651 C OPYRIGHT Ó 2015
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
A commentary by T. Bradley Edwards, MD, is linked to the online version of this article at jbjs.org.
Three-Dimensional Imaging and Templating Improve Glenoid Implant Positioning Joseph P. Iannotti, MD, PhD, Scott Weiner, DO, Eric Rodriguez, BS, Naveen Subhas, MD, Thomas E. Patterson, PhD, Bong Jae Jun, PhD, and Eric T. Ricchetti, MD Investigation performed at the Department of Orthopaedic Surgery, Orthopaedic and Rheumatologic Institute, Cleveland Clinic, Cleveland, Ohio
Background: Preoperative quantitative assessment of glenoid bone loss, selection of the glenoid component, and definition of its desired location can be challenging. Placement of the glenoid component in the desired location at the time of surgery is difficult, especially with severe glenoid pathological conditions. Methods: Forty-six patients were randomly assigned to three-dimensional computed tomographic preoperative templating with either standard instrumentation or with patient-specific instrumentation and were compared with a nonrandomized group of seventeen patients with two-dimensional imaging and standard instrumentation used as historical controls. All patients had postoperative three-dimensional computed tomographic metal artifact reduction imaging to measure and to compare implant position with the preoperative plan. Results: Using three-dimensional imaging and templating with or without patient-specific instrumentation, there was a significant improvement achieving the desired implant position within 5° of inclination or 10° of version when compared with two-dimensional imaging and standard instrumentation. Conclusion: Three-dimensional assessment of glenoid anatomy and implant templating and the use of these images at the time of surgery improve the surgeon’s ability to place the glenoid implant in the desired location. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
G
lenoid component failure remains the primary cause of long-term clinical failure following total shoulder arthroplasty despite advances in implant design and surgical technique1. Glenoid component malposition, incomplete correction of bone pathological conditions, and persistent humeral head subluxation are factors associated with glenoid loosening 2-10. Preoperative planning and patient-specific instruments have grown in popularity across a wide range of orthopaedic
subspecialties to improve the accuracy of implant positioning. Total knee arthroplasty11-18, total hip arthroplasty19-21, hip resurfacing22, pelvic and acetabular procedures23-25, and spinal deformities26,27 have all utilized patient-specific instrument technology with varying degrees of success. Recently, patientspecific instrumentation was found to improve glenoid component placement in both the version and inclination planes when compared with standard two-dimensional surgical planning28,29.
Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, one or more of the authors has a patent or patents, planned, pending, or issued, that is broadly relevant to the work. Finally, one or more of the authors has had another relationship, or has engaged in another activity, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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The goal of this study was to evaluate the use of threedimensional preoperative imaging of glenoid pathological conditions and implant templating with or without the use of patient-specific instrumentation and to compare these results with historical controls using two-dimensional imaging with standard instrumentation. We hypothesized that threedimensional imaging and the use of patient-specific instrumentation would result in more accurate placement of the glenoid component. Materials and Methods Study Design
F
orty-six patients with end-stage primary glenohumeral osteoarthritis gave written consent to participate in an institutional review board-approved randomized clinical trial (Cleveland Clinic institutional review board 12-997; registered in ClinicalTrials.gov as NCT01801241). All enrolled patients completed the study, and there were no complications or adverse events. Patients were treated surgically by one of two fellowship-trained shoulder surgeons with extensive experience in shoulder arthroplasty and in use of the technology used in this study (J.P.I. and E.T.R.). All patients underwent anatomic total shoulder arthroplasty that was performed with use of the Global AP Humeral Implant, Global APG Implant, or GLOBAL STEPTECH APG Glenoid Component (DePuy Synthes, Warsaw, Indiana) and standard instrumentation. All patients in the randomized clinical trial had three-dimensional preoperative computed tomographic (CT) imaging and preoperative glenoid component templating using custom-designed three-dimensional planning software (OrthoVis; Custom Orthopaedic Solutions, Cleveland, Ohio). Multiple standardized threedimensional and two-dimensional images of the glenoid with the templated glenoid implant and the location of the guide pin were available to the surgeons at the time of surgery. The patients were then randomized by a research assistant into two groups using a block of thirty methods. In one group (n = 25), the surgeons were given a sterile, surrogate, three-dimensional model of the glenoid bone with the guide pin in the desired location based on the preoperative plan. In addition, a reusable and adjustable instrument was used as a patient-specific instrument (three-dimensional intelligent reusable instrument) to transfer the guide pin location in relation to the glenoid morphology from the surrogate model to the patient. In the other three-dimensional group (n = 21), guide pin and component placement was performed using only the images provided in the operating room derived from the three-dimensional software templating and standard instrumentation provided by the implant manufacturer (GLOBAL STEPTECH APG Glenoid Component; DePuy Synthes). The three-dimensional imaging group and the three-dimensional intelligent reusable instrument group were compared with a nonrandomized historical control group of seventeen patients who had surgical planning using only two-dimensional CT imaging without implant templating or computer measurements of glenoid bone loss. The same instrumentation and implants 28 were provided by the same manufacturer for the historical control group . All patients in all three groups had preoperative anteroposterior Grashey and axillary radiographs. All patients had CT scans performed preoperatively using 0.6-mm axial slice thickness of the entire scapula and proximal humerus with the arm by the side of the body. The CT acquisition parameters were 140 kVp, 300 mA with dose modulation on, 0.6-mm collimation, a 512 matrix, no gantry tilt, and a field of view to capture the entire scapula.
