Periprosthetic fractures adjacent to total knee implants: treatment and clinical results.
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Femoral Fractures↗
Biomedical subjects
G A Engh
Publications and source records attributed to G A Engh.
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.
Equipment Design↗
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.
Aged↗
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.
Adult↗
Titanium prosthetic wear debris in remote bone marrow. A report of two cases.
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Acetabulum↗
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.
Aged↗
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.
Bone Diseases↗
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.
Aged↗
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.
Adult↗
Osteolysis of the distal femur after total knee arthroplasty.
An 11.1% incidence of femoral osteolysis (30 cases in 28 patients) was identified in a series of 271 primary total knee arthroplasties. Two minimally constrained total knee designs (Synatomic [Depuy, Warsaw, IN] and Porous-Coated Anatomic [PCA, Howmedica, Rutherford, NJ] were used in this patient population. Femoral osteolysis was observed in 26 Synatomic and 4 PCA knees. The average follow-up period was 52 months (range, 24-96 months). Osteolytic lesions were identified radiographically, adjacent to the nonporous-coated (smooth) regions of the anterior and posterior flanges of the Synatomic and PCA femoral components. The average time to the diagnosis of femoral osteolysis was 31 months (range, 7-96 months). The average patient age at the time of primary total knee arthroplasty was 63 years (range, 43-83 years) and the average weight was 180 lb. (range, 107-278 lb.). Sixteen of the 30 cases were in men. All of the cases with femoral osteolysis had cementless implantation. Tissue specimens were obtained from the 18 cases requiring revision. Implants remained in situ an average of 66 months (range, 15-96 months) prior to revision. In 16 of the 18 cases revised, the femoral component was clinically and radiographically stable. Six of 18 cases were revised for severe osteolysis. The remaining 12 cases were revised for failed metal-backed patellae, failed cementless tibial fixation, or advanced polyethylene wear. Wear of the thin tibial inserts and patellar components were the two sources of particulate polyethylene. Polyethylene debris was observed in all tissue specimens. In cases with failed metal-backed patellae or impingement of the tibial locking pin-and-clip, fine metallic debris was also noted in tissue specimens. Microscopic evaluation of the osteolytic tissue revealed a florid histiocytic response with occasional giant cells. Intracellular submicron particulate polyethylene was identified with polarized light microscopy and oil-red-O staining techniques. In the study population, statistically significant factors associated with femoral osteolysis included male gender (P < .05), younger age (P < .05), increased patient weight (P < .05), positive tibial osteolysis (P < .001), osteoarthritis (P < .07), and length of time in situ (P < .001). In addition, patients with a Synatomic prosthesis were at increased risk for osteolysis compared to patients with a PCA device (P < .02). The authors postulate that histiocytic granuloma gained access to the proximal femur primarily via the unbonded interface between the smooth metal and bone.
Adult↗
The painful total knee replacement and the influence of component design.
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Biocompatible Materials↗
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.
Bone Cements↗
Polyethylene wear of metal-backed tibial components in total and unicompartmental knee prostheses.
We examined 86 polyethylene inserts, retrieved from total and unicompartmental knee prostheses after an average of 39.5 months in situ, grading them from 0 to 3 for seven modes of polyethylene degradation. Severe wear, with delamination or deformation, was observed in 51% of the implants, and was associated with time in situ, lack of congruency, thin polyethylene, third-body wear debris, and heat-pressed polyethylene. Significant under-surface cold flow was identified in some areas of unsupported polyethylene, and was associated with delamination in the load-bearing areas of thin inserts above screw holes in the underlying metal tray. We recommend the use of thicker polyethylene inserts, particularly in young, active patients and in designs with screw holes in the tibial baseplate. Thin polyethylene inserts which are at risk for accelerated wear and premature failure should be monitored radiographically at annual intervals.
Aged↗
Use of a semitendinosus tendon autogenous graft for rupture of the patellar ligament after total knee arthroplasty. A report of seven cases.
