Absence of Latissimus Dorsi Muscle in Delayed Breast Reconstruction: Conversion to a Thoracodorsal Artery Perforator Flap.

CASE REPORT
A 62-year-old woman presented for delayed right breast reconstruction following a right modified radical mastectomy for invasive ductal carcinoma. Physical examination revealed a flat right chest wall with well-healed scars but did not specifically evaluate the morphology of the LD muscle.
The surgical plan entailed harvesting a pedicled LD musculocutaneous flap for volume replacement without an implant. After standard posterior incision, no identifiable LD muscle was noted, with only a thin layer of fascia overlying the ribs. Dissection confirmed the complete absence of LD muscle tissue, and further exploration revealed that the thoracodorsal artery and vein were preserved within the subscapular region.
Given this anatomical variation, the procedure was converted to a TDAP flap, using the skin paddle supplied by the thoracodorsal vessels (Figs. 1, 2). The flap was mobilized carefully, preserving the vascular pedicle. Following elevation, perfusion was assessed clinically and found to be adequate, with no signs of venous congestion observed. The flap was transposed anteriorly through a subcutaneous tunnel to the mastectomy site and inset to recreate the breast contour. The donor site was closed primarily. A retrospective review of the computed tomography scan confirmed the absence of the right LD muscle, which had been overlooked (Fig. 3).
The postoperative course was uneventful, with no flap necrosis. At 6-month follow-up, the reconstructed breast maintained volume and shape, with no evidence of flap compromise or donor site morbidity.

DISCUSSION
The LD muscle is critical in various reconstructive procedures, including breast reconstruction, where its robust vascular supply via the thoracodorsal artery provides a reliable flap option.1 Congenital absence of the LD muscle is an exceptionally rare anatomical anomaly, documented primarily through cadaveric studies and isolated case reports.2,3 Its absence has also been linked to Poland syndrome.4,6
Preoperative identification of this anomaly is challenging, as routine imaging is not mandatory and rarely focuses on detailed muscular anatomy unless specifically indicated, as in cases of Poland syndrome.7 Some authors suggest preoperative evaluation of the thoracodorsal pedicle integrity using computed tomography angiography or ultrasound, particularly in patients with prior surgery, axillary radiotherapy, or lymph node dissection.8,9
In breast reconstruction, the unexpected absence of the LD muscle necessitates prompt intraoperative adaptation. Conversion to a TDAP flap represents a feasible alternative, capitalizing on the preserved vascular pedicle. This approach preserves donor site vascularity and allows for sufficient soft tissue coverage, albeit with less muscle bulk. The TDAPs, which arise from the descending branch of the thoracodorsal artery, provide a reliable vascular supply to the overlying skin and subcutaneous tissue. The standard skin paddle for a LD muscle flap typically includes the region where TDAPs are most abundant, enhancing the reliability of perforator-based flap designs. These perforators have a relatively consistent anatomical location, typically found around 10 cm below the posterior axillary fold and approximately 2 cm posterior to the lateral border of the LD muscle, facilitating their intraoperative identification. This dependable vascularity and predictable location support the use of the TDAP flap as a reliable option with acceptable aesthetic outcomes, especially for partial reconstructions in patients with small-to moderate-sized breast volumes.5,10
Although other reconstructive options were considered, in our case, a pedicled LD musculocutaneous flap without implant was initially planned as the most suitable option, given the patient’s preference and the ample volume available at the donor site. In the absence of the LD muscle, other reconstructive approaches—such as free tissue transfer (eg, deep inferior epigastric perforator flap), implant-based reconstruction, or local flaps—may be considered but can be limited by comorbidities, donor site availability, prior radiation, or surgical expertise. Microsurgical experience was vital in this case: avoiding injury to the thoracodorsal pedicle required recognition of variant anatomy, confident intraoperative judgment to change the flap design over fascia rather than muscle, and delicate vessel handling.
Our case reinforces the need for surgical teams to anticipate anatomical variants and remain flexible in reconstructive planning. Thorough knowledge of thoracodorsal vascular anatomy facilitates successful conversion to fasciocutaneous flaps when the muscle is absent. In addition, a detailed preoperative physical examination and improved preoperative imaging protocols focusing on donor site musculature could help minimize unexpected intraoperative findings.

CONCLUSIONS
The congenital absence of the LD muscle is a rare but significant consideration in breast reconstruction. When identified intraoperatively, conversion to a TDAP flap is an effective alternative, preserving vascularity and achieving satisfactory reconstructive outcomes. Preoperative awareness and adaptable surgical strategies are essential to manage this anomaly successfully.

DISCLOSURE
The authors have no financial interest to declare in relation to the content of this article.