Osteophytes are bony spurs on normal bone that develop as an adaptive reparative process due to excessive stress at/near a joint. As osteophytes develop from normal bone, they are not always well depicted in common imaging techniques (e.g. CT, MRI). This creates a challenge for preoperative planning and image-guided surgical methods that are commonly incorporated in the clinical routine of orthopaedic surgery.

The study examined the accuracy of osteophyte detection in clinical CT and MRI scans of varying types of joints.

The investigation was performed on fresh-frozen ex-vivo human resected joints identified as having a high potential for presentation of osteophytes. The specimens underwent varying imaging protocols for CT scanning and clinical protocols for MRI. After dissection of the joint, the specimens were subjected to structured 3D light scanning to establish a reference model of the anatomy. Scans from the imaging protocols were segmented and their 3D models were co-registered to the light scanner models. The quality of the osteophyte images were evaluated by determining the Root Mean Square (RMS) error between the segmented osteophyte models and the light scan model.

The mean RMS errors for CT and MRI scanning were 1.169mm and 1.419mm, respectively. Comparing the different CT parameters, significance was achieved with scanning at 120kVp and 1.25mm slice thickness to depict osteophytes; significance was also apparent at a lower voltage (100kVp).

Preliminary results demonstrate that osteophyte detection may be dependent on the degree of calcification of the osteophyte. They also illustrate that while some imaging parameters were more favourable than others, a more accurate osteophyte depiction may result from the combination of both MRI and CT scanning.

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has been a popular alternative treatment for young patients with hip osteoarthritis. Despite its advantages over total hip arthroplasty, the use of MoMHRA remains controversial. Achieving the correct positioning of the prosthetic is a concern due to the difficulty and novelty of this procedure. Furthermore, it has been reported that post-operative management using 2D radiographs contains high degrees of variance leading to poor detection of prosthetic malpositioning. In order to compensate for the lack of available technology, current literature has suggested the use of blood metal ion levels as indirect predictors of prosthetic malpositioning due to the abnormal release of metal ions, particularly Chromium and Cobalt, as a result of increase wear and tear. The purpose of this study was to determine whether 2D/3D registration technology can report prosthetic orientation in vivo and, to establish whether 3D technology can accurately deduce prosthetic wear by correlating prosthetic angles with metal ion counts.

To begin this study, post-operative x-rays (n=72) were used as the two-dimensional media to measure acetabular orientation. Only the acetabular component was examined in this study and acetabular orientation was defined as the function of inclination and version angles. Virtual three-dimensional models of the native, pre-operative pelvises and the acetabular implant were generated and were manually superimposed over the post-operative x-ray images according to anatomical landmarks. A manual 2D/3D registration program was specifically designed for this task. Inclination and version angles of the 2D/3D registered product were measured. Post-operative CT models, which offer the most accurate depiction of the prosthetic in vivo, were generated for validation. Contrary to the study's hypotheses and current literature, no significant difference was observed between 2D vs. 2D/3D vs. CT data, suggesting that 2D and 2D/3D measurements were similar to the results of the gold standard CT model (although 2D/3D measurements were more precise compared to 2D media). Furthermore, statistical analyses revealed no significant correlation in either 2D or 2D/3D compared to metal ion levels, although a stronger trend was demonstrated using 2D/3D measurements. These results are suggestive that 2D/3D registered measurements are equivocal to those using the conventional 2D x-ray and, manual 2D/3D registered measurements do not demonstrate greater efficacy in predicting prosthetic wear. Moreover, the data from this study also revealed insignificant correlations between the angles of acetabular orientation and metal ion release. Combined angles within and beyond the acceptable ranges for inclination (30°–50°) and version (5°–20°) angles did not produce significant trends with metal ion release. These results lead to the paradoxical conclusion that acetabular orientation does not influence prosthetic wear. The findings of this study are inconsistent with the reports in current literature and further investigation is required.

