Predictors of dislocations after reverse shoulder arthroplasty: a study by the ASES complications of RSA multicenter research group.

BACKGROUND: Instability after reverse shoulder arthroplasty (RSA) is one of the most frequent complications and remains a clinical challenge. Current evidence is limited by small sample size, single-center, or single-implant methodologies that limit generalizability. We sought to determine the incidence and patient-related risk factors for dislocation after RSA, using a large, multicenter cohort with varying implants. METHODS: A retrospective, multicenter study was performed involving 15 institutions and 24 American Shoulder and Elbow Surgeons members across the United States. Inclusion criteria consisted of patients undergoing primary or revision RSA between January 2013 and June 2019 with minimum 3-month follow-up. All definitions, inclusion criteria, and collected variables were determined using the Delphi method, an iterative survey process involving all primary investigators requiring at least 75% consensus to be considered a final component of the methodology for each study element. Dislocations were defined as complete loss of articulation between the humeral component and the glenosphere and required radiographic confirmation. Binary logistic regression was performed to determine patient predictors of postoperative dislocation after RSA. RESULTS: We identified 6621 patients who met inclusion criteria with a mean follow-up of 19.4 months (range: 3-84 months). The study population was 40% male with an average age of 71.0 years (range: 23-101 years). The rate of dislocation was 2.1% (n = 138) for the whole cohort, 1.6% (n = 99) for primary RSAs, and 6.5% (n = 39) for revision RSAs (P < .001). Dislocations occurred at a median of 7.0 weeks (interquartile range: 3.0-36.0 weeks) after surgery with 23.0% (n = 32) after a trauma. Patients with a primary diagnosis of glenohumeral osteoarthritis with an intact rotator cuff had an overall lower rate of dislocation than patients with other diagnoses (0.8% vs. 2.5%; P < .001). Patient-related factors independently predictive of dislocation, in order of the magnitude of effect, were a history of postoperative subluxations before radiographically confirmed dislocation (odds ratio [OR]: 19.52, P < .001), primary diagnosis of fracture nonunion (OR: 6.53, P < .001), revision arthroplasty (OR: 5.61, P < .001), primary diagnosis of rotator cuff disease (OR: 2.64, P < .001), male sex (OR: 2.21, P < .001), and no subscapularis repair at surgery (OR: 1.95, P = .001). CONCLUSION: The strongest patient-related factors associated with dislocation were a history of postoperative subluxations and having a primary diagnosis of fracture nonunion. Notably, RSAs for osteoarthritis showed lower rates of dislocations than RSAs for rotator cuff disease. These data can be used to optimize patient counseling before RSA, particularly in male patients undergoing revision RSA.

Risk factors of acromial and scapular spine stress fractures differ by indication: a study by the ASES Complications of Reverse Shoulder Arthroplasty Multicenter Research Group.

