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Biomedical subjects

L A Whiteside

Publications and source records attributed to L A Whiteside.

At least 19 recordsLinked to original sources
PubMed2001

Long-term followup of the bone-ingrowth Ortholoc knee system without a metal-backed patella.

Between June 1981 and January 1984, 265 Ortholoc-I femoral and tibial components were implanted using bone-ingrowth technique in 202 patients. Five knees (five patients) were lost to followup and 66 knees were excluded because the patients died, leaving 184 knees (165 patients) with 15 to 18 years followup. One knee loosened during the 15- to 18-year followup period and was revised, and five knees were revised for infection. Survival rate at 18 years considering loosening was 98.6%. At 15 years after surgery, 79.9% of patients did not have pain, 10.1% had mild pain, 8% had moderate pain, and 2% had severe pain. At 18 years after surgery, 77.6% did not have pain, 7.2% had mild pain, 5.2% had moderate pain, and 1% had severe pain. Knee flexion was 110 degrees preoperatively and increased to a mean of 115 degrees at 2 years postoperative, then remained unchanged for the rest of the followup. Intramedullary alignment proved to be highly effective, and has become the standard for total knee arthroplasty instrumentation systems. Total knee replacement with bone-ingrowth technique was a reliable and effective means of treating the end-stage arthritic knee. In patients who required revision surgery, excellent bone stock remained and revision with bone-ingrowth technique was accomplished easily.

Aged↗
PubMed2001

Stability after medial collateral ligament release in total knee arthroplasty.

Six knees from cadavers were tested for change in stability after release of the medial collateral ligament with posterior cruciate-retaining and substituting total knee replacements. Load deformation curves of the joint were recorded in full extension and 30 degrees, 60 degrees, and 90 degrees flexion under a 10 N-m varus and valgus torque, 1.5 N-m internal and external rotational torque, and a 35 N anterior and posterior force to test stability in each knee. The intact specimen and posterior cruciate ligament-retaining total joint replacement were tested for baseline comparisons. The superficial medial collateral ligament was released, followed by release of the posterior cruciate ligament. The knee then was converted to a posterior-stabilized implant. After medial collateral ligament release, valgus laxity was statistically significantly greater at 30 degrees, 60 degrees, and 90 degrees flexion after posterior cruciate ligament sacrifice than it was when the posterior cruciate ligament was retained. The posterior-stabilizing post added little to varus and valgus stability. Small, but significant, differences were seen in internal and external rotation before and after posterior cruciate ligament sacrifice. The posterior-stabilized total knee arthroplasty was even more rotationally constrained in full extension than the knee with intact medial collateral ligament and posterior cruciate ligament.

Arthroplasty, Replacement, Knee↗
PubMed2001

Fixation of the Quatroloc femoral component: a biomechanical and clinical study.

The current study was designed to test the hypothesis that press-fit femoral components with proximal press-fit and distal mechanical interlock can achieve fixation sufficient to allow bone ingrowth in osteoporotic and in normal bone. The addition of steps along the tapered distal stem improved fixation in osteoporotic bone enough to reduce micromotion to less than 20 microm in response to physiologic axial and torsional load. The clinical portion of the study included 226 consecutive hips (223 patients) with 2- to 4-year clinical results after total hip arthroplasty with a rectangular femoral component using proximal porous coating and distal mechanical interlock. Patient age ranged from 36 to 92 years. At 2 years postoperative, 4% of the patients with Type A (normal) femoral bone, 3% with Type B (intermediate) bone, and no patients with Type C (osteoporotic) bone had thigh pain. No clinical cases of loosening have occurred in normal or osteoporotic femurs.

Adult↗
PubMed2000

Functional medical ligament balancing in total knee arthroplasty.

