Introduction

Many worldwide regulatory authorities recommend regular surveillance of metal-on-metal hip arthroplasty patients given high failure rates. However concerns have been raised about whether such regular surveillance, which includes asymptomatic patients, is evidence-based and cost-effective. We determined: (1) the cost of implementing the 2015 MHRA surveillance in “at-risk” Birmingham Hip Resurfacing (BHR) patients, and (2) how many asymptomatic hips with adverse reactions to metal debris (ARMD) would have been missed if patients were not recalled.

Introduction

We investigated predictors of poor outcomes following metal-on-metal hip arthroplasty (MoMHA) revision surgery performed for adverse reactions to metal debris (ARMD), to help inform the revision threshold and type of reconstruction.

Recent studies have demonstrated that implant-specific blood metal ion thresholds exist in unilateral and bilateral metal-on-metal (MoM) hip arthroplasty patients, with these thresholds being most effective for identifying patients at low-risk of adverse reactions to metal debris (ARMD). We investigated whether these new blood metal ion thresholds could effectively identify patients at risk of ARMD in an external cohort of MoM hip arthroplasty patients.

We performed a validation study involving 803 MoM hip arthroplasties implanted in 710 patients at three European centres (323=unilateral Birmingham Hip Resurfacing (BHR); 93=bilateral BHR; 294=unilateral Corail-Pinnacle). All patients underwent whole blood metal ion sampling. Patients were divided into those with ARMD (revised for ARMD or ARMD on imaging; n=75), and those without ARMD (n=635). Previously devised implant-specific blood metal ion thresholds (cobalt=2.15μg/l for unilateral BHR; maximum cobalt or chromium=5.5μg/l for bilateral BHR; cobalt=3.57μg/l for unilateral Corail-Pinnacle) were applied to the validation cohort, with receiver operating characteristic curve analysis used to establish the discriminatory characteristics for each respective threshold.

The area under the curve, sensitivity, specificity, positive predictive value and negative predictive value for distinguishing between patients with and without ARMD for each implant-specific threshold were respectively: unilateral BHR=89.4% (95% CI=82.8%-96.0%), 78.9%, 86.7%, 44.1%, 96.9%; bilateral BHR=89.2% (95% CI=81.3%-97.1%), 70.6%, 86.8%, 54.5%, 93.0%; unilateral Corail-Pinnacle=76.9% (95% CI=63.9%-90.0%), 65.0%, 85.4%, 24.5%, 97.1%. The 7μg/l UK MHRA threshold missed significantly more patients with ARMD compared with the implant-specific thresholds (4.9% vs. 2.8%; p=0.0003).

This external multi-centre validation study has confirmed that MoM hip arthroplasty patients with blood metal ion levels below newly devised implant-specific thresholds have a low-risk of ARMD. Compared to implant-specific thresholds, the currently proposed fixed MHRA threshold missed more patients with ARMD.

We recommend using implant-specific thresholds over fixed thresholds when managing MoM hip arthroplasty patients.

Aims

To determine ten-year failure rates following 36 mm metal-on-metal (MoM) Pinnacle total hip arthroplasty (THA), and identify predictors of failure.

Aims

We investigated whether blood metal ion levels could effectively identify patients with bilateral Birmingham Hip Resurfacing (BHR) implants who have adverse reactions to metal debris (ARMD).

Introduction

We investigated whether blood metal ions could effectively identify bilateral metal-on-metal hip patients at risk of adverse reactions to metal debris (ARMD).

Aim:

AIS causes a loss of trunk height. This paper documents this loss against sitting height standards and assesses formulae for adjusting height loss back to the standard.

Introduction

Monitoring of scoliosis is traditionally done with radiographs, which can be associated with an increased risk of cancer secondary to multiple exposures over many years. This study investigated whether the findings from surface topography can be used to monitor scoliosis curves and how much this method affects outcome scores in patients with scoliosis. This study therefore had two subsets: (1) to investigate whether lateral asymmetry (LA) from ISIS2 surface topography can predict radiographic Cobb angle, providing an alternative non-invasive means of monitoring patients with scoliosis (LA and Cobb subset); and (2) to establish the relationships between the magnitude of the deformity in scoliosis, measured by Cobb angle on radiograph and volumetric asymmetry (VA) with the ISIS2 surface topography, and the patient perception of self-image and mental health, measured with SRS-22 scores (Cobb, VA, and SRS subset).

Purpose of the study

To establish the relation between the magnitude of the deformity in scoliosis, measured by cobb angle on radiograph & Volumetric asymmetry with the ISIS2 surface topography, and the patient perception of self image and mental health, measured with SRS-22 scores.

Purpose of the study

Monitoring of scoliosis is traditionally done with radiographs which can be associated with an increased risk of cancer secondary to multiple exposures over many years. This study investigates whether lateral asymmetry (LA) from ISIS2 surface topography can predict radiographic cobb angle, to provide an alternative non- invasive means of monitoring scoliosis patients.

Plain radiography has traditionally been used to investigate and monitor patients with adolescent idiopathic scoliosis. The X-ray allows a calculation of the Cobb angle which measures the degree of lateral curvature in the coronal plane. ISIS2 is a surface topography system which has evolved from ISIS, but with much higher precision and speed. It measures the three dimensional shape of the back using structured light and digital photography. This system has the benefit of not requiring any radiation. Lateral asymmetry is the ISIS clinical parameter estimating the curve of the spine in the coronal plane. The aim of this study was to compare this parameter to the Cobb angle measured on plain X-ray.

