Modeling Ultrafast Laser Ablation on the Glenoid Bone for the Fitting of a Prosthetic Screw

In order to fit prosthetic screws, mechanical drilling of the bone has been the norm since the development of modern surgery. However, bone reabsorption, hyperthermia and thermo necrosis could occur depending on the exposure time to the drill and elevated temperature in the surrounding bone due to friction and drill pressure. Non-contact ablation using a CO2 laser can potentially increase the accuracy of the bone drilling and reduce the amount of friction applied to the bone, thus reducing the thermal effects on the surrounding tissue. A model of laser ablation of the human glenoid bone was done on COMSOL with a governing equation of transient state heat transfer from laser to bone. This heat transfer was then correlated to bone loss. According to previous studies, bone disintegration occurs at approximately 613 Kelvin. The bone’s geometry was simplified to a 2-D axisymmetric cylinder. The two domains of the 5mm deep screw region were also 2D-axisymmetric cylinders with varying radius and depth. The phase field model was used to take into account the ablation process of bone. Because the bone essentially disintegrates into “gas-like” particles after reaching this temperature, the phase field model was used to determine the downward velocity of the “air-bone” interface. An adaptive mesh was also developed to move in conjunction with the moving interface. The laser pattern consisted of consecutive concentric cylindrical shells, with the first pulse at the center of the targeted ablated site and the following pulses were cylindrical shells of increasing area. However, because the radial scanning speed was extremely small compared to the pulse duration, concentric cylindrical shells were assumed to occur simultaneously, creating a constant area of laser ablation for each of the two screw domains. Because the CO2 laser did not have a significant penetration depth as the heat generated by the laser was absorbed mainly at the bone surface, input laser heating was modeled as constant flux. Finally, the modeling results for laser ablation were compared to factors in mechanical bone drilling. By varying the input flux of the laser within a range of 300 W/cm2 to 1200 W/cm2 and measuring the total ablation time and the total damage in the surrounding tissue, an optimal flux range between 1050 W/cm2 and 1100 W/cm2 was found to minimize the end time (approximately 0.55 seconds) and thermal damage to the surrounding bone (3.5 mm3). Compared to mechanical drilling, laser ablation with the optimized flux value was much faster than mechanical drilling which can drill at approximately 0.33 mm per second. Generally, less surgery time decreases a patient’s risk when under anesthesia. An increased amount of thermal damage may also lead to refractures, loosening of the prosthetic and permanent loss of tissue function. As laser ablation minimized both these parameters, this model demonstrates that laser ablation of bone is a viable method to consider in future surgical orthopedic work

Recurrent cervical cancer after trachelectomy diagnosed by hysteroscopy: A case report

Surveillance for cervical cancer recurrence after radical trachelectomy is challenging and warrants additional research to establish evidence-based screening guidelines. Papanicolaou (Pap smear) with HPV testing, physical exam, and symptom reporting remain the standard of care despite high false positive rates. In this patient with a history of early-stage cervical adenocarcinoma status post radical trachelectomy, a diagnosis of recurrence was made hysteroscopically, prompting evaluation of the utility of this technique for screening and management of patients with suspected recurrent cervical cancer after trachelectomy

Incisional infiltration versus transversus abdominis plane block of liposomal bupivacaine after midline vertical laparotomy for suspected gynecologic malignancy: a pilot study

Background: To evaluate whether incisional infiltration of liposomal bupivacaine would decrease opioid requirement and pain scores after midline vertical laparotomy for suspected or known gynecologic malignancy compared with transversus abdominis plane (TAP) block with liposomal bupivacaine. Methods: A prospective, single blind randomized controlled trial compared incisional infiltration of liposomal bupivacaine plus 0.5% bupivacaine versus TAP block with liposomal bupivacaine plus 0.5% bupivacaine. In the incisional infiltration group, patients received 266 mg free base liposomal bupivacaine with 150 mg bupivacaine hydrochloride. In the TAP block group, 266 mg free base bupivacaine with 150 mg bupivacaine hydrochloride was administered bilaterally. The primary outcome was total opioid use during the first 48-hour postoperative period. Secondary outcomes included pain scores at rest and with exertion at 2, 6, 12, 24 and 48 h after surgery. Results: Forty three patients were evaluated. After interim analysis, a three-fold higher sample size than originally calculated was required to detect a statistically significant difference. There was no clinical difference between the two arms in mean opioid requirement (morphine milligram equivalents) for the first 48 h after surgery (59.9 vs. 80.8, p = 0.13). There were no differences in pain scores at rest or with exertion between the two groups at pre-specified time intervals. Conclusion: In this pilot study, incisional infiltration of liposomal bupivacaine and TAP block with liposomal bupivacaine demonstrated clinically similar opioid requirement after gynecologic laparotomy for suspected or known gynecologic cancer. Given the underpowered study, these findings cannot support the superiority of either modality after open gynecologic surgery

Development of laparoscopic skills in skills-naïve trainees using self-directed learning with take-home laparoscopic trainer boxes

Background: To determine if take home laparoscopic trainer boxes with only self-directed learning can develop laparoscopic skills in surgically naive learners. Methods: 74 starting PGY1 OB/Gyn residents and OB/Gyn clerkship medical students volunteered for the study. Learners performed a laparoscopic peg transfer task with only task instructions and no additional training. Initial tasks were recorded and scored. The participants took home a laparoscopic trainer box for 3 weeks to practice without guidance and returned to perform the same task for a second/final score. Initial and final scores were compared for improvement. This improvement was compared to practice and variables such as demographics, surgical interest, comfort with laparoscopy, and past experiences. Results: Mean peg transfer task scores improved from 287 (SD = 136) seconds to 193 (SD = 79) seconds (p < 0.001). Score improvement showed a positive correlation with number of home practice sessions with a linear regression R2 of 0.134 (p = 0.001). More practice resulted in larger increases in comfort levels, and higher comfort levels correlated with better final task scores with a linear regression R2 of 0.152 (p < 0.001). Interest in a surgical specialty had no impact on final scores or improvement. Playing a musical instrument and having two or more dexterity-based hobbies was associated with a better baseline score (p = 0.032 and p = 0.033 respectively), but no difference in the final scores or score improvement. No other past experiences impacted scores. Conclusions: Our study demonstrates that the use of home laparoscopic box trainers can develop laparoscopic skills in surgical novices even without formal guidance or curriculum