Olecranon fracture fixation with a new implant: Biomechanical and clinical considerations

This study aims to describe the first clinical results in the treatment of dislocated olecranon fractures with 2.2-mm, fine-threaded wires with a washer. Furthermore, in the second part of the article, the stability of these new implants has been compared to standard tension band wiring in a sawbone model.

Patients

The radiological and clinical outcomes in 24 patients (mean age: 53.6 years) with 24 isolated Mayo type I and II fractures of the olecranon were evaluated in a prospective study after open reduction and internal fixation (ORIF) with a new fixation device (FFS; Orthofix™). The quality of reduction with the implementation of 24 FFS constructions was compared with 24 tension band-wiring procedures performed by six different surgeons in a standard sawbone Mayo type IIa fracture model. Stability was tested in all constructs using a single cycle load to failure protocol (group I), cyclic loading for 300 cycles between 10 and 500 N (group II) and incremental sinusoidal loading from 10 to 200 N with an incremental increase of 10 N per cycle (group III) in a laboratory study.

Results

The Morrey elbow score was excellent in 23 patients and good in one patient, with mean DASH score of 1.6. No implant migration, secondary dislocation or nonunion was observed. In the sawbone model, the quality of reduction was the same with the FFS implants compared to the tension band wiring in the sawbone model. Here, bending moments in all three groups showed no significant difference, whereas displacement at failure was significantly greater in the tension band-wiring group at a single cycle load (p = 0.017).

Conclusion

Clinical results were comparable to tension band wiring and stability of the implants in the sawbone model was the same; thus, we conclude that the FFS technique can serve as an alternative treatment option for isolated olecranon fractures.     

A figure-eight suture loop with Kirschner wires for fixation of anteromedial coronoid process fractures: A case series

PurposeSufficient fixation of an anterior or anteromedial facet fracture of the coronoid process in fracture-dislocation of elbow is important to maintain joint stability. The purpose of this study was to report our experience with 11 patients who were managed with an original fixation technique using a “figure-eight” suture loop.MethodsFrom February 2010 to March 2011, 11 cases with a fracture of the anterior or anteromedial facet of the coronoid process were treated by coronoid fixation using a figure-eight suture loop. For cases with comminuted fractures, to prevent a suture from sliding into the fracture line, a 3- or 4-hole phalanx plate was enclosed in the suture loop to compress multiple fragments. Accompanying injuries, such as a radial head fracture or olecranon fracture, were fixed with repair of lateral collateral ligament injuries.ResultsOn final evaluations at an average of 18 months after injury, the mean elbow arc of motion was 125.5° and the mean forearm rotation arc of 124.1°. All fractures were united with an average postoperative score according to the Mayo Elbow Performance Index of 91 points. All patients achieved satisfactory scores (seven excellent, four good). All 11 fractures were united at final follow-up with no joint incongruity, dislocation, or subluxation of the injured elbow.ConclusionsThe figure-eight suture loop technique is an easy and effective technique to fix anterior or anteromedial facet fractures of the coronoid process.     

Corticocancellous olecranon autograft for metacarpal defect reconstruction: a case report

Background

High-energy injuries to the hand frequently lead to bone defects as well as soft tissue loss. Early bone grafting of defects is well established in the literature; however, few options are available for autologous corticocancellous grafts. Most frequently cited studies describe the iliac crest or the distal radius donor sites.

Methods

In this case report, we describe a new technique of obtaining corticocancellous bone graft from the olecranon.

Results

Complete union of the segmental defect was achieved with this technique.

Conclusions

The olecranon donor site is outside the zone of injury and therefore safe to access, but within the upper extremity, thus avoiding the need for harvest from a distant site such as the iliac crest or the distal femur. Additional benefits of this site are the greater volume of graft that can be harvested compared to the distal radius as well as a more optimal ratio of cancellous to cortical graft available, compared to the iliac crest where the graft may be excessively cortical in nature.     

