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Zygomatic dysmorphology in unicoronal synostosis
Journal of Plastic, Reconstructive & Aesthetic Surgery (2013) 66, 1096e1102
Zygomatic dysmorphology in unicoronal synostosis Miles J. Pfaff, Kenneth Wong, John A. Persing, Derek M. Steinbacher* Plastic and Reconstructive Surgery, Yale University School of Medicine, New Haven, CT, USA Received 12 December 2012; accepted 6 April 2013
KEYWORDS Unicoronal synostosis; UCS; Zygoma; Zygmata; Malar; Hypoplasia; Volume; Volumetric analysis; Morphometric; Morphometry
Summary Introduction: Unicoronal synostosis (UCS) imparts a fronto-facial deformity, the hallmark feature being orbital and forehead dysmorphology. The facial and malar regions also consistently display asymmetry, however, zygomatic structural characteristics have not been investigated. The purpose of this study is to objectively analyze the zygomata of UCS patients compared to normal controls. Methods: Three dimensional-computed tomographic images and demographic information were obtained from normal control and UCS patients. Volumetric and morphometric analyses were performed and results statistically analyzed. P values <0.05 were considered statistically significant. Results: A total of 68 zygomatic sides were analyzed: twelve control (6 females; mean age: 6.6 months) and 22 UCS patients (10 females; mean age: 5.1 months). The affected side was right in 55% (n Z 12) and left in 45% (n Z 10) of UCS patients. The affected zygomata were volumetrically deficient compared to unaffected and normal control zygomata. Unaffected zygomata demonstrated diminished volume compared to norms. Morphometrically, affected zygomata differed, while both the unaffected and control zygomata were similar. Age stratification revealed marked differences in zygomatic volume and morphometry between the affected and unaffected zygomata was greatest at an early age interval. Conclusion: The affected UCS zygomata are on average smaller compared to unaffected and normal control zygomata. Moreover, distinct morphometric differences exist on the affected zygomata versus both unaffected and control zygomata. These differences are not addressed by commonly employed treatment approaches. Further studies evaluating the growth effect of UCS zygomatic morphology should be entertained. ª 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ1 (203) 785 4559; fax: þ1 203 785 7514. E-mail address: [email protected] (D.M. Steinbacher). 1748-6815/$ - see front matter ª 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bjps.2013.04.025
Zygomatic dysmorphology in UCS
Introduction Unicoronal synostosis (UCS) represents approximately 20e30% of nonsyndromic craniosynostosis.1,2 Fusion of the coronal suture results in anterior plagiocephaly, or “twisted head”, with a requisite orbito-facial asymmetry.3,4 The frontal and orbital dysmorphologies have been welldescribed.5e7 The facial and mandibular asymmetry has also been studied,8e10 but little emphasis has been placed on the zygomatic dysmorphology. The zygoma is a keystone of the face, comprising a significant portion of the orbit, cheek, and temporomandibular joint. Zygomatic morphology is influenced by its frontal, temporal, sphenoid, and maxillary articulations to provide facial width and contour.11,12 Moreover, the zygoma provides structural support to the orbits and temporomandibular joint,11,12 where it may also influence mandibular condyle position.13,14 The zygoma on the UCS ipsilateral side appears anteriorly displaced compared to the contralateral side. This dysmorphology may be relative to the supraorbital retrusion but an absolute displacement secondary to compensatory expansion of the ipsilateral temporal bone may also be responsible.3,4,15 Despite zygomatic contribution to facial asymmetry in UCS, the zygoma is not typically emphasized or addressed during craniofacial reconstruction. To date, no studies have morphometrically analyzed and compared the extent of zygomatic maldevelopment to normal age- and sex-matched controls. The aim of this study is to objectively evaluate zygomatic morphology in UCS compared to the contralateral unaffected side and to normal age- and sex-matched controls. Furthermore, we compare the contralateral unaffected side of UCS patients to normal controls to investigate the relative bilaterality of this condition. This study focuses on an underemphasized aspect of UCS, further contributing to the characterization of a highly prevalent congenital deformity and offering greater understanding of the facial dysmorphology and asymmetric characteristics of this disorder.