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Aged↗
Osteolysis after total knee arthroplasty without cement.
The prevalence and characteristics of osteolysis were studied after 174 consecutive total knee arthroplasties, performed without cement; 16 per cent (twenty-seven) of the implants (in twenty-six patients) were identified as being associated with osteolysis. The diagnosis was made an average of thirty-five months after the operation. Fifteen (56 per cent) of the twenty-seven prostheses were revised after an average of forty-five months in situ. The remaining twelve implants were still in situ five years or more postoperatively. In the patients who were managed with revision, six implants were judged to be stable radiographically and intraoperatively. The remaining nine implants were loose. The average age of the patients who had osteolysis was sixty-three years, and the average weight was seventy-six kilograms (168 pounds). Eighteen of the twenty-six patients who had osteolysis were women. The medial aspect of the tibial metaphysis was the most common site for resorption of bone (twenty-four knees). Sequential radiographs demonstrated progressive extension of the osteolytic process around the tibial base-plate of the prosthesis and distally into the tibial metaphysis along the screw-bone interface in all patients. Histological evaluation of tissue obtained at the revision procedures revealed sheets of histiocytes and occasional giant cells. Intracellular particulate polyethylene and metal were found; most particles were less than one micrometer in size, although particles as large as three micrometers were identified. Mechanical failure of the thin, modular, polyethylene tibial insert; excessive abrasion of the prominent polyethylene tibial eminence, with secondary wear and impingement of the pin on the femoral component; and failure of the metal-backed patellar component all contributed to the extensive amount of polyethylene and the variable amount of metal debris that were generated. Corrosion between the angulated titanium screws and the cobalt-chromium base-plate also contributed particulate metal to the osteolytic process locally. This study demonstrated that osteolysis occurs in association with cementless total knee replacement.
Adult↗
Preoperative flexion. Does it influence postoperative flexion after posterior-cruciate-retaining total knee arthroplasty?
This study analyzed data from 313 posterior-cruciate-sparing total knee replacements to determine the influence of preoperative flexion on postoperative flexion. The patients with limited flexion preoperatively demonstrated an improvement in flexion postoperatively. By contrast, patients with more than 105 degrees of flexion preoperatively demonstrated a decrease in flexion postoperatively. The study indicated a migration towards the mean range of motion. These findings were true for the total pool of patients and for each subgroup of patients based on diagnosis, cement status of the tibia, and implant type. The data suggests that flexion does not change beyond the first postoperative year.
Aged↗
The metal-backed patella. An invitation for failure?
Thirty-one cases of failed metal-backed patellar components requiring revision surgery are reviewed. Two modes of implant failure onset were noted. Within each group, delays in patient presentation and diagnosis of the failed component were encountered. The syndrome of the failed metal-backed patellar component is proposed. The authors conclude that: (1) more of these failures will be seen in the future; (2) this patient population needs appropriate counsel concerning the signs and symptoms of this syndrome as well as more frequent follow-up evaluations; (3) surgeons treating this complication should be prepared to revise all components; and (4) the use of metal-backed patellar components should be discontinued.
Aged↗
Comparative experience with intramedullary and extramedullary alignment in total knee arthroplasty.
A comparative analysis of intramedullary and extramedullary alignment was performed in 72 consecutive total knee arthroplasties, using the Moreland Knee Instrument System adapted for the Synatomic knee (DePuy). Six measurements were made from full-length anteroposterior radiographs taken 3 months after operation. Thirty-five of 40 (87.5%) of the intramedullary aligned patients had correct alignment (defined as 4 degrees-10 degrees of femoral component valgus). Using the same criterion, 22 of 32 (68.8%) of the extramedullary aligned patients were correctly aligned. The difference between intramedullary and extramedullary alignment was statistically significant at P less than .1. A correct tibiofemoral angle was achieved in 88% of the intramedullary aligned patients, compared to 73% of the extramedullary aligned patients.
Adult↗