Wear debris released by hip prosthesis analysed by microcomputed tomography

Total hip arthroplasty uses commercial devices that combine different types of biomaterials. Among them, metals, ceramics and metal oxides can be used either in the prosthesis itself or in the cement used to anchor them in the bone. Over time, all of these materials can wear out and release particles that accumulate in the periprosthetic tissues or can migrate away. We used histology blocks from 15 patients (5 titanium metallosis, 5 alumina prostheses, 5 with altered methacrylic cement) to perform a microCT study and compare it with conventional histology data. An EDS-SEM analysis was done to characterise the atomic nature of the materials involved. A morphometric analysis was also performed in 3D to count the particles and assess their density and size. The metallic particles appeared to be the largest and the ceramic particles the finest. However, microCT could not reveal the wear particles of radiolucent biomaterials such as polyethylene and the very fine zirconia particles from cement fragmentation. MicroCT analysis can reveal the extent of the accumulation of these debris in the periprosthetic tissues. LAYOUT DESCRIPTION: Hip prostheses progressively degrade in the body by releasing wear debris. They accumulate in the periprosthetic tissues. Microcomputed tomography was used to image three types of radio-opaque wear debris: metal, ceramic and zirconia used in the bone cements.

Clinical and radiological outcomes of a cohort of 9 patients with anatomical fractures of the cuboid treated by locking plate fixation

INTRODUCTION

Cuboid fractures are very rare. Hence, their treatment has not been standardized. Advances in imaging techniques, particularly three-dimensional computed tomography (3D CT), and the introduction of cuboid-specific plates has improved the care of these injuries. The aim of this study was to determine the radiological and clinical outcomes of anatomical reconstruction of comminuted cuboid fractures with a locking plate.

HYPOTHESIS

Fixation of comminuted cuboid fractures with a cuboid-specific locking plate leads to stable anatomical reduction and good functional outcomes.

MATERIAL AND METHODS

This was a retrospective study of 9 consecutive cases of comminuted cuboid fracture treated at a single hospital between January 2009 and December 2015. A 3D CT scan was performed preoperatively with subtraction of the posterior tarsal bone to allow the articular facets to be viewed and analyzed. Fracture fixation was done with a Locking Cuboid Plate (DePuy Synthes™). Associated lesions in the foot were treated during the same procedure. The patients were reviewed by an independent observer who performed a clinical examination, and determined the AOFAS and Maryland Foot Score. The success of the reconstruction was determined by comparing the parameters on weight-bearing X-rays views between the fixed and non-operated cuboid.

RESULTS

The mean follow-up was 4.1 years (range 1-6). The Maryland Foot Score was 93.1 [86-100] and the AOFAS was 91.9 [82-100]. The reconstruction was anatomical and long lasting in all 9 cases. There was no foot misalignment in the frontal plane, based on the radiographs (hindfoot axis 5.5° [0-9]). The mean Djian-Annonier angle was 123.9° [108-130].

CONCLUSION

Cuboid fractures can be treated effectively through appropriate imaging and with a cuboid-specific locking plate as evidenced by very good midterm clinical and radiological outcomes in this study.

LEVEL OF EVIDENCE

IV Retrospective study.

Reconstruction of large diaphyseal bone defect by simplified bone transport over nail technique: A 7-case series

Reconstruction of large diaphyseal bone defect is complex and the complications rate is high. This study aimed to assess a simplified technique of segmental bone transport by monorail external fixator over an intramedullary nail.A prospective study included 7 patients: 2 femoral and 5 tibial defects. Mean age was 31years (range: 16-61years). Mean follow-up was 62 months (range: 46-84months). Defects were post-traumatic, with a mean length of 7.2cm (range: 4 to 9.5cm). For 3 patients, reconstruction followed primary failure. In 4 cases, a covering flap was necessary. Transport used an external fixator guided by an intramedullary nail, at a rate of 1mm per day. One pin was implanted on either side of the distraction zone. The external fixator was removed 1 month after bone contact at the docking site. Mean bone transport time was 11 weeks (range: 7-15 weeks). Mean external fixation time was 5.1months (range: 3.5 to 8months). Full weight-bearing was allowed 5.7months (range: 3.5-13months) after initiation of transport. In one patient, a pin had to be repositioned. In 3 patients, the transported segment re-ascended after external fixatorablation, requiring repeat external fixation and resumption of transport. There was just 1 case of superficial pin infection. Reconstruction quality was considered "excellent" on the Paley-Marr criteria in 6 cases. The present technique provided excellent reconstruction quality in 6 of the 7 cases. External fixation time was shorter and resumption of weight-bearing earlier than with other reconstruction techniques, notably including bone autograft, vascularized bone graft or the induced membrane technique. Nailing facilitated control of limb axis and length. The complications rate was 50%, comparable to other techniques. This study raises the question of systematic internal fixation of the docking site, to avoid any mobilization of the transported segment. The bone quality, axial control and rapidity shown by the present technique make it well-adapted to reconstruction of diaphyseal bone defect.

LEVEL OF EVIDENCE

Four-case series.

