The distal radio ulnar joint. The influence of geometry and ligament on simulated Colles' fracture. An experimental study

Finite element analysis of different locking plate fixation methods for the treatment of ulnar head fracture

Background

Ulnar head fractures are increasingly higher with the growing proportion of the elderly people. Failure to achieve a stable anatomic reduction of ulna head fracture may lead to a distal radioulnar joint (DRUJ) dysfunction and nonunion of the distal radius. Due to the lack of the postoperative reporting outcomes and the biomechanical studies, it has not been well established about the optimal management of the comminuted distal ulna head fracture. Hence, the purpose of this study is to use finite element analysis to explain the advantages and disadvantages of ulnar-side locking plate fixation compared with dorsal-side locking plate fixation and its screw arrangement in the treatment of ulnar head fractures.

Methods

FE models of the ulnar head fracture and the models of ulnar-side locking plate and dorsal-side plate with two or three distal screws was constructed. In order to simulate forces acting on the ulnar and the osteosynthesis material during daily-life activity in subjects who underwent reconstructive surgery, we applied three loading conditions to each model, viz. 20 N axial compression, 50 N axial compression, 1 N∙m torsion moment, 1 N∙m lateral bending moments, and 1 N∙m extension bending moments. Under these conditions, values of the von Mises stress (VMS) distribution of the implant, peak VMS, the relative displacement of the head and shaft fragments between the fracture ends and the displacement and its direction of the models were investigated.

Results

The stress values of ulnar-side plates were lower than those of dorsal-side plates. And the ulnar-plate fixation system also has smaller maximum displacement and relative displacement. When adding a screw in the middle hole of the ulnar head, the values of model displacement and the peak stress in fixation system are lower, but it may evidently concentrate the stress on the middle screw.

Conclusions

In conclusion, our study indicated that ulnar-side locking plates resulted in a lower stress distribution in the plate and better stability than dorsal-side locking plates for ulnar head fracture fixation. Adding an additional screw to the ulnar head could increase the stability of the fixation system and provide an anti-torsion function. This study requires clinical confirmation of its practicality in the treatment of ulnar head fractures. This study requires clinical confirmation as to its practicality in the treatment of ulnar head fracture.

A Technique for Treating Dorsal Instability of the Distal Radioulnar Joint

We describe a technique for the treatment of chronic dorsal instability of the distal radioulnar joint by creating a strong dorsal radioulnar restraint using opposing flaps from the extensor retinaculum and dorsal capsule of the radioulnar joint. This technique has been used in 18 patients and has proven to be very easy and reliable with all patients demonstrating good stability of the distal radioulnar joint at final follow-up.

The Proximal Ligamentous Component of the Triangular Fibrocartilage Complex

The proximal ligamentous component of the triangular fibrocartilage complex (TFCC) was studied anatomically using 15 fresh-frozen cadaver hand forearm specimens. Changes in the length of either side of this component were analysed during forearm rotation with the complete three-dimensional structure of the TFCC preserved. The proximal ligamentous component consists of three portions: dorsal, central and palmar. The dorsal and palmar portions connect the radius and ulna directly. These were recognized in all specimens whereas the central portion was not constant. The morphology of the proximal component was categorized into three types: fan-shaped, V-shaped, and funnel-shaped in five wrists each. Changes in ligament length during forearm rotation were measured using fine wires under slight tension that paralleled the ligaments from origin to insertion. The dorsal and palmar portions demonstrated three trends: the dorsal portion increased in length from supination to pronation whereas the palmar portion increased in length from pronation to supination; the length of the dorsal portion remained almost constant as the palmar portion increased in length from pronation to supination; the length of the palmar portion remained almost constant while the dorsal portion lengthened from supination to pronation. These variations appear to be related to which portion of the ligament was attached nearest to the centre of the ulnar fovea, where the rotational axis of the forearm passes. The portion attaching nearest to the fovea demonstrated a nearly isometric length pattern, whereas the portion which attached at a distance showed greater extensibility. These findings suggest that the proximal component of the TFCC corresponds to a true radioulnar ligament, and the isometric and eccentric fibres act mutually during forearm rotation.

