Tri-Lock Bone Preservation Stem Clinical Results of the Tri-lock BPS Femoral Stem at One Year Follow-Up William L. Healy, M.D. Lahey Clinic Medical Center Burlington, Massachusetts Introduction Cementless femoral stems with a flat, tapered wedge design have performed with success when used in hip replacement procedures with reported ten to fifteen year survivorship from ninety-five to one hundred percent. 1-9 The Tri-lock Femoral Stem (DePuy Orthopaedics, Warsaw, Indiana) is a cementless, flat, tapered wedge femoral stem, which has been used for hip reconstructions since 1981. 1,7,8,9 The clinical success of the Trilock Femoral Stem is based on a simple reproducible surgical technique that achieves initial fixation and allows long term, durable fixation. In 2008, the Tri-lock Femoral Stem was modified in order to improve the proximal geometry of the femoral stem, increase range of motion and stability of the reconstructed hip, facilitate implantation of the stem from any surgical approach, and preserve proximal femoral bone. The new Tri-lock Bone Preservation Stem (BPS) maintained the successful flat tapered wedge design, which was associated with durable fixation and clinical success. Similar to the original Tri-Lock, the Tri-lock BPS Femoral Stem was designed as a broach only femoral system. The new porous coating (Gription, DePuy Orthopaedics, Warsaw, Indiana) on the Tri-Lock BPS offers an enhanced coefficient of friction when compared to Porocoat porous coating, which is on the original Tri-Lock. The author gratefully acknowledges the contributions of Adam Rana, M.D., Jared A. Toman, M.D., and John Garfi, M.D. to this report. WLH
Table 1: Femoral Stem Sizes Stem Size Number Implanted 0 1 1 2 2 2 3 6 4 11 Gription The length of the Tri-lock BPS Femoral Stem was shortened, and the lateral distal tip of the stem was beveled in order to facilitate implantation. This report will present the early clinical results of fiftyseven consecutive Tri-lock BPS Femoral Stems with a minimum of one year follow-up. Methods and Materials Fifty-seven Tri-lock BPS Femoral Stems were implanted in 57 hips in 56 patients who had primary hip replacement operations performed between March 2008 and April 2009. The Tri-lock BPS cohort included 34 men and 22 women. The mean age of the patients was 65.4 years with a range from 17 to 92 years. All patients presented with hip pain and limitation of function. The diagnoses for these 57 hip replacement operations included: 51 osteoarthritis, 5 rheumatoid arthritis, and 1 osteonecrosis. Proximal femoral morphology was classified by the Dorr Classification; 16 Dorr A femurs, 35 Dorr B femurs, and 6 Dorr C femurs. The mean body mass index was 27.9 with a range of 20.6 to 48.2. All 57 operations were performed by one surgeon in one hospital using one surgical approach (modified direct lateral). One standardized clinical pathway was used for all patients, and one clinical team cared for all patients. All 57 hip replacement operations used the Trilock BPS Femoral Stem (DePuy Orthopaedics, Warsaw, Indiana). The most common size implanted was #5 (13 Stems); the median size implanted was #5; the smallest size implanted was #0, and the largest size implanted was #9. All stems were high offset stems. (Table 1) 5 13 6 11 7 7 8 2 9 2 10 0 11 0 12 0 All hips were reconstructed with modular cobalt-chrome femoral heads, which articulated with highly crosslinked polyethylene acetabular liners (Marathon, DePuy Orthopaedics, Warsaw, Indiana). Forty-nine hips used 36 mm femoral heads and eight hips used 32 mm femoral heads. The most common femoral neck length was 8.5 mm (22 femoral heads) with a range of 1.5 mm to 15.5 mm. All hips were reconstructed with a Pinnacle acetabular cup (DePuy Orthopaedics, Warsaw, Indiana). All cups used screw fixation. The most common Pinnacle acetabular cup size used was 54 mm (20 cups). The median cup size was 54 mm, with a range from 52 mm to 64 mm. Clinical and radiographic information was collected prospectively and entered into a computerized joint replacement registry. Patient questionnaires were completed by patients without assistance from the operating surgeon or midlevel practitioner. Clinical evaluation included a 10 point visual analog pain score and the Harris Hip Score. Patients were asked to rate pain by intensity on a 10 point scale and by location of discomfort. Thigh pain was defined as pain in 2
