The failure mode of two reabsorbable fixation systems: Swivelock with Fibertape versus Bio-Corkscrew with Fiberwire in bovine rotator cuff

BackgroundDespite technical advances in rotator cuff surgery, recurrent or persistent defects in the repaired tendon continue to occur. The improved strength of sutures and suture anchors has shown that the most common site of failure is the suture–tendon interface. The purpose of this study was to compare two different types of repair under both cyclic and load-to-failure conditions. The hypothesis is that the use of a fixation system with knotless anchor and taped suture results in better biomechanical performance, under both cyclic and load-to-failure conditions.MethodsThirty bovine shoulder specimens were randomly assigned to two group tests: the Swivelock 5-mm anchor with Fibertape (Group A) and the Bio-Corkscrew 5 mm with Fiberwire (Group B). We simulated the reconstruction of a rotator cuff tear with a single-row technique, performing a tenodesis with types A and B fixation. Each specimen underwent cyclic testing from 5 to 30 N for 30 cycles, followed by load-to-failure testing, in order to calculate the ultimate failure load (UFL).ResultsLoad-to-failure tests revealed a significantly higher UFL in Group A than in Group B. Wire fixing failed at the anchor loop whereas tape fixing failed at the sutures, suture–tendon interface, and anchors. Cyclic testing revealed no significantly greater slippage between the two groups. Stiffness values were not statistically significantly different. In all cases, tendons remained intact until the end of the cyclic testing.ConclusionsThe tape structure is biomechanically stronger than the wire structure.     

A double button adjustable loop device is biomechanically equivalent to tension band wire in the fixation of transverse patellar fractures—A cadaveric study

IntroductionTension-band wire fixation of patellar fractures is associated with significant hardware-related complications and infection. Braided polyester suture fixation is an alternative option. However, these suture fixations have higher failure rates due to the difficulty in achieving rigid suture knot fixation. The Arthrex syndesmotic TightRope, which is a double-button adjustable loop fixation device utilizing a 4-point locking system using FibreWire, may not only offer stiff rigid fixation using a knotless system, but may also obviate the need for implant removal due to hardware related problems. The aim of our study is to compare the fixation rigidity of patella fractures using Tightrope versus conventional tension-band wiring (TBW) in a cadaveric model.Materials and methodsTBW fixation was compared to TightRope fixation of transverse patella fractures in 5 matched pairs of cadaveric knees. The knees were cyclically brought through 0–90° of motion for a total of 500 cycles. Fracture gapping was measured before the start of the cycling, and at 50, 100, 200 and 500 cycles using an extensometer. The mean maximum fracture gapping was derived. Failure of the construct was defined as a displacement of more than 3 mm, patella fracture or implant breakage.ResultsAll but one knee from each group survived 500 cycles. The two failures were due to a fracture gap of more than 3 mm during cycling. There was no significant difference in the mean number of cycles tolerated. There was no implant breakage. There was no statistical significant difference in mean maximum fracture gap between the TBW and TightRope group at all cyclical milestones after 500 cycles (0.3026 ± 0.4091 mm vs 0.3558 ± 0.7173 mm, p = 0.388).ConclusionsWe found no difference between the TBW and Tightrope fixation in terms of fracture gapping and failure. With possible lower risk of complications such as implant migration and soft tissue irritation, we believe tightrope fixation is a feasible alternative in fracture management of transverse patella fractures.     

Biomechanical analysis of medial patellofemoral ligament reconstruction: FiberTape® with knotless anchors versus a semitendinosus tendon autograft with soft anchors

