Patient-specific instrumentation in primary total shoulder arthroplasty: a meta-analysis of clinical outcomes
Article information
Abstract
Background
The introduction of patient-specific instrumentation (PSI) in total shoulder arthroplasty (TSA) has improved implant positioning accuracy. However, whether PSI yields additional clinical benefit compared to standard instrumentation (SI) in the setting of primary TSA (anatomic and reverse) remains unclear.
Methods
PubMed, Cochrane, Embase, and Google Scholar were queried through August 2024. Inclusion criteria consisted of studies that compared PSI to SI in TSA (anatomic and reverse). Key outcomes analyzed included adverse events, patient-reported outcomes, and discrepancies between planned and achieved implant positioning.
Results
Five retrospective studies, three randomized controlled trials, and one prospective study met the inclusion criteria. There was no difference in complications (odds ratio [OR], 1.00; 95% CI, 0.16 to 6.10; P=1.00), reoperation (OR, 1.35; 95% CI, 0.37 to 4.91; P=0.65), American Shoulder and Elbow Surgeons score (mean difference [MD], 1.61; 95% CI, –4.08 to 7.30; P=0.58), Constant-Murley Score (MD, 3.06; 95% CI, –3.68 to 9.81; P=0.37), version error (MD, –0.76; 95% CI, –2.51 to 0.99; P=0.40), and inclination error (MD, –2.8; , 95% CI, –5.82 to 0.05; P=0.05) between the two groups.
Conclusions
This study found no significant differences in patient-reported outcomes, complication rates, or implant positioning accuracy between PSI and SI in primary TSA. Future randomized controlled trials comparing these two types of instrumentation would be useful to assess whether a benefit exists for PSI in the setting of primary TSA.
Level of evidence
III.
INTRODUCTION
Patient-specific instrumentation (PSI) is a novel technique in orthopedic surgery that aims to enhance implant positioning by accounting for individual anatomical variation [1]. PSI involves the use of preoperative imaging and advanced computer modeling to create customized surgical guides that align with the patient's unique anatomical features. These guides are then used intraoperatively to ensure that implants are positioned with a high degree of accuracy [2]. In orthopedics, the application of PSI has been extensively studied with respect to procedures such as knee and hip arthroplasty, where it has been associated with improved alignment and reduced variability in component placement [3-5].
The potential benefits of PSI in orthopedics include enhanced surgical precision, reduced operative time, and fewer complications related to implant alignment compared to standard instrumentation (SI) [6-8]. However, despite the promise of PSI, evidence from hip and knee arthroplasty studies suggests that while PSI is innovative, it does not necessarily lead to superior clinical outcomes compared to SI [9-11]. This uncertainty regarding the additional clinical benefit of PSI is particularly evident in the context of total shoulder arthroplasty (TSA). Prior research on PSI in reverse shoulder arthroplasty (RSA) and anatomic total shoulder arthroplasty (ATSA) have yielded mixed results, with some studies reporting minor improvements in implant positioning, while others found no advantage over SI [12-15]. Prior studies on PSI in TSA employed diverse methodologies, and there is currently no consensus on its clinical effectiveness for enhancing patient outcomes, cost-efficiency, longevity, or its influence on operation time, highlighting a critical gap in the literature.
To address this research gap, our study undertakes a meta-analysis of existing literature comparing PSI and SI in the context of primary TSA (anatomic and reverse). By synthesizing data from various studies, this meta-analysis aims to provide a clearer understanding of whether PSI use in shoulder arthroplasty offers any tangible clinical benefit over SI in order to guide future surgical practice and research in this area.
METHODS
Search Strategy
Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, PubMed, Cochrane, Embase, and Google Scholar (pages 1–20) were searched through August 2024 [16] to find articles comparing PSI to SI in the setting of TSA (RSA and ATSA). The following keywords and Boolean terms “patient-specific,” “shoulder,” “arthroplasty,” and “replacement” were used. Supplementary articles were added by going through reference lists from articles and Internet searches. The process is summarized in the PRISMA flowchart (Fig. 1).
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart for article selection.
Inclusion criteria encompassed studies that directly compared PSI to SI in the context of TSA. Eligible studies had to report clinical, radiographic, or surgical outcomes relevant to the efficacy or accuracy of PSI versus SI. Exclusion criteria included non-comparative studies, studies derived from national databases (to prevent potential patient overlap), and studies that lacked relevant outcomes, such as those reporting outcomes not evaluated by any of the other included studies [12].
