Reasons and Risk Factors for Delayed Discharge After Total Knee Arthroplasty Using an Opioid-Sparing Discharge Protocol

BACKGROUND

In this study, we aimed to assess the length of hospital stay after total knee arthroplasty in a European healthcare setting. We also aimed to investigate risk factors and reasons for delayed discharge when using an opioid-sparing fast-track protocol.

METHODS

From our institutional database, we retrospectively identified all primary elective unilateral total knee arthroplasties performed during January to December 2015. Both patient-related and surgery-related variables were collected from our databases. Risk factors were analyzed using multivariable logistic regression analysis.

RESULTS

The median length of stay (LOS) was 3 days. Independent risk factors for delayed discharge were higher age, higher American Society of Anesthesiologists score, general anesthesia, surgery performed toward the end of the week, longer duration of surgery, longer stay in the post-anesthesia care unit, and shorter preoperative walking distance. The main reasons for delayed discharge were delayed functional recovery and pain.

CONCLUSION

This study identified several independent risk factors for an LOS longer than 3 days. These risk factors add to the current knowledge on which patients have an increased risk of prolonged LOS, and which patients should be targeted when striving to further reduce the LOS.

Dislocation of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty

INTRODUCTION

Dislocation of large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA) is a rare complication. This study aimed to determine the incidence and risk factors for dislocation of LDH MoM THAs and HRAs.

METHODS

This retrospective analysis considered 4038 cementless LDH MoM THAs and HRAs, 3207 THAs in 2912 patients and 831 HRAs in 757 patients. The end of follow-up was revision due to dislocation. Incidence of dislocation was evaluated from this study population of 4038, and study groups were formed. The study was designed as a case-control study, and a threefold stratified randomised control group was formed. Demographic data were collected and radiological analyses were performed in the study groups.

RESULTS

There were 26/3207 (0.8%) early dislocations in the THA group, and 6/831 (0.7%) in the HRA group ( p = 0.9). Most LDH THA dislocations occurred in a group with head size ⩽ 38 mm (18/26) ( p < 0.001). In dislocated hips, there were more dysplastic acetabula and post-traumatic hips than in the control group ( p = 0.036). In the dislocation group, the mean acetabulum component anteversion angle was 19.6° (standard deviation [SD] 13.4°) and in the control group it was 23.2° (SD 10.4°) ( p = 0.006); 7/32 (21.8%) of dislocated THAs needed revision surgery, and mean time to revision from the index surgery was 1.2 (SD 2.6) years.

DISCUSSION

Dislocations occurred more often in THAs of head size ⩽ 38 mm and with a smaller anteversion angle of the acetabulum component. Hip dysplasia and post-traumatic osteoarthritis were more common in patients with dislocation.

Fibular head avulsion fractures accompanying operative treated medial tibial plateau fractures

OBJECTIVE

The aims of this work are to determine how frequently medial tibial plateau fractures are accompanied by fibular head avulsion fractures and evaluate the sensitivity of radiographs detecting them, and also to assess if the presence of fibular fracture is correlated with long-term functional outcome and peroneal nerve damage.

MATERIALS AND METHODS

A retrospective chart review of operated patients with medial tibial plateau fractures at level I trauma center during 2002-2008 was performed. From 63 patients imaged preoperatively, 59 had CT and radiographs, three had only CT, and one only radiograph. The presence and fragment size of fibular fracture were retrospectively evaluated. Body mass index (BMI) and functional outcome measurements (the Modified Lysholm knee score and WOMAC) were available for 46 patients.

RESULTS

Fourteen out of 63 patients (22.2%) had fibular fractures. Of the 59 patients with both CT and radiographs, 12 had fibular fractures, and of these, nine were seen with both modalities and three only in CT. Functional scores were available for ten patients with fibular fracture. Patients with fibular fracture seen on radiographs had a significantly higher score on WOMAC function (26 vs. 7; p = 0.027). The patients with fibular fractures had also higher BMI (p = 0.035). Of the six patients with peroneal nerve damage, 50% had fibular fracture.

CONCLUSIONS

In patients with operatively treated medial tibial plateau fracture, the fibular fractures are relatively common. Detecting it is important, as it may be associated with worse functional scores and peroneal nerve paresis. Some fibular fractures may remain undetected on radiographs, hence preoperative CT is recommended.

Infection safety of dexamethasone in total hip and total knee arthroplasty: a study of eighteen thousand, eight hundred and seventy two operations

PURPOSE

Dexamethasone has been shown to prevent post-operative nausea and vomiting (PONV) and seems to reduce post-operative pain. Both factors, which can extend the hospital stay, delay rehabilitation, and impact patient satisfaction. Because of the immunosuppressive and glucose-rising effects of dexamethasone, there has been concern of its safety in arthroplasty surgery. The purpose of our study was to examine infection safety of dexamethasone in arthroplasty surgery with enough large study material to reliably detect a possible, even small, difference in infection incidence.

METHODS

A total of 18,872 consecutive primary and revision hip and knee arthroplasties were analyzed with data gathered from clinical information databases and a surgical site infection surveillance database with prospective data collection. Also, emergency operations due to fractures were included except for hip hemiarthroplasties.

RESULTS

During the follow-up, 189 (1.0%) prosthetic joint infections (PJIs) occurred: 0.8% after primary arthroplasty and 1.9% after revision arthroplasty. Dexamethasone was used in 2922 (15.5%) operations. The PJI rate in the dexamethasone group was 1.1% (31/2922) and in the non-dexamethasone group 1.0% (161/15950), with no significant difference in the risk of PJI between the two groups (OR 1.052, 95% CI 0.715-1.548, P = 0.773).

CONCLUSIONS

In our study material, the use of a single 5-10 mg dose of dexamethasone did not increase the incidence of post-operative PJI. A low dose of dexamethasone may be safely used to prevent PONV and as part of multimodal analgesia on patients undergoing arthroplasty operation.

A Consultation Phone Service for Patients With Total Joint Arthroplasty May Reduce Unnecessary Emergency Department Visits

BACKGROUND

Different measures for reducing costs after total joint arthroplasty (TJA) have gained attention lately. At our institution, a free-of-charge consultation phone service was initiated that targeted patients with TJA. This service aimed at reducing unnecessary emergency department (ED) visits and, thus, potentially improving the cost-effectiveness of TJAs. To our knowledge, a similar consultation service had not been described previously. We aimed at examining the rates and reasons for early postdischarge phone calls and evaluating the efficacy of this consultation service.

METHODS

During a 2-month period, we gathered information on every call received by the consultation phone service from patients with TJAs within 90 days of the index TJA procedure. Patients were followed for 2 weeks after making a call to detect major complications and self-initiated ED visits. Data were collected from electronic medical charts regarding age, gender, type of surgery, date of discharge, and length of hospital stay.

RESULTS

We analyzed 288 phone calls. Calls were mostly related to medication (41%), wound complications (17%), and mobilization issues (15%). Most calls were resolved in the phone consultation. Few patients (13%) required further evaluation in the ED. The consultation service failed to detect the need for an ED visit in 2 cases (0.7%) that required further care.

CONCLUSION

The consultation phone service clearly benefitted patients with TJAs. The service reduced the number of unnecessary ED visits and functioned well in detecting patients who required further care. Most postoperative concerns were related to prescribed medications, wound complications, and mobilization issues.

