Numelock II Polyaxial Locking System - Stryker

Indications 

Numelock II ® 

Polyaxial Locking System 

Operative Technique 

Osteotomy Applications

Contents 

Rationale 3 

Features and Benefits 4 

Indications 5 

Preoperative Planning 6 


• General Principles 6 

Ordering Information 

• Plates 9 

• Screws 10 

• Instruments 10 

• Cases and Trays 11 

Special acknowledgements are made to Professor Albert van Kampen, M.D., PhD 

and Dr. Robert Gaasbeek, M.D. of the University Medical Centre Nijmegen, 

the Netherlands, for sharing their technical and surgical expertise in the review of 

this Operative Technique.

Rationale 

The Numelock II® polyaxial locking mechanism provides the option of adjustability 

in the range of screw trajectories through a broad continuum of positions. 

This mechanism can be adjusted to meet the requirements of many osteotomies 

around the knee. This feature allows the Numelock II® plates to be correctly 

situated with respect to the patient’s anatomy, while each individual locking screw 

is accurately targeted to address the configuration of the osteotomy site and 

resulting bone segments. 

Plates 

The Numelock II® polyaxial locking 

system is designed to facilitate 

treatment with high tibial and distal 

femoral osteotomies. The shape, 

material properties and surface quality 

of the implants take into account the 

stringent demands of surgeons for 

high fatigue strength, optimized 

transfer of loading forces and a 

straightforward, standardized operative 

technique with broad applicability. 

For the purposes of safety, 

traceability and convenience, 

all plates are packaged sterile. 

Material 

Composition 

The implants are produced from 

316LVM Stainless Steel. ASTM F138 

and F139/ISO 5832-1 material 

standards provide rigid specifications 

that define the chemical composition, 

microstructural characteristics and 

mechanical properties of implant 

quality Stainless Steel. These standards 

ensure that 316LVM Stainless Steel, 

even if provided by different suppliers, 

is consistent and compatible. 

The material used for all Numelock II® 

plates and screws meets these 

standards. 

Locking Screws 

The Numelock II® locking screws used 

with the Numelock II® Osteotomy 

Plates have a thread diameter of 

6.5mm. All Numelock II® locking 

screws are packaged sterile and are 

provided in lengths from 27mm to 

85mm (27mm – 45mm in 3mm 

increments and 50mm – 85mm in 

5mm increments). The locking screws 

have a unique core design and thread 

pattern in the head and tip areas. 

As the screw is threaded into the 

locking mechanism (see below), 

its conical head part engages with 

the corresponding threads in the ring, 

which then expands into the plate, 

securely locking the position of the 

screw at the chosen angle and 

direction. 

Polyaxial Locking 

Mechanism 

Every hole of each osteotomy plate 

(except Ref. No. STP2Y76S) is 

equipped with an integral polyaxial 

locking mechanism which will accept 

6.5mm diameter Numelock II® 

locking screws. 

The screw securely locks into the plate 

at the desired angle and direction. 

Prior to final locking of the 

Numelock II ® screw within the 

mechanism, the ring is designed to 

rotate freely. This attribute can be used 

to pull a bone segment into alignment 

(see Operative Technique – General 

Principles, Step Six, for additional 

information on this feature). 

Instrumentation 

The Numelock II® instruments are 

designed for accuracy and ease of 

use and precisely engage with all 

Numelock II® implant components. 

The storage trays conveniently house 

the instrument set. 

This mechanism permits the screws to 

be targeted through a cone of up to 30° 

in all directions. This capability allows 

the surgeon to aim each screw at an 

optimal trajectory within the 30° cone. 

3

Features and Benefits 

Features 

Axially stable, locking fixation 

Polyaxial locking mechanism 

30º range of screw insertion angles 

All plates and screws packaged sterile 

Screws with unique thread and conical 

core design 

Ring Driver permits screw 

and bone segment adjustments 

Numelock screws accept 

standard hex drivers 

Rounded plate ends 

Drill guide constrains screw 

insertion angle 

Numelock II ® Screw Depth Gauge 

gives direct value 

Benefits 

• High stability; protection against 

primary and secondary losses of 

reduction; limited plate contact with 

periostium; reliable purchase in 

normal and osteoporotic bone. 

• Screws positioned according to 

osteotomy surface or to avoid another 

implant; plate positioned to meet 

needs of patient anatomy. 

• Adjustability in range of screw 

trajectories for optimized fixation. 

• Safety, traceability, convenience. 

• Low insertion torque and secure 

locking; reduced possibility of 

cross-threading and cold welding. 

• Distance of bone to plate can be 

accurately adjusted; bone segments 

may be pulled towards plate. 

• Screws can be removed with standard 

hex drivers at end of treatment, in case 

of plate extraction. 

• Reduced potential for soft tissue 

irritation. 

