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Biomedical subjects

John J Callaghan

Publications and source records attributed to John J Callaghan.

At least 19 recordsLinked to original sources
PubMed2007

Nonidentical and outlier duty cycles as factors accelerating UHMWPE wear in THA: a finite element exploration.

Wear rate and wear direction vary considerably within total hip arthroplasty (THA) patient cohorts. Third body effects and wide-ranging differences in patient activity levels are two factors suspected of contributing to wear variability. A sliding-distance-coupled contact finite element formulation was used to test the hypothesis that nonidentical duty cycles (differing activities, or change of third body challenge) produce accelerations in polyethylene wear. Effects of nonidentical duty cycles, time-variant femoral head roughening, and outlier gait inputs were investigated. Without femoral head roughening, combination walk/stair-climb wear simulations did not result in appreciably higher volumetric wear than a walk-only simulation, but when a roughened zone was included, walk/stair-climb volumetric wear increased by approximately 57% above that of a similarly roughened walk-only simulation. To investigate time-variant femoral head roughening, wear simulations were begun with femoral head roughening at one location on the femoral head, switching to another location halfway through the simulation. Results varied depending on roughening sites, but cases of substantial increase in wear involved a transient jump in wear rate shortly after the change of head roughening location. Outlier duty cycles were simulated by increasing or decreasing the joint contact force and range of motion inputs, to levels at the 97.5th and 2.5th percentiles of a population of normal subjects. The resulting wear showed an increase or decrease closely proportional to the percentage by which each input (force or range of motion) was changed.

Arthroplasty, Replacement, Hip↗
PubMed2007

Stability of fused versus nonfused THA femoral impaction grafts.

Impaction grafting for THA involves compacting morselized cancellous bone (MCB) into a cavitary defect to build up bone stock. Ideally, the MCB subsequently remodels into a new contiguous cancellous lattice. A recent laboratory model of MCB fusion allows simulating an impaction graft construct in this ideal eventual clinical state. The purpose of the present study was to determine the relative stability of femoral impaction graft constructs in which the MCB has fused versus that for MCB in the freshly impacted nonfused condition. Cemented femoral impaction graft constructs were created in composite femurs. For fused constructs, the MCB was mixed with an amine epoxy that causes the MCB to set up into a contiguous structure biomechanically comparable to intact cancellous bone in compression. The constructs were loaded with 500,000 physiologic gait cycles. Three-dimensional motion was measured between the femur and the stem. The fused femoral impaction grafts were much more stable than the nonfused grafts at the proximal stem location, but MCB fusion had only a modest effect on distal stem stability. These results indicate that most of the opportunity to reduce femoral stem micromotion and migration lies proximal, and that steps to enhance impaction graft remodeling and fusion are most effectively focused proximally.

Arthroplasty, Replacement, Hip↗
PubMed2007

Total hip arthroplasty with a cemented, polished, collared femoral stem and a cementless acetabular component. A follow-up study at a minimum of ten years.

BACKGROUND: Recent studies have suggested that cemented femoral components with a polished surface may provide superior long-term fixation when compared with femoral components with a roughened surface. The purpose of this study was to evaluate the results of total hip arthroplasty with a cemented femoral component with a polished surface finish and compare them with the results of total hip arthroplasty performed with a similar design of cemented femoral component with a rougher surface finish. METHODS: We retrospectively reviewed a consecutive group of 132 patients (149 hips) in whom primary total hip arthroplasty had been performed by one surgeon using a cemented collared femoral component with a polished (0.1-microm Ra) surface finish and a cementless acetabular component. Ninety-eight patients (115 hips) were followed for a minimum of ten years. We compared the survivorship of this prosthesis with that of a femoral component of similar design but with rougher surfaces (matte or grit-blasted). RESULTS: No polished stems were revised because of aseptic loosening or demonstrated radiographic evidence of loosening; however, eight hips (5.4%) with a polished stem demonstrated osteolysis distal to the greater or lesser tro-chanter. In contrast, six stems (2.0%) with a matte surface finish of 0.8-microm Ra were revised because of aseptic loosening, and an additional five stems were seen to be loose radiographically. Eleven stems (9.2%) with a grit-blasted surface finish of 2.1-microm Ra were revised because of aseptic loosening, and an additional four stems were seen to be loose radiographically. The difference in the prevalence of revision due to aseptic loosening between the group with the 0.1-microm Ra surface and the group with the 2.1-microm Ra surface was significant (p = 0.001), as was the difference between the prevalence of revision due to aseptic loosening between the group with the 0.8-microm Ra surface and the group with the 2.1-microm Ra surface (p = 0.001). No cups were revised because of aseptic loosening, and one hip had radiographic signs of acetabular loosening. CONCLUSIONS: This study demonstrated excellent durability of a prosthesis consisting of a cemented, collared, polished femoral component and a cementless acetabular component. While no hips were revised because of aseptic loosening, distal femoral osteolysis was observed in eight hips (5.4%), a higher prevalence than has been reported by others after similar durations of follow-up of tapered, collarless, polished femoral components.

