An improved traction system for fragile bones

The problems of transcutaneous tibial pins for skeletal traction in elderly patients are considered, and the reasons behind loosening of the pin are discussed. A novel method of skeletal traction using two pins is proposed.     

The Effect of Axial Tension on the Load Bearing Capacity of Traction Pins

Skeletal traction is often used in the conservative treatment of fractures. Although a small diameter traction pin causes less trauma, its use is limited by the strength of the pin and the holding power of the bone. Both theoretical analysis and in vitro experiments were conducted to investigate the bending resistance of traction pins subjected to an applied traction force. the results of this study indicate that thin K-wires could be used successfully as traction pins. Excessive bending of these wires could be prevented by applying tension. the possibility of a pin cutting through bone is minimal if the cortical bone structure of the patient is normal. However, further in vivo study is necessary to ascertain whether necrosis might occur due to excessive contact stress between the pin and the bone.     

The Effect of Axial Tension on the Load Bearing Capacity of Traction Pins

Skeletal traction is often used in the conservative treatment of fractures. Although a small diameter traction pin causes less trauma, its use is limited by the strength of the pin and the holding power of the bone. Both theoretical analysis and in vitro experiments were conducted to investigate the bending resistance of traction pins subjected to an applied traction force. the results of this study indicate that thin K-wires could be used successfully as traction pins. Excessive bending of these wires could be prevented by applying tension. the possibility of a pin cutting through bone is minimal if the cortical bone structure of the patient is normal. However, further in vivo study is necessary to ascertain whether necrosis might occur due to excessive contact stress between the pin and the bone.     

Fluid accumulation and the rapid spread of bacteria in the pathogenesis of external fixator pin track infection

An animal model was used to study the pathogenesis of pin track infection. The roles of fluid accumulation around the pin/bone interface and mechanical loosening of the pin were specifically studied. In addition, the spread of bacteria in relation to the clinical appearance of the pin track was assessed. This study demonstrated that fluid accumulation around the interface is an important factor in the spread of infection from the superficial wound track to the medulla of the bone. Spread occurs despite the absence of mechanical pin loosening, and can occur before any clinical features of infection are apparent.     

An <Emphasis Type="Italic">in Vivo</Emphasis> Experimental Comparison of Stainless Steel and Titanium Schanz Screws for External Fixation

Abstract Objective: To compare the clinical benefits of stainless steel (SS) to titanium (Ti) on reducing pin track irritation/infection and pin loosening during external fracture fixation. Methods: A tibial gap osteotomy was created in 17 sheep and stabilized with four Schanz screws of either SS or Ti and an external fixation frame. Over the 12 week observation period, pin loosening was assessed by grading the radiolucency around the pins and measuring the extraction torque on pin removal at sacrifice. Irritation/infection was assessed with weekly clinical pin track grading. A histological analysis of the tissue adjacent to the pin site was made to assess biocompatibility. Results: A statistically non-significant trend for less bone resorption around Ti pins was found during the early observation period. However, at sacrifice, there was no difference between the two materials. Also, there was no difference in the extraction torque, and there was similar remodeling and apposition of the bone around the pins. A statistically non-significant trend for more infection about SS pins at sacrifice was found. Histology showed a slightly higher prevalence of reactionary cells in SS samples, but was otherwise not much different than around Ti pins. Conclusions: There is no clinically relevant substantial advantage in using either SS or Ti pins on reducing pin loosening or pin track irritation/infection.     

Stiffness of small-bone external fixation methods: an experimental study

A variety of small-bone external fixation methods were evaluated to determine bending and torsional stiffness. Several methods of external pin stabilization with bone cement and with a commercial device were used. Among experimental variables examined were: the number of pins, pin diameter, pin length, pin spacing, and pin threading. The most rigid fixation was achieved with four pins held with a wire-reinforced bone cement fixator. Pin diameter was the most significant variable in the determination of stiffness with this configuration.     

