Analytic Route to Tunneling Splittings Using Semiclassical Perturbation Theory.

We present an efficient, analytical, and simple route to approximating tunneling splittings in multidimensional chemical systems, directly from ab initio computations. The method is based on the Wentzel-Kramers-Brillouin (WKB) approximation combined with the vibrational perturbation theory. Anharmonicity and corner-cutting effects are implicitly accounted for without requiring a full potential energy surface. We test this method on the following three systems: a model one-dimensional double-well potential, the isomerization of malonaldehyde, and the isomerization of tropolone. The method is shown to be efficient and reliable.

Hydrogen tunnelling in the rearrangements of carbenes: the role of dynamical calculations.

Tunnelling controlled chemical reactions are those which preferably proceed through pathways with high but narrow potential energy barriers, via quantum tunnelling, resulting in a product that would be disfavoured classically. These reactions are very sensitive to barrier width, height and temperature and so dynamical theoretical methods are required to describe these processes. Recent experimental work on charge-tagged phenyl pyruvic acid derivatives has found, in contrast to similar systems, no evidence of tunnelling control. Using semiclassical transition state theory, we rationalise these results and find tunnelling is significant in this system.

New Developments in Semiclassical Transition-State Theory.

This Feature Article describes some recent developments and applications of the Semiclassical Transition-State Theory (SCTST) for treating quantum tunneling in chemical reactions. A reduced dimensional form of the SCTST is discussed and is shown to be particularly efficient, as the required number of electronic structure calculations is reduced to an absolute minimum. We also describe how an alternative formulation of SCTST developed by Hernandez and Miller [ Chem. Phys. Lett. 1993 , 214 , 129 ], the SCTST-θ, has advantages in allowing for straightforward applications of the SCTST for any form of the potential expansion at the transition state. We also illustrate the power of SCTST in applications to more complex systems. We show how polyatomic modes such as internal rotations and torsions can be treated efficiently in SCTST calculations. We also describe some applications of the method to hydrogen atom tunneling in unimolecular reactions including the degradation of chemical nerve agents and the decay of the atmospherically important Criegee intermediates.

Catalysis and tunnelling in the unimolecular decay of Criegee intermediates.

The unimolecular decay of Criegee intermediates is the major producer of OH radicals in the atmosphere. Here, Semi-Classical Transition State Theory (SCTST) in full and reduced dimensions is used to determine thermal rate constants for their unimolecular decay, as well as their decay catalysed by a single water molecule. These reactions shed light on the applicability of SCTST for catalysed hydrogen transfer reactions.

The floating hip: complications and outcomes.

BACKGROUND: To perform a descriptive study of the course, treatment decisions, complications, and outcome of patients suffering simultaneous ipsilateral fractures of the femur and pelvis. METHODS: Medical records and radiographs of 57 patients were reviewed retrospectively. RESULTS: The average follow-up was 28 months. Fifteen patients (26%) had an acetabular fracture, 17 (30%) had a pelvic ring fracture, and 25 (44%) had both fractures concomitant with the ipsilateral femoral fracture. Eighty percent of acetabular fractures and 55% of pelvic ring fractures were treated surgically. Femur fractures underwent operation in 94% of cases. When multiple operative settings were used, the femur fracture was always fixed at the first operation. Complications included deep venous thrombosis (DVT) (12%), heterotopic ossification (HO) (34%), femoral head avascular necrosis (AVN) (2%), osteoarthritis (OA) (16%), and traumatic sciatic nerve palsy (33%). At least partial nerve palsy resolution occurred in 53% of patients. CONCLUSIONS: Ipsilateral injuries to the femur and the pelvis or acetabulum ("floating hip") are severe injuries usually caused by high-energy trauma. The acetabulum and pelvic ring are more commonly fractured together than either alone. The femur fracture will most commonly be addressed first, as in 65% of our cases in which both components were addressed at the same setting, and 100% of cases in which they were addressed in separate settings. Delays of surgery were common because of severity of systemic trauma. Surgeons should be aware of the high incidence of sciatic nerve palsy as well as treatment options and potential complications associated with this devastating combination of injuries.

