Although the importance of sound statistical principles in the design and analysis of data has gained prominence in recent years, biostatistics, the application of
Introduction: The Scottish Arthroplasty Project (SAP) publishes an annual report including infection rates post-arthroplasty having obtained their results from the patients’ ICD-10 codes. The aim of this project was to validate the THR infection rate for one unit as published in the 2006 Scottish Arthroplasty Project (SAP) Report. Method: The details of the SAP results were obtained. The BGH keeps its own record of post-operative THR infections; only those that met the dates and criteria of the SAP 2006 report were included and compared. The ICD-10 coding status was analysed in more detail. Results: Published rate of infection in the 2006 SAP report after total hip replacement is three times lower than the unit recorded. 12 patients were eligible (1.49% infection rate), the SAP report recorded 4 cases of infection. The SAP searches for infection only using three ICD-10 codes. Six ICD-10 codes had been used to classify these 12 patients. Discussion: A recent cardiac surgery study comparing postoperative mortality rates from hospital
Introduction. Unlike the NJR, no surgeon driven national database currently exists for ligament surgery in the UK and therefore information on outcome and adverse event is limited to case series. Methods. Prospectively collected Hospital episode
Background: Diagnostic and operative codes are routinely collected on every patient admitted to hospital in England and Wales (hospital episode
The infected TKA is one of the most challenging complications of knee surgery, but spacers can make them easier to treat. An articulating spacer allows weight bearing and range of motion of the knee during rehabilitation. This spacer is made using antibiotic-impregnated bone cement applied to the tibial and femoral implants. For our purpose, 4.8g powdered tobramycin is mixed with 2gm vancomycin and one batch of antibiotic. Cement is applied early to the components, but applied late to the femur, tibia, and patella to allow molding to the defects and bone without solid adherence to bone. Patients have tailored intravenous antibiotic therapy for 6 weeks for treatment of various gram-positive and gram-negative organisms. At 10–12 weeks patients are revised to a cemented revision total knee arthroplasty using standard cementing techniques. From our experience, range of motion before reimplantation was 5 – 90 degrees. Follow-up averaged 73 months for fifty patients with 90% good to excellent results; 10% had a recurrence of infections. Use of an articulating spacer achieves soft tissue compliance, allows for ease of re-operation, reduced postoperative pain, improved function, and eradicates infection equal to standards reported in the literature.
Deep peri-prosthetic infection after partial or total knee arthroplasty is a disconcerting problem for patient and surgeon alike. The diagnosis of infection is sometimes obvious but frequently requires that the surgeon maintain a substantial index of suspicion for infection as the cause of pain or poor outcome after any joint arthroplasty. While surgical debridement with component retention is appropriate in a subgroup of patients with an acute peri-prosthetic infection, most delayed and chronic infections are best treated with component resection. With carefully selected patients and very aggressive debridement protocols some success has been demonstrated in Europe with single-stage exchange for infection. Most surgeons in North America, however, are unfamiliar with the very aggressive debridement techniques employed at European centers that promote single stage replant; and few surgeons in North America are currently comfortable in cementing a hinged total knee replacement in place for the typical infected TKA nor do they have the patience to re-prep and drape with an entirely new OR setup after debridement and prior to the insertion of the new implant − 2 steps that are often mentioned as important to the success of single stage exchange. The pre-eminent role of two-stage exchange as the definitive treatment was established over 30 years ago. Two-stage exchange remains the gold-standard in treatment with an established track record from multiple centers and with multiple different types of infecting organisms. Some of the historical problems with two-stage exchange, such as limited mobility during the interval stage, have been mitigated with the development of effective articulating spacer techniques. Further, the emergence of drug resistant bacteria and the possibility of fungal infection make two-stage exchange the best choice for the majority of patients with deep periprosthetic joint infection in 2017.
