The efficacy of magnetic resonance imaging and ultrasound in detecting disruptions of the forearm interosseous membrane: a cadaver study

Radiographic Comparison of Forearm Symmetry in Healthy Individuals and its Importance in the Diagnosis of Longitudinal Radioulnar Dissociation

PURPOSE

Longitudinal radioulnar dissociation (LRD) is an injury often missed upon initial presentation. A recent study examined a radiographic screening test in cadavers that showed increased interosseous distance when the interosseous ligament (IOL) was divided. For this test to be clinically useful, it is necessary for uninjured forearms to have similar interosseous spaces. The purpose of this study was to determine the typical differences between right and left interosseous spaces of healthy individuals.

METHODS

Anterior-posterior x-rays of bilateral forearms in maximum supination of 28 surgical residents with no history of injury were obtained. These images were uploaded into a picture archiving and communication system and then digitized. The length of the radius was measured (Xr). The maximum interosseous distance (Dmax) between the radius and ulna as well as the interosseous distance at a location 0.3 Xr from the distal radioulnar joint was measured. The right and left arm distances were compared. Also, an outlier analysis was used to evaluate forearm rotational asymmetry between right and left arms.

RESULTS

The outlier analysis revealed two sets of forearm x-rays were rotationally different compared to the rest of the group due to asymmetric arm positioning; these data were excluded from the analysis. The average difference in Dmax was 1.7 mm (standard deviation [SD] 1.5) between right and left arms, and this was found at a position of 0.28 Xr on average. The difference in interosseous distance measured at a fixed location 0.3 Xr was 1.6 mm (SD 1.5). No significant difference was found between the paired right and left arms for Dmax or at 0.3 Xr.

CONCLUSIONS

There does not appear to be any significant difference between the maximum interosseous distance of right and left arms in healthy individuals. Therefore, analyzing bilateral forearm x-rays may be a simple LRD screening test.

CLINICAL RELEVANCE

Understanding the degree of normal variation in the forearm bone spacing might inform evaluation of abnormal forearm bone alignment resulting from LRD.

Elbow Dislocation With Associated Essex-Lopresti Injury: A Case Treated Conservatively

A 23-year-old woman suffered a posterior elbow dislocation, distal radius intraarticular fracture, distal radioulnar joint subluxation, and coronoid process fracture, suggesting an Essex-Lopresti injury variant. Closed reduction for the elbow dislocation was performed, and the limb was immobilized at a 90-degree angle with the forearm in a neutral position with a long posterior splint. Three months later complete fracture healing was noted radiologically. One year post-injury full range of motion regarding flexion, pronation, and supination was achieved with only 10 degrees of extension deficit remaining, suggesting a case of Essex-Lopresti injury managed conservatively with excellent results.

Essex-Lopresti Lesions and Longitudinal Radioulnar Instability: A Narrative Review

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An Essex-Lopresti injury (ELI) is classically described as a radial head fracture with a concomitant interosseous ligament complex (IOC) injury. However, multiple injury patterns may be present, and an interosseous membrane (IOM) injury should be evaluated for in any axial load injury through the forearm. ELI may result in longitudinal radioulnar instability (LRUI).

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Diagnosis of an IOC injury can be difficult. Evaluation begins with standard wrist and elbow radiographs and is supplemented with radiographs and intraoperative maneuvers to assess for proximal radial migration. Magnetic resonance imaging and ultrasonography may be useful in the acute setting, although indications and the clinical importance of the findings remain unclear.

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Surgical management of an acute ELI is focused on restoration of radial length and temporary distal radioulnar joint (DRUJ) stabilization. Radial head excision in the acute setting should be approached with caution because proximal migration may not be present acutely but may develop over time. The indication for acute IOM repair and reconstruction remains unclear.

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Surgical management of a chronic ELI is focused on restoration of radial length, wrist leveling, and treatment of degenerative changes (either at the radiocapitellar joint or the DRUJ). Reconstruction of the central band can restore forearm load transfer and produce favorable functional outcomes, but its indications continue to be debated.