The influence of distal screw length on the primary stability of volar plate osteosynthesis--a biomechanical study

Background

Extensor tendon irritation is one of the most common complications following volar locking plate osteosynthesis (VLPO) for distal radius fractures. It is most likely caused by distal screws protruding the dorsal cortex. Shorter distal screws could avoid this, yet the influence of distal screw length on the primary stability in VLPO is unknown. The aim of this study was to compare 75 to 100 % distal screw lengths in VLPO.

Methods

A biomechanical study was conducted on 11 paired fresh-frozen radii. HRpQCT scans were performed to assess bone mineral density (BMD) and bone mineral content (BMC). The specimens were randomized pair-wise into two groups: 100 % (group A) and 75 % (group B) unicortical distal screw lengths. A validated fracture model for extra-articular distal radius fractures (AO-23 A3) was used. Polyaxial volar locking plates were mounted, and distal screws was inserted using a drill guide block. For group A, the distal screw tips were intended to be flush or just short of the dorsal cortex. In group B, a target screw length of 75 % was calculated. The specimens were tested to failure using a displacement-controlled axial compression test. Primary biomechanical stability was assessed by stiffness, elastic limit, and maximum force as well as with residual tilt, which quantified plastic deformation.

Results

Nine specimens were tested successfully. BMD and BMC did not differ between the two groups. The mean distal screw length of group A was 21.7 ± 2.6 mm (range: 16 to 26 mm), for group B 16.9 ± 1.9 mm (range: 12 to 20 mm). Distal screws in group B were on average 5.6 ± 0.9 mm (range: 3 to 7 mm) shorter than measured. No significant differences were found for stiffness (706 ± 103 N/mm vs. 660 ± 124 N/mm), elastic limit (177 ± 25 N vs. 167 ± 36 N), maximum force (493 ± 139 N vs. 471 ± 149 N), or residual tilt (7.3° ± 0.7° vs. 7.1° ± 1.3°).

Conclusion

The 75 % distal screw length in VLPO provides similar primary stability to 100 % unicortical screw length. This study, for the first time, provides the biomechanical basis to choose distal screws significantly shorter then measured.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-015-0283-8) contains supplementary material, which is available to authorized users.

Clinical and ultrasonographic evidence of a proximal positional fault of the radius. A case report

Positional faults are considered a possible underlying mechanism mimicking the symptoms of a joint sprain. Despite numerous clinical studies indicating the presence of positional faults, there is limited evidence of imaging studies confirming positional faults. This case report is a preliminary study that offers clinical and ultrasonographic evidence of a proximal positional fault of the radius, treated successfully with manual therapy techniques. Three weeks after a bike fall on the outstretched hand, the patient in this study presented with right wrist pain and a lack of progress with conventional conservative treatment (NSAIDs, rest and immobilization). Clinical findings indicating a proximal positional fault of the radius included pain during active pronation increased by associating a passive movement of the radius in a proximal direction and it was reduced by associating a passive movement of the radius in a distal direction. Ultrasonographic (US) images showed a reduction of radio-capitellar distance on the right side (11.4 mm) compared to the left side (13.3 mm). A positive response with a distal mobilization of the radius supported the proximal positional fault of the radius. After two manual therapy sessions, the patient had recovered normal asymptomatic function. The outcomes used to assess function and pain were active pronation range of motion, the Spanish version of the DASH questionnaire and a 0-10 numeric pain rating scale. Each measure was conducted prior and after each treatment session and one week post treatment. The patient was re-examined at 6 months follow-up, during which US images, demonstrated a normalization of the right radio-capitellar distance.

Assessment of a novel biomechanical fracture model for distal radius fractures

Background

Distal radius fractures (DRF) are one of the most common fractures and often need surgical treatment, which has been validated through biomechanical tests. Currently a number of different fracture models are used, none of which resemble the in vivo fracture location. The aim of the study was to develop a new standardized fracture model for DRF (AO-23.A3) and compare its biomechanical behavior to the current gold standard.

