Shared morphology of slipped capital femoral epiphysis and femoroacetabular impingement in early-onset arthritis

Subtle Slipped Capital Femoral Epiphysis Is not Associated With Idiopathic Cam Morphology

BACKGROUND

The etiology of idiopathic cam morphology remains unclear. One theory suggests that subtle slipped capital femoral epiphysis (SCFE) leads to proximal femoral changes resulting in cam morphology. The purpose of this study was to evaluate the association between subtle SCFE and cam morphology in a large osteological collection.

METHODS

We examined 962 cadaveric hips to measure 2 markers of cam morphology, alpha angle and anterior femoral head-neck offset (AHNO), and a validated, objective marker of subtle SCFE deformity (calcar ridge line offset). When the femur is viewed medially, the calcar ridge line extends from the lesser trochanter proximally along the postero-inferior femoral neck and points toward the fovea. In SCFE-like deformity, the fovea deviates posteriorly from this projected line. Pearson correlations were performed to evaluate for possible association of calcar ridge line offset with alpha angle and AHNO. In addition, a multiple regression analysis was performed to determine the influence of age, alpha angle, and AHNO on calcar ridge line offset.

RESULTS

There was no clinically relevant association between the calcar ridge line offset and alpha angle (r=-0.02, P=0.58) or AHNO (r=0.08, P=0.012). Furthermore, specimens whose calcar ridge line deviated 1 SD above the mean (more SCFE-like deformity) had a smaller alpha angle (46.6±9.1 vs. 48.3±10.6, P=0.046) and greater AHNO (0.83±0.19 vs. 0.77±0.16, P<0.001), both reflecting less cam-like morphology. On regression analysis, increasing age and increasing AHNO (decreased cam morphology) predicted increased calcar ridge line offset, though the model accounted for only 1.2% of the variance.

CONCLUSIONS

Subtle SCFE-like deformity, as objectively measured from the calcar ridge line, was not predictive of more cam-like morphology, and in fact mild opposite associations were found. Further study is needed to identify other potential etiologies of idiopathic cam morphology.

CLINICAL RELEVANCE

We present evidence from a large, well-documented osteological collection indicating that subtle SCFE is not associated with idiopathic cam morphology.

Combined Imhauser osteotomy and osteochondroplasty in slipped capital femoral epiphysis through surgical hip dislocation approach

PURPOSE

Treatment of moderate to severe stable slipped capital femoral epiphysis (SCFE) remains a challenging problem. Open reduction by modified Dunn procedure carries a considerable risk of osteonecrosis (ON). Imhauser osteotomy is capable of realigning the deformity without the risk of ON, but the remaining metaphyseal bump is implicated with significant chondro-labral lesions and accelerated osteoarthritis. We conducted this study to evaluate the efficacy and safety of Imhauser osteotomy combined with osteochondroplasty (OCP) through the surgical hip dislocation (SHD) approach.

METHODS

A prospective series of 23 patients with moderate-severe stable SCFE underwent Imhauser osteotomy and OCP through SHD. The mean age was 14.4 years (13 to 20) and the mean follow-up period was 45 months (24 to 66). The outcome measures included clinical and radiological parameters and Harris hip score (HHS) was used as a functional score.

RESULTS

The mean HHS improved significantly from 65.39 to 93.3. The limb length discrepancy improved by a mean of 1.72 cm. The mean flexion and abduction arcs showed a significant improvement (mean increase of 37.5° and 18.5°, respectively). The mean internal rotation demonstrated the most significant improvement (mean increase of 38.5°). All the radiographic parameters improved significantly; including anterior and lateral slip angles (mean improvement 37.52° and 44.37°, respectively). The mean alpha angle decreased by 39.19°. The articulo-trochanteric distance significantly increased to a mean of 23.26 mm. No cases of ON or chondrolysis were identified.

CONCLUSION

Combined Imhauser osteotomy and OCP through the surgical dislocation approach provide a comprehensive and safe management of moderate to severe stable SCFE.

LEVEL OF EVIDENCE

IV.

Biomechanical Evaluation of the Depth of Resection During Femoral Neck Osteoplasty for Anterior Impingement Following Slipped Capital Femoral Epiphysis

BACKGROUND

Femoroacetabular impingement as a result of slipped capital femoral epiphysis (SCFE) has been treated traditionally with a proximal femoral osteotomy, but open and arthroscopic femoral osteoplasty is becoming increasingly popular. Cam lesions result from excess bone primarily at the anterolateral femoral head-neck junction. SCFEs result from posterior and inferior slippage of the femoral epiphysis, causing the metaphysis to move anteriorly. This study's purpose was to compare fourth-generation sawbones standard femurs with SCFE femurs to determine whether bone resection from the anterior metaphysis results in similar biomechanical properties.

