Kinematic analysis of the distal radioulnar joint after a simulated progressive ulnar-sided wrist injury

Analyzing the reduction quality of the distal radioulnar joint after closed K-wire transfixation in a cadaver model: is supination or neutral position superior?

INTRODUCTION

Distal radioulnar joint (DRUJ) instabilities are challenging and their optimal treatment is controversial. In special cases or when reconstruction of the stabilizing triangular fibrocartilage complex (TFCC) fails, K-wire transfixation can be performed. However, no consensus has been reached regarding the rotational position of the forearm in which this should be done. Therefore, it was investigated whether anatomical reduction would best be achieved by transfixation in neutral position or supination of the forearm.

MATERIALS AND METHODS

Twelve cadaveric upper limbs were examined before dissection of the DRUJ stabilizing ligaments and after closed transfixation in both positions by C-arm cone-beam CT. Whether this was first done in neutral position or in supination was randomized. The change in the radioulnar ratio (RR) in percentage points (%points) was analyzed using Student's t-test. RR was used since it is a common and sensitive method to evaluate DRUJ reduction, expressing the ulnar head's position in the sigmoid notch as a length ratio.

RESULTS

The analysis showed an increased change in RR in neutral position with 5.4 ± 9.7%points compared to fixation in supination with 0.2 ± 16.1%points, yet this was not statistically significant (p = 0.404).

CONCLUSIONS

Neither position leads to a superior reduction in general. However, the result was slightly closer to the anatomical position in supination. Thus, transfixation of the DRUJ should be performed in the position in which reduction could best be achieved and based on these data, that tends to be in supination. Further studies are necessary to validate these findings and to identify influential factors.

What's the best surgical repair technique of an ulnar styloid fracture? A biomechanical comparison of different techniques

INTRODUCTION

8-10% of all Ulnar styloid fractures (USF) accompanying distal radius fractures are addressed surgically. The surgical fixation has to counteract forces of translation and rotation acting on the distal radioulnar joint (DRUJ). The different technics used were never compared biomechanically. Our study aims to compare the effects of different techniques of USF fixation on the forearm rotation and the dorsal-palmar (DP)-translation of the DRUJ.

MATERIAL AND METHODS

9 forearm specimens were mounted on a custom testing system. Load was applied for Pronosupination and DP-translation with the forearm placed in neutral position, pronation and supination. The positional change of the DRUJ was measured using a MicroScribe. Six different, sequential conditions were tested in the same specimen: intact, USF and 4 repair techniques (2 K-wire, tension band wiring (TBW), headless compression screw, suture anchor).

RESULTS

The USF significantly increased DP-translation and pronosupination compared to the intact condition. The DP-translation in neutral was reduced significantly with all four techniques compared to the USF condition. TBW and suture anchor also showed a significant difference to the K-wire fixation. In supination only the TBW and suture anchor significantly decreased DP-Translation. The rotational stability of the DRUJ was only restored by the K-wire fixation and the TBW.

CONCLUSIONS

All four USF repair techniques partially restored translational stability; however, only K-wire fixation and TBW techniques restored rotational stability. TBW was biomechanically superior to the other techniques as it restored translational stability and rotational stability.

Increase of weight-bearing capacity of patients with lesions of the TFCC using a wrist brace

STUDY DESIGN

Retrospective cross-sectional case series.

BACKGROUND

Lesions of the triangular fibrocartilage complex (TFCC) can result in pain during axial load and unstable distal radioulnar joint (DRUJ). Conventional wrist orthoses decrease initial pain sufficiently but also prevent any movement during recovery and do not contribute to the stabilization of the DRUJ.

PURPOSE

In this retrospective analysis, we tested if the weight-bearing capacity of patients with lesions of the triangular fibrocartilage complex was increased by wearing a brace that stabilizes the distal radioulnar joint.

METHODS

Twenty-three patients had an arthroscopically confirmed TFCC lesion. We compared preoperative dynamic weight-bearing capacity of both hands with and without a commercially available wrist brace (WristWidget). Subgroup analysis was performed for stability of the distal radioulnar joint and etiology of the TFCC lesion. The dynamic ulnar variance was measured in a modified weight bearing test. We used parametric tests for normally distributed values.

