Are Quadrilateral Surface Buttress Plates Comparable to Traditional Forms of Transverse Acetabular Fracture Fixation?

Background

Several construct options exist for transverse acetabular fracture fixation. Accepted techniques use a combination of column plates and lag screws. Quadrilateral surface buttress plates have been introduced as potential fixation options, but as a result of their novelty, biomechanical data regarding their stabilizing effects are nonexistent. Therefore, we aimed to determine if this fixation method confers similar stability to traditional forms of fixation.

Questions/purposes

We biomechanically compared two acetabular fixation plates with quadrilateral surface buttressing with traditional forms of fixation using lag screws and column plates.

Methods

Thirty-five synthetic hemipelves with a transverse transtectal acetabular fracture were allocated to one of five groups: anterior column plate + posterior column lag screw, posterior column plate + anterior column lag screw, anterior and posterior column lag screws only, infrapectineal plate + anterior column plate, and suprapectineal plate alone. Specimens were loaded for 1500 cycles up to 2.5x body weight and stiffness was calculated. Thereafter, constructs were destructively loaded and failure loads were recorded.

Results

After 1500 cycles, final stiffness was not different with the numbers available between the infrapectineal (568 ± 43 N/mm) and suprapectineal groups (602 ± 87 N/mm, p = 0.988). Both quadrilateral plates were significantly stiffer than the posterior column buttress plate with supplemental lag screw fixation group (311 ± 99 N/mm, p < 0.006). No difference in stiffness was identified with the numbers available between the quadrilateral surface plating groups and the lag screw group (423 ± 219 N/mm, p > 0.223). The infrapectineal group failed at the highest loads (5.4 ± 0.6 kN) and this was significant relative to the suprapectineal (4.4 ± 0.3 kN; p = 0.023), lag screw (2.9 ± 0.8 kN; p < 0.001), and anterior buttress plate with posterior column lag screw (4.0 ± 0.6 kN; p = 0.001) groups.

Conclusions

Quadrilateral surface buttress plates spanning the posterior and anterior columns are biomechanically comparable and, in some cases, superior to traditional forms of fixation in this synthetic hemipelvis model.

Clinical Relevance

Quadrilateral surface buttress plates may present a viable alternative for the treatment of transtectal transverse acetabular fractures. Clinical studies are required to fully define the use of this new form of fixation for such fractures when accessed through the anterior intrapelvic approach.     

髋臼后壁骨折三种内固定方式的生物力学研究及临床意义

背景：锁定重建接骨板已应用于髋臼后壁骨折的治疗,但关于其固定髋臼后壁骨折生物力学稳定性的研究报道甚少。目的：比较锁定重建接骨板、重建接骨板及单纯拉力螺钉固定髋臼后壁骨折的生物力学稳定性。 方法：取成人新鲜半骨盆标本18个,制成髋臼后壁骨折模型,随机分成三组。A组用2枚拉力螺钉固定,B组用重建接骨板固定,C组用锁定重建接骨板固定。进行轴向加载实验,测定各组骨折的纵向位移、内固定失效时的载荷及轴向刚度,以比较各内固定方式的稳定性。 结果：在相同载荷下,B组、C组骨折的纵向位移小于A组,B组、C组内固定失效时的载荷及轴向刚度大于A组,有统计学差异（P＜0.05）;B组与C组在纵向位移、内固定失效时的载荷及轴向刚度之间无统计学差异（P＞0.05）。 结论：锁定重建接骨板与重建接骨板的内固定稳定性优于单纯拉力螺钉内固定,锁定重建接骨板与重建接骨板内的固定稳定性相似,均可用于髋臼后壁骨折的内固定治疗。     

双柱拉力螺钉固定治疗横断髋臼骨折

目的　回顾分析双柱拉力螺钉固定治疗横断髋臼骨折的疗效。方法　 1 3例髋臼横断骨折分别采用Smith Peterson入路或者后外侧K -L入路结合前侧髂腹股沟入路行切开复位 ,前后柱拉力螺钉沿其功能轴固定。术后平均随访 4年 2个月 ,按照美国矫形外科医师协会 (AAOS)标准评估患髋功能。结果　 1 3例中 1 2例获解剖复位 ,1例复位欠佳。术中、术后无严重并发症。患髋术后功能优良率为 85 %。结论　双柱拉力螺钉固定技术是一种治疗髋臼横断骨折的有效方法 ,但技术要求较高 ,应严格掌握手术适应证     

