The Knee Society Index of Severity for failed total knee arthroplasty: practical application

Previous classifications of severity for total knee arthroplasty revisions have been based largely on bone loss of the femur and tibia. These approaches failed to address the more technically difficult issues in revision surgery such as surgical exposure, contractures, extremity alignment, implant removal, soft tissue stability (in the anteroposterior and in the sagittal planes), extensor mechanism integrity, and patellar revisability. Through the Knee Society, the authors developed a severity index that incorporated these latter factors into one measure. The current authors describe the application of the Knee Society Index of Severity for failed total knee arthroplasty and its method of scoring.

Morselized bone grafting of defects in revision total knee arthroplasty

In a prospective, multicenter study evaluating one revision knee system, 33 of 409 patients underwent morselized bone grafting for tibial and femoral defects. Fifty-four percent of defects were bicondylar and the defect volumes averaged 36 cc3. There was no difference in preoperative or postoperative knee scores between patients undergoing morselized grafting and the entire group. Radiographic evaluation showed remodeling of the grafted areas consistent with viable incorporation of the graft. The incidence of radiolucent lines, at 2 years followup, was not different between the patients who received grafting and the patients who did not receive grafting. There have been no clinical failures or reoperations in the patients who received morselized bone grafting. Morselized bone grafting seems to offer a viable alternative in the reconstruction of osseous defects in patients undergoing revision total knee arthroplasty.

The Knee Society Index of Severity for failed total knee arthroplasty: development and validation

Compared with primary knee replacement, total knee arthroplasty revision surgery is a more complex procedure and accounts for greater expenditures of healthcare resources at each clinical stage. Overall, patients having revision procedures have poorer functional outcomes and higher complication rates than patients having primary arthroplasty. Despite the expanded scope of revision problems and the rapidly emerging technology in revision surgery, the long-term success of any method remains in question. Because there is little consensus on the timing of revision surgery, optimal surgical reconstruction, and the type of prosthesis to be implanted, the Knee Society began development of an Index of Severity for Failed Total Knee Arthroplasty. Fifty-four percent of Knee Society members completed an 82-item questionnaire that determined their clinical impression about potential risk factors for the outcomes of revision surgery for failed total knee replacements. Using these results, a consensus group developed the final version of the index. The result of the nominal group process was the Knee Society Index of Severity, which was based on eight distinct domains. Each domain was divided into attributes and weights based on the questionnaire responses and consensus meeting. Actual case scenarios from five institutions were used to test interrater reliability and validity. The interrater reliability of the average score of all ratings was 0.95; the correlation of the criterion rating with the mean rating was 0.77. When three outliers were not included, the Pearson product correlation increased to 0.92. These data support the application of the Knee Society Index of Severity as a critical component of risk factor studies, effectiveness research, and cost-effectiveness analysis involving revisions of total knee replacements.

Patient satisfaction and outcome after septic versus aseptic revision total knee arthroplasty

A consecutive series of revision total knee arthroplasties performed at 3 university-affiliated centers by 3 surgeons was prospectively studied. The same implant was used in all cases. The evaluation included a Knee Society clinical score (KSCS); SF-36; satisfaction survey; and radiographs preoperatively, at 6 and 12 months postoperatively, and annually thereafter. Follow-up averaging 36 months (range, 24-60 months) was obtained in 125 of 138 knees (91%). Twenty-eight knees were infected, and 26 of 28 knees were treated successfully with 2-stage exchange with an interval of 4 to 6 weeks using an antibiotic-impregnated spacer block and intravenous antibiotics. The remaining 99 knees were revised for reasons other than infection, including aseptic component loosening, progressive osteolysis, and component instability. Preoperatively, patients with infection had a significantly decreased arc of motion compared with patients without infection (79 degrees vs 92 degrees; P<.05). There was a strong trend for the infected knees to have a lower preoperative KSCS than the noninfected knees, although this trend did not achieve statistical significance (76 vs. 92; P =.11). Postoperatively, patients with infection continued to have a significantly decreased range of motion (89 degrees vs. 99 degrees; P =.05). The postoperative KSCS was markedly lower in the septic versus aseptic revisions (115 vs. 135; P =.02). Patients with infection had a significantly lower function score (44 vs. 57; P =.03). A significantly higher percentage of patients stated that they were unable to return to normal activities of daily living after septic versus aseptic revision total knee arthroplasty (24% vs. 7%; P<.05). Despite the inferior functional result, patients expressed an equal degree of satisfaction with the results of their treatment in septic versus aseptic revision cases.

