Joint distraction for thumb base osteoarthritis

Carpometacarpal 1 (CMC1) osteoarthritis affects 36% of people over 55 years and
is more prevalent in woman. Established OA of the CMC1 joint severely affects
hand function due to pain, weakness, and deformity, all resulting in marked
disability. Most patients are forced to make adjustments to work and leisure
activities.
In early phases in the progression of CMC1 osteoarthritis, conservative
treatment methods can bring relief to some patients. However, for some other
patients symptom relief with these non-operative managements is inadequate or
only temporary. The majority of progressive cases eventually requires some form
of operative intervention to regain functionality. In the past decades, a
multitude of surgical interventions have been proposed and used. However, no
single operative technique has gained fully satisfactory results.
In recent years, joint distraction has been proven a very adequate, minimally
invasive method to treat osteoarthritis in knees and ankles. This novel and
very promising approach to osteoarthritis has not yet been applied to the
common problem of thumb base osteoarthritis.

To evaluate the effect of CMC1 joint distraction in patients with failed
conservative treatment of Eaton Littler grade II or III CMC osteoarthritis.
The hypothesis is that results will mirror those in knee and ankle joint
distraction, yielding reduced pain and improved functionality based on
(partial) cartilage regeneration, as measured by the MHQ and DASH
questionnaire, VAS score, strength and range of motion. In these cases,
invasive surgery (trapezectomy/ prosthesis/arthrodesis) may be delayed or
prevented.

A pilot study (pilot I) of 5 patients will precede a non-randomised,
non-blinded, prospective study (pilot II) with 15 patients with a 1-year follow
up period.

A standard hand distraction device will be placed over the affected CMC1 joint
under regional or general anesthesia. The external fixator will be anchored
transcutaneously with 2 proximal pins in the trapezium and two distal pins in
the first metacarpal, thus bridging the CMC1 joint. Intra-operatively the joint
will be distracted 1.0 mm. Postoperatively, patients will distract the joint
themselves by 0.5 mm/day, until a total distraction of 3.0 mm is reached four
days later. This will be checked on X-ray. The distractor is left in situ for a
total period of 8 weeks. To protect the distractor and to prevent
inconveniences to the patient due to the distractor, a custom made brace will
be fitted to cover the distractor. Hygiene instructions regarding pin entry
point maintenance will be given and evaluated during postoperative visits.
After 8 weeks the frame is removed in the outpatient clinic, followed by
standard care physical therapy.

Clinic visits
Patients will be requested to visit the outpatient clinic preoperatively, every
2 weeks during the distraction therapy and at 3, 6 and 12 months
postoperatively. These clinic visits are in accordance to the standard hand
surgery follow up visits and are not altered for study participation. At clinic
visits, patients are asked to fill out questionnaires (VAS, MHQ and DASH). At
these visits, patients will also be seen by a hand therapist for measurements
of strength and range of motion.
Surgical treatment and postoperative care
Added burden associated with study participation is the 8 weeks of distractor
presence instead of 4 weeks of plaster of Paris which is the norm for invasive
surgery. A potential risk is that of disappointing results of the distractor
treatment. In these cases, the initially indicated invasive surgical procedure
can still be performed, albeit with delay caused by study participation.
Standard X-ray imaging will be done at clinic visits pre-operatively,
perioperatively, during distraction therapy (every 2 weeks), after distractor
removal at 8 weeks, and at 3, 6 and 12 months postoperatively.
Complications associated with distractor treatment
Participation risks are associated with the placement and presence of the
distractor device. All potential complications are expected to occur in the
same prevalence as those known for established therapies such as metacarpal
bone distraction or external fixation of comminuted fractures of the hand.
These potential complications include:
1. pin tract infections. Incidence of pin tract infections in hand fractures is
6% according to the literature. Patients will be educated daily distractor
hygiene routines. At clinic visits the presence of infections is evaluated. In
the very unlikely case of a severely neglected pin tract infection, progression
into osteomyelitis of the trapezium or first metacarpal could occur. Early and
established pin tract infections can be adequately treated with oral and local
antibiotics.
2. Loosening or dislodging of the device due to direct external forces. To
prevent snagging or bumping of the distractor device, a customized
thermoplastic splint is fashioned directly after placement of the device to
provide cover and protection. If for any reason the device is loosened or
dislodged, re-fixation or removal will follow varying per case.
3. disappointing result. In case distraction therapy yields insufficient
results, the established options of invasive surgery will still be possible.
Study participation is not expected to influence results of the chosen invasive
surgery procedure, albeit the timing procedure will have been postponed for
study participation.