The Impact of Complex Loadings on the Structure of the L2-L3 Intervertebral Disc in a Sheep Spine Cadaver Model: A Biomechanical and Histological Evaluation

Background The human vertebral column generates movements under versatile, dynamic loads. Understanding how the spine reacts to these movements and loads is crucial for developing new spine implants and surgical treatments for intervertebral disc injuries. Mechanically uni-axial compression models have been extensively studied. However, the spine's daily loading is not limited to compression, so it is crucial to measure its behavior in all movements (flexion-extension, rotation, and axial compression). Methods This study utilized L1-L5 segments from 19 healthy adult sheep spines. The L2-L3 disc of the first spine underwent only histological evaluation without biomechanical testing to define basic histological parameters. The remaining 18 were divided into three groups of six and subjected to biomechanical tests. Different mechanisms for three groups of spinal segments were prepared, and tests were performed on Shimadzu AG-IS 10 KN (Universal Drawing Press, Kyoto, Japan). An axial load (800 N) was applied to the first group, an axial load with 15 degrees of flexion to the second group, and an axial load with 10 degrees of rotation plus 15 degrees of flexion to the third group. A biomechanical evaluation of the maximum elongation amounts (MEAs) was performed and compared between the groups. Then, the L2-L3 discs were removed from the sheep spines, and a histological examination of the discs was conducted using Hematoxylin-Eosin (HE), Alcian Blue (AB), and Masson's Trichrome (MT) staining. Results The mean MEA ± Standard Deviation (Range) was 1.39 ± 0.38 (0.91-1.94) for Group 1, 2.02 ± 0.75 (0.91-3.01) for Group 2, and 2.47 ± 1.09 (0.64-3.9) for Group 3. Biomechanically, although MEAs increased from Group 1 to Group 3 (meaning that the mean MEAs increased as the number of types of applied force increased), there was no statistically significant difference between the groups regarding the MEAs (P = 0.092). Histologically, no significant differences were observed between all groups after HE staining. In all groups, hypercellularity, edema in the connective tissue, separation between tissue layers, delamination, and signs of swelling and necrosis in the cells were observed similarly. For the AB staining, there was a decrease in the glycosaminoglycan (GAG) structure in the tissue samples compared to the control tissue, but no significant differences were observed between the groups. However, it was observed that the stratification in Group 3 was slightly more deteriorated than in the other groups. For the MT staining, collagen structure deterioration was observed in all groups. It was observed that the amount of collagen was significantly reduced compared to the control tissue. Conclusion As a result, when the axial load is applied biomechanically, there is more displacement of the vertebral discs in Group 3 with multidimensional movements. Furthermore, histological studies revealed deterioration between tissue layers when exposed to complex movements, and the degradation of stratification in group 3 compared to other loading combinations in groups 2 and 3 may indicate the role of complex loads in the formation of disc herniation.

The evaluation of a de novo biplanar distal humerus plate: A biomechanical study

Objectives

Materials and methods

Results

Conclusion

The primary factor for suture configuration at rotator cuff repair: Width of mattress or distance from tear edge

OBJECTIVES

The aims of this study was first to investigate whether the bite size or the bite distance from the tear edge is of primary importance in mattress suture configuration for rotator cuff repair. Secondly, whether the use of a 450 left side bent Arthro-Pierce™ (Smith & Nephew, Andover, USA) during suture passage can be more effective on the strength of the configuration compared to a straight Arthro-Pierce™.

MATERIALS AND METHODS

Twenty-eight bovine infraspinatus muscle tendons were randomized into four groups. Group 1; 5 mm wide 'bite size' × 15 mm length 'distance from the tear edge's mattress'; Group 2: 7.5 mm × 10 mm; Group 3: 15 mm × 5 mm 'using straight Arthro-Pierce™' and Group 4: 5 mm × 15 mm using left sided 450 bent Arthro-Pierce™. The repair specimens underwent cyclic loading prior to loading the failure testing. Cyclic elongation (mm), peak-to-peak displacement (mm), ultimate load (N), stiffness (N/mm) and failure mode were recorded for each specimen.

