Absolut TM Cemented Stem. Surgical Technique

Transcription

1 Absolut TM Cemented Stem Surgical Technique

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3 Contents ABSOLUT Cemented Stem 2 Absolut Confidence 2 Absolut Reproducibility 2 Absolut Choice 2 Pre-Operative Planning 3 Suggested Templating Method 3 Surgical Technique 4 Surgical Exposure 4 Femoral Neck Resection 4 Acetabulum Preparation 4 Femoral Canal Preparation 5 Femoral Canal Opening 5 Rasping 6 Trial Reduction 7 Medullary Bone Plug 7 Centraliser 8 Cementing 8 Stem Insertion 8 Femoral Head Assembly 8 Implant Dimensions 9 Instrument Catalogue 10 Implants Catalogue 12 1 Contents

4 ABSOLUT Cemented Stem Absolut Confidence With a highly polished finish and double-tapered collarless design, the Absolut Cemented Stem has the confidence of the clinically proven taper-slip philosophy 1, 2, 3. Manufactured from forged cobalt chrome alloy (CoCr), the Absolut not only exhibits superior fatigue and yield strength over stainless steel stems, but due to the components greater rigidity the transmission of stress is more even throughout the entire cement mantle 4, 5. The lateral shoulder of the Absolut Stem has been de-bulked, decreasing the risk of greater trochanteric fracture during rasping. The Absolut features a scalloped neck to maximize the hip joint s range of motion and to minimize any risk of impingement. Fig. 1 Absolut Reproducibility The Absolut stem offers offset independent of leg length (ability to increase/decrease femoral offset and without subsequently affecting without leg length). affecting leg length). The Absolut stem has been designed for ease of intraoperative decision making with all measurements following logical parameters: neck neck shaft shaft angle angle. 2. Sizes 00 and 000 offer mm offset, size 0 offers and 2. mm, and offsets 50mm and offset sizes 1-4 measurements offer, and are 50mm from Centre offsets. The of Rotation offset measurements (COR) to the midline are from of centre the stem of Rotation which in (COR) turn to corresponds the midline to of the anatomical stem which femoral in turn axis. corresponds to the anatomical femoral axis. 3. Stem length is measured from stem tip to the resection line. 3. Stem length is measured from stem tip to the resection line. 4. Neck Neck height height is is measured measured from from medial medial resection resection border border to to the the neutral COR of of the the femoral head. Markings on the proximal femoral stem enable the surgeon to adjust leg length intra-operatively by cementing the stem proud (or short) of the resection level. These markings indicate increases in leg length from the resection line that is equivalent to the available options of femoral head length. Holes through the femoral rasp correspond to these markings for complete reproducibility from trialling off the rasp to definitive implantation. Fig. 2 Absolut Choice Available in seven stem sizes (000-4), combined with three stem offset options of mm, mm and 50mm, the Absolut stem covers the patient population of femoral geometry. A 12/14 neck trunion enables a wide range of head and cup selections and grants the surgeon the preferred choice of bearing materials that are deemed appropriate for the patient's pathology. Fig. 3 2 Absolut TM Stem System

5 Pre-Operative Planning Suggested Templating Method Determine neck resection. Note the distance from the shoulder of the selected femoral stem to the lesser trochanter. Templates are printed with graduated markings for reference. Preoperative planning is important, however the versatility of the Absolut Hip Stem allows simple intraoperative adjustments to leg length and offset. The overall objective of preoperative planning is to enable the surgeon to gather anatomic parameters to enable optimal placement of the femoral implant. The specific goals include (but are not limited to): Assessment of leg length Assessment of femoral offset Anticipated component sizing (especially for very small or very large femora) Determination of the osteotomy level (above the lesser trochanter) Overall alignment of the implant. 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 Absolut Hip System Templates use standard 120% magnification, which is close to the average magnification on most clinical radiographs. Magnification for larger patients or obese patients may be greater than 120% because their osseous structures are farther away from the surface of the film. To determine the magnification of any radiograph, a standardized marker may be placed at the level of the femur when exposing the film. This is especially important with digital templating. Computer based templating programmes are available. The centre of rotation of the femoral head should be determined on the preoperative radiograph. Acetabular component templates and/or templating the opposite hip may help. Overlay the template on the A/P radiograph so the midline of the implant is aligned with the anatomical axis in the femoral canal. Then move the template superiorly or inferiorly so the chosen head level mark is superimposed on the centre of rotation of the femoral head. The 12/14 taper and the, and 50mm Offset alternatives provide multiple options to re-establish correct offset and leg length. Stem sizing is performed by choosing the stem size so the rasp that fits the proximal femur will achieve an adequate cement mantle. The cement mantle has been incorporated into the templates to allow for a 2mm or 3mm cement mantle and corresponds to the rasp of the same size. Size 00 and 000 stems are only supplied with a 2mm cement mantle rasp. Note: The final component size is to be determined intra-operatively. Templating is for planning purposes only MM OFFSET 50MM OFFSET MM OFFSET ABSOLUT CEMENTED STEM Cement SIZE GM REV 4 120% MAGNIFICATION THIS TEMPLATE IS FOR SURGICAL PLANNING PURPOSES ONLY Surgical Technique 3 SIZE 1