BACKGROUND: Both patient and implant related variables have been implicated in the incidence of acromial (ASF) and scapular spine fractures (SSF) following reverse shoulder arthroplasty (RSA); however, previous studies have not characterized nor differentiated risk profiles for varying indications including primary glenohumeral arthritis with intact rotator cuff (GHOA), rotator cuff arthropathy (CTA), and massive irreparable rotator cuff tear (MCT). The purpose of this study was to determine patient factors predictive of cumulative ASF/SSF risk for varying preoperative diagnosis and rotator cuff status. METHODS: Patients consecutively receiving RSA between January 2013 and June 2019 from 15 institutions comprising 24 members of the American Shoulder and Elbow Surgeons (ASES) with primary, preoperative diagnoses of GHOA, CTA and MCT were included for study. Inclusion criteria, definitions, and inclusion of patient factors in a multivariate model to predict cumulative risk of ASF/SSF were determined through an iterative Delphi process. The CTA and MCT groups were combined for analysis. Consensus was defined as greater than 75% agreement amongst contributors. Only ASF/SSF confirmed by clinical and radiographic correlation were included for analysis. RESULTS: Our study cohort included 4764 patients with preoperative diagnoses of GHOA, CTA, or MCT with minimum follow-up of 3 months (range: 3-84). The incidence of cumulative stress fracture was 4.1% (n = 196). The incidence of stress fracture in the GHOA cohort was 2.1% (n = 34/1637) compared to 5.2% (n = 162/3127) (P < .001) in the CTA/MCT cohort. Presence of inflammatory arthritis (odds ratio [OR] 2.90, 95% confidence interval [CI] 1.08-7.78; P = .035) was the sole predictive factor of stress fractures in GHOA, compared with inflammatory arthritis (OR 1.86, 95% CI 1.19-2.89; P = .016), female sex (OR 1.81, 95% CI 1.20-2.72; P = .007), and osteoporosis (OR 1.56, 95% CI 1.02-2.37; P = .003) in the CTA/MCT cohort. CONCLUSION: Preoperative diagnosis of GHOA has a different risk profile for developing stress fractures after RSA than patients with CTA/MCT. Though rotator cuff integrity is likely protective against ASF/SSF, approximately 1/46 patients receiving RSA with primary GHOA will have this complication, primarily influenced by a history of inflammatory arthritis. Understanding risk profiles of patients undergoing RSA by varying diagnosis is important in counseling, expectation management, and treatment by surgeons.

A validated algorithm using current literature to judge the appropriateness of anatomic total shoulder arthroplasty utilizing the RAND/UCLA appropriateness method.

BACKGROUND: Currently, appropriateness criteria evaluating when to perform total shoulder arthroplasty (TSA) is lacking. In the absence of society guidelines and limited quality evidence, the RAND/University California in Los Angeles (UCLA) method provides a suitable alternative to evaluate appropriateness and assist in clinical decision making. Given the rise in utilization, appropriateness criteria for TSA have the potential to be an extremely powerful tool for improving quality of care and controlling costs. Thus, the goal of this study was to test explicit criteria to assess the appropriateness of TSA decision making using the RAND/UCLA appropriateness method. METHODS: A review of recent scientific literature to gather available evidence about the use, effectiveness, efficiency, and the risks involved in surgical intervention was performed by a shoulder/elbow fellowship trained physician. Based on pertinent variables including age, rotator cuff status, previous surgical management, mobility, symptomatology, and imaging classifications, 186 clinical scenarios were created. Appropriateness criteria for TSA were developed using a modified Delphi method with a panel consisting of American Shoulder and Elbow Surgeons (ASES) members. A second panel of ASES members rated the same scenarios, with reliability testing performed to compare groups. RESULTS: Panel members reached agreement in 40 (64%) indications. TSA was appropriate in 15 (24%) of indications. For patients with severe symptomatology, TSA was often appropriate for patients aged <75 years and inconclusive or inappropriate for patients aged >75 years. Among patients aged <65 years, TSA varied between appropriate and inconclusive, often dependent on Walch classification. For patients with moderate symptomatology, TSA was inappropriate or inconclusive for patients aged <65 or >75 years. When compared to the second panel's results, moderate agreement was obtained with a weighted kappa statistic of 0.56. CONCLUSIONS: Using the RAND/UCLA method, ASES members created an appropriateness decision tree for pertinent patient variables. This presents the data in a manner that streamlines the clinical decision-making process and allows for rapid and more reliable determination of appropriateness for practitioners. The decision tree is based on a combination of clinical experience from high-volume ASES-member surgeons and a comprehensive review of current evidence. This tool can be used as part of a broader set of factors, including individual patient characteristics, prior studies, and expert opinion, to inform clinical decision making, improve quality of care, and control costs.

Classification of instability after reverse shoulder arthroplasty guides surgical management and outcomes.

