The effect of screw type on the biomechanical properties of SCARF and crescentic osteotomies of the first metatarsal

The basilar crescentic osteotomy is a popular method for correcting moderate to severe hallux valgus. However, inadvertent dorsiflexion of the osteotomy can result from intraoperative malposition or from malunion after fixation failure. The mechanical properties of osteotomies are dependent on the nature of the osteotomy and the type of fixation. This study examines the mechanical properties of the SCARF and crescentic osteotomies of the first metatarsal by using a cannulated asymmetric pitched screw or AO cancellous screws. Sixteen human cadaveric first metatarsal specimens were tested in plantar to dorsiflexion cantilever bending by using a mechanical testing machine. The data was compared with our recent work on the mechanical properties of the SCARF and crescentic osteotomies. Ultimate load and stiffness of the SCARF osteotomy were superior to the crescentic osteotomy but were not dependent on screw type. Screw type was a prominent factor in the stiffness but not in the strength of the crescentic osteotomy. The ultimate load and the stiffness of SCARF osteotomy fixed with the cannulated asymmetric pitched screws were not significantly different compared with AO screws (ultimate load, 124.6 N [SD = 56.8] v 105.3 N [SD = 57.0]; stiffness, 52.0 N/mm [SD = 48.0] v 31.8 N/mm [SD = 19.0]). Modes of failure were fracture of the cortical bone bridge between the screw hole and the osteotomy in all crescentic osteotomies and fracture of the proximal dorsal bridge in all SCARF osteotomies. The superior mechanical properties of the SCARF osteotomy, fixed with cannulated asymmetric pitched screws, make this a more secure construct, with less risk of malunion than the crescentic osteotomy. Stiffness is an important mechanical factor that helps distinguish the mechanical performance of different osteotomy techniques.     

Analysis of Three Types of Fixation of the Weil Osteotomy

This study assessed 3 methods of fixation for the Weil osteotomy. A total of 40 bone models were divided equally into 4 groups: a control group consisting of intact lesser rays; and Weil osteotomies that were fixated with 2 crossed Kirschner wires (0.045-in K-wires), 2.0-mm cortical screws, or cannulated 2.4-mm cortical screws. Each specimen was stressed in a computer-controlled hydraulic tensile testing machine, and maximum load, energy to failure, and stiffness were recorded. The following mean load to failure measurements were found: control, 62.9 Newtons (N); K-wire, 22.9 N; cannulated screw, 31.3 N; and noncannulated screw, 19.9 N. There was no statistical difference among the 3 groups of fixation methods in terms of the maximum load. The mean energy to failure of the control group was 326 joule (J); K-wire, 79 J; cannulated screw, 163 J; and noncannulated screw, 66 J. The cannulated screw generated a statistically greater amount of energy at failure than the noncannulated screw (P < .05). The mean structural stiffness of the control group was 7.3 N/mm; K-wire, 2.8 N/mm; cannulated screw 3.3 N/mm; and noncannulated screw, 3.2 N/mm. There was no statistical difference in structural stiffness among the 3 groups of fixation methods. The results indicated a trend toward better biomechanical stability with the 2.4-mm cannulated screw than the 2.0-mm noncannulated screw for fixation of the Weil osteotomy.     

Biomechanical stability of bioabsorbable screws for fixation of acetabular osteotomies

The purpose of this study was to compare the biomechanical stability of triple innominate osteotomies fixed with either bioabsorbable or stainless steel screws. Triple innominate osteotomies were performed on composite hemipelves and fixed with either three 4.5-mm bioabsorbable screws or three stainless steel 4.5-mm screws. Two screws were placed from the iliac wing into the acetabular fragment, and 1 screw was placed from below the acetabular fragment into the iliac wing. Eight specimens for each screw type were biomechanically tested in an anatomical position (replicating weight bearing) and in a flexed and abducted position (replicating spica cast positioning). Specimens were cyclically loaded between 10 and 450 N to simulate the hip contact force in this population. Lower screws were then removed, and specimens were tested under identical conditions. Fragment displacement (mm) and construct stiffness (N/mm) were compared with a 2-way analysis of variance (P < 0.05). There were no significant differences between materials for fragment displacement or construct stiffness. Anatomical position showed significantly less displacement than spica position for both materials. Initial displacement in the spica position was significantly less during lower loads for stainless steel fixation. Bioabsorbable screws demonstrate comparable biomechanical stability to stainless steel screws in anatomical and spica positions at physiological loads. Flexion and abduction of the femur adversely affect the stability of the construct for both materials. Bioabsorbable screws behave similarly to steel screws when stabilizing triple innominate osteotomies and would have the advantage of not requiring a second surgery for screw removal. Confirmation of biocompatibility should be completed before widespread clinical application.     

