Patella implant research is often overlooked despite its importance as the third compartment in a total knee replacement. Wear and fracture of resurfaced patellae can lead to implant failure and revision surgeries. New simulation techniques have been developed to analyze the performance of patella designs as they interact with the trochlear groove in total knee components, and clinical validation is sought to ensure that these simulations are appropriate. The objective of this work was to subject several patellar designs to patient-derived deep knee bend (DKB) inputs on a 6 degree of freedom (DOF) simulator and compare the resultant wear scars to clinical retrievals. Previously reported DKB profiles were developed based on Introduction
Materials and Methods
Aseptic loosening of total knee replacements is a leading cause for revision. It is known that micromotion has an influence on the loosening of cemented implants though it is not yet well understood what the effect of repeated physiological loading has on the micromotion between implants and cement mantle. This study aims to investigate effect of physiological loading on the stability of tibial implants previously subjected to simulated intra-operative lipid/marrow infiltration. Three commercially available fixed bearing tibial implant designs were investigated in this study: ATTUNE®, PFC SIGMA® CoCr, ATTUNE® S+. The implant designs were first prepared using a LMI implantation process. Following the method described by Maag et al tibial implants were cemented in a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. The samples were subjected to intra- operative range of motion (ROM)/stability evaluation using an AMTI VIVO simulator, then a hyperextension activity until 15 minutes of cement cure time, and finally 3 additional ROM/stability evaluations were performed. Implant specific physiological loading was determined using telemetric tibial implant data from Orthoload and applying it to a validated FE lower limb model developed by the University of Denver. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the above model, 6 degree of freedom kinetics and kinematics for each activity was determined for each posterior stabilized implant design. Prior to loading, the 3-D motion between tibial implant and bone analog (micromotion) was measured using an ARAMIS Digital Image Correlation (DIC) system. Measurement was taken during the simulated DKB at 0.25Hz using an AMTI VIVO simulator while the DIC system captured images at a frame rate of 10Hz. The GOM software calculated the distance between reference point markers applied to the posterior implant and foam bone. A Matlab program calculated maximum micromotion within each DKB cycle and averaged that value across five cycles. The implant specific loading parameters were then applied to the three tibial implant designs. Using an AMTI VIVO simulator each sample was subjected to 50,000 DKB and 120,000 SD cycles at 0.8Hz in series; equating to approximately 2 years of physiological activity. Following loading, micromotion was measured using the same method as above.Introduction
Methods
One of the main surgical goals when performing a total knee replacement (TKR) is to ensure the implants are properly aligned and correctly sized; however, understanding the effect of alignment and rotation on the biomechanics of the knee during functional activities is limited. Cardiff University has unique access to a group of local patients who have relatively high frequency of poor alignment, and early failure. This provides a rare insight into how malalignment of TKR's can affect patients from a clinical and biomechanical point of view to determine how to best align a TKR. This study aims to explore relationship clinical surgical measurements of Implant alignment with in-vivo joint kinematics. 28 patient volunteers (with 32 Kinemax (Stryker) TKR's were recruited. Patients undertook single plane video fluoroscopy of the knee during a step-up and step-down task to determine TKR in-vivo kinematics and centre of rotation (COR). Joint Track image registration software (University of Florida, USA) was used to match CAD models of the implant to the x-ray images. Hip-Knee-Ankle (HKA) was measured using long-leg radiographs to determine frontal plane alignment. Posterior tibial slope angle was calculated using radiographs. An independent sample t-test was used to explore differences between neutral (HKA:-2° to 2°), varus (≥2°) and valgus alignment (≤-2°) groups. Other measures were explored across the whole cohort using Pearson's correlations (SPSS V23). There was found to be no statistical difference between groups or correlations for HKA. The exploratory analysis found that tibial slope correlated with Superior/Inferior translation ROM during step up (r=−0.601, p<0.001) and step down (r=−.512, p=0.03) the position of the COR heading towards the lateral (r=−.479, p=0.006) during step down. Initial results suggest no relationship between frontal plane alignment and in-vivo. Exploratory analyses have found other relationships that are worthy of further research and may be important in optimizing function.
