Capsular Closure Does Not Affect Development of Heterotopic Ossification After Hip Arthroscopy Eyal Amar, M.D., Yaniv Warschawski, M.D., Thomas G. Sampson, M.D., Ehud Atoun, M.D., Ely L. Steinberg, M.D., and Ehud Rath, M.D.
Purpose: The purpose of this study was to evaluate the role of capsular closure after hip arthroscopy in reduction of the incidence of heterotopic ossification (HO). Methods: One hundred (50 study group, 50 control group) consecutive hip arthroscopy procedures with radiographic follow-up of more than 9 weeks were included in the study. The study group consisted of 50 patients in whom capsular closure with 2 No. 1 polydioxanone (PDS) sutures was performed, and a control group consisted of 50 patients in whom the capsule remained open after capsulotomy. HO was assessed by radiographs using the Brooker classification. Statistical analysis of the data was carried out with the c-square or Fisher exact test and Student t test, when appropriate, at a significance level of .05. Results: Thirty-six (36%) patients had radiographic evidence of postoperative HO (14 patients in the capsular closure group). No significant difference was found regarding sex, side of operation, age, or HO rate between the study and the control groups (P ¼ .778, P ¼ .123, P ¼ .744, and P ¼ .144, respectively). Furthermore, no significant difference was found in the rate of HO with potential clinical significance (Brooker classification > I) between the control and study groups (P ¼ .764). Conclusions: Capsular closure did not seem to alter the rate of HO when compared with a control group of patients in whom the capsulotomy was not repaired. Level of Evidence: Level III, retrospective comparative study.
H
eterotopic ossification (HO) is the formation of bone in nonskeletal tissue, usually between the muscle and the joint capsule; it results from an alteration in the normal regulation of osteogenesis.1,2 The findings of ectopic bone range from clinically insignificant on radiographic findings to restrictive and painful clinical conditions that affect hip function. Despite numerous reports in the literature about HO after open hip surgery, little is known and documented about this complication after hip arthroscopy. The incidence of HO
From the Department of Orthopedics, Sackler Faculty of Medicine, Tel Aviv Medical Center (E.Amar, Y.W., E.L.S., E.R.), Tel Aviv University, Tel Aviv, Israel; Department of Hip Arthroscopy, Post Street Orthopaedics and Sports Medicine (T.G.S.), San Francisco, California, U.S.A.; Barzilai Medical Center Campus, Faculty of Health Sciences, Ben-Gurion University (E.Atoun), Ashkelon, Israel The authors report the following potential conflict of interest or source of funding: T.G.S. received fees for expert testimony from Allstate, State Farm, and others. E.Atoun receives support from Mininvasive Ltd. Received February 4, 2014; accepted August 26, 2014. Address correspondence to Eyal Amar, M.D., Department of Orthopedics, Tel Aviv Medical Center, 6 Weizman Street, Tel Aviv 64239, Israel. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/1487/$36.00 http://dx.doi.org/10.1016/j.arthro.2014.08.026
after hip arthroscopy in the few studies found in the literature ranges from 0% to 44%.3-8 A suggested model for a heterotopic environment conducive to osteogenesis is an interaction between injured periosteum and necrotic or damaged muscle that may induce periosteal bone production, as implicated by animal models.9,10 Further evidence to support this model was shown in an animal study in which a plastic membrane introduced between the periosteum and muscle failed to stimulate ectopic bone formation.11 This model may correlate with arthroscopic treatment of various hip pathologic processes (e.g., labral tear and femoroacetabular impingement) in which the introduction of “injured periosteum” during an osteoplasty performed in proximity to a possibly injured muscle results from portal establishment and instrument insertion. This proximity is enabled by capsulotomy, which is commonly performed during hip arthroscopy to allow better visualization and instrument navigation. No gold standard has yet been set for the optimal technique of capsulotomy, the amount of resection, and indications for capsular repair. Prevention of HO after hip arthroscopy is not routinely indicated at our institution. The purpose of this study, therefore, was to evaluate the role of capsular closure after hip arthroscopy in
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Fig 1. Intraoperative photographs of a 26-year-old man who underwent arthroscopic treatment for mixed FAI of his left hip. Image is viewed through a lateral portal using a 70 lens. (A) Femoral head-neck junction after osteotomy (asterisk) is seen, as is open capsule with gap between its edges (double-headed arrow), and polydioxanone (PDS) suture (short arrow). (B) Disappearance of the gap and closure of the capsule (arrow).
reduction of HO. The study’s hypothesis was that capsular closure would reduce the rate of HO.
Methods This was a retrospective comparative study. At our center, clinical and outcomes data are collected on all patients undergoing arthroscopic surgery of the hip. This study was approved by the local institutional review board. The study period was between July 2011 and March 2013. The study included evaluation of 143 consecutive hip arthroscopies performed by the senior author (E.R.) for hip jointerelated pain. Exclusion criteria were radiographic follow-up of less than 9 weeks, previous hip surgery, and the presence of periarticular ossification (a possible manifestation of femoroacetabular impingement [FAI]) on a preoperative pelvic radiograph and refusal of the patient to undergo radiography at routine postoperative follow-up. We excluded 43 patients from this study: 27 had a postoperative period of less than 9 weeks, 9 had had previous hip surgery, and 7 refused to participate in the study. We used to routinely leave the capsule open and found that the HO rate was 44% in the 50-patient group. With the study hypothesis in mind, we changed our routine and recruited the next 50 consecutive patients, in whom we closed the capsule. One hundred patients in 2 groups were included in the study without randomization. The control group consisted of 50 patients in whom the capsule remained open and the study group consisted of the next 50 consecutive patients in whom capsular closure was performed. No HO prophylaxis was administered preoperatively or postoperatively. The indication for surgery, procedure performed (e.g., labrum repair or femoral or acetabular osteoplasty), number of anchors used in the procedure, surgery time, and radiographic follow-up time were documented.
