A quantitative analysis of the hip shuck test during robotic arm-assisted total hip arthroplasty

Background: The shuck test is a subjective method used intraoperatively to measure soft tissue tension during total hip arthroplasty (THA). This study aimed to introduce and quantify the shuck length vector magnitude in patients undergoing robotic arm-assisted THA, and identify factors affecting its value. Methods: This prospective cohort study analysed 95 primary THAs performed on 87 patients. Surgical data and intraoperative soft tissue tension measurements were recorded using the Mako robotic arm-assisted system. An exploratory analysis of factors affecting the shuck length vector magnitude was performed. Results: The mean shuck length vector magnitude was 8.7 mm. Shuck length vector magnitude was significantly higher in males as compared to females ( p = 0.017). A strong inverse correlation was found between increased hip offset and hip length on shuck length vector magnitude ( p < 0.001 and p = 0.004, respectively). Shuck length vector magnitude was not affected by femoral head size ( p = 0.674) and arthritis severity ( p = 0.141). Conclusions: This study demonstrates that it is possible to quantify soft tissue tension using the shuck test during robotic-assisted THA. Restoring hip offset is crucial for optimising joint stability. Future research should establish a threshold for acceptable shuck length vector magnitude and correlate this with dislocation rates and patient reported outcomes.