Biomedical subjects

J B Martinez

Publications and source records attributed to J B Martinez.

3 recordsLinked to original sources

PubMed2001

Robotic assisted, laparoscopic pelvic lymph node dissection in humans.

PURPOSE: We evaluate the feasibility and efficacy of robotic assisted, laparoscopic pelvic lymph node dissection for locally advanced prostate cancer staging. MATERIALS AND METHODS: Robotic assisted, laparoscopic pelvic lymph node dissection was performed in 10 consecutive patients with mainly T3 M0 prostatic carcinoma (robotic group). Operative, postoperative and pathological parameters were compared with the results of the last 10 patients undergoing conventional, laparoscopic pelvic lymph node dissection performed with similar indications by the same operator (laparoscopy group). RESULTS: All operations were performed according to the established protocol with no specific intraoperative or postoperative complications. No conversion was required, and no technical incidents were observed in the robotic group. Mean operating time plus or minus standard deviation for the robotic group was 125 +/- 57 minutes (range 75 to 215), significantly longer than that for the laparoscopy group, which was 60 +/- 15 minutes (p = 0.0013). In the robotic group 2 patients presented with postoperative lymphoceles revealed in 1 by deep venous thrombosis and in the second by obturator pain. In the laparoscopy group 1 patient presented with acute urinary retention. The histological results concerning the number of lymph nodes removed were similar in both groups (p = 0.5). CONCLUSIONS: We show the technical feasibility of robotic assisted, laparoscopic pelvic lymph node dissection in humans. Although the benefit of this technique has not yet been established, predictable technological improvements would suggest the development of telesurgery and an improved precision of surgical procedure.

Aged↗

PubMed1998

Experimental factors governing the internal stress state of the intervertebral disc.

This paper presents an experimental study of the response of the intervertebral disc to short-term static-axial loading within the conceptual framework of mechanical consolidation as applied to swelling materials. An experimental technique developed previously for articular cartilage was used to load the disc in compression and measure simultaneously the matrix internal excess pore pressure under both radially constrained and radially unconstrained conditions. Specifically the short-term pattern of development of the hydrostatic excess pore pressure was investigated. The average ratio of the maximum excess pore pressure u(i) to the nominal applied stress for unconstrained loading was approximately 1.9 while for constrained loading it was about 1.4. This behaviour is interpreted in terms of the generation of a pore pressure in the nucleus which reflects a non-uniform partitioning of the applied load across the inhomogeneous structure of the disc. These results provide a quantitative insight into the role that physico-chemically generated swelling plays in determining the internal mechanical response of the disc to an externally applied load and suggest a quantitative means of investigating the important influence of degenerative changes on the internal stress state of the disc without needing to pierce the annular wall in order to insert a pressure sensing device.

Animals↗

PubMed1997

Biomechanics of load-bearing of the intervertebral disc: an experimental and finite element model.

This paper presents an experimental and finite element study of the biomechanical response of the intervertebral disc to static-axial loading in which classical consolidation theory was used to analyse its time-dependent response. A newly developed experimental technique was employed to load the disc in compression and measure simultaneously the matrix internal pressure and creep strain for the full consolidation process. It is shown that, upon loading, the disc develops a maximum hydrostatic excess pore pressure which gradually decays as water is exuded from the matrix. During this decay process, the applied load is progressively transferred to the solid components of the matrix until the load is borne in full by the solid at the end of consolidation. Material properties for the tissue were then obtained from the experimental stress-strain data and used in the finite element study in the development of a finite element solution based on Biot's theory of coupled solid-fluid interaction. An axisymmetric formulation was employed and the disc modelled as an anisotropic, non-linear poroelastic solid. A sensitivity analysis of the material properties for the structural components of the disc was carried out and the biomechanical response to compressive loading evaluated and compared to experimental data. The results show that the matrix permeability plays a significant role in determining the transient response of the tissue. Annular disruptions of the disc were shown to result in an increase in the nuclear principal stresses suggesting that disrupted regions of the annulus fibrosus play a reduced role in load bearing.

Animals↗