ALLOFIT ACETABULAR HIP SYSTEM

Surgical Technique

Unique ridgelock surface designed for easy implantation and stability

™

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ALLOFIT ACETABULARSYSTEM

Developed in conjunction with:

Nikolaus Boehler, MDUniversity Professor of Orthopedic Surgery

General Hospital Linz, Austria

Wolfgang Schwaegerl, MDUniversity Professor of Orthopedic Surgery

Vienna, Austria

CONTENTS

INTRODUCTION ................................................................... 2PREOPERATIVE PLANNING ............................................ 3EXPOSURE OF THE ACETABULUM ............................. 3REAMING THE ACETABULUM ....................................... 4SELECTION OF IMPLANT SIZE ..................................... 5IMPLANTING THE TITANIUM SHELL WITHOUTSCREWHOLES ....................................................................... 6IMPLANTING THE TITANIUM SHELL WITH SCREWHOLES ....................................................................... 7INSERTION OF SCREWS ................................................... 8FITTING OF THE TRIAL INSERT .................................... 9FITTING OF THE CUP INSERT ......................................10REMOVING THE LINER ...................................................10ORDERING INFORMATION ........................................... 11

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ALLOFIT ACETABULARSYSTEM Since its first use in 1993, the Allofit Acetabular Cup System has gained popularity among hundreds of orthopedic surgeons. It provides the surgeon with a reliable prosthesis that is easy to handle. The surgeon can individually select the acetabular components most suitable in an economical and practical framework.

Its unique geometry assures minimal bone resection and aims to reestablish a secure and physiological load transfer through the periphery of the cup. The Allofit Acetabular Cup System features a patented Ridgelock™ macro structure that greatly supports primary stability of the 3mm titanium shell. Permanent secondary fixation is achieved by the choice of a grit-blasted commercially pure titanium surface.

To prevent failure due to incomplete metal backing of the insert, the Allofit System offers sufficient polyethylene wall thickness for inserts. All screwholes in the titanium shell are designed so they can be sealed. The congruent insert is seated and secured in the shell by a snap mechanism that firmly holds the insert in place.

Allofit offers an industry-leading set of alternative bearing options, addressing the most dominant complications in THA—late loosening and dislocation.

Durasul® highly crosslinked polyethylene, which has shown no measurable wear on a physiological hip simulator. Available in standard and hooded options and 28 and 32mm articulating diameters.

Metasul® metal-on-metal inserts used for over 15 years in more than 200,000 patients worldwide. Available in standard and hooded options and 28mm articulating diameter.

Sulene™ conventional polyethylene with increased crosslinking and improved long-term stability due to gamma sterilization under nitrogen gas atmosphere. Available in 28 and 32mm articulating diameters.

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Preoperative PlanningPreoperative planning is undertaken using the X-ray templates and a current X-ray of the pelvis, in which the inferior edge of the symphysis lies in the center of the picture. The object of the planning is to determine the most favorable position of the implant and its approximate size, as well as to anticipate possible operative difficulties. A stable acetabular floor capable of bearing loads and a solid lateral bony cover are desirable. The prerequisite for the implantation of a primary stable cup is an extensively maintained bony circumference of the acetabulum.

In dysplasia cases, the pre-operative planning helps in deciding whether the implant position must be strengthened by bone graft material. The axis of the artificial joint should approximate physiological conditions as closely as possible.

The opening plane of the cup should form an angle of 40-45° to the pelvis horizontal line. The subchondral sclerosis line between oriel and lacrimal figure serves as a reference point for estimating the cup diameter. The cup will receive an anteversion of 10-15° intraoperatively. It is also to be kept in mind that the correct cup orientation depends on the position of the femoral implant.

ApproachAny usual approach is possible.

Exposure of the AcetabulumThe capsule is preferably excised in its entire circumference to the extent that an easy introduction of reamers is possible. Remove fibrous, cartilaginous and bone structures preventing the preparation of the acetabulum.

Fig. 1

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Fig. 2

Reaming the AcetabulumThe next stage is preparation of the acetabulum with the spherical reamers until the predetermined size has been reached. The desired objective is based upon the following conditions:

• anatomically formed implant support

• preservation of bone stock to assure a solid support of the implant

• certainty of anchoring the cup shell in good vascular bone

The objective is the creation of the geometrical and physiological requirements for a primary and permanently stable implantation of the titanium shell.

