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Intramedullary plugs in total hip arthroplasty
Intramedullary Plugs in Total Hip Arthroplasty A Comparative Study Niels O. B. T h o m s e n , M D , T i m T o f t g a a r d J e n s e n , M D , B e n t U h r b r a n d , M D , a n d Niels Boel M o s s i n g , M D
Abstract: The quality of cement packing was radiographically evaluated using three different types of intramedullary plugs in 77 total hip arthroplasties. The Thackray polyethylene plug (38 mm, disc-shaped), with its large and flexible diameter, was best able to seal the femoral canal and produced significantly better cement packing compared to both the autologous bone plug and the Richard polyethylene plug (18.5 ram, bullet-shaped). Key words: total hip arthroplasty, intramedullary plug.
Loosening of the femoral stem is the most frequent cause of failure after total hip arthroplasty (THA).5"7 Improper cementation has been found to be significantly related to this failure. 4"5 In 1978, Oh et al. presented a method to improve fixation of the prosthesis by sealing the distal part of the femoral canal with an intramedullary plug. 7 The plug prevents cement from being displaced distally in the canal and increases the intramedullary pressure at the bone-cement interface during insertion of the stem. Since 1981 we have used polyethylene plugs. However, in a number of cases the plug failed to seal the femoral canal properly. Today various types of plugs are available, but only a few studies concerning their use have been published.~,6 This study evaluated cement packing in THA using two different polyethylene plugs and a perioperatively prepared autologous bone plug.
head (Fig. 1), the size depending on the size of the drill used in preparing the medullary canal (9, 11, 13, or 15 ram). The Richards polyethylene plug was 18.5 mm and bullet-shaped, with two flanges (Fig. 1). The Thackray polyethylene plug was 38 ram, disc-shaped, and had spiral-slanted cuts (Fig. 1). Seventy-seven patients were included in our study. Twenty-five patients were allocated to an autologous bone plug (median age, 69 years; range, 48-80 years), but in three patients it was impossible to prepare the bone plug because of a severely destroyed femoral head. Twenty-nine patients were allocated to the Richards polyethylene plug (median age, 70 years; range, 52-88 years) and 23 patients to the Thackray polyethylene plug (median age, 75 years; range, 59-81 years). All operations were performed using a posterior approach. The femoral canal was opened with a flexible drill and was reamed according to the largest suitable stem. Drilling was performed distally to the decided positioning of the medullary plug to prepare a rim for the plug. An inserter, marked in centimeters, secured proper placement. The plug was placed about 20 mm below the expected position of the tip of the stem. The femoral canal was flushed and dried and, using a cement gun, was filled in a retrograde direction with a doughy mix of Simplex methyl methacrylate (3 minutes mixing time). A suction catheter was used during the introduction of the ce-
Materials and Methods In a prospective randomized study, three different types of intramedullary plugs in THA were tested. The bone plug was made from the removed femoral From the Department of Orthopaedic Surgery, SoenderborgHospital, Soenderborg, Denmark. Reprint requests: Niels O. B. Thomsen, MD, Department of Orthopaedic Surgery, Gentofte Hospital, DK-2900 Hellerup, Denmark.
415
416
The Journal of Arthroplasty Vol. 7 Supplement 1992 small amounts of cement extending distally to the plug; poor, insufficient cement packing in three or more zones and cement often extending distally to the plug.
Results
Fig. 1. (Left) Bone plug drills and bone plug. (Top right) Richards polyethylene plug. (Bottom right) Thackray polyethylene plug.
