Histologic anatomy of the triangular fibrocartilage

Histologic examination of the TFC reveals parallel, longitudinally oriented collagen fibers peripherally, while the more central articular disc is made up of interweaving obliquely oriented sheets of collagen fibers. This suggests a peripheral region experiencing tensile loads between the region of origin from the radius and the area of insertion into the ulna. The fiber orientation in the central region is more compatible with a structure experiencing multidirectional stresses. The articular disc origin from the radius is reinforced by collagen bundles projecting out from the radius for 1 to 2 mm. A large number of traumatic tears are oriented parallel to the radial origin of the TFC and located approximately 1 to 2 mm from the origin site. This corresponds to the junction of the short, radially oriented fibers and the remainder of the articular disc. The inner 80% of the articular disc is avascular, as is its radial attachment. Traumatic tears in this region would have a low healing potential unless some method for introducing additional vascularity was undertaken, such as reattachment through drill holes in the radius, allowing neovascularization of this otherwise avascular region.     

Corrective osteotomy of malunited distal radius fractures

The malunion of the distal radius may result in shortening, radial impaction, volar angulation, dorsal displacement or rotatory deformity. For restoration, the anatomy and kinematics of the distal radioulnar joint and the triangular fibrocartilaginous complex (TFCC) are of importance. This nonunion consists of the articular disk, a meniscus homologue, the ulnar collateral ligament, and the dorsal and palmar radioulnar ligaments. Malunion of the distal radioulnar joint leads to an increase in loading on the individual parts, as well as pain and a decrease in supination and pronation. Osteotomy is indicated if the angulation of the malunion is more than 20 degrees in the frontal or sagittal plane. Corrective osteotomy requires detailed preoperative planning with calculation of the correct position in all planes. The most common operation that has proved to be effective is osteotomy of the radius, insertion of a trapezoidal bone graft in place, and internal fixation with a dorsal or volar plate.     

The dorsopalmar stability of the distal radioulnar joint

Sixteen fresh-frozen adult human cadaveric upper extremities were used in a biomechanical analysis of distal radioulnar joint (DRUJ) stability. The relative contribution to stability of the DRUJ by the surrounding anatomic structures presumed to stabilize the joint was analyzed with respect to forearm rotation and wrist flexion and extension using a purpose-built 4-axis materials testing machine. The dominant structures stabilizing the DRUJ were the ligamentous components of the triangular fibrocartilage complex proper. The major constraint to dorsal translation of the distal ulna relative to the radius is the palmar radioulnar ligament. Palmar translation of the distal ulna relative to the radius is constrained primarily by the dorsal radioulnar ligament, with secondary constraint provided by the palmar radioulnar ligament and interosseous membrane. The ulnocarpal ligaments and extensor carpi ulnaris subsheath did not contribute significantly to DRUJ stability; however, approximately 20% of DRUJ constraint is provided by the articular contact of the radius and ulna. These relationships were consistent regardless of wrist position or degree of forearm rotation.     

三角纤维软骨复合体解剖及生物力学研究

目的从解剖完整的腕关节入手,阐明三角纤维软骨复合体各组成部分的解剖特点,评估三角纤维软骨复合体(TFCC)对于维持远侧桡尺关节稳定的重要性。方法对8个新鲜解冻的腕关节和6个经甲醛浸泡的腕关节进行显微解剖。同时对影响远侧桡尺关节稳定性的因素作了初步的评估。前臂中旋位,垂直于尺骨予20N拉力下测量尺骨相对于桡骨的位移,然后先后切断掌背侧桡尺韧带,测量尺骨相对于桡骨的位移变化。结果发现掌背桡尺韧带由三角纤维软骨盘外周增厚而成,止于尺骨茎突基底部,是维持远侧桡尺关节稳定性的主要因素之一,切断掌背侧桡尺韧带会导致远侧桡尺关节明显不稳。结论TFCC由三角纤维软骨盘、掌背侧桡尺韧带、尺骨月骨韧带、尺骨三角骨韧带、尺侧腕伸肌下腱鞘、半月板同源物、尺侧囊组成。掌背桡尺韧带是维持远侧桡尺关节稳定性的主要因素之一,掌背侧桡尺韧带损伤会导致远侧桡尺关节明显不稳。     

Traumatic disruption of the triangular fibrocartilage complex. Pathoanatomy.

