- Email: [email protected]
Periacetabular Osteotomy for Mild or Borderline Acetabular Dysplasia
ARTICLE IN PRESS
Periacetabular Osteotomy for Mild or Borderline Acetabular Dysplasia Jennifer D. Marland, PT, DPT, and James D. Wylie, MD, MHS Evaluating the adolescent and young adult hip can be challenging given the rapid evolutions in the field over the last 10-20 years. One of the more difficult groups of patients to evaluate are those that fall into the mild or borderline acetabular dysplasia. We must determine whether the patient’s pain and chondrolabral disease is due to their acetabular morphoplogy or their associated femoral morphology and therefore is more of an unstable or an impingement hip. A thorough history, physical examination, and imaging evaluation are needed to determine the best treatment option in these patients. When this evaluation determines that the patient is suffering from a primary instability problem, these patients are best treated with a surgery that improves the stability of the hip. Here we describe the patient evaluation and periacetabular osteotomy technique in the mild or borderline dysplastic patient. Oper Tech Orthop 00:100782 © 2020 Elsevier Inc. All rights reserved.
KEYWORDS mild acetabular dysplasia, periacetabular osteotomy, hip arthroscopy, young adult, Hip pain
Introduction dolescent and young adult hip surgery is a field that has changed significantly over the last 30 years. This started with the description of the periacetabular osteotomy (PAO) by Dr Ganz.1 Subsequently, the descriptions of femoroacetabular impingement and the surgical dislocation approach, and the significant advances in hip arthroscopy have shaped the field today.2-4 Over the last 20 years, these operations have become safer and more efficacious at treating adolescent and young adult hip pain. While true dysplastic patients now are reliably treated with PAO and patients with obvious femoroacetabular impingement are mostly treated with arthroscopy, there is still a question of the right treatment for the patient with mild or borderline dysplasia. These patients also commonly have concomitant cam morphology and it is sometimes not clear which of these pathologies is driving the patients symptoms.5 Treatment options include PAO with or without hip arthroscopy to address labral pathology or hip arthroscopy with treatment of concomitant labral pathology
A
The Orthopedic Specialty Hospital, Intermountain Healthcare, Murray, UT. Address reprint requests to James D, Wylie MD, MHS, The Orthopedic Specialty Hospital, Intermountain Healthcare, 5848 South Fashion Blvd. Suite 120, Murray, UT 84107. E-mail: [email protected]
https://doi.org/10.1016/j.oto.2020.100782 1048-6666/© 2020 Elsevier Inc. All rights reserved.
with capsular plication, with or without cam resection. This article will describe the patient evaluation to determine which patients with mild or borderline dysplasia that may benefit from PAO and describe the surgical technique and correction goals.
Patient Evaluation History Patient history starts with a description of the pain including location, duration, timing, severity, aggravating factors, and alleviating factors. Differentiating between impingement and instability pain can be difficult. Impingement pain is more common in deep hip flexion positions like sitting for long periods of time, squatting, going up/down stairs, and pivoting and twisting. Structurally unstable hips can have more generalized pain including muscular and trochanteric in nature. The pain can happen more commonly in weight bearing positions that may or may not be in deep hip flexion. The history of prior hip arthroscopy and the capsular management during that surgery is important to determine whether they may have postoperative instability from prior capsulotomy that was either not repaired or did not completely heal. 1
ARTICLE IN PRESS J.D. Marland and J.D. Wylie
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Physical Examination Objective examination starts with watching the patient perform gait. In-toeing or out-toeing, or an inward facing patella can be a sign of femoral versional abnormalities.6 Range of motion is then tested in supine (flexion, and internal rotation (IR) and external rotation (ER) in 90° of flexion). It is important to provide downward pressure on the knee and feel for the end range of the motion of the hip joint, as the pelvis can move and you can overestimate hip range of motion. If a patient has greater than 30° of IR in 90° of flexion, then the patient may have more instability as opposed to impingement. Flexion adduction and IR testing loads the labrum and can provoke pain in the setting of chondrolabral pathology, this is not specific of underlying anatomy/pathology. It is important to notice the degree of IR at end range of motion. Range of motion is also tested in the prone position and increased IR above 60° can be a sign of increased femoral and/or acetabular anteversion, both markers of a more unstable hip.7 Flexion, abduction, and ER can cause groin pain with chondrolabral pathology and lateral pain with trochanteric pathology. Apprehension testing (extension and ER with the opposite leg/hip held to the chest in flexion) can lead to groin pain in patients with chondrolabral pathology and a sense of apprehension in patients with structural instability, similar to the apprehension test in the shoulder.8 Strength testing of hip abduction is performed in the side-lying position with the hip in flexion, neutral, and extension. Testing in extension requires coordinated contraction of the gluteus medius and maximus, which can be inhibited in patients with hip pain. Weakness can be a sign of potential ability to improve with a structured strengthening program. Beighton criteria to assess ligamentous laxity with thumb to forearm, metacarpal phalangeal (MCP) hyperextension, elbow hyperextension, knee hyperextension, and whether the patient can place their palms on the floor with the knees in extension should be assessed in all patients.9 More positive criteria indicate of more ligamentous laxity, with a total of 4 or greater considered go be indicative of generalized ligamentous laxity.9
Radiographs A comprehensive radiographic evaluation includes a standing anteroposterior (AP) pelvis radiograph, a false profile radiograph, and lateral radiograph to evaluate the anterior and the anterosuperior head neck junction. We use a frog lateral radiograph to visualize the anterior aspect of the femur (3:00) and a 45° Dunn lateral radiograph to evaluate the anterosuperior aspect of the femur (1:30).10 The AP pelvis radiograph with the feet in neutral evaluates the lateral aspect of the femur (12:00).10 Important radiographic measurements on each of the radiographic view are listed in Table and illustrated in Figure 1.