Introduction

Computer-assisted methods for acetabulum cup navigation have shown to be able to improve the accuracy of the procedure, but are time-consuming and difficult to use. The goal of this project was to develop an easy-to-use navigation technique, requiring minimal equipment for acetabular cup alignment.

Introduction

Osteochondral autologous autograft (also called mosaic arthroplasty) is the preferred treatment method for very large osteochondral defects in the ankle. For long-term success of this procedure, the transplanted plugs should reconstruct the curvature of the articular surface. The different curvatures between femoral-patella joint and the dome of the talus makes the reconstruction difficult and requires lots of experience.

Femoroacetabular impingement is a condition in which the femoral head/neck region abnormally contacts the acetabulum, limiting the range of motion of the hip and often associated with pain, damage, and loss of function. The pathophysiology of osteoarthritic changes stemming from impingement syndromes has been linked to the shape of the hip; however, little is known about the influence of the soft tissues to this process.

In this pilot study, we used computer-assisted navigation technology to track motion on a cadaver that had mild bilateral cam-impingement lesions, and then performed a virtual simulation to locate sites of impingement. We hypothesised that soft tissues contribute to the degree and location of impingement, so we compared impingements across three different dissection states: (i) all soft tissues intact; (ii) post-capsulectomy; with only the labrum and ligamentum teres remaining; and (iii) disarticulated, with labrum and ligamentum teres removed.

With ethical approval, we used one fresh frozen cadaver pelvis that was sectioned above the fifth lumbar vertebra and at the knee. The femurs and pelvis were implanted with fiducial screws as an accurate means for surface-based image registration. With all soft tissues intact, tissues were imaged using computed tomography with a slice thickness of 0.625 mm. The CT scans were imported into Mimics (v13.0, Materialise, Belgium) and carefully segmented, with particular detail to the articular regions and fiducials, to create 3D digital models of the pelvis and femurs.

On each side, optical local coordinate reference (LCR) bodies were attached at the proximal femur and iliac crest to permit spatial tracking with an Optotrak Certus camera (Northern Digital Inc., Waterloo, Canada). The 3D digital models were imported into the VSS navigation system (iGO Technologies, Kingston, Canada) and scrupulously registered to the anatomy using the fiducial screws and a calibrated probe. The pose of the femur and pelvis were recorded throughout a series of twelve movements involving various combinations of flexion-extension, abduction-adduction, internal-external rotation and circumduction, as well as functional movements typical of a clinical hip screening. Soft tissues were selectively removed and the movements were repeated post-capsulectomy and completely disarticulated.

The recorded pose data were applied to the 3D digital models to perform a computational simulation of the movements during the trials. The pose data were expressed in coordinates of the anterior pelvic plane to compute angles of motion in the principal directions (flexion, abduction, rotation). The motion data were further filtered so that only comparable ranges of motion were present for data analysis. Algorithms were developed to determine bone-on-bone impingement locations by finding contact points between the models.

Impingement locations were plotted on the digital models of the femur and pelvis in order to establish zones of impingement. The surface area of each impingement zone was computed by using a Crust-based algorithm that triangulated impingement points encompassing a region, and then summed the surface area of each triangle to estimate the total impingement surface area.

Upon visual inspection, it was immediately apparent that impingements tended to occur in well-defined regions. On the femur, these were found along aspects of the head-neck junction, especially on or near osteophytes. On the pelvis, impingement regions were found along the acetabular rim and extending into the lunate region.

With soft tissues intact, both femurs and pelvis had prominent anterior and posterior impingement zones. In contrast, post-capsulectomy impingement zones were predominately confined to the anterior region. It should be noted, however, that the total impingement area decreased post-capsulectomy, representing only about 25% of the total area of impingements when all soft tissues were intact. This was also true in the disarticulated state.

Both femurs had mild posterior cam lesions, the right worse than the left. Impingements were seen at these sites with soft tissues intact, but diminished almost entirely post-capsulectomy. The anterior lesions were located contra coup to these cam lesions.

