Initial results of the Anser: A novel intramedullary device for fixation of midshaft clavicle fractures.
An explorative case series

Rationale & Background information

Fractures of the clavicle are common, comprising up to 5% of all fractures in
adults [1]. Most clavicle fractures are localized at the level of the
mid-diaphyseal third [2].
Because of the specific sigmoid shaped anatomy and muscle insertions the
majority of these fractures are displaced and/or shortened. These two features
have been found to be poor predictors of outcome concerning non-unions,
persistent posttraumatic symptoms and cosmetics in conservatively treated
mid-shaft clavicle fractures. (MSCF). [3,4,5].
For this reason lately the tendency has been to surgically reduce and fixate
MSCF. Currently the gold standard for these operations is fixation by using a
(angle-stable) plate and screws. This method creates a rigid fixation of the
fracture elements and aims for primary bone healing. It re-establishes and
maintains the normal length and alignment of the clavicle. Patients are able to
quickly start rehabilitating. There have been reports that plate fixation leads
to better rates of union, less mal-unions and increased patient satisfaction in
comparison to conservative therapy [6,7]. The downsides of this procedure are a
large incision with subsequent scarring, neuropathy of the supraclavicular
nerve and increased risk of infection. Hardware irritation necessitating a
secondary operative intervention of 21-80% have been reported [8,9].

Another frequently used technique to reduce and align MSCF is applying
intramedullary devices. These devices are rigid pins (Hagie, Knowles, Rockwood)
(Zimmer Biomet), flexible pins such as titanium elastic nails (TEN)
(Depuy/Synthes) or partially flexible devices such as the CRX Collarbone Pin
(Sonoma Orthopedic Products).
The rigid and partially flexible devices aim for primary bone healing and
require an inside-out open reduction operative technique which means loss of
the fracture hematoma, increased risk of infection and scar over the fracture.
It has produced a variety of results concerning functional outcomes and
complication rates [10-12]. Millet et al. reports nonunion rates up to 8.6%.
All Rockwood Pins are removed during a second intervention [10-12].

The TEN aims for secondary fracture healing by not evacuating the fracture
hematoma with all its bone healing substances. Closed reduction rates are
reported between 29-93% are reported [13,14] but are generally around 50-60%
[15-20]. Good results have been reported using TEN concerning functional
outcomes and nonunion rates [21-23]. TEN is minimally invasive; it requires
smaller incisions. Because of the flexibility of TEN it allows itself to follow
the shape of the clavicle and re-align the fractured clavicle. The downside of
TEN is that they do not protect the MSCF from secondary shortening and
subsequently forming of a, possibly symptomatic, malunion. Secondary shortening
>5mm is reported to be up to 37.5% [17,18,24]. Another negative feature of TEN
is implant migration because the device is not fixated within the clavicle.
This leads to revision rates described between 0-35.3% [16,22]. Hardware
removal, in general, is performed after union in 100% of cases [14,15, 20-24].


The Anser is a novel device for the intramedullary fixation of the fractured
clavicle aiming to combine the pros of both plate and intramedullary devices
into one. Its goal is to reduce the clavicle and preserve its length in a
minimally invasive manner. Its design consists of a flexible base pin
fabricated from a titanium alloy that has the capabilities to follow the
sigmoid-shaped intramedullary canal. The pin has a blunted tip to prevent
perforation and a self-tapping screw thread to fixate within the bone on the
medial side of the fracture. On the lateral side the base pin has a plurality
of indentations that allow the surgeon to decide on the correct length of the
clavicle and the pin intra-operatively. The lateral fixation is anchored by the
lateral fixation device which screws itself into the cortical bone on the
lateral side and at the same time fixes itself around the base pin in one of
the previously mentioned indentations. This position is then secured by the
endcap. To prevent friction on the implant during rotation of the clavicle
around its axial axis during motion of the arm, the lateral fixation device
will allow rotation around the base pin whilst continuing to secure its
appropriate length. The system creates an intramedullary internal fixator. It
is hypothesized that due to its design, in the majority of cases, does not need
hardware removal, leading to a decline in re-operations and costs compared to
the current devices used.

References

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The goals of this study are to evaluate the initial performance, safety and
functional results of the Anser; A novel intramedullary device for fixation of
midshaft clavicle fractures.
The primary outcome measures will be union rate, complication rate and
functional outcome scores.
Secondary outcomes will be closed reduction rate, operative time,
image-intensifier time, hospital stay, incision length, time to radiological
union, pain, re-operation, health related quality of life and cosmetic
satisfaction.

Prospective consecutive post-market case series. Therapeutic study. 3 Dutch
hospitals are involved which are the Radboud university medical center (RUMC),
Rijnstate Arnhem (RA) and Admiraal de Ruyter Ziekenhuis Goes (AdR). RUMC is a
Level 1 trauma center. RA and AdR are Level 2 trauma centers. Participating
departments will be those of Orthopedics and Trauma Surgery.
The primary outcome measures will be union rate, complication rate and
functional outcome scores.
Secondary outcomes will be closed reduction rate, operative time,
image-intensifier time, hospital stay, incision length, time to radiological
union, pain, re-operation, health related quality of life and cosmetic
satisfaction.
Follow up will be at 12 months. Early results will be reported after 3 months.

The surgical technique for the Anser will be as described in the implant
brochure. Patients are administered prophylactic antibiotics. With a general
anesthetic, the patient is placed in a beach-chair position with the arm draped
freely. The anatomic landmarks of the shoulder will be identified and marked.
The image-intensifier in positioned in such a way that is possible to image the
entire clavicle in two planes. The lateral entry point at the posterior aspect
of the conoid process is identified. A stab incision is made and soft tissues
are spread until the conoid process is in sight. The intramedullary canal
opened using a pointed drill and tissue protector. The base pin is implanted
using the pindriver or hand-held pindriver. Once the base pin reaches the
fracture site closed reduction is attempted using percutaneous clamps. The base
pin is passed through the medial fragment. The last centimeters towards the
sterno-clavicular joint the hand-held pindriver is used. Once adequate grip is
obtained the base pin is in place. Positioning of the base pin is checked using
the image intensifier in two planes. With a cannulated tap the lateral cortex
is prepared for the lateral fixation device. Placement of the lateral fixation
device. Reduction of the checked and secured by placement of the endcap. The
pin is cut flush to the endcap. Irrigation of the wound followed by closure of
the skin. After coverage of the wound a sling is applied. Post-operatively an
X-ray in two planes will be made.

Postoperatively, patients are given a sling but are encouraged to start with
pain-dependent mobilization after 1 week and to discard the sling as soon as
possible thereafter. Load bearing is not recommended before osseous
consolidation. After 2 weeks passive guided exercises will be prescribed by a
physical therapist. Patients are advised to take pain medication when
necessary. The patient is requested to record - on a daily basis immediately
following surgery - the pain experienced as well as the type and amount of
analgesics used. Pain is assessed with a VAS pain 10-point scale (0 = no pain
and 10 = extremely painful).

3 additional outpatient clinic visits. 2 x 2 additional X-rays. It is
hypothesized less re-operations and less complications will occur compared to
the numbers described in current literature in which current fixation devices
are used.