Document:

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                                                                   EXHIBIT 10.31

AMENDMENT TO REVENUE INTERESTS ASSIGNMENT AGREEMENT AND STOCK PURCHASE
----------------------------------------------------------------------
                              AGREEMENT
                              ---------

         This AMENDMENT TO REVENUE INTERESTS ASSIGNMENT AGREEMENT AND STOCK
PURCHASE AGREEMENT (this "Amendment") is entered into as of March 22, 2002 by
and among Orthovita, Inc., a Pennsylvania corporation ("Orthovita"), Vita
Special Purpose Corp., a Delaware corporation and wholly-owned subsidiary of
Orthovita ("Assignor"), and Paul Capital Royalty Acquisition Fund, L.P., a
Delaware limited partnership ("Assignee").

                              B A C K G R O U N D

         WHEREAS, Orthovita, Assignor and Assignee have entered into a Revenue
Interests Assignment Agreement dated as of October 16, 2001 (the "Assignment
Agreement"), pursuant to which Assignor sold and assigned to Assignee, and
Assignee purchased from Assignor, the Assigned Interests, which represent
certain interests in revenues generated by certain sales of Orthovita's
products;

         WHEREAS, as a condition to the Assignment Agreement, Assignee purchased
2,582,645 shares of Orthovita's Common Stock (the "Shares") under a certain
Stock Purchase Agreement dated as of October 16, 2001 between Orthovita and
Assignee (the "Stock Purchase Agreement");

         WHEREAS, certain sections of the Assignment Agreement provide that
Assignor is entitled to certain credits (the "Equity Credits") to be applied
against amounts payable to Assignee in respect of the Assigned Interests, with
the amounts of such Equity Credits based on the proceeds realized from
Assignee's sale of the Shares;

         WHEREAS, Orthovita and Assignor have agreed to waive all of their right
and interest in and to the Equity Credits in consideration of Assignee's
agreement to forfeit and surrender all of its right and interest in and to
860,882 of the Shares (the "Surrendered Shares") and to reduce the repurchase
price of the Assigned Interests as described herein;

         NOW, THEREFORE, in order to implement the foregoing and in
consideration of the mutual agreements contained herein and for other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, Orthovita, Assignor and Assignee, intending to be legally bound
hereby, agree as follows:

1.       Definitions.  Except as expressly provided otherwise herein,
         -----------
capitalized terms used but not otherwise defined herein shall have the meanings
ascribed to them in the Assignment Agreement.
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2.       Amendments to Assignment Agreement. Orthovita and Assignor hereby waive
         ----------------------------------
all of their right and interest in and to the Equity Credits.  Accordingly, the
amendments set forth below are hereby made to the Assignment Agreement:

         a.       Section 2.02(c) is deleted in its entirety.

         b.       Section 2.02(d)(ii) is amended and restated in its entirety to
read as follows:

         "(ii) in the event that the aggregate of the Daily Amounts received by
         Assignee during any period commencing on the first day of each Fiscal
         Year and ending on the last day of a fiscal quarter, taking into
         account the Advance Payments made in respect of such Fiscal Year and
         any true-up payment previously made under this Section 2.02(d)(ii) in
         respect of such Fiscal Year, (x) is less than the Weighted Average
         Applicable Percentage of Net Sales for such period, then on the
         applicable True-Up Date, Assignor shall pay to Assignee an amount equal
         to such difference, or (y) is greater than the Weighted Average
         Applicable Percentage of Net Sales for such period, then on the
         applicable True-Up Date, Assignee shall pay to Assignor an amount equal
         to such difference attributable to any payments previously made by
         Assignor in respect of such Fiscal Year, (any amount payable pursuant
         to the preceding clause (x) or clause (y), a "True-Up Amount").
         Assignor shall, within five (5) Business Days after receipt of any
         amounts in respect of any accounts previously written-off for which no
         Applicable Percentage of Net Sales were paid to Assignee, remit to
         Assignee the Applicable Percentage (such Applicable Percentage to be
         based upon the Applicable Percentage at the time that such accounts
         were written-off) of any such recoveries."

