Imaging Diagnosis of Tumors and Tumorlike Conditions of the Shoulder

Abstract

Anatomic compartments are defined by natural barriers that also limit the spread of a tumor [1]. Local staging of a malignancy depends on which anatomic compartments are involved and this determination is best accomplished with cross-sectional imaging, preferably magnetic resonance imaging (MRI). Although several staging systems exist, they are all based on the histologic grade of the tumor, the local extent of the lesion, and the presence of metastases. Regarding local extent, lesions confined to one specific compartment are considered intracompartmental. Extracompartmental lesions have spread beyond the compartment of origin [1]. Another consideration requiring knowledge of compartmental anatomy is planning a biopsy path. Resection of the biopsy track is no problem if an amputation is performed but may cause significant difficulties in the case of limb-salvage procedures if inappropriately placed. The radiologist must have a clear understanding of the relevant compartmental anatomy for staging a tumor and avoid unnecessarily contaminating uninvolved anatomic compartments during biopsy. When biopsying a bone or soft-tissue tumor it is advisable to discuss your biopsy approach with the surgeon performing the resection. Failure to do so may result in the biopsy tract within an anatomic region needed for limb-sparing surgery. Different compartments specific to the upper extremity and shoulder include the muscles and fascia covering the dorsal scapula (infraspinatus, teres minor, and rhomboid muscles), the supraspinatus and deltoid compartments, and the anterior and posterior compartments of the upper arm (Fig. 12.1) [1]. The anterior compartment contains the biceps, brachialis, coracobrachialis, and brachioradialis muscles. The posterior compartment is primarily the triceps musculature [2]. More general compartments are the skin and subcutaneous fat, the muscle, the nerves and vessels, the parosseous space, the bones, and the joints [2]. When describing a lesion, it is important to note which compartments are involved. When performing a biopsy of the shoulder through the deltoid muscle, the path should be through the anterior deltoid. The axillary nerve innervates the deltoid muscle from posterior to anterior. If a needle track is chosen in the posterior two-thirds of the muscle, the remaining anterior portion of the deltoid may become denervated and functionless after resection of the posterior muscle [2] and may require amputation.

The authors have nothing to disclose.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official nor as reflecting the views of the departments of the army, navy, or defense.