Surgical techniques for intramedullary headless screw fixation of metacarpal and proximal phalanx fractures

INTRODUCTION

Metacarpal and phalangeal fractures are among the common upper extremity injuries, with an estimated annual incidence of 13.6 and 68/100,000 US persons/year for the metacarpal and phalangeal fractures, respectively.^[1,2]

If surgical fixation is indicated, various techniques and approaches have been described for managing metacarpal and phalangeal fractures with variable outcomes.^[3,4] The management options vary according to the surgical approaches (open vs. closed percutaneous fixation) and the fixation tools, which might include Kirschner wire (K-wires), mini plates, cerclage wiring, external fixation, and intramedullary screws.^[3,5]

Although all the previously described methods proved effective in managing such fractures, and every technique has its indications and drawbacks, intramedullary headless screw (IMHS) fixation showed promising results and superiority in terms of fracture union, functional outcomes, complication rates, and cosmetic appearance compared to other techniques.^[3,6,7]

The current technical note describes different techniques for using IMHS fixation percutaneously to manage metacarpal and phalanx fractures.

OPERATIVE TECHNIQUE

Pre-operative assessment and planning: Plain radiographs (posteroanterior [PA], lateral, and oblique views) are typically obtained. In cases of intra-articular fractures, a computed tomography (CT) scan may be required.

1. Planning : Assessment of the affected metacarpal or phalanx bony anatomy included intramedullary width and the bone length, to give an idea about the expected screws length and diameter. The narrowest medullary canal width should be measured (after considering the radiograph’s magnification), in the PA view for the metacarpals and in the lateral view for the phalanges. In general, the width of the screw should fit the narrowest medullary canal after reaming (to avoid bone blowout or entrapment of the screw), and the length should be about 4–6 mm shorter than the bone length.

2. Implants [Figure 1]: We prefer to use one of the following titanium headless screws based on the fracture nature. In general, fully threaded screws are preferable for fractures that are comminuted, spiral, or oblique, while partially threaded screws are better suited for transverse fractures.

   

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   Figure 1:

   Various types of screws used for intramedullary fixation of the metacarpal and phalangeal fractures.

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   1. Acutrak 4 mm headless cannulated screw: A fully threaded cannulated screw with a 1.4 mm guide wire and a drill bit of 2.7 mm or 3.2 mm (these screws are preferably used with comminuted fractures).

   2. Herbert 3.5 mm headless cannulated screw: A partially threaded screw at the ends with a guide wire of 1.4 mm and a drill bit of 2.7 mm. The countersink drill bit is 3.2 mm.

   3. Herbert 2.7 mm headless cannulated screw: A partially threaded screw at the ends with a guide wire of 1 mm and a drill bit of 2.5 mm.

Anesthesia: This technique could be carried out under general or regional anesthesia; however, if the patient’s condition allows wide awake local anesthesia, no tourniquet (WALANT) is preferable.

Patient position: Usually, the patient is supine on an arm radiolucent table (as the surgery is performed under fluoroscopic control).

Surgical details: After proper sterilization and draping, a retrograde approach was utilized for the metacarpal fracture, while an antegrade approach was preferred for the phalangeal fractures.

I. Retrograde IMHS fixation of metacarpal fractures [Figures 1 and 2]:

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Figure 2:

Retrograde technique for metacarpal fracture fixation. (a) Pre-operative plain radiographs showing a transverse fracture of the 4th metacarpal (red arrow). (b) Guide wire (yellow arrow) insertion through the metacarpal head. (c) Improper fracture reduction while advancing the guide wire (yellow arrow) in the medullary canal. (d) The guide wire (yellow arrow) is advanced to engage the proximal fracture segment after obtaining proper fracture reduction. (e) Provisional screw diameter assessment by a screw overlying the medullary canal (green arrow). (f) Reaming of the medullary canal in a retrograde fashion (from distal to proximal) using a cannulated drill bit (white arrow). (g) A clinical image showing the distal screw entry point through a small skin incision (black arrow).

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In all cases, closed reduction (CR) was attempted under fluoroscopy; however, if CR cannot be obtained (which might be caused by soft tissue entrapment), an open reduction is performed.

The metacarpophalangeal (MCP) joint is flexed to 90° while maintaining gentle traction to ease CR. If the preliminary fracture reduction is satisfactory, a guide wire (of proper size) is driven percutaneously through the dorsal one-third of the metacarpal head in a retrograde fashion (from distal to proximal). Once the guidewire reaches the fracture level, the fracture reduction is confirmed under fluoroscopy. Then, the guidewire is advanced to the metacarpal base (it is optional to advance the wire to engage the carpometacarpal joint for better stability to avoid unintended removal when reaming) [Figure 2a-d].

