Introduction

The hip is an inherently stable articulation between the femoral head and the acetabulum. Unlike the shoulder, the primary component of hip stability is determined by its constrained osseous anatomy. Although traumatic hip subluxations and dislocation are well documented, recently there has been heightened interest in atraumatic instability as a source of recalcitrant hip pain and symptoms. In these cases, redundant or incompetent capsular–labral structures lead to microinstability. There is a dynamic and transient incongruency or subluxation within the femoroacetabular articulation that results in abnormal force distributions across the hip joint and ultimately in worsening capsular redundancy and injury, chondrolabral injuries, and femoral neck impingement at high flexion angles (i.e., secondary impingement). This ignites clinical symptoms and starts a cascade of pathologic events that result in hip pain, stiffness, flexion contractures, labral pathology, and degeneration of the hip. The causes of hip instability and capsular laxity are multifactorial and include such things as intrinsic ligamentous laxity, connective tissue diseases, overuse or repetitive activities, iatrogenic injuries, subtle hip subluxation injuries, and prior dislocations.

The mainstay of treatment for capsular laxity and atraumatic instability has been conservative. There have been a few reports of open capsular plication as a method of treatment, but these have mostly been for posttraumatic instability. Recently, improved understanding and imaging of the prearthritic hip has led to the development of arthroscopic treatment approaches. Early experience was primarily focused on arthroscopic thermal capsular shrinkage and capsulorrhaphy, which produced promising early results. However, because thermal capsulorrhaphy has recently fallen out of favor for addressing shoulder instability because it can result in collagen disruption, chondrolysis, and high long-term failure rates, there has been gradual movement toward arthroscopic hip capsular plication. This burgeoning technique provides the advantages of a reproducible and durable capsulorrhaphy with the desired amount of plication controlled by the surgeon without the potentially adverse affects of thermal shrinkage. We present here a review of atraumatic hip instability and capsular laxity, and we will discuss their relevant anatomy, evaluation, imaging studies, and management principles as well as arthroscopic techniques of capsular plications in both the central and peripheral compartments.

Basic science

The hip is a constrained diarthrodial joint. The femoral head is an approximation of a sphere, and, under normal osseous parameters, the acetabulum covers approximately 170 degrees of the femoral head. The labrum is a fibrocartilage structure that further deepens the acetabulum. It functions to enhance stability by establishing a negative intra-articular pressure within the hip joint, preserving joint congruity, and limiting the fluid expression that acts as an important sealing function. The labrum also plays a role in helping to contain the femoral head in extremes of range of motion, especially in flexion. Its role in providing rotational stability is still unknown.

The surrounding capsular envelope consists of three ligaments: the iliofemoral ligament (i.e., the Y ligament of Bigelow), the pubofemoral ligament, and the ischiofemoral ligament (Figure 15-1). The iliofemoral ligament has a medial and lateral limb proximally, and distally it forms a deep circular band that surrounds the femoral neck in a leash-like fashion; this area is called the zona orbicularis. This “Y ligament” is the strongest, and it prevents the anterior translation of the hip during extension and external rotation when its fibers tighten. In flexion, these fibers loosen, which leads to a “screw home” effect in full extension. The pubofemoral ligament is slightly inferior to the iliofemoral ligaments, and it also controls external rotation in extension. The ischiofemoral ligament is a posterior structure that controls internal rotation in flexion and extension. Other secondary hip stabilizers include the ligamentum teres and the psoas tendon, which may provide important stability in cases of dysplasia or static ligament deficiencies.

Figure 15–1 The three primary capsular ligaments around the hip. The anterior ligamentous constraints of the hip are seen in the anterior view and include the iliofemoral and pubofemoral ligaments. The ischiofemoral ligament is the primary posterior restraint.

With permission from AJSM, Vol. 31, No. 6.

The causes of chronic atraumatic hip instability and capsular laxity are multifactorial. Primary causes include milder forms of intrinsic ligamentous laxity as well as more extreme cases of connective tissue diseases such as Marfan syndrome or Ehlers-Danlos syndrome, with which patients may be able to voluntarily or habitually dislocate their hips. The more common (but less well-recognized) secondary causes are overuse and repetitive activities such as golf, dancing, gymnastics, and martial arts. In these cases, there is repetitive hip rotation with an axial load. Other secondary causes include iatrogenic injuries and subtle forms of trauma, including hip subluxations and even prior dislocations.

