- Email: [email protected]
The effect of pulsed irrigation on the incidence of heterotopic ossification after total hip arthroplasty
The Journal of Arthroplasty Vol. 16 No. 5 2001
The Effect of Pulsed Irrigation on the Incidence of Heterotopic Ossification After Total Hip Arthroplasty R. J. S. Sneath, FRCS,* F. D. Bindi, FRCS,* J. Davies, FRCS,* and E. J. Parnell, FRCS†
Abstract: Heterotopic ossification (HO) is a common complication of total hip arthroplasty (THA). Pulsed lavage is being used with increasing frequency for THA. A prospective randomized, double-blind trial was initiated to determine if pulsed lavage affected the incidence of HO. A total of 94 THAs in 91 patients were analyzed. No significant difference in the incidence of HO was found between the 2 groups. Hypertrophic osteoarthritis was found to be a significant risk factor for HO. The findings suggest that the osteogenic precursor cells thought to be involved in the pathogenesis of HO possibly are derived from within the local soft tissues in the proximity of the hip joint. Key words: heterotopic, ossification, pulsed, lavage, hip, arthroplasty.
ated with increased cost, extended hospital stay, and the potential risk of carcinogenesis [14]. These methods have been restricted to patients with an increased risk of HO. Published factors that affect the incidence of HO include the type of approach [5], the type of prosthesis [4], previous HO after an operation on the hip [4], hypertrophic osteoarthritis [3], and male gender [4]. A more acceptable method of reducing the incidence of HO is required. Pulsed lavage is being used with increasing frequency in THA. This study was initiated to determine if pulsed lavage affected the incidence of HO.
Heterotopic ossification (HO) is a common finding in radiographs of patients who have undergone total hip arthroplasty (THA). Studies give a variable incidence of 8% to 90% [1,2], although more recent studies give an incidence of 42% to 57% [3– 6]. HO is responsible for pain and limitation of postoperative motion in 3% to 10% of THA patients [2,7,9]. Methods successful in preventing the formation of HO are the use of nonsteroidal anti-inflammatory drugs (NSAIDs) [6,10,11] and local radiotherapy [12–14]. These methods are not ideal. Cella et al [15] reported noncompliance with NSAIDs in one third of patients. Local radiotherapy is associ-
Materials and Methods A prospective randomized, double-blind trial was initiated. The inclusion criteria for the trial were patients with idiopathic osteoarthritis and no previous history of surgery to either hip. Between March 1995 and September 1996, 115 primary THAs in 112 patients were performed at the Princess Royal Hospital, Haywards Heath, and entered into the trial. Patients were randomized into 2 groups by selection from a series of sealed enve-
From the *Department of Orthopaedics, North West Thames Rotation, London; and †Department of Orthopaedic Surgery, The Princess Royal Hospital, Haywards Heath, Sussex, United Kingdom. Submitted October 31, 2000; accepted December 4, 2000. No benefits or funds were received in support of this study. Reprint requests: E. J. Parnell, FRCS, Consultant Orthopaedic Surgeon, The Princess Royal Hospital, Lewes Road, Haywards Heath, West Sussex, RH16 4EX UK. Copyright © 2001 by Churchill Livingstone威 0883-5403/01/1605-0001$35.00/0 doi:10.1054/arth.2001.23562
547
548 The Journal of Arthroplasty Vol. 16 No. 5 August 2001
Fig. 1. Anteroposterior radiographs of hip joints involved in the trial showing (A) atrophic, (B) normotrophic, and (C) hypertrophic osteoarthritis, according to Bombelli’s classification [16].
