Morphology of the Radial Attachment of the Radioulnar Ligament and Surrounding Landmarks.

PURPOSE: The triangular fibrocartilage complex (TFCC) is composed of dorsal and palmar radioulnar ligaments (RULs). A common injury pattern of the RUL is the avulsion of the ulnar insertion, which can be treated by arthroscopic or open repair. Although the general method of TFCC reconstruction is a tendon graft with a bone tunnel, detailed information regarding the radial attachment of the RUL is unclear. This study aimed to clarify the morphology of the radial attachments of the palmar radioulnar ligament (PRUL), dorsal radioulnar ligament (DRUL), and short radiolunate ligament (SRL) using three-dimensional imaging. METHODS: A total of 29 upper limbs (16 formalin-fixed and 13 embalmed by Thiel's embalming method) of Japanese cadavers were used. After gross observation, we marked the attachments of the PRUL, DRUL, and SRL using 0.7-mm diameter pins. We created three-dimensional images of the radius, outlining the PRUL, DRUL, and SRL attachments. The software application calculated the centers of the PRUL and DRUL attachments. RESULTS: The PRUL attachment was horizontally shaped. The center of the PRUL was 1.5 mm proximal and 5.8 mm radial to the tip of the palmar pyramid formed by the palmar cortex and the radioulnar and radiocarpal joint surfaces. The DRUL attachment was vertically shaped. The center of the DRUL was 2.0 mm proximal and 1.7 mm radial from the tip of the dorsal pyramid formed by the dorsal cortex and the radioulnar and radiocarpal joint surfaces. The length of the SRL was 9.2 mm. The SRL and PRUL were strongly conjoined. CONCLUSIONS: The anatomical center on the RUL attachment of the radius can be determined from osseous landmarks. CLINICAL RELEVANCE: The findings of this study contribute to the understanding of RUL attachment to the distal radius and may assist surgeons in performing anatomical reconstruction of TFCC.

Anatomy of the distal radioulnar ligament in cats.

OBJECTIVES: The aim of this study was to describe the anatomy of the distal radioulnar ligament in the cat, using gross and histological sections from cadaveric feline carpi. METHODS: Eight feline cadaveric distal radioulnar joints were included in the study, including six that were paraffin- and two that were polymethyl methacrylate-embedded. Each of the sections of the distal radioulnar joint and ligament were viewed macroscopically and microscopically using a dissection microscope and a standard light microscope with polarising capacity. RESULTS: On gross examination, the distal radioulnar ligament could be seen as a triangular-shaped structure extending between the dorsal surface of the distal radius and ulna. The centre of the ligament had a greater density of tightly packed collagen fibres, while fibrocartilage was identified at the site of both the radial and ulnar entheses. Articular cartilage was noted to extend to the most proximal part of the bulbous portion of the distal ulna and corresponding axial aspect of the distal radius. CONCLUSIONS AND RELEVANCE: In the cat, there appears to be a less extensive interosseous component of the distal radioulnar ligament compared with the dog and cheetah. Instead, the ligament follows the articular surfaces of the distal radius and ulna. These anatomical differences may account for increased rotation of the feline antebrachium and have clinical implications, particularly with regard to the management of antebrachiocarpal joint injuries.

Biomechanical evaluation of interference screw fixation techniques for distal radioulnar ligament reconstruction: a cadaveric experimental study.

INTRODUCTION: In the reconstruction of distal radioulnar ligaments (DRULs), interference screws can be used for antegrade or retrograde fixation of grafts to the ulna. However, the biomechanics of interference screw fixation are currently unknown. This study aimed to determine the biomechanical effects of these two fixations on the distal radioulnar joint (DRUJ) in a cadaveric model and to investigate the appropriate initial tension. MATERIALS AND METHODS: A total of 30 human cadaver upper extremities were used, and the DRULs were reconstructed according to Adams' procedure. First, eight specimens were randomly divided into two groups: antegrade and retrograde, followed by translational testing and load testing. Then, the other eight specimens were divided into the two groups above, and the contact mechanics, including forces, areas, and pressures, were measured. Finally, to investigate the appropriate initial tension, the remaining 14 specimens were fixed with interference screws under different tensions in an antegrade way, and the translational testing was repeated as before. RESULTS: In the neutral position, antegrade fixation exhibited less translation than retrograde fixation (7.21 ± 0.17 mm versus 10.77 ± 1.68 mm, respectively). The maximum failure load was 70.45 ± 6.20 N in antegrade fixation, while that in retrograde fixation was 35.17 ± 2.95 N (P < 0.0001). Antegrade fixation exhibited a larger increase in contact force than retrograde fixation (99.72% ± 23.88% versus 28.18% ± 10.43%) (P = 0.001). The relationship between tension and displacement was nonlinear (Y = - 1.877 ln(x) + 7.94, R2 = 0.868, P < 0.0001). CONCLUSIONS: Compared with retrograde fixation, the antegrade fixation of interference screws may be a more reliable surgical technique, as it shows a higher failure load and stability. In addition, to avoid the risk of potential arthritis caused by anterograde fixation, we propose an equation to determine the appropriate initial tension in DRUL reconstruction.