Methods

Variable angle locking volar plates (ADAPTIVE, Medartis) were mounted on 10 pairs of fresh-frozen radii. The osteotomy location was alternated within each pair (New: 10 mm wedge 8 mm / 12 mm proximal to the dorsal / volar apex of the articular surface; Gold standard: 10 mm wedge 20 mm proximal to the articular surface). Each specimen was tested in cyclic axial compression (increasing load by 100 N per cycle) until failure or −3 mm displacement. Parameters assessed were stiffness, displacement and dissipated work calculated for each cycle and ultimate load. Significance was tested using a linear mixed model and Wald test as well as t-tests.

Results

7 female and 3 male pairs of radii aged 74 ± 9 years were tested. In most cases (7/10), the two groups showed similar mechanical behavior at low loads with increasing differences at increasing loads. Overall the novel fracture model showed a significant different biomechanical behavior than the gold standard model (p < 0,001). The average final loads resisted were significantly lower in the novel model (860 N ± 232 N vs. 1250 N ± 341 N; p = 0.001).

Conclusion

The novel biomechanical fracture model for DRF more closely mimics the in vivo fracture site and shows a significantly different biomechanical behavior with increasing loads when compared to the current gold standard.

IRREDUCIBLE CHRONIC PALMAR DISLOCATION OF THE DISTAL RADIOULNAR JOINT – A CASE REPORT

We report a rare case of irreducible chronic palmar dislocation of the distal radioulnar joint (DRUJ). This case showed that the dislocated ulnar head was impacted to the palmar cortex of the radius probably due to the dynamic force of the pronator quadratus muscle. Re-attachment of the ulnar styloid and partial resection of the ulnar head were necessary to make the reduction of the DRUJ possible. The continuity of the radioulnar ligament to the ulnar head was restored and the stability of DRUJ was maintained after reduction.

Pathomechanisms of ulnar ligament lesions of the wrist in a cadaveric distal radius fracture model

BACKGROUND AND PURPOSE

Mechanisms of injury to ulnar-sided ligaments (stabilizing the distal radioulnar joint and the ulna to the carpus) associated with dorsally displaced distal radius fractures are poorly described. We investigated the injury patterns in a human cadaver fracture model.

METHODS

Fresh frozen human cadaver arms were used. A dorsal open-wedge osteotomy was performed in the distal radius. In 8 specimens, pressure was applied to the palm with the wrist in dorsiflexion and ulnar-sided stabilizing structures subsequently severed. Dorsal angulation was measured on digitized radiographs. In 8 other specimens, the triangular fibrocartilage complex (TFCC) was forced into rupture by axially loading the forearm with the wrist in dorsiflexion. The ulnar side was dissected and injuries were recorded.

RESULTS

Intact ulnar soft tissues limited the dorsal angulation of the distal radius fragment to a median of 32(o) (16-34). A combination of bending and shearing of the distal radius fragment was needed to create TFCC injuries. Both palmar and dorsal injuries were observed simultaneously in 6 of 8 specimens.

INTERPRETATION

A TFCC injury can be expected when dorsal angulation of a distal radius fracture exceeds 32(o). The extensor carpi ulnaris subsheath may be a functionally integral part of the TFCC. Both dorsal and palmar structures can tear simultaneously. These findings may have implications for reconstruction of ulnar sided soft tissue injuries.

Where is the distal fracture line location of dorsally displaced distal radius fractures?

No consensus currently exists on the facture location of dorsally displaced distal radius fractures (DRFs). We present a systematic evaluation of the distal fracture line (DFL) location of DRFs and possible influencing factors. Determining the average location of DRFs provides a basis for developing more sensitive tests to determine bone strength using a variety of imaging techniques and for developing improved biomechanical models to test fracture characteristics and surgical implants. Initial radiographs of 157 DRFs dorsally displaced DRFs in patients aged 40-74 years were identified, patient and trauma specific data were collected, and standard radiographic measurements and (AO) fracture classification were performed. The dorsal and palmar DFL locations relative to the corresponding apex of the lunate facet were measured. The DFL was located dorsally 7.9 ± 2.7 mm and palmarly 11.7 ± 3.9 mm proximal to the corresponding lunate fossa apex. The dorsal DFL was significantly distal to the palmar one (p  < 0.001), but the two did not correlate (r² = 0.018, p = 0.095). DFL location was independent of age, energy of the fall, and fracture complexity.

