Healing and remodeling of articular incongruities in a rabbit fracture model

A New Method for Creating Impact-Induced Intra-Articular Fractures in a Rabbit Model Induces Severe Post-Traumatic Osteoarthritis

OBJECTIVES

The objective of this work was to develop a model of intra-articular fracture (IAF) in a rabbit and document the speed and severity of degenerative joint changes after fracture fixation.

METHODS

With Institutional Animal Care & Use Committee approval, impact-induced IAFs were created in the distal tibia of 16 New Zealand White rabbits. Fractures were fixed with a plate and screws. Pain and function were monitored at regular postoperative intervals with limb loading analysis. Twelve or 26 weeks after fracture, animals were euthanized for histological assessment of cartilage degeneration and micro-computed tomography analysis of bone histomorphometry.

RESULTS

Eleven animals successfully completed the study. Maximum foot force in the fractured limb was 41% ± 21% lower than preoperative values ( P = 0.006) 12 weeks after fracture and remained 25% ± 13% lower ( P = 0.081) after 26 weeks. Cortical bone mineral density in micro-computed tomography images was 34% ± 13% lower 12 weeks after fracture ( P < 0.001) and remained (42% ± 8%) lower 26 weeks after fracture ( P < 0.001). Twelve weeks after fracture, Mankin scores of cartilage degeneration were significantly higher in the medial talus ( P = 0.007), lateral talus ( P < 0.001), medial tibia ( P = 0.017), and lateral tibia ( P = 0.002) of the fractured limb compared with the uninjured contralateral limb. Average Mankin scores in the talus increased from 12 to 26 weeks (5.9 ± 0.9 to 9.4 ± 0.4; P < 0.001 lateral; 5.4 ± 1.8 to 7.8 ± 2.0; P = 0.043 medial), indicating substantial and progressive joint degeneration.

CONCLUSIONS

The ankle joint of the New Zealand White rabbit provides the smallest available model of impact-induced IAF that can be treated with clinically relevant techniques and replicates key features of healing and degeneration found in human patients.

Prospective evaluation of the surgical stabilization and outcome of canine tibial plateau fractures in three cases

OBJECTIVE

To report the surgical approaches and stabilization of lateral and medial tibial plateau fractures (TPF), as well as the long-term outcome following repair.

STUDY DESIGN

Prospective series of three client-owned dogs.

ANIMALS

Three dogs.

METHODS

For the two lateral TPF cases (Unger type 41-B1), the surgical approach included separation of the lateral collateral ligament and long digital extensor tendon. The lateral meniscus was elevated to allow visualization of the tibial surface and assess fracture reduction. The first case was repaired using two 2.0 mm lag screws (with washers). The second case sustained a lateral TPF, fibular fracture and concurrent tubercle of Gerdy fracture. Both tibial fractures were stabilized using two 2.0 mm lag screws with washers and two 0.9 mm Kirschner wires (K-wires). A third case, diagnosed with an Unger type 41-B2 medial TPF, was treated using 0.9 mm K-wires and 22-gauge tension band.

RESULTS

There were no major complications noted. One minor complication occurred (screw yield two weeks postoperatively). By 8 weeks, all patients reached clinical union with good limb function. Owners were contacted 9-36 months postoperatively. LOAD scores and examinations were performed for two of three patients; the third patient was not contactable after relocating out of state. Both cases with completed questionnaires had a LOAD score of 5/52.

CONCLUSION

Tibial plateau fractures are rare in canine patients. While challenging, they can be successfully managed using a combination of lag screws, K-wires, and tension band.

CLINICAL SIGNIFICANCE

Surgical stabilization of TPF is feasible and may reduce the risk of meniscal injury.

Accuracy of the Surface Contour of Three-Dimensional-Printed Canine Pelvic Replicas

OBJECTIVE

The aim of this study was to determine the differences in surface contour between models of native pelvic bones and their corresponding three-dimensional (3D)-printed replicas.

STUDY DESIGN

Digital 3D models of five cadaveric hemipelves and five live dogs with contralateral pelvic fractures were generated based on computed tomographic images and 3D printed. The 3D-printed replicas underwent 3D scanning and digital 3D models of the replicas were created. The digital 3D model of each replica was superimposed onto the model of the native hemipelvis. Errors in the replicas were determined by comparing the distances of 120,000 corresponding surface points between models. The medial surface, lateral surface and dorsal surface of the acetabulum (DSA) of each hemipelvis were selected for further analysis. The root mean square error (RMSE) was compared between various selected areas using a one-way repeated measures analysis of variance, followed by a Bonferroni post-hoc test.

RESULTS

The RMSE of the hemipelvis was 0.25 ± 0.05 mm. The RMSE significantly decreased from the medial surface (0.28 ± 0.06mm), to the lateral surface (0.23 ± 0.06mm), to the DSA (0.04 ± 0.02mm) (p < 0.001).

CONCLUSION

The 3D-printed replicas were adequate in serving as a template for the pre-contouring of bone plates in fracture repair of pelvic fractures, particularly those that demand accurate reduction such as acetabular fractures.

Establishment of a finite element model and stress analysis of intra-articular impacted fragments in posterior malleolar fractures

Background

Intra-articular impacted fragments (IAIFs) are considered articular surface fragments resulting from impact and compressive forces. The malreduction of IAIFs in posterior malleolar fractures has been associated with talar subluxation and long-term post-traumatic arthritis. In this study, we establish IAIF defect finite element models of different sizes in posterior malleolar fractures and explored how IAIF defects predict the onset of post-traumatic arthritis.

Methods

A reliable three-dimensional finite element model of the normal ankle was established. Finite element models with different sizes of IAIF defects were created to calculate ankle joint contact stress. The finite element data were recorded and analyzed.

Results

There was a linear relationship between the size of the IAIF defect and MCS with IAIF defects in the posterolateral region. The result of Pearson linear correlation analysis was r = 0.963, P = 0.009. The regression equation was MCS = 0.087*AI + 2.951 (AI, area of IAIF) by simple linear regression analysis. When the IAIF defect was in the posteromedial region, there was also a linear relationship between the size of the IAIF defect and MCS. The result of Pearson linear correlation analysis was r = 908, P = 0.033. The regression equation was MCS = 0.065*AI + 1.841. The MCS was increased mainly in the border of the IAIF defect.

