Ulnar impingement syndrome, subacromial impingement syndrome, a clear text!

Ulnar impingement syndrome

Ulnar pain of the wrist joint is more common clinically, and injuries to the bone and cartilage, ligament structure, tendons and nerves of the ulnar wrist can cause ulnar pain symptoms of the wrist, and wrist impingement syndrome is one of the common causes, including ulnar impingement syndrome, ulnar crush syndrome, ulnar styloid impingement syndrome, ulnar wrist impingement syndrome secondary to ulnar styloid disconnection and hook-moon impingement syndrome
.

Ulnar impingement syndrome, also known as ulnar impingement syndrome, occurs when the ulnar head strikes the ulnar head and the ulnar wrist, that is, between the ulna and the triangular fibrocartilage complex (TFCC), the lunar bone, and the triangular bone
.

Most common in patients with positive ulna variation, and occasionally in patients with ulnar neutral variation or negative ulna variation
.
The most common predisposing factors include congenital positive ulna variation, premature closure of the distal radial epiphysis, malunion of distal radius fractures, Essex-Lopresti fractures, and previous radial head resection
.

These factors lead to the relative length of the ulna or an increase in the degree of dorsitime tilt of the distal radius, causing excessive ulnar load on the wrist joint, which leads to the occurrence of ulnar wrist collision syndrome, causing a series of pathological changes, including triangular fibrocartilage (TFC) degenerative injury (Palmer type II injury), malacia of the lunar, triangular and ulnar head cartilage, tear of the lunar triangle ligament, and eventually lead to distal radial ulnar joint and ulnar wrist
。

In addition, in patients without significant ulnar radius structural abnormalities, ulnar impingement syndrome may be due to
intermittent overload of the ulnar wrist.

The main clinical manifestations are ulnar pain in the wrist joint, and the symptoms are aggravated when the ulna variation is relatively increased with forceful grasping, forearm pronation, or ulnar deviation of the wrist joint, and it is aggravated during activity and relieved
at rest.

Imaging findings: typical findings on standard posteroanterior (shoulder abduction 90°, elbow flexion 90°, wrist neutrality) include positive ulnar variation, occasionally neutral ulnar variation or negative ulnar variation, and other factors contributing to relatively long ulnar or increased dorsicity tilt at the distal radius, such as deformity healing of distal radius fractures (figure 1); Sclerosis and subchondral capsular changes on the ulnar surface of the proximal lunar bone, radial side of the proximal triangular bone, and ulnar head (Fig.
1, 2).

Fig.
1 Ulnar impingement syndrome
secondary to malunion of distal radius fracture.
Female, 66 years old, right wrist joint pain
after healing from fracture of distal radius on the right side.
Orthographic x-ray of the wrist joint showed that the distal radius fracture was deformed and healed, followed by relatively long ulna, positive variation of the ulna, and osteosclerosis changes on the ulnar side of the proximal lunar bone (↑)

Fig.
2 Ulnar impingement syndrome
caused by positive ulnar variation.
Male, 48 years old, right wrist joint pain
.
Positive ulna variation on wrist x-ray, osteosclerosis cyst on ulnar flank proximal lunar bone (↑)

CT can show subtle changes in bone structure more clearly than x-rays; Ulnar wrist osteoarthritis changes
may be seen in advanced stages.
MRI is helpful in showing occult lesions, TFC, and damage to the lunar delta ligament, typically including ulnar flank of the proximal lunar bone, radial side of the proximal delta bone, ulnar bone marrow edema, articular surface sclerosis, articular cartilage defect, subchondral capsular change, TFC morphological irregularity, thinning, perforation (Fig.
3, 4), some patients may have a lunar delta ligament tear, and late presentation of ulnar wrist osteoarthritis
.

