The final follow-up plain radiograph is sufficient for clinical evaluation of polyethylene wear in total hip arthroplasty: A study of validity and reliability

Background and purpose

Radiostereometric analysis (RSA) is a highly accurate tool for assessment of polyethylene (PE) wear in total hip arthroplasty (THA); however, PE wear measurements in clinical studies are often limited to plain radiographs. We evaluated the agreement between PE wear measured with PolyWare software, which uses plain radiographs, and by model-based RSA, which uses stereo radiographs.

Methods

Measurements of PE wear postoperatively and at final follow-up (after mean 6 years) on plain radiographs of 12 patients after cementless THA were evaluated with PolyWare software and the results were compared with those from RSA as the gold standard (Model-based RSA using elementary geometrical shape models; EGS-RSA). With PolyWare, we either used the final radiographic follow-up (PW1) only or both the postoperative follow-up and the final follow-up (PW2).

Results

The 2D mean wear measured (in mm) was 0.80, 1.07, and 0.60 for the PW2, PW1, and RSA method. 2D intra-method repeatability was similar for PW1 and RSA with limits of agreement (LOAs, in mm) of ± 0.22, and ± 0.23, respectively. 2D inter-method concurrent validity was best between PW1 and EGS-RSA with LOAs of ± 0.55. For 2D linear wear measurements, the PW1 method had a clinical repeatability similar to that of RSA.

Interpretation

PW1 is sufficient for retrospective determination of 2D wear from medium-term wear measurements above 0.5 mm, It alleviates the need for baseline plain radiographs, has a clinical precision similar to that of RSA, and is easy and inexpensive to use.Wear of polyethylene (PE) components is widely regarded as the main factor limiting longevity of total hip arthroplasty (THA) (Cooper et al. 1992). Clinical studies have shown that periprosthetic osteolysis and aseptic loosening is strongly related to wear rates of above 0.2 mm/year (Sochart 1999, Dowd et al. 2000).Radiostereometric analysis (RSA) is the most accurate tool for in vivo assessment of PE wear (Kärrholm et al. 1997, von Schewelov et al. 2004, Bragdon et al. 2006), and it is regarded as the gold standard (Ilchmann et al. 1995). However, many radiographic in vivo studies of PE wear in THA are restricted to measurements on plain radiographs because the RSA set-up is expensive and not widely available. Measurement of PE wear on plain radiographs is often limited to 2D analysis because poor quality of cross-table lateral radiographs is a common problem (Sychterz et al. 1999b, 2001). Although PE wear is known to occur multidirectionally (Yamaguchi et al. 1997, Akisue et al. 1999), the bulk of the wear is detectable on the anterior-posterior radiographs alone (Sychterz et al. 1997, Hui et al. 2003, Martell et al. 2003). Based on the availability of radiographs and investigator preferences, some authors favor analysis of serial radiographs (Sychterz et al. 1997, Kim et al. 2001, Hernigou and Bahrami 2003) to describe the pattern of wear and the steady-state wear (Sychterz et al. 1999a, Bragdon et al. 2006), whereas others use 2 radiographic follow-ups (postoperative and latest) (Kraay et al. 2006), or only the latest radiographic follow-up with the assumption of zero wear at baseline (Norton et al. 2002)Little is known about the conformity between PE wear results measured with RSA and computerized methods using plain radiographs (Ilchmann et al. 1995, von Schewelov et al. 2004, Bragdon et al. 2006). Our group has questioned the conformity of 2D PE wear measurements based on serial, 2, or 1 radiographic follow-up (Stilling et al. 2009b). We determined that there was a statistically significant difference between all approaches, but we were unable to determine which strategy best reflected the true extent of wear (Stilling et al. 2009b). In addition, we recently showed that model-based RSA is an accurate tool for measurement of PE wear in good agreement with the true wear (Stilling 2009).We have now studied the intra-method repeatability and concurrent validity between 2 methods (PolyWare and EGS-RSA) for measurement of PE wear in THA, in a group of patients with an average follow-up of 6 years. We wanted to determine (1) whether there would be a difference in repeatability between the methods, (2) whether there would be a difference in wear measured using 1 or 2 radiographic follow-ups with the PolyWare method, and (3) whether either of the 2 PolyWare measurement strategies (1 or 2 radiographic follow-ups) would give results similar to the wear measured by RSA (concurrent validity).     

A Hybrid Algorithm of Event-Driven and Time-Driven Methods for Simulations of Granular Flows

The classical discrete element approach (DEM) based on Newtonian dynamics can be divided into two major groups, event-driven methods (EDM) and time-driven methods (TDM). Generally speaking, TDM simulations are suited for cases with high volume fractions where there are collisions between multiple objects. EDM simulations are suited for cases with low volume fractions from the viewpoint of CPU time. A method combining EDM and TDM called Hybrid Algorithm of event-driven and time-driven methods (HAET) is presented in this paper. The HAET method employs TDM for the areas with high volume fractions and EDM for the remaining areas with low volume fractions. It can decrease the CPU time for simulating granular flows with strongly non-uniform volume fractions. In addition, a modified EDM algorithm using a constant time as the lower time step limit is presented. Finally, an example is presented to demonstrate the hybrid algorithm.     