T H R E E -D I M E N S I O N A L I M A G I N G A N D T E M P L AT I N G I M P R O V E GLENOID IMPLANT POSITIONING
head to the center of the glenoid were determined on the mid-axial two31 dimensional image as described by Walch et al. . The glenoid implants were selected by the treating surgeon and included either standard or augmented glenoid components (STEPTECH APG components, DePuy Synthes). For the two-dimensional imaging historical control group, the surgeons were asked to place the glenoid component in 0° of retroversion and 0° of inclination relative to the plane of the scapula using the two-dimensional images and reference lines. The prescribed position of the implant was then compared with the actual postoperative implant position. This was our standard of care for total shoulder arthroplasty in 2009.
Preoperative Planning and Templating for the Three-Dimensional Imaging Groups Digital Imaging and Communication in Medicine (DICOM) files of the preoperative CT imaging were entered into a shoulder arthroplasty-specific preoperative planning software application (OrthoVis, Custom Orthopaedic Solutions) and were reformatted into three-dimensional representations of the bones. The humerus and scapula were segmented into separate files. The plane of the scapula was defined by landmarks placed on the scapula trigonum, the 28,29,32 inferior angle, and the center of the glenoid, as previously described . The line between the trigonum and the center of the glenoid fossa determines the transverse scapula line. This line extends through the center of the medial aspect of the glenoid vault and exits near the anterior scapula body. Three landmarks placed on the surface of the glenoid fossa defined the plane of the glenoid and thereby defined the version and inclination of the glenoid fossa to the plane of the scapula. Two-dimensional images in the axial, transverse, and coronal planes were defined on the basis of these planes (Fig. 1). The surgeon then selected a standard or augmented glenoid component (STEPTECH APG component, DePuy Synthes) template in the planning software that allowed for correction of glenoid version and inclination between 0° and 10°, relative to the plane of the scapula, with the least amount of bone removal. The amount and location of bone removal and the location of the fixation pegs were visualized for that implant in that location. The location of the implant defined the location of the guide pin to be placed at the time of surgery to replicate the desired location of the implant. Preoperative implant type and position as defined by the surgeon were then used as the goal of
Preoperative Planning for the Two-Dimensional Imaging Group In the two-dimensional imaging group, the two-dimensional CT imaging in the coronal, axial, and sagittal planes were provided to the surgeon with axial planes 28 perpendicular to the plane of the scapula . The surgeon used these images to determine the glenoid version according to the method described by Friedman 30 et al. and inclination as defined as the perpendicular (0°) to a vertical line from the center of the glenoid to the medial border of the scapula in the coronal plane images. The glenoid morphology and the relationship of the humeral
Fig. 1
Landmarks to define the plane of the scapula and the plane of the glenoid.
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TABLE I Walch Type Groups† Walch Type*
Three-Dimensional Imaging (N = 21)
Three-Dimensional Intelligent Reusable Instrument (N = 25)
Two-Dimensional Imaging (N = 17)
A1
4
3
4
A2
7
5
5
B1
2
2
1
B2
6
12
6
C
2
3
1
*There was no significant difference in type of glenoid morphology (Walch classification). †There was a significant difference in the frequency of use of an augmented component between the two-dimensional imaging group (which did not use any augmented components) and both of the three-dimensional imaging groups (four augmented components for the three-dimensional imaging group and eight augmented components for the three-dimensional intelligent reusable instrument group).
surgery and were compared with the actual postoperative implant position. A standardized set of two-dimensional and three-dimensional images showing the location of the implant before and after bone preparation were available to
the surgeon at the time of surgery (Fig. 2). Depth of reaming was shown on the two-dimensional and three-dimensional imaging showing the preoperative bone contour and post-reaming bone removed (Figs. 2-C and 2-D).
Fig. 2
Preoperative images showing implant location before (Figs. 2-A and 2-B) and after (Figs. 2-C and 2-D) bone preparation.
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Fig. 3
Fig. 3-A Stereolithography-printed bone model with preoperatively planned guide pin hole placed in the model such that a guide pin is placed as shown in Figs. 3-B and 3-E. Fig. 3-B SmartBone with guide pin in place. Fig. 3-C Placement of intelligent reusable instrument on the SmartBone model. Fig. 3-D Intelligent reusable instrument on glenoid with guide pin placed in the bone. Fig. 3-E Comparison of pin position in glenoid to pin position in a three-dimensional SmartBone model.
