**Summary of Safety and Probable Benefit**

**I. General Information**

Device Generic Name: Prosthesis, finger, semi-constrained, pyrolytic
carbon, uncemented

Device Trade Name: Ascension^®^ PIP

Applicant Name and Address: Ascension Orthopedics, Inc.

> 8200 Cameron Road, C-140
>
> Austin, TX 78754

Date of Humanitarian Use Device Designation: December 12, 2001

Humanitarian Device Exemption (HDE) Number: H010005

Date of Panel Recommendation: None

Date of Good Manufacturing Practice Inspection: April 16 -- 18, 2001

Date of Notice of Approval to the Applicant: March 22, 2002

**II. Indications for Use**

The Ascension PIP is indicated for use in arthroplasty of the proximal
interphalangeal (PIP) joint when the patient:

-   Has soft tissue and bone that can provide adequate stabilization and
    fixation under high-demand loading conditions after reconstruction;
    and

-   Needs a revision of a failed PIP prosthesis, or has pain, limited
    motion, or joint subluxation/dislocation secondary to damage or
    destruction of the articular cartilage.

**III. Contraindications**

-   Inadequate bone stock at the implantation site;

-   Active infection in the PIP joint;

-   Nonfunctioning and irreparable PIP musculotendinous system;

-   Physical interference with or by other prostheses during
    implantation or use;

-   Procedures requiring modification of the prosthesis; or

-   Skin, bone, circulatory and/or neurological deficiency at the
    implantation site.

**IV. Warnings and Precautions**

**WARNINGS**

-   Do not modify the Ascension PIP implant in any manner. Reshaping the
    implant using cutters, grinders, burrs, or other means will damage
    the structural integrity of the device and could result in implant
    fracture and/or particulate debris.

-   Do not match proximal and distal component sizes except as indicated
    in the following table. The wear behavior of component size
    combinations designated "Do Not Match" has not been evaluated, and
    is unknown.

**Allowable Ascension PIP Component Size Combinations**

  ------------- --------- ------------- ------------- ------------- -------------
                          **Proximal                                
                          Component**                               

                          **Size 10**   **Size 20**   **Size 30**   **Size 40**

  **Distal      **Size    ****         ****         Do Not Match  Do Not Match
  Component**   10**                                                

                **Size    ****         ****         ****         Do Not Match
                20**                                                

                **Size    Do Not Match  ****         ****         ****
                30**                                                

                **Size    Do Not Match  Do Not Match  ****         ****
                40**                                                
  ------------- --------- ------------- ------------- ------------- -------------

-   Do not grasp the Ascension PIP implant with metal instruments, or
    instruments with teeth, serrations, or sharp edges. Implants should
    be handled only with instrumentation provided by Ascension
    Orthopedics. Ascension PIP implants are made of pyrocarbon, which is
    a ceramic-like material. Mishandling implants could cause surface
    damage and reduce their strength, and could result in implant
    fracture and/or particulate debris.

-   Do not use Ascension PIP components in combination with proximal and
    distal components from other products. The wear behavior of
    Ascension PIP components against proximal and distal component from
    other products has not been evaluated, and could damage the
    structural integrity of the device and result in implant fracture
    and/or particulate debris.

**PRECAUTIONS**

-   Do not use the Ascension PIP in a joint where soft tissue
    reconstruction cannot provide adequate stabilization. Similar to the
    natural joint, the Ascension PIP attains stabilization from the
    surrounding capsuloligamentous structures. If soft tissue
    reconstruction cannot provide adequate stabilization, the device may
    subluxate or dislocate, lateral or longitudinal deformities may
    occur, or minimal motion or loss of motion may occur.

-   Obtain proper training prior to use. Surgeons should obtain training
    from a qualified instructor prior to implanting the Ascension PIP to
    ensure thorough understanding of the indications, implantation and
    removal techniques, instrumentation, and post-operative
    rehabilitation protocol.

-   Inspect the articulating surfaces of the Ascension PIP to insure
    they are clean and free of all debris prior to use. Foreign debris
    could result in excessive wear.

-   Do not resterilize this device. Resterilization could lead to
    mishandling and surface damage that could result in implant fracture
    and/or particulate debris.

-   Do not reuse this device. Any implant that has been damaged,
    mishandled, or removed from the sterile field may have surface
    damage that could result in implant fracture and/or particulate
    debris and should be discarded.

-   Do not use excessive impact force on the broach. Excessive impact
    force may cause bone fracture. Remove and reinsert broach frequently
    to obtain maximum cutting efficiency.

-   Do not use excessive impact force to seat the proximal sizing trial.
    Excessive impact force could cause sizing trial fracture. The sizing
    trial collar should abut the osteotomy after 2 impacts. If not,
    re-broach to increase cavity size and/or remove additional bone to
    provide clearance for the saddle area.

-   Do not use excessive impact force to remove the proximal sizing
    trial. Excessive impact force could cause sizing trial fracture. If
    possible, the sizing trial should be removed without the use of a
    hammer. If a sizing trial does fracture, and it is not possible to
    easily remove the remaining stem fragment, a k-wire driven into the
    fragment may provide sufficient purchase for removal. Then,
    re-broach to increase cavity size and/or remove additional bone to
    provide clearance for the saddle area.

-   Do not use excessive impact force to seat the implant components,
    especially if there has been a prior sizing trial fracture.
    Excessive impact force could cause component fracture. The component
    collar should abut the osteotomy after 2 impacts. If not, re-broach
    to increase cavity size or remove additional bone to provide
    clearance for the saddle area on the proximal component.

**V. Device Description**

The Ascension PIP is a two-component, bi-condylar, semi-constrained
total joint prosthesis designed to replace the articulating surfaces of
the proximal interphalangeal joint. Each component has an articulating
surface, a sub-articular collar, and an intramedullary stem. Two convex
articulating surfaces on the proximal component engage with and glide on
two mating concave articulating surfaces on the distal component. This
bi-condylar articulation allows joint flexion-extension motion while
restricting abduction-adduction motion. Component stems have an anatomic
shape, and are designed to be press-fit into the intramedullary canal.
Components achieve fixation by means of direct implant/bone apposition.
Bone cement is not required.