With soft tissues intact, impingements tended to occur in external rotation and abduction. With soft tissues removed there was a pronounced shift towards impingements occurring in internal rotation. Impingements were also noted in large flexion angles and large abduction-adduction angles in the absence of soft tissues.

Although it is widely accepted that the hip is spherical in shape and has ball-and-socket kinematics, recent work suggests that the osteoarthritic hip is aspherical and that translational motion is present. On a very limited series, this work is supportive of the latter observation: if hip motion is purely spherical, a decrease in impingements post-capsulectomy is exceedingly hard to describe. However, if soft tissues cause translatory motion, then their absence logically should lead to a change in the impingement pattern (which we found).

This preliminary study provides a methodology for studying the effects of soft tissue on impingements. We conclude that soft tissues do indeed play an important role in impingement and may even contribute to the development of impingement lesions. Limitations include a small sample size, so further studies are required prior to conclusively establishing impingement patterns in passive kinematics of cadaver hips.

Hip Resurfacing Arthroplasty (HRA) is a surgical technique that has become more popular in recent years for the treatment of hip osteoarthritis in young patients. For these patients, an HRA offers the advantages of preserving the physiologic anatomy of a patient's femoral head size and neck offset, which has been theoretically suggested to improve range of motion and muscle function, as well as preserving bone stock for future revision surgeries. Although the improvements in quality of life outcomes in patients undergoing total hip arthroplasty (THA) are well-documented, there is a lack of literature documenting the improvements in quality of life in patients undergoing HRA.

The purpose of this study was to compare the accuracy and precision of acetabular component placement in cadavers using conventional techniques and CT-based individualised guides by both orthopaedic trainees and surgeons.

Seven cadaveric pelvises underwent a computerised tomography (CT) scan and a three-dimensional virtual model was created. Based on this model, cup orientation was planned for 40 degrees of inclination and 20 degrees of anteversion and an individualised guide was designed. A physical model of the individualised guide was created using a Rapid Prototyping machine (dimension SST, Stratasys, Inc., USA).

The pelvises were mounted in the lateral position and covered with a soft tissue envelope exposing only the acetabulum as would be visualised during a lateral approach to the hip. A total of 26 participants (16 orthopaedic surgery residents, 10 orthopaedic surgeons) were asked to use an acetabular cup impactor to place the cup in 40 degrees of inclination and 20 degrees of anteversion. This was first completed for all seven pelvises using conventional placement. Each participant was then instructed on how to use the individualised guide. They were provided with the guide and an individualised acetabular model to practice placement. Once they were comfortable with the system they were then asked to use the individualised guides in each of the seven pelvises.

An optoelectronic navigation system was used to evaluate the accuracy of the placement of the acetabular cup. An Optotrak Certus Motion Tracking System (Northern Digital Inc., Waterloo, Canada) was used. An optoelectronic marker was attached to the acetabulum and a combined pair-point and surface matching was performed. After the guide was placed in the acetabulum, a tracked axial pointing device was aligned inside the guidance cylinder and its three-dimensional orientation stored. The angle deviation between the achieved position and the planned cup orientation was calculated.

There were no statistically significant differences between trainees and surgeons in either conventional placement or use of the individualised guides. There were no statistically significant differences in anteversion between the groups. The individualised guide showed statistical improvement in the absolute deviation from planned inclination compared to conventional placement (4.2° vs. 9.1°, p< 0.001) as well as a reduction in standard deviation (3.3 vs. 5.9, p< 0.001).

The use of individualised guides can improve the accuracy and precision in the placement of acetabular component positioning. The current guide design controls well for inclination, which is a key factor in the function of a total hip arthroplasty. Based on this data, we will implement design changes to better address version of the component. Future work will likely include comparison to computer-assisted cup placement as well.

Purpose: The purpose of this clinical trial was to investigate the accuracy of a novel method for computer-assisted distal radius osteotomy, in which computer-generated patient-specific plastic guides were used for intra-operative guidance. Our hypothesis was that these guides combine the accuracy and precision of computer-assisted techniques with the ease of use of mechanical guides.