Predictors of osteoarthritis following operative treatment of medial tibial plateau fractures

PURPOSE

To determine factors influencing the development of posttraumatic osteoarthritis (OA) following medial tibial plateau fractures and to evaluate concomitant injuries associated with these fractures.

MATERIALS AND METHODS

A chart review of patients with operatively treated medial tibial plateau fractures admitted to our Level I trauma centre from 2002 to 2008 was performed. Of 63 patients, 41 participated in a clinical and radiographic examination. The mean age was 47 years (range 16-78) and the mean follow-up time was 7.6 (range 4.7-11.7) years. All patients had preoperative computed tomography (CT) scans and postoperative radiographs. At the end of follow-up, standing radiographs, mechanical axis, and CT scans were evaluated.

RESULTS

Of the 41 patients, 24 had no or mild (Kellgren-Lawrence grade 0-2) OA and 17 had severe (grade 3-4) OA. Initial articular depression measured from preoperative CT scans was a significant predictor of OA (median 1.8mm vs 4.5mm, p=0.009). Fracture line extension to the lateral plateau (p=0.68) or fracture comminution (p=0.21) had no effect on the development of posttraumatic OA, nor did articular depression at the end of follow-up (p=0.68) measured from CT scans. Mechanical axis >4° of varus and ≥2mm articular depression or step-off were associated with worse WOMAC pain scores, but did not affect other functional outcome scores. Six patients (10%) had permanent peroneal nerve dysfunction. Ten patients (16%) required LCL reconstruction and nine (14%) ACL avulsions were treated at the time of fracture stabilisation.

CONCLUSIONS

The amount of articular depression measured from preoperative CT scans seems to predict the development of posttraumatic OA, probably reflecting the severity of chondral injury at the time of fracture. Restoration of mechanical axis and articular congruence are important in achieving a good clinical outcome.

Intraoperative Complications and Mid-Term Follow-Up of Large-Diameter Head Metal-on-Metal Total Hip Arthroplasty and Hip Resurfacing Arthroplasty

BACKGROUND AND AIMS

Large-diameter head total hip arthroplasty and hip resurfacing arthroplasty were popular in Finland from 2000 to 2012 for the treatment of hip osteoarthritis. The aim of this retrospective study was to investigate the mid-term survival of large-diameter head total hip arthroplasty patients operated on in three university hospitals and to compare these results to the survival of hip resurfacing arthroplasty patients.

MATERIAL AND METHODS

A total of 3860 hip arthroplasties (3029 large-diameter head total hip arthroplasties in 2734 patients and 831 hip resurfacing arthroplasties in 757 patients) were operated on between January 2004 and December 2009. The mean follow-up was 4.3 years (range: 0.3-8.0 years) in the total hip arthroplasty group and 5.1 years (range: 1.7-7.9 years) in the hip resurfacing arthroplasty group. Cox multiple regression model and Kaplan-Meier survival analysis were used to study the survival of the total hip arthroplasties and the hip resurfacing arthroplasties. Intraoperative complications and reasons for revisions were also evaluated.

RESULTS

In Cox regression analysis, the hazard ratio for revision of hip resurfacing arthroplasty was 1.5 compared with large-diameter head total hip arthroplasty (95% confidence interval: 1.0-2.2) ( p = 0.029). The cumulative Kaplan-Meier survival rate was 90.7% at 7.7 years for the large-diameter head total hip arthroplasty (95% confidence interval: 86.8-94.6) and 92.2% at 7.6 years for hip resurfacing arthroplasty (95% confidence interval: 89.9-94.6). There were a total of 166/3029 (5.5%) intraoperative complications in the large-diameter head total hip arthroplasty group and 20/831 (2.4%) in the hip resurfacing arthroplasty group ( p = 0.001). Revision for any reason was performed on 137/3029 (4.5%) of the arthroplasties in the large-diameter head total hip arthroplasty group and 52/831 (6.3%) in the hip resurfacing arthroplasty group ( p = 0.04).

CONCLUSION

The mid-term survival of both of these devices was poor, and revisions due to adverse reactions to metal debris will most likely rise at longer follow-up. There were more intraoperative complications in the large-diameter head total hip arthroplasty group than in the hip resurfacing arthroplasty group.

Revision Total Hip Arthroplasty for Fractured Ceramic Bearings: A Review of Best Practices for Revision Cases

BACKGROUND

Total hip arthroplasty revision for a fractured ceramic bearing is rare but offers unique challenges. The purpose of this review was to provide a summary of existing literature on fractured ceramic bearings.

METHODS

Two authors performed a literature search of the MEDLINE OVID and PubMed databases with the following search terms: ceramic, fracture, total hip arthroplasty, and revision.

RESULTS

The search identified 228 articles of which 199 were selected for review.

CONCLUSIONS

It is mandatory to perform a complete synovectomy and thorough debridement of the fractured ceramic fragments. A well-fixed acetabular component should be removed if either the locking mechanism is damaged or the component is malpositioned. If the femoral stem taper is damaged, the femoral stem should be removed. However, if minimal damage is present, the femoral stem may be retained and revised using a fourth generation ceramic head with a titanium sleeve. Metal bearings should be avoided and revision with ceramic bearings should be performed whenever possible.

The current state of orthopaedic residency in 18 European countries

PURPOSE

The aim of this study was to compare differences in current orthopaedic and trauma training programs across Europe.

METHODS

A questionnaire was sent to the FORTE (Federation of Orthopaedic Trainees in Europe) representatives of 25 different European countries, of which 18 responded. The questionnaire included demographic information and information concerning the structure of the training programs, including duration, selection, and mandatory training requirements.

RESULTS

The number of trainees per specialist varied between countries from a ratio of 1:2 to 1:7. Residency was generally five to six years in all the countries. In more than half of the countries selection was interview-based. Nearly all countries utilized a logbook. About 80% of the participating countries had a final examination. When assessing the components of training it was found that only one country (the United Kingdom) had mandatory minimum requirements for (1) courses, (2) surgical procedures, (3) research and (4) leadership. Nearly 40% of the participating countries had only one or none of these four components as a mandatory training requirement.

CONCLUSIONS

There are many similarities in training programs, but some important differences remain in overall requirements and final qualification. The main limitation of this study was that we were unable to get data from all the European countries. FORTE will continue to serve as a forum for sharing best practices with the ultimate goal of improving and harmonizing the level of orthopaedic training across Europe. Future studies should aim to include further details about training programs as well as to include data from more countries.

The role of outpatient visit after operative treatment of ankle fractures

It is a common practice that patients have a scheduled follow-up visit with radiographs following ankle fracture surgery. The aim of this study was to evaluate whether an early outpatient visit (<3 weeks) after ankle fracture surgery resulted in a change in patient management. For this study, 878 consecutive operatively treated ankle fracture patients with an early outpatient clinical-radiological visit were reviewed. The outcome measure was a change in treatment plan defined as any procedure, medication, or surgical intervention that is not typically implemented during the uncomplicated healing process of an acute fracture. A change in treatment plan was observed in 9.8% of operatively treated ankle fracture patients. The mean age of the patients was 48 years and the mean follow-up time was 64 months. Of the changes in treatment plan, 91% were exclusively due to clinical findings such as infection. Only three of 878 patients required a change in their treatment plan based merely on the findings of the radiographs taken at the outpatient visit. Only 37% of the patients requiring a change in their postoperative management had solicited an unanticipated visit before the scheduled outpatient visit due to clinical problems such as infection or a cast-related issue. Our study showed that every tenth operatively treated ankle fracture patient requires a change in their treatment plan due to a clinical problem such as infection or a cast-related issue. Although at hospital discharge all patients are provided with written instructions on where to contact if problems related to the operated ankle emerge, only one third of the patients are aware of the clinically alarming symptoms and seek care when problems present. Our findings do not support obtaining routine radiographs at the early outpatient visit in an ankle fracture patient without clinical signs of a complication.

