Promoting bone callus formation by taking advantage of the time-dependent fracture gap strain modulation.

Delayed union and non-union of fractures continue to be a major problem in trauma and orthopedic surgery. These cases are challenging for the surgeon. In addition, these patients suffer from multiple surgeries, pain and disability. Furthermore, these cases are a major burden on healthcare systems. The scientific community widely agrees that the stability of fixation plays a crucial role in determining the outcome of osteosynthesis. The extent of stabilization affects factors like fracture gap strain and fluid flow, which, in turn, influence the regenerative processes positively or negatively. Nonetheless, a growing body of literature suggests that during the fracture healing process, there exists a critical time frame where intervention can stimulate the bone's return to its original form and function. This article provides a summary of existing evidence in the literature regarding the impact of different levels of fixation stability on the strain experienced by newly forming tissues. We will also discuss the timing and nature of this "window of opportunity" and explore how current knowledge is driving the development of new technologies with design enhancements rooted in mechanobiological principles.

Bone defect filling with a novel rattan-wood based not-sintered hydroxyapatite and beta-tricalcium phosphate material (b.Bone™) after tricortical bone graft harvesting - A consecutive clinical case series of 9 patients.

Harvesting of tricortical bone graft from the iliac crest is an integral part of bone defect reconstruction in orthopaedic surgery. There are several options for filling the iliac crest defect area to avoid hematoma, pain, hernias and cosmetic issues, including different gelatin-based and other alternative biomaterials. Recently, a novel rattan-wood based not-sintered hydroxyapatite and beta-tricalcium phosphate material (b.Bone™, GreenBone ORTHO S.p.A Faenza, Italy) was shown to promote bone healing in an experimental setting. The goal of the current work is to report clinical and radiographical outcomes of a consecutive case series of 9 patients with defect filling at the iliac crest with this novel scaffold biomaterial after tricortical bone graft harvesting with a minimum follow-up of 6 months. All 9 patients (8 male, 1 female) with an average age of 42.7 years (range: 18-76 years) had tricortical bone graft harvesting from the iliac crest for different reconstructive procedures at the extremities and received blocks of the biomaterial with an average size of 26.3 × 16.8 × 10 mm (length, height, width; range: 15 × 15 × 10 to 40 × 20 × 10 mm). Intraoperative handling of the biomaterial was easy and the blocks could be customized to the individual size of the defect with standard surgical instruments and were press-fitted into the defect. All 9 patients showed uneventful wound healing at the iliac crest and 7 patients reported no pain (VAS: 0) and two patients only mild pain (VAS:1 and VAS:3) after an average follow-up of 9.8 months (range: 6-16 months). There was no post-operative hematoma, surgical revision or other implant-related complications at the iliac crest. In all patients, good radiographical integration without dislocation of the implant and good bony integration was observed. The use of this novel biomaterial for iliac crest defect filling was associated with good clinical and radiographical outcomes after an average follow-up of 9.8 months.

Lateral para-olecranon approach: surgical guide and anatomical considerations to the anconeus branch: is there a nerve-free zone?

PURPOSE: In the last decades, total elbow arthroplasty, elbow osteosynthesis and revision surgery have been more popularized. The study aimed to assess the course of the anconeus branch of the radial nerve in relation to two variations of the lateral para-olecranon approach, considering iatrogenic nerve injuries. METHODS: The study consisted of 120 upper extremities from 60 Thiel-embalmed human specimens. Two randomized versions of the lateral para-olecranon approach (centrally orientated: P1 and laterally orientated: P2) were performed. The olecranon and the intersection points to the anconeus branch of the radial nerve were determined as anatomical landmarks. The measurements were assessed by two independent observers. Differences were analyzed using the Student's t test; associations were computed with the Pearson correlation (r). An alpha of 0.05 (p) and a confidence interval of 95% were set. RESULTS: The intersection points averaged 12.3 cm (SD 1.8, range 8.2-16.8) for P1 versus 5.5 cm (SD 1.4, range 3.0-9.2) for P2 (p ≤ 0.001). Statistically significantly higher values for male and longer humeral specimens were revealed (all values: p < 0.05). Comparison of left and right sides yielded no difference. Excellent inter-rater agreements were found (ICC = 0.902, range 0.860-0.921). A correlation was evaluated between the humeral length and the distances in both approaches (P1: r = 0.550, p < 0.001, P2: r = 0.669, p < 0.001). CONCLUSION: The data presented here allow preservation of the anconeus branch. The P1 forms a potential advantage by owing a broader safe zone. Using the centrally orientated approach seems to provide adequate nerve protection during surgery for one of the motor branches for extension of the elbow joint and might result in improved postoperative benefits.