Distal radius instability and stiffness: common complications of distal radius fractures

Emphasis in the literature over the past hundred years regarding distal radius fracture management has been on restoration of anatomic radio-carpal alignment. Until the two most recent decades, little emphasis has been placed on the great morbidity and compromise to upper limb function associated with distal radio-ulna joint (DRUJ) pathology occurring with fractures of the distal radius. This article emphasizes that attention to restoration of anatomy of the DRUJ should be considered at least as important as that given to the radio-carpal relationship. This article also points out how stiffness of forearm rotation can result from a well-treated distal radius fracture and how this complication can be treated to restore healthy upper limb function.

The management of distal ulnar fractures in adults: a review of the literature and recommendations for treatment

The distal ulna represents the fixed point around which the radius and the hand acts in daily living. The significance of distal ulnar fractures is often not appreciated and often results in inadequate treatment in comparison to its larger counterpart; the radius. There is little guidance in the current literature as how to manage these fractures and their associated injuries. This paper aims to critically review the current literature and combine it with treatment suggestions based on the experience of the authors to help guide investigation and management of these often complex injuries.

Osteotomy of dorsally displaced malunited fractures of the distal radius: no loss of radiographic correction during healing with a minimally invasive fixation technique and an injectable bone substitute

BACKGROUND AND PURPOSE

Malunion after a distal radius fracture can be treated with an osteotomy of the distal radius. Often autologous iliac crest bone graft is used to fill the gap, but this is associated with donor site morbidity. Instead of bone graft, we have used a slow-resorbing bone substitute in combination with a minimally invasive fixation technique.

PATIENTS AND METHODS

25 consecutive patients with a dorsal malunion after a distal radius fracture underwent an osteotomy. A TriMed buttress pin and a radial pin plate were used for fixation, and Norian SRS as bone substitute. The patients were followed for a minimum of 1 year and range of motion, grip strength, DASH scores, and the radiographic correction were measured.

RESULTS

Forearm rotation improved from 137 degrees to 155 degrees , flexion/extension from 102 degrees to 120 degrees , and radioul-nar deviation from 32 degrees to 43 degrees . Grip strength increased from 62% of the contralateral hand to 82%. DASH scores decreased from 36 to 23. Radiographically, all osteotomies but 1 healed and the radiographic correction achieved was consistent over the first year.

INTERPRETATION

Osteotomy of the distal radius is effective in increasing motion and grip strength after a malunited distal radial fracture. Patient satisfaction is high and subjective results measured with DASH are good. Using a bone substitute, the operation can be performed as an outpatient procedure and donor-site pain avoided. No loss of the radiographic correction achieved was noted during osteotomy healing.

Contact area inside the distal radioulnar joint: effect of axial loading and position of the forearm

BACKGROUND

A biomechanical study was performed to define the normal profiles of contact area inside the distal radioulnar joint and how these profiles change as a result of damage to the distal radioulnar ligaments.

METHODS

Twelve cadaver arms were used and a custom-made jig was designed to allow axial loading of the hand. Tekscan sensor film was used to measure the contact area inside the joint. Measurements were taken with different loads and in different positions of the forearm. The same measurements were taken after dividing either the volar or dorsal distal radioulnar ligament. Finally the measurements were repeated after reconstruction of the divided ligament.

FINDINGS

The contact area increases with axial loading of the hand and is greater in supination than pronation. Division of a single distal radioulnar ligament increases the contact area inside the distal radioulnar joint (123% of normal) and reconstruction of the divided distal radioulnar ligament restores the contact patterns towards the normal values (113% of normal).

