Improved accuracy of computer assisted glenoid implantation in total shoulder arthroplasty: an in-vitro randomized controlled trial

Preoperative planning for accurate glenoid component positioning in reverse shoulder arthroplasty

BACKGROUND

Glenoid component positioning in reverse shoulder arthroplasty (RSA) is challenging. Patient-specific instrumentation (PSI) has been advocated to improve accuracy, and is based on precise preoperative planning. The purpose of this study was to determine the accuracy of glenoid component positioning when only the glenoid surface is visible, compared to when the entire scapula is visible on a 3D virtual model.

METHODS

CT scans of 30 arthritic shoulders were reconstructed in 3D models. Two surgeons then virtually placed a glenosphere component in the model while visualizing only the glenoid surface, in order to simulate typical intraoperative exposure ("blind 3D" surgery). One surgeon then placed the component in an ideal position while visualizing the entire scapula ("visible 3D" surgery). These two positions were then compared, and the accuracy of glenoid component positioning was assessed in terms of correction of native glenoid version and tilt, and avoidance of glenoid vault perforation.

RESULTS

Mean version and tilt after "blind 3D" surgery were +1.4° (SD 8.8°) and +7.6° (SD 6°), respectively; glenoid vault perforation occurred in 17 specimens. Mean version and tilt after "visible 3D" surgery were +0.3° (SD 0.8°) and +0.1° (SD 0.5°), respectively, with glenoid vault perforation in 6 cases. "Visible 3D" surgery provided significantly better accuracy than "blind 3D" surgery (P<0.05).

CONCLUSION

When the entire scapula is used as reference, accuracy is improved and glenoid vault perforation is less frequent. This type of visualization is only possible with pre-operative 3D CT planning, and may be augmented by PSI.

LEVEL OF EVIDENCE

Basic science study. Level III.

Patient-specific glenoid guides provide accuracy and reproducibility in total shoulder arthroplasty

AIMS

Patient-specific glenoid guides (PSGs) claim an improvement in accuracy and reproducibility of the positioning of components in total shoulder arthroplasty (TSA). The results have not yet been confirmed in a prospective clinical trial. Our aim was to assess whether the use of PSGs in patients with osteoarthritis of the shoulder would allow accurate and reliable implantation of the glenoid component.

PATIENTS AND METHODS

A total of 17 patients (three men and 14 women) with a mean age of 71 years (53 to 81) awaiting TSA were enrolled in the study. Pre- and post-operative version and inclination of the glenoid were measured on CT scans, using 3D planning automatic software. During surgery, a congruent 3D-printed PSG was applied onto the glenoid surface, thus determining the entry point and orientation of the central guide wire used for reaming the glenoid and the introduction of the component. Manual segmentation was performed on post-operative CT scans to compare the planned and the actual position of the entry point (mm) and orientation of the component (°).

RESULTS

The mean error in the accuracy of the entry point was -0.1 mm (standard deviation (sd) 1.4) in the horizontal plane, and 0.8 mm (sd 1.3) in the vertical plane. The mean error in the orientation of the glenoid component was 3.4° (sd 5.1°) for version and 1.8° (sd 5.3°) for inclination.

CONCLUSION

Pre-operative planning with automatic software and the use of PSGs provides accurate and reproducible positioning and orientation of the glenoid component in anatomical TSA. Cite this article: Bone Joint J 2016;98-B:1080-5.

Patient-Matched Implementation for Reverse Total Shoulder Arthroplasty

Introduction

Three-dimensional (3D) preoperative planning and patient-specific instrumentation (PSI) improve accuracy of glenoid component implantation in reverse shoulder arthroplasty.

Indications & Contraindications

Step 1 Preoperative Virtual 3D Planning Video 1

Use a 3D software tool for virtual preoperative planning of glenoid component implantation.

Step 2 Patient Positioning and Surgical Approach Video 2

Place the patient in a semi-beach-chair position and perform a standard deltopectoral approach.

Step 3 Humeral Preparation Video 3

Prepare the humeral side for implantation of the humeral component using standard instrumentation.

Step 4 Glenoid Exposure and Preparation Video 4

Expose the glenoid and prepare the glenoid surface for component implantation.

Step 5 Glenoid Preparation and Implantation of the Glenoid Baseplate Using 4 PSI Guides Video 5

Use the 4 PSI guides to prepare the glenoid for component implantation according to the preoperative plan.

Step 6 Definitive Implantation of the Components and Reduction Video 6

Implant the glenosphere and humeral component and reduce the prosthesis.

Step 7 Postoperative Rehabilitation Protocol

Start passive and active-assisted exercises immediately, and begin muscle strengthening and active exercises at 6 weeks.

Results

A recent prospective, comparative study assessed the influence of 3D preoperative planning and PSI guidance of glenoid component positioning in total shoulder arthroplasty and reverse shoulder arthroplasty¹⁸.

Pitfalls & Challenges

Improved accuracy of K-wire positioning into the glenoid vault by intraoperative 3D image intensifier-based navigation for the glenoid component in shoulder arthroplasty

INTRODUCTION

This article aimed to show that navigation, based on an intraoperative mobile 3D image intensifier, can improve the accuracy of central K-wire placement into the glenoid vault for glenoid component.

HYPOTHESIS

The navigated k-wire placement is more accurate and shows a smaller deviation angle to the standard centerline compared to the classical "free hand technic".