Material and methods This is a retrospective study approved by the Yale University Institutional Review Board (HIC: 1101007932). Computed tomography (CT) scans of normal and non-syndromic UCS patients were identified and manipulated using a 3D
1097 software platform (Materialise; Leuven, Belgium). Demographic information from all patients included in this study was collected from medical charts. CT scans from children without craniofacial disorders or conditions were obtained for patient care purposes and used for normal control analysis. When comparing UCS and normal control patients, a sub-set of UCS children were age- and sex-matched to the control group to minimize group heterogeneity. For volumetric analysis, zygomata from normal control and UCS patients (Figure 1) were digitally segmented along anatomic sutures (frontozygomatic, zygomaticosphenoid, zygomaticotemporal, and zygomaticomaxillary) as described previously16 with axial and coronal CT slices used to help guide digital segmentation of the zygomata (Supplemental Figure 1). Morphometric landmarks on UCS and control patients were identified to perform all measurements (Tables 1 and 2, Supplemental Figure 2). 3D-rendered images were used for all measurements except the Orbital-Malar angle (2D lateral image). Three groups were analyzed: 1) normal control, and, in the UCS group, 2) contralateral unaffected, and 3) ipsilateral affected zygomata. Volume was calculated in cubic millimeters (mm3) and angles in degrees ( ). For ratio calculations, the smaller zygoma in control patients was taken as the numerator and larger zygoma taken as the denominator; in UCS patients, the affected side was taken as the numerator and the unaffected side taken as the denominator. Statistical analysis was performed using Microsoft Excel (Version 14.0.0, Microsoft Office 2011, Microsoft; Redmond, WA) and SPSS Statistics (Version 19, IBM; Armonk, NY). Intra- and inter-observer reliability was tested and found to be similar between both groups of measurements (p Z 0.8 and p Z 0.5, respectively). Comparisons between affected and unaffected sides were conducted using a paired t test; a two-tailed student’s t test was used to compare the affected and unaffected sides to normal controls and for ratio comparisons. An observed P value of 0.05 was considered statistically significant.
Results A total of 68 zygomata were analyzed. There were twelve normal control (six females) and 22 UCS patients (twelve females). The mean age in months of the control and UCS groups was 6.6 1.8 and 5.1 4.7, respectively. Within the UCS group, twelve patients demonstrated right-sided and ten left-sided synostosis. For age- and sex-matched
Figure 1 Craniofacial dysmorphology in UCS. Four month-old female patient with right-sided UCS. Note prominence of the malar eminence and elongation of the zygomaticosphenoid articulation on the affected side.
1098 Table 1
M.J. Pfaff et al. Morphometric landmarks.
Measurements
Abbreviation
Definition
Zygomaticomaxillary point
ZM
Frontozygomatic point
FZ
Lateral orbital rim junction point
LO
Frontal zygoma buttress point
ZB
Orbitale Supraorbitale Zygion
Or SOr Z
Point most superior at zygomaticomaxillary suture along the infra-orbital rim Point most anteromedial at frontozygomatic suture along the lateral orbital rim Point perpendicular to junction of the tangent lines to the lateral and infra-orbital rim Point perpendicular to junction of the tangent lines to the lateral orbital rim and zygomatic arch Point most inferior along the infra-orbital rim Point most superior along the superior orbital rim Point most lateral along the zygomatic arch
comparisons between normal control and UCS zygomata, a subset of UCS patients (12 UCS patients; six females; mean age: 6.4 3.8; P Z 0.9, normal control patient age versus UCS patient age) were evaluated to compare the affected and unaffected zygomata to normal control zygomata. Morphometric analyses of the zygomata of UCS patients are presented in Table 3. Zygomatic volume of the affected side was marginally reduced compared to the unaffected side at 1484.8 mm3 and 1551.3 mm3 (p Z 0.104), respectively. The Zygomaticosphenoid angle was more acute on the affected side than unaffected side at 70.6 versus 83.8 (p < 0.001). Moreover, the affected side had a more acute Frontal Zygomatic angle at 121.6 compared to the unaffected side at 124.2 (p Z 0.126). The Lateral Orbital Rim and the Fronto-Orbital Zygomatic angle were more obtuse on the affected side than unaffected side: 114.6 versus 109.7 (p < 0.001) and 125.8 versus 113.9 (p Z 0.002). Affected zygomata compared to matched-controls revealed a mean volume decrement (Table 4): 1624.0 mm3 and 1933.9 mm3 (p Z 0.057), respectively. The Zygomaticosphenoid and Frontal Zygomatic angles were more acute on the affected sides than in controls: 70.0 versus 80.1 (p < 0.001) and 128.5 versus 121.8 (p Z 0.02). The affected sides demonstrated more obtuse Lateral Orbital Rim and Fronto-Orbital Zygomatic angles when compared to controls: 113.8 versus 109.1 (p Z 0.005) and 131.0 versus 122.3 (p < 0.001). Comparison of volumetric ratios of normal control and UCS zygomata were found to be similar at 0.96 and 0.96, respectively (p Z 0.87) (Supplemental Table 1). With the exception of zygomatic volume, comparison of the unaffected side to normal controls demonstrated a high