Fracture-dislocations of the forearm joint: a systematic review of the literature and a comprehensive locker-based classification system

BACKGROUND

Monteggia, Galeazzi, and Essex-Lopresti injuries are the most common types of fracture-dislocation of the forearm. Uncommon variants and rare traumatic patterns of forearm fracture-dislocations have sometimes been reported in literature. In this study we systematically review the literature to identify and classify all cases of forearm joint injury pattern according to the forearm joint and three-locker concepts.

METHODS

A comprehensive search of the PubMed database was performed based on major pathological conditions involving fracture-dislocation of the forearm. Essex-Lopresti injury, Monteggia and Galeazzi fracture-dislocations, and proximal and/or distal radioulnar joint dislocations were sought. After article retrieval, the types of forearm lesion were classified using the following numerical algorithm: proximal forearm joint 1 [including proximal radioulnar joint (PRUJ) dislocation with or without radial head fractures], middle radioulnar joint 2, if concomitant radial fracture R, if concomitant interosseous membrane rupture I, if concomitant ulnar fracture U, and distal radioulnar joint 3 [including distal radioulnar joint (DRUJ) dislocation with or without distal radial fractures].

RESULTS

Eighty hundred eighty-four articles were identified through PubMed, and after bibliographic research, duplication removal, and study screening, 462 articles were selected. According to exclusion criteria, 44 full-text articles describing atypical forearm fracture-dislocation were included. Three historical reviews were added separately to the process. We detected rare patterns of two-locker injuries, sometimes referred to using improper terms of variant or equivalent types of Monteggia and Galeazzi injuries. Furthermore, we identified a group of three-locker injuries, other than Essex-Lopresti, associated with ulnar and/or radial shaft fracture causing longitudinal instability. In addition to fracture-dislocations commonly referred to using historical eponyms (Monteggia, Galeazzi, and Essex-Lopresti), our classification system, to the best of the authors' knowledge, allowed us to include all types of dislocation and fracture-dislocation of the forearm joint reported in literature. According to this classification, and similarly to that of the elbow, we could distinguish between simple dislocations and complex dislocations (fracture-dislocations) of the forearm joint.

CONCLUSIONS

All injury patterns may be previously identified using an alphanumeric code. This might avoid confusion in forearm fracture-dislocations nomenclature and help surgeons with detection of lesions, guiding surgical treatment.

LEVEL OF EVIDENCE

V.

Problems of Eponymous Proportions: The History Behind Recognizing Forearm Instability Issues

Three predictable patterns of forearm fracture-dislocation-Essex-Lopresti, Monteggia, and Galeazzi-can occur and are eponymously labeled for the investigators who appreciated their unique characteristics and offered a framework by which to understand them. Recognition of these injuries and subsequent investigation and increased understanding of these lesions have resulted in improved understanding about forearm anatomy and stability. Management of the component of instability differs based on the type of fracture-dislocation, the timing of intervention, and surgeon preference. Despite advances in understanding and treating these injuries, nuances of these lesions may remain challenging to modern-day surgeons.

MRI Correlation of Radial Head Fractures and Forearm Injuries

Background: Radial head fractures can be associated with soft tissue injuries of the forearm and wrist. The Essex-Lopresti injury can lead to significant morbidity, especially if the diagnosis is not made acutely. Better identification of such injuries is needed to allow optimal surgical treatment and prevent long-term sequelae. We used magnetic resonance imaging (MRI) to correlate the degree of soft tissue injuries with radial head fractures. Methods: Sixteen pairs of forearms with an associated radial head fracture in 15 patients prospectively underwent an MRI within 2 weeks of their injury. MRI findings were correlated with fracture type, associated soft tissue injury, and presence of symptomatic wrist pain. Results: According to the modified Mason classification, there were 8 type I, 5 type II, and 3 type III radial head fractures. Wrist pain was reported in 8 of 16 extremities, and 2 had associated wrist pathology, including an acute scaphoid fracture in 1 patient and a preexisting stage II scapholunate advanced collapse (SLAC) wrist in another patient. The MRI findings included an elbow effusion in all 16 patients, edema in the proximal third of the radius in 15 extremities, which extended to the middle third in 3 extremities, edema of the interosseous membrane (IOM) in 5 extremities, and edema of the soft tissues including the supinator and/or pronator quadratus in 13 extremities. Conclusions: Eighty percent of patients with edema of the IOM had associated wrist pain. Soft tissue injuries of the forearm did not correlate with the severity of the radial head fracture.