Latissimus dorsi transfer for irreparable rotator cuff tears: a longitudinal study

Latissimus dorsi transfer is indicated for isolated posterior superior defects of the rotator cuff. Additional lesions limit the success of the outcome, but they are relatively frequent in revision surgery. We analyzed their influence on the postoperative function in 52 patients with an irreparable tear of the rotator cuff (35 primary operations, 17 revision surgeries). We observed a continuous improvement in the Constant score from 36 to 69 points, also in ROM, strength, relief of pain and of different subjective parameters for the entire group in consecutive examinations at 11.1, 35.7 and 50.2 months. We found increased osteoarthritis (from 1.0 to 1.5 mm), as well as a decrease in the acromiohumeral distance (from 5.6 to 4.7 mm). In contrast, we detected a slight decrease in the values in the revision group and in the presence of an additional subscapularis lesion.     

Posterolateral rotatory instability of the elbow with insufficient coronoid process of the ulna: a report of 3 patients

Congruity of the ulnohumeral joint, especially its anterior portion, is an important stabilizer of the elbow joint. We report on 3 patients in whom the insufficiency of the coronoid process, such as nonunion or a flattened trochlear notch, was associated with posterolateral rotatory instability of the elbow. In our opinion, addressing the anterior bony integrity of the ulnohumeral joint, in addition to the ligamentous stabilizer and mechanical axis, is essential to achieve stability in these circumstances. This issue is discussed with a review of the literature.     

Square-lashing technique in segmental spinal instrumentation: a biomechanical study

Sublaminar wires have been used for many years for segmental spinal instrumentation in scoliosis surgery. More recently, stainless steel wires have been replaced by titanium cables. However, in rigid scoliotic curves, sublaminar wires or simple cables can either brake or pull out. The square-lashing technique was devised to avoid complications such as cable breakage or lamina cutout. The purpose of the study was therefore to test biomechanically the pull out and failure mode of simple sublaminar constructs versus the square-lashing technique. Individual vertebrae were subjected to pullout testing having one of two different constructs (single loop and square lashing) using either monofilament wire or multifilament cables. Four different methods of fixation were therefore tested: single wire construct, square-lashing wiring construct, single cable construct, and square-lashing cable construct. Ultimate failure load and failure mechanism were recorded. For the single wire the construct failed 12/16 times by wire breakage with an average ultimate failure load of 793 N. For the square-lashing wire the construct failed with pedicle fracture in 14/16, one bilateral lamina fracture, and one wire breakage. Ultimate failure load average was 1,239 N For the single cable the construct failed 12/16 times due to cable breakage (average force 1,162 N). 10/12 of these breakages were where the cable looped over the rod. For the square-lashing cable all of these constructs (16/16) failed by fracture of the pedicle with an average ultimate failure load of 1,388 N. The square-lashing construct had a higher pullout strength than the single loop and almost no cutting out from the lamina. The square-lashing technique with cables may therefore represent a new advance in segmental spinal instrumentation.     

Rib cage surgery for the treatment of scoliosis: a biomechanical study of correction mechanisms.

Rib shortening or lengthening are surgical options that are used to address the cosmetic rib cage deformity in scoliosis, but can also alter the equilibrium of forces acting on the spine, thus possibly counteracting in a mechanical way the scoliotic process and correcting the spinal deformities. Although rib surgeries have been successful in animal models, they have not gained wide clinical acceptance for mechanical correction of scoliosis due to the lack of understanding of the complex mechanisms of action involved during and after the operation. The objective of this study was to assess the biomechanical action of different surgical approaches on the rib cage for the treatment of scoliosis using a patient-specific finite element model of the spine and rib cage. Several unilateral and bilateral rib shortening/lengthening procedures were tested at different locations on the ribs (convex/concave side of the thoracic curvature; at the costo-transverse/costo-chondral joint; 20 and 40 mm adjustments). A biomechanical analysis was performed to assess the resulting geometry and load patterns in ribs, costo-vertebral articulations and vertebrae. Only slight immediate geometric variations were obtained. However, concave side rib shortening and convex side rib lengthening induced important loads on vertebral endplates that may lead to possible scoliotic spine correction depending on the remaining growth potential. Convex side rib shortening and concave side rib lengthening produced mostly cosmetic rib cage correction, but generated inappropriate loads on the vertebral endplates that could aggravate vertebral wedging. This study supports the concept of using concave side rib shortening or convex side rib lengthening as useful means to induce correction of the spinal scoliotic deformity during growth, though the effects of growth modulation from induced loads must be addressed in more detail to prove the usefulness of rib shortening/lengthening techniques.     

