Recent studies on animal models focused on the effect of preserving tendon remnant of rotator cuff on tendon healing. A positive effect by combining tendon remnant preservation and small bone vents on the greater tuberosity in comparison with standard tendon-to-bone repair has been shown. The purpose of the present clinical study was to evaluate the efficacy of biologic augmentation of arthroscopic rotator cuff repair by maintaining tendon remnant on rotator cuff footprint combined with small bone vents of the greater tuberosity. A retrospective study was conducted. All patients who underwent arthroscopic rotator cuff repair associated with small bone vents (nanofractures) and tendon footprint preservation were considered eligible for the study. Inclusion criteria were: diagnosis of full-thickness rotator cuff tear as diagnosed at preoperative magnetic resonance imaging (MRI) and confirmed at the time of surgery; minimum 24-month of follow-up and availability of post-operative MRI performed not earlier than 6 months after surgery. Exclusion criteria were: partial thickness tears, irreparable tears, capsulo-labral pathologies, calcific tendonitis, gleno-humeral osteoarthritis and/or previous surgery. Primary outcome was the ASES score. Secondary outcomes were: Quick-DASH and WORC scores, and structural integrity of repaired tendons by magnetic resonance imaging (MRI) performed six months after surgery. A paired t-test was used to compare pre- and postoperative clinical outcomes. Subgroup analysis was performed according to tear size. Significance was set at p < 0.05. The study included 29 patients (M:F = 15:14). Mean age (+ SD) of patients was 61.7 + 8.9 years. Mean follow-up was 27.4 ± 2.3 months. Comparison between pre- and postoperative functional scores showed significant clinical improvement (p < 0.001). Subgroup analysis for tear size showed significant differences in the QuickDASH score (0.04). Particularly, a significant difference in the QuickDASH score could be detected between medium and large tears (p=0.008) as well as medium and massive lesions (p=0.04). No differences could be detected between large and massive tears (p= 0.35). Postoperative imaging showed healed tendons in 21 out of 29 (72%) cases. Preservation of tendon remnant combined with small bone vents in the repair of medium-to-massive full-thickness rotator cuff tears provided significant improvement in clinical outcome compared to baseline conditions with complete structural integrity in 72% of the cases

To date, the fixation of proximal humeral fractures with angular stable locking plates is still insufficient with mechanical failure rates of 18% to 35%. The PHILOS plate (DePuy Synthes, Switzerland) is one of the most used implants. However, this plate has not been demonstrated to be optimal; the closely symmetric plate design and the largely heterogeneous bone mineral density (BMD) distribution of the humeral head suggest that the primary implant stability may be improved by optimizing the screw orientations. Finite element (FE) analysis allows testing of various implant configurations repeatedly to find the optimal design. The aim of this study was to evaluate whether computational optimization of the orientation of the PHILOS plate locking screws using a validated FE methodology can improve the predicted primary implant stability. The FE models of nineteen low-density (humeral head BMD range: 73.5 – 139.5 mg/cm3) left proximal humeri of 10 male and 9 female elderly donors (mean ± SD age: 83 ± 8.8 years) were created from high-resolution peripheral computer tomography images (XtremeCT, Scanco Medical, Switzerland), using a previously developed and validated computational osteosynthesis framework. To simulate an unstable mal-reduced 3-part fracture (AO/OTA 11-B3.2), the samples were virtually osteotomized and fixed with the PHILOS plate, using six proximal screws (rows A, B and E) according to the surgical guide. Three physiological loading modes with forces taken from musculoskeletal models (AnyBody, AnyBody Technology A/S, Denmark) were applied. The FE analyses were performed with Abaqus/Standard (Simulia, USA). The average principal compressive strain was evaluated in cylindrical bone regions around the screw tips; since this parameter was shown to be correlated with the experimental number of cycles to screw cut-out failure (R2 = 0.90). In a parametric analysis, the orientation of each of the six proximal screws was varied by steps of 5 in a 5×5 grid, while keeping the screw head positions constant. Unfeasible configurations were discarded. 5280 simulations were performed by repeating the procedure for each sample and loading case. The best screw configuration was defined as the one achieving the largest overall reduction in peri-screw bone strain in comparison with the PHILOS plate. With the final optimized configuration, the angle of each screw could be improved, exhibiting significantly smaller average bone strain around the screw tips (range of reduction: 0.4% – 38.3%, mean ± SD: 18.49% ± 9.56%). The used simulation approach may help to improve the fixation of complex proximal humerus fractures, especially for the target populations of patients at high risk of failure

