Jinn Lin

Locked nailing for displaced surgical neck fractures of the humerus

OBJECTIVE To report experience with a newly devised humeral locked nail for treating surgical neck fractures of the humerus. This device has the advantages of a small diameter for minimal tissue trauma and transfixing locking screws for reliable fixation. METHODS From 1993 to 1996, 21 consecutive severely displaced surgical neck fractures of the humerus were antegrade nailed with humeral locked nails; 2 fractures were associated with dislocation and 1 fracture was a comminuted metaphyseal fracture with a failed plating. The average age of patients was 65.8 years; average follow-up time was 19.2 months. The proximal screws were applied upward in 5 patients and downward in 16 patients. Static locking was performed in 8 patients, dynamic locking in 13 others. RESULTS The average operation time was 55 minutes. No patients needed blood transfusion. All fractures eventually achieved union with an average time to union of 14.8 weeks. On the basis of Neer criteria for outcome analysis, excellent or satisfactory results were obtained for 86% of the patients (18 of 21 patients). No patients had deep infection, implant failure, malunion, osteonecrosis, or nail migration that interfered with joint motion. Due to technique errors, one patient had shoulder joint impingement caused by protrusion of the proximal nail tip. CONCLUSION The operative method reported here has the advantages of minimal tissue trauma, minimal hardware application, sufficient fixation, and easy operative technique, and it can be a worthy alternative for the treatment of severely displaced surgical neck fractures of the humerus.

Biomechanical comparison of antegrade and retrograde nailing of humeral shaft fracture.

A pair controlled study was conducted to compare biomechanical properties of antegrade and retrograde nailing of humeral fractures. First, six paired fresh anatomic specimen humeri were used to compare the properties of humeri fractured at the middle to distal diaphyses junction that were nailed from the retrograde approach with the Humeral Locked nail with those of contralateral intact humeri. An 18 additional pairs were divided into three equal groups by distal, proximal, or middiaphysis location of a standardized 5-mm bone defect to simulate unstable fractures. The retrograde and antegrade nailings were performed in each pair in a random manner. Nail and bone constructs were tested for bending stiffness by nondestructive three-point bending and for torsional stiffness by destructive torsional tests. Compared with intact humeri, fractured humeri fixed with nails had 28.6% posteroanterior and 31.4% mediolateral bending stiffness, 22.5% torsional stiffness, and 43.3% failure torque. For distal fractures, retrograde nailing showed significantly more initial stability and higher bending and torsional stiffness; for proximal fractures, antegrade nailing showed similar properties. For middle to distal diaphyses junction fractures, retrograde and antegrade nailing were indistinguishable. The defect created as an entry portal for retrograde nailing reduced the bone strength only 11.1%. These results suggest that retrograde nailing, which is less detrimental to shoulder function than is antegrade nailing, is an acceptable alternative treatment for humeral shaft fractures. In addition, nailing from the short to the long bone segments can improve mechanical properties of the fixation construct because of better nail and bone interface purchase.

Treatment of humeral shaft delayed unions and nonunions with humeral locked nails.

OBJECTIVE To report experience with use of humeral locked nails in treating humeral delayed unions and nonunions. The following techniques yielded encouragingly good results: static locking, short-to-long segment nailing, bone grafting, fracture compression, and minimal surgical trauma. DESIGN AND METHODS A total of 41 consecutive patients with 13 delayed unions and 28 nonunions were treated with humeral locked nails. Delay from trauma to surgery averaged 4.2 months for delayed union and 15.5 months for nonunion. The average age of patients was 50.2 years; average follow-up time was 23.2 months. There were 7 proximal-third fractures, 21 middle-third fractures, and 13 distal-third fractures. The antegrade approach was used for 13 fractures and retrograde for 28. Open nailing was performed in 39 fractures and closed nailing in 2. If the fracture motion was still present after nail insertion, axial compression of the fracture site was specially applied. Bone grafting was performed in the fractures with open nailing. Thirty-four fractures were nailed with 8-mm nails, and 7 fractures were nailed with 7-mm nails. RESULTS With a single operation, all but two patients achieved osseous union in, on average, 5.6 months. One of these two patients eventually gained union after another surgery with fracture compression along the original nail and concurrent bone grafting. The second patient, undergoing hemodialysis for chronic renal failure, had persistent nonunion. At follow-up, for patients with antegrade nailing, all but four patients had less than 20 degrees limitation of shoulder abduction. For patients with retrograde nailing, all but two had less than 10 degrees limitation of elbow motion. Only the patient with persistent nonunion had continual pain and significant impairment of arm function. CONCLUSIONS Humeral locked nailing seems to be effective for humeral delayed unions or nonunions. It may be an acceptable alternative for fractures unsuited for plate fixation, such as those with comminution, osteoporosis, or a severely adhered radial nerve.

