Subchondral bone mineral density patterns representing the loading history of the wrist joint

Ten cadaver wrists were examined with CT-Absorptiometry in order to assess bone density in the subchondral bone. In normal wrists the distal radius contained two centroids of bone density, one in the lunate fossa and another in the scaphoid fossa. Pathologically altered wrists showed a shift in bone density towards the scaphoid fossa, with the subchondral bone in the lunate fossa and distal ulna becoming less dense. Bone density patterns in the wrist reflect the long-term force transmission. As bone density alters according to loading conditions, this method can be used to determine force transmission patterns before and after wrist surgery.     

Pressure distribution in the radiocarpal joint measured with a densitometer designed for pressure-sensitive film.

To measure the pressure distribution in the radiocarpal joint, a biomechanical study was done with fresh cadavers and pressure-sensitive film. With a load of 100 newtons, the contact locations were identified for 27 different wrist positions and the peak articular pressures and contact area were measured. Normal wrists were studied first, then modified to show different ulnar variances, and then to be models of malunited Colles' fractures of increasing severity. The contact locations of the scaphoid and the lunate were separate, and the mean peak articular pressures were 2.8 and 2.7 megapascals, respectively, for the normal wrists. In the radiolunate articulation, this mean increased by 27% with 2.5 mm ulnar minus variance and decreased by 22% with 2.5 mm ulnar plus variance. In the models of malunited Colles' fracture, the contact locations shifted from volar to dorsal, and the contact area decreased as the deformity became worse.     

Madelung's deformity: quantitative radiographic comparison with normal wrists

Four measurements, ulnar tilt, lunate subsidence, lunate fossa angle and palmar carpal displacement, on wrist radiographs of 26 patients with Madelung's deformity and 48 normal subjects were compared. The range of measurements on wrists with Madelung's deformity was wider than on normal wrists, with severe deformities having very abnormal values. Some Madelung's patients had values that were within the normal range for each of the four measurements. Measurement of the lunate fossa angle demonstrated the least overlap between normal wrists and wrists of patients with Madelung's deformity with only two in the normal range. A lunate fossa angle over 29 degrees may help identify early Madelung's deformity.     

Radiographic changes in wrists with ulnar plus variance observed over a ten-year period

This study provides additional radiographic information concerning the long-term effect of ulnar impingement. Films of 198 wrists of 102 patients with vibration disease observed over ten or more years were reviewed. All the wrists showed ulnar plus variance of more than 0 mm except seven. Degenerative changes were found in 58 wrists and were seen only on the ulnar side of the wrist, especially in the ulnoproximal area of the lunate. Most of the degenerative changes in the wrists with ulnar plus variance had progressed or changed during the ten or more years. Ulnar plus variance may play an important role in inducing or causing progression of degenerative change in the wrist.     

In vivo radiocarpal kinematics and the dart thrower's motion

BACKGROUND: Wrist motion is dependent on the complex articulations of the scaphoid and lunate at the radiocarpal joint. However, much of what is known about the radiocarpal joint is limited to the anatomically defined motions of flexion, extension, radial deviation, and ulnar deviation. The purpose of the present study was to determine the three-dimensional in vivo kinematics of the scaphoid and lunate throughout the entire range of wrist motion, with special focus on the dart thrower's wrist motion, from radial extension to ulnar flexion. METHODS: The three-dimensional kinematics of the capitate, scaphoid, and lunate were calculated from serial computed tomography scans of both wrists of fourteen healthy male subjects (average age, 25.6 years; range, twenty-two to thirty-four years) and fourteen healthy female subjects (average age, 23.6 years; range, twenty-one to twenty-eight years), which yielded data on a total of 504 distinct wrist positions. RESULTS: The scaphoid and lunate primarily flexed or extended in all directions of wrist motion, and their rotation varied linearly with the direction of wrist motion (R2= 0.90 and 0.82, respectively). Scaphoid and lunate motion was significantly less along the path of the dart thrower's motion than in any other direction of wrist motion (p < 0.01 for both carpal bones). The scaphoid and lunate translated radially (2 to 4 mm) when extended, but they did not translate appreciably when flexed. CONCLUSIONS: The dart thrower's path defined the transition between flexion and extension rotation of the scaphoid and lunate, and it identified wrist positions at which scaphoid and lunate motion approached zero. These findings indicate that this path of wrist motion confers a unique degree of radiocarpal stability and suggests that this direction, rather than the anatomical directions of wrist flexion-extension and radioulnar deviation, is the primary functional direction of the radiocarpal joint.     

