BACKGROUND: The evolution of warfare has resulted in a surge of high-energy blast injuries predominantly involving the lower extremities. Once thought to impact only forward-deployed military, such mechanisms of injury are becoming a harsh reality even in civilian territory. Proficiency in surgical techniques for extremity damage control is vital for surgeons, regardless of specialty. To evaluate and train surgical residents and attending surgeons in critical limb-salvage techniques, Theater Hospital Operations Replication (THOR) has been proposed as a high-fidelity training platform to enhance extremity surgery teaching practices and assess proficiency in fasciotomy, vascular shunting, and knee-spanning external fixation in a simulated, resource-limited environment. QUESTIONS/PURPOSES: Given the importance of proficiency and efficiency in surgeon ability to perform fasciotomies, vascular shunting, and placement of external fixators, in this study, we proposed two research questions: (1) Does repetition-based training within the THOR model improve surgeon knowledge and technical skill? (2) Are there differences in skill outcome when utilizing the THOR model based on surgical specialty (orthopaedic versus general) and/or level in training (attending versus resident)? METHODS: This was an observational learning outcome study performed in the bioskills lab at a single institution, the Naval Medical Center Portsmouth, in which 26 surgeons completed a same-day course consisting of pretraining assessment, cadaver training on three damage-control surgery techniques in a high-fidelity THOR environment, and post-training assessment. The surgeons were either general surgeons or orthopaedic surgeons and consisted of both residents and attending surgeons. Subjects underwent a pretraining knowledge assessment, followed by two rounds of performing simulated surgery. The first round of surgery included guidance and instruction from board-certified orthopaedic surgeons. After a short break for the subjects to review the material, the second round was completed without instruction. To answer our first question of how repetition-based training impacts surgical skill, our metrics included: Objective Structured Assessment of Technical Skills (OSATS) scores (range 1 to 5, scored lowest to highest, where higher scores represent optimal skill performance), procedural accuracy, a 10-question knowledge assessment administered before and after training (scored 0 to 10, where higher scores represent competency of the anatomy and procedure steps), and total procedure time. To address our second question, data on demographic characteristics were collected on all participants, which included surgical specialty, year in training, and gender. RESULTS: The general surgery residents' cohort demonstrated improvement in both mean ± SD OSATS scores (2.4 ± 0.7 before training versus 3.6 ± 0.6 after training, mean difference 1.2 [95% CI 0.4 to 2.0]; p = 0.01) and procedure duration (23 ± 7 minutes before training versus 16 ± 5 minutes after training, mean difference 6 minutes [95% CI 4 to 9]; p = 0.001) for external fixator procedures after THOR. Similar results were seen in fasciotomies after THOR. The orthopaedic surgery residents' cohort showed similar improvements in reducing procedure duration when performing knee-spanning external fixator surgery, as well as exhibited improvements during vascular shunting procedures in both mean ± SD OSATS scores (previously 3.3 ± 0.9 versus 4.0 ± 0.9, mean difference 0.7 [95% CI 0.2 to 1.2]; p = 0.01) and procedure duration (23 ± 5 minutes versus 14 ± 8 minutes, mean difference 10 minutes [95% CI 4 to 15]; p = 0.003) after THOR. When we compared the cohorts, general surgery attending surgeons demonstrated an improvement in vascular shunting procedure duration after instruction with the THOR model (19 ± 3 minutes versus 12 ± 4 minutes, mean difference 7 minutes [95% CI 1 to 13]; p = 0.03) and in overall knowledge scores (4.3 + 0.5 versus 8.0 ± 1.6, mean difference 3.8 [95% CI 0.5 to 7.0]; p = 0.04). The orthopaedic surgery attending surgeons yielded no improvement for any metric, pretraining and post-training. Using the prescores as a covariate, for almost all metrics analyzed, there were no differences between surgeon groups based on specialty after completing the repeated training. CONCLUSION: Use of the high-fidelity THOR training model improved proficiency in the examined sample of extremity damage-control procedures, thus demonstrating its efficacy in enhancing surgical skills and short-interval knowledge retention while simultaneously highlighting the importance of cadaver simulation training in enhancing surgical preparedness for complex trauma. CLINICAL RELEVANCE: The high-fidelity THOR training model represents a promising modality for preparing surgeons for extremity combat trauma management in resource-limited, high-stress environments. Whether in a wartime environment or in the civilian sector, efficient and skilled intervention are crucial in managing patient morbidity. Differences of a few minutes per procedure can mean all the difference in damage control, especially when compounded in situations where vascular shunting, knee-spanning external fixation, and lower leg four-compartment fasciotomy have to be performed together by both orthopaedic and general surgeons. The observational period in this study spanned 1 day and thus does not provide information on retention of long-term skills or knowledge. A follow-on study can assess how time from initial training to final evaluation impacts overall skill competency and knowledge.