Post-traumatic catamenial sciatica.

This article presents a unique case of posttraumatic extrapelvic endometriosis presenting as a gluteal mass causing cyclic sciatica. A 38-year-old woman presented with an enlarging right buttock mass over the previous 6 years. She also had symptoms of radicular pain referred to the right leg and foot with sitting and daily activity. Four years prior to noticing the mass, she sustained a gunshot wound through the lower abdomen while 5 months pregnant. Excisional biopsy of the gluteal mass revealed endometrioma. Sciatica is a common and painful disorder that is believed to have an incidence of 40% in the adult population. Sciatica is most often due to intraspinal pathology affecting the lumbar nerve roots. There are many recognized extraspinal etiologies for sciatica in the literature including aneurysms, sciatic hernia, abcess, neoplasm, trochanteric wire, piriformis syndrome, ischial fracture, a posteriorly flexed uterus, and even an intrauterine device following uterine perforation. Similarly, endometriosis is a gynecologic condition that represents a significant health problem for women of reproductive age as it occurs in up to 50% of premenopausal women and 71% to 87% in women with chronic pelvic pain. Although rare, endometriosis has a well known ability to migrate outside of the abdominal cavity and proliferate ectopically under the control of systemic estrogen.

Enhanced fracture and soft-tissue healing by means of anabolic dietary supplementation.

BACKGROUND: Malnutrition is common in hospitalized injured patients. It contributes to delayed fracture-healing and increased morbidity. However, relatively little attention has been directed toward nutritional strategies for augmenting musculoskeletal recovery after a fracture. This animal study was designed to examine the effects of dietary protein intake and the role of conditionally essential amino acids in muscle and bone-healing after a fracture. METHODS: One hundred adult male rats were used. Ten rats served as controls and received a 15% protein diet throughout the study. The remaining ninety rats received a 6% protein diet for five weeks to induce protein malnutrition. The rats underwent intramedullary nailing and closed midshaft fracture of one femur. After the fracture, they were separated into three isocaloric dietary groups. Group P6 received a diet with 6% protein; Group P15, a diet with 15% protein; and group P30, a diet with 30% protein with conditionally essential amino acids. At two, four, and six weeks after surgery, ten animals from each group were killed and the femora were evaluated with dual x-ray absorptiometry, histomorphometric assessment of callus, and torsional testing. The quadriceps muscles were analyzed for total mass, total protein content, and for mRNA expression of insulin-like growth factor-1 (IGF-1), IGF-2, IGF receptors, actin, myosin, and vascular endothelial growth factor (VEGF). RESULTS: The P30 group demonstrated elevations in albumin, body mass, muscle mass, total protein content of muscle, and bone mineral density in the fracture callus compared with the P6 diet group at six weeks (p < 0.05). Molecular analysis of muscle revealed that IGF-1, IGF-2, IGF receptors, myosin, actin, and VEGF gene expression were significantly (p < 0.001) higher in the P6 group compared with the P30 group. Biomechanical testing of the femora, however, showed no significant differences. CONCLUSIONS: Dietary supplementation with conditionally essential amino acids in malnourished animals had anabolic effects on bone mineralization, body mass, and muscle mass.

Anterior trochanteric slide osteotomy for primary total hip arthroplasty. Review of nonunion and complications.

The radiographic results of 73 anterior trochanteric slide osteotomies were retrospectively reviewed at an average of 36 months after primary hip arthroplasty to determine the incidence of nonunion of the trochanter and complications related to trochanteric hardware. In each case, the trochanter was retracted anteriorly, with the gluteus medius and vastus lateralis muscle insertions left intact. Reattachment was performed with 2 monofilament wires or cables passed through the lesser trochanter in each case. Ninety-two percent of the trochanters healed; nonunion was associated with anterior displacement of the trochanteric fragment with external rotation of the femur. The incidence of repeat surgery for hardware-related problems was 28%. Although the slide osteotomy prevented proximal migration of the trochanteric fragment, the incidence of hardware complications was too high to justify the routine use of this approach in primary hip arthroplasty.