the anterior thigh below the inguinal area, and pain rated 3 or greater on the 10 point scale was considered clinically significant. 10 The mean pre-operative pain score for these patients was 6.6 with a range from 1 to 10. The mean pre-operative Harris Hip Score for these patients was 51.8 with a range from 22 to 72. Radiographic evaluation was performed with a standardized anteroposterior radiograph of the pelvis and hips and a cross table lateral view of the affected hip. The radiographs of the femoral stems were evaluated for implant position, change in implant position, femoral stem subsidence, femoral stem loosening, and implant failure. Ideal implant position was defined as neutral alignment of the stem in the proximal femur with medial cortical contact at the calcar and lateral cortical contact at the lateral shoulder of the femoral stem. Clinical examination was performed at six weeks, one year, and latest follow up. Radiographic examination was performed at six weeks, 1 year, and at latest followup. The mean follow up for these patients was 1.2 years with a range from 1 to 2 years. Minimum follow up was 1 year. Results Fifty-seven primary total hip arthroplasty (THA) procedures were performed on 56 patients. All patients were available for clinical evaluation with minimum one year follow up. Fifty-six of 57 patients were available for radiographic examination with minimum one year follow up. Three complications were encountered following these 57 THA procedures. One intraoperative fracture occurred in a 55 year old male with a Dorr A femur. This was the second case in the series. The fracture was a nondisplaced crack in the calcar, which occurred during insertion of the Tri-Lock BPS femoral stem. The fracture was treated by removing the stem, applying a cerclage wire to the proximal femur proximal to the lesser trochanter, and reimplanting the same femoral component. The patient was treated with foot flat partial weight bearing for six weeks. This complication had no adverse impact on patient outcome. venous thrombosis and one patient had a pulmonary embolus. These thrombo-embolic complications were treated with no adverse impact on patient outcome. Patient reported pain using the 10 point visual analog pain scale improved significantly for all patients after THA. The pain score improved from a mean preoperative pain score of 6.6 (range 1-10) to a mean follow up pain score of 0.5 (range 0-3). Three patients reported a pain score greater than or equal to 3, which was considered clinically significant pain. Two patients reported buttock and trochanteric discomfort. One patient reported only trochanteric discomfort. All three patients were treated with an extended course of physical therapy. One patient was treated with a trochanteric injection of lidocaine/cortisone. No patient complained of thigh pain. (Table 2) Table 2: Post -op Pain Score...0.5 Range...0-3 Thigh Pain...0 Harris Hip Score...85.1 Range...52-96 Complications Intra-Operative Fracture...1 Infection...0 Dislocation...0 D.V.T....1 P.E.............................. 1 Re-operations...0 Revisions...0 Decreased Pain: Yes... 57 (100%) No...0 Improved Function: Yes...55 (96%) No...2 Satisfied with THA: Yes...56 (98%) No...1 Two patients encountered venous thrombo-embolic disease following their THA. One patient had a deep 3
Table 2: Pre-op Hips... 57 Patients... 56 Mean Follow-up (years)... 1.2 Range... 1-2 Minimum... 1 Male... 34 Female... 22 Mean Age (years)... 65.4 Range... 17-92 Mean BMI... 27.9 Range... 20.6-48.2 Diagnosis OA... 51 RA... 5 Osteonecrosis... 1 Dorr Classification A... 16 B...35 C...06 Pain Score...6.6 Range...1-10 Harris Hip Score...51.8 Range...22-72 The Harris Hip Score improved significantly for all 57 patients. The mean pre-operative Harris Hip Score of 51.8 (range 22-72) improved to a mean follow up Harris Hip Score of 85.1 (range 52-96). Pain score and Harris Hip Scores were examined according to Dorr Classification. There was no clinical difference in mean pain score or mean Harris Hip Scores between Dorr Classifications (Table 3). Table 3: Results by Dorr Classification Pain Score Harris Hip Score Pre-op F/U Pre-op F/U Dorr A 6.6 0.5 53.3 83.3 Dorr B 6.5 0.6 52.0 86.0 Dorr C 7.2 0.2 7.0 84.7 All patients were asked outcome questions regarding pain, function, and patient satisfaction. All 57 patients stated that the THA operation with a Tri-lock BPS Femoral Stem was associated with decreased pain. Fiftyfive patients (96%) stated that the THA operation with a Tri-lock BPS Femoral Stem was associated with improved function. The two patients who stated that the operation did not increase their function presented pre-operatively with a rupture of the gluteus medius and minimus muscular tendinous junction, which was discovered and repaired at the time of operation. Fifty-six patients (98%) expressed satisfaction with their THA operation with a Tri-lock BPS Femoral Stem. One patient who was not satisfied complained of a one centimeter leg length discrepancy with the operative side being