Abstract

Background

While posterior cruciate retaining (PCR) implants are a more common total knee arthroplasty (TKA) design, newer bi-cruciate retaining (BCR) TKAs are now being considered as an option for many patients, especially those that are younger. While PCR TKAs remove the ACL, the BCR TKA designs keep both cruciate ligaments intact, as it is believed that the resection of the ACL greatly affects the overall kinematic patterns of TKA designs. Various fluoroscopic studies have focused on determination of kinematics but haven't defined differentiators that affect motion patterns. This research study assesses the importance of the cruciate ligaments and femoral geometry for Bi-Cruciate Retaining (BCR) and Posterior Cruciate Retaining (PCR) TKAs having the same femoral component, compared to the normal knee.

Follow-up of arthroplasty varies widely across the UK. The aim of this NIHR-funded study was to employ a mixed-methods approach to examine the requirements for arthroplasty follow-up and produce evidence-based and consensus-based recommendations. It has been supported by BHS, BASK, BOA, ODEP and NJR.

Four interconnected work packages have recently been completed: (1) a systematic literature review; (2a) analysis of routinely collected National Health Service data from four national data sets to understand when and which patients present for revision surgery; (2b) prospective data regarding how patients currently present for revision surgery; (3) economic modelling to simulate long-term costs and quality-adjusted life years associated with different follow-up care models and (4) a Delphi-consensus process, involving all stakeholders, to develop a policy document to guide appropriate follow-up care after primary hip and knee arthroplasty.

We will present the following Recommendations:

For ODEP10A∗ minimum implants, it is safe to disinvest in routine follow-up from 1 to 10 years post non-complex hip and knee replacement provided there is rapid access to orthopaedic review

Aims

Robotic-assisted total knee arthroplasty (RA-TKA) has been introduced to provide accurate bone cuts and help achieve the target knee alignment, along with symmetric gap balancing. The purpose of this study was to determine if any early clinical benefits could be realized following TKA using robotic-assisted technology.

Introduction

Many fluoroscopic studies on total knee arthroplasty (TKA) have identified kinematic variabilities compared to the normal knee, with many subjects experiencing paradoxical motion patterns. The intent of this study was to investigate the results of a newly designed PCR TKA to determine kinematic variabilities and assess these kinematic patterns with those previously documented for the normal knee.

Introduction

Postoperative pain is a concern for patients undergoing Total Knee Arthroplasty (TKA) and plays an important role in opioid consumption, length of stay, and postoperative function. The purpose of this study was to compare outcomes in patients who underwent primary TKA comparing femoral and sciatic (F+S) combination motor nerve block versus an adductor canal and the interspace between the popliteal artery and the capsule of the posterior knee (ACB+IPACK) combination sensory nerve block.

Introduction

The use of cementless TKA's has been gradually increasing over the past several years given the increasing life expectancy of our patient population. Cementless TKA's have not been rapidly adopted due to the challenges and uncertainty of tibial fixation especially in elderly patients. With the advent of new technologies, the results of cementless TKA's with the potential for long term biologic fixation may now be equivalent or better than cemented TKA's. A highly porous tibial baseplate was developed based on proximal tibial anatomy using CT scans using 3D printing technology with focus on length, location and design of press-fit pegs.

Presence of superficial wound infection following total joint replacement (TJR) increases risk of deep prosthetic infection and revision surgery. Early identification and management are advocated.

We conducted an audit to identify the number of suspected wound infections, treatment received, and whether diagnosis was supported by microbiological evidence. Early complication data were collected for all TJRs completed in a 12-month period (2012, n=314). Medical records were reviewed for all complications and summarised data were compared with data from 2010/11.

Forty-nine complications were recorded (47 in 2010/11) with increase in number of bacteriologically confirmed wound infections (from 2 to 6) and in number of serious wound infections (n=3).

Review of medical records showed that patients were treated in the community with antibiotics despite lack of objective microbiological evidence. Two of three serious wound infections were preceded by prolonged antibiotic prescription in the community.