BackgroundWith the use of synthetic materials for medial patellofemoral ligament (MPFL) reconstruction, graft harvest is not necessary and this may facilitate post-operative rehabilitation. The purpose of this study was to compare the structural properties of MPFL reconstruction using a modern synthetic material (FiberTape® (FT), Arthrex) with knotless anchors or a semitendinosus (ST) tendon autograft with soft anchors.MethodsNine human fresh-frozen amputated knees were used in this study. After the tensile strength of the native MPFL was measured, the MPFLs were reconstructed using two different surgical procedures, FT with knotless anchors (group A) and a ST with soft anchors (group B). Mechanical testing to failure of the reconstructed MPFLs was performed, and the ultimate load (N), stiffness (N/mm), and failure mode were recorded.ResultsThe mean (±standard deviation) ultimate load of the native MPFL was 130.6 ± 28.7 N, and all native MPFLs failed at the femoral insertion site. Ultimate load of group A was significantly higher than that of the native MPFL (175.9 ± 34.1 N, p < 0.05). In contrast, the ultimate load of group B was significantly lower than that of the native MPFL (102.7 ± 21.4 N, p < 0.05). The mean stiffness was significantly higher for MPFLs in group A (17.4 ± 4.3 N/mm) than in group B (8.5 ± 1.8 N/mm, p < 0.05). In group A, 5 specimens failed via a knotless anchor pullout at the femoral side, 3 via pullout of knotless anchors at the patella side and 1 via fracture (cheese cut) of the femur without breakage of knotless anchor. In group B, all specimens failed via soft anchor pullout at the patella side. There was no incidence of rupture of FT or ST.ConclusionFT with knotless anchors was stronger than a ST with soft tissue anchors for MPFL reconstruction.     

Revisability of polyetheretherketone suture anchors utilised in primary and revision Bankart repair

BackgroundPolyetheretherketone (PEEK) suture anchors are frequently used in Bankart shoulder stabilisation. This study analyzed the primary stability and revisability of PEEK anchors in-vitro in case of primary Bankart repair and revision Bankart repair after failed primary repair.MethodsTo simulate primary Bankart repair, 12 anchors (Arthrex PEEK PushLock® 3.5 mm) were implanted in 1, 3, 5, 7, 9 and 11 o'clock positions in cadaveric human glenoids and then cyclically tested. To simulate revision Bankart repair, 12 anchors were implanted in the same manner, over-drilled and 12 new anchors of the same diameter were implanted into the same bone socket as the primary anchors and then cyclically tested. The maximum failure loads (F_max), system displacements, force at clinical failure and modes of failure were recorded.ResultsOne primary anchor failed prematurely due to a technical problem. Three out of 12 revision anchors (25%) dislocated while setting the 25 N preload. The F_max, the displacement and clinical failure of the remaining 9 revision anchors were non-significant when compared to the 11 primary repair anchors. The main mode of failure in the primary and revision Bankart surgery group was suture slippage. Anchor dislocations were observed four times in the primary and once in the revision repair groups.ConclusionsRevision Bankart repair using PEEK anchors of the same diameter in a pre-existing bone socket is possible but bears high risk of premature anchor failure and can jeopardize the reconstruction. PEEK suture anchor in revision Bankart surgery should be implanted in a new bone socket if possible.     

Anterior-inferior tibiofibular ligament anatomical repair and augmentation versus trans-syndesmosis screw fixation for the syndesmotic instability in external-rotation type ankle fracture with posterior malleolus involvement: A prospective and comparative study

PurposeSyndesmosis injury is common in external-rotation type ankle fractures (ERAF). Trans-syndesmosis screw fixation, the gold-standard treatment, is currently controversial for its complications and biomechanical disadvantages. The purpose of this study was to introduce a new method of anatomically repairing the anterior-inferior tibiofibular ligament (AITFL) and augmentation with anchor rope system to treat the syndesmotic instability in ERAF with posterior malleolus involvement and to compare its clinical outcomes with that of trans-syndesmosis screw fixation.Methods53 ERAFs with posterior malleolus involvement received surgery, and the syndesmosis was still unstable after fracture fixation. They were randomised into screw fixation group and AITFL anatomical repair with augmentation group. Reduction quality, syndesmosis diastasis recurrence, pain (VAS score), time back to work, Olerud–Molander ankle score and range of motion (ROM) of ankle were investigated.ResultsOlerud–Molander score in AITFL repair group and screw group was 90.4 and 85.8 at 12-month follow-up (P > 0.05). Plantar flexion was 31.2° and 34.3° in repair and screw groups (P = 0.04). Mal-reduction happened in 5 cases (19.2%) in screw group while 2 cases (7.4%) in repair group. Postoperative syndesmosis re-diastasis occurred in 3 cases in screw group while zero in repair group (P > 0.05). Pain score was similar between the two groups (P > 0.05). Overall complication rate and back to work time were 26.9% and 3.7% (P = 0.04), 7.15 months and 5.26 months (P = 0.02) in screw group and repair group, respectively.ConclusionsFor syndesmotic instability in ERAF with posterior malleolus involvement, the method of AITFL anatomical repair and augmentation with anchor rope system had an equivalent functional outcome and reduction, earlier rehabilitation and less complication compared with screw fixation. It can be selected as an alternative.     