Important: Extreme caution must be used when reaming in order to prevent excessive removal of bone and not to alter the morphology of the acetabulum.

The central acetabular floor is first reamed with a relatively small reamer and deepened according to the preoperative planning. The use of centering pins is optional. When the necessary depth has been reached, the reamer is moved to an inclination of about 40° and a hemispherical support is formed with the use of larger reamers. This cranial reamer direction is maintained until:

1. the necessary depth has been attained; and

2. 50-60% of the acetabular roof has been reamed to bleeding bone.

The anterior and posterior acetabular roof must remain stable and solid. The reaming process has ended when these conditions have been achieved.

To obtain optimal implant support and to avoid thermal necrosis, the final reamer should be operated by hand. In normal cases, it will be introduced to a depth such that its equator is entirely covered by bone. Dysplastic hips represent an exception because it is necessary to create an additional abutment.

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Selection of the Implant SizeIt is possible to test whether a cup of a given diameter can be implanted in the optimum position with the aid of the trial shell. The size indication of the trial shell corresponds to the reamer last used. After attachment to the cup setting instrument, the trial shell is tapped in up to the bony acetabular floor at the desired abduction and anteversion. It should show stable seating under pulling, rotating and careful tilting loads. The contact between acetabular floor and trial shell can be tested with the measurement hook, after the setting instrument has been unscrewed.

If the trial shell does not have a sufficiently firm seat, it must be checked as to whether the edge of the trial implant is anchored in bone. If this is not the case, the acetabulum must be suitably deepened with the reamer last used. If the trial shell is not seated firmly enough in spite of a sufficient bony enclosure, the next largest trial shell is selected. In case of soft bone, additional primary anchoring with at least two cancellous bone screws should be performed.

Caution: To protect the acetabulum, the trial shell is about 1mm smaller than the implant of the same size designation. This is because the definitive prosthesis has a surface macro structure that is not present on the trial shell. The implant will thus have a firmer seat compared to the trial.

The trial shell is then removed by tipping out.

Fig. 3

SELECTION OF THE IMPLANT SIZESize marked on reamer, shell, implant

Actual trial shell (mm)

Actual size implant (mm)

Corresponding liner size

46 47 48 FF

48 49 50 GG50 51 52 HH52 53 54 II54 55 56 JJ56 57 58 KK58 59 60 LL60 61 62 MM62 63 64 NN64 65 66 OO66* 67 68 PP68* 69 70 QU*sizes not available without screwholes

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Implanting the Titanium Shell without ScrewholesThe titanium shell is completely screwed to the setting instrument and tapped in with the desired abduction and anteversion. The anteversion depends on the selected operative approach, the anatomical conditions and the femoral implant. It is absolutely necessary to align the cup before final impaction and to maintain the selected setting direction.

The measurement hook is used to check whether the implant was driven to the acetabular floor. As can be seen in Figure 7, because of the specific geometry of the cup, a small gap of about 1mm might be present at the dome area even if the cup is completely seated. The shell must maintain its stable seating under pulling, rotational and tilting loads.

A threaded dome hole plug is supplied with every implant. The hole at the pole of the titanium shell must be seated with it, otherwise the cup insert cannot be mounted correctly. The dome hole plug is placed on the corresponding placement instrument and screwed into the borehole.

If a trial reduction with a trial insert is planned, do not insert the dome hole plug (see page 9).

Fig. 4

Fig. 5

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Implanting the Titanium Shell with ScrewholesThe titanium shell is completely screwed to the shell setting instrument and is tapped in with the desired abduction and anteversion. The anteversion depends on the operative approach selected, the anatomical conditions, and the femoral implant. It is absolutely necessary to correctly align the shell before final impaction, since its position can no longer be altered afterwards.

A notch in the equator of the shell indicates the main direction of the screwholes. The holes must be placed correctly in the direction of the resulting hip forces. No other orientation is suitable biomechanically and such an orientation may moreover entail the danger of vascular and nerve lesions by the screws.

