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1.  Three-dimensional mechanical evaluation of joint contact pressure in 12 periacetabular osteotomy patients with 10-year follow-up 
Acta orthopaedica  2009;80(2):155-161.
Background and purpose
Because of the varying structure of dysplastic hips, the optimal realignment of the joint during periacetabular osteotomy (PAO) may differ between patients. Three-dimensional (3D) mechanical and radiological analysis possibly accounts better for patient-specific morphology, and may improve and automate optimal joint realignment.
Patients and methods
We evaluated the 10-year outcomes of 12 patients following PAO. We compared 3D mechanical analysis results to both radiological and clinical measurements. A 3D discrete-element analysis algorithm was used to calculate the pre- and postoperative contact pressure profile within the hip. Radiological angles describing the coverage of the joint were measured using a computerized approach at actual and theoretical orientations of the acetabular cup. Quantitative results were compared using postoperative clinical evaluation scores (Harris score), and patient-completed outcome surveys (q-score) done at 2 and 10 years.
Results
The 3D mechanical analysis indicated that peak joint contact pressure was reduced by an average factor of 1.7 subsequent to PAO. Lateral coverage of the femoral head increased in all patients; however, it did not proportionally reduce the maximum contact pressure and, in 1 case, the pressure increased. This patient had the lowest 10-year q-score (70 out of 100) of the cohort. Another hip was converted to hip arthroplasty after 3 years because of increasing osteoarthritis.
Interpretation
The 3D analysis showed that a reduction in contact pressure was theoretically possible for all patients in this cohort, but this could not be achieved in every case during surgery. While intraoperative factors may affect the actual surgical outcome, the results show that 3D contact pressure analysis is consistent with traditional PAO planning techniques (more so than 2D analysis) and may be a valuable addition to preoperative planning and intraoperative assessment of joint realignment.
doi:10.3109/17453670902947390
PMCID: PMC2689368  PMID: 19404795
2.  Outcome of periacetabular osteotomy 
Acta orthopaedica  2005;76(3):303-313.
Background
Due to wide variations in acetabular structure of individuals with hip dysplasia, the measurement of the acetabular orientation may not be sufficient to predict the joint loading and pressure distribution across the joint. Addition of mechanical analysis to preoperative planning, therefore, has the potential to improve the clinical outcome.
We analyzed the effect of periacetabular osteotomy on hip dysplasia using computer-aided simulation of joint contact pressure on regular AP radiographs. The results were compared with the results of surgery based on realignment of acetabular angles to the normal hip.
Patients and methods
We studied 12 consecutive periacetabular osteotomies with no femoral head deformity. The median age of patients, all females, was 35 (20−50) years. The median follow-up was 2 years (1.3−2.2). Patient outcome was measured with the total score of a self-administered questionnaire (q-score) and with the Harris hip score. The pre- and postoperative orientation of the acetabulum was defined using reconstructed 3D CT-slices to measure angles in the three anatomical planes. Peak contact pressure, weight-bearing area, and the centroid of the contact pressure distribution (CP-ratio) were calculated.
Results
While 9 of 12 cases showed decreased peak pressure after surgery, the mean changes in weight-bearing area and peak contact pressure were not statistically significant. However, CP-ratio changed (p < 0.001, paired t-test) with surgery. For the optimal range of CP-ratio (within its mid-range 40−60%), the mechanical outcome improved significantly.
Interpretation
Verifying the correlation between the optimal CP-ratio and the outcome of the surgery requires additional studies on more patients. Moreover, the anatomically measured angles were not correlated with the ranges of CP-ratio, suggesting that they do not always associate with objective mechanical goals of realignment osteotomy. Mechanical analysis, therefore, can be a valuable tool in assessing two-dimensional radiographs in hip dysplasia.
PMCID: PMC2745131  PMID: 16156455
3.  Combined Periacetabular and Femoral Osteotomies for Severe Hip Deformities 
Periacetabular osteotomy (PAO) is an effective acetabular reorientation technique for treatment of symptomatic acetabular dysplasia. In hips with severe deformities, an adjunctive femoral osteotomy (PFO) may optimize correction, joint stability, and congruency. We analyzed the clinical and radiographic results of combined PAO/PFO in treating severe hip deformities. Second, we compared the clinical results of patients treated with PAO/PFO with patients treated with isolated PAO for lesser deformities. Twenty-five patients (28 hips) treated with PAO/PFO were reviewed and followed a minimum of 16 months (mean, 44 months). The matched PAO cohort included 25 patients (28 hips). For the PAO/PFO group, the average Harris hip score improved from 60.9 to 86.3. Eighty-nine percent of the patients demonstrated at least a 10-point improvement in the hip score and 75% had a Harris hip score over 80 points. Radiographic evaluation demonstrated consistent deformity correction. The PAO/PFO group had a lower average Harris hip score preoperatively, yet hip function after surgery was comparable between groups. These data indicate combined PAO/PFO is associated with improved hip function in most patients. These clinical results are comparable to those obtained with isolated PAO for lesser hip deformities.
Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-009-0810-1
PMCID: PMC2866920  PMID: 19333669
4.  Evaluation of a computerized measurement technique for joint alignment before and during periacetabular osteotomy 
Periacetabular osteotomy (PAO) is intended to treat a painful dysplastic hip. Manual radiological angle measurements are used to diagnose dysplasia and to define regions of insufficient femoral head coverage for planning PAO. No method has yet been described that recalculates radiological angles as the acetabular bone fragment is reoriented. In this study, we propose a technique for computationally measuring the radiological angles from a joint contact surface model segmented from CT-scan data. Using oblique image slices, we selected the lateral and medial edge of the acetabulum lunate to form a closed, continuous, 3D curve. The joint surface is generated by interpolating the curve and the radiological angles are measured directly using the 3D surface. This technique was evaluated using CT data for both normal and dysplastic hips. Manual measurements made by three independent observers showed minor discrepancies between the manual observations and the computerized technique. Inter-observer error (mean difference±standard deviation) was 0.04±3.53° Observer 1; −0.46±3.13° for Observer 2; and 0.42±2.73° for Observer 3. The measurement error for the proposed computer method was −1.30±3.30°. The computerized technique demonstrates sufficient accuracy compared to manual techniques, making it suitable for planning and intraoperative evaluation of radiological metrics for periacetabular osteotomy.
doi:10.1080/10929080701541855
PMCID: PMC2716292  PMID: 17786597
Periacetabular osteotomy; inter-observer error; radiographic angles; preoperative planning; acetabular coverage; cartilage segmentation
5.  Postoperative acetabular retroversion causes posterior osteoarthritis of the hip 
International Orthopaedics  2007;33(3):625-631.
We retrospectively reviewed 68 hips in 62 patients with acetabular dysplasia who underwent curved periacetabular osteotomy. Among the 68 hips, 33 had acetabular retroversion (retroversion group) and 35 had anteversion (control group) preoperatively. All hips were evaluated according to the Harris hip score. Radiographic evaluations of acetabular retroversion and posterior wall deficiency were based on the cross-over sign and posterior wall sign, respectively. The clinical scores of the two groups at the final follow-up were similar. In the retroversion group, 12 hips had anteverted acetabulum postoperatively. The posterior wall sign disappeared in these hips, but remained in 21 hips with retroverted acetabulum postoperatively. Among the 21 hips with retroverted acetabulum, posterior osteoarthritis of the hip developed postoperatively in five hips. When performing corrective osteotomy for a dysplastic hip with acetabular retroversion, it is important to correct the acetabular retroversion to prevent posterior osteoarthritis of the hip due to posterior wall deficiency.
doi:10.1007/s00264-007-0507-6
PMCID: PMC2903116  PMID: 18157533
6.  Cartilage Thickness in the Hip Measured by MRI and Stereology Before and After Periacetabular Osteotomy 
Background
Untreated hip dysplasia can result in a degenerative process joint and secondary osteoarthritis at an early age. While most periacetabular osteotomies (PAOs) are performed to relieve symptoms, the osteotomy is presumed to slow or prevent degeneration unless irreparable damage to the cartilage has already occurred.
Questions/purposes
We therefore determined (1) whether changes in the thickness of the cartilage in the hip occur after PAO, and (2) how many patients had an acetabular labral tear and whether labral tears are associated with thinning of the cartilage after PAO.
Patients and Methods
We prospectively followed 22 women and four men with hip dysplasia with MRI before PAO and again 1 year and 2½ years postoperatively to determine if cartilage thinning (reflecting osteoarthritis) occurred. The thickness of the femoral and acetabular cartilage was estimated with a stereologic method. Three and one-half years postoperatively, 18 of 26 patients underwent MR arthrography to investigate if they had a torn acetabular labrum.
Results
The acetabular cartilage thickness differed between 1 and 2½ years postoperatively (preoperative 1.40 mm, 1 year postoperatively 1.47 mm, and 2½ years postoperatively 1.35 mm), but was similar at all times for the femoral cartilage (preoperative 1.38 mm, 1 year postoperatively 1.43 mm, and 2½ years postoperatively 1.38 mm.) Seventeen of 18 patients had a torn labrum. The tears were located mainly superior on the acetabular rim.
