Deltoid Fibrosis- Causes, Diagnosis, and Treatment

Last Updated on October 17, 2025

Deltoid fibrosis is a condition characterized by fibrotic shortening of one or more segments of the deltoid muscle, leading to a fixed abduction deformity of the shoulder and limitation of adduction. The condition results from fibrous replacement of muscle tissue, altering the muscle’s length-tension relationship and disturbing normal shoulder biomechanics.

The condition is encountered predominantly in children and young adults from regions where intramuscular injections in the deltoid are a common practice. Although its incidence has declined with improved awareness and vaccination techniques, deltoid fibrosis remains a significant cause of acquired shoulder deformity in several parts of Asia.

Early recognition is essential because untreated cases can lead to progressive skeletal adaptation and compensatory scoliosis. Surgical release of the fibrotic bands generally restores normal alignment and movement, provided that the diagnosis is made before secondary joint changes occur. The prevalence of the condition varies from very rare in the USA to 10% in Taiwan.

Etiology and Pathophysiology

Deltoid fibrosis most commonly develops following repeated intramuscular injections into the deltoid region during childhood[1]. The underlying mechanism involves localized muscle injury and subsequent fibrotic replacement of muscle fibers, leading to permanent shortening and loss of elasticity.

Relevant Anatomy of the Deltoid Muscle

The deltoid muscle originates from the clavicle, the acromion, and the scapular spine and inserts on the deltoid tubercle on the humerus. It has three parts: anterior, middle, and posterior. The deltoid muscle is the main abductor of the shoulder. The anterior part participates in forward flexion and internal rotation, whereas the posterior portion is involved in extension and external rotation.

Causes of Deltoid Fibrosis

Contractures of the deltoid, in order of frequency, are common in the middle, posterior, and anterior parts. More than one part may be affected simultaneously.

Intramuscular injections, trauma, and congenital factors [1] have been mainly associated with causation. But the exact cause is not known. Studies have suggested that a muscle abnormality may initially exist, making them susceptible to injury and the development of deltoid fibrosis [1].

Injection-Induced Mechanism

When medications such as penicillin, antipyretics, or analgesics are injected repeatedly into the same region, the following sequence of events may occur:

• Chemical or mechanical trauma to muscle fibers.
• Localized myonecrosis due to the toxic effects of drug vehicles or high injection pressure.
• Inflammatory response and fibrosis replace contractile tissue with dense connective tissue.
• Progressive shortening of the fibrotic bands produces a fixed contracture over time.

Children are particularly susceptible because of smaller muscle bulk and increased vulnerability to ischemic injury from intramuscular injections. The posterior and middle portions of the deltoid are most frequently affected, correlating with the common sites of injection.

Other Causes

Although injection-induced fibrosis is by far the most frequent cause, other etiologic factors include:

• Post-traumatic fibrosis following blunt injury or hematoma formation in the deltoid muscle.
• Post-inflammatory myositis, leading to segmental fibrosis.
• Iatrogenic scarring after surgical procedures or deep abscess drainage.
• Idiopathic cases, where no clear inciting factor can be identified.

However, there are reported cases of deltoid fibrosis where there is no history of deltoid injections or trauma.

Development of Deformities

Replacement of normal contractile fibers by inelastic fibrous tissue, which prevents normal elongation of the involved muscle segment during shoulder motion. The functional consequence depends on which part of the deltoid muscle is predominantly affected- anterior, middle, or posterior.

Mechanics of Deformity [2]

Under physiological conditions, coordinated contraction and relaxation of deltoid fibers allow smooth abduction, adduction, and rotation of the arm. When a fibrotic band develops within the muscle, it acts as a non-yielding tether. During adduction, the shortened fibrous segment restricts the descent of the humerus, maintaining the arm in an abducted and externally rotated position.

Chronic imbalance of muscle forces leads to:

• Scapular elevation and lateral rotation as compensatory mechanisms to permit partial adduction. A fibrous band may cause dimpling of the skin.
• Flattening of the head of the humerus and drooping of the acromion may be seen due to constant contracture.
• Altered glenohumeral rhythm, resulting in inefficient shoulder mechanics. [3]
• Secondary postural changes, including compensatory scoliosis on the affected side and prominence of the scapular border.

Patterns of Fibrosis

The clinical deformity correlates closely with the fibers involved:

• Anterior fibers: Arm held in mild flexion and abduction
• Middle fibers (most common): Arm held away from the trunk in abduction
• Posterior fibers: Arm held in abduction and slight extension

Secondary Musculoskeletal Effects [2]

If untreated during growth, the persistent abnormal posture may cause:

• Adaptive remodeling of the scapula and clavicle.
• Contracture of surrounding soft tissues, including fascia and skin.
• Weakness and thinning of uninvolved deltoid segments from disuse.
• Psychological distress due to visible shoulder asymmetry.

