Congenital Limb Duplication and Spinal Dysraphism: A Rare Case Report Highlighting Single-Stage Multidisciplinary Surgery and Life-Changing Outcome

Introduction

Congenital polymelia is a rare condition in which an individual is born with an extra limb, with an estimated incidence of 1 in 100 000 births [1]. The cause of this disorder is not fully understood, but it is hypothesized be a result of disrupted embryonic development [2,3]. While the exact etiology remains elusive, proposed mechanisms include disruptions to the HOX genes, teratogenic or environmental insults during early gestation, or incomplete twinning and signaling pathway errors. Therefore, it is often associated with other congenital anomalies, such as spinal dysraphism and vertebral malformations [3,4]. Spinal dysraphism refers to a heterogeneous group of congenital anomalies characterized by the incomplete closure of the neural tube and overlying midline structures, such as bone and soft tissue. To our knowledge, only a handful of cases have been reported, and this is the first documented case report of congenital polymelia with complex spinal dysraphism published in Indonesia. This case is particularly instructive as it highlights the diagnostic and therapeutic challenges in a low-resource setting, demonstrating the successful application of a complex, single-stage multidisciplinary surgery that resulted in a life-changing functional outcome for the patient.

Case Report

A 19-month-old girl came to our clinic with her parents due to the existence of an accessory limb since she was born, that grew larger over time. It consisted of a visible bone-like structure protruding from the skin and eventually developed a pressure ulcer causing discomfort lying down. She had difficulty walking independently and was using her toys for assistance (Figure 1).

The patient was a second child without any known maternal or antenatal risk factors or illness. Her mother reported a full-term pregnancy with no complications. There was no history of maternal illness, fever, radiation exposure, or consumption of medications (including folic acid, which was not taken), alcohol, or illicit drugs during the antenatal period. There was no family history of congenital anomalies. Her developmental milestones were normal. Physical examination revealed an irregular, incomplete accessory limb-like mass arising from the lower back at the sacral region, pointing caudally (Figure 2). It resembled a flexed thigh with a partially developed foot containing only a single toe. Specific neurological examination of the lower extremities revealed normal muscle tone, power, and deep tendon reflexes. Sensation to light touch was intact. There were no signs of neurogenic bladder or bowel abnormalities and anal tone was normal. Her range of motion was not limited, her extremities were normal, and her cranial, thoracoabdominal, and urogenital examinations were normal.

Radiological investigations provided comprehensive diagnosis. Pelvic radiographs (Figure 3) and a 3-dimensional computed tomography (CT) scan (Figure 4) confirmed polymelia, detailing the limb’s accessory pelvic and leg bones, while CT-angiography identified its vascular supply, which originated from the common iliac artery (Figure 5). Crucially, a lumbosacral MRI confirmed an associated spinal dysraphism in the form of an S3 lipomyelocele (Figure 6). A cranial CT scan showed no associated cerebral anomalies.

A single-stage multidisciplinary surgery was performed (Figure 7). The procedure began with lipomyelocele resection, followed by ablation of the supernumerary limb. After incising the skin and subcutaneous layers, standard deep dissection was performed down to the fibro-osseous attachments of the underdeveloped hemipelvis. Ligation of arteries was performed before the accessory limb was removed. The postoperative period was uneventful, and she began learning to walk 2 weeks after surgery. She achieved independent ambulation 3 months later, requiring no further aids (Figure 8).

Discussion

Congenital polymelia concomitant with spinal dysraphism is a collective term for congenital defects that affect the spine and spinal cord [5]. Spinal dysraphism prevalence is approximately 1.47/1000 live births [1,6]. To date, there have been 29 cases documented in the scientific database, with a proportion of female to male patients of 19 to 10. The key feature in our patient was congenital polymelia with spinal dysraphism.

Congenital polymelia is thought to arise from disturbances during very early embryogenesis, particularly in processes involving twinning and limb bud formation. The most widely accepted mechanism is incomplete or asymmetric monozygotic twinning, in which one embryo (the parasitic twin) fails to fully develop while its residual limb buds remain attached to the normally growing fetus. This phenomenon typically occurs when the embryonic disc divides abnormally around the second week of development. A second contributing mechanism involves abnormal duplication of limb buds, caused by disruptions in key signaling centers that regulate limb patterning, such as the apical ectodermal ridge and the zone of polarizing activity. Errors in morphogen pathways – particularly the Sonic Hedgehog signaling axis – may lead to ectopic limb formation or duplication. Although environmental and vascular factors have been suggested, most cases remain sporadic. Overall, congenital polymelia is considered a multifactorial anomaly involving errors in embryonic axis formation, twinning, and limb-field regulation [7–9]. Some literature suggests that this condition is 4 times more likely to be found in female than in male infants [10,11]. A summary of the demographic and clinical features from a review of 29 previously reported cases is presented in Table 1.

