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n Feature Article Factors That Predict Blood Loss After Bernese Periacetabular Osteotomy Eduardo N. Novais, MD; Patrick M. Carry, MS; Lauryn A. Kestel, BS; Jason Koerner, BS; Gee Mei Tan, MD abstract Although strategies to reduce bleeding and avoid allogeneic transfusion have been described, there is controversy about the factors associated with blood loss after Bernese periacetabular osteotomy. This study was conducted to determine risk factors for postoperative blood loss. After institutional review board approval was obtained, a retrospective review was conducted of 41 young patients who underwent periacetabular osteotomy for symptomatic acetabular dysplasia over a 3-year period. Of these patients, two-thirds donated blood before surgery. A Cell Saver Elite autotransfusion system (Haemonetics, Braintree, Massachusetts) was used intraoperatively in all cases. Hemoglobin and hematocrit were obtained before surgery and during the hospital stay. The primary outcome variable was the percentage of total blood volume lost during surgery. Univariate analysis was performed to test the association between potential predictors of blood volume loss. Candidate variables that were significant at alpha=0.15 were tested with multivariate analysis. The average percentage of blood volume lost during surgery was 30.3% (95% confidence interval, 25.1%-35.5%). Univariate analysis showed that operative time, arthrotomy, femoral head-neck osteochondroplasty, labral procedure, male sex, and age were prognostic factors associated with increased blood volume loss. However, operative time (average, 294.6 minutes; range, 204-444 minutes) was the only independent predictor of increased blood loss in the final model. Additional procedures, such as femoral head-neck osteochondroplasty and labral repair or debridement performed through an anterior hip arthrotomy at the time of periacetabular osteotomy, were associated with increased operative time. The findings suggest that all patients undergoing periacetabular osteotomy, including those having concomitant procedures, may benefit from pre- and intraoperative strategies to conserve blood and avoid allogeneic transfusion. [Orthopedics. 2016; 39(6):e1147-e1153.] NOVEMBER/DECEMBER 2016 | Volume 39 • Number 6 B ernese periacetabular osteotomy increasingly has been performed for the treatment of symptomatic acetabular dysplasia.1,2 Periacetabular osteotomy is a technically challenging procedure that is associated with a steep learning curve and a potentially high rate of complications, including major blood loss.3,4 Previous studies estimated blood loss of 300 to 4500 mL.1,2,5 However, advances in surgical technique have led to less blood loss.6-8 A recent study of complications after periacetabular osteotomy performed by a group of experiThe authors are from the Department of Orthopaedic Surgery (ENN), Boston Children’s Hospital, Boston, Massachusetts; and the Musculoskeletal Research Center, Department of Orthopaedic Surgery (PMC, LAK) and the Department of Anesthesiology (GMT), Children’s Hospital Colorado, and the University of Colorado School of Medicine (JK), Aurora, Colorado. The authors have no relevant financial relationships to disclose. The authors thank Carol Ingraham, RN, and Amy Edstrom, RN, for assistance with data collection. Correspondence should be addressed to: Eduardo N. Novais, MD, Department of Orthopaedic Surgery, Boston Children’s Hospital, 300 Longwood Ave, Hunnewell Bldg, Boston, MA 02215 ([email protected]). Received: April 25, 2016; Accepted: July 7, 2016. doi: 10.3928/01477447-20160819-08 e1147 n Feature Article enced surgeons reported mean estimated blood loss of 714 mL (range, 100-3900 mL). This wide range of reported blood loss may be related to the length of the procedure.9 This is of great importance because now periacetabular osteotomy is more commonly performed with concomitant procedures to correct associated intra-articular pathology.10-13 Several strategies, including autologous preoperative blood donation5 and intraoperative use of cell saver systems,9,14 have been reported for the management of blood loss associated with periacetabular osteotomy. Independent of the method used, the vast majority of patients require red blood cell transfusion.5,9,14,15 Although allogeneic blood transfusion is currently accepted as a safe procedure, with