A New Femoral Cement Restrictor Ashok John
Samuel
Paul, MBBS,
Pattison Hodgkinson,
FRCS,* and
MB, ChB, FRCSt
Abstract: The authors report on the clinical trial of a new femoral cement restrictor for use during hip arthroplasty. Instrumentation and technique are described. The restrictor has three components made of high-density polyethylene that fit one inside the other and is available in small, medium, and large sizes. The advantages of this new restrictor are ease of use and secure fixation in the femoral canal when deployed. Because of its inherent strength and design, small particles do not break off during insertion. The apex of the restrictor points proximally and is cupped. This helps in centralizing the stem. It also assists in obtaining good cement pressurization as it does not distally migrate in the femoral canal when pressurization is attempted. Aiso, no cement escapes distally beyond it. Furthermore, should revision surgery be required, the restrictor can be easily removed without the need for windowing the femoral cortex. Key words: femoral cement restrictor, hip arthroplasty.
Materials and Methods
4). Within the lower end of the restrictor there is a metal ball bearing (Fig. 3), which appears on postoperative radiographs as a radiopaque spot (Fig. 5). The restrictor comes in three s i z e s - - s m a l l , medium, and l a r g e - - a n d fits femoral canals of diameters ranging from 8 m m to 23 m m .
The cement restrictor is m a d e of three high-density polyethylene (HDPE) components, 2 "leafed" cylinders, and an inverted cone. The cylinders are slotted one inside the other and the cone is secured centrally. The leaves have flanged tips to ensure good fixation. The HDPE c o m p o n e n t s fit one inside the other and w h e n deployed they spread out like an umbrella. The leaves also interdigitate w h e n deployed, and they prevent any cement leakage beyond the plug. The restrictor is secured in a plastic holder (Fig. 1) and loaded onto the introducer, making sure that the restrictor is properly seated (Fig. 2). Once this is done, the screw at the top end of the introducer is loosened and the plug is inserted into the femoral canal to the desired level by checking the markings on the introducer (Fig. 3). The handle of the introducer is then squeezed; this withdraws the inverted cone into the space in the center of the two leafed cylinders and acts as a wedge, deploying the plug that spreads out, and is firmly secured in the femoral canal (Fig.
Discussion Femoral cement restrictors are widely used during cemented hip arthroplasty, and it is well established that their use improves femoral c o m p o n e n t fixation.l,3 The original restrictors were m a d e of metal but more recent ones are m a d e of high-density polyethylene 5 and acrylate. 6 In 1981 Mallory 4 reported the use of plastic plugs and in 1984 Wroblewski 7 reported the use of b o n e plugs. 7 In 1990 Egund 2 described the use of a centralizing device m a d e of highdensity polyethylene that fits over the tip of the stem of the introducer. High-density polyethylene restrictors are widely available. The ones m o r e c o m m o n l y used are often thin and flimsy, and at times small particles break off during insertion and b e c o m e difficult to centralize. Furthermore, because the restrictors deform easily
From the *University of Manchester, Manchester, United Kingdom and J-Ancoats Hospital, Manchester, United Kingdom.
Reprint requests: A. S. Paul, Tutor in Orthopaedics, c/o Ancoats Hospital, Oldmill Street, Manchester M4 6EB, United Kingdom.
411
412
The Journal of Arthroplasty Vol. 7 Supplement 1992
Fig. 1. Components of the femoral cement restrictor: an introducer, with markings and screw at proximal end, and the three parts of the restrictor. Note two leafed cylinders, one inside the other, and the metal ball in the base of the cone. The plastic loader.
Fig. 2. Restrictor is assembled and loaded onto introducer.
Fig. 3. Components just before insertion.
and are designed with the apex pointing distally, they migrate distally in the canal w h e n pressurization is attempted. Removal of HDPE restrictors at revision surgery is often very difficult unless the femoral cortex is w i n d o w e d , as the restrictor tends to migrate distally. The n e w femoral cement restrictor was designed to overcome these problems. Its apex points
proximally, and w h e n in place it does not migrate, even w h e n pressurized. This can be confirmed on postoperative radiographs by measuring the distance from the cut in the femoral neck to the radiopaque spot. This distance is checked perioperatively and selected with the help of the markings o n the stem of the introducer. The femoral c e m e n t restrictor is m o r e
Femoral Cement Restrictor
•
Paul and Hodgkinson
413
Fig. 4. Shape of restrictor when deployed, Note that the leaves interdigitate and spread.
problems were encountered with the introducer. The tendency was to place the plug in a m o r e distal position than necessary. The introducer has n o w been modified, and practice has improved the positioning of the restrictor. There have been no loose fragments of material found in the canal. Femoral cement restrictors have b e e n used in our hospital for m o r e than a year and we r e c o m m e n d its use. Furthermore, should revision be required, the n e w femoral cement restrictor, by nature of its design, should allow for fairly easy removal by drilling a hole through its middle.
