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.     

腕尺桡偏运动时腕韧带长度变化的活体研究

目的 研究腕关节在尺桡偏运动过程中,腕关节韧带长度的变化.方法 对6名志愿者腕关节进行CT扫描,获得腕关节在桡偏20°至尺偏40°内每隔20°的运动范围内各腕骨及尺桡骨远段三维重建图像.男3名,女3名,仅研究单侧右侧腕关节.年龄20～32岁,平均24岁.在腕关节尺桡偏运动过程中,在重建各腕骨及尺桡骨结构图像上以软件测量掌、背侧腕韧带的长度.结果 腕关节尺偏时桡舟头韧带、长桡月韧带、背侧腕间韧带止于舟骨、大多角骨和小多角骨部分的长度较中立位显著伸长,分别伸长(2.4±0.3)mm、(2.3±0.8)mm、(1.2±0.6)mm、(1.2±1.2)mm与(2.6±1.0)mm,差异均有统计学意义(P＜0.05);腕关节桡偏时尺头韧带与背侧桡腕韧带长度显著伸长(P＜0.05),分别为(0.8±0.6)mm和(1.0±0.5)mm.结论 在腕关节尺桡偏运动时,桡舟头韧带、长桡月韧带、背侧腕间韧带于桡偏位缩短,尺头韧带、背侧桡腕韧带长度于尺偏位缩短.这些位置可能使不同腕韧带张力降低,有利于损伤韧带的修复.     

Biomechanical evaluation of the ligamentous stabilizers of the scaphoid and lunate: part III

PURPOSE: This study continued our previous investigations of the ligaments stabilizing the scaphoid and lunate in which we examined the scapholunate interosseous ligament, the radioscaphocapitate, and the scaphotrapezial ligament. In this current study, we examined the effects of sectioning the dorsal radiocarpal ligament, dorsal intercarpal ligament, scapholunate interosseous ligament, radioscaphocapitate, and scaphotrapezial ligaments. In the current study, the scapholunate interosseous ligament, radioscaphocapitate, and scaphotrapezial ligaments were sectioned in a different order than performed previously. METHODS: Three sets of 8 cadaver wrists were tested in a wrist joint motion simulator. In each set of wrists, only 3 of the 5 ligaments were cut in specific sequences. Each wrist was moved in continuous cycles of flexion-extension and radial-ulnar deviation. Kinematic data for the scaphoid and lunate were recorded for each wrist in the intact state, after the 3 ligaments were sectioned in various sequences and after the wrist was moved through 1,000 cycles of motion. RESULTS: Dividing the dorsal intercarpal or scaphotrapezial ligaments did not alter the motion of the scaphoid or lunate. Dividing the dorsal radiocarpal ligament alone caused a slight statistical increase in lunate radial deviation. Dividing the scapholunate interosseous ligament after first dividing the dorsal intercarpal, dorsal radiocarpal, or scaphotrapezial ligaments caused large increases in scaphoid flexion and lunate extension. CONCLUSIONS: Based on these findings, we concluded that the scapholunate interosseous ligament is the primary stabilizer and that the other ligaments are secondary stabilizers of the scapholunate articulation. Dividing the dorsal radiocarpal, dorsal intercarpal, or scaphotrapezial ligaments after cutting the scapholunate interosseous ligament produces further changes in scapholunate instability or results in changes in the kinematics for a larger portion of the wrist motion cycle.     

Experimental carpal displacement induced by ligamental lesions]

Ligamentous lesions were created experimentally in 40 fresh cadaver wrists. The precise localization of traumatic rupture of the ligaments and the subsequent carpal imbalance were defined by the comparison between the experimental results and the clinical displacements. The displacements may be permanent, sequential or induced by external forces. Lesions of capsular ligaments cause the displacement. There are 3 functional units; the distal scaphoid complex; the palmar ligaments which form a "belt", consisting of the lateral external ligament, the radiocarpal ligaments an the radiate ligament; the medial ligaments, which also form a "belt" consisting of the palmar triquetral ligaments on each side of the triquetrum. The sprains are caused by a lesion of a functional unit. The lateral sprain is characterized by a lesion of the distal scaphoid complex. The scaphoid moves into a horizontal position, causing a dorsal deviation of the lunate and a scapholunate diastasis. The central sprain is induced by a rupture of the palmar "belt", causing an anteroposterior radiocarpal or mediocarpal drawer movement. The medial sprain is induced by the rupture, of different extents, of the medial ligaments. On examination, there is either a click or a palmar deviation of the lunate, sometimes with a lunotriquetral diastasis. The dislocations of the wrist are caused by lesion of several ligamentous units.     

