Background: Preoperative 3D planning and intraoperative navigation for shoulder arthroplasty has recently gained interest because of the potential to enhance the surgeon’s understanding of glenoid anatomy and improve the accuracy of glenoid component positioning. The purpose of our study was to assess the impact of preoperative 3D planning on the surgeon’s selection of the glenoid component (standard vs. augmented) and compare duration of surgery with and without intraoperative navigation.

Methods: We retrospectively analyzed 200 consecutive patients who underwent shoulder arthroplasty. The first group of 100 patients underwent shoulder arthroplasty using standard 2D preoperative planning based on standard radiographs and computed tomographic scans. The second group of 100 patients underwent shoulder arthroplasty using 3D preoperative planning and intraoperative navigation. Type of glenoid component and operative time were recorded in each case.

Results: For the group of patients with standard preoperative planning, only 15 augmented glenoid components were used, whereas in the group of patients with 3D preoperative planning and navigation, 54 augments were used (P < .001). The operative time was 11 minutes longer for the procedures that used intraoperative navigation, compared with those that did not (P < .001). This difference diminished as the surgeon became more proficient with the navigation technique.

Conclusion: Use of preoperative 3D planning changes the surgeon’s understanding of the patient’s glenoid anatomy. In our study, using 3D planning increased the likelihood that the surgeon selected an augmented glenoid component compared with 2D planning. Intraoperative navigation slightly lengthened the duration of surgery, but this became insignificant as part of a learning curve within 6 months.

Background: Intraoperative computer navigation has been introduced recently to assist with placement of the glenoid component. The aim of this study was to evaluate the learning curve of a single surgeon performing computer navigation of glenoid implant placement in primary reverse total shoulder arthroplasty (RTSA).

Methods: Following training with the intraoperative computer navigation system, we conducted a prospective case-series study of the first 24 consecutive patients undergoing a primary RTSA with navigation performed by a single surgeon. Surgical times, complications, and accuracy of glenoid positioning compared with the preoperative plan were evaluated. Surgical times were compared with the preceding non-navigated series of 24 consecutive primary RTSA cases. Postoperative 3-dimensional computed tomography scans were performed to evaluate glenoid component version and inclination compared with the preoperative plan.

Results: The total surgical time was 77.3 minutes (standard deviation [SD], 11.8 minutes) in the navigated RTSA cohort and 78.5 minutes (SD, 18.1 minutes) in the non-navigated series. A significant downward trend in the total surgical time was observed in the navigated cohort (P = .038), which flattened after 8 cases. No learning curve was observed in deviation of glenoid version or inclination from the preoperative plan. The mean deviation of achieved version from planned version was 3° (SD, 2°), and the mean deviation of achieved inclination from planned inclination was 5° (SD, 3°).

Conclusion: Findings from this study suggest that intraoperative computer navigation will not require substantially increased operating times compared with standard surgical techniques. With prior surgeon training, approximately 8 operative cases are required to achieve proficiency in intraoperative computer navigation of the glenoid component.

Recently, three-dimensional (3D) planning, patient-specific instruments, and navigation system have been developed to improve the accuracy of baseplate placement in reverse shoulder arthroplasty (RSA). The purpose of this study was to evaluate baseplate placement using the navigation system. Sixty-four shoulders in 63 patients who underwent RSA for rotator cuff tear arthropathy or irreparable rotator cuff tears were enrolled. Conventional RSA was performed in 31 shoulders and navigated RSA using pre-operative planning software was performed in 33 shoulders. The use of augmented baseplates, the version and inclination of the baseplate, and screw length were compared between conventional RSA and navigated RSA. Augmented baseplates were used more frequently in navigated RSA than in conventional RSA (20 vs 9 shoulders, p = 0.014). Baseplate alignment was 1.0° (SD 5.1) of retroversion and 2.4° (SD 6.8) of superior inclination in conventional RSA and 0.2° (SD 1.9) of anteversion and 0.3° (SD 1.7) of superior inclination in navigated RSA. Compared with conventional RSA, precision of baseplate version and inclination were higher in navigated RSA (both p < 0.001). Superior, inferior, and posteroinferior screws were significantly longer in navigated RSA than in conventional RSA (p = 0.021, 0.001 and < 0.001, respectively). Precision of superior and inferior screw lengths was significantly higher in navigated RSA than in conventional RSA (both p = 0.001). Our results suggest that adoption of pre-operative planning software increased augmented baseplate use to minimize the glenoid reaming. The navigation system allows placement of the baseplate accurately, according to the pre-operative plan. Furthermore, the navigation system enables monitoring of screw length and direction in real time.