Table 2
degree of similarity among all measurements (Table 5). The zygomata of the unaffected side trended toward a reduced volume compared to controls at 1639.9 mm3 and 1933.9 mm3 (p Z 0.078), respectively. The Zygomaticosphenoid and Frontal Zygomatic angles differed slightly compared to controls: 77.9 versus 80.1 (p Z 0.400) and 124.4 versus 128.5 (p Z 0.125). Lastly, the measurements of the Lateral Orbital Rim and Fronto-Orbital Zygomatic angles of the unaffected side and controls were 107.9 and 109.1 (p Z 0.985) and 121.9 and 122.3 (p Z 0.853), respectively. Stratification by age revealed that zygomatic bone volume of the affected and unaffected sides within the age range of 0e2 months old was 1278.5 mm3 and 1394.4 mm3 (p Z 0.064), 1319.7 mm3 and 1315.1 mm3 at 3e6 months old (p Z 0.956), and 2031.7 mm3 and 2075.9 mm3 at 7e12 months old (p Z 0.673) (Table 6 and Supplemental Figure 3). Normal control zygomatic volume at 3e6 months of age were 1832.7 mm3 (versus affected side: p Z 0.032; versus unaffected side: p Z 0.038) and 1998.5 mm3 at 7e13 months of age (versus affected side: p Z 0.706; versus unaffected side: p Z 0.973). The Zygomaticosphenoid angle of the affected and unaffected sides within the age range of 0e2 months old was 72.0 and 89.2 (p < 0.001), 69.5 and 77.9 at 3e6 months of age (p Z 0.361), and 66.3 and 75.1 at 7e13 months of age (p Z 0.077), respectively. The normal control Zygomaticosphenoid angle at 3e6 months of age was 80.6 (versus affected side: p Z 0.029; versus unaffected side: p Z 0.554), 80.3 at 7e13 months of age (versus affected side: p Z 0.001; versus unaffected side: p Z 0.156). The Frontal Zygomatic angle of the affected and unaffected sides was 120.1 and 122.0 at 0e2 months of age (p Z 0.302), 120.7 and 126.6 at 3e6 months of age
Morphometric measurements.
Measurements
Definition
Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle, *
Volume of the zygoma Angle formed between Angle formed between Angle formed between Angle formed between
*, Measurement performed on 2-dimensional lateral image.
line line line line
ZM to FZ and line FZ to Z ZM to ZB and line ZB to Z ZM to LO and line LO to FZ SOr and Or
Zygomatic dysmorphology in UCS Table 3
1099
Affected versus unaffected zygomata.
Measurement
Affected 3
Zygomatic volume, mm Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Unaffected
P
N
Mean
SD
Range
N
Mean
SD
Range
22 22 22 21 21
1484.8 70.6 121.6 114.6 125.8
418.7 8.6 8.0 4.7 10.2
846.1e2654.9 57.2e92.1 104.9e138.9 103.9e123.4 100.44e140.8
22 22 22 21 21
1551.3 83.8 124.2 109.7 113.9
441.9 10.0 7.0 7.4 11.9
958.9e2776.8 59.8e100.9 109.2e135.5 90.8e123.6 89.7e132.5
0.104 <0.001 0.126 <0.001 0.002
N, Number of zygomata; SD, standard deviation.
(p Z 0.369), and 123.9 and 125.8 at 7e13 months of age (p Z 0.242), respectively. The Frontal Zygomatic angle in controls within the age range of 3e6 months was 125.9 (versus affected side: p Z 0.202; versus unaffected side: p Z 0.850) and 130.6 at 7e13 months of age (versus affected side: p Z 0.136; versus unaffected side: p Z 0.233). The Lateral Orbital Rim angle of the affected and unaffected sides was 114.9 and 110.8 at 0e2 months of age (p Z 0.020), 115.0 and 106.2 at 3e6 months of age (p Z 0.108), and 114.1 and 111.0 at 7e13 months of age (p Z 0.231). In normal controls, the Lateral Orbital Rim angle at 3e6 months of age was 109.8 (versus affected side: p Z 0.023; versus unaffected side: p Z 0.091), and 111.0 at 7e13 months of age (versus affected side: p Z 0.233; versus unaffected side: p Z 0.710). Lastly, Fronto-Orbital Zygomatic angle in the affected and unaffected side at 0e2 months of age was 120.7 and 105.7 (p < 0.001), 131.2 and 120.7 at 3e6 months of age (p Z 0.046), and 131.8 and 123.8 at 7e13 months of age (p Z 0.034), respectively. In controls, the Fronto-Orbital Zygomatic angle was 120.4 at 3e6 months of age (versus affected side: p Z 0.021; versus unaffected side: p Z 0.953) and 123.2 at 7e13 months of age (versus affected side: p Z 0.002; versus unaffected side: p Z 0.798).