An anatomic guide for arthroscopic visualization of the wrist capsular ligaments

Wrist arthroscopy allows examination of the palmar capsular wrist ligaments without extensive exposure. Arthroscopic examination of the wrist requires an accurate knowledge of the ligamentous anatomy as seen from inside the joint. In this study 13 fresh cadaver wrists were examined from the inside out to provide a visual guide for ligament identification during arthroscopy. The major palmar capsular ligaments seen from the inside of the wrist at the radiocarpal joint include the radioscaphoid, radioscaphocapitate, radiolunate, radioscapholunate, ulnolunate, ulnotriquetral ligaments, and the ulnar capsule. At the midcarpal joint, the scaphocapitate, radioscaphocapitate, triquetrocapitate, and triquetrohamate ligaments are identified palmarly. Dorsally, constant capsular structures at the radiocarpal joint are the radiolunate and radioulnotriquetral ligaments along with a prominent synovial fold.     

Radiocarpal articular contact characteristics with scaphoid instability

The relative importance of the three major periscaphoid ligament complexes in maintaining the normal radiocarpal articulation was assessed. Pressure-sensitive film recorded the changes in radioscaphoid and radiolunate articular contact that occurred with sequential ligament sectioning in 12 cadaver wrists. Alterations in the radiocarpal articular contact as a result of ligament disruption are evident in the absence of the recognizable static x-ray changes of carpal instability. The scapholunate interosseous ligament is essential in preventing scapholunate diastasis and dorsoradial subluxation of the proximal scaphoid. Rotatory subluxation of the scaphoid occurs when disruption of the scapholunate interosseous ligament is coupled with disruption of either the palmar intracapsular radiocarpal ligaments or the scaphotrapezial ligament complex. These data help explain the development of degenerative arthritis caused by carpal ligamentous instability.     

晚期月骨无菌性坏死舟骨环形征的解剖学及生物力学研究

目的明确稳定舟骨近极的韧带及断裂后桡腕关节面应力的改变,阐明舟骨环形征的临床意义. 方法实验分为两部分,分别通过5侧上肢标本的解剖学观察,确定稳定舟骨近极的韧带;通过桡侧、尺侧屈腕肌腱及桡侧、尺侧伸腕肌腱,垂直加载12 kg负荷5分钟,应用压敏薄膜及FPD-305E、FPD-306E系统,分别测量腕关节中立、掌屈、背伸、尺偏及桡偏时,正常及韧带断裂后舟骨窝、月骨窝应力的变化. 结果解剖学观察发现,稳定舟骨近极的韧带为:桡舟头韧带、长桡月韧带及舟月骨间韧带,其中长桡月韧带和舟月骨间韧带起到限制舟骨近极向背侧移位的作用.生物力学研究结果表明,在稳定舟骨近极的韧带断裂后,背伸位时,舟骨窝桡侧亚区应力(0.90±0.43)与正常(0.85±0.15)无差异,但掌侧(0.59±0.20)、尺侧(0.52±0.05)及背侧亚区(0.58±0.23)应力较正常(相对应力为0.77±0.13、0.75±0.08、0.68±0.09)减小;中立、掌屈、桡偏及尺偏位时,舟骨窝内各亚区应力与正常相比增大或无差异;而月骨窝在中立位时,各亚区的应力增大;掌屈、背伸、桡偏及尺偏位时,各亚区的应力减小或无差异. 结论在月骨无菌性坏死ⅢB期,舟骨窝承受的负荷增加,在治疗方法的选择上,应注意矫正舟骨的旋转半脱位,防止后期出现桡舟关节创伤性关节炎.     

Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study

PURPOSE: To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model. METHODS: Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension. RESULTS: Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion. CONCLUSIONS: The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.     

