John Frino and Young-Jo Kim
DEFINITION
Surgical dislocation of the hip can be done safely to treat a number of conditions, including femoroacetabular impingement (FAI), labral tears, chondral injuries, reduction of femoral neck fractures, reduction of acute severe slipped capital femoral epiphysis (SCFE), or any condition that requires wide complete access to the hip joint.9
There is little morbidity associated with this procedure, and avascular necrosis of the femoral head is a rare complication.2
This technique allows functional assessment of motion intraoperatively.
ANATOMY
The blood supply to the femoral head is mainly from the medial femoral circumflex artery (MFCA) (FIG 1A).10
The intact external rotator muscles, most notably the obturator externus muscle, protect the MFCA during the dislocation (FIG 1B).4
PATHOGENESIS
In FAI, anatomic deformity leads to abnormal contact between the proximal femur and the acetabular rim at the terminal extent of motion.
In cam impingement, an abnormal bump on the femoral neck passes into the hip beneath the labrum and mechanically damages the labrum and cartilage of the acetabulum.
Pincer impingement occurs with overcoverage of the acetabular rim impinging on the anterior femoral neck or head–neck junction with terminal flexion.
Both cam and pincer impingement can, and frequently do, coexist.
The early chondral and labral lesions that occur in physically active adolescents and young adults can progress and result in degenerative joint disease of the hip.
Causes of FAI can be idiopathic, secondary to a SCFE, anterior overcoverage of the hip with a retroverted acetabulum, residual deformity from Perthes disease, or posttraumatic changes.
NATURAL HISTORY
A pistol-grip deformity of the femoral head has been associated with early arthrosis of the hip.6
End-stage osteoarthrosis of the hip, once thought to be mainly idiopathic, is now believed to be a result of mild deformities similar to those caused by childhood diseases of the hip such as developmental hip dysplasia, SCFE, and LeggCalvé-Perthes.1
PATIENT HISTORY AND PHYSICAL FINDINGS
FAI usually presents in active adolescents or young adults with slow-onset groin pain, which may be exacerbated by athletic activities.
FIG 1 • A. Vascular anatomy of the femoral head. Note the proximity of the terminal branches of the medial femoral circumflex artery (MFCA) to the insertion of the piriformis tendon. B. Intraoperative photograph showing the path of the MFCA over and behind the intact short external rotators, including the quadratus femoris (Q) and the obturator externus (OE).
Many patients have difficulty sitting for long periods and adjust their seating posture to decrease lumbar lordosis to allow less flexion at the hips. Frequently they complain of difficulty getting into or out of a car.
There can be a family history of hip pain, early arthrosis, or hip arthroplasty.
Patients may walk with an antalgic gait, favoring the side of impingement. A foot-progression angle externally rotated may indicate a chronic SCFE or femoral retroversion.
The impingement test, if positive, shows reproducible groin pain with internal rotation, which is relieved with external rotation.
The physical examination should include both flexion and internal rotation range-of-motion tests.
Patients with impingement will have less than 90 degrees of true hip flexion.
Patients with impingement will have less internal rotation in flexion than extension, and may have a compensatory external rotation of the hip as it is flexed.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs should include an anteroposterior (AP) view of the pelvis and a true lateral view of the hip held in 15 to 20 degrees of internal rotation (FIG 2A,B).
Computed tomography scans with twoand threedimensional reconstructions are helpful for preoperative planning and detecting subtle femoral head–neck junction prominence (FIG 2C,D).
Magnetic resonance imaging can further delineate the labral and cartilage pathology (FIG 2E). If the study is performed with gadolinium and high-resolution sagittal oblique or radial sequences, labral pathology can be detected.