METHODS

A custom fourth-generation composite SCFE sawbone was created with a 30-degree slip angle. Control group consisted of fourth-generation composite standard nondeformed medium femurs. The femoral neck at the head-neck junction was divided into 4 quadrants. All resections were done in the anterolateral quadrant. Twenty SCFE sawbones and 20 standard sawbones were divided into 4 subgroups based on resection depths of 0%, 10%, 30%, and 50% of the metaphysis at the head-neck junction. After resection, all proximal femurs were loaded to failure in an Instron testing machine to determine the ultimate load to failure, stiffness, and energy to failure.

RESULTS

The standard femurs were significantly stronger than the SCFE femurs (P<0.001) and the strength of the femurs decreased significantly as the resection amount increased (P<0.001). Similarly, the standard femurs withstood significantly more energy before failing than the SCFE femurs (P<0.001) and the energy to failure decreased significantly with varying resection amounts (P<0.001).

CONCLUSIONS

SCFE femurs demonstrate a significant reduction in strength and energy to failure after osteoplasty compared with nondeformed femurs in a sawbone model. Strength and energy to failure are inversely proportional to the depth of bone resection.

CLINICAL RELEVANCE

Aggressive femoral neck osteoplasty for treatment of a SCFE deformity may lead to increased risk of fracture. Further studies are necessary to determine the safe depth of resection in a clinical setting.

Origin of Cam Morphology in Femoroacetabular Impingement

Cam morphology of the proximal femur is an abnormal contour of the femoral head-neck junction present in approximately 15% to 25% of the asymptomatic population, predominantly in males. Alpha angle and femoral head-neck offset ratio are 2 objective measurement tools that define cam morphology. Both primary (idiopathic) and secondary cam deformity develops through distinct mechanisms. The cause of primary (idiopathic) cam morphology remains incompletely understood. Mounting evidence suggests that idiopathic cam morphology develops during adolescence through alterations in the capital femoral epiphysis in response to participation in vigorous sporting activity. While the exact cause of epiphyseal extension has not yet been determined, preliminary evidence suggests that epiphyseal extension may reflect a short-term adaptive response to provide stability to the physis at the long-term cost of the development of cam morphology. Commonly recognized causes of secondary cam deformity include frank slipped capital femoral epiphysis, Legg-Calve-Perthes disease, and deformity after fracture of the proximal femur. Recent studies also support subtle slipped capital femoral epiphysis as a unique and silent cause of a small percentage of subjects previously thought to have idiopathic cam deformity.

Femoroacetabular impingement in children and adolescents

PURPOSE OF REVIEW

The present review discusses the etiology, clinical presentation, and management of femoroacetabular impingement (FAI) in the pediatric population, including etiologic and diagnostic controversies, management options, and outcomes.

RECENT FINDINGS

New evidence demonstrates conflicting results regarding how and when primary FAI develops in relation to skeletal maturity. Recent studies also discuss the effects of sex, race, and sports on FAI development and radiographic considerations in the pediatric population. Recent literature demonstrates good to excellent outcomes in the operative management of FAI in children and adolescents.

SUMMARY

FAI is a source of pediatric hip pain and can occur primarily or secondarily. It is characterized by anterior hip pain, made worse with flexion activities, decreased hip internal rotation, and a positive impingement sign. Pathologic values for radiographic measures of FAI are not clearly defined in the pediatric population. As FAI is a risk factor for osteoarthritis, early intervention in specific patients may be indicated. Hip arthroscopy, surgical hip dislocation, or combined mini-open and arthroscopic approaches are utilized, with good to excellent short, and mid-term functional results. Further study is required in the pediatric population to identify potential preventive strategies, to delineate the pathologic radiographic values of FAI, to define specific indications for operative management, and to examine long-term outcomes to determine optimal management.

Twelve percent of hips with a primary cam deformity exhibit a slip-like morphology resembling sequelae of slipped capital femoral epiphysis

BACKGROUND

In some hips with cam-type femoroacetabular impingement (FAI), we observed a morphology resembling a more subtle form of slipped capital femoral epiphysis (SCFE). Theoretically, the morphology in these hips should differ from hips with a primary cam-type deformity.

QUESTIONS/PURPOSES

We asked if (1) head-neck offset; (2) epiphyseal angle; and (3) tilt angle differ among hips with a slip-like morphology, idiopathic cam, hips after in situ pinning of SCFE, and normal hips; and (4) what is the prevalence of a slip-like morphology among cam-type hips?

