Exhibit 5.1

[LETTERHEAD OF SIMPSON THACHER & BARTLETT LLP]

October 17, 2014

HCA Inc.

One Park Plaza

Nashville, Tennessee 37203

Ladies and Gentlemen:

We have acted as counsel to HCA Inc., a Delaware corporation (the “Company”), HCA Holdings, Inc., a Delaware corporation and the direct parent of the Company (“Holdings”), and the subsidiaries of the Company listed on Schedules I and II hereto (collectively, the “Subsidiary Guarantors” and, together with Holdings, the “Guarantors”) in connection with the Registration Statement on Form S-3 (File No. 333-175791), as amended by Post-Effective Amendments Nos. 1, 2, 3 and 4 thereto (as amended, the “Registration Statement”), filed by the Company and the Guarantors with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), relating to the issuance thereunder by the Company of (i) $600,000,000 aggregate principal amount of 4.25% Senior Secured Notes due 2019 (the “2019 Notes”) and (ii) $1,400,000,000 aggregate principal amount of 5.25% Senior Secured Notes due 2025 (together with the 2019 Notes, the “Notes”), each unconditionally guaranteed (collectively, the “Guarantees”) (i) on a senior unsecured basis by Holdings and (ii) jointly and severally, on a senior secured basis by each of the Subsidiary Guarantors, pursuant to the Underwriting Agreement, dated October 7, 2014 (the “Underwriting Agreement”), among the Company, the Guarantors and the underwriters named therein.

We have examined the Registration Statement as it became effective under the Act; the prospectus, dated December 10, 2012 (the “Base Prospectus”), as supplemented by the prospectus supplement, dated October 7, 2014 (together with the Base Prospectus, the “Prospectus”), filed by the Company and the Guarantors pursuant to Rule 424(b) of the rules and regulations of the Commission under the Act; the Indenture, dated as of August 1, 2011 (the “Base Indenture”), among the Company, Holdings, Law Debenture Trust Company of New York, as trustee (the “Trustee”) and Deutsche Bank Trust Company Americas, as registrar, paying agent and transfer agent (in each capacity, the “Registrar”), as supplemented by the Supplemental Indenture No. 9, dated as of October 17, 2014 (together with the Base Indenture, the “2019 Notes Indenture”), among the Company, the Guarantors, the Trustee and the Registrar, relating to the 2019 Notes and the Supplemental Indenture No. 10, dated as of October 17, 2014 (together with the Base Indenture, the “2025 Notes Indenture,” and the 2019 Notes Indenture and the 2025 Notes Indenture together, the “Indentures”), among the Company, the Guarantors, the Trustee and the Registrar, relating to the 2025 Notes; duplicates of the global notes representing the Notes; and the Underwriting Agreement.

We also have examined the originals, or duplicates or certified or conformed copies, of such records, agreements, documents and other instruments and have made such other investigations as we have deemed relevant and necessary in connection with the opinions hereinafter set forth. As to questions of fact material to this opinion, we have relied upon certificates or comparable documents of public officials and of officers and representatives of the Company and the Guarantors.

In rendering the opinions set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us

as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents. We also have assumed that the Indentures are the valid and legally binding obligations of the Trustee.

We have assumed further that (1) each of the Guarantors listed on Schedule I (the “Schedule I Guarantors”) is validly formed and existing, (2) the Indentures have been duly authorized, executed and delivered by each of the Schedule I Guarantors in accordance with the law of its state of incorporation or formation, and (3) the execution, delivery and performance of the Indentures and the issuance and performance of the Guarantees by each of the Schedule I Guarantors do not and will not violate the law of its state of incorporation or formation or any other applicable law (except that we make no such assumption with respect to the law of the State of New York and the federal law of the United States).

Based upon the foregoing, and subject to the qualifications, assumptions and limitations stated herein, we are of the opinion that:

Our opinions set forth above are subject to (i) the effects of bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other similar laws relating to or affecting creditors’ rights generally, (ii) general equitable principles (whether considered in a proceeding in equity or at law) and (iii) an implied covenant of good faith and fair dealing.

We do not express any opinion herein concerning any law other than the law of the State of New York, the federal law of the United States, the Delaware General Corporation Law, the Delaware Limited Liability Company Act and the Delaware Revised Uniform Limited Partnership Act.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the Current Report on Form 8-K of the Company filed with the Commission in connection with the offer and sale of the Notes and to the use of our name under the caption “Legal Matters” in the Prospectus included in the Registration Statement.

Schedule I

Guarantors Incorporated or Formed in Jurisdictions Other Than

the State of Delaware or Constituting Delaware General Partnerships

or Delaware Limited Liability Partnerships

Schedule II

Guarantors That Are Corporations, Limited Liability Companies or Limited

Partnerships Incorporated or Formed in the State of Delaware