Adult↗
PubMed2006

Computer-assisted surgery: a wine before its time: in the affirmative.

A number of investigators have demonstrated, in their hands, the potential for computer-assisted navigation to improve precision and accuracy in obtaining optimal knee alignment in the total knee arthroplasty construct. However, it will be difficult to demonstrate improvement in revision and loosening rates. In addition, there are concerns for computer glitches, training of personnel, extra time requirements, and cost and ability to demonstrate improvements in clinical results to warrant these concerns. Reproducibility of these improvements in precision and accuracy in the hands of the less experienced surgeon must be documented.

Arthroplasty, Replacement, Knee↗
PubMed2006

Design factors influencing performance of constrained acetabular liners: finite element characterization.

Constrained acetabular liners are utilized to deal with the infrequent but devastating problem of recurrent dislocation. While an encouraging treatment of last resort, the clinical performance of contemporary constrained liners has been somewhat mixed. There are multiple factors contributing to this variability, one of which is the limited understanding of the intrinsic mechanical characteristics of these specialty devices. To address this issue, a three-dimensional, materially nonlinear, multi-surface contact finite element model of a representative constrained liner was created. The model was physically validated, and then used for parametric testing to explore the effects of individual design features. The model was exercised for both intra-operative assembly and lever-out dislocation. It was found that the coefficient of friction between the femoral head and the liner substantially affected both the force required to seat the femoral head into the liner during assembly, and the peak moment resisting dislocation (226% increase in assembly force for friction coefficients of 0.2 versus 0.0; 49% reduction in dislocation moment for friction coefficients of 0.013 versus 0.135). As expected, the cup opening radius also had a dominant effect on both maneuvers: decreasing the opening radius from 13.9 to 13.6 mm increased assembly force by 506 N and increased the dislocation moment by over 3.5 N-m, whereas the influence of other design parameters was much more modest.

Acetabulum↗
PubMed2006

Problematic sites of third body embedment in polyethylene for total hip wear acceleration.

A computational model was developed to identify the sites of third body particle embedment in a total hip acetabular component surface that are most problematic in terms of roughening the overpassing regions of the femoral head counterface, leading in turn to most severely accelerated polyethylene wear. The analytical approach used was to calculate loci of acetabular sites that, during the gait cycle, overpass previously documented regions of kinetically most critical femoral head roughening. Instantaneous local contact stress and sliding distance were postulated as factors contributing to the severity of the femoral head scratching/roughening which would be expected, due to otherwise-similar particles embedded along each such acetabular overpass locus. The computational results showed that the location of debris embedment was a potent determinant of the amount of polyethylene wear acceleration expected. The data also showed that the supero-lateral aspect of the acetabular cup is consistently and by far the most problematic area for third body particle embedment.

Acetabulum↗
PubMed2006

Current etiologies and modes of failure in total knee arthroplasty revision.

UNLABELLED: Although total knee arthroplasty is a very effective intervention and increasing in prevalence, failures do occur. We studied patients presenting for total knee arthroplasty revision to determine any modifiable causes of failure, both short and long term, and where future efforts should be directed to reduce the incidence of failure. A multicenter prospective observational cohort study of 318 consecutive patients, with minimum 1 year follow-up, undergoing total knee arthroplasty revision was performed. Associations between modes of failure were also assessed. The mean time from primary procedure to total knee arthroplasty revision was 7.9 years. Many patients (64.4%) had more than one cause of failure. Thirty-one percent of patients were early (< 2 years) failures at a mean of 11 months. These had a higher prevalence of infection, perioperative factors and comorbidities. Late failures occurred at a mean of 119.2 months. Other major causes of failure included instability (28.9%), wear (24.5%) and component loosening suggesting the importance of modifications in technique, implants and other areas. Application of these findings will ultimately reduce revision numbers through continued refinement of total knee arthroplasty practice and through further specific investigation of these modes of failure. LEVEL OF EVIDENCE: Therapeutic study, level II-2 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed2006

Internet promotion of MIS and CAOS in TKA By Knee Society members.

Minimally invasive surgery (MIS) and computer-assisted orthopaedic surgery (CAOS) options for total knee arthroplasty (TKA) have become increasingly popular. However, few controlled studies document their efficacy and safety. We examined the Internet for Knee Society members' websites to evaluate the level of promotion for these procedures in terms of direct (surgeon endorsed) and indirect (surgeon associated) information. On 92 websites, 22.7% made indirect reference to MIS TKA, while only 10.9% made a direct reference. Of the sites referencing MIS TKA, faster recovery was reported on 90% of indirect sites and 50% of direct sites. Specific risks were discussed on only 35% of indirect sites, and on only 20% of direct sites. CAOS TKA was discussed on 6.5% of indirect sites and on 5.4% of direct sites. Although MIS and CAOS TKA are frequently discussed on the Internet, only a small percentage of KS members directly promote these techniques (10.9% and 5.4%, respectively). Information was often indirectly associated with KS surgeons through institutional websites or hospital affiliations. Information indirectly associated with a surgeon may be mistaken as endorsing the procedure by a prospective patient.