Discussion Zygomatic growth is a complex process driven by the developing cranial base, intrinsic bone growth, and functional stress produced by the surrounding associated soft tissues. Facial width and anteroposterior growth of the upper and mid-facial skeleton are determined in part by bone growth that occurs along the synchondroses (i.e. sphenoethmoidal synchondrosis) of the cranial base, which
Table 4
also influence anterior cranial fossa development.17,18 Zygomatic bone growth is also dependent upon bone deposition along the posterior surface of the malar body with concomitant resorption along the anterior (facial) surface that occurs in coordination with maxillary growth.11,12 Furthermore, skeletal responses to functional stress (or lack thereof) placed on the bone by the associated soft tissues may contribute to zygomatic morphology.19 Premature suture fusion in UCS imparts a fronto-facial deformity, most notably of the supra-orbital and forehead regions; however, maxillary, nasal, and mandibular abnormalities also exist.37,10,14,20,21 Furthermore, as documented in previous reports3,4,15 and objectively analyzed in the present study, the zygomata of UCS patients also demonstrate dysmorphic features. It is posited that restricted development of the ipsilateral cranial vault drives compensatory expansion of the squamous temporal bone; the effect is anterior displacement of the body of the zygoma, resulting in a more forward-projecting malar eminence.15 Moreover, superolateral elevation of the orbital rim (Harlequin deformity) on the affected side, a consequence of restricted downward movement of the lateral aspect of the greater wing of the sphenoid, results in asymmetrical vertical growth of the sphenoid process of the zygoma (lateral orbital rim).5,7 Interestingly, the severity of this deformity may also be dictated by fusion of the frontosphenoidal suture.22 In UCS, the cranial base and anterior cranial fossa are notably maldeveloped,23e25 and, as a result, may influence abnormal growth of the developing zygomata. As with other facial bones, zygomatic growth is in part influenced by the surrounding soft tissue stresses, especially the muscle of mastication.16,26 In UCS, mandibular and temporomandibular joint displacement, with corresponding malocclusion and asymmetry, have been documented.14,21 Such
Affected versus normal control zygomata*.
Measurement Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Affected
Normal Control
P
N
Mean
SD
Range
N
Mean
SD
Range
12 12 12 12 12
1624.0 70.0 121.8 113.8 131.0
454.4 9.7 9.3 4.3 5.5
1058.6e2776.8 57.2e92.1 104.9e139.0 103.9e121.1 121.6e140.8
24 24 24 24 24
1933.9 80.1 128.5 109.1 122.3
420.5 6.0 6.7 4.3 5.8
1015.3e2574.1 66.8e87.1 114.0e140.0 98.1e114.9 112.05e134.1
N, Number of zygomata analyzed; *, Age- and sex-matched comparison.
0.057 <0.001 0.021 0.005 <0.001
1100 Table 5
M.J. Pfaff et al. Unaffected versus normal control zygomata*.
Measurement
Contralateral control 3
Zygomatic volume, mm Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Normal control
P
N
Mean
SD
Range
N
Mean
SD
Range
12 12 12 12 12
1639.9 77.9 124.4 107.9 121.9
490.9 8.9 8.0 6.6 6.8
958.9e2654.9 59.8e90.5 109.2e135.5 90.8e114.6 108.1e132.5
24 24 24 24 24
1933.9 80.1 128.5 109.1 122.3
420.5 6.0 6.7 4.3 5.8
1015.3e2574.1 66.8e87.1 114.0e140.0 98.1e114.9 112.05e134.1
0.078 0.400 0.125 0.985 0.853
N, Number of zygomata analyzed; SD, standard deviation *, Age- and sex-matched comparison.
observations raise the possibility of masticatory aberrations contributing to zygomatic maldevelopment, in addition to temporal bone maldevelopment; however, further studies analyzing soft tissue morphology are necessary. Lastly, the zygomatic deformity, particularly the prominence of the malar eminence, may be accentuated by supraorbital flattening of the frontal bone on the affected side. Improved CT imaging has allowed for better characterization of craniofacial osseous and soft tissue dysmorphology.5e7,16,20,27e29 The present study sought to objectively evaluate the zygomatic deformity in UCS using CT-based 3D-rendered images and found that, of the 22 UCS patients, zygomatic volume of the affected side was, on average, reduced compared to the unaffected side; however, the difference did not achieve statistical significance (Table 3). Morphometric analysis of the zygoma and frontoorbital structures also demonstrated significant differences in zygomatic morphology. The zygomaticosphenoid angle was more acute on the affected side than the unaffected side. Superolateral growth of the sphenoid process of the zygoma on the affected side may be responsible for this finding as there was only a modest decrease in the
Table 6
angulation of the frontal portion of the zygoma (Frontal Zygomatic angle) when compared to the unaffected side. As expected, the lateral orbital rim angle and fronto-orbital zygomatic angle were more obtuse than the unaffected side. This observation is likely a result of superolateral elevation of the sphenoid process, frontal bone flattening, and anterior projection of the malar eminence on the affected side. When compared to age- and sex-matched normal controls, both the affected and unaffected sides were, on average, volumetrically deficient (Table 4). This observation is also supported by our comparison of the ratios of the zygomata in controls and UCS patients (Supplemental Table 1). With the exception of the frontal zygomatic angle, the morphometric measurements of the affected zygoma in UCS patients differed significantly compared to normal controls in a similar pattern when compared to the unaffected side. Again, in response to temporal bone expansion, the zygoma is projected anteriorly resulting in prominence of the malar eminence. Interestingly, we found the zygomaticofrontal angle to be more constricted on the affected side than in controls, providing further quantitative
Zygomatic growth over time.
