Distally Based Abductor Hallucis Muscle Flap: Anatomic Basis and Clinical Application

Redefining the vascular anatomy of the medial gastrocnemius muscle: A computed tomography angiography study

BACKGROUND

The medial gastrocnemius (GN) muscle flap is a historical reconstructive option in lower limb reconstruction. The flap is proximally based on the medial sural artery, and it is assumed not possible to harvest a distally based flap because of the absence of other minor pedicles. The aim of this study is to investigate the presence and the anatomy of a distal secondary pedicle given off by the posterior tibial artery (PTA).

METHODS

A retrospective CTA study was performed of 120 limbs between April 2018 and June 2020. 3D reconstruction was performed to delineate the anatomy of the distal secondary pedicle, if present. The distance of the pedicle, if found, from the intermalleolar line to the patella was noted. The number of pedicles, if multiple, was documented, as well as branches to the soleus muscle and the skin.

RESULTS

A distal pedicle to the gastrocnemius muscle was found in 64% of limbs. The average location from the intermalleolar line is 168 mm. The branching pattern from the PTA showed an isolated vessel going to the distal medial gastrocnemius (32.8%), two branches to the medial gastrocnemius and skin (39.3%), two branches to the medial gastrocnemius and soleus (24.6%), and three branches to the medial gastrocnemius, soleus, and the skin (3.3%).

CONCLUSIONS

This study confirms the presence of the secondary axial distal pedicle of the GN muscle. Furthermore, this study confirms that there is a likely association between the distal medial gastrocnemius pedicle and the PTA skin perforators.

Proximally Based Split Abductor Hallucis Turnover Flap for Medial Hindfoot Reconstruction: A Case Report

Limited reconstructive options exist for soft tissue defects of the foot and ankle because of a lack of surrounding tissue. Although microsurgical free flaps have become a popular treatment modality for this anatomic region, pedicled muscle flaps can provide robust coverage of small foot wounds with significantly less donor site comorbidity. One such muscle is the abductor hallucis, which can be used as a proximally based turnover flap to cover medial hindfoot defects. However, complete distal disinsertion of the muscle may lead to loss of support over the medial arch and first metatarsophalangeal joint, leading to pes planus and hallux valgus. In this case report, we describe a modified technique of a split abductor hallucis turnover flap for a young patient with a chronic, traumatic medial heel wound complicated by calcaneal osteomyelitis. By preserving part of the muscle's distal tendinous attachment, this technique allows for adequate soft tissue coverage while maintaining long-term biomechanical function.

Reconstruction of Defects in the Weight-Bearing Plantar Area Using the Innervated Free Medial Plantar (Instep) Flap

BACKGROUND

Defects in the weight-bearing heel or forefoot are commonly derived from chronic wounds, acute trauma, or tumor excision. Reconstruction of such defects pose a significant challenge to provide a flap that is stable, durable, and sensate. Several flaps have been described for reconstruction of plantar defects, but recurrent ulcerations and/or the need of additional procedures are common. This article provides the approach and outcomes of innervated free medial plantar flap for weight-bearing plantar defects reconstruction.

METHODS

Chart review was performed of 17 consecutive patients with defects in the weight-bearing heel and/or forefoot who were treated with innervated free medial plantar flaps between the years 1999 and 2016. Eleven patients were male, and 6 patients were female. The mean age was 29.5 years (range, 4-52 years). One case was combined heel/forefoot defect, 7 were heel defects, and 9 were forefoot defects. Indications were acute trauma, secondary reconstruction after trauma, and tumor excision.

RESULTS

The mean defect size was 8.0 ± 5.4 cm × 5.1 ± 2.1 cm, and mean flap size was 9.7 ± 1.4 cm × 6.4 ± 0.9 cm. One flap suffered from arterial thrombosis, which necessitated reoperation, and was salvaged. For the remaining cases, the postoperative course was uneventful. The mean follow-up time was 59.3 (±51.3.6) months. Two patients received minor flap corrections due to hyperkeratosis and hypertrophic scar, and 2 patients required donor site correction owing to partial loss of skin graft. One patient succumbed within 1 year owing to metastatic disease. All patients that were followed more than 1 year (n = 15) could sense blunt touch of the flap. Ten patients underwent 2-point discrimination test. No patient had recurrence of ulceration.

