Gavin Olender

Biomechanical Comparison of Arthroscopically Performable Techniques for Suprapectoral Biceps Tenodesis

PURPOSE The aim of this study was to biomechanically compare the cyclic and ultimate failure load (UFL) of 4 widely used techniques for arthroscopically performable suprapectoral tenodesis of the long head of the biceps tendon (LHB). METHODS We used 28 fresh-frozen human cadaveric specimens (mean age, 65 years [range, 43 to 78 years; SD, 6.7 years]; 43% male specimens) to investigate 4 different techniques for LHB tenodesis. All techniques were performed in an open manner, with localization at the entrance of the bicipital groove. Two suture anchor techniques (Healix [DePuy Mitek, Raynham, MA], 5.5 mm, with modified lasso-loop stitch; BioSwiveLock [Arthrex, Naples, FL], 5.5 mm, with interlocking Krackow stitch) and two techniques using tenodesis screws (Bio-Tenodesis screw [Arthrex], 8 × 23 mm; Biceptor [Smith & Nephew, Andover, MA], 8 × 25 mm) were investigated. Under a 10-N preload, an axial cyclic load with 100 cycles, 1-Hz frequency, and 50-N maximum load was applied. UFL was evaluated with an axial traction of 0.2 mm/s. LHB displacement during testing was measured by 3-dimensional photogrammetry. RESULTS All techniques had a mean displacement of less than 3 mm after cyclic loading. The highest UFL was measured with the Bio-Tenodesis screw (mean, 218.3 N; range, 134.0 to 313.0 N; SD, 59.7 N) and the lowest with the BioSwiveLock (mean, 111.2 N; range, 60.0 to 156.8 N; SD, 32.3 N). The Healix had the second highest UFL (mean, 187.1 N; range, 144.7 to 245.0 N; SD, 35.5 N), followed by the Biceptor (mean, 173.9 N; range, 147.0 to 209.3 N; SD, 27.2 N). There was no significant difference between the Healix, Bio-Tenodesis screw, and Biceptor (P > .05), but the Healix and Bio-Tenodesis screw had a significantly higher UFL than the BioSwiveLock (P < .01). The failure mode was either suture cutout or failure at the anchor-suture-bone interface or of the tendon itself and was generally dependent on technique. CONCLUSIONS All techniques resisted cyclic testing without a higher grade of displacement, and all devices except the BioSwiveLock had a satisfactory UFL whereas different failure mechanisms were present. The modified lasso-loop stitch provides sufficient tendon fixation and is equivalent to interference screws. CLINICAL RELEVANCE The lasso-loop suture anchor technique is an appropriate alternative for suprapectoral LHB tenodesis compared with tenodesis screw techniques.

Changes in strain patterns after implantation of a short stem with metaphyseal anchorage compared to a standard stem: an experimental study in synthetic bone.

Short stem hip arthroplasties with predominantly metaphyseal fixation, such as the METHA® stem (Aesculap, Tuttlingen, Germany), are recommended because they are presumed to allow a more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Therefore, the METHA short stem and the Bicontact® standard stem (Aesculap, Tuttlingen, Germany) were tested biomechanically in synthetic femora while strain gauges monitored their corresponding strain patterns. For the METHA stem, the strains in all tested locations including the region of the calcar (87% of the non-implanted femur) were similar to conditions of synthetic bone without implanted stem. The Bicontact stem showed approximately the level of strain of the non-implanted femur on the lateral and medial aspect in the proximal diaphysis of the femur. On the anterior and posterior aspect of the proximal metaphysis the strains reached averages of 78% and 87% of the non-implanted femur, respectively. This study revealed primary metaphyseal anchorage of the METHA short stem, as opposed to a metaphyseal-diaphyseal anchorage of the Bicontact stem.

Minimally Invasive Osteotomy for Symptomatic Bunionette Deformity Is Not Advisable for Severe Deformities: A Critical Retrospective Analysis of the Results

