Developing a Biomechanical Testing Setup of the Pelvis-Part I: Computational Design of Experiments.

Biomechanics of the human pelvis and the associated implants are still a medical and engineering debated topic. Today, no biomechanical testing setup is dedicated to pelvis testing and associated reconstructive implants with accepted clinical relevance. This paper uses the computational experiment design procedure to numerically design a biomechanical test stand that emulates the pelvis physiological gait loading. The numerically designed test stand reduces the 57 muscles and joints' contact forces iteratively to only four force actuators. Two hip joints' contact forces and two equivalent muscle forces with a maximum magnitude of 2.3 kN are applied in a bilateral reciprocating action. The stress distribution of the numerical model of the developed test stand is very similar to that of the numerical model of the pelvis with all 57 muscles and joint forces. For instance, at the right arcuate line, the state of stress is identical. However, at the location of superior rami, there is a deviation ranging from 2% to 20% between the two models. The boundary conditions and the nature of loading adopted in this study are more realistic regarding the clinical relevance than state-of-the-art. The numerically developed biomechanical testing setup of the pelvis in this numerical study (Part I) was found to be valid for the experimental testing of the pelvis. The construct of the testing setup and the experimental testing of an intact pelvis under gait loading are discussed in detail in Part II: Experimental Testing.

Developing a Biomechanical Testing Setup of the Pelvis-Part II: Experimental Testing.

Biomechanical testbench emulating the physiological loading of the pelvis is crucial in developing reconstructive implants for fragility fractures of the pelvis. Additionally, it will help understand the influence of the common daily loading on the pelvic ring. However, most reported experimental studies were mainly comparative with simplified loading and boundary conditions. In Part I of our study, we described the concept of the computational experiment design to design and construct a biomechanical testbench emulating the gait movement of the pelvis. The 57 muscles and joints' contact forces were reduced to four force actuators and one support, producing a similar stress distribution. The experimental setup is explained in this paper and some experimental results are presented. In addition, a series of repeatability and reproducibility tests were conducted to assess the test stand capabilities of replicating the gait physiological loading. The calculated stresses and the experimentally recorded strains showed that the pelvic ring response to the loading always follows the loaded leg side during the gait cycle. Furthermore, the experimental results of the pelvis displacement and strain at selected locations match the numerical ones. The developed test stand and the concept of computational experiment design behind it provide guidelines on how to design biomechanical testing equipment with physiological relevance.

Anterior buttress plate is successful for treating posterior sterno-clavicular dislocation.

PURPOSE: Traumatic posterior instability of the sternoclavicular joint is a potentially life-threatening injury. In contrast to the low incidence there is a plethora of different strategies to treat this lesion. It was the objective of this retrospective analysis to evaluate and further develop current strategies. METHODS: In this retrospective analysis all posterior dislocations that were diagnosed and treated between 2011 and 2018 were included. In this 7 year period, eight male patients (median age 32 years) were operated. RESULTS: Three patients were not diagnosed at the primary institution and were referred later. Five patients were treated with an anterior buttress plate with clavicular stabilisation only. One patient was stabilized with a temporary sternoclavicular arthrodesis. Two patients were operated using an autologous tendon graft. All of the patients underwent an immediate postoperative CT-scan that documented the anatomical articulation. All patients treated with a plate underwent implant removal. A final CT examination after removal documented the maintenance of the anatomic alignment. CONCLUSIONS: The buttress plate technique with clavicular screw fixation is a sufficient treatment to restore and preserve a normal sternoclavicular alignment. The technique finds its indication in unidirectional posterior instability. LEVEL OF EVIDENCE: IV.

Surgical anatomy of medial open-wedge high tibial osteotomy: crucial steps and pitfalls.

