Distal Radius Intramedullary Nail (DRIM-Nail) for the fixation of extra-articular fractures

Ladislav Nagy

In response to various clinical complications following fixation of distal radius fractures using CRPP and ORIF techniques, a collaboration between the University of Balgrist, Disrad AG, the AO Technical Commission's Hand Expert Group, the AO's Development Incubator and 41medical has witnessed the design and development of an intramedullary implant indicated for unstable A3 and A2 extraarticular fractures of the distal radius.

Distal radius fractures are the most common orthopedic injury accounting for 17.5% of all fractures in adults. These fractures generally occur from a fall on the outstretched hand, and roughly 50% of distal radius fractures are intraarticular. Diagnosis is made clinically and radiographically with orthogonal radiographs of the wrist. Treatment can be nonoperative or operative depending on fracture stability and fracture displacement as well as patients' age and activity demands.

Operative treatment encompasses several techniques from closed reduction percutaneous pinning (CRPP) to open reduction internal fixation (ORIF) to external fixation for fracture reduction and stabilization. While CRPP is an appropriate option for mainly extraarticular fractures, internal fixation using plates and screws remains the most common option for the surgical treatment of distal radius fractures. Achieving and maintaining anatomical reduction is the primary goal of distal radius fracture fixation because it makes it possible to limit loss of function which is an important outcome for young, active, and independent patients.

The implantation of plates and screws in the distal radius is appropriate for unstable, intraarticular, compound, and/or comminuted fractures and allows stable fixation compatible with early mobilization on only protective removable splinting. Drawbacks of such internal fixation, however, is the necessity of additional soft-tissue injury for the exposure during implantation; thereafter, the potential to irritate tendons near the components, causing tendinopathy and possible tendon rupture. Currently, the most common complications directly related to distal radius plate fixation includes tenosynovitis, tendon attrition, and rupture often necessitating hardware removal. The most obvious obstacle when adopting CRPP besides the limited stability of the construct and the necessity of lengthy immobilization is the extension of pins outside of the bone which can cause an increased risk of infection (Fig 2).

In response to such potential complications in the fixation of extraarticular distal radius fractures, a collaboration between the University of Balgrist, Disrad AG, the AO Technical Commission Hand Expert Group, the AO's Development Incubator and 41medical has witnessed the design and development of an intramedullary implant. With the advent of this new device, a decrease in soft-tissue complication is expected. The implant utilizes the principles of load sharing, subchondral screw divergence, and locked fixed-angle fixation. The intramedullary implant is inserted through a small skin incision at the radial styloid and does not further devascularize the fracture fragments. The limited surgical dissection and rigid fracture fixation allows for minimal postoperative mobilization and an early return to function. The newly approved DRIM-Nail is a valuable addition to the arsenal of distal radius fracture treatment options, which can rapidly have patients on the path to recovery.

Finding an industrial partner for the AO-approved DRIM-Nail is ongoing (as of November 2022). The nail is 7.0 mm in diameter and single packed as a 'one size fits all' sterile implant. The nail itself is made from titanium and the additional 2.5 mm diameter screws for fixation (ranging from 14−36 mm) are made of stainless steel (Fig 3). The instrument set is lean but comprehensive and intuitive to use. All instruments are nonsterile and validated according to 41medical reprocessing.

The development of the DRIM-Nail represents the eventual success of a long-standing AO Technical Commission project introduced into the Hand Expert Group in 2010 and driven specifically by Swiss surgeons Ladislav Nagy and Andreas Schweizer at Balgrist University Hospital in Zurich. Following more than a decade in the making, the DRIM-Nail project has finally evolved from a concept to a market-ready product, commemorating a significant milestone in the history of the AO Technical Commission. Because of the successful collaboration with both Disrad AG and 41medical AG, the AO has now access to an intramedullary device for the fixation of extraarticular distal radius fractures.

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Case 1

(kindly provided by Ladislav Nagy, MD, Balgrist Universtity Hospital, Zurich, Switzerland)

The following figures document a clinical case of a 25-year-old woman who sustained a displaced, unstable extra-articular fracture of the left distal radius while snowboarding.

After closed reduction a dorsal re-dislocation of 25° occurred (Fig 4a). There are additional apparent signs of instability: dorsal comminution (Fig 4a) and fracture of the ulnar styloid (Fig 4b). Therefore, a considerable potential for further dislocation is present which is likely to occur in a cast. Furthermore, this young, active, and demanding patient wishes to return to her activities as early as possible. This can only be achieved with an operative fracture fixation. The nail was chosen instead of a plate. This allowed an almost instant functional use of her hand, permitted the patient to return to work at 2 weeks postoperatively without additional fixation or a splint and full unprotected function of her wrist at six weeks.

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