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M J Lopez

Publications and source records attributed to M J Lopez.

85 records · Page 5Linked to original sources

Development and evolution of pelvic exenteration: historical notes.

Fifty years after the development of pelvic exenteration, the operation remains a gold standard in the surgical management of advanced pelvic malignancy. The operation has evolved through several predictable phases including technical improvements, lowered morbidity and mortality, and improved patient selection. Despite progress in supportive peri-operative care, pelvic exenteration is a major undertaking that should be performed in centers with proven interest and expertise in the field. We trace the early developments of the operation, the period of maturation, and the current place of this procedure in the armamentarium of the oncologic surgeon.

Female↗

Pelvic exenteration for advanced pelvic malignancy.

Pelvic exenteration is a demanding, yet potentially curative operation, for patients with advanced pelvic cancer. The majority will present with recurrence after prior surgery and radiotherapy. After exenteration, 5-year survival is 40% to 60% in patients with gynecologic cancer as compared to 25% to 40% for patients with colorectal cancer. Physiologic age and absence of co-morbidities appear to be more important when selecting patients for exenteration than chronological age. Careful pre-operative staging, including either computed tomography (CT) scan or magnetic resonance imaging (MRI), usually will identify patients with distant metastases, extrapelvic nodal disease, or disease involving the pelvic sidewall (which generally precludes surgery). The recent application of intra-operative radiotherapy or postoperative high-dose brachytherapy for patients with more advanced pelvic disease, which may include sidewall involvement, may expand the standard indications for exenteration. However, the intent of this procedure, with or without radiotherapy, should be resection of all tumor with the aim of cure since the place of palliative exenteration is controversial at best. The operative details of exenteration are presented, as are two surgical approaches to composite resection of pelvic structures in continuity with sacrectomy. Filling the pelvis with large tissue flaps, usually a rectus abdominus flap, has decreased morbidity rates, particularly with small bowel complications. Peri-operative mortality is usually 5% to 10%, and significant morbidity occurs in over 50% of patients. Restorative techniques for both urinary and gastrointestinal tracts can diminish the need for stomas and, along with vaginal reconstruction, can significantly improve quality of life for many patients after exenteration. These advances in surgery and radiotherapy help make the procedure a viable option for patients with otherwise incurable pelvic malignancy.

Female↗

The influence of pre-operative radiation therapy on the patterns of recurrence in rectal adenocarcinoma.

From January 1976 to December 1994, we evaluated the institutional experience of local recurrence and survival in patients with rectal adenocarcinoma treated with pre-operative radiation therapy (PRT) as compared to those treated with radical surgery alone. There were 412 patients, divided into two groups: 259 patients (142 males and 117 females) in Group I and 153 patients (88 males and 65 females) in Group II. The median age was 56 years. Group I patients with locally advanced tumors, either tethered or fixed, received PRT at doses of 45 Gy delivered to the pelvis in two fields; 4 to 8 weeks later, radical surgery was performed. Patients with mobile tumors underwent radical surgery only (Group II). The operative mortality was 4.6% in Group I as compared to 1.9% in Group II (P = 0.18). At median follow-up of 89 months, there were local recurrences in 12.9% of Group I as compared to 36.2% in Group II (P = 0.0000001). The administration of PRT was associated with a low rate of local recurrence, but this improvement corresponded with a high morbidity rate, especially in patients who underwent abdominoperineal resection or pelvic exenteration.

Adenocarcinoma↗

Pelvic exenteration for carcinoma of the colon and rectum.

Carcinoma of the colon and rectum is one of the most common causes of cancer deaths in the United States. The mortality of patients treated by surgery alone is 55% within 5 years of surgery. Despite efforts to decrease local recurrence and their concomitant problems of pain and disability, a significant number of patients will still have pelvic recurrences that carry a significant morbidity. In selected cases, pelvic exenteration may cure or provide palliation of the symptoms of colorectal carcinoma. Pre-operative evaluation is performed to detect signs of unresectability. During surgery, exploration is performed for evidence of metastases to the liver, omentum, and peritoneum, followed by an assessment of the local extent of the tumor. The margins of resection must be clear even if resection of contiguous organs or bony structures is necessary. The urinary tract is resected with an ileal loop, sigmoid or transverse colon conduits, or continent urinary diversion. Depending upon the involvement of neighboring structures, exenterative pelvic surgery can be modified for organ preservation.

