Dataset Information

Calcar screw position in proximal humerus fracture fixation: Don't miss high!

ABSTRACT: INTRODUCTION:In locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of "missing" the calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model. MATERIALS AND METHODS:This experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups. RESULTS:Cadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p?=?0.003, p?=?0.034) and axial stiffness (p?=?0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p?=?0.020), increased axial stiffness (p?=?0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement. DISCUSSION:The distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness. RESULTS:from the Sawbones model were more definitive and provided further evidence that proximal calcar screw placements are undesirable and distal implant placement may provide improved construct stability. CONCLUSION:Successful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.

SUBMITTER: Mehta S

PROVIDER: S-EPMC7413303 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Calcar screw position in proximal humerus fracture fixation: Don't miss high!

Mehta Samir S Chin Matthew M Sanville Jennifer J Namdari Surena S Hast Michael W MW

Injury 20180211 3

<h4>Introduction</h4>In locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of "missing" the calcar during plate positioning. ...[more]

PMID: 29452734

Similar Datasets

Project description:Joint-preserving surgical treatment of complex unstable proximal humerus fractures remains challenging, with high failure rates even following state-of-the-art locked plating. Enhancement of implants could help improve outcomes. By overcoming limitations of conventional biomechanical testing, finite element (FE) analysis enables design optimization but requires stringent validation. This study aimed to computationally enhance the design of an existing locking plate to provide superior fixation stability and evaluate the benefit experimentally in a matched-pair fashion. Further aims were the evaluation of instrumentation accuracy and its potential influence on the specimen-specific predictive ability of FE. Screw trajectories of an existing commercial plate were adjusted to reduce the predicted cyclic cut-out failure risk and define the enhanced (EH) implant design based on results of a previous parametric FE study using 19 left proximal humerus models (Set A). Superiority of EH versus the original (OG) design was tested using nine pairs of human proximal humeri (N = 18, Set B). Specimen-specific CT-based virtual preoperative planning defined osteotomies replicating a complex 3-part fracture and fixation with a locking plate using six screws. Bone specimens were prepared, osteotomized and instrumented according to the preoperative plan via a standardized procedure utilizing 3D-printed guides. Cut-out failure of OG and EH implant designs was compared in paired groups with both FE analysis and cyclic biomechanical testing. The computationally enhanced implant configuration achieved significantly more cycles to cut-out failure compared to the standard OG design (p < 0.01), confirming the significantly lower peri-implant bone strain predicted by FE for the EH versus OG groups (p < 0.001). The magnitude of instrumentation inaccuracies was small but had a significant effect on the predicted failure risk (p < 0.01). The sample-specific FE predictions strongly correlated with the experimental results (R2 = 0.70) when incorporating instrumentation inaccuracies. These findings demonstrate the power and validity of FE simulations in improving implant designs towards superior fixation stability of proximal humerus fractures. Computational optimization could be performed involving further implant features and help decrease failure rates. The results underline the importance of accurate surgical execution of implant fixations and the need for high consistency in validation studies.

Project description:BackgroundProximal humerus fractures treated in the face of ipsilateral injuries to the shoulder girdle may be predisposed to worse clinical outcomes.Questions/purposesThe purpose of this investigation was to examine outcomes of proximal humerus fractures treated with open reduction internal fixation (ORIF) using an endosteal augment in the presence of a concomitant shoulder girdle injury in comparison to isolated proximal humerus fractures treated with ORIF and endosteal augment.MethodsA prospective database was used to identify proximal humerus fractures with ipsilateral shoulder girdle injuries (glenohumeral and acromioclavicular dislocation, fractures of the acromion, clavicle, scapula, or humeral diaphysis). These were compared to isolated proximal humerus fractures treated in the same fashion (ORIF with endosteal augment). Minimum of 1 year follow-up was required for inclusion. Outcomes assessed included range of motion (ROM), development of avascular necrosis (AVN), hardware-related complications, reoperation, and subjective outcome assessments including the Disabilities of Arm Shoulder and Hand questionnaire (DASH), Constant score, UCLA rating scale, and the Short Form-36 (SF-36).ResultsFifteen ipsilateral injuries were seen in 14 patients. Seventy-seven isolated proximal humerus fractures were available for comparison. The ipsilateral injury group had significantly worse forward flexion (141 vs 156°, p = 0.02), external rotation (56 vs 64°, p = 0.03), higher rates of avascular necrosis (4 of 14, 28.6% vs 1 of 77, 1.3%, p = 0.002), and inferior SF-36 physical health scores (48.5 vs 63.5; p = .04). Despite these differences, no significant differences were seen with hardware-related complications or DASH, Constant score, or UCLA rating scale results. No patients required secondary reconstructive procedures.ConclusionDespite a statistically higher rate of AVN and decreased ROM, patient-based outcomes of proximal humerus fractures with ipsilateral shoulder injuries approached those seen in isolated proximal humerus fractures. This suggests that these injuries can achieve similarly good clinical results provided any associated shoulder pathology is identified and treated appropriately.

Dataset Information

Calcar screw position in proximal humerus fracture fixation: Don't miss high!

Publications

Calcar screw position in proximal humerus fracture fixation: Don't miss high!

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets