Bone turnover and the accumulation of microdamage are impacted by the presence of skeletal metastases which can contribute to increased fracture risk. Treatments for metastatic disease may further impact bone quality. The present study aims to establish a preliminary understanding of microdamage accumulation and load to failure in osteolytic vertebrae following stereotactic body radiotherapy (SBRT), zoledronic acid (ZA), or docetaxel (DTX) treatment. Twenty-two six-week old athymic female rats (Hsd:RH-Foxn1rnu, Envigo, USA) were inoculated with HeLa cervical cancer cells through intracardiac injection (day 0). Institutional approval was obtained for this work and the ARRIVE guidelines were followed. Animals were randomly assigned to four groups: untreated (n=6), spine stereotactic body radiotherapy (SBRT) administered on day 14 (n=6), zoledronic acid (ZA) administered on day 7 (n=5), and docetaxel (DTX) administered on day 14 (n=5). Animals were euthanized on day 21. T13-L3 vertebral segments were collected immediately after sacrifice and stored in −20°C wrapped in saline soaked gauze until testing. µCT scans (µCT100, Scanco, Switzerland) of the T13-L3 segment confirmed tumour burden in all T13 and L2 vertebrae prior to testing. T13 was stained with BaSO. 4. to label microdamage. High resolution µCT scans were obtained (90kVp, 44uA, 4W, 4.9µm voxel size) to visualize stain location and volume. Segmentations of bone and BaSO. 4. were created using intensity thresholding at 3000HU (~736mgHA/cm. 3. ) and 10000HU (~2420mgHA/cm. 3. ), respectively. Non-specific BaSO. 4. was removed from the outer edge of the cortical shell by shrinking the segmentation by 105mm in 3D. Stain volume fraction was calculated as the ratio of BaSO. 4. volume to the sum of BaSO. 4. and bone volume. The L1-L3 motion segments were loaded under axial compression to failure using a µCT compatible loading device (Scanco) and force-displacement data was recorded. µCT scans were acquired unloaded, at 1500µm displacement and post-failure. Stereological analysis was performed on the L2 vertebrae in the unloaded µCT scans. Differences in mean stain volume fraction, mean load to failure, and mean bone volume/total volume (BV/TV) were compared between treatment groups using one-way ANOVAs. Pearson's correlation between stain volume fraction and load to failure by treatment was calculated using an adjusted load to failure divided by BV/TV. Stained damage fraction was significantly different between treatment groups (p=0.0029). Tukey post-hoc analysis showed untreated samples to have higher stain volume fraction (16.25±2.54%) than all treatment groups (p<0.05). The ZA group had the highest mean load to failure (195.60±84.49N), followed by untreated (142.33±53.08N), DTX (126.60±48.75N), and SBRT (95.50±44.96N), but differences did not reach significance (p=0.075). BV/TV was significantly higher in the ZA group (49.28±3.56%) compared to all others. The SBRT group had significantly lower BV/TV than the untreated group (p=0.018). Load divided by BV/TV was not significantly different between groups (p=0.24), but relative load to failure results were consistent (ZA>Untreated>DTX>SBRT). No correlations were found between stain volume fraction and load to failure. Focal and systemic cancer treatments effect microdamage accumulation and load to failure in osteolytic vertebrae. Current testing of healthy controls will help to further separate the effects of the tumour and cancer treatments on bone quality

Bone turnover and the accumulation of microdamage are impacted by the presence of skeletal metastases which can contribute to increased fracture risk. Treatments for metastatic disease may further impact bone quality. The present study aims to establish a preliminary understanding of microdamage accumulation and load to failure in osteolytic vertebrae following stereotactic body radiotherapy (SBRT), zoledronic acid (ZA), or docetaxel (DTX) treatment. Twenty-two six-week old athymic female rats (Hsd:RH-Foxn1rnu, Envigo, USA) were inoculated with HeLa cervical cancer cells through intracardiac injection (day 0). Institutional approval was obtained for this work and the ARRIVE guidelines were followed. Animals were randomly assigned to four groups: untreated (n=6), spine stereotactic body radiotherapy (SBRT) administered on day 14 (n=6), zoledronic acid (ZA) administered on day 7 (n=5), and docetaxel (DTX) administered on day 14 (n=5). Animals were euthanized on day 21. T13-L3 vertebral segments were collected immediately after sacrifice and stored in −20°C wrapped in saline soaked gauze until testing. µCT scans (µCT100, Scanco, Switzerland) of the T13-L3 segment confirmed tumour burden in all T13 and L2 vertebrae prior to testing. T13 was stained with BaSO. 4. to label microdamage. High resolution µCT scans were obtained (90kVp, 44uA, 4W, 4.9µm voxel size) to visualize stain location and volume. Segmentations of bone and BaSO. 4. were created using intensity thresholding at 3000HU (~736mgHA/cm. 3. ) and 10000HU (~2420mgHA/cm. 3. ), respectively. Non-specific BaSO. 4. was removed from the outer edge of the cortical shell by shrinking the segmentation by 105mm in 3D. Stain volume fraction was calculated as the ratio of BaSO. 4. volume to the sum of BaSO. 4. and bone volume. The L1-L3 motion segments were loaded under axial compression to failure using a µCT compatible loading device (Scanco) and force-displacement data was recorded. µCT scans were acquired unloaded, at 1500µm displacement and post-failure. Stereological analysis was performed on the L2 vertebrae in the unloaded µCT scans. Differences in mean stain volume fraction, mean load to failure, and mean bone volume/total volume (BV/TV) were compared between treatment groups using one-way ANOVAs. Pearson's correlation between stain volume fraction and load to failure by treatment was calculated using an adjusted load to failure divided by BV/TV. Stained damage fraction was significantly different between treatment groups (p=0.0029). Tukey post-hoc analysis showed untreated samples to have higher stain volume fraction (16.25±2.54%) than all treatment groups (p<0.05). The ZA group had the highest mean load to failure (195.60±84.49N), followed by untreated (142.33±53.08N), DTX (126.60±48.75N), and SBRT (95.50±44.96N), but differences did not reach significance (p=0.075). BV/TV was significantly higher in the ZA group (49.28±3.56%) compared to all others. The SBRT group had significantly lower BV/TV than the untreated group (p=0.018). Load divided by BV/TV was not significantly different between groups (p=0.24), but relative load to failure results were consistent (ZA>Untreated>DTX>SBRT). No correlations were found between stain volume fraction and load to failure. Focal and systemic cancer treatments effect microdamage accumulation and load to failure in osteolytic vertebrae. Current testing of healthy controls will help to further separate the effects of the tumour and cancer treatments on bone quality

Objectives. Periprosthetic femoral fractures (PFFs) have a higher incidence with cementless stems. The highest incidence among various cementless stem types was observed with double-wedged stems. Short stems have been introduced as a bone-preserving alternative with a higher incidence of PFF in some studies. The purpose of this study was a direct load-to-failure comparison of a double-wedged cementless stem and a short cementless stem in a cadaveric fracture model. Methods. Eight hips from four human cadaveric specimens (age mean 76 years (60 to 89)) and eight fourth-generation composite femurs were used. None of the cadaveric specimens had compromised quality (mean T value 0.4 (-1.0 to 5.7)). Each specimen from a pair randomly received either a double-wedged stem or a short stem. A materials testing machine was used for lateral load-to-failure test of up to a maximal load of 5000 N. Results. Mean load at failure of the double-wedged stem was 2540 N (1845 to 2995) and 1867 N (1135 to 2345) for the short stem (p < 0.001). All specimens showed the same fracture pattern, consistent with a Vancouver B2 fracture. The double-wedged stem was able to sustain a higher load than its short-stemmed counterpart in all cases. Failure force was not correlated to the bone mineral density (p = 0.718). Conclusion. Short stems have a significantly lower primary load at failure compared with double-wedged stems in both cadaveric and composite specimens. Surgeons should consider this biomechanical property when deciding on the use of short femoral stem. Cite this article: A. Klasan, M. Bäumlein, P. Dworschak, C. Bliemel, T. Neri, M. D. Schofer, T. J. Heyse. Short stems have lower load at failure than double-wedged stems in a cadaveric cementless fracture model. Bone Joint Res 2019;8:489–494. DOI: 10.1302/2046-3758.810.BJR-2019-0051.R1

Purpose: New high-strength sutures demonstrate high failure loads, but may be more likely to slip compared with polyester sutures. The purpose of this study was to determine the knot security and ultimate failure load of 8 common sutures tied with 6 arthroscopic knots. The hypothesis was that knots tied using high-strength sutures would not slip and demonstrate greater tensile strengths than polyester suture. Method: Eight different sutures (Ethibond, FiberWire, ForceFiber, Hi-Fi, MagnumWire, Maxbraid, Ortho-cord and Ultrabraid) were tied with 6 arthroscopic knots (Duncan, Revo, San Diego, SMC, Tennessee and Weston.) Knots were backed up with 4 reversed half-hitches on alternating posts. Each suture-knot combination was tied 10 times for a total of 480 knots tested. Cyclic testing was performed followed by loading to failure. Mode of failure, ultimate failure load and force during slippage was recorded. Results: FiberWire demonstrated the highest failure load (259.70N+/−85.81) and Ethibond the lowest (143.92N+/−16.56) (p< 0.05). Knots tied with Ethibond slipped 22.4% of the time compared with 31.7%–40.0% for high-strength sutures. Frequent slippage occurred with Duncan loops (97.5%) and Weston knots (86.3%) while the SMC (1.3%) and Revo knots (3.6%) rarely slipped (p< 0.05). Mean failure loads were highest for the Revo (280.99N +/− 57.01) and SMC knots (274.89N +/−57.90) compared with all others (p< 0.05). Conclusion: Our results demonstrate that knots tied with Ethibond were least likely to slip and yielded a more consistent (narrow standard deviation) but overall lower ultimate tensile strength than all of the high strength sutures. Early slippage of some knots tied with high-strength suture was responsible for greater variability with some failing at sub-maximal loads. The Duncan loop and Weston knots were the most likely to slip

The ideal treatment method regarding various defect sizes after local aggressive tumor resection is unknown. We investigated the biomechanical properties of metaphyseal defect filling regarding different defect sizes and fixation methods. Ninety-one sheep tibias were divided into five groups as 21 tibias per four study groups and 7 tibias in the control group. Study groups were further divided into three subgroups according to 25%, 50% and 75% metaphyseal defect size. Control group tibias were left intact. In study group 1, a metaphyseal defect was created and no further process was applied. Metaphyseal defects were filled with cement without fixation in group 2. Cement filling and fixation with 2 screws were performed in group 3. In addition to cement filling, plate-screw fixation was performed in group 4. Axial loading test was applied to all tibias and the results were compared between study subgroups and control group. Plate-screw fixation was found to have the best biomechanical properties in all defect sizes. Load to failure for screw fixation was found to be significantly decreased between 25% and 50% defect size (P<0.05). However, load to failure for isolated cement filling was not affected from defect size (p>0.05). In conclusion, size of the defect predicts the fixation method in addition to filling with cement. Filling with cement in metaphyseal defects was found to be biomechanically insufficient. In addition to filling with cement, additional screw fixation in less than 25% defects and plate-screw fixation in more than 25% defects may decrease tibial plateau fracture or metaphyseal fracture risk after local aggressive tumor resection

Extensor mechanism and abductor reconstructions in total joint arthroplasty are problematic. Growing tendon into a metallic implant would have great reconstructive advantages. With the introduction of porous metal implants, it was hoped that tendons could be directly attached to implants. However, the effects of the porous metal structure on tissue growth and pore penetration is unknown. In this rat model, we investigated the effect of pore size on tendon repair fixation using printed titanium implants with differing pore sizes. There were four groups of six Sprague Dawley rats (n = 28) plus control (n=4). Implants had pore sizes of 400µm (n=8), 700µm (n=8), and 1000µm (n=8). An Achilles tendon defect was created, and the implant positioned and sutured between the cut ends. Harvest occurred at 12-weeks. Half the specimens underwent tensile load to failure testing, the other half fixed and processed for hard tissue analysis. Average load to failure was 72.6N for controls (SD 10.04), 29.95N for 400µm (SD 17.95), 55.08N for 700µm (SD 13.47), and 63.08N for 1000µm (SD 1.87). The load to failure was generally better in the larger pore sizes. Histological evaluation showed that there was fibrous tendon tissue within and around the implant material, with collagen fibers organized in bundles. This increases as the pore diameter increases. Printing titanium implants allows for precise determination of pore size and structure. Our results showed that tendon repair utilizing implants with 700µm and 1000µm pores exhibited similar load to failure as controls. Using a defined pore structure at the attachment points of tendons to implants may allow predictable tendon to implant reconstruction at the time of revision arthroplasty

This study aims to compare the biomechanical properties of the “Double Lasso-Loop” suture anchor (DLSA) technique with the commonly performed interference screw (IS) technique in an ex vivo ovine model. Fourteen fresh sheep shoulder specimens were used in this study. Dissection was performed leaving only the biceps muscle attached to the humerus and proximal radius before sharply incised to simulate long head of biceps tendon (LHBT) tear. Repair of the LHBT tear was performed on all specimens using either DSLA or IS technique. Cyclical loading of 500 cycles followed by load to failure was performed on all specimens. Tendon displacement due to the cyclical loading at every 100 cycles as well as the maximum load at failure were recorded and analysed. Stiffness was also calculated from the load displacement graph during load to failure testing. No statistically significant difference in tendon displacement was observed from 200 to 500 cycles. Statistically significant higher stiffness was observed in IS when compared with DSLA (P = .005). Similarly, IS demonstrated significantly higher ultimate failure load as compared with DSLA (P = .001). Modes of failure observed for DSLA was mostly due to suture failure (7/8) and anchor pull-out (1/8) while IS resulted in mostly LHBT (4/6) or biceps (2/6) tears. DSLA failure load were compared with previous studies and similar results were noted. After cyclical loading, tendon displacement in DLSA technique was not significantly different from IS technique. Despite the higher failure loads associated with IS techniques in the present study, absolute peak load characteristics of DLSA were similar to previous studies. Hence, DLSA technique can be considered as a suitable alternative to IS fixation for biceps tenodesis

We hypothesised that diet-induced obesity (DIO) would result in inferior enthesis healing in a rat model of rotator cuff (RC) repair and that dietary intervention in the peri-operative period would improve enthesis healing. A total of 78 male Sprague-Dawley rats were divided into three weight-matched groups from weaning and fed either: control diet (CD), high-fat diet (HFD), or HFD until surgery, then CD thereafter (HF-CD). After 12 weeks, the left supraspinatus tendon was detached, followed by immediate surgical repair. At 2 and 12 weeks post-surgery, animals were culled, and RCs harvested for biomechanical and histological evaluation. Body composition and metabolic markers were assessed via DEXA and plasma analyses, respectively. DIO was established in the HFD and HF-CD groups before surgery and subsequently reversed in the HF-CD group after surgery. Histologically, the appearance of the repaired entheses was poorer in both the HFD and HF-CD groups compared with the CD group at 12 weeks after surgery, with semiquantitative scores of 6.2 (P<0.01), 4.98 (P<0.01), and 8.7 of 15, respectively. The repaired entheses in the HF-CD group had a significantly lower load to failure (P=0.03) at 12 weeks after surgery compared with the CD group, while the load to failure in the HFD group was low but not significantly different (P=0.10). Plasma leptin were negatively correlated with histology scores and load to failure at 12 weeks after surgery. DIO impaired enthesis healing in this rat RC repair model, with inferior biomechanical and histological outcomes. Restoring normal weight with dietary change after surgery did not improve healing outcomes. Circulating levels of leptin significantly correlated with poor healing outcomes. This pre-clinical rodent model demonstrates that obesity is a potentially modifiable factor that impairs RC healing and increases the risk of failure after RC surgery

Insertional Achilles tendinitis with considerable degeneration that failed non-operative treatment typically requires tendon debridement and reattachment to bone. It is common practice for tendons to be reattached back with anchor sutures, but this poses a challenge to patients who are not able to afford them. Bony anchorage of tendons may be performed by passing sutures through tunnels, but the strength of repair compared to by using anchors is not known. We investigated the load at clinical and catastrophic failure of these two methods of reattachment. Sixteen paired Achilles tendons along with the calcaneus were harvested from eight fresh frozen cadavers. Paired randomization was done. For the anchor suture group, two 5’0 anchors with polyethylene #2 sutures were used for reattachment whereas for the suture only group, tendons were reattached to bone using braided polyester #2 sutures via two bony tunnels. All samples were mounted on a materials testing system and preloaded at 50N for 60sec before load to failure at a rate of 1mm/sec. With the assumption that preloading has removed tendon crimp and any subsequent extension is a result of gapping at the repair site, loads at 5mm, 10mm, 15mm, and 20mm of extension were noted as well as the maximal load at failure. We found higher loads were needed to cause an extension of 5 to 20mm in the suture only group compared to the anchor suture group but these data were not significant. On the other hand, the anchor suture group required higher loads before catastrophic failure occurred compared to the suture only group, but this again is not significant. We conclude that suture only reattachment of the Achilles tendon is comparable in strength with anchor suture reattachment, and this method of reattachment can be considered for patients who do not have access to anchor sutures

The extracortical single-button (SB) inlay repair is one of the most preferred distal biceps tendon repair techniques. However, specific complications such as neurovascular injury and non-anatomic repairs have led to the development of techniques that utilize intracortical double-button (DB) fixation. To compare the biomechanical stability of the extracortical SB repair with the anatomical DB repair technique. Controlled laboratory study. The distal biceps tendon was transected in 18 cadaveric elbows from 9 donors. One elbow of each donor was randomly assigned to the extracortical SBor anatomical DB group. Both groups were cyclically loaded with 60N over 1000 cycles between 90° of flexion and full extension. The elbow was then fixed in 90° of flexion and the repair construct loaded to failure. Gap-formation and construct stiffness during cyclic loading, and ultimate load to failure was analysed. After 1000 cycles, the anatomical DB technique compared with the extracortical SB technique showed significantly less gap-formation (mean difference 1.2 mm; p=0.017) and significantly more construct stiffness (mean difference 31 N/mm; p=0.023). Ultimate load to failure was not significantly different comparing both groups (SB, 277 N ±92 vs. DB, 285 N ±135; p=0.859). The failure mode in the anatomical DB group was significantly different compared with the extracortical SB technique (p=0.002) and was due to fracture avulsion of the BicepsButton in 7 out of 9 specimens (vs. none in SB group). Our study shows that the intracortical DB technique produces equivalent or superior biomechanical performance to the SB technique. The DB repair technique reduces the risk of nerve injury and better restores the anatomical footprint of biceps tendon. The DB technique may offer a clinically viable alternative to the SB repair technique

Neer Type-IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. A novel plating technique using a superior lateral locking plate with antero-posterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment has been designed to enhance stability. The purpose of this study was to biomechanically compare three different clavicle plating constructs. 24 fresh-frozen cadaveric shoulders were randomised into three groups (n=8 specimens). Group 1: lateral locking plate only (Medartis Aptus Superior Lateral Plate); Group 2: lateral locking plate with CC stabilisation (Nr. 2 FiberWire); and Group 3: lateral locking plate with two AP locking screws stabilising the lateral fragment. Data was analysed for gap formation after cyclic loading, construct stiffness and ultimate load to failure, defined by a marked decrease in the load displacement curve. After 500 cycles, there was no statistically significant difference between the three groups in gap-formation (p = 0.179). Ultimate load to failure was significantly higher in Group 3 compared to Group 1 (286N vs. 167N; p = 0.022), but not to Group 2 (286N vs. 246N; p = 0.604). There were no statistically significant differences in stiffness (Group 1: 504N/mm; Group 2: 564N/mm; Group 3: 512N/mm; p = 0.712). Peri-implant fracture was the primary mode of failure for all three groups, with Group 3 demonstrating the lowest rate of peri-implant fractures (Group 1: 6/8; Group 2: 7/8, Group 3: 4/8; p = 0.243). The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications

Aims. A growing number of fractures progress to delayed or nonunion, causing significant morbidity and socioeconomic impact. Localized delivery of stem cells and subcutaneous parathyroid hormone (PTH) has been shown individually to accelerate bony regeneration. This study aimed to combine the therapies with the aim of upregulating fracture healing. Methods. A 1.5 mm femoral osteotomy (delayed union model) was created in 48 female juvenile Wistar rats, aged six to nine months, and stabilized using an external fixator. At day 0, animals were treated with intrafracture injections of 1 × 10. 6. cells/kg bone marrow mesenchymal stem cells (MSCs) suspended in fibrin, daily subcutaneous injections of high (100 μg/kg) or low (25 μg/kg) dose PTH 1-34, or a combination of PTH and MSCs. A group with an empty gap served as a control. Five weeks post-surgery, the femur was excised for radiological, histomorphometric, micro-CT, and mechanical analysis. Results. Combination therapy treatment led to increased callus formation compared to controls. In the high-dose combination group there was significantly greater mineralized tissue volume and trabecular parameters compared to controls (p = 0.039). This translated to significantly improved stiffness (and ultimate load to failure (p = 0.049). The high-dose combination therapy group had the most significant improvement in mean modified Radiographic Union Score for Tibia fractures (RUST) compared to controls (13.8 (SD 1.3) vs 5.8 (SD 0.5)). All groups demonstrated significant increases in the radiological scores – RUST and Allen score – histologically compared to controls. Conclusion. We demonstrate the beneficial effect of localized MSC injections on fracture healing combined with low- or high-dose teriparatide, with efficacy dependent on PTH dose. Cite this article: Bone Joint Res 2021;10(10):659–667

Proximal humeral shaft fractures are commonly treated with long straight locking plates endangering the radial nerve distally. The aim of this study was to investigate the biomechanical competence in a human cadaveric bone model of 90°-helical PHILOS plates versus conventional straight PHILOS plates in proximal third comminuted humeral shaft fractures. Eight pairs of humeral cadaveric humeri were instrumented using either a long 90°-helical plate (group1) or a straight long PHILOS plate (group2). An unstable proximal humeral shaft fracture was simulated by means of an osteotomy maintaining a gap of 5cm. All specimens were tested under quasi-static loading in axial compression, internal and external rotation as well as bending in 4 directions. Subsequently, progressively increasing internal rotational loading until failure was applied and interfragmentary movements were monitored by means of optical motion tracking. Flexion/extension deformation (°) in group1 was (2.00±1.77) and (0.88±1.12) in group2, p=0.003. Varus/valgus deformation (°) was (6.14±1.58) in group1 and (6.16±0.73) in group2, p=0.976. Shear (mm) and displacement (°) under torsional load were (1.40±0.63 and 8.96±0.46) in group1 and (1.12±0.61 and 9.02±0.48) in group2, p≥0.390. However, during cyclic testing shear and torsional displacements and torsion were both significantly higher in group 1, p≤0.038. Cycles to catastrophic failure were (9960±1967) in group1 and (9234±1566) in group2, p=0.24. Although 90°-helical plating was associated with improved resistance against varus/valgus deformation, it demonstrated lower resistance to flexion/extension and internal rotation as well as higher flexion/extension, torsional and shear movements compared to straight plates. From a biomechanical perspective, 90°-helical plates performed inferior compared to straight plates and alternative helical plate designs with lower twist should be investigated in future paired cadaveric studies

Recently, a new suture was designed to minimize laxity in order to preserve consistent tissue approximation while improving footprint compression after tendon repair. The aims of this study were: (1) to compare the biomechanical competence of two different high strength sutures in terms of slippage and failure load, (2) to investigate the influence of both knots number and different media (air, saline and fat) on the holding capacity of the knots. Alternating surgical knots of two different high-strength sutures (group1: FibreWire; group2: DynaCord; n = 105) were tied on two roller bearings with 50N tightening force. Biomechanical testing was performed in each medium applying ramped monotonic tension to failure defined in terms of either knot slippage or suture rupture. For each group and medium, seven specimens with either 3, 4, 5, 6, or 7 knots each were tested, evaluating their knot slippage and ultimate load to failure. The minimum number of knots preventing slippage failure and thus resulting in suture rupture was determined in each group and medium, and taken as a criterium for better performance when comparing the groups. In each group and medium failure occurred via suture rupture in all specimens for the following minimum knot numbers: group1: air – 7, saline – 7, fat – 7; group2: air – 6; saline – 4; fat – 5. The direct comparison between the groups when using 7 knots demonstrated significantly larger slippage in group1 (6.5 ± 2.2 mm) versus group2 (3.5 ± 0.4 mm) in saline (p < 0.01) but not in the other media (p ≥0.52). Ultimate load was comparable between the two groups for all three media (p ≥ 0.06). The lower number of required knots providing sufficient repair stability, smaller slippage levels and identical suture strength, combined with the known laxity alleviation effect demonstrate advantages of DynaCord versus FibreWire

Bone turnover and microdamage are impacted by skeletal metastases which can contribute to increased fracture risk. Treatments for metastatic disease may further impact bone quality. This study aimed to establish an understanding of microdamage accumulation and load to failure in healthy and osteolytic vertebrae following cancer treatment (stereotactic body radiotherapy (SBRT), zoledronic acid (ZA), or docetaxel (DTX)). Forty-two 6-week old athymic female rats (Hsd:RH-Foxn1rnu, Envigo) were studied; 22 were inoculated with HeLa cervical cancer cells through intracardiac injection (day 0). Animals were randomly assigned to four groups: untreated (healthy=5, osteolytic=6), SBRT on day 14 (healthy=6, osteolytic=6), ZA on day 7 (healthy=4, osteolytic=5), and DTX on day 14 (healthy=5, osteolytic=5). Animals were euthanized on day 21. L1-L3 motion segments were compression loaded to failure and force-displacement data recorded. T13 vertebrae were stained with BaSO. 4. and µCT imaged (90kVp, 44uA, 4.9µm) to visualize microdamage location and volume. Damage volume fraction (DV/BV) was calculated as the ratio of BaSO. 4. to bone volume. Differences in mean load-to-failure were compared using three-way ANOVA (disease status, treatment, cells injected). Differences in mean DV/BV between treatment groups were compared using one-way ANOVA. Treatment had a significant effect on load-to-failure (p=0.004) with ZA strengthening the healthy and osteolytic vertebrae. Reduced strength post SBRT seen in the metastatic (but not the healthy) group may be explained by greater tumor involvement secondary to higher cell injection concentrations. Untreated metastatic samples had higher DV/BV (16.25±2.54%) compared to all treatment groups (p<0.05) suggesting a benefit of treatment to bone quality. Focal and systemic cancer treatments were shown to effect load-to-failure and microdamage accumulation in healthy and osteolytic vertebrae. Developing a better understanding of how treatments effect bone quality and mechanical stability is critical for effective management of patients with spinal metastases

Abstract. Introduction. All-tissue quadriceps tendon (QT) is becoming an increasingly popular alternative to hamstrings tendon (HT) and bone-tendon-bone (BTB) autograft for anterior cruciate ligament (ACL) reconstruction. The relatively short graft length however dictates that one, or both, ends rely on suture fixation. The strength of this construct is therefore extremely important. This study evaluates whether the use of a novel fixation technique can improve the tensile properties of the construct compared to a Krackow suture, and a looped tendon (suture free) gold standard. Methods. Eighteen porcine flexor tendons were tested, across three groups; suture-tape Krackow, looped tendon, and the novel ‘strain suture’. Biomechanical testing simulated the different stages of ACL graft preparation and loading (60N preload for 10 minutes, 10 cycles from 10N to 75N, and 1000 cycles from 100N to 400N). Elongation and load to failure were recorded, and stiffness calculated for each construct. Results. The mean elongation was significantly improved for the strain suture compared to the suture tape Krackow for preload, 10 cycle and 1000 cycle testing protocols respectively (1.36mm vs 4.93mm, p<001; 0.60mm vs 2.72mm, p<0.001; 2.95mm vs 29.08mm, p<0.001). Compared with the looped tendon, the strain suture demonstrated similar results for preload and 10 cycle elongation, but greater elongation during the 1000 cycle stage. Stiffness of the latter two constructs was similar. Conclusions. Augmentation of the suture fixation using this novel technique provides a construct that is significantly superior to currently practised suture techniques, and similar in elongation and stiffness to a looped graft

Aims. Many biomechanical studies have shown that the weakest biomechanical point of a rotator cuff repair is the suture-tendon interface at the medial row. We developed a novel double rip-stop (DRS) technique to enhance the strength at the medial row for rotator cuff repair. The objective of this study was to evaluate the biomechanical properties of the DRS technique with the conventional suture-bridge (SB) technique and to evaluate the biomechanical performance of the DRS technique with medial row knots. Methods. A total of 24 fresh-frozen porcine shoulders were used. The infraspinatus tendons were sharply dissected and randomly repaired by one of three techniques: SB repair (SB group), DRS repair (DRS group), and DRS with medial row knots repair (DRSK group). Specimens were tested to failure. In addition, 3 mm gap formation was measured and ultimate failure load, stiffness, and failure modes were recorded. Results. The mean load to create a 3 mm gap formation in the DRSK and DRS groups was significantly higher than in the SB group. The DRSK group had the highest load to failure with a mean ultimate failure load of 395.0 N (SD 56.8) compared to the SB and DRS groups, which recorded 147.1 N (SD 34.3) and 285.9 N (SD 89.8), respectively (p < 0.001 for both). The DRS group showed a significantly higher mean failure load than the SB group (p = 0.006). Both the DRS and DRSK groups showed significantly higher mean stiffness than the SB group. Conclusion. The biomechanical properties of the DRS technique were significantly improved compared to the SB technique. The DRS technique with medial row knots showed superior biomechanical performance than the DRS technique alone

Aims. Rotator cuff (RC) tears are common musculoskeletal injuries which often require surgical intervention. Noninvasive pulsed electromagnetic field (PEMF) devices have been approved for treatment of long-bone fracture nonunions and as an adjunct to lumbar and cervical spine fusion surgery. This study aimed to assess the effect of continuous PEMF on postoperative RC healing in a rat RC repair model. Methods. A total of 30 Wistar rats underwent acute bilateral supraspinatus tear and repair. A miniaturized electromagnetic device (MED) was implanted at the right shoulder and generated focused PEMF therapy. The animals’ left shoulders served as controls. Biomechanical, histological, and bone properties were assessed at three and six weeks. Results. Extension of the tendon from preload to the maximum load to failure was significantly better in the PEMF-treated shoulders at three weeks compared to controls (p = 0.038). The percentage strain was significantly higher in the PEMF group at both timepoints (p = 0.037). Collagen organization was significantly better (p = 0.034) as was tissue mineral density in the PEMF-treated group at three weeks (p = 0.028). Tendon immunohistochemistry revealed a prominent increase in type I collagen at the repair site at three weeks following continuous PEMF treatment compared with controls. None of the other tested parameters differed between the groups. Conclusion. MED-generated PEMF may enhance early postoperative tendon-to-bone healing in an acute rat supraspinatus detachment and repair model. Superior biomechanical elasticity parameters together with better collagen organization suggest improved RC healing. Cite this article: Bone Joint Res 2021;10(5):298–306

Operative fixation is the treatment of choice for a rupture of the distal tendon of biceps. A variety of techniques have been described including transosseous sutures and suture anchors. The poor quality of the bone of the radial tuberosity might affect the load to failure of the tendon repair in early rehabilitation. The aim of this study was to determine the loads to failure of different techniques of fixation and to investigate their association with the bone mineral density of the radial tuberosity. Peripheral quantitative computed tomography was carried out to measure the trabecular and cortical bone mineral density of the radial tuberosity in 40 cadaver specimens. The loads to failure in four different techniques of fixation were determined. The Endobutton-based method showed the highest failure load at 270 N (. sd. 22) (p < 0.05). The mean failure load of the transosseous suture technique was 210 N (. sd. 66) and that of the TwinFix-QuickT 5.0 mm was 57 N (. sd. 22), significantly lower than those of all other repairs (p < 0.05). No significant correlation was seen between bone mineral density and loads to failure. The transosseous technique is an easy and cost-saving procedure for fixation of the distal biceps tendon. TwinFix-QuickT 5.0 mm had significantly lower failure loads, which might affect early rehabilitation, particularly in older patients

Objectives. This study investigated the biomechanical performance of decellularized porcine superflexor tendon (pSFT) grafts of varying diameters when utilized in conjunction with contemporary ACL graft fixation systems. This aimed to produce a range of ‘off-the-shelf’ products with predictable mechanical performance, depending on the individual requirements of the patient. Methods. Decellularized pSFTs were prepared to create double-bundle grafts of 7 mm, 8 mm, and 9 mm diameter. Femoral and tibial fixation systems were simulated utilizing Arthrex suspension devices and interference screws in bovine bone, respectively. Dynamic stiffness and creep were measured, followed by ramp to failure from which linear stiffness and load at failure were measured. The mechanisms of failure were also recorded. Results. Dynamic stiffness was found to increase with greater graft diameter, with significant differences between all groups. Conversely, dynamic creep reduced with increasing graft diameter with significant differences between the 7 mm and 9 mm groups and the 8 mm and 9 mm groups. Significant differences were also found between the 7 mm, 8 mm, and 9 mm groups for linear stiffness, but no significant differences were found between groups for load at failure. The distribution of failure mechanisms was found to change with graft diameter. Conclusion. This study showed that decellularized pSFTs demonstrate comparable biomechanical properties to other ACL graft options and are a potentially viable option for ACL reconstruction. Although grafts can be stratified by their diameter to provide varying biomechanical properties, it may be more appropriate to alter the fixation technique to stratify for a greater diversity of biomechanical requirements. Cite this article: Bone Joint Res 2019;8:518–525

Previously, we showed that case-specific non-linear finite element (FE) models are better at predicting the load to failure of metastatic femora than experienced clinicians. In this study we improved our FE modelling and increased the number of femora and characteristics of the lesions. We retested the robustness of the FE predictions and assessed why clinicians have difficulty in estimating the load to failure of metastatic femora. A total of 20 femora with and without artificial metastases were mechanically loaded until failure. These experiments were simulated using case-specific FE models. Six clinicians ranked the femora on load to failure and reported their ranking strategies. The experimental load to failure for intact and metastatic femora was well predicted by the FE models (R. 2. = 0.90 and R. 2. = 0.93, respectively). Ranking metastatic femora on load to failure was well performed by the FE models (τ = 0.87), but not by the clinicians (0.11 < τ < 0.42). Both the FE models and the clinicians allowed for the characteristics of the lesions, but only the FE models incorporated the initial bone strength, which is essential for accurately predicting the risk of fracture. Accurate prediction of the risk of fracture should be made possible for clinicians by further developing FE models.

The absence of menisci in the knee leads to early degenerative changes. Complete radial tears of the meniscus are equivalent to total meniscectomy and repair should be performed if possible. The purpose of this study was to biomechanically compare the cross suture, hashtag and crosstag meniscal repairs using all-inside implants for radial tears. Radial tears were created at the mid-body of 36 fresh-frozen lateral human menisci and then repaired, in randomiSed order, with Fast-Fix™ 360s (Smith & Nephew, Andover, MA) using the cross suture, hashtag and crosstag techniques. The repaired menisci were tested using an Instron Electropuls E10000 (Instron, Norwood, MA). The tests consisted of cyclic loading from 5 to 30N at 1Hz for 500 cycles, then a load to failure test. Displacement following cyclic loading, load at 3mm of displacement, load to failure, and stiffness were recorded. Any differences between repairs were assessed using Kruskal-Wallis and Mann Whitney tests (p<0.05). Cross suture repairs displaced more following cyclic loading and resisted less load to failure than both the hashtag and crosstag repairs. However, these differences were not statistically significant. The average displacement following cyclic loading of cross suture, hashtag, and crosstag repairs was 4.34 mm (±2.02 mm), 3.46 mm (±2.12 mm), and 3.24 mm (±1.52 mm) respectively (p=0.33). Maximal load to failure was 64.83 N (±17.41 N), 74.52 N (±9.03 N), and 74.98N (±10.50N), respectively (p=0.419). All-inside cross suture, hashtag and crosstag repairs all displaced >3mm with cyclic loading, which is the threshold for meniscal insufficiency. This contrasts previous studies using inside-out sutures, where crosstag and hashtag repairs resisted cyclic loading (< 3mm). Inside-out suturing for radial tears of the lateral meniscus currently remains the gold standard

Introduction and Objective. Distal femoral fractures are commonly treated with a straight plate fixed to the lateral aspects of both proximal and distal fragments. However, the lateral approach may not always be desirable due to persisting soft-tissue or additional vascular injury necessitating a medial approach. These problems may be overcome by pre-contouring the plate in helically shaped fashion, allowing its distal part to be fixed to the medial aspect of the femoral condyle. The objective of this study was to investigate the biomechanical competence of medial femoral helical plating versus conventional straight lateral plating in an artificial distal femoral fracture model. Materials and Methods. Twelve left artificial femora were instrumented with a 15-hole Locking Compression Plate – Distal Femur (LCP-DF) plate, using either conventional lateral plating technique with the plate left non-contoured, or the medial helical plating technique by pre-contouring the plate to a 180° helical shape and fixing its distal end to the medial femoral condyle (n=6). An unstable extraarticular distal femoral fracture was subsequently simulated by means of an osteotomy gap. All specimens were tested under quasi-static and progressively increasing cyclic axial und torsional loading until failure. Interfragmentary movements were monitored by means of optical motion tracking. Results. Initial axial stiffness was significantly higher for helical (185.6±50.1 N/mm) versus straight (56.0±14.4) plating, p<0.01. However, initial torsional stiffness in internal and external rotation remained not significantly different between the two fixation techniques (helical plating:1.59±0.17 Nm/° and 1.52±0.13 Nm/°; straight plating: 1.50±0.12 Nm/° and 1.43±0.13Nm/°), p≥0.21. Helical plating was associated with significantly higher initial interfragmentary movements under 500 N static compression compared to straight plating in terms of flexion (2.76±1.02° versus 0.87±0.77°) and shear displacement under 6 Nm static rotation in internal (1.23±0.28° versus 0.40±0.42°) and external (1.21±0.40° versus 0.57±0.33°) rotation, p≤0.01. In addition, helical plating demonstrated significantly lower initial varus/valgus deformation than straight plating (4.08±1.49° versus 6.60±0.47°), p<0.01. Within the first 10000 cycles of dynamic loading, helical plating revealed significantly bigger flexural movements and significantly lower varus/valgus deformation versus straight plating, p=0.02. No significant differences were observed between the two fixation techniques in terms of axial and shear displacement, p≥0.76. Cycles to failure was significantly higher for helical plating (13752±1518) compared to straight plating (9727±836), p<0.01. Conclusions. Although helical plating using a pre-contoured LCP-DF was associated with higher shear and flexion movements, it demonstrated improved initial axial stability and resistance against varus/valgus deformation compared to straight lateral plating. Moreover, helical plate constructs demonstrated significantly improved endurance to failure, which may be attributed to the less progressively increasing lever bending moment arm inherent to this novel fixation technique. From a biomechanical perspective, helical plating may be considered as a valid alternative fixation technique to standard straight lateral plating of unstable distal femoral fractures