The measurement hook is used to test whether the implant was driven to the acetabular floor. As can be seen in Figure 7, because of the specific geometry of the cup, a small gap of about 1mm might be present at the dome area even if the cup is completely seated. The shell must maintain its stable position under pulling, rotational and tilting loads.

A threaded dome hole plug is supplied with every implant. The hole at the pole of the titanium shell must be sealed with it, otherwise the cup insert cannot be mounted correctly. The dome hole plug is placed on the corresponding placement instrument and screwed into the borehole.

If a trial reduction with a trial insert is planned, the dome hole must not yet be closed (see page 9).

Fig. 6

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Insertion of ScrewsFlat-head cancellous bone screws (Ø 6.5 mm, reference #4301-07-015/070) must be used. To simplify the initial insertion of the screws, 3.2mm holes are drilled through the subchondral bone. The use of an angular drill gear with a drill guide is recommended because it facilitates the correct orientation of the holes in the center of the screw funnel and vertically to the shell and off-center insertion of the screws can lead to damage of the screw or the screwhole and to a possible dislodgement of the shell.

Tapping of the drill holes is only recommended in cases of especially hard bone.

Since the screws are only to be anchored in cancellous bone, lengths of up to 30mm are normally sufficient. The screws must not penetrate the opposite cortex. The geometry of the screw funnel permits the screws to be oriented within a range of 30 degrees.

Caution: The specified Ti-6Al-4V screws have a lower shearing resistance than screws made of steel or CoCrMo alloys.

It is recommended to check whether all screws are completely seated before impacting the insert. Projecting screw heads would make the fitting of the cup insert impossible.

Screwholes in the titanium shell that are not used can each be sealed with a screw plug. The plug is placed on the appropriate setting instrument and fixed in the screw funnel of the titanium shell with a light tap. These screw plugs are intended for one-time use only, and cannot be removed any more once inserted.

Fig. 7

Fig. 8

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Fitting of the Trial InsertWash the operative site thoroughly and carefully clean the titanium shell.

It is recommended to manually place the trial insert into the implanted shell.

The trial insert can be fixed into the titanium shell by screwing in the attachment screw into the dome hole of the implant. If the dome hole plug has already been placed into the shell, it must temporarily be removed.

Femoral ComponentIf alternative bearing surfaces are used, care must be taken to select the appropriate femoral head.

After implanting the femoral component, a trial reduction is made to determine the correct size of acetabular insert to be implanted. The trial insert is then removed.

Fig. 9

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Removing the LinerIf the disassembly of an already firmly seated insert becomes necessary, the following procedure is often successful: A cancellous bone screw is inserted into the polyethylene insert after making a small pilot drill hole. This is done centrally in the case of polyethylene inserts and decentrally between articulating surface and shell edge with Metasul inserts, if the polyethylene body is sufficiently strong for the purpose. It is also possible to attempt to lever out the insert at the edge with one or two osteotomes.

The inside edge of the shell, where the locking mechanism for the insert is located, must be protected if a new insert is to be fitted.

If a new insert can no longer be reliably anchored in the old shell, the shell must be replaced.

Follow-up TreatmentA partial loading of the operated hip during the first 6 weeks is advisable.

Fitting of the Cup Insert Interposed tissues in the titanium shell or at the shell edge must be avoided since they prevent the insert from snapping in. The shell edge must be free from any tissue and particular attention must be paid to the posterior-inferior bony edge of the acetabulum.

Caution: The dome hole plug must be properly inserted before impaction of the insert. It is important that the dome hole plug is in place as it plays a vital role in the alignment of the insert.

The size of cup inserts is indicated with a letter code. This code corresponds to the size indicated on the corresponding titanium shell (see table on page 5) The appropriate modular liner attachment is screwed onto the liner impactor.

The insert is then attached to the setting instrument, introduced into the cleaned shell, and is carefully centered. The polyethylene guide nipple must be centered in the hole of the dome hole plug before impaction.

A couple of firm hammer blows on the setting instrument are sufficient to snap the insert into the shell. Once fully impacted, the phase of the liner will be approximately 2mm above the rim of the titanium shell. If the insert was not properly aligned, deformation of the guiding nipple might occur—the insert can not be impacted and a new insert must be used.

In order to avoid any scratching of the delicate surface, Metasul liners must be handled with care.

