We have previously developed a radiographic technique, the oblique posterior condylar view, for assessment of the posterior aspect of the femoral condyles after total knee arthroplasty. The purpose of this study was to confirm the validity of this radiographic view based upon intra-operative findings at revision total knee arthroplasty. Lateral and oblique posterior condylar views were performed for 11 knees prior to revision total knee arthroplasty, and radiolucent lines or osteolysis of the posterior aspect of the femoral condyles were identified. These findings were compared with the intra-operative appearance of the posterior aspects of the femoral condyles. Statistical analysis showed that sensitivity and efficacy were significantly better for the oblique posterior condylar than the lateral view. This method can, therefore, be considered as suitable for routine follow-up radiographs of the femoral component and in the pre-operative planning of revision surgery.

We carried out a prospective randomised study to evaluate the blood loss in 60 patients having a total knee arthroplasty and divided randomly into two equal groups, one having a computer-assisted procedure and the other a standard operation. The surgery was carried out by a single surgeon at one institution using a uniform approach. The only variable in the groups was the use of intramedullary femoral and tibial alignment jigs in the standard group and single tracker pins of the imageless navigation system in the tibia and femur in the navigated group.

The mean drainage of blood was 1351 ml (715 to 2890; 95% confidence interval (CI) 1183 to 1518) in the computer-aided group and 1747 ml (1100 to 3030; CI 1581 to 1912) in the conventional group. This difference was statistically significant (p = 0.001). The mean calculated loss of haemoglobin was 36 g/dl in the navigated group versus 53 g/dl in the conventional group; this was significant at p < 0.00001.

There was a highly significant reduction in blood drainage and the calculated Hb loss between the computer-assisted and the conventional techniques. This allows the ordering of less blood before the operation, reduces risks at transfusion and gives financial saving. Computer-assisted surgery may also be useful for patients in whom blood products are not acceptable.

Compartment syndrome is a rare complication of total knee arthroplasty that requires early recognition and prompt decompression in order to prevent long-term disability. We have found only one previous case report in the literature. We present a series of seven cases from four hospitals and five surgeons. Six of the cases resulted in the loss of at least one compartment, and one resulted in amputation. Four of the cases resulted in legal action.

We suggest that important risk factors contributing to the development of this condition include complex surgery, soft-tissue compromise, previous surgery, and possibly vascular disease. Delay in the diagnosis and hence delay in decompression was common in our series, and in five cases appeared to be related to the use of a postoperative epidural infusion for pain relief. The presence of associated neurological compromise may have also been a significant factor in the delay to diagnosis in two cases.

We report a consecutive series of 16 revision total knee arthroplasties using the Total Condylar III system in 14 patients with inflammatory arthritis which were performed between 1994 and 2000. There were 11 women and three men with a mean age of 59 years (36 to 78). The patients were followed up for 74 months (44 to 122).

The mean pre-operative Knee Society score of 37 points (0 to 77) improved to 88 (61 to 100) at follow-up (t-test, p < 0.001) indicating very good overall results. The mean range of flexion improved from 62° (0° to 120°) to 98° (0° to 145°) (t-test, p < 0.05) allowing the patients to stand from a sitting position. The mean Knee Society pain score improved from 22 (10 to 45) to 44 (20 to 50) (t-test, p < 0.05). No knee had definite loosening, although five showed asymptomatic radiolucent lines. Complications were seen in three cases, comprising patellar pain, patellar fracture and infection.

These results suggest that the Total Condylar III system can be used successfully in revision total knee arthroplasty in inflammatory arthritis.

Twenty patients underwent simultaneous bilateral medial unicompartmental knee arthroplasty. Pre-operative hip-knee-ankle alignment and valgus stress radiographs were used to plan the desired post-operative alignment of the limb in accordance with established principles for unicompartmental arthroplasty. In each patient the planned alignment was the same for both knees. Overall, the mean planned post-operative alignment was to 2.3° of varus (0° to 5°).

The side and starting order of surgery were randomised, using conventional instrumentation for one knee and computer-assisted surgery for the opposite side.

The mean variation between the pre-operative plan and the achieved correction in the navigated and the non-navigated limb was 0.9° (sd 1.1; 0° to 4°) and 2.8° (sd 1.4; 1° to 7°), respectively. Using the Wilcoxon signed rank test, we found the difference in variation statistically significant (p < 0.001).

Assessment of lower limb alignment in the non-navigated group revealed that 12 (60%) were within ± 2° of the pre-operative plan, compared to 17 (87%) of the navigated cases.