Advanced Imaging Magnetic resonance imaging (MRI) and computed tomography (CT) are the advanced imaging modalities most
Table Important Radiographic Measures to Evaluate the Hip by Radiographic View Radiographic View
Important Measurements
Standing anteroposterior Pelvis
Lateral center edge angle Tonnis angle Anterior wall index Posterior wall index Femoroepiphyseal acetabular roof index Femoral neck shaft angle Femoral alpha angle Crossover sign Posterior wall sign Ischial spine sign
False profile Laterals: 45˚ Dunn lateral Frog lateral
Anterior center edge angle Femoral alpha angle
commonly employed in the hip. MRI can be arthrogram or nonarthrogram. Three Tesla (T) field strength magnets can provide detailed evaluation of the chondrolabral junction without the need for an arthrogram, but 1.5 T or lower magnets need an arthrogram injection to properly evaluate the labrum and the chondrolabral junction. Given the ionizing radiation that the patient is exposed to during CT scanning, it is important to optimize protocols for the hip preservation patient to decrease radiation exposure. MRI with or without arthrogram can evaluate the femoral and acetbular articular cartilage for thickness and areas of full-thickness defect. or subchondral cystic change indicative of degenerative disease. It also evaluates the integrity of the chondrolabral junction and intrasubstance signal in the labrum. In the setting of prior failed hip arthroscopy, arthrogram can be used to investigate for capsular integrity, capsular volume, and capsular defects in area of prior capsulotomy.11 CT provides 3-dimensional bony morphology of the hip and quantifies the acetabular coverage and version at multiple levels. In addition, the morphology of the femoral head/neck junction is qualitatively evaluated in 3 dimensions, which can make it easier to evaluate the femoral-sided cam morphology. Axial imaging through the knee is important to quantify femoral version.
Rationale for Treatment Decision While the lateral center edge angle (LCEA) has traditionally been used as the primary marker to diagnose acetabular dysplasia, a more thorough evaluation is needed to fully understand the patient’s acetabular coverage and hip anatomy (Fig. 1).5 When these other variables/measures (female gender, femoral anteversion, anterior wall index [AWI], posterior wall index [PWI], anterior center edge angle [ACEA], and femoroepiphyseal acetabular roof [FEAR index]) point towards an unstable hip then PAO with or without arthroscopy is the treatment of choice.5 Specifically, anterior instability can be
ARTICLE IN PRESS PAO for Mild or Borderline Acetabular Dysplasia
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Figure 1 Important radiographic measures to evaluate the hip. (A) Lateral center edge angle (LCEA) measured on the right hip and Tonnis Angle measured on the left hip. Both are measured in relation to a line normalized to the pelvis or femoral heads. In addition, they are measured in relation to the sclerotic sourcil of the weight bearing aspect of the acetabulum and not all the way to the edge of the bone. (B) Anterior wall index measured on the right hip. Anterior wall measured in line with femoral neck (red line “A”) as coverage of the femoral head, to calculate divide this number by the radius of the femoral head (blue line “R”). Posterior wall index measured on the left hip. Posterior wall measured in line with femoral neck (red line “P”) as coverage of the femoral head, to calculate divide this number by the radius of the femoral head (blue line “R”). (C) Femoroepiphyseal acetabular roof (FEAR) Index, this angle is formed by the middle third of the femoral physeal scar and the acetabular roof as measured in the Tonnis angle. (D) Crossover sign (blue anterior wall, Red posterior wall), posterior wall sign (red posterior wall medial to center of head (star)), and ischial spine sign (white writing and arrow). (E) Anterior center edge angle (ACEA) measured to the edge of the sourcil in relation to the vertical. (H) Femoral Alpha angle where the head neck junction loses sphericity in relation to a line through the center of the femoral neck. (Color version of figure is available online.)
seen in (more commonly) female patients with an LCEA less than 25 and 1 or more of the following other factors: femoral anteversion over 20°, AWI less than 0.3, an ACEA less than 20 degrees, a FEAR index that is laterally opening, or an elevated Beighton index (>4 points). Alternatively, patients with a PWI less than 0.8 with acetabular retroversion (positive crossover and ischial spine signs) may benefit from PAO due to instability from combined borderline lateral coverage and posterior wall deficiency.5 This can also be associated with a femoral-sided cam lesion and/or relative or absolute femoral retroversion that can accentuate the posterior instability. A treatment algorithm is presented in Figure 2. In some patients isolated arthroscopy can be an appropriate treatment in borderline dysplastic patients. A large cam deformity can act as a lever that accentuates the posterior instability and an appropriate femoroplasty for the cam lesion, removing the lever for posterior instability can result in an excellent outcome.12 In addition, in patients with an LCEA between 20° and 25° that have none of the above radiographic or clinical risk factors for instability may be candidates to be treated with isolated arthroscopy with femoroplasty and/or labral repair followed by capsular plication.13 However, surgeons should not perform any significant acetabuloplasty in these patients and should always perform a
capsular repair/plication with multiple stitches given their risk of postoperative instability. After deciding to go forward with a PAO, the next decision to make is whether an adjunctive arthroscopy is needed. Abnormal signal at the labrochondral and bony labral junction is indicative of labral tearing or chondrolabral injury. In
Figure 2 Treatment algorithm for young adults with hip pain and borderline acetabular dysplasia. ACEA, anterior center edge angle; AWI, anterior wall index; CT, computed tomography; FEAR, femoroepiphyseal acetabular roof; PAO, periacetabular osteotomy; PWI, posterior wall index; ROM, range of motion.
ARTICLE IN PRESS 4 addition, an elevated alpha angle on the femoral side indicative of a cam deformity should be treated either during arthroscopy or through an open arthrotomy to protect against post-PAO impingement.
