Slipped capital femoral epiphysis (SCFE) continues to be a challenging clinical condition for several reasons, the first 3 are related to the low incidence of this condition. First, SCFE is relatively uncommon with an incidence of 1 in 10,000 cases which makes study of large SCFE populations difficult; second, the 2 types of SCFE classified by the Loder et al1 classification divide the patients into stable and unstable groups further decreasing the numbers; third, “advances in surgical technique” have provided more options to treat these patients necessitating further division of the numbers; fourth, the outcomes of treatment are strongly influenced by the general health condition of these patients and finally, the differences between North American patients and European and Asian families with respect to body mass index and general health make comparison between these populations difficult.
This paper will be divided into describing the diagnosis and management of 3 clinical entities: stable SCFE; the unstable SCFE and finally, the healed SCFE with significant deformity. The data and information provided will be drawn from 3 main sources: the current literature, my own personal experience and finally, the experience of the representative sample of the polled North American surgeons who either have a focus on hip surgery or perform hip surgery as a part of their general pediatric practice.
The long-term outcome following treatment of SCFE is challenging to study as many patients are difficult to find and often have moved away from the original location where they received treatment. The current long-term reports reviewed the outcome of patients who have treated with in situ pinning, the standard treatment in North America. Larson et al2 reviewed 146 hips at an average16 year follow-up and reported 21 (12%) patients having reconstructive surgery and an additional 8 (5.5%) requiring total hip arthroplasty, with 33% of the remaining hips having some painful symptoms. The average visual analog scale score was 23.4 with worse visual analog scale pain and stiffness scores in those patients who had more severe residual SCFE; however, the overall average Harris Hip score (HHS) was 90. These data provide some conflicting information as the overall HHS was actually quite good but a number of patients had previous reconstructive surgery including total hip arthroplasty and a number of the remaining patients were painful. The Iowa experience reported by Carney et al3 followed 124 patients at 41-year follow-up showing worse Iowa hip scores with more severe SCFE and when reduction was attempted acutely or when realignment was performed for residual deformity. Escott and colleagues reported our experience of 64 patients at Texas Scottish Rite Hospital following in situ pinning to not only determine hip function but also to evaluate the general health outcome of these patients. At 20-year follow-up, patients were more likely to have diabetes, obesity, and hypertension when compared with the US population and 72% of patients were considered to be obese defined by a body mass index of >30 cm/kg2.4 In this group of patients there was no associate between slip angle and the short form-12, Harris Hip score, or the University of California at Los Angeles activity score. Although not specifically reported in that study, the average modified Harris Hip score was 84.4 with 29% of patients having a fair or poor score (Fig. 1).
Displacement of the epiphysis primarily posteriorly, with some medial displacement or when viewed differently as the proximal femoral metaphysis displaced anteriorly, there is significant potential damage to the hip joint. Femoroacetabular impingement (FAI) is a term describing the abutment of the femoral head and the acetabulum due to some abnormal morphologic change in the acetabulum and/or proximal femur.5 The morphologic changes in SCFE provides perhaps the most severe example of FAI as both pincer (abnormally deep-seated acetabulum) and cam (abnormal proximal femur) are present. On the acetabular side there is retroversion and profunda or protrusion,6,7 whereas on the femoral side there is a significant cam deformity due to anterior displacement of the metaphysis. Clinical studies show the damage created by this abnormal relationship with a high incidence of damage which worsens with more severe deformity. Rab et al8 used finite element analysis to define progressive acetabular injury with mild, moderate, and severe SCFE. Leunig et al9 and the Swiss group reported on 13 consecutive hips with an injury pattern first affecting the labrum and then the acetabular cartilage. In total, 39 stable SCFE patients were reviewed by Sink et al10 following an open surgical hip dislocation procedure in which 34 patients had an abnormal labrum, whereas 33 patients had cartilage injury.