lopes. The contents of each envelope was revealed just before the operation started and instructed as to which type of irrigation was to be used. Intraoperative irrigation in group 1 was provided by a 50-mL syringe and limited to 500 mL of room-temperature normal saline. This amount was thought to be the average amount of irrigation used by this unit’s surgeons before the trial. In group 2, pulsed lavage with 3 L of room-temperature normal saline was used. The bone and soft tissues were irrigated in both groups. The pulsed lavage equipment consisted of a pulsed irrigation pump, hand piece, and tubing (OrthoTec, Stryker UK, Reading, England). Patients routinely had a pelvic radiograph taken preoperatively, immediately postoperatively, and 1 year postoperatively. All radiographs were interpreted by a blinded review with 2 independent orthopaedic registrars. The patients’ preoperative grade of osteoarthritis was classified as atrophic, normotrophic, or hypertrophic, according to Bombelli [16] (Fig. 1). The grade of HO at 1 year was classified according to Brooker et al [17] (Fig. 2): Grade 0: no HO Grade 1: 1 or 2 areas of ossification, each ⬍1 cm in diameter Grade 2: more widespread isolated areas of ossification from the proximal femur or acetabular rim covering less than half of the distance between the femur and the pelvis Grade 3: ossification covering more than half of the distance between the femur and the pelvis but not bridging the entire distance Grade 4: ossification bridging the entire distance between the femur and the pelvis Patients were subjected to exclusion criteria that were established before the start of the trial and
consisted of the following features, which at the time were thought to affect the incidence of HO: 1. Superficial or deep infection 2. Dislocation 3. Hematoma 4. Fever for 5 days postoperatively 5. Use of radiation or diphosphonates 6. Drains in situ for ⬎48 hours 7. Sterile secretion (noninflammatory wound secretion lasting ⬎24 hours) The exclusion criteria were implemented by a blinded review of the patients’ notes. Administration of NSAIDs was documented carefully at this time. The trial had no influence on the preoperative or postoperative administration of NSAIDs. Statistical analysis of the results was made using the chi-square test and the Kruskal-Wallis test. Data were analyzed to confirm an even distribution between the 2 irrigation groups of cases with known risk factors for HO. The groups within the risk factors for HO of patient gender, type of osteoarthritis, and postoperative NSAIDs were analyzed separately.
Results Twenty-one patients were excluded from the trial: 10 patients had a sterile wound secretion, 4 had a fever for 4 days postoperatively, 3 had superficial infections, 2 had hematomas, and 2 had drains left in for 72 hours. This left 94 THAs in 91 patients available for analysis. There were 61 women and 33 men (male-to-female ratio 1:1:85). The average age of the patients was 72 years (range, 38 –95 years). The incidence of HO in this group of primary THAs was 57.4%. Most cases with HO were graded
Irrigation and Heterotopic Ossification •
Sneath et al.
549
Fig. 2. Anterposterior radiographs of total hip arthroplasties involved in the trial showing (A) grade 1, (B) grade 2, (C) grade 3, and (D) grade 4 heterotopic ossification, according to the classification of Brooker et al [17].
1 or 2 (42.6%). Only 2 cases had any progression of HO after 6 months; both cases increased their grade of HO by 1. HO developed in 54.2% of hips in the pulsed lavage irrigation group and in 60.9% of hips in the syringe irrigation group. No statistical significance was found to exist between the 2 methods of irrigation in relation to HO (chi-square P value ⫽ .456) (Table 1). There was no statistically significant variation of cases with known risk factors for HO between the 2 irrigation groups (Table 2). Analysis
Table 1. Distribution of Heterotopic Ossification Between the 2 Irrigation Groups Type of Irrigation
Grade of Heterotopic Ossification
Pulsed Lavage
Syringe
Totals
0 1 2 3 4 Totals
22 13 7 4 2 48
18 17 3 7 1 46
40 30 10 11 3 94
550 The Journal of Arthroplasty Vol. 16 No. 5 August 2001 Table 2. Distribution of Cases With Heterotopic Ossification Risk Factors Type of Irrigation
No arthroplasties Mean age (y) Patient gender M F Type of OA Atrophic Normotrophic Hypertrophic Preoperative NSAIDs Yes No Postoperative NSAIDs Yes No Cement Yes No
Pulsed Lavage
Syringe
48 71
46 73
19 29
14 32
10 21 17
14 21 11
23 19
21 25
4 38
13 33
33 8
41 5
Missing Data 0 0 0 0
6 6 7
OA, osteoarthritis; NSAIDs, nonsteroidal anti-inflammatory drugs.
of groups with or without known risk factors for HO produced no statistical significance in relation to irrigation. From an analysis of the known risk factors for HO, only the type of osteoarthritis was shown to influence the incidence of HO statistically (Table 3).
