Biomedical subjects

T Gruen

Publications and source records attributed to T Gruen.

4 recordsLinked to original sources

PubMed1997

Functional results in total hip replacement in patients 65 years and older.

Total hip arthroplasty in patients 65 years and older has been very durable in long term results. Eighty-nine hips in 79 patients were observed for 5 to 9 years to determine the importance of advancing age and deterioration of activity levels to durability of total hip replacement. The age of patients was 65 years or older at the time of surgery. A classification of function was used that graded activity level. During the average 6.24 years of postoperative followup, 22% of the patients died, 38% had medical problems that reduced their functional level, and 10% reduced their function because of their hip surgery. Hip related deterioration occurred only in those patients with a cementless stem. There was decreasing measured wear with increasing age; otherwise, neither age nor activity change in this study was related to loss of fixation of components, osteolysis, or bone remodeling. Increasing age and decreasing activity in patients 65 years and older does not seem to be the primary reason for durability of total hip arthroplasty in these patients. In this age group, the durability of hip replacement is related mostly to the quality of fixation.

Aged↗

PubMed1997

A simple assessment of bone quality prior to hip arthroplasty: cortical index revisited.

OBJECTIVE: To determine from routine clinical radiographs the diversity of cortical bone structural quality, i.e. the cortical index, of the proximal femur in 117 hips prior to hip arthroplasty and to evaluate its variance associated with patient demographic variables (gender, age at the time of surgery, height, weight, body mass index (BMI), and preoperative diagnosis). DESIGN: A cross-sectional study was conducted using preoperative anteroposterior radiographs of the hip from 110 consecutive patients with 117 hip arthroplasty procedures, in which the patients at the time of surgery had an average age of 69.9 years (range, 19 to 92 years). The primary diagnosis leading to hip surgery was either degenerative joint disease (68 hips) or femoral neck fracture (49 hips). The cortical index, as a measure of cortical bone structural quality, was determined by one experienced reader for the proximal femur of each hip from conventional preoperative anteroposterior radiographs. Correlation analysis was performed between the cortical index and patient demographic variables to assess factors associated with the cortical index. RESULTS: For the entire cohort the average femoral cortical index was 47.9% (range, 25.8% to 64.8%). The hips in female patients had a lower average cortical index than in male patients (mean value of 46.9% and 50.0% respectively). Statistical analysis demonstrated highest significant positive correlation between cortical index and BMI (r = +.441, p < 0.0001) and with body weight (r = +0.396, p < 0.0001). Significant negative correlation was also found between cortical index and age at the time of hip surgery (r = -0.423, p < 0.0001). Significant differences were found between the cortical index and preoperative diagnosis with lower values among the hips diagnosed with femoral neck fractures (mean value, 43.9%) compared to hips with degenerative joint disease (mean value, 50.9%). CONCLUSION: A simple radiogrammetric parameter obtained from routine radiographs, i.e. the femoral cortical index, was found to demonstrate diversity of cortical bone structural quality among patients prior to hip arthroplasty. The cortical index decreased with older patients and increased with heavier (weight) and obese (BMI) patients. It was significantly lower among the hips with femoral neck fractures in patients who were predominantly fragile older females with lower body mass index, which would corroborate published studies associating lower bone mass with risk of hip fracture.

Adult↗

PubMed1982

Porous ingrowth fixation of the femoral component in a canine surface replacement of the hip.

Prosthetic fixation by growth of bone into porous implants coated with a sintered layer of cobalt chrome beads offers an attractive alternative to acrylic cementation. Experiments on dogs demonstrate that bone ingrowth occurred into the femoral component of a hip surface replacement. Methods of stabilizing prostheses in order to promote bone ingrowth must not interfere with the uniformity of stress transfer at the bone - implant interface. Ingrowth occurred as early as the second week postimplantation. The absence of any fibrous membrane formation in the interface between bone and metal suggests that sintered chrome cobalt is a highly compatible biological system, and that fixation by bone ingrowth is stable and does not promote osteoclasis and progression to a fibrous membrane at the interface.

Animals↗

PubMedDate not supplied

Improved methods for quantitative radiographic evaluation with particular reference to total-hip arthroplasty.

The range of magnification factors in 40'' and 72'' radiographs were calibrated using three simple mathods. The relationship between X-ray source to cassette distance, object to cassette distance and magnification factors was determined experimentally for both 40'' and 72'' radiographs. The resulting nomogram showed that: (1) there was no significant magnification difference between centered (AP-hip) and offset (AP-pelvis) radiographs; (2) magnification factors of 40'' films were twice those of 72'' films for the same object to cassette distances; and (3) due to the smaller magnification range of 72'' films (1 to 13%) compared to 40'' films (1 to 26%) there was less chance of error in determining magnification factors for the larger film distances. The skin radiation dosage for the patient was similar in both procedures. Magnification factors were also calculated from 414 A-P radiogrphs of total-hip prosthesis, using the femoral ball as a calibration standard. This provided magnifications of 20 per cent +/- 6(2SD) for 40'' films and by extrapolation on the nomogram gave corresponding values of 10 per cent +/- 3 for the 72'' films. The associated hip to cassette distances (L), also obtained from the nomogram, varied from 125 to 205 mm, average 165 mm. In subsequent clinical trials using 72'' films, it was possible to represent the patients as either small (L less than 145 mm) medium (145 less than or equal to L less than or equal to 185 mm) or large (L greater than 185 mm) with corresponding magnification factors of 8, 10 and 12 per cent, respectively. The error with this simplification was still within +/-21/2 per cent. For 40'' films the corresponding magnification factors for small, medium or large patient categories were 16, 20 and 24 per cent respectively with likely errors within +/-5 per cent. Magnification factors were also calculated from the radiographic image of a 100 mm long rod which had been attached to the patien's thigh. The overall accuracy with this method was comparable to the techniques described above and had the advantage that every radiograph featured its own scale, a particularly important feature for preoperative films which have no implant for calibration purposes. As a result of such simple calibration procedures, it was possible to identify the overall magnification variations and specify particular magnification factors within +/-21/2 per cent (72'' films) or +/-5 per cent (40'' films).

Arthroplasty↗