The aim of this study was to investigate the exploration history, key theories, methods, and techniques involved in the evolution from the intracapsular method to the extracapsular method for arthroscopic treatment of tennis elbow, and explore the effectiveness and safety of extracapsular method on the basis of retrospective analysis of 43 cases.

Background: Arthroscopic surgery is widely used in the treatment of refractory tennis elbow due to its advantages of minimally invasive, safe and direct vision. Intra-capsular arthroscopy(intracapsular method), which is performed via natural cavity, is the mainstream arthroscopic procedure. However, intracapsular method requires the damage of joint capsule and may cause intraoperative neurovascular injury and other complications. In view of the defects of intracapsular method, the surgical scheme of the extracapsular arthroscopy (referred to as "extracapsular method") has emerged. The aim of this study was to investigate the exploration history, key theories, methods, and techniques involved in the evolution from the intracapsular method to the extracapsular method for arthroscopic treatment of tennis elbow, and explore the effectiveness and safety of extracapsular method.

Methods: Qualitative data were collected via focus group interview. 7 surgeons who were selected through purposive sampling discussed on the theories, methods, and technical specifications of the transition from intracapsular method to extracapsular method. Qualitative data were analysed using NVivo11. Quantitative data of consecutive 43 patients were analysed to evaluate the effectiveness and safety of the extracapsular method. Descriptive analysis was conducted to analyse the demographic characteristics and clinical outcomes after surgery.

Inclusion Criteria:

1. Diagnosis was refractory tennis elbow;
2. Standard extracapsular method was used for surgery.

Exclusion Criteria:

1. Patient had past history of joint infection, joint tuberculosis, or osteomyelitis, or the upper limb had undergone surgery within the past 6 months;
2. Diagnosis was combined with severe heart, brain, kidney, or another organ dysfunction;
3. Case was complicated with other serious elbow joint diseases or injuries;
4. Patient did not sign the informed consent form.

the quantitative data of 43 patients (14 men and 29 women) were reviewed. The minimum age was 35 years, and the maximum age was 55 years old, with an average of 44.4 years.