Predictive Outcome Modeling of Preoperative Clinical Symptoms and Electrodiagnostic Data in Tarsal Tunnel Surgery.

Scott R Millis,Frederick Carington,Geoffrey K Seidel,Michael T Andary,Salma Al Jamal,Brian G Loder,Eric Weidert

doi:10.1055/s-0041-1731747

Abstract

Background The relationship between tarsal tunnel syndrome (TTS), electrodiagnostic (Edx) findings, and surgical outcome is unknown. Analysis of TTS surgical release outcome patient satisfaction and comparison to Edx nerve conduction studies (NCSs) is important to improve outcome prediction when deciding who would benefit from TTS release. Methods Retrospective study of 90 patients over 7 years that had tarsal tunnel (TT) release surgery with outcome rating and preoperative tibial NCS. Overall, 64 patients met study inclusion criteria with enough NCS data to be classified into one of the following three groups: (1) probable TTS, (2) peripheral polyneuropathy, or (3) normal. Most patients had preoperative clinical provocative testing including diagnostic tibial nerve injection, tibial Phalen's sign, and/or Tinel's sign and complaints of plantar tibial neuropathic symptoms. Outcome measure was percentage of patient improvement report at surgical follow-up visit. Results Patient-reported improvement was 92% in the probable TTS group ( n = 41) and 77% of the non-TTS group ( n = 23). Multivariate modeling revealed that three out of eight variables predicted improvement from surgical release, NCS consistent with TTS ( p = 0.04), neuropathic symptoms ( p = 0.045), and absent Phalen's test ( p = 0.001). The R 2 was 0.21 which is a robust result for this outcome measurement process. Conclusion The best predictors of improvement in patients with TTS release were found in patients that had preoperative Edx evidence of tibial neuropathy in the TT and tibial nerve plantar symptoms. Determining what factors predict surgical outcome will require prospective evaluation and evaluation of patients with other nonsurgical modalities.

Highlights

Tarsal tunnel syndrome (TTS) is difficult to diagnose without universal agreement on the diagnostic criteria
The best predictors of improvement in patients with TTS release were found in patients that had preoperative Edx evidence of tibial neuropathy in the tarsal tunnel (TT) and tibial nerve plantar symptoms
64 patients with TTS surgical decompression and Edx nerve conduction studies (NCSs) data descriptive group statistics are presented in ►Table 1

Summary

Introduction

Tarsal tunnel syndrome (TTS) is difficult to diagnose without universal agreement on the diagnostic criteria. TTS often has diffuse, poorly localizable, plantar symptoms and physical examination findings fail to confirm tibial nerve compression.[1] Electrodiagnostic (Edx) evaluation assists in confirmation of neurophysiologic abnormalities within the tarsal tunnel (TT).[2,3] Edx studies have documented measurable changes of tibial nerve conduction studies (NCSs) with good outcomes following surgical decompression.[2,4,5,6,7] These studies had small patient numbers and primarily assessed tibial motor and MP and LP sensory nerve action potentials (SNAPs) but not mixed nerve action potentials (MNAPs). MNAPs (historically labeled compound nerve action potentials or CNAPs) measure both sensory and motor action potentials along the MP and LP nerve branches of the tibial nerve. The relationship between tarsal tunnel syndrome (TTS), electrodiagnostic (Edx) findings, and surgical outcome is unknown. Analysis of TTS surgical release outcome patient satisfaction and comparison to Edx nerve conduction studies (NCSs) is important to improve outcome prediction when deciding who would benefit from TTS release

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