A new operative approach in the correction of external coxa saltans: the snapping hip.

BACKGROUND: External snapping hip is an entity that describes a snap that is felt on the lateral aspect of the hip. Several surgical interventions are described. HYPOTHESIS: The external snapping hip can be corrected with a simple procedure that is minimally invasive and less demanding than other techniques. STUDY DESIGN: This is a retrospective review from June 1994 until January 2002 looking at released external snapping hips. METHODS: There were 16 patients with 17 hips; follow-up was in 15 patients with 16 snapping hips. Twelve patients with 13 hips were contacted by telephone interview, and 3 were followed up by their most recent chart note. All underwent the same procedure performed by the senior author. The questionnaire was conducted at an average of 32.5 months after surgery (range, 9-74 months). For 3 patients, chart-only follow-up was at 6 weeks, 3 months, and 6 months, respectively. RESULTS: Fourteen of 16 hips remained asymptomatic after final surgical release (2 hips needed a second release). All patients contacted by telephone would undergo the same procedure again if faced with the same symptoms. CONCLUSIONS: This technique is simpler than most of those previously described with the benefit of no formal postoperative regimen and comparable results.

Surgical correction of internal coxa saltans: a 20-year consecutive study.

PURPOSE: To report the complications associated with surgical correction of internal snapping hip. STUDY DESIGN: Retrospective review. METHODS: A review of 92 cases of internal coxa saltans (12 bilateral) from 1982 to 2002 was performed to identify complications following primary surgical correction. An inguinal approach was used for iliopsoas tendon fractional lengthening. The average follow-up time per patient was 5.4 years. RESULTS: A total of 40 complications occurred in 32 patients. Complications included persistent hip pain (n = 6), sensory deficit (n = 8), and hip flexor weakness persisting longer than 1 month (n = 3). Additionally, painful bursa formation (n = 1), hematoma requiring reexploration (n = 1), and superficial infection (n = 1) were noted. Some patients developed recurrent snapping after a 3-month snapping-free interval (n = 9), and some patients never had complete resolution of snapping and were considered failures (n = 11). Of these failures/recurrences, 8 patients had a second tenotomy with 4 failures. Two had a third tenotomy, with 1 failure. CONCLUSIONS: In this series, primary iliopsoas tendon lengthening in patients with internal coxa saltans was without any complication in only 60% of patients; however, overall patient satisfaction was 89%.

Short segment bone-on-bone instrumentation for single curve idiopathic scoliosis.

STUDY DESIGN: Retrospective case series review. OBJECTIVES: To evaluate the outcomes of a new short segment anterior scoliosis technique with complete removal of the discs, bone-on-bone apposition of the vertebral bodies, and dual rod instrumentation. To evaluate a new preop planning technique for scoliosis instrumentation. SUMMARY OF BACKGROUND DATA: Scoliosis surgery traditionally was performed via a posterior approach, but anterior scoliosis instrumentation has proven to be superior regarding the amount of curve correction and the number of segments saved from instrumentation. METHODS: Thirty-one patients with single curve idiopathic scoliosis less than 75 degrees were operated using the bone-on-bone surgical technique with dual rod instrumentation (Kaneda Anterior Scoliosis System, Depuy AcroMed, Raynham, MA from 1996 until 2001). Average follow-up was 40 months (range 15-77 months). RESULTS: Surgical correction of the major curve averaged 73.9% over the instrumented levels and 51.4% over the entire curve. The average number of discs fused was 4.6 for thoracic curves and 3.3 for thoracolumbar and lumbar curves. There were no implant-related complications or nonunions. The compensatory curves spontaneously improved by an average of 38.6%. Uneventful healing of all fusions occurred-most within 8 to 12 weeks. One compensatory thoracic curve progressed and posterior instrumentation was done 28 months after correction of the major thoracolumbar curve. CONCLUSIONS: Surgical correction was achieved in over half the levels that would have been operated by standard posterior segmental fixation. Bony healing due to the bone-on-bone apposition was achieved uneventfully after apical correction of the spinal curvature in all patients. Use of dual rod instrumentation (Kaneda Anterior Scoliosis System) is fundamental in maintaining the correction of the curvature achieved in the operating room. The preoperative planning technique worked well.