Discussion The incidence of HO in this trial is comparable to the rates published in the more recent studies on HO [3– 6]. Several previously published risk factors for HO [3–5] were not found to influence significantly the incidence of HO in this trial. This finding must be interpreted with caution because this trial was initiated only to elicit the influence of intraoperative irrigation on the incidence of HO. The risk factor analysis does suggest, however, that the type of osteoarthritis is a statistically powerful predictor of HO. The process of HO is thought to result from the differentiation of mesenchymal cells into osteoprogenitor cells, although the precise mechanism is unknown [18]. The cellular differentiation into osteoblastic tissue has been noted to occur by 16 hours after operation, with peak response noted at approximately 32 hours [19]. This response time suggests that the degree of HO is set at an early postoperative stage. Trials studying the effective-
ness of NSAIDs or local radiotherapy as a preventive measure for HO support this suggestion. A postoperative 5-day course of NSAIDs has been shown to reduce significantly the incidence of HO [6]. Local radiotherapy has to be given within 4 days after the operation to be effective [12,13]. Chalmers et al [20] proposed that an inducing agent and an environment conducive to osteogenesis are required in addition to osteogenic precursor cells. Theories have proposed that the inducing agent or the mesenchymal cells (or both) arise from bone at the time of the operation [18,21], although systemic agents also have been proposed [22]. If the inducing agent or precursor cells were released from the bone intraoperatively, thorough irrigation could be expected to have an association with a lower incidence of HO. The lack of correlation between irrigation and incidence of HO indicates this is unlikely to be the mechanism. It is accepted that the pulsed lavage does not remove all the bone debris, but the 2 types of irrigation should produce a differential in the level of bone debris left at the end of the operation. Rockwood and Horne [23] found that the increased production of bone debris that is associated with uncemented THA did not produce a significantly higher incidence of HO when compared with cemented THA. Pellegrini and Gregoritch [14] showed that a single 8-gray fraction given in opposed anteroposterior fields before THA reduced significantly the incidence of postoperative HO. Because the radiation was confined to the proximity of the hip, it was suggested that the osteogenic precursor cells are derived from the local tissues within the operative field. The radiation was not directed at bone but at the soft tissues where HO develops; it is possible that the osteogenic precursor cells are not derived from bone but from the local soft tissues. We accept
Table 3. Statistical Probability of Previously Published Risk factors Influencing Heterotopic Ossification Risk Factor Patient age Patient gender Type of osteoarthritis Preoperative NSAIDs Postoperative NSAIDs Type of irrigation Operative approach Type of prosthesis Use of cement
Chi-Square P Value .545 .119 .017* .828 .927 .456 .695 .728 .885
* Denotes statistical significance (P⬎.05). NSAIDs, nonsteroidal anti-inflammatory drugs.
Irrigation and Heterotopic Ossification •
that the method of shielding in this study would not have prevented a proportion of radiation reaching the bone. Hypertrophic osteoarthritis was found to be the most significant risk factor for HO. The origin of the osteogenic precursors remains unknown. Our data suggest that HO is not influenced significantly by the degree of intraoperative irrigation during THA. These data appear to support Pellegrini’s [14] conclusion that the osteogenic precursor cells are derived from the soft tissues rather than the bone debris.
