Effect of compliant layers within piezoelectric composites on power generation providing electrical stimulation in low frequency applications.

For patients that use tobacco or have diabetes, bone healing after orthopedic procedures is challenging. Direct current electrical stimulation has shown success clinically to significantly improve bone healing in these difficult-to-fuse populations. Energy harvesting with piezoelectric material has gained popularity in the last decade, but is challenging at low frequencies due to material properties that limit total power generation at these frequencies. Stacked generators have been used to increase power generation at lower voltage levels but have not been widely explored as a load-bearing biomaterial to provide DC stimulation. To match structural compliance levels and increase efficiency of power generation at low frequencies, the effect of compliant layers between piezoelectric discs was investigated. Compliant Layer Adaptive Composite Stacks (CLACS) were manufactured using five PZT discs connected electrically in parallel and stacked mechanically in series with a layer of low modulus epoxy between each disc. The stacks were encapsulated, keeping PZT and overall volume constant. Each stack was electromechanically tested by varying load, frequency, and resistance. As compliant layer thickness increased, power generation increased significantly across all loads, frequencies, and resistances measured. As expected, increase in frequency significantly increased power output for all groups. Similarly, an increase applied peak-to-peak mechanical load also significantly increased power output. The novel use of CLACS for power generation under load and frequencies experienced by typical orthopedic implants could provide an effective method to harvest energy and provide power without the use of a battery in multiple low frequency applications.

Parents make the difference: a randomized-controlled trial of a parenting intervention in Liberia.

BACKGROUND: The objective of this study was to evaluate the impact of a brief parenting intervention, 'Parents Make the Difference'(PMD), on parenting behaviors, quality of parent-child interactions, children's cognitive, emotional, and behavioral wellbeing, and malaria prevention behaviors in rural, post-conflict Liberia. METHODS: A sample of 270 caregivers of children ages 3-7 were randomized into an immediate treatment group that received a 10-session parent training intervention or a wait-list control condition (1:1 allocation). Interviewers administered baseline and 1-month post-intervention surveys and conducted child-caregiver observations. Intent-to-treat estimates of the average treatment effects were calculated using ordinary least squares regression. This study was pre-registered at ClinicalTrials.gov (NCT01829815). RESULTS: The program led to a 55.5% reduction in caregiver-reported use of harsh punishment practices (p < 0.001). The program also increased the use of positive behavior management strategies and improved caregiver-child interactions. The average caregiver in the treatment group reported a 4.4% increase in positive interactions (p < 0.05), while the average child of a caregiver assigned to the treatment group reported a 17.5% increase (p < 0.01). The program did not have a measurable impact on child wellbeing, cognitive skills, or household adoption of malaria prevention behaviors. CONCLUSIONS: PMD is a promising approach for preventing child abuse and promoting positive parent-child relationships in low-resource settings.

Radiation exposure to surgical staff during F-18-FDG-guided cancer surgery.

PURPOSE: High-energy gamma probes have recently become commercially available, developed for (18)F-FDG probe-guided surgery. The radiation received by the staff in the operating room might limit the use of it, but has never been determined. We therefore wanted to measure the absorbed staff doses at operations where patients had received a preoperative injection of (18)F-FDG. METHODS: Thirty-four patients with different cancers (breast cancer, melanoma, gastrointestinal cancers, respectively) were operated. At every operation the surgeon was monitored with a TLD tablet on his finger of the operating hand and a TLD tablet on the abdomen. The surgeon and anaesthesiologist were also monitored using electronic dosimeters placed in the trousers lining at 25 operations. RESULTS: The dose rate to the surgeon's abdominal wall varied between 7.5-13.2 microSv/h, depending on tumour location. The doses to the anaesthesiologists and the finger doses to the surgeon were much lower. About 350-400 MBq, i.e. ca. eight times higher activities than those used in the present study are supposed to be necessary for guiding surgery. It can be calculated from the body doses measured that a surgeon can perform between 150-260 h of surgery without exceeding permissible limits for professional workers. CONCLUSIONS: The radiation load to the operating staff will generally be so small that it does not present any limitation for FDG-guided surgery. However, it is recommended to monitor the surgical staff considering that the surgeon may be exposed to other radiation sources, and since the staff often includes women of child-bearing age.

Radiation doses to staff involved in sentinel node operations for breast cancer.

