Three-dimensional analysis of baseplate screw penetration in reverse total shoulder arthroplasty: risk of iatrogenic suprascapular neuropathy by screw violation

Ten technical aspects of baseplate fixation in reverse total shoulder arthroplasty for patients without glenoid bone loss: a systematic review

The aim of this systematic review was to collect evidence on the following 10 technical aspects of glenoid baseplate fixation in reverse total shoulder arthroplasty (rTSA): screw insertion angles; screw orientation; screw quantity; screw length; screw type; baseplate tilt; baseplate position; baseplate version and rotation; baseplate design; and anatomical safe zones. Five literature libraries were searched for eligible clinical, cadaver, biomechanical, virtual planning, and finite element analysis studies. Studies including patients >16 years old in which at least one of the ten abovementioned technical aspects was assessed were suitable for analysis. We excluded studies of patients with: glenoid bone loss; bony increased offset-reversed shoulder arthroplasty; rTSA with bone grafts; and augmented baseplates. Quality assessment was performed for each included study. Sixty-two studies were included, of which 41 were experimental studies (13 cadaver, 10 virtual planning, 11 biomechanical, and 7 finite element studies) and 21 were clinical studies (12 retrospective cohorts and 9 case-control studies). Overall, the quality of included studies was moderate or high. The majority of studies agreed upon the use of a divergent screw fixation pattern, fixation with four screws (to reduce micromotions), and inferior positioning in neutral or anteversion. A general consensus was not reached on the other technical aspects. Most surgical aspects of baseplate fixation can be decided without affecting fixation strength. There is not a single strategy that provides the best outcome. Therefore, guidelines should cover multiple surgical options that can achieve adequate baseplate fixation.

Suprascapular nerve injury after reverse total shoulder arthroplasty: correlation with screw out of vault penetration and functional situation: prospective study

BACKGROUND

Baseplate screws have been suggested as a possible cause of suprascapular neuropathy after reverse total shoulder arthroplasty. This study aims to investigate the association between screw penetration out of the vault, electromyographic study, and the clinical outcomes.

METHODS

A total of 31 patients who underwent reverse total shoulder arthroplasty for cuff tear arthropathy were prospectively enrolled. They were followed up for a minimum of 24 months. All patients underwent computed tomography 6 months postoperatively to determine the extraosseous position of the screws (perforation of the second bone cortex and protrusion into the supra- or infraspinatus fossa). Electrodiagnostic evaluation was performed preoperatively and postoperatively to stablish any relation between cortex perforation of the screw and suprascapular nerve (SSN) injury. Clinical outcomes pre- and postoperatively (Constant score, ranges of motion, and visual analog scale) of patients with and without documented injury were recorded.

RESULTS

A total of 14 patients (45.2%) had an abnormal preoperative SSN electrodiagnostic study (chronic or disuse injuries), and 6 patients (19.4%) had an abnormal postoperative study (acute injury). Of the 6 patients, 2 cases appeared over the pre-existing lesion and 4 appeared over an intact preoperative nerve, all of them affecting the infraspinatus branch of the SSN. Perforation of the second cortex was detected for 60% of superior screws and 40% of posterior screws. The mean lengths of the superior and posterior screws were 30 and 18.2 mm, respectively. Patients with screw perforation of the second cortex were assessed as having a high risk of nerve injury (40% vs. 9.5%).

CONCLUSIONS

Preoperative SSN injuries do not have a significant clinical impact and do not predispose to an acute postoperative SSN lesion. The Constant score and visual analog scale score for patients with acute SSN injuries were not statistically different from those without SSN injury. The extraosseous position of the screw increases the probability of an SSN injury to 31%. This risk is higher with the posterior screw, which leads us to question whether it is really necessary to use it.