Relationship between Fracture of the Ulnar Styloid Process and DRUJ Instability: A Biomechanical Study.

Background There has been clinical question in the treatment of ulnar styloid fracture with distal radius fracture, surgical fixation of the styloid fragment, or ignorance of the fragment. We examined relationship between size of the ulnar styloid fracture and distal radioulnar joint (DRUJ) stability biomechanically to answer the above clinical question. Methods Changes in the dorsopalmar stiffness of the DRUJ after experimentally simulating in four types of ulnar styloid fractures were examined in cadavers. After tip, middle, base-horizontal, and base-oblique type of styloid fractures were made sequentially, changes in dorsopalmar DRUJ stiffness were measured using the MTS machine in the intact wrist, for each fracture, at 60 degrees pronation, neutral, and 60 degrees supination, respectively. Additional cutting of the radioulnar ligament (RUL) at the fovea was also simulated with the base-horizontal fracture. Results The tip and middle type fractures did not demonstrate significant loss of stiffness compared with the intact. The base-horizontal fracture demonstrated only significant loss of stiffness in the dorsal direction (radius palmar; ulnar dorsal) with forearm in neutral rotation. The base-oblique fracture demonstrated significant loss of dorsopalmar stiffness of the DRUJ. Additional section of the RUL with the base-horizontal fracture induced significant loss of stiffness of the DRUJ compared with the intact. Conclusions Because the RUL originates from the fovea as well as from the base of the ulnar styloid, these results suggest that DRUJ instability closely correlates with how much of the bony fragment includes the originating portions of the RUL. The findings further suggest that larger base-oblique and base-horizontal fragments with resultant DRUJ instability must be reattached, but that even base-horizontal fragment as well as tip and middle ulnar styloid fragment can be ignored when there is no instability.

Arthroscopic ligament-specific repair for triangular fibrocartilage complex foveal avulsions: a minimum 2-year follow-up study.

This study reports the arthroscopic ligament-specific repair of the triangular fibrocartilage complex (TFCC) that anatomically restores both the volar and dorsal radioulnar ligaments into their individual foveal footprints. Twenty-five patients underwent arthroscopic ligament-specific repair with clinical and radiological diagnoses of TFCC foveal avulsions. The mean age was 28 years (range 14-47) and the mean follow-up was 31 months (range 24-47). Following arthroscopic assessment, 20 patients underwent double limb radioulnar ligament repairs and five had single limb repairs. At final follow-up, there were significant improvements in wrist flexion-extension, forearm pronation-supination and grip strength. There were also significant improvements in pain and patient-reported outcomes as assessed by the patient-rated wrist evaluation, Disabilities of the Arm, Shoulder and Hand score and modified Mayo wrist scores. Arthroscopic ligament-specific repair of the TFCC does not require specialist dedicated equipment or consumables and offers a viable method of treating these injuries.Level of evidence: IV.

Topographical Anatomy of the Distal Ulna Attachment of the Radioulnar Ligament.

PURPOSE: The deep component of the distal radioulnar ligament provides translational stability and rotational guidance to the forearm. However, controversy exists regarding the importance of this structure as well as the nature of its attachment to the distal ulna. We aimed to evaluate the topographic anatomy of the distal ulna attachment of both the superficial and the deep components of the radioulnar ligament and to assess the relationship between its internal and its external morphometry. METHODS: Thirteen human distal ulnae attached by ulnar part of the distal radioulnar ligament were scanned using micro-computed tomography and reconstructed in 3 dimensions. In addition, the distal radioulnar ligaments were examined under polarized light microscopy to determine the histological characteristics of collagen contained within the ligaments. RESULTS: The deep limbs have broad marginal insertions at the fovea, whereas the superficial limbs have a circular and condensed insertion to the ulnar styloid. The center of the deep limb was separated from the base of the ulnar styloid by a mean of 2.0 ± 0.76 mm, and this distance was positively correlated with the width of the ulnar styloid. The mean distance between the center of the ulnar head and the center of the fovea was 2.4 ± 0.58 mm. The proportion of collagen type I was lower in the deep limb than in the superficial limb. CONCLUSIONS: This new observation of the footprint of the radioulnar ligament in the distal ulna indicates that the deep limb may serve as an internal capsular ligament of the distal radioulnar joint, whereas the superficial limb as the external ligament. CLINICAL RELEVANCE: Knowledge of the topographic anatomy of the radioulnar ligament's attachment to the distal ulna may provide a better understanding of distal radioulnar ligament-related pathologies.

