Kyeong-Jin Han

Long-term clinical study and multiscale analysis of in vivo biodegradation mechanism of Mg alloy

Significance In the past decade, countless studies have been performed to control the mechanical and corrosion property of magnesium-based alloy, which degrades in the physiological environment, to overcome the flaws of the inert implant materials and shift the paradigm of conventional bone fixation devices. Controlled degradation of Mg-5wt%Ca-1wt%Zn alloy results in the formation of biomimicking calcification matrix at the degrading interface to initiate the bone formation process. This process facilitates early bone healing and allows the complete replacement of biodegradable Mg implant by the new bone within 1 y of implantation, as demonstrated in 53 cases of successful long-term clinical study. There has been a tremendous amount of research in the past decade to optimize the mechanical properties and degradation behavior of the biodegradable Mg alloy for orthopedic implant. Despite the feasibility of degrading implant, the lack of fundamental understanding about biocompatibility and underlying bone formation mechanism is currently limiting the use in clinical applications. Herein, we report the result of long-term clinical study and systematic investigation of bone formation mechanism of the biodegradable Mg-5wt%Ca-1wt%Zn alloy implant through simultaneous observation of changes in element composition and crystallinity within degrading interface at hierarchical levels. Controlled degradation of Mg-5wt%Ca-1wt%Zn alloy results in the formation of biomimicking calcification matrix at the degrading interface to initiate the bone formation process. This process facilitates early bone healing and allows the complete replacement of biodegradable Mg implant by the new bone within 1 y of implantation, as demonstrated in 53 cases of successful long-term clinical study.

Pseudoaneurysm after tibial nailing.

This is a case report of a patient with a pseudoaneurysm of the anterior tibial artery after lateral to medial distal locking of an intramedullary nail for a tibia shaft fracture.

Subacromial impingement syndrome secondary to scapulothoracic dyskinesia

The authors describe two cases of subacromial impingement syndrome of the shoulder secondary to scapular dyskinesia caused by a tumor in young adults. The two tumors, an osteochondroma and a ganglion, were located in the scapulothoracic joint and inhibited normal kinesis of the scapula during arm motion.

Trabecular microstructure of the human lunate in Kienböck’s disease

The trabecular microstructure of normal lunates and lunates with Kienböck’s disease was investigated using micro-computed tomography (micro-CT). Five lunates with advanced Kienböck’s disease were obtained during lunate excision and scaphocapitate fusion, and five control lunates were from embalmed cadavers. Microstructural morphometric parameters were measured using micro-CT images. Trabeculations of lunates with Kienböck’s disease were 2.67 times denser and 1.84 times thicker than those of normal lunates. Furthermore, bone surface areas were 1.43 times greater and bone volume 2.67 times greater, and structural model indices were significantly lower in lunates with Kienböck’s disease. The study estimated that high mechanical stress would be applied to lunates with Kienböck’s disease, and suggests that new bone formation and collapse may play important roles in the microstructural changes in the lunate with advanced Kienböck’s disease.

Digital nerve schwannoma of the hand.

