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Purpose: Glenoid component loosening is a potential complication of reverse total shoulder arthroplasty (rTSA), occurring in part due to lack of adequate screw purchase in quality scapular bone stock. This study was to determine the efficacy of a surgeon-designed, 3D-printed patient-specific instrumentation (PSI) compared to conventional instrumentation (CI) in achieving longer superior and inferior screw lengths for glenoid component fixation., Methods: A multi-centre retrospective analysis of patients who underwent rTSA between 2015 and 2020. Lengths of the superior and inferior locking screws inserted for fixation of the glenoid baseplate component were recorded and compared according to whether patients received PSI or CI. Secondary outcomes included operative duration and incidence of complications requiring revision surgery., Results: Seventy-three patients (31 PSI vs. 42 CI) were analysed. Average glenoid diameter was 24.5 mm (SD: 3.1) and 81% of patients had smaller glenoid dimensions compared to the baseplate itself. PSI produced significantly longer superior (44.7 vs. 30.7 mm; P < 0.001) and inferior (43.0 vs. 31 mm; P < 0.001) mean screw lengths, as compared to CI. A greater proportion of maximal screw lengths for the given rTSA construct (48 mm) were observed in the PSI group (71.9% vs. 11.9% superior, 59.4% vs. 11.9% inferior). Operative duration was not statistically significantly different between the PSI and CI groups (150 min vs. 169 min, respectively; P = 0.229). No patients had radiographic loosening of the glenoid component with an average of 2-year follow-up., Conclusion: PSI facilitates longer superior and inferior screw placement in the fixation of the glenoid component for rTSA. With sufficient training, PSI can be designed and implemented by surgeons themselves., (© 2023. The Author(s).)

Conventional evaluation of the stability of bone screws focuses on pullout strength, while neglecting lateral migration resistance. We measured pullout strength and lateral migration resistance of bone screws and determined how these characteristics relate to screw stability of locking plate (LP) and dynamic compression plate (DCP) fixation. Pullout strength and lateral migration resistance of individual bone screws with buttress, square, and triangular thread designs were evaluated in polyurethane foam blocks. The screw types with superior performance in each of these characteristics were selected. LP and DCP fixations were constructed using the selected screws and tested under cyclic craniocaudal and torsional loadings. Subsequently, the association between individual screws' biomechanical characteristics and fixation stability when applied to plates was established. Screws with triangular threads had superior pullout strength, while screws with square threads demonstrated the highest lateral migration resistance; they were selected for LP and DCP fixations. LPs with square-threaded screws required a larger force and more cycles to trigger the same amount of displacement under both craniocaudal and torsional loadings. Screws with triangular and square threads showed no difference in DCP fixation stability under craniocaudal loading. However, under torsional loading, DCP fixation with triangular-threaded screws demonstrated superior fixation stability. Lateral migration resistance is the primary contributor to locking screw fixation stability when applied to an LP in resisting both craniocaudal and torsional loading. For compression screws applied to a DCP, lateral migration resistance and pullout strength work together to resist craniocaudal loading, while pullout strength is the primary contributor to the ability to resist torsional loading.

Screw loosening is a common complication in plate fixation. However, the underlying mechanism is unclear. This study investigated screw loosening mechanisms by finite element analysis (FEA) simulation and clinical X-ray feature analysis. Two FEA models incorporated bone heterogeneity and orthotropy, representing fracture fixation using dynamic compression plate (DCP) and locking compression plate (LCP), were developed. These models were used to examine the volume of bone exceeding a certain stress value around each screw under physiologically-relevant loading conditions. These damaged bone was then separated and compared by the axial stress and radial stress of each screw. In addition, features of patients' X-ray images showing screw loosening were analyzed to validate the loosening features simulated by the models. The FEA study showed that more damaged bone was found at the central two screws which gradually decreased toward the two end screws in all groups. More bone was damaged by the radial stress of each screw than by the axial stress. The radiological analysis of screw loosening showed that bone loss occurred at the screw closest to the fracture line first then subsequent bone loss at the screws further away from the fracture line occurred. This study found that the two screws nearest to the fracture line are more vulnerable to loosening. The radial stress of the screw plays a larger role in screw loosening than the axial stress. Bone resorption triggered by the high radial stress of screws is indicated as the mechanism of screw loosening in the diaphyseal plate fixation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1498-1507, 2019., (© 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