Risk Factors for Deep Infection Following Plate Fixation of Proximal Tibial Fractures

BACKGROUND

The risk factors are unclear for deep surgical site infection after plate fixation of proximal tibial fractures. The objective of this study was to identify the patient and surgical procedure-related risk factors for infection using established criteria for deep surgical site infection.

METHODS

A total of 655 proximal tibial fractures were treated with open reduction and plate fixation at our center between 2004 and 2013. We identified 34 patients with deep surgical site infection. A control group of 136 patients was randomly selected from the non-infected cohort. Potential risk factors for deep surgical site infection were identified by reviewing surgical, medical, and radiographic records. Independent risk factors for infection were identified from multivariable logistic regression analysis using a stepwise procedure.

RESULTS

The prevalence of deep surgical site infection was 5.2%, the mean age of affected patients was 55 years (range, 16 to 84 years), and 35% of patients were female. Twenty-eight of 34 deep infections were diagnosed within 2 months (acute onset), and only 6 infections were diagnosed >6 months after the index surgical procedure. Nine of the 28 acute-onset infections were treated with antibiotic therapy and debridement. Seventeen patients (50%) required muscle flap coverage, and 5 patients (15%) eventually required above-the-knee amputation. In the multivariable logistic regression analysis with odds ratios (ORs) and 95% confidence intervals (95% CIs), independent predictors of infection were patient age of ≥50 years (OR, 3.6 [95% CI, 1.3 to 10.1]); obesity, defined as a body mass index of ≥30 kg/m(2) (OR, 6.5 [95% CI, 2.2 to 18.9]); alcohol abuse (OR, 6.7 [95% CI, 2.4 to 19.2]); OTA/AO-type-C fracture (OR, 2.8 [95% CI, 1.1 to 7.5]); use of a temporary spanning external fixator (OR, 3.9 [95% CI, 1.4 to 11.1]); and a 4-compartment fasciotomy (OR, 4.5 [95% CI, 1.3 to 15.7]).

CONCLUSIONS

There is high morbidity associated with deep surgical site infection in plated proximal tibial fractures. Patients who are ≥50 years of age, obese patients, those with a history of alcohol abuse, or those with an OTA/AO-type-C fracture are at high risk for infection. Performing a fasciotomy also increases the risk of deep infection and should be implemented with meticulous technique when deemed necessary.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparison of Digital and Conventional Radiostereometric Image Analysis in an Ankle Phantom Model

Background and Aims:

Radiostereometric analysis (RSA) allows accurate three-dimensional measurements of micromotion in skeletal structures. The current RSA techniques are based on the analysis of scanned plain films. This study was undertaken to compare digital filmless RSA technique to conventional scanning technique using a phantom model of the ankle mortise.

Material and Methods:

In the first experiment, the relative displacement of the markers inserted to the fibula in relation to the markers inserted to the tibia was studied by means of double examinations and the precision of DICOM images were compared to scanned images of printed radiographs. In the second experiment, the film pair of double examination was re-imported or re-scanned and self-compared in order to show merely the error related to the image processing.

Results:

The precision of RSA using scanned images of printed radiographs was compatible to DICOM images. However, the mean error of rigid body fitting (ME) values were significantly lower in use of DICOM images compared with scanned radiographs, indicating less deformation of rigid body segments in filmless analysis.

Conclusions:

Precision of the RSA method was improved under the completely filmless environment. Therefore, this technique can be recommended for clinical studies of radiostereometric analysis.

Predictors of Postoperative Wound Necrosis Following Primary Wound Closure of Open Ankle Fractures

BACKGROUND

Most open malleolar ankle fracture wounds can be closed primarily after meticulous debridement. However, the development of wound necrosis following operative treatment of open malleolar ankle fractures can have catastrophic consequences. The aim of this study was to identify risk factors predisposing to postoperative wound necrosis following primary wound closure of open malleolar ankle fractures.

METHODS

A total of 137 patients with open malleolar ankle fractures were identified. The open fracture wound was primarily closed in 110 of 137 (80%) patients, and postoperative wound necrosis occurred in 18 (16%) of these patients. These patients were compared to the open fracture patients without wound necrosis. Twenty possible risk factors for the development of wound necrosis were studied with logistic regression analysis.

RESULTS

The variables that were independently associated with an increased risk for postoperative wound necrosis included ASA class ≥2, Gustilo grade III open injury, and the use of pulsatile lavage at index surgery.

CONCLUSIONS

Our study showed that ASA class ≥2, Gustilo grade III open injury, and the use of pulsatile lavage at index surgery were the most important factors predisposing to postoperative wound necrosis following primary wound closure of open malleolar ankle fractures. The findings warrant a further study specifically comparing primary and delayed wound closure in patients with Gustilo grade III open malleolar ankle fractures and different ASA classes. Also, the role of pulsatile lavage should be re-evaluated.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Risk factors for intraoperative calcar fracture in cementless total hip arthroplasty

BACKGROUND AND PURPOSE

Intraoperative periprosthetic femoral fracture is a known complication of cementless total hip arthroplasty (THA). We determined the incidence of--and risk factors for--intraoperative calcar fracture, and assessed its influence on the risk of revision.

PATIENTS AND METHODS

This retrospective analysis included 3,207 cementless THAs (in 2,913 patients). 118 intraoperative calcar fractures were observed in these hips (3.7%). A control group of 118 patients/hips without calcar fractures was randomly selected. The mean follow-up was 4.2 (1.8-8.0) years. Demographic data, surgical data, type of implant, and proximal femur morphology were evaluated to determine risk factors for intraoperative calcar fracture.

RESULTS

The revision rates in the calcar fracture group and the control group were 10% (95% CI: 5.9-17) and 3.4% (CI: 1.3-8.4), respectively. The revision rate directly related to intraoperative calcar fracture was 7.6%. The Hardinge approach and lower age were risk factors for calcar fracture. In the fracture group, 55 of 118 patients (47%) had at least one risk factor, while only 23 of118 patients in the control group (20%) had a risk factor (p = 0.001). Radiological analysis showed that in the calcar fracture group, there were more deviated femoral anatomies and proximal femur bone cortices were thinner.

INTERPRETATION

Intraoperative calcar fracture increased the risk of revision. The Hardinge approach and lower age were risk factors for intraoperative calcar fracture. To avoid intraoperative fractures, special attention should be paid when cementless stems are used with deviant-shaped proximal femurs and with thin cortices.