PURPOSE: To give an overview of the basic knowledge of the functional surgical anatomy of the proximal lower leg and the popliteal region relevant to medial high tibial osteotomy (HTO) as key anatomical structures in spatial relation to the popliteal region and the proximal tibiofibular joint are usually not directly visible and thus escape a direct inspection. METHODS: The surgical anatomy of the human proximal lower leg and its relevance for HTO are illustrated with a special emphasis on the individual steps of the operation involving creation of the osteotomy planes and plate fixation. RESULTS: The posteriorly located popliteal neurovascular bundle, but also lateral structures such as the peroneal nerve, the head of the fibula and the lateral collateral ligament must be protected from the instruments used for osteotomy. Neither positioning the knee joint in flexion, nor the posterior thin muscle layer of the popliteal muscle offers adequate protection of the popliteal neurovascular bundle when performing the osteotomy. Tactile feedback through a loss-of-resistance when the opposite cortex is perforated is only possible when sawing and drilling is performed in a pounding fashion. Kirschner wires with a proximal thread, therefore, always need to be introduced under fluoroscopic control. Due to anatomy of the tibial head, the tibial slope may increase inadvertently. CONCLUSIONS: Enhanced surgical knowledge of anatomical structures that are at a potential risk during the different steps of osteotomy or plate fixation will help to avoid possible injuries. LEVEL OF EVIDENCE: Expert opinion, Level V.

Experimental and numerical assessment of two reconstructive techniques for the fragility fractures of the pelvis type Ia.

Anterior pelvic ring fractures are common in geriatric patients. The Supraacetabular External Fixator (SEF) is a relatively simple and effective surgical procedure. On the other hand, there is the option of a Subcutaneous Iliopubic Plate (SIP) osteosynthesis. Only limited comparative biomechanical data of these two devices are available. Therefore, this biomechanical study's objective was to compare the stabilizing effect of the SEF versus the SIP in a model of Fragility Fractures of the Pelvis (FFP) type Ia. A test stand for pelvic biomechanics testing that emulates the gait loading cycle with physiological relevance was used. The osteotomy on the right pelvic ring was stabilized either with the SEF or the SIP. Strain gauges were used to measure strain in the pelvic ring. The osteotomy's spatial interfragmentary displacement (SID) was monitored using a 3D digital image correlation system. The SEF stabilization reduced the SID by approximately 10%, whereas the locking SIP could reduce displacement by about 62%. Additionally, the SIP reduced the stress/strain levels by 67% in the posterior pelvic ring. We could demonstrate that the SIP is superior to SEF in treating FFP type Ia as it significantly reduced the osteotomy's SID and the strain in the posterior pelvic ring.

The role of the bilateral subcutaneous plate in the minimal invasive stabilization of fragility fractures of the pelvis.

Introduction: Anterior pelvic ring fractures are common in geriatric patients. Current treatment algorithms recommend osteosynthesis if no pain free mobilisation is possible. For this a multitude of surgical techniques have been described. Among these the Supraacetabular External Fixator (SEF) is regarded a simple and effective surgical procedure. However, this technique is associated with significant drawbacks.Alternatively, there is the option of an internal fixator or a formal plate osteosynthesis. It is the objective of this case report to present the Subcutaneous Iliopubic Plate (SIP) in a fragility fracture of the anterior and posterior pelvic ring. Case report: An 83-year-old female patient sustained a fracture of the anterior pelvic ring, the lateral sacrum and the medial femoral neck. After initially refusing any surgery, the patient agreed to have the endoprosthesis implanted first, and then secondarily to dorsoventral osteosynthesis of the pelvis. Dorsally a transiliosacral screw osteosynthesis was performed. Anteriorly a bilateral subcutaneous iliopubic plate-osteosynthesis was chosen, a plate position that is anterior to the aponeurosis. Conclusions: The subcutaneous plate has proven to be a quick and uncomplicated surgical procedure that is significantly better tolerated by patients than external stabilization.

Quality indicators in the treatment of geriatric hip fractures: literature review and expert consensus.

