Fractures of the Sacrum: Classification, Clinical Picture, Diagnosis and Treatment

The sacrum is a triangular bone of five fused vertebrae, located between the two pelvic bones. The upper part connects to the fifth lumbar vertebrae and the lower part to the coccyx.

Fractures of the sacrum can range from simple, stable injuries to complex, unstable, and potentially neurologically dangerous fractures (neurologic complication rates as high as 25%).

Etiology

Fractures of the sacrum occur for a variety of reasons, including non-traumatic ones:

1. High-energy trauma: motor vehicle accidents, falls from significant heights.
2. Low-energy trauma: especially in elderly patients with osteoporosis or metabolic bone disease.
3. Pathologic fractures: due to tumor infiltration or prior radiation therapy.
4. Stress fractures: seen in athletes due to repetitive stress.

There are two main mechanisms of damage:

1. Direct trauma: a severe blow to the pelvis or lower back.
2. Indirect injury: due to the applied traumatic force transmitted through the femur to the pelvis at the time of injury.

Fractures of the sacrum are often associated with pelvic ring injuries and may be combined with fractures of the lumbar spine or acetabulum.

Epidemiology

Fractures of the sacrum usually occur as part of a complex of pelvic ring injuries (30-45% of cases). Often, sacral fractures occur in two heterogeneous groups of patients:

1. Young people exposed to high-energy trauma (e.g., motor vehicle collisions).
2. Elderly people, especially women, as a result of low-energy trauma (as a complication of the course of osteoporosis).

Classification of sacral fractures

There are several classification systems, but the most widely used is the Denis classification, based on anatomic location in relation to the sacral neural foramen.

Classified by Denis

This classification divides sacral fractures into three anatomical zones, damage in each of which has its own risks and peculiarities.

Anatomical classification of sacral fractures according to Denis

3D models of sacral fractures:

Fracture of the sacrum, zone 1 (Denis classification)

Fracture of the sacrum, zone 2 (Denis classification)

Fracture of the sacrum, zone 3 (Denis classification)

Fractures in the third zone can be either longitudinal or transverse. In turn, fractures in the third zone can be divided into 4 types:

• Type 1 – only kyphotic deformity at the fracture site (no displacement).
• Type 2 – kyphotic angular deformity with anterior displacement of the distal sacrum.
• Type 3 – kyphotic angular deformity with complete displacement of broken fragments.
• Type 4 – S1 segment splinter fracture (results from axial compression).

For fractures in the third zone, there is also a morphologic classification based on the shape of the fracture lines:

• H-shaped;
• ʎ-shaped;
• T-shaped;
• U-shaped.

Thus, a U-shaped fracture resulting from an axial impact on the sacrum resulting in spinopelvic dissociation with concomitant damage to neurologic structures, according to the Denis classification, is a fracture in the third zone of the fourth type.

In fractures involving the lumbosacral junction, the Isler classification is applicable. According to the classification, there are 3 types of fractures:

• Type 1 – the fracture line runs lateral to the articular surfaces of L5-S1.
• Type 2 – the fracture line passes through the articular surface of L5-S1.
• Type 3 – the fracture line runs medial to the articular surface of L5-S1.

Thus the Isler classification can be used to describe fractures in the second zone in detail (Denis classification).

Diagnosis of sacral fractures

Diagnosis of sacral fracture is based on clinical evaluation and radial examination techniques.

Clinical evaluation

1. History: trauma or fall, low back or pelvic pain.
2. Manual examination: localized soreness, swelling, sacral deformity, bruising, pain during pelvic manipulation, possible neurologic abnormalities (e.g., weakness, numbness), vaginal examination in women to rule out overt trauma, rectal examination.

Radiation methods of research

1. Radiography: may not detect sacral fractures, especially if they are not displaced (sensitivity of the method is 30%).
2. CT (computed tomography): the gold standard, reveals the nature of the fracture, displacement and nerve involvement.
3. MRI (magnetic resonance imaging): useful in the context of evaluating nerve or soft tissue injuries and in the diagnosis of stress fractures.

Clinical Manifestations

Typical clinical presentation of a sacral fracture:

1. Pain: localized in the lower back, buttocks or pelvis, increases with movement or weight lifting.
2. Swelling and bruising in the projection of the sacrum.
3. Neurologic signs: may include numbness, weakness, bowel or bladder dysfunction (occurs with sacral nerve injury, usually with fractures in zones 2 and 3).
4. Associated injuries: pelvic ring rupture, lower extremity fractures, internal organ injuries.

Treatment of sacral fractures

Conservative treatment

The methodology for conservative treatment of a sacral fracture is as follows:

1. Pain control with analgesics.
2. Bed rest and limited body weight bearing with gradual progression to mobilization with crutches or support canes.
3. Physical therapy to restore mobility in adjacent joints and muscle strength.