Role of Cages in Revision Arthroplasty of the Acetabulum

➤ The outcome of acetabular revision is heavily influenced by the degree of associated bone loss.➤ Uncemented hemispherical acetabular components can be used in the majority of acetabular revisions, although occasionally the degree of bone loss precludes the stability of the hemispherical component at the correct anatomic level or there is minimal bleeding host bone left for biologic fixation.➤ Massive acetabular bone loss resulting in the need for bone grafts or highly porous augments involving more than half of the acetabulum is one of the main indications for the use of cages.➤ The cup-cage reconstruction is based on bone-grafting the deficient acetabulum and securing a hemispherical, highly porous metal component with multiple screws to bridge the discontinuity and off-loading the hemispherical component with a titanium cage spanning from ischium to ilium.➤ In addition to managing pelvic discontinuities, the cup-cage construct can also be used in hips without discontinuity as the hemispherical, highly porous metal component is used to restore bone stock.➤ In situations in which there is not enough bleeding host bone to secure a hemispherical component, a highly porous metal augment can be used to address the osseous deficiency. The augment is also protected with a cage to assist bone ingrowth.

Arthroplasty for Pertrochanteric Hip Fractures

The mainstay of treatment of pertrochanteric fractures is internal fixation using a sliding hip screw or a cephalomedullary device. However, in patients with ipsilateral hip osteoarthritis or avascular necrosis of the femoral head, or inflammatory arthritis, arthroplasty should be considered as the primary treatment modality to reduce the likelihood of a secondary procedure. Unstable fracture patterns with concomitant poor bone quality represent a challenge for internal fixation, with high rates of lag screw cut-out and hardware failure. Prosthetic replacement for unstable pertrochanteric fractures has therefore been considered as an alternative primary treatment option. Further prospective randomized trials are required.

Contemporary demographics and complications of patients treated for open ankle fractures

Open ankle fractures are rare injuries with a high likelihood of wound complications and subsequent infections. There is limited information about the complications and outcomes of these injuries in different age groups. The aim of this study was to assess the contemporary demographics and complications related to this injury. We performed a chart review of all the 3030 patients treated for ankle fractures at a Level 1 trauma centre from 2006 to 2011. 137 (4.5%) patients had an open ankle fracture. The demographic data, injury mechanism, comorbidities, and fracture type were collected. Treatment, complications, length of stay and number of outpatient visits were also recorded. The mean age of the patients was 60 years and 56% were women. Most fractures were Weber type B with a medial sided wound (93%). Only 20% of the fractures were the result of high-energy trauma, and 31% were Gustilo grade III injuries. Immediate internal fixation was performed in 82% of patients, and the wound was primarily closed in most cases (80%). The incidence of postoperative wound necrosis and deep infection was 18% and 17%, respectively. There were more deep infections if pulsatile lavage was used during the wound debridement (p=0.029). About 14 (10%) patients required a flap reconstruction to cover the soft-tissue defect. Every other patient (54%) had a complication, and 21 patients (15%) suffered a long-term disability related to the injury. The number complications did not differ for nighttime and daytime operations (p=0.083). High-energy injuries were more common in younger patients (p<0.001) and these patients also had more lateral sided open wounds than older patients (p=0.002). Interestingly, younger patients also had significantly more complications (p=0.024), suffered more often from chronic pain (p=0.003), and required more flap reconstructions (p=0.026), reoperations (p=0.026), and outpatient clinic visits (p=0.006). Open ankle fractures have a high complication rate and often require multiple surgical procedures. In young patients these injuries are more likely to be the consequence of high-energy trauma leading to more complications and subsequently increased healthcare resource utilisation.

Factors associated with outcome of spinopelvic dissociation treated with lumbopelvic fixation

Spinopelvic dissociation is a rare high-energy injury, which is frequently associated with lumbosacral plexus and cauda equina deficits. During an 18-year period, 36 consecutive patients with a H-type sacral fracture and spinopelvic dissociation were treated using lumbopelvic fixation with a minimum follow-up of 18 months. We evaluated factors prognostic of outcome after standardised surgical fixation and neural decompression. Neurological recovery was assessed by Gibbons’ criteria. Pelvis Outcome Scale (POS clinical score) was used to evaluate the clinical outcome. Despite excellent or good radiological results in the vertical components of the sacral fractures having been achieved in all patients, 15 patients (42%) had a poor clinical outcome. The degree of initial translational displacement in the transverse sacral fracture was significantly associated with neurological recovery (as defined by a change in Gibbons score) (p = 0.038) and final POS clinical score (p < 0.001). Both neurological recovery and clinical outcome were worse in patients with completely displaced fractures than in patients with a partially displaced sacral fracture. The degree of residual translational displacement and kyphosis in the transverse sacral fracture were also associated with clinical outcome (POS clinical score) (p = 0.011 and p = 0,018, respectively). However, Roy-Camille classification (type 2 vs. type 3), age, gender, ISS, timing of surgery, and sacral laminectomy did not have a statistically significant association with the outcome. Based on the results, Roy-Camille sacral fracture classification (type 2 vs. type 3) was not prognostic of neurological impairment. Thus further categorisation of the transverse sacral fractures as partially displaced or completely displaced could be used to predict the rate of neurological recovery following lumbopelvic fixation. Accurate reduction of all sacral fracture components seems to be associated with better clinical outcome.

Flap reconstruction for soft-tissue defects with exposed hardware following deep infection after internal fixation of ankle fractures

The aim of the present study was to determine the outcome for patients treated with flap reconstruction following deep ankle fracture infection with exposed hardware. Out of 3041 consecutive ankle fracture operations in 3030 patients from 2006 to 2011, we identified 56 patients requiring flap reconstruction following deep infection. Thirty-two of these patients could be examined at a follow-up visit. Olerud-Molander Ankle (OMA) score, 15D score, Numeric Rating Scale (NRS), and clinical examination were used to assess the outcome. A total of 58 flap reconstructions were performed in 56 patients with a mean age of 57 years (range 25–93 years) and mean follow-up time of 52 months. The most commonly used reconstruction was a distally based peroneus brevis muscle flap with a split-thickness skin graft. A microvascular free flap was required in only one patient. 22 (39%) patients required subsequent surgical interventions because of a flap-related complication. With flap reconstruction, hardware could eventually be salvaged in 53% of patients with a non-consolidated fracture. The mean OMA score was fair or poor in 53% of the patients, and only 56% had recovered their pre-injury level of function. Half of the patients had shoe wear limitations. The 15D score showed a significantly poorer health-related quality of life compared to an age-standardised sample of the general population. The mean pain NRS was 2.1 (range 0–6), and the mean satisfaction NRS was 6.6 (range 0–10). Our study showed that successful treatment of a soft-tissue defect with exposed hardware following ankle fracture infections can be achieved with local flaps. Despite eventual reconstructive success, complications are common. Patients perceive a poorer health-related quality of life, have shoe wear limitations, and only half of them achieve their pre-injury level of function.

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines. A systematic review

BACKGROUND AND PURPOSE

Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.

METHODS

We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.

RESULTS

153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000-2005) and 92 after the guidelines were introduced (2006-2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.

INTERPRETATION

The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.

A comprehensive analysis of patients with malreduced ankle fractures undergoing re-operation

PURPOSE

The present study aimed to determine the most common surgical errors resulting in early re-operation following ankle fracture surgery.

METHODS

We performed a chart review to determine the most common types of malreductions that led to early re-operation following ankle fracture surgery. From 2002 to 2011, we identified 5,123 consecutive ankle fracture operations in 5,071 patients. Seventy-nine patients (1.6%) which underwent re-operation due to malreduction detected in postoperative radiographs. These patients were compared with an equal number of age- and sex-matched controls which did not need further surgery.