A biomechanical study of conventional acetabular internal fracture fixation versus locking plate fixation

Background

Conventional internal fixation entails the use of an interfragmentary lag screw along with a plate. Not all acetabular fractures are amenable to the placement of an interfragmentary lag screw, and the fracture may be displaced during tightening of the interfragmentary lag screw. Locking plates are a possible solution. We sought to determine whether a locking plate construct can provide stability equivalent to that provided with a conventional construct for transverse acetabular fractures.

Methods

We used 5 paired fresh-frozen cadaveric acetabula. We fixed one side with the conventional technique and the other side with a locking plate. We subjected each fixation to a cyclic compressive force up to 500 cycles, followed by compressive force until failure. We monitored 3-dimensional motion of the fracture.

Results

The average fracture gap at 50 N compressive force after 500 loading cycles was 0.41 (standard deviation [SD] 0.49) mm for the conventional plate and lag screw construct compared with 0.76 (SD 0.62) mm for the locked plate construct (p = 0.46). The force to failure, as defined by 2 mm of fracture gap, was 848 (SD 805) N for the conventional plate and lag screw construct compared with 506 (SD 277) N for the locked plate fixation (p = 0.34).

Conclusion

The locking plate construct is as strong as the conventional plate plus interfragmentary lag screw construct for fixing transverse acetabular fractures. Locking plates may improve management of acetabular fractures by eliminating the need for placement of an interfragmentary lag screw. Furthermore, they may be helpful in revision hip arthroplasty in patients with pelvic discontinuity.     

Medial malleolar fractures: a biomechanical study of fixation techniques

Fracture fixation of the medial malleolus in rotationally unstable ankle fractures typically results in healing with current fixation methods. However, when failure occurs, pullout of the screws from tension, compression, and rotational forces is predictable. We sought to biomechanically test a relatively new technique of bicortical screw fixation for medial malleoli fractures. Also, the AO group recommends tension-band fixation of small avulsion type fractures of the medial malleolus that are unacceptable for screw fixation. A well-documented complication of this technique is prominent symptomatic implants and secondary surgery for implant removal. Replacing stainless steel 18-gauge wire with FiberWire suture could theoretically decrease symptomatic implants. Therefore, a second goal was to biomechanically compare these 2 tension-band constructs. Using a tibial Sawbones model, 2 bicortical screws were compared with 2 unicortical cancellous screws on a servohydraulic test frame in offset axial, transverse, and tension loading. Second, tension-band fixation using stainless steel wire was compared with FiberWire under tensile loads. Bicortical screw fixation was statistically the stiffest construct under tension loading conditions compared to unicortical screw fixation and tension-band techniques with FiberWire or stainless steel wire. In fact, unicortical screw fixation had only 10% of the stiffness as demonstrated in the bicortical technique. In a direct comparison, tension-band fixation using stainless steel wire was statistically stiffer than the FiberWire construct.     

Generating stability in elderly acetabular fractures—A biomechanical assessment

Background & objectivesAs the overall health and life expectancy increases in the United States, the incidence of fragility fractures in elderly patients also continues to increase. Given their medical comorbidities and decreased bone mineral density, acetabular fractures in the elderly population present a significant challenge to the orthopaedic trauma surgeon. The anterior column posterior hemitransverse (ACPHT) fracture pattern is a common fracture pattern in this population, and is often associated with central subluxation/dislocation of the femoral head with articular impaction. This study sought to delineate the most stable fixation construct in ACPHT fracture patterns in the elderly population.Materials and methodsThe sample consisted of 3 groups of synthetic hemipelves (N = 15), which were tested in order to compare stiffness by measuring motion at fracture lines under applied loads. The three groups of unique quadrilateral plate fixation were as follows: a specialty quadrilateral surface plate; 4 long peri-articular screws parallel to the quadrilateral surface into the ischium,; and an 8 hole infrapectineal buttress plate. Digital imaging system measured construct motion under load. Construct stiffness was estimated by linear regression of load between 50 and 850 N versus average relative motion (average of relative motion at 200 points along the line of the osteotomy). Permanent deformation was estimated as the magnitude of relative motion upon unloading.ResultsUsing ANOVA with Tukey’s test to determine construct stiffness in loading, the group long peri-articular screws was found to have significantly higher stiffness than either of the other groups. Maximal fracture displacement was located at the intersection of the low transverse fracture line in the posterior column and the free quadrilateral surface fragment.ConclusionsResults indicate that the best fixation construct for this ACPHT acetabular fracture pattern includes independent lag screws across the anterior column and a pelvic brim plate with long periarticular screws maximizing posterior column fixation and preventing medialization of the free quadrilateral fragment. Although there are potential patient considerations that may complicate the placement of all 4 long screws, in most patients one or more of these screws can be safely placed in order to help prevent secondary displacement.     