Measurement
Age range Affected (months) side N
Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13
Value
Unaffected side SD
N
Value
Control
SD
N
Value
Affected Affected Unaffected versus versus versus unaffected control control SD
P
10 1278.5 225.6 10 1394.4 288.5 0 e e 0.064 6 1319.1 136.9 6 1315.1 256.7 10 1832.7 484.6 0.956 5 2031.7 486.1 5 2075.9 483.4 14 1998.5 338.9 0.673 10 72.0 4.3 10 89.2 6.9 0 e e <0.001 6 69.5 11.4 6 77.9 10.8 10 80.6 5.5 0.361 5 66.3 8.3 5 75.1 7.4 14 80.3 6.1 0.077 10 120.1 5.4 10 122.0 5.7 0 e e 0.302 6 120.7 8.3 6 126.6 6.3 10 125.9 6.3 0.369 5 123.9 10.6 5 125.8 8.7 14 130.6 6.4 0.242 10 114.9 4.3 10 110.8 7.3 0 e e 0.020 5 113.5 3.9 5 106.2 9.1 10 109.8 2.9 0.178 5 114.1 5.7 5 110.1 5.3 14 111.0 4.0 0.231 10 120.7 11.2 10 105.7 10.5 0 e e <0.001 5 131.2 5.4 5 120.7 8.0 10 120.4 7.6 0.046 5 131.8 5.6 5 123.8 5.4 14 123.2 3.8 0.034
N, Number of zygomata analyzed; SD, standard deviation.
P
P
e 0.032 0.706 e 0.029 0.001 e 0.202 0.136 e 0.067 0.233 e 0.021 0.002
e 0.038 0.973 e 0.554 0.156 e 0.850 0.233 e 0.278 0.710 e 0.953 0.798
Zygomatic dysmorphology in UCS evidence of anterior zygomatic displacement or repositioning. All measurements of the unaffected side were similar to normal controls. In UCS, the contralateral frontal bone inferior border (superior orbital rim) is thought to be depressed and would therefore produce a larger angle than in normal controls; however, unexpectedly, the Frontoorbital angle was similar to controls (Table 5). When stratified by age, zygomatic volume differed most significantly earlier in life, with the affected side trending smaller than the unaffected side and differing significantly compared to normal controls (Table 6). In addition, the unaffected side was significantly smaller than controls. By 7e13 months of age, however, the volumes of the affected and unaffected sides reached that of normal values. This finding is similar to the observation seen by Langford and colleagues20: maxillary volume, although deficient at an early age when compared to controls, approached that of normal values by seven months of age. Differences in craniometric measurements followed in a similar pattern, with the exception of the Fronto-orbital Zygomatic angle on the affected side. Zygomatic morphometry differed the greatest within the earlier age period between the affected side when compared to the unaffected side and to normal controls with the exception of the Fronto-Orbital Zygomatic angle, which differed significantly in all time periods. Measurements of the unaffected side were similar in all time points when compared to controls. These observed differences in zygomatic volume and morphometry at an earlier age, however, may be confounded by the fact that those who presented with more severe craniofacial distortion were as a result diagnosed at an earlier age. The aim of surgical intervention in UCS is to restore the craniofacial skeleton and prevent developmental and functional deficits. A multitude of surgical techniques have been proposed, all sharing the common goal of releasing the fused suture with concomitant correction of the frontoorbital deformity to establish normal contour and symmetry.15,30e35 It remains unclear whether commonly employed treatment approaches that alter the cranial vault and, in effect, normalize cranial base morphology,24 influence normal zygomatic growth and positioning. A similar concern was raised by Hansen and Mulliken regarding the deviated nasal root in UCS.31,35 With the held belief that traditional approaches not addressing the nasal root deformity would fail to ameliorate nasal root angulation, Hansen and Mulliken described a bilateral fronto-orbital procedure incorporating the nasal bones within the supraorbital bar; post-operative nasal root angulation significantly improved in UCS patients when compared to those that underwent other procedures that did not involve nasal radix reconstruction.31 Although a parallel may be drawn between the nasal radix and the zygomatic deformities, reconstruction of the zygoma may not be necessary (or technically feasible). Furthermore, the observation that zygomatic volume and morphometry (except the Frontoorbital Zygomatic angle) trended toward normal values over time (Table 6) suggests that the deformity may improve with time, thus obviating the need for surgical reconstruction. Further analyses studying the effects of surgical intervention on the degree of zygomatic dysmorphology and whether these changes relate to cranial base normalization would be welcomed.
1101
Conclusion In unicoronal synostosis, the affected zygomata were volumetrically deficient and morphometrically different compared to unaffected and normal control sides. The contralateral unaffected side were similar to normal controls, with the exception of a deficient zygomatic volume. These differences in zygomatic morphology appear to be greatest at an earlier age interval.