Arthroplasty, Replacement, Knee↗
PubMed2006

Improved results using extensively coated THA stems at minimum 5-year followup.

The Prodigy femoral component was extensively coated along its entire length, except for a smooth bullet-shaped distal tip. At a minimum 5 year followup we compared the results of that stem to those of a proximally coated first generation femoral component at comparable followup to address the question of which design performed better. For the extensively coated cohort, 86 patients (100 hips) underwent total hip arthroplasty by a single surgeon. At final followup, no patients were lost to followup and no hips were revised for aseptic loosening. Clinically, 3% of patients reported thigh pain (versus 15% in the proximally coated group). Radiographically, all hips had evidence of bone ingrowth (versus 94% in the PCA group). As expected with an extensively coated device there were fewer radiolucencies around the lower half of the prosthesis as well as less distal femoral lysis compared to the proximally coated stem.

Adolescent↗
PubMed2006

Results of Charnley total hip arthroplasty with use of improved femoral cementing techniques. a concise follow-up, at a minimum of twenty-five years, of a previous report.

UNLABELLED: The current study was performed to determine the status, at a minimum of twenty-five years, of a prospective, single-surgeon series of patients treated with primary Charnley total hip arthroplasty with a contemporary femoral cementing technique that included use of a distal cement plug and a retrograde cement-delivery system. Since our review at a minimum of twenty years postoperatively, two primary total hip prostheses were revised (one because of acetabular loosening, and one because of femoral loosening). Of the original cohort of 357 hips (320 patients), ten (2.8%) had revision of the femoral stem because of aseptic loosening. Forty-nine patients (fifty-two hips, 14.6%) who had been in the initial study group were still living at the time of the present review. Five hips (10%) in living patients had required a femoral revision because of aseptic loosening. Including those that were revised, eight femoral components (17%) in living patients were seen to be loose radiographically. Although this study demonstrates the remarkable durability of the femoral fixation obtained with the polished flatback Charnley prosthesis and the contemporary cementing technique, there was some deterioration of the results with time. These results provide a standard for comparison with cementless fixation after hips treated with that technique have been followed for a similar duration. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Adult↗
PubMed2006

Intrapelvic migration of the trial femoral head during total hip arthroplasty: is retrieval necessary? A report of four cases.

When testing intra-operative range of motion during a total hip arthroplasty procedure with trial components, there is potential for the femoral head to dissociate from the trial neck. We report the dissociation of the trial femoral head with migration of the head into the pelvis while checking for anterior stability of the total hip arthroplasty construct. Options for retrieval of the head are outlined.

Aged↗
PubMed2005

The role of implant constraint in revision total knee arthroplasty: not too little, not too much.

The goal of revision total knee arthroplasty is to restore the anatomical alignment of the knee and to provide a stable joint. Joint stability is obtained by balancing the various knee ligaments remaining at the time of revision surgery and by using an implant with added stability if necessary. Understanding the limits of the various designs available (cruciate retaining, cruciate substituting, valgus-varus constraining, and linked) should help the surgeon construct a stable and durable construct.

Arthroplasty, Replacement, Knee↗
PubMed2005

Blood management: issues and options.

Blood management in the perioperative period of the total joint arthroplasty procedure has evolved over the last 3 decades. Strategies have changed and are changing based on a better understanding of blood loss and blood replacement options in this patient population. Patient-specific options based on preoperative hemoglobin levels and patient comorbidities as well as anticipated blood loss have been developed and studied. Patient-specific blood management programs have provided cost-efficient care with low morbidity.

Algorithms↗
PubMed2005

A laboratory simulation for morselized bone graft fusion: apparent modulus under operatively based femoral impaction kinetics.

The purpose of this study was to determine the apparent modulus changes accompanying a novel procedure for simulating in situ fusion of morselized cancellous bone femoral impaction grafts. An experienced surgeon's habitual intra-operative impaction grafting protocol was first quantified in human cadaver femurs, using a customized impulse force hammer. A corresponding standardized impaction procedure was then defined, and was used to prepare impaction grafts in axisymmetric metallic fixturing designed to replicate the nominal geometry of femoral canal confinement. Impaction graft fusion was simulated by mixing morselized cancellous bone with an amine-based epoxy adhesive before the impaction, then allowing the mixture to fuse after the impaction (J. Biomech. 34 (2001) 811). Force/deflection behavior of the unfused and fused impaction grafts was measured for both the (tapered) proximal and (untapered) distal portions of the grafts. Apparent modulus was then calculated from force/deflection stiffness. The impaction graft fusion simulation increased apparent modulus by an order of magnitude over the unfused state, for mixture parameters appropriate to have the fused graft apparent modulus be comparable to the compressive modulus of intact femoral cancellous bone.

Arthroplasty, Replacement, Hip↗