Bone Graft for Nonunion of Right Thumb Proximal Phalanx Fracture

Abstract

In this video, we describe a surgical technique for the treatment of an unstable nonunion of a proximal phalangeal fracture of the thumb. The video describes the surgical exposure, preparation of the nonunion site, harvesting of autogenous iliac corticocancellous bone graft, bone grafting of the defect, and stabilization with K-wire fixation.

Case Overview

This video describes the surgical treatment of an established nonunion of a proximal phalangeal fracture in a young teenage girl. This procedure was carried out at a mission hospital in Central America. As in many such cases, a precise history is not available, but it appears that this may have been an open fracture that became infected. This led to a nonunion. At the time of presentation, the nonunion was completely unstable and the distal part of the thumb was severely angulated and incapable of pinch and grasp. The flexor pollicis longus was functional, but it was not clear if the long extensor tendon was intact. Because of the unstable nature of this nonunion and no prospect of healing with any other form of treatment, we elected to perform a structural bone graft to facilitate union and improve stability and function in this thumb. The choice of bone graft is based on several factors. The iliac crest is a reliable source of structural graft. This is essential to provide mechanical support to the surgical construct. Autogenous bone graft has osteogenic and osteoinductive properties that make it the best choice in a nonunion situation.

The surgery is performed under general anesthesia and tourniquet control. The left upper extremity and ipsilateral iliac crest are prepped and draped in a sterile manner. The incision is made on the dorsal of the digit extending from the distal segment proximally to the metacarpal area. Deep to the subcutaneous plane, the extensor tendon was found to be scarred and deficient. The nonunion site was easily identified and filled with fibrous tissue. This fibrous tissue was excised and the opposing ends of the nonunion were identified. Excision of all interposed tissue, including fibrocartilaginous and fibrous tissue, must be performed meticulously to expose the healthy bleeding bone surface. Once this is achieved, the thumb is gently distracted and brought out to length. The resulting defect is now measured.

An autogenous iliac graft is harvested by making an incision over the anterior crest. The iliac apophysis is split down the middle and reflected to expose the bony iliac crest. A bicortical piece of bone is harvested, slightly larger than the measured defect. The iliac incision is repaired anatomically by approximating the split apophysis with heavy absorbable sutures and the fascia and skin in a routine manner. 

The bone graft is now trimmed to fit the defect. Oversizing by a millimeter or two in length allows the graft to be gently impacted into position at the nonunion site. The inherent stability of this construct is now obvious, but it is wise to stabilize this with a smooth K-wire. This K- wire should be drilled proximally into the head and neck of the metacarpal to provide adequate stability. If the graft construct is not very stable, an additional K-wire may be inserted to provide rotational stability. In this case, however, this was not found necessary. The soft tissues are now repaired in an anatomic fashion. A nonadherent bulky compressive dressing is applied followed by immobilization in a plaster splint. Once the incision is healing well and the postoperative swelling stabilized, a thumb spica cast is applied. This cast protects the thumb and K-wire from inadvertent mishaps and should be left in place until graft healing is evident. The pin is easily removed at this stage. If there is any question of graft healing, then the cast may be reapplied for an additional period.

Follow-up x-rays are typically obtained every 4 weeks until bony union occurs. Typical heal times are 10–12 weeks.

In this patient, due to the lack of a functioning extensor tendon, additional surgery may be necessary at a later stage to stabilize the distal joint

Discussion

This article presents the surgical management of nonunion following fracture of the proximal phalangeal element in the thumb of an 11-year old child. This case was performed during a surgical mission in Honduras with the World Surgical Foundation. 

Fracture of the metacarpals and phalanges is prevalent and represents approximately 40% of upper extremity fractures.¹ Nonunion is a complication following fracture that is defined as the absence of bone union that will not heal without further intervention. Depending on the location of the ununited fracture, the patient may present with pain, loss of function, instability, or shortening of the limb or digit. Nonunion is relatively rare and occurs in less than one percent of all fractures.² However, several factors have been implicated in the increased risk of nonunions. A few of these risk factors include the severity of trauma with soft tissue loss, inherently precarious blood supply such as in scaphoid and femoral neck fractures, infection, and inadequate stabilization. Systemic factors such as smoking and poorly controlled diabetes have been recognized as increasing the risk of nonunion in otherwise uncomplicated fractures. 

A nonunion can be categorized as either hypertrophic or atrophic.³ Hypertrophic nonunion is characterized by abundant callus formation and is due to inadequate immobilization. Treatment consists of stabilizing the fracture, usually by surgical fixation. On the other hand, atrophic nonunion (as in the patient presented) is due to the failure of osteogenesis with little or no callus or bridging bone. Factors that reduce bone cell viability such as infection and loss of blood supply lead to atrophic nonunions. In children, these factors may also involve the growth plate leading to premature growth arrest. Surgical principles in the treatment of atrophic nonunion include resection of unhealthy and nonviable bone and soft tissue, bone grafting to provide an osteoconductive and osteogenic environment, and internal fixation to achieve mechanical stability.

