- Email: [email protected]
Cemented primary total hip arthroplasty using a direct anterior approach
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E M I N A R S
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R T H R O P L A S T Y
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Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/sart
Cemented primary total hip arthroplasty using a direct anterior approach Luke G. Menkena, Zachary P. Berlinerb, Nate Mercerc, and Jose A Rodrigueza,* a
Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, NY, USA Orthopedic Surgery Residency Program, Boston University School of Medicine, Boston, MA, USA c The State University of New York Upstate Medical University, Syracuse, NY, USA b
A R T I C L E I N F O
AB STR ACT
Keywords:
Total hip arthroplasty is one of the most successful surgeries used in medicine today.
Total hip arthroplasty
A major complication associated with significant comorbidity for THA is periprosthetic
Cemented
fracture. A number of risk factors associated with periprosthetic fracture have been identi-
Direct anterior approach
fied, including the use of uncemented femoral fixation. In patients with significant risk
Surgical technique
factors, we use a collarless, composite beam cemented stem in order to mitigate the risk of periprosthetic fractures. This article describes the surgical technique utilized to obtain a safe and effective cemented fixation through the direct anterior approach of the hip. Ó 2019 Elsevier Inc. All rights reserved.
1. Introduction The total hip arthroplasty (THA) is one of the most successful surgeries used in medicine today. The number of THA procedures is expected to continually increase in the near future [1]. One of the complications associated with significant morbidity for THAs is periprosthetic fracture about the femur. With the increase in total procedures, the incidence of periprosthetic fractures is also projected to rise [2]. Early periprosthetic fractures have been correlated with specific patient risk factors as well as specific surgeon-related risk factors. Patient risk factors include the female gender, age greater than 65 years old, and a previous diagnosis of osteoporosis [3 5]. Surgeon-related risk factors include choosing uncemented stem fixation and using a direct anterior approach for exposure [6 9]. Femoral exposure through the direct anterior approach is considered by some to be more technically challenging than with direct lateral or posterior approaches. Recent data has suggested increased level of femoral complications such as loosening and periprosthetic fracture with direct anterior approach surgery [10]. Failure to achieve adequate exposure
and visualization of the femoral canal can predispose to improper broaching and potentially increase the risk of perioperative femoral fracture [11]. Some authors have credited the learning curve as being a significant risk factor for periprosthetic fracture with the direct anterior approach [9,10,12]. Patients with poor bone quality have been shown to be at increased risk for fracture during non-cemented total hip replacements [5,6]. When combined with the potential difficulty in accessing the canal with DAA, patients may be at even greater risk for periprosthetic fracture. In this article, we describe strategies to mitigate these risks including technical steps to achieve adequate femoral exposure and visualization, and proper surgical technique for femoral cement fixation in order to prevent periprosthetic fracture.
2. Indications and contraindications Risk factors that predispose patients to periprosthetic fractures are well documented in the literature. Numerous registry studies have shown female gender to be positively correlated with fracture. A meta-analysis done by Zhu, et al.
* Corresponding author. Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. E-mail address: [email protected] (J.A. Rodriguez). https://doi.org/10.1053/j.sart.2019.02.006 1045-4527/Ó 2019 Elsevier Inc. All rights reserved.
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Figure 1 – Extended incision (10 cm) for initial exposure of the femur.