Three-Dimensional Intelligent Reusable Instrument Group A sterile stereolithography SmartBone model of the glenoid containing the guide pin in the location determined in the preoperative planning software (OrthoVis, Custom Orthopaedic Solutions) was provided at the time of surgery (Fig. 3-A). At the time of surgery, the surgeon (J.P.I. or E.T.R.) confirmed that his surgical exposure and the resulting patient glenoid anatomy matched the SmartBone model (Fig. 3-B). Once confirmed, a reusable, adjustable instrument (Glenoid Intelligent Reusable Instrument System; Custom Orthopaedic Solutions) with instructions for use on the stereolithography model was provided. The intelligent reusable instrument has a cannulated handle placed over the guide pin on the bone model, and three or four adjustable peripheral legs, each having a specified leg length (in 1-mm increments), are fitted to the glenoid, with two or three legs over the rim of the glenoid and one or two legs contacting the posterior half of the glenoid surface. The legs were adjusted to contact the bone model as shown in the instructions, and their location was locked by tightening the collet. The location of the legs was marked on the SmartBone model (Fig. 3-C). The intelligent reusable instrument was then removed from the SmartBone model and placed onto the patient’s glenoid in the same location as shown on the
SmartBone model. The guide pin was then drilled into the glenoid through the intelligent reusable instrument device (Fig. 3-D). After removing the intelligent reusable instrument, the pin position in the glenoid was then compared with the pin position of the SmartBone model to check for accuracy (Fig. 3-E). The accuracy of this technology is based on the accuracy of the preoperative CT scans to represent the actual bone morphology and the accuracy of the surgical procedure to remove all soft tissues from the glenoid bone and sufficient exposure to accurately place the intelligent reusable instrument. All osteophytes that were present in the model were preserved after the glenoid exposure as landmarks in the three-dimensional imaging group and the three-dimensional intelligent reusable instrument group. These osteophytes were then removed at the discretion of the surgeon after placement of the guidewire, glenoid preparation, and placement of the glenoid trial.
Standard Instrumentation The surgeons used instrumentation provided by the implant company with either the two-dimensional imaging or the three-dimensional templating images (STEPTECH glenoid component, DePuy Synthes). These instruments were used on the basis of the best judgment of the surgeon and the images available at the time of surgery.
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Fig. 4
Coronal (Fig. 4-A), axial (Fig. 4-B), and sagittal (Fig. 4-C) images of preoperative implant (green) superimposed over postoperative implant (purple).
Measurement of Implant Location All patients in all groups (the three-dimensional intelligent reusable instrument group, the three-dimensional imaging group, and the two-dimensional imaging group) had a postoperative CT scan of their shoulder within three weeks of the operation with the arm by their side. The CT acquisition parameters were 140 kVp, 300 mA with dose modulation on 0.6-mm collimation, a 512 matrix, and a field of view to capture the entire scapula. Iterative metal artifact reduction was applied to the postoperative scans to reduce the interference and to allow more precise measurements of the final implant position in the regis33,34 tration software . The preoperative and postoperative three-dimensional CT images of the scapula were superimposed with use of custom-designed software (VolNinja; ImageIQ, Cleveland, Ohio), and the composite image was loaded into the preoperative planning software (OrthoVis, Custom Orthopaedic Solutions). Two non-surgeon investigators (S.W. and E.R.) independently blinded to the patient treatment group fit a virtual model of the surgically implanted glenoid component over the implant visualized within the CT images. This allowed measurement and comparison of the actual implant location in orientation and location with the preoperatively planned implant location (Fig. 4). To improve the visualization of the polyethylene implant on the postoperative CT scan, 1-mm tantalum beads were placed in each of the three peripheral pegs of the implant at the time of surgery. A metal wire was placed by the manufacturer in the central peg of the implant. Implant orientation was defined in degrees as a deviation in version and inclination relative to the preoperative plan.
Location was defined in millimeters in the anteroposterior and superoinferior direction of the center peg of the implant relative to the preoperative implant.
