Surgical Technique CHARNLEY CHARNLEY, THE WORLD S MOST SUCCESSFUL HIP IMPLANT

Transcription

1 Surgical Technique CHARNLEY CHARNLEY, THE WORLD S MOST SUCCESSFUL HIP IMPLANT

2 The pre-operative preparation and surgical approach have been described by: Mr MH Stone M Phil FRCS (Ed), Mr D McDonald FRCS and Dr OS Husby MD. Pre-operative planning The principles of low frictional The Charnley Total Hip System torque arthroplasty laid down by offers the surgeon a comprehensive Sir John Charnley in the early 1950 s, based on the mm diameter femoral head, have proved remarkably reliable. 1 Long term results for Charnley implants, achieved by surgeons working in centres worldwide, continue to set the standard by which all other implants must range of pre-operative planning templates with 20% magnification. Pre-operative templating allows the surgeon to judge the appropriate position, size and neck offset of the implant in order to restore the patient s normal anatomy. A radiograph showing the AP view be judged. 2 of the proximal femur, internally AP view Today s Charnley hip is the result rotated 15, provides the most the correct anatomical position of of a thirty year learning curve - important information: a level for the acetabular component relative with each new development setting higher and higher standards in design, materials and manufacturing. A range of twenty six femoral sizes provides the surgeon with a stem choice to suit every patient, and comprehensive instrumentation designed to assure accuracy, the neck resection which will restore leg length; the appropriate neck offset for a natural position of the femoral head; and the lateral/medial dimensions of the femoral canal which determine the overall size of the implant. The AP view also presents the to landmarks such as the tear drop. The lateral view showing the amount of femoral bow, helps to confirm the diameter of the femoral canal and highlights abnormalities in this plane which might affect the position of the implant. assists the surgeon to produce position of femur relative to the consistent, reliable clinical results. bony landmarks of the pelvis, and 2

3 Surgical Technique Patient positioning The Charnley Hip may be implanted using any of the standard surgical approaches for total hip arthroplasty. This technique outlines the surgical procedure for the direct lateral and posterior approaches. The lateral approach In the lateral approach, the patient is positioned square on the table in the supine position or the lateral position. In the supine position the patient is supported under the affected hip to relax the muscles. The hip is flexed, adducted and internally rotated. The posterior approach In the posterior approach, the patient should be in a true lateral position. With the knees slightly bent, the feet should be near the bottom of the table. A posterior support is used in the low lumbar region. This should be positioned so that it does not interfere with access during surgery. The anterior support is placed on the anterior, superior iliac spine, slightly towards the abdominal side so that it will not prevent the hip flexing during surgery. A sand bag is placed in front of the lower ankle, underneath the canvas, to prevent the leg extending. A pillow may be placed between the legs and held in position with a strap, to give the pelvis a more symmetrical position. It is important that with the pillow in position, the operator can feel both heels and the front of the knees, to allow leg length to be measured intraoperatively. With the patient in this position the pelvis tends to flex approximately 20 into an anteverted position. Appreciation of this will allow correct orientation of the cup during cementing. Well padded support is used to support the upper arm. Lateral approach The initial incision is centred over the greater trochanter. The line of the incision runs distally from the tip of the greater trochanter along the axis of the femur, and proximally, it runs posteriorly in a straight line into the buttock. Posterior approach The landmark for the initial incision is based over the tip of the greater trochanter. With the leg slightly flexed, the incision follows a gentle curve (convex anteriorly) extending approximately 8cm - 10cm (depending on the size of the patient) proximally and distally away from the trochanter. Standard draping procedure is followed. 3

