Distal radio-ulnar ligament motion during supination and pronation

Wrist and Distal Radioulnar Joint Arthroplasty: Maximizing Results in Difficult Conditions

Traditional management of wrist arthritis consists of proximal row carpectomy, partial carpal fusions, or, in the event of pancarpal arthritis, total wrist fusion. Although proximal row carpectomy and partial wrist fusions preserve some motion at the wrist while relieving pain symptoms, the quality of results obtained from these procedures is not predictable or optimal in many instances. Management of hip, knee, ankle, and shoulder joints has evolved from arthrodesis to arthroplasty. The wrist joint is following the same pattern of evolution with the advent of reliable designs.

The distal radio ulnar joint: a journey of discovery and invention of the Aptis prosthesis

This article describes the journey the authors took in discovering a new distal radioulnar joint prosthesis. The beginning deals with the problems we can potentially create for patients when we blindly follow the literature without any critical thinking. By challenging the established thinking on the function of the forearm, a new way of looking at the distal radioulnar joint emerged. Through trial, error and a moment of desperation, a new solution was found that allow us to relive pain and improve function for our patients with distal radioulnar joint pathologies.

Outcomes of Isolated Radial Osteotomy for Volar Distal Radioulnar Joint Instability Following Radial Malunion in Children

PURPOSE

The radius bone has a slight dorsoradial bow that allows for full forearm pronosupination around the ulna. However, radial malunion can lead to reversal of the radial bow and subsequent volar instability of the distal radioulnar joint (DRUJ), predominantly in supination. This study assessed the outcomes of corrective radial osteotomy for volar DRUJ instability after radial malunion in children.

METHODS

The charts of 7 children (2 boys and 5 girls) treated with corrective radial osteotomy for volar DRUJ instability after a radius fracture or deformity were reviewed. Demographic, diagnostic, treatment, and complication information was collected for each patient. Radiographs at initial injury, fracture union, diagnosis of DRUJ instability, and final follow-up were reviewed for radiographic measurements of radial deformity and subsequent correction.

RESULTS

Fractures included 4 distal radius, 2 proximal radius, and 1 plastic deformation of the radial shaft. Volar DRUJ instability was diagnosed an average of 2.7 years (range, 1-6 years) after fracture at an average age of 13.6 years (range, 12-17 years). Two of 7 patients had persistent symptoms despite having undergone previous soft tissue surgery for DRUJ instability. Radial osteotomy was performed on all patients (3 dorsal and 4 volar approaches), with an average sagittal plane correction of 23° ± 10° (range, 14° to 40°). Osteotomy site varied (3 proximal third, 1 middle third, and 3 distal third) based on the apex of maximal deformity. Patients were observed an average of 2.3 years (range, 1.0-5.7 years). At final follow-up, all patients had a stable DRUJ and no patient required soft tissue stabilization.

CONCLUSIONS

Apex volar malunion of radial fractures may result in volar instability of the DRUJ. Radial osteotomy restored the normal apex dorsal radial bow and effectively stabilized the DRUJ without the need for soft tissue repair. Osteotomy should be tailored to the specific site of radiographic deformity.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

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 Shape of the Triangular Fibrocartilage During Pronation–Supination

We studied the changes in the shape of the triangular fibrocatilage (TFC: disc proper) which occur during forearm rotation in disarticulated and articulated wrists. The influence of artificial 3 mm ulnar lengthening on distortion of the disc was also examined. In the disarticulated wrists, slight distortion of the central and radial portions of the TFC was observed in the ulnar neutral variance specimens. More distortion was noted in the radial and central portions of the TFC in specimens with positive ulnar variance or with the ulna lengthened. However, in the articulated wrist, the TFC demonstrated little change in shape during pronosupination even in the ulnar positive variance wrists or with the ulna lengthened. There was no significant change in palmar and dorsal peripheral lengths of the TFC in ulnar neutral, ulnar positive or ulna-lengthened specimens at three rotatory positions of the forearm. These findings suggest that changes in ulnar variance which occur during forearm rotation can produce distortion on the TFC, but the carpus helps to maintain the shape of the TFC during pronation–supination, even with positive ulnar variance.

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.

Reconstruction of the Distal Oblique Bundle of the Interosseous Membrane: A Technique to Restore Distal Radioulnar Joint Stability

The distal radioulnar ligament reconstruction is a technique that may be used for distal radioulnar joint instability without arthritis and failed nonsurgical management; clinical results demonstrate resolved or improved stability. Recent literature has focused on the distal oblique bundle of the interosseous membrane and its contributions to stability. This article describes a technically simple surgical technique to reconstruct the distal oblique bundle and restore distal radioulnar joint stability.

