First Dorsal Metacarpal Artery-pedicled Second Metacarpal Vascularized Bone Graft for Nonunion after Thumb Carpometacarpal Arthrodesis

Abstract

Arthrodesis is a reliable surgical procedure for treating thumb carpometacarpal osteoarthritis. However, the most frequent and problematic complication of arthrodesis is nonunion. Although postarthrodesis-related nonunion is a common complication, the indications and results of revision procedures for this pathological condition have not been well documented. A 59-year-old man underwent arthrodesis for thumb carpometacarpal osteoarthritis, which resulted in painful nonunion 7 months after the surgery. We performed revision surgery for this pathological condition, using first dorsal metacarpal artery-pedicled second metacarpal vascularized bone graft. This method resulted in successful bone union and pain relief. First dorsal metacarpal artery-pedicled second metacarpal vascularized bone grafting could be an alternative method for nonunion, which is a common complication after thumb carpometacarpal arthrodesis.

Arthrodesis is a reliable surgical procedure for treating thumb carpometacarpal (CMC) osteoarthritis because it provides strong grip strength, pinch strength, and pain relief.¹ The most frequent and problematic complication of arthrodesis is nonunion, with a frequency of up to 39%.^2–4 Despite recent improvements in fixation materials and surgical methods, nonunion still occurs. Postoperative nonunion associated with thumb CMC arthrodesis is sometimes asymptomatic and does not necessarily require revision surgery⁵; however, symptomatic cases require additional surgery, including trapezial resection arthroplasty, with or without tendon interposition and revision arthrodesis.⁶ Considering that arthrodesis is mainly used for young patients and manual workers who wish to obtain stable and painless thumbs,^1,2 revision arthrodesis could be the first choice for revision surgery. However, revision arthrodesis and its outcomes for this pathological condition have not been well documented.⁶ Here, we present a case of thumb CMC osteoarthritis that was treated by first dorsal metacarpal artery (FDMA)-pedicled second metacarpal vascularized bone grafting.

CASE REPORT

A 59-year-old man with painful bilateral thumb CMC osteoarthritis (right, Eaton stage III; left, Eaton stage II) visited our hospital. His key pinch strength was 6.5 kg/4.0 kg (right/left), and visual analog scale for pain was 100/76 (right/left). Because the right thumb had more severe pain than the left thumb, the patient underwent arthrodesis using a locking plate for the right thumb, and a removable thumb spica splint was subsequently applied for 6 weeks. However, the arthrodesis resulted in painful nonunion at 7 months postoperatively.

We then performed revision surgery using an FDMA-pedicled second metacarpal vascularized bone graft (VBG). Under brachial plexus block anesthesia and tourniquet control, the screws and plate were removed, and the fibrotic scar tissue in the nonunion site was excised. Next, a longitudinal skin incision was made at the radial border of the second metacarpal. By careful subcutaneous dissection, the FDMA was identified on the fascia of the first interosseous muscle. The periosteal branch of the FDMA on the radial aspect of the second metacarpal head was preserved. A 10 × 5-mm VBG was elevated to avoid damage to the collateral ligament of the second metacarpophalangeal joint with a surgical sagittal saw and a chisel, and the VBG was moved into the nonunion site through the subcutaneous tunnel in the first dorsal intermetacarpal space (Figs. 1 and 2). After the release of the tourniquet, the vascularity of the VBG was confirmed. Because the VBG was too small to fill the space of the nonunion site, cancellous bone obtained from the distal radius was additionally grafted. The VBG was grafted and fixed using a 0.7-mm Kirshner wire. Finally, the CMC joint was fixed with a 2.0-mm locking plate and 2.4-mm headless compression screw.

Fig. 1.: The schema of the FDMA-pedicled vascularized bone grafting. The second metacarpal head is vascularized from the superficial artery (SA) and deep artery (DA) of the FDMA. RA, radial artery.

