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Arthroscopic anatomy of the hip
Arthroscopy: The Journal of Arthroscopic and Related Surgery 6(4):26&273 Published by Raven Press, Ltd. 0 WXl Arthroscopy Association of North America
Arthroscopic Anatomy of the Hip Marcel Dvorak, M.D., C. P. Duncan, M.D., and Brian Day, M.D.
Summary: The arthroscopic anatomy of the hip has been studied using a number of portals. Both distraction and positioning are necessary to allow insertion of instruments, and to allow exposure of the important anatomical structures. The internal anatomy of the hip joint is described in detail based on the arthroscopic view from the different portals. This study helps orient those interested in arthroscopy of the hip. Key Word: Hip, internal anatomy.
Arthroscopy, long recognized as a diagnostic and therapeutic technique in disorders of the knee, has also been found clinically useful in the shoulder, elbow, wrist, ankle, and temporomandibular joint. Arthroscopy of the hip joint, however, has not been properly assessed regarding technique, normal arthroscopic anatomy, or the indications for its clinical application. The first recorded attempts at direct visualization of the hip joint through an instrument were published by Burman in 1931 (1). Gross (2) published his experience with arthroscopy of congenitally dislocated hips. Short chapters have appeared in several texts (3,4). Reports of arthroscopy for the removal of cement fragments (5) and other debris (6) after total hip replacement have appeared in the literature. Holgersson (7) examined 15 hips and, although he voiced concern over its limitations, found the procedure useful for investigating patients considered for a synovectomy. Parisien (8) was able to visualize one-third of the femoral head and less than one-third of the acetabulum using an anterior approach. Eriksson (9) determined that 300 to 900 Newtons of distraction of the femur were necessary to allow adequate visualization of the articular surface of the acetabulum.
He found the technique useful for removal of loose bodies, for synovial biopsy, and for partial synovectomy. More recently, Dorfmann (10) and Glick (11) have presented their clinical experiences with hip arthroscopy. Glick felt that clinical indications for arthroscopy of the hip included unresolved pain, loose bodies, and pain secondary to avascular necrosis. Other indications might include synovitis, suspected labral tears, osteochondritis dissecans, chondrolysis, and septic arthritis. The purpose of this paper is to describe the normal arthroscopic anatomy of the hip joint and some standard approaches and their limitations. MATERIALS AND METHODS Fifteen hips were arthroscoped in eight cadavers. In five hips the arthroscopy was performed in intact specimens. In seven others, a limited exposure of the muscle planes was carried out to guide the insertion of the instruments. In three specimens dissection was carried down to the capsule of the joint prior to insertion of the arthroscope. Anatomical dissections were carried out in all cadavers to verify the arthroscopic anatomy. Standard 4.0 mm arthroscopes were used with 25 and 70” optics.
From the Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada. Address correspondence and reprint requests to Brian Day, M.D., at the University Hospital, UBC Site FF158, 2211 Wesbrook Mall, Vancouver, BC V6T lW5, Canada.
REVIEW OF GROSS ANATOMY The hip joint is a multiaxial ball and socket synovial joint between the femoral head, which forms 264
HIP ANATOMY
two-thirds of a sphere, and the cuplike acetabulum with its horseshoe-shaped articular surface. The head of the femur is covered with hyaline cartilage, except for the fovea, to which the ligament of the head is attached (Fig. 1). The acetabular labrum is attached to the rim of the acetabulum. Where the acetabular fossa opens inferiorly, the labrum is attached to the transverse acetabular ligament (Fig. 2). The proximal attachment of the articular capsule is just beyond the labrum into the bone of the acetabulum and the transverse acetabular ligament (Fig. 3). Distally, the attachment of the fibrous capsule is to the intertrochanteric line anteriorly. Posteriorly, the attachment is loose and is a finger breadth proximal to the intertrochanteric crest. Four main groups of fibers form the intrinsic ligaments of the capsule. Anteriorly the iliofemoral ligament or ligament of Bigelow is shaped like an inverted “Y.” It takes its origin from the anterior inferior iliac spine and anterior acetabular rim and inserts into the intertrochanteric line. It becomes tightly stretched across the anterior femoral neck when the hip joint is in full extension (Fig. 4). The pubofemoral ligament arises from the anteromedial acetabular rim and the iliopubic eminence. Its fibers extend laterally and merge with the medial fibers of the iliofemoral ligament. It is a broad weak ligament. The ischiofemoral ligament has a broad origin from the ischial portion of the acetabular rim. It inserts into the neck of the femur just medial to the base of the greater trochanter (Fig. 5). The fourth group of fibers, the zona orbicularis, is a circular ring that forms a deep collar around the neck of the femur (Fig. 6).
