To investigate changes in quadriceps and hamstrings muscle groups during sustained isokinetic knee flexion and extension.

125 paediatric participants (45 males and 80 females, mean age 14.2 years) were divided into two groups: participants with a confirmed ACL tear (ACLi, n = 64), and puberty- and activity-level matched control participants with no prior history of knee injuries (CON, n = 61). Participants completed a series of 44 repetitions of isokinetic knee flexion and extension at 90 deg/ sec using a Biodex dynamometer (Biodex Medical Systems Inc, Shirley, New York). Surface EMG sensors (Delsys Incorporated, Natick, MA) simultaneously recorded the quadriceps and hamstring activations. Muscle function was assessed as the change in quadriceps activation and extension torque were calculated using the percent difference between the mean of the first five trials, and the mean of the last five trials.

ACLi participants had significantly higher percent change in quadriceps activation for both healthy and injured legs, in comparison to CON dominant leg. As such, the healthy leg of the ACLi participants is activating significantly more than their health matched controls, while also demonstrating reduced muscular endurance (less torque in later repetitions). Therefore, we conclude that the non-injured limb of the ACLi participant is not performing as a healthy limb. Since return to activity clearance following ACLi implies return to sport against age- and activity matched opponents, clearing young athletes based on the non-injured contralateral limb may put them at greater risk of reinjury.

To investigate differences in the drop vertical jump height in female adolescents with an ACL injury and healthy controls and the contribution of each limb in this task. Forty female adolescents with an ACL injury (ACLi, 15.2 ± 1.4 yrs, 164.6 ± 6.0 cm, 63.1 ± 10.0 kg) and thirty-nine uninjured (CON, 13.2 ± 1.7 yrs, 161.7 ± 8.0 cm, 50.6 ± 11.0 kg) were included in this study. A 10-camera infrared motion analysis system (Vicon, Nexus, Oxford, UK) tracked pelvis, thigh, shank, and foot kinematics at 200Hz, while the participants performed 3 trials of double-legged drop vertical jumps (DVJ) on two force plates (Bertec Corp., Columbus, USA) sampled at 2000Hz.The maximum jump height normalised by dominant leg length was compared between groups using independent samples t-test. The maximum vertical ground reaction force (GRFz) and sagittal ankle, knee and hip velocities before take-off were compared between limbs in both groups, using paired samples t-test. The normalised jump height was 11% lower in the ACLi than in the CON (MD=0.04 cm, p=0.020). In the ACLi, the maximum GRFz (MD=46.17N) and the maximum velocities of ankle plantar flexion (MD=79.83°/s), knee extension (MD=85.80°/s), and hip extension (MD=36.08°/s) were greater in the non-injured limb, compared to the injured limb. No differences between limbs were found in the CON.

ACL injured female adolescents jump lower than the healthy controls and have greater contribution of their non-injured limb, compared to their injured limb, in the DVJ task. Clinicians should investigate differences in the contribution between limbs during double-legged drop vertical jump when assessing patients with an ACL injury, as this could help identify asymmetries, and potentially improve treatment, criteria used to clear athletes to sport, and re-injury prevention.

To investigate if the countermovement jump height differs between ACL injured and uninjured female adolescents and to explore kinematic differences between limbs. Additionally, the association between isometric knee extension strength and jump height was investigated.

Thirty-one ACL injured female adolescents (ACLi, 15.3 ± 1.4yrs, 163.9 ± 6.6cm, 63.0 ± 9.3kg) and thirty-eight uninjured (CON, 13.2±1.7yrs, 161.7 ± 8.1cm, 50.6 ± 11.1kg) participated in this study. All participants performed a countermovement jump task, with 3D kinematics collected using a motion analysis system (Vicon, Nexus, Oxford, UK) at 200Hz, and a maximum isometric knee extension task on an isokinetic dynamometer (Biodex Medical Systems, New York, USA) for three trials. The peak torque was extracted from the isometric trials. Independent samples t-test compared the maximum jump height normalised by the dominant leg length between groups, paired samples t-test compared the maximum hip and knee extension and ankle plantar flexion velocities before take-off between limbs in both groups, and a Pearson's correlation test investigated the association between the isometric knee extension strength and jump height.