METHODS

In 34 fresh frozen sheep scapulae, 17 K-wire placements using the navigation (group 1) were compared with 17 using standard "face plane technique" (group 2). The relation to glenoid standard and alternative centerlines (CL) and the position within the glenoid vault were analyzed.

RESULTS

In groups 1 and 2 the angle between the K-wire and standard CL was 2.2° and 4.7°, respectively (P=0.01). The angle between the K-wire and alternative CL was 14.4° for group 1 and 17.2° for group 2 (P=0.02). More navigated K-wire positions were identified within a 5mm corridor along the glenoid vault CL (52 vs. 39; P=0.004).

DISCUSSION

Intraoperative 3D image intensifier-based navigation was more accurate and precise than standard K-wire placement.

TYPE OF STUDY AND LEVEL OF PROOF

Basic science study, evidence level III.

Accuracy of patient-specific instrumentation in anatomic and reverse total shoulder arthroplasty

PURPOSE

Glenoid component malposition is associated with poor function and early failure of both anatomic and reverse total shoulder arthroplasty. Glenoid positioning is challenging particularly in the setting of bone loss or deformity. Recently, the use of computer assistance has been shown to reduce implantation error. The aim of this study is to evaluate the accuracy of patient-specific instrumentation in cases of anatomic and reverse shoulder replacement in vivo.

METHODS

Twenty patients underwent total shoulder arthroplasty using a computed tomography (CT)-based patient-specific instrumentation (PSI) system, ten anatomic and ten reverse. Preoperative three-dimensional digital templating of glenoid component position was undertaken and surgery then performed using a custom-made guide. Postoperative CT scans were used to compare final implanted component position to the preoperatively planned position in the same patient.

RESULTS

Final component position and orientation closely reflected the preoperatively templated position. Mean deviation in the glenoid version from planned was 1.8° ±1.9° (range, 0.1°-7.3°). Mean deviation in inclination was 1.3° ±1.0° (range, 0.2°-4.5°). Mean deviation in position on the glenoid face was 0.5 ± 0.3 mm (range, 0.0-1.3 mm) in the anteroposterior plane and 0.8 ± 0.5 mm (range, 0.0-1.9 mm) in the superoinferior plane. Actual achieved version was within 7° of neutral in all cases except for one where it was deliberately planned to be outside of this range.

CONCLUSION

PSI in both anatomic and reverse shoulder arthroplasty is highly accurate in guiding glenoid component implantation in vivo. The system can reliably correct bony deformity.

A patient-specific guide for optimizing custom-made glenoid implantation in cases of severe glenoid defects: an in vitro study

BACKGROUND

Glenoid component and screw malpositioning in cases of severe glenoid defects might result in complications. We examined the efficacy of a surgical method to treat severe glenoid defects, including a custom-made glenoid component and accurate screw positioning, using a patient-specific positioning guide.

METHODS

Glenoid defects were created in 10 cadaveric shoulders. Computed tomography images were used to plan reversed shoulder arthroplasty and design patient-specific glenoid components. A patient-specific positioning guide was designed for 5 specimens. The remaining 5 specimens were implanted without the guide. Computed tomography images were used to determine the postoperative glenoid component and screw positions. Differences from the preoperatively planned implant and screw positions were calculated.

RESULTS

The patient-specific positioning guide significantly reduced the angular deviations from the planned glenoid implant positioning (P < .05) and also significantly improved the positioning of the screws (P < .001). In the group without the guide, the average total intraosseous screw length was 52% of the ideal preoperatively planned length compared with 89% for the group with the guide. A strong correlation (r = -0.85) was found between the orientation of the implant and the postoperative total intraosseous screw length.

CONCLUSIONS

A patient-specific positioning guide significantly improves the position and fixation of a custom-made glenoid component in cases of severe glenoid defects.

Is a generic targeting guide useful for glenoid component placement in shoulder arthroplasty?

BACKGROUND

This study compared postoperative glenoid component version using traditional instrumentation to a generic glenoid targeting guide during total or reverse total shoulder arthroplasty.

METHODS

Glenoid component version was measured on postoperative radiographs of 184 shoulders (traditional, 109; targeting guide, 75). Demographics, preoperative imaging, and operative technique were identified from medical records. Absolute deviation from neutral version and standard deviations (SDs) were calculated.

RESULTS

Average mean ± SD deviation in component version for the traditional technique group was 10° ± 7° compared with 9° ± 6° for the targeting guide group (P = .37; SD P = .12). No significant difference was noted based on operation, body mass index, preoperative version, or operative indication. For the last 30 shoulders in the targeting group, the absolute mean deviation was 6° compared with 11° in the first 30 of that group (P < .01) and 10° in the entire traditional group (P = .01). The SD in the last 30 shoulders in the targeting group was 5° compared with 7° in the first 30 in that group (P = .04) and 7° in the traditional group (P < .01).

CONCLUSIONS

No significant difference in component accuracy was noted between the 2 techniques. The narrower SD in the targeting group, although not statistically significant, suggests less glenoid placement in the extremes of version. A learning curve was noted with the targeting guide, with significantly improved accuracy in later patients.