Surgical Technique All arthroscopic procedures were performed with the patient in the supine position under general anesthesia on an orthopaedic traction table. The surgical technique and portal establishment were performed according to the surgical technique previously described by Weiland and Philippon.12 Interportal capsulotomy using a hooked radiofrequency probe (VAPR; DePuy Mitek, Raynham, MA) was performed in all cases to facilitate instrument maneuverability, as previously described by Bedi et al.13 A thorough diagnostic evaluation of the hip was performed with the use of a 70 arthroscope. Acetabuloplasty and labral reattachment with anchors was performed if indicated. The traction was released and the arthroscope was inserted into the peripheral compartment through the lateral portal. Femoral osteoplasty of the head-neck junction was carried out if indicated. In the study group, a capsular closure was performed with 2 polydioxanone sutures (PDS II; Ethicon, Somerville, NJ) (Fig 1). Postoperative rehabilitation was similar for most patients except those with microfractures who were prescribed noneweight-bearing restriction for 6 weeks and in patients with labral repairs who were instructed not to bear weight for 3 weeks. Early range-of-motion exercises were encouraged to prevent soft tissue adhesions and promote early recovery. Passive motion was first restored, followed by active motion and then strength. Postoperative Evaluation Patients were evaluated after surgery at 2 weeks, 6 weeks, 3 months, 6 months, and 1 year. Anteroposterior (AP) and frog position radiographs were taken routinely postoperativelydat 2 weeks after surgery to rule out fracture and at 9 weeks or later to
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HETEROTOPIC OSSIFICATION AFTER CAPSULAR CLOSURE Table 1. Brooker Classification of Heterotopic Ossification14 Degree I II
III
IV
Description Islands of bone within the soft tissues around the hip Bone spurs from the pelvis or proximal end of the femur, leaving at least 1 cm between opposing bone surfaces Bone spurs from the pelvis or proximal end of the femur, reducing the space between opposing bone surfaces to less than 1 cm Apparent bone ankylosis of the hip
identify patients in whom HO had developed. Mean follow-up interval for the control and study groups was 12.1 months (range, 6 to 17.9 months) and 13.3 months (range, 6 to 23.3 months), respectively. The radiographs were taken in one of our imaging division’s machines (not necessarily the same machine consistently). The radiographs were reviewed by a senior surgeon (E.Amar) who was not involved in the operation or in the patient follow-up. Findings consistent with HO were classified according to the Brooker classification (Table 1).14 No reliability analysis was performed. Statistical Analysis Statistical analysis of the data was carried out with the c-square or Fisher exact test for categorical variables and Student t test for scale variables, at a significance level of .05. A multivariate logistic regression analysis in a backward logistic regression (LR) model was carried out to estimate the relationship between dependent and independent variables. IBM SPSS Statistics, version 21 for Windows (SPSS, Chicago, IL) was used for all analyses. Our working hypothesis was that capsular closure would markedly reduce HO rate to less than 10%, which is the rate mentioned in other studies.3-7 Post hoc power analysis was carried out with IBM
SPSS Sample Power (SPSS, Chicago, IL) and showed that 50 patients in each group would yield power of more than 95%.
Results In this study, 100 patients with a mean age of 37.5 years (range, 18 to 68 years) were recruited. The control group consisted of 31 men and 19 women; the mean age of the control group was 36.7 years (range, 18 to 68 years). The study group consisted of 30 men and 20 women; the mean age of the study group was 38.2 years (range, 18 to 68 years) (Table 2). The mean follow-up was 12.7 months (range, 6 to 23.3 months). The control group did not significantly differ from the study group regarding age, sex, surgery time, and procedure performed (Table 2). The leading indication for operation in our study was the diagnosis of FAI, which was found in 56 patients, followed by isolated labral tears, which were found in 20 patients. Other indications included subspinal impingement resulting from a low anterior inferior iliac spine in 12 patients, Legg-Calvé-Perthes disease in 4 patients, osteoarthritis in 2 patients, and internal snapping hip, developmental dysplasia of the hip, chondroblastoma, hip pain, pigmented villonodular synovitis, and synovial chondromatosis in 1 patient each. Radiographic findings of HO were recorded in 36 (36%) of 100 patients (22 findings in the control group) (Fig 2). There were 64 (64%) patients with no HO (28 in the control group), 17 (17%) with grade 1 HO (13 in the control group), 15 (15%) with grade 2 HO (5 in the control group), and 4 (4%) with grade 3 HO (all in the control group), as shown in Figure 3. The control and study groups did not differ significantly in HO rate (Table 2). The control and study groups also did not differ significantly regarding procedure performed during arthroscopy. The 2 groups had a similar proportion of labrum repair
Table 2. Baseline Characteristics of Patients Undergoing Hip Arthroscopy Variable Number Sex Men Women Age, yr, mean SE (range) Surgery time, min, mean SE (range) Follow-up, mo, mean SE (range) Heterotopic ossification Procedure performed Acetabular osteoplasty Femoral osteoplasty Labral repair Anterior inferior iliac spine decompression Microfractures Iliopsoas release
Capsule Open 50 (50)
Capsule Closed 50 (50)
31 (62) 19 (38) 36.7 2.27 (18-68) 126.6 4.08 (78-176) 12.1 0.53 (6-18) 22 (44)
30 (60) 20 (40) 38.2 1.96 (18-68) 117.4 3.35 (77-168) 13.2 0.65 (6-23) 14 (28)
P Value
Total 100
.425
45 42 45 4 3 0
(90) (84) (90) (8) (6) (0)
NOTE. Data presented as n (%) unless otherwise indicated. SE, standard error.