Complications of halo fixation of the cervical spine

Halo fixators play an integral role in stabilizing the cervical spine. They are most widely used after upper cervical to midcervical spine fractures and dislocations and as a supplement to various surgical fixation techniques. Compared with supine cervical traction techniques, halo fixators allow early patient mobilization and shorten hospital stays. The incidence of halo-fixator complications remains high. Minor complications include pin loosening, localized infection, periorbital edema, superficial pressure sores, and unsightly scars. Major complications include pin penetration, osteomyelitis, subdural abscess, nerve palsies, fracture overdistraction, and persistent instability. Many of these potential complications can be avoided with proper pin placement and meticulous pin care.     

Induction and prevention of pin loosening in external fixation: an in vivo study on sheep tibiae.

In external fixation of fractures, pin loosening is a major concern. Preloading the pins is generally done to ensure their stability within the bone cortex. The effect of radial preload and bending preload in reducing resorption at the pin/bone interface was tested. Schanz screws were fixed to live sheep tibiae using a pneumatically operated external fixator frame. Evaluation was based on radiological observation and fluorochrome histology using sequential labels. Though not completely absent, bone resorption was minimal in the radial preload group, compared with the two other groups. More important, the bone-to-pin contact surface in the radial preload group was found to be almost intact after 5 weeks. In this study, radial preload appears to be superior to bending preload in terms of minimizing the problems of pin loosening.     

Anodic plasma chemical treatment of titanium Schanz screws reduces pin loosening

OBJECTIVE: This study was designed to assess the benefits of a new Anodic Plasma Chemical calcium-phosphate (APC-CaP) surface treatment on reducing pin track infection and pin loosening in comparison to anodized titanium (Ti) during external fracture fixation. METHODS: A tibial midshaft, transverse, 6-mm gap osteotomy was created in 17 adult female Swiss alpine sheep. The tibia was stabilized with an external fixator and 4 Schanz screws of Ti or APC-CaP-treated Ti. The sheep were examined during a 12-week observation period. Infection was assessed with weekly clinical pin track grading and microbiologic assessment at sacrifice. Pin loosening was assessed by grading for radiolucency on biweekly radiographs and by measuring extraction torque on pin removal. In vivo bending stiffness measurements were performed to determine gap healing. A qualitative histologic assessment of the tissue adjacent to pin sites was also performed. RESULTS: A trend (P = 0.056) for less infection around APC-CaP pins was found at 6 weeks, but the strength of this difference diminished with time. Significantly more radiolucency was found around Ti pins after 8 (P = 0.011) and 12 (P < 0.001) weeks. At all pin sites, the extraction torque for APC-CaP pins was higher than for Ti pins (P = 0.007). No difference in the progression of gap healing was found. Histology showed bone growth at the implant surface in the form of distance osteogenesis for Ti and contact osteogenesis for APC-CaP. CONCLUSIONS: This study has shown that the APC-CaP surface improves the clinical performance of Ti pins with respect to pin loosening and pin track infection.     

Heterotopic ossification of the quadriceps following distal femoral traction: a report of three cases and a review of the literature

SUMMARY: We present the previously unreported complication of symptomatic heterotopic ossification of the quadriceps following placement of a large-diameter Steinmann pin for the purpose of temporary skeletal traction. Following the development of distal quadriceps heterotopic bone formation in three patients, we conducted a comprehensive search of the literature using the Medline database from 1966 to the present. A variety of publications, including review articles, case reports, and randomized prospective studies, were used for the literature review. This potential complication should be considered when using a large-diameter Steinmann pin in the distal femur for skeletal traction.     

Bone properties affect loosening of half-pin external fixators at the pin-bone interface