Note: The modular liner attachment for Metasul 28mm liners can also be used for polyethylene 28mm liners.

Fig. 10

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Ordering InformationALLOFIT SHELLSCatalog No. Description4242 Allofit Shell 46/FF4243 Allofit Shell 48/GG4244 Allofit Shell 50/HH4245 Allofit Shell 52/II4246 Allofit Shell 54/JJ4247 Allofit Shell 56/KK4248 Allofit Shell 58/LL4249 Allofit Shell 60/MM4250 Allofit Shell 62/NN4251 Allofit Shell 64/OO

ALLOFIT-S SHELLSCatalog No. Description4262 Allofit-S Shell 46/FF4263 Allofit-S Shell 48/GG4264 Allofit-S Shell 50/HH4265 Allofit-S Shell 52/II4266 Allofit-S Shell 54/JJ4267 Allofit-S Shell 56/KK4268 Allofit-S Shell 58/LL4269 Allofit-S Shell 60/MM4270 Allofit-S Shell 62/NN4271 Allofit-S Shell 64/OO4272 Allofit-S Shell 66/PP4273 Allofit-S Shell 68/QU

ALLOFIT DOME HOLE PLUGCatalog No. Description

001.00004.000 Dome Hole Plug

ALLOFIT SCREWHOLE SEALSCatalog No. Description

001.00004.001 Screwhole Seals 7 pcs.

STANDARD METASUL INSERTSCatalog No. Description01.00010.407 Alpha Metasul 28 Standard GG/28

01.00010.408 Alpha Metasul 28 Standard HH/2801.00010.409 Alpha Metasul 28 Standard II/2801.00010.410 Alpha Metasul 28 Standard JJ/2801.00010.411 Alpha Metasul 28 Standard KK/2801.00010.412 Alpha Metasul 28 Standard LL/2801.00010.413 Alpha Metasul 28 Standard MM/2801.00010.414 Alpha Metasul 28 Standard NN/2801.00010.415 Alpha Metasul 28 Standard OO/2801.00010.416 Alpha Metasul 28 Standard PP/2801.00010.417 Alpha Metasul 28 Standard QU/28

HOODED METASUL INSERTSCatalog No. Description01.00010.507 Alpha Metasul 28 Hooded GG/28

STANDARD DURASUL INSERTSCatalog No. Description01.00013.206 Alpha Durasul 28 Standard FF/28

01.00013.207 Alpha Durasul 28 Standard GG/2801.00013.208 Alpha Durasul 28 Standard HH/2801.00013.209 Alpha Durasul 28 Standard II/2801.00013.210 Alpha Durasul 28 Standard JJ/2801.00013.211 Alpha Durasul 28 Standard KK/2801.00013.212 Alpha Durasul 28 Standard LL/2801.00013.213 Alpha Durasul 28 Standard MM/2801.00013.214 Alpha Durasul 28 Standard NN/2801.00013.215 Alpha Durasul 28 Standard OO/2801.00013.216 Alpha Durasul 28 Standard PP/2801.00013.217 Alpha Durasul 28 Standard QU/28

HOODED DURASUL INSERTSCatalog No. Description01.00013.306 Alpha Durasul 28 Hooded FF/28

01.00013.307 Alpha Durasul 28 Hooded GG/2801.00013.308 Alpha Durasul 28 Hooded HH/2801.00013.309 Alpha Durasul 28 Hooded II/2801.00013.310 Alpha Durasul 28 Hooded JJ/2801.00013.311 Alpha Durasul 28 Hooded KK/2801.00013.312 Alpha Durasul 28 Hooded LL/2801.00013.313 Alpha Durasul 28 Hooded MM/2801.00013.314 Alpha Durasul 28 Hooded NN/2801.00013.315 Alpha Durasul 28 Hooded OO/2801.00013.316 Alpha Durasul 28 Hooded PP/2801.00013.317 Alpha Durasul 28 Hooded QU/28

TRAY 1 (Sizes 46 to 58)Catalog No. Description8604 Instrument Case Size 48 to 567139 Instrument Tray Cover