The last type of atraumatic hip instability involves osseous anatomic abnormalities on either the acetabular side or the femoral side. Inclination, version, and other osseous parameters of the weight-bearing surface affect the soft-tissue structures that surround the hip. For cases in which there is a deficiency of the bony acetabulum (dysplasia) or excessive femoral anteversion or valgus, there is more reliance on the surrounding soft-tissue structures. McKibbin has quantified this with an index of combined femoral and acetabular version that predicts increased stress to the anterior capsulolabral structures. He defined the McKibbin index as the sum of the angles of femoral and acetabular anteversion, with a total of more than 60 denoting severe instability.

Brief history and physical examination

The diagnosis of traumatic hip injuries has improved with increased attention and a heightened index of suspicion; however, the diagnosis of atraumatic hip instability remains difficult and confusing. Because the differential diagnosis of hip pain is quite broad, an accurate history is critical. Any overuse activities with repetitive stresses should heighten awareness, because these activities may injure the iliofemoral ligament or labrum and alter the balance of forces in the hip. In addition, a thorough family history and a review of systems should be performed to rule out connective tissue disorders.

During the physical examination, the patient’s spine should first be examined to rule out other causes of hip pain. This should be followed by an examination of the elbows, hands, and knees to look for signs of hypermobility. Attention should also be paid to the patient’s skin and eyes. Next, the range of motion of both hips should be assessed. These patients often have an increased range of motion as a result of capsular laxity, but any significant increase in internal rotation should heighten one’s suspicion of increased femoral anteversion or other osseous abnormalities. This is followed by a thorough neurovascular examination that includes the reflexes. Next, specific hip testing should be performed, including the Ober test, the bicycle test, the psoas test, and the impingement test. In many cases, this process alters dynamic stabilizers (e.g., the iliopsoas) and leads to psoas and flexion contractures, internal coxa saltans, low back pain, and sacroiliac joint pain. Finally, hip-specific testing for capsular laxity should be performed. Patients with this condition will usually experience anterior hip pain while in the supine position with passive hip extension and external rotation (Figure 15-2, A). Patients may also have increased external rotation in full extension and distraction on the affected side (see Figure 15-2, B). Philippon and colleagues classified capsular laxity on the basis of these physical examination findings from grade 1 (mild) to grade 4 (severe), with grade 4 representing collagen vascular diseases.

Figure 15–2 A, Apprehension test performed with the hip in extension, abduction, and external rotation, which can be positive in patients with both acetabular dysplasia and capsular laxity. B, Increased external rotation in extension of the affected limb in a patient with capsular laxity.

Imaging and diagnostic studies

The radiologic workup begins with plain radiographs, including an anteroposterior view of the pelvis, a weight-bearing anteroposterior view, and a cross-table lateral view of the affected hip. Additional studies that may be necessary include Judet oblique films to further assess the acetabulum. False-profile views are used to assess for dysplasia, and computed tomography scans with spot views of the distal femoral epicondyles can be used to assess for acetabular and femoral anteversion. Various radiographic indices have been described to assess osseous undercoverage; these include but are not limited to the Tönnis angle, the center-edge angle of Wiberg, the anterior center-edge angle of Lequesne and de Seze, the femoral head extrusion, and the subluxation index. Acetabular version can also be estimated on radiographs by assessing the relationship of the anterior and posterior walls. A crossover sign and a prominent ischial spine both represent a retroverted acetabulum. The degree of retroversion can be estimated by the location of the crossover of the anterior wall, with more inferior crossing suggesting increased retroversion.

Magnetic resonance imaging (MRI) is critical for the evaluation of atraumatic instability. In the acute setting of traumatic hip injuries, numerous studies have demonstrated that MRI may aid in the diagnosis of chondral injuries, loose bodies, labral tears, femoral head contusions, sciatic nerve injuries, and ligament disruptions. Likewise, in the setting of chronic atraumatic injuries, MRI is also very useful to find subtle derangements in capsulolabral structures (Figure 15-3) as well as osteonecrosis.

Figure 15–3 Sagittal fat suppressed magnetic resonance arthrogram of a patient with capsular laxity and a labral tear from probable neck impingement or secondary impingement from an extreme range of motion.

Indications

Capsular laxity and atraumatic instability are difficult entities to assess, define, and ultimately treat; their management is still being developed. With the advent of better diagnostic and therapeutic capabilities, it is becoming increasingly clear that these pathologies exist. If a patient has a physical examination and history that are consistent with capsulolabral injury and instability and if appropriate imaging studies corroborate the clinical suspicion, then a trial of physical therapy and anti-inflammatory medication may be appropriately administered in an attempt to break the cycle of painful capsulolabral pathology. If conservative management fails and the patient has significant pain relief after an intra-articular anesthetic injection, then hip arthroscopy can be considered; however, because of the dearth of literature and unclear outcomes of this therapy, the mainstay of treatment for capsular laxity should still be conservative.

