Tool-tissue interaction force in glioma surgery

Among neurosurgical patients, using sensorized bipolar forceps, we have previously shown that high force error is often associated with bleeding, low force error with need to repeat the task, and force variability with both. Using a sub-group of glioma patients, here we further interrogate if forces of tool–tissue interaction would be similar, as intra-operative differentiation between normal brain and tumor can be difficult.

The SmartForceps System, a force-sensing bipolar forceps with an intelligent software interface, allows monitoring, recording and uploading intra-operative tool–tissue forces. Twelve surgeons participated including 2 expert (10 + years of experience), 4 novice (PGY 1–3) and 6 intermediate (PGY 5–6 and fellows) surgeons. Force profile for 5 predetermined surgical tasks, i.e., dissection, coagulation, retracting, pulling, and manipulating, were recorded.

Force data from 1206 trials (16 patients) were analyzed. The mean (SD) for tumor coagulation was 0.32 ± 0.24 N. Force exerted by novice surgeons was significantly lower than expert and intermediate surgeons (0.21 [0.19] vs. 0.33 [0.27] and 0.33 [0.22]; p < 0.0001). There was no difference in the force profiles between intermediate and expert. Force variability decreased from novice (0.90) to intermediate (0.81) and to expert (0.66). Oligodendroglioma required lower coagulation forces than grade 2 astrocytoma and high-grade gliomas (0.23 [0.14] vs 0.49 [0.30] and 0.33 [0.25]; p < 0.0001).

The study demonstrated that novice surgeons used lower forces than the intermediate or expert. This may in part reflect their hesitancy and difficulty differentiating normal brain from pathology. The gradual reduction in force variability from novice to expert surgeon is interesting, and may correspond to the learning curve.