Introduction. In recent years, there has been a growing interest, in many fields of medicine, in the use of bone adhesives that are biodegraded to non-toxic products and resorbed after fulfilling their function in contact with living tissue. Biomechanical properties of newly developed bone glue, such as adhesion to bone and elastic modulus were tested in our study. Material and methods. Newly developed injectable biodegradable “self-setting” bone adhesive prepared from inorganic tricalcium phosphate powder and aqueous solution of organic thermogelling polymers was used for ex-vivo fixing fractured pig femur. Ex-vivo biomechanical tests were performed on 45 fresh pig femurs. Control group consist of 10 healthy bones, tested group was created by 35 bones with artificial fractures in diaphysis – oblique (O) and bending wedge (BW) type of fracture. Tested group were divided to following 4 subgroups (sg); sg1 – O fracture (n=15) glued together with 3 different type of bone adhesives, sg2 BW fracture (n=5) glued together with bone adhesive (n=5); sg3 – BW fracture fixed with locking compression plate (LCP), n=5; sg4 – BW fracture fixed with LCP in combination with bone adhesive. Three-point bending force and shear compression tests were performed on linear electrodynamic test instrument (ElectroPuls E10000, Instron). Femurs from sg1, sg2 and sg4 were tested on Micro-CT before and after biomechanical testing. Results. Shear compression tests in sg1 without amino acids modification showed that it is needed force of 0.5 mPa to recreate fracture, however, modification with amino acids increased glue strength to 3 mPa. Three-point bending force test in sg2 showed reduced force of 250 N to recreate fracture, anyhow in sg4 force needed to initiate the fracture was increased up to 5000 N. Conclusion. Newly developed injectable biodegradable “self- setting” bone adhesive represents new possibility how to fix small bone fragments in comminuted fractures and simultaneous chance how to improve and accelerate bone healing process. Acknowledgement. Project no. AOTEU-R-2016-064 was supported by AOTRAUMA, Switzerland

Summary Statement. An alternative way to assess three dimensional skin motion artefacts of kinematic models is presented and applied to a novel kinematic foot model. Largest skin motion is measured in the tarsal region. Introduction. Motion capture systems are being used in daily clinical practise for gait analysis. Last decade several kinematic foot models have been presented to gain more insight in joint movement in various foot pathologies. No method is known to directly measure bone movement in a clinical setting. Current golden standard is based on measurement of motion of skin markers and translation to joint kinematics. Rigid body assumptions and skin motion artefacts can seriously influence the outcome of this approach and rigorous validation is required before clinical application is feasible. Validation of kinematic models is currently done via comparison with bone pin studies. However, these studies can only assess major bones in a highly invasive way; another problem is the non-synchronous measurement of skin markers and bone pins. Recently the Glasgow Maastricht kinematic foot model, which comprises all 26 foot segments, has been presented. To validate the model we propose a novel non-invasive method for the assessment of skin motion artefact, involving loaded CT data. Patients & Methods. 25 subjects (healthy and pathological feet) have undertaken CT scans. These CT-scans have been obtained in 1 unloaded and 3 varying loading conditions. CT-slices are 3D reconstructed and segmented. The principal axes of the segmented bones were derived from the surface points of the bones. These principal axes are used to compute bone orientation. Subsequently, coordinate systems of bones in the different loading conditions were matched. Markers were translated and rotated to orientations of their corresponding bones. Maximal distance between markers is calculated per subject to asses the influence of skin motion. Results. Preliminary results of 9 subjects show largest positional differences for markers associated with the cuneiform lateralis (5.7 ± 3.2 mm) and cuneiform intermedium (7.7 ± 3.7 mm). Smallest positional differences are found on the hallux proximalis (0.9 ± 0.34mm). Spatial resolution is too small to accurately calculate orientation of smaller bones, therefor distal phalanges 2–5 are not taken into account in the analysis. Discussion/Conclusion. Skin motion is a major cause of inaccuracy in gait analysis. This is the first study presenting an automated non-invasive method to calculate the 3D orientation of skin markers with respect to the coordinate system of the corresponding bone(s). Largest skin motion is measured in the tarsal region. Future work will be in calculation of the effect of skin motion in the accuracy of joint angle calculation