Meniscal allograft transplantation is undertaken to improve pain
and function in patients with a symptomatic meniscal deficient knee
compartment. While case series have shown improvements in patient
reported outcome measures (PROMs), its efficacy has not been rigorously
evaluated. This study aimed to compare PROMs in patients having
meniscal transplantation with those having personalized physiotherapy
at 12 months. A single-centre assessor-blinded, comprehensive cohort study,
incorporating a pilot randomized controlled trial (RCT) was performed
on patients with a symptomatic compartment of the knee in which
a (sub)total meniscectomy had previously been performed. They were
randomized to be treated either with a meniscal allograft transplantation
or personalized physiotherapy, and stratified for malalignment of
the limb. They entered the preference groups if they were not willing
to be randomized. The Knee injury and Osteoarthritis Outcome Score (KOOS),
International Knee Documentation Committee (IKDC) score and Lysholm
score and complications were collected at baseline and at four,
eight and 12 months following the interventions.Aims
Patients and Methods
Patellar instability most frequently presents
during adolescence. Congenital and infantile dislocation of the
patella is a distinct entity from adolescent instability and measurable
abnormalities may be present at birth. In the normal patellofemoral
joint an increase in quadriceps angle and patellar height are matched
by an increase in trochlear depth as the joint matures. Adolescent
instability may herald a lifelong condition leading to chronic disability
and arthritis. Restoring normal anatomy by trochleoplasty, tibial tubercle transfer
or medial patellofemoral ligament (MPFL) reconstruction in the young
adult prevents further instability. Although these techniques are
proven in the young adult, they may cause growth arrest and deformity
where the physis is open. A vigorous non-operative strategy may
permit delay of surgery until growth is complete. Where non-operative
treatment has failed a modified MPFL reconstruction may be performed
to maintain stability until physeal closure permits anatomical reconstruction.
If significant growth remains an extraosseous reconstruction of
the MPFL may impart the lowest risk to the physis. If minor growth
remains image intensifier guided placement of femoral intraosseous
fixation may impart a small, but acceptable, risk to the physis. This paper presents and discusses the literature relating to
adolescent instability and provides a framework for management of
these patients. Cite this article:
There is a lack of information about the association between patellofemoral osteoarthritis (PFOA) and both adolescent Anterior Knee Pain (AKP) and previous patellar dislocations. This case-control study involved 222 participants from our knee arthroplasty database answering a questionnaire. 111 patients suffering PFOA were 1:1 matched with a unicompartmental tibiofemoral arthritis control group. Multivariate correlation and binary logistic regression analysis was performed, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated. This analysis helps us assess the effect of both variables whilst adjusting for major confounders, such as previous surgery and patient-reported instability. An individual is 7.5 times more likely to develop PFOA if they have suffered adolescent AKP (OR 7.5, 95% CIs 1.51–36.94). Additionally, experiencing a patellar dislocation increases the likelihood of development of PFOA, with an adjusted odds ratio of 3.2 (95% CIs 1.25–8.18). A 44-year difference in median age of first dislocation was also observed between the groups. This should bring into question the traditional belief that adolescent anterior knee pain is a benign pathology. Patellar dislocation is also a significant risk factor. These patients merit investigation, we encourage clinical acknowledgement of the potential consequences when encountering patients suffering from anterior knee pain or patellar dislocation.
The aim of this study was to document the survivorship and patient reported outcome of the Avon patello-femoral replacement in a consecutive series with follow up of 10 years or more. All cases performed in Bristol from 1996 onwards were prospectively recorded. Follow up was at 1,2,5,7,10,12 and 15 years with the Bristol Patella Score, the Oxford and WOMAC scores and SF12. Implant survival was analysed using the Kaplan-Meier method. There were 323 PFJ replacements (280 individuals). Follow up was available for 286 cases in 250 patients (89% follow up). The 10 year survival rate was 77%, falling to 67% at 15 years. The most common reason for revision was tibio-femoral progression (45/74 revisions), with loosening or polyethylene wear recorded in 8 cases. The best results were seen in the youngest and the oldest patients. Good improvements were seen in PROMs, with the mean OKS improving from 19.5 to 34.1 at 2 years and 32.7 at the 15 years. The Avon patello-femoral knee replacement is a successful long-term treatment for isolated patello-femoral knee osteoarthritis, although further improvements are expected in subsequent series, particularly as indications for surgery have evolved over time.