BACKGROUND: Revision of unstable reverse shoulder arthroplasty (RSA) remains a significant challenge. The purpose of this study was to determine the reliability of a new treatment-guiding classification for instability after RSA, to describe the clinical outcomes of patients stabilized operatively, and to identify those with higher risk of recurrence. METHODS: All patients undergoing revision for instability after RSA were identified at our institution. Demographic, clinical, radiographic, and intraoperative data were collected. A classification was developed using all identified causes of instability after RSA and allocating them to 1 of 3 defined treatment-guiding categories. Eight surgeons reviewed all data and applied the classification scheme to each case. Interobserver and intraobserver reliability was used to evaluate the classification scheme. Preoperative clinical outcomes were compared with final follow-up in stabilized shoulders. RESULTS: Forty-three revision cases in 34 patients met the inclusion for study. Five patients remained unstable after revision. Persistent instability most commonly occurred in persistent deltoid dysfunction and postoperative acromial fractures but also in 1 case of soft tissue impingement. Twenty-one patients remained stable at minimum 2 years of follow-up and had significant improvement of clinical outcome scores and range of motion. Reliability of the classification scheme showed substantial and almost perfect interobserver and intraobserver agreement among all the participants (κ = 0.699 and κ = 0.851, respectively). DISCUSSION: Instability after RSA can be successfully treated with revision surgery using the reliable treatment-guiding classification scheme presented herein. However, more understanding is needed for patients with greater risk of recurrent instability after revision surgery.

Total shoulder arthroplasty with minimum 5-year follow-up: does the presence of subchondral cysts in the glenoid increase risk of failure?

BACKGROUND: This study evaluated the effect of cystic changes in the glenoid on postoperative outcomes and implant survival after total shoulder arthroplasty (TSA). MATERIALS AND METHODS: From 2004 to 2012, 75 patients underwent TSA for primary osteoarthritis with minimum 5-year follow-up. Preoperative 3-dimensional models based on computed tomography imaging were created for all patients. A qualitative evaluation of cystic osteoarthritis was performed through survey grading by 3 fellowship-trained shoulder surgeons. The extent of cyst formation in the glenoid (no cysts, small, medium, or large) was assigned for every patient. In addition, quantitative evaluation was performed on 3-dimensional glenoid models. Functional outcomes, radiographic findings, and the need for revision were compared between group 1 (large and medium cysts) and group 2 (small and no cysts). RESULTS: Qualitative evaluation of cyst formation resulted in the following distribution: no cysts in 8 patients (11%), small cyst formation in 27 (36%), medium cysts in 19 (25%), and large cysts in 21 patients (28%; κ = 0.605). The difference in total cyst volume between group 1 and group 2 was significant (P = .004). The overall revision rate was 7% (5 of 75). All revised patients were in the groups with medium or large cysts. There were no statistical differences in American Shoulder and Elbow Surgeons (ASES) Standardized Shoulder Assessment scores or presence of radiographic loosening among the study groups. CONCLUSION: Qualitative computed tomography evaluation of cystic osteoarthritis correlates with quantitative analysis of cyst volume. Severe cyst formation portends a higher risk of failure at midterm follow-up. Cystic disease did not affect functional outcome or the presence of radiographic glenoid loosening.

Difficulty in decision making in the treatment of displaced proximal humerus fractures: the effect of uncertainty on surgical outcomes.

