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Biomedical subjects

C A Zahiri

Publications and source records attributed to C A Zahiri.

9 recordsLinked to original sources
PubMed2000

Relationship between body mass index and activity in hip or knee arthroplasty patients.

The weight of patients has not been demonstrated to have a consistent effect on the rate of polyethylene wear in clinical studies of total joint replacement. For this reason, we analyzed the relationship between quantitative activity, measured with a pedometer, and body mass index, a measure of obesity. Data were acquired for 209 individuals, 22-82 years of age; all were independent community walkers. One hundred and fifty-one had a well functioning total hip or knee replacement. Analysis of variance was used to evaluate the relationship between activity and body mass index, with adjustments for confounding variables. The 58 individuals with no total joint prosthesis averaged 7,781 steps per day, which was higher (p < 0.01) than those with a total hip (5,869 steps per day) or knee (4,597 steps per day) replacement. The subjects with no total joint prosthesis were, however, younger than the patients with a prosthesis (p < 0.01), and the body mass index of the patients with a total knee replacement was higher than that of the patients with a hip replacement and that of the subjects with no prosthesis (p < 0.01). After adjustment for differences in age, gender, and Charnley class, a higher body mass index (greater obesity) was associated with lower activity (p = 0.05). With regard to the rate of polyethylene wear, decreased ambulatory activity may counterbalance increased weight, which could, at least in part, explain why weight has not had a consistent effect on polyethylene wear in clinical studies. Wear is a function of use, not time. The effect of obesity on activity should be considered in radiographic studies of wear and other outcome assessments of total joint replacements.

Adult↗
PubMed2000

The significance of stem-cement loosening of grit-blasted femoral components.

This study analyzed 15 patients who underwent revision for loosening at the stem-cement interface. The femoral components were from the same manufacturer and had grit-blast roughened surfaces. An apparent radiographic deficiency in the cement mantle was present in at least one zone in 1 3 patients. In 9 of 12 patients with localized osteolysis, the osteolysis developed in a zone with an apparent radiographic cement mantle defect. Loosening occurred due to tension failure of the stem-cement interface followed by axial subsidence and movement into relative retroversion. Motion between the stem and the cement mantle fueled an abrasive wear mechanism between the roughened metal surface and the cement mantle, generating excessive metal and cement particles that gained access to endosteal bone via defects in the cement mantle and resulting in localized osteolysis. Although the roughened surface played a central role in these failures, it is unlikely the layer of polymethylmethacrylate (precoat) played a role in the mechanism of failure. In some cases, debonding occurred as a result of tension failure of the metal-precoat interface. In others, tension failure occurred within the cement mantle, leaving the precoat and some cement from the mantle on the stems. There was no difference in the mechanism of failure of stems with precoat proximally compared to stems with precoat proximally and distally. One stem had no precoat; findings in this patient were indistinguishable from the others. The significance of debonding depends on the surface roughness of the stem. Debonding carries a poorer prognosis with a rougher stem surface because of abrasive wear with the generation of numerous metal and cement particulates, which can lead to rapid osteolysis if there are cement mantle defects. Stems with a higher metal-cement bond strength may require a higher quality cement mantle for long-term success.

Adult↗
PubMed2000

Radiographic analysis to determine the treatment outcome in developmental dysplasia of the hip.

The purpose of this retrospective study was to determine whether pretreatment radiographic findings of patients less than 6 months old with developmental dysplasia of the hip can predict treatment outcome. Medical records and radiographs were reviewed in a cohort of 35 patients (44 hips) less than 6 months old with a diagnosis of hip dislocation at one institution. Using pretreatment anteroposterior radiographs, we measured the superior gap (distance between the proximal metaphysis to Hilgenreiner's line) and the medial gap (distance between the femoral calcar and the lateral pelvic wall at that level) and analyzed these data along with the type of splint used (Pavlik harness verses other abduction orthosis). Medical records and radiographs from an aged-matched cohort of 20 patients (23 hips) treated at a second institution were analyzed by using the same clinical and radiographic criteria of hip dislocation. Of the 44 dislocated hips, 29 failed with a trial of splintage (66%). Of the 23 dislocated hips from the second institution, 16 failed a trial of splintage (70%). Statistical analysis evaluating the age of the patient, medial and superior gaps, and harness type revealed that an abnormal superior and medial gap consistently predicted success or failure of splintage. We concluded that infants with pretreatment radiographs revealing a superior gap equal to or less than 3 mm, or a medial gap equal to or greater than 10 mm should not be treated with an initial trial of splintage because failure is likely.

Chi-Square Distribution↗
PubMed1999

Lessons learned from loosening of the McKee-Farrar metal-on-metal total hip replacement.