Twelve patients with idiopathic adolescent scoliosis underwent both a standing AP spine X-ray and an ISIS2 scan on multiple occasions. Both scan and X-ray were done within one month of each other. No patient underwent surgery during the study period. The Cobb angle and the degree of lateral asymmetry were calculated.

Twelve patients mean age 12.5 years (range 10-16) were investigated using both ISIS2 and X-ray. They had a mean 2.3 (1-5) combined investigations allowing for 30 comparisons. The correlation between the two measurements was r =0.63 (p=0.0002). The Cobb angle measured on ISIS2 was less than that measured by radiograph in 27 out of 30 comparisons. The mean difference between the measurements was mean 6.4° with a standard deviation of 8.2° and 95% confidence interval of 3.3° to 9.4°.

In adolescent idiopathic scoliosis, curve severity and rib hump severity are related but measure different aspects of spinal deformity. As expected, these relate closely but not precisely. ISIS2 offers the promise of monitoring scoliosis precisely, without adverse effects from radiation. The small numbers in this series focus on the group of patients with mild to moderate curves at risk of progression. In this group, ISIS2 was able to identify curve stability or progression, without exposing the subjects to radiation.

Background: Scoliotic deformity has been traditionally measured by Cobb angle using radiography. This parameter gives a measure of the lateral curve in the spine in the coronal plane. However, patients are often more concerned about their rib humps or other volumetric asymmetries in the surface of their backs. There is often little relation between Cobb angle and the magnitude of the asymmetry. A method of quantifying volumetric deformity, especially if it requires no radiation, would therefore be useful for spinal surgeons and patients alike.

Methods: The three dimensional shape of the back is measured using structured light and digital photography with ISIS2, a non-commercial surface topography system. Markers are placed on bony landmarks so that the surface can be related to body axes. A zero plane is defined through the sacrum and the vertebra prominens, parallel to the line between the markers on the dimples of Venus. A curve is fitted through the markers on the spinous processes on the measured surface and is used as the line of symmetry. The difference in the areas between the surface and the zero plane on each side of the symmetry line is then calculated for each horizontal (transverse) section. The left and right volumetric asymmetry parameters are then calculated by summing the area differences on each side and normalising for back length. These parameters range from zero for a perfect straight back with no transverse asymmetry to over 70 for extreme transverse asymmetry. The variability in these parameters was investigated using pairs of photographs of 59 patients. Two photographs were taken with the patient walking around the room between them. Left and right volumetric asymmetry was then calculated for each measurement and Bland-Altman analysis was carried out.

Results: The mean difference between pairs of measurements was −0.10, the standard deviation was 2.03 and the 95% tolerance limits covering 95% of the population were −4.8 to 4.6 for left volumetric asymmetry; the mean difference was 0.46, standard deviation was 3.13 and the 95% tolerance limits covering 95% of the population were −6.8 to 7.7 for right volumetric asymmetry. There was no evidence of bias from the Bland-Altman plots.

Conclusions: The variability in the volumetric asymmetry was low in comparison to the levels found for subjectively classified ‘moderate’ deformity. Change in degree of volumetric deformity can be monitored by ISIS2 volumetric asymmetry.

ISIS2 is a surface topography system measuring the three-dimensional shape of the back in scoliosis patients using digital photography with structured light. Lateral asymmetry is the ISIS clinical parameter estimating the curve of the spine in the coronal plane [1]. The shape of the back changes with patient stance, breathing and muscle tension. Although ISIS2 uses bony landmark markers to minimise the effect of stance, there will still be variations from measurement to measurement. The aim of this work is to quantify the variability in lateral asymmetry measurements. The patients were asked to stand in the patient stand in a relaxed normal pose; the feet were placed just outside the blocks on the footplate, the abdomen rested lightly against the crossbar of the stand, and the arms were supported away from the sides of the body by the arm rests. Two photographs were taken with the patient walking around the room between them. The mean difference between pairs of measurements on 62 patients was 0.12°, the standard deviation was 1.64° and the 95% limits of agreement were −3.10° to 3.34°. A plot of difference against mean showed no significant evidence of a relationship between them (r = −0.10). The standard deviation for intraob-server measurement of Cobb angle has been reported as ranging from 1.4° to 3.3° [2,3,4] and clinically significant change is generally regarded as greater than 5°. This experiment shows that intraobserver variability in lateral asymmetry is thus sufficiently low to detect clinically significant changes in the curve of the spine.

An automated system has been developed to measure three-dimensional back shape in scoliosis patients using structured light. The low-cost system uses a digital camera to acquire a photograph of a patient with coloured markers on palpated bony landmarks, illuminated by a pattern of horizontal lines. A user-friendly operator interface controls the lighting and camera and leads the operator through the analysis. The system presents clinical information about the shape of the patient’s deformity on screen and as a printed report. All patient data (both photographs and clinical results) are stored in an integral database. The database can be interrogated to allow successive measurements to be plotted for monitoring the deformity.

The system is non-invasive, requiring only a digital photograph to be taken of the patient’s back. Identification of the bony landmarks allows all clinical data to be related to body axes. This reduces the effects of variability in patient stance. Measurement of a patient, including undressing, landmark marking and dressing, can be carried out in approximately 10 minutes. The clinical results presented are based on the old ISIS report. This includes:

transverse sections at 19 levels from vertebra prominens to sacrum.

Additionally, a three-dimensional wire-frame plot, a coloured contour plot and a pair of bilateral asymmetry plots give visual impressions of any deformity in the measured back.