## 4 Discussion
There is no doubt that substance P is a crucial neuropeptide for pain transmission, but all we can say was that the reactivity was not that significant in this particular study. The subacromial bursa has been implicated as the primary pain-producing tissue in the shoulder, whereas it also plays a role in blood supply to the rotator cuff, proprioception, and lubrication [33]. The fact that downregulation of inflammatory cytokines is expressed in subacromial bursitis by anti-inflammatory agents provides biologic evidence for a pain source that can be controlled clinically [34]. The fact that the subacromial bursa possesses a high density of free nerve endings comprised of both myelinated and non-myelinatedfibers that outnumber the surrounding structures may have resulted in the relatively high expression of every pain-related factor in both groups [15; 35]. In fact, relatively high expression of pain-related factors from the subacromial bursa can simply result from the rotator cuff tear itself with a high probability. Still, even though the difference was not always statistically significant, the collective response toward a pathologic LHBT implies that the subacromial space may also be affected by the condition of the LHBT. Although enrollment in this study was confined to patients with rotator cuff tears with or without LHBT lesions, we believe that the strength of this study is in providing basic information that can be applied clinically in a direct manner. To the best of our knowledge, biological evidence that could justify the extent of surgical treatment of rotator cuff tears with an abnormal LHBT has not yet been provided in any published studies. There is no doubt that the treatment of tendons with the apparent pathology should be dealt with as a priority. However, regarding the result that adjacent anatomical structures are affected by the condition of the LHBT, with significantly increased expression of pain-related factors and neuropeptides, the possibility remains of having suboptimal results even after the successful repair of the torn supraspinatus or LHBT with the incubated pathology remaining in the untreated structures. The finding that an abnormal LHBT is a pain source that affects surrounding tissues clinically supports the need for surgical treatment for an abnormal LHBT. For instance, tenotomy not only removes the pain source directly but may also prevent further influence of the LHBT on adjacent structures that may also contribute to pain generation, even after repair of the torn cuff. Furthermore, in cases of patients with concomitant stiffness, release of the rotator interval along with anterior capsuelectomy may not only contribute to the improvement of ROM but may also its role on removing the actual pain source. Early postoperative motion was acquired by the preemptive release of the rotator interval in patients with rotator cuff tears [36]. The benefit of rotator interval release can be one of the clinical backgrounds to our results. In addition, thorough subacromial burstectomy under the circumstances of a pathologic LHBT may contribute to postoperative pain reduction. The results of this study should be interpreted with some limitations. First, the number of patients was relatively small and power analysis was not performed for this particular study. Second, we were not able to guarantee that all the enrolled patients were in the same pathologic condition of rotator cuff tears or LHBT pathology within the group. We tried our best to keep the LHBT as the only variable, but the enrolled patients may have been in different statuses of evaluated tissues, including the rotator cuff. This might have affected the expression of pain-related factors in the evaluated tissues. Third, analyses were conducted using only two analytical methods, which were RT-PCR and immunohistochemistry. RT-PCR and immunohistochemistry only describe what genes or proteins are being expressed at the time of harvest, so progression toward the problem cannot be clearly revealed.