Colorectal Neoplasms↗

The effect of radiofrequency energy on the ultrastructure of joint capsular collagen.

This study evaluated the effect of radiofrequency energy on the histological and ultrastructural appearance of joint capsular collagen. Femoropatellar joint capsular specimens from adult sheep were treated with one of three treatment temperatures (45 degrees C, 65 degrees C, and 85 degrees C) with a radiofrequency generator or served as control in a randomized block design. Twenty-four specimens (n = 6) were processed for histological examination as well as ultrastructural analysis using transmission electron microscopy. A computer-based area determination program was used to calculate the area affected in histological samples. Histological changes consisted of thermal tissue damage characterized by collagen fiber fusion and fibroblastic nuclear pyknosis at all application temperatures with clear demarcations between treated and untreated tissue. Mean tissue affected ranged from 50.4% for 85 degrees C to 22.5% for 45 degrees C. There was a strong correlation between treatment temperature and percent area affected (P < .001, R2 = .65). Ultrastructural alterations included a general increase in cross-sectional fibril diameter and loss of fibril size variation with increasing treatment temperature. Longitudinal sections of collagen fibrils showed increased fibril diameter and the loss of cross-striations in the treated groups. Thermally induced ultrastructural collagen fibril alteration is likely the predominant mechanism of tissue shrinkage caused by application of radiofrequency energy.

Animals↗

An in vitro biomechanical comparison of interlocking nail constructs and double plating for fixation of diaphyseal femur fractures in immature horses.

OBJECTIVE: To compare the biomechanical properties of intact immature horse femurs and 3 stabilization methods in ostectomized femurs. ANIMAL OR SAMPLE POPULATION: Eighteen pairs of femurs from immature horses aged 1 to 15 months, and weighing 68 to 236 kg. METHODS: Thirty-four immature horse femurs were randomly assigned to 1 of 5 test groups: 1) interlocking intramedullary nail (IIN) (n = 6); 2) IIN with a cranial dynamic compression plate (I/DCP) (n = 6); 3) 2 dynamic compression plates (2DCP) (n = 8); 4) intact femurs tested to failure in lateromedial (LM) bending (n = 6); and 5) intact femurs tested to failure in caudocranial (CaCr) bending (n = 8). Mid-diaphyseal ostectomies (1 cm) were performed in all fixation constructs. Biomechanical testing consisted of 4 nondestructive tests: CaCr bending, LM bending, compression, and torsion, followed by bending to failure. All groups were tested to failure in LM bending with the exception of 1 group of intact femurs tested to failure in CaCr bending. Stiffness and failure properties were compared among groups. RESULTS: The 2DCP-femur construct had greater structural stiffness in nondestructive bending than the IIN-femur construct in either LM or CaCr bending, and the I/DCP-femur construct in LM bending. Only the I/DCP and 2DCP fixations were similar to intact bone in nondestructive-bending tests. In addition, the 2DCP-femur construct had greater structural and gap torsional stiffness than the I/DCP-femur construct, and greater gap torsional stiffness than the IIN-femur construct. However, all of the fixation methods tested, including the 2DCP-femur construct, had lower structural stiffness in torsional loading compared with intact bone. No significant differences in structural stiffness were found between intact bones and femur constructs tested nondestructively in compression. In resistance to LM bending to failure, the 2DCP-femur construct was superior to the IIN-femur construct, yet similar to the I/DCP-femur construct. Also, evaluation of yield and failure loads revealed no significant differences between intact bone and any of the femur constructs tested to failure in LM bending. CONCLUSIONS: In general, the 2DCP-femur construct provided superior strength and stiffness compared with the IIN and I/DCP-femur constructs under bending and torsion. CLINICAL RELEVANCE: Double plating of diaphyseal comminuted femoral fractures in immature horses may be the best method of repair, because in general, it provides the greatest strength and stiffness in bending and torsion.