Operative Technique and Case Examples The technique for the borderline dysplastic is no different than those with moderate or severe dysplasia. The incision is just 1-2 cm distal to the anterior superior iliac spine (ASIS) and iliac crest that extends down to superficial to the hip joint center (Fig. 3). In larger patients, (body mass index of 35 or greater) a traditional Smith-Peterson incision that curves down the thigh can be helpful for exposure. Dissection is taken through the superficial subcutaneous tissues down to the fascia. Full-thickness flaps can be mobilized to allow a smaller skin incision and a mobile skin window. The external obliques are then elevated off of the pelvic brim, there is a small fat-layer just superficial to the periosteum that marks the optimal dissection plane. The external obliques should be released to the apex of the iliac crest as it flares out laterally. The periosteum on the iliac brim is then incised and a Cobb is used to elevate the illiacus off of the inner table of the pelvis and a sponge is placed to bluntly dissect this interval. The interval between the tensor-fascialata (TFL) and the Sartorius is identified distally and the
Figure 3 Oblique incision for periacetabular osteotomy on a left hip, visualized from the left side of the patient, just distal to the ASIS (circle) and the illac brim/crest (dotted line)
J.D. Marland and J.D. Wylie fascia of the TFL is incised lateral to the interval. Blunt dissection of the TFL off of the fascia of this interval brings you down to the fat overlying the direct head of the rectus femoris tendon. Dissection through the fat identifies this tendon and you can follow this up to the anterior inferior iliac spine (AIIS). An ASIS osteotomy is then completed with a straight osteotome and the Cobb is used to elevate this medially along with the prior dissected external oblique. Fascia above the direct head rectus is further released distally allowing retraction of the medial structures. Dissection of the illiacus out of the pelvis around the AIIS allows further retraction of the medial tissues. The illiocapsularis is then dissected directly off of the medial aspect of the AIIS down to the anterior hip capsule. Dissection is then continued over the front of the hip capsule. A lane (blunt) retractor is then placed around the anterior hip capsule and down to the ischium. Fluoroscopy is used to visualize a correct position on the ischium just distal to the inferior joint and the Lane is replaced with the thin Ganz osteotome (Fig. 4A). The ischium is then cut to a depth of 1 cm starting with the medial cortex, the lateral cortex, and then the central aspect (Fig. 4B). Dissection is then completed along the superior periosteum of the superior pubic ramus. The lane retractor is used to dissect the posterior aspect of the periosteum into the obturator foramen. A distinct pop is generally heard when the illiopectineal fascia is dissected from the obturator foramen. The periosteum is then dissected anteriorly about 1 cm medial to the illiopectineal eminence. A second lane retractor is then placed subperiosteally anterior to the ramus. This is then replaced with a #3 Crego retractor. The posterior Lane retractor can be felt impacting the Crego retractor. This tells you they are both subperiosteal and are protecting the contents of the obturator foramen. I prefer to use a straight osteotome to cut the superior pubic ramus. Care is taken to be medial to the illiopectineal eminence, perpendicular to the ramus and aimed towards the Crego retractor in the foramen (Fig. 4C). The inflection point of the iliac and posterior column osteotomy is then marked with the fluoroscopy in the false profile position with either an osteotome or a burr (Fig. 4D). A 1.5 cm window is then dissected in the abductors at the distal aspect of the ASIS. A Lane retractor is then placed lateral to the illium in line with the planned iliac cut. The iliac cut is then completed with a sagittal saw to the prior marked inflection point. A straight handled ostetome is then used to cut the posterior column to the prior ischial osteotomy (Fig. 4D). The medial cortex is cut first and the cut is completed at the pelvic brim. A laminar spreader is then placed in the iliac cut and the Ganz osteotome is used to complete the lateral cortex of the posterior column. After the fragment is free, it is repositioned using a schantz pin with a T-handle chuck inserted in the ASIS and a pointed reduction clamp around the superior ramus/pubic root. After appropriate correction the fragment is provisionally fixed with 3/32 Kirshner wires. The correction is dependent upon the deformity being corrected to achieve the correction goal. It is some combination of forward flexion (to increase anterior coverage), lateral tilting (to increase lateral coverage and decrease the Tonnis angle), and
ARTICLE IN PRESS PAO for Mild or Borderline Acetabular Dysplasia
Figure 4 (A)Fluoroscopic posteroanterior view showing the Ganz osteotome on the ischium approximately 1 cm distal to the joint. (B) False profile view showing appropriate depth of the ishcial osteotomy. (C) Fluoroscopic posteroanterior view showing #3 Crego retractor around the anterior pubic ramus and lane retractor around the posterior pubic ramus protecting the contents of the Obturator foramen while a straight osteotome (star) cuts the superior pubic ramus medial to the illiopectineal eminence. (D) False profile fluoroscopic view showing the inflection point (star) of the iliac cut (superior dotted line) and posterior column osteotomy (solid line). Connecting to the prior partial ischial osteotomy (inferior dotted line).
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ARTICLE IN PRESS J.D. Marland and J.D. Wylie
6 IR (anteversion) of the fragment. After you are happy with the correction, the Kirshner wires are measured with a free wire and replaced with small fragment screws for definitive fixation. Correction goals for the PAO in these patients are similar to those with moderate or severe dysplasia. However, in these patients sometimes it is easier to fully correct their coverage because there is a more normal acetabulum to work with. Correction goals are an LCEA around 30°, a Tonnis angle of 0°, an ACEA of 30° and a PWI of 1.0. The AWI goal is 0.4 but sometimes it is difficult to correct all of the measures at the same time and therefore the AWI is commonly lower than 0.4. The first case presented here is a 20 year-old female patient with a borderline LCEA (19°) (Fig. 5A). She has secondary markers on instability including a low AWI (0.25), elevated femoral anteversion on CT (25°), and Beighton criteria of 9/9. She also had pain and an instability sensation with anterior apprehension testing and 35° of IR in 90° of flexion. Three-dimension reconstruction of her hip CT shows anterior wall deficiency with an almost completely uncovered femoral head and 30° of acetabular anteversion a 2-o’Clock (Fig. 5B). She underwent PAO to improve lateral and anterior coverage with a resulting LCEA of 32° (Fig. 5C) The second case presented here is an 18-year-old male who complains of on and off bilateral left worse than right hip pain for multiple years. He has pain that is worst with weight bearing activities and excellent range of motion on exam with 40° of IR in flexion. His gait shows inward facing patellae and a normal foot progression angle, likely indicating increased anteversion and external tibial torsion. On Radiographs he has an LCEA of 19 (Fig. 6A) and an ACEA of 27 (Fig. 6B). He
has retroversion with a posterior wall sign and crossover sign. (Fig. 6A) His PWI is clearly deficient at 0.45. His MR-arthrogram showed a labral tear (Fig. 6C), so he was treated with arthroscopy for labral repair (Fig. 6D) and PAO to improve lateral and posterior coverage of his hip (Fig. 6E).
Evidence There have been multiple papers looking at outcomes in borderline dysplastic patients. Of these, mostly they represent case series of patients either undergoing hip arthroscopy or PAO. McClincy et al reported 2 studies, 1 looking at diagnosis of borderline acetabular dysplasia and the other looking at outcomes of PAO. 5,14 They reported excellent outcomes of PAO in patients with LCEA from 18°-25°, but both papers noted that the patients undergoing PAO were selected for that surgery due to secondary markers of instability like ACEA, AWI, Tonnis angle, and FEAR index. Similarly, Livermore et al showed excellent results of PAO in patients with an LCEA between 18° and 25° at 5-year follow-up.15 When treating borderline dysplasia along with impingement or labral pathology with arthroscopy there are multiple reports of good outcomes, including a recent systematic review of these reports.13 Other studies have identified risk factors for failure in these patients, including an ACEA less than 17 degrees and a Tonnis angle over 15° and an AWI of less than 0.4 in female patients.16,17 PAO is also a useful treatment in borderline dysplastic patients because the natural history studies support a risk for developing arthritis in an LCEA of less than 25° or 30° The longest and largest longitudinal study of osteoarthritis
Figure 5 (A) Preoperative standing anteroposterior pelvis radiograph showing borderline lateral center edge angle and anterior wall deficiency. (B) Three-dimensional computed tomography of the hip shows high acetabular anteversion caused by anterior wall deficiency and an uncovered femoral head anteriorly. (C) A 6-week postoperative Supine AP pelvis radiograph showing improved lateral and anterior coverage after periacetabular osteotomy.