In addition, footnote number 2 is deleted in its entirety.

         c.       The beginning of the first sentence of Section 5.07(a) is
amended and restated in its entirety to read as follows:

         "(a) In the event that a Purchase Option Event shall occur during the
         Term, the Assignee shall have the right, but not the obligation (the
         "Assignee Option Repurchase"), exercisable within two hundred seventy
          --------------------------
         (270) days of its receipt of written notice from the Assignor of the
         Purchase Option Event (the "Purchase Option Exercise Period"), to
                                     -------------------------------
         require the Assignor to repurchase from the Assignee the Assigned
         Interests for a repurchase price equal to the difference between (x) an
         amount (the "Base Amount") that, when added together with all amounts
         paid to Assignee in respect of the Assigned Interests (including,
         without limitation, amounts paid under Section 5.07(d), Advance Payment
         Amounts, and all amounts payable in respect of Net Sales) and not
         repaid by Assignee to Assignor (the "Prior Amounts"), causes the sum of
         the Base Amount and the Prior Amounts (the "Total Sum") to equal the

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         Aggregate Purchase Price when the Total Sum is discounted annually at
         the Applicable Discount Rate to the date or dates on which the
         Aggregate Purchase Price or installments thereof were paid to Assignor,
         and (y) $3,333,333 (such difference is referred to as the "Assignee
                                                                    --------
         Option Repurchase Price"); . . ."
         -----------------------

         d.       The first sentence of Section 5.07(c) is amended and restated
in its entirety to read as follows:

         "In the event that a Call Option Event shall occur, then Assignor shall
         have the option ("Assignor Option Repurchase"), to repurchase the
                           --------------------------
         Assigned Interests for a repurchase price ("Assignor Option Repurchase
                                                     --------------------------
         Price") equal to $16,666,667 less any amounts received by Assignee
         -----
         pursuant to Section 5.07(d), Advance Payment Amounts for the Fiscal
         Year in which the Call Option Event occurs; provided, however, that if
         the event constituting a Call Option Event also constitutes a Purchase
         Option Event, and each of Assignee and Assignor exercise the Assignee
         Option Repurchase and the Assignor Option Repurchase, respectively,
         within 40 days of each other, the repurchase price shall equal the
         average of the Assignor Option Repurchase Price and the Assignee Option
         Repurchase Price; provided, further, that if (i) the Call Option Event
         that results in the Assignor exercising the Assignor Option Repurchase
         occurs during the Purchase Option Exercise Period of a separate, prior
         Purchase Option Event that did not also constitute the Call Option
         Event at issue, and (ii) Assignee exercises its Assignee Option
         Repurchase in respect thereof within 40 days of receipt of notice of
         the exercise by Assignor of the Assignor Option Repurchase, then,
         notwithstanding anything contained in Section 5.07(a) to the contrary,
         the repurchase price shall equal the greater of the Assignee Option
         Repurchase Price and the Assignor Option Repurchase Price."

         e.       The phrase ", and as provided in Section 2.02(c) hereof" is
deleted from the first sentence of Section 7.02 (Effect of Termination).

         f.       The phrase ", and in the last sentence of Section 2.02(c)," is
deleted from the second sentence of Section 8.01 (Survival).

         g.       The definition of the term "Transferees" contained in Section
                                              -----------
1.01 is deleted.

         h.       The beginning of the first sentence of Section 5.10
(Remittance to Lockbox Account) is amended to replace the phrase "Within sixty
(60) days after the date of this Agreement" with "On or before May 31, 2002".

3.       Amendments to Stock Purchase Agreement. Assignee hereby waives all of
         --------------------------------------
its right and interest in and to the Surrendered Shares. Accordingly, the
amendments set forth below are hereby made to the Stock Purchase Agreement.
Capitalized terms used in

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Section 3 of this Amendment but not otherwise defined herein shall have the
meanings ascribed to them in the Stock Purchase Agreement.

         a.       Section 4.7 (Registration Statement) is amended to change the
date by which Orthovita is obligated to file the Initial Registration Statement
(as such term is defined in the Stock Purchase Agreement) from 45 days after
the Closing Date to May 15, 2002.

         b.       The parties further agree that all references to "Investor
Shares" as used in Section 4.7 of the Stock Purchase Agreement shall mean the
1,721,763 Shares that are not being surrendered and forfeited pursuant to this
Amendment (the "Remaining Shares").

4.       Representations and Warranties of Assignee. Assignee hereby makes the
         ------------------------------------------
following representations and warranties to Orthovita as of the date hereof:

         a.       Assignee is the record and beneficial owner of, and has good
and marketable title to, the Surrendered Shares, free and clear of any and all
Liens or options in favor of, or claims of, any other Person.

         b.       Assignee hereby makes all of the representations and
warranties set forth in Section 3.2(c) of the Stock Purchase Agreement to
Orthovita as of the date hereof with respect to the Remaining Shares, including
without limitation, that it is an "accredited investor" within the meaning of
Rule 501 of Regulation D promulgated under the Securities Act of 1933, as
amended.