锁定重建接骨板治疗髋臼横行骨折的生物力学研究

背景：髋臼横形骨折治疗较为困难,常采用内固定的治疗方法。近年来有学者尝试采用锁定重建接骨板,但对其的研究报道较少。 目的：比较4种不同锁定重建接骨板后方入路内固定方式治疗髋臼横行骨折的生物力学稳定性。 方法：采用成人防腐标本10具,制成髋臼横行骨折模型20个,随机分为4组,每组5个标本。A组：重建接骨板两端各固定3枚螺钉。B组：重建接骨板两端各固定3枚螺钉及距骨折线最近的两侧螺孔各1枚螺钉。C组：锁定重建接骨板两端各3枚单皮质螺钉。D组：锁定重建接骨板两端各3枚单皮质螺钉及距骨折线最近的两侧螺孔各1枚单皮质螺钉。行轴向的加载实验,记录内固定失效时最大负载和轴向刚度。 结果：A、B、C、D组所能承受的最大负载分别为（180.60±11.781）N、（240.80±7.981）N、（243.80±11.755）N和（438.00±23.227）N;轴向刚度分别为（95.21±6.32）N/mm、（123.47±23.95）N/mm、（126.39±18.52）N/mm和（227.35±13.74）N/mm。除B、C两组数据比较无统计学差异（P〉0.05）,其余各组的最大负载和轴向刚度差异均有统计学意义（〈0.05）。 结论：髋臼横形骨折采用接骨板后方入路内固定时,锁定重建接骨板固定的稳定性优于重建接骨板,而且距骨折线最近的两侧螺孔给予螺钉固定能增强内固定的稳定性。     

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.     

Fixation of quadrilateral plate fractures of the acetabulum using the buttress screw: A novel technique

IntroductionQuadrilateral plate fractures constitute one of the most challenging components of acetabular fractures. The objective of this study is to describe and evaluate the novel technique of buttress screw fixation of the quadrilateral plate component of the acetabular fractures.Patients & methodsForty cases of acetabular fracture with associated quadrilateral plate component were included in the study. Mean age was 35 years (range, 16 − 68 years), with a mean follow-up 16.4 months (range, 9 − 36 months). Fixation of the quadrilateral plate was achieved by one or more buttress screws. The screws were inserted through the reconstruction plate, and placed close to the edge of the pelvic brim. To effectively achieve the 3-point fixation principle, the screw was inserted through the plate hole then outside the bone rubbing on the pelvic surface of the quadrilateral plate.ResultsAnatomical reduction of the quadrilateral plate component of the fractures was achieved in all but one patient. The modified Merle D’Aubigné and Postel score was excellent in 13 cases, good in 23 cases, fair in three cases, and poor in one case. No screw displacement or failures were observed during follow-up evaluation. No major complications related to this technique were observed in this series.ConclusionButtress screw fixation of the quadrilateral plate fracture component in associated acetabular fractures is a safe and effective technique for reduction and fixation of these challenging fractures with no major complications related to this novel technique.     