Conclusion
Cartilage thickness 2½ years after surgery compared with preoperatively was unchanged indicating the osteoarthritis had not progressed during short-term followup after PAO.
doi:10.1007/s11999-010-1310-z
PMCID: PMC2882008  PMID: 20232180
7.  Medial Translation of the Hip Joint Center Associated with the Bernese Periacetabular Osteotomy 
This study assessed medial translation of the hip joint achieved by the Bernese periacetabular osteotomy (PAO) in correcting residual acetabular dysplasia deformities. 86 hips in 75 patients with an average age of 25 years (range, 12-50) were treated for symptomatic acetabular dysplasia with a periacetabular osteotomy. Radiographic analysis was performed to assess correction of the acetabular deformity with specific attention to the horizontal position of the hip joint center. All hips were followed until bony union of the iliac osteotomy and the average follow-up was 28 months. The lateral center edge angle improved an average 31.6° (-0.4° preoperative, 31.2° at follow-up). Anterior center edge angle improved 39.3° (-4.5° to 34.8°). The acetabular roof obliquity improved an average 21.8° (25.1° to 3.3°). Preoperatively, the average distance from the medial aspect of the femoral head to the ilioischial line was 17.6 mm. This distance was decreased to an average 7.8 mm postoperatively. This change resulted in an average medial translation of the hip joint center of 9.8 mm, (range -6 to 31mm). Overall, some degree of medial translation of the hip joint center was obtained in 79 (92%) of the hips. 4 (5%) were maintained in the same horizontal position, and 3 (3%) had slight lateral repositioning. For the hips translated medially, the average change was 10.0 mm, and 72% of all hips had an optimal correction with the distance between the medial aspect of the femoral head and the ilioischial line being between 0 and 10 mm. This study demonstrates that in addition to optimizing femoral head coverage, a major and distinct advantage of the periacetabular osteotomy is reproducible and consistent medial translation of the hip joint center.
PMCID: PMC1888407  PMID: 15296205
8.  Volumetric computerized tomography as a measurement of periprosthetic acetabular osteolysis and its correlation with wear 
Arthritis Research  2001;4(1):59-63.
Osteolysis, which is considered to be a major source of morbidity following total hip joint replacement, has been notoriously difficult to measure accurately, particularly in the acetabular area. In order to study periacetabular osteolysis, specialized software for computerized tomography (CT) scan image analysis has been developed. This software (3D-CT) eliminates metal artifacts, allows three-dimensional segmentation of the CT image, and reconstructs the segmented image to provide an accurate representation and measurement of volume for osteolytic lesions. In the present study, 20 patients underwent periacetabular osteolytic volume determination using 3D-CT, functional assessment (using the Harris Hip Scale, the Western Ontario and McMaster University Osteoarthritis Index, and the short form 36 questionnaire), and two-dimensional analysis of volumetic polyethylene wear using digitalized plain films. Periacetabular osteolysis correlated directly with the polyethylene wear rate (relative risk [RR] = 0.494, P = 0.027). If one patient with an acetabular revision, one patient with recurrent dislocation, and one patient with a Biomet prosthesis are excluded, then the correlation between wear and osteolysis is improved (RR = 0.685, P = 0.002). In summary, the current study demonstrates both the feasibility of CT imaging of periacetabular osteolysis and the correlation between polyethylene wear and osteolytic volume, providing a potential outcome measure for clinical trials that are designed to examine interventions in this complex disease process.
PMCID: PMC64853  PMID: 11879538
3D-segmented computerized tomography; aseptic loosening; osteolysis; prosthesis
9.  Periacetabular osteotomy for the treatment of dysplastic hip with Perthes-like deformities 
International Orthopaedics  2007;33(1):71-75.
We retrospectively evaluated 17 hips in 16 patients who underwent a periacetabular osteotomy for the treatment of dysplastic hip with Perthes-like deformities. These residual deformities were graded using the Stulberg classification system. There were three class II hips, 11 class III hips and three class IV hips preoperatively. The average age of the patients at surgery was 36.9 years and the average follow-up was 6.6 years. The average Harris hip score significantly improved from the preoperative value of 68.2 points to 91.1 points postoperatively. The average postoperative range of motion in all directions did not change significantly from the preoperative value. The average postoperative Harris hip score of class IV hips was smaller than that of the class II or class III hips. The standard radiographic evaluations also showed significant improvements postoperatively. Periacetabular osteotomy without combined femoral osteotomies, as a treatment for patients with Perthes-like deformities, produced good clinical and radiographic results.
doi:10.1007/s00264-007-0476-9
PMCID: PMC2899206  PMID: 17999061
10.  Does Previous Reconstructive Surgery Influence Functional Improvement and Deformity Correction After Periacetabular Osteotomy? 
Background
The Bernese periacetabular osteotomy (PAO) is commonly used to surgically treat residual acetabular dysplasia. However, the degree to which function and radiographic deformity are corrected in patients with more severe deformities that have undergone previous reconstructive pelvic or femoral osteotomies is unclear.
Questions/purposes
We evaluated hip pain and function, radiographic deformity correction, complications, reoperations, and early failures (conversion to THA) associated with PAO in hips treated with previous reconstructive hip surgery.