Regression forest-based automatic estimation of the articular margin plane for shoulder prosthesis planning

In shoulder arthroplasty, the proximal humeral head is resected by sawing along the cartilage-bone transition and replaced by a prosthetic implant. The resection plane, called articular margin plane (AMP), defines the orientation, position and size of the prosthetic humeral head in relation to the humeral shaft. Therefore, the correct definition of the AMP is crucial for the computer-assisted preoperative planning of shoulder arthroplasty. We present a fully automated method for estimating the AMP relying only on computed tomography (CT) images of the upper arm. It consists of two consecutive steps, each of which uses random regression forests (RFs) to establish a direct mapping from the CT image to the AMP parameters. In the first step, image intensities serve as features to compute a coarse estimate of the AMP. The second step builds upon this estimate, calculating a refined AMP using novel feature types that combine a bone enhancing sheetness measure with ray features. The proposed method was evaluated on a dataset consisting of 72 CT images of upper arm cadavers. A mean localization error of 2.40mm and a mean angular error of 6.51° was measured compared to manually annotated ground truth.

The association of incomplete glenoid component seating and periprosthetic glenoid radiolucencies after total shoulder arthroplasty

BACKGROUND

Radiolucent lines surrounding prosthetic glenoid components are commonly seen after unconstrained total shoulder arthroplasty and can be a harbinger of subsequent glenoid component failure. Whether less than 100% glenoid seating is associated with the development of radiolucent lines around glenoid prostheses is unknown. This study investigated the association between incomplete glenoid component seating and periprosthetic glenoid radiolucencies.

METHODS

Thirty-six unconstrained total shoulder arthroplasties were performed in 29 patients for primary glenohumeral osteoarthritis with a minimum 2-year follow-up. All were implanted with a partially cemented all-polyethylene glenoid prosthesis. Patients were evaluated with standardized plain films preoperatively and postoperatively and with thin-cut computed tomography (CT) scans at the latest follow-up. The Lazarus and Yian classifications were used to assess radiolucency and seating on radiographs and CT scans. Ratings were calculated for intraobserver and interobserver reliability and given κ, the Kendall coefficient, and interclass correlation coefficient values.

RESULTS

At a mean of 43 months (range 24-26 months) after surgery, neither Lazarus plain film radiolucency scores (P = .78) nor Yian CT radiolucency scores (P = .68) were associated with Lazarus plain film seating scores. Neither Lazarus plain film radiolucency scores (P = .25) nor Yian CT radiolucency scores (P = .91) were associated with modified Lazarus CT scan seating scores. CT allowed for better intraobserver and interobserver reliability in all categories.

CONCLUSION

Radiolucencies around a partially cemented glenoid component were not associated with the degree of component seating. Complete seating of the glenoid component is not necessary to achieve radiographic implant stability at a mean follow-up of 43 months.

Computer algorithms for three-dimensional measurement of humeral anatomy: analysis of 140 paired humeri

BACKGROUND

In the presence of severe osteoarthritis, osteonecrosis, or proximal humeral fracture, the contralateral humerus may serve as a template for the 3-dimensional (3D) preoperative planning of reconstructive surgery. The purpose of this study was to develop algorithms for performing 3D measurements of the humeral anatomy and further to assess side-to-side (bilateral) differences in humeral head retrotorsion, humeral head inclination, humeral length, and humeral head radius and height.

METHODS

The 3D models of 140 paired humeri (70 cadavers) were extracted from computed tomographic data. Geometric characteristics quantifying the humeral anatomy in 3D were determined in a semiautomatic fashion using the developed computer algorithms. The results between the sides were compared for evaluating bilateral differences.

RESULTS

The mean bilateral difference of the humeral retrotorsion angle was 6.7° (standard deviation [SD], 5.7°; range, -15.1° to 24.0°; P = .063); the mean side difference of the humeral head inclination angle was 2.3° (SD, 1.8°; range, -5.1° to 8.4°; P = .12). The side difference in humeral length (mean, 2.9 mm; SD, 2.5 mm; range, -8.7 mm to 10.1 mm; P = .04) was significant. The mean side difference in the head sphere radius was 0.5 mm (SD, 0.6 mm; range, -3.2 mm to 2.2 mm; P = .76), and the mean side difference in humeral head height was 0.8 mm (SD, 0.6 mm; range, -2.4 mm to 2.4 mm; P = .44).

CONCLUSIONS

The contralateral anatomy may serve as a reliable reconstruction template for humeral length, humeral head radius, and humeral head height if it is analyzed with 3D algorithms. In contrast, determining humeral head retrotorsion and humeral head inclination from the contralateral anatomy may be more prone to error.

Patient-specific instrument guidance of glenoid component implantation reduces inclination variability in total and reverse shoulder arthroplasty

BACKGROUND

The aim of this study was to assess the influence of 3-dimensional (3D) preoperative planning and patient-specific instrument (PSI) guidance of glenoid component positioning on its inclination in total shoulder arthroplasty (TSA) and reverse shoulder arthroplasty (RSA).

MATERIALS AND METHODS

Thirty-six shoulder arthroplasties (12 TSAs, 24 RSAs) were analyzed, of which 18 procedures (6 TSAs, 12 RSAs) were executed using preoperative 3D planning and patient-specific guides to position the central guide pin for glenoid component implantation. In 9 cases, the glenoid anatomy was severely distorted through wear or previous surgery. The inclination of the glenoid component was measured by 2 observers, using the angle between the glenoid baseplate and the floor of the supraspinatus fossa (angle β) on postoperative radiographs.

RESULTS

For TSA, the average angle β was 74 ± 9 in the PSI group and 86 ± 12 in the non-PSI group; for RSA, the average angle β was 83 ± 7 in the PSI group and 90 ± 17 in the non-PSI group. Extreme angles β, which represent extreme values of glenoid component inclination, are more likely to occur in the non-PSI group than in the PSI group (P < .001 for TSA; P = .02 for RSA).