ment to remove blood from the femoral canal. In all cases the Richards series II prosthesis, the largest suitable stem, was used. Cortical indexes were measured on preoperative radiographs. 2 Postoperative standardized radiographs were analyzed for quality of cement packing in five zones, as described by Kristiansen and Jensen. 4 The valgns-varus coefficient was measured. 4 The location of the plug in relation to the tip of the prosthesis and the a m o u n t of cement extending distally to the plug were recorded. The quality of cement packing was defined as follow: excellent, at least 2 m m of cement surrounding the stem, no voids, and no radiolucent lines; acceptable, less than 2 m m of cement in one or two zones, locally radiolucent lines of less than 1 m m and only
There were no differences in the three groups regarding age distribution, cortical indexes, and valgus-varus coefficients (Table 1). The quality of cement packing with the Thackray polyethylene plug was significantly better compared to both the bone plug and the Richards polyethylene plug (Mann-Whitney U test, P = .02 and P = .03, respectively, Table 2). There was a tendency toward poor-quality cement packing in patients with a cortical index below the median index (.166), but the result was not significant. The median distances from the tip of the femoral stem to the plug were 32 m m for the bone plug, 39 m m for the Richards plug, and 24 m m for the Thackray plug. This suggests that the Richards plug, compared to the Thackray plug, was pushed distally in the femoral canal during cementation (Mann-Whitney U test, P = .03) (Fig. 2B,C). Cement extending distally to the plug was seen in seven cases in the bone plug group (Fig. 2A) and in five cases in the Richards plug group but was not seen at all in the Thackray plug group.
Discussion Stauffer reported a probability of 29.9% for loosening of the femoral c o m p o n e n t 10 years after insertion of a Charnley prosthesis, without plugging the femoral canal. 9 Lindberg and Carlson reported 40% stem loosening in the Brunswik total hip prosthesis after 5 years. 5 New techniques to improve the cementation of the femoral component, such as pressurized cementation and the use of intramedullary plugging, have been introduced during the last decade. In 1978, Oh et al. demonstrated that a close-fitting plug increases the
Table 1. Results of 74 THAs Using Three Different Types of Intramedullary Plugs
Type of Plug Autologous bone Richard Thackray
No. of Patients
Average
22 29 23
0.16 0.16 0.15
Cortical Index Range
0.06-0.26 0.08-0.25 0.07-0.21
Valgus-Varus Coefficient Average Range
0.61 0.59 0.53
0.26-0.76 0.26-0.73 0.28-0.75
Intramedullary Plugs in THA
Table 2. Quality of Cement Packing in 74 THAs Using Three Different Types of Intramedullary Plugs Type of Plug Autologous bone Richard Thackray
Quality of Cement Packing Excellent Acceptable 5 10 14
10 11 8
Poor
7 8 1
pressure during insertion of the f e m o r a l stem, thereby allowing cement into the trabecular lining of the canal. 7 Using this technique, Harris et al. reported only 1.7% definite loosening after 5 years. 3 Today, although several types of plugs are available, routine application of a plug does not guarantee proper cementation. Satisfactory results using bone plugs have been reported. 1~ In a c c o r d a n c e w i t h Mallory et al., 6 we
•
Thomsen et al.
417
found this technique to be unreliable. In some cases the femoral head was unfit for use, and it was difficult to prepare a close-fitting plug in patients with a wide medullary canal (Fig. 2A). Polyethylene plugs are easily inserted, and some studies found t h e m to be superior to bone plugs in w i t h s t a n d i n g pressurized c e m e n t a t i o n in vitro. 1,6 This is in accordance with our findings. Cement plugs have been used by several authors, 3,7 but this type of plug is not c o m m o n in Scandinavia and we have no experience with it. In some cases pieces of the Thackray plug broke off during insertion. Some studies have s h o w n that an a b u n d a n c e of polyethylene particles in the medullary canal m a y cause a cellular reaction, leading to osteolytic destruction of the bone. 8"~° However, the broken pieces are easily flushed out w h e n preparing the femoral canal before cementation.
Fig. 2. (A) Cement extends distally to the bone plug, causing poor cement packing. (B) Richards polyethylene plug pushed distally in the canal. (C) Thackray polyethylene plug firmly attached in the canal, giving excellent cement packing.