BACKGROUND: The use of radioactive compounds for sentinel node biopsy is now a generally accepted part of the surgical treatment of breast cancer and melanoma, with the risk of radiation exposure to the operating team. The aim of this investigation was to study the levels of this exposure in relation to the permissible radiation dose limits. METHODS: The radiation exposure to the hands and bodies of the operating surgeons (the 'risk persons') was measured by thermoluminescent dosimeters in 79 operations and to the pathologists handling the specimens in 17 cases. Radioactivity and dose rate measurement from tumours and breast specimens were also performed. RESULTS: During an operation the mean skin dose (+/-SD) to the thermoluminescent dosimeters placed at the hand and the abdominal wall were 0.04 +/- 0.04 mSv (79 operations) and 0.01 +/- 0.02 mSv (67 operations) respectively. For the pathologist, the mean hand dose per operation was below the detection limit (17 operations). Correlation between the measured dose rate and the radioactive content of the tumours was 0.998. CONCLUSIONS: The radiation exposure to the staff involved in sentinel node (SN) biopsy for breast cancer using radioactive labelled tracers will be considerably below the permissible limits, even with high numbers of SN biopsy procedures. Pregnant staff members should participate in <100 SN operations.

Factors of importance for scintigraphic non-visualisation of sentinel nodes in breast cancer.

PURPOSE: The aim of this study was to analyse different factors of possible significance for non-visualisation of sentinel nodes (SNs) by preoperative lymphoscintigraphy, in order to enable improvement of the success rate of SN visualisation through modification or alteration of some of the factors. METHODS: Between March 1998 and January 2003 we analysed a series of 442 women with unilateral stage T1 and clinical N0 breast cancer. Lymphoscintigraphy was performed after periareolar or peritumoural injection of 99mTc-albumin nanocolloid, with image acquisition after 2-6 h or 18-24 h. Until January 2001, all patients received around 20 MBq tracer, irrespective of time to operation. From January 2001, patients injected on the day before surgery received at least 100 MBq while patients injected on the day of surgery received around 50 MBq. RESULTS: An SN was visualised in 87% of the patients, and at surgery the SN was detected with the hand-held gamma probe in 42% of the remaining patients. By multiple logistic regression analysis, statistically significant independent variables that increased the risk for non-visualisation were increasing age (p=0.0007), increasing body weight (p=0.0189) and peritumoural injection (p<0.0001). Significant interaction was found for imaging time and injected activity (p=0.0017). CONCLUSION: This study conclusively shows that the risk of unsuccessful SN imaging increases with age and body weight. Our findings suggest that the scintigraphic success rate may be improved by periareolar (rather than peritumoural) injection. Early and late imaging procedures are equally efficient, but if a late imaging procedure is used, activity (adjusted for physical decay) in the patient on day 2 should be more than 10 MBq.

Intraoperative frozen section examination of axillary sentinel lymph nodes in breast cancer.

The study presents the results from intraoperative frozen section assessment of axillary sentinel lymph nodes (SLNs) in breast cancer. Routine histological frozen sections from one level were used, two sections stained with haematoxylin and eosin. Immunohistochemistry for cytokeratins was applied to the permanent SLN paraffin sections only. Axillary dissection was performed on all SLN-positive cases regardless of the size of the metastatic deposits. With a detection rate of 83%, 272 patients entered the study over a period of 46 months. A total of 61 cases were SLN positive by frozen section analysis. The paraffin sections gave an additional 23 SLN-positive cases. The false-negative rate for frozen sections was then 27% (23/84). Micrometastases were found in 28 of 84 cases, and macrometastases in 56. The false-negative rate of frozen sections for micrometastases was 71% (20/28), and for macrometastases 5% (3/56). A total of 73% (61/84) of the patients underwent axillary surgery as a one-step procedure.

Toxicological studies on Lactose Oxidase from Microdochium nivale expressed in Fusarium venenatum.

