Intramedullary Cannulated Screw Fixation Using Noncannulated Instruments for Proximal Phalanx Fracture

Hand fractures account for 19% of all adult fractures, with proximal phalanx fractures comprising 22% of these injuries.1 The treatment approach is primarily determined by the stability of the fracture assessed at the time of diagnosis. Stable fractures can often be managed nonsurgically with methods such as splinting, while unstable fractures typically require surgical intervention to ensure proper length, alignment, and rotation. Several fixation methods are available, each with distinct features. Kirschner wire (K-wire) fixation generally is associated with less disruption to surrounding soft tissues; however, its fixation strength is somewhat limited, and patients usually need to undergo a period of immobilization after the procedure. Plate and screw fixation provides stronger fixation but necessitates more extensive dissection resulting in higher risk of soft tissue adhesions, stiffness and potential loss of range of motion leading to functional impairment.2 Intramedullary compression screws have shown encouraging outcomes due to simplicity of the surgical technique, preservation of soft tissue, and the potential for earlier rehabilitation. Their effectiveness for specific fracture types is still under investigation but has shown to be equivalent to plating in biomechanical studies.3 The ideal fixation method should provide sufficient rigidity to withstand the forces encountered during early movement while also reducing damage to the surrounding soft tissues. Brewer et al4 evaluated health care costs and outcomes associated with intramedullary screw fixation versus Kirschner wire (K-wire) fixation for hand fractures and found that uncomplicated intramedullary screw fixation demonstrated significantly lower follow-up costs compared with K-wire fixation. Optimizing the screw length is biomechanically advantageous as larger longitudinal screw length to bone length ratio was shown to create stiffer constructs less prone to bending failure, thus, accurate measurement of the optimal screw length is imperative. Despite their increasing application, the use of cannulated screws is constrained by higher costs and the necessity for specialized cannulated instrumentation, including screwdrivers, drills, and depth gauges, which may further elevate the financial barriers to their adoption. Here, we describe a technique that allows for intramedullary insertion of a cannulated screw for a proximal phalanx fracture in the event that the associated drill, screwdriver, and depth gauge are not available. For instance, this may be beneficial in the event that the only available set of cannulated instruments has already been used, or instrument sterility was compromised. We believe this technique may be beneficial for surgeons who work in a resource poor environment or are facing other factors outside of their control that may limit access to the specific cannulated instruments. TECHNIQUE We have demonstrated the technique below using a cadaver specimen in the laboratory, accompanied by fluoroscopy images obtained intraoperatively from a patient using the same technique. The surgery is performed with the wide-awake local anesthesia without tourniquet (WALANT) technique. 1% lidocaine with 1:1000000 epinephrine is injected using a 25 G needle. The area proximal to the metacarpophalangeal joint, where the screw will be inserted from, is injected with 5 mL, followed by a digital block with 5 mL, either with a dorsal or volar digital block. At this point, we recommend ensuring that the K-wire can pass through the cannulated screw. Manual reduction of finger malrotation is performed before the insertion of the hardware. The metacarpophalangeal joint is flexed to ∼60 degrees, and the proximal phalanx is gently translated dorsally to facilitate K-wire insertion at a slight dorsal entry point near the base of the proximal phalanx. This entry point is positioned to be centered in the apex of the proximal phalanx concavity when viewed from the anteroposterior view. A K-wire is advanced, confirming its position using fluoroscopy to be centered on both AP and lateral views, and is advanced just proximal to the fracture line (Fig. 1).FIGURE 1: K-wire entry point position shown on anteroposterior (AP) fluoroscopy and on a cadaver. The entry point is slightly dorsal on the lateral view and centered in the apex of the proximal phalanx concavity on the AP view.Under manual traction (or other preferred reduction method), the fracture is reduced, and the K-wire is advanced into the distal fragment. The provisional resduction is confirmed on fluoroscopy. To confirm the wire is advancing in the intramedullary canal, it is recommended to oscillate the wire while advancing. In the absence of a manufacturer-designed depth gauge for screw sizing, we recommend using one of 2 methods: (1) use a second identical K-wire to measure the size difference, (2) imaging the screw over the finger to assess its size in both the