PURPOSE: Even though hip fracture care pathways have evolved, mortality rates have not improved during the last 20 years. This finding together with the increased frailty of hip fracture patients turned hip fractures into a major public health concern. The corresponding development of an indicator labyrinth for hip fractures and the ongoing practice variance in Europe call for a list of benchmarking indicators that allow for quality improvement initiatives for the rapid recovery of fragile hip fractures (RR-FHF). The purpose of this study was to identify quality indicators that assess the quality of in-hospital care for rapid recovery of fragile hip fracture (RR-FHF). METHODS: A literature search and guideline selection was conducted to identify recommendations for RR-FHF. Recommendations were categorized as potential structure, process, and outcome QIs and subdivided in-hospital care treatment topics. A list of structure and process recommendations that belongs to care treatment topics relevant for RR-FHF was used to facilitate extraction of recommendations during a 2-day consensus meeting with experts (n = 15) in hip fracture care across Europe. Participants were instructed to select 5 key recommendations relevant for RR-FHF for each part of the in-hospital care pathway: pre-, intra-, and postoperative care. RESULTS: In total, 37 potential QIs for RR-FHF were selected based on a methodology using the combination of high levels of evidence and expert opinion. The set consists of 14 process, 13 structure, and 10 outcome indicators that cover the whole perioperative process of fragile hip fracture care. CONCLUSION: We suggest the QIs for RR-FHF to be practice tested and adapted to allow for intra-hospital longitudinal follow-up of the quality of care and for inter-hospital and cross-country benchmarking and quality improvement initiatives.

Influence of pubic symphysis stiffness on pelvic load distribution during single leg stance.

This study focuses on the influence of the softening and stiffening of pubic symphysis on the load distribution within the bones of the pelvic ring under the physiological loadings of the single leg stance. Muscle forces and joint reaction forces were first determined by inverse dynamics and applied to a linear finite element model of the pelvis. With normal pubic symphysis stiffness, high Von Mises stresses are located on the anterior surface to the sacrum around the sacroiliac joint and on the superior ramus, both on the side of the weight-bearing leg. Softening of the pubic symphysis redirects the load backward, decreases the stresses at the anterior pelvis, and increases them at the posterior pelvis. A stiffening of the pubic symphysis redirects the load forward, increases the load on the posterior pelvis, and decreases them at the anterior pelvis. This investigation highlights the significance of the pubic symphysis on the load distribution of the pelvis and in maintaining the integrity of the structures. Its role should not be neglected when analyzing the pelvis.

The portal of Neviaser: a valid option for antegrade nailing of humerus fractures.

INTRODUCTION: The objective of this retrospective non-randomized study was to evaluate the portal of Neviaser (PN) as an alternative approach in antegrade humeral nailing. METHODS: The surgical approach for the straight antegrade intramedullary nail (SAIN) was either the anterolateral delta-split (group 2, n = 79) or the portal of Neviaser (group 3, n = 27). Length of surgery and time of radiation were extracted from charts. Patients stabilized using the PN were followed for a clinical and radiological exam. At follow-up we evaluated the DASH (Disability of the Arm, Shoulder and Hand) and CMS (Constant-Murley Score). RESULTS: Between 10.2015 and 12.2018 191 proximal and diaphyseal humeral fractures were operated using either an angular stable extramedullary device (group 1, PHILOS®, n = 85) or a straight humeral nail (MultiLoc®, n = 106). Time of radiation and intervention followed a normal distribution. The mean length of surgery was 172.9 min (SD 91.5) in group 1, 121.5 min (SD 54.1) in group 2 and 96.4 min (SD 33.7) in group 3 (p < 0.01). Time of radiation was significantly different with 1.1 min (SD 0.6: group 1), 3.1 min (SD 1.6: group 2) and 2.9 min (SD 1.7: group 3) (p < 0.01). After a mean interval of 21.5 months (range 6-43 months) 14 / 27 patients of group 3 were available for a clinical and radiological follow-up. The mean DASH in group 3 was 25, the CMS reached 70. The age and sex weighted CMS mean value was 96%. Forward flexion was 131°, abduction 125°. The ratio of strength affected versus non-affected side was 4.4: 6.2 kg. CONCLUSIONS: The portal of Neviaser is a feasible and safe approach and is an alternative to the anterolateral delta-split. Length of surgery and time of radiation were significantly shorter. LEVEL OF EVIDENCE: IV.

Finite element analysis of the pelvis including gait muscle forces: an investigation into the effect of rami fractures on load transmission.