shows female gender to have a pooled odds ratio of 1.5 compared to male gender [3]. Increasing age is a significant risk factor as well. Patients over 65 years old have been shown to have an odds ratio of 2.5 compared to their younger counterparts [4]. Osteoporosis has been highly associated with intraoperative periprosthetic fracture and remains a significant comorbidity for postoperative fracture [5]. All of these factors are associated with poor bone quality, and from this we can conclude that poorer bone leads to a much higher risk of fracture intra- and post-operatively. Surgeon choices during the operation can predispose patients to periprosthetic fracture of the femur. A plethora of sources have equated uncemented fixation with a higher periprosthetic fracture rate compared with cemented fixation. The incidence of postoperative proximal femur fractures in primary THA using uncemented stems have been reported to be between 0.47 7.1% [6]. When compared to cemented fixation, which has a reported periprosthetic fracture rate in primary
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THA between 0.07 3.1% [6], one can appreciate the benefit of using cement fixation in patients who have predisposing risk factors for fracture. Even with cement technique there still remains a risk for fracture, especially with particular types of implants. There are different types of implants for cemented fixation and the surgeon must consider which type will be used. The primary cemented stem options are collarless, polished, tapered (CPT) stems or composite beam stems. A study from the National Joint Registry Data of the United Kingdom shows the relative risk of CPT stems and periprosthetic fractures is 3.91 compared to 0.41 for a collared, composite beam [7]. The direct anterior approach (DAA) is another factor that has been associated with higher complication rates in the literature. Although often times it coincides with the learning curve of surgeons learning this new approach, a number of studies have shown higher rate of periprosthetic fracture in DAA compared to the posterior approach [8,9]. Contraindications for this procedure are divided between contraindications for a direct anterior approach and contraindications for using cement technique. History of prior respiratory compromise is a contraindication for cementing hip as the pressurization of the cement can lead to emboli that will eventually reach the respiratory system [13]. Cement is also relatively contraindicated in young, active patients, where aseptic loosening of the stem is more prevalent than in older populations [14]. The DAA is relatively contraindicated in patients who have a large abdominal panniculus as this can effect wound healing and increase risk of infection [15].
3. Surgical technique The standard DAA incision begins 2 cm distal and 2 cm lateral to the ASIS, which can be readily palpated in most patients.
Figure 2 – (A) Interval exploration between the piriformis tendon and conjoined tendon seen at the tip of the electrocautery. (B) Conjoined tendon and superior capsule retraction with release of the tendon. (C) Piriformis flipped posterior to the greater trochanter and away from the canal leading to complete exposure of the inner trochanter.
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Figure 3 – Posterolateral entry point into the canal. The leg is in external rotation, extension, and adduction to get proper excursion of the femur.
In order to obtain proper femoral exposure for cementing, the surgeon should extend the incision 2 cm proximally to about the level of the ASIS (Fig. 1). The incision is made over the tensor fascia lata (TFL) muscle angled along the course of the TFL fibers down to the level of the fascia. The dissection is then continued medial to the TFL down to capsule as previously described [16]. This includes identifying and ligating the lateral femoral circumflex vessels, capsulotomy, neck osteotomy, femoral head removal, acetabular preparation, and reaming followed by cup placement. In patients with ligamentous laxity, we aim to keep the vertical band of the iliofemoral ligament mostly intact for increased postoperative stability in the anterior capsule. Once the acetabular component is in place, the femoral exposure can begin. The femoral hook is placed around the femur making sure to hug the vastus lateralis circumferentially. If the hook is placed too posteriorly or medially there are neurovascular bundles at risk. Once the femoral hook is in position, the bed is placed in approximately 20° of trendelenberg and the foot of the bed is dropped to approximately 45°. The femoral elevator is attached
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to the bed and the femoral hook is secured to the elevator. In order to get better exposure of the femur, the conjoined tendon and superior capsule must be released. In order to release the conjoined tendon, an interval must be created between the conjoined tendon and the piriformis. After establishing an interval, the conjoined tendon can be freely released [17]. As the conjoined tendon retracts, the superior capsule retracts with it and it allows the inner aspect of the posterior trochanter to be exposed. Once proper release is obtained, the femur is placed in abduction and the femoral retractor is depressed. This maneuver will allow the piriformis to flip behind the trochanter and move it from the surgical field. Afterwards, we place the leg in increasing amounts of external rotation and adduction to achieve direct access to the femoral canal. Because of this technique, we are able to keep the piriformis insertion intact (Fig. 2). The entry point into the femoral canal is a critical step especially in cemented femoral stems. The surgeon should utilize a posterolateral entry point into the canal in order to have the ability to place the cemented stem in neutral position within the femoral canal (Fig. 3). If the stem is not placed neutrally, there is not