Imaging diagnosis
Case 86
【Progress】
She received intramuscular injection of analgesic agent at the painful sites several times, reducing pain.
【Discussion】
In shoulder joint, dislocation or sublocation of humerus head most occurs forward and downward (1). When this happens or the humeral head comes to return to the right position, it can occur that the lateral posterior side of humeral head and the anterior lower glenoid labium are injured at the same time. Namely, the anterior glenoid labium impacts the lateral posterior humeral head. The injury (cortical depression or compression fracture) of the humeral head is called Hill-Sachs lesion and the injury of the lower glenoid labium is called Bankart’s lesion. Hill-Sachs lesion is reported to be present in 40 to 90% of patients with repeated subluxation or dislocation, called shoulder instability (2, 3).
The dislocation usually occurs when the arm is pulled to upwards and outwards. Once the dislocation occurs, 70% of the patients experience the repeated shoulder dislocation probably because the ligaments and the capsules to support the joint are easily damaged and become weakened (1-3). The repeated dislocation gradually makes the humeral head flattening, falling into a loose shoulder which is known to dislocate even while sleeping (1-3). In fact, our patient experienced the worsening of shoulder pain when turning over in bed at night.
The shoulder joint is composed of humeral head and socket (glenoid) with labrum and is protected or covered with capsule, ligaments and muscles (4, 5). As the ligaments, superior glenoid humeral ligament, middle glenoid ligament and inferior glenoid ligaments are listed. As the muscles, supraspinatus, infraspinatus, teres minor and subcapularis are listed. When anterior inferior dislocation of the shoulder joint occurs, not only Hill-Sachs lesion and Bankart lesion are found, but also the injury of inferior glenoid humeral ligament can occur.
MRI protocols listed for articular cartilage and ligaments including shoulder joint are T1WI, T2WI, fat suppression T2WI and proton density WI (5, 6). T1WI produces the high signal-to-noise ratio, useful in showing muscular-skeletal anatomy. T2WI and fat suppression T2WI have the poorest signal-to-noise ratio but useful in showing edematous lesion such as tendon or ligament tear and tumor. Proton density WI produces the highest signal-to-noise ratio, providing better resolution than T2WI and is useful in showing anatomical details, especially excellent evaluating regions obscured by high signal intensity on T2WI (6). In our case, proton density WI is useful in showing Bankart lesion and fat suppression T2WI is useful to show Hill-Sachs lesion.
【Summary】
We present a fifty nine-year-old female suffering from left shoulder pain, which getting worsened even while sleeping at night. MRI with proton density WI and fat suppression T2WI showed defect of inferior glenoid labrum and injury of posterior-lateral site of the humeral bone, called Bankard lesion and Hill-Sachs lesion, respectively. It is borne in mind that shoulder joint dislocation most occurs forwards and downwards, inducing Bankard lesion and Hill-Sachs lesion. Further, inferior glenoid humeral ligament can be damaged when severe dislocation occur, which was not in our case.
【References】
1.Calandra, Joseph. "The incidence of Hill-Sachs lesions in initial anterior shoulder disloactions". The Journal of Arthroscopic & Related Surgery. 1989; 5 (4): 254–257. PMID 2590322. doi:10.1016/0749-8063(89)90138-2. Retrieved 11 May 2014.
2.Taylor DC, et al. "Pathologic changes associated with shoulder dislocations. Arthroscopic and physical examination findings in first-time, traumatic anterior dislocations". Am J Sports Med. 1997;25 (3): 306–11. PMID 9167808. doi:10.1177/036354659702500306.
3.Calandra JJ,et al. . "The incidence of Hill-Sachs lesions in initial anterior shoulder dislocations". Arthroscopy. 1989; 5 (4): 254–7. PMID 2590322. doi:10.1016/0749-8063(89)90138-2.
4.Pancione L, et al. "Diagnosis of Hill-Sachs lesion of the shoulder. Comparison between ultrasonography and arthro-CT". Acta Radiol. 1997; 38 (4): 523–6. PMID 9240671. doi:10.1080/02841859709174380.
5.Kirkley A, et al. "Agreement between magnetic resonance imaging and arthroscopic evaluation of the shoulder joint in primary anterior dislocation of the shoulder". Clin J Sport Med. 2003;13 (3): 148–51. PMID 12792208.
6.Horst K, et al. Assessment of coincidence and defect sizes in Bankart and Hill-Sachs lesions after anterior shoulder dislocation: a radiological study. Br J Radiol. 2004;87 (915): 20130673.
2017.12.27