Abstract

Abstract

Total knee arthroplasty (TKA) aims to alleviate pain and restore joint biomechanics to an equivalent degree to age-matched peers.

Zimmer Biomet's Nexgen TKA was the most common implant in the UK between 2003 and 2016. This study compared the biomechanical outcomes of the Nexgen implant against a cohort of healthy older adults to determine whether knee biomechanics is restored post-TKA.

Patients with a primary Nexgen TKA and healthy adults >55 years old with no musculoskeletal deficits or diagnosis of arthritis were recruited locally.

Eligible participants attended one research appointment. Bilateral knee range of motion (RoM) was assessed with a goniometer. A motorised arthrometer (GENOUROB) was then used to quantify the anterior-posterior laxity of each knee. Finally, gait patterns were analysed on a treadmill. An 8-camera Vicon motion capture system generated the biomechanical model.

Preliminary statistical analyses were performed in SPSS (α = 0.05; required sample size for ongoing study: n=21 per group).

The patient cohort (n=21) was older and had a greater BMI than the comparative group (n=13). Patients also had significantly poorer RoM than healthy older adults. However, there were no inter-group differences in knee laxity, walking speed or cadence. Gait kinematics were comparable in the sagittal plane during stance phase. Peak knee flexion during swing phase was lower in the patient group, however (49.0° vs 41.1°).

Preliminary results suggest that knee laxity and some spatiotemporal and kinematic parameters of gait are restored in Nexgen TKA patients.

While knee RoM remains significantly poorer in the patient cohort, an average RoM of >110° was achieved. This suggests the implant provides sufficient RoM for most activities of daily living. Further improvements to knee kinematics may necessitate additional rehabilitation.

Future recruitment drives will concentrate on adults over the age of 70 for improved inter-group comparability.

Abstract

Our unpublished data has indicated that the perivascular stem cells (PSCs) have increased chondrogenic potential compared to mesenchymal stem cells (MSCs) derived in culture. There has been a recent change in the theory that stem cells work by a paracrine effect rather than differentiation. There are minimal data demonstrating the persistence of implanted stem cells when used for engraftment. This study aimed to develop an autologous large animal model for perivascular stem cells as well as to determine if cells were retained in the articular cartilage defects.

The reactivity of anti-human and anti-ovine antibodies was ascertained using immunohistochemistry and fluorescence-activated cell sorting (FACS). A panel of antibodies were combined and used to identify and purify pericytes (CD34-CD45-CD146+) and adventitial cells (CD34+CD45-CD146-) using FACS. The purified cells were cultured and their identity checked using FACS. These cultured cells demonstrated osteogenic, adipogenic and chondrogenic potential.

Autologous ovine PSCs (oPSCs) were isolated, cultured and transfected using a GFP virus. The transfection rate was 88%. The cells were implanted into an articular cartilage defect on the medial femoral condyle using a hydrogel, four weeks following implantation the condyle was explanted and confocal laser scanning microscopy demonstrated the presence of oPSCs in the defect. Histology did not demonstrate any repair tissue at this early time point.

These data have confirmed the viability our large animal model and that the implanted stem cells were retained in the defect four weeks following implantation.

Opening-wedge High Tibial Osteotomy (HTO) has been shown to be an effective procedure to treat mild to moderate osteoarthritis of the medial compartment of the knee in active individuals. It has also become a mandatory surgical adjunct to articular cartilage restoration when there is preoperative mal-alignment. However, its efficacy is directly correlated with the accuracy of the correction, which must be within 3° of the preoperative target. Achieving this goal is a significant challenge with conventional techniques. Therefore, computer-assisted navigation protocols have been developed; however, they do not adequately address the technical difficulties associated with this procedure. We present an integrated solution dedicated to the opening-wedge HTO. Advantages to the technique we propose include: 1) a minimum number of implanted bone trackers, 2) depth control of the saw, 3) improved 3-D accuracy in the location of the lateral tibial hinge, and 4) micrometric adjustment of the degree of correction. The proof of concept has been completed on all six specimens. The following key points have been validated: a) Compatibility with a minimally-invasive (5–6 cm) surgical incision b) The compact navigation station can be placed close to the operative field and manipulated through a sterile draping device c) Only two trackers are necessary to acquire the required landmarks and to provide 3-D control of the correction. These can be inserted within the surgical wound without any secondary incisions d) The optimised guide accurately controlled the external tibial hinge in all six cases e) The implant cavity could be milled effectively f) The distractor used to complete the desired realignment maintained stability of the distraction until final fixation with the PEEK implant g) The PEEK implant could be fixed to the tibia with excellent stability in a low-profile fashion. The solution presented here has the potential to help surgeons perform a medial opening-wedge HTO more safely and accurately. This will likely result in an increase in the number of HTOs performed for both isolated medial compartment osteoarthritis as well as for lower extremity realignment in association with cartilage restorative procedures.