Scapholunate ligament reconstruction using a periosteal flap of the iliac crest: a biomechanical study

Introduction Advances continue to improve direct reconstruction of the dorsal scapholunate (SL) ligament, which is the strongest part of the entire SL ligament and is known as the turning point between the scaphoid and lunate. This study was designed to compare the biomechanical properties of the dorsal SL ligament with those of a periosteal flap of the iliac crest, which is a new graft candidate for dorsal SL reconstruction.Materials and methods A bone-ligament-bone complex was harvested for biomechanical testing from the iliac crest and the dorsal SL complex. Ten specimens could be prepared in each group. After potting the bone blocks in methylmethacrylate for stable fixation, the specimens were tested, using a servohydraulic testing system, at a rate of 10 mm/min.Results Failure displacement, failure force, failure stress, energy to failure, and stiffness were assessed for both groups. Eight specimens in each group were tested successfully. In the ligament group, six specimens failed at the ligament level, whereas two failed at the insertion of the scaphoid. In the periosteum group, all eight specimens failed at the ligament level. The failure force of the dorsal SL ligament averaged 171.8 N, failure stress was 10.3 N/mm², and failure displacement amounted to 2.9 mm. Energy to failure was 269.1 N-mm, and stiffness averaged 77.2 N/mm. Failure force of the periosteal flap amounted to 144.3 N, failure stress was 9.9 N/mm², failure displacement was 3.0 mm, and energy to failure was 217.9 N-mm. Stiffness of the periosteal flap measured 60.5 N/mm. Comparison of the dorsal SL ligament and the periosteal flap of the iliac crest revealed no significant biomechanical differences.Conclusion Therefore, the biomechanical properties of the periosteal flap recommend its use for reconstruction of the dorsal SL ligament.     

Metaphyseal locking plate as an external fixator for open tibial fracture: Clinical outcomes and biomechanical assessment

ObjectiveThis study aimed to evaluate the outcome of using a metaphyseal locking plate as a definitive external fixator for treating open tibial fractures based on biomechanical experiments and analysis of clinical results.MethodsA metaphyseal locking plate was used as an external fixator in 54 open tibial fractures in 52 patients. The mean follow-up was 38 months (range, 20–52 months). Moreover, static axial compression and torsional tests were performed to evaluate the strength of the fixation techniques.ResultsThe average fracture healing time was 34.5 weeks (range, 12–78 weeks). At 4 weeks postoperatively and at the final follow-up, the average Hospital for Special Surgery knee score was 85 (range, 81–100) and 94 (range, 88–100), respectively, and the American Orthopaedic Foot and Ankle Society score was 88 (range, 80–100) and 96 (range, 90–100), respectively. Based on the static test result, the axial stiffness was significantly different among groups (p = 0.002), whereas the torsional stiffness showed no significant difference (p = 0.068).ConclusionsClinical outcomes show that the use of locking plate as a definitive external fixator is an alternative choice for tibial fractures after obtaining appropriate fracture reduction. However, external locked plating constructs were not as strong as standard locked plating constructs. Therefore, the use of external locked plating constructs as a definitive treatment warrants further biomechanical study for construct strength improvement.     

