Rapid carpal collapse after nonoperative extra-articular distal radius fracture treatment
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A 72-year-old woman was originally seen by her primary care physician for left wrist pain after a ground level fall. Due to persistent pain and swelling, the patient underwent radiographs.
Imaging demonstrated an extra-articular distal radius fracture (DRF) with acceptable alignment in the coronal and sagittal planes (Figure 1). Chondrocalcinosis throughout the proximal row of the carpus, as well as moderate dorsiflexion of the lunate, was also noted. The patient was referred to and evaluated by a board-certified orthopedic hand surgeon at 1 week from time of injury. Radiographs of the left wrist again demonstrated an extra-articular DRF with maintained radial height and inclination, minimal dorsal tilt and continued dorsiflexion of the lunate (Figure 2). She was placed into a short arm cast with plans for nonoperative management.
Source: Nader Shourbaji, MD
Three weeks later, the patient returned to clinic with improved wrist pain. There was interval callus formation on radiographs with maintained radial inclination and height. The dorsal tilt slightly increased with worsening dorsiflexion of the lunate and dorsal subluxation of the capitate (Figure 3). At 6 weeks from time of injury, the patient was transitioned into a removable wrist brace. She began working with occupational therapy on range of motion and strengthening. The patient denied tenderness to palpation over the carpus or the distal radius. Her radiographs demonstrated a healed DRF with severe carpal instability (Figure 4).
What would you expect to see on follow-up imaging?
See answer below.
Radiographic follow-up, effective radiolunate flexion calculation
We analyzed the wrist radiographs from each follow-up appointment (Table). On the anteroposterior (AP) radiographs, two measurements were used to evaluate the coronal alignment: radial inclination and radial height. Radial inclination was measured as the angle between a line perpendicular to the long axis of the radius and a line parallel to the radial articular surface. Radial height was measured as the distance between two parallel lines, one starting at the radial styloid and the other at the lunate facet. On the lateral radiographs, four measurements were used to evaluate the sagittal alignment: radial tilt, scapholunate, radiolunate angle and capitolunate angles. Radial tilt was measured as the angle between the perpendicular line to the long axis of the radial shaft and a line drawn from the palmar apex to the dorsal apex of the distal radius. We denoted flexion as positive and extension as negative. The lunate axis was defined as a line perpendicular to the line tangential to its poles. The scaphoid axis was the line tangential to the proximal and distal palmar poles. The capitate axis was the line from the midportion of the proximal to the midportion of the distal articular surfaces. Therefore, the scapholunate angle was measured as the angle between the scaphoid and the lunate axes. The radiolunate angle was between the longitudinal axis of the radius and the lunate. The capitolunate angle was between the capitate and lunate axes.
The effective radiolunate flexion (ERLF), originally outlined by Ajay K. Gupta, MD, and colleagues describes the movement of the lunate in relation to the distal radius to distinguish type 1 from type 2 carpal instability adaptive (type 1 < 25° and type 2 > 25°). ERLF is defined as dorsal tilt plus 11 minus the radiolunate angle. At all follow-up visits, the ERLF was calculated to be less than 25°, corresponding to type 1 or midcarpal malalignment. Although the patient was demonstrating signs of carpal malalignment at that time, the decision was made to continue with nonoperative treatment given her minimal to mild symptoms.
Clinical outcome and discussion
By 5 months from time of injury, the patient’s wrist range of motion was symmetric to her uninjured wrist, and she had returned to her previous activities without restrictions. At her 1-year follow-up, the patient noted occasional wrist pain with activities but similar function and strength as the contralateral wrist.
A case is presented of a 65-year-old woman who underwent nonoperative treatment of an extra-articular DRF with initial acceptable anatomic alignment based on radial inclination, height and tilt. During the course of 6 weeks, the patient developed worsening midcarpal malalignment with significant dorsiflexion of the lunate and dorsal subluxation of the capitate. In addition, the radial dorsal tilt became more pronounced. The scapholunate interval remained consistently within normal limits, suggesting intact intrinsic ligaments. This case demonstrates rapid progression of midcarpal malalignment in response to a dorsally tilted DRF. Regardless of the severe radiographic features, the patient returned to full activities without limitations.