The surgical pathology in 42 cases of traumatic triangular fibrocartilage complex (TFCC) disruption comprised a spectrum of injury resulting in five basic stages of increasingly severe ulnar wrist instability. In all cases, detachment of the articular disk from its ulnar insertion was the principal cause of distal radioulnar joint instability; in 28 (67%), concomitant injury to the adjacent extensor carpi ulnaris sheath, the ulnocarpal ligaments, or the peritriquetral ligaments compounded the instability. Thus, rather than an isolated event, peripheral disruption of the disk often proved the major constituent of multicomponent lesions--lesions consistently suitable for repair. In this series of destabilizing TFCC disruption requiring operative treatment, awareness that some injuries selectively affect the articular disk, whereas others compromise wider zones of wrist anatomy, was essential to successful surgery.     

Surgical approaches to the distal radioulnar joint

For the distal radioulnar joint (DRUJ) to be stable, not only do the articulating surfaces need to be congruent and well aligned but also the capsule and ligaments need to be mechanically and sensorially competent. According to recent investigations, ligaments should not be regarded as simple static structures maintaining articular alignment but as complex arrangements of collagen fibers containing mechanoreceptors, which are able to generate neural reflexes aiming at a more efficient and a more definitive muscular stabilization. By careful planning and meticulous execution of surgical incisions to approach the DRUJ, the nerve endings innervating the capsule and DRUJ ligaments may be safeguarded, thus preserving the proprioceptive function of the joint.     

An anatomic reconstruction of the distal radioulnar ligaments for posttraumatic distal radioulnar joint instability

Fourteen patients with posttraumatic distal radioulnar joint instability were treated with a reconstruction of the distal radioulnar ligaments. The technique is anatomically accurate, is reproducible, and requires less dissection than previously described techniques. Candidates for the procedure had joint instability and an irreparable triangular fibrocartilage complex. Ten patients had bidirectional instability. Two patients had a concurrent corrective osteotomy of the distal radius for a malunion. The procedure restored stability and relieved symptoms in 12 of 14 patients at 1 to 4 years' follow-up evaluation. One patient with a deficient sigmoid notch and one with ulnocarpal ligament injury did not achieve full stability. All patients attained near full pronation and supination. The procedure is an effective treatment for an unstable distal radioulnar joint when its articular surfaces are intact and the other wrist ligaments are functional, and it can be used in combination with a distal radius corrective osteotomy.     

Anatomy and biomechanics of the interosseous membrane: its importance in the longitudinal stability of the forearm

The interosseous membrane (IOM) links the ulna and the radius and acts as an extrinsic ligament, assisting the proximal radioulnar joint (PRUJ) and distal radioulnar joint (DRUJ) ligaments. It checks dissociating forces, transmits forces from one forearm bone to the other, and coordinates loading forces. The anterior plane of descending fibers from the radius checks the proximal displacement of this bone. Intermediate descending fibers are the strongest. The posterior plane, with ascending fibers from the radius, checks its proximal displacement. An early repair of a torn IOM is feasible and should be performed. This can be associated with an augmentation procedure.     

Sigmoid notch reconstruction using osteoarticular graft in a severely comminuted distal radius fracture: a case report

A case of a young patient with a severely comminuted intra-articular distal radius fracture dislocation and severe injury of the distal radioulnar joint is presented. Early reconstruction of the sigmoid notch and radioulnar ligaments was performed using the remaining scaphoid facet of the distal radius articular surface, an autogenous tendon graft for ligament reconstruction, and radioscapholunate arthrodesis. The patient was able to return to his manual work without limitations. We present additional information on the comparative anatomy of the sigmoid notch and scaphoid facet that may guide surgeons in treating this severe injury.     

