Kinematic alignment in total knee arthroplasty

Kinematic alignment (KA) is an alternative philosophy for aligning a total knee replacement (TKR) which aims to restore all three kinematic axes of the native knee.

Many of the studies on KA have actually described non-KA techniques, which has led to much confusion about what actually fits the definition of KA.

Alignment should only be measured using three-dimensional cross-sectional imaging. Many of the studies looking at the influence of implants/limb alignment on total knee arthroplasty outcomes are of limited value because of the use of two-dimensional imaging to measure alignment, potentially leading to inaccuracy.

No studies have shown KA to be associated with higher complication rates or with worse implant survival; and the clinical outcomes following KA tend to be at least as good as mechanical alignment.

Further high-quality multi-centre randomized controlled trials are needed to establish whether KA provides better function and without adversely impacting implant survival.

Cite this article: EFORT Open Rev 2020;5:380-390. DOI: 10.1302/2058-5241.5.200010

Can the surgical checklist reduce the risk of wrong site surgery in orthopaedics?--Can the checklist help? Supporting evidence from analysis of a national patient incident reporting system

BACKGROUND

Surgical procedures are now very common, with estimates ranging from 4% of the general population having an operation per annum in economically-developing countries; this rising to 8% in economically-developed countries. Whilst these surgical procedures typically result in considerable improvements to health outcomes, it is increasingly appreciated that surgery is a high risk industry. Tools developed in the aviation industry are beginning to be used to minimise the risk of errors in surgery. One such tool is the World Health Organization's (WHO) surgery checklist. The National Patient Safety Agency (NPSA) manages the largest database of patient safety incidents (PSIs) in the world, already having received over three million reports of episodes of care that could or did result in iatrogenic harm. The aim of this study was to estimate how many incidents of wrong site surgery in orthopaedics that have been reported to the NPSA could have been prevented by the WHO surgical checklist.

METHODS

The National Reporting and Learning Service (NRLS) database was searched between 1st January 2008- 31st December 2008 to identify all incidents classified as wrong site surgery in orthopaedics. These incidents were broken down into the different types of wrong site surgery. A Likert-scale from 1-5 was used to assess the preventability of these cases if the checklist was used.

RESULTS

133/316 (42%) incidents satisfied the inclusion criteria. A large proportion of cases, 183/316 were misclassified. Furthermore, there were fewer cases of actual harm [9% (12/133)] versus 'near-misses' [121/133 (91%)]. Subsequent analysis revealed a smaller proportion of 'near-misses' being prevented by the checklist than the proportion of incidents that resulted in actual harm; 18/121 [14.9% (95% CI 8.5-21.2%)] versus 10/12 [83.3% (95%CI 62.2-104.4%)] respectively. Summatively, the checklist could have been prevented 28/133 [21.1% (95%CI 14.1-28.0%)] patient safety incidents.

DISCUSSION

Orthopaedic surgery is a high volume specialty with major technical complexity in terms of equipment demands and staff training and familiarity. There is therefore an increased propensity for errors to occur. Wrong-site surgery still occurs in this specialty and is a potentially devastating situation for both the patient and surgeon. Despite the limitations of inclusion and reporting bias, our study highlights the need to match technical precision with patient safety. Tools such as the WHO surgical checklist can help us to achieve this.

Internal construct validity of the Oxford Knee Scale: evidence from Rasch measurement

OBJECTIVE

Symptomatic knee osteoarthritis (OA) is present in 1 in 8 patients age >60 years and is associated with significant activity limitation. Several tools have been devised to assess knee problems. The goal of this study was to evaluate the Oxford Knee Scale (OKS) against strict modern psychometric standards through application of the Rasch measurement model.

METHODS

A total of 224 OKS assessments were included from patients with a clinical diagnosis of knee OA. Data from the OKS were fitted to the Rasch measurement model. We examined the validity of the item scoring functions, the presence of item bias or differential item functioning, the fit of data to model expectations, and whether or not the item set formed a unidimensional scale, thus giving a valid summed score.

RESULTS

The mean age of the 224 patients was 61 years (range 26-90) and 61.5% were women. After rescoring some items, the scale showed good fit to the Rasch model, with a chi-square interaction statistic of 42.663 (36 df, P = 0.206). Overall targeting of the scale (to the patients) was good, with high reliability.