Conclusions

A small IAIF defect in the posterior malleolus will result in a high MCS, and the MCS in the posterolateral region is larger than the MCS in the posteromedial region when the size of the IAIF defect is the same. We obtain the regression equation of MCS and area of IAIF defect. This indicates that patients are more prone to post-trauma arthritis when the size of IAIF defects is more than 17.8 mm² in the posterolateral region and more than 40.9 mm² in the posteromedial region.

Trial registration Retrospectively registered.

A new finite element model of intra-articular impacted fragment in posterior malleolar fractures: A technical note

Intra-articular impacted fragment (IAIF) was considered as the articular surface fragment resulting from impact and compressive forces. Malreduction of IAIF in posterior malleolar fractures was associated with the cause of talus subluxation and long-term arthritis. The effect of IAIF on ankle pressure and stress has not been studied, and it's difficult to do this in cadaver bone. So we established IAIF defect finite element model in posterior malleolar fractures and explored the effect of IAIF defect in ankle joint. We also discussed the relation between IAIF defect and post-traumatic arthritis.

Initial displacement of the intra-articular surface after articular fracture correlates with PTA in C57BL/6 mice but not "superhealer" MRL/MpJ mice

Posttraumatic arthritis (PTA) occurs commonly after articular fracture and may arise, in part, from joint surface incongruity after injury. MRL/MpJ (MRL) "super-healer" mice are protected from PTA compared to C57BL/6 (B6) mice following articular fracture. However, the relationship between the initial displacement of the articular surface, biologic response, and susceptibility to PTA after fracture remains unclear. The objective of this study was to assess whether joint incongruity after articular fracture, as measured by in vivo micro-computed tomography (microCT), could predict pathomechanisms of PTA in mice. B6 and MRL mice (n = 12/strain) received a closed articular fracture (fx) of the left tibial plateau. Articular incongruity was quantified as bone surface deviations (BSD) for each in vivo microCT scan obtained from pre-fx to 8 weeks post-fx, followed by histologic assessment of arthritis. Serum concentrations of bone formation (PINP) and bone resorption (CTX-I) biomarkers were quantified longitudinally. Both strains showed increases in surface incongruity over time, as measured by increases in BSD. In B6 mice, acute surface incongruity was significantly correlated to the severity of PTA (R ²  = 0.988; p = .0006), but not in MRL mice (R ²  = 0.224; p = .220). PINP concentrations significantly decreased immediately post-fx in B6 mice (p = .023) but not in MRL mice, indicating higher bone synthesis in MRL mice. MRL/MpJ mice demonstrate a unique biologic response to articular fracture such that the observed articular bone surface displacement does not correlate with the severity of subsequent PTA. Clinical Relevance: Identifying therapies to enhance acute biologic repair following articular fracture may mitigate the risk of articular surface displacement for PTA.

Influence of interlocking thread screws to repair simulated adult canine humeral condylar fractures

OBJECTIVE

To determine the influence of interlocking screw threads on the biomechanical properties of repaired canine humeral condylar fractures.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Thirty-six humeral condyles.

METHODS

Simulated fractures of the lateral aspect of the humeral condyle were stabilized by a 3.5 mm interlocking thread screw (ITS) or 3.5 mm buttress thread screw placed in lag (BTS-L) or positional fashion (BTS-P) and axially loaded at a walk, trot, 2-mm displacement, and failure cycles. Compact flute drill bits (CFBs) were used for ITS constructs and standard flute drill bits (SFB) for BTS constructs. The effects of bit type on drilling parameters and screw type on screw insertion properties and fragment stability were assessed.

RESULTS

CFB produced a 6°C greater temperature increase (p = .042) and required 20 N higher torque (p = .003) than SFB. Insertional torque was greater for ITS than BTS-P (p = .001) and BTS-L (p = .001). Condylar fragment rotation at failure was lower in ITS (lsmean ± SE, 8.3° ± 1.9°) than BTS-L constructs (14.5° ± 2.3°, p = .011). ITS resisted greater loads (1503 ± 105 N) than BTS-P (1189 ± 99 N, p = .038) but not BTS-L (1249 ± 123 N, p = .121) constructs.

CONCLUSION

Biomechanical performance of constructs was improved with ITS rather than BTS fixation.

CLINICAL SIGNIFICANCE

ITS can be considered for stabilization of humeral condylar fractures in adult dogs.

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.

Articular reductions - how close is close enough? A narrative review

Intra-articular fractures are a unique subset of fractures as they involve a varying extent of damage to cartilage. The impact of this articular fracture causes significant microscopic and macroscopic changes, as well as biomechanical irregularities, which can lead to further cartilage damage, and ultimately cascade down the dreaded path to arthritis. It is generally believed that an anatomic reduction of an articular fracture is the necessary goal of treatment for these injuries, however it yet to be delineated how perfect this reduction has to be. A comprehensive literature review was carried out to create a best available evidence guide to the acceptability of upper extremity and lower extremity articular fracture reductions. Ultimately, a perfect anatomic reduction is the best strategy to minimize abnormal loading and wear patterns, however this should be balanced with the realistic factors of each individual case, such as the level of difficulty, joint involved, surgical timing, and patient activity levels.

Contralateral Lateral Femoral Condyle Allografts Provide an Acceptable Surface Match for Simulated Classic Osteochondritis Dissecans Lesions of the Medial Femoral Condyle

Background:

Osteochondral allograft transplantation is an effective technique for repairing large lesions of the medial femoral condyle (MFC), but its use is limited by graft availability.

Purpose/Hypothesis:

The present study aimed to determine whether contralateral lateral femoral condyle (LFC) allografts can provide an acceptable surface match for posterolateral MFC lesions characteristic of classic osteochondritis dissecans (OCD). The hypothesis was that LFC and MFC allografts will provide similar surface contour matches in all 4 quadrants of the graft for posterolateral MFC lesions characteristic of OCD.

Study Design:

Controlled laboratory study.