Statistical Analysis A power analysis was performed with use of the difference between the threedimensional imaging and the three-dimensional imaging with the intelligent reusable 28 instrument based on the means and standard deviations from a prior study . Sample sizes for achieving an 80% level of power assume a 5% level of significance, and those comparisons were done with use of the Welch two-sample t test. Adequate power for detecting these same differences in inclination or version between the threedimensional imaging group and the three-dimensional intelligent reusable instrument group was eight patients for inclination or thirty-four patients for version. We designed the study to have a minimum of twenty patients in each group. A post hoc power analysis, using the same statistical methods, determined that the number of patients that would have been required to show a difference between the threedimensional imaging group and the three-dimensional intelligent reusable instrument group for version or inclination would be approximately 2000 patients in each group, to detect a difference in version of 0.27°, which we believe to not be clinically important. Agreement between raters was assessed with use of both intraclass correlation coefficients and the probability of being within a predefined range of each other (2° or 1 mm), with 95% confidence intervals (95% CIs) determined by an exact binomial test. The Fisher exact test was used to define the difference in version and inclination between groups for >5° or >10°. When a significant difference was found,
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TABLE II Estimated Absolute Deviations from Plan for All Technology Three-Dimensional Imaging Group* (N = 21)
Three-Dimensional Intelligent Reusable Instrument Group* (N = 25)
Two-Dimensional Imaging Group* (N = 17)
Inclination
4.1 (2.7 to 5.5)
3.1 (2.1 to 4.2)
11.1 (8.2 to 14.1)
Version
4.3 (3.1 to 5.5)
4.0 (3.0 to 5.1)
6.9 (4.8 to 9.0)
Anteroposterior position
1.7 (1.2 to 2.2)
1.1 (0.8 to 1.5)
1.8 (1.2 to 2.5)
Superoinferior position
1.5 (0.9 to 2.2)
0.9 (0.5 to 1.3)
2.2 (1.3 to 3.1)
Measurement
*The values are given as the mean difference between the planned and actual implant position for each group, with the 95% CI in parentheses.
pairwise comparisons between groups were performed with use of the Holm correction to adjust p values for multiple comparisons. Significance was set at p < 0.05. All analyses were done with use of R software (version 3.0.2.; R Foundation for Statistical Computing, Vienna, Austria).
subsidiary of the Cleveland Clinic; one author of this study (J.P.I.) is also the chair of the scientific advisory board of Custom Orthopaedic Solutions.
Source of Funding
T
One of the authors of this study (J.P.I.) received grants from the State of Ohio Biomedical Research and Development Third Frontier Program. Funds were used to pay for salary support for three of the authors of this study (S.W., E.R., and T.E.P.), statistical analysis, preoperative and postoperative image analysis, the SmartBone models, and the intelligent reusable instruments. Custom Orthopaedic Solutions, which is the manufacturer of the SmartBone model, OrthoVis software, and the Glenoid Intelligent Reusable System, which were used in this study, is a
Results Implant Location: Inter-Rater Correlations he two non-physician experienced readers blinded to the surgical group (S.W. and E.R.) each independently measured in all patients in all three groups the postoperative implant location compared with the preoperative location of the implant. The two sets of measurements had intraclass correlation coefficients of ‡0.96 for all measurement outcomes. The two sets of measurements were averaged for the statistical analysis.
TABLE III Estimated Differences in Deviation from Plan Between Technologies Estimated Difference*
P Value
20.98 (23.21 to 1.26)
0.67
Inclination Three-dimensional intelligent reusable instrument compared with three-dimensional imaging Two-dimensional imaging compared with three-dimensional imaging
7 (2.78 to 11.22)
5° of inclination (p = 0.001) in the two-dimensional imaging group when compared with the three-dimensional imaging group or the threedimensional intelligent reusable instrument group. The raw data for deviation from plan for all patients are shown on scatter plots (see Appendix). There was no significant difference in implant position when comparing the three-dimensional imaging group and the three-dimensional intelligent reusable instrument group. There was no difference in the accuracy of implant placement between surgeons or with the severity of glenoid bone loss within the threedimensional imaging group and the three-dimensional intelligent reusable instrument group. Discussion he ideal position for placement of a glenoid component in any one patient or the best implant to use to achieve that goal has not been clearly established. Most surgeons attempt to correct pathologic inclination or version with corrective reaming (reaming the high side35), use of an augmented glenoid6, use of a bone graft36, or some combination of these methods. Failure to adequately correct pathologic glenoid version and placement of the glenoid component in >15° of retroversion may result in early component osteolysis10, resulting from persistent posterior translation of the center of the humeral head5 and eccentric posterior loading of the glenoid component. Finite element studies demonstrate that >10° of component retroversion results in high stresses at the bone-implant interface8. On the basis of these studies, we consider that ideal implant placement is between 0° and 10° of retroversion and superior inclination in relation to the plane of the
T
T H R E E -D I M E N S I O N A L I M A G I N G A N D T E M P L AT I N G I M P R O V E GLENOID IMPLANT POSITIONING
scapula. We considered the evidence in the literature to define clinically important deviation in implant position from plan to be between 5° to 10°. The use of an augmented glenoid component in the current study as well as in our previous study28 allowed for correction of pathologic glenoid version or inclination to within 0° to 10° of component version and inclination when there was more severe glenoid bone loss. There is no clinical evidence to establish the correct vertical position of the component (inclination) or the consequences of a deviation from a desired position. In this study, we assumed that the surgeon had a preoperative plan for placing the implant. The technology evaluated in this study was therefore limited to demonstrating how well each technology was able to achieve the desired plan. Achieving a desired plan did not mean that it was the correct plan or that it would produce the optimal clinical outcome. Further evaluation and research are required to address these limitations. The post hoc power analysis found that a large number of subjects would be required to detect a significant difference between the three-dimensional imaging group and the threedimensional intelligent reusable instrument group in the ability to accurately implant a glenoid component. Moreover, the difference detected would be
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
A commentary by T. Bradley Edwards, MD, is linked to the online version of this article at jbjs.org.
