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2. Purpose Background Diagnostic studies have developed enhanced protocols to detect specific injury to the plantar plate2,5,6. Principle stabilizer of the MTP joint The integrity is essential to stabilize the proximal phalanx of the lesser toes4. Descriptions of plantar plate ruptures on MRI have been well documented by Yao et al1,2 Gregg et al3 found that MRI was high in sensitivity but low in specificity in cadavers.

3. Purpose To assess the utility of magnetic resonance imaging (MRI) in diagnosing injury of the plantar plate ligament to the second metatarsophalangeal (MTP) joint To determine the reliability of MRI as a diagnostic tool with correlation to intra-operative observations as a reference standard. Prospective, diagnostic study EBM Level of evidence: II (prospective diagnostic)

4. Methods IRB approved Prospectively enrolled consecutive adult subjects after clinical suspicion of plantar plate pathology Power analysis for this research has determined the need for at least 45 subjects Alpha level = 0.05, Observed R2 = 0.15, Observed Power = 0.80). Sensitivity, specificity, positive predictive values and negative predictive values were calculated using this model. All statistical analysis were performed by an outside consultant statistician using SPSS version 14.0 (SPSS Science Inc, Chicago, Ill).

5. Methods Inclusion Criteria Clinical diagnosis Healthy male or female, ages 18-75 Failed at non-operative treatments for a period of at least three months Elected for surgical correction Exclusion Criteria Previous surgery to 2nd MTP joint region Known allergy to contrast dye Chronic kidney disease Women who are pregnant Any contraindications to MRI, including history of implanted pacemaker, loose shrapnel, ocular implants, or ventricular stents

6. Methods MRI to be performed at 0.31 T (O-Scan Extremity MRI, BiosoundEsaote Inc, Indianapolis, IN). Evaluation included coronal T1-weighted images coronal T2-weighted images coronal fast-spin-echo short tau inversion recovery images sagittal T1-weighted images sagittal T2-weighted images sagittal fast-spin-echo short tau inversion recovery images One fellowship-trained musculoskeletal radiologist created the protocol and evaluated the MRI data Two different attending surgeons performed the surgeries. One foot & ankle fellow was present to observe all intra-operative findings.

7. Results Demographics All 41 patients (45 feet) elected to have surgery to the case foot From August 2010 until May 2011, 41 patients (45 feet) underwent MRI scan for suspected plantar plate pathology. Thirty eight were female and three male with an average age of 52.4

8. Results MRI Reading 39 cases were read as “tear” 6 cases were read as “no tear” Visual inspection All 39 were confirmed “tear” 4 of 6 were confirmed “no tear” 2 of 6 were in fact “tears”

9. Results

10. Results Sensitivity = 95% Specificity = 100% Positive Predictive Value = 100% Negative Predictive Value = 67%

11. Discussion MRI appears to be good a “ruling-in” test for a tear MRI does not appear to give false positives. However, MRI may not be as accurate for “ruling-out” a tear. Accurate predictive values from MRI results may be meaningful for those who: Wish to repair the plantar plate ligament May not recognize the prevalence of this pathology in lesser MTP joint deformities.

12. Discussion Strength Prospective, diagnostic Power analysis to determine needed sample size Statistical analysis Simple, reproducible study Weakness Assessor bias No blinding

13. Conclusions We hope with these protocols more clinicians can assess the utility of magnetic resonance imaging in the diagnosis of injury to the plantar plate ligament We are planning to evaluate the utility of diagnostic ultrasound vs MRI in assessing plantar plate tears

14. References Yao L, Cracchiolo A, Farahani K, et al. Magnetic resonance imaging of plantar plate rupture. Foot Ankle Int. 1996;17:33-36. Yao L, Do HM, Cracchiolo A, et al. Plantar plate of the foot: findings on conventional arthrography and MR imaging. AJR Am J Roentgenol. 1994;163:641-644. Gregg JM, Silberstein M, Schneider T, et al. Sonography of plantar plates in cadavers: correlation with MRI and histology. AJR Am J Roentgenol. 2006;186:948-955. Yu GV, Judge MS, Hudson JR, et al. Predislocation syndrome. Progressive subluxation/dislocation of the lesser metatarsophalangeal joint. J Am Podiatr Med Assoc. 2002;92:182-199. Powless SH, Elze ME. Metatarsophalangeal joint capsule tears: an analysis by arthrography, a new classification system and surgical management. J Foot Ankle Surg. 2001;40:374-389. Karpman RR, MacCollum MS, 3rd. Arthrography of the metatarsophalangeal joint. Foot Ankle. 1988;9:125-129. Weil Jr L, Sung W, Weil Sr LS, et al. Anatomic Plantar Plate Repair. Tech Foot Ankl Surg. 10(1):33-39, March 2011.