Analysis of these results led to a new system for management of suspected wound infection in TJR patients. A ‘wound care card’ is issued at time of discharge and early assessment by a specialist orthopaedic nurse is available. Early results indicate a beneficial effect with potential to improve patient experience and long-term outcome, and to reduce overuse of antibiotics.

Unicompartmental knee replacement (UKR) is associated with higher revision rates than total knee replacement and it has been suggested that surgeons should receive specific training for this prosthesis. We investigated the outcome of all UKR in a district general hospital over ten years.

All patients who had received UKR from 2003 to 2013 were identified from theatre records, as were all revision knee arthroplasties. We contacted all patients (or their GP) with no known revision to ascertain UKR status. A life table analysis was used for three categories: all surgeons and types of UKR, Oxford UKR only and Oxford UKR by surgeons with specific training.

There were 319 UKR (one loss to follow up), four types of prosthesis, 21 failures and a 5-year cumulative survival rate of 91.54%. There were 310 Oxford UKR with 17 failures and 5-year survival 93.56%. Surgeons with training in use of Oxford UKR completed 242 replacements with 10 failures and 5-year survival of 95.68%.

In comparison with results for Oxford UKR in 11th annual NJR report, our results are satisfactory and support continued use of this prosthesis in a non-specialist centre. Our established programme of surveillance will monitor the survival of UKR in our hospital.

Aim:

To Determine The Effect Of Posterior Instrumented Fusion On Lung Function In Patients With Idiopathic Scoliosis Aged 8–11.

Introduction: Of all hip arthroplasties conducted annually, a proportion will subsequently require revision for aseptic loosening and periprosthetic osteolysis. Osteolysis may develop ‘silently’ and monitoring of patients is recommended. This should include x-rays as progressive changes in size of a lesion may indicate a potential failure. Area measurement of osteolysis has been achieved in a number of ways but with techniques that are not readily available in routine clinical practice. The aim of this study was to develop a method for routine assessment of hip arthroplasty to quantify osteolytic changes seen on x-ray, applicable by any health professional and with good inter-observer reliability.

Methods: A morphometric grid is superimposed on an object of interest and the number of test points that fall within a defined area counted. A specialized grid was developed and initial testing was conducted on twenty simulated osteolytic lesions. Subsequent testing was on thirty-five arthroplasty x-rays with evidence of osteolytic lesions. Four observers recorded the number of crosses seen over each lesion. The observers were representative of health professions and levels of experience involved in arthroplasty review.

Data was analysed for both inter-observer and test-retest reliability using the intra-class correlation coefficient and the Bland-Altman method (use of two methods provides a better estimation of accuracy).

Results: The results for intra-class correlation coefficients on both simulated and actual lesions were all excellent (range 0.90 to 0.98) as confirmed by visual representation using the Bland-Altman method.

Discussion: Regular follow-up of hip arthroplasty with x-ray ensures that changes are monitored even when symptoms are absent. We believe that this tool can improve the process through quantitative assessment of osteolytic lesions. The scientific development supports the reliability of the tool when used by a number of raters and the simplicity of application makes it a useful addition to an arthroplasty clinic.

Introduction: Disc degeneration causes structural and biochemical tissue changes resulting in altered stresses that may affect vertebral bone remodelling. We hypothesized that disc degeneration alters vertebral cortical strains and disc mechanics of the motion segment, with and without the presence of zygapophyseal joints.

Methods: Twenty human lumbar functional spinal units (FSUs) were strain gauged on the lateral and anterior vertebral cortices, below the inferior endplate. Each FSU was preloaded overnight (0.2 MPa) in a bath and subjected to dynamic compression (1 MPa), flexion/extension/lateral bending (500N + 5 Nm), and axial rotation (5 Nm), before and after removal of the zygapophyseal joints. After testing, discs were macroscopically assessed and graded (1–4) for degeneration. Stiffness, phase angle (energy absorption) and principal strains were calculated. ANOVAs with the dependent variable of principal strain/stiffness/phase angle versus disc grade were performed for each testing direction.