Methods
We retrospectively reviewed 63 patients who had undergone 67 PAOs after a previous reconstructive hip procedure. We compared preoperative hip scores and radiographic parameters with postoperative values at most recent followup. We recorded complications, need for nonarthroplasty revision surgery, and failures. Minimum followup was 2 years.
Results
Five of the 67 hips (8%) were converted to THA between 24 and 118 months. The average followup for the remaining 62 hips was 60 months (range, 24–147 months). The average Harris hip score improved 11 points, and postoperatively, 83% of the hips had pain component scores of greater than 30 (none, slight, or mild pain). Radiographically, there were improvements in lateral center-edge angle (25°), anterior center-edge angle (23°), Tönnis angle (17°), and medialization of the hip center (8 mm). Complications occurred in 13 hips (19%). Seven hips (10%) underwent a subsequent surgical procedure to address residual pain or deformity.
Conclusions
PAO performed after previous reconstructive hip surgery improves hip function and corrects residual dysplasia deformities. These procedures are inherently more complex than primary PAO and are associated with a considerable risk of perioperative complications, reoperations, and early treatment failures.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-011-2158-6
PMCID: PMC3254768  PMID: 22042717
11.  A Modification of Periacetabular Osteotomy Using a Two-Incision Approach 
In residual hip dysplasia periacetabular osteotomy (PAO) can improve insufficient coverage of the femoral head. It requires a broad dissection of the pelvic bones and detachment of muscle insertions, however. We have developed a modification of the Bernese periacetabular osteotomy with reduced soft tissue exposure. It uses two small skin incisions and offers therefore the perspective of nicer scars but also increases the risk of technical complications due to impaired vision. To be able to draft these risks, the clinical and radiographic results of 23 patients with PAO through the modified Smith-Petersen approach of Ganz (group A) and 24 patients with our two-incision modification (group B) have been reviewed retrospectively with an average follow-up of 19 (group A) and 12 (group B) months postoperatively.
Functional improvement (Harris Hip Score) and center-edge-angle normalization did not differ significantly in both groups. Scars of patients in group B were significantly shorter. However, the overall patient satisfaction (as measured with a visual analogous scale) was the same in both groups. 4 patients in group A and one patient in group B developed superficial or deep wound infections.
In conclusion, the experience with our cohort study showed that approach-related morbidity can be reduced without increasing the risk for the individual patient. This observation clearly holds a promise for further minimal invasive approaches as well as for further morbidity reduction of PAO.
Level of Evidence: Retrospective comparative study (Level III).
doi:10.2174/1874325000701010013
PMCID: PMC2684705  PMID: 19461904
12.  What Factors Predict Failure 4 to 12 Years After Periacetabular Osteotomy? 
Background
The goal of periacetabular osteotomy (PAO) is to delay or prevent osteoarthritic development in dysplastic hips. However, it is unclear whether the surgical goals are achieved and if so in which patients. This information is essential to select appropriate patients for a durable PAO that achieves its goals.
Questions/purposes
We therefore (1) determined hip survival rates; (2) determined how many preserved hips were functionally unsuccessful after PAO; and (3) identified demographic, clinical, and radiographic factors predicting failure after PAO.
Methods
We retrospectively reviewed 316 patients (401 hips) who had PAO between December 1998 and May 2007. We evaluated radiographic parameters of dysplasia and osteoarthritis and obtained WOMAC scores. Through inquiry to the National Registry of Patients, we identified conversions to THA. Risk factors for conversion to THA were assessed. Minimum followup was 4 years (mean, 8 years; range, 4–12 years).
Results
The overall Kaplan-Meier hip survival rate was 74.8% at 12.4 years. A WOMAC pain score of 10 or more, suggesting clinical failure, was observed in 13% of preserved hips at last followup. Higher age, preoperative Tönnis grade of 2, incongruent hip, postoperative joint space width of 3 mm or less, and postoperative center-edge angle of less than 30° or more than 40° predicted conversion to THA.
Conclusions
PAO preserved three of four hips with most functioning well at 4- to 12-year followup. When planning surgery, surgeons should attempt to achieve hip congruence and a center-edge angle of between 30° to 40° to improve the durability of PAO.
Level of Evidence
Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-012-2386-4
PMCID: PMC3462869  PMID: 22576934
13.  Factors predicting the failure of Bernese periacetabular osteotomy: a meta-regression analysis 
International Orthopaedics  2008;33(6):1483-1488.
