Biomedical subjects

J Alfaro-Adrián

Publications and source records attributed to J Alfaro-Adrián.

5 recordsLinked to original sources

PubMed2002

The effect of anteversion on femoral component stability assessed by radiostereometric analysis.

Internal rotation of a femoral stem within the femur, with posterior migration of the femoral head (PHM) relative to the femur, is an important mode of failure. The relationship between anteversion and rotational stability for the Exeter (Howmedica International Ltd, London, UK) and Charnley Elite (DePuy International Ltd, Leeds, UK) stems was investigated using radiostereometric analysis (RSA). For the Elite, there was a significant (P=.01) correlation between anteversion and PHM, whereas for the Exeter, there was no significant correlation (P=.6). Increasing anteversion of the Elite was associated with decreasing PHM and increased stability. Of stems, 20% of the Elite and none of the Exeter were classified as having reduced rotational stability because their PHM was >2 SDs from the mean. All reduced rotational stability implants had anteversion substantially <20 degrees. Polished collarless tapered stems such as the Exeter seem to have enhanced rotational stability. For conventional stems, increasing anteversion increases stability. It is recommended that these stems are anteverted 20 degrees.

Hip Prosthesis↗

PubMed2001

Should total hip arthroplasty femoral components be designed to subside? A radiostereometric analysis study of the Charnley Elite and Exeter stems.

The Charnley Elite and the Exeter stems have different design concepts: The former is designed not to subside, whereas the latter is expected to subside. This radiostereometric analysis study compares the early migration of the 2 stems. For both implants, the 1st year migration was about 4 times faster than the 2nd year. The Exeter migration was predominantly distal (1 mm/y in the 1st year). It also showed slight collapse into valgus, and the head migrated slowly posteriorly (0.3 mm/y in the 1st year). In contrast, the Elite had slow distal migration (0.2 mm/y in the 1st year) and rapid posterior head migration (0.8 mm/y in the 1st year). Four Elites and no Exeters had rapid posterior head migration rates (mean 2.8 mm/y in the 1st year and 0.8 mm/y in the 2nd year). The Elite and the Exeter stems have fundamentally different early patterns of migration, which affect their long-term function; 20% of the Elites and none of the Exeters had rapid posterior head migration in the 1st year and the 2nd year and are likely to fail early. Polished, collarless, tapered designs, such as the Exeter, may be more forgiving than conventional stems designed not to subside.

Activities of Daily Living↗

PubMed2001

Reconstruction does not reduce tibial translation in the cruciate-deficient knee an in vivo study.

We have assessed the effectiveness of reconstruction of the anterior cruciate ligament (ACL) in reducing functional tibial translation (TT). The gait of 11 ACL-deficient patients was studied using Vicon equipment before and after surgery. Measurements of the angle between the patellar tendon and the long axis of the tibia were obtained in order to calculate TT in the sagittal plane relative to the uninjured limb during standing and walking. Before surgery, patients did not show abnormal TT on the injured side, but after surgery significant anterior TT was found in the operated limb for every parameter of gait. Abnormal anterior TT occurring during activity does not seem to be reduced by reconstruction; rather, it increases. It may be that the increased translation results from relaxation of excess contraction of the hamstring muscles, since compensatory muscle activity no longer is required in a reconstructed knee. The reduction of TT may not be an appropriate objective in surgery on the ACL.

Adult↗

PubMed1999

One- or two-stage bilateral total hip replacement.

It is not clear whether bilateral hip replacement should be done in 1 or 2 stages. The total number of total hip replacements (THRs) done in our center between 1989 and 1995 was approximately 4,000. The number of hips that were bilateral was 404, or 9% of the total number of THRs performed during this time period. Of these bilateral hip replacements, 190 (95 patients) were done as a 1-stage procedure, whereas 214 (107 patients) were done in 2 stages with 2 to 24 months in between the operations. In contrast to previous studies, there were no significant preoperative differences between the 2 groups of patients having 1-stage or 2-stage THRs, and, in particular, the comorbidity assessed by the American Society of Anesthesiologists (ASA) grade was not significantly different. Our results demonstrate that, in our patient population, bilateral THR was equally safe whether performed as a 1-stage or 2-stage procedure. This was the case in the low-risk (ASA 1 and 2) and high-risk (ASA 3 and 4) patient subgroups. One-stage bilateral THR is cheaper and involves less time in the hospital.

Aged↗

PubMed1999

Cement migration after THR. A comparison of charnley elite and exeter femoral stems using RSA.

Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail. Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates. Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interfaces.

Aged↗