CPT 12/14 HIP SYSTEM. Surgical Technique for Femoral Impaction Grafting in Revision THR

Transcription

1 CPT 12/14 HIP SYSTEM Surgical Technique for Femoral Impaction Grafting in Revision THR

2 SURGICAL TECHNIQUE FOR FEMORAL IMPACTION GRAFTING IN REVISION THR USING CPT 12/14 HIP SYSTEM Donald W. Howie, Ph.D., F.R.A.C.S. Professor of Orthopaedics & Trauma University of Adelaide Adelaide, South Australia Douglas E. Padgett, M.D. Associate Professor of Orthopedic Surgery Hospital for Special Surgery New York, NY BY: Clive P. Duncan, M.D., FRCSC Professor and Chairman Department of Orthopaedics University of British Columbia Vancouver, British Columbia Marc J. Philippon, M.D. Director of Sports Medicine/Hip Disorders Clinical Assistant Professor Department of Orthopedic Surgery University of Pittsburgh Pittsburgh, PA 1

3 CONTENTS INTRODUCTION DESIGN PHILOSOPHY Collarless Polished Taper Design System Size Offering CPT Femoral Impaction Grafting Technique STEPS FOR IMPACTION GRAFTING PREOPERATIVE PLANNING SURGICAL TECHNIQUE Approach Osteotomies Determination of Leg Length Dislocation, Removal of Components, and Acetabular Implantation Selection of the Procedure IMPACTION GRAFTING PROCEDURE Bone Graft Preparation Preparation of Graft Site Determination of Stem Size and Length Tamp Assembly Establishing a Bone Reference Point Determination of Distal Femoral Packer Guide Wire and Intramedullary Bone Plug Insertion Distal Graft Packing Distal Graft Preparation for a Long Stem Component Impaction with Femoral Tamps Monoblock Tamping Trial Reduction Proximal Bone Reconstruction Modular Tamping Proximal Packing and Torque Test Reconnect Tamp Cement Application Implantation Wound Closure REFERENCES

4 INTRODUCTION Since the introduction of femoral impaction grafting for stem revision in the early 1990s, there have been numerous reports of mid-term clinical success reported in the literature While impaction grafting is technically demanding, and there have been adverse reports, it is now recognized that there are distinct advantages to the technique, including both preservation of bone and remodeling of impacted bone graft to living bone The innovative CPT 12/14 Modular Tamping System simplifies femoral impaction grafting. This system has a broad range of sizes to address the difficult revisions, and is designed to provide a simple four-step impaction process: 1. Pack graft with Distal Femoral Packers. 2. Impact graft with assembled Femoral Tamps. 3. Remove Guide Wire and perform trial reduction. 4. Use Proximal Tamp to impact and pack proximal graft. An important advantage of using femoral impaction grafting and a cemented stem in younger and middle-aged patients is that the femur can be revised in many cases using a standard length stem, thereby not transgressing the isthmus of the femur and so minimizing stress shielding, thigh pain, and future problems of revision of a long stem. Impaction grafting can be used routinely for revision, and the clinical results when the technique is used at first revision are excellent. 1, 4, 5, 9-12 Also, impaction grafting can be used selectively when other techniques are less desirable, such as: cases involving a large canal with osteoporotic bone which will not support a large cementless stem, cases of angular deformity, cases where there is a distal TKR stem, or cases involving patients who are having their third or fourth revision. 22,23 Despite the success of femoral impaction grafting, even in salvage situations, two types of complications; component subsidence and periprosthetic fracture, have been reported. 15,22,24 It is now recognized that the risk of complications can be minimized by well-designed instruments and surgical technique. Important techniques in femoral impaction grafting include the use of an instrument system which both simplifies the technique and enhances distal bone packing 30 while providing an adequate cement mantle. 31,32 It is important to protect areas of bone loss 36 by having available a comprehensive range of standard stems and to use longer stems when necessary. Several other factors are thought to be important by some authors, including choice of graft material Historically, fresh-frozen allograft has been used with success, while washing the graft and other techniques have also been proposed. 30,34 The use of onlay allograft struts 35 has also been reported, and avoidance of distal stress risers 30 is recommended. 3

5 The enhanced CPT 12/14 System addresses the above issues by providing a modular impaction system to simplify the technique while also permitting an optimized cement mantle and providing an expanded range of standard stems, with the option of three offsets and a comprehensive range of long stems and extended offsets. DESIGN PHILOSOPHY Collarless Polished Taper Design Collarless, polished tapered stems can be used for impaction grafting and have been the stem of choice for revision surgeons using impaction grafting techniques. Collarless, polished tapered stems have proven to be successful during more than 25 years of clinical use in primary hip arthroplasty The CPT 12/14 Hip System has continued this tradition of success since the introduction of the original CPT Hip stem more than a decade ago. 37, The combination of a collarless prosthesis with a highly polished surface and double taper wedge allows the prosthesis to slightly subside within the cement mantle to achieve a strong, self-locking construct. System Size Offering The CPT 12/14 Hip System includes primary and long stem components (Table 1). Five primary stems, from size 1 through size 5, are available in up to three offsets. Additionally, seven long stem options, which include two valgus neck stems that provide leg length options without altering offset, are available. The CPT 12/14 Hip System is available in Zimaloy Colbalt-Chromium- Molybdenum Alloy only. Stem choices are listed below, along with their length and, in parentheses, the number of millimeters longer than the standard CPT 12/14 Hip Stem (sizes 1-5), which is 130mm. The stem length is defined as the distance from the stem tip to the intersection of the medial curve and the osteotomy line. Offset Stem Size Stem Length Standard Extended Extra-Extended Size 1 130mm X X Size 2 130mm X X X Size 3 130mm X X X Size 4 130mm X X X Size 5 130mm X X X Size 2, 180mm 180mm (+50mm) X Size 2, 180mm VN 180mm (+50mm) X Size 3, 180mm 180mm (+50mm) X Size 3, 180mm VN 180mm (+50mm) X Size 4, 200mm 200mm (+70mm) X Size 4, 230mm 230mm (+100mm) X Size 4, 260mm 260mm (+130mm) X 4