Radioscapholunate ligament: a gross anatomic and histologic study of fetal and adult wrists

The radioscapholunate ligament was studied using fifty-four dissected adult cadaver wrists. Four of these wrists had arterial perfusions with colored latex and serial sections were made of twenty-one wrists from fetuses ranging in size from 23 to 230 millimeters crown-rump length. The radioscapholunate ligament was consistently identified between the long and short radiolunate ligaments, emerging through the palmar capsule of the radiocarpal joint. It was found to be a neurovascular structure surrounded by synovial tissue with vascular origins from the anterior interosseous and radial arteries and a neural origin from the anterior interosseous nerve. On entering the radiocarpal joint it attaches proximally to the interfacet prominence on the articular surface of the radius and distally to form the proximal membrane of the scapholunate interosseous ligament system. We found no anatomic evidence that this structure should be considered a ligament in a traditional mechanical sense. However, this structure may be clinically important as the vascular supply of the scapholunate interosseous ligament, as well as a sensory pathway from the scapholunate articulation.     

腕投掷运动时腕关节韧带长度变化的活体研究

目的 探讨腕关节在投掷运动过程中腕关节韧带长度的变化.方法 对6例志愿者腕关节进行CT扫描,获取腕关节在投掷运动过程中的5个位置,即桡偏20°背伸60°,桡偏10°背伸30°,中立位,尺偏20°掌屈30°,尺偏40°掌屈60°时各腕骨、尺桡骨远段的三维重建图像,在重建图像基础上利用Mimics软件测得在腕关节投掷运动过程中掌、背侧腕关节韧带的长度.结果 腕关节由中立位至桡偏20°背伸60°时桡舟头韧带、长桡月韧带、尺头韧带、尺三角韧带长度显著伸长,分别延长(3.4±0.5)、(2.0±0.2)、(2.6±0.5)、(2.1±0.4)mm,差异均有统计学意义(P<0.05);腕关节由中立位至尺偏400掌屈60°时背侧桡腕韧带、背侧骨间韧带止于小多角骨部分长度显著伸长,分别延长(1.7 ±0.2)、(3.8 ±0.4)mm,差异有统计学意义(P<0.05).尺月韧带、背侧骨问韧带止于舟骨部分在投掷运动过程中其长度均较中立位时旱增长趋势.结论 腕关节在桡背伸至尺掌屈运动过程中,桡舟头韧带、长桡月韧带、尺头韧带、尺三角韧带缩短,提示张力减低,背侧桡腕韧带、背侧骨间韧带止于小多角骨部分伸长,张力增大,尺月韧带、背侧骨间韧带止于舟骨部分于中立位时张力最小,其变化规律有助于指导临床腕关节韧带损伤的修复.     

Radial styloidectomy: an anatomical study with special reference to radiocarpal intracapsular ligamentous morphology

This study determines the anatomical relationship of the radiocarpal ligaments to the radial styloid process, and the effect of three specific styloidectomies on the integrity of these ligaments. Thirty fresh cadaveric wrists were dissected. The origins, insertions, and dimensions of each ligament was determined. The thirty wrists were divided randomly into three equal groups and the ten wrists in each group had three types of styloidectomy: short oblique, vertical oblique, and horizontal. The styloid fragments and wrists were then reexamined to determine the integrity of the ligaments. All styloidectomies removed the radial collateral ligament origin. Vertical oblique styloidectomy removed additionally 92% of the radioscaphocapitate and 21% of the radiolunatotriquetral ligament. Horizontal styloidectomy removed 95% of the radioscaphocapitate, and 46% of the radiolunatotriquetral ligament. These findings indicate that the degree of radiocarpal ligament disruption that occurs after styloidectomy may be predicted accurately by correlating the amount of styloid removed, with the consistent ligamentous anatomy of this area.     

Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study

PURPOSE: Carpal kinematics have been studied widely yet remain difficult to understand fully. The noninvasive measurement of carpal kinematics through medical imaging has become popular. Studies have shown that with radial deviation the scaphoid and lunate flex whereas the capitate moves radiodorsally relative to the lunate. This study investigated the midcarpal and radiocarpal contributions to radial and ulnar deviation of the wrist. This was accomplished through noninvasive characterization of the scaphoid, lunate, and capitate using 3-dimensional medical imaging of the wrist in radial and ulnar deviation. METHODS: Eight fresh-frozen and thawed cadaveric wrists were used in an experimental set-up that positioned the wrist through spring-scale actuation of the 4 wrist flexor and extensor tendon groups. The wrists were scanned by computed tomography in neutral and full radial and ulnar deviation. Body mass-based local coordinate systems were used to track the motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion and Euler angles were calculated from neutral to radial and ulnar deviation for the capitate relative to the radius, lunate, and scaphoid and for the lunate and scaphoid relative to the radius. RESULTS: The capitate, scaphoid, and lunate moved in a characteristic manner relative to the radius and to one another. Radial and ulnar deviation occurred primarily in the midcarpal joint. Midcarpal motion accounted for 60% of radial deviation and 86% of ulnar deviation. In radial deviation the proximal row flexed and the capitate extended; the converse was true in ulnar deviation. CONCLUSIONS: Radioulnar deviation (in-plane motion) occurred mostly through the midcarpal joint, with a lesser contribution from the radiocarpal joint. The results of our study agree with previous investigations that found the scaphoid and lunate flex in radial deviation (out-of-plane motion) relative to the radius whereas the capitate extends (out-of-plane motion) relative to the scaphoid/lunate (with the converse occurring in ulnar deviation). Our study shows how these out-of-plane motions combine to produce in-plane wrist radioulnar deviation. The use of 3-dimensional visualization greatly aids in the understanding of these motions. The results of our study may be useful clinically in understanding the consequences of isolated midcarpal fusions in the treatment of wrist instability.     

The dorsal ligaments of the wrist: anatomy, mechanical properties, and function.

The purpose of this study was to examine the anatomy and mechanical properties of the dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) ligaments of the wrist and to better understand the functional design of the dorsal ligaments. The DRC ligament was consistently found to originate from the dorsal margin of the distal radius and extended ulnar obliquely and distally. Its radial fibers attached to the lunate and lunotriquetral interosseous ligament. The DRC ligament then inserted onto the dorsal tubercle of the triquetrum. The DIC ligament originated from the triquetrum and extended radially and attached onto the lunate, inserted into the dorsal groove of the scaphoid, and then extended to the trapezium. The DRC and DIC ligaments together, in their lateral V configuration, act effectively as a dorsal radioscaphoid ligament that has the ability to vary its length by changing the angle between the 2 arms of the V. The DRC-DIC ligaments' lateral V configuration allows normal carpal kinematics while maintaining its indirect dorsal stabilizing effect on the scaphoid throughout the range of motion of the wrist.     

Biomechanical evaluation of ligamentous stabilizers of the scaphoid and lunate

This study evaluated the effects of sectioning the scapholunate interosseous ligament, radioscaphocapitate ligament, and scaphotrapezial ligament on the kinematics of the scaphoid and lunate. Eight cadaver upper extremities were placed in a wrist joint simulator and moved in continuous cycles of flexion-extension and radial-ulnar deviation. Positional data of the scaphoid and lunate were obtained in the intact state, after the scapholunate ligament was cut; after the scapholunate and scaphotrapezial ligaments were cut; after the scapholunate, scaphotrapezial, and radioscaphocapitate ligaments were cut; and after all 3 ligaments were cut and the specimen was placed through an additional 1,000 cycles of flexion-extension. Cutting the scapholunate ligament caused changes in scaphoid and lunate motion during flexion-extension, but not radial-ulnar deviation. Additional sectioning of the scaphotrapezial ligament followed by the radioscaphocapitate ligament caused further kinematic changes in these carpal bones. One thousand cycles of motion after all 3 ligaments were sectioned caused additional kinematic changes in the scaphoid and lunate. The scapholunate ligament appears to be the primary stabilizer between the scaphoid and lunate. The radioscaphocapitate and scaphotrapezial ligaments are secondary restraints. Repetitive cyclic motion after ligament sectioning appears to have additional deleterious effects on carpal kinematics.     