Method: In a consecutive series of 9 patients we tested the accuracy of the proposed method. Prior to surgery, CT scans were obtained of both radii and ulnae in neutral rotation. Three-dimensional virtual models for both the affected and unaffected radius and ulna were created. The models of the unaffected radius and ulna were reflected to serve as a template for the correction. Custom-made software was used to plan the correction. The locations of the distal and proximal drill holes for the plate were saved and the locations of the distal holes before the osteotomy were determined. The design of a patient-specific instrument guide was calculated, into which a mirror image of intra-operative accessible bone structure of the distal radius was integrated. This allowed for unique positioning of the guide intra-operatively. For each planned drill location a guidance hole was incorporated into the guide. A plastic model of the guide was created using a rapid prototyping machine. Intra-operatively, a conventional incision was made and the guide was positioned on the distal end of the radius. The surgeon drilled the holes for the plate screws into the intact radius. The guide was removed and the surgeon performed the osteotomy using the conventional technique and shaved the bone from the distal radius fragment to accommodate the plate. Using the pre-drilled holes the plate was affixed to the distal radius fragment. The distal fragment was reduced until the proximal screw holes in the plate aligned with the pilot holes in the bone. To analyze the accuracy of the intra-operative procedure we compared the post-operative alignment of the radius with the planned alignment. A lateral and an A/P digitally reconstructed radiograph (DRR) of the plan were calculated. These DRRs were used to evaluate the radial inclination, the volar tilt and the ulnar variance of the planned alignment. Post-operative lateral and A/P X-Rays were used to determine the same three post-operative radiographic indices. The post-operative values were compared with the planned values.

Results: We found an average deviation for the radial inclination of 0.5°(StDev 1.8), for the volar tilt of 0.7°(StDev 2.3), and for the ulnar variance of 0.8mm (StDev 1.9).

Conclusion: These results show that the computer-generated instrument guides accurately achieved the planned alignment. The guides were easy to integrate into the surgical workflow and eliminated the need for intra-operative fluoroscopy for guidance of the procedure.

Purpose: We compare the accuracy and precision of patient-specific plastic guides versus computer-assisted navigation for distal radius osteotomy (DRO). We hypothesize that guides would provide similar accuracy and precision compared to computer-assisted surgery, and that they would be faster to use than navigated surgery.

Method: We used CT scans, computer models, and planned corrections of radii from seven patients who had previously received computer-assisted DRO. The planned correction included the locations and directions of the screw holes for the fixation plate on the intact deformed radius. Using computer-assisted technique, the surgeon drills the holes for the fixation plate using computer navigation before performing the osteotomy; after cutting the radius, the plate is fixated to the distal radius, and the distal radius is distracted until the holes in the proximal radius align with the holes of the fixation plate. A patient-specific guide can be manufactured that fits on the intact deformed radius to guide the drilling of the screw holes. The guide is designed so that it mates exactly with the dorsal surface of the radius. Each guide was designed using custom software and manufactured in ABS plastic using a 3D printer. The surgeon places the guide on the radius and uses a metal drill sleeve in each guide hole to guide the drilling of the plate screw holes. We manufactured urethane plastic phantoms of the seven deformed radii. Our laboratory experiment had six surgeons each perform four computer-assisted and four patient-specific guide procedures on the phantom radii; the specimen and type of guidance were randomly chosen. The time from the start of the procedure to when the shaping of the distal radius was completed was recorded; we did not record the time required to cut and fixate the radius because this time does not depend on the type of guidance used. The plated phantoms were assessed for errors in ulnar variance, radial inclination, and volar tilt as compared to the planned correction.