sufficient room for the cement to create a 2 mm mantle circumferentially, and mantle defects can lead to complications long term such as osteolysis and aseptic loosening [18] (Fig. 4). After marking the entry point with an electrocautery, the canal can be broached using either a high-speed burr or a box osteotome. Following entry to the canal we will place the canal finder into the canal. This allows us to set our anteversion by compressing the cancellous bone medially and also to position the leg to make sure there is no soft tissue impingement when the canal finder sits neutrally in the canal (Fig. 5). Broaching the canal is done in standard fashion; beginning two sizes below our planned stem size. It is important to note how the broach is sitting in the canal. The distance from the cortical bone to the implant templated on the preoperative plan should be approximately the same when grossly visualized during surgery. This will help the surgeon assess neutral stem placement and prevent any varus or valgus error. The
Figure 4 – (A) Posterior entry point with corresponding stem alignment. Posterior entry allows for neutral stem alignment in the sagittal plane. (B) Anterior entry point with corresponding stem alignment. An anterior point complicates neutral stem placement increasing the likelihood of mantle defect.
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Figure 5 – (A) Canal finder within canal demonstrating soft tissue impingement at the surgeon’s fingertip with neutral alignment of the canal finder. (B) Canal finder within the canal clear of the soft tissue with neutral alignment following further adduction of the operative leg.
preoperative plan is also useful for ensuring the gross neck cut is equal to that of the preoperative plan to maintain proper leg length. If this is not the case and the residual neck is longer than planned, the surgeon can calcar ream in order to remove the excess cortical bone to achieve the ideal stem placement (Fig. 6). Once the correctly sized broach is within the canal, a trial neck and head is placed, the hip is reduced, followed by provocative testing for stability. Testing is performed by passively externally rotating and adducting the leg in neutral position, as well as in extension. The goal is to maintain full range of motion, avoiding neck-socket impingement in external rotation and extension in order to prevent any anterior dislocation. At this point, we assess clinical leg length, radiographic leg length, and broach appearance within the canal on the image intensifier. Once the surgeon is satisfied with the sizing of the stem and the neck, cement preparation begins. Third-generation cement technique is utilized [18,19]. As the surgical technician mixes the cement with the help of a vacuum, the
Figure 7 – Placement of cement restrictor 1.5 cm distal to the prosthesis tip with the collar position marked on the restrictor inserter.
Figure 6 – Intraoperative fluoroscopy demonstrating insufficient neck cut, thus necessitating calcar reaming.
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Figure 8 – Cement pressurization showing pressurization attachment and surgeon digitally pressurizing the medial neck for increased tactile feel.
surgeon can plan the cement restrictor. The final prosthesis is used in order to measure the restrictor position at 1.5 2 cm distal to the prosthesis tip starting from the level at which the collar will sit in the canal (Fig. 7). After the restrictor is placed, the canal is thoroughly irrigated with pulse lavage. The irrigation is performed systematically in quadrants; posterior, medial, anterior, and lateral at both the distal and proximal aspects of the canal. The canal is then filled with absorbent vaginal packing in order to dry the cancellous bone. While the canal dries, a cement centralizer is placed onto the prosthesis and the cement is loaded into a cement gun. Before the cement can be placed into the canal, the proper consistency must be obtained. The cement is at a proper consistency once
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a 1 cm segment of cement extruded from the nozzle of the cement gun no longer bends to gravity, it no longer has its initial shine, and it no longer sticks to a gloved finger. It is important to ensure hypotensive anesthesia during this portion of the procedure to minimize bleeding and maintain a proper bed for cement interdigitation. Cement is then inserted into the canal, slowly, from distal to proximal. Once the canal is filled, the cement must be pressurized in order to increase the interdigitation of the cement into the cancellous bone. This is achieved by adding the pressurizing attachment to the cement gun followed by the surgeon digitally pressurizing the medial portion of the canal (Fig. 8). By using their finger, the surgeon is able to get a tactile sensation of the amount of pressurization as it increases with cement gun injection. After filling and pressurizing the canal, the stem can be placed. The stem is coated with cement prior to insertion to prevent any marrow contents from adhering directly to the implant. Stem placement is critical as previously discussed, and must be placed in a neutral position to prevent any long-term complications. The version must also be appropriate and this is checked before the final position is held in place. Any excess cement is removed, followed by a final digital pressurization laterally so that a small fingerprint is apparent in the lateral shoulder on postoperative x-ray. The final step of the procedure is to reduce the hip and reassess leg length and provocative stability testing. It is imperative to ensure that the final construct remains stable. The incision is then closed layer-by-layer to avoid any potential spaces where hematoma or seroma could form. Upon completion of surgery, the postoperative x-rays should look identical to the preoperative plan with desired leg length realized and exceptional clinical stability (Fig. 9).