BACKGROUND: Decision making in the management of proximal humerus fractures can be difficult in situations in which the surgeon is uncertain of the ideal treatment. METHODS: Two shoulder surgeons operatively treated 476 proximal humerus fractures from 1998-2014 with open reduction-internal fixation (ORIF), hemiarthroplasty, or reverse shoulder arthroplasty. Operative treatment was stratified by year to determine the evolution of technological influences on treatment over time. To evaluate the effect of uncertainty, 274 clinical vignettes were created for all patients with 1 year of follow-up or more and reviewed by 3 fellowship-trained shoulder surgeons to determine the type of treatment for each case. To evaluate the effect of certainty, range of motion for each patient with unanimous agreement on treatment was analyzed. RESULTS: ORIF treatment increased from 40% to 62% after release of the proximal humerus locking plate. Introduction of the fracture stem in 2011 increased reverse shoulder arthroplasty for fractures from 8.8% to 44.3%. Unanimous agreement on either operative or nonoperative treatment occurred 70.5% of the time. Only 63.5% of patients received the actual treatment selected (P = .001). Patients for whom unanimous agreement matched actual treatment in the ORIF treatment group showed improvement of forward elevation (144° vs 123°, P = .005) and abduction (129° vs 103°, P = .002). CONCLUSION: Successful management of displaced proximal humerus fractures requires both technical and decision-making abilities. The difficulty in making these decisions is reflected by the agreement of experienced shoulder surgeons only 63.5% of the time regarding the treatment performed. When uncertainty occurs, patients may have reduced outcomes as seen in the ORIF treatment group.

Reverse shoulder arthroplasty in patients younger than 55 years: 2- to 12-year follow-up.

BACKGROUND: This study reports the outcomes of reverse shoulder arthroplasty (RSA) in patients younger than 55 years with midterm to long-term follow-up. METHODS: Sixty-seven patients (average age, 47.9 years; range, 21-54 years) were identified who underwent RSA with an average 62.3 months of follow-up (24-144 months). There were 35 patients (group 1) who had a failed arthroplasty and 32 patients (group 2) who underwent primary RSA. Clinical outcomes included the American Shoulder and Elbow Surgeons (ASES) score, Simple Shoulder Test (SST) score, and range of motion. Complications included radiographic failures (fracture, dislocation, notching, loosening), infections, and nerve palsies. RESULTS: Group 1 showed significant improvements in flexion and abduction but not in external or internal rotation. Group 2 showed significant improvements in flexion, abduction, and internal rotation but not in external rotation. Both groups showed significant improvements in ASES and SST scores. In group 1, ASES score improved from 24.4 to 40.8 (P = .003), and SST score improved from 1.3 to 3.2 (P = .043). In group 2, ASES score improved from 28.1 to 58.6 (P < .001), and SST score improved from 1.3 to 4.5 (P = .004). The total complication rate was 22.4%. The total reoperation rate was 13.4%, and the revision rate was 8.9%. The implant retention rate was 91% at last follow-up. CONCLUSION: RSA in patients younger than 55 years provides significant clinical improvements with high implant retention at up to 12 years. Patients undergoing revision RSA begin with worse function than those undergoing primary RSA, but they can expect similar degrees of improvement. Complications were higher but reoperation rates were lower in the revision group. No mechanical failures occurred in the primary group, with infection the cause of all revisions.

Complex trauma to the shoulder girdle, including the proximal humerus, the clavicle, and the scapula: current concepts in diagnosis and treatment.

Fractures to the shoulder girdle are common injuries in an aging population. Many techniques and theories lie behind the treatment of such injuries. Knowledge and understanding of current concepts for diagnosing and treating proximal humeral, clavicular, and scapular fractures and the theory behind them will help surgeons make informed decisions with regard to patient care.

What is the effect of postoperative scapular fracture on outcomes of reverse shoulder arthroplasty?

