OASIR

Orthopaedic and Sport Injury Research

THREE DIMENSIONAL GAIT ANALYSIS OF FIXED BEARING AND MOBILE BEARING TOTAL KNEE PROSTHESES DURING WALKINGDebate is on-going regarding the hypothetical functional advantages of mobile bearing (MB) total knee prostheses, with few studies comparing fixed bearing (FB) and MB groups using three dimensional motion analysis. The aim of this study was to compare three dimensional spatiotemporal, knee kinematic, and knee kinetic parameters at pre-surgery, three months post-surgery, and nine months post-surgery during walking. Sixteen patients undergoing primary unilateral total knee replacement (TKR) surgery were randomised to receive either a FB (n = 8) or MB (n = 8) total knee prosthesis. Eight age and gender matched controls underwent the same protocol on one occasion. A 12 camera Vicon system integrated with four force plates was used. No significant differences between FB and MB groups were found at any time point in the spatiotemporal parameters. The MB group was found to have a significantly reduced frontal knee ROM at pre-surgery than the FB group (FB = 14.92 ± 4.02°; MB = 8.87 ± 4.82°), with the difference not observed at 3 or 9 months post-surgery. No further significant kinematic or kinetic differences were observed between FB and MB groups. FB and MB groups differed from controls in 3 and 7 parameters at pre-surgery, 8 and 8 parameters at 3 months post-surgery, and 6 and 5 parameters at 9 months post-surgery, respectively. No functional advantages were offered in knees implanted with MB prostheses during walking, with both groups indicative of similar differences when compared to normal knee biomechanics at 3 and 9 months following prosthesis implantation. SENSITIVITY AND SPECIFICITY OF TECHNETIUM BONE SCAN WITH SPECT SCAN IN THE IDENTIFICATION OF PERIPROSTHETIC KNEE INFECTION?1Caplan, N., 2Lees, D., 2Peakman, D., 2Bartholomew, P., 1St Clair Gibson, A. & 2Kader, D.Radionuclide imaging is often regarded as the imaging modality of choice for suspected periprosthetic infections. It is also believed that bone scintigraphy is sensitive for identifying the failed knee joint replacement. However, in the recent AAOS guidance the strength of recommendation for the use of nuclear imaging in the diagnosis of periprosthetic infections was “weak”.This study determined the sensitivity and specificity of bone scan with single photon emission computed tomography (SPECT) in detecting infection within the knee and its overall value in the management of this group of patients. The main advantage of SPECT scan is the ability to view the reconstructed image in multiple planes and to spatially define the anatomic location of various areas of increased or decreased radiopharmaceutical uptake.Sixty three patients (32 male), who reported to a specialist painful knee arthroplasty clinic with chronic pain following previous total knee replacement, were included in this study. All patients received a preoperative technetium bone scan with SPECT. Patients then received single or two stage revision knee surgery, where evidence of infection was documented. The sensitivity and specificity of bone scan in suggesting infection were then calculated.Twenty one patients (33%) had a bone scan that was suggestive of infection. Sixteen patients (27%) had an infection in the knee. The sensitivity of bone scan in predicting infection was 67%, and the specificity was 75%.Bone scintigraphy is more specific than sensitive, with a high negative predictive value, and is useful as a screening test. FEMORAL NECK ANTEVERSION IN KNEES WITH PATELLAR INSTABILITY AND CONTRALATERAL ASYMPTOMATIC KNEES?1Caplan, N., 2Lees, D., 2Newby, M., 1Ewen, A., 1St Clair Gibson, A. & 2Kader, D.Femoral neck anteversion (FNA) is often considered as a common contributing factor in recurrent patella dislocation. This study compared the range of FNA in knees with instability with that of asymptomatic knees.We reviewed sixty patients (42 female, 18 male) with recurrent unilateral patellar dislocation, were included in the study. All patients underwent bilateral long leg computed tomography as a part of a standard protocol to evaluate patients with patella instability. The FNA in both hips were measured by a senior radiologist. In addition, the angle of compensatory external tibial torsion (ETT) was measured. FNA and ETT were compared statistically between the unstable and contralateral asymptomatic knee using an independent samples t test with a significance level of p<0.05. 95% confidence intervals were also determined. Mean FNA in the unstable knee was 18.9 (±11.2) degrees, compared to 18.7 (±10.4) degrees in the stable knee. FNA was not different between unstable and asymptomatic knees (p=0.899, CI=-3.6-4.1). FNA was similar in 10% of patients between unstable and asymptomatic, greater in the unstable knee in 27% of patients and greater in the asymptomatic knee in 25% of patients. ETT was 32.6 (±6.3) degrees and 32.4 (±7.9) degrees in the symptomatic and asymptomatic knees, respectively. This difference was not significant (p=0.900, CI=-2.4-2.7).These findings suggest that in this cohort of patients the FNA was not related to instability, even in patients with high ETT, and thus may not be as common a contributing factor in symptomatic patella instability as previously thought. IS TIBIAL TUBEROSITY-TROCHLEAR GROOVE DISTANCE AN APPROPRIATE MEASURE FOR THE