Distal oblique bundle reconstruction and distal radioulnar joint instability

Background This study created an anatomic reconstruction of the distal oblique bundle (DOB) of the interosseous membrane to determine its effect on distal radioulnar joint (DRUJ) instability and compare this technique with distal radioulnar ligament (DRUL) reconstruction. Questions/Purposes We hypothesized that this reconstruction would provide equivalent stability to DRUL reconstruction and that combining the two techniques would enhance stability. Methods Six cadaveric upper limbs were affixed to a custom frame. The volar/dorsal translation of the radius relative to the ulna was measured in 60° pronation, neutral, and 60° supination. Translation was sequentially measured with the DRUJ intact, with sectioned DRULs and triangular fibrocartilaginous complex (TFCC), and with sectioned DOBs. Reconstructions were performed on the DRULs, on the DOB tensioned in both neutral and supination, and employing both techniques. Results The DOB reconstruction, tensioned both in the neutral position and in 60° supination, was more stable than the partial and complete instability in 6/6 specimens in pronation and the neutral position and in 5/6 specimens in supination. The DOB reconstruction and the DOB reconstruction tensioned in supination were more stable than the DRUL reconstruction in 4/6 patients. Combining the two techniques did not further reduce translation. Conclusions The DOB reconstruction is capable of improving stability in the unstable DRUJ.

Functional anatomy of the distal radioulnar joint in health and disease

The distal radioulnar joint (DRUJ) is critical to the function of the forearm as a mechanical unit. This paper is concerned with the concepts and observations that have changed understanding of the function of the DRUJ, notably with respect to the biomechanics of this joint. The DRUJ has been shown to be important in acting to distribute load and removal of the ulna head leads to the biomechanical equivalent of a one-bone forearm. The soft tissues with topographical relations to the distal forearm and DRUJ have also been investigated in our experimental series with findings including the description of a clinical disorder termed subluxation-related ulna neuropathy syndrome.

Arthroscopic reconstruction of triangular fibrocartilage complex (TFCC) with tendon graft for chronic DRUJ instability

PURPOSE

To report the 10-years' experience of a novel arthroscopic assisted anatomical TFCC reconstruction in treatment of chronic DRUJ instability resulting from irreparable TFCC injuries.

MATERIALS AND METHODS

15 patients (7 males, 8 females) with mean age of 37 (17-49) suffering from irreparable TFCC injuries received arthroscopic assisted reconstruction using palmaris longus graft. Three skin incisions were made with creation of one radial and one ulna tunnel for passage of graft following the path of dorsal and palmar radio-ulnar ligaments under fluoroscopic and arthroscopic guidance. The joint capsule was kept intact. Early mid-range forearm rotation was started since 4th week postoperatively.

RESULTS

The mean follow-up was 85.53 months (32-138). Mayo wrist score improved from 62.5 to 88 (p<0.05). Comparing contralateral side, total prono-supination range increased from 76.6% to 92.1% and grip strength increased from 56.1% to 76.9%. Twelve patients resumed previous jobs. No evidence of DRUJ arthritis was noticed. Complications included 2 late graft ruptures and one unexplained dystonia.

CONCLUSIONS

Our arthroscopic assisted approach on TFCC reconstruction is safe, produces comparable results as the standard technique and may achieve better range of motion with less soft tissue dissection and earlier mobilization.

Anatomy and biomechanics of the distal radioulnar joint

The distal radioulnar joint (DRUJ) is a complex articulation allowing significant rotational and translational motion. Stability of the DRUJ depends on bony contact, intrinsic stabilizers of the triangular fibrocartilage complex, and extrinsic stabilizers of the distal forearm. Understanding the anatomy of this articulation is paramount in clinical decision making for the treatment of disorders involving the DRUJ.

The functional anatomy of forearm rotation

The elbow, forearm and wrist act as a unified structure to provide a stable, strong and highly mobile strut for positioning the hand in space and for conducting load-bearing tasks. An understanding of the relevant anatomy and biomechanics is important for the surgeon assessing and treating disorders of forearm function. This paper is concerned with illuminating the principles and concepts governing forearm rotation and load-bearing functions.

