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PubMed1996

A differential scanning calorimetry study of retrieved orthopedic implants made of ultrahigh molecular weight polyethylene.

Differential scanning calorimetry (DSC) was used to examine thermal and thermooxidative properties of ultrahigh molecular weight polyethylene (UHMW-PE) of five acetabular components of failed orthopedic implants retrieved at revision of total hip arthoplasty. The results were compared with controls (unimplanted acetabular cups, a 20-year-old slab of UHMW-PE, and raw material). Profiles of exothermic peaks indicated increased levels of oxidation in all retrieved cups. In three retrieved cups, DSC revealed an additional peak of endotherm that was not seen in control samples. The additional endotherm peaks were not artifacts due to oxidation during scanning, heat buildup during cutting of the samples, or the sterilization method after retrieval. The additional peak was associated with the bulk of the polymer that was extracted with hexane. It varied in relative area, depending on its original location of the sample in a cup, implicating local variability in the extent of changes in material property. The distribution of the changes suggests that, during implantation, tissue exposure and friction affected the level of oxidation and degree of crystallinity in the UHMW-PE to a greater degree than did loading alone. Overall results showed that DSC may be a useful tool in evaluating changes in the properties of UHMW-PE orthopedic components in vivo.

Acetabulum↗
PubMed2001

A simple method of determining the modulus of orthopedic bone cement.

Accurate determination of the elastic modulus of surgical bone cements is of primary importance, when evaluating the stresses within the cement mantle in Total Joint Arthroplasty. This article presents a new method of determining the modulus of surgical bone cements from the biaxial flexural test. The biaxial flexural test is not currently employed in mainstream orthopedic mechanical testing, which is surprising because most loading in orthopedic applications is biaxial in nature. Nor has this method been utilized for dental materials, even though the biaxial flexure test has been used for many years in this field. It has been demonstrated that the modulus of surgical bone cements can be determined from the biaxial flexural test, and these results are in agreement with results from compressive and bending tests.

Bone Cements↗
PubMed2005

Opioid use by patients in an orthopedics spine clinic.

OBJECTIVE: Concerns regarding the efficacy, toxicity, tolerance, dependence, and abuse of opioids have limited their use for patients with chronic spine pain. In our previous study of rheumatology clinic patients, opioid analgesics were found to be highly effective, produced only mild side effects, and had few instances of opioid abuse. The purpose of this study was to replicate our previous study in another large cohort of patients with nonmalignant pain due to well-defined spinal diseases. METHODS: Opioid use was studied in 230 orthopedics spine clinic patients by retrospective analysis of prescriptions for 3 years and cross-sectional analysis of efficacy and toxicity by patient interviews. Opioid use and stability of the daily dose over 3 years were derived from computerized pharmacy records. Medical records, operative reports, and radiographic studies were reviewed to determine the reason for dosage escalations and to detect instances of abuse or addiction behaviors. Patients were interviewed to determine the efficacy, frequency, and types of side effects and instances of obtaining opioids from sources outside the Veterans Affairs system. RESULTS: Opioids were prescribed for 152 of the 230 patients, for < 3 months (short-term [STO]) in 94, > or =3 months (long-term [LTO]) in 58, and none in 72 (no opioid [NTO]). Medications prescribed were codeine, oxycodone, propoxyphene, tramadol, morphine, meperidine, fentanyl, or hydroxycodone, either alone or in combination. Interviews were completed in 72 STO, 50 LTO, and 45 NTO patients. Pain severity (0-10 scale) was not different in patients with different spinal pathologies. Opioids significantly reduced the back pain severity score from 8.3 +/- 1.5 to 4.5 +/- 2.2 (mean +/- SD). Mild side effects (most commonly, constipation and sedation) were reported by 58% of the opioid-treated patients but rarely caused them to stop taking the medication. There was no significant increase from the mean +/- SD initial opioid dosage of 5.0 +/- 12.2 30-mg codeine equivalents per day (30 mg oral codeine = 5 mg oral morphine) to the mean peak dosage of 7.9 +/- 12.5 and the mean recent dosage of 4.3 +/- 6.3, suggesting that tolerance to opioid analgesia did not appear to occur in these patients. Dosage escalations of > 2 30-mg codeine equivalents occurred 19 times in 17 LTO patients and was due to worsening of the underlying painful condition, complications of spine surgery, or unrelated surgical or medical problems in all but 3 of them (5%). These 3 patients also displayed other abuse behaviors. Abuse behaviors were not more frequent in those with or without a history of abuse/addiction. CONCLUSION: This study provides data on the efficacy, toxicity, tolerance, and abuse or addiction behaviors with opioid therapy in a large cohort of patients in an orthopedics spine clinic. The results provide objective data from patients with well-defined spine diagnoses to challenge the position that opioid treatment is inappropriate for chronic nonmalignant pain. This study provides clinical evidence to support and protect physicians treating patients with chronic musculoskeletal diseases, who may be reluctant to prescribe opioids because of possible sanctions from regulatory agencies. More important, it will benefit patients by permitting them to receive these effective, safe medications.