40 38 47 8 5 1
(80) (76) (94) (16) (10) (2)
.619 .083 .161 .144 .161 .310 .715 .357 .715 1
61 39 37.5 1.50 (18-68) 121.9 2.65 (77-176) 12.7 0.42 (6-23) 36 (36) 85 80 92 12 8 1
(85) (80) (92) (12) (8) (1)
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Fig 2. (A) Pelvic anteroposterior (AP) radiograph of 21-year-old male patient who underwent left hip arthroscopy for treatment of FAI taken 7 months after operation, showing HO lesion grade I according to Brooker classification. (B) Pelvic AP radiograph of 44-year-old male patient who underwent left hip arthroscopy for treatment of FAI taken 6 months after operation, showing HO lesion grade II according to Brooker classification. (C) Pelvic AP radiograph of 34-year-old male patient who underwent right hip arthroscopy for treatment of FAI taken 10 months after operation, showing HO lesion grade II according to Brooker classification.
(P ¼ .715), acetabular osteoplasty (P ¼ .161), and femoral osteoplasty (P ¼ .310) (Table 2). Patient selection, treatment allocation, and the incidence and types of HO seen in each group are shown in Figure 4. A multivariate logistic regression analysis in a backward LR model was carried out to estimate the relationship between the dependent variable (incidence of HO) and independent variables (age, sex, capsular management, labral management, acetabuloplasty, femoral osteochondroplasty, and the presence of FAI). This analysis showed that none of the abovementioned independent variables had a significant effect on the dependent variable. Because the clinical manifestation of HO has a wide spectrum, ranging from small clinically insignificant foci
of ossification to massive deposits of bone throughout the body, we analyzed the difference between the control and study groups regarding the incidence of lesions with potential clinically significant HO (i.e., grade II or higher). We did not find a significant difference between the aforementioned groups regarding lesions with potential clinically significant HO (P ¼ .799). A similar analysis was performed for the patient group with FAI as the leading intraoperative diagnosis. HO radiographic findings were recorded in 24 (42.8%) of 56 patients (16 in the control group). No significant difference was noted regarding age, sex, surgery time, HO rate, or clinically significant HO rate (P ¼ .916, P ¼ .402, P ¼ .759, P ¼ .431, and P ¼ .235, respectively). Furthermore, a multivariate logistic regression analysis in a backward LR model was carried out to estimate the relationship between the dependent variable (incidence of HO) and independent variables (age, sex, capsular management, labral management, acetabuloplasty, and femoral osteochondroplasty). This analysis found that none of the abovementioned independent variables had significant effect on the dependent variable.
Discussion
Fig 3. Distribution of HO lesions between control and study groups according to lesion grade.
The control and study groups did not differ statistically regarding age, sex, surgery time, and HO rate. The principal result of this study showed an incidence of 44% HO in the control group and 28% HO in the study group. Despite numerous reports in the literature about HO after open hip surgery, little is known and documented about this complication after hip arthroscopy. In the
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Fig 4. Patient selection, treatment allocation, and the incidence and types of HO seen in each group.
few studies found in the literature, this incidence ranges from 1.6% to 44%3-8,15 (Table 3). Soft tissue trauma can induce heterotopic bone formation by inductive bone growth factor release from damaged cells. Animal experiments implicate an interaction between injured periosteum and necrotic or damaged muscle, which induces the periosteum to produce bone.9 Further evidence to support this model was presented by Rath et al.,16 who showed that debridement of necrotic gluteus minimus muscle diminishes HO after acetabular fracture fixation.16 Aho et al.11 showed that a plastic membrane introduced between the periosteum and muscle failed to stimulate ectopic bone formation. On the basis of this theory, we hypothesized that isolating the muscles surrounding the hip from the injured bone by capsular closure may reduce the rate of HO after hip arthroscopy.
The hip capsule is considered crucial to hip joint stability,17,18 but despite its key contribution to joint stability, no gold standard has yet been set for the optimal technique of capsulotomy, the amount of resection, and indications for capsular repair. Moreover, our literature search for capsular closure after hip arthroscopy studies yielded a few recent case reports on postoperative hip instability after hip arthroscopy,19-21 surgical technique notes,22-24 and a current concept for capsular management during hip arthroscopy.13 In the latter current concept, Bedi et al.13 advocated capsular closure using side-to-side stiches in FAI management and capsular plication in the management of instability. These recommendations were made mainly to enhance postoperative joint stability. According to our literature search, no recommendations for capsular management could be found regarding HO rate reduction.
Table 3. Studies Reporting Heterotopic Ossification Rate in Patients Undergoing Hip Arthroscopy Total No. Heterotopic Study of Patients Ossification Rate (%) Remarks 96 6 Study set to evaluate the early outcomes of arthroscopic management of Larson and Giveans, 20083 femoroacetabular impingement; HO mentioned as complication Clohisy et al., 20104 35 11.4 Study set to evaluate the early clinical and radiographic outcomes of combined hip arthroscopy and limited open osteochondroplasty; HO mentioned as complication Randelli et al., 20105 300 1.6 Study set to evaluate HO prevalence after hip arthroscopy for FAI and its relation with NSAID prophylaxis Zbeda et al., 20116 698 4.7 Study set to evaluate the incidence of HO after arthroscopic procedures for FAI Bedi et al., 20127 616 4.7 Study set to report the short-term incidence, severity, and location of HO in patients undergoing hip arthroscopy 66 12 HO rate mentioned as part of surgical technique description Ong et al, 201315 Rath, et al. 20138 50 44 Study set to assess the incidence of HO after hip arthroscopy Current study Control group 50 44 e Capsule closed 50 28 Study set to evaluate the role of capsular closure in prevention of HO NSAID, nonsteroidal anti-inflammatory drug.