Is radiographic measurement of distal femoral torsion reliable?

BACKGROUND

Distal femur torsion (DFT) is a crucial parameter in knee replacement surgery. The reference standard for measuring DFT is posterior condylar angle (PCA) measurement using computed tomography (CT). The objective of this study was to assess the feasibility and reliability of a radiographic PCA measurement method.

MATERIALS AND METHODS

We studied 125 osteoarthritic knees in 79 patients (42 women and 37 men) with a mean age of 71.6 ± 8.8 years (range 47 to 86 years); 32 knees were aligned, 85 in varus, and eight in valgus. DFT was measured on an antero-posterior (AP) radiograph of the knee in 90° of flexion (known as the seated AP view). The PCA was defined as the angle subtended by the tangent to the posterior condyles and the transepicondylar axis (anatomic PCA [aPCA]) or the line connecting the lateral epicondyle to the medial sulcus (surgical PCA [sPCA]). The PCA was conventionally recorded as positive in the event of external torsion and negative in the event of internal torsion. PCA measurements were performed three times by each of five observers to allow assessments of inter-observer and test-retest reliabilities.

RESULTS

aPCA was consistently negative (mean, -6.1 ± 1.6°) (range, 0 to -10°); inter-observer and test-retest reliability were satisfactory (0.54<rw 0.80). sPCA was positive in 41 knees and negative in 84 knees) (mean, -0.3 ± 1.4°) (range, -5° to +2°); inter-observer and test-retest reliabilities were poor (0.28<r<0.69). A weak but significant correlation was found between aPCA and coronal alignment, with a trend towards greater internal torsion in the group of valgus knees.

CONCLUSION

Radiographic measurement of DFT is simple and non-invasive. Measurement reproducibility was satisfactory for aPCA but not for sPCA. aPCA showed marked inter-individual variability and tended to increase when the knee was in valgus. Mean aPCA values were comparable to those reported using CT. In contrast to CT, radiographic DFT measurement can easily be incorporated into the pre- and postoperative work-ups for knee replacement surgery, provided the patient can achieve 90° of knee flexion.

LEVEL OF EVIDENCE

Level IV, prospective cohort study.

Internal fixation of complex fractures of the tarsal navicular with locking plates. A report of 10 cases

INTRODUCTION

Tarsal navicular fractures are rare and treatment of comminuted fractures is especially difficult. Since 2007, the authors have had access to 3D reconstruction from CT scan images and specific locking plates, and they decided to evaluate whether these elements improved management of these severe cases.

MATERIALS AND METHODS

Between 2007 and 2011, 10 comminuted tarsal navicular fractures were treated in a prospective study. All of the fractures were evaluated by 3D reconstruction from CT scan images, with suppression of the posterior tarsal bones. The surgical approach was chosen according to the type of lesion. Reduction was achieved with a mini-distractor when necessary, and stabilized by AO locking plate fixation (Synthes™). Patient follow-up included a clinical and radiological evaluation (Maryland Foot score, AOFAS score). Eight patients underwent postoperative CT scan.

RESULTS

All patients were followed up after a mean 20.5 months. Union was obtained in all patients and arthrodesis was not necessary in any of them. The mean Maryland Foot score was 92.8/100, and the AOFAS score 90.6/100. One patient with an associated comminuted calcaneal fracture had minimal sequella from a compartment syndrome of the foot.

DISCUSSION

The authors did not find any series in the literature that reported evaluating tarsal navicular fractures by 3D reconstruction from CT scan images. The images obtained after suppression of the posterior tarsal bones systematically showed a lateral plantar fragment attached to the plantar calcaneonavicular ligament, which is essential for stability, and which helped determine the reduction technique. Locking plate fixation of these fractures has never been reported.

CONCLUSION

Comminuted fractures of the tarsal navicular were successfully treated with specific imaging techniques in particular 3D reconstructions of CT scan images to choose the surgical approach and the reduction technique. Locking plate fixation of the navicular seems to be a satisfactory solution for the treatment of these particularly difficult fractures.

LEVEL OF EVIDENCE

Level IV.

Total talar fracture - inter- and intra-observer reproducibility of two classification systems (Hawkins and AO) for central talar fractures

INTRODUCTION

We evaluated the inter- and intra-observer reproducibility of two classification systems for central talar fractures (Hawkins, as modified by Canal and Kelly and then by us; AO/AOT).

HYPOTHESIS

The analysis and classification of these fractures will be better with CT scans than with X-rays.

MATERIAL AND METHODS

Four observers evaluated 39 X-ray and CT scan files twice in the span of six weeks; each evaluation entailed classifying the fractures and describing their main features. Cohen's Kappa coefficient for inter-rater agreement was calculated and analysed.

RESULTS

The inter- and intra-observer reproducibility with CT scans was better with X-rays for most of the parameters evaluated. The modified Hawkins classification provided better reproducibility than the AO/AOT one. However, this classification system was not perfect, even after modifications and use of CT scans.