CONCLUSIONS

The3D preoperative surgical planning and PSI guidance reduce variability in glenoid component inclination and avoid extreme inclination errors for TSA and RSA.

Can an extracorporeal glenoid aiming device be used to optimize the position of the glenoid component in total shoulder arthroplasty?

PURPOSE

Successful total shoulder arthroplasty (TSA) requires a correct position of the glenoid component. This study compares the accuracy of the positioning with a new developed glenoid aiming device and virtual three-dimensional computed tomography (3D-CT) scan positioning.

MATERIALS AND METHODS

On 39 scapulas from cadavers, a K-wire (KDev) was positioned using the glenoid aiming device. It consists of glenoid components connected to the aiming device, which cover 150° of the inferior glenoid circle, has a fixed version and inclination and is available with several different radii. The aiming device is stabilized at the most medial scapular point. The K-wire is drilled from the center of the glenoid component to this most medial point. All scapulas were also scanned with CT and 3D reconstructed. A virtual K-wire (Kct) was positioned in the center of the glenoid and in the scapular plane. Several parameters were compared. Radius of the chosen glenoid component (rDev) and the virtual radius of the glenoid circle (rCT), spinal scapular length with the device (SSLdev) and virtual (SSLct), version and inclination between KDev and Kct, difference between entry point and exit point ("Matsen"-point).

RESULTS

Mean rDev: 14 mm ± 1.7 mm and mean rCT: 13.5 mm ± 1.6 mm. There was no significant difference between SSLdev (110.6 mm ± 7.5 mm) and SSLct (108 mm ± 7.5 mm). The version of KDev and Kct was -2.53° and -2.17° and the inclination 111.29° and 111.66°, respectively. The distance between the "Matsen-point" device and CT was 1.8 mm.

CONCLUSION

This glenoid aiming device can position the K-wire on the glenoid with great accuracy and can, therefore, be helpful to position the glenoid component in TSA. The level of evidence: II.

Testing of a novel pin array guide for accurate three-dimensional glenoid component positioning

BACKGROUND

A substantial challenge in total shoulder replacement is accurate positioning and alignment of the glenoid component. This challenge arises from limited intraoperative exposure and complex arthritic-driven deformity. We describe a novel pin array guide and method for patient-specific guiding of the glenoid central drill hole. We also experimentally tested the hypothesis that this method would reduce errors in version and inclination compared with 2 traditional methods.

METHODS

Polymer models of glenoids were created from computed tomography scans from 9 arthritic patients. Each 3-dimensional (3D) printed scapula was shrouded to simulate the operative situation. Three different methods for central drill alignment were tested, all with the target orientation of 5° retroversion and 0° inclination: no assistance, assistance by preoperative 3D imaging, and assistance by the pin array guide. Version and inclination errors of the drill line were compared.

RESULTS

Version errors using the pin array guide (3° ± 2°) were significantly lower than version errors associated with no assistance (9° ± 7°) and preoperative 3D imaging (8° ± 6°). Inclination errors were also significantly lower using the pin array guide compared with no assistance.

DISCUSSION AND CONCLUSION

The new pin array guide substantially reduced errors in orientation of the central drill line. The guide method is patient specific but does not require rapid prototyping and instead uses adjustments to an array of pins based on automated software calculations. This method may ultimately provide a cost-effective solution enabling surgeons to obtain accurate orientation of the glenoid.

Consequences of reaming with flat and convex reamers for bone volume and surface area of the glenoid; a basic science study

Background

The effect of reaming on bone volume and surface area of the glenoid is not precisely known. We hypothesize that (1) convex reamers create a larger surface area than flat reamers, (2) flat reamers cause less bone loss than convex reamers, and (3) the amount of bone loss increases with the amount of version correction.

Methods

Reaming procedures with different types of reamers are performed on similar-sized uniconcave and biconcave glenoids created from Sawbones foam blocks. The loss of bone volume, the size of the remaining surface area, and the reaming depth are measured and evaluated.

Results

Reaming with convex reamers results in a significantly larger surface area than with flat reamers for both uniconcave and biconcave glenoids (p = 0.013 and p = 0.001). Convex reamers cause more bone loss than flat reamers, but the difference is only significant for uniconcave glenoids (p = 0.007).

Conclusions

In biconcave glenoids, convex reamers remove a similar amount of bone as flat reamers, but offer a larger surface area while maximizing the correction of the retroversion. In pathological uniconcave glenoids, convex reamers are preferred because of the conforming shape.

Benefit of intraoperative navigation on glenoid component positioning during total shoulder arthroplasty

INTRODUCTION

The objective of this study was to review and synthesize the current best evidence for the use of intraoperative navigation in the implantation of glenoid components in total shoulder prostheses.

METHODS

We conducted a systematic, online search using PubMed, EMBASE, CCTR, and CINAHL using "Arthroplasty, Replacement"(Mesh) AND (shoulder) AND (navi* OR computer). Data on study design and quality as well as accuracy of positioning and complications were extracted independently and in duplicate. After assessment of study heterogeneity, DerSimonian-Laird random effect models were used to pool data from the individual studies.