Results: Assessment of disc degenerative condition revealed six grade 2 discs, eight grade 3, and six grade 4. Age and degeneration were highly correlated (r=0.80, P< 0.0001). The effect of disc grade on stiffness was significant overall in most loading directions, before and after removal of zygapophyseal joints (P< 0.008), apart for axial rotation (P> 0.587). Post-hoc multiple comparisons for all loading directions apart for axial rotation revealed that the stiffness of grade 4 discs was significantly larger than grades 2 and 3 discs in most loading directions.

For phase angle (approximate magnitude 5°), no significant overall effects due to degeneration were found across any loading direction (P> 0.2). ANOVA analyses on maximum/minimum principal strains found no significant effect due to disc grade (P> 0.063). However, a small number of significant effects due to disc grade were found at particular strain gauge locations for the isolated disc in flexion, the intact FSU in extension, and the intact FSU/isolated disc in right lateral bending.

Discussion: This study represents the first of its kind to investigate the effects of disc degeneration on vertebral bone cortical strain and disc mechanical properties. Significant increases in stiffness were found with increasing degeneration in all test directions apart for axial rotation. Changes in disc stiffness were consistent with other studies and may be a result of the structural and biochemical changes within the disc that accompany the degenerative process.

The non-significant small phase angles suggest that the disc behaves more like an elastic solid than a poroelastic material, and that dehydration associated with degeneration does not adversely affect damping. Principal strains were not significantly affected by disc degeneration overall, suggesting that the cortical shell adjacent to the disc-endplate boundary maintains a relatively homeostatic condition, with more dramatic architectural changes probably occurring within the trabecular bone. Applications of this research include providing important validation data for analytical/finite element models of the intact FSU and isolated disc segment, and a better understanding of the magnitudes of cortical strains that need to be maintained in order to avoid damaging vertebral bone stress-shielding effects after treatments for disc degeneration.

The anulus fibrosus of the human lumbar intervertebral disc has a complex, hierarchical structure comprised of collagens, proteoglycans and elastic fibres. Recent histological studies have suggested that the elastic fibre network may play an important functional role. In this study, it was hypothesised that elastic fibres enhance the mechanical integrity of the extracellular matrix transverse to the direction of the collagen fibres.

Using a combination of biochemically verified enzymatic treatments and biomechanical tests, it was demonstrated that degradation of elastic fibres resulted in a significant reduction in both the initial modulus and the ultimate modulus, and a significant increase in the extensibility, of radially oriented anulus fibrosus specimens. Separate treatments and mechanical tests were used to account for any changes attributable to non-specific degradation of glycosaminoglycans. Additionally, histological assessments provided a unique perspective on structural changes in the elastic fibre network in radially oriented specimens subjected to tensile deformations.

The results of this study demonstrate that elastic fibres play an important and unique role in the mechanical properties of the anulus fibrosus, and provide the basis for the development of improved material models to describe intervertebral disc mechanical behaviour.

The rate of homologous blood transfusion (HBT) following primary total hip replacement (THR) can be as high as 30–40% and is not without risk. Postoperative blood salvage (POS) with autologous blood transfusion may minimize the necessity for HBT but the clinical, haematological and economic benefits have yet to be clearly demonstrated for primary THR.

The aim of this randomized prospective study was, therefore, to determine if the use of post-operative salvage affects post-operative haemoglobin and haematocrit values and reduces the rate of homologous blood transfusion. Secondary outcome measures included length of hospital stay and patient satisfaction. A cost analysis was also conducted on the basis of the results obtained.

The patients were randomized during the operation (at the point of reduction of the primary THR) to receive either two Medinorm vacuum drains or the autologous retransfusion system. A power calculation estimated that 72 patients would be required in each group to detect a significant difference of 0.7 gdL-1 in post operative haemoglobin level (at 80% power with an value of 0.05). This assumed a standard deviation of 1.5 gdL-1 obtained from a previous retrospective study.