Magnetic resonance imaging evaluation of the distal oblique bundle in the distal interosseous membrane of the forearm

Background

Some cadaveric studies have reported the role of the distal oblique bundle (DOB) in the distal radioulnar joint stability. We aimed to determine whether the presence of the DOB can be identified and its thickness can be measured in magnetic resonance imaging (MRI) examinations.

Methods

We retrospectively reviewed 468 wrist and forearm MRIs. Inclusion criteria were wrist or forearm MRIs taken in patients older than 18 years of age, and exclusion criteria were patients with acute wrist or forearm fractures, infections, or malignant tumors. We selected 80 MRIs that provided adequate coverage of the distal interosseous membrane (DIOM). The thickness of the DIOM in the T2-weighted transverse plane was measured on the picture archiving and communicating system. We used a model-based clustering method to determine whether some individuals have thicker DIOMs that can be considered as the DOB.

Results

The thickness of the DIOM demonstrated a bimodal distribution, indicating the presence of patients with a thick DIOM (DOB). The model-based clustering method indicated that the optimal cutoff point was 1.0 mm. Twenty-six individuals (32.5%) had thick DIOMs with a mean thickness of 1.4 mm (standard deviation, 0.2 mm), while 54 individuals (67.5%) had thin DIOMs with a mean thickness of 0.6 mm (standard deviation, 0.2 mm).

Conclusion

Our study demonstrates that it is possible to identify the DOB and measure its thickness using MRI. Future in-vivo studies of the DOB using MRI in patients with distal radioulnar joint pathologies may reveal its role in the distal radioulnar joint stability.

Longitudinal instability of the forearm

The Essex Lopresti lesion is a rare triad of injury to the radial head, interosseous membrane of the forearm and distal radio-ulnar joint, which results in longitudinal instability of the radius. If unrecognized this leads to chronic pain and disability which is difficult to salvage. Early recognition and appropriate treatment is therefore desirable to prevent long-term problems. The aim of this article is to review the pathoanatomy of longitudinal radius instability and use the existing literature and authors' experience to provide recommendations for recognition and treatment of acute and chronic forearm instability, including description of the author's technique for interosseous membrane reconstruction.

Management of the Essex-Lopresti Injury

Essex-Lopresti injuries (ELIs) are characterized by fracture of the radial head, disruption of the forearm interosseous membrane, and dislocation of the distal radioulnar joint. This injury pattern results in axial and longitudinal instability of the forearm. Initial radiographs may fail to reveal the full extent of the injury, and therefore diagnosis in the acute setting requires a high index of suspicion. Early recognition and treatment are preferred as failure to fully treat the problem may result in chronic wrist pain from ulnar abutment or chronic elbow pain from radiocapitellar arthrosis. In this article the presentation, relevant anatomy, and management options for ELIs are overviewed, and a summary of outcomes reported in the literature is provided. Additionally, the preferred surgical technique of the senior author is presented, which involves reconstruction of the interosseous membrane with a local pronator rerouting autograft.

Intraoperative Technique for Evaluation of the Interosseous Ligament of the Forearm

PURPOSE

To introduce a technique for the diagnosis of interosseous ligament (IOL) disruption based on lateral displacement of the radius after radial head resection and to determine the cutoff value of the lateral displacement for the diagnosis of disruption, the best elbow position for testing, and the diagnostic performance of the technique in different positions.

