Faculty Bibliography

BACKGROUND: There is a dearth of literature examining the causes of cam-type femoroacetabular impingement (FAI) and when such morphology appears. The purpose of the current study was to analyze how the ossific portion of the proximal femur develops over time with respect to standard cam-type FAI parameters. METHODS: A collection of 193 femurs from cadavers aged 4 to 21 years were evaluated. The age, sex, ethnicity, and status of the proximal femoral physes (open or closed) of each were recorded. Each specimen was digitally photographed in standardized anteroposterior and modified axial positions. From these photographs, the anterior offset, anterior offset ratio (AOR), and alpha-angle were determined. A cam lesion was defined as an alpha-angle >55 degrees on the lateral view. RESULTS: The mean age of the specimens was 17.5+/-4.2 years. The majority were male (69%) and African American (79%) with closed physes (78%). There were significant differences among discrete age groups with respect to alpha-angle (P=0.01), anterior offset (P<0.01), and AOR (P<0.01). In addition, younger femurs with open physes had a significantly higher mean alpha-angle (P<0.01), lower mean anterior offset (P<0.01), and higher mean AOR (P<0.01) compared with older ones with closed physes. Specimens defined as having a cam deformity had a statistically higher alpha-angle (P<0.01) and lower anterior offset (P<0.01), but there was no difference in AOR values compared with specimens without a cam lesion (P=0.1). CONCLUSIONS: The apparent decline in alpha-angles as age increases indicates that the traditional alpha-angle in younger patients measures a different anatomic parameter (ossified femur excluding the cartilaginous portion) than in older patients (completely ossified femur). This suggests that the bony alpha-angle is inappropriate in the evaluation of cam lesions in the immature physis. The AOR, rather than the anterior offset, may be more accurate in the evaluation of the growing proximal femur. CLINICAL RELEVANCE: This study provides novel insight into, and enhances the understanding of, the development of cam-type FAI.

INTRODUCTION: Growth modulation has been recognized as early as 1905 in the orthopaedic literature. It uses growth potential to correct deformities with an easy procedure; thus avoiding osteotomies and their associated risks if the problem is to be addressed later in adulthood. The tension band plate (TBP) has replaced the Blount staple for growth modulation due to its ease of application and better complication profile, namely implant breakage and extrusion. However, the unpredictable time to effect of the TBP is still an issue. We are not aware of any study that has looked into the use of a locking plate compared to a non-locked plate in growth modulation. We hypothesize that the locking plate will be superior to the nonlocking plate in predicting the time to effect in growth modulation. METHODS: A Sawbones model was created to simulate pediatric metaphyseal bone. One-millimeter thick medium-low density closed-cell urethane foam was fixed to medium density, open-cell urethane foam using Gorilla glue (Figure 1b). Blocks were then made measuring 3x2x2.5 cm in dimensions. A two-hole foot plate (THLP) that allowed for locking and non-locking configurations was selected to test the hypothesis. The test specimen consisted of two blocks held together using the implant being studied (Figure 1a). Metal clips were applied on the contralateral side of the block for loading purposes. There were four test groups in this study. Groups 1 and 2 had the conventional TBP with parallel and divergent screw configurations, respectively. Groups 3 and 4 had the THLP in non-locked and locked configurations, respectively. The four groups were tested using a pulley loading apparatus (Figure 1c) with weight increments of 500 grams to a maximum of 2500 grams. Distraction across the blocks was measured using a caliper. The data obtained was then analyzed using the Kruskall-Wallis one-way analysis of variance on Stata to look for differences in distraction among the groups. RESULTS: There was a significant difference between the groups at loads of 1500 grams and higher (Figure 2). A Post Hoc Dunn's test was then performed to look into the source of difference. There was a significant difference showing a superiority of the THLP in the locking configuration over the conventional TBP in both parallel and divergent screw configurations. There was also a significant superiority, though to a lesser extent, of the THLP in the locking over the non-locking configuration (Figure 3). DISCUSSION: The aim of guided growth is to achieve a point fixation on one side of the physis that will result in a pressure gradient, leading to an incremental increase in growth away from that point fixation. Traditionally the Blount staple achieved this desired effect. The complications of the staple, namely extrusion and breakage, made this implant less appealing. The TBP replaced the Blount staple for its ease of application and better complication profile. Biomechanical studies looked into the best screw configuration to achieve the desired effect and parallel screws were reported to be superior to others. However, the time to effect is still an issue, which may be critical in children with little growth potential remaining. By locking the plate, we achieved a point fixation superior to the non-locked plate and conventional TBP. This is a Sawbone study. Further studies on animal models are needed to confirm these findings and to elucidate whether the locked plate maintains the same safety profile as the TBP