Methods:

Ten fresh-frozen recipient human MFCs were each size-matched to 1 ipsilateral medial and 1 contralateral LFC donor (N = 30 condyles). After a nano–computed tomography (nano-CT) scan of the native recipient condyle, a 20-mm circular osteochondral “defect” was created 1 cm posterior and 1 cm medial to the roof of the intercondylar notch (n = 10). A size-matched, random-order donor MFC or LFC plug was then harvested, transplanted, and scanned with nano-CT. Nano-CT scans were then reconstructed, registered to the initial scan of the recipient MFC, and processed in MATLAB to determine the height deviation (d_RMS) between the native and donor surfaces and percentage area unacceptably (>1 mm) proud (%A_proud) and sunken (%A_sunk). Circumferential step-off height (h_RMS) and percentage circumference unacceptably (>1 mm) proud (%C_proud) and sunken (%C_sunk) were measured using DragonFly software. The process was then repeated for the other allograft plug.

Results:

Both MFC and LFC plugs showed acceptable step-off heights in all 4 quadrants (range, 0.53-0.94 mm). Neither allograft type nor location within the defect had a significant effect on step-off height (h_RMS), surface deviation (d_RMS), %A_proud, or %A_sunk. In general, plugs were more unacceptably sunken than proud (MFC, 13.4% vs 2.4%; LFC, 13.2% vs 8.1%), although no significant differences in %C_sunk were seen between allograft types or locations within the defect. In LFC plugs, %C_proud in the lateral quadrant (28.0% ± 26.1%) was significantly greater compared with all other quadrants (P = .0002).

Conclusion:

The present study demonstrates that 20-mm contralateral LFC allografts provide an acceptable surface match for posterolateral MFC lesions characteristic of OCD.

Clinical Relevance:

With comparable surface matching, MFC and LFC allografts can be expected to present similar stresses on the knee joint and achieve predictably positive clinical outcomes, thus improving donor availability and reducing surgical wait times for matches.

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.

Biomechanical Evaluation of Promising Different Bone Substitutes in a Clinically Relevant Test Set-Up

(1) Background: Bone substitutes are essential in orthopaedic surgery to fill up large bone defects. Thus, the aim of the study was to compare diverse bone fillers biomechanically to each other in a clinical-relevant test set-up and to detect differences in stability and handling for clinical use. (2) Methods: This study combined compressive strength tests and screw pullout-tests with dynamic tests of bone substitutes in a clinical-relevant biomechanical fracture model. Beyond well-established bone fillers (ChronOS^TM Inject and Graftys^® Quickset), two newly designed bone substitutes, a magnesium phosphate cement (MPC) and a drillable hydrogel reinforced calcium phosphate cement (CPC), were investigated. (3) Results: The drillable CPC revealed a comparable displacement of the fracture and maximum load to its commercial counterpart (Graftys^® Quickset) in the clinically relevant biomechanical model, even though compressive strength and screw pullout force were higher using Graftys^®. (4) Conclusions: The in-house-prepared cement allowed unproblematic drilling after replenishment without a negative influence on the stability. A new, promising bone substitute is the MPC, which showed the best overall results of all four cement types in the pure material tests (highest compressive strength and screw pullout force) as well as in the clinically relevant fracture model (lowest displacement and highest maximum load). The low viscosity enabled a very effective interdigitation to the spongiosa and a complete filling up of the defect, resulting in this demonstrated high stability. In conclusion, the two in-house-developed bone fillers revealed overall good results and are budding new developments for clinical use.

[Preliminary effectiveness of carpal arthroscopic adjuvant treatment of intra-articular fractures of distal radius]

Objective

To investigate the early-term effectiveness of carpal arthroscopy in the treatment of intra-articular fractures of distal radius.

Methods

The clinical data of 50 cases of intra-articular fractures of distal radius between January 2015 and December 2017 were retrospectively analyzed. According to the different methods of intraoperative assisted treatment, the patients were divided into the trial group (11 cases with carpal arthroscopy assisted treatment) and the control group (39 cases with traditional open reduction). There was no significant difference between the two groups in general data such as gender, age, affected side, cause of injury, time from injury to operation, and preoperative displacement ( P>0.05), which were comparable. Six patients in the trial group had triangular fibrocartilage complex (TFCC) injury and received one-stage repair. Postoperative X-ray films were taken to estimate the fracture reduction. Patient-Rated Wrist Evaluation (PRWE) wrist function score and modified Mayo score were used at 3 months after operation to evaluate the function of the wrist. The range of wrist flexion, extension, pronation, and supination motion of the two groups were recorded and compared at 3 months after operation. Patients in the trial group were further divided into the reduction group after arthroscopic exploration (group A, 6 cases) and the simple cleaning group after arthroscopic exploration (group B, 5 cases), and their wrist motions were compared.

Results

The operation time of the trial group was greater than that of the control group ( t=11.08, P=0.00). There was no significant difference in intraoperative blood loss and fracture reduction between the two group ( P>0.05). X-ray film at 1 day after operation showed that the degree of fracture displacement was significantly decreased when compared with preoperative one in each group ( P<0.05), but no significant difference was found between the two groups at 1 day after operation ( t=0.19, P=0.85). Patients in both groups were followed up 8-20 months, with an average of 12 months. There was no significant difference in fracture healing time between the two groups ( t=0.52, P=0.60). At 3 months after operation, the PRWE score, modified Mayo score, and wrist motions in the trial group were all better than those in the control group ( P<0.05). There was no significant difference in wrist motions between group A and group B ( P>0.05).

Conclusion

Carpal arthroscope assisted treatment of intra-articular fractures of distal radius can achieve good reduction and postoperative function. Meanwhile, TFCC, ligament, articular cartilage, and other injuries can be repaired in one stage.

Articular Incongruity in the Lower Extremity: How Much Is Too Much?

Intraarticular fractures carry a significant risk for posttraumatic osteoarthritis, and this risk varies across different joint surfaces of the lower extremity. These differences are likely due to the anatomic and biomechanical specifics of each joint surface. High-quality human studies are lacking to delineate the threshold articular incongruity that significantly increases risk for posttraumatic osteoarthritis and diminished clinical outcomes for many joint surfaces. Even with anatomic reduction of the articular surface, close attention must be paid to mechanical axis and joint stability to optimize outcomes.

