Interfragmentary Lag Screw Research Articles

The influence of different osteosynthesis configurations with locking compression plates (LCP) on stability and fracture healing after an oblique 45° angle osteotomy

BackgroundLocking compression plates are used in various configurations with lack of detailed information on consequent bone healing. Study designIn this in vivo study in sheep 5 different applications of locking compression plate (LCP) were tested using a 45° oblique osteotomy simulating simple fracture pattern. 60 Swiss Alpine sheep where assigned to 5 different groups with 12 sheep each (Group 1: interfragmentary lag screw and an LCP fixed with standard cortex screws as neutralisation plate; Group 2: interfragmentary lag screw and LCP with locking head screws; Group 3: compression plate technique (hybrid construct); Group 4: internal fixator without fracture gap; Group 5: internal fixator with 3mm gap at the osteotomy site). One half of each group (6 sheep) was monitored for 6weeks, and the other half (6 sheep) where followed for 12weeks. MethodsX-rays at 3, 6, 9 and 12weeks were performed to monitor the healing process. After sacrifice operated tibiae were tested biomechanically for nondestructive torsion and compared to the tibia of the healthy opposite side. After testing specimens were processed for microradiography, histology, histomorphometry and assessment of calcium deposition by fluorescence microscopy. ResultsIn all groups bone healing occurred without complications. Stiffness in biomechanical testing showed a tendency for higher values in G2 but results were not statistically significant. Values for G5 were significantly lower after 6weeks, but after 12weeks values had improved to comparable results. For all groups, except G3, stiffness values improved between 6 and 12weeks. Histomorphometrical data demonstrate endosteal callus to be more marked in G2 at 6weeks. Discussion and conclusionAll five configurations resulted in undisturbed bone healing and are considered safe for clinical application.

Lapidus Arthrodesis with a Single Lag Screw and a Locking H-Plate

The aim of this pilot study was to assess if using an interfragmental lag screw and a Darco ® locking H-plate for the modified Lapidus arthrodesis in the treatment of hallux abducto valgus deformity (1) would allow for earlier weight bearing than previously described and (2) would indicate whether any changes would occur radiographically with the earlier weight bearing. Twenty-one metatarsocuneiform arthrodeses, in 18 patients, were retrospectively evaluated through chart review and postoperative radiographs. Original diagnoses included painful hallux abducto valgus and osteoarthritis of the first metatarsocuneiform joint. The mean age of the patients was 48 (range, 16 to 70) years. The mean follow-up duration was 38.5 (range, 29 to 60) months. The overall radiographic osseous union rate was 90.5% (19/21 feet), although there were 2 asymptomatic nonunions. There were no cases of fixation failure, and the surgical correction was preserved on follow-up radiographs. Overall, the mean time to full weight bearing was 4.7 (range, 3 to 7.5) weeks, and it was a mean of 8 (range, 7 to 10) weeks before the patient was back to wearing comfortable shoes. The authors concluded that metatarsocuneiform arthrodesis fixated with 1 interfragmentary lag screw and a Darco ® locking H-plate provides sufficient stability to allow earlier weight bearing than has been previously described with other internal fixation constructs.

Behandlung der Talusfraktur

Talusfrakturen gehören zu den seltenen Fußfrakturen, führen aber potenziell zu schweren Komplikationen. Die gängigen Frakturklassifikationen beruhen auf konventionellen Röntgenaufnahmen, die Computertomografie ist jedoch bei jeder Fraktur obligat. Offene Frakturen, Luxationen oder Extrusionen müssen notfallmäßig reponiert und stabilisiert werden. Alle dislozierten Talusfrakturen stellen eine absolute Operationsindikation dar. Die Zugangswahl wird vom Frakturtyp und dem Weichteilschaden bestimmt. Die anatomische Reposition der Gelenkflächen und der Talusform und die Stabilisierung mit Zugschrauben stellt meistens die Methode der Wahl dar. Das Ergebnis wird vom Dislokationsgrad bzw. dem Weichteilschaden, aber oftmals auch von der unzulänglichen Versorgung beeinflusst. Verzögerte Konsolidierungen, Pseudarthrosen und sekundäre Fehlstellungen sollten möglichst frühzeitig Gelenk erhaltend korrigiert und notwendige Arthrodesen auf die betroffenen Gelenke beschränkt werden. Dieser Artikel behandelt detailliert Klassifikation, operative Behandlung, Indikationsstellung und Komplikationen von Talushalsfrakturen. Die Körper- und Kopffrakturen werden ebenfalls diskutiert.