We compared time-dependent changes in the biomechanical properties of single-and double-row repair of a simulated acute tear of the rotator cuff in rabbits to determine the effect of the fixation techniques on the healing process. A tear of the supraspinatus tendon was created in 80 rabbits which were separated into two equal groups. A single-row repair with two suture anchors was conducted in group 1 and a double-row repair with four suture anchors in group 2. A total of ten intact contralateral shoulder joints was used as a control group. Biomechanical testing was performed immediately post-operatively and at four and eight weeks, and histological analysis at four and eight weeks. The mean load to failure in group 2 animals was greater than in group 1, but both groups remained lower than the control group at all intervals. Histological analysis showed similar healing properties at four and eight weeks in both groups, but a significantly larger number of healed tendon-bone interfaces were identified in group 2 than in group 1 at eight weeks (p < 0.012). The ultimate load to failure increased with the number of suture anchors used immediately post-operatively, and at four and eight weeks. The increased load to failure at eight weeks seemed to be related to the increase in the surface area of healed tendon-to-bone in the double-row repair group

Suture anchor have been used in surgical procedure of tendon or ligament repair. Recently, there has been developed an all suture anchor (soft anchor) which can be used even when the insertion area is narrow. But, the stability of soft anchors due to narrow zone has not been elucidated. This purpose of this study was to investigate stability of soft anchors with respect to their fixation intervals. Polyurethane foams with two different bone densities (10 pcf; 0.16g / cm³, 20 pcf; 0.32g / cm³) were used. All suture anchors and conventional suture anchors were fixed at 10mm, 5mm, and 2.5mm intervals. The failure load was measured using a mechanical testing machine. The average load to failure of conventional suture anchor were 200.4N, 200.2N, 184.7N in the 10mm, 5mm and 2.5mm interval with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with the 20 pcf foam bone respectively. Average load to failure load of soft anchor was 97.3N, 93.9N and 76.9N with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with 20 pcf foam bone. Suture screw spacing and bone density are important factors in anchor pullout strength. In osteoporotic bone density, insertion of the suture screw interval of 5 mm might be necessary

There is a growing trend towards using pre-clinical models of atrophic non-union. This study investigated different fixation devices, by comparing the mechanical stability at the fracture site of tibia bone fixed by either intramedullary nail, compression plate or external fixator. 40 tibias from adult male Wistar rats' cadavers were osteotomised at the mid-shaft and a gap of 1 mm was created and maintained at the fracture site to simulate criteria of atrophic non-union model. These were divided into five groups (n=8 in each): the first group was fixed with 20G intramedullary nail, the second group with 18G nail, the third group with 4-hole plate, the fourth group with 6-hole plate, and the fifth group with external fixator. Tibia was harvested by leg disarticulation from the knee and ankle joints, the soft tissues were carefully removed from the leg, and tibias were kept hydrated throughout the experiment. Each group was then subdivided into two subgroups for mechanical testing: one for axial loading (n=4) and one for 4-point bending (n=4). Statistical analysis was carried out by ANOVA with a fisher post-hoc comparison between groups. A p-value less than 0.05 was considered statistically significant. Axial load to failure data and stiffness data revealed that intramedullary nails are significantly stronger and stiffer than other devices, however there was no statistically significant difference axially between the nail thicknesses. In bending, load to failure revealed that 18G nails are significantly stronger than 20G. We concluded that 18G nail is superior to the other fixation devices, therefore it has been used for in-vivo experiments to create a novel model of atrophic non-union with stable fixation

Although 3D-printed porous dental implants may possess improved osseointegration potential, they must exhibit appropriate fatigue strength. Finite element analysis (FEA) has the potential to predict the fatigue life of implants and accelerate their development. This work aimed at developing and validating an FEA-based tool to predict the fatigue behavior of porous dental implants. Test samples mimicking dental implants were designed as 4.5 mm-diameter cylinders with a fully porous section around bone level. Three porosity levels (50%, 60% and 70%) and two unit cell types (Schwarz Primitive (SP) and Schwarz W (SW)) were combined to generate six designs that were split between calibration (60SP, 70SP, 60SW, 70SW) and validation (50SP, 50SW) sets. Twenty-eight samples per design were additively manufactured from titanium powder (Ti6Al4V). The samples were tested under bending compression loading (ISO 14801) monotonically (N=4/design) to determine ultimate load (F. ult. ) (Instron 5866) and cyclically at six load levels between 50% and 10% of F. ult. (N=4/design/load level) (DYNA5dent). Failure force results were fitted to F/F. ult. = a(N. f. ). b. (Eq1) with N. f. being the number of cycles to failure, to identify parameters a and b. The endurance limit (F. e. ) was evaluated at N. f. = 5M cycles. Finite element models were built to predict the yield load (F. yield. ) of each design. Combining a linear correlation between FEA-based F. yield. and experimental F. ult. with equation Eq1 enabled FEA-based prediction of F. e. . For all designs, F. e. was comprised between 10% (all four samples surviving) and 15% (at least one failure) of F. ult. The FEA-based tool predicted F. e. values of 11.7% and 12.0% of F. ult. for the validation sets of 50SP and 50SW, respectively. Thus, the developed FEA-based workflow could accurately predict endurance limit for different implant designs and therefore could be used in future to aid the development of novel porous implants. Acknowledgements: This study was funded by EU's Horizon 2020 grant No. 953128 (I-SMarD). We gratefully acknowledge the expert advice of Prof. Philippe Zysset

There is a growing trend towards using pre-clinical models of atrophic non-union. This study investigated different fixation devices, by comparing the mechanical stability at the fracture site of tibia bone fixed by either intramedullary nail, compression plate or external fixator. 40 tibias from adult male Wistar rats' cadavers were osteotomised at the mid-shaft and a gap of 1 mm was created and maintained at the fracture site to simulate criteria of atrophic non-union model. These were divided into five groups (n=8 in each): the first group was fixed with 20G intramedullary nail, the second group with 18G nail, the third group with 4-hole plate, the fourth group with 6-hole plate, and the fifth group with external fixator. Tibia was harvested by leg disarticulation from the knee and ankle joints, the soft tissues were carefully removed from the leg, and tibias were kept hydrated throughout the experiment. Each group was then subdivided into two subgroups for mechanical testing: one for axial loading (n=4) and one for 4-point bending (n=4). Statistical analysis was carried out by ANOVA with a fisher post-hoc comparison between groups. A p-value less than 0.05 was considered statistically significant. Axial load to failure data and stiffness data revealed that intramedullary nails are significantly stronger and stiffer than other devices, however there was no statistically significant difference axially between the nail thicknesses. In bending, load to failure revealed that 18G nails are significantly stronger than 20G. We concluded that 18G nail is superior to the other fixation devices, therefore it has been used for in-vivo experiments to create a novel model of atrophic non-union with stable fixation

The concept of decellularised xenografts as a basis for anterior cruciate ligament (ACL) reconstruction was introduced to overcome limitations in alternative graft sources such as substantial remodelling delaying recovery and donor site morbidity. This study aimed to measure the biomechanical properties of decellularised porcine super flexor tendon (pSFT) processed to create ACL grafts of varying diameters, with a view to facilitating production of stratified ‘off the shelf’ products with specified functional properties for use in ACL reconstructive surgery. Decellularisation was carried out using a previously established procedure, including antibiotic washes, low concentration detergent (0.1% sodium dodecyl sulphate) washes and nuclease treatments. Decellularised pSFTs were prepared to create double-bundle grafts of 7, 8 and 9mm diameter (n=6 in each group). Femoral and tibial fixations were simulated utilising Arthrex suspension devices (Tightrope®) and interference screws in bovine bone respectively. Dynamic stiffness and creep were measured under cyclic loading between 50–250N for 1000 cycles at 1Hz. This was followed by ramp to failure at 200mm/min from which linear stiffness and load at failure were measured. Data were analysed using either 1- or 2-way ANOVA as appropriate with Tukey post-hoc analysis (p<0.05). Significant differences were found between all groups for dynamic stiffness and between 7 & 9mm and 8 & 9mm groups for dynamic creep. Significant differences were also found between 7, 8 & 9mm groups for linear stiffness (167.8±4.9, 186.9±16.6 & 216.3±12.4N/mm respectively), but no significant differences were found between groups for load at failure (531.5±58.9, 604.1±183.3 & 627.9±72.4N respectively). This study demonstrated that decellularised pSFTs possess comparable biomechanical properties to other ACL graft options (autografts and allografts). Furthermore, grafts can be stratified by their diameter to provide varying biomechanical profiles depending on the anatomy and individual needs of the recipient

Abstract. Objectives. To evaluate mechanical properties of three suture-tendon constructs, the Krackow stitch (KS), the modified Prusik knot (PK) and the Locking SpeedWhip (LSW), using human cadaveric quadriceps grafts (QT). Methods. Thirty QT grafts were obtained from human cadaver specimens and an equal number of tendon-suture constructs were prepared for three stitches: KS, PK and LSW. The constructs were mounted in a materials testing machine (ElectroPuls E10000, Instron, Norwood, MA) and subject to tensile loading based on an established protocol. Load and displacement data for each tendon-suture construct were recorded. Results. Seven of 10 LSW specimens failed due to suture pullout before completing cyclic loading. Comparisons of the 3 successful LSW specimens (LSW3) were made to the KS and PK groups. All KS and PK specimens failed by suture breakage in load to failure stage. PK and LSW3 showed greater elongation after pretensioning than KS (7.29 ± 2.05, 7.05 ± 0.70, and 5.39 ± 0.95 mm respectively, p = 0.016 and p = 0.018). PK, LSW, and LSW3 showed greater elongation after preload than KS. Peak loads of PK (316.16 ± 18.31N), KS (296.00 ± 18.73N), and LSW (227.43 ± 76.20 N) were significantly different; LSW3 (319.33 ± 9.39 N) was not different from any group. KS was stiffer than PK (97.19 ± 8.03 vs 84.53 ± 6.72 N/mm, p = 0.0012). No differences were seen between the groups for elongation after cyclic loading or cross-sectional area. Conclusions. KS is the better of the sutured methods based on elongations and less risk of suture pullout. Excessive tendon tearing may initiate in the range of 100–200N with the LSW technique. PK provides similar performance to LSW and LSW3 in terms of elongations, but has the advantage of faster preparation time and less cost of the needle. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

We describe a new a technique for reconstructiing the ulnar collateral ligament (UCL) of the elbow, and test this new technique biomechanically comparing it with an established technique. The UCL is commonly injured in the throwing athlete. We describe a reconstruction using semi-tendinosis allograft with humeral fixation by interference knot. 30 fresh frozen cadaveric arms were harvested and amputated at the mid-humerus. Soft tissue was stripped to the level of the elbow sparing the UCL. The native ligament was ruptured in a materials testing machine (Bionix 858, MTS) by placing a rotational torque on the humerus, with the elbow was fixed at a right angle. Load to failure and stiffness were noted. These arms were randomly assigned to be reconstructed with one of three techniques: 1. Palmaris longus allograft with docking technique humeral fixation 2. Palmaris longus allograft with interference knot humeral fixation 3. Semitendinosis allograft with interference knot humeral fixation The techniques were then tested in the materials testing machine, load to failure and stiffness were noted. Group 1: load to failure 13.31 N/m (+/− 4.2) and stiffness 19.4 N/mm. Group 2: load to failure 13.86 N/m (+/− 5.5) and stiffness 19.1 N/mm. Group 3: load to failure 20.57 (+/− 7.4) and stiffness 20.4 N/mm. The semitendinosis interference technique had a significantly higher strength (p< 0.005) but was not significantly stiffer. None of the techniques approached the strength or stiffness of the native ligament: load to failure 34.2 N/mm and stiffness 45.3N/mm. A new technique to reconstruct the UCL of the elbow uses interference knot fixation in the humeral tunnel. When a palmaris longus allograft is used this technique has a similar biomechanical profile to the established docking technique. When semi-tendinosis is used this technique is significantly stronger and may result in earlier rehabilitation in the clinical setting

This study asseses the biomechanical properties of the Locking Volar T-Plate. It compares the axial load to failure to more traditional plating methods including the T-Plate and Pi-Plate. All three plates were tested for axial load to failure in both a dorsally comminuted model and a highly comminuted model with disruption of both the volar and dorsal cortices. The data in this study indicates may support volar plating for dorsally comminuted distal radius fractures. The pirpose of this study was to compare the biomechanical properties of three distal radius plates. The Locking Volar T-Plate performs equally as well regardless of the presence of volar comminution while the other systems do not. It also outperforms both other systems when volar comminution is present. This study provides biomechanical data of the Volar Locking T-Plate. Three distal radius plating systems were used on left radii after having either a segmental or dorsal wedge osteotomy performed to simulate severely comminuted and dorsally comminuted distal radius fractures respectively. Group One was plated with an AO stainless steel Pi plate, Group Two with a stainless steel T-plate volarly and Group Three with a stainless steel Locking Volar T-Plate. Specimens in all six of these groups (three groups with each type of osteotomy) were tested in axial loading to determine their load to failure. The load to failure was significantly higher with the Locking Volar T-Plate than the T-plate (p = 0.001) and Pi plate (p < 0.001) in the severely comminuted model. There was no significant difference between the groups in the dorsally comminuted model. There was no significant difference in the load to failure of the Locking Volar T-Plate between both models and between it’s the load to failure in the severely comminuted model and that of the Pi plate in the dorsally comminuted model. There has been limited data to date on the Locking Volar T-Plate. Studies, such as this one will provide biomechanical evidence supporting its use

Aims. Options for the treatment of intra-articular ligament injuries are limited, and insufficient ligament reconstruction can cause painful joint instability, loss of function, and progressive development of degenerative arthritis. This study aimed to assess the capability of a biologically enhanced matrix material for ligament reconstruction to withstand tensile forces within the joint and enhance ligament regeneration needed to regain joint function. Materials and Methods. A total of 18 New Zealand rabbits underwent bilateral anterior cruciate ligament reconstruction by autograft, FiberTape, or FiberTape-augmented autograft. Primary outcomes were biomechanical assessment (n = 17), microCT (µCT) assessment (n = 12), histological evaluation (n = 12), and quantitative polymerase chain reaction (qPCR) analysis (n = 6). Results. At eight weeks, FiberTape alone or FiberTape-augmented autograft demonstrated increased biomechanical stability compared with autograft regarding ultimate load to failure (p = 0.035), elongation (p = 0.006), and energy absorption (p = 0.022). FiberTape-grafted samples also demonstrated increased bone mineral density in the bone tunnel (p = 0.039). Histological evaluation showed integration of all grafts in the bone tunnels by new bone formation, and limited signs of inflammation overall. A lack of prolonged inflammation in all samples was confirmed by quantification of inflammation biomarkers. However, no regeneration of ligament-like tissue was observed along the suture tape materials. Except for one autograft failure, no adverse events were detected. Conclusion. Our results indicate that FiberTape increases the biomechanical performance of intra-articular ligament reconstructions in a verified rabbit model at eight weeks. Within this period, FiberTape did not adversely affect bone tunnel healing or invoke a prolonged elevation in inflammation. Cite this article: Bone Joint J 2019;101-B:1238–1247

Introduction. Suture anchor have been used in surgical procedure of tendon or ligament repair. Recently, there has been developed an all suture anchor (soft anchor) which can be used even when the insertion area is narrow. But, the stability of soft anchors due to narrow zone has not been elucidated. This purpose of this study was to investigate stability of soft anchors with respect to their fixation intervals. Methods. Polyurethane foams with two different bone densities (10 pcf; 0.16g / cm³, 20 pcf; 0.32g / cm) were used. All suture anchors and conventional suture anchors were fixed at 10mm, 5mm, and 2.5mm intervals. The failure load was measured using a mechanical testing machine. Results. The average load to failure of conventional suture anchor were 97.3N, 93.9N, and 76.9N in the 10mm, 5mm and 2.5mm interval with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with the 20 pcf foam bone respectively. Average load to failure load of soft anchor was 97.3N, 93.9N and 76.9N with 10pcf foam bones and 200.4 N, 200.2 N and 184.7 N with 20 pcf foam bone. Conclusion. Suture screw spacing and bone density are important factors in anchor pullout strength. In osteoporotic bone density, insertion of the suture screw interval of 5 mm might be necessary

The anterolateral ligament (ALL) has been recently recognized as a distinct stabilizer for internal rotation in the ACL-deficient knee and it has been hypothesized that ALL reconstruction may play an important role in improving anterolateral instability following ACL reconstruction. Both the gracilis tendon (GT) and a portion of the iliotibial band (ITB) have been suggested as graft materials for ALL reconstruction, however, there is an ongoing debate concerning whether GT or ITB are appropriate grafting materials. Furthermore, there is limited knowledge in how the mechanical properties of these potential grafts compare to the native ALL. Consequently, the aim of this study was to characterize the elastic (Young's modulus and failure load) and viscoelastic (dynamic and static creep) mechanical properties of the ALL and compare these results with the characteristics of the grafting materials (GT and ITB), in order to provide guidance to clinicians with respect to graft material choice. Fourteen fresh-frozen cadaveric knees (85.2±12.2 yr) were obtained. The ALL, ITB, and the distal (GTD) and proximal gracilis tendons (GTP) (bisected at mid portion) were harvested from each donor and tested with a dynamic material testing frame. Prior to testing, the cross-sectional area of each tissue was measured using a casting method and the force required to achieve a min-max stress (1.2–12 MPa) for the testing protocol was calculated (preconditioning (20 cycles, 3–6 MPa), sinusoidal cycle (200 cycles, 1.2–12 MPa), dwell at constant load (100 s, 12 MPa), and load to failure (3%/s)). Kruskall-Wallis tests were used to compare all tissue groups (p<0.05). The Young's modulus of both ALL (181.3±63.9 MPa) and ITB (357.6±94.4 MPa) are significantly lower than GTD (835.4±146.5 MPa) and GTP (725.6±227.1 MPa). In contrast, the failure load of ALL (124.5±40.9 N) was comparable with GTD (452.7±119.3 N) and GTP (433±133.7 N), however, significantly lower than ITB (909.6±194.7 N). Dynamic creep of the ALL (0.5±0.3 mm) and ITB (0.7±0.2 mm) were similar (p>0.05) whereas the GTD (0.26±0.06 mm) and GTP (0.28±0.1 mm) were significantly lower. Static creep progression of the ALL (1.09±0.4 %) was highest across all tissues, while GTD (0.24±0.05 %) and GTP (0.25±0.0.04 %) were lowest and comparable with ITB (0.3±0.07 %) creep progression. Since grafts from the ITB, GTD and GTP were comparable to the ALL only for certain mechanical properties, there was no clear preference for using one over another for ALL reconstruction. Therefore, further studies should be performed in order to evaluate which parameters play a vital role to determine the optimum grafting choice

