Poland syndrome is a rare congenital condition defined by unilateral absence of the sternocostal (lower) head of the pectoralis major muscle, usually combined with a variably affected hand on the same side. It is also called Poland anomaly because the findings are a developmental field defect rather than a true genetic syndrome.

The condition is uncommon and almost always sporadic. Reported incidence varies widely, from roughly 1 in 7,000 to 1 in 100,000 live births, with a commonly quoted figure of about 1 in 30,000 newborns. It is described more often on the right side and more often in males, but left-sided and female cases occur and must not be excluded by these tendencies.

The clinical picture is extremely variable. At the mild end, a person has only a missing portion of pectoralis major and may not be diagnosed until adolescence or adulthood, sometimes incidentally. At the severe end, there is rib and costal cartilage deficiency, breast and nipple hypoplasia, and a markedly affected hand. The condition matters for appearance, chest wall stability and, most importantly for the orthopaedic and hand surgeon, hand function.

The most widely accepted explanation is the subclavian artery supply disruption sequence. Around the sixth to eighth week of gestation, a temporary reduction in blood flow through the developing subclavian artery and its branches is thought to impair growth of the structures supplied on that side. Because the subclavian artery and its branches supply both the anterior chest wall and the developing upper limb, a single vascular insult can explain why the chest and the hand on the same side are affected together. This theory is supported by case reports showing similar disruption patterns in other vascular territories.

The defining anatomical feature is absence of the sternocostal head of pectoralis major. The clavicular head is usually preserved, which is why some shoulder function is retained. The spectrum of structures that may be involved includes:

• Pectoralis major: absence of the sternocostal head, sometimes with the whole muscle absent.
• Pectoralis minor: frequently absent or hypoplastic.
• Ribs and costal cartilages: hypoplasia or aplasia, classically of the second to fourth or third to fifth segments.
• Breast and nipple: hypoplasia or complete absence (amastia and athelia).
• Subcutaneous tissue and skin: thinning over the affected chest.
• Other muscles: latissimus dorsi, serratus anterior and other shoulder-girdle muscles can be hypoplastic or absent.
• Hand: symbrachydactyly with short, webbed or absent middle phalanges and digits.

The functional consequences depend on what is missing. Absence of pectoralis major alone causes mainly cosmetic asymmetry with surprisingly preserved strength. Rib deficiency can cause paradoxical chest wall motion or a lung hernia. Hand involvement determines grasp, pinch and overall upper-limb function.

Classification describes severity and helps plan reconstruction, but it does not replace an individual functional assessment. Chest wall classifications describe the skeletal and soft-tissue deficit, while hand classifications describe the digital deficiency.

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Presentation depends on severity and age. A newborn may be noted to have an asymmetric chest, an absent anterior axillary fold or an abnormal hand. An older child or adult may present for cosmetic reasons, with breast asymmetry at puberty, or even incidentally on imaging done for another reason. Adults occasionally present when the chest wall defect is mistaken for trauma or another pathology.

History should define:

• when the difference was first noticed and whether it has changed with growth;
• which structures are involved: chest contour, breast, nipple and the hand;
• hand function: grasp, pinch, dressing, writing, sport and any aids used;
• breathing symptoms or a visible bulge that changes with coughing or straining;
• the patient's and family's main concern: appearance, function or psychosocial impact;
• family history (usually negative, since most cases are sporadic).

Examination should be deliberate:

1. Inspect both sides of the chest with the patient relaxed and then with the hands pushed onto the hips to contract pectoralis major. The absent sternocostal head and lost anterior axillary fold become obvious.
2. Palpate for the pectoral muscle mass, the costal cartilages and any rib step-off or soft, pulsatile defect.
3. Look for paradoxical chest wall movement or a bulge on coughing that suggests a lung hernia.
4. Assess the breast and nipple-areolar complex, especially in females after puberty.
5. Examine the same-side latissimus dorsi by resisted shoulder extension or adduction, because it may also be deficient.
6. Examine the hand in detail: number, length and webbing of digits, nail size, grasp, pinch and overall function.
7. Assess shoulder and upper-limb strength; clavicular head preservation often keeps function reasonable.
8. Note any other anomalies, since rare associations are reported.