Each component of the Ascension PIP is fabricated from a thick
pyrocarbon layer encasing a graphite substrate. The graphite substrate
material in the Ascension PIP is impregnated with a small amount (1
atomic percent) of tungsten. This small amount of tungsten renders the
graphite substrate radiopaque so that Ascension PIP components are
clearly visible on radiographs.

Ascension PIP components are provided in four sizes. To ensure proper
fitting to the patient, the proximal and distal component sizes are
interchangeable. Each component can be matched with an opposite
component of the same size, one size smaller, or one size larger.

An alpha-numeric coding system in parallel with a two-level color coding
system is used to distinguish both implant sizes, and proximal and
distal components. A full set of surgical instrumentation including
x-ray overlay sizing templates, alignment guides, cutting guides,
broaches, and sizing trial devices is available.

On the proximal component, the articular surface terminates at a
bi-planar sub-articular collar that includes a vertical plane on the
dorsal aspect, and an oblique plane on the volar aspect. This bi-planar
design is intended to preserve collateral ligament insertion sites and
other soft tissue structures surrounding the joint when articular
cartilage is removed during the osteotomy. Both the vertical and oblique
collar planes are offset from the center of rotation of the prosthesis.
This offset is intended to minimize bone removal and preserve soft
tissue structures such as the volar plate attachment site.

On the distal component, the sub-articular collar is a single vertical
plane. The uni-planar feature of this collar is intended to simplify the
surgical technique necessary to properly prepare the bone so that it
mates congruently with the implant.

The Ascension PIP has an "intercondylar groove" between the condyles of
the proximal component and an "intercondylar notch" on the dorsal aspect
of the distal component. These design features are intended to allow the
Ascension PIP to accommodate the extensor expansion "central slip"
during joint flexion and extension. During joint flexion, the
Intercondylar Centering Pad (ICP), a distinct region on the volar
surface of the central slip, mates with the intercondylar groove thus
centering the central slip between the condyles of the proximal
component. As flexion increases, the central slip follows the ICP and
wraps onto the intercondylar notch, thus enhancing lateral stability of
the central slip. In addition, the intercondylar notch in the distal
component maintains the anatomic attachment site of the central slip
median band as it inserts into the base of the middle phalanx.

Accurate placement of the Ascension PIP is intended to result in a total
joint arthroplasty that reestablishes functional joint mechanics. Design
features are intended to preserve the insertion sites for the collateral
ligaments and provide for a free, unobstructed pathway for the
collateral and retinacular ligaments in order to contribute to joint
stability and function. Anatomic shaped component stems are designed to
fill the medullary canal and promote component fixation. The prosthesis
is designed to accommodate maximum anatomic range of motion. Motion
allowed by all sizes of the prosthesis is 20° of hyperextension and 100°
of flexion in the sagittal plane, and ± 0° of radial and ulnar motion.

**VI. Alternative Practices and Procedures**

Non-surgical early stage treatments include joint injections,
anti-inflammatory drug therapy (e.g. aspirin, non-steroidal
anti-inflammatory drugs), avoiding heavy stress through the joints or
heavy use of the fingers and hand, and physical therapy exercises to
maintain joint range of motion and splints to correct finger deformity.
Resting splints worn at night may slow the rate of disease progression.

Surgical intervention may restore some range of motion and is typically
used when non-surgical measures no longer give relief. Surgical
treatment may include fusion of the bones, interposition arthroplasty
with tendon, or resection arthroplasty with a silicone rubber spacer.
Individuals who are very active and use their hands for heavy labor may
not be good candidates for resection arthroplasty with a silicone rubber
spacer.

**VII. Marketing History**

Ascension Orthopedics, Inc., is distributing the Ascension PIP in the
following countries and regions: European Community (CE Mark), Canada,
Australia, and South Africa.

The Ascension PIP has not been withdrawn from any market for any reason
related to safety or effectiveness of the device.

**VIII. Potential Adverse Effects of the Device on Health**

The Ascension PIP has been used clinically in Europe, Canada, Australia
and South Africa. Through December 31, 2001, 164 devices have been
implanted. No serious adverse events or complications have been reported
for these devices. There have been reports of intra-operative
complications as summarized in the following table. All of these
complications were uneventful and were resolved immediately. The
fractured proximal sizing trials and components were removed and new
components were successfully inserted, while the bone fractures were
grossly stable and the medullary canals ultimately were properly
prepared and implant components were successfully inserted. No sequelae
have been reported for any of these complications.

**Summary of Ascension PIP Adverse Events and Complications**

+----------------------------------------------------+-----------------+
|                                                    | **Implants      |
|                                                    | (%)**           |
|                                                    |                 |
|                                                    | **n = 164**     |
+----------------------------------------------------+-----------------+
| Bone fracture (intra-operative)                    | 3 (1.8%)        |
+----------------------------------------------------+-----------------+
| Proximal sizing trial fracture (intra-operative)   | 6 (3.7%)        |
+----------------------------------------------------+-----------------+
| Proximal component fracture (intra-operative)      | 3 (1.8%)        |
+----------------------------------------------------+-----------------+

Information on these intra-operative complications was acquired and
evaluated in accordance with the sponsor's ISO 9001 compliant Customer
Feedback System. The severity and affect on the patient's health due to
the adverse event was determined by follow-up communication with the
source of the information. For complications summarized in the table
above, no reports of sequelae were received over the course of this
follow-up communication. The mean time and range of this follow-up
communication was 28 days post-operative (range 13 -- 54 days).

In addition, although not intended for use in the PIP joint, clinical
results and adverse effects for the Pyrocarbon metacarpophalangeal (MCP)
implant have been reported in the premarket approval application (PMA)
for the Ascension MCP.[^1] Please note that the "Pyrocarbon MCP" is an
earlier version of the Ascension MCP that was used clinically to support
the safety and effectiveness of the Ascension MCP. Adverse effects for
the Ascension PIP may be similar to those reported for the Pyrocarbon
MCP because both devices share numerous identical attributes including
design concept, construction, materials, and insertion and fixation
methods. In addition, the primary objectives of PIP total joint
arthroplasty are identical to those of MCP total joint arthroplasty,
namely, relief of pain due to articular damage or destruction, and
improvement in joint range of motion. Similarities between the Ascension
PIP and Pyrocarbon MCP are further elaborated below in section X
(Summary of Clinical Experience). Reported adverse effects identified
below are those observed while using the Pyrocarbon MCP device.