ARTICLE IN PRESS PAO for Mild or Borderline Acetabular Dysplasia
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Figure 6 (A) Standing anteroposterior pelvis radiograph showing borderline lateral center edge angle with posterior wall deficiency leading to acetabular retroversion. (B) False profile radiograph shows normal anterior center edge angle. (C) Axial oblique magnetic resonance imaging sequence showing tearing of the anterior superior labrum with contrast extending full thickness through the labrum (arrow). (D) Arthroscopic image showing labrum after labral repair, viewed from the anterolateral portal. (E) Postoperative supine anteroposterior pelvis radiograph 2 weeks after periacetabular osteotomy showing improved lateral and posterior coverage of the femoral head.
development in female patients with dysplasia followed over 1000 females for 20 years and found that for every degree of LCEA below 28 there was a 13% increased chance of developing osteoarthritis.18 In addition, other studies have shown LCEAs under 30° or 25° to be associated with an increased risk of osteoarthritis.19 This suggests that the lateral rim overload that likely leads to osteoarthritis in dysplasia may extend up at least to an LCEA of 25 degrees. Therefore, PAO may be a better long-term treatment if acetabular coverage is improved to normalize forces on the articular cartilage.
Conclusions In patients with borderline or mild acetabular dysplasia (as defined by the LCEA) that have other signs of bony instability or ligamentous laxity are best treated with PAO. Specifically, patients with borderline LCEA and an AWI less than 0.30, a FEAR index that is laterally facing, an ACEA of less than 20, femoral anteversion over 20° or a Beighton index greater than 5 points or a combination of these factors may suffer from anterior hip instability despite a borderline LCEA measure. In addition, patients with a PWI less than 0.8 with acetabular retroversion (positive crossover and ischial spine
signs) may suffer from instability from combined borderline lateral coverage and posterior wall deficiency. Both of these patient populations may be best treated with PAO with or without adjunctive arthroscopy to address intra-articular pathology. More comparative studies are needed to define the best treatment for the borderline dysplastic patient and the different borderline dysplastic subtypes.
Conflict of Interest JDM has no conflicts. JDW is on the editorial board of Arthroscopy, is a committee member with AOSSM, and received research funding from Arthrex, Inc in 2016-2017.
References 1. Ganz R, Klaue K, Vinh TS, et al: A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clin Orthop Relat Res 232:26-36, 1988. 2. Ganz R, Gill TJ, Gautier E, et al: Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 83:1119-1124, 2004 3. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement: A cause for osteoarthritis of the hip. Clin Orthop Relat Res 417:112-120, 2003
ARTICLE IN PRESS 8 4. Fayad TE, Khan MA, Haddad FS: Femoroacetabular impingement: An arthroscopic solution. Bone Joint J 95-B(11 Suppl A):26-30, 2013 5. McClincy MP, Wylie JD, Yen Y-M, et al: Mild or borderline hip dysplasia: Are we characterizing hips with a lateral center-edge angle between 18° and 25° appropriately? Am J Sports Med 47:112-122, 2019 6. Martin HD, Shears SA, Palmer IJ: Evaluation of the hip. Sports Med Arthrosc 18:63-75, 2010 7. Kraeutler MJ, Garabekyan T, Pascual-Garrido C, et al: Hip instability: A review of hip dysplasia and other contributing factors. Muscles Ligaments Tendons J 6:343-353, 2016 8. Leunig M, Siebenrock KA, Ganz R: Rationale of periacetabular osteotomy and background work. Instr Course Lect 50:229-238, 2001 9. Juul-Kristensen B, Schmedling K, Rombaut L, et al: Measurement properties of clinical assessment methods for classifying generalized joint hypermobility—A systematic review. Am J Med Genet C Semin Med Genet 175:116-147, 2017 10. Uemura K, Atkins PR, Anderson AE, et al: Do your routine radiographs to diagnose cam femoroacetabular impingement visualize the region of the femoral head-neck junction you intended? Arthroscopy 35:1796-1806, 2019 11. McCormick F, Slikker W, Harris JD, et al: Evidence of capsular defect following hip arthroscopy. Knee Surg Sports Traumatol Arthrosc 22:902-905, 2014 12. Canham CD, Yen Y-M, Giordano BD: Does femoroacetabular impingement cause hip instability? A systematic review. Arthroscopy 32:203208, 2016
J.D. Marland and J.D. Wylie 13. Tang H-C, Dienst M: Surgical outcomes in the treatment of concomitant mild acetabular dysplasia and femoroacetabular impingement: A systematic review. Arthroscopy 2019. Article in press 14. McClincy MP, Wylie JD, Kim YJ, et al: Periacetabular osteotomy improves pain and function in patients with lateral center-edge angle between 18° and 25°, but are these hips really borderline dysplastic? Clin Orthop Relat Res 477:1145-1153, 2019 15. Livermore AT, Anderson LA, Anderson MB, et al: Correction of mildly dysplastic hips with periacetabular osteotomy demonstrates promising outcomes, achievement of correction goals, and excellent five-year survivorship. Bone Joint J 101-B(6_Supple_B):16-22, 2019 16. Hatakeyama A, Utsunomiya H, Nishikino S, et al: Predictors of poor clinical outcome after arthroscopic labral preservation, capsular plication, and cam osteoplasty in the setting of borderline hip dysplasia. Am J Sports Med 46:135-143, 2018 17. Christensen JC, Marland JD, Miller CJ, et al: Trajectory of clinical outcomes following hip arthroscopy in female subgroup populations. J Hip Preserv Surg 6:25-32, 2019 18. Thomas GE, Palmer AJ, Batra RN, et al: Subclinical deformities of the hip are significant predictors of radiographic osteoarthritis and joint replacement in women. A 20 year longitudinal cohort study. Osteoarthritis Cartilage 10:1504-1510, 2014 19. Wylie JD, Peters CL, Aoki SK: Natural history of structural hip abnormalities and the potential for hip preservation. J Am Acad Orthop Surg 19, 2018. Article in press
Periacetabular Osteotomy for Mild or Borderline Acetabular Dysplasia Jennifer D. Marland, PT, DPT, and James D. Wylie, MD, MHS Evaluating the adolescent and young adult hip can be challenging given the rapid evolutions in the field over the last 10-20 years. One of the more difficult groups of patients to evaluate are those that fall into the mild or borderline acetabular dysplasia. We must determine whether the patient’s pain and chondrolabral disease is due to their acetabular morphoplogy or their associated femoral morphology and therefore is more of an unstable or an impingement hip. A thorough history, physical examination, and imaging evaluation are needed to determine the best treatment option in these patients. When this evaluation determines that the patient is suffering from a primary instability problem, these patients are best treated with a surgery that improves the stability of the hip. Here we describe the patient evaluation and periacetabular osteotomy technique in the mild or borderline dysplastic patient. Oper Tech Orthop 00:100782 © 2020 Elsevier Inc. All rights reserved.
