Calcific tendonitis is one of the most common causes of nontraumatic shoulder pain, primarily affecting women aged 30–60 years (1). It most commonly occurs in the supraspinatus tendon (2, 3), often triggered by minor trauma or overexertion. Calcific tendonitis causes severe shoulder pain and restricts joint movement. Approximately 2.7%–20% of patients with calcific tendonitis are asymptomatic, and 35%–45% are incidentally detected on simple radiographs (4), as symptoms arise following the formation of calcified deposits. When the calcific deposits exceed 1.5 cm in diameter, symptoms worsen and can lead to muscle spasms, tears, bursitis, and adhesive capsulitis. These complications significantly impact patients’ quality of life (5, 6). It is essential to differentiate the pain caused by calcific tendonitis from rare complications unrelated to disease progression, such as long head of the biceps pathologies or osteolysis of the greater tuberosity (7), as all of these conditions significantly affect patients’ quality of life. The conventional diagnostic approach involves using standard x-rays in the anterior-posterior, outlet, and axillary positions, as well as CT for follow-up (8, 9). MRI is utilized to identify possible complications, such as rotator cuff injuries (10). This approach aligns with clinical consensus, as it allows for lesion localization and assessment of deposition texture and morphology. Patients with acute exacerbation of the disease or failure of nonsurgical treatment, defined as persistent symptomatic calcific tendinitis after at least 6 months of nonsurgical treatment, including standardized nonsurgical treatment for at least 3 months, may require surgical intervention (11). Arthroscopic removal of calcified lesions provides significant pain relief and promotes postoperative shoulder function recovery (6). Therefore, arthroscopic treatment is a suitable option for cases where conservative treatment has failed and acute pain is unresponsive to conservative management.

However, arthroscopic treatment of calcific tendonitis still presents several challenges (12). The key issue lies in the rapid and accurate localization of the lesion during surgery to minimize operation time and iatrogenic injury (12). Currently, most surgeons rely on empirical localization, observing “storm” changes or using spinal puncture needles to locate “strawberry spots” and areas of calcific swelling (13). However, this traditional localization method heavily relies on experience and direct observation, which can lead to delays in the procedure and unnecessary trauma for inexperienced surgeons. As research and surgical techniques continue to advance, new preoperative localization methods have been proposed. Kayser concluded that preoperative ultrasound localization significantly improved treatment outcomes and increased the rate of successful removal of calcific foci (14). Ultrasound has been utilized to guide wire placement for preoperative localization of calcific foci (15). Similarly, Robert achieved significant results by using an internal ultrasound 10 mm probe for guidance during cleanup procedures (16). A recent study of ultrasound-guided arthroscopic resection of calcifying tendinitis showed successful results in terms of functional recovery and pain relief, but the effect of ultrasound-guided arthroscopic resection on exploration time and operation time was not explored (17). Imaging techniques are also widely employed in both diagnosis and surgical assistance. Although CT and x-ray imaging are commonly used for the diagnosis of calcific tendonitis, their true value in preoperative preparation for calcific debridement has not been fully appreciated (18). Moreover, due to changes in body position and the effects of necessary traction during surgery, the location of calcific foci that were directly marked and preoperatively localized often differs from the preoperative condition. The current trend in treatment involves targeted examination and localization for patients with different factors that may affect intraoperative localization, such as ligament and tendon strength and joint laxity. Considering that ultrasound and 3D-CT imaging are predominantly used in academia to assist with localization, exploring the further application of 3D imaging in localization and combining it with ergonomics to infer the location of calcific foci after postural changes may be a novel approach to consider.

Based on the findings from previous studies, we propose a method for locating calcific foci using preoperative 3D CT imaging and assessing the changes in position caused by postural adjustments during formal surgery. This approach involves utilizing geometric formulas to minimize operative time and reduce intraoperative injuries while ensuring the effectiveness of arthroscopic treatment.