DISCUSSION

CT scans are an essential tool for the analysis of all talar fractures. We modified the Hawkins classification (as modified by Canal and Kelly) to include a Type 0 (no displacement or less than 2mm), include frontal body fractures that are displaced like neck fractures and take into account comminuted fractures and other trauma in the area.

LEVEL OF PROOF

IV - retrospective clinical study.

Total talar fracture - long-term results of internal fixation of talar fractures. A multicentric study of 114 cases

INTRODUCTION

Displaced talar neck and body fractures are rare and challenging for the surgeon. Results are often disappointing due to inadequate reduction or internal fixation and high rates of osteoarthritis and osteonecrosis. Very few published series describe the long-term results after internal fixation of talar factures. One of the goals of the 2011 SOO meeting symposium was to specifically evaluate the long-term results after internal fixation of talar fractures. This study included only central fractures.

MATERIAL AND METHODS

We reviewed the results of 114 central talar fractures that had been treated by internal fixation between 1982 and 2006 in nine hospitals in the Western part of France. The clinical and radiological follow-up was 111 months on average. All the patients with a radiological assessment had at least 5 years of follow-up.

RESULTS

Poor reduction was apparent in 33% of cases. The average Kitaoka score was 70/100, which corresponds to an average functional level. At the last follow-up evaluation, 34% of cases had osteonecrosis and 74% had peritalar osteoarthritis. Secondary fusion was required in 25% of cases with an average follow-up of 24 months.

DISCUSSION

The complication rate for talar fractures was high, mostly due to osteonecrosis and osteoarthritis; these conditions had an impact on the final outcome. The outcome could be improved by better evaluating these fractures with a CT scan, developing dual surgical approaches to best preserve the bone vascular supply and achieve better reduction, and improving the internal fixation hardware, especially the use of plates for comminuted fractures.

Treatment of complex fractures of the distal radius: a prospective randomised comparison of external fixation 'versus' locked volar plating

The traditional treatment of severely impacted fractures of the distal radius involves bridging external fixation and maintaining reduction by applying continuous traction. The recent technique using fixed-angle screws within volar plates is reported restore the radial length and the articular profile whilst avoiding joint distraction. It is also believed to produce better and quicker clinical results. To test these claims, we carried out a randomised controlled comparison of the efficiency of external fixation (EF) 'versus' open reduction and internal fixation (ORIF) in treating severely impacted fractures of the distal radius. A total of 39 patients were treated with EF, eventually associated with percutaneous pinning, whereas 36 underwent ORIF with a locked volar plate. There was no significant difference in the two groups with regard to changes in the ulnar variance. Articular reduction was poor in two patients in the EF group with residual step-offs exceeding 2mm; another patient of the EF group suffered a secondary loss of reduction, healing with a severe articular malunion (>2mm). By contrast, articular reduction was satisfactory in all the patients of the ORIF group. The clinical results on the Green and O'Brien rating were significantly better in the ORIF group than in the EF group (p<0.01 at 6 weeks, p<0.05 at 6 months). Nevertheless, open reduction and volar plating did not yield better subjective results than EF. However, although not statistically significant, patients treated by ORIF seemed to resume their usual activities quicker than those treated with EF, suggesting that this technique may be adapted to a greater extent in the case of active, young individuals.

Effect of hyperoxia on glutathione levels and glutamic acid uptake in endothelial cells

Intracellular glutathione was increased by 80% after exposure of bovine pulmonary arterial endothelial cells to 80% O2 (hyperoxia) for 24 h. No change in glutathione occurred in cells exposed to hypoxia (3% O2) for a corresponding period of time. The rate of uptake of [3H]glutamic acid also increased by 35-55% after 24 h of exposure of cells to hyperoxia, whereas exposure to hypoxia had no effect on the [3H]glutamic acid uptake. The increase in glutamic acid uptake reflected a specific effect on amino acid transport systems rather than a change in cell membrane permeability. The major portion of the increased uptake was inhibited by the elimination of sodium and the addition of the competitive inhibitor, cystine, to the incubation medium. Thus increases in glutamic acid uptake parallel increases in cellular glutathione, and glutamic acid may be a regulating factor in the increase in glutathione after exposure to hyperoxia.

Characterization of glutamic acid uptake by bovine pulmonary arterial endothelial cells

L-Glutamic acid uptake by bovine pulmonary arterial endothelial cells in culture increased linearly with time up to 30 min and did not show saturation with increased substrate concentration up to 6 X 10(-3) M. The uptake per cell decreased as cell density increased and was lowest when the cells became fully confluent. Most of the uptake was sodium dependent, although the relative contribution of sodium-independent uptake increased with an increase in cell density. Cysteic and aspartic acid strongly inhibited L-glutamic acid uptake, but at higher cell densities this effect was less pronounced than at low densities. Other amino acids, including leucine, glutamine, and serine, exerted a modest inhibitory effect at both high and low cell densities. Thus pulmonary arterial endothelial cells contain similar membrane transport systems for L-glutamic acid as those previously described for fibroblasts, hepatocytes, and nerve cells. However, quantitative properties of the transport systems differ depending on the state of cellular density in monolayers.