The aim of this study is to document the outcome of a large cohort of patients treated with the Bereiter trochleoplasty with between 1 and 12 years of follow up. 215 consecutive cases in 186 patients were recorded prospectively. All patients were offered yearly clinical and radiological review. PROMs were recorded including the IKDC, OKS, Kujala and SF-12. Patients unable to attend clinic were assessed with PROMS and radiographs from their local institutions where possible. There were 133 females and 53 males, with a mean age of 21 (14–38). There were no infections and only 6 patients reported further dislocations. There was one flap breakdown and no identified cases of secondary osteoarthritis. PROMs were available for 194 cases in 167 patients (90% follow up). 84% of patients were satisfied, 87% felt their symptoms had improved and 69% had gone back to sport. All scores improved (all p<0.001) except for the SF-12 mental score (p=0.42), with averages comparable to the results of MPFL reconstruction. Good outcomes were observed despite the difficult patient population in which these cases were performed. The Bereiter trochleoplasty is an effective method of treating recurrent patella instability in patients with severe trochlea dysplasia.
For many patients, total knee replacement (TKR) provides pain relief and restores motion for many years [1]. Some patients, however, experience early failures and require revision surgery. One of the suggested contributors to early failure has been excessive wear due to malalignment [2]. Previous work has shown that varus-valgus malalignment results in extreme condylar loading and could lead to high wear [3]. The purpose of this experiment, therefore, was to evaluate medial/lateral load sharing in an in vitro wear simulation. Wear testing was conducted on midsized Attune and Sigma fixed bearing cruciate substituting TKR components (DePuy Synthes). The two systems differ in many aspects; notably, Attune employs antioxidant-stabilized moderately-crosslinked polyethylene and a gradually changing sagittal femoral curvature while Sigma uses remelted moderately-crosslinked polyethylene and a mulit-radius femoral design. Wear was evaluated across a wide range of medial/lateral (M/L) load splits: 10/90, 60/40, and 90/10 using an AMTI six-station knee simulator (Figure 1). Simulation was conducted for 3 million cycles using at 1 Hz using previously described methods [4] with ‘High Kinematic’ displacement controlled inputs in 25% bovine calf serum (Hyclone) at 37 ± 2°C supplemented with sodium azide and EDTA. Polyethylene wear was determined gravimetrically with load soak compensation every 0.5 Mcyc.Introduction
Methods
Previous studies have demonstrated the need of accurate reduction of ankle syndesmosis. Measurement of syndesmosis is difficult on plain radiographs. Recently, a difference of 2mm in anterior and posterior measurements at incisura of the inferior tibio-fibular joint on CT has been described as a measure of malreduction (depicted as ‘G’ for ease of description). Our practice changed towards routine post operative bilateral CT following syndesmosis fixation to assess the reduction and identify potential problems at an early stage. The aim of this primarily radiological study was to determine if the use of bilateral cross sectional imaging brings additional benefit above the more conventional practice of unilateral imaging. Between 2007 and 2009, nineteen patients with ankle fractures involving the syndesmosis were included in the study group who had bilateral CT post operatively. The values of ‘G’ and the mean diastasis (MD) were calculated, representing the average measurement between the fibula and the anterior and posterior incisura.Introduction
Method