418
The Journal of Arthroplasty Vol. 7 Supplement 1992
We found the best quality of cement packing using a polyethylene plug with a large and flexible diameter (Thackray). This is in accordance with the findings of Beim et al. 1 The diameter of the Richards p l u g - - e v e n t h o u g h w e used the largest availab l e - d i d not firmly secure the sealing in all cases. A large flexible plug is especially important if the femoral stem is longer t h a n 5 inches, because the diameter of the femoral canal often expands distally. On the basis of our study we conclude that: (1) an autologous b o n e plug is not available for patients with severely destroyed femoral heads, and sufficient sealing of the canal is often difficult to obtain; (2) the bullet-shaped polyethylene plug (Richards) is easy to insert, but firm a t t a c h m e n t in the canal is not always obtained; (3) the polyethylene plug with a wide and flexible diameter (Thackray) gave the best cement packing around the stem.
References I. Beim GM, Lavernia C, Convery FR: Intramedullary plugs in cemented hip arthroplasty. J Arthroplasty 4: 139, 1989
2. Fredensborg N, Nilsson BE: Cortical index of the femoral neck. Acta Radiol 18:492, 1977 3. Harris WH, McGann WA: Loosening of the femoral component after use of the medullary-plug cementing technique. J Bone Joint Surg 64A:I063, 1982 4. Kristiansen B, Jensen JS: Biomechanical factors in loosening of the Stanmore hip. Acta Orthop Scand 56: 21, 1985 5. Lindberg HO, Carlsson AS: Mechanical loosening of the femoral component in total hip replacement: Brunswik design. Acta Orthop Scand 54:557, 1983 6. Mallory TH: A plastic intermedullary plug for total hip arthroplasty. Clin Orthop 155:37, 1981 7. Oh I, Carlson CE, Tomford MW, Harris WH: Improved fixation of the femoral component after total hip replacement using a methacrylate intrameduUary plug. J Bone Joint Surg 60A:608, 1978 8. Ohlin A, Kindblom LG: The ultrastructure surrounding the Christiansen total hip. Acta Orthop Scand 59: 629, 1988 9. Stauffer RN: Ten-year follow-up study of total hip replacement. J Bone Joint Surg 64A:983, 1982 10. Wroblewski BM: Wear of high-density polyethylene on bone and cartilage. J Bone Joint Surg 61B:498, 1979 11. Wroblewski BM, Van der Rijt A: Intramedullary cancellus bone plug to improve femoral stem fixation in the Charnley low-friction arthroplasty. J Bone Joint Surg 66A:639, 1984
Abstract: The quality of cement packing was radiographically evaluated using three different types of intramedullary plugs in 77 total hip arthroplasties. The Thackray polyethylene plug (38 mm, disc-shaped), with its large and flexible diameter, was best able to seal the femoral canal and produced significantly better cement packing compared to both the autologous bone plug and the Richard polyethylene plug (18.5 ram, bullet-shaped). Key words: total hip arthroplasty, intramedullary plug.
Loosening of the femoral stem is the most frequent cause of failure after total hip arthroplasty (THA).5"7 Improper cementation has been found to be significantly related to this failure. 4"5 In 1978, Oh et al. presented a method to improve fixation of the prosthesis by sealing the distal part of the femoral canal with an intramedullary plug. 7 The plug prevents cement from being displaced distally in the canal and increases the intramedullary pressure at the bone-cement interface during insertion of the stem. Since 1981 we have used polyethylene plugs. However, in a number of cases the plug failed to seal the femoral canal properly. Today various types of plugs are available, but only a few studies concerning their use have been published.~,6 This study evaluated cement packing in THA using two different polyethylene plugs and a perioperatively prepared autologous bone plug.