KEYWORDS mild acetabular dysplasia, periacetabular osteotomy, hip arthroscopy, young adult, Hip pain
Introduction dolescent and young adult hip surgery is a field that has changed significantly over the last 30 years. This started with the description of the periacetabular osteotomy (PAO) by Dr Ganz.1 Subsequently, the descriptions of femoroacetabular impingement and the surgical dislocation approach, and the significant advances in hip arthroscopy have shaped the field today.2-4 Over the last 20 years, these operations have become safer and more efficacious at treating adolescent and young adult hip pain. While true dysplastic patients now are reliably treated with PAO and patients with obvious femoroacetabular impingement are mostly treated with arthroscopy, there is still a question of the right treatment for the patient with mild or borderline dysplasia. These patients also commonly have concomitant cam morphology and it is sometimes not clear which of these pathologies is driving the patients symptoms.5 Treatment options include PAO with or without hip arthroscopy to address labral pathology or hip arthroscopy with treatment of concomitant labral pathology
A
The Orthopedic Specialty Hospital, Intermountain Healthcare, Murray, UT. Address reprint requests to James D, Wylie MD, MHS, The Orthopedic Specialty Hospital, Intermountain Healthcare, 5848 South Fashion Blvd. Suite 120, Murray, UT 84107. E-mail: [email protected]
https://doi.org/10.1016/j.oto.2020.100782 1048-6666/© 2020 Elsevier Inc. All rights reserved.
with capsular plication, with or without cam resection. This article will describe the patient evaluation to determine which patients with mild or borderline dysplasia that may benefit from PAO and describe the surgical technique and correction goals.
Patient Evaluation History Patient history starts with a description of the pain including location, duration, timing, severity, aggravating factors, and alleviating factors. Differentiating between impingement and instability pain can be difficult. Impingement pain is more common in deep hip flexion positions like sitting for long periods of time, squatting, going up/down stairs, and pivoting and twisting. Structurally unstable hips can have more generalized pain including muscular and trochanteric in nature. The pain can happen more commonly in weight bearing positions that may or may not be in deep hip flexion. The history of prior hip arthroscopy and the capsular management during that surgery is important to determine whether they may have postoperative instability from prior capsulotomy that was either not repaired or did not completely heal. 1
ARTICLE IN PRESS J.D. Marland and J.D. Wylie
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Physical Examination Objective examination starts with watching the patient perform gait. In-toeing or out-toeing, or an inward facing patella can be a sign of femoral versional abnormalities.6 Range of motion is then tested in supine (flexion, and internal rotation (IR) and external rotation (ER) in 90° of flexion). It is important to provide downward pressure on the knee and feel for the end range of the motion of the hip joint, as the pelvis can move and you can overestimate hip range of motion. If a patient has greater than 30° of IR in 90° of flexion, then the patient may have more instability as opposed to impingement. Flexion adduction and IR testing loads the labrum and can provoke pain in the setting of chondrolabral pathology, this is not specific of underlying anatomy/pathology. It is important to notice the degree of IR at end range of motion. Range of motion is also tested in the prone position and increased IR above 60° can be a sign of increased femoral and/or acetabular anteversion, both markers of a more unstable hip.7 Flexion, abduction, and ER can cause groin pain with chondrolabral pathology and lateral pain with trochanteric pathology. Apprehension testing (extension and ER with the opposite leg/hip held to the chest in flexion) can lead to groin pain in patients with chondrolabral pathology and a sense of apprehension in patients with structural instability, similar to the apprehension test in the shoulder.8 Strength testing of hip abduction is performed in the side-lying position with the hip in flexion, neutral, and extension. Testing in extension requires coordinated contraction of the gluteus medius and maximus, which can be inhibited in patients with hip pain. Weakness can be a sign of potential ability to improve with a structured strengthening program. Beighton criteria to assess ligamentous laxity with thumb to forearm, metacarpal phalangeal (MCP) hyperextension, elbow hyperextension, knee hyperextension, and whether the patient can place their palms on the floor with the knees in extension should be assessed in all patients.9 More positive criteria indicate of more ligamentous laxity, with a total of 4 or greater considered go be indicative of generalized ligamentous laxity.9
Radiographs A comprehensive radiographic evaluation includes a standing anteroposterior (AP) pelvis radiograph, a false profile radiograph, and lateral radiograph to evaluate the anterior and the anterosuperior head neck junction. We use a frog lateral radiograph to visualize the anterior aspect of the femur (3:00) and a 45° Dunn lateral radiograph to evaluate the anterosuperior aspect of the femur (1:30).10 The AP pelvis radiograph with the feet in neutral evaluates the lateral aspect of the femur (12:00).10 Important radiographic measurements on each of the radiographic view are listed in Table and illustrated in Figure 1.
