Spread of infection, in an animal model, after intramedullary nailing of an infected external fixator pin track

In-vitro external fixation pin-site model proof of concept: A novel approach to studying wound healing in transcutaneous implants

External fixation is an essential surgical technique for treating trauma, limb lengthening and deformity correction, however infection is common, with infection rates ranging from 4.5 to 100% of cases. Throughout the literature researchers and clinicians have highlighted a relationship between excessive movement of the pin and skin and an increase in the patient's risk of infection, however, currently no studies have addressed this role of pin-movement on pin-site wounds. This preliminary study describes a novel in vitro pin-site model, developed using a full-thickness human skin equivalent (HSE) model in conjunction with a bespoke mechanical system which simulates pin-movement. The effect of pin-movement on the wound healing response of the skin equivalents was assessed by measuring the expression of pro-inflammatory cytokines. Six human skin equivalent models were divided into three test groups: no pin as the control, static pin-site wound and dynamic pin-site wound (n = 3). On day 3 concentrations of IL-1α and IL-8 showed a significant increase compared to the control when a static fixation pin was implanted into the skin equivalent (p < 0.05) and (p < 0.005) respectively. Levels of IL-1α and IL-8 increased further in the dynamic sample compared to the static sample (p < 0.05) and (p < 0.0005). This study demonstrates for the first time the application of HSE model to study external-fixation pin-movement in vitro. The results of this study demonstrated pin-movement has a negative effect on soft-tissue wound-healing, supporting the anecdotal evidence reported in the literature, however further analysis of wound heading would be required to verify this hypothesis.

The potential of sheep in preclinical models for bone infection research - A systematic review

Background

Reliable animal models are critical for preclinical research and should closely mimic the disease. With respect to route of infection, pathogenic agent, disease progression, clinical signs, and histopathological changes. Sheep have similar bone micro- and macrostructure as well as comparable biomechanical characteristics to humans. Their use in bone research is established, however their use in bone infection research is limited. This systematic review will summarise the key features of the available bone infection models using sheep, providing a reference for further development, validation, and application.

Method

This systematic review was designed according to the PRISMA guidelines and registered with PROSPERO. Quality was assessed using SYRICLE's risk of bias tool adapted for animal studies. PubMed, MEDLINE, Web of Science and EMBASE were searched until March 2022.1921 articles were screened by two independent reviewers, and 25 were included for analysis.

Results

Models have been developed in nine different breeds. Staphylococcus aureus was used in the majority of models, typically inoculating 108 colony forming units in tibial or femoral cortical defects. Infection was established with either planktonic or biofilm adherent bacteria, with or without foreign material implanted. Most studies used both radiological and microbiological analyses to confirm osteomyelitis.

Conclusions

There is convincing evidence supporting the use of sheep in bone infection models of clinical disease. The majority of sheep studied demonstrated convincing osteomyelitis and tolerated the infection with minimal complications. Furthermore, the advantages of comparable biology and biomechanics may increase the success for translating in vivo results to successful therapies.

The Translational potential of this article

In the realm of preclinical research, the translation to viable clinical therapies is often perilous, and the quest for reliable and representative animal models remains paramount. This systematic review accentuates the largely untapped potential of sheep as large animal models, especially in bone infection research. The anatomical and biomechanical parallels between sheep and human bone structures position sheep as an invaluable asset for studying osteomyelitis and periprosthetic joint infection. This comprehensive exploration of the literature demonstrates the robustness and translational promise of these models. Furthermore, this article underscores the potential applicability for sheep in developing effective therapeutic strategies for human bone infections.

Vancomycin-Loaded, Nanohydroxyapatite-Based Scaffold for Osteomyelitis Treatment: In Vivo Rabbit Toxicological Tests and In Vivo Efficacy Tests in a Sheep Model

The treatment for osteomyelitis consists of surgical debridement, filling of the dead space, soft tissue coverage, and intravenous administration of antimicrobial (AM) agents for long periods. Biomaterials for local delivery of AM agents, while providing controllable antibiotic release rates and simultaneously acting as a bone scaffold, may be a valuable alternative; thus, avoiding systemic AM side effects. V-HEPHAPC is a heparinized nanohydroxyapatite (nHA)/collagen biocomposite loaded with vancomycin that has been previously studied and tested in vitro. It enables a vancomycin-releasing profile with an intense initial burst, followed by a sustained release with concentrations above the Minimum Inhibitory Concentration (MIC) for MRSA. In vitro results have also shown that cellular viability is not compromised, suggesting that V-HEPHAPC granules may be a promising alternative device for the treatment of osteomyelitis. In the present study, V-HEPHAPC (HEPHAPC with vancomycin) granules were used as a vancomycin carrier to treat MRSA osteomyelitis. First, in vivo Good Laboratory Practice (GLP) toxicological tests were performed in a rabbit model, assuring that HEPHAPC and V-HEPHAPC have no relevant side effects. Second, V-HEPHAPC proved to be an efficient drug carrier and bone substitute to control MRSA infection and simultaneously reconstruct the bone cavity in a sheep model.