Figure 3, 4 Ulnar impingement syndrome
.
Female, 56 years old, with ulnar pain
in the left wrist joint.
Images of wrist coronal T1WI (Fig.
3) and proton density-weighted fat suppression sequence (Fig.
4) show positive variation of ulna, malocconacia of the ulnar flank and ulnar head of the lunar bone, and changes in subchondral bone marrow edema (↑); Proton density-weighted fat inhibition sequences clearly show significant thinning of triangular fibrocartilage (Fig.
4 Long↑) and lunar delta ligament injury (Fig.
4▲)

A common differential diagnosis of ulnar impingement syndrome: Kienböck′s disease
.
In Kienböck′s disease, abnormal signals in the lunar bone are more diffuse or predominantly involve the radial side of the lunar bone (Figures 5, 6), while in ulnar impingement syndrome, abnormal signals in the lunar bone involve the ulnar flank
of the lunar bone.
In addition, in Kienböck′s disease, the ulna and triangular bones are usually not affected
.

Figure 5, 6 Kienböck′s disease
.
Female, 32 years old, left wrist joint pain
.
Images of wrist coronal T1WI (Fig.
5) and proton density-weighted fat suppression sequence (Fig.
6) show negative variation of ulna, diffuse inhomogeneous T1WI low signal in the lunar bone, and uneven high intensification (↑) in fat suppression sequence, which is different
from ulnar impingement syndrome, which mainly affects the ulnar flank of the proximal lunar bone.

Additional content:

Kienböck's disease, or aseptic necrosis of the lunar bone, is one of the main causes of
wrist pain.
It is more common in young and middle-aged male manual workers aged 20-40, and most of them are unilateral disease; Begins with ischemic necrosis of the lunar bone, secondary to synovitis and traumatic arthritis; Late stage results in reduced grip strength, intractable wrist pain, and loss of
function.

Subacromial impingement syndrome

Shoulderimpingement syndrome (SIS) refers to the friction, compression and impact of the rotator cuff, bursa, labrum and other structures during forward flexion, abduction and other activities of the shoulder joint, causing inflammation and injury, shoulder pain, mobility disorders and other clinical symptoms
.

Generalized shoulder impingement syndrome mainly includes subacromial impingement syndrome, subcoracoid impingement syndrome, and internal impingement syndrome; Shoulder impingement syndrome in the narrow sense refers specifically to subacromial impingement syndrome
.

Literature reports that 44%~65% of shoulder pain is caused
by subacromial impingement syndrome.
The impact occurs in the subacromial space, the upper boundary of which is the coracoidal shoulder arch composed of the acromion, coracoid process, coracoidal shoulder ligament and acromioclavicular joint, and the lower boundary is the humeral head and large tubercles, and the space contains structures such as the supraspinatus tendon, the biceps longus tendon, and the subacromial capsule
.
A variety of reasons can lead to absolute or relative narrowing of the subacromial space, when the shoulder joint is lifted and abducted, the soft tissue structure between the coracoidal shoulder arch and the humerus is squeezed and impacted, causing corresponding clinical symptoms
.

Common causes can be divided into primary and secondary causes, sometimes both
.

For patients with suspected subacromial impingement syndrome:

Radiographic findings can be divided into etiological signs and impact-related injuries
.

1.
Etiological signs:

(1) Amicromion
.

The acromion morphology is generally assessed on supraspinatus outlet radiographs (figure 1) or on the oblique sagittalittal plane of CT/MR, which is typically the first image
of the lateral acromioclavicular joint.

The acromion morphology is divided into 4 types, type I is flat, type II is bowed, type III is hooked, and type IV.
is convex downward anti-arch, of which type III acromion is the most likely to cause subacromial impact (Fig.
2, 3).

The normal acromion inclined approximately horizontally or slightly anteriorly upward, and the anterior-downward or outward-lower sloping acromion and low average acromion may result in a narrow subacromial space (Figure 4).

Subacromial bone spurs often indicate the presence of a long-term chronic impact (figures 5, 6).

Fig.
1 X-ray to evaluate acromion morphology
.
X-rays of the outlet position of the supraspinatus muscle show that the anterior part of the acromion is hook-shaped (↑), which is a type III acromion
.