The study was screened from inpatients with calcific tendonitis at our department from June 2016 to January 2024. We obtained 51 previous cases of calcific tendonitis and retrospectively analyzed the data. Cases were divided into localized (26) and non-localized (25) groups based on whether or not CT scans were used to localize the calcified foci preoperatively. The study conformed to the CONSORT (Consolidated Standards of Reporting Trials) statement. The study was approved by the Ethics Committee of Peking University Shenzhen Hospital (No. 2023-160). Eligible patients were aged between 18 and 65 years with a diagnosis of calcific tendonitis. In all patients, a suitable course of nonoperative management had failed, they should be assessed according to per inclusion or exclusion criteria (Table 1). Inclusion criteria:(1) Between 18 and 65 years of age; (2) Patients diagnosed with calcific tendonitis of the supraspinatus muscle based on clinical manifestations, medical history, physical examination and imaging examination; (3) After standardized conservative treatment, the patient still cannot get obvious relief or the symptoms are persistent; (4) Patients with calcified supraspinatus tendon during arthroscopy. Exclusion criteria: (1) The presence of severe osteoarthritis in the affected shoulder, history of previous shoulder surgery, cervical spondylosis, neurological diseases of the upper limb, and other disorders that affect the outcome; (2) Preoperative orthopantomogram or 3D CT scan of the shoulder joint cannot show the calcified foci of the rotator cuff, or cannot clearly show the position and size of the deposits through different planes; (3) Patients with arthroscopic findings of superficial calcification foci on the synovial margin or joint margin or obvious rotator cuff tear; (4) Patients with calcification foci larger than 1.5 cm in diameter; (5) Patients who are unable to tolerate surgery or have cognitive function or psychiatric disorders that prevent them from cooperating with follow-up visits. All surgery was performed by experienced, fellowship-trained shoulder surgeons.

Calcific tendonitis of the supraspinatus tendon is a prevalent condition, yet its exact pathogenesis remains elusive. The formation of calcific deposits primarily occurs within 1.0 cm proximal to the superior portion of the greater tuberosity of the humerus, specifically in the subacromial crest. This region is characterized by poor vascularity, making it particularly susceptible to stress-related damage. The combination of degeneration and cumulative strain further increases the likelihood of calcium deposition in this area.

Among the available therapies for calcific tendonitis, conservative treatments such as medications, corticosteroid injections, and physical therapy are typically attempted as initial options. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed, although their long-term use carries risks of gastrointestinal, cardiovascular, and renal complications (19). While conservative treatment approaches have been widely used, they have not completely replaced surgical interventions. This is mainly due to the uncertainty surrounding their efficacy, as few high-quality clinical studies have demonstrated their superiority over surgery for symptomatic calcific tendonitis. With advancements in technology, extracorporeal shock wave therapy (ESWT) and Ultrasound-Guided Needling and Lavage (UGNL) have emerged as alternative treatment options. ESWT has been recommended as a second-line opion when conservative drug therapy fails, with reported success rates ranging from 60% to 80% in available studies (20, 21). However, the optimal pulse energy for ESWT remains inconclusive, and potential complications such as erythema, petechiae, and mild subdermal hematoma may occur. These complications often resolve on their own without medical intervention (22). UGNL is a technique that employs ultrasound guidance to remove calcium deposits from specific areas. It has demonstrated effectiveness in both short-term and long-term treatment of calcific tendinopathy (23). However, similar to ESWT, there is no established gold standard for ultrasound-guided percutaneous irrigation based on evidence-based medicine (6).

A recent clinical study indicated that both UGNL and ESWT were successful in improving function and reducing pain, with high satisfaction rates at 1-year follow-up. However, UGNL was found to be more effective in eliminating calcified deposits, while additional treatment was more common in the ESWT group (24, 25). Another study by Frassanito reported that combining Kinesio taping with ESWT appeared to enhance recovery from calcific tendinopathy of the rotator cuff and produced a faster treatment response compared to ESWT alone (26).

Overall, while conservative treatments are commonly employed as the initial approach for calcific tendonitis, the efficacy of these therapies compared to surgical interventions remains uncertain (27). Surgical treatment is comparable to non-surgical treatment for pain improvement, with the advantage being functional improvement (28). Ultrasound radiomics has been proposed to predict the success of US-guided percutaneous irrigation for calcific tendinopathy of the shoulder (29). Extracorporeal shock wave therapy and ultrasound-guided percutaneous irrigation have shown promise, but further research is needed to establish standardized guidelines and determine their optimal use.

In routine surgery for calcific tendinopathy, the use of shoulder radiography and CT is often necessary for diagnosis and preoperative localization. However, accurate localization of the lesion typically relies on the surgeon's intraoperative probing and empirical judgment. Currently, it is believed that arthroscopic visualization of an intra-tendon bulge with increased vascular tissue is a reliable marker of calcium deposition (30). Additionally, a “storm” effect observed in the interstitial space serves as an indicator of successful puncture of the calcified site (13). However, visual observation and empirical exploration carry certain risks, including the possibility of overlooking inconspicuous lesions under the microscope and potential injuries resulting from prolonged exploration time.

