The biomechanics of subscapularis repair in reverse shoulder arthroplasty: The effect of lateralization and insertion site.

Functional outcomes of subscapularis (SSc) repair following reverse shoulder arthroplasty (RSA) remains controversial. SSc repair in combination with glenosphere lateralization was reported to yield worse clinical outcomes compared with the non-lateralized glenosphere. The aim of this biomechanical study was to investigate how glenosphere lateralization and different re-insertion sites can affect the biomechanics of the SSc after RSA. Nine patient-specific RSA shoulder models were created from patients' computed tomography scans. Moment arms and SSc length were calculated for abduction, forward flexion, and internal rotation in 20° and 90° abduction for three configurations of glenosphere lateralization (standard/+0, +5, and +10 mm) and three SSc repair sites (native, superior, and inferior) and compared with the native shoulder. When compared with the native shoulder, RSA resulted in large adducting SSc moment arms that were antagonistic to the deltoid. Glenosphere lateralization had no effect on SSc moment arms in any motion. However, lateralization increased SSc tension beyond its anatomic length for +5 and +10 mm of lateralization when attached to its native insertion. A superior SSc repair site created the least adductive moment arm as well as the least amount of SSc lengthening. Increased glenosphere lateralization showed a significant increase in the SSc length, which in combination with its adductive moment arm can be antagonistic to deltoid function. However, a superior SSc repair site may help reduce the adductive SSc moment arm and allow for reduced tension on the repair as its length in that location is less than that of the native SSc. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:888-894, 2020.

Knee Pain After Intramedullary Nailing of Tibia Fractures: Prevalence, Etiology, and Treatment.

Intramedullary nailing is often the treatment of choice for fractures of the tibia, but postoperative knee pain is common after this procedure. Potential etiologies include implant prominence, injury to intra-articular structures, patellar tendon or fat pad injury, damage to the infrapatellar branch of the saphenous nerve, and altered biomechanics. Depending on the etiology, described treatment options include observation, implant removal, assessment and treatment of injured intra-articular structures, and selective denervation. Careful attention to appropriate starting point and implant selection combined with more recently described semiextended nailing techniques may aid in prevention of knee pain.

The prevalence of sacroiliac joint degeneration in asymptomatic adults.

BACKGROUND: Degenerative changes of the sacroiliac joint have been implicated as a cause of lower back pain in adults. The purpose of this study was to determine the prevalence of sacroiliac joint degeneration in asymptomatic patients. METHODS: Five hundred consecutive pelvic computed tomography (CT) scans, made at a tertiary-care medical center, of patients with no history of pain in the lower back or pelvic girdle were retrospectively reviewed and analyzed for degenerative changes of the sacroiliac joint. After exclusion criteria were applied, 373 CT scans (746 sacroiliac joints) were evaluated for degenerative changes. Regression analysis was used to determine the association between age and the degree of sacroiliac joint degeneration. RESULTS: The prevalence of sacroiliac joint degeneration was 65.1%, with substantial degeneration occurring in 30.5% of asymptomatic subjects. The prevalence steadily increased with age, with 91% of subjects in the ninth decade of life displaying degenerative changes. CONCLUSIONS: Radiographic evidence of sacroiliac joint degeneration is highly prevalent in the asymptomatic population and is associated with age. Caution must be exercised when attributing lower back or pelvic girdle pain to sacroiliac joint degeneration seen on imaging. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Short same-segment fixation of thoracolumbar burst fractures.

INTRODUCTION: Minimizing the number of vertebral levels involved in fusion of a spine fracture is a common goal of internal fixation. This is achievable by utilizing traditional short-segment posterior fixation (SSPF). However, in SSPF there is reported up to a 54% incidence of instrument failure or unfavorable clinical outcome. Short-segment posterior fixation with pedicle fixation at the level of the fracture (short same-segment fixation) suggests biomechanical advantages toward maintenance of kyphosis correction and reducing failure rates. However its clinical efficacy is largely unknown. METHODS: The team conducted a retrospective review of 25 thoracolumbar burst fracture patients who were treated with short same-segment fixation between September 2005 and April 2009. The primary outcome measure was incidence of reoperation and loss of kyphosis correction within the follow-up period. Long-term functional status and pain was also assessed. RESULTS: Average duration of the most recent follow-up was 21.64 months (range 3 to 42 months). Two patients (8%) required reoperation due to either hardware failure or pseudoarthrosis. Mean pre-operative kyphosis was 14.49°. Average post-operative kyphosis was -0.74° (lordosis). Average follow-up kyphosis of all cases was 10.78°. Excluding failures, average follow-up kyphosis was 8.67°. A mean of 15.23° of kyphosis correction was attained from pre-operation to post-operation (P < 0.0001). Average loss of kyphosis correction from immediate post-operation to most recent follow-up was -11.51° and -9.51 excluding the two failures (P < 0.0001). Average pre-operative to most-recent follow-up kyphosis correction was 3.72° (P = 0.067) and 5.51° excluding failures (P = 0.0024). At initial one-month follow-up, average disability score was 52.63% (range 16% to 84%). At most recent follow-up, average disability score was 5.5% (range 0% to 16%). One patient was lost to long-term follow-up. Mean difference from one-month follow-up to most recent follow-up (excluding failures) was 47.27% (P < 0.0001). CONCLUSIONS: Short same-segment fixation decreases implantation failure rate and reoperation rate compared to traditional SSPF, however long-term kyphosis correction was not maintained. Despite this loss of kyphosis correction, clinical pain and disability improved at long-term follow-up.