Support This work was supported by the Charles Ohse Grant from the Department of Surgery, Yale University School of Medicine.
Financial disclosures All authors have no commercial associations or disclosures that may pose or create a conflict of interest with the information presented within this manuscript.
Product used in this study Materialise Surgicase CMF Pro Version 8.0 for Windows; Leuven, Belgium.
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.bjps.2013.04.025.
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symmetry in coronal craniosynostosis. J Exp Zool B Mol Dev Evol 2012;318:109e22. http://dx.doi.org/10.1002/jezb.21449. Kane AA, Kim YO, Eaton A, et al. Mandibular dysmorphology in unicoronal synostosis and plagiocephaly without synostosis. Cleft Palate Craniofac J 1996;33:418e23. http://dx.doi.org/10.1597/15451569(1996)033<0418:MDIUSA>2.3.CO;2. Kane AA, et al. Quantification of osseous facial dysmorphology in untreated unilateral coronal synostosis. Plast Reconstr Surg 2000;106:251e8. Enlow DH. A morphogenetic analysis of facial growth. Am J Orthod 1966;52:283e99. Enlow DH, Bang S. Growth and remodeling of the human maxilla. Am J Orthod 1965;51:446e64. Me ´rida-Velasco JR, Rodrı´guez-Va ´zquez JF, Me ´rida-Velasco JA, Sa ´nchez-Montesinos I, Espı´n-Ferra J, Jime ´nez-Collado J. Development of the human temporomandibular joint. Anat Rec 1999; 255:20e33. Pelo S, Marianetti TM, Cacucci L, et al. Occlusal alterations in unilateral coronal craniosynostosis. Int J Oral Maxillofac Surg 2011;40:805e9. http://dx.doi.org/10.1016/j.ijom.2011.02.023. David LR, Fisher D, Argenta L. New technique for reconstructing the affected cranium and orbital rim in unicoronal craniosynostosis. J Craniofac Surg 2009;20:194e7. http://dx.doi.org/10.1097/SCS.0b013e318191cf33. Wong KR, Pfaff MJ, Chang CC, Travieso R, Steinbacher DM. A range of malar and masseteric hypoplasia exists in treacher collins syndrome. J Plast Reconstr Aesthet Surg 2012. http://dx.doi.org/10.1016/j.bjps.2012.07.028. Enlow DH, Hans MG. Essentials of facial growth. Saunders; 1996. Enlow DH, Azuma M. Functional growth boundaries in the human and mammalian face. Birth Defects Orig Artic Ser 1975;11:217e30. Moss ML, Salentijn L. The primary role of functional matrices in facial growth. Am J Orthod 1969;55:566e77. Langford RJ, Sgouros S, Natarajan K, et al. Maxillary volume growth in craniosynostosis. Plast Reconstr Surg 2003;111: 1598e604. http://dx.doi.org/ 10.1097/01.PRS.0000057972.87632.ec. Di Rocco C, Velardi F. Nosographic identification and classification of plagiocephaly. Childs Nerv Syst 1988;4:9e15. Showalter BM, David LR, Argenta LC, Thompson JT. Influence of frontosphenoidal suture synostosis on skull dysmorphology in unicoronal suture synostosis. J Craniofac Surg 2012;23: 1709e12. http://dx.doi.org/10.1097/SCS.0b013e31826beecc.
M.J. Pfaff et al. 23. Abramson DL, Janecka IP, Mulliken JB. Abnormalities of the cranial base in synostotic frontal plagiocephaly. J Craniofac Surg 1996;7:426e8. 24. Marsh JL, Vannier MW. Cranial base changes following surgical treatment of craniosynostosis. Cleft Palate J 1986;23(Suppl. 1):9e18. 25. Richtsmeier JT, Grausz HM, Morris GR, Marsh JL, Vannier MW. Growth of the cranial base in craniosynostosis. Cleft Palate Craniofac J 1991;28:55e67. http://dx.doi.org/10.1597/15451569(1991)028<0055:GOTCBI>2.3.CO;2. 26. Hall JG. Importance of muscle movement for normal craniofacial development. J Craniofac Surg 2010;21:1336e8. http://dx.doi.org/10.1097/SCS.0b013e3181ebcd4f. 27. Travieso R, Chang CC, Terner JS, et al. A range of condylar hypoplasia exists in treacher collins syndrome. J Oral Maxillofac Surg 2012. http://dx.doi.org/10.1016/j.joms.2012.04.031. 28. Steinbacher DM, Gougoutas A, Bartlett SP. An analysis of mandibular volume in hemifacial microsomia. Plast Reconstr Surg 2011;127:2407e12. http://dx.doi.org/10.1097/ PRS.0b013e3182131cc8. 29. Steinbacher DM, Wink J, Bartlett SP. Temporal hollowing following surgical correction of unicoronal synostosis. Plast Reconstr Surg 2011;128:231e40. http://dx.doi.org/10.1097/ PRS.0b013e318218fcab. 30. Fearon JA. Beyond the bandeau: 4 variations on frontoorbital advancements. J Craniofac Surg 2008;19:1180e2. http://dx.doi.org/10.1097/SCS.0b013e3181764b3e. 31. Hansen M, Padwa BL, Scott RM, Stieg PE, Mulliken JB. Synostotic frontal plagiocephaly: anthropometric comparison of three techniques for surgical correction. Plast Reconstr Surg 1997;100:1387e95. 32. Marchac D, Renier D. Treatment of craniosynostosis in infancy. Clin Plast Surg 1987;14:61e72. 33. Matushita H, Alonso N, Cardeal DD, de Andrade F. Frontalorbital advancement for the management of anterior plagiocephaly. Childs Nerv Syst 2012;28:1423e7. http://dx.doi.org/ 10.1007/s00381-012-1765-1. 34. Mesa JM, Fang F, Muraszko KM, Buchman SR. Reconstruction of unicoronal plagiocephaly with a hypercorrection surgical technique. Neurosurg Focus 2011;31:E4. http://dx.doi.org/ 10.3171/2011.6.FOCUS1193. 35. Hansen M, Mulliken JB. Frontal plagiocephaly. Diagnosis and treatment. Clin Plast Surg 1994;21:543e53.