265
surface
FIG. 2. Anatomy of the acetabulum.
RESULTS Approaches The first approach evaluated was the anterolateral portal. The entry point is found at the cross section of a line drawn vertically from the anterior superior iliac spine and a line horizontal from the symphysis pubis (Fig. 7). The arthroscope is directed 45” medially and 45” cephalad. The lateral femoral cutaneous nerve of the thigh and the femoral artery are easily avoided. Two paratrochanteric approaches were used, one anterior and one posterior. The anterior paratrochanteric portal is found 3 cm anterior and 1 cm inferior to the tip of the greater trochanter. The posterior paratrochanteric portal is found similarly, although posterior to the tip of the trochanter (Fig. 8).
Attachment of capsul eater hanter
Intertrochanteric crest
FIG. 1. Anatomy of the proximal femur.
FIG. 3. Anterior and posterior extent of capsule of the hip joint.
Arthroscopy,
Vol. 6, No. 4, 1990
266
M. DVORAK
ET AL.
Ant. inf. iliac spine
Acetabular labru Zona orbicularis tr
Zona orbicularis
FIG. 6. Cross section through the hip joint and capsule revealing the collar-like zona orbicularis. FIG. 4. Anterior (ant) ligaments of the hip capsule-the iliofemoral or “Y” ligament of Bigelow and the pubofemoral ligament. Inf, inferior.
The anterior paratrochanteric portal allows perforation of the capsule closer to the intertrochanteric line than does the anterolateral approach. With the anterior trochanteric portal more of the arthroscope is within the joint and the surgeon has more maneuverability. This is also the easiest approach to reproducibly enter the hip without fluoroscopic guidance. Technique The hip joint was first inflated with 100 cc of saline through a spinal needle. Initially, the hip was positioned in 45” of flexion and 30” of internal rotation in order to provide as much redundant capsule
FIG. 5. The posterior chiofemoral ligament.
Arthroscopy,
ligament of the hip joint, i.e., the is-
Vol. 6, No. 4, 1990
anteriorly as possible. This facilitated the insertion of the arthroscope through either of the two anterior portals. Due to the wider field of view and greater maneuverability, the anterior paratrochanteric portal was often the initial portal attempted. If the hip is externally rotated in an attempt to relax the posterior capsule and allow easier insertion through the posterior paratrochanteric portal, the sciatic nerve is at risk as the surgeon attempts to penetrate the capsule with the sharp trochar. It is recommended that the hip be held in neutral rotation and great care be taken in using the posterior paratrochanteric portal.
FIG. 7. Entry point for the anterolateral portal. Arthroscope is inserted at the cross section of a horizontal line from the symphysis and a vertical line from the anterior superior iliac spine. Arthroscope is directed 45” medially and 45” cephalad. Lat, lateral; n, nerve; ant, anterior; sup, superior.