METHODS

We retrospectively compared the three-dimensional anatomy of hips with a slip-like morphology (29 hips), in situ pinning for SCFE (eight hips), idiopathic cam deformity (171 hips), and 30 normal hips using radial MRI arthrography. Normal hips were derived from 17 asymptomatic volunteers. All other hips were recruited from a series of 277 hips (243 patients) seen at a specialized academic hip center between 2006 and 2010. Forty-one hips with isolated pincer deformity were excluded. Thirty-six of 236 hips had a known cause of cam impingement (secondary cam), including eight hips after in situ pinning of SCFE (postslip group). The 200 hips with a primary cam were separated in hips with a slip-like morphology (combination of positive fovea sign [if the neck axis did not intersect with the fovea capitis] and a tilt angle [between the neck axis and perpendicular to the basis of the epiphysis] exceeding 4°) and hips with an idiopathic cam. We evaluated offset ratio, epiphyseal angle (angle between the neck axis and line connecting the center of the femoral head and the point where the physis meets the articular surface), and tilt angle circumferentially around the femoral head-neck axis. Prevalence of slip-like morphology was determined based on the total of 236 hips with cam deformities.

RESULTS

Offset ratio was decreased anterosuperiorly in idiopathic cam, slip-like, and postslip (eg, 1 o'clock position with a mean offset ranging from 0.00 to 0.14; p < 0.001 for all groups) compared with normal hips (0.25 ± 0.06 [95% confidence interval, 0.13-0.37]) and increased posteroinferiorly in slip-like (eg, 8 o'clock position, 0.5 ± 0.09 [0.32-0.68]; p < 0.001) and postslip groups (0.55 ± 0.12 [0.32-0.78]; p < 0.001) and did not differ in idiopathic cam (0.32 ± 0.09 [0.15-0.49]; p = 0.323) compared with normal (0.31 ± 0.07 [0.18-0.44]) groups. Epiphyseal angle was increased anterosuperiorly in the slip-like (eg, 1 o'clock position, 70° ± 9° [51°-88°]; p < 0.001) and postslip groups (75° ± 13° [49°-100°]; p = 0.008) and decreased in idiopathic cam (50° ± 8° [35°-65°]; p < 0.001) compared with normal hips (58° ± 8° [43°-74°]). Posteroinferiorly, epiphyseal angle was decreased in slip-like (eg, 8 o'clock position, 54° ± 10° [34°-74°]; p < 0.001) and postslip (44° ± 11° [23°-65°]; p < 0.001) groups and did not differ in idiopathic cam (76° ± 8° [61°-91°]; p = 0.099) compared with normal (73° ± 7° [59°-88°]) groups. Tilt angle increased in slip-like (eg, 2/8 o'clock position, 14° ± 8° [-1° to 30°]; p < 0.001) and postslip hips (29° ± 10° [9°-48°]; p < 0.001) and decreased in hips with idiopathic cam (-7° ± 5° [-17° to 4°]; p < 0.001) compared with normal (-1° ± 5° [-10° to 8°]) hips. The prevalence of a slip-like morphology was 12%.

CONCLUSIONS

The slip-like morphology is the second most frequent pathomorphology in hips with primary cam deformity. MRI arthrography of the hip allows identifying a slip-like morphology, which resembles hips after in situ pinning of SCFE and distinctly differs from hips with idiopathic cam. These results support previous studies reporting that SCFE might be a risk factor for cam-type FAI.

Arthroscopic treatment of mild to moderate deformity after slipped capital femoral epiphysis: intra-operative findings and functional outcomes

PURPOSE

To identify intra-articular pathology during arthroscopic osteochondroplasty for slipped capital femoral epiphysis (SCFE)-related femoroacetabular impingement and determine functional outcomes after treatment.

METHODS

Nine hips in 9 patients (6 male and 3 female patients; mean age, 17.5 years; age range, 13.5 to 26.9 years) underwent hip arthroscopy for femoroacetabular impingement after in situ pinning of the SCFE. Medical records, radiographs, and intraoperative images were reviewed to determine the severity of disease and damage to the hip joints. For all patients, we obtained the modified Harris Hip Score and Hip Outcome Score (HOS) preoperatively and at a minimum of 12 months postoperatively, as well as a Likert scale of perceived change in physical activity.

RESULTS

All 9 treated patients had some degree of labral or acetabular cartilage injury at the time of arthroscopy, which was a mean of 58.6 months (range, 18 to 169 months) after in situ pinning. The alpha angle improved from 75° preoperatively to 46° postoperatively (P < .001). The mean follow-up period was 28.6 months (range, 12.6 to 55.6 months). The mean modified Harris Hip Score improved from 63.6 preoperatively to 91.4 postoperatively (P = .005). Similarly, the mean HOS activities-of-daily living scale improved from 70.2 to 93.3 (P = .010), and the HOS sports scale improved from 53.4 to 88.9 (P = .004). Most patients reported significant improvement on a physical-activity Likert scale, with 4 reporting much improved, 3 reporting improved, and 1 reporting slightly improved physical activity. One patient reported an unchanged activity level. No patients reported a worse activity level after surgery.

CONCLUSIONS

Post-SCFE cartilage and/or labral damage develops in patients with symptomatic mild to moderate SCFE deformity, and arthroscopic treatment improved functional outcomes in a small cohort of patients at short-term follow-up.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.