RESULTS

The systematic search revealed 359 manuscripts in total. After exclusion of duplicates and irrelevant publications, 6 groups of 247 shoulders from 5 studies were included. The pooled weighted mean difference for deviation from neutral version was -6.4° (95 %CI -7.9 to -5.3) in favor of navigation, which is consistent with a statistically significant difference (p < 0.01). In the navigation group, 2 superior glenoid screws were reported as perforating compared to 5 screws (1 inferior, 4 superior) in the control group. There was no difference in tilt at a WMD of 2.7 (95 %CI -1.4 to 6.8, p = 0.192).

CONCLUSIONS

Navigation allows for significantly more accurate glenoid version, but the clinical meaningfulness of the absolute improvement over standard techniques is questionable. However, navigation is a valuable teaching tool that might prove very beneficial not for the patient at hand, but for those treated by the operating surgeon in the future.

LEVEL OF EVIDENCE

Level II-meta-analysis of non-homogenous controlled trials.

Accuracy of patient-specific guided glenoid baseplate positioning for reverse shoulder arthroplasty

BACKGROUND

The accuracy of reproducing a surgical plan during shoulder arthroplasty is improved by computer assistance. Intraoperative navigation, however, is challenged by increased surgical time and additional technically difficult steps. Patient-matched instrumentation has the potential to reproduce a similar degree of accuracy without the need for additional surgical steps. The purpose of this study was to examine the accuracy of patient-specific planning and a patient-specific drill guide for glenoid baseplate placement in reverse shoulder arthroplasty.

METHODS

A patient-specific glenoid baseplate drill guide for reverse shoulder arthroplasty was produced for 14 cadaveric shoulders based on a plan developed by a virtual preoperative 3-dimensional planning system using thin-cut computed tomography images. Using this patient-specific guide, high-volume shoulder surgeons exposed the glenoid through a deltopectoral approach and drilled the bicortical pathway defined by the guide. The trajectory of the drill path was compared with the virtual preoperative planned position using similar thin-cut computed tomography images to define accuracy.

RESULTS

The drill pathway defined by the patient-matched guide was found to be highly accurate when compared with the preoperative surgical plan. The translational accuracy was 1.2 ± 0.7 mm. The accuracy of inferior tilt was 1.2° ± 1.2°. The accuracy of glenoid version was 2.6° ± 1.7°.

CONCLUSION

The use of patient-specific glenoid baseplate guides is highly accurate in reproducing a virtual 3-dimensional preoperative plan. This technique delivers the accuracy observed using computerized navigation without any additional surgical steps or technical challenges.

Application of the fulcrum axis to estimate the central scapular axis

BACKGROUND

Glenoid resurfacing can be a challenging component of total shoulder arthroplasty when significant glenoid retroversion or deformity is present. The purpose of this study was to determine whether a newly designed glenoid-targeting guide using the parallel relationship between glenoid version and an anatomic fulcrum axis could accurately estimate the central axis of the scapula.

MATERIALS AND METHODS

Three orthopaedic surgeons used a newly designed glenoid-targeting guide to place a guide pin into 6 normal Sawbones scapulae (Pacific Research Laboratories, Vashon Island, WA, USA), 6 retroverted Sawbones scapulae, 8 cadaveric scapular specimens, and 5 cadaveric shoulder specimens. Angles of deviation from the central scapular axis and from perpendicular to the fulcrum axis were measured.

RESULTS

The mean pin deviation angle from the central scapular axis and the mean fulcrum deviation angle for the normal Sawbones scapulae were 1.7° (SD, 1.2°) and 2.1° (SD, 1.5°), respectively. For altered retroverted Sawbones scapulae, the mean deviation angles were 1.8° (SD, 1.2°) and 2.8° (SD, 1.6°), respectively. The combined mean pin deviation angle and mean fulcrum deviation angle for cadaveric shoulder specimens were 2.8° (SD, 3.3°) and 2.3° (SD, 2.3°), respectively. The surgeons' results did not differ significantly whether using Sawbones models, cadaveric scapular specimens, or cadaveric shoulder specimens.

CONCLUSION

A glenoid-targeting guide based on the relationship of the fulcrum axis and glenoid version can be used to accurately estimate the central scapular axis. Such a tool can be accurate and reliable intraoperatively, aiding in glenoid component placement to within 5° of ideal version, irrespective of glenoid deformity.

A glenoid reaming study: how accurate are current reaming techniques?

BACKGROUND

Correct reaming of a degenerative glenoid can be a difficult procedure. We investigated how the quality of the reamed surface is influenced by different reamers, by the surgeon's experience, and by glenoid erosion patterns.

MATERIAL AND METHODS

Three shoulder surgeons performed reaming procedures with different types of reamers (flat, convex, K-wire guided, and nipple guided) on a series of similarly sized uniconcave and biconcave glenoids. The reproducibility of reaming and the effect of different reamers on different-shaped glenoids were measured and evaluated.

RESULTS

The center and direction of reaming were constant for all surgeons in the case of type A glenoids. For type B2 glenoids, the center and direction of reaming differed significantly between surgeons. The congruity of the reamed surface was better after flat reaming than after convex reaming. Whether the reamers were guided by a central K-wire or by a nipple had no significant effect on the reamed surface. The experience of the surgeon had no effect on the congruity of reaming.

CONCLUSIONS

Reaming of a uniconcave glenoid is reproducible, but reaming of a biconcave glenoid seems much more difficult. Erosion and deformity of the glenoid influence the accuracy of reaming the most. Surgical experience plays a less important role. We conclude that there is a need for guidance in reaming of biconcave glenoids.