Fixation of the offset V osteotomy: Mechanical testing of 4 constructs

The purpose of this study was to assess 4 methods of fixation for the offset V osteotomy. Maximum load, failure energy, and stiffness were determined in a control group and in 4 different test models. There were 10 specimens for each group. The control group consisted of intact first ray sawbones. An offset V osteotomy was performed on each specimen in each of the 4 test groups. The osteotomies were fixated either with two 2.0-mm cortical screws, two 2.7-mm cortical screws, two 3.5-mm cortical screws, or one 2.7-mm cortical screw and a 0.045-in Kirschner wire, respectively. Each model was then loaded to failure with a computerized hydraulic-tensile testing machine. Results for maximum load to failure for all 4 fixation constructs showed a mean ranging from 113.0 to 144.0 N, a mean energy to failure ranging from 272.2 to 365.0 J, and a mean stiffness ranging from 21.3 to 27.0 N/mm. There were no statistically significant differences detected among the individual constructs. In the group fixated with 3.5-mm screws, there were statistically significant differences in all 3 parameters compared with the control group. In the groups fixated with 2.7-mm screws, 2.0-mm screws, and the 2.7-mm screw and Kirschner wire, there were statistically significant differences in the maximum load and the failure energy, but not in stiffness, when compared with the control group. These findings suggest that all 4 constructs provide similar mechanical properties when utilized for the fixation of the offset V osteotomy.     

Comparison of Fixation Techniques in Oblique and Biplanar Chevron Medial Malleolar Osteotomies; a Finite Element Analysis

This study aimed to evaluate different fixation techniques and implants in oblique and biplanar chevron medial malleolar osteotomies using finite element analysis. Both oblique and biplanar chevron osteotomy models were created, and each osteotomy was fixed with 2 different screws (3.5 mm cortical screw and 4.0 mm malleolar screw) in 2 different configurations; (1) 2 perpendicular screws, and (2) an additional third transverse screw. Nine simulation scenarios were set up, including 8 osteotomy fixations and the intact ankle. A bodyweight of 810.44 N vertical loading was applied to simulate a single leg stand on a fixed ankle. Sliding, separation, frictional stress, contact pressures between the fragments were analyzed. Maximum sliding (58.347µm) was seen in oblique osteotomy fixed with 2 malleolar screws, and the minimum sliding (17.272 µm) was seen in chevron osteotomy fixed with 3 cortical screws. The maximum separation was seen in chevron osteotomy fixed with 2 malleolar screws, and the minimum separation was seen in oblique osteotomy fixed with 3 cortical screws. Maximum contact pressure and the frictional stress at the osteotomy plane were obtained in chevron osteotomy fixed with 3 cortical screws. The closest value to normal tibiotalar contact pressures was obtained in chevron osteotomy fixed with 3 cortical screws. This study revealed that cortical screws provided better stability compared to malleolar screws in each tested osteotomy and fixation configuration. The insertion of the third transverse screw decreased both sliding and separation. Biplanar chevron osteotomy fixed with 3 cortical screws was the most stable model.     

Coronal fractures of the distal femoral condyle: a biomechanical evaluation of four internal fixation constructs

This study evaluated different fixation methods in posterior femoral condyle coronal fractures. A standardised osteotomy was created in synthetic composite femurs and fixed with one of four methods (one 3.5 mm diameter screw, two 3.5 mm screws, one 6.5 mm screw, two 6.5 mm screws). The stiffness and mean loads to specified displacements were measured. The stiffness of two 6.5 mm screws was significantly greater than both single 3.5 mm screw (3567 versus 2584N/mm; p=0.0075) and double 3.5 mm screws (3567 versus 2080N/mm; p=0.003). There was no statistical difference in the stiffness of one 6.5 mm screw compared to either the single or double 3.5mm screws. Increasing the screw diameter and using two screws increased the load at 1, 2 and 3 mm of displacement. In the fixation of posterior femoral condyle fractures, two 6.5 mm screws are more rigid than either single or double 3.5 mm screws. The use of a second screw marginally increases the rigidity of fixation. If 3.5 mm screws are used in the fixation of posterior femoral condyle fractures, at least two screws should be used to approximate the biomechanical stability of a single 6.5 mm screw.     