minimal risk of transfusion-transmitted infection, transfusion-associated morbidity remains a concern.16 Few studies have described blood conservation methods used during periacetabular osteotomy. A single study suggested that tranexamic acid reduced blood loss and transfusion requirements.15 Further, previous studies showed conflicting results on potential risk factors for increased blood loss.9,14 Identification of patients who are at increased risk for blood loss during periacetabular osteotomy potentially could allow more specific strategies to conserve blood and avoid allogeneic transfusion. The goal of the current study was to investigate patient-specific and operative factors associated with blood loss during periacetabular osteotomy. Materials and Methods After institutional review board approval was obtained, a retrospective cohort study design was used to identify factors associated with blood loss during periacetabular osteotomy. A total of 41 patients underwent periacetabular osteotomy at the study institution between January 2012 and June 2015. No patient was excluded from the study; however, e1148 because of the small number of patients who underwent bilateral procedures (n=7), data were collected from the first procedure only. The medical records of all subjects were reviewed retrospectively. Demographic and clinical variables included sex, age at surgery, body mass index, affected side, history of surgery, year of surgery, operative approach (classic approach with release of the rectus femoris tendon vs rectus-sparing approach), common additional intra-articular operative procedures performed through an arthrotomy (osteochondroplasty of the femoral head-neck junction, acetabular labrum debridement and repair), operative time, estimated blood loss, estimated total blood volume, and preoperative hemoglobin. Blood volume was estimated as weight in kilograms*70 for male patients and weight in kilograms*65 for female patients. Among subjects with multiple preoperative blood draws, the hemoglobin level obtained during the blood draw closest to the date of surgery was recorded as the preoperative hemoglobin value (range, <1-24 days). Indications for surgery included a history of activity-related pain for a minimum of 3 months, acetabular dysplasia defined by a lateral center edge angle of Wiberg17 of 20° or less and acetabular roof obliquity of Tönnis18 greater than 10° on anteroposterior pelvic radiograph, concentric reduction of the joint on functional abduction view, and absence of arthritic changes (Tönnis arthritis grade II or less). General endotracheal anesthesia with a total intravenous anesthetic was used in all cases. No specific hypotensive anesthesia protocol to reduce blood loss was used, and tranexamic acid was not administered. Periacetabular osteotomy was performed with a classic approach, with transection of the rectus femoris, as described originally by Ganz et al1 in patients in whom arthrotomy was planned before surgery. Surgery was performed with an approach that spared the rectus femoris in patients with no history of catching or locking of the hip, more than 20° internal rotation with the hip flexed, and no signs of acetabular labrum tear on preoperative magnetic resonance imaging.6 A standard unipolar electrocautery device, set at 30/30 W, was used during all periacetabular osteotomy procedures. All bony cuts were performed through a single approach from inside the pelvis, without dissection of the abductor muscles.19 The acetabular fragment was fixed with 3 or 4 screws measuring 4.5 mm. After fixation, hip motion was tested. If less than 90° flexion or less than 20° internal rotation in flexion was noticed, arthrotomy was performed to correct for potential impingement. After arthrotomy, femoral head-neck osteochondroplasty was performed with a high-speed burr when indicated, and the labrum was reattached with suture anchors when a fullthickness labral tear was encountered. Partial labral debridement was performed in patients with a hypertrophic labrum with extensive degenerative changes. The wound was closed in standard fashion, and no drains were used after surgery. Techniques used to minimize intraoperative blood loss included electrocautery of blood vessels and application of bone wax to fill small bone holes. Similar techniques were used for all patients in the study cohort. Patients were allowed to