Surgical treatment of a ruptured giant renal artery aneurysm--case report and literature review

Renal artery aneurysms are the second most common visceral artery aneurysms after splenic artery aneurysms, and before hepatic artery aneurysms. The study presented a case of a ruptured giant right renal artery aneurysm in a female patient. The presented case is worth mentioning, due to the giant size of the lesion. The diameter of the aneurysm exceeded 10 cm. Available literature data mentioned single reports of such large aneurysms located in the renal arteries. In spite of the fact that renal artery aneurysms are the second most common visceral artery aneurysms, their management is accompanied by some controversy. Literature data mentioned the dominance of endovascular techniques. However, surgical treatment remains to be the most effective and radical method.     

Soft-tissue sarcoma of the thigh: Surgical margin influences local recurrence but not survival in 152 patients

Between 1979 and 1998, 152 patients with a soft-tissue sarcoma arising in the thigh were surgically treated in the Sarcoma Center in Aarhus, Denmark. We studied clinicopathologic factors prognostic for local recurrence and survival. 27 patients (18%) had a low-grade tumor, 26 (17%) an intermediate-grade and 99 (65%) a high-grade tumor.

27 patients (18%) were amputated and 125 (82%) had a local resection. 21 (14%) underwent a marginal resection, 82 (54%) a wide resection and 49 (32%) a compartmental resection. 32 patients were also given radiotherapy, 11 of these had a marginal resection.

The 5-year local recurrence-free rate was 91%. Multivariate analysis selected marginal resection and histological high grade as unfavorable prognostic factors for local recurrence. The 5-year survival rate was 68%. High age and histological high grade were unfavorable prognostic factors for survival in a multivariate analysis. Surgical margin influenced local recurrence, but not the overall survival.     

Kinematics of the ligamentous unstable elbow joint after application of a hinged external fixation device: a cadaveric study

We studied the kinematics of 8 ligamentous unstable elbow joint preparations after application of the Orthofix elbow external fixation device. Valgus, varus, external rotatory, and internal rotatory load tests were performed in lateral collateral ligament (LCL)-deficient and LCL/medial collateral ligament (MCL)-deficient joints. After placement of the fixator, the mean extension decreased significantly to 19.5 degrees +/- 7.2 degrees in the LCL-deficient joint and to 19.1 degrees +/- 6.6 degrees in the LCL/MCL-deficient joint compared with the mean extension of the intact joint, which was 10.5 degrees +/- 4.2 degrees. After application of the fixator, valgus displacement was significantly decreased by 4.0 degrees +/- 3.4 degrees in the LCL-deficient joint and by 3.6 degrees +/- 3.3 degrees in the LCL/MCL-deficient joint compared with the intact joint. External rotatory displacement was significantly decreased in the LCL-deficient joint by 4.9 degrees +/- 3.7 degrees and in the LCL/MCL-deficient joint by 5.0 degrees +/- 4.7 degrees. Internal rotatory displacement was significantly decreased by 3.3 degrees +/- 2.7 degrees in the LCL-deficient joint, but it was not significantly changed in the LCL/MCL-deficient joint. The Orthofix elbow external fixator guided elbow motion to a more varus position compared with the intact elbow and decreased the range of motion of the joint, constraining mainly extension. We conclude that the fixator stabilized the ligamentous unstable elbow joint efficiently but at the expense of changes in the normal motion pattern.     

Mechanical restitution curves: a possible load independent assessment of contractile function.

OBJECTIVE: The time constant of mechanical restitution (T((MRC))), proposed to reflect changes in calcium release and uptake, has been shown to increase in left ventricular (LV) failure, and might have a potential as an index of contractile function. However, in vivo studies of the effect on T((MRC)) of changing loading conditions in the normal and failing heart have not been reported. Consequently, in this study, we tested the hypothesis that the increase in T((MRC)) in vivo is independent of preload and afterload. METHODS: Left ventricular pressure-volume loops were assessed at baseline in eight open chest pigs using the combined pressure-volume conductance catheter technique during right atrial pacing at 120b/min. Mechanical restitution curves (MRC) were constructed during four different loading conditions in all eight animals: uninfluenced load, reduced preload (balloon catheter in v. cava inferior), increased afterload (balloon catheter in descending aorta), and increased preload combined with reduced afterload (aortocaval shunting). Acute LV failure was then induced by microembolization through the left main coronary artery, and the experimental protocol was repeated. Contractile response was defined as the maximal first derivative of pressure (dP/dt(max)), and T((MRC)) was calculated using a least square approximation algorithm. RESULTS: Hemodynamic data 30min after microembolization showed decreased mean arterial pressure (98+/-14-67+/-10mmHg, (mean+/-SD) P<0.0001) and dP/dt(max) (1482+/-193-1001+/-125mmHg/s, P=0.001). Stroke volume decreased from 30+/-5 to 20+/-5ml (P<0.0001) compared to baseline, and preload recruitable stroke work decreased from 52+/-7 to 31+/-10mmHg (P=0.002). T((MRC)) increased in all eight animals after induction of LV failure at all loading conditions. There was no difference between the different loading conditions at baseline, nor at LV heart failure, but T((MRC)) increased significantly after the induction of heart failure (ANOVA, two ways). CONCLUSIONS: We have shown that the left ventricular T((MRC)) increases after developed heart failure. The increase in T((MRC)) was independent on loading conditions and thus have a potential for a contractility index.     