A 45-year-old woman presented with a 6-month history of a small nodule with intermittent sharp pain in the right palm. There was no history of trauma or infection in the area. She had worked in an electronic company for several years, and the sharp pain usually occurred when grasping and moving the hard cases of electric home appliances. No visible mass or skin changes were evident over the affected area, but a firm 0.5 cm sized nodule was palpated 2.5 cm proximal to the metacarpophalangeal joint of the index finger. The nodule was mobile and Tinel’s sign was positive on percussion. Plain radiographs were unremarkable, but MRI revealed a subcutaneous, well-defined 5 × 10 mm ovoid mass, superficial to the flexor tendon sheath and lumbrical muscles at the metacarpal neck level (Figure 1). The patient underwent surgical exploration because of continuing discomfort. At surgery, a 4 × 8 mm peanut-shell shaped segmental expansion was noted in the radial digital nerve of the index finger (Figure 2). Intraneural microdissection of the expanded segment of the nerve and enucleation of a 3 × 7 mm ovoid mass was carried out, preserving all fascicles. The cut surface of the specimen was whitish yellow and had a homogeneous texture. Histology revealed a multi-lobulated, plexiform, well-encapsulated lesion composed of spindle cells positive for S-100 protein with an Antoni A pattern. At 1 week after surgery, the neuropathic symptoms had subsided completely. At the last follow-up, 4 years after surgery, there was no evidence of recurrence and no sensory deficit was found by the two-point discrimination test. Schwannomas or neurilemmomas are benign encapsulated tumours of the nerve sheath (Greenfield et al., 2002) and are usually solitary. Schwannomas involving the digital nerves are rare and are typically located on the palmar side of the hand, but they also occur distal to the proximal interphalangeal joint (Holdsworth, 1985). The treatment of choice is extracapsular or intracapsular removal under magnification. A preoperative diagnosis may be made, based on a high index of suspicion from the history and physical examination. However schwannomas are uncommon (less than 5% of the soft tissue tumours of the arm) and the symptoms they cause are sometimes indistinguishable from other lesions such as neuroma-incontinuity, nerve entrapment, perineural adhesions and external nerve compression (Kang et al., 2000). MRI and ultrasonography are useful for delineating perineural lesions and for the differential diagnosis of soft tissue tumours. However ultrasonography has limited ability to identify the type of tumour. Although some MRI features, such as an ill-defined margin, central necrosis and heterogeneity are helpful for distinguishing between malignant peripheral nerve sheath tumours (MPNST) and benign tumours (BPNST), the lesions may sometimes appear similar (Walker et al., 2011). So the possibility of an MPNST should always be considered, although its prevalence is very low (about 0.001% of general population).

Intraneural ganglion in the digital nerve of the thumb: A case report

Intraneural ganglion cysts of the peripheral nerve in the upper extremity are uncommon and usually originate within the epineurium of the peripheral nerve. The current report discusses a 57-year-old woman with a neuropathic nodular mass on the thenar area of the left hand. Magnetic resonance images showed a lobulated, homogeneous mass of high signal intensity on T2-weighted images and low signal intensity with peripheral enhancement on T1-weighted images. Excisional biopsy and histopathologic examination confirmed an intraneural ganglion cyst of the digital nerve of the thumb. A successful result was obtained by surgical treatment, and there was no recurrence of abnormal sensation and paraesthesia during the 3-year follow-up period.

Reimplantation of an Extruded Humeral Segment into an Intact Periosteal Envelope in a Child

Traumatic bone extrusion followed by successful bone-segment reimplantation is uncommon1-4. When bone loss is minimal, open fractures may heal by stabilization alone, and small amounts of bone loss can generally be treated with an autogenous or allogenic bone graft. Large segmental bone defects may occur at the time of injury or after surgical debridement of devitalized bone, and may require large grafts, multiple grafts, vascularized bone grafts, or bone transport5-7. The benefits of reimplanting an extruded segment include maintenance of the original skeletal structure, avoidance of morbidity associated with autogenous bone harvesting, and avoidance of allograft bone procedures or prolonged bone transport procedures. Regardless of the sterilization method used, reimplantation of a devascularized bone segment after meticulous wound debridement and sound bone stabilization is associated with an elevated risk of infection. However, the literature lacks guidelines regarding the sterilization, timing of reimplantation, and stabilization of extruded bone segments1-4. We describe a case of early reimplantation of an extruded humeral segment in a child. The patient and her family were informed that data from this case would be submitted for publication, and they provided consent. A three-year-old girl fell from a third-floor balcony of an apartment and sustained an injury to the right arm and elbow. Her general condition was good, and she was alert and oriented. Other injuries included only a small scalp laceration and multiple superficial abrasions over the lower extremities. Physical examination revealed a 3-cm transverse laceration on the posterior aspect of the distal part of the right arm (just proximal to the olecranon) with moderate contamination, and gross motion indicating skeletal instability. A missing segment of humerus measuring 7.5 cm was retrieved by the parents from the scene approximately sixty minutes after the accident. The …