Mini-open carpal tunnel release: technique, feasibility and clinical outcome compared to the conventional procedure in a long-term follow-up.

We sought to evaluate the findings of our anatomically landmarks based mini-open procedure (MCTR) through a palmar approach and to compare its outcome and practicability to the conventional method (OCTR). The study consisted of 100 matched patients (n = 50 MCTR, n = 50 OCTR) with a minimum follow-up of three years. The outcome was characterized via the Disabilities of Arm, Shoulder and Hand Score (DASH), Symptom Severity Scale (SSS), Functional Status Scale (FSC), and Visual Analogue Scale (VAS). All adverse events were observed. An alpha of 0.05 and a confidence level of 95% were set for statistical analyses. Both techniques showed comparable functional results in a long-term period (mean follow-up MCTR: 60 months and OCTR: 54 months). MCTR versus OCTR at mean: DASH: 4.6/8.3 (p = 0.398), SSS: 1.3/1.2 (p = 0.534), FSC: 1.3/1.2 (p = 0.617), VAS: 0.4/0.7 (p = 0.246). The MCTR convinced through a lower rate of scar sensibility (MCTR: 0% vs. OCTR: 12%, 0/50 vs. 6/50; p = 0.007) and pillar pain, as well as a shortened recovery period and surgical time relative to the OCTR. Low complication rates were observed in both groups, no recurrences had to be documented. The MCTR procedure revealed a similar good clinical outcome as the conventional technique. MCTR is a minimally-invasive, reliable, fast and simple procedure with an obvious benefit regarding scar sensibility.

Variable fixation promotes callus formation: an experimental study on transverse tibial osteotomies stabilized with locking plates.

BACKGROUND: A new locking screw technology, named variable fixation, has been developed aiming at promoting bone callus formation providing initial rigid fixation followed by progressive fracture gap dynamisation. In this study, we compared bone callus formation in osteotomies stabilized with standard locking fixation against that of osteotomies stabilized with variable fixation in an established tibia ovine model. METHODS: A 3 mm tibial transverse osteotomy gap was stabilized in three groups of six female sheep each with a locking plate and either 1) standard fixation in both segments (group LS) or 2) variable fixation in the proximal and standard fixation in the distal bone segment (group VFLS3) or 3) variable fixation in both segments (group VFLS6). The implantation site and fracture healing were compared between groups by means of radiologic, micro tomographic, biomechanical, and histological investigations. RESULTS: Compared to LS callus, VFLS3 callus was 40% larger and about 3% denser, while VFLS6 callus was 93% larger and its density about 7.2% lower. VFLS3 showed 65% and VFLS6 163% larger amount of callus at the cis-cortex. There wasn't a significant difference in the amount of callus at the cis and trans-cortex in groups featuring variable fixation only. Investigated biomechanical variables were not significantly different among groups and histology showed comparable good healing in all groups. Tissues adjacent to the implants did not show any alteration of the normal structure in all groups. CONCLUSIONS: Variable fixation promoted the formation of a larger amount of bone callus, equally distributed at the cis and trans cortices. The histological and biomechanical properties of the variable fixation callus were equivalent to those of the standard fixation callus. The magnitude of variable fixation had a biological effect on the formation of bone callus. At the implantation site, the usage of variable fixation did not raise additional concerns with respect to standard fixation. The formation of a larger amount of mature callus suggests that fractures treated with variable fixation might have a higher probability to bridge the fracture gap. The conditions where its usage can be most beneficial for patients needs to be clinically defined.