Changes in radiocarpal loading characteristics after proximal row carpectomy

PURPOSE: To document the changes in wrist loading that occur after proximal row carpectomy in a cadaver model. METHODS: The normal radioulnar carpal pressure distributions of 7 cadaver wrists were measured using super-low-pressure-sensitive film. Proximal row carpectomies were performed and the loading characteristics re-evaluated. RESULTS: In the lunate fossa the contact area increased 37%, the average contact pressure increased 57%, and the location of the contact moved radially 5.5 mm. With wrist motion between 40 degrees of extension and 20 degrees of flexion the volar/dorsal excursion of the lunate fossa contact point increased by 108%. CONCLUSIONS: Significant changes in radiocarpal loading occur after proximal row carpectomy. The increased radiocarpal excursion with wrist motion may explain the low incidence of radiocapitate arthritis in patients who have had proximal row carpectomy.     

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.     

Subchondral bone mineral density patterns representing the loading history of the wrist joint after lunate-capitate-triquetrum-hamate arthrodesis

This study examined patterns of bone mineral density (BMD) of the wrist by computed tomography–absorptiometry to evaluate force transmission patterns in vivo in patients with complaints of wrist instability requiring lunate-capitate-triquetrum-hamate (LCTH) arthrodesis. These patterns represent long-term force transmission through the wrist joint because BMD differs under different loading conditions. BMD studies of the wrist joint in vivo can evaluate the long-term force transmission through the joint under physiological and pathological conditions and before and after wrist surgery. The scaphoid fossa is relatively unloaded after LCTH arthrodesis, and a decrease in BMD is observed in the lunate fossa.     

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.     

Ulnar shortening osteotomy in idiopathic ulnar impaction syndrome

BACKGROUND: Idiopathic ulnar impaction syndrome can be defined as a degenerative condition of the ulnar aspect of the wrist in patients with congenital or dynamic positive ulnar variance without a history of fracture or premature physeal arrest. The purpose of this study was to evaluate the clinical features of idiopathic ulnar impaction syndrome and the outcomes of ulnar shortening osteotomy for this group of patients. METHODS: Thirty-one wrists in twenty-nine patients with idiopathic ulnar impaction syndrome were treated with an ulnar shortening osteotomy. Ulnar variance was measured on an anteroposterior radiograph of the wrist, and radioulnar distance was measured on a lateral radiograph, with the forearm in neutral rotation, to evaluate any displacement of the ulnar head from the distal aspect of the radius. All patients were followed clinically and radiographically for a mean of thirty-two months. RESULTS: An average preoperative ulnar variance of +4.6 mm (range, 2 to 7.5 mm) was reduced to an average of -0.7 mm (range, -4 to +1 mm) postoperatively. Preoperatively, the modified Gartland and Werley score was an average (and standard deviation) of 69.5 +/- 7.6, with twenty-four wrists rated poor and seven rated fair. Postoperatively, the score improved to an average of 92.5 +/- 8.0, with twenty-four wrists rated excellent; five, good; one, fair; and one, poor. Dorsal subluxation of the distal aspect of the ulna was found concomitantly in nine wrists, and it was found to be reduced by the shortening osteotomy. Seven patients had cystic changes in the carpal bones preoperatively, but these were not evident one to two years after the operation. CONCLUSIONS: Ulnar shortening osteotomy improved wrist function in patients with idiopathic ulnar impaction syndrome and reduced the subluxation of the distal radioulnar joint, which is commonly found in these patients. Degenerative cystic changes of the ulnar carpal bones appear to resolve following the shortening osteotomy.     