Treatment of intra-articular fracture of distal radius fractures with fluoroscopic only or combined with arthroscopic control: A prospective tomodensitometric comparative study of 40 patients

BACKGROUND

Considering articular distal radius fractures treated with volar plate, we hypothesized that articular radio-carpal displacement was better reduced with arthroscopic control than with only fluoroscopic control.

METHODS

Forty patients with similar articular radius fracture (type C according to AO classification) and high functional needs were treated with volar plate fixation. They were divided in two comparative groups: 20 patients in Fluoroscopic group and 20 patients in Arthroscopic group. Pre and postoperative radiographs and tomodensitometric images were analysed by an independent observer. We evaluate extra and intra-articular displacements according to "Patient Accident Fracture" classification.

RESULTS

We observed a better reduction of the radio-carpal step-off and gap in the arthroscopic group, with a statistically significant difference (p<0.05). The index of postoperative intra-articular reduction was better in the fluoroscopic group (5.5) than in the arthroscopic group (2.2) with a significant difference (p<0.05).

CONCLUSIONS

According to these results, arthroscopy is useful to perform a better articular radio-carpal reduction in distal radius fracture.

LEVEL OF EVIDENCE

Level 3.

Effect of Low-Intensity Pulsed Ultrasound on Joint Injury and Post-Traumatic Osteoarthritis: an Animal Study

This study investigated the therapeutic potential of low-intensity pulsed ultrasound (LIPUS) in post-traumatic osteoarthritis (PTOA). Intra-articular fracture of the medial tibial plateau was surgically created in 30 rats. LIPUS was applied to the operated joints either for the first 2 wk (LIPUS_1-2 group) or in weeks 4 and 5 after intra-articular fracture (LIPUS_4-5 group). In controls, the operated knees were not treated with LIPUS (LIPUS₀ group). The rats were monitored with weekly gait analysis and euthanized at week 8. Among the altered gait parameters, the maximal and average paw print areas in the LIPUS_1-2 and LIPUS_4-5 groups, but not the LIPUS₀ group, had either reached baseline or significantly recovered (70%, p <0.05) by week 8. PTOA pathology in both the LIPUS_1-2 and LIPUS_4-5 groups was less severe than that in the LIPUS₀ group (Mankin score: 5.4 and 4.5 vs. 8.8, p <0.05). In conclusion, LIPUS treatment partially improved the gait of the affected limbs and reduced cartilage degeneration in PTOA.

Total knee replacement in a dog with a non-union type B3 tibial plateau fracture

A six-year-old German Shorthaired Pointer was presented with a 12 month history of left pelvic limb lameness following trauma. Clinical examination revealed marked thickening and reduced range-of-motion of the left stifle and radiographs were suggestive of a nonunion type B3 tibial plateau fracture with severe secondary osteoarthritis. Total knee replacement was performed with adjunctive stabilization of the proximal tibial fracture fragment. Clinical follow-up at six and 12 months with quantitative gait analysis revealed significant improvement in limb function.

Therapeutic opportunities to prevent post-traumatic arthritis: Lessons from the natural history of arthritis after articular fracture

An estimated 12% of patients seeking surgical intervention for symptomatic arthritis have an etiology of post-traumatic arthritis (PTA). The onset of PTA is rapid in the setting of articular fracture (AF). The investigation began with development of a murine model of a closed AF that develops PTA. In the process of characterizing this model a technique was developed for assessing quantitative synovial fluid biomarker concentrations. The work began with observations of the natural history of PTA development in the C57BL/6 strain of mice. A species of mice (MRL/MpJ) was found that is protected from PTA after AF. Further work identified key differences between mouse strains that did and did not develop PTA. This knowledge led to an intervention based on anti-cytokine (interleukin 1 receptor antagonist, (IL-1Ra) delivery in the C57BL/6 strain of mice that successfully prevented PTA following AF. This success in preventing PTA in the murine model has elucidated several important clinical implications: 1) Pro-inflammatory cytokines play an important role in the development of PTA after joint injury, 2) Pharmacologic intervention can lessen the severity of PTA after an AF, and 3) The murine AF model of joint injury provides a novel means of studying mechanisms of PTA development.

Subchondral fracture of the femoral head after acetabular fracture: a case report

INTRODUCTION

Preventing post-traumatic osteoarthritis is a challenging problem following acetabular fracture. Progressive osteoarthritis is considered to be caused by an irregular articular surface of the acetabular roof or cartilage injury, but little is known about the pathogenesis of collapse of the femoral head after acetabular fracture. We report a case of post-traumatic osteoarthritis after acetabular fracture in which subchondral fracture of the femoral head contributed to the progressive collapse of the femoral head and osteoarthritis. To the best of our knowledge, there has been no previous report of subchondral fracture of the femoral head after acetabular fracture.

CASE PRESENTATION

A 58-year-old Japanese man fell from a ladder. He was diagnosed with a left acetabular fracture, which was managed conservatively. He developed left coxalgia six months after injury and was seen at our institution one year after the onset of pain. The left acetabular fracture had fused, but his left femoral head had collapsed. The images at the time of injury showed a fracture of the acetabular roof, and an approximately 2mm step-off existed in the articular surface. Retrospective evaluation of the plain radiographs and computed tomography images showed that his femoral head had progressively collapsed. Our patient underwent total hip arthroplasty. Histopathologic findings demonstrated that the collapse of his femoral head was caused by a subchondral fracture of his femoral head.

CONCLUSION

Our experience with this case indicates that in addition to post-traumatic osteonecrosis, subchondral fracture may need to be considered in cases with progressive collapse of the femoral head after acetabular fracture.

Second-look arthroscopy after surgical treatment of Schatzker type II plateau fractures through the lateral submeniscal approach

MAIN PROBLEM

To evaluate cartilage healing using second-look arthroscopic examination in tibia plateau fracture patients who have undergone open reduction and internal fixation with a submeniscal approach technique.

METHODS

Between January 2007 and January 2010, we used second-look arthroscopy during 18-24-month follow-up of 20 patients with Schatzkar type II tibial plateau fractures who had undergone open reduction and internal fixation with a submeniscal approach technique. We classified patients according to step-off, knee range of motion, and Knee Society Score, and compared the results with those obtained by arthroscopy.