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Limitations Our study showed no difference between the study and control groups. This may stem from a lack of sample size or power calculation and consequent risk of type II bias. In addition, the radiographic follow-up was not carried out during a constant period, a fact that may also introduce bias. Still, all the patients had a minimum of 9-week radiographic follow-up because in humans, ossification is evident radiographically by 6 weeks and does not progress further at 12 to 24 weeks.25,26 The fact that the radiographs were read by a single surgeon who was not blinded constitutes another limitation. Our study was a comparative but not randomized trial, which may somewhat weaken the validity of the conclusions. The first 50 patients were allocated to the control group, and the subsequent 50 patients were allocated to the study group. Although our controls are not matched, the fact that most patients in both groups underwent treatment of similar pathologic hip conditions (i.e., FAI or labral tear, or both) allowed us to compare the presence of HO because the exposure of muscle and bone was similar in both groups.
Conclusions Capsular closure did not seem to alter the rate of HO when compared with a control group of patients in whom the capsulotomy was not repaired.
References 1. Kaplan FS, Hahn GV, Zasloff MA. Heterotopic ossification: Two rare forms and what they can teach us. J Am Acad Orthop Surg 1994;2:288-296. 2. Shafritz AB, Shore EM, Gannon FH, et al. Overexpression of an osteogenic morphogen in fibrodysplasia ossificans progressiva. N Engl J Med 1996;335:555-561. 3. Larson CM, Giveans MR. Arthroscopic management of femoroacetabular impingement: Early outcomes measures. Arthroscopy 2008;24:540-546. 4. Clohisy JC, Zebala LP, Nepple JJ, Pashos G. Combined hip arthroscopy and limited open osteochondroplasty for anterior femoroacetabular impingement. J Bone Joint Surg Am 2010;92:1697-1706. 5. Randelli F, Pierannunzii L, Banci L, Ragone V, Aliprandi A, Buly R. Heterotopic ossifications after arthroscopic management of femoroacetabular impingement: The role of NSAID prophylaxis. J Orthop Traumatol 2010;11:245-250. 6. Bedi A, Zbeda RM, Bueno VF, Downie B, Dolan M, Kelly BT. The incidence of heterotopic ossification after hip arthroscopy. Am J Sports Med 2012;40:854-863. 7. Bedi A, Zbeda RM, Bueno VF, Downie B, Dolan M, Kelly BT. The incidence of heterotopic ossification after hip arthroscopy. Am J Sports Med 2012;40:854-863. 8. Rath E, Sherman H, Sampson TG, Ben Tov T, Maman E, Amar E. The incidence of heterotopic ossification in hip arthroscopy. Arthroscopy 2013;29:427-433.
9. Zaccalini PS, Urist MR. Traumatic periosteal proliferations in rabbits. The enigma of experimental myositis ossificans traumatica. J Trauma 1964;4:344-357. 10. Michelsson JE, Rauschning W. Pathogenesis of experimental heterotopic bone formation following temporary forcible exercising of immobilized limbs. Clin Orthop Relat Res 1983:265-272. 11. Aho HJ, Aro H, Juntunen S, Strengell L, Michelsson JE. Bone formation in experimental myositis ossificans. Light and electron microscopy study. APMIS 1988;96:933-940. 12. Weiland DE, Philippon MJ. Arthroscopic technique of femoroacetabular impingement. Oper Tech Orthop 2005;15:256-260. 13. Bedi A, Galano G, Walsh C, Kelly BT. Capsular management during hip arthroscopy: From femoroacetabular impingement to instability. Arthroscopy 2011;27:1720-1731. 14. Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am 1973;55:1629-1632. 15. Ong C, Hall M, Youm T. Surgical technique: Arthroscopic treatment of heterotopic ossification of the hip after prior hip arthroscopy. Clin Orthop Relat Res 2013;471:1277-1282. 16. Rath EM, Russell GV Jr, Washington WJ, Routt ML Jr. Gluteus minimus necrotic muscle debridement diminishes heterotopic ossification after acetabular fracture fixation. Injury 2002;33:751-756. 17. Ito H, Song Y, Lindsey DP, Safran MR, Giori NJ. The proximal hip joint capsule and the zona orbicularis contribute to hip joint stability in distraction. J Orthop Res 2009;27:989-995. 18. Myers CA, Register BC, Lertwanich P, et al. Role of the acetabular labrum and the iliofemoral ligament in hip stability: An in vitro biplane fluoroscopy study. Am J Sports Med 2011;39:85S-91S (suppl). 19. Benali Y, Katthagen BD. Hip subluxation as a complication of arthroscopic debridement. Arthroscopy 2009;25:405-407. 20. Matsuda DK. Acute iatrogenic dislocation following hip impingement arthroscopic surgery. Arthroscopy 2009;25: 400-404. 21. Ranawat AS, McClincy M, Sekiya JK. Anterior dislocation of the hip after arthroscopy in a patient with capsular laxity of the hip. A case report. J Bone Joint Surg Am 2009;91:192-197. 22. Mei-Dan O, Young DA. A novel technique for capsular repair and labrum refixation in hip arthroscopy using the SpeedStitch. Arthrosc Tech 2012;1:e107-e112. 23. Slikker W III, Van Thiel GS, Chahal J, Nho SJ. The use of double-loaded suture anchors for labral repair and capsular repair during hip arthroscopy. Arthrosc Tech 2012;1:e213-e217. 24. Harris JD, Slikker W III, Gupta AK, McCormick FM, Nho SJ. Routine complete capsular closure during hip arthroscopy. Arthrosc Tech 2013;2:e89-e94. 25. Ritter MA, Vaughan RB. Ectopic ossification after total hip arthroplasty. Predisposing factors, frequency, and effect on results. J Bone Joint Surg Am 1977;59:345-351. 26. McLaren AC. Prophylaxis with indomethacin for heterotopic bone. After open reduction of fractures of the acetabulum. J Bone Joint Surg Am 1990;72:245-247.