In the treatment of atrophic nonunion, there are many different graft materials or graft substitutes available to fill the gap generated during debridement. Examples include autogenous bone, allograft bone, bone marrow aspirates, demineralized bone matrix, bone morphogenetic proteins, platelet-rich plasma, and ceramics.⁴ With regards to the optimal graft material, autogenous bone has long been recognized as the gold standard. Autogenous tissue is favorable in that it is the only graft material that provides osteogenic, osteoinductive, and osteoconductive properties.⁵ Other advantages of an autogenous graft are that there is no risk of eliciting an immune response, no risk of disease transmission, and generally reliable availability. The major disadvantage of autografts is that they necessitate some level of donor site morbidity and are subject to potential risks such as the injury of nerves and blood vessels, hematoma formation, infection, and persistent pain.⁵ Autogenous graft material harvested from many different locations has been used successfully to treat nonunion following a phalangeal fracture. For structural grafts needed to bridge a gap, the iliac crest is the best source for multiple reasons.^6-10 These include ease of harvest, abundant supply of corticocancellous bone, and no serious functional deficit. For phalangeal nonunions not needing a structural graft, bone from the distal radius or proximal ulna is an easier local choice. The amount of bone needed for phalangeal fracture nonunions is small, but in other situations harvesting a larger volume of iliac crest graft has led to substantial local morbidity. This has led to surgeons seeking other sources including bone graft substitutes.

In recent years, much progress has been made in novel bone graft substitutes and clinical trials reveal that bone graft substitutes can be used successfully in many situations that previously required an autogenous bone graft.¹¹ However, these substitutes are expensive and although they may have osteoconductive and osteoinductive properties, none have the osteogenic potential of autogenous bone graft and thus it remains the gold standard in the treatment of established nonunion.¹¹

In this patient, the iliac corticocancellous bone graft functioned as a structural graft by virtue of its solid construct and stability afforded by slight overdistraction. In many diaphyseal phalangeal nonunions, this kind of construct allows immediate inherent stabilization. Supplemental fixation is usually with K-wires although small plates can be used, especially in adults where K-wire fixation is deemed unsatisfactory. Surgical stabilization allows an early range of motion. However, stability should never be compromised in favor of early mobilization in situations where the fixation is precarious as in porotic bone, in children, and uncooperative patients. In this particular case, since the patient lived in a rural area without access to frequent follow-up, we preferred to immobilize the digit until healing was complete.

Unfortunately, given the rarity of nonunion following phalangeal fractures, there have been few studies that have reported outcomes following surgical management of phalangeal atrophic nonunion. The most comprehensive investigations relevant to the case presented include two retrospective studies by Al-Qattan et al. In 2010, Al-Qattan reviewed the cases of four pediatric patients (mean age = 2.5 years) suffering from atrophic nonunion of the proximal phalanx of the thumb.¹² All patients had been previously treated with closed reduction and splinting of fractures 6–8 months before the presentation. Each patient underwent removal of dead bone, autogenous graft placement, and internal fixation with a single K-wire. The final follow-up was 1–2 years with the primary outcome measured being a range of motion of the interphalangeal (IP) joint.¹³ At follow-up, the average range of motion was found to be 8° with a range of 5–10°. Subsequently, a follow-up study was published, which assessed outcomes in four pediatric patients, this time with nonunion of digits other than the thumb. In this study, the primary outcome was the Total Active Motion (TAM) of the operated finger compared with the TAM of the same finger on the contralateral side. The TAM of the postoperative digits was, on average, 71.5% that of the control digits. The inability to achieve a full or near-complete range of motion in these digits reflects on the complex nature of finger nonunions where the integrity of the flexor and extensor tendon units and adjacent joint contractures provide unique challenges not seen in long bone nonunions. Although union can be achieved with bone-grafting techniques, the resultant scarring of the tendons ligaments from the initial insult and subsequent surgeries often leads to permanent loss of active and passive motion. 

In summary, phalangeal nonunions are rare given the frequency of fractures involving the hand. In most cases, there are obvious causes leading to nonunion. Ideally one must do everything to prevent this adverse outcome. This includes meticulous wound care and antibiotic prophylaxis in open fractures, smoking cessation, and optimal control of diabetes. In established nonunions autogenous bone grafting with internal fixation remains the gold standard of treatment.

Disclosures

Nothing to disclose.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.