Function of the anterior and posterior oblique portions of the medial collateral ligament and the posterior capsule in flexion and extension was evaluated in eight knee specimens after posterior cruciate retaining total knee arthroplasty. The posterior oblique portion of the medial collateral ligament was released subperiosteally in four specimens, and the anterior portion was released in four specimens. The medial posterior capsule was released in each group, then the remaining portion of the medial collateral ligament was released. Release of the posterior oblique portion produced moderate laxity at full extension and at 30 degrees flexion, and posterior capsule release produced additional laxity in full extension. Release of the anterior portion produced major laxity at 60 degrees and 90 degrees flexion. Complete medial collateral ligament release increased laxity significantly in both groups in flexion and extension. This rationale was tested in a clinical study of 82 knees (76 patients) in which 62 (76%) required medial collateral ligament release to correct varus deformity during posterior cruciate retaining total knee arthroplasty. Twenty-two knees (35.5%) were tight medially in extension only, and were corrected by releasing the posterior oblique portion. Thirty-one knees (50%) were tight medially in flexion only, and were corrected by releasing the anterior portion. Nine knees (14.5%) were tight medially in flexion and extension and required complete medial collateral ligament release, but three knees (4.8%) remained tight in extension and required medial posterior capsule release to correct flexion contracture and medial ligament contracture. Seventeen (27%) had partial posterior cruciate ligament release to correct excessive rollback of the femoral component on the tibial surface.

Arthroplasty, Replacement, Knee↗
PubMed2000

Contact stresses with an unresurfaced patella in total knee arthroplasty: the effect of femoral component design.

Compressive contact stresses between the patella and the anterior femur were measured with a digital electronic sensor before and after total knee arthroplasty (TKA) in 10 cadaver knee specimens. Contact stresses were measured first in normal knees, then after TKA with the Insall-Burstein Total Condylar, Miller Galante II, Ortholoc II, Porous Coated Anatomic, and Profix knee prostheses implanted without resurfacing the patella. The Insall-Burstein, Miller-Galante II, and Ortholoc II prostheses had significantly higher contact stresses than the normal knee throughout the flexion arc. The Porous Coated Anatomic, which has a smooth patellar groove, maintained contact area as in the normal knee and did not have significantly higher contact stresses at flexion angles <90 degrees. At flexion angles > or =105 degrees, patellofemoral contact occurred in two small areas as the patella encountered the intercondylar notch in all components except the Profix. The Profix maintained full contact and low compressive stresses throughout the full flexion arc because of its posteriorly extended patellar groove. Design features of the patellofemoral portion of TKA components are important factors that affect contact stresses in the patellofemoral joint. These features likely will affect the clinical results of TKA with an unresurfaced patella.

Arthroplasty, Replacement, Knee↗
PubMed1999

Knee stability in meniscal bearing total knee arthroplasty.

The effect of a meniscal bearing on knee laxity in anterior cruciate ligament-sacrificing total knee arthroplasty was evaluated in 7 cadaver knees using a knee testing device that measured knee flexion angle as well as laxity to medial-lateral, anterior-posterior [AP], and rotational loads. A standard fixed tibial component and mobile tibial components (AP sliding, rotationally sliding, and AP and rotationally sliding) were used to evaluate AP, rotational, and varus-valgus stability and maximal flexion and extension with the neutrally positioned and malrotated tibial tray. The AP movable components increased AP laxity, and the fixed component decreased rotational laxity significantly when compared with the normal knees. The rotationally movable components did not change knee laxities significantly even when the tibial tray was malrotated. No significant difference among the components was detected when the maximal flexion and extension angles were compared in the neutrally positioned tibial tray. Malrotation of the tibial tray decreased the maximal extension angle in the fixed component. This study showed that the rotationally movable component can achieve near-normal laxity regardless of tibial tray rotation, but AP mobility of the bearing produces AP laxity that could lead to implant failure.

Adult↗
PubMed1999

The effect of varus tilt on contact stresses in total knee arthroplasty: a biomechanical study.

The contact stress produced in the tibiofemoral joint from a varus-tilted tibial component was tested in five total knee prostheses. Peak and mean stresses were measured with a digital electronic sensor under compressive load at 15 degrees and 90 degrees flexion. Stresses were measured with the tibial component tilted 0 degrees and 5 degrees in the mediolateral direction. At a 5 degree tilt, the Advantim, the Miller-Galante II, and the Omnifit prostheses, which have a flat configuration on the femoral and tibial surfaces in the coronal plane, had significantly greater stresses than the LCS and the Profix prostheses, which have tibial and femoral components with matching curved surfaces in the coronal plane. These results suggest that the femoral component surface should have a radius of curvature that matches that of the tibial articular surface in the coronal plane to achieve a large contact area even in varus-valgus tilting.

