Relative contributions of the supraspinatus cord and strap tendons to shoulder abduction and translation.

BACKGROUND: The supraspinatus (SS) is formed by a larger anterior bipennate muscle with a cord-like tendon and a posterior unipennate muscle with a strap-like tendon. There is a tendinous connection between the 2 SS subunits. Yet, the relative mechanical contribution of the SS cord and SS strap musculotendinous units to load transmission and subsequent shoulder abduction force is unknown. We hypothesized that a simulated SS cord vs. an SS strap tear would generate less shoulder abduction force and, further, an intact SS cord would offset the expected abduction loss from an SS strap tear, but the inverse would not be true. MATERIALS AND METHODS: Twenty fresh-frozen cadaveric specimens were tested in a shoulder simulator with physiological load vectors applied to the upper and lower subscapularis, SS cord, SS strap, infraspinatus, and teres minor. The roles of the SS cord and SS strap muscles were delineated by varying their loads, while keeping constant loads on other muscles. The randomized testing trials included a native condition and 4 test cases that simulated tears by dropping the load and force transfer via the SS cord-to-SS strap connection by adding the load. Testing was completed at both 0° and 30° of abduction. During each test, shoulder abduction force, rotator cuff strains, and humeral translation were measured. RESULTS: Simulated isolated SS cord and SS strap tears led to a significantly lower shoulder abduction force (P < .001). A simulated cord tear at 0° and 30° reduced the abduction force by 53% and 38%, respectively. A simulated strap tear at 0° and 30° dropped the abduction force by 27% and 23%, respectively. The decline in the abduction force was larger for the SS cord tear vs. SS strap tear (P ≤ .001). An SS cord tear with full-load transfer to the strap was able to recover to native values at both 0° and 30° (P ≥ .288). Likewise, an SS strap tear with full-load transfer to the SS cord showed a similar recovery to native values at both 0° and 30° (P ≥ .155). During full-load transfer, the tendon strain followed the loading pattern. An SS cord tear or SS strap tear did not cause a change in humeral translation (P ≥ .303). DISCUSSION: The mechanical findings support the efficacy of nonoperative treatment of small (<10 mm) SS tears,11 because an intact SS strap tendon can effectively offset the abduction loss of a torn SS cord tear and vice versa.

Orthopaedic trauma epidemiology after Hurricane Maria in the Puerto Rico Trauma Centre.

PURPOSE: Hurricane Maria is the most devastating natural phenomenon in the recent history of Puerto Rico. Due to its destructive path through the island, the Puerto Rico Trauma Center (PRTC) remained the only hospital managing orthopaedic trauma in the immediate post-disaster period. We investigated the impact of this hurricane on the orthopaedic trauma epidemiology in the PRTC. METHODS: We evaluated the admissions by the orthopaedic surgery service in terms of demographics, mechanisms of injury, and orthopaedic diagnoses for two months after the impact of Hurricane Maria (HM) on September 20, 2017. We compared our study group with the same two month period for two years prior (2015 and 2016) and after (2018 and 2019) as control periods. A p value of < 0.05 was considered statistically significant. RESULTS: We included 384 admissions from September 20 to November 20, 2017. The majority were males (63%) and had an average age of 54 years. The most-reported mechanism of injury was fall from standing height (FFSH), showing a significant increment compared with the control periods. Contrarily, motor vehicle accidents (MVA) showed a significant reduction. Among the orthopaedic diagnoses, the hip + pelvis category showed a significant decline within the study group. CONCLUSIONS: This study highlighted the impact of HM on the orthopaedic trauma epidemiology at the PRTC. Our findings provide valuable evidence to healthcare institutions to better prepare to manage the potential changes in the orthopaedic trauma epidemiology after a major atmospheric event.

Non-union in a hook of hamate fracture of a skeletally immature baseball player.

An isolated hook of hamate fracture is an extremely rare condition in skeletally immature patients. Early diagnosis and treatment are vital for the functional outcome of athletes such as baseball players. The hook of hamate fracture may be missed at initial presentation due to nonspecific symptoms and false-negative radiographs, which may eventually lead to a nonunion. Currently, there is no clear indication of surgical intervention for nonunion of the hook of hamate in a skeletally immature patient. This report presents the case of a twelve-year-old skeletally immature male with a hook of hamate fracture who underwent surgical bone fragment excision three months after initial injury due to a nonunion of the hamate bone. At the two-year postoperative visit, excellent results were obtained, and patient was able to continue his sports activity without any functional impairment.