Kinematic analysis of ankle stiffness in subjects with and without flat foot

BackgroundAlthough the magnitude of ankle motion is influenced by joint congruence and ligament elasticity, there is a lack of understanding on ankle stiffness between subjects with and without flat foot.ObjectiveThis study investigated a quantified ankle stiffness difference between subjects with and without flat foot.MethodsThere were forty-five age- and gender-matched subjects who participated in the study. Each subject was seated upright with the tested foot held firmly onto a footplate that was attached to a torque sensor by the joint-driving device.ResultsThe flat foot group (mean ± standard deviation) demonstrated increased stiffness during ankle dorsiflexion (0.37 ± 0.16 for flat foot group, 0.28 ± 0.10 for control group; t = −2.11, p = 0.04). However, there was no significant group difference during plantar flexion (0.35 ± 0.15 for flat foot group, 0.33 ± 0.07 for control group; t = 0.64, p = 0.06).ConclusionThe results of this study indicated that the flat foot group demonstrated increased ankle stiffness during dorsiflexion regardless of demographic factors. This study highlights the need for kinematic analyses and joint stiffness measures during ankle dorsiflexion in subjects with flat foot.     

Biomechanical comparison of stability of tibiotalocalcaneal arthrodesis with two different intramedullary retrograde nails

BackgroundThe aim of the study was to compare the initial construct stability of two retrograde intramedullary nail systems for tibiotalocalcaneal arthrodesis (TTCF) (A3, Small Bone Innovations; HAN, Synthes) in a biomechanical cadaver study.MethodsNine pairs of human cadaver bones were instrumented with two different retrograde nail systems. One tibia from each pair was randomized to either rod. The bone mineral density was determined via tomography to ensure the characteristics in each pair of tibiae were similar. All tests were performed in load-control. Displacements and forces were acquired by the sensors of the machine at a rate of 64 Hz. Specimens were tested in a stepwise progression starting with six times ±125N with a frequency of 1 Hz for 250 cycles each step was performed (1500 cycles). The maximum load was then increased to ±250N for another 14 steps or until specimen failure occurred (up to 3500 cycles).ResultsAverage bone mineral density was 67.4 mgHA/ccm and did not differ significantly between groups (t-test, p = .28). Under cyclic loading, the range of motion (dorsiflexion/plantarflexion) at 250N was significantly lower for the HAN-group with 7.2 ± 2.3 mm compared to the A3-group with 11.8 ± 2.9 mm (t-test, p < 0.01). Failure was registered for the HAN after 4571 ± 1134 cycles and after 2344 ± 1195 cycles for the A3 (t-test, p = .031). Bone mineral density significantly correlated with the number of cycles to failure in both groups (Spearman-Rho, r > .69, p < 0.01).ConclusionsThe high specimen age and low bone density simulates an osteoporotic bone situation. The HAN with only lateral distal bend but two calcaneal locking screws showed higher stability (higher number of cycles to failure and lower motion such as dorsiflexion/plantarflexion during cyclic loading) than the A3 with additional distal dorsal bend but only one calcaneal locking screw. Both constructs showed sufficient stability compared with earlier data from a similar test model.Clinical relevanceThe data suggest that both implants allow for sufficient primary stability for TTCF in osteoporotic and consequently also in non-osteoporotic bone.Level of evidenceNot applicable, experimental basic science study.     

Biomechanical analysis of endobutton versus screw fixation after Lisfranc ligament complex sectioning

BackgroundOur goal was to compare diastasis after endobutton and screw fixation after Lisfranc ligament complex sectioning.MethodsTwenty-four (12 pairs) fresh-frozen cadaveric feet were assigned to endobutton or screw fixation and loaded to 343 N. Displacement (first–second metatarsal bases) was measured in intact feet and after ligament sectioning (Lisfranc, medial–intermediate cuneiform ligaments), fixation, and 10,000 cycles.ResultsThe mean change in diastasis for endobutton and screw fixation under initial loading was 1.0 mm (95% CI, 0.2–1.9 mm) and 0.0 mm (95% CI, ?0.4 to 0.4 mm), respectively (p = 0.017). After cyclic loading, diastasis decreased (mean, ?0.7 mm, 95% CI, ?1.2 to ?0.1 mm) in the endobutton group but was unchanged in the screw group (p = 0.035).ConclusionsDiastasis after endobutton fixation was significantly greater than after screw fixation under initial loading but did not increase further after cyclic loading.     