Purpose: The purpose of this study was to evaluate the role of capsular closure after hip arthroscopy in reduction of the incidence of heterotopic ossification (HO). Methods: One hundred (50 study group, 50 control group) consecutive hip arthroscopy procedures with radiographic follow-up of more than 9 weeks were included in the study. The study group consisted of 50 patients in whom capsular closure with 2 No. 1 polydioxanone (PDS) sutures was performed, and a control group consisted of 50 patients in whom the capsule remained open after capsulotomy. HO was assessed by radiographs using the Brooker classification. Statistical analysis of the data was carried out with the c-square or Fisher exact test and Student t test, when appropriate, at a significance level of .05. Results: Thirty-six (36%) patients had radiographic evidence of postoperative HO (14 patients in the capsular closure group). No significant difference was found regarding sex, side of operation, age, or HO rate between the study and the control groups (P ¼ .778, P ¼ .123, P ¼ .744, and P ¼ .144, respectively). Furthermore, no significant difference was found in the rate of HO with potential clinical significance (Brooker classification > I) between the control and study groups (P ¼ .764). Conclusions: Capsular closure did not seem to alter the rate of HO when compared with a control group of patients in whom the capsulotomy was not repaired. Level of Evidence: Level III, retrospective comparative study.
H
eterotopic ossification (HO) is the formation of bone in nonskeletal tissue, usually between the muscle and the joint capsule; it results from an alteration in the normal regulation of osteogenesis.1,2 The findings of ectopic bone range from clinically insignificant on radiographic findings to restrictive and painful clinical conditions that affect hip function. Despite numerous reports in the literature about HO after open hip surgery, little is known and documented about this complication after hip arthroscopy. The incidence of HO
From the Department of Orthopedics, Sackler Faculty of Medicine, Tel Aviv Medical Center (E.Amar, Y.W., E.L.S., E.R.), Tel Aviv University, Tel Aviv, Israel; Department of Hip Arthroscopy, Post Street Orthopaedics and Sports Medicine (T.G.S.), San Francisco, California, U.S.A.; Barzilai Medical Center Campus, Faculty of Health Sciences, Ben-Gurion University (E.Atoun), Ashkelon, Israel The authors report the following potential conflict of interest or source of funding: T.G.S. received fees for expert testimony from Allstate, State Farm, and others. E.Atoun receives support from Mininvasive Ltd. Received February 4, 2014; accepted August 26, 2014. Address correspondence to Eyal Amar, M.D., Department of Orthopedics, Tel Aviv Medical Center, 6 Weizman Street, Tel Aviv 64239, Israel. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/1487/$36.00 http://dx.doi.org/10.1016/j.arthro.2014.08.026
after hip arthroscopy in the few studies found in the literature ranges from 0% to 44%.3-8 A suggested model for a heterotopic environment conducive to osteogenesis is an interaction between injured periosteum and necrotic or damaged muscle that may induce periosteal bone production, as implicated by animal models.9,10 Further evidence to support this model was shown in an animal study in which a plastic membrane introduced between the periosteum and muscle failed to stimulate ectopic bone formation.11 This model may correlate with arthroscopic treatment of various hip pathologic processes (e.g., labral tear and femoroacetabular impingement) in which the introduction of “injured periosteum” during an osteoplasty performed in proximity to a possibly injured muscle results from portal establishment and instrument insertion. This proximity is enabled by capsulotomy, which is commonly performed during hip arthroscopy to allow better visualization and instrument navigation. No gold standard has yet been set for the optimal technique of capsulotomy, the amount of resection, and indications for capsular repair. Prevention of HO after hip arthroscopy is not routinely indicated at our institution. The purpose of this study, therefore, was to evaluate the role of capsular closure after hip arthroscopy in
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Fig 1. Intraoperative photographs of a 26-year-old man who underwent arthroscopic treatment for mixed FAI of his left hip. Image is viewed through a lateral portal using a 70 lens. (A) Femoral head-neck junction after osteotomy (asterisk) is seen, as is open capsule with gap between its edges (double-headed arrow), and polydioxanone (PDS) suture (short arrow). (B) Disappearance of the gap and closure of the capsule (arrow).
reduction of HO. The study’s hypothesis was that capsular closure would reduce the rate of HO.
Methods This was a retrospective comparative study. At our center, clinical and outcomes data are collected on all patients undergoing arthroscopic surgery of the hip. This study was approved by the local institutional review board. The study period was between July 2011 and March 2013. The study included evaluation of 143 consecutive hip arthroscopies performed by the senior author (E.R.) for hip jointerelated pain. Exclusion criteria were radiographic follow-up of less than 9 weeks, previous hip surgery, and the presence of periarticular ossification (a possible manifestation of femoroacetabular impingement [FAI]) on a preoperative pelvic radiograph and refusal of the patient to undergo radiography at routine postoperative follow-up. We excluded 43 patients from this study: 27 had a postoperative period of less than 9 weeks, 9 had had previous hip surgery, and 7 refused to participate in the study. We used to routinely leave the capsule open and found that the HO rate was 44% in the 50-patient group. With the study hypothesis in mind, we changed our routine and recruited the next 50 consecutive patients, in whom we closed the capsule. One hundred patients in 2 groups were included in the study without randomization. The control group consisted of 50 patients in whom the capsule remained open and the study group consisted of the next 50 consecutive patients in whom capsular closure was performed. No HO prophylaxis was administered preoperatively or postoperatively. The indication for surgery, procedure performed (e.g., labrum repair or femoral or acetabular osteoplasty), number of anchors used in the procedure, surgery time, and radiographic follow-up time were documented.
