Effect of infrapatellar nerve block on chronic anterior knee pain after tibial nailing.

Intramedullary nailing is considered to be the treatment of choice for tibia
shaft fractures due to the high union rates, good functional and predictable
results, low infection and deformity rates. Nevertheless, postoperative pain
and discomfort at the anterior aspect of the knee is one of the most frequent
complications after tibial nailing. In a meta-analysis Katsoulis et al report a
mean prevalence of anterior knee pain after tibial nailing of 47.4%. In a
previous study we found a prevalence of 38% in patients treated in our
hospital. It has been attributed to multiple factors such as injury to
cartilage, the retropatellar fat pad, the patellar tendon, and nail protrusion.
No publication has yet provided conclusive data regarding the etiology of
anterior knee pain after tibial nailing and it remains a complex problem.
The medullary canal is best approached on the laterale side of medial
epicondyl. The incision can be vertical, and placed medially or laterally from
the patellar tendon (parapatellar approach). An incision on top of the patellar
tendon is also an possibility (transpatellar approach). The incision can also
be placed horizontal. There is no 'gold standard' for incision placement for
tibial nailing and a vast intersurgical variaty exists. A study comparing the
medial parapatellar and the transpatellar incision showed no difference in
anterior knee pain. No other studies comparing different incisions are known.
Several anatomic structures around the knee are prone to injury during nail
insertion, including the infrapatellar branch of the saphenous nerve. The
infrapatellar nerve arises from the saphenous nerve distal to the adductor
canal. It then courses laterally to cross the patellar tendon in a transverse
way. Cutaneous sensation of the anterior aspect of the knee and the anterior
inferior knee capsule is supplied by the infrapatellar nerve. Iatrogenic injury
to the nerve will result in predictable sensory loss lateral or downstream to
the incision. Additionally, in some individuals neuropathic pain can develop
(hypalgesia, dysesthesia or allodynia). This neuropathic component of the pain
may even persist in the absence of any peripheral noxious stimuli or ongoing
peripheral inflammation. Infrapatellar nerve injury can be caused by surgical
trauma. Sensory disturbances have been reported following arthroscopic and open
knee surgery in the (medial) knee region. Also neuroma formation and reflex
sympathetic dystrophy following infrapatellar nerve injury have been reported.
Injury to the infrapatellar nerve is not widely recognized after tibial
nailing. Only few authors mention infrapatellar nerve injury after this
procedure. In a recent study we showed that injury to infrapatellar nerve was
found in 60% of all patients. In patients with chronic anterior knee pain
significantly more sensory distubnaces were detected.
The position of the infrapatellar nerve changes when the knee is flected. When
a scar has formed after insertion of an intramedullary nail, this sliding
mechanism is disrupted. When the infrapatellar nerve runs through the scar
tissue and the knee is flected, traction on the nerve may cause neuropatic pain
on the anterior aspect of the knee.
A local subcutaneous injection in the scar on the knee with lidocaine will
cause only local anaesthesia of the skin that is supplied by the infrapatellar
nerve. Sensation of the deeper (intra-articular) structures remains intact.
With this intervention an association between chronic anterior knee pain and
involvement of the infrapatellar nerve can be detected. This had not yet been
studied.

To study the effect of a nerve block of the infrapatellar nerve with local
infiltration with lidocaine or saline on chronic anterior knee pain after
tibial nailing.

Secondairy objectives:
- to measure knee pain on a VAS for eight different activities at least six
months after treatment with an intramedullairy nail
- to measure altered sensibility in the dermatome of the infrapatellar nerve
after tibial nailing

A double blind randomised cross over trial with patients treated at St.
Elisabeth Hospital Tilburg, Hospital Gelderse Vallei Ede, Erasmus MC Rotterdam
and Radboudumc Nijmegen.

Patients treated with a tibiashaft fractuur treated with an intramedullary nail
who have knee pain more than six months with a VAS score > 4 for more than
three activities or one activity with a VAS of more than seven. A physical exam
will be performed. All eight activities will be perfomed again, under
supervision.

Prior to the start of the study, patients were randomly assigned to a treatment
sequence, lidocian followed by saline or the other way arounf, by
computer-generated random numbers. A co-worker otherwise not participating in
the study will open the randomisation envelope and prepare a syringe of 5 ml
lidocaine and 5 ml saline. The preparation of the study drug will be done
seperate from the area where the nerve block will be performed to ensure a
complete blinding procedure. The syringes will subsequently be marked according
to the randomization sequence and handed over to the investigator.

After the nerve block patients will again perform all activities listed under
supervision. And this is repeated again after nerve block with the second
fluid.

Nerve block with lidocaine versus placebo medial from the patella (anatomical
position of the proximal part of the infrapatellar nerve).

In total the visit will be approximately 30 minutes.
Lidocaine is a frequently used local anesthetic. Reactions to lidocaine are
characteristic of those associated with other amide-type local anesthetics. A
major cause of adverse reactions to this group of drugs is excessive plasma
levels, which may be due to overdosage, unintentional intravascular injection,
or slow metabolic degradation. The most commonly encountered acute adverse
experiences which demand immediate counter-measures are related to the central
nervous system and the cardiovascular system. These adverse experiences are
generally dose related and due to high plasma levels which may result from
overdosage, rapid absorption from the injection site, diminished tolerance, or
from unintentional intravascular injection of the local anesthetic solution.
Subcutaneous injection with 5 ml of sodiumchloride has negligible risk.