Three-Dimensional Imaging and Templating Improve Glenoid Implant Positioning Joseph P. Iannotti, MD, PhD, Scott Weiner, DO, Eric Rodriguez, BS, Naveen Subhas, MD, Thomas E. Patterson, PhD, Bong Jae Jun, PhD, and Eric T. Ricchetti, MD Investigation performed at the Department of Orthopaedic Surgery, Orthopaedic and Rheumatologic Institute, Cleveland Clinic, Cleveland, Ohio
Background: Preoperative quantitative assessment of glenoid bone loss, selection of the glenoid component, and definition of its desired location can be challenging. Placement of the glenoid component in the desired location at the time of surgery is difficult, especially with severe glenoid pathological conditions. Methods: Forty-six patients were randomly assigned to three-dimensional computed tomographic preoperative templating with either standard instrumentation or with patient-specific instrumentation and were compared with a nonrandomized group of seventeen patients with two-dimensional imaging and standard instrumentation used as historical controls. All patients had postoperative three-dimensional computed tomographic metal artifact reduction imaging to measure and to compare implant position with the preoperative plan. Results: Using three-dimensional imaging and templating with or without patient-specific instrumentation, there was a significant improvement achieving the desired implant position within 5° of inclination or 10° of version when compared with two-dimensional imaging and standard instrumentation. Conclusion: Three-dimensional assessment of glenoid anatomy and implant templating and the use of these images at the time of surgery improve the surgeon’s ability to place the glenoid implant in the desired location. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
G
lenoid component failure remains the primary cause of long-term clinical failure following total shoulder arthroplasty despite advances in implant design and surgical technique1. Glenoid component malposition, incomplete correction of bone pathological conditions, and persistent humeral head subluxation are factors associated with glenoid loosening 2-10. Preoperative planning and patient-specific instruments have grown in popularity across a wide range of orthopaedic
subspecialties to improve the accuracy of implant positioning. Total knee arthroplasty11-18, total hip arthroplasty19-21, hip resurfacing22, pelvic and acetabular procedures23-25, and spinal deformities26,27 have all utilized patient-specific instrument technology with varying degrees of success. Recently, patientspecific instrumentation was found to improve glenoid component placement in both the version and inclination planes when compared with standard two-dimensional surgical planning28,29.
Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, one or more of the authors has a patent or patents, planned, pending, or issued, that is broadly relevant to the work. Finally, one or more of the authors has had another relationship, or has engaged in another activity, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
J Bone Joint Surg Am. 2015;97:651-8
d
http://dx.doi.org/10.2106/JBJS.N.00493
652 TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O LU M E 97-A N U M B E R 8 A P R I L 15, 2 015 d
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The goal of this study was to evaluate the use of threedimensional preoperative imaging of glenoid pathological conditions and implant templating with or without the use of patient-specific instrumentation and to compare these results with historical controls using two-dimensional imaging with standard instrumentation. We hypothesized that threedimensional imaging and the use of patient-specific instrumentation would result in more accurate placement of the glenoid component. Materials and Methods Study Design
F
orty-six patients with end-stage primary glenohumeral osteoarthritis gave written consent to participate in an institutional review board-approved randomized clinical trial (Cleveland Clinic institutional review board 12-997; registered in ClinicalTrials.gov as NCT01801241). All enrolled patients completed the study, and there were no complications or adverse events. Patients were treated surgically by one of two fellowship-trained shoulder surgeons with extensive experience in shoulder arthroplasty and in use of the technology used in this study (J.P.I. and E.T.R.). All patients underwent anatomic total shoulder arthroplasty that was performed with use of the Global AP Humeral Implant, Global APG Implant, or GLOBAL STEPTECH APG Glenoid Component (DePuy Synthes, Warsaw, Indiana) and standard instrumentation. All patients in the randomized clinical trial had three-dimensional preoperative computed tomographic (CT) imaging and preoperative glenoid component templating using custom-designed three-dimensional planning software (OrthoVis; Custom Orthopaedic Solutions, Cleveland, Ohio). Multiple standardized threedimensional and two-dimensional images of the glenoid with the templated glenoid implant and the location of the guide pin were available to the surgeons at the time of surgery. The patients were then randomized by a research assistant into two groups using a block of thirty methods. In one group (n = 25), the surgeons were given a sterile, surrogate, three-dimensional model of the glenoid bone with the guide pin in the desired location based on the preoperative plan. In addition, a reusable and adjustable instrument was used as a patient-specific instrument (three-dimensional intelligent reusable instrument) to transfer the guide pin location in relation to the glenoid morphology from the surrogate model to the patient. In the other three-dimensional group (n = 21), guide pin and component placement was performed using only the images provided in the operating room derived from the three-dimensional software templating and standard instrumentation provided by the implant manufacturer (GLOBAL STEPTECH APG Glenoid Component; DePuy Synthes). The three-dimensional imaging group and the three-dimensional intelligent reusable instrument group were compared with a nonrandomized historical control group of seventeen patients who had surgical planning using only two-dimensional CT imaging without implant templating or computer measurements of glenoid bone loss. The same instrumentation and implants 28 were provided by the same manufacturer for the historical control group . All patients in all three groups had preoperative anteroposterior Grashey and axillary radiographs. All patients had CT scans performed preoperatively using 0.6-mm axial slice thickness of the entire scapula and proximal humerus with the arm by the side of the body. The CT acquisition parameters were 140 kVp, 300 mA with dose modulation on, 0.6-mm collimation, a 512 matrix, no gantry tilt, and a field of view to capture the entire scapula.