There is no clear evidence regarding the outcome of Bernese periacetabular osteotomy (PAO) in different patient populations. We performed systematic meta-regression analysis of 23 eligible studies. There were 1,113 patients of which 61 patients had total hip arthroplasty (THA) (endpoint) as a result of failed Bernese PAO. Univariate analysis revealed significant correlation between THA and presence of grade 2/grade 3 arthritis, Merle de’Aubigne score (MDS), Harris hip score and Tonnis angle, change in lateral centre edge (LCE) angle, late proximal femoral osteotomies, and heterotrophic ossification (HO) resection. Multivariate analysis showed that the odds of having THA increases with grade 2/grade 3 osteoarthritis (3.36 times), joint penetration (3.12 times), low preoperative MDS (1.59 times), late PFO (1.59 times), presence of preoperative subluxation (1.22 times), previous hip operations (1.14 times), and concomitant PFO (1.09 times). In the absence of randomised controlled studies, the findings of this analysis can help the surgeon to make treatment decisions.
doi:10.1007/s00264-008-0643-7
PMCID: PMC2899154  PMID: 18719916
14.  Arthroscopic labral repair concomitantly performed with curved periacetabular osteotomy 
A 23-year-old female presented with pain in the left hip. Radiological examination showed developmental dysplasia of the hip (DDH) combined with acetabular retroversion and posterior wall deficiency. Findings in the physical examination were coincident with femoroacetabular impingement. At surgery, we performed curved periacetabular osteotomy concomitant with arthroscopic labral repair and osteochondroplasty, simultaneously addressing dysplastic acetabulum and femoroacetabular impingement. The final follow-up examination at 18 months showed satisfactory outcome with the D’Aubigne and Postel hip score of 17/18. In addition to accurate diagnosis, the arthroscopic procedure for associated intra- and peri-articular problems seems to help improve the surgical outcome of periacetabular osteotomy performed for patients with DDH.
Level of evidence IV.
doi:10.1007/s00167-013-2362-x
PMCID: PMC3956971  PMID: 23338661
Hip; Arthroscopy; Osteotomy
15.  Mid-term results of Bernese periacetabular osteotomy for developmental dysplasia of hip in middle aged patients 
International Orthopaedics  2013;37(4):589-594.
Purpose
To address the question, compared to having hip replacement with latent revision, does Bernese periacetabular osteotomy (PAO) before primary hip replacement occupy a preferable treatment strategy for middle aged (aged 35–54 years) hip dysplasia patients? We assessed the mid-term functional outcome and survivorship of PAO in those patients.
Methods
Forty-one hips in 36 patients at middle age at the time of surgery (mean age, 39.5 years; range, 35–47 years) were retrospectively identified out of a total PAO cohort of 315 patients. Eleven of the 41 PAO hips also underwent osteochondroplasty at the femoral head-neck junction. Radiographic parameters of lateral centre edge angle, anterior centre edge angle and hip joint medialisation were investigated using the Harris Hip Score (HHS).
Results
The average follow-up was 5.1 years (range, two to ten years). Radiographic parameters postoperatively improved into the normal range, whereas no progression was found from preoperative Tonnis osteoarthritis score. Forty hips survived at the last follow-up, with HHS Score improved from 63.7 to 88.4. Compared to the sole PAO group, both postoperative alpha angle and range of joint motion improved in the PAO combined with osteochondroplasty group. However, no difference in HHS score was found.
Conclusions
Good survivorship and improved joint function were identified in middle-aged Chinese patients following PAO with or without osteochondroplasty. We prudently suggest PAO as an alternative strategy for treating DDH in those patients.
doi:10.1007/s00264-013-1790-z
PMCID: PMC3609987  PMID: 23381611
16.  What Are the Factors Associated With Acetabular Correction in Perthes-like Hip Deformities? 
Background
Perthes-like hip deformities encompass variable proximal femoral abnormalities and associated acetabular dysplasia that can be reconstructed with contemporary hip preservation procedures. Nevertheless, the necessity and indications for surgical correction of associated acetabular dysplasia have not been established.
Questions/Purposes
We determined whether patient-specific factors (sex, age, BMI, previous surgery, hip pain and function) and/or structural deformity characteristics (radiographic parameters of acetabular morphology) were associated with our indications for acetabular reorientation in surgical reconstruction of Perthes-like hip deformities.
Methods
We compared patient-specific characteristics and radiographic parameters of acetabular morphology in 94 patients (97 hips) with residual Perthes deformities who underwent joint preservation surgery without or with a periacetabular osteotomy (PAO) as part of the reconstruction.
Results
Patient sex, BMI, preoperative Harris hip score, and previous hip surgery were not associated with our indications for a combined femoral and PAO procedure. Radiographic parameters associated with the indication for a PAO included the lateral center-edge angle, anterior center-edge angle, acetabular inclination, and acetabulum-head index. No or mild secondary osteoarthritis and joint congruency were associated with the indication for a PAO as part of the reconstruction.
Conclusions
Contemporary hip preservation surgery for residual Perthes deformities covers a wide spectrum of procedures. We believe a PAO should be considered in the surgical treatment plan for symptomatic patients having radiographic parameters indicating acetabular dysplasia, no or mild secondary osteoarthritis, and adequate joint congruity.