**PYROCARBON MCP REPORTED ADVERSE EFFECTS**

In a retrospective case history review, 53 patients received 147
Pyrocarbon MCP prostheses and had last evaluations at an average of 8.5
years (range 1.7 months -- 17.2 years) after implantation. The most
commonly reported adverse events were:

-   Recurrent deformity;

-   Subluxation / dislocation;

-   Re-operation for soft tissue reconstruction;

-   Implant removal

-   Implanted joint pain; and

-   Synovitis.

A detailed discussion and complete list of the frequency and rate of
complications and adverse events identified for the Pyrocarbon MCP
implant is provided below in section X (Summary of Clinical Experience).

**POTENTIAL ADVERSE EFFECTS**

Potential adverse effects associated with total joint prostheses and
surgery in general include, but are not limited to:

-   Pain;

-   Bleeding;

-   Infection;

-   Swelling;

-   Damage to surrounding blood vessels, nerves, or soft tissue;

-   Implant migration within the bones;

-   Implant loosening;

-   Excessive implant wear and particulate debris;

-   Allergic or foreign body reaction;

-   Implant fracture;

-   Bone fracture;

-   Implant subluxation or dislocation;

-   Finger deformity (radial or ulnar deviation, supination or
    pronation);

-   Reduction or loss of joint motion;

-   Loss of finger or hand function; or

-   Lengthening or shortening of the finger.

These adverse effects may lead to additional surgery and could result
in:

-   Implant removal;

-   Joint fusion;

-   Amputation; or

-   Death

**IX. Summary of Pre-Clinical Studies**

The sponsor performed the following pre-clinical studies to demonstrate
the safety of the Ascension PIP:

-   Mechanical testing of Ascension PIP components;

-   Finite element analyses of Ascension PIP contact stress;

-   Biocompatibility testing of the pyrocarbon material and the sizing
    trial polymer material; and

-   Animal testing of Pyrocarbon MCP implants.

Recognized standards were used in the design and conduct of these
pre-clinical studies where appropriate. Prior to commencing FEA and
mechanical testing of the implant, the biomechanics literature was
reviewed to establish proper test loads and support conditions for the
testing program.

All pre-clinical studies revealed that the Ascension PIP is capable of
supporting functional joint motion and grip and pinch strength for the
long term. Pre-clinical study results are summarized below.

**Mechanical Testing**

The objectives of the mechanical testing were to characterize the
mechanical properties of the Ascension PIP. Mechanical testing evaluated
the following Ascension PIP characteristics:

-   Wear resistance;

-   Fracture strength;

-   Cyclic endurance (fatigue resistance);

-   Axial load fracture strength; and

-   The affect of articulating surface contact.

All testing was performed on final sterilized proximal and distal
components. Test specimens were mounted and loaded to simulate
biologically demanding physiologic support and loading conditions.
Specimen mounting and loading conditions were determined based on a
review of the biomechanics
literature.[^2]^,^[^3]^,^[^4]^,^[^5]^,^[^6]^,^[^7]^,^[^8]^,^[^9]^,^[^10]^,^[^11]^,^[^12]^,^[^13]^,^[^14]^,^
[^15]^,^[^16]^,^[^17]^,^[^18]^,^[^19]^,^[^20]^,^[^21]^,^[^22]
Biomechanically demanding loads were determined to be 83 lb. for
strength, endurance, and contact testing, and 14 lb. for cyclic wear
testing.

Results from all *in vitro* testing demonstrate that the Ascension PIP
has adequate wear resistance, strength, and endurance (i.e., resistance
to cyclic fatigue). Further, results show that the device is capable of
supporting demanding biomechanical loads. Brief descriptions of the
tests conducted and the corresponding results are summarized below.

**Wear Resistance**

Wear testing in a cyclic articulation joint motion simulator was
conducted to evaluate wear resistance of the Ascension PIP. Specimens
were tested at 4 Hz in bovine serum at room temperature with an axial
load of 14 lb. for 10 million cycles. Size 10 proximal components were
articulated against size 20 distal components in order to maximize
radial clearance and, therefore, contact pressure. This was the only
Ascension PIP size combination tested because previous testing of
Ascension MCP components has demonstrated that: 1) wear behavior is
independent of device size; and 2) the smallest size device and largest
radial clearance results in the smallest contact area and highest
contact stress. A total of six Ascension PIP wear couples were tested; a
seventh couple was not subjected to wear testing and served as a
non-wear pyrocarbon control.

The control device was a commercially available, two-component PIP
implant that has a CoCr proximal component and an UHMWPE (polyethylene)
distal component. Two control devices were used; one device was
subjected to wear testing while the other was used as a non-wear
control. The control devices were finished sterilized devices purchased
from a commercial distributor.

The Ascension PIP device exhibited adequate wear resistance under the
test conditions outlined above. Proximal and distal components did not
show measurable material removal (resolution ≈ 0.0002 inch) at 10
million cycles. Wear was characterized by an absence of macroscopic
material removal from the articulating surface, and by the occasional
shallow scratch 0.3 -- 1.0 micrometers deep on the articulating surface.

In contrast, the control device exhibited 0.0025 inches of wear on the
distal polyethylene component at 10 million cycles. The CoCr proximal
component did not show measurable material removal (resolution ≈ 0.0002
inch), but did exhibit scratches on the articulating surface 0.3 -- 0.5
micrometers deep.

These results demonstrate the Ascension PIP exhibits adequate wear
resistance under the test conditions outlined above.

**Fracture Strength**

Strength tests were conducted to evaluate the fracture strength and
failure mode of the Ascension PIP. Size 10 and 40 proximal and distal
components were tested because these sizes represent the smallest and
largest size components, respectively, and because previous fracture
strength testing of Ascension MCP components demonstrated that the
smallest size components exhibited the lowest fracture strength.
Specimens were held with 1/3 of the stem proximal to the collar
unsupported and the distal 2/3 of the stem rigidly supported. Specimens
were oriented so that loading produced bending in the sagittal plane.
The load angle was 38 degrees for proximal components and 13 degrees for
distal components. Testing was conducted at room temperature in air.

The failure mode for all specimens was catastrophic crack propagation.
For proximal specimens, the primary fracture location was on the stem
where it extended above the fixture, although some components exhibited
secondary fracture locations on the head. Distal specimens exhibited
primary fracture locations on both the stem where it extended above the
fixture, and on the head.