CONCLUSION

Data from the OKS were consistent with the expectations of the unrestricted (partial credit) derivation of the Rasch model. The targeting of the instrument shows good coverage of thresholds across the whole construct and has good reliability (internal consistency) with a high patient separation. Consequently, this scale can be used in confidence with the knowledge that it is a unidimensional scale largely free of bias.

Issues relating to long-term follow-up in hip arthroplasty surgery: a review of 598 cases at 7 years comparing 2 prostheses using revision rates, survival analysis, and patient-based measures

We reviewed 598 cemented Charnley and Hi-nek total hip arthroplasties at 7 years. Data were obtained from general practitioners, hospital medical notes, microfilm, and patient questionnaires. Outcome measures were revision rates, survival analysis, 12-item Oxford Hip Score, and satisfaction ratings. There were 471 Charnley (79%) and 127 Hi-nek (21%) total hip arthroplasties; 139 deaths (23%) occurred, and 5 (<1%) were lost to follow-up. Characteristics of the Charnley and Hi-nek patient groups were similar, with more information missing for Charnley cases. Revision rates were Charnley, 37 (8%), and Hi-nek, 6 (5%) (not significant). Survival analysis revealed no difference between the 2 groups (P = .23). The patients' median Oxford Hip Score was low/good (19), slightly worse for the Hi-nek group (not significant). Taking all evidence together, neither implant was outperforming the other at 7 years.

Primary human osteoblast proliferation and prostaglandin E2 release in response to mechanical strain in vitro

The application of mechanical loads to bone cells in vitro has been found to generate variable responses, which may in part be due to the source of the cell used and the characteristics of the strain applied. The aim of this study was to establish a system for applying well-defined physiological levels of mechanical strain to a well-defined population of human osteoblast-like cells. Human bone-derived cells obtained from the greater trochanter of the femur during total hip arthroplasty for osteoarthritis were cultured in the presence of 10 nmol/L dexamethasone and 100 mumol/L L-ascorbate-2-phosphate. Replicates of cells from each patient were loaded on separate occasions using controlled cyclical strains of 4000 microstrain (mu epsilon) or less. Strain gauges recorded reliable, reproducible strains between 1000 and 6000 mu epsilon. To establish reproducibility, sequential explant cultures derived from two patients were studied. A consistent increase (p < 0.05) in proliferation between replicates and explants derived from one patient subjected to 1600 mu epsilon on separate occasions was observed. Cells derived from sequential explants of the second patient showed no consistent increase in proliferation between replicates and explants. Three of six patients showed a significant increase (p < 0.05) in PGE2 production after 5 h in response to stretch (4000 mu epsilon) in all replicates on separate occasions, whereas, in the other three populations of cells, no increase in PGE2 was measured in any of the replicates. These results show that the application of highly controlled strains causes a significant effect on human bone cells, but only in a proportion of subjects. The response is consistent between sequential explants derived from the same patient. The implications of this study are that human osteoblast-like cells do respond to physiological strain in vitro, although some cells are more strain sensitive than others.

Total hip replacement in renal transplant patients

Of 1197 renal transplant recipients on the Oxford Transplant Programme, 25 (2%) needed arthroplasties for painful osteonecrosis of the hip. Nine of them had bilateral operations, giving a total of 34 primary total hip replacements (THR). The mean time from onset of symptoms to THR was 2.4 years and from transplantation to THR 5.1 years. The mean follow-up was 5.1 (1 to 14) years. THR relieved the pain in all the patients, but survival analysis indicated a lower survival rate than is usual for primary THR. There were eight major complications. One graft-related problem, early acute tubular necrosis, resolved rapidly after immediate treatment. One patient developed deep infection at 3.5 years after THR which settled with conservative treatment. Five hips developed aseptic loosening requiring revision arthroplasty at a mean of 8.8 years' follow-up. One patient had a non-fatal pulmonary embolism. THR is the treatment of choice for patients with painful osteonecrosis of the hip after renal transplant, but has higher rates of both early and late complications. Surgery should be performed in close association with a renal transplant unit.