RESULTS

The weight-bearing capacity of the hand with TFCC lesion was significantly lower than of the control hand (16 verus 36 kg; p <0.001). The relative load of the affected hand compared to the unaffected hand increased from 48 % (CI 37-60, SD 27) to 59 % (CI 47-72, SD 29 with a brace. The device had no effect on the control hand. Twelve patients with unstable DRUJ had a lower weight-bearing capacity compared to the eleven with stable joint. The percentage improvement with bracing was higher for those with unstable joints (versus stable) and traumatic lesions (versus degenrative).

CONCLUSION

The use of a wrist brace significantly increases the weight-bearing capacity and therefore the maximum tolerated axial load of patients with a lesion of the TFCC. Patients with traumatic lesion or unstable DRUJ tend to show lower values than with degenerative lesions or stable joints.

Effect of wrist position on distal radioulnar joint stability: a biomechanical study

We investigated distal radioulnar joint (DRUJ) stability in different wrist positions and examined the relative contribution of each ligamentous component of the triangular fibrocartilage complex (TFCC) to DRUJ stability. We used nine fresh-frozen cadavers. The humerus and ulna were fixed at 90° elbow flexion. The radiocarpal unit was translated relative to the ulna in dorsopalmar directions with the wrist in five positions. Displacement of the unit was measured by an electromagnetic tracking device. Magnitudes of displacement were compared between different wrist positions in various sectioning stages: ulnocarpal ligament (UCL) sectioning, radioulnar ligaments (RUL) sectioning, and extensor carpi ulnaris (ECU) floor sectioning. Wrist position and sectioning stage significantly influenced the displacement. In intact wrists, the displacement in wrist extension was significantly lower than that in neutral. However, after UCL sectioning, there were no longer any significant differences. After RUL sectioning, the displacement in radial deviation was significantly lower than that in neutral. Following ECU floor sectioning, there were no longer any significant differences. Thus, in intact wrists, DRUJ stability in wrist extension is likely due to tightening of the UCL. After complete RUL sectioning, DRUJ is stabilized in radial deviation due to tightening of the ECU floor.

Biomechanical study of the extensor carpi ulnaris as a dynamic wrist stabilizer

PURPOSE

To investigate the dynamic stabilizing effect of the extensor carpi ulnaris (ECU) on the distal radioulnar joint (DRUJ) and the ulnocarpal joint in a simulated model of triangular fibrocartilage complex (TFCC) injury.

METHODS

Using 8 fresh-frozen cadavers, we fixed the humerus and ulna at 90° of elbow flexion, and the radius and hand were allowed to rotate freely around the ulna. Passive mobility was tested by translating the radiocarpal unit relative to the ulna along dorsal-palmar directions. Unit displacement was measured by an electromagnetic tracking device in different forearm rotations and under varied loading to the wrist motor tendons. Magnitudes of displacement were compared between different loading patterns of the prime wrist movers in the TFCC-sectioned wrists. The effect of sectioning the ECU subsheath was analyzed.

RESULTS

When physiological loads were applied to all of the prime wrist movers, the magnitude of displacement during passive mobility testing decreased in supination and neutral rotation. After ECU tendon loading was released, mobility increased again in supination and neutral rotation. When the load was applied only to the ECU tendon, mobility decreased in supination and neutral rotation as compared with unloaded. Little change in the mobility was found in pronation regardless of the tendon loading pattern. After sectioning of the ECU subsheath, the stabilizing effect of the ECU decreased in neutral rotation.

CONCLUSIONS

In a neutral wrist position with complete sectioning of the TFCC, the ECU dynamically stabilized the DRUJ and the ulnocarpal joint in supination and neutral forearm rotation. The ECU subsheath assisted ECU tendon stabilization on the ulnar side of the wrist, especially in the neutral rotation.

CLINICAL RELEVANCE

Maintaining the ECU and its subsheath may reduce DRUJ instability in patients with TFCC injuries.