Motion analysis in two dimensions of radial-ulnar deviation of type I versus type II lunates

The motions of 2 different types of lunate (type I, no medial hamate facet; type II, medial hamate facet) were evaluated and compared during radial-ulnar deviation of the wrist using radiography and magnetic resonance imaging. Ten right wrists (5 type I and 5 type II lunates) were studied using posteroanterior and lateral x-rays. Six of the 10 normal volunteers (3 type I and 3 type II lunates) were studied using magnetic resonance imaging in 6 positions of radial-ulnar deviation. In the radiographic study the ulnar shift ratio of the lunate (USR), the shortest distance between the proximal ulnar tip of the lunate and the distal ulnar edge of the sigmoid notch of the radius (R-L), the closest distance between the distal ulnar tip of the lunate and the proximal pole of the hamate (L-H), the radius of curvature of the proximal head of the capitate (Cr) on posteroanterior view, and the radiolunate angle on lateral view were measured in each wrist in each of the 6 positions. There were statistically significant differences between type I and II lunates with regard to average maximum ulnar deviation of USR and R-L, total change of USR, R-L distance and L-H distance, average L-H distance and Cr distance in all positions, and average radiolunate angle in neutral and 15 degrees ulnar deviation. In the magnetic resonance imaging study the wrists with a type I lunate did not have contact between the lunate and hamate in any position; the wrists with a type II lunate did have contact between the hamate and the lunate, but only in ulnar deviation. The results of this study demonstrate that the kinematics of a type I lunate are different from those of a type II lunate during radial-ulnar deviation of the wrist.     

Anatomical study of radiocarpal joint--degenerative change and morphometry]

The present investigator studied following degenerative changes of the articular cartilage of the radiocarpal joint: the ruptures of the scapholunate and the lunotriquetral interosseous ligaments (S-L lig., L-T lig.), the shape of the scaphoid and the lunate fossa of the distal radius. We studied 120 wrist joints from 74 cadaveric specimens (age 20-97, average age 68). The cartilaginous changes were correlated significantly with age (p < 0.01). The cartilaginous changes were most commonly found in the ulnar demarcation of the lunate, next commonly, in the radiodorsal demarcation of the scaphoid fossa, thirdly, in the radiodorsal demarcation of the scaphoid and finally, in the radial demarcation of the scaphoid fossa. Clearly, the cartilaginous changes in the ulnar demarcation of the lunate intensified proportionally as the ulnar variance increased (p < 0.05) and as the radial inclination decreased (p < 0.05). The S-L lig. and the L-T lig. ruptures increased as the age of the specimens increased. The cartilaginous changes of the interosseous ligament rupture group were stronger than those of the non ligament rupture group (p < 0.01). The concavity of the scaphoid fossa in the dorsovolar direction exhibited an S shaped curve, a convexity on the dorsal side and a concavity on the volar side. The other concavities exhibited a smooth concave curve. From these results, it was concluded that the stability of the wrist joint in extention and the cartilaginous changes of the radioscaphoid joint were due to the volar concavity of the scaphoid fossa of the radius.     

The effect of radial shortening on wrist joint mechanics in cadaver specimens with inherent differences in ulnar variance

PURPOSE: To assess load changes in the wrist and forearm resulting from surgically-induced radial shortening in wrists with inherent differences in ulnar variance. METHODS: Eleven fresh cadaver upper extremities, 4 with ulnar-plus variance of 2 mm or greater and 7 with ulnar-minus variance of 2 mm or greater were used. The radius and ulna of each specimen were instrumented with load cells, a 15-mm segment of the radius was resected and replaced with aluminum blocks of various sizes, and the specimens were loaded with 143 N (32 lb) at 1-mm differences of radial length. The load distribution between the radius and ulna was measured. RESULTS: The load distribution in the specimens with an ulnar-plus variance averaged 69% through the radius and 31% through the ulna. In the wrists with ulnar-minus variance, the load distribution averaged 94% through the radius and 6% through the ulna. The mean force in the ulna increased and the mean force in the radius decreased with incremental shortening of the distal end of the radius. The mean force through the ulna in the ulnar-plus-variance group was always higher than that of the ulnar-minus-variance group. When compared not by the number of millimeters of radial shortening but by the adjusted ulnar variance, there was no difference between the ulnar-plus-variance and the ulnar-minus-variance groups. CONCLUSIONS: Wrists with ulnar-minus variance could accommodate radial shortening without as much increase in the ulna load as wrists with ulnar-plus variance. The clinical relevance is that a patient with an ulnar-minus variance may accommodate more radial shortening after a wrist fracture without developing an ulnar impaction syndrome than a patient with an ulnar-plus-variant wrist.     