Figure 9 – Postoperative film compared to preoperative template. Proper offset, implant positioning and canal fill is achieved.
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4. Conclusion Utilizing a cemented femoral stem in high-risk populations may prevent early periprosthetic fractures. Patients with pathologies leading to poor bone quality are at an increased risk of periprosthetic fracture due to the tighter fit design of uncemented stems. Cemented stems have shown good long term survival, comparing favorably to uncemented fixation in some studies [20]. We choose to use collared, composite beam stems because they have been shown to have the lowest incidence of periprosthetic fractures between cemented implant designs. Proper femoral exposure through the DAA is the key to obtaining ideal cemented fixation. The exposure can be achieved without release of the piriformis tendon with appropriate leg manipulation and conjoined tendon release. Stem insertion must be neutral in both the coronal and sagittal planes in order to avoid cement mantle defects that can be associated with long-term complications. With meticulous preoperative planning and reproducible surgical technique, cement fixation is easily achievable through the DAA.
Disclosure Jose A Rodriguez: Paid consultant for Medacta, Exactech, Conformis, and Smith & Nephew.
R E F E R E N C E S
[1] Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Jt Surg Am 2007;89(4):780–5. [2] Papadimitropoulos EA, Coyte PC, Josse RG, Greenwood CE. Current and projected rates of hip fracture in Canada. Can Med Assoc J 1997;15(10):1357–63. [3] Zhu Y, Chen W, Sun T, Zhang X, Liu S, Zhang Y. Risk factors for the periprosthetic fracture after total hip arthroplasty: a systematic review and meta-analysis. Scand J Surg 2015; 104:139–45. [4] Abdel MP, Watts CD, Houdek MT, Lewallen DG, Berry DJ. Epidemiology of periprosthetic fracture of the femur in 32 644 primary total hip arthroplasties. Bone Joint J 2016;98-B (4):461–7. [5] Franklin J, Malchau H. Risk factors for periprosthetic femoral fracture. Injury 2007;38:655–60.