Arthroplasty, Replacement, Knee↗
PubMed1999

Cementless fixation issues in revision total knee arthroplasty.

Although massive solid allografts can be expected to vascularize and form new bone, variable amounts of replacement as well as collapse and necrosis may be prominent features of these large block allografts. Immunocompatibility seems to be an important factor in allograft healing and incorporation. Large block allograft of the acetabulum appears to be more likely to succeed if autograft is used. Rejection appears to be a significant factor in survival of large allografts. Although bone itself is not highly immunogenic, the role of marrow elements in the cancellous bone graft may be crucial. When possible, marrow contents should be washed carefully from the interstices of cancellous bone to remove cellular elements that do not contribute to osteoinduction but do produce an inflammatory immune response that can compromise healing and bone formation. Washing and soaking the components in antibiotic solution has the additional benefit of making available a reservoir of antibiotic that is released slowly during the postoperative period. Morcellized cancellous bone, rather than finely ground bone which tends to be destroyed by phagocytosis, is the best available choice for reconstructing large volumes of deficient bone stock. Fixation is completely dependent on the existing bone, so that massive defects must be protected until sufficient rigidity develops in the grafted material to allow sharing of weightbearing loads. Clinical experience has shown that migration of the tibial component after reconstruction with morcellized allograft is rare during the first 2 to 5 years after surgery (Fig. 8). These results are surprising in light of reported experience with structural allografts of the acetabulum. Jasty and Harris reported loosening of acetabular components after 4 years in 32% of their cases. The biologic behavior of morcellized allograft differs from that of block allograft, however. Vascularization and ossification are rapid and a permanent, competent loadbearing structure is achieved by filling large deficient areas. The biologic response obtained with the correct technique appears to be early and vigorous. It does not seem likely that progressive collapse would occur after remodeling and healing have been established (Fig. 9). Bone graft handling probably is crucial to the success of grafting of the knee. Antibiotic soaking and washing, removal of bone marrow, and adequate support of the implants are all necessary factors for consistent success of this technique. The results of this salvage procedure have been encouraging. The grafting technique appears to provide long-term support for the implants, so that repeat revision is unlikely.

Adult↗
PubMed1999

Evaluation of tibial component fixation in specimens retrieved at autopsy.

Fixation of the tibial component was evaluated in eight knees retrieved at autopsy by comparing their radiographs with measurements of micromovement between the component and the tibial plateau. Micromovement in the one cemented Miller-Galante and seven cementless Ortholoc components, which had been implanted for a range of 3 days to 57 months, was measured with linearly variable differential transducers under anteroposterior shear and axial compressive loads. Micromovement between the tibial component and the screws and between the tibial component and the bone after the screws were removed also was measured in the cementless specimens. Minimal micromovement in most of the implants suggests that the tibial components were well fixed. Micromovement between the tibial tray and the screws also was minimal in the cementless components. Removing the screws did not significantly affect micromovement, except in the specimen retrieved 3 days after surgery and in the specimen with a complete radiolucent line under the component. The cementless tibial components fixed with screws, pegs, and stem were as stable as the component secured with cement. Partial radiolucencies were not associated with greater micromotion than that of bone ingrown areas, but the component with complete radiolucency did have greater micromotion than that of all of the other specimens.

Biomechanical Phenomena↗
PubMed1999

Selective ligament release in total knee arthroplasty of the knee in valgus.

