Introduction
Slipped capital femoral epiphysis SCFE (Slipped Capital femoral epiphysis) is a common hip disorder in adolescents that may lead to osteoarthritis in adult life. The natural history of untreated SCFE is a progressive displacement of the femoral head relative to the femoral neck and shaft, with subsequent deterioration of hip function that correlates with the initial severity of the deformity.(1) Increased severity of displacement at presentation has been associated with prolonged duration of symptoms and complications.(2)
Carney et al. reviewed a cohort of patients with SCFE with a mean of 41 years after initial presentation. The development of osteoarthritis worsened with increasing slip severity and when deliberate reduction was performed. They recommended that in situ pinning was the best method for treating SCFE regardless of severity. They noted that the reduction of displacement had a very high complication rate compared to the methods available at the time.(3) Carney et al. also pointed out that avascular necrosis (AVN) and chondrolysis were more common when reduction had been performed and were associated with a worse outcome.(1) The current treatment of SCFE is controversial. Historically, the main goal of treatment was to prevent further displacement of the epiphysis of the proximal femur, optimise function and prevent or delay the development of osteoarthritis.(3) Although AVN and chondrolysis are the most encountered and feared complications, the treatment of severely unstable slip by in situ pinning often leaves the patient with residual femoral head-neck deformity due to lack of reduction.(4) This non-anatomic head-neck deformity may result in femoral-acetabular impingement (FAI), which may, in turn, lead to the early onset of osteoarthritis due to acetabular cartilage damage. For this reason, some surgeons now advocate surgical hip dislocation and reduction of the epiphysis (modified Dunn procedure) as a treatment method for severe slips.(4,5) This achieves the immediate correction of the femoral head-neck deformity and possibly prevents the early development of degenerative changes in the hip.(6)
The current treatment options are percutaneous in situ pinning or surgical hip dislocation and reduction of the epiphysis, with percutaneous in situ pinning remaining the gold standard of treatment for both stable and unstable SCFE. Slipped capital femoral epiphysis occurs in skeletally immature patients with remaining growth and remodelling potential. Long-term studies have shown that the risk of impingement diminishes with time due to metaphyseal remodelling.(4,7) Despite this, concern remains about residual femoral-neck deformity and the risk of FAI observed with pinning in situ of severe slips.
The original Dunn procedure (sub-capital osteotomy) has been able to fully correct the femoral neck deformity in patients with severe SCFE. Still, the rate of AVN (17%) associated with this technique is high.(8) In 1996, Leunig et al. described a modification of Dunn's procedure by Ganz in which sub-capital realignment is combined with surgical hip dislocation. The authors included an open hip dislocation with monitoring and protecting the epiphyseal blood supply. Of the 30 hips treated with this procedure between 1996 and 2005, Lawane et al. reported that none of the patients developed AVN after an average follow-up of four years.(9)
Ziebarth et al. reproduced similar results after using the modified Dunn procedure in 40 patients with SCFE treated at two institutions. Twelve of the 40 patients were classified as unstable SCFE, and the rest were stable. None of the patients had developed AVN at three years’ follow-up, and only one patient developed residual impingement. Three other patients had screw breakage.(10,11) Although the results are promising, the short duration of follow-up and the lack of a control group does not favour this technique over percutaneous in situ pinning.(10)
For this reason, Ziebarth et al. reviewed 43 patients with SCFE at ten-year follow-up. Seventy percent of these patients included were from the previous study. The authors reported no incidence of AVN in this cohort, and no hip was converted to total hip arthroplasty because of osteoarthritis. However, six patients had persistent impingement deformity.(9) A significant limitation of this study is that all the hips included were treated with the modified Dunn procedure irrespective of stability or severity of slip. Only five patients (12%) had unstable slips in the group. Among the unstable slips, the majority (63%) were classified as a moderate slip by the Southwick classification. Stable slips have been shown to have an excellent outcome even when treated with in situ pinning; therefore, the promising results reflected by Ziebarth et al. could be due to the high numbers of moderate slips (63%) and mild slips (23%) included in their study. It would be more relevant to look purely at the unstable severe slips where the likelihood of complications is much higher.(11)
In 2013, Sankar et al. published the results of 27 patients with unstable SCFE (the most extensive series of unstable slips, according to the author) who were treated at five different institutions with a modified Dunn procedure by fellowship-trained paediatric orthopaedic surgeons. Patients had an average of one-year follow-up. Seven of the 27 patients (26%) developed AVN at follow-up, and four patients (14%) had broken implants for which revision was done. The authors concluded that, although this surgical technique can restore the functional anatomy of the hip and possibly prevent early degenerative changes, this technique should be considered with caution because of its complexity and high rate of AVN.(12)
When comparing these two treatment methods (pinning in situ and modified Dunn procedure), Souder et al. found no significant difference in outcome (osteonecrosis) after treating unstable SCFEs. Three of the seven unstable slips treated with in situ pinning developed AVN, while two of the seven unstable slips treated with modified Dunn procedure developed AVN. However, patients with stable SCFEs had a better outcome and no AVN when treated with in situ pinning, compared to the modified Dunn procedure (20% AVN).(13)
This study aimed to assess patient-based outcomes and radiological outcomes of patients with SCFE treated by in situ pinning at our institution.