腕关节神经支切断与假体置换治疗月骨缺血性坏死

目的防止月骨缺血性坏死后腕骨排列进行性紊乱，缓解腕痛，增加握力，改善功能。方法１９９２年１月～１９９７年１月，采用腕关节神经支切断，月骨假体置换术治疗月骨缺血性坏死６例。结果术后随访最短１０个月，最长５４个月，平均随访时间３２个月，优良率８３．３％。结论骨间前、后神经腕关节支切断术联合月骨假体置换术治疗月骨缺血性坏死，术后能获得无痛的关节。腕关节神经支切断联合假体置换是治疗月骨缺血性坏死的一种效果较好的方法     

Subchondral bone mineral density patterns representing the loading history of the wrist joint after a proximal row carpectomy

To evaluate force transmission patterns in vivo of patients with complaints of wrist instability requiring a proximal row carpectomy, bone mineral density (BMD) patterns of the wrist were established using computed tomography absorptiometry. Normal wrists show a BMD pattern in which the scaphoid fossa and lunate fossa of the distal radius contain a center of force transmission. Wrists with pathology of the proximal carpal row or distal radius show a shift of BMD towards the dorsal edge and the styloid process of the scaphoid fossa. After a proximal row carpectomy, the BMD of the scaphoid fossa decreases, and a BMD center is formed in the center of the lunate fossa, demonstrating that the force transmission is concentrated in its center.     

Force transmission through the distal ulna: effect of ulnar variance, lunate fossa angulation, and radial and palmar tilt of the distal radius.

The relationship between the amount of force transmitted through the distal ulna and seven radiologically apparent anatomic parameters (ulnar variance, radial tilt, palmar tilt, lunate fossa angulation, carpal height, carpal ulnar distance, and ulnar head inclination) was examined in 58 fresh cadaver forearms. A positive, although very weak, relationship was found between the amount of force and the ulnar variance (r = 0.44). This suggests that a clinically more positive ulnar variant wrist will not necessarily cause more force to be transmitted to the head of the ulna than a wrist with a more negative ulnar variance, primarily because the triangular fibro-cartilage complex is thicker in arms with a more negative ulnar variance. Changes in ulnar variance of a forearm due to ulnar lengthening or radial shortening do, however, dramatically alter the force transmission. No other relationships were found between the ulnar force and the other radiologic parameters.     

The influence of articular morphology on non-traumatic degenerative changes of the distal radioulnar joint. A radiographic study

We examined 248 wrist X-rays of patients over 50 years of age to find out if ulnar variance, orientation of the sigmoid notch and ulnar head inclination play a role in the development of non-traumatic osteoarthritis of the distal radioulnar joint. Minor degenerative changes, viz. focal joint space narrowing and/or lipping, or small osteophytes at the inferior edge of the ulnar head, were present in 13% of the X-rays of these wrists. They were significantly more frequent in wrists with a more inclined ulnar head and significantly less present in wrists with an oblique, distally orientated sigmoid notch. There was no significant association with ulnar variance or age. This study suggests that articular morphology may play a role in the development of degenerative changes of the distal radioulnar joint.     

