High-energy trauma or osteomyelitis can lead to complex composite defects in fingers with extensive bone loss. When the finger can be salvaged, bone stabilization becomes the first step of the reconstruction. However, there is often a deficit of bone tissue required for adequate reconstruction. Classic solutions include the use of bone grafts or vascularized bone grafts to fill the bone defect. However, these procedures are not practical in the context of emergency hand situations in which salvage is the primary goal.

Initially described by Masquelet and Begue² for large diaphyseal bone defects caused by tumor resection, trauma, or osteoarthritis, the induced membrane technique is a two-stage procedure allowing bone reconstruction. The concept is to place space-maintaining material in the region of the defect. This leads to a foreign body reaction, which creates a membrane mimicking the periosteum. Once this is formed, bone graft can be placed in the periosteal sleeve. Recently, Flamans and colleagues³ applied the Masquelet technique to the hand with promising results.

The first stage involves soft tissue and bone debridement followed by implantation of a polymethyl methacrylate cement spacer in the area of the bone deficit and/or defect. Bone stabilization is then provided with internal and/or external fixation. Soft tissue defects may need to be addressed with free flap coverage.

The second stage is performed 2 months later. The periosteal membrane is incised and the spacer is removed. Autologous cancellous bone graft is placed within the membrane.

The results in the hand are from studies with small numbers but are promising. There are over 15 other studies investigating this technique in bone reconstruction outside the hand.^4–7

Clinical results in the literature

For clinical results in the literature, see Table 1.

Table 1 Summary of the available clinical results of the Masquelet technique in hand surgery

Tendons are essential to hand function and are frequently involved in hand injuries. When tendon deficits exist, the current solution is to harvest expendable autologous tendon grafts (ie, palmaris, plantaris) or use tendon allograft. However, the extrasynovial nature of these tendons increases the resulting adhesions at the repair sites and often leads to a suboptimal functional outcome.⁸

Tendon tissue engineering may be a future solution in cases requiring extensive tendon reconstruction. Neotendons would ideally have the capacity to reduce adhesions and have adequate tensile strength, allowing early active rehabilitation and normal mobility.

Bioengineered tendon constructs first consist of a scaffold—natural or synthetic.⁹ Some hand surgeons choose to follow Gillies’ reconstructive principle of replacing “like with like” and use decellularized human tendon scaffolds¹⁰ from a donor bank. Other surgeons choose collagen derivatives,¹¹ polysaccharides, small intestine submucosa,¹² or human umbilical veins¹³ as natural scaffolds; whereas the synthetic scaffold uses polymers such as poly(a-hydroxyl acid)s, polylactic acid,¹⁴ or polypropylene. The ideal candidate remains to be decided. Natural scaffolds have the advantage of a high affinity to host cells allowing tissue ingrowth, but they theoretically are associated with potential risks such as disease transmission. Synthetic scaffolds have the advantage of being free of disease transmission and are easier to manufacture on a large scale. Being synthetic, however, results in less binding with the host’s cells and, therefore, less tissue proliferation. In addition, both types of scaffolds are subject to rejection (immunologic or foreign body reaction). Considerable research is underway, dedicated to creating the ideal tendon scaffold to meet the requirements of biodegradability, biocompatibility, superior mechanical properties, and optimal processing.

The second aspect of tissue-engineered tendon constructs is the addition of cells with regenerative and differentiation potential that can be used to seed these scaffolds. Several lines of cells have been studied, such as tenocytes,^15,16 adipose-derived stem cells,¹⁷ bone marrow stromal cells,^18,19 and fibroblasts. No significant differences were found between these four cell types in their ability to populate the scaffold.²⁰ To date, it is unclear whether reseeding improves the biomechanical properties of these constructs.

The third area of focus includes strategies to further enhance in vivo regeneration and incorporation of tissue-engineered tendons. The most promising concepts include growth factor supplementation,^21,22 mechanical stimuli,^17,23,24 and contact guidance.

Peripheral nerve injuries are common and 60% of these are reported to occur in the upper extremities.²⁵ The current gold standard procedure for managing such injuries is a tensionless end-to-end nerve repair. When the defect is so great that an end-to-end suture will create tension, an autologous nerve graft is performed, creating donor site morbidity and uncertain outcomes depending on the host site vascularization and the level at which the injury occurs. The need for peripheral nerve repair and regeneration strategies is, therefore, high on the priority list in research.

Many strategies have been tested, such as sutureless nerve repair using fibrin glue,²⁶ laser activated chitosan,²⁷ and end-to-side neurorrhaphy.²⁸ Nerve conduits are also a popular solution for segmental nerve defects of up to 3 cm²⁹ and have been studied since as early as the late nineteenth century. Different types of conduits exist from biologic (eg, vein, arteries) to synthetic materials (eg, collagen, caprolactone, polyglycolic acid), giving promising results in small series studies. However, randomized studies of a larger scale are needed. Brooks and colleagues³⁰ report the clinical outcome of 132 nerve injuries in a multicenter study for processed nerve allografts with recovery and safety comparable to autografts and better than nerve conduits.

The latest development in nerve regeneration is molecular and cell therapy. The goal is to augment allografts or conduits by adding cells to lower immunogenicity and increase nerve regeneration. Several types of constructs combining allografts or synthetic conduits with cells have been tested, such as adipose-derived stem cells,³¹ bone marrow–derived stem cells, Schwann cells, or (more recently) dorsal root ganglion cells.³² However, all of these combinations are still in the early stages of experimentation.