Total knee arthroplasty has become an established operation. Cemented fixation of the components has given satisfactory results and is accepted as the gold standard. Cement failure with aseptic loosening, however, is a possible long term complication. This is particularly important in view of the increasing number of younger patients who can benefit from this procedure. Hence the attraction of using implants fixed by direct osseointegration of bone into the implant, by passing the potential weak link of the cement. The objective of this study was to determine the mid-term clinical, radiological and functional outcomes after navigated cementless and cemented implantation of total knee arthroplasties without patella resurfacing done by a single surgeon.Introduction
Objectives
Wolff's Law proposes that trabecular bone adapts in response to mechanical loading and that trabeculae align with the trajectory of predominant loads. The current study is aimed to investigate trabecular orientation in the tibia in patients with osteoarthritis of the knee. Consistent with Wolff's Law, it was hypothesised that orientation would reflect the mechanical loading of the joint and hence that there would be a correlation between the trabecular orientation and the mechanical axis of the lower limb. 51 anonymised radiographs from patients with osteoarthritis were analysed using ImageJ (National Institute of Health). Each patient had both a standard anteroposterior radiograph of the knee and a long leg view taken while weight bearing. For each anteroposterior radiograph, the angle of the femoral shaft and tibial shaft were measured. The femoral shaft – tibial shaft (FS -TS) angle was then calculated as the difference between the two, as described by Sheehy et al. (2011). A medial rectangle was selected with the top, bottom, medial and lateral borders being the sclerotic bone, the growth line, the bone edge and the centre of the medial tibial spine. Corresponding measurements were done on the lateral side. Trabecular orientation of both areas was measured using OrientationJ (an ImageJ plugin). In all cases the medial and lateral orientation angles were expressed relative to the angle of the tibial shaft. The mechanical axis of the lower limb was measured from the full length radiographs by calculating the angle formed by the femoral and tibial axes, as described by Goker and Block. All measurements were done independently by two observers, SAS and SL.Introduction
Methods
Recent publications have supported the anatomic placement of anterior cruciate grafts to optimise knee function. However, anatomic placement using the anteromedial portal has been shown to have a higher failure rate than traditional graft placement using the transtibial method. This is possibly due to it being more technically difficult and to the short femoral tunnel compromising fixation methods. It also requires the knee to be in hyper flexion. This position is not feasible during with a tourniquet in situ on the heavily muscled thighs of some athletes. Hypothesis: That navigation can be used to place the femoral tunnel in the anatomic position via a more medial transtibial tunnel. 25 patients underwent Navigated Anterior Cruciate reconstruction with quadruple hamstring grafts. The Orthopilot™ 3.0 ACL (BBraun Aesculap, Tuttlingen) software was used. The femoral and tibial ACL footprints were marked on the bones with a radio frequency probe and registered. The pivot shift test, anterior drawer and internal and external rotation were registered. A navigated tibial guide wire was inserted at 25° to the sagittal plane and 45° to the transverse plane exiting through the centre of the tibial footprint. The guide wire was advanced into the joint to just clear of the surface of the femoral footprint with the knee in 90° flexion. Flexion/extension of the knee was done to determine the closest position of the guide wire tip to the centre of the anatomical femoral footprint. If the tip was within 2mm of the centre of footprint, the position was accepted. If not the tibial guide wire was repositioned and the process repeated. The tibial tunnel was drilled, followed by transtibial drilling of the femoral tunnel. A screen shot was done to allow determination of the shape and area of the tunnel aperture relative to the femoral footprint using ImageJ (National Institute of Health). The graft was fixed proximally with an Arthrex ACL Tightrope® and distally with a Genesys™ interference screw. The pivot shift test, anterior drawer and internal and external rotation were repeated and recorded using the software.Background
Methods
There have been mixed reports of the contribution of the anterior cruciate ligament (ACL) to the overall envelope of tibial rotational stability. The effect of single bundle ACL reconstruction on the separate components of internal and external rotational stability respectively is also unclear. We determined the internal and external rotation, and antero-posterior movement of the knee before and after single bundle computer assisted reconstruction of the anterior cruciate ligament (ACL) in 57 patients. The Orthopilot® ACL (v2) software (BBraun, Aesculap) was used. The mean overall range of tibial rotation was also significantly reduced from 30.5 degrees to 16 degrees (p<
0.0001). The mean internal rotation was significantly reduced from 16 degrees to 8 degrees (p<
0.0001). Mean external rotation was also significantly reduced from 15 degrees to 8 degrees (p<
0.0001). Unlike previous studies we did not find a greater reduction of internal rotation compared with external rotation. The mean antero-posterior movement of the tibia was significantly reduced from 12mm to 4mm (p<
0.0001). The results of this study seem to indicate that computer assisted single bundle ACL reconstruction results in a significant intraoperative improvement in both internal and external rotatory stability as well as a significant improvement in antero-posterior stability.