Size 10 components exhibited lower average fracture strength than larger
size 40 components. Overall, size 10 distal components exhibited the
lowest average fracture strength of 149 lb. with a range from 134 to 182
lb. This fracture strength is greater than a biomechanically demanding
load for the PIP joint of 83 lb.

These results demonstrate that Ascension PIP components are capable of
supporting loads exceeding a biomechanically demanding load.

**Cyclic Endurance (Fatigue Resistance)**

Cyclic endurance tests were conducted to evaluate the fatigue endurance
behavior of the Ascension PIP. Size 10 proximal and distal components
only were tested because they exhibited the lowest average fracture
strength compared to larger sizes and therefore represent a rigorous and
demanding test condition. As with the strength test, specimens were held
with 1/3 of the stem proximal to the collar unsupported and the distal
2/3 of the stem rigidly supported. Specimens were oriented so that
loading produced bending in the sagittal plane. The load angle was 38
degrees for proximal components and 13 degrees for distal components.
Specimens were subjected to an 8.3 to 83 lb. sinusoidal load at 30 Hz
for 10 million cycles at room temperature in air.

All test specimens survived the 8.3 to 83 lb. cyclic load for 10
millions cycles. Visual and dye penetration inspection revealed that the
applied cyclic load did not damage the test specimens. Furthermore,
endurance testing did not reduce the average fracture strength of test
specimens as compared to non-endurance tested components.

These results demonstrate that Ascension PIP components exhibit adequate
fatigue resistance, and are capable of supporting a biomechanically
demanding load in the long term.

**Axial Load Fracture Strength**

An axial load strength test was conducted to evaluate the fracture load
and failure mode of Ascension PIP components subjected to applied load
acting parallel to the axis of the stem. Size 10 proximal and distal
components only were tested because they exhibited the lowest average
fracture strength as compared to larger size devices and, therefore,
represent a rigorous and demanding test condition. Specimens were held
with 1/3 of the stem proximal to the collar unsupported and the distal
2/3 of the stem rigidly supported, and oriented so that the longitudinal
axis of the specimen was vertical.

For all specimens, the failure mode was catastrophic crack propagation,
and the primary fracture location was on the component head. Proximal
components exhibited lower average fracture strength than distal
components. Size 10 proximal components exhibited the average fracture
strength of 159 lb. with a range from 147 to 175 lb. This fracture
strength is greater than a biomechanically demanding load for the PIP
joint of 83 lb.

These results demonstrate that Ascension PIP components are capable of
supporting loads exceeding a biomechanically demanding load.

**Articulating Surface Contact Test**

The articulating surface contact testing was conducted to determine the
extent of damage on the articulating surface due to a biomechanically
demanding load. Size 10 and size 40 proximal and distal components were
tested because these sizes represent the smallest and largest size
components, respectively, and because fracture strength testing
demonstrated that the smallest size components exhibited the lowest
fracture strength. Specimens were subjected to a biomechanically
demanding load of 83 lb. with a mating component. Mating component sizes
were chosen to maximize radial clearance and contact stress. The
proximal test specimens were loaded with a size 40 distal component, and
distal test specimens were loaded with a size 10 proximal component. As
with the strength and endurance testing, specimens were held with 1/3 of
the stem proximal to the collar unsupported and the distal 2/3 of the
stem rigidly supported. Testing was conducted at room temperature in
air.

The articulating surface was inspected before and after the applied
load. Visual inspection with a stereo microscope and with dye
penetration revealed that the applied load did not damage the
articulating surface of the specimens.

These results demonstrate that the Ascension PIP is capable of
supporting a biomechanically demanding load without sustaining damage to
the articulating surface.

**Mechanical Testing Summary**

A brief summary of the mechanical test results discussed above is
provided in the following table.

**Summary of Mechanical Test Results for the Ascension PIP**

+--------------+--------------------------+----------------------------+
| **Test**     | **Device Type and Size** | **Results**                |
+--------------+--------------------------+----------------------------+
| Wear Test    | Size 10 Proximal         | Measurable wear did not    |
|              |                          | occur on                   |
|              | articulating against a   |                            |
|              |                          | Ascension PIP components   |
|              | Size 20 Distal           |                            |
|              |                          | (sensitivity = 0.0002      |
|              |                          | inch).                     |
+--------------+--------------------------+----------------------------+
|              | For comparison, wear     | Measurable wear did not    |
|              | testing of a             | occur on                   |
|              | commercially available   |                            |
|              | CoCr-on-UHMWPE PIP       | the CoCr proximal          |
|              | implant was performed.   | components                 |
|              |                          |                            |
|              |                          | (sensitivity = 0.0002      |
|              |                          | inch).                     |
|              |                          |                            |
|              |                          | Wear on the UHMWPE distal  |
|              |                          | component was              |
|              |                          | approximately 0.0025       |
|              |                          | inches.                    |
+--------------+--------------------------+----------------------------+
| Strength     | Size 10 Proximal         | 155 ± 5 lb. (147 -- 163)   |
| Test         |                          |                            |
|              | Size 40 Proximal         | 217 ± 30 lb. (182 -- 254)  |
|              |                          |                            |
|              | Size 10 Distal           | 149 ± 14 lb. (134 -- 182)  |
|              |                          |                            |
|              | Size 40 Distal           | 254 ± 42 lb. (198 -- 325)  |
+--------------+--------------------------+----------------------------+
| Endurance    | Size 10 Proximal         | No failures occurred.      |
| Test         |                          |                            |
|              | Size 10 Distal           | All specimens survived 10  |
|              |                          | million cycles with 83 lb. |
|              |                          | maximum load.              |
+--------------+--------------------------+----------------------------+
| Axial Load   | Size 10 Proximal         | 159 ± 10 lb. (147 -- 175)  |
| Strength     |                          |                            |
| Test         | Size 10 Distal           | 201 ± 33 lb. (154 -- 247)  |
+--------------+--------------------------+----------------------------+
| Articulating | Size 10 and 40 Proximal  | No damage occurred on      |
| Surface      |                          | articulating surfaces      |
| Contact Test | Size 10 and 40 Distal    | subjected to 83 lb. load.  |
+--------------+--------------------------+----------------------------+

**FEA Contact Stress Analysis**

Finite element stress analysis (FEA) was conducted to determine the
contact stresses in the Ascension PIP device. The effect of variations
in radial clearance was also examined. A size 10 proximal component in
contact with a size 20 distal component was analyzed because it is the
size combination that results in the smallest contact area, largest
radial clearance, and, therefore, the highest contact stress. FEA models
assumed that a biomechanically demanding load of 83 lb. was applied to a
[single condyle]{.underline}, a very rigorous loading condition that is
realized only when the entire joint reaction force is supported by a
single condyle. Under clinical conditions, the joint reaction force
normally is supported by both condyles with each supporting
approximately ½ of the entire load. Thus, FEA models evaluated a
"worst-case" loading condition.