RESULTS

The most common indication for re-operation was syndesmotic malreduction (47 of 79 patients, 59%). Four main types of errors related to syndesmotic reduction or fixation were identified, with the most common being fibular malpositioning within the tibiofibular incisura. Other indications for re-operation were fibular shortening and malreduction of the medial malleolus. Fracture dislocation, fracture type, posterior malleolar fracture, associated medial malleolar fracture, duration of index surgery, and fixation of an associated medial malleolar fracture with other than two parallel screws were also associated with re-operation. Correction of the malreduction was successfully achieved in the majority (84%) of cases needing further surgery.

CONCLUSION

Early re-operation after ankle fracture surgery was most commonly caused by errors related to syndesmotic reduction or failure to restore fibular length. In the majority of cases, postoperative malreduction was successfully corrected in the acute setting.

Risk factors for deep surgical site infection following operative treatment of ankle fractures

BACKGROUND

Surgical site infection is one of the most common complications following ankle fracture surgery. These infections are associated with substantial morbidity and lead to increased resource utilization. Identification of risk factors is crucial for developing strategies to prevent these complications.

METHODS

We performed an age and sex-matched case-control study to identify patient and surgery-related risk factors for deep surgical site infection following operative ankle fracture treatment. We identified 1923 ankle fracture operations performed in 1915 patients from 2006 through 2009. A total of 131 patients with deep infection were identified and compared with an equal number of uninfected control patients. Risk factors for infection were determined with use of conditional logistic regression analysis.

RESULTS

The incidence of deep infection was 6.8%. Univariate analysis showed diabetes (odds ratio [OR] = 2.2, 95% confidence interval [CI] = 1.0, 4.9), alcohol abuse (OR = 3.8, 95% CI = 1.6, 9.4), fracture-dislocation (OR = 2.0, 95% CI = 1.2, 3.5), and soft-tissue injury (a Tscherne grade of ≥1) (OR = 2.6, 95% CI = 1.3, 5.3) to be significant patient-related risk factors for infection. Surgery-related risk factors were suboptimal timing of prophylactic antibiotics (OR = 1.9, 95% CI = 1.0, 3.4), difficulties encountered during surgery, (OR = 2.1, 95% CI = 1.1, 4.0), wound complications (OR = 4.8, 95% CI = 1.6, 14.0), and fracture malreduction (OR = 3.4, 95% CI = 1.3, 9.2). Independent risk factors for infection identified by multivariable analyses were tobacco use (OR = 3.7, 95% CI = 1.6, 8.5) and a duration of surgery of more than ninety minutes (OR = 2.5, 95% CI = 1.1, 5.7). Cast application in the operating room was independently associated with a decreased infection rate (OR = 0.4, 95% CI = 0.2, 0.8).

CONCLUSIONS

We identified several modifiable risk factors for deep surgical site infection following operative treatment of ankle fractures.

Low BMD affects initial stability and delays stem osseointegration in cementless total hip arthroplasty in women: a 2-year RSA study of 39 patients

BACKGROUND AND PURPOSE

Immediate implant stability is a key factor for success in cementless total hip arthroplasty (THA). Low bone mineral density (BMD) and age-related geometric changes of the proximal femur may jeopardize initial stability and osseointegration. We compared migration of hydroxyapatite-coated femoral stems in women with or without low systemic BMD.

PATIENTS AND METHODS

61 female patients with hip osteoarthritis were treated with cementless THA with anatomically designed hydroxyapatite-coated femoral stems and ceramic-ceramic bearing surfaces (ABG-II). Of the 39 eligible patients between the ages of 41 and 78 years, 12 had normal systemic BMD and 27 had osteopenia or osteoporosis. According to the Dorr classification, 21 had type A bone and 18 had type B. Translational and rotational migration of the stems was evaluated with radiostereometric analysis (RSA) up to 2 years after surgery.

RESULTS

Patients with low systemic BMD showed higher subsidence of the femoral stem during the first 3 months after surgery than did those with normal BMD (difference = 0.6, 95% CI: 0.1-1.1; p = 0.03). Low systemic BMD (odds ratio (OR) = 0.1, CI: 0.006-1.0; p = 0.02), low local hip BMD (OR = 0.3, CI: 0.1-0.7; p = 0.005) and ageing (OR = 1.1, CI: 1.0-1.2; p = 0.02) were risk factors for delayed translational stability. Ageing and low canal flare index were risk factors for delayed rotational stabilization (OR = 3, CI: 1.1-9; p = 0.04 and OR = 1.1, CI: 1.0-1.2; p = 0.02, respectively). Harris hip score and WOMAC score were similar in patients with normal systemic BMD and low systemic BMD.

INTERPRETATION

Low BMD, changes in intraosseous dimensions of the proximal femur, and ageing adversely affected initial stability and delayed osseointegration of cementless stems in women.

Dislocation of hip hemiarthroplasty following posterolateral surgical approach: a nested case-control study

PURPOSE

Hip hemiarthroplasty dislocation is a serious complication in treatment of displaced intracapsular hip fractures. We investigated factors associated with an increased risk of dislocation after cemented hip hemiarthroplasty following the posterolateral approach.

METHODS

Between January 2002 and December 2008, 602 hip fractures were treated with cemented unipolar hip hemiarthroplasty. A registry-based analysis was carried out to determine the total number of hemiarthroplasty dislocations in these patients. A control group of 96 patients without dislocation was randomly selected. Logistic regression analysis was performed to evaluate clinical and operative factors associated with dislocation.

RESULTS

Thirty-four patients (5.6%) experienced at least one dislocation. Most were the result of a fall and occurred within two months after surgery. There was a trend for increased dislocation in patients who had been operated on more than 48 hours after admission and in patients who had a longer operative time. Smaller centre-edge angle and hip offset were observed in patients with dislocation. Recurrent dislocation was a significant problem, as 18 patients (62%) experienced multiple dislocations.

CONCLUSIONS

The risk of hemiarthroplasty dislocation following the posterolateral surgical approach may be reduced by prompt surgical treatment and fall prevention in the early postoperative period. Patients with smaller acetabular coverage seem more predisposed to dislocation after the posterolateral approach and may be more suitable for other surgical approaches.

Quality of intertrochanteric cancellous bone as predictor of femoral stem RSA migration in cementless total hip arthroplasty

In cementless total hip arthroplasty, osteoporosis may jeopardize the achievement of immediate stability and lead to migration of anatomically shaped femoral stems. Poor quality of proximal cancellous bone per se may also affect the rate of osseointegration. In a selected group of female total hip arthroplasty patients (mean age 64 years) with unremarkable medical history, intertrochanteric cancellous bone biopsy was taken from the site of stem implantation. Local bone quality, determined by structural μCT imaging and destructive compression testing of the biopsy tissue, was used as the predictor of three-dimensional stem migration determined by radiostereometric analysis (RSA) up to 24 months. The patients exhibited major differences in mechanical properties of the intertrochanteric cancellous bone, which were closely related to the structural parameters calculated from μCT data. Unexpectedly, the major differences observed in the quality of trochanteric cancellous bone had only minor reflections in the RSA migration of the femoral stems. In statistical analysis, the μCT-based bone mineral density quartile (low, middle, high) was the only significant predictor for stem translation at 24 months (p=0.022) but only a small portion (R(2)=0.16) of the difference in translation could be explained by changes in bone mineral density quartile. None of the other parameters investigated predicted stem migration in translation or rotation. In conclusion, poor quality of intertrochanteric cancellous bone seems to contribute to the risk of implant migration less than expected. Probably also the importance of surgical preservation of intertrochanteric cancellous bone has been over-emphasized for osseointegration of cementless stem.

