Essex lopresti injuries (ELIs) to the forearm are classically defined as fracture of the radial head, distal radioulnar joint (DRUJ) injury, and disruption of the interosseous membrane (IOM) [1, 2, 3]. The usual mechanism for such an injury is axial compression to the forearm while the elbow is extended [2, 3]. Extent of injury to the IOM is variable and thus contributes to a reported 60% of missed diagnoses at initial presentation [4, 5]. While there is a consensus for IOM reconstruction in chronic cases of longitudinal radioulnar instability [3, 6, 7, 8], there is minimal information regarding support for acute IOM reconstruction and surgical technique for such cases ^[5]. Prior literature in this area has focused on cadaveric, biomechanic, or chronic reconstruction studies [9, 10, 11, 12]. We found only five documented cases of acute reconstruction with varying surgical techniques with a maximum of 1-year follow-up [8, 13, 14, 15]. Of these, one uses an isolated ankle syndesmosis suture-button construct ^[13], and the other uses a FiberTape-dog button construct with a radial head replacement ^[15]. We present a case of early diagnosis of IOM disruption in the setting of ELI, the surgical technique for acute reconstruction of IOM with the CMC Mini TightRope(Arthrex Inc., Naples, FL).

A 40-year-old male presented to the emergency department with complaints of left arm pain after a pedestrian struck incident while walking across the street. Initial radiographs demonstrated a comminuted radial head fracture, radial styloid fracture, and ulnar styloid fracture along with positive ulnar variance (Fig. 1). On physical examination, the patient was neurovascular intact but with tenderness to the elbow, wrist, and along the volar aspect of the forearm. The patient also had a positive piano key test at the wrist. The patient was subsequently diagnosed with an Essex Lopressti Injury, placed into a sugar-tong splint, and indicated for surgical fixation.

Surgery

A standard Kocher approach to the elbow joint was used to expose the radial head fracture. Comminuted fragments and loose bodies within the joint were removed. At this point, an intraoperative radius pull test ^[16] demonstrated greater than 3 mm of proximal migration, confirming injury to the IOM. The radial head ostectomy was then completed followed by a radial head replacement. Reconstruction of the IOM was accomplished using a CMC Mini TightRope (Arthrex Inc., Naples, FL) similar to as described by Meals et al. ^[11]. The ulna was marked at 1/3^rd from the ulnar styloid, and the radius was marked at 3/5th from the radial styloid. Blunt dissection at these sites was carried out to the shafts while being careful to protect sensory nerve branches. Then, with the forearm in pronation, a 1.1 mm K wire from the CMC Mini TightRope (Arthrex Inc., Naples, FL) set was advanced obliquely under fluoroscopic guidance through the cortices of the radius and ulna, angling distally. A 2.0 mm cannulated drill was used to overdrill the K-wire. The tightrope was then inserted using a suture passer and the second button was loaded onto the suture and then tensioned against the ulnar shaft under fluoroscopy. Finally, the DRUJ and radial styloid were then close reduced and pinned with three 1.6 mm Kirschner wires. Final intraoperative fluoroscopy images are shown in Fig. 2.

Follow-up

The patient was postoperatively placed into a hinged elbow brace locked at 90° of flexion for 1 week. The brace was then unlocked in flexion and limited to 30° of extension for the 2^nd week. Extension was increased by 10° each week and subsequently unlocked by the 5^th week. Pins were removed at 4 weeks post-operative, and physical therapy was initiated for elbow range of motion (ROM) and forearm pronosupination. Strengthening was initiated at 8 weeks postoperatively, and the brace was discontinued at 3-month post-operative. Table 1 documents DASH scores, and ROM measurements of the wrist, elbow, and forearm. Figs 3 and 4 illustrate radiographic follow-up at 6 months and 2 years.