Is there a benefit of proximal locking screws in osteoporotic distal radius fractures? – A biomechanical study

IntroductionThe distal radial fracture is a common fracture and frequently seen in geriatric patients. During the last years, volar plating has become a popular treatment option. While the application of locking screws at the distal fragment is widely accepted, there is no evidence for their use at the radial shaft.Materials and methodsIn six osteoporotic pairs of matched human cadaver radii an extra-articular model creating an AO 23-A2.1 fracture was employed. Osteosynthesis were performed using the APTUS 2.5 Adaptive TriLock Distal Radius System (Medartis AG) with locking (LS) or non-locking screws (NLS) for proximal fixation. Biomechanical testing was performed in a staircase fashion: starting with 50 cycles at 200 N, the load was continuously increased by 50 N every 80 cycles up to a maximum force of 400 N. Finally, load to failure was analyzed with failure defined as sudden loss of force measured (20%) or major deformation of the radii (10 mm).ResultsAt 200 N, 250 N, 300 N, 400 N and load to failure, the NLS group showed a higher degree of elastic modulus. In contrast, the LS group showed higher elastic modulus at 350 N. Maximum force was higher in the LS group without reaching statistical significance. Reasons for loss of fixation were longitudinal shaft fractures, horizontal peri-implant fractures and distal cutting out. No difference was seen between the two groups concerning the development of the above mentioned complications.ConclusionOur study did not show biomechanical superiority for distal radius fracture fixation by using locking screws in the proximal holes in an osteoporotic cadaver study. At load to failure, longitudinal shaft fractures and peri-implant fractures seemed to be a more relevant problem rather than failure of the proximal fixation.     

Overtightening of the syndesmosis revisited and the effect of syndesmotic malreduction on ankle dorsiflexion

BackgroundAnkle syndesmotic injuries are a significant source of morbidity and require anatomic reduction to optimize outcomes. Although a previous study concluded that maximal dorsiflexion during syndesmotic fixation was not required, methodologic weaknesses existed and several studies have demonstrated improved ankle dorsiflexion after removal of syndesmotic screws.The purposes of the current investigation are: (1) To assess the effect of compressive syndesmotic screw fixation on ankle dorsiflexion utilizing a controlled load and instrumentation allowing for precise measurement of motion. (2) To assess the effect of anterior & posterior syndesmotic malreduction after compressive syndesmotic screw fixation on ankle dorsiflexion.Material and methodsFifteen lower limb cadaveric leg specimens were utilized for the study. Ankle dorsiflexion was measured utilizing a precise micro-sensor system after application of a consistent load in the (1) intact state, (2) after compression fixation with a syndesmotic screw and (3) after anterior & (4) posterior malreduction of the syndesmosis.ResultsFollowing screw compression of the nondisplaced syndesmosis, dorsiflexion ROM was 99.7 ± 0.87% (mean ± standard error) of baseline ankle ROM. Anterior and posterior malreduction of the syndesmosis resulted in dorsiflexion ROM that was 99.1 ± 1.75% and 98.6 ± 1.56% of baseline ankle ROM, respectively. One-way ANOVA was performed showing no statistical significance between groups (p-value = 0.88).Two-way ANOVA comparing the groups with respect to both the reduction condition (intact, anatomic reduction, anterior displacement, posterior displacement) and the displacement order (anterior first, posterior first) did not demonstrate a statistically significant effect (p-value = 0.99).ConclusionMaximal dorsiflexion of the ankle is not required prior to syndesmotic fixation as no loss of motion was seen with compressive fixation in our cadaver model. Anterior or posterior syndesmotic malreduction following syndesmotic screw fixation had no effect on ankle dorsiflexion. Poor patient outcomes after syndesmotic malreduction may be due to other factors and not loss of dorsiflexion motion.Level of Evidence: IV     

Biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation: A finite element analysis