BACKGROUND: The objective of the study is to investigate the load transmission within the pelvic ring under physiological loading during gait and to correlate these results with clinical findings. In a second approach, we analysed how load distribution is altered by fractures of the anterior pelvic ring. METHODS: Muscle forces and joint reaction forces are calculated by inverse dynamics and implemented in a finite element pelvis model including the joints. RESULTS: With the intact configuration and according to the moment of the gait, left and right superior and inferior rami show the highest stresses of the model, corresponding to the typical location of an anterior pelvic ring fracture. A superior ramus fracture induces larger stresses to the lower ramus and a slight increase of stresses on the posterior structures. A total disruption of anterior rami redirects the loads to the back of the pelvis and introduces significantly higher stresses on the posterior structures. CONCLUSIONS: This investigation enhances the understanding of the biomechanics of the pelvis and highlights the important role of the rami in load carrying and in maintaining integrity of the pelvic ring.

[Open reduction and internal fixation by primary subtalar arthrodesis for intraarticular calcaneal fractures]. / Offene Reposition und Osteosynthese mit primärer subtalarer Arthrodese bei intraartikulärer Kalkaneusfraktur.

OBJECTIVE: To prevent the development of painful posttraumatic degenerative joint disease by a primary one-stage procedure to treat calcaneal fractures involving obvious comminution or severe and extensive cartilage damage to the subtalar facet. INDICATIONS: Sanders type IV calcaneal fractures with severe and extensive cartilage destruction. The definitive indication for arthrodesis can only be established intraoperatively. CONTRAINDICATIONS: Severe closed IIIrd or IV nd degree soft-tissue injury according to Tscherne & Oestern. Open fractures. Vascular impairment. Diabetes mellitus. Generalized or local inactivity osteoporosis > grade I according to Kanis. Age > approximately 50 years. SURGICAL TECHNIQUE: Extended lateral approach. Osteosynthesis of the calcaneal fracture, reconstruction of axes, subtalar facet denuded of cartilage, bone graft from the anterior iliac crest, arthrodesis by screw fixation of the subtalar joint. POSTOPERATIVE MANAGEMENT: After edema has subsided, mobilization without a cast and partial loading up to 15 kg for 12 weeks. Clinical and radiologic review after 6 and 12 weeks. RESULTS: This operation is performed very rarely. Within a retrospective study including patients over a period of 14 years (1990-2004), a total of 434 patients with a calcaneal fracture were treated surgically. Primary subtalar arthrodesis was performed in only six of these patients. Healing within 4 months was achieved in all six patients. The clinical and radiologic follow-ups took place on average after 4.9 years (2.5-7.5 years). Radiologically, almost anatomic reconstruction of the axes could be achieved (Gissane and Böhler angles, talometatarsal and talocalcaneal angles, calcaneal length and width). The functional outcomes were also good to very good with an average AOFAS (American Orthopaedic Foot and Ankle Society) Score of 88 points (63-94 points) and a Hanover Score of 84 points (62-90 points).

BMP-2-transduced human bone marrow stem cells enhance neo-bone formation in a rat critical-sized femur defect.

Synthetic graft materials are considered as possible substitutes for cancellous bone, but lack osteogenic and osteoinductive properties. In this study, we investigated how composite scaffolds of ßTCP containing osteogenic human bone marrow mesenchymal stem cells (hBMSCs) and osteoinductive bone morphogenetic protein-2 (BMP-2) influenced the process of fracture healing. hBMSCs were loaded into ßTCP scaffolds 24 h before implantation in a rat critical-sized bone defect. hBMSCs were either stimulated with rhBMP-2 or transduced with BMP-2 by gene transfer. The effect of both protein stimulation and gene transfer was compared for osteogenic outcome. X-rays were conducted at weeks 0, 1, 3, 6, 9 and 12 post-operatively. In addition, bone-labelling fluorochromes were applied at 0, 3, 6 and 9 weeks. Histological analysis was performed for the amount of callus tissue and cartilage formation. At 6 weeks, the critical-sized defect in 33% of the rats treated with the Ad-BMP-2-transduced hBMSCs/ßTCP scaffolds was radiographically bridged. In contrast, in only 10% of the rats treated with rhBMP2/hBMSCs, 12 weeks post-treatment, the bone defect was closed in all treated rats of the Ad-BMP-2 group except for one. Histology showed significantly higher amounts of callus formation in both Ad-BMP-2- and rhBMP-2-treated rats. The amount of neocartilage was less pronounced in both BMP-2-related groups. In summary, scaffolds with BMP-2-transduced hBMSCs performed better than those with the rhBMP2/hBMSCs protein. These results suggest that combinations of osteoconductive biomaterials with genetically modified MSCs capable of secreting osteoinductive proteins may represent a promising alternative for bone regeneration. Copyright © 2015 John Wiley & Sons, Ltd.

