radial deviation. This study confirmed that the same ligament configuration was found on MRI and on dissection. The scaphotrapezial ligament, dorsal intercarpal ligament and radial collateral ligament fibers merge along the dorsal ridge of the scaphoid. The fibers of the radial collateral and radioscaphocapitate ligaments could be distinguished in only 4/10 specimens. Wrist position changes from intracarpal pronation to supination produced major changes in angle between the scaphotrapezial and dorsal intercarpal ligaments, while other position changes affected this angle only slightly. 3D MRI sequences allow these structures to be systematically analyzed in case of scapholunate instability. Further studies should be conducted to assess the biomechanical properties of these ligaments and the clinical consequences of isolated injury in this region.

Anatomical and Clinical Concepts in Distal Radius Volar Ulnar Corner fractures

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.

Fragment specific fixation with APTUS wrist system for volar rim fractures of the distal radius: a multicentric study

PURPOSE

Volar rim fractures of the distal radius are a spectrum of pathology that must be well identified and treated to achieve good outcomes and avoid surgical failures. New devices of fragment specific fixation have been developed during the last decades to fix this fragment. The purpose of this retrospective study was to evaluate the ability of APTUS^® wrist distal radius system to securely fix different types of volar rim fractures.

METHODS

Patients with at least 1 year of follow-up and a preoperative CT-scan evaluation of the fracture pattern were included in the study. Clinical, radiological and functional outcomes were assessed.

RESULTS

Sixty-eight patients with an average follow-up of 34, 1 months (12-61) were included in the study. There were no clinical and radiological complications, including loss of reduction, device failure and tendon ruptures. No patients required hardware removal. Wrist range of motion in flexion-extension averaged 96°, while in pronation-supination 144°. At final follow-up mean visual analogue scale pain was 1,8. Questionnaires, as dissabilities of the arm, shouldder and hand (DASH) score and patient-related wrist evolution (PRWE) score were 6,6 and 3 respectively. Grip strenght measured 86% compared to the normal side.

CONCLUSION

APTUS^® wrist presents a versatile set of fragment specific fixation plates able to easily and securely fix all types of volar rim fracture. The system can be used with other devices without any kind of interference between them. When correctly placed and used with the right indications, no late complications can be recorded.

Safety of Releasing the Volar Capsule During Open Treatment of Distal Radius Fractures: An Analysis of the Extrinsic Radiocarpal Ligaments' Contribution to Radiocarpal Stability

PURPOSE

The contribution of the extrinsic radiocarpal ligaments to carpal stability continues to be studied. Clinically, there is a concern for carpal instability from release of the volar extrinsic ligaments during volar plating of distal radius fractures in which the integrity of the dorsal ligaments may be unknown. The primary hypothesis of this study was that serial sectioning of radiocarpal ligaments would lead to progressive ulnar translation of the carpus.

METHODS

We studied the stabilizing roles of the radioscaphocapitate (RSC), short radiolunate (SRL), long radiolunate (LRL), and dorsal radiocarpal (DRC) ligaments. We sequentially sectioned these ligaments in 2 groups of 5 matched pairs and measured the motion of the scaphoid and lunate with the wrist in passive neutral alignment, radial deviation, ulnar deviation, and simulated grip. Displacement of the lunate in the radioulnar plane was used as a surrogate for carpal translation. The groups differed only by the order in which the ligaments were sectioned.

RESULTS

In the intact state, the lunate translated ulnarly during simulated grip and radial deviation, whereas radial translation, relative to its position under resting tension, was observed during ulnar deviation. With serial sectioning, the lunate displayed increased ulnar translation in all wrist positions for both groups 1 and 2. The magnitude of ulnar translation exceeded 1 mm after sectioning the LRL plus RSC along with either the DRC or the SRL.

CONCLUSIONS

Sectioning of either the DRC or SRL ligaments along with release of the RSC and LRL ligaments leads to notable although minimal (<2 mm) ulnar lunate translation.