Indications for conservative treatment are:

1. Stable fractures (without displacement and with displacement up to 1 cm, isolated, without neurologic deficit).
2. Stress fractures in patients with osteoporosis without displacement.
3. Absence of concomitant pelvic ring instability.

Most low-energy stable fractures consolidate well when treated conservatively.

Surgical treatment

The technique for surgical treatment of the fracture is as follows:

1. Open repositioning and internal fixation (ORIF): plates, screws, sacroiliac and lumbopelvic fixation.
2. Percutaneous fixation of the iliosacral joint with screws.
3. Decompression: with concomitant neurologic pathology.

Indications for surgical treatment are:

1. Unstable fractures or fractures associated with pelvic ring rupture.
2. Displaced fractures greater than 1 cm.
3. Neurologic deficit due to compression of nerve roots or cauda equina (usually in zone 2 and 3 fractures).
4. Patients with open fractures or multiple injuries who require early mobilization.

Timely surgical treatment aims to stabilize the pelvis, relieve neurological compression, and allow for early active rehabilitation.

Prognosis in sacral fracture

The prognosis after sacral fracture is multifactorial and depends primarily on the anatomic type of fracture and the treatment strategy chosen.

Conservative treatment of sacral fracture is generally excellent for type 1 fractures, as well as some type 2 fractures. Long-term complications are rare, but some patients may experience chronic pain syndrome.

Surgical treatment achieves fracture stability and reduces the risk of nonunion of the bone fragments. Surgical treatment, in turn, also carries risks in the form of infectious complications, fracture or metal migration. Infection in the surgical area and migration of the metalwork in turn significantly increase the risk of non-union of the fracture. Treatment of fractures in zone 3 is usually surgical. Early decompression may improve outcomes if neurologic symptoms are present. However, persistent neurologic impairment is common.

Thus, for zone 1 fractures, most patients return to baseline activity level with good results. Zone 2 fractures may have long-term sensory and motor impairment in the lower extremities, but many patients return to full activities of daily living with a structured rehabilitation program. In Zone 3 fractures, 60% of patients may have persistent neurological impairment, usually related to bowel, bladder or sexual function.

Metabolic disorders of bone tissue, such as osteoporosis, are an unfavorable prognostic factor because of the risk of delayed and incomplete fracture union. Associated injuries to bony and soft tissue structures also have a negative impact on the prognosis of trauma outcome. Early surgical intervention, in the presence of neurologic deficits, is the key to achieving optimal treatment outcomes.

Summary data on rehabilitation potential and prognosis after sacral fracture of different localizations

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Rehabilitation after a sacral fracture

Rehabilitation after a sacral fracture is highly individualized. The type and severity of the fracture, the presence of neurologic impairment, surgical interventions and patient-related factors (age, comorbidities) influence the pace and focus of rehabilitation.

Rehabilitation measures are aimed at healing the fracture, restoring mobility, preventing complications, and eliminating and treating neurological disorders, if any.

Summary of the phases of rehabilitation after sacral fracture

1. Rehabilitation after conservative treatment (stable fractures)

Rehabilitation after stable fractures of the sacrum, which are treated using conservative methods, consists in strict limitation of limb loading up to 2 weeks from the date of injury. From the second week, squatting is allowed within the bed under pain control. During 3-4 weeks, verticalization with the help of auxiliary devices is allowed.

Physical exercises are aimed at maintaining and restoring the strength of the muscles of the lower limbs and cortex. Exercises with a high impact load on the lower limbs should be avoided and closed circuit exercise machines (exercise bikes) should be chosen as cardio exercises. Stretching is also an integral part of rehabilitation.

2. Rehabilitation after surgical treatment (unstable fractures)

Displaced or unstable fractures require surgical treatment. Rehabilitation measures in the early postoperative period include protection of the synthesized sacrum. The allowable limb support is determined by the stability achieved and the type of fusion used.

In order to prevent the formation of contractures of the joints of the lower limbs, exercises within the bed without the use of weights are indicated. Gradual mobilization, verticalization with the help of auxiliary orthopedic devices under pain control.

Progression of loading begins at 6-12 weeks, if there is radiological confirmation of the beginning of fracture consolidation. Subsequently, training is aimed at stabilization and normalization of gait, return to daily activity, work and sports.

3. Neurorehabilitation (for persistent neurological disorders)

In persistent neurological disorders, neurorehabilitation is an important aspect of recovery. Neurorehabilitation includes both physiotherapy and occupational therapy. It is important to strengthen the muscles not affected by the pathologic process and prevent decubitus ulcers in areas with impaired sensitivity. Assistive orthopedic devices should be used for mobility. Training in bowel and bladder function regulation may be required. Functional electrical stimulation is sometimes used to improve muscle activation in partially denervated muscles.

Patient education is essential to adherence to the recovery regimen. Early, structured rehabilitation aimed at restoring mobility, strength and functional independence provides the best results, especially when coordinated by a multidisciplinary team of specialists.