Preliminary Biomechanical Proof of Concept for a Hybrid Locking Plate/Variable Pitch Screw Construct for Anterior Fixation of Type II Odontoid Fractures

STUDY DESIGN.: A human cadaveric biomechanical proof-of-concept study. OBJECTIVE.: To test whether adding a locking plate to the anterior surface of C2 attaching directly to the interfragmentary screw may reduce potential for anterior screw cutout and improve construct strength. SUMMARY OF BACKGROUND DATA.: The most common mode of failure for screw fixation of dens fractures is via cutout at the anterior body of C2. METHODS.: A human, cadaveric model of type II dens fractures was created and fixed using either a headless, fully threaded variable pitch screw (FTVPS) or a screw with an attachable locking plate construct (LPC). Following quasistatic loading to failure, stiffness and load to failure were compared using t tests. Mode of failure was determined from radiographical and gross inspection. RESULTS.: Load to failure was greater for the LPC than for the FTVPS alone (498 N vs. 362 N, P = 0.04). The LPC consistently failed via compression of cancellous bone posterior to the lag screw, whereas the FTVPS constructs failed via cutout of the screw from the anterior C2 body. CONCLUSION.: Locking plate supplementation of anterior screw fixation of type II odontoid fractures improves construct strength and changes the failure mechanism from anterior screw cutout to posterior displacement of the screw. An attachable locking plate/interfragmentary screw construct may improve clinical outcomes for these fractures.     

First metatarsophalangeal joint arthrodesis: quantitative mechanical testing of six-hole dorsal plate versus crossed screw fixation in cadaveric specimens.

Quantitative strength analysis of first metatarsophalangeal joint arthrodesis was performed using two fixation techniques: a small 6-hole plate with an interfragmentary screw or two crossed lag screws. Twelve matched-pair fresh-frozen cadaveric specimens (24 trials) were used for direct comparison of each of the two fixation techniques. All joint surfaces were prepared with power conical reamers utilizing a standard technique. The fixation construct was stressed to failure on each specimen using a computer-integrated materials tester. Fixation stiffness defined as force (load) over displacement and point of ultimate failure was evaluated. The six-hole plate and interfragmentary screw fixation method was a statistically stiffer form of fixation (p > .01) and displayed a greater point of ultimate failure (p > .002) under the laboratory conditions.     

Comparison of lateral locking plate and antiglide plate for fixation of distal fibular fractures in osteoporotic bone: a biomechanical study

OBJECTIVES: The purpose of this study was to compare the biomechanical properties of posterolateral antiglide plating and lateral locked plating for fixation of displaced short oblique fractures of the fibula in osteoporotic bone. METHODS: Short oblique fractures of the distal fibula at the level of the syndesmosis were simulated with a fibular osteotomy and ligamentous sectioning in 18 paired fresh frozen ankles. The fractures were fixed with either a lateral locking plate with an independent lag screw or a posterolateral antiglide plate with a lag screw through the plate. The specimens were tested under a torsional load to failure. The torque to failure, angular rotation at failure, and construct stiffness of the two groups were compared. RESULTS: The torque to failure and construct stiffness were significantly greater on the side with the posterolateral antiglide plate than on the side with the the lateral locking plate (P = 0.01 and 0.005, respectively). CONCLUSIONS: The posterolateral antiglide plate demonstrated improved biomechanical stability as compared to the lateral locking plate in osteoporotic bone. In situations where fixation needs to be optimized, use of an antiglide plate may be favored over a lateral locking plate construct.     

Clinical results of minimal screw plate fixation of forearm fractures

Traditional plating technique for forearm fractures specifies implant selection based on achieving a minimum number of "cortices" of screw fixation on either side of the fracture. Recent biomechanical data suggest that plates with fewer screws provide equivalent strength of fixation compared with standard compression plating techniques in forearm fractures. As described in this article, we retrospectively reviewed a surgeon's experience at a regional level I trauma center to evaluate the clinical outcome of this newer fixation strategy. Seventy-eight fractured bones were plated using "minimal" screw technique--less than the traditionally recommended 6 cortices of screw purchase. Nonunion or fixation failure occurred in 7 fractures (5 patients), producing a union rate of 91% (71/78). All nonunions were atrophic and occurred in open fractures with bone loss. No construct failed because of fixation loss caused by having too few screws. Minimal screw plate technique was stable fixation, despite not having 6 cortices on both sides of the fracture. Technical emphasis should be on adequate plate length rather than number of cortices of fixation in each segment.     

Clinical results of minimal screw plate fixation of forearm fractures.