IntroductionLocal bone yielding at the pin–bone interface of external fixation half-pins has been known to initiate fixator loosening. Deterioration of bone properties due to ageing and disease can lead to an increase in the risk of pin loosening. This study determines the extent, locations and mechanics of bone yielding for unilateral external fixation systems at the tibial midshaft with changes in age-related bone structure and properties. The study also evaluates the effect of the number of pins used in the fixation system and use of titanium pins (in place of steel) on bone yielding.MethodsWe employ nonlinear finite element (FE) simulations. Strain-based plasticity is used to simulate bone yielding within FE analyses. Our analyses also incorporate contact behaviour at pin–bone interfaces, orthotropic elasticity and periosteal–endosteal variation of bone properties.ResultsThe results show that peri-implant yielded bone volume increases by three times from young to old-aged cases. The use of three, rather than two half-pins (on either side of the fracture), reduces the volume of yielded bone by 80% in all age groups. The use of titanium half-pins resulted in approximately 60–65% greater volumes of yielded bone.ConclusionsWe successfully simulate half-pin loosening at the bone–implant interface which has been found to occur clinically. Yielding across the full cortical thickness may explain the poor performance of these devices for old-aged cases. The models are able to identify patients particularly at risk of half-pin loosening, who may benefit from alternative fixator configurations or techniques such as those using pre-tensioned fine wires.     

刻槽针内固定治疗股骨颈骨折生物力学研究与临床应用

目的：验证刻槽针治疗股骨颈骨折较普通斯氏针更具有锚固性，方法：通过生物力学试验，采用均质木块与牛股骨按骨折固定方式钉入直径4mm斯氏针与刻槽针，置弹簧拉力试验机上进行拔出力对比，并将刻槽针临床应用于50例股骨颈骨折的治疗，结果：斯氏针在木块上平均拔出力为10．2kg，刻槽针为21．00kg，为斯氏针的2倍，斯氏针在牛股骨上的平均拔出力为5．7kg,刻槽针为14．5kg，为斯氏针的2．45倍，刻槽针临床应用效果良好，结论：刻槽针治疗股骨颈骨折较斯氏针固定牢固，临床应用证实无脱针，折针发生。     

Thermal response and torque resistance of five cortical half-pins under simulated insertion technique

A model was developed that can quantitate heat generation during placement of half-pins in cortical bone. Five half-pins were tested to assess differences in insertion torque, heat generation, and microdamage at the pin-bone interface. Thin thermocouple probes were placed 0.5 mm from the track of the pin and within the pin to measure its temperature during insertion. Scanning electron microscopy was used to view the pin-bone interface to assess the microdamage during placement. The design of the tip of the pin influenced insertion torque and heat generation. Higher heat generation was measured when a thermocouple was placed within the pin itself and less was measured when thermocouple probes were placed within bone samples 0.5 mm from the impending pin track. Furthermore, insertion torque and thermal responses were related, but there were no significant differences in microdamage to bone when different pins and drilling/tapping techniques were used. Due to the significant heat generation at the pin-bone interface, proper cooling with saline irrigation should be applied during pin insertion regardless of the design of the pin. The microdamage observed at the surface of the pin track may have significant implications with regard to loosening of pins, but such effects must be studied with in vivo models.     

Halo Skeletal Fixation: Techniques of Application and Prevention of Complications

The halo skeletal fixator provides the most rigid cervical immobilization of all orthoses. However, complications such as pin loosening and infection are common. Appreciation of local anatomy and adherence to established application guidelines should minimize pin-related problems. A relatively safe zone for anterior pin placement is located 1 cm above the orbital rim and superior to the lateral two thirds of the orbit. Posterior pin-site locations are less critical; positioning on the posterolateral aspect of the skull, diagonal to the contralateral anterior pins, is generally desirable. Pins should enter the skull perpendicular to the cortex, with the ring or crown sitting below the widest portion of the skull and passing about 1 cm above the helix of the ear. Pins are inserted at a torque of 8 in-lb and retightened once to 8 in-lb at 48 hours. A loose pin can be retightened to 8 in-lb if resistance is met; otherwise, a loose pin should be replaced at a nearby site. Superficially infected pins are managed with local pin care and oral antibiotics. Persistent or severe infections require pin replacement to a nearby site, parenteral antibiotic therapy, and incision and drainage as needed. In-ability to maintain acceptable cervical reduction with a halo fixator is an indication for alternative treatment, such as internal fixation or traction.     

Does the cement mantle thickness influence the glenoid loosening in anatomic total shoulder arthroplasty? An experimental study

Background

Glenoid component loosening is the most frequent failure mode. Few data are available on the effect of thickness of cement on glenoid loosening. The purpose of this study is to determine if the cement mantle thickness influences the mode and localization of loosening. Our hypotheses are: 1) failure is caused by traction stresses generated within the cement mantle and 2) a thicker cement mantle amplifies the rocking horse effect.

