Thierry Scheerlinck

CT analysis of defects of the cement mantle and alignment of the stem IN VITRO COMPARISON OF CHARNLEY-KERBOUL FEMORAL HIP IMPLANTS INSERTED LINE-TO-LINE AND UNDERSIZED IN PAIRED FEMORA

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed. When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

Finite element analysis of the effect of cementing concepts on implant stability and cement fatigue failure

Background and purpose Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the “French paradox”. Furthermore, previous studies have indicated that the type of bone supporting the cement mantle may affect implant survival. To further evaluate the mechanical consequences of variations in cementing technique, we studied the effect of implant size and type of bone supporting the cement mantle on the mechanical performance of cemented total hip arthroplasty, using finite element analysis. Methods In a generic 2-dimensional plane-strain finite element model of a transverse section of a cemented total hip arthroplasty with a Charnley-Kerboull stem, we varied implant size and type of bone supporting the cement mantle. The models were subjected to 2 × 106 cycles of an alternating loading pattern of torque and a transverse load. During this loading history, we simulated cement fatigue crack formation and tracked rotational stability of the implant. Results Canal-filling stems produced fewer cement cracks and less rotation than undersized stems. Cement mantles surrounded by trabecular bone produced more cement cracks and implant rotation than cement mantles surrounded by cortical bone. Interpretation Our investigation provides a possible explanation for the good clinical results obtained with canal-filling Charnley-Kerboull implants. Our findings also indicate that inferior mechanical properties are obtained with these implants if the cement is supported by trabecular bone, which may be minimized by an optimal cementing technique.

Development and validation of an automated and marker-free CT-based spatial analysis method (CTSA) for assessment of femoral hip implant migration In vitro accuracy and precision comparable to that of radiostereometric analysis (RSA)

Background and purpose — We developed a marker-free automated CT-based spatial analysis (CTSA) method to detect stem-bone migration in consecutive CT datasets and assessed the accuracy and precision in vitro. Our aim was to demonstrate that in vitro accuracy and precision of CTSA is comparable to that of radiostereometric analysis (RSA). Material and methods — Stem and bone were segmented in 2 CT datasets and both were registered pairwise. The resulting rigid transformations were compared and transferred to an anatomically sound coordinate system, taking the stem as reference. This resulted in 3 translation parameters and 3 rotation parameters describing the relative amount of stem-bone displacement, and it allowed calculation of the point of maximal stem migration. Accuracy was evaluated in 39 comparisons by imposing known stem migration on a stem-bone model. Precision was estimated in 20 comparisons based on a zero-migration model, and in 5 patients without stem loosening. Results — Limits of the 95% tolerance intervals (TIs) for accuracy did not exceed 0.28 mm for translations and 0.20° for rotations (largest standard deviation of the signed error (SDSE): 0.081 mm and 0.057°). In vitro, limits of the 95% TI for precision in a clinically relevant setting (8 comparisons) were below 0.09 mm and 0.14° (largest SDSE: 0.012 mm and 0.020°). In patients, the precision was lower, but acceptable, and dependent on CT scan resolution. Interpretation — CTSA allows detection of stem-bone migration with an accuracy and precision comparable to that of RSA. It could be valuable for evaluation of subtle stem loosening in clinical practice.

Fractures of the Upper Tibia and Arthroscopic Techniques

Treatment and outcome of fractures of the upper part of the tibia are related to fracture type and associated lesions. An accurate anatomic reduction as well as a stable fixation allowing early mobilization are prerequisites for a successful result. Due to the high complication rate associated with open surgery for fractures of the tibial plateau, percutaneous techniques have become increasingly popular. Associated with fluoroscopy, arthroscopy has become a precious tool for diagnosis and fracture reduction over the past 15 years. Meanwhile, minimally invasive osteosynthesis techniques have evolved progressively. Concomitant use of external fixation has widened indications to less stable or bicondylar fractures, although severely comminuted and complex fractures in younger patients seem best suited to open treatment. The different techniques, advantages, and disadvantages as well as limitations, risks, and results of arthroscopy-guided percutaneous treatment are reviewed. The good short-term results obtained by pioneers were later confirmed in larger series. Midterm clinical and radiologic studies have demonstrated the stability of the results at more than 5 years.

