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

Computer modeling and validation testing for glenoid component rotation and optimal glenoid screw angles for reverse shoulder arthroplasty in an Asian population

PURPOSE

Good initial fixation of glenoid component for reverse total shoulder arthroplasty (RTSA) relies on component placement and screw purchase in the scapula bone. This is especially difficult in an Asian population with small glenoid geometry. Optimal glenoid component roll angle and screw angulation to achieve the longest screws for best fixation has not been defined in the current literature.

METHODS

Computer 3D modelling of 133 scapulas with RTSA performed were analyzed to determine patient specific optimal glenoid roll angle (GRA) for the longest bi-cortical screws attainable. The cranial-caudal angle (CCA), anterior-posterior angle (APA) and lengths for the superior and inferior screws were measured. Validation testing using calculated average (CA) angles and rounded average (RA) angles to the nearest 5 degree were recomputed for each case to determine the bi-cortical screw lengths achievable. The CA and RA screw lengths were compared against patient specific modelling using paired-sample t-tests.

RESULTS

Average GRA was - 1.6°, almost perpendicular to the long axis of the glenoid and achieves an average bi-cortical screw length of 51.3 mm and 45.5 mm for the superior and inferior screws respectively. The CCA and APA were 9.1° cranial and 6.5° posterior for the superior screw and screw angulation of 11.2° caudal and 0.7° anterior for the inferior screw. Validation testing shows statistically shorter screw lengths in the CA and RA models compared to patient specific modelling (p < 0.01).

CONCLUSION

Validation testing with average angles for GRA, CCA and APA demonstrates strong patient heterogeneity and anatomical variation. Despite this, screw lengths attainable in the RA group were > 38 mm with good safety profile. Surgeons may consider the additional use of navigation-assisted, or 3D printed patient specific instrumentation to optimize baseplate and screw configuration for RTSA.

Geometric accuracy of low-dose CT scans for use in shoulder musculoskeletal research applications

Computed tomography (CT) imaging is frequently employed in a variety of musculoskeletal research applications. Although research studies often use imaging protocols developed for clinical applications, lower dose protocols are likely possible when the goal is to reconstruct 3D bone models. Our purpose was to describe the dose-accuracy trade-off between incrementally lower-dose CT scans and the geometric reconstruction accuracy of the humerus, scapula, and clavicle. Six shoulder specimens were acquired and scanned using 5 helical CT protocols: 1) 120 kVp, 450 mA (full-dose); 2) 120 kVp, 120 mA; 3) 120 kVp, 100 mA; 4) 100 kVp, 100 mA; 5) 80 kVp, 80 mA. Scans were segmented and reconstructed into 3D surface meshes. Geometric error was assessed by comparing the surfaces of the low-dose meshes to the full-dose (gold standard) mesh and was described using mean absolute error, bias, precision, and worst-case error. All low-dose protocols resulted in a >70 % reduction in the effective dose. Lower dose scans resulted in higher geometric errors; however, error magnitudes were generally <0.5 mm. These data suggest that the effective dose associated with CT imaging can be substantially reduced without a significant loss of geometric reconstruction accuracy.

Augmented reality-assisted intraoperative navigation increases precision of glenoid inclination in reverse shoulder arthroplasty

BACKGROUND

Reverse total shoulder arthroplasty (RTSA) is the standard of care for patients with glenohumeral osteoarthritis and rotator cuff deficiency. Preoperative RTSA planning based on medical images and patient-specific instruments has been established over the last decade. This study aims to determine the effects of using augmented reality-assisted intraoperative navigation (ARIN) for baseplate positioning in RTSA compared to preoperative planning. It is hypothesized that ARIN will decrease deviation between preoperative planning and postoperative baseplate positioning. Moreover, ARIN will decrease deviation between the (senior) more (>50 RTSAs/yr) and less experienced (junior) surgeon (5-10 RTSAs/yr).

METHODS

Preoperative CT scans of 16 fresh-frozen cadaveric shoulders were obtained. Baseplate placements were planned using a validated software. The data were then converted and uploaded to the augmented reality system (NextAR; Medacta International). Each of the 8 RTSAs were implanted by a senior and a junior surgeon, with 4 RTSAs using ARIN and 4 without. A postoperative CT scan was performed in all cases. The scanned scapulae were segmented, and the preoperative scan was laid over the postoperative scapula by the nearest iterative point cloud analysis. The deviation from the planned entry point and trajectory was calculated regarding the inclination, retroversion, medialization (reaming depth) and lateralization, anteroposterior position, and superoinferior position of the baseplate. Data are reported as mean ± standard deviation (SD) or mean and 95% confidence interval (CI). P values < .05 were considered statistically significant.

RESULTS

The use of ARIN yielded a reduction in the absolute difference between planned and obtained inclination from 9° (SD: 4°) to 3° (SD: 2°) (P = .011). Mean difference in planned-obtained inclination between surgeons was 3° in free-hand surgeries (95% CI: -4 to 10; P = .578), whereas this difference reduced to 1° (95% CI: -6 to 7, P = .996) using ARIN. Retroversion, medialization (reaming depth) and lateralization, anteroposterior position, and superoinferior position of the baseplate were not affected by using ARIN. Surgical duration was increased using ARIN for both the senior (10 minutes) and junior (18 minutes) surgeon.

CONCLUSIONS

The implementation of ARIN leads to greater accuracy of glenoid component placement, specifically with respect to inclination. Further studies have to verify if this increased accuracy is clinically important. Furthermore, ARIN allows less experienced surgeons to achieve a similar level of accuracy in component placement comparable to more experienced surgeons. However, the potential advantages of ARIN in RTSA are counterbalanced by an increase in operative time.

Experimental guide wire placement for total shoulder arthroplasty in glenoid models: higher precision for patient-specific aiming guides compared to standard technique without learning curve

BACKGROUND

Patient-specific aiming devices (PSAD) may improve precision and accuracy of glenoid component positioning in total shoulder arthroplasty, especially in degenerative glenoids. The aim of this study was to compare precision and accuracy of guide wire positioning into different glenoid models using a PSAD versus a standard guide.

METHODS

Three experienced shoulder surgeons inserted 2.5 mm K-wires into polyurethane cast glenoid models of type Walch A, B and C (in total 180 models). Every surgeon placed guide wires into 10 glenoids of each type with a standard guide by DePuy Synthes in group (I) and with a PSAD in group (II). Deviation from planned version, inclination and entry point was measured, as well as investigation of a possible learning curve.

RESULTS

Maximal deviation in version in B- and C-glenoids in (I) was 20.3° versus 4.8° in (II) (p < 0.001) and in inclination was 20.0° in (I) versus 3.7° in (II) (p < 0.001). For B-glenoid, more than 50% of the guide wires in (I) had a version deviation between 11.9° and 20.3° compared to ≤ 2.2° in (II) (p < 0.001). 50% of B- and C-glenoids in (I) showed a median inclination deviation of 4.6° (0.0°-20.0°; p < 0.001) versus 1.8° (0.0°-4.0°; p < 0.001) in (II). Deviation from the entry point was always less than 5.0 mm when using PSAD compared to a maximum of 7.7 mm with the standard guide and was most pronounced in type C (p < 0.001).

CONCLUSION

PSAD enhance precision and accuracy of guide wire placement particularly for deformed B and C type glenoids compared to a standard guide in vitro. There was no learning curve for PSAD. However, findings of this study cannot be directly translated to the clinical reality and require further corroboration.

Comparison of 3D computer-assisted planning with and without patient-specific instrumentation for severe bone defects in reverse total shoulder arthroplasty

BACKGROUND

Preoperative planning is an integral aspect of managing complex deformity in reverse shoulder arthroplasty (RSA). The purpose of this study was to compare the success of patient-specific instrumentation (PSI) and 3D computer-assisted planning with standard instrumentation (non-PSI) in achieving planned corrections of the glenoid among patients undergoing RSA with severe bony deformity requiring glenoid bone grafts.

