A preliminary study of joint surface changes after an intraarticular fracture: a sheep model of a tibia fracture with weight bearing after internal fixation

Influence of articular step-off on contact mechanics in fractures of the posterolateral-central tibial plateau - a biomechanical study

BACKGROUND

The posterior quadrants of the tibial plateau are frequently involved in OTA type C tibial plateau fractures. The biomechanical influence of a residual articular step-off of the posterolateral-central (PLC) segment, which is difficult to visualize intraoperatively, remains unclear. Therefore, aim of this study was to investigate the contact area and stress of the tibial plateau in cases of different articular step-offs of the PLC segment.

METHODS

Seven human cadaveric knees were used to simulate articular impressions of the PLC segment with step-offs of 1 mm, 3 mm, and 5 mm. The knees were axially loaded up to 150 N during a total of 25 dynamic cycles of knee flexion up to 90°. Pressure mapping sensors were inserted into the medial and lateral joint compartments beneath the menisci to measure articular contact area and stress.

RESULTS

Between 60° and 90° of knee flexion, increasing PLC segment impressions of the tibial plateau led to increasing contact stress and a significantly reduced contact area. The largest decrease in the contact area was 30 %, with an articular step-off of 5 mm (0.003). An increase in contact stress, especially from a 3-mm step-off, was measured, with a doubling of the mean contact stress at 3-mm and 5-mm step-offs and 90° knee flexion (p = 0.06/0.05).

CONCLUSION

From a biomechanical point of view, posterior impressions of the PLC segment greater than a 1-mm step-off should be addressed as anatomically as possible, especially in active patients with the need for higher knee flexion angles.

Revisiting the management of tibial plateau fractures

Three-dimensional imaging has changed the understanding and management of tibial plateau fractures. In the 1970s, Schatzker proposed a classification for tibial plateau fractures, which highlighted the morphology of the six principal types. More recently, this original classification was complimented by an extended one underscoring the importance of understanding where the split wedge fragment(s) is/are located in three dimensions. The extended classification introduced the split wedge fragment and the continuity of the rim as the determinants of joint stability and the critical role that this plays in the management of tibial plateau fractures. The current manuscript re-emphasizes contemporary concepts of tibial plateau stability and depicts key issues which must be considered when planning the definitive surgical fixation of tibial plateau fractures.

A lateral fracture step-off of 2mm increases intra-articular pressure following tibial plateau fracture

INTRODUCTION

The aim of this study was to evaluate the effects of increasing posttraumatic step-offs after lateral tibial plateau fracture reduction on the intra-articular pressure.

MATERIALS AND METHODS

In eight fresh-frozen human cadaveric knees with intact menisci, a standardized sagittal osteotomy of the lateral tibial condyle was performed as an OTA/AO type 41-B1 fracture-model. The fragment was fixed by a customized sled including an angular stable tibia plate to evaluate step-offs from 0 mm to 8 mm in 1mm increments. In a servo-hydraulic testing machine, an axial force was applied to the tibial plateau in 0° (700N), 15° (700N), 30° (700N), 60° (350N), and 90 ° (350N) of flexion while the joint pressure was recorded by two pressure sensors.

RESULTS

A 1mm step-off did not result in an increased joint pressure. At 60° of flexion a 2mm step-off increased the lateral joint pressure by 61.84kPa (P = 0.0027). In 30° of flexion, a 3mm step raised the lateral joint pressure by 66.80kPa (p = 0.0017), whereas in 0°, 15° and 90° of flexion, a 4mm step increased the pressure by >50kPa (P < 0.05). Concomitant medial joint pressure increments were lower than those in the lateral plateau. A significant increase of 19-24kPa in the medial joint pressure was detected in 90° of flexion with a 1mm lateral step (P = 0.0075), in 15° and 60° of flexion with a 2mm step (P < 0.05), in 0° of flexion with a 4mm step (P = 0.0215) and in 30° of flexion with a 7mm step (P = 0.0487).

CONCLUSION

Lateral fracture step-offs of 2mm or larger should be reduced intraoperatively to avoid large increases in lateral joint pressure.