Zygomatic dysmorphology in unicoronal synostosis Miles J. Pfaff, Kenneth Wong, John A. Persing, Derek M. Steinbacher* Plastic and Reconstructive Surgery, Yale University School of Medicine, New Haven, CT, USA Received 12 December 2012; accepted 6 April 2013
KEYWORDS Unicoronal synostosis; UCS; Zygoma; Zygmata; Malar; Hypoplasia; Volume; Volumetric analysis; Morphometric; Morphometry
Summary Introduction: Unicoronal synostosis (UCS) imparts a fronto-facial deformity, the hallmark feature being orbital and forehead dysmorphology. The facial and malar regions also consistently display asymmetry, however, zygomatic structural characteristics have not been investigated. The purpose of this study is to objectively analyze the zygomata of UCS patients compared to normal controls. Methods: Three dimensional-computed tomographic images and demographic information were obtained from normal control and UCS patients. Volumetric and morphometric analyses were performed and results statistically analyzed. P values <0.05 were considered statistically significant. Results: A total of 68 zygomatic sides were analyzed: twelve control (6 females; mean age: 6.6 months) and 22 UCS patients (10 females; mean age: 5.1 months). The affected side was right in 55% (n Z 12) and left in 45% (n Z 10) of UCS patients. The affected zygomata were volumetrically deficient compared to unaffected and normal control zygomata. Unaffected zygomata demonstrated diminished volume compared to norms. Morphometrically, affected zygomata differed, while both the unaffected and control zygomata were similar. Age stratification revealed marked differences in zygomatic volume and morphometry between the affected and unaffected zygomata was greatest at an early age interval. Conclusion: The affected UCS zygomata are on average smaller compared to unaffected and normal control zygomata. Moreover, distinct morphometric differences exist on the affected zygomata versus both unaffected and control zygomata. These differences are not addressed by commonly employed treatment approaches. Further studies evaluating the growth effect of UCS zygomatic morphology should be entertained. ª 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: þ1 (203) 785 4559; fax: þ1 203 785 7514. E-mail address: [email protected] (D.M. Steinbacher). 1748-6815/$ - see front matter ª 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bjps.2013.04.025
Zygomatic dysmorphology in UCS
Introduction Unicoronal synostosis (UCS) represents approximately 20e30% of nonsyndromic craniosynostosis.1,2 Fusion of the coronal suture results in anterior plagiocephaly, or “twisted head”, with a requisite orbito-facial asymmetry.3,4 The frontal and orbital dysmorphologies have been welldescribed.5e7 The facial and mandibular asymmetry has also been studied,8e10 but little emphasis has been placed on the zygomatic dysmorphology. The zygoma is a keystone of the face, comprising a significant portion of the orbit, cheek, and temporomandibular joint. Zygomatic morphology is influenced by its frontal, temporal, sphenoid, and maxillary articulations to provide facial width and contour.11,12 Moreover, the zygoma provides structural support to the orbits and temporomandibular joint,11,12 where it may also influence mandibular condyle position.13,14 The zygoma on the UCS ipsilateral side appears anteriorly displaced compared to the contralateral side. This dysmorphology may be relative to the supraorbital retrusion but an absolute displacement secondary to compensatory expansion of the ipsilateral temporal bone may also be responsible.3,4,15 Despite zygomatic contribution to facial asymmetry in UCS, the zygoma is not typically emphasized or addressed during craniofacial reconstruction. To date, no studies have morphometrically analyzed and compared the extent of zygomatic maldevelopment to normal age- and sex-matched controls. The aim of this study is to objectively evaluate zygomatic morphology in UCS compared to the contralateral unaffected side and to normal age- and sex-matched controls. Furthermore, we compare the contralateral unaffected side of UCS patients to normal controls to investigate the relative bilaterality of this condition. This study focuses on an underemphasized aspect of UCS, further contributing to the characterization of a highly prevalent congenital deformity and offering greater understanding of the facial dysmorphology and asymmetric characteristics of this disorder.