Three-dimensional preoperative planning software and a novel information transfer technology improve glenoid component positioning

BACKGROUND

We hypothesized that a novel surgical method, in which three-dimensional (3-D) preoperative planning software is generated to create a patient-specific surgical model that is used with a reusable and adjustable tool, could substantially improve the positioning accuracy of the glenoid guide pin used in total shoulder arthroplasty. We tested this method using bone models from patients with shoulder pathology and compared the results with those achieved using surgical methods representing the current standard of care.

METHODS

Three surgeons with a variety of surgical experience placed a guide pin in nine bone models from patients with a variety of glenohumeral arthritis severity using (1) standard instrumentation alone, (2) standard instrumentation and 3-D preoperative surgical planning, and (3) the reusable transfer device and 3-D preoperative surgical planning. A postoperative 3-D computed tomography scan of the bone model was made and registered to the preoperative plan, and the differences between the actual and planned pin locations and trajectories were measured.

RESULTS

Use of the standard instrumentation combined with 3-D preoperative planning software improved guide pin positioning compared with standard instrumentation and preoperative planning using 2-D imaging. The accuracy of pin positioning increased by 4.5° ± 1.0° in version (p &lt; 0.001), 3.3° ± 1.3° in inclination (p = 0.013), and 0.4 ± 0.2 mm in location (p = 0.042). Use of the adjustable and reusable device and the 3-D software improved pin positioning by a further 3.7° ± 0.9° in version, 8.1° ± 1.2° in inclination, and 1.2 ± 0.2 mm in location (p &lt; 0.001 for all) compared with standard instrumentation and the 3-D software; the improvement compared with use of standard instrumentation with 2-D imaging was 8.2° ± 0.9° in version, 11.4° ± 1.2° in inclination, and 1.7 ± 0.2 mm in location (p &lt; 0.001 for all).

CONCLUSIONS

Use of 3-D preoperative planning and use of the patient-specific bone model and transfer device both improved the positioning accuracy of the pin used to guide placement of the glenoid component in total shoulder arthroplasty.

CLINICAL RELEVANCE

Proper positioning of the glenoid component would be expected to improve the function and durability of the joint replacement.

Use of a custom alignment guide to improve glenoid component position in total shoulder arthroplasty

PURPOSE

Total and reverse total shoulder arthroplasty (TSA) are used to treat patients with glenohumeral joint osteoarthritis. The revision rate remains high compared with hip and knee arthroplasty. Glenoid component loosening is an important complication and may be caused by poor positioning of the component. We aimed to evaluate the safety and accuracy of a custom glenoid jig created using preoperative computed tomography (CT) imaging with 3D modelling for glenoid component implantation.

METHODS

Preoperative CT scans of each shoulder (N = 7) were obtained. Implants were virtually aligned and custom templates were created for intraoperative use. A two-part custom jig was manufactured for alignment of the central peg and the peripheral screws. Three-dimensional orientation of the component and screws was evaluated in postoperative CT scans. The difference between the preoperative plan and the result was then calculated.

RESULTS

No technical difficulties or complications occurred. The mean absolute difference between the planned alignment and the postoperative placement of the glenoid component in the three-dimensional space was 3.4 mm (SD = 1 mm). The total average difference for all screws (N = 10) was 6.3° (SD = 3.2°).

CONCLUSION

A CT-based custom glenoid component alignment can reliably guide the placement of the glenoid component during conventional and reverse TSA. This custom jig may be useful for optimizing glenoid component position in the setting of reverse and TSA.

Development and validation of a new method of 3-dimensional assessment of glenoid and humeral component position after total shoulder arthroplasty

HYPOTHESIS

This study evaluates the intrarater and inter-rater reliability of 3-dimensional (3D) computed tomography (CT) measurements of component position and alignment after total shoulder arthroplasty (TSA).

MATERIALS AND METHODS

Two patients and one whole-body cadaver with anatomic TSA implants underwent CT scans of the shoulder with a 0.6-mm slice thickness in two different arm positions (supine arm down or lateral decubitus arm up) on the same day. Test-retest reliability of component measurements within and between 5 observers was determined, as were any differences in measurements based on arm position. Precision and 95% confidence intervals were determined for the following measurements: glenoid component position (anterior-posterior, superior-inferior, and medial-lateral), glenoid component orientation (version, inclination, and roll), and humeral-glenoid alignment (HGA). HGA was defined in the anterior-posterior and superior-inferior dimensions.

RESULTS

The range of precision for measurement of the position of the glenoid implant across observers was between 0.2 and 0.5 mm, and for orientation, it was between 1.2° and 1.5°. The range of precision for measurement of HGA across observers was between 0.7 and 1.2 mm. There was no significant difference in the precision of measurements between the two imaged arm positions.

DISCUSSION AND CONCLUSION

The described method of 3-dimensional CT imaging can provide very precise and reproducible assessment of component position after TSA. Ultimately, correlation of these measurements with clinical outcome, anatomic factors, prosthetic design, and surgical factors will allow for better understanding of the causes of implant failure.

Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty

Glenoid bone deficiency and eccentric posterior wear are difficult problems faced by shoulder arthroplasty surgeons. Numerous options and techniques exist for addressing these issues. Hemiarthroplasty with concentric glenoid reaming may be a viable alternative in motivated patients in whom glenoid component failure is a concern. Total shoulder arthroplasty has been shown to provide durable pain relief and excellent function in patients, and numerous methods and techniques can assist in addressing bone loss and eccentric wear. However, the ideal amount of version correction in cases of severe retroversion has not yet been established. Asymmetric reaming is a commonly used technique to address glenoid version, but correction of severe retroversion may compromise bone stock and component fixation. Bone grafting is a technically demanding alternative for uncontained defects and has mixed clinical results. Specialized glenoid implants with posterior augmentation have been created to assist the surgeon in correcting glenoid version without compromising bone stock, but clinical data on these implants are still pending. Custom implants or instruments based on each patient's unique glenoid anatomy may hold promise. In elderly, sedentary patients in whom bone stock and soft-tissue balance are concerns, reverse total shoulder arthroplasty may be less technically demanding while still providing satisfactory pain relief and functional improvements.

Percutaneous navigated screw fixation of glenoid fractures

BACKGROUND

Open or percutaneous arthroscopic-based procedures are reported to fix unstable or displaced intra-articular glenoid fractures. Approach related morbidity has to be considered for open procedures, and arthroscopic-based procedures are demanding. Therefore an alternative percutaneous navigated approach is described.

TECHNICAL PROCEDURE

In an experimental setting an operative workflow was simulated to evaluate the best position of the patient on the operation table, the operating room set up and the fixation technique for the dynamic reference base of the navigation system. Based on two clinical cases, screw fixation of glenoid fractures via a posterior percutaneous approach is described, using a 2D-fluoroscopic based navigation system. Compared to the common approaches, the advantages and disadvantages of this procedure are discussed.

CONCLUSION

The described technique of percutaneous navigated screw fixation of glenoid fractures is an alternative minimal invasive procedure. A reduction of approach related morbidity and more rapid return to function could be expected. The intraoperative results and postoperative functional outcome of both cases are promising.

Comparison of patient-specific instruments with standard surgical instruments in determining glenoid component position: a randomized prospective clinical trial

BACKGROUND

Glenoid component malposition for anatomic shoulder replacement may result in complications. The purpose of this study was to define the efficacy of a new surgical method to place the glenoid component.

METHODS

Thirty-one patients were randomized for glenoid component placement with use of either novel three-dimensional computed tomographic scan planning software combined with patient-specific instrumentation (the glenoid positioning system group), or conventional computed tomographic scan, preoperative planning, and surgical technique, utilizing instruments provided by the implant manufacturer (the standard surgical group). The desired position of the component was determined preoperatively. Postoperatively, a computed tomographic scan was used to define and compare the actual implant location with the preoperative plan.

RESULTS

In the standard surgical group, the average preoperative glenoid retroversion was -11.3° (range, -39° to 17°). In the glenoid positioning system group, the average glenoid retroversion was -14.8° (range, -27° to 7°). When the standard surgical group was compared with the glenoid positioning system group, patient-specific instrumentation technology significantly decreased (p < 0.05) the average deviation of implant position for inclination and medial-lateral offset. Overall, the average deviation in version was 6.9° in the standard surgical group and 4.3° in the glenoid positioning system group. The average deviation in inclination was 11.6° in the standard surgical group and 2.9° in the glenoid positioning system group. The greatest benefit of patient-specific instrumentation was observed in patients with retroversion in excess of 16°; the average deviation was 10° in the standard surgical group and 1.2° in the glenoid positioning system group (p < 0.001). Preoperative planning and patient-specific instrumentation use resulted in a significant improvement in the selection and use of the optimal type of implant and a significant reduction in the frequency of malpositioned glenoid implants.

CONCLUSIONS

Novel three-dimensional preoperative planning, coupled with patient and implant-specific instrumentation, allows the surgeon to better define the preoperative pathology, select the optimal implant design and location, and then accurately execute the plan at the time of surgery.

Total shoulder arthroplasty does not correct the orientation of the eroded glenoid

BACKGROUND AND PURPOSE

Alignment of the glenoid component with the scapula during total shoulder arthroplasty (TSA) is challenging due to glenoid erosion and lack of both bone stock and guiding landmarks. We determined the extent to which the implant position is governed by the preoperative erosion of the glenoid. Also, we investigated whether excessive erosion of the glenoid is associated with perforation of the glenoid vault.

METHODS

We used preoperative and postoperative CT scans of 29 TSAs to assess version, inclination, rotation, and offset of the glenoid relative to the scapula plane. The position of the implant keel within the glenoid vault was classified into three types: centrally positioned, component touching vault cortex, and perforation of the cortex.

RESULTS

Preoperative glenoid erosion was statistically significantly linked to the postoperative placement of the implant regarding all position parameters. Retroversion of the eroded glenoid was on average 10° (SD10) and retroversion of the implant after surgery was 7° (SD11). The implant keel was centered within the vault in 7 of 29 patients and the glenoid vault was perforated in 5 patients. Anterior cortex perforation was most frequent and was associated with severe preoperative posterior erosion, causing implant retroversion.

INTERPRETATION

The position of the glenoid component reflected the preoperative erosion and "correction" was not a characteristic of the reconstructive surgery. Severe erosion appears to be linked to vault perforation. If malalignment and perforation are associated with loosening, our results suggest reorientation of the implant relative to the eroded surface.

