Complications of calcific tendinitis of the shoulder: a concise review
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Calcific tendinitis (CT) of the rotator cuff (RC) muscles in the shoulder is a disorder which remains asymptomatic in a majority of patients. Once manifested, it can present in different ways which can have negative effects both socially and professionally for the patient. The treatment modalities can be either conservative or surgical. There is poor literature evidence on the complications of this condition with little consensus on the treatment of choice. In this review, the literature was extensively searched in order to study and compile together the complications of CT of the shoulder and present it in a clear form to ease the understanding for all the professionals involved in the management of this disorder. Essentially there are five major complications of CT: pain, adhesive capsulitis, RC tears, greater tuberosity osteolysis and ossifying tendinitis. All the above complications have been explained right from their origin to the control measures required for the relief of the patient.
Level of evidence 5.
KeywordsCalcific tendinitis Shoulder Rotator cuff Complications
Calcifying tendinitis (CT) of the shoulder is a frequently occurring painful disorder characterized by the presence of calcified deposits in the tendons of the rotator cuff (RC) mainly affecting the supraspinatus tendon but occasionally is seen in the infraspinatus and subscapularis [1, 2, 3, 4, 5].
To our knowledge no review articles have been elaborated on the complications of CT. Hence, in this paper a literature review has been done on the various complications or sequelae of the CT of the shoulder preceded by a brief overview on its histopathology, classification and diagnostic imaging.
Histopathology and classification
The evolution of CT essentially passes through 3 distinct stages: pre-calcific, calcifying and post-calcific . In the pre-calcific stage, numerous factors stimulate a metaplastic change of the tenocytes into chondrocytes. This is followed by the calcific stage which is subdivided into three phases—formation, resting and resorption—characterized by deposition of amorphous calcium phosphate followed by vascularisation and finally by resorption which coincides with significant clinical pain. The post calcific stage is demonstrated by the collagenisation of the lesion by fibroblasts . Intra-operatively, the gross specimens of CT can be either in the form of a sandy tough mass or a toothpaste-like fluid or an amorphous mass composed of many small round or ovoid bodies . The material of these deposits has been identified to be calcium carbonate apatite . This carbonate apatite has been further classified as an A and B-type apatite . Chiou et al.  studied the chemical components in CT and found that both types of the carbonate apatite varied in quantities during the formative, resting and resorption phases. Histochemical studies have demonstrated the presence of extracellular matrix vesicles near calcified deposition of the RC [26, 31, 32] and the authors have tried to correlate this finding in the pathogenesis of CT. Normally, the vesicles are inhibited from mineralization but in the presence of any pathology, the inhibitory stimulus may be lost leading to vesicles getting mineralized.
Radiological classification of the calcific tendinitis of the shoulder according to the current literature evidence
Bosworth et al. 
Large (>1.5 cm)
Medium (in between)
Small (rarely seen)
Depalma et al. 
Type I (fluffy, amorphous and ill defined)
Type II (defined and homogeneous)
Type I (well demarcated, dense)
Type II (soft contour and dense or sharp contours and transparent)
Type III (soft contours, translucent and cloudy)
Mole’ et al. 
Type A (dense, rounded, sharply delineated)
Type B (multilobular, radiodense, sharp)
Type C (radiolucent, heterogeneous, irregular outline)
Type D (dystrophic calcific deposits)
Maier M et al.  assessed the intra- and interobserver reliability of the various classification systems using plain radiographs and CT scans and concluded that all the scores showed insufficient reliability and reproducibility. Although marginal improvement could be seen using CT scans it still remained statistically insignificant to be recommended as a routine investigation.
The first imaging modalities to identify CT were X-ray and ultrasound, as calcium deposits are readily identifiable on both. Radiograms should be performed in anterior-posterior (AP)—neutral, internal rotation and external rotation—axillary and outlet view. On radiographs calcific deposits appear homogeneous, amorphous densities without trabeculation, which allows a differentiation from heterotopic ossification or accessory ossicles . Most of calcifications are ovoid, and the margins may be smooth or ill-defined. Ultrasound (US) is advantageous in the diagnosis of CT as it helps to detect other associated conditions as well such as rotator cuff tears and long head of the biceps (LHB) pathologies ; moreover, it also characterizes deposit consistency, their tendon location, and can be helpful to assist injections and bursal lavage . According to the morphology of the calcium deposit, US has been used to classify the different type of CT due to its ability to discriminate between well defined calcifications with strong shadowing, and those with faint or absent shadowing. Chiou et al.  classifies calcific depositions into four shapes: an arc shape (echogenic arc with clear shadowing), a fragmented or punctate shape (at least two separate echogenic spots or plaques, with or without shadowing), a nodular shape (echogenic nodule without shadowing), and a cystic shape (a bold echogenic wall with an anechoic area, weak internal echoes or layering content). Conditions associated with non arc-shape calcifications include hypervascularity, widening of subacromial-subdeltoid bursa and the large size of calcifications. High resolution US in combination with color Doppler can differentiate between formative or resorptive status. In the resorptive phase, the deposits are nearly liquid and can be successfully aspirated. US has been also used with success in overhead athletes to identify CT showing a prevalence greater than that reported in the general population and that the presence of calcific tendinopathy correlates positively with age . CT scan and MRI should be reserved for doubtful cases . Computed tomography has an excellent resolution to detect calcium deposit as high density foci of solid stippled or amorphous character, but the cost and the exposure to radiation limit its use. MRI should not be used as a first line imaging modality, because deposits appear as vague regions of low signal on T1 and T2, and can be missed. Some enhancement around the deposit can be seen after contrast, and surrounding areas of hyperintensity on T2, due to peripheral edema or subacromial-subdeltoid bursal fluid are possible. MRI is advisable when the deposit is so large as to produce a strong shadow on US thus confusing it with RCTs.
