Regional pain sx
of not only the osseous structures of the hip, but more importantly, the soft tissue structures, including muscle, synovium, and acetabular labrum in multiple orthogonal planes. For evaluation of the capsulolabral structures in the hip, magnetic resonance (MR) arthrography increases the sensitivity and accuracy when compared with a conventional MRI . Byrd et al  recently demonstrated that MR arthrography was much more sensitive than conventional MRI for detecting various lesions, but leads to twice as many false-positive interpretations. In addition, this study showed that a response to an intra-articular injection of bupivacaine was a 90% reliable indicator of intraarticular abnormality. More recently, however, Mintz et al  demonstrated that a noncontrast MRI of the hip, using an optimized protocol, can noninvasively identify labral and chondral pathology with a high degree of accuracy.
The management of atraumatic instability is still quite unclear. With the advent of better diagnostic and therapeutic capabilities, it is becoming increasingly more recognized as a real entity. If a patient has a physical examination and history consistent with capsulolabral injury and instability, and appropriate imaging studies corroborate the clinical suspicion, then a trial of physical therapy and anti-inflammtories may be appropriately administered in an attempt to break the cycle of painful capsulolabral pathology. If this fails and the patient has pain relief after an intraarticular anesthetic injection, then hip arthroscopy may be appropriate.
Recently, success has been reported with anatomic restoration of the labrum and a reduction in capsular laxity . To reduce the volume of the capsule, thermal capsulorrhaphy and/or capsular plication may be performed (Fig. 9). Although controversial, the use of thermal energy has been used as a means of shrinking redundant or lax connective tissues using the mechanism of collagen denaturation [39-41]. Arthroscopic thermal modification of collagen in the hip capsular tissue combined with labral debridement appears to be an effective treatment option for patients with chronic hip instability. During this procedure, the capsule is probed and if excessive laxity is present, a focal thermal cap-sulorrhaphy is performed with a flexible probe at a temperature of 67°C and 40 watts. Phillipon  uses three passes performed in a cornfield pattern. No charring should be seen, and capsular contraction should be visualized. If capsular redundancy is still present after this procedure, plication may also be performed by passing and tying a nonabsorbable No. 2 braided suture through the capsule (Fig. 10). One limb of the suture is passed through the medial limb of the Y-ligament (iliofemoral ligament) and the other limb is passed through
Fig. 9. Arthroscopic image demonstrating thermal capsulloraphy.
the lateral limb. Additional sutures can be passed through the posterior capsule. If further tension is required, sutures can be passed through the more superior capsule under direct visualization within the peripheral compartment. These steps are repeated until excellent capsule tension is observed and there is stability to the capsule upon rotational testing.
Philippon  reported on 10 patients who had intractable hip pain with subtle signs of instability on examination combined with visualization of redundant capsular tissue during arthroscopy and underwent labral tear debridement with thermal capsulorrhaphy. The patients were allowed to weight bear as tolerated, and had rotation and extension precautions for 18 days. Preliminary results showed excellent outcomes with the first eight patients resuming their preinjury athletic activities with minimal or no pain.
On the extreme end of the atraumatic instability spectrum are patients with generalized ligamentous laxity or collagen disorders. The clinician should be aware of the subtle variants of generalized joint laxity (hyperextension of the elbows, hypermobility of the shoulders, and increased finger and wrist laxity) . Patients may also have an underlying connective tissue disorder such as Ehlers-Danlos syndrome or Marfan syndrome, and may be able to voluntarily or habitually dislocate their hips . The diagnosis is usually quite clear based upon the generalized findings as well as genetic testing in these patients.
Another category of atraumatic instability exists and consists of patients with anatomic deficiencies. When deviation occurs from "normal" bony anatomy, the hip must rely more on the soft tissue structures including the capsule and labrum for stability. Tonnis et al  evaluated the radiographs and CT scans of 356 hips in 181 patients and calculated the McKibbin instability index. They demonstrated that patients with a normal McKibbin instability index had the lowest rates of pain and osteoarthritis and had balanced ranges of rotation of the hip. As the McKibbin instability index approached the upper and lower extremes, patients had significantly more pain, osteoarthritis and altered degrees of hip rotation. They concluded that a McKibbin instability index of less than
20 is a major cause of osteoarthritis, pain and altered rotation of the hip. Due to a small sample size, patients with an increased McKibbin instability index had a tendency toward increased pain and osteoarthritis but definite conclusions were not possible [2,8].
If a patient has significant dysplasia, the role of hip arthroscopy is less well defined because addressing soft tissue pathology without addressing the underlying bony deformity may increase the failure rate of the surgical procedure. Nonetheless, several reports in the literature have reported good and excellent results in the management of labral pathology in patients with dysplasia [43,44]. These reports have discussed the role of labral debridement in patients with dysplastic hips and new mechanical symptoms associated with labral injury. In our experience, there is a significant role for labral repair in these patients, as preservation of the soft tissue anatomy will likely provide improved outcome in patients with overall bony deficiency. In cases of severe dysplasia the role of reorientation osteotomy should be examined [3,45].
It is important to differentiate whether the bony deformities are primary or secondary in nature. Bellabarba et al  described a cohort of patients that had longstanding painful snapping in the groin with no history of trauma. Using manual longitudinal traction under fluoroscopy, these patients were diagnosed with idiopathic hip instability and had evidence of mild acetabular dysplasia on plain radiographs. They postulated that the main pathologic process in these patients was capsular laxity, which resulted in clinically insignificant, yet radio-grapically detectable acetabular dysplasia. One of these patients was treated with a posterior imbrication capsulorrhaphy and her symptoms of pain, coxa saltans, and gait disturbances disappeared. Thus, in some patients the bony deformity may be secondary to soft tissue abnormalities.
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