Technique of Ulnar Shortening

Ulnar shortening or recession is a common treatment for an expanding number of clinical indications. This procedure has become more reliably performed because of specialized equipment that permits the creation of 2 precise 45-degree osteotomy surfaces and a known amount of ulnar shortening. Further refinements in technique have facilitated compression of the osteotomy surfaces and application of an interfragmentary lag screw at a specified angle. More recently, advancements in technology have increased the surgical options available to the surgeon and have provided for a low-profile surgical plate that may be placed on either the ulnar subcutaneous border or the volar-ulnar surface. In addition, osteotomy widths ranging from 3.5 to 18.1 mm may be performed with the available equipment. The complication rate of ulnar shortening is very low, and the overall clinical success rate is encouragingly quite high.

Peripheral talar fractures

Peripheral fractures of the talus are uncommon and often overlooked. CT scanning has become the imaging modality of choice and is necessary for decision making on treatment. Displaced peripheral fractures have to be managed with open reduction and internal fixation. Precise anatomical reduction is necessary to achieve a good result. A rigid internal fixation with interfragmentary lag screws is the method of choice in almost all fractures, which allows early postoperative mobilization. The outcome is related to the degree of the chondral lesion and the degree of instability of the subtalar joint, but it may be poor due to the treatment. Early diagnosis and proper treatment achieve the best possible results and prevent long-term complications. Typical complications of the fracture are nonunion and malalignment with slight subtalar instability or osseous overgrowth with secondary impingement and posttraumatic subtalar arthritis.

Functional load of plates in fracture fixation in vivo and its correlate in bone healing

In clinical practice efforts are made to apply a fixation plate on the side opposite the strongest muscle pull. This achieves an optimal distribution of compression between the fragment ends (principle of tension band plating). This is however frequently impossible for anatomical or surgical reasons. In an ‘in vivo’ study lasting 8 weeks a standardized oblique osteotomy was performed on the tibia of 16 sheep in four different models of tension band plating (a contoured and an overbent plate with or without an interfragmentary lag screw) were assessed. Tension on the plate surface was recorded by strain gauges for different gait speeds on the treadmill. These measurements were performed throughout the experiment. Radiographs were taken at regular intervals in order to assess stability and polychrome sequential labelling and microradiographs served to investigate the healing process. Possible relationships and/or interactions between plate tension and bone healing were investigated. Implant loading under bending strain was reduced the most for the combination of plate overbending with a lag screw. The insertion of a lag screw reduces the surface strain on the plate whether it is contoured or overbent. The bending and torsional forces are greatest if a straight plate is used alone and the principle of tension band plating is not applied. Direct bone healing was only observed in the group with contoured plate and lag screw. Overbending combined with a lag screw provided only a relatively unstable fixation. A residual gap immediately beneath the plate permits “dynamic compression” since the screws slide towards the osteotomy when loaded producing bone resorption under the plate and signs of screw loosening. The models with contoured and overbent plates without a lag screw were histologically assessed as very unstable with signs of secondary fragment displacement, obvious callus formation, resorption at the fragment ends and under the plate, delayed and diminished Haversian remodelling and corrosion sites at the screw heads and at the adjacent site on the plate hole. In all groups, stripping of the periosteum under the plate was associated with porosis of the corresponding cortex as a sign of temporarily impaired blood supply. A relationship between implant loading and/or unloading (stress shielding) could not be demonstrated. Callus formation, measured quantitatively on the radiographs, is directly related to the strain on the plate. Direct bone healing is rapid and is seen histologically three weeks postoperatively, particularly for fixations with contoured plate and lag screw. The early appearance of fixation callus in the presence of an intact blood supply indicates a primary instability of the osteosynthesis. Later, it may be an indication of secondary instability. The time at which osteons appear, their number and location provides information on the stability of the osteosynthesis. At a time when indirect fracture reduction and stabilization using minimally invasive techniques and implants is being propagated, additional ways and means must be sought to assess clinically the load on the implants and the risk of implant failure.

