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Biomedical subjects

L Lidgren

Publications and source records attributed to L Lidgren.

At least 19 recordsLinked to original sources
PubMed1999

Interface gap after implantation of a cemented femoral stem in pigs.

We studied the interface gap around cemented femoral stems. Fresh pig femora were used. Bone cement mixed under vacuum or at atmospheric pressure was injected into the femoral canal and a cobalt chrome stem was then implanted. The femora were sectioned transversely from the minor trochanter and distally by using a high-pressure water cutter. Most of the interfaces had intimate contact. However, in all specimens, small gaps were found at the bone-cement and cement-stem interfaces. The gaps at the interfaces between the bone and cement and the cement and stem were measured, using a computerized video digital system. They occupied about 10% of the circumference at the bone-cement interface and about 15% of the circumference at the cement-stem interface, irrespective of the mixing procedures. Most gaps were less than 100 mu at the interfaces. In conclusion, cemented implants in the animal model showed that small gaps are found at the interfaces directly after implantation. These gaps may be weak points and initiate debonding when loading the prostheses.

Animals↗
PubMed1999

Validation of the Swedish Knee Arthroplasty Register: a postal survey regarding 30,376 knees operated on between 1975 and 1995.

The Swedish Knee Arthroplasty Register is dependent on the participating clinics regarding accuracy of information. As the register is prospective, and since revision is used as the endpoint in survival analyses, it is important that all revisions of registered primary arthroplasties are reported. To validate the register, we sent a questionnaire to all living patients with 30,796 knees registered as having been operated on from 1975-1995. Of living patients, 99% could be located and 93% answered. We found that one fifth of the revisions had not been reported and that relatively fewer revisions were lost to follow-up during the first decade of the register than in the following years. To investigate whether the Patient Administrative System (PAS), a database based on ICD coding and run by the Swedish health authorities, could be used to locate missing revisions found by the postal survey, we compared this database with the Swedish Knee Arthroplasty Register. 84% of the missing revisions revealed by the postal survey were found by using this method. Hence after the survey and the use of the PAS to find unreported revisions in deceased and non-responding patients, we estimate that 94% of all revisions are accounted for. Apart from a generally higher cumulative revision rate, conclusions reported from the Register in recent years regarding survivorship seem to be unaffected by the underreporting.

Arthroplasty, Replacement, Knee↗
PubMed1999

Use of unicompartmental instead of tricompartmental prostheses for unicompartmental arthrosis in the knee is a cost-effective alternative. 15,437 primary tricompartmental prostheses were compared with 10,624 primary medial or lateral unicompartmental prostheses.

Unicompartmental knee arthroplasty (UKA) is known to have a higher risk of revision than tricompartmental arthroplasty (TKA), while UKA implants are generally less expensive than TKA implants. We estimated the costs of implants and hospital stay of both procedures and related the cost difference at primary operation to the difference in number of revisions to be expected. We compared 15,437 primary TKAs and 10,624 primary medial or lateral UKAs. The operations were all done on patients with arthrosis during 1985-1995. By matching patients in the Swedish Patient Administration System with the Swedish National Knee Arthroplasty Register, the groups could be compared regarding the length of the hospital stay. The cumulative revision rate (CRR) and the relative risk of revision were calculated with survival statistics, as well as the risk of a second revision and the risk of infection. The weighted mean cost of the commonest implants in each group was used as an estimate of the implant cost. We found that the TKA patients were, on average, 2 years older at operation and had a lower CRR than the UKA patients-i.e., 10-year CRR of 12% and 16%, respectively. After adjusting for age, gender and year of operation, UKA patients were found to have a 2-day shorter hospital stay and fewer serious complications than TKA patients. The mean estimated cost of a unicompartmental implant was 57% of that of a tricompartmental implant. We conclude, that by using UKA instead of TKA in appropriate patients, money can be saved, even after taking into account the increased number of revisions to be expected.