Level of Evidence
Level III, prognostic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-012-2507-0
PMCID: PMC3492615  PMID: 22895688
17.  Cotyloplasty in Cementless Total Hip Arthroplasty for an Insufficient Acetabulum 
Clinics in Orthopedic Surgery  2010;2(3):148-153.
Background
Cotyloplasty is a technique that involves making a perforation of the medial wall of a shallow acetabulum and then inserting an acetabular cup with the medial aspect of its dome beyond the Kohler line. The purpose of this study was to evaluate the results of cementless total hip arthroplasty (THA) using cotyloplasty with focusing on the amount of medial cup protrusion.
Methods
Sixteen hips with insufficient acetabulum in sixteen patients were treated by cementless THA using cotyloplasty. The average patient age was 47 years. The diagnoses included dysplastic hip (12) and infection sequelae (4). All the patients were followed up for at least 2 years. Clinically, the Harris hip scores were assessed and radiologically, the amount of cup protrusion, the hip center movement and cup fixation were evaluated.
Results
The average Harris hip score improved from 57 to 94 postoperatively. The average proportion of cup surface beyond the Kohler line was 44.1% and the hip centers were medialized by an average of 23 mm. Stable fixation of the acetabular cup was achieved in all the cases except one. In this one case, migration of the cup was detected 2 weeks postoperatively and a reoperation was performed.
Conclusions
Using cotyloplasty, good coverage of the acetabular cup was obtained without a block bone graft, and the hip joint centers were medialized. However, the safety margin for the amount of protrusion should be established.
doi:10.4055/cios.2010.2.3.148
PMCID: PMC2915393  PMID: 20808585
Cotyloplasty; Hip dysplasia; Insufficient acetbulum; Total hip replacement; Cementless
18.  Physical Activity Level Improves After Periacetabular Osteotomy for the Treatment of Symptomatic Hip Dysplasia 
Background
Hip pain secondary to acetabular dysplasia can prevent participation in recreational activities.
Questions/Purposes
We retrospectively evaluated the physical activity level and pain after periacetabular osteotomy (PAO) for the treatment of symptomatic hip dysplasia.
Methods
Forty-seven female and four male patients with a mean age of 27 years underwent a PAO. Physical activity (UCLA) and pain (WOMAC) were assessed preoperatively, at 1 year, and at minimum 2 years postoperatively. Multivariable linear regression identified substantial, independent factors associated with postoperative activity level.
Results
The UCLA activity scores were on average higher at 1 year and remained higher at minimum 2 years when compared with preoperative scores. Mean postoperative WOMAC pain scores assessed at 1 year and at least 2 years were lower than mean preoperative scores. Age and preoperative physical activity level were strong independent predictors for activity level at 1 year and at minimum 2 years after surgery. Postoperative pain level was a moderate predictor for the level of activity at minimum 2-year followup.
Conclusions
Physical activity level improves after PAO. Younger age and higher activity levels before surgery and lower level of pain after surgery are predictive factors for postoperative level of activity in the short term. The data presented here may be useful to counsel the active young adult with symptomatic hip dysplasia about the improvement of level of activity to be expected after PAO.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-012-2578-y
PMCID: PMC3563783  PMID: 23212768
19.  Periacetabular Osteotomy for Acetabular Dysplasia in Patients Older than 40 Years: A Preliminary Study 
The functional outcomes of periacetabular osteotomy (PAO) and factors predicting outcome in the older patient with acetabular dysplasia are not well understood. We therefore retrospectively determined the functional outcome of 70 patients (87 hips) over age 40 treated with PAO in three institutions; we also determined whether preoperative factors, particularly the presence of osteoarthritis, influenced the survival of the hip or time to total hip arthroplasty after PAO. The average age at surgery was 43.6 years. The minimum followup was 2 years (mean, 4.9 years; range, 2–13 years). Twenty-one hips (24%) had undergone total hip arthroplasty (THA), at a mean of 5.2 years after PAO (range, 1.9–7.6 years). Surviving hips had a mean improvement in Harris hip score from 60.7 to 90.3 and in total WOMAC pain score from 8.7 to 3. We observed no differences in preoperative or postoperative radiographic measurements or preoperative clinical function scores (HHS, WOMAC) in hips surviving and hips having THA. The risk of THA at 5 years after PAO was 12% in hips with preoperative Tönnis Grade 0 or 1 and 27% for Tönnis Grade 2. Our preliminary study suggests that PAO will give satisfactory functional and pain scores in patients over age 40 having dysplastic hips with mild or no arthrosis.
Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-009-0824-8
PMCID: PMC2866943  PMID: 19421831
20.  Polygonal triple (Kotz) osteotomy (over 10 years experience) 
International Orthopaedics  2006;31(3):279-285.