Bunionette, or tailor’s bunion, is a painful protrusion on the plantar and/or lateral aspect of the fifth metatarsal head. Until recently, there have been very good results reported in literature when minimally invasive therapy is used to treat this deformity. In this study, the authors critically review the outcome of patients operated by the minimal invasive technique. A total of 31 feet were retrospectively reviewed with a mean follow-up of 52 months (range 14-106 months). The results were related to the preoperative severity of the bunionette deformity. The mean intermetatarsal angle IV/V was reduced from 12° to 7.5° postoperatively. The American Orthopaedic Foot and Ankle Society score showed good and excellent values (80-100 points) at follow-up in 16 (12 type I, 4 type III) feet. Fourteen (2 type I, 5 type II, 7 type III) feet were rated as satisfactory (60-80 points) and one (type III) foot with fair (56 points). Nine patients (5 type II and 4 type III) indicated that they would not undergo the operative procedure again. Our results show inclusive evidence that minimal invasive osteotomies have a good clinical outcome in the treatment of high-grade deformities. The best future option is to consider the classification of the deformity before a minimally invasive operation is to take place. Levels of Evidence : Prognostic, Level IV, Case series

Noninvasive induction implant heating: An approach for contactless altering of mechanical properties of shape memory implants

This article shows an approach to change the properties of an orthopaedic shape memory implant within biological tissue, using contactless induction heating. Due to inducing the one way-memory effect, triggered by the rise of temperature within the implant, the geometry and hence the mechanical properties of the implant itself, are altered. The power uptake of the implant, depending on the induction parameters as well as on its position within the induction coil, is shown. Thermographic measurements are carried out in order to determine the surface temperature distribution of the implant. In order to simulate biological tissue, the implant was embedded in agarose gel. Suitable heating parameters, in terms of a short heating process in combination with a reduced heat impact on the surrounding environment, were determined.

Digital stereophotogrammetry based on circular markers and zooming cameras: evaluation of a method for 3D analysis of small motions in orthopaedic research.

BackgroundOrthopaedic research projects focusing on small displacements in a small measurement volume require a radiation free, three dimensional motion analysis system. A stereophotogrammetrical motion analysis system can track wireless, small, light-weight markers attached to the objects. Thereby the disturbance of the measured objects through the marker tracking can be kept at minimum. The purpose of this study was to develop and evaluate a non-position fixed compact motion analysis system configured for a small measurement volume and able to zoom while tracking small round flat markers in respect to a fiducial marker which was used for the camera pose estimation.MethodsThe system consisted of two web cameras and the fiducial marker placed in front of them. The markers to track were black circles on a white background. The algorithm to detect a centre of the projected circle on the image plane was described and applied. In order to evaluate the accuracy (mean measurement error) and precision (standard deviation of the measurement error) of the optical measurement system, two experiments were performed: 1) inter-marker distance measurement and 2) marker displacement measurement.ResultsThe first experiment of the 10 mm distances measurement showed a total accuracy of 0.0086 mm and precision of ± 0.1002 mm. In the second experiment, translations from 0.5 mm to 5 mm were measured with total accuracy of 0.0038 mm and precision of ± 0.0461 mm. The rotations of 2.25° amount were measured with the entire accuracy of 0.058° and the precision was of ± 0.172°.ConclusionsThe description of the non-proprietary measurement device with very good levels of accuracy and precision may provide opportunities for new, cost effective applications of stereophotogrammetrical analysis in musculoskeletal research projects, focusing on kinematics of small displacements in a small measurement volume.

The impact of seating forces from a cementless femoral component in hip resurfacing arthroplasty on the femoral head - A cadaver study using μ-CT analysis

Recent studies have assumed micro-fractures of the femoral head during hip resurfacing arthroplasty as a possible reason for fractures at the implant/neck junction. The purpose of this study was to analyze whether implantation of a cementless femoral hip resurfacing component which requires high seating forces, causes micro-fractures of the femoral head. A cementless hip resurfacing femoral component was installed on 20 human, cadaveric femoral heads with an impaction device that generated 4.5 kilonewton force in one group and by hand in the other. Before and after impaction, the specimens were scanned with a μ-CT-System. The CT datasets were segmented and registered for detection of small trabecular fractures. The average percentage of shared voxels was 80.29% (standard deviation 3.24%). Change in bone structure after impaction (19.71%) was found on the surfaces of all samples. No formation that was ascribed to fracture was found. No difference between the specimens that were impacted by hand or by impaction device was noted. No fractures of the cancellous femoral head during installation of a cementless femoral THR component occurred. Cementless hip resurfacing might not increase the risk of fracturing the cancellous femoral head during implantation in a cadaveric μ-CT study.

Ex-vivo-µCT-Untersuchungen zu möglichen Mikrofrakturierungen des Hüftkopfs bei der Implantation eines zementfreien Oberflächenersatzes am Hüftgelenk

AIM Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head. METHOD After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbH & Co., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures. RESULTS Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction. CONCLUSION At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.