Synthesis, 68Ga labeling and preliminary evaluation of DOTA peptide binding vascular adhesion protein-1: a potential PET imaging agent for diagnosing osteomyelitis

INTRODUCTION

Vascular adhesion protein-1 (VAP-1) is an infection/inflammation-inducible endothelial glycoprotein. Based on our previous studies, the most VAP-1-selective peptide (VAP-P1) was 1,4,7,10-tetraazacyclododecane-N',N'',N''',N-tetraacetic acid (DOTA)-conjugated, 68gallium (68Ga)-labeled (named [68Ga]DOTAVAP-P1) and evaluated preliminarily.

METHODS

Targeting was evaluated by using VAP-1-transfected cells. Biodistribution of [68Ga]DOTAVAP-P1 was studied by positron emission tomography imaging of healthy rats and rats with bone inflammation caused by Staphylococcus aureus infection. Uptake of [(68)Ga]DOTAVAP-P1 in osteomyelitis was compared with negative control peptide and competition with an excess of unlabeled DOTAVAP-P1.

RESULTS

[68Ga]DOTAVAP-P1 bound more efficiently to VAP-1-transfected cells than to controls. In rats, [68Ga]DOTAVAP-P1 cleared rapidly from blood circulation, excreted quickly in urine and showed an in vivo half-life of 26+/-2.3 min. Imaging of osteomyelitis demonstrated modest target-to-background ratio. Studies with the negative control peptide and competitors revealed a significantly lower uptake at the infection site compared to [68Ga]DOTAVAP-P1.

CONCLUSIONS

The results represent a proof-of-concept that infection-induced VAP-1 can be targeted by [68Ga]DOTA peptide. [68Ga]DOTAVAP-P1 is just the first candidate peptide and an essential opening for developing VAP-1-specific imaging agents.

Female patients with low systemic BMD are prone to bone loss in Gruen zone 7 after cementless total hip arthroplasty

BACKGROUND AND PURPOSE

Factors that lead to periprosthetic bone loss following total hip arthroplasty (THA) may not only depend on biomechanical implant-related factors, but also on various patient-related factors. We investigated the association between early changes in periprosthetic bone mineral density (BMD) and patient-related factors.

PATIENTS AND METHODS

39 female patients underwent cementless THA (ABG II) with ceramic-ceramic bearing surfaces. Periprosthetic BMD in the proximal femur was determined with DXA after surgery and at 3, 6, 12, and 24 months. 27 patient-related factors were analyzed for their value in prediction of periprosthetic bone loss.

RESULTS

Total periprosthetic BMD was temporarily reduced by 3.7% at 3 months (p < 0.001), by 3.8% at 6 months (p < 0.01), and by 2.6% at 12 months (p < 0.01), but recovered thereafter up to 24 months. Preoperative systemic osteopenia and osteoporosis, but not the local BMD of the operated hip, was predictive of bone loss in Gruen zone 7 (p = 0.04), which was the only region with a statistically significant decrease in BMD (23%, p < 0.001) at 24 months. Preoperative serum markers of bone turnover predicted the early temporary changes of periprosthetic BMD. The other patient-related factors failed to show any association with the periprosthetic BMD changes.

INTERPRETATION

Female patients with low systemic BMD show greater bone loss in Gruen zone 7 after cementless THA than patients with normal BMD. Systemic DXA screening for osteoporosis in postmenopausal patients before THA could be used to identify patients in need of prophylactic anti-resorptive therapy.

(68)Ga-DOTAVAP-P1 PET imaging capable of demonstrating the phase of inflammation in healing bones and the progress of infection in osteomyelitic bones

PURPOSE

Differentiation between bacterial infection and nonbacterial inflammation remains a diagnostic challenge. Vascular adhesion protein 1 (VAP-1) is a human endothelial protein whose cell surface expression is induced under inflammatory conditions, thus making it a highly promising target molecule for studying inflammatory processes in vivo. We hypothesized that positron emission tomography (PET) with gallium-68-labeled 1,4,7,10-tetraazacyclododecane-N',N'',N''',N''''-tetraacetic acid-peptide targeted to VAP-1 ((68)Ga-DOTAVAP-P1) could be feasible for imaging the early inflammatory and infectious processes in healing bones.

MATERIALS AND METHODS

Thirty-four Sprague-Dawley rats with diffuse Staphylococcus aureus tibial osteomyelitis and 34 rats with healing cortical bone defects (representing the inflammation stage of healing) were PET imaged using (68)Ga-DOTAVAP-P1 as a tracer. In addition, peripheral quantitative computed tomography and conventional radiography were performed. Bone samples for quantitative bacteriology and specimens were also processed for histomorphometry of inflammatory and infectious reactions.

RESULTS

PET imaging showed an uptake of (68)Ga-DOTAVAP-P1 in both the osteomyelitic bones and the healing cortical bone defects during the first 36 h after surgery. Thereafter, only the osteomyelitic tibias were delineated by PET. The osteomyelitic and control animals showed a similar uptake of the (68)Ga-DOTAVAP-P1 at 24 h, whereas a significant difference was observed at 7 days (p < 0.0001).

CONCLUSIONS

The current study showed that PET imaging with the new (68)Ga-DOTAVAP-P1 is capable of accurately demonstrating the phase of inflammation in healing bones and the progress of bacterial infection in osteomyelitic bones. Consequently, this novel imaging agent allowed for the differentiation of bone infection due to S. aureus and normal bone healing as soon as 7 days after onset.

The incidence of osteopenia and osteoporosis in women with hip osteoarthritis scheduled for cementless total joint replacement

INTRODUCTION

The co-existence of osteoporosis (OP) and osteoarthritis (OA) remains obscure. No systematic studies have been carried out to exclude the possibility that especially female osteoarthritic patients selected for cementless total hip arthroplasty (THA) suffer from primary or secondary OP.

METHODS

A subgroup of fifty-three female patients (average age, 64.7 years) with advanced primary hip OA scheduled for cementless THA were recruited for DXA and laboratory screening. Before surgery, bone mineral density (BMD) of the lumbar spine, the proximal femurs and the distal forearm were measured. The serum concentrations of calcium, 25-hydroxyvitamin D, parathyroid hormone and biochemical markers of bone resorption and formation were determined to exclude secondary OP.

RESULTS

The prevalence of OP (T score <-2.5) and osteopenia (-1.0 >T score >-2.5) were 28% and 45%, respectively. Statistically, OP was related to patient's age, low BMI, postmenopausal status and not having estrogen replacement therapy. Five patients (9%) had laboratory findings of secondary OP. Two of them were found to have a parathyroid adenoma. The prevalence of vitamin D insufficiency [S-25(OH)D levels <or=50 nmol/l] was 36% (n=19). As a sign of high bone turnover, the patients with reduced BMD values showed significantly increased serum levels of osteocalcin (p=0.049), intact procollagen type I N propeptide (p=0.040) and N-terminal crosslinking telopeptide of type I collagen (p=0.046). The BMC of the femoral necks of the osteoarthritic hips were significantly higher (p<0.001) and the BMC of the trochanter regions significantly lower (p=0.005) compared to the contralateral hips.

