Osteonecrosis (ON) of the femoral head (FH) remains a serious complication following traumatic injury and surgical intervention about the hip joint, especially in young, active patients. Following femoral neck fracture (FNF) and surgical fixation, rates of ON have been reported ranging from 5.9% to 50%,1,2 with one study reporting small segmental areas of ON in 87% of subjects based on magnetic resonance imaging (MRI) findings.3 The development of ON is thought to begin with compromised blood flow setting off a series of events resulting in cellular death within the FH.3,4 Although the initial stages may be asymptomatic, the condition may progress to FH collapse, causing pain and functional impairment.3,4 Recent literature reports poor patient-reported quality of life and pain scores among patients with ON resulting in FH collapse.5,6 Further affecting patient quality of life is the complicated treatment of femoral head osteonecrosis. For patients with FH collapse, total hip arthroplasty is frequently indicated, which can lead to complications and revision surgeries, especially in younger patients.6
Traumatic injury and surgical interventions about the hip joint, including FNF fixation, surgical hip dislocation, arthroscopic femoral osteochondroplasty, and antegrade intramedullary femoral nailing, all can disrupt the blood supply to the FH, potentially leading to symptomatic ON and FH collapse. The current authors therefore present relevant literature to describe the vascularity of the FH as well as its implications during the aforementioned surgical procedures. They also explore ways to minimize iatrogenic vascular compromise and femoral head osteonecrosis.
Vascularity to the Femoral Head
It is widely accepted that the FH derives its blood supply primarily from the retinacular system via the medial femoral circumflex artery (MFCA),7,8 with the superior retinacular branch believed to be more dominant than the inferior branch.7–9 Multiple cadaveric injection studies incorporating advanced imaging and gross dissection have corroborated these findings by mapping the precise extra- and intra-articular course of the circumflex arterial system (medial and lateral femoral circumflex arteries) and quantifying the relative arterial contribution to the FH.7,10–12
Medial Femoral Circumflex Artery
The MFCA is a branch off of the profunda femoris artery or, less frequently, off of the common femoral artery. The MFCA usually branches within the femoral triangle and courses posteriorly behind the hip, and its extra-articular portion can be divided into 3 segments—the transverse, ascending, and deep MFCA (Figure 1).12 The transverse portion of the vessel courses posteriorly between the iliopsoas and pectineus muscles. It then ascends toward the intertrochanteric crest as the ascending segment, traveling within adipose tissue between the obturator externus and quadratus femoris muscles. Finally, as the deep MFCA, it crosses over the obturator externus tendon and then follows an intracapsular course, deep to the conjoined tendon of the short external rotators. Each of these 3 segments gives off branches that supply blood to the femoral head and neck.
Illustration of the ascending and deep portions of the medial femoral circumflex artery (MFCA) and their anatomical relationships to the external rotators about the hip joint. (Reprinted with permission from Sculco PK, Lazaro LE, Su EP, et al. A vessel-preserving surgical hip dislocation through a modified posterior approach: assessment of femoral head vascularity using gadolinium-enhanced MRI. J Bone Joint Surg Am. 2016;98(6):475–483. https://journals.lww.com/jbjsjournal.)
Based on a cadaveric study by Lazaro et al12 examining the intra-articular terminal branches of the MFCA (Figure 2), the transverse segment consistently gives off the inferior retinacular artery (IRA), which exits inferomedially, approximately 4 cm from the lesser trochanter. This branch travels for approximately 1 cm before penetrating the capsule at the level of the anterior–inferior femoral neck. After entering the capsule, it courses obliquely within the inferior retinacula of Weitbrecht, a fibrous extension of the capsule that is elevated off of the bony surface of the femoral neck. It then travels for approximately 2.4 cm along the inferior femoral neck before penetrating the femoral head–neck junction (FHNJ) posteroinferiorly to become intraosseous. An average of 5 terminal branches come off of this vessel and penetrate the FHNJ posteriorly.12 The IRA supplies the inferior FH, and it has been suggested that it provides an important source of blood flow to the FH when the deep MFCA (supplying the superior retinacular artery [SRA]) is disrupted.13,14
Gross dissection photograph of the posterior aspect of the femoral head–neck junction showing the posterior course of the medial femoral circumflex artery (MFCA) and the intracapsular course of its terminal branches. The transverse MFCA gives off the inferior retinacular artery, which can be seen within the inferior retinacula of Weitbrecht (fibrous extension of the capsule elevated off of the femoral neck) before penetrating the femoral head–neck junction posteroinferiorly, giving off an average of 5 terminal branches. The transverse MFCA transitions to the ascending MFCA at the anterior surface of the quadratus femoris. As it ascends proximally, it ultimately gives off a mean of 2 terminal branches. The ascending MFCA becomes the deep MFCA at the distal border of the obturator externus tendon. The deep MFCA gives off the superior retinacular artery, giving off a mean of 6 terminal branches that travel within the superior retinacula of Weitbrecht and penetrate the superior femoral head–neck junction posteriorly 80% of the time. Lazaro et al12 provide a more in-depth description of the terminal branch pattern of the MFCA.