Traditional plating technique for forearm fractures specifies implant selection based on achieving a minimum number of "cortices" of screw fixation on either side of the fracture. Recent biomechanical data suggest that plates with fewer screws provide equivalent strength of fixation compared with standard compression plating techniques in forearm fractures. As described in this article, we retrospectively reviewed a surgeon's experience at a regional level I trauma center to evaluate the clinical outcome of this newer fixation strategy. Seventy-eight fractured bones were plated using "minimal" screw technique--less than the traditionally recommended 6 cortices of screw purchase. Nonunion or fixation failure occurred in 7 fractures (5 patients), producing a union rate of 91% (71/78). All nonunions were atrophic and occurred in open fractures with bone loss. No construct failed because of fixation loss caused by having too few screws. Minimal screw plate technique was stable fixation, despite not having 6 cortices on both sides of the fracture. Technical emphasis should be on adequate plate length rather than number of cortices of fixation in each segment.     

Comparative fatigue strengths and stabilities of metacarpal internal fixation techniques

To study quantitative differences in the fatigue strength and stability obtained with 5 types of internal fixation of metacarpal fractures, 105 preserved human metacarpals were cyclically tested in bending, torsion, and axial loading after oblique osteotomies of the metacarpal and internal fixation. The dorsal plate with lag screw was superior in all modes, followed by the two dorsal lag screws, crossed Kirschner wire tension banding, and intramedullary Kirschner wire fixation. The five intramedullary and the paired intramedullary Kirschner wire fixations were not statistically different. The fatigue life of the plate fixation was significantly larger in bending (1.5 times), torsion (1.6 times), and axial loading (2.5 times) than the second strongest fixation, two dorsal lag screws. Its initial rigidity was significantly higher in axial loading (1.5 times) but was not statistically different in bending and torsion.     

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.     

涉及髋臼四边体骨折的治疗体会

目的探讨采用髂腹股沟入路、Kocher-Langenbeck入路或联合入路切开复位骨盆重建钢板结合拉力螺钉内固定治疗涉及髋臼四边体骨折的临床疗效。方法自2006年5月至2011年4月我科治疗的24例涉及髋臼四边体骨折患者,其中男17例,女7例;年龄18～59岁,平均38.5岁。骨折按Letournel分类,后柱骨折2例,后柱伴后壁骨折2例,横形骨折3例,"T"形骨折3例,前柱伴后半横形骨折2例,双柱骨折12例。结果 24例均获得随访,时间6～36个月,平均21个月。临床疗效按照改良后的Modified d′Aubigne and Postel髋关节评分标准,优13例,良6例,可3例,差2例,优良率79.16%。结论髂腹股沟入路、Kocher-Langenbeck入路或联合入路骨盆重建钢板结合拉力螺钉内固定治疗髋臼四边体骨折,具有显露清楚、便于骨折复位、固定稳定、临床效果满意等优点,是治疗涉及髋臼四边体骨折合并股骨头中心脱位的有效方法。     

Comparison of two methods of screw fixation in periacetabular osteotomy

The optimal method of fixation during periacetabular osteotomy is unknown. Periacetabular osteotomies were created on both sides of six whole pelves from fresh cadavers and were fixed randomly either with three long 4.5-mm cortical screws from the iliac crest to the osteotomized fragment (iliac fixation) or with two such screws supplemented by a transverse screw from the acetabular segment to the ilium (transverse fixation). Pelvis loading in simulated push-off phase of the gait cycle was accomplished using a custom-made fixture. Linear potentiometers measured displacements at the pubic and ischial osteotomies. Fracture site stiffness was calculated from actuator force and pubic osteotomy displacement data. Displacement of the pubic osteotomy averaged 12.8 mm in the iliac fixation group and average 12.45 mm in the transverse group fixation. The ultimate loads beyond which catastrophic failure occurred were measured from 531.27 N to 1103.3 N (mean, 741.5 N) and 660.9 N to 1273.9 N (mean, 930.8 N), respectively. Effective stiffness ranged from 38.9 N/mm to 117 N/mm in the iliac fixation group (mean, 77.8 N/mm), and from 99 N/mm to 315 N/mm in the transverse construct (mean, 182 N/mm). Although the transverse screw provided statistically significantly greater local stiffness to the periacetabular construct fixation, neither type of fixation provided enough stability to allow immediate weightbearing after periacetabular osteotomy.     