髂骨不同置钉方式在腰-髂重建结构中稳定性的生物力学研究

目的 评价髂骨单枚短钉、单枚长钉和双枚短钉技术对腰-髂固定结构稳定性的生物力学影响.方法 7具成人新鲜尸体L_(2-)骨盆标本用于实验.于L_(3-5)间行椎弓根钉固定,并将该结构定义为本研究的完整状态.完整状念测试后,制作骶骨全切的失稳模型,并进行三种髂骨钉技术的L_(3-)髂骨间钉-棒稳定重建,A组:双侧单枚髂骨短钉;B组:双侧单枚髂骨长钉;C组:双侧双枚髂骨短钉.三种髂骨置钉技术均在同一标本上按随机顺序建立,短钉和长钉的长度分别为70 mm和130 mm.在MTS材料实验机上,给标本施加800 N压缩和7 N·m扭转载荷,记录L_(3-)髂骨间的结构刚度并比较.结果 A、B、C组的结构压缩刚度分别是完整状态的73%、76%和108%,A组与B组间差异无统计学意义(P>0.05),然而A和B组的结构压缩刚度低于完整状态和C组,差异有统计学意义(P<0.05). A、B、C组的结构扭转刚度分别占初始状态的72%、79%和109%,A、B两组间、完整状态与C组间差异均无统计学意义(P>0.05);但是,A、B组的结构扭转刚度低于完整状态和C组,差异有统计学意义(P<0.05).结论骶骨完全切除后,单枚髂骨长钉难以恢复局部的初始稳定性,双侧双枚髂骨短钉在抗压缩和扭转方面均显著高于双侧单枚髂骨钉结构,并且可获得与初始状态同等的稳定性.     

髂骨双钉在腰-髂重建结构中的生物力学优势

目的 评价髂骨单钉与髂骨双钉技术对腰-髂重建结构稳定性的影响.方法 7具成人新鲜尸体L2-骨盆标本,于L3-L5行椎弓根钉固定,将该结构定义为完整状态.对完整状态进行测试后制作骶骨全切失稳模型,每一标本均应用四种髂骨钉技术行L3-髂骨钉-棒稳定重建:A组,髂骨单枚短钉;B组,髂骨单枚长钉;C组,置入髂骨上、下柱的髂骨双枚短钉;D组,置入髂骨下柱的髂骨双枚短钉.髂骨钉的安装及测试顺序随机产生.在MTS材料试验机上,对标本施加800 N压缩和7 N·m扭转载荷,记录L3-髂骨的结构刚度.结果 (1)轴向压缩下,四组的压缩刚度依次为完整状态的73%、76%、98%和112%,A组和B组低于完整状态及C组和D组(P<0.05).其中A组与B组差异无统计学意义,D组与C组差异有统计学意义(P<0.05).(2)在扭转测试中,四组的扭转刚度依次为完整状态的72%、79%、105%和109%,A组和B组低于其他三组(P<0.05).其中A组与B组,完整状态、C组与D组间的差异无统计学意义.结论 对骶骨完全切除所导致的失稳,单枚髂骨短钉与长钉均难以恢复局部的初始稳定性;而双枚髂骨短钉在抗压缩与抗扭转能力方面均高于单枚髂骨钉,可获得与初始状态等同的稳定性.     

Biomechanical advantages of dual over single iliac screws in lumbo-iliac fixation construct