BACKGROUND: Postoperative scapular fracture is a common complication after reverse shoulder arthroplasty (RSA). The purpose of this study was to determine its effect on RSA patient outcomes. METHODS: A retrospective, case-control study of 25 nonoperatively treated postoperative scapular fractures after RSA were analyzed with a minimum 2-year follow-up from surgery and 1-year follow-up from fracture. Eligible patients were matched 1:4 to a control group for age, sex, follow-up time, surgery indication, and primary operation vs revision. Outcome measures, including American Shoulder and Elbow Surgeons (ASES) score and range of motion, were compared between fracture cases and controls. Also analyzed were radiographic features, including fracture location (acromion vs scapular spine) and healing. RESULTS: Incidence of scapular fracture after RSA in this series was 3.1%. Fractures occurred from 1 to 94 months postoperatively. The revision rate was higher in the fracture group (8% vs. 2%) but did not reach statistical significance (P = .18). Fracture patients had improved (ΔASES, 21) but inferior clinical outcomes, with a postoperative ASES score of 58.0 compared with 74.2 (P ≤ .001). Change in range of motion also diminished in the fracture group, with a mean gain of 26° forward elevation compared with 76° (P < .001). Fracture location (P = .54) or healing (P = .40) did not affect outcome. CONCLUSION: Postoperative scapular fractures may occur at any point postoperatively; increasing incidence is likely as longer follow-up becomes available. This complication leads to inferior clinical results compared with controls. However, patients show improvement compared with their preoperative measurements, even at longer-term follow-up. Patients with postoperative scapular fractures may have increased risk of revision. LEVEL OF EVIDENCE: Level III, case-control study, treatment study.

Arthrodesis for failed total elbow arthroplasty with deep infection.

BACKGROUND: Elbow arthrodesis is typically reserved as a salvage procedure. Current literature suggests that satisfactory outcomes can be expected if fusion occurs. There is a paucity of literature on outcomes of elbow arthrodesis after failed elbow arthroplasty with deep infection. METHODS: Five elbow arthrodeses were performed after a failed elbow arthroplasty due to deep infection. Clinical data were retrospectively reviewed for all surviving patients. Fusion angle, complications, and time to fusion or resection arthroplasty were recorded. The procedure was considered a failure if resection arthroplasty was required or there was a failure of bone union after 1 year. RESULTS: The average age at arthrodesis was 49 years (range, 35-69 years). One patient died 3 months after arthrodesis and was excluded from analysis. No patients had confirmed union at final follow-up. Two developed a fibrous union and were not symptomatic. All patients required at least 1 reoperation; 6 reoperations were required in total for the entire group. Three patients required revision arthrodesis after hardware failure. Two patients ultimately underwent a resection arthroplasty. One patient required débridement and hardware removal after wound dehiscence. Other complications included 2 patients with transient ulnar neuritis. CONCLUSION: Elbow arthrodesis is not recommended as a salvage procedure for failed total elbow arthroplasty after infection because of a high reoperation rate and difficulty in achieving solid fusion.

Scapular fractures after reverse shoulder arthroplasty: evaluation of risk factors and the reliability of a proposed classification.

BACKGROUND: The aims were to determine the sensitivity of plain radiographs to detect scapular fractures after reverse shoulder arthroplasty (RSA), to test the reliability of a proposed classification, and to evaluate risk factors. MATERIALS AND METHODS: We matched 53 patients with scapular fractures after RSA to 212 control patients. Clinical risk factors were assessed by correlating comorbidities. Independent observers reviewed radiographs to assess fracture detection accuracy and test the reliability of a proposed classification. Radiographic risks were evaluated by measuring acromial thickness, acromial tilt, glenoid-to-tuberosity distance, and acromion-to-tuberosity (AT) distance. RESULTS: Independent reviewers accurately diagnosed 78.8% of fractures and 97.4% of controls with good inter-rater reliability (κ = 0.782) and excellent intrarater reliability (κ = 0.862). Inter-rater reliability of the classification was moderate (κ = 0.422). Osteoporosis significantly increased the risk of fracture (odds ratio, 1.97; 95% confidence interval, 1.00-3.91); however, no difference was found for other comorbidities or between preoperative and postoperative radiographic parameters. A significant difference occurred between groups from the postoperative radiographs to the most recent radiographs for AT distance (0.4 ± 5.5 mm for control group and 8.3 ± 7.6 mm for fracture group, P < .001) and acromial tilt (1.8° ± 6.3° for control group and 14° ± 15° for fracture group, P < .001). Of 16 scapular spine fractures, 14 occurred from a screw tip; however, screw orientation and length were not different between groups. CONCLUSION: Osteoporosis is a significant risk factor for scapular fractures after RSA. The current classification has only moderate reliability, suggesting that an alternative classification method is needed. Decreasing AT distance and increasing acromial tilt on consecutive radiographs may improve fracture detection. Advanced imaging may be needed to confirm the diagnosis. Whereas most scapular spine fractures occurred from a screw, the surgical technique did not increase the relative risk.