Computer-assisted surgery significantly improves the post-operative alignment of medial unicompartmental knee arthroplasty compared to conventional techniques in patients undergoing bilateral simultaneous arthroplasty. Improved alignment after arthroplasty is associated with better function and increased longevity.

We assessed the reproducibility and accuracy of four ratios used to measure patellar height, namely the Blackburne-Peel, Caton-Deschamps, Insall-Salvati and modified Insall-Salvati, before and after total knee arthroplasty. The patellar height was measured, by means of the four ratios, on the pre- and post-operative lateral radiographs of 44 patients (45 knees) who had undergone total knee arthroplasty. Two independent observers measured the films sequentially, in identical conditions, totalling 720 measurements per observer. Statistical analysis, comparing both observers and ratios, was carried out using the intraclass correlation coefficient.

Before operation there was greater interobserver variation using either the Insall-Salvati or modified Insall-Salvati ratios than when using the Caton-Deschamps or Blackburne-Peel methods. This was because of difficulty in identifying the insertion of the patellar tendon. Before operation, there was a minimal difference in reliability between these methods. After operation the interobserver difference was greatly reduced using both the Caton-Deschamps and Blackburne-Peel methods, which use the prosthetic joint line, compared with the Insall-Salvati and modified Insall-Salvati, which reference from the insertion of the patellar tendon.

The theoretical advantage of using the Insall-Salvati and modified Insall-Salvati ratios in measuring true patellar height after total knee arthroplasty needs to be balanced against their significant interobserver variability and inferior reliability when compared with other ratios.

We investigated the changes in surface roughness of retrieved femoral components in 18 men and four women at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was for 55.6 months. Eighteen implants were retrieved for aseptic loosening and four for infection. The surface changes in the articulating areas were inspected visually and the roughness (Ra) analysed with a profilometer. Parallel scratching and burnishing were the two main forms of damage. The mean Ra measurements in the articulating areas showed no statistically significant difference when compared with those in a control area on either side of the patellar groove at the apex of the femoral flange. This suggests that it is not essential to revise a well-fixed and correctly aligned femoral component where the polished surface has become burnished or bears fine parallel scratches, if the revision is conducted solely for failure of the tibial component.

We sought to determine the degree of correlation between the condition of the patellar articular cartilage and patellofemoral symptoms and function in osteoarthritic patients undergoing total knee arthroplasty. The depth of the osteoarthritic lesion, as graded by the Outerbridge classification and its size and location were assessed to determine the condition of the patellar cartilage in 80 consecutive osteoarthritic knees undergoing total knee arthroplasty. The association between the condition of the cartilage and patellofemoral symptoms and function was investigated by correlation analysis.

The depth and size of the lesion had a significant but weak correlation with anterior knee pain (r = −0.300 and −0.289; p = 0.007 and 0.009, respectively), whereas location had no significant association (p > 0.05). None had a significant association with patellofemoral functional parameters (chair-rising, stair-climbing, and quadriceps power) (p > 0.05).

Our study indicates that patellofemoral symptoms and function are not completely determined by the condition of the cartilage. Caution should be taken when the symptoms and functional limitations are attributed to a lesion in the patellofemoral joint in making a decision regarding patellar resurfacing in total knee arthroplasty.

We performed a randomised, prospective study of 80 mobile-bearing total knee arthroplasties (80 knees) in order to measure the effects of varus-valgus laxity and balance on the range of movement (ROM) one year after operation. Forty knees had a posterior-cruciate-ligament (PCL)-retaining prosthesis and the other 40 a PCL-sacrificing prosthesis. In the balanced group (69 knees) in which the difference between varus and valgus was less than 2°, the mean ROM improved significantly from 107.6° to 117.7° (p < 0.0001). By contrast, in the 11 knees which were unbalanced and in which the difference between varus and valgus laxity exceeded 2°, the ROM decreased from a mean of 121.0° to 112.7° (p = 0.0061). We conclude that coronal laxity, especially balanced laxity, is important for achieving an improved ROM in mobile-bearing total knee arthroplasty.

We undertook a prospective, randomised study using a non-invasive transcranial Doppler device to evaluate cranial embolisation in computer-assisted navigated total knee arthroplasty (n = 14) and compared this with a standard conventional surgical technique using intramedullary alignment guides (n = 10). All patients were selected randomly without the knowledge of the patient, anaesthetists (before the onset of the procedure) and ward staff. The operations were performed by a single surgeon at one hospital using a uniform surgical approach, instrumentation, technique and release sequence. The only variable in the two groups of patients was the use of single tracker pins of the imageless navigation system in the tibia and femur of the navigated group and intramedullary femoral and tibial alignment jigs in the non-navigated group.