Aims: To determine load to failure for four different meniscal repair techniques, and to assess gapping across repairs under cyclical loading. Background: Studies comparing the biomechanical properties of different meniscal repair systems are limited, and most have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Load to failure using high loads may, therefore, not be the most physiologically relevant in-vitro test for repair of circumferential tears, and measuring increases in gapping across repair sites under cyclical loading at lower loads may be of greater importance. Methods: Bovine menisci were divided vertically, 5mm from the peripheral edge to simulate a circumferential tear, and then repaired using one to four techniques: vertical loop sutures using 1 -PDS, bioabsorbable Meniscal Arrows (Atlantech), Meniscal Fasteners (Mitek) or T-Fix Suture Bars (Acufex). Nine specimens were tested in each group using an Instron 5500 materials testing machine to determine load to failure. A further nine specimens in each group were tested by cyclic loading between 5N and 10N at 20mm/min for 25 cycles, using a digital micrometer to measure initial gapping, and a Differential Variable Reluctance Transducer to measure the progressive increase in gapping across the repair site during the cyclical loading. Data was analysed by ANOVA and Tukey’s multiple comparison post test using Prism (GraphPad) software. Results: The mean loads to failure (with s.d.) in Newtons were: Sutures 72.7 (22.0), Arrows 34.2 (15.4), Fasteners 40.8 (13.4), and T-Fix 49.1 (13.8). The load to failure was significantly greater with the Sutures compared to the Arrows (p< 0.001), the Fasteners (p< 0.001) or the T-Fix (p< 0.05). The mean gapping across the repairs after 25 load cycles (with s.d.) in millimetres was: Sutures 3.3 (1.0), Arrows 2.2 (0.9), Fasteners 4.0 (0.6) and TFix 3.5 (0.7). The mean gapping was significantly less for the Arrows compared to the Sutures (p< 0.05), the Fasteners (p< 0.01), or the T-Fix (p< 0.05). Conclusions: These results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold with the least increase in gapping across a repair under cyclical loading by this test protocol

Studies comparing the biomechanical properties of different meniscal repair systems are limited, and most have simply investigated load to failure. Meniscal tissue is highly anisotropic, and far weaker under tension in the radial direction. Loading to failure using high radially orientated loads may, therefore, not be the most physiologically relevant in-vitro test for repair of circumferential tears, and determining increases in gapping across repair sites under cyclical loading at lower loads may be of greater importance. This study aimed to determine the load to failure for 4 different meniscal repair techniques, and to assess gapping across repairs under cyclical loading. Bovine menisci were divided vertically, 5mm from the peripheral edge to simulate a circumferential tear, and then repaired using 1 of 4 techniques: vertical loop sutures using 2-0 PDS, bioabsorbable Meniscal Arrows (Atlantech), T-Fix Suture Bars (Acufex) or Meniscal Fasteners (Mitek). 9 specimens were tested in each group using an Instron 5565 materials testing machine with Merlin control software to determine load to failure. A further 9 specimens in each group were tested by cyclical loading between 5N and 10N at 20mm/min for 25 cycles. Gapping across the repairs under cyclical loading was measured using a digital micrometer and a Differential Voltage Reluctance Transducer. The peak load to failure values for each repair method did not appear to fit a Gaussian distribution, but were skewed to the left due to some samples failing at lower loads than the main cluster. Results were analysed using the Kruskal-Wallis test, with Dunn’s multiple comparison post test. The results for gapping across the repairs from the cyclical testing all appeared to fit the Gaussian distribution, and these were analysed by Analysis of Variance, with Tukey’s multiple comparison post test. All analysis was performed using Prism (Graph-pad) Software. The mean loads to failure for each of the repair groups were: Sutures 72.7 N, T-Fix 49.1 N, Fasteners 40.8 N, and Arrows 34.2 N. The load to failure was significantly greater with the Suture group compared to the Arrows (p< 0.01) or the Fasteners (p< 0.05). The mean gapping across the repairs for each of the repair groups after 25 loading cycles were: Sutures 3.29mm, Arrows 2.18mm,Fasteners 3.99mm,andT-Fix 3.47mm.The mean gapping was significantly less for the Arrows compared to the Sutures (p< 0.05), the Fasteners (p< 0.01), or the T-Fix (p< 0.05). The results confirm that meniscal repair by suturing gives the highest load to failure, but show that Arrows give superior hold under lower loads, with the least gapping across repairs under cyclical loading by this testing protocol

Coronoid fractures account for 2 to 15% of the cases with elbow dislocations and usually occur as part of complex injuries. Comminuted fractures and non-unions necessitate coronoid fixation, reconstruction or replacement. The aim of this biomechanical study was to compare the axial stability achieved via an individualized 3D printed prosthesis with curved cemented intramedullary stem to both radial head grafted reconstruction and coronoid fixation with 2 screws. It was hypothesized that the prosthetic replacement will provide superior stability over the grafted reconstruction and screw fixation. Following CT scanning, 18 human cadaveric proximal ulnas were osteotomized at 40% of the coronoid height and randomized to 3 groups (n = 6). The specimens in Group 1 were treated with an individually designed 3D printed stainless steel coronoid prosthesis with curved cemented intramedullary stem, individually designed based on the contralateral coronoid scan. The ulnas in Group 2 were reconstructed with an ipsilateral radial head autograft fixed with two anteroposterior screws, whereas the osteotomized coronoids in Group 3 were fixed in situ with two anteroposterior screws. All specimens were biomechanically tested under ramped quasi-static axial loading to failure at a rate of 10 mm/min. Construct stiffness and failure load were calculated. Statistical analysis was performed at a level of significance set at 0.05. Prosthetic treatment (Group 1) resulted in significantly higher stiffness and failure load compared to both radial head autograft reconstruction (Group 2) and coronoid screw fixation, p ≤ 0.002. Stiffness and failure load did not reveal any significant differences between Group 2 and Group 3, p ≥ 0.846. In cases of coronoid deficiency, replacement of the coronoid process with an anatomically shaped individually designed 3D printed prosthesis with a curved cemented intramedullary stem seems to be an effective method to restore the buttress function of the coronoid under axial loading. This method provides superior stability over both radial head graft reconstruction and coronoid screw fixation, while achieving anatomical articular congruity. Therefore, better load distribution with less stress at the bone-implant interface can be anticipated. In the clinical practice, implementation of this prosthesis type could allow for early patient mobilization with better short- and long-term treatment outcomes and may be beneficial for patients with irreparable comminuted coronoid fractures, severe arthritic changes or non-unions

Introduction: Open Repair of the Achilles tendon is associated with problems of wound breakdown and infection. Percutaneous methods have been associated with sural nerve injury. The Achillon system avoids these problems. However no studies have assessed the strength of this repair and whether it allows early active rehabilitation. Materials/Methods: Simulated Achilles tendon ruptures in sheep Achilles tendons were repaired using either the Achillon method or a two strand Kessler technique with a No.2 Ticron Suture. The tendon diameter was measured in all cases, and was matched for both groups (mean 9mm, range 8–10mm). Specimens were loaded to failure using an Instron tensile testing machine. Results: Mean load to failure for the Achillon method was 153.13N ±59.64 (range 65–270), and the mean load to failure for the Kessler Repair was 123.13N ±24.19 (range 75–150). This difference was not statistically significant p=0.209. A Pearson’s correlation coefficient was carried out for each group to see if mean load to failure was related to tendon diameter. There were statistically significant higher mean loads to failure for wider tendon repaired by the Achillon method p=0.047, however this was not the case with Kessler repairs p=0.231. Discussion: The Achillon repair had a similar load to failure as the 2 strand Kessler repair. These results support the use of early active rehabilitation following the Achillon repair and we could not demonstrate stretching at the repair site. As this method is minimally invasive and does not grasp the tendon it may also have less effect on disruption of tendon blood supply and allow faster healing. Conclusion: The Achillon repair has comparable tensile strength to Kessler Repair, and is a biomechanically sound method of repair of the acutely rupture Achilles tendon in suitable Patients

Introduction: Open Repair of the Achilles tendon is associated with problems of wound breakdown and infection. Percutaneous methods have been associated with sural nerve injury. The Achillon system avoids these problems. However no studies have assessed the strength of this repair and whether it allows early active rehabilitation. Materials/Methods: Simulated Achilles tendon ruptures in sheep Achilles tendons were repaired using either the Achillon method or a two strand Kessler technique with a No.2 Ticron Suture. The tendon diameter was measured in all cases, and was matched for both groups (mean 9mm, range 8–10mm). Specimens were loaded to failure using an Instron tensile testing machine. Results: Mean load to failure for the Achillon method was 153.13N ± 59.64 (range 65–270), and the mean load to failure for the Kessler Repair was 123.13N ± 24.19 (range 75–150). This difference was not statistically significant p=0.209. A Pearson’s correlation coefficient was carried out for each group to see if mean load to failure was related to tendon diameter. There were statistically significant higher mean loads to failure for wider tendon repaired by the Achillon method p=0.047, however this was not the case with Kessler repairs p=0.231. Discussion: The Achillon repair had a similar load to failure as the 2 strand Kessler repair. These results support the use of early active rehabilitation following the Achillon repair and we could not demonstrate stretching at the repair site. As this method is minimally invasive and does not grasp the tendon it may also have less effect on disruption of tendon blood supply and allow faster healing. Conclusion: The Achillon repair has comparable tensile strength to Kessler Repair, and is a biomechanically sound method of repair of the acutely rupture Achilles tendon in suitable patients

A total of 20 pairs of fresh-frozen cadaver femurs were assigned to four alignment groups consisting of relative varus (10° and 20°) and relative valgus (10° and 20°), 75 composite femurs of two neck geometries were also used. In both the cadaver and the composite femurs, placing the component in 20° of valgus resulted in a significant increase in load to failure. Placing the component in 10° of valgus had no appreciable effect on increasing the load to failure except in the composite femurs with varus native femoral necks. Specimens in 10° of varus were significantly weaker than the neutrally-aligned specimens. The results suggest that retention of the intact proximal femoral strength occurs at an implant angulation of ≥ 142°. However, the benefit of extreme valgus alignment may be outweighed in clinical practice by the risk of superior femoral neck notching, which was avoided in this study

We tested four types of surgical repair for load to failure and distraction in a bovine model of Achilles tendon repair. A total of 20 fresh bovine Achilles tendons were divided transversely 4 cm proximal to the calcaneal insertion and randomly repaired using the Dresden technique, a Krackow suture, a triple-strand Dresden technique or a modified oblique Dresden technique, all using a Fiberwire suture. Each tendon was loaded to failure. The force applied when a 5 mm gap was formed, peak load to failure, and mechanism of failure were recorded. The resistance to distraction was significantly greater for the triple technique (mean 246.1 N (205 to 309) to initial gapping) than for the Dresden (mean 180 N (152 to 208); p = 0.012) and the Krackow repairs (mean 101 N (78 to 112; p < 0.001). Peak load to failure was significantly greater for the triple-strand repair (mean 675 N (453 to 749)) than for the Dresden (mean 327.8 N (238 to 406); p < 0.001), Krackow (mean 223.6 N (210 to 252); p <  0.001) and oblique repairs (mean 437.2 N (372 to 526); p < 0.001). Failure of the tendon was the mechanism of failure for all specimens except for the tendons sutured using the Krackow technique, where the failure occurred at the knot. The triple-strand technique significantly increased the tensile strength (p = 0.0001) and gap resistance (p = 0.01) of bovine tendon repairs, and might have advantages in human application for accelerated post-operative rehabilitation

Purpose: The study in vitro compares primary fixation strength of two arthroscopic flip knots; clinical knot security and ultimate load to failure. SMC knot is well known and frequently used arthroscopic knot. SAK (Secure Arthroscopic Knot) is fully instrumental knot, easy to master, with short learning curve. Published 10 years ago, during that period it is predominantly used by senior author in arthroscopic shoulder procedures. Materials and Methods: Curved metal rods are put in grips of the Universal Testing Machine and positioned centraly in vertical orientation 5 mm apart. The curvature of each rod was wrapped with 2 mm deerskin soaked in saline. Arthorscopic canulla was positioned in holder on the same position during testing procedure for all knots. Knots – 8 SAK and 8 SMC – were constructed outside the canulla, slided and positioned with arthroscopic knot pusher on the concave side of the caudal rod. Four additional loops (left-right alternatively) were put on the knot. Orthocord was used in all procedures, and all knots were performed by the same surgeon. The construct was preloaded with 7 N and distracted 0, 1mm/s. Ultimate tensile load (UF) and clinical load to failure (CF) were determined. Clinical load to failure is defined as force that distract knot for 3 mm. Data distribution was analysed and parametric statistics was performed. Results: Clinical failure for SAK is 249±29 N, and for SMC 191±40 N, and this difference is significant on the level of 5 %. Ultimate failure of SAK is 292±34 N and for SMC 276±39 N, and this difference is not significant. SAK failured with breakage in 7 out of 8 measurments, and SMC failured equaly by slipage and breakage. Discussion/Conclusion: The study imitated in vivo condition, slipage of knots during test was eliminated using deerskin which simulated human tissue. Both knots are equally strong regarding ultimate load to failure in hands of the experienced shoulder arthroscopist. Secure arthroscopic knot (SAK) presented greater load to clinical failure comparing with SMC knot. Autors can recomend SAK as an easy and safe arthroscopic flip knot

Summary. We found an increased natural expression of the growth factors bFGF, BMP-12, VEGF, and TGF-b1 during tendon healing of rat Achilles tendons. External application of these growth factors improved the tendons failure load in the early healing phase. Introduction. Tendon ruptures recover slowly and the healing of injuries can be devastating. Growth factors are known to influence tendon healing. However, only little is understood about growth factors in a healing tendon. Aim of this study was to investigate the influence of growth factors on tendon healing of rats following their natural expression. Methods. The Achilles tendon of rats were transected and resutured. First the expression of bFGF, BMP-12, VEGF and TGF-b1 was assessed by immunohistochemical analysis 1 to 8 weeks after surgery. Second the maximal failure load of healed Achilles tendons was measured dependent on the external application of bFGF, TGF-b1 and BMP-12. Results. The natural expression of bFGF (p<0.05), BMP-12 (p<0.05), TGF-b1, and VEGF was highest 1 week after transection. VEGF expression persisted during the remaining period whereas bFGF and BMP-12 declined. TGF-b1 expression peaked again after 8 weeks. A combined application of bFGF, TGF-b1 and BMP-12 resulted in a 4fold greater load to failure after 1 week (p<0.05), whereas a sequential treatment of these growth factors increased the load to failure even 5.5fold (p<0.05). Conclusion. During natural tendon healing the growth factors bFGF, BMP-12, VEGF, and TGF-b1 are differentially expressed. Additional administration of the mentioned growth factors can improve the load to failure in the early healing phase of rat Achilles tendons

Bone-patellar tendon-bone autografts, hamstring autografts or allografts are widely used grafts for ACL revision surgeries. Also use of quadriceps autograft for both primary and revision ACL surgeries is in an increasing popularity due to its biomechanical superior properties and less donor site morbidity. However, although several fixation techniques and devices for quadriceps tendon graft fixation on femoral side have been reported, literature lacks about biomechanical studies comparing properties of these different fixation techniques and devices. We aimed to investigate whether there is a difference between the fixation techniques of quadriceps tendon graft by using different fixation techniques and devices on the femoral side in terms of stiffness and amount of slippage in the tunnel. Full-thickness central parts of quadriceps tendons from paired knees of twenty five calf knees were fixed through a 10mm x 25mm tunnel in twenty five paired sheep femurs. Quadriceps tendon patellar side with soft tissue ending fixed with four different fixation devices (adjustable suspensory system (group 1), absorbable interference screw (group 2), titanium interference screw (group 3) and adjustable suspensory system + absorbable interference screw (group 4)) and quadriceps tendon with a patellar bone plug fixed with a titanium interference screw (group 5) were tested in a servohydraulic materials testing machine. 10 samples were included in each group. After applying a preload of 10 N, a cyclic force was applied for 20 cycles from 10N to 110N at a 1 hertz frequency. Amount of slippage in the tunnel was calculated as the difference measured in millimeters between length at 10 N after 20 cycles and starting length at 10 N (Graph 1). To determine the stiffness, a single load-to-failure cycle was performed at a strain rate of 20 mm/min as the last step (Figure 1). Rupture of the graft was not seen in any of the samples. Median values of amount of slippage in the tunnel were 6,41mm, 5,99mm, 3,01mm, 4,83mm, and 3,94mm respectively. Median values of maximum load at failure were 464N, 160N, 350N, 350N and 389N respectively. Amount of slippage in the tunnel was highest in the group 1 and was lowest in the group 3 (p<0.001). Group 1 was found to be most resistant group against load-to-failure test and group 2 was the weakest (p<0.001). However inter-group analyses between group 3 and 5 revealed that, although group 3 had the least slippage in the tunnel, group 5 was better in terms of stiffness, but there was no statistically significant difference (p=0,124 and 0,119 respectively). There was a significant difference between group 2 and 3 in both amount of slippage in the tunnel and stiffness (p=0,001 and 0.028 respectively)(Table 1). Our study revealed that, although quadriceps graft with a bone plug fixed with metal interference screws is widely presumed to be a stable fixation technique, there was no significant difference in terms of stiffness when compared with quadriceps graft with soft tissue ending fixed with a metal interference screw. Although adjustable suspensory device group was the best in the terms of resistance against load-to-failure, it was the worst in terms of amount of slippage from the tunnel. Thus, if a suspensory device is to be used, it must be kept in mind that a strong 20 cycles of intra-operative tension force must be applied to prevent further slippage of the graft in the tunnel which can result in failure of reconstruction. For any figures or tables, please contact the authors directly

Proximal humerus fractures (PHF) are the third most common fractures in the elderly. Treatment of complex PHF has remained challenging with mechanical failure rates ranging up to 35% even when state-of-the-art locked plates are used. Secondary (post-operative) screw perforation through the articular surface of the humeral head is the most frequent mechanical failure mode, with rates up to 23%. Besides other known risk factors, such as non-anatomical reduction and lack of medial cortical support, in-adverse intraoperative perforation of the articular surfaces during pilot hole drilling (overdrilling) may increase the risk of secondary screw perforation. Overdrilling often occurs during surgical treatment of osteoporotic PHF due to minimal tactile feedback; however, the awareness in the surgical community is low and the consequences on the fixation stability have remained unproved. Therefore, the aim of this study was to evaluate biomechanically whether overdrilling would increase the risk of cyclic screw perforation failure in unstable PHF. A highly unstable malreduced 3-part fracture was simulated by osteotomizing 9 pairs of fresh-frozen human cadaveric proximal humeri from elderly donors (73.7 ± 13.0 ys, f/m: 3/6). The fragments were fixed with a locking plate (PHILOS, DePuy Synthes, Switzerland) using six proximal screws, with their lengths selected to ensure 6 mm tip-to-joint distance. The pairs were randomized into two treatment groups, one with all pilot holes accurately predrilled (APD) and another one with the boreholes of the two calcar screws overdrilled (COD). The constructs were tested under progressively increasing cyclic loading to failure at 4 Hz using a previously developed setup and protocol. Starting from 50 N, the peak load was increased by 0.05 N/cycle. The event of initial screw loosening was defined by the abrupt increase of the displacement at valley load, following its initial linear behavior. Perforation failure was defined by the first screw penetrating the joint surface, touching the artificial glenoid component and stopping the test via electrical contact. Bone mineral density (range: 63.8 – 196.2 mgHA/cm3) was not significantly different between the groups. Initial screw loosening occurred at a significantly lower number of cycles in the COD group (10,310 ± 3,575) compared to the APD group (12,409 ± 4,569), p = 0.006. Number of cycles to screw perforation was significantly lower for the COD versus APD specimens (20,173 ± 5,851 and 24,311 ± 6,318, respectively), p = 0.019. Failure mode was varus collapse combined with lateral-inferior translation of the humeral head. The first screw perforating the articular surface was one of the calcar screws in all but one specimen. Besides risk factors such as fracture complexity and osteoporosis, inadequate surgical technique is a crucial contributor to high failure rates in locked plating of complex PHF. This study shows for the first time that overdrilling of pilot holes can significantly increase the risk of secondary screw perforation. Study limitations include the fracture model and loading method. While the findings require clinical corroboration, raising the awareness of the surgical community towards this largely neglected risk source, together with development of devices to avoid overdrilling, are expected to help improve the treatment outcomes