Immunohistochemical analysis of wrist ligament innervation in relation to their structural composition

PURPOSE: To analyze ligament innervation and the structural composition of wrist ligaments to investigate the potential differences in sensory and biomechanical functions. METHODS: The ligaments analyzed were the dorsal radiocarpal, dorsal intercarpal, scaphotriquetral, dorsal scapholunate interosseous, scaphotrapeziotrapezoid, radioscaphoid, scaphocapitate, radioscaphocapitate, long radiolunate, short radiolunate, ulnolunate, palmar lunotriquetral interosseous, triquetrocapitate, and triquetrohamate ligaments. The ligaments were harvested from 5 cadaveric, fresh-frozen specimens. By using the immunohistochemical markers p75, Protein Gene Product 9.5, and S-100 protein, the mechanoreceptors and nerve fibers could be identified. RESULTS: The innervation pattern in the ligaments was found to vary distinctly, with a pronounced innervation in the dorsal wrist ligaments (dorsal radiocarpal, dorsal intercarpal, scaphotriquetral, dorsal scapholunate interosseous), an intermediate innervation in the volar triquetral ligaments (palmar lunotriquetral interosseous, triquetrocapitate, triquetrohamate), and only limited/occasional innervation in the remaining volar wrist ligaments. The innervation pattern also was reflected in the structural differences between the ligaments. When present, mechanoreceptors and nerve fibers were consistently found in the loose connective tissue in the outer region (epifascicular region) of the ligament. Hence, ligaments with abundant innervation had a large epifascicular region, as compared with the ligaments with limited innervation, which consisted mostly of densely packed collagen fibers. CONCLUSIONS: The results of our study suggest that wrist ligaments vary with regard to sensory and biomechanical functions. Rather, based on the differences found in structural composition and innervation, wrist ligaments are regarded as either mechanically important ligaments or sensory important ligaments. The mechanically important ligaments are ligaments with densely packed collagen bundles and limited innervation. They are located primarily in the radial, force-bearing column of the wrist. The sensory important ligaments, by contrast, are richly innervated although less dense in connective tissue composition and are related to the triquetrum. The triquetrum and its ligamentous attachments are regarded as key elements in the generation of the proprioceptive information necessary for adequate neuromuscular wrist stabilization.     

The ligaments of the wrist.

The ligaments of the wrist were studied by dissecting ten fixed and seven fresh frozen wrists. In three other specimens multiple cross-sections were prepared. These studies show that the wrist ligaments can be classified into two groups: extrinsic and intrinsic. In the extrinsic group, the deep volar radiocarpal ligaments are three strong and very important structures connecting the radius to the capitate, the radius to the lunate, and, in a deeper layer, the radius to both the scaphoid and the lunate. A ligamentous deficiency was noted frequently between the capitate and the lunate. There also are very strong volar connections between the radius and the medial or ulnar carpus. These studies suggest that certain patients with a generalized ligamentous laxity and weakness will develop a pathological disruption of the volar ligaments with trauma. These torn volar ligaments should be repaired or reconstructed, for repair of only the dorsal ligaments seldom will provide good stability to such wrists.     

腕舟骨周围韧带解剖学研究

目的观察和研究分布在腕舟骨周围的腕外源性或内源性韧带的结构及特点。方法采用１４侧成人尸体上肢，分离和解剖出舟骨周围的韧带，观察并记录其起止点、行程、长宽度及解剖结构特征。结果在舟骨周围观察到８根韧带，为桡舟头韧带（ＲＳＣ）、桡舟月韧带（ＲＳＬ）、桡月韧带（ＲＬ）、背侧腕间韧带（ＤＩＣ）、桡三角骨韧带（ＲＴ）、和舟月骨间韧带（ＳＬＩＬ）、舟骨大多角和舟骨小多角骨间韧带。ＲＳＣ、ＤＩＣ和ＳＬＩＬ对舟骨的位置、稳定性和运动尤为重要。结论腕舟骨周围存在复杂的韧带结构，其中ＲＳＣ、ＤＩＣ和ＳＬＩＬ对舟骨的稳定，舟骨骨折后畸形的形成、舟骨不稳定的形成起着重要作用。这些韧带的结构或功能在治疗腕不稳定中应予以恢复     