The anatomic restoration of the labrum (i.e., labral repair) and a reduction in capsular laxity either by capsular plication or thermal capsulorrhaphy have been described, with favorable preliminary results. In most cases, we perform capsular plication, because it is a reliable and measured reduction in capsular volume that is similar to the treatment of the shoulder. On rare occasions, when there is minimal capsular redundancy, we perform a thermal capsulorrhaphy; however, in most cases, we use the thermal device primarily as an adjunct. For cases in which atraumatic instability is a result of poor osseous coverage (e.g., acetabular dysplasia, excessive femoral valgus, increased femoral anteversion), hip arthroscopy should be approached with extreme caution, and redirectional osteotomies should be considered.

Surgical technique

The arthroscopic technique begins with adequate and appropriate anesthesia. Most often a general anesthetic is used with muscle relaxation, but regional anesthesia is also a possibility. With the patient supine on the operating room table, an examination under anesthesia is performed. Internal and external rotation is noted in full extension and in flexion and then compared with the nonoperative side. A flexion, abduction, and external rotation (FABER) test is then performed, with the distance from the lateral side of the affected knee being to the top of the operative table. As with external rotation, the affected limb often exhibits an increased amount of external rotation. Next, the hip is distracted, and a subjective evaluation of the necessary force needed to distract the hip joint is performed. Finally, if there is any concern regarding frank anterior instability, the limb is placed in extension, abduction, and external rotation, and a fluoroscopic image is performed to document this.

At this point, both of the patient’s feet are well padded, and the patient’s extremities are well secured to the fracture table. A well-padded perineal post is placed in between the patient’s extremities. The nonoperative limb is placed in full extension and mild abduction and then in minimal traction. The operative limb is put through a traction maneuver, which consists of abduction around the perineal post, axial traction, and adduction. Appropriate traction is then confirmed fluoroscopically. In cases of capsular laxity, minimal traction is usually needed to adequately distract the joint (Figure 15-4). The limb is then placed in internal rotation, which decreases the amount of hip distraction, reduces femoral anteversion, and subluxes the femoral head anteriorly, which enables the easy instrumentation of the joint. At this point, traction time is noted and documented.

Figure 15–4 With minimal traction, patients with capsular laxity with or without labral tears require little force to have adequate distraction. A, Before traction. B, After minimal traction.

The operative side is then prepped and draped in a sterile fashion. After confirming that preoperative antibiotics have been administered, a standard anterolateral arthroscopic portal is established under fluoroscopic guidance, which is then followed by an anterior portal, which is established under direct visualization with a 70-degree scope. At this point, a thorough diagnostic arthroscopy is performed, with careful attention paid to the capsulolabral structures in the central compartment. Any obvious peripheral labral tears are addressed surgically to enhance stability.

We currently perform three different arthroscopic techniques for atraumatic hip instability: central plication, peripheral plication, and thermal capsulorrhaphy. In many cases, a combination of techniques is performed. As stated previously, in most cases, we perform thermal capsulorrhaphy as an adjunct; rarely do we still use it as a primary mode of treatment. The technique begins as described previously. The capsule is then probed, and, if excessive laxity is present, a focal thermal capsulorrhaphy is performed. A flexible probe (Smith & Nephew, Andover, MA) is used at a temperature of 67 °C and a power of 40 W. We use a technique that is similar to that described by Philippon and colleagues, who used a three-pass cornfield pattern. Care is taken to avoid any charring of tissue, but capsular contraction should be visualized (Figure 15-5). If capsular redundancy is still present after this procedure, a plication may also be performed, which is described later in this chapter.

Figure 15–5 Intraoperative photo of a thermal capsulorrhaphy being performed with a flexible probe with minimal charring.