Age Distribution↗
PubMed1998

Renal dysfunction after total knee replacement is not aggravated by bone cement.

BACKGROUND: Total knee replacement (TKR) has been associated with postoperative renal dysfunction. The use of monomeric methylmethacrylate (MMA) bone cement causes hypotension by several mechanisms. METHODS: In 30 patients undergoing TKR with (n = 16), or without (n = 14) bone cement, serum levels of creatinine, cystatin C and creatine kinase (CK) and urinary levels of creatinine and markers for glomerular (albumin, IgG) and tubular (protein HC) function were recorded preoperatively and on days 1, 2, 4 and 8 postoperatively. RESULTS: There were no changes in serum creatinine. Both groups had a transient, 5-fold rise in CK and a continuous increase in cystatin C. The urinary concentration of proteins increased postoperatively with a peak in the glomerular markers on day 1 and in the tubular marker on day 2. There were no significant differences in proteinuria between the groups. The 95% CIs for the difference in the means of the AUCs of the logarithmically transformed values for the proteins were never more than 19%. On day 8 all proteins had returned to their preoperative levels. CONCLUSION: Postoperatively, there was a transient increased leakage of proteins, indicating glomerular and tubular dysfunction. This was not influenced by the use of MMA bone cement.

Aged↗
PubMed1998

Revision of unicompartmental knee arthroplasty: outcome in 1,135 cases from the Swedish Knee Arthroplasty study.

From 1975 through 1995, 45,025 knee arthroplasties were recorded in the prospective Swedish Knee Arthroplasty study. By the end of 1995, 1,135 of 14,772 primary unicompartmental knee arthroplasties (UKA) for localized, mainly medial arthrosis had been revised. The Marmor/Richards and St. Georg sledge/Endo-Link prostheses were used in 65%. Mean age at revision was 72 (71) years. 232 revisions were performed as an exchange UKA (partial in 97) and 750 as a total knee arthroplasty (TKA). 153 were revised by other modes. In medial UKA, the indication for revision was component loosening in 45% and joint degeneration in 25% and in lateral UKA, the corresponding figures were 31% and 35%, respectively. In 94 cases, unicompartmental components were added to the initially untreated compartment, in 14 with partial exchange of a component. The CRRR was estimated using survival statistics. After only 5 years, the risk of having a second revision was more than three times higher for failed UKAs revised to a new UKA (cumulative rerevision rate (CRRR 26%) than for those revised to a TKA (CRRR 7%). This difference remained, even if those revised before 1985, when modern operating technique was introduced, were excluded (CRRR 31% and 5%, respectively). UKA is a safe primary procedure, when performed with well-designed components and modern surgical technique. It gives documented good patient satisfaction, range of motion, pain relief and relatively few serious complications. However, once failed, the knee should be revised to a TKA. This applies to most modes of failure. Not even joint degeneration of the unoperated compartment can be safely treated by adding contralateral components; CRRR after this procedure was 17%, while it was 7% when converted to a TKA.

Aged↗
PubMed1997

Integrated system for preparation of bone cement and effects on cement quality and environment.

We developed a prepacked mixing system for the preparation of bone cement. The system is based on mixing and collection of bone cement under a vacuum and serves as both the storage and mixing device for the cement components, thereby minimizing the exposure of the operating staff to the monomer and the risk for contamination of the cement during preparation. We evaluated the system using Palacos R and Simplex P. The cement produced was compared with cement obtained from a commercially available mixing system. Temperature evolution during curing, handling characteristics, density, and porosity of the cement obtained were analyzed. The results showed that the experimental system produces cement with physical properties (i.e., setting times and temperature, porosity, and density) equal to or better than those obtained with commercially available systems. Reducing the amount of monomer in the experimental system led to a reduction of the curing temperature without compromising the physical properties of the cements.

Biocompatible Materials↗
PubMed1997

Pharmacokinetics of cloxacillin in patients undergoing hip or knee replacement.

