Tradition Hip Primary Surgical Technique

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1 Design Rationale Many total hip designs in today s marketplace do not take advantage of the known forces present in the femur. Long term stability of a total hip prosthesis requires an implant design and fixation technique that simulates the normal transmission of weight bearing forces through the prosthesis to the supporting bone structure. Fully porous coated stems have shown to transfer stresses distally, resulting in increased proximal bone resorption. Tradition Hip Primary Surgical Technique Normal bone physiology must be accommodated by transferring stresses to the bone-prosthesis interface in both the magnitude and the direction that prevailed normally at the level of resection and replacement. The implant must load the bone over the largest possible surface area of the remodeled cortical arc, and in the normal direction of the trabecular pattern. The implant must be stress relieved along the surfaces of the stem in favor of proximal support at the undersurface of the platform provided by the collar. The design of the Tradition Hip emphasizes the importance of Physiological Stress Loading. The stem is available with or without proximal porous coating. When cement is used, it is limited to the proximal 2 or so of the stem. The horizontal angle of the platform places the bone-prosthetic juncture perpendicular to the resultant force projection and the normal trabecular pattern of the supporting bone. Resistance to torque is augmented by the lateral fin and striated stem surfaces. The Tradition Hip is available in three stem lengths; long, short and the Living Hip extra-short stem. Each length is available in 9 sizes, with additional larger sizes available upon special request. ISO FM Caution: The re-useable instruments provided must be thoroughly cleaned and sterilized per BioPro s validated cleaning and sterilization method prior to use.

2 Pre-Operative Planning Overlay templates are provided to allow accurate pre-operative planning and physiologic reproduction hip arthroplasty. Align appropriately sized template over radiographs in desired implant position. To assist in determining the depth and angle of resection, align the Angle Guide with the proposed resection line on the template/radiograph and adjust the sliding depth gauge inline with the greater trochanter. Surgical Exposure The hip may be exposed through any standard incision at the discretion and preference of the surgeon. The instrumentation is designed to allow minimally invasive surgery consistent with current surgical techniques and practices. Surgical Technique After dislocation, measure the diameter of the femoral head to provide a preliminary estimation of the size of the acetabular component or bi-polar component to be used. Fig. A Resect the femoral head with an oscillating saw in a horizontally directed plane from the base of the neck laterally to the base of the head medially and at an anteverted angle of 5-10 degrees. Anatomic references may be determined by adjusting the sliding depth gauge on the Angle Guide as determined preoperatively via radiographs and templates (Fig A). The angle of the osteotomy should approximate the angle of the platform of the femoral component. Please note, the cut is more horizontal than most typical resections and designed to transfer compressive loads to the cortical bone (Fig B). The resection should include the removal of bone from the inner aspect of the greater trochanter at its juncture with the neck of the femur. Insufficient removal of bone in this area may result in an undesirable medial tilt and varus placement of the implant and an associated eccentric and incomplete press fit of the stem in the medullary canal. Fig. B 2

3 Femoral Preparation Access to the intramedullary canal is gained with use of the box chisel. Canal should now be opened with an intramedullary reamer (Fig C). Multiple sized reamers are provided to allow sizing correlating to implant size. Surgeon should ream to a depth at which corticle chatter is achieved or desired implant size is met, determined by chosen length of stem. If using the extra-short stem, it is not necessary to ream to any significant depth. To further assist with avoiding stem misalignment, utilize fin cutting broach to remove bone from the inner aspect of the greater trochanter to allow easier application of compaction broaches (Fig D). The trial axle stem is now inserted in the appropriate anteverted plane, commencing with a stem that is somewhat smaller than the estimated size of the medullary canal and increasing the size progressively until the desired press fit has been obtained. The stem should be sufficient in dimension to provide rigid fixation against twisting or toggling motions, but should not be oversized to the extent that the implant cannot be impacted distally in the medullary canal with sufficient ease to assure complete dynamic seating of the platform on the supporting cortical arc. In the event that the first tightly fitted broach is too large and cannot be fully seated without undue force, the appropriately sized intramedullary reamer is used to enlarge the canal isthmus sufficiently to provide the desired press fit. Fig. D Fig. C 3