An approach to the valgus knee based on anatomic function of ligaments in flexion and extension consistently yields a knee that is balanced in flexion and extension when the implants have been positioned correctly. Two hundred thirty-one knees had a valgus deformity (range, 12 degrees-45 degrees) and were corrected with valgus alignment to 5 degrees by resecting the intact joint surfaces to match implant thickness. Femoral joint surfaces were aligned in 5 degrees valgus to the long axis of the femur and parallel to the epicondylar axis of the femur in flexion and extension. The tibial surfaces were aligned perpendicular to the long axis of the tibia. For knees that were tight in flexion and extension, the lateral collateral ligament and popliteus tendon were released. Those knees that remained tight only in extension had release of the iliotibial band. Posterior capsular release was done only when necessary for persistent lateral ligament tightness. Neither ligament advancement procedures nor varus or valgus stabilized implant systems were needed to achieve stability with this procedure. The knees with ligament releases all fell within a range of 4 degrees to 7 degrees mean varus and valgus laxity, and were not significantly different from one another. No cases of clinical instability occurred, and joint stability did not deteriorate with time.

Arthroplasty, Replacement, Knee↗
PubMed1998

Contact stress analysis in meniscal bearing total knee arthroplasty.

The effect of a mobile meniscal bearing on tibiofemoral contact stress was tested with a standard fixed tibial component and with movable tibial components (anteroposterior sliding, rotationally sliding, and anteroposterior and rotationally sliding). A digital electronic sensor was used to detect tibiofemoral contact location in five cadaver knees, then the location was reproduced while peak and mean stresses were measured under compressive load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion. Stresses were measured when the tibial component was normally aligned and at 15 degrees internal and 15 degrees external rotation. To evaluate the effect of excessive overhang of the polyethylene articular surface, undersurface stress of the rotationally sliding component was also measured with a 30 degrees and a 45 degrees malrotated tibial tray. Uppersurface stresses of the fixed-bearing components were significantly higher at full extension than those recorded in components with rotational mobility. Undersurface stresses were always lower than uppersurface stresses, but correlated with uppersurface stresses. Undersurface stresses of the rotationally sliding component gradually increased as the malrotation angle of the tray increased. A mobile meniscal bearing surface appears to offer an advantage over a standard fixed component when rotational malalignment of the tibial component occurs. However, with severe rotational malalignment, edge contact markedly increases undersurface stresses, which could cause deformity and subluxation.

Adult↗
PubMed1998

Effect of patellar meniscus on patellofemoral contact stress in total knee arthroplasty.

The effect of a meniscus of fibrous tissue (patellar meniscus), on patellofemoral contact area and stresses was evaluated. Two knees with total knee arthroplasty and dome-shaped patellar components were retrieved at autopsy. Both had substantial fibrous menisci surrounding the dome of the patellar component. Contact area and contact stresses were measured with a digital electronic sensor, first with the patellar meniscus intact, then again after the patellar meniscus was removed. No dramatic difference was detected in patellofemoral contact area and contact stresses between the patellas with an intact or removed patellar meniscus, and there was no detectable load under the patellar meniscus. The results of this case study suggest that fibrous tissue surrounding the dome-shaped patellar component does not share compressive loads with the patellar component.

Aged↗
PubMed1998

Predictive value of early radiographic findings in cementless total hip arthroplasty femoral components: an 8- to 12-year follow-up.

Total hip replacement was performed in 119 patients (124 hips) with an uncemented Ortholoc femoral component between 1982 and 1987. Eight patients (9 hips) died, and 13 patients (15 hips) were lost to follow-up, leaving 98 patients (100 hips) followed for 8 to 12 years. Pain scores and anteroposterior and lateral radiographs of the femoral component from the 2-year follow-up visit were evaluated. Twenty-four of the 100 hips were revised for aseptic loosening. Radiographic criteria were highly effective in predicting those cases that would require revision. Radiolucent lines occurred at a higher frequency in all Gruen zones of the revision group radiographs, and the differences were statistically significant in zones 1, 7, 8, and 14 (P < .001). Proximal radiolucent lines were present in all of the revision cases and in 45% of the nonrevision cases. Radiolucent lines occurring on the lateral view alone were a statistically significant predictor of future need for revision (P < .001). Presence of radiolucent lines around the porous coating was 100% sensitive and 55% specific in predicting future revision. Absence of radiolucent lines around the porous coating was 100% sensitive and 45% specific in predicting no need for revision in the first 8 years.

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