Classification and Morphological Parameters of the Scapular Spine: Implications for Surgery

Variations in the Anatomic Morphology of the Scapular Spine and Implications on Fracture After Reverse Shoulder Arthroplasty

INTRODUCTION

This study evaluates the role of anatomic scapular morphology in acromion and scapular spine fracture (SSAF) risk after reverse shoulder arthroplasty (RSA).

METHODS

Twelve scapular measurements were captured based on pilot study data, including scapular width measurements at the acromion (Z1), middle of the scapular spine (Z2), and medial to the first major angulation (Z3). Measurements were applied to 3D-CT scans from patients who sustained SSAF after RSA (SSAF group) and compared with those who did not (control group). Measurements were done by four investigators, and the intraclass correlation coefficient was calculated. Regression analysis determined trends in fracture incidence.

RESULTS

One hundred forty-nine patients from two separate surgeons (J.L., A.M.) were matched by age and surgical indication of whom 51 sustained SSAF after reverse shoulder arthroplasty. Average ages for the SSAF and control cohorts were 78.6 and 72.1 years, respectively. Among the SSAF group, 15 were Levy type I, 26 Levy type II, and 10 Levy type 3 fractures. The intraclass correlation coefficient of Z1, Z2, and Z3 measurements was excellent (0.92, 0.92, and 0.94, respectively). Zone 1 and 3 measurements for the control group were 18.6 ± 3.7 mm and 3.2 ± 1.0 mm, respectively, compared with 22.5 ± 5.9 mm and 2.0 ± 0.70 mm in the SSAF group, respectively. The fracture group trended toward larger Z1 and smaller Z3 measurements. The average scapular spine proportion (SSP), Z1/Z3, was significantly greater in the control 6.20 ± 1.80 versus (12.60 ± 6.30; P < 0.05). Regression analysis showed a scapular spine proportion of ≤5 was associated with a fracture risk <5%, whereas an SSP of 9.2 correlated with a 50% fracture risk.

DISCUSSION

Patients with a thicker acromions (Z1) and thinner medial scapular spines (Z3) have increased fracture risk. Understanding anatomic scapular morphology may allow for better identification of high-risk patients preoperatively.

Variability in the distance between the suprascapular notch with the spine of the scapulae and the acromion

INTRODUCTION

The suprascapular notch lies in the superior border of the scapula and is a passageway for the suprascapular nerve that is sensory to the shoulder joint. Suprascapular nerve block involves injection of local anaesthetic into the suprascapular notch, either ultrasound guided or blind, using the spine of scapula and/or the medial border of the acromion as surface landmarks.

AIM

To investigate the anatomic variations that exist between the distance of the notch from the spine of scapula and acromion.

METHOD

Ninety-two dry scapulae were measured with a digital calliper for their length of the spine, distance between the midpoint of the spine and base of the suprascapular notch and distance between the medial border of the acromion and the base of the suprascapular notch. These measurements were compared for variations in the scapular bony landmarks, the spine and the acromion to determine the site for the injection.

RESULTS

Measurement reliability was assessed by intraclass correlation, Cronbach's alpha being 0.99, 0.97 and 0.91 for length of spine, distance from spine and distance from acromion respectively. The distance from the acromion had less variation in measurement (3.73 ± 0.42 cm) but a flatter distribution when compared to distance from the spine of the scapula (3.32 ± 0.39 cm).

CONCLUSION

Length of the spine of the scapula appeared not to influence either distance from the acromion or distance from the spine of scapula. There is potential for greater variability in placement of nerve blocks that use acromion as the bony reference. Key Points • Dry scapular measurement using electronic Vernier callipers is accurate (0.91-0.97). • There is potential for greater variability in placement of blind nerve blocks that use acromion as the bony reference to locate the suprascapular notch.

Mitigating Fracture of the Acromion and Scapular Spine After Reverse Shoulder Arthroplasty: A Critical Analysis Review of Patient and Surgical Risk Factors

LEVEL OF EVIDENCE

Level V. Narrative Review. See Instructions for Authors for a complete description of levels of evidence.

