Acute, Unstable, Slipped Capital Femoral Epiphysis: Is There a Role for In Situ Fixation? Dennis R. Wenger, MD*w and James D. Bomar, MPH*

Background: Slipped capital femoral epiphysis, a common disorder in adolescents, may be increasing in incidence in North America because of the obesity epidemic. In most cases, the slip is mild and can be treated with in situ fixation. Even in more severe cases of a stable slip, in situ fixation remains a widely accepted choice. When the slip is acute and unstable, treatment remains controversial. We reviewed the orthopaedic literature and our personal experience in managing acute, unstable slipped capital femoral epiphysis. The reported range of avascular necrosis (AVN) is high and the literature shows no clear recommendations for the best treatment choice. Treatment choices include: in situ stabilization with possible later corrective osteotomy, formal manipulative closed reduction plus screw fixation, partial reduction through an open approach with the hip joint decompressed (Parsch method), and anatomic reduction by the modified Dunn method. Review of the literature and our experience suggests a high AVN rate in acute unstable slips no matter what treatment method is selected. Most North American reports suggest an AVN rate with in situ screw fixation ranging from 20% to 50%. The method described by Parsch, which includes an urgent, open capsulotomy, joint decompression, and gentle partial reduction, shows a low AVN rate as reported from his institution (< 10%). The AVN rate reported for anatomic reduction (modified Dunn procedure) performed through an open surgical hip dislocation was initially quite low, but after being restudied in North American centers appears to be about 25%. Conclusions: Safe treatment of an acute unstable slip remains problematic. The literature suggests that these patients should be treated urgently; however, simple in situ stabilization results in a high AVN rate. A likely safer modification is to open the hip anteriorly to decompress the joint and to stabilize after partial reduction as described by Parsch. The modified Dunn method is becoming more widely used, but results in North American centers cite a significant AVN rate. Key Words: slipped capital femoral epiphysis, in situ pinning, partial reduction, avascular necrosis (J Pediatr Orthop 2014;34:S11–S17)

From the *Rady Children’s Hospital; and wDepartment of Orthopedic Surgery, University of California, San Diego, CA. None of the authors received financial support for this study. The authors declare no conflicts of interest. Reprints: Dennis R. Wenger, MD, 3030 Children’s Way, Suite 410, San Diego, CA 92123. E-mail: [email protected] Copyright r 2014 by Lippincott Williams & Wilkins

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lipped capital femoral epiphysis (SCFE) is a common orthopaedic condition in adolescents. Most slips have gradual displacement, maintaining structural continuity. These stable slips are successfully treated with in situ fixation. In situ fixation is widely accepted for mild slips, accepted by most for moderate slips, and questioned by some for severe slips. In more severe cases, an osteotomy can be performed later if there is significant femoral headneck deformity that would predispose to early hip arthritis (hip impingement). An acute, unstable slip, which is the topic of this paper, offers a very different circumstance. Often, these hips have had gradual deformation over time, which is not recognized. The child then has an injury or twist with sudden, catastrophic separation of the epiphysis from the femoral neck and presents with inability to walk and marked pain when examining the hip. Loder et al1 have carefully studied this group and has classified these patients as having an unstable slip. Further analysis of this classification, which will be expanded upon in the Discussion section, suggests that our ability to define stable versus unstable slips may be less certain than once thought.2 Further experience with open reduction of acute unstable slips suggests that some of those hips that were thought to be unstable actually already have early callous formation, implying evolving stability. Currently, when faced with an unstable slip, the treating surgeon has 4 options. (1) In situ stabilization (often this ends up with an unintentional partial reduction because placement of the patient on the operating table, and particularly on a fracture table, may partially reduce the epiphysis. The epiphysis can then be pinned in situ). (2) Purposeful, manipulative reduction of the unstable slip without opening the capsule. This method is thought to have a high avascular necrosis (AVN) rate because there may be callous present posteriorly, which impedes blood flow through the posterior leash of vessels. Vascular flow can then be further compromised by a reduction maneuver. (3) Open reduction of the hip through an anterolateral approach (Parsch method).3 The capsule is opened and any hematoma is decompressed. Gentle pressure on the neck will often partially reduce the epiphysis, but only to the point where it was before the acute component of the slip; in some cases, the reduction is complete. The hip is then stabilized with pins or screws.