• Limits screw head protrusion 

for reduced soft tissue irritation; 

insures optimal surface contact of ring 

to plate. 

• No compensation required 

for Numelock II ® locking screws. 

4

Indications 

The Numelock II ® Osteotomy System’s 

implants and instruments facilitate 

performance of high tibial and distal 

femoral osteotomies using the opening 

and closing wedge techniques. 

Specific indications include the 

following: 

• Unicompartmental osteoarthritis. 

• Congenital and post traumatic 

varus or valgus deformities and 

malalignments. 

• Posterolateral knee instability. 

The physician’s education, training 

and professional judgment must be 

relied upon to choose the most 

appropriate device and treatment 

option. Conditions presenting an 

increased risk of failure include: 

• Presence of inflammatory arthritis. 

• Severe joint instability cannot be 

treated through osteotomy alone; 

additional ligament reconstruction 

is required. 

• Any active or suspected latent 

infection or marked local inflammation 

in or about the affected area. 

• Compromised vascularity that would 

inhibit adequate blood supply to the 

osteotomy or the operative site. 

• Bone stock compromised by disease, 

infection or prior implantation that 

cannot provide adequate support 

and/or fixation of the devices. 

• Material sensitivity documented or 

suspected. 

• Obesity. An overweight or obese 

patient can produce loads on the 

implant which can lead to failure of 

the fixation of the device or to failure 

of the device itself. 

• Patients having inadequate tissue 

coverage over the operative site. 

• Implant utilization that would 

interfere with anatomical structures 

or physiological performance. 

• Any mental or neuromuscular 

disorder which could create an 

unacceptable risk of fixation 

failure or complications in 

postoperative care. 

• Other medical or surgical 

conditions which would preclude 

the potential benefit of surgery. 

5


Preoperative Planning 

The surgeon must first determine and 

clearly characterize the nature and 

extent of the deformity being 

corrected. For this purpose, full-length, 

standing (long axial alignment) AP 

radiographs need to be obtained. 

The x-rays must include the hip, 

knee and talus, standing in extension. 

The x-ray beam should be centered 

on the knee in question. It is also 

recommended that a standing lateral 

view and an anteroposterior view of 

the knee bent at 45° be obtained. 

These x-rays are then used to classify 

the orientation and magnitude of the 

deformity to be corrected using 

standard methods as described in the 

literature. The mechanical axis of the 

patient is defined by a line drawn from 

the center of the femoral head to the 

center of the tibial-talar joint. 

The radiographic evaluation is also 

used to determine the site of the 

osteotomy, the method of correction 

(opening or closing wedge) 

and positioning of the plate. 

General Principles 

It is recommended that any osteotomy 

be performed on a radiolucent table 

to allow visualization of the hip, knee 

and ankle. During the procedure, 

it is necessary for the surgeon to have 

a clear view of the entire extremity 

from the iliac crest to the talus. 

A choice of incision consistent with the 

anatomical region in question is made 

by the surgeon, based on personal 

experience and patient considerations. 

When treating a tibial deformity 

with a closing wedge osteotomy, 

the tibiofibular joint will prevent 

correction unless the fibula or the 

tibiofibular ligaments are cut. 

One option is to perform an oblique 

fibular osteotomy through a small 

incision in the proximal middle third 

of the fibula. 

Step One – Closing Wedge 

Osteotomy and Opening 

Osteotomy Wedge Sizing 

• The Cutting Guide (Ref. No. GCTP) 

in conjunction with fluoroscopic 

control permits accurate incisions to 

be made for closing wedge osteotomies. 

The first cut is made parallel to the 

joint line without the Cutting Guide. 

Insertion of two K-wires may be 

helpful in establishing the plane 

and location of the first cut. 

• After completion of the first cut, the 

Cutting Guide’s flange (see Fig. 1) is 

placed into this incision. Adjustment 

of the graduated scale allows for 

precise angulation of the second 

cutting line. For right leg osteotomies, 

use the side of the scale indicated by 

the letter “D.” For left leg osteotomies 

use the side of the scale marked “G.” 

Note: The “D” represents “Droite” 

(Right) and the “G” represents 

“Gauche” (Left) in French. 

• When performing an opening wedge 

osteotomy, a bone spreader can be 

used to pry open the osteotomy site 

and keep it from collapsing, while 

a bone clamp is used to secure the 

opposite aspect so that it does not 

displace. It is often useful to keep 

a small corner of the far cortex intact 

to help maintain stability. 

• Use the Trial Wedges (Ref. No. 

10CALES) to ensure that the correct 

angular position is maintained and 

also to help open the osteotomy gap. 

If bone filler is used, these Trial 

Wedges can also help in determining 

the correct size and shape of the 

actual wedge to be implanted in the 

gap. The Trial Wedges are conveniently 

held and manipulated into position 

with the Holder (Ref. No. PRCAL). 

