Plating displaced proximal humeral fractures is associated with a high rate of screw perforation. Dynamization of the proximal screws might prevent these complications. The aim of this study was to develop and evaluate a new gliding screw concept for plating proximal humeral fractures biomechanically. Eight pairs of three-part humeral fractures were randomly assigned for pairwise instrumentation using either a prototype gliding plate or a standard PHILOS plate, and four pairs were fixed using the gliding plate with bone cement augmentation of its proximal screws. The specimens were cyclically tested under progressively increasing loading until perforation of a screw. Telescoping of a screw, varus tilting and screw migration were recorded using optical motion tracking.Aims
Methods
The traditional transosseus flexor hallucis longus (FHL) tendon
transfer for patients with Achilles tendinopathy requires two incisions
to harvest a long tendon graft. The use of a bio-tenodesis screw
enables a short graft to be used and is less invasive, but lacks
supporting evidence about its biomechanical behaviour. We aimed,
in this study, to compare the strength of the traditional transosseus
tendon-to-tendon fixation with tendon-to-bone fixation using a tenodesis
screw, in cyclical loading and ultimate load testing. Tendon grafts were undertaken in 24 paired lower-leg specimens
and randomly assigned in two groups using fixation with a transosseus
suture (suture group) or a tenodesis screw (screw group). The biomechanical
behaviour was evaluated using cyclical and ultimate loading tests.
The Student’s Aims
Materials and Methods
The primary stability of the cementless Oxford Unicompartmental Knee Replacement (OUKR) relies on interference fit (or press fit). Insufficient interference may cause implant loosening, whilst excessive interference could cause bone damage and fracture. The aim of this study was to identify the optimal interference fit by measuring the force required to seat the tibial component of the cementless OUKR (push-in force) and the force required to remove the component (pull-out force). Six cementless OUKR tibial components were implanted in 12 new slots prepared on blocks of solid polyurethane foam (20 pounds per cubic foot (PCF), Sawbones, Malmo, Sweden) with a range of interference of 0.1 mm to 1.9 mm using a Dartec materials testing machine HC10 (Zwick Ltd, Herefordshire, United Kingdom) . The experiment was repeated with cellular polyurethane foam (15 PCF), which is a more porous analogue for trabecular bone.Objectives
Materials and Methods
Adolescent idiopathic scoliosis (AIS) is a complex
3D deformity of the spine. Its prevalence is between 2% and 3% in the
general population, with almost 10% of patients requiring some form
of treatment and up to 0.1% undergoing surgery. The cosmetic aspect
of the deformity is the biggest concern to the patient and is often
accompanied by psychosocial distress. In addition, severe curves
can cause cardiopulmonary distress. With proven benefits from surgery,
the aims of treatment are to improve the cosmetic and functional
outcomes. Obtaining correction in the coronal plane is not the only
important endpoint anymore. With better understanding of spinal
biomechanics and the long-term effects of multiplanar imbalance,
we now know that sagittal balance is equally, if not more, important.
Better correction of deformities has also been facilitated by an
improvement in the design of implants and a better understanding
of metallurgy. Understanding the unique character of each deformity
is important. In addition, using the most appropriate implant and
applying all the principles of correction in a bespoke manner is important
to achieve optimum correction. In this article, we review the current concepts in AIS surgery. Cite this article:
The aim of this study was to evaluate two hypotheses. First,
that disruption of posterior bundle of the medial collateral ligament
(PMCL) has to occur for the elbow to subluxate in cases of posteromedial
rotatory instability (PMRI) and second, that ulnohumeral contact
pressures increase after disruption of the PMCL. Six human cadaveric elbows were prepared on a custom-designed
apparatus which allowed muscle loading and passive elbow motion
under gravitational varus. Joint contact pressures were measured
sequentially in the intact elbow (INTACT), followed by an anteromedial
subtype two coronoid fracture (COR), a lateral collateral ligament (LCL)
tear (COR + LCL), and a PMCL tear (COR + LCL + PMCL).Aims
Materials and Methods
Accurate placement of the acetabular component is essential in
total hip arthroplasty (THA). The purpose of this study was to determine
if the ability to achieve inclination of the acetabular component
within the ‘safe-zone’ of 30° to 50° could be improved with the
use of an inclinometer. We reviewed 167 primary THAs performed by a single surgeon over
a period of 14 months. Procedures were performed at two institutions:
an inpatient hospital, where an inclinometer was used (inclinometer
group); and an ambulatory centre, where an inclinometer was not
used as it could not be adequately sterilized (control group). We excluded
47 patients with a body mass index (BMI) of > 40 kg/m2,
age of > 68 years, or a surgical indication other than osteoarthritis
whose treatment could not be undertaken in the ambulatory centre.