Conventional bicortical pin substitution with a novel unicortical pin in external fixation: A biomechanical study

INTRODUCTION

As most patients with polytrauma or open fractures are converted from temporary external fixation to definite stabilization, the prevention of complications such as infection is especially important. To overcome the high risk of infection associated with the use of the conventional bicortical pin for temporary external fixation, the authors developed a novel unicortical pin and analyzed it in a biomechanical study.

METHODS

The unicortical pin consisted of an inner screw, purchasing the cortical bone, and an outer sleeve with 6 spikes. A bicortical pin was used for the purpose of comparison. A fracture gap model was stabilized using a monoplanar configuration. Both the unicortical pins (Uni group) and bicortical pins (Bi group) underwent axial compressive and torsional load testing using a servo-hydraulic testing machine. Stiffness, load to failure, and mode of failure were documented.

RESULTS

Stiffness and load to failure of the Uni group (average, 40.5 N/mm and 1098.4 N, respectively) were greater than that of the Bi group (average, 33.7 N/mm and 968.6 N, respectively) in the axial compressive load test (P = 0.008 and 0.032). Stiffness and load to failure of the Uni group (average, 1.2 Nm/degree and 1.7 Nm, respectively) were also significantly higher than those of the Bi group (average, 0.8 Nm/degree and 0.6 Nm, respectively) in the torsional load test (P = 0.008 and 0.016). All pins in the Bi group were bent at the pin-synthetic bone interface without synthetic bone failure. Contrarily, the Uni group did not show any pin bending or failure. However, in the axial compression test, partial cracks in the synthetic bone were found at the interface with spikes in the outer shell. In addition, in the torsion test, incomplete fractures were seen through the inner screws' holes.

CONCLUSION

Compared with the conventional bicortical pin, the newly designed unicortical pin significantly increased fracture stability under both axial compressive and torsional loads. The unicortical pin can be considered an alternative biomechanical solution to obtain adequate stability when performing external fixation of fractures.

Establishment of a localized acute implant-associated Staphylococcus aureus bone infection model in sheep

Orthopedic implant-associated bacterial infections with Staphylococcus aureus constitute a major clinical problem, and large pre-clinical animal models remain scarce. The aim of this study was to establish a standardized method of a localized, acute S. aureus bone infection in the presence of complex implanted devices in a sheep model. Four sheep underwent surgery receiving a complex implanted metallic device with a component stabilizing a bone defect created in the left tibial metaphysis, and an attached component placed in adjacent soft tissue. The bone defect was inoculated with S. aureus strain ATCC25293 (1 × 104 CFU). Twenty one days later, the surgery site was macroscopically evaluated, tissue samples and implants harvested for bacterial cell count quantification and tissue samples histologically analyzed. The animals exhibited clinical signs of localized infection (e.g. swelling, lameness, pain) but did not develop symptoms of sepsis. After euthanasia, macroscopic assessment revealed a localized bone and soft tissue infection at the surgery site. Histologically, an acute inflammation with neutrophils but also signs of bone destruction with necrosis was noted. An ovine model of a localized, acute S. aureus bone infection with complex implants was successfully established and could be used to test novel treatments against orthopedic implant-associated infections.

Experimental reproduction of periprosthetic joint infection: Developing a representative animal model

BACKGROUND

Infection after arthroplasty (prosthetic joint infection; PJI) is a devastating complication that can lead to functional loss of the affected limb. The purpose of the present study is to develop an animal model of PJI using a three-dimensional printed species-specific implant, which is a step forward for future research to develop new therapeutic strategies.

METHODS

Fifteen New Zealand White rabbits were employed to reproduce PJI by intra-articular inoculation of 10⁵ cfu/ml of Staphylococcus aureus ATCC® 29213. Three-dimensional printing technology was used to design a species-specific four-millimeter-thick implant maintaining the anatomical irregularities of the tibial-articular surface. Response to bacterial inoculation was monitored by clinical (weight and temperature), hematological (leukocyte, lymphocyte and platelet counts) and biochemical (erythrocyte sedimentation rate) analyses at the time of inoculation and seven days thereafter, when microbiological samples for culture were also taken.