OBJECTIVE: The pharmacokinetics of cloxacillin was investigated in 14 men and 24 women undergoing cemented hip (n = 19; age range 56-90) or knee replacement surgery (n = 19; age range 51-84) for osteoarthritis. Cloaxacillin 1 g was given intravenously as a bolus dose at the induction of anesthesia, and plasma samples and urine were collected for 6 h. Drug levels were determined using HPLC. RESULTS: Preoperative serum creatinine levels were 84 mumol.l-1 in hip patients and 72 mumol.l-1 in knee patients. The calculated values for creatinine clearance were 63 and 85 ml.min-1.1.73 m-2, respectively. Total clearance of cloxacillin was 134 ml.min-1.1.73 m-2 in eighteen evaluated patients undergoing hip replacement, and 162 ml.min-1.1.73 m-2 in eighteen patients undergoing knee surgery. Renal clearance was 72 and 79 ml.min-1.1.73 m-2, respectively. Non-renal clearance was 57 ml.min-1.1.73 m-2 in hip patients and 77 ml.min-1.1.73 m-2 in knee patients. Renal clearance of cloxacillin correlated with the estimated creatinine clearance (r = 0.652). Although women received higher doses than men (median 2.02 vs 2.32 mmol.1.73 m-2), there were no sex differences in clearance corrected for body surface area. CONCLUSION: Total clearance of cloxacillin was lower in patients undergoing hip replacement than in patients undergoing replacement of the knee, but there was no difference between men and women.

Aged↗
PubMed1997

Wear in retrieved condylar knee arthroplasties. A comparison of wear in different designs of 280 retrieved condylar knee prostheses.

The plastic components of 280 retrieved unicondylar and total knee arthroplasties were studied. Wear was visually scored using a relative ranked data method. Although wear on the components was highly variable, several conclusions could be drawn regarding the nature and causes. Wear was associated more with the medial than the lateral condyle. Delamination was the most severe type of wear and occurred in short (< 5 year)-, medium (5-10 years)-, and long (> 10 years)-term retrievals. In the short term, delamination wear was associated with hot pressing of the tibial plastic or with fracture of the tibial baseplate. For a single design, a significant difference in the amount of delamination on hot-pressed and non-hot-pressed tibial components was observed. In medium- and long-term retrieved specimens of the designs with moderately high conformity, delamination wear was associated with restriction of rotational movement of the femoral component or with abrupt changes in the radius of the tibial component. In flatter, less conforming designs, wear was associated with laxity, such that the polyethylene delaminated toward the edges of the tibial component. Wear attributed to cement abrasion or entrapment occurred on the more conforming designs. Delamination was associated with the presence of fusion defects in the polyethylene but could also occur in the absence of such defects. That delamination was the principal were type and that this is caused by a fatigue mechanism mean that the incidence of failure could accelerate considerably over follow-up periods beyond 10 years. Designs of moderate conformity without abrupt changes in radii may prolong the duration of plastic tibial components before serious delamination occurs.

Cementation↗
PubMed1997

Knee arthroplasty in rheumatoid arthritis. A report from the Swedish Knee Arthroplasty Register on 4,381 primary operations 1985-1995.

The Swedish Knee Arthroplasty Register has data on 4,381 primary operations performed 1985-1995 for rheumatoid arthritis. Of these, 192 were performed with unicompartmental prostheses and 4143 with tricompartmental. 77% were women and the mean age was 66 years. There were 126 first, 20 second, and 1 third revision in tricompartmental arthroplasties, mainly for loosening, infection and patellar problems. There were 38 first, 3 second, and 1 third revision in unicompartmental arthroplasties, mainly for progression of RA and loosening. Cumulative revision rates (Kaplan-Meier) were calculated. Tricompartmental knees had a 10-year cumulative revision rate of 5% and uni-knees 25%. Patients treated before 1990, men and patients younger than 55 had higher revision rates than patients treated after 1990, women and older patients, respectively. Cemented tibial components resulted in lower revision rates than uncemented ones. There was no significant difference in revision rates between patellar replaced and unreplaced knees or between the 9 commonest implant types.