Patterns of triangular fibrocartilage complex (TFCC) injury associated with severely dorsally displaced extra-articular distal radius fractures

PURPOSE

The aim of the study was to examine triangular fibrocartilage (TFCC) injury patterns associated with unstable, extra-articular dorsally displaced distal radius fractures.

METHODS

Twenty adult patients with an Arbeitsgemeinschaft für Osteosynthesefragen (AO), type A2 or A3, distal radius fracture with an initial dorsal angulation greater than 20° were included. Nine had a tip fracture (distal to the base) of the ulnar styloid and 11 had no such fracture. They were all openly explored from an ulnopalmar approach and TFCC injuries were documented. Eleven patients also underwent arthroscopy and intra-articular pathology was recorded.

RESULTS

All patients had TFCC lesions of varying severity, having an extensor carpi ulnaris subsheath avulsion in common. Eighteen out of 20 also displayed deep foveal radioulnar ligament lesions, with decreasingly dorsal fibres remaining. The extent of this foveal injury could not be appreciated by radiocarpal arthroscopy.

CONCLUSIONS

Severe displacement of an extra-articular radius fracture suggests an ulnar-sided ligament injury to the TFCC. The observed lesions concur with findings in a previous cadaver study. The lesions follow a distinct pattern affecting both radioulnar as well as ulnocarpal stabilisers.

Structural properties of 6 forearm ligaments

PURPOSE

To first determine the structural properties of 6 forearm ligaments and then to create linear and nonlinear analytical models of each ligament from these properties.

METHODS

We nondestructively tested the annular ligament, dorsal and palmar radioulnar ligaments, and the distal, central, and proximal bands of the interosseous ligament from 7 fresh cadaver forearms in a servohydraulic testing apparatus. We performed testing with the bone-ligament-bone constructs positioned corresponding to neutral forearm rotation as well as in 45° of supination and 45° of pronation. Based on a mechanical creep test of each ligament, we computed a linear and nonlinear ligament stiffness value for each ligament. We then compared these computed analytical responses to loading with loading data when each ligament was tested at 1.0 and 0.05 mm/s. We analyzed differences among ligaments and forearm positions using 1-way and 2-way analyses of variance.

RESULTS

The stiffnesses for the distal band and the dorsal radioulnar ligament were statistically less when the constructs were positioned in supination compared with neutral forearm rotation. At all forearm positions, the linear stiffness of the central band was greater than that for the distal band of the interosseous ligament, the proximal band of the interosseous ligament, and the dorsal radioulnar and palmar radioulnar ligaments. In neutral forearm rotation, the linear stiffness of the central band was statistically greater than the annular ligament. The experimental loading behavior of each ligament was better modeled by a nonlinear stiffness than a linear one.

CONCLUSIONS

The central band of the interosseous membrane is the stiffest stabilizing structure of the forearm. Any structure used to replace the central band or other forearm ligaments should demonstrate a nonlinear response to loading.

CLINICAL RELEVANCE

In considering a reconstruction for the forearm, the graft used should have a nonlinear response to loading and be one that is similar to the normal, original ligament.

Surgical approach to the triangular fibrocartilage complex

There are few descriptions of the surgical exposure of the ulnar aspect of the wrist. The anatomy of the dorsoulnar aspect of the wrist was explored in 7 cadaver wrists with special attention to developing a surgical approach to the dorsum of the radio-ulno-carpal joint. Using the experience from previous authors and the knowledge gained from our cadaveric dissections, a surgical approach was designed that provides wide exposure of the dorsoulnar aspect of the wrist. The anatomic layers are dissected in a distinct pattern that allows preservation of the extensor carpi ulnaris and its sheath as well as a strong closure of each layer and restoration of the anatomy. Minimal postoperative immobilization is required, and rehabilitation can be started as early as 2 weeks postoperatively. This approach provides access to the distal radioulnar joint, triangular fibrocartilage complex, distal ulna, and lunotriquetral joint, thus allowing multiple possible procedures through a single, universal approach.