Does computer-assisted navigation improve baseplate screw configuration in reverse shoulder arthroplasty? A systematic review and meta-analysis of comparative studies

Introduction

Navigation technologies have improved accuracy and precision in positioning glenoid components during shoulder arthroplasty. The influence of navigation on baseplate screw placement has not been independently investigated. This study aimed to evaluate and synthesize the best scientific evidence on the influence of intraoperative navigation on the length and number of screws for primary baseplate fixation in reverse total shoulder arthroplasty procedures.

Methods

In August 2022, PubMed, Scopus, and Embase databases were accessed. We analyzed the screw purchase length, the number of screws required for the fixation of the baseplate, and the proportion of cases fixed with two screws in all clinical trials, comparing navigation to standard instrumentation for reverse shoulder arthroplasty. Following an evaluation of the heterogeneity of the studies, DerSimonian-Laird random-effects models were utilized to merge data from separate studies.

Results

The systematic search revealed a total of 2034 articles. After excluding duplicates and irrelevant studies, 633 shoulder arthroplasties from 6 trials were included in the analysis. The pooled mean difference in screw purchase length was 5.839 mm (95 %CI 4.496 to 7. 182) in favor of navigation (P < .001). In addition, significant differences were also found in the number of screws per case (- 0.547, 95 %CI -0.890 to -0.203, P = .002) and in the proportion of cases fixed with two screws (Odds Ratio 3.182 95 %CI 1.057 to 9.579, P = .040) in favor of the navigation group.

Conclusions

Intraoperative navigation improves the baseplate screw placement, allowing for a greater screw purchase length and fewer screws to achieve primary fixation of the glenoid component during reverse shoulder arthroplasty. It is unclear whether these improvements will increase the longevity of the prosthesis or the clinical outcomes of the patients.

Internal rotation of the shoulder in the beach chair position may increase the risk of iatrogenic suprascapular nerve injury at the spinoglenoid notch during surgical treatment for shoulder instability

PURPOSE

Suprascapular nerve (SN) at the spinoglenoid notch is a mobile structure which is vulnerable to iatrogenic injury from screw or guidewire penetration during shoulder surgery such as Latarjet procedure or SLAP/Bankart repairs. The primary objective is to identify the distance between posterior glenoid and SN in different shoulder abduction and rotation. The secondary objective is to identify the distance in standard lateral decubitus position.

METHODS

Nineteen shoulders from 10 Thiel embalmed soft cadavers were used in this study. The dissection of posterior shoulder was done to identify the SN at spinoglenoid notch. The distance between the posterior glenoid rim and the SN was measured. In beach chair position, the SN distance from six combinations of shoulder position was obtained: adduction/90° internal rotation (ADIR), adduction/neutral rotation (ADN), adduction/90° external rotation (ADER), 45° abduction/90° internal rotation (ABIR), 45° abduction/neutral rotation (ABN), 45° abduction/90° external rotation (ABER). Subsequently, the suprascapular nerve distance was measured in standard lateral decubitus position with 10 lbs. longitudinal traction.

RESULTS

In the beach chair position with the shoulder in adduction, the mean distances between the glenoid and the SN in ADIR, ADN and ADER were 15.0 ± 3.3, 19.3 ± 2.6 and 19.5 ± 3.1 mm, respectively. During shoulder abduction, the mean distances when the shoulder was in ABIR, ABN and ABER were 15.2 ± 3.4, 19.4 ± 3.0 and 19.3 ± 2.6 mm, respectively. The mean distance for the lateral decubitus position was 19.3 ± 2.4 mm. The distance between the glenoid and SN was significantly shorter when the shoulder was positioned in internal rotation than in neutral (p < 0.001) or external rotation (p < 0.001) when compared to the same shoulder abduction position. The lateral decubitus position had comparable SN distance with the shoulder position of abduction/neutral rotation in beach chair position.

CONCLUSION

The SN was closest to posterior glenoid rim if the shoulder was in internal rotation. Therefore, shoulder internal rotation must be avoided during guidewire and cannulated screw placement in the Latarjet procedure and drill bit insertion during anchor placement in SLAP/Bankart repair.