Apart from pre-operative planning, the surgeon may decide on the appropriately sized screw (in terms of width and length) by overlaying it over the bone under fluoroscopy [Figure 2e]. The metacarpal bone is drilled by the appropriate drill bit in respect to the selected screw diameter, ensuring that the narrowest part of the canal is reamed to accommodate the screw threads [Figure 2f]. This was achieved through a small incision is made at the entry point of the guide wire in line with the extensor tendon [Figure 2g].

To guard against possible rotational deformity during screw insertion, the fingers are flexed into the palm to set an appropriate flexion cascade and minimize malrotation. The screw is then inserted and advanced hand-driven, ensuring that the screw threads are engaging the intramedullary cortical bone with good purchase. Then, the screw head should be buried just beneath the subchondral bone.

Final confirmation of the fracture reduction and screw position is confirmed by fluoroscopy [Figures 3,3a]. The guidewire is removed, and the entry site is closed with a single suture.

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Figure 3:

Retrograde technique for metacarpal fracture fixation (cont.). (a) Fluoroscopy radiographic images showing the final intramedullary headless screw (IMHS) (blue arrow) position and fracture reduction. (b) Intraoperative clinical images showing fingers in full flexion and extension (the patient was operated on under wide awake local anesthesia no tourniquet). (c) Last follow-up (12 months) plain radiographs showing fracture union and maintained IMHS position. (d) Clinical images at the last follow-up showing fingers’ full range of motion and proper alignment.

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II. Antegrade IMHS fixation of proximal phalanx fractures [Figures 4 and 5]:

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Figure 4:

Antegrade technique for proximal phalanx fracture fixation. (a) Pre-operative plain radiographs showing comminuted fracture of the index finger proximal phalanx (red arrow). (b) Fracture reduction was obtained by manipulation and traction under fluoroscopic guidance (red circle). (c and d) The guide wire (yellow arrow) is initially inserted in a retrograde manner (from distal to proximal) through the phalanx. (e) The guide wire is advanced and retrieved from the phalanx base just dorsal to the metacarpal head (white arrow). (f) Reaming is started in an antegrade fashion (white arrow). (g) The final screw is inserted (blue arrow), and its position and final fracture reduction are checked under fluoroscopy.

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Figure 5:

Antegrade technique for proximal phalanx fracture fixation (cont.). (a) Fluoroscopy radiographic images showing the final intramedullary headless screw (IMHS) (blue arrow) position and fracture reduction. (b) Intraoperative clinical images showing fingers in full flexion and extension (the patient was operated under wide awake local anesthesia no tourniquet) and the entry point for the screw (orange arrow). (c) Last follow-up (8 months), plain radiographs showing fracture union and maintained IMHS position. (d) Clinical images at the last follow-up showing fingers’ full range of motion and proper alignment.

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The same CR trial as for the metacarpal fractures is applicable; however, the proximal interphalangeal (PIP) joint should be flexed [Figure 4a and b].

First, a guidewire is advanced percutaneously in a retrograde (from distal to proximal) fashion through the dorsal one-third of the phalangeal head, crossing the fracture site and reaching the phalanx base [Figure 4c and d]. The MCP joint should now be flexed to 70°, and the proximal phalanx base is pushed dorsally to achieve a dorsal subluxation. (N.B.: In this particular step, flexing the MCP joint to 90° should be avoided, as this might hinder the dorsal displacement of the proximal phalanx base owing to the dorsal capsule and the collateral ligaments).

The guide wire is advanced till exiting the skin, dorsal to the metacarpal head, without violating it [Figure 4e]. The same technique for assessing the appropriate screw diameter, described for the metacarpal fracture, is repeated. A small incision is carried out at the site of the guide wire’s exit point, and then, the phalangeal medullary canal is reamed in an antegrade fashion using the appropriate drill bit [Figure 4f]. To prevent rotational deformity during screw placement, the finger is firmly held to the adjacent finger. Finally, the screw is inserted, and its position and fracture reduction are checked under fluoroscopy [Figures 4g and 5a]. Then, the guide wire is removed, and the skin incision is closed using a single suture.

