Exhibit 4.28

CENTERPULSE
USA HOLDING CO.
12 East Greenway Plaza
Suite 1000
Houston, Texas 77046

January 21,
2003

SNIA
S.p.A.
Via Borgonuovo 14
20121 Milan, Italy

Gentlemen:

This
document constitutes Amendment No. 2 (this "Amendment No. 2") to the Stock Purchase Agreement, dated as of November 26, 2002, among Centerpulse Ltd.,
Centerpulse USA Holding Co. and SNIA S.p.A., as amended by Amendment No. 1 thereto (the "Purchase Agreement"). Capitalized terms used herein and not otherwise defined herein shall have the
respective meanings ascribed to such terms in the Purchase Agreement.

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[signature
page follows]

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| |  | Sincerely,                 
| |  | ---------------------------
| |  | CENTERPULSE USA HOLDING CO.
| |  | By:                        
| |  | Name:                      
| |  | Title:                     
| |  | CENTERPULSE LTD.           
| |  | By:                        
| |  | Name:                      
| |  | Title:                     
| |  | CENTERPULSE LTD.           
| |  | By:                        
| |  | Name:                      
| |  | Title:                     

Agreed
to and Accepted:

SNIA
S.p.A.

|By:    |  | /s/CARLO VANOLI |  |  |  | 
|------ |  | --------------- |  |  |  | 
|Name:  |  | Carlo Vanoli    |  |  |  | 
|Title: |  | COO             |  |  |  | 

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EXHIBIT A

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Section 3.03Capital Stock of Target Companies

|                                             |  |      |  | Authorized                |  | Outstanding              
|-------------------------------------------- |  | ---- |  | ------------------------- |  | -------------------------
|
|Centerpulse USA Holding Co.                  |  | CMI  |  | 0                         |  | 1,000                    
|Centerpulse                                  |  | CVNL |  | 0                         |  | 301                      
|Sulzer Carbomedics International Holding Co. |  | MIT  |  | 100,000,000               |  | 100,000                  
|Centerpulse Germany Holding GmbH             |  | CVD  |  | EUR 512,000 share capital |  | EUR 512,000 share capital

|     |  |                                |  | Authorized |  | Outstanding
|---- |  | ------------------------------ |  | ---------- |  | -----------
|
|CMI  |  | Sulzer Carbomedics UK Ltd.     |  | 0          |  | 1,000      
|CMI  |  | Sulzer Cardiovascular SA       |  | 0          |  | 165,000    
|CMI  |  | Sulzer Cardiovascular AG       |  | 0          |  | 5,000      
|CMI  |  | Sulzer Medica Canada Inc.      |  | Unlimited  |  | Unlimited  
|CMI  |  | Sulzer Carbomedics Canada Ltd. |  | 0          |  | 100        
|CVNL |  | Cardio Medical BV              |  | 0          |  | 400        

The
Shares are subject to a security interest pursuant to that certain Facility Agreement for Centerpulse Orthopedics Inc. arranged by UBS Warburg Ltd. with UBS AG,
Stamford Branch dated October 29, 2002, to be released prior to Closing.

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EXHIBIT B

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Section 3.15Material Contracts

(a)    The
following is a list of contracts with respect to the Valves Business to which any Target Company is a party as of the date of this Agreement:

Unless
otherwise noted, none of the contracts in this subsection (i) entitled "Indebtedness" rise to the threshold of $500,000.



(ii)Leases of Personal Property:

CVNL:



Sulzer Cardiovascular AG:



Sulzer Medica Canada:



CVD:



Sulzer Carbomedics UK:



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(iii)Non-Competition:

Target Company as Distributor:



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CMI:

CMI
has granted exclusive distribution rights and has not explicitly reserved its rights to sell its products in the territories related to the following distributors: Biomedic S.A.R.L., EMSO Limited,
Med Tech Equipmed SA, Pimex Medical Equipment, Phama-Cos Limited and C. Nicolai GmbH & Co. KG.