For the central compartment technique, a minimal capsulotomy is performed anteriorly around the anterior portal in the medial limb of the iliofemoral ligament with either a beaver blade or an arthroscopic shaver to create some working room, to improve visualization, to create bleeding edges to help with healing. Then an 8.25 mm × 9 cm cannula (Arthrex, Naples, FL) is placed through the anterior working portal. A soft-tissue penetrator (Spectrum Suture Hook, Largo, FL) is then inserted through the anterior cannula. The penetrator pierces the medial portion of the iliofemoral ligament at the most medial extent of the intended plication. A No. 1 polydioxanone (PDS) suture (Ethicon, Somerville, NJ) is then shuttled into the joint as the penetrator is removed. Next, a soft-tissue penetrator/grasper (Bird Beak; Arthrex, Naples, FL) is inserted through the working portal and used to penetrate the lateral aspect of the iliofemoral ligament at the level of the desired plication. The PDS suture that was previously passed through the capsule and into the joint is grasped and removed from the joint through the cannula. The PDS suture is then used to shuttle a FiberWire suture (Arthrex, Naples, FL) through the capsule as the working suture. A suture grasper is run along the length of the suture to ensure that no tangles exist. The FiberWire suture is checked to verify that it slides. Under direct visualization, the amount of tension and the ultimate plication are observed. Multiple passes, each being a separate plication, can be performed if more reduction in volume or a greater plication is desired. If not, then a blind, extracapsular, locking, sliding knot is tied with a knot pusher and followed by three half-hitch knots to back up the locking sliding knot; the suture is then cut (Figure 15-6, A through E).

Figure 15–6 Arthroscopic technique for the central compartment plication of a right hip. A, The arthroscope is in the lateral portal, and the camera is directed anteriorly as a nerve hook shows some labral fraying as a result of hypermobility. B, A small capsular window is made to create edges for the capsule to heal, and a polydioxanone (PDS) suture is passed through the medial limb of the anterior capsule. C, After a tissue penetrator device grabs the PDS suture and pulls it out through the lateral limb, the PDS suture now incorporates both limbs of the plication. D, The limbs of the PDS are then shuttled for a FiberWire suture (Arthrex, Naples, FL). E, An extracapsular locking arthroscopic knot is tied to plicate the tissue.

For the peripheral compartment technique, traction is unnecessary, and the operative limb is placed in approximately 20 degrees to 30 degrees of flexion. The arthroscope is retracted from its intra-articular position into a position just under the capsule in the peripheral compartment, which can be performed from either the anterolateral portal or the anterior portal. A prior skin portal can be used (either anterolateral or anterior), or a new distal accessory portal can be established with a spinal needle under direct visualization. In unique situations, an osteoplasty is performed in addition to a capsular plication as a result of secondary impingement or neck impingement from an extreme range of motion. In these cases, a small capsulotomy may be established with an arthroscopic shaver in the anterior capsule to aid visualization.

An arthroscopic cannula (Arthrex, Naples, FL) is placed in the anterior working portal. In an identical manner to the intra-articular plication technique, a curved soft-tissue penetrator (Spectrum Suture Hook, Largo, FL) passes a No. 1 PDS suture (Ethicon, Somerville, NJ) after piercing the medial portion of the iliofemoral ligament at the most medial extent of the intended plication. This is most commonly performed from an “outside-in” vantage point, unlike the central technique, which is “inside out.” Next, a Bird Beak (Arthrex, Naples, FL) captures the most lateral extent of intended plication, and a FiberWire (Arthrex, Naples, FL) is shuttled into position. As before, this process may be repeated through the same working portal until the desired amount of plication is achieved. Multiple configurations of capsular sutures can also be used, including a linear series of plications or even a crossing configuration like a “multi-pleat” technique. The plication is completed by tying a locking, sliding knot and backing it with three half-hitch knots. After sufficient capsular tension is achieved, stability is tested with gentle rotational testing. A technique similar to that of capsular plication may be used for posterior plication that involves the use of the appropriate posterior portals, but the posterior neurovascular structures must be carefully considered (Figure 15-7, A through E).

Figure 15–7 Arthroscopic technique for the peripheral compartment plication of a left hip. A, The arthroscope is in the anterolateral portal, and the camera is directed proximally to visualize the two limbs of the anterior capsule that will be plicated. B and C, A tissue penetrator is used to shuttle a polydioxanone (PDS) suture into the capsule through the medial limb and then the lateral limb of the plication. D, The PDS suture then incorporates both limbs of the plication. E, The PDS is exchanged for a FiberWire suture (Arthrex, Naples, FL), and both limbs of the plication are brought together with an arthroscopic knot.

Postoperative rehabilitation

The focus of the early postoperative period is on a gradual return of pain-free hip motion while protecting the capsular plication. For anterior plications, no external rotation or extension beyond neutral or abduction beyond 20 degrees of the involved hip is allowed. For patients with posterior capsular plications, internal rotation, flexion of more than 60 degrees, and adduction of more than 10 degrees are not allowed during the first 3 weeks after surgery. Patients are restricted to 30% partial weight bearing with crutches for the first few weeks and then gradually advanced. If a femoral osteoplasty is performed, patients may be protected longer. Patients may ride a stationary bicycle with no resistance, perform gluteal and quadriceps sets, and participate in heel slides and calf pumps. For those who underwent a posterior capsular plication, flexion is limited to 60 degrees when using the stationary bicycle for the first 6 weeks after the procedure. Although we routinely use continuous passive motion devices, for these patients we usually do not.