METHODS

A retrospective case-control study was performed, including all patients that underwent RSA with combined bone grafting procedures (BIO-RSA or structural bone grafting) for severe glenoid deformity by a single study between June 2016 and July 2023. Patients were required to have preoperative and postoperative CT scans as well as preoperative 3D planning performed for inclusion. Patients were divided into two groups based on the use of 3D computer-assisted planning with or without PSI (PSI vs. non-PSI). The corrected inclination and version were measured by two separate reviewers on preoperative and postoperative 2D CT scans and compared to their corresponding preoperative planning goals utilizing bivariate analyses.

RESULTS

We identified 45 patients that met our inclusion criteria (22 PSI and 23 non-PSI). Preoperative inclination (mean ± SD) (PSI 10.12° ± 15.86°, non-PSI 9.43° ± 10.64°; P = .864) and version (PSI -18.78° ± 18.3°, non-PSI -17.82° ± 11.49°; P = .835) measurements were similar between groups. No significant differences in the mean deviation (error) between the postoperative and planned inclination (PSI 5.49° ± 3.72; non-PSI 6.91° ± 5.05; P = .437) and version (PSI 8.37° ± 5.7; non-PSI 5.37° ± 4.43; P = .054) were found between groups. No difference in the rate of outliers (>10° error) was noted in inclination (P = .135) or version (P = .445) between groups. Greater planned version correction was correlated with greater error when PSI was utilized (PSI r = 0.519, P = .013; non-PSI r = 0.362, P = .089).

CONCLUSION

Both PSI and 3D computer-assisted planning without PSI (non-PSI) appear to be useful techniques to achieve version and inclination correction among patients undergoing RSA with severe glenoid deformity required glenoid bone grafting with no clear superiority of one method over the other. Surgeons should be aware that when utilizing PSI, slightly greater error in achieving version goals may occur as version correction is increased.

Artificial intelligence- and computer-assisted navigation for shoulder surgery

Background: Over the last few decades, shoulder surgery has undergone rapid advancements, with ongoing exploration and the development of innovative technological approaches. In the coming years, technologies such as robot-assisted surgeries, virtual reality, artificial intelligence, patient-specific instrumentation, and different innovative perioperative and preoperative planning tools will continue to fuel a revolution in the medical field, thereby pushing it toward new frontiers and unprecedented advancements. In relation to this, shoulder surgery will experience significant breakthroughs. Main body: Recent advancements and technological innovations in the field were comprehensively analyzed. We aimed to provide a detailed overview of the current landscape, emphasizing the roles of technologies. Computer-assisted surgery utilizing robotic- or image-guided technologies is widely adopted in various orthopedic specialties. The most advanced components of computer-assisted surgery are navigation and robotic systems, with functions and applications that are continuously expanding. Surgical navigation requires a visual system that presents real-time positional data on surgical instruments or implants in relation to the target bone, displayed on a computer monitor. There are three primary categories of surgical planning that utilize navigation systems. The initial category involves volumetric images, such as ultrasound echogram, computed tomography, and magnetic resonance images. The second type is based on intraoperative fluoroscopic images, and the third type incorporates kinetic information about joints or morphometric data about the target bones acquired intraoperatively. Conclusion: The rapid integration of artificial intelligence and deep learning into the medical domain has a significant and transformative influence. Numerous studies utilizing deep learning-based diagnostics in orthopedics have remarkable achievements and performance.

Technological innovations in shoulder replacement: current concepts and the future of robotics in total shoulder arthroplasty

BACKGROUND

Total shoulder arthroplasty (TSA) has been rapidly evolving over the last several decades, with innovative technological strategies being investigated and developed in order to achieve optimal component precision and joint alignment and stability, preserve implant longevity, and improve patient outcomes. Future advancements such as robotic-assisted surgeries, augmented reality, artificial intelligence, patient-specific instrumentation (PSI) and other peri- and preoperative planning tools will continue to revolutionize TSA. Robotic-assisted arthroplasty is a novel and increasingly popular alternative to the conventional arthroplasty procedure in the hip and knee but has not yet been investigated in the shoulder. Therefore, the purpose of this study was to conduct a narrative review of the literature on the evolution and projected trends of technological advances and robotic assistance in total shoulder arthroplasty.

METHODS

A narrative synthesis method was employed for this review, rather than a meta-analysis or systematic review of the literature. This decision was based on 2 primary factors: (1) the lack of eligible, peer-reviewed studies with high-quality level of evidence available for review on robotic-assisted shoulder arthroplasty, and (2) a narrative review allows for a broader scope of content analysis, including a comprehensive review of all technological advances-including robotics-within the field of TSA. A general literature search was performed using PubMed, Embase, and Cochrane Library databases. These databases were queried by 2 independent reviewers from database inception through November 11, 2022, for all articles investigating the role of robotics and technology assistance in total shoulder arthroplasty. Inclusion criteria included studies describing "shoulder arthroplasty" and "robotics."

RESULTS

After exclusion criteria were applied, 4 studies on robotic-assisted TSA were described in the review. Given the novelty of this technology and limited data on robotics in TSA, these studies consisted of a literature review, nonvalidated experimental biomechanical studies in sawbones models, and preclinical proof-of-concept cadaveric studies using prototype robotic technology primarily in conjunction with PSI. The remaining studies described the technological advancements in TSA, including PSI, computer-assisted navigation, artificial intelligence, machine learning, and virtual, augmented, and mixed reality. Although not yet commercially available, robotic-assisted TSA confers the theoretical advantages of precise humeral head cuts for restoration of proximal humerus anatomy, more accurate glenoid preparation, and improved soft-tissue assessment in limited early studies.

CONCLUSION

The evidence for the use of robotics in total hip arthroplasty and total knee arthroplasty demonstrates improved component accuracy, more precise radiographic measurements, and improved early/mid-term patient-reported and functional outcomes. Although no such data currently exist for shoulder arthroplasty given that the technology has not yet been commercialized, the lessons learned from robotic hip and knee surgery in conjunction with its rapid adoption suggests robotic-assisted TSA is on the horizon of innovation. By achieving a better understanding of the past, present, and future innovations in TSA through this narrative review, orthopedic surgeons can be better prepared for future applications.

Patients who have intraoperative deviations in their preoperative plan have inferior clinical and radiographic outcomes after anatomic total shoulder arthroplasty

BACKGROUND

Three-dimensional computed tomography preoperative planning has become adopted among shoulder arthroplasty surgeons. Prior studies have not examined outcomes in patients in whom the surgeon implanted prostheses that deviated from the preoperative plan compared with patients in whom the surgeon followed the preoperative plan. The hypothesis of this study was that clinical and radiographic outcomes would be equivalent between patients undergoing anatomic total shoulder arthroplasty that had a deviation in the components predicted in the preoperative plan and patients who did not have a change in the components predicted in the preoperative plan.

METHODS

A retrospective review of patients who had preoperative planning for anatomic total shoulder arthroplasty from March 2017 through October 2022 was performed. Patients were stratified into 2 groups: patients in whom the surgeon used components that deviated from those anticipated by the preoperative plan (changed group), and patients in whom the surgeon used all of the components anticipated by the preoperative plan (planned group). Patient-determined outcomes including the Western Ontario Osteoarthritis Index, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation, Simple Shoulder Test (SST), and Shoulder Activity Level were recorded preoperatively, at 1 year, and at 2 years. Preoperative and 1-year postoperative range of motion was recorded. Radiographic parameters to assess restoration of proximal humeral anatomy included humeral head height, humeral neck angle, humeral centering on the glenoid, and postoperative restoration of the anatomic center of rotation.

RESULTS

A total of 159 patients had intraoperative changes to their preoperative plan, and 136 patients underwent arthroplasty without changes to their preoperative plan. The planned group had higher scores than the group that had a deviation in the preoperative plan for every patient-determined outcome metric at every postoperative time point with statistically significant improvements found in the SST and Single Assessment Numeric Evaluation at 1-year and the SST and American Shoulder and Elbow Surgeons score at 2-year follow-up. No differences were found in range of motion metrics between the groups. Patients who did not have a deviation in their preoperative plan had more optimal restoration of their postoperative radiographic center of rotation than patients who did have a deviation in their preoperative plan.

CONCLUSIONS

Patients who have intraoperative changes to their preoperative plan have (1) inferior postoperative patient-determined outcome scores at 1 and 2 years after surgery and (2) a larger deviation in the postoperative radiographic restoration of the humeral center of rotation than patients who did not have intraoperative changes from the initial plan.