After transitioning to the ascending segment of the MFCA at the anterior surface of the quadratus femoris, this segment travels along the distal border of the obturator externus superiorly, giving off between 1 and 3 branches that enter the capsule posteriorly.12 Once intracapsular, these branches ultimately give off between 1 and 3 terminal branches that penetrate the FHNJ posteroinferiorly (Figure 2).
Along the distal border of the obturator externus tendon, the ascending MFCA transitions into the deep MFCA. It gives off the trochanteric branch laterally as it continues to cross over the tendon of the obturator externus posteriorly, then traveling deep to the conjoined tendon (obturator internus, superior and inferior gemelli) before penetrating the joint capsule posterosuperiorly. Intracapsularly, it travels as the SRA, which historically has been viewed as the most important branch supplying blood to the FH.3 Ultimately, an average of 6 terminal branches are given off by this vessel, traveling within the superior retinacula of Weitbrecht before penetrating the FHNJ posterosuperiorly (Figure 2).12
Lateral Femoral Circumflex Artery
Although less significant than the MFCA, the lateral femoral circumflex artery (LFCA) also supplies blood to the femoral head and neck (Figure 3). One cadaveric study using MRI quantitative perfusion analysis reported that the relative contributions of the MFCA and the LFCA to FH vascularity were 82% and 18%, respectively.7 However, the LFCA made a greater contribution to the anteroinferior femoral neck at 48%. The LFCA branches off of the profunda femoris, or less commonly from the common femoral artery, coursing laterally and anteriorly around the hip joint. Posterior to the rectus femoris, it branches into ascending, transverse, and descending branches.8 The ascending branch courses superiorly behind the rectus femoris along the intertrochanteric line, supplying the capsule. The ascending LFCA also gives rise to the anterior retinacular artery, which enters the capsule and can supply the femoral neck at various levels (Figure 3).8 Intracapsularly, an average of 2.1 terminal branches have been found to penetrate the anteroinferior femoral neck, with terminal branches rarely found supplying the FHNJ.7 The transverse and descending branches of the LFCA contribute less significantly to FH blood supply.
Subtraction 3-dimensionally reformatted computed tomography images of a cadaveric specimen following injection with barium sulfate and polyurethane. The anterior view (A) shows the lateral femoral circumflex artery terminal branch (blue arrow), while the posterior view (B) shows the medial femoral circumflex artery giving off its terminal branches, the superior retinacular artery (superior blue arrow) and inferior retinacular artery (inferior blue arrow).
Inferior Gluteal Artery
The inferior gluteal artery contributes to the blood supply of the hip through its anastomotic connections with the MFCA. Grose et al11 performed a cadaveric injection dissection study and found an anastomosis between the inferior gluteal artery and the MFCA near the obturator externus tendon in 7 of 8 specimens. Branching from the internal iliac artery, the inferior gluteal artery descends down the gluteal region alongside the sciatic nerve, ultimately giving off branches that contribute to an anastomosis with the MCFA. The terminal vessel branching from this anastomosis passes under the posterior capsule and then ascends along the superior portion of the femoral neck before terminating in the arteries supplying the FH.11
The foveal artery often branches from the obturator artery and runs within the ligament of the head of the femur to penetrate the FH. Although older anatomical studies report anastomoses between the foveal artery, the retinacular vessels, and the intraosseous vessels of the FH, the importance of the foveal artery's vascular contribution is questionable. In 1965, Sevitt and Thompson15 performed a cadaveric injection study in which reliable anastomotic connections between the foveal artery and the other vessels of the FH were observed in some specimens but not others. More recently, a cadaveric study by Kalhor et al16 showed a small caliber foveal artery with limited contribution in 8 of 15 specimens. Therefore, the foveal artery may contribute more significantly in some individuals than others.