Purpose: To compare locking and non-locking single and dual plating constructs in maintaining posteromedial fragment reduction in a bicondylar tibial plateau fracture model. We hypothesized that posteromedial fragment fixation with medial and lateral non-locked constructs would tolerate higher loads than lateral locked constructs alone. Method: Thirty adult-sized composite tibiae were identically fractured into an AO 41-C1.3 pattern. Six plate constructs were tested:. lateral 8-hole 3.5 mm conventional non-locking proximal tibial plate [CP];. CP + posteromedial 6 hole 3.5 mm limited contact dynamic compression plate [CP + LCDCP];. CP + postero-medial 6 hole 1/3 tubular plate [CP + 1/3 tubular];. 8-hole 3.5mm Proximal Tibial Locking plate [PTLP];. 8-hole 3.5 mm LCP (locking compression plate) proximal tibia plate [LCP];. 9-hole Less Invasive Stabilization System [LISS] plate. Specimens were cyclically loaded to failure or a maximum load of 4000N. Load at posteromedial fragment failure was recorded. Results: Fragment failure occurred at the posteromedial fragment first. The CP + 1/3 tubular construct had the highest average load to failure (3040 N). In two instances, the CP + 1/3 tubular construct did not fail under the highest loads applied and was the only construct to have specimens that did not fail by 4000 N. The CP + 1/3 tubular plating construct demonstrated significantly higher load at failure compared with the PTLP (p=0.036), the LCP (p=0.004), and the LISS (p=0.012). The CP + 1/3 tubular group did not demonstrate a significant difference in load at failure when compared with the CP (p=0.093) or the CP + LCDCP (p=0.108). The LISS demonstrated a significantly higher load at failure compared to the LCP (p=0.046) but not to the PTLP (p=0.800). Conclusion: The posteromedial fragment tolerated higher loads with the CP + 1/3 tubular plate construct. The superiority of the dual plate construct may in part be due to the unreliable penetrance of the posteromedial fragment by the laterally applied locking screws

Basic engineering principles dictate that unplugged screw holes serve as sites of the concentration of stress and the initiation and growth of cracks (1,2). The idea of filling the holes were tested previously in the literature showing promising results (3). However there's either adverse results which might be a design mistake (4). The purpose of this study was to determine if the use of specially designed screw hole inserts in empty locking screw holes improves the strength and failure characteristics of locking plates. Forty two 7-hole locking LC/DCP plates were mounted on cylindric UHMW Polyethylene blocks with a 1-cm gap between blocks, simulating a fracture with comminution and bone loss. 21 plates had a screw hole insert placed in the center hole (centered over the simulated fracture), while 21 of the plates remained empty in the center hole. The plate–block constructs were placed in a mechanical testing machine and subjected to a series of loading conditions. The axial, bending and torsional stiffness and displacements needed for failure of each plate-block construct was calculated. The Statistical analysis was performed by Mann Whitney-U test for independent variables. All plates were then loaded to failure. There were significant difference in the axial load to failure (p=0.017), bending load to failure (p<0.01) and bending diplacements (p<0.01) of the test groups favoring the screw hole insert group as a higher mechanical strength. In conclusion the study demonstrates that the addition of the specially designed locking screw hole insert does significantly change the stength of the locking LC/DCP plates and might be suggested in the clinical application

We aimed to establish if radiological parameters, dual energy x-ray absorbtiometry (DEXA) and quantitative CT (qCT) could predict the risk of sustaining a femoral neck fracture following hip resurfacing. Twenty-one unilateral fresh frozen femurs were used. Each femur had a plain AP radiograph, DEXA scan and quantitative CT scan. Femurs were then prepared for a Birmingham Hip Resurfacing femoral component with the stem shaft angle equal to the native neck shaft angle. The femoral component was then cemented onto the prepared femoral head. No notching of the femoral neck occurred in any specimens. A repeat radiograph was performed to confirm the stem shaft angle. The femurs were then potted in a position of single leg stance and tested in the axial direction to failure using an Instron mechanical tester. The load to failure was then analysed with the radiological, DEXA and qCT parameters using multiple regression. The strongest correlation with the load to failure values was the total mineral content of the femoral neck at the head/neck junction using qCT r= 0.74 (p< 0.001). This improved to r=0.76 (p< 0.001) when neck width was included in the analysis. The total bone mineral density measurement from the DEXA scan showed a correlation with the load to failure of r=0.69 (p< 0.001). Radiological parameters only moderately correlated with the load to failure values; neck width (r=0.55), head diameter (r= 0.49) and femoral off-set (r=0.3). This study suggests that a patient’s risk of femoral neck fracture following hip resurfacing is most strongly correlated with total mineral content at the head/neck junction and bone mineral density. This biomechanical data suggests that the risk of post-operative femoral neck fracture may be most accurately identified with a pre-operative quantitative CT scan through the head/neck junction combined with the femoral neck width

We aimed to establish if radiological parameters, dual energy x-ray absorbtiometry (DEXA) and quantitative CT (qCT) could predict the risk of sustaining a femoral neck fracture following hip resurfacing. 21 unilateral fresh frozen femurs were used. Each femur had a plain AP radiograph, DEXA scan and quantitative CT scan. Femurs were then prepared for a Birmingham Hip Resurfacing femoral component with the stem shaft angle equal to the native neck shaft angle. The femoral component was then cemented onto the prepared femoral head. No notching of the femoral neck occurred in any specimens. A repeat radiograph was performed to confirm the stem shaft angle. The femurs were then potted in a position of single leg stance and tested in the axial direction to failure using an Instron mechanical tester. The load to failure was then analysed with the radiological, DEXA and qCT parameters using multiple regression. The strongest correlation with the load to failure values was the total mineral content of the femoral neck at the head/neck junction using qCT r= 0.74 (p< 0.001). This improved to r=0.76 (p< 0.001) when neck width was included in the analysis. The total bone mineral density measurement from the DEXA scan showed a correlation with the load to failure of r=0.69 (p< 0.001). Radiological parameters only moderately correlated with the load to failure values; neck width (r=0.55), head diameter (r= 0.49) and femoral off-set (r=0.3). This study suggests that a patient’s risk of femoral neck fracture following hip resurfacing is most strongly correlated with total mineral content at the head/neck junction and bone mineral density. This biomechanical data suggests that the risk of post-operative femoral neck fracture may be most accurately identified with a pre-operative quantitative CT scan through the head/neck junction combined with the femoral neck width

Purpose: To determine if administration of recombinant bFGF in an alginate gel would increase early healing mechanical parameters in acutely injured rat rotator cuff tendon at specific time points. Method: Sprague Dawley rats were randomly divided into 2 groups and had surgically created 1mm (half tendon width) full thickness injuries at exactly 2mm from insertion site of Infraspinatus on the humerus. 200ng of bFGF or vehicle control was administered to randomly chosen rats. Tendons were harvested at 1 week, 2 weeks and 4 weeks. In both groups, the Infraspinatus tendon was dissected, and left attached to the humerus. At the time of testing, the intact portion of the injured tendon was divided sharply across tendon fibers at the level of the injury leaving only the healing tissue callus in continuity with the remaining proximal and distal portions of the tendon and loaded to failure. Results: At 1 week the injury group’s average load to failure was 0.60N versus 0.61N in the bFGF injury group P = 1.000. At 2 weeks the injury group’s average load to failure increased to 1.03N versus 2.08N in the bFGF injury group P = 0.440 At 4 weeks the injury group’s average load to failure increased to 3.93N versus 5.56N in the bFGF injury group P = 0.008 representing a 41% increase in ultimate load. At 4 weeks, callus size of the injury group was 0.4mm2 versus 2.7mm2 in the bFGF injury group P < 0.001. Stiffness at 4 weeks for the injury tendons was 2.15 N/mm versus 3.54 N/mm in the bFGF group P = 0.008. Conclusion: At 4 weeks healing tissue of acutely injured rotator cuff exposed to bFGF has an increase in ultimate load to failure (41% compared to control), increase in tendon callus size and stiffness. Our findings suggest a role of bFGF or similar growth factors in accelerating the healing of injured rotator cuff tendon

Aim. To undertake a biomechanical study to determine the existence of any difference in the early tibial component fixation to bone, between two widely used techniques of cementation, which may confer an influence on implant survival. Method. 20 tibial saw bones were prepared by standard methods using extramedullary instrumentation to receive a fixed bearingtibial component (PFC, DePuy). Under controlled laboratory conditions, thetibial trayswere implanted with CMW cement using either of the two following cementation techniques (10 implants in each group): Full cementation–application of cement to the undersurface of the tibial tray, the keel, the cut surface of the tibia and its stem hole. Surface cementation – application of cement only to the undersurface of thetibial tray and the cut surface of the tibia. 72 hours after implantation, the fixation of the cemented components was assessed by determining the load to failure under controlled tensile stresses (using an Instron Electro-mechanical tensile tester). Results. The data suggested a two-stage process to failure with an initial de-bonding load preceding a peak load before failure. Highly significant differences between the two techniques were observed. The mean initial de-bond load for fully cemented implants was 1115N, compared to 590N for the surface cemented group (p<0.00005). The mean peak load before failure was also significantly greater in the fully cemented group (1830N vs 1370N, p<0.001). Conclusion. Full cementation of the tibial component in total knee arthroplasty confers greater initial fixation to bone than surface cementation and may therefore positively influence implant longevity

Many pre-clinical models of atrophic non-union do not reflect the clinical scenario, some create a critical size defect, or involve cauterization of the tissue which is uncommonly seen in patients. Atrophic non-union is usually developed following high energy trauma leading to periosteal stripping. The most recent reliable model with these aspects involves creating a non-critical gap of 1mm with periosteal and endosteal stripping. However, this method uses an external fixator for fracture fixation, whereas intramedullary nailing is the standard fixation device for long bone fractures. OBJECTIVES. To establish a clinically relevant model of atrophic non-union using intramedullary nail and (1) ex vivo and in vivo validation and characterization of this model, (2) establishing a standardized method for leg positioning for a reliable x-ray imaging. Ex vivo evaluation: 40 rat's cadavers (adult male 5–6 months old), were divided into five groups (n=8 in each): the first group was fixed with 20G intramedullary nail, the second group with 18G nail, the third group with 4-hole plate, the fourth group with 6-hole plate, and the fifth group with an external fixator. Tibiae were harvested by leg disarticulation from the knee and ankle joints. Each group was then subdivided into two subgroups for mechanical testing: one for axial loading (n=4) and one for 4-point bending (n=4) using Zwick/Roell® machine. Statistical analysis was carried out by ANOVA with a fisher post-hoc comparison between groups. A p-value less than 0.05 was considered statistically significant. To maintain the non-critical gap, a spacer was inserted in the gap, the design was refined to minimize the effect on the healing surface area. In vivo evaluation was done to validate and characterize the model. Here, a 1 mm gap was created with periosteal and endosteal stripping to induce non-union. The fracture was then fixed by a hypodermic needle. A proper x-ray technique must show fibula in both views. Therefore, a leg holder was used to hold the knee and ankle joints in 90º flexion and the foot was placed in a perpendicular direction with the x-ray film. Lateral view was taken with the foot parallel to the x-ray film. Ex vivo: axial load stiffness data revealed that intramedullary nails are significantly stronger and stiffer than other devices. Bending load to failure showed that 18G nails are significantly stronger than 20G, thus it is used for the in vivo experiments. In vivo: final iteration revealed 3/3 non-union, and in controls with the periosteum and endosteum intact but with the 1mm non-critical gap, it progressed to 3/3 union. X-ray positioning: A-P view in supine position, there was an unavoidable degree of external rotation in the lower limb, thus the lower part of the fibula appeared behind the tibia. To overcome this, a P-A view of the leg was performed with the body in prone rather, this arrangement allowed both upper and lower parts of the fibula to appear clearly in both views. We report a novel model of atrophic non-union, the surgical procedure is relatively simple and the model is reproducible

The strength of the intact and four reconstruction techniques (figure-eight, docking, single strand utilizing interference screws, and a single strand) of the medial collateral ligament (MCL) of the elbow were compared. Twenty cadaveric specimens were tested with a cyclic valgus loading protocol. The peak loads to failure of the MCL reconstructions were inferior compared to the intact ligament (p< 0.05). The docking and single strand reconstruction utilizing an endobutton for ulnar fixation were equivalent and had greater initial strength than the interference screws or figure-eight technique. It is suggested that improved interference screws are required for this repair. The purpose of this study was to compare the initial strength of the intact medial collateral ligament (MCL) of the elbow and four reconstruction techniques. The docking and endobutton reconstructions showed equivalent peak load to failure. Improved interference screws are required before they are employed clinically. The average peak load to failure or 5mm of joint gapping was 142.5±39.4N for the intact, 53.0±9.5N for the docking, 52.5±10.4N for the endobutton, 41.0±16.0N for the interference screw, and 33.3±7.1N for the figure-eight reconstructions. The peak load to failure was higher for the intact specimens compared to any of the reconstructions (p< 0.001). The docking reconstruction showed higher peak loads than the figure-eight or interference screw reconstruction, and the endobutton reconstruction showed higher peak loads than the figure-eight reconstruction (p< 0.004). There was no difference in peak loads between the docking and endobutton reconstructions (p> 0.05). Twenty (ten pairs) unpreserved cadaveric upper extremities were mounted in a custom jig with the elbow at 90°, and a valgus force was applied 12cm from the elbow joint. The specimens were loaded starting at 20N with the load increased in increments of 10N (200 cycles at each load), until either complete ligament failure or a 5mm increase in the distance between the attachment sites of the MCL. The results support that a single strand or multistrand ligament reconstruction can be equivalent with respect to maximal peak loads and cyclic loading. There are concerns with regard to the use of interference screw fixation in the clinical situation

We compared internal fixation augmented with a trabecular metal implant to internal fixation augmented with morcellized bone grafting for depressed lateral tibial plateau fractures. Six cadaveric tibia pairs were prepared and tested on a MTS machine for both cyclic loading and static load to failure. Results showed greater resistance in cyclic loading and load to failure in the trabecular metal group. We found half the loss of reduction of the tibial articular surface compared after cyclic loading over 10 000 cycles. These surprising results show the biomechanical superiority of our trabecular metal construct over the current standard of care. Restoration and maintenance of the plateau surface are the key points in the treatment of tibial plateau fractures. Any deformity of the articular surface jeopardises the future of the knee by causing osteoarthritis and axis deviation. The purpose of this study is to develop a more solid way to fix the Shatzker III fracture and to test a trabecular metal implant in the trauma setting for the first time. Six matched pairs of fresh frozen human cadaveric tibias were fractured and randomly assigned to be treated with either the standard of care (two 4,5mm cortical raft screws augmented with morcellized bone graft) or the new method (the same screws supporting a 2 cm diameter trabecular metal disc placed under the comminuted articular surface). The specimens were tested in cyclic loading and put at load to failure. The trabecular metal construct showed 40% less caudad displacement of the articular surface (1,43 mm vs 0,81 mm) in cyclic loading (p< 0.05). Its mechanical failure occurred at a mean of 3275 N compared to 2650 N for the standard of care construct (p< 0,05). The current study shows the biomechanical superiority of our trabecular metal construct compared to the current standard of treatment with regards to both its resistance to caudad displacement of the articular surface in cyclic loading and its strength at load to failure. Trabecular metal is a good metaphyseal void filler in the studied fracture

Aim. The purpose of this study was to develop and test the utility of a hybrid barbed-suture in the core repair of digital flexor tendon injuries. Despite offering advantages over traditional suture methods, concerns over the cost, strength to failure and biocompatibility of barbed sutures have hindered their development. Moreover the recent designs have been very complex. We have attempted to develop and test a simple barbed suture, to assess it's viability in flexor tendon repair and in particular to establish a baseline for the efficacy and modes of failure barbed sutures, in order to help provide a basis for future research. Method. The barbed suture device was constructed by inserting 3 steel barbs into the weaved construct of a braided polyester suture. The barbed sutures were inserted into 28 porcine lateral extensor tendons yielding a single sided core repair. Tensile testing of the repair was undertaken using a tabletop load frame with the distal end of the tendon fixed in a cryo clamp. Linear load testing to failure was undertaken. Maximum load, repair excursion and repair stiffness were recorded. Results. The barbed suture technique demonstrated a maximum load to failure of 40.4±16.4N. The excursion of the repair at failure point was 31.4±11.6mm. The stiffness of the repair derived from the linear elastic portion of the load displacement curve was 1.0±0.6N/mm. Conclusions. Use of this barbed suture construct offers a fast, easily applied method of flexor tendon repair. The maximum load to failure is comparable to the commonly used non-barbed suture methods. The suture excursion and stiffness findings suggest gap formation at low loads. Failure of the barbed suture seemed to be resisted by the collagen links between longitudinal tendon fibres. Further developments of this very modifiable construct may lead to a viable alternative to the current repair techniques

Summary. Strong mechanical fixation is critical to the success of rotator cuff repairs. In this comparative study in cadaveric shoulders, single-tendon full-thickness supraspinatus tears were repaired using two different types of PEEK knotless suture anchors-ReelX STT (Stryker) and Opus Magnum PI (Arthrocare)-using a single-row technique in both instances. Cyclic testing was performed followed by loading until mechanical failure. No significant difference was observed in gap formation, measured as the distance between the supraspinatus tendon and bone at the repair site, during cyclic loading. However, the maximum load was statistically higher for repairs with the ReelX anchor. Purpose. The objective of this study was to compare the gap formation during cyclic loading and maximum repair strength of single-row full thickness supraspinatus repairs performed using two different types of PEEK knotless suture anchors in a cadaveric model. Methods. Nine matched pairs of cadaveric shoulders were used in this study. All soft tissue was removed except for the supraspinatus, and a full thickness tear was formed. Single-row repairs were performed with two anchors per repair using either the Opus Magnum PI (Arthrocare) or the ReelX STT (Stryker). The specimens were mounted to an Instron at 45° to simulate an anatomic direction of load, and fiducial markers were placed on the repair in anterior and posterior positions. A 10 N preload was applied and held for 60 seconds, and then the tendon was cycled from 10 N to 90 N at 0.25 Hz for 500 cycles, followed by load to failure at 1 mm/s. A video digitizing system was used to track the markers and measure gap formation during loading. Gap formation was calculated by subtracting the distance between the markers at 10 N preload from the maximum displacement at 5 and 500 cycles. Paired t-tests were used to compare the cyclic displacement and max load. Results. One specimen from each of two matched pairs (one from each anchor group) failed during cyclic loading, leaving seven matched pairs for analysis. No significant difference was found in cyclic displacement between the two groups in either anterior or posterior positions at 5 and 500 cycles. However, maximum load to failure was significantly greater for repairs performed with the ReelX STT anchors (289N ± 57N) as compared to the OPUS anchors (178N ± 36N), with a p=0.009. Conclusions. These results suggest that the anchor type chosen for cuff repairs may affect the overall stability of the repair. Achieving stable fixation is critical for promoting healing of the tendon back to bone and to the long-term success of the repair, and using anchors that provide stronger fixation may decrease the occurrence of post-surgical tears and instability. The ReelX STT anchor outperformed the Opus Magnum PI anchor in terms of supporting significantly higher loads before failure, potentially leading to stronger repairs clinically

