The Cost Effectiveness of Unicompartmental versus Total Knee Arthroplasty.

This study examines the potential cost savings for the health system and the community in a broadly accessible model through the increased utilization of unicompartmental knee arthroplasty (UKA) using robotic arm-assisted UKA (raUKA) versus conventional total knee arthroplasty (cTKA). We retrospectively reviewed 240 patients where the first 120 consecutive raUKA performed during this period were matched to 120 cTKAs. Clinical data from the medical records and costs for procedure for each component were collected. Bivariate analyses were performed on the data to determine if there were statistically significant differences by surgery type in clinical outcomes and financial costs. There was a significantly lower cost incurred for raUKA versus cTKA with an average saving of AU$7,179 per case. The operating time (86.0 vs. 75.9 minutes; p = 0.004) was significantly higher for raUKA, but the length of stay was significantly lower (1.8 vs. 4.8 days; p < 0.001). There was a significant difference in the use of opioids between raUKA and cTKA (125.0 morphine equivalent [ME] vs. 522.1 ME, p < 0.001). This study demonstrated that the use of raUKA rather than cTKA in suitably indicated patients may realize significant cost savings.

Hemiarthroplasty vs Total Hip Arthroplasty for the Management of Displaced Neck of Femur Fractures: A Systematic Review and Meta-Analysis.

BACKGROUND: Displaced femoral neck fractures (DFNF) are common and can be treated with osteosynthesis, hemiarthroplasty (HA), or total hip arthroplasty (THA). There is no consensus as to which intervention is superior in managing DFNF. METHODS: Studies were identified through a systematic search of the MEDLINE database, EMBASE database, and Cochrane Controlled Trials. Included studies were randomized or controlled trials (1966 to August 2018) comparing THA with HA for the management of DFNF. (https://www.crd.york.ac.uk/PROSPERO Identifier: CRD42018110057). RESULTS: Seventeen studies were included totaling 1364 patients (660 THA and 704 HA). THA was found to be superior to HA in terms of risk of reoperation, Harris Hip Score and Quality of Life (Short Form 36). Overall, the risk of dislocation was greater in THA group than HA in the first 4 years, after which there was no difference. There was no difference between THA and HA in terms of mortality or infection. CONCLUSION: Overall, THA appears to be superior to HA. THA should be the recommended intervention for DFNF in patients with a life expectancy >4 years and in patients younger than 80 years. However, both HA and THA are reasonable interventions in patients older than 80 years and with shorter life expectancy.

Impact of Image-Derived Instrumentation on Total Knee Arthroplasty Revision Rates: An Analysis of 83,823 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: Computer navigation and image-derived instrumentation (IDI) are technology-based methods developed to improve outcomes and potentially reduce revision total knee arthroplasty (TKA). IDI refers to the use of manufactured, patient-specific surgical jigs. Conflicting reports exist on IDI-associated improvements in outcomes. The primary aim of the current study was to compare the rates of revision among TKA cases in which components were initially implanted with use of IDI, computer navigation, or neither of these methods ("other" TKA). The secondary aim was to determine whether the outcomes of IDI differed for specific subgroups. METHODS: Data were obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for the 3 TKA groups: IDI, computer-navigated, and other TKA. The study period was from the first IDI procedure recorded by the AOANJRR (April 2010) to December 31, 2016. The analysis was restricted to primary TKA cases undertaken for osteoarthritis and involving patellar resurfacing and the use of a cross-linked polyethylene insert. Subanalyses were performed to evaluate the effects of age, sex, implantation method, IDI manufacturer, prosthetic design, and prosthesis type on the rates of revision. Kaplan-Meier estimates of survivorship described the time to first revision. Hazard ratios (HRs, Cox proportional hazards models) with adjustment for age and sex were used to compare revision rates. RESULTS: IDI was used in 5,486 primary TKA procedures. There was no significant difference among the groups in the cumulative percent revision (CPR) at 5 years: 3.3% (95% confidence interval [CI], 2.4% to 4.6%) for IDI, 2.4% (95% CI, 2.2% to 2.7%) for the computer-navigated group, and 2.5% (95% CI, 2.3% to 2.7%) for other TKA. Posterior-stabilized TKA with use of the IDI method had a significantly higher rate of revision at >3 months (HR, 1.45 [95% CI, 1.02 to 2.04]; p = 0.036), as did IDI TKA in the ≤65-year-old patient cohort (HR, 1.52 [95% CI, 1.10 to 2.09]; p = 0.010), compared with computer-navigated TKA. Patellar revision was significantly more likely in the IDI group. CONCLUSIONS: IDI TKA demonstrated no overall difference in early to mid-term revision rates compared with standard implantation methods. However, elevated rates of revision were seen with posterior-stabilized TKA, in patients ≤65 years of age, and for patellar revision, meaning that this method should be used with some caution and requires further study. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Complications related to therapeutic anticoagulation in total hip arthroplasty.