III. Retrograde IMHS fixation of proximal phalanx fractures [Figure 6]:

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Figure 6:

Retrograde technique for proximal phalanx fracture fixation. (a) Long oblique fracture of the middle finger proximal phalanx (red arrow) in a pediatric patient. (b) After confirming proper fracture reduction, the guide wire (yellow arrow) is inserted in a retrograde fashion. (c) Provisional screw diameter assessment by a screw overlying the medullary canal (green arrow). (d) Reaming of the medullary canal in a retrograde fashion (from distal to proximal) using a cannulated drill bit (white arrow). (e) The final screw is inserted (blue arrow), and its position and final fracture reduction are checked under fluoroscopy. (f) Last follow-up (10 months), plain radiographs showing fracture union and maintained intramedullary headless screw position (red circle). (g) Clinical images at the last follow-up showing fingers’ full range of motion and proper alignment.

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This technique might be appropriate in pediatric patients [Figure 6a]. The same steps as prescribed with the antegrade technique are followed; however, instead of retrieving the guide wire proximally, it is kept engaging the subchondral bone of the phalanx base or might be advanced to the MCP joint for better stability [Figure 6b-d]. Then, the screw is prepared and inserted in a retrograde fashion (from the phalanx head [distal] to the base [proximal]) [Figure 6e].

Post-operative care: Most patients are operated under WALANT, allowing for the immediate assessment of the fingers’ passive and active range of motion (ROM) [Figures 3b and 5b]. There is no need to apply a splint; buddy strapping is enough to guard against rotational deformity. The patient is encouraged to mobilize the fingers as early as possible. Patients are advised to follow-up in the outpatient clinic for radiological and functional assessment [Figures 3c-d, 5c-d, 6f-g].

DISCUSSION

Although various techniques have been described for managing metacarpal and phalangeal fractures, IMHS fixation has proven to be an efficient technique that has gained popularity in recent years.^[3,7] Using IMHS fixation for managing metacarpal or proximal phalanx fractures showed equivalent and more often superior results compared to other fixation techniques.^[6,7,8-13 ]

Kibar et al.,^[14] conducted a randomized controlled trial to compare the outcomes of using IMHS fixation (37 fractures) versus miniplate fixation (40 fractures) for metacarpal fractures in patients with a mean age of 33 and 32 years, respectively. The average operative time was significantly longer with the plate fixation, 42 ± 10 versus 22.5 ± 10 min (P < 0.001). After 1 year of follow-up, the authors reported no significant difference between both techniques regarding the visual analog scale (VAS) score (0.9 vs. 0.8), disabilities of the Arm, Shoulder, and Hand (DASH) score (3.7 vs. 4), grip strength (40 vs. 39 kg, and 94% vs. 92% of healthy side), and union rate (97.5% vs. 100%) (P > 0.05). Furthermore, the fingers’ total active motion (TAM) was comparable between both groups (260° vs. 266°); however, the authors reported that none of the patients who had IMHS fixation had loss of flexion or extension compared to the other side, compared to eight patients with a defective ROM in the plate fixation group. Hardware removal was required for four patients in the plate group and none in the IMHS fixation group. Furthermore, the overall rate of complications was higher in the plate group (secondary operation, non-union, and stiffness) compared to IMHS fixation groups (P < 0.001).^[14]

To compare the results of IMHS versus K-wire fixation of metacarpal fractures (five patients in each technique), de Jesus et al.,^[15] they reported no difference regarding fracture union time (P = 0.643), no difference regarding the DASH score (P = 0.952), and patient in the IMHS fixation group attained slightly better hand grip strength (95.4% vs. 93.9%) when compared to the contralateral side. The TAM was better in the IMHS fixation group, 281° compared to 264° in the K-wire fixation group; however, this did not reach statistical significance (P = 0.444).^[15]

Silins et al.,^[16] compared plate fixation to antegrade IMHS fixation in 14 and 17 proximal phalanx fractures in patients having a mean age of 46 (16–82) years. After an average follow-up of 9 months, the authors reported that TAM was significantly better in the IMHS fixation group, at 246° compared to 205° (P = 0.02). Furthermore, ROM and extension lag of individual joints (MCP, PIP, and distal interphalangeal) were significantly better with the IMHS fixation (P < 0.01 and P = 0.03). No difference was found in the hand grip strength, VAS score, and QuickDASH score (P = 0.46, P = 0.79, and P = 0.68). The patients who had screws fixation returned to work quicker than those who had plate fixation, 5.6 versus 9.9 weeks (P = 0.05). The average operative time was significantly longer in the plate fixation group, at 71 min versus 36 min (P < 0.01). The rate of hardware removal was considerably lower in the IMHS group compared to the plate fixation group, 17.6% versus 93%.^[16]