DIAGNOSIS AND MANAGEMENT OF THE STABLE MILD SCFE
In North America, we continue to be plagued by a missed diagnosis when patients present to a health care provider with a stable SCFE as the provider may be distracted by the thigh or knee pain and no specific hip symptoms (Fig. 2). It is important to help with the education process of our primary care providers who see many types of patients requiring a significant breadth of knowledge. When SCFE patients are identified in the emergency room or in the clinic it provides an opportunity for the orthopaedist to point out the important distinguishing SCFE characteristics in the history and physical examination. This should lead the practitioner to order an anteroposterior and frog-leg lateral radiograph which confirms the diagnosis.
For the stable SCFE with mild deformity the standard agreed-upon treatment is in situ pinning with a single screw and generally leads to satisfactory results with little risk of complication (Fig. 3). Some consider performing an osteochondroplasty at the completion of the pinning when patients have <15 degrees of internal rotation at 90 degrees of hip flexion. This is relatively new thinking with little evidence for improvement over traditional methods. In addition, only small deformities can be adequately addressed with this technique and many of these mild abnormalities will not be symptomatic and remodel with time.11,12 When the patient is skeletally immature with an open triradiate cartilage, prophylactic pinning of the opposite side is appropriate13 (Fig. 3).
DIAGNOSIS AND MANAGEMENT OF THE STABLE SEVERE SCFE
For the severe stable SCFE, the traditional treatment has been in situ pinning followed by delayed reconstructive surgery if symptoms arise (Fig. 4). With publication of more “long-term” 20-year follow-up, it is clear that the outcomes are not always great and there is a strong suggestion that an inverse relationship between slip severity and outcome is seen. Coupled with the development of more aggressive osteotomy techniques that allow for greater correction at the site of deformity, there has been a movement toward deformity correction to prevent intra-articular damage and to prolong the longevity of the hip. In addition to the traditional method of treatment just described, 2 other options provide deformity improvement: pinning in situ together with an intertrochanteric osteotomy and a corrective osteotomy through the physis to gain correction through the area of deformity as described by Dunn and colleagues.14,15 Reduction of the epiphysis with internal fixation is generally performed through a surgical hip dislocation approach as described by Ganz and colleagues to allow for full access to the hip and safe reduction of the epiphysis to limit vascular changes to the femoral head.16 The poll of North American surgeons demonstrated an equal distribution choosing 1 of the 3 options with the most aggressive surgeons choosing to perform a surgical hip dislocation/modified Dunn osteotomy. It should be remembered that in situ pinning for stable SCFE has essentially no risk for avascular necrosis (AVN) which is not the case when more aggressive treatment like a modified Dunn osteotomy is carried out.
MANAGEMENT OF THE UNSTABLE SCFE
The important distinction between the stable and unstable SCFE directly predicts the likelihood of AVN with the Loder et al1 paper describing an incidence of 47% for unstable SCFE compared with essentially 0% with stable SCFE. Today, the incidence of AVN following treatment of an unstable SCFE is lower as summarized by Zaltz et al17 who compiled more recent studies and determined the incidence to be 23.9%. The studies summarized in this manuscript report a wide occurrence of AVN and is dependent on the surgical technique, the timing of reduction, the method of monitoring the blood flow and other factors.
Fixation with 2 screws is generally thought to be necessary in the unstable SCFE and the polled surgeons unanimously agreed with this regardless of the method of reduction (incidental, formal, or open). The time to treatment generally falls into 2 categories: urgent reduction (but not emergently) in two thirds of surgeons, whereas the remaining felt that treatment within 24 hours was satisfactory and would not jeopardize flow to the epiphysis. Following surgical treatment, 60% of surgeons recommended watchful waiting with serial radiographs, whereas the remaining were split between obtaining a bone scan (30%) versus an magnetic resonage imaging (MRI). In the poll 30% of surgeons would choose the surgical approach depending on whether (and how much of) a reduction was seen with an incidental repositioning. For these surgeons, an adequate reduction would be followed by in situ pinning, whereas a formal open reduction would be performed if inadequate. The remaining 70% of surgeons were evenly split between performing a surgical hip dislocation/modified Dunn osteotomy and in situ pinning with joint decompression (Fig. 5).