Biomechanical testing of the LCP--how can stability in locked internal fixators be controlled?

New plating techniques, such as non-contact plates, have been introduced in acknowledgment of the importance of biological factors in internal fixation. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability, e.g. fracture motion, and the risk of implant failure can best be controlled. The results of a study based on in vitro experiments with composite bone cylinders and finite element analysis using the Locking Compression Plate (LCP) for diaphyseal fractures are presented and recommendations for clinical practice are given. Several factors were shown to influence stability both in compression and torsion. Axial stiffness and torsional rigidity was mainly influenced by the working length, e.g. the distance of the first screw to the fracture site. By omitting one screw hole on either side of the fracture, the construct became almost twice as flexible in both compression and torsion. The number of screws also significantly affected the stability, however, more than three screws per fragment did little to increase axial stiffness; nor did four screws increase torsional rigidity. The position of the third screw in the fragment significantly affected axial stiffness, but not torsional rigidity. The closer an additional screw is positioned towards the fracture gap, the stiffer the construct becomes under compression. The rigidity under torsional load was determined by the number of screws only. Another factor affecting construct stability was the distance of the plate to the bone. Increasing this distance resulted in decreased construct stability. Finally, a shorter plate with an equal number of screws caused a reduction in axial stiffness but not in torsional rigidity. Static compression tests showed that increasing the working length, e.g. omitting the screws immediately adjacent to the fracture on both sides, significantly diminished the load causing plastic deformation of the plate. If bone contact was not present at the fracture site due to comminution, a greater working length also led to earlier failure in dynamic loading tests. For simple fractures with a small fracture gap and bone contact under dynamic load, the number of cycles until failure was greater than one million for all tested constructs. Plate failures invariably occurred through the DCP hole where the highest von Mises stresses were found in the finite element analysis (FEA). This stress was reduced in constructions with bone contact by increasing the bridging length. On the other hand, additional screws increased the implant stress since higher loads were needed to achieve bone contact. Based on the present results, the following clinical recommendations can be made for the locked internal fixator in bridging technique as part of a minimally invasive percutaneous osteosynthesis (MIPO): for fractures of the lower extremity, two or three screws on either side of the fracture should be sufficient. For fractures of the humerus or forearm, three to four screws on either side should be used as rotational forces predominate in these bones. In simple fractures with a small interfragmentary gap, one or two holes should be omitted on each side of the fracture to initiate spontaneous fracture healing, including the generation of callus formations. In fractures with a large fracture gap such as comminuted fractures, we advise placement of the innermost screws as close as practicable to the fracture. Furthermore, the distance between the plate and the bone ought to be kept small and long plates should be used to provide sufficient axial stiffness.     

Comparison of metacarpal plating methods

PURPOSE: Most metacarpal fractures are stable and can be treated with nonsurgical stabilization. However, some metacarpal fractures are treated with open reduction and internal fixation because of an open fracture, instability, or multiple fractures. Newer plate designs have emerged that allow a shorter plate and screw construct. We sought to determine the relative strength of 3 different methods of metacarpal plating for unstable fractures. METHODS: We tested our hypothesis in a transverse metacarpal fracture model using fourth-generation, biomechanical testing grade composite sawbones (Sawbones; Pacific Research Laboratories, Vashon, WA). The metacarpals were divided into 3 groups of 15 bones. Group 1 was plated with a standard 6-hole, 2.3-mm plate with 6 nonlocking bicortical screws in standard AO fashion. Group 2 was plated with a 6-hole, double-row, 3-dimensional (3D) plate with 3 nonlocking screws on either side of the fracture aiming for convergence of the screws. Group 3 was plated with a 2.4-mm plate using 6 nonlocking screws and standard AO technique. The metacarpals were then tested to failure in cantilever bending mode. RESULTS: All constructs broke through the bone. No plate failure or screw pullout was seen. Group 1 had a load to failure of 264 N +/- 14. Group 2 had a load to failure of 302 N +/- 17. Group 3 had a load to failure of 274 N +/- 20. The load to failure was highest in group 2 (3D plate). All differences were statistically significant. CONCLUSIONS: All 3 methods produced a strong construct. The load to failure was highest in group 2 (3D plate). Double-row plates with converging screws provide adequate or superior strength of fixation when compared with standard plate constructs.