RESULTS

The mean ultimate load in Group 1 was higher compared to group 3. The peak to peak displacement was higher in Group 4 compared to Group 1 (p < 0.05). The predominant failure mode in Groups 1, 2 and 4 was suture rupture. The Group 3 most specimens failed due to suture cut through the tendon.

CONCLUSION

Bite size from the edge of the tendon seems to be more important than the width of the mattress. The curve of the suture passing device may also have an effect on the strength of the suture tendon interface.

Biomechanical comparison of headless antegrade screw versus retrograde cortical screw for coronoid fracture fixation

OBJECTIVE

Posterior-to-anterior directed screws are stronger than anterior-to-posterior directed screws for coronoid fracture fixation. Anterior approaches that facilitate direct reduction and fixation of coronoid fractures have been described. The present study was based on the hypothesis that anterior-to-posterior headless screw (Acutrak Mini® 3.5 mm × 26 mm, Acumed, Hillsboro, Oregon, USA) fixation of coronoid fractures would be as strong as posterior-to-anterior 2.7 mm Association for Osteosynthesis (AO) cortical screw fixation.

METHODS

This study included 14 ulnas obtained from 14 formalin-preserved adult cadavers. Coronoid type 2 fractures were created and fixed randomly using anterior-to-posterior headless screws (antegrade group) and posterior-to-anterior 2.7 mm AO cortical screws (retrograde group). The experimental constructs were loaded until 2 mm of displacement. Failure load (N), fixation stiffness (Nmm-1), and indentation stiffness were calculated.

RESULTS

Failure load was higher in the retrograde screw group (p=0.03), whereas loading stiffness values of the fixation devices and bones did not differ between the 2 fixation groups (p>0.05).

CONCLUSION

The present study failed to show that anterior-to-posterior directed headless screw fixation of coronoid fractures could adequately replace posterior-to-anterior placed screw fixation.

Operative treatment of chondroblastoma: a study of 11 cases

Aim of the study was to review the radiological, clinical results of 11 chondroblastoma cases treated at our institute between 2003-2013. All patients with chondroblastoma included in this study underwent intra-lesional curettage+/-bone grafting. Follow up for healing of chondroblastoma lesions and detection of any local recurrence was assessed on clinical and radiological bases. The functional outcome was assessed by the Musculoskeletal Tumour Society scoring system. The mean follow-up period was 6.1 years. There were three recurrences (two femoral head, one proximal tibia). The mean Musculoskeletal Tumour Society functional score was 21. First line aggressive treatment seems appropriate for chondroblastoma especially when localized at lower extremities.

Reliability of threaded locking screws

OBJECTIVE

A frequent problem for interlocking nailing that affects the treatment of the fracture is locking screw deformation. The aim of this study is to determine whether bending resistance is different between high, low, and unthreaded locking screws of interlocking femoral nails.

METHODS

Ninety screws were used in this experimental study, with 10 screws used in each of 9 groups. Three-point bending tests were performed on 6 groups of 5 mm screws (titanium, stainless steel, crossed with unthreaded, low threaded, and high threaded) and the same 3 thread types of 5.5 mm stainless steel screws in a 30-mm inner diameter steel tube, imitating the level of the lesser trochanter. An axial compressor was used to determine the yield points for permanent deformation in the locking screws by way of 3-point bending tests.

RESULTS

The mean yield point value of the 3-point bending tests of 5-mm low threaded stainless steel locking screws was 2071 N, 53% less than that of unthreaded screws (3169 N). The mean yield point value of 5-mm high threaded stainless steel locking screws was 556 N, 272% less than that of low threaded screws (2071 N).

CONCLUSION

To avoid locking screw deformation, high threaded screws must not be used as locking screws. In cases of unreliable patients, 5-mm low threaded screws should not be used in the nailing of comminuted or oblique femur shaft fractures. All 5-mm unthreaded screws and 5.5-mm low threaded stainless steel screws can be used safely in full weight-bearing conditions of unreliable patients.