For the first 3 to 6 weeks, light resistance may be added to the stationary bicycle. Straight-leg raises may begin, and crutches should be weaned slowly, with the goal of full weight bearing by 6 weeks. Pool exercises of walking, jogging, and swimming with a buoy may begin. From 6 weeks to 3 months postoperatively, increased resistance is added to the stationary bicycle, plyometrics is incorporated into the pool regimen, and seated rowing and elliptical machine use can begin. Hip flexor stretches should start along with toe raises with weights. After 3 months, slow jogging may begin on even ground, and closed-chain exercises should be initiated. After 5 months, patients may begin strengthening exercises and functional training. Full return to sport begins when normal strength is attained, when the patient can run at full speed without a limp, and when the patient regains the full range of motion.

Results

Overall, the literature is quite limited with regard to atraumatic instability and capsular laxity (Table 15-1). In terms of thermal capsulorrhaphy, the trend has been to move away from this modality because of the high rate of associated complications. Although the use of thermal energy as a means of shrinking redundant or lax connective tissues by collagen denaturation has been extensively studied in the shoulder, there are only a few available studies in the hip. Philippon reported about 10 patients who had intractable hip pain with subtle signs of instability on examination in combination with the visualization of redundant capsular tissue during arthroscopy and labral tears. These patients underwent labral tear debridement with thermal capsulorrhaphy. They were allowed to bear weight as tolerated, and they had rotation and extension precautions for 18 days. Preliminary results showed excellent outcomes with regard to the first 8 patients resuming their preinjury athletic activities with minimal or no pain.

The literature about capsular plications is even more sparse. Bellabarba and colleagues described a group of patients that had long-standing painful groin pain and snapping with no history of trauma. With the use of traction under fluoroscopy, these patients were diagnosed with idiopathic hip instability, but they also had mild evidence of acetabular dysplasia on radiographs. The authors postulated that the main pathologic process in these patients was capsular laxity rather than the dysplasia. One of these patients was treated with a posterior imbrication capsulorrhaphy, and her symptoms improved. However, it must be stressed that osseous deficiencies usually supersede soft-tissue abnormalities in the majority of cases.

In the literature, capsular laxity and instability secondary to post-traumatic injury are better defined. Open anatomic restoration of the capsulolabral structures has controlled symptoms and instability. These repairs have been performed for both anterior and posterior instability. For posterior instability, a soft-tissue Bankart-type repair has been performed. For anterior instability, an osseous repair of the anterior inferior iliac spine has been used as a means to repair the iliofemoral ligament.

Complications

There are three groups of complications related to these techniques. The first are the general complications that are associated with hip arthroscopy, which include but are not limited to infection, nerve injuries, and vascular injuries; these are relatively minor. The unique complications associated with capsular plications are recalcitrant pain, recurrent capsular laxity, and overt instability or dislocation. The last set of complications is related to thermal capsulorrhaphy and includes chondrolysis, capsular injury and degeneration, and higher failure rates.

Summary

Recently, a growing understanding of atraumatic instability and capsular laxity of the hip joint has evolved as an underappreciated cause of hip pain. The burgeoning field of hip arthroscopy and the application of advanced arthroscopic techniques have provided the ability to address hip instability in a minimally invasive fashion. Thermal capsular shrinkage is a described technique for the treatment of capsular laxity; however, as a result of the growing concern about its associated complications in shoulder surgery results, its use has generally fallen out of favor.

We present our techniques for arthroscopic capsular plication to address capsular laxity. Our techniques are similar and adapted from those used successfully to address glenohumeral instability. The advantages of these techniques are that they enable the surgeon to determine the amount of capsule to be plicated, they provide a durable construct that provides adequate stability until the capsule heals, and they avoid any of the potential complications associated with thermal procedures. The central compartment technique allows for capsular plication without violation of the peripheral compartment, whereas the peripheral compartment technique allows for plication in a traction-free environment while the iliofemoral ligament is not under tension. The disadvantages of arthroscopic capsular plication include a requirement of proficiency with advanced arthroscopic techniques, motion around the hip being protected until the capsule is fully healed, and the potential for recurrent capsular laxity and instability. Overall, this method of addressing capsular laxity is useful because it may be used for both traumatic and atraumatic conditions. It provides a relatively easy, predictable, and durable method for the plication of pathologic tissue.