RESULTS

Radiologically, 16 cases (80 %) were reduced within 2 mm of step-off. In 11 of these cases, according to the Outerbridge classification, we checked for chondromalacia from grade II to III. We observed 2 mm of step-off in four cases, and each had chondromalacia of at least grade III. The Knee Society Score was associated with chondromalacia grade (p < 0.05).

CONCLUSION

Even in patients with normal joint range of motion and good clinical and radiological results, the actual condition of the articular cartilage varied significantly. Therefore, more long-term and regular follow-up is needed for proximal plateau fractures.

In vivo hip joint contact distribution and bony impingement in normal and dysplastic human hips

Our objectives were to clarify the 3D articular contact areas of the in vivo normal hip joint and acetabular dysplasia during specific positions using magnetic resonance imaging (MRI), voxel-based registration, and proximity mapping. Forty-two normal and 24 dysplastic hips were examined. MRI was performed at four positions: neutral; 45° flexion; 15° extension; and the Patrick position. Femur and pelvis bone models were reconstructed at the neutral position and superimposed over the images of each different position using voxel-based registration. The inferred cartilage contact and bony impingement were investigated using proximity mapping. The femoral head translated in the anterior or posteroinferior, anterosuperior, and posteroinferior direction from neutral to 45° flexion, 15° extension, and the Patrick position, respectively. Multiple regression analyses showed age, femoral head sphericity, and acetabular sphericity to be associated with higher hip instability. The present technique using subject-specific models revealed the in vivo hip joint contact area in a population of healthy individuals and dysplastic patients without radioactive exposure. These results can be used for analyzing disease progression in the dysplastic hip and pathogenesis of acetabular labral tear.

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.

Bone graft substitutes for articular support and metaphyseal comminution: what are the options?

Subchondral and metaphyseal bone defects pose a great challenge for the Orthopaedic surgeon not only because the support for the articular surface has been lost but also because the mechanism for the nourishment of articular cartilage through the subchondral plate is distorted. A number of options are available to the surgeons, none of them perfect. Autografting has an appreciable high rate of harvest site morbidity, allograft is associated with infection transmission and host immunologic response. These realities have stimulated interest in supplying bone replacement materials (demineralised bone matrix, synthetic bone substitutes, bone morphogenic proteins). This paper presents the indications and applications of bone substitutes for metaphyseal defects and subchondral support in orthopaedic trauma.

Acute joint pathology and synovial inflammation is associated with increased intra-articular fracture severity in the mouse knee

OBJECTIVE

Post-traumatic arthritis is a frequent cause of disability and occurs most commonly and predictably after articular fracture. The objective of this investigation was to examine the effect of fracture severity on acute joint pathology in a novel murine model of intra-articular fracture.

DESIGN

Low and high energy articular fractures (n=25 per group) of the tibial plateau were created in adult male C57BL/6 mice. The acute effect of articular fracture severity on synovial inflammation, bone morphology, liberated fracture area, cartilage pathology, chondrocyte viability, and systemic cytokines and biomarkers levels was assessed at 0, 1, 3, 5, and 7 days post-fracture.

RESULTS

Increasing intra-articular fracture severity was associated with greater acute pathology in the synovium and bone compared to control limbs, including increased global synovitis and reduced periarticular bone density and thickness. Applied fracture energy was significantly correlated with degree of liberated cortical bone surface area, indicating greater comminution. Serum concentrations of hyaluronic acid (HA) were significantly increased 1 day post-fracture. While articular fracture significantly reduced chondrocyte viability, there was no relationship between fracture severity and chondrocyte viability, cartilage degeneration, or systemic levels of cytokines and biomarkers.

CONCLUSIONS

This study demonstrates that articular fracture is associated with a loss of chondrocyte viability and increased levels of systemic biomarkers, and that increased intra-articular fracture severity is associated with increased acute joint pathology in a variety of joint tissues, including synovial inflammation, cortical comminution, and bone morphology. Further characterization of the early events following articular fracture could aid in the treatment of post-traumatic arthritis.

Post-traumatic osteoarthritis: improved understanding and opportunities for early intervention

Even with current treatments of acute joint injuries, more than 40% of people who suffer significant ligament or meniscus tears, or articular surface injuries, will develop osteoarthritis (OA). Correspondingly, 12% or more of all patients with lower extremity OA have a history of joint injury. Recent research suggests that acute joint damage that occurs at the time of an injury initiates a sequence of events that can lead to progressive articular surface damage. New molecular interventions, combined with evolving surgical methods, aim to minimize or prevent progressive tissue damage triggered by joint injury. Seizing the potential for progress in the treatment of joint injuries to forestall OA will depend on advances in (1) quantitative methods of assessing the injury severity, including both structural damage and biologic responses, (2) understanding of the pathogenesis of post-traumatic OA, taking into account potential interactions among the different tissues and the role of post-traumatic incongruity and instability, and (3) application of engineering and molecular research to develop new methods of treating injured joints. This paper highlights recent advances in understanding of the structural damage and the acute biological response following joint injury, and it identifies important directions for future research.

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.

Basic science of intra-articular fractures and posttraumatic osteoarthritis

Intra-articular fractures represent the primary etiologic factor leading to posttraumatic osteoarthritis. The pathomechanisms linking intra-articular fractures to end-stage cartilage destruction are poorly understood. However, fracture-related chondrocyte death has been linked to posttraumatic osteoarthritis. Researchers have made significant progress in understanding the pathomechanical link between injury and chondrocyte death. This article reviews recent basic scientific progress investigating intraarticular fractures and fracture-related chondrocyte death and dysfunction.

The use of beta-TCP in the surgical treatment of tibial plateau fractures

The objective of this study was to evaluate the outcome of using beta-TCP in the treatment of depression tibial plateau fractures. A total of 124 patients with depression tibial fractures were included in this study and followed for a minimum of 12 months. All the cases were treated with open reduction and internal fixation, and grafted with beta-TCP ceramic. The clinical and radiological outcomes were assessed using Hospital for Special Surgery (HSS) score of knee and Rasmussen score during the follow-up. No obvious redisplacement was found at the follow-up assessment. Most of the patients had excellent HSS score and Rasmussen clinical score. Bone healing was noted in all fractures and Schatzker II-type fractures had the best functional outcome. The results suggested that using beta-TCP combined with open reduction and rigid internal fixation was an effective treatment for depression fractures of the tibial plateau.