[A biomechanical study on effect of deep radioulnar ligaments on the distal radioulnar joint rotatory stability repaired by bone suture anchors].

Objective: To discuss the role of the bone suture anchors for repair of avulsed deep radioulnar ligaments in maintaining the rotatory stability of the distal radioulnar joint. Methods: Nine upper limbs specimens were selected from fresh adult cadavers to make wrist joint-bone capsular ligaments complex specimen. All the specimens were tested under conditions of intact (normal group), deep radioulnar ligaments injury (injury group), and deep radioulnar ligaments injury repaired with anchoring (repair group). The internal and external rotation torque values were recorded in 45° wrist extension, neutral position, and 45° wrist flexion by AG-IS series MS biomechanical testing system. The statistic software was used to compare difference in rotation torque between groups. Results: In 45° wrist extension, neutral position, and 45° wrist flexion, the internal rotation torque values in normal group were (0.83±0.33), (0.86±0.34), and (0.36±0.30) N·m respectively; the external rotation torque values were (0.86±0.38), (0.44±0.22), and (0.25±0.21) N·m respectively. The internal rotation torque values in injury group were (0.18±0.17), (0.22±0.17), and (0.16±0.15) N·m respectively; the external rotation torque values were (0.27±0.26), (0.13±0.17), and (0.04±0.04) N·m respectively. The internal rotation torque values in repair group were (0.79±0.34), (0.73±0.33), and (0.41±0.23) N·m respectively; the external rotation torque values were (0.80±0.39), (0.41±0.22), (0.41±0.40) N·m respectively. In 45° wrist extension, neutral position, and 45° wrist flexion, the internal and external rotation torque values in injury group were significantly lower than those in normal group and repair group ( P<0.05), but no significant difference was found between repair group and normal group ( P>0.05). Conclusion: The deep radioulnar ligaments are important structure for maintaining rotatory stability of distal radioulnar joint. Bone anchoring of the avulsed deep radioulnar ligaments to the ulna fovea is critically important in reconstructing function anatomy of the distal radioulnar joint.

The ulnar side of the wrist: Clinically relevant anatomy and biomechanics.

BACKGROUND: In the hectic environment of a hand therapy clinic, the opportunity to carefully consider the relationships among pathology, pathomechanics, surgical repair techniques, tissue healing, postoperative management, and rehabilitation program development and progression is limited. Clinicians often default to seeking a protocol, a recipe to follow. OBJECTIVES: Using the ulnar side of the wrist as an example, relevant anatomy and biomechanics are directly related to several commonly seen pathologies, including fractures, ligament injuries, and instability. CONCLUSION: Armed with knowledge of anatomy, biomechanics, and surgical procedures, the need for a protocol disappears. Each patient can be individually managed according to his or her unique set of variables and responses to injury, repair, healing, and recovery of function.

How does wrist position affect the length of the distal radioulnar ligament: a three-dimensional image study in vivo?

PURPOSE: This study was designed to investigate the length changes of the distal radioulnar ligament at different wrist positions and to determine the effect of hyperextension on the distal radioulnar ligament and to find out the most vulnerable position where the distal radioulnar ligament rupture and foveal avulsion. METHODS: We obtained computed tomography scans of the wrists for 12 volunteers including two groups: hyperextension group and hyperextension with maximal rotation group. The images were reconstructed to the three-dimensional bone structures with customized software. The four portions of the distal radioulnar ligament were measured and analyzed statistically. RESULTS: No significant differences were noted in the lengths of the each portion of the distal radioulnar ligament among neutral position, wrist hyperextension, and hyper-radial extension. From neutral position to hyperextension with maximal pronation, the lengths of the palmar superficial radioulnar ligament (psRU) and dorsal deep radioulnar ligament (ddRU) decreased significantly, whereas the dorsal superficial radioulnar ligaments (dsRU) and palmar deep radioulnar ligament (pdRU) increased significantly. From neutral position to hyperextension with maximal supination, the lengths of the pdRU and dsRU ligaments decreased significantly, and the lengths of psRU and ddRU ligaments changed little. CONCLUSIONS: The factor of hyperextension has little effect on the length of the distal radioulnar ligament and the distal radioulnar ligament may be under great tension at the position of hyperextension with maximal pronation. These findings can provide more information to understand the pathomechanics of the triangular fibrocartilage complex injury caused by a fall on the outstretched hand and can provide information relevant to the distal radioulnar ligament restoration.