6 Surgical Technique Surgical Exposure The approach to the hip varies and is influenced to a degree by the pathology present and the surgeon s preference. The Absolut Hip Stem can be inserted with equal ease using a posterolateral, anterolateral, anterior, straight lateral or transtrochanteric approach. Femoral Neck Resection Exposing the femoral neck may be assisted by retractors placed superiorly and inferiorly. The neck osteotomy level will vary depending on the size of the patient, the neck angle, and preoperative templating. The versatility of the Absolut Hip Stem allows a wide range of insertion levels. The resection level may be determined through use of the Resection Guide provided with the Absolut Hip System. If you choose to use the Osteotomy Guide, please note that one guide is provided for all stem sizes. Superimpose the guide on the proximal femur. The longitudinal axis of the guide should be parallel to the longitudinal axis of the femur. The centre of rotation holes are labelled appropriately for each of the offset options available (, and 50mm). All holes refer to the Medium (+0mm) head centre. If preferred, the Osteotomy Guide can also be positioned by using the scale on the medial edge of the guide to move the templated distance above the lesser trochanter, or by aligning the lateral scale with the tip of the greater trochanter. The level of the neck osteotomy may be marked on the bone. Note that the angle of the osteotomy cut is approximately degrees to the long axis of the femur. Acetabulum Preparation After the femoral neck osteotomy is complete, prepare and implant the acetabular components. 4 Absolut TM Stem System

7 Femoral Canal Preparation Expose the proximal femur so there is unimpeded access to the canal for insertion of the stem. Use a femoral elevator and a trochanteric retractor that adequately retracts the gluteus medius and gluteus minimus muscles to assist with the exposure. Firmly but carefully rotate the femur while the leg is flexed at the knee to aide in femoral exposure. It is critical that the gluteus medius tendon is retracted laterally to expose the greater trochanter. The medial part of the trochanter must be removed to ensure neutral placement of the Rasp and stem, thereby avoiding varus stem placement. Femoral Canal Opening Open the proximal femur to the piriform fossa by using the box chisel or a combination of the awl, a gouge, or rongeurs. A burr may be helpful in sclerotic bone. The use of trochanteric power reamers should be confined to removing only lateral trochanteric bone. Power reamers should not be used to prepare the femoral canal because of the danger of excessive cancellous bone removal and resultant minimal cement interdigitation. Locate and open the femoral canal using the awl. Then widen the femoral canal with the awl while working laterally and posteriorly into the greater trochanter. Ensure that the awl is aligned axially within the femoral canal, using femoral landmarks and the knee as guides. Surgical Technique 5

8 Rasping Begin femoral rasping with a rasp that is one to two sizes smaller than the templated size. Then use sequentially larger rasps until the templated size is reached, or until adequate resistance is obtained. Avoid over-rasping; leaving an adequate bed of 3mm to 4mm of cancellous bone proximally. The entire procedure may be achieved through hand rasping only, using light taps with the mallet to dislodge the rasp. Alternatively, the mallet may be used to gently insert the rasps. The rasps should advance with each moderate tap of the mallet. Rasp laterally and posteriorly in the femoral neck to aid in optimal placement of the rasp and final component. Anteversion may be determined by choosing a standard degree of anteversion of approximately 10 degrees, or by the patient s natural anteversion, or at the surgeon s discretion based on the particular patient. Soft cancellous bone may be removed with a curette from regions the rasp did not reach, especially laterally and medially at the level of the lesser trochanter. 6 Absolut TM Stem System