SAPS 3 is not superior to SAPS 2 in cardiac surgery patients

Objectives. Cardiac surgery patients are excluded from SAPS2 but included in SAPS3. Neither score is evaluated for this exclusive population; however, they are used daily. We hypothesized that SAPS3 may be superior to SAPS2 in outcome prediction in cardiac surgery patients. Design. All consecutive patients undergoing cardiac surgery between January 2007 and December 2010 were included in our prospective study. Both models were tested with calibration and discrimination statistics. We compared the AUC of the ROC curves by DeLong's method and calculated OCC values. Results. A total of 5207 patients with mean age of 67.2 ± 10.9 years were admitted to the ICU. The mean length of ICU stay was 4.6 ± 7.0 days and the ICU mortality was 5.9%. The two tested models had acceptable discriminatory power (AUC: SAPS2: 0.777–0.875; SAPS3: 0.757–893). SAPS3 had a low AUC and poor calibration on admission day. SAPS2 had poor calibration on Days 1–6 and 8. Conclusions. Despite including cardiac surgery patients, SAPS3 was not superior to SAPS2 in our analysis. In this large cohort of ICU cardiac surgery patients, performance of both SAPS models was generally poor. In this subset of patients, neither scoring system is recommended.     

Preoperative factors associated with red blood cell transfusion in hip fracture patients

Introduction

Red blood cell (RBC) transfusion is a frequently used treatment in patients admitted with a fractured hip, but the use remains an area of much debate. The aim of this study was to determine preoperative factors associated with the risk of receiving a red blood cell transfusion in hip fracture patients.

Method

The study included 986 consecutive hip fracture patients (aged 60 years or above). The patients were identified from a database of all hip fracture patients admitted to Bispebjerg University Hospital. Data for the database are collected via chart review and data extraction from the hospitals laboratory system, public registries and from the Capital Region Blood Bank Database.

Results

Overall transfusion rate was 58.7 %. The univariate analyses showed that transfusion rate was higher among women (p = 0.004), older patients (p < 0.0001), patients with high ASA scores (p < 0.0001), patients with more severe fractures (p < 0.0001), patients with lower admission haemoglobin levels (p < 0.0001), patients not admitted from own home (p = 0.02) and patients taking aspirin (p = 0.007) or other platelet inhibitors (p = 0.01) on admission. In the multivariate analysis, increasing age, ASA ≥3, being admitted from own home, extracapsular fractures, decreasing admission haemoglobin and use of platelet inhibitors were all significantly associated with the risk of receiving a RBC transfusion.

Conclusion

Several readily available preoperative factors in the form of age, residence, ASA, admission haemoglobin, medication and type of fracture were independently associated with the likelihood of receiving a red blood cell transfusion in patients admitted with a fractured hip.     

Superior fixation and less periprosthetic stress-shielding of tibial components with a finned stem versus an I-beam block stem: a randomized RSA and DXA study with minimum 5 years’ follow-up

Background and purpose — The stem on the tibial component of total knee arthroplasty provides mechanical resistance to lift-off, shear forces, and torque. We compared tibial components with finned stems (FS) and I-beam block stems (IS) to assess differences in implant migration.

Patients and methods — In a patient-blinded RCT, 54 patients/knees (15 men) with knee osteoarthritis at a mean age of 77 years (70–90) were randomly allocated to receive tibial components with either a FS (n = 27) or an IS (n = 27). Through 5 to 7 years’ follow-up, implant migration was measured with RSA, periprosthetic bone mineral density (BMD) was measured with DXA, and surgeons reported American Knee Society Score (AKSS).

Results — At minimum 5 years’ follow-up, maximum total point motion (MTPM) was higher (p = 0.04) for IS (1.48?mm, 95% CI 0.81–2.16) than for FS (0.85?mm, CI 0.38–1.32) tibial components. Likewise, total rotation (TR) was higher (p = 0.03) for IS (1.51?, CI 0.78–2.24) than for FS (0.81?, CI 0.36–1.27). Tibial components with IS externally rotated 0.50° (CI –0.06 to 1.06) while FS internally rotated 0.09° (CI –0.20 to 0.38) (p = 0.03). Periprosthetic bone stress-shielding was higher (p < 0.01) up to 2 years’ follow-up for IS compared with FS in the regions medial to the stem (–13% vs. –2%) and posterior to the stem (–13% vs. –2%). Below the stem bone loss was also higher (p = 0.01) for IS compared with FS (–6% vs. +1%) up to 1-year follow-up. Knee score improved similarly in both groups up to 5 years’ follow-up.

Interpretation — Periprosthetic bone stress-shielding medial and posterior to the stem until 2 years, and tibial component migration at 5 years, was less for a finned compared with an I-shaped block stem design.

Trial registration: ClinicalTrials.gov identifier: NCT00175136.