REAMERSCatalog No. Description840.6002 Spherical Reamer 42840.6003 Spherical Reamer 44840.6004 Spherical Reamer 46840.6005 Spherical Reamer 48840.6006 Spherical Reamer 50840.6007 Spherical Reamer 52840.6008 Spherical Reamer 54840.6009 Spherical Reamer 56840.6010 Spherical Reamer 58

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GUARD FOR REAMERCatalog No. Description840.6043 Guard for Reamer 44840.6044 Guard for Reamer 46840.6045 Guard for Reamer 48840.6046 Guard for Reamer 50840.6047 Guard for Reamer 52840.6048 Guard for Reamer 54840.6049 Guard for Reamer 56840.6050 Guard for Reamer 58

REAMER HANDLECatalog No. Description

MPF310034 Reamer Handle

CENTERING PINSCatalog No. Description

840.6108 Centering Pin S

840.6109 Centering Pin M

840.6020 Centering Pin L

FIXATION SCREWCatalog No. Description

8635 Fixation Screw M8

TRIAL SHELLSCatalog No. Description8609 Trial Shell Size 46

8610 Trial Shell Size 488611 Trial Shell Size 508612 Trial Shell Size 528613 Trial Shell Size 548614 Trial Shell Size 568615 Trial Shell Size 58

TRIAL INSERTSCatalog No. Description8623 Trial Insert Size FF/28

8624 Trial Insert Size GG/288625 Trial Insert Size HH/288626 Trial Insert Size II/288627 Trial Insert Size JJ/288628 Trial Insert Size KK/288629 Trial Insert Size LL/28

TRAY 2 (Sizes 60 to 68)Catalog No. Description8605 Instrument Case Size 60 to 687139 Instrument Tray Cover

REAMERSCatalog No. Description840.6011 Spherical Reamer 60840.6012 Spherical Reamer 62840.6013 Spherical Reamer 64840.6014 Spherical Reamer 66840.6015 Spherical Reamer 68

GUARD FOR REAMERCatalog No. Description840.6051 Guard for Reamer 60840.6052 Guard for Reamer 62840.6053 Guard for Reamer 64840.6054 Guard for Reamer 66840.6055 Guard for Reamer 68

TRIAL SHELLSCatalog No. Description8616 Trial Shell Size 608617 Trial Shell Size 628618 Trial Shell Size 648619 Trial Shell Size 668620 Trial Shell Size 68

TRIAL INSERTSCatalog No. Description8630 Trial Insert Size MM/288631 Trial Insert Size NN/288632 Trial Insert Size OO/288633 Trial Insert Size PP/288634 Trial Insert Size QU/28

TRAY 3 (Setting Instruments)Catalog No. Description8606 Instrument Setting Instruments Case7139 Instrument Tray Cover

SETTING INSTRUMENTSCatalog No. Description7344 Impactor 28

8638 Impactor Straight for Titanium Shell01.00019.005 Impactor Straight for Alpha Liner01.00009.001 Dome Hole Plug Instrument01.00019.004 Impactor Curved for Alpha Liner (optional)8639 Setting Instrument for Screw Plug5633 Control Hook01.00019.107 Liner Attachment Standard 2801.00019.109 Liner Attachment Hooded 2801.00019.110 Liner Attachment Hooded 327843 Positioning Guide75.12.00-10 Impactor Curved for Titanium Shell (optional)8667 Adapter for Curved Impactor 75.12.00-10

(optional)

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TRAY 4 (INTER-OP INSTRUMENTATION FOR BONE SCREWS)Catalog No. Description9366-99-160 Inter-Op Acetabular System Screw

Instrument Case9366-99-161 Inter-Op Acetabular System Screw

Instrument Tray #1

INSTRUMENTATION FOR BONE SCREWSCatalog No. Description9366-00-015 Straight Hex Head Screwdriver9366-00-016 Universal Joint Hex Head Screwdriver9366-00-017 Universal Joint Hex Head Shaft (Optional)9366-00-040 Flexible Depth Gauge9366-00-041 Inter-Op Acetabular System Drill Bit Size

3.2mm/35mm

9366-00-042 Inter-Op Acetabular System Drill Bit Size 3.2mm/50mm

1001

-28-

032

Rev.

3/2

004

Prin

ted

in U

SA ©

2004

Zim

mer

Please refer to package inserts for complete product information, including contraindications, warnings, precautions, and adverse effects.

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