CONCLUSION

Against a general belief, OA does not seem to protect a patient from generalized primary OP. The majority (74%) of the female hip OA patients were osteopenic or osteoporotic with signs of increased bone turnover. The observed prevalence of reduced BMD corresponds with the published data of age-matched population. An unexpectedly high number of patients required preoperative consultation with an endocrinologist. The altered distribution of BMD observed in the proximal femurs may explain the lower prevalence of fractures reported in the femoral necks of osteoarthritic hips.

In vitro and in vivo testing of bioabsorbable antibiotic containing bone filler for osteomyelitis treatment

The use of local antibiotics from a biodegradable implant is appealing concept for treatment of chronic osteomyelitis. Our aim was to develop a new drug delivery system based on controlled ciprofloxacin release from poly(D/L-lactide). Cylindrical composite pellets (1.0 x 0.9 mm) were manufactured from bioabsorbable poly(D/L-lactide) matrix and ciprofloxacin (7.4 wt %). In vitro studies were carried out to delineate the release profile of the antibiotic and to verify its antimicrobial activity by means of MIC testing. A long-term study in rabbits was performed to validate the release of ciprofloxacin from the composite in vivo. Therapeutic level of ciprofloxacin (>2 microg/mL) was maintained between 60 and 300 days and the concentration remained below the potentially detrimental level of 20 microg/mL in vitro. The released ciprofloxacin had retained its antimicrobial properties against common pathogens. In an exploratory long-term in vivo study with three rabbits, ciprofloxacin could not be detected from the serum after moderate filling (160 mg) of the tibia (follow-up 168 days), whereas after high dosing (a total dose of 1,000 mg in both tibias) ciprofloxacin was found temporarily at low serum concentrations (14-34 ng/mL) during the follow-up of 300 days. The bone concentrations of ciprofloxacin could be measured in all samples at 168 and 300 days. The tested copolylactide matrix seems to be a promising option in selection of resorbable carriers for sustained release of antibiotics, but the composite needs modifications to promote ciprofloxacin release during the first 60 days of implantation.

In vitro and in vivo release of ciprofloxacin from osteoconductive bone defect filler

OBJECTIVES

Impregnation of antimicrobial agents within biodegradable carriers with osteoconductive properties could provide the means for one-stage surgical treatment of osteomyelitis. In this study, the in vitro and in vivo antibiotic release from this type of bone defect filler was characterized.

METHODS

Cylindrical pellets (2.5 x 1.5 mm) were manufactured from bioabsorbable poly(L-lactide-co-glycolide) (PLGA) matrix, ciprofloxacin [8.3 +/- 0.1% (w/w)] and osteoconductive bioactive glass microspheres (90-125 microm) [27 +/- 2% (w/w)]. In vitro studies were carried out to delineate the release profile of the antibiotic. The antimicrobial activity of the release antibiotic was verified with MIC testing. In a time-sequence study in the rabbit, pellets were surgically implanted in the proximal tibia and the antibiotic concentrations achieved in bone were measured at 1, 2, 3, 4, 5 and 6 months.

RESULTS

In vitro elution studies showed sustained release of ciprofloxacin at a therapeutic level (>2 microg/mL) over a time period of 4 months. The released ciprofloxacin had maintained its antimicrobial capacity against five standard ATCC strains. In vivo, the delivery system produced high local bone concentrations (247.9 +/- 91.0 mug/g of bone) for a time period of 3 months with no significant systemic exposure. Histomorphometry and micro-CT imaging confirmed new bone formation around the pellets within 3 months as a sign of an independent osteoconductive property of the composite.

CONCLUSIONS

The tested composite seems to be a promising option for local therapy of surgically treated bone infections. The main advantages are the antibiotic release for a definite time period with therapeutic concentrations, which may minimize slow residual release at suboptimal concentrations.

Comparison of 18F-FDG and 68Ga PET imaging in the assessment of experimental osteomyelitis due to Staphylococcus aureus

PURPOSE

Although positron emission tomography (PET) using 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) is a promising imaging modality for bone infections, the technique may still give false-positive results due to unspecific uptake in healing bone. This experimental study compared 18F-FDG and 68Ga in PET imaging of osteomyelitis and normal bone healing.

METHODS

A diffuse osteomyelitis model of the tibia was applied in the rat (n=50). Two weeks after operation, PET imaging with 18F-FDG and 68Ga was performed, followed by peripheral quantitative computed tomography (pQCT) and radiography. Osteomyelitis was verified by quantitative bacteriology. In addition to in vivo imaging, ex vivo measurements of tissue radioactivity were performed to verify uptake of the tracers.

RESULTS

Compared with controls with normal bone healing, the osteomyelitic tibias showed increased SUV ratios (i.e. radioactivity ratios between the operated and non-operated sides) for both 18F-FDG (1.74+/-0.37) and 68Ga (1.62+/-0.28) (P<0.001). Ex vivo measurements also showed increased tracer accumulation in the infected bone (P=0.003 for 18F-FDG and P<0.001 for 68Ga). The intensity of 68Ga uptake reflected pathological changes of osteomyelitic bones measured by pQCT. The uptake of 18F-FDG, however, did not show as close a correlation with the anatomical changes. The healing bones without infection exhibited slightly elevated uptake of 18F-FDG (SUV ratio 1.16+/-0.06), but 68Ga did not accumulate in the healing bone, as judged on the basis of both in vivo imaging (SUV ratio 1.02+/-0.05) and ex vivo measurements (SUV 0.92+/-0.21) (P=0.003 and P=0.022 compared with 18F-FDG uptake, respectively).

CONCLUSION

This study suggests the feasibility of 68Ga PET imaging of bone infections. However, further studies are needed to clarify the value of 68Ga PET for clinical purposes.

Efficacy of ciprofloxacin-releasing bioabsorbable osteoconductive bone defect filler for treatment of experimental osteomyelitis due to Staphylococcus aureus

The concept of local antibiotic delivery via biodegradable bone defect fillers with multifunctional properties for the treatment of bone infections is highly appealing. Fillers can be used to obliterate surgical dead space and to provide targeted local bactericidal concentrations in tissue for extended periods. Eventually, the osteoconductive component of the filler could guide the healing of the bone defect. The present experimental study was carried out to test this concept in a localized Staphylococcus aureus osteomyelitis model in the rabbit (n = 31). A metaphyseal defect of the tibia was filled with a block of bone cement, followed by insertion of a bacterial inoculum. After removal of the bone cement and surgical debridement at 2 weeks, the defect was filled with a ciprofloxacin-containing (7.6% +/- 0.1%, by weight) composite (treated-infection group) or with a composite without antibiotic (sham-treated group). Both a positive control group (untreated-infection group) and a negative control group were also produced. The treatment response, monitored by positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose ([18F]FDG) at 3 and 6 weeks, showed rapidly decreasing amounts of [18F]FDG uptake in the treated-infection group (P = 0.001 compared with the results for the untreated-infection group at 6 weeks). The bacteriological analysis confirmed the eradication of the bone pathogen in the treated-infection group. However, three animals had culture-positive soft tissue infections. All animals in the sham-treated and untreated-infection groups had culture-positive bone infections with typical radiographic changes of osteomyelitis. Histomorphometry, peripheral quantitative computed tomography, and backscattered electron imaging of scanning electron microscopy images verified the osteoconductive properties of the bioactive glass microspheres within the composite. The median bone ciprofloxacin concentrations were 1.2 and 2.1 microg/g at two anatomic locations of the tibia. This is the first report to show the value of [18F]FDG PET for quantitative monitoring of the treatment response in bone infections. The collaborative results of bacteriologic and [18F-FDG] PET studies showed that use of the multifunctional composite was successful for eradication of the S. aureus pathogen from bone.