IDENTIFICATION OF KNEES WITH PATELLAR INSTABILITY?1Caplan, N., 2Lees, D., 3Newby, M., 1Ewen, A., 1St Clair Gibson, A. & 1,2Kader, D.Tibial tuberosity-trochlear groove distance (TT-TG) has been regarded as a useful tool for establishing therapeutic choices for patellar instability. A threshold of 20mm is often regarded as pathologic and used as an indication for Tibial Tuberosity Medialisation to restore stability.Recently, we showed that TT-TG negatively correlated with the quadriceps angle, suggesting that in isolation, neither provide a valid measure of instability. It was also similar in both knees of patients with unilateral instability. This study aimed to compare TT-TG distance between both knees in patients with unilateral stability and assess weather this measurement is a decisive element in the management decisions for patellar instability, as described by Dejour et al. Sixty two patients (18 male), reporting to a specialist patella clinic in the NHS for recurrent unilateral patellar dislocation, were included in the study. Patients underwent bilateral long leg computed tomography scan, according to the Lyon protocol, to determine TT-TG distance in both knees. TT-TG distances in stable and unstable patellofemoral joints in the same individual were compared statistically.Mean TT-TG in the unstable knee was 16.9 (±4.9) mm, compared to 15.6 (±5.6) mm in the stable knee, with a mean difference of 1.3mm (confidence interval = -0.5-3.2). TT-TG was not significantly different between stable and unstable knees (t(122)=1.404, p=0.163). The lack of difference in TT-TG distance between stable and unstable knees suggests that TT-TG distance is not a decisive element in establishing therapeutic choices for patellar instability. It should, therefore, be used with caution during clinical evaluations. DETRIMENTAL EFFECTS OF WEARING A KNEE RANGE OF MOTION BRACE ON SPATIOTEMPORAL CHARACTERISTICS OF WALKING1Caplan, N., 1Meanwell, J., 1Ewen, A., 1St Clair Gibson, A. & 1,2Kader, D.Knee range of motion (ROM) braces are often worn following injury to provide protection to the ligamentous structures of the knee. The aims of this study were to investigate whether spatiotemporal characteristics of walking are influenced by wearing unlocked ROM brace, and the extent to which limiting extension affects walking spatiotemporal characteristics. Seven healthy males were asked to walk under three conditions: normal walking, wearing unlocked ROM brace, and wearing a ROM brace locked to prevent the last 30 degrees of extension. An optoelectronic system running the length of the walkway measured stance and swing durations and the position of successive foot strikes, in order to calculate walking speed, stride length, step length and cadence. Paired samples t tests were used to determine statistically significant pairwise differences.Wearing the unlocked ROM brace caused significant reductions in stride length (p<0.05), step length (p<0.01) and walking speed (p<0.05), compared to walking with no brace. Limiting extension to 30 degrees did not cause any changes in stride length (p=0.882), step length (p=0.810), cadence (p=0.617), or walking speed (p=0.855) compared to wearing the brace unlocked.Wearing a ROM brace locked or unlocked both significantly reduces walking spatiotemporal characteristics, likely due to proprioceptive changes elicited by the application of the brace. Clinicians should consider using unlocked ROM brace, whenever possible, in preference to locked brace to avoid further damage to the normal motor patterns that would otherwise be influenced by reduced range of motion. CONSTRAINED CONDYLAR KNEE SYSTEMS: COMPARING FIVE COMMONLY USED BRANDS IN THE UK1Deiary Kader, 1Michail Kokkinakis, 1Ramsay Refaie, 2Nick Caplan, 1Jonathan M LougheadPurposeConstrained condylar knee (CCK) implants are commonly used in a revision setting. They are designed to fix the prosthesis to the host bone at epiphysis and diaphysis to provide good construct stability and provide flexibility to balance the knee in the coronal and sagittal planes. There are many knee revision systems available and the contemporary revision knee surgeon has a difficult task to identify the ideal implant for an individual patient's needs. Although these systems seem to serve the same purpose, they are based on contrasting philosophies. Some of the CCKs are very versatile and user friendly while others are very complex making the procedure and the task of the surgeon difficult.ScopeIn this presentation we aim to highlight the potential advantages and limitations of the five most commonly used CCK revision systems in the UK and provide a detailed description of each design along with their published follow up data and outcomes in various National Joint Registry (NJR) reports.MethodWe analysed each system in depth and tabulated the differences in various CCK implant materials, design, sizes, offset options, stem design, stem diameter, stem locking mechanism, bearing options, augment types and options, metaphyseal fixation and instrumentation. We also reviewed the outcome of these systems in the literature and the NJR.ConclusionsThere is limited data to support the use of any particular CCK system. The newer systems may offer versatility but surgeons’ skills and experience may still be the determining factor in the success of revision surgery.

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