267
HIP ANATOMY
Arthroscopic Anatomy of the Hip Joint The femoral
aratrochanteric
head and acetabular
labrum
Identifying the joint line is the key to orientating oneself to the arthroscopic anatomy of the hip. This is best done initially through the anterior paratrochanteric portal using the 25” arthroscope. Gentle rotation of the hip will readily identify the joint line (Fig. 9). It is easy to appreciate the raised rim of the acetabular labrum. Expert and accurate positioning of the hip and the arthroscope is necessary to visualize the maximum possible surface area of the femoral articular cartilage without distracting the joint. With the combination of three portals, up to 80% of the circumference of the femoral head can be seen as well as almost all of the acetabular labrum. The neck of the femur
FIG. 8. The anterior (ant) and posterior (post) paratrochanteric portals are found 3 cm anterior and posterior to the greater trochanter. n, nerve.
Care must be taken not to disrupt the retinacular vessels along the neck of the femur with excessively forceful insertion techniques. Fluoroscopy was not used in this cadaver study but would certainly help insertion in a clinical setting.
FIG. 9. Acetabular head.
The femoral neck is best seen with the 70” arthroscope from either of the two paratrochanteric portals (Fig. 10). The deep intraarticular longitudinal fibers of synovium seen reflecting upward along the neck of the femur are known as the retinacula of the neck of the femur. They often contain blood vessels originating from the medial femoral circumflex artery and supplying the head. Looking anteriorly from the posterior paratrochanteric portal with the 70” arthroscope, the ligament of Weitbrecht (Fig. 11) is occasionally seen on the posterosuperior neck of the femur.
labrum and femoral
Arthroscopy,
Vol. 6, No. 4, 1990
268
M. DVORAK
ET AL.
FIG. 10. Neck of the femur and superior retinacular fold. Sup, superior.
The intrinsic ligaments of the capsule The zona orbicularis is the most obvious of the four groups of intrinsic capsular ligaments (Fig. 12). These fibers tighten, forming a collar around the neck of the femur when the hip is in internal rotation. So tightly are these fibers applied to the neck of the femur that they may be easily mistaken for the acetabular labrum (Fig. 13). External rotation of the hip allows the zona orbicularis to relax and fall
FIG. 11. Ligament of Weitbrecht on the posterosuperior neck of the femur.
Arthroscopy,
Vol. 6, No. 4, 1590
away from the neck of the femur. Fronds of synovium protrude from under the orbicular fibers as they relax, clearly differentiating them from the acetabular labrum (Fig. 14). It is difficult to see any of the fibers of the iliofemoral ligament. Occasionally, with the 70” arthroscope in the posterior paratrochanteric portal, the surgeon can look anteriorly over the superior neck of the femur. As the hip is extended, the iliofemoral
269
HIP ANATOMY
FIG. 12. Zona orbicularis encircling the #mlneck.
ligament stands out as the anterior capsule becomes tightly applied to the anterior neck of the femur (Fig. 15). On viewing the posterior capsule, a thickening can be seen originating from the acetabulum and sloping laterally (Fig. 16). This is the inferior edge of the ischiofemoral ligament.
The acetabular articular surface acetabular fossa
and
Significant traction forces were necessary to distract the hip joint to allow visualization of the acetabular articular surface. This is best performed with the 30” arthroscope inserted through the anterior paratrochanteric portal. It is very common to injure the acetabular labrum and articular surfaces during insertion attempts. With care, the arthroscope can be inserted between the distracted articular surfaces to examine them (Fig. 17). Occasionally, the acetabular fossa and the ligament of the head can be seen (Fig. 18). More often, however, the fat pad from the acetabular fossa expands into the joint with traction and obscures the view. The fovea on the head could not be seen. DISCUSSION
FIG. 13. Zona orbicularis, seen to the right, tightly applied to femoral neck and mimicking the acetabular labrum.