6 The long-stem CPT 12/14 Components are of two types, those with a continuous taper, and the longer stems with a dual taper. The four 180mm (+50mm) long stems have a continuous taper from proximal to distal and are suitable for many routine revisions. The two valgus neck (VN) stems are important because they allow for more options in adjusting neck length and center of rotation of the reconstructed hip. In particular, the valgus neck stems can be used to accommodate two common scenarios in revision surgery: a high hip center or proximal femoral bone loss. The three longer stems, 200mm (+70mm), 230mm (+100mm), and 260mm (+130mm), are used for more severe proximal and distal bone damage. These stems have a distinctive dualtaper design in that they maintain the double taper principle of the collarless tapered stem, but have two consecutive tapers from proximal to distal. The proximal taper blends into the stem taper. The dual taper is designed to maximize the advantages of a tapered cemented stem. CPT 12/14 Femoral Impaction Grafting Technique The CPT Hip System has been used for more than a decade to reconstruct the femur at revision surgery. The CPT 12/14 Impaction Grafting Instrumentation has been improved through the design of modular tamps, which provide a means of impacting allograft distally, then impacting proximally. The modular system allows the surgeon first to concentrate on reconstruction of the femur, then to establish leg length and stability, and finally to focus on proximal impaction. The long stem range has been expanded to include seven long stems. The technique of cemented long stem revision is successful at long term and is applicable in many routine revisions. 43 In middle aged and younger patients, where bone restoration is a priority, or in cases of major bone loss, or where a long stem is contraindicated, the CPT 12/14 Stem can be combined successfully with impaction grafting using the CPT 12/14 Femoral Impaction Grafting Technique to help restore bone. 5

7 20 STEPS FOR IMPACTION GRAFTING 1PREOPERATIVE PLANNING Template to provide a basis for judging appropriate reconstructive, leg length, and offset targets to achieve during surgery. 4ACETABULAR COMPONENT Proceed to implantation of the acetabular component and note new center of hip rotation. 2APPROACH Expose the hip joint using your approach of choice. More extensive exposure is required for impaction grafting surgery. 5PREPARE BONE GRAFT AND GRAFT SITE Prepare the bone graft chips and cancellous cubes. Contain any distal bone defects with mesh and cerclage wire. Clear and cleanse the proximal femoral canal. This can often be completed by using an oversized Rasp laterally. A proximal femur cerclage wire, or a temporary cable may be applied instead of a surgical mesh. 3LEG LENGTH MEASUREMENT AND COMPONENT REMOVAL Prior to dislocating the hip, obtain a baseline measurement of leg length using your preferred method. Carefully dislocate the hip and remove the acetabular and femoral components, bone cement, and residual membranes. 6CHOOSE STEM The stem should extend to a depth that is twice the femur diameter beyond the most distal cortical defect. Extra Stem Standard Extended Extended Valgus Length Offset Offset Offset Neck 130mm Size 1-5 Size 1-5 Size mm Size 2 Size 3 Size 2,3 200mm Size 4 230mm Size 4 260mm Size 4 6

8 7IDENTIFY STARTER TAMP Assemble a number of Tamp Assemblies using Locking Screws and the Locking Rod. Insert the largest possible Tamp Assembly, to the intended depth in the femur, in the correct version and varus/valgus position. This will be designated the Starter Tamp. The Final Tamp is usually one or two sizes smaller than the Starter Tamp. 9IDENTIFY STARTER PACKER Insert the largest possible diameter Distal Femoral Packer to the bone plug depth. This is the Starter Packer. 8ESTABLISH BONE REFERENCE POINT Undertake trial reduction with a rasp/trial or an assembled tamp to determine the correct depth of stem insertion. Mark the level where the lateral shoulder of the tamp or rasp meets the medial side of the greater trochanter. This is the Bone Reference Point. Bone Reference Point Locking Screw WIRE AND BONE PLUG 10GUIDE INSERTION Thread the Guide Wire onto the bone plug and slide the Starter Packer over the Guide Wire. Insert the bone plug to the appropriate bone plug depth mark on the packer, ie 130 Plug, 180 Plug, etc. If a distal bone pedestal or retained cement is used as a plug, drill the Guide Wire using the packers to centralize. 7

9 11DISTAL GRAFT PACKING Introduce 10cc of bone graft chips. Beginning with the Starter Packer, impact the graft. Sequentially add 5cc of morselized allograft between packing. Pack the distal graft until the Distal Pack mark on the Distal Femoral Packer is level with the Bone Reference Point. Graft Corers are available to remove graft, if necessary. 13FINAL TAMP AND TRIAL REDUCTION If using primary stems, use the next smaller size tamp assembly from the Starter Tamp. Continue alternating graft insertion and tamping until the desired final tamp size is stable. Remove the Guide Wire and Rasp Handle. Perform a trial reduction for leg length, stem orientation, and choose offset. 12 FEMORAL TAMP IMPACTION Introduce 5cc of allograft and begin hand packing with the Starter Tamp as defined in Step 7. Alternately add 5cc of allograft and tamp, checking anteversion each time. Impact until the shoulder of the Starter Tamp is level with the Bone Reference Point. With the tamp in place, apply proximal mesh if necessary and not already applied. Continue grafting and tamping until the entire canal is lined circumferentially with impacted allograft. 14PROXIMAL BONE RECONSTRUCTION If depth of insertion or position requires adjustment, reinsert the Guide Wire and retamp. Otherwise, leave the Final Tamp in place, modularize the tamp and undertake proximal graft impaction. Note: Do not use the MIS CPT Rasp Handle ( ) with any impact grafting instruments. 8