Introduction: Accurate placement of implants is of paramount importance in total shoulder arthroplasty (TSA). The reported variance of glenoid version post shoulder replacement is ± 11° 1,2. Efforts to improve this variability has led to the increased use of preoperative planning using 3D CT generated bone models. Some TSA systems use preoperative planning software combined with patient specific instrumentation to enhance the surgeon’s ability to execute his or her preoperative plan. These systems can be limited in their benefit, as intraoperative adjustment is either restricted or not possible, and their accuracy has been called into question2,3. Computer assisted surgery (CAS) offers the potential of improved accuracy while following a preoperative plan, as well as the flexibility for intraoperative adjustment during the procedure. This study compares the accuracy of implantation of reverse total shoulder arthroplasty (rTSA) glenoid implants using a CAS navigation system verses traditional non-navigated techniques in 30 cadaveric shoulders relative to a preoperative plan using 3D CT software.

Methods: High resolution 1mm slice thickness CT scans were obtained on 30 cadaveric shoulders from 15 matched pair specimens. Each CT scan was segmented and the digital models were incorporated into a preoperative planning software. Five fellowship trained orthopedic shoulder specialists used this software to virtually place a rTSA glenoid implant in six cadavers each, positioning the implant as they deemed best fit. The specimens were randomized with respect to side and split equally into a cohort utilizing the CAS system or a cohort utilizing conventional instrumentation, for a total of three shoulders in each cohort per surgeon. A BaSO4 PEEK surrogate implant identical in geometry to the rTSA glenoid implant used in the preoperative planning software was used for every specimen. BaSO4 PEEK was used in lieu of metal implants to maintain high CT image resolution with the least amount of CT artifact possible. All procedures were performed following the preoperative plan on each specimen. In the CAS cohort, each surgeon used the system to register the native cadaveric bones to each respective CT, perform the TSA procedure, and implant the surrogate rTSA implant. The surgeons then performed the TSA procedure without the CAS system on the opposing side of the matched pair using conventional instrumentation. After the procedures, CT scans were repeated on each specimen. The postoperative scan was segmented to extract the digital models, and the pre- and postoperative scapulae models were overlaid and aligned using a best-fit match algorithm. The preoperative planned position was exported from the CAS system, and variance between the virtual planned position of the implant and the executed surgical position of the surrogate implant was calculated.

Results: Result are detailed below in table 1. For version, implants placed using the CAS navigation system showed significantly less deviation from the preoperative plan than those placed using conventional techniques without navigation (1.9 ± 1.9° vs 5.9 ± 3.5°; p < .001). For inclination, implants placed using the CAS navigation system also showed significantly less deviation from the preoperative plan than those placed using conventional techniques without navigation (2.4 ± 2.5° vs 6.3 ± 6.2°; p = .031). No significant difference was noted between the two cohorts regarding deviation from the preoperative plan in anterior-posterior and superior-inferior positioning on the glenoid face (1.5 ± 1.0mm CAS cohort, 2.4 ± 1.3mm non-navigated cohort; p = .055). Finally, no significant difference was found for deviation from preoperative plan for reaming depth (1.1 ± 0.7mm CAS cohort, 1.3 ± 0.9mm non-navigated cohort; p =.397).

Conclusion: The results of this study demonstrate that this CAS navigation system facilitates a surgeon’s ability to more accurately reproduce their intended glenoid implant version and inclination (with respect to their preoperative plan), compared to conventional non-navigated techniques. This has the potential to improve implant longevity and patient function. Future work will determine if more accurate and precise implant placement is associated with improved clinical outcomes.

Background: Fixation of the glenoid baseplate in reverse total shoulder arthroplasty (rTSA) is an important factor in the success of the procedure. There is limited information available regarding the effect of navigation on fixation characteristics. Therefore, the aims of this study were to determine whether computed tomography–based computer navigation improved the glenoid base plate fixation by (1) increasing the length of screw purchase, (2) altering screw angulation, and (3) decreasing central cage perforation in patients undergoing rTSA.