Arthroscopy of the hip may not at first seem as rewarding as arthroscopy of other joints. There are, however, structures of clinical significance that can be better assessed with arthroscopy than with any technique apart from arthrotomy. Using the three portals described, 80% of the circumference of the femoral head can be seen and most of the acetabular labrum is visible. The anterior paratrochanteric portal is the most immediately rewarding due to the larger portion of the arthroscope that is intracapsular, thus leading to greater Arthroscopy,
Vol. 6, No. 4, 1990
270
M. DVORAK
ET AL.
FIG. 14. Orbicular fibers encircling the inferior neck of the femur. Inf, inferior
maneuverability and a wider field of view. Insertion of the arthroscope and any instruments requires a capable assistant to accurately position the leg. Alternatively, limb holding devices, including prerobotic limb manipulators, are available (Fig. 19). Constantly changing positions are necessary to accentuate the zona orbicularis and other capsular structures, as well as to expose the appropriate areas of the femoral head and neck. It is only during the final part of the arthroscopic
examination that traction is necessary in order to view the acetabular articular surface and contents of the acetabular fossa. Abduction and internal rotation of the hip during insertion attempts utilizing the posterior paratrochanteric portal put the sciatic nerve at significant risk of damage from the sharp trochar. It would seem that ensuring free mobility is important to allow easy, accurate, and atraumatic insertion of the arthroscope and instruments. The surgeon is also able to orient himself to the often
FIG. 15. Iliofemoral ligament, or “Y” ligament of Bigelow, tightly applied to rL_ __r_2__ lan”l-d C_-___l necn. ___a. l-Up TT1_1s 1_ ,___: mt: anlen”I ,“SP tioned in extension and external I?Ootation.
Arthroscopy,
Vol. 6. No. 4, 1990
HIP ANATOMY
271
FIG . 16. Inferior edge of the ischiofemoral ligament in the posterior capsule.
confusing anatomy by being able to freely move the leg. The posterior paratrochanteric portal provides the best view of the posterior acetabular labrum. With the 70” scope, the posterosuperior femoral neck as well as the anterior hip capsule can be seen easily. Due to the narrow field of view within the hip joint capsule, and because of the relative depth of
soft tissues, triangulation is difficult. There have, however, been reports of operative arthroscopy for the removal of loose bodies (9,l l), retained cement fragments and other debris (5,6), synovial biopsy, and even partial synovectomy (9). A recent study has also shown the value of operative arthroscopy in the management of chondromatosis (12). It is beyond the scope of this study to suggest indications for hip arthroscopy in the clinical set-
FIG. 17. Acetabll&X ticuliar surface.
Arthroscopy,
Vol. 6, No. 4, 1990
M. DVORAK
272
ET AL.
FIG. 18. Ligament of the head of the fe-
mur.
ting. It is possible, however, to conjecture that hip arthr oscopy will be found useful in the treatment of tears of the acetabular labrum, synovitis, chondrolysis, loose bodies, osteochondritis dissecans, septic
arthritis, and arthritic pain with minimal ratdiographic findings. Of particular interest are the plications of arthroscopy in the pediatric age gr ‘OUP CAW.
FIG. 19. Arthrobot lower limb positioner.
Arthroscopy,
Vol. 6, NO. 4, 1990
I
HIP ANATOMY
REFERENCES 1. Burman MS. Arthroscopy or the direct visualization of joints. J Bone Joint Surg 1931;4:669-95. 2. Gross RH. Arthroscopy in hip disorders in children. Orthop Rev 1977;6:43-9. 3. Johnson L. Diagnostic and surgical arthroscopy: the knee and other joints. St. Louis: C.V. Mosby, 1981. 4. Shahriarree M, O’Connor RD. Arthroscopic surgery. Philadelphia: Lippincott, 1984. 5. Vakilif S, Warren RF. Entrapped foreign body within the acetabular cup in THR. Clinica/ Orthop 1980;15O:lS9-62. 6. Nordt W, Giangarra CE, Levy I, Habermann ET. Arthroscopic removal of entrapped debris following dislocation of a total hip arthroplasty. Arthroscopy 1987;3:19&8.