10 15PROXIMAL GRAFT IMPACTION Disassemble the Final Tamp by removing the Locking Screw and thread the Guide Rod Extension through the Proximal Tamp and into the Distal Tamp. Partly withdraw the Proximal Tamp up to the double-line mark on the Guide Rod and pack 5cc of allograft around the proximal Tamp by hand with the Proximal Packers. To pack a large amount of graft proximally, remove the Proximal Tamp and insert graft. Otherwise, withdraw the Proximal Tamp. Using a mallet, impact the graft by impacting the Proximal Tamp down to reach the Distal Tamp, determined by when the single line on the Guide Rod becomes visible. Continue alternating graft insertion and Proximal Tamp impaction until the proximal canal is evenly and solidly packed with allograft. PROXIMAL PACKING 16FINAL AND TORQUE TEST Withdraw the Proximal Tamp about 1cm and use the Proximal Packers to impact cancellous cubes (5mm x 5mm x 10mm and 5mm x 5mm x 5mm) and smaller allograft pieces. Then reseat the Proximal Tamp. Test the tamp in the posterior direction to between 40 and 50 in.-lbs. If the tamp moves, perform further impaction. 9

11 17RECONNECT TAMP When the tamp is stable, remove the Guide Rod Extension. Reconnect the Locking Rod and tighten with the screwdriver. Withdraw the assembled tamp a few millimeters and reinsert. Retighten the Locking Rod. Then withdraw the Tamp Assembly 1cm and reseat the tamp gently. 19IMPLANTATION Assemble the stem onto the Stem Inserter, then attach the wingless Revision Distal Centralizer. Slowly insert the stem to the appropriate position while maintaining axial alignment and anteversion. Perform a trial reduction. Attach the femoral head. 18CEMENT APPLICATION Remove the Tamp Assembly. Place Horsecollar over proximal graft. Fill the canal with cement in a retrograde fashion, and pressurize the cement. Cement Restrictor Plate (optional use) 20WOUND CLOSURE 10 Close the wound in layers.

12 PREOPERATIVE PLANNING Comprehensive preoperative planning is helpful in revision surgery to prepare for a variety of potential circumstances. This begins with careful preoperative templating. Template the femur and plan stem length, depth of insertion, bone plug site, extent of bone grafting, and the need for proximal reconstruction. These may need to be modified according to intraoperative findings, but provide a base for planning. The purpose of preoperative templating is to: 1. Gain an accurate three-dimensional understanding of the bony anatomy and cortical defects. 2. Estimate the stem size and length and the site of the distal bone plug, or the possibility of using an existing bone pedestal or retained distal cement as a plug. 3. Determine the possible centers of rotation of the reconstruction (anatomic or new hip center). 4. Predict limb lengths based on the hip center, and the height of the calcar and lesser trochanter, in conjunction with clinical measurement and preoperative radiographs. 5. Determine the appropriate relationship between the height of the tip of the trochanter or other lateral landmark, and the center of femoral head rotation. 6. Determine potential difficulties in implant removal and insertion. 7. If necessary, plan the level and type of femoral or trochanteric osteotomy, and the bed for its reattachment. 8. Determine the need for bone mesh containment for reconstruction of proximal or distal cortical defects. In femoral templating, it is important to appreciate that magnification of the size of the femur will vary depending on the distance from the x-ray source to the film and the distance from the patient to the film. The CPT Hip System Templates use standard 20 percent magnification, which is close to the average magnification on most clinical x-ray films. Magnification for larger patients or obese patients may be greater than 20 percent because their osseous structures are farther away from the surface of the film. To determine the magnification of any x-ray film, use a standardized marker at the level of the femur when exposing the film. Begin by obtaining a complete set of good quality radiographs, including: 1. An A/P of the pelvis centered on the pubis. 2. An A/P and lateral of the length of the femur. For patients with acetabular bone deficiency, obturator and iliac oblique views may be helpful. Note the important reference points on the radiographs, including: 1. The existing center of rotation of the failed hip arthroplasty. 2. The location of the anatomic center of rotation of the hip (based on the contralateral hip, preoperative views of the failed hip, or using the teardrop and Kohler s lines for reference). 3. The offset of the failed hip arthroplasty. 4. The normal offset. 5. The level of the calcar. 11

13 6. The height of the tip of the greater trochanter, or other lateral landmark, in relation to the center of the femoral head. In addition, assess any acetabular and femoral bone deficiencies or angular deformities of the femur, and all other factors related to the failed implant. Template for the acetabular component first. In the absence of any significant bone deficiencies, select the hemispherical acetabular transparency that makes the best circumferential contact with the remaining bone stock, positioning the implant in appropriate abduction. If there is major bone loss or socket break-out, template for either a smaller acetabular component at a higher than normal hip center, or a close-toanatomic center with the use of a large hemispherical component reconstruction cage, segmental allograft, or Trabecular Metal implant. Indicate these possibilities as potential centers of rotation on the radiographs. Next, template for the femoral component to determine its optimum size and length, as well as its position. Please note, CPT 12/14 Stems should not be seated proud for impaction grafting procedures. Clearly delineate areas of major osteolysis, stress risers, femoral perforations, and points of angulation or malrotation, all of which influence the size and length of the stem required. Determine the extent of bone grafting, if required, and the need for proximal reconstruction with mesh, distal containment of defects with mesh, and the use of strut allografts. These may have to be modified intraoperatively, but will provide a base for planning. Select the template that best fits the proximal femur, leaving room for bone graft and cement. The outline of the prosthesis is indicated by a solid line and the outline of the cement mantle created by the rasp is indicated by a dashed line on the template. Align the femoral template so that it is centered in the diaphysis and then move the template so that the center of the femoral head and the osteotomy line are appropriately positioned to restore the planned amount of leg length. While aligning the femoral template in the canal, the presence of incongruities or an excessive bow or angulation in the A/P or lateral planes will become evident. After indicating the planned center of rotation on the radiograph, and the proper position of the femoral component, determine the optimal head position and stem offset. By having the choice of a standard neck angle or a valgus neck angle, the 180mm stems allow versatility in the choice of neck height and hip center. A valgus neck stem, which provides an additional 15mm of leg length, may be used to gain leg length in a high hip center, or to provide a stronger construct by seating the stem distally in bone. When templating, and intraoperatively, aim to achieve leg length without using the longer heads, which have a skirt. These are reserved for situations where an unplanned increase in leg length is required. 12