INTERPRETATION

The results show that axial loading of the hand and position of the forearm has a significant effect on the contact area inside the distal radioulnar joint. The study also shows that injury of the distal radioulnar ligament disturbs the normal profiles of contact.

Treatment of injuries to the ulnar side of the wrist occurring with distal radial fractures

We still do not know how to best treat the DRUJ condition that was recognized 200 years ago by Abraham Colles and later addressed in Frykman's classic thesis. To improve the outcome, we must recognize the differences be-tween osteoporotic and other fractures and understand the importance of ligament injuries,especially in patients under the osteoporotic age. However, our current problem is that neither the initial ligament injury nor the posttraumatic laxity is detectable with radiographic methods,which creates future challenges regarding diagnosis and treatment. We therefore have to critically analyze each fracture in each patient and be aware of the complexity of the entire injury to the wrist.

Reconstructive procedure for unstable radial-sided triangular fibrocartilage complex avulsions

PURPOSE

Radial-sided avulsions of the triangular fibrocartilage complex (TFCC) (Palmer 1D) with distal radioulnar joint (DRUJ) instability remain a challenging pathology to treat. We tested an intra-articular reconstruction that addresses unstable radial-sided TFCC avulsions.

METHODS

Ten preserved, dissected, cadaveric forearm specimens with intact TFCC and without ulnar-positive variance had biomechanical testing using a hydraulic testing device. The measurement of total displacement of the ulna relative to the radius was performed with an applied load ranging from 20 N in a volar direction to 20 N in a dorsal direction. Specimens were tested sequentially with intact TFCC, with surgically induced Palmer 1D lesions, and after reconstruction of the TFCC. All tests were performed at neutral, maximal pronation, and maximal supination.

RESULTS

The mean total displacements of the DRUJ of the specimens at neutral rotation were as follows: 4.1 +/- 0.4 mm for the intact specimens compared with 11.8 +/- 0.8 mm after creation of the tear and 3.9 +/- 0.7 mm for the reconstructed specimens. In maximal pronation the mean total displacements were as follows: 2.4 +/- 0.3 mm intact versus 4.9 +/- 0.7 mm for torn and 2.1 +/- 0.3 mm after reconstruction. In maximal supination the mean total displacements were as follows: 1.4 +/- 0.2 mm intact versus 5.7 +/- 1.3 mm for torn and 1.0 +/- 0.1 mm after reconstruction. All specimens obtained the preoperative pronation and supination motion after the reconstruction.

CONCLUSIONS

Current procedures are unable to restore DRUJ stability without a significant limitation of pronation and supination. This intra-articular reconstruction of radial-sided TFCC avulsions succeeded in restoring baseline stability to the DRUJ without interfering with pronation/supination.

Open repair of the ulnar disruption of the triangular fibrocartilage complex with double three-dimensional mattress suturing technique

Open repair technique of the ulnar disruption of the triangular fibrocartilage complex is described. This technique is indicated for a fresh or a relatively fresh (less than 1 year after the initial injury) ulnar foveal detachment tear, horizontal tear, and proximal slit tear of the triangular fibrocartilage complex, all of which are accompanied by severe dorsal, palmar, or multidirectional instability of the distal radioulnar joint. A chronic tear greater than 1 year from initial injury and a fresh triangular fibrocartilage complex tear without distal radioulnar joint instability, such as central slit tear, are excluded from our indications. A dorsal C-shaped skin incision, a longitudinal incision of the radial edge of the extensor carpi ulnaris subsheath and the dorsal distal radioulnar joint capsule, exposes the distal radioulnar joint. A small, 5-mm longitudinal incision at the origin of the radioulnar ligament exposes its fovea detachment and/or the proximal slit tear of the triangular fibrocartilage complex. The disrupted radioulnar ligament is sutured in a pullout fashion to the ulna with a 3-dimensional double mattress technique through 2 bone tunnels that is precisely made at the central portion of the fovea with 1.2-mm K-wire. An additional horizontal mattress suture is used for closure of the small incision made at the radioulnar ligament, then the extensor carpi ulnaris is repaired. This open-repair technique is complex and requires precise technical skills; however, early results have been more rewarding than the conservative treatment.