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[6] Sidler-Maier CC, Waddell JP. Incidence and predisposing factors of periprosthetic proximal femoral fractures: a literature review. Int Orthop 2015;39:1673–82. [7] Palan J, Smith MC, Gregg P, Mellon S, Kulkarni A, Tucker K, et al. The influence of cemented femoral stem choice on the incidence of revision for periprosthetic fracture after primary total hip arthroplasty. Bone Joint J 2016;98-B (10):1347–54. [8] Malek IA, Royce G, Bhatti SU, Whittaker JP, Phillips SP, Wilson IRB, et al. A comparison between the direct anterior and posterior approaches for total hip arthroplasty. Bone Joint J 2016;98-B(6):754–60. [9] Woolson ST, Pouliot MA, Huddleston JI. Primary total hip arthroplasty using an anterior approach and a fracture table. J Arthroplasty 2009;24(7):999–1005. [10] Meneghini RM, Elston AS, Chen AF, Kheir MM, Fehring TK, Springer BD. Direct anterior approach: risk factor for early femoral failure of cementless total hip arthroplasty. J Bone Jt Surg 2017;99(2):99–105. [11] Barton C, Kim PR. Complications of the direct anterior approach for total hip ar throplasty. Orthop Clin NA 2009;40:371–5. [12] Angerame MR, Fehring TK, Masonis JL. Early failure of primary total hip arthroplasty: is surgical approach a risk factor? J Arthroplasty 2018;33:1780–5. [13] Issack PS, Lauerman MH, Helfet DL, Sculco TP, Lane JM. Fat embolism and respiratory distress associated with cemented femoral arthroplasty. Am J Orthop 2009;38(2):72–6. [14] Pedersen AB, Mehnert F, Havelin LI, et al. Association between fixation technique and revision risk in total hip arthroplasty patients younger than 55 years of age. Results from the Nordic Arthroplasty Register Association. Osteoarthr Cartil 2014;22:659–67. [15] Post ZD, Orozco F, Diaz-Ledezma C, Hozack WJ, Ong A. Direct anterior approach for total hip arthroplasty: indications, technique, and results. J Am Acad Orthop Surg 2014;22 (9):595–603. [16] Lovell TP. Single-incision direct anterior approach for total hip arthroplasty using a standard operating table. J Arthroplast 2008;23(7):64–8. [17] Rodriguez JA, Kamara E, Cooper HJ. Applied anatomy of the direct anterior approach for femoral mobilization. JBJS Essent Surg Tech 2017;7(2):1–14. [18] Barrack RL. Early failure of modern cemented stems. J Arthroplast 2000;15(8):1036–50. [19] Ranawat CS, Maynard MJ. Modern technique of cemented total hip arthroplasty. Tech Orthop 1991;6(3):17–25. € rrholm J. Uncemented and [20] Hailer NP, Garellick G, Ka cemented primary total hip arthroplasty in the Swedish Hip Arthroplasty Register Evaluation of 170,413 operations. Acta Orthop 2010;81(1):34–41.
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Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/sart
Cemented primary total hip arthroplasty using a direct anterior approach Luke G. Menkena, Zachary P. Berlinerb, Nate Mercerc, and Jose A Rodrigueza,* a
Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, New York, NY, USA Orthopedic Surgery Residency Program, Boston University School of Medicine, Boston, MA, USA c The State University of New York Upstate Medical University, Syracuse, NY, USA b
A R T I C L E I N F O
AB STR ACT
Keywords:
Total hip arthroplasty is one of the most successful surgeries used in medicine today.
Total hip arthroplasty
A major complication associated with significant comorbidity for THA is periprosthetic
Cemented
fracture. A number of risk factors associated with periprosthetic fracture have been identi-
Direct anterior approach
fied, including the use of uncemented femoral fixation. In patients with significant risk
Surgical technique
factors, we use a collarless, composite beam cemented stem in order to mitigate the risk of periprosthetic fractures. This article describes the surgical technique utilized to obtain a safe and effective cemented fixation through the direct anterior approach of the hip. Ó 2019 Elsevier Inc. All rights reserved.
1. Introduction The total hip arthroplasty (THA) is one of the most successful surgeries used in medicine today. The number of THA procedures is expected to continually increase in the near future [1]. One of the complications associated with significant morbidity for THAs is periprosthetic fracture about the femur. With the increase in total procedures, the incidence of periprosthetic fractures is also projected to rise [2]. Early periprosthetic fractures have been correlated with specific patient risk factors as well as specific surgeon-related risk factors. Patient risk factors include the female gender, age greater than 65 years old, and a previous diagnosis of osteoporosis [3 5]. Surgeon-related risk factors include choosing uncemented stem fixation and using a direct anterior approach for exposure [6 9]. Femoral exposure through the direct anterior approach is considered by some to be more technically challenging than with direct lateral or posterior approaches. Recent data has suggested increased level of femoral complications such as loosening and periprosthetic fracture with direct anterior approach surgery [10]. Failure to achieve adequate exposure
and visualization of the femoral canal can predispose to improper broaching and potentially increase the risk of perioperative femoral fracture [11]. Some authors have credited the learning curve as being a significant risk factor for periprosthetic fracture with the direct anterior approach [9,10,12]. Patients with poor bone quality have been shown to be at increased risk for fracture during non-cemented total hip replacements [5,6]. When combined with the potential difficulty in accessing the canal with DAA, patients may be at even greater risk for periprosthetic fracture. In this article, we describe strategies to mitigate these risks including technical steps to achieve adequate femoral exposure and visualization, and proper surgical technique for femoral cement fixation in order to prevent periprosthetic fracture.