In osteoporotic hip fractures, fracture collapse is deliberately allowed by commonly used implants to improve dynamic contact and healing. The muscle lever arm is, however, compromised by shortening. We evaluated a cohort of 361 patients with AO/OTA 31.A1 or 31.A2 intertrochanteric fracture treated by the dynamic hip screw (DHS) who had a minimal follow-up of 3 months and an average follow-up of 14.6 months and long term survival data. The amount of fracture collapse and shortening due to sliding of the DHS was determined at the latest follow-up and graded as minimal (<1 cm), moderate (1-2 cm), or severe (>2 cm). With increased severity of collapse, more patients were unable to maintain their premorbid walking function (minimal collapse = 34.2%, moderate = 33.3%, severe = 62.8%, and p = 0.028). Based on ordinal regression of risk factors, increased fracture collapse was significantly and independently related to increasing age (p = 0.037), female sex (p = 0.024), A2 fracture class (p = 0.010), increased operative duration (p = 0.011), poor reduction quality (p = 0.000), and suboptimal tip-apex distance of >25 mm (p = 0.050). Patients who had better outcome in terms of walking function were independently predicted by younger age (p = 0.036), higher MMSE marks (p = 0.000), higher MBI marks (p = 0.010), better premorbid walking status (p = 0.000), less fracture collapse (p = 0.011), and optimal lag screw position in centre-centre or centre-inferior position (p = 0.020). According to Kaplan-Meier analysis, fracture collapse had no association with mortality from 2.4 to 7.6 years after surgery. In conclusion, increased fracture collapse after fixation of geriatric intertrochanteric fractures adversely affected walking but not survival.

Purpose: To develop a reference for the distal screw length in volar locking plate fixation for distal radial fractures in an East Asian population., Methods: 12 pairs of forearm specimens from 11 male and one female East Asian cadavers were scanned using computed tomography. On sagittal images of the distal radius, the mean cortex-to-cortex distance of 8 quadrants was measured as a reference for the distal screw length. In addition, intra-operative 3-dimensional fluoroscopy of 10 male and 10 female patients who underwent volar locking plate fixation for distal radial fractures was used to validate the distal screw length in the cadaveric reference. 76 distal locking screws were applied in the 8 quadrants; their cortex-to-cortex distances were measured., Results: The mean cortex-to-cortex distances at quadrants A, B, C, D, E, F, G, and H were 15.4 mm, 19.6 mm, 20.8 mm, 20.0 mm, 13.3 mm, 18.0 mm, 18.8 mm, and 17.4 mm, respectively. In 45% of the specimens, the 2 screws inserted at quadrants C and D were longest. Distal screws (quadrants A to D) were significantly longer than proximal screws (quadrants E to H) [p=0.02]. In intra-operative 3-dimensional fluoroscopic images, 2 of the 76 distal locking screws penetrated the dorsal cortex (one in quadrant A and one in quadrant F). The mean screw length was 88.0% of the cortex-to-cortex distance. Referenced to the cadaveric data, 88.2% of the screws could be safely inserted without penetrating the dorsal cortex, and the remaining 11.8% of screws (5 at quadrant D, one at quadrant B, and 3 at quadrant C; all in female patients) could potentially cause dorsal cortex penetration of 2 to 4 mm. In male patients, the mean screw length was 76.1% of the cortex-to-cortex distance based on the cadaveric reference. In female patients, when the screw length was 4 mm less than the cadaveric reference, the mean screw length would be 72.0% of the referenced cortex-to-cortex distance, with no dorsal cortex penetration., Conclusion: In female patients, the screw length should be 4 mm less than the cadaveric reference to avoid dorsal cortex penetration.

Femoral neck system (FNS) is a novel fixed-angle gliding device combining a sliding bolt and an anti-rotational screw to treat femoral neck fractures. It was proven to have comparable biomechanical strength to sliding hip screws. Tip-to-apex distance (TAD) is an established assessment for fixation quality in sliding hip screws. The purpose of our study was to evaluate whether TAD can be used in FNS implant to predict fixation failure. Seventy-six patients receiving FNS fixation for intra-capsular hip fracture were included. TAD was measured from post-operative radiographs and clinical outcomes were collected with a mean follow-up of 14.1 months. The mean TAD for patients who experienced fixation failure was 20.7 mm, versus 19.7 mm for those who did not (p = 0.395). Subgroup analysis among fractures with good reduction quality, defined as no varus angulation, less than 5 degrees of retroversion, and less than 4 mm cortical translation, did not demonstrate statistically significant difference in the mean TAD between failure and non-failure group (20.7 mm vs 19.5 mm, p = 0.68). We conclude that in our study of modest sample size, there was not demonstrable association between TAD and fixation failure in intra-capsular neck of femur patients treated with FNS. [ABSTRACT FROM AUTHOR]

Purpose: Distal radius fractures are associated with a high incidence of triangular fibrocartilage complex (TFCC) tears. This study aims to evaluate the status of TFCC after the healing of distal radius fractures, and its clinical significance.Methods: Wrist arthroscopies were performed on 43 distal radius fractures, with an average age of 54 years old.Results: Twenty-six complete tears and 15 partial healed tears were noted. Five out of eight patients with intact TFCC tears had neither signs nor symptoms, while eight patients with TFCC tears had no complaint. While no association was found between ulnar wrist pain and TFCC tears, there was association between DRUJ instability and TFCC tears and fovea tears. The function outcome did not differ with respect to the integrity of TFCC.Conclusions: A large majority of TFCC tears remained unhealed after the union of distal radius fractures. However, not all patients with tear were symptomatic. [ABSTRACT FROM AUTHOR]