RESULTS

All animals recovered from surgery and all displayed full weight-bearing four days postoperatively. Fourteen of the 15 tested animals (93.3%) presented positive microbiological cultures. A statistically significant increase was found in the number of platelets and leukocytes, as well as a significant decrease in the percentage of lymphocytes, with P = 0.0001 in all cases.

CONCLUSIONS

An experimental model faithfully reproducing the periprosthetic infection environment and achieving a high rate of infection has been designed. The use of three-dimensional printed species-specific implants allows rapid postoperative recovery of animals and the development of a stable biofilm. These characteristics make it an interesting model to study its pathogenesis and possible therapeutic strategies.

Is the proximity of external fixator pins to eventual definitive fixation implants related to the risk of deep infection in the staged management of tibial pilon fractures?

INTRODUCTION

In the staged management of tibial pilon fractures, overlap between definitive internal fixation and external fixation pin sites has been investigated as a risk factor for infection with equivocal conclusions. Our aim was to determine if overlap or proximity of definitive internal fixation to external fixation pin sites influences the risk of deep infection.

PATIENTS AND METHODS

We reviewed 280 AO/OTA 43B or 43C type distal tibia fractures in 277 patients at two level-one trauma centers. Patients underwent staged management using early temporizing external fixation followed by definitive open reduction and plate fixation. Primary outcome was the association between pin site overlap and the development of deep infection. Secondary outcome was the relationship between development of deep infection and the distance from pin site to definitive fixation.

RESULTS

The average duration between external fixation and definitive internal fixation was 14 days. 24% of fractures developed deep infection requiring surgical intervention. There was no association between pin site overlap and the development of deep infection (p = 0.18). There was no relationship between infection and the distance between proximal plate extent and pin site (p = 0.13).

DISCUSSION

We identified no association between pin site overlap and the development of deep infection. We suggest that temporizing external fixation pins should be placed so as to obtain optimal stability of the construct with lesser emphasis on aiming to be absolutely outside the zone of future fixation.

LEVEL OF EVIDENCE

Level III Therapeutic Retrospective Comparative study.

3D printing in experimental orthopaedic surgery: do it yourself

INTRODUCTION

Periprosthetic infection is considered an increasing incidence pathology whose therapeutic strategies can be defined as unsatisfactory. Currently, animal models are employed to study its physiopathology and strategic therapies, but non-species-specific materials are implanted as foreign bodies. The use of these implants implies intrinsic instability, which hinders the development of a biofilm on their surfaces and complicates the post-operative recovery of the animal. The objective of the present study is the design of a species-specific implant for the New Zealand white (NZW) rabbit by means of 3D printing.

MATERIALS AND METHODS

A CT scan of the knee of a NZW rabbit was performed, and the tibial surface was reconstructed in order to fabricate a species-specific tibial plateau using Horos^® and Autodesk^® Meshmixer™ software. This implant was inserted in fifteen NZW rabbits, and the assessment of its stability was based on the position of the limb at rest and the animal weight-bearing capacity. Biofilm formation on the surface was demonstrated by crystal violet staining.

RESULTS

A 1.81 cm × 1 cm × 1.24 cm stainless steel implant was designed. It consisted of a 4-mm-thick tibial plate with a rough surface and an eccentric metaphyseal anchoring. All of the animals exhibited hyperflexion of the operated limb immediately post-operative, and 100% could apply full weight bearing from day 5 after surgery.

CONCLUSIONS

The species-specific design of implants in experimental surgery encourages rapid recovery of the animal and the development of a biofilm on their surfaces, making them ideal for the study of the physiopathology and for establishing possible therapeutic targets for prosthetic infection.

Infection-free rates and Sequelae predict factors in bone transportation for infected tibia: a systematic review and meta-analysis

Background

Tibia infected nonunion and chronic osteomyelitis are challenging clinical presentations. Bone transportation with external or hybrid fixators (combined external and internal fixators) is versatile to solve these problems. However, the infection-free rates of these fixator systems are unknown. Additionally, the prognosis factors for results of bone transportation are obscure. Therefore, this systematic review and meta-analysis was conducted to answer these questions.

Methods

A systematic review was conducted following the PRISMA-IPD guidelines. Relevant publications from January 1995 to September 2018 were compiled from Medline, Embase, and Cochrane. The infection-free rates of external and hybrid fixators were achieved by synthesizing aggregate data and individual participant data (IPD). IPD was analyzed by two-stage method with logistical regression to identify prognosis factors of sequelae.

Results

Twenty-two studies with 518 patients were identified, including 11 studies with 167 patients’ IPD, and 11 studies with 351 patients’ aggregate data. The infection-free rate of hybrid fixator group was 86% (95%CI: 79–94%), lower than that of external fixator which was 97% (95%CI: 95–98%,). The number of previous surgeries was found predict factor of bone union sequelae (p = 0.04) and function sequelae(p < 0.01); The external fixation time was found predict factor of function sequelae (p = 0.015).