ELIs are complicated and disabling forearm injuries and can lead to poor outcomes if not appropriately managed [4, 7]. Disruption of the IOM in this injury can lead to various symptomatology. Initial presentation may have subtle signs to the extent of the injury such as dorsal forearm tenderness and wrist pain with palpation ^[5]. Chronic injuries may present with symptoms related to persistent longitudinal instability to the forearm such as lateral elbow pain and ulnar-sided wrist pain due to ulnar abutment ^[2]. Acute reconstruction of the IOM is seldom documented [8, 13, 14, 15]. This case is unique as it details acute reconstruction of the IOM with the CMC Mini TightRope(Arthrex Inc., Naples, FL), a rehab protocol, and long-term patient outcome. The major function of the IOM is to transmit load from the wrist to elbow, with transfer of load between the radius and ulna while maintaining forearm and DRUJ stability [15, 17]. The anatomical composition of the IOM includes the proximal oblique cord, the dorsal oblique accessory cord, the central band, accessory bands, and the distal oblique bundle [5, 15]. With the central band being the widest and thickest ligament, it is the major load-bearing component [5, 6]. Its approximate position and orientation is a volar origin at 3/5^th from the distal radius with dorsal insertion on the ulna 1/3^rd from distal ulna with an angle of 21° oblique to the forearm’s longitudinal axis ^[6]. This allows the fibers of the central band to function to resist both longitudinal dislocation forces and transverse radioulnar splaying during axial loading ^[18]. Biomechanical studies on the IOM have illustrated the importance of its role in forearm stability. Birkbeck et al. ^[19] demonstrated that, with a transected IOM, the radius and ulna bore load independently. Hotchkiss et al. ^[20] found that, with a radial head excised, the IOM bears 90% of axial load through the forearm, 71% from the central band alone. While the radial head functions as the primary restraint to proximal migration of the radius, the IOM and triangular fibrocartilage complex are important secondary stabilizers if the radial head is absent [6, 21]. Rabinowitz et al. ^[21] demonstrated that proximal migration is minimal under an axial load when both are intact; however, when compromised, proximal migration of the radius occurs with resultant increased radiocapitellar joint forces and load through the radius. Historically, ELIs are addressed with radial head fixation or replacement and DRUJ reduction ^[6]. When the disruption of the IOM persists beyond the initial injury period, lack of restoration of load transfer leads to longitudinal radioulnar dissociation (LRUD) ^[17]. There is a strong support for central band reconstruction in the setting of chronic cases of LRUD due to its potential to restore longitudinal stability and decrease the sequelae of LRUD such as distal ulnar impaction and radiocapitellar joint overload [6, 7, 12]. However, the low healing potential of the central band and documentation of poorer outcomes in the setting of delayed diagnosis support a role for acute IOM reconstruction [4, 7]. In current literature, there is no consensus regarding acute reconstruction of the IOM in such injuries. Options for reconstruction based on cadaveric studies or chronic cases include suture button construct, bone tendon bone autograft, achilles allograft, or autograft with various tendons such as palmaris or flexor carpi radialis [2, 7, 12, 22]. Direct repair can also be considered in cases where the central band is torn from its ulnar border [3, 23]. In previously documented cases of acute reconstruction of the IOM, surgeons have used ankle Syndesmosis TightRope (Arthrex Inc., Naples, FL) ^[13], Fiber-Tape (Arthrex Inc., Naples, FL) ^[15], pronator teres autograft ^[14], cadaveric tendon allograft ^[8], and Ultratape (Smith and Nephew, Watford, UK) ^[8]. To our knowledge, our case is the first to document the use of the CMC Mini TightRope (Arthrex Inc., Naples, FL) for IOM reconstruction with a longer term outcome of 2 years postoperatively. The CMC Mini TightRope (Arthrex Inc., Naples, FL) is classically indicated for thumb suspension after resection of the trapezium in thumb CMC joint arthroplasty ^[24]. In our case, however, we used it to provide a tensioned reduction of the radius and ulna and to reinforce their longitudinal stability. This allowed us to remove pins earlier at 4 weeks postoperatively and begin ROM ultimately contributing to improved patient functional outcomes. A similar suture button construct has previously been investigated in cadaveric studies. Drake et al. ^[9] compared forearms with excised radial heads and a sectioned IOM found that a Mini TightRope restored stability equal to that of an intact IOM. Kam et al. ^[10] found that Mini TightRope reconstruction significantly reduced distal ulnar impaction forces and radioulnar displacement when tested without a radial head replacement. Further reduction was obtained when used in conjunction with a radial head implant. Limitations of this case include that, despite our attempt to recreate the anatomic orientation of the central band, our oblique axis was closer to 40° rather than 20°. In addition, as seen in follow-up radiographs, slight increase in ulnar variance was observed as compared to intraoperative images, demonstrating mild loss of longitudinal radioulnar reduction. However, variations in radiographic technique, patient positioning, and subsequent dynamic ulnar variance ^[25] make it difficult to accurately quantify the difference. Despite this, with the long-term follow up obtained, we are able to show minimal change between the 6 months and 2-year time points, confirming the overall maintained stability of the forearm with the surgical technique and rehab protocol employed and as compared to the time of injury. This was further reflected in the patient’s functional measurements and asymptomatic presentation. Randomized controlled studies regarding the use of acute IOM reconstruction would be beneficial to further support the findings of this case presentation.

This case demonstrates the importance of early diagnosis of IOM damage in the setting of ELI and the benefits of early ROM and pin removal with acute reconstruction of IOM using a suture button construct. Excellent ROM, decent maintenance of longitudinal radioulnar reduction, and painless function were observed at the final follow-up of 2-year postoperatively.

Chronic effects of persistent radioulnar dissociation after ELI can lead to poor outcomes. Acute reconstruction of the forearm IOM in the setting of ELIs with a Mini TightRope suture button construct can allow for early DRUJ pin removal and ROM due to maintained radioulnar longitudinal stability with subsequent great functional outcomes.