Advanced Imaging Magnetic resonance imaging (MRI) and computed tomography (CT) are the advanced imaging modalities most
Table Important Radiographic Measures to Evaluate the Hip by Radiographic View Radiographic View
Important Measurements
Standing anteroposterior Pelvis
Lateral center edge angle Tonnis angle Anterior wall index Posterior wall index Femoroepiphyseal acetabular roof index Femoral neck shaft angle Femoral alpha angle Crossover sign Posterior wall sign Ischial spine sign
False profile Laterals: 45˚ Dunn lateral Frog lateral
Anterior center edge angle Femoral alpha angle
commonly employed in the hip. MRI can be arthrogram or nonarthrogram. Three Tesla (T) field strength magnets can provide detailed evaluation of the chondrolabral junction without the need for an arthrogram, but 1.5 T or lower magnets need an arthrogram injection to properly evaluate the labrum and the chondrolabral junction. Given the ionizing radiation that the patient is exposed to during CT scanning, it is important to optimize protocols for the hip preservation patient to decrease radiation exposure. MRI with or without arthrogram can evaluate the femoral and acetbular articular cartilage for thickness and areas of full-thickness defect. or subchondral cystic change indicative of degenerative disease. It also evaluates the integrity of the chondrolabral junction and intrasubstance signal in the labrum. In the setting of prior failed hip arthroscopy, arthrogram can be used to investigate for capsular integrity, capsular volume, and capsular defects in area of prior capsulotomy.11 CT provides 3-dimensional bony morphology of the hip and quantifies the acetabular coverage and version at multiple levels. In addition, the morphology of the femoral head/neck junction is qualitatively evaluated in 3 dimensions, which can make it easier to evaluate the femoral-sided cam morphology. Axial imaging through the knee is important to quantify femoral version.
Rationale for Treatment Decision While the lateral center edge angle (LCEA) has traditionally been used as the primary marker to diagnose acetabular dysplasia, a more thorough evaluation is needed to fully understand the patient’s acetabular coverage and hip anatomy (Fig. 1).5 When these other variables/measures (female gender, femoral anteversion, anterior wall index [AWI], posterior wall index [PWI], anterior center edge angle [ACEA], and femoroepiphyseal acetabular roof [FEAR index]) point towards an unstable hip then PAO with or without arthroscopy is the treatment of choice.5 Specifically, anterior instability can be
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Figure 1 Important radiographic measures to evaluate the hip. (A) Lateral center edge angle (LCEA) measured on the right hip and Tonnis Angle measured on the left hip. Both are measured in relation to a line normalized to the pelvis or femoral heads. In addition, they are measured in relation to the sclerotic sourcil of the weight bearing aspect of the acetabulum and not all the way to the edge of the bone. (B) Anterior wall index measured on the right hip. Anterior wall measured in line with femoral neck (red line “A”) as coverage of the femoral head, to calculate divide this number by the radius of the femoral head (blue line “R”). Posterior wall index measured on the left hip. Posterior wall measured in line with femoral neck (red line “P”) as coverage of the femoral head, to calculate divide this number by the radius of the femoral head (blue line “R”). (C) Femoroepiphyseal acetabular roof (FEAR) Index, this angle is formed by the middle third of the femoral physeal scar and the acetabular roof as measured in the Tonnis angle. (D) Crossover sign (blue anterior wall, Red posterior wall), posterior wall sign (red posterior wall medial to center of head (star)), and ischial spine sign (white writing and arrow). (E) Anterior center edge angle (ACEA) measured to the edge of the sourcil in relation to the vertical. (H) Femoral Alpha angle where the head neck junction loses sphericity in relation to a line through the center of the femoral neck. (Color version of figure is available online.)
seen in (more commonly) female patients with an LCEA less than 25 and 1 or more of the following other factors: femoral anteversion over 20°, AWI less than 0.3, an ACEA less than 20 degrees, a FEAR index that is laterally opening, or an elevated Beighton index (>4 points). Alternatively, patients with a PWI less than 0.8 with acetabular retroversion (positive crossover and ischial spine signs) may benefit from PAO due to instability from combined borderline lateral coverage and posterior wall deficiency.5 This can also be associated with a femoral-sided cam lesion and/or relative or absolute femoral retroversion that can accentuate the posterior instability. A treatment algorithm is presented in Figure 2. In some patients isolated arthroscopy can be an appropriate treatment in borderline dysplastic patients. A large cam deformity can act as a lever that accentuates the posterior instability and an appropriate femoroplasty for the cam lesion, removing the lever for posterior instability can result in an excellent outcome.12 In addition, in patients with an LCEA between 20° and 25° that have none of the above radiographic or clinical risk factors for instability may be candidates to be treated with isolated arthroscopy with femoroplasty and/or labral repair followed by capsular plication.13 However, surgeons should not perform any significant acetabuloplasty in these patients and should always perform a
capsular repair/plication with multiple stitches given their risk of postoperative instability. After deciding to go forward with a PAO, the next decision to make is whether an adjunctive arthroscopy is needed. Abnormal signal at the labrochondral and bony labral junction is indicative of labral tearing or chondrolabral injury. In
Figure 2 Treatment algorithm for young adults with hip pain and borderline acetabular dysplasia. ACEA, anterior center edge angle; AWI, anterior wall index; CT, computed tomography; FEAR, femoroepiphyseal acetabular roof; PAO, periacetabular osteotomy; PWI, posterior wall index; ROM, range of motion.
ARTICLE IN PRESS 4 addition, an elevated alpha angle on the femoral side indicative of a cam deformity should be treated either during arthroscopy or through an open arthrotomy to protect against post-PAO impingement.