walk with crutches with touchdown weight bearing for 6 to 8 weeks, according to radiographic healing. Preoperative autologous blood donation within 4 weeks of surgery was recommended for all patients However, 13 (32%) patients did not donate blood before surgery for multiple reasons, including out-of-state residence, vasovagal reaction at the time of donation, inability to achieve good intravenous access, refusal to donate, and fever. A Cell Saver Elite autotransfusion system (Haemonetics, Braintree, Massachusetts) was used for all patients during surgery. Hemoglobin Copyright © SLACK Incorporated n Feature Article and hematocrit were collected daily during the hospital stay. All patients with available predonated blood received an autologous transfusion. Unforeseen transfusion was defined as transfusion (autologous or allogeneic) performed intraoperatively after recommendation by the anesthesiologist, based on hemodynamic status and hemoglobin or hematocrit level. Data were not collected on specific triggers for postoperative transfusion, but the indication for allogeneic transfusion was a low hemoglobin level (≤8 g/dL)20 or the presence of symptoms associated with acute anemia that compromised rehabilitation with physical therapy. The number of patients who met the absolute criteria for blood transfusion was recorded. Absolute criteria for blood transfusion included unplanned perioperative allogeneic or autologous blood transfusion and postoperative blood draw showing a hemoglobin level of 8 g/dL or less.20 Primary outcome variables included the percentage of total blood volume lost during surgery, which was calculated as the estimated blood loss divided by the calculated total circulating blood volume. Estimated blood loss was obtained from anesthesia records based on the volume calculated by the cell saver system. Statistical Methods Descriptive statistics were used to summarize the demographic and clinical characteristics of all patients. Multivariate linear regression analysis was used to identify variables associated with the percentage of blood volume lost during surgery. Univariate analysis was used to test the association between the following candidate predictors and the percentage of blood volume lost during surgery: operative time, procedures performed at the time of periacetabular osteotomy, age, sex, preoperative hemoglobin level, body mass index, cumulative procedure count since the start of the study period (a surrogate variable for surgical learning curve), and history of previous surgery. During the model-building step of analysis, a strong correlation was observed between operative time and the procedure variables osteochondroplasty (Spearman’s rho=0.59, P<.0001), arthrotomy (Spearman’s rho=0.57, P<.0001), and labral procedure (Spearman’s rho=0.31, P=.0465). The authors concluded that this group of variables was representative of the complexity and invasiveness of the surgery. Because operative time was the strongest predictor of percentage of blood volume lost in this grouping of variables, it was the only variable included in the multivariate model. Candidate variables that were significant at alpha=0.15 were tested in the multivariate model. Results Most (88%) of the patients included in this study were female. Mean age at surgery was 19 years (range, 11-36 years). The approach sparing the rectus femoris was used in 18 (44%) of patients, whereas 23 (56%) patients underwent the classic approach, with transection of the rectus femoris. Of the patients, 39.0% (95% confidence interval, 24.1%-54.0%) met the absolute criteria for blood transfusion. Patient demographics and concomitant procedures performed at the time of periacetabular osteotomy are shown in Table 1. The average percentage of blood volume lost during surgery was 30.3% (95% confidence interval, 25.1%-35.5%). Operative time, arthrotomy, femoral head-neck osteochondroplasty, labral procedure, male sex, and age were prognostic factors associated with increased percentage of blood volume loss in the univariate analysis. (Table 2). However, operative time was the only independent predictor of increased blood loss in the final model. After controlling for sex and age, the percentage of blood volume lost during surgery increased by 1.1 percentage points for every 10-minute increase NOVEMBER/DECEMBER 2016 | Volume 39 • Number 6 Table 1 Demographics, Patient Characteristics, and