Polyethylene failure in a PCA unicompartmental knee prosthesis

Rupture of the femoral component and severe metallosis of the knee 10 years after unicompartmental knee arthroplasty (UKA): a case report

A case of a 71-year-old man with femoral and tibial osteolysis and severe metallosis of the knee, resulting from abrasive wears of the metal components of a unicompartmental knee arthroplasty, that leaded to the rupture of the femoral component of the prosthesis is reported. An unicompartmental prosthesis, in a varus knee, was implanted in 2007. In March 2017, the patient felt that his knee was becoming increasingly unstable with pain and increasing disability. At clinical evaluation there was an effusion, 110° of flexion and – 10° of extension and a slight instability at the varus/valgus stress tests. BMI was 35. In a CT scan performed in June 2017 no signs of alteration were evident, but an X-Ray performed in January 2018 showed a rupture of the femoral component. A revision surgery was performed in February 2018. At the time of revision surgery, the synovitis and the metallosis were evident. A cemented total knee arthroplasty was performed. Samples of the fluid and surface did not show any bacterial growth. Histological examination confirmed the presence of a massive metallosis. The patient had a satisfactory rehabilitation. According to the literature, metallosis and rupture of the prosthetic components due to polyethylene wear after UKA is a common complication. In our case report the elevated BMI and varus knee accelerated the wear of the polyethylene. The aim of this case report is to enhance how an appropriate diagnosis (clinical and radiographic) and early treatment can lead to a successful result. (www.actabiomedica.it)

Severe metallosis after unicompartmental knee arthroplasty

We report on a case of a patient who had femoral osteolysis and severe metallosis of the knee joint resulting from the secondary abrasive wear of the metal-backed tibial component of a unicompartmental knee arthroplasty due to massive wear of tibial polyethylene. The failure was diagnosed 11 years after implantation. This metallosis affected the intra-articular tissues and the subchondral bone.

Two-stage operation for treatment of a large dissecting popliteal cyst after failed total knee arthroplasty

A symptomatic popliteal cyst after total knee arthroplasty (TKA) is rare, occurring most frequently as a result of intra-articular knee pathology. We present a case of a large dissecting popliteal cyst 7 years after TKA with symptoms of severe calf pain and functional disability. The symptomatic cyst was excised completely in a first-stage operation, and the severely worn TKA was corrected by a second-stage surgical procedure. The patient in this report was pain free and had satisfactory range of knee motion 5 years after the index revision TKA, without recurrence of effusion or popliteal cyst formation.

Polyethylene wear debris and tissue reactions in knee as compared to hip replacement prostheses

Differences in bearing surface conformity and wear mechanisms suggest that the polyethylene (PE) wear debris generated by total knee replacement (TKR) prostheses should be different than that in total hip replacement prostheses (THR). To address this issue, PE wear debris and the cellular response in periprosthetic tissues from 19 failed TKRs was compared to that from 24 failed THRs using polarized light microscopy and a semiquantitative grading system. The foreign-body inflammatory reaction in the THR case was characterized by plump macrophages with a diffuse cytoplasmic birefringence when examined under polarized light, indicating the presence of multiple submicron particles of PE. The majority of PE particles were less than 1 mum in size and only a small fraction of the total were greater than 10 mum. The foreign-body inflammatory reaction in the TKR cases was characterized by giant cells with fewer macrophages. In the TKR specimens, the size range of PE particles was broader than in the hips. PE particles between 2 and 20 mum were frequent in TKR specimens; particles less than 1 mum in length were less common than in the THR specimens. Diffuse cytoplasmic birefringence was not a characteristic of the TKR cases. These histologic differences were so consistently distinct that the source of the specimen (i.e., from a THR or TKR) could be blindly determined by light microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Contact stress analysis of the tibial component of prosthetic knee implants

The engineering problems associated with implantation into the human body of prosthetic knee implants and some of the outstanding issues facing engineering designers in this growing sector of orthopaedic medicine are described. The contact behaviour of polymeric tibial components was modelled using a stainless steel indentor in contact with an Araldite CT200 block which contained embedded strain gauges. The block was subjected to normal and sliding loads and the stresses in the block were evaluated using the strain data; the results were compared with results obtained from finite element analysis. The results are considered in the light of recent experience with non-conforming knee implants.

Early failure of the porous coated anatomic cemented unicompartmental knee arthroplasty. Aids to diagnosis and revision

Unicompartmental knee arthroplasty (UKA) is performed less frequently than total (tricompartmental) knee arthroplasty (TKA). This study examined the range of presenting symptoms and usefulness of diagnostic tests to determine the failure mode; the outcome of surgical revision of failed UKA is also reported. From a consecutive prospective series of 43 Porous Coated Anatomic (Howmedica, Rutherford, NJ) UKAs performed between 1985 and 1992 and followed for an average of 64 months, 12 cases have come to revision surgery (28%). The average time to failure was 37 months. Symptoms preceded revision surgery by an average of 10 months. The most common presenting symptom was pain (100%), followed by swelling (92%), reduced range of motion (42%), instability (42%), and clicking (17%). Failure was caused by polyethylene wear in 50%, loosening of the femoral component in 42%, and progression of patellofemoral arthritis in one patient. The combination of single leg standing anteroposterior radiographs and supine lateral radiographs detected most causes of UKA failure. A bone scan was confirmatory in every case of suspected loosening of the femoral component. Arthroscopy diagnosed polyethylene wear in two cases and progression of joint arthritis in one case and was not helpful in one case. Revision surgery was done with primary TKA components, and follow-up periods averaged 27 months. Bone stock deficiency was found in 58%, but required bone-grafting in only one case. Revision surgery successfully restored pain-free function and range of motion in all cases. Two-year postrevision Hospital for Special Surgery scores are equal to those for primary TKA. Survivorship analysis showed a 33% failure rate at 57 months after Porous Coated Anatomic UKA when revision was the endpoint and a 41% failure rate when unsatisfactory clinical status was the endpoint. Regular follow-up evaluation is suggested for the Porous Coated Anatomic UKA.

A case of massive osteolysis after knee prosthesis polyethylene failure

A case of massive osteolysis of the distal femur in response to particulate polyethylene from a broken uncemented tibial component is described. The osteolysis was so extensive that it made the revision arthroplasty extremely difficult. Early detection and early revision is recommended.

Multicenter study of unicompartmental knee revision. PCA, Marmor, and St Georg compared in 3,777 cases of arthrosis

The prospective Swedish Knee Arthroplasty Project contained 772 PCA, 1564 Marmor and 1441 St Georg unicompartment prostheses, implanted for gonarthrosis during the period December 1983-July 1990. Follow-up was performed in September 1991. There was a significant difference in the cumulative revision rate after only 2 years, increasing to 15 percent for the PCA, compared with 5-7 percent for the two other types. The difference between PCA and Marmor/St Georg was loosening of the femoral component. Major polyethylene wear was noted in a quarter of the revised PCA tibial components. The wear pattern of Marmor/St Georg was not analyzed in this study.