Aged↗
PubMed2003

The effects of degree of crosslinking on the fatigue crack initiation and propagation resistance of orthopedic-grade polyethylene.

Crosslinked ultrahigh molecular weight polyethylene (UHMWPE) has been recently approved by the Food and Drug Administration for use in orthopedic implants. The majority of commercially available UHMWPE orthopedic components are crosslinked using e-beam or gamma radiation. The level of crosslinking is controlled with radiation dose and free radicals are eliminated through heat treatments to prevent long-term degradation associated with chain scission or oxidation mechanisms. Laboratory studies have demonstrated a substantial improvement in the wear resistance of crosslinked UHMWPE. However, a concern about the resistance to fatigue damage remains in the clinical community, especially for tibial components that sustain high cyclic contact stresses. The objective of this study was to investigate both the initiation and propagation aspects of fatigue cracks in radiation crosslinked medical-grade UHMWPE. This work evaluated three levels of radiation, which induced three crosslink densities, on the fatigue crack propagation and total fatigue life behavior. Both as-received UHMWPE, as well as those that underwent an identical thermal history as the crosslinked UHMWPE were used as controls. Fractured crack propagation specimens were examined using scanning electron microscopy to elucidate fatigue fracture mechanisms. The results of this work indicated that a low crosslink density may optimize the fatigue resistance from both a crack initiation and propagation standpoint.

Acrylic Resins↗
PubMed2007

Antimicrobial susceptibility of coagulase-negative staphylococci on tissue allografts and isolates from orthopedic patients.

Allograft infection occurs at a rate not different from that of similar procedures with large allografts or sterilized prosthetic devices and is usually caused by coagulase-negative staphylococci (CNS). CNS are feared for their limited antimicrobial susceptibility. We aimed at investigating this risk. CNS were isolated from 260 of 1461 allograft tissue grafts and compared with 384 consecutive clinical isolates from a general orthopedic population (258 patients). The CNS were identified and examined for their susceptibility to nine antibiotics used in routine practice. Staphylococcus epidermidis was the most commonly identified (35%) and the most resistant species of the allograft isolates. Comparing the overall antibiotic susceptibility patterns, clinical pathogens were significantly more resistant to six of the nine antibiotics (p < 0.01), namely penicillin, oxacillin, erythromycin, clindamycin, ofloxacin, and gentamicin. In conclusion, massive allograft infection is a well-known life-threatening surgical risk. However, we did demonstrate that allograft-related in contrast to orthopedic clinics-related CNS, are susceptible to commonly used first and second line antibiotics.

Adolescent↗
PubMed1998

Limiting models for calcification in fibrous tissues adjacent to orthopedic implants: variational indicator functions and influences of implant stiffness.

Calcification and eventual integration of orthopedic implants into bone is important to many load-bearing devices, and the influence of load and implant stiffness on this process are assessed in this mathematical modelling study. Three research questions are posed in this study. First, can limiting material models provide useful information on the overall behavior of the tissue adjacent to a loaded orthopedic implant? Second, can the limiting models lead to optimization criteria? Third, can an optimization approach be used to differentiate between the four prospective remodeling rate equations which are proposed? The answers are yes, yes, and no, respectively. A two degree of freedom lumped parameter model for axial loading of an intramedullary implant is considered. Two limiting composite material models are used, and the strain energy density in the calcified and non-calcified phases are assessed as stimuli for calcification. The rate equations posed here assume that the calcified material volume fraction decreases at high strain-energy densities, and increases at small strain-energy densities. In all four cases (both models, both phases) the steady states for these rate equations find equilibrium points of indicator functions which are a weighted sum of total strain energy and the mass of calcified tissue in the layer considered. The weights on strain-energy density and mass differ in each case. This shows that for appropriate choices of parameters, all four models can yield the same results, and it also shows that an optimization approach does not uniquely determine the appropriate rate equation in these cases. The rate equations showed complicated dynamic behavior and a phase-plane analysis was used which led to upper bounds on load, which depended on implant stiffness and distal support. The predictions of the four cases studied are compared.

