Hendrik Jansen

Effective combination of bone substitute and screws in the jail technique: a biomechanical study of tibial depression fractures

PurposeThe aim of this study was to investigate a new drillable calcium phosphate cement (Norian drillable Synthes GmbH) as a bone substitute either alone or in combination with screws in the jail technique (Petersen et al. Unfallchirurg Mar 109(3):219–234, 2006; Petersen et al. Unfallchirurg Mar 109(3):235–244, 2006) with regard to the primary stability in lateral tibial depression fractures.MethodsLateral depression fractures of the tibial plateau were created in a biomechanical fracture model. After reduction they were stabilised with bone substitute (group one), bone substitute with additional four screws in the jail technique (group two) or four screws only (group three). Displacement under cyclic loading, stiffness and maximum load in load-to-failure tests were determined.ResultsThe groups with the bone substitute showed a lower displacement of the depressed articular fragment under cyclical loading and a higher stiffness. The maximum load was higher for the groups with screws.ConclusionsOnly the combination of bone substitute and screws prevented secondary loss of reduction and, at the same time, provided enough stability under maximum load.

Immunohistochemical and Molecular Characterization of the Human Periosteum

Purpose. The aim of the present study was to characterize the cell of the human periosteum using immunohistological and molecular methods. Methods. Phenotypic properties and the distribution of the cells within the different layers were investigated with immunohistochemical staining techniques and RT-PCR, focussing on markers for stromal stem cells, osteoblasts, osteoclasts and immune cells. Results. Immunohistochemical results revealed that all stained cells were located in the cambium layer and that most cells were positive for vimentin. The majority of cells consisted of stromal stem cells and osteoblastic precursor cells. The density increased towards the deeper layers of the cambium. In addition, cells positive for markers of the osteoblast, chondrocyte, and osteoclast lineages were found. Interestingly, there were MHC class II-expressing immune cells suggesting the presence of dendritic cells. Using lineage-specific primer pairs RT-PCR confirmed the immunofluorescence microscopy results, supporting that human periosteum serves as a reservoir of stromal stem cells, as well as cells of the osteoblastic, and the chondroblastic lineage, osteoclasts, and dendritic cells. Conclusion. Our work elucidates the role of periosteum as a source of cells with a high regenerative capacity. Undifferentiated stromal stem cells as well as osteoblastic precursor cells are dominating in the cambium layer. A new outlook is given towards an immune response coming from the periosteum as MHC II positive immune cells were detected.

The influence of soft tissue trauma on bone regeneration after acute limb shortening

Reconstructing posttraumatic tibial defects is often challenging. Some authors recommend acute limb shortening. We determined whether soft tissue trauma affects the formation of regenerated bone after acute shortening and monofocal lengthening. Twenty-two rabbits were divided into two equal groups. In the test group, 90 minutes of ischemia and 30 minutes of tibialis anterior muscle contusion at 100 kPa induced substantially elevated pressure as an onset of compartment syndrome. The untreated hind limb acted as the paired control. An external fixator was applied and the limb was shortened 10 mm through bone resection. After a latency period, distraction was performed for 10 days until the natural length was restored. New bone formation was evaluated mechanically, radiographically, and histomorphometrically. Osseous consolidation occurred in all animals. Normalized mechanical values of the newly reconstructed tibia indicated torsional strength was lower in the trauma group than in controls (46% ± 18.5% versus 64% ± 16.7%). Average normalized callus diameters were smaller in the trauma group than in controls (1.27 ± 0.14 versus 1.6 ± 0.16), as were callus volumes (37% ± 5.9% versus 44% ± 10.3%). Although soft tissue trauma affected the formation of regenerated bone, our results suggest reconstruction of tibial defects using a monofocal technique is consistent, even in the presence of blunt trauma and elevated compartment pressure.

Simultaneous posterior fracture dislocation of the shoulder following epileptic convulsion

Shoulder dislocations with fractures are a possible complication of an epileptic seizure and are often missed on the first sight. The incidence of sustaining an avascular humeral head necrosis (AVN) is high, and primary prosthetic replacement is the choice of treatment. In this paper, we describe such a rare case: a 48-year-old male patient sustained simultaneous bilateral posterior shoulder dislocation with fractures of both humeral heads following the first episode of an epileptic convulsion. On the left side, open reduction and internal fixation were performed with angle stable plate osteosynthesis. In the same operation, a hemi-prosthesis was implanted on the right side. One and a half years postoperatively, function on the right side is unsatisfying and AVN is seen on the left side and secondary prosthetic replacement had to be performed. In case of a shoulder dislocation with a complex fracture after an epileptic seizure, prosthetic replacement is the choice of treatment.