Animals↗

An in vitro biomechanical comparison of two interlocking-nail systems for fixation of ostectomized equine third metacarpal bones.

OBJECTIVE: To compare the mechanical properties of 2 interlocking-nail systems for fixation of ostectomized equine third metacarpi (MC3): (1) a standard interlocking nail with 2 parallel screws proximal and distal to a 1-cm ostectomy; and (2) a modified interlocking nail with 2 screws proximal and distal to a 1-cm ostectomy with the screws offset by 30 degrees. ANIMAL OR SAMPLE POPULATION: Twelve pairs of adult equine forelimbs intact from the midradius distally. METHODS: Twelve pairs of equine MC3 were divided into 2 test groups (6 pairs each): torsion and caudocranial 4-point bending. Standard interlocking nails (6-hole, 13-mm diameter, 230-mm length) were placed in 1 randomly selected bone from each pair. Modified interlocking nails (6-hole, 13-mm, 230-mm length, screw holes offset by 30 degrees) were placed in the contralateral bone from each pair. All bones had 1-cm mid-diaphyseal ostectomies. Six construct pairs were tested in caudocranial 4-point bending to determine stiffness and failure properties. The remaining 6 construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t test within each group. Significance was set at P <.05. RESULTS: Mean (+/-SEM) values for the MC3-standard interlocking-nail composite and the MC3-modified interlocking-nail composite, respectively, in 4-point bending were: composite rigidity, 3,119 +/- 334.5 Nm/rad (newton. meter/radian) and 3,185 +/- 401.2 Nm/rad; yield bending moment, 205.0 +/- 18.46 Nm and 186.7 +/- 6.17 Nm; and failure bending moment, 366.4 +/- 21.82 Nm and 378.1 +/- 20.41 Nm. There were no significant differences in the biomechanical values for bending between the 2 fixation methods. In torsion, mean (+/-SEM) values for the MC3-standard interlocking-nail composite and the MC3-modified interlocking-nail composite were: composite rigidity, 135.5 +/- 7.128 Nm/rad and 112.5 +/- 7.432 Nm/rad; gap stiffness, 207.6 +/- 10.57 Nm/rad and 181.7 +/- 12.89 Nm/rad; and yield load, 123.3 +/- 2.563 Nm and 107.5 +/- 8.353 Nm, respectively. Composite rigidity and gap stiffness for standard interlocking-nail fixations were significantly higher than the modified interlocking-nail fixation technique in torsion. Yield load had a tendency to be higher for the standard interlocking-nail fixation (P =.15). CONCLUSIONS: No significant differences in biomechanical properties were identified between a standard interlocking nail and one with the screw holes offset by 30 degrees in caudocranial 4-point bending. The standard interlocking nail was superior to the modified interlocking nail in torsional gap stiffness and composite rigidity. The torsional yield load also tended to be higher for the standard interlocking nail. CLINICAL RELEVANCE: The standard interlocking nail with parallel screw holes is superior to a modified interlocking nail with the screw holes offset by 30 degrees in ostectomized equine MC3 bones in vitro when tested in torsion.

Animals↗

Cephalad distribution of three differing volumes of new methylene blue injected into the epidural space in adult goats.