I.
273
Holgersson S, Brattstrom H, Mogensen B, Lindgren L. Arthroscopy of the hip in juvenile chronic arthritis. J Pediatr Orthop 1981;1:273-8.
8. Parisien JS. Arthroscopy Hospital Joint Diseases
of the hip. Present status bulletin 1985;45:127-32.
9. Eriksson E, Arvidsson I, Arvidsson H. Diagnostic and operative arthroscopy of the hip. J Orthop 1986;9:169-76. 10. Dorfmann H, Boyer T, Henry P, Debie B. A simple approach to hip arthroscopy. Arthroscopy 1988;4: 141-2. 11. Glick JM, Sampson TG, Gordon RB, Behr JT, Schmidt E. Hip arthroscopy by the lateral approach. Arthroscopy 1987;3:4-12.
12. Witwity T, Uhlmann RD, Fischer J. Arthroscopic management of chondromatosis of the hip joint. Arthroscopy 1988;4:5%.
Arthroscopy, Vol. 6, No. 4, 1990
Arthroscopic Anatomy of the Hip Marcel Dvorak, M.D., C. P. Duncan, M.D., and Brian Day, M.D.
Summary: The arthroscopic anatomy of the hip has been studied using a number of portals. Both distraction and positioning are necessary to allow insertion of instruments, and to allow exposure of the important anatomical structures. The internal anatomy of the hip joint is described in detail based on the arthroscopic view from the different portals. This study helps orient those interested in arthroscopy of the hip. Key Word: Hip, internal anatomy.
Arthroscopy, long recognized as a diagnostic and therapeutic technique in disorders of the knee, has also been found clinically useful in the shoulder, elbow, wrist, ankle, and temporomandibular joint. Arthroscopy of the hip joint, however, has not been properly assessed regarding technique, normal arthroscopic anatomy, or the indications for its clinical application. The first recorded attempts at direct visualization of the hip joint through an instrument were published by Burman in 1931 (1). Gross (2) published his experience with arthroscopy of congenitally dislocated hips. Short chapters have appeared in several texts (3,4). Reports of arthroscopy for the removal of cement fragments (5) and other debris (6) after total hip replacement have appeared in the literature. Holgersson (7) examined 15 hips and, although he voiced concern over its limitations, found the procedure useful for investigating patients considered for a synovectomy. Parisien (8) was able to visualize one-third of the femoral head and less than one-third of the acetabulum using an anterior approach. Eriksson (9) determined that 300 to 900 Newtons of distraction of the femur were necessary to allow adequate visualization of the articular surface of the acetabulum.
He found the technique useful for removal of loose bodies, for synovial biopsy, and for partial synovectomy. More recently, Dorfmann (10) and Glick (11) have presented their clinical experiences with hip arthroscopy. Glick felt that clinical indications for arthroscopy of the hip included unresolved pain, loose bodies, and pain secondary to avascular necrosis. Other indications might include synovitis, suspected labral tears, osteochondritis dissecans, chondrolysis, and septic arthritis. The purpose of this paper is to describe the normal arthroscopic anatomy of the hip joint and some standard approaches and their limitations. MATERIALS AND METHODS Fifteen hips were arthroscoped in eight cadavers. In five hips the arthroscopy was performed in intact specimens. In seven others, a limited exposure of the muscle planes was carried out to guide the insertion of the instruments. In three specimens dissection was carried down to the capsule of the joint prior to insertion of the arthroscope. Anatomical dissections were carried out in all cadavers to verify the arthroscopic anatomy. Standard 4.0 mm arthroscopes were used with 25 and 70” optics.
From the Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada. Address correspondence and reprint requests to Brian Day, M.D., at the University Hospital, UBC Site FF158, 2211 Wesbrook Mall, Vancouver, BC V6T lW5, Canada.