应用自研弹性牵引支架治疗手指关节内骨折的疗效分析

目的：总结应用克氏针自制支架行弹性牵引治疗指骨关节内骨折的疗效。方法2014年2月至2015年2月,中国人民解放军第二六六医院骨科应用克氏针支架弹性牵引治疗52例（52指）指骨关节内骨折患者,随访并评估患者的术后恢复情况,观察有无断针、针道感染等并发症发生情况,采用中华医学会手外科学会手部肌腱修复后功能评价系统评价患指术后功能。结果所有患者骨折全部愈合,愈合时间为6~12周,平均为8周。术后无钢针断裂、松动及针道感染等并发症。按中华医学会手外科学会手部肌腱修复后功能评价系统评定手指功能,优25例（25指）,良22例（22指）,可5例（5指）,优良率为90.38%。结论应用克氏针支架弹性牵引治疗指骨关节内骨折具有微创、固定可靠、可早期锻炼、适用范围广泛等优点,为指骨关节内骨折的治疗提供了一种新的思路。     

生理盐水在儿童骨牵引针道护理中的应用研究

目的探讨生理盐水在儿童骨牵引针道护理应用的可行性。方法将2017年1月至2018年12月华中科技大学同济医学院附属武汉儿童医院小儿骨科收治的208例骨牵引患儿,根据入院时间段分为对照组(113例)和观察组(95例)。对照组使用75%乙醇对骨牵引针道进行常规护理(2次/d),观察组按需使用生理盐水对骨牵引针道进行护理。采用中文版儿童疼痛行为量表(FLACC)评估患儿针道护理时的疼痛情况,Checketts Otterburns感染分级系统评估患儿针道感染情况。结果针道护理时,观察组的FLACC评分为(1.58±0.71)分,优于对照组的(2.06±0.86)分,差异有统计学意义(t=4.280,P<0.001)。观察组发生针道Ⅰ度感染2例,感染发生率为2.11%(2/95);对照组发生针道Ⅰ度感染4例,Ⅲ度感染1例,感染发生率为4.42%(5/113);两组针道感染发生率比较,差异无统计学意义(Z=-1.15,P=0.248)。结论儿童骨牵引针道采用生理盐水按需护理,可预防针道感染发生,减轻针道护理时的疼痛刺激,提高患儿舒适度。     

The small pin circular fixator for distal tibial pilon fractures with soft tissue compromise

A Monticelli-Spinelli small pin circular external fixator was used in combination with closed reduction or a limited open reduction internal fixation in five cases in an attempt to salvage a satisfactory result in distal tibia pilon fractures when associated soft tissue compromise prevented standard fixation with plates and screws. The small pin fixator enhances the ability to perform a closed reduction through a technique that uses distraction with pins in the tibia and calcaneus, combined with correction of angulation by tensioning wires with a stop nut. Small pin stabilization of these comminuted fractures allows early patient mobilization. The small diameter pins support the soft cancellous bone fragments. This technique attempts to combine the benefits of traction, external fixation, and limited internal fixation. We recommend this technique as a salvage procedure when plates and screws are contraindicated because of poor bone and soft tissue conditions.     

The halo fixator

The halo fixator may be used for the definitive treatment of cervical spine trauma, preoperative reduction in the patient with spinal deformity, and adjunctive postoperative stabilization following cervical spine surgery. Halo fixation decreases cervical motion by 30% to 96%. Absolute contraindications include cranial fracture, infection, and severe soft-tissue injury at the proposed pin sites. Relative contraindications include severe chest trauma, obesity, advanced age, and a barrel-shaped chest. In children, a computed tomography scan of the head should be obtained before pin placement to determine cranial bone thickness. Complications of halo fixation include pin loosening, pin site infection, and skin breakdown. A concerning rate of life-threatening complications, such as respiratory distress, has been reported in elderly patients. Despite a paucity of contemporary data, recent retrospective studies have demonstrated acceptable results for halo fixation in managing some upper and lower cervical spine injuries.