Summary Statement. We analysed impaction bone grafting used together with cemented or uncemented fixation in acetabular revision surgery. The overall risk for re-revision did not differ between the cemented and uncemented group. However, aseptic loosening was more common in the cemented group. Background. Several surgical techniques address bone defects in cup revision surgery. Bone impaction grafting, introduced more than thirty years ago, is a biologically and mechanically appealing method. The primary aim of this study was to evaluate the effect of bone impaction grafting when used with uncemented and cemented fixation in cup revision surgery. Uncemented cups resting on more than 50% host bone were used as controls. Patient and Methods. Cup fixation was studied in ninety hips (eighty-two patients), revised due to loosening between 1993 and 1997. There were fifty-three isolated cup and thirty-seven total revisions. Patients were followed for thirteen years using conventional radiography, radiostereometry (RSA), Harris Hip score and a pain questionnaire. Peroperatively the surgeon assessed the acetabular bone bed vitality. In hips where the cup was judged to rest on > 50% vital bone (group I, n=43), an uncemented cup was used. If the cup was resting on ≤ 50% living bone, uncemented (group IIa, n=21,) or cemented (group IIb, n=26) technique was chosen, according to the surgeon's preference. The mean age of patients at index revision was 61±12 years, 56% were females. The most common index diagnosis was primary osteoarthritis (n=45) followed by rheumatoid arthritis (n=10). Results. At thirteen years, acetabular component failure had necessitated a second revision in 6/7/8 hips in Groups I/IIa/IIb respectively. These re-revisions were performed 1–10 (mean 7.1) years after index revision. Moreover four cup / liner revisions were performed in hips with femoral loosening, not allowing further RSA measurements. These twenty-five hips were followed until re-revision. Deceased patients (n=21) and patients with deteriorating medical condition, not able to attend the follow-up (n=7), were censored in the survival statistics. Aseptic loosening was the most common reason of re-revision. However, in the uncemented groups (I/IIa), four cups were re-revised due to liner wear, osteolysis or instability. In the total study population, and up to two years, the median proximal migration was lowest in Group I followed by Group IIa and Group IIb (p≤0,006). At thirteen years the mean proximal migration was highest in Group IIb 1.29 mm (SD 1.23) followed by Group I 0.30 mm (SD 0.40) and Group IIa 0.22 mm (SD 0.22), p = 0.05. In cases subsequently re-revised because of loosening or with radiographically loose cups at the last follow-up, a higher proximal migration was observed compared to the non-revised and radiographically well-fixed group (up to seven years: p < 0.001; thirteen years: p=0.04). Discussion/Conclusion. We found an increased risk for rerevision in cases with less than 50% host bone-implant contact. These cups showed high early proximal migration, measured by RSA, indicating poor initial fixation. Rate of re-revision due to any reason did not differ between cemented and uncemented cups. The cemented group (IIb) had a higher risk of being re-revised due to aseptic loosening. Poor bone stock, use of small bone chips, inferior impaction technique, and no or restricted contact with living bone are probable reasons for failures when extensive bone grafting is needed