14 SURGICAL TECHNIQUE Approach Position the patient for routine hip surgery. Extensive exposure is recommended, especially in difficult revision cases. Osteotomies An approach using trochanteric osteotomy is not routinely advised before impaction grafting because it removes the lateral support for grafting and for attaching medial mesh. If necessary, however, a trochanteric slide can be useful for difficult exposure, and an extended trochanteric approach can be used to remove femoral components. If an extended trochanteric osteotomy is performed, plan to use a long stem, and reduce the osteotomy, holding it with cables prior to impaction grafting. Determination of Leg Length After exposing the joint, obtain a baseline leg length measurement before dislocating the hip. There are several methods to measure leg length. One method is to place one pin in the iliac wing and a cautery mark or a pin in the greater trochanter. With the leg in the neutral position, measure the distance between the two reference points. It is important that the measurement be taken with the leg in the neutral position so the position can be easily and accurately reproduced after the new implant has been inserted. Leave the proximal pin in place, but remove the trochanteric pin, if used, and mark the pin site with electrocautery so it can be replaced for remeasurement. Dislocation, Removal of Components, and Acetabular Implantation Carefully dislocate the hip to avoid the risk of fracture of the sometimes fragile femoral bone stock. Remove the implants and insert the acetabular component. Note the new center of hip rotation. Selection of the Procedure Inspect the metaphyseal and diaphyseal regions for a neocortex, sclerotic bone formation, and remaining bone cement in the case of a cemented implant. Use this information to choose the appropriate procedure for femoral preparation. If using a standard revision technique, proceed with the Surgical Technique for Femoral Revision. If using an impaction grafting technique, proceed with the surgical technique outlined here. 13

15 IMPACTION GRAFTING PROCEDURE Impaction grafting has been shown to reconstitute bone in revision situations. The CPT 12/14 Hip System includes modular impaction grafting instruments that enhance as well as simplify the technique. Among the key instruments in the impaction grafting instrument set are (Fig. 1): Distal Femoral Packers, which are cannulated larger diameter rods used initially to pack the distal allograft area. Corers, which are designed to remove excessive graft or cylindrical plugs of graft up to 7cm long, are supplied for complicated cases and the use of longer stems. Tamps for primary stem sizes 1-5, long stem sizes 2, 180mm, 3, 180mm and 4, 200mm through 260mm are available as modular instruments. Each Tamp Assembly consists of a proximal Tamp, a distal Tamp, and a Locking Screw or Locking Rod. The proximal Tamp is fixed to the distal Tamp with the Locking Screw or Locking Rod. The Tamp Assembly is initially used as a monoblock Tamp. While the Locking Screw and Locking Rod perform the same function, the Locking Rod is longer to facilitate its application and tightening when access to the proximal Tamp is difficult. Fig. 1 14

16 Several essential items specific to impaction grafting should be available during surgery. These include: 1. Morselized bone chips from at least two fresh, frozen, or irradiated femoral heads, although more may be needed in cases with severe bone loss. The allograft should be obtained only from a recognized bone bank and it is helpful if the supply is local should more be needed intraoperatively. 2. A sterile bone mill to convert the femoral heads to bone chips of manageable size if this has not been performed preoperatively. 3. The CPT 12/14 Primary Instrument Set, the CPT 12/14 Revision Supplementary Instrument Set, and the CPT 12/14 Impaction Grafting Instrument Set. 4. The appropriate size implants. The CPT 12/14 Hip System offers primary sizes with regular, extended, and extra-extended offsets, as well as long stem sizes with standard and valgus neck angles and extra long stems with a dual taper design. The size 0, small, and extrasmall are not recommended for impaction grafting. A long stem should be considered for distal bone defects or severe deficiencies, including defects requiring mesh reconstruction that extend below the lesser trochanter or defects involving more than half the femoral circumference, making mesh reconstruction less secure. 5. A medullary bone plug and standard bone cement accessories. 6. A supply of reconstruction meshes, cerclage wires, and cables. Bone Graft Preparation Two to three femoral heads are usually needed. Remove soft tissue from the femoral heads and conservatively remove the articular cartilage while preserving subchondral bone. The ideal size of bone chips ranges from less than 1mm up to 4mm for intramedullary impaction. Approximately half a femoral head should be divided with a saw into 5mm x 5mm x 5mm and 5mm x 5mm x 10mm cancellous cubes for final packing into the proximal femur at the osteotomy level. There are a number of techniques to further prepare bone. One technique is to wash the bone chips in saline heated to 45 C, then strain over a 200 micron strainer or pack. Add antibiotic powder if desired. It is always advisable to have additional allograft material available in case it is needed intraoperatively. During impaction, bone chips should be delivered 5cc at a time by using a spoon or alternating 10cc syringes with their ends cut off. Preparation of the Graft Site Remove the proximal femoral contents, and thoroughly clear and cleanse the femoral canal. Expose the femur and shield the surrounding tissues with gauze. Cement remaining in the distal canal can be used as a plug if it is distal enough, well fixed, more than 2cm below significant cortical bone damage, and infection has not been present. 15