Methods: Patients undergoing rTSAs using navigation (NAV, N = 27) and manual technique (MAN, N = 23) from January 2014 to July 2017 were analyzed in a case-control design. Screw purchase length and central cage perforation were assessed using multiplanar computed tomography.

Results: Median screw purchase length was significantly longer in the NAV group for both anterior (20 mm vs. 15 mm, P <.01) and posterior screws (20 mm vs. 13 mm, P <.01). In addition, the NAV group displayed significantly lower incidences of inadequate screw purchase (<22 mm) for the anterior (64.7% vs. 95.2%, P =.03) and posterior (70.6% vs. 100%, P =.01) screws. Significant differences in axial and coronal screw angulation were observed between groups. Similarly, the NAV group displayed significantly reduced incidence of central cage perforation (17.7% vs. 52.4%, P = .04).

Conclusion: The use of computer-assisted navigated rTSA contributes to significant alterations in screw purchase length, screw angulation, and central cage perforation of the glenoid baseplate compared with non-navigated methods.

Background: Accurate glenoid component placement is important to prevent glenoid component failure in total shoulder arthroplasty (TSA). Navigation may reduce the variability of glenoid component version and inclination; therefore, the aims of this study were to determine, in patients undergoing TSA, whether computer navigation improved the ability to achieve neutral postoperative version and inclination, as well as achieve the individualized preoperative plan.

Methods: Patients undergoing TSA using navigation (computer-assisted surgery [CAS], n ¼ 33) or the conventional technique (n ¼ 27) from January 2014 to July 2017 were recruited and compared. Preoperative and postoperative version and inclination, as well as postoperative inferior overhang, were measured using computed tomography scans.

Results: The CAS group had more than twice as many augmented glenoid components as the conventional group (45.5% vs. 19.2%). CAS significantly reduced the between-patient variability in postoperative version and led to a greater proportion of components positioned in ‘‘neutral’’ alignment for both inclination and version (P < .015). The incidence of neutral inclination or version postoperatively was significantly higher in the CAS group, and the glenoid was implanted within 5 of the surgical plan in more than 70% of cases, with more than 40% displaying no detectable difference.

Conclusion: An integrated system of 3-dimensional surgical planning, augmented glenoid components, and intraoperative navigation may reduce the risk of glenoid placement outside of a neutral position in patients undergoing TSA compared with conventional methods. This study demonstrated the capacity for CAS to replicate the surgical plan in a majority of cases.

Background: Little guidance exists regarding the minimum screw length and screw quantity necessary to achieve fixation with reverse shoulder arthroplasty (rTSA); to that end, this study quantifies the displacement of two different sizes of glenoid baseplates using multiple different screw lengths and quantity of screws in a low density polyurethane bone substitute model.

Methods: This rTSA glenoid loosening test was conducted according to ASTM F 2028-17. To independently evaluate the impact of screw quantity and screw length on rTSA glenoid fixation in two different sizes of glenoid baseplates, baseplates were constructed using 2, 4, and 6 screws (for the larger baseplate only) with 3 different poly-axial locking compression screws lengths. A two-tailed unpaired student’s t-test compared the baseplate displacement associated with each construct and between baseplate sizes. (p<0.05)

Results: Both sizes of glenoid baseplates remained well-fixed after cyclic loading regardless of screw length or screw quantity. Baseplates with 2 screws had significantly greater displacement than baseplates with 4 and 6 screws. No differences were overserved between baseplates of 4 and 6 screws (for the larger baseplate). Both baseplates with 18mm screws had significantly greater displacement than baseplates with 30mm and 46mm screws. For the larger baseplate, 30mm screws had significantly greater displacement than baseplates with 46mm screws in the S/I direction.

Discussion: rTSA glenoid fixation in two different size baseplates is impacted by both screw quantity and screw length for the 2 sizes of baseplates tested in this study. Irrespective of screw quantity, longer screws had significantly better fixation. Irrespective of screw length, the use of more screws had significantly better fixation, up to a point, as the use of >4 screws showed no incremental benefit. Finally, longer screws can be used as a substitute for additional fixation if it is not feasible to use more screws.