Surgical Implications of Femoral Head and Neck Blood Supply
Open Reduction and Internal Fixation for Femoral Neck Fractures
Femoral neck fractures can lead to vascular compromise and femoral head osteonecrosis, with rates reported ranging from 5.9% to 50%.1,2 The most worrisome complication of ON is its progression to FH collapse, causing pain, discomfort, and the risk of conversion to a total hip arthroplasty. In young, active patients, this can lead to a lifetime of impairment and debilitating surgical procedures, including revision arthroplasty.
A study at the current authors' institution used dynamic contrast-enhanced MRI to quantify residual perfusion to the FH following displaced FNF in patients ultimately treated with open reduction and internal fixation. Postoperative MRI revealed small segmental areas of femoral head osteonecrosis in 87% of patients.3 These segments of ON were all located in the anterior aspect of the superomedial quadrant of the FH, which corresponded to the area exhibiting the greatest decrease in perfusion on MRI preoperatively. This specific area of the FH is supplied by the SRA, suggesting that the SRA was compromised by the injury. Residual blood flow to the FH likely came from the IRA following damage to the SRA. Because the IRA lies within the inferior retinacula of Weitbrecht, which is elevated off of the femoral neck, this vessel may be protected during FNF and injury about the hip joint.3 The IRA therefore serves a protective function, revascularizing the FH when the SRA is compromised, via extensive anastomoses.10
Another study of patients with FNF demonstrated decreased arterial inflow and venous outflow in the vessels supplying the FH, suggesting that vascular compromise may arise from the trauma itself, hemarthrosis leading to intracapsular vessel tamponade, or both.17,18 These multiple etiologies of retinacular vessel compression must be taken into account when treating patients presenting with FNFs. Therefore, in patients with displaced FNFs indicated for open reduction and internal fixation, the current authors recommend early anatomical reduction to quickly reduce compression of the retinacular branches, minimizing the effect of tamponade from hemarthrosis with intra-articular capsular decompression.3,19
Surgical Hip Dislocation
Surgical hip dislocation allows full exposure of the FH and acetabulum. It is often a crucial step in procedures treating intra-articular hip conditions, including femoroacetabular impingement, FH and acetabular fractures, childhood hip diseases, and cartilage injury, and for exposure during hip resurfacing.13,20,21 However, disruption of the arterial supply to the FH during posterior surgical hip dislocation can lead to iatrogenic ON. Ganz et al22 described an anterior surgical hip dislocation approach through a trochanteric flip osteotomy. This approach provides access to the hip joint while preserving the posterior hip structures, including the MFCA and its retinacular branches.22 Because of complications such as osteotomy nonunion and symptomatic hardware, as well as unfamiliarity with the technique, many surgeons still prefer a standard posterior approach during hip resurfacing.20
During the standard posterior approach, which involves a posterior hip dislocation, incising the conjoint tendon or the obturator externus tendon can damage the deep MFCA, while the ascending MFCA can be injured during takedown of the quadratus femoris.20 Posterior capsulotomy along the capsular femoral attachment can damage the terminal vessels of the MFCA. Damage to these vessels through a posterior approach is corroborated by a study revealing histological evidence of ON in 92% of failed hip resurfacing arthroplasties, which compromised 3% of the initial study cohort.23 Another study found increased biochemical markers of ischemia postoperatively in patients who underwent hip resurfacing with a posterior approach compared with an anterolateral approach, further elucidating the vascular risk of the posterior approach.24
To overcome the known risk of vascular disruption during the standard posterior approach,13,14,20 two vascular-preserving surgical modifications have been proposed. The modified posterior approach involves the same deep dissection as the standard posterior approach, although the capsulotomy incision is at the acetabular attachment rather than at the femoral attachment,14,20 posing less risk to the MFCA branches as they become intracapsular near the femoral attachment of the hip capsule (Figure 4). Another vessel-sparing approach involves modifying the location of the quadratus femoris myotomy and the tenotomies of the conjoined tendon and obturator externus to 2.5 cm medial (away) from their insertions on the greater trochanter, in addition to performing a T-type capsulotomy closer to the acetabular rim (Figure 5).13
Magnetic resonance images (MRI) of cadaveric specimens and corresponding gross dissection photographs showing significantly decreased perfusion and increased blood vessel disruption following a surgical hip dislocation through a standard posterior approach (A), better maintenance of perfusion and fewer disrupted vessels following a modified posterior approach (B), and greatest preservation of perfusion and intact vasculature following an anterior surgical hip dislocation via a trochanteric flip osteotomy (C). Abbreviation: MFCA, medial femoral circumflex artery.