High tibial Osteotomy (HTO) realigns the forces in the knee to slow the progression of osteoarthritis. This study relates the changes in knee joint biomechanics during level gait to glutamate signalling in the subchondral bone of patients pre and post HTO. Glutamate transmits mechanical signals in bone and activates glutamate receptors to influence inflammation, degeneration and nociception in arthritic joints. Thus glutamate signalling is a mechanism whereby mechanical load can directly modulate joint pathology and pain. 3D motion analysis was used to assess level gait prior to HTO (n=5) and postoperatively (n=2). A biomechanical model of each subject was created in Visual3D (C-motion. Inc) and used for biomechanical analysis. Gene expression was analysed by RT-PCR from bone cores from anterior and posterior drill holes, subdivided according to medial or lateral proximal tibia from HTO patients (n=5).BACKGROUND
METHODS
Patients with knee osteoarthritis frequently complain that they develop pain in other joints due to over-loading during gait. However, there have been no previous studies examining the effect of knee arthritis on the other weight bearing joints. The aim of this study was to examine the loading of the hips and contra-lateral knee during gait in a cohort of patients pre- and post knee replacement. Twenty patients with single joint osteoarthritis awaiting knee replacement and 20 healthy volunteers were recruited. Gait analysis during level gait and at self selected speed was performed using a 12 camera Vicon motion analysis system. The ground reaction force was collected using EMG electrodes attached to the medial and lateral hamstrings and quadriceps bilaterally. Patients were invited to return 12 months post-operatively. Data was analysed using the Vicon plug-in-gait model and statistical testing was performed with SPSS v16.0 using ANCOVA to account for gait speed.Introduction
Methods
To review the Five year survivorship of Kinnemax TKA performed at the NHS Treatment Cantre, Weston-Super-Mare (WSM), and compare it to a similar cohort from our institution. As part of the government's initiative to reduce waiting times for major joint surgery in Wales, the Cardiff and Vale NHS Trust (CAVOC) sent 224 patients (258 knees) to the NHS Treatment Centre in Weston-Super-Mare (WSM) for total knee arthroplasty. Controversy remains as to the unexpectedly high revision rates previously seen.Purpose
Introduction
The use of a quadrupled hamstring graft in ACL reconstruction is well established. There are many described techniques in securing graft fixation, the optimal method is not yet established. The aim of this study was to review the results of a single surgeon series using the above implants looking at functional outcome for the patient and implant survivorship. Patients were recruited for the study who had completed 8 months of post-op rehabilitation following primary ACL reconstruction and that had received the same surgical technique using the same implants from one surgical team. Patients undergoing a revision procedure were excluded. All patients received the same post-operative rehabilitation. Those who met the inclusion criteria were contacted via a postal survey using the Lysholm and Tegner questionnaires. In total 77 patients were eligible for inclusion, consisting of 10 females and 67 males with a mean age of 31 (range 16-56). A 77% survey return rate was achieved with average follow up of 25 months (range 9-44). The mean Lysholm score was 82.1, with 59% ranking their knee as good or excellent. On average patients dropped 1.8 levels on the Tegner activity rating from a pre-injury average of 7.5 to post rehabilitation average of 5.7. There was a 100% survivorship of implants with no revisions undertaken due to implant failure. The study has shown that this cohort of patients has produced self reported outcomes analogous to findings in the current literature. No obvious problem with implants was observed. It has highlighted the multiple factors associated with the outcome of ACL reconstruction and demonstrates that the quadrupled HT graft using Bio-Intrafix and Rigidfix implants produces short to mid-term functional and activity levels in keeping with the literature standard.
