Isolated epiphyseal distal ulnar injuries are uncommon. Only seven cases have been reported in the literature of distal ulnar radial injuries wthout radial fracture.
This article presents a case of epiphyseal injury of the distal ulna without associated radial fracture.
A 13-year-old boy presented with right wrist joint pain. In February 1998, the patients arm was forcibly twisted by another person, with excessive pronation of the right forearm. Pain developed in the wrist joint, but was left untreated. The pain persisted and the patient was taken to a nearby hospital in June. Epiphyseal injury of the right distal ulna was diagnosed based on plain radiographic findings. The pain was treated conservatively, but there was no relief. In January 1999, the patient was referred to our department.
Slight swelling of the right wrist joint was observed on examination, but there was no local warmth or any distinct deformity. Pain on movement and tenderness was noted on the ulnar side of the right wrist joint and in the radioulnar joint region. Palmar dorsiflexion and wrist flexion were restricted; the restriction of palmar dorsiflexion was particularly marked.
No distinct bony injury of the radius was revealed on plain radiographs obtained at the time of initial examination (Figure 1). Epiphyseolysis (Salter-Harris Classification type I) of the distal ulna was observed and the ulnar length was shortened by 4 mm. Plain radiographs obtained on admission to our department revealed improvement of the epiphyseolysis, but the ulnar variant had changed to -8 mm and the radial tilt had increased to 43° associated with growth disturbance of the ulna (Figure 2).
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Figure 1: Plain AP (A) and lateral (B) radiographs obtained at the time of initial examination in the previous hospital (4 months after the injury).
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Figure 2: Plain AP (A) and lateral (B) radiographs 11 months after the injury.
A wrist arthrogram revealed no distinct injury of the triangular fibrocartilage complex.
Based on the above findings and observations, none of the joint components were judged to have been injured, and incompatibility of the radioulnar articular surface due to ulnar growth disturbance was thought to be responsible for the pain. Ulnar lengthening surgery using external skeletal fixation was performed.
The unilateral external skeletal fixator was used and osteotomy was performed 9 cm distal to the olecranon (Figure 3).
Figure 3: Application of an external fixator.
Ulnar lengthening was initiated 13 days postoperatively (ie, after callus had appeared) at the rate of .5 mm/day. Since the callus formation was found to be favorable, the rate of lengthening was increased to 1 mm/day 36 days postoperatively. At 54 days postoperatively, when zero variant was obtained comparable to that on the healthy side, the lengthening was stopped. After ensuring consolidation 138 days postoperatively, the external fixator was removed. The healing index was 56.2 days/cm.
Plain radiographs obtained one year postoperatively (Figure 4) revealed 35° radial tilt, indicating improvement of the radial deformation. Subsequently, the ulnar variant changed to -4 mm again along with growth. However, the tenderness and pain on movement on the ulnar side of the right wrist joint and radioulnar triangular region resolved and the ROM at the wrist joint improved.
Figure 4: Plain radiographs one year postoperatively show 20° radial tilt and -1 mm ulnar variant on the healthy side, and 35° radial tilt and -4 mm ulnar variant on the affected side.
An analysis of the reported cases of isolated epiphyseal injury of the distal ulna revealed that the cause of injury was a traffic accident or a fall in most cases. There were no reports of the injury occurring as a result of forceful twisting of the arm, as in our case.1-5
All reported patients had received early treatment after injury. Treatments include open reduction in 4 patients and external fixation in 3. As residual disturbance, slightly restricted ROM at the wrist joint was noted in 2 patients, but there was no pain or disturbance of the activities of daily living.2,5 In our patient, however, the initial treatment was delayed and ulnar growth disturbance had occurred. Since the patient had restricted ROM and pain on movement of the wrist joint, bone lengthening surgery was performed.
According to Nelson et al,6 palmar dorsiflexion of the wrist joint produces a shearing force and often results in Salter-Harris Classification type I or II injury, and radioulnar flexion further facilitates the development of type III or IV injuries due to the excessive axial pressure. Hinohara and Asaga4 proposed the following mechanism: when the forearm is in the pronated position, addition of strong ulnar flexion simultaneously with dorsiflexion of the wrist joint causes excessive increase in the axial pressure to the ulna, resulting in the development of isolated epiphyseal injury of the distal ulna.