Exercise-induced bronchoconstriction depends on exercise load

Exercise-induced bronchoconstriction (EIB) is often used as a measure of bronchial hyperresponsiveness and employed in epidemiological studies. Different tests are used, including free running tests with poor standardization of exercise load. The present study aimed to assess the role of exercise load in relationship to level of EIB.

METHODS

20 asthmatic children, 9-17 years old with a history of EIB, underwent two treadmill test with 85% and 95% exercise load. The children ran with increasing speed for the first 2 min until reaching a heart rate of 85% or 95% of calculated maximum (220-age) and maintained this speed for the last 4 min. Lung function was measured before running, and 0, 3, 6, 10 and 15 min after the run. Borg scale for perceived exertion was employed for children's self-evaluation of exercise load.

RESULTS

Peak heart rate, mean Borg score during 85% exercise load was 178.7/13.6 and during 95% was 194.3/18.2 (P<0.001). Maximum fall in FEV1 after 85% exercise load was 8.84% vs. 25.11% after 95% (P<0.001). Nine subjects (40%) fell > or = 10% in FEV1 after 85% exercise load vs. 20 subjects (100%) after 95% exercise load. EIB from the 95% exercise load test had markedly higher correlation with serum ECP (r=0.77, P<0.001).

CONCLUSION

Exercise load is essential for the interpretation of EIB, and strict standardization of exercise tests should be undertaken. The EIB from the high exercise load tests seemed better correlated to inflammatory activity than the low exercise load test.

The results of retaining a well-fixed patellar component in revision total knee arthroplasty

The results of revision total knee arthroplasty (TKA) in which a well-fixed patellar component was left in place (retained) were compared with those in which the patellar component was revised to a cemented all-polyethylene component. The patella was retained in 34 cases, 12 of which were metal-backed, and was revised in 39 cases. Data collected on all patients included a Knee Society clinical and radiographic score, SF36, a patellofemoral questionnaire, and a satisfaction survey. There were no differences in clinical score, responses to specific patellofemoral questions, or patient satisfaction between the 2 groups. Retaining a well-fixed patellar component at the time of revision TKA appears to be a viable option with equivalent short-term results to those obtained when the patellar component is revised.

The Ranawat Award. Comparison of surgical approaches in total knee arthroplasty

A series of 123 revision total knee replacements performed at three centers and followed up for 2 to 4 years was evaluated. In cases in which exposure could be obtained with undue tension on the patellar tendon, the surgical approach was modified using either quadriceps turndown (14 cases) or tibial tubercle osteotomy (15 cases). The remaining 94 patients underwent a standard operative approach that consisted of a medial parapatellar capsular incision which in 31 cases was combined with a quadriceps snip. The results were compared using the Knee Society clinical score, a patient satisfaction survey, and a patellofemoral questionnaire. Postoperatively, the group of patients who had a quadriceps snip was equivalent to the group of patients who underwent a standard approach in every parameter measured, and the groups therefore were combined for comparison purposes. The patients who had quadriceps turndown and the tibial tubercle osteotomy had equivalent scores postoperatively both of which were significantly lower than the standard group. The group of patients who had quadriceps turndown had a significantly greater increase in arc of motion than the tibial tubercle osteotomy group. The tibial tubercle osteotomy group had a lower degree of extension lag but a higher percentage of patients who had difficulty with kneeling and stooping and a higher percentage of patients who had difficulty with kneeling and stooping and a higher percentage of patients who thought the surgery was unsuccessful in relieving pain and unsuccessful in returning them to normal daily activities.