Procedures Performed During Periacetabular Osteotomy Variable Value Female, No. 36 (87.8%) Right hip, No. 23 (56.1%) Previous pelvic osteotomy, No. 1 (2.4%) Year of surgery, No. 2012 13 (31.7%) 2013 13 (31.7%) 2014 12 (29.3%) 2015 3 (7.3%) Age, mean (SD), y 19 (6.3) Body mass index, mean (SD), kg/m2 22 (3.3) Preoperative hemoglobin, mean (SD), g/dL 12.8 (2.0) Approach, No. Classic approach 23 (56.1%) Rectus sparing 18 (43.9%) Arthrotomy, No. 19 (46.3%) Osteochondroplasty of femoral head-neck junction, No. 15 (36.6%) Labral repair or debridement, No. 4 (9.8%) Osteoplasty of anterior inferior iliac spine, No. 7 (17.1%) Operative time, mean (SD), min 294.6 (57.7) in operative time (95% confidence interval, 0.2%-1.9%; P=.0099). In the multivariate analysis, age and sex were not independently predictive of percentage of blood loss during surgery. After controlling for sex and operative time, the percentage of blood volume lost during surgery increased by 0.6 percentage points for every 1-year increase in age (95 confidence interval, -0.1% to 1.4%; P=.0837). After controlling for operative e1149 n Feature Article Table 2 Variables Related to Percentage of Blood Volume Lost During Surgery: Univariate Analysis Variable Comparison Estimate Lower to Upper P Demographic/clinical characteristic Sexa Body mass index a Age Male vs female 13.0% -2.6% to 28.6% .0996 Per 5-unit increase -2.4% -10.5% to 5.8% .5577 Per 1-y increase 0.9% 0.1% to 1.7% .0358 Preoperative hemoglobin Per 1-unit increase 0.2% -2.6% to 3.7% .715 Learning curve Per 5 procedures or experiences -0.4% -2.7% to 1.8% .7013 Operative timea Per 10-min increase 1.4% 0.5% to 2.2% .0017 Labral procedure Yes vs no 22.7% 6.5% to 38.9% .0073 Osteochondroplasty Yes vs no 10.6% 0.2% to 21.0% .0459 Arthrotomy Yes vs no 12.1% 2.2% to 21.9% .0177 Surgical complexity/invasiveness a Variables tested in the multivariate model. Table 3 Operative Time Associated With Different Procedure Combinations No. Mean, min Range, min 2 (5%) 392 385-398 13 (32%) 335 237-444 Periacetabular osteotomy+arthrotomy+labral procedure 2 (5%) 307 299-315 Periacetabular osteotomy+arthrotomy 2 (5%) 279 259-299 Periacetabular osteotomy 4 (10%) 273 229-344 18 260 204-327 Procedure Classic Periacetabular osteotomy+arthrotomy+labral procedure+osteochondroplasty head/neck Periacetabular osteotomy+arthrotomy+osteochondroplasty head/neck Rectus-sparing periacetabular osteotomy time and age, the percentage of blood volume lost was an average of 9.1% higher in male subjects compared with female subjects (95% confidence interval, -5.0% to 23.1%; P=.1991). Only 2 of 19 (10.5%) patients undergoing arthrotomy had no intra-articular e1150 procedures. Of the patients, 15 (79%) were treated for asphericity of the femoral head with osteochondroplasty of the head-neck junction; 2 (10.5%) were treated with labral repair, and 2 (10.5%) were treated with labral debridement. Average operative time was 294.6 min- utes (range, 204-444 minutes). Operative time was increased when periacetabular osteotomy was performed in conjunction with intra-articular procedures, such as osteochondroplasty of the femoral head-neck junction and labral repair or debridement (Table 3). Only 1 patient had a transfusion complication when an intravenous line failed during autologous blood transfusion and caused infiltration to the right forearm, with hematoma formation. The infiltration was managed with thermal manipulation and application of warm compresses. Discussion Although different blood-conserving strategies, including the use of predonated autologous blood, cell saver autotransfusion, and tranexamic acid, have been described to avoid allogeneic transfusion, there is no universally accepted protocol to manage blood loss associated with periacetabular osteotomy.5,9,14,15 Periacetabular osteotomy increasingly has been performed with arthrotomy11,13 or in combination with hip arthroscopy12,21,22 because of evidence that femoroacetabular impingement adversely affects the outcome of periacetabular osteotomy 23-25 and because of the high prevalence of intra-articular pathology.10,11 Findings on predictive factors associated with blood loss during periacetabular osteotomy are limited and conflicting, and this study was conducted to determine patient and procedure risk factors related to blood loss in a cohort of 41 young patients undergoing periacetabular