Perivascular stem cells (PSCs) from lipoaspirate demonstrate increased purity and immaturity with greater engraftment potential than standard mesenchymal stem cells (MSCs). MSCs from the infra-patellar fat pad (IFP) have previously demonstrated increased chondrogenic potential. This study investigated the availability and potential of PSCs harvested from the infra-patellar fat pad of the human knee for musculoskeletal regeneration.

Tissue sections of IFP were stained with markers for PSCs, MSCs and endothelial cells to confirm their presence and location. Samples were obtained from patients undergoing TKR (n=13) or ACL reconstructions (n=10). Pericytes and adventitial cells made up 3.8% and 21.2% respectively of the stromal vascular fraction. The total number of pericytes and adventitial cells were 4.6±2.2×104 and 16.2±3.2×104 respectively. Cells were cultured both separately and combined. Cell identity was ascertained using fluorescence-activated cell sorting, immunocytochemistry and PCR. Cultured PSCs were differentiated using chondrogneic, osteogenic, adipogenic and myogenic medias. Differentiation was determined using Alcian Blue, Alizarin red, Oil Red O and myosin staining.

This study demonstrates that the IPFP is a viable source of PSCs that can be harvested either arthroscopically or through an arthrotomy by orthopaedic surgeons for cell-based musculoskeletal regeneration. Their potential now needs to be compared to conventional MSCs.

Perivascular stem cells (PSCs) from lipoaspirate demonstrate increased purity and immaturity with greater engraftment potential than standard mesenchymal stem cells (MSCs). MSCs from the infra-patellar fat pad (IFP) have previously demonstrated increased chondrogenic potential. This study investigated the availability and potential of PSCs harvested from the infra-patellar fat pad of the human knee for musculoskeletal regeneration.

Sections of IFP were stained with markers for PSCs, MSCs and endothelial cells to confirm their presence and location. Samples were obtained from patients undergoing TKR (n=13) or ACL reconstructions (n=10). Pericytes and adventitial cells made up 3.8% and 21.2% respectively of the stromal vascular fraction. The total number of pericytes and adventitial cells were 4.6±2.2×10⁴ and 16.2±3.2×10⁴ respectively. Cells were cultured both separately and combined. Cell identity was ascertained using fluorescence-activated cell sorting and immunocytochemistry. Cultured PSCs were differentiated using chondrogneic, osteogenic, adipogenic and myogenic medias. Differentiation was determined using Alcian Blue, Alizarin red, Oil Red O and mysosin staining.

This study demonstrates that the IFP is a viable source of PSCs that can be harvested either arthroscopically or through an arthrotomy by orthopaedic surgeons for cell-based musculoskeletal regeneration. Their potential now needs to be compared to conventional MSCs.

This study investigated confocal laser scanning microscopy (CLSM) as a novel method of imaging of chondrocytes on a collagen membrane used for articular cartilage repair. Cell viability and the effects of surgery on the cells were assessed.

Cell images were acquired under four conditions: 1, Pre-operative 2, After handling 3, Heavily grasped with forceps 4, Cut around the edge. Live and dead cell stains were used. Images were obtained for cell counting and morphology. Mean cell density was 1.12–1.68 ± 0.22 × 10⁶ cells/cm² in specimens without significant trauma (n=25 images), this decreased to 0.253 × 10⁶ cells/cm² in the specimens that had been grasped with forceps (p <0.001) (5 images). Cell viability on delivery grade membrane was 86.8±2.1%. The viability dropped to 76.3 ± 1.6% after handling and 35.1 ± 1.7% after crushing with forceps. Where the membrane was cut with scissors, there was a band of cell death where the viability dropped to 17.3 ± 2.0% compared to 73.4 ± 1.9% in the adjacent area (p <0.001). Higher magnification revealed cells did not have the rounded appearance of chondrocytes.

CLSM can quantify and image the fine morphology of cells on a MACI membrane. Careful handling of the membrane is essential to minimise chondrocyte death during surgery.