Image-derived instrumentation vs. conventional instrumentation with 3D planning for glenoid component placement in reverse total shoulder replacements: a randomized controlled trial

Hypothesis

Glenoid baseplate positioning for reverse total shoulder arthroplasty (rTSA) is important for stability and longevity, with techniques such as image-derived instrumentation (IDI) developed for improving implant placement accuracy. We performed a single-blinded randomized controlled trial comparing glenoid baseplate insertion accuracy with 3D preoperative planning and IDI jigs vs. 3D preoperative planning and conventional instrumentation.

Methods

All patients had a preoperative 3D computed tomography to create an IDI; then underwent rTSA according to their randomized method. Repeat computed tomography scans performed at six weeks postoperatively were compared to the preoperative plan to assess for accuracy of implantation. Patient-reported outcome measures and plain radiographs were collected with 2-year follow-up.

Results

Forty-seven rTSA patients were included (IDI n = 24, conventional instrumentation n = 23). The IDI group was more likely to have a guidewire placement within 2mm of the preoperative plan in the superior/inferior plane (P = .01); and exhibited a smaller degree of error when the native glenoid retroversion was >10° (P = .047). There was no difference in patient-reported outcome measures or other radiographic parameters between the two groups.

Conclusion

IDI is an accurate method for glenoid guidewire and component placement in rTSA, particularly in the superior/inferior plane and in glenoids with native retroversion >10°, when compared to conventional instrumentation.

Surgeon-designed patient-specific instrumentation improves glenoid component screw placement for reverse total shoulder arthroplasty in a population with small glenoid dimensions

PURPOSE

Glenoid component loosening is a potential complication of reverse total shoulder arthroplasty (rTSA), occurring in part due to lack of adequate screw purchase in quality scapular bone stock. This study was to determine the efficacy of a surgeon-designed, 3D-printed patient-specific instrumentation (PSI) compared to conventional instrumentation (CI) in achieving longer superior and inferior screw lengths for glenoid component fixation.

METHODS

A multi-centre retrospective analysis of patients who underwent rTSA between 2015 and 2020. Lengths of the superior and inferior locking screws inserted for fixation of the glenoid baseplate component were recorded and compared according to whether patients received PSI or CI. Secondary outcomes included operative duration and incidence of complications requiring revision surgery.

RESULTS

Seventy-three patients (31 PSI vs. 42 CI) were analysed. Average glenoid diameter was 24.5 mm (SD: 3.1) and 81% of patients had smaller glenoid dimensions compared to the baseplate itself. PSI produced significantly longer superior (44.7 vs. 30.7 mm; P < 0.001) and inferior (43.0 vs. 31 mm; P < 0.001) mean screw lengths, as compared to CI. A greater proportion of maximal screw lengths for the given rTSA construct (48 mm) were observed in the PSI group (71.9% vs. 11.9% superior, 59.4% vs. 11.9% inferior). Operative duration was not statistically significantly different between the PSI and CI groups (150 min vs. 169 min, respectively; P = 0.229). No patients had radiographic loosening of the glenoid component with an average of 2-year follow-up.

CONCLUSION

PSI facilitates longer superior and inferior screw placement in the fixation of the glenoid component for rTSA. With sufficient training, PSI can be designed and implemented by surgeons themselves.

Early clinical outcomes following navigation-assisted baseplate fixation in reverse total shoulder arthroplasty: a matched cohort study

BACKGROUND

Accurate placement of the glenoid baseplate is an important technical goal of reverse total shoulder arthroplasty (RSA). The use of computer navigated instrumentation has been shown to improve the accuracy and precision of intraoperative execution of preoperative planning. The purpose of this study was to compare early clinical outcomes of patients undergoing navigated RSA vs. a non-navigated matched cohort.

METHODS

A retrospective review of a prospectively collected shoulder arthroplasty database was used to identify 113 patients from a single institution who underwent navigated primary RSA with a minimum 2-year follow-up. A matched cohort of 113 non-navigated RSAs was created based on sex, age, follow-up, and preoperative diagnosis. Preoperative and postoperative range of motion, functional outcome scores, and complications were reported.

RESULTS

A total of 226 shoulders with a mean age of 71 years were evaluated after navigated (113) or non-navigated (113) RSAs. The mean follow-up was 32.8 months (range: 21-54 months). At the final postoperative follow-up, the navigated group had better active forward elevation (135° vs. 129°, P = .023), active external rotation (39° vs. 32°, P = .003), and Constant scores (71.1 vs. 65.5, P = .003). However, when comparing improvements from the preoperative state, there was no statistically significant difference in range of motion or functional outcome scores between the groups. Complications occurred in 1.8% (2) of patients undergoing navigated RSA compared with 5.3% (6) in the non-navigated group (P = .28). Scapular notching (3.1% vs. 8.0%, P = .21) and revision surgery (0.9% vs. 3.5%, P = .37) were more common in non-navigated shoulders.

CONCLUSION

At early follow-up, navigated and non-navigated RSAs yielded similar rates of improvement in range of motion and functional outcome scores. Notching and reoperation was more common in non-navigated shoulders, but did not reach statistical significance. Longer follow-up and larger cohort size are needed to determine if intraoperative navigation lengthens the durability of RSA results and reduces the incidence of postoperative complications.

Does fluoroscopy improve baseplate position compared to conventional technique in reverse shoulder arthroplasty? A preliminary study

Background

Accurate placement of glenoid component in reverse shoulder arthroplasty remains a challenge for surgeons of all levels of expertise; however, no studies have evaluated the utility of fluoroscopy as a surgical assistance method.

Methods

Prospective comparative study of 33 patients undergoing primary reverse shoulder arthroplasty during a 12-month period. Fifteen patients had a baseplate placed using the conventional "free hand" technique (control group), and 18 patients using intraoperative fluoroscopy assistance group, in a case-control design. Postoperative glenoid position was evaluated on postoperative Computed Tomography (CT) scan.

Results

The mean deviation of version and inclination for fluoroscopy assistance vs. control group was 1.75° (0.675-3.125) vs. 4.2° (1.975-10.45) (p = .015), and 3.85° (0-7.225) vs. 10.35° (4.35-18.75) (p = .009). The distance from the central peg midpoint to the inferior glenoid rim (fluoroscopy assistance 14.61 mm/control 4.75 mm, p = .581) and the surgical time (fluoroscopy assistance 1.93 ± 0.57/control 2.18 ± 0.44 h, p = .400) showed no differences, with an average radiation dose of 0.45 mGy and fluoroscopy time of 14 s.

Conclusions

Accurate axial and coronal scapular plane positioning of glenoid component is improved with intraoperative fluoroscopy at the cost of a greater radiation dose and without differences in surgical time. Comparative studies are needed to determine whether their use in relation to more expensive surgical assistance systems result in similar effectiveness.L evel of evidence : Level III, therapeutic study.

Application of 3D printed patient-specific instruments in the treatment of large tibial bone defects by the Ilizarov technique of distraction osteogenesis

Background

The Ilizarov technique of distraction osteogenesis is an effective treatment for tibia defect. However, repeated attempts to reduce due to the complexity of the bone defect during the operation will increase the operation time and iatrogenic injury, and excessive radiation exposure. Three-dimensional (3D)-printed patient-specific instrument (PSI) for preoperative 3D planning and intraoperative navigation have the advantages of accuracy and visualization. The purpose of this study is to investigate whether 3D-printed PSI is helpful to correct tibial bone defects accurately and effectively.

Method

From May 2019 to September 2022, 19 patients with tibial bone defects were treated, including 9 males and 10 females, aged 37 to 64 years. There were 4 cases in proximal tibia, 9 in midshaft tibia and 6 in distal tibia. All were treated with Ilizarov technique of distraction osteogenesis. 3D-printed PSI was used in 9 cases, while traditional surgery was used in 10 cases. All patients underwent computed tomography before surgery. Computer software was used to analyze the measurement results, design and print PSI. During the operation, PSI was used to assist in reduction of tibia. Operation times were recorded in all cases, the number of fluoroscopy during the operation, and the varus/valgus, anteversion/reversion angle after the operation were measured. All measurement data were expressed by means ± SD, and Student's t test was used to examine differences between groups. The chi square test or Fisher's precise test was used to compare the counting data of the two groups.