Fig. 2.: Intraoperative pictures of the FDMA-pedicled VBG. A, The VBG is harvested from the radial aspect of the second metacarpal head. B, The VBG is moved into the thumb carpometacarpal joint. White arrows show the VBG.

After revision surgery, a thumb spica cast was worn for 6 weeks. At 6 months, CT showed partial union around the VBG at the dorsal aspect of the CMC joint, whereas the cancellous bone at the palmar aspect of the CMC joint was absorbed. (See figure, Supplemental Digital Content 1, which shows three consecutive slices of computed tomography images at 6 months after revision arthrodesis. Partial bone union is observed around vascularized bone that was grafted at the dorsal aspect of the thumb CMC joint. https://links.lww.com/PRSGO/C452.) During the final follow-up at 24 months, the key pinch strength of the right hand was 7.5 kg, and the visual analog scale for pain was 0. Radiographs showed complete bone union of the thumb CMC joint (Fig. 3), and the patient was able to resume his preoperative occupation as a factory worker.

Fig. 3.: Anteroposterior radiographs of the right-hand at 24 months after revision arthrodesis showing bone union of the thumb carpometacarpal joint.

DISCUSSION

In the present case, we used FDMA-pedicled second metacarpal VBG with a locking plate and headless compression screw for the pathological condition and obtained successful bone union. To achieve osseous union, adequate bone contact between the first metacarpal base and trapezium, stability of fixation, and good vascularity of the fusion site are important. If the bony contact is poor, a bone graft is required. Previous studies have utilized several types of bone grafts obtained from the ilium, radius, and olecranon;⁶ however, no comparative study has analyzed their success rates. An anatomical study of the vascularity of the trapezium demonstrated that nutrient arteries were richer in the dorsal and lateral aspects than in the palmar aspect.⁷ If plate fixation is used for the initial surgery, the vascular supply to the trapezium is likely to decrease. Therefore, in the present case, we used FDMA-pedicled second metacarpal VBG for nonunion after thumb CMC arthrodesis, because VBG is advantageous in such conditions.

The vascular anatomy of this VBG was analyzed in detail by Brunelli et al.⁸ The FDMA has two branches: the superficial branch running through the subdermal layer over the first interosseous muscle, and the deep branch running along the second metacarpal. Anastomosis between two branches lies on the radial aspect of the second metacarpal head; therefore, this VBG is supplied by the antegrade flow of the superficial branch and reverse flow of the deep branch.^8,9 Clinically, VBG has been used for revascularization of the lunate in Kienbock disease⁹ and recurrent nonunion of the scaphoid,⁸ and up to 12 × 6 mm was harvested without complications in their studies. However, there are no reports regarding the application of VBG for nonunion after thumb CMC arthrodesis. We believe that this VBG has advantages, including easy dissection and a long pedicle that reaches the thumb CMC joint easily. However, this method has several disadvantages. First, hypoplasia of the superficial branch of the FDMA has been reported in 5%–15% of cases in anatomical studies.⁸ Interestingly, Nakanishi et al¹⁰ reported the application of VBGs from the second metacarpal base for nonunion after CMC arthrodesis. When the FDMA-pedicled second metacarpal VBG cannot be raised for the reason mentioned above, their procedure will become an alternative. The second limitation is the harvestable size of the VBG. As in the present case, an additional bone graft might be required for the treatment of nonunion after thumb CMC arthrodesis. The third is the risk of collateral ligament injury during graft harvest. Another limitation is that stability with the headless compression screw and locking plate fixation and the additional 6 weeks of cast immobilization might have contributed to successful bone union in addition to VBG. Despite these limitations, this procedure may be an alternative in such pathological conditions.

CONCLUSIONS

We reported a case of postarthrodesis-associated nonunion of the thumb CMC joint treated with FDMA-pedicled second metacarpal VBG. This procedure could be a choice for treating nonunion, which is a common complication of thumb CMC arthrodesis.