Calcifying tendinitis (CT) of the shoulder is a common disease of the rotator cuff in which calcium particles are deposited in one or more tendons of the rotator cuff. This can result in a typical pattern of pain, impairments in daily living and decreased range of motion. This disease mainly affects individuals between 30 and 60 years of age and females are more often affected by this condition [
1‐
6]. The etiology of CT of the shoulder is still a matter of dispute. Several hypothesis have been postulated including a degenerative hypothesis, repetitive microtrauma, tenocyte necrosis, reactive and endochondral ossification. All leading to a postulated same end point in which that a locally decreased oxygen tension or hypoxia initiates the formation of the calcific deposit [
2].
Initially, the treatment consists of conservative measures such as anti-inflammatory drugs, ice-therapy, physical therapy and/or corticosteroid injections [
2,
7‐
10]. However, if this conservative treatment fails additional treatments must be considered. Historically, the next step treatment has been a surgical procedure [
1]. However, other –less invasive– treatment modalities such as needle aspiration of the calcific deposits (NACD) and focused extracorporeal shockwave therapy (ESWT) have emerged. Over the past years both minimal invasive treatments have proven to be effective therapeutic options [
9,
11‐
13]. NACD showed promising results mainly in non-comparing studies [
14]. In addition, ESWT has also been proven to be effective, especially high-energy ESWT [
11]. Although in the available orthopedic literature both treatment methods seem to be viable options, evidence comparing both treatment methods is limited [
15]. Two randomized controlled trials (RCTs) have evaluated and compared the effectiveness of NACD compared to ESWT. In 2014, a RCT was published in which radial shock wave therapy was compared to NACD [
16]. However, radial shock wave therapy have been shown to be less effective than focused ESWT and therefore this comparison different from the current study [
13]. In 2020, the most recent RCT was published. Louwerens et al [
15] compared a protocol of ESWT with four sessions of high-energy focused ESWT to ultrasound guided NACD. Both studies showed that both treatment modalities were effective in treating calcifying tendinitis of the shoulder with low complication rates. However, both studies used markedly different treatment protocols compared to the current study [
15,
16]. Therefore, the exact place of NACD or ESWT in the treatment paradigm of CT is not clear yet [
10].
Besides, there is very limited evidence available about the cost-effectiveness of any intervention of CT of the shoulder. As far as we are aware, only Haake et al. [
7] published results concerning the cost-effectiveness of the treatment of CT. They found that ESWT costs society €1.750 to € 3.500 as a results of being unfit to work compared to €9.710 to €19.440 after surgical treatment for therapy resistant CT of the shoulder. However, there is no data available about the comparison between the minimal invasive techniques (e.g. NACD vs ESWT) [
7].
Therefore, this randomized controlled trial (RCT) has several objectives. The primary objective is to compare the short and midterm effectiveness of NACD and ESWT as treatment options for conservative therapy resistant CT to define a preferable minimal invasive treatment. The hypothesis is superiority of either NACD or ESWT regarding functional outcome after 12 months. The secondary objective is to compare the cost-effectiveness of both minimal invasive techniques.