ObjectiveTo determine the biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation.MethodA three-dimensional model was established based on CT images from a healthy volunteer. The simulation of lateral malleolus fracture, and the modeling and assembly of plate were completed by referring to characteristics of Weber B lateral malleolus fractures, as well as the technical characteristics of open reduction and internal fixation of lateral plate. Operating conditions were set up for groups A−D. The proximal end of the model was restrained in all four groups, 200 N of upward force and 100 N of backward force were applied at anterior of talus head in order to simulate the dorsiflexion of ankle joint. Biomechanical differences of the lateral plate were observed under various conditions of different ligament ruptures.ResultsThe maximum stress value of group A was the smallest, approximately 78.47 N, while that of group C was the largest, approximately 238.83 N. The maximum stress value of group B was about 91.69 N; and that of group D was about 184.08N. Importantly, location of the maximum stress in group D (CUT ATaF) was displaced from the posterior edge to the anterior edge of the plate, which was different from those of the other three groups.ConclusionsThe anterior talofibular ligament injury may be a major contributing factor to the stress of lateral plate fixation following Weber B lateral malleolus fracture. It should be considered as an essential risk factor for evaluation of the stability in these fractures.     

In vitro comparison of standard and knotless metal suture anchors

Purpose: Clinical experience after failed Knotless suture anchor (Mitek, Westwood, MA) fixations suggested that the Knotless anchor provides considerably less fixation stability than a standard metal anchor. The purpose of this study was to analyze soft tissue fixation to bone comparing a standard and a Knotless metal suture anchor. Type of Study: In vitro study. Methods: The Mitek GII and Mitek Knotless suture anchors were tested on 7 human cadaveric fresh-frozen glenoids. The anchors were inserted into the glenoid rims, and the sutures of the anchors were fixed to a metal hook attached to the cross-head of a testing machine. Cyclic loading was performed. The gap formation between the metal hook and the glenoid rim, the ultimate failure loads and the modes of failure were determined. Results: The mean gap formation was significantly greater for the Knotless anchor (3.8 ± 1.4 mm) than for the GII anchor (2.4 ± 0.5 mm) after 25 cycles with 50 N repeated load (P = .04). The largest gap of a Knotless fixation was 5.3 mm compared with 3.0 mm for the GII. The ultimate failure load was not significantly different for the Knotless anchor (179 N) and for the GII anchor (129 N). Both anchors failed by either rupture of the suture material or by pullout of the anchors. Conclusions: The GII anchor allows significantly less displacement than the Knotless anchor. Ultimate tensile strength and mode of failure are similar. Greater displacement results in larger gap formation between the soft tissue and the bone. This might weaken and jeopardize the repair. Clincial Relevance: If reattached soft tissues are subjected to postoperative loading, gap formation may result when using the Knotless anchor. For these conditions, suture fixation with knots may be used instead.     

The feasibility of point-of-care ankle ultrasound examination in patients with recurrent ankle sprain and chronic ankle instability: Comparison with magnetic resonance imaging

ObjectiveTo evaluate the feasibility of point-of-care ankle ultrasound compared with magnetic resonance imaging (MRI) for diagnosing major ligaments and Achilles tendon injuries in patients with recurrent ankle sprain and chronic instability, and to evaluate inter-observer reliability between an emergency physician and a musculoskeletal radiology fellow.Material and methodsA prospective cross-sectional study was conducted in an emergency department. Patients with recurrent ankle sprain and chronic instability were recruited. An emergency physician and a musculoskeletal radiology fellow independently evaluated the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), distal anterior tibiofibular ligament (ATiFL), deltoid ligament, and Achilles tendon using point-of-care ankle ultrasound. Findings were classified normal, partial tear, and complete tear. MRI was used as the reference standard. We calculated diagnostic values for point-of-care ankle ultrasound for both reviewers and compared them using DeLong's test. Intra-class correlation coefficients (ICCs) were calculated for agreement between each reviewer and the reference standard, and between the two reviewers.ResultsEighty-five patients were enrolled. Point-of-care ankle ultrasound showed acceptable sensitivity (96.4–100%), specificity (95.0–100%), and accuracy (96.5–100%); these performance markers did not differ significantly between reviewers. Agreement between each reviewer and the reference standard was excellent (emergency physician, ICC = 0.846–1.000; musculoskeletal radiology fellow, ICC = 0.930–1.000), as was inter-observer agreement (ICC = 0.873–1.000).ConclusionPoint-of-care ankle ultrasound is as precise as MRI for detecting major ankle ligament and Achilles tendon injuries; it could be used for immediate diagnosis and further pre-operative imaging. Moreover, it may reduce the interval from emergency department admission to admission for surgical intervention, and may save costs.     