A new carbohydrate oxidase, Lactose Oxidase, with high specificity of oxidizing the disaccharide lactose to lactobionic acid has been found. This enzyme opens up for a variety of applications. A programme of toxicological studies was conducted to establish the safety of Lactose Oxidase to be used as a processing aid in the food industry. The enzyme used in this study was produced by a submerged fermentation of Fusarium venenatum and contained a gene code from Microdochium nivale. Oral administration to rats of up to 10 mL/kg bodyweight (bw)/day (equivalent to a total organic solids dosage of 900 mg/kg bw/day or a Lactose Oxidase dosage of 344 LOXU/kg bw/day) for 13 weeks did not cause any adverse effect. Lactose Oxidase was not found to be mutagenic in the bacterial reverse mutation assay, nor did it cause chromosomal aberrations in cultured human lymphocytes. The maximum recommended dosage of Lactose Oxidase is 50 LOXU/kg liquid whey protein concentrate. The safety margin for exposure is estimated to be at least 6.2 x 10(4) for daily diary product consumption. In conclusion Lactose Oxidase can be considered as safe for use in the food industry.

In vitro evaluation of biomechanical effects of multiple hemilaminectomies on the canine lumbar vertebral column.

OBJECTIVE: To conduct an in vitro investigation of the biomechanical characteristics of the canine lumbar spinal column in flexion and extension and measure the destabilizing effects of multiple consecutive unilateral and bilateral hemilaminectomies. SAMPLE POPULATION: 30 isolated multisegmental spinal units (L1-L4) from nonhypochondroplastic dogs weighing 15 to 30 kg. PROCEDURES: Physically normal and surgically altered spinal specimens were subjected to 4-point bending in flexion and extension to determine effects of multiple consecutive hemilaminectomies on the basis of analysis of test system load-displacement data. Six groups with 5 spinal columns in each were defined on the basis of the following procedures: hemilaminectomy at L2-L3, 2 adjacent hemilaminectomies at L1-L3, 3 adjacent hemilaminectomies at L1-L4, bilateral hemilaminectomies at L2-L3, 2 bilateral hemilaminectomies at L1-L3, and no hemilaminectomy (intact). Spinal stability before and after surgery was determined in all groups. Each group served as its own control for nondestructive testing. Spinal strength was evaluated through destructive testing to determine deformation at failure, strength to failure, and mode of catastrophic failure. The intact group served as the control for destructive testing. RESULTS: Stability in extreme flexion and extreme extension did not change significantly following any hemilaminectomy procedure. Postoperative stability within the neutral zone was significantly decreased in all groups. Range of motion within the neutral zone was not significantly different from the intact condition in any group. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple hemilaminectomies did not decrease stiffness of the lumbar spinal column during flexion and extension. These results support clinical recommendations regarding multiple consecutive hemilaminectomies in dogs.

Smoking as a risk factor for wound healing and infection in breast cancer surgery.

AIM: Clinical studies suggest that smoking is associated with wound necrosis after breast cancer surgery. However, the significance of smoking as a risk factor for wound infection, skin flap necrosis, and epidermolysis when adjusting for other potential risk factors remains to be studied. METHODS: From June 1994 through August 1996, 425 patients underwent breast cancer surgery as simple mastectomy, modified radical mastectomy, or breast conserving surgery. The patients were evaluated postoperatively for wound infection, skin flap necrosis, and epidermolysis. Association between these complications and 17 patient, operative, and postoperative variables were analysed by three separate multiple logistic regression analyses. RESULTS: When compared to non-smoking, smoking was significantly associated with wound infection after all types of surgery (light smoking (1-14 grams per day): [odds ratio (OR)=2.95, 95% confidence interval (95% CI)=1.07-8.16], and heavy smoking (>/=15 grams per day): OR=3.46 (1.52-7.85). A similar significant association was found as regards skin flap necrosis and epidermolysis after simple mastectomy and modified radical mastectomy: both light and heavy smoking were predictive for skin flap necrosis: light smoking: OR=6.85 (1.96-23.90), heavy smoking: OR=9.22 (2.91-29.25) and for epidermolysis: light smoking: OR=3.98 (1.52-10.43) and heavy smoking: OR=4.28 (1.81-10.13). No significant dose-response relation was disclosed. Other risk factors and confounders associated with complicated wound healing were adjusted for in the analysis: diabetes, obesity, alcohol, NSAIDs, duration of surgery, and surgical experience. CONCLUSION: Independent of other risk factors, smoking is predictive for post-mastectomy wound infection, skin flap necrosis, and epidermolysis.

Fossil evidence of water lilies (Nymphaeales) in the Early Cretaceous.