5.       No Material Adverse Change. Orthovita hereby represents and warrants to
         --------------------------
Assignee that as of the date hereof, since October 16, 2001, there has been no
material adverse change in the business, assets, financial condition, results of
operations, prospects or properties of the Company and its subsidiaries taken as
a whole, except as has been disclosed in any filings with the Securities and
Exchange Commission made by the Company prior to the date hereof pursuant to
Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended. The
parties agree that losses incurred in the ordinary course of business shall not
be deemed a material adverse change.

6.       Stock Certificate. Simultaneous with the execution and delivery hereof,
         -----------------
Assignee shall deliver to Orthovita the original share certificate representing
the Shares (the "Original Certificate"). Within two business days after
Orthovita's receipt of the Original Certificate, Orthovita shall issue and
deliver to Assignee a share certificate or certificates representing the
Remaining Shares, which certificate or certificates shall be registered in
Assignee's name or such name as Assignee designates.

7.       Release of Claims. Assignee, for itself and its affiliates, hereby
         -----------------
waives any and all claims: (i) to the Surrendered Shares issued by Orthovita;
(ii) to a refund of that portion of the purchase price paid by Assignee for the
Surrendered Shares; (iii) relating to the failure of Orthovita to have filed a
registration statement covering the resale of the Shares within 45 days after
the Closing Date pursuant to the Stock Purchase Agreement; and (iv)

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relating to the parties' failure to have executed a Lockbox Agreement within 60
days after the Closing Date.

8.       Governing Law. This Amendment shall be governed by and construed
         -------------
under the laws of the State of New York without giving effect to its conflict
of laws provisions.

9.       Amendments and Waivers. Neither this Amendment nor any provision
         ----------------------
thereof may be amended, modified, discharged or terminated, except by an
instrument in writing, signed by the party against whom any modification,
amendment, discharge or termination is sought. Any term or condition of this
Amendment may be waived at any time by the party that is entitled to the
benefit thereof, but no such waiver shall be effective unless set forth in a
written instrument duly executed by or on behalf of the party waiving such term
or condition. No waiver by any party of any term or condition of this
Amendment, in any one or more instances, shall be deemed to be or construed as
a waiver of the same or any other term or condition of this Amendment on any
future occasion. All remedies, either under this Amendment or by law or
otherwise afforded, will be cumulative and not alternative.

10.      Entire Agreement. This Amendment and the documents referred to herein
         ----------------
constitute the entire agreement among the parties with respect to the subject
matter hereof and thereof, and no party shall be liable or bound to any other
party in any manner by any warranties, representations or covenants except as
specifically set forth herein or therein.

11.      Counterparts. This Amendment may be executed in counterparts, each of
         ------------
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

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     IN WITNESS WHEREOF, the parties have executed this Amendment as of the date
first written above.

                                    ORTHOVITA, INC.

                                    By: /s/ Bruce Peacock
                                        -----------------
                                            Bruce Peacock,
                                            Chief Executive Officer

                                    VITA SPECIAL PURPOSE CORP.

                                    By: /s/ Joseph M. Paiva
                                         -------------------
                                            Joseph M. Paiva,
                                            Vice President

                                    PAUL CAPITAL ROYALTY ACQUISITION FUND, L.P.

                                    By: Paul Capital Management, LLC, its
                                    General Partner

                                        By:  /s/ Walter Flamenbaum
                                             ---------------------
                                                 Walter Flamenbaum, M.D.,
                                                 Managing Member

                                      6<PAGE>

                                                                   Exhibit 10.19

                               TECHNISOURCE, INC.
                       NONQUALIFIED STOCK OPTION AGREEMENT

This Nonqualified Stock Option Agreement (the "Agreement"), effective as of
August 17, 2001 (the "Date of Grant"), is made by and between Technisource,
Inc., a Florida corporation (the "Company"), and Andrew C. Hill (the
"Participant").

                                   Background
                                   ----------

The Company has established the Technisource, Inc. Long-Term Incentive Plan (the
"Plan"). The Company wishes to grant to the Participant a Nonqualified Stock
Option pursuant to the terms of the Plan.

Therefore, in consideration of the mutual covenants contained in this Agreement
and other good and valuable consideration, the Company and the Participant agree
as follows:

1.   Grant of Option. In consideration of service to the Company and for other
     good and valuable consideration, the Company grants to the Participant a
     Nonqualified Stock Option (the "Option") to purchase 25,000 shares of the
     Company's common stock. The Company grants the Option in accordance with
     the terms and conditions of the Plan and this Agreement.

2.   Option Price. The urchase price of the shares of stock covered by the
     Option shall be the Fair Market Value of the stock on the Date of Grant,
     which was $1.51 per share.