Arthroscopically measured syndesmotic stability after screw vs. suture button fixation in a cadaveric model

BackgroundAppropriate management of ankle syndesmotic instability is needed to prevent the development of complications. Previous biomechanical studies have evaluated movement of the fibula after screw or suture button fixations with different results, most likely being caused by variations in experimental setups that did not mirror the in vivo clinical setting. This study aimed to arthroscopically compare in a cadaveric model the stability of syndesmotic fixation with either a suture button or syndesmotic screw.MethodsEight fresh matched pairs of human ankle cadaver specimens (above knee) underwent arthroscopic assessment with (1) intact ligaments, (2) after complete disruption, and (3) after repair with either a quadracortical syndesmotic screw or suture button construct. In every stage, four loading conditions were considered under 100N of direct force: 1) unstressed, 2) lateral hook test, 3) anterior to posterior (AP) translation test, and 4) posterior to anterior (PA) translation test. Coronal plane tibiofibular diastasis, as well as sagittal plane tibiofibular translation, were arthroscopically measured.ResultsCoronal plane anterior and posterior tibiofibular diastasis and sagittal plane tibiofibular translation were measured using probes of increasing diameters. Following screw fixation, syndesmotic stability was similar to the uninjured syndesmosis in the coronal plane (anterior, median 0.0 mm [IQR 0.0–0.3] vs. 0.3 mm [IQR 0.2–0.3]; p = 0.57; posterior, median 0.1 mm [IQR 0.0–0.4] vs. 0.2 mm [IQR 0.1–0.3]; p = 1.0) but more rigid in the sagittal plane (median 0.0 mm [IQR 0.0–0.1] vs. 1.0 mm [IQR 0.4–1.5]; p = 0.012). Repairing the unstable syndesmosis with a suture button construct resulted in coronal plane stability similar to the uninjured syndesmosis (anterior, median 0.2 mm [IQR 0.1–0.3] vs. 0.2 mm [IQR 0.1–0.3]; p = 0.48; posterior, median 0.2 mm [IQR 0.1–0.3] vs. 0.3 mm [IQR 0.1–0.5]; p = 0.44). However, sagittal plane fibular motion remained unstable as compared to the uninjured syndesmosis (median 2.2 mm [IQR 1.6–2.6] vs. 0.8 mm [IQR 0.4–1.3]; p = 0.012).ConclusionCurrent fixation methods for syndesmotic disruption maintain coronal plane fibular stability. Screw and suture button constructs, however, respectively resulted in greater or insufficient constraint to fibular motion in the sagittal plane as compared to the intact syndesmotic ligament. These findings suggest that neither traditional screw nor suture button fixations optimally stabilize the syndesmosis, which may have implications for postoperative care and clinical outcomes.     

A biomechanical study comparing proximal femur nail and proximal femur locking compression plate in fixation of reverse oblique proximal femur fractures

BackgroundThe reverse oblique trochanteric fractures are common fractures and its treatment poses a challenge. The purpose of this study was to compare the biomechanical parameters of the construct using proximal femoral nail (PFN) and proximal femoral locking compression plates (PFLCP) in these fractures using cadaveric specimens.Materials and MethodsTwenty freshly harvested cadaveric femoral specimens were randomly assigned to two groups after measuring bone mineral density, ten of which were implanted with PFN and the other ten with PFLCP. The constructs were made unstable to simulate reverse oblique trochanteric fracture (AO type 31A3.3) by removing a standard size posteromedial wedge. These constructs were tested in a computer controlled cyclic compressive loading with 200 kg at a frequency of 1 cycle/s (1 Hz) and test was observed for 50,000 cycles or until implant failure, whichever occurred earlier. Peak displacements were measured and analysis was done to determine axial stiffness and subsidence in axial loading.ResultsAll the specimens in PFN group completed 50,000 cycles and in PFLCP group, seven specimens completed 50,000 cycles. Average subsidence in PFN group was 1.24 ± 0.22 mm and in PFLCP group was 1.48 ± 0.38 mm. The average stiffness of PFN group (72.6 ± 6.8 N/mm) was significantly higher than of PFLCP group (62.4 ± 4.9 N/mm) (P = 0.04). The average number of cycles sustained by PFLCP was 46634 and for PFN group was 50,000 (P = 0.06).ConclusionThe PFN is biomechanically superior to PFLCP in terms of axial stiffness, subsidence and number of specimens failed for the fixation of reverse oblique trochanteric fractures of femur.     