Revision knee arthroplasty with patella replacement versus bony shell

A study was undertaken to assess the clinical results of revision total knee arthroplasty in which an unresurfaced bony shell was left after removing a patellar component versus those in which a patellar component was implanted. Followup was obtained in 123 of 130 consecutive revision total knee replacements (94%) from three centers. In 21 knees a shell of patellar bone was left and 92 knees had a patellar component in place. Ten patients had a patellectomy and were excluded from consideration. The group with the bony shell had a lower postoperative knee score but the preoperative Knee Society clinical score was significantly lower as well in this group of patients. Compared with the group of patients with the patellar component in place, the group of patients with knees left with a bony shell had a significantly higher percentage of patients who had difficulty using stairs, a higher percentage of patients who were not satisfied with their surgery, and a higher percentage of patients who rated their surgery as unsuccessful in returning them to normal daily activities. When a patellar component was not able to be implanted in revision total knee arthroplasty, a lower quality result was observed.

Cold air inhalation and exercise-induced bronchoconstriction in relationship to metacholine bronchial responsiveness: different patterns in asthmatic children and children with other chronic lung diseases

Cold air inhalation and exercise-induced bronchoconstriction (EIB) have both been used as measures of bronchial responsiveness. Both stimuli are often combined in the Nordic climate. The main objective of the present study was to investigate the climatic influence of cold temperatures upon exercise-induced asthma. The secondary aims were: (a) to assess metacholine bronchial hyper-responsiveness and EIB in children with bronchial asthma (n = 32; mean age 10.8 years) compared to children with other chronic lung diseases (CLD) (n = 26, mean age 10.1 years); and (b) to assess the influence of cold air inhalation upon EIB in the two groups of children. Methods used were: (a) the metacholine concentration causing a reduction in FEV1 of 20% (PC20-M), (b) maximum FEV1 fall (delta FEV1) after submaximal treadmill run (EIB test); and (c) delta FEV1 after submaximal treadmill run while inhaling cold (-20 degrees C) dry air (CA-EIB test). Geometric mean PC20-M did not differ significantly between the asthma children (1.28 mg ml-1) and the CLD children (2.90 mg ml-1). In the asthma children, mean delta FEV1 after EIB test was 12.8% vs 21.8% after adding cold air (P < 0.0001), compared to 5.2 and 7.4%, respectively (P = 0.03), in the CLD group. Maximum sensitivity and specificity for the EIB test were 69.8% at a fall in FEV1 of 6.8%; for the CA-EIB test, 72% at a fall in FEV1 of 10.2%; and for metacholine provocation, 56% at a PC20-M of 1.5 mg ml-1. In conclusion, children with bronchial asthma are substantially more sensitive to cold air than children with CLD, and EIB is markedly increased by cold air inhalation in asthmatic children, maintaining the specificity of the EIB test and increasing the sensitivity. The low sensitivity of the EIB test is probably influenced by the use of inhaled steroids. Metacholine inhalation test has less specificity and sensitivity in discriminating asthma from other chronic lung diseases.

Tibial insert undersurface as a contributing source of polyethylene wear debris

Sixty-seven ultrahigh molecular weight polyethylene tibial inserts from cementless total knee arthroplasties were retrieved at autopsy and revision surgery and analyzed for evidence of articular and nonarticular surface wear after a mean implantation time of 62.8 months (range, 4-131 months). Polyethylene cold flow and abrasive wear on the nonarticular insert surface (undersurface) were assigned a wear severity score (Grade 0-4). The severity of articular wear was assessed quantitatively and graded. Corresponding prerevision radiographs were evaluated for evidence of tibial metaphyseal osteolysis and osteolysis around tibial fixation screws. Exact nonparametric conditional inference methods were used to establish correlations between different variables and the occurrence of tibial metaphyseal osteolysis. Severe Grade 4 wear of the tibial insert undersurface was associated with tibial metaphyseal osteolysis or osteolysis around fixation screws. Time in situ statistically was related to Grade 4 undersurface wear and tibial metaphyseal osteolysis. The occurrence of tibial osteolysis was not related statistically to articular wear severity, insert thickness, or implant type. The main articulation between the femoral implant and ultrahigh molecular weight polyethylene insert has been assumed to be the primary source of polyethylene debris contributing to osteolysis and total knee arthroplasty implant failure. The undersurface of the insert is an additional source of polyethylene debris contributing to tibial metaphyseal osteolysis. To lessen polyethylene debris produced at this modular interface, the tibial implant locking mechanism should fix the insert firmly to the metal backing to decrease relative micromotion. Because motion between the insert and metal backing may be inevitable, the wear characteristics of the inner tray surface should be optimized to minimize wear debris production at this other articulation.