CONCLUSIONS

The innervated medial plantar flap is an excellent solution for treatment of medium-to-large defects in the weight-bearing heel or forefoot. It provides glabrous skin that is stable, durable, and sensate. The long-term results are good, with no patient afflicted by recurrent ulceration during the follow-up time.

Reverse Distally Based Abductor Hallucis Muscle Flap for Soft Tissue Coverage of the First Metatarsophalangeal Joint Wounds

Loss of soft tissue coverage distally around the foot poses threats of amputation of the exposed boney structures. An amputation of a portion of the foot leads to loss of the biomechanical structural integrity of the foot. This promulgates an imbalance with its inherent risks of developing new ulcers. This in turn potentiates the limb loss cycle. The reverse abductor hallucis muscle flap is ideally suited for small to moderate-sized defects in the vicinity of the first metatarsophalangeal joint based on its arc of rotation. In this article, we present cases of 5 patients who failed local wound care and healing by secondary intention for at least 6 months duration. The patients were treated successfully using reverse abductor hallucis muscle flap.

Giant schwannoma of the first metatarsal: a rare entity

Schwannomas of osseous origin are rare, and schwannomas of the short tubular bones are even rarer. These benign-looking tumors are difficult to diagnose using imaging alone. However, histopathologic evaluation of a biopsy specimen can establish the diagnosis by identifying Antoni type A and B zones. Curettage and bone grafting will probably be adequate for treatment because malignant changes are unlikely. Large lesions can require en bloc excision and reconstruction. We describe what appears to be only the second case of a schwannoma in the first metatarsal of the foot in a 48-year-old woman. The lesion was poorly contained, with obvious breaks in the cortical shell. The diagnosis was confirmed by pathologic analysis. The lesion was successfully treated with en bloc resection and reconstruction with a nonvascularized fibular graft.

Reconstruction of massive midfoot bone and soft tissue loss as a result of blast injury

Lower extremity blast injuries represent a unique challenge to surgeons and often involve complex, limb-threatening wounds with extensive soft tissue and bone loss. Surgical treatment of these injuries can be difficult because of limited autogenous resources for reconstruction of the defect. In this article, we describe a technique for medial column reconstruction using iliac crest bone graft and soft tissue coverage with an abductor hallucis rotational flap combined with a split-thickness skin graft. This method addresses the extensive bone and soft tissue defects that frequently characterize blast injuries to the foot, and may be applicable in other situations where trauma or infection has caused extensive destruction of the medial column.

Vascular Anatomy of Plantar Muscles

Many reports on the plantar arteries and the deep plantar arch exist, but none of them focus on the arterial pedicles of the plantar muscles. They mainly discuss the deep plantar arch, its variations, and location. This study plans to determine the location and origin of arterial pedicles of all the plantar muscles as a preliminary study for designing new flaps. The study was carried out on 20 feet from 10 cadavers aged from 35 to 67 years. After an injection of latex via popliteal arteries, dissection of the arteries was carried out under a microscope. Abductor hallucis and flexor hallucis brevis muscles receive their main blood supply from the medial plantar artery; abductor digiti minimi and flexor digiti minimi brevis muscles receive their main blood supply from the lateral plantar artery. The flexor digitorum brevis muscle receives branches from both arteries. Adductor hallucis and plantar interosseous muscles receive branches from plantar metatarsal arteries. Quadratus plantae is directly nourished from a branch of the posterior tibial artery. No distal anastomoses between the medial and lateral plantar arteries were identified, except 1 specimen in which the medial plantar artery made anastomosis with the deep plantar arch. As a result, the arterial pedicles of all the plantar muscles were defined, and based on these findings, new flaps can be planned or existing flaps can be modified.