9 Trial Reduction Bury the teeth of the final rasp to the resection level and disengage the rasp handle. On the proximal rasp the holes anteriorly and posteriorly represent a reference if adjusting leg length is desirable. They correspond to etchings on the definitive stem for reproducibility between trialling and definitive implantation. As an added feature they also correlate to the selection of the femoral head lengths available (-3.5, 0, 3.5, 7, 10.5mm). Each Absolut Hip Stem offers three offsets options completely independent to any changes in leg length. Select the trial offset neck (,, 50mm) chosen during pre-operative planning. Then select the head of choice and reduce. Adjust neck/head combination if necessary to optimize joint stability, leg length, and range of motion. Sizes 000, 00 and 0 offer a decreased selection of neck offsets to maintain implant strength. Medullary Bone Plug The internal diameter of the femoral canal can be established using the sounds supplied by inserting them down the femoral canal, with the required depth for the chosen stem size indicated on the sound shaft. Choose the appropriate plug needed for cement restriction. One technique is to use the plug with the core size that corresponds to the last sound that passed through the isthmus thereby ensuring a tight fit. Please note that the proximal diameter of the bone plug (cement restrictor) is 2mm larger than the corresponding medullary sound. Bone Plug Size Proximal Diameter Distal Diameter Small 10mm 7mm Medium 14mm 10mm Large 18mm 14mm X-Large 22mm 18mm Insertion is performed by first threading the desired bone plug onto the introducer. Then, aligning the introducer with the centreline of the stem, insert the plug by gently hammering the introducer to the desired depth. Optimal depth can be established against the markings on the plug inserter to the lateral osteotomy line as indicated in the image opposite. Once the plug is in place and checked it will not move with gentle pressure applied to the introducer, the introducer can be removed by simply unthreading it from the bone plug. Depth markings appear on both the medullary sounds and inserter. Size 1-4 markings are for size 1, 2, 3 and 4 stems whilst the size 0 markings are for size 0, 00 and 000 stems. Surgical Technique 7

10 Centraliser Fit the centraliser to the distal tip of the stem. Choose the appropriate centraliser needed from the chart below based on the stem size. The XS centraliser fits all stem sizes and is provided for Dorr A type femurs where the recommended centraliser size may not fit in the femoral canal. This centraliser will ensure a minimum 2mm gap from the stem's distal tip to the cortical bone. Cementing The preferred cementing technique is chosen by the surgeon. Stem Insertion Femoral Head Assembly Once the cement has hardened, the Femoral Head Trial may be used during a trial reduction to assess the leg length, range of motion, stability, abductor tension, and to confirm final femoral head size. Check to ensure that the trunnion taper is clean and dry. Place the femoral head on the taper with a twisting motion until it locks on the taper. 8 Absolut TM Stem System

11 Implant Dimensions STEM STEM STEM STEM OFFSET SIZE OFFSET A/P M/L STEM STEM NECK HEIGHT (F) A/P WIDTH M/LWIDTH STEMLENGTH STEMLENGTH OFFSET OFFSET (E) (E) NECK HEIGHT (F) (A) (B) (C) (D) WIDTH WIDTH LENGTH LENGTH +0 (A) (B) (C) (D) Surgical Technique 9

12 Instrument Catalogue ABSOLUT CEMENTED HIP SYSTEM CASE 1 GM ABSOLUT FEMORAL HEAD IMPACTOR HANDLE GM ABSOLUT FEMORAL HEAD IMPACTOR ADAPTOR GM ABSOLUT STEM INSERTER GM ABSOLUT PLUG INTRODUCER GM ABSOLUT STRAIGHT RASP HANDLE GM ABSOLUT CURVED RASP GM ABSOLUT RESECTION GUIDE HANDLE GM ABSOLUT RESECTION GUIDE GM ABSOLUT AWL GM ABSOLUT BOX CHISEL GM Absolut TM Stem System