17 At this stage, inspect the femur for cortical defects and contain distal defects with mesh and cerclage wire or cable. Choose a stem that is long enough to extend beyond distal areas of cortical deficiency. Also, the stem should extend beyond distal wires or cables applied around a femur with thin cortices because these may act as a stress raiser unless a strut graft is applied. A cerclage wire is usually applied to the proximal femur for protection of the femur during trial reduction and impaction. The Zimmer Cable-Ready Cable Grip System cable may be temporarily locked in place and later unlocked to hold the mesh. Note that a wire may be preferable to a cable in the proximal region, adjacent to the joint. If a proximal mesh is required, impact the distal canal up to the proximal extent of the femur and apply the mesh. Mold the mesh around any residual lesser trochanter or, if preferred, trim the lesser trochanter flat with a saw. Use wires and cables to anchor the mesh. A wire may be preferable to cable in the proximal region, adjacent to the joint. If a trochanteric slide or osteotomy has been undertaken, the lateral deficiency can be restored in its distal part by using a lateral mesh, and the trochanter reattached after the stem has been cemented. Begin by ensuring bone is adequately removed from the trochanter so as to enhance axial alignment by using a gouge, rongeurs, rasps, or a power burr. Use primary or long stem rasps to rasp laterally. Gently remove bone from the femur as necessary to partially or fully seat the rasp. If desired, a primary or long stem rasp can be used to prepare the femoral canal and remove bone laterally. The rasp can also be used for trial reduction to determine and provide the depth of insertion of the stem while simultaneously providing an estimate of leg length. If the rasp is not stable, insert the Trial Locating Pin through the depth holes in the rasp and combine this with lap pads to stabilize the rasp in the canal. After determining depth of insertion, mark a Bone Reference Point as described below. Note that the tamps for the primary and 180mm stems are larger than the rasps so the rasps should not be used to assess tamp size. 16

18 Determination of Stem Size and Length Determine the stem length required based on the extent of bone loss observed during preoperative and intraoperative assessment. A long stem component is recommended for significant proximal and/or distal deficiencies. As a guide, the stem should extend beyond the most distal cortical defect two femur diameters. The graft should be contained by bone or mesh up to the osteotomy. In the absence of distal defects, a standard stem with or without mesh is often used. When there is major deficiency proximally or distally, a long stem is recommended. If a trochanteric slide or osteotomy has been necessary, the rotational stability of the impaction grafting is somewhat lessened and a longer than standard stem may be indicated. Tamp Assembly Assemble the modular femoral tamps using either the Locking Screw or Locking Rod (Fig. 2). Both can be slightly tightened with a hex-head screwdriver. Use the Tamp Assemblies to gauge the size of the canal. The Tamp Assemblies are equivalent in size to the implant of the same number plus an allowance for a relatively thick cement mantle. For example, a size 3 Tamp Assembly creates a cavity for a size 3 implant with cement. Considering the planned depth of insertion and length of stem, as well as any bone defects, determine the largest Tamp Assembly that can be inserted in the femur in the correct version and varus/valgus position. The CPT 12/14 System includes primary stems sizes 1 through 5 (130mm long) and seven long revision stem options. Sizes 2, 180mm and 3, 180mm are available in a valgus neck configuration. The advantage of the valgus neck stems is additional leg length without additional offset, which may be advantageous in revision surgery. Size 4 long stems are available in 200mm, 230mm, and 260mm lengths. Fig. 2 17

19 It is important that the stem is aligned straight in the femur to prevent varus positioning. Lateralization of the femoral opening is usually required when a round-backed prosthesis is being converted to a straight stem such as the CPT 12/14 Stem. The insertion of the tamp can be helpful to define the amount of bone dissection required around the proximal opening. Excess bone can be removed using a burr and femoral rasps. Establishing a Bone Reference Point With the starter Tamp Assembly or a Rasp in place, mark the level where the lateral shoulder of the tamp or rasp meets the medial side of the greater trochanter (Fig. 3). This is the recommended Bone Reference Point for depth of insertion of the stem, as well as the bone plug, the Distal Femoral Packers, and the Tamp Assemblies. It is necessary to ascertain the largest tamp, designated the Starter Tamp, that can be inserted in the correct position in the femur. The starter Tamp should be well lateralized, in the correct varus/valgus alignment, anteversion, and at the planned depth of insertion. The length of the stem should take into account the bone defects. The starter Tamp is chosen by beginning small and progressively increasing the tamp size. Use the starter Tamp, or a larger Rasp to do a trial reduction for leg length and offset check. This will also help to define the proposed depth of insertion of the Tamp and stem. This should be done gently. Make an initial estimate of the final stem size that is likely, based on preoperative templating and operative findings. Designate the corresponding tamp as the Final Tamp. This may be changed during the procedure. When using standard 130mm length stems, the final Tamp is usually one or two sizes smaller than the starter Tamp. Fig. 3 18

20 If the bone stock is inadequate at the greater trochanter, use an alternative reference point such as the level of the osteotomy cut, the medial calcar, or the lesser trochanter. Note the distance from the Alternative Reference Point to the shoulder of the Starter Tamp or the rasp used in trial reduction (Fig. 4). 1.5cm Determination of Distal Femoral Packer Determine the safe insertion depth for each Distal Femoral Packer. Begin with the 10mm Distal Femoral Packer. Then sequentially increase the size and record the largest Distal Femoral Packer size that can be inserted to the intended bone plug depth without impinging on the canal wall. This is designated the Starter Packer and will be the first Distal Femoral Packer used to impact the distal allograft. If the femoral canal flares considerably above the intended bone plug site, sequentially larger diameter Distal Femoral Packers can be used as more allograft is added. Continue to insert larger diameter Distal Femoral Packers and record the depth that each can be inserted without impingement on the cortical walls. Do not use these Distal Femoral Packers until the impacted graft reaches these levels. Fig. 4 19