Proximal femoral fractures remain the most common reason for admission to hospital following orthopaedic injury, with an annual cost of £1.7 billion to the National Health Service and social care services. Fragility fractures of the hip in the elderly are a substantial cause of mortality and morbidity. Revision surgery for any cause carries a higher morbidity, mortality, healthcare- and social economic burden. Which patients suffer failed surgery and the reasons for failure have not been established. The aim of this study was to determine which patients are at risk of failed proximal femoral fracture surgery, the mechanism and cause fo failed surgery and modifiable patient factors associated with failure of hip fracture surgery.

From prospectively collected data of 795 consecutive proximal femoral fractures admitted between July 2007 and July 2008, all peri-operative and post-operative complications were identified.

55 (6.9%) patients were found to have developed a surgical complication requiring further intervention. Risk factors included younger age (p=0.01), smoking (p=0.01) and cannulated screw fixation (p<0.01). Cannulated screw fixation was associated with a 30.9% complication rate. Mechanical cause was the most common reason for cannulated screw failure. Hip hemiarthroplasty most commonly failed by infective causes. Inter-trochanteric and subtrochanteric fracture fixation had very low failure rates. Surgical complication was not found to be associated with an increased mortality but a post-operative medical complication (21.8%) was associated with higher rate of mortality at 4-years (78.5%) and shorter time to mortality. (Median time 0.16 years (95% CI 0.00–0.33).

Open or closed fracture of the tibial shaft is a common injury. There is no long-term outcome data of patients after tibial shaft fracture utilising modern treatment methods. This study assessed pain and function of 1509 consecutive patients with a tibial shaft fracture at 12–22 years following injury. Secondary outcomes included: effect on employment, effect of social deprivation, necessity for hardware removal and comparative morbidity following fasciotomy.

Prospective study of 1509 consecutive adult patients with a tibial shaft fracture (1990–1999) at a high-volume trauma unit. 1034 were male, and the mean age at injury was 40 years. Fractures were classified according to AO, and open fractures graded after Gustillo and Anderson. Time to fracture union, complication rate, hardware removal and incidence of anterior knee pain were recorded. Employment and assessment of social deprivation were detailed. Function was assessed at 12 to 22 years post injury using the Short Musculoskeletal Functional Assessment and Short Form 12 questionnaires.

87% of fractures united without further intervention. Social deprivation was associated with higher incidence of fracture and poorer functional and economic outcomes. 11.5% patients underwent fasciotomy which correlated with poorer long-term outcome. Tibial shaft fracture had high mortality in the elderly. At long-term follow-up 25% of patients have anterior knee pain and 20% ankle discomfort after IM nailing.

This is the largest and longest study assessing functional and economic outcomes of tibial shaft fracture. This is the first paper to describe ankle pain following tibial IM nailing at long-term follow-up.

It is widely accepted by orthopaedic surgeons that antibiotics should be withheld until aspiration has been performed to increase the odds of identifying an organism in septic arthritis. Patients often present to other specialties that may not be as familiar with these principles.

Twenty-five of forty-nine patients with septic arthritis of the native or prosthetic knee had received antibiotics prior to review by the orthopaedic service. Patients were significantly less likely to demonstrate an organism on initial microscopy (entire cohort p=0.001, native knees p=0.006, prosthetic knees p=0.033) or on subsequent culture (entire cohort p=0.001, native knees p=0.017, prosthetic knees p=0.012) of their aspirate if they had received antibiotics. The sensitivity of microscopy dropped from 0.58 to 0.12 when patients had received antibiotics (native knees 0.46 to 0, prosthetic knees 0.72 to 0.27). The sensitivity of the culture dropped from 0.79 to 0.28 when the patient had received antibiotics (native knees 0.69 to 0.21, prosthetic knees 0.91 to 0.36).

Patients treated with empirical antibiotics are less likely to demonstrate an organism on microscopy and culture of their initial aspirate. There is a significantly high false negative rate associated with knee aspiration, particularly with prior administration of antibiotics.