References 1. Lazansky M: Complications revisited: the debit side of total hip replacement. Clin Orthop 95:96, 1973 2. Rosendahl S, Christoffersen JK, Norgaard M: Paraarticular ossification following total hip replacement: 70 arthroplasties ad modum Moore, using McFarland’s approach. Acta Orthop Scand 48:400, 1977 3. Goel A, Sharp D: Heterotopic bone formation after hip replacement: the influence of the type of osteoarthritis. J Bone Joint Surg Br 73:255, 1991 4. Nollen A, van Douveren F: Ectopic ossification in hip arthroplasty: a retrospective study of predisposing factors in 637 cases. Acta Orthop Scand 64:185, 1993 5. Pai V: Heterotopic ossification in total hip arthroplasty: the influence of the approach. J Arthroplasty 9:199, 1994 6. Gebuhr P, Sletgård J, Dalsgård J, et al: Heterotopic ossification after hip arthroplasty: a randomised double-blind multicenter study of tenoxicam in 147 hips. Acta Orthop Scand 67:29, 1996 7. Ling R: Complications of total hip replacement. Churchill Livingstone, Edinburgh, 1984 8. Sodemann B, Persson P-E, Nilsson O: Periarticular heterotopic ossification after total hip arthroplasty for primary coxarthrosis. Clin Orthop 237:150, 1988 9. Morrey B, Adams R, Cabanela M: Comparison of heterotopic bone after anterolateral, transtrochanteric, and posterior approaches for total hip arthroplasty. Clin Orthop 188:160, 1984 10. Schmidt S, Kjærsgaard Andersen P, Pedersen N, et al: The use of indomethacin to prevent the formation of heterotopic bone after total hip replacement: a ran-
11.
12.
13.
14.
15.
16.
17.
18. 19.
20.
21. 22.
23.
Sneath et al.
551
domised, double-blind clinical trial. J Bone Joint Surg Am 70:834, 1988 Knahr K, Salzer M, Eyb R, et al: Heterotopic ossification with total hip endoprostheses in various models of thrombosis prophylaxis. J Arthroplasty 3:1, 1988 Ayers D, Evarts C, Parkinson J: The prevention of heterotopic ossification in high-risk patients by lowdose radiation therapy after total hip arthroplasty. J Bone Joint Surg Am 68:1423, 1986 Parkinson J, Evarts C, Hubbard L: Radiation therapy in the prevention of heterotopic ossification after total hip arthroplasty. p. 211. In The hip: Proceedings of the Tenth Open Scientific Meeting of the Hip Society. CV Mosby, St. Louis, 1982 Pellegrini V Jr, Gregoritch S: Preoperative irradiation for prevention of heterotopic ossification following total hip arthroplasty. J Bone Joint Surg Am 78:870, 1996 Cella J, Salvati E, Sculco T: Indomethacin for the prevention of heterotopic ossification following total hip arthroplasty: effectiveness, contraindications, and adverse effects. J Arthroplasty 3:229, 1988 Bombelli R: Osteoarthritis of the hip: classification and pathogenesis: the role of osteotomy as a consequent therapy, 2nd ed. Springer-Verlag, Berlin, 1983 Brooker A, Bowerman J, Robinson R, Riley L Jr: Ectopic ossification following total hip replacement: incidence and a method of classification. J Bone Joint Surg Am 55:1629, 1973 Thomas B: Heterotopic bone formation after total hip arthroplasty. Orthop Clin North Am 23:347, 1992 Tonna E, Cronkite E: Auto radiographic studies of cell proliferation in the periosteum of intact and fractured femora of mice utilizing DNA labelling with (3H) thymidine. Proc Soc Exp Biol Med 107:719, 1961 Chalmers J, Gray D, Rush J: Observations on the induction of bone in soft tissue. J Bone Joint Surg Br 57:37, 1975 Puzas J, Evarts C, Brand J: The stimulus for bone formation. Hip 25, 1987 DeLee J, Ferrari A, Charnley J: Ectopic bone formation following low friction arthroplasty of the hip. Clin Orthop 121:53, 1976 Rockwood P, Horne J: Heterotopic ossification following uncemented total hip arthroplasty. J Arthroplasty 5(suppl):43, 1990
The Effect of Pulsed Irrigation on the Incidence of Heterotopic Ossification After Total Hip Arthroplasty R. J. S. Sneath, FRCS,* F. D. Bindi, FRCS,* J. Davies, FRCS,* and E. J. Parnell, FRCS†
Abstract: Heterotopic ossification (HO) is a common complication of total hip arthroplasty (THA). Pulsed lavage is being used with increasing frequency for THA. A prospective randomized, double-blind trial was initiated to determine if pulsed lavage affected the incidence of HO. A total of 94 THAs in 91 patients were analyzed. No significant difference in the incidence of HO was found between the 2 groups. Hypertrophic osteoarthritis was found to be a significant risk factor for HO. The findings suggest that the osteogenic precursor cells thought to be involved in the pathogenesis of HO possibly are derived from within the local soft tissues in the proximity of the hip joint. Key words: heterotopic, ossification, pulsed, lavage, hip, arthroplasty.