REVIEW OF GROSS ANATOMY The hip joint is a multiaxial ball and socket synovial joint between the femoral head, which forms 264
HIP ANATOMY
two-thirds of a sphere, and the cuplike acetabulum with its horseshoe-shaped articular surface. The head of the femur is covered with hyaline cartilage, except for the fovea, to which the ligament of the head is attached (Fig. 1). The acetabular labrum is attached to the rim of the acetabulum. Where the acetabular fossa opens inferiorly, the labrum is attached to the transverse acetabular ligament (Fig. 2). The proximal attachment of the articular capsule is just beyond the labrum into the bone of the acetabulum and the transverse acetabular ligament (Fig. 3). Distally, the attachment of the fibrous capsule is to the intertrochanteric line anteriorly. Posteriorly, the attachment is loose and is a finger breadth proximal to the intertrochanteric crest. Four main groups of fibers form the intrinsic ligaments of the capsule. Anteriorly the iliofemoral ligament or ligament of Bigelow is shaped like an inverted “Y.” It takes its origin from the anterior inferior iliac spine and anterior acetabular rim and inserts into the intertrochanteric line. It becomes tightly stretched across the anterior femoral neck when the hip joint is in full extension (Fig. 4). The pubofemoral ligament arises from the anteromedial acetabular rim and the iliopubic eminence. Its fibers extend laterally and merge with the medial fibers of the iliofemoral ligament. It is a broad weak ligament. The ischiofemoral ligament has a broad origin from the ischial portion of the acetabular rim. It inserts into the neck of the femur just medial to the base of the greater trochanter (Fig. 5). The fourth group of fibers, the zona orbicularis, is a circular ring that forms a deep collar around the neck of the femur (Fig. 6).
265
surface
FIG. 2. Anatomy of the acetabulum.
RESULTS Approaches The first approach evaluated was the anterolateral portal. The entry point is found at the cross section of a line drawn vertically from the anterior superior iliac spine and a line horizontal from the symphysis pubis (Fig. 7). The arthroscope is directed 45” medially and 45” cephalad. The lateral femoral cutaneous nerve of the thigh and the femoral artery are easily avoided. Two paratrochanteric approaches were used, one anterior and one posterior. The anterior paratrochanteric portal is found 3 cm anterior and 1 cm inferior to the tip of the greater trochanter. The posterior paratrochanteric portal is found similarly, although posterior to the tip of the trochanter (Fig. 8).
Attachment of capsul eater hanter
Intertrochanteric crest
FIG. 1. Anatomy of the proximal femur.
FIG. 3. Anterior and posterior extent of capsule of the hip joint.
Arthroscopy,
Vol. 6, No. 4, 1990
266
M. DVORAK
ET AL.
Ant. inf. iliac spine
Acetabular labru Zona orbicularis tr
Zona orbicularis
FIG. 6. Cross section through the hip joint and capsule revealing the collar-like zona orbicularis. FIG. 4. Anterior (ant) ligaments of the hip capsule-the iliofemoral or “Y” ligament of Bigelow and the pubofemoral ligament. Inf, inferior.
The anterior paratrochanteric portal allows perforation of the capsule closer to the intertrochanteric line than does the anterolateral approach. With the anterior trochanteric portal more of the arthroscope is within the joint and the surgeon has more maneuverability. This is also the easiest approach to reproducibly enter the hip without fluoroscopic guidance. Technique The hip joint was first inflated with 100 cc of saline through a spinal needle. Initially, the hip was positioned in 45” of flexion and 30” of internal rotation in order to provide as much redundant capsule
FIG. 5. The posterior chiofemoral ligament.
Arthroscopy,
ligament of the hip joint, i.e., the is-
Vol. 6, No. 4, 1990
anteriorly as possible. This facilitated the insertion of the arthroscope through either of the two anterior portals. Due to the wider field of view and greater maneuverability, the anterior paratrochanteric portal was often the initial portal attempted. If the hip is externally rotated in an attempt to relax the posterior capsule and allow easier insertion through the posterior paratrochanteric portal, the sciatic nerve is at risk as the surgeon attempts to penetrate the capsule with the sharp trochar. It is recommended that the hip be held in neutral rotation and great care be taken in using the posterior paratrochanteric portal.