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head to the center of the glenoid were determined on the mid-axial two31 dimensional image as described by Walch et al. . The glenoid implants were selected by the treating surgeon and included either standard or augmented glenoid components (STEPTECH APG components, DePuy Synthes). For the two-dimensional imaging historical control group, the surgeons were asked to place the glenoid component in 0° of retroversion and 0° of inclination relative to the plane of the scapula using the two-dimensional images and reference lines. The prescribed position of the implant was then compared with the actual postoperative implant position. This was our standard of care for total shoulder arthroplasty in 2009.
Preoperative Planning and Templating for the Three-Dimensional Imaging Groups Digital Imaging and Communication in Medicine (DICOM) files of the preoperative CT imaging were entered into a shoulder arthroplasty-specific preoperative planning software application (OrthoVis, Custom Orthopaedic Solutions) and were reformatted into three-dimensional representations of the bones. The humerus and scapula were segmented into separate files. The plane of the scapula was defined by landmarks placed on the scapula trigonum, the 28,29,32 inferior angle, and the center of the glenoid, as previously described . The line between the trigonum and the center of the glenoid fossa determines the transverse scapula line. This line extends through the center of the medial aspect of the glenoid vault and exits near the anterior scapula body. Three landmarks placed on the surface of the glenoid fossa defined the plane of the glenoid and thereby defined the version and inclination of the glenoid fossa to the plane of the scapula. Two-dimensional images in the axial, transverse, and coronal planes were defined on the basis of these planes (Fig. 1). The surgeon then selected a standard or augmented glenoid component (STEPTECH APG component, DePuy Synthes) template in the planning software that allowed for correction of glenoid version and inclination between 0° and 10°, relative to the plane of the scapula, with the least amount of bone removal. The amount and location of bone removal and the location of the fixation pegs were visualized for that implant in that location. The location of the implant defined the location of the guide pin to be placed at the time of surgery to replicate the desired location of the implant. Preoperative implant type and position as defined by the surgeon were then used as the goal of
Preoperative Planning for the Two-Dimensional Imaging Group In the two-dimensional imaging group, the two-dimensional CT imaging in the coronal, axial, and sagittal planes were provided to the surgeon with axial planes 28 perpendicular to the plane of the scapula . The surgeon used these images to determine the glenoid version according to the method described by Friedman 30 et al. and inclination as defined as the perpendicular (0°) to a vertical line from the center of the glenoid to the medial border of the scapula in the coronal plane images. The glenoid morphology and the relationship of the humeral
Fig. 1
Landmarks to define the plane of the scapula and the plane of the glenoid.
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TABLE I Walch Type Groups† Walch Type*
Three-Dimensional Imaging (N = 21)
Three-Dimensional Intelligent Reusable Instrument (N = 25)
Two-Dimensional Imaging (N = 17)
A1
4
3
4
A2
7
5
5
B1
2
2
1
B2
6
12
6
C
2
3
1
*There was no significant difference in type of glenoid morphology (Walch classification). †There was a significant difference in the frequency of use of an augmented component between the two-dimensional imaging group (which did not use any augmented components) and both of the three-dimensional imaging groups (four augmented components for the three-dimensional imaging group and eight augmented components for the three-dimensional intelligent reusable instrument group).
surgery and were compared with the actual postoperative implant position. A standardized set of two-dimensional and three-dimensional images showing the location of the implant before and after bone preparation were available to
the surgeon at the time of surgery (Fig. 2). Depth of reaming was shown on the two-dimensional and three-dimensional imaging showing the preoperative bone contour and post-reaming bone removed (Figs. 2-C and 2-D).
Fig. 2
Preoperative images showing implant location before (Figs. 2-A and 2-B) and after (Figs. 2-C and 2-D) bone preparation.
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Fig. 3
Fig. 3-A Stereolithography-printed bone model with preoperatively planned guide pin hole placed in the model such that a guide pin is placed as shown in Figs. 3-B and 3-E. Fig. 3-B SmartBone with guide pin in place. Fig. 3-C Placement of intelligent reusable instrument on the SmartBone model. Fig. 3-D Intelligent reusable instrument on glenoid with guide pin placed in the bone. Fig. 3-E Comparison of pin position in glenoid to pin position in a three-dimensional SmartBone model.