Interfragmentary lag screws and external fixation for severe open tibial fractures: a biomechanical and clinical study

The stability offered by the interfragmentary lag screw with a unilateral external fixator frame was studied in both experimental and prospective clinical studies. The in-vitro stability of the fixation with and without the interfragmentary lag screw was tested by a universal testing machine in compression, four-point bending, and torsion in 18 human tibiae. The in-vivo study was conducted prospectively in 18 patients with 19 severe open tibial fractures. All patients were treated with one definite surgical procedure on admission. The interfragmentary lag screw increased the sytem stiffness 47.4 times in compression, 9.9 times in bending, and 3.2 times in torsion. The immediate one-stage care of severe open fractures with a simple external fixation system in combination with the interfragmentary lag screw shortens hospitalization and may enhance healing.

Precision oblique osteotomy for shortening of the ulna

The obstacles of prolonged healing time and technically demanding osteotomy and plate fixation in the performance of ulnar shortening osteotomies have been overcome by a precision system that includes a 45° osteotomy and 2.7 mm interfragmentary lag screw. In 23 transverse osteotomies healing time averaged 21 weeks with one nonunion. In 17 precision oblique osteotomies healing time averaged a substantially shorter 11 weeks. Biomechanical data obtained from cadaveric testing comparing these two constructs demonstrated a structural stiffness that was clearly greater in torsion testing for the oblique osteotomy. No biomechanical difference was identified in the anteroposterior and lateral bending tests. The system permits the reliable performance of two parallel osteotomy cuts, allowing the removal of a precise amount of bone. The compression device and specialized plate permit easy coaptation of the osteotomy surfaces, which are locked into position by a precise 22° interfragmentary lag screw. The surgical procedure is more quickly completed, and the frustration of this previously challenging procedure is now completely removed.

Refracture after removal of a condylar plate from the distal third of the femur.

Of 103 patients who had a fracture of the distal third of the femur that was treated by open reduction and internal fixation with a condylar blade-plate, sixty-two had removal of the plate after the fracture had united. The mean interval between injury and removal of the plate was twenty-six months. Six patients (10 per cent) sustained a refracture that was unrelated to major trauma; the refracture occurred twelve to ninety-three days after removal of the plate. Five of the six refractures occurred through a hole of a supplemental interfragmentary lag-screw. The use of such screws significantly increased the risk of refracture after removal of the hardware (p less than 0.01). The refractures were treated by intramedullary nailing in five patients and by replating in one, and union was achieved in all six patients. Routine removal of a condylar blade-plate after union of a fracture of the distal third of the femur cannot be recommended, especially in the presence of supplemental fixation with interfragmentary screws.

Significance of postoperative stability for bony reparation of comminuted fractures

The significance of postoperative mechanical stability to bone repair of comminuted fractures was investigated in an animal experimental study comparing four commonly employed operative methods of fracture stabilization: 1. Plate osteosynthesis combined with lag screw fixation; 2. Bridging plate osteosynthesis; 3. External fixation; 4. Static interlocking intramedullary nailing. As fracture model, a triple wedge osteotomy of the right sheep tibia was used. In regard to biomechanical strength, the method which gave best postoperative stability, plate osteosynthesis in combination with interfragmentary lag screws, did not result in the best bone repair. In this experimental setup, stabilization by bridging methods, inducing bone healing by secondary intention, gave better bone regeneration in the experimental fractures.

Nonunion of the Humeral Shaft

Retrospective review of records of 26 patients with nonunion of the humeral shaft revealed several factors frequently associated with the development of nonunion. The fractures were transverse and short oblique and treated per primam with hanging casts or open reduction. Surgical fixation was unstable. The types of nonunion were atrophic in 19 patients, hypertrophic in five patients, and synovial pseudarthrosis in two patients. Twenty-four of 26 nonunions (92%) treated with bone grafts and rigid internal fixation healed in an average of 5.6 months. Overall, 47 surgical procedures, including prior procedures, were performed on these 26 nonunions. The average number of operations per patient was 1.8. Successful platings produced immobilization, consisting of an average of 6.8 points of cortical fixation above the nonunion and 7.1 cortices below. Rigid fixation was not obtained in the unsuccessful procedures. Unsuccessful platings were noted to have unstable fixation, with an average of 2.7 points of cortical fixation above the nonunion and 3.0 cortices below. Bone grafting was performed in only 55% of the unsuccessful platings. Optimal treatment of nonunions of the humeral shaft consists of resecting atrophic nonunions, shortening the bones, drilling sclerotic areas, and apposing bleeding diaphyseal surfaces; open reduction with internal fixation with a broad compression plate, including at least six points of cortical fixation above and below the nonunion; compression of the nonunion by means of interfragmentary lag screws, prestressing of the plate, dynamic compression by the plate, or direct compression by the external compression device; and autogeneic cancellous iliac bone grafts.