The ACLi jumped 13% lower compared to the CON (p=0.022). In the ACLi, the maximum hip and knee extension and ankle plantar flexion velocities were greater in the non-injured limb, compared to the injured limb; however, no differences between limbs were found in the CON. The isometric knee extension strength of both limbs was positively correlated with jump height (limb 1: r=0.329; p=0.006, and limb 2: r=0.386; p=0.001; whereas limb 1 corresponds to the ACLi injured limb and CON non-dominant limb, and limb 2 to the ACLi non-injured limb and CON dominant limb).

ACL injured female adolescents present lower jump height than controls and greater contribution of their non-injured limb, compared to their injured limb, during a countermovement jump task. Also, current results indicate that jump height is positively related to isometric knee extension strength measure.

Objectives

As tumours of bone and soft tissue are rare, multicentre prospective collaboration is essential for meaningful research and evidence-based advances in patient care. The aim of this study was to identify barriers and facilitators encountered in large-scale collaborative research by orthopaedic oncological surgeons involved or interested in prospective multicentre collaboration.

Stronger flexor tendon repair techniques achieving excellent zero time biomechanics are considered the cornerstone of the early active motion rehabilitation protocols in digital flexor tendon surgery. Stronger suture materials are being introduced constantly without being tested biomechanically. The purpose of this study was to identify the role of the suture material on the flexor tendon repair techniques.

Seventy two tendon segments from thirty six cadaveric flexor tendons were lacerated and repaired with 2 different repair techniques and 3 different suture materials. The repair techniques involved an easier form of the popular Strickland technique and the stronger Modified Becker technique. Ethilon, Ethibond and the newer Fiberwire sutures were used, creating a wide range of materials with diverse biomechanical properties. The repair constructs were tested in an in vitro linear load to failure model where the ultimate strength, the 2 mm gap load and the mode of failure were recorded. Furthermore, a similar test was performed using only suture materials tied in a loop in order to compare the materials without any tendon or repair technique interaction.

The Modified Becker repairs demonstrated higher loads to failure than the Modified Strickland repairs irrespective of the suture material. Stronger suture materials increased significantly the strength of the modified Becker repair. The biomechanical characteristics of the modified Strickland technique were not influenced by the different suture materials. The 2 mm gap loads were not influenced by the suture material with either technique. The mode of failure was by suture breakage in the case of the Modified Becker repair and mostly by suture pullout in the case of the modified Strickland technique. The superior strength characteristics of the Fiberwire over the rest of the suture materials were also observed in the suture material study.

Suture materials do not have a significant effect on the biomechanical characteristics of every flexor tendon repair technique. Techniques most likely to benefit are those that grasp the tendon substance tightly and are limited only by the breaking strength of the suture material itself.

Introduction: The use of self-tapping screws has become increasingly popular since it allows for a rapid screw placement avoiding the tapping step during ORIF of fractures.. While sharing the same basic principle of cutting flutes and partial threads at the tip, at least four types of screw design is currently available, varying in the number and shape of cutting flutes. The purpose of this biomechanical study was to research for any significant difference between the various self-tapping screws

Material and Methods: Three different designs of 4.5-mm self-tapping screws and one standard 4.5 screw serving as control were compared for pull-out strength after insertion into an adult human non-embalmed cadaveric humeri. All specimens were machined to a 5 mm uniform cortical thickness. Four equidistant 3.2 mm holes were drilled into each specimen by an MTS mounted drill. All screws were inserted randomly in one of the four positions using a hand screwdriver. The cortical bone specimen was secured between two metal plates to the base of a MTS machine while a uniaxial tensile force was applied to the jig for screw removal at a rate of 0.833 mm/sec until holding power had decreased to 25 % of the maximum. Load displacement curves were recorded. Resulting data was analyzed using paired student-t tests. P values of less then 0.05 were considered statistically significant.

Results: The mean load-to-failure was 97.4167N (S.D. 13.29924) for the Synthes control screw, 69.2333N (S.D. 4.48360) for the Synthes self-tapping screw, 67.15 (S.D. 11.23864) for the Stryker self-tapping screw, and 55.0667 (S.D. 8.59271) for the ODI self-tapping screw. A significant difference was found between the mean pull-out strength of the Synthes control screw when compared to each of the three self-tapping screws (Pairs 1–3, P < 0.05). Furthermore, the mean pull-out strength of the ODI self-tapping screw was found to be significantly less than Stryker self-tapping screw (Pair 6, P < 0.05). There was no significant difference between Synthes self-tapping screws and Stryker self-tapping screws (Pair 5, P < 0.05).