Methods
We retrospectively reviewed SCFE patients treated at two public hospitals (Charlotte Maxeke Johannesburg Academic Hospital and Chris Hani Baragwanath Academic Hospital) in Johannesburg, South Africa. All patients treated for SCFE with in situ hip pinning and at least two years of follow-up were included in the review. Patients with incomplete radiology records and those who were not contactable were excluded from the study. Twenty-six patients with SCFE treated by in situ pinning at these institutions were retrospectively reviewed between January 2011 and December 2016.
Preoperative X-rays were assessed and classified using the Loder classification, which assesses stability.(14) They were also classified in terms of severity according to the Southwick classification.(15)
The severity of slips was measured on pre-operative radiographs. Outcome measures included the modified Harris hip score (HSS) (16) and a visual analogue pain score.(17) The modified HHS assesses pain, physical activity, and range of motion (ROM) in patients who have undergone hip surgery. The modified HSS score consists of 100 points (0‒100); a score < 70 indicates a poor outcome; 70‒79, a fair outcome; 80‒89, a good outcome; and a score of 90–100, an excellent outcome.
Data was analyzed using descriptive statistics. Statistical tests were performed to evaluate the relationship between the severity of slips and functional outcomes. A P-value < 0.05 was considered statistically significant. Ethical clearance of the study was obtained from the Human Research Ethics Committee of the University of Witwatersrand.
Results
Seventy-six patients with SCFE were identified from the surgical registers. Forty-eight patients could not be traced through the available contact details, and two patients were excluded due to the absence of pre-operative radiographs.
Among those lost to follow-up, 30 patients were not contactable; in addition, twelve patients were from neighbouring countries, five declined to be part of the study, and one died from a brain tumour.
Of the 26 patients included in the study, 16 were males (61.5%), and 10 were females (38.4%). Ten patients (38%) had bilateral hip involvement. The pathology was almost equally distributed between the right and left hip. Twenty of this study's 26 patients (76.9%) were above the 85th percentile for body weight. The mean age at surgery was 12.7 years (9 to 15 years), and the mean follow-up was 3.3 years (2 to 7 years). The hips were classified radiologically into three groups according to Southwick neck-shaft angle: mild SCFE, moderate SCFE, and severe SCFE (Table 4.1). They were further classified clinically into stable and unstable hips, according to Loder.
Demographics and Outcomes.
| Severity of slips | n | Age | BMI | Pain score | Modified HHS |
|---|---|---|---|---|---|
| Mild SCFE | 13 | 11.6 | 28.8 | 1.23 | 96.7 |
| Moderate SCFE | 12 | 13.0 | 31.6 | 2.16 | 92.4 |
| Severe SCFE | 11 | 13.4 | 24.7 | 2.36 | 87.9 |
| Mean (SD) | 12.7(2.1) | 28.3(6.5) | 1.9(1.0) | 92.3(5.7) | |
| P-value | 0.058 | 0.994 | 0.003 |
HHS= Harris hip score
Thirteen hips were classified as mild SCFE with a mean age of 11.6 years. All the hips in this group were clinically classified as stable. The patients had a mean pain score of 1.23 and a mean modified HHS of 96.7.
