Sönke P. Frey

Biomechanical comparison of the Locking Compression superior anterior clavicle plate with seven and ten hole reconstruction plates in midshaft clavicle fracture stabilisation

PurposeThe purpose of this study was to characterise the biomechanical properties of the seven hole superior anterior clavicle LCP (locking compression plate) and to compare these with the properties of commonly applied implants used for the stabilisation of clavicular midshaft fractures such as the locking 7- and ten hole reconstruction plate.MethodsTwenty-four synthetic clavicles were used. A transverse midshaft fracture was induced. The clavicles were fixed with angle stable clavicle LCPs, seven hole and ten hole reconstruction plates (n = 8 each). Twenty cycles of axial compression and torsion were performed for each sample, which was followed by 1,000 cycles of three point bending and ultimately bending to failure. Axial, torsional and cantilever bending stiffness were calculated from the data recorded.ResultsThe clavicle LCP showed the highest overall stiffness compared to the seven and ten hole reconstruction plate. Significantly higher stiffness values were found for axial compression and external rotation. In the load-to-failure tests, the ten hole reconstruction plate especially showed early signs of plastic deformation, which might account for early plate insufficiency so frequently observed clinically.ConclusionThe results indicate that the clavicle LCP, as compared to the reconstruction plates, leads to superior biomechanical stability in the treatment of midshaft clavicle fractures.

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.

Local application of VEGF compensates callus deficiency after acute soft tissue trauma--results using a limb-shortening distraction procedure in rabbit tibia.

Acute soft tissue trauma influences callus formation and fracture healing. Several studies showed a relationship between angiogenesis and bone formation during distraction osteogenesis. The purpose of this study was to investigate the influence of controlled release of vascular endothelial growth factor (VEGF) on callus formation in a limb‐shortening distraction procedure after acute compartment syndrome. Acute soft tissue trauma with critical increased compartment pressure was generated in 22 rabbits, and the limb was shortened simulating fracture site debridement. In the test group (n = 11), a VEGF‐coated collagen matrix was locally applied around the fracture, while no collagen was applied in the control group (n = 11). Following 10 days in limb shortening, a gradual distraction of 0.5 mm/12 h was performed using an external fixation device and followed up for 40 days. Osseous consolidation occurred in all animals. Average callus diameter (1.54 ± 0.8 vs. 1.27 ± 0.14 mm) and torsional strength (72% vs. 46% of normal) were significantly higher in the test versus the control group. Blood vessel formation increased with a significantly higher number of vessels (6.3 vs. 3.81/mm2) and larger cross‐sectional area (>40 µm, 90.5% vs. 86%) in the test versus control group. The results showed that locally applied VEGF stimulates fracture healing after acute soft tissue trauma and might be an option for fracture treatment in cases with severe soft tissue damage.

Total tibia replacement using an allograft (in a patient with adamantinoma). Case report and review of literature

AbstractIntroductionAdamantinoma is a very rare, low-grade, malignant bone tumour that accounts for approximately 0.4% of all primary bone tumours. Radiographically, adamantinomas vary in length, have a clearly defined outline, with a bubbly appearance and increase the width of the bone. Histologically, epithelial cells, endothelial cells synovial cells have been implicated as cells of origin.Case presentationWe present a case of adamantinoma of the tibia, in which a resection of the whole tibia and reconstruction with a total tibia allograft was necessary.DiscussionThe histological diagnosis is sophisticated. It is often difficult to distinguish an adamantinoma from other tumours. The most frequent described method to treat adamantinoma is wide resection and the use of an allograft. The most common complication is fracture presented similarly in our patient. ConclusionA total tibia allograft as presented in our case is not described in the literature. It fractured due the first year after implantation. Using a prosthesis system instead of the allograft might have saved the limb of our patient.

A Locking Contoured Plate for Distal Fibular Fractures: Mechanical Evaluation in an Osteoporotic Bone Model Using Screws of Different Length

Osteoporotic bone with poor mechanical capacity provides limited stability after fixation of ankle fractures. Stabilization with an implant providing increased fixation strength in osteoporotic bone could reduce failure rates of fixation and allow a more functional treatment. The purpose of this study was to evaluate a locking contoured plate for fixation of distal fibular fractures in comparison with a conventional contoured plate in an osteoporotic bone model. Eighty cylinders of osteoporotic bone surrogates were fixed with the two plates. We performed torque-to-failure and cyclic testing experiments using screws of different length with a Zwick/Roell testing machine. The locking system showed higher torque-to-failure and maximum torque levels as compared with the conventional plate in torque-to-failure experiments and torsional cyclic testing. The locking contoured plate provides improved fixation strength in the osteoporotic bone model. The locking system may be appropriate for fixation of distal fibular fractures, especially in osteoporotic bone with poor mechanical capacity.

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.

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.

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.