FEA contact area solutions agreed within 6% of values measured
experimentally. Larger radial clearance resulted in smaller contact area
and higher contact stress. The highest maximum contact stress was
determined to be approximately 17.4 ksi; maximum contact stress for
nominal radial clearance conditions was determined to be approximately
11.9 ksi . These values are higher than that reported for the Ascension
MCP (5.8 ksi in the smallest size 10 device), and roughly 33% - 54% of
the 32.5 -- 36.2 ksi fracture stress estimated for pyrocarbon
components. However, this contact stress is associated with a
"worst-case" loading condition in which a [single condyle]{.underline}
supports the entire joint reaction force (83 lb.); actual contact stress
should be less. In addition, contact stress during endurance testing of
Ascension PIP size 10 proximal components (loaded with a flat, steel
platen) was determined to be a [minimum]{.underline} of 21.7 ksi. This
is approximately 25% higher than the highest maximum contact stress for
the maximum radial clearance condition, and 82% higher than the maximum
contact stress in components with nominal radial clearance. As discussed
in the Cyclic Endurance section above, visual and dye penetration
inspection of endurance test specimens revealed that the cyclic load did
not damage the test specimens even through 10 million cycles of applied
load.

These contact stress analysis results together with endurance test
results demonstrate that the Ascension PIP is capable of supporting a
biomechanically demanding load in the long term without sustaining
damage to the articulating surface.

**Biocompatibility Testing**

Biocompatibility testing was conducted to demonstrate the
biocompatibility of the pyrocarbon material used in Ascension PIP
components and the polymer material used in Ascension PIP sizing trials.
Test specimens were manufactured under the exact same conditions as used
in processing PIP components and sizing trials. Biocompatibility studies
were conducted in accordance with ISO 10993 and U.S. Pharmacopeia 23,
1995.

Studies revealed that the pyrocarbon used in the PIP devices is
non-cytotoxic, has a weak allergenic potential, is a negligible
irritant, non-pyrogenic, non-mutagenic, and has physiochemical
properties exceeding the minimum U.S.P. levels set for plastics. In
addition, studies revealed that the polymer material used in the PIP
sizing trials is non-cytotoxic, a negligible irritant, and has weak
allergenic potential.

**Animal Testing**

Although not intended for use in the PIP joint, results of animal
testing for the Pyrocarbon MCP implant have been reported in the PMA for
the Ascension MCP.Error: Reference source not found Please note that the
"Pyrocarbon MCP" is an earlier version of the Ascension MCP that was
used clinically to support the safety and effectiveness of the Ascension
MCP. The objectives of the animal testing were to demonstrate the
potential for biological fixation of pyrocarbon components in bone
and/or soft tissue, and to evaluate the clinical suitability of the
uncemented, semi-constrained, two-component design concept. The
Pyrocarbon MCP has a number of features that are identical to the
Ascension PIP. Identical characteristics include anatomic design
concept, construction, materials, and insertion and fixation methods.
Similarities between the Ascension PIP and Pyrocarbon MCP are further
elaborated below in section X (Summary of Clinical Experience). Because
the devices are identical in a number of critical aspects, the results
from the animal testing with the Pyrocarbon MCP are applicable to the
Ascension PIP.

Five Pyrocarbon MCP prostheses and one Steffee (metal and polyethylene)
MCP prosthesis were implanted into the long finger metacarpophalangeal
joints of baboons. Four of the Pyrocarbon MCP implants were inserted
without bone cement; the fifth Pyrocarbon MCP implant and the Steffee
implant were inserted using bone cement. Nine months after insertion,
the implants and surrounding tissues were removed *en bloc* and
evaluated radiographically and histologically.

Histologic evidence of direct appositional bone fixation along the
medullary stem was observed in one of the uncemented Pyrocarbon MCP
specimens, and a combination of bone fixation with an interposing
fibrous tissue membrane was observed in the others. There was no
evidence of bone resorption around the stems of the uncemented
Pyrocarbon MCP implants, and functional fixation was obtained with all
of the uncemented Pyrocarbon MCP implants. No foreign body reaction was
observed in the soft tissues, and no evidence of intracellular particles
was present with the uncemented Pyrocarbon MCP implants.

The cemented Pyrocarbon MCP implant showed evidence of bone resorption
at the cement-bone interface around one component, and intermittent
lucent lines along the cement-bone interface on the other component.
Evidence of bone resorption and gross implant loosening was observed in
the cemented metal and polyethylene implant.

In conclusion, the results of this animal study demonstrate the
potential for biological fixation of Pyrocarbon MCP implants in bone
and/or soft tissue, and confirm the clinical suitability of the
uncemented, semi-constrained, two-component Ascension PIP implant design
concept.

**X. Summary of Clinical Experience**

The clinical use of the Ascension PIP has been summarized in Section
VIII (Potential Adverse Effects of the Device on Health). In addition,
although not intended for use in the PIP joint, clinical results and
adverse effects for the Pyrocarbon metacarpophalangeal (MCP) implant
have been reported in the PMA for the Ascension MCP.Error: Reference
source not found Please note that the "Pyrocarbon MCP" is an earlier
version of the Ascension MCP that was used clinically to support the
safety and effectiveness of the Ascension MCP. As shown in the following
table, the Ascension PIP has a number of features that are identical to
the Pyrocarbon MCP. Identical characteristics include anatomic design
concept, construction, materials, and insertion and fixation methods. In
addition, the primary objectives of PIP total joint arthroplasty are
identical to those of MCP total joint arthroplasty, namely, relief of
pain due to articular damage or destruction, and improvement in joint
range of motion.