osteotomy. Operative time was the strongest independent factor associated with blood loss during periacetabular osteotomy. After controlling for sex and age, the percentage of blood volume lost during surgery increased by 1.1 percentage points for every 10-minute increase in operative time (95% confidence interval, 0.2%-1.9%; P=.0099). Similarly, Lee et al9 found 11% greater loss per hour of surgery. In contrast, Pulido et al14 did Copyright © SLACK Incorporated n Feature Article not find an association between duration of surgery and blood loss. This discrepancy may be related to differences in operative time and measurement of blood loss reported in these 3 studies. Pulido et al14 reported the lowest mean operative time of 132 minutes, but the current study and the study of Lee et al9 reported an average of 295 minutes and 255 minutes, respectively (Table 4). Several factors, such as surgeon experience and operating room staff and surgical team familiarity with periacetabular osteotomy, may affect operative time. However, in the current study, the number of procedures performed before the current surgery, a surrogate for the surgeon’s experience, was not a predictor of blood loss. In the current study, the addition of intra-articular procedures to treat femoral head-neck asphericity and labral tears was the most important factor associated with increased operative time. However, Lee et al9 did not find that arthrotomy was an independent risk factor for increased blood loss. They provided no details about procedures performed through the arthrotomy. In the current study, routine arthrotomy was not performed at the time of periacetabular osteotomy, and the authors used more selective criteria for opening the joint. As a consequence, an intra-articular procedure was performed after arthrotomy in 89.5% of cases. These findings are in agreement with a previous study of 151 patients undergoing periacetabular osteotomy that reported asphericity of the femoral head-neck junction in 85% of cases and labral pathology in 21% of cases at the time of arthrotomy.11 Wingerter et al15 studied the use of tranexamic acid to reduce blood loss in 100 patients undergoing periacetabular osteotomy. Their study included 34 patients who underwent hip arthroscopy in the same setting and found no difference in blood loss in arthroscopically treated vs nonarthroscopically treated patients. De- spite the increased operative time, it is possible that intra-articular procedures performed through an arthroscopic approach before periacetabular osteotomy do not affect blood loss. Most bleeding that occurs during periacetabular osteotomy happens as a result of pelvic osteotomy. In the current study, arthrotomy was performed after periacetabular osteotomy, and additional bone bleeding may have continued during arthrotomy and the intra-articular procedure. It is possible that performing open arthrotomy before osteotomy may not affect blood loss. However, performing arthrotomy after periacetabular osteotomy allows assessment and correction of subtle impingement, which may be limited if arthrotomy is performed first. Further studies are necessary to identify patients who will benefit from intraarticular procedures and to establish the best approach to the joint at the time of periacetabular osteotomy. There is controversy as to whether patient sex affects blood loss associated with periacetabular osteotomy. Lee et al9 suggested that male sex was the only preoperative patient characteristic associated with higher blood loss. In contrast, Pulido et al14 did not find an association between patient sex and the need for transfusion. In this study, after controlling for age and operative time, sex was not associated with blood loss. This observation suggests that sex may not be directly related to blood loss during periacetabular osteotomy. Male sex may be representative of more complex cases that often require additional procedures and additional operative time. Previous studies26,27 suggested that there are sexdependent anatomic and biologic differences in male patients vs female patients undergoing periacetabular osteotomy and that these changes make the surgery more challenging in male patients and may lead to a higher prevalence of hip impingement and postoperative complications. NOVEMBER/DECEMBER 2016 | Volume 39 • Number 6 Limitations This study had several limitations. First, autologous