Chondrocyte Culture Parameters for Matrix-Assisted Autologous Chondrocyte Implantation Affect Catabolism and Inflammation in a Rabbit Model.

Cartilage defects represent an increasing pathology among active individuals that affects the ability to contribute to sports and daily life. Cell therapy, such as autologous chondrocyte implantation (ACI), is a widespread option to treat larger cartilage defects still lacking standardization of in vitro cell culture parameters. We hypothesize that mRNA expression of cytokines and proteases before and after ACI is influenced by in vitro parameters: cell-passage, cell-density and membrane-holding time. Knee joint articular chondrocytes, harvested from rabbits (n = 60), were cultured/processed under varying conditions: after three different cell-passages (P1, P3, and P5), cells were seeded on 3D collagen matrices (approximately 25 mm³) at three different densities (2 × 105/matrix, 1 × 106/matrix, and 3 × 106/matrix) combined with two different membrane-holding times (5 h and two weeks) prior autologous transplantation. Those combinations resulted in 18 different in vivo experimental groups. Two defects/knee/animal were created in the trochlear groove (defect dimension: ∅ 4 mm × 2 mm). Four identical cell-seeded matrices (CSM) were assembled and grouped in two pairs: One pair giving pre-operative in vitro data (CSM-i), the other pair was implanted in vivo and harvested 12 weeks post-implantation (CSM-e). CSMs were analyzed for TNF-α, IL-1ß, MMP-1, and MMP-3 via qPCR. CSM-i showed higher expression of IL-1ß, MMP-1, and MMP-3 compared to CSM-e. TNF-α expression was higher in CSM-e. Linearity between CSM-i and CSM-e values was found, except for TNF-α. IL-1ß expression was higher in CSM-i at higher passage and longer membrane-holding time. IL-1ß expression decreased with prolonged membrane-holding time in CSM-e. For TNF-α, the reverse was true. Lower cell-passages and lower membrane-holding time resulted in stronger TNF-α expression. Prolonged membrane-holding time resulted in increased MMP levels among CSM-i and CSM-e. Cellular density was of no significant effect. We demonstrated cytokine and MMP expression levels to be directly influenced by in vitro culture settings in ACI. Linearity of expression-patterns between CSM-i and CSM-e may predict ACI regeneration outcome in vivo. Cytokine/protease interaction within the regenerate tissue could be guided via adjusting in vitro culture parameters, of which membrane-holding time resulted the most relevant one.

Effect of COX-2 inhibition on tendon-to-bone healing and PGE2 concentration after anterior cruciate ligament reconstruction.

BACKGROUND: Non-steroidal anti-inflammatory drugs are commonly used to reduce pain and inflammation in orthopaedic patients. Selective cyclooxygenase-2 (COX-2) inhibitors have been developed to minimize drug-specific side effects. However, they are suspected to impair both bone and tendon healing. The objective of this study is to evaluate the effect of COX-2 inhibitor administration on tendon-to-bone healing and prostaglandin E (PGE2) concentration. METHODS: Thirty-two New Zealand white rabbits underwent reconstructions of the anterior cruciate ligaments and were randomized into four groups: Two groups postoperatively received a selective COX-2 inhibitor (Celecoxib) on a daily basis for 3 weeks, the two other groups received no postoperative COX-2 inhibitors at all and were examined after three or 6 weeks. The PGE2 concentration of the synovial fluid, the osseous integration of the tendon graft at tunnel aperture and midtunnel section, as well as the stability of the tendon graft were examined via biomechanic testing. RESULTS: After 3 weeks, the PGE2 content of the synovial fluid in the COX-2 inhibitor recipients was significantly lower than that of the control group (p = 0.018). At the same time, the COX-2 inhibitor recipients had a significantly lower bone density and lower amount of new bone formation than the control group (p = 0.020; p = 0.028) in the tunnel aperture. At the 6-week examination, there was a significant increase in the PGE2 content within synovial fluid of the COX-2 inhibitor recipients (p = 0.022), whose treatment with COX-2 inhibitors had ended 3 weeks earlier; in contrast, the transplant stability decreased and was reduced by 37% compared to the controls. CONCLUSIONS: Selective COX-2 inhibitors cause impaired tendon-to-bone healing, weaken mechanical stability and decrease PGE2 content of the synovial fluid. The present study suggests a reluctant use of COX-2 inhibitors when tendon-to-bone healing is intended.