The treatment of severely comminuted intra-articular fractures of the distal radius

Comminuted fractures of the distal end of the radius are caused by high-energy trauma and present as shear and impacted fractures of the articular surface of the distal radius with displacement of the fragments. The force of the impact and the position of the hand and carpal bone determine the pattern of articular fragmentation and their displacement and the amount and the extent of frequent concommitant ligament and carpal bone injury. The result of the osseous lesion in comminuted fractures was termed "pilon radiale", which emphasizes the amount of damage to the distal radius and the difficulties to be expected in restoring the articular congruity. Besides this the additional injury, either strain of disruption of the ligaments and the displacement of the carpus and/ or the triangular fibrocartilage complex will equally influence the functional outcome. This review will expand on the relevant anatomy, correct classification and diagnosis of the fracture, diagnostic tools and operative treatment options. Current treatment concepts are analysed with regard to actual literature using the tools of evidence based medicine criteria. A new classification of severely comminuted distal radius fractures is proposed using CT data of 250 complex intraarticular radius fractures. Finally a standardized treatment protocol using external fixation in combination with minimal invasive internal osteosynthesis is described.

Use of an ulnar head endoprosthesis for treatment of an unstable distal ulnar resection: review of mechanics, indications, and surgical technique

Resection of the distal ulna for post-traumatic arthritis can lead to an unstable forearm joint through loss of the normal articular contact through the distal radioulnar joint and loss of soft tissue constraint. The resulting convergence instability can lead to residual pain, weakness, and loss of function. Restabilization of the forearm joint with implantation of an ulnar head endoprosthesis can re-establish the mechanical continuity of the forearm, reducing pain and improving strength and function. The anatomy, mechanics,rationale, and indications for surgical replacement of the distal ulna are presented. Important tenets of proper ulnar head implant insertion are given to provide a guide for use of the implant. Preliminary results after 2 years of clinical experience are encouraging.

The effect of ulnar shortening on lunate and triquetrum motion--a cadaveric study

BACKGROUND

Ulnar shortening osteotomy is a widely used procedure for a number of pathologic conditions. However, there is little biomechanical data on its effect on the surrounding soft tissue structures. Therefore, the objective of this study was to determine the effects of progressive ulnar shortening on the distal radioulnar joint and the proximal carpal bones.

METHODS

The kinematics and strain between the ulnar styloid, lunate, and triquetrum were evaluated with varying supination and pronation forces. Six fresh-frozen cadaveric upper extremity specimens were tested after progressive ulnar shortening using a custom jig. Biomechanical measurements including strain and translation were made by evaluating the change in position of the digitizing markers on the carpal bones, radius and ulna.

FINDINGS

There were significant changes in marker positions with respect to intact specimens for each amount of shortening at the ulnar styloid (P<0.001), the lunate (P<0.001), and triquetrum (P<0.001). With progressive ulnar shortening, the strain data demonstrated that there was no significant change in lunato-triquetral strain, but demonstrated a significant increase in both ulno-triquetral and ulno-lunato strain (P<0.04).

INTERPRETATION

Progressive ulnar shortening increases ulno-triquetral and ulno-lunato strains with an ensuing reduction in motion between the carpal bones.

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.

Influence of the pronator quadratus and supinator muscle load on DRUJ stability

PURPOSE

To determine the effects of altering the load contributions of the pronator quadratus and supinator muscles on in vitro distal radioulnar joint (DRUJ) stability during pronation and supination and before and after ulnar head excision.

METHODS

Multiple pronation trials were conducted with incremental loading of the pronator quadratus relative to the pronator teres muscle; supination trials were similarly conducted with incremental loading of the supinator relative to the biceps muscle. All trials were conducted using an upper-limb apparatus capable of simulating muscle/tendon loading and displacement. Stability measurements included dorsal-volar translations of the radius relative to the ulna and DRUJ diastasis and convergence.

RESULTS

Increased pronator quadratus loading did not affect intact DRUJ stability but effects were noted after ulnar head excision when the forearm was positioned between neutral and full pronation. Incremental loading of the supinator muscle did not modify DRUJ stability in the intact or ulnar head excised state.

CONCLUSIONS

Pronator quadratus muscle activity aggravates forearm instability after ulnar head excision. Immobilization of the forearm in mid- to full supination should minimize pronator quadratus activity and optimize soft-tissue healing. This information may be useful to develop in vitro muscle-loading scenarios and analytical forearm models.