Result

All PSI matched well with the corresponding tibia bone defect, and were consistent with the preoperative plan and intraoperative operation. The affected limb had a good reduction effect. The operation time from the beginning of PSI installation to the completion of Ilizarov ring fixator installation was 31.33 ± 3.20 min, while that in the traditional operation group was 64.10 ± 6.14 min (p < 0.001). The times of fluoroscopy in the PSI group during operation was 10.11 ± 1.83, and that in the traditional operation group was 27.60 ± 5.82. The reduction effect of tibia in PSI group was better than that in traditional operation group, with the average angle of PSI group is 1.21 ± 0.24°, and that of traditional operation group is 2.36 ± 0.33° (p < 0.001).

Conclusion

The PSI simplifies procedures, reduces the difficulty of the operation, improves the accuracy of the operation, and provides a good initial position when used in distraction osteogenesis to treat the tibial defects.

Accuracy of free-hand humeral head resection planned on 3D-CT models in shoulder arthroplasty: an in vitro analysis

INTRODUCTION

Three-dimensional planning of humeral head osteotomy in shoulder arthroplasty (SA) is understudied. This study evaluated whether a standard osteotomy technique along the anterosuperior anatomic neck (ASOT) could be surgically reproduced as pre-operatively planned on 3D-CT models.

MATERIAL AND METHODS

Pre-operative planning in 12 cadaver shoulders was performed on a 3D-CT model of the humerus to calculate the planned osteotomy plane (planned OP). The osteotomy was then performed using a free-hand technique, and a post-operative CT scan was obtained for analysis (performed OP). Planes were compared with regards to inclination, retroversion, and resected humeral head thickness so the accuracy could be quantified.

RESULTS

The absolute errors between the performed and planned OP were 2° (0-10°), 5° (0-14°), and 4 mm (1-7 mm) for inclination, retroversion, and resected head thickness, respectively. Deviation < 10° for inclination and retroversion and < 5 mm for resected humeral head thickness between planned and performed OP was achieved in 92%, 83%, 58% of cases, respectively. No differences were found for inclination (p = 0.289), whereas retroversion and resected head thickness were smaller than planned (p ≤ 0.027).

CONCLUSIONS

Pre-operative planning of the ASOT using a 3D-CT model is accurate within a threshold of 10° when using a free-hand technique in 92% of cases for inclination. Retroversion and resected head thickness differed from the pre-operative plan, thereby limiting the unrestricted use of humeral head osteotomy planning from 3D-CT models in SA. These findings are a reference for further studies to develop and quantify the accuracy of pre-operative planning software including cutting guides for SA using 3D-CT models.

LEVEL OF EVIDENCE

Basic science article.

Patient-specific instrumentation reduces deviations between planned and postosteotomy humeral retrotorsion and height in shoulder arthroplasty

BACKGROUND

Patient-specific instrumentation (PSI) may potentially improve humeral osteotomy in shoulder arthroplasty. The purpose of this study was to compare the deviation between planned and postosteotomy humeral inclination, retrotorsion, and height in shoulder arthroplasty, using PSI vs. standard cutting guides (SCG).

METHODS

Twenty fresh-frozen cadaveric specimens were allocated to undergo humeral osteotomy using either PSI or SCG, such that the 2 groups have similar age, gender, and side. Preosteotomy computed tomography (CT) scan was performed and used for the 3-dimensional (3D) planning. The osteotomy procedure was performed using a PSI designed for each specimen or an SCG depending on the group. A postosteotomy CT scan was performed. The preosteotomy and postosteotomy 3D CT scan reconstructions were superimposed to calculate the deviation between planned and postosteotomy inclination, retrotorsion, and height. Outliers were defined as cases with 1 or more of the following deviations: >5° inclination, >10° retrotorsion, and >3 mm height. The deviation and outliers in inclination, retrotorsion, and height were compared between the 2 groups.

RESULTS

The deviations between planned and postosteotomy parameters were similar among the PSI and SCG groups for inclination (P = .260), whereas they were significantly greater in the SCG group for retrotorsion (P < .001) and height (P = .003). There were 8 outliers in the SCG group, compared with only 1 outlier in the PSI group (P = .005). Most outliers in the SCG group were due to deviation >10° in retrotorsion.

CONCLUSION

After 3D planning, PSI had less deviation between planned and postosteotomy humeral retrotorsion and height, relative to SCG.

The addition of preoperative three-dimensional analysis alters implant choice in shoulder arthroplasty

BACKGROUND

The primary objective of the present study was to investigate how preoperative imaging modalities including 3D computed tomography (CT) scans with preoperative planning software affect implant choice for shoulder arthroplasty.

METHODS

X-ray, uncorrected 2D CT scans, and 3D CT scans from 21 patients undergoing primary arthroplasty were reviewed by five shoulder surgeons. Each surgeon measured glenoid version, inclination and humeral head subluxation, and then selected an anatomic or reverse shoulder arthroplasty implant based only on these imaging parameters. Each surgeon virtually positioned the implant. Agreement between surgeons and changes in plan for individual surgeons between imaging modalities were assessed.

RESULTS

Average measurements of native version, inclination, and subluxation were similar across all imaging modalities with very good interobserver reliability. Overall, there was a high rate of variability in choice of implant depending on imaging modality. Agreement on implant selection between surgeons improved from 68.6% using x-ray to 80.0% with 3D CT. Introducing age added significant variability, reducing agreement on implant choice to 61.0% with 3D CT.

CONCLUSIONS

The use of preoperative 3D planning changes implant choice in nearly one-third of cases compared to plain radiographs and improves surgeon agreement on implant choice compared to x-ray and 2D CT.Level of evidence: III.

Patient-specific instrumentation improves the reproducibility of preoperative planning for the positioning of baseplate components with reverse total shoulder arthroplasty: a comparative clinical study in 39 patients

BACKGROUND

The application of patient-specific instrumentation (PSI) for reverse total shoulder replacement has been rapidly increasing, which could reduce errors in implant positioning. Although PSI theoretically holds promise, evidence of the accuracy and reliability of PSI in shoulder replacement surgery is limited.

METHODS

Thirty-nine shoulders that underwent reverse total shoulder arthroplasty were included in this study and categorized into two groups: the conventional (n = 20) and PSI (n = 19) groups. Screw (length and angle) and baseplate (version, inclination, translation, and rotation) positioning were calculated based on postoperative computed tomography images using a three-dimensional measurement tool. The difference between the values of the preoperative target and postoperative measurement was calculated to evaluate the reproducibility of preoperative planning. Screw involvement in the suprascapular and spinoglenoid notches was assessed. Thus, the correlation between the position of the baseplate and the screws was assessed.

RESULTS

The mean differences between the planned length and angle (anteroposterior and superoinferior angles) and postoperative measurement in the PSI group were significantly smaller than those in the conventional group. Similarly, the mean difference in baseplate rotation between the planned and postoperative measurements in the PSI group was significantly lower than that in the conventional group (4.5° vs 10.6°; P < .001). The spinoglenoid notch was involved in 10 cases in the conventional group and 2 cases in the PSI group, and this difference was significant (P = .014). Overall, the mean difference between the preoperative and postoperative version, inferior inclination, and rotation values for the baseplate position was significantly correlated with the values for screw position (length and angle).

CONCLUSIONS

PSI improves the reproducibility of preoperative planning for baseplate and screw positioning and reduces the risk of neurovascular injury in reverse total shoulder arthroplasty.

Preoperative planning of baseplate position in reverse shoulder arthroplasty: Still no consensus on lateralization, version and inclination

INTRODUCTION

In the context of reverse shoulder arthroplasty, some parameters of glenoid baseplate placement follow established golden rules, while other parameters still have no consensus. The assessment of glenoid wear in the future location of the glenoid baseplate varies among surgeons. The objective of this study was to analyze the inter-observer reproducibility of glenoid baseplate 3D positioning during virtual pre-operative planning.

METHOD

Four shoulder surgeons planned the glenoid baseplate position of a reverse arthroplasty in the CT scans of 30 degenerative shoulders. The position of the glenoid guide pin entry point and the glenoid baseplate center was compared between surgeons. The baseplate's version and inclination were also analyzed.

