Increased torsional stability by a novel femoral neck locking plate

Increased torsional stability by a novel femoral neck locking plate. The role of plate design and pin configuration in a synthetic bone block model, Brattgjerd et al. Clin. Biomech (2018) in press, accepted manuscript.

Abstract:

Background
In undisplaced femoral neck fractures, internal fixation remains the main treatment, with mechanical failure as a frequent complication. As torsional stable fixation promotes femoral neck fracture healing, the Hansson Pinloc® System with a plate interlocking pins, was developed from the original hook pins. Since its effect on torsional stability is undocumented the novel implant was compared with the original configurations.

Methods
Forty-two proximal femur models custom made of two blocks of polyurethane foam were tested. The medial block simulated the cancellous head, while the lateral was laminated with a glass fiber filled epoxy sheet simulating trochanteric cortical bone. Two hollow metal cylinders with a circumferential ball bearing in between mimicked the neck, with a perpendicular fracture in the middle. Fractures were fixated by two or three independent pins or by five configurations involving the interlocking plate (two pins with an optional peg in a small plate, or three pins in a small, medium or large plate). Six torsional tests were performed on each configuration to calculate torsional stiffness, torque at failure and failure energy.

Findings
The novel configurations improved parameters up to an average of 12.0 (stiffness), 19.3 (torque) and 19.9 (energy) times higher than the original two pins (P < 0.001). The plate, its size and its triangular configuration improved all parameters (P = 0.03), the plate being most effective, also preventing permanent failure (P < 0.001). Interpretation The novel plate design with its pin configuration enhanced torsional stability. To reveal clinical relevance a clinical study is planned.

Highlights:

  • The Hansson Pinloc® system increased torsional parameters with a factor of up to 20.
  • The plate per se, its size and its triangular configuration improved all parameters.
  • The plate itself was the most effective novel component of the fixation.
  • Torsional failure by twisting of the pins was prevented by the plate itself.

Corrective osteotomy in symptomatic clavicular malunion using computer-assisted 3-D planning and patient-specific surgical guides

Open access article Corrective osteotomy in symptomatic clavicular malunion using computer-assisted 3-D planning and patient-specific surgical guides, Grewal, Dobbe, Kloen, J. Orthopaedics (2018) 15(2):438-441

Abstract:

Surgical correction of a symptomatic clavicular malunion requires simultaneous adjustment of the translation as well as the rotation in multiple planes. We describe a corrective osteotomy for a clavicle malunion using 3-D computer assisted preoperative-planning combined with patient-specific surgical guides, along with the benefits and disadvantages of this approach. This method enabled quantifying the malunion by comparing the malunited bone with the normal contralateral clavicle as a template. The postoperative results were encouraging with symmetrical shoulder anatomy and functional improvement. Therefore, we recommend this technique in patients with a symptomatic clavicle malunion, as it allows successful correction of the deformity.

clavicle-deformity-preoperative
Preoperative alignment planning. A–C: 3D model of the deformed clavicle: Green mirrored contralateral bone Red affected clavicle White planned state. D-E:
Zanca view F: Peroperative view.

A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole

finite-element-im-nail

A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole, by Mortazavi, Farahmand, Behzadipour, Yeganeh, Aghighi

Abstract:

Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model predictions and the experimental observations. There was a three-point contact pattern between the nail and medullary canal, only on the proximal fragment of the fractured bone. The nail deflection was much larger in the sagittal plane and increased for the larger diameter nail, as well as for more distally fractured or intact femur. The altered position of the distal hole was predicted by the model with an acceptable error (mean: 0.95; max: 1.5 mm, in different tests) to be used as the compensatory information for fine tuning of proximally mounted targeting systems.

finite-element-simulation-nail-bone
Simulation of the nail–bone interaction during intramedullary nailing. (a) Transitional phase: With the proximal end of the femur utterly fixed, the nail is driven into the medullary canal by an increasing pushing force, (b) Stable phase: With the nail inserted in the medullary canal and the proximal and distal ends of the bone constrained by spherical and revolute joints, respectively, the nail and bone reach static equilibrium.