A Post-Traumatic Osteoarthritic Model of Hip Following Fracture of Acetabulum in Rabbit: A Preliminary Study by Macroscopic and Radiographic Assessment

Objective

To develop a post‐traumatic osteoarthritic model of hip following fracture of acetabulum in rabbit for revealing biochemical mechanism of post‐traumatic osteoarthritis.

Methods

A total of 36 mature male New Zealand white rabbits were equally divided into sham group (n = 12), non‐ORIF group (n = 12), and open reduction and internal fixation (ORIF) group (n = 12). Except for the sham group, rabbits had survival surgeries to create acetabular fractures of dorsal wall for simulating dashboard impaction mechanism. The ORIF group received open reduction and internal fixation, while fractures in the non‐ORIF group were left as displaced but transverse fracture and dislocation was reduced. Besides intraoperative appearance and postoperative recovery, macroscopic and radiographic characteristics of the hips were recorded and assessed by a radiographic scoring scale at 3 weeks, 6 weeks, and 6 months, respectively.

Results

Out of 24 modeled acetabula, 21 (87.5%) were pure dorsal wall fractures as proposed and the remaining three were associated fractures (dorsal wall plus transverse fracture) accompanied by dorsal dislocation or not. All hips were stable, and no sciatic nerve injury was observed. One rabbit in the ORIF group died of deep infection 4 days after surgery. Rabbits in the sham and ORIF groups returned to normal gait in 2 weeks, but animals in the non‐ORIF group suffered from limping and restricted movement. As the time progressed, the hips in the non‐ORIF group experienced progressive and severe degeneration which exhibited dramatically malformed and hypertrophic joints at 6 months, but the ORIF group maintained much better morphological structure. Corresponding to morphological changes, the average radiographic scores of the non‐ORIF group increased from 1.25 at 3 weeks to 2.75 at 6 months and showed statistically significant difference when compared to the sham group at all three time points (P = 0.011, 0.011, 0.015, respectively, <0.0167). Although the scores of the ORIF group showed apparent improvements (increased from 0.67 at 3 weeks to 2.00 at 6 months), there was no significant difference between the two modeled groups at all three time points.

Conclusion

The fracture model with high consistency and reproducibility showed progressive post‐traumatic osteoarthritic changes which could be improved by open reduction and internal fixation surgery and provided an alternative selection for investigating potential pathogenesis and pathology of post‐traumatic osteoarthritis following fracture of acetabulum.

Cartilage and subchondral bone distributions of the distal radius: a 3-dimensional analysis using cadavers

OBJECTIVE

To quantify the spatial distributions of cartilage and subchondral bone thickness of the distal radius.

DESIGN

Using 17 cadaveric wrists, three types of 3-dimensional models were created: a cartilage-bone model, obtained by laser scanning; a bone model, rescanned after dissolving the cartilage; and a subchondral bone model, obtained using computed tomography. By superimposing the bone model onto the cartilage-bone and the subchondral bone models, the cartilage and subchondral bone thickness were determined. Measurements along with the spatial distribution were made at fixed anatomic points including the scaphoid and lunate fossa, sigmoid notch and interfossal ridge, and compared at each of these four regions.

RESULTS

Cartilage thickness of the interfossal ridge (0.89 ± 0.23 mm) had a larger average thickness compared to that of the scaphoid fossa (0.70 ± 0.18 mm; p = 0.004), lunate fossa (0.75 ± 0.17 mm; p = 0.044) and sigmoid notch (0.64 ± 0.13 mm; p < 0.001). Subchondral bone was found to be thickest at the scaphoid (2.18 ± 0.72 mm) and lunate fossae (1.94 ± 0.93 mm), which were both thicker than that of sigmoid notch (1.63 ± 1.06 mm: vs scaphoid fossa, p = 0.020) or interfossal ridge (1.54 ± 0.84 mm: vs scaphoid fossa, p = 0.004; vs lunate fossa, p = 0.048). In the volar-ulnar sub-regions of the scaphoid and lunate fossa, the subchondral bone thickened.