Bone and Bones↗
PubMed1996

Ischemic preconditioning--a new concept in orthopedic and reconstructive surgery.

The duration of tourniquet-induced ischemia during orthopedic and reconstructive surgery is limited by the risk of ischemia and reperfusion injury to skeletal muscle. This study evaluated the potential of ischemic preconditioning (short periods of ischemia with intermittent reperfusion) to improve skeletal muscle function after ischemia and reperfusion in a rodent model. Preconditioning was found to improve force, contractility, and performance and to decrease fatigue of skeletal muscle. In contrast, energy-rich phosphates, measured concurrently, were not affected by preconditioning, suggesting mechanisms other than energy preservation to be involved. In summary, preconditioning may enable prolongation of orthopedic and reconstructive procedures.

Animals↗
PubMed1986

[Bacteriologic studies of the use of incision drapes in orthopedic operations].

The usefulness of plastic adhesive drapes for the prophylaxis of wound infections following to orthopedic operations was investigated in a prospectively randomized study including 123 patients. The drape was used in 68 cases, 55 patients were operated without drape. In order to carry out qualitative bacteriological examinations, smears were taken prior to, one and two hours after the beginning and after the end of the operations. Bacterial infestation in the operation area was found in 30 patients (54.5%) operated without drape and in 30 patients (44.1%) in whose operations the drape was employed. Most of the bacteria found were coagulase-negative staphylococci, in some cases corynebacteria and aerobic spore-forming organisms. There were no postoperative wound infections. No evidence of a significant difference was shown by a statistical evaluation of the results using the chi 2 test. The use of incision drapes for the prophylaxis of postoperative wound infections is therefore not necessary in orthopedic surgery.

Bacteria↗
PubMed2002

The anesthetic management of a patient with Emery-Dreifuss muscular dystrophy for orthopedic surgery.

PURPOSE: To report a patient with Emery-Dreifuss muscular dystrophy (EDMD) coming for an orthopedic procedure, with potential problems of sudden cardiac death, difficult airway, and neuromuscular disorders who was managed successfully by permanent pacemaker insertion, total iv anesthesia (TIVA), laryngeal mask insertion (LMA) insertion and continuous epidural blockade. CLINICAL FEATURES: A 22-yr-old man with known EDMD presented for triple arthrodesis of his right foot and fractional lengthening of his hamstrings bilaterally. Anesthesia was induced with a TIVA technique, and maintained throughout the operative period. A suspected difficult airway was managed by the use of a LMA, and analgesia for the peri-, and postoperative period provided by a continuous epidural infusion. The patient's perioperative course was uneventful. CONCLUSION: EDMD is a rare disorder. However, anesthesia is often required for orthopedic procedures. This case report illustrates the many potential difficulties that may be encountered. Regional anesthesia combined with light general anesthesia offers a method of avoiding many of these difficulties.

Adult↗
PubMed2005

Xenon does not reduce opioid requirement for orthopedic surgery.