4 Lateral approach With the initial incision made, work down through the subcutaneous tissue over the proximal femur to the fascia lata, which appears at the base of the wound. Posterior approach Split the fascia lata distally from the greater trochanter, in line with its fibres. The opening is then extended proximally, in line with the initial incision. Equal exposure should be achieved both proximally and distally, to allow the femur to be fully visualised and mobilised during insertion of the prosthesis. Soft tissue is cleared away and the sciatic nerve may be identified for reference during acetabular preparation. Position a Charnley retractor in the deep fascia layer at the anterior rim of the abductor muscles and at the gluteus maximus, and extend the retractor so that the proximal femur is exposed. With the leg adducted, the greater trochanter is presented into the centre of the wound. Using diathermy, incise from the tip of the greater trochanter through the anterior third of the tendonous attachment of the gluteus medius, cutting around the trochanter to allow a cuff of tissue for reattachment. Extend the incision along the line of the femur toward the quadriceps muscles. Further exposure is achieved proximally by splitting the abductor muscles in line with their fibres. The skin and fat are divided, clearing the deep fascia along the length of the incision. The deep fascia is opened. Using blunt dissection, the muscles are split in line with their fibres. The Charnley initial incision retractor is inserted with the C-Arm concave towards the head. The anterior blade is placed on the musculo tendonous junction of the deep fascia, and a similar position is adopted for the posterior blade. The distal free edge of the trochanteric bursa is then exposed. A pair of Mayo scissors is inserted under this free edge and slid proximally along the posterior margin of the femur. The bursa is then lifted, remaining attached only on its proximal and anterior side. This exposes the fat of the short rotator muscles and the free edge of the gluteus medius muscle. A plane is developed with the Mayo scissors deep to the free edge of the gluteus medius muscle and the greater trochanter. The anterior blade of the initial incision retractor is then inserted into this gap between the posterior edge of the gluteus medius and the greater trochanter. The fat is swept posteriorly off the short rotators using a swab. At this point, diathermy should not be used in close proximity to the sciatic nerve. The sciatic nerve may be visible in the depth of the posterior part of the wound. If not immediately visible, it may be felt but it is not necessary to expose the nerve. 4

5 A continuous flap is opened, from the abductors to the quadriceps. This will be reattached on completion of the procedure. Further exposure is achieved by dividing the abductor muscles in line with their fibres, using blunt dissection. A blunt nosed retractor is placed over the anterior lip of the joint capsule. Radially incise the anterior capsule, and excise the anterior flap. With the capsule fully excised, the hip can be dislocated without force. Release the inferior capsule on the neck of the femur, taking care to ensure that the abductor muscles remain attached to the posterior part of the femoral neck. It is important to fully release both the inferior and posterior capsule so that the femur can be safely delivered into the wound without risk of fracture. The tendons from piriformis proximally, superior gemellus, tendon of obturator internus, inferior gemellus and quadratus femoris muscle are now exposed. The quadratus femoris is left undisturbed and a stay suture is passed through the other tendons several times, using a number 1 vicryl suture. This is then attached to an artery forcep. The tendons of the short rotators, except for the quadratus femoris, are then cut with a diathermy point between the stay suture and the trochanter. The incision should start proximally and run parallel to the sciatic nerve from the tip of the trochanter to the inferior gemellus muscle. The leg is then rotated internally and the line of the cut turns in an anterior direction toward the assistant. This exposes the posterior capsule. A finger is placed anterior to the sciatic nerve, between the cut tendons and the capsule. The incision is turned into a T-shape by cutting the capsule anteriorly away from the operator s finger. At this stage it is usually possible to flex the hip and internally rotate the femur. The head will dislocate and, as the knee is brought into adduction, the neck will come fully into view. It is often necessary to cut the tight capsular fibres around the neck of the femur with diathermy. 5

6 Femoral initiation Accurate positioning of the entry point will avoid implant malalignment. The aim of stem positioning is to centralise the stem in both the AP and lateral projections. Approach through the piriformis fossa leads to neutral AP and neutral lateral stem positioning within an even cement mantle. Entry point posterior and lateral at the piriformis fossa. Posterior cortex is resected. Free access is gained to the femoral canal. Correctly aligned stem in line with the long axis of the femur, allowing for an even cement mantle. Correctly aligned stem Entry point too anterior and medial. Malaligned stem Posterior view Stem aligned centrally in the canal Posterior view Stem in varus Correctly aligned stem Malaligned stem Ensure that the femur is presented well into the wound to provide good access during preparation of the femoral canal. Access the femoral canal at the piriformis fossa, using the Excel initiator attached to the T handle. NB. It is important to ensure that the entry point is positioned laterally and posteriorly to ensure correct orientation of the stem within the femoral canal. i.e. the entry point, shaft of initiator and long axis of the femur are coincident. Entry point to the femur at the piriformis fossa Lateral view Stem aligned centrally in the canal Correctly aligned stem Lateral view Stem in retroversion and tip against posterior cortex Malaligned stem Medial view Stem aligned centrally in the canal Medial view Stem in retroversion and tip against posterior cortex 6