References
Fig. 5. Postoperative radiograph, showing position of the plug. Note that there is no cement beyond the plug in the femoral canal.
rigid, does not deform, and allows centralization of the femoral stem by virtue of its cupped apex. The restrictor's position can be confirmed by the radiopaque ball bearing on postoperative radiographs. We have had excellent results in our series of 25 patients. The restrictor has been used for cemented total hip arthroplasties and hemiarthroplasties. In all patients the stem and plug were well centralized. There was no cement beyond the plug and it had not migrated distally. In two early cases, some technical
1. Beim GM: Intramedullary plugs in cemented hip arthroplasty. J Arthoplasty 4:139, 1989 2. Egund N: Improved positioning of the femoral stem with a centralizing device, Acta Orthop Scand 6:236, 1990 3. Harris WH, McGann WA: Loosening of the femoral component after use of the medullary plug cementing technique. J Bone Joint Surg 66A:1064, 1986 4. Mallory ON: A plastic intramedullary plug for total hip arthroplasty. Clin Orthop 155:37, 1981 5. Noble PC, Hammerman SM, Alexander JW et al: Innovation in cementing techniques in total hip replacement. Scientific exhibition Annual Meeting of the American Academy of Orthopaedic Surgeons, San Francisco, CA, 1987 6. Oh I, Carlson CE, Tomford MW, Harris WF: Improved fixation of the femoral component after total hip replacement using a metha-acrylate intramedullary plug. J Bone Joint Surg 60A:680, 1973 7. Wroblewski BM, Van Der Rijt A: Intramedullary cancellous bone block to improve femoral stem fixation in Charnley low-friction arthroplasty. J Bone Joint Surg 66A:639, 1984
Samuel
Paul, MBBS,
Pattison Hodgkinson,
FRCS,* and
MB, ChB, FRCSt
Abstract: The authors report on the clinical trial of a new femoral cement restrictor for use during hip arthroplasty. Instrumentation and technique are described. The restrictor has three components made of high-density polyethylene that fit one inside the other and is available in small, medium, and large sizes. The advantages of this new restrictor are ease of use and secure fixation in the femoral canal when deployed. Because of its inherent strength and design, small particles do not break off during insertion. The apex of the restrictor points proximally and is cupped. This helps in centralizing the stem. It also assists in obtaining good cement pressurization as it does not distally migrate in the femoral canal when pressurization is attempted. Aiso, no cement escapes distally beyond it. Furthermore, should revision surgery be required, the restrictor can be easily removed without the need for windowing the femoral cortex. Key words: femoral cement restrictor, hip arthroplasty.
Materials and Methods
4). Within the lower end of the restrictor there is a metal ball bearing (Fig. 3), which appears on postoperative radiographs as a radiopaque spot (Fig. 5). The restrictor comes in three s i z e s - - s m a l l , medium, and l a r g e - - a n d fits femoral canals of diameters ranging from 8 m m to 23 m m .
The cement restrictor is m a d e of three high-density polyethylene (HDPE) components, 2 "leafed" cylinders, and an inverted cone. The cylinders are slotted one inside the other and the cone is secured centrally. The leaves have flanged tips to ensure good fixation. The HDPE c o m p o n e n t s fit one inside the other and w h e n deployed they spread out like an umbrella. The leaves also interdigitate w h e n deployed, and they prevent any cement leakage beyond the plug. The restrictor is secured in a plastic holder (Fig. 1) and loaded onto the introducer, making sure that the restrictor is properly seated (Fig. 2). Once this is done, the screw at the top end of the introducer is loosened and the plug is inserted into the femoral canal to the desired level by checking the markings on the introducer (Fig. 3). The handle of the introducer is then squeezed; this withdraws the inverted cone into the space in the center of the two leafed cylinders and acts as a wedge, deploying the plug that spreads out, and is firmly secured in the femoral canal (Fig.