Introduction. Bending tests are commonly used to evaluate the mechanical behaviour of small animal bones. To test whole bones, it is normal that soft tissue should be removed before testing. However, cleaning the specimens might disturb the callus, interfering with the mechanical properties. This study compares mechanical properties of rat tibia between specimen with and without muscle cleaning. Materials and methods. 12 male Wistar rats aged 3–4 months were used. Soft tissues including skin and muscle were removed from right tibias (Group A), whereas muscles on the left tibia were left intact (Group B). 4-point bending was used to find the ultimate load, stress and Young's modulus. Results. All specimens displayed a basic failure pattern from load-displacement graph. Mean ultimate load of 105.2N (S.E.M.=7.60, n=12) for group A and 101.6N (S.E.M.=7.32, n=12) group B. Mean stress at failure of 281.50MPa (S.E.M.=34.98, n=12) was found for group A 288.70MPa (S.E.M.=20.83, n=12) for group B. Mean Young's modulus was 8.97GPa (S.E.M.=1.44, n=12) for group A and 10.05GPa (S.E.M=0.69, n=12) for group B. No statistical differences for any mechanical properties were found between groups for either t-test(p>0.05) or Bland-Altman plot. Discussion. No differences in mechanical properties were found with or without soft tissue. Therefore, biomechanical testing of small specimen bending without removing muscle can be used. The advantages of this technique are reduced specimen preparation time and decreasing risk of creating a stress raiser at the callus

Objectives

To compare the therapeutic potential of tissue-engineered constructs (TECs) combining mesenchymal stem cells (MSCs) and coral granules from either Acropora or Porites to repair large bone defects.

Objectives

Lengthening osteotomies of the calcaneus in children are in general grafted with bone from the iliac crest. Artificial bone grafts have been introduced, however, their structural and clinical durability has not been documented. Radiostereometric analysis (RSA) is a very accurate and precise method for measurements of rigid body movements including the evaluation of joint implant and fracture stability, however, RSA has not previously been used in clinical studies of calcaneal osteotomies. We assessed the precision of RSA as a measurement tool in a lateral calcaneal lengthening osteotomy (LCLO).

The feasibility of bone transport with bone substitute and the factors which are essential for a successful bone transport are unknown. We studied six groups of 12 Japanese white rabbits. Groups A to D received cylindrical autologous bone segments and groups E and F hydroxyapatite prostheses. The periosteum was preserved in group A so that its segments had a blood supply, cells, proteins and scaffold. Group B had no blood supply. Group C had proteins and scaffold and group D had only scaffold. Group E received hydroxyapatite loaded with recombinant human bone morphogenetic protein-2 and group F had hydroxyapatite alone.

Distraction osteogenesis occurred in groups A to C and E which had osteo-conductive transport segments loaded with osteo-inductive proteins. We conclude that scaffold and proteins are essential for successful bone transport, and that bone substitute can be used to regenerate bone.

Our aim was to assess the intra- and inter-observer reliability in the establishment of the anterior pelvic plane used in imageless computer-assisted navigation. From this we determined the subsequent effects on version and inclination of the acetabular component.

A cadaver model was developed with a specifically-designed rod which held the component tracker at a fixed orientation to the pelvis, leaving the anterior pelvic plane as the only variable. Eight surgeons determined the anterior pelvic plane by palpating and registering the bony landmarks as reference points. The exact anterior pelvic plane was then established by using anatomically-placed bone screws as reference points.

The difference between the surgeons was found to be highly significant (p < 0.001). The variation was significantly larger for anteversion (sd 9.6°) than for inclination (sd 6.3°). The present method for registering pelvic landmarks shows significant inaccuracy, which highlights the need for improved methods of registration before this technique is considered to be safe.