Muscle Strength Quantification in Small Animals : A New Transcutaneous Technique in Rabbits

The objective of this study was to develop a new, simple, and noninvasive technique to measure the force produced by dorsi‐flexion of the foot in small animals. In addition, this study aimed to quantitatively describe changes in muscle and soft tissue structures using histomorphometry. The recovery of the dorsi‐flexing muscles in the tibialis anterior compartment in New Zealand White rabbits was evaluated after musculoskeletal trauma by measuring isometric contractions after submaximal transcutaneous electrical stimulation of the peroneal nerve. The trauma included muscle and bone trauma that was treated with limb shortening followed by distraction osteogenesis. Muscle contractions were initiated at an amplitude of 5.1 mA for a duration of 2.56 ms at intervals of 50 ms. Based on consecutive measurements of the force on days 5, 10, 15, 20, 25, and 30 postsurgery, a positive trend in recovery of the stimulated force produced by dorsi‐flexion of the foot was observed. The muscle strength at 30 days postsurgery was compared to that measured presurgery (baseline): 55% of the animals had dorsi‐flexion strength that was 60% below that of the presurgery baseline muscle strength; 36% of the animals had dorsi‐flexion strength that was greater than 60% of the baseline measure, indicating that there was a significant decrease in force produced by dorsi‐flexion of the foot after trauma on all testing days (p < 0.01) and that a severe muscular injury was set with limited recovery. This technique provides a new option for examining muscle regeneration and rehabilitation in small animals.

How safe is minimally invasive pedicle screw placement for treatment of thoracolumbar spine fractures

Study designProspective analysis of patients who underwent minimally invasive posterior instrumentation.ObjectiveThe purpose of this study was to evaluate the safety of minimally invasive pedicle screw placement in patients with unstable thoracic and lumbar spine fractures using the conventional fluoroscopy technique.Summary of background dataAlthough wound infection, haematoma, and new neurological deficit due to screw malplacement remain a common source of morbidity, estimates of their rates of occurrence remain relatively limited.Methods2052 percutaneous pedicle screws in 433 consecutive patients were evaluated. The accuracy of pedicle screw placement was based on evaluation of axial 3-mm slice computed tomography scans. Morbidity and mortality data were collected prospectively.ResultsA total of 2029 of 2052 screws (99%) had a good or excellent position. 5 screws (0.2%) showed a higher grade violation of the medial pedicle wall. Seven patients (1.8%) needed revision due to screw malposition (3 pat.), surgical site infection, postoperative haematoma, implant failure (2 pat.), and technical difficulties.ConclusionsMinimally invasive transpedicular instrumentation is an accurate, reliable, and safe procedure to treat thoracic and lumbar spine fractures.

Does plastic suture deformation induce gapping after tendon repair? A biomechanical comparison of different suture materials

Plastic deformation of sutures creates an irreversible extension during load. To test our hypothesis that such plastic deformation causes gap formation after tendon repair, we determined the plasticity of five different suture materials commonly used in tendon surgery. Prolene, Polydioxanone (PDS), Ethibond, Vicryl, and FiberWire sutures were biomechanically tested to determine their offset yield strength, initial extension, creep, relaxed elongation, peak-to-peak displacement, stiffness, and maximum tensile strength under static, constant, and cyclic loading. In addition, 35 porcine hindlimb tendons were used to evaluate gap formation and the biomechanical behavior of the suture materials after tendon repair. Prolene had a low offset yield strength and high initial extensions at 30, 60, and 90N combined with relatively large creep, relaxed elongation, and peak-to-peak displacement. Aside from the low maximum tensile strength and stiffness, these parameters indicate an early plastic deformation during loading. The material properties of PDS were generally better for suturing than those of Prolene, but no difference was found in offset yield strength or initial extension. In contrast to the monofilament materials Prolene and PDS, the braided Ethibond, Vicryl, and FiberWire materials showed significantly less plastic deformation. The lowest amount of plastic deformation was found in the FiberWire and the results for Ethibond and Vicryl were equal. Gap formation occurred at the lowest tension force in the Prolene group, but only FiberWire required a significantly larger tension force to produce gapping at the repair site, indicating a higher resistance to gap formation. The results of this study show that plastic deformation occurs at a lower tension force in the monofilament sutures Prolene and PDS than in the braided materials Ethibond, Vicryl, and FiberWire. After tendon repair, FiberWire likely prevents gap formation, whereas Prolene induces gapping through low-tension plastic deformation. Therefore, plastic deformation should be considered when selecting suture materials for tendon repair surgery.