Conclusions

Hybrid fixators may be associated with a greater risk of infection-recurrence in the treatment of tibia infected nonunion and chronic osteomyelitis. The number of previous surgeries and external fixation time can be used as predictors of outcomes. Proper fixators and meticulously designed surgery are important to avoid unexpected operations and shorten external fixation time.

Two-stage treatment in patients with patients with high-energy femoral fractures does not lead to an increase in deep infectious complications: a propensity score analysis

Purpose

In patients following severe trauma sometimes the physiological condition or soft tissue status may not allow definitive fixation of a femoral fracture. In these patients, an external fixator can be placed to temporarily stabilise the fracture, after which definitive fixation can be performed in a second procedure. The aim of this study was to compare the postoperative wound infection and union rates of patients treated with direct intramedullary nailing (IMN) and patients treated with the ‘two-stage treatment’.

Methods

All patients with high-energy femoral fractures treated with IMN between 2000 and 2016 in a single Level 1 trauma centre were eligible. Electronic charts were reviewed for patient and surgical characteristics; furthermore, the development of complications was noted. A propensity score analysis was performed to assess the attributed risk of the external fixator on the development of postoperative wound infections.

Results

A total of 149 patients were included in this study; 93 underwent direct IMN and 56 underwent the two-stage treatment. Patients who underwent two-stage treatment were more severely injured, reflected by lower EMV and higher ISS on admission. Patients in the two-stage treatment group had a significant higher risk of postoperative wound infections (OR: 4.698, 95% CI: 1.203–18.339) but not a higher risk on deep postoperative wound infections (OR 2.345, 95% CI: 0.439–12.540). Union rate did not differ between the two groups (94% vs 94% NS).

Conclusions

The two-stage treatment is a safe treatment option in patients with a high-energy femoral fracture in terms of postoperative wound infections. Union rates are also comparable between the two treatment groups.

A novel murine model of established Staphylococcal bone infection in the presence of a fracture fixation plate to study therapies utilizing antibiotic-laden spacers after revision surgery

Mice are the small animal model of choice in biomedical research due to the low cost and availability of genetically engineered lines. However, the devices utilized in current mouse models of implant-associated bone infection have been limited to intramedullary or trans-cortical pins, which are not amenable to treatments involving extensive debridement of a full-thickness bone loss and placement of a segmental antibiotic spacer. To overcome these limitations, we developed a clinically faithful model that utilizes a locking fracture fixation plate to enable debridement of an infected segmental bone defect (full-thickness osteotomy) during a revision surgery, and investigated the therapeutic effects of placing an antibiotic-laden spacer in the segmental bone defect. To first determine the ideal time point for revision following infection, a 0.7 mm osteotomy in the femoral mid-shaft was stabilized with a radiolucent PEEK fixation plate. The defect was inoculated with bioluminescent Staphylococcus aureus, and the infection was monitored over 14 days by bioluminescent imaging (BLI). Osteolysis and reactive bone formation were assessed by X-ray and micro-computed tomography (micro-CT). The active bacterial infection peaked by 5 days post-inoculation, however the stability of the implant fixation became compromised by 10-14 days post-inoculation due to osteolysis around the screws. Thus, day 7 was defined as the ideal time point to perform the revision surgery. During the revision surgery, the infected tissue was debrided and the osteotomy was widened to 3mm to place a poly-methyl methacrylate spacer, with or without vancomycin. Half of the groups also received systemic vancomycin for the remaining 21 days of the study. The viable bacteria remaining at the end of the study were measured using colony forming unit assays. Volumetric bone changes (osteolysis and reactive bone formation) were directly measured using micro-CT image analysis. Mice that were treated with local or systemic vancomycin did not display gross pathology at the end of the study. While localized vancomycin delivery alone tended to decrease the bacterial burden and osteolysis, these effects were only significant when combined with systemic antibiotic therapy. This novel mouse model replicates key features of implant-associated osteomyelitis that make treatment extremely difficult, such as biofilm formation and osteolysis, and imitates the clinical practice of placing an antibiotic-laden spacer after infected tissue debridement. In addition, the model demonstrates the limitations of current PMMA spacers and could be an invaluable tool for evaluating alternative antimicrobial treatments for implant-associated bone infection.