anteroposterior and lateral views. The K-wire is then advanced to exit the distal articular surface of the proximal phalanx while the proximal interphalangeal joint is held in maximal flexion. If the wire is correctly positioned in the proximal phalanx intramedullary canal, it will exit at the groove between the condyles of the head of the proximal phalanx. This may serve as an additional visual confirmation of the correct positioning of the K-Wire. A stab incision is made at the K-wire site proximally at the MCP joint down to bone to allow passage of instrumentation without injury to soft tissues, particularly the extensor mechanism. At this point, the K-wire can be slowly pulled back from the distal articular surface under fluoroscopic view just until the proximal articular subchondral bone. A tap with a soft tissue protector or countersink may be used at this point to initiate an opening tract for the screw. This is accomplished by following the K-wire as it is slowly withdrawn. In the event that thick cortices are encountered, tapping alone may not be sufficient, and drilling across the isthmus may be necessary and should be performed in the same manner as the advancing the tap above by following the K-wire as it is withdrawn. The K-wire is then pushed back retrograde to allow for the screw insertion in its tract. The screw is then inserted into the newly created aperture and advanced gradually while simultaneously withdrawing the K-wire from the opposite end of the phalanx (Fig. 2). It is essential to periodically check fluoroscopically to confirm that the K-wire tract is maintained by the advancing screw. Maintenance of the fracture reduction during screw advancement can be performed through continued manual traction or the use of percutaneously applied sharp reduction forceps, depending on the fracture pattern. Throughout this process, the screwdriver should remain engaged with the screw head to ensure stability. Adequate seating of the screw and screw depth can be confirmed fluoroscopically, ensuring all distal threads are across the fracture site and only within the distal fragment.FIGURE 2: The K-wire is being withdrawn as the screw is advanced. The K-Wire must remain in the screw to allow for the guided insertion.The skin incision is closed with absorbable suture, and the distal K-wire hole is closed with Steristrip. Rehabilitation protocols are determined by the surgeon’s preference and may involve either immobilization in the position of safety for 3 weeks or an early active range of motion protocol with minimal soft dressing. The authors prefer the latter approach for optimal recovery. EXPECTED OUTCOME We believe one of the advantages of this technique is allowing for early active range of motion rehabilitation protocol. With this protocol, our experience has been that patients can regain functional range of motion by 4 to 6 weeks. Here we demonstrate our patient at 4 weeks with no pain and excellent range of motion of his operative small finger treated with this technique (Fig. 3), and his postoperative radiographs are also presented in Figure 3.FIGURE 3: Four weeks postoperative with early motion allowed. Patient is painless and functional with <1 cm pulp to palm distance of operative digit. X-rays-lateral, AP, and oblique of operative digit at the same 4-week follow-up appointment.POTENTIAL COMPLICATIONS The primary complications include potential injury to the articular surfaces of both the proximal phalanx base and the metacarpal head, which would occur in a similar manner and at a similar rate to those associated with the traditional cannulated screw technique. In addition, the K-wire being driven out distally creates an additional insult to the distal articular cartilage of the proximal phalanx. This is especially salient as the PIP joint is prone to stiffness after any injury. The articular surface defect reported by Borbas et al5 indicates that only 4.6% of the articular surface is involved for 2.2 mm antegrade cannulated screw and 8.5% for 3.0 mm screws, and a retrograde cannulated screw through the P1 head creates an articular cartilage defect of 13% to 18% with a 2.5 mm screw and 19% to 25% with a 3.0 mm screw. We believe that early mobilization facilitated by intramedullary fixation of the proximal phalanx can help reduce the risk of stiffness in the proximal interphalangeal (PIP) joint. Although we have not experienced this issue, it is important to note that this technique carries the risk of losing the K-wire path when advancing the screw in softer bone, therefore, advancing under fluoroscopic visualization is key during insertion. CONCLUSION This fluoroscopic-guided K-wire Seldinger-type technique we described previously is a safe and effective way to use headless compression screws when cannulated screw system screwdrivers or drills are not available. This technique will still allow the insertion of a cannulated screw of appropriate length and diameter for IM screw fixation of the proximal phalanx fracture.

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