42 Nonunion in Metacarpal Fractures
42.1 Patient History Leading to the Specific Problem
A 28-year-old patient suffered an avulsion amputation of the third ray when catching his left hand in a dough mixer. The patient was a heavy smoker. At admission to the emergency department, he showed a complete avulsion of soft tissue of the middle finger. Initial treatment was carried out by primary mid-shaft metacarpal ray resection of the third ray and transposition of the second ray onto the third metacarpal. Stabilization was performed via a 2.0-mm nonlocking plate osteosynthesis (▶Fig. 42.1a) using three screws distally and two screws proximally to the osteotomy site. The patient developed a painful hypertrophic nonunion (▶Fig. 42.1b) and a reosteosynthesis had to be performed using a four-hole 2.7-mm stainless steel plate 6 months after primary treatment (▶Fig. 42.1c). Another half year later, the patient presented again with a persistent hypertrophic nonunion in the proximal third of his third metacarpal, rendering motion painful. Again, the pseudarthrosis was resected and a reosteosynthesis was performed using an eight-hole 2.4-mm titanium T-plate and filling the defect with an autologous bicortical corticocancellous bone graft from his left iliac crest (▶Fig. 42.1d) 7 months later.
Fig. 42.1 X-rays of a patient suffering an avulsion amputation of the third ray after (a) initial treatment by resection of the third ray and transposition of the second ray. (b) Failure to heal resulted in a nonunion and (c) a reosteosynthesis was performed using a stronger 2.7-mm plate. (d) No bone healing could be achieved and a reosteosynthesis using a 2.4-mm plate with interposition of autologous cancellous bone graft from the iliac crest was performed.
Fig. 42.2 Case presenting nonunion in metacarpal fractures. Intraoperative photographs 19 months after initial treatment. After resection of the nonunion, (a) a combination of Osigraft (rhBMP-7) and Vitoss (Beta TriCalciumPhosphate-Matrix) was applied and (b) the nonunion again stabilized with a 2.4-mm plate. (c) The area of the defect was then covered with a local periosteal transposition flap.
Fig. 42.3 Case presenting nonunion in metacarpal fractures. For additional stability, an external fixator was applied as shown on postoperative X-rays.
In due course, the bone failed again to heal. In order to induce bone healing after careful resection of the nonunion, a combined application of Osigraft (rhBMP-7) and Vitoss (Beta TriCalciumPhosphate-Matrix) as well as a local viable periosteal transposition flap covering the area of the defect as well as the plate was used (▶Fig. 42.2). Osteosynthesis was performed with an eight-hole 2.4-mm titanium locking plate. In addition, an external fixator, bridging the third carpometacarpal (CMC III) joint and the nonunion was applied for optimal stability for 5 m onths (▶Fig. 42.3). ▶Table 42.1 summarizes the patient’s surgical history prior to definitive treatment.
42.2 Anatomic Description of the Patient’s Current Status
After his last operation (26 months after the accident and 7 months after the fourth attempted osteosynthesis), the patient was able to perform full flexion and extension of his fingers. In due course, an inadequate trauma caused a cracking noise in the hand according to the patient.
At admission, the patient presents with painful swelling of the proximal third metacarpal. Closing the fist and opening the fingers is impaired due to pain. Conventional radiography and CT scans reveal a persistent hypotrophic pseudarthrosis in the proximal third of the metacarpal and a failure of the titanium plate. The site of antecedent grafting is almost completely absorbed.
Fracture healing is known to be a complex process. Mutual interaction of cellular, molecular, environmental, and mechanical factors influences bone regeneration. Impairment of only one of these factors at any point of healing will have a negative impact on the consolidation of the fractured bone and may lead to development of a nonunion.
Nonunions of the metacarpals are extremely uncommon and are usually associated with open fractures, severe soft-tissue injury, or infection. Excessive development of heat when sawing the bone can lead to cell death of osteoblasts, increasing the risk of nonunion.
Nonunions can be subdivided into hypertrophic and hypotrophic pseudarthroses. In hypertrophic nonunions, healing usually is prevented by increased interfragmentary motion due to insufficient fixation or inadequate immobilization. In hypotrophic nonunions, impaired nutrition, for example, due to limited vascularization, prevents the bone from healing. In addition, smoking adversely influences bone healing by prolongation of healing in long bones and can increase of the rate of nonunions. In metacarpals, mostly hypotrophic nonunions are found.