不同内固定方法治疗踝关节后侧骨-韧带损伤的生物力学研究

目的通过生物力学及有限元分析法,了解踝关节后侧骨-韧带结构损伤及不同内固定手术对踝关节旋转稳定性的影响。方法随机选取6具成人新鲜小腿-足标本。通过DDL实验机垂直和扭转加载,并通过数字散斑相关法分析1正常状态、2切除小块后踝、3切除后踝和下胫腓联合韧带(SL)、4固定SL、5固定后踝、6同时固定SL和后踝后,踝关节内、外旋至4 Nm时胫骨、腓骨和距骨的相对位移。构建踝关节三维有限元模型(3D-FEM),并模拟相关生物力学工况。结果单纯后踝骨折时存在踝关节内旋不稳定,后踝骨折合并SL断裂时存在内、外旋不稳定。在3种内固定组,踝关节内、外旋时各骨间相对位移与正常组差异均无统计学意义(P0.05)。组间两两比较,仅固定后踝与联合固定SL和后踝组,在内旋时距骨与胫骨在矢状面水平位移差异有统计学意义(P=0.03)。3D-FEM的趋势结果与相关生物力学研究相似。结论根据本研究的结果,在后踝骨折合并SL损伤时,单纯固定后踝或SL均可较好恢复踝关节的旋转稳定性;同时固定SL和后踝可能导致踝关节旋转僵硬。     

Free-hand versus novel specialised jig guidance for the passing of intramedullary wires in olecranon fracture fixation: A comparative study

The treatment of olecranon fractures frequently involves the use of tension-band fixation. Although associated with high union rates, this method has a high incidence of morbidity associated with soft tissue compromise and limitation of range of movement requiring frequent re-operation for removal of metal.We describe the use of a simple jig to ensure intramedullary placement of longitudinal K-wires and compare the accuracy of placement of Kirschner (K)-wires using this device with the traditional free-hand method.We found the distance from the centre of the medullary canal, the range and standard deviations of K-wire positions to be significantly more precise when the jig was used. This has applications for the use of the device, both with standard metallic radio-opaque wires and potentially with bio-absorbable pins.     

Plate fixation for Letenneur type I Hoffa fracture: a biomechanical study

BackgroundA coronal fracture of the posterior femoral condyle, also known as a Hoffa fracture, is an unusual injury, and there are only a handful of case reports or series exploring it. The optimal fixation method of these intraarticular fractures remains controversial; improper or unstable fixation usually lead to an unsatisfactory prognosis. The use of posterior–anterior or reversed lag screw fixation is still a popular method. Additional buttress plating is also recommended for fixation of these difficult fractures. The purpose of this study was to compare the mechanical strength of four different fixation patterns for this uncommon fracture.Material and methodsSixteen sawbone simulated models of Letenneur type I Hoffa fractures were created with one of four fixation patterns: two screws implanted in the anterior–posterior (AP) direction or posterior–anterior (PA) direction; one screw in the PA direction with a plate implanted in the posterior position of the distal femoral condyle or with a plate in the lateral position. Biomechanical testing was performed to determine the post-fixation axial stiffness, the maximum load to failure and the fragment vertical displacement for each of the four constructs.ResultsThe plate fixation patterns whether implanted in the posterior or lateral position were shown to provide higher overall axial stiffness and load to failure, and less vertical displacement than the other two patterns of pure screw fixation. Among these constructs, the lateral plate fixation was found to provide the highest stiffness and load to failure and the least displacement for the posterior condylar fragments, followed by the posterior plate fixation. The lowest overall stiffness and load to failure and the largest vertical displacement were found in the construct with the AP direction placed screws.ConclusionIt was concluded that the lateral position implanted plate is biomechanically the strongest fixation method for Letenneur type I Hoffa fractures. However, this plate fixation is not recommended for all cases. The choice of internal fixation pattern depends on the surgeons.