The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part II.

BACKGROUND: Globally, reverse shoulder arthroplasty (RSA) has moved away from the Grammont design to modern prosthesis designs. The purpose of this study was to provide a focused, updated systematic review for each of the most common complications of RSA by limiting each search to publications after 2010. In this part II, the following were examined: (1) instability, (2) humerus/glenoid fracture, (3) acromial/scapular spine fractures (AF/SSF), and (4) problems/miscellaneous. METHODS: Four separate PubMed database searches were performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Overall, 137 studies for instability, 94 for humerus/glenoid fracture, 120 for AF/SSF, and 74 for problems/miscellaneous were included in each review, respectively. Univariate analysis was performed with chi-square and Fisher exact tests. RESULTS: The Grammont design had a higher instability rate vs. all other designs combined (4.0%, 1.3%; P < .001), and the onlay humerus design had a lower rate than the lateralized glenoid design (0.9%, 2.0%; P = .02). The rate for intraoperative humerus fracture was 1.8%; intraoperative glenoid fracture, 0.3%; postoperative humerus fracture, 1.2%; and postoperative glenoid fracture, 0.1%. The rate of AF/SSF was 2.6% (371/14235). The rate for complex regional pain syndrome was 0.4%; deltoid injury, 0.1%; hematoma, 0.3%; and heterotopic ossification, 0.8%. CONCLUSIONS: Focused systematic reviews of recent literature with a large volume of shoulders demonstrate that using non-Grammont modern prosthesis designs, complications including instability, intraoperative humerus and glenoid fractures, and hematoma are significantly reduced compared with previous studies. As the indications continue to expand for RSA, it is imperative to accurately track the rate and types of complications in order to justify its cost and increased indications.

The modern reverse shoulder arthroplasty and an updated systematic review for each complication: part I.

BACKGROUND: Globally, reverse shoulder arthroplasty (RSA) has moved away from the Grammont design to modern prosthesis designs. The purpose of this 2-part study was to systematically review each of the most common complications of RSA, limiting each search to publications in 2010 or later. In this part (part I), we examined (1) scapular notching (SN), (2) periprosthetic infection (PJI), (3) mechanical failure (glenoid or humeral component), and (4) neurologic injury (NI). METHODS: Four separate PubMed database searches were performed following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Overall, 113 studies on SN, 62 on PJI, 34 on mechanical failure, and 48 on NI were included in our reviews. Univariate analysis was performed with the χ2 or Fisher exact test. RESULTS: The Grammont design had a higher SN rate vs. all other designs combined (42.5% vs. 12.3%, P < .001). The onlay humeral design had a lower rate than the lateralized glenoid design (10.5% vs. 14.8%, P < .001). The PJI rate was 2.4% for primary RSA and 2.6% for revision RSA. The incidence of glenoid and humeral component loosening was 2.3% and 1.4%, respectively. The Grammont design had an increased NI rate vs. all other designs combined (0.9% vs. 0.1%, P = .04). CONCLUSIONS: Focused systematic reviews of the recent literature with a large volume of RSAs demonstrate that with the use of non-Grammont modern prosthesis designs, complications including SN, PJI, glenoid component loosening, and NI are significantly reduced compared with previous studies. As the indications for RSA continue to expand, it is imperative to accurately track the rates and types of complications to justify its cost and increased indications.

