Surface roughness of retrieved CoCrMo alloy femoral components from PCA artificial total knee joints.

In this study, we analyzed the surface roughness of retrieved cobalt-chromium-molybdenum (CoCrMo) femoral components of porous coated anatomic (PCA) artificial total knee joints, using a white light interference surface profilometer (WLISP). Thirty-eight PCA retrieved specimens obtained from the Anderson Clinic (Arlington, VA) were used. The artificial knees were originally implanted between 1982-1993, and the specimens were retrieved during revision surgeries between 1988-1996. We examined specimens damaged by three wear modes: femoral component against the ultra high molecular weight polyethylene (UHMWPE) articular surface (mode I), femoral component against the metal tibial tray (because of UHMWPE tibial component wear-through) (mode II), and femoral component against metal-debris-embedded-UHMWPE (with metal debris from the porous coating) (mode III). The mean surface roughness of each femoral component was the average of 80 surface roughness measurements. The in vivo alloy femoral component surfaces were rougher by an order of magnitude over controls, and the alloy surfaces were predominantly worn by the formation of parallel scratches in the direction of articulation. There was no correlation between the surface roughness of the femoral components and patient age, sex, weight, and total time of implantation. Significant surface roughness increases accompanied mode II and mode III wear. Different carbide morphologies were found on different femoral component surfaces, indicating that a variety of sintering processes, with different times and temperatures, may have been applied to the alloy femoral components during manufacture. Metal component roughness may be important to the wear of UHMWPE components and the success of total artificial knee joint.

Surgical technique of the midvastus arthrotomy.

For more than 25 years most surgeons have used a medial parapatellar surgical approach for total knee arthroplasty because this technique affords simplicity and excellent exposure to all compartments of the knee. This article describes how the midvastus muscle splitting approach achieves surgical exposure equivalent to that of the standard medial parapatellar approach, while preserving the integrity of the vastus medialis insertion into the medial border of the quadriceps tendon. This total knee arthroplasty approach divides the vastus medialis muscle in the direction of its fibers, as opposed to the traditional method of splitting the quadriceps tendon above the patella. The limited disruption of the extensor mechanism improves the rapid restoration of quadriceps muscle control. In addition, a more stable patellofemoral articulation is evidenced by a marked reduction in the need for lateral retinacular releases.

4- to 10-year results with the anatomic modular total knee.

The outcome of 186 consecutive total knee arthroplasties performed with the Anatomic Modular Knee is reported. One hundred forty-two knees had followup of 4 to 10 years (mean, 6.9 years). Two knees required revision of all components, one because of infection and the other for instability. Seven patients underwent exchange of the modular tibial polyethylene insert at an average of 84 months postoperatively. The mean age of these seven patients at primary arthroplasty was 54 years. No implant showed clinical or radiographic evidence of loosening and there were no complications related to patellofemoral articulation. The revision rate of the femoral, tibial, and patellar components was two of 142 or 1.4%. The revision rate including exchange of the polyethylene insert was nine of 142 or 6.3%. This minimally constrained posterior cruciate retaining modular design performed well at intermediate followup. The absence of patellofemoral complications and aseptic loosening was notable. Wear related phenomena were the most common indications for reoperation and these occurred in younger, active individuals with relatively thin polyethylene bearings. The relative value of modular tibial inserts and the outcome of isolated polyethylene exchanges warrant additional study.

The Coventry Award. Modular tibial insert micromotion. A concern with contemporary knee implants.

This study investigates micromotion between modular tibial components, one of the causes of wear on the undersurface of polyethylene inserts. The authors measured motion at the interface of nine contemporary total knee implant designs by mechanically testing the implants in a servohydraulic testing machine. Anteroposterior and mediolateral motion between the tibial insert and baseplate were measured with an extensometer placed across the interface. These tests revealed that in all implants analyzed, sufficient motion occurred to create fretting at the modular interface. Although the testing configuration in this study was not a stimulation of in situ loading patterns, the authors observed hundreds of microns of motion even under a 100 N load and variability between implants of the same design, showing that there is room for improvement among locking mechanisms in modular total knee implants.

Treatment of major defects of bone with bulk allografts and stemmed components during total knee arthroplasty.