Automated Estimation of Hip Prosthesis Migration: a Feasibility Study

A common complication associated with hip arthoplasty is prosthesis migration, and for most cemented components a migration greater than 0.85 mm within the first six months after surgery, are an indicator for prosthesis failure. Currently, prosthesis migration is evaluated using X-ray images, which can only reliably estimate migrations larger than 5 mm. We propose an automated method for estimating prosthesis migration more accurately, using CT images and image registration techniques. We report on the results obtained using an experimental set-up, in which a metal prosthesis can be translated and rotated with respect to a cadaver femur, over distances and angles applied using a combination of positioning stages. Images are first preprocessed to reduce artefacts. Bone and prosthesis are extracted using consecutive thresholding and morphological operations. Two registrations are performed, one aligning the bones and the other aligning the prostheses. The migration is estimated as the difference between the found transformations. We use a robust, multi-resolution, stochastic optimization approach, and compare the mean squared intensity differences (MS) to mutual information (MI). 30 high-resolution helical CT scans were acquired for prosthesis translations ranging from 0.05 mm to 4 mm, and rotations ranging from 0.3° to 3° . For the translations, the mean 3D registration error was found to be 0.22 mm for MS, and 0.15 mm for MI. For the rotations, the standard deviation of the estimation error was 0.18° for MS, and 0.08° for MI. The results show that the proposed approach is feasible and that clinically acceptable accuracies can be obtained. Clinical validation studies on patient images will now be undertaken.

Midterm Follow-up of Treating Volar Marginal Rim Fractures with Variable Angle Lcp Volar Rim Distal Radius Plates

BACKGROUND Specific treatment of the volar marginal rim fragment of distal radius fractures avoids occurance of volar radiocarpal dislocation. Although several fixation systems are available to capture this fragment, adequately maintaining internal fixation is difficult. We present our experience of the first 10 cases using the 2.4 mm variable angle LCP volar rim distal radius plate (Depuy Synthes®, West Chester, US), a low-profile volar rim-contouring plate designed for distal plate positioning and stable buttressing of the volar marginal fragment. METHODS Follow-up patient satisfaction, range of motion, grips strength, functional scoring with the QuickDASH and residual pain with a numeric rating scale were assessed. Radiological evaluation consisted in evaluating fracture consolidation, ulnar variance, volar angulation and maintenance of the volar rim fixation. RESULTS The female to male ratio was 5:5 and the mean age was 52.2 (range, 17-80) years. The mean follow-up period was 11 (range, 5-19) months postoperatively. Patient satisfaction was high. The mean total flexion/extension range was 144° (range, 100-180°) compared to the contralateral uninjured side 160° (range, 95-180°). The mean total pronation/supination range was 153° (range, 140-180°) compared to the contralateral uninjured side 170° (range, 155-180°). Mean grip strength was 14 kg (range, 9-22), compared to the contralateral uninjured side 20 kg (range, 12-25 kg). Mean pre-injury level activity QuickDASH was 23 (range, 0-34.1), while post-recovery QuickDASH was 25 (range 0-43.2). Residual pain was 1.5 on the visual numerical pain rating scale. Radiological evaluation revealed in all cases fracture consolidation, satisfactory reconstruction of ulnar variance, volar angulation and volar rim. We encountered no flexor tendon complications, although plate removal was systematically performed after fracture consolidation. CONCLUSIONS The 2.4 mm variable angle LCP volar rim distal radius plates is a valid treatment option for treating the volar marginal fragment in distal radius fractures.

Effect of Transcutaneous Electric Nerve Stimulation on Pain after Total Knee Arthroplasty: A Blind Randomized Controlled Trial

Abstract Transcutaneous electric nerve stimulation (TENS) has proven to be effective for postsurgical pain relief. However, there is a lack of well‐constructed clinical trials investigating the effect of TENS after total knee arthroplasty (TKA). In addition, previous investigations reported that low‐ and high‐frequency TENSs produced analgesic tolerance after 4 or 5 days of treatment. The aim of this study is to explore the effect of burst TENS on pain during hospitalization after TKA and to investigate whether burst TENS produces analgesic tolerance after 4 or 5 days of treatment. This stratified, triple blind, randomized controlled trial was approved by the University Hospital Brussels. Sixty‐eight subjects were screened for eligibility before surgery; 54 were found eligible and 53 were included in the analyses. Patients were allocated to either a burst TENS or sham burst TENS group. TENS was applied daily during continuous passive mobilization. Knee pain intensity, knee range of motion, and analgesic consumption were assessed daily. Patients received burst TENS (N = 25) or sham burst TENS (N = 28). No significant differences in knee pain intensity were found between the groups (p > 0.05). Within the TENS and the sham TENS groups, the difference in knee pain before and after treatment did not evolve over time (p > 0.05). This study found no effects of burst TENS compared with sham burst TENS on pain during hospitalization after TKA.