Primary stability and stiffness in ankle arthrodes—Crossed screws versus anterior plating

BackgroundAnkle arthrodesis is commonly used for the treatment of osteoarthritis or failed arthroplasty. Screw fixation is the predominant technique to perform ankle arthrodesis. Due to a considerable frequency of failures research suggests the use of an anatomically shaped anterior double plate system as a reliable method for isolated tibiotalar arthrodesis. The purpose of the present biomechanical study was to compare two groups of ankle fusion constructs – three screw fixation and an anterior double plate system – in terms of primary stability and stiffness.MethodsSix matched-pairs human cadaveric lower legs (Thiel fixated) were used in this study. One specimen from each pair was randomly assigned to be stabilized with the anterior double plate system and the other with the three-screw technique. The different arthrodesis methods were tested by dorsiflexing the foot until failure of the system, defined as rotation of the talus relative to the tibia in the sagittal plane. Experiments were performed on a universal materials testing machine. The force required to make arthrodesis fail was documented. For calculation of the stiffness, a linear regression was fitted to the force–displacement curve in the linear portion of the curve and its slope taken as the stiffness.ResultsFor the anatomically shaped double-plate system a mean load of 967 N was needed (range from 570 N to 1400 N) to make arthrodesis fail. The three-screw fixation method resisted a mean load of 190 N (range from 100 N to 280 N) (p = 0.005). In terms of stiffness a mean of 56 N/mm (range from 35 N/mm to 79 N/mm) was achieved for the anatomically shaped double-plate system whereas a mean of 10 N/mm (range from 6 N/mm to 18 N/mm) was achieved for the three-screw fixation method (p = 0.004).ConclusionsOur biomechanical data demonstrates that the anterior double-plate system is significantly superior to the three-screw fixation technique for ankle arthrodesis in terms of primary stability and stiffness.     

Biomechanical results of percutaneous calcaneal osteotomy using two different osteotomy designs

BackgroundPercutaneous osteotomy of calcaneus has been proposed to reduce the complication rate and became more and more popular. The bone cut can be performed as a straight or chevron-like (V) osteotomy using a Shannon burr. Comparative studies of straight or V-osteotomy as like as one or two screws in percutaneous calcaneal osteotomies are missing in the literature. We hypothesize that the V-osteotomy will result in a higher stiffness in biomechanical testing as the straight osteotomy using single screw for fixation.MethodsThe straight osteotomy (9 fresh–frozen specimens) and V-osteotomy (9 fresh–frozen specimens) was performed and the calcaneal tuberosity was moved 10 mm medially and slightly rotated. One 6,5 mm cancellous compression screw was used for osteosynthesis. Specimens were preconditioned with 100 N over 100 cycles. The force was increased after every 100 N by 100 N from 200 to 500 N. This was followed by cyclic loading with 600 N for 500 cycles.ResultsDespite the higher mean values of the group with V-osteotomy, no significant difference was registered between the two groups regarding the stiffness at all force levels. A higher failure rate was observed in the group with straight osteotomy.ConclusionThe moderate correlation of bone density and stiffness in the V-group, and significantly lower failure rate with no secondary dislocation in fluoroscopy indicates the superiority of the V-osteotomy in the present study. Whether the demonstrated advantages can be reflected in clinical practice should be investigated in further studies.Level of clinical evidence: 5     

Efficacy of repair techniques of the Achilles tendon: A meta-analysis of human cadaveric biomechanical studies