Bleeding-related wound complications cause significant morbidity in lower limb arthroplasty surgery. Patients who require therapeutic anticoagulation in the perioperative period are potentially at higher risk for these complications. This is a retrospective case-control study reviewing all primary total hip arthroplasties performed in a single center during a 5-year period and comparing outcomes of the patients on warfarin with a double-matched control group of patients not on warfarin. The warfarin group had a significantly higher risk of deep joint infection (9% vs 2.2%), hematoma/wound ooze (28% vs 4%), and superficial infection (13.5% vs 2.2%). Managing patients undergoing total hip arthroplasty with therapeutic anticoagulation is a balance between the risk of thromboembolic disease and bleeding-related complications. Improved understanding of this risk will better allow patients to make an informed decision regarding their elective arthroplasty surgery.

Is there a need for routine follow-up after primary total hip arthroplasty?

BACKGROUND: The objective of routine outpatient assessment of well-functioning patients after primary total hip arthroplasty (THA) is to detect asymptomatic failure of prostheses to guide recommendations for early intervention. We have observed that the revision of THAs in asymptomatic patients is highly uncommon. We therefore question the need for routine follow-up of patients after THA. METHODS: A prospective analysis of an orthopaedic database identified 158 patients who received 177 revision THAs over a four-year period. A retrospective chart review was conducted. Patient demographics, primary and revision surgery parameters and follow-up information were recorded and cross-referenced with Australian Orthopaedic Association National Joint Replacement Registry data. RESULTS: One hundred ten THAs in 104 patients (average age 70.4 (SD 9.8 years)). There were 70 (63.6%) in total, 13 (11.8%) femoral and 27 (24.5%) acetabular revisions. The indications for revision were aseptic loosening (70%), dislocation (8.2%), peri-prosthetic fracture (7.3%), osteolysis (6.4%) and infection (4.5%). Only four (3.6%) were asymptomatic revisions. A mean of 5.3 (SD 5.2 and 1.9 (SD 5.3)) follow-up appointments were required before revision in patients with and without symptoms, respectively. The average time from the primary to revision surgery was 11.8 (SD 7.23) years. CONCLUSIONS: We conclude that patients with prostheses with excellent long-term clinical results as validated by joint registries, routine follow-up of asymptomatic THA should be questioned and requires further investigation. Based on the work of this study, the current practice of routine follow-up of asymptomatic THA may be excessively costly and unnecessary, and a less resource-intensive review method may be more appropriate.

Saccadic lens instability increases with accommodative stimulus in presbyopes.

An SRI dual Purkinje image (dPi) eye tracker was used to measure lens wobble following saccades with increasing accommodative effort as an indirect measure of ciliary muscle function in presbyopes. Ten presbyopic subjects executed 32 four-degree saccades at 1-s intervals between targets arranged in a cross on illuminated cards at each of 9 viewing distances ranging from 0.5- to 8-D accommodative demands. Post-saccadic lens wobble artifacts were extracted by subtraction of P1 (H(1)/V(1)) position signals from P4 signals (Theta(H)/Theta(V)), both of which were sampled by the eye tracker at 100 Hz. A ray tracing eye model was also employed to model the fourth Purkinje image shifts for a range of lens translations and tilts. Combining all saccades from all subjects showed a significant positive relationship between lens wobble artifact amplitude and accommodative demand. Eye model simulations indicated that artifacts of the amplitude measured could arise from either lens tilts (in the range of 2-4 degrees) or lens translations (in the range of 0.1 to 0.2 mm). Saccadic lens wobble artifacts increase with accommodative effort in presbyopes, indicating preserved ciliary muscle function and greater relaxation of zonular tension with accommodative effort. Variation across subjects may reflect differences in accommodative effort, ciliary muscle function for a given effort, and/or in intraocular anatomy.