Clinical and radiographic data for 15 McKee-Farrar hip replacements that had failed because of aseptic loosening (4 stem loosening, 9 cup loosening, and 2 loosening of both components) between 0.6 and 21 years (average, 8.3 years) were compared with 15 hips in which the McKee-Farrar total hip replacement has survived between 21 and 26 years. Hips that loosened were biomechanically disadvantaged compared with those that demonstrated long-term survival. Radiographic evaluation demonstrated that in hips that were revised for aseptic femoral loosening, the offset was decreased by a mean of 1.4, whereas it was increased by a mean of 4.9 mm in the surviving hips (P = .04). Further, in hips revised for aseptic loosening, the center of rotation was medialized by a mean of only 1.4 mm, whereas the center of rotation was medialized by a mean of 6.4 mm in the surviving hips (P = .1). Unfavorable biomechanics results in increased joint reaction forces that could contribute to loosening of these prostheses. Five of 6 McKee-Farrar stems revised for aseptic loosening compared with 7 of 15 surviving stems were in varus (P = .1) and, as a result, had cement mantle defects in zones III and VII. Thus, in the McKee-Farrar, similar to what has been seen in hips with metal-on-plastic bearings, curved stems are associated with varus positioning, cement mantle defects, and loosening. Wear of the metal-on-metal articulation does not appear to be the cause of failure in these cases. Wear could not be detected radiographically. At revision surgery, there was no indication of excessive bearing wear or gross metal staining of periprosthetic tissues. Microscopic analysis of tissue sections demonstrated both metal and polymethylmethacrylate particles of variable size and shape. The variability of the particles suggests that they are likely the result of loosening and that they were not generated by bearing surface wear that could cause loosening. Although it is hoped that improvements in the wear resistance of the bearing will increase survivorship, this experience and analysis of the McKee-Farrar total hip replacement illustrates the importance of the implant design, biomechanics of the reconstruction, and role of surgical implantation technique.

Arthroplasty, Replacement, Knee↗
PubMed1998

Assessing activity in joint replacement patients.

Outcome evaluations of lower extremity joint reconstructions should include an assessment of patient activity. In vivo wear assessments of total joint prostheses should be based on a measure of use, not time in situ or a proxy such as age or gender; however, clinicians lack a simple method to reliably assess the activity of patients with joint replacement. The modern pedometer can be a satisfactory means of quantifying the use of lower extremity joints. The pedometer, however, requires special effort on the part of the physician or evaluator and the patient. Therefore, we compared the quantitative assessment of walking activity of 100 total joint replacement patients, as measured with a pedometer, to the UCLA activity score and a simple visual analog scale that can easily be employed during a routine office evaluation. Both the UCLA activity rating (P = .002) and the visual analog scale rating of the investigator (P = .00001) had a strong correlation with the average steps per day as recorded by the pedometer. There was, however, up to a 15-fold difference in the average steps per day for individual patients with the same UCLA score. The visual analog scale as rated by the patients of their own activity did not have as strong a correlation with the pedometer data (P = .08) as did patient age (P = .049). For practical reasons, the pedometer is probably best reserved for the evaluation of extreme cases of activity (or inactivity). This study indicates that both the UCLA activity rating and the investigator visual analog scale are valid for routine activity assessment in a clinical setting. Adjustments of the UCLA activity score for the frequency and intensity of activity, as can be done with the investigator visual analog scale, increase the accuracy of the activity rating.

Activities of Daily Living↗
PubMed1997

Limb salvage in advanced chronic osteomyelitis in children.

Chronic osteomyelitis of the entire tibial shaft was treated in 9 children by medical and surgical management in 3 stages. In stage 1, the involved shaft was excised with debridement of the periosteum. Stage 2 consisted of continuous suction-irrigation of the periosteal space with local and systemic antibiotics. In stage 3, the ipsilateral fibular shaft was transferred into the tibial periosteal envelope with the muscles of the middle third and its blood supply. After 18 months, the transferred fibula grew into a new tibia in every case so that the children were able to carry out all their activities of daily living. This method remains the best way of salvaging the limb when the entire tibia is involved.

Child↗
PubMed1997

Anterior shoulder dislocation reduction technique--revisited.

Acute anterior shoulder dislocations are extremely painful conditions that force patients to present to emergency rooms or physicians' offices immediately. The diagnosis usually is established through a careful history and examination, and may be confirmed by appropriate radiography. The immediate treatment objective is to achieve reduction as early as possible, preferably through a closed reduction method with the least discomfort. Current methods of reduction are based on either traction or leverage maneuvers, with each having its own merits and disadvantages. This article, however, revisits the subject by a comprehensive literature review. It addresses obstacles to reduction and reports a closed reduction technique for the acute anterior dislocations of the shoulder that uses both traction and leverage maneuvers simultaneously. In addition, the technique eliminates failing factors of current reduction methods such as the surgeons' weakening or slippery grip when using traction methods. It is expected, by virtue of the method, that it would reduce the chances for complications such as humeral shaft fractures as can occur in leverage maneuvers. This method addresses all potential anatomical and pathological features of acute anterior dislocations of the shoulder to facilitate an earlier and more comfortable reduction.

Adolescent↗
PubMed1994

Arthroscopy language.

The authors have devised an "arthroscopy language" to make orthopaedic surgeons' intraoperative communication clear, comprehensive, and concise. This language specifically eliminates surgeons' "freestyle" conversation at the most crucial moments of their procedure, when concentration and the coordinated work of two surgeons are essential. The language uses current arthroscopic terminology and new words that have been adapted by the authors to describe all the basic maneuvers that are used during any arthroscopic procedure. The authors believe the language brings the necessary scientific sophistication into arthroscopic surgeons' speech in the operating theater.

Arthroscopes↗