PurposeAchilles injuries are very common, mainly among young athletes. When indicated, the surgical treatment aims for strong repairs that can resist distraction and consequently ruptures. The majority of the published clinical meta-analyses reported comparisons between broad treatment modalities such as conservative treatment, open, and minimally invasive surgery.MethodsA meta-analysis has been conducted to assess further clinical and biomechanical variables on human cadavers related to the efficacy of Achilles repair. A total of 26 studies with 596 legs met the inclusion criteria. The maximal load to failure was set as the primary outcome. Eleven studies were amenable to meta-analysis.ResultsIn the reinsertion group, the analysis of the single row vs. double row subgroup showed a significantly higher strength for the latter (1.27, 95% CI = 0.748–1.806, I² = 81%, P < 0.0001). In the mid-tendon repair group, the Achillon vs. Krackow sutures and the Bunnell vs. Krackow sutures subgroups showed no difference while the Bunnell and Krakow sutures were significantly stronger than the Kessler sutures (0.96, 95% CI = 0.510–1.405, I² = 63.3%, P < 0.0001 and 1.37, 95% CI = 2.286–0.468, I² = 83.4%, P = 0.003; respectively).ConclusionsThe assessment of heterogeneity located variables such as age, suture/material type, number of strands, type of testing machine and software, preloading, ankle position and loading type as potential confounders. The results of this meta-analysis are likely to have a significant impact in clinical practice.     

Simple radiographic assessment of bone quality is associated with loss of surgical fixation in patients with proximal humeral fractures

AimThis study aimed to determine if the ratio of cortical thickness to shaft diameter of the humerus, as measured on a simple anterior-posterior shoulder radiograph, is associated with surgical fixation failure.Patients and Methods64 consecutive fractures in 63 patients (mean age 66.1years, range 35–90) operated with surgical fixation between March 2011 and July 2014 using PERI-LOC locking plate and screws (Smith and Nephew, UK) were identified. Predictors of bone quality were measured from preoperative radiographs, including ratio of the medial cortex to shaft diameter (medial cortical ratio, MCR). Loss of fixation (displacement, screw cut out, or change in neck-shaft angle >4 degrees) was determined on follow-up radiographs.ResultsLoss of fixation occurred in 14 patients (21.9%) during the follow up. Patients were older in the failure group 72.8 vs. 64.2 years (p = 0.007). The MCR was significantly lower in patients with failed fixation 0.170 vs 0.202, p = 0.019. Loss of fixation is three times more likely in patients with a MCR <0.16 (41% vs. 14%, p = 0.015). Increased fracture parts led to increased failure rate (p = 0.0005).ConclusionMedial cortex ratio is significantly associated with loss of surgical fixation and may prove to be a useful adjunct for clinical decision making in patients with proximal humeral fractures.     

Periarticular raft constructs and fracture stability in split-depression tibial plateau fractures

ObjectivesTo evaluate relative fracture stability yielded by screws placed above a lateral plate, as well as locking and non-locking screws placed through a plate in a split depression tibia plateau fracture model.MethodsCadaver tibia specimens (mean age 74.1 years) were randomised across 3 groups: Groups 1: raft-construct outside the plate, 2: non-locking raft screws through the plate, and 3: locking raft screws through the plate. Displacement of the depressed fragment was recorded with force values from 400 N to 1600 N in increasing 400 N increments. The force required to elicit lateral plateau fragment displacement of 5 mm, 10 mm, and 15 mm was also recorded.ResultsNone of the mechanical testing results demonstrated statistical significance with p-values of <0.05. Cyclic testing of Groups 1, 2, and 3 at 400 N revealed displacements of 0.54 mm, 0.64 mm, and 0.48 mm, respectively. At 800 N, displacements were 1.36 mm, 1.4 mm, and 1.4 mm, respectively. At 1200 N, displacements were 2.4 mm, 1.9 mm, and 2.1 mm, respectively. At 1600 N, displacements were 2.8 mm, 2.5 mm, and 2 mm, respectively. Resistance to displacement data demonstrated the mean force required to displace the fracture 5 mm in Groups 1, 2, and 3 were 250 N, 330 N, and 318 N, respectively. For 10 mm of displacement, forces required were 394 N, 515 N, and 556 N, respectively. For 15 mm of displacement, forces required were 681 N, 853 N, and 963 N, respectively. Compared to combined groups using screws through the plate, Group 1 demonstrated lower displacement ≤800 N, but demonstrated greater displacement >800 N. Group 2 demonstrated greatest resistance to plateau displacement of 5 mm compared to Group 1 or 3, while Group 3 was most resistant to greater displacement. The combined group using screws through the plate (Groups 2 + 3) was consistently more resistant than Group 1 at all levels of displacement.ConclusionsDesigns utilising screws through the plate trended towards statistically significant improved stability against plateau displacement relative to utilising screws outside the plate. Our study also suggests that there is no significant benefit of locking screws over non-locking screws in this unicondylar tibia plateau fracture model.