Data Extraction
Eligibility of the included studies was determined independently by two reviewers. Extracted data consisted of adverse events (complications, reoperations), patient-reported outcome measures (PROMs; American Shoulder and Elbow Surgeons [ASES] score, and Constant-Murley Score [CMS]), and the error between planned and achieved component placements (version and inclination). Two independent reviewers extracted data, and discrepancies were resolved through discussion. Interobserver reliability was assessed using Cohen’s kappa, yielding κ=0.82, indicating excellent agreement.
Risk of Bias Assessment
The Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used to assess the risk of bias in these non-randomized studies by two authors independently [17], excluding studies with a critical risk of bias. As for randomized controlled trials, the risk of bias was assessed in a similar fashion using the Cochrane Risk-of-Bias tool [18].
Statistical Analysis
All statistical analyses were conducted using Review Manager 5.4 (The Cochrane Collaboration, 2020). For continuous data, results were reported as the mean difference (MD) with 95% CI, while dichotomous data were described using the odds ratio (OR). To assess differences between studies, heterogeneity was evaluated using statistical tests (Q tests and I2 statistics). If substantial variability was found among the studies (defined as P ≤0.05 or I2 >50%), a random-effects model was applied, which accounts for variation across different study populations. If variability was low (P >0.05 or I2 <50%), a fixed-effect model was used, assuming a consistent effect across studies. Statistical significance was set at P <0.05.
RESULTS
Characteristics of the Included Studies
Five retrospective studies, three randomized controlled trials, and one prospective study met the inclusion criteria [14,19-26]. These studies included 537 patients with 288 in the PSI group (54%) and 249 in the SI group (46%). The main characteristics of the included studies are summarized in Table 1. Funnel plots to assess for publication bias were not used since less than 10 studies were included, as recommended by Cochrane Handbook for Systematic Reviews of Interventions. Two of the cohort studies had a moderate risk of bias, and the remaining four had a low risk of bias. In fact, eight studies were at moderate risk of selection and confounding bias. In addition, two studies had a moderate risk of bias due to missing data (Table 2). The included randomized controlled trials were at low risk of bias in all of the evaluated domains.
Characteristics of the included studies
Bias assessment of the included cohort studies
Adverse Events
Seven studies comprising 456 patients reported complication data (247 in the PSI group and 209 in the SI group) and four studies comprising 350 patients reported reoperation data (195 in the PSI group and 155 in the SI group). PSI had no effect on the rate of complications (OR, 1.00; 95% CI, 0.16 to 6.10, P=1.00; I2=71%) (Fig. 2A). Furthermore, no difference was seen in reoperation rate (OR, 1.35; 95% CI, 0.37 to 4.91; P=0.65, I2=2%) (Fig. 2B) between the two groups at an average follow-up period of 1.7 years.
Forest plots showing the difference in the rate of (A) complications and (B) reoperations. PSI: patient-specific instrumentation, SI: standard instrumentation, M-H: Mantel-Haenszel method.
Patient-Reported Outcome Measures
Two studies including 225 patients reported ASES and CMS scores (146 in the PSI group and 79 in the SI group). No difference was seen between the two groups in ASES (MD, 1.61; 95% CI, –4.08 to 7.30; P=0.58, I2=0%) (Fig. 3A) and CMS (MD, 3.06; 95% CI, –3.68 to 9.81; P=0.37, I2=63%) (Fig. 3B).
Forest plots showing the difference in (A) American Shoulder and Elbow Surgeons (ASES) score and (B) Constant-Murley Score (CMS). PSI: patient-specific instrumentation, SI: standard instrumentation, SD: standard deviation, IV: inverse variance method.
Placement Errors
Four studies including 151 patients reported version and inclination errors (75 in the PSI group and 76 in the SI group). No difference was seen between the two groups in version error (MD, –0.76; 95% CI, –2.51 to 0.99; P=0.40, I2=66%) (Fig. 4A) and inclination error (MD, –2.89; 95% CI, –5.82 to 0.05; P=0.05, I2=76%) (Fig. 4B).
Forest plots showing the difference in (A) version error and (B) inclination error. PSI: patient-specific instrumentation, SI: standard instrumentation, SD: standard deviation, IV: inverse variance method.
DISCUSSION
Accurate positioning and secure initial fixation of prosthetic components are critical factors for successful TSA [7,8]. Accuracy and implant positioning have been improved with the creation and implementation of PSI [27-31]. However, the usage of PSI in the setting of primary shoulder replacement is not standard care yet. This is likely because whether increased implant placement accuracy benefits PROMs or decreases complications remains unclear, as well as the increased costs associated with PSI. The current findings suggest that PSI does not provide significant clinical or radiographic advantages over SI in primary TSA, which aligns with previous studies on PSI in knee and hip arthroplasty.