Comparison of cemented vs uncemented acetabular component positioning using an imageless navigation system.

Hip navigation was used as an assessment tool to compare ability to reproduce trial and definitive acetabular placement in total hip arthroplasty, using cemented and uncemented components. We demonstrated a significant difference in reproducibility between components. Of 20 uncemented cups, 4 (20%) deviated from the target inclination by 5 degrees or more compared to none of 21 in the cemented group (P = .048). Of the 20 uncemented cups, 7 (35%) deviated from the target version by 5 degrees or more compared to none of 21 in the cemented group (P = .003). This may explain higher rates of revision for dislocation with uncemented components. There was also a significant difference between the groups with regard to deviation from planned leg length (P < .001).

Uncorrected wavefront error and visual performance during RGP wear in keratoconus.

PURPOSE: To examine the relationship between uncorrected residual wavefront error and visual performance (VP) in rigid gas permeable (RGP) contact lens-wearing keratoconic eyes. METHODS: Seven eyes from six subjects (six moderate, one severe) were studied (mean +/- SD age: 42.71 +/- 11.38 years). Significant corneal scarring was an exclusion criterion. Measurements were taken with RGP lenses in place. After pupil dilation, the VP measures of high contrast logMAR visual acuity (VA) and Pelli-Robson contrast sensitivity (PRCS) were measured through a 5-mm artificial pupil. Wavefront error was measured using a Shack-Hartmann wavefront sensor and calculated over 5 mm. For both VP and wavefront error, comparisons were made to previously collected normal values by calculating the interval encompassing 95% of normals, then reporting how many of the seven keratoconic eyes fell outside the normal interval. Additionally, second to sixth order aberrations were processed into four previously reported image quality metrics: root mean square of the wavefront (RMSw), root mean square of the slope (RMSs), average blur strength (Bave) and diameter containing 50% light energy (D50) and regressed against VP measures. RESULTS: Five of seven keratoconic eyes fell outside the normal interval (-0.23 to 0.09) for VA and two of seven fell outside the normal interval (1.59 to 2.03) for PRCS. Five of seven keratoconic eyes fell outside the normal interval (0.07 to 0.35 microm) for total higher order RMS. Linear regressions demonstrated relationships between both VA and PRCS and the image quality metrics RMSw, D50, RMSs, and Bave with R values for VA = 0.30, 0.30, 0.47, 0.62, and PRCS = 0.21, 0.15, 0.45, 0.75 respectively. CONCLUSIONS: VP in RGP-wearing keratoconic eyes is reduced and higher order wavefront aberrations are elevated compared to normals. Metrics of retinal image quality demonstrate a relationship between keratoconic VP and residual wavefront aberrations. This relationship suggests developing corrections that more completely correct aberrations may improve visual performance in keratoconus.

Three-dimensional relationship between high-order root-mean-square wavefront error, pupil diameter, and aging.

We report root-mean-square (RMS) wavefront error (WFE) for individual aberrations and cumulative high-order (HO) RMS WFE for the normal human eye as a function of age by decade and pupil diameter in 1 mm steps from 3 to 7 mm and determine the relationship among HO RMS WFE, mean age for each decade of life, and luminance for physiologic pupil diameters. Subjects included 146 healthy individuals from 20 to 80 years of age. Ocular aberration was measured on the preferred eye of each subject (for a total of 146 eyes through dilated pupils; computed for 3, 4, 5, 6, and 7 mm pupils; and described with a tenth-radial-order normalized Zernike expansion. We found that HO RMS WFE increases faster with increasing pupil diameter for any given age and pupil diameter than it does with increasing age alone. A planar function accounts for 99% of the variance in the 3-D space defined by mean log HO RMS WFE, mean age for each decade of life, and pupil diameter. When physiologic pupil diameters are used to estimate HO RMS WFE as a function of luminance and age, at low luminance (9 cd/m2) HO RMS WFE decreases with increasing age. This normative data set details (1) the 3-D relationship between HO RMS WFE and age for fixed pupil diameters and (2) the 3-D relationship among HO RMS WFE, age, and luminance for physiologic pupil diameters.