Prevalence of the distal oblique bundle of the interosseous membrane of the forearm: an anatomical study.

A study was undertaken to examine the presence of the distal oblique bundle of the forearm in a large sample in order to describe its true prevalence. The study sample consisted of 200 cadaveric forearms. Fifteen were excluded due to defects in the distal interosseous membrane. In the remaining 185 specimens, the distal interosseous membrane was examined following removal of soft tissue, to determine whether a distal oblique bundle was present and whether there were connecting fibres to the distal radio-ulnar joint. The distal oblique bundle was observed in 53 specimens (29%). In 45 of these forearms (85%), one or more connecting fibres to the distal radio-ulnar joint were identified. The presence of a distal oblique bundle in 29% is less frequent than that reported in previous literature. The presence of the distal oblique bundle should be noted and may be of importance in the management of disorders of the distal radio-ulnar joint.

Biomechanical evaluation of straight antegrade nailing in proximal humeral fractures: the rationale of the "proximal anchoring point".

PURPOSE: Varus failure is one of the most common failure modes following surgical treatment of proximal humeral fractures. Straight antegrade nails (SAN) theoretically provide increased stability by anchoring to the densest zone of the proximal humerus (subchondral zone) with the end of the nail. The aim of this study was to biomechanically investigate the characteristics of this "proximal anchoring point" (PAP). We hypothesized that the PAP would improve stability compared to the same construct without the PAP. METHODS: Straight antegrade humeral nailing was performed in 20 matched pairs of human cadaveric humeri for a simulated unstable two-part fracture. RESULTS: Biomechanical testing, with stepwise increasing cyclic axial loading (50-N increments each 100 cycles) at an angle of 20° abduction revealed significantly higher median loads to failure for SAN constructs with the PAP (median, 450 N; range, 200-1.000 N) compared to those without the PAP (median, 325 N; range, 100-500 N; p = 0.009). SAN constructs with press-fit proximal extensions (endcaps) showed similar median loads to failure (median, 400 N; range, 200-650 N), when compared to the undersized, commercially available SAN endcaps (median, 450 N; range, 200-600 N; p = 0.240). CONCLUSIONS: The PAP provided significantly increased stability in SAN constructs compared to the same setup without this additional proximal anchoring point. Varus-displacing forces to the humeral head were superiorly reduced in this setting. This study provides biomechanical evidence for the "proximal anchoring point's" rationale. Straight antegrade humeral nailing may be beneficial for patients undergoing surgical treatment for unstable proximal humeral fractures to decrease secondary varus displacement and thus potentially reduce revision rates.

Resuscitation with polymeric plasma substitutes is permissive for systemic inflammatory response syndrome and sepsis in multiply injured patients: a retrospective cohort study.