7 Canal reaming Reaming guide Prosthesis catalogue Distal reamer number Description diameter (mm) Flanged Extra Heavy Flanged Roundback Roundback 40 Narrow Roundback Flanged Extra Heavy Flanged Long Neck Long Neck 1 Extra Heavy Long Neck 1 Long Stem Long Neck Long Neck 2 Extra Heavy Long Neck 2 Long Stem /4 Neck CDH SNS35 11 Attach the Excel canal probe to the T handle and introduce the probe into the femoral canal in line with the femur. Maintain a neutral orientation and ensure that the probe does not impinge on the entry hole. If the entry point is correct, the probe should pass down the femur easily. Introduce the first reamer and begin to enlarge the cavity, progressively increasing the size of reamer until the reaming diameter corresponds to the predetermined implant size (see table) Magnum Magnum CD Extra Small Straight Thick Stem Flanged Flanged 40 Long Stem Extra Heavy Flanged 40 Long Stem Extra Small 11 7

8 Femoral neck resection Acetabular preparation The level of the neck resection is determined during preoperative templating. The cut will be approximately 1cm - 2cm above the lesser trochanter or distal to the articular margin. Centre the neck resection guide along the neutral axis of the femur and mark the 45 resection line using diathermy. Perform the osteotomy using an oscillating saw, taking care to maintain the correct angle. If the posterior approach is being used, two Trethowan retractors are placed around the femoral neck at this stage. Cut the ligamentum teres and remove the femoral head. If a bone plug is to be used in the distal femur to restrict the cement, this may now be taken from the exposed cancellous bone of the proximal femur. Excise the remaining capsule from around the acetabulum. Ensure that the rim and bed of the acetabulum are clear of soft tissues and osteophytes using the Charnley ring curette and Charnley small curette. Beginning with the smallest diameter reamer, progressively ream away the remaining soft tissues in the acetabular bed. Remove all remaining articular cartilage and any medial osteophytes until healthy, bleeding subchondral bone is exposed and a symmetrical, hemispherical dome is achieved. The reamer should be introduced in 45 of abduction and 15 of anteversion. NB. If the posterior approach is employed, it should be remembered that this position puts the pelvis in approximately 20 of anteversion which must be compensated for during acetabular reaming and cup placement. 8

9 Acetabular sizing Drill multiple holes in the roof of the acetabulum using the collared Charnley acetabular preparation drill to encourage extensive intrusion of the cement into the interstices of the bone. NB. Care should be taken to avoid the medial wall of the acetabulum. This is a triangle of bone based on the transverse ligament. Smooth the edges of the drill holes and remove the debris using a small curette. Use the spoon to feel for any cysts which may not have been revealed by radiological examination. Attach the phantom cup and trial flange to the cup introducer and check the size of the acetabulum. Trim the rim of the trial flange so that it just fits within the rim of the acetabulum. Using the trial as a guide, cut the flange of the definitive cup to match. Lavage and clear the acetabulum of debris. 9

10 Cup implantation Femoral canal preparation Attach the cup to the cup introducer. Introduce the cement into the acetabular bed and insert the cup. The cement should be fully contained behind the rim of the cup, and the rim well supported by the cement. Align the shaft of the introducer with the anterior superior iliac spine and rotate the handle posteriorly to give of anteversion. (Using the posterior approach, anteversion of the pelvis requires the cup holder to be orientated at approximately of anteversion relative to the long axis of the patient.) Locate the cup pusher on the back of the cup introducer and pressurise the cement. Once the cement has begun to polymerise, the cup pusher can be applied directly to the cup and pressure maintained until polymerisation is complete. The rim of the acetabulum should be checked for any remaining osteophytes and cement debris which might cause impingement. To protect the cup, cover it with a clean swab. Attention may now be turned to the femur. Using the leading edge of the anteversion osteotome positioned laterally toward the greater trochanter, enlarge the entry point to the femoral canal and establish of anteversion for broach alignment. Reverse the osteotome and extend the entry point medially toward the lesser trochanter. Remove a wedge of cancellous bone approximately the same size and shape as the proximal section of the prosthesis. 10 of anteversion Shaft of the introducer parallel to the superior and inferior illiac spines. Long axis of the patient 10