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(4) Anatomic reduction of the proximal femoral epiphysis upon the neck, including possible femoral neck shortening (modified Dunn approach). This procedure gives full exposure of the head and neck and allows one to identify and protect the posterior leash of blood vessels that supply the femoral head. The femoral neck can be shortened to aid in reduction without tension on the feeding vessels. Developed by Dunn4 in England and modified in Bern, Switzerland, this method is now used in many North American centers. The purpose of this paper is to describe the role of in situ stabilization as a treatment method for acute, unstable SCFE and to briefly review the reported results of the treatment choices noted above.



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The arguments against in situ pinning include that some cases are simply too severe to consider in situ pinning. The displaced femoral epiphysis may be positioned at right angles to the femoral neck. Thus at least a partial reduction is required in such cases, even though this may increase the risk for AVN. Such cases make the concept of capsular decompression more attractive.6 In considering current treatment options for acute unstable slips, simple, closed in situ fixation alone may no longer be the best treatment choice. Because some cases require partial reduction, some authors advise opening the hip capsule anteriorly to minimize intraarticular pressure (and the risk for AVN) for an unstable slip.6

PARSCH METHOD (PARTIAL REDUCTION) DESCRIPTION OF TREATMENT CHOICES Decision making in selecting the best treatment for acute unstable SCFE focuses on 2 important factors. One is the need to avoid AVN, and for most surgeons and patients, this is the paramount consideration. The second major factor is the quality of the joint articulation after slip stabilization. For an acute unstable slip, where the femoral head is often markedly displaced, pinning in situ might decrease the chances for AVN, but would leave the joint deformed, requiring a subsequent reconstructive surgery.

IN SITU STABILIZATION The treatment philosophies of in situ stabilization have been based on the important long-term outcome studies of patients studied by Boyer et al.5 Their study suggested that in situ fixation was the most satisfactory treatment for almost all slips (Fig. 1). Even more severe stable slips had better results when pinned in situ as compared with patients in whom reduction was attempted. They did note that in 12 acute slips (which were reduced), 3 developed AVN. The strongest reason for in situ pinning is that the technique for surgical stabilization of the slip is well understood; although, the incidence of subsequent AVN remains problematic. With the addition of open capsulotomy to decompress any hematoma, the method likely becomes safer.6 In addition, SCFE is a common condition which should have treatment options that can be performed by a typical orthopaedic surgeon. As almost every orthopaedic surgeon knows how to “pin a hip,” most have the skills to perform a safe, effective in situ pinning of SCFE. The in situ treatment approach is further supported by the fact that urgent stabilization is required to minimize the chances of AVN. In situ fixation implies acceptance of some residual deformity that needs to be considered as “cam impingement” can cause articular damage and premature arthritis. This deformity may require correction with a late osteotomy; however, this osteotomy can be performed at a referral center because there is no urgency as to when it should be performed.

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The compromise method, published by Parsch et al,3 seems to be a good option for the acute, unstable slip, in that it decompresses the hip joint and allows open, “guided” partial reduction. Although some controversy remains regarding whether hip joint pressure is increased in SCFE, Herrera-Soto et al6 performed a study on patients with unstable slips and found that interosseous pressure was elevated before treatment. They noted an increase in intra-articular pressure after a manipulative reduction only, and reported that this pressure could be decreased by capsulotomy. With the Parsch method the patient is placed on a regular operating table to avoid any fracture table stresses to the vascular structures of the hip, and an anterior arthrotomy is performed with a longitudinal capsulotomy. This allows decompression of any potential increase in intraoperative pressure. The femoral head and neck are visualized and the degree of acute slip can then be evaluated. Parsch has found that one can then determine any chronic deformation and then partially reduce the epiphysis only to the point where it had been located just before the acute event. The slip is then stabilized with pins or screws (Fig. 2). This avoids overreduction of the epiphysis, which would increase the risk for AVN, particularly if there were a component of chronic epiphyseal movement before the acute event. The published series from Parsch suggests a 5% AVN rate, which is remarkably lower than other publications.