The "Gull Sign": a harbinger of failure for internal fixation of geriatric acetabular fractures.

OBJECTIVES: To identify factors affecting the outcomes of surgery for acetabular fracture in patients over the age of 60 years. DESIGN: Retrospective review of records and radiographs; current examination, radiographs and outcome surveys when possible. SETTING: Academic, Level 1 trauma center. PATIENTS/PARTICIPANTS: Forty-eight patients over age 60 with displaced acetabulum fractures. INTERVENTION: Surgical reduction and fixation. MAIN OUTCOME MEASUREMENTS: Clinical ratings and radiographic evaluations, Short Musculoskeletal Functional Assessment survey (SMFA), SF-36, and hip-specific questions. Radiographs were evaluated using the criteria of Matta. RESULTS: Ten patients died since surgery. Four were lost to follow-up. Seven had >12 months of follow-up information in the chart. Twenty-seven had current evaluations for the study. Average follow-up was 37 months, range 1-114 months. The average age at surgery was 71.6 years (range 61-88). No perioperative deaths occurred. Initial reductions achieved: 61% anatomic, 34% imperfect, and 5% poor. A specific radiographic finding (superomedial dome impaction) predictive of failure was identified. This was designated the "Gull Sign." These patients had inadequate reduction, early fixation failure, or medial/superior joint narrowing and subluxation. Functional outcomes in patients with current examination were similar to age-matched controls. Radiographic outcomes: 30% excellent, 30% good, 9% fair, 23% poor, and 7% arthroplasty. Anatomic reduction was closely related to good or excellent radiographic result. CONCLUSIONS: While some patients over sixty years of age can have satisfactory functional outcomes after acetabular fracture fixation, a significant number will have failure of the procedure. Osteopenic patients with superomedial dome impaction (the Gull Sign) did not benefit from attempted open reduction and internal fixation in this series.

Lumbar spine arthroplasty: early results using the ProDisc II: a prospective randomized trial of arthroplasty versus fusion.

This study represents the first 39 patients with at least 6-month follow-up enrolled in a prospective randomized Food and Drug Administration study evaluating the safety and efficacy of the ProDisc II versus the control, a 360 degrees lumbar spinal fusion. Data were collected preoperatively and at 6 weeks, 3 months, and 6 months postoperatively. Visual Analog Scale (VAS), Oswestry Low Back Pain Disability Questionnaire (ODQ), and patient satisfaction rates were evaluated at these intervals, as well as range of motion, return to work, and recreational and ambulatory status. There were 28 ProDisc patients and 11 who underwent fusion. Six patients had two-level surgery. Estimated blood loss (ProDisc = 69 mL versus fusion = 175 mL) and operative time (ProDisc = 75 minutes versus fusion = 219 minutes) were significantly different (P < 0.01). Hospital stays were shorter (ProDisc = 2.1 days versus fusion = 3.5 days [P < 0.01]) for ProDisc patients. There was a significantly greater reduction in the ODQ scores at 3 months in the ProDisc group compared with the fusion group (P < 0.05). No difference was noted in VAS. A trend was identified at 6 months in patient satisfaction rates favoring ProDisc versus fusion (P = 0.08), and motion was significantly improved in ProDisc patients compared with the fusion group (P = 0.02). Ambulatory status as well as recreational activity improved faster in the ProDisc group. The data suggest that total disc arthroplasty may be an attractive option as opposed to lumbar fusion for the surgical treatment of disabling mechanical low back pain secondary to lumbar disc disease.

Proximal femoral radiographic changes after lateral transtrochanteric intramedullary nail placement in children.