Epidural anesthesia and analgesia are popular regional anesthetic techniques in many animal species. However, we have not found any reports of studies in animals that have investigated the extent of cephalad migration and level of sensory blockade achieved based only on the volume of drug injected into the epidural space. The purpose of this study was to determine if there is a relationship between the volume (mL/kg) of an injectate injected epidurally and the extent of its cephalad migration within the epidural space. Twelve adult goats were randomly assigned to three treatment groups based on the volume of 0.12% New Methylene Blue (NMB), 0.1, 0.2, or 0.3 mL/kg, injected into the epidural space. The site and speed of injection, animal position, and direction of needle bevel were held constant. All injections were performed at the lumbo-sacral space immediately following euthanasia. At necropsy, the vertebral columns were transected longitudinally. The extent of cephalad migration of dye within the epidural space was easily determined by staining of the dura. Measurements were rounded to the nearest intervertebral space to which the dye had migrated. The individual making assessments was blinded to all treatments. In goats treated with 0.1, 0.2, or 0.3 mL/kg NMB, the number of stained spinal segments was 3.5 +/- 0.6, 6.5 +/- 0.9, and 8.8 +/- 0.6, (mean +/- SEM), respectively. Linear regression performed on the data was significant (P < .05) with R2 = 0.86. There was a strong linear relationship between volume (mL/kg) of epidurally injected NMB and cranial migration, with the larger volumes producing more cephalad spread within the epidural space. These results provide evidence for the volume of epidural injectate needed to produce a desired level of sensory blockade in adult goats.

Animals↗

An in vitro biomechanical comparison of an interlocking nail system and dynamic compression plate fixation of ostectomized equine third metacarpal bones.

OBJECTIVE: To compare the mechanical properties of two stabilization methods for ostectomized equine third metacarpi (MC3): (1) an interlocking nail system and (2) two dynamic compression plates. Animal or Sample Population-Ten pairs of adult equine forelimbs intact from the midradius distally. METHODS: Ten pairs of equine MC3 were divided into two test groups (five pairs each): caudocranial four-point bending and torsion. Interlocking nails (6 hole, 13-mm diameter, 230-mm length) were placed in one randomly selected bone from each pair. Two dynamic compression plates one dorsally (12 hole, 4.5-mm broad) and one laterally (10 hole, 4.5-mm broad) were attached to the contralateral bone from each pair. All bones had 1 cm mid-diaphyseal ostectomies. Five construct pairs were tested in caudocranial four-point bending to determine stiffness and failure properties. The remaining five construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite, respectively, in four-point bending were: composite rigidity, 3,454+/-407.6 Nm/rad and 3,831+/-436.5 Nm/rad; yield bending moment, 276.4+/-40.17 Nm and 433.75+/-83.99 Nm; failure bending moment, 526.3+/-105.9 Nm and 636.2+/-27.77 Nm. There was no significant difference in the biomechanical values for bending between the two fixation methods. In torsion, mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite were: composite rigidity, 124.1+/-16.61 Nm/rad and 262.4+/-30.51 Nm/rad; gap stiffness, 222.3+/-47.32 Nm/rad and 1,557+/-320.9 Nm/rad; yield load, 94.77+/-7.822 Nm and 130.66+/-20.27 Nm, respectively. Composite rigidity, gap stiffness, and yield load for double plate fixation were significantly higher compared with interlocking nail fixation in torsion. CONCLUSIONS: No significant differences in biomechanical properties were identified between an interlocking nail and double plating techniques for stabilization of ostectomized equine MC3 in caudocranial four-point bending. Double plating fixation was superior to interlocking nail fixation in torsion.

Animals↗

Voice rehabilitation practices among head and neck surgeons.

Voice rehabilitation practices among head and neck surgeons were surveyed to determine the proportional contribution of various methods of speech support and the impact of recent developments in this field. Of the 400 head and neck surgeons contacted, 212 (53%) responded and 196 provided data. Noninvasive methods of speech support continue to predominate in this country. Esophageal speech is used by all surgeons in some of their patients. The introduction of tracheoesophageal puncture techniques for prosthetic placement has added a new dimension to speech rehabilitation and is used almost 30% of the time by those who use it (88% of surgeons surveyed). The proportional use of the most common methods of speech support is almost identical between head and neck surgeons of a general surgical background and otolaryngologists. The incidence of total failures to achieve voice rehabilitation is less than 10%.

General Surgery↗