METHODS

We used 10 fresh-frozen cadavers. After resection of the radial head, a Steinman pin was placed into the radius medullary canal and used to mark the pin location on the capitellum. We applied 1 kg force to pull the proximal radius laterally and measured the displacement in full supination, neutral, and full pronation of the forearm with the elbow in extension and then in 90° flexion. All measurements were performed once with the IOL intact and again with it cut. To assess diagnostic efficacy, receiver operating characteristics curves were constructed. To determine the quality of the technique, we measured the area under the receiver operating characteristics curve for each position. We also determined the cutoff value to obtain the highest sensitivity and specificity.

RESULTS

The area under the curve of the test in extension-supination and flexion-supination showed that these positions were excellent for the diagnosis of IOL disruption. The cutoff value of 5.5 mm lateral displacement in extension-supination had 100% sensitivity and 90% specificity. In flexion-supination, the cutoff value of 9 mm had 100% sensitivity and 90% specificity for the diagnosis of IOL disruption.

CONCLUSIONS

This maneuver was reliable and accurate in cadavers with complete IOL disruption. It is likely that in an intraoperative setting, these results will be reproducible.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Management of complications of forearm fractures

Forearm fractures may be complicated by the disruption of the distal radioulnar, proximal radioulnar, or radiocapitellar joints. The key principles in treating this unique subset of fractures include early recognition and management of the injury and restoration and maintenance of the anatomic alignment. This articles addresses radial diaphyseal fractures with distal radioulnar joint disruption, proximal ulnar fractures with radiocapitellar disruption, and disruption of the forearm longitudinal axis and how to properly recognize and manage these forearm fracture-dislocations.

The treatment of the acute Essex-Lopresti injury

The Essex-Lopresti injury (ELI) of the forearm is a rare and serious condition which is often overlooked, leading to a poor outcome. The purpose of this retrospective case study was to establish whether early surgery can give good medium-term results. From a group of 295 patients with a fracture of the radial head, 12 patients were diagnosed with ELI on MRI which confirmed injury to the interosseous membrane (IOM) and ligament (IOL). They were treated by reduction and temporary Kirschner (K)-wire stabilisation of the distal radioulnar joint (DRUJ). In addition, eight patients had a radial head replacement, and two a radial head reconstruction. All patients were examined clinically and radiologically 59 months (25 to 90) after surgery when the mean Mayo Modified Wrist Score (MMWS) was 88.4 (78 to 94), the mean Mayo Elbow Performance Scores (MEPS) 86.7 (77 to 95) and the mean disabilities of arm, shoulder and hand (DASH) score 20.5 (16 to 31): all of these indicate a good outcome. In case of a high index of suspicion for ELI in patients with a radial head fracture, we recommend the following: confirmation of IOM and IOL injury with an early MRI scan; early surgery with reduction and temporary K-wire stabilisation of the DRUJ; preservation of the radial head if at all possible or replacement if not, and functional bracing in supination. This will increase the prospect of a good result, and avoid the complications of a missed diagnosis and the difficulties of late treatment.

Forearm instability

Forearm instability results from trauma, which disrupts the radial head, the interosseous membrane, and the triangular fibrocartilage complex. Inadequate treatment of injuries to these forearm stabilizers may result in the complex problem of chronic longitudinal forearm instability. Delayed recognition and/or treatment of injuries producing forearm dissociation has led to poor patient outcomes, which makes timely recognition of the injury pattern imperative. This article discusses relevant aspects of forearm anatomy and current concepts in the diagnosis and treatment options for this complex injury pattern.

A historical perspective on the Essex-Lopresti injury

An Essex-Lopresti injury is a fracture of the radial head with concomitant dislocation of the distal radioulnar joint and rupture of the interosseous membrane. Poor outcomes have been associated with this rare injury if the dislocation of the distal radioulnar joint is missed in the acute setting. This injury is named after the British orthopedic surgeon Peter Essex-Lopresti, who made a number of important observations about this injury in 1951. Peter Essex-Lopresti was a promising young surgeon, and his untimely death at the age of 35 brought an early end to a remarkable career. This article investigates the evolution of treatment for this injury and sheds light on the life of the surgeon for whom the injury is named.