3.   Adjustments in Option. If the outstanding shares of stock subject to the
     Option are changed into or exchanged for a different number or kind of
     shares of the Company or other securities of the Company by reason of
     merger, consolidation, recapitalization, reclassification, stock split,
     stock dividend or combination of shares, the shares subject to the Option
     and the price per share shall be equitably adjusted to reflect such
     changes. Such adjustment in the Option shall be made without change in the
     total price applicable to the unexercised portion of the Option (except for
     any change in the aggregate price resulting from rounding-off of share
     quantities or prices) and with any necessary corresponding adjustment in
     the Option price per share. Any such adjustment made by the Committee shall
     be final and binding upon the Participant, the Company and all other
     interested persons.

4.   Person Eligible to Exercise Option. During the lifetime of the Participant,
     only the Participant may exercise the Option or any portion of the Option.
     After the death of the Participant, any exercisable portion of the Option
     may, prior to the time when the Option becomes unexercisable under the
     terms of the Plan, be exercised by the Participant's personal
     representative or by any other person empowered to do so under the
     Participant's will, trust or under then applicable laws of descent and
     distribution.

5.   Manner of Exercise. The Option, or any portion of the Option, shall be
     exercised only in accordance with the provisions of the Plan and this
     Agreement. The person exercising the Option

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     shall give to the Company a written notice that shall: (i) state the number
     of Shares with respect to which the Option is being exercised; and (ii)
     specify a date (other than a Saturday, Sunday or legal holiday) not less
     than five nor more than ten days after the date of such written notice, as
     the date on which the Shares will be purchased. Such tender and conveyance
     shall take place at the principal office of the Company during ordinary
     business hours, or at such other hour and place agreed upon by the Company
     and the person or persons exercising the Option. On the date specified in
     such written notice, the Company shall accept payment for the Option Shares
     in cash, by bank or certified check, by wire transfer, or by such other
     means as may be approved by the Committee and shall deliver to the person
     or persons exercising the Option in exchange therefor an appropriate
     certificate or certificates for fully paid nonassessable Shares or
     undertake to deliver certificates within a reasonable period of time. In
     the event of any failure to take up and pay for the number of Shares
     specified in such written notice on the date set forth therein (or on the
     extended date as above provided), the right to exercise the Option shall
     terminate with respect to such number of Shares, but shall continue with
     respect to the remaining Shares covered by the Option and not yet acquired
     pursuant thereto.

     The person who exercises the Option shall warrant to the Company that, at
     the time of such exercise, such person is acquiring his or her Option
     Shares for investment and not with a view to, or for or in connection with,
     the distribution of any such Shares, and shall make such other
     representations, warranties, acknowledgments, and affirmations, if any, as
     the Committee may require. In such event, the person acquiring such Shares
     shall be bound by the provisions of an appropriate legend which shall be
     endorsed upon the certificate(s) evidencing his or her Option Shares issued
     pursuant to such exercise. The Company may delay issuance of the Shares
     until completion of any action or obtaining any consent that the Company
     deem necessary under any applicable law (including without limitation state
     securities or "blue sky" laws).

6.   Conditions to Issuance of Stock Certificates. The shares of stock
     deliverable upon the exercise of the Option, or any portion thereof, may be
     either previously authorized but unissued shares or issued shares which
     have been reacquired by the Company. Such shares shall be fully paid and
     nonassessable.

7.   Rights of Shareholders. The Participant shall not be, nor have any of the
     rights or privileges of, a shareholder of the Company in respect of any
     shares purchasable upon the exercise of any part of the Option unless and
     until certificates representing such shares shall have been issued by the
     Company to the Participant.

8.   Vesting and Exercisability. A Participant's interest in the Option shall
     vest according to the provisions of this Section 8 and shall be exercisable
     as to not more than the vested percentage of the shares subject to the
     Option at any point in time. The Option shall become 100% vested on August
     16, 2002. The Committee, in its sole and absolute discretion, may
     accelerate the vesting of the Option at any time. In the event of a Change
     in Control of the Company, any unvested portion of the Option shall
     immediately become 100% vested and the Board of Directors of the Company
     may, but is not required to, terminate the Option effective upon the date
     of the Change in Control and make a cash payment to the Participant equal
     to the difference between

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     the exercise price of the Option and the fair market value of the shares
     that would have been subject to the terminated Option on the date of the
     Change in Control

     A "Change in Control" shall mean when (i) any person, including a "group"
     as defined in Section 13(d)(3) of the Securities Exchange Act of 1934, as
     amended, who does not currently own ten percent or more of the Company's
     capital stock becomes the beneficial owner of thirty-three percent or more
     of the capital stock of the Company, (ii) the Company is merged into any
     other company and the holder's of the Company's common stock immediately
     prior to such merger fail to hold at least fifty percent of the common
     stock of the Company immediately following such merger, or substantially
     all of the Company's assets are acquired by any other entity, or (iii)
     three or more directors nominated by the Board to serve as a director, each
     having agreed to serve in such capacity, fail to be elected in a contested
     election of directors.

