Rhizarthrosis is an osteoarthritis of the thumb saddle joint. The thumb saddle joint or simply saddle joint is located at the base of the thumb; it is formed by the saddle-shaped polygon leg belonging to the carpal and the base of the first metacarpal bone, which sits like a rider on the saddle. The wide, loose capsule of the joint gives the saddle joint the freedom of movement of a ball joint, whereby the thumb can be opposed to the other fingers and spread outwards. Due to the heavy stress on the joint, it can be explained that the joint wears off and arthrosis develops (rhizarthrosis).
Rhizarthrosis: a common disease
Rhizarthrosis is the most common finger and wrist osteoarthritis and affects men and preferably women over the age of 50 years. Hormonal influences play a role, but also genetic factors, because a familial accumulation is clearly established.
Mechanical overload of the thumb saddle joint, more rarely a rheumatic disease (chronic polyarthritis) or poorly healed fracture with joint involvement can then lead to increased wear of the articular cartilage and be the cause of osteoarthritis.
If additional finger joint arthrosis occurs, it is called polyarthrosis.
Origin of a rhizarthrosis
As with other arthrosis, there is a gradual change in the cartilage with cracking and cartilage degeneration due to high joint loading or pre-damage. An accompanying reaction of the joint capsule is inflammatory joint irritation with joint effusion, which in turn promotes cartilage degradation.
Finally, when the cartilage is almost completely degraded, bone rubs on bone, a painful restriction of movement is the result. Bone remodeling processes (osteophytes) are the result of remodeling of the bone and thickening of the bone near the joint occurs with narrowing of the joint space.
Symptoms: pain and decreased strength
In the foreground of the complaints are pains that are located in the lower part of the thumb bale at the transition to the carpal. In the initial stage, the pain is mainly noticeable under load, for example when opening screw caps or wringing out of cleaning rags. In these everyday activities, the reduced power when gripping falls on.
In addition, a swelling in the area of the saddle joint is recognizable and more and more noticeable is that the thumb can be spread less. The thumb is pulled (in adduction) and is slightly bent.
The radiograph clarifies the diagnosis
The medical examination shows a bulge of the saddle joint and misalignment to the rear; the spread of the thumb is limited. The diagnosis of osteoarthritis of the thumb saddle joint is clearly clarified by the X-ray image, which shows a narrowed joint space.
The radiologist distinguishes between four stages of rhizarthrosis depending on the extent of the malposition of the joint and the joint wear, which is indicated by the bony attachments and the width of the joint space.
Since articular arthrosis often occurs in conjunction with carpal tunnel syndrome, there should be an additional neurological examination for nocturnal pain and numbness.
Immobilization and anti-inflammatory
A healing of a rhizarthrosis is not possible, but a relief of discomfort and improvement of mobility. In the foreground of conservative treatment is to stop the inflammatory process in the joint.
This includes the protection and immobilization of the joint with tapes and special braces (orthoses), which are worn under stress and at night, administration of anti-inflammatory and analgesic anti-inflammatory drugs (NSAIDs) and physical therapy.
This is done by:
In case of severe discomfort injections of local anesthetics or cortisone may induce a longer relief of the discomfort; However, you should be sparing with such injections into the joint, as there is a risk of infection.
Surgery for persistent complaints
If the symptoms do not respond to these measures or if there is already an overstretching in the adjacent metacarpophalangeal joint, one should think about an operation. There are a number of different procedures available, which are presented in detail below:
- Resection Suspensionsarthroplastik
- Artificial saddle joint (prosthesis)
In this most common and proven surgical procedure, the polygon (trapezium) is removed, and then part of the adjacent wrist flexor tendon is connected to the metacarpal bone of the thumb to fill the cavity and provide better stability.
The approximately one-hour operation has good to very good results in long-term studies. It is performed either under general anesthesia or with anesthesia of the brachial plexus (plexus anesthesia). The follow-up treatment is immobilization with a plaster splint for two weeks and subsequent treatment with a thumb bandage for four weeks.
Then mobilization through physiotherapy and occupational therapy takes place over six weeks. After about three to six months, the old strength and flexibility usually returns, usually without pain.
Artificial saddle joint (prosthesis)
For implantation there is a choice between partial and complete dentures made of plastic, silicone or metal. The immobilization in this case only takes four weeks before the physiotherapeutic treatment can begin.
The disadvantage of this method, however, is the risk of loosening or fracture of the prosthesis, and the period for a final assessment is still too low.
Arthroscopy in case of rhizarthrosis
In the initial stage of rhizarthrosis, the inflammatory process in the joint can be stopped by ablating inflammatory tissue and smoothing the articular surface during arthroscopy. At the same time, the dissipating pain fibers can be severed, so that the perception of pain is reduced.
The more extensive resection-suspension arthroplasty can be postponed by several years, because the rhizarthrosis can not be completely eliminated with this measure.