The development of iliac screws has provided a markedly easier way for spino-pelvic instrumentation than the classical Galveston technique. However, high rates of iliac screw loosening and breakage are usually reported, especially in cases where bilateral single iliac screws are used. Therefore, there is a need for exploring more stable iliac fixation techniques. Thus, the objective of this study was to compare the biomechanical effects of bilateral single and dual iliac screws on the stability of L3-iliac fixation construct under total sacrectomy condition. In this study, L2-pelvic specimens were harvested from seven fresh human cadavers. After biomechanically testing the intact state simulated by L3-L5 pedicle screw fixation, destabilization was introduced by total sacrectomy. Upon destabilization, L3-iliac screw-rod reconstructions were performed by four different techniques as follows: (1) bilateral single short iliac screws (Single-Short); (2) bilateral single long iliac screws (Single-Long); (3) bilateral dual short iliac screws, placed in the upper and lower iliac columns (Dual-UL); and (4) bilateral dual short iliac screws, all placed in the lower iliac column (Dual-Lower). These four iliac screw fixation techniques were sequentially preformed in the same specimen, and the lengths of the short and long iliac screws were 70 and 130 mm, respectively. Biomechanical testing was performed on a material testing machine under 800 N compression and 7 Nm torsion loading modes to evaluate the construct stiffness. In compression, the stiffness of the L3-iliac fixation constructs of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 73, 76, 98, and 108% of the intact state, respectively. No significant differences were detected between Single-Short and Single-Long (P = 0.589) techniques. However, the compressive stiffness of these two techniques was significantly lower than the intact state, and the Dual-UL and Dual-Lower techniques (P < 0.05). There was no statistical difference between the intact condition and the Dual-Lower technique (P = 0.109). Interestingly, Dual-Lower exhibited notably higher compressive stiffness than Dual-UL (+10.3%, P = 0.049). In torsion, the stiffness of Single-Short, Single-Long, Dual-UL, and Dual-Lower techniques were 72, 79, 105, and 109% of the intact condition, respectively. No significant differences were detected between Single-Short and Single-Long techniques (P = 0.338), and also among Dual-UL, Dual-lower techniques, and the intact state (P > 0.05). However, Single-Short and Single-Long techniques provided markedly lower construct torsional stiffness than the other three groups (P < 0.05). For lumbo-illiac reconstruction after total sacrectomy, even the use of bilateral single, long iliac screws do not help in restoring the local stability to the intact condition. However, dual iliac screws provide much higher construct stability than single iliac screw techniques. Therefore, dual iliac screw technique should be preferred for treating the unstable situation caused by total sacrectomy.     

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。     

Stoppa入路在髋关节发育不良髋臼周围截骨术中的应用

 目的 探讨Stoppa入路联合髂嵴切口应用于髋关节发育不良髋臼周围截骨术的安全性及有效性。方法2011年9月至2012年7月接受髋臼周围截骨术中应用Stoppa入路的髋关节发育不良患者18例20髋,女15例17髋,男3例3髋。患者年龄19~35岁,平均29岁。手术切口采用腹部横切口（即Stoppa入路）联合髂嵴切口（髂腹股沟入路的外侧窗）。记录手术时间、切口长度、术中出血量和异体血输血量,术后12个月门诊随访时评估髋关节功能、影像学征象和手术相关并发症。结果 手术时间125~180 min,平均145 min。Stoppa入路腹部横切口长5~10 cm,平均7 cm;髂嵴切口长4~8 cm,平均6 cm;切口总长度为12~16 cm,平均13 cm。术中出血量为500~1 600 ml,平均800 ml;异体血输血量为400~2 400 ml,平均1 161 ml。术后随访14~22个月,平均19.6个月。Harris髋关节评分由术前（80.3±8.5）分改善至术后12个月时（93.5±5.2）分,平均改善（13.2±6.0）分;中心边缘角由术前7.5°±5.4°改善至30.0°±4.6°,平均改善22.5°±4.5°。手术前后Harris髋关节评分与中心边缘角的差异均有统计学意义。全部截骨均愈合,愈合时间3~6个月,平均3.3个月。2髋耻骨支截骨延迟至术后6个月愈合。3例术后出现一过性股外侧皮神经麻痹,未予特殊处理。结论 Stoppa入路联合髂嵴切口能够安全有效地完成髋臼周围截骨术,可以代替传统的髂腹股沟入路用于无须髋关节探查的轻度髋关节发育不良患者。     

Plating of metacarpal fractures: unicortical or bicortical screws?

Mid-shaft transverse osteotomies were performed in 18 cadaveric metacarpals and randomly divided into two groups. Using dorsally applied plates for repair, one group was secured using 6mm unicortical screws, while bicortical screws were used in the second group. The metacarpals were tested to failure with a four-point bending protocol using a servo-hydraulic testing machine and a 1kN load cell. The mean load to failure was 596N (SD=142) for the unicortical and 541N (SD=171) for the bicortical group. The stiffness was 333N/mm (SD=116) for the unicortical and 458N/mm (SD=158) for the bicortical group. Both load to failure and stiffness were not statistically significant between the two groups. Failure occurred by fracture at the screw-bone interface in all specimens: no screw pull-out was observed. No biomechanical advantage was found when using bicortical screws in metacarpal fracture plating.     