With the advancement of surgical techniques, several preoperative localization methods have been proposed, with ultrasound techniques being the most widely utilized. Kayser suggested that preoperative ultrasound localization significantly improves treatment outcomes and increases the clearance rate of calcification (14). However, their study did not demonstrate a positive effect of ultrasound localization on operative time and overall course reduction, possibly due to the learning curve associated with the technique. On the other hand, Sigg used ultrasound-guided wires for preoperative localization of calcified foci, which improved localization accuracy but introduced additional unpredictable risks (15). Robert (16) performed cleanup with a 10 mm internal ultrasound probe for guided localization, but the size and flexibility of the probe posed limitations. The 1 mm probe was not suitable, while the 10 mm probe was too large, although the proposed protocol was feasible in their case study. The modification of the probe by adding a sleeve could lead to damage during the exploration process, and current stage does not require probe modification for this procedure (31). Sabeti-Aschraf placed a puncture needle on the deposit under ultrasound guidance and marked it on the skin preoperatively using a ballpoint pen (32). This method is effective and reduces exposure to ionizing radiation from intraoperative radiography, but it carries a risk of greater variability, especially when deposits are located at the muscle-tendon junction, making them challenging to locate. In the pursuit of newer surgical methods, the academic community has predominantly focused on ultrasound techniques, which to some extent has limited the exploration of alternative approaches to improving surgical protocols. Ultrasound mainly provides two-dimensional images, making it difficult to fully understand the position and relationship of the lesion in three-dimensional space, which makes it difficult to meet the need for an in-depth understanding of the overall condition of the shoulder joint. The quality of its imaging is highly dependent on the operator's experience and skills, and there are difficulties in identifying deep calcified lesions; the clinical information provided is less comprehensive than that provided by CT in terms of ruling out other potential shoulder joint lesions, such as bone tumors, fractures, and so on. And compared to MRI, CT has the following advantages: better anatomical detail than MRI in terms of bone and calcification, easier to locate accurately, faster scanning speed, and higher accessibility and lower cost. In light of this, we propose an enhanced solution that involves utilizing preoperative 3D imaging to assist in localization.

In this study, a rigorous screening and random grouping process was implemented to effectively analyze the proposed surgical method while controlling variables. Although there were no significant differences in ASES, VAS, and patient satisfaction scores between the two groups regarding symptom improvement, the duration of surgery and intraoperative exploration time indicated that the method could effectively reduce operation time, particularly the time spent on intraoperative lesion exploration.

In conclusion, the pursuit of minimally invasive, individualized, and precise medical treatments has long been a goal embraced by clinicians in the field of surgery. In our study, we emphasized the importance of utilizing each patient's personalized imaging and 3D reconstruction results, along with a comprehensive understanding of the specific surgical traction force resulting from the displacement of the corresponding structures of the shoulder joint. This approach allowed us to accurately determine the surgical access and exploration location, thereby reducing the likelihood of intraoperative medical-induced injuries. Our study and method have effectively addressed the technical challenges associated with utilizing 3D imaging technology for the treatment of calcific tendonitis through shoulder arthroscopy, providing orthopedic surgeons with a reliable solution for effectively and precisely locating calcific foci, reducing operative time, minimizing intraoperative ionizing radiation exposure, and avoiding unnecessary harm. Consequently, this method can significantly reduce damage to the skin surface and internal structures caused by probe poking, ultimately leading to shorter operation times. This study has several limitations: it is retrospective, possesses a low level of evidence, and is conducted at a single center. The sample size is relatively small, and the investigation only evaluated short-term efficacy. The amount of radiation associated with CT cannot be ignored. Future research with extended follow-up is necessary to better understand the impact of 3D-CT localization on recurrence rates and long-term function. Additionally, other positioning modalities were not compared in this study, which presents an opportunity for future investigations to explore this and various rotator cuff component positioning techniques.

The preoperative localization of calcified tendinitis lesions using the precise positioning concept, facilitated by a mathematical model supported by 3D-CT reconstruction technology, offers significant benefits in terms of reducing intraoperative lesion exploration time and overall operation time.