OBJECTIVE: Multiple trauma is often accompanied by systemic inflammatory response syndrome (SIRS). The aim of this study was to investigate the impact of polymeric plasma substitutes on the development of SIRS or sepsis. METHODS: We included 2969 patients aged ≥16 years with an Injury Severity Score (ISS) >16 in this study. The sample was subdivided into three groups: patients who did not receive colloids and those who received <5L colloids and >5L colloids within the first 48 h. Data were analyzed using IBM SPSS® for Windows version 22.0; analysis of variance was used for continuous normally distributed data and Kruskal-Wallis test for categorical data. The predictive quality of colloid treatment was analyzed using the receiver operating characteristic (ROC) curves. Independent predictively was analyzed by binary logistic regression. Data were considered significant if P < 0.05. Data are presented as the mean ± standard deviation. RESULTS: The SIRS score increased with the amount of colloid used (1.9 ± 1.4 vs. 2.4 ± 1.2 vs. 3.2 ± 0.9; P < 0.001). However, the predictive quality was low, with an area under the ROC of 0.693 for SIRS and 0.669 for sepsis (P < 0.001). Binary logistic regression revealed colloids as an independent factor for the development of SIRS and sepsis (odds ratios: SIRS 3.325 and sepsis 8.984; P < 0.001). CONCLUSION: Besides other factors, colloids have a significant permissive effect and are independent predictors for the development of SIRS and sepsis in multiply injured patients. Trial registration 'Retrospektive Analysen in der Chirurgischen Intensivmedizin' No. St. V. 01-2008.

Fresh frozen plasma is permissive for systemic inflammatory response syndrome, infection, and sepsis in multiple-injured patients.

BACKGROUND: The correction of coagulopathy with fresh frozen plasma (FFP) is one of the main issues in the treatment of multiple-injured patients. Infectious and septic complications contribute to an adverse outcome in multiple-injured patients. Here, we investigated the role of FFP in the development of inflammatory complications given within the first 48 hours. METHODS: A total of 2033 patients with multiple injuries and an Injury Severity Score greater than 16 points and aged 16 years or older were included. The population was subdivided into 2 groups: those who received FFP and those who did not. The data were analyzed using SPSS version 22.0. Associations between the data were tested using Pearson correlation. Independent predictivity was analyzed by binary logistic regression and multivariate regression. Data were considered as significant if P<.05. RESULTS: The prothrombin time at admission was significantly lower (68.5%±23.3% vs 81.8%±21.0% normal; P<.001) in the group receiving FFP. The application of FFP led to a more severe systemic inflammatory response syndrome (SIRS) grade (3.0±1.2 vs 2.2±1.4; P<.001), to a higher infection rate (48% vs 28%; P<.001), and to a higher sepsis rate (29% vs 13%; P<.001) in the patients receiving FFP. The correlations between SIRS and the incidence of infections and sepsis increased with the amount of FFP applied (P<.001). CONCLUSIONS: Treatment with FFP of bleeding patients with multiple injuries enhances the risk of SIRS, infection, and sepsis; however, a multifactorial genesis has to be postulated.

Direct transplantation of native pericytes from adipose tissue: A new perspective to stimulate healing in critical size bone defects.

BACKGROUND AIMS: Fractures with a critical size bone defect (e.g., open fracture with segmental bone loss) are associated with high rates of delayed union and non-union. The prevention and treatment of these complications remain a serious issue in trauma and orthopaedic surgery. Autologous cancellous bone grafting is a well-established and widely used technique. However, it has drawbacks related to availability, increased morbidity and insufficient efficacy. Mesenchymal stromal cells can potentially be used to improve fracture healing. In particular, human fat tissue has been identified as a good source of multilineage adipose-derived stem cells, which can be differentiated into osteoblasts. The main issue is that mesenchymal stromal cells are a heterogeneous population of progenitors and lineage-committed cells harboring a broad range of regenerative properties. This heterogeneity is also mirrored in the differentiation potential of these cells. In the present study, we sought to test the possibility to enrich defined subpopulations of stem/progenitor cells for direct therapeutic application without requiring an in vitro expansion. METHODS: We enriched a CD146+NG2+CD45- population of pericytes from freshly isolated stromal vascular fraction from mouse fat tissue and tested their osteogenic differentiation capacity in vitro and in vivo in a mouse model for critical size bone injury. RESULTS: Our results confirm the ability of enriched CD146+NG2+CD45- cells to efficiently generate osteoblasts in vitro, to colonize cancellous bone scaffolds and to successfully contribute to regeneration of large bone defects in vivo. CONCLUSIONS: This study represents proof of principle for the direct use of enriched populations of cells with stem/progenitor identity for therapeutic applications.