long. Radiographic review was available for 56 of 57 hips at minimum one year follow up. All femoral stems were in neutral position in the femoral canal with endosteal cortical contact at the medial femoral calcar and at the lateral shoulder of the femoral stem. There was no change in implant position from the initial post-operative radiographs until the follow up radiographs. There was no subsidence of the femoral stems, no loosening of the femoral stems, and no implant failures. Discussion In this series of 57, consecutive primary THA procedures performed with a Tri-lock BPS Femoral Stem, patients generally reported pain relief and improved function as measured by a 10 point visual analog pain score and a Harris Hip Score. Radiographic evaluation noted predictable positioning of the femoral stem in the femoral canal with successful initial fixation. No thigh pain was observed in these 57 patients who were treated with Tri-lock BPS Femoral Stems with minimum one year follow up. In this regard, the Tri-lock BPS Femoral Stem compares favorably with the original Trilock Femoral Stem, which demonstrated a 5.0% incidence of thigh pain (7.0% for cobalt chrome; 3.1% for titanium). 9 One potential explanation for this improvement in thigh pain is the shortening of the Tri-lock BPS Femoral Stem, which reduces the extent of the stem in the femoral diaphysis and places more dependence on proximal metaphyseal fixation. 4
There was no clinical difference in mean pain scores or mean Harris Hip Scores among the three proximal femoral shapes; Dorr A, B, and C. The clinical success of the Tri-lock BPS Femoral Stem at minimum one year follow up may be attributed to its specific design features a straight collarless porous coated modular femoral stem with a flat, tapered wedge design of the intraosseous body that fits into a medial/ lateral slot created in the proximal femoral canal by hand broaching. Axial stability, rotational stability, and initial fixation are provided by wedging the femoral stem into the medial and lateral endosteal cortices. Conclusion In this preliminary series, the Tri-lock BPS Femoral Stem provided successful femoral reconstruction at a minimum one year follow up with successful clinical outcomes and a low rate of complication. On the basis of these findings, we will continue to use the Tri-lock BPS Femoral Stem, and we will re-evaluate this cohort with minimum two year follow-up. In this series, femoral stems were placed in the appropriate position in A/P and lateral planes. One potential risk for shorter femoral stems, which was not observed in this series, is placement in a slightly flexed or extended position. Flexion or extension malposition can be avoided by careful surgical technique, which broaches the proximal femur in a neutral varus/valgus and flexion/ extension position. One potential disadvantage of a flat, tapered wedge femoral stem design is the risk for proximal femoral fracture that may occur with filling of the proximal femoral metaphysis with a metal wedge. In this series, one intraoperative calcar crack was observed at the time of femoral stem implantation into a patient with a Dorr A femur. This fracture was treated with a cerclage wire, and the fracture healed without further complication. Tri-Lock BPS at One Year The strength of this preliminary report of hip replacement surgery with a Tri-lock BPS Femoral Stem is its prospective study design and its objective detailed follow up. There are two major weaknesses to this study. First, this is a preliminary report with minimum one year follow up. The results will have more credibility with a minimum two year follow up. Second, the report is presented by a member of the surgical design team for the Tri-lock BPS Femoral Stem. In an effort to avoid bias in reporting these clinical results, the data was prepared by the department s orthopaedic database coordinator, and the data was audited by two orthopaedic surgeons who have no connection to the Tri-lock BPS Femoral Stem Design Team. 5
References 1. Burt CF, Garvin KL, Otterberg ET, et al. A femoral component inserted without cement in total hip arthroplasty. A study of the Trilock component with average ten-year duration of follow-up. J Bone Joint Surg 1998; 80:952. 2. Keisu KS, Orozco F, Sharkey PF, et al. Primary cementless total hip arthroplasty in octogenarians. Two to eleven-year follow-up. J Bone Joint Surg Am. 2001; 83-A(3):359. Erratum in: J Bone Joint Surg Am 2002 Jan; 84-A: 100. 3. McLaughlin JR, Lee KR. The outcome of total hip replacement in obese and non-obese patients at 10-18 years. J Bone Joint Surg Br 2006;88:1286 4. McLaughlin JR, Lee KR. Total hip arthroplasty with an uncemented femoral component. Excellent results at ten year follow-up. J Bone Joint Surg Br 1997; 79:900. 