It is worth noting that although we described the technique for IMHS fixation, it is a surgeon’s preference regarding which fixation method for metacarpal and phalangeal fractures to be used, as other methods of fixation showed comparable results, as shown in a systematic review and meta-analysis by DelPrete et al.^[3] The authors included 26 studies on metacarpal fractures, where 762 patients had K-wire fixation, 195 patients had plating, and 304 patients were treated by IMHS fixation, and all the groups had comparable mean age. They found a significantly lower mean DASH score with IMHS fixation (0.6 [95% confidence interval (CI), 0.2–1.0]) compared to K-wire (7.4 [95% CI, 4.8–9.9]) and plating (9.8 [95% CI, 5.3–14.3]), P < 0.05. However, there was no difference between the three techniques regarding the mean TAM, 248.4°, 253.7°, and 240.7° for the IMHS fixation, plating, and k-wires, respectively. Furthermore, no significant difference was detected in the mean radiographic fracture union time among different fixation techniques: IMHS (5.9 weeks), K-wires (6.5 weeks), or plating (8.2 weeks). Finally, no difference was found regarding the infection rates between different fixation methods: 5% (3–6%) for K-wires, 3% (1–8%) for plating, and 2% (1–5%) for IMHS, but the reoperation rates were significantly lower for the IMHS fixation group 4% (2–7%), compared with K-wires at 11% (7–16%) and plating at 0.11 (0.07–0.17), P < 0.05.

The IMHS fixation technique offers several advantages, as it is minimally invasive with reduced soft tissue dissection, which decreases the incidence of post-operative adhesions and lowers the risk of periosteal blood supply disruption.^[17,18] Being an intramedullary fixation device, it has a biomechanical advantage related to load sharing and resistance to axial and loading forces.^[19] A biomechanical comparison between IMHS and mini plates for metacarpal shaft fracture fixation was conducted by Dyrna et al., in a cadaveric study, where the authors reported that IMHS fixation using a 3.0 mm screw showed significantly higher stiffness and load to failure than a 4-hole dorsal plate.^[20] The headless nature of the screws, combined with their burial below the subchondral bone, prevents further soft tissue and tendon irritation.^[21] Furthermore, to prove the minimal injury to the articular surface, Ten Berg et al., conducted a CT-based study, reporting that when 2.4 and 3.0 mm screws were inserted into an intact metacarpal head, it resulted in an articular cartilage defect of 4% and 5%, respectively, which was considered a minimal injury.^[22] Finally, the technique is quick, surgeon-friendly, can be performed as an outpatient procedure, has a better cosmetic appearance, and has a relatively lower complication rate.^[23,24]

It is essential to note that surgeons considering this technique should be aware of its associated risks and limitations.

The technique is sensitive to a proper entry point, which, if falsely positioned, might lead to fracture malreduction.^[23] Care should be taken when performing fracture reduction to restore alignment and rotation, as malreduction or residual rotational deformity can affect functional outcomes.^[23] It may be inappropriate for certain fracture patterns, such as in cases of comminuted fractures, where the use of partially threaded screws can lead to compression at the fracture site, potentially resulting in further bone shortening. Furthermore, it could not be used in fractures near or involving the articular surface.^[25] Using drill bits of inappropriate sizes might result in articular surface injury.^[13] If the surgeon miscalculated the screws diameter, it might end up blowing out the metacarpal or the phalanx. In such a case, if the surgeon felt undue resistance while inserting the screw, redoing the medullary canal reaming is advisable.^[13,26] For any reason, if the screws need to be removed, this is more challenging compared to other fixation methods, especially if the screw was broken after a new trauma.^[13] Regarding the cost-effectiveness of the technique, IMHS fixation appears to be more expensive than using K-wires.^[13,27] Finally, its use in pediatric fractures is debatable due to the fear of injuring the epiphyseal plate with further growth arrest.^[13,28]

CONCLUSION

Various fixation techniques have been proposed for managing metacarpal and phalangeal fractures; however, IMHS fixation is one of these techniques that has proven superior in terms of functional, radiological, and complication outcomes. The technique allows rigid stability and early mobilization; it is fast, simple, and has better cosmetic results. However, surgeons willing to adopt this technique should exercise caution when selecting the entry point and choosing the appropriate screws to use.