Results: The results for the computer-assisted procedures were: ulnar variance error (−0.2 +/ − 2.0 mm), radial inclination error (−0.9 +/ − 6.1 deg), volar tilt error (−0.9 +/ − 1.9 deg). The results for the customized jig procedures were: ulnar variance error (−0.7 +/ − 0.6 mm), radial inclination error (−1.0 +/ − 1.4 deg), volar tilt error (−0.4 +/ − 2.2 deg). There were no significant differences detected in the means of the measurements (significance level 0.05) using the two-sample t-test. Significant differences were detected in the variances of the ulnar variance and radial inclination errors (significance level 0.05) using Levene’s test. It took (705 +/ − 144 sec) to perform the computer-assisted procedures and (214 +/ − 98 sec) to perform the customized guide procedures. The differences between the means and variances were statistically significant.

Conclusion: Patient-specific guides are as accurate, more precise, and require less time than computer-assisted navigation for DRO.

For hip resurfacing arthroplasty, precise planning and implantation of the components is necessary for long-term success. Earlier studies have shown that a computer-assisted technique can achieve higher accuracy than conventional technique. However, many of the proposed computer systems add additional complexity, time and cost to the surgery. This study investigated the use of rapid prototyping as an accurate, fast and cost-effective solution for computer-aided hip resurfacing.

From a CT scan of each patient, a 3-dimensional computer model of the proximal femur was produced and the drilling trajectory for the central pin of the stem was planned. To transfer this plan to the patient, surface-matched plastic drilling templates were created using a rapid prototyping machine. Depending on the surgical approach, these templates contained a mirror-image of parts of the anterior or posterior femoral head and neck. These mirror-image templates helped to exactly position the drilling guide on the bone during surgery, which ensures a precise transformation of the preoperative plan into the surgical field. To test the accuracy and reproducibility of this system, we created plastic models of three cadaver femurs using the rapid prototyping machine. For each of these femurs one anterior and one posterior drilling template were generated. Each template was applied three times to the femur model and the direction of the drilling target was recorded and axis deviations measured.

The average deviation between the planned and the template-guided drill direction was 1.3° for the anterior approach and 1.2° for the posterior approach. The reproducibility for the drilling axis was measured for the anterior approach as 0.4° and posterior 0.3°.

In comparison to previous published results for computer-assisted hip resurfacing, our results show similar or better accuracy. Further in-vitro and in-vivo experiments will be performed to obtain statistically significant accuracy measurements and intraoperative feasibility tests. Our early results show great potential for this technique for accurate and in-expensive guidance for hip resurfacing.

Hip resurfacing has recently become an alternative for total hip replacement, especially for younger and more active patients. Although early results are encouraging, there are reports of failure as a result of malpositioning of the femoral component. To help overcome this problem we developed a CT-guided computer-assisted system for the planning and guidance of the femoral component during hip resurfacing.

3D isosurface models were generated from a CT scan of the pelvis and proximal femur. By superimposing virtual prosthetic components, the surgeon preoperatively determined the size, position and orientation of the femoral component. Intraoperatively, an optoelectronic navigation system was used for realtime CT-guidance of the insertion of the alignment pin for the femoral component.

In a laboratory study, the precision of the intraoperative guidance system was investigated. One experienced and one inexperienced surgeon performed one posterior and one anteriolateral approach on 10 different plastic bone models. After each procedure, the alignment-pin orientation was compared to the planned orientation.

In a preliminary clinical study, 27 patients underwent the computer-assisted method and 13 patients were operated on using conventional technique. Both posterior and anteriolateral surgical approaches were used. Pre-operative and postoperative neck-shaft angles were compared using Student’s t-test.

In the laboratory study, the mean deviations between planned and navigated alignment-pin orientation was 0.65° (StDev 0.9°) for the experienced surgeon, and 0.13° (StDev 0.7°) for the inexperienced surgeon. The mean deviation of anteversion angles were measured as 0.31° (StDev 0.8°) for the experienced surgeon and 0.01° (StDev 0.9°) for the inexperienced surgeon.

