Distal insertion of the clavicular portion of pectoralis major muscle: anatomical study.

PURPOSE: Several descriptions of the anatomy of the pectoralis major (PM) have been published. However, the precise description of its distal humeral insertion, which is involved in traumatic tears, remains controversial. The distal tendon is classically described as being made of two layers, one anterior (ALPM) and one posterior (PLPM), which regroup at their distal edge. The clavicular head (CH) participates in the ALPM according to most authors. However, others describe a more superficial termination in a close relationship with the deltoid humeral insertion. The objective of this anatomical work is to precisely describe the anatomy of the CH and its relationship with the rest of the distal PM tendon and the distal deltoid tendon. MATERIALS: Twenty-three fresh cadaveric specimens were dissected (41 shoulders). The entire PM as well as the deltoid were exposed. Several measurements were collected to establish the relationships between the distal tendon of the CH and the PM, the deltoid and the bony landmarks. RESULTS: In all cases, the CH muscular portion sits on the ALPM but does not participate in the connective structure of the PM distal tendon. The inferolateral part of its distal end gives a thin tendinous portion that inserts lower on the humerus in conjunction with the distal tendon of the deltoid. In 24.4%, this tendon was more difficult to isolate but was always observed. CONCLUSIONS: The distal tendon of the PM only comes from the muscle fibres of its sternal head. The CH fibres do not contribute to this tendon but appear to terminate in a separate tendon fusing with the humeral insertion of the deltoid: the deltopectoral tendon. This could explain the different patterns of tears observed in clinical practice.

Arthroscopic approach in initial training: Study of a novice cohort using inverse direct and indirect approaches and its implication in the development of training programs.

INTRODUCTION: Arthroscopic training includes successive stages of observation, reproduction and then repetition. Learning through simulation in 2D virtual reality makes it possible to repeat these different stages to enhance the learner's experience in complete safety and a shorter timeframe. Some procedures require inversion of the optical and instrumental approaches in the axial plane, disrupting the existing psychomotor and technical skills. The objective of this study was to compare the degree of difficulty and the distribution of results for the same exercise carried out alternately in classical holding and inverted holding of the instruments in a cohort of novice learners. MATERIALS AND METHODS: Twenty-two medical students, novices in arthroscopic surgery, participated in the study. Each performed an exercise consisting of grasping ten targets with arthroscopic forceps and placing them in a basket on the VirtaMed ArthroS™ simulator. The exercise was performed with the scope and grasping instrument pointed away from the operator, "catch the stars front" (CTSF), then directed towards the operator, "catch the stars back" (CTSB). The simulator recorded several parameters making up an overall composite score ("overall performance score", OPS) out of 120 points. Voluntary abandonment of the exercise was also collected. RESULTS: All students completed the CTSF exercise but 6 dropped out of the CTSB exercise (27%, p=0.01). In the CTSF exercise, the average OPS was higher with 45.9 points versus 22.8 points in the CTSB exercise (p<0.001). By detailing the components of the OPS score, the parameters of interest on the Fundamentals of Arthroscopic Training (FAST) module of the simulator included: the distance traveled by the scope and the grasping forceps was significantly greater in the CTSB group (p<0.001), the duration of the exercise was significantly greater in the CTSB group (p<0.001), the time spent with the instruments in the videoscopic field was significantly lower in the CTSB group (p=0.001) and finally the absence of a significant difference in the camera alignment compared to the horizontal plane between the two groups. CONCLUSION: The exercise with the instruments directed towards the operator is more difficult with a greater distribution for all the secondary criteria except for the camera alignment, which suggests that it could be more discriminating. The dropout rate is also higher. It would therefore be interesting to introduce CTSB type training in initial training programs in arthroscopy. LEVEL OF EVIDENCE: III, comparative prospective study.