There were thus 120 patients in the study, 68 in the inclinometer
group and 52 in the control group. The inclination angles of the acetabular
component were measured from de-identified plain radiographs by
two blinded investigators who were not involved in the surgery.
The effect of the use of the inclinometer on the inclination angle
was determined using multivariate regression analysis.Aims
Patients and Methods
It is important to consider sagittal pelvic rotation when introducing
the acetabular component at total hip arthroplasty (THA). The purpose
of this study was to identify patients who are at risk of unfavourable
pelvic mobility, which could result in poor outcomes after THA. A consecutive series of 4042 patients undergoing THA had lateral
functional radiographs and a low-dose CT scan to measure supine
pelvic tilt, pelvic incidence, standing pelvic tilt, flexed-seated
pelvic tilt, standing lumbar lordotic angle, flexed-seated lumbar
lordotic angle, and lumbar flexion. Changes in pelvic tilt from
supine-to-standing positions and supine-to-flexed-seated positions
were determined. A change in pelvic tilt of 13° between positions was
deemed unfavourable as it alters functional anteversion by 10° and
effectively places the acetabular component outside the safe zone
of orientation.Aims
Patients and Methods
The posterior malleolus of the ankle is the object
of increasing attention, with considerable enthusiasm for CT scanning
and surgical fixation, as expressed in a recent annotation in Cite this article:
The best method of treating unstable pelvic fractures that involve
the obturator ring is still a matter for debate. This study compared
three methods of treatment: nonoperative, isolated posterior fixation
and combined anteroposterior stabilization. The study used data from the German Pelvic Trauma Registry and
compared patients undergoing conservative management (n = 2394),
surgical treatment (n = 1345) and transpubic surgery, including
posterior stabilization (n = 730) with isolated posterior osteosynthesis
(n = 405) in non-complex Type B and C fractures that only involved the
obturator ring anteriorly. Calculated odds ratios were adjusted
for potential confounders. Outcome criteria were intraoperative
and general short-term complications, the incidence of nerve injuries,
and mortality.Aims
Patients and Methods
In order to address acetabular defects, porous metal revision acetabular components and augments have been developed, which require fixation to each other. The fixation technique that results in the smallest relative movement between the components, as well as its influence on the primary stability with the host bone, have not previously been determined. A total of 18 composite hemipelvises with a Paprosky IIB defect were implanted using a porous titanium 56 mm multihole acetabular component and 1 cm augment. Each acetabular component and augment was affixed to the bone using two screws, while the method of fixation between the acetabular component and augment varied for the three groups of six hemipelvises: group S, screw fixation only; group SC, screw plus cement fixation; group C, cement fixation only. The implanted hemipelvises were cyclically loaded to three different loading maxima (0.5 kN, 0.9 kN, and 1.8 kN).Objectives
Methods
The aim of this prospective study was to evaluate the intermediate-term
outcomes after revision anatomical ankle ligament reconstruction
augmented with suture tape for a failed modified Broström procedure. A total of 30 patients with persistent instability of the ankle
after a Broström procedure underwent revision augmented with suture
tape. Of these, 24 patients who were followed up for more than two
years were included in the study. There were 13 men and 11 women.
Their mean age was 31.8 years (23 to 44). The mean follow-up was 38.5
months (24 to 56) The clinical outcome was assessed using the Foot
and Ankle Outcome Score (FAOS) and the Foot and Ankle Ability Measure
(FAAM) score. The stability of the ankle was assessed using stress
radiographs.Aims
Patients and Methods
The aim of this retrospective multicentre study was to evaluate
mid-term results of the operative treatment of Monteggia-like lesions
and to determine the prognostic factors that influence the clinical
and radiological outcome. A total of 46 patients (27 women and 19 men), with a mean age
of 57.7 years (18 to 84) who had sustained a Monteggia-like lesion
were followed up clinically and radiologically after surgical treatment.
