Maquet's line passes from the centre of the femoral head to the centre of the body of the talus. The distance of this line from the centre of the knee on a long-leg radiograph provides the most accurate measure of coronal alignment. Malalignment causes abnormal forces which may lead to loosening after knee replacement. We report a series of 115 Denham knee replacements performed between 1976 and 1981 using the earliest design of components, inserted with intramedullary guide rods. Patients were assessed clinically and long-leg standing radiographs were taken before operation, soon after surgery and up to 12 years later. In two-thirds of the knees (68%) Maquet's line passed through the middle third of the prosthesis on postoperative films and the incidence of subsequent loosening was 3%. When Maquet's line was medial or lateral to this, an error of approximately +/- 3 degrees, the incidence of loosening at a median period of eight years was 24%. This difference is highly significant (p = 0.001). Accurate coronal alignment appears to be an important factor in prevention of loosening. Means of improving the accuracy of alignment and of measuring it on long-leg radiographs are discussed.

Review of the radiographs of 882 consecutive metal-to-polyethylene hip replacements after a mean follow-up of 6.8 years showed 72 cases (8%) of aseptic femoral loosening, all of which showed a lucent zone or black line between metal and cement. In 97% of the series this appeared within two years of the arthroplasty. Progress of loosening was unpredictable and only 24% had significant symptoms. Improved technique with methylmethacrylate cement in Stanmore prostheses had reduced loosening after two years from 7.9% to 0.4%. Methods of detection of early loosening are discussed.

Late degenerative changes are known to follow meniscectomy, but there is little agreement on their incidence or on which patients are most at risk. A total of 210 patients have been reviewed 10 to 22 years after meniscectomy, and long leg radiographs taken of both knees. Radiological degeneration was seen in 18%, while 7% had significant symptoms and signs. Statistical analysis showed increased changes in older patients, in those with abnormal leg alignment, and in those who had undergone lateral as against medial meniscectomy. Our findings emphasise the important mechanical function of the meniscus and support the current cautious approach to meniscectomy, especially for patients in high risk groups. They also indicate the value of early high tibial osteotomy for symptomatic varus deformity after medial meniscectomy.

One thousand patients who received 1112 total joint replacements between 1966 and 1980 were followed up prospectively for an average of six years. These patients were not advised to take antibiotics prophylactically to cover subsequent dental or surgical procedures and, so far, only three cases of haematogenous infection at the site of the joint replacement have developed. Two hundred and twenty-four patients did subsequently undergo dental or surgical procedures and 284 patients developed infections in the respiratory tract, urinary tract or at multiple sites; none of these patients developed haematogenous infection. But of 40 patients who suffered recurrent skin ulceration and infection, three (7.5%) developed haematogenous infection of the replaced joint; two of these belonged to a group of 134 patients with rheumatoid arthritis. These results suggest that transient bacteraemia is not likely to infect a replaced joint in otherwise healthy patients. But an infected skin lesion producing chronic bacteraemia, or septicaemia due to a virulent organism, may well do so and patients with rheumatoid arthritis are at greater risk than those with osteoarthritis.

Arthrodesis of the knee is sometimes needed for failed total knee replacement, but fusion can be difficult to obtain. We describe a method of arthrodesis that uses the simple, inexpensive, Portsmouth external fixator. Bony union was obtained in all six patients treated with this technique. These results are compared with those obtained by other methods of arthrodesis.

An account is given of 38 patients with complicated tibial fractures who were treated by the Portsmouth method of external fixation. Twenty-one patients had multiple injuries and 30 had compound fractures of the tibia. Eighteen fractures wounds were infected, 17 cases required bone grafts and 13 had skin grafts. Thirty-four fractures united in an average time of six months; three patients underwent below-knee amputations; one with neurofibromatosis remains ununited. Those treated primarily by external fixation did better than those in whom external fixation was used after failure of another method. Most fresh fractures united with external callus; and the significance of this in relation to the rigidity of fixation is discussed. The method is easy to use, effective and economical. Improvements to permit adjustment of position and testing for union are suggested. We advise the use of this method of external fixation as the primary treatment for complicated tibial fractures where there is a significant risk of infection or non-union.

Static force transmission at the knee is analysed using measurements from radiographs showing the position of the line of body weight and also the bones of the knee in their correct orientation during function. With this technique it is possible to suggest values for a variety of forces acting at the knee. During function the degree of knee flexion is not as important as the angle that the thigh makes with the vertical. The tension in the extensor mechanism is not the same above and below the patella. Failure to recognise these two features results in fundamental errors. The patella, the effects of patellectomy and of forward displacement of the attachment of the patellar ligament are discussed. The importance of the transmission of force in the coronal plane is emphasised with particular reference to total knee replacement. It is suggested that small errors of geometry, as seen in the anteroposterior radiograph, can produce large changes of load.