Tendon graft--ulna fixation in distal radio-ulnar joint stabilisation; biomechanical comparison of three graft-bone fixation methods

A common distal radio-ulnar joint (DRUJ) stabilisation procedure uses a tendon graft running from the lip of the radial sigmoid notch to the ulnar fovea and through a bony tunnel to the ulnar shaft, before being wrapped round the distal ulna and sutured to itself. Such graft fixation can be challenging and requires a considerable tendon length. The graft length could be reduced by fixing the graft to the ulna using a bone anchor or interference screw. The aim of this study was to compare the strength of three distal ulna graft fixation methods (tendon wrapping and suturing, bone anchor and interference screw). Four human cadaveric ulnae were used. A tendon strip was run through a tunnel in the distal ulna and secured by: (1) wrapping round the shaft and suturing it to itself, (2) a bone anchor and (3) an interference screw in the bone tunnel. Load to failure was determined using a custom-made apparatus and an Instron machine. Maximum failure load was highest for the bone anchor fixation (99.3 +/- 23.7 N) followed by the suturing (96.2 +/- 12.1 N), and the interference screw fixation (46.9 +/- 5.6 N). There was no significant difference between the tendon suturing and bone anchor methods, but the tendon suturing was statistically significantly higher compared to the interference screw (P = 0.028). In performing anatomical stabilisation of the DRUJ fixation of the tendon graft to the distal ulna with a bone anchor provides the most secure fixation. This may make the stabilisation technique less demanding and require a smaller tendon graft.

A study of functional outcomes following implantation of a total distal radioulnar joint prosthesis

This paper reports a long-term follow-up measuring pain, range of motion and weight-bearing ability, following implantation of a total distal radioulnar joint prosthesis. This prosthesis differs from excision arthroplasties and ulnar head replacements by replacing all three components of the distal radioulnar joint, viz. the sigmoid notch, the ulnar head and the triangular fibrocartilage. The design allows longitudinal migration of the radius throughout pronation and supination, as well as load bearing of the wrist. Thirty-one patients receiving the prosthesis returned or were interviewed by telephone at a mean of 5.9 (range 4-9) years. Pronation increased from a mean of 65.5 degrees (range 5-90 degrees ) to 74 degrees (range 20-90 degrees ) and supination from 53 degrees (range 5-90 degrees ) to 70 degrees (range 20-90 degrees ) while greatly diminishing and/or eliminating pain. Grip increased from a mean of 10 kg (22 lbs) to 24 kg (52 lbs). Weight bearing was restored or increased in 29 of 31 patients.

Effects of distal radius malunion on distal radioulnar joint mechanics--an in vivo study

Patients with a malunited distal radius often have painful and limited forearm rotation, and may progress to arthritis of the distal radioulnar joint (DRUJ). The purpose of this study was to determine if DRUJ congruency and mechanics were altered in patients with malunited distal radius fractures. In nine subjects with unilateral malunions, interbone distances and dorsal and palmar radioulnar ligament lengths were computed from tomographic images of both forearms in multiple forearm positions using markerless bone registration (MBR) techniques. The significance of the changes were assessed using a generalized linear model, which controlled for forearm rotation angle (-60 degrees to 60 degrees ). In the malunited forearm, compared to the contralateral uninjured arm, we found that ulnar joint space area significantly decreased by approximately 25%, the centroid of this area moved an average of 1.3 mm proximally, and the dorsal radioulnar ligament elongated. Despite our previous findings of insignificant changes in the pattern of radioulnar kinematics in patients with malunited fractures, we found significant changes in DRUJ joint area and ligament lengthening. These findings suggest that alterations in joint mechanics and soft tissues may play an important role in the dysfunction associated with these injuries.

Distal radioulnar joint instability in distal radius fractures: the role of sigmoid notch and triangular fibrocartilage complex revisited

The stabilising effects of various structures of the distal radioulnar joint (DRUJ) have been heavily debated. This biomechanical cadaveric study examined the effects of the volar and dorsal lips of the sigmoid notch and the volar and dorsal aspects of the triangular fibrocartilage complex (TFCC) on DRUJ stability. Sequential fractures of the distal radius and sectioning of the TFCC were performed followed by measurements of ulnar translation with the forearm in pronation, neutral and supination. A dorsal lunate facet fracture created instability in pronation. Lunate facet fractures alone did not create instability in other forearm positions. Sectioning of the volar TFCC after loss of the dorsal TFCC by a dorsal lunate facet fracture caused DRUJ instability with the forearm in neutral position. Sectioning of the dorsal TFCC after loss of the volar TFCC due to a volar lunate facet fracture created instability in neutral and pronated positions.