FIG. 7. Entry point for the anterolateral portal. Arthroscope is inserted at the cross section of a horizontal line from the symphysis and a vertical line from the anterior superior iliac spine. Arthroscope is directed 45” medially and 45” cephalad. Lat, lateral; n, nerve; ant, anterior; sup, superior.
267
HIP ANATOMY
Arthroscopic Anatomy of the Hip Joint The femoral
aratrochanteric
head and acetabular
labrum
Identifying the joint line is the key to orientating oneself to the arthroscopic anatomy of the hip. This is best done initially through the anterior paratrochanteric portal using the 25” arthroscope. Gentle rotation of the hip will readily identify the joint line (Fig. 9). It is easy to appreciate the raised rim of the acetabular labrum. Expert and accurate positioning of the hip and the arthroscope is necessary to visualize the maximum possible surface area of the femoral articular cartilage without distracting the joint. With the combination of three portals, up to 80% of the circumference of the femoral head can be seen as well as almost all of the acetabular labrum. The neck of the femur
FIG. 8. The anterior (ant) and posterior (post) paratrochanteric portals are found 3 cm anterior and posterior to the greater trochanter. n, nerve.
Care must be taken not to disrupt the retinacular vessels along the neck of the femur with excessively forceful insertion techniques. Fluoroscopy was not used in this cadaver study but would certainly help insertion in a clinical setting.
FIG. 9. Acetabular head.
The femoral neck is best seen with the 70” arthroscope from either of the two paratrochanteric portals (Fig. 10). The deep intraarticular longitudinal fibers of synovium seen reflecting upward along the neck of the femur are known as the retinacula of the neck of the femur. They often contain blood vessels originating from the medial femoral circumflex artery and supplying the head. Looking anteriorly from the posterior paratrochanteric portal with the 70” arthroscope, the ligament of Weitbrecht (Fig. 11) is occasionally seen on the posterosuperior neck of the femur.
labrum and femoral
Arthroscopy,
Vol. 6, No. 4, 1990
268
M. DVORAK
ET AL.
FIG. 10. Neck of the femur and superior retinacular fold. Sup, superior.
The intrinsic ligaments of the capsule The zona orbicularis is the most obvious of the four groups of intrinsic capsular ligaments (Fig. 12). These fibers tighten, forming a collar around the neck of the femur when the hip is in internal rotation. So tightly are these fibers applied to the neck of the femur that they may be easily mistaken for the acetabular labrum (Fig. 13). External rotation of the hip allows the zona orbicularis to relax and fall
FIG. 11. Ligament of Weitbrecht on the posterosuperior neck of the femur.
Arthroscopy,
Vol. 6, No. 4, 1590
away from the neck of the femur. Fronds of synovium protrude from under the orbicular fibers as they relax, clearly differentiating them from the acetabular labrum (Fig. 14). It is difficult to see any of the fibers of the iliofemoral ligament. Occasionally, with the 70” arthroscope in the posterior paratrochanteric portal, the surgeon can look anteriorly over the superior neck of the femur. As the hip is extended, the iliofemoral
269
HIP ANATOMY
FIG. 12. Zona orbicularis encircling the #mlneck.
ligament stands out as the anterior capsule becomes tightly applied to the anterior neck of the femur (Fig. 15). On viewing the posterior capsule, a thickening can be seen originating from the acetabulum and sloping laterally (Fig. 16). This is the inferior edge of the ischiofemoral ligament.