Surgical Technique All arthroscopic procedures were performed with the patient in the supine position under general anesthesia on an orthopaedic traction table. The surgical technique and portal establishment were performed according to the surgical technique previously described by Weiland and Philippon.12 Interportal capsulotomy using a hooked radiofrequency probe (VAPR; DePuy Mitek, Raynham, MA) was performed in all cases to facilitate instrument maneuverability, as previously described by Bedi et al.13 A thorough diagnostic evaluation of the hip was performed with the use of a 70 arthroscope. Acetabuloplasty and labral reattachment with anchors was performed if indicated. The traction was released and the arthroscope was inserted into the peripheral compartment through the lateral portal. Femoral osteoplasty of the head-neck junction was carried out if indicated. In the study group, a capsular closure was performed with 2 polydioxanone sutures (PDS II; Ethicon, Somerville, NJ) (Fig 1). Postoperative rehabilitation was similar for most patients except those with microfractures who were prescribed noneweight-bearing restriction for 6 weeks and in patients with labral repairs who were instructed not to bear weight for 3 weeks. Early range-of-motion exercises were encouraged to prevent soft tissue adhesions and promote early recovery. Passive motion was first restored, followed by active motion and then strength. Postoperative Evaluation Patients were evaluated after surgery at 2 weeks, 6 weeks, 3 months, 6 months, and 1 year. Anteroposterior (AP) and frog position radiographs were taken routinely postoperativelydat 2 weeks after surgery to rule out fracture and at 9 weeks or later to
227
HETEROTOPIC OSSIFICATION AFTER CAPSULAR CLOSURE Table 1. Brooker Classification of Heterotopic Ossification14 Degree I II
III
IV
Description Islands of bone within the soft tissues around the hip Bone spurs from the pelvis or proximal end of the femur, leaving at least 1 cm between opposing bone surfaces Bone spurs from the pelvis or proximal end of the femur, reducing the space between opposing bone surfaces to less than 1 cm Apparent bone ankylosis of the hip
identify patients in whom HO had developed. Mean follow-up interval for the control and study groups was 12.1 months (range, 6 to 17.9 months) and 13.3 months (range, 6 to 23.3 months), respectively. The radiographs were taken in one of our imaging division’s machines (not necessarily the same machine consistently). The radiographs were reviewed by a senior surgeon (E.Amar) who was not involved in the operation or in the patient follow-up. Findings consistent with HO were classified according to the Brooker classification (Table 1).14 No reliability analysis was performed. Statistical Analysis Statistical analysis of the data was carried out with the c-square or Fisher exact test for categorical variables and Student t test for scale variables, at a significance level of .05. A multivariate logistic regression analysis in a backward logistic regression (LR) model was carried out to estimate the relationship between dependent and independent variables. IBM SPSS Statistics, version 21 for Windows (SPSS, Chicago, IL) was used for all analyses. Our working hypothesis was that capsular closure would markedly reduce HO rate to less than 10%, which is the rate mentioned in other studies.3-7 Post hoc power analysis was carried out with IBM
SPSS Sample Power (SPSS, Chicago, IL) and showed that 50 patients in each group would yield power of more than 95%.
Results In this study, 100 patients with a mean age of 37.5 years (range, 18 to 68 years) were recruited. The control group consisted of 31 men and 19 women; the mean age of the control group was 36.7 years (range, 18 to 68 years). The study group consisted of 30 men and 20 women; the mean age of the study group was 38.2 years (range, 18 to 68 years) (Table 2). The mean follow-up was 12.7 months (range, 6 to 23.3 months). The control group did not significantly differ from the study group regarding age, sex, surgery time, and procedure performed (Table 2). The leading indication for operation in our study was the diagnosis of FAI, which was found in 56 patients, followed by isolated labral tears, which were found in 20 patients. Other indications included subspinal impingement resulting from a low anterior inferior iliac spine in 12 patients, Legg-Calvé-Perthes disease in 4 patients, osteoarthritis in 2 patients, and internal snapping hip, developmental dysplasia of the hip, chondroblastoma, hip pain, pigmented villonodular synovitis, and synovial chondromatosis in 1 patient each. Radiographic findings of HO were recorded in 36 (36%) of 100 patients (22 findings in the control group) (Fig 2). There were 64 (64%) patients with no HO (28 in the control group), 17 (17%) with grade 1 HO (13 in the control group), 15 (15%) with grade 2 HO (5 in the control group), and 4 (4%) with grade 3 HO (all in the control group), as shown in Figure 3. The control and study groups did not differ significantly in HO rate (Table 2). The control and study groups also did not differ significantly regarding procedure performed during arthroscopy. The 2 groups had a similar proportion of labrum repair
Table 2. Baseline Characteristics of Patients Undergoing Hip Arthroscopy Variable Number Sex Men Women Age, yr, mean SE (range) Surgery time, min, mean SE (range) Follow-up, mo, mean SE (range) Heterotopic ossification Procedure performed Acetabular osteoplasty Femoral osteoplasty Labral repair Anterior inferior iliac spine decompression Microfractures Iliopsoas release
Capsule Open 50 (50)
Capsule Closed 50 (50)
31 (62) 19 (38) 36.7 2.27 (18-68) 126.6 4.08 (78-176) 12.1 0.53 (6-18) 22 (44)
30 (60) 20 (40) 38.2 1.96 (18-68) 117.4 3.35 (77-168) 13.2 0.65 (6-23) 14 (28)
P Value
Total 100
.425
45 42 45 4 3 0
(90) (84) (90) (8) (6) (0)
NOTE. Data presented as n (%) unless otherwise indicated. SE, standard error.