Biomechanical comparison of transosseous re-fixation of the deep fibres of the distal radioulnar ligaments versus deep and superficial fibres: a cadaver study.

PURPOSE: We hypothesized that the re-fixation of the deep and superficial fibres of the distal radioulnar ligaments provide improved stability compared to reconstruction of the deep fibres alone. METHODS: Fourteen fresh-frozen cadaver upper extremities were used for biomechanical testing. Transosseous re-fixation of the deep fibres of the distal radioulnar ligaments alone (single mattress suture group; n = 7) was compared to the transosseous re-attachment of the deep and superficial fibres (double mattress suture group; n = 7). Cyclic load application provoked palmar translation of the radius with respect to the rigidly affixed ulna. Creep, stiffness, and hysteresis were obtained from the load-deformation curves, respectively. Testing was done in neutral forearm rotation, 60° pronation, and 60° supination. RESULTS: The re-fixation techniques did not differ significantly regarding the viscoelastic parameters creep, hysteresis, and stiffness. Several significant differences of one cycle to the consecutive one within each re-fixation group could be detected especially for creep and hysteresis. No significant differences between the different forearm positions could be detected for each viscoelastic parameter. CONCLUSIONS: The re-fixation techniques did not differ significantly regarding creep, hysteresis, and stiffness. This means that the additional re-attachment of the superficial fibres may not provide greater stability to the DRUJ. Bearing in mind that the study was a cadaver examination with a limited number of specimens we may suppose that the re-attachment of the superficial fibres seem to be unnecessary. A gradual decline of creep and hysteresis from first to last loading-unloading cycle is to be expected and typical of ligaments which are viscoelastic.

Selection of tendon grafts for distal radioulnar ligament reconstruction and report of a modified technique.

PURPOSE: To investigate the graft length necessary to complete a distal radioulnar ligament reconstruction and assess the suitability of several tendon graft sources. METHODS: We measured the graft length needed to complete the distal radioulnar ligament reconstruction in 7 fresh-frozen cadaver specimens. The pure tendon lengths of 7 tendon graft sources were measured: palmaris longus, extensor indicis proprius, slips of extensor digiti minimi and abductor pollicis longus, and portions of flexor carpi ulnaris, flexor carpi radialis, and extensor carpi ulnaris. A modified technique that allows for a shorter length of graft is also described, and the suitability of each graft source for this technique was assessed. RESULTS: The mean graft lengths needed to complete the original and modified reconstructions were 138 mm and 89 mm, respectively. The average length of the tendon graft when measured as pure tendon was: palmaris longus (127 mm), slip of extensor digiti minimi (112 mm), extensor indicis proprius (100 mm), partial flexor carpi radialis (87 mm), slip of abductor pollicis longus (69 mm), partial flexor carpi ulnaris (67 mm), and partial extensor carpi ulnaris (67 mm). The palmaris longus was too short for the original technique in the majority of specimens but was sufficient to complete the modified technique in every specimen that had a palmaris longus. Six specimens also had an extensor indicis proprius of suitable length for the modified technique. CONCLUSIONS: The length of donor graft required for the modified reconstruction was significantly less than that needed for the original reconstruction. Three specimens had no donor tendons sufficiently long to complete the original technique if a pure tendon graft were used, whereas the modified technique could be completed in all specimens. CLINICAL RELEVANCE: Many tendon graft sources in the upper extremity are of insufficient length to complete the distal radioulnar ligament reconstruction as described. A modified technique using suture anchors may be a useful alternative in such cases.

Radiographic and Arthroscopic Assessment of DRUJ Instability Due to Foveal Avulsion of the Radioulnar Ligament in Distal Radius Fractures.