2. Indications and contraindications Risk factors that predispose patients to periprosthetic fractures are well documented in the literature. Numerous registry studies have shown female gender to be positively correlated with fracture. A meta-analysis done by Zhu, et al.
* Corresponding author. Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. E-mail address: [email protected] (J.A. Rodriguez). https://doi.org/10.1053/j.sart.2019.02.006 1045-4527/Ó 2019 Elsevier Inc. All rights reserved.
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Figure 1 – Extended incision (10 cm) for initial exposure of the femur.
shows female gender to have a pooled odds ratio of 1.5 compared to male gender [3]. Increasing age is a significant risk factor as well. Patients over 65 years old have been shown to have an odds ratio of 2.5 compared to their younger counterparts [4]. Osteoporosis has been highly associated with intraoperative periprosthetic fracture and remains a significant comorbidity for postoperative fracture [5]. All of these factors are associated with poor bone quality, and from this we can conclude that poorer bone leads to a much higher risk of fracture intra- and post-operatively. Surgeon choices during the operation can predispose patients to periprosthetic fracture of the femur. A plethora of sources have equated uncemented fixation with a higher periprosthetic fracture rate compared with cemented fixation. The incidence of postoperative proximal femur fractures in primary THA using uncemented stems have been reported to be between 0.47 7.1% [6]. When compared to cemented fixation, which has a reported periprosthetic fracture rate in primary
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THA between 0.07 3.1% [6], one can appreciate the benefit of using cement fixation in patients who have predisposing risk factors for fracture. Even with cement technique there still remains a risk for fracture, especially with particular types of implants. There are different types of implants for cemented fixation and the surgeon must consider which type will be used. The primary cemented stem options are collarless, polished, tapered (CPT) stems or composite beam stems. A study from the National Joint Registry Data of the United Kingdom shows the relative risk of CPT stems and periprosthetic fractures is 3.91 compared to 0.41 for a collared, composite beam [7]. The direct anterior approach (DAA) is another factor that has been associated with higher complication rates in the literature. Although often times it coincides with the learning curve of surgeons learning this new approach, a number of studies have shown higher rate of periprosthetic fracture in DAA compared to the posterior approach [8,9]. Contraindications for this procedure are divided between contraindications for a direct anterior approach and contraindications for using cement technique. History of prior respiratory compromise is a contraindication for cementing hip as the pressurization of the cement can lead to emboli that will eventually reach the respiratory system [13]. Cement is also relatively contraindicated in young, active patients, where aseptic loosening of the stem is more prevalent than in older populations [14]. The DAA is relatively contraindicated in patients who have a large abdominal panniculus as this can effect wound healing and increase risk of infection [15].
3. Surgical technique The standard DAA incision begins 2 cm distal and 2 cm lateral to the ASIS, which can be readily palpated in most patients.
Figure 2 – (A) Interval exploration between the piriformis tendon and conjoined tendon seen at the tip of the electrocautery. (B) Conjoined tendon and superior capsule retraction with release of the tendon. (C) Piriformis flipped posterior to the greater trochanter and away from the canal leading to complete exposure of the inner trochanter.
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Figure 3 – Posterolateral entry point into the canal. The leg is in external rotation, extension, and adduction to get proper excursion of the femur.