RESULTS

The 3D positioning of the pin entry point was achieved within ± 4 mm for nearly 100% of the shoulders. The superoinferior, anteroposterior and mediolateral positions of the baseplate center were achieved within ± 2 mm for 77.2%, 67.8% and 39.4% of the plans, respectively. The 3D orientation of the glenoid baseplate within ± 10° was inconsistent between the four surgeons (weak agreement, K=0.31, p=0.17).

DISCUSSION

The placement of the glenoid guide pin was very consistent between surgeons. Conversely, there was little agreement on the lateralization, version and inclination criteria for positioning the glenoid baseplate between surgeons. These parameters need to be studied further in clinical practice to establish golden rules. Three-dimensional information from pre-operative planning is beneficial for assessing the glenoid deformity and for limiting its impact on the baseplate position achieved by different surgeons.

LEVEL OF EVIDENCE

III. Case control study.

What is the deviation in 3D preoperative planning software? A systematic review of concordance between plan and actual implant in reverse total shoulder arthroplasty

BACKGROUND

Three-dimensional (3D) preoperative planning software for reverse total shoulder arthroplasty (rTSA) has been implemented in recent years in order to increase accuracy, improve efficiency, and add value to the outcome. A comprehensive literature review is required to determine the utility of preoperative 3D planning software in guiding orthopedic surgeons for implant placement in rTSA. We hypothesize that implementation of 3D preoperative planning software in the setting of rTSA leads to high concordance with minimal deviation from the preoperative plan.

METHODS

A comprehensive and iterative literature review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) using the PubMed, Embase, OVID Medline, Scopus, Cinahl, Web of Science, and Cochrane databases for original English-language studies evaluating the impact of preoperative planning software usage on rTSA outcomes published from January 1, 2000, to present. Blinded reviewers conducted multiple screens. All included studies were graded based on level of evidence, and data concerning patient demographics and postoperative outcomes were extracted.

RESULTS

Nine articles met inclusion criteria (1 level II, 3 level III, and 5 level IV articles), including 415 patients and 422 shoulders. Of the patients who underwent rTSA, 235 were female and 140 were male, although 3 studies (n = 40) did not report sex breakdowns for rTSA patients. The average age was 72.7 years. Four studies (79 shoulders) reported implant final position as mean deviation from planned version and planned inclination. Six studies (n = 236) reported screw angle deviation, fixation, length, and concordance. Concordance with the preoperative plan was measured in 3 studies (n = 178), resulting in complete concordance of 90% (n = 100), arthroplasty type concordance (rTSA vs. TSA) of 100% (n = 100), and glenosphere size concordance between 93% (n = 100) and 88% (n = 76). For screw length concordance, baseplate screw matched by 81% (n = 76) and 100% (n = 2), and upper (n = 35) and lower (n = 35) screw length concordance was observed as 74% and 69%, respectively. The use of preoperative planning (n = 178) was associated with low deviation from preoperative plan, more 2-screw fixations, and longer average screw length in comparison with an unplanned cohort.

CONCLUSION

The use of preoperative planning software in the setting of rTSA results in minimal deviation from preoperative plan. High levels of concordance in screw angle, screw length, and glenosphere size were observed. Further prospective studies should be conducted to further substantiate these results.

Three dimensional patient-specific guides for guide pin positioning in reverse shoulder arthroplasty: An experimental study on different glenoid types

INTRODUCTION

Incorrect positioning is one of the main factors for glenoid component loosening in reverse shoulder arthroplasty and component placement can be challenging. This study aimed to assess whether Patient-Specific Instrumentation (PSI) provides better guide pin positioning accuracy and is superior to standard guided and freehand instrumentation methods in cases of glenoid bone deformity.

MATERIALS AND METHODS

Based on the Walch classification, five different scapula types were acquired by computed tomography (CT). For each type, two different surgeons placed a guide pin into the scapula using three different methods: freehand method, conventional non-patient-specific guide, and PSI guide. Each method was repeated five times by both surgeons. In these experiments, a total of 150 samples of scapula models were used (5 × 2 × 3 × 5 = 150). Post-operative CT scans of the samples with the guide pin were digitally assessed and the accuracy of the pin placement was determined by comparison to the preoperative planning on a three-dimensional (3D) model.

RESULTS

The PSI method showed accuracies to the preoperative plan of 2.68 (SD 2.10) degrees for version angle (p < .05), 2.59 (SD 2.68) degrees for inclination angle (p < .05), and 1.55 (SD 1.26) mm for entry point offset (p < .05). The mean and standard deviation errors compared to planned values of version angle, inclination angle, and entry point offset were statistically significant for the PSI method for the type C defected glenoid and non-arthritic glenoid.

CONCLUSION

Using the PSI guide created by an image processing software tool for guide pin positioning showed advantages in glenoid component positioning over other methods, for defected and intact glenoid types, but correlation with clinical outcomes should be examined.

Risk of penetration of the baseplate peg in reverse total shoulder arthroplasty for an Asian population

PURPOSE

Baseplate positioning may affect clinical outcome after reverse total shoulder arthroplasty (RTSA). The aim of this study was to evaluate the risk of penetration of the baseplate peg in RTSA.

METHODS

Forty-four patients with rotator cuff arthropathy or massive rotator cuff tears were included. Using their computed tomography data, ten insertion patterns of the baseplate pegs were simulated. First, in the axial plane, the baseplate was placed perpendicular to the Friedman axis (Friedman placement) and parallel to the glenoid surface (glenoid placement). Second, each of these placements were classified into the following groups: The baseplate peg was placed 2 mm anterior to the long axis of the glenoid (group A2), 1 mm anterior (group A1), on the long axis (group C0), 1 mm posterior (group P1), and 2 mm posterior (group P2). Cases in which the baseplate peg was within the scapular neck were defined as non-penetration, and the non-penetration rates among each group were evaluated and compared between sexes, and their relationship with patient height was evaluated.

RESULTS

In both the Friedman and glenoid placements, the non-penetration rate was significantly higher in groups A2 (68.2% and 70.5%) and A1 (65.9% and 65.9%) compared with groups P1 (18.2% and 29.5%) and P2 (9.1% and 13.6%; p < 0.001) and in males than in females (p < 0.05). Furthermore, the non-penetration rate tended to be higher as the patient's height increased.

CONCLUSIONS

It is recommended that the baseplate peg be placed anterior to the long axis of the glenoid.

Patient-specific Instrumentation Versus Standard Surgical Instruments in Primary Reverse Total Shoulder Arthroplasty: A Retrospective Comparative Clinical Study

Aims

Patient-specific instrumentation (PSI) in primary shoulder arthroplasty has been studied; results supported the positive impact of the PSI on the glenoid positioning. Nevertheless, no clinical outcomes have been reported. We compare the clinical outcomes of primary reverse total shoulder arthroplasty using PSI versus the standard methods.

Methods

Fifty-three patients with full records and a minimum of 24-months follow-up were reviewed, 35 patients received primary standard RSTA, and 18 patients received primary PSI RSTA. All patients were operated on in a single center. The median follow-up was 46 months (53 months in the standard group vs 39 months in the PSI group).

Results

There was an overall significant post-operative improvement in the whole cohort (P< 0.05). The standard group had more deformed glenoids (B2, B3, C&D) and significantly low preoperative constant score and forward flexion (P=0.02 & 0.034). Compared to the PSI group (all were A1, A2, B1 &one type D), there were no statistically significant differences in any clinical outcome postoperatively. PSI neither prolonged the waiting time to surgery (P=0.693) nor the intraoperative time (P=0.962). Radiologically, PSI secured a higher percentage of optimum baseplate position and screw anchorage; however, no statistical correlation was found.

Conclusion

In this series, both groups achieved comparable good outcomes. PSI did not achieve significantly better clinical outcomes than Standard after primary RSTA. Yet comparison has some limitations. PSI did not negatively impact the waiting time or the surgical time.

The Accuracy of Three-Dimensional CT Scan Software in Predicting Prosthetic Utilization in Total Shoulder Arthroplasty

INTRODUCTION

Recent innovations in shoulder arthroplasty include three-dimensional (3D) CT software imaging that can be used to predict which prosthetic implants will be used intraoperatively. Correct prediction of the implants may optimize supply chain logistics for the surgeon, hospital, ambulatory surgery center, and the implant company. The purpose of this study was to examine a single surgeon's experience with this software to determine its predictive accuracy in determining which implants would be used intraoperatively.