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Management is shaped by severity, age, function and the patient's priorities. The aim is not to make the chest and hand perfectly normal; it is to improve contour, restore chest wall stability where the skeleton is deficient, and maximise hand function. A multidisciplinary team of paediatric, plastic, thoracic and hand surgeons, with psychology and developmental support, gives the best results.

Two principles guide sequencing. First, the hand is usually addressed early because grasp and pinch develop in childhood and influence the whole upper limb. Second, chest and breast reconstruction are usually staged to growth and puberty, since adding an implant or shaping the breast before maturity risks asymmetry as the child grows.

The operative plan must be explicit before the incision: which deficit is being corrected, whether the latissimus dorsi is available, whether the skeleton needs stabilisation, and the timing relative to growth and puberty.

Not every absent pectoral muscle or chest asymmetry is Poland syndrome, and the hand difference can be confused with other congenital limb conditions. The distinction matters because management and associated risks differ.

Most Poland syndrome evidence is observational, so several practical questions remain genuinely unsettled. Examiners reward a candidate who can name the uncertainty rather than overstate the data.

• Cause. The subclavian artery supply disruption sequence is the leading theory and is supported by case reports, but it is not proven for every case and some atypical phenotypes are hard to explain by a single vascular event.
• Timing of chest reconstruction. There is no agreed age; many surgeons stage definitive work to puberty and skeletal maturity, but the evidence is observational and confounded by severity.
• Best reconstructive technique. Latissimus dorsi flap, custom implant and autologous perforator flaps all report good outcomes; comparative data are weak and choice depends on the deficit, donor availability and surgeon experience.
• Management of the latissimus-absent chest. When the usual donor is also missing, the optimal alternative (implant versus distant autologous flap) is not settled.
• Hand reconstruction thresholds. When to lengthen, transfer toes or use prosthetics in severe hands depends on function and family goals rather than a fixed algorithm.
• Cancer awareness. Rare reports link the hypoplastic breast and the condition with malignancy; the practical message is awareness and individualised screening, not routine intensive surveillance.

There is no high-level society guideline or implant registry specific to Poland syndrome; it is a rare, non-arthroplasty congenital condition, so practice is guided by paediatric, plastic and hand surgical principles, narrative reviews and surgical series rather than registry data. The points below frame a globally consistent approach.

Global epidemiology

• Poland syndrome is rare, with reported incidence ranging from about 1 in 7,000 to 1 in 100,000 and a commonly quoted figure near 1 in 30,000 newborns.
• It is usually sporadic and unilateral, described more often on the right side and in males, although left-sided and female cases occur and should not be excluded by these tendencies.
• The hand difference sits within the symbrachydactyly spectrum and is the feature most relevant to early function.

Side-by-side principles across practice settings

Registry note

• Arthroplasty registries (NJR, AJRR, AOANJRR, SHAR, NZJR) do not capture Poland syndrome because no joint implant is used. Outcome evidence comes from single-centre and multicentre surgical cohorts and case series, which is why reporting is heterogeneous and complication rates, although generally low, are imprecise.

High- versus limited-resource practice variation

• In well-resourced settings, CT and MRI with 3D reconstruction, custom implants, microsurgical free flaps and toe-to-hand transfer expand the reconstructive options.
• In limited-resource settings, clinical assessment and plain radiographs drive decisions, and reconstruction may rely on pedicled latissimus dorsi flaps or simpler implants. The core principle, treat the hand for function and stage the chest for contour and stability, is universal.

Complications relate to the deformity itself, to reconstruction and to expectations.

When shown a patient with an absent pectoral muscle or chest asymmetry, structure the answer in this order:

1. Diagnosis: unilateral absence of the sternocostal pectoralis major with an ipsilateral hand difference, consistent with Poland syndrome.
2. Cause: mention the subclavian artery supply disruption sequence as the leading theory and that it is usually sporadic.
3. Define the deficit: pectoralis major and minor, ribs and cartilages, breast and nipple, latissimus dorsi and the hand.
4. Assess function: chest wall stability and breathing, plus detailed hand grasp and pinch.
5. Imaging: clinical diagnosis confirmed; CT or MRI with 3D reconstruction and hand radiographs when reconstruction is planned.
6. Plan: treat the hand early for function; stage chest and breast reconstruction to growth and puberty.
7. Counsel: aim for improved contour, stability and function rather than a perfectly normal chest or hand, with multidisciplinary and psychological support.