Aims. The traditional transosseus flexor hallucis longus (FHL) tendon transfer for patients with Achilles tendinopathy requires two incisions to harvest a long tendon graft. The use of a bio-tenodesis screw enables a short graft to be used and is less invasive, but lacks supporting evidence about its biomechanical behaviour. We aimed, in this study, to compare the strength of the traditional transosseus tendon-to-tendon fixation with tendon-to-bone fixation using a tenodesis screw, in cyclical loading and ultimate load testing. Materials and Methods. Tendon grafts were undertaken in 24 paired lower-leg specimens and randomly assigned in two groups using fixation with a transosseus suture (suture group) or a tenodesis screw (screw group). The biomechanical behaviour was evaluated using cyclical and ultimate loading tests. The Student’s t-test was performed to assess statistically significant differences in bone mineral density (BMD), displacement, the slope of the load-displacement curves, and load to failure. Results. The screw group showed less displacement (loosening) during cyclical loading, which was significant during 300, 500, 600, 700, 800, 900, and 1000 cycles (p < 0.05: other cycles: 0.079 < p < 0.402). Compared with the suture group, the screw group had higher mean ultimate load values (133.6 N, . sd. 73.5 vs 110.1 N,. sd. 46.2; p = 0.416). Conclusion. Fixation of the FHL tendon with a tenodesis screw enables a less invasive procedure to be undertaken and shows similar biomechanical behaviour and primary strength compared with fixation using a transosseus suture. Cite this article: Bone Joint J 2018;100-B:1175–81

Introduction. In order to prepare hamstring autograft, suture fixation to the tendon is required to secure and handle the tendon during harvest and preparation. We use a simple, grasping suture which doesn't require suture of the tendon, thus saving time and avoiding violation of the graft itself. We present this technique, with results of mechanical testing compared to a standard whip suture, traditionally used to handle hamstring autograft. Methods and materials. Twelve uniform ovine flexor tendons were prepared. A number two braided polyester suture was used in all cases. Six tendons were prepared with a standard, non-locking whip-suture, maintaining uniformity of suture bite and working length between samples. Six tendons were prepared with the utility suture, also taking care to maintain uniformity. The suture was applied by tying the thread around the tendon with a single-throw granny knot then symmetrically wrapping the suture ends from proximal to distal and securing with another single throw, allowing compression of the tendon with longitudinal tension on the suture. All the samples were tested to failure in uniaxial tension in a materials testing machine. Peak load values and load/displacement curves were acquired and results analysed with a two-sample T-test assuming significance at P<0.05. Results. Modes of failure between the groups, as characterised by the load/displacement curves were quite distinct. Peak load to failure was lower in the utility suture group but all failures occurred when the suture snapped. Thus the peak load to failure of the suture/tendon construct exceeded the breaking strain of the suture material. Conclusion. The grasping utility suture described here is sufficiently strong to harvest and handle hamstring autograft without passing a needle through the graft, saving time and avoiding violation of the graft itself. The lower loads at failure, despite failure occurring due to suture snapping, may reflect differing knot orientation between groups

Medial Displacement Osteotomy (MDO) of the os calcis is used to correct the hind foot valgus in a flat foot deformity. Screw fixation is commonly used although contemporary locking plate systems are now available. This study tested the hypothesis that a 10mm MDO would support a higher load to failure with a locked step plate than with a single cannulated screw. Materials and Methods. Eight pairs of embalmed cadaveric limbs harvested 10cm below the knee joint were axially loaded using a mechanical testing rig. Two pairs served as non-operated controls loaded to 4500N. The remaining limbs in pairs underwent a 10mm MDO of the os calcis and were stabilised with a locked step plate or a 7mm cannulated compression screw. One pair was loaded to 1600N (twice body weight) as a pilot study and the remaining 5 pairs were loaded to failure up to 4500N. The force-displacement curve and maximum force were correlated with observations of the mechanism of failure. Results. In one pair of control limbs, failure occurred with fractures through both os calcis bones, whilst the other pair did not undergo mechanical failure to 4500N. In the pilot osteotomy, the plate did not fail whilst loss of fixation with the screw was observed below 1600N. For the remaining five pairs, the median (with 95% Confidence Intervals) of the maximum force under load to failure were 1778.81N (1099.39 – 2311.66) and 826.13N (287.52 – 1606.67) for the plate and screw respectively (Wilcoxon Signed Rank test p=0.043). In those with screw fixation loaded to 4500N, the tuberosity fragment consistently failed by rotation and angulation into varus. Conclusion. In this model of load to failure with a medial displacement os calcis osteotomy, a locked step plate supported a significantly higher maximum force than a single large cannulated screw

Avulsion fractures of the tip of the olecranon are a common traumatic injury. Kirshner-wire fixation (1.6mm) with a figure of eight tension band wire (1.25mm) remains the most popular technique. Hardware removal mat be required in up to 80% of cases. Modern suture materials have very high tensile strength coupled with excellent usability. In this study we compare a repair using 1.6mm k-wires with a 1.25mm surgical steel, against a repair that uses two strands of 2 fibrewire. Twelve Pairs of cadaveric arms were harvested. A standard olecranon osteotomy was performed to mimic an avulsion fracture. In each pair one was fixed using standard technique, 2 × 1.6mm transcortical ?-wire plus figure of 8 loop of 1.25mm wire. The other fixed with the same ?-wires with a tension band suture of 2.0 fibrewire (two loops, one figure of 8 and one simple loop). The triceps tendon was cyclically loaded (10-120 Newtons) to simulate full active motion 2200 cycles. Fracture gap was measured with the ‘Smart Capture’ motion analysis system. The arm was fixed at 90 degrees and triceps tendon was loaded until fixation failure, ultimate load to failure and mode of failure was noted. The average gap formation at the fracture site for the suture group was 0.91mm, in the wire group 0.96mm, no specimen in either group produced a significant gap after cyclical loading. Mean load to failure for the suture group was 1069 Newtons (SD=120N) and in the wire group 820 Newtons (SD=235N). Both types of fixation allow full early mobilisation without gap formation. The Suture group has a significantly higher load to failure (p=0.002, t-test). Tension Band suture allows a lower profile fixation, potentially reducing the frequency of wound complications and hardware removal

Our aim was to compare the biomechanical strength modified side-to-side repair with modified pulvertaft technique keeping overlap length, anchor points, type of suture, suture throw and amount of suture similar. In our study, we have used turkey tendons. Two investigators performed 34 repairs during one summer month. All mechanical testing was carried out using the tensile load testing machine. Variables measured were maximum load, load to first failure, modulus, load at break, mode of failure, site of failure, tensile strain, and tensile stress. The statistical comparison was carried by Levene's test and T test for means. The mean maximum load tolerated by modified side-to-side repair was 50.3N(S.D13.7) and that by modified pulvertaft 46.96N(S.D: 16.4), overall it was 48.29 N (S.D: 14.57). The tensile stress at maximum load for modified pulvertaft and modified side-to-side repair was 4.2MPa(S.D: 3.1) and 4.7 MPa (S.D: 3.8) respectively {Overall 4.3MPa(S.D: 3.5)}. The tensile stress at yield was 4.01 MPa (S.D: 3.1) and 5.5 MPa (S.D: 3.7) respectively for modified pulvertaft and modified side-to-side repair {overall 4.44 MPa (S.D: 3.45)}. The tensile strain at maximum load respectively for side-to-side and modified pulvertaft repair was 7.87%(S.D: 33.3) and 7.84%(S.D: 34.02) respectively. We found no statistical difference between 2 repairs in terms of strength, load to first failure, and maximum load to failure. The suture cut through was the commonest mode of failure. Our study uniquely compares two techniques under standard conditions, and contrary to existing evidence found no difference

Hip fractures constitute the most debilitating complication of osteoporosis with a steadily increasing incidence in an aging population. Intramedullary nailing of osteoporotic proximal femoral fractures can be challenging because of poor implant anchorage in the femoral head. Recently, cement augmentation of PFNA blades with Polymethylmethycrylate (PMMA) has shown promising results by enhancing the cutout resistance in proximal femoral fractures. The aim of this biomechanical study was to assess the impact of cement augmentation on the fixation strength of TFNA blades and screws within the femoral head, and compare its effect with head elements placed in a center or antero–posterior off–center positions. Eight groups were formed out of 96 polyurethane foam specimens with low density, simulating isolated femoral heads with severe osteoporotic bone. The specimens in each group were implanted with either non–augmented or PMMA–augmented TFNA blades or screws in a center or antero–posterior off–center position, 7 mm anterior or 7 mm posterior. They were mechanically tested in a setup simulating an unstable pertrochanteric fracture with lack of postero–medial support and load sharing at the fracture gap. All specimens underwent progressively increasing cyclic loading until catastrophic construct failure. Varus–valgus and head rotation angles were monitored by an inclinometer mounted on the head. A varus collapse of 5° or a 10° head rotation were defined as the clinically relevant failure criterion. Load at failure for specimens with augmented TFNA head elements (screw center: 3799 N ± 326 (mean ± SD); blade center: 3228 N ± 478; screw off–center: 2680 N ± 182; blade off–center: 2591 N ± 244) was significantly higher compared to the respective non–augmented specimens (blade center: 1489 N ± 41; screw center: 1593 N ± 120; blade off–center: 1018 N ± 48; screw off–center: 515 N ± 73), p<0.001. In both non–augmented and augmented specimens, the failure load in center position was significantly higher compared to the respective off–center position, regardless of head element, p<0.001. Non–augmented TFNA blades in off–center position revealed significantly higher load at failure versus non–augmented screws in off–center position, p<0.001. Cement augmentation clearly enhances fixation stability of TFNA blades and screws. Non–augmented blades outperformed screws in antero–posterior off–center position. Positioning of TFNA blades in the femoral head is more forgiving than TFNA screws in terms of failure load. Augmentation with TFNA has not been approved by FDA

Introduction: Reconstruction of the original footprint of the supraspinatus tendon is mandatory in achieving proper clinical result after reconstrucitve rotator cuff surgery. Methods: Twenty four cadaveric sheep shoulder and 12 live sheep sacrificed 3 months after rotator cuff reconstruction were tested. Arthroscopic transosseous technique and double row techniques were compared according to static load immediately after reconstruction (sheep cadaver) and after tissue healing took place (in vivo on sheep). In clinical work we analysed results of 120 patients operated on by the senior author employing different arthroscopic Methods: of rotator cuff reconstructionas. Results: Transosseous technique and double row technique have comparable biomechanical primary ultimate load to failure (160 N and 137 N comparatively) and equal ultimate load to failure after the tissue heals (302 N and 246 N respectively). Immediately after the reconstruction in double row group we noticed significant fragility in comparison to elasticity of the tendon-bone complex in transosseous group. We operated 67 shoulders (56%) with arthroscopic transosseous technique. We did not noticed complications of bone anchor, but in two patients we had rerupture of sutures that had to be reoperated on. Discussion: Arthroscopic transosseous technique uses less amount of bone anchors, optimaly reconstructs “footprint”, and has equal ultimate static load to failure as double row technique. But, double row technique is much more fragile than transosseous method in immediate postoperative period. Arthroscopic transosseous technique is technicaly demanding procedure that guarantee optimal clinical result

Introduction: The aim of this research project was to establish a simple, reliable and repeatable externally fixed femoral fracture model. The rat was selected, as it was a suitable animal for use in a model of fracture repair and ovariectomy induced osteoporosis, both of which were to be investigated in future experiments. There are femoral fracture models described in the literature based on the insertion of an intramedullary nail prior to inducing a fracture. We felt, based on our experience of the unilateral externally fixed mouse fracture model, that external fixation would allow us to carry out radiographical and histological analysis of fracture healing without any of the tissue trauma caused by the insertion and removal of the intramedullary device. Materials and Methods: A unilateral external fixator was chosen due to its simplicity. Four threaded stainless steel pins pass through holes in an aluminium plate with nuts placed on the pin above and below the plate. The holes in the plate were 0.1mm bigger than the pins and unthreaded allowing the plate to slide freely over the pins. Tightening of the upper nut compressed the plate against the lower nut holding the pin securely. 41 female Sprague-Dawley rats, aged between 12 and 18 weeks, were used. They were anaesthetised using a standard mixture of hypnorm and midazolam and analgesia, fluids and antibiotic were administered subcutaneously prior to surgery. The femur was exposed through a lateral approach and a standardised osteotomy was made prior to the application of the fixator plate. Accurate reduction was confirmed visually at the time of surgery and also by way of a post-op x-ray. 25 animals were sacrificed at 4 days and 1, 2, 4, 6 and 8 weeks for histology. The fractured limbs were harvested, fixed, decalcified and paraffin embedded as per standard protocol and serial sections were cut. These were stained with H& E and alcian blue and analysed 15 animals were sacrificed at 4,6 or 8 weeks for biomechanical strength testing. Four-point bending was carried out on freshly harvested femurs stored in normal saline between harvest and testing. Both limbs were tested and the fractured limbs were standardised relative to the unfractured limb. Maximum load to failure was recorded and stiffness was calculated from the load-displacement curve. Results: No post-operative complications of fixation failure or infection occured. On histological assessment at D4 a predominantly lymphocytic inflammatory response was seen within the fracture haematoma. This inflammatory response was replaced with endosteal and periosteal new bone between wks 1 and 2. Bridging of the fracture gap was seen at week 6. Both stiffness and load to failure increased with increasing time. There was a statistically significant improvement in the percentage stiffness and percentage load to failure between 4 and 8 weeks (p=0.03 and p=0.018 respectively). The difference in load to failure between 6 and 8 weeks was also significantly different (p=0.042). Discussion: A simple, reliable and repeatable externally fixed rat femoral fracture model has been established

Purpose: Recent advances in arthroscopic shoulder surgery has expanded the options available to surgeons repairing rotator cuff tears. There are now a variety of suture techniques that arthroscopists can use to fix tears but limited data on which might work best, particularly for double row techniques. The objective of this study was to compare the initial cyclic loading and load to failure properties of two arthroscopic double row fixation with that of the open double row technique. Method: Thirty sheep shoulders were harvested and the infraspinatus tendons dissected free from all surrounding muscles and osseous attachments. Three double row stitch configurations (arthroscopic standard, arthroscopic mason-allen, open mason-allen) were performed and tested. The shoulders were then secured in a material testings machine and cyclically loaded between 5 and 100 N at 0.20 Hz for 10 cycles and then loaded to failure under displacement control at 1 mm/sec. Stiffness and ultimate load were measured and compared. The failure type, either through suture or anchor pull out, was also recorded. Results: None of the specimens failed under cyclic loading. The ultimate load to failure was significantly higher for the open double row and the arthroscopic mason-allen compared to the standard double row technique. No significant differences in stiffness were found among the stitches. All failures occurred at the suture-tendon junction. Conclusion: In this in vitro cadaver sheep study, the arthroscopic mason-allen and open mason-allen techniques had a significantly higher ultimate load to failure than the standard double row technique. Stitching methods that strengthen the tendon-suture interface can improve the strength of double row rotator cuff repairs

Fractures of the anteromedial facet (AO/OTA 21-B1.1, O'Driscoll Type 2, subtype 3) are associated with varus posteromedial rotational instability of the ulnohumeral joint and early post-traumatic arthritis. The purpose of this study was to examine the stability of plate (locking and non-locking) vs screw constructs in the fixation of anteromedial coronoid facet fractures in a sawbone model. An anteromedial coronoid facet fracture (AO/OTA 21-B1.1) was simulated in 24 synthetic ulna bones. They were then assigned into 3 fracture fixation groups: non-locking plate fixation, locking plate fixation, and dual cortical screw fixation. An AO 2.0 mm screw and plate system was used for the plate fixation groups and 2.0 mm cortical screws were used for the screw-only group. Following fixation, each construct was potted in bismuth alloy and secured to a servohydraulic load frame. Each construct was cycled in tension and then in compression at 0.5Hz. For both cycling modalities, an incremental loading pattern was used starting at 40 N and increased by 20 N every 200 cycles up to 200N. Fracture fragment displacement was recorded with an optical tracking system. Following cyclic loading each construct was loaded to failure (displacement >2 mm) at 10mm/min. Tension cycling – All constructs in the plated groups (locking and non-locking constructs) survived the cyclic tension loading protocol (to 200N) with maximum fragment displacement of 12.60um and 14.50um respectively. There was no statistical difference between the plated constructs at any load level. No screw-only fixed construct survived the tension protocol with mean force at failure of 110N (range 60–180N). Compression Testing – All constructs in the plated groups (locking and non-locking constructs) survived the cyclic compression loading protocol (to 200N), while all but one of the screw-only fixation constructs survived. Fracture fragment displacement was significantly greater in the screw-only repair group across all loading levels when compared to the plated constructs. There was no statistically significant difference in fragment motion between the locking and non-locking groups. Failure Testing – The maximum load at failure in the screw-only group (281.9 N) was significantly lower than locking and non-locking constructs (587.0 N and 515.5N respectively, p <0.05). There was no difference between the locking and non-locking group in mean load to failure or mean stiffness. Screw construct stiffness (337.2 N/mm) was lower than the locking and non-locking constructs (682.9 N/mm and 479.1 N/mm respectively) however this did not reach statistical significance (p=0.051). Fixation of anteromedial coronoid fractures is best achieved with a plating technique. Locking plates did not offer any advantage over conventional plates. Isolated screw fixation might not provide adequate stability for these fractures which could result in loss of reduction leading to post-traumatic arthrosis or instabilility

Femur fractures are a complication of hip arthroplasty. When the stem is well fixed, fracture fixation is the preferred treatment option. Numerous fixation methods have been advocated, using plates and/or allograft struts. The study was conducted to determine the biomechanical characteristics of three constructs currently used for fixation of these fractures. Vancouver type B1 periprosthetic femur fractures were created distal to a cemented hip stem implanted in third generation composite femurs. The fractures were fixed with one of three constructs: 1- A non-locking plate and allograft strut (NLP-A) 2- A locking plate and allograft strut (LP-A) 3- A locking plate alone. (LP) The struts were held in place with cables. There were five specimens in each group. Following fixation, the constructs underwent sinusoidal cyclic loading from 200 to 1200 N for 100000 cycles. Stiffness of the constructs was determined in bending, torsion and axial compression before and after cyclic loading. Axial load to failure was also determined. Overall, cyclic loading had little effect on the mechanical properties of these constructs. The two constructs with allografts were significantly stiffer in coronal plane bending than the construct consisting of only a locking plate. There were no significant differences in axial or torsional stiffness between the constructs. Load to failure of the NLP-A (4095 N) and LP-A (4007 N) constructs was significantly greater than the LP construct (3398 N) (p=0.023 and p=0.044 respectively). All three constructs tested retained their mechanical characteristics following 100000 cycles of loading. Our initial concerns that the cables holding the allograft strut would loosen appear unfounded. Allograft strut-plate constructs are stiffer in bending and have a higher load to failure than a stand-alone locking plate. When an allograft plate construct is chosen, locking screws provide no mechanical advantage in this experimental model