CLINICAL RELEVANCE

Isolated sectioning of individual radiocarpal ligaments, such as for visualization of the articular surface of the distal radius, leads to minimal ulnar translation. Because prior clinical work found no clinical complications after volar capsule release, it is posited that translation less than 2 mm creates subclinical changes in carpal mechanics.

Biomechanical considerations on a CT-based treatment-oriented classification in radius fractures

A wide range of different classifications exist for distal radius fractures (DRF). Most of them are based on plane X-rays and do not give us any information on how to treat these fractures. A biomechanical understanding of the mechanical forces underlying each fracture type is important to treat each injury specifically and ensure the optimal choice for stabilization. The main cause of DRFs are forces acting on the carpus and the radius as well as the position of the wrist in relation to the radius. Reconstructing the mechanism of the injury gives insight into which structures are involved, such as ruptured ligaments, bone fragments as well as the dislocated osteoligamentous units. This article attempts to define certain key fragments, which seem crucial to reduce and stabilize each type of DRF. Once the definition is established, an ideal implant can be selected to sufficiently maintain reduction of these key fragments. Additionally, the perfect approach is selected. By applying the following principles, the surgeon may be assisted in choosing the ideal form of treatment approach and implant selection.

The radial and ulnar collateral ligaments of the wrist are true ligaments

PURPOSE

Our hypothesis in this study is that the radial and ulnar collateral ligaments of the wrist exist and are true ligaments which can be visualized by high-resolution ultrasonography (US).

METHODS

High-resolution US examination of the radial and ulnar collateral ligaments of the wrist was performed on 56 fresh cadaveric wrists. The visibility of these ligaments was assessed by four observers who classified the ligaments in consensus as well seen, adequately seen, or not seen. Surgical dissections of 12 radial collateral ligaments and 12 ulnar collateral ligaments were then performed and the ligaments were classified as present or absent. The US and dissection results were then compared. To confirm that the dissected structures represent true ligaments a histologic examination of the ligaments was performed.

RESULTS

All examined radial and ulnar collateral ligaments were seen on the US examination. The radial collateral ligament was seen between the radial styloid and radial aspect of the scaphoid. The ulnar collateral ligament was seen between ulnar styloid process and the triquetrum. On all surgical dissections, the radial collateral ligament was present at the floor of the first extensor compartment and the ulnar collateral ligament was at the floor of the sixth extensor compartment. Both ligaments were proven to be true capsular ligaments on both dissection and histologic examinations.

CONCLUSION

The radial and ulnar collateral ligaments of the wrist are true ligaments and can be seen at the floor of the first and the sixth extensor compartments, respectively, using high-resolution US. Based on their anatomic location, they most likely provide static stability to the wrist joint.

Association of scapholunate dissociation and two-part articular fractures of the distal radius

Scapholunate dissociation may occur in association with distal radial fractures and is easily missed at initial presentation. The aim of this study was to examine variances in the scapholunate distance with respect to subtypes of two-part partial articular distal radial fractures. Axial computed tomography (CT) scans of acute two-part intra-articular radial fractures were assessed retrospectively from 80 patients and compared to 20 controls. From each scan, two images were analysed to identify the scaphoid, lunate and articular fracture line in the distal radius for fracture type categorization. The images were overlaid on a standardized distal radius template and the scapholunate distance measured. Significant increase in the scapholunate distance was noted in fracture subtypes: radial styloid oblique; dorsal ulnar column; sagittal ulnar column; and volar coronal. We conclude that these findings support the need for a higher index of suspicion for scapholunate dissociation in these distal radial fracture subtypes. Level of evidence: III.