Aged↗
PubMed1997

Renal impairment after hip or knee arthroplasty. Urinary excretion of protein markers studied in 59 patients.

We studied renal function during and after surgery in 38 patients undergoing total hip replacement (THR) and 21 patients undergoing total knee replacement (TKR). Serum creatinine and renal excretion of albumin, IgG, protein HC and creatinine were recorded preoperatively and on days 1, 2, 4, and 8. THR patients were randomized to treatment with (n 17) or without (n 21) prophylactic isoxazolyl penicillins, which all TKR patients had. In all 3 groups, the urinary concentration of proteins increased postoperatively with a peak in the glomerular markers (albumin, IgG) on days 1 and 2, and in the tubular marker (protein HC) on days 2 and 4. There were no statistically significant differences between the groups. On day 8, all urinary protein concentrations had essentially returned to their preoperative levels. Serum creatinine decreased by 10% in THR patients on day 1 and then returned to baseline levels, but there was a gradual increase up to 13% in TKR patients.

Aged↗
PubMed1997

Effects of lamination on the strength of bone cement.

To improve cement penetration into the cancellous bone of the acetabulum in hip arthroplasty, sequential cementation of each anchoring hole may be feasible. Since this procedure creates laminations in the cement, we have determined the conditions under which such laminations affect the strength of the cement. Cement bars made at 2, 3 or 4 minutes after the start of cement mixing and with either dry laminations or laminations including blood or saline were tested for tensile strength. Solid unlaminated bars were used as references. Dry and saline laminations made up to 4 minutes after the start of cement mixing did not reduce the strength of the cement. However, there was a time-dependent decrease in cement strength if blood was entrapped in the interface. In such cases, there was a decrease in strength for laminations made at 4 minutes, at 3 minutes this was less pronounced and at 2 minutes no weakening at all was noted. Our findings indicate that a sequential cementation procedure is permissible as regards cement strength, provided it is performed with 2-3 minutes after the start of cement mixing. If the cement area is kept free from blood, the time may be prolonged up to 4 minutes, without the risk of weakening the cement strength.

Biomechanical Phenomena↗
PubMed1996

Overall cancer incidence not increased after prosthetic knee replacement: 14,551 patients followed for 66,622 person-years.

It is unknown whether patients as a consequence of prosthetic joint replacement are at a higher risk of developing cancer. We therefore analyzed cancer incidence following prosthetic knee replacement (TKR). The observed cancer incidence in 14,551 patients from the population-based Swedish Knee Arthroplasty Register who have undergone TKR because of osteoarthrosis (OA, n = 10,120) or rheumatoid arthritis (RA, n = 4431) were compared with the expected cancer incidence for a Swedish reference population. The cohort was followed for a total of 66,622 person-years. We followed 33% of the patients with OA and 59% of those with RA for more than 5 years. All patients who underwent TKR, whether for OA or for RA, had lower than expected total cancer incidence. We found a markedly low incidence of colorectal carcinoma, especially in patients with RA. Our results do not indicate an increased incidence of cancer following TKR.

Arthritis, Rheumatoid↗
PubMed1996

Different effects of phagocytosable particles during bone formation versus remodeling.