40 38 47 8 5 1
(80) (76) (94) (16) (10) (2)
.619 .083 .161 .144 .161 .310 .715 .357 .715 1
61 39 37.5 1.50 (18-68) 121.9 2.65 (77-176) 12.7 0.42 (6-23) 36 (36) 85 80 92 12 8 1
(85) (80) (92) (12) (8) (1)
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Fig 2. (A) Pelvic anteroposterior (AP) radiograph of 21-year-old male patient who underwent left hip arthroscopy for treatment of FAI taken 7 months after operation, showing HO lesion grade I according to Brooker classification. (B) Pelvic AP radiograph of 44-year-old male patient who underwent left hip arthroscopy for treatment of FAI taken 6 months after operation, showing HO lesion grade II according to Brooker classification. (C) Pelvic AP radiograph of 34-year-old male patient who underwent right hip arthroscopy for treatment of FAI taken 10 months after operation, showing HO lesion grade II according to Brooker classification.
(P ¼ .715), acetabular osteoplasty (P ¼ .161), and femoral osteoplasty (P ¼ .310) (Table 2). Patient selection, treatment allocation, and the incidence and types of HO seen in each group are shown in Figure 4. A multivariate logistic regression analysis in a backward LR model was carried out to estimate the relationship between the dependent variable (incidence of HO) and independent variables (age, sex, capsular management, labral management, acetabuloplasty, femoral osteochondroplasty, and the presence of FAI). This analysis showed that none of the abovementioned independent variables had a significant effect on the dependent variable. Because the clinical manifestation of HO has a wide spectrum, ranging from small clinically insignificant foci
of ossification to massive deposits of bone throughout the body, we analyzed the difference between the control and study groups regarding the incidence of lesions with potential clinically significant HO (i.e., grade II or higher). We did not find a significant difference between the aforementioned groups regarding lesions with potential clinically significant HO (P ¼ .799). A similar analysis was performed for the patient group with FAI as the leading intraoperative diagnosis. HO radiographic findings were recorded in 24 (42.8%) of 56 patients (16 in the control group). No significant difference was noted regarding age, sex, surgery time, HO rate, or clinically significant HO rate (P ¼ .916, P ¼ .402, P ¼ .759, P ¼ .431, and P ¼ .235, respectively). Furthermore, a multivariate logistic regression analysis in a backward LR model was carried out to estimate the relationship between the dependent variable (incidence of HO) and independent variables (age, sex, capsular management, labral management, acetabuloplasty, and femoral osteochondroplasty). This analysis found that none of the abovementioned independent variables had significant effect on the dependent variable.
Discussion
Fig 3. Distribution of HO lesions between control and study groups according to lesion grade.
The control and study groups did not differ statistically regarding age, sex, surgery time, and HO rate. The principal result of this study showed an incidence of 44% HO in the control group and 28% HO in the study group. Despite numerous reports in the literature about HO after open hip surgery, little is known and documented about this complication after hip arthroscopy. In the
HETEROTOPIC OSSIFICATION AFTER CAPSULAR CLOSURE
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Fig 4. Patient selection, treatment allocation, and the incidence and types of HO seen in each group.
few studies found in the literature, this incidence ranges from 1.6% to 44%3-8,15 (Table 3). Soft tissue trauma can induce heterotopic bone formation by inductive bone growth factor release from damaged cells. Animal experiments implicate an interaction between injured periosteum and necrotic or damaged muscle, which induces the periosteum to produce bone.9 Further evidence to support this model was presented by Rath et al.,16 who showed that debridement of necrotic gluteus minimus muscle diminishes HO after acetabular fracture fixation.16 Aho et al.11 showed that a plastic membrane introduced between the periosteum and muscle failed to stimulate ectopic bone formation. On the basis of this theory, we hypothesized that isolating the muscles surrounding the hip from the injured bone by capsular closure may reduce the rate of HO after hip arthroscopy.
The hip capsule is considered crucial to hip joint stability,17,18 but despite its key contribution to joint stability, no gold standard has yet been set for the optimal technique of capsulotomy, the amount of resection, and indications for capsular repair. Moreover, our literature search for capsular closure after hip arthroscopy studies yielded a few recent case reports on postoperative hip instability after hip arthroscopy,19-21 surgical technique notes,22-24 and a current concept for capsular management during hip arthroscopy.13 In the latter current concept, Bedi et al.13 advocated capsular closure using side-to-side stiches in FAI management and capsular plication in the management of instability. These recommendations were made mainly to enhance postoperative joint stability. According to our literature search, no recommendations for capsular management could be found regarding HO rate reduction.
Table 3. Studies Reporting Heterotopic Ossification Rate in Patients Undergoing Hip Arthroscopy Total No. Heterotopic Study of Patients Ossification Rate (%) Remarks 96 6 Study set to evaluate the early outcomes of arthroscopic management of Larson and Giveans, 20083 femoroacetabular impingement; HO mentioned as complication Clohisy et al., 20104 35 11.4 Study set to evaluate the early clinical and radiographic outcomes of combined hip arthroscopy and limited open osteochondroplasty; HO mentioned as complication Randelli et al., 20105 300 1.6 Study set to evaluate HO prevalence after hip arthroscopy for FAI and its relation with NSAID prophylaxis Zbeda et al., 20116 698 4.7 Study set to evaluate the incidence of HO after arthroscopic procedures for FAI Bedi et al., 20127 616 4.7 Study set to report the short-term incidence, severity, and location of HO in patients undergoing hip arthroscopy 66 12 HO rate mentioned as part of surgical technique description Ong et al, 201315 Rath, et al. 20138 50 44 Study set to assess the incidence of HO after hip arthroscopy Current study Control group 50 44 e Capsule closed 50 28 Study set to evaluate the role of capsular closure in prevention of HO NSAID, nonsteroidal anti-inflammatory drug.
