Determination of Hounsfield value for CT-based design of custom femoral stems.
Ct and advanced computer-aided design techniques offer the means for designing customised femoral stems. Our aim was to determine the Hounsfield (HU) value of the bone at the corticocancellous interface, as part of the criteria for the design algorithm. We obtained transverse CT images from eight human cadaver femora. The proximal femoral canal was rasped until contact with dense cortical bone was achieved. The femora were cut into several sections corresponding to the slice positions of the CT images. After obtaining a computerised image of the anatomical sections using a scanner, the inner cortical contour was outlined and transferred to the corresponding CT image. The pixels beneath this contour represent the CT density of the bone remaining after surgical rasping. Contours were generated automatically at nine HU levels from 300 to 1100 and the mean distance between the transferred contour and each of the HU-generated contours was computed. The contour generated along the 600-HU pixels was closest to the inner cortical contour of the rasped femur and therefore 600 HU seem to be the CT density of the corticocancellous interface in the proximal part of cadaver femora. Generally, femoral bone with a CT density beyond 600 HU is not removable by conventional reamers. Thus, we recommend the 600 HU threshold as one of several criteria for the design of custom femoral implants from CT data. (+info)
Hydroxyapatite-coated femoral stems. Histology and histomorphometry around five components retrieved at post mortem.
We performed a histological and histomorphometric examination in five cadaver specimens of the femoral and acetabular components and the associated tissue which had been recovered between 3.3 and 6.2 years after primary total hip arthroplasty (THA) using a proximal hydroxyapatite (HA)-coated titanium alloy implant. All had functioned well during the patients' life. All the stems were fixed in the femur and showed osseointegration of both the proximal and distal parts. The amount of residual HA was greatest in the distal metaphyseal sections, indicating that the rate of bone remodelling may be the main factor causing loss of HA. The level of activity of the patient was the only clinical factor which correlated with loss of coating. The percentage of bone-implant osseointegration was almost constant, regardless of the amount of HA residue, periprosthetic bone density or the time of implantation. HA debris was seldom observed and if present did not cause any adverse or inflammatory reaction. Partial debonding did occur in one case as a result of a polyethylene-induced inflammatory reaction. (+info)
The inadequacy of standard radiographs in detecting flaws in the cement mantle.
Radiological assessment of the cement mantle is used routinely to determine the outcome of total hip replacement. We performed a simulated replacement arthroplasty on cadaver femora and took standard postoperative radiographs. The femora were then sectioned into 7 mm slices starting at the calcar, and high-resolution faxitron radiographs were taken of these sections. Analysis of the faxitron images showed that defects in the cement mantle were observed up to 100 times more frequently than on the standard films. We therefore encourage the search for a better technique in assessing the cement mantle. (+info)
Level of amputation following failed arterial reconstruction compared to primary amputation--a meta-analysis.
OBJECTIVES: To determine if the level of amputation after failed vascular reconstruction was comparable to the level of amputation after primary amputation. DESIGN AND METHODS: Medline literature search (1975-1996), meta-analysis. RESULTS: The odds ratio of transtibial to transfemoral (TT/TF) amputations was 927/657 = 1.41 (95% confidence limits: 1.278-1.561) in postrevascularisation amputation (PRVA) and 1590/1162 = 1.37 (95% confidence limits: 1.269-1.477) in primary amputation (PA) (p = 0.65). The pooled data show that the number of conversions from transtibial (TT) to transfemoral (TF) amputations due to amputation stump complications were 85/369 (23%) in PRVA against 93/752 (12.4%) in PA (p < 0.01). CONCLUSIONS: We could not detect any difference in TT/TF ratio between PRVA and PA. However, the risk of conversion i.e. reamputation to a higher level is higher after PRVA compared to PA. The chance of having a successful transtibial amputation is approximately 58% for postrevascularisation amputation as well as for primary amputations. An aggressive approach towards vascular reconstruction seems justified. (+info)
Can transvaginal fetal biometry be considered a useful tool for early detection of skeletal dysplasias in high-risk patients?