We reviewed the results an average of fifty months (range, twenty-four to 120 months) after the use of thirty-five allografts in thirty patients during primary or revision total knee replacement. Twenty-nine femoral-head allografts, five distal femoral allografts, and one proximal tibial allograft were used in conjunction with a long-stemmed implant to reconstruct large osseous defects. The patients were evaluated clinically, radiographically, and subjectively (with use of a questionnaire). Twenty-six (87 per cent) of the thirty patients had a good or excellent clinical result, and no revisions were necessary. As none of the patients had collapse of the graft, subsidence of the implant, or revision, we believe that the outcome of treatment with a femoral-head allograft, particularly in association with a component inserted with cement, is excellent. Four non-porous-coated components were placed without cement on structural allografts. Radiographically, three of those components subsided, but none of the three needed revision and two were associated with a good clinical result. Our current practice is to cement components in all arthroplasties involving grafting. Our findings suggest that the use of a stemmed component reduces the stress on the allograft, host bone, and fixation interface. In addition, such a component contributes to the longevity of a total knee replacement associated with a bone graft. Additional studies with long-term follow-up are necessary to confirm this outcome.

Analysis of polyethylene wear debris using micro-Raman spectroscopy: a report on the presence of beta-carotene.

This paper describes micro-Raman spectroscopy of ultra-high molecular weight polyethylene wear debris isolated from revised knee replacements. The novel application of micro-Raman spectroscopy to the analysis of in vivo-generated wear debris was used to evaluate the chemical nature of individual, retrieved polyethylene particles. The analysis revealed the presence of beta-carotene on particles from both synovial fluid and tissue samples. Raman analysis of retrieved polyethylene tibial inserts also revealed localized beta-carotene signals within the primary wear region. In this paper, a mechanism is suggested that may account for the coupling of beta-carotene and polyethylene wear debris. We also discuss the origin of beta-carotene within the implanted joint and the implications that beta-carotene, an anti-oxidant, has for the overall host response to polyethylene orthopedic components.

A midvastus muscle-splitting approach for total knee arthroplasty.

This study presents a modification of the medial parapatellar surgical approach for total knee arthroplasty. This approach separates the vastus medialis muscle in the direction of its fibers beginning at the superior pole of the patella. One hundred eighteen consecutive total knee arthroplasty cases, performed by a single surgeon, were randomized prospectively to receive a medial parapatellar or midvastus muscle-splitting surgical approach. The frequency of lateral retinacular releases was recorded, patellar tilt and translation were measured, and quadriceps strength was tested. The midvastus muscle-splitting approach provided excellent exposure to all knees. Patellar stability and quadriceps strength were equivalent for the two approaches. It is concluded that the midvastus muscle-splitting approach is an efficacious alternative to the medial parapatellar approach for primary total knee arthroplasties.

Separation and characterization of polyethylene wear debris from synovial fluid and tissue samples of revised knee replacements.

A study was made of in vivo-generated polyethylene wear particles as separated from synovial fluid samples and from tissue samples surrounding total knee arthroplasty. A comparison of particle size and morphology between the two particle groups was made to assess any effects of selective tissue capture, and macrophage encapsulation and digestion. In addition, a Raman spectroscopy technique was evaluated that enables positive identification of individual wear particles. The particles of the same size range found in the synovial fluid and tissue samples exhibited a comparable morphology. Notably, submicron-sized debris was present in both the synovial fluid and tissue samples surrounding knees with osteolysis. The novel micro-Raman analysis of individual particles was successful in the categorizing of wear debris as polyethylene or nonpolyethylene.

The management of bone defects in revision total knee arthroplasty.

The number of failed total knees with large bone defects is increasing. This is related to the large number of total knee arthroplasty procedures that are being performed in an increasingly active patient population. Long-term results are needed to compare clinical outcome and survivorship of allograft reconstruction versus custom prosthetic components. A benefit to using allograft reconstruction is that the bone deficiency is not increased as occurs with custom devices, and may be decreased with incorporation of the graft. In our current economic climate there are advantages to using allografts, despite costs as high as $1,600 for processing of a proximal or distal femur. In comparison, custom prostheses are not as cost effective. A material that can unite and gradually incorporate with host bone increases the potential for long-term success. Allograft may be used as part of a reconstructive armamentarium for total knee arthroplasty. Allografts are not implants and must be used as physiologic material. The early results are comparable or superior to traditional methods of reconstruction. The augmented bone stock in allograft knees remains a theoretical advantage and may facilitate subsequent revisions.

The Ranawat Award. Histology of nine structural bone grafts used in total knee arthroplasty.