Heterotope Ossifikation – Komplikation oder Chance?

So far, there has been no clear explanation of the pathophysiological relationships in the development of HO. There is little experimental data dealing with the post-traumatic inflammatory response in terms of a balance between the repair of damaged muscle cells and the opposite response in its development. There are numerous indications regarding possible predisposing factors, such as existence of surrounding tissue hypoxia or the function of pro-angiogenic (VEGF e.g.) and osteoinductive (BMP e.g.) factors. These different scientific approaches offer the opportunity to clinically intervene. In our opinion, early intervention seems to make the most sense in terms of effectiveness and recurrence of HO. An important pathomechanism seems to be chronic inflammation. Currently, non-steroidal anti-inflammatory drugs are the most commonly prescribed prophylaxis drugs. The effectiveness and efficacy of non-steroidal anti-inflammatory drugs is limited by the time-limited release and the side effect potential. Therefore, it is interesting to focus future research towards the cross-talks between immunosuppressive downregulation of the inflammatory response and its effect on the balance between muscle regeneration and the development of HO.

Active controlled motion in early rehabilitation improves outcome after ankle fractures: a randomized controlled trial:

Objective: To evaluate the use of active controlled motion (ACM) after unstable ankle fractures needing initial partial weight-bearing. Design: Prospective randomized controlled trial. Setting: Inpatient and outpatient clinic. Subjects: A total of 50 patients with unstable ankle fractures and the need for partial weight-bearing for six weeks. Interventions: Randomization in two groups: physiotherapy alone or physiotherapy with an additional ACM device. Main measures: Follow-up after 6 and 12 weeks. Range of motion, visual analogue scale for foot and ankle (VAS FA), Philip score, Mazur score, American Orthopaedic Foot & Ankle Society (AOFAS) score and dynamic pedobarography. Results: Range of motion was better in the ACM group at six weeks (mean 49° ± 11.1° vs. 41.3° ± 8.1°). Questionnaires revealed better outcome after six weeks in the VAS FA (56 ± 13.7 vs. 40.6 ± 10.5), Mazur score (64.4 ± 12.3 vs. 56.7 ± 11) and AOFAS score (71.2 ± 12 vs. 63.6 ± 8.7) (P > 0.02 for all). Better outcome after 12 weeks in all questionnaires (VAS FA, 77.7 ± 13.8 vs. 61.4 ± 16.3; Philip score, 79.1 ± 10.9 vs. 60.1 ± 21.7; Mazur score, 83.9 ± 10.7 vs. 73.1 ± 14.1; AOFAS score, 87.5 ± 7.9 vs. 75.2 ± 11.7) (P < 0.01 for all). Pressure balance was better under the midfoot region after 12 weeks in the ACM group (ΔP 4.4 N vs. 34.0 N; P = 0.01). The ACM group had an earlier return to work after 10.5 (range, 3–17) versus 14.7 (range, 9–26) weeks (P = 0.02). Conclusion: The use of ACM for patients needing initial partial weight-bearing after operatively treated unstable ankle fractures in the first six postoperative weeks leads to better clinical and functional results and an earlier return to work.

A rare case of Hoffa fracture combined with lateral patellar dislocation

The coronal unicondylar fracture of the distal femur (AO 33-B3) is a rare intraarticular injury within the weight bearing area of the knee, initially described by Albert Hoffa in 1904. We report an unusual combination of a Hoffa fracture with lateral patellar dislocation in a young adult. Our patient sustained the injury by a sudden twist of his leg during sports. He presented clinically with knee swelling, dislocation of the patella, and localized tenderness; unable to bare weight. After plane radiograph confirmed the injury, manual reduction of the patella was done by hyperextension of the knee and medialward pressure. Afterwards, a CT scan and MRI were conducted. The injury was surgically treated with lag-screws, locking-plate and MPFL-reconstruction.