CONCLUSIONS

Our data can be applied when treating distal radius fractures. Cartilage thickness was less than 1 mm across the articular surface, which may give an insight into threshold for an acceptable range of step-offs. The combined findings of subchondral bone appreciate the importance of the volar-ulnar corner of the distal radius in the volar locking plate fixation.

3D printing of implants for patient-specific acetabular fracture fixation: an experimental study

PURPOSE

To test the effect of 3D printed implants, designed according to surgeon's individual plan, on the accuracy of reduction of an acetabular fracture model.

METHODS

Seven identical standardized plastic bone models of an anterior column/posterior hemi-transverse acetabular fracture were used. A CT of one plastic fracture model was made. Using preoperative planning software, three surgeons independently planned the reduction and fixation procedure and designed implants and drill guides. The designed implants and guides were then 3D printed. Each surgeon first executed his plan using his 3D printed plates and guides on one fracture model and then performed another procedure on an identical model with standard implants and instrumentation. Displacement of the fragments at the weight-bearing fracture lines in the acetabulum was measured after fixation. Linear mixed effect models were used to evaluate the effect of different solutions to the same fracture pattern.

RESULTS

Mean (SD) displacement of the fracture line between the ischium and stable fragment was 1.1 (0.9) mm for the standard implant and 0.8 (0.6) mm for the 3D printed implant, while the displacements of the fracture line between the stable fragment and anterior column were 0.6 (0.6) and 0.3 (0.3) for the standard and 3D printed methods, respectively (p < 0.001). Mean (SD) fracture line step-off at any fracture line for the standard implant was 1.2 (0.9) mm and 0.4 (0.4) mm for the 3D printed implant (p = 0.022).

CONCLUSIONS

Patient-specific 3D printed plates and drill guides may facilitate retaining accurate reduction and fixation of select acetabular fracture patterns.

Regional Distribution of Articular Cartilage Thickness in the Elbow Joint: A 3-Dimensional Study in Elderly Humans

During elbow procedures, reconstruction of the joint (including the articular cartilage) is important in order to restore elbow function; however, the regional distribution of elbow cartilage is not completely understood. The purpose of the present study was to investigate the 3-dimensional (3-D) distribution patterns of cartilage thickness of elbow bones (including the distal part of the humerus, proximal part of the ulna, and radial head) in order to elucidate the morphological relationship among them.

Complex Tibial Plateau Fractures Treated by Hybrid External Fixation System: A correlation of followup computed tomography derived quality of reduction with clinical results

BACKGROUND

Tibial plateau fractures are common due to high energy injuries. The principles of treatment include respect for the soft tissues, restoring the congruity of the articular surface and reduction of the anatomic alignment of the lower limb to enable early movement of the knee joint. There are various surgical fixation methods that can achieve these principles of treatment. Recognition of the particular fracture pattern is important, as this guides the surgical approach required in order to adequately stabilize the fracture. This study evaluates the results of the combined treatment of external fixator and limited internal fixation along with the advantages using postoperative computed tomography (CT) scan after implant removal. Materials and.

METHODS

55 patients with a mean age of 42 years (range 17-65 years) with tibial plateau fracture, were managed in our institution between October 2010 and September 2013., Twenty fractures were classified as Schatzker VI and 35 as Schatzker V. There were 8 open fractures (2 Gustilo Anderson 3A and 6 Gustilo Anderson 2). All fractures were treated with closed reduction and hybrid external fixation (n = 21/38.2%) or with minimal open reduction internal fixation and a hybrid system (n = 34/61.8%). After the removal of the fixators, CT-scan was programmed for all the cases, for correlation with the results. At final followup, the American Knee Society Score (AKSS) was administered.