It is unclear when the avascular event occurs. A selective angiography study strongly suggests continued displacement of the epiphysis resulting in obstruction of the lateral epiphyseal vessels while reduction of the displaced epiphysis restores flow.18 It is generally thought that the femoral epiphyseal blood flow is present at the time of the injury and in the process of performing reduction or fixation or some other event surrounding the process of surgery, the blood flow is jeopardized. With the introduction of pressure and flow measurement tools it is possible to understand the status of the perfusion to the epiphysis in hopes of predicting long-term viability of the femoral head.19 These monitors have been typically used in the setting of an open technique; however, they are now being used during percutaneous pinning when the catheter is sent down the center of the screw tract following pinning. Schrader et al20 recently reported on 23 hips, both stable and unstable, in which the flow was measured at the time of a percutaneous pinning and showed no evidence of AVN. In the unstable SCFE setting, the monitoring identified some hips in which femoral head perfusion was low which prompted the surgeons to decompress the capsule further with subsequent restoration of epiphyseal flow.
The open reduction technique using the surgical hip dislocation procedure became popular with Reinhold Ganz’s description of the approach to gain access to the hip and this provided greater exposure of the head when performing the procedure as described by Dunn and colleagues.15,21 The early results were very promising with the report from the combined Bern, Switzerland, and Boston series showing no patient with AVN following this approach for both stable and unstable SCFE. This was followed by a couple of studies reporting a much higher incidence of AVN of 26% by Sankar et al22 and 29% by Souder et al.23 The challenge is that an unstable SCFE is a very rare condition and so experience and data collection are very slow to accumulate. The patients often present with a variety of different characteristics that may make risk adjustment for the occurrence of AVN difficult including the size of the patient, and the timing of presentation relative to the injury. The incidence of AVN must be weighed against other treatments for the same diagnosis, in the same region of the world and treated by the same surgeon. For example, the 29% incidence of AVN in unstable SCFE reported by Souder et al23 should be taken into consideration with respect to the incidence of AVN reported by the same authors of 43% when performing in situ pinning. In the last 18 years at our institution we have favored the open technique with a surgical hip dislocation procedure and modified Dunn technique performed by myself or Dave Podeszwa. We retrospectively reviewed our initial experience from 1999 to 2008 with an overall AVN incidence of 16.6% for the unstable SCFE.24 Since 2008 we have been performing a randomized, controlled trial comparing this open technique with the technique of performing a gentle closed reduction with internal fixation. It is too early to analyze or reveal the results but it is clear that the results seem to be moving toward less complications for both techniques which may be a reflection of several factors including the attention to detail paid to both procedures, the timing of surgery and a dedicated team for this diagnosis. Several things are important for a successful open approach to these hips. First, the retinacular vessel dissection is required to safely isolate the soft tissue sleeve allowing for the epiphysis to be displaced posteriorly providing access to the proximal metaphysis. Second, shortening the femoral neck and partially resecting the posterior and medial femoral neck to allow for a tensionless reduction of the epiphysis onto the metaphysis. Third, secure fixation with 2 screws or multiple wires and compliance with non–weight-bearing until healing occurs. Fourth, the epiphysis must be monitored for perfusion throughout the procedure to provide the best chance for femoral head viability at the time of surgery and hopefully into the future (Fig. 6).
DIAGNOSIS AND MANAGEMENT OF SCFE WITH RESIDUAL SYMPTOMATIC DEFORMITY
The patient who presents with a significant proximal femoral deformity will complain of pain secondary to FAI and/or functional limitations secondary to limited range of motion (ROM). The evaluation of the patient who presents with radiographic findings of a severe SCFE together with symptoms requires an initial good history and physical examination and radiographs. Advanced imaging with an MRI-arthrogram is generally necessary and was preferred by most in the surgeon poll to determine the status of the intra-articular structures. Some surgeons only required radiographs and some add a computed tomographic scan to understand the exact osseous bony deformity.