FIG 2 • AP pelvis (A) and true lateral (B) radiographs, which show the lack of femoral head–neck offset anteriorly (arrow in B) that is causing cam impingement. Three-dimensional reconstructions of the same pelvis from an AP (C) and a slightly left-rotated (D) perspective. The large “bumps” (arrows) obscuring the anterior femoral head–neck junction account for the lack of offset appreciated in B. E. T1-weighted sagittal MRI showing a large anterior osteophyte (arrow).
DIFFERENTIAL DIAGNOSIS
FAI
Labral tear
Hip dysplasia
SCFE
Acetabular retroversion
NONOPERATIVE MANAGEMENT
Nonoperative management includes cessation of aggravating activities, and symptomatic treatment using nonsteroidal anti-inflammatories.
Physical therapy to strengthen the hip musculature does not address the mechanical impingement of FAI.
SURGICAL MANAGEMENT
Hip pathology may be addressed through hip arthroscopy. However, it may be difficult to dynamically assess hip mechanics before and after débridement.
Femoral head–neck osteoplasty may be performed through an anterior approach to the hip without a surgical dislocation. However, the articular cartilage of the acetabulum and most of the femoral head cannot be evaluated with this limited approach.
Preoperative Planning
All imaging studies are reviewed.
The lack of femoral head–neck offset is best appreciated on the true lateral view of the hip (see FIG 2A,B), or on the axial cuts or 3D reconstruction of a CT scan.
A CT scan that includes cuts through the distal femoral condyles may be used to accurately measure the amount of femoral version.7
After general anesthesia is administered, the patient's hips are examined. The amount of true hip flexion and internal and external rotation with the hip extended and hip flexed are noted and compared to the preoperative assessment.
Positioning
The patient is placed in the full lateral position, secured on a pegboard. A flat-top cushion (with a half-moon–shaped cutout for the down leg) placed beneath the operative side helps to stabilize the leg during the approach (FIG 3A–C).
A hip drape with a sterile side bag is used, which will capture the leg during the dislocation maneuver (FIG 3D).
Approach
The approach consists of an anterior dislocation through a Kocher-Langenbeck or a Gibson approach with a trochanteric flip osteotomy (FIG 4A,B).
A Kocher-Langenbeck incision is followed by splitting the gluteus maximus muscle.
The abductors and gluteus maximus muscles can be spared by performing a Gibson approach, which proceeds between the gluteus medius and maximus (FIG 4C,D).5
The Gibson approach may result in less hip extensor dysfunction but may make anterior exposure more difficult.
A Z-shaped capsulotomy is made to allow entry to the hip joint while protecting the deep branch of the MFCA (FIG 4E).2
FIG 3 • A–C. The patient is positioned full lateral on a pegboard. Before patient preparation, the surgeon should ensure that the leg can be flexed and adducted fully and is not blocked by the anterior inferior peg. D. Position of the leg in the sterile leg holder after dislocation. The hip is flexed, adducted, and externally rotated.
FIG 4 • A,B. The trochanteric osteotomy with the attached vastus lateralis and gluteus medius. The tendon of the piriformis (arrow) remains attached to the stable trochanteric base. C,D. The Kocher-Langenback approach splits the gluteus maximus while the Gibson approach spares the gluteus maximus by using the plane between it and the gluteus medius. E. Path of the Z-shaped capsulotomy (solid line). The limb along the posterior aspect of the acetabulum protects the entry of the terminal branches of the medial femoral circumflex artery (white dashed line) and allows access to the hip joint and femoral head (black dashed line).
TECHNIQUES
SURGICAL HIP DISLOCATION BY A TRANSTROCHANTERIC APPROACH
Approach to Hip Capsule
A longitudinal lateral incision is made, centered over the junction between the anterior and middle thirds of the greater trochanter (TECH FIG 1A).
The fascia lata is split distally in line with the incision. The proximal dissection progresses through the interval between the anterior edge of the gluteus maximus and the tensor (TECH FIG 1B).
The proximal 4 to 5 cm of fascia of the vastus lateralis is incised and the vastus muscle fibers are reflected anteriorly.