Distal radius fractures: a comparison of tension band wiring versus ulnar outrigger external fixation for the management of distal radioulnar instability

PURPOSE

To retrospectively compare the results of immobilization of the forearm in supination with the results of tension band fixation of the ulnar styloid in 35 patients with distal radius fractures, fracture of the base of the ulnar styloid, and distal radioulnar joint instability treated with external fixation.

METHODS

Thirty-five patients with fractures of the distal radius, fracture of the base of the ulnar styloid, and unstable distal radioulnar joint had external fixation with adjunctive percutaneous pins and allograft bone to reduce and stabilize the distal radius fracture anatomically. Only those patients with an associated ulnar styloid base fracture displaced over 2 mm with gross distal radioulnar joint instability relative to the contralateral wrist were included in this study. Group 1 consisted of patients in whom the ulnar styloid base fracture was treated with conventional tension band wiring techniques. Group 2 patients were treated with a supplemental outrigger from the external fixator to the ulna and locked in 60 degrees of forearm supination. Groups 1 and 2 had an average follow-up period of 40 and 36 months, respectively.

RESULTS

Group 2 had significantly better supination than group 1. In terms of functional outcome it was found that there was no significant difference for the Disabilities of the Arm, Shoulder, and Hand and the Gartland and Werley scores between the 2 treatment groups. There was a lower rate of complications and fewer secondary procedures were required in group 2. The incidence of distal ulna resection was 4 of the 35 patients (2 patients in each group).

CONCLUSIONS

Our results indicate that patients in whom the ulnar styloid can be reduced and maintained in supination can be treated effectively with fixed supination outrigger external fixation. This method resulted in a statistically significant improvement in supination and a lower rate of distal radioulnar joint complications, and it required fewer secondary procedures.

Distal radioulnar joint dorsal instability treated with dorsal capsular reconstruction

Six patients with post-traumatic distal radioulnar joint dorsal instability were treated with dorsal capsular reconstruction. This new technique of reconstruction requires less extensive dissection than the previously described methods in the literature and requires no tendon graft. A total of six patients treated from 1999 to 2001 were included in this study. Two were males and four were females. The average age of patients was 30 years and all the instabilities were secondary to trauma. One of them had associated minimally displaced distal radius fracture. All patients had arthrogram and arthroscopy done before the reconstruction and had no significant triangular fibrocartilage complex injury. The surgery consisted of duplication capsulorrhaphy of the dorsal capsular structures of the distal radioulnar joint. All patients had satisfactory results after the operations in terms of pain relief, range of motion and stability.

Estimating joint contact areas and ligament lengths from bone kinematics and surfaces

We present a novel method for modeling contact areas and ligament lengths in articulations. Our approach uses volume images generated by computed tomography and allows the in vivo and noninvasive study of articulations. In our method, bones are modeled both implicitly (scalar distance fields) and parametrically (manifold surfaces). Using this double representation, we compute interbone distances and estimate joint contact areas. Using the same types of representation, we model ligament paths; in our model, the ligaments are approximated by the shortest paths in a three-dimensional space with bone obstacles. We demonstrate the method by applying our contact area and ligament model to the distal radioulnar joints of a volunteer diagnosed with malunited distal radius fracture in one forearm. Our approach highlights focal changes in the articulation at the distal radioulnar joint (location and area of bone contact) and potential soft-tissue constraints (increased "length" of the distal ligaments and ligament-bone impingement in the injured forearm). Results suggest that the method could be useful in the study of normal and injured anatomy and kinematics of complex joints.

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 distal radioulnar joint as a load-bearing mechanism--a biomechanical study

PURPOSE

A biomechanical study was performed to define the normal profiles of force transmission across the distal radioulnar joint (DRUJ) and their alteration as the result of surgical modification of the joint and its ligaments.

METHODS

Twelve cadaver arms were used in this investigation. A custom-made jig was designed to hold the arm and allow axial loading of the hand. Force transmitted across the DRUJ was measured with sensor film. The axial force transmitted through the ulna and radius was measured with strain gauges mounted to the surface of each bone and the strain in the dorsal and volar distal radioulnar ligaments (DRUL) was measured with differential variable reluctance transducers. Measurements of force and strain with the DRUJ in the surgically unmodified condition were performed in various positions of forearm rotation and with sequential loads. Subsequently, the same series of measurements was performed after DRUL division and after reconstruction of the ligament. The effect of excision of the ulna head (Darrach's procedure) was also studied.

