Kinematic data from in-vivo fluoroscopy measurements during a step-up activity was used to determine the relative tibial-femoral position as a function of knee flexion angle for each model. Medial and lateral force distribution was adapted from loads measured in-vivo with an instrumented implant during a step-up activity. The affect that varying the bearing thickness has on the stresses in the bearing was investigated. In addition, varus-valgus mal-alignment was investigated by rotating the femoral component through 10 degrees.
We report on a group of 20 metal-on-metal resurfaced hips (17 patients) presenting with a soft tissue mass associated with various symptoms. We describe these masses as pseudotumours. All patients underwent plain radiography and fuller investigation with CT, MRI and ultrasound. Where samples were available, histology was performed. All patients in this series were female. Presentation was variable; the most common symptom was pain or discomfort in the hip region. Other symptoms included spontaneous dislocation, nerve palsy, an enlarging mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. Fourteen of the 20 cases (70%) have so far required revision to a conventional hip replacement and their symptoms have either settled completely or improved substantially since the revision surgery. Two of the three bilateral cases have asymptomatic pseudotumours on the opposite side. We estimate that about 1% of patients develop a pseudotumour in the first five postoperative years after a hip resurfacing. The cause of these pseudotumours is unknown and is probably multi-factorial, further work is required to define this; they may be manifestations of a metal sensitivity response. We are concerned that with time the incidence of these pseudotumours will increase.
The purpose of this study was to determine if a single physiotherapy intervention would enable patients to kneel following Unicompartmental knee arthroplasty (UKA). Kneeling is an important functional activity that is frequently not performed after knee arthroplasty, thus affecting a patient’s ability to carry out basic tasks of everyday life. There is however no clinical reason why patients should not kneel and many with proposed knee surgery ask about the possibility of kneeling after their operation. Sixty adults participated in a prospective randomised controlled trial with blinded assessments. At 6 weeks post-operatively UKA patients were randomised to either the Routine care group where no advice on kneeling was given or to the Kneeling intervention group where participants were taught and given advice on how to kneel and were encouraged to do so. They were re-assessed at 1 year. The primary outcome measure was Question 7 of the Oxford Knee Score which asks the question “Could you kneel down and get up again afterwards?” Pre-operatively there was no difference in the kneeling ability of the two groups. At 1 year the difference in kneeling ability between the two groups was highly significant (p<
0.05). Spearman’s correlation coefficient showed no significant association between a change in score of Question 7 at 1 year and the following factors; scar position, numbness, range of flexion, arthritic involvement of other joints and pain. Linear regression analysis also confirmed that these factors were not successful in predicting a change in kneeling ability. This study showed that the single factor predictive of kneeling ability was the physiotherapy intervention provided at 6 weeks post-operatively and it is suggested that kneeling should be incorporated into patient’s post-operative rehabilitation programmes.
revision surgery and poor functional outcome as the end-points.
This study reports a clinical comparison of new and old establishing whether this modified implant has maintained the established normal kinematic profile of the Oxford UKR.
Knee kinematics were assessed by analysing the movement of the femur relative to the tibia using the PTA.
We report the clinical, radiographic and histologic features of these cases.
There were no infections in this series. Three subjects required revision surgery.
This study suggests that resurfacing arthoplasty can also induce a local hypersensitivity reaction in response to metal wear debris. It therefore raises new concerns regarding the long-term safety of this procedure.
This study assesses the functional in vivo kinematics of Advanced Medial Pivot (AMP) TKR and compares it to kinematics of the normal knee.
The purpose of the study: to determine if Patient height-and gender could be used to predict component size With a minimally invasiveapproach for unicompartmental knee replacement. Material and methods: One hundred x-rays of patients (44 men, 56 women), who had undergone Oxford UKR, were reviewed. The preoperative radiographs were assessed for component size using the standard template. The postoperative x-rays were reviewed to determine-whether the ideal component size had been used or if not what could be the most appropriate. Patient’s height was recorded. The proportion of patients for whom an appropriate size could be selected by either template or height measurements was calculated. Current templating system accurately predicted the ideal size in 67%. In no case was the size incorrect by more than one size. The following size bands were set according to height. For men: size small in patients less than160 cm, medium less than 170 cm and large less than 180cm. For women: size small in patients less than 165 cm, medium less than 175cm and large less than 185 cm. Height accurately predicted the ideal size in75%. In no case was the assessment of component size incorrect by more than one size. As the Oxford femoral component is spherical, its size is not critical and it is acceptable to use one size too large or too small. Both height and templating safely predicted an acceptable size in all cases and predicted the ideal size in about 70% >
Conclusion: Gender specific height should be used to predict the component size in situations were templating is difficult as in digital x-rays orsuperimposition of the two femoral condyles, and non-standardised x-raymagnification.
The indications for unicompartmental knee arthroplasty (UKA) remain controversial; in particular the threshold of disease in the patellofemoral compartment is debated. Whilst some authorities ignore the condition of the patellofemoral joint, others consider pre-existing patellofemoral osteoarthritis (PFOA) a contra-indication to UKA. The aim of this study was to determine the influence of PFOA on the outcome of medial UKA. This prospective study involved one hundred consecutive patients who had undergone cemented medial Oxford UKA (phase 3), via a minimally invasive approach, at least one year previously. Patients were divided into two groups according to the presence or absence of full thickness cartilage loss (FTCL) on the patella or trochlea at operation. A pre-operative skyline radiograph was graded using the Altman score, by an independent Musculoskeletal Radiologist. Outcome was evaluated with the Knee Society Score (AKSS) and the Oxford Knee Score (OKS, maximum 48). Groups were compared for differences in knee score and Altman grade using a one way ANOVA. Repeat analysis was performed using the presence of anterior knee pain (AKP) as the group defining variable. There were 28 patients with FTCL, and both groups were well matched for age, gender and activity levels. Analysis showed no significant difference in post operative knee scores between groups with either the presence of FTCL or the presence of AKP pre-operatively as a factor. There was no significant difference in Altman grade between groups. Intra-operative evidence of PFOA in patients with medial compartment osteoarthritis does not prejudice the outcome of UKA. Even the inclusion of patients with symptomatic AKP, without necessarily having PFOA, does not affect the outcome after UKA. These short results are encouraging, but longer follow up is required.