blood donation was recommended for all patients; however, one-third of the patients could not donate blood before surgery. Predonated autologous blood was transfused more liberally than allogeneic blood. The proportion of patients who received allogeneic transfusion in this study was lower than in previous studies.5,14,15 However, this study did not investigate factors associated with increased risk of transfusion because there were no specific trigger criteria for transfusion. However, this study identified factors associated with blood loss during surgery that are expected to affect the rate of postoperative transfusion. This limitation is likely inherent to the retrospective design of the study. Second, it is possible that total blood loss during surgery was underestimated because the calculation was made solely by the cell saver autotransfusion system. However, this method was used consistently in every patient in the study cohort, so the risk of misclassification may not be a concern. Third, the preoperative hemoglobin level may have been lower in patients who donated blood before surgery. This could have affected the rate of postoperative transfusion.14 However, no association was found between preoperative hemoglobin level and blood loss. Future well-designed prospective studies are needed to clarify the threshold for the preoperative hemoglobin level that is associated with greater need for blood transfusion after periacetabular osteotomy and to determine the need for and effect of autologous predonation. Conclusion Blood loss during periacetabular osteotomy is directly dependent on the length of surgery. Strategies to reduce the use of allogeneic blood, such as autologous preoperative donation, as well as procedures that minimize blood loss during surgery, such as the use of hypotensive anesthesia and tranexamic acid, should be evalu- e1151 e1152 2015 2012 2013 41 7.2 (11-36) 19 27 (17-47) 50 (TXA) 28 (±9.7) 25.6 (12-49) 30 (13-49) 7.3 4.5 7.9 3.6 (No TXA) 50 169 2011 2011 141 108 2003 2009 107 1996 (19-28) (192-444) 295 NA NA (±81.6) 255 (77-216) 132 NA NA NA (200-5400) 1244 489 639 (200-3900) 925 (±268) 478 18 (44%) 23 (46%) 11 (22%) 82 (49%) NA NA (±2.0) 12.8 NA NA (±3.3) 36.1 (10.1-16.6) 13 (12.9-13.7) 13.25 (1250-4380) 2500a 12.95 (12-13.3) 1905 (13.1-14.3) 13.50 Mean Preop Hgb (Range or ±SD), g/dL (1089-2661) a NA NA 2100a (1350-3000) No. of Arthrotomies Mean Estimated Intraoperative BL (Range or ±SD), mL 9.74 (±1.7) NA NA NA (7-13.2) 9.8 (9.13-10.9) 10.25 (8.3-10.2) 8.85 (10.4-12.4) 11.45 Mean Postop Hgb (Range or ±SD), g/dL 28 (68.3%) Variable Variable Majority (2%) 2/108 100% 0 0 Autologous Preop Donation Abbreviations: BL, blood loss; Hgb, hemoglobin; NA, not applicable; Postop, postoperative; Preop, preoperative.; TXA, tranexamic acid. a Median blood loss. Current study Wingerter et al15 Lee et al9 Pulido et al14 2005 9.2 24 82 1999 19 (15-24) 8 24 2005 18 6.3 1999 22 Mean Age (Range or ±SD), y (19-31) 1996 Atwal et al5 Ratio, Female to Male 1999 Year Study No. of Hips Mean Operative Time (Range or ±SD), min Yes Yes Yes Yes Yes Yes Yes Yes Cell Saver Predictors of Blood Loss Reported in Previous Periacetabular Osteotomy Studies Table 4 17.1% 24% 48% NA 21 (20%) 13 (16%) 12 (67%) 18 (82%) No. of Allogeneic Transfusions Operative time predicted blood loss Use of TXA reduced blood loss and transfusion Preoperative hematocrit predicted postoperative hematocrit Operative time predicted blood loss Operative time was not a predictive factor Preoperative Hgb was predictive of transfusion NA NA NA Predictive Factors n Feature Article Copyright © SLACK Incorporated n Feature Article ated in well-designed prospective studies. Patients undergoing periacetabular osteotomy with expected longer duration of surgery, including those with planned associated procedures, may benefit from these strategies. 9. Lee CB, Kalish LA, Millis MB, Kim YJ. Predictors of blood loss and haematocrit after periacetabular osteotomy. Hip Int. 2013; 23(suppl 9):S8-S13. References 11. Ginnetti JG, Pelt CE, Erickson JA, Van Dine C, Peters CL. Prevalence and treatment of intraarticular pathology recognized at the time of periacetabular osteotomy for the dysplastic hip. Clin Orthop Relat Res. 2013; 471(2):498-503. 1. Ganz R, Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias: technique and preliminary results. Clin Orthop Relat Res. 1988; 232:2636. 