The severity of deformity depends on both the extent of fibrosis and the age at onset, with younger children exhibiting greater skeletal adaptation due to ongoing growth.

Clinical Presentation of Deltoid Fibrosis

Deltoid fibrosis typically presents in school-age children or adolescents who are otherwise healthy. The onset is insidious, and parents often notice that one shoulder appears elevated or that the child cannot bring the arm fully to the side of the body. The condition is painless in most cases and may remain unnoticed until cosmetic asymmetry or postural deviation becomes obvious.

Symptoms

• Shoulder adduction restriction: The child cannot rest the affected arm against the trunk; the limb remains abducted by 15°–45°.
• Shoulder asymmetry: The affected shoulder appears higher, with prominence of the deltoid contour.
• Difficulty with activities: Challenges in wearing shirts, sleeping on the affected side, or maintaining posture.
• Discomfort or fatigue: It is felt in the neck and upper back due to compensatory muscle use.

Patient should be enquired about the history of injections, similar contracture in other parts of the body, and a family history of similar contractures.

Physical Findings [2]

On examination, one may notice a dimple over the deltoid skin.

• Fixed abduction deformity is seen along with variable presence of other deformities, depending on the part of the deltoid involved
  • Abducted – Middle portion
  • Flexed and abducted – Anterior portion
  • Extended and abducted – Posterior Portion
• Winging of the scapula on attempted adduction. [2]
• A palpable fibrotic band within the deltoid, most often in the middle or posterior segment.
• Restricted adduction, forward flexion, and extension. Rotation is generally not affected. may be variably affected
• Localized atrophy or flattening of the deltoid contour

In long-standing cases, patients may develop compensatory:

• Lateral tilting of the scapula and spinal curvature toward the opposite side.
• Altered gait and trunk balance when carrying objects.
• Psychosocial concerns related to cosmetic appearance, particularly in adolescents.

In severe cases involving the anterior or posterior parts, the subluxation/dislocation of the humeral head may occur. Examination should also look for high-riding scapula [Sprengel deformity] or other abnormalities like scoliosis or chest wall abnormality.

Motion of the neck, glenohumeral joint, and scapula should be assessed. Look for evidence of contractures elsewhere in both the upper and the lower extremities.

The absence of pain, preserved muscle power, and the presence of a palpable fibrotic band distinguish deltoid fibrosis from paralytic or inflammatory shoulder disorders.

Differential Diagnosis

Because deltoid fibrosis presents as a painless shoulder deformity with restricted adduction, several other conditions must be differentiated clinically.

Congenital Shoulder Dislocation

• Present since birth or early infancy, often associated with other musculoskeletal anomalies.
• Limitation involves multiple planes of motion, not only adduction.
• No palpable fibrotic band within the deltoid.
• Radiographs may reveal malposition of the humeral head relative to the glenoid.

Obstetric Brachial Plexus Palsy (Erb’s Palsy)

• History of birth trauma or shoulder dystocia.
• Characteristic “waiter’s tip” posture with weakness, not fixed contracture.
• Muscle power is reduced in the deltoid and biceps; the passive range of motion is often full.
• Electromyography confirms neurogenic etiology.

Rotator Cuff or Capsule Contracture

• Occurs after shoulder immobilization or inflammation in adults.
• Restriction is global, affecting rotation and elevation, not selective adduction.
• Painful arc is often present, unlike the painless nature of deltoid fibrosis.

Post-Burn or Post-Traumatic Contracture

• Obvious skin scarring, pigmentation, or grafts overlying the shoulder.
• Fibrosis involves the skin and subcutaneous tissue rather than the isolated deltoid muscle.
• Restricted motion corresponds to scar orientation.

Scoliosis or Postural Shoulder Elevation

• Apparent shoulder asymmetry without true limitation of glenohumeral motion.
• Full, symmetrical shoulder movements when tested individually.
• Absence of fibrotic thickening on palpation.

Investigations

The diagnosis of deltoid fibrosis is primarily clinical, supported by a clear history of repeated intramuscular injections and the presence of a localized fibrotic band. However, imaging studies and ancillary tests may assist in confirming the diagnosis, defining the extent of fibrosis, and ruling out alternative causes of shoulder deformity.

Plain Radiography

X-rays are mainly mainly to exclude bony abnormalities such as congenital dislocation, clavicular deformity, or post-traumatic malalignment. X-rays are typically normal. In long-standing cases, subtle secondary changes like scapular tilting or clavicular elevation may be evident.

Ultrasonography

It is non-invasive, inexpensive, and useful for mapping the location and thickness of fibrosis before surgery. High-resolution ultrasound can reveal hyperechoic fibrotic bands within the deltoid muscle.

MRI

MRI provides the most detailed visualization of soft tissue architecture. It demonstrates areas of low-signal intensity representing fibrous tissue, atrophy, and loss of normal muscle architecture in affected segments. Intact glenohumeral and rotator cuff structures, confirming that the pathology is intramuscular. MRI is particularly helpful in surgical planning, especially in recurrent or extensive cases.