Patterns of subchondral bone mineralization in the distal radioulnar joint

PURPOSE: Studies have shown that it is possible to derive direct knowledge about the actual mechanical conditions of the wrist by analyzing the subchondral mineralization. The aim of the present study was to evaluate the distribution of the subchondral bone mineralization of the distal radioulnar joint (DRUJ) noninvasively in living subjects by using computed tomography (CT) osteoabsorptiometry to gain new information about the long-term loading conditions. METHODS: Twenty-two wrist joints were investigated in 11 healthy young subjects by means of CT osteoabsorptiometry. The CT scans of the DRUJ were taken in the axial plane in neutral position of the forearm and in both maximum pronation and supination. The CT datasets of 1.5-mm sections were obtained and then transferred to an image-analyzing system. The subchondral bone plate in each section was isolated, reconstructed in 3 dimensions, and converted into a false color series. RESULTS: The maximum subchondral bone density in the sigmoid notch of the radius was found along the distal border in all wrists. It was located dorsally in 10 wrists, palmarly in 8 wrists, and centrally in 4 wrists. The maximum bone density on the corresponding articular surface of the ulna was found dorsally in 10 cases, centrally in 8 cases, and palmarly in 4 cases. In 13 cases the maximum bone density was found in direct opposition on radius and ulna in neutral position. A statistically significant difference could not be detected in subjects with an ulna minus variance nor in those with a DRUJ angulation greater than 10 degrees . CONCLUSIONS: Our results show that in the sigmoid notch the load is transmitted through either the dorsal or palmar parts of the joint. In contrast the maximum bone density on the side of the ulna was found dorsally and centrally. We conclude that the ulna receives the maximum load in neutral position and supination, whereas because of the dorsopalmar translation of the ulnar head the radius may lead the ulna with either its palmar or dorsal borders during pronosupination. The ligamentous apparatus, the shape of the joint, and the ulna variance, however, may influence load transmission.     

Calcium pyrophosphate dihydrate crystal deposition patterns in the triangular fibrocartilage complex

To define the patterns of calcium pyrophosphate dihydrate (CPPD) crystal deposition in the triangular fibrocartilage complex (TFCC), we examined the wrists of five adult, fresh-frozen cadavers using light and scanning electron microscopy and the wrist radiographs of 10 patients with a clinical diagnosis of CPPD disease. The radiographs consistently showed mineral deposits near or on the proximal and distal surfaces of the radial half of the TFCC. Light and electron microscopy showed that CPPD crystals formed distinct clusters sharply demarcated from uninvolved fibrocartilage. The density of crystal packing within clusters varied with the sharpness of demarcation of the clusters from the surrounding tissue. TFCC defects were consistently found in the vicinity of CPPD crystals, and degeneration of the articular cartilage on the ulnar half of the proximal surface of the lunate was associated with CPPD crystal deposition in the radial half of the TFCC. These observations suggest that degenerative tears of the TFCC and degeneration of the articular cartilage of the lunate are associated with CPPD crystal deposits in the TFCC.     

MSCT图像重建技术在尺骨撞击综合征中的应用

目的评价MSCT图像重建技术在尺骨撞击综合征诊断中的应用价值。方法回顾性分析经腕关节镜检查证实的18例尺骨撞击综合征患者MSCT图像重建技术及标准后前位X线平片检查的影像资料,对尺骨变异、月骨及三角骨异常变化进行统计学分析。结果⑴MSCT图像重建技术及标准后前位X线平片检查测量出的尺骨变异差异无统计学意义(t=0.3562,P>0.05);⑵MSCT图像重建显示18例尺骨阳性变异15例,占总例数83.3%,其中阳性变异超过2 mm者11例,占总阳性变异的73.3%;中性及阴性变异3例,占总例数16.7%;⑶MSCT重建技术显示月骨和/或三角骨异常变化14例,占总例数77.8%,其中单纯月骨异常变化8例,月骨及三角骨同时异常变化5例,单纯三角骨异常变化1例。标准后前位X线平片能显示月骨和/或三角骨异常变化10例,占总例数55.6%,其中单纯月骨异常变化6例、月骨及三角骨同时异常变化4例,无单纯三角骨异常变化;⑷MSCT图像重建技术测量尺骨阳性伴月骨及三角骨异常变化14例,占总例数77.8%,尺骨阳性变异不伴月骨及三角骨异常变化1例,占总例数5.6%。阳性变异大于2 mm伴月骨及三角骨异常变化11例,占总例数61.1%,月骨及三角骨异常变化例数的78.6%。无尺骨中性及阴性变异伴月骨及三角骨异常变化。结论MSCT图像重建技术及后前位X线平片测量尺骨变异无统计学差异;尺骨撞击综合征发展过程中尺骨阳性变异呈易感因素;尺骨阳性变异大于2 mm时易引起月骨、三角骨异常变化;MSCT图像重建技术可以很好地显示尺骨变异及月骨、三角骨骨质硬化情况。