Uncemented total knee arthroplasty (TKA) implants were designed as an alternative to cemented implants. However, critical studies revealed a unique set of complications. At the same time, cemented prostheses continue to yield excellent results. To address some of the issues with uncemented implants, porous coatings were introduced. This follow-up study reports the early results of Plasmapore® coating in Navigated uncemented rotating platform TKA. 277 patients who had consecutively undergone a Navigated TKA procedure with the e.motion knee endoprostheses were followed up at the Bluespot Knee Clinic in Blackpool, UK. Of these 277 patients, 91 received an uncemented TKA between May 2005 and September 2007. The prosthesis is coated with a 350μm plasma-sprayed titanium layer. All procedures were carried out by the senior author (SACS). The Orthopilot navigation system was used to accurately restore the axial alignment of the implants. Men comprised 51% and women 49%. The mean age was 69 years and the mean BMI was 30. There were 50 right and 41 left knees. The mean operating time was 59 minutes. Of the 91 patients who received an uncemented e.motion TKA, 84 patients had at least 1 follow-up assessment. The average follow-up period for these 84 cases was 7 months. The integrated Knee Society Score (KSS) defined as the sum of functional and clinical KSS, was recorded for all 91 patients preoperatively and had a mean of 78. The KSS had increased to 182 after 4 months, 193 after 1 year and 198 after 2 years. Oxford score was recorded for 87 of the 91 patients preoperatively. The average preoperative score was 44. It had decreased to 18 after 4 months, and 16 after 1 year and 13 after 2 years. Radiological examination showed no evidence of periprosthetic lucency and no subsidence. There were 5 DVTs with 2 pulmonary embolisms, 2 cases of reflex sympathetic dystrophy, 2 stitch abscesses, 2 haematomas, and 9 cases of wound erythema. These preliminary findings compare favourably with published series of cemented TKAs. They have prompted a more detailed review which is in progress.
Previous studies of osteoarthritic knees have examined the relationship between the variables body mass index (BMI) and weight on the one hand and coronal plane deformity on the other. There is a consensus that weight and BMI are positively correlated to the degree and progression of a varus deformity. However, there does not appear to be a consensus on the effect of these variables on knees with a valgus deformity. Indeed, the view has been expressed that in knees with a severe deformity a relationship might not exist. A review of these studies reveals that in all cases, the alignment of the lower limb was obtained from a standing antero-posterior long leg radiograph. In no cases was the deformity in the sagittal plane measured. This study analyses the relationship between BMI, weight, deformity in the sagittal plane and valgus deformity. The study group consisted of 73 patients with osteoarthritis and valgus knees. All of them had failed conservative treatment for their symptoms and were listed for navigated TKA. Their weight and height were measured two weeks preoperatively and the BMI calculated. At operation the coronal and sagittal deformities were measured using the Orthopilot® navigation system (BBraun Aesculap, Tuttlingen). The results were analysed using SPSS 15. Regression analysis showed a significant relationship (p<
0.05) with a negative correlation between valgus deformity and weight. the correlation coefficient for flexed knees (−0.59) showed a moderately strong relationship whereas that for extended knees (−0.38) showed a relatively weak relationship. It is acknowledged that there is an increased force on the lateral compartment with increased valgus deformity. a larger deformity causes a larger moment arm about the centre of the knee. this study has shown that at the time of surgery, individuals with lower weights have larger valgus deformities. we postulate, therefore, that when the moment due to the weight of the individual and the length of the moment arm exceeds a certain value, a symptomatic threshold is crossed. in the presence of a fixed flexion deformity, the force on the patella-femoral joint is increased, contributing further to the onset of discomfort. Further investigation into the subsets of valgus knees appears to be warranted.