ated with increased cost, extended hospital stay, and the potential risk of carcinogenesis [14]. These methods have been restricted to patients with an increased risk of HO. Published factors that affect the incidence of HO include the type of approach [5], the type of prosthesis [4], previous HO after an operation on the hip [4], hypertrophic osteoarthritis [3], and male gender [4]. A more acceptable method of reducing the incidence of HO is required. Pulsed lavage is being used with increasing frequency in THA. This study was initiated to determine if pulsed lavage affected the incidence of HO.
Heterotopic ossification (HO) is a common finding in radiographs of patients who have undergone total hip arthroplasty (THA). Studies give a variable incidence of 8% to 90% [1,2], although more recent studies give an incidence of 42% to 57% [3– 6]. HO is responsible for pain and limitation of postoperative motion in 3% to 10% of THA patients [2,7,9]. Methods successful in preventing the formation of HO are the use of nonsteroidal anti-inflammatory drugs (NSAIDs) [6,10,11] and local radiotherapy [12–14]. These methods are not ideal. Cella et al [15] reported noncompliance with NSAIDs in one third of patients. Local radiotherapy is associ-
Materials and Methods A prospective randomized, double-blind trial was initiated. The inclusion criteria for the trial were patients with idiopathic osteoarthritis and no previous history of surgery to either hip. Between March 1995 and September 1996, 115 primary THAs in 112 patients were performed at the Princess Royal Hospital, Haywards Heath, and entered into the trial. Patients were randomized into 2 groups by selection from a series of sealed enve-
From the *Department of Orthopaedics, North West Thames Rotation, London; and †Department of Orthopaedic Surgery, The Princess Royal Hospital, Haywards Heath, Sussex, United Kingdom. Submitted October 31, 2000; accepted December 4, 2000. No benefits or funds were received in support of this study. Reprint requests: E. J. Parnell, FRCS, Consultant Orthopaedic Surgeon, The Princess Royal Hospital, Lewes Road, Haywards Heath, West Sussex, RH16 4EX UK. Copyright © 2001 by Churchill Livingstone威 0883-5403/01/1605-0001$35.00/0 doi:10.1054/arth.2001.23562
547
548 The Journal of Arthroplasty Vol. 16 No. 5 August 2001
Fig. 1. Anteroposterior radiographs of hip joints involved in the trial showing (A) atrophic, (B) normotrophic, and (C) hypertrophic osteoarthritis, according to Bombelli’s classification [16].