Influence of exposure time and pupil size on a Shack-Hartmann metric of forward scatter.

PURPOSE: To determine the influence of exposure time and pupil size on a Shack-Hartmann (S/H) derived metric of forward scatter (MAX_SD) using a physical model of nuclear cataract. METHODS: A physical model eye was developed and mounted to a S/H wavefront sensor. The eye model consisted of a lens, variable pupil, simulated cataract, and retina. Located behind the pupil, a cuvette contained one of five polystyrene microsphere solutions simulating five levels of nuclear cataract severity. Cataract severity was described using a S/H derived metric of forward scatter (MAX SD), which measures aspects of forward scatter contained in the S/H lenslet point spread functions (PSF). To determine the impact of exposure time and pupil size, measurements of MAX_SD were regressed against cataract severity for three different exposure times and three different pupil sizes. RESULTS: MAX_SD was well correlated to cataract severity. Exposure time had the largest influence, and pupil size had the smallest influence on the forward scatter metric. When pupil size and exposure time were allowed to vary and image saturation was allowed to occur, MAX SD explained 83% of the variance in cataract severity. Excluding images where saturation occurred, holding optimal exposure time constant, and varying pupil size, MAX_SD explained 97% of the variance in cataract severity. CONCLUSIONS: The ability of the forward scatter metric derived from S/H measurements to predict cataract severity for a longitudinal study is optimized by selecting a patient-specific exposure at the initial cataract assessment to avoid saturation and maximize the dynamic range of the system. This patient-specific exposure should be used in all future visits.

Viewpoint: patient-centered medical care requires a patient-centered medical record.

If patient-centered medicine is to become a widespread reality in academic medical centers, educational initiatives must include reform of the medical record. The medical record is part of the hidden, or informal, curriculum of medical school and residency that defines for students and residents the essential ingredients of competent medical care. Whatever its merits, the conventional, problem-oriented medical record (POMR) is a pathology-oriented record that helps perpetuate a disease-focused, biomedical model of practice Patient-centered medicine requires a patient-centered medical record (PCMR), one that addresses the person and perspective of the patient as competently as it addresses the patient's disease. The author proposes a PCMR that includes a concise, upfront Patient Profile; speaks of "chief concerns," not "chief complaints"; makes Patient Perspective a captioned component of the History of Present Illness; replaces the POMR's formula SOAP (Subjective, Objective, Assessment, Plan) with HOAP (History, Observations, Assessment, Plan); includes important patient perspectives on the Problem List; and calls for additional, written attention to the person and perspective of the patient throughout the course of medical care Patient-centered records can guide and teach clinicians at every level of training and experience to practice patient-centered medicine. Moreover, such records can also provide measurable evidence that this teaching has been successful.

Quantifying scatter in Shack-Hartmann images to evaluate nuclear cataract.

PURPOSE: Quantify and localize lenticular forward scatter using Shack-Hartmann wavefront sensing (SHWS) as single-valued metrics and a scatter map, and to examine the relationships between forward scatter and backscatter metrics and visual acuity. METHODS: We obtained SHWS images from 148 patients in the Texas Investigation of Cataract Optics study. Patient age was 22 to 84 years, with Lens Opacities Classification System III (LOCS III) nuclear opalescence (NO) scores ranging from 0.8 to 5.6. Visual acuities were measured at photopic (280 cd/m2) high (VA(PHC)) and low contrast (VA(PLC)) and mesopic (0.75 cd/m2) high (VA(MHC)) and low contrast (VA(MLC)). Scattering was described in a scatter map and by five single-valued metrics characterizing SHWS lenslet point spread functions. The relationships between scatter and visual acuity were tested using linear regression. RESULTS: Visual acuities decreased proportional to both LOCS III NO (R2=up to 39%) and scatter metrics (R2=up to 21%). Stepwise multiple linear regression improved visual acuity prediction by including a backscatter and a forward scatter metric (R2 up to 51.2%). For the subjects over age 60 years (N=46, 68.8+/-6.12 years), the forward scatter metrics explain as much variance in visual acuities (R2=up to 29%) as LOCS III NO (R2=up to 26%). Combined they accounted for up to 48.8% of visual acuity variance. CONCLUSION: Forward light scatter can be quantified using SHWS and the resulting metrics explain significant variance in visual acuity, especially in the aging eye. Together with a backscatter metric they explain approximately 50% of the variance in VA.