11 Broaching Trial reduction Attach a broach, smaller than that determined during preoperative templating, to the in line broach handle. With the broach parallel to the long axis of the femur and at right angles to the tibia, pass the broach down the canal in neutral orientation, with of anteversion. To avoid varus alignment with the femoral axis, position the broach laterally toward the greater trochanter. Progressively increase the size of broach until a cavity is prepared which matches the size planned during pre-operative templating. When the final broach is seated at the resection line, fit the trial head onto the neck of the broach and reduce the hip. Check for impingement and joint stability through adduction, rotation and flexion. Remove the trial head and re-engage the in line broach handle to extract the broach. Introduce the cement restrictor and ensure that it is firmly seated in the femoral canal at the depth indicated by the size of the definitive implant (see table overleaf). Using a bone brush and irrigation, ensure that the femoral canal is clear of blood and loose debris. 11

12 Cement restrictor depths Stem implantation Dimensions in millimetres. Cement Cement Prosthesis Broach restrictor restrictor description description size depth Flanged 40 F Extra Heavy Flanged 40 F40EH Roundback 40 RB Roundback 40 Narrow RB40N Roundback 45 RB Flanged 45 F Extra Heavy Flanged 45 F45EH Long Neck 1 LN Long Neck 1 Extra Heavy LN1EH Long Neck 2 L Long Neck 2 Extra Heavy LN2EH Long Neck 1 Long Stem LN1LS Long Neck 2 Long Stem LN2LS /4 Neck 3/4N CDH CDH SNS35 SNS Magnum 40 M Magnum 45 M CDH Extra Small CDHES Standard Thick Stem SNS Resection Stem N/A 15 Stem 40 N/A Flanged 35 SNS Flanged 40 Long Stem FL Extra Heavy Flanged 40 Long Stem EHFL Extra Small CDHES These measurements are taken from the medial edge of the neck osteotomy and allow for 20mm of cement distal to the tip of the prosthesis. If a bone block is to be used, this distance may be varied according to surgeon preference. In these instances, increased reaming depth is required to accommodate the longer stem length. The recommended broach should be used as a rasp to prepare the femur and a trial implant is used to assess joint function and stability. Attach the definitive femoral implant, with its cover in place, to the Charnley introducer. Insert the cement, filling the femoral canal and pressurise the cement. (Effective pressurisation should result in the extrusion of blood through the cortex at the rim of the proximal femur.) Introduce the implant, in line with the femoral axis i.e. down the piriformis fossa. Remove the implant cover and maintain pressure on the femoral head, using the head pusher, until polymerisation is complete. Remove all excess cement, taking care not to scratch the femoral head, and irrigate thoroughly to clear away any remaining debris from the joint. Carry out a final reduction to check joint stability function. Introduce the first drain into the joint and reattach the tendonous tissue below the flap of the abductor muscles. Place the second drain behind the trochanter and close the wound. In the posterior approach, after the first drain has been introduced the short rotator muscles are reattached to the posterior edge of the gluteus medius tendon. 12

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14 Acetabular Instruments Acetabular Implants Grater Shaft with Hudson Fitting Acetabular Reamer 38mm Acetabular Reamer 40mm Acetabular Reamer 42mm Acetabular Reamer 44mm Acetabular Reamer 46mm Acetabular Reamer 48mm Acetabular Reamer 50mm Acetabular Reamer 52mm Acetabular Reamer 54mm Acetabular Reamer 56mm Acetabular Reamer 58mm Acetabular Reamer 60mm Acetabular Prep Drill Charnley Charnley Std Cup / Charnley Std Cup / Charnley Std Cup / Charnley Std Cup / Charnley Std Cup / Charnley LPW Cup / Charnley LPW Cup / Charnley LPW Cup / Charnley LPW Cup / Charnley LPW Cup / Charnley LPW Cup / Cup Introducer mm Cup Trial 40mm Cup Trial 43mm Cup Trial 47mm Cup Trial 50mm Cup Trial 53mm Trimming Scissors Cup Pusher Handle Cup Pusher Head mm Cemented Acetabular Instrument Tray Cemented Acetabular Templates Charnley Flanged Cup / Charnley Flanged Cup / Charnley Flanged Cup / Charnley Flanged Cup / Charnley Flanged Cup / Charnley Flanged Cup Std Small Charnley Flanged Cup Std Large Charnley Flanged Cup Offset Bore Charnley Ogee Cup / Charnley Ogee Cup / Charnley Ogee Cup / Charnley Ogee Cup / Charnley Ogee Cup / Charnley Ogee Cup Std Small Charnley Ogee Cup Std Large 13