A novel method of image-based navigation in fracture surgery

The treatment of three- and four-part fractures of the humeral head is still controversially discussed. Some advocate primary arthroplasty while the results of primary fixation seem to be superior if no necrosis of the humeral head develops. Today navigation is used in orthopaedic surgery mainly for interventions on the spine, the pelvis and arthroplasty. In trauma surgery it is still rarely used and some technical problems need to be overcome. We report on a case of a three part fracture of the humeral head with mini-open reduction and fixation with image-based guided headless compression screws. For the fixation each screw was placed on the first trial, total radiation time was 60 s. At 12-month follow-up assessment radiographs showed a consolidated fracture, no loosening of the screws and a good glenohumeral articulation. The patient had free function of the shoulder and no pain, the constant score was 98 and the dash score 0. There is no evidence of a necrosis of the humeral head. The literature focuses on shoulder arthroplasty. There are no reports on the use of image-based guidance in shoulder traumatology so far. In conclusion, the described technique allows an accurate fixation of the humeral head fracture as the guidance system (Surgix) ensures the "first try first hit" screw positioning. The new system was integrated in the workflow and supports the surgeon as an aiming device. The role of navigation system in enhancing minimally invasive surgery of the shoulder should be further explored.

Effect of glenoid deformity on glenoid component placement in primary shoulder arthroplasty

BACKGROUND

Malposition of the glenoid component can result in premature component loosening or instability. This study was designed to test the ability of an experienced shoulder surgeon to position the glenoid component using standard preoperative planning and surgical bone preparation.

MATERIALS AND METHODS

Thirteen patients having primary total shoulder arthroplasty were evaluated using 3-dimensional surgical simulator. Ideal version was considered to have version as close to perpendicular to the plane of the scapula, with complete contact of the back side of the component on glenoid bone and maintenance of the center peg of the component within bone.

RESULTS

The average retroversion angle was 13° (mean, standard deviation [SD] 12°), with a range of 1-42°. In 7 of these 13 cases, preoperative glenoid retroversion was greater or equal to 10°. In 3 cases, the component was malpositioned with greater than 10° of ideal version. In cases with less than 10° of preoperative retroversion, the glenoid component was placed within 10° of ideal version in all cases.

CONCLUSION

Traditional methods to correct moderate to severe glenoid deformity and place the glenoid component within 5° of the ideal position are not consistent. Optimal glenoid component placement can be achieved when there is minimal bone deformity. Retroversion greater or equal to 20° makes it difficult to place a pegged glenoid component perpendicular to the plane of the scapula by asymmetric reaming without center peg perforation.

Accuracy of placement of the glenoid component in reversed shoulder arthroplasty with and without navigation

HYPOTHESIS

Navigation can improve accuracy of placement of the glenoid component in reversed shoulder arthroplasty.

MATERIAL AND METHODS

A glenoid component of a reversed shoulder prosthesis was implanted in 14 paired scapulohumeral cadaver specimens. Seven procedures with standard instrumentation were compared with 7 procedures using navigation. The intraoperative goal was to place the component centrally in the glenoid in the axial plane and 10° inferiorly tilted in the frontal plane. Glenoid component version and tilt and screw placement were studied using CT scan and macroscopic dissection.

RESULTS

The mean version of the glenoid component in the standard instrumentation group was 8.7° of anteversion, compared with 3.1° of anteversion in the navigated group. The mean tilt of the glenoid component was 0.9° in the standard group and 5.4° of inferior tilt in the navigated group. Using navigation, the range of error for version was 8° (SD 3.3°) compared to 12° (SD 4.1°) in controls. For tilt, the range of error was 8° (SD 3.6°) in navigated specimens and 16° (SD 6.0°) for controls. In the control group, there were no perforations of the central peg, but 1 inferior screw and 4 superior screws were malpositioned. In the navigation group, no central peg perforated, all inferior screws were correctly positioned, and 2 superior screws were malpositioned.

CONCLUSION

Computer navigation was more accurate and more precise than standard instrumentation in its placement of the glenoid component in reversed shoulder arthroplasty.

Glenoid version: how to measure it? Validity of different methods in two-dimensional computed tomography scans

HYPOTHESIS

Recognition of the glenoid version is important for evaluation of different pathologies such as degenerative wear, shoulder instability, or congenital deformity. Surgical strategies can change significantly in the presence of major retroversion. There is no consensus on the method to use to evaluate version. This study compared different measurement strategies in 116 patients with shoulder computed tomography (CT) scans. We hypotheses that the methods will give different value for evolution.

METHODS

Shoulder axial CT images were reviewed, and the image inferior to the base of the coracoid was selected. The glenoid version was measured according to the Friedman method and the scapula body method. Three orthopedic surgeons independently examined the images 2 times, and intraobserver and interobserver reliability was calculated using intraclass correlation (ICC).

RESULTS

Group 1 (n = 53): The average glenoid version was significantly different between the 2 measurement techniques for all 3 observers, with an average of -7.29° for the scapula body method and -10.43° for Friedman method. For group 2 (B2 glenoid group, n = 63): The most reliable method for measurement of B2 glenoid (glenoid with posterior erosion) version was the association of the Friedman line for the scapula axis and the intermediate glenoid line, with excellent intraobserver reliability (ICC > 0.957) and interobserver reliability (ICC = 0.954).

DISCUSSION

The glenoid version measurement is reliable on a 2D CT Scan. According to correlation found in our paper and those of the literature it seems that there is no advantage on 3D CT Scan to assess version in terms of reliability of measures.

CONCLUSION

Combining the Friedman method to determine the scapula axis with an intermediate glenoid line in B2 glenoid yield the most reliable measurements.