The advent of computer-assisted knee replacement surgery has focused interest on the alignment of the components. However, there is confusion at times between the alignment of the limb as a whole and that of the components. The interaction between them is discussed in this article. Alignment is expressed relative to some reference axis or plane and measurements will vary depending on what is selected as the reference. The validity of different reference axes is discussed. Varying prosthetic alignment has direct implications for surrounding soft-tissue tension. In this context the interaction between alignment and soft-tissue balance is explored and the current knowledge of the relationship between alignment and outcome is summarised.

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject's legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiation dose was 2.7 mSV. The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation.

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Background: Patients with chronic low back pain present physicians with diagnostic and therapeutic problems. Physical treatments tend to have low success rates and it is postulated that this may be because low back pain can be a manifestation of abnormal illness behaviour. Methods: A structured prospective study determined the prevalence of somatization in a sample of 131 adult patients with chronic low back pain using the Illness Behaviour Questionnaire (IBQ) and the Modified Somatic Perception Questionnaire (MSPQ). The scores on these psychological questionnaires were compared with the blind interpretation of pain distribution drawings and with the results of a mechanical classification of the patient's symptoms and signs. Results: Fifty‐four per cent of patients had four or more (out of five) abnormal illness indicators. The MSPQ values for the group were significantly above the control values in the literature. Thirty‐two per cent of pain diagrams were thought to be incompatible with an organic cause when assessed by an orthopaedic surgeon and sixty‐two per cent when assessed by a psychiatrist. Conclusions: Psychosocial factors are dominant in the presentation of chronic low back pain in adults and the disorder is not primarily a musculoskeletal one.

A technique for performing allograft-augmented revision total knee replacement (TKR) using computer assistance is described, on the basis of the results in 14 patients. Bone deficits were made up with impaction grafting. Femoral grafting was made possible by the construction of a retaining wall or dam which allowed pressurisation and retention of the graft. Tibial grafting used a mixture of corticocancellous and morsellised allograft. The position of the implants was monitored by the computer system and adjusted while the cement was setting. The outcome was determined using a six-parameter, quantitative technique (the Perth CT protocol) which measured the alignment of the prosthesis and provided an objective score.The final outcomes were not perfect with errors being made in femoral rotation and in producing a mismatch between the femoral and tibial components. In spite of the shortcomings the alignments were comparable in accuracy with those after primary TKR. Computer assistance shows considerable promise in producing accurate alignment in revision TKR with bone deficits.

The relative risk of total knee arthroplasty (TKA), high tibial osteotomy (HTO), and medial unicompartment (UKA) replacement for medial compartment arthritis is presented. Risk is defined as the product of the probability of an event occurring and its consequence. To define consequence, 2 related scales of impact (1 systemic and 1 local) are suggested. The probability of a complication is derived from the incidence as found in the published literature and expressed as a decimal of 1. The cumulative risk is expressed as the sum of the risks of all individual complications. The overall impact of specific comorbidities has been calculated when their influence on the incidence of a particular complication is known. Of the 3 operations, TKA has the highest cumulative risk of systemic complications and HTO is the most likely to produce local technical problems. UKA is the safest of the procedures. The relative risk of TKA:HTO:UKA is 1.00:1.01:0.31. For TKA, the greatest additional risk is morbid obesity, which increases overall risk by 31% by virtue of a 7.8-fold increase in infection rate. Cardiorespiratory disease, diabetes mellitus, smoking, and cirrhosis of the liver increase cumulative risk by 20%, 17%, and 17%, respectively.The authors conclude that a quantitative assessment of operative risk is possible and useful. However, it depends on the availability of reliable complication incidence data.

The rapid transit system for patients with Sixty nine patients admitted to a metropolitan teaching hospital were considered for the system and 50 were accepted. Their age distribution and level of general ill health were comparable with those in other series. The rapid transit system resulted in 90% of patients accepted being discharged to their homes within the first five days, with a lower morbidity and a mortality at three months of 7%.Using the rapid transit system rehabilitation in the original environment is difficult only if the patient lives alone, and even then temporary support is often enough to allow them to return home.