Risk of suprascapular nerve injury during glenoid baseplate fixation for reverse total shoulder arthroplasty: a cadaveric study.

BACKGROUND: Reverse total shoulder arthroplasty (rTSA) is an effective treatment for patients with advanced rotator cuff arthropathy. During implantation of the glenoid baseplate, screws are inserted through the glenoid face into the scapular body to achieve adequate fixation. Placement of peripheral baseplate screws in the superior and posterior glenoid may increase the risk of injury to the suprascapular nerve (SSN). The purpose of this cadaveric study was to evaluate the risk of SSN injury with placement of baseplate screws in the superior and posterior direction. METHODS: Twelve cadaveric shoulders were implanted with glenoid baseplates. A bicortical 44-mm screw was placed in both the superior and posterior glenoid baseplate screw holes. Following implantation, the SSN was dissected and visualized through a posterior shoulder approach. The distance from the tip of the screws to the SSN and the distance from the screw's scapular exiting hole to the SSN was recorded. Average distances were calculated for each measurement. RESULTS: The superior screw contacted the SSN in 8 of the 12 specimens (66%). For the superior screw, the average distance from the exiting point in the scapula to the SSN was 9.2 ± 6.3 mm, with the shortest distance being 3.9 mm. The posterior screw contacted the SSN in 6 of 12 specimens (50%). For the posterior screw, the average distance from the exiting point to the SSN was 8.9 ± 3.8 mm, with the shortest distance to the nerve being 2.2 mm. CONCLUSION: Placement of the superior and posterior screws in the glenoid baseplate during rTSA risks injury to the SSN. The safe zone for superior- and posterior-directed baseplate screw is <2 mm from its exiting point on the scapula. Therefore, precise measurements of screw lengths in this area is important in avoiding injury to the SSN.

Rotator cuff to deltoid and pectoralis tendon to anatomic neck distances: methods for anatomic restoration of humeral height and tuberosity position in proximal humerus fractures for operative fixation and arthroplasty.

INTRODUCTION: Proper anatomic tuberosity reduction and restoration of humeral height during surgical treatment of proximal humerus fractures leads to fewer complications and better outcomes. In the presence of significant displacement and comminution in proximal humerus fractures, the assessment of the correct tuberosity position and humeral height can be challenging. The goal of this cadaveric study was to provide new and useful measurements for intraoperative guidance of proper tuberosity position and humeral height when treating proximal humerus fractures with open reduction internal fixation, anatomic hemiarthroplasty, or reverse total shoulder arthroplasty. METHODS: A total of 28 cadaveric shoulders were dissected with a deltopectoral approach. The distance between the insertion of the supraspinatus tendon and the superior aspect of the deltoid tendon was measured (cuff to deltoid distance [CDD]). Secondly, the distance between the superior aspects of the pectoralis major tendon to the medial aspect of the anatomic neck (PND) was measured. Further, we sought to determine if these measurements would correlate to patient height and differ between gender. RESULTS: The average age of the donors was 65.3 years (64% male). The CDD and PND were 87.6 ± 10.6 and 16.6 ± 6.9 mm, respectively (mean ± standard deviation). There were no differences between females and males for the CDD (86.9 ± 9.4 vs. 87.2 ± 15.2 mm, P = .96) and PND (16.3 ± 9.1 vs. 17.1 ± 5.9 mm, P = .76). There was no correlation between the cadaver height and CDD (R2 = 0.1) and PND (R2 = 0.3). DISCUSSION: In this study, we describe 2 new measurement tools that can readily be applied intraoperatively during surgical treatment of proximal humerus fractures to aid in tuberosity reduction and humeral height assessment. These measurements were found to be independent of patient height and gender and can be used as a reference tool for most patients.

Acute exertional compartment syndrome of the lumbar paraspinal muscles in a weightlifter. A case report.