In order to obtain proper femoral exposure for cementing, the surgeon should extend the incision 2 cm proximally to about the level of the ASIS (Fig. 1). The incision is made over the tensor fascia lata (TFL) muscle angled along the course of the TFL fibers down to the level of the fascia. The dissection is then continued medial to the TFL down to capsule as previously described [16]. This includes identifying and ligating the lateral femoral circumflex vessels, capsulotomy, neck osteotomy, femoral head removal, acetabular preparation, and reaming followed by cup placement. In patients with ligamentous laxity, we aim to keep the vertical band of the iliofemoral ligament mostly intact for increased postoperative stability in the anterior capsule. Once the acetabular component is in place, the femoral exposure can begin. The femoral hook is placed around the femur making sure to hug the vastus lateralis circumferentially. If the hook is placed too posteriorly or medially there are neurovascular bundles at risk. Once the femoral hook is in position, the bed is placed in approximately 20° of trendelenberg and the foot of the bed is dropped to approximately 45°. The femoral elevator is attached
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to the bed and the femoral hook is secured to the elevator. In order to get better exposure of the femur, the conjoined tendon and superior capsule must be released. In order to release the conjoined tendon, an interval must be created between the conjoined tendon and the piriformis. After establishing an interval, the conjoined tendon can be freely released [17]. As the conjoined tendon retracts, the superior capsule retracts with it and it allows the inner aspect of the posterior trochanter to be exposed. Once proper release is obtained, the femur is placed in abduction and the femoral retractor is depressed. This maneuver will allow the piriformis to flip behind the trochanter and move it from the surgical field. Afterwards, we place the leg in increasing amounts of external rotation and adduction to achieve direct access to the femoral canal. Because of this technique, we are able to keep the piriformis insertion intact (Fig. 2). The entry point into the femoral canal is a critical step especially in cemented femoral stems. The surgeon should utilize a posterolateral entry point into the canal in order to have the ability to place the cemented stem in neutral position within the femoral canal (Fig. 3). If the stem is not placed neutrally, there is not sufficient room for the cement to create a 2 mm mantle circumferentially, and mantle defects can lead to complications long term such as osteolysis and aseptic loosening [18] (Fig. 4). After marking the entry point with an electrocautery, the canal can be broached using either a high-speed burr or a box osteotome. Following entry to the canal we will place the canal finder into the canal. This allows us to set our anteversion by compressing the cancellous bone medially and also to position the leg to make sure there is no soft tissue impingement when the canal finder sits neutrally in the canal (Fig. 5). Broaching the canal is done in standard fashion; beginning two sizes below our planned stem size. It is important to note how the broach is sitting in the canal. The distance from the cortical bone to the implant templated on the preoperative plan should be approximately the same when grossly visualized during surgery. This will help the surgeon assess neutral stem placement and prevent any varus or valgus error. The
Figure 4 – (A) Posterior entry point with corresponding stem alignment. Posterior entry allows for neutral stem alignment in the sagittal plane. (B) Anterior entry point with corresponding stem alignment. An anterior point complicates neutral stem placement increasing the likelihood of mantle defect.
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Figure 5 – (A) Canal finder within canal demonstrating soft tissue impingement at the surgeon’s fingertip with neutral alignment of the canal finder. (B) Canal finder within the canal clear of the soft tissue with neutral alignment following further adduction of the operative leg.
preoperative plan is also useful for ensuring the gross neck cut is equal to that of the preoperative plan to maintain proper leg length. If this is not the case and the residual neck is longer than planned, the surgeon can calcar ream in order to remove the excess cortical bone to achieve the ideal stem placement (Fig. 6). Once the correctly sized broach is within the canal, a trial neck and head is placed, the hip is reduced, followed by provocative testing for stability. Testing is performed by passively externally rotating and adducting the leg in neutral position, as well as in extension. The goal is to maintain full range of motion, avoiding neck-socket impingement in external rotation and extension in order to prevent any anterior dislocation. At this point, we assess clinical leg length, radiographic leg length, and broach appearance within the canal on the image intensifier. Once the surgeon is satisfied with the sizing of the stem and the neck, cement preparation begins. Third-generation cement technique is utilized [18,19]. As the surgical technician mixes the cement with the help of a vacuum, the
Figure 7 – Placement of cement restrictor 1.5 cm distal to the prosthesis tip with the collar position marked on the restrictor inserter.