The gluteus maximus, along with the fascia of the gluteus medius, which is left on the undersurface of the gluteus maximus for protection, is reflected posteriorly to expose the gluteus medius and insertion.
A 1to 1.5-cm-thick trochanteric osteotomy is made with an oscillating saw, leaving the piriformis tendon and short external rotators intact on the remaining base of the greater trochanter (TECH FIG 1C).
TECH FIG 1 • A. The proposed incision after the patient is prepared and draped. B. The Gibson approach is between the gluteus maximus and medius. Note the trochanteric branches of the medial femoral circumflex artery on the greater trochanter (black arrow). C. The trochanteric osteotomy is made with an oscillating saw. D. The fascia over the piriformis tendon (bottom arrow) is divided to develop the interval between it and the capsular minimus (top arrow). E. A 1to 1.5-cm trochanteric wafer is lifted anteriorly with the gluteus medius and vastus lateralis left attached. F. The anterior capsule is completely exposed before the arthrotomy is made.
The fascia overlying the piriformis tendon is incised to identify the tendon and the interval between the piriformis and capsular minimus muscles (TECH FIG 1D).
The trochanteric wafer is next reflected and flipped anteriorly with its attached sleeve of vastus lateralis and the gluteus medius (TECH FIG 1E).
The capsular minimus is elevated in an anterior direction off the hip capsule by carefully dissecting in the interval between the posterior edge of the capsular minimus and the piriformis tendon (TECH FIG 1F).
An assistant may use a right-angled retractor to assist with the exposure of the capsule.
Progressive hip flexion, external rotation, and adduction further aid the exposure.
The hip capsule is exposed up to the rim of the acetabulum.
Hip Arthrotomy and Dislocation
A Z-shaped capsulotomy is then performed, with the longitudinal arm of the Z in line with the anterior neck of the femur.
The distal arm of the capsulotomy extends anteriorly well proximal to the lesser trochanter.
The proximal arm is extended posteriorly along the acetabular rim, just distal to the labrum and well proximal to the retinacular branches of the MFCA entering the capsule posteriorly to supply the femoral head (TECH FIG 2).
TECH FIG 2 • The longitudinal limb of the capsulotomy is first made. This will allow visualization and prevent inadvertent cutting of the labrum while the posterior limb of the capsulotomy is made.
Depending on the pathology, the hip is brought through a range of motion to determine areas of impingement in a dynamic fashion.
The leg is then placed in the sterile side bag, flexed, externally rotated, and adducted while the hip is subluxated anteriorly through the arthrotomy.
A bone hook placed around the anterior femoral neck may be needed to subluxate the hip.
The ligamentum teres is then divided using curved meniscus scissors to allow full dislocation of the hip.
Dynamic Assessment and Osteoplasty
The entire femoral head and acetabulum can now be assessed for chondral flaps or labral tears, which can be repaired using suture anchors spaced about 7 to 10 mm apart or débrided.
TECH FIG 3 • A. The hips have been dislocated and the lack of femoral head–neck offset as well as the cartilage damage is readily apparent (black arrow). B. The femoral head–neck offset has been restored, eliminating the cam-type femoroacetabular impingement. C. The black arrow shows the restoration of the femoral head–neck offset (compare with FIG 2B).
The aspherical segment of the femoral head at the head–neck junction can be resected using a quarter-inch osteotome and rongeur (TECH FIG 3A,B).
After re-establishing sphericity of the femoral head, the hip is reduced and the results of the débridement are assessed by bringing the hip through a range of motion and confirming the relief of impingement and improvement in range of motion.
Intraoperative fluoroscopy showing a lateral of the hip in 90 degrees of flexion will determine if the femoral head–neck offset has been re-established (TECH FIG 3C).
TECH FIG 4 • The trochanteric osteotomy is fixed with two or three 3.5-mm screws.