9.   Duration of Option. Except as specified below, the Option shall expire on
     August 16, 2011. Notwithstanding the foregoing, the Option may expire prior
     to August 16, 2001 in the following circumstances:

     a.   In the case of the Participant's death, the Option shall expire on the
          one-year anniversary of the Participant's death.

     b.   If the Participant's employment or affiliation with the Company
          terminates as a result of his total and permanent disability, the
          Option will expire on the one-year anniversary of the Participant's
          last day of employment.

     c.   If the Participant ceases employment or affiliation with the
          Company for any reason other than death or disability, the Option
          shall expire 90 days following the last day that the Participant is
          employed by the Company.

     d.   Notwithstanding any provisions set forth above in this Section 9,
          if the Participant shall (i) commit any act of malfeasance or
          wrongdoing affecting the Company or its affiliates, (ii) breach any
          covenant not to compete or employment agreement with the Company or
          any affiliate, or (iii) engage in conduct that would warrant the
          Participant's discharge for cause, any unexercised part of the Option
          shall expire immediately upon the earlier of the occurrence of such
          event or the last day the Participant is employed by the Company.

10.  Administration. The Committee shall have the power to interpret this
     Agreement and to adopt such rules for the administration, interpretation
     and application of the Agreement as are consistent herewith and to
     interpret or revoke any such rules. All actions taken and all
     interpretations and determinations made by the Committee in good faith
     shall be final and binding upon the Participant, the Company and all other
     interested persons. No member of the Committee shall be personally liable
     for any action, determination or interpretation made in good faith with
     respect to this Agreement or any similar agreement to which the Company is
     a party.

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11.  Transfer of Option. Unless otherwise permitted by applicable laws and
     approved in advance by the Committee, the Option shall not be transferable
     by the Participant and shall be exercisable, during the Participant's
     lifetime, only by such Participant or, in the event of the Participant's
     incapacity, his guardian or legal representative. Except as otherwise
     permitted herein, the Option shall not be assigned, pledged, or
     hypothecated in any way (whether by operation of law or otherwise) and
     shall not be subject to execution, attachment, or similar process and any
     attempted transfer, assignment, pledge, hypothecation or other disposition
     of the Option or of any rights granted thereunder contrary to the
     provisions of this Section 11, or the levy of any attachment or similar
     process upon an option or such rights, shall be null and void. This Section
     11 shall not prevent transfers by will or by the applicable laws of descent
     and distribution.

12.  Shares to be Reserved. The Company shall at all times during the term of
     the Option reserve and keep available such number of shares of stock as
     will be sufficient to satisfy the requirements of this Agreement.

13.  Notices. Any notice to be given under the terms of this Agreement to the
     Company shall be addressed to the Company in care of its Secretary and any
     notice to be given to the Participant shall be addressed to him at the
     address given beneath his signature below. By a notice given pursuant to
     this Section 13, either party may hereafter designate a different address
     for notices to be given to him. Any notice which is required to be given to
     the Participant shall, if the Participant is then deceased, be given to the
     Participant's personal representative if such representative has previously
     informed the Company of his status and address by written notice under this
     Section 13. Any notice shall have been deemed duly given when enclosed in a
     properly sealed envelope addressed as aforesaid, deposited (with postage
     prepaid) in a United States postal receptacle.

14.  Titles. Titles are provided herein for convenience only and are not to
     serve as a basis for interpretation or construction of this Agreement.

15.  Incorporation of Plan by Reference. The Option is granted in accordance
     with the terms and conditions of the Plan, the terms of which are
     incorporated herein by reference, and the Agreement shall in all respects
     be interpreted in accordance with the Plan. Any term used in the Agreement
     that is not otherwise defined in the Agreement shall have the meaning
     assigned to it by the Plan.

                                       4

<PAGE>

The Company and the Participant have executed this Agreement effective as of the
date first written above.
                                      TECHNISOURCE, INC.

                                      By:________________________________
                                      Name:  James F. Robertson
                                      Title:  President, Chief Operating Officer

                                      ___________________________________
                                      Andrew C. Hill

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