The acetabular articular surface acetabular fossa
and
Significant traction forces were necessary to distract the hip joint to allow visualization of the acetabular articular surface. This is best performed with the 30” arthroscope inserted through the anterior paratrochanteric portal. It is very common to injure the acetabular labrum and articular surfaces during insertion attempts. With care, the arthroscope can be inserted between the distracted articular surfaces to examine them (Fig. 17). Occasionally, the acetabular fossa and the ligament of the head can be seen (Fig. 18). More often, however, the fat pad from the acetabular fossa expands into the joint with traction and obscures the view. The fovea on the head could not be seen. DISCUSSION
FIG. 13. Zona orbicularis, seen to the right, tightly applied to femoral neck and mimicking the acetabular labrum.
Arthroscopy of the hip may not at first seem as rewarding as arthroscopy of other joints. There are, however, structures of clinical significance that can be better assessed with arthroscopy than with any technique apart from arthrotomy. Using the three portals described, 80% of the circumference of the femoral head can be seen and most of the acetabular labrum is visible. The anterior paratrochanteric portal is the most immediately rewarding due to the larger portion of the arthroscope that is intracapsular, thus leading to greater Arthroscopy,
Vol. 6, No. 4, 1990
270
M. DVORAK
ET AL.
FIG. 14. Orbicular fibers encircling the inferior neck of the femur. Inf, inferior
maneuverability and a wider field of view. Insertion of the arthroscope and any instruments requires a capable assistant to accurately position the leg. Alternatively, limb holding devices, including prerobotic limb manipulators, are available (Fig. 19). Constantly changing positions are necessary to accentuate the zona orbicularis and other capsular structures, as well as to expose the appropriate areas of the femoral head and neck. It is only during the final part of the arthroscopic
examination that traction is necessary in order to view the acetabular articular surface and contents of the acetabular fossa. Abduction and internal rotation of the hip during insertion attempts utilizing the posterior paratrochanteric portal put the sciatic nerve at significant risk of damage from the sharp trochar. It would seem that ensuring free mobility is important to allow easy, accurate, and atraumatic insertion of the arthroscope and instruments. The surgeon is also able to orient himself to the often
FIG. 15. Iliofemoral ligament, or “Y” ligament of Bigelow, tightly applied to rL_ __r_2__ lan”l-d C_-___l necn. ___a. l-Up TT1_1s 1_ ,___: mt: anlen”I ,“SP tioned in extension and external I?Ootation.
Arthroscopy,
Vol. 6. No. 4, 1990
HIP ANATOMY
271
FIG . 16. Inferior edge of the ischiofemoral ligament in the posterior capsule.
confusing anatomy by being able to freely move the leg. The posterior paratrochanteric portal provides the best view of the posterior acetabular labrum. With the 70” scope, the posterosuperior femoral neck as well as the anterior hip capsule can be seen easily. Due to the narrow field of view within the hip joint capsule, and because of the relative depth of
soft tissues, triangulation is difficult. There have, however, been reports of operative arthroscopy for the removal of loose bodies (9,l l), retained cement fragments and other debris (5,6), synovial biopsy, and even partial synovectomy (9). A recent study has also shown the value of operative arthroscopy in the management of chondromatosis (12). It is beyond the scope of this study to suggest indications for hip arthroscopy in the clinical set-
FIG. 17. Acetabll&X ticuliar surface.
Arthroscopy,
Vol. 6, No. 4, 1990
M. DVORAK
272
ET AL.
FIG. 18. Ligament of the head of the fe-
mur.
ting. It is possible, however, to conjecture that hip arthr oscopy will be found useful in the treatment of tears of the acetabular labrum, synovitis, chondrolysis, loose bodies, osteochondritis dissecans, septic
arthritis, and arthritic pain with minimal ratdiographic findings. Of particular interest are the plications of arthroscopy in the pediatric age gr ‘OUP CAW.
FIG. 19. Arthrobot lower limb positioner.
Arthroscopy,
Vol. 6, NO. 4, 1990
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HIP ANATOMY
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