Functional outcome following scapulothoracic dissociation.

BACKGROUND: Scapulothoracic dissociation is an infrequent injury that is often accompanied by neurovascular injuries with a potentially devastating outcome. The aim of this study was to evaluate the functional outcome following scapulothoracic dissociation. METHODS: During a twenty-four-year period, we treated twenty-five patients with a scapulothoracic dissociation. The average age was 32.5 years. The average Injury Severity Score was 22 points. Nine patients had a complete brachial plexus avulsion, and ten had an incomplete brachial plexus avulsion. Three patients died from their associated injuries, and six patients required an above-the-elbow amputation. The outcome was assessed with use of the Short-Form 36-Item Health Survey, and the shoulder function of the patients who had not had an amputation was evaluated with use of the Subjective Shoulder Rating System. The degree of initial scapular lateralization was quantified with the scapula index. RESULTS: The average duration of follow-up was 12.6 years. The physical and mental component summary scores and the scores on the role-physical, general health, vitality, and mental health subscales of the Short-Form 36-Item Health Survey were significantly lower for patients with a complete brachial plexus avulsion (p < 0.05). The Subjective Shoulder Rating System score was also significantly lower in patients with a complete brachial plexus avulsion (33.8 points compared with 72.5 points for the patients with no or an incomplete avulsion, p = 0.046). The average scapula index was 1.29 +/- 0.19. The scores on the Short-Form 36-Item Health Survey scales and the Subjective Shoulder Rating System score did not correlate with the initial scapula index (p > 0.05). CONCLUSIONS: The presence of a complete brachial plexus avulsion is predictive of a poor functional outcome in a patient with a scapulothoracic dissociation. Therefore, we suggest a modification of the classification of the severity of this injury, with complete brachial plexus avulsion considered to be the most severe injury type. LEVEL OF EVIDENCE: Prognostic study, Level II-1 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Total hip arthroplasty in young patients using the thrust plate prosthesis: clinical and radiological results.

INTRODUCTION: The standard treatment for patients who require total hip replacement is the implantation of an intramedullary diaphyseal anchored hip prosthesis. A bone-sparing thrust plate hip prosthesis (TPP) can be used as an alternative device for young patients. The TPP relies on proximal femoral metaphyseal fixation. The theoretical advantage of leaving diaphyseal bone intact is easier conversion to a stemmed prosthesis. This retrospective study evaluated the medium- and short-term results after total joint replacement using the third generation TPP. MATERIALS AND METHODS: Between 1997 and 2001, 58 TPPs were used for 52 patients. Clinical and demographic data were obtained from the patients' charts and our electronic database. Their average age at time of surgery was 40.9+/-11.4 years. At follow-up, the Harris hip score, residual pain, required pain medication, and the ability to lie on the operated side were documented. Radiographic evaluation included standardized radiographs of the hip joint and the pelvis. RESULTS: Four patients required revision surgery (6.9%). For 51 of the remaining 54 TPPs, a postoperative functional and radiological status was obtained. The average follow-up was 26+/-11.0 months. 88% of the patients experienced some or complete relief of pain. The median Harris hip score at follow-up was 73+/-20.5 points. A postoperative hip dislocation occurred in 5 patients (8.6%). CONCLUSION: Since many patients experienced some or complete relief of pain, the TPP can be recommended as a feasible implant for the treatment of hip disorders requiring total hip arthroplasty in young patients. Revision surgeries are facilitated by the good bone stock remaining in the proximal femur.