Commentary & Perspective

Commentary & Perspective on
"The Insensate Foot Following Severe Lower Extremity Trauma: An Indication for Amputation?"
by Michael J. Bosse, MD, et al.

Commentary & Perspective by
Andrew H. Schmidt, MD*,
Hennepin County Medical Center, Minneapolis, Minnesota

Integrity of the tibial nerve has been considered an important factor that influences outcome after severe lower-extremity trauma. Lange et al. were among the first to suggest a protocol for limb salvage or amputation after open tibial fractures, and included "anatomically complete disruption of the posterior tibial nerve in adults" as one of two absolute indications for amputation1. Although the criteria for anatomic disruption of the tibial nerve has been reiterated by subsequent investigators2,3, a more pragmatic but less precise definition of tibial nerve injury has evolved: namely, loss of plantar sensation. In the clinical venue, an insensate plantar foot is assumed to represent dysfunction of the tibial nerve, and in the absence of anatomic verification of nerve disruption, this factor often is considered when making a decision about amputation4.

The Lower Extremity Assessment Project (LEAP) is a prospective, multicenter observational outcome study of 601 patients with high-energy, limb-threatening lower extremity injuries. The presence or absence of plantar sensation was one of many data items collected by the LEAP investigators; therefore, this database provides a possible means of evaluating whether the presence or absence of plantar sensation influences outcome after limb salvage.

Bosse et al. compared the one and two-year outcomes of three groups of patients: an amputation group of twenty-six patients without plantar sensation, a salvage group of twenty-nine patients without plantar sensation, and a matched salvage control group of twenty-nine patients with plantar sensation.

The authors found that the outcomes were comparable among all three groups, and that in both groups of salvaged limbs, the same proportion of patients (55%) had normal plantar sensation. There are two possible explanations for these results. The first is that more than half of the patients in the insensate group regained plantar sensation while just less than half of the patients with initial intact plantar sensation later lost sensation. The second (and in my opinion more likely) explanation is that accurate assessment of plantar sensation in these severely injured patients is just not possible.

Interestingly, only one patient in the insensate limb salvage group still had an insensate foot two years after injury. Therefore, I would surmise that the one and two-year outcomes of the salvaged limbs were similar because the patients in each group were similar; nearly all had regained plantar sensation. This report, then, neither confirms nor refutes the long-held opinion that anatomic tibial nerve disruption should be a primary factor in the decision to amputate a limb after severe trauma. The long-term functional outcome of patients with permanent tibial nerve injury remains undocumented.

When faced with a severe open tibial fracture, many factors must be considered in the decision to proceed with limb salvage or early amputation. Tibial nerve disruption should still be considered an important factor in this decision, but the degree of injury of that nerve should be determined by noting its anatomic integrity rather than by assessing plantar sensation. The latter finding is simply too unreliable for clinical decision-making.

*The author did not receive grants or outside funding in support of his research for or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Lange RH, Bach AW, Hansen ST Jr, Johansen KH. Open tibial fractures with associated vascular injuries: prognosis for limb salvage. J Trauma. 1985;25:203-8.
2. Clarke P, Mollan RA. The criteria for amputation in severe lower limb injury. Injury. 1994;25:139-43.
3. Lange RH. Limb reconstruction versus amputation decision making in massive lower extremity trauma. Clin Orthop Relat Res. 1989;243:92-9.
4. MacKenzie EJ, Bosse MJ, Kellam JF, Buress AR, Webb LX, Swiontkowski MF, Sanders R, Jones AL, McAndrew MP, Patterson B, McCarthy ML, Rohde CA; LEAP Study Group. Factors influencing the decision to amputate or reconstruct after high-energy lower extremity trauma. J Trauma. 2002;52:641-9.