Highlights:

  • There is a three-point contact pattern between the intramedullary nail and medullary canal, only on the proximal fragment of the fractured bone.
  • Nail deflection during intramedullary nailing occurs mainly in sagittal plane.
  • Patient specific modeling can predict the nail deflection with a reasonably good accuracy.
  • Patent specific modeling can be used to provide the compensatory information for fine tuning of proximally mounted targeting systems during intramedullary nailing.

Functional classification of the medial ulnar collateral ligament

Open access research article Functional Classification of the Medial Ulnar Collateral Ligament: An In Vivo Kinematic Study With Computer-Aided Design, by Kholinne, Zulkarnain, Lee, Adikrishna, & Jeon, Orth. J. Sports Med. (2018).

Abstract:

Background:
It has been widely accepted that the anterior and posterior bundles of the medial ulnar collateral ligament (MUCL) tighten at extension and flexion, respectively. However, this belief is based on anatomic data acquired from cadaveric studies. The advancement of 3-dimensional (3D) model technology has made possible the simulation of dynamic movement that includes each ligament bundle fiber to analyze its functional properties. To date, no study has analyzed ligament kinematics at the level of the fibers while also focusing on their functional properties.

Purpose:
To propose a new classification for functional properties of the MUCL based on its kinematic pattern.

Study Design:
Descriptive laboratory study.

Methods:
Five healthy elbow joints were scanned by use of computed tomography, and 3D models were rendered and translated into vertex points for further mathematical analysis. The humeral origin and ulnar insertion of the MUCL fiber groups were registered. Each vertex point on the origin side was randomly connected to the insertion side, with each pair of corresponding points defined as 1 ligament fiber. Lengths of all the fibers were measured at 1° increments of elbow range of motion (ROM). Ligament fibers were grouped according to their patterns. Mean coverage area for each group, expressed as the percentage of ligament fibers per group to the total number of fibers, was calculated.

Results:
Four major bundle groups were found based on fiber length properties. Kinematic simulation showed that each group had a different kinematic function throughout elbow ROM. Mean coverage area of groups 1, 2, 3, and 4 was 8% ± 4%, 10% ± 5%, 42% ± 6%, and 40% ± 8%, respectively. Each group acted as a dominant stabilizer in certain arcs of motion. Reciprocal activity was observed between groups 1 and 3 along with groups 2 and 4 to produce synergistic properties of maintaining elbow stability.

Conclusion:
Detailed analysis of fibers of the MUCL allows for further understanding of its kinematic function. This study provides MUCL group coverage area and kinematic function for each degree of motion arc, allowing selective reconstruction of the MUCL according to mechanism of injury.

Clinical Relevance:
Understanding the dominant functional fibers of the MUCL will benefit surgeons attempting MUCL reconstruction and will enhance further anatomic study.

elbow-footprint-registration
(A) Footprint registration for the humeral and ulnar sides of the medial ulnar collateral ligament using the freeform patch function. (B) Selected areas exported into a cloud of vertex points.

Computed methods to convert conventional 2D radiological hindfoot measurements to a 3D setting using weightbearing CT

hindfoot-alignment-3d

Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to a 3D setting using weightbearing CT, by Burssens et al. Int J CARS (2018).

Abstract:

Purpose
The exact radiographic assessment of the hindfoot alignment remains challenging. This is reflected in the different measurement methods available. Weightbearing CT (WBCT) has been demonstrated to be more accurate in hindfoot measurements. However, current measurements are still performed in 2D. This study wants to assess the use of computed methods to convert the former uniplanar hindfoot measurements obtained after WBCT towards a 3D setting.