The radioulnar joint in distal radial fractures

We searched The Cochrane Library and Medline regarding the radioulnar joint in distal radial fractures and found no randomized or controlled studies. This review presents the descriptive literature by summarizing accepted views and controversies. There is only weak support for the commonly accepted treatments. Current research has shown that distal radial fractures are often associated with ligament injuries not seen on radiographs. These injuries can lead to laxity of the DRU-joint and subsequent worse outcome, which indicates that we must have a complete diagnosis including ligament injuries if we want to understand better the fracture and its sequelae. Randomized studies should be done before advocating surgical treatment of these unforeseen injuries.

The role of the distal radioulnar ligaments, interosseous membrane, and joint capsule in distal radioulnar joint stability

The individual contribution of the distal radioulnar ligaments to dorsal and palmar translational stability during forearm rotation remains controversial. Furthermore, the role of the distal radioulnar joint capsule as a restraint and contributor to stability has not been investigated. A biomechanical study was performed in 11 fresh cadaver specimens to simultaneously measure dorsal and palmar radioulnar ligament tension. Joint rotation and radial translation were measured after sequential excision of the disk, interosseous membrane, joint capsule, and radioulnar ligaments. Results confirmed that the dorsal ligament tightens during pronation while the palmar ligament becomes progressively lax; the converse occurred during supination. Translational stability remained intact at all positions throughout the sectioning sequence until one of the radioulnar ligaments was sectioned. The most significant increases in translation occurred after sectioning the dorsal radioulnar ligament in pronation and after sectioning the palmar radioulnar ligament in supination. Forearm rotation increased significantly after excising either hemicapsule.

A cadaveric study of the anatomy and stability of the distal radioulnar joint in the coronal and transverse planes

Fifty preserved cadaver wrist specimens were studied. The anatomy of the distal radioulnar joint is complex, with varying configurations in the transverse and midcoronal planes. There is disparity in the radii of curvature of the sigmoid notch and the ulna-articular surface in the transverse plane, with resultant articular incongruity. Motion at the distal radioulnar joint is, hence, likely to be a combination of sliding and rotation with a small area of true appositional contact. The palmar osteocartilaginous lip of the sigmoid notch, along with the interosseous membrane, may be of importance in distal radioulnar stability. Palmar and dorsal radioulnar ligaments may act as "check-rein" ligaments, especially when seen with the "flat face" (type A) sigmoid notch.

Reconstructive osteotomy for malunion of the distal radius

Common misconceptions about distal radius fractures result in undertreatment of many fractures, particularly in an active population. Loss of reduction of the fracture may cause a symptomatic malunion. Fourteen patients with an average age of 39 years (range, 21-65 years) underwent reconstructive procedures for radial malunions. The common malunion healed in a position of dorsal angulation, loss of radial inclination, and radial shortening. Ten patients had been treated by closed means, and 4 had undergone earlier surgical procedures without acceptable healing position of the fracture. Seven patients underwent a radial osteotomy alone, 5 patients had an osteotomy with an ulnar leveling procedure, and 2 patients had a Sauvé-Kapandji procedure alone. The average improvement in radial inclination was 14 degrees (range, 0 degrees-34 degrees), volar tilt 21 degrees (range, 2 degrees-33 degrees), and improvement in a positive ulnar variance by 6.8 mm (range, 0-48 mm). The complication rate was 29%, with a followup of 29 months (range, 12-43 months). Functional improvement was notable in 12 of 14 patients. Surgical reconstruction for malunions is technically difficult and may not completely restore the anatomy. Patient satisfaction, however, in terms of increased function, decreased pain, and decreased deformity is sufficiently high to warrant reconstructive treatment.