**Comparison of Ascension PIP and Pyrocarbon MCP Design Attributes**

  ----------------------------------- ---------------- -------------------
  **Attribute**                       **Ascension      **Pyrocarbon MCP**
                                      PIP**            

  two-component, total joint implant  yes              yes

  semi-constrained articulation       yes              yes

  articulation type                   ball-and-cup     bi-condylar

  proximal component bi-planar collar yes              yes

  distal component uni-planar collar  yes              yes

  intramedullary stem                 yes              yes

  press-fit insertion                 yes              yes

  direct bone apposition fixation     yes              yes

  pyrocarbon construction             yes              yes

  graphite substrate                  yes              yes
  ----------------------------------- ---------------- -------------------

Therefore, because of these similarities, the clinical safety outcomes
for the Pyrocarbon MCP are summarized below.

**Pyrocarbon MCP Reported Adverse Effects**

**Complications and Adverse Events**

In a retrospective case history review, 53 patients received 147
Pyrocarbon MCP prostheses and had last evaluations at an average of 8.5
years (range 1.7 months -- 17.2 years) after implantation. The patient
population consisted of 45 females and 8 males with a mean age of 57.5
years (range 21 -- 78 years). Patients were diagnosed with one of four
conditions: 43 (81%) patients had rheumatoid arthritis (RA), 2 (4%) had
systemic lupus erythematosus (SLE), 5 (9%) had arthritis due to trauma
(TA), and 3 (6%) had osteoarthritis (OA). For patients diagnosed with RA
or SLE, the mean time from diagnosis until implantation of the first
Pyrocarbon MCP was more than 16 years (range 3-36 years).

The most commonly reported adverse events were:

-   Recurrent deformity;

-   Subluxation / dislocation;

-   Re-operation for soft tissue reconstruction;

-   Implant removal;

-   Implanted joint pain; and

-   Synovitis

A complete list of the frequency and rate of complications and adverse
events identified for the Pyrocarbon MCP implant is shown in the table
below.

**Pyrocarbon MCP Complications and Adverse Events**

+----------------------------+--------+-----------+-------+----------+
| **Complication / Adverse   | **Impl | **%       | **    | **%      |
| Event**                    | ants** | I         | Patie | Pa       |
|                            |        | mplants** | nts** | tients** |
|                            | **(N = |           |       |          |
|                            | 147)** |           | **(N  |          |
|                            |        |           | =     |          |
|                            |        |           | 53)** |          |
+----------------------------+--------+-----------+-------+----------+
| Recurrent Deformity        | 49     | 33%       | 20    | 38%      |
+----------------------------+--------+-----------+-------+----------+
| Subluxation/Dislocation    | 31     | 21%       | 17    | 32%      |
+----------------------------+--------+-----------+-------+----------+
| Soft-tissue Re-operation   | 22     | 15%       | 11    | 21%      |
+----------------------------+--------+-----------+-------+----------+
| Implant Removal            | 21     | 14%       | 11    | 21%      |
+----------------------------+--------+-----------+-------+----------+
| Implanted joint pain       | 13     | 9%        | 11    | 21%      |
+----------------------------+--------+-----------+-------+----------+
| Synovitis                  | 24     | 16%       | 10    | 19%      |
+----------------------------+--------+-----------+-------+----------+
| Stiffness / Loss of Motion | 12     | 8%        | 6     | 11%      |
+----------------------------+--------+-----------+-------+----------+
| Subsidence                 | 9      | 6%        | 6     | 11%      |
+----------------------------+--------+-----------+-------+----------+
| Loosening                  | 7      | 5%        | 5     | 9%       |
+----------------------------+--------+-----------+-------+----------+
| Black Tissue Stain         | 7      | 5%        | 4     | 8%       |
+----------------------------+--------+-----------+-------+----------+
| Implant modification       | 5      | 3%        | 3     | 6%       |
+----------------------------+--------+-----------+-------+----------+
| Radiographic changes:      |        |           |       |          |
+----------------------------+--------+-----------+-------+----------+
| lucency                    | 4      | 3%        | 3     | 6%       |
+----------------------------+--------+-----------+-------+----------+
| sclerosis                  | 1      | 1%        | 1     | 2%       |
+----------------------------+--------+-----------+-------+----------+
| heterotopic bone           | 2      | 1%        | 2     | 4%       |
+----------------------------+--------+-----------+-------+----------+
| cyst                       | 1      | 1%        | 1     | 2%       |
+----------------------------+--------+-----------+-------+----------+
| erosion                    | 2      | 1%        | 1     | 2%       |
+----------------------------+--------+-----------+-------+----------+
| Superficial Wound          | \--    | \--       | 2     | 4%       |
| Infection                  |        |           |       |          |
+----------------------------+--------+-----------+-------+----------+
| Sensory Abnormality        | 3      | 2%        | 2     | 4%       |
+----------------------------+--------+-----------+-------+----------+
| Excessive erythema         | 2      | 1%        | 2     | 4%       |
+----------------------------+--------+-----------+-------+----------+
| Implant Fracture:          |        |           |       |          |
+----------------------------+--------+-----------+-------+----------+
| in vivo fracture           | 0      | 0%        | 0     | 0%       |
+----------------------------+--------+-----------+-------+----------+
| intra-op fracture:         |        |           |       |          |
+----------------------------+--------+-----------+-------+----------+
| at implantation            | 4      | 3%        | 4     | 8%       |
+----------------------------+--------+-----------+-------+----------+
| at removal                 | 6      | 4%        | 3     | 6%       |
+----------------------------+--------+-----------+-------+----------+
| Bone Fracture:             |        |           |       |          |
+----------------------------+--------+-----------+-------+----------+
| in vivo fracture           | 0      | 0%        | 0     | 0%       |
+----------------------------+--------+-----------+-------+----------+
| intra-op fracture          | 3      | 2%        | 2     | 4%       |
+----------------------------+--------+-----------+-------+----------+

**Implant Removals**

A total of 21 (14%) Pyrocarbon MCP implants were removed from 11 (21%)
patients. No implants were removed for implant fracture or clinical
complications such as bone fracture, infection, sensory abnormality,
allergic or foreign body reaction, iatrogenic complications or wound
complications. Three (2%) implants were removed for loosening while 18
implants (12%) were removed for deformity associated with disease
progression related to RA/SLE (extensor lag, flexion contracture, ulnar
deviation, subluxation or dislocation). All removed implants were
successfully revised; fifteen were replaced with silicone spacers, four
Pyrocarbon MCP implants were reinserted with bone cement, and two new
Pyrocarbon MCP implants were used. Of the 21 implants that were removed,
6 implants were removed less than 1 year after implantation; 9 implants
were removed between 1 and 5 years after implantation; and 6 implants
were removed greater than 5 years after implantation (range 5-11 years).