The Mayo Modified Wrist Score (MMWS), Mayo Elbow Performance Score
(MEPS), Broberg and Morrey Score, and Disabilities of the Arm, Shoulder
and Hand (DASH) score were used for evaluation at a mean of 65 months
(27 to 111) postoperatively. All ulnar fractures were stabilized
using a proximally contoured or precontoured locking compression
plate. Mason type I fractures of the radial head were treated conservatively, type
II fractures were treated with reconstruction, and type III fractures
with arthroplasty. All Morrey type II and III fractures of the coronoid
process was stabilized using lag screws.Aims
Patients and Methods
Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain. A total of 16 composite tibias were implanted with an Oxford Domed Lateral Partial Knee implant using cutting guides to define tibial slope and resection depth. Four implant positions were assessed: standard (5° posterior slope); 10° posterior slope; 5° reverse tibial slope; and 4 mm increased tibial resection. Using an electrodynamic axial-torsional materials testing machine (Instron 5565), a compressive load of 1.5 kN was applied at 60 N/s on a meniscal bearing via a matching femoral component. Tibial strain beneath the implant was measured using a calibrated Digital Image Correlation system.Objectives
Methods
Little biomechanical information is available about kinematically aligned (KA) total knee arthroplasty (TKA). The purpose of this study was to simulate the kinematics and kinetics after KA TKA and mechanically aligned (MA) TKA with four different limb alignments. Bone models were constructed from one volunteer (normal) and three patients with three different knee deformities (slight, moderate and severe varus). A dynamic musculoskeletal modelling system was used to analyse the kinematics and the tibiofemoral contact force. The contact stress on the tibial insert, and the stress to the resection surface and medial tibial cortex were examined by using finite element analysis.Objectives
Materials and Methods
To assess the effect of high tibial and distal femoral osteotomies
(HTO and DFO) on the pressure characteristics of the ankle joint. Varus and valgus malalignment of the knee was simulated in human
cadaver full-length legs. Testing included four measurements: baseline
malalignment, 5° and 10° re-aligning osteotomy, and control baseline
malalignment. For HTO, testing was rerun with the subtalar joint
fixed. In order to represent half body weight, a 300 N force was applied
onto the femoral head. Intra-articular sensors captured ankle pressure.Aims
Materials and Methods
The aim of this study was to investigate the effect of a posterior
malleolar fragment (PMF), with <
25% ankle joint surface, on
pressure distribution and joint-stability. There is still little
scientific evidence available to advise on the size of PMF, which
is essential to provide treatment. To date, studies show inconsistent
results and recommendations for surgical treatment date from 1940. A total of 12 cadaveric ankles were assigned to two study groups.
A trimalleolar fracture was created, followed by open reduction
and internal fixation. PMF was fixed in Group I, but not in Group
II. Intra-articular pressure was measured and cyclic loading was
performed.Aims
Materials and Methods
Loss of motion following spine segment fusion results in increased strain in the adjacent motion segments. However, to date, studies on the biomechanics of the cervical spine have not assessed the role of coupled motions in the lumbar spine. Accordingly, we investigated the biomechanics of the cervical spine following cervical fusion and lumbar fusion during simulated whiplash using a whole-human finite element (FE) model to simulate coupled motions of the spine. A previously validated FE model of the human body in the driver-occupant position was used to investigate cervical hyperextension injury. The cervical spine was subjected to simulated whiplash exposure in accordance with Euro NCAP (the European New Car Assessment Programme) testing using the whole human FE model. The coupled motions between the cervical spine and lumbar spine were assessed by evaluating the biomechanical effects of simulated cervical fusion and lumbar fusion.Objectives
Methods
Secondary fracture healing is strongly influenced by the stiffness of the bone-fixator system. Biomechanical tests are extensively used to investigate stiffness and strength of fixation devices. The stiffness values reported in the literature for locked plating, however, vary by three orders of magnitude. The aim of this study was to examine the influence that the method of restraint and load application has on the stiffness produced, the strain distribution within the bone, and the stresses in the implant for locking plate constructs. Synthetic composite bones were used to evaluate experimentally the influence of four different methods of loading and restraining specimens, all used in recent previous studies. Two plate types and three screw arrangements were also evaluated for each loading scenario. Computational models were also developed and validated using the experimental tests.Objectives
Methods