Introduction: It has been suggested that notching of the femoral neck during hip resurfacing weakens the proximal femur and predisposes to femoral neck fracture. We aimed to examine the effect of neck notching during hip resurfacing on the strength of the proximal femur. Methods: 3. rd. generation composite femurs that have been shown to replicate the biomechanical properties of human bone were utilised. The bone was secured in a position of single leg stance and tested with an Instron mechanical tester. Imageless computer navigation was used to position the initial guide wire during head preparation. Six specimens were prepared without a superior notch being made in the neck of the femur, six were prepared in an inferiorly translated position to cause a 2mm notch in the superior femoral neck and six were prepared with a 5mm notch. The femoral component was then cemented in place. All specimens had radiographs taken to ensure that the stem shaft angle was kept constant. The specimens were then loaded to failure in the axial direction. Results: The 2mm notched group (mean load to failure 4034N) were significantly weaker than the un-notched group (mean load to failure 5302N) when tested to failure (p=0.017). The 5mm notched group (mean load to failure 3121N) were also significantly weaker than the un-notched group (p=0.0003) and the 2mm notched group (p=0.046). All fractures initiated at the superior aspect of the neck, at the component bone interface. All components were positioned in the same coronal alignment +/−2 degrees. Discussion: A superior notch of 2mm in the femoral neck weakens the proximal femur by 24% and a 5mm notch weakens it by 41%. This study provides biomechanical evidence that notching of the femoral neck may lead to an increased risk of femoral neck fracture following hip resurfacing

Introduction: We aimed to examine the effect of neck notching during hip resurfacing on the strength of the proximal femur. Methods: Third generation composite femurs that have been shown to replicate the biomechanical properties of human bone were utilised. Imageless computer navigation was used to position the initial guide wire during head preparation. Six specimens were prepared without a superior notch being made in the neck of the femur, six were prepared in an inferiorly translated position to cause a 2mm notch in the superior femoral neck and six were prepared with a 5mm notch. All specimens had radiographs taken to ensure that the stem shaft angle was kept constant. The specimens were then loaded to failure in the axial direction with an Instron mechanical tester. A three dimensional femoral finite element model was constructed and molded with a femoral component constructed from the dimensions of a Birmingham Hip Resurfacing. The model was created with a superior femoral neck notch of increasing depths. Results: The 2mm notched group (mean load to failure 4034N) were significantly weaker than the un-notched group (mean load to failure 5302N) when tested to failure (p=0.017). The 5mm notched group (mean load to failure 3121N) were also significantly weaker than the un-notched group (p=0.0003) and the 2mm notched group (p=0.046). All fractures initiated at the superior aspect of the neck, at the component bone interface. The finite element model revealed increasing Von Mises stresses with increasing notch depth. Discussion: A superior notch of 2mm in the femoral neck weakens the proximal femur by 24% and a 5mm notch weakens it by 41%. This study provides biomechanical evidence that notching of the femoral neck may lead to an increased risk of femoral neck fracture following hip resurfacing due to increasing stresses in the region of the notch

Rotator cuff tendons are typically reattached to the proximal humerus using either transosseous sutures or suture anchors. Their primary mode of failure is at the tendon bone interface 1. Surgical adhesives are used to bond cartilage, tendons and bone, and to close wounds. In an attempt to increase the tendon-bone interface we investigated the addition of a novel adhesive secreted from a species of Australian frog (Notaden bennetti) 2 to different methods of rotator cuff repair. Forty two fresh frozen sheep infraspinatus tendons were repaired using 3 different techniques: transosseous sutures; two Mitek RC Quickanchors with 1 suture per anchor and two Opus Magnum anchors with 1 suture per anchor all using a mattress stitch configuration. In each group 7 shoulders were repaired with the addition of a small amount of frog glue to the infraspinatus footprint while 7 were used as control with no adhesive. Mechanical testing was performed using a mechanical tensile testing machine. The strongest construct in the control groups was the Mitek suture anchors (mean 86±5 N) followed by the Opus suture anchor (69±6N) and transosseous repair (50±6N). This proved significant (p< 0.05) between both metallic anchors and the transosseous repair.{BR}The addition of frog glue resulted in a significant increase in load to failure and total energy required until failure in all repair techniques (p< 0.01). There was a 2 fold increase in load to failure of both the Opus Magnum (143±8N) and Mitek RC Fastin (165N±20 N) anchors while the transosseous repair (86± 8 N) had a 1.7 fold increase in its load to failure. This data suggests that:. suture anchor fixation is a stronger construct requiring a larger amount of total force to fail than transosseous repair using a one suture repair technique, that. the addition of an adhesive to the tendon-bone interface significantly enhances both ultimate load and total energy required to failure in all repair types. The unique properties of this frog glue (strong, flexible, sets in water and biocompatibility) may ultimately lead to the production of a useful adjunct for rotator cuff repair in humans

Introduction: It has been suggested that femoral component alignment in the coronal plane affects the risk of sustaining femoral neck fracture following hip resurfacing. Previous literature suggests that increasing the stem shaft angle to an extreme valgus position produces the most favourable biomechanical properties following femoral component insertion. We examined the effects of femoral component alignment during hip resurfacing on proximal femur strength. Methods: 3. rd. generation composite femurs shown to replicate biomechanical properties of human bone were used. The bones were secured in a position of single leg stance and tested with an Instron mechanical tester. Imageless computer navigation was used to position the guide wire during femoral head preparation. Specimens were placed in 115, 125 and 135 degrees of stem shaft angulation. No notching was made in the femoral neck during head preparation. The femoral components were cemented in place. Radiographs were taken ensuring that stem shaft angles were correct. Specimens were loaded to failure in the axial direction. Results: A component position of 115 degrees compared to 125 degrees reduced load to failure from 5475N to 3198N (p=0.009). A position of 135 degrees (5713N) compared to 125 degrees (5475N) did not significantly alter the load to failure (p=0.347). Component positioning at a stem shaft angle below 125 degrees resulted in a significant reduction in strength of the proximal femur. Placement of the component at 115 degrees reduced the load to failure by 42%. Discussion: Our findings suggest that a varus orientation may be at risk for causing femoral neck fracture. The advantages of increasing valgus angle beyond 125 degrees may not provide as much reduction in the incidence of femoral neck fracture as previously suggested, particularly when considering the inherent risk of femoral neck notching in these positions

We measured the initial fixation strength of a new graft, bone-hamstring-bone (BHB), for reconstruction of the anterior cruciate ligament (ACL) in 79 porcine knees and compared it with that of the normal porcine ACL and of the bone-patellar tendon-bone (BPB) graft. All specimens were subjected to ultimate load to failure and cyclic loading tests to assess the amount of graft slippage. The ultimate load to failure for the intact ACL was 1266 +/- 250 N, for the BPB graft 663 +/- 192 N and for the BHB graft 354 +/- 92 N (p < 0.01). After cycling to 235 N (the maximum load for all groups without failure) the average residual displacements after removal of the load for the ACL, BPB and BHB grafts were 0.031 +/- 0.013 cm, 0.078 +/- 0.033 cm, and 0.322 +/- 0.222 cm, respectively (p < 0.01). For the BHB graft the load to failure was less and the amount of graft slippage was more than for the BPB graft. Neither form of reconstruction was as strong as the intact ACL

This study was designed to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6]. Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. Memphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Germany). The prosthesis was initially planned for neutral version and translated anterior, or posterior, to create a femoral neck notch. The femora were fixed in a single-leg stance and tested with axial compression. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups: 2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension. We tested the femora flexed at 25° flexion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one- way ANOVA:. Results: Testing Group Mean load to failure Significance. Neutral (Control) 4303.09 ± 911.04N. Superior 5mm 2423.07 ± 424.16N p=0.003. Anterior 5mm in 25° flexion 3048.11 ±509.24N p=0.087. Posterior 5mm in 25° extension3104.61±592.67N p=0.117. The anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group. Our data suggests that anterior and posterior 2mm notches are not significantly weaker in axial compression. The anterior 5mm notches was not significant in axial compression (p=0.38), but trended towards significance in flexion (p=0.087). A 5mm posterior notch was not significant. (p=0.995, p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous published data (p=0.003). Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however a 5mm anterior femoral neck notch may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking given the reduction in strength noted after testing in flexion. Posterior 5mm notches are not likely to fracture. Hip resurfacing is commonly performed on active patients and 5mm notching of anterior cortex has clinically important implications

Introduction: The classic teaching in flexor tendon repair suggests that a 10mm bite is important for the integrity of the repair regardless of the other features of the technique. Although this has been widely accepted since Bunnell’s first descriptions of accurate flexor tendon repair there appear to be little data to support it. An extensive review of the literature showed no biomechanical data relating specifically to size of bite in flexor tendon repair. We hypothesised that decreased bite may cause less damage to the tendon during repair while still offering adequate mechanical strength. Aim: To investigate the effect of different bite sizes on the mechanical properties of flexor tendon repairs. Methods: Twenty fresh-frozen cadaveric flexor tendons were divided at their centres. One side of a modified Kessler repair was used on each side taking a 6mm bite on one side and a 10mm bite on the other. The tendons underwent tensile testing on a mechanical testing frame by pulling on the ends of the suture with the tendon secured in pneumatic grips. Data for stiffness and ultimate load to failure were recorded. Results: An increased bite size made no significant difference to stiffness of the repairs. There was a difference in load to failure noted but this was not significant. The ultimate load to failure was noted after the specimens had been distracted over 2mm, which would result in clinical failure. Conclusions: These results suggested that a 10mm bite may be excessive in flexor tendon repair and could cause more tissue damage than lesser bites. Further study of in vivo effects of decreased bite size is required

Background & Objectives: The objective of this study was to develop a rat model of fracture repair. Fixation of experimental fractures is generally internal {Kirschner wire/intramedullary (IM) nail} or external (single/double plane devices). Internal fixation using the IM-fixated model of a standard closed fracture is well described in rats. However, nail insertion can disrupt fracture site morphology and limit x-ray analysis. We planned to create an externally fixated femoral model, to optimise our outcome measures and facilitate the further investigation of bone healing within the department. Methods: A simple four pin unilateral external fixator was designed and constructed from four stainless steel pins, secured to a stainless steel plate with nuts. Forty-one female Sprague-Dawley rats, (12–18wks), were used. Following anaesthesia the right femur was exposed and a mid-femoral osteotomy made prior to fixator application. Post-operative x-rays were taken to confirm reduction. Animals were assigned to groups for biomechanical strength testing (BST) or histology. Fifteen animals (fractured and contralateral limbs) were sacrificed at 4, 6 or 8 weeks for BST (four-point bending). Maximum load to failure was recorded and stiffness calculated from the load displacement curve obtained. Both parameters were standardised as a percentage of the contralateral limb. Twenty-five fractured limbs were used for histological analysis at day 4, and 1, 2, 4, 6 or 8 weeks. Results: Satisfactory reduction was confirmed in all animals post operatively and no complications were noted. Histological assessment at day 4 demonstrated a predominantly lymphocytic inflammatory response within the fracture haematoma. This was replaced with endosteal and periosteal new bone between weeks 1 and 2. Bridging of the fracture gap was seen at week 6. Stiffness and load to failure increased with increasing time. There was a statistically significant improvement in the percentage stiffness (p=0.035) and load to failure (p=0.012) between 4 and 8 weeks. Conclusion: A simple reproducible externally fixated rat model has been established and characterised by radiography, histology and four point bending. This model has since proven to be of value in the study of the role of lipid lowering and anti-inflammatory drugs as well as cell therapy on fracture repair

Surgeons performing hip resurfacing ante-vert and translate the femoral component anterior to maximize head/neck offset and educe impingement. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6]. This study was esigned to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck. Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. emphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Grmany). The virtual prosthesis was initially planned for neutral version and translated anterior, or posterior, to create the notch. The femora were fixed in a single-leg stance and tested with axial compression using a mechanical testing machine. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups:2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension We tested the femora flexed at 25° flex-ion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one-way ANOVA:. Results: Testing Group Mean load to failure Significance Neutral (Control) 4303.09 ± 911.04N Anterior 2mm 3926.62 ± 894.17N p=0.985 Anterior 5mm 3374.64 ± 345.65N p=0.379 Posterior 2mm 4208.09 ± 1079.81N p=1.0 Posterior 5mm 3988.07 ± 728.59N p=0.995 Superior 5mm 2423.07 ± 424.16N p=0.003 Anterior 5mm in 25° flexion 3048.11 ±509.24N p=0.087 Posterior 5mm in 25° extension 3104.61±592.67N p=0.117 Both the anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group. Our data suggests that anterior and posterior 2mm notches are not statistically significantly weaker in axial compression. The anterior 5mm notches tend towards significance in axial compression (p=0.38) and bordered significance in flexion (p=0.087). The 5mm posterior notches were not significantly weakened in axial compression (p=0.995), but tended towards significance in extension (p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous data published (p=0.003). We are currently assessing offset and other variables that may reduce data spread. Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however 5mm anterior notches may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking. Posterior 5mm notches are not likely to fracture with normal gait, but may fracture with higher impact activities that promote weight bearing in extension. Hip resurfacing is commonly performed on active patients and ultimately 5mm notching in the anterior or posterior cortices has clinically important implications

Introduction: Selective COX-2 (Cyclooxygenase-2) inhibitors have been found to impede fracture healing. The effect of selective COX-2 inhibitors on tendon healing in a bone tunnel, however, is unknown. Methods: The authors performed bilateral anterior cruciate ligament reconstructions in 32 rabbits and used peripheral quantitative computed tomography (pQCT) to compare tendon-to-bone healing between tunnel aperture and midtunnel regarding bone mineral density (BMD) and ingrowth of new bone. Each animal was assigned to one of four groups. Two groups received selective COX-2 inhibitors orally for 3 weeks (Cele-coxib; 10 mg/kg/d), the two other groups received no COX-2 inhibitors (controls). The animals were sacrificed 3 and 6 weeks after surgery. In biomechanical testing maximum load to failure and stiffness of the tendon grafts were calculated from the load displacement curve and failure modes were recorded. To assess indirectly the effect on local COX-2 activity the synovial content of Prostaglandin E2 (PGE2), the major metabolite of arachnidonic acid metabolism and catalyzed by COX-2, was measured by Enzyme-linked Immunosorbent Assay (ELISA). Results: Animals treated with selective COX-2 inhibitors had significantly lower BMD at the tunnel aperture (P=.02). In all groups the BMD at the tunnel aperture was significantly higher in comparison with the midtunnel (P< .05). In the controls ingrowth of new bone was greater at the tunnel aperture at 3 weeks (P=.028). After 3 weeks of COX-2 inhibitor administration synovial fluid concentrations of PGE2 were significantly lowered (P=.018) and increased more than threefold by 6 weeks after surgery and 3 weeks after last drug administration (P=.022), while in the controls there was a decrease in PGE2 between week 3 and 6. At 6 weeks the controls exhibited a twofold increase in maximum load to failure (3 weeeks: 28.2±20.9 N; 6 weeks: 59.6±53.6 N; P=.394), whereas the COX-2 inhibitor treated specimens decreased 1.9fold (3 weeks: 69.3±50.5 N; 6 weeks: 37.4±16.8 N; P=.24). Maximum load to failure values correlated with PGE2 changes, but not statistically significant (r. 2. = −0,502; p=0,056). Failure modes at 3 and 6 weeks were rupture and degloving, respectively, of the tendon graft. Discussion: This study revealed decreased bone mineral density at the tunnel aperture at 3 weeks, an increase of the inflammatory mediator PGE2 and decreased graft stability with time after treatment with selective COX-2 inhibitors. Untreated controls appeared to have a more physiological healing course with a continuous decrease in PGE2 and an increase in graft stability. Our results suggest, that selective COX-2 inhibitors may delay tendon healing in a bone tunnel

Introduction The four strand cruciate tendon repair has been described as the ideal technique, as it combines simplicity with the biomechanical advantages of four-strands. We wanted to determine if increasing the size of the locking loop increases the repair strength, and the gain in biomechanical integrity that various peripheral techniques provides. Methods Forty-eight deep flexor tendons harvested from sheep hindlimbs were randomly divided into six groups of eight. All tendons were sharply transected. Initially, four groups were repaired using the cruciate core technique without a peripheral suture. The locking loops were set at 50%, 33%, 25%, or 10% of the volar CSA and then tested to failure. The final two groups of tendons were repaired using the established optimal locking loop size. These two groups were combined with either the simple running or the interlocking horizontal mattress (IHM) peripheral suture. These were then tested to failure and biomechanically assessed. Results Repairs with locking loops of 25% had the greatest biomechanical properties; with load to two millimetre gap formation, load to failure and stiffness of 10N, 46.3 and 3.9N/mm respectively. Those with a 33%, 50% and 10% locking loops followed this. Those with 10% locking loops failed due to the suture material sliding out of the tendon. All other groups failed by suture breakage. Using the cruciate core technique with a 25% volar CSA locking loop, the load to two millimetre gap formation, load to failure and stiffness was 32.9N, 47.2N, and 7.6N/mm respectively when combined with the simple running peripheral suture and 46.4N, 79.4N and 9.9N/mm respectively when combined with the IHM repair. The IHM/cruciate combination was significantly better than the simple running/cruciate repair. Using the IHM technique in your tendon repair, this study demonstrates that the peripheral suture can provide approximately 75%, 40% and 60% of the total load to two millimetre gap formation, load to failure and stiffness respectively. Conclusions Unlike the Kessler technique, increasing the size of the locking loop in the cruciate method decreases the repair strength. The ideal sized bite seems to be approximately 25% of the volar cross-sectional area. Additional, the peripheral suture is biomechanically vital to the integrity of the repair. In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source

Background. Instability is one of the most common complications after total hip arthroplasty (THA), particularly when using the posterior approach. Repair of the posterior capsule has proven to significantly decrease the incidence of posterior hip dislocation. The purpose of the present study is to evaluate if braided polyblend suture provides a stronger repair of the posterior soft tissues when compared to a non-absorbable suture repair after a posterior approach to the hip. Methods. Ten cadaveric hips from donors who were a mean (and standard deviation) of 80 ± 9 years old at the time of death were evaluated after posterior soft tissue repair utilizing two different techniques. Five specimens were repaired using no. 2 non-absorbable sutures while five specimens had a repair utilizing braided polyblend suture with a rucking hitch knot technique. Cadaveric specimens were matched based upon age, sex, and laterality. Biomechanical tensile testing using the Instron E10000 Mechanical Testing System and the mechanism of failure were assessed. Results. The ultimate load to failure was three times higher using braided polyblend suture (390.00 ± 129.08 N) compared to non-absorbable sutures (122.81 ± 82.41 N) after posterior soft tissue repair (P<.01). In the braided polyblend suture cohort, the mechanism of failure occurred as the braided suture pulled through the posterior soft tissues. However, in the non-absorbable suture repair, failure took part at the suture knot. Conclusion. The use of our braided polyblend suture technique provides for a stronger repair of the posterior soft tissues when compared to non-absorbable suture repair following a posterior approach to the hip joint