Patient expectations and their fulfilment are an important factor in determining patient-reported outcome and satisfaction of hip (THR) and knee replacement (TKR). The aim of this prospective cohort study was to examine the expectations of patients undergoing THR and TKR, and to identify differences in expectations, predictors of high expectations and the relationship between the fulfilment of expectations and patient-reported outcome measures. During the study period, patients who underwent 346 THRs and 323 TKRs completed an expectation questionnaire, Oxford score and Short-Form 12 (SF-12) score pre-operatively. At one year post-operatively, the Oxford score, SF-12, patient satisfaction and expectation fulfilment were assessed. Univariable and multivariable analysis were performed. Improvements in mobility and daytime pain were the most important expectations in both groups. Expectation level did not differ between THR and TKR. Poor Oxford score, younger age and male gender significantly predicted high pre-operative expectations (p < 0.001). The level of pre-operative expectation was not significantly associated with the fulfilment of expectations or outcome. THR better met the expectations identified as important by patients. TKR failed to meet expectations of kneeling, squatting and stair climbing. High fulfilment of expectation in both THR and TKR was significantly predicted by young age, greater improvements in Oxford score and high pre-operative mental health scores. The fulfilment of expectations was highly correlated with satisfaction.

Distal radius fractures are common, yet the long-term functional outcome of these patients is unknown. This study investigated the long-term functional outcomes after distal radius fracture (DRF) in adult patients 16–23 years following injury. Secondary aims were to establish morbidity, mortality and function related to pattern of injury and patient demographics.

Introduction

It is estimated 5% of patients over 65 years receive warfarin therapy. This paper aims to analyse whether a time delay to hip fracture fixation while waiting for the patients International Normalised Ratio (INR) to return to normal increases the mortality risk.

‘High flexion’ polyethylene tibial tray inserts are available from total knee replacement (TKR) manufacturers. There is currently no published data available that examines how much extra knee flexion these new implants give or if there are any wear consequences for the change in design. The high flexion inserts are narrower posteriorly than standard inserts and have chamfers anteriorly and on the post in cruciate sacrificing designs.

This prospective randomised controlled trial of 100 patients undergoing posterior stabilised TKR compared knee flexion, measured intra-operatively by a computer navigation system, of the standard and high flexion trial inserts in the same knee. Patients were then randomised to receive either a standard or ‘high flexion’ definitive component and the stability assessed. The post-operative knee flexion of all patients was measured at six months.

High flexion inserts did not give significantly more knee flexion than standard inserts either per-operatively at the trial insert stage, or at six months post-op and resulted in marginally more anterior draw. The average per-operative difference in flexion between standard and high flex inserts measured in the same knee was 3.2° (range -4-18°) The average knee flexion at 6 months post op was 106° for both groups. The average change in knee flexion comparing pre and post op was 2.3° for the high flex group and 0.6° for the standard insert group.

Laboratory Tek scan contact pressure analysis at the surface of the standard and high flexion designs was not significantly different, but the thinner polyethylene of the high flexion design raises questions about wear characteristics. High flexion polyethylene inserts are probably not justified in terms of improved knee flexion, but may be a useful option in certain technical circumstances during TKR such as patella baja or if the patella impinges on the post in deep flexion.

There is limited literature regarding the outcome of hip and knee arthroplasty (THR and TKR) in the Super-Elderly (≥80yrs). The aim is to compare the outcome of THR and TKR in the Super-Elderly with a standard-age cohort of patients. From January 2006 to August 2008; 1290 TKR and 1344 THR were performed at the study institute. Comorbidity, length of stay, patient satisfaction, Oxford knee or hip scores, and SF12 scores were recorded prospectively. The Oxford Score and SF12 were recorded at one year. The mode age range was 65-74yrs for TKR (n=492) and THR (n=495), deemed the standard cohort. 185 TKR and 171 THR were performed in the Super-Elderly. Outcome in this cohort was compared to the standard.

The standard cohort had a greater absolute improvement in Oxford knee scores (15.8 and 14.7.p=0.2). Improvement of absolute Oxford hip scores revealed no difference (20.0 and 20.2.p=0.8), but the Super-Elderly had a greater improvement in pain components (11.0 vs.12.0.p=0.05) with a lesser improvement of the functional components (9.0.vs.8.2.p=0.05). There was a greater improvement in the physical component of the SF-12 score in the standard cohort for both TKR and THR (10.6.vs.7.9.p=0.05 and 14.4.vs.10.4.p=<0.01, respectively).

No significant difference was seen in comorbidities, but the Super-Elderly patients had a longer hospital stay for TKR (6.2.vs.8.3.p=0.01) and THR (5.9.vs.9.0.p=0.01).

The Super-Elderly were more satisfied with their surgery (p=0.05).

Super-Elderly patients have comparable outcomes to their younger counterparts and are more satisfied with their surgery, but they may require a longer length of stay.