Fractures of the radial head

Most fractures of the radial head are stable undisplaced or minimally displaced partial fractures without an associated fracture of the elbow or forearm or ligament injury, where stiffness following non-operative management is the primary concern. Displaced unstable fractures of the radial head are usually associated with other fractures or ligament injuries, and restoration of radiocapitellar contact by reconstruction or prosthetic replacement of the fractured head is necessary to prevent subluxation or dislocation of the elbow and forearm. In fractures with three or fewer fragments (two articular fragments and the neck) and little or no metaphyseal comminution, open reduction and internal fixation may give good results. However, fragmented unstable fractures of the radial head are prone to early failure of fixation and nonunion when fixed. Excision of the radial head is associated with good long-term results, but in patients with instability of the elbow or forearm, prosthetic replacement is preferred. This review considers the characteristics of stable and unstable fractures of the radial head, as well as discussing the debatable aspects of management, in light of the current best evidence.

The Essex-Lopresti lesion

The Essex-Lopresti lesion represents a severe injury of the forearm unit. In the 1940s, it’s pathology and consequences have already been mentioned by several authors. Over the course of time, the pathophysiology of the lesion was displayed in more detail. Therefore, an intensive analysis of the involved anatomic structures was done. The interosseous membrane was shown to play a major role in stabilising the forearm unit, in the situation of a fractured radial head, which is the primary stabiliser of the longitudinal forearm stability. Moreover, biomechanical analyses showed a relevant attribution of the distal radio-ulnar joint to the forearm stability. If, in the case of a full-blown Essex-Lopresti lesion, the radial head, the interosseous membrane and the distal radio-ulnar joint are injured, proximalisation of the radius will take place and will come along with secondary symptoms at the elbow joint and the wrist. According to actual studies, the lesion seems to occur more often than realised up to now. Thus, to avoid missing the complex injury, subtle clinical diagnosis combined with adequate imaging has to be undertaken. If the lesion is confirmed, several operative treatment options are available, yet not proofed to be sufficient.

Magnetic resonance imaging technology in evaluating the presence and integrity of the anterior oblique ligament of the thumb

This investigation examines the reliability and reproducibility of magnetic resonance imaging (MRI) technology in evaluating the anterior oblique ligament (AOL) of the trapeziometacarpal joint (TMC) of the thumb, in order to establish an effective imaging protocol to use in the early identification of conditions leading to degenerative arthritis. We used cadaver specimens, three hand surgeons independently rated from X-rays each specimen. The specimens were then scanned in a General Electric MRI machine with a standard wrist coil. An effort was made to reproduce the image of the AOL - with a unique technique to obtain images of the obliquely oriented thumb and its ligaments. Following the MRI, the specimens were dissected to expose the AOL and visualize the TMC joint. A standard MRI fiducial was sewn to the proximal and distal extent of the volar side of the AOL. The soft tissues were replaced and the skin was closed. They were then rescanned following the same protocol, and pre and post-dissection ligament-labeled specimens were compared. Following dissection and tagging of the AOL ligament, a repeat MRI confirmed its location and validated the protocol in all cases. The open dissection and ligament tagging confirmed that what was visualized was in fact the structure of interest. This investigation demonstrated that with an appropriate MRI protocol it is feasible to guide the scanner to catch appropriate images of a ligament that is closely correlated with degenerative arthritis.

The role of ultrasound and magnetic resonance imaging in the evaluation of the forearm interosseous membrane. A review

The interosseous membrane of the forearm is an important structure to consider in cases of elbow and forearm trauma; it can be injured after elbow or forearm fractures, leading to longitudinal forearm instability. Diagnosis of interosseous membrane injuries is challenging, and failure in diagnosis may result in poor clinical outcomes and complications. Magnetic resonance imaging and ultrasound have shown to be valuable methods for the evaluation of this important structure. Both techniques have advantages and limitations, and its use should be adapted to each specific clinical scenario. This article presents an up-to-date literature review regarding the use of ultrasound and magnetic resonance imaging in the forearm interosseous membrane evaluation.