13 ABSOLUT CEMENTED HIP SYSTEM CASE 2 GM ABSOLUT TRIAL FEMORAL HEAD Left: 36mm (+7), Right: 36mm (+10.5) ABSOLUT TRIAL FEMORAL NECK MM OFFSET HEAD SIZE (MM) OFFSET (MM) GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM GM ABSOLUT TRIAL FEMORAL NECK MM OFFSET GM ABSOLUT TRIAL FEMORAL NECK 50MM OFFSET GM ABSOLUT RASPS (3mm CATALOGUE Mantle) NUMBER (2mm Mantle) SIZE SIZE GM Absolut Rasp Absolut Size 00Rasp Size S1 NA GM GM Absolut Absolut Rasp Size 000 NA GM GM Absolut Rasp Absolut Size Rasp 1 Size 00 GM GM GM Absolut Rasp Absolut Size 2Rasp Size 0 GM GM GM Absolut Rasp Absolut Size 3Rasp Size 1 GM GM GM Absolut Rasp Absolut Size 4Rasp Size 2 GM GM Absolut Rasp Size 3 GM GM Absolut Rasp Size 4 ABSOLUT MEDULLARY SOUNDS SIZE SGM SGM SGM SGM Absolut Medullary Sound Small Absolut Medullary Sound Medium Absolut Medullary Sound Large Absolut Medullary Sound Extra Large Surgical Technique 11

14 Implants Catalogue ABSOLUT CEMENTED STEM SIZE GM mm Offset Size 0 GM mm Offset Size 1 1 GM mm Offset Size 2 Size 2 GM mm Offset Size 3 GM mm Offset Size 3 GM mm Offset Size 4 GM mm Offset Size 4 GM mm Offset Size 0 GM GM mm mm Offset Size Size 10 GM GM mm Offset Size 21 GM GM mm Offset Size 32 GM GM mm Offset Size 43 GM GM mm Offset Size 1 mm Offset Size 4 GM mm Offset Size 2 GM mm Offset Size 1 GM mm Offset Size 3 GM GM mm Offset Size 2 50mm Offset Size 4 Material: Cobalt Chrome (CoCr) GM GM mm mm Offset Offset Size Size 003 GM mm Offset Size 000 BONE PLUG SIZE GM Bone Plug Small GM Bone Plug Medium GM Bone Plug Large GM Bone Plug Extra Large Material: Polyethylene CENTRALISER SIZE GM Centraliser Small Material: Polymethyl Methacrylate (PMMA) CENTRALISER SIZE GM Centraliser Medium Material: Polymethyl Methacrylate (PMMA) CENTRALISER SIZE GM Centraliser Large Material: Polymethyl Methacrylate (PMMA) CENTRALISER SIZE REFERENCES 1. Ling R, Charity J, Clive Lee A, Whitehouse S, Timperley A, Gie G. The Long-Term Results of the Original Exeter Polished Cemented Femoral Component. J Arthroplasty June; GM GM Centraliser Extra Large Small 24(4): Burston B, Yates P, Hook S, Moulder E, Whitley E, Bannister G. Cemented Polished Tapered Stems in Patients Less Than 50 Years of Age: A Minimum 10-year Follow-Up. J Arthroplasty Aug;25(5): Hook S, Moulder E, Yates Material: P, Burston Polymethyl B, Whitley Methacrylate E, Bannister (PMMA) G. The Exeter Universal stem. A Minimum Ten-Year Review From An Independent Centre. J Bone Joint Surg [Br] 2006;88B: Material: Polymethyl Methacrylate (PMMA) 4. GM Absolut Cemented Stem - Stem Fatigue Testing Report REV 0 5. GM Absolut Cemented Stem - Neck Fatigue Testing Report REV 0 12 Absolut TM Stem System

15 REFERENCES 1. Ling R, Charity J, Clive Lee A, Whitehouse S, Timperley A, Gie G. The Long-Term Results of the Original Exeter Polished Cemented Femoral Component. J Arthroplasty June; 24(4): Burston B, Yates P, Hook S, Moulder E, Whitley E, Bannister G. Cemented Polished Tapered Stems in Patients Less Than 50 Years of Age: A Minimum 10-year Follow-Up. J Arthroplasty Aug;25(5): Hook S, Moulder E, Yates P, Burston B, Whitley E, Bannister G. The Exeter Universal stem. A Minimum Ten-Year Review From An Independent Centre. J Bone Joint Surg [Br] 2006;88B: GM Absolut Cemented Stem - Stem Fatigue Testing Report REV 0 5. GM Absolut Cemented Stem - Neck Fatigue Testing Report REV 0

16 Global Orthopaedic Technology Unit 10, 7 Meridian Place Norwest Business Park Baulkham Hills NSW 2153 Australia PO Box 77 Baulkham Hills BC NSW 2153 Australia Toll Free: Phone: Fax: info@globalortho.com.au globalortho.com.au Manufactured by Global Manufacturing Technology Unit 5, 12 Boden Road Seven Hills NSW 2147 Australia GM Absolut Surgical Technique REV 11