Exercise in knee osteoarthritis: do treatment outcomes relate to bone marrow lesions? A randomized trial.

Abstract Purpose: Exercise is effective for reducing knee osteoarthritis (OA) pain but effect sizes vary widely. Moreover, not all knee OA patients perceive beneficial effects. Tailoring specific exercises to subgroups of knee OA patients may increase effectivity. Bone marrow lesions (BMLs) have been suggested as a criterion to define such subgroups. This study aimed to investigate whether BMLs’ presence/absence is related to treatment outcomes in a group of knee OA patients who exercised for 18 weeks. Methods: Subjects with symptomatic knee OA started a strength or walking exercise program. BMLs’ presence at baseline was assessed. Pain was assessed before and after the intervention with the intermittent and constant osteoarthritis pain (ICOAP) questionnaire. Also the global perceived effect (GPE) on the patient’s complaints was rated. Results: Thirty-five patients (strength (N = 17) and walking (N = 18)) were analyzed for BMLs. BMLs were present in 25 (71%) knees. Five (14%) patients dropped out and 19 (54%) improved (GPE ≥5). All dropouts had BMLs, but no difference was seen between dropouts and retainers (p > 0.05). Pain scores did not differ between intervention groups (p > 0.05) or between patients with BMLs and without BMLs (p > 0.05). Conclusions: Pain scores and GPE was not different between knee OA patients with and without baseline BMLs in this sample. Implications for Rehabilitation Both walking and strengthening exercises are effective means of improving pain in patients with knee osteoarthritis. In a relatively small sample, this study shows that the presence or absence of subchondral bone marrow lesions, as seen on magnetic resonance images, is not related to treatment outcomes.

Impact of implant size on cement filling in hip resurfacing arthroplasty

Larger proportions of cement within femoral resurfacing implants might result in thermal bone necrosis. We postulate that smaller components are filled with proportionally more cement, causing an elevated failure rate. A total of 19 femoral heads were fitted with polymeric replicas of ReCap (Biomet) resurfacing components fixed with low-viscosity cement. Two specimens were used for each even size between 40 and 56 mm and one for size 58 mm. All specimens were imaged with computed tomography, and the cement thickness and bone density were analyzed. The average cement mantle thickness was 2.63 mm and was not correlated with the implant size. However, specimen with low bone density had thicker cement mantles regardless of size. The average filling index was 36.65% and was correlated to both implant size and bone density. Smaller implants and specimens with lower bone density contained proportionally more cement than larger implants. According to a linear regression model, bone density but not implant size influenced cement thickness. However, both implant size and bone density had a significant impact on the filling index. Large proportions of cement within the resurfacing head have the potential to generate thermal bone necrosis and implant failure. When considering hip resurfacing in patients with a small femoral head and/or osteoporotic bone, extra care should be taken to avoid thermal bone necrosis, and alternative cementing techniques or even cementless implants should be considered. This study should help delimiting the indications for hip resurfacing and to choose an optimal cementing technique taking implant size into account.

Ultrasonographic evaluation of the distance between the flexor pollicis longus tendon and volar prominence of the plate as a function of volar plate positioning and pronator quadratus repair — A cadaver study

Flexor tendon injury after volar plating of distal radius fractures is due to friction against the plate. To assess this risk, the distance between the flexor pollicis longus (FPL) and the volar prominence of the plate was measured with ultrasonography under various conditions: a standard plate fixed proximal or distal to the watershed line and a low-profile volar rim plate, with and without transection of the pronator quadratus (PQ). Distance from the FPL to the volar prominence of the plate decreased significantly when the PQ was cut and when a standard plate was placed distal to the watershed line, with the tendon often bulging over the plate. No statistical difference was measured between a volar rim plate and a standard plate distal to the watershed line. Our results confirm the importance of positioning the volar plate proximal to the watershed line and of repairing the PQ.