Operative Technique and Case Examples The technique for the borderline dysplastic is no different than those with moderate or severe dysplasia. The incision is just 1-2 cm distal to the anterior superior iliac spine (ASIS) and iliac crest that extends down to superficial to the hip joint center (Fig. 3). In larger patients, (body mass index of 35 or greater) a traditional Smith-Peterson incision that curves down the thigh can be helpful for exposure. Dissection is taken through the superficial subcutaneous tissues down to the fascia. Full-thickness flaps can be mobilized to allow a smaller skin incision and a mobile skin window. The external obliques are then elevated off of the pelvic brim, there is a small fat-layer just superficial to the periosteum that marks the optimal dissection plane. The external obliques should be released to the apex of the iliac crest as it flares out laterally. The periosteum on the iliac brim is then incised and a Cobb is used to elevate the illiacus off of the inner table of the pelvis and a sponge is placed to bluntly dissect this interval. The interval between the tensor-fascialata (TFL) and the Sartorius is identified distally and the
Figure 3 Oblique incision for periacetabular osteotomy on a left hip, visualized from the left side of the patient, just distal to the ASIS (circle) and the illac brim/crest (dotted line)
J.D. Marland and J.D. Wylie fascia of the TFL is incised lateral to the interval. Blunt dissection of the TFL off of the fascia of this interval brings you down to the fat overlying the direct head of the rectus femoris tendon. Dissection through the fat identifies this tendon and you can follow this up to the anterior inferior iliac spine (AIIS). An ASIS osteotomy is then completed with a straight osteotome and the Cobb is used to elevate this medially along with the prior dissected external oblique. Fascia above the direct head rectus is further released distally allowing retraction of the medial structures. Dissection of the illiacus out of the pelvis around the AIIS allows further retraction of the medial tissues. The illiocapsularis is then dissected directly off of the medial aspect of the AIIS down to the anterior hip capsule. Dissection is then continued over the front of the hip capsule. A lane (blunt) retractor is then placed around the anterior hip capsule and down to the ischium. Fluoroscopy is used to visualize a correct position on the ischium just distal to the inferior joint and the Lane is replaced with the thin Ganz osteotome (Fig. 4A). The ischium is then cut to a depth of 1 cm starting with the medial cortex, the lateral cortex, and then the central aspect (Fig. 4B). Dissection is then completed along the superior periosteum of the superior pubic ramus. The lane retractor is used to dissect the posterior aspect of the periosteum into the obturator foramen. A distinct pop is generally heard when the illiopectineal fascia is dissected from the obturator foramen. The periosteum is then dissected anteriorly about 1 cm medial to the illiopectineal eminence. A second lane retractor is then placed subperiosteally anterior to the ramus. This is then replaced with a #3 Crego retractor. The posterior Lane retractor can be felt impacting the Crego retractor. This tells you they are both subperiosteal and are protecting the contents of the obturator foramen. I prefer to use a straight osteotome to cut the superior pubic ramus. Care is taken to be medial to the illiopectineal eminence, perpendicular to the ramus and aimed towards the Crego retractor in the foramen (Fig. 4C). The inflection point of the iliac and posterior column osteotomy is then marked with the fluoroscopy in the false profile position with either an osteotome or a burr (Fig. 4D). A 1.5 cm window is then dissected in the abductors at the distal aspect of the ASIS. A Lane retractor is then placed lateral to the illium in line with the planned iliac cut. The iliac cut is then completed with a sagittal saw to the prior marked inflection point. A straight handled ostetome is then used to cut the posterior column to the prior ischial osteotomy (Fig. 4D). The medial cortex is cut first and the cut is completed at the pelvic brim. A laminar spreader is then placed in the iliac cut and the Ganz osteotome is used to complete the lateral cortex of the posterior column. After the fragment is free, it is repositioned using a schantz pin with a T-handle chuck inserted in the ASIS and a pointed reduction clamp around the superior ramus/pubic root. After appropriate correction the fragment is provisionally fixed with 3/32 Kirshner wires. The correction is dependent upon the deformity being corrected to achieve the correction goal. It is some combination of forward flexion (to increase anterior coverage), lateral tilting (to increase lateral coverage and decrease the Tonnis angle), and
ARTICLE IN PRESS PAO for Mild or Borderline Acetabular Dysplasia
Figure 4 (A)Fluoroscopic posteroanterior view showing the Ganz osteotome on the ischium approximately 1 cm distal to the joint. (B) False profile view showing appropriate depth of the ishcial osteotomy. (C) Fluoroscopic posteroanterior view showing #3 Crego retractor around the anterior pubic ramus and lane retractor around the posterior pubic ramus protecting the contents of the Obturator foramen while a straight osteotome (star) cuts the superior pubic ramus medial to the illiopectineal eminence. (D) False profile fluoroscopic view showing the inflection point (star) of the iliac cut (superior dotted line) and posterior column osteotomy (solid line). Connecting to the prior partial ischial osteotomy (inferior dotted line).
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ARTICLE IN PRESS J.D. Marland and J.D. Wylie
6 IR (anteversion) of the fragment. After you are happy with the correction, the Kirshner wires are measured with a free wire and replaced with small fragment screws for definitive fixation. Correction goals for the PAO in these patients are similar to those with moderate or severe dysplasia. However, in these patients sometimes it is easier to fully correct their coverage because there is a more normal acetabulum to work with. Correction goals are an LCEA around 30°, a Tonnis angle of 0°, an ACEA of 30° and a PWI of 1.0. The AWI goal is 0.4 but sometimes it is difficult to correct all of the measures at the same time and therefore the AWI is commonly lower than 0.4. The first case presented here is a 20 year-old female patient with a borderline LCEA (19°) (Fig. 5A). She has secondary markers on instability including a low AWI (0.25), elevated femoral anteversion on CT (25°), and Beighton criteria of 9/9. She also had pain and an instability sensation with anterior apprehension testing and 35° of IR in 90° of flexion. Three-dimension reconstruction of her hip CT shows anterior wall deficiency with an almost completely uncovered femoral head and 30° of acetabular anteversion a 2-o’Clock (Fig. 5B). She underwent PAO to improve lateral and anterior coverage with a resulting LCEA of 32° (Fig. 5C) The second case presented here is an 18-year-old male who complains of on and off bilateral left worse than right hip pain for multiple years. He has pain that is worst with weight bearing activities and excellent range of motion on exam with 40° of IR in flexion. His gait shows inward facing patellae and a normal foot progression angle, likely indicating increased anteversion and external tibial torsion. On Radiographs he has an LCEA of 19 (Fig. 6A) and an ACEA of 27 (Fig. 6B). He
has retroversion with a posterior wall sign and crossover sign. (Fig. 6A) His PWI is clearly deficient at 0.45. His MR-arthrogram showed a labral tear (Fig. 6C), so he was treated with arthroscopy for labral repair (Fig. 6D) and PAO to improve lateral and posterior coverage of his hip (Fig. 6E).
Evidence There have been multiple papers looking at outcomes in borderline dysplastic patients. Of these, mostly they represent case series of patients either undergoing hip arthroscopy or PAO. McClincy et al reported 2 studies, 1 looking at diagnosis of borderline acetabular dysplasia and the other looking at outcomes of PAO. 5,14 They reported excellent outcomes of PAO in patients with LCEA from 18°-25°, but both papers noted that the patients undergoing PAO were selected for that surgery due to secondary markers of instability like ACEA, AWI, Tonnis angle, and FEAR index. Similarly, Livermore et al showed excellent results of PAO in patients with an LCEA between 18° and 25° at 5-year follow-up.15 When treating borderline dysplasia along with impingement or labral pathology with arthroscopy there are multiple reports of good outcomes, including a recent systematic review of these reports.13 Other studies have identified risk factors for failure in these patients, including an ACEA less than 17 degrees and a Tonnis angle over 15° and an AWI of less than 0.4 in female patients.16,17 PAO is also a useful treatment in borderline dysplastic patients because the natural history studies support a risk for developing arthritis in an LCEA of less than 25° or 30° The longest and largest longitudinal study of osteoarthritis
Figure 5 (A) Preoperative standing anteroposterior pelvis radiograph showing borderline lateral center edge angle and anterior wall deficiency. (B) Three-dimensional computed tomography of the hip shows high acetabular anteversion caused by anterior wall deficiency and an uncovered femoral head anteriorly. (C) A 6-week postoperative Supine AP pelvis radiograph showing improved lateral and anterior coverage after periacetabular osteotomy.
