Personalized lattice-structured prosthesis as a graftless solution for mandible reconstruction and prosthetic restoration: A finite element analysis

Oral cavity tumors are a prevalent cause of mandible reconstruction surgeries. The mandible is vital for functions like oralization, respiration, mastication, and deglutition. Current mandible reconstruction methods have low success rates due to complications like plate fracture or exposure, infections, and screw loosening. Autogenous bone grafts are commonly used but carry the risk of donor region morbidity. Despite technological advances, an ideal solution for mandible reconstruction remains elusive. Additive manufacturing in medicine offers personalized prosthetics from patient-specific medical images, allowing for the creation of porous structures with tailored mechanical properties that mimic bone properties. This study compared a commercial reconstruction plate with a lattice-structured personalized prosthesis under different biting and osseointegration conditions using Finite Element Analysis. Patient-specific images were obtained from an individual who underwent mandible reconstruction with a commercial plate and suffered from plate fracture by fatigue after 26 months. Compared to the commercial plate, the maximum von Mises equivalent stress was significantly lowered for the personalized prosthesis, hindering a possible fatigue fracture. The equivalent von Mises strains found in bone were within bone maintenance and remodeling intervals. This work introduces a design that doesn't require grafts for large bone defects and allows for dental prosthesis addition without the need for implants.

In vitro estimation of the energy loss through turbulence in a porcine aortic valve stenosis model and silicone ascending aorta phantom using backlight particle tracking velocimetry

Introduction

Patients suffering from low-flow, low-gradient aortic stenosis present a decreased stroke volume due to decreased contraction or relaxation function of the left ventricle. As a low stroke volume tends to cause a low transvalvular flow, transvalvular pressure gradient (TVPG) and effective orifice area, the clinician cannot rely on those parameters with confidence for the evaluation of aortic stenosis severity. Hence new diagnostic parameters have to be developed. Energy loss through turbulence associated with aortic stenosis represented the wasted left ventricle work. Currently, echocardiographic measurement of the turbulence intensity is not validated for clinical evaluations of aortic stenosis.

Methods

Two porcine aortic valves were harvested and inserted in a flow loop that replicates the pulsatile flow of the heart. A stiffening of the valves was achieved by treating them with formaldehyde. The stiffening was externally confirmed by a custom-made force-displacement device quantifying the rigidity of the leaflet yielding two stiffness grades per valve. Each valve was tested under three different mean flow rates (1, 2.5, and 4 l/min) at each of the two stiffness grades. Moreover the pressure in the left ventricle chamber and in the aortic chamber was recorded to calculate the TVPG. Particle tracking velocimetry measurements into the transparent silicone ascending aorta phantom allowed the computation of the turbulent kinetic energy (TKE), to evaluate the energy loss due to turbulence.

Results

We could confirm the enhanced rigidity of the valve leaflets with our custom device (data not shown) and measure a consistent increase in TVPG across all mean flow rates between the two stiffness grades. Moreover, an explicit increase of the TKE in the aortic phantom could be measured after the stiffening process (73.1% under 1 l/min, and 43% under both 2.5 and 4 l/min). In addition, a good correlation (R = 0.86) between the mean TVPG and the TKE was found.

Conclusions

This project demonstrated the possibility of quantifying the energy loss attributed to turbulence for porcine valves in vitro for native and added stiffness grade. This project lays the foundation for the development of a new diagnostic tool for the assessment of stenosis severity in patients with low-flow, low-gradient aortic stenosis in cardiac imaging tool such as echocardiography.

Funding Acknowledgement

Type of funding sources: None. TVPG and its correlation with TKEIntensity graphs of the TKE

Choroidal metastases. Echographic experience from 42 patients

Over an 18 year period 42 patients with ocular metastases, age 30-75 years, 27 female and 15 male, were evaluated echographically. The right eye was affected in 18, the left in 17, and both eyes in 7. The most frequent primary tumours were carcinomas from breast (n = 25), lung (n = 6), and urinary bladder (n = 2). The choroidal metastases appeared mainly flat-infiltrating or dome-shaped, on B-scan. A-scan generally revealed high or medium reflectivity, however with important exceptions. Atypical cases are discussed. Usually eyes with metastases should not be enucleated. Accordingly, ultrasonic evaluation and follow-up is of obvious importance.

Day surgery for mucosal-hemorrhoidal prolapse using a circular stapler and modified regional anesthesia

PURPOSE

In 1993, prolapse reduction using the circular stapler for the treatment of hemorrhoidal disease was proposed. The procedure is characterized by minimal postoperative pain. In this study we evaluated the above technique using regional anesthesia to identify the advantages and feasibility of stapled hemorrhoidectomy, with special focus on the efficacy of same-day discharge.

METHODS

From December 1997 to November 1999, we performed 70 consecutive reduction corrections of mucosal hemorrhoidal prolapse using the circular stapler with regional anesthesia (a technical modification of Marti's posterior perineal block). Our series included 41 males and 29 females with a mean age of 43.4 (range, 25-74) years. Three patients were affected by second-degree hemorrhoids and 67 by third-degree hemorrhoids.

RESULTS

Sixty-two patients were discharged three hours after the operation in good general condition and without pain, whereas eight patients were discharged the day after for early complications, consisting of two cases of early bleeding, three cases of urinary retention, and three cases of persistent severe pain requiring prolonged medical treatment.