lopes. The contents of each envelope was revealed just before the operation started and instructed as to which type of irrigation was to be used. Intraoperative irrigation in group 1 was provided by a 50-mL syringe and limited to 500 mL of room-temperature normal saline. This amount was thought to be the average amount of irrigation used by this unit’s surgeons before the trial. In group 2, pulsed lavage with 3 L of room-temperature normal saline was used. The bone and soft tissues were irrigated in both groups. The pulsed lavage equipment consisted of a pulsed irrigation pump, hand piece, and tubing (OrthoTec, Stryker UK, Reading, England). Patients routinely had a pelvic radiograph taken preoperatively, immediately postoperatively, and 1 year postoperatively. All radiographs were interpreted by a blinded review with 2 independent orthopaedic registrars. The patients’ preoperative grade of osteoarthritis was classified as atrophic, normotrophic, or hypertrophic, according to Bombelli [16] (Fig. 1). The grade of HO at 1 year was classified according to Brooker et al [17] (Fig. 2): Grade 0: no HO Grade 1: 1 or 2 areas of ossification, each ⬍1 cm in diameter Grade 2: more widespread isolated areas of ossification from the proximal femur or acetabular rim covering less than half of the distance between the femur and the pelvis Grade 3: ossification covering more than half of the distance between the femur and the pelvis but not bridging the entire distance Grade 4: ossification bridging the entire distance between the femur and the pelvis Patients were subjected to exclusion criteria that were established before the start of the trial and
consisted of the following features, which at the time were thought to affect the incidence of HO: 1. Superficial or deep infection 2. Dislocation 3. Hematoma 4. Fever for 5 days postoperatively 5. Use of radiation or diphosphonates 6. Drains in situ for ⬎48 hours 7. Sterile secretion (noninflammatory wound secretion lasting ⬎24 hours) The exclusion criteria were implemented by a blinded review of the patients’ notes. Administration of NSAIDs was documented carefully at this time. The trial had no influence on the preoperative or postoperative administration of NSAIDs. Statistical analysis of the results was made using the chi-square test and the Kruskal-Wallis test. Data were analyzed to confirm an even distribution between the 2 irrigation groups of cases with known risk factors for HO. The groups within the risk factors for HO of patient gender, type of osteoarthritis, and postoperative NSAIDs were analyzed separately.
Results Twenty-one patients were excluded from the trial: 10 patients had a sterile wound secretion, 4 had a fever for 4 days postoperatively, 3 had superficial infections, 2 had hematomas, and 2 had drains left in for 72 hours. This left 94 THAs in 91 patients available for analysis. There were 61 women and 33 men (male-to-female ratio 1:1:85). The average age of the patients was 72 years (range, 38 –95 years). The incidence of HO in this group of primary THAs was 57.4%. Most cases with HO were graded
Irrigation and Heterotopic Ossification •
Sneath et al.
549
Fig. 2. Anterposterior radiographs of total hip arthroplasties involved in the trial showing (A) grade 1, (B) grade 2, (C) grade 3, and (D) grade 4 heterotopic ossification, according to the classification of Brooker et al [17].
1 or 2 (42.6%). Only 2 cases had any progression of HO after 6 months; both cases increased their grade of HO by 1. HO developed in 54.2% of hips in the pulsed lavage irrigation group and in 60.9% of hips in the syringe irrigation group. No statistical significance was found to exist between the 2 methods of irrigation in relation to HO (chi-square P value ⫽ .456) (Table 1). There was no statistically significant variation of cases with known risk factors for HO between the 2 irrigation groups (Table 2). Analysis
Table 1. Distribution of Heterotopic Ossification Between the 2 Irrigation Groups Type of Irrigation
Grade of Heterotopic Ossification
Pulsed Lavage
Syringe
Totals
0 1 2 3 4 Totals
22 13 7 4 2 48
18 17 3 7 1 46
40 30 10 11 3 94
550 The Journal of Arthroplasty Vol. 16 No. 5 August 2001 Table 2. Distribution of Cases With Heterotopic Ossification Risk Factors Type of Irrigation
No arthroplasties Mean age (y) Patient gender M F Type of OA Atrophic Normotrophic Hypertrophic Preoperative NSAIDs Yes No Postoperative NSAIDs Yes No Cement Yes No
Pulsed Lavage
Syringe
48 71
46 73
19 29
14 32
10 21 17
14 21 11
23 19
21 25
4 38
13 33
33 8
41 5
Missing Data 0 0 0 0
6 6 7
OA, osteoarthritis; NSAIDs, nonsteroidal anti-inflammatory drugs.
of groups with or without known risk factors for HO produced no statistical significance in relation to irrigation. From an analysis of the known risk factors for HO, only the type of osteoarthritis was shown to influence the incidence of HO statistically (Table 3).
