Exhibit 4.1

Exhibit 4.1

NUMBER AMEDICA® SHARES

C 0102 US SPINE®

AMEDICA CORPORATION

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

SEE REVERSE FOR CERTAIN DEFINITIONS

This Certifies that is the owner of

FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $0.01 PAR VALUE, OF Amedica Corporation transferable on the books of the Corporation in person or by duly authorized attorney upon the surrender of this Cetificate properly endorsed. This Certificate is not valid until countersigned by the Transfer Agent and registered by the Registrar.

Witness the facsimile signatures of the Corporation’s duly authorized officers.

Dated:

CERTIFICATE OF STOCK

CHIEF FINANCIAL OFFICER

CHAIRMAN OF THE BOARD

COUNTERSIGNED AND REGISTERED:

AMERICAN STOCK TRANSFER & TRUST COMPANY, LLC

(NEW YORK, N.Y.)

TRANSFER AGENT AND REGISTRAR

AUTHORIZED SIGNATURE

The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:

TEN COM — as tenants in common

TEN ENT — as tenants by the entireties

JT TEN — as joint tenants with right of survivorship and not as tenants in common

UNIF GIFT MIN ACT — as Custodian for

(Cust) (Minor)

under Uniform Gifts to Minors

Act

(State)

UNIF TRAN MIN ACT — as Custodian for

(Cust) (Minor)

under Uniform Transfers to Minors

Act

(State)

Additional abbreviations may also be used though not in the above list.

For value received, hereby sell, assign and transfer unto

PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE

(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

shares of the common stock represented by the within Certificate, and do hereby irrevocably constitute and appoint

Attorney to transfer the said stock on the books of the within named Corporation with full power of substitution in the premises.

Dated

X

NOTICE: THE SIGNATURE(S) TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME(S) AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.

X

ALL GUARANTEES MUST BE MADE BY A FINANCIAL INSTITUTION (SUCH AS A BANK OR BROKER) WHICH IS A PARTICIPANT IN THE SECURITIES TRANSFER AGENTS MEDALLION PROGRAM (“STAMP”), THE NEW YORK STOCK EXCHANGE, INC. MEDALLION SIGNATURE PROGRAM (“MSP”), OR THE STOCK EXCHANGES MEDALLION PROGRAM (“SEMP”) AND MUST NOT BE DATED. GUARANTEES BY A NOTARY PUBLIC ARE NOT ACCEPTABLE.

This certificate also evidences and entitles the holder hereof to certain Rights as set forth in a Rights Agreement (the Rights Agreement) between Sigma-Aldrich Corporation (the Company) and Computershare Investor Services, LLC, as Rights Agent, as it may from time to time be supplemented or amended, the terms of which are incorporated herein by reference and a copy of which is on file at the principal executive offices of the Company. Under certain circumstances, as set forth in the Rights Agreement, such Rights may expire or may be redeemed, exchanged or be evidenced by separate certificates and no longer be evidenced by this certificate. The Company will mail to the holder of this certificate a copy of the Rights Agreement without charge promptly after receipt of a written request therefor. Under certain circumstances, Rights issued to or held by Acquiring Persons or their Affiliates or Associates (as defined in the Rights Agreement) and any subsequent holder of such Rights may become null and void.