BACKGROUND: Dysplastic hip may present with acetabular retroversion with or without femoral retroversion. This retroversion, if not accounted for when performing a periacetabular osteotomy (PAO), will lead to anterior hip pain and early osteoarthritis. A reverse PAO involves anteverting the acetabulum while still obtaining lateral coverage. The purpose of this study was to investigate the relationship between rotational malalignment of acetabulum and femur on 2-dimensional computed tomographic (CT) scans of hips that underwent Bernese PAO and its role in the surgical decision making. METHODS: This retrospective, case-control study examined and compared preoperative 2-dimensional CT scans of hips that underwent reverse PAO to the hips that underwent traditional PAO. RESULTS: Twelve hips underwent reverse PAO from 2005 to 2010. Twelve hips were randomly selected from a cohort of 52 hips that underwent traditional PAO during same time period. Hips that underwent reverse PAO showed crossover sign on preoperative radiographs, but not on postoperative radiographs. Crossover sign was negative preoperatively and postoperatively on hips that underwent traditional PAO. The 2 groups were similar in regards to preoperative lateral center-edge angle, acetabular index, and anterior center-edge angle on plain radiographs and showed significant improvement after surgery.On preoperative CT scans both acetabulae and femurs were retroverted in reverse PAO group. Comparison of the 2 groups demonstrated that acetabular version (16.5+/-4.9 degrees vs. 25.3+/-5.6 degrees, P=0.001), femoral version (12.8+/-10.4 degrees vs. 31.9+/-8 degrees, P<0.001), and McKibbins Instability Index (29.3+/-11.9 degrees vs. 57.1+/-9.8 degrees, P<0.001) were significantly lower for the reverse PAO than the traditional PAO group. Anterior Acetabular Sector Angle (determines anterior coverage) was significantly higher in reverse PAO group, 53.1+/-13.7 degrees versus 39.7+/-10.4 degrees (P=0.013). CONCLUSIONS: Retroverted acetabulae seem to be associated with reduced femoral version. Given that retroverted acetabulum and retroverted femur have additive effect and increase chances of anterior hip pain, preoperative identification of correct acetabular, and femoral version by CT scan or MRI is necessary to determine which hip need reverse PAO as opposed to traditional PAO. LEVEL OF EVIDENCE: Level III-Therapeutic.

Gradual distal fibula lengthening (DFL), in conjunction with other procedures, was used to correct ankle valgus and short fibulae in three pediatric patients with multiple hereditary exostoses (MHE). The average amount of DFL was 15 mm with a mean follow-up of 2.9 years. Final radiographs showed that all three patients had a stable ankle mortise without evidence of talar tilt or widening. In conclusion, gradual DFL has the advantage of restoring anatomy in cases of ankle valgus due to short fibulae and MHE, and may be performed in conjunction with other procedures.

BACKGROUND: The most widely used treatment for slipped capital femoral epiphysis (SCFE) is in situ fixation. In an attempt to reduce the chances of impingement, osteoarthritis, and osteonecrosis, surgeons have started adopting newer surgical techniques. The purpose of this study was to determine the current pattern of treating SCFE. METHODS: A questionnaire was sent electronically to all of the members of the Pediatric Orthopaedic Society of North America. The data were analyzed dividing surgeons into academic versus private practice, years of practice, and number of SCFEs treated per year. RESULTS: Of 990 members, 277 (28%) responded to the survey.Type of practice (academic, n=181 vs. private, n=51): For unstable severe SCFE, surgeons in academic practice use the surgical hip dislocation (SHD) approach significantly more frequently (35.7% vs. 14.9%; P=0.02). A radiolucent table is used significantly more frequently in academic practice for both stable (50.6% vs. 29.8%; P=0.01) and unstable (39.6% vs. 15.2%; P=0.002) SCFE. Fully threaded cannulated screws (44.4% vs. 27.1%; P=0.03), open capsular decompression (63.9% vs. 32.4%; P=0.001), contralateral pinning (79% vs. 58.7%; P=0.005), and postoperative magnetic resonance imaging (MRI) (15.5% vs. 3.9%; P=0.03) are significantly more frequent in academic practice.Years of practice (15 y, n=140): For severe stable SCFE, surgeons practicing for /=10, n=136): For unstable severe SCFE, surgeons treating >/=10/y perform SHD significantly more frequently (38.6% vs. 26.1%; P=0.02) and do in situ fixation with manual reduction significantly less frequently (11.8% vs. 21.8%; P=0.02). Radiolucent table (54.3% vs. 38%; P=0.01), 7.5 mm screw versus 6.5 mm (62% vs. 45.4%; P=0.01), contralateral pinning (78.9% vs. 67.8%; P=0.04), postoperative MRI (17.6% vs. 9.3%; P=0.04), and postoperative computed tomography (14.7% vs. 7%; 0.04) are significantly more frequent among surgeons doing >/=10/y. Elective implant removal is more common among surgeons treating <10/y (16.2% vs. 6.9%; P=0.02). CONCLUSIONS: Treatment of SCFE varies significantly depending on the surgeon's type of practice, years in practice, and numbers treated per year. Surgeons in academic practice, surgeons with