RESIDUAL JOINT DEFORMITY AND TREATMENT METHOD Joint deformity also must be considered when doing any type of partial reduction. Abraham et al7 studied the proximal femora of 2 groups of patients who had relatively early total hip arthroplasty in adult life. One group had prior SCFE as the cause of their premature arthritis, and the other group had primary osteoarthritis. The patients with post-SCFE deformity required total hip arthroplasty 11 years earlier than those who had primary osteoarthritis. They noted the pistol grip type of deformity at the femoral head and neck junction, which was r

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Acute and Unstable SCFE: In Situ Fixation

FIGURE 1. A, Anteroposterior and frog views of the pelvis in a 12-year-old boy with a severe, unstable SCFE of the left hip. B, The left hip was pinned in situ, with 2 screws used (as very unstable slips can continue to migrate when only 1 screw is used). The right hip was prophylactically pinned. C, Follow-up at 1-year postoperatively. Excellent remodeling is occurring and the patient is asymptomatic. SCFE indicates slipped capital femoral epiphysis.

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FIGURE 2. A, Radiographs of a 10-year-old girl who had occasional left hip aching and then had a fall with severe left hip pain. Note acute unstable left hip SCFE (Image courtesy of K. Keeler). B, Intraoperative views. Parsch-type approach with capsular decompression, partial reduction, and screw fixation (Image courtesy of K. Keeler). C, Films taken 9 months after surgery. The hip is functioning well. SCFE indicates slipped capital femoral epiphysis.

found to impinge on the acetabulum. This creates an abnormal articulation and subsequent wear of the thinner superolateral articular surface of the femoral head. They

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confirmed that this anatomy, with a resulting lack of head and neck offset in an unreduced or partially reduced slip, potentially accelerates wear in the hip joint. r

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Acute and Unstable SCFE: In Situ Fixation

FIGURE 3. A, AP and frog radiographs of a 13-year-old boy with unstable SCFE of the right hip. B, Images after treatment with open anatomic reduction using the modified Dunn procedure. C, Radiographs taken 1-year postoperatively. This hip was successfully treated with anatomic reduction. SCFE indicates slipped capital femoral epiphysis.

Their paper suggested that in treating SCFE, the strong central articular cartilage of the femoral head should be returned to the dome of the acetabulum. In traditional methods, with in situ fixation of a slip, this would be achr

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ieved by performing a late proximal femoral osteotomy of the Southwick or Imhauser type. The goal of such an osteotomy is to flex the hip in the intertrochanteric area to bring the femoral head into the acetabular dome. www.pedorthopaedics.com |

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Abraham noted that the peripheral articular cartilage on the femoral head is substantially thinner than the central articular cartilage and, therefore, a flexion osteotomy is required for this redirection. It should be noted that if one performs an in situ fixation of a relatively severe slip and then removes the anterior bump of the femoral neck to prevent impingement, one still does not have central cartilage directed into the center of the acetabulum.