21 The extent of grafting and the distal bone plug site should be chosen with the following considerations: 1. The stem tip should extend beyond major cortical bone damage, and at least two femoral diameters beyond major cortical segmental defects. 2. The distal bone plug should be at least 2cm below the distal extent of the tamp. The tamp is approximately 2cm longer than the corresponding stem. The Distal Femoral Packer has a single line, labeled 130 PLUG, 180 PLUG, etc (Fig. 5). Guide Wire and Intramedullary Bone Plug Insertion Bone Plug Depth Assuming there is not a need to place the bone plug more distally because of significant cortical bone damage, the depth of the Allen Medullary Bone Plug should be 2cm below the tip of the Distal Tamp (Fig. 6). This depth is marked on Distal Femoral Packers as 130 Plug, 180 Plug, etc. and corresponds to approximately 4cm below the stem tip. Alternatively, the depth required can be read by comparing the Medullary Canal Sizer length to the ruler marks on the packer (Fig. 7). 4cm 2cm 2cm Fig. 5 Fig. 6 Fig. 7 20

22 Bone Plug Size Use either the Distal Femoral Packers or the Medullary Canal Sizers to determine the size of the bone plug that will be stable at the appropriate bone plug depth. The Distal Femoral Packers can be used to gauge the size of bone plug required provided the packers can pass distally without being obstructed by angular deformity of the femur, leading to a false impression of the size of the femoral canal. One technique is to use an Allen Medullary Bone Plug core diameter equal to the size of the largest Medullary Canal Sizer that just passes through the narrowed region of the femur (note that the bone plug core diameter is used and not the outer flange diameter). Insertion Thread the Guide Wire onto the Allen Medullary Bone Plug and slide the Starter Packer over the Guide Wire (Fig. 8). Gently tap the Distal Femoral Packer and bone plug to the selected distal bone plug site and check to ensure that the bone plug is stable. If the tip of the stem will be below the isthmus, there are a number of options. 1. Gently tapping the bone plug in place or adding a second larger bone plug often provides a stable bone plug. 2. A temporary K-wire can be inserted across the femoral canal and the bone plug tapped down to rest on the wire, which is removed at the end of the procedure. 3. A small amount of cement can be used by introducing it through a cement gun nozzle and placing the bone plug on top of the polymerized cement. 4. In uncommon situations when the first bone plug is inadequate but a larger core diameter may not fit, a larger bone plug can have some of its core and flange removed with rongeurs so that it passes more easily through the isthmus, but will still lodge in the femur. Fig. 8 21

23 Use of a Bone or Cement Pedestal as a Bone Plug A distal bone pedestal can be used as a plug if there is not severe thinning of the cortices immediately above the plug, which may be prone to fracture. In these cases, remove the pedestal and bypass the very thin cortices with the stem. Similarly, a distal cement plug can be retained and used if there is not severe osteolysis immediately above it, the adjacent cortices are not severely thinned, and there has been no infection. If a distal bone or cement pedestal is used as a plug and the center of the pedestal is central in the canal, use the Starter Packer to centralize the Guide Wire and drill the wire into the pedestal. If the pedestal is off center, use a narrower packer to position the distal wire in the appropriate position in the bone plug. Distal Graft Packing Initially introduce 10cc of graft and impact so as to enhance the bone plug fixation. Then introduce 5cc at a time of morselized allograft into the femoral canal around the Guide Wire. Adding too much graft at one time may cause a void in the graft. Pass the Starter Packer, as determined on page 19, over the Guide Wire and pack the bone graft distally with the Starter Packer (Fig. 9). Remove the Starter Packer and introduce another 5cc of graft. Then reintroduce the Starter Packer and pack the graft again. Repeat this procedure until the line on the Starter Packer marked Distal Pack is even with the Bone Reference Point (Fig.10 ). Note: If necessary, use a larger diameter Distal Femoral Packer to match the increasing size of the femoral canal as the graft builds proximally. Use the measurements made earlier to avoid inserting a Distal Femoral Packer to a depth that will impinge on the canal walls. 22 Fig. 9 Fig. 10

24 Distal Graft Preparation for a Long Stem Component If a long stem CPT 12/14 Component will be implanted, use Distal Femoral Packers to graft up to the Distal Pack level on the packers. Then use the Graft Corer over the Guide Wire to remove a central core of impacted distal graft. Use of the Bone Graft Corers The Graft Corers can remove a cylindrical plug 10mm or 12mm in diameter and up to 7cm long. The corers can be used in two different ways, either to remove bone graft that may inadvertently become trapped in the distal canal during tamping with standard 130mm length stems, or routinely to remove distal graft during long stem impaction grafting. For graft removal during standard 130mm length tamping, use the 130 tamp etch mark. In general, the 10mm diameter Graft Corer is recommended for use distally and the 12mm Graft Corer for use more proximally. Fig. 11 Beginning with the 10mm Graft Corer, attach the corer to a T-handle (Fig. 11). Insert the corer to the level of the graft and, while applying pressure, turn the T-handle to penetrate the impacted graft. Then, without twisting the T-handle, withdraw the corer to remove the graft core. Use the side slot in the corer to remove graft for reuse. The etch marks on the corers provide a reference for removing allograft plugs. One side is labeled with the tamp lengths for each stem length and the other side is labeled with the recommended core depth by stem length. Remove graft until the 130 CORE, 180 CORE, etc., etch mark reaches the Bone Reference Point (Fig. 12). This will remove bone to within 4cm of the chosen tamp length. Fig

