8.1 Introduction

With the wide variety of distal radius fracture types, no single method of distal radius fracture treatment has demonstrated superior outcomes across all patients. ¹ Choosing the appropriate method of fixation for any given fracture variant contributes to improved outcomes. Displaced and unstable fracture patterns require operative stabilization in active patients for optimal outcome. Volar locking plate (VLP) fixation for distal radius fracture has become popular over the last 15 years; however, the reported risk of complication ranges between 16 and 27%, ^{2 , 3} including tendon irritation or rupture, carpal tunnel syndrome, loss of reduction, hardware failure, nerve irritation, and complex regional pain syndrome. ^{2 , 3} Hardware removal rates in the first year are reported in 15 to 34% of patients. ⁴

Complications of tendon and nerve irritation, hardware prominence, and need for hardware removal are not confined to volar plates; indeed, the complication rate of dorsal plating, including hardware removal and tendon complications, ranges between 15.4 and 50% in several series. ^{5 , 6 , 7} A meta-analysis of 12 studies that compare complications of volar and dorsal plating for distal radius fractures found no overall difference in the rate of complications, and an increased rate of neuropathy and carpal tunnel syndrome and decreased risk of tendinopathy in volar plating as compared to dorsal plating. ⁸

Intramedullary (IM) fixation is common in both upper and lower extremity long bone fractures. IM fixation is successful in achieving restoration of bony anatomy, allowing early return to function, and minimizes soft tissue disruption through smaller incisions. Given the close proximity and dense collection of tendons and nerves to the distal radius, IM fixation poses an attractive alternative to conventional plating techniques.

There are several types of IM fixation that have been described for use in distal radius fracture fixation, including intramedullary nails (IMNs), cannulated pins, and an IM cage device. The Micronail (Wright Medical Technology, Inc., Arlington, TN) is a rigid IMN that is inserted through the radial styloid with three distal fixed-angle locking screws (▶Fig. 8.1). ⁹ A similar IMN system is the Targon DR (B. Braun, Melsungen, Germany) and previously the Sonoma WRx wrist fracture nail, which was previously available but as of this publication, currently off the market. ^{10 , 11}

The T-Pin (Union Surgical, LLC, Philadelphia, PA) is a cannulated, self-drilling, self-tapping threaded pin implant (▶Fig. 8.2). ¹² The T-Pin is placed percutaneously into the radial styloid of extra-articular distal radius fractures and provides a more rigid, fixed-angle solution than smooth Kirschner wires (K-wires). ¹³

Recently, the Distal Radius System (DRS) Implant (Conventus Orthopedics, Maple Grove, MN) was introduced (▶Fig. 8.3). ¹⁴ The DRS Implant is a nitinol expandable balloon-shaped scaffold implant that is placed immediately beneath the subchondral plate of the distal radius through a proximal hole in the dorsal or radial diaphysis. The implant is secured in place proximally with two diaphyseal screws. Individual fragment fixation is performed distally to fix articular fragments using percutaneous 2.7-mm cannulated screws (▶Fig. 8.4). These cannulated screws gain locked fixation of the fracture fragments by threading through the four-ply nitinol cage.

Biomechanical studies have been performed to evaluate the stiffness of a number of different IM devices. The Targon DR was compared to the Synthes 2.4-mm titanium VLP with axial- and dorsal-eccentric loading as well as load to failure in an extra-articular dorsal wedge osteotomy model used to simulate an Association for Osteosynthesis (AO) A3 type fracture; the IMN was significantly stiffer with both axial- and dorsal-eccentric loading and had higher stability in load-to-failure testing. ¹⁵ The Conventus DRS IM scaffold implant was compared to two commercially available volar plates: the stiffness of the IM scaffold was not statistically different from the VLP but was significantly stiffer than a nonlocking stainless steel T-plate. ¹⁴ From a strictly mechanical perspective, IM constructs for distal radius fracture fixation appear to be at least equivalent to volar plate constructs.