head (Fig. 1), the size depending on the size of the drill used in preparing the medullary canal (9, 11, 13, or 15 ram). The Richards polyethylene plug was 18.5 mm and bullet-shaped, with two flanges (Fig. 1). The Thackray polyethylene plug was 38 ram, disc-shaped, and had spiral-slanted cuts (Fig. 1). Seventy-seven patients were included in our study. Twenty-five patients were allocated to an autologous bone plug (median age, 69 years; range, 48-80 years), but in three patients it was impossible to prepare the bone plug because of a severely destroyed femoral head. Twenty-nine patients were allocated to the Richards polyethylene plug (median age, 70 years; range, 52-88 years) and 23 patients to the Thackray polyethylene plug (median age, 75 years; range, 59-81 years). All operations were performed using a posterior approach. The femoral canal was opened with a flexible drill and was reamed according to the largest suitable stem. Drilling was performed distally to the decided positioning of the medullary plug to prepare a rim for the plug. An inserter, marked in centimeters, secured proper placement. The plug was placed about 20 mm below the expected position of the tip of the stem. The femoral canal was flushed and dried and, using a cement gun, was filled in a retrograde direction with a doughy mix of Simplex methyl methacrylate (3 minutes mixing time). A suction catheter was used during the introduction of the ce-
Materials and Methods In a prospective randomized study, three different types of intramedullary plugs in THA were tested. The bone plug was made from the removed femoral From the Department of Orthopaedic Surgery, SoenderborgHospital, Soenderborg, Denmark. Reprint requests: Niels O. B. Thomsen, MD, Department of Orthopaedic Surgery, Gentofte Hospital, DK-2900 Hellerup, Denmark.
415
416
The Journal of Arthroplasty Vol. 7 Supplement 1992 small amounts of cement extending distally to the plug; poor, insufficient cement packing in three or more zones and cement often extending distally to the plug.
Results
Fig. 1. (Left) Bone plug drills and bone plug. (Top right) Richards polyethylene plug. (Bottom right) Thackray polyethylene plug.
ment to remove blood from the femoral canal. In all cases the Richards series II prosthesis, the largest suitable stem, was used. Cortical indexes were measured on preoperative radiographs. 2 Postoperative standardized radiographs were analyzed for quality of cement packing in five zones, as described by Kristiansen and Jensen. 4 The valgns-varus coefficient was measured. 4 The location of the plug in relation to the tip of the prosthesis and the a m o u n t of cement extending distally to the plug were recorded. The quality of cement packing was defined as follow: excellent, at least 2 m m of cement surrounding the stem, no voids, and no radiolucent lines; acceptable, less than 2 m m of cement in one or two zones, locally radiolucent lines of less than 1 m m and only
There were no differences in the three groups regarding age distribution, cortical indexes, and valgus-varus coefficients (Table 1). The quality of cement packing with the Thackray polyethylene plug was significantly better compared to both the bone plug and the Richards polyethylene plug (Mann-Whitney U test, P = .02 and P = .03, respectively, Table 2). There was a tendency toward poor-quality cement packing in patients with a cortical index below the median index (.166), but the result was not significant. The median distances from the tip of the femoral stem to the plug were 32 m m for the bone plug, 39 m m for the Richards plug, and 24 m m for the Thackray plug. This suggests that the Richards plug, compared to the Thackray plug, was pushed distally in the femoral canal during cementation (Mann-Whitney U test, P = .03) (Fig. 2B,C). Cement extending distally to the plug was seen in seven cases in the bone plug group (Fig. 2A) and in five cases in the Richards plug group but was not seen at all in the Thackray plug group.
Discussion Stauffer reported a probability of 29.9% for loosening of the femoral c o m p o n e n t 10 years after insertion of a Charnley prosthesis, without plugging the femoral canal. 9 Lindberg and Carlson reported 40% stem loosening in the Brunswik total hip prosthesis after 5 years. 5 New techniques to improve the cementation of the femoral component, such as pressurized cementation and the use of intramedullary plugging, have been introduced during the last decade. In 1978, Oh et al. demonstrated that a close-fitting plug increases the
Table 1. Results of 74 THAs Using Three Different Types of Intramedullary Plugs
Type of Plug Autologous bone Richard Thackray
No. of Patients
Average
22 29 23
0.16 0.16 0.15
Cortical Index Range
0.06-0.26 0.08-0.25 0.07-0.21
Valgus-Varus Coefficient Average Range
0.61 0.59 0.53
0.26-0.76 0.26-0.73 0.28-0.75
Intramedullary Plugs in THA
Table 2. Quality of Cement Packing in 74 THAs Using Three Different Types of Intramedullary Plugs Type of Plug Autologous bone Richard Thackray
Quality of Cement Packing Excellent Acceptable 5 10 14
10 11 8
Poor
7 8 1
pressure during insertion of the f e m o r a l stem, thereby allowing cement into the trabecular lining of the canal. 7 Using this technique, Harris et al. reported only 1.7% definite loosening after 5 years. 3 Today, although several types of plugs are available, routine application of a plug does not guarantee proper cementation. Satisfactory results using bone plugs have been reported. 1~ In a c c o r d a n c e w i t h Mallory et al., 6 we
•
Thomsen et al.