Three-Dimensional Intelligent Reusable Instrument Group A sterile stereolithography SmartBone model of the glenoid containing the guide pin in the location determined in the preoperative planning software (OrthoVis, Custom Orthopaedic Solutions) was provided at the time of surgery (Fig. 3-A). At the time of surgery, the surgeon (J.P.I. or E.T.R.) confirmed that his surgical exposure and the resulting patient glenoid anatomy matched the SmartBone model (Fig. 3-B). Once confirmed, a reusable, adjustable instrument (Glenoid Intelligent Reusable Instrument System; Custom Orthopaedic Solutions) with instructions for use on the stereolithography model was provided. The intelligent reusable instrument has a cannulated handle placed over the guide pin on the bone model, and three or four adjustable peripheral legs, each having a specified leg length (in 1-mm increments), are fitted to the glenoid, with two or three legs over the rim of the glenoid and one or two legs contacting the posterior half of the glenoid surface. The legs were adjusted to contact the bone model as shown in the instructions, and their location was locked by tightening the collet. The location of the legs was marked on the SmartBone model (Fig. 3-C). The intelligent reusable instrument was then removed from the SmartBone model and placed onto the patient’s glenoid in the same location as shown on the
SmartBone model. The guide pin was then drilled into the glenoid through the intelligent reusable instrument device (Fig. 3-D). After removing the intelligent reusable instrument, the pin position in the glenoid was then compared with the pin position of the SmartBone model to check for accuracy (Fig. 3-E). The accuracy of this technology is based on the accuracy of the preoperative CT scans to represent the actual bone morphology and the accuracy of the surgical procedure to remove all soft tissues from the glenoid bone and sufficient exposure to accurately place the intelligent reusable instrument. All osteophytes that were present in the model were preserved after the glenoid exposure as landmarks in the three-dimensional imaging group and the three-dimensional intelligent reusable instrument group. These osteophytes were then removed at the discretion of the surgeon after placement of the guidewire, glenoid preparation, and placement of the glenoid trial.
Standard Instrumentation The surgeons used instrumentation provided by the implant company with either the two-dimensional imaging or the three-dimensional templating images (STEPTECH glenoid component, DePuy Synthes). These instruments were used on the basis of the best judgment of the surgeon and the images available at the time of surgery.
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Fig. 4
Coronal (Fig. 4-A), axial (Fig. 4-B), and sagittal (Fig. 4-C) images of preoperative implant (green) superimposed over postoperative implant (purple).
Measurement of Implant Location All patients in all groups (the three-dimensional intelligent reusable instrument group, the three-dimensional imaging group, and the two-dimensional imaging group) had a postoperative CT scan of their shoulder within three weeks of the operation with the arm by their side. The CT acquisition parameters were 140 kVp, 300 mA with dose modulation on 0.6-mm collimation, a 512 matrix, and a field of view to capture the entire scapula. Iterative metal artifact reduction was applied to the postoperative scans to reduce the interference and to allow more precise measurements of the final implant position in the regis33,34 tration software . The preoperative and postoperative three-dimensional CT images of the scapula were superimposed with use of custom-designed software (VolNinja; ImageIQ, Cleveland, Ohio), and the composite image was loaded into the preoperative planning software (OrthoVis, Custom Orthopaedic Solutions). Two non-surgeon investigators (S.W. and E.R.) independently blinded to the patient treatment group fit a virtual model of the surgically implanted glenoid component over the implant visualized within the CT images. This allowed measurement and comparison of the actual implant location in orientation and location with the preoperatively planned implant location (Fig. 4). To improve the visualization of the polyethylene implant on the postoperative CT scan, 1-mm tantalum beads were placed in each of the three peripheral pegs of the implant at the time of surgery. A metal wire was placed by the manufacturer in the central peg of the implant. Implant orientation was defined in degrees as a deviation in version and inclination relative to the preoperative plan.
Location was defined in millimeters in the anteroposterior and superoinferior direction of the center peg of the implant relative to the preoperative implant.