Discussion The incidence of HO in this trial is comparable to the rates published in the more recent studies on HO [3– 6]. Several previously published risk factors for HO [3–5] were not found to influence significantly the incidence of HO in this trial. This finding must be interpreted with caution because this trial was initiated only to elicit the influence of intraoperative irrigation on the incidence of HO. The risk factor analysis does suggest, however, that the type of osteoarthritis is a statistically powerful predictor of HO. The process of HO is thought to result from the differentiation of mesenchymal cells into osteoprogenitor cells, although the precise mechanism is unknown [18]. The cellular differentiation into osteoblastic tissue has been noted to occur by 16 hours after operation, with peak response noted at approximately 32 hours [19]. This response time suggests that the degree of HO is set at an early postoperative stage. Trials studying the effective-
ness of NSAIDs or local radiotherapy as a preventive measure for HO support this suggestion. A postoperative 5-day course of NSAIDs has been shown to reduce significantly the incidence of HO [6]. Local radiotherapy has to be given within 4 days after the operation to be effective [12,13]. Chalmers et al [20] proposed that an inducing agent and an environment conducive to osteogenesis are required in addition to osteogenic precursor cells. Theories have proposed that the inducing agent or the mesenchymal cells (or both) arise from bone at the time of the operation [18,21], although systemic agents also have been proposed [22]. If the inducing agent or precursor cells were released from the bone intraoperatively, thorough irrigation could be expected to have an association with a lower incidence of HO. The lack of correlation between irrigation and incidence of HO indicates this is unlikely to be the mechanism. It is accepted that the pulsed lavage does not remove all the bone debris, but the 2 types of irrigation should produce a differential in the level of bone debris left at the end of the operation. Rockwood and Horne [23] found that the increased production of bone debris that is associated with uncemented THA did not produce a significantly higher incidence of HO when compared with cemented THA. Pellegrini and Gregoritch [14] showed that a single 8-gray fraction given in opposed anteroposterior fields before THA reduced significantly the incidence of postoperative HO. Because the radiation was confined to the proximity of the hip, it was suggested that the osteogenic precursor cells are derived from the local tissues within the operative field. The radiation was not directed at bone but at the soft tissues where HO develops; it is possible that the osteogenic precursor cells are not derived from bone but from the local soft tissues. We accept
Table 3. Statistical Probability of Previously Published Risk factors Influencing Heterotopic Ossification Risk Factor Patient age Patient gender Type of osteoarthritis Preoperative NSAIDs Postoperative NSAIDs Type of irrigation Operative approach Type of prosthesis Use of cement
Chi-Square P Value .545 .119 .017* .828 .927 .456 .695 .728 .885
* Denotes statistical significance (P⬎.05). NSAIDs, nonsteroidal anti-inflammatory drugs.
Irrigation and Heterotopic Ossification •
that the method of shielding in this study would not have prevented a proportion of radiation reaching the bone. Hypertrophic osteoarthritis was found to be the most significant risk factor for HO. The origin of the osteogenic precursors remains unknown. Our data suggest that HO is not influenced significantly by the degree of intraoperative irrigation during THA. These data appear to support Pellegrini’s [14] conclusion that the osteogenic precursor cells are derived from the soft tissues rather than the bone debris.
