Persistent Animation Deformity in the Denervated Latissimus Dorsi Pedicled Flap

Background: Optimal management of the thoracodorsal nerve in pedicled latissimus dorsi flaps for mastectomy reconstruction is controversial. The incidence and etiology of animation deformity despite muscle denervation remain poorly-understood. This study examines the incidence and risk factors of persistent animation to guide patient management.

Methods: A retrospective review of a single surgeon’s practice identified breasts reconstructed with a pedicled latissimus dorsi flap including transection of a single branch of the thoracodorsal nerve. The incidence and severity of postoperative animation deformity were examined with identification of potential causative factors: age, BMI, indication for mastectomy, radiation therapy, chemotherapy, hormone therapy, and timing to reconstruction. Patients completed a survey to assess lifestyle implications. A cadaveric dissection of ten latissimus muscles identified anatomical causes of persistent muscle innervation.

Results: Forty-one reconstructions with a minimum follow-up of two years (average 6.25 years) identified no significant relationship between postoperative animation and patient or treatment factors. While absent in the first postoperative year, animation deformity was identified in 90% of patients on long-term follow-up, with 32% reporting pain, and 25% indicating lifestyle interferences. This high frequency of animation correlated with cadaveric results that identified multiple branches of thoracodorsal nerve innervating the latissimus in 9/10 specimens. The distance between nerve branches was 5.4 ± 0.7mm, with the point of bifurcation (5/10) or trifurcation (4/10) located 19.7 ± 2.3mm proximal to the superior muscle margin.

Conclusion: Persistent animation deformity, despite nerve transection, is likely attributable to anatomical differences in the branching patterns of the thoracodorsal nerve, rather than patient or therapeutic factors. While early follow-up may imply adequate denervation, transection of a single nerve branch is insufficient for long-term prevention of animation deformity in most patients. Exploration for additional nerve branches is suggested; however, not at the risk of endangering the vascular pedicle. Preoperative patient counselling is therefore recommended.