Shoulder impingement syndrome comprises three distinct types: subacromial impingement, subcoracoid impingement, and internal impingement [12, 14, 15]. However, clinical understanding of shoulder impingement often remains limited, and these various forms of impingement are occasionally amalgamated and addressed as subacromial impingement. Currently, there has been a surge in research focusing on the pathology of subscapularis tendon tears and associated risk factors. Friedman et al. [11] initially proposed the concept of CHD, which refers to the minimal distance between the coracohumeral apex and the minor tubercle of the humerus measured by MRI in the internal rotation position of the shoulder joint. They observed that healthy individuals have an average CHD of approximately 10 mm, while patients presenting coracoid impingement symptoms have an average CHD of 5.5 mm. Richards et al. [16] further emphasized the close association between a narrowed subcoracoid space and subscapularis tendon injuries. Ting DS et al. [17] reported that the typical subcoracoid space spans between 8 to 11 mm and established a correlation between subscapularis tendon injuries due to coracoid impingement and the reduction in CHD. Furthermore, Dugarte et al. [18] highlighted that the CHD diminishes as the internal rotation angle of the shoulder joint increases, with a substantial decrease occurring when internal rotation surpasses 45°. Bone contact frequently arises with internal rotation ranging between 50° to 60°. The decline in CHD significantly increases the risk of friction between the coracoid and the subscapularis tendon, leading to further damage, including the manifestation of partial or full-thickness tears within the subscapularis tendon. Therefore, restoring an adequate subcoracoid space not only enhances the surgical workspace but also safeguards the repaired subscapularis tendon, preventing re-tearing due to coracoid impingement and associated abrasive influences [19].
In this study, preoperative MRI measurements in Group A indicated a mean CHD range of 5.21±0.48. Following coracoplasty, the postoperative 24-month follow-up exhibited a mean CHD range of 9.41±0.7, which was statistically significant. However, the precise role of CHD as a research indicator for subcoracoid impingement still requires further discussion and research [4]. In Group A, all 40 patients underwent coracoplasty during the operation, allowing for complete release of the anterior compartment of the subscapular tendon until the base of the coracoid process and associated tendon were fully exposed. The evaluation of the CHD was performed during the internal rotation position of the shoulder joint, with measurements exceeding 8mm from the base of the coracoid process to the target coracohumerus, employing a 4.0mm grinding head as the reference scale. Furthermore, the findings revealed that patients in Group A, who underwent subscapularis tendon repair combined with coracoplasty, exhibited superior UCLA, ASES, and VAS scores at the 24-month postoperative mark compared to Group B, which underwent isolated subscapularis tendon repair. Notably, no cases of re-tearing were observed in Group A during the follow-up period, whereas one case of re-tearing was reported in Group B. However, given the relatively small sample size and short follow-up duration, it is challenging to definitively attribute the retear to the absence of coracoplasty in Group B. In terms of external rotation and internal rotation, both groups showed an increase in external rotation angle postoperatively compared to preoperative values, with no statistically significant differences at 1 month postoperatively. This may be attributed to the routine 4 weeks of postoperative immobilization. However, at the 24-month follow-up, the group that underwent subscapularis tendon repair combined with coracoplasty demonstrated a significant improvement in external rotation and internal rotation compared to the group that underwent isolated subscapularis tendon repair. Additionally, there was no significant distinction in the range of forward flexion motion between the two groups at the 24-month postoperative evaluation. Overall, the functional scores exhibited a significant increase in both groups postoperatively compared to the preoperative values (p<0.01). Based on the statistical analyses of each indicator, it may reveal that patients in Group A had better recovery outcomes than those in Group B, except for the forward flexion range of motion.
Currently, the evaluation of subscapularis tendon injuries during arthroscopy commonly involves the utilization of two prominent classification systems: the Fox and Romeo classification [20] and the Lafosse classification [21]. The Fox and Romeo classification , introduced in 2003, categorizes subscapularis tendon injuries into four types based on tear severity: Type I signifies partial tears, Type II represents greater than 25% full-thickness tears, Type III indicates greater than 50% full-thickness tears, and Type IV denotes a complete tear of the subscapularis tendon. On the other hand, The Lafosse classification, proposed in 2007, characterizes subscapularis tendon injuries into five categories based on tear location and associated factors: Type I involves partial tears in the upper third of the tendon, Type II denotes a complete tear in the upper third of the tendon, Type III signifies a complete tear in the upper two-thirds of the tendon with no tear in the lower third and limited tendon retraction, Type IV indicates a complete tear of the tendon from the lesser tuberosity with fat infiltration grade 3 or lower and the humeral head remaining centered without touching the coracoid during external rotation. Finally, Type V represents a complete tendon tear with the humeral head displaced forward and upward, contacting the coracoid, along with fat infiltration grade 3 or higher. In this specific study, the Lafosse classification was employed, revealing 46 cases of Type I, 26 cases of Type II, and 8 cases of Type III. Due to the primary focus of comparing the influence of coracoplasty on subscapularis tendon repair prognosis , further in-depth research is needed for effective analysis of these subtypes later.
In 2002, Burkhart [22] initially introduced arthroscopic subscapularis tendon repair surgery, which has gained attention from arthroscopic surgeons for subscapularis tendon injuries. Currently, the dominant surgical techniques include single-row fixation, double-row fixation, and tendon transfers involving various muscles [23]. Lorbach et al. [24] highlighted that the double-row fixation approach yields superior biomechanical properties and clinical outcomes compared to single-row fixation. However, there exist dissenting viewpoints as well. Yoon et al. [25] suggested that, for patients with good muscle quality, there exists no significant difference in treatment outcomes between the two fixation methods. In this study, although single-row fixation or simple suture repair and ligamentous fixation methods were employed, only one case was observed re-tearing among all 80 patients during the follow-up period. Therefore, whether double-row fixation or tendon transfers display better clinical outcomes for subscapularis tendon injuries remains unclear.
In conclusion, subcoracoid impingement syndrome could potentially serve as a significant factor in the development of subscapularis tendon injuries. The combined approach of subscapularis tendon repair and coracoplasty exhibits superior efficacy compared to isolated subscapularis tendon repair for cases of subscapularis tendon injuries caused by coracoid impingement. However, it is important to acknowledge the limitations of this study, including a relatively small sample size and a short follow-up duration. These findings may be used as a basic reference for arthroscopic shoulder surgeons. However, more research is needed in this field for universal clinical application.