It is important to determine the issues the patient is facing and what can be potentially done to improve these concerns. When pain is the primary complaint the location of the pain “generator” is important to identify so it can be addressed. Pain located deep in the groin is generally considered to be coming from an intra-articular problem and my preference is for assessment of the joint with an MRI-arthrogram. This will help determine whether enough damage has occurred from impingement to consider a concomitant hip arthroscopy or surgical hip dislocation or whether an osteotomy alone will suffice. A large anterior or anterolateral labral tear should be addressed at the same time. If ROM is the primary problem without significant pain then a proximal femoral osteotomy or a modified Dunn is the only procedure necessary. Because the primary deformity is posterior translation of the proximal femoral epiphysis we generally prefer an Imhauser-type flexion osteotomy with or without rotation of the distal segment depending on the axial plane motion following provisional fixation of the flexion osteotomy. It is important to direct the distal osteotomy perpendicular to the femoral shaft to allow one to rotate the distal segment to restore good ROM of the leg (Fig. 7). The outcome of proximal femoral osteotomies is somewhat mixed with an AVN rate of between 2% and 14% and functional outcomes (with a variety of different scoring systems) of good/excellent in 70% to 90% of patients.25–31 The vast majority of the surgeons polled prefer an intertrochanteric osteotomy and also feel it is necessary to simultaneously look inside the joint through a surgical hip dislocation approach.
A subcapital femoral osteotomy provides the greatest improvement in deformity correction since it is at the level of the deformity; however, it carries the greatest risk of AVN. Generally, this osteotomy is performed when the physis is still open and avoids a true femoral neck osteotomy. In general, it is thought that this procedure should be avoided in the severe stable SCFE or in the previously pinned SCFE unless there are no good options to correct the deformity. These indications could include delayed healing of the physis due to severe deformity with a chronic “nonunion” of the physis or when the deformity is so great that an intertrochanteric osteotomy is not feasible (>60 degrees of deformity). Some of the original series from Ganz and colleagues reported outstanding deformity correction with very low rates of AVN.32 However, with time the results have become more mixed with a relatively high incidence of AVN and postoperative hip dislocations. This has resulted in significant and appropriate caution against performing this procedure except for extenuating circumstances and only when experienced surgeons are present.33,34 Upasani and colleagues reported on 43 very challenging hips treated at a tertiary care center where a modified Dunn procedure was performed with a complication rate (to include AVN)35 of 37% which was related to the severity of the condition and was higher when a low-volume surgeon was in the room.33 Similarly, Anderson et al35 reported on 12 hips with an AVN rate of 17%.
In summary, there is variation in the evaluation and treatment of patients with SCFE in North America most likely due to more opportunities for treatment including more aggressive surgical techniques. However, most would agree that in situ pinning with a single screw remains the treatment of choice for the stable, mild SCFE with a possible arthroscopic approach to correct mild loss of femoral head-neck offset. For the severe, stable SCFE most surgeons would plan to perform in situ pinning with either a concomitant or delayed reconstruction through an intertrochanteric approach. For the unstable SCFE, the traditional methods of fixation following an incidental reduction is being challenged by a more formal closed reduction or the open approach to achieve a reproducible reduction while monitoring the epiphyseal blood flow. Continued study to better understand the pathophysiology of AVN and its risk factors are necessary to avoid this very debilitating complication and will require large series of patients studied in a prospective way.
The author acknowledges those who took the time to provide their answers to the questions he posed: Drs Mark Adamczyk, Jose Herrera-Soto, Simon Kelley, Young-Jo Kim, Kevin Klingele, Randy Loder, Jeff Martus, Todd Milbrandt, Mike Millis, Eduardo Novais, Matt Oetgen, David Podeszwa, Sanjeev Sabharwal, Woody Sankar, Perry Schoenecker, Tim Schrader, Ernie Sink, Mihir Thacker, Salil Upasani, Klane White, Marci Woiczik, and Ira Zaltz.
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