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Limitations Our study showed no difference between the study and control groups. This may stem from a lack of sample size or power calculation and consequent risk of type II bias. In addition, the radiographic follow-up was not carried out during a constant period, a fact that may also introduce bias. Still, all the patients had a minimum of 9-week radiographic follow-up because in humans, ossification is evident radiographically by 6 weeks and does not progress further at 12 to 24 weeks.25,26 The fact that the radiographs were read by a single surgeon who was not blinded constitutes another limitation. Our study was a comparative but not randomized trial, which may somewhat weaken the validity of the conclusions. The first 50 patients were allocated to the control group, and the subsequent 50 patients were allocated to the study group. Although our controls are not matched, the fact that most patients in both groups underwent treatment of similar pathologic hip conditions (i.e., FAI or labral tear, or both) allowed us to compare the presence of HO because the exposure of muscle and bone was similar in both groups.
Conclusions Capsular closure did not seem to alter the rate of HO when compared with a control group of patients in whom the capsulotomy was not repaired.
References 1. Kaplan FS, Hahn GV, Zasloff MA. Heterotopic ossification: Two rare forms and what they can teach us. J Am Acad Orthop Surg 1994;2:288-296. 2. Shafritz AB, Shore EM, Gannon FH, et al. Overexpression of an osteogenic morphogen in fibrodysplasia ossificans progressiva. N Engl J Med 1996;335:555-561. 3. Larson CM, Giveans MR. Arthroscopic management of femoroacetabular impingement: Early outcomes measures. Arthroscopy 2008;24:540-546. 4. Clohisy JC, Zebala LP, Nepple JJ, Pashos G. Combined hip arthroscopy and limited open osteochondroplasty for anterior femoroacetabular impingement. J Bone Joint Surg Am 2010;92:1697-1706. 5. Randelli F, Pierannunzii L, Banci L, Ragone V, Aliprandi A, Buly R. Heterotopic ossifications after arthroscopic management of femoroacetabular impingement: The role of NSAID prophylaxis. J Orthop Traumatol 2010;11:245-250. 6. Bedi A, Zbeda RM, Bueno VF, Downie B, Dolan M, Kelly BT. The incidence of heterotopic ossification after hip arthroscopy. Am J Sports Med 2012;40:854-863. 7. Bedi A, Zbeda RM, Bueno VF, Downie B, Dolan M, Kelly BT. The incidence of heterotopic ossification after hip arthroscopy. Am J Sports Med 2012;40:854-863. 8. Rath E, Sherman H, Sampson TG, Ben Tov T, Maman E, Amar E. The incidence of heterotopic ossification in hip arthroscopy. Arthroscopy 2013;29:427-433.
9. Zaccalini PS, Urist MR. Traumatic periosteal proliferations in rabbits. The enigma of experimental myositis ossificans traumatica. J Trauma 1964;4:344-357. 10. Michelsson JE, Rauschning W. Pathogenesis of experimental heterotopic bone formation following temporary forcible exercising of immobilized limbs. Clin Orthop Relat Res 1983:265-272. 11. Aho HJ, Aro H, Juntunen S, Strengell L, Michelsson JE. Bone formation in experimental myositis ossificans. Light and electron microscopy study. APMIS 1988;96:933-940. 12. Weiland DE, Philippon MJ. Arthroscopic technique of femoroacetabular impingement. Oper Tech Orthop 2005;15:256-260. 13. Bedi A, Galano G, Walsh C, Kelly BT. Capsular management during hip arthroscopy: From femoroacetabular impingement to instability. Arthroscopy 2011;27:1720-1731. 14. Brooker AF, Bowerman JW, Robinson RA, Riley LH Jr. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am 1973;55:1629-1632. 15. Ong C, Hall M, Youm T. Surgical technique: Arthroscopic treatment of heterotopic ossification of the hip after prior hip arthroscopy. Clin Orthop Relat Res 2013;471:1277-1282. 16. Rath EM, Russell GV Jr, Washington WJ, Routt ML Jr. Gluteus minimus necrotic muscle debridement diminishes heterotopic ossification after acetabular fracture fixation. Injury 2002;33:751-756. 17. Ito H, Song Y, Lindsey DP, Safran MR, Giori NJ. The proximal hip joint capsule and the zona orbicularis contribute to hip joint stability in distraction. J Orthop Res 2009;27:989-995. 18. Myers CA, Register BC, Lertwanich P, et al. Role of the acetabular labrum and the iliofemoral ligament in hip stability: An in vitro biplane fluoroscopy study. Am J Sports Med 2011;39:85S-91S (suppl). 19. Benali Y, Katthagen BD. Hip subluxation as a complication of arthroscopic debridement. Arthroscopy 2009;25:405-407. 20. Matsuda DK. Acute iatrogenic dislocation following hip impingement arthroscopic surgery. Arthroscopy 2009;25: 400-404. 21. Ranawat AS, McClincy M, Sekiya JK. Anterior dislocation of the hip after arthroscopy in a patient with capsular laxity of the hip. A case report. J Bone Joint Surg Am 2009;91:192-197. 22. Mei-Dan O, Young DA. A novel technique for capsular repair and labrum refixation in hip arthroscopy using the SpeedStitch. Arthrosc Tech 2012;1:e107-e112. 23. Slikker W III, Van Thiel GS, Chahal J, Nho SJ. The use of double-loaded suture anchors for labral repair and capsular repair during hip arthroscopy. Arthrosc Tech 2012;1:e213-e217. 24. Harris JD, Slikker W III, Gupta AK, McCormick FM, Nho SJ. Routine complete capsular closure during hip arthroscopy. Arthrosc Tech 2013;2:e89-e94. 25. Ritter MA, Vaughan RB. Ectopic ossification after total hip arthroplasty. Predisposing factors, frequency, and effect on results. J Bone Joint Surg Am 1977;59:345-351. 26. McLaren AC. Prophylaxis with indomethacin for heterotopic bone. After open reduction of fractures of the acetabulum. J Bone Joint Surg Am 1990;72:245-247.