CONCLUSION

Our study shows that, in selected cases, it is possible to perform day surgery for patients with hemorrhoidal disease using a circular stapler device when combined with regional anesthesia.

Hemorrhoidectomy with posterior perineal block: experience with 400 cases

PURPOSE

The aim of this study was to evaluate the advantages and feasibility of hemorrhoidectomy using regional anesthesia (posterior perineal block).

METHODS

From March 1994 to December 1998 we performed 400 hemorrhoidectomies with regional anesthesia in an overnight-stay regimen in our department (Colo-Rectal Unit). Posterior perineal block involves anesthesia of the deep plains (infiltration of the inferior hemorrhoidal nerves, the posterior branch of the internal pudendal nerves, and the anococcygeal nerves) and anesthesia of the superficial plains (block of the inferior gluteal nerves and of perineal branches of minor nerves from the sacral plexus).

RESULTS

Posterior perineal block was always effective; optimal to satisfactory intraoperative analgesia was obtained in 379 patients (95.2 percent), whereas in 17 cases (4.2 percent) intravenous analgesic drugs were administered. No conversion to general anesthesia was needed. Urinary retention was 7.8 percent. In our study most of patients (70 percent) reported no pain at all for five to ten hours. Ninety-two percent of patients were discharged in the first 24 hours.

CONCLUSIONS

Posterior perineal block allows the surgeon to perform radical hemorrhoidectomies in an overnight-stay regimen with safe and effective intraoperative and postoperative analgesia, sphincter relaxation, and low incidence of urinary retention. Experience of the surgeon combined with careful surgical handling are of great importance for success in this technique.

Value and limits of endorectal ultrasonography for preoperative staging of rectal carcinoma

In rectal cancer, the depth of tumor infiltration and metastatic involvement of lymph nodes are important prognostic factors. Endosonography of the rectum, combining the advantages of both endoscopy and sonography, provides information not available from other imaging diagnostic techniques. From January 1989 to December 1997, 85 patients affected by rectal carcinoma were submitted to preoperative evaluation with endorectal ultrasonography. In 75 cases the results obtained with the endosonography were compared to the histology of the resected specimens. Overall accuracy in staging depth of infiltration was 90.7%. Overstaging occurred in 4% of patients, whereas understaging occurred in 5.3%. In staging lymph nodal involvement, overall accuracy was 76%, sensitivity was 69.8%, specificity was 84.4%, positive predictive value was 85.7%, and negative predictive value was 67.5%. Endorectal ultrasound is a safe and accurate diagnostic method for staging both tumor invasion and lymph node metastatic involvement, and for selecting an appropriate surgical strategy in patients affected by rectal cancer.

[Bleeding in diverticular disease of the colon]

The incidence of bleeding from diverticular disease ranges from 3 to 30%. Haemorrhage is more common when the whole colon is affected; the source is more frequently in the right colon. Typically, the bleeding is massive, with 15% of the patients admitted in shock. It nearly always stops spontaneously, but recurrence rate is high. Chronic blood loss suggests alternative sources. Emergency angiography detects aetiology and site of the haemorrhage in most of the patients. Vasopressin infusion can frequently stop the bleeding. Colonoscopy is profitable only when bleeding stops, after a rapid clearing of the colon. On the other hand, intraoperative colonoscopy could be useful in emergency cases when urgent surgery is clearly indicated. Surgical treatment is requested only in few patients: segmental resections (generally right hemicolectomy) are indicated when there is evidence of the source of the blood loss. In the other cases sub-total or total colectomy are justified and provide better and safer results.

[Esophageal perforations. Diagnosis and treatment]

Perforation of the esophagus was retrospectively analysed in six patients. The age span was 30 years to 81 years, and the male to female ratio was 2 to 1. Each case was studied with regard to presentation, etiology, treatment and complications. The diagnosis was made at postmortem examination only in 1 patient. The perforation was iatrogenic in 1 of the patients and spontaneous in 5. Management was nonoperative in 3 cases and primary repair with drainage was performed in 2 patients. Overall mortality rate for the series was 33%. This series accumulated from a review of the literature emphasizes the importance of the influence of different methods of treatment and time lapsed between occurrence and therapy.

[Crohn's disease in the elderly]

Primary Crohn's disease in the elderly is a not frequent pathology, which however have distinguished from the reheightening or relapse of an inflammatory illness risen up in juvenile age. The Authors compare the personal experience (6 cases on 120 patients operated for Crohn's disease) with the data of the literature. The more frequent localization stays the ileo-colic one, also if in the elderly present better impact the cases of Crohn's colitis (pancolitis or left colitis), with frequent and- perianal implications. The symptomatology is not pathognomonic and above all in the cases of colitis sets problems of differential diagnosis with other pathologies, among which the diverticular disease, that on the other hand, can also coexist with the inflammatory illness. A pharmacological treatment is desiderable, but frequently doesn't result effective. The surgical conservative therapy is not always possible and could be necessary resort to maiming interventions, like massive ileal resections or a total proctocolectomy. From the prognostic point of view, the course appears from the beginning or very favorable (with low index of relapse) or tumultuous (with acute manifestations, which require an emergency surgery, wighted by a more elevated rates of mortality and morbidity.