There were 82 patients in the Medinorm vacuum drain group and 76 patients in the autologous retransfusion group. In the group with the autologous system, 76% of the patients were retransfused with a mean of 252mls. There was no significant difference between the groups when comparing haemoglobin and haematocrit values. However, significantly fewer patients in the group with the autologous system had a postoperative haemoglobin value less than 9.0 gdL-1 (8% vs. 20%, p = 0.035). Furthermore, significantly fewer patients with the autologous retransfusion system required a transfusion of homologous blood (8% vs. 21%, p = 0.022). There was a small overall cost saving in this group.

This study has shown that use of an autologous retransfusion system for primary THR reduces the necessity for HBT and is cost effective. POS also results in significantly fewer patients dropping their post-operative haemoglobin level below 9.0 gdL-1. As a result our unit routinely uses the autologous retransfusion system for primary THR.

Introduction: NICE guidelines (2000) stipulated three-year follow-up data compatible with satisfactory performance at 10 years as a minimum requirement for hip implants. We reviewed the performance of two devices in use in our department which fell outside these requirements. The Cenator cup (Corin Medical) is a cemented device, and the EPF cup (Plus Orthopedics) is uncemented (equatorially expanded, screw option, polished inside, porous HA coated).

Patients and Methods: 117 Cenator and 110 EPF cups inserted during the period 12/09/2000–28/01/2003 were assessed at 3 years by the following: Oxford Hip Score, satisfaction (visual analogue scale), details of femoral component, age, sex, BMI and any complications. Radiological assessment included Charnley Grade, concentricity, superior cover, cup inclination, migration, radiolucent lines, and linear wear at 3 years. Statistical associations with radiolucent lines or linear wear were calculated.

Results: The mean age of patients with Cenator cups was 81 (range 61–102) and EPF cups 67 (39–86). Oxford Hip Scores averaged 10 (0–41)(Cenator) and 7 (0–29)(EPF). Cup inclination range was 30–65° (mean 47). Linear wear > 1mm was observed in 18 Cenator and 53 EPF cups. Early radiolucent lines behind EPF cups closed (all cases), and superior cover improved in 8%. Progressive radiolucencies > 1mm were seen behind 37 Cenator cups. One of each type was revised for deep sepsis. Four other minor reoperations occurred. Statistical association was demonstrated between superior cover and progressive radiolucencies (Cenator), and between sex, cup size and inclination and linear wear (EPF).

Discussion: Crucial markers of prognosis were observed (progressive radiolucencies and linear wear) but survivorship at three years for aseptic loosening was 100%. Our results indicate satisfactory performance at three years in accordance with NICE guidelines, and suggest acceptability of both devices. Our methods may be applicable to similar implants currently in use but not yet endorsed by suitable published outcome data.

Background Prescriptive guidelines for selection of implants for hip arthroplasty are likely to become increasingly established, on grounds of safety, cost and effectiveness. Such guidelines were introduced in the UK by the National Institute of Clinical Excellence (NICE) in 2000. Most departments were non-compliant in one or more respects, and knowledge of the recommendations was limited among clinicians. Concern exists that the recommendations may replace the Bolam Test in cases of clinical negligence in future.

Materials and Methods The recommendations of NICE, from the initial documentation to the present, were scrutinised alongside experience of other nationally-funded or managed healthcare systems in Europe and North America. The evolution of guidance from 1999 onwards, together with the areas of potential difficulty were identified.

Results Potential difficulties were encountered in relation to a number of implants in widespread use in the UK, particularly in relation to the choice of acetabular component (cup), despite the fact that cup loosening accounts for a third of revisions. The use of cup and stem from different manufacturers was also identified as a cause of concern.

Discussion Departments face a choice of adopting the recommendations of NICE in their entirety or continuing with established practice, with the attendant risk of future litigation should certain implants prove to be unacceptable as clinical results become available through the National Registry. Continuation with established practice may be acceptable, even in respect of implants not recommended by NICE, provided data collection activity is maintained. We propose an algorithm through which individual departments may maintain compliance with NICE without altering departmental practice.