Acetabular Doppler signals were obtained in 14 patients in the computer-assisted group and nine (90%) in the conventional group, in whom high-intensity signals were detected in seven computer-assisted patients (50%) and in all of the non-navigated patients.

In the computer-assisted group no patient had more than two detectable emboli, with a mean of 0.64 (SD 0.74). In the non-navigated group the number of emboli ranged from one to 43 and six patients had more than two detectable emboli, with a mean of 10.7 (sd 13.5). The difference between the two groups was highly significant using the Wilcoxon non-parametric test (p = 0.0003).

Our findings show that computer-assisted total knee arthroplasty, when compared with conventional jig-based surgery, significantly reduces systemic emboli as detected by transcranial Doppler ultrasonography.

In a series of 1304 patients (1867 knees), the results of simultaneous and staged bilateral total knee arthroplasty were compared with each other and with unilateral total knee arthroplasty. The bilateral procedures had a significantly higher rate of complications than unilateral procedures, almost entirely because of thromboembolic problems. However, this did not correspond to an increase in mortality. If a bilateral procedure was indicated, then a simultaneous procedure had no increased risk over a staged procedure. There was no increase in cardiovascular complications, the rate of deep-vein thrombosis or pulmonary embolism or mortality. The rate of infection was lower with a bilateral procedure and the overall revision rate was less than 1% in all groups. The prosthesis functioned as well in all groups in the medium and longer term periods.

We feel that simultaneous bilateral total knee arthroplasty is a safe and successful procedure when compared with a staged bilateral procedure. It also has the added benefit of single anaesthetic, reduced costs and decreased total recovery time when compared to a staged bilateral procedure. For these reasons it should be considered as an option in the presence of bilateral knee joint disease.

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique.

In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year.

The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term.

We present a comparison of the results of the Oxford unicompartmental knee arthroplasty in patients younger and older than 60 years of age. The ten-year all-cause survival of the < 60 years of age group (52) was 91% (95% confidence interval (CI) 12), while in the ≥ 60 years of age group (512), the figure was 96% (95% CI 3). For the younger group, the mean Hospital for Special Surgery score at ten-year follow-up (n = 21) was 94 of 100, compared with a mean of 86 of 100 for the older group (n = 135). The results show that the Oxford unicompartmental arthroplasty can achieve ten-year results that are comparable to total knee arthroplasty in patients < 60 years of age. We conclude that for patients aged over 50, age should not be considered a contraindication for this procedure.

We measured the contact areas and contact stresses at the post-cam mechanism of a posterior-stabilised total knee arthroplasty when a posterior force of 500 N was applied to the Kirschner Performance, Scorpio Superflex, NexGen LPS Flex Fixed, and NexGen LPS Flex Mobile knee systems. Measurements were made at 90°, 120°, and 150° of flexion both in neutral rotation and 10° of internal rotation of the tibial component. Peak contact stresses at 90°, 120°, and 150° were 24.0, 33.9, and 28.8 MPa, respectively, for the Kirschner; 26.0, 32.4, and 22.1 MPa, respectively, for the Scorpio; and 34.1, 31.5, and 32.5 MPa, respectively, for the NexGen LPS Flex Fixed. With an internally rotated tibia, the contact stress increased significantly with all the fixed-bearing arthroplasties but not with the NexGen LPS Flex Mobile arthroplasty. The post-cam design should be modified in order to provide a larger contact area whilst avoiding any impingement and edge loading.

We performed a prospective, randomised trial of 44 patients to compare the functional outcomes of a posterior-cruciate-ligament-retaining and posterior-cruciate-ligament-substituting total knee arthroplasty, and to gain a better understanding of the in vivo kinematic behaviour of both devices.

At follow-up at five years, no statistically significant differences were found in the clinical outcome measurements for either design. The prevalence of radiolucent lines and the survivorship were the same. In a subgroup of 15 knees, additional image-intensifier analysis in the horizontal and sagittal planes was performed during step-up and lunge activity. Our analysis revealed striking differences. Lunge activity showed a mean posterior displacement of both medial and lateral tibiofemoral contact areas (roll-back) which was greater and more consistent in the cruciate-substituting than in the cruciate-retaining group (medial p < 0.0001, lateral p = 0.011). The amount of posterior displacement could predict the maximum flexion which could be achieved (p = 0.018). Forward displacement of the tibiofemoral contact area in flexion during stair activity was seen more in the cruciate-retaining than in the cruciate-substituting group. This was attributed mainly to insufficiency of the posterior cruciate ligament and partially to that of the anterior cruciate ligament. We concluded that, despite similar clinical outcomes, there are significant kinematic differences between cruciate-retaining and cruciate-substituting arthroplasties.