Biomechanical comparison of a 2 and 3 proximal screw-configured antegrade piriformis intramedullary nail with a trochanteric reconstruction nail in an unstable subtrochanteric fracture model

OBJECTIVE: The objective of this study was to test the stiffness and ultimate load to failure of new intramedullary (IM) nail proximal screw configurations as compared to a trochanteric reconstruction nail. METHODS: Twenty-one synthetic composite femurs were mounted on a Material Testing System and tested in axial compression 5 times. The femurs had an 1 of 2 IM nail types inserted with 1 of 3 proximal screw configurations: a 3-screw configuration with 2 transverse screws and a screw angled into the femoral neck; a 2-screw design with a single transverse screw and a single screw angled into the femoral neck; 2 parallel screws angled into the femoral neck. There were 7 specimens in each group. An unstable fracture (OTA/AO 32-C3.2) was created. and the stiffness of these constructs was tested in compression 5 times. Each construct was then loaded to failure in compression. RESULTS: The 3-screw construct provided more axial stiffness (214 N/mm +/- 75) than either the 2-screw construct (123 N/mm +/- 32) or the trochanteric reconstruction nail (127 N/mm +/- 21) (P = 0.017 and 0.035 for 3-screw vs. 2-screw and recon respectively, P = 0.45 for 2-screw vs. recon). Load-to-failure testing demonstrated similarity among the different screw configurations (3-screw = 2230 N +/- 265, 2-screw = 2283 N +/- 260, Reconstruction nail = 2121 N +/- 156) (P = 1.0 all groups). CONCLUSIONS: The proximal 3-screw configuration provided more stiffness than either the 2-screw configuration or trochanteric reconstruction nail. The 2-screw configuration performed equally to a standard trochanteric reconstruction nail in stiffness testing. The ultimate loads to failure for the 3 tested constructs were not significantly different.     

髂骨钉置入深度对腰椎-骨盆重建结构的生物力学影响

目的 比较髂骨长钉和短钉对腰椎-骨盆重建结构的生物力学影响.方法 7具成年防腐尸体L3-骨盆标本用于实验.使用脊柱椎弓根钉后路系统对L4-S1椎间活动度进行固定,并将这一状态定义为骶髂关节完整状态.完整状态测试后,将骶骨全部切除,联合髂骨钉行L4-L5-骨盆的稳定重建.根据髂骨钉置入长度顺序分为短钉组和长钉组.其中短钉长度定义为过坐骨切迹水平2 mm,长钉长度定义为穿透髂前下棘前方皮质2 mm.在858型MTS材料实验机上,给标本施加800N轴向压缩和7 Nm轴向旋转载荷后,行髂骨钉轴向拔出实验,记录压缩和旋转刚度、最大拔出力,并加以分析.结果 髂骨短钉和长钉的置入长度分别为(70±2)mm和(138±4)mm.髂骨短钉和长钉的重建结构,在压缩实验中分别获得脊柱.骨盆间初始刚度的53.3%±13.6%和57.6%±16.2%;在旋转实验中,分别恢复脊柱-骨盆间初始刚度的55.1%±11.9%和62.5%±9.2%;长钉和短钉结构间的压缩和旋转刚度均无显著差异(P>0.05);但是,两者的轴向压缩及旋转刚度均显著低于完整状态组(P<0.05).髂骨长钉的最大拔出力显著高于髂骨短钉(P<0.05).结论 在生理载荷下,髂骨短钉的脊柱-骨盆重建结构可获得与髂骨长钉同等的力学稳定性;髂骨短钉的置入深度仅为长钉的一半,可降低置入的风险.但是,无论髂骨长钉或短钉的脊柱.骨盆重建装置均难以恢复局部的初始稳定性.     