To review the results of a single surgeon series using the above implants looking at functional outcome and implant survivorship. The outcome of ACL reconstruction is multi-factorial. There are many described ways of securing a 4-srandd hamstring ACL graft with no clear gold standard.AIMS
BACKGROUND
Patients with knee osteoarthritis (OA) often tell us that they put extra load on the joints of the opposite leg as they walk. Multiple joint OA is common and has previously been related to gait changes due to hip OA (Shakoor et al 2002). The aim of this study was to determine whether patients with medial compartment knee OA have abnormal biomechanics of the unaffected knee and both hips during normal level gait. Twenty patients (11 male, 9 female), with severe medial compartment knee OA and no other joint pain were recruited. The control group comprised 20 adults without musculoskeletal pain. Patients were reviewed, x-rays were examined and WOMAC and Oxford knee scores were completed. A 12 camera Vicon (Vicon, Oxford) system was used to collect kinematic data (100Hz) on level walking and the ground reaction force was recorded using three AMTI force plates (1000Hz). Surface electrodes were placed over medial and lateral quadriceps and hamstrings bilaterally to record EMG data (1000Hz). Kinematics and kinetics were calculated using the Vicon ‘plug-in-gait’ model. A co-contraction index was calculated for the EMG signals on each side of the knee, representing the magnitude of the combined readings relative to their maximum contraction during the gait cycle. Statistical comparisons were performed using t-tests with Bonferroni's correction for two variables and ANOVA for more than two variables (SPSS v16).Introduction
Methods
Systems for collecting information about patient care are increasingly common in orthopaedic practice. Databases can allow various comparisons to be made over time. Significant decisions regarding service delivery and clinical practice may be made based on their results. We set out to determine the number of cases needed for comparison of Thirty-day mortality, inpatient wound infection rates and mean hospital length of stay, with a power of 80% for the demonstration of an effect at a significance level of p<
0.05. We analysed two years of prospectively collected data on 1,050 hip fracture patients admitted to a city teaching hospital. Power calculations were performed using standard equations from the literature. Detection of a 10% difference in 30 day mortality would require 14,065 patients in each arm of any comparison, demonstration of a 50% difference would require 643 patients in each arm; For wound infections, demonstration of a 10% difference in incidence would require 23,921 patients in each arm and 1127 patients for demonstration of a 50% difference; For length of stay, a difference of 10% would require 1,479 patients and 6660 patients for a 50% difference. Our data helps to illustrate the importance of sample size when interpreting the results of performance monitoring. Since a unit as large as our own only admits 525 patients per year, comparisons between trusts would require very prolonged data collection. Within a single unit the demonstration of poor performance by one surgeon or one team would clearly be impossible. Statistically meaningful analyses will only be possible with major multi-centre collaborations, as will be possible if hospital Trusts participate in the National Hip Fracture Database.
As part of the government’s initiative to reduce waiting times for major joint surgery in Wales, the Cardiff and Vale NHS Trust sent 224 patients (258 knees) to the NHS Treatment Centre in Weston-Super-Mare for total knee replacement. The Kinemax total knee replacement system was used in all cases. The cumulative survival rate at three years was 79.2% (95% confidence interval (CI) 69.2 to 86.8) using re-operation for any cause as an endpoint and 85.3% (95% CI 75.9 to 91.8) using aseptic revision as an endpoint. This is significantly worse than that recorded in the published literature. These poor results have resulted in a significant impact on our service.
Experience has shown that oblique fractures can be slow to heal and this has been attributed to excess shear at the fracture site. We routinely treat fractures with hybrid external fixation. In previous studies, olive wires placed through the fracture site reduced shear and this has improved healing times. When the fracture is oblique in the sagittal plane, anatomical constraints prevent the use of olive wires and a new solution is required. A sawbone tibia with a distal sagittal plane oblique fracture (70° obliquity) was stabilised with a Sheffield Hybrid Fixator. In a pilot study various methods of fixation were tested and six were chosen for further testing. Since the pull-out strength of threads in the plastic bone was poor, olive wires cut behind the olive were used as a mechanically equivalent model for the push-pull system. Seventy degree steerage pins could not be used so 25° pins were tested instead. Cyclic compressive forces (at 10mm/min) of up to 200N axially and in four off-axis positions were applied using a universal testing machine. Fracture site linear motion in three dimensions was measured using an inter-fragmentary motion device, sampled at 100Hz. A standard frame was tested before and after each adaptation and all six methods were applied sequentially to each model. The results suggest that: I) Arched wires are effective especially under greater bends, 2) Push-pull wires are effective and provide a minimally disruptive solution, 3) Steerage pins are effective especially at steeper obliquities but this may not always be practical, and 4) Placing a half pin in the distal fragment is beneficial but less effective than the use of 2 transverse half pins acting in a compression system (Hutson technique).