An unrestricted hand function depends on sufficient stability of osseous structures as well as the integrity of surrounding tissue especially gliding structures. Due to initial soft-tissue damage, futile attempts of bridging the gap, and sometimes repeated surgical measures, nonunions almost always lead to severe impairment of hand function. Even after bony healing, a limited function of the hand can be expected.
42.3 Recommended Solution to the Problem
According to radiographic findings, the patient moved from a repetitive hypertrophic nonunion to a hypotrophic pseudarthrosis, leading to implant failure. In due course of treatment, the main focus moved from just improving stability by using a stronger type of osteosynthesis to additional improvement of nutrition and blood supply at the osteotomy site by introducing growth factors and a local vascularized periosteal flap. Eventually, these attempts failed to demonstrate bony union.
In order to achieve bone healing, a different approach has to be chosen. Healthy bone with independent blood supply has to be introduced to the site of the nonunion. This can be achieved by transplanting a free vascularized corticocancellous bone graft. These grafts can be harvested from the iliac crest or other sources such as the medial femoral condyle, fibula, scapula, or humerus. The inclusion of a skin flap additionally enables the monitoring of vascularization of the graft.
First, the site of nonunion has to be debrided without any compromise. Any macroscopically identifiable necrotic tissue has to be removed. Bony ends of the metacarpal have to be debrided until bleeding spots are seen. The size of the defect and the distance to the appropriate donor vessel have to be measured and accordingly an appropriate vascularized graft has to be chosen. When choosing a graft from the iliac crest, it has to be ensured that the donor site is unscathed. In this specific case, the contralateral right side is chosen, because previously a corticocancellous graft has been harvested from the left side in prior surgeries. A free microvascular osteocutaneous graft is planned to monitor the vascular supply.
42.3.1 Recommended Solution to the Problem
• Treatment shall focus on the underlying problem—vascularization and stability.
• Complete resection of the pseudarthrosis and replacement with a vascularized graft.
• Large defects or persistent nonunions can be bridged by a free vascularized bone graft taken from the iliac crest, fibula scapula, or humerus.
• In order to monitor vascularization, an osteocutaneous graft can be chosen.
42.4 Technique
The patient is taken to the operating theater and placed in a supine position with his left arm and hand placed on an arm table. Under general anesthesia, the left arm and the right iliac crest are prepared with sterilized solution and an upper arm tourniquet is applied.
42.4.1 Left Hand
The preexisting scar along the transposed index finger is incised, followed by exposure of the broken titanium plate (▶Fig. 42.4a,b). If the finger position is acceptable prior to surgery, its orientation should be held by temporarily transfixing the third to the fourth metacarpal using two 1.25-mm K-wires. The broken plate is then removed. Subsequently, the pseudarthrosis is resected taking care to remove all scar tissue (▶Fig. 42.4c).
The bony ends of the metacarpal are exposed followed by step-by-step resection with a burr and/or an oscillating saw with open tourniquet until cancellous bone and bleeding spots are identified, making sure scar tissue and sclerotic bone are resected completely. Care is to be taken to avoid excessive heat development by continuous cooling with water. The dimension of the resulting bony defect is measured. The incision is then extended radially and proximally toward the radial artery in the snuffbox. Care has to be taken not to damage branches of the superficial branch of the radial nerve. The dorsal branch of the radial artery and the cephalic vein are identified and marked with vessel loops.
42.4.2 Right Iliac Crest
An incision over the inguinal ligament reaching from the palpable femoral artery along the inguinal ligament toward the superior anterior iliac spine is carried out and advanced along the iliac crest retaining a skin flap according to the expected cutaneous defect on the left hand, advancing through the lower border of the internal abdominal muscle using the fiber-splitting technique. Subsequently severing the internal oblique and transverse abdominal muscles, the pedicle of the deep circumflex iliac artery is identified (▶Fig. 42.5a). The skin flap is incised medially and the pedicle developed along its craniolateral course. The iliac muscle is lifted off the ilium and the bone resection is planned. The most ventral site of the osteotomy should be about 3 cm dorsal of the superior anterior iliac spine, in order to prevent fracture of the iliac bone. Incision of the flap and preparation of the iliac bone from laterally, followed by osteotomy and harvest of the osteocutaneous flap (▶Fig. 42.5b). Care has to be taken of the cutaneous branch of the lateral femoral nerve.
