The quality of bone in the skeleton depends on the amount of bone, geometry, microarchitecture and material properties, and the molecular and cellular regulation of bone turnover and repair. This study aimed to identify material and structural factors that alter in fragility hip fracture patients treated with antiresorption therapies (FxAr) compared to fragility hip fracture patients not on treatment (Fx).

Bone from the intertrochanteric site, femoral head (FH: FxAr = 5, Fx = 8), compression screw cores and box chisel were obtained from patients undergoing hemi-arthroplasty surgery, FxAr (6f, 2m, mean 79 and range [64–89] years), and Fx (7f, 1m, age 85 [75–93] years). Control bone was obtained at autopsy (9f, 4m, 77 [65–88] years). Treated patients were on various bisphosphonates. Samples were resin-embedded, for quantitative backscattered electron imaging of the degree of mineralisation and assessment of bone architecture. Trabecular bone volume fraction (BV/TV) and architectural parameters were not significantly different between FxAr and Fx groups.

Both groups showed normal distributions of weight (wt) % Ca; however, the FxAr was less mineralised than the Fx and the control group (mean wt % Ca: FxAr = 24.3%, Fx = 24.8%, Control = 24.9%). When comparing the FH specimens only, we found that BV/TV in the FxAr was greater than the Fx group (18% vs 15%). All other parameters were not significantly different. In addition, the mineralisation was greater in the FxAr group compared to the Fx group (25.5 % vs 25.0%) but was not significantly different.

Collectively, these data suggest the effect on bone of antiresorptives may be different for patients on antiresorptive treatment that do not subsequently fracture. Assessment of bone material property data together with other bone quality measures may hold the key to better understanding of antiresorptive treatment efficacy.

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.

Introduction: Adequate bone in the femoral head and neck is a prerequisite in ensuring the longevity of a surface arthroplasty. The pistol grip deformity is one of the most common bony abnormalities of the femoral head encountered at the time of resurfacing. Severe flattening results in segmental bone loss requiring adjustments in the alignment of the femoral component to achieve optimal orientation. However, very little is known as to how the femoral implant positioning will be affected by increasing deformity. The purpose of this study was to classify the deformity of the femoral head to better understand how it influences the alignment of the femoral component during surface arthroplasty. This classification was then used to determine whether the femoral implant can be safely inserted with optimal alignment despite progressive deformity of the femoral head and neck.

Methods: The classification was developed using plain radiographs and computer tomography scans from 61 patients (66 hips) who presented with primary osteoarthritis prior to hip resurfacing. Surface arthroplasty simulations were generated with three-dimensional computed tomography to quantify the change in femoral component orientation from the neutral position that would allow optimal alignment. The biomechanical parameters were also calculated to determine the influence of the deformity on the final implant position.

Results: There were 47 men and 14 women, with a mean age of 50.3 years (range, 33 to 63 years). Three categories of femoral head deformity were created using a modified femoral head ratio (Normal ≥0.9, Mild = 0.75 – 0.9 and Severe < 0.75). There were a total of 32 normal hips (48%), 23 hips (35%) with mild deformity and 11 hips (17%) with severe deformity of the proximal femur. A severe deformity required significantly more superior translation of the entry point (p=0.027) and greater reaming depth (p=0.012) to allow safe insertion in relative valgus without notching. This could be achieved while preserving length discrepancy (p=0.17) and minimizing the component-head size difference (p=0.16), although femoral offset was significantly reduced (p=0.025).

Conclusion: A classification of femoral head deformity was created to better understand how progressive deformity influences the alignment of the femoral component during surface arthroplasty. This classification is simple and easily measured using standard AP radiographs of the hip. We found that the femoral component can be safely inserted with optimal alignment during surface arthroplasty by modifying the surgical technique in the face of severe deformity.

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.

Our research group has recent clinical experience with our novel computer-assisted method of bone deformity correction using the Taylor spatial frame (Smith & Nephew, Memphis, TN). Practitioners of the Taylor spatial frame admit that there is a steep learning curve in using the frame. This is in large part due to the difficulty in accurately measuring 13 frame parameters and mounting the frame to the patient without inducing residual rotational and translational errors. Our technique aims to reduce complications due to these factors by preoperatively planning the desired correction and calculating the correction based on the actual three-dimensional location of the frame with respect to the anatomy, rather than from traditional radiographs. The surgeon has greater flexibility in choosing the position of the rings since this technique does not depend on placing the rings in a particular configuration.

Four clinical procedures have been performed at Kingston General Hospital (Kingston, ON, Canada) to date. The first patient presented with a proximal tibial growth-plate arrest that was secondary to a fracture. The result was a recurvatum deformity secondary to an eccentric growth arrest anteriorly. This deformity caused a stretch of the posterior capsule and posterior cruciate ligament that produced an unstable knee. The achieved correction, measured radiographically, was from an initial; − 14 degrees to a final +7 degrees of posterior slope.

The second patient presented with a proximal tibial soft tissue imbalance that was thought would eventually lead to a recurvatum deformity. An increase in the posterior slope of the tibia was induced to compensate for the soft tissue deformity. The radiographic correction was an increase in posterior slope from +7 degrees to +14 degrees and from 5 degrees varus to 8 degrees varus.

The third patient patient presented with a partially-healed malunited tibial fracture with 14 degrees of proximal tibial varus and 16 degrees of posterior slope. In spite of an uncomplicated frame application, the patient was not compliant with post-operative care and the frame was removed before correction could be achieved.

The fourth patient underwent a limb lengthening. At the time of writing, the adjustment schedule had not been completed.

Our computer-assisted procedure appears to be an effective method of improving Taylor spatial frame use. The senior surgeon (DPB) noted that the procedure is easy to perform, he no longer needs to measure the 13 frame parameters, and he can plan the correction in three dimensions. We also have the ability to modify the pace of the correction schedule to accommodate the rate of bone growth for each individual patient. Drawbacks of the technique include the requirements for a preoperative CT scan and a segmentation of the scan to produce the three-dimensional computer models.