Dynamization at the near cortex in locking plate osteosynthesis by means of dynamic locking screws: an experimental study of transverse tibial osteotomies in sheep.

BACKGROUND: Locking plates are widely used in fracture fixation, mainly for meta-diaphyseal fractures, comminuted fractures, fractures with a critical-size bone defect, periprosthetic fractures, osteotomies, and fractures in osteoporotic bone. The aim of this animal study was to evaluate the effect on bone-healing of dynamization of locking plate constructs by means of new 5.0-mm dynamic locking screws (in the DLS group), which allow near-cortex micromotion, compared with a more rigid construct utilizing standard bicortical locking-head screws (in the LS group). Use of dynamic locking screws allows modulation of the stiffness of existing locking compression plate systems via parallel interfragmentary micromotion. METHODS: A standardized diaphyseal tibial osteotomy (90°, 3-mm fracture gap) was performed and stabilized with a six-hole large-fragment locking compression plate in twelve female sheep (six in each group). Radiographs were made postoperatively and then weekly from week three until sacrifice at nine weeks. Macroscopic, biomechanical, histologic, and radiographic assessments and microcomputed tomography were performed. RESULTS: The callus in the tested specimens in the DLS group had better biomechanical stability, with a significantly greater maximum failure moment (mean and standard deviation [SD] as a percentage of intact, 55.15 ± 20.65 compared with 26.80 ± 14.96 in the LS group; p = 0.021). The DLS group also had greater periosteal callus volume at the near cortex (mean volume and SD as a percentage of the tibial shaft volume, 36.21% ± 10.08% compared with 18.98% ± 8.61% in the LS group; p = 0.026) and in the intercortical region (mean volume and SD as a percentage of the bone volume of the tibial shaft, 3.56% ± 0.52% compared with 2.64% ± 0.98% in the LS group; p = 0.045), as shown by microcomputed tomography. The DLS group also had significantly greater torsional stiffness (mean and SD as a percentage of intact, 84.88 ± 13.51 compared with 58.89 ± 20.61 in the LS group; p = 0.027). CONCLUSIONS: Controlled micromotion and nearly homogeneous interfragmentary strain at the fracture site, together with the stable bicortical fixation achieved by the new dynamic locking screw, led to more uniform callus formation, significantly more callus formation at the near cortex, and biomechanically more competent bone-healing compared with use of rigid locking plate constructs with locking-head screws.

Dynamic-locking-screw (DLS)-leads to less secondary screw perforations in proximal humerus fractures.

BACKGROUND: Loss of reduction and screw perforation causes high failure rates in the treatment of proximal humerus fractures. The purpose of the present study was to evaluate the early postoperative complications using modern Dynamic Locking Screws (DLS 3.7) for plating of proximal humerus fractures. METHODS: Between 03/2009 and 12/2010, 64 patients with acute proximal humerus fractures were treated by angular stable plate fixation using DLSs in a limited multi-centre study. Follow-up examinations were performed three, six, twelve and twenty-four weeks postoperatively and any complications were carefully collected. RESULTS: 56 of 64 patients were examined at the six-month follow-up. Complications were observed in 12 patients (22%). In five cases (9%), a perforation of the DLS 3.7 occurred. CONCLUSIONS: Despite the use of modern DLS 3.7, the early complications after plating of proximal humerus fractures remain high. The potential advantage of the DLS 3.7 regarding secondary screw perforation has to be confirmed by future randomized controlled trials.

Obesity and overweight as a risk factor for pneumonia in polytrauma patients: a retrospective cohort study.