Dorsal angulation of the distal radius is a common position of malunion in nonoperatively treated DRFs. Due to loss of the normal architecture of the distal radius, the carpal alignment changes. This can result in either the proximal carpal row angulating dorsally with compensatory flexion of the distal carpal row or dorsal subluxation of the entire carpus, type 1 and type 2, respectively. There is no ligamentous or capsular disruption identified in this adaptive process.
The carpus is a link system that has the potential to collapse if the extrinsic and intrinsic ligaments of the wrist are destabilized. As the proximal carpal row is an intercalated segment without tendon attachment, the alignment depends largely on adjacent contact areas, the extrinsic and intrinsic ligaments, and the position of the wrist. The strong extrinsic volar wrist ligaments — the short and long radiolunate, radioscapholunate and radioscaphocapitate — influence the pull of the lunate in response to the location of the distal radius. Intrinsically, the scapholunate and lunotriquetral ligaments affect the alignment of the lunate such that when one is injured, the lunate is pulled in the direction of the other. Biomechanical studies found a significant change in load distribution at the radiocarpal joint with at least 20° dorsal tilt. The contact areas move dorsally, especially at the ulnocarpal and radioscaphoid articulations. In addition, the axial rotation of the scaphoid and lunate increases with dorsal angulation. Thus, the extrinsic ligaments contribute mainly to the “adaptive” midcarpal instability. It is unlikely that the strong extrinsic ligaments were injured from our patient’s low-energy ground level fall. While some believe the carpus realigns to compensate angulation from the malunited DRF, others argue the carpal instability is due to extrinsic factors, mainly from the initial trauma. In this case, a small change in dorsal radial tilt led to significant carpal collapse, possibly in the setting of a preexisting potential for instability.
Changes in carpal kinematics may lead to mechanical overload of the radiocarpal and midcarpal joints. This can lead to loss of wrist motion, pain, arthritis and diminished extensor tendon efficiency. Interestingly, even in the setting of severe distal radius malunions, older patients can regain baseline function. The development of midcarpal malalignment has typically been identified as a gradual progression after the healing of the fracture, thought to be due to continued loading of a biomechanically altered wrist. There have been several studies assessing the effects of malunited distal radii on alignment and resultant functional outcomes. However, timing to midcarpal malalignment has not been addressed. We demonstrate rapid progression of midcarpal malalignment during the fracture healing period of 6 weeks.
Small alterations in radial tilt following a DRF due to a low-energy mechanism can be associated with severe “adaptive” carpal instability that progresses rapidly during the healing process. The patient presented in this case study initially displayed osteoarthritic changes throughout the wrist and hand with mild malalignment of the carpus. Although, her malalignment significantly worsened as the DRF healed in a dorsally tilted malunion, her wrist function was not impaired, and she remains pain free at 1 year from time of injury. While this case highlights a unique outcome of pain-free carpal instability in an older patient, surgical management in the form of arthrodesis or proximal row carpectomy should be considered in refractory patients with persistent symptoms.
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- For more information:
- Nicole Look, MD, an orthopedic surgery resident, can be reached at the University of Colorado, Department of Orthopaedic Surgery, 12631 E. 17th Ave., Mail Stop B202, Aurora, CO 80045; email: nicole.look@cuanschutz.edu.
- Nader Shourbaji, MD, can be reached at North Oaks Orthopaedic Specialty Center,15813 Paul Vega MD Dr., Suite 100, Hammond, LA 70403; email: shourbajin@northoaks.org.
- Edited by Steven D. Jones Jr., MD, and Donald (DJ) Scholten, MD, PhD. Jones is a chief resident in the department of orthopedic surgery at the University of Colorado. He will pursue a fellowship in sports medicine at Stanford University following residency completion. Scholten is a chief resident in the department of orthopedic surgery at Wake Forest University School of Medicine in Winston-Salem, North Carolina. He will be a sports medicine fellow at the University of Michigan following residency. For information on submitting Orthopedics Today Grand Rounds cases, please email: orthopedics@healio.com.
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Arora R, et al. J Bone Joint Surg Am. 2011;doi:10.2106/JBJS.J.01597.
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