Preventing avascular necrosis following surgical management of pediatric slipped capital femoral epipysis is a critical goal. The direct intraosseous pressure monitor is a readily available and affordable technique that can easily be used by surgeons around the world.
Operative management of children with chronic high-grade slipped capital femoral epiphysis can be challenging and controversial.1 While avascular necrosis (AVN) of the femoral head is a devastating complication following osteotomy of the femoral neck, reduction by cuneiform osteotomy may be necessary to restore the normal relationship of the femoral head and neck and possibly delay the onset of degenerative joint disease in severe chronic, or acute-on-chronic, slips.2 The rate of AVN following cuneiform osteotomies of the femoral neck has been reported to range between 4.5% and 15%.3-7
These statistics underscore the primary importance of protecting the extraosseous branches of the medial femoral circumflex artery during surgical dislocation and subsequent femoral neck osteotomy in treating chronic slipped capital femoral epiphysis. Even with great care, intraoperative vessel compromise is possible. Ideally, a technique allowing immediate detection, and thus prevention, of vascular compromise would be incorporated as a standard surgical practice.
In order to provide an effective and readily available means to reproduce intraoperative pressure monitoring of the femoral head to ensure viability, we devised a simple and cost-effective technique involving direct intraosseous pressure (DIP) monitoring that has been a useful adjunct in 2 recent cases.
Following diagnosis of a grade III slipped capital femoral epiphysis, surgical management via cuneiform osteotomy was selected and performed after informed consent was obtained from the patients guardians.
The osteotomy can be performed with or without surgical dislocation of the hip for visualization. In the 2 patients in the current article, hip dislocation was performed as described by Ganz et al,8 using a trochanteric flip osteotomy. Using this approach, the hip can be exposed, subluxated, and dislocated in the anterior direction, while respecting the integrity of the external rotator muscles. In adults, this technique allows for a gap of up to 11 cm between the femoral head and the acetabulum, giving a nearly 360° view of both structures. In children, a smaller gap is created but a similar circumferential view of the hip architecture can be obtained. Such a circumferential exposure may not be needed in all cases.
| |Figure 1:
Intraoperative image showing intraosseous placement of spinal needle pressure monitor into antero-superior margin of the patients left femoral head after trochanteric flip osteotomy (TO).
| |Figure 2:
Waveform tracing from direct intraosseous pressure monitoring device (superior waveform) demonstrating direct correlation with heart rate waveforms from the pulse oximeter plethysmograph tracing (inferior waveform).
Once adequate visualization of the anterior femoral neck was achieved, a single 2-mm drill hole was made in the peripheral edge of the superior-anterior femoral head, and bleeding was observed directly from this drill hole. A 3-inch, 18-gauge spinal needle was then connected via sterile tubing to an arterial pressure monitoring system controlled by the anesthesiologist. The needle was advanced into the drill hole so that the tip was adjacent to the subchondral bone of the femoral head, and was flushed briefly by the anesthesiologist to establish a fluid column within the femoral head (Figure 1).
Waveform pressure tracings were then observed and correlated directly with concurrent pulse oximetry plethysmograph tracings of the patients heart rate (Figure 2). The monitors display settings can be calibrated by the anesthesiologist to amplify the visual appearance of the direct intraosseous pressure waveform, which is generally in a low-pressure range.
Obliteration of the direct intraosseous pressure waveform could be achieved with gentle digital compression of the retinaculum (Figure 3), which is the posterosuperior soft tissue structure containing the terminal branches of the medial femoral circumflex artery that directly provide femoral head vascularity. Immediate return of a pulsatile waveform within the femoral head was visualized on the direct intraosseous pressure readings after release of this retinacular occlusion.
| |Figure 3:
Obliteration of direct intraosseous pressure monitor waveform (superior waveform) within the femoral head with digital occlusion of the posterior retinacular vessels. The pulse oximeter plethysmograph tracing is seen inferiorly.
A cuneiform osteotomy was then performed, with great care taken not to place retractors in the posterior aspect of the femoral neck. The femoral neck and trochanteric osteotomies were each secured with two 6.0-mm cannulated screws (Figure 4). The hip was then reduced back into the acetabulum.
At each step during the surgical exposure of the femoral head, femoral neck osteotomy, femoral neck fixation, and hip reduction into the acetabulum, an intraosseous arterial waveform could be assessed using direct intraosseous pressure monitoring to provide ongoing visual confirmation of femoral head arterial perfusion.
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|Figure 4: AP (A) and lateral (B) postoperative radiographs demonstrating fixation of cuneiform and trochanteric osteotomies of the right hip with 6.0-mm cannulated screws. |
The direct intraosseous pressure monitoring technique was used adjunctively in 2 pediatric cases at our institution in 2006. The patients, a 10-year-old girl and a 13-year-old boy, both had a chronic grade III slipped capital femoral epiphysis. The female patient presented with an acute-on-chronic slip, and a preoperative magnetic resonance imaging (MRI) confirmed the absence of AVN. Both patients were managed surgically with the techniques described above and were followed in the outpatient setting with serial examination and radiographs. At 2-year follow-up, both patients had healed their osteotomies and neither patient had residual hip pain nor demonstrated evidence of AVN on hip radiographs.