METHODS

A retrospective review of patients undergoing total shoulder arthroplasty (TSA) performed by a single surgeon was performed. Inclusion criteria were patients undergoing anatomic (aTSA) or reverse (rTSA) TSA examined preoperatively with the 3D CT planning software. A chart review was performed to compare the accuracy of the preoperative plan in predicting the actual prostheses implanted at surgery.

RESULTS

Two hundred seventy-eight shoulders from 260 patients were included. One hundred fifty-one shoulders underwent aTSA, and 127 shoulders underwent rTSA. The surgeon was able to predict the type of arthroplasty (anatomic versus reverse) implanted in 269 of 278 (97%) shoulders. Using the 3D CT software, the surgeon was able to predict all the implants implanted in 68 shoulders (24%). For aTSA, 3D CT imaging successfully predicted all implants implanted in 43 shoulders (28%), glenoid implants implanted in 120 of 148 shoulders (81%), and humeral implants implanted in 54 shoulders (36%). For rTSA, 3D CT imaging successfully predicted all implants implanted in 26 shoulders (20%), glenoid implants implanted in 106 shoulders (83%), and humeral implants implanted in 39 shoulders (31%).

CONCLUSIONS

The 3D CT software combined with surgeon's judgment provided a high accuracy (97%) in determining the type of arthroplasty, a moderately high accuracy in determining the glenoid implants (81% to 83%), a low accuracy in determining humeral implants (31% to 36%), and a low accuracy in determining all prostheses used for each surgery (20% to 28%).

LEVEL OF EVIDENCE

LOE IV-Diagnostic Case Series.

Influence of glenoid wear pattern on glenoid component placement accuracy in shoulder arthroplasty

Background

Accurate glenoid component placement in shoulder arthroplasty is often difficult even with the use of preoperative planning. Computer navigation and patient-specific guides increase component placement accuracy, but which patients benefit most is unknown. Our purpose was to assess surgeons' accuracy in placing a glenoid component in vivo using 3-dimensional preoperative planning and standard instruments among various glenoid wear patterns.

Methods

We conducted a retrospective review of 170 primary anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA) performed at a single institution. Commercially available preoperative planning software was used in all arthroplasties with multiplanar 2-dimensional computed tomography and a 3-dimensional implant overlay. After registration of intraoperative bony landmarks to the navigation system, participating surgeons with knowledge of the preoperative plan were blinded to the computer screen and attempted to implement their preoperative plan by simulating placement of a central-axis glenoid guide pin. Two hundred thirty-three screenshots of surgeon's simulated guide pin placement were included. Glenoid displacement, error in version and inclination, and overall malposition from the preoperatively planned target point were stratified by posterior wear status (with [Walch B2 or B3] or without [A1, A2, or B1]) and Walch classification (A1, A2, B1, B2, or B3). The glenoid component was considered malpositioned when version or inclination errors exceeded 10° or the starting point displacement exceeded 4 mm.

Results

For rTSA, errors in version were greater for glenoids with posterior wear compared with those without (8.1° ± 5.6° vs. 4.7° ± 4.0°; P < .001). On post hoc analysis, B2 glenoids had greater version error than A1, A2, and B1 glenoids. A greater proportion of glenoids undergoing rTSA that possessed posterior wear had an error in version >10° compared with those without (31% vs. 8%; P < .001). Consequently, glenoids undergoing rTSA with posterior wear were malpositioned at a greater rate compared with those without (73% vs. 53%). In contrast, glenoids undergoing aTSA with and without posterior wear did not differ based on displacement error, version error, inclination error, or malposition occurrence.

Conclusions

Posterior glenoid bone loss more commonly resulted in glenoid version errors exceeding 10 degrees and component malposition in rTSA, but not for aTSA. Malposition was still relatively high in patients without significant posterior wear for both aTSA (36%) and rTSA (53%). Surgeons should consider alternate techniques beyond preoperative planning and standard instrumentation when performing shoulder arthroplasty in patients with posteriorly worn glenoids.

Preoperative three-dimensional computer planning for reverse total shoulder arthroplasty and bone grafting for severe glenoid deformity

BACKGROUND

Computer assisted planning without patient specific instrumentation may be utilized to guide reverse total shoulder arthroplasty baseplate placement. The purpose of this study was to determine the difference between planned and achieved inclination and retroversion correction with three-dimensional preoperative computer assisted planning in reverse total shoulder arthroplasty without patient specific instrumentation with bone grafting for severe glenoid erosion.

METHODS

Preoperative three-dimensional computer assisted planning without patient specific instrumentation was performed on 15 patients undergoing primary reverse total shoulder arthroplasty with glenoid bone grafting for severe glenoid erosion. On preoperative and immediate postoperative computed tomography slices, two-dimensional retroversion and inclination were measured. Preoperative three-dimensional baseline retroversion and inclination and planned postoperative three-dimensional retroversion and inclination were measured. Planned and achieved version and inclination changes were compared.

RESULTS

The planned and achieved retroversion corrections were 18° and 12°, respectively (p < 0.001). The planned and achieved inclination corrections were 11° and 11°, respectively (p = 0.803).

CONCLUSIONS

Three-dimensional computer assisted planning without patient specific instrumentation in the setting of reverse total shoulder arthroplasty with severe glenoid erosion requiring bone grafting can accurately guide baseplate placement. All cases in which failure to correct retroversion or inclination within 10° of planning occurred in patients with severe erosion (B3 or E3 glenoids), therefore patient specific guides may be warranted in these cases to improve accuracy of implantation.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Computer-Assisted Preoperative Planning and Patient-Specific Instrumentation for Glenoid Implants in Shoulder Arthroplasty

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Glenoid component positioning affects implant survival after total shoulder arthroplasty, and accurate glenoid-component positioning is an important technical aspect.

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The use of virtual planning and patient-specific instrumentation has been shown to produce reliable implant placement in the laboratory and in some clinical studies.

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Currently available preoperative planning software programs employ different techniques to generate 3-dimensional models and produce anatomic measurements potentially affecting clinical decisions.

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There are no published data, to our knowledge, on the effect of preoperative computer planning and patient-specific instrumentation on long-term clinical outcomes.

Does computerized CT-based 3D planning of the humeral head cut help to restore the anatomy of the proximal humerus after stemless total shoulder arthroplasty?

BACKGROUND

Restoration of proximal humeral anatomy (RPHA) after total shoulder arthroplasty (TSA) has been shown to result in better clinical outcomes than is the case in nonanatomic humeral reconstruction. Preoperative virtual planning has mainly focused on glenoid component placement. Such planning also has the potential to improve anatomic positioning of the humeral head by more accurately guiding the humeral head cut and aid in the selection of anatomic humeral component sizing. It was hypothesized that the use of preoperative 3-dimensional (3D) planning helps to reliably achieve RPHA after stemless TSA.

METHODS

One hundred consecutive stemless TSA (67 males, 51 right shoulder, mean age of 62 ±9.4 years) were radiographically assessed using pre- and postoperative standardized anteroposterior radiographs. The RPHA was measured with the so-called circle method described by Youderian et al. We measured deviation from the premorbid center of rotation (COR), and more than 3 mm was considered as minimal clinically important difference. Additionally, pre- and postoperative humeral head diameter (HHD), head-neck angle (HNA), and humeral head height (HHH) were measured to assess additional geometrical risk factors for poor RPHA.

RESULTS

The mean distance from of the premorbid to the implanted head COR was 4.3 ± 3.1 mm. Thirty-five shoulders (35%) showed a deviation of less than 3 mm (mean 1.9 ±1.1) and 65 shoulders (65%) a deviation of ≥3 mm (mean 8.0 ± 3.7). Overstuffing was the main reason for poor RPHA (88%). The level of the humeral head cut was responsible for overstuffing in 46 of the 57 overstuffed cases. The preoperative HHD, HHH, and HNA were significantly larger, higher, and more in valgus angulation in the group with accurate RPHA compared with the group with poor RPHA (HHD of 61.1 mm ± 4.4 vs. 55.9 ± 6.6, P < .001; HHH 8.6±2.2 vs. 7.6±2.6, P = .026; and varus angulation of 134.7° ±6.4° vs. 131.0° ±7.91, P = .010).