BACKGROUND: Obesity is a growing problem in western societies. The aim of this retrospective cohort study was to determine the association between the overweight and obese polytrauma patients and pneumonia after injury. METHODS: A total of 628 patients with an Injury Severity Score (ISS) of 16 or greater and 16 years or older were included in this retrospective study. The sample was subdivided into three groups as follows: body mass index (BMI) of less than 25 kg/m2; BMI of 25 kg/m2 to 30 kg/m2; and BMI more than 30 kg/m2. The Murray score was assessed at admission and at its maximum during hospitalization to determine pulmonary problems. Pneumonia was defined as bacteriologically positive sputum with appropriate radiologic and laboratory changes (C-reactive protein and interleukin 6). Data are given as mean ± SEM. One-way analysis of variance and the Kruskal-Wallis test were used for the analyses, and the significance level was set at p < 0.05; Bonferroni-Dunn test was performed as post hoc analysis. RESULTS: The Abbreviated Injury Scale (AIS) score for the thorax was 3.2 ± 0.1 in the group with a BMI of less than 25 kg/m2, 3.3 ± 0.1 in the group with a BMI of 25 kg/m2 to 30 kg/m2, and 2.8 ± 0.2 in the group with BMI of more than 30 kg/m2 (p = 0.044). The Murray score at admission was elevated with increasing BMI (0.8 ± 0.8 for BMI < 25 kg/m2, 0.9 ± 0.9 for BMI 25­30 kg/m2, and 1.0 ± 0.8 for BMI > 30 kg/m2; p = 0.137); the maximum Murray score during hospitalization revealed significant differences (1.2 ± 0.9 for BMI < 25 kg/m2, 1.6 ± 1.0 for BMI 25­30 kg/m2, and 1.5 ± 0.9 for BMI > 30 kg/m2; p < 0.001). The incidence of pneumonia also increased with increasing BMI (1.6% for BMI < 25 kg/m2, 2.0% for BMI 25­30 kg/m2, and 3.1% for BMI > 30 kg/m2; p = 0.044). CONCLUSION: Obesity leads to an increased incidence of pneumonia in a polytrauma situation. LEVEL OF EVIDENCE: Prognostic/epidemiologic study, level IV.

Influence of peri-implant bone quality on implant stability.

INTRODUCTION: Insufficient primary stability is still reported for proximal humerus fractures in elderly patients. Fixation stability could be improved by aiming locking screws at bone volumes with better properties. The aims of this study were to investigate the bone regions engaged by the locking screws of a Proximal Humeral Nail (MultiLoc PHN), and to evaluate the influence of peri-screw bone quality on bone-nail construct stability. MATERIALS AND METHODS: Twelve cadaveric humeri were divided into two groups. The distal locking part of the PHN was fixed to the specimens. The nails were removed and the bones scanned using HR-pQCT. Bone properties were evaluated at the locations where the proximal locking screws would have been positioned after complete instrumentation. A three-part fracture model was used for mechanical testing of the instrumented bones, considering axial displacement and varus deformation as parameters of interest. RESULTS: The secondary locking screws targeted bone volumes in the posteromedial part of the humerus with statistically significant higher quality, thus reducing varus deformation. Significant correlation was found between axial displacement and bone properties at the primary proximal screws. Significant correlation was found between the varus deformation and apparent BMD at the secondary locking screws. CONCLUSION: The findings of this study confirmed that directing the proximal locking screws at bone regions with better properties can improve fixation stability.

The dynamisation of locking plate osteosynthesis by means of dynamic locking screws (DLS)-an experimental study in sheep.

In this in vivo study a new generation of locking screws was tested. The design of the dynamic locking screw (DLS) enables the dynamisation of the cortex underneath the plate (cis-cortex) and, therefore, allows almost parallel interfragmentary closure of the fracture gap. A 45° angle osteotomy was performed unilaterally on the tibia of 37 sheep. Groups of 12 sheep were formed and in each group a different osteotomy gap (0, 1 and 3mm) was fixed using a locking compression plate (LCP) in combination with the DLS. The healing process was monitored radiographically every 3 weeks for 6, respectively 12 weeks. After this time the sheep were sacrificed, the bones harvested and the implants removed. The isolated bones were evaluated in the micro-computed tomography unit, tested biomechanically and evaluated histologically. The best results of interfragmentary movement (IFM) were shown in the 0mm configuration. The bones of this group demonstrated histomorphometrically the most distinct callus formation on the cis-cortex and the highest torsional stiffness relative to the untreated limb at 12 weeks after surgery. This animal study showed that IFM stimulated the synthesis of new bone matrix, especially underneath the plate and thus, could solve a current limitation in normal human bone healing. The DLS will be a valuable addition to the locking screw technology and improve fracture healing.