The Trial Wedge is removed after 

stabilization of the osteotomy site. 

Flange 

Graduated Scale 

Figure 1 

6


Step Two – Plate Contouring 

• The selected plate may require some 

contouring. When shaping the 

implant, the Numelock II® polyaxial 

mechanisms must be protected by 

grasping the plate with two Bending 

Forceps (Ref. No. PFTP3I), ensuring 

that the single rounded knob of each 

of the Bending Forceps is securely 

seated in the holes adjacent to the 

area of the plate that is being bent 

(See Figure 2). If twisting of the plate 

is required, a single Forceps, in 

combination with a Plate Bending 

Iron (Ref. No. TRTP3), may be used. 

Step Three – Pre-drilling for 

Locking Screw Placement 

• Once the required shape has been 

fashioned, the plate should be 

positioned on the bone for optimal 

stability and ultimate fixation. 

• Make certain that the locking 

mechanisms are correctly oriented: 

The slotted sides of the rings must all 

be turned to face upwards (away from 

the underside of the plate). 

• The Numelock II® Drill Guide 

(Ref. No. GM35 for use with a 3.5mm 

drill bit or Ref. No. GM45 for use 

with a 4.5mm drill bit) is threaded 

into the locking mechanism of one of 

the holes (See Figure 3). The 3.5mm 

drill bit is recommended for normal 

bone. The Drill Guide is then 

positioned at the required angle and 

the appropriate diameter drill bit is 

used to create a pilot hole for screw 

insertion. The Drill Guide constrains 

the drilling angle to within 30°, 

ensuring optimal screw head profile 

to minimize possible soft tissue 

irritation. 

• If hard cortical bone is encountered, 

use the tip of the Cutting Screwdriver 

(Ref. No. TASH7) to incise the near 

cortex. Additionally, a 4.5mm drill bit 

may be used to overdrill the near 

cortex in case of hard bone. The Tap 

(Ref. No. TVSH7) may be used to 

further prepare a pilot hole that was 

drilled using the 4.5mm drill bit. 

Step Four – Depth Measurement 

• Using the Depth Gauge (Ref. No. JA65), 

measure the depth of the pilot holes 

directly through the plate 

(See Figure 4). 

Figure 2 

Note: Special care must be taken to 

prevent damage to the locking 

mechanism. To protect the 

mechanism from damage, apply 

bending only between the locking 

holes. Do not back bend the plate. 

The Bending Forceps 

(Ref. No. PFTP3I) and Plate 

Bending Irons (Ref. No. TRTP3) 

must not be used to bend the 

femoral plates as they are already 

pre-contoured in an optimal 

manner. 

Figure 3 

• It is important to preplan the angles 

of inclination for each of the locking 

screws to optimize the fixation 

of both osteotomy segments. 

Extreme caution needs to be exercised 

to avoid collision of any screws inside 

the bone and to avoid penetration 

of the joint surfaces.When feasible, 

to avoid such intersection of the 

Numelock II® screws within the bone, 

it is desirable to place them at 

divergent angles to each other. 

Figure 4 

The Depth Gauge provides the actual 

length of the screw required. 

Note that the “Y” Shaped Plate with 

Compression Hole (Ref. No. STP2Y76S) 

uses standard 4.5mm SPS cortical 

screws in the shaft. Use the Depth 

Gauge from the Basic Fragment SPS 

set (Ref. No. 702878) for correct 

measurement of the diaphyseal screws 

in this plate. 

7


Step Five – Locking Screw 

Placement 

• Using the Cutting Screwdriver 

(Ref. No. TASH7), insert the 

Numelock® locking screw as far as 

possible without locking the ring 

mechanism. Prevent rotation of the 

ring mechanism by engaging the 

Holding Spanner’s (Ref. No. CESH7) 

teeth with the corresponding slots in 

the ring (See Figure 5). 

Step Six – Final Adjustments/ 

Repositioning/Transport 

• To adjust the position of the bone 

with respect to the plate or to pull 

a bone segment closer to the plate, 

use the Ring Driver (Ref. No. TVESH7). 

By turning the ring clockwise with 

the Ring Driver, the bone is moved 

closer to the plate as required. 

Note: If using this feature to realign 

two bone segments, the 

orientation of screw placement 

must be parallel to the plane of 

the osteotomy line associated 

with these two segments. 

Step Seven – Final Locking 

• When all desired adjustments are 

complete, lock each Numelock II® 

screw with the Screwdriver while 

holding the ring steady with the 

Holding Spanner. Firm tightening 

of the screws ensures stability. 

After locking, it is no longer possible 

to rotate the ring without damaging 

the locking mechanism. 

Figure 5 

Repeat Steps Three through Five 

for all screw positions. If transport 

or repositioning of a bone segment 

is required, see Step Six. 