The reason why pain has been considered as a complication in this review is due to the fact that this condition remains primarily asymptomatic in most of the patients . When CT becomes symptomatic, the pain is extremely severe and is typically shooting type in the area of the shoulder with no radiation to elbow or hand . In the acute phase, the pain tends to be so severe so as to allow only limited shoulder motion with marked tenderness. In the chronic or subacute phase, pain can be severe but generally shoulder motion is allowed . The cause of occurrence of pain in CT is either due to an inflammatory response to the local chemical pathology or to direct mechanical irritation . Neer classically described four types of pain peculiar to calcium deposition. First is the pain that is caused by the chemical irritation of the tissue by calcium. The second is the pain caused by tissue pressure due to its swelling. The third is an impingement-like pain caused by bursal thickening or irritation by the deposit itself. The fourth is the pain caused by a chronic stiffening of the glenohumeral joint due to voluntary prolonged immobilization by the patient to avoid possible irritation by the deposits with abduction or overhead activities . Substance P is involved in the pain transmission caused by the stimulation of A delta/C fibers by certain noxious stimuli in the dorsal horn of the spinal cord. It is also contained in the small sensory neurons of the peripheral tissue. It’s release from the sensory neurons play a significant role in mediating neurogenic inflammation . Gotoh M et al.  studied the relation of the amount of substance P in the subacromial bursa and the shoulder pain in patients with rotator cuff diseases with radioimunoassay and immunohistochemistry. He found an increase in the number of immunoreactive nerve fibres in the synovial tissue of patients with rotator cuff diseases. These fibres were predominantly located around the blood vessels, suggesting an active role in its regulation and subsequent inflammation. He also hypothesized that certain mechanical (impingement) and chemical (bursitis) factors could be a source for the noxious stimuli inducing increased amounts of substance P in the afferent nerves. The conclusion of his study was that the subacromial bursa was the site associated with shoulder pain caused by rotator cuff disease.
We suggest to pay special attention to patients with persistent pain due to chronic CT. This subpopulation requires periodical outpatient visit (every 4 months) to exclude stiffness and monitor the evolution of calcium deposit with ultrasound; in addition, radiograms should be performed annually to assess the morphology of the deposit and its relationship with the underneath bone. NSAIDs are recommended when the pain score is more than 5 on a Visual Analogic scale (0–10). A standard program of physiotherapy including self aided mobilization and home exercises are prescribed to prevent stiffness. ESWT may be advised to foster calcium resorption, while other physical therapies (Laser, Transcutaneous electrical nerve stimulation) may help to treat associated LHB tendinopathies.
In addition, we do believe that some of the other complications listed below could be an important source of chronic and resistant pain in CT.
Another interesting association of stiffness and CT is found in the post operative phase in arthroscopy. In a study by Jacobs et al.  the incidence of frozen shoulder after surgery was 18 % and the cause was considered to be the irritation of the glenohumeral capsule by residual calcium debris and hence thorough lavage was recommended to avoid such a possibility. Although he did not have literature evidence to support his claim, this assumption may not be entirely misplaced. In the section on pain previously described, one cause for it was considered to be stiffening due to voluntary prolonged immobilization. Conversely, the pain produced could further limit the compliance of the patient with respect to physiotherapy and rehabilitation thus producing a vicious cycle. Overall this association would usually lead to a prolonged recovery phase with regards to strength and motion.
Rotator cuff tears
Greater tuberosity osteolysis
The ideal treatment for the CT of the shoulder is not well established and for some aspects still controversial. The clinical course may be complicated by several conditions that should be diagnosed and treated when we manage a patient with CT of the RC. Whereas pain and stiffness are generally recognized and treated, the risk of RC tears ìs not well considered and the related surgical approach is a concern. Greater tuberosity osteolysis is less known and often not identified on radiograms or ultrasound, therefore, we would suggest to investigate with MRI in those patients with persistent chronic pain and doubtful standard X-ray. Finally, ossifying tendinitis is very rare and only recently reported as complication of CT that should be considered and investigated with X-ray in subjects with CT already treated with conservative or operative measures. We do believe that this review gives a quick summary of the potential complications of the CT, inviting all professionals (orthopaedic surgeons, physiatrists, radiologists and physiotherapists) who deal with this disease to consider not only the regular course of the CT but also the complications that must be identified and treated as well as possible.
Conflict of interest
The patients represented in this study provided informed consent to the publication of their clinical cases.
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