The effect of dorsally angulated distal radius fractures on distal radioulnar joint congruency and forearm rotation

A biomechanical cadaver study was performed to evaluate the effect of dorsally angulated distal radius fractures on the distal radioulnar joint. Frykman I distal radius fractures were simulated, and laxity measurements were taken with and without sectioning the triangular fibrocartilage complex and the interosseous membrane. The findings of this study were threefold. First, measured in terms of radial diastasis, incongruency of the distal radioulnar joint occurred with increasing dorsal tilt of the distal radius. It became most dramatic with a change of more than 20 degrees of dorsal angulation of the distal radius. This corresponds to approximately 10 degrees of dorsal tilt of the articular surface of the distal radius, as measured on an x-ray film. Second, increased dorsal angulation caused interosseous membrane tightness and limited maximum pronation and maximum supination. Third, distal radioulnar joint dislocation did not occur until both the triangular fibrocartilage complex and interosseous membrane were sectioned. These results reveal the importance of anatomic reduction of the distal radius fracture and evaluation of damaged soft tissue structures.

Effects of radial deformity on distal radioulnar joint mechanics

A cadaver experiment was performed to study the effects of radial deformity on the kinematics of the distal radioulnar joint and the anatomic configuration of the triangular fibrocartilage. Radial shortening caused the greatest disturbance in kinematics and the most distortion of the triangular fibrocartilage. Decreased radial inclination and dorsal angulation caused intermediate changes. Dorsal displacement produced minimal changes. Radial deformity did not produce distal radioulnar joint dislocation. These results provide biomechanical evidence of an important relationship between radial malunion and persistent symptoms in the distal radioulnar joint.

Radiographic and orthopedic evaluation of wrist trauma

This paper was written to enable radiologists to contribute more usefully to the diagnosis and treatment of various wrist injuries. All imaging modalities are discussed to equip the radiologist for his difficult task. We present a systematic approach to the evaluation of wrist trauma patients beginning with initial plain films and proceeding through more invasive or sophisticated studies in order to achieve a definitive diagnosis. Toward this end a flow chart has been developed as a quick reference source. The authors have then described the anatomy and kinematics of the wrist to further the radiologist's understanding of the forces involved and the injuries produced by trauma. From this foundation individual injuries are then discussed together with the best methods of making the proper diagnosis of each. Criteria for adequate treatment of various injuries are also presented.

Effects of radioulnar instability on the radiocarpal joint: a biomechanical study

Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film and a microcomputer-based videodigitizing system to assess the effect of increasing radioulnar instability on the load distribution within the proximal carpal joint. Three stages of radioulnar instability were studied: (1) an avulsion fracture at the base of the ulna styloid; (2) an avulsion fracture at the base of the ulna styloid plus disruption of the dorsal portion of the distal radioulnar joint capsule; and (3) an avulsion fracture at the base of the ulna styloid, disruption of the dorsal portion of the distal radioulnar joint capsule, and disruption of the radioulnar interosseous membrane. All stages of radioulnar instability demonstrated a decrease in the lunate contact area in positions with the forearm in supination. In stage 3 instability there was also less lunate contact area in positions with the forearm in neutral pronation/supination. In stage 3 instability the lunate high pressure area centroid was abnormally palmar in all positions and the scaphoid high pressure area centroid was abnormally palmar in positions with the forearm in pronation or supination.

Repair of the triangular ligament in Colles' fracture. No effect in a prospective randomized study

We present a prospective and randomized study of two different treatments of extraarticular Colles' fracture with a fractured ulnar styloid. The study comprised 41 patients with 2 years' follow-up; 22 patients were treated with closed manipulation and an above-the-elbow plaster cast, whereas in 19 patients the avulsed ulnar styloid was transfixed and/or the triangular ligament was repaired after closed reduction of the fractured radius. In all the operated on patients, a complete rupture of the triangular ligament was found. Good reduction of all the fractures was achieved primarily according to the radiographic examination. At follow-up the alignment had deteriorated, with no difference between the two treatment groups. Neither did the findings in the wrist arthrograms differ between the two groups nor did the subjective complaints of the patients. We conclude that repair of the ruptured triangular ligament in extraarticular fractures of the distal radius is not better than conventional treatment.

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.