Note: To guarantee maximum stability, 

fill all Numelock II® holes with 

a locking screw of appropriate 

length. 

Postoperative Care 

The physician’s education, training and 

professional judgment must be relied 

upon to establish the most appropriate 

postoperative care regimen for each 

individual patient. The following 

recommendations may be considered 

at the surgeon’s discretion: 

• Some patients may need to spend 

several days in the hospital after an 

osteotomy procedure. Deep muscle 

compartment drains may need to be 

considered postoperatively as well as a 

suitable pain management protocol. 

• If warranted, continuous passive 

motion may begin during the second 

postoperative day to help restore 

mobility. When appropriate, 

toe-touch weight-bearing with 

crutches may follow. 

• Follow-up radiographs are 

recommended at six weeks after 

surgery. Weight-bearing may be 

gradually increased at the surgeon’s 

discretion or when there is 

radiographic evidence of union. 

Full weight-bearing may begin when 

there is full consolidation of the 

osteotomy site, typically at around 

eight to ten weeks for men and ten 

to twelve weeks for women. 

8

Ordering Information – Osteotomy Plates 

Stainless Steel, Packaged Sterile 

MEDIAL DISTAL FEMORAL, CLOSING 

Locking Screws Diameter 6.5mm 

MEDIAL PROXIMAL TIBIAL “Y” SHAPED, OPENING 


StSt Length Side Locking Shaft 

REF mm Holes Holes 

SFBIPOSTDS 91 Right 6 3 

SFBIPOSTGS 91 Left 6 3 



STP2Y70S 69 Sym 4 2 


STP2Y114S 114 Sym 4 2 

LATERAL PROXIMAL TIBIAL “L” SHAPED, CLOSING 


MEDIAL PROXIMAL TIBIAL “L” SHAPED, OPENING 




STP2L61FDS 59 Right 4 2 

STP2L61FGS 59 Left 4 2 



STP2L64ODS 63 Right 4 2 

STP2L64OGS 63 Left 4 2 

59mm 



STP2L64FDS 63 Right 4 2 

STP2L64FGS 63 Left 4 2 

MEDIAL PROXIMAL TIBIAL “Y” SHAPED, 

OPENING WITH COMPRESSION HOLE 


Standard Screws Diameter 4.5mm (for shaft holes only) 




63mm 

9

Ordering Information – Screws / Instruments 

6.5mm diameter Locking Screws, 

Stainless Steel, Packaged Sterile 

StSt 

Length 

REF 

mm 

S7SH27S 27 

S7SH30S 30 

S7SH33S 33 

S7SH36S 36 

S7SH39S 39 

S7SH42S 42 

S7SH45S 45 

S7SH50S 50 

S7SH55S 55 

S7SH60S 60 

S7SH65S 65 

S7SH70S 70 

S7SH75S 75 

S7SH80S 80 

S7SH85S 85 

6.5mm Instrumentation 

REF 

GCTP 

PRCAL 

10CALES 

PFTP3I 

TRTP3 

GM35 

MCA35195 

GM45 

MCA45195 

TVSH7 

JA65 

CESH7 

Description 

Cutting Guide 

Holder for Trial Wedges 

Set of 10 Trial Wedges 

Bending Forceps (Two Required) 

Plate Bending Iron 

Drill Guide for 3.5mm Drill Bit 

3.5mm Drill Bit 

Drill Guide for 4.5mm Drill Bit 

4.5mm Drill Bit 

Tap 

Depth Gauge 

Holding Spanner 

TASH7 

TVESH7 

Cutting Screwdriver 

Ring Driver 

10

Ordering Information – Cases and Trays 

REF 

Description 

Metal Case configuration 

CSA2F240 Storage Case, Instruments 

11

Trauma, Extremities & Deformities 

Trauma, Extremities & Deformities 

Biologics 

Biologics 

Surgical Products 

Surgical Products 

Neuro & ENT 

Neuro & ENT 

Stryker Trauma AG 

Bohnackerweg 1 

CH-2545 Selzach 

Switzerland 

www.osteosynthesis.stryker.com 

The information presented in this brochure is intended to demonstrate a Stryker product. Always refer to the package 

insert, product label and/or user instructions before using any Stryker product. Surgeons must always rely on their own 

clinical judgment when deciding which products and techniques to use with their patients. Products may not be available 

in all markets. Product availability is subject to the regulatory or medical practices that govern individual markets. Please 

contact your Stryker representative if you have questions about the availability of Stryker products in your area. 

Stryker Corporation or its subsidiary owns the registered trademark: Stryker 

Stryker Corporation or its subsidiary owns, uses or has applied for the following trademarks: Numelock II 

Literature Number: 982196 

LOT A4106 

Copyright © 2006 Stryker 

Printed in Switzerland

Numelock II Polyaxial Locking System - Stryker

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