2. Siebenrock KA, Leunig M, Ganz R. Periacetabular osteotomy: the Bernese experience. Instr Course Lect. 2001; 50:239-245. 3. Clohisy JC, Schutz AL, St John L, Schoenecker PL, Wright RW. Periacetabular osteotomy: a systematic literature review. Clin Orthop Relat Res. 2009; 467(8):2041-2052. 10. Domb BG, Lareau JM, Baydoun H, Botser I, Millis MB, Yen YM. Is intraarticular pathology common in patients with hip dysplasia undergoing periacetabular osteotomy? Clin Orthop Relat Res. 2014; 472(2):674-680. 12.Peters CL, Sierra RJ. Report of breakout session: intraarticular work during periacetabular osteotomy. Simultaneous arthrotomy or hip arthroscopy? Clin Orthop Relat Res. 2012; 470(12):3456-3458. joint. In: Tönnis D, ed. Congenital Dysplasia and Dislocation of the Hip. New York, NY: Springer; 1987:100-142. 19. Murphy SB, Millis MB. Periacetabular osteotomy without abductor dissection using direct anterior exposure. Clin Orthop Relat Res. 1999; 364:92-98. 20. Carson JL, Grossman BJ, Kleinman S, et al. Red blood cell transfusion: a clinical practice guideline from the AABB. Ann Intern Med. 2012; 157(1):49-58. 21.Domb BG, LaReau JM, Hammarstedt JE, Gupta A, Stake CE, Redmond JM. Concomitant hip arthroscopy and periacetabular osteotomy. Arthroscopy. 2015; 31(11):2199-2206. 22. Redmond JM, Gupta A, Stake CE, Domb BG. The prevalence of hip labral and chondral lesions identified by method of detection during periacetabular osteotomy: arthroscopy versus arthrotomy. Arthroscopy. 2014; 30(3):382-388. 4. Davey JP, Santore RF. Complications of periacetabular osteotomy. Clin Orthop Relat Res. 1999; 363:33-37. 13. Nassif NA, Schoenecker PL, Thorsness R, Clohisy JC. Periacetabular osteotomy and combined femoral head-neck junction osteochondroplasty: a minimum two-year followup cohort study. J Bone Joint Surg Am. 2012; 94(21):1959-1966. 5. Atwal NS, Bedi G, Lankester BJ, Campbell D, Gargan MF. Management of blood loss in periacetabular osteotomy. Hip Int. 2008; 18(2):95-100. 14. Pulido LF, Babis GC, Trousdale RT. Rate and risk factors for blood transfusion in patients undergoing periacetabular osteotomy. J Surg Orthop Adv. 2008; 17(3):185-187. 6. Novais EN, Kim YJ, Carry PM, Millis MB. The Bernese periacetabular osteotomy: is transection of the rectus femoris tendon essential? Clin Orthop Relat Res. 2014; 472(10):3142-3149. 24. Myers SR, Eijer H, Ganz R. Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. 1999; 363:93-99. 15. Wingerter SA, Keith AD, Schoenecker PL, Baca GR, Clohisy JC. Does tranexamic acid reduce blood loss and transfusion requirements associated with the periacetabular osteotomy? Clin Orthop Relat Res. 2015; 473(8):2639-2643. 25. Beaulé PE, Dowding C, Parker G, Ryu JJ. What factors predict improvements in outcomes scores and reoperations after the Bernese periacetabular osteotomy? Clin Orthop Relat Res. 2015; 473(2):615-622. 7. Peters CL, Erickson JA, Anderson MB, Anderson LA. Preservation of the rectus femoris origin during periacetabular osteotomy does not compromise acetabular reorientation. Clin Orthop Relat Res. 2015; 473(2):608614. 8.Troelsen A, Elmengaard B, Søballe K. Comparison of the minimally invasive and ilioinguinal approaches for periacetabular osteotomy: 263 single-surgeon procedures in well-defined study groups. Acta Orthop. 2008; 79(6):777-784. 16. Spahn DR, Moch H, Hofmann A, Isbister JP. Patient blood management: the pragmatic solution for the problems with blood transfusions. Anesthesiology. 2008; 109(6):951-953. 17. Wiberg G. Studies on dysplastic acetabulum and congenital subluxation of the hip joint with special reference to the complication of osteoarthritis. Acta Chir Scand. 1939; 83(suppl 58):28-38. 18. Tönnis D. General radiography of the hip NOVEMBER/DECEMBER 2016 | Volume 39 • Number 6 23. Albers CE, Steppacher SD, Ganz R, Tannast M, Siebenrock KA. Impingement adversely affects 10-year survivorship after periacetabular osteotomy for DDH. Clin Orthop Relat Res. 2013; 471(5):1602-1614. 26. Duncan ST, Bogunovic L, Baca G, Schoenecker PL, Clohisy JC. Are there sexdependent differences in acetabular dysplasia characteristics? Clin Orthop Relat Res. 2015; 473(4):1432-1439. 27. Ziebarth K, Balakumar J, Domayer S, Kim YJ, Millis MB. Bernese periacetabular osteotomy in males: is there an increased risk of femoroacetabular impingement (FAI) after Bernese periacetabular osteotomy? Clin Orthop Relat Res. 2011; 469(2):447-453. e1153