We evaluated the results of polygonal triple (Kotz) osteotomy for the treatment of acetabular dysplasia over 10 years. This study included 31 hips of 27 patients who had the Kotz osteotomy for acetabular dysplasia. The mean age was 21.5 years. We performed the original Kotz osteotomy for the first 22 hips (group I), while the modified Kotz osteotomy through an intra-pelvic approach without damage to the abductor muscle was applied for the last 9 hips (group II). Patients were evaluated by clinically and radiologically. The average follow-up was 106 months in group I, and 18 months in group II. The Trendelenburg gait was unchanged for four patients in group I and for one patient in group II. The Harris Hip Score improved in all patients postoperatively. Radiographic assesment showed improvement in both groups in terms of the angle of CE, VCE, and Sharp postoperatively(P<0.05). The complication rate per hip was 0.29. The original Kotz osteotomy achieves adequate coverage for the treatment of acetabular dysplasia, and patients are generally satisfied by this procedure. Nonetheless, the modified Kotz osteotomy provides recovery of the abductor muscle strength in the early postoperative period and subsequently decreases the rate of the Trendelenburg gait compared to the original Kotz osteotomy.
doi:10.1007/s00264-006-0203-y
PMCID: PMC2267592  PMID: 16915400
21.  Evaluation of acetabular versions after a curved periacetabular osteotomy for dysplastic hips 
International Orthopaedics  2009;34(4):473-477.
The purpose of this study is to investigate the early clinical and radiographic findings related to acetabular orientation after a curved periacetabular osteotomy (CPO). 106 dysplastic hips of 88 patients underwent CPO were investigated retrospectively with an average follow-up of 3.6 years. Conventional anteroposterior radiographs were used to measure the radiographic findings and range of motion were used for clinical evaluations. A significant improvement was noted in radiographic measurements including lateral centre-edge angle, acetabular index, and acetabular angle of Sharp. However, a high rate of postoperative acetabular retroversion was observed (62% hips) and a marked decrease in free flexion was noted. The Tönnis scale revealed a one-grade progression in most retroversion hips. Acetabular retroversion is a high risk factor leading to degenerative osteoarthritis of hip. Therefore, special consideration must be taken in surgical planning and careful intraoperative confirmation is required whilst manoeuvring the acetabular fragment in CPO.
doi:10.1007/s00264-009-0785-2
PMCID: PMC2903143  PMID: 19424696
22.  ASSESSMENT OF WALKING PATTERN PRE AND POST PERI-ACETABULAR OSTEOTOMY 
Background
Adult hip dysplasia (AHD) is a common etiology of hip pain in the young adult. Patients with adult hip dysplasia may present with hip pain and early degenerative changes resulting from elevated cumulative hip-contact stress. While there are numerous studies using radiographic parameters coupled with general and disease-specific health status measures to demonstrate that periacetabular osteotomy improves the orientation of the acetabulum, decreases pain and improves function, to our knowledge there is only one study that utilized gait analysis to demonstrate an objective functional alteration. The purpose of the present study was to prospectively evaluate the walking pattern and assess the activity level of patients undergoing periacetabular osteotomy for symptomatic adult hip dysplasia.
Methods
Institutional review board approval was obtained for collection and review of data on 55 patients who underwent periacetabular osteotomy at one institution by the senior author (TM) between the years 2007-2009. Walking pattern characteristics were assessed including velocity, cadence, stride
length of the affected side, and percent of single-limb support on the affected limb using GaitRite® walking pattern analysis. Activity was assessed as average steps/day over a consecutive seven-day period. As a secondary analysis, the disease-specific and generalized health status outcome measures of all patients who underwent periacetabular osteotomy were reviewed.
Results
At an average of 11.5 months post periacetabu-lar osteotomy the walking patterns of 27 patients were available for review. Several trends were observed, including an approximate 5% increase in walking velocity (118 cm/sec to 125 cm/sec), and a 4.5 % increase in stride length (132 cm to 138 cm, p=0.01). At a mean 9.5 months following surgery, 26 patients reported an 8.75% decrease in average steps taken daily (4598 steps/day to 4196 steps/day). A significant improvement in SF-36 PC scores (p<0.01), the WOMAC hip pain and function scores (p<0.01) and the HHS (p<0.01) was noted during the same period.
Conclusion
At an average of 11.5 months following periacetabular osteotomy for the treatment of symptomatic hip dysplasia, a trend toward increased walking velocity and a significant increase in stride length was noted. A significant improvement in pain relief as well as improved physical function was observed in the short term. Subgroup analysis of patients without pre-existing osteoarthritis (as compared to those with pre-existing osteoarthrosis) revealed increased walking velocity, stride length of the affected limb, and percent of gait cycle in single support on the affected limb following periacetabular osteotomy. Further prospective studies are needed to fully clarify the long-term impact of the periacetabular osteotomy on patients with symptomatic hip dysplasia.