Nerve Studies

Electromyography (EMG) and nerve conduction studies are performed when neurogenic weakness or Erb’s palsy is suspected. Findings are typically normal in deltoid fibrosis, supporting a myopathic mechanical contracture rather than a neuropathic origin.

Histopathology

It is rarely necessary, but when done, it shows dense collagen deposition and atrophic residual muscle fibers. and absence of inflammatory infiltrate, confirming post-traumatic fibrosis rather than active myositis.

Treatment

The management of deltoid fibrosis depends on the severity of deformity, functional limitation, and extent of fibrosis. While mild cases may be managed conservatively, established contractures almost always require surgical release to restore normal shoulder contour and function.

Conservative Management

Conservative treatment has a limited role and is suitable only for mild, non-progressive deformities or early cases in young children.

Conservative management includes

• Stretching exercises
• Gentle passive and active-assisted adduction exercises
• Focus on improving scapulothoracic coordination and preventing secondary postural changes.

Surgical Management

Indications

• Persistent functional limitation or cosmetic deformity.
• Fixed abduction deformity >20–30°.
• Failure of conservative management.
• Age> 5 years
• Progressively increasing contracture
• Painful contracture

Procedure

Several approaches have been described, with selection depending on the location of the fibrotic band. If more than one portion of the deltoid is involved, releasing the entire deltoid tendon provides better results. The fibrotic tissue is identified and released [4], ensuring preservation of viable muscle and the axillary nerve. Adduction is tested intraoperatively to confirm complete release.

Postoperatively, the arm is immobilized in adduction for 10–14 days using an adduction sling or body bandage. Physiotherapy begins after wound healing. The emphasis is on maintaining full adduction and scapular stabilization during rehabilitation.

Complications

• Incomplete release resulting in residual deformity.
• Axillary nerve injury if the dissection extends too medially.
• Hematoma formation or wound infection.
• Recurrence (rare) due to incomplete excision of fibrotic tissue.

Outcomes

With complete release and adequate postoperative physiotherapy, the shoulder symmetry and full range of motion are usually restored. Recurrence is uncommon, and long-term prognosis is excellent. Early intervention in growing children prevents secondary skeletal adaptation.

Prognosis

The prognosis of deltoid fibrosis is generally excellent, particularly when the diagnosis is made early and surgical release is performed before secondary skeletal or postural adaptations occur. The outcome depends on several factors, including the extent of fibrosis, duration of deformity, and quality of postoperative rehabilitation.

Psychological satisfaction is high due to the visible correction of deformity and restored normalcy in posture and movement.

Factors Associated with Suboptimal Outcome

• Delayed presentation beyond adolescence.
• Extensive fibrosis involving multiple muscle segments.
• Secondary joint stiffness from prolonged abnormal posture.
• Poor compliance with postoperative physiotherapy.

With appropriate surgical management and rehabilitation, deltoid fibrosis remains one of the most gratifying conditions to treat, offering near-complete reversal of deformity and restoration of shoulder symmetry.

Prevention

Deltoid fibrosis is a preventable condition, and its near disappearance in regions with improved healthcare practices underscores the importance of preventive measures. The key lies in avoiding the primary cause, repeated or improper intramuscular injections into the deltoid region, especially during childhood.

Safe Injection Practices

• Avoid deltoid injections in children under five years of age, where muscle mass is insufficient to absorb injected volume safely.
• Prefer the anterolateral thigh (vastus lateralis) or gluteal region for intramuscular drug delivery in pediatric patients.
• Use appropriate needle size and depth, ensuring that injections are placed within the muscle belly rather than subcutaneously or too superficially, which increases risk of local necrosis.
• Rationalize the use of intramuscular medications—opt for oral or intravenous routes when feasible.

Proper Technique and Asepsis

• Employ trained personnel for administration to prevent chemical or mechanical trauma to muscle fibers.
• Maintain aseptic precautions to avoid localized inflammation or abscess formation, which may trigger fibrosis.

References

1. Banerji D, De C, Pal AK, Das SK, Ghosh S, Dharmadevan S. Deltoid contracture: a study of nineteen cases. Indian J Orthop. 2008 Apr;42(2):188-91. [PubMed]
2. Vadapalli S. Anterior Dislocation of the Shoulder Due to an Idiopathic Deltoid Contracture-the Report of a Rare Presentation. J Clin Diagn Res. 2013 Feb;7(2):371-3. [PubMed]
3. Kibler WB, Sciascia A, Wilkes T. Scapular dyskinesis and its relation to shoulder injury. J Am Acad Orthop Surg. 2012 Jun. 20(6):364-72. [PubMed]
4. Chen WJ, Wu CC, Lin YH, Shih CH. Treatment of deltoid contracture in adults by distal release of the deltoid. Clin Orthop Relat Res. 2000 Sep. (378):136-42. [PubMed]