Previously, small phagocytosable particles of high density polyethylene (HDPE) but not Ti6-Al4-V alloy, at a concentration of 10(8) particles/mL inhibited net bone formation in vivo after 3 weeks in the bone harvest chamber (BHC). These findings reflected the effects of particles during the phase of bone ingrowth. In this study, we tested whether these effects persisted or were different during the phase of bone maturation and remodeling. BHCs were bilaterally implanted in mature male NZW rabbits. After a 6-week period for osseointegration, the contents of the chamber were harvested and discarded. One percent sodium hyaluronate, the carrier, was then placed within the canal of the chambers bilaterally and the tissue within the chambers was harvested 3 weeks later. HDPE particles were then inserted unilaterally for a 3-week period, followed by Ti6-Al4-V for 3 weeks, HDPE for 6 weeks, and Ti6-Al4-V for 6 weeks. The side chosen for each treatment was switched consecutively; the nonimplanted, contralateral chamber served as a control. At 3 weeks the control treatments yielded trabeculae of woven bone in a fibrovascular stroma. By 6 weeks, the peripheral trabeculae were thicker, and a central marrow cavity was developing. Bone ingrowth was less with HDPE particles at 3 and 6 weeks compared to controls. Ti6-Al4-V particles did not inhibit bone ingrowth at 3 weeks but showed a trend at 6 weeks. The characteristics of particles affect the differentiation, maturation, and remodeling of mesenchymal tissue differently.

Alloys↗
PubMed1996

Polyethylene and titanium alloy particles reduce bone formation. Dose-dependence in bone harvest chamber experiments in rabbits.

Particles similar to those generated from joint replacements affect net bone formation within the Bone Harvest Chamber in rabbits. Whether these effects depend on the concentration of particulate materials is unknown. In this study, we performed a histomorphologic and morphometric analysis of net bone formation in the Bone Harvest Chamber in the presence of different concentrations of phagocytosable particles of high density polyethylene and titanium 6-aluminum 4-vanadium alloy. Chambers were implanted in 9 mature New Zealand white rabbits bilaterally. Concentrations of 10(6), 10(7) and 10(8) polyethylene particles/mL, and 10(8) and 10(9) particles/ mL of titanium alloy in 1% sodium hyaluronate carrier were implanted for 3-week periods in sequence in each of the chambers. 3-week control periods in which nothing was implanted in the chamber were included between the treatments. Increasing concentrations of polyethylene particles were associated with a more marked foreign body response and fibrosis. Net bone formation for the three polyethylene doses was reduced by 11%, 21% and 33% of controls, respectively. For titanium alloy, net bone formation was reduced by 8% and 56% of controls, for concentrations of 10(8) and 10(9) particles/mL, respectively. Our findings suggest possible adverse effects of wear debris on net bone formation and bony remodeling in the prosthetic bed, when concentrations of specific particles reach critical local levels.

Alloys↗
PubMed1995

Effects of particulate high-density polyethylene and titanium alloy on tissue ingrowth into bone harvest chamber in rabbits.

The purpose of this study was to determine whether small, phagocytosable particles of titanium alloy (Ti) and high-density polyethylene (HDPE) have an adverse effect on bone ingrowth. The bone harvest chamber (BHC) was implanted bilaterally in the proximal tibial metaphysis of six mature rabbits. The BHC has a transverse 1-mm wide pore providing a continuous canal through the chamber for tissue ingrowth. After an initial 6-week period for osseointegration of the BHC, the contents of the canal were harvested repeatedly at 3 weekly intervals. This could be done with the chamber in place, without disturbing its exterior surface or the surrounding bone. The carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with particles of HDPE or Ti averaging 4.7 +/- 2.1 and 3.0 +/- 2.6 microns, respectively. The contralateral chamber was left empty and served as a control. The chambers were harvested repeatedly, alternating experimental and control sides. The sections from the control side, and those containing Healon alone demonstrated extensive trabecular bone in a fibrovascular stroma. The sections containing Ti alloy particles were qualitatively and quantitatively similar to the control sections and those containing Healon, except for the presence of small black granules of Ti alloy, dispersed in the fibrovascular stroma or phagocytosed by scattered macrophages. The sections containing HDPE particles were infiltrated and engulfed by mononuclear and multinuclear histiocytic cells in a highly fibrous stroma. The majority of the multinucleated cells present were interpreted as being foreign body giant cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