Statistical Analysis A power analysis was performed with use of the difference between the threedimensional imaging and the three-dimensional imaging with the intelligent reusable 28 instrument based on the means and standard deviations from a prior study . Sample sizes for achieving an 80% level of power assume a 5% level of significance, and those comparisons were done with use of the Welch two-sample t test. Adequate power for detecting these same differences in inclination or version between the threedimensional imaging group and the three-dimensional intelligent reusable instrument group was eight patients for inclination or thirty-four patients for version. We designed the study to have a minimum of twenty patients in each group. A post hoc power analysis, using the same statistical methods, determined that the number of patients that would have been required to show a difference between the threedimensional imaging group and the three-dimensional intelligent reusable instrument group for version or inclination would be approximately 2000 patients in each group, to detect a difference in version of 0.27°, which we believe to not be clinically important. Agreement between raters was assessed with use of both intraclass correlation coefficients and the probability of being within a predefined range of each other (2° or 1 mm), with 95% confidence intervals (95% CIs) determined by an exact binomial test. The Fisher exact test was used to define the difference in version and inclination between groups for >5° or >10°. When a significant difference was found,
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TABLE II Estimated Absolute Deviations from Plan for All Technology Three-Dimensional Imaging Group* (N = 21)
Three-Dimensional Intelligent Reusable Instrument Group* (N = 25)
Two-Dimensional Imaging Group* (N = 17)
Inclination
4.1 (2.7 to 5.5)
3.1 (2.1 to 4.2)
11.1 (8.2 to 14.1)
Version
4.3 (3.1 to 5.5)
4.0 (3.0 to 5.1)
6.9 (4.8 to 9.0)
Anteroposterior position
1.7 (1.2 to 2.2)
1.1 (0.8 to 1.5)
1.8 (1.2 to 2.5)
Superoinferior position
1.5 (0.9 to 2.2)
0.9 (0.5 to 1.3)
2.2 (1.3 to 3.1)
Measurement
*The values are given as the mean difference between the planned and actual implant position for each group, with the 95% CI in parentheses.
pairwise comparisons between groups were performed with use of the Holm correction to adjust p values for multiple comparisons. Significance was set at p < 0.05. All analyses were done with use of R software (version 3.0.2.; R Foundation for Statistical Computing, Vienna, Austria).
subsidiary of the Cleveland Clinic; one author of this study (J.P.I.) is also the chair of the scientific advisory board of Custom Orthopaedic Solutions.
Source of Funding
T
One of the authors of this study (J.P.I.) received grants from the State of Ohio Biomedical Research and Development Third Frontier Program. Funds were used to pay for salary support for three of the authors of this study (S.W., E.R., and T.E.P.), statistical analysis, preoperative and postoperative image analysis, the SmartBone models, and the intelligent reusable instruments. Custom Orthopaedic Solutions, which is the manufacturer of the SmartBone model, OrthoVis software, and the Glenoid Intelligent Reusable System, which were used in this study, is a
Results Implant Location: Inter-Rater Correlations he two non-physician experienced readers blinded to the surgical group (S.W. and E.R.) each independently measured in all patients in all three groups the postoperative implant location compared with the preoperative location of the implant. The two sets of measurements had intraclass correlation coefficients of ‡0.96 for all measurement outcomes. The two sets of measurements were averaged for the statistical analysis.
TABLE III Estimated Differences in Deviation from Plan Between Technologies Estimated Difference*
P Value
20.98 (23.21 to 1.26)
0.67
Inclination Three-dimensional intelligent reusable instrument compared with three-dimensional imaging Two-dimensional imaging compared with three-dimensional imaging
7 (2.78 to 11.22)
5° of inclination (p = 0.001) in the two-dimensional imaging group when compared with the three-dimensional imaging group or the threedimensional intelligent reusable instrument group. The raw data for deviation from plan for all patients are shown on scatter plots (see Appendix). There was no significant difference in implant position when comparing the three-dimensional imaging group and the three-dimensional intelligent reusable instrument group. There was no difference in the accuracy of implant placement between surgeons or with the severity of glenoid bone loss within the threedimensional imaging group and the three-dimensional intelligent reusable instrument group. Discussion he ideal position for placement of a glenoid component in any one patient or the best implant to use to achieve that goal has not been clearly established. Most surgeons attempt to correct pathologic inclination or version with corrective reaming (reaming the high side35), use of an augmented glenoid6, use of a bone graft36, or some combination of these methods. Failure to adequately correct pathologic glenoid version and placement of the glenoid component in >15° of retroversion may result in early component osteolysis10, resulting from persistent posterior translation of the center of the humeral head5 and eccentric posterior loading of the glenoid component. Finite element studies demonstrate that >10° of component retroversion results in high stresses at the bone-implant interface8. On the basis of these studies, we consider that ideal implant placement is between 0° and 10° of retroversion and superior inclination in relation to the plane of the
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scapula. We considered the evidence in the literature to define clinically important deviation in implant position from plan to be between 5° to 10°. The use of an augmented glenoid component in the current study as well as in our previous study28 allowed for correction of pathologic glenoid version or inclination to within 0° to 10° of component version and inclination when there was more severe glenoid bone loss. There is no clinical evidence to establish the correct vertical position of the component (inclination) or the consequences of a deviation from a desired position. In this study, we assumed that the surgeon had a preoperative plan for placing the implant. The technology evaluated in this study was therefore limited to demonstrating how well each technology was able to achieve the desired plan. Achieving a desired plan did not mean that it was the correct plan or that it would produce the optimal clinical outcome. Further evaluation and research are required to address these limitations. The post hoc power analysis found that a large number of subjects would be required to detect a significant difference between the three-dimensional imaging group and the threedimensional intelligent reusable instrument group in the ability to accurately implant a glenoid component. Moreover, the difference detected would be