Tibial plateau fractures in elderly patients

Tibial plateau fractures are complex injuries which, if not adequately treated, can lead to invalidating sequelae. They constitute on average about 1% of all fractures, and up to 8% in patients over 65 years, and can be caused by both high- and low-energy trauma. Unlike in younger subjects, treatment of tibial plateau fractures in the elderly is not univocal and depends on the patient's functional needs, bone quality and systemic comorbidities. In this retrospective study, 49 patients with a mean age of 72 years, who underwent surgical treatment of a tibial plateau fracture, were assessed by the Rasmussen's clinical and radiological grading systems. Clinical and radiographic outcomes were satisfactory in 75.5 and 59.1% of cases, respectively. Data were also analyzed, in terms of fracture type, age and gender, to detect any statistically significant correlation between these parameters and clinical and radiographic outcomes.

Schatzker classification of tibial plateau fractures: use of CT and MR imaging improves assessment

The Schatzker classification system for tibial plateau fractures is widely used by orthopedic surgeons to assess the initial injury, plan management, and predict prognosis. Many investigators have found that surgical plans based on plain radiographic findings were modified after preoperative computed tomography (CT) or magnetic resonance (MR) imaging. The Schatzker classification divides tibial plateau fractures into six types: lateral plateau fracture without depression (type I), lateral plateau fracture with depression (type II), compression fracture of the lateral (type IIIA) or central (type IIIB) plateau, medial plateau fracture (type IV), bicondylar plateau fracture (type V), and plateau fracture with diaphyseal discontinuity (type VI). Management of type I, II, and III fractures centers on evaluating and repairing the articular cartilage. The fracture-dislocation mechanism of type IV fractures increases the likelihood of injury to the peroneal nerve or popliteal vessels. In type V and VI fractures, the location of soft-tissue injury dictates the surgical approach and the degree of soft-tissue swelling dictates the timing of definitive surgery and the need for provisional stabilization with an external fixator. CT and MR imaging are more accurate than plain radiography for Schatzker classification of tibial plateau fractures, and use of cross-sectional imaging can improve surgical planning.

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.

Treatment of intra-articular fractures of the distal radius

In a randomised prospective study, 20 patients with intra-articular fractures of the distal radius underwent arthroscopically- and fluoroscopically-assisted reduction and external fixation plus percutaneous pinning. Another group of 20 patients with the same fracture characteristics underwent fluoroscopically-assisted reduction alone and external fixation plus percutaneous pinning. The patients were evaluated clinically and radiologically at follow-up of 24 months. The Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire and modified Mayo wrist score were used at 3, 9, 12 and 24 months postoperatively. In the arthroscopically- and fluoroscopically-assisted group, triangular fibrocartilage complex tears were found in 12 patients (60%), complete or incomplete scapholunate ligament tears in nine (45%), and lunotriquetral ligament tears in four (20%). They were treated either arthroscopically or by open operation. Patients who underwent arthroscopically- and fluoroscopically-assisted treatment had significantly better supination, extension and flexion at all time points than those who had fluoroscopically-assisted surgery. The mean DASH scores were similar for both groups at 24 months, whereas the difference in the mean modified Mayo wrist scores remained statistically significant.

Although the groups are small, it is clear that the addition of arthroscopy to the fluoroscopically-assisted treatment of intra-articular distal radius fractures improves the outcome. Better treatment of associated intra-articular injuries might also have been a reason for the improved outcome.

Rodent models for the study of articular fracture healing

The goal of this study was to document the healing time course and expression of ex vivo cell-based gene delivery in articular fracture models in the mouse and rat. Articular medial intercondylar femoral osteotomy was performed in the stifle (knee) joints of hairless immunocompetent mice and medial or lateral similar osteotomy was performed in athymic nude rats. Genetically modified cells expressing luciferase were delivered in a three-dimensional alginate matrix directly into the osteotomy site. Sensitivity of an in vivo imaging system to detect expression of luciferase was compared between rodents in this fracture model. Osteotomy healing was assessed using high-detail radiography, helical computed tomography (CT), high-field magnetic resonance imaging, and histology. The mouse model was less satisfactory because the small size of the murine femur made reliable assessment of fracture healing restricted to histopathology, and complications occurred in 11/24 mice (45.8%), most frequently transverse supracondylar femoral fracture postoperatively. Gene expression was inconsistently confirmed in mice in vivo for 11 days (p < .003). In rats, high-detail radiography and CT were used to assess osteotomy healing. Magnetic resonance imaging (4.7 T) in rats could produce three-dimensional images that would permit assessment of bone and cartilage, but was time-consuming and expensive. In rats, the only surgical complication, transverse femoral fracture, was reduced from 83.3% with the medial osteotomy to 0% with a lateral osteotomy. In vivo imaging confirmed gene expression in the alginate/cell constructs in rats for at least 4 days (p < .05). The nude rat model has the advantage of larger femora and the ability to implant xenograft cells. A lateral intercondylar osteotomy of the distal femur in the rat can be used to study the healing of articular fractures.

Fragmented coronoid process in the dog: is there a role for incongruency?

Fragmented coronoid process in the dog is a common yet frustrating and poorly understood condition. Elbow joint incongruency, which refers to malalignment of the joint surfaces of the elbow, has been proposed as a key factor in the pathogenesis of fragmented coronoid process, and various surgical procedures have been devised to treat the proposed incongruency. However, precise characterisation of incongruency present in cases of fragmented coronoid process has not been reported consistently. In this article, the literature relating to the pathogenesis of fragmented coronoid process, the role of incongruency and its implications are reviewed.

