Biomechanical alignment of the knee is a major determinant in the outcome of Total Knee Arthroplasty. However, the best method to assess the alignment is yet undecided. Conventional methods use hip to ankle “long” standing x-rays but these suffer from technical difficulties and hence are a potential for error. Short x-rays are considered to have doubtful accuracy.

This study aimed to assess if the “short” AP x-rays could be used to assess the lower limb axis within a range of statistically insignificant and clinically acceptable difference.

The results indicate the readings from the short x-rays were not statistically different from those obtained from the long x-rays in four sets of observations. The largest difference between any two readings was 0.68 degrees. The analysis of data showed that the measurements from the short x-rays could indeed be used to assess the long axis of the lower limb with the provison that there is no gross femoral shaft deformity.

Introduction: The aims of this study are:

To report and validate the early migration rates of the collarless polished tapered hip replacement using manual and computer measurements

To report early clinical results of the CPT hip

Patients and methods: 80 patients undergoing primary total hip replacement in a single centre were prospectively recruited into the trial. There were 59 females and 21 males: age range 31–84 years, (mean 68 years sd 9.86). Surgery was performed through an anterolateral approach in all cases. A standard cementing technique using a cement gun and cement restrictor was employed. The patients had standardised anteroposterior standing hip radiographs taken post operatively, then yearly. The migration was measured along the long axis of the femoral component In the anteroposterior plane, using the tip of the greater trochanter as a bony landmark. Measurements were made by two independent observers (specialist registrars). Plain radiographs were measured manually using a ruler and set square and digitised images using a software package designed in-house at Dundee University. Correction for magnification was incorporated. Hip assessments were performed at each review by an independent reviewer.

Results: The mean migration rates and 95% confidence intervals (Cl) and mean Harris pain and Harris hip scores and Std Deviations were:

There was no significant difference between inter or intra observer measurements for hip migration.

This is the first study to date that we are aware of that describes the subsidence rates of the CPT hip which includes validation by inter and intra observer readings.

Introduction: The aims of this paper are to compare the results of Measuring migration rates on radiographs manually and by computer assisted analysis of digitised images.

Methods: Standardised anteroposterior standing hip radiographs taken post operatively and then yearly following hip replacement were used. The radiographs were then scanned at 150 dpi (gray scale) and saved as tif files. The migration was measured manually by drawing a line along the long axis of the femoral component connecting the distal tip, to the notch, which is used to impact the stem proximally. This gives us the length of the hip replacement and an axis along which migration can be measured. The tip of the greater trochanter was selected as a bony landmark. On the plain radiographs two sets of readings were made by one observer. The digitized images were then analysed in the same way using a software package (designed in-house at the University of Dundee). Two sets of readings were performed by observer one and a second set by an independent observer. Statistics: Inter and Intra observer rates were calculated using a paired sample t test.

Results: For the manual readings intra observer mean difference was 0.53mm (Cl 0.31–0.74mm). Comparing manual vs computer readings for observer one there was a correlation of 0.89. For the computer readings intra observer mean difference was 0.36mm (CI 0.64–0.8mm) and inter observer mean difference 0.16 mm, both non-significant differences. This evidence shows that the readings made manually and by computer were not significantly different and that there was no significant inter and intra observer variation. The advantage of computer storage and reading being the faster analysis, the ability to store and access large numbers of radiographs. The disadvantages being the need to scan the radiographs to allow measurement.

Introduction: The aims of this paper are to compare the results of measuring migration rates on radiographs manually and by computer assisted analysis of digitised images.

Methods: Standardised anteroposterior standing hip radiographs taken post operatively and then yearly following hip replacement were used. The radiographs were then scanned at 150 dpi (gray scale) and saved as tif files. The migration was measured manually by drawing a line along the long axis of the femoral component connecting the distal tip, to the notch which is used to impact the stem proximally. This gives us the length of the hip replacement and an axis along which migration can be measured. The tip of the greater trochanter was selected as a bony landmark. On the plain radiographs two sets of readings were made by one observer. The digitised images were then analysed in the same way using a software package (designed in house at the University of Dundee). Two sets of readings were performed by observer one and a second set by an independent observer.

Statistics: Inter and Intra observer rates were calculated using a paired sample t test.

Results: For the manual readings intra observer mean difference was 0.53 mm (CI 0.31–0.74 mm). Comparing manual vs computer readings for observer one there was a correlation of 0.89. For the computer readings intra observer mean difference was 0.36 mm (CI 0.64–0.8 mm) and inter observer mean difference 0.16 mm. Both non significant differences. This evidence shows that the readings made manually and by computer were not significantly different and that there was no significant inter and intra observer variation. The advantage of computer storage and reading being the faster analysis, the ability to store and access large numbers of radiographs. The disadvantages being the need to scan the radiographs to allow measurement.

Tibiofemoral alignment has a direct correlation with the survival of total knee arthroplasty. Traditionally, it has been measured using a goniometer on radiographs. We describe new software which measures this alignment on scanned radiographs by automatically detecting bones in the image.

Two surgeons used conventional methods and two clerical officers used the computerised routine to assess 58 radiographs of the knee on two occasions. There were no significant differences between any of the paired comparisons. The largest mean difference detected was 1.19°. Across all comparisons, the mean correlation was 0.755. A standardised routine for measuring tibiofemoral alignment was the greatest factor in reducing error in our study.

These results show that non-medical staff can reliably use the software to measure tibiofemoral alignment. It has the potential to measure all the parameters recommended by the Knee Society.

We describe a method of audit of a type of total knee replacement, including some details of the organisational difficulties of administering multicentre studies, and draw attention to how this can be done using industrial funding without prejudicing the study. This is a prospective record of 1439 patients who had an Insall-Burstein II (IBII) prosthesis implanted between 1990 and 1994. The data were collected using the American Knee Society scoring system. A method of storing radiographs digitally at low cost is also described.

The results emphasise the need for the long-term collection of data on commonly used devices implanted by a cross-section of surgeons. We conclude that for most patients the IBII cemented, posteriorly stabilised, cruciate-substituting prosthesis will relieve pain and give excellent functional results throughout the patients’ remaining years with a very small incidence of revision, except in cases of infection.