Radial head arthroplasty using a metatarsal osteochondral autograft

PurposeTreatment of comminuted fractures of the radial head is controversial, and considerable effort has been made to restore optimal function of the elbows, either by surgical reconstruction or prosthetic replacement. This report presents our experiences in treatment of unreconstructable radial head or neck fractures using osteochondral autografts harvested from the base of the second metatarsal bones.MethodsFive patients with radial head and one with a radial neck fracture underwent treatment with osteochondral autografts. After excision of the unreconstructable radial head, the second metatarsal base was harvested and transplanted to the radius using the intramedullary nailing technique.ResultsThe reconstructed elbows were examined clinically and radiographically for a mean period of 44.8 months (range, 24–72 months). At the last follow-up, in flexion-extension, the mean elbow mobility was 130°/10°. In supination-pronation, the mean elbow mobility was 73.3°/66.7°, with a mean loss of supination of 19.2° and loss of pronation of 12.5°. Grip strength was 91%, compared with the contralateral limb. The mean Mayo Elbow Performance Score was 94.2. The mean score of AOFAS rating system to the lesser toe was 93.7 points.ConclusionRadial head arthroplasty with an osteochondral autograft from the second metatarsal base appears to be an effective alternative for treatment of unreconstructable radial head fractures. A larger group of patients and a longer follow-up period will be required in order to ease concerns regarding the donor site; however, none of the patients who underwent this procedure showed any complications during follow-up.

Do Cerclage Cables Delay the Time to Bone Union in Patients with an Unstable Humeral Shaft Fracture Treated with Intramedullary Nails

Purpose To evaluate the time to bone union after open reduction and internal fixation with cerclage cables followed by intramedullary nailing (IMN) for unstable humeral shaft fractures. Materials and Methods Patients with a humeral shaft fracture treated by IMN were enrolled. One group of patients was treated via open reduction and internal fixation with cables followed by IMN (cable group; n=32), while the other group was treated with a conventional closed IMN (non-cable group; n=64). The length of time to bone union and functional scores [Disabilities of the Arm, Shoulder and Hand (DASH) and University of California, Los Angeles (UCLA) scores] were measured for all patients. Results No significant differences were found in terms of age, gender, injury type, or smoking history between the two groups, except for the type of fracture. The cable group had significantly more complex types of fracture than the non-cable group (p<0.001). The mean time to bone union was 3.9 months in the cable group, while in the non-cable group, it was 4.4 months (p=0.041). The incidence of postoperative complications, such as non-union, delayed union, and radial nerve palsy, was similar between the two groups (p>0.05). No differences were identified in terms of DASH and UCLA scores (28.8 and 32.1 in the cable group and 26.4 and 32.6 in the non-cable group, respectively; p=0.335 and 0.264). Conclusion In unstable humeral shaft fractures treated by IMN, open reduction and internal fixation with additional cerclage cables do not delay the length of time to bone union or increase the rate of other complications.

Stepwise percutaneous leverage technique to avoid posterior interosseous nerve injury in pediatric radial neck fracture.

Objectives: To introduce a stepwise percutaneous leverage technique to avoid posterior interosseous nerve (PIN) injury in pediatric patients with radial neck fractures and to evaluate the clinical outcome and the predisposing factors affecting the outcome. Design: Retrospective case series study. Setting: University level 1 trauma center. Patients: Thirty-four children with a radial neck fracture, who were treated using a stepwise percutaneous leverage technique, were included in the study. Intervention: The radial head fragment was reduced by pulling the first Steinmann pin proximally as a lever. Then, the kinked soft tissue was released by removal of the Steinmann pin with buttressing the radial head by the operators thumb. The second Steinmann pin was inserted into relaxed soft tissue for fixation of the radial head. Main Outcome Measurements: We used the Métaizeau classification as a radiologic result and Mayo Elbow Performance Score (MEPS) as a clinical outcome. Regression analysis was performed to identify the predisposing factors affecting the outcome. Results: There was no occurrence of PIN palsy. According to the Métaizeau classification, 23 cases were classified as excellent, 9 as good, 1 as fair, and 1 as poor. The average MEPS was 97.6 points. Based on the regression analysis, only the postoperative Métaizeau classification was confirmed as a risk factor of a relatively poor outcome. Conclusions: The stepwise percutaneous leverage technique can be considered a good option in the treatment of pediatric radial neck fractures, because it ensures excellent results by avoiding injury to soft tissues including the PIN. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.