5. Parvizi J, Keisu KS, Hozack WJ, et al. Primary total hip arthroplasty with an uncemented femoral component. A long-term study of the Taperloc stem. J Arthroplasty. 2004 Feb; 19:151. William L. Healy, M.D. 6. Sakalkale DP, Eng K, Hozack WJ, et al. Minimum 10 year results of a tapered cementless hip replacement. Clin Orthop Relat Res.1999; 138. 7. Teloken MA, Bissett G, Hozack WJ et al. Ten to fifteen year follow-up after total hip arthroplasty with a tapered cobalt-chromium femoral component (Trilock) inserted without cement. J Bone Joint Surg Am. 2002; 84-A:2140. 8. Pellegrini VD Jr, Hughes SS, Evarts CM. A collarless cobalt-chrome femoral component in uncemented total hip arthroplasty. Five-to eight-year follow-up. J Bone Joint Surg Br. 1992; 74:814. 9. Healy WL, Tilzey JF, Iorio R, Specht LM, Sharma S. Prospective Randomized Comparison of Cobalt- Chrome and Titanium Trilock Femoral Stems. Journal of Arthroplasty 2009; 24;831. 10. Barrack RL, Paprosky W, Butler RA, et al. Patients perception of pain after total hip arthroplasty. J Arthroplasty 2000; Total Hip Prostheses, Self-Centering Hip Prostheses and Hemi-Hip Prostheses Important This Essential Product Information sheet does not include all of the information necessary for selection and use of a device. Please see full labeling for all necessary information. Intended Use/Indications Total Hip Arthroplasty (THA) is intended to provide increased patient mobility and reduce pain by replacing the damaged hip joint articulation in patients where there is evidence of sufficient sound bone to seat and support the components. THA is indicated for a severely painful and/or disabled joint from osteoarthritis, traumatic arthritis, rheumatoid arthritis or congenital hip dysplasia; avascular necrosis of the femoral head; acute traumatic fracture of the femoral head or neck; failed previous hip surgery; and certain cases of ankylosis. Self-Centering Hip Prostheses and Hemi-Hip Prostheses are intended to be used for hemi-hip arthroplasty where there is evidence of a satisfactory natural acetabulum and sufficient femoral bone to seat and support the femoral stem. Hemi-hip arthroplasty is indicated in the following conditions: Acute fracture of the femoral head or neck that cannot be reduced and treated with internal fixation; fracture dislocation of the hip that cannot be appropriately reduced and treated with internal fixation; avascular necrosis of the femoral head; non-union of femoral neck fractures; certain high subcapital and femoral neck fractures in the elderly; degenerative arthritis involving only the femoral head in which the acetabulum does not require replacement; and pathology involving only the femoral head/ neck and/or proximal femur that can be adequately treated by hemi-hip arthroplasty. Contraindications THA and hemi-hip arthroplasty are contraindicated in cases of: active local or systemic infection; loss of musculature, neuromuscular compromise or vascular deficiency in the affected limb, rendering the procedure unjustifiable; poor bone quality; Charcot s or Paget s disease; for hemi-hip arthroplasty pathological conditions of the acetabulum that preclude the use of the natural acetabulum as an appropriate articular surface. Ceramic heads are contraindicated in revision surgery when the femoral stem is not being replaced or for use with any other than a polyethylene or metal-backed polyethylene cup. In the USA and Canada, ceramic heads are not approved for use with metal inserts. Warnings and Precautions Ceramic coated femoral stem prostheses are indicated for uncemented press fit fixation. CAUTION: DO NOT USE BONE CEMENT FOR FIXATION OF A CERAMIC COATED PROSTHESIS. Components labeled for Cemented Use Only are to be implanted only with bone cement. The following conditions tend to adversely affect hip replacement implants: excessive patient weight, high levels of patient activity, likelihood of falls, poor bone stock, metabolic disorders, history of infections, severe deformities leading to impaired fixation or improper positioning, tumors of the supporting bone structures, allergic reactions to materials, tissue reactions, and disabilities of other joints. Adverse Events The following are the most frequent adverse events after hip arthroplasty: change in position of the components, loosening of components, wear or fracture of components, dislocation, infection, peripheral neuropathies, tissue reaction. 6
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DePuy Orthopaedics, Inc. 700 Orthopaedic Drive Warsaw, IN 46581-0988 USA Tel: +1 (800) 366 8143 Fax: +1 (574) 267 7196 www.depuy.com DePuy Orthopaedics, Inc. 2010. All rights reserved. 0612-69-510 3M 1210