Microstructure of the Distal Radius and Its Relevance to Distal Radius Fractures

Background  There is a paucity of information on the microstructure of the distal radius, and how this relates to its morphology and function. Purpose  This study aims to assess the microanatomical structure of the distal radius, and relate this to its morphology, function, and modes of failure. Methods  Six dry adult skeletal distal radii were examined with microcomputed tomography scan and analyzed with specialist computer software. From 3D and 2D images, the subchondral, cortical, and medullary trabecular were assessed and interpreted based on the overall morphology of the radius. Results  The expanded distal radial metaphysis provides a wide articular surface for distributing the articular load. The extrinsic wrist ligaments are positioned around the articular perimeter, except on the dorsal radial corner. The subchondral bone plate is a 2 mm multilaminar lattice structure, which is thicker below the areas of the maximal articular load. There are spherical voids distally, which become ovoid proximally, which assist in absorbing articular impact. It does not have Haversian canals. From the volar aspect of the lunate facet, there are thick trabecular columns that insert into the volar cortex of the radius at the metaphyseal-diaphyseal junction. For the remainder of the subchondral bone plate, there is an intermediate trabecular network, which transmits the load to the intermediate trabeculae and then to the trabecular arches. The arches pass proximally and coalesce with the ridges of the diaphyseal cortex. Conclusion  The distal radius morphology is similar to an arch bridge. The subchondral bone plate resembles the smooth deck of the bridge that interacts with the mobile load. The load is transmitted to the rim, intermediate struts, and arches. The metaphyseal arches allow the joint loading forces to be transmitted proximally and laterally, providing compression at all levels and avoiding tension. The arches have a natural ability to absorb the impact which protects the articular surface. The distal radius absorbs and transmits the articular impact to the medullary cortex and intermediate trabeculae. The medullary arches are positioned to transmit the load from the intermediate trabeculae to the diaphysis. Clinical Relevance  The microstructure of the distal radius is likely to be important for physiological loading of the radius. The subchondral bone plate is a unique structure that is different to the cancellous and cortical bone. All three bone types have different functions. The unique morphology and microstructure of the distal radius allow it to transmit load and protect the articular cartilage.

Melone's Concept Revisited: 3D Quantification of Fragment Displacement

We applied quantitative 3D computed tomography to 50 complete articular AO type C fractures of the distal radius and tested the null hypothesis that fracture fragments can be divided according to Melone's concept (radial styloid and volar and dorsal lunate facet fragments) and that each fragment has similar (1) displacement and (2) articular surface area. Thirty-eight fractures fit the Melone distribution of fragments. Radial styloid fragments were most displaced, and volar lunate fragments were least displaced. Volar lunate fragments had the largest articular surface area. While these findings confirm Melone's concepts, the finding that volar lunate fragments are relatively large and dorsal lunate fragments relatively small suggests that alignment of the volar lunate fragment with the radial styloid may be the key element of treatment and the dorsal lunate fragment may not routinely benefit from specific reduction and fixation.

Characteristics of secondary arthrofibrosis after intra-articular distal radius fracture

PURPOSE

The purpose of this study was to assess characteristics of radiocarpal arthrofibrosis after intra-articular distal radius fractures (DRF).

PATIENTS AND METHODS

In this study 20 patients who underwent wrist arthroscopy at the time of implant removal after volar plating for intra-articular DRF were included retrospectively. The direction of fibrous tissue formation (FTF) and its rigidity were investigated. The findings were correlated to the course of intraarticular fracture lines seen in the preoperative CT, patient age and AO fracture types.

RESULTS

In all patients FTF spanned the radiocarpal joint. Fibrous tissue formations extended from previous fracture gaps to the scapholunate interosseous ligament and/or capsule. Four basic types of FTF (Type 1-4) and two combination types (Type 1a, 2a) were found. Fibrotic fans with dorsal capsular attachment (Type 1, 30 %) and its combination with dorsal capsule obliteration (Type 1a, 40 %) were the most common findings. Mild rigidity was present in 3 (15 %), moderate in 7 (35 %), and severe rigidity in 10 cases (50 %). Fracture lines crossing the radius extensor compartments or interfacet ridge, cartilage defects and C3 fractures showed the highest risk to develop severely rigid fibrous tissue formations. In older patients and in more comminuted fractures the number of rigid fibrous tissue formations was higher.

CONCLUSIONS

Fracture severity correlates with the development of rigid intra-articular FTF. In case of rigid FTF with restricted wrist motion arthroscopic debridement may be considered at the time of hardware removal.