CONCLUSION

Restoration of proximal humeral anatomy after stemless TSA using computed tomography (CT)-based 3D planning was not precise. A poorly performed humeral head cut was the main reason for overstuffing, which was seen in 88% of the cases with inaccurate RPHA. Preoperative small HHD, low HHH, and varus-angulated HNA are risk factors for poor RPHA after stemless TSA.

Assessing the Value to the Patient of New Technologies in Anatomic Total Shoulder Arthroplasty

BACKGROUND

Publications regarding anatomic total shoulder arthroplasty (TSA) have consistently reported that they provide significant improvement for patients with glenohumeral arthritis. New TSA technologies that have been introduced with the goal of further improving these outcomes include preoperative computed tomography (CT) scans, 3-dimensional preoperative planning, patient-specific instrumentation, stemless and short-stemmed humeral components, as well as metal-backed, hybrid, and augmented glenoid components. The benefit of these new technologies in terms of patient-reported outcomes is unknown.

METHODS

We reviewed 114 articles presenting preoperative and postoperative values for commonly used patient-reported metrics. The results were analyzed to determine whether patient outcomes have improved over the 20 years during which new technologies became available.

RESULTS

The analysis did not identify evidence that the results of TSA were statistically or clinically improved over the 2 decades of study or that any of the individual technologies were associated with significant improvement in patient outcomes.

CONCLUSIONS

Additional research is required to document the clinical value of these new technologies to patients with glenohumeral arthritis.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Advanced Templating for Total Shoulder Arthroplasty

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Longitudinal clinical and radiographic success of total shoulder arthroplasty (TSA) is critically dependent on optimal glenoid component position.

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Historically, preoperative templating utilized radiographs with commercially produced overlay implant templates and a basic understanding of glenoid morphology.

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The advent of 3-dimensional imaging and templating has achieved more accurate and precise pathologic glenoid interrogation and glenoid implant positioning than historical 2-dimensional imaging.

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Advanced templating allows for the understanding of unique patient morphology, the recognition and anticipation of potential operative challenges, and the prediction of implant limitations, and it provides a method for preoperatively addressing abnormal glenoid morphology.

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Synergistic software, implants, and instrumentation have emerged with the aim of improving the accuracy of glenoid component implantation. Additional studies are warranted to determine the ultimate efficacy and cost-effectiveness of these technologies, as well as the potential for improvements in TSA outcomes.

Does commercially available shoulder arthroplasty preoperative planning software agree with surgeon measurements of version, inclination, and subluxation?

BACKGROUND

Preoperative planning with commercially available imaging software in shoulder arthroplasty may allow for improved decision-making and more accurate placement of the glenoid component.

METHODS

A total of 81 consecutive shoulder computed tomography scans obtained for preoperative planning purposes for shoulder arthroplasty were analyzed by commercially available software from 4 companies (Blueprint: Wright Medical, Memphis, TN, USA; GPS: Exactech, Gainesville, FL, USA; Materialise: DJO, Vista, CA, USA; and VIP: Arthrex, Naples, FL, USA) and by 5 fellowship-trained sports medicine/shoulder surgeons. Inclination, version, and subluxation of the humerus were measured in a blinded fashion on axial and coronal sequences at the mid-glenoid. Surgeon measurements were analyzed for agreement and were compared with the 4 commercial programs.

RESULTS

Surgeon reliability was acceptable for version (intraclass correlation coefficient [ICC]: 0.876), inclination (ICC: 0.84), and subluxation (ICC: 0.523). Significant differences were found between surgeon and commercial software measurements in version (P = .03), inclination (P = .023), and subluxation (P < .001). Software measurements tended to be more superiorly inclined (average -2° to 2° greater), more retroverted (average 2°-5° greater), and more posteriorly subluxed (average 7°-10° greater) than surgeon measurements. In comparing imaging software measurements, only Blueprint was found to produce significantly different version measurements than surgeon measurements (P = .02).

CONCLUSION

Preoperative planning software for shoulder arthroplasty has limited agreement in measures of version, inclination, and subluxation measurements, whereas surgeons have high inter-reliability. Surgeons should be cautious when using commercial software planning systems and when comparing publications that use different planning systems to determine preoperative glenoid deformity measurements.

Computer navigation leads to more accurate glenoid targeting during total shoulder arthroplasty compared with 3-dimensional preoperative planning alone

BACKGROUND

Commercially available preoperative planning software is now widely available for shoulder arthroplasty. However, without the use of patient-specific guides or intraoperative visual guidance, surgeons have little in vivo feedback to ensure proper execution of the preoperative plan. The purpose of this study was to assess surgeons' ability to implement a preoperative plan in vivo during shoulder arthroplasty.

METHODS

Fifty primary shoulder arthroplasties from a single institution were retrospectively reviewed. All surgical procedures were planned using a commercially available software package with both multiplanar 2-dimensional computed tomography and a 3-dimensional implant overlay. Following registration of intraoperative visual navigation trackers, the surgeons (1 attending and 1 fellow) were blinded to the computer navigation screen and attempted to implement the plan by simulating placement of a central-axis guide pin. Malposition was assessed (>4 mm of displacement or >10° error in version or inclination). Data were then blinded, measured, and evaluated.

RESULTS

Mean displacement from the planned starting point was 3.2 ± 2.0 mm. The mean error in version was 6.4° ± 5.6°, and the mean error in inclination was 6.6° ± 4.9°. Malposition was observed in 48% of cases after preoperative planning. Malposition errors were more commonly made by fellow trainees vs. attending surgeons (58% vs. 38%, P = .047).

CONCLUSIONS

Despite preoperative planning, surgeons of various training levels were unable to reproducibly replicate the planned component position consistently. Following completion of fellowship training, significantly less malposition resulted. Even in expert hands, the orientation of the glenoid component would have been malpositioned in 38% of cases. This study further supports the benefit of guided surgery for accurate placement of glenoid components, regardless of fellowship training.

Do individualized humeral retroversion and subscapularis repair affect the clinical outcomes of reverse total shoulder arthroplasty?

BACKGROUND

This study aimed to evaluate the effects of an individualized angle of humeral retroversion and subscapularis repair on clinical outcomes after reverse total shoulder arthroplasty (RTSA) using a lateralized prosthesis.

METHODS

A retrospective analysis of 80 patients who underwent RTSA and had a minimum of 2 years' follow-up was performed. Individualization was based on the native retroversion angle, quantified from computed tomography images. Clinical outcomes (forward flexion, external rotation at the side, internal rotation at the back, functional scores, and pain) were compared between patients with individualized retroversion (group I, n = 52) and patients with a fixed retroversion angle of 20° (group II, n = 28). Group I was further subdivided into patients with a retroversion angle of 20° or less (subgroup A, n = 21) and patients with a retroversion angle greater than 20° (subgroup B, n = 31). We also compared outcomes in group I between patients with (n = 40) and without (n = 12) subscapularis repair.

RESULTS

Ranges of motion including external rotation and internal rotation, functional scores, and pain relief were significantly better in group I than in group II (P < .05 for all). No differences in clinical outcomes were found between subgroups A and B, although outcomes for both of these subgroups were better than those for group II (P < .05 for all). Subscapularis repair was not correlated with superior clinical outcomes.

CONCLUSIONS

Individualized humeral retroversion may provide superior clinical outcomes to those of implantation of the humeral component at a fixed angle of 20° of retroversion. Repair of the subscapularis may not be essential for superior clinical outcomes in patients treated using a lateralized RTSA prosthesis.

Patient-specific planning in shoulder arthroplasty

AIMS

Patient-specific instrumentation has been shown to increase a surgeon's precision and accuracy in placing the glenoid component in shoulder arthroplasty. There is, however, little available information about the use of patient-specific planning (PSP) tools for this operation. It is not known how these tools alter the decision-making patterns of shoulder surgeons. The aim of this study was to investigate whether PSP, when compared with the use of plain radiographs or select static CT images, influences the understanding of glenoid pathology and surgical planning.