Background As the triangular fibrocartilage complex (TFCC) anchors the distal radius to the ulna via the radioulnar ligament (RUL), a severely displaced distal fragment of the radius may be associated with a foveal avulsion of the TFCC. The purpose of this retrospective study was to assess, radiographically and arthroscopically, the relationship between displacement of the radius, the ulnar styloid, and avulsion of the RUL resulting in distal radioulnar joint (DRUJ) instability. Materials and Methods Twenty-nine wrists of 29 patients with intra- and extra-articular distal radius fractures/malunion who underwent reduction or a corrective osteotomy of the displaced/malunited fracture, and/or wrist arthroscopy, were assessed radiographically and arthroscopically. Radial translation, radial inclination, radial shortening, volar or dorsal tilt, and the presence of an ulnar styloid fracture with more than 4 mm of displacement were measured from the initial films. Radiocarpal arthroscopy was used to assess peripheral lesions of the TFCC, while DRUJ arthroscopy was used to assess the foveal attachment. The relationship between displacement of the distal radius or the ulnar styloid fracture and the TFCC injury, including avulsion of the RUL, was recorded. Results Univariate analysis revealed that increased radial translation, decreased radial inclination, increased radial shortening, and an ulnar styloid fragment radially displaced by more than 4 mm were significant predictors of RUL avulsion at the fovea. Volar or dorsal tilt of the radius and ulnar variance did not correlate with RUL avulsion or TFCC injuries. Multiple logistic regression analysis revealed that radial translation was an independent risk factor of foveal avulsion of the RUL. Conclusions Increased radial translation and radial shortening and decreased radial inclination of the distal fragment can be associated with a foveal avulsion of the RUL. Radial translation can be an independent risk factor of foveal avulsion of the RUL.

Subluxation of the Palmar Radioulnar Ligament As a Cause of Blocked Forearm Supination: A Case of DRUJ Locking.

We report a case of locking of the distal radioulnar joint (DRUJ) due to interposition of a flap of the palmar radioulnar ligament (RUL) torn from the triangular fibrocartilage complex (TFCC). We released the blockage by elevating the flap and partially resecting a portion of the triangular fibrocartilage (TFC) arthroscopically.

Palmar reconstruction of the triangular fibrocartilage complex for instability of the distal radioulnar joint: a biomechanical study.

We developed a new triangular fibrocartilage complex reconstruction technique for distal radioulnar joint instability in which the palmar portion of the triangular fibrocartilage complex was predominantly reconstructed, and evaluated whether such reconstruction can restore stability of the distal radioulnar joint in seven fresh cadaver upper extremities. Distal radioulnar joint instability was induced by cutting all soft-tissue stabilizers around the distal ulna. Using a palmar approach, a palmaris longus tendon graft was sutured to the remnant of the palmar radioulnar and ulnocarpal ligaments. The graft was then passed through a bone tunnel created at the fovea and was sutured. Loads were applied to the radius, and dorsopalmar displacements of the radius relative to the ulna were measured using an electromagnetic tracking device in neutral rotation, 60° supination and 60° pronation. We compared the dorsopalmar displacements before sectioning, before reconstruction and after reconstruction. Dorsopalmar instability produced by sectioning significantly improved in all forearm positions after reconstruction.

Anatomic reconstruction of the radioulnar ligament.

INTRODUCTION: Twenty-five patients (19 males and six females) were included in the study based on: chronic symptoms of distal radioulnar joint instability, demonstrable instability on examination, MRI evidence of radioulnar ligament deficiency, and arthroscopic findings of foveal disruption of the radioulnar ligament. MATERIALS AND METHODS: Exclusion criteria were: distal radius malunion, congenital malformation of the sigmoid notch, DRUJ arthritis, and less than 24 months minimum follow-up. Mean age was 35 years old with a mean interval from injury to surgery of 5 months. Surgery began with arthroscopic confirmation of the chronic foveal detachment followed by open reconstruction of the radioulnar ligament using the palmaris longus tendon. The specific method employed three drill tunnels corresponding to the true anatomic points of attachment of the radioulnar ligament. Patients were examined post-operatively at 2 weeks, 4 weeks, 6 weeks, 12 weeks, and 6 months. RESULTS AND DISCUSSION: Final evaluation averaged 51 (±14) months following surgery. Measures obtained before and after treatment included: wrist range of motion, forearm range of motion, grip strength, examination findings of distal radioulnar joint instability, and Disabilities of Arm, Shoulder, and Hand (DASH) scores. Pre-operative and post-operative measures were compared using the paired Student's t test, accepting a p value of 0.05 as statistically significant. All patients healed the reconstruction without major complications and demonstrated distal radioulnar joint stability at the 6-week examination. Mean ranges of motion, in degrees, pre-/post-operative were: wrist flexion 53 (±13)/61 (±10), wrist extension 53 (±13)/62 (±15), supination 65 (±12)/74 (±7), and pronation 66 (±11)/71 (±8). Grip strengths expressed as % contralateral pre-/post-operative were: 57 (±23)/79 (±25). The differences in these measures were not found to be statistically significant. The mean pre-/post-operative DASH scores were: 62 (±16)/7 (±3). This difference was found to be statistically significant. CONCLUSION: Reconstruction of the RUL with a free palmaris longus tendon graft using the truly anatomic points of original RUL attachment at both the ulna and radius restored DRUJ stability and improved DASH scores without limiting forearm or wrist motion.