PMCID: PMC3215120  PMID: 22096426
23.  Anterior Delayed Gadolinium-enhanced MRI of Cartilage Values Predict Joint Failure After Periacetabular Osteotomy 
Background
Several available compositional MRIs seem to detect early osteoarthritis before radiographic appearance. Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) has been most frequently used in clinical studies and reportedly predicts premature joint failure in patients undergoing Bernese periacetabular osteotomies (PAOs).
Questions/Purposes
We asked, given regional variations in biochemical composition in dysplastic hips, whether the dGEMRIC index of the anterior joint would better predict premature joint failure after PAOs than the coronal dGEMRIC index as previously reported.
Methods
We retrospectively reviewed 43 hips in 41 patients who underwent Bernese PAO for hip dysplasia. Thirty-seven hips had preserved joints after PAOs and six were deemed premature failures based on pain, joint space narrowing, or subsequent THA. We used dGEMRIC to determine regional variations in biochemical composition. Preoperative demographic and clinical outcome score, radiographic measures of osteoarthritis and severity of dysplasia, and dGEMRIC indexes from different hip regions were analyzed in a multivariable regression analysis to determine the best predictor of premature joint failure. Minimum followup was 24 months (mean, 32 months; range, 24–46 months).
Results
The two cohorts were similar in age and sex distribution. Severity of dysplasia was similar as measured by lateral center-edge, anterior center-edge, and Tönnis angles. Preoperative pain, joint space width, Tönnis grade, and coronal and sagittal dGEMRIC indexes differed between groups. The dGEMRIC index in the anterior weightbearing region of the hip was lower in the prematurely failed group and was the best predictor.
Conclusions
Success of PAO depends on the amount of preoperative osteoarthritis. These degenerative changes are seen most commonly in the anterior joint. The dGEMRIC index of the anterior joint may better predict premature joint failure than radiographic measures of hip osteoarthritis and coronal dGEMRIC index.
Level of Evidence
Level II, prognostic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-012-2519-9
PMCID: PMC3492640  PMID: 22907475
24.  Bernese Periacetabular Osteotomy in Males: Is There an Increased Risk of Femoroacetabular Impingement (FAI) After Bernese Periacetabular Osteotomy? 
Background
The Bernese periacetabular osteotomy (PAO) is a popular option for treating symptomatic acetabular dysplasia. We noted symptomatic impingement after PAO in several male patients.
Questions/purposes
We therefore determined (1) the incidence of clinical signs of FAI after PAO in the male population; and (2) whether any factors were associated with the positive impingement signs after PAO in males.
Patients and Methods
We retrospectively reviewed 38 males who underwent 46 periacetabular osteotomies (PAO) between 2000 and 2007. Clinical and radiographic data were analyzed with the focus on pre- and postoperative incidence of femoroacetabular impingement. Minimum followup was 12 months (average, 43 months; range, 12–90 months).
Results
We found a positive impingement sign in 19 of the 46 hips during the preoperative examination compared to 22 (47.8%) hips postoperatively. The ROM (flexion and internal rotation) decreased postoperatively compared to preoperatively. Radiographic parameters of coverage LCE-, ACE- and Tönnis angle improved into the normal range. Twenty hips had postoperative heterotopic ossification to varying degrees, mostly minor. WOMAC scores improved in the function and pain domains postoperatively.
Conclusions
Despite normalization of coverage we found a high postoperative rate of clinical signs of FAI after PAO in males.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-010-1544-9
PMCID: PMC3018207  PMID: 20848246
25.  The management of acetabular malunion with traumatic arthritis by total hip arthroplasty  
Objective: To explore the treatment strategies and clinical effect of the acetabular malunion with traumatic arthritis by total hip arthroplasty.
Methodology: A retrospective analysis was conducted on 47 cases of acetabular malunion with traumatic arthritis from June 2000 to December 2009. All the patients underwent total hip arthroplasty with bone grafting or titanium cage for bone defect of the acetabulum. Harris hip scoring system was used for evaluating the functional recovery of the hip joint.
Results: Thirty three cases had an average of 47 months follow-up. No prosthesis was loosened and the function of hip joint was improved obviously with the Harris hip scores improving from 43.5 to 87.6. However, there were one case of sciatic nerve injury and four cases of heterotopic ossification postoperatively.
Conclusion: Total hip arthroplasty might be an effective treatment of acetabular malunion with traumatic arthritis. Proper evaluation and reasonable reconstruction of acetabular defect as well as reasonable selection of prosthesis are essential to obtain an excellent outcome.
doi:10.12669/pjms.291.2900
PMCID: PMC3809163  PMID: 24353538
Acetabular fracture; Traumatic arthritis; Total hip arthroplasty; Harris scoring system

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