BLOG: Volar lunate dislocation
Click Here to Manage Email Alerts
Editor’s note: For 2020, the Physician Assistants in Orthopaedic Surgery awarded four $5,000 scholarships to PA students with an interest in orthopedics.
Part of the eligibility requirement for the scholarship is to author a publishable paper from either a research project or a case study. This year, we decided to also publish executive summaries of their work on Healio’s Physician Assistants in Orthopaedic Surgery blog. The summary of the first of the four winners comes after the following introduction.
This case study describes a perilunate dislocation that was initially missed after a traumatic distal radius styloid fracture. The pathophysiology, diagnosis and treatment options for this injury are reviewed, as well as the surgical treatment of this patient’s wrist and postoperative outcomes.
- Sam Dyer, PA-C, MHS
PAOS president
Case study
A 27-year-old man presented for an orthopedic consultation 3 days after falling onto his outstretched right wrist while motorcycling at 30 to 35 mph. Radiographs confirmed a right radial styloid fracture and he was placed in a short-arm cast for 4 weeks. Upon removal of the cast, the patient had severe right wrist pain, swelling and numbness within the median nerve distribution.
Repeat radiographs demonstrated interval healing of the fracture, but also irregularity of the carpus. A hand/wrist orthopedic surgeon was consulted and the patient was diagnosed as having a right volar lunate dislocation. He later underwent a right lunate open reduction and internal fixation of a volarly dislocated lunate, scapholunate ligament reconstruction using Mayo-modified tenodesis, right lunotriquetral ligament repair and extended incision open carpal tunnel release.
Postoperatively, the patient was immobilized for 6 weeks and had a removal of deep hardware procedure thereafter. At nearly 5 months from the initial injury, the patient was able to resume work as a heavy equipment operator without restrictions.
Pathophysiology
Lunate and perilunate dislocations are uncommon injuries of the upper extremity. Lunate dislocations involve the volar displacement and rotation of the bone while the remainder of the carpus articulates normally with the radius. This results in the lunate dislocating into the carpal tunnel. Perilunate dislocations occur when the radiolunate articulation is not compromised but the remainder of the carpal bones are dorsally displaced. These injuries are typically related to forceful loading, such as falling, onto the wrist while extended.
A classification system was proposed by Mayfield and colleagues in 1980, which relates to progression of perilunate instability based off radiographs, disrupted articulations and ligamentous injuries.
Epidemiology
Carpal dislocations are estimated to occur in less than 10% of all wrist injuries. Perilunate dislocations represent roughly 7% of these injuries, with lunate dislocations comprising an even smaller percentage of this population.
Clinical presentation
Individuals with lunate dislocations typically present after a high impact fall onto an extended wrist. Commonly reported symptoms include wrist pain, swelling and decreased sensation and/or paresthesia in the median nerve distribution secondary to carpal tunnel injury. Physical exam may demonstrate tenderness at the lunate, fingers and the wrist to be in slight flexion, reduced sensation of the radial 3.5 fingers and weakness with resisted thumb flexion, opposition or abduction. Stability testing with a Watson test to assess the scapholunate ligament can be performed but is often deferred in the acute setting.
Diagnosis
Acute volar lunate dislocations are usually diagnosed by a lateral view radiographs of the affected wrist, which demonstrates a “spilled teacup” sign where the lunate is displaced volarly and rotated while the metacarpals, carpus and distal radius remain in anatomic alignment. Unfortunately, these abnormalities are sometimes overlooked. AP or PA views can demonstrate subtle irregularities but are generally benign.
Clenched fist views can be considered to evaluate for scapholunate articulation widening. A wrist CT without contrast can be considered if there is concern for an occult fracture. An MRI or MRA of the wrist are often obtained for further evaluation of the ligamentous structures for surgical planning.
Treatment
Operative treatment is recommended for acute volar lunate dislocations to reduce the high likelihood of long-term sequelae. Many surgical methods are employed for the management of lunate dislocations including dorsal, volar or combined approaches to an ORIF of the lunate. K-wires are most widely used for fixation. The scapholunate ligament is often repaired using suture anchors in patients with an acute presentation. The lunotriquetral ligament can sometimes be repaired with suture anchors, but this is less commonly performed as there is little research suggesting long-term benefit. An open carpal tunnel release can be performed in the setting of median nerve distribution symptoms.
Recovery and rehabilitation recommendations vary. This specific patient was placed in a short-arm splint for 2 weeks postoperatively and then transitioned to a short-arm cast for 4 weeks. At 6 weeks postoperatively, the K-wires were removed under fluoroscopy in the operating room. He then used a removable splint when active for an additional 6 weeks while attending hand therapy twice weekly. Maximizing wrist range of motion was the priority for the initial 6 weeks of hand therapy. He gradually returned to weight-bearing activities thereafter.
Despite appropriate surgical management, complications are not uncommon and may require proximal row carpectomy, scapholunate ligament reconstruction or wrist arthrodesis if pain, reduced function or impaired structural integrity exists.
Prognosis
Though prompt operative treatment is advised following an acute volar lunate dislocation, long-term consequences are still common. Complications can include reduced mobility and strength, degenerative changes, avascular necrosis or Kienbock’s disease, scapholunate advanced collapse, decreased sensation or paresthesia within the median nerve distribution, and wrist joint instability.
References:
Bednar MS, et al. Hand Surgery. In: Skinner HB, McMahon PJ. eds. Current Diagnosis & Treatment in Orthopedics, 5e. McGraw-Hill. https://accessmedicine-mhmedical-com.pearl.stkate.edu/content.aspx?bookid=675§ionid=45451715. Accessed July 3, 2020.
Dixon A. Lunate dislocation: Radiology reference article. Radiopaedia Blog RSS. https://radiopaedia.org/articles/lunate-dislocation. Accessed July 3, 2020.
Kennedy S, et al. Clin Ortho Rel Res. 2012;doi:10.1007/s11999-012-2275-x.
Ott F, et al. BMJ Case Reports. 2013;doi:http://dx.doi.org.pearl.stkate.edu/10.1136/bcr-2013-009062.
Wingelaar M, et al. Lunate dislocation and basic wrist kinematics. J Plast Surg. 2016. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4997775/. Accessed July 3, 2020.
www.uptodate.com/contents/evaluation-of-the-adult-with-acute-wrist-pain?search=volar+lunate+dislocations. Accessed July 3, 2020.
www.uptodate.com/contents/lunate-fractures-and-perilunate-injuries?search=volar+lunate+dislocation. Accessed July 3, 2020.
Collapse