Methods
Forty-eight patients, mean age of 39.6 ± 13.2 years, with absence of hindfoot pathology were included. A WBCT was obtained, and images were subsequently segmented and analyzed using computer-aided design operations. In addition to the hindfoot angle (HA), other ankle and hindfoot parameters such as the anatomical tibia axis, talocalcaneal axis (TCA), talocrural angle, tibial inclination (TI), talar tilt, and subtalar vertical angle were determined in 2D and 3D.

Results
The mean HA2D was 0.79∘ of valgus ± 3.2 and the HA3D was 8.08∘ of valgus ± 6.5. These angles differed significantly from each other with a P<0.001. The correlation between both showed to be good by a Pearson correlation coefficient (r) of 0.72 ( P<0.001). The ICC3D showed to be excellent when compared to the ICC2D, which was good. Similar findings were obtained in other angles. The highest correlation was seen between the TI2D and TI3D (r = 0.83, P<0.001) and an almost perfect agreement in the TCA3D ( ICC3D=0.99). Conclusion This study shows a good and reliable correlation between the HA2D and HA3D. However, the HA3D overcomes the shortcomings of inaccuracy and provides valuable spatial data that could be incorporated during computer-assisted surgery to assess the multiplanar correction of a hindfoot deformity.

subtalar-vertical-angle
Measurement of the subtalar vertical angle in 3D (SVA3D). a The surface of the posterior facet of the subtalar joint was marked (red contour). The most posterior and anterior point of the marked surface was calculated in the direction of the AP (x-) axis (blue dots). This allowed to determine the length of the posterior facet by a software operated connection of both points. The mid-point of this distance was calculated and used as an origin to fit a plane parallel to the coronal plane at a distance of -5mm, 0mm, and +5mm to mimic, respectively, the posterior, middle, and anterior SVA as described by Colin et al. [9].b The contour of the posterior facet running in themiddle subtalar plane was used to determine the inclination (dashed line) by connecting the calculated most medial with the most lateral point. c The intersection of this subtalar axis with the vertical (z-) axis became the middle SVA. d Depiction of the middle SVA in a 3D hindfoot configuration

Single-use and patient-specific instrumentation can be reliably used in primary total knee arthroplasty

patient-specific-knee

Can a Single-Use and Patient-Specific Instrumentation Be Reliably Used in Primary Total Knee Arthroplasty? A Multicenter Controlled Study, by Abane et al. Arthroplasty (2018)

Abstract

Background
The aim of this controlled multicenter study is to evaluate the clinical and radiologic outcomes of primary total knee arthroplasty (TKA) using single-use fully disposable and patient-specific cutting guides (SU) and compare the results to those obtained with traditional patient-specific cutting guides (PSI) vs conventional instrumentation (CI).

Methods
Seventy consecutive patients had their TKA performed using SU. They were compared to 140 historical patients requiring TKA that were randomized to have the procedure performed using PSI vs CI. The primary measure outcome was mechanical axis as measured on a standing long-leg radiograph using the hip-knee-ankle angle. Secondary outcome measures were Knee Society and Oxford knee scores, operative time, need for postoperative transfusion, and length of hospital stay.

Results
The mean hip-knee-ankle value was 179.8° (standard deviation [SD] 3.1°), 179.2° (SD 2.9°), and 178.3° (SD 2.5°) in the CI, PSI and SU groups, respectively (P = .0082). Outliers were identified in 16 of 65 (24.6%), 15 of 67 (22.4%), and 14 of 70 (20.0%) knees in the CI, PSI, and SU group, respectively (P = .81). There was no significant difference in the clinical results (P = .29 and .19, respectively). Operative time, number of unit transfusion, and length of hospital stay were not significantly different between the 3 groups (P = .45, .31, and 0.98, respectively).

Conclusion
The use of an SU in TKA provided similar clinical and radiologic results to those obtained with traditional PSI and CI. The potential economic advantages of single-use instrumentation in primary TKA require further investigation.

Keywords
total knee arthroplastysingle useinstrumentationpatient specificoutcomes

Level of Evidence
Therapeutic Level II