Clinical outcomes of single-bundle versus double-bundle ACL reconstruction in adolescent elite athletes: A retrospective comparative study.

OBJECTIVE: The aim of the study was to evaluate the single bundle (SB) and double bundle (DB) anterior cruciate ligament (ACL) reconstruction in terms of graft survival, complications, and patient reported functional outcomes in adolescent athletes. METHODS: In this retrospective study, 89 elite adolescent athletes who underwent either SB or DB ACL reconstruction were included. All patients were then divided into two groups: group 1 including 51 patients with SB ACL reconstruction (31 male, 20 female; mean age = 15.4 ± 1.03 years) and group 2 including 38 patients with DB ACL (30 male, 8 female; mean age = 15.7 ± 1.3 years). Clinical data were obtained, comprising skeletal maturity, sports type, ACL reconstruction technique, Lachman scores, KT-1000™ arthrometer measurement, additional meniscal procedures as well as International Knee Documentation Committee (IKDC) score, Cincinnati score, and graft size. RESULTS: The mean follow-up period was 53.1 ± 8.6 months in group 1 and 46.4± 9.1 months in group 2 (P = 0.61). The type of ACL reconstruction technique (SB or DB), gender, skeletal maturity, sports type, additional meniscal procedures and Lachman scores were not associated with the re-rupture of the ACL (P > 0.05). Moreover, ACL reconstruction technique did not effect the rate of re-rupture of an ACL. There were 21 re-ruptures (23.5%) and 11 (12.3%) contralateral ACL ruptures in total. Among 21 reruptures, 12 of them were in the DB group while nine of them in the SB group (P > 0.05). The groups did not differ with respect to age, the injured side, the time from injury to surgery, the postoperative follow-up time, or the preoperative physical examination results KT-1000 device (SSD), Cincinnati score, IKDC objective and subjective score,Lachman test and pivot-shift test). CONCLUSION: There are no differences in the re-rupture of an ACL, patient reported outcomes, and complications in adolescent elite players, when either an SB or DB technique is performed. LEVEL OF EVIDENCE: Level III, Therapeuthic Study.

Onlay fibula autografting technique and its comparison with cortical allograft for the reconstruction of periprosthetic bone defects around the femur.

BACKGROUND: Bone defect around the femur related to revisions or periprosthetic fractures (PFF) is an issue. We present a bone defect reconstruction technique in femoral revisions and/or PFF using fibula autograft and compared our radiological and clinical results to that of allograft. METHODS: A total of 53 patients who underwent revision hip arthroplasty and/or PFF fixation with the use of cortical fibula autograft (FG group) or cortical allograft (CG group) were evaluated. After exclusions, 20 patients who had minimum two years of follow-up were investigated for each group, for their radiological and clinical outcomes. RESULTS: In FG and CG groups, the median ages were 69.5(44-90) and 62(38-88) years, follow-ups were 59(28-72) and 120(48-216) months, defect lengths were seven (1-10) and ten (1-17) cm, and grafts lengths were 16.5(10-30) and 20(12-37) cm, respectively. The rate of graft incorporation was 90% in each group and median time to incorporations were seven (4-12) and 12(6-24) months (p < 0.001), and graft resorption (moderate and severe) rates were 10% and 25% (p = 0.41), respectively. Median Harris Hip (77.6 vs 78.0), WOMAC (23.2 vs 22), SF-12 physical (50.0 vs 46.1), and SF-12 mental (53.8 vs 52.5) scores were similar between the groups, respectively. Kaplan-Meier survivorship analyses revealed an estimated mean survival of 100% at six years in FG group and 90% at 14 years in CG group. CONCLUSION: In the reconstruction of periprosthetic bone defects after femoral revision or PPF, onlay cortical fibula autografts provide comparable clinical and radiological outcomes to allografts. Its incorporation is faster, it is cost-effective and easy to obtain without apparent morbidity.

Trends in the treatment of infected knee arthroplasty.

