Alignment of total knee arthroplasty: the relationship to radiolucency around the tibial component.

Between January 1982 and July 1985, 122 cemented 'Accord' total knee replacements were performed. Out of this number, 21 were lost to follow-up because of death (in 16), revision (2) due to infection, and failure to attend (3). The post-operative alignment of 101 prostheses were compared to the incidence of radiolucencies around the tibial component at 5 years follow-up. The mechanical axis was used as a reference. The mean alignment was 0.99 degrees valgus with a standard deviation of 2.48 degrees. Some 72% of knees were within 3 degrees and 94% within 5 degrees of true alignment. Using two methods of assessing radiolucencies there was a non-significant relationship between the alignment and radiolucencies. The alignment tolerance with this prosthesis is, therefore, at least 5 degrees.

The collateral ligament flexion-extension test (CLEFT) in total knee replacement.

We present a simple preoperative clinical test, the collateral ligament extension-flexion test (CLEFT). In patients undergoing total knee arthroplasty, with a preoperative valgus or varus deformity, this test establishes which knees have balanced collateral ligaments. It predicts which knees will not require soft tissue adjustment during the course of their surgery despite, in some cases, large deformities. The mechanism of the test is based on the observation that, in certain patients, a deformity present in extension is seen to correct in flexion. The sensitivity of this observation was checked in 44 consecutive patients undergoing total knee arthroplasty, and who had either a valgus or varus deformity in extension greater than 10 degrees. In 34 patients the test was positive, and none of these required ipsilateral collateral ligament release. All of the 10 patients with a negative test required soft tissue adjustment. In patients undergoing unconstrained total knee arthroplasty this test is reliably predictive of those knees with preoperative deformity which can be corrected simply by correctly aligned bone cuts. It supports the principle of bony resection prior to soft tissue adjustment in this form of surgery.

Factors affecting the range of movement of total knee arthroplasty.

We have investigated those factors which influence the range of movement after total knee arthroplasty, including sex, age, preoperative diagnosis and preoperative flexion deformity and flexion range. We also compared cemented and cementless tibial fixation, the influence of collateral ligament and lateral parapatellar releases and of replacement of the patella, and of the period of postoperative immobilisation. We reviewed 516 Johnson-Elloy (Accord) knee arthroplasties performed between 1982 and 1989, with a minimum follow-up of 12 months. The most important factors in the range of flexion achieved after arthroplasty are the diagnosis and the preoperative range of flexion. In patients with osteoarthritis there was a mean loss of flexion; in rheumatoid arthritis there was a mean gain. In both groups, the stiffer knees gained motion and the more mobile knees lost it. Post-operative range of motion was not influenced significantly by cement fixation, collateral ligament or patellar retinacular releases, prolonged immobilisation or patellar replacement.

Five to eight year results of the Johnson-Elloy (Accord) total knee arthroplasty.

Between February 1982 and December 1985, 133 knees in 107 patients were replaced with a cemented Johnson-Elloy (Accord) total knee arthroplasty. Thirty-five knees were lost during the follow-up period because of death in 29, revision in 3, infection in 1, and refusal of follow-up evaluation in 2. The results of the remaining 98 knees in 76 patients with a 5-8 year follow-up period are presented. The procedure was carried out in all cases presenting for surgery, irrespective of pathology and degree of deformity. The range of flexion achieved as a mean of 93.5 degrees in the osteoarthritic group and 100 degrees in the rheumatoid arthritic group. Eighty-seven percent of the osteoarthritic group and 95% of the rheumatoid arthritic group achieved between 10 degrees and 50 degrees of rotation at 90 degrees of flexion, which was maintained for the duration of the study. Adequate stability in both groups, valgus-varus and rotation in extension, and anteroposterior in flexion was achieved. Survivorship was 97.7% at 80 months.

Accuracy of intramedullary alignment in total knee replacement.

The accuracy of a system of intramedullary alignment using 6 mm rods was assessed in 100 patients undergoing total knee replacements. Post-operative, full length weight-bearing X-rays were used; the mechanical axis from head was used as the reference axis. The method of calculating the errors produced by flexion and rotation of the limb in relation to the X-ray beam is described, the mean deviation from the mechanical axis in 100 cases being 0.67 degrees valgus with a standard deviation of 2.47 degrees. The maximum error was 6.68 degrees valgus and 4.62 degrees varus. The purpose of this study is twofold, first to assess the accuracy of this system of intramedullary alignment and, second, to develop a method of correcting for apparent radiological misalignment using standard radiographic equipment.