The intra-operative radius joystick test to diagnose complete disruption of the interosseous membrane

Disruption of the interosseous membrane is easily missed in patients with Essex-Lopresti syndrome. None of the imaging techniques available for diagnosing disruption of the interosseous membrane are completely dependable. We undertook an investigation to identify whether a simple intra-operative test could be used to diagnose disruption of the interosseous membrane during surgery for fracture of the radial head and to see if the test was reproducible. We studied 20 cadaveric forearms after excision of the radial head, ten with and ten without disruption of the interosseous membrane. On each forearm, we performed the radius joystick test: moderate lateral traction was applied to the radial neck with the forearm in maximal pronation, to look for lateral displacement of the proximal radius indicating that the interosseous membrane had been disrupted. Each of six surgeons (three junior and three senior) performed the test on two consecutive days. Intra-observer agreement was 77% (95% confidence interval (CI) 67 to 85) and interobserver agreement was 97% (95% CI 92 to 100). Sensitivity was 100% (95% CI 97 to 100), specificity 88% (95% CI 81 to 93), positive predictive value 90% (95% CI 83 to 94), and negative predictive value 100%). This cadaveric study suggests that the radius joystick test may be useful for detecting disruption of the interosseous membrane in patients undergoing open surgery for fracture of the radial head and is reproducible. A confirmatory study in vivo is now required.

UNUSUAL PATTERN OF ESSEX-LOPRESTI INJURY WITH NEGATIVE PLAIN RADIOGRAPHS OF THE WRIST: A CASE REPORT AND LITERATURE REVIEW

The Essex-Lopresti injury consists of a fracture of the radial head, rupture of the interosseous membrane and disruption of the distal radioulnar joint. The greatest challenge with this injury pattern is the diagnosis, because it is frequently missed and the attention usually focused on the elbow joint. In this paper we report an unusual pattern of Essex-Lopresti injury with a radial neck fracture, a tear of the interosseous membrane and a disruption of the distal radioulnar joint in which initial wrist radiographs did not show significative abnormalities. Open reduction and internal fixation for the radial head fracture was performed. Forearm rotation was locked with two Kirschner wires from ulna to radius to allow interosseous membrane to heal.

This case is even more difficult to diagnose than classic Essex-Lopresti pattern because of the absence of radius shortening, due to this specific radius fracture pattern, and also the absence of distal radioulnar joint dislocation. When treating a radial head fracture but also a radial neck fracture, interosseous membrane injury should be suspected to avoid misleading in diagnosis.

Forearm instability

Forearm instability is a complex problem resulting from traumatic disruption of the forearm stabilizers: the radial head, the interosseous membrane, and the triangular fibrocartilage complex. Dissociation of the forearm unit is often underrecognized and therefore inadequately treated, leading to poor patient outcomes. The goals of this article are to impart an understanding of the forearm anatomy and the current concepts in the diagnosis and treatment options for this complicated problem.

Longitudinal radioulnar dissociation: identification and treatment of acute and chronic injuries

In this article we describe the fundamental concepts that were established by Essex-Lopresti over 50 years ago and explore the current concepts in anatomy, biomechanics, diagnosis, and treatment for longitudinal radioulnar dissociation. Moreover, we present encouraging results for treating chronic injuries to the IOM achieved by bone-ligament-bone (BLB) reconstruction using a patellar tendon graft, giving hope for this seemingly unforgiving injury. A treatment algorithm is also provided to aid in the management of acute and chronic longitudinal radioulnar dissociation.

[Diagnosis and treatment of the Essex-Lopresti lesion. Literature review and four case reports]

BACKGROUND

A fracture of the radial head in combination with a rupture of the interosseous membrane and lesion of the distal radioulnar joint known as Essex-Lopresti lesion is a rare injury. Usually it is caused by a high-energy trauma. Initially unrecognized distal radioulnar dislocations often show poor results.