15 Ordering Information Charnley Base Broaching Instrument Set Base Tray Charnley Tray Base and Lid Charnley Neck Osteotomy Guide Elite In-Line Broach Handle Elite Femoral Prosthesis Holder Elite Trial Femoral Head Std Charnley /Elite Broach RB40 N Charnley /Elite Broach RB Charnley /Elite Broach FL Charnley /Elite Broach FL40 EH Charnley /Elite Broach LN Charnley /Elite Broach RB Charnley /Elite Broach FL Charnley /Elite Broach FL45 EH Charnley Excel Femoral Instrument Set Top Tray Charnley Tray Excel Insert Charnley Curette Small Charnley Curette Medium Charnley Curette Large Charnley Ring Curette Excel T Handle Excel IM Initiator Muller Awl Reamer with Hudson End Canal Reamer Canal Reamer Canal Reamer Canal Reamer Anteversion Osteotome Medium Excel Femoral Head Impactor Alternative Top Tray Instrument Set Charnley Broaching Instrument Set Top Tray Charnley Tray Broaching Insert Charnley /Elite Broach SNS Charnley /Elite Broach Magnum Charnley /Elite Broach LN1 EH Charnley /Elite Broach LN1 LS Charnley /Elite Broach LN Charnley /Elite Broach LN2 EH Charnley /Elite Broach LN2 LS Charnley /Elite Broach CDH Extra Small Charnley /Elite Broach CDH Charnley /Elite Broach 3/4 Neck Charnley /Elite Broach Magnum Restrictor Trial Introducer Cement Restrictor Trial Cement Restrictor Trial Cement Restrictor Trial Cement Restrictor Trial Cement Restrictor Trial Cement Restrictor Trial Cement Restrictor Trial 7 Femoral Implants Charnley Extra Heavy Flanged Charnley Flanged Charnley Roundback Charnley Roundback 40 Narrow Charnley Roundback Charnley Flanged Charnley Flanged Charnley Extra Heavy Flanged Charnley Long Neck Charnley Long Neck 1 Extra Heavy Charnley Long Neck Charnley Long Neck 2 Extra Heavy Charnley Long Neck 1 Long Stem Charnley Long Neck 2 Long Stem Charnley 3/4 Neck Charnley CDH Charnley Extra Small Charnley 15 Stem Charnley Resection Stem Charnley Flanged 40 Long Stem Charnley SNS Charnley Straight Thick Stem Charnley Extra Heavy Flanged 40 Long Stem Charnley Magnum Charnley Magnum Charnley CDH Extra Small Cement Restrictor Size Cement Restrictor Size Cement Restrictor Size Cement Restrictor Size Cement Restrictor Size Cement Restrictor Size Cement Restrictor Size 7 14

16 References: 1. Kabo MJ, Gebhard J, Loren G, Amstutz H. In Vivo Wear of Polyethylene Acetabular Components. J Bone Joint Surg (Br), 75-B, 254-8, Kavanagh B, Wallrichs S, Dewitz M, Berry D, Currier B, Ilstrup D, Coventry M. Charnley Low Friction Arthroplasty of the Hip. J of Arthrop, 9, No 3, This publication is not intended for distribution in the USA Charnley and Ogee are registered trademarks and Elite is a trademark of DePuy International Ltd. Excel is a trademark of DePuy Orthopaedics, Inc DePuy International Limited. All rights reserved. Cat No: DePuy International Ltd St Anthony s Road Leeds LS11 8DT England Telephone: +44 (113) Fax: +44 (113)