Second-look arthroscopy after arthroscopy-assisted treatment of tibial plateau fractures

The only way to show the healing potential in hyaline cartilage after the treatment of tibial plateau fractures in humans is the second-look arthroscopy. Our aim is to examine the healing potential of the hyaline cartilage in tibial plateau fractures treated with arthroscopy-assisted surgery. We applied second-look arthroscopy to the 12 patients out of 52 who had tibial plateau fractures treated by arthroscopy-assisted surgery. The mean age was 41. The tibial plateau fractures were classified according to Schatzker classification. The period between the primary surgical treatment and second-look arthroscopy was on an average of 19 months. Step-off was detected in 3 out of 12 patients. Hyaline cartilage of nine patients who did not have step-off was found obviously on the fracture line. None of them had displacement. Three patients out of 12 were above 50 years old and the average follow-up period was 26 months. Grade II-III chondral defect was detected on the fracture line and femoral condyle in patients above 50 years. For patients below 50 years old, the follow-up period was 21 months and grade I-II chondral defect was detected on the fracture line and femoral condyle. Until now in literature, tibial plateau fractures have been evaluated clinically and radiologically, but in our cases we directly saw the lesion. Cartilage healing is limited in human beings. On the fracture line, cartilage defect continues, although anatomic reduction has been achieved. Moreover, if there is step-off, insufficient healing potential appears. Although we did not have enough cases, we can say that in tibial plateau fractures anatomic reduction is mandatory. Contrary to the common idea, step-off is not tolerated by hyaline cartilage.

Mesenchymal stem cell-mediated gene delivery of bone morphogenetic protein-2 in an articular fracture model

In articular fractures, both bone and cartilage are injured. We tested whether stem cells transduced with bone morphogenetic protein 2 (BMP2) can promote bone and cartilage repair. Distal femoral articular osteotomies in nude rats were treated with stem cells, either wild-type or transduced with an adenoviral (Ad) BMP2. Cells were delivered in alginate (ALG) carrier or by direct injection in saline solution. Gene expression of these cells at the osteotomy site was confirmed by in vivo imaging. At day 14, only the group that received AdBMP2 stem cells by direct injection showed completely healed osteotomies, while other groups remained unhealed (P < 0.0003). In ALG groups, bone healing was impeded by the development of a chondroid mass, most pronounced in the AdBMP2 ALG group (P < 0.002). We were successful in achieving repair of both bone and cartilage in vivousing direct stem cell injection. Our data suggests that BMP2 augmentation might be critically important in achieving this effect.

The effect of surface incongruity of grafted plugs in osteochondral grafting: a report of five cases

Although grafted osteochondral plugs should ideally have a smooth surface for mosaicplasty, surface incongruity is sometimes evident at the time of surgery. There may be no problem if there is depression of the grafted plugs, but graft protuberance may have an adverse effect. We studied five knees in five patients who had incongruity (protuberance or depression) of grafted osteochondral plugs at the time of mosaicplasty. The mean age at surgery was 36.6 years (range, 15-65 years), and the mean follow-up period was 32.9 months (range, 24-49 months). All patients underwent second-look arthroscopy after a mean post-surgical period of 14.8 months (range, 3-18 months). We divided the cases so that there were two in the protuberant group (P) and three in the depressed group (D). In P, all patients had a catching sensation about 4 months after surgery, and sometimes pain in the knee joint. Second-look arthroscopy revealed fissuring of the plugs and fibrillation around the recipient site. In D, there were no symptoms due to the depressed plugs. Second-look arthroscopy showed that the depressed areas were covered with fibrocartilage-like tissue, and that the joint surface was smooth. In conclusion, our clinical results and second-look arthroscopic evaluation suggest that isolated osteochondral plug depressions of not greater than 1 mm could still promote acceptable cartilage healing leading to good clinical outcomes. However, plug protuberance at mosaicplasty should always be avoided.

Determination of in-vivo articular cartilage contact areas of human talocrural joint under weightbearing conditions

OBJECTIVE

The knowledge of in-vivo cartilage contact biomechanics is important to the understanding of the pathogenesis of joint diseases such as osteoarthritis. This study investigated the in-vivo contact areas of human talocrural joint under weightbearing conditions that simulated the stance phase of walking using a combined magnetic resonance (MR) and dual-orthogonal fluoroscopic imaging technique.

DESIGN

Nine healthy ankles of living subjects were recruited for this study. The in-vivo talocrural joint positions were recorded using the dual-orthogonal fluoroscopic images at three ankle positions that simulated those occurring during the stance phase of walking: heel strike, mid-stance, and toe off. Three-dimensional (3D) models of the talocrural joints were created from MR images and used to reproduce the in-vivo ankle positions recorded on the fluoroscopic images. The talocrural cartilage contact area was defined as the overlap area of the distal tibial and the proximal talar cartilage surfaces. The method was validated using an in-vitro experimental setup to evaluate its accuracy in determination of cartilage contact area.

RESULTS

The validation study demonstrated that the articular cartilage contact area of the talocrural joint determined using the imaging technique was approximately 4% lower than that of the experimental measurement. In the nine living ankles, the average cartilage coverage area was 964.9+/-156.1 mm(2) on the distal tibia and 1304.8+/-208.4 mm(2) on the proximal talus. The average talocrural cartilage contact areas were 272.7+/-61.1 mm(2) at heel strike, 416.8+/-51.7 mm(2) at mid-stance, and 335.7+/-64.5 mm(2) at toe off. The contact area at mid-stance was significantly larger than those at heel strike and toe off, while the contact area at toe off was significantly larger than that at heel strike.

CONCLUSION

The combined dual fluoroscopic and MR imaging technique was shown to be capable of determining in-vivo talocrural cartilage contact areas. During the simulated stance phase of walking, the contact areas were less than 44% and 31% of the cartilage coverage areas of the distal tibia and the proximal talus, respectively. These data may be useful for understanding in-vivo biomechanical function of the cartilage as well as the etiology of osteoarthritis.