Our patient was thought to show Salter-Harris Classification type I injury based on the findings on plain radiographs obtained at the time of initial examination. The prognosis of type I injury generally is believed to be favorable, with no growth disturbance expected to remain if treatment is appropriately conducted by reduction. The reason for the growth disturbance of the ulna noted in our patient seems to be that the injury initially was not treated appropriately with reduction, and was left untreated for 4 months from the time of initial examination. However, as suggested by Hinohara and Asaga,4 with the extremely strong ulnar flexion added to dorsiflexion of the wrist joint with the forearm in pronation at the time of injury in this patient and the excessive force along the long axis causing epiphyseal crush and destruction, the condition was consequently judged to be a Salter-Harris Classification type V injury.
Nelson et al6 also have indicated that growth disturbance accompanying epiphyseal injury of the distal ulna leads to extension of stiff soft tissue and results in increased radial tilt. In our patient, the so-called tethering effect (ie, the distal end of the radius on the ulnar side becoming extended by the radioulnar ligament and the extensor retinaculum) was thought to have been responsible for the injury.
Ulnar lengthening surgery using external fixation was performed using Callotasis method in the present patient. Osteotomy was performed as centrally as possible for preventing subluxation of the radial head due to the extension force because the tendinous part of the forearm interosseous membrane shows an oblique course from the proximal radius to the distal ulna and the stiffest fibers adhere to the ulna along the distal 1/4 of the bone.7 Since the healing index was 56.2 days/cm and a lengthening device needed to be applied for a prolonged period, there was the risk of pin tract infection. However, shortening the period of device application could be achieved and the risk of such infection was avoided by innovations in dynamization. Innovations in dynamization also are needed for the prevention of fracture.7
Lengthening was stopped when the ulnar variant became 0 mm because of concerns about the development of ulna-pushing-up syndrome. One year postoperatively, there was no pain and ROM was favorable. Plain radiographs, however, revealed that the ulnar variant had become -4 mm again. We continue monitoring the course of the patient because of the possible development of arthrosis changes due to radioulnar triangular incompatibility and the possibility that a second bone lengthening surgery may be required.
- Aso K, Akimoto N, Yoshida S, Masumi S, Kawashima M, Kondo M. Clinical study of epiphyseal injury of the distal ulna. Kossetsu. 1994; 16:289-293.
- Engber WD, Keene JS. Irreducible fracture-Separation of the distal ulnar epiphysis. Report of a case. J Bone Joint Surg Am. 1985; 67:1130-1132.
- Evans DL, Stauber M, Frykman GK. Irreducible epiphyseal plate fracture of the distal ulna due to interposition of the extensor carpi ulnaris tendon. A case report. Clin Orthop. 1990; 251:162-165.
- Hinohara S, Asaga Y. Isolated epiphyseal separation of the distal ulna: a case report. Orthop Surg Traumatol. 1994: 37:1507-1510.
- Takeda H, Hirano T, Yonemitsu H. Isolated ulnar epiphyseal fracture. A case report. Japanese Journal of Traumatology and Occupational Medicine. 1996; 44:443-445.
- Nelson OA, Buchanan JR, Harrison CS. Distal ulnar growth arrest. J Hand Surg Am. 1984; 9:164-171.
- Masada K, Ohno H. Progressive lengthening of the forearm bones using a unilateral external fixator. Orthop Surg Traumatol. 1998; l41:117-121.
Drs Yamamoto, Tateiwa, Takaaki, Miyajima, Nagai, and Imakiire are from the Department of Orthopedic Surgery, Tokyo Medical University, Tokyo, Japan.
The authors thank Professor J. Patrick Barron of the International Medical Communications Center of Tokyo Medical University for his review of this manuscript.
Reprint requests: Kengo Yamamoto, MD, PhD, Dept of Orthopedic Surgery, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.