(iv)Clinical Application Research Studies:

CMI Optiform Study:



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CMI AnnuloFlex Study:



CMI Synergy ST Study:



CMI Synergy PC Study:



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CMI LVMR Study:



CMI Oxford Study:



CMI Top Hat Study:



CMI Other Studies:



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CVD Studies:



Sulzer Cardiovascular SA Studies:



Consulting Agreements:



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(v)Distributor/ Reseller Agreements:

CMI Representative AgreementsUnited States:



Distribution Network AgreementsROW International Sales:



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Distribution Network AgreementsWestern Europe:



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Distribution Network AgreementsCVD:



Distribution Network AgreementsSulzer Cardiovascular AG:



Distribution Network AgreementsCVNL:



Distribution Network AgreementsSulzer Cardiovascular SA:



Distribution Network AgreementsTarget Company as Distributor:



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(vi)Intercompany Agreements:



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(vii)Joint Venture/ Strategic Alliance/ Collaboration Agreements material to the Valves Business:



(viii)Leases of Real Property:



(ix)Purchase or Sale Agreements:

Unless
otherwise noted, none of the contracts in this subsection (ix) entitled "Purchase or Sale Agreements" rise to the threshold of $500,000.

Manufacturing Agreement:



O.E.M. Supply Contracts:



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Purchase Agreements:



Consignment Agreements:Each of the Target Companies is a party to numerous consignment arrangements with various hospitals around the
world regarding the consignment of its products.

Software Licenses and Maintenance Agreements:

CMI:



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Sulzer Cardiovascular SA:



MIT:



Sulzer Medica Canada:



Sulzer Carbomedics UK:



(x)Sole Source Supply Contract:



(xi)Contracts with Employees:

Change of Control Agreements:

CMI:



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Mitroflow:



Employment Agreements:



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Retention Agreements:



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Sales Bonus Arrangements:

Sales Bonus Arrangements exist between the Target Companies and the following persons:

|J. P. Beydon       |  | Mike Heuer           
|------------------ |  | ---------------------
|R. Gora            |  | Mike Barrett         
|D. Crouzet         |  | Walter Albertz       
|J. L. Norre        |  | Kevin J. Anderson    
|Kees Feller        |  | Peter P. Barcia Jr.  
|Koen Junggeburth   |  | Ronald S. Bell       
|Don Graham         |  | Thomas D. Birdsall   
|Gayl Cryer         |  | Jonathan M. Coleman  
|Dave Fleming       |  | John M. Conners Jr.  
|Shelley van Gelder |  | Ronda M. Diverde     
|Doug Green         |  | Glendon E. Durham    
|Norman Manocchio   |  | Mark Hamlet          
|Stephen Murphy     |  | Ken Harris           
|Jim Ulrich         |  | Jeffrey P. Kaye      
|Scott Dick         |  | James F. Lambert     
|Paul Parsons       |  | Barbara N. Logan     
|Michelle Becker    |  | Garland M. Lowe      
|Maria Rigante      |  | James J. McCabe      
|Juan Querol        |  | Scott L. McCormick   
|Roberto Caudillo   |  | Thomas P. Mellos     
|Linda Printz       |  | John P. Musachia     
|John Bassford      |  | James E. Poole       
|Ian Smith          |  | Geraldine O. Richards
|Mark Fitzpatrick   |  | Joseph S. Smith      
|Jim Deegan         |  | Robert W. Stiles     
|Manfred Eggar      |  | Pierre M. Twer       
|Cameron M. Wallace |  | David J. Van Deusen  

Tuition Reimbursement Agreements:



(xiii)Other Material Contracts:

Unless
otherwise noted, none of the contracts in this subsection (xiii) entitled "Other Material Contracts" rise to the threshold of $500,000.

CMI:



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CVD:



Sulzer Carbomedics UK:



Sulzer Cardiovascular SA:



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MIT:



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