Anatomic considerations of locked humeral nailing

To investigate the risk of axillary nerve injury by the proximal locking screws in antegrade nailing of humeral fractures, the anatomy of the axillary nerve was examined in 20 fresh anatomic specimen humeri, which subsequently were nailed antegrade with specially designed humeral locked nails. The axillary nerve was found to be on average 45.6 mm below the tip of the greater tuberosity; it was jeopardized by insertion of the lower proximal locking screw in one of the 20 specimens. Short humeri, humeri with small heads, or too deeply inserted nails may increase the risk of nerve injury; likewise, a lower location and more horizontal direction of the locking screws and a greater curvature of the nail can heighten the risk. In addition to the examination of the axillary nerve, a geometric study of these anatomic specimen was performed and was aimed at improving retrograde nailing technique and thus treatment results. The humeral geometry indicated that for the best linearity in the sagittal plane, an entry portal incorporating the superior margin of the olecranon fossa would be recommended for the 14 humeri with a distal humeral offset less than 4 mm, whereas a supracondylar entry portal would be recommended for the six humeri with an offset larger than 4 mm. For best linearity in the coronal plane, the entry portal and nailing direction should be more lateral in humeri with a smaller humeral elbow angle.

Ultrasound Stimulates NF-κB Activation and iNOS Expression Via the Ras/Raf/MEK/ERK Signaling Pathway in Cultured Preosteoblasts

It has been shown that ultrasound (US) stimulation accelerates fracture healing in the animal models and non‐operatively clinical uses. Nitric oxide (NO) is a crucial early mediator in mechanically induced bone formation. Here we found that US‐mediated inducible nitric oxide synthase (iNOS) expression was attenuated by Ras inhibitor (manumycin A), Raf‐1 inhibitor (GW5074), MEK inhibitor (PD98059), NF‐κB inhibitor (PDTC), and IκB protease inhibitor (TPCK). US‐induced Ras activation was inhibited by manumycin A. Raf‐1 phosphorylation at Ser338 by US was inhibited by manumycin A and GW5074. US‐induced MEK and ERK activation was inhibited by manumycin A, GW5074, and PD98059. Stimulation of preosteoblasts with US activated IκB kinase α/β (IKK α/β), IκBαphosphorylation, p65 phosphorylation at Ser276, p65, and p50 translocation from the cytosol to the nucleus, and κB‐luciferase activity. US‐mediated an increase of IKK α/β, IκBα, and p65 phosphorylation, κB‐luciferase activity and p65 and p50 binding to the NF‐κB element was inhibited by manumycin A, GW5074, and PD98059. Our results suggest that US increased iNOS expression in preosteoblasts via the Ras/Raf‐1/MEK/ERK/IKKαβ and NF‐κB signaling pathways. J. Cell. Physiol. 220: 196–203, 2009.

Increasing nail-cortical contact to increase fixation stability and decrease implant strain in antegrade locked nailing of distal femoral fractures: a biomechanical study.

BACKGROUND Proximity of the distal locking screw to the fracture site potentially can cause implant failure in locked nailing of distal femoral fractures. In this biomechanical study, we investigated the effects of nail-cortical contact and nail purchase in the distal subchondral bone on fixation stability and implant strain. METHODS Using fiberglass artificial femurs, we fixed five different distal femoral osteotomies with specially manufactured locked nails representing different conditions of nail-cortical contact. In each condition, six femur-nail constructs were loaded on the femoral head axially with 700 N; then we measured the fixation stability and strain at the superiormost distal locking screw and nail hole. The tests were conducted both with and without nail purchase in distal subchondral bone. RESULTS When there was no nail-cortical contact, the load transmitted to the distal femoral fragment was completely borne by the nail and the distal locking screws. Low fixation stability and high strain on the distal screw and nail hole resulted. Greater nail-cortical contact increased the fixation stability and decreased strains on the distal screw and nail hole. Purchase of the nail tip in distal subchondral bone significantly increased the fixation stability and decreased nail hole strain except in the situation of long nail-cortical contact. The screw strain was significantly reduced in all conditions, and the reduction in strain was significantly greater than that associated with the nail hole, 32% +/- 8% versus 15.7% +/- 2.5% (p = 0.002). CONCLUSIONS In locked nailing of distal femoral fractures, the prime factor determining fixation stability and implant strain is nail-cortical contact. In situations without nail-cortical contact, a longer nail with purchase in the subchondral bone of the distal femur is recommended.

Reducing Limping by Tibial Lengthening Along Nails in Adult Unilateral Developmental Dysplasia of the Hip with High Dislocation

BACKGROUND/PURPOSE Treatment of adult neglected developmental dysplasia of the hip (DDH) with high dislocation is still not established. The main concern of young patients is leg-length discrepancy (LLD), which leads to limping gait and impaired body image. Such patients usually ask for a minimally invasive treatment that can improve the LLD. METHODS Between 1993 and 2003, 17 patients with neglected DDH with high dislocation (mean age, 22.8 years) were treated by tibial lengthening using the Ilizarov external fixator over an intramedullary nail. The inclusion criteria were unmarried young adults, unilateral lesion, significant limping or unsightly gait with psychologic discomfort, marked shortening > 4 cm with the block test, and benefit from a shoe-lift. Exclusion criteria were patients older than 30 years, hip pain as the chief complaint, and compensated low hip dislocation without significant limping. RESULTS All 17 patients had eventual bone consolidation without further operation. The mean external fixation index was 14.2 day/cm. Bone formation was good in all patients with a mean consolidation index of 57.7 day/cm. At an average follow-up period of 7.8 years, the limping was much improved from a moderate or severe degree to a mild degree in all patients. No patients had equinus contracture. All patients were satisfied with their treatment results. There were two complications: transient loss of big toe extension and mild wound infection. CONCLUSION Tibial lengthening can improve limping in adult patients with neglected DDH and high dislocation with a low morbidity. Lengthening along intramedullary nails can effectively reduce the external fixation time, improve bone formation, and prevent complications.