RESULTS

Force varied significantly (p <.05) with the applied load and with forearm position, being greater in supination than pronation (sensor film data). Force transmitted through the ulna varied in an approximately reciprocal pattern with that of the radius. The greatest forces through the ulna occurred in supination and therefore mirrored the change in force transmission across the DRUJ. Between 32% and 34%, respectively, of the applied load (5-10 kg) was transmitted through the ulna and the remainder was transmitted through the radius (strain gauge data). Division of either the volar or the dorsal DRUL tended to increase the force transmitted across the DRUJ (p =.09), and reconstruction of the disrupted DRUL restored the force pattern toward the previous values (not significant) (differential variable reluctance transducer data). Excision of the ulna head disrupted the force transmission profiles, producing the biomechanical equivalent of a 1-bone forearm. Only 1.8% and 2.7% of the applied force (10 kg and 5 kg), respectively, was transmitted through the ulna (strain gauge data only).

CONCLUSIONS

The data show consistent and characteristic force transmission profiles across the DRUJ and through both ulna and radius. The joint is important in the transmission of load and its anatomic integrity should be respected in surgical procedures if normal biomechanics are to be preserved.

Biomechanical function of the distal radioulnar and ulnocarpal wrist ligaments

PURPOSE

This study was designed to provide quantitative information concerning the functions of the ligaments that stabilize the distal radioulnar joint (DRUJ). This joint permits the radius to rotate around a nearly fixed ulna allowing supination and pronation of the hand. Understanding their function is important in developing procedures for reconstruction.

METHODS

Using a ligament tension transducer that hooked under the center of the ligament and deflected it laterally while measuring the force required, we determined the tensions in 6 ligaments in 9 cadaver arms in pronation and supination of the hand. These ligaments included those of the DRUJ: palmar distal radioulnar ligament (PDRUL) and dorsal distal radioulnar ligament (DDRUL); and the ulnocarpal joint ligaments: ulnolunate ligament (ULL), ulnotriquetral ligament (UTL), and the ulnocarpal collateral ligament (UCCL), which includes the subsheath of the extensor carpi ulnaris, and the dorsal ulnocarpal ligament (DUCL).

RESULTS

For the ligaments of the DRUJ in supination, the mean tension in the PDRUL (2.6 N) was greater than that of the DDRUL (0.8 N), whereas in pronation the mean tension in the PDRUL (1.1 N) was less than that of the DDRUL (1.7 N). For the ulnocarpal ligaments in supination, the ligament tensions in the ULL, UTL, and the UCCL were significantly greater than the same ligaments with the forearm pronated. The DUCL tension remained unchanged throughout supination and pronation.

CONCLUSIONS

In supination of the forearm all ligaments except for the DDRUL had equivalent tensions, indicating their role in stabilizing the joint to this motion. In pronation ligament tensions generally were lower but were distributed over all 6 ligaments tested. DUCL tension was equivalent in both supination and pronation, unlike the other ligaments that had greater tensions in supination.

An analysis of the constraint properties of the distal radioulnar ligament attachments to the ulna

Nine cadaver upper extremities were tested to evaluate the constraint properties of the dorsal and palmar radioulnar ligaments at their foveal and styloid attachments to the ulna. The specimens were tested by anterior and posterior displacement of the radius relative to the ulna with the forearm in pronation, supination, and neutral rotation. There were no statistically significant differences in the relative percent of constraint contribution of the styloid and foveal ligament insertions. In neutral forearm rotation total displacement after sectioning both ligament insertions tended to be larger in palmar than in dorsal displacement. A similar trend was observed with 60 degrees forearm supination. In the pronated position, however, the trend was reversed with larger total displacement in dorsal displacement.

Assessment of the position of the distal portion of the ulna in lateral projection radiographs of the wrist: analysis of the influence of pronation-supination and flexion-extension on the pisoscaphoid and the ulnotriquetral distances: a cadaver study

RATIONALE AND OBJECTIVES

Accurate assessment of the distal radioulnar joint is of paramount importance for the detection of possible dislocation or subluxation. Using a cadaveric model, the authors attempted to establish a quantitative method that would allow identification of normal and abnormal distal radioulnar joint anatomy on well-positioned and rotated conventional radiographs.