A systematic review of animal models for Staphylococcus aureus osteomyelitis

Staphylococcus aureus (S. aureus) osteomyelitis is a significant complication for orthopaedic patients undergoing surgery, particularly with fracture fixation and arthroplasty. Given the difficulty in studying S. aureus infections in human subjects, animal models serve an integral role in exploring the pathogenesis of osteomyelitis, and aid in determining the efficacy of prophylactic and therapeutic treatments. Animal models should mimic the clinical scenarios seen in patients as closely as possible to permit the experimental results to be translated to the corresponding clinical care. To help understand existing animal models of S. aureus, we conducted a systematic search of PubMed and Ovid MEDLINE to identify in vivo animal experiments that have investigated the management of S. aureus osteomyelitis in the context of fractures and metallic implants. In this review, experimental studies are categorised by animal species and are further classified by the setting of the infection. Study methods are summarised and the relevant advantages and disadvantages of each species and model are discussed. While no ideal animal model exists, the understanding of a model's strengths and limitations should assist clinicians and researchers to appropriately select an animal model to translate the conclusions to the clinical setting.

Modelling for conflict: the legacy of ballistic research and current extremity in vivo modelling

Extremity ballistic injury is unique and the literature intended to guide its management is commonly misinterpreted. In order to care for those injured in conflict and conduct appropriate research, clinicians must be able to identify key in vivo studies, understand their weaknesses and desist the propagation of miscited and misunderstood ballistic dogma. This review provides the only inclusive critical overview of key studies of relevance to military extremity injury. In addition, the non-ballistic studies of limb injury, stabilisation and contamination that will form the basis from which future small animal extremity studies are constructed are presented. With an awareness of the legacy of military wound models and an insight into available generic models of extremity injury and contamination, research teams are well placed to optimise future military extremity injury management.

Vancomycin-modified implant surface inhibits biofilm formation and supports bone-healing in an infected osteotomy model in sheep: a proof-of-concept study

BACKGROUND

Implant-associated infections contribute to patient morbidity and health care costs. We hypothesized that surface modification of titanium fracture hardware with vancomycin would support bone-healing and prevent bacterial colonization of the implant in a large-animal model.

METHODS

A unilateral transverse mid-diaphyseal tibial osteotomy was performed and repaired with a titanium locking compression plate in nine sheep. Four control animals were treated with an unmodified plate and five experimental animals were treated with a vancomycin-modified plate. The osteotomy was inoculated with 2.5 × 106 colony-forming units of Staphylococcus aureus. The animals were killed at three months postoperatively, and implants were retrieved aseptically. Microbiologic and histologic analyses, scanning electron and confocal microscopy, and microcomputed tomography were performed.

RESULTS

All animals completed the study. Compared with the treatment cohort, control animals exhibited protracted lameness in the operatively treated leg. Gross findings during necropsy were consistent with an infected osteotomy accompanied by a florid and lytic callus. Microcomputed tomography and histologic analysis of the tibiae further supported the presence of septic osteomyelitis in the control cohort. Thick biofilms were also evident, and bacterial cultures were positive for Staphylococcus aureus in three of four control animals. In contrast, animals treated with vancomycin-treated plates exhibited a healed osteotomy site with homogenous remodeling, there was no evidence of biofilm formation on the retrieved plate, and bacterial cultures from only one of five animals were positive for Staphylococcus aureus.

CONCLUSIONS

Vancomycin-derivatized plate surfaces inhibited implant colonization with Staphylococcus aureus and supported bone-healing in an infected large-animal model.

Development of a broad spectrum polymer-released antimicrobial coating for the prevention of resistant strain bacterial infections

More than 400,000 primary hip and knee replacement surgeries are performed each year in the United States. From these procedures, approximately 0.5-3% will become infected and when considering revision surgeries, this rate has been found to increase significantly. Antibiotic-resistant bacterial infections are a growing problem in patient care. This in vitro research investigated the antimicrobial potential of the polymer released, broad spectrum, Cationic Steroidal Antimicrobial-13 (CSA-13) for challenges against 5 × 10(8) colony forming units (CFU) of methicillin-resistant Staphylococcus aureus (MRSA). It was hypothesized that a weight-to-weight (w/w) concentration of 18% CSA-13 in silicone would exhibit potent bactericidal potential when used as a controlled release device coating. When incorporated into a polymeric device coating, the 18% (w/w) broad-spectrum polymer released CSA-13 antimicrobial eliminated 5 × 10(8) CFU of MRSA within 8 h. In the future, these results will be utilized to develop a sheep model to assess CSA-13 for the prevention of perioperative device-related infections in vivo.