4 Once desired broaching has been accomplished, the calcar is prepared to match the platform of the femoral stem. Apply the calcar planer directly over broach trunion until flush with broach (Fig E). After sufficient planing has been attained, the trial stem platform is applied directly over the trunnion of the broach. The chosen size neck length and head size trial is then applied to trial stem platform (Fig F). The neck length should provide sufficient joint tension to prevent dislocation of the articulation when the hip is carried through the normal range of motion in all directions. The joint should also be lax enough to allow complete extension of the hip and slight separation of the prosthetic articulation when manual traction is applied to the extremity. A variety of neck lengths is available, from -6 to +18, for appropriate joint tensioning. Fig. E Fig. F 4

5 Femoral Implantation The trial stem is removed and replaced by the matching implant stem, being certain that it is placed in the identical anteverted position so that there will be flush contact between the undersurface of the platform and the total surface area of the supporting cortical arc. If implant has been positioned properly, there should be no identifiable space remaining in any area around the total perimeter of the platform/bone interface. Please note, the platform applies physiological stress to the bone matrix as seen in Fig G. This configuration loads the supporting bone down along the normal cortical pathways in a proximal-to-distal mode, thus minimizing the potential for the scenario of stress relief. The dissolution of proximal bone is commonly induced in stems that depend on the major burden of prosthetic support distally. The Tradition stem applies forces proximally in a physiologic manner, preserving bone. Fig. G Note: When using the Living Hip extra-short stem, pay special attention to collar placement on the calcar. Due to the minimal length of the stem, the stem may not assist in proper prosthetic alignment. The femoral head component of the predetermined trial-tested length and size is impacted onto the stem trunion and the hip is reduced and is again tested for stability and tension. If the articulation appears too lax, the next longer head can be used. Optional Techniques If the implant is stabilized with cement the non-porous coated implant should be used and the cement should be limited to the proximal two inches of the medullary canal. A bolus of relatively soft methacrylate is introduced into the intramedullary canal and is impacted into the inner surfaces of the canal. The implant stem is then introduced down the center of the cement cylinder and is driven distally until the platform meets the calcar. When cement is desirable, it is only necessary to apply the cement to the proximal aspect of the Tradition stem to allow proper transmission of forces. 5

6 Acetabular Preparation Standard protocols are followed with inclination and reaming. BioPro recommends reaming line to line, 45 o inclination and o aversion (Fig H). Fig. H BiPolar Preparation Determine the size of the femoral head with the use of the circular head templates as shown in Figure I. Choose the closest approximation of the natural femoral head. Fig. I 6

7 Final fitting of BiPolar head is done utilizing BiPolar sizing handles and trials (Fig J). Once the BiPolar head size has been choson, verify implant sizing, fit and range of motion with trial femoral head and trial BiPolar implant. If happy with sizing, impact final femoral head onto trunion of femoral stem. Snap BiPolar head over the installed femoral head. Insert the BiPolar head into the acetabulum (Fig K). Fig. J Fig. K Tech note: In the event it is necessary to remove the BiPolar head from the femoral head, place the pin distractor into the holes in the underside of the BiPolar head (Fig L). This will release the lock ring and allow the BiPolar head to be removed. Fig. L 7

8 Postoperative Management The patient leaves the operating room with the hip maintained in abduction and slight flexion with the assistance of a triangular abductor pillow. The abductor pillow remains in place, particularly for night immobilization, for five to eight days, depending on the observed intraoperative stability of the joint. Progressive in-bed exercises are commenced on the first or second postoverative day, consistent with the level of discomfort. The drainage tube is removed when it is no longer productive, usually within 24 to 48 hours. The patient is allowed out of bed and is ambulated progressively with the aid of crutches or a walker on the first to third day postoperatively, commensurate with hip discomfort and within limitations imposed by the motivation and general strength of the patient. Full weight bearing is allowed on the first postoperative day, based on the patient s bone quality and the surgeon s preference. The horizontal platform allows for good distribution of compressive forces and is initially stable, consistent with initial weight bearing as tolerated. The use of a cane or crutch is advised until the patient is able to ambulate without any meaningful discomfort or limp. The individual recuperative potential of total hip patients is, of course, influenced by a variety of factors including age, overall general health and strength, the pathological condition of the hip, etc. The postoperative management and the rehabilitation regime must, therefore, be approached with a measure of flexibility in accordance with the judgement of the attending surgeon Lapeer Road Port Huron, MI ISO FM Brochure No rev