Diminished suture strength after robotic needle driver manipulation.

Robot-assisted minimally invasive surgery has become a routine surgical option for the treatment of prostate cancer. Despite its technical advancements, the da Vinci(®) Surgical System still lacks haptic feedback to the surgeon, resulting in a maximally applied compressive force by the robotic needle driver during every grasping maneuver. Without this perceptional sense of touch and grip control, repetitive robotic needle driver manipulation may unknowingly lead to irreparable damage to fine sutures used during delicate anastomotic repairs. For robotic prostatectomy, any such loss of integrity can potentially lead to premature breakdown of the urethrovesical anastomosis and urine extravasation, especially important for a less-than-perfectly fashioned anastomotic repair. Although it has already been established that overhandling of sutures using handheld laparoscopic instruments can lead to reduced suture strength, it has not been established to what extent this may occur after robotic surgical procedures. We present analytical data and analyses concerning the failure strength of fine sutures commonly used for urethrovesical anastomotic repair during robotic prostatectomy, after repetitive robotic needle driver manipulation. When compared with noncompromised monofilament suture controls, the average maximal failure force after repetitive robotic manipulation was significantly reduced by 35% (p < 0.0001). Similarly, the average maximal failure force of braided sutures was significantly reduced after repetitive robotic manipulation by 3% (p = 0.009). This work demonstrates that significant reductions in monofilament and braided suture strength integrity can occur after customary repetitive manipulation by robotic needle drivers in an ex vivo model, with further research warranted in the in vivo setting.

A method for the consistent creation and quantitative testing of postoperative pelvic adhesions in a porcine model.

INTRODUCTION: The assessment of methods for the prevention of postoperative pelvic adhesions is hampered by the lack of a quantifiable adhesion measurement technique. Currently available methods for adhesion model assessment rely on qualitative grading scales; a quantitative method would have many attendant benefits, including standardized reporting. METHODS: A technique was developed to generate consistent and significant adhesions in a swine model that are suitable for quantitative assessment using a Material Testing System (MTS) machine platform. In this method, the uterine horns are cannulated and then attached to the pelvic sidewall using loose silk sutures. The underlying sidewall and adjacent uterine serosa are injured with electrocautery. Following a two-week survival the entire complex of uterine horn and sidewall are excised en bloc and prepared for MTS testing. RESULTS: Extrication of the adhesion, as measured by the MTS platform, generates a quantitative assessment of adhesion strength that can be scaled and analyzed to produce several continuous variable descriptions. DISCUSSION: This technique represents a novel quantitative method for adhesion assessment in an animal model. This quantitative technique may then be applied to accurately assess a range of adhesion prevention techniques, producing results which can be standardized for comparison.

Novel method used to test pullout parameters of different nephrostomy catheters.

PURPOSE: To present a novel in-vitro pig model for testing the design and function of different internal catheter constructs, along with the resulting exit wound resulting from removal. MATERIALS AND METHODS: We compared the pullout parameters of two nephrostomy catheters that differ only in their internal loop design. RESULTS: Greater force, work, and displacement are necessary to extricate catheters with a double loop without increasing exit-wound size. CONCLUSION: Although the differences were not statistically significant, results from this model have potential clinical implications that may prompt further design modifications and prototype development to improve the retention of catheters in the kidney, thus reducing patient discomfort and costs associated with repeated catheter placement.

Measuring flexion in knee arthroplasty patients.

Flexion following total knee arthroplasty can be visually estimated, measured with a goniometer placed against the patient's leg, or measured from a lateral radiograph of the flexed knee. Three examiners, in a blinded fashion, estimated the degree of maximal knee flexion and measured the flexion with a goniometer for 27 knees in 16 patients. A lateral knee radiograph then was taken and the flexion angle was measured from the radiograph by 2 different methods. Although interobserver and intraobserver correlation coefficients were high (0.79 and 0.92), 45% of the visual estimates and 22% of the goniometer measurements differed by 5 degrees or greater from the radiographic measurements. These differences increased as the flexion angle increased. Body mass index did not affect the accuracy of the estimates or goniometer measurements.

Prosthetic metals have a variable necrotic threshold in human fibroblasts: an in vitro study.

The generation of metal particles from prosthetic joints has been an evolving problem in orthopedics. Numerous factors have been involved including cells, metals, and responding cytokines, but determining roles of these factors or cascades of factors has been elusive. This laboratory has published threshold levels for commercially pure titanium (CpTi), which led to cell necrosis, but noted that cell viability differed among donor patients. To compliment the previous work we examined two other metals, Tantalum (Ta) and cobalt-chrome (CoCr), while making comparative measurements in these different donor patients. Retrieved human fibroblasts (superior medial plica) were cultured in a standard manner and exposed to various dosages of the three metals. Cell counts and interleukin (IL) 6 were used as dependent variables within a three-way analysis of variance. The data show that fibroblast necrosis was significantly affected by both type and mass of metal, with each metal having a distinct threshold (CpTi most necrotic, followed by Ta and CoCr). The cell counts and IL-6 at control levels varied significantly among all three donors. However, the response to the metals and dosages did not differ among tissue donors. Thus, although each patient had a different starting value for cell counts and IL-6, they responded to the metal particles in the same proportionate manner.