bubble_chart Overview

Acute simple traumatic lumbocrural pain mainly involves injuries to the ligaments and bones of the spine, with muscles rarely affected. Mild vertebral compression fractures or articular process fractures are often overlooked due to minor trauma or inconspicuous symptoms, leading to chronic lumbocrural pain. Over 90% of acute simple traumatic spinal lumbocrural pain occurs in the lumbosacral and sacroiliac joints, with lesions sometimes appearing in one location or simultaneously in both. Therefore, simple traumatic spinal lumbocrural pain can be further classified into three types: lumbosacral joint injury, sacroiliac joint injury, and combined lumbosacral and sacroiliac joint injuries.

bubble_chart Pathological Changes

The lumbosacral joint serves as the pivotal structure of the upright human spine, acting as a transitional zone where the mobile lumbar vertebrae transform into the fixed sacrum, and the anteriorly convex lumbar spine shifts to the posteriorly convex sacrum. It functions as a bridge transferring trunk dynamics to the lower limbs through the sacroiliac joint and ilium. Consequently, the lumbosacral region is more susceptible to external forces than other areas. To counteract these adverse effects and maintain the stability of the lumbosacral joint, this region is reinforced with numerous ligaments of varying depths and positions, such as the anterior and posterior longitudinal ligaments, joint capsule, lumbosacral and sacroiliac ligaments, supraspinous and interspinous ligaments, and ligamentum flavum. These ligaments may suffer sprains or tears under heavy impact or external force, and may even lead to articular process fractures.

The movement of the lumbosacral joint primarily involves flexion, extension, and lateral bending, with limited rotation. The orientation of the inferior articular processes of the fifth lumbar vertebra and the superior articular processes of the first sacral vertebra varies—some are parallel to the sagittal plane of the body, allowing greater flexibility in spinal flexion, extension, lateral bending, and rotation. Others align with the coronal plane, restricting lateral bending and rotation. In some individuals, asymmetry between the bilateral joints results in uncoordinated movement direction and range, which is one reason why the lumbosacral joint is prone to sprains.

When the human body bends forward while carrying a heavy load, and the back extensor and gluteus maximus muscles cannot sufficiently counteract the external force, part of the force may be transmitted to the ligaments of the lumbosacral joint, causing ligament sprains or tears, or even leading to articular process fractures. Forces from the side or oblique angles are often not absorbed and instead transmitted to the sacroiliac and lower limb joints, potentially resulting in ligament sprains or tears.

The sacroiliac joint surface is ear-shaped and uneven, formed by the first, second, and third sacral vertebrae and the ilium. The sacral vertebrae are larger superiorly and smaller inferiorly, wider anteriorly and narrower posteriorly, preventing downward or backward displacement but predisposing to forward, rotational, or lateral displacement. Stability is maintained by robust ligaments such as the sacroiliac, sacrotuberous, and sacrospinous ligaments, preventing the sacrum from shifting into the pelvis. These ligaments vary in direction, length, and complexity, and combined with the uneven sacroiliac joint surface, even slight displacement can lead to joint incongruity, partial ligament sprains or tears, and significant low back and leg pain.

During late pregnancy, hormonal imbalances can loosen the ligaments around the sacroiliac joint, reducing its stability and causing low back and leg pain. Prolonged bed rest, constitutional weakness, or general/spinal anesthesia may also relax these ligaments, leading to similar symptoms. Rotational, oblique, or lateral forces acting on the body must pass through the sacroiliac joint to reach the lower limbs. If these forces are not buffered or absorbed, the sacroiliac joint may suffer a sprain. Due to the complexity of force direction and nature, a single patient may simultaneously experience sprains in both the lumbosacral and sacroiliac joints—a critical consideration in diagnosis.

bubble_chart Clinical Manifestations

(1) Spontaneous lumbago and leg pain When a sprain occurs, the patient suddenly experiences back pain—sharp and intense, with clear localization, allowing the patient to pinpoint the exact painful area, which aids in diagnosis. Sometimes, after the sprain, the patient may feel a crisp snapping sound or a tearing sensation, followed by a reduction in pain. In other cases, the pain may not be obvious at the time of the sprain but worsens after rest or upon waking the next day. The lower back becomes stiff, movement becomes difficult, and the back muscles may spasm, even radiating pain to the posterior thigh, causing leg pain.

(2) Local tenderness In the early stages of a sprain, most patients exhibit localized tender points, which assist in diagnosis. Occasionally, due to spasms of the piriformis muscle compressing the sciatic nerve trunk, the tender point may be located at the sciatic notch, where the sciatic nerve exits.

(3) Radiating or referred neuralgia The areas affected by radiating or referred neuralgia are typically the buttocks, posterior thigh, and the anteromedial region of the thigh root—areas innervated by the posterior femoral cutaneous nerve and the sciatic nerve. There are three reasons for such neuralgia:

1. The ligaments, muscles, and other soft tissues around the lumbosacral and sacroiliac joints are innervated by the posterior branches of the 4th and 5th lumbar nerves and the sacral nerves, while their anterior branches form the sciatic nerve and the posterior femoral cutaneous nerve. Thus, reflexive neuralgia often occurs.

2. The sciatic nerve and posterior femoral cutaneous nerve bundles lie close to the anterior aspect of the sacroiliac joint and the piriformis muscle. When ligaments in this area bleed or develop edema due to a sprain, the nerves are directly irritated, causing radiating neuralgia. If the piriformis muscle spasms, it can also compress the sciatic nerve trunk, leading to radiating neuralgia and localized tenderness at the sciatic notch.

3. If soft tissues around the intervertebral foramen swell after a sprain, the sciatic nerve roots may be directly compressed within the foramen, resulting in radiating sciatica.

(4) Spasms of the back extensors or gluteus maximus Many patients experience spasms in one or both sides of the back extensors or gluteus maximus after a sprain. These spasms are particularly noticeable when standing or bending forward and may ease when lying prone. During tenderness examination, the muscle spasms immediately recur, which aids in diagnosis.

(5) Scoliosis More than half of the patients develop scoliosis of varying degrees. The direction of the curvature is related to ligament sprains, tears, and nerve irritation or compression. Scoliosis serves to alleviate pain from sprained or torn ligaments and reduce symptoms of nerve irritation or compression. The presence, direction, and severity of scoliosis depend on the pathological changes in the nerves and ligaments. {|107|}

bubble_chart Treatment Measures

If the sprain is severe and small fractures such as articular processes are found during examination, it should be treated as a fracture.

If it is only a tear of the tendon or ligament, bed rest for 3 to 6 weeks is required. Since the repair of ligaments and other soft tissues, the dissipation or absorption of hematomas, and the recovery of muscle and ligament function take 3 to 6 weeks, vigorous tuina tuina should not be performed during this period, but appropriate physical therapy can be administered to aid recovery.