In the clinical study, we measured the neck-shaft angle in the computer-assisted group to be an average of 133° preoperatively and 134° postoperatively (p=0.16), and in the conventional group to be an average of 136° pre-operatively and 135° postoperatively (p=0.79). There were no significant differences between pre-operative and post-operative measurements between the groups. However, there was a significantly lower standard deviation in the postoperative computer-assisted group: it was 6.6°, compared to 13.3° in the conventional group (Levene’s test for equality of variances, p=0.004).

We conclude, based on our results, that a CT-guided system can help to prevent femoral misalignment during a hip resurfacing by increasing the intraoperative precision.

Introduction and Aims: There is very little scientific evidence of which activities to avoid or which are safe following total hip arthroplasty (THA). Our aims were to conduct a survey of Canadian orthopaedic surgeons’ exercise recommendations after THA and to examine the relation between physical activities and hip pain in THA patients.

Method: Patients who had a primary THA five to seven years previously because of osteoarthritis were administered the well-validated Minnesota Leisure-Time Physical Activity Questionnaire, which assesses the frequency, intensity and duration of physical activities. Patients reported on current physical activities and sports and recalled activity two years after their surgery. They also reported whether they had pain in the affected hip during specific activities and if they reduced their activity because of pain. A survey was mailed to 466 Ontario orthopaedic surgeons to determine the types of physical activities recommended to patients following THA.

Results: Results of the surgeon survey indicate that all surgeons allowed walking, stair climbing and swimming. Nearly all did not allow jogging, squash or racquetball. There was considerable disagreement among the surgeons regarding other activities, e.g., downhill skiing and heavy household activities. Seventy-one male (mean age ± SD; 61 ± 8) and 97 female (61 ± 7) THA patients were interviewed. Over 80% of respondents reported bending and lifting activities. About half the respondents reported non-weightbearing activities such as swimming. A higher proportion of men than women reported golf, racquet sports and shovelling snow, whereas a higher proportion of women than men reported doing housework. Hip pain was most frequently reported during lifting and bending activities. Patients were least likely to report pain during non-weightbearing activities. Nearly all patients who reported pain, reduced their activity level. Thus our preliminary data suggest that bending and lifting impact activities appear to cause the most pain and result in reduced activity levels. Our results also show that some patients participate and experience pain in non-recommended activities. Some allowed activities, such as stair climbing, cause pain.

Conclusion: Bending and lifting activities cause the most pain and result in reduced activity. Patients participate and experience pain in activities that surgeons do not recommend. Some recommended activities cause pain. This is one of the first studies to quantify activity and show a relation between activities and pain in THA patients.

Background: Successful total knee arthroplasty requires component alignment according to the mechanical axes and restoration of ideal knee kinematics. This requires adequate ligament balancing, stable tibia-femoral and patello-femoral joints, and a non-restricted range of motion.

We developed a computer assisted total knee arthroplasty system to help the surgeon achieving more intra-operative accuracy.

Material and methods: An OPTOTRAK camera is used to track relative motions between femur, tibia, and instruments. In contrast to other systems we avoid fixation of reference bases onto acetabulum and foot. The surgeon generates a representation of the patient’s anatomy using the technique of “surgeon defined anatomy”. Based on recorded landmarks the system calculates the femoral and tibial mechanical axes, the position of the knee joint line, the level of the defects on femoral and tibial side, the anatomically best fitting femoral component size, the femoral ventral level, and the natural tibial rotation. These values enable an initial planning situation, which features alignment of the tibial and femoral distal resection planes according to the mechanical axes as well as the definition of the anterior and posterior femoral resection planes with respect to the ventral cortex and the prosthesis design. To consider soft-tissue behaviour the surgeon loads both collateral ligaments in extension and flexion, a

Results: During a clinical study we performed thirteen total knee arthroplasties. Postoperatively passive extension was 0.8-4.2° (mean 1.9°) in the coronal plane and 0.2-3.9° (mean 1.8°) in the sagittal plane. Varus-valgus instability was 7.2°. The results of the subsequent patients of this ongoing study will be available during the conference.