8.2 Indications

The indications for IM fixation depend on the fracture type, the extent of soft tissue injury, and whether the fracture can be reduced either closed or percutaneously. ¹⁶ Impacted articular fractures, AO type C3 fractures, articular shear fractures or marginal rim fractures, and fractures with extensive metaphyseal/diaphyseal extension are generally contraindicated for IM fixation. Contraindications also include pediatric fractures with open physes, open fractures with inadequate soft tissue coverage, and active or recent local infection.

Fracture indications vary to some extent by the type of IM implant. The main indications for the use of the T-Pin is an unstable nonarticular dorsally displaced distal radius fracture; it can also be used for simple displaced radial styloid fractures. ¹³ Some AO type B fractures can be treated with an IMN, a few examples of which are seen in three published series describing Micronail fixation in AO types B1 and B3 fractures. ^{16 , 17 , 18 , 19} Most of the treated fractures in the Micronail series are types A1, A2, A3, C1, and C2. Provided the fracture can be reduced closed, the IM cage device has the ability to fix more difficult and multifragmentary articular fractures using percutaneous locked articular screws. IM fixation has also been described for osteotomy and fixation of malunited distal radius fractures. ²⁰

8.3 Intramedullary Nail: Surgical Technique

The technique for insertion of the distal radius IMN (Micronail, Wright Medical Technologies, Arlington, TN) employs two limited incision approaches: one radial and one dorsal. The procedure is performed under general or regional anesthesia, and tourniquet control may be used at the surgeon’s discretion. ²¹ Closed reduction is performed using standard techniques, and the fracture is provisionally fixed with a percutaneous 1.6-mm K-wire inserted through the dorsoulnar corner of the radius, and engaging the volar radial diaphyseal cortex proximal to the fracture site. In the event that an acceptable reduction cannot be attained, a dorsal 2-cm incision is made 1 cm proximal to Lister tubercle and a K-wire or Freer elevator is used to manipulate the articular fragment(s) into acceptable alignment. This same incision can be extended later for the proximal fixation. Temporary K-wire fixation should be placed as far ulnarly as possible to avoid interference with the IMN placement.

A 2- to 3-cm incision is made along the midsagittal axis of the radius over the radial styloid and blunt dissection carried out through subcutaneous tissue, identifying and protecting superficial radial sensory nerve branches. A subperiosteal interval between the first and second dorsal compartments is developed, and a long (at least 12-cm) 1.6-mm K-wire is introduced through the radial styloid, just a few millimeters proximal to the tip. A 6.1-mm cannulated starter drill is inserted through the starter drill/K-wire guide and over the guidewire, and a cortical window is opened. If necessary, a small rongeur can be used to open the window proximally to allow for insertion of the awl. The awl is inserted and directed into the IM canal across the reduced fracture, taking care to hug the radial cortex. After the awl, the canal across the fracture line is sequentially broached until a good proximal fill is achieved while ensuring that the fracture remains reduced. It is necessary to ensure that the awl does not penetrate the radial cortex. ²¹

The nail is sized, using the same size nail as the last broach, when the broach does not spin in the medullary canal. There are four sizes of nail available, and if there is a question, downsizing is recommended. The nail is trialed, the nail and insertion jig are assembled, and the nail is inserted. It is critical to ensure the nail is fully seated before proceeding. The insertion jig then remains in place for insertion of the three divergent fixed-angle locking subchondral screws.

After fluoroscopic confirmation of fracture reduction, proximal fixation with bicortical screws is performed. A 2-cm dorsal incision is made approximately 1 cm proximal to Lister tubercle. Careful dissection is performed down through the interval between the second and third dorsal compartments to the dorsal cortex of the radius. The aiming guide on the insertion jig is used, and two interlocking proximal screws are placed. The incisions are closed, and a volar wrist splint is placed. Injury and postoperative images are shown for a 58-year-old female patient who sustained a dorsally displaced distal radius fracture (▶Fig. 8.5, ▶Fig. 8.6). Five months postoperatively, she had experienced no complications and had recovered excellent range of motion (▶Fig. 8.7).