Accuracy and precision of radiostereometric analysis in the measurement of three-dimensional micromotion in a fracture model of the distal radius

The purpose of the current study was to verify the feasibility of radiostereometric analysis (RSA) in monitoring three-dimensional fracture micromotion in fractures of the distal radius. The experimental set-up consisted of a simulated model of an extra-articular Colles' fracture, including metallic beads inserted into the bone on either side of the fracture site. The model was rigidly fixed to high precision micrometer stages allowing controlled translation in three axes and rotation about the longitudinal and transverse axes. The whole construct was placed inside a RSA calibration cage with two perpendicular radiographic film cassettes. Accuracy was calculated as the 95% prediction intervals from the regression analyses between the micromotion measured by RSA and actual displacements measured by micrometers. Precision was determined as the standard deviation of five repeated measurements of a 200 microm displacement or a 0.5 degrees rotation along a specific axis. Translations from 25 microm to 5mm were measured with an accuracy of +/-6 microm and translations of 200 microm were measured with a precision of 2-6 microm. Rotations ranging from 1/6 degrees to 2 degrees were measured with an accuracy of +/-0.073 degrees and rotations of 1/2 degrees were measured with a precision of 0.025 degrees -0.096 degrees . The number of markers and their configuration had greater impact on the accuracy and precision of rotation than on those of translation. Aside from the unknown rate of clinical marker loosening, the current results favor the use of at least four markers in each bone fragment in distal radius fractures. These results suggest a strong rationale for the use of RSA as an objective tool for comparing different treatment modalities and novel bone graft substitutes aimed at stabilization of fractures of the distal radius.

Efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to Staphylococcus aureus

Impregnation of antimicrobial agents within biodegradable orthopedic implants provides a possibility for local antimicrobial prophylaxis of biomaterial-related infections. The objective of this study was to evaluate the efficacy of a bioabsorbable ciprofloxacin containing bone screw (Ab-PLGA) in the prevention of biomaterial-related infection due to Staphylococcus aureus in a rabbit model. Animals in Group I (n=8) received a Ab-PLGA screw contaminated with S. aureus, while animals in Group II (n=8) received a stainless steel (SS) screw contaminated with S. aureus. In two negative control groups, the animals received a Ab-PLGA screw (Group III, n=4) or a SS screw (Group IV, n=4) without bacterial contamination. 18F-FDG-PET imaging, performed at 6 weeks, was applied as a novel quantitative in vivo imaging modality of implant-related infection. Infection was verified by swab cultures, direct cultures of the retrieved implant, and quantitative cultures of pulverized bone. The concentrations of ciprofloxacin in serum and local bone tissue were determined by a high performance liquid chromatographic (HPLC) method with fluorescence (FLD) detection. In the group of contaminated Ab-PLGA screws, all cultures were negative. In the group of contaminated SS screws, all cultures of retrieved implants and six cultures out of eight of pulverized bone were positive for inoculated S. aureus. In negative control groups, all cultures were negative except one contaminant (S. cohnii) found in a SS screw culture. Verified infection of contaminated SS screws was collaborated by the increased 18F-FDG-PET uptake (P=0.004 compared with the group of contaminated Ab-PLGA screws). The mean bone tissue concentration of ciprofloxacin varied from 2.54 to 0.83 microg/g bone as a function of distance from the implantation site. The serum concentration of ciprofloxacin remained undetectable and below the resolution of the analytic method (<5.0 ng/ml). This study confirmed the in vivo efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to S. aureus.

Precision measurements of the RSA method using a phantom model of hip prosthesis

Radiostereometric analysis (RSA) has become one of the recommended techniques for pre-market evaluation of new joint implant designs. In this study we evaluated the effect of repositioning of X-ray tubes and phantom model on the precision of the RSA method. In precision measurements, we utilized mean error of rigid body fitting (ME) values as an internal control for examinations. ME value characterizes relative motion among the markers within each rigid body and is conventionally used to detect loosening of a bone marker. Three experiments, each consisting of 10 double examinations, were performed. In the first experiment, the X-ray tubes and the phantom model were not repositioned between one double examination. In experiments two and three, the X-ray tubes were repositioned between one double examination. In addition, the position of the phantom model was changed in experiment three. Results showed that significant differences could be found in 2 of 12 comparisons when evaluating the translation and rotation of the prosthetic components. Repositioning procedures increased ME values mimicking deformation of rigid body segments. Thus, ME value seemed to be a more sensitive parameter than migration values in this study design. These results confirmed the importance of standardized radiographic technique and accurate patient positioning for RSA measurements. Standardization and calibration procedures should be performed with phantom models in order to avoid unnecessary radiation dose of the patients. The present model gives the means to establish and to follow the intra-laboratory precision of the RSA method. The model is easily applicable in any research unit and allows the comparison of the precision values in different laboratories of multi-center trials.

Comparative 18F-FDG PET of experimental Staphylococcus aureus osteomyelitis and normal bone healing

PET using (18)F-FDG is a promising imaging modality for bone infections, based on intensive consumption of glucose by mononuclear cells and granulocytes. The method may have limitations in distinguishing uncomplicated bone healing from osteomyelitis. Bone healing involves an inflammatory phase that represents a highly activated state of cell metabolism and glucose consumption, mimicking infection on PET images. This laboratory study of a standardized model was designed to compare the (18)F-FDG PET characteristics of normal bone healing with those of local osteomyelitis.

METHODS

A localized osteomyelitis model of the rabbit tibia was created by modifying a previously reported canine model. In the osteomyelitic group (n = 8), a standardized metaphyseal defect of the proximal right tibia was surgically created and filled with a block of orthopedic bone cement, followed by injection of a predetermined amount (0.1 mL) of Staphylococcus aureus (strain 52/52A/80, 1 x 10(5)/mL) into the space around the cement. The control group of animals with normal bone healing (n = 8) underwent the same procedure, but the bacterial injection was replaced by a sterile saline injection. The bone cement was surgically removed during debridement at 2 wk. Osteomyelitis was confirmed with positive bacterial cultures during the debridement and 6 wk later at the time of sacrifice. (18)F-FDG PET and peripheral quantitative CT were performed 3 and 6 wk after the debridement. The presence of osteomyelitic bone changes on plain radiographs was classified according to a previously published system.

RESULTS

Before surgery, the standardized uptake values of (18)F-FDG did not differ markedly between the right and left tibias. In the control animals, uncomplicated bone healing was associated with a temporary increase in (18)F-FDG uptake at 3 wk (P = 0.007), but it returned almost to normal by 6 wk. In the experimental animals, localized osteomyelitis resulted in an intense continuous uptake of (18)F-FDG, which was higher than that of healing and intact bones at 3 wk (P = 0.014 and P < 0.001, respectively) and at 6 wk (P < 0.001).

CONCLUSION

(18)F-FDG PET seems to be an efficient tool in the differentiation of uneventful bone healing from bone healing complicated by localized osteomyelitis.