Outcome of Reverse Shoulder Arthroplasty for Patients With Parkinson's Disease: A Matched Cohort Study.

Parkinson's disease (PD) is a progressive neurologic disorder that affects the musculoskeletal system. Currently, the use of reverse shoulder arthroplasty (RSA) for patients with PD has not been adequately studied. The authors sought to determine if RSA provided similar functional outcomes for patients with PD compared with a matched cohort of patients without PD. Between 2004 and 2011, 10 patients with PD (4 men, 6 women) underwent RSA. Patients with PD were matched to patients without PD at a 1:4 ratio based on age (average, 76 years; range, 63-85 years), sex (16 men, 24 women), preoperative diagnosis, and length of follow-up (average, 43 months; range, 24-128 months). Outcome measures included range of motion, visual analog scale (VAS) score, Simple Shoulder Test (SST) score, American Shoulder and Elbow Society (ASES) score, and complication rates. Patients with PD had improvements in SST scores, ASES total scores, and forward flexion; however, they did not show statistically significant improvements in VAS scores, ASES function scores, or other range of motion parameters. There was a significant difference in postoperative functional outcome scores, SST scores, and internal/external rotation between the 2 groups, but no difference in postoperative pain scores, ASES total scores, forward flexion, or abduction. Complications occurred in 4 of 10 patients with PD and 6 of 40 patients without PD. Compared with the matched cohort, patients with PD achieved similar reduction of pain but inferior clinical function following RSA. Improvement in range of motion was less predictable and complication rates were significantly higher in patients with PD. [Orthopedics. 2017; 40(4):e675-e680.].

Biomechanical comparison of polyaxial-type locking plates and a fixed-angle locking plate for internal fixation of distal femur fractures.

OBJECTIVES: To test the stability to axial loading of 2 new polyaxial locking screw-plate designs and analyze different angles of screw insertion. The noncontact bridging (NCB) polyaxial locking plate (Zimmer) and the POLYAX plate (DePuy) were compared with a fixed-angle less invasive stabilization system (LISS; Synthes). METHODS: Twenty-five synthetic femurs were divided into 5 groups and assigned fixation with the LISS plate (group I), POLYAX plate (groups IIA and IIB), or NCB plate (groups IIIA and IIIB). The polyaxial constructs were divided into parallel and crossed distal condylar screw configurations. Each construct was tested under axial loading and stressed to failure at a displacement rate of 5 mm/min with a preload of 100 N. Outcome measurements included stiffness, load to failure, peak force, and mode of failure. RESULTS: All LISS and POLYAX constructs failed by plastic deformation of the plate, whereas 9 of 10 NCB constructs failed by an intra-articular lateral condyle fracture. No failures occurred at the screw-plate interface in either polyaxial constructs. Load to failure of the LISS was 33% greater than the parallel POLYAX (P < 0.01) and 24% greater than the crossed POLYAX (P < 0.01). Load to failure of NCB (parallel and crossed) were 24% greater than the parallel POLYAX (P < 0.01 and P < 0.01, respectively) and 15% greater than the crossed POLYAX (P < 0.01 and P = 0.02, respectively). The POLYAX also had significantly lower stiffness and peak force compared with the LISS and NCB. There was no difference between the LISS and NCB with regard to stiffness, load to failure, and peak force. Parallel and crossed polyaxial constructs showed no difference in stiffness or failure loads. CONCLUSIONS: There were no failures of either polyaxial screw-plate interface despite large forces and screw angle did not affect the overall strength of these constructs, supporting the biomechanical soundness of both polyaxial device designs under axial loading. However, the POLYAX supported smaller loads compared with the LISS and NCB while under axial loading. In addition, the mode of failure of the NCB plate, creating an intra-articular fracture propagating from the distal posterior screw hole, may be of some concern. Additional testing is needed to determine the clinical importance of the demonstrated differences among these plate designs.