Hydrophobic polycationic coatings that inhibit biofilms and support bone healing during infection

Adhesion of microorganisms to biomaterials with subsequent formation of biofilms on such foreign bodies as orthopedic trauma hardware is a critical factor in implant-associated infections; once a biofilm has been established, its microorganisms become recalcitrant to the host's immune surveillance and markedly resistant to drugs. We have previously reported that painting with the hydrophobic polycation N,N-dodecyl,methyl-PEI (PEI = polyethylenimine) renders solid surfaces bactericidal in vitro. Herein we observe that N,N-dodecyl,methyl-PEI-derivatized titanium and stainless steel surfaces resist biofilm formation by Staphylococcus aureus compared to the untreated ones. Using imaging, microbiology-, histopathology-, and scanning electron microscopy (SEM) experiments in a clinically relevant large-animal (sheep) trauma model, we subsequently demonstrate in vivo that orthopedic fracture hardware painted with N,N-dodecyl,methyl-PEI not only prevents implant colonization with biofilm but also promotes bone healing. Functionalizing orthopedic hardware with hydrophobic polycations thus holds promise in supporting bone healing in the presence of infection in veterinary and human orthopedic patients.

Fixator-assisted nailing and consecutive lengthening over an intramedullary nail for the correction of tibial deformity

We report the results of using a combination of fixator-assisted nailing with lengthening over an intramedullary nail in patients with tibial deformity and shortening. Between 1997 and 2007, 13 tibiae in nine patients with a mean age of 25.4 years (17 to 34) were treated with a unilateral external fixator for acute correction of deformity, followed by lengthening over an intramedullary nail with a circular external fixator applied at the same operating session. At the end of the distraction period locking screws were inserted through the intramedullary nail and the external fixator was removed.

The mean amount of lengthening was 5.9 cm (2 to 8). The mean time of external fixation was 90 days (38 to 265). The mean external fixation index was 15.8 days/cm (8.9 to 33.1) and the mean bone healing index was 38 days/cm (30 to 60).

One patient developed an equinus deformity which responded to stretching and bracing. Another developed a drop foot due to a compartment syndrome, which was treated by fasciotomy. It recovered in three months. Two patients required bone grafting for poor callus formation.

We conclude that the combination of fixator-assisted nailing with lengthening over an intramedullary nail can reduce the overall external fixation time and prevent fractures and deformity of the regenerated bone.

Ilizarov external fixation and then nailing in management of infected nonunions of the tibial shaft

BACKGROUND

Ilizarov technique is useful in the management of infected nonunions of the tibia. Its main drawback is the long duration of external fixation (EF) with marked patient discomfort. Several techniques have been described for early removal of EF to avoid this problem.

METHODS

Between September 2000 and October 2001, a prospective study at a tertiary trauma center was performed. Thirty-three patients with infected nonunion of the tibial shaft were included. The eradication of infection was by debridement, followed by limb reconstruction using segment transport technique with Ilizarov EF system. When the transported segment reached the docking site, we offered the patients removal of EF, and replacement by intramedullary (I M) fixation with bone graft at the docking site. Advantages and risks were explained to all patients. Patients (N = 17) who accepted this technique were compared with patients (N = 16) who preferred to continue in EF till full bone union, with bone graft at the docking site used in both groups. Mean age of the patients was 29 years, and mean duration of nonunion was 12.6 (range, 6-22) months. Average duration of follow-up from the date of presentation was 36 (range, 22-48) months. Main outcome measurements were assessment of bone and functional outcome using the classification of the Association for the Study and Application of the Method of Ilizarov, EF index, radiographic consolidation index, healing time, duration of EF, and complications

RESULTS

The average duration of EF in the first group was 3.1 month, meanwhile in the second group it was 8.5 months. The Association for the Study and Application of the Method of Ilizarov bony and functional outcome assessment score showed no statistically significant difference between the two techniques on follow-up.

CONCLUSION

Early removal of EF and replacement by intramedullary nail can achieve complete healing for infected nonunion of the tibial shaft with shorter duration of EF; nearly one-third the usual duration of EF and give the same functional and bony outcome as the classic technique. It is a relatively safe technique but the risk of infection recurrence must be explained to the patient.

Risk factors for deep infection in secondary intramedullary nailing after external fixation for open tibial fractures

BACKGROUND

Risk factors for deep infection in secondary intramedullary nailing (IMN) after external fixation (EF) for open tibial fractures were investigated by multivariate analysis following univariate analyses.

METHODS

Forty-two open tibial fractures were treated with secondary IMN after EF. The open tibial fractures were classified according to the criteria proposed by Gustilo et al.: type II, 11; type IIIA, 8; type IIIB, 22 and type IIIC, 1. Locked IMNs with limited reaming were performed in 27 patients, and locked IMNs without reaming in 15 patients. The following factors contributing to deep infection were selected for analysis: age, gender, Gustilo type (II or III), fracture grade by AO type (A or B+C), fracture site, existence of multiple trauma (Injury Severity Score, ISS<18 or ISS> or = 18), existence of floating knee injury, debridement time (< or = 6 h or > 6 h), reamed (R) versus unreamed (UR) nailing, duration of external fixation (< or = 3 weeks or >3 weeks), interval between removal of EF and IMN (< or = 2 weeks or >2 weeks), skin closure time (< or = 1 week or >1 week), existence of superficial infection (+ or -) and existence of pin tract infection (+ or -). The relationship between deep infection and the above factors was evaluated by univariate analyses.