Anatomical transosseous fixation of the deep and superficial fibers of the radioulnar ligaments

Introduction

The triangular fibrocartilage complex is in conjunction with the interosseous membrane the most important stabilizer of the distal radioulnar joint. Lesions of the triangular fibrocartilage complex may cause instability of the distal radioulnar joint with serious consequences. Therefore, the goal is to reconstruct and provide stability to prevent further harm.

Surgical technique

Based on the anatomical configuration of the radioulnar ligaments, we present a technique which addresses both the deep and the superficial fibers of the radioulnar ligaments. This surgical procedure can be performed either openly or arthroscopically assisted. Two osseous 2-mm tunnels starting from the ulnar neck to the foveal surface are created. A nonabsorbable suture is passed through the tunnels and the triangular fibrocartilage using a 20-gauge venipuncture needle in order to attach the deep fibers. Then a third osseous tunnel starting from the lateral base of the styloid process to the medial aspect is created. The suture is passed through this tunnel and through the triangular fibrocartilage and around the styloid process palmarily using the same needle as before in order to anchor the superficial fibers anatomically. After reducing the ulna head the sutures are tightened.

Conclusion

This technique is quite simple and addresses the anatomical configuration of the radioulnar ligaments.     

The anatomy of the ligaments of the wrist and distal radioulnar joints

The ligaments of the wrist are responsible for guiding and constraining the complex motion of the carpal bones relative to the forearm bones, the metacarpals, and contiguous carpal bones. The majority of wrist ligaments are found within the joint capsule as organized thickenings composed of parallel collagen fascicles, small caliber nerves and blood vessels, and lined on their deep surfaces by synoviocytes. The palmar radiocarpal ligament complex is composed of the radioscaphocapitate, long radiolunate, radioscapholunate and short radiolunate ligaments. The ulnocarpal ligaments include the ulnolunate, ulnotriquetral and ulnocapitate ligaments. Dorsally, the radiocarpal joint is spanned by the dorsal radiocarpal ligament. Palmar ligaments connecting the proximal and distal carpal rows include the scaphotrapeziotrapezoid, scaphocapitate, triquetrocapitate and triquetrohamate ligaments. Within each row are interosseous ligaments connecting adjacent carpal bones, each divisible into dorsal and palmar components. There are unique regions within some of the ligaments, such as a zone of fibrocartilage in the proximal regions of the scapholunate and lunotriquetral interosseous ligaments, and strong deep regions connecting the trapezoid, capitate, and hamate. The distal radioulnar joint is connected by the triangular fibrocartilage complex, composed of a fibrocartilaginous disc and the palmar and dorsal radioulnar ligaments. The ulnocarpal ligaments attach to the palmar radioulnar ligament rather than directly to the ulna, allowing increased independence between wrist and forearm motion.     

The blood supply of the human distal radioulnar joint and the microvasculature of its articular disk.

The arterial blood supply of the distal radioulnar joint was investigated in 35 upper extremities taken from 22 fresh cadavers (11 newborns and 11 adults using the India ink injection and tissue-clearing techniques according to Spalteholz). Microvasculature of the articular disk of the distal radioulnar joint was also performed in 35 articular disks taken from 22 fresh human cadavers, 11 newborn and 11 adults using the same technique. It was found that the general blood supply to the joint is received mainly from the palmar and dorsal branches of the anterior interosseous artery. These branches, after dividing at the proximal border of the pronator quadratus, arborize in a fanlike fashion around the joint and their small ramifications penetrate and vascularize the capsule and the articular disk from the palmar, dorsal, and medial sides. The terminal branches of the anterior interosseous artery reinforced by the posterior interosseous artery and a small branch of the ulnar artery give the direct peridiscal vessels to the palmar, medial, and dorsal margins of the articular disk, which arborize and anastomose with one another and form the terminal capillary networks that end at the peripheral segments of the disk in a series of terminal capillary loops, leaving the inner segments devoid of blood vessels. The posterior interosseous artery anastomoses at the distal part of the forearm with one of the terminal rami of the dorsal branch of the anterior interosseous artery and, in that way, contribute to the vascularization of the dorsal capsule of the distal radioulnar joint. The ulnar artery gives off a small branch that anastomoses with one of the terminal ramifications of the palmar branch of the anterior interosseous artery and contributes to the formation of a small arterial arch on the anteromedial side of the distal ulna, supplying the anteromedial capsule and the basistyloid area of the ulna. Both ulnar and radial arteries contribute to the vascularity of the joint through the collateral network of the palmar and dorsal carpal arches. In the articular disk, the major central portion of the disk is avascular and only its peripheral, palmar, medial, and dorsal margins are vascularized. The proportion of vascularized zone to avascular zone depends on the age of the subject and, in newborns, is approximately 33%. In adults, only 25% of the peripheral segments are vascularized.(ABSTRACT TRUNCATED AT 400 WORDS)     

