Evgenij Bobrowitsch

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.

Increased glenohumeral translation and biceps load after SLAP lesions with potential influence on glenohumeral chondral lesions: a biomechanical study on human cadavers.

PurposeThe aim of the study was to evaluate the stabilizing function of the long head of biceps tendon (LHB) and its tension, both without and with the presence of SLAP lesion to analyze a potentially occurring humeral chondral print of LHB with consecutive glenohumeral chondral lesions in SLAP lesions.MethodsTestings were performed on 21 fresh frozen human cadaver shoulders with intact shoulder girdle by a 5 axis industrial robot with a force/moment sensor and 20 N joint compression, 50 N force in anterior, posterior, anterosuperior, and anteroinferior direction, and 0°, 30°, 60° of abduction. LHB was connected over a force measuring sensor with 5 N and 25 N preload. A type IIC SLAP lesion was created arthroscopically.ResultsA significant increase in anterior and anteroinferior translation was evaluated, whereas the LHB tension increased significantly in at most anterior and anterosuperior direction. The highest increase in translation and LHB tension after SLAP lesion was measured in anterior translation in at most 60° of abduction.The glenohumeral translation was significantly higher in SLAP lesions without LHB tenotomy than after isolated LHB tenotomy.ConclusionsSLAP lesions lead to increased glenohumeral translation and concurrently LHB tension and load in at most anterior direction. The increased anterior glenohumeral instability and the increased LHB load pressing on the humeral head might cause glenohumeral chondral lesions with a typical chondral print-like lesion on the humeral head underneath the LHB.

The influence of superior labrum anterior to posterior (SLAP) repair on restoring baseline glenohumeral translation and increased biceps loading after simulated SLAP tear and the effectiveness of SLAP repair after long head of biceps tenotomy

HYPOTHESIS Biomechanical studies have shown increased glenohumeral translation and loading of the long head biceps (LHB) tendon after superior labrum anterior to posterior (SLAP) tears. This may explain some of the typical clinical findings, including the prevalence of humeral chondral lesions, after SLAP lesions. The first hypothesis was that SLAP repair could restore the original glenohumeral translation and reduce the increased LHB load after SLAP lesions. The second hypothesis was that SLAP repair after LHB tenotomy could significantly reduce the increased glenohumeral translation. MATERIALS AND METHODS Biomechanical testing was performed on 21 fresh frozen human cadaveric shoulders with an intact shoulder girdle using a sensor-guided industrial robot to apply 20 N of compression in the joint and 50 N translational force at 0°, 30°, and 60° of abduction. LHB loading was measured by a load-cell with 5 N and 25 N preload. Type IIC SLAP lesions were created arthroscopically, and a standardized SLAP repair was done combined with or without LHB tenotomy. RESULTS No significant difference of glenohumeral translation and increased LHB load in SLAP repair compared with the intact shoulder was observed under 5 N and 25 LHB preload, except for anterior translation under 25 N LHB preload. After LHB tenotomy after SLAP lesions, no significant difference of translation was observed with or without SLAP repair. CONCLUSIONS SLAP repair without associated LHB tenotomy helps normalize glenohumeral translation and LHB loading. The stabilizing effect of the SLAP complex is dependent on the LHB. After biceps tenotomy, SLAP repair does not affect glenohumeral translation.

Biomechanical Effectiveness of an Arthroscopic Posterior Bankart Repair Versus an Open Bone Block Procedure for Posterior Shoulder Instability

Background: The most effective surgical treatment for traumatic posterior shoulder instability remains unclear. Hypothesis: An arthroscopic posterior Bankart repair is as effective as an open posterior bone block–capsulorrhaphy procedure regarding the restoration of humeral displacement with posterior and inferior forces. Study Design: Controlled laboratory study. Methods: Biomechanical testing of 16 human shoulders was performed in 3 testing conditions: after ventilation (intact joint), after creation of a posteroinferior Bankart lesion with an additional cut of the posterior band of the inferior glenohumeral ligament, and after surgical shoulder stabilization. The shoulder stabilization was performed either by an open posterior bone block procedure and glenoid-based T-capsulorrhaphy or by an arthroscopic Bankart repair. Testing was performed in 2 positions—the sulcus test position and the jerk test position—with a passive humerus load of 50 N applied in the posterior, posteroinferior, and inferior directions. Results: After the arthroscopic repair, there was no significant difference between the translation and the intact state for all tested directions. The bone block repair–capsulorrhaphy caused a significant decrease of posterior translation (sulcus test and jerk test positions) and posteroinferior translation (jerk test position). But the resulting posterior and posteroinferior translation was even significantly lower than the translation measured for the intact joints. However, the reduction of inferior translation, compared with that of the defect condition, was not significant after the bone block repair (sulcus test and jerk test positions). Compared with that of the intact joint, inferior translation after the bone block repair was significantly higher. Conclusion: The posterior bone block repair–capsulorrhaphy overcorrects posterior translation and does not effectively restore inferior stability, whereas the arthroscopic posterior Bankart repair restores posterior and inferior laxity of the intact joint. Clinical Relevance: An arthroscopic posterior capsulolabral repair more precisely restores posterior and inferior glenohumeral joint laxity and is therefore recommended as the first choice of treatment.

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.

Biomechanical In Vitro - Stability Testing on Human Specimens of a Locking Plate System Against Conventional Screw Fixation of a Proximal First Metatarsal Lateral Displacement Osteotomy

Introduction: The aim of this study was to examine resistance to angulation and displacement of the internal fixation of a proximal first metatarsal lateral displacement osteotomy, using a locking plate system compared with a conventional crossed screw fixation. Materials and Methodology: Seven anatomical human specimens were tested. Each specimen was tested with a locking screw plate as well as a crossed cancellous srew fixation. The statistical analysis was performed by the Friedman test. The level of significance was p = 0.05. Results: We found larger stability about all three axes of movement analyzed for the PLATE than the crossed screws osteosynthesis (CSO). The Friedman test showed statistical significance at a level of p = 0.05 for all groups and both translational and rotational movements. Conclusion: The results of our study confirm that the fixation of the lateral proximal first metatarsal displacement osteotomy with a locking plate fixation is a technically simple procedure of superior stability.