RESULTS

All patients were evaluated with a minimum of 12 months (range 12-21 months) followup. Average time to union was 15.5 weeks (range 13-19 weeks). The postoperative joint congruity as evaluated in the postoperative CT-scan was <2 mm of articular step-off in 8 patients (14.5%), between 2 and 4 mm in 18 patients (32.7%) and over 4 mm in 29 (52.7%). The injured limb mechanical axis was restored within 5° compared to the contralateral limb in 36 cases (65%) and with an angulation >5° in 19 cases (35%). Patients with residual joint depression <3.5 mm had a 95% chance of having excellent AKSS knee score results and 80% chance of having excellent AKSS function scores. On the other hand, residual joint depression of >4.5 mm displayed a 100% chance of getting poor-fair scores both in AKSS knee and AKSS function score. The association of a postoperative mechanical axis within 5° of the contralateral limb and improved knee scores was statistically significant for the AKSS function and total scores but not for the AKSS knee score. The AKSS was negatively correlated with postoperative joint depression magnitude which was statistically significant. Only the amount of joint collapse was verified as a prognostic factor in a multivariate logistic regression analysis.

CONCLUSIONS

The postoperative CT-scan shows important information about bone healing, and an exact image of the reduction and the shaft alignment. Postoperative radiographs may have led to an underestimation of the degree of residual displacement. On the contrary, CT-scan demonstrates the exact grade of articular displacement and depending on CT-scan results one can better manage the postoperative rehabilitation.

Articular cartilage thickness at the distal radius: a cadaveric study

PURPOSE

Articular stepoffs that occur after fracture and are greater in size than the thickness of the articular surface seem to result in arthritis. The thickness of a joint's cartilage may, therefore, set the limit for acceptable stepoff when treating fractures. The goal of our study was to determine the thickness of the articular cartilage at the distal radius.

METHODS

We conducted a cadaveric study of 19 wrists to measure the thickness of cartilage at the distal radius. After harvest, we made multiple slices of each radius and used a standardized technique to directly measure the articular cartilage in the scaphoid and lunate fossae and along the interfossal ridge.

RESULTS

The average cartilage thickness in our cohort was 0.6 mm. The average articular surface thickness was < 1 mm in all measured areas (scaphoid fossa, 0.7 mm; interfossal ridge, 0.8 mm; lunate fossa, 0.6 mm). Among the samples, 98% had an average thickness of < 1 mm. The maximum recorded thickness was 1.1 mm.

CONCLUSIONS

Our study quantifies the thickness of the articular cartilage at the distal radius. Our finding of cartilage thicknesses of < 1 mm is consistent with multiple clinical studies, suggesting that stepoffs of > 1 mm result in radiographic signs of arthritis. This provides further evidence linking the thickness of articular cartilage to radiographic outcomes and, possibly, clinical outcomes.

CLINICAL RELEVANCE

Our findings provide anatomic support for using 1 mm or less as an acceptable articular stepoff size in the treatment of fractures of the distal radius.

Management of the distal radioulnar joint and ulnar styloid fracture

Fractures of the distal radius and ulnar styloid have the potential to disturb the normal function of the distal radioulnar joint (DRUJ), resulting in loss of motion, pain, arthritis, or instability. The DRUJ can be adversely affected by several mechanisms, including intra-articular injury with step-off, shortening, and angulation of an extra-articular fracture; injury to the radioulnar ligaments; ulnar styloid avulsion fracture; and injury of secondary soft tissue stabilizers. This article discusses the management of the DRUJ and ulnar styloid fracture in the presence of a distal radius fracture.

Articular step-off and risk of post-traumatic osteoarthritis. Evidence today

The goal of treatment in intra-articular fractures is to obtain anatomical restoration of the articular surface and stable internal fixation. Studies have attempted to specify how accurately an articular fracture needs to be reduced to minimise the chances of a poor clinical outcome. In this study, the current evidence with regard to articular step-offs and risk of post-traumatic osteoarthritis (POA) is evaluated. A literature review based on pre-specified criteria, revealed 36 articles for critical analysis related to intra-articular injuries of distal radius, acetabulum, distal femur and tibial plateau.In the distal radius, step-offs and gaps detected with precise measurement techniques have been correlated with a higher incidence of radiographic POA, but in the second 5 years after injury, a negative clinical impact of these radiographic changes has not been convincingly demonstrated. Restoring the superior weight-bearing dome of the acetabulum to its pre-injury morphology decreases POA and improves patient outcomes. Involvement of the posterior wall, however, seems to bean adverse prognostic sign. This effect may be independent of articular reduction. In the tibial plateau, articular incongruities appear to be well tolerated, and factors only partially related to articular reduction are more important in determining outcome than articular step-off alone;these include joint stability, retention of the meniscus, and coronal alignment. Based on observational approach and evaluation of the studies, factors other than just the extent of articular displacement affect the management of articular fractures. Different joints and even different areas of the same joint appear to have different tolerances for post-traumatic articular step-offs.