Retrograde femoral nailing in elderly patients: outcome and functional results.

Functional outcome after retrograde femoral intramedullary nailing was investigated in 35 patients older than 60 years (mean, 86 years) with 36 fractures, comprising 15 (41.7%) shaft and 21 (58.3%) distal fractures; overall, 7 (19.4%) periprosthetic fractures occured. Twenty-two (62.9%) of 35 patients were evaluated at a mean 16.5-month follow-up with the Lyshom-Gillquist score and the SF-8 questionaire. Primary union rate was 97.8%, with no significant differences in duration of surgery, bone healing, mobilization, and weight bearing among different fracture types; periprosthetic fractures revealed a significantly delayed mobilization (P=.03). Complications occured significantly more often among distal femoral fractures (P=.009), including all revision surgeries. The most frequently encountered complication was loosening of distal locking bolts (n=3). Lysholm score results were mainly influenced by age-related entities and revealed fair results in all fractures (mean in the femoral shaft fracture group, 78.1 vs mean in the distal femoral fracture group, 74.9; P=.69), except in the periprosthetic subgroup, which had good results (mean, 84.8; P=.23). This group also had increased physical parameters according to SF-8 score (P=.026). No correlation existed between SF-8 physical parameters and patient age or surgery delay, whereas a negative correlation existed between patient age and SF-8 mental parameters (P=.012). Retrograde femoral intramedullary nailing is commonly used in elderly patients due to reliable bone healing, minimal soft tissue damage, and immediate full weight bearing. It also offers a valid alternative to antegrade nailing in femoral shaft fractures.

Biomechanical evaluation of two intramedullary nailing techniques with different locking options in a three-part fracture proximal humerus model.

BACKGROUND: Osteosynthesis of unstable proximal humerus fractures still remains challenging. The aim of this study was to investigate two intramedullary nailing techniques with different locking options in a three-part fracture model and prove whether two new fixation concepts, introducing additional locking screw-in-screws inserted through the head of the proximal screws, and a calcar screw, provide better stability. METHODS: A biomechanical testing model for three-part proximal humerus fractures including cyclic axial loading with increasing peak load and simultaneous pulling forces at the rotator cuff was used to test 12 pairs of human cadaver humeri, assigned to four groups and instrumented with either Targon PH (T1) or MultiLoc PHN in 3 different configurations (standard M1; two additional screw-in-screw M2; one additional calcar screw and two screw-in-screw M3). FINDINGS: Initial range of motion in internal-external rotation and mediolateral translation was smallest in M3 (1.82°; 0.11mm), biggest in T1 (3.63°; 0.51mm) and significantly different between these two groups (p=0.02 and p=0.04, respectively). M3 showed minimum head migration along the nail and varus tilting after 5000 cycles (0.31mm; 0.20°) and 10000 cycles (1.59mm; 0.34°). M2 and M3 performed better than M1 and T1 regarding varus collapse. The highest number of cycles to failure was observed for M3 (20733) and the lowest for T1 (10083) with significant difference between these two groups (p=0.04). INTERPRETATION: The configuration with two screw-in-screw and a calcar screw was superior in most aspects. The screw-in-screws were found to contribute against varus collapse. Both new fixation concepts could provide better stability in proximal humerus fractures.

Osseointegration and biocompatibility of different metal implants--a comparative experimental investigation in sheep.

BACKGROUND: In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep. METHODS: Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically. RESULTS: Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials. CONCLUSION: This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.