**Summary of Implant Removals**

+-----------------------------+-------------+------------+-------------+
|                             | **All       | **O        | **RA/SLE**  |
|                             | Diagnoses** | A/Trauma** |             |
|                             |             |            | **(N=45     |
|                             | **(N=53     | **(N=8     | patients)** |
|                             | patients)** | p          |             |
|                             |             | atients)** |             |
+-----------------------------+-------------+------------+-------------+
| Number of Implants          | 147         | 9          | 138         |
+-----------------------------+-------------+------------+-------------+
|                             |             |            |             |
+-----------------------------+-------------+------------+-------------+
| Number of Removals          | 21 (14%)    | 1 (11%)    | 20 (14%)    |
+-----------------------------+-------------+------------+-------------+
| Reason for Removal          |             |            |             |
+-----------------------------+-------------+------------+-------------+
| Fracture                    | 0 (0%)      | 0 (0%)     | 0 (0%)      |
+-----------------------------+-------------+------------+-------------+
| Loosening, Subsidence,      | 3 (2%)      | 1 (11%)    | 2 (1%)      |
| Migration                   |             |            |             |
+-----------------------------+-------------+------------+-------------+
| Clinical Complication       | 0 (0%)      | 0 (0%)     | 0 (0%)      |
+-----------------------------+-------------+------------+-------------+
| Disease Progression         | 18 (12%)    | 0 (0%)     | 18 (13%)    |
+-----------------------------+-------------+------------+-------------+

**Soft Tissue Re-Operations**

Eleven (11) soft tissue re-operation procedures were performed on a 22
(15%) joints in 11 (21%) Pyrocarbon MCP patients. Procedures were
performed to correct recurrent MCP joint deformities such as implant
subluxation/dislocation, ulnar/radial deviation, extension lag or loss
of motion, or extension contracture. All but one of the soft tissue
re-operations was on RA/SLE patients. Three (3) of the 22 implants were
eventually removed, all due to recurrent subluxation or dislocation.
Sixteen (16) of the 22 joints were operated on less than 1 year
post-implantation.

**Summary of Soft Tissue Re-operations**

+----------------------------+-------------+------------+-------------+
|                            | **All       | **O        | **RA/SLE**  |
|                            | Diagnoses** | A/Trauma** |             |
|                            |             |            | **(N=45     |
|                            | **(N=53     | **(N=8     | patients)** |
|                            | patients)** | p          |             |
|                            |             | atients)** |             |
+----------------------------+-------------+------------+-------------+
| Number of Implants         | 147         | 9          | 138         |
+----------------------------+-------------+------------+-------------+
|                            |             |            |             |
+----------------------------+-------------+------------+-------------+
| Number of Implants         | 22 (15%)    | 1 (11%)    | 21 (15%)    |
| Re-operated                |             |            |             |
+----------------------------+-------------+------------+-------------+
| Reason for Re-operation    |             |            |             |
+----------------------------+-------------+------------+-------------+
| Subluxation / Dislocation  | 7 (5%)      | 0 (0%)     | 7 (5%)      |
+----------------------------+-------------+------------+-------------+
| Ulnar / Radial Deviation   | 7 (5%)      | 1 (11%)    | 6 (4%)      |
+----------------------------+-------------+------------+-------------+
| Extension Lag / Loss of    | 5 (3%)      | 0 (0%)     | 5 (4%)      |
| Motion                     |             |            |             |
+----------------------------+-------------+------------+-------------+
| Extension Contracture      | 3 (2%)      | 0 (0%)     | 3 (2%)      |
+----------------------------+-------------+------------+-------------+

**Intraoperative Implant Fractures**

There were a total of 10 intraoperative Pyrocarbon MCP implant
fractures, i.e., fractures that occurred during either implantation or
revision of the device. Four of the 10 intraoperative fractures occurred
during the implantation of 295 components for a rate of 1.4% (4/295). In
3 of the 4 cases, the fractured component was easily removed and a new
Pyrocarbon MCP component was inserted while in the fourth case, the
fragment was left *in situ* and a silicone spacer was inserted. Six of
the 10 fractures occurred during implant revision and removal of 42
components (21 devices) for a rate of 14% (6/42). Five of these
fractured devices were replaced with a silicone spacer while the 6^th^
fractured device was essentially intact and was reinserted with bone
cement. All intraoperative fractures were uneventful and no *sequelae*
resulted.

**Black Staining of Tissue and Synovitis**

There were reports of black staining of tissue and synovitis. However,
in the tissue samples evaluated by the histopathologist, there were no
reports of an adverse tissue reaction to the Pyrocarbon MCP joint
implant, carbon particles, or "fine particulate matter."

> ***Black Staining of Tissue***

A total of 7 implants caused black stained tissue in 4 of 53 patients
for a rate of 7.5% (4/53). Four (4) events occurred during removal of
implants from each finger on one patient's hand. All four fractured
implants were removed by drilling them out of the bone. After the
drilling process, black stained tissue was observed in each finger. No
tissue samples were taken from this patient.

In addition, there were 3 events observed during operations to remove
implants that were potentially loose in 3 patients. Tissue samples from
these three patients were excised during removal for histopathologic
examination. The histopathologist concluded that the tissue did not
reveal any negative tissue reaction. All implants were revised. Two (2)
implants were revised to silicone spacers and 1 Pyrocarbon MCP implant
was reinserted with cement.

> ***Synovitis***

A total of 24 synovitis events were reported for 10 patients for a rate
of 19% (10/53). Tissue samples were available for examination from 5/24
joints including samples from 2 RA patients and one Trauma patient. The
histopathologist's review concluded that there was no adverse tissue
reaction to the implant, carbon particles, or "fine particle matter" in
these samples.