Essential treatment methods for infected knee arthroplasty involve DAIR (debridement, antibiotics, and implant retention), and one and two-stage exchange arthroplasty.Aggressive debridement with the removal of all avascular tissues and foreign materials that contain biofilm is mandatory for all surgical treatment modalities.DAIR is a viable option with an acceptable success rate and can be used as a first surgical procedure for patients who have a well-fixed, functioning prosthesis without a sinus tract for acute-early or late-hematogenous acute infections with no more than four weeks (most favourable being < seven days) of symptoms. Surgeons must focus on the isolation of the causative organism with sensitivities to bactericidal treatment as using one-stage exchange.One-stage exchange is indicated when the patients have:minimal bone loss/soft tissue defect allowing primary wound closure,easy to treat micro-organisms,absence of systemic sepsis andabsence of extensive comorbidities.There are no validated serum or synovial biomarkers to determine optimal timing of re-implantation for two-stage exchange.Antibiotic-free waiting intervals and joint aspiration before the second stage are no longer recommended. The decision to perform aspiration should be made based on the index of suspicion for persistent infection.Re-implantation can be performed when the treating medical team feels that the clinical signs of infection are under control and serological tests are trending downwards. Cite this article: EFORT Open Rev 2020;5:672-683. DOI: 10.1302/2058-5241.5.190069.

Long-term results of osteochondral autograft transplantation of the talus with a novel groove malleolar osteotomy technique.

OBJECTIVES: This study aims to evaluate the long-term results of osteochondral autograft transfer (OAT) of talar lesions performed using a modified osteotomy technique. PATIENTS AND METHODS: This retrospective study included 20 consecutive patients (11 males, 9 females; mean age 33.5±11 years; range, 15 to 56 years) (21 ankles) with osteochondral lesions of the talus (OLT) treated with the OAT system between August 2002 and October 2008. We performed a modified sulcus groove osteotomy, which provides better exposure of medial and central lesions. After a minimum duration of 10 years following surgery, patients' clinical functions were evaluated according to the American Orthopaedic Foot and Ankle Society (AOFAS) ankle- hindfoot scale and visual analog scale (VAS). The Tegner-Lysholm scoring system was used to determine the levels of knee activity. RESULTS: The mean follow-up period was 143.5 (range, 120 to 186) months. The mean AOFAS scores significantly improved from 60.4±7.4 (range, 48 to 70) preoperatively to 86.2±9.2 (range, 60 to 94) at the last follow-up (p≤0.05). The mean ankle VAS score significantly decreased from 6.3±0.4 (range, 5 to 7) preoperatively to 2.0±1.4 (range, 0 to 4). The mean Tegner-Lysholm score for this group was 89.7±11.7 (range, 68 to 100). Revision surgery was performed in only two patients because of impingement and arthritis. Recurrent knee pain at the donor site of the osteochondral autograft was observed in three (14%) patients. CONCLUSION: In the present study, good to excellent results were obtained in the treatment of OLT with OAT for a minimum follow-up duration of 10 years. This novel technique can also simplify the steep learning curve, which is challenging for surgeons.

Dual-mobility cups in revision acetabular reconstructions: Short-term outcomes in high-risk patients for instability.

OBJECTIVE: The aim of this study was to evaluate the performance of dual-mobility (DM) cup systems for revision total hip arthroplasty (rTHA) in patients who had high risk for instability. METHODS: We prospectively followed up 34 hips of 30 patients (27 females, 3 males; mean age: 66.1 (range: 33 to 89) years) who underwent rTHA with DM cups for aseptic loosening in 23 hips, infection treatment as second or single stage in nine hips, and instability in two hips. Clinical functions of the patients were evaluated using the Harris Hip Score (HHS), and radiological migration or loosening of the DM cups were recorded. The survival of the components was calculated with the Kaplan-Meier survival analysis and failure was defined as any dislocation of the polyethylene (PE) insert, intraprosthetic dislocation (IPD), aseptic loosening of any component or total hip system revision due to any reason. RESULTS: The mean duration of follow-up was 3.52 (range: 2.05 to 6.26) years. There was one dislocation of PE insert (2.9%), which was treated with closed reduction. There were two (5.8%) re-revisions for cemented DM cup due to migration. There was one PE insert and head change due to subacute infection. The mean HHS increased from 42.8 ± 6.7 (range: 34 to 60) points preoperatively to 87.3 ± 5.8 (range: 75 to 98) points postoperatively. The cumulative survival rate of the DM cup system was 91.2% (95% CI: 81.6-100%) with any revision, 94.1% (95% CI: 86.2-100%) with aseptic loosening and %97.1 (%95 CI: 91.4-100%) with dislocation as the end point at 3.5 years. CONCLUSION: Dual-mobility cups may provide good stability and represent a good option for revision acetabular reconstruction in patients who have high risk for instability. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Long-term results of cementless total hip arthroplasty for the treatment of ankylosed hip.

PURPOSE: The purpose of this study was to report the long-term results of total hip arthroplasty (THA) for the treatment of ankylosed hip. METHODS: Twenty-nine consecutive THAs were performed in 26 patients. The mean age of the patients at the time of the operation was 43.3 years (range, 19-69 years). We used cementless fixation in all hips and the mean duration of follow-up was 10.1 years (range, 4.5-20 years). Radiological evaluation of components, osteolysis, radiolucent lines and loosening were assessed. The Harris Hip Score (HHS), range of motion (ROM), limb-length discrepancy and walking capacity with or without any support were used preoperatively and at final follow-up for clinical evaluation. Survivorship analysis was conducted using the Kaplan-Meier method using second revision for any reason as the endpoint. RESULTS: The mean HHS was 85.6 (range, 55-98) points and mean ROM was 110.5° for flexion. The mean limb-length discrepancy improved from 4.1 cm to 1.1 cm. Positive Trendelenburg sign was recorded in 31% of the patients and 24% of patients needed any support for walking postoperatively. We observed surgical complications related to abductor arm in 25% of the patients. Radiolucency on the acetabular side was seen on one or more zones in 15 patients (16 hips). One aseptic acetabular component loosening was observed. On the femoral side, 11 patients demonstrated non-progressive radiolucent lines and osteolysis around the stem was seen in four hips but there was no aseptic stem loosening. The Kaplan-Meier survival rate considering revision for any reason as the endpoint was 81.5%, for aseptic loosening 91.3%, for a worst-case scenario of 66.4% at 10 years. CONCLUSION: Cementless fixation showed good to excellent results at 10 years. Preoperative and postoperative abductor status of the patient is critical for patient satisfaction.

Dual offset metaphyseal-filling stems in primary total hip arthroplasty in dysplastic hips after a minimum follow-up of ten years.

PURPOSE: The aim of this study was to assess the long-term performance of tapered one-third proximally coated stems in dysplastic hips. METHODS: This study included 135 dysplasia patients (150 hips) who underwent a total hip arthroplasty and had a minimum follow-up of ten years. Single design tapered stems were used in all patients. There were 112 women (83%) and 23 men (17%) with a mean age of 45 years (23 to 72) at the time of surgery. The mean follow-up was 14.7 years (10 to 16.8). For clinical evaluation, the Harris Hip Score and Merle D'Aubigne scale were used pre-operatively and at the final follow-up. Implant survival was calculated using Kaplan-Meier survivorship analysis, with failure defined as a component revision for any reason. RESULTS: Overall, one stem was revised for a deep infection. There were no other femoral stem revisions secondary to loosening, wear, periprosthetic fracture, or instability. Radiographic evaluation showed excellent stem osteointegration in all cases. Kaplan-Meier survivorship, with stem revision for any reason as the end point, was 98% at 14 years (95% confidence interval 92.5 to 99.8). CONCLUSION: This study demonstrates that a dual offset tapered stem achieved excellent survivorship and stability, as well as good clinical outcome scores with minimal thigh pain and stress shielding in patients with arthritis and developmental dysplasia of the hip; a dual offset tapered stem may be a suitable option for primary total hip arthroplasty in this group.

Intraoperative neuromonitoring of anterior root muscle response during hip surgery under spinal anesthesia.

The aim of this study was to evaluate the anterior root muscle (ARM) response monitorability during total hip arthroplasty (THA) under spinal anesthesia. A total of 20 adults (64.6 ± 13.87 years old) were monitored using ARM response and free-run electromyography during THA. To elicit the ARM response from muscles, percutaneous stimulation of the lumbosacral roots was performed by self-adhesive electrodes placed over the skin of the projection of the first and third lumbar interspinous space (anode) and over the abdominal skin of the umbilicus (cathode). Latency and amplitude values of the ARM response were recorded from both sides (non-operated and operated) and from five muscles as follows: rectus femoris (RF), vastus lateralis (VL), biceps femoris long-head (BF), Tibialis Anterior (TA) and gastrocnemius. The most recorded ARM response in a muscle was the TA (n = 38); the least recorded AMR response in a muscle was the BF (n = 33). The mean stimulus intensities for the non-operated and the operated sides were 462.5 ± 112.8 V and 520.0 ± 172.3 V (p = 0.834), respectively. The mean latencies and amplitude values of the ARM response from muscles were as follows: 8.8 ± 1.4 ms; 98.8 ± 114.5 µV for RF; 9.8 ± 2.1 ms; 119.1 ± 122.23 µV for VL; 9.5 ± 1.6 ms; 39.6 ± 30.3 µV for BF; 15.1 ± 1.9 ms; 146.6 ± 150.9 µV for TA; 15.6 ± 2.4 ms; 81.0 ± 99.9 µV for Gastrocnemius. The present study demonstrates that the ARM response could easily and safely be obtained during THA under spinal anesthesia. This non-invasive technique may have a potential to detect early neurological deficit in patients who need complex hip surgery under spinal anesthesia.

Dual-mobility bearings for patients with abductor-trochanteric complex insufficiency.

INTRODUCTION: The purpose of this study was to summarise the performance of dual-mobility cup systems for revision total hip arthroplasty in patients with abductor-trochanteric complex deficiency. METHODS: We prospectively followed 17 patients (20 hips) with a mean age of 64.5 years (range 33-89 years) who underwent acetabular reconstruction with dual-mobility cups for aseptic loosening in 12 hips, infection treatment as second or single stage in 6 hips, and instability in 2 hips. All of the patients had abductor insufficiency. We evaluated the clinical Harris Hip scores (HHS) and radiographs for migration, loosening, and osteolysis. The survival of the components was calculated according to Kaplan-Meier survivorship analysis, and failure was defined as any dislocation, acetabular component or total hip revision for any reason. RESULTS: The mean duration of follow-up was 38.1 months (range 24-98 months). There were 2 (12.5%) revisions for cemented cup migration after 11 months and 19 months respectively. There were no dislocations. At the last follow-up, the mean HHS increased from 42 points preoperatively to 86 points. The cumulative survival rate of the dual-mobility cup system was 93% (95% confidence interval 88-98.7%) at 5 years, with any revision as the end point. CONCLUSION: Dual-mobility cups may provide excellent stability in patients with abductor-trochanteric complex insufficiency.

Long-term retrospective study on the placement of the cementless acetabular cup and clinical outcomes in patients undergoing femoral head autografting for hip dysplasia and total hip arthroplasty.

BACKGROUND: Placement of acetabular cup in the dysplastic hip is a challenging procedure. Using bulk femoral head autograft to increase the bony coverage of the cup is one of the techniques, which have been described. The impact of cup position on cup and autograft survival is a controversial issue. We aimed to determine whether the position of cementless acetabular cup used in conjunction with femoral head autograft in dysplastic hips affected the autograft-host incorporation with its final radiographic appearance and the cup survivorship into the second decade. METHODS: Thirty-eight dysplastic hips with varying Crowe types in 31 patients (30 women and one man) were included. The mean age was 47 years (range, 29-64 years) and the mean follow-up was 20.3 years (range, 14.8-25.9 years). The initial postoperative and final radiographs were evaluated. The survival rate of the cups was analysed using Kaplan-Meier statistics and the log-rank test. Multivariate analysis was used to evaluate the effect of variables (Crowe type, radiographic initial host bone coverage over the cup and position of the cup) on survivorship. RESULTS: The acetabular cups were positioned anatomical in 27/38 hips according to Ranawat measurement technique. Trabecular bridging at graft-host interface was seen in all cases at an average 22.1 months. Neither acetabular cup position nor initial host bone coverage over acetabular cup less than 50% had any significant effect on either cup survival or final radiographic appearance of the graft. The 20-year cup survival rate without aseptic revision was 66% (95 CI, 52%-84%). No revision was performed due to graft resorption. CONCLUSION: Twenty-year survival rate of the cementless cup combination with femoral head autograft showed no significant differences whether it was placed at high or anatomic hip centre. The final radiographic appearance of the autograft was not affected from either the cup location or the initial radiographic horizontal host bone coverage.

Total hip arthroplasty with step-cut subtrochanteric femoral shortening osteotomy in high riding hip dislocated patients with previous femoral osteotomy.