Discussion Femoral cement restrictors are widely used during cemented hip arthroplasty, and it is well established that their use improves femoral c o m p o n e n t fixation.l,3 The original restrictors were m a d e of metal but more recent ones are m a d e of high-density polyethylene 5 and acrylate. 6 In 1981 Mallory 4 reported the use of plastic plugs and in 1984 Wroblewski 7 reported the use of b o n e plugs. 7 In 1990 Egund 2 described the use of a centralizing device m a d e of highdensity polyethylene that fits over the tip of the stem of the introducer. High-density polyethylene restrictors are widely available. The ones m o r e c o m m o n l y used are often thin and flimsy, and at times small particles break off during insertion and b e c o m e difficult to centralize. Furthermore, because the restrictors deform easily
From the *University of Manchester, Manchester, United Kingdom and J-Ancoats Hospital, Manchester, United Kingdom.
Reprint requests: A. S. Paul, Tutor in Orthopaedics, c/o Ancoats Hospital, Oldmill Street, Manchester M4 6EB, United Kingdom.
411
412
The Journal of Arthroplasty Vol. 7 Supplement 1992
Fig. 1. Components of the femoral cement restrictor: an introducer, with markings and screw at proximal end, and the three parts of the restrictor. Note two leafed cylinders, one inside the other, and the metal ball in the base of the cone. The plastic loader.
Fig. 2. Restrictor is assembled and loaded onto introducer.
Fig. 3. Components just before insertion.
and are designed with the apex pointing distally, they migrate distally in the canal w h e n pressurization is attempted. Removal of HDPE restrictors at revision surgery is often very difficult unless the femoral cortex is w i n d o w e d , as the restrictor tends to migrate distally. The n e w femoral cement restrictor was designed to overcome these problems. Its apex points
proximally, and w h e n in place it does not migrate, even w h e n pressurized. This can be confirmed on postoperative radiographs by measuring the distance from the cut in the femoral neck to the radiopaque spot. This distance is checked perioperatively and selected with the help of the markings o n the stem of the introducer. The femoral c e m e n t restrictor is m o r e
Femoral Cement Restrictor
•
Paul and Hodgkinson
413
Fig. 4. Shape of restrictor when deployed, Note that the leaves interdigitate and spread.
problems were encountered with the introducer. The tendency was to place the plug in a m o r e distal position than necessary. The introducer has n o w been modified, and practice has improved the positioning of the restrictor. There have been no loose fragments of material found in the canal. Femoral cement restrictors have b e e n used in our hospital for m o r e than a year and we r e c o m m e n d its use. Furthermore, should revision be required, the n e w femoral cement restrictor, by nature of its design, should allow for fairly easy removal by drilling a hole through its middle.
References
Fig. 5. Postoperative radiograph, showing position of the plug. Note that there is no cement beyond the plug in the femoral canal.
rigid, does not deform, and allows centralization of the femoral stem by virtue of its cupped apex. The restrictor's position can be confirmed by the radiopaque ball bearing on postoperative radiographs. We have had excellent results in our series of 25 patients. The restrictor has been used for cemented total hip arthroplasties and hemiarthroplasties. In all patients the stem and plug were well centralized. There was no cement beyond the plug and it had not migrated distally. In two early cases, some technical
1. Beim GM: Intramedullary plugs in cemented hip arthroplasty. J Arthoplasty 4:139, 1989 2. Egund N: Improved positioning of the femoral stem with a centralizing device, Acta Orthop Scand 6:236, 1990 3. Harris WH, McGann WA: Loosening of the femoral component after use of the medullary plug cementing technique. J Bone Joint Surg 66A:1064, 1986 4. Mallory ON: A plastic intramedullary plug for total hip arthroplasty. Clin Orthop 155:37, 1981 5. Noble PC, Hammerman SM, Alexander JW et al: Innovation in cementing techniques in total hip replacement. Scientific exhibition Annual Meeting of the American Academy of Orthopaedic Surgeons, San Francisco, CA, 1987 6. Oh I, Carlson CE, Tomford MW, Harris WF: Improved fixation of the femoral component after total hip replacement using a metha-acrylate intramedullary plug. J Bone Joint Surg 60A:680, 1973 7. Wroblewski BM, Van Der Rijt A: Intramedullary cancellous bone block to improve femoral stem fixation in Charnley low-friction arthroplasty. J Bone Joint Surg 66A:639, 1984