PURPOSE: Is to test the hypothesis that 70% xenon has a relevant opioid sparing effect compared to a minimum alveolar concentration (MAC)-equivalent combination of N(2)O and desflurane. METHODS: In this randomized, controlled study of 30 patients undergoing major orthopedic surgery, we determined the plasma alfentanil concentration required to suppress response to skin incision in 50% of patients (Cp(50)) anesthetized with xenon (70%) or a combination of N(2)O (70%) and desflurane (2%). A response was defined as movement, pressor response > 15 mmHg, heart rate > 90 beats x min(-1), autonomic reactions or a combination of these. At skin incision, alfentanil was administered at a randomly selected target plasma concentration thereafter the concentration was increased or decreased according to the patient's response. After skin incision, desflurane was adjusted to maintain the bispectral index below 60 and prevent responsiveness in both groups. RESULTS: The Cp(50) (+/- standard error) of alfentanil was 83 +/- 48ng x mL(-1) with xenon and 49 +/- 26 ng x mL(-1) with N(2)O/desflurane (P =0.451). During surgery five xenon and 15 N(2)O/desflurane patients were given desflurane at 1.0 +/- 0.5 volume % and 2.5 +/- 0.7 volume %. The total age adjusted MAC was 0.97 +/- 0.07 and 0.94 +/- 0.07 respectively (P = 0.217). The intraoperative plasma alfentanil concentrations were 95 +/- 80 and 93 +/- 60 ng x mL(-1) respectively (mean +/- SD; P = 0.451). Patients given xenon were slightly more bradycardic, whereas blood pressure was similar. CONCLUSION: Xenon compared to a MAC-equivalent combination of N(2)O and desflurane does not substantially reduce opioid requirement for orthopedic surgery. A small but clinically irrelevant difference cannot be excluded, however.

Adult↗
PubMed2002

[Proven and unproven hygiene measures in orthopedics].

Postoperative wound infections develop in approximately 2-5% of all patients after orthopedic surgery. After urinary tract infection and pneumonia, such wound infections (15%) are the third most frequent type of hospital-acquired infection. In this review we summarize all proven and unproven hygiene measures available in orthopedics, giving special attention to those implemented with the aim of preventing and controlling postoperative wound infections. Routine application only of hygiene procedures of proven efficacy will be an important contribution to economic and ecological quality assurance in hospital.

Cross Infection↗
PubMed2003

[Evidence-based antibiotic prophylaxis in aseptic orthopedic surgery].

Disagreement exists on the topic of antibiotic prophylaxis in aseptic orthopedic surgery. No evidence on the usefulness of prophylactic antibiotic administration exists with regard to non-complex aseptic surgeries without placement of osteosynthetic material. Likewise, no undisputed evidence exists on the usefulness of antibiotic prophylaxis with regard to aseptic orthopedic surgeries involving placement of osteosynthetic material. However, the majority of experts agree on antibiotic prophylaxis in the latter cases. In contrast clear evidence does exist regarding the usefulness of antibiotic prophylaxis with first- or second-generation cephalosporins for surgeries of the hip involving fracture treatment or prosthetic replacement. The prophylactic use of glycopeptides should be confined to cases of high MRSA or MRSE risk. Administration of prophylactic antibiotics should precede incision time by around 30 min and tourniquet inflation by at least 10 min. Antibiotic administration may be repeated in the OR when surgery lasts longer than 3 h. The use of local antibiotics in bone cement has not proven useful as a prophylactic measure.

Anti-Bacterial Agents↗
PubMed2004

[Indications for blood transfusion during orthopedic surgery].

Ageing of the population increases the number of large orthopedic surgical interventions in elder people. High perioperative blood loss together with a reduced tolerance to anemia increase the transfusion probability in this patient subgroup. The expected cost explosion in the transfusion system (cost intensive quality management, imbalance between the number of donors and recipients) as well as the remaining transfusion related risk of hemolysis, infection and immunosuppression reflect the high socio-economic significance of the development of institutional transfusion programs. The present article summarizes: (1) the (patho-) physiology of anemia compensation, (2) the decision making for transfusion in healthy patients and patients with cardiovascular disease, and (3) the currently applied pre- and intraoperative techniques to reduce allogeneic transfusion in orthopedic patients.

Aged↗
PubMed2005

[Diabetic muscle infarction-an orthopedic disease pattern?].

Diabetic muscle infarction (DMI) is a largely unfamiliar disease. It affects mainly patients around 40 years of age with long-standing diabetes and concomitant end-organ complications. The symptoms represent a classic pattern of a musculoskeletal disease with muscle pain without trauma, swelling, and functional impairment. Although its short-term prognosis is good, with improvement of the symptoms over weeks or months under analgesia and rest, a high recurrence rate of up to 60% can be observed. Additionaly, the long-term survival of patients after DMI is reduced mostly due to major vascular complications. Since many diabetic patients are in orthopedic care for musculoskeletal disorders, the orthopedic surgeon should be aware of this disease to avoid unnecessary invasive diagnostic procedures and initiate suitable therapy. Furthermore, a better knowledge of the disease could lead to definite conclusions regarding its real incidence and aid in establishing new therapeutic measures for prophylaxis and better long-term survival.