Cell-Laden and Cell-Free Matrix-Induced Chondrogenesis versus Microfracture for the Treatment of Articular Cartilage Defects: A Histological and Biomechanical Study in Sheep

OBJECTIVE

The aim of this study was to evaluate the regenerative potential of cell-laden and cell-free collagen matrices in comparison to microfracture treatment applied to full-thickness chondral defects in an ovine model.

METHODS

Animals (n = 30) were randomized into 5 treatment groups, and 7-mm full-cartilage-thickness defects were set at the trochlea and medial condyle of both knee joints and treated as follows: 2 scaffolds in comparison (collagen I/III, Chondro-Gide(®); collagen II, Chondrocell(®)) for covering microfractured defects (autologous matrix-induced chondrogenesis), both scaffolds colonized in vitro with autologous chondrocytes (matrix-associated chondrocyte transplantation), or scaffold-free microfracture technique. One year after surgery, cartilage lesions were biomechanically (indentation test), histologically (O'Driscoll score), and immunohistochemically (collagen type I and II staining) evaluated.

RESULTS

All treatment groups of the animal model induced more repair tissue and showed better histological scores and biomechanical properties compared to controls. The average thickness of the repair tissue was significantly greater when a scaffold was used, especially the collagen I/III membrane. However, none of the index procedures surpassed the others from a biomechanical point of view or based on the histological scoring. Collagen type II expression was better in condylar defects compared to the trochlea, especially in those treated with collagen I/III membranes.

CONCLUSION

Covering of defects with suitable matrices promotes repair tissue formation and is suggested to be a promising treatment option for cartilage defects. However, it failed to improve the biomechanical and histological properties of regenerated articular cartilage compared to microfracture alone in an ovine model under the given circumstances.

Post-traumatic distal humerus non-union : Open reduction and internal fixation: long-term results

The objective of this paper is to evaluate the long-term functional results achieved after open reduction and internal fixation of 24 distal humerus non-unions. Non-unions were extra-articular-extracapsular (11 cases), extra-articular-intracapsular (8 cases) and intra-articular (5 cases). Preoperative elbow range of motion averaged 45 degrees. Time between original trauma and revision surgery averaged 14 months. Stabilisation methods varied according to type and location of the non-union. Follow-up averaged 46 months (range: 18-108). Elbow range of motion at last examination averaged 98 degrees . Flexion averaged 110 degrees and extension loss averaged 17 degrees . The disabilities of the arm, shoulder and hand (DASH) score averaged 16 points. Secondary transposition of the ulnar nerve was necessary in three cases. Sixteen patients reported no pain at last examination, seven had mild pain and one had moderate pain. Distal humerus non-unions present different characteristics; consequently, surgical treatment must be individualised for each patient. Even though they are demanding procedures, bony union and good long-term functional results were achieved.

Biochemical and biomechanical properties of lesion and adjacent articular cartilage after chondral defect repair in an equine model

BACKGROUND

Chondral defects may lead to degradative changes in the surrounding cartilage, predisposing patients to developing osteoarthritis.

PURPOSE

To quantify changes in the biomechanical and biochemical properties of the articular cartilage adjacent to chondral defects after experimental defect repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Specimens were harvested from tissue within (lesion), immediately adjacent to, and at a distance from (remote area) a full-thickness cartilage defect 8 months after cartilage repair with genetically modified chondrocytes expressing insulin-like growth factor-I or unmodified, control chondrocytes. Biomechanical properties, including instantaneous Young's and equilibrium aggregate moduli, were determined by confined compression testing. Biochemical properties, such as water and proteoglycan content, were also measured.