BACKGROUND: To evaluate the long-term clinical and radiological outcomes of cementless total hip arthroplasty (THA) in high riding hip dislocated patients with previous proximal femoral osteotomy. METHODS: Twenty-one consecutive patients with a mean age forty-two years were treated with cementless THA Step-cut subtrochanteric femoral osteotomy was performed in all twenty-eight hips. Metal on polyethylene (MoP) and ceramic on ceramic (CoC) bearings were used in two different consecutive time periods. The mean follow-up time was twelve years. Harris hip score, limb length discrepancy, complications, union status of the osteotomy, survivorship of constructs were the criteria for evaluation. RESULTS: The mean Harris hip score improved from 39.5 to 88.7 points. The mean limb length discrepancy in unilateral cases decreased from 54.5 mm to 12.3 mm. The mean amount of femoral shortening was 37 mm. The mean union time was 3.5 months and there were no delayed union and non-union. There were three cup and two femoral revisions due to osteolysis in patients who had MoP. There was only one femoral revision in patients who had CoC. The Kaplan Meier survivorship with an end point of any revision of the stem and the acetabular component was 94% (95% CI, 75%-98%) and 92% (95% CI, 74%-99%) at ten years respectively. CONCLUSIONS: Total hip arthroplasty with subtrochanteric step-cut femoral shortening is a successful technique to improve the hip functions and reconstruct limb length discrepancy in young patients with proximal femoral deformities.

The cementless fibre mesh coated anatomic femoral stem: 12 to 23 years clinical and radiological outcome study.

INTRODUCTION: The aim of this study was to assess the long-term clinical and radiographic results, and possible reasons for failure of two versions of the cementless fibre-metal coated anatomical femoral component. METHODS: 99 patients (119 hips) were evaluated at an average of 16.7 years (range, 12 to 23 years) following primary THA. Developmental dysplasia of the hip (DDH) was the most common pathology (n = 37 hips). Structural femoral head autografts were used to increase cup coverage in 23 hips. Vertical and horizontal migration of acetabular and femoral components and osteolysis around the components were assessed using conventional radiolography. For clinical evaluation, the Harris Hip Score and Merle D'Aubigne scale were used preoperatively and at final follow up. Implant survival was calculated according to the Kaplan-Meier survivorship analysis and failure was defined as component's revision for any reason. RESULTS: The cumulative survival rate of the anatomical femoral stem was 64.2% at 19.8 years, with a worst-case scenario of 41%. The cumulative survival rate of the total hip arthroplasty was 51% at 19.8 years, with a worse case scenario of 38%. The mean preoperative Harris Hip Score of 42 points improved to 88 postoperatively. The mean preoperative Merle D'Aubigne functional score of 3.5 improved to 5.2 points at the time of final follow-up. In 36 hips (41.6%) osteolysis was found in Gruen zone 1, proximal to the ingrowth surface. CONCLUSIONS: The cementless fibre-metal coated anatomical femoral component showed favourable long-term clinical and radiological results. Proximal coating seems to protect bone implant interface from wear debris induced osteolysis during the second decade.

Biomechanical comparison of oblique and step-cut osteotomies used in total hip arthroplasty with femoral shortening.

BACKGROUND: Various types of shortening osteotomies and prosthesis are used for femoral reconstruction in total hip arthroplasty of the high hip dislocation. This biomechanical study investigates whether step-cut osteotomies result in better stability than oblique osteotomies and cylindrical femoral stems enhance stability of the osteotomy more than conical stems, and which osteotomy and prosthesis type maintain the stability better after cyclical loading. METHODS: Oblique and step-cut shortening osteotomies were compared under axial and rotational forces, using synthetic femur models and conical or cylindrical femoral prostheses. The models underwent cyclic loading for 10,000 cycles at 3 Hz (100-1000 N axial bending or 0.5-10 Nm torque). After the completion of cyclic loading, the models were loaded until failure. Stiffness values before and after cyclical loading, and failure loads were the outcome parameters. Relative displacements at the osteotomy sites were also measured using 3-Dimensions Digital Imaging Correlation System. RESULTS: The mean failure load was significantly higher in conical prosthesis groups under axial forces. In torsion tests, the mean stiffness of conical prosthesis groups after cyclical loading was higher in oblique osteotomies. The other parameters were similar between the groups. CONCLUSIONS: According to the results of the study, although some individual statistically significant parameters were obtained, step-cut osteotomies, which are technically challenging procedures, were not found biomechanically superior to oblique osteotomies, with neither conical nor cylindrical prostheses.