RESULTS

Seven (16.7%) of the 42 open tibia fractures developed deep infections. All deep infections occurred in Gustilo type III (22.6%, 7/31). Only the skin closure time was a significant factor affecting the occurrence of deep infection on the present analysis (p = 0.006).

CONCLUSION

The present evaluation showed that early skin closure within 1 week is the most important factor in preventing deep infections when treating open tibial fractures with secondary IMN after EF.

The risk of local infective complications after damage control procedures for femoral shaft fracture

OBJECTIVES

To determine infection rates after damage control orthopaedics (DCO) and primary intramedullary nailing (1' IMN) in multiply injured patients with femoral shaft fracture.

DESIGN

Retrospective case analysis.

SETTING

Level I trauma center.

PATIENTS

All patients with New Injury Severity Score (NISS) >20 and femoral shaft fracture (AO 32-) treated in our unit between 1996 and 2002.

INTERVENTION

Damage control orthopaedics, defined as primary external fixation of the femoral shaft fracture and subsequent conversion to an intramedullary nail, or primary IMN.

MAIN OUTCOME MEASUREMENTS

Rates of infection classified as contamination (positive swabs with no clinical change), superficial, deep (requiring surgery), and removal of hardware (those requiring removal of femoral instrumentation or amputation).

RESULTS

A total of 173 patients with 192 fractures were included; 111 fractures were treated by DCO and 81 by primary IMN. Mean follow-up was 19.1 months [median, 16.7, range, 1 (patient died)-67 months]. DCO patients had a significantly higher NISS and more grade III open fractures (P<0.001). IMN procedures took a median of 150 minutes compared with 85 minutes for DCO (P<0.0001). Although wound contamination (including contaminated pin sites) was more common in the DCO group (P<0.05), the risk of infectious complications was equivalent (P=0.86). Contamination was significantly more likely when conversion to IMN occurred after more than 14 days (P<0.05); however, this did not lead to more clinically relevant infections. Logistic regression analysis showed that although a DCO approach was not associated with infection, delay before conversion in the DCO group might be [P=0.002 for contamination and removal of hardware, P=0.065 for serious infection (deep or worse), not significant for other infection outcomes]. Grade III open injury also was significantly associated with serious infection in all patients (P<0.05).

CONCLUSIONS

Infection rates after DCO for femoral fractures are comparable to those after primary IMN. We see no contraindication to the implementation of a damage control approach for severely injured patients with femoral shaft fracture where appropriate. Pin-site contamination was more common where the fixator was in place for more than 2 weeks. For patients treated by using a DCO approach, conversion to definitive fixation should be performed in a timely fashion.

Axial correction of pes varus by transverse-opening wedge osteotomy and T-plate fixation with beta-tricalcium phosphate (beta-TCP) transplantation in dachshunds

Axial correction was performed surgically in two miniature dachshunds presenting with lateral patellar dislocation and limping caused by pes varus. Pes varus had resulted from asymmetric closure of the physis of the distal tibia. Prior to surgery, osteotomy was simulated by measuring X-ray films to determine the distance required for the wedge opening. Transverse-opening wedge osteotomy was performed on the medial side of the distal tibia, and beta-tricalcium phosphate (beta-TCP) was inserted in a wedge shape into the area created by the cuneiform osteotomy. Finally, the tibia was fixed by a veterinary 1.5/2.0-mm T-plate. Both dogs were able to walk a few days after surgery, and the lateral dislocation of the patella normalized almost completely in about one month. At two months, X-ray films showed that the implant had remained in position without any dislocation, and the beta-TCP had fused with the surrounding bone.

Cementless total hip arthroplasty and limb-length equalization in patients with unilateral Crowe type-IV hip dislocation

BACKGROUND

Total hip arthroplasty in patients with unilateral congenital high dislocation of the hip (Crowe type IV) presents many challenges, including the problem of a marked limb-length discrepancy. The purpose of this retrospective study was to analyze the results of total hip replacement with limb-length equalization in these patients.

