Tibial patho-morphology has been described as a factor that predisposes to medial compartment osteoarthritis of the knee in 2D analysis. The aim of this study was to investigate whether the morphology of normal and pre-OA medial compartments are really different in 3 dimensions. A total of 20 normal (group A) and 20 pre-OA knees (group B) were included. Group A consisted of contra-lateral knees of young patients awaiting hip surgery and group B of asymptomatic contra-lateral knees of patients awaiting unicompartmental knee arthroplasty (UKA). Using 3D reconstructions from CT scans, femurs were aligned to the transcondylar and anatomical axes. The medial femoral extension facet was modelled as a sphere. Its radius and the offsets between its centre and the medial flexion facet centre were measured. The tibias were aligned to a flat portion of the flexion facet (flexion facet plane. A model of analysis was developed by rotating several increments towards and away from the midline to obtain several sagittal section images. For each sagittal section the extension facet angle (EFA), its length, and the submeniscal plane angle and length were analysed.Introduction
Method
The trochlear groove plays a major role in the mechanics and patho-mechanics of the patellofemoral joint. Our primary goal was to compare normal, osteoarthritic and dysplastic PFJs in terms of angles and distances. Computed tomography scans of 40 normal knees (>55 years old), 9 knees with patellofemoral osteoarthritis (group A) and 12 knees with trochlear dysplasia (group B) were analysed using 3D software. The femurs were orientated using a robust frame of reference. A circle was fitted to the trochlear groove. The novel trochlear axis was defined as a line joining the centres of two spheres fitted to the trochlear surfaces, lateral and medial to the trochlear groove. The relationship between the femoral trochlea and the tibiofemoral joint was measured in term of angles and distances (offsets).T-test for paired samples was used (p<0.05).Introduction
Method
Unicompartmental knee arthroplasty (UKA) has
advantages over total knee arthroplasty but national joint registries report
a significantly higher revision rate for UKA. As a result, most
surgeons are highly selective, offering UKA only to a small proportion
(up to 5%) of patients requiring arthroplasty of the knee, and consequently
performing few each year. However, surgeons with large UKA practices
have the lowest rates of revision. The overall size of the practice
is often beyond the surgeon’s control, therefore case volume may
only be increased by broadening the indications for surgery, and
offering UKA to a greater proportion of patients requiring arthroplasty
of the knee. The aim of this study was to determine the optimal UKA usage
(defined as the percentage of knee arthroplasty practice comprised
by UKA) to minimise the rate of revision in a sample of 41 986 records
from the for National Joint Registry for England and Wales (NJR). UKA usage has a complex, non-linear relationship with the rate
of revision. Acceptable results are achieved with the use of 20%
or more. Optimal results are achieved with usage between 40% and
60%. Surgeons with the lowest usage (up to 5%) have the highest
rates of revision. With optimal usage, using the most commonly used
implant, five-year survival is 96% (95% confidence interval (CI)
94.9 to 96.0), compared with 90% (95% CI 88.4 to 91.6) with low
usage (5%) previously considered ideal. The rate of revision of UKA is highest with low usage, implying
the use of narrow, and perhaps inappropriate, indications. The widespread
use of broad indications, using appropriate implants, would give
patients the advantages of UKA, without the high rate of revision. Cite this article:
The contraindications for unicompartmental knee replacement (UKR) remain controversial. The views of many surgeons are based on Kozinn and Scott’s 1989 publication which stated that patients who weighed more than 82 kg, were younger than 60 years, undertook heavy labour, had exposed bone in the patellofemoral joint or chondrocalcinosis, were not ideal candidates for UKR. Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR. In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospective series of 1000 UKRs. The outcome was assessed using the Oxford knee score, the American Knee Society score, the Tegner activity score, revision rate and survival. The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication. Overall, 678 UKRs (68%) were performed in patients who had at least one potential contraindication and only 322 (32%) in patients deemed to be ideal. The survival at ten years was 97.0% (95% confidence interval 93.4 to 100.0) for those with potential contraindications and 93.6% (95% confidence interval 87.2 to 100.0) in the ideal patients. We conclude that the thresholds proposed by Kozinn and Scott using weight, age, activity, the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR.