Kienbock's disease: diagnosis and treatment

Kienbock's disease, or osteonecrosis of the lunate, can lead to chronic, debilitating wrist pain. Etiologic factors include vascular and skeletal variations combined with trauma or repetitive loading. In stage I Kienbock's disease, plain radiographs appear normal, and bone scintigraphy or magnetic resonance imaging is required for diagnosis. Initial treatment is nonoperative. In stage II, sclerosis of the lunate, compression fracture, and/or early collapse of the radial border of the lunate may appear. In stage IIIA, there is more severe lunate collapse. Because the remainder of the carpus is still uninvolved, treatment in stages II and IIIA involves attempts at revascularization of the lunate-either directly (with vascularized bone grafting) or indirectly (by unloading the lunate). Radial shortening in wrists with negative ulnar variance and capitate shortening or radial-wedge osteotomy in wrists with neutral or positive ulnar variance can be performed alone or with vascularized bone grafting. In stage IIIB, palmar rotation of the scaphoid and proximal migration of the capitate occur, and treatment addresses the carpal collapse. Surgical options include scaphotrapeziotrapezoid or scaphocapitate arthrodesis to correct scaphoid hyperflexion. In stage IV, degenerative changes are present at the midcarpal joint, the radiocarpal joint, or both. Treatment options include proximal-row carpectomy and wrist arthrodesis.     

What is the implication of scaphoid ring sign in advanced Kienb?ck's disease? Is it a sign of advanced carpal collapse or rotary scaphoid subluxation?

OBJECTIVE: To discuss the clinical implication of scaphoid ring sign in Lichtman's X-ray IIIB stage of the lunate avascular necrosis. METHODS: In a series of 17 cases of advanced Kienb?ck's diseases, carpal height (CH) and carpal height ratio (CHO) were measured in posteroanterior X-ray view (PA) preoperatively, which included seven cases in stage IIIA and 10 cases in stage IIIB. Radioscaphoid angles were also measured in the lateral X-ray view. All these measurements above were to study what were the differences between stages IIIA and IIIB. In addition, five fresh normal wrist specimens were dissected to observe the ligaments stabilizing the proximal pole of scaphoid. RESULTS: The results of CH and CHR between stages IIIA and IIIB were similar, which illustrated no significant difference in carpal collapse between two substages, however, the results of RSA were significantly different between two substages, which implied the position of the proximal pole of scaphoid changed in two substages. Based on the results of anatomical observation, three ligaments were important to stabilize the proximal pole of scaphoid, namely the radioscaphocapitate (RSC) ligament, long radiolunate (LRL) ligament and scapholunate interosseous ligament (SLIL). The function of RSC ligament was to restrict palmar subluxation of the proximal pole of scaphoid; LRL and SLIL were to restrict dorsal transposition of the proximal pole of scaphoid. CONCLUSION: Based on the results, we suppose the scaphoid ring sign is the implication of rotary scaphoid subluxation in stage IIIB, which was caused by destructions of LRL and SLIL ligaments. All procedures aimed at stage IIIB must account for this important factor.     

In vivo elongation of the palmar and dorsal scapholunate interosseous ligament

PURPOSE: To investigate the elongation of the palmar and dorsal subregions of the scapholunate interosseous ligament (SLIL) in healthy human subjects throughout a complete range of wrist motion. METHODS: The 3-dimensional in vivo kinematics of the scaphoid and lunate were determined in both wrists of 13 female and 13 male volunteers from computed tomography volume images. For each wrist the palmar and dorsal insertions of the SLIL were identified on reconstructed surface models of the scaphoid and lunate. The interbone distances between the palmar and dorsal sites were calculated for the neutral wrist position. Elongations were then calculated after applying the 3-dimensional kinematics to the scaphoid and lunate. A multiple linear regression model was used to determine if elongations varied significantly as a function of wrist flexion/extension and radioulnar deviation. RESULTS: From pure wrist extension to pure wrist flexion, the fibers of the SLIL at the palmar insertion site increased significantly, from 29% shortening to 27% elongation, and the dorsal insertion decreased from 26% to 4% shortening with respect to the fiber lengths in the neutral position. From pure radial deviation to pure ulnar deviation, the elongation of the palmar insertion significantly decreased from 9% elongation to 21% shortening. There was no notable change in dorsal elongation with wrist radioulnar deviation. The multiple linear regression model predicted that there would be minimal elongation of the palmar and dorsal fibers at the wrist position along the dart thrower's path from radial extension to ulnar flexion. CONCLUSIONS: In vivo elongation of the palmar and dorsal fibers of the SLIL varied with wrist position. The palmar fibers lengthened and the dorsal fibers shortened with wrist flexion and the opposite occurred with wrist extension. Scapholunate interosseous ligament elongation was minimal as the wrist was positioned along the dart thrower's path.