Measuring visual acuity--mesopic or photopic conditions, and high or low contrast letters?

PURPOSE: To develop single-valued wavefront aberration metrics that correlate strongly with visual performance. The purpose of this study is to explore whether photopic high contrast visual acuity (VA) is an appropriate visual performance reference and whether mesopic and/or low contrast testing provides any advantage. METHODS: Subjects from the Texas Investigation of Cataract Optics study (N = 148) ranged in age from 21.6 to 83.8 years and from clear lens to dense nuclear cataract. Visual acuity was measured under four conditions: photopic high (VA(PHC)) and low (VA(PLC)) contrast, mesopic high (VA(MHC)) and low (VA(MLC)) contrast (photopic = 280 cd/m(2), mesopic = 0.75 cd/m(2)). Variables were tested for compliance with normality (-2.00 < skew and kurtosis < 2.00) and transformed if required. Linear regression and Bland-Altman 95% limits of agreement (+/-1.96 SD) were used to examine relationships between VA variables and between VA and wavefront aberration metrics. RESULTS: The two photopic measures VA(PHC) (skew = 2.57, kurtosis = 12.2) and VA(PLC) (1.67, 5.41) were poorly distributed, but the two mesopic measures VA(MHC) (0.88, 1.67) and VA(MLC) (0.29, -0.18) were normally distributed. Strong correlations existed between the (transformed) VA variables (R: 0.53 to 0.84). However, limits of agreement ranged over 0.30 to 0.42 logMAR, whereas retest data suggested a range of 0.15. All four were offered in stepwise multiple linear regression for 30 wavefront metrics: 20 included VA(MLC) alone, two included VA(PLC), two included VA(MHC) and six included both VA(MLC) and VA(MHC); R(2) averaged 25%. CONCLUSION: Although strongly correlated, low contrast and/or mesopic VA testing provides different information. Wave aberration metrics correlates better with VA(MLC) making this the visual performance test of choice.

Optimal pupil size in the human eye for axial resolution.

A computer model that incorporates the monochromatic aberrations of the eye is used to determine the optimal pupil size for axial and lateral resolution as it applies to retinal imaging instruments such as the confocal scanning laser ophthalmoscope. The optimal pupil size for axial resolution, based on the aberrations of 15 subjects, is 4.30 mm +/- 1.19 mm standard deviation (sd), which is larger than that for lateral resolution [2.46 mm +/- 0.66 mm (sd)]. When small confocal pinholes are used, the maximum detected light is obtained with a pupil size of 4.90 mm +/- 1.04 mm sd. It is recommended to use larger pupil sizes in imaging applications where axial resolution is desired.

Automated image analysis technique for measurement of femoral component subsidence in total hip joint replacement.

A new technique for the measurement of subsidence of the femoral components is proposed. The method relies on the implantation of two ball markers around the femoral stem. A single radiographic image of the hip is analysed using image-processing techniques to minimize subjectivity related to manual identification of landmarks. Dimensions of the stem are used to correct for magnification and out-of-plane rotations resulting from radiographic positioning. This technique has been applied to a specific design of implant (Exeter). A study of the effect of radiographic positioning has been conducted using a cadaveric bone phantom. Results for the variation in the measurement of axial migration compared to the neutral position (in millimetres) were: 0.942 (10 degrees extension); 0.347 (20 degrees flexion); -0.435 (40 degrees internal rotation); 0.187 (30 degrees external rotation) for distances measured between the bone marker and the implant. Results for distances measured between the implant and the cement centralizer were: 0.107 (10 degrees extension); -0.277 (20 degrees flexion); 0.085 (40 degrees internal rotation); 0.280 (30 degrees external rotation). The variations from within a more realistic range of positions demonstrate that axial migration measurements of ca. 0.5 mm between the bone and implant, and less than 0.3 mm between the implant and the bone cement, may be expected.