Background: Diagnostic and operative codes are routinely collected on every patient admitted to National Health Service (NHS) hospitals in England and Wales (hospital episode
Aims. Describe a statistical and economic analysis plan for the Distal Radius Acute Fracture Fixation Trial 2 (DRAFFT2) randomized controlled trial. Methods. DRAFFT2 is a multicentre, parallel, two-arm randomized controlled trial. It compares surgical fixation with K-wires versus plaster cast in adult patients who have sustained a dorsally displaced fracture of the distal radius. The primary outcome measure is the Patient-Rated Wrist Evaluation (PRWE, a validated assessment of wrist function and pain) at 12 months post-randomization. Secondary outcomes are measured at three, six, and 12 months after randomization and include the PWRE, EuroQoL EQ-5D-5L index and EQ-VAS (visual analogue scale), complication rate, and cost-effectiveness of the treatment. Results. This paper describes the full details of the planned methods of analysis and descriptive
Two-stage treatment of chronically infected TKA is the most common form of management in North America and most parts of the world. One-stage management has pros and cons which will not be discussed in this lecture. There is great variation of techniques and timing and little data to definitively support one technique or timing approach vs. another. Most methods are based on empirical success and logic. At the time of surgery, the first step is removal of infected implants. All metallic implants and cement should be removed. The most common places to leave cement behind inadvertently include patellar lug holes, femoral lug holes, and the anterior proximal tibia behind the tibial tubercle. Formal synovectomy should be performed. The next step is typically antibiotic-impregnated spacer placement. There are pros and cons of dynamic and static spacers with no clear evidence of superiority of one vs. another. Dynamic spacers work satisfactorily with mild to moderate bone loss, but more severe bone loss is usually better treated with static spacers and a cast. Most antibiotic spacers are made of methyl methacrylate cement with addition of high-dose antibiotics. In most cases, doses of 4–8 gm of antibiotics per pack of cement are preferred. The type of dosing depends on the specific antibiotic and the type of cement used. The most common antibiotics used are vancomycin and gentamycin. When the femoral canals have been instrumented, antibiotic-impregnated cement wands are usually placed in the medullary canal, as the medullary canals have been shown to have high risk of residual bacteria being present. The resection interval may vary and there is no clear evidence of a “best” resection interval. Practically speaking, most surgeons use a resection period of 8–16 weeks depending on the type of spacer utilised. During the resection interval, serum markers (ESR and CRP) are followed periodically. One anticipates a decline or normalization of these parameters prior to second stage reimplantation procedure. There has not been a demonstrated advantage to reaspiration of the knee before reimplantation in most circumstances. At the time of reimplantation, the spacers are removed and the knee is redebrided. The key at the time of reimplantation is to obtain good implant fixation but to also balance this with the potential for manageable extraction of the implants at some later date. Good implant fixation is important because failure rates due to mechanical failure are approximately equal to those of failure due to reinfection by 10 years. It is important to remember that reinfection risk is at least 10% by ten years, and therefore extractability of implants is also important. Post-operative management typically includes IV antibiotics, followed by oral antibiotics until final intra-operative cultures are available. The results of two-stage reimplantation are reported in many series. Most show approximately 85–95% rate of successful eradication of infection in the first five years. Reinfections, often with different organisms, may occur even late after reimplantation. By ten years after surgery survival free of mechanical failure and infection in most series drops to 80% or less due to recurrent infections and mechanical failures.
Purpose. To establish the reliability of reporting and recording revision hip and knee arthroplasties by comparing data in the National Joint Registry (NJR), Hospital Episode
Computer navigation has the potential to revolutionise orthopaedic surgery, although according to the latest 7. th. Annual NJR Report, only 2% of the 5 800 unicompartmental knee replacements (UKRs) performed in 2009 were carried out using ‘image guidance.’ The report also states an average 3-year revision rate for UKRs of 6.5%. Previous NJR data has shown that this figure rises up to 12% for certain types of prosthesis. We suspect that a significant proportion of these revisions are due to failure secondary to component malpositioning. We therefore propose that the use of computer navigation enables a more accurate prosthesis placement, leading to a reduction in the revision rate for early failure secondary to component malpositioning. Our early results of one hundred consecutive computer navigated UKRs are presented and discussed. Ninety-two patients having had one hundred consecutive computer navigated UKRs were reviewed both clinically and radiographically. The Smith & Nephew Accuris fixed-bearing modular prosthesis was used in all cases, with the ‘Brainlab’ navigation system. Pre-operative aim was neutral tibial cut with three degrees posterior slope. Post-operative component alignment was measured with PACs web measuring tools. Patients were scored clinically using the Oxford Knee Score. Our patient cohort includes 54 male knees and 46 female knees. Average age is 66.6yrs. Average length of stay was 3.7 days, (range 2–7.) With respect to the tibial component, average alignment was 0.7° varus, and 2.32° posterior slope. All components were within the acceptable 3 degrees deviation. Functional scores are very satisfactory, with an overall patient satisfaction rate of 97%. To date, only one UKR has required revision. This was due to ongoing medial pain due to medial overhang, not related to computer navigation. There was one superficial infection, with full resolution following a superficial surgical washout, debridement and antibiotics. Unlike complications reported in the NJR, we report no peri-prosthetic fractures or patella tendon injuries. Our results demonstrate accurate prosthesis placement with the use of computer navigation. Furthermore, clinical scores are highly satisfactory. Our current revision rate is 1% at a mean of 27 months post-op. Although longer-term follow-up of our group is required, our results compare very favourably to
With many stakeholders, healthcare decisions are complex. However, patient interests should be prioritized. This maximizes healthcare value (quality divided by cost), simultaneously minimizing costs (objective) and maximizing quality (subjective). Unfortunately, even ‘high value’ procedures like total knee arthroplasty (TKA) suffer from recovery assessment subjectivity (i.e. high assessment variability) and increasing costs. High TKA costs and utilization yield high annual expenditures (∼$22B), including postoperative physical therapy (PT) accounting for ∼10% of total costs (∼$2.3B annually). Post-TKA PT is typically homogenous across subjects ensuring most recover, however recent work shows outcomes unimpacted by PT. Accordingly, opportunities exist improving healthcare value by simultaneously reducing unnecessary PT expenditures and improving outcomes. However, discerning recovery completion relies on discrete ROM measures captured clinically and subjective clinician experience (i.e. intuition about recovery). Accordingly, our goal was developing objective post-TKA performance assessment methods utilizing gait knee ROM and statistical analyses to categorize patient recovery (‘accelerated,’ ‘delayed,’ or ‘normal’). We first established statistical reasons for current post-TKA rehabilitation including risk-reward tradeoffs between incorrectly ascribing ‘poor recovery’ to well-recovering patients (T1 error) or ‘good recovery’ to poorly-recovering patients (T2 error) using methods described by Mudge et al. and known TKA volumes/rehabilitation costs. Next, previously captured gait ROM data from well-healed patients was utilized establishing standard recovery curves. These were then utilized to assess newly captured patient recovery. Following IRB approval, we prospectively captured gait ROM from 10 TKA patients (3M, 69±13 years) 1-week pre-TKA and 6-weeks immediately post-TKA. Performance was compared to recovery curves via control charts/Shewhart rules (daily performance) as well as standard deviation thresholds (weekly performance) establishing recovery as ‘accelerated,’ ‘delayed,’ or ‘normal.’ The categorization was extrapolated to US TKA population and savings/expenses quantified. Statistical analyses were performed in Minitab with statistical significance set to α<0.05.Introduction
Methods
Objective. In ex vivo hip fracture studies femoral pairs
are split to create two comparable test groups. When more than two
groups are required, or if paired femurs cannot be obtained, group
allocation according to bone mineral density (BMD) is sometimes
performed. In this statistical experiment we explore how this affects
experimental results and sample size considerations. Methods. In a hip fracture experiment, nine pairs of human cadaver femurs
were tested in a paired study design. The femurs were then re-matched
according to BMD, creating two new test groups. Intra-pair variance
and paired correlations in fixation stability were calculated. A
hypothetical power analysis was then performed to explore the required sample
size for the two types of group allocation. . Results. The standard deviation (. sd. ) of the mean paired difference
in fixation stability increased from 2 mm in donor pairs to 5 mm
in BMD-matched pairs. Intra-pair correlation was 0.953 (Pearson’s
r) in donor pairs and non-significant at -0.134 (Pearson’s r) in
BMD-matched pairs. Required sample size to achieve a statistical
power of 0.8 increased from ten pairs using donor pairs to 54 pairs
using BMD-matched pairs. Conclusion. BMD cannot be used to create comparable test groups unless sample
size is increased substantially and paired