BACKGROUND: Recent reports have described osteonecrosis of the femoral head after intramedullary nailing of the femur through the piriformis fossa in children. Other reports have raised concerns about the development of femoral neck narrowing and valgus deformity of the proximal part of the femur after intramedullary nailing through the tip of the greater trochanter. We evaluated the radiographic changes in the proximal part of the femur following intramedullary nailing through the lateral trochanteric area at a minimum of two years postoperatively in twenty-five affected extremities. The mean age of the patients at the time of the index procedure was ten years and six months. METHODS: A retrospective radiographic review was performed to look for proximal femoral changes. Specifically, the radiographs were examined for evidence of osteonecrosis. The articulotrochanteric distance, femoral neck diameter, and neck-shaft angle were measured on the initial and final radiographs. RESULTS: No patient had evidence of osteonecrosis of the femoral head. The articulotrochanteric distance decreased by a mean of 0.4 mm, the femoral neck diameter increased by a mean of 4.9 mm, and the neck-shaft angle decreased by a mean of 1.4 degrees. Compared with a group of seventeen patients with adequate initial and final radiographs of the contralateral side, the final mean articulotrochanteric distance was 4.5 mm less on the involved side than on the uninvolved side, the mean femoral neck diameter was 0.7 mm less on the involved side than on the uninvolved side, and the mean neck-shaft angle was 3.2 degrees less on the involved side than on the uninvolved side. No patient had development of clinically important femoral neck narrowing or valgus deformity. Statistically, the likelihood that these data represent a group with a mean 3-mm increase in the articulotrochanteric distance is <1%. The likelihood that these data represent a group with a mean 3.2-mm decrease in the ultimate femoral neck diameter is <1%. The likelihood that these data represent a group with a mean 5 degrees increase in the neck-shaft angle is <1%. CONCLUSIONS: Lateral transtrochanteric intramedullary nailing in children who are nine years of age or older does not produce clinically important femoral neck valgus deformity or narrowing, and we did not observe osteonecrosis of the femoral head after this procedure.

Upper extremity functional assessment after anterior spinal fusion via thoracotomy for adolescent idiopathic scoliosis: prospective study of twenty-five patients.

STUDY DESIGN: A prospective review of upper extremity function in 25 patients after anterior thoracotomy for instrumentation and fusion of thoracic adolescent idiopathic scoliosis was conducted. OBJECTIVE: To assess the effects of anterior spinal fusion with open thoracotomy on upper extremity function. SUMMARY OF BACKGROUND DATA: The treatment of idiopathic scoliosis through anterior thoracotomy and spinal fusion using instrumentation is a new method for correcting and stabilizing patients with major thoracic and thoracolumbar curves. No studies have assessed the functional outcome for the upper extremities after anterior open thoracotomy that involves splitting through the latissimus dorsi and serratus anterior muscles. METHODS: For this study, 25 adolescent patients with idiopathic scoliosis treated surgically were examined over a 3-year period. The average patient age was 15 years and 3 months, with a range of 11 years and 11 months to 20 years and 9 months. Preoperative activities of daily living, active range of motion, and strength were recorded by an independent occupational therapist (L.P.) for both upper extremities. Postoperative measurements were assessed at 1, 3, 6, 12, and 24 months. All the patients underwent a right thoracotomy with ribs used for autograft. The left upper extremity served as the control limb. No patients had associated anomalies or previous upper extremity surgery. All the patients underwent an upper extremity postoperative stretching and strengthening protocol. RESULTS: At 1 month, 35% of the patients had some difficulty with activities of daily living, primarily in tying their shoes and cutting meat with a knife during meals (P = 0.03). However, by 3 months, all the patients could equivocally and independently perform activities of daily living: dressing, bathing, grooming, attending to hygiene, and feeding (P = 1). Full active range of motion in their upper extremities and shoulder was achieved in all the patients by 1 month (P = 1). All 25 patients had regained normal, bilaterally symmetric strength by 3 months (P = 0.25). No postoperative complications occurred. CONCLUSIONS: Patients undergoing anterior spinal fusion with instrumentation after open thoracotomy can expect to regain full function of the ipsilateral upper extremity in terms of strength, active range of motion, and activities of daily living within 3 months. Compliance with a structured postoperative flexibility and strengthening protocol is recommended to optimize functional outcomes. A novel rehabilitation protocol for the upper extremities is presented.