Osteotomy Fixation
The trochanteric wafer is reduced and held in position with a towel clip.
Three 3.5-mm small fragment screws are placed to secure the trochanter. Fluoroscopy confirms reduction and fixation of the osteotomy (TECH FIG 4).
Alternatively, 4.0 cannulated screws may be used and guidewire position confirmed radiographically before screw insertion.
Closure
The Z-shaped capsulotomy is loosely repaired using absorbable 2-0 suture (TECH FIG 5).
The fascia of the vastus lateralis is closed with a running absorbable suture. The fascia lata and the fascia between the tensor and gluteus maximus are reapproximated.
Skin is closed in routine fashion.
TECH FIG 5 • The Z-shaped capsulotomy is loosely reapproximated with absorbable suture.
POSTOPERATIVE CARE
The hip is held flexed and in neutral rotation by placing two pillows under the leg and one under the greater trochanter.
The patient is placed in a continuous passive motion machine for 6 hours a day, set from 30 to 80 degrees of flexion.
Prophylaxis for deep venous thrombosis is individualized; however, all patients should be started on mechanical compression devices immediately.
After the epidural is removed, out-of-bed ambulation is permitted with one-sixth body weight partial weight bearing.
Range-of-motion exercises are started, but care is taken to protect the greater trochanter osteotomy by limiting adduction to midline, and avoiding resisted abduction exercises for 6 weeks.
Some patients may benefit from heterotopic ossification prophylaxis using indomethacin.
AP view of the pelvis or hip and true lateral hip radiographs are obtained 6 weeks postoperatively. Weight bearing is increased to full and hip-strengthening exercises are prescribed.
OUTCOMES
Ganz has performed over 1200 surgical hip dislocations with no cases of osteonecrosis reported.3
Generally, outcomes are excellent if the correct pathology is addressed in a joint without significant pre-existing arthrosis.
In a clinical assessment in adults by Murphy et al8 using the Merle d'Aubigne scale, hip scores improved significantly.
COMPLICATIONS
Avascular necrosis of the femoral head can occur if care is not taken to follow the technique and to preserve the retinacular vessels.
Femoral neck fracture if the femoral head–neck junction is aggressively débrided
Sciatic or femoral nerve neurapraxia
Greater trochanteric nonunion
Heterotopic ossification
Repeat labral tear
Continued arthrosis of the joint
REFERENCES
· Aronson J. Osteoarthritis of the young adult hip: etiology and treatment. AAOS Instruct Course Lect 1986;35:119–128.
· Ganz R, Gill T, Gautier E, et al. Surgical dislocation of the adult hip. J Bone Joint Surg Br 2001;83B:1119–1124.
· Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement. Clin Orthop Relat Res 2003;417:111–119.
· Gautier E, Ganz K, Krügel N, et al. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br 2000;82B:679–683.
· Gibson A. Posterior exposure of the hip joint. J Bone Joint Surg Br 1950;32B:183–186.
· Goodman D, Feighan J, Smith A, et al. Subclinical slipped capital femoral epiphysis: relationship to osteoarthrosis of the hip. J Bone Joint Surg Am 1997;79A:1489–1497.
· Murphy S, Simon S, Kijewski P, et al. Femoral anteversion. J Bone Joint Surg Am 1987;69A:1169–1176.
· Murphy S, Tannast M, Kim Y-J, et al. Debridement of the adult hip for femoroacetabular impingement: indications and preliminary clinical results. Clin Orthop Relat Res 2004;429:178–181.
· Spencer S, Millis M, Kim Y-J. Early results of treatment for hip impingement syndrome in slipped capital femoral epiphysis and pistol grip deformity of the femoral head–neck junction using the surgical dislocation technique. J Pediatr Orthop 2006;26:281–285.
· Trueta J, Harrison MHN. The normal vascular anatomy of the femoral head in adult man. J Bone Joint Surg Br 1953; 35B:442–461.