25 Impaction with Femoral Tamps Assemble the predetermined starter Tamp Assembly using the Locking Screw. This is the largest tamp that previously fit the femur in correct orientation. Have the assistant assemble one or two smaller size tamps if it is planned to decrease the tamp size during impaction, which is routinely advised for standard length tamp impaction. Attach the starter Tamp Assembly to the Rasp Handle (Fig. 13a). Do not use the MIS CPT Rasp Handle ( ) with any impaction grafting instruments. Introduce 5cc of allograft into the femoral canal, and insert the Tamp Assembly over the Guide Wire. Use a mallet to drive the tamp into the allograft, being careful to ensure correct orientation and anteversion, always tending toward a valgus position (Fig. 13b). Note: Whether using standard stems or long stems, if any of the tamps do not advanceadequately or fail to seat to the appropriate depth, remove the Tamp Assembly and use the 10mm and 12mm Graft Corers to remove distal bone as necessary (See Use of the Bone Graft Corers above). When using long stems and impaction grafting in a capacious femur, a wider cavity for cement can be made with the corers than the tamps, if required. Advance the 10mm Graft Corer the full distance to the designated TAMP mark on the corer. Advance the 12mm Graft Corer to the CORE mark, which will be 4cm from the end of the tamp. Then, continue tamping. A surgeon may then choose to use a standard cement gun nozzle with a distal outer diameter of 11.25mm. Fig. 13a Fig. 13b 24

26 Remove the Tamp Assembly and insert another 5cc of allograft. Then reinsert the tamp and impact it again. Repeat this procedure several times until the entire canal is lined circumferentially with impacted allograft. Check the orientation of the tamp each time it is inserted to ensure correct alignment of the prosthesis. Continue impacting until the Starter Tamp shoulder is level with the Bone Reference Point and bone graft has reached the proximal extent of the femur. Once the allograft has been impacted to the top of the canal, use the next smallest tamp until the desired tamp size is reached. When using standard length stems, this is usually one or two sizes smaller than the first tamp used. The size of the Final Tamp determines the size of the implant to be used. Trial Reduction Remove the Guide Wire and Rasp Handle. Attach the appropriate Cone Provisional to the trunnion of the tamp (Fig. 14). Use Table below to determine the appropriate combination. Attach a Femoral Head Provisional and perform a trial reduction to check leg length and offset. If necessary, the leg length may be slightly adjusted by changing the depth of insertion of the stem at insertion; however, it is not recommended to seat the stem proud in impaction grafting procedures. Eventually, the femoral canal is solidly and evenly packed with allograft and the Tamp Assembly has initial stability. Monoblock Tamping The advantage of the modular impaction grafting technique is focused proximal reconstruction. However, if desired, graft impaction can be completed via a monoblock tamp technique using the Tamp Assemblies. Tamp to the Final Tamp and proceed to proximal packing. Fig. 14 Available Cone Provisionals Standard Extended Extra-Extended Valgus Tamp Assembly Size Offset Offset Offset Neck 1 1STD 1EXT 2 2 STD 2 EXT 2 XEXT 3 3 STD 3 EXT 3 XEXT 4 4 STD 4 EXT 4 XEXT 5 5 STD 5 EXT 5 XEXT 2X180 2 STD 2X180 VN 3X180 3 EXT 3X180 VN 4X200 4 EXT 4X230 4 EXT 4X260 4 EXT 25

27 Proximal Bone Reconstruction If depth of insertion or position requires adjustment, reinsert the guide wire and retamp. Otherwise, leave the Final tamp in place, modularize the tamp and undertake proximal graft impaction. If mesh is required to contain the graft proximally and it has not already been applied, leave the tamp in place to act as a guide. Apply medial mesh so the graft is contained up to the neck cut mark. Modular Tamping With the Final Tamp in situ, remove the Locking Screw and thread the Guide Rod Extension through the Proximal Tamp into the Distal Tamp shaft and tighten gently with the screwdriver. The single line mark on the Guide Rod Extension will now be at the level of the superior face of the tamp. Reattach the Rasp Handle and withdraw the Proximal Tamp. To pack a large amount of graft proximally, remove the proximal Tamp and insert graft. Otherwise, withdraw the proximal Tamp 3cm to 5cm, stopping the tamp shoulder before the double-line mark on the Guide Rod Extension. With the Proximal Tamp withdrawn approximately 5cm, the Proximal Tamp will still be engaged on the Distal Tamp and the Distal Tamp acts as a guide during impaction (Fig. 15). Add 5cc of graft around the Fig

28 Proximal Tamp and pack this distally with the smaller Proximal Packer. Impact the proximal Tamp until it reaches the Distal Tamp indicated by when the single-line mark on the Guide Rod Extension becomes visible. The Proximal Tamp has then reached the distal Tamp and impaction is ceased. Continue alternating graft insertion and Proximal Tamp impaction until the proximal canal is evenly and solidly packed with allograft. Proximal Packing and Torque Test Withdraw the Proximal Tamp approximately 1cm, and use the Proximal Packers to impact cancellous cubes (5mm x 5mm x 5mm and/or 5mm x 5mm x 10mm) and smaller allograft pieces (Fig. 16). This will create a stable, reconstituted bone mantle at the osteotomy level. Use the Proximal Packers only to compress the graft; they should not be wedged aggressively between the tamp and the cortex as this may dislodge or push the tamp out of alignment. Reseat the proximal Tamp down to the distal Tamp. If desired, the surgeon may perform a torque test to check rotational stability. Torque test the tamp to 50 in.-lbs. by rotating the tamp in a posterior direction (Fig. 17). A torque wrench and Rasp Handle Adapter are provided in the CPT 12/14 Impaction Grafting Instrument Set. If the tamp moves at 50 in.-lbs., perform further impaction. Fig. 16 Fig