METHODS

From 1988 to 1996, fifty-six patients (forty-seven women and nine men) with unilateral Crowe type-IV dislocation of the hip were treated with a cementless total hip arthroplasty at a mean age of 35.4 years. The preoperative limb-length discrepancy averaged 4.9 cm. Prior to the total hip arthroplasty, forty-eight patients with a limb-length discrepancy of >4.0 cm underwent iliofemoral distraction with use of an external fixator for eight to seventeen days. The acetabular cup was placed in the anatomical position in every patient. Shortening femoral osteotomies were not required.

RESULTS

The iliac fixator pins loosened in six patients. No patient had a pin-site infection, hip joint infection, or nerve palsy. At the time of follow-up, at an average of 147.2 months, the Harris hip score averaged 90.2 points. Overall, the mean lengthening after the total hip arthroplasty was 4.6 cm. There were no revisions of the femoral stem. Nine cups were revised, four because of polyethylene wear and five because of loosening.

CONCLUSIONS

We were able to safely place the acetabular cup at the anatomical position without femoral shortening by bringing the femoral head to the normal level preoperatively; thus, we could restore nearly normal limb length. We believe that our twelve-year results are similar to those of total hip arthroplasty in patients without dysplasia.

Tibial lengthening: technique for speedy lengthening by external fixation and secondary internal fixation

BACKGROUND

The conventional Ilizarov technique for tibial lengthening is frequently time-consuming, causes suffering, and is associated with many complications. This study takes a retrospective approach to investigate the outcome of applying a slightly speedier procedure using an Ilizarov apparatus and secondary internal fixation.

METHODS

Twelve adult patients displaying tibial shortening (median, 4.0 cm; mean, 4.6 cm; range, 3.0-12.0 cm) with various causes were treated with or without tibial osteotomy and stabilized using an Ilizarov lengthening apparatus. Postoperatively, lengthening of 1 to 1.5 mm/day was performed until the desired length was achieved. External fixation was then converted to internal fixation and either pure autogenous bone graft, or a mixture of autogenous and allogenous bone graft was supplemented. Postoperatively, protected weight bearing was advised until bony union was achieved.

RESULTS

Eleven patients were followed up for a median of 3.4 years (mean, 4.0 years; range, 2.1-6.7 years) and solid union was achieved in all cases. Median external fixation occurred after 1.8 months (mean, 1.9 months; range, 1.2-4.5 months) and the median time until union after internal fixation was 4.5 months (mean, 4.8 months; range, 4-6 months). Two patients with rigid equinus feet required concomitant Achillis tendon lengthening. No other significant complications were noted. Classification of the results revealed that improvement from an unsatisfactory to a satisfactory outcome was achieved in all patients (p < 0.001).

CONCLUSION

The described technique shortens the external fixation period and reduces patient suffering. Moreover, a high union rate and a low complication rate are achieved. Subjectively and objectively, patients can achieve satisfactory outcomes. Consequently, the described technique may be considered as an alternative to conventional techniques when indicated.

Reaming bone grafting to treat tibial shaft aseptic nonunion after plating

OBJECTIVE

To investigate the effects of using intramedullary reaming to provide cancellous bone graft, and reamed intramedullary nail stabilisation to provide fragment stability on treating tibial shaft aseptic nonunions after plating.

METHODS

31 consecutive patients with tibial shaft aseptic nonunions after plating were prospectively treated. Indications for this technique included a tibial shaft nonunion with an inserted plate, a fracture level fit for traditional or locked nail stabilisation, absence of suspected infection and segmental bony defect at the time, and shortening of less than 2 cm. The plate was removed and the marrow cavity was reamed as widely as possible. A stable unlocked or locked intramedullary nail was then inserted. No extra cancellous bone graft was supplemented.

RESULTS

28 patients were followed up for a median period of 2.2 years (range, 1.0-5.2 years). All patients achieved solid union. The median union period was 4.5 months (range, 3.0-7.5 months). There were no significant complications.

CONCLUSION

When reamed intramedullary nails are used to treat tibial shaft aseptic nonunions after plating, supplemented cancellous bone grafting can be spared. Despite the technique being simplified, the success rate is high. We therefore recommend its wide use to treat all suitable cases.

Early intramedullary nailing in an animal model of a heavily contaminated fracture of the tibia

An ovine model was developed to study the outcome following intramedullary nailing of a heavily contaminated fracture. Animals in the control group received no treatment directed at controlling infection, whereas those in the treatment group received wound debridement, lavage and the use of appropriate systemic antibiotics. Despite this, infection developed at the osteotomy site and along the entire length of the implant in all animals in both groups. It was felt that standard methods of wound management might be inadequate when applied at the time of intramedullary nailing since the spread of contamination following the use of reamers was demonstrated in all animals. Results from this study support the clinical impression that heavily contaminated fractures should not be treated by primary intramedullary nailing.