The stability of internal fixation in the proximal phalanx

A biomechanical study was performed to assess quantitative differences in the stability obtained with five commonly used types of internal fixation used in proximal phalangeal fractures. The techniques included dorsal plating, dorsal plating combined with an interfragmentary lag screw, two interfragmentary lag screws, tension-band technique, and crossed Kirschner wires. Rigidity and strength in apex palmar bending were determined after oblique osteotomy and fixation of the proximal phalanx. The failure modes for each fixation technique were also observed and described. The results showed that both of the techniques that used interfragmentary lag screws across the oblique osteotomies provided significantly more rigidity than did dorsal plating alone or the wired configurations but that measurements of strength were similar between all techniques tested. Dorsal plates were at a mechanical disadvantage on the compression surface in our apex palmar bend test and consequently provided no more rigidity and strength than did the wired techniques. The tension band technique represented a combination of stiff and flexible intraosseous wires without strict application of tension band principles and provided intermediate rigidity and strength. Rigidity and strength in intact proximal phalanges in the controls were significantly greater than in all techniques tested.

Comparison of internal fixation techniques in metacarpal fractures

A biomechanical study assessed quantitative differences in the stability that was obtained by five commonly used types of internal fixation employed in metacarpal fractures. The techniques included dorsal plating, dorsal plating combined with an interfragmentary lag screw, crossed Kirschner wires, a single intraosseous wire combined with a single oblique Kirschner wire, and a single intraosseous wire alone. Rigidity and strength in torsion and bending were determined after transverse osteotomy and fixation of the metacarpal were performed. The failure modes for each fixation technique were also observed and described. Significant differences in rigidity were found between the plated configurations (with or without an interfragmentary lag screw) and the wired configurations in both apex dorsal bending and axial torsion. The three wired configurations were not significantly different from each other except in torsion. Analysis of the bending moments that were required to produce both yield and failure in apex dorsal bending and also the energy absorbed to yield showed similar disparity between plated and wired techniques. For metacarpal fixation, dorsal plating with or without lag screws provides significantly more stability than do wired techniques and approaches that provided by intact bones.

Internal fixation of fractures and non-unions of the humeral shaft. Indications and results in a multi-center study.

We performed ninety-six internal-fixation procedures for fracture or non-union of the humeral shaft in eighty-four patients, with a mean follow-up of 32.6 months (range, three months to fourteen years). The primary indications for operative intervention included humeral shaft fracture in a patient with multiple trauma, non-union, inadequate reduction of a humeral shaft fracture by closed methods, pathological humeral-shaft fracture, and progressive radial-nerve palsy. Methods of internal fixation included compression plates and screws and intramedullary Küntscher nails or Rush rods. The use of an AO/ASIF compression plate or interfragmentary lag screws with an AO/ASIF neutralization plate in twenty-seven multiply-injured patients resulted in a union rate of 100 per cent and generally good motion of the shoulder and elbow. Five multiply-injured patients also obtained good results through fixation by a modified Hackethal technique using two Rush rods. The use of intramedullary Küntscher nails resulted in a rate of union of 91 per cent in eleven multiply injured patients. Ten patients with non-union of a humeral shaft fracture had an 80 per cent rate of union with the use of an AO/ASIF compression plate. The use of a Küntscher nail in eleven patients with non-union resulted in a rate of union of only 73 per cent and frequently caused subacromial impingement. Fractures of the humeral shaft that had had an inadequate reduction by closed means or were associated with progressive radial-nerve palsy were best managed by a compression plate or the modified Hackethal technique.(ABSTRACT TRUNCATED AT 250 WORDS)