Phylogenetic analyses have identified the water lilies (Nymphaeales: Cabombaceae and Nymphaeaceae), together with four other small groups of flowering plants (the 'ANITA clades': Amborellaceae, Illiciales, Trimeniaceae, Austrobaileyaceae), as the first diverging lineages from the main branch of the angiosperm phylogenetic tree, but evidence of these groups in the earliest phases of the angiosperm fossil record has remained elusive. Here we report the earliest unequivocal evidence, based on fossil floral structures and associated pollen, of fossil plants related to members of the ANITA clades. This extends the history of the water lilies (Nymphaeales) back to the Early Cretaceous (125-115 million years) and into the oldest fossil assemblages that contain unequivocal angiosperm stamens and carpels. This discovery adds to the growing congruence between results from molecular-based analyses of relationships among angiosperms and the palaeobotanical record. It is also consistent with previous observations that the flowers of early angiosperms were generally very small compared with those of their living relatives.

Fossil flowers of ericalean affinity from the Late Cretaceous of Southern Sweden.

Charcoalified fossil flowers of a new genus and species (Paradinandra suecica) with affinities to Ericales s.l. (sensu lato) are described from the Late Cretaceous (Santonian-Campanian) from Southern Sweden. The flowers are pentamerous, hypogynous, and actinomorphic. Aestivation of sepals and petals is imbricate-quincuncial. The androecium consists of an outer whorl with single episepalous stamens and an inner whorl with paired epipetalous stamens. Pollen is small and probably tricolpate. Three carpels form a syncarpous ovary with numerous campylotropous ovules on parietal placentae. The styles are free for most of their length. The structure of mature fruits and seeds is unknown. Clear distinction of sepals and petals, possible dehiscence of anthers by restricted slits, presence of a nectary, and the general floral construction (salverform corolla) with a canalized access to the floral center clearly indicate insect pollination of the fossil flowers. Comparisons with extant taxa demonstrate that Paradinandra suecica shares many similarities with Ericales s.l. and in particular with members of Ternstroemiaceae, Theaceae, and Actinidiaceae. However, it is neither identical to any one genus of these families nor to any of the previously described ericalean taxa from the Cretaceous and thus provides further evidence of the diversity of Cretaceous ericalean plants.

[Tension-free herniotomy using the Lichtenstein's method. Results of five years' experience]. / Tensionsfri herniotomi a.m. Lichtenstein. Resultater af fem års erfaring med metoden.

The results after 230 initial open tension-free hernioplasties a.m. Lichtenstein for groin hernias are evaluated 24 months after operation. Of the 167 primary operations 57% were performed under local analgesia, and 68% of the patients were discharged on the day of operation after primary herniotomy. Infection occurred after 2.7% of the operations, but in no case did the mesh have to be removed. Complications occurred after 7.4% of the operations, necessitating reoperation after 4.3% of the operations. After 24 months 96% of live patients were controlled for recurrences. After 154 primary herniotomies 2.6% recurred. No indirect hernia recurred, 3.6% of direct hernias recurred. After 57 operations for secondary hernias 7.0% recurred. Thirty-eight different surgeons operated 1-19 hernias (median 4). It is concluded that recurrences after open tension-free hernia-repairs are rare, complications few, the operation is simple to perform and can be done under local analgesia in a same day regime.

Negative pressure intrusion cementing technique for total knee arthroplasty.

Negative pressure intrusion (NPI) is an alternative cementing technique for the tibial baseplate of total knee arthroplasty that uses a suction cannula in the proximal tibia to remove excess fluids and fat before cementing. This technique was compared with standard third-generation positive pressure intrusion (PPI) techniques in an in vitro implantation and analysis of 6 pairs of cadaveric tibiae. Six matched pairs of fresh frozen tibiae were prepared by cutting the tibial surfaces, standard cleaning and surface drying, then performing PPI and NPI on 1 of each pair. No objective differences were noted on radiographs or direct cement depth measurement analysis. Scanning electron micrograph evaluation revealed that the PPI specimens had consistently more voids in the cement-bone composite, and the NPI specimens had consistently narrower empty spaces between bone and cement, resulting in tighter fill in NPI specimens. NPI was shown to enhance characteristics known to improve tensile and shear strength in cement-bone composites.

An approach to long-range electron transfer mechanisms in metalloproteins: in situ scanning tunneling microscopy with submolecular resolution.

