| Abstract |
Background: Hip fracture is the general term for fracture of the
proximal (upper) femur. Extracapsular fractures are further defined as those
fractures that traverse the femur within the area of bone bounded by the
intertrochanteric line proximally up to a distance of five centimetres below
the distal part of the lesser trochanter .
The incidence of fractures of the proximal femur shows an increase as
the population ages. It is estimated that 1.26 million hip fractures occurred in
adults in 1990, with predictions of numbers rising to 7.3–21.3 million by
2050. These fractures are an economic burden because they occur in patients
with co-morbidities which influence the quality of life of the patients and
also increase the cost of treatment for the health systems.
Facing this problem the evidence-based literature supports surgical
fixation and immediately mobilization with the exception of medically
unstable patients who must be treated nonsurgically. Operative treatment of
extracapsular hip fractures was introduced in the 1950s using a variety of
different implants that may be either extramedullary or intramedullary in
nature.
Two types of implant are used in the treatment of patients with
intertrochanteric hip fracture: an SHS with a side plate, and an
intramedullary (IM) nail with an SHS co The sliding hip screw has been a
gold standard of treatment for low-energy intertrochanteric fractures with
good results overall. However, fracture collapse, medialization of the femur,
and limb shortening are the known complications related to this type of
fixation. Cephalomedullary nails are biomechanically superior for load
transfer and have a biological advantage as minimal invasive techniques can
be used for implantation; both advantages are thought to relate to a shorter
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healing and recovery times with improved functional outcome. There is,
however, a risk of iatrogenic fracture, additional fracture comminution
during nail insertion, and of suboptimal closed fracture reduction.
Up to date there is lack of consensus between the surgeons regarding the
appropriate treatment for intertrochanteric hip fractures. On the other hand,
improvements in nail design and increasing surgeon experience with
intramedullary implants have almost equalized the difference in
complications or revision rates between the two types of implants.
Aim: The purpose of this study was to compare a new dual lag screw
cephalomedullary nail with the classic sliding hip screw for the treatment of
low-energy extra-capsular fractures of the hip in the elderly. In the first part
of this study the two implants were compared biomechanically at the
Biomechanics Laboratory, Legacy Research & Technology Center, Portland,
Oregon 97215, USA in collaboration with the Trauma & Orthopaedic
Surgery School Of Medicine, University of Leeds, Leeds General Infirmary,
Great George Street, Leeds, LS1 3EX, UK. In the second part a randomized
prospective study was design comparing the two fracture fixation implants
and was conducted at the department of Orthopaedics & Traumatology at the
University Hospital of Crete.
Results: Five dual lag screw implants (Endovis, Citieffe) and five single
lag screw implants (DHS, Synthes) were tested in the Hip Implant
Performance Simulator (HIPS) of the Legacy Biomechanics Laboratory.
This model simulated osteoporotic bone, an unstable fracture, and biaxial
rocking motion representative of hip loading during normal gait. All
constructs were loaded up to 20,000 cycles of 1.45 kN peak magnitude
under biaxial rocking motion. The migration kinematics was continuously
monitored with 6-degrees of freedom motion tracking system and the
number of cycles to implant cut-out was recorded.
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The dual lag screw implant exhibited significantly less migration and
sustained more loading cycles in comparison to the DHS single lag screw.
All DHS constructs failed before 20,000 cycles, on average at 6,638 ± 2,837
cycles either by cut-out or permanent screw bending. At failure, DHS
constructs exhibited 10.8 ± 2.3° varus collapse and 15.5 ± 9.5° rotation
around the lag screw axis. Four out of five dual screws constructs sustained
20,000 loading cycles. One dual screw specimens sustained cut-out by
medial migration of the distal screw after 10,054 cycles. At test end, varus
collapse and neck rotation in dual screws implants advanced to 3.7 ± 1.7°
and 1.6 ± 1.0°, respectively.
One hundred and sixty-five patients with low-energy intertrochanteric
fractures, classified as AO/OTA 31A, were prospectively included during a
2-year period (2005–2006). Patients were randomized into two groups:
group A included 79 hip fractures managed with sliding hip screws and
group B included 86 fractures treated with cephalomedullary nails. Delay to
surgery, duration of surgery, time of fluoroscopy, total hospital stay,
implant-related complications, transfusion requirements, re-operation
details, functional recovery, and mortality were recorded. The mean followup
was 36 months (24–56 months). The mean surgical time was statistically
significantly shorter and fluoroscopy time longer for the group B. No
intraoperative femoral shaft fractures occurred. There was no statistically
significant difference in the functional recovery score, reoperation, and
mortality rates between the 2 groups. A new type of complication, the socalled
Z-effect phenomenon, was noticed in the cephalomedullary nail
group.
Conclusion: The single and double lag screw implants demonstrated a
significantly different migration resistance in surrogate specimens under gait
loading simulation with the HIPS model. In this model, the double screw
construct provided significantly greater resistance against varus collapse and
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neck rotation in comparison to a standard DHS lag screw implant. In
contrary to biomechanical advantages of two lag screw implants there are no
statistically significant differences between the two techniques in terms of
type and rate of complications, functional outcome, reoperation and
mortality rates when comparing the SHS and the cephalomedullary nail for
low energy AO/OTA 31A intertrochanteric fractures. Our data do not
support recommendations for the use of one implant over the other
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