Treatment of infected nonunion of the juxta-articular region of the distal tibia.

OBJECTIVE: The purpose of this study was to summarize our clinical results with distraction osteogenesis for the treatment of infected tibial nonunion around the ankle joint. METHODS: Between 1994 and 2009, 13 patients with a mean age of 50 years (range: 27-79 years) underwent tibial reconstruction for the treatment of infected nonunion of the distal tibia, with a mean bone loss of 4.8 cm (range: 1-7 cm). Lengthening over an intramedullary nail as a second procedure was used in 2 patients, bifocal compression and distraction technique in 5 cases, compression with Ilizarov external fixator in 5 cases, and Taylor Spatial Frame (TSF, Smith Nephew, Memphis, TN, USA) in 1 case. At final follow-up, functional and radiographic results were evaluated according to Paley's bone and functional healing criteria. RESULTS: Mean duration of follow-up was 36 months. Mean external fixation time was 198 days, and mean external fixation index was 29 days/cm. According to Paley's bone healing criteria, there were 10 excellent, 2 good, and 1 poor result(s); additionally, according to Paley's functional healing criteria, there were 5 excellent, 6 good, and 2 fair results. There were 11 problems, 5 obstacles, and 1 sequel according to Paley's classification of complications. There was 1 persisting nonunion, which underwent revision with a retrograde intramedullary nail. CONCLUSION: External fixator and/or combined treatment are effective and reliable methods to treat infected nonunion of the distal tibia. Every patient should be evaluated according to their infection level and bony defects for reconstruction.

Acute traumatic posterior fracture dislocation of the elbow in pediatric patients: impact of surgery time and associated fractures on outcome.

This study assessed the effect of the time interval from initial injury to surgery and the presence of associated fracture on functional outcomes after acute posterior elbow fracture dislocation. Twenty-six pediatric patients were evaluated with respect to operation time point (within 24 h vs. later) and associated fracture retrospectively. The Mayo Elbow Performance Index (MEPI) score was used to assess functional results. The MEPI score was 91 (80-100) in patients with one associated fracture and 83 (75-95) (P=0.02) in patients with more than one associated fracture. The MEPI score in patients treated within 24 h was 90.3 (75-95) and in those treated later than 24 h, it was 88.6 (75-100) (P=0.6). Treatment time (within 24 h vs. later) does not affect outcomes, but increasing numbers of associated injuries affect outcomes negatively. Level of study: Level IV case series.

Arthroscopic labral repair versus labral debridement in patients with femoroacetabular impingement: a minimum 2.5 year follow-up study.

PURPOSE: To compare the clinical results of labral repair with labral debridement in patients undergoing arthroscopy for femoroacetabular impingement. METHODS: Between July 2008 and December 2011, 67 patients (73 hips) underwent arthroscopic treatment for femoroacetabular impingement. The repair group consisted of 33 patients; 18 hips with pincer only, 1 with CAM only and 15 with combined impingement. The debridement group contained 34 patients; 6 with pincer only, 5 with CAM only and 28 with combined type. The mean age in the repair group was 33.5 years (range, 30-61) and in the debridement group was 39.5 years (range, 18-59 y). At the time of last follow-up, patient's hip function was evaluated with ROM of the hip; daily Hip Outcome scores (dHOS) and Visual Analogue Score (VAS). RESULTS: The mean follow-up was 45.2 month in the repair group and 47.2 month in debridement group. Daily hip outcome scores were significantly improved from preoperatively to last follow-up in both groups (p<0.05). However, there were no statistical significant difference in dHOS between repair and debridement groups (p>0.05) at last follow-up. 2 patients in the repair group and 1 patient in the debridement group had undergone total hip replacement at an average of 16 months (range, 4-32 m) after arthroscopic treatment. Hip joint instability occurred in 1 patient in the repair group due to aggressive capsular resection. This was treated by a periacetabular osteotomy. CONCLUSIONS: No difference in hip functional outcomes was observed between labral debridement and labral repair in arthroscopic treatment of femoroacetabular impingement.