In situ scanning tunneling microscopy (STM) of redox molecules, in aqueous solution, shows interesting analogies and differences compared with interfacial electrochemical electron transfer (ET) and ET in homogeneous solution. This is because the redox level represents a deep indentation in the tunnel barrier, with possible temporary electronic population. Particular perspectives are that both the bias voltage and the overvoltage relative to a reference electrode can be controlled, reflected in spectroscopic features when the potential variation brings the redox level to cross the Fermi levels of the substrate and tip. The blue copper protein azurin adsorbs on gold(111) via a surface disulfide group. Well resolved in situ STM images show arrays of molecules on the triangular gold(111) terraces. This points to the feasibility of in situ STM of redox metalloproteins directly in their natural aqueous medium. Each structure also shows a central brighter contrast in the constant current mode, indicative of 2- to 4-fold current enhancement compared with the peripheral parts. This supports the notion of tunneling via the redox level of the copper atom and of in situ STM as a new approach to long-range electron tunneling in metalloproteins.

Structure and dynamics of the metal site of cadmium-substituted carboxypeptidase A in solution and crystalline states and under steady-state peptide hydrolysis.

PAC spectra (perturbed angular correlation of gamma-rays) of cadmium-substituted carboxypeptidase A (CPD) show that the enzyme in solution imposes a flexible, pH- and chloride-dependent coordination structure on the metal site, in contrast to what is found in the crystalline state. A much more restricted coordination geometry occurs for the steady-state peptide intermediates of Bz-Gly-l-Phe and Bz-Gly-Gly-l-Phe in solution, suggesting that substrate binding locks the structure in a rigid conformation. The results further indicate that the peptide intermediate has a six-coordinated metal coordination geometry with an OH- ligand at the solvent site and a carbonyl oxygen at an additional ligand site. In marked contrast, conformational rigidity is not induced by the inhibitor/poor substrate Gly-L-Tyr nor by the products of high turnover substrates, Bz-Gly, Bz-Gly-Gly, and L-Phe. These results are consistent with an intact scissile peptide bond in the enzyme-substrate complex of Bz-Gly-L-Phe and Bz-Gly-Gly-L-Phe. A single nuclear quadrupole interaction (NQI) is observed for the crystalline state of the enzyme between pH 5.7 and pH 9.4. This NQI agrees with calculations based on the metal coordination geometry for cadmium in crystalline CPD derived from X-ray diffraction studies. A single broad distribution of NQIs is observed for CPD in sucrose solutions and 0.1 M NaCl at pH values below 6.5. This NQI (NQI-1') has parameters very close to those for the crystalline state. The enzyme metal site, characterized by this NQI, is converted into two new enzyme metal sites over the pH range of 6.5-8.3. The metal coordination sphere of one of these has a NQI (NQI-1) with parameters similar to those at lower pH values (NQI-1') while the other NQI (NQI-2) is characterized by markedly different NQI parameters. Angular overlap model (AOM) calculations indicate that the coordination sites giving NQI-1' and NQI-1 both have a metal-bound water molecule while the coordination site giving NQI-2 has a metal-bound hydroxide ion. PAC results at pH 8.3-10.5 indicate that in this pH range the two metal coordination geometries related to NQI-1 and NQI-2 occur in a pH independent ratio of 2:1, with the one with the water ligand being the most abundant species. The observed pH-independent equilibrium between the two different metal coordination geometries for cadmium can be explained by an equilibrium between tautomeric forms of a hydrogen bond between the Glu-270 carboxyl group and the metal-bound water (Glu-270 COO-...(HOH)M <==> Glu-270 COOH...(OH-)M) being slow on the time scale of a PAC experiment, i.e., slower than 0.5 micros. We finally suggest that NQI-1' observed at low pH reflects an enzyme species containing a metal-coordinated water molecule and the protonated carboxyl group of Glu-270.

Comparison of tenoxicam by intramuscular injection or wound infiltration for analgesia after inguinal herniorrhaphy.