OBJECTIVE: To evaluate the possibility of an early diagnosis of skeletal dysplasias in high-risk patients. METHODS: A total of 149 consecutive, uncomplicated singleton pregnancies at 9-13 weeks' amenorrhea, with certain menstrual history and regular cycles, were investigated with transvaginal ultrasound to establish the relationship between femur length and menstrual age, biparietal diameter and crown-rump length, using a polynomial regression model. A further eight patients with previous skeletal dysplasias in a total of 13 pregnancies were evaluated with serial examinations every 2 weeks from 10-11 weeks. RESULTS: A significant correlation between femur length and crown-rump length and biparietal diameter was found, whereas none was observed between femur length and menstrual age. Of the five cases with skeletal dysplasias, only two (one with recurrent osteogenesis imperfecta and one with recurrent achondrogenesis) were diagnosed in the first trimester. CONCLUSIONS: An early evaluation of fetal morphology in conjunction with the use of biometric charts of femur length against crown-rump length and femur length against biparietal diameter may be crucial for early diagnosis of severe skeletal dysplasias. By contrast, in less severe cases, biometric evaluation appears to be of no value for diagnosis. (+info)
Diacerhein treatment reduces the severity of osteoarthritis in the canine cruciate-deficiency model of osteoarthritis.
OBJECTIVE: To determine if diacerhein protects against the early stages of joint damage in a canine model of osteoarthritis (OA). METHODS: OA was induced in 20 adult mongrel dogs by transection of the anterior cruciate ligament of the left knee. Beginning the day after surgery, dogs in the active treatment group were dosed twice a day with capsules of diacerhein, providing a total daily dose of 40 mg/kg, for 32 weeks. Dogs in the control group received placebo capsules on the same schedule. Pathology in the unstable knee was assessed arthroscopically 16 weeks after surgery and by direct observation when the dogs were killed 32 weeks after surgery. The severity of gross joint pathology was recorded, and samples of the medial femoral condyle cartilage and the synovial tissue adjacent to the central portion of the medial meniscus were collected for histologic evaluation. Water content and uronic acid concentration of the articular cartilage from the femoral condyle were determined, and collagenolytic activity in extracts of cartilage pooled from the medial and lateral tibial plateaus was assayed against 14C-labeled collagen fibers. RESULTS: Diacerhein treatment slowed the progression of OA, as measured by grading of gross changes in the unstable knee at arthroscopy 16 weeks after cruciate ligament transection (P = 0.04) and at the time the animals were killed, 32 weeks after surgery (P = 0.05). However, 32 weeks after ACL transection, the mean proteoglycan concentration and water content of the OA cartilage and the level of collagenolytic activity in extracts of the cartilage were not significantly different in the diacerhein treatment group than in the placebo treatment group. CONCLUSION: Diacerhein treatment significantly reduced the severity of morphologic changes of OA compared with placebo. These findings support the view that diacerhein may be a disease-modifying drug for OA. (+info)
Nocardia osteomyelitis in a pachymeningitis patient: an example of a difficult case to treat with antimicrobial agents.
Antimicrobial agents played a miraculous role in the treatment of bacterial infections until resistant bacteria became widespread. Besides antimicrobial-resistant bacteria, many factors can influence the cure of infection. Nocardia infection may be a good example which is difficult to cure with antimicrobial agents alone. A 66-year-old man developed soft tissue infection of the right buttock and thigh. He was given prednisolone and azathioprine for pachymeningitis 3 months prior to admission. Despite surgical and antimicrobial treatment (sulfamethoxazole-trimethoprim), the infection spread to the femur and osteomyelitis developed. The case showed that treatment of bacterial infection is not always as successful as was once thought because recent isolates of bacteria are more often resistant to various antimicrobial agents, intracellular parasites are difficult to eliminate even with the active drug in vitro, and infections in some sites such as bone are refractory to treatment especially when the patient is in a compromised state. In conclusion, for the treatment of infections, clinicians need to rely on laboratory tests more than before and have to consider the influence of various host factors. (+info)
Quantitative histology of the human growth plate.
This paper describes a study in the human femur of the relationship between cell division in growth cartilage and overall bone growth. Growth rates for the distal femur from birth to eighteen years were determined from serial radiographs available from the Harpenden Growth Study; An average of 1-4 cm/year was found for the ages of five to eight years. The development of the growth plate is illustrated in a series of photomicrographs of femur sections. These sections were also used for quantitative histology; The length of the proliferation zone was estimated from cell counts to be twenty-four cells per column. On the basis of this value and the measured growth rate, an approximate mean cycle time of twenty days was found for the proliferating cells of the human growth plate. Since the corresponding cycle time is two days for rodent growth plates, which also have a different structure, it is unwise to extrapolate the findings in this tissue from mouse to man. (+info)