BACKGROUND: Compartment syndrome (CS) is a well-known phenomenon in orthopaedics associated with traumatic injury to an extremity or over exertion which ultimately leads to prolonged and elevated intrafascial pressures. CS was initially described by Volkmann in 1881[1]. With any active muscle, there is a transient rise in intrafascial pressure from resting range of approximately 3 mmHg to 7.95 mmHg [2]. When this increase in pressure is too great or not transient, then a subsequent compartment syndrome develops. The consequences of such physiologic imbalance can induce muscle necrosis, nerve damage, vascular compromise, functional deficits, and potentially loss of limb[3,4]. Typical initial presentation of CS includes pain out of proportion to the severity of injury, which is intensified with passive motion of the muscle within the affected fascial compartment.[4] Non musculoskeletal manifestations of CS generally present themselves as the syndrome progresses and can include rhabdomyolysis, myoglobinuria, acute kidney injury, or acute tubular necrosis [4]. These non musculoskeletal manifestations of CS are potential etiologies causing patients to present for treatment [4]. PURPOSE: There have been approximately 20 previous case reports on paraspinal compartment syndrome with a combination of surgical and medical treatments in these patients. We will present a case of paraspinal CS in an avid weightlifter and discuss diagnostic and treatment options surrounding this syndrome. STUDY DESIGN: Case Report. PATIENT SAMPLE: This is a report of a single patient who presented to Duke University Medical Center. METHODS: We report the case of a 29 year old male with paraspinal compartment syndrome who was treated with fasciotomies. This was considered an IRB exempt study by our IRB as such informed consent was not obtained by the patient prior to publication. RESULTS: This patients had resolution of symptoms after surgical intervention which continued through follow up. CONCLUSION: Paraspinal compartment syndrome can be effectively treated with surgical fasciotomy.

In Vivo Anterior Cruciate Ligament Deformation During a Single-Legged Jump Measured by Magnetic Resonance Imaging and High-Speed Biplanar Radiography.

BACKGROUND: The in vivo mechanics of the anterior cruciate ligament (ACL) and its bundles during dynamic activities are not completely understood. An improved understanding of how the ACL stabilizes the knee is likely to aid in the identification and prevention of injurious maneuvers. PURPOSE/HYPOTHESIS: The purpose was to measure in vivo ACL strain during a single-legged jump through use of magnetic resonance imaging (MRI) and high-speed biplanar radiography. We hypothesized that ACL strain would increase with the knee near extension, and a peak in ACL strain would occur just before landing from the jump, potentially due to quadriceps contraction in anticipation of landing. STUDY DESIGN: Descriptive laboratory study. METHODS: Models of the femur, tibia, and ACL attachment sites of 8 male participants were generated from MRI scans through use of solid modeling. High-speed biplanar radiographs were obtained from these participants as they performed a single-legged jump. The bone models were registered to the biplanar radiographs, thereby reproducing the in vivo positions of the joint throughout the jump. ACL and bundle elongations were defined as the centroid to centroid distances between attachment sites for each knee position. ACL strain was defined as ACL length normalized to its length measured in the position of the knee at the time of MRI. RESULTS: Peaks in ACL strain were observed before toe-off and 55 ± 35 milliseconds before initial ground contact. These peaks were associated with the knee positioned at low flexion angles. Mean ACL strain was inversely related to mean flexion angle (rho = -0.73, P < .001), such that ACL strain generally increased with knee extension throughout the jumping motion. ACL bundle lengths were significantly (rho > 0.85, P < .001) correlated with overall ACL length. CONCLUSION: These findings provide insight into how landing in extension can increase the risk of ACL injury. Specifically, this study shows that peak ACL strain can occur just before landing from a single-legged jump. Thus, when an individual lands on an extended knee, the ACL is relatively taut, which may make it particularly vulnerable to injury, especially in the presence of a movement perturbation or unanticipated change in landing strategy. CLINICAL RELEVANCE: This study provides a novel measurement of dynamic ACL strain during an athletic maneuver and lends insight into how landing in extension can increase the likelihood of ACL failure.