METHODS

Four cadaveric wrists, in which subsequent sectioning confirmed the absence of disease, and one cadaveric wrist with a circumscribed lesion of the triangular fibrocartilaginous complex were studied. Defined movements in flexion and extension (+/- 10 degrees, 20 degrees, 30 degrees ) and in pronation and supination (+/- 10 degrees, 20 degrees, 30 degrees ) as well as combined flexion/extension and pronation/supination were performed. The ulnotriquetral and the pisoscaphoid distances were assessed in each position. Correlation with cryosections was achieved.

RESULTS

A strong linear correlation between the degree of pronation or supination and the pisoscaphoid and ulnotriquetral distances was noted. Flexion and extension produced no significant effect on the pisoscaphoid distance, but a defined shift of the ulnotriquetral distance occurred with increasing flexion and extension.

CONCLUSIONS

If all parameters are taken into account, this correlation aids in estimating the degree of possible malpositioning of the wrist during radiography and the degree of subluxation of the distal radioulnar joint. Tabular data with parameters to correct for instances of malrotated images and to estimate the extent of dislocation or malrotation of the distal radioulnar joint are provided.

A dynamic simulator to evaluate distal radio-ulnar joint kinematics

In order to perform cadaveric biomechanical studies of the human forearm and distal radio-ulnar joint, a dynamic simulator has been constructed. The device is based upon a Plexiglas frame, to which the ulna is secured in a vertical orientation and the humerus in a horizontal orientation. The hand is secured in a sliding bar linkage to a stepper-motor that is used to rotate the forearm. The tendons to be loaded are connected to pneumatic actuators that provide agonist and antagonist muscle loading resulting in torque along the forearm axis. The muscle loading profiles and magnitudes are programmable as a function of the pronation-supination position and direction. A magnetic tracking system is used to collect three-dimensional kinematics data of up to four segments, in conjunction with the muscle tendon loads, forearm torque and other prescribed experimental measures. All functions are under PC control using custom software written with LabVIEW (National Instruments, Austin, TX). For the DRUJ testing, the validity of the tendon loading protocol to produce physiologic torque/rotation patterns was verified using in vivo data. The relationship of individual muscle forces to forearm torque was determined by a cadaveric study.

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.

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.

Functional anatomy of the triangular fibrocartilage complex

The functional anatomy of the triangular fibrocartilage complex (TFCC) was investigated in 20 fresh cadavers. Dynamic changes in the TFCC during rotation were also examined from both the proximal and distal aspects. In our analysis, the TFCC was separated into three components. The distal component was stable, functioning like a hammock to suspend the ulnar carpus. The proximal component was the fan-shaped triangular ligament, the true radioulnar ligament. This was found to originate from the fovea of the ulna in a vertical fashion and was easily twisted during rotation. The third component, the ulnar collateral ligament, also twisted during rotation. When analysed by coronal section, the internal portion of the TFCC was found to be loose, and probably serves as a cushion to absorb local deformities in the TFCC during rotation.

A new technique of reattachment after traumatic avulsion of the TFCC at its ulnar insertion

One female and seven male patients (median age 25.5) presented with traumatic avulsion of the triangular fibrocartilage complex (TFCC), type 1B according to Palmer's classification. Reattachment of the TFCC near its anchoring point was combined with an intraarticular shortening osteotomy of the ulnar head. This provides an excellent approach to the TFCC and a well vascularized anchoring surface. The mooring point is biomechanically appropriate and the tissues with the best biomechanical properties are used. The functional results with a mean follow-up of 3 years were encouraging, as demonstrated by the significant improvement of pain (P = 0.017). All patients were able to return to their previous occupation; no further surgery was necessary to the distal radio-ulnar joint and no impairment of pronation and supination was detected. The final wrist score reflects the subjective results defined by the patient. However the correlation is not linear and the wrist scores are superior to the degree of satisfaction defined by the patient.

Reconstruction of the dorsal ligament of the triangular fibrocartilage complex

The distal radio-ulnar ligaments (DRUL) are key components of the triangular fibrocartilage complex (TFCC). The dorsal DRUL tightens during pronation of the forearm and helps to stabilize this motion. 12 women and three men at our clinic have been treated for DRUJ instability secondary to dorsal DRUL rupture or attenuation. Their chief complaint was pain. The dorsal DRUL was reconstructed using a tendon graft, the ends of which were anchored in the bone of the radius and ulna. This technique has been shown to correct dynamic DRUJ instability in carefully selected patients, decreasing or eliminating pain and restoring normal function.