Illustrations showing vessel-preserving modifications to a surgical hip dislocation, including modifying the location of the quadratus femoris tenotomy (A), modifying the location of the tenotomies of the short external rotators and the obturator externus (OE) (B), and performing a T-type capsulotomy (C). Abbreviations: m, muscle; MFCA, medial femoral circumflex artery; n, nerve. (Reprinted with permission from Sculco PK, Lazaro LE, Su EP, et al. A vessel-preserving surgical hip dislocation through a modified posterior approach: assessment of femoral head vascularity using gadolinium-enhanced MRI. J Bone Joint Surg Am. 2016;98(6):475–483. https://journals.lww.com/jbjsjournal.)
These modified techniques have demonstrated maintenance of perfusion to the FH and FHNJ, similar to the trochanteric flip osteotomy, in cadaveric studies using quantitative MRI analysis.13,20 One study using MRI compared the vascularity to the FH following 3 hip dislocation approaches, including the trochanteric flip osteotomy, modified posterior approach, and standard posterior approach. The trochanteric flip osteotomy group showed the best maintenance of perfusion, the modified posterior approach showed moderate maintenance of perfusion (likely because of protective blood supply from the IRA), and the standard posterior approach showed a significant decrease in perfusion.20 Therefore, the current authors believe that the standard posterior approach should be avoided whenever possible.
Arthroscopic Femoral Osteochondroplasty
Femoroacetabular impingement is a known risk factor for the development of hip osteoarthritis, warranting preventive surgery in certain patients.25,26 While historically treated by open surgical hip dislocation, femoroacetabular impingement caused by anterior–superior cam lesions has been successfully treated by arthroscopic techniques, although there is a paucity of literature describing the effects of the arthroscopic technique on FH vascularity. A recent series involving 258 patients reported one questionable case of ON (<0.4%) following arthroscopic treatment.27 One cadaveric study at the current authors' institution indicated that treatment of anterior cam lesions with arthroscopic osteochondroplasty is comparable to that with open osteoplasty.26 Another arthroscopic cadaveric study showed no evidence of disruption to the vessels supplying the FH when the resection margin was limited to a 150° arc along the anterior FHNJ between the 6-o'clock position (180°) inferiorly up to the 1-o'clock position (30°) superiorly as represented by an imaginary clock face (Figure 6).25 This implies that the posterior retinacular vessels can be preserved during arthroscopic treatment of cam lesions as long as the resection remains in the anterior safe zone.
Images of the femoral head and neck viewed as a clock face based on right hip equivalents as used in the cadaveric study of Lazaro et al28 evaluating arthroscopic femoral osteochondroplasty resection margins. A clock face including 360° markings was applied with the 12-o'clock position (0°) oriented toward the most superior aspect of the femoral neck and the 6-o'clock position (180°) oriented toward the most inferior aspect of the femoral neck to allow for the precise measurement of resection margins in all specimens (A). Bright blue is used to indicate the arthroscopic resection margins, with the standard resection margin (B) and the extended resection margin (C) shown. In the extended group, extending the resection margin an average of 41.3° posterior to 12 o'clock resulted in decreased perfusion of the femoral head.
To expand on this knowledge, Lazaro et al28 performed a cadaveric study using quantitative MRI to quantify the effect of arthroscopic osteochondroplasty margins on FH perfusion. They found that extending the arc of resection to a mean of 41.3° posterior to the 12-o'clock position decreased FH perfusion by 28% on average (Figure 6). They noted that perfusion was still maintained if the resection margin was extended posterior to 12-o'clock by 10° or less. Rupp and Rupp29 evaluated 14 patients with cam-type femoroacetabular impingement who underwent arthroscopic osteochondroplasty that extended to the posterolateral head. Postoperative MRI revealed no evidence of femoral head osteonecrosis in any of these patients. However, this study was limited by its small size and wide range of postoperative MRI (7 to 44 months). To the current authors' knowledge, this is the only clinical series reporting on arthroscopic osteochondroplasty extending posteriorly. Furthermore, the current authors are not aware of any in vivo studies quantifying perfusion to the FH following arthroscopic osteochondroplasty. They recognize the need for future larger, long-term studies evaluating the impact of posterior resection on FH vascularity and rates of ON. However, on the basis of current evidence, the authors recommend caution when extending the posterior resection limit beyond 10° posterior to the 12-o'clock position to leave the posterior retinacular branches intact during arthroscopic femoral osteochondroplasty.