METHODS

A case-based survey presented surgeons with a patient's history, physical examination, and, sequentially, radiographs, select static CT images, and PSP with a 3D imaging program. For each imaging modality, the surgeons were asked to identify the Walch classification of the glenoid and to propose the surgical treatment. The participating surgeons were grouped according to the annual volume of shoulder arthroplasties that they undertook, and responses were compared with the recommendations of two experts.

RESULTS

A total of 59 surgeons completed the survey. For all surgeons, the use of the PSP significantly increased agreement with the experts in glenoid classification (x² = 8.54; p = 0.014) and surgical planning (x² = 37.91; p < 0.001). The additional information provided by the PSP also showed a significantly higher impact on surgical decision-making for surgeons who undertake fewer than ten shoulder arthroplasties annually (p = 0.017).

CONCLUSIONS

The information provided by PSP has the greatest impact on the surgical decision-making of low volume surgeons (those who perform fewer than ten shoulder arthroplasties annually), and PSP brings all surgeons in to closer agreement with the recommendations of experts for glenoid classification and surgical planning. Cite this article: Bone Joint J 2020;102-B(3):365-370.

Accuracy of patient-specific instrumentation in shoulder arthroplasty: a systematic review and meta-analysis

Background

There has been significant recent emphasis on the use of patient-specific instrumentation (PSI) in shoulder arthroplasty. However, clinical data are lacking to support the increased time and expense associated with PSI. Our purposes were to determine whether PSI significantly improves implantation accuracy during total shoulder arthroplasty (TSA) and to analyze available techniques and correlation with clinical outcomes. We hypothesized that PSI may improve glenoid component position radiographically but without correlation with clinical outcomes.

Methods

The MEDLINE, Scopus, Embase, and Cochrane Library databases were queried. Included articles reported use of any preoperative or intraoperative PSI techniques, models, or guides to assist with TSA prosthesis implantation. The primary outcomes were mean deviation from the preoperative plan in version (in degrees), inclination (in degrees), and entry-point offset on the glenoid (in millimeters).

Results

Among the included articles, 518 TSA procedures (352 anatomic and 166 reverse) were performed. The mean postoperative errors in both version and inclination angles were 5° or less in 20 articles (90.9%) using PSI. Meta-analysis revealed no statistically significant differences in version error (P > .999, I ² = 64.6%), inclination error (P = .702, I ² = 82.2%), or positional offset (P = .777, I ² = 85.7%) between PSI and standard instrumentation. No data regarding patient-reported outcome measures, range of motion, strength, or glenoid component loosening and longevity were reported.

Conclusions

Meta-analysis revealed no significant differences in accuracy between PSI and standard instrumentation. Although PSI may possess the potential to improve TSA techniques, further investigations regarding long-term clinical outcomes, impact on operating room time, and cost-effectiveness are warranted before PSI can be routinely recommended over conventional instrumentation.

Novel 3-dimensionally printed patient-specific guide improves accuracy compared with standard total shoulder arthroplasty guide: a cadaveric study

Background

Patient-specific instrumentation (PSI) systems for total shoulder arthroplasty (TSA) can improve glenoid component placement, but may involve considerable expense and production delays. The purpose of this study was to evaluate a novel technique for in-house production of 3-dimensionally printed, patient-specific glenoid guides. We hypothesized that our PSI guide would improve the accuracy of glenoid guide pin placement compared with a standard TSA guide.

Methods

We randomized 20 cadaveric shoulders to receive pin placement via the PSI guide (n = 10, study group) or standard TSA guide (n = 10, control group). PSI guides were designed to fit each glenoid based on 3-dimensional scapular models constructed from computed tomography scans. A presurgical plan was created for the guide pin trajectory in neutral version and inclination based on individual scapular anatomy. After pin placement, 3-dimensional models from repeated computed tomography scans were superimposed to calculate deviation from the presurgical plan for each specimen.

Results

Inclination deviation was significantly lower in the PSI group than in the standard guide group (1.5° ± 1.6° vs. 6.4° ± 5.0°, P = .009). The glenoid entry site exhibited significantly less deviation in the PSI group (0.8 ± 0.6 mm vs. 2.1 ± 1.2 mm, P = .008). The average production cost and time for the PSI guides were $29.95 and 4 hours 40 minutes per guide, respectively.

Conclusions

The PSI guide significantly improved the accuracy of glenoid pin placement compared with the standard TSA guide. Our PSI guides can be produced in-house, inexpensively, and with substantially reduced time compared with commercially available guides.

Glenoid component positioning and guidance techniques in anatomic and reverse total shoulder arthroplasty: A systematic review and meta-analysis

BACKGROUND

Positioning of the glenoid component is one of the most challenging steps in shoulder arthroplasty, and prosthesis longevity as well as functional outcomes is considered highly dependent on accurate positioning. This review considers the evidence supporting surgical navigation and patient-specific instruments for glenoid implant positioning in anatomic and reverse total shoulder arthroplasty.

METHODS

A systematic literature search was performed for studies assessing glenoid implant positioning accuracy as measured by cross-sectional imaging on live subjects or cadaver models. Meta-analysis of controlled studies was performed to estimate the primary effects of navigation and patient-specific instruments on glenoid implant positioning error. Meta-analysis of absolute positioning outcomes was also performed for each group incorporating data from controlled and uncontrolled studies.

RESULTS

Nine studies, four controlled and five uncontrolled, with 258 total subjects were included in the analysis. Meta-analysis of controlled studies supported that both navigation and patient-specific instruments had a moderate statistically significant effect on improving glenoid implant positioning outcomes. Meta-analysis of absolute positioning outcomes demonstrates glenoid implant positioning with standard instrumentation results in a high rate of malposition.

DISCUSSION

Navigation and patient-specific instruments improve glenoid positioning outcomes. Whether the improvement in positioning outcomes achieved translate to better clinical outcomes is unknown.

Thoughts on a new surgical assistance method for implanting the glenoid component during total shoulder arthroplasty. Part 1: Statistical modeling of the native premorbid glenoid

INTRODUCTION

The aim of this study was to identify points on the scapula that can be used to predict the anatomy of the native premorbid glenoid.

MATERIAL AND METHODS

Forty-three normal scapulas reconstructed in 3D and positioned in a common coordinate system were used. Twenty points distributed over the blade of the scapula (portion considered normal and used as a reference) and the glenoid (portion considered pathological and needing to be reconstructed) were captured manually. Thirteen distances (X) between two points not on the glenoid and 31 distances (Y) between two points of which at least one was on the glenoid were then calculated automatically. A multiple linear regression model was applied to calculate the Y distances from the X distances. The best four equations were retained based on their coefficient of determination (R²) to explain a point on the glenoid being reconstructed (p<0.05). In the first scenario, the glenoid was modeled assuming it was completely destroyed. In the second scenario, only the inferior portion of the glenoid was worn.

RESULTS

For a completely destroyed glenoid, the mean error for a chosen distance for a given point on the glenoid was 2.4 mm (4.e-3mm; 12.5mm). For a partially damaged glenoid, the mean error was 1.7mm (4.e-3mm; 6.5mm) for the same distance evaluated for a given point on the glenoid.

DISCUSSION/CONCLUSION

The proposed statistical model was used to predict the premorbid anatomy of the glenoid with an acceptable level of accuracy. A surgeon could use this information during the preoperative planning stage and during the actual surgery by using a new surgical assistance method.

Scapular Notching in Reverse Total Shoulder Arthroplasty

Scapular notching is a common radiographic finding occurring after reverse total shoulder arthroplasty, and it refers to an erosive lesion of the inferior scapular neck because of the impingement of the humeral implant during adduction. The clinical importance of notching is unclear, and the optimal treatment of severe notching is unknown. The incidence and severity of scapular notching is related to prosthetic design and surgical technique. Implant design factors include size, shape, and position of the glenosphere, inclination of the humeral neck-shaft angle, implant offset, and native scapular anatomy. Scapular notching may lead to deterioration of functional outcomes and glenoid implant loosening and failure. Lateral offset, inferior glenosphere overhang, and careful consideration of the presurgical glenoid morphology may help prevent scapular notching. Currently, there is limited evidence to direct the management of scapular notching, and further research is needed to elucidate optimal prevention and treatment strategies.