Twelve hips were classified as moderate SCFE and clinically as stable slips. The mean age was 13 years. The mean pain score was 2.16, and the functional outcome was excellent in all hips, with an average modified HHS of 92.24.
The third group consisted of eleven hips classified as severe SCFE. Five of these hips were clinically classified as unstable, and six of them were stable. The mean age was 13 years. The patients’ mean pain score was 2.36, and their functional score was relatively lower, with an average modified HHS of 87.89.
Patients with mild and moderate SCFE had significantly (p = <0.003) better functional hip outcomes (Harris hip score) than patients with severe SCFE. The subjective pain based on the visual analogue score (Figure 4.1) showed increasing severity with the increase in the severity of the slip, but this was statistically insignificant. (Table 4.1)
Two complications were reported in this study and were both observed in patients with severe and unstable slips. No complications were reported in the mild and moderate SCFE groups or in severe stable slips. The overall complication rate for AVN (1 hip) was 2.78%, and for FAI (one hip) was 2.78%. These two complications occurred in severe slips, further classified as unstable according to Loder's classification. The complication rate within the severe group was 18.1% (Table 4.2).
Discussion
Treatment of SCFE remains controversial, especially for severe and unstable slips. Several approaches for treating SCFE have been described in the literature with different outcomes, especially for acute severe slips (Southwick angle > 50°). As a result, some surgeons (9,10) currently advocate for open surgical hip dislocation and reduction of acute severe slip, as opposed to the traditional method of treatment with in situ percutaneous pinning. The treatment protocol for SCFE patients at our institution has been in situ percutaneous pinning, irrespective of the severity of the slip. Patients presenting with symptomatic deformity after remodelling of the metaphysis would then be considered for surgical correction with Southwick intertrochanteric osteotomy. Anecdotally, we have believed that there is a sufficient remodelling potential of the metaphysis after pinning in situ, and that these patients are satisfied in terms of pain and function.
The twenty-six patients included in this study were followed up for at least two years after surgery, when the affected metaphysis was expected to be fully remodelled. None of these patients, including the patient with impingement, required an osteotomy to improve functional outcomes, as his symptoms were minimal.
The results of our study show a statistically significant difference between the three groups in terms of functional outcome (Harris hip score). The severe SCFE group had an inferior functional outcome compared to moderate SCFE and mild SCFE. There was a reduced functional outcome with progressive severity of the hips. The severe SCFE group had an inferior outcome compared to the mild and moderate groups. The patients with severe SCFE reported more pain than the other two groups; however, this was not statistically significant.
The mild and moderate SCFE groups have achieved excellent functional outcomes. However, according to the interpretation of the modified HHS, the lower functional outcome in the severe SCFE group is nevertheless regarded as a good outcome.
Thirty-one of the 36 hips (86.1%) presented as stable slips, and five hips (13.8%) were noted to be unstable on presentation. All the hips in the mild and moderate SCFE groups were stable and had excellent patient-reported outcomes. The literature supports our findings: Hips with stable slips have excellent outcomes and a low rate of avascular necrosis (0%) compared to hips with unstable slips, which have a high rate of avascular necrosis (47%).(14)
Although our SCFE patients with severe slips were comfortable with daily living activities, two were not capable of performing sporting activities due to limited hip range of motion and pain. These two patients had AVN and FAI, respectively. This suggests that the long-term functional outcome in our study was related to the specific complications rather than the severity of the slip. In their retrospective study, Carney et al. reported a correlation between the severity of the slip and poor outcomes at long-term follow-up.(1)
Our study found a low rate of AVN and FAI for severe SCFE (18% combined) after in situ pinning, and the AVN rate for the whole study population was only 2.78%. This is lower than the AVN rate (10-47%) reported in the literature and much less than the AVN rate reported with the modified Dunn procedure.(12)
Conclusions
Our study suggests that in situ percutaneous pinning using a single screw is safe and effective and has a low rate of AVN. This study also found a correlation between complications and long-term functional outcomes. High patient satisfaction regarding pain and functional capacity suggests that metaphyseal remodelling is effective and might delay the early development of osteoarthritis due to impingement. We found no evidence to support that surgical hip dislocation and reduction of the epiphysis provide a better long-term clinical outcome than in situ percutaneous pinning, regardless of the severity of the slip. Thus, pinning in situ remains the standard treatment for all SCFE cases.