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Figure 6 (A) Standing anteroposterior pelvis radiograph showing borderline lateral center edge angle with posterior wall deficiency leading to acetabular retroversion. (B) False profile radiograph shows normal anterior center edge angle. (C) Axial oblique magnetic resonance imaging sequence showing tearing of the anterior superior labrum with contrast extending full thickness through the labrum (arrow). (D) Arthroscopic image showing labrum after labral repair, viewed from the anterolateral portal. (E) Postoperative supine anteroposterior pelvis radiograph 2 weeks after periacetabular osteotomy showing improved lateral and posterior coverage of the femoral head.
development in female patients with dysplasia followed over 1000 females for 20 years and found that for every degree of LCEA below 28 there was a 13% increased chance of developing osteoarthritis.18 In addition, other studies have shown LCEAs under 30° or 25° to be associated with an increased risk of osteoarthritis.19 This suggests that the lateral rim overload that likely leads to osteoarthritis in dysplasia may extend up at least to an LCEA of 25 degrees. Therefore, PAO may be a better long-term treatment if acetabular coverage is improved to normalize forces on the articular cartilage.
Conclusions In patients with borderline or mild acetabular dysplasia (as defined by the LCEA) that have other signs of bony instability or ligamentous laxity are best treated with PAO. Specifically, patients with borderline LCEA and an AWI less than 0.30, a FEAR index that is laterally facing, an ACEA of less than 20, femoral anteversion over 20° or a Beighton index greater than 5 points or a combination of these factors may suffer from anterior hip instability despite a borderline LCEA measure. In addition, patients with a PWI less than 0.8 with acetabular retroversion (positive crossover and ischial spine
signs) may suffer from instability from combined borderline lateral coverage and posterior wall deficiency. Both of these patient populations may be best treated with PAO with or without adjunctive arthroscopy to address intra-articular pathology. More comparative studies are needed to define the best treatment for the borderline dysplastic patient and the different borderline dysplastic subtypes.
Conflict of Interest JDM has no conflicts. JDW is on the editorial board of Arthroscopy, is a committee member with AOSSM, and received research funding from Arthrex, Inc in 2016-2017.
References 1. Ganz R, Klaue K, Vinh TS, et al: A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clin Orthop Relat Res 232:26-36, 1988. 2. Ganz R, Gill TJ, Gautier E, et al: Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 83:1119-1124, 2004 3. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement: A cause for osteoarthritis of the hip. Clin Orthop Relat Res 417:112-120, 2003
ARTICLE IN PRESS 8 4. Fayad TE, Khan MA, Haddad FS: Femoroacetabular impingement: An arthroscopic solution. Bone Joint J 95-B(11 Suppl A):26-30, 2013 5. McClincy MP, Wylie JD, Yen Y-M, et al: Mild or borderline hip dysplasia: Are we characterizing hips with a lateral center-edge angle between 18° and 25° appropriately? Am J Sports Med 47:112-122, 2019 6. Martin HD, Shears SA, Palmer IJ: Evaluation of the hip. Sports Med Arthrosc 18:63-75, 2010 7. Kraeutler MJ, Garabekyan T, Pascual-Garrido C, et al: Hip instability: A review of hip dysplasia and other contributing factors. Muscles Ligaments Tendons J 6:343-353, 2016 8. Leunig M, Siebenrock KA, Ganz R: Rationale of periacetabular osteotomy and background work. Instr Course Lect 50:229-238, 2001 9. Juul-Kristensen B, Schmedling K, Rombaut L, et al: Measurement properties of clinical assessment methods for classifying generalized joint hypermobility—A systematic review. Am J Med Genet C Semin Med Genet 175:116-147, 2017 10. Uemura K, Atkins PR, Anderson AE, et al: Do your routine radiographs to diagnose cam femoroacetabular impingement visualize the region of the femoral head-neck junction you intended? Arthroscopy 35:1796-1806, 2019 11. McCormick F, Slikker W, Harris JD, et al: Evidence of capsular defect following hip arthroscopy. Knee Surg Sports Traumatol Arthrosc 22:902-905, 2014 12. Canham CD, Yen Y-M, Giordano BD: Does femoroacetabular impingement cause hip instability? A systematic review. Arthroscopy 32:203208, 2016
J.D. Marland and J.D. Wylie 13. Tang H-C, Dienst M: Surgical outcomes in the treatment of concomitant mild acetabular dysplasia and femoroacetabular impingement: A systematic review. Arthroscopy 2019. Article in press 14. McClincy MP, Wylie JD, Kim YJ, et al: Periacetabular osteotomy improves pain and function in patients with lateral center-edge angle between 18° and 25°, but are these hips really borderline dysplastic? Clin Orthop Relat Res 477:1145-1153, 2019 15. Livermore AT, Anderson LA, Anderson MB, et al: Correction of mildly dysplastic hips with periacetabular osteotomy demonstrates promising outcomes, achievement of correction goals, and excellent five-year survivorship. Bone Joint J 101-B(6_Supple_B):16-22, 2019 16. Hatakeyama A, Utsunomiya H, Nishikino S, et al: Predictors of poor clinical outcome after arthroscopic labral preservation, capsular plication, and cam osteoplasty in the setting of borderline hip dysplasia. Am J Sports Med 46:135-143, 2018 17. Christensen JC, Marland JD, Miller CJ, et al: Trajectory of clinical outcomes following hip arthroscopy in female subgroup populations. J Hip Preserv Surg 6:25-32, 2019 18. Thomas GE, Palmer AJ, Batra RN, et al: Subclinical deformities of the hip are significant predictors of radiographic osteoarthritis and joint replacement in women. A 20 year longitudinal cohort study. Osteoarthritis Cartilage 10:1504-1510, 2014 19. Wylie JD, Peters CL, Aoki SK: Natural history of structural hip abnormalities and the potential for hip preservation. J Am Acad Orthop Surg 19, 2018. Article in press