Standardization and Reproducibility of Dynamic Stress Testing for Occult Pelvic Ring Instability.

INTRODUCTION: Examination under anesthesia (EUA) (stress fluoroscopy) is commonly done after pelvic ring injury to identify occult instability because unstable disruptions may displace causing morbidity. The force applied during EUA for these injuries has not been standardized. The purpose of this study was to examine the forces used during the EUA by experienced orthopaedic trauma pelvic surgeons. METHODS: Orthopaedic traumatologists performed simulated EUA on a cadaver at two North American pelvis and acetabular courses using internal rotation (IR), external rotation, and push-pull maneuvers while wearing a handheld dynamometer to measure force. All surgeons used a comparable method, and each performed EUA multiple times. Maximum forces were measured in Newton (N). RESULTS: Eighteen surgeons participated. Four had been practicing for <5 years, six for 5 to 10 years, six for 11 to 20 years, and two for >20 years. Surgeons applied a force ranging from 40.4 to 374.9 N during IR, 72.9 to 338.4 N during external rotation, and 25 to 323 N during push-pull, with notable variability seen between surgeons. Three surgeons (18%) had >50-N variability on serial trials of a single EUA maneuver (IR). DISCUSSION: This is the first study evaluating the forces applied during pelvic EUA used to assess ring stability. Notable variability existed among surgeons performing EUA and in serial examinations by the same surgeon. Additional study is needed to standardize the displacement measured and threshold for instability that guides management.

Assessment of Force Applied During Examination Under Anesthesia Used to Determine Stability in Posterior Wall Acetabular Fractures.

OBJECTIVES: Determination of hip instability associated with posterior wall acetabular fractures may be difficult. Thus, dynamic stress examination under anesthesia (EUA) was developed as a tool for guiding treatment. EUA uses positioning of the hip and application of force across the hip to detect instability. While aspects of the EUA technique seems consistently described in the literature and practiced by surgeons, some components are ill-defined. The goal of this study was to assess standardization of applied force during EUA among experienced acetabular surgeons. METHODS: Fellowship-trained orthopaedic trauma surgeons with experience in acetabular fracture treatment performed EUA for posterior wall instability on an intact, fresh human cadaver. All surgeons used a similar method, and each expert performed EUA multiple times separated by a brief hiatus. The maximum force applied along the femur's vector in Newtons (N) was measured using a hand-held digital dynamometer. RESULTS: The EUAs of 19 surgeons were evaluated. Five surgeons had been practicing for <5 years, six for 6 to 10 years, five for 11 to 20 years, and three for >20 years. The mean force applied during EUA was 173N, with a notable variability between surgeons (range, 77-368N). Notable variability was also observed between sequential measures of individual surgeons with six surgeons (31.6%) having a >50N range on repeat trials. CONCLUSION: This is the first study to report force applied during an EUA to assess for posterior wall acetabular fracture stability. Notable variability was observed among surgeons performing the examination and in repeated examinations by the same surgeon, suggesting that results of EUA may be surgeon-dependent. Further study is needed to determine what optimal applied force should be used to assess hip stability after a posterior wall acetabular fracture. LEVEL OF EVIDENCE: Level V. An assessment of a diagnostic tool.

Analysis of 101 Mechanical Failures in Distal Femur Fractures Treated with 3 Generations of Precontoured Locking Plates.

OBJECTIVES: To evaluate mechanical treatment failure in a large patient cohort sustaining a distal femur fracture treated with a distal femoral locking plate (DFLP). DESIGN: This retrospective case-control series evaluated mechanical treatment failures of DFLPs. SETTING: The study was conducted at 8 Level I trauma centers from 2010 to 2017. PATIENTS AND PARTICIPANTS: One hundred one patients sustaining OTA/AO 33-A and C distal femur fractures were treated with DFLPs that experienced mechanical failure. INTERVENTION: The intervention included the treatment of a distal femur fracture with a DFLP, affected by mechanical failure (implant failure by loosening or breakage). MAIN OUTCOME MEASURE: The main outcome measures included injury and DFLP details; modes and timing of failure were studied. RESULTS: One hundred forty-six nonunions were found overall (13.4%) including 101 mechanical failures (9.3%). Failures occurred in different manners, locations, and times depending on the DFLPs. For example, 33 of 101 stainless steel (SS) plates (33%) failed by bending or breaking in the working length, whereas no Ti plates failed here ( P < 0.05). Eleven of 12 failures with titanium-Less Invasive Stabilization System (92%) occurred by lost shaft fixation, mostly by the loosening of unicortical screws (91%). Sixteen of 44 variable -angled-LCP failures (36%) occurred at the distal plate-screw junction, whereas only 5 of 61 other DFLPs (8%) failed this way ( P < 0.05). Distal failures occurred on average at 23.7 weeks compared with others that occurred at 38.4 weeks ( P < 0.05). Variable -angled-LCP distal screw-plate junction failures occurred earlier (mean 21.4 weeks). CONCLUSION: Nonunion and mechanical failure occurred in 14% and 9% of patients, respectively, in this large series of distal femur fracture treated with a DFLP. The mode, location, presence of a prosthesis, and timing of failure varied depending on the characteristics of DFLP. This information should be used to optimize implant usage and design to prolong the period of stable fixation before potential implant failures occur in patients with a prolonged time to union. LEVEL OF EVIDENCE: Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.