Angulated screw placement in the lateral condylar buttress plate for supracondylar femoral fractures

Certain supracondylar femoral fractures are not amenable to internal fixation with fixed angle devices. In these instances, the condylar buttress plate is the recommended alternative; however, this is a less rigid device. Because of the decreased rigidity and strength of this device, there is a tendency toward varus angulation and malunion. In six fresh-frozen human knee specimens, segmental osteotomies were created to mimic supracondylar femoral fractures. The medial cortex was completely removed to make the fracture unstable to varus deformity. The fracture was fixed with a lateral condylar buttress plate using 4.5 mm screws. Each specimen was tested once with all the screws installed perpendicular to the plate, and again with the middle screw, just proximal to the fracture, angled 45 degrees diagonally across the fracture into the subchondral bone of the medial femoral condyle. For the construct with all screws placed perpendicular to the buttress plate, the initial stiffness was 410 N/mm, and after 1000 cycles it was 230 N/mm. With a screw placed diagonally across the fracture site, stiffness increased to 833 N/mm on the first cycle, and 796 N/mm after 1000 cycles. In all specimens with the screws placed perpendicular to the plate, the distal fragment had a permanent varus deformity after 1000 cycles, under no load, of 0.91 mm. For the diagonal screw condition, the average magnitude for all six specimens was 0.42 mm. This simple means of screw angulation in the plate strengthened the overall construct to resist the tendency toward varus deformity. The attractive features include the ease of application, and the use of an existing construct.     

Mechanical comparison of two types of fixation for proximal first metatarsal crescentic osteotomy

BACKGROUND: The proximal crescentic osteotomy is an effective technique for correcting a widened 1-2 intermetatarsal angle associated with moderate to severe hallux valgus deformities. However, postoperative dorsal malunion at the osteotomy site from loss of fixation has been reported. The purpose of this study was to evaluate the biomechanical characteristics of a new custom-designed plate and compare it to the traditional screw and Kirschner wire construct. METHODS: Twenty identical Sawbone (Pacific Research Laboratories, Vashon, WA) models were used for the study. A proximal crescentic osteotomy was done on each specimen, and 10 were secured with a dorsomedial plate (group I). The remaining 10 models were fixed with a screw and Kirschner wire combination (group II). Physiologic cyclical testing was done using a mechanical testing machine to evaluate dorsal displacement of the metatarsal. Load-to-failure testing was then done on each specimen to evaluate ultimate failure and stiffness of the constructs. Groups I and II were statistically compared using paired t-testing. RESULTS: The mean dorsal displacement of the first metatarsal head after 1000 cycles was 0.19 mm (SD = 0.09 mm) for group I and 0.28 mm (SD = 0.15) for group II, and the difference was not statistically significant (p = 0.08). Group I demonstrated statistically superior ultimate failure strength (95.2 N) and stiffness (26.8 N/mm) compared to group II (73.7 N, 19.4 N/mm). CONCLUSIONS: Based on Sawbone models, dorsal plate fixation of proximal crescentic osteotomy provides a stronger construct than the traditional screw and Kirschner wire construct. The clinical use of the specially-designed plate described in this study may lower the incidence of dorsal malunions that occur postoperatively and may decrease the occurrence of transfer metatarsalgia. Its application may be particularly helpful in patients with poor bone quality.     

Biomechanical Comparison of Internal Fixation Techniques for the Akin Osteotomy of the Proximal Phalanx

The Akin osteotomy is performed at the proximal phalanx for correction of an abducted great toe in a hallux abducto valgus deformity. Several internal fixation techniques have been widely advocated; however, their respective stabilities have not been compared. A biomechanical analysis was performed comparing 5 commonly used fixation techniques for the Akin osteotomy to determine the strongest method in simulated weightbearing in sawbone models. An Akin osteotomy was uniformly performed on 25 sawbones and fixated with 5 different internal fixation types, including a 2-hole locking plate and locking screws, a heat-sensitive memory staple (8 mm × 8 mm), a 28-gauge monofilament wire, 2.7-mm bicortical screws, and crossed 0.062-in. Kirschner wires. The results of simulated weightbearing load to failure rates with an Instron compression device demonstrated the following mean load to failures: crossed Kirschner wire, 57.05 N; 2-hole locking plate, 36.49 N; monofilament wire, 35.69 N; heat-sensitive memory staple, 34.32 N; and 2.7-mm bicortical screw, 13.66 N. Statistical analysis demonstrated the crossed Kirschner wire technique performed significantly better than the other fixation techniques (p < .007); the 4 other techniques were found not to be significantly different statistically (p = .041) from each another. Our study results suggest a crossing Kirschner wire construct significantly increases the stability of the Akin osteotomy in a sawbone model. This might be clinically extrapolated in an effort to improve patient outcomes because these osteotomies can undergo nonunion and malunion, resulting in postoperative pain and swelling.     

A comparison of the fixation stability of multiple screw constructs for two types of pelvic osteotomies

Periacetabular osteotomies are performed to improve femoral head coverage in a variety of clinical conditions. The stability of the osteotomy fragment between Ganz's periacetabular osteotomy was compared with that of Tonnis's triple innominate osteotomy under simulated weight-bearing conditions with a variety of screw constructs using three-dimensional analysis of fragment displacement and angular rotation. Generally, small amounts of displacement (<2 mm) and angular rotation (<3 degrees) were encountered for each fixation technique. Because the Ganz procedure violates the triradiate cartilage, it is not feasible in the immature patient. Thus, an understanding of fixation requirements in other available osteotomies to maintain fragment position is necessary.     

Periazetabuläre Osteotomie zur Behandlung der Hüftgelenkdysplasie unter Verwendung eines ilioinguinalen Zugangs

Objective

Three-dimensional osteotomy around the acetabulum in order to restore coverage of the femoral head without compromising pelvic stability and to alleviate pain.

Indications

Painful hip dysplasia in young patients with poor coverage of the femoral head.

Contraindications

Open epiphyseal plates. Lack of congruency between femoral head and acetabulum. Advanced osteoarthritis. Flexion < 90°.

Surgical Technique

Ilioinguinal incision according to Letournel. Three osteotomies. First osteotomy: superior pubic ramus. Second osteotomy, first step: iliac cut from midpoint between anterior superior and anterior inferior iliac spine to 1 cm above the pelvic brim; second step: iliac cut at an angle of 110–120° to first step aiming at the ischial spine 4 cm below the pelvic brim. Third osteotomy, first step: anterior ischial osteotomy beneath the acetabulum; second step: ischial osteotomy from the lower end of the second osteotomy (second step) to the already created anterior ischial osteotomy. The orientation of the acetabulum is changed to the desired position with help of a Schanz screw, temporary fixation with Kirschner wires. Image intensifier control. Fixation of fragment with three 3.5-mm cortical screws.

Results

From 1994 until 2001, 32 periacetabular osteotomies in 31 patients were performed. 28 patients had a follow-up for ≥ 1 year. 27 of 28 patients were satisfied at follow-up. The unsatisfied patient suffered from severe pain due to a partial lesion of the sciatic nerve. One hip has been converted to total hip arthroplasty 7 years later. No intraoperative injury to large vessels, no thromboembolic complication. No accidental osteotomy into the hip.     

Transverse displacement of the proximal segment after bilateral sagittal osteotomy: a comparison of lag screw fixation versus miniplates with monocortical screw technique.

PURPOSE: The purpose of the present study was to compare lag screw fixation versus miniplates with monocortical screw technique with respect to the amount of transverse displacement of the proximal segment after bilateral sagittal osteotomy (BSO) for mandibular advancement surgery. PATIENTS AND METHODS: We conducted a multicenter, retrospective investigation of 82 patients who underwent a mandibular advancement with BSO and rigid internal fixation. Forty-five patients from Denmark and Sweden, the miniplate fixation group, received a rigid fixation consisting of miniplates with monocortical screws. Thirty-seven patients from the Mayo Clinic, the lag screw fixation group, received a rigid fixation with lag screw fixation of the mandible. The transverse displacement and angulation of the proximal segments were measured on posterior-anterior cephalometric radiographs, using the best-fit method. RESULTS: After BSO, 44 of 45 patients in the miniplate fixation group showed an increased transverse intergonion distance with a mean of 5.0 mm and an increase transverse interramus width with a mean of 2.4 mm. Thirty-six of 37 patients in the lag screw fixation group had an increased intergonial width with a mean of 5.6 mm, and 35 of 37 patients showed an increased transverse interramus width with a mean of 3.3 mm. t tests showed that there were no significant differences between the 2 groups with respect to these 2 variables. CONCLUSIONS: Our results indicate that transverse displacements of the proximal segments occur after BSO surgery with both miniplate or lag screw fixation technique. Attention and future studies should focus on possible complications that transverse displacement of the proximal segment may cause.