Aims. to investigate the stiffness and strength of completely unstable pelvic fractures þxated both anteriorly and posteriorly under cyclic loading conditions. Methods: In 12 specimens a Tile C1 pelvic fracture was created. We compared the intact situation to anterior plate þxation combined with one or two SI screws. In 2000 measurements each pelvis was loaded with a maximum of 400N. The translation and rotation stiffness of the þxations were calculated using a 3-dimensional video system. Furthermore the load to failure and the number of cycles before failure were determined. Results: Both translation and rotation stiffness of the intact pelvis were superior to the þxated pelvis. No difference in stiffness was found between the techniques with one or two sacroiliac screws. However a signiþcantly higher load to failure and signiþcantly more loading cycles before failure could be achieved using two sacroiliac screws compared to one screw. Conclusions: Although the combination of anterior plate þxation combined with two sacroiliac screws is not as stable as the intact pelvis, in this study embalmed aged pelves could be loaded repeatedly with physiological forces. Given the fact that the average trauma patient is younger and given the fact that the quality (or grip) of the þxation was a signiþcant covariable for longer endurance of the þxation, this suggests that further clinical research into direct postoperative weight bearing can be undertaken safely

Aim: To biomechanically achieve both the most ideal and the strongest core and periferal suture method by combining 2 and 4 strand core sutures with the simple running and a new locking periferal suture techniques. Materials and Methods: Fourty flexor digitorum pro-fundus tendons from sheep hindlimbs were studied. The tendons were then repaired using 4 different repair techniques: Group 1 – control, Group 2 – 2 strand modified Kessler’s core suture and simple running periferal suture, Group 3 – 2 strand modified Kessler’s core suture and a new multilocking loop periferal suture, Group 4 – 4 strand modified Kessler’s core suture and simple running periferal suture, Group 5 – 4 strand modified Kessler’s core suture and a new multilocking loop periferal suture. After tenoraphy all fresh sheep cadavers tendons were tested to failure using a distraction rate of 20 mm/min. Maximal strength, 2 mm gap formation force, load to failure, stiffness, method of failure and rate of tendon resistance were assessed. After and before tenoraphy, front – back and side sizes were measured. Results: Maximal strength was 496, 32, 94, 45 and 100 Newtons for Groups 1, 2, 3, 4 and 5 respectively. There was a significantly statistical difference between the groups (p< 0.0001). Load to 2 mm gap formation was 23, 63, 36 and 72 Newtons for Groups 2, 3, 4 and 5 respectively. There was a significantly statistical difference between the groups (p< 0.0001). Load to failure was 3,783 0,285 0,505 0,41 and 0,572 Joule for Groups 1, 2, 3, 4 and 5 respectively. There was a significantly statistical difference between the groups (p< 0.0001). Tendon stiffness was 42.6, 5.16, 11.2, 5.8 and 12.6 Newton/milimetre for Groups 1, 2, 3, 4 and 5 respectively. There was a significantly statistical difference between the groups (p< 0.0001). The rate of tendon resistance was 0.97, 0.8, 1.0 and 0.91 for Groups 2, 3, 4 and 5 respectively. There was no significantly statistical difference between these groups (p=0.747> 0.05). All the simple running repairs failed by suture pullout, while all the new multilocking loop periferal suture repairs failed by suture breakage. Conclusion: The new multilocking loop periferal suture was the best performer overall, with greater ultimate strength, load to failure, 2 mm gap formation force and stiffness

Aims. The aim of this study was to compare biomechanical properties of pre-contoured plate fixation using different screw fixation modes in a mid-shaft clavicle fracture model. Methods. Fourth generation biomechanical clavicle sawbones with a mid-shaft osteotomy were plated in one of three modes: nonlocking bicortical, locking bicortical and locking unicortical mode. The specimens were then tested to failure in four-point bending and pull-off tests. Results. Failure due to fracture through the sawbone was more common in nonlocking bicortical mode while plate bending was more common in the locking bicortical group. The ultimate load at failure was significantly lower in the locking bicortical group compared to the nonlocking bicortical group, however there was no significant difference between the locking unicortical group and nonlocking bicortical group. In the pull-off tests 100% of nonlocking bicortical and locking bicortical plates failed by fracture of the sawbone. 100% of the locking unicortical plates failed by plate and screw pull-off from the sawbone. The load at failure was highest for the locking unicortical plate but this was not significantly different to the other groups. Conclusion. This study shows that specimens fixed with locking unicortical screw fixation withstood comparable or superior loads in four-point bending and pull-off test when compared to nonlocking bicortical and locking bicortical screw fixation. In addition both locking screws and unicortical screws appear to provide a protective effect against periprosthetic sawbone fracture. Locking unicortical screw fixation of pre-contoured plates may be a viable alternative in the fixation of mid-shaft clavicle fractures

Objectives. All-suture anchors are increasingly used in rotator cuff repair procedures. Potential benefits include decreased bone damage. However, there is limited published evidence for the relative strength of fixation for all-suture anchors compared with traditional anchors. Materials and Methods. A total of four commercially available all-suture anchors, the ‘Y-Knot’ (ConMed), Q-FIX (Smith & Nephew), ICONIX (Stryker) and JuggerKnot (Zimmer Biomet) and a traditional anchor control TWINFIX Ultra PK Suture Anchor (Smith & Nephew) were tested in cadaveric human humeral head rotator cuff repair models (n = 24). This construct underwent cyclic loading applied by a mechanical testing rig (Zwick/Roell). Ultimate load to failure, gap formation at 50, 100, 150 and 200 cycles, and failure mechanism were recorded. Significance was set at p < 0.05. Results. Overall, mean maximum tensile strength values were significantly higher for the traditional anchor (181.0 N, standard error (. se). 17.6) compared with the all-suture anchors (mean 133.1 N . se. 16.7) (p = 0.04). The JuggerKnot anchor had greatest displacement at 50, 100 and 150 cycles, and at failure, reaching statistical significance over the control at 100 and 150 cycles (22.6 mm . se. 2.5 versus 12.5 mm . se. 0.3; and 29.6 mm . se. 4.8 versus 17.0 mm . se. 0.7). Every all-suture anchor tested showed substantial (> 5 mm) displacement between 50 and 100 cycles (6.2 to 14.3). All-suture anchors predominantly failed due to anchor pull-out (95% versus 25% of traditional anchors), whereas a higher proportion of traditional anchors failed secondary to suture breakage. Conclusion. We demonstrate decreased failure load, increased total displacement, and variable failure mechanisms in all-suture anchors, compared with traditional anchors designed for rotator cuff repair. These findings will aid the surgeon’s choice of implant, in the context of the clinical scenario. Cite this article: N. S. Nagra, N. Zargar, R. D. J. Smith, A. J. Carr. Mechanical properties of all-suture anchors for rotator cuff repair. Bone Joint Res 2017;6:82–89. DOI: 10.1302/2046-3758.62.BJR-2016-0225.R1

Aims. This study aimed to establish the optimal fixation methods for calcaneal tuberosity avulsion fractures with different fragment thicknesses in a porcine model. Methods. A total of 36 porcine calcanea were sawed to create simple avulsion fractures with three different fragment thicknesses (5, 10, and 15 mm). They were randomly fixed with either two suture anchors or one headless screw. Load-to-failure and cyclic loading tension tests were performed for the biomechanical analysis. Results. This biomechanical study predicts that headless screw fixation is a better option if fragment thickness is over 15 mm in terms of the comparable peak failure load to suture anchor fixation (headless screw: 432.55 N (SD 62.25); suture anchor: 446.58 N (SD 84.97)), and less fracture fragment displacement after cyclic loading (headless screw: 3.94 N (SD 1.76); suture anchor: 8.68 N (SD 1.84)). Given that the fragment thickness is less than 10 mm, suture anchor fixation is a safer option. Conclusion. Fracture fragment thickness helps in making the decision of either using headless screw or suture anchor fixation in treating calcaneal tuberosity avulsion fracture, based on the regression models of our study. Cite this article: Bone Joint Res 2023;12(8):504–511

This study was undertaken to assess for equivalence or superiority in tendon reconstruction techniques. This is an in vitro analysis of several, different, reconstruction techniques for chronic Achilles tendon ruptures. The surgical techniques have been borne out of surgical preference rather than biomechanical principles with little published research into their comparability. Surgical preferences are a result of the supposed benefits of reduced operative time, single operative incision and decreased morbidity. An animal model, after human cadaveric tissue dissection to guide the specimen construction, was used to compare the different techniques using bovine bone and tendon and tested using a material testing machine. Ultimate load to failure was recorded for all specimens and statistical analysis of the results was undertaken. A statistically significant difference was shown between all the techniques by analysis of variance. This will guide clinical application of these techniques. The use of bone tunnels, through which the flexor hallucis longus tendon can be passed, were found to be biomechanically superior, with regard to ultimate load to failure, to either bone anchors or end-to-end tendon suture techniques. Interference screws were found to have a large range in their ultimate load suggesting a lack of consistency in the results. The mean of the bone tunnel group (482.8N, SD 83.6N) is significantly (p < 0.01) higher than the mean of the bone anchor group (180.2N, SD 19.3N), which is, in turn, significantly (p < 0.01) higher than the mean of the Bunnell group (73.7N, SD 20.9N). This study is larger than any previous study found in the literature with regard to number of study groups and allows the techniques to be compared side by side

Aims. The aim of this study was to investigate the effect of a posterior malleolar fragment (PMF), with < 25% ankle joint surface, on pressure distribution and joint-stability. There is still little scientific evidence available to advise on the size of PMF, which is essential to provide treatment. To date, studies show inconsistent results and recommendations for surgical treatment date from 1940. Materials and Methods. A total of 12 cadaveric ankles were assigned to two study groups. A trimalleolar fracture was created, followed by open reduction and internal fixation. PMF was fixed in Group I, but not in Group II. Intra-articular pressure was measured and cyclic loading was performed. Results. Contact area decreased following each fracture, while anatomical fixation restored it nearly to its intact level. Contact pressure decreased significantly with fixation of the PMF. In plantarflexion, the centre of force shifted significantly posteriorly in Group II and anteriorly in Group I. Load to failure testing showed no difference between the groups. Conclusion. Surgical reduction of a small PMF with less than 25% ankle joint surface improves pressure distribution but does not affect ankle joint stability. Cite this article: Bone Joint J 2018;100-B:95–100

The August 2024 Trauma Roundup³⁶⁰ looks at: Does topical vancomycin prevent fracture-related infections in closed fractures undergoing open reduction and internal fixation? A randomized controlled trial; Is postoperative splinting advantageous after upper limb fracture surgery?; Does suprapatellar nailing resolve knee pain?; Locking versus non-locking plate fixation in comminuted talar neck fractures: a biomechanical study using cadaveric specimens; Revolutionizing recovery metrics: PROMIS versus SMFA in orthopaedic trauma care; Dorsal hook plating of patella fractures: reliable fixation and satisfactory outcomes; The impact of obesity on subtrochanteric femur fracture outcomes; Low-dose NSAIDs (ketorolac) and cytokine modulation in orthopaedic polytrauma: a detailed analysis.

The December 2023 Trauma Roundup³⁶⁰ looks at: Distal femoral arthroplasty: medical risks under the spotlight; Quads repair: tunnels or anchors?; Complex trade-offs in treating severe tibial fractures: limb salvage versus primary amputation; Middle-sized posterior malleolus fractures – to fix?; Bone transport through induced membrane: a randomized controlled trial; Displaced geriatric femoral neck fractures; Risk factors for reoperation to promote union in 1,111 distal femur fractures; New versus old – reliability of the OTA/AO classification for trochanteric hip fractures; Risk factors for fracture-related infection after ankle fracture surgery.

Purpose: The purpose of this biomechanical study is to compare the double reconstruction plate osteosynthesis versus double tension band osteosynthesis in the fixation of osteoporotic supracondylar humeral fractures. Materials and Methods: Sixteen fresh cadavers (mean age: 75, range:70–80) were randomized into two experimental groups. Same supracondylar transverse humeral fractures were formed in both groups. Fractures in the first group, were fixed with double tension band technique using 2mm in diameter Kirschner wires and 1mm in diameter tension wires. Fractures in the second group, were fixed with double reconstruction plate osteosynthesis using 3,5mm reconstruction plates each fixing medial and lateral columns. Distal fragment was fixed with only one screw. Axial loading, maximum load, failure load and failure patterns were analysed. Statistical analysis was performed with SPSS 13.90 soft ware program. Groups were compared with Mann Whitney U test. Results: Minimum load reqired for fracture displacement was statistically higher in double reconstruction plate osteosynthesis group (p< 0.005). Minumum load reqired for fixation failure was statistically higher in double reconstrution plate osteosynthesis group (p< 0,020). Conclusion: Fracture healing mainly depends on a stable fracture fixation. Double plate ostesynthesis should be preferred over double tension band technique in osteoporotic supracondylar humeral fractures as it provides more stability

Aims

The aim of this study was to compare the functional and radiological outcomes and the complication rate after nail and plate fixation of unstable fractures of the ankle in elderly patients.

The aim of this study was to determine the biomechanical behavior of two different implants used in the fixation of proximal humerus fractures. The two implants in this study are specifically designed for the fixation of proximal humerus fractures and both utilize the concept of fixed angle locking screws. Bone densitometry was performed prior to fracture production and fixation. A reproducible three-part fracture was created in paired human cadaveric bone and then fixed using the locking screw implants. Stress/strain curves for the bone-implant construct were created for loads applied in cantilever bending and torsion to determine the relative stiffness below the yield point. Following this each construct was tested to failure with a valgus bending load. The locking nail implant provided a significantly stiffer construct in torsion, valgus, extension and flexion at loads below failure threshold. The valgus load to failure was significantly higher for the nail. The mode of failure was different between implants

Background and Aims: Plate fixation of acute mid-shaft clavicle fractures is becoming increasingly popular. However limb and life threatening complications such as injury to the subclavian vessels have been reported. One possible solution to reduce the risk of this complication is the use of unicortical screw fixation. The aim of this study was to compare biomechanical properties of pre-contoured plate fixation using different screw fixation modes in a mid-shaft clavicle fracture model. Methods: Fourth generation biomechanical clavicle sawbones with a mid-shaft osteotomy were plated in one of three modes: nonlocking bicortical, locking bicortical and locking unicortical mode. The specimens were then tested to failure in four-point bending and pull-off tests. Results: Failure due to fracture through the sawbone was more common in nonlocking bicortical mode while plate bending was more common in the locking bicortical group. The ultimate load at failure was significantly lower in the locking bicortical group compared to the nonlocking bicortical group, however there was no significant difference between the locking unicortical group and nonlocking bicortical group. In the pull-off tests 100% of nonlocking bicortical and locking bicortical plates failed by fracture of the sawbone. 100% of the locking unicortical plates failed by plate and screw pull-off from the sawbone. The load at failure was highest for the locking unicortical plate but this was not significantly different to the other groups. Conclusion: This study shows that specimens fixed with locking unicortical screw fixation withstood comparable or superior loads in four-point bending and pull-off test when compared to nonlocking bicortical and locking bicortical screw fixation. In addition both locking screws and unicortical screws appear to provide a protective effect against periprosthetic sawbone fracture. Locking unicortical screw fixation of pre-contoured plates may be a viable alternative in the fixation of mid-shaft clavicle fractures

INTRODUCTION: Medial open-wedge HTO is an alternative in the treatment of medial knee OA for the young and active patient. However this technique leaves an open gap that requires stable fixation to achieve bony healing. As a bone substitute injectable calcium-phosphate-cements could be an alternative to autograft. MATERIAL AND METHODS: Biomechanical testings were performed on open wedge HTO to investigate load to failure and displacement after cyclic loading (viscous and/or damaged material response). A medial 10 mm open-wedge osteotomy was performed on 7 pairs of composite (Sawbone) left tibiaes, and 8 pairs of preserved cadaver tibiaes. Osteosynthesis where performed with the Dynafix system. In half of the bones the gap was filled with 15 g of Calcibon®. The composite tibiaes were loaded at a ramp speed of 20 mm/min and failures of the constructs were recorded visually. On the cadaver tibiaes, cyclical loading were performed with a maximum load of 2250 N. RESULTS: Filling of the gap with Calcibon® resulted in significant different load-to-failure patterns with failure at 10.2 kN compared to 2.7 kN in the group without Calcibon®. Displacement at the end of cyclical loading was 1.2 mm in the group with Calcibon® and 2.7 mm in the group without Calcibon®. This difference also was significant. CONCLUSION: The injectable calcium-phosphate-cement Calcibon® enhances primary stability during load to failure and during cyclical loading in open wedge osteotomies on proximal tibia. Clinical studies are performed to investigate whether Calcibon® has any clinical advantage on wedge healing and stability

Subscapularis tenotomy (SST) has been the preferred approach for shoulder arthroplasty for decades but recent controversy has propelled lesser tuberosity osteotomy (LTO) as a potential alternative. Early work by Gerber suggested improved healing and better outcomes with LTO although subscapularis muscular atrophy occurred in this group as well with unknown long-term implications. However, we previously performed a biomechanical study showing that some of the poor results following tenotomy may have been due to historic non-anatomic repair techniques. Surgical technique is critical to allow anatomic healing – this is true of both SST or LTO techniques. A recent meta-analysis of biomechanical cadaveric studies showed that LTO was stronger to SST at “time-zero” with respect to load to failure but there were no significant differences in cyclic displacement. A recent study evaluated neurodiagnostic, functional, and radiographic outcomes in 30 patients with shoulder arthroplasty who had SST. The authors found that the EMG findings were normal in 15 patients but abnormal in the other 15 and that these abnormalities occurred in 5 muscle groups (not just the subscapularis). In another study, patient outcomes were inferior in those patients who had documented subscapularis dysfunction following SST compared to patients who had LTO (none of whom had subscap dysfunction). The literature is not clear, however, on ultimate outcomes based on subscapularis dysfunction post-arthroplasty with some studies showing no difference and others showing significant differences

Aims. to investigate whether the stability of partially unstable pelvic fractures can be improved by combining plate þxation of the symphysis with a posterior sacroiliac screw. Methods: In 6 specimens a Tile B1 (open book) pelvic fracture was created. We compared the intact situation to isolated anterior plate þxation and plate with SI screw þxation. Using a 3-dimensional video system we measured the translation and rotation stiffness of the þxations and the load to failure. Results: Neither absolute displacements at the os pubis or at the sacroiliac joint or stiffness of the ilium in respect to the sacrum were signiþcantly different for the techniques with or without sacroiliac screw or the intact situation. Load to failure was only reached in one of the six cases. In all other cases the þxation of the pelvis to the frame failed before failure of the þxation itself. In these cases a load of about 1000N or more could be applied. Conclusions: The addition of a sacroiliac screw in a Tile B1 fracture does not give signiþcant additional stability. Although cyclic loading was not tested, in these experiments forces could be applied similar to full body weight. Clinical experiments into direct postoperative weight bearing are recommended to examine the clinical situation

Aims

Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon.

Aims

The risk of mechanical failure of modular revision hip stems is frequently mentioned in the literature, but little is currently known about the actual clinical failure rates of this type of prosthesis. The current retrospective long-term analysis examines the distal and modular failure patterns of the Prevision hip stem from 18 years of clinical use. A design improvement of the modular taper was introduced in 2008, and the data could also be used to compare the original and the current design of the modular connection.