Locked 90°-double plating of scapular spine fracture after reverse shoulder arthroplasty with union and good outcome despite plate adjacent acromion fracture

We report the case of a 74-year-old woman who sustained a scapular spine (SS) fracture after a fall 4 weeks after reverse shoulder arthroplasty (RSA). Open reduction and internal fixation (ORIF) with locked 90°-double plating resulted in union of the SS fracture with a good outcome (subjective shoulder value: 80%; Constant score 67; 1 year) despite of an adjacent lateral acromion fracture 3 weeks after ORIF. This is the second description in the literature of a successful double plate ORIF with union of an SS fracture after RSA. SS fractures are known to lead to poor RSA outcomes with a high mal-union rate and non-union rate. We describe the positioning of the plates and technical steps for successful ORIF to avoid complications, discuss the aftercare and report the outcome.

Does ORIF of rare scapular spine fractures sustained after reverse shoulder arthroplasty benefit elderly patients? A case-series appraisal

PURPOSE

Scapular spine fractures sustained after reverse shoulder arthroplasty (RSA) are debilitating for elderly patients with osteoporosis. We examined the 1-year postoperative outcomes of open reduction and internal fixation (ORIF) in a small case-series, and hypothesised that patients undergoing surgical treatment for post-RSA scapular spine fractures would improve in function and pain.

METHODS

Five consecutive RSA patients within our shoulder arthroplasty register who sustained a scapular spine fracture underwent ORIF using a double plating technique. Standard radiographs and clinical/patient-rated assessments of Constant-Murley (CS), Shoulder Pain And Disability Index (SPADI), Subjective Shoulder Value (SSV) and visual analogue scale (VAS) pain were made up to 12months post-ORIF. Patients were also asked to rate their satisfaction since the surgery. Post-ORIF complications were documented. All post-RSA data were used as a baseline measure for comparison with post-fracture outcomes.

RESULTS

Mean CS, SPADI and SSV scores as well as pain were similar to pre-fracture scores. All patients improved in function and pain, and would undergo the same procedure again. Individual cases of iatrogenic pneumothorax and screw loosening were reported.

CONCLUSIONS

ORIF is a viable option with adequate improvements in function and pain for elderly patients with debilitating scapular spine fractures after RSA.

Free-Floating Scapular Spine: A Rare Shoulder Injury

A specific treatment protocol for managing scapular spine fractures does not currently exist. The purpose of our report is to describe this type of injury and detail our treatment management in order to better elucidate this rare pathology. We present a case of a 26-year-old female with an acute scapular spine and base fracture after a motor vehicle collision. Successful treatment of an acute free-floating scapular spine fracture was achieved with open reduction and internal fixation utilizing an elbow plate. Since scapular spine fractures are an unfortunate, rare injury, it may impose difficult challenges to the treating surgeon. With our case report, we hope to contribute to the overall knowledge of scapular spine fractures and offer our experience with a successful and appropriate treatment option in our patient.

Morphologic variations of the scapula in 3-dimensions: a statistical shape model approach

BACKGROUND

Morphologic variations of the scapula and acromion have been found to be associated with shoulder pathology. This study used statistical shape modelling to quantify these variations in healthy shoulders.

MATERIALS AND METHODS

A statistical shape model of the scapula was created using 3-dimensional computed tomography reconstructions of 108 survey-confirmed nonpathologic shoulders of 54 patients. The mean shape and the 95% confidence interval were calculated and analyzed in the first 5 shape modes.

RESULTS

The first 5 shape modes consisted of consecutively sized (72% of total variation), rotation of the coracoacromial complex (5%), acromial shape and slope (4%), shape of the scapular spine (2%), and acromial overhang (2%).

DISCUSSION AND CONCLUSION

In healthy shoulders, a certain variation in rotation of the coracoacromial complex and in acromial shape and slope was observed. These new parameters might be correlated with shoulder pathology such as glenohumeral osteoarthritis or rotator cuff tears.