MATERIAL AND METHOD

Four case reports are presented to discuss the trauma mechanism together with diagnostic and treatment options. Especially the accuracy of ultrasound to diagnose an interosseous membrane disruption was evaluated.

RESULTS

After an average of 35 months all patients were examined using the Morrey score and the modified score of Green and O'Brien. Initially the extent of the injury was not diagnosed in three cases. According to the score values the average results have been fair.

CONCLUSIONS

An early diagnosis is the key for the correct treatment of an Essex-Lopresti lesion based on the classification of Edwards and Jupiter. In addition to the clinical and radiological assessment ultrasound should be used to diminish the rate of unrecognized interosseous membrane disruptions.

The “muscular hernia sign”: an original ultrasonographic sign to detect lesions of the forearm’s interosseous membrane

The total disruption of the forearm's interosseous membrane can lead to an Essex-Lopresti syndrome. The diagnosis must be done early for a better prognostic. Incomplete lesions can aggravate and an early diagnosis of incomplete lesions is a challenging problem. Magnetic resonance imaging is the gold standard but remains expensive, and is hard to obtain in an emergency. On the contrary, ultrasonography is cheap, accessible in an emergency, and dynamical tests can be performed easily. Twelve fresh frozen forearms were randomized in four groups. The membrane was divided into three parts (proximal, middle, and distal thirds). Each group was prepared with variable patterns of lesions. Two radiologists performed an ultrasonographic (US) examination of these forearms. They were blinded with respect to the lesional status of the forearms. Each examination consisted of two stages: static and dynamic. During the dynamic examination, the radiologist looked for the "muscular hernia sign". The results of their examinations were compared with the real lesional status. The static examination was very efficient in the proximal and middle parts of the membrane, and less reliable in the distal third. With the dynamical examination, no mistake occurred at the proximal and middle parts of the forearm, and there was only one at the distal part. The US examination of the interosseous membrane is very efficient to detect incomplete lesions, mostly, if dynamical tests are performed looking for a "muscular hernia sign".

Forearm interosseous membrane trauma: MRI diagnostic criteria and injury patterns

OBJECTIVE

Define criteria for interosseous membrane (IOM) injury diagnosis using MRI, and characterize patterns of IOM disruption following forearm trauma. Our hypothesis is that most IOM injuries occur along the ulnar insertion, and MRI should be obtained following forearm trauma to assess IOM competency.

DESIGN

Sixteen cadaver forearms were subjected to longitudinal impact trauma. Prior to and following injury, MR images were examined by a board-certified musculoskeletal radiologist using pre-defined criteria for determining IOM integrity. Each specimen was dissected and the viability/pattern of injury examined. The MRI and dissection results were compared using a double-blinded methodology.

RESULTS

Eight of the 16 specimens demonstrated IOM trauma. Seven specimens demonstrated complete IOM disruption from the ulnar insertion, and one revealed a mid-substance tear with intact origin and insertion. The dorsal oblique bundle was disrupted in four specimens. MRI analysis identified IOM injury in seven of the eight forearms. The injury location was correctly identified in six specimens when compared to dissection observations. MRI determination of IOM injury demonstrated a positive predictive value of 100%, a negative predictive value of 89%, a sensitivity of 87.5% and a specificity of 100%.

CONCLUSION

Our findings demonstrate the accuracy of MRI in identifying IOM disruption, and its ability to localize specific injuries in a clinically relevant model of forearm trauma. The injury patterns demonstrated most lesions occurred along the IOM's ulnar insertion, and in half of the injured specimens there was concomitant dorsal oblique bundle disruption.

Diagnosis and treatment of longitudinal instability of the forearm

Radio-ulnar dissociation can result from high-injury trauma that the compressive forces traverse the wrist forearm and elbow. This injury can be thought of as an "unhappy triad" of radial head fracture, triangular fibrocartilage complex failure, and a tear of the interosseous membrane. The radius is the primary stabilizer of the forearm with the forearm interosseous membrane enabling load sharing between the radius and the ulna. The central one-third of the interosseous membrane is 3 times stronger than the membranous portion and approaches the strength of the anterior cruciate ligament for determining interosseous membrane injury. Imaging studies with proven diagnostic efficacy include magnetic resonance imaging and ultrasound. Surgical treatment should be considered when circumstances imply longitudinal instability of the forearm. Surgical treatment includes open reduction/internal fixation or prosthetic replacement of the radial head as well as repair of the disrupted triangular fibrocartilage complex. Successful treatment of radioulnar dissociation is predicated on early diagnosis of the condition.