Fig.
2, 3 MR image
of type III acromion with subacromial impingement syndrome.
Shoulder joint MR sweeps oblique sagittal plane

Figure 4 MR image
of shoulder tilt.
Shoulder MR sweep oblique sagittal plane T1WI shows that the anterior acromion is sloping forward and downward (↑), and the subacromial space is narrow

Fig.
5,6 MR image
of subacromial bone spur with subacromial impingement syndrome.
Shoulder MR sweep oblique coronal T1WI (Fig.
5) and adipotope T2WI (Fig.
6) show hyperplasia of osteophytes at the inferior edge of the acromion (↑), narrowing of the subacromial space, thickening of the supraspinatus tendon, increased signal (△), and subacromial-subdeltoid cyst effusion

(2) Acroclavicular joint
.

Acroclavicular joint degeneration may present with hyperostosis with lower margin spur formation, joint effusion, joint capsule thickening, and possible impact
with the rotator cuff.

(3) Kerracoid-shoulder ligaments
.

Thickening and calcification of the coracoid-shoulder ligament is best shown in the oblique sagittal plane, where bone spurs may form at the acromion attachment and the tip points to the coracoid process (Figures 7, 8, 9).

Fig.
7 X-ray
of acromion bone spur.
Supraspinatus exit position, anterior inferior edge of acromion, bone spurs at the attachment of the coracoidal shoulder ligament (↑)

Figure 8,9 MR image
of bone spurs with subacromial impingement syndrome at the attachment of the coracoidal shoulder ligament.
Shoulder joint MR sweep oblique sagittal plane T1WI (Fig.
8) showed bone spur formation at the acromial attachment of the coracoid shoulder ligament (↑), narrowing of the subacromial space, oblique coronal fat inhibition T2WI (Fig.
9), increased signal of the superior supraspinal tendon, discontinuity of bursa surface fibers (↑), subacromial-deltoid subcapsular effusion, synovial hyperplasia

(4) Amicion ossicles
.

Acapromial subossification center usually completed ossification at the age of 22~25, if the ossification center does not heal as expected, the unhealed part is called acromion ossicle, the best observation on the X-ray axillary axis or CT/MR cross-section, sometimes the "double acromioclavicular joint sign" can be seen on the supraspinatus outlet position or the oblique sagittal plane of CT/MR (Fig.
10, 11, 12).

The acromion ossicles can be unstable, and spurs may form at the cartilage junction or at the lower edge of the pseudoarticular, causing impact
with the rotator cuff.
On MRI, the presence of liquid hyperintensity at the junction of cartilage often indicates acromion ossicle instability
.
Sclerosis may also occur at the junction of cartilage, subchondral cysts, and bone marrow edema
.

Fig.
10,11 X-ray of acromion
ossicles.
The axillary axis (Fig.
10) shows a translucent line shadow of the acromion, the edge is slightly hardened, and its walk is roughly perpendicular to the acromioclavicular joint (↑), which is considered to be acromial ossicles; Supraspinatus outlet (Fig.
11) shows "double acromioclioclavicle sign" (↑)

Fig.
12 MR image
of acromion ossicles.
Shoulder joint MR sweep cross-sectional fat inhibition T2WI showed acromion ossicle, its cartilage junction is hyperintense (↑), and cystic changes can be seen at the distal end of the clavicle

(5) Subacromio-humeralinterval (AHI).

The width of AHI varies from person to person, and it is currently believed that the smaller the AHI, the higher
the probability of impact.
Several studies have found that the diagnosis of subacromial impingement syndrome and rotator cuff injury is high
when AHI is < 7mm.

However, it has been reported in the literature that AHI is related to shoulder joint position and muscle activity, and the minimum AHI value decreases with the increase of shoulder abduction angle, and the load is applied at different abduction angles, and the AHI value when the abductor muscle contracts is smaller than the AHI
when the adductor muscle contracts.
Therefore, functional MRI may be more helpful in finding the cause
of subacromial impingement.

2.
Impact-related damage:

(1) The most common injury is the injury of the rotator cuff tendon, especially the supraspinatus tendon
.

Edema and inflammation of rotator cuff tendons are manifested in MR as:

(2) Often accompanied by subacromial-deltoid subdeltoid bursitis, bursa effusion and synovial thickening
can be seen.

(3) It can be accompanied by injuries to structures such as the labrum, biceps longitos, tendons, etc.
, but it is relatively rare
.