Background: Tranexamic acid has been shown to be effective in reducing blood loss and transfusion requirement in cardiac surgery and total knee replacement surgery. The most effective dose of tranexamic acid in hip arthroplasty surgery is not yet known. We investigated the effect of a pre-operative bolus 1g intravenous tranexamic acid on intra- and post-operative blood loss, transfusion requirement, and risk of venous thromboembolism following total hip arthroplasty.

Results: We report a cohort comparison study of 73 patients who underwent primary hip arthroplasty. Thirty-six patients received tranexamic acid (TA group), and thirty-seven received no tranexamic acid (control group). Blood loss was measured directly intra-operatively, and indirectly post-operatively by haemoglobin and haematocrit measurement. Deep vein thrombosis (DVT) was investigated by venography.

Patient demographics were similar between both groups. There was no significant difference in intra-operative blood loss between both groups. The early post-operative blood loss and total blood loss were significantly less in the tranexamic acid group. This effect of tranexamic acid was more significant in females who showed a dose-related relationship between tranexamic acid dose and blood loss. Fewer patients in the tranexamic acid group required blood transfusion. There was no increased incidence of DVT in the tranexamic acid group.

The use of a single pre-operative 1g bolus of tranexamic acid administered before surgery is a safe, cost-effective method of reducing post-operative blood loss following total hip arthroplasty. The effect is more significant in females at this dose.

Aim: To assess the functional outcome and longevity of patients who are mentally competent when they sustain an intra-capsular fracture of the femoral neck.

Methods: Prospective cohort study of fifty female patients over the age of seventy years of age with a displaced intra-capsular fracture of the femoral neck. Patients with known, cognitive impairment terminal illness or active infection were excluded from the study. Patients were treated with a large head total hip replacement. Functional outcome was assessed using the the Barthel index score and the Charnley-modified Merle d’Aubigne score yearly for five years. The Oxford hip score was also recorded annually from three to ten years post op. The date and cause of death were recorded from hospital notes and death certificates.

Results: The mean age at time of femoral neck fracture was 81 years. Three patients died before discharge from hospital. The mortality rates were 18% at twelve months, 28% at two years, 44% at five years and 92% at ten years. Those patients surviving had mean Oxford scores of 24 at 3 years, 26 at 5 years, 23 at 7 years and 25 at ten years. The cause of death was ischaemic heart disease in 22%, cancer in 10%, bronchopneumonia in 12% and simply ‘old age’ in 14%.

Conclusion: Elderly female patients who are not cognitively impaired at the time of displaced intra-capsular fracture of the femoral neck have a 56% chance of living five years. Function scores in the survivors are maintained, and are better than would be expected if the patients had undergone hip hemiarthroplasty. Total hip replacement in this population may be justified.

Aims: Minimum ten year clinical, radiological and postmortem results of the flexible Cambridge Cup. This acetabular prosthesis was designed to replace the horseshoe shaped articular cartilage and provide physiological loading with minimal resection of healthy bone.

Method: Fifty female patients aged over 70 years with a displaced intra-capsular fracture of the femoral neck were recruited to the ethically-approved prospective study. They underwent implantation of the Cambridge Cup, which has an outer polybutyleneterephthalate shell and an inner UHMWPE bearing, with a Thompson-type hemiarthroplasty. The cups were manufactured with a 60μm plasma-sprayed coating of hydroxyapatite. This was removed from half the cups to simulate the effects of long-term HA resorption. Implants were sterilised by gamma irradiation in air. Independent clinical and radiological assessments were undertaken before discharge, at 6 weeks, one year, 18 months, two -, five-, seven- and ten years. Patients were scored using the Barthel Index, the Charnley-modified Merle d’Aubigne scores and latterly the Oxford hip score. The date and cause of death were obtained from hospital records and death certificates. Fifteen Cambridge Cups were retrieved post-mortem for histological and wear analysis

Results: The mean functional scores recovered to levels before fracture. These scores decreased with advancing age at five years. The mortality rates were 16%, 28%, 46% and 92% at 1, 2, 5 and 10 years. The Oxford hip scores in patients surviving between five and ten years were maintained.

The HA coated implants remained asymptomatic. Three uncoated components required revision for migration. No evidence of accelerated UHMWPE wear was seen on retrievals or radiographs. Histological analysis of the retrieved HA coated specimens showed excellent bony fixation, uncoated cups showed predominantly fibrous tissue.

Conclusion: The uncemented Cambridge Cup was implanted in a challenging environment of osteoporotic bone. Clinical, radiographic and post-mortem results up to ten years are excellent.