We determined differences in preoperative and postoperative metric variables using the paired t test (comparison of preoperative and postoperative alpha angle, NAHS, VAS for pain, ROM) and in metric variables of different groups (ie, patients with and without THA) using the unpaired t test. Before this, a test for normal statistical distribution of values and the Levene test were performed in all analyses to prove variances in the two groups were equal. SPSS® software (Version 15.0; SPSS Inc, Chicago, IL) was used for all analyses.
No operation was cancelled for intraoperative adverse events. In all cases, we could sufficiently observe the joint. In no patient did we identify iatrogenic labral damage resulting from arthroscopically entering the joint. Complications occurred in 12 (11%) hips. All were minor, including dysesthesia/hypesthesia of pudendal and lateral cutaneous femoral nerves in nine, and sciatic nerve neurapraxia with hypesthesia of the instep region in two. One very obese female patient sustained a superficial tear of her labia minora resulting from the traction device. All complications resolved completely without additional treatment within months. There were no femoral neck fractures related to surgery and the postoperative MRI did not reveal any evidence of osteonecrosis of the femoral head.
The 96 hips (91%) not requiring THA had improved NAHS, range of flexion and internal rotation, pain, and alpha angle (Table 2). In the preoperative examination, 99 hips (94%) had a positive anterior impingement sign. At the latest followup, this had decreased to 17 hips (18%).
When comparing patients with a pure cam impingement (n = 57, 54.3%) with those having mixed impingement treated with rim trimming (n = 48, 45.7%), no differences were found with respect to preoperative Tönnis grade, chondral damage, NAHS, ROM, or VAS for pain.
In nine hips (9%), THA subsequently was performed, including five surface replacements and four conventional hip prostheses. The average age of these patients (46.1 years) was similar to (p = 0.1) the average age (40.5 years) of the rest of the cohort at the time of index surgery. Five of these patients preoperatively had osteoarthritis Tönnis Grade II, and four had Grade I. Intraoperatively, we observed Grade 3 osteochondral lesions in four hips and Grade 2 in five hips. The average preoperative and postoperative alpha angles were similar (both p = 0.7) to those of the rest of the patients. The preoperative NAHS was lower (p = 0.04) than that in the rest of the cohort. No other reoperations were performed in the rest of the cohort.
Open surgical hip dislocation and femoroacetabular correction for FAI is a well-accepted method of treatment for FAI associated with none or only mild chondral damage and yields good to excellent results in short- and midterm followups [1, 4, 25]. However, this operation is associated with a large surgical exposure, several weeks of partial weightbearing, and a considerable number of short- and long-term complications, such as pain over the trochanteric region, which makes screw removal necessary [1, 24]. Arthroscopic therapy for FAI has become a promising alternative. However, the procedure is associated with several technical difficulties, such as safe entering of the joint capsule, and few outcome studies are available [15, 29, 33]. We therefore describe a technique that provides a way to securely penetrate the joint capsule, which enables sufficient observation of the pathologic head-neck region and arthroscopic correction for FAI. We then report the complication rate; the number of patients who had subsequent THA; and the NAHS , ROM, pain, impingement sign, and alpha angle in patients with and without subsequent THA after surgery using this technique.
The two major limitations of our study are the lack of a control group and the short followup. A longer followup is necessary to determine whether, and especially in which patients, correction for FAI may avert the pathologic sequence of events starting with impingement and resulting in end-stage arthrosis at a young age. Labrum resection instead of labrum refixation might be another limitation of this study. Recently published studies seem to favor labrum refixation instead of resection [5, 10, 11, 30]. But, as all of these studies have short followups, no definitive judgment on this issue can be made at this time.
Another potential flaw of the study might be the use of a not well-established grading system for cartilage lesions. However, we decided to use this grading scale because, at the time of the first patients, no validated and widely used cartilage grading system was available that took into account the specific lesions associated with FAI. We therefore thought it would be helpful to use a grading system that derives from the classic Outerbridge classification  but includes the special issues of FAI cartilage lesions in terms of limited extent of typical impingement lesions and later including the whole joint.
Arthroscopic correction for FAI seems to be a feasible surgical treatment. No arthroscopy was canceled because of surgical difficulties. Sufficient observation of the diseased area with our technique of extraarticular preparation of the capsule and entering the joint under direct visual control were achieved in all cases. We did not identify any patient with osteonecrosis of the femoral head nor any femoral neck fractures related to the surgery. The number of neurologic complications in our series seems high at first sight compared with numbers reported in other studies [7, 14, 30]. However, this might be because we were searching explicitly for dysesthesia/paresthesia instead of noting what patients reported . Nerve lesions have been reported to be a particular risk of hip arthroscopy because the anterolateral portal is in proximity to the superior gluteal neurovascular bundle, whereas the anterior portal is in proximity to the lateral femoral cutaneous nerve and the femoral neurovascular bundle . The primary risk of traction is injury to the sciatic nerve . We believe this is best minimized by directly controlled traction not exceeding the extent needed to enter the central compartment, by keeping the hip in slight flexion, and by keeping traction time as short as possible. Pudendal traction neurapraxia risk can be reduced with the use of a padded perineal bolster [16, 31].
Our arthroscopic approach as described previously might be a step in this direction, allowing use of traction only after establishing the arthroscopic portals and under direct visual control, thus keeping traction time and force at a strict minimum. The average traction time of 28.6 minutes in our series is far less that reported  owing to the fact that it was used only after having placed the portals and after capsulotomy. Another factor for shorter traction time compared with reported time might be the fact that no labral refixation was performed in our study cohort. The method of entering the capsule under direct visual control avoids iatrogenic labrum and cartilage damage.
Clinical and radiographic results from other studies can be compared with our outcome only with precautions. Most of the studies use outcome scores designed for patients with osteoarthritis, such as the WOMAC and Harris hip score [7, 14] (Table 3). This may lead to a larger number of higher scores because these scores consider a wider range of intensity of symptoms and are less sensitive to the differences in minimally symptomatic patients at or before the beginning of osteoarthritis. We believe the NAHS  is a more appropriate, reliable, and validated outcome measure for this group of patients. In general, the postoperative average of 84.6 points is comparable to what is reached in other studies [7, 21]. Data for postoperative ROM are sparse. However, our results are in accordance with those of Stähelin et al. . Our data suggest pain relief similar to that reported in two studies [21, 34]. In our study, the average postoperative alpha angle, as measured on MRI, was 50.3°, which suggests good correction of the underlying disorder. However, comparison to other studies is difficult, as these measurements rarely are provided.
Nine percent of our patients underwent THA during followup. This percentage seems in accordance with other studies with similar followups and patient ages. In a recent study of 112 patients with an average age of 40.6 years and a mean followup of 2.3 years, 10 patients (9%) underwent THAs during followup . Proper indication for FAI correction is mandatory to achieve good results in terms of pain relief, increase of ROM, and prevention of osteoarthritis. Additional studies are needed to better characterize the group of patients most benefiting from this procedure and to determine long-term outcome of arthroscopically treated FAI. It cannot fully be excluded that a part of the pain reduction in short- and midterm followups is related to labral débridement rather than removal of the impinging bony formation.
We presented a new technique of extracapsular preparation and capsular penetrance under direct visual control for treatment of FAI. We found postoperative improvement in all outcome measures at an average followup of 2.3 years. The long-term development after correction for FAI is required to see if the symptomatic relief persists.
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