**XI. Conclusions Drawn from Studies and Clinical Experience**

Pre-clinical testing of the Ascension PIP device demonstrated that the
wear resistance, fracture strength, fatigue resistance, and resistance
to articulating surface contact damage of the Ascension PIP is
acceptable for its intended use. In addition, biocompatibility testing
indicates the device is non-cytotoxic, has weak allergenic potential, is
a negligible irritant, non-pyrogenic, non-mutagenic, and has
physiochemical properties exceeding the minimum U.S.P. levels set for
plastics.

Compared to current treatment alternatives, such as arthrodesis or
resection arthroplasty with a silicone spacer, the Ascension PIP may
provide the potential benefits of increased motion and function, and may
be used on patients whose strength and motion demands would exceed the
capabilities of the currently available one-piece silicone spacers.

Therefore, based on Ascension PIP pre-clinical testing, and the animal
and clinical data for the Pyrocarbon MCP, it is reasonable to conclude
that the probable benefit to health from using the Ascension PIP for the
target population outweighs the risk of illness or injury, taking into
account the probable risks and benefits of currently available devices
or alternative forms of treatment, when used as indicated in accordance
with the directions for use.

**XII. Panel Recommendations**

This HDE was not taken to a meeting of the Orthopedics and
Rehabilitation Devices Panel because this panel has previously reviewed
marketing applications for other finger prostheses. Therefore, it was
determined the Panel had already provided input into acceptable kinds of
data needed to assess safety and probable benefit.

**XIII. CDRH Decision**

CDRH has determined that based on the data submitted in the HDE, the
Ascension PIP joint implant will not expose patients to an unreasonable
or significant risk of illness or injury, and the probable benefit to
health from using the device outweighs the risks of illness or injury,
and issued an approval letter on March 22, 2002.

**XIV. Approval Specifications**

Instructions for use: See Labeling.

Indications for Use: See section II above.

Hazards to Heath from Use of the Device: See Contraindications,
Warnings, and Precautions in sections III and IV above.

**XV. References**

[^1]: PMA P000057, approved on November 19, 2001.

[^2]: An KN, Chao EY, Cooney WE, Linschied RL, "Normative model of human
    hand for biomechanical analysis," *J Biomech*, Vol. 12, No. 10,
    775-788, 1979.

[^3]: Chao EY, An KN, "Determination of internal forces in human hand,"
    *ASCE J Eng Mech*, Vol. 104, 255-272, 1978.

[^4]: Sarrafian SK, Kazarian LE, Topouzian LK, "Strain variation in the
    components of he extensor apparatus of the finger during flexion and
    extension. A biomechanical study," *J Bone and Joint Surg*, Vol.
    52A, No. 5, 980-990, 1970.

[^5]: Valero-Cuevas FJ, Zajac FE, Burgar CG, "Large index-fingertip
    forces are produced by subject-independent patterns of muscle
    excitation," *J Biomech*, Vol. 31, No. 8, 693-703, 1998.

[^6]: Weightman L, Amis AA, "Finger joint force predictions related to
    design of joint replacements," *J Biomed Eng*, Vol. 4, No. 3,
    197-205, 1982.

[^7]: Napier JR, "The prehensile movements of the hand," *J Bone and
    Joint Surg*, Vol. 34B, No. 4, 902-913, 1956.

[^8]: Landsmeer JMF, "Power grip and precision handling," *Ann Rheum
    Dis*, Vol. 21, 164-168, 1962.

[^9]: Swanson AB, Matev IB, deGroot G, "The strength of the hand," *Bull
    Prosthet Res*, Vol. 10, No. 14, 145-153, Fall 1970.

[^10]: Walker, Erkman, "Clinical evaluation of finger joints," [Human
    Joints and their Artificial Replacements]{.underline}, editor C.C.
    Thomas, Springfield, Illinois, 348-351, 1977.

[^11]: Chao et al, "Hand functional strength assessment and its clinical
    application," [Biomech of the Hand]{.underline}, Chapter 5, 97-129,
    1989.

[^12]: Boatright JR, Kiebzak GM, O\'Niel DM, Peindl RD, "Measurement of
    thumb abduction strength: Normative data and a comparison with grip
    and pinch strength," *J Hand Surg*, Vol. 22A, No. 5, 843-848, 1997.

[^13]: Josty IC, Tyler MPH, Shewell PC, Roberts NH, "Grip and pinch
    strength variations in different types of work," *J Hand Surg*, Vol.
    22B, No. 2, 266-269, 1977.

[^14]: Linscheid RL, Dobyns JH, "Total joint arthroplasty - The hand,"
    *Mayo Clinic Proc*, Vol. 54, No. 8, 516-526, 1979.

[^15]: Hagert CG, "Advances in hand surgery: Finger joint implants,"
    *Surg Annu*, Vol. 10, 253-275, 1978.

[^16]: Chao et al, "Muscle and joint forces in the hand," [Biomech of
    the Hand]{.underline}, Chapter 3, 53-72, 1989.

[^17]: Berme N, Paul JP, Purves WK, "A biomechanical analysis of the
    metacarpophalangeal joint," *J Biomechanics*, Vol. 10, No. 7,
    409-412, 1977.

[^18]: Beevers DJ, Seedhom BB, "Design of a non-constrained,
    non-cemented, modular, metacarpophalangeal prosthesis," *Proc Inst
    Mech Eng \[H\]*, Vol. 209, No. 3, 185-195, 1995.

[^19]: Tamie K, Ryu J, An KN, Linscheid RL, Cooney WP, Chao YS,
    "Three-dimensional geometric analysis of the metacarpophalangeal
    joint," *J Hand Surg*, Vol. 13A, No. 4, 521-529, 1998.

[^20]: Sibly TF, Unsworth A, "Wear of cross-linked polyethylene against
    itself: A material suitable for surface replacement of the finger
    joint," *J Biomed Eng*, Vol. 13, No. 3, 217-220, 1991.

[^21]: Stokoe SM, Unsworth A, Viva C, Haslock I, "A finger function
    simulator and the laboratory testing of Swanson prostheses," *Proc
    Inst Mech Eng \[H\]*, Vol. 204, No. 4, 233-240, 1990.

[^22]: Dumbleton JH, [Tribology of Natural and Artificial
    Joints]{.underline}, Chapter 3, pp. 52, Elsevier Scientific
    Publishing Co., 1981.