The distal radioulnar joint. Anatomic and functional considerations.

The distal radioulnar joint is functionally coupled with the proximal radioulnar joint, thus forming a mechanism for the longitudinal rotation of the hand. Distal radioulnar mobility is derived from the geometry of the joint, joint surfaces, and radioulnar connections. There is a structural and functional separation between the distal radioulnar and carpal joints, giving the possibility of pronation and supination in every position of the hand to the forearm. As for the stability of the joints involved, the ulnar articular disk plays an essential role. Being part of both distal radioulnar and carpal joints, the disk has very specific morphologic features that not only are individualized to the function of both joints but also stabilize the joints in their independent movements. Developmental data give the strong impression of an architectural scheme, of which the distal radioulnar joint is only a part. Traumatic lesions at the distal radioulnar joint and disturbances in normal distal radioulnar alignment have to be viewed, therefore, in a wider context.     

Reconstruction for DRUJ Instability

The skeletal architecture of the DRUJ provides minimal inherent stability, as the sigmoid notch is shallow and its radius of curvature is 50% greater than that of the ulnar head [Af Ekenstam F, Hagert CG. Anatomical studies on the geometry and stability of the distal radio ulnar joint. Scand J Plast Reconstr Surg 1985;19(1):17–25]. Due to its incongruent articulation, the DRUJ relies strongly on the surrounding soft tissues for stability. The triangular fibrocartilage complex (TFCC) is generally accepted as the major soft tissue stabilizer of the DRUJ of which the volar and dorsal radioulnar ligaments are the primary components. Restoration of the radioulnar ligaments offers the best possibility to restore the normal DRUJ primary constraints and kinematics. This article presents an update of the procedure developed by the senior author that anatomically reconstructs the palmar and dorsal radioulnar ligaments at their anatomic origins and insertions.     

The congruence of the distal radioulnar joint

The functional anatomy of the distal radioulnar joint was studied in 10 healthy volunteers. The joint surfaces of both the ulnar head and the sigmoid notch of the radius form arcs of circles with small areas of contact because the diameters of the circles are different. The distal radioulnar joint is congruent throughout its range of motion, but the area of contact shifts from dorsal in the sigmoid notch in pronation to volar in supination. The insertion of the distal radioulnar ligaments on the ulnar head explains the congruence of the joint.     

The congruence of the distal radioulnar joint. A magnetic resonance imaging study

The functional anatomy of the distal radioulnar joint was studied in 10 healthy volunteers. The joint surface of both the ulnar head and the sigmoid notch of the radius form arcs of circles with small areas of contact because the diameters of the circles are different. The distal radioulnar joint is congruent throughout its range of motion, but the area of contact shifts from dorsal in the sigmoid notch in pronation to volar in supination. The insertion of the distal radioulnar ligaments on the ulnar head explains the congruence of the joint.     

Histology of the alar and transverse ligaments.

Seven sets of human transverse and alar ligaments, after tensile testing, and eight corresponding ligaments without testing, were examined histologically with respect to their fiber composition and fiber orientation. Various staining techniques were supplemented by polarized light microscopy. Both the transverse and the alar ligaments consist of collagen fibers, with very few elastic fibers in the peripheral layer. In the central portion of the transverse ligament, the collagen fibers cross each other at an angle of approximately 30 degrees. Close to the dens, the transverse ligaments show on their ventral side a transition into fibrocartilage. Except for the immediate site of failure, no differences became evident between tested specimens and controls. The collagen, as the almost exclusive constituent, together with the fiber orientation determine the mechanical properties of these ligaments. This supports the hypothesis that the ligaments could be irreversibly overstretched or even ruptured when the head is rotated and, in addition, flexed by impact trauma, especially in unexpected rear-end collisions.     