Incongruity-dependent changes of contact stress rates in human cadaveric ankles

Cartilage biosynthetic transduction and injury characteristics have been shown to be particularly sensitive to changes in contact stress rates. This study investigated incongruity-associated changes in contact stress rates that resulted from an articular surface stepoff of the distal tibia in human cadaveric ankles. Ten human cadaveric ankles were subjected to quasi-physiologic stance-phase motion and loading and instantaneous contact stresses were captured at 132 Hz over the entire articular surface using a custom-fabricated stress transducer. An osteoarticular fragment consisting of the anterolateral 25% of the distal tibia was osteotomized. Testing was repeated after displacing the fragment proximally between 0.0 mm to 4.0 mm in 1.0 mm increments. Transient contact stress measurements were used to calculate contact stress rates. Compared to intact ankles, the anatomic configuration had modest increases in global and peak postitive and negative contact stress rates throughout the motion cycle. In contrast, stepoff specimens had significant increases in global and complete motion cycle peak positive and negative contact stress rates, as high as 3.1X intact values in specimens with a 4.0 mm stepoff. Contour plots of contact stress rates also demonstrated an instability event during motion. An anterolateral stepoff of the distal tibia caused significant changes in positive and negative contact stress rates in cadaveric ankles. Incongruity-associated changes in contact stress rates and incongruity-associated instability events may be important pathomechanical determinants of post-traumatic arthritis.

Current concepts and techniques in posttraumatic arthritis

Posttraumatic arthrosis is a commonly encountered clinical problem, but the pathoetiology of its development is not yet clarified. Many contributing mechanical biologic factors interplay with the traumatic event that necessarily precedes the posttraumatic syndrome. New biologic concepts involving the ability of the cartilage to repair and how such healing can be promoted are being realized in new modalities of treatment. The traumatic event as such and the resulting pathomechanical consequences require new ways of evaluation.

Stance-phase aggregate contact stress and contact stress gradient changes resulting from articular surface stepoffs in human cadaveric ankles

OBJECTIVE

Determine how stepoff incongruities of the distal tibia affect aggregate (whole-cycle) contact stresses and contact stress gradients for a complete motion cycle in human cadaveric ankles.

METHOD

Ten human cadaveric ankles were subjected to quasiphysiologic forces during stance-phase range of motion. Each specimen was loaded intact, with anatomic reduction of the anterolateral quarter of the distal tibia, and with increasing stepoffs of the anterolateral fragment up to 4.0mm. Transient contact stresses were measured using a custom-built, real-time stress transducer that sampled stresses at 132Hz at 1472 separate foci (sensels). Aggregate stresses were calculated by summing the sequential transient stress values multiplied by the transient sampling duration for the complete motion cycle at each sensel. Transient contact stress gradients were calculated at each sensel using a central-differencing formula applied to adjacent transient stress measurements. Aggregate contact stress gradients were calculated by vector summation of sequential transient stress gradients multiplied by the sampling duration.

RESULTS

Compared to the intact configuration, anatomic reduction of the fragment caused minimal changes in aggregate contact stresses and stress gradients (30% increase compared to intact values). In contrast, stepoffs caused substantial increases (200% increase compared to intact values) in peak and mean whole-cycle stresses and gradients.

CONCLUSIONS

Aggregate contact stresses and stress gradients quantify loading history for the complete motion cycle. Incongruity-associated changes in aggregate stresses and gradients are a surrogate for "accumulated" damage over a motion cycle in stepoff specimens. These loading abnormalities may be important determinants of posttraumatic arthritis.

The effect of angled osteochondral grafting on contact pressure: a biomechanical study

BACKGROUND

Flush osteochondral plugs can reduce contact pressure compared with an empty defect in the articular cartilage. However, incongruities such as graft angulation have an unknown effect.

HYPOTHESIS

Incongruity of the articular cartilage after osteochondral transplantation affects articular surface contact pressure.

STUDY DESIGN

Controlled laboratory study.

METHODS

An 80-N load was applied with a material testing system for 120 seconds to the femoral condyles of 50 fresh swine knees. Contact pressures were measured using Prescale super low film. Five conditions were tested: (1) intact articular surface; (2) surface with 4.5-mm-diameter circular defect; (3) defect grafted with a flush 4.5-mm-diameter plug from the contralateral condyle; (4) defect grafted with a 30 degrees angled 4.5-mm-diameter plug, with lower edge flush (tip elevated with respect to the adjacent surface); and (5) defect grafted with a 30 degrees plug, with tip flush to the adjacent surface (lower edge sunk). Angled grafts were obtained using a rotational bearing vise aligned with a 30 degrees fixed-angle track. The film was digitally scanned and analyzed, and standard statistical tests were performed.

RESULTS

Mean peak pressures of intact cartilage (8.57 kg/cm2), flush graft (9.81 kg/cm2), and sunk and angled graft (9.15 kg/cm2) were not significantly different (P < .5). The mean pressures for defects (12.01 kg/cm2) and the elevated angled graft (14.50 kg/cm2) were significantly (P < .05) higher than that of intact cartilage.

CLINICAL RELEVANCE

Slightly sunk grafts were still able to reduce elevated contact pressures to normal levels. However, elevated angled grafts increased contact pressure. These results suggest that it is preferable to leave an edge slightly sunk rather than elevated.

Contact stress transients during functional loading of ankle stepoff incongruities

Cartilage deformation demonstrates viscoelastic behavior due to its unique structure. However, nearly all contact studies investigating incongruity-associated changes in cartilage surface stresses have been static tests. These tests have consistently measured only modest increases in contact stresses, even with large incongruities. In this study, an experimental approach measuring real-time contact stresses in human cadaveric ankles during quasi-physiologic motion and loading was used to determine how stepoff incongruities of the distal tibia affected contact stresses and contact stress gradients. Peak instantaneous contact stresses, in ankles with stepoffs between 1.0 and 4.0mm of the anterolateral articular surface, increased by between 2.3 x and 3.0 x compared to the corresponding intact ankle values. Peak instantaneous contact stress gradients in stepoff configurations increased by between 1.9 x and 2.6 x the corresponding intact configuration values. Anatomic reduction of the displaced fragment restored intact contact stresses and contact stress gradients. Intact and anatomic configurations demonstrated a heterogeneous population of low-magnitude, randomly oriented contact stress gradient vectors in contrast to high-magnitude, preferentially oriented gradients in stepoff configurations. Peak instantaneous contact stresses may be important pathomechanical determinants of post-traumatic arthritis. Abnormal contact stress gradients could cause regional pathological disturbances in cartilage stress and interstitial fluid distribution. Measuring contact stresses and contact stress gradients during motion allowed potential incongruity-associated pathologic changes in loading that occur over the complete motion cycle to be investigated.