417
found this technique to be unreliable. In some cases the femoral head was unfit for use, and it was difficult to prepare a close-fitting plug in patients with a wide medullary canal (Fig. 2A). Polyethylene plugs are easily inserted, and some studies found t h e m to be superior to bone plugs in w i t h s t a n d i n g pressurized c e m e n t a t i o n in vitro. 1,6 This is in accordance with our findings. Cement plugs have been used by several authors, 3,7 but this type of plug is not c o m m o n in Scandinavia and we have no experience with it. In some cases pieces of the Thackray plug broke off during insertion. Some studies have s h o w n that an a b u n d a n c e of polyethylene particles in the medullary canal m a y cause a cellular reaction, leading to osteolytic destruction of the bone. 8"~° However, the broken pieces are easily flushed out w h e n preparing the femoral canal before cementation.
Fig. 2. (A) Cement extends distally to the bone plug, causing poor cement packing. (B) Richards polyethylene plug pushed distally in the canal. (C) Thackray polyethylene plug firmly attached in the canal, giving excellent cement packing.
418
The Journal of Arthroplasty Vol. 7 Supplement 1992
We found the best quality of cement packing using a polyethylene plug with a large and flexible diameter (Thackray). This is in accordance with the findings of Beim et al. 1 The diameter of the Richards p l u g - - e v e n t h o u g h w e used the largest availab l e - d i d not firmly secure the sealing in all cases. A large flexible plug is especially important if the femoral stem is longer t h a n 5 inches, because the diameter of the femoral canal often expands distally. On the basis of our study we conclude that: (1) an autologous b o n e plug is not available for patients with severely destroyed femoral heads, and sufficient sealing of the canal is often difficult to obtain; (2) the bullet-shaped polyethylene plug (Richards) is easy to insert, but firm a t t a c h m e n t in the canal is not always obtained; (3) the polyethylene plug with a wide and flexible diameter (Thackray) gave the best cement packing around the stem.
References I. Beim GM, Lavernia C, Convery FR: Intramedullary plugs in cemented hip arthroplasty. J Arthroplasty 4: 139, 1989
2. Fredensborg N, Nilsson BE: Cortical index of the femoral neck. Acta Radiol 18:492, 1977 3. Harris WH, McGann WA: Loosening of the femoral component after use of the medullary-plug cementing technique. J Bone Joint Surg 64A:I063, 1982 4. Kristiansen B, Jensen JS: Biomechanical factors in loosening of the Stanmore hip. Acta Orthop Scand 56: 21, 1985 5. Lindberg HO, Carlsson AS: Mechanical loosening of the femoral component in total hip replacement: Brunswik design. Acta Orthop Scand 54:557, 1983 6. Mallory TH: A plastic intermedullary plug for total hip arthroplasty. Clin Orthop 155:37, 1981 7. Oh I, Carlson CE, Tomford MW, Harris WH: Improved fixation of the femoral component after total hip replacement using a methacrylate intrameduUary plug. J Bone Joint Surg 60A:608, 1978 8. Ohlin A, Kindblom LG: The ultrastructure surrounding the Christiansen total hip. Acta Orthop Scand 59: 629, 1988 9. Stauffer RN: Ten-year follow-up study of total hip replacement. J Bone Joint Surg 64A:983, 1982 10. Wroblewski BM: Wear of high-density polyethylene on bone and cartilage. J Bone Joint Surg 61B:498, 1979 11. Wroblewski BM, Van der Rijt A: Intramedullary cancellus bone plug to improve femoral stem fixation in the Charnley low-friction arthroplasty. J Bone Joint Surg 66A:639, 1984