Antegrade Intramedullary Femoral Nailing
Antegrade intramedullary femoral nailing remains the primary treatment for femoral diaphyseal and subtrochanteric fractures. Although uncommon, avascular necrosis of the FH has been a reported complication,30,31 as the deep MFCA can be injured at the proximal femoral entry point.32,33 One cadaveric study using quantitative MRI analysis compared the piriformis fossa with the greater trochanteric entry point and found that with piriformis fossa entry, the reamer path came closer to the deep MFCA (40% of specimens had the reamer path within 1 mm of the artery) and more retinacular branches were damaged.32
Clinically, ON following antegrade intramedullary femoral nailing is more frequently found in skeletally immature patients. One case of ON was found in a recent series of 542 patients who underwent antegrade intramedullary femoral nailing (0.2%).30 This patient was 15 years old and underwent antegrade intramedullary femoral nailing through the piriformis fossa entry point. No one in the adult group (20 years or older) or the greater trochanter entry point group developed ON. However, in another case report, a 21-year-old man with a femoral shaft fracture underwent antegrade femoral nailing through a piriformis entry point and was noted to have avascular necrosis of the FH on radiographs postoperatively.31 On the contrary, a prospective randomized comparison of piriformis and greater trochanteric entry points did not report ON, but did report equal functional hip outcomes between both groups at 12-month follow-up,34 implying that both entry points are safe and effective.
The piriformis fossa entry point is associated with closer proximity to the deep MFCA and a theoretically increased risk of vascular disruption and ON, although current literature does not indicate higher rates of ON in skeletally mature patients undergoing this technique. However, the current authors do recommend that the proximity of the piriformis fossa entry point to the deep MFCA be taken into account during femoral nailing, especially in pediatric patients. The piriformis entry point should be avoided or used with caution, and multiple errant entry attempts should be avoided to minimize the odds of vessel disruption, as the deep MFCA and its SRA branch are the main contributors to FH blood flow.
The deep MFCA's superior retinacular branch provides the greatest contribution to the blood supply to the FH, especially the posterior superior region. The inferior retinacular branch, which comes off of the transverse MFCA, mainly supplies the inferior FH and is an important source of perfusion when the deep MFCA is compromised. Intracapsularly, these retinacular branches travel in the retinacula of Weitbrecht before giving off terminal branches that penetrate the FH. The LFCA also contributes a smaller amount to FH perfusion, with its greatest contribution to the anterior–inferior femoral neck.7
The complex anatomical relationships of these vessels to the musculature surrounding the hip joint make them susceptible to injury during trauma and hip surgery. To avoid the development of femoral head osteonecrosis and possible FH collapse, it is imperative that surgeons operating about the hip joint understand these intricate anatomical relationships and take certain precautions. Displaced FNFs indicated for fixation should be anatomically reduced in a timely fashion to restore the vascular anatomy and minimize the detrimental effects of hemarthrosis on the intracapsular vessels. Well-documented modifications to the standard posterior surgical hip dislocation should be performed to preserve FH perfusion, or an anterior dislocation through a trochanteric flip osteotomy should be performed when feasible. Hip arthroscopy, particularly for cam-type femoroacetabular impingement, is safe regarding FH vascularity as long as resection margins are not extended more than 10° posteriorly beyond the 12-o'clock position.28 However, caution is advised when resecting lesions that extend posteriorly, as this is where the primary vessels enter. Finally, although antegrade intramedullary nailing for femoral diaphyseal fractures is generally safe, the deep MFCA is at risk of injury during piriformis fossa entry, and multiple errant entry attempts should be avoided.
Although femoral head osteonecrosis is rare following the aforementioned surgical procedures, it is still of great concern because of its debilitating effects on patient quality of life and the need for further surgery, including total hip arthroplasty. Furthermore, young, active patients can be gravely affected. As surgery about the hip joint continues to evolve, especially arthroscopic interventions, it is imperative that surgeons understand the precise vascular anatomy of the FH in relation to these procedures. To preserve the arterial supply to the FH, the retinacular system must remain intact. Efforts should focus on techniques to minimize iatrogenic vascular damage, especially to the retinacular vessels, to maximize surgical outcomes across multiple orthopedic specialties.