Fehlklassifikation extraartikulärer distaler Radiusfrakturen in konventionellen Röntgenaufnahmen

Thirty-five displaced fractures of the distal radius, classified by standard radiographs as extra-articular type A2 and A3 fractures according to the AO classification, were investigated before operative treatment by computed tomography. The comparative analysis surprisingly revealed an involvement of the articular surface of the distal radius in 57%. The intra-articular fractures were classified after CT as C1 in 15%, C2 in 65%, and C3 in 20%. The distal radioulnar joint was involved in 80% of the type C injuries and showed a dorsal subluxation in 17% of all cases. Similar to the results of type A2 and A3 fractures, type B and C fractures of the distal radius also may be underestimated in standard radiographs. This concerns important components such as the involvement of the radiocarpal joint surface and concomitant injuries of the distal radioulnar joint. Since joint congruency is an important predictor of outcome, CT scanning should be used more generously for planning and controlling surgical therapy.     

Ulnar-positive variance as a predictor of distal radioulnar joint ligament disruption

PURPOSE: Previous cadaveric data show that disruption of the triangular fibrocartilage complex (TFCC) at the wrist allows 0.5 to 3.0 mm of proximal radius migration. Anatomic studies have documented the presence of superficial and deep fibers of both the palmar and the dorsal distal radioulnar joint (DRUJ) ligaments. The aim of this study was to determine the contribution of the superficial and deep fibers of the DRUJ ligaments to longitudinal forearm stability as measured by ulnar-positive variance. METHODS: Eight fresh-frozen cadaver specimens were included in this study. Each specimen was secured with external fixation clamps to a sequential loading frame with the elbow in 90 degrees of flexion and the forearm and wrist in neutral pronation supination, neutral ulnar-radial deviation, and neutral volar-dorsal angulation. The radial head was resected and a force gauge was applied to the proximal radius. The peripheral TFCC was identified through an incision between the fifth and sixth extensor compartments and the dorsal capsulotomy of the DRUJ capsule. After baseline measurement sequential transection of the superficial and deep fibers of the TFCC was performed. Before and after each step load application and removal were performed by attaching an 88.90-N weight to the end of a force gauge and via longitudinal traction on the proximal part of the radius, and ulnar variance was measured with wrist fluoroscopy. RESULTS: Transection of the superficial TFCC fibers resulted in radius migration of 0.70 mm. This migration, however, was not significantly different from that observed at baseline. After both the superficial and deep TFCC fibers were transected the radius migrated proximately with load. This change of ulnar variance was significantly greater than that observed at baseline or after transection of only the superficial TFCC fibers. CONCLUSIONS: Traumatic injury to the TFCC with radiographic evidence of ulnar-positive variance may be an indication of disruption of the deep TFCC fibers.     

Assessment of articular displacement of distal radius fractures

Intraarticular step and gap displacements represent the most common indication for surgical treatment of distal radius fractures. Most often, treatment decision making relies only on good-quality plain radiographs taken before and after reduction with measurement accuracy maximized by using the longitudinal axis method. When plain radiographs alone prove insufficient, CT scans or tomograms will significantly improve interobserver and intraobserver reliability of measurements, especially when evaluated using the arc method. Tomography is an effective method for postoperative evaluation of fractures immobilized in splints or casts. The role of MRI in assessing intraarticular distal radius fractures is limited to confirming injuries to carpal ligaments or the triangular fibrocartilage complex. Intraoperatively, we use fluoroscopy to obtain 30 degrees cephalad posteroanterior views and as 22 degrees lateral views to best observe articular surface reduction. Our current operative indications include fractures with radiocarpal or distal radioulnar joint step or gap deformities greater than 1-2 mm, gross distal radioulnar joint instability, or those with extensive metaphyseal comminution rendering them particularly unstable after closed reduction. In general, we tend to lean toward operative fixation in younger, more active patients.