The efficacy of ultrasound in the evaluation of dynamic scapholunate ligamentous instability

BACKGROUND

The accuracy of diagnostic imaging modalities that are currently used to evaluate dynamic scapholunate ligamentous instability is equivocal. Ultrasound is commonly used for a wide variety of diagnostic purposes in orthopaedics. The purpose of the present study was to determine the efficacy of ultrasound in the diagnosis of dynamic scapholunate ligamentous instability.

METHODS

Two groups of individuals were prospectively studied. Group A included patients with a clinical diagnosis of unilateral dynamic scapholunate ligamentous instability, and Group B included asymptomatic volunteer control subjects. Dynamic ultrasound examinations of the dorsal portion of the scapholunate ligament in both wrists of all individuals were performed by radiologists. The radiologists were blinded with regard to the group to which each person belonged as well as with regard to the affected wrist in the patients in Group A. Arthroscopic examinations of the affected wrist in all of the patients in Group A were then performed by surgeons who were blinded with regard to the results of the ultrasound examination, and the results of the arthroscopic and ultrasound examinations were compared. The ability of ultrasound to discern asymptomatic from symptomatic individuals was also determined.

RESULTS

Over a period of 1.5 years, a total of sixty-four wrists were evaluated in fourteen patients (Group A) and eighteen normal subjects (Group B). All fourteen nonaffected wrists in Group A and all thirty-six wrists in Group B were correctly identified as normal with use of ultrasound. Of the fourteen affected wrists in Group A, thirteen were found to have scapholunate ligament laxity on the basis of arthroscopy (twelve wrists) or arthrotomy (one wrist); six of these thirteen wrists had been correctly identified as abnormal with use of ultrasound (a true-positive result), and seven had false-negative results. There was one true-negative result. The ability of ultrasound to differentiate between normal and abnormal wrists was significant (p < 0.001). For the sixty-four wrists, statistical analysis revealed that ultrasound had a sensitivity of 46.2%, a specificity of 100%, and an accuracy of 89.1%.

CONCLUSIONS

We conclude that ultrasound has a high specificity and accuracy but a low sensitivity for the evaluation of dynamic scapholunate ligamentous instability, and we recommend its use as an adjunct to other diagnostic modalities for this purpose.

Sonographic evaluation of lower extremity interosseous membrane injuries: retrospective review in 3 patients

OBJECTIVE

To describe the sonographic findings of lower extremity interosseous membrane disruption with computed tomographic and surgical correlation.

METHODS

Three patients with sonographic evaluation of the lower extremity interosseous membrane were identified through the clinical experience of 1 author over a 5-year period. Sonographic images of the symptomatic and unaffected lower extremities were retrospectively characterized and correlated with computed tomographic and surgical findings by 2 fellowship-trained musculoskeletal radiologists.

RESULTS

The normal interosseous membrane was identified in the asymptomatic lower extremities in all 3 patients, which appeared as a thin, hyperechoic (nearly equal to bone cortex) line, continuous from the tibia to the fibula. The abnormal interosseous membrane in all 3 cases appeared abnormally hypoechoic, poorly defined, and discontinuous at the tibia. A proximal fibular fracture was shown on sonography in 1 of 3 symptomatic lower extremities with radiographic evidence of a fracture. The sonographic findings correlated with the computed tomographic images. Distal tibiofibular syndesmosis injuries were confirmed and treated at surgery in 2 patients.

CONCLUSIONS

Sonography can show both normal and injured interosseous membranes of the lower extremity, as well as associated proximal fibular fractures.