Various authors have attempted to address the high incidence of AVN following management of fractures and deformity about the femoral neck.
Gill et al9 prospectively assessed the risk of AVN following femoral neck fracture in 64 patients by directly visualizing bleeding from 2-mm drill holes placed into the femoral head during anterior capsulotomy in conjunction with fixation. None of the 56 patients with bleeding from the drill holes in the femoral head fragment developed AVN, while all 8 patients with no bleeding after reduction went on to develop AVN. Cho et al10 performed an analogous experiment using cannulated screws yielding similar results.
Nötzli et al11 proposed a technique where a laser Doppler flometry probe was inserted in the femoral head via a 3.5-mm cortical window to assess perfusion within the femoral head during surgical dislocation of the hip. This study showed that laser Doppler flometry provides proof for the clinical observation that perfusion of the femoral head is maintained after dislocation if specific surgical precautions are followed.
A similar technique of laser Doppler flometry monitoring was used by Beaulé et al12 to monitor femoral head perfusion in 10 patients with advanced osteoarthritis having metal-on-metal hip resurfacing by means of a vascular-preserving surgical approach.
More recently, Watanabe et al13 measured intramedullary oxygen tension directly during surgery using polarographic oxygen electrodes and an oxygen monitor at 4 distinct locations in 17 patients with 18 femoral neck fractures treated by internal fixation: 1 cm distal from the joint surface, 1 cm proximal from the fracture site, 1 cm distal from the fracture site, and 1 cm proximal from the lateral wall. This group found significant differences in the distribution of intramedullary oxygen tension of the femoral head in those patients who later developed AVN.
Despite these technical advances using laser Doppler flometry and polarographic oxygen electrodes as oxygen sensors, the necessary equipment to clinically replicate such monitoring may be unavailable or prohibitively expensive in many parts of the world. In fact, such equipment is not currently available for intraoperative use at our facility, which is a combined level I adult and pediatric trauma center.
Our described method for direct intraosseous pressure monitoring of the femoral head is a modification of the laser Doppler technique described by Nötzli et al.11 It represents a simplified and inexpensive method of intraosseous arterial pressure monitoring using a single 2-mm cortical window and materials commonly available to surgeons around the world. Perhaps most importantly, the technique serves to emphasize the paramount importance of meticulous surgical dissection and dislocation for this procedure, which strives to preserve the integrity of the posterior retinaculum and medical femoral circumflex vessels.
Our described direct intraosseous pressure monitoring technique appears to have been a beneficial intraoperative adjunct in 2 pediatric patients treated with cuneiform femoral neck osteotomy for high-grade chronic slipped capital femoral epiphysis. Both children healed their osteotomies well, experienced functional improvement in their affected hips, and had not developed AVN at 2-year follow-up. While 2 cases is insufficient to make a statement on the broader use of this technique, a larger cohort could not be established in 2006 due to the relative rarity of the described procedure at our institution.
Prospective studies are warranted to further investigate this technique and establish a correlation of the technique with postoperative femoral head AVN on a larger scale. Moreover, future studies might examine subtle anatomic variations of femoral head intraosseous blood flow by placing the direct intraosseous pressure monitor needle in a variety of locations within the femoral head. Additionally, this technique might be applied by traumatologists seeking to assess femoral head viability during fracture fixation of the femoral head and neck, or by hip surgeons seeking to assess femoral head viability during hip resurfacing procedures.
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- Ganz R, Gill TJ, Gautier E, Ganz K, Krügel N, Berlemann U. Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br. 2001; 83(8):1119-1124.
- Gill TJ, Sledge JB, Ekkernkamp A, Ganz R. Intraoperative assessment of femoral head vascularity after femoral neck fracture. J Orthop Trauma. 1998; 12(7):474-478.
- Cho M, Lee S, Shin D, et al. A predictive method for subsequent avascular necrosis of the femoral head (AVNFH) by observation of bleeding from the cannulated screw used for fixation of intracapsular femoral neck fractures. J Orthop Trauma. 2007; 21(3):158-164.
- Nötzli HP, Siebenrock KA, Hempfing A, Ramseier LE, Ganz R. Perfusion of the femoral head during surgical dislocation of the hip. Monitoring by laser Doppler flowmetry. J Bone Joint Surg Br. 2002; 84(2):300-304.
- Beaulé PE, Campbell P, Shim P. Femoral head blood flow during hip resurfacing. Clin Orthop Relat Res. 2007; (456):148-152.
- Watanabe Y, Terashima Y, Takenaka N, Kobayashi M, Matsushita T. Prediction of avascular necrosis of the femoral head by measuring intramedullary oxygen tension after femoral neck fracture. J Orthop Trauma. 2007; 21(7): 456-461.
Drs Rubin, Smith, and DeLuca are from the Department of Orthopaedics and Rehabilitation, Yale-New Haven Hospital; and Mr Galante is from Yale University School of Medicine, New Haven, Connecticut.
Drs Rubin, Smith, and Deluca and Mr Galante have no relevant financial relationships to disclose.
Correspondence should be addressed to: Lee E. Rubin, MD, Yale-New Haven Hospital, 800 Howard Ave, YPB 1st Fl, PO Box 208071, New Haven, CT 06520.