We compared wound infiltration with small-dose tenoxicam (7.5 mg) to intramuscular (IM) administration of the same dose to treat pain after herniorrhaphy. In a randomized, double-blind study, 50 patients received either preoperative wound infiltration with tenoxicam, 7.5 mg in 40 mL of 0.9% saline (WI group; n = 25) or IM tenoxicam 7.5 mg (IM group; n = 25). In each group a saline placebo of equal volume was given by the alternate route, i.e., those who received wound infiltration with tenoxicam received 0.75 mL of 0.9% saline IM; those who received IM tenoxicam received 40 mL of 0.9% saline for wound infiltration. Postoperative pain was assessed with a verbal pain scale and a visual analog scale (VAS) at rest and during movement and cough, 1, 2, 4, 6, and 24 h postoperatively. Wound tenderness was assessed with an electronic algometer preoperatively, and 2, 4, and 6 h postoperatively. The need for supplementary analgesics (acetaminophen and morphine) was registered. No differences were observed between groups in VAS pain scores, verbal rating pain scores, pain pressure thresholds, or in need for supplementary analgesics. We conclude that tenoxicam 7.5 mg has no local analgesic effect on postoperative pain after herniorrhaphy.

The tension-free hernioplasty in a randomized trial.

BACKGROUND: The tension-free hernioplasty as introduced by Lichtenstein has gained increasing acceptance during the last decade although the technique has not been evaluated in a randomized trial. METHODS: This randomized study compares the 2-year follow-up results after 102 tension-free hernioplasties with implantation of a prolene mesh in all groin hernias to 53 Cooper ligament repairs in direct hernias and 53 abdominal ring repairs in indirect hernias. RESULTS: After tension-free repairs five hernias recurred (5%), and after either Cooper ligament or abdominal ring repair, 16 recurrences were found (15%) (P = 0.025). No indirect hernias recurred after a tension-free repair; 2 recurred after abdominal ring repair (4%; NS). The recurrence rate after tension-free repairs for primary direct inguinal hernias was 7% as compared with 30% after Cooper ligament repair (P = 0.0081). No difference in complication rate between the tested methods was found. CONCLUSION: Recurrence rate is reduced to one-third after tension-free herniotomies as compared with the conventionel herniotomies without increase in complication rate.

[Streptococcus bovis as the cause of combined endocarditis of the aortic, mitral and tricuspid valves]. / Streptococcus bovis som årsag til kombineret aorta-, mitral- og trikuspidalklapendocarditis.

A case of combined endocarditis of the aortic-, mitral- and tricuspid valves in an otherwise healthy cattle farmer is described. The infective agent was Streptococcus bovis. The relation between S. bovis infection and endocarditis is discussed.

[Ambulatory ST-segment monitoring after acute myocardial infarction]. / Ambulant ST-segmentmonitorering efter akut myokardieinfarkt.

Over the last decade the concept of silent myocardial ischaemia has received considerable attention. Without doubt, the increased use of ambulatory ST-segment monitoring is the most important reason for the growing interest in this field. The prevalence of ambulatory ischaemia after myocardial infarction seems to be lower than in other subgroups with coronary artery disease. In postinfarction patients, however, a greater proportion of ischaemic episodes are silent. At present there is substantial evidence that ambulatory ischaemia provides prognostic information in different subsets of patients with previous myocardial infarction, but there is considerable disagreement about how this is expressed in terms of cardiac events. Patient selection, small patient numbers, and different timing of ambulatory monitoring are proposed as important reasons for the inconsistent findings. The precise role of postinfarction ambulatory ST-segment monitoring in clinical practice has yet to be established.

Effect of bone block removal and patellar prosthesis on stresses in the human patella.

Thermoelastic stress analysis was used to examine stresses on the anterior surface of patellae after patellar bone block excision for autogenous graft anterior cruciate ligament reconstruction. Complications of anterior cruciate ligament injury often lead to degenerative changes in the knee that can require total knee joint replacement. It was hypothesized that stresses in a bone block-compromised patella may be increased even further by insertion of a patellar prosthesis. All patellae were first tested intact and then were retested after a sequence of surgical modifications including patellar prosthesis implantation, tapered bone block excision, square bone block excision, and both shapes of excised bone blocks with a patellar prosthesis in place. Stresses in patellae with bone blocks excised were significantly greater than stresses in intact patellae. The anterior surface stress pattern in the loaded patella was significantly altered by excision of a bone block. There were no significant differences between maximum stress in patellae with tapered and square bone blocks excised. A finite element analysis showed that excision of a larger trapezoid-shaped bone block greatly increased maximum stress levels. Insertion of a patellar prosthesis did not significantly alter stress patterns or maximum stress levels in the patella.