Figure 6 – Intraoperative fluoroscopy demonstrating insufficient neck cut, thus necessitating calcar reaming.
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Figure 8 – Cement pressurization showing pressurization attachment and surgeon digitally pressurizing the medial neck for increased tactile feel.
surgeon can plan the cement restrictor. The final prosthesis is used in order to measure the restrictor position at 1.5 2 cm distal to the prosthesis tip starting from the level at which the collar will sit in the canal (Fig. 7). After the restrictor is placed, the canal is thoroughly irrigated with pulse lavage. The irrigation is performed systematically in quadrants; posterior, medial, anterior, and lateral at both the distal and proximal aspects of the canal. The canal is then filled with absorbent vaginal packing in order to dry the cancellous bone. While the canal dries, a cement centralizer is placed onto the prosthesis and the cement is loaded into a cement gun. Before the cement can be placed into the canal, the proper consistency must be obtained. The cement is at a proper consistency once
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a 1 cm segment of cement extruded from the nozzle of the cement gun no longer bends to gravity, it no longer has its initial shine, and it no longer sticks to a gloved finger. It is important to ensure hypotensive anesthesia during this portion of the procedure to minimize bleeding and maintain a proper bed for cement interdigitation. Cement is then inserted into the canal, slowly, from distal to proximal. Once the canal is filled, the cement must be pressurized in order to increase the interdigitation of the cement into the cancellous bone. This is achieved by adding the pressurizing attachment to the cement gun followed by the surgeon digitally pressurizing the medial portion of the canal (Fig. 8). By using their finger, the surgeon is able to get a tactile sensation of the amount of pressurization as it increases with cement gun injection. After filling and pressurizing the canal, the stem can be placed. The stem is coated with cement prior to insertion to prevent any marrow contents from adhering directly to the implant. Stem placement is critical as previously discussed, and must be placed in a neutral position to prevent any long-term complications. The version must also be appropriate and this is checked before the final position is held in place. Any excess cement is removed, followed by a final digital pressurization laterally so that a small fingerprint is apparent in the lateral shoulder on postoperative x-ray. The final step of the procedure is to reduce the hip and reassess leg length and provocative stability testing. It is imperative to ensure that the final construct remains stable. The incision is then closed layer-by-layer to avoid any potential spaces where hematoma or seroma could form. Upon completion of surgery, the postoperative x-rays should look identical to the preoperative plan with desired leg length realized and exceptional clinical stability (Fig. 9).
Figure 9 – Postoperative film compared to preoperative template. Proper offset, implant positioning and canal fill is achieved.
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4. Conclusion Utilizing a cemented femoral stem in high-risk populations may prevent early periprosthetic fractures. Patients with pathologies leading to poor bone quality are at an increased risk of periprosthetic fracture due to the tighter fit design of uncemented stems. Cemented stems have shown good long term survival, comparing favorably to uncemented fixation in some studies [20]. We choose to use collared, composite beam stems because they have been shown to have the lowest incidence of periprosthetic fractures between cemented implant designs. Proper femoral exposure through the DAA is the key to obtaining ideal cemented fixation. The exposure can be achieved without release of the piriformis tendon with appropriate leg manipulation and conjoined tendon release. Stem insertion must be neutral in both the coronal and sagittal planes in order to avoid cement mantle defects that can be associated with long-term complications. With meticulous preoperative planning and reproducible surgical technique, cement fixation is easily achievable through the DAA.
Disclosure Jose A Rodriguez: Paid consultant for Medacta, Exactech, Conformis, and Smith & Nephew.
R E F E R E N C E S
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