ANATOMIC REDUCTION Anatomic reduction of the femoral head, by the modified Dunn procedure, further developed and popularized by Ganz and colleagues, in Bern, Switzerland,8–12 was designed to provide anatomic reduction of the femoral head atop the femoral neck (using a technique of surgical hip dislocation) with great attention given to the superoposterior vascular blood supply to the epiphysis. Because extensive vascular studies were performed on cadavers to develop this approach, the method is designed to minimize the risk for AVN. In addition, anatomic reduction minimizes the risk for premature joint deterioration. The initial reports from Switzerland reported a low AVN rate (Fig. 3). The technique is demanding and requires careful training. The surgeon must take extreme care to protect the posterior leash of vessels and to protect them throughout the surgical procedure. The femoral neck often needs to be shortened to allow repositioning of the head upon the femoral neck. Although the Swiss reports are promising, the North American experience has shown a higher percentage of AVN (Fig. 4) following this procedure, with Sankar et al13 recently reporting a 26% AVN rate.

DISCUSSION

FIGURE 4. A, Three-dimensional CT images of an acute unstable SCFE (left hip) in a 12-year-old boy (plain films not available). B, Radiographs taken after anatomic reduction using the modified Dunn method. The right hip had prophylactic pinning. C, Films taken 4 months postoperatively suggest satisfactory healing. D, Radiographs taken 9 months postoperatively. The patient now has severe avascular necrosis and may require an early total hip replacement. SCFE indicates slipped capital femoral epiphysis.

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Many issues remain in both defining the “unstable slip” and in determining the safest, most predictable method for treatment. Our experience in treating unstable slips both with the closed and open method has brought up a concern regarding our ability to exactly classify a stable versus unstable slip.2 Loder noted that stability can be defined either clinically or radiographically with the clinical method determined by whether the patient can walk. Imaging methods include an ultrasound study to detect a hip effusion. The presence of a hip joint effusion without radiographic signs of remodeling confirms an unstable slip. Many North American centers (including ours) do not routinely perform an ultrasound study and use the, perhaps less reliable, clinical method. Examination of SCFE at the time of open anatomic reduction has made declaration of stability more difficult.2 We have seen hips that we called unstable on clinical grounds, yet when the hip was opened, well-formed callous was noted in the area between the metaphysis and the displaced epiphysis. It is possible that the episode of pain which led to the patient’s urgent presentation was due to synovitis/impingement without true instability. In such cases, if one proceeds with anatomic reduction, the callous must be removed and the slip “destabilized” r

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before anatomic reduction can be achieved. In situ stabilization may be a safer method. Even though exact confirmation of stability may be difficult in some cases, general application of the concept remains critical in analyzing SCFE treatment methods. We have not experienced AVN with in situ pinning in a series of 64 stable SCFE cases treated in our center over the last 5 years. During the same time period, 10 stable slips were treated with anatomic reduction and 2 developed AVN. Unstable slip treatment remains problematic. Over the same time period, we treated 7 unstable slips with in situ fixation and 3 of the 7 developed AVN (43%). We also treated 7 unstable slips using the modified Dunn method, and 2 of the 7 developed AVN (29%).14 This closely corresponds with the report by Sankar et al13 noted above. Treatment of the acute, unstable slip remains unsatisfactory. More scientific assessment of blood flow before, during, and following surgical treatment will help to make its treatment more predictable.

SUMMARY With current understanding, there is limited support for in situ fixation alone for acute unstable SCFE. Because of the high risk for AVN in any unstable slip, we understand the trend toward anatomic reduction (Ganz method); however, the procedure is demanding and only a few North American centers have the concentrated patient volume (to develop expertise) and a “call coverage” system to implement this surgical method. Even in these centers, the AVN rate remains concerning. Referring all acute unstable slips to major referral centers remains economically impractical and potentially delays treatment; furthermore, the concept does not yet have the firm literature support required to justify the expense and organization of such a system. Faced with these limitations, we suggest the method of Parsch, which includes urgent, open treatment of acute unstable slips with the capsule opened anteriorly and the joint decompressed, followed by partial reduction and pinning. We view this to be the safest method currently available for treating acute unstable SCFE. An AVN rate of

Acute, unstable, slipped capital femoral epiphysis: is there a role for in situ fixation?

Slipped capital femoral epiphysis, a common disorder in adolescents, may be increasing in incidence in North America because of the obesity epidemic. ...
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