In our analysis, there was no difference in the rate of adverse events at an average follow-up of 1.7 years. at an average follow-up of 1.7 years. Previously, improving component position was shown to increase the longevity of the implant by decreasing the risk of component loosening and failure over time [32]. Therefore, the absence of differences in adverse events could be explained by the absence of differences in version or inclination errors between PSI and SI seen in our analysis. In fact, from the studies included in our version and inclination error analysis, only one study found reduced version error with PSI [20], while two studies an advantage in terms of inclination errors [21,24]. Nevertheless, two of these showed studies found the difference in errors to be around 2°, posing the question of whether this difference has clinical relevance. Furthermore, recent advancements in SI techniques, including improved preoperative planning and intraoperative imaging, may have reduced the advantages previously attributed to PSI [15].
As for PROMs, no difference was seen in ASES and CMS between the two groups. However, one must note that only two studies were included for each of these two analyses, likely making them underpowered to detect small differences. Both of the studies that were included did not report a difference in PROMs between the two groups. Therefore, despite being potentially underpowered to detect a difference, our findings support that PSI in primary shoulder replacement does not differ clinically from SI. Something else to consider in the setting of PSI is its potential association with higher cost and more production delays caused by outsourcing. In fact, while no cost analysis is available for PSI in TSA, PSI in total knee arthroplasty added $1,787 compared to SI [33]. Such inconveniences can make the implementation of PSI in standard care for primary shoulder replacement more challenging.
These findings have important clinical implications, as they suggest that the routine use of PSI in primary shoulder arthroplasty may not provide meaningful benefit in terms of implant positioning, complication rates, or patient-reported outcomes. While PSI is designed to enhance surgical precision, its lack of demonstrable clinical superiority in this setting raises questions about its cost-effectiveness and necessity in routine practice. Without clear evidence of improved outcomes, the additional costs and logistical challenges associated with PSI—including increased preoperative planning, outsourcing delays, and higher financial burden—may not justify its widespread adoption. Instead, future research should focus on identifying specific patient populations that may derive the most benefit from PSI, such as those with severe anatomical deformities or complex revisions, where precision in implant positioning is more critical. Furthermore, multicenter studies with larger patient cohorts, standardized PROMs, and objective radiographic evaluations are needed to assess the potential long-term benefits of PSI.
The present study has several limitations. As a systematic review, findings depend on the variables examined by the studies meeting inclusion criteria. Furthermore, the results of this meta-analysis are pooled, as granular data was not available, which precludes performing subgroup analysis based on demographics and other vairbales such as the type of TSA. In addition, the short follow-up period in this study might have limited our findings regarding the risk of reoperation and complications, which may vary with longer follow-up. Finally, few studies were included in the some of the analyzed outcomes, making our study potentially underpowered to detect small differences. Given the small number of included studies (n<5) in analyses with high heterogeneity, formal sensitivity analysis was not feasible. However, a comparison between fixed-effects and random-effects models showed no substantial change in the results, suggesting robustness. Nonetheless, variations in study design, sample size, follow-up periods, and the implant used may have contributed to heterogeneity.
CONCLUSIONS
This meta-analysis found no statistically significant differences in patient-reported outcomes (ASES and CMS), complication rates, or implant positioning accuracy between PSI and SI in primary TSA. Our study shows that despite the established increases in accuracy using PSI in severe proximal humeral bone loss, its standard implementation in primary TSA cannot be supported. Future randomized controlled trials should evaluate PSI versus SI using larger patient cohorts, longer follow-up periods, and standardized radiographic and clinical outcome measures to determine whether PSI offers any long-term benefit over SI.
Notes
Author contributions
Conceptualization: AK, JAA. Data curation: MD, TP. Formal analysis: MD. Investigation: MD, AK. Methodology: Project administration: Writing – original draft: MD, TP, PB, MYF, WK. Writing – review & editing: JGH, JAA, AZK. All authors read and agreed to the published version of the manuscript.
Conflict of interest
AZK would like to disclose receiving support from Stryker and DePuy and serving as a paid presenter or speaker for Enovis. JAA would like to disclose royalties from a company or supplier disclosures: Osteocentric Technologies, Enovis, Zimmer-Biomet, Stryker, Globus Medical Inc. Stocks in: Shoulder Jam, Aevumed, OBERD, OTS Medical, Orthobullets, Atreon, Restore 3D. Research support from a company or supplier as a PI disclosures: Enovis, Arthrex. Royalties, financial or material support from publishers: Wolters Kluwer, Slack Orthopaedics, Elsevier. Board member/committee appointments for a society disclosures: American Shoulder and Elbow Society, Mid Atlantic Shoulder and Elbow Society, Shoulder 360, Pacira.
Funding
None.
Data availability
Contact the corresponding author for data availability.
Acknowledgments
None.