The cross section radiographs and histology of nine bone grafts were examined to determine whether grafts are durable enough to support a total knee implant when the load is shared by host bone, graft bone, and a stemmed component. All cases had cemented total knee arthroplasties with stemmed components adjacent to bulk grafts. The cases included autografts and allografts, which had been in situ for an average of 41 months (range, 20-62 months). Seven of the grafts were retrieved postmortem from three patients (four knees), and two were retrieved at revision surgery from one patient. The allografts all were intact, but had not revascularized. The autografts were viable bone. New bone was being laid down on the dead graft bone at the periphery of the allografts. No change in the bone to cement interface, no graft collapse, no development of radiolucent lines, and no component loosening occurred in these cases. The promising clinical results of bone grafts in total knee arthroplasties were confirmed by the examination of these grafts at the cellular level. Using stemmed components in bone grafted knee reconstructions may have increased graft durability and protected the grafts from fatigue failure.

Comparison of closed-suction drainage and no drainage after primary total knee arthroplasty.

One hundred thirty-six primary total knee arthroplasty patients were randomized for the use of closed-suction, nonreinfusable wound drains. Blood loss was identical in the drained and undrained groups. Forty percent of undrained wounds compared with 0% of drained wounds required dressing reinforcement. Sixty-nine percent of undrained wounds compared with 39% of drained wounds developed ecchymosis, measuring 92 cm2 in the undrained group and 28 cm2 in the drained group. This study concludes that a simple wound drain effectively minimizes the undesirable accumulation of blood in the surrounding soft tissues and the postoperative wound dressing after total knee arthroplasty.

Influence of surgical approach on lateral retinacular releases in total knee arthroplasty.

The rate of lateral retinacular releases in 2 groups of patients who underwent knee surgery performed by the senior author is compared and the factors that contribute to these differing rates are discussed. The first group of subjects consists of 88 patients who had total knee arthroplasties performed with a standard medial parapatellar approach between August 1987 and August 1988. The second group is comprised of 88 patients who had total knee arthroplasties through a midvastus surgical arthrotomy that splits the fibers of the vastus medialis muscle. This method is used by the senior author for all primary total knee arthroplasties. Lateral retinacular releases were performed in 50% of the cases in the medial parapatellar group versus only 3% of the cases in the midvastus group. Patellofemoral instability occurs as a consequence of incising the quadriceps tendon in the medial parapatellar approach and results in the need to perform lateral retinacular releases. The reduction in lateral retinacular releases is attributed to the fact that the midvastus approach leaves the connection of the vastus medialis to the quadriceps tendon intact.

Characterization of submicron polyethylene wear debris from synovial-fluid samples of revised knee replacements using a light-scattering technique.

The objectives of this study were to determine whether submicron-sized ultra-high-molecular-weight polyethylene (UHMWPE) wear debris was present in synovial fluid surrounding knee implants, and to report on the utility of a light-scattering technique for the in situ analysis of submicron-sized wear debris. The measured light-scattering coefficients of the implant synovial fluid samples were significantly larger than the coefficients of the control samples (p < 0.0001). The enhanced light scattering was attributed to the presence of submicron UHMWPE particles. This is consistent with light-scattering considerations and a Raman spectroscopy survey of synovial fluid. The mean particle volume fraction of UHMWPE was 1.11 x 10(-5) cm3/mL for the six implant samples, with mean particle diameters in the range of 200-300 nm. The UHMWPE volume fractions were found to differ by a factor of 2 between the osteolytic and nonosteolytic cases. The current findings warrant further work to determine the role of submicron polyethylene debris in the wear mechanisms of biomaterials and in the development of osteolysis following total knee replacement.

Tibial osteolysis in cementless total knee arthroplasty. A review of 25 cases treated with and without tibial component revision.

Revision total knee arthroplasty was performed in 25 knees with tibial osteolysis that was identified radiographically and confirmed histologically. Eighteen knees had focal osteolysis in the medial tibial plateau, 2 in the lateral plateau, and 5 in both plateaus. Three surgical treatment options were used: (1) exchange of the modular tibial polyethylene insert with screw removal; (2) revision of the tibial component with curettage and optional grafting of the defect; (3) and full revision of all components. The clinical and radiographic results of partial and full revision remain excellent 2 to 6 years (mean, 41 months) postrevision arthroplasty for 23 knees. Clinical failure with pending revision occurred in 1 patient with polyethylene exchange without the removal of tibial fixation screws, and in 1 patient with progression of osteolysis adjacent to the femoral component 2 years after tibial component revision. Tibial defects have not progressed, and new lesions have not developed with simple curettage of the defect and removal of sources of particulate. Tibial baseplates remain radiographically stable. Component revision of the tibial component, femoral component, or both, required the insertion of long-stemmed revision components and frequently the use of major structural allografts. These revisions have faired well, although the long-term stability of components supported with major structural allografts is unknown.