Implants in total hip replacement (THR) are associated with different clinical and cost-effectiveness profiles,. We estimate the costs and outcomes for NHS patients in the year after THR associated with implant bearing materials using linked routinely collected data. We linked NJR primary elective THR patients for osteoarthritis to HES and National PROMs. We estimated health care costs, health-related quality of life indices, and revision risks, in the year after primary and revision THRs overall. We used generalised linear models adjusting for patient and hospital characteristics and estimated 10-year cumulative probability of revision. We imputed utilities using chained equations for half the sample with missing PROMS. We linked 577,973 elective primary THRs and 11,812 subsequent revisions. One year after primary THR, patients with the cemented THRs using cobalt chrome or stainless steel head with HCLPE liner/cup cost the NHS, on average, £13,101 (95%CI £13,080,£13,122), had an average quality-of-life score of 0.788 (95%CI 0.787,0.788), and a 10-year revision probability of 1.9% (95%CI 1.6,2.3). Compared to the reference, patients receiving a cemented THR with delta ceramic head and HCLPE liner/cup, hybrid THR with delta ceramic head and HCLPE liner/cup, and hybrid THR with alumina head and HCLPE liner/cup had lower 1-year costs (-£572 \[95% CI -£775,-£385\], -£346 \[-£501,-£192\], -£371 \[-£574,-£168\] respectively), better quality of life (0.007 \[95% CI 0.003,0.011\], 0.013 \[0.010,0.016\], 0.009 \[0.005,0.013\] respectively), and lower 10-year revision probabilities (1.4% \[1.03,2.0\], 1.5 \[1.3,1.7\], 1.6%\[1.2,2.1\] respectively). Implant bearing materials are associated with varying mean costs and health outcomes after primary THR. Ours is the first study to derive costs and health outcomes from large, linked databases using multiple imputation methods to deal with bias. Our findings are useful for commissioning and procurement decisions and to inform a subsequent cost-effectiveness model with more granular detail on THR implant types.
Hip and knee joint replacement is nowadays one of the most common surgeries in Germany. The frequency of peri- and post-operative complications varies depending on the study. Since 2001, every hospital in Germany is required to report any peri- and post-operative complication to an external institute for quality control. The purpose of this study was to evaluate the published data of these institutes and to differentiate between the rate of peri- and early postoperative complications of conventional and computer navigated surgical procedures. The hypothesis of the study was that there is no increase in the rate of peri- and early post-operative complications as a result of the navigated surgical procedure. A retrospective analysis of the data on primary total knee and hip replacements between 2004 and 2012 were conducted. The share of navigated procedures, additional operating time due to navigation, the peri- and early post-operative surgical and general rates of complications and the comparison of patient population (age, sex and ASA-classification) were subject of the analysis.Introduction
Materials and Methods
The Kaplan-Meier estimation is widely used in orthopedics to
calculate the probability of revision surgery. Using data from a
long-term follow-up study, we aimed to assess the amount of bias
introduced by the Kaplan-Meier estimator in a competing risk setting. We describe both the Kaplan-Meier estimator and the competing
risk model, and explain why the competing risk model is a more appropriate
approach to estimate the probability of revision surgery when patients
die in a hip revision surgery cohort. In our study, a total of 62 acetabular
revisions were performed. After a mean of 25 years, no patients
were lost to follow-up, 13 patients had undergone revision surgery
and 33 patients died of causes unrelated to their hip.Objectives
Methods
Currently implemented accuracy metrics in open-source libraries for segmentation by supervised machine learning are typically one-dimensional scores [1]. While extremely relevant to evaluate applicability in clinics, anatomical location of segmentation errors is often neglected. This study aims to include the three-dimensional (3D) spatial information in the development of a novel framework for segmentation accuracy evaluation and comparison between different methods. Predicted and ground truth (manually segmented) segmentation masks are meshed into 3D surfaces. A template mesh of the same anatomical structure is then registered to all ground truth 3D surfaces. This ensures all surface points on the ground truth meshes to be in the same anatomically homologous order. Next, point-wise surface deviations between the registered ground truth mesh and the meshed segmentation prediction are calculated and allow for color plotting of point-wise descriptive
Aims. The aims of this study were to assess quality of life after hip fractures, to characterize respondents to patient-reported outcome measures (PROMs), and to describe the recovery trajectory of hip fracture patients. Methods. Data on 35,206 hip fractures (2014 to 2018; 67.2% female) in the Norwegian Hip Fracture Register were linked to data from the Norwegian Patient Registry and