29 Guide Rod Extension Reconnect Tamp Reconnect the Proximal Tamp and Distal Tamp in situ by removing the Guide Rod Extension and inserting the Locking Rod through the Proximal Tamp, and then tightening this into the Distal Tamp with the screwdriver (Fig. 18). Tap the Tamp assembly out a few millimeters and then reimpact it and retighten the Locking Rod firmly with the screwdriver. Check to ensure that the tamp is at the appropriate depth as determined during the trial reduction. Then tap the Tamp Assembly out approximately 1cm and gently reseat it by hand so it can be easily withdrawn immediately prior to cementing. Screwdriver Check to ensure that the inverted Cement Restrictor Plate or polymer horse collar Cement Restrictor Seal will fit over the proximal femur and contain graft during cementing, and trim the polymer horse collar Cement Restrictor Seal if necessary to fit. Locking Rod Just prior to cementing, insert a thin suction tube down the guide wire hole in the tamp to remove blood. Immediately before cement insertion, carefully remove the tamp from the neomedullary canal. Note: Throughout the impaction grafting procedure, there is the possibility that graft will become caught between the proximal and distal Tamps. Use a guide wire, curette, and saline to clean the instruments. Fig

30 Cement Application For standard 130mm stems and 180mm long stems, use a cement gun with a small diameter nozzle that has been cut to the length of the stem. This facilitates cement injection into the narrow distal stem area. A Miller Bone Cement Injector with a flexible nozzle ( ) with a 9.5mm OD or a Miller Tapered Cement Nozzle ( ) which tapers to a 6.1mm OD are recommended. A Miller Injector with a flexible nozzle ( ) can be used with the smallest tamp. Trim the nozzle to the length of the stem. For size 4 200mm-260mm long stems or any stem where the 12mm Graft Corer has been used down to near the distal part of the cement mantle, a standard cement nozzle can be used to deliver cement to the canal. The cement nozzle has a distal outer diameter of 11.5mm, and gently tapers proximally. Fill the canal in a retrograde fashion without disturbing the impacted bone graft. Use the polymer horse collar Cement Restrictor Seal, which may be trimmed to fit over the proximal femur, to contain graft during cement injection. One useful technique is to apply the horse collar and inject the cement in a retrograde fashion through the collar or an inverted Cement Restrictor Plate. When the canal is filled, break off the cement nozzle and inject additional cement through the Femoral Pressurizer Seal (Fig. 19). It is also acceptable to apply the CPT Cement Pressurizer directly to the allograft, thus forcing the cement into the allograft and maintaining pressure until the cement reaches a doughy state. Implantation Attach the distal centralizer to the femoral stem (Fig. 20) with a twisting motion. Two distal centralizers are available. For impaction grafting applications, the wingless Revision Distal Centralizer is recommended. It is not packaged with the stem, but is available individually sterile packaged. If only the Standard Distal Centralizer is available, remove the wings to prevent disruption of the graft as the stem is inserted. Fig. 19 Fig

31 Attach the femoral component to the Stem Inserter by placing the release lever in the engage position, marked E and turning the barrel to thread the inserter onto the stem (Fig. 21). A small pin engages the dimple on the stem shoulder to control component anteversion during insertion. Fig. 21 Introduce the stem through the polymer horse collar Cement Restrictor Seal (Fig. 22). Place the thumb or finger over the medial anterior femoral neck while inserting the stem to maintain cement pressure and to ensure that the stem does not move into varus. There should be approximately 5mm of cement on the medial side of the stem. Slowly advance the stem into the cement mantle. The Stem Inserter has a mark along the stem center line to aid in insertion (Fig. 23). The Stem Inserter also has a threaded hole between the handle and barrel to assemble an anteversion rod. 30 Fig. 22 Fig. 23

32 The Tamp Extractor Rod may be used as an anteversion rod. The anteversion rod may be assembled on either side and represents a reference for zero degrees of anteversion. Slowly advance the stem into the cement mantle. Insert the stem to the final position using the osteotomy etch mark and stabilize the stem with one hand while removing the inserter with the other. Note: Impacting the stem with a mallet should be avoided, but can be used if necessary. One technique is for the surgeon to maintain the stem orientation and anteversion while an assistant taps the stem into position. It is recommend to gently push a small amount of cement over the lateral shoulder of the stem (Fig. 24). This helps prevent the remote possibility that the stem will back out inadvertently should a postoperative dislocation require reduction. A small amount of cement may also be left over the proximal graft so that the graft is contained and not affected by cleaning lavage of the hip. Gently remove excess cement. If not already applied, place the polymer horse collar Cement Restrictor Seal around the proximal body of the stem to apply pressure until the cement is set. Once the cement has hardened, the Femoral Head Provisional may be used to confirm final femoral head size. Assess the leg length, range of motion, stability, and abductor tension one final time. Verify that the neck taper is clean and dry. Place the femoral head on the taper with a twisting motion until it locks on the taper. Place a pack or swab over the femoral head to protect it and then seat the femoral head with one sharp blow using the Femoral Head Impactor and mallet. Test the security of the head fixation by trying to remove the head by hand. Protect the femoral head with gauze and hold it away from the acetabulum to avoid inadvertent impingement. Then clean the acetabulum, and reduce the joint. Remove the gauze from the femoral head as the head is reduced. Wound Closure After obtaining hemostasis, insert a Hemovac Wound Drainage Device, if desired. Then close the wound in layers. Fig