Diabetic Angiopathies↗
PubMed2001

[Diagnostic control. Psychiatric comorbidity in patients of technical orthopedic units].

Because of the new hospital finance law a DRG (Diagnosis Related Groups) controlled discount liquidation under consideration of the medical impairment becomes necessary. In this paper the importance of a correct and complete description of the psychic comorbidity for the development of German-Refined-DRGs (GR-DRGs) in the orthopedic field is described. Therefore we analysed data of orthopedic in-patients, who are diagnosed by consultation of the clinic for psychosomatics and psychotherapy. A psychic comorbidity (ICD-10 Chapter F (V)) was diagnosed by 95% of the consulted patient. 30% of the patients showed difficulties in coping with their disease. 40% suffered from chronical psychoneurotic patterns and conflicts, which can be explained (a) as consequence of a difficult psychosocial adaptation by chronic disease or after an amputation (b) as basic mental disorders (c) as cause of the orthopaedic complications. Therefore the number of indications for a psychotherapeutic or psychiatric treatment is very high. The knowledge about a psychic comorbidity can--beside financial aspects--help the team on the orthopaedic station in the treatment of difficult patient.

Adaptation, Psychological↗
PubMed2004

Aprotinin and major orthopedic surgery.

Aprotinin is a potent pharmacological agent that reduces bleeding and limits blood transfusion requirements in current surgical practice. Many studies have been conducted in orthopedic surgery. In several trials performed in total hip replacement (THR) and total knee replacement (TKN) patients, aprotinin only moderately decreased blood-loss-replacement requirements. Conversely, when aprotinin was used in patients at high risk for bleeding (cancer, sepsis, redone surgery), it developed a potent hemostatic activity and decreased blood transfusion significantly. No increase in deep vein thrombosis and pulmonary embolism was observed. The only major side effect could be the potential occurrence of an anaphylactoid reaction. Prophylactic administration of aprotinin should be considered in extensive spine surgery and in high-risk major orthopedic operations. The decision to use aprotinin should be guided by a risk/benefit analysis.

Aprotinin↗
PubMed2003

Prions and orthopedic surgery.

Prions are a novel class of infectious agents that cause subacute encephalopathy in man and animals as human Creutzfeldt-Jakob disease (CJD), sheep scrapie and bovine spongiform encephalopathy (BSE). Previously, prions were shown to be transmitted by neuro- and ophthalmosurgical measures and by application of brain-derived therapeutic hormones. Recently, prions have been detected in blood specimens of experimentally infected monkeys indicating a principal threat to transfusion medicine, furthermore in human or bovine materials used in reconstructive surgery. In this article the risk of prion transmission from the surgeon to the patient or vice versa during (orthopedic) surgery is reevaluated including the issues of blood transfusion. This is accomplished based on recent epidemiologic findings and biometric calculations on the spread of prions in animals and humans as well as in terms of experimental data on artificially contaminated medical materials and devices. The overall risk of prion transmission in orthopedic surgery is considered very low if adequately prepared and sterilized materials and devices are used.

Animals↗
PubMed1991

Alterations in thyroid hormones, cortisol, and catecholamine concentration in patients after orthopedic surgery.

Changes in serum and plasma concentrations of thyroid hormones, cortisol, and catecholamines were measured simultaneously in 16 patients undergoing major elective orthopedic surgery. Blood samples were collected preoperatively and at 2, 6, 24, 48, 96, and 168 hr after surgery. A significant decrease in TT3 and FT3 and an increase in rT3 were noted after surgery. TT4 started to decrease 48 hr after surgery whereas FT4 showed no significant change over the same period of time. The concentration of TSH fell progressively after surgery reaching a nadir by Day 7. The concentrations of cortisol were increased markedly throughout the course after surgery. Adrenaline and noradrenaline levels were increased markedly during the first 24 hr postsurgery. Both the thyroglobulin and TBG together with albumin concentration values were decreased after surgery as compared to preoperative values. It is concluded that the changes in thyroid hormone levels after major elective orthopedic surgery seem to be independent of changes in plasma catecholamines and/or cortisol concentrations.

Adolescent↗