Complex limb duplication is often a sentinel marker for other systemic abnormalities. Anorectal malformation is the most commonly associated anomaly, a link explained by the shared embryological origin of the hindgut and caudal spine from the cloaca. While our patient had no other major malformations, the proximity of the accessory limb to the anus required careful consideration [2,10,12–15].

Spinal dysraphism can be divided into open and closed forms. Open spinal dysraphism includes myelomeningocele, hemi-myelomeningocele, myeloschisis, and hemi-myelocele. Closed dysraphism ranges from enteric fistulas and cord malformation to filar and intradural lipomas, such as lipomyelocele in 50% of cases [5].

The limb duplication in our patient was associated with lipomyelocele. This phenomenon is related to embryonic development. Disturbances during the migration of mesenchymal cells to form the vertebral arches in the fourth and fifth weeks of embryonic development can lead to incomplete closure of the spinal cord and malformations like spinal dysraphism, congenital scoliosis, and spinal lipomas [16]. Non-contrast CT is the preferred modality for assessing the accessory limb and associated defects. Three-dimensional CT scans are crucial for surgical planning, providing a detailed view of the bone components, while CT-angiography helps minimize the risk of bleeding.

Management of congenital polymelia with spinal dysraphism requires extensive planning and a multidisciplinary team, due to the high possibility of complications. Our patient lived in a remote province in a rural area of our country that lacked basic healthcare facilities. The surgical team decided to operate on the patient only after a year of observation, as she was a high-risk candidate for complex surgery due to her age. Our multidisciplinary team consisted of doctors from orthopedics, neurosurgery, and plastic surgery. Neurosurgeons addressed the spinal dysraphism, carefully resecting the lipomyelocele and untethering the spinal cord to prevent future neurological deficits. Orthopedic surgeons undertook ablation of the accessory limb. After incising the skin and subcutaneous layers, standard deep dissection was performed down to the fibro-osseous attachments of the underdeveloped hemipelvis. Ligation of arteries was performed before the accessory limb was removed. Finally, the plastic surgeon ensured adequate soft tissue coverage and a durable, tension-free wound closure to prevent infection and wound dehiscence.

The surgery was successful, and there were no complications. The patient was discharged on the 7th postoperative day. She underwent age-appropriate physical therapy to improve balance, gait, and strength, and was followed up at 1, 3, and 6 months postoperatively. She was able to begin walking independently 6 months postoperatively (Figure 9).

This case report highlights that although this is a complex disorder, it can be successfully treated. We emphasize the importance of a delicate approach, with the resection of the spinal dysraphism completed first, followed by resection of the accessory limb.

The management of polymelia with spinal dysraphism varies significantly across the literature, and comparisons with existing reports highlight the uniqueness of our approach. Our single-stage multidisciplinary intervention contrasts with the staged management strategies often described in similar complex cases. For instance, Wasnik et al reported 2 cases of rudimentary third lower limbs associated with spinal dysraphism, but their report focused primarily on the radiological diagnosis and did not detail a unified surgical outcome comparable to the functional recovery seen in our patient [17]. Saaiq et al emphasized the importance of soft tissue coverage in the resection of well-developed accessory limbs; our case mirrors this necessity but applies it to a rudimentary limb, demonstrating that even less-developed structures require complex plastic reconstruction to prevent wound complications [10]. Finally, the association with spinal dysraphism in our patient is consistent with the findings of Wilkes et al and Saaiq et al, reinforcing the embryological link between these entities, yet our report adds to this body of knowledge by documenting a successful functional outcome in an under-reported population in a resource-limited setting [10,14].

Currently, there is no standardized approach to treating limb duplication with spinal dysraphism and various cases have multiple variations. There are no clear indications on conservative or operative management [4,10,18]. In our case, since a pressure sore had developed and the extra limb was interfering with the patient’s ability to walk independently, we decided to operate on the patient after various additional examinations were done to make sure she was physically capable of undergoing a complex surgery.

Conclusions

Management of congenital polymelia with spinal dysraphism requires extensive planning and a collaborative approach from various medical specialties. Various diagnostic measures should be done prior to any surgery, to give the best possible understanding of the defect, due to its variability and uniqueness in different patients. In our rare case, the congenital deformity hindered the patient’s ability to ambulate. Therefore, an adequate surgical approach – ablation of the limb and repair of the associated lipomyelocele – was conducted to help improve the patient’s quality of life. This case contributes to the limited global literature on polymelia and suggests that a single-stage, multidisciplinary surgical correction is a safe and effective strategy for similar complex anomalies, even in resource-limited settings.