References 1. Lazansky M: Complications revisited: the debit side of total hip replacement. Clin Orthop 95:96, 1973 2. Rosendahl S, Christoffersen JK, Norgaard M: Paraarticular ossification following total hip replacement: 70 arthroplasties ad modum Moore, using McFarland’s approach. Acta Orthop Scand 48:400, 1977 3. Goel A, Sharp D: Heterotopic bone formation after hip replacement: the influence of the type of osteoarthritis. J Bone Joint Surg Br 73:255, 1991 4. Nollen A, van Douveren F: Ectopic ossification in hip arthroplasty: a retrospective study of predisposing factors in 637 cases. Acta Orthop Scand 64:185, 1993 5. Pai V: Heterotopic ossification in total hip arthroplasty: the influence of the approach. J Arthroplasty 9:199, 1994 6. Gebuhr P, Sletgård J, Dalsgård J, et al: Heterotopic ossification after hip arthroplasty: a randomised double-blind multicenter study of tenoxicam in 147 hips. Acta Orthop Scand 67:29, 1996 7. Ling R: Complications of total hip replacement. Churchill Livingstone, Edinburgh, 1984 8. Sodemann B, Persson P-E, Nilsson O: Periarticular heterotopic ossification after total hip arthroplasty for primary coxarthrosis. Clin Orthop 237:150, 1988 9. Morrey B, Adams R, Cabanela M: Comparison of heterotopic bone after anterolateral, transtrochanteric, and posterior approaches for total hip arthroplasty. Clin Orthop 188:160, 1984 10. Schmidt S, Kjærsgaard Andersen P, Pedersen N, et al: The use of indomethacin to prevent the formation of heterotopic bone after total hip replacement: a ran-
11.
12.
13.
14.
15.
16.
17.
18. 19.
20.
21. 22.
23.
Sneath et al.
551
domised, double-blind clinical trial. J Bone Joint Surg Am 70:834, 1988 Knahr K, Salzer M, Eyb R, et al: Heterotopic ossification with total hip endoprostheses in various models of thrombosis prophylaxis. J Arthroplasty 3:1, 1988 Ayers D, Evarts C, Parkinson J: The prevention of heterotopic ossification in high-risk patients by lowdose radiation therapy after total hip arthroplasty. J Bone Joint Surg Am 68:1423, 1986 Parkinson J, Evarts C, Hubbard L: Radiation therapy in the prevention of heterotopic ossification after total hip arthroplasty. p. 211. In The hip: Proceedings of the Tenth Open Scientific Meeting of the Hip Society. CV Mosby, St. Louis, 1982 Pellegrini V Jr, Gregoritch S: Preoperative irradiation for prevention of heterotopic ossification following total hip arthroplasty. J Bone Joint Surg Am 78:870, 1996 Cella J, Salvati E, Sculco T: Indomethacin for the prevention of heterotopic ossification following total hip arthroplasty: effectiveness, contraindications, and adverse effects. J Arthroplasty 3:229, 1988 Bombelli R: Osteoarthritis of the hip: classification and pathogenesis: the role of osteotomy as a consequent therapy, 2nd ed. Springer-Verlag, Berlin, 1983 Brooker A, Bowerman J, Robinson R, Riley L Jr: Ectopic ossification following total hip replacement: incidence and a method of classification. J Bone Joint Surg Am 55:1629, 1973 Thomas B: Heterotopic bone formation after total hip arthroplasty. Orthop Clin North Am 23:347, 1992 Tonna E, Cronkite E: Auto radiographic studies of cell proliferation in the periosteum of intact and fractured femora of mice utilizing DNA labelling with (3H) thymidine. Proc Soc Exp Biol Med 107:719, 1961 Chalmers J, Gray D, Rush J: Observations on the induction of bone in soft tissue. J Bone Joint Surg Br 57:37, 1975 Puzas J, Evarts C, Brand J: The stimulus for bone formation. Hip 25, 1987 DeLee J, Ferrari A, Charnley J: Ectopic bone formation following low friction arthroplasty of the hip. Clin Orthop 121:53, 1976 Rockwood P, Horne J: Heterotopic ossification following uncemented total hip arthroplasty. J Arthroplasty 5(suppl):43, 1990