Discussion and conclusion: Self tapping screws with three short cutting flutes performed better than those with two long cutting flutes. Despite of the different designs and length of the cutting flutes in self-tapping screws, they all have less pull out strength than regular screws

Surgeons often protect Tendon-bone reconstructions such as rotator cuff repairs by off loading them. We investigated the effect of limb position and boundary conditions in an in-vitro rabbit patella tendon-bone repair model. Patella tendons were repaired back to the tibia in eight hindlimb cadavers with 2 mitek anchors(Mitek, Westwood, MA) and 3-0 Ethibond (Ethicon, Sommerville, NJ) using two techniques, one involving simple sutures and the other involving crossing over between the sutures. A loading mechanism through the patella tendon was constructed using static weights over a pulley mechanism. The contact area and force at the PT-bone interface were measured using a TekScan pressure sensor (6911, TekScan, South Boston, MA). The contact footprint (area and normal force) was acquired under four configurations: (1) knee full extension with interface unloaded, (2) knee 45° flexion with interface unloaded, (3) knee full flexion with interface loaded by limb weight alone, (4) tendon loaded with limb weight and 20N force applied through tendon loading mechanism. The contact area force footprint changed substantially between the different suture techniques and loading configurations. Crossing over of sutures appears to provide an increased and more evenly distributed force across the tendon-bone interface. Repair off-loading was accompanied by a decrease in the contact footprint force and pressure. The force in both suture techniques increased with increasing flexion angle and was substantially increased by both bearing the weight of the dependent limb and by an axial load in the patellar tendon. Off loading a repair may not provide optimal environment for healing.

Aim: To define the contact force and contact area at the glenoid labrum-bone interface between suture sites in an open transosseous Bankart repair, and to assess how these contact parameters are altered by tying adjacent sutures to each other.

Methods: Twelve capsulolabral avulsion lesions were created in fresh-frozen human shoulder specimens and were repaired using a standard transosseous suture technique. The contact forces and contact areas were measured at the labrum-bone interface between sutures before and after repair. Using the free suture ends, either a single or double strand knot was then tied between adjacent suture sites and the contact parameters were measured again.

Results: The contact forces and contact areas under the soft tissue bridges between transosseous sutures were mildly increased during repair (before repair: average force=5.53g, area=2.25mm²; after repair: force=11.7g, area=3.13mm²). However, both the contact forces and areas increased significantly when a single or double strand of suture was tied over the soft tissue bridge. The double strand technique resulted in a significantly greater increase in contact forces and areas than the single strand technique (single strand average force=70.1g, area=6.75mm²; double strand average force=95.15g, area=8.0mm² p< 0.05).

Conclusions: The contact parameters between labrum and bone in a Bankart repair were increased when the suture strands from adjacent transosseous repair sites were linked. Increasing contact force or contact area may improve healing at the bone-soft tissue interface, and may reduce the risk of “spot welding” repairs. This, in turn, may reduce the failure rate of Bankart repairs.

Introduction: Arthrodesis of the shoulder joint is appropriate for several conditions, including paralysis, degenerative disease, infection, and salvage of failed arthroplasty. Two common complications of shoulder fusion, non-union and unacceptable arm position, may reflect failure to achieve rigid fixation during the surgical procedure. Numerous fixation techniques have been described, including plate fixation, external fixation, and screw fixation.

Aim: To compare the biomechanics of five fixation techniques of shoulder fusion in a human cadaveric model.

Methods: Twenty-five shoulder fusions were carried out in fresh-frozen human cadaveric specimens with the following five techniques: screw fixation alone (n=5), external fixation alone (n=5), external fixation supplemented with screw fixation (n=5), single plate fixation (n=5), and double plate fixation (n=5). Each specimen was tested on a servo-hydraulic machine under repeated physiologic loads to determine the bending and torsional stiffness.

Results: There was a statistically significant difference in bending and torsional stiffness between all five fixation techniques (ANOVA, p< 0.05). Normalised bending (B) and torsional (T) stiffness, in descending order, were: double plate (B=1.0, T=1.0), single plate (B=0.77, T=0.89), external-fixation with screws (B=0.68, T=0.74), external-fixation alone (B=0.40, T=0.53), and screws alone (B=0.13, T=0.26).

Discussion & Conclusion: Statistically significant differences in bending and torsional stiffness have been identified using five different techniques of shoulder fusion. The risk of the most common complications of this surgical procedure, non-union and unacceptable arm position, may be minimised if these biomechanical findings are applied to surgical decision-making.