Investigating bilateral symmetry of the human wrist joint and clinical relevance

Wrist problems are responsible for a significant social-economic problem for
employers and the community. Complaints about the wrist are a reason for long
absence periods from work. This has substantial financial consequences due to
workers compensation, medical expenses, and productivity losses. Malfunctioning
of the wrist often leads to reduced quality of life and has profound
consequences for the involved patients. Due to the complex anatomy, treatment
of wrist injuries is often very difficult. Treatment outcomes are variable by
lack of quantitative data. Therefore it is of great importance for the patient
and the medical doctor to have a clear understanding of the exact anatomy for
ensuring optimal patient care.

The anatomy of the wrist joint is probably the most complex of all the joints
in the body. It consists of two long bones (the radius and the ulna) and two
rows of four small bones (the eight carpal bones). Hand surgeons are just
beginning to realize in how many ways the wrist can be injured. In the
literature there are already numerous studies that report anatomical databases,
including in vivo kinematic data as well as the bone anatomy. Different
morphologic patterns of anatomy in the wrist bones have been identified and
classified. Still there is unknown data that requires further research for the
sake of new techniques in treating wrist problems. One of the new techniques in
wrist surgery is computer-assisted correction osteotomy for malunions of the
distal radius.

Fractures of the distal radius constitute about one sixth of all fractures seen
in the emergency room. Union with deformity (malunion) is the most common
complication after a distal radius fracture. This can cause pain, arthrosis,
reduced range of motion, reduced grip strength, carpal instability, cosmetic
deformity, late neuropathy, or tendon rupture. Sometimes a corrective osteotomy
is required to restore normal function. This procedure involves cutting the
distal radius near its original fracture site, improve the position of the
radius, followed by fixation of this new situation. Often this new situation is
supported by a bone graft and a fixation plate. A corrective osteotomy should
correct all components of the malunion, not only the angular deformities and
the shortening but also the distal fragment shifts. There is a clear
correlation between the accuracy of reconstruction of the anatomy of the wrist
and its eventual function. For optimal outcome, proper planning is important.

Lately, patient-specific treatment techniques for malunions of the distal
radius are introduced in the literature, in which the malunited wrist is
realigned to match the unaffected wrist. For this technique computer-assited
three-dimensional modelling is used. One advantage of using three-dimensional
modelling is planning of rotations in three dimensions. A preoperative plan is
made by obtaining CT scans of both forearms. A computer provides
three-dimensional reconstruction and creates virtual models of both radii. By
comparison of the deformed distal end of the radius with a similar model of the
uninjured wrist, values are calculated for the angles and lengts to be
corrected by osteotomy. By using the preoperative planner a virtual osteotomy
can be conducted and the malunited distal radius fragment is realigned to best
fit the surface geometry of the unaffected template wrist. In this way the hand
surgeon can calculate the displacements which need to be achieved.

Appreciation and knowledge of the patient-specific anatomy of the wrist is
crucial for pre-operative planning in the treatment of distal radius malunion.

Despite of the growing knowledge about the anatomy of the human wrist joint,
little is known about its bilateral symmetry. Naturally there is an anatomical
variation in wrists between individuals. But lately, in literature the
assumption is made that there could be a symmetry between the right and left
forearm in each individual. Obviously, the idea of using the correct
measurements of the patients own healthy wrist seems better than using the
common standardized measurements for the angles and length of the radius. An
anatomic study is necessary since the question if there is a high grade of
bilateral symmetry of the wrist joint is of great clinical relevance.

Aforementioned studies on new techniques in correction osteotomy for malunions
of the distal radius propose methods where the uninjured wrist could serve as a
model for the affected wrist. This new approach could mean a break-through in
the research on treatment of distal radius malunions. However, the assumption
that there is indeed a symmetry between the left and right radius is not based
on scientific evidence. Since the analysis about the bilateral symmetry of the
radius is valuable information, we would like to perform an anatomical study to
examine if the assumption is justly.

Because not only the radius, but all the other bones in the wrist joint are
important too in various wrist injuries, we plan on analysing the whole
forearm, including also the ulna and carpal bones. In this way we can collect
important data and create a basis for further research in future studies on
treating distal radius malunion and other surgical procedures as well. The
information about bilateral symmetry is also useful to evaluate changes in
anatomy that occur during trauma or other diseases of the wrist, next to distal
radius malunion. In addition we can study if there is an influence of right- or
left-handedness on the final length and shape of the wrist bones.

Relevance for science, technology or society
This research will contribute to a greater understanding of the anatomy and
common changes in the anatomy of the wrist. This is crucial for the design and
execution of new improved surgical procedures for various wrist abnormalities.
The goal of this study is to investigate the bilateral symmetry in the human
wrist and it*s clinical applicability. Todays hand surgeon has to remain up to
date on the expanding information base, this information will allow for a
better understanding and treatment of injuries of the wrist. Better operative
techniques will improve the quality of care, the quality of life for the
involved patients, and will reduce the lost working time. In the end, this will
reduce the societies expenses due to workers compensation, medical expenses,
and productivity losses. Since the functionality of the hand is essential in
almost any professional environment, improvement of wrist functionality will
have a direct impact on the economic value as well as the social functioning of
the patient involved.

The aim of this study is to investigate the bilateral symmetry of the human
wrist joint and its clinical applicability. The analysis of the bilateral
symmetry of the wrist is of great clinical relevance. If there appears to be a
high grade of bilateral symmetry, it could mean a break-through in the research
on treatment of various wrist abnormalities. We hope to gain valuable
anatomical information and to create a basis for further research in studies on
various wrist pathology and surgical techniques.

This study is a descriptive laboratory study and anatomical study. The aim is
to gain valuable anatomical information about the wrist joint. Regular dose CT
scans of both forearms are obtained (2 scans in total). Then scans will be
compared with 3D matching software to evaluate the bilateral symmetry of the
forearm.

The radiation exposure of scans is estimated to be 0,26 mSv for each
participant. This is comparable to 6 weeks background exposure to the natural
radiation in The Netherlands.