A sibling risk study that shows a statistically significant increase in risk for anteromedial osteoarthritis of the knee. Anteromedial osteoarthritis is a distinct phenotype of osteoarthritis. Previous studies have shown a genetic aetiology to both hip and knee osteoarthritis. The aim of this study was to determine the sibling risk of antero-medial osteoarthritis of the knee. We conducted a retrospective cohort study of 132 probands with primary anteromedial osteoarthritis, who had undergone unicompartmental arthroplasty. Sibling were identified as having symptomatic knee problems by postal Oxford Knee Score (OKS). A positive OKS was defined as an OKS+/− 2SD of the mean of the proband group. Sibling spouses were used as controls. Those siblings &
spouses that were symptomatic from the OKS were invited to undergo Knee X-rays, to look for radiological signs of osteoarthritis. Osteoarthritis was diagnosed as greater than Grade II on the Kell-gren Lawrence classification. The pattern of disease was noted and it was considered if the sibling were suitable for a unicompartmental knee arthroplasty. The prevalence and sibling risk of anteromedial osteoarthritis was determined using a randomly selected single sibling per proband family. The prevalence was determined in the 103 single proband sibling pairs. There was a statistically significant risk within the sibling group P= 0.024 using the Chi square test. The relative risk of anteromedial osteoarthritis was. 3.21(95% CI 1.08 to 9.17) Genetic factors play a major role in the development of anteromedial osteoarthritis.
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.
Proprioception protects joints against injurious movements and is critical for joint stability maintenance under dynamic conditions. Knee replacement effect on proprioception in general remains elusive. This study aimed to evaluate the changes in proprioceptive performance after knee replacement; comparing Total (TKA) to Unicompartmental Knee Arthroplasty (UKA). Thirty-four patients with osteoarthritis were recruited; 15 patients underwent TKA using the AGC prosthesis and 19patients underwent UKA using the Oxford prosthesis. Both cruciate ligaments were preserved in the UKA group, while only the PCL was preserved in TKA patients. Patients’ age was similar in both groups.>
Joint Position Sense (JPS) and postural sway were used as measures of proprioception. Both groups were assessed pre- and 6 months post-operatively in both limbs. JPS was measured as the error in actively and passively reproducing five randomly ordered knee flexion angles between 30 and 70°using an isokinetic dynamometer. Postural sway (area and path) was measured during single leg stance using a Balance Performance Monitor. Functional outcome was assessed using the Oxford Knee Score (OKS). Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups. Post-operatively, both groups had significant improvement of JPS in the operated limb (UKA mean4.64°, SD1.44° and TKA mean5.18°, SD1.35°). No changes in JPS were seen in the control side. A significant improvement (P<
0.0001) in sway area and path was found in the UKA group only in both limbs. No significant changes in sway occurred in either limb of TKA patients. The OKS improved from 21.4 to 35.5 for TKA patients and from 23.9 to 38for UKA patients. Both UKA and TKA improve proprioception as assessed by JPS. However, UKA alone improves postural sway in both limbs. This may impart explain why UKA patients function better than TKA patients
Oxford Unicompartmental knee arthroplasty (UKA) is now performed using a minimally invasive surgical (MIS) technique. Although early results are encouraging, the studies assessing outcome could be criticised for the restricted number of patients and limited follow-up. Aim of this study was to assess clinical outcome and prosthetic survival rate inpatients with minimally invasive Oxford medial UKA. This prospective study assessed 500 consecutive patients, who underwent cemented Oxford UKA for medial OA using MIS technique. Patients were assessed using objective and functional Knee Society Score (KSS). This study has confirmed preliminary findings that Oxford UKA using a minimally invasive approach is safe, reliable and effective.
Joint Position Sense (JPS) &
sway were used as measures of proprioception performance. Both groups were assessed pre- and 6 months post-op. JPS was measured using an isokinetic dynamometer (KinCom, Chatanooga Ltd) as the error in actively and passively reproducing fi ve randomly ordered knee fl exion angles (30°, 40°, 50°, 60° and 70°). Sway (area, path and velocity) was measured during single leg stance using a Balance Performance Monitor (SMS Medical) for 30-second interval. Functional outcome was assessed using the Oxford Knee Score (OKS). Pre-operatively, no differences in JPS or sway were found between limbs in either group. No differences existed between the two groups. Post-operatively, both groups had signifi cant improvement of JPS in the operated limb only (Mean ± standard deviation for UKA 4.64±1.44° and for TKA 5.18±1.35°). No changes in JPS were seen in the control side. Group 2 patients showed signifi cant improvement in both sway area and path (p<
.0001) for both limbs post-operatively. No signifi cant post-operative changes in sway occurred in either limb of Group 1 patients. The OKS improved post-operatively in both groups, rising from 21.4 to 35.5 for Group 1 patients and from 23.9 to 38 for Group 2 patients.
When the Oxford unicompartmental meniscal bearing arthroplasty (UCA) is used in the lateral compartment of the knee 10% of the bearings dislocate. An in-vitro cadaveric study was performed to investigate if the anatomy and joint geometry of the lateral compartment was a contributory factor in bearing dislocation. More specifically, the study investigated if the soft tissue tension of the lateral compartment, as determined by the length of the lateral collateral ligament (LCL), was related to bearing dislocation. A change in length of greater than 2 mm is sufficient to allow the bearing to dislocate. The Vicon Motion Analysis System (Oxford Metrics, Oxford, UK) was used to assess length changes in the LCL of seven cadaveric knees. Measurements were made of the LCL length through knee flexion and of the change in LCL length when a varus force was applied at a fixed flexion angle. Measurements were made in the normal knee and with the knee implanted with the Oxford prosthesis. In the intact knee the mean LCL change was 5.5mm (8%) over the flexion range. After implantation with the Oxford UCA the mean change in length was only 1 mm (1%). There was a significant difference in the LCL length at 90° (p=0.03) and 135° (p=0.01) of knee flexion compared to the intact knee. When a varus force was applied the LCL length change of the intact knee (5.4 mm) was significantly different (p=0.02) to that of the knee with the prosthesis implanted (2.7 mm) This study used a new method to dynamically measure LCL length. It found that after implantation of the Oxford lateral UCA the LCL remains isometric over the flexion range and does not slacken in flexion as it in the normal knee. This would suggest that the soft tissue tension was adequate to contain the bearing within the joint. However, when a varus force was applied the LCL did not sufficiently resist a displacing force producing an LCL length change greater than 2 mm. The evidence provided by this study is contradictory. The “lack of change in LCL length through flexion” suggests that the ligament remains tight through range and is unlikely to allow dislocation. However, the amount of distraction possible when an adducting moment is applied is sufficient to allow bearing dislocation. The length tension properties of the lateral structures are therefore implicated in the mechanism of dislocation.