RESULTS

The instantaneous Young's modulus, equilibrium modulus, and proteoglycan content increased, whereas water content decreased with increasing distance from the repaired lesion. The instantaneous Young's and equilibrium moduli of the adjacent articular cartilage were 80% and 50% that of remote area samples, respectively, whereas water content increased 0.9% and proteoglycan content was decreased by 35%. No significant changes in biomechanical and biochemical properties were found either in the lesion tissue or in adjacent cartilage with genetic modification of the chondrocytes.

CONCLUSION

Articular cartilage adjacent to repaired chondral defects showed significant remodeling 8 months after chondral defect repair, regardless of whether genetically modified or unmodified cells were implanted.

CLINICAL RELEVANCE

Changes in the biochemical and biomechanical properties of articular cartilage adjacent to repaired chondral defects may represent remodeling as part of an adaptive process or degeneration secondary to an altered distribution of joint forces. Quantification of these changes could provide important parameters for assessing progress after operative chondral defect repair.

Remodeling of articular defects in an animal model

When treating displaced intraarticular fractures, the goal has been to restore normal articular cartilage contour to decrease local contact stresses that may lead to the development of posttraumatic osteoarthritis. To confirm observations that articular cartilage step-offs can remodel with time and to determine how the articular surface and subchondral bone remodels after an intraarticular fracture, joint surface changes were examined in a weightbearing sheep model with an intraarticular fracture. Articular surface pressure changes were observed across a 1-mm osteotomy. Twelve weeks after an intraarticular osteotomy, there was a decrease in differential pressure distribution between the normal articular cartilage and the depressed articular surface. Histologic analysis showed thinning of the articular cartilage on the high side of the osteotomy with collagen compression and bending of the collagen fibrils. On the low side of the osteotomy, increased chondrocyte cellularity and hypertrophy were observed. In addition, bending of collagen fibrils was observed in an unloaded state in an attempt to form a smooth overlapping shelf at the osteotomy site. Because intraarticular incongruency, with resultant joint contact pressure differences, seems to be involved in the development of posttraumatic arthritis, methods to improve cartilage remodeling may improve outcome after intraarticular fractures.

Experimental tibial plateau fractures augmented with calcium phosphate cement or autologous bone graft

BACKGROUND

Depression fractures of the tibial plateau are often managed with use of internal fixation and autologous bone-grafting to maintain an anatomical reduction. Bone-grafting, however, provides only limited stability. As calcium phosphate cements have appropriate mechanical properties, they may provide a more suitable alternative. The objective of this study was to compare the effect of a calcium phosphate cement with that of impacted cancellous autograft for maintaining an anatomical reduction in an experimental model of a tibial plateau fracture.

METHODS

Standardized cylindrical subchondral defects that were 8 mm in diameter and 10 mm deep were created bilaterally beneath the subchondral bone of the articular cartilage in the lateral tibial plateau of goats. An osteotome was used to fracture the overlying subchondral plate and articular cartilage. The plateau fracture fragment was completely depressed into the subchondral defect and then was anatomically reduced. The defects were randomly filled with either calcium phosphate cement or cancellous autograft. No internal fixation was used. The tibiae were harvested at varying time-periods that ranged from twenty-four hours to eighteen months. The stiffness of the healing augmented plateau fractures was determined. Histological specimens were assigned a score for degenerative changes. Loss of anatomic reduction was demonstrated in photomicrographs, and the amount of subsidence of the osteochondral fragment was measured in whole-mount histological sections.

RESULTS

The prevalence and degree of fracture subsidence was significantly reduced at all time-points in the defects treated with calcium phosphate cement compared with those filled with autograft (p < 0.05). There were no significant differences in fracture stiffness between the two treatment groups at any of the time-points examined. The calcium phosphate cement was rapidly resorbed, and the volume fraction of the calcium phosphate cement was decreased to 4% at six months. The trabecular bone volume in the defects was restored to that of the intact controls at six months in both treatment groups.

CONCLUSIONS

Cancellous autograft did not maintain an anatomical reduction of the tibial plateau fractures in this model. In contrast, augmentation with calcium phosphate cement prevented subsidence of the fracture fragment and maintained articular congruency as the fracture healed. The improved articular congruency reduced the prevalence and severity of degenerative changes in the joint.