- Schwartsmann CR, Lammerhirt HM, Spinelli LF, Ungaretti Neto ADS. Treatment of displaced femoral neck fractures in young patients with DHS and its association to osteonecrosis. Rev Bras Ortop. 2017;53(1):82–87. doi:10.1016/j.rbo.2017.01.007 [CrossRef]
- Luo D, Zou W, He Y, et al. Modified dynamic hip screw loaded with autologous bone graft for treating Pauwels type-3 vertical femoral neck fractures. Injury. 2017;48(7):1579–1583. doi:10.1016/j.injury.2017.05.031 [CrossRef]
- Lazaro LE, Dyke JP, Thacher RR, et al. Focal osteonecrosis in the femoral head following stable anatomic fixation of displaced femoral neck fractures. Arch Orthop Trauma Surg. 2017;137(11):1529–1538. doi:10.1007/s00402-017-2778-8 [CrossRef]
- Hamada H, Takao M, Sakai T, Sugano N. Subchondral fracture begins from the bone resorption area in osteonecrosis of the femoral head: a micro-computerised tomography study. Int Orthop. 2018;42(7):1479–1484. doi:10.1007/s00264-018-3879-x [CrossRef]
- Uesugi Y, Sakai T, Seki T, et al. Quality of life of patients with osteonecrosis of the femoral head: a multicentre study. Int Orthop. 2018;42(7):1517–1525. doi:10.1007/s00264-018-3897-8 [CrossRef]
- Osawa Y, Seki T, Takegami Y, Kasai T, Higuchi Y, Ishiguro N. Do femoral head collapse and the contralateral condition affect patient-reported quality of life and referral pain in patients with osteonecrosis of the femoral head?Int Orthop. 2018;42(7):1463–1468. doi:10.1007/s00264-018-3867-1 [CrossRef]
- Dewar DC, Lazaro LE, Klinger CE, et al. The relative contribution of the medial and lateral femoral circumflex arteries to the vascularity of the head and neck of the femur: a quantitative MRI-based assessment. Bone Joint J. 2016;98-B(12):1582–1588. doi:10.1302/0301-620X.98B12.BJJ-2016-0251.R1 [CrossRef]
- Seeley MA, Georgiadis AG, Sankar WN. Hip vascularity: a review of the anatomy and clinical implications. J Am Acad Orthop Surg. 2016;24(8):515–526. doi:10.5435/JAAOS-D-15-00237 [CrossRef]
- Zlotorowicz M, Szczodry M, Czubak J, Ciszek B. Anatomy of the medial femoral circumflex artery with respect to the vascularity of the femoral head. J Bone Joint Surg Br. 2011;93(11):1471–1474. doi:10.1302/0301-620X.93B11.26993 [CrossRef]
- Boraiah S, Dyke JP, Hettrich C, et al. Assessment of vascularity of the femoral head using gadolinium (Gd-DTPA)-enhanced magnetic resonance imaging: a cadaver study. J Bone Joint Surg Br. 2009;91(1):131–137. doi:10.1302/0301-620X.91B1.21275 [CrossRef]
- Grose AW, Gardner MJ, Sussmann PS, Helfet DL, Lorich DG. The surgical anatomy of the blood supply to the femoral head: description of the anastomosis between the medial femoral circumflex and inferior gluteal arteries at the hip. J Bone Joint Surg Br. 2008;90(10):1298–1303. doi:10.1302/0301-620X.90B10.20983 [CrossRef]
- Lazaro LE, Klinger CE, Sculco PK, Helfet DL, Lorich DG. The terminal branches of the medial femoral circumflex artery: the arterial supply of the femoral head. Bone Joint J. 2015;97-B(9):1204–1213. doi:10.1302/0301-620X.97B9.34704 [CrossRef]
- Sculco PK, Lazaro LE, Su EP, et al. A vessel-preserving surgical hip dislocation through a modified posterior approach: assessment of femoral head vascularity using gadolinium-enhanced MRI. J Bone Joint Surg Am. 2016;98(6):475–483. doi:10.2106/JBJS.15.00367 [CrossRef]
- Steffen RT, De Smet KA, Murray DW, Gill HS. A modified posterior approach preserves femoral head oxgenation during hip resurfacing. J Arthroplasty. 2011;26(3):404–408. doi:10.1016/j.arth.2009.12.018 [CrossRef]
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