Correlation between the course of the medial plantar artery and the morphology of the abductor hallucis muscle

The abductor hallucis muscle flap is commonly used as a proximally-based flap in the management of ankle, heel, and midfoot lesions, where it is ideally suited for closing defects. This study investigates the anatomical details of this muscle in 13 fresh male cadavers. The medial plantar artery (MPA) was studied by dissection and macroscopic analyses to document the relationship of its superficial and deep branches with respect to the abductor hallucis muscle (AHM). Three main patterns could be described. In Pattern A (54%) the MPA divides into two branches. The deep branch reaches the deep surface of the AHM, supplying its proximal part, and the superficial branch courses between the AHM and the flexor digitorum brevis, to end as the first plantar metatarsal artery. The latter supplies two to three small branches to the distal part of the AHM. The fibers of the AHM end symmetrically on the two sides of the tendon and the muscle presents an arciform shape. The MPA, in Pattern B (38%), lacks a deep branch and continues along the lateral border of the AHM as a superficial branch that supplies proximal and distal collaterals to the muscle. The muscle fibers of the AHM end mainly on the medial side of the tendon. The muscle belly presents an arciform shape and is located on the medial margin of the foot superomedially with respect to Pattern A. In Pattern C (8%) the MPA continues as a large deep branch on the deep surface of the AHM and ends as the medial collateral artery of the big toe. A smaller superficial branch of the MPA provides a few collaterals to the AHM from its proximal part and to the flexor digitorum brevis in its distal part. The AHM fibers end mainly on the lateral side of the tendon and morphologically the muscle presents a straight line on the sole of the foot compared to Pattern A. Although Patterns B and C, from a surgical point of view, necessitate interruption of the main trunk of the MPA, Pattern A may permit the vascularization of the muscles of the medial side of the sole of the foot by the superficial trunk of the MPA. Because preoperative radiological study of the plantar vessels correlate with the morphological characteristics of the AHM observed during surgery, such imaging may be useful in determining the appropriate flap design based on the patient's unique pattern of MPA branching.

Versatility of the Abductor Hallucis Muscle as a Conjoined or Distally-Based Flap

Soft tissue coverage of the medial ankle and foot remains a difficult, challenging, and often frustrating problem to patients as well as surgeons. To our knowledge, the abductor hallucis muscle flap is not frequently used and only a few well documented cases were found in literature. The purpose of this paper is to report and to present the long-term results of a series of four patients who underwent reconstruction of foot and ankle defects with the abductor hallucis muscle flap. In two cases, the abductor hallucis muscle flap was transposed in combination with a medialis pedis flap to cover a medial ankle defect, whereas in another case it was combined with a medial plantar flap. In this latter case, the muscle flap served to fill up a calcaneal dead space after osteomyelitis debridement, whereas the cutaneous flap was used to replace debrided skin at the heel. The abductor hallucis flap was used as a distally-based turnover flap to cover a large forefoot defect in a fourth case. Follow-up period ranged between 18 and 64 months (mean 43.3). In the early postoperative period, two flaps healed completely In two patients marginal flap necrosis occurred which was subsequently skin grafted. No donor-site complication occurred in any of the patients. In all cases, protective sensation of the skin was satisfactory as early as 6 months. In two cases mild hyperkeratosis at the skin graft border to the sole skin (non-weight bearing area of medial plantar and medialis pedis flap donor site) was present, but probably related to poor foot care. All patients were fully mobile as early as 3 months after treatment. In the long-term follow-up (43.3 months), all flaps provided with durable coverage. Functional gait deficit due to consumtion of the abductor hallucis muscle was not apparent. Our long-term results demonstrated that the abductor hallucis muscle flap is a versatile, and reliable flap suitable for the reconstruction of foot and ankle defects. Utilizing the abductor hallucis muscle as a pedicled flap (distally or proximally-based) with or without conjoined regional fasciocutaneous flaps offers a successful and durable alternative to microsurgical tree flaps for small to moderate defects over the calcaneus region, medial ankle, medial foot, and forefoot with exposed bone, tendon, or joint.