Material and methods This is a retrospective study approved by the Yale University Institutional Review Board (HIC: 1101007932). Computed tomography (CT) scans of normal and non-syndromic UCS patients were identified and manipulated using a 3D
1097 software platform (Materialise; Leuven, Belgium). Demographic information from all patients included in this study was collected from medical charts. CT scans from children without craniofacial disorders or conditions were obtained for patient care purposes and used for normal control analysis. When comparing UCS and normal control patients, a sub-set of UCS children were age- and sex-matched to the control group to minimize group heterogeneity. For volumetric analysis, zygomata from normal control and UCS patients (Figure 1) were digitally segmented along anatomic sutures (frontozygomatic, zygomaticosphenoid, zygomaticotemporal, and zygomaticomaxillary) as described previously16 with axial and coronal CT slices used to help guide digital segmentation of the zygomata (Supplemental Figure 1). Morphometric landmarks on UCS and control patients were identified to perform all measurements (Tables 1 and 2, Supplemental Figure 2). 3D-rendered images were used for all measurements except the Orbital-Malar angle (2D lateral image). Three groups were analyzed: 1) normal control, and, in the UCS group, 2) contralateral unaffected, and 3) ipsilateral affected zygomata. Volume was calculated in cubic millimeters (mm3) and angles in degrees ( ). For ratio calculations, the smaller zygoma in control patients was taken as the numerator and larger zygoma taken as the denominator; in UCS patients, the affected side was taken as the numerator and the unaffected side taken as the denominator. Statistical analysis was performed using Microsoft Excel (Version 14.0.0, Microsoft Office 2011, Microsoft; Redmond, WA) and SPSS Statistics (Version 19, IBM; Armonk, NY). Intra- and inter-observer reliability was tested and found to be similar between both groups of measurements (p Z 0.8 and p Z 0.5, respectively). Comparisons between affected and unaffected sides were conducted using a paired t test; a two-tailed student’s t test was used to compare the affected and unaffected sides to normal controls and for ratio comparisons. An observed P value of 0.05 was considered statistically significant.
Results A total of 68 zygomata were analyzed. There were twelve normal control (six females) and 22 UCS patients (twelve females). The mean age in months of the control and UCS groups was 6.6 1.8 and 5.1 4.7, respectively. Within the UCS group, twelve patients demonstrated right-sided and ten left-sided synostosis. For age- and sex-matched
Figure 1 Craniofacial dysmorphology in UCS. Four month-old female patient with right-sided UCS. Note prominence of the malar eminence and elongation of the zygomaticosphenoid articulation on the affected side.
1098 Table 1
M.J. Pfaff et al. Morphometric landmarks.
Measurements
Abbreviation
Definition
Zygomaticomaxillary point
ZM
Frontozygomatic point
FZ
Lateral orbital rim junction point
LO
Frontal zygoma buttress point
ZB
Orbitale Supraorbitale Zygion
Or SOr Z
Point most superior at zygomaticomaxillary suture along the infra-orbital rim Point most anteromedial at frontozygomatic suture along the lateral orbital rim Point perpendicular to junction of the tangent lines to the lateral and infra-orbital rim Point perpendicular to junction of the tangent lines to the lateral orbital rim and zygomatic arch Point most inferior along the infra-orbital rim Point most superior along the superior orbital rim Point most lateral along the zygomatic arch
comparisons between normal control and UCS zygomata, a subset of UCS patients (12 UCS patients; six females; mean age: 6.4 3.8; P Z 0.9, normal control patient age versus UCS patient age) were evaluated to compare the affected and unaffected zygomata to normal control zygomata. Morphometric analyses of the zygomata of UCS patients are presented in Table 3. Zygomatic volume of the affected side was marginally reduced compared to the unaffected side at 1484.8 mm3 and 1551.3 mm3 (p Z 0.104), respectively. The Zygomaticosphenoid angle was more acute on the affected side than unaffected side at 70.6 versus 83.8 (p < 0.001). Moreover, the affected side had a more acute Frontal Zygomatic angle at 121.6 compared to the unaffected side at 124.2 (p Z 0.126). The Lateral Orbital Rim and the Fronto-Orbital Zygomatic angle were more obtuse on the affected side than unaffected side: 114.6 versus 109.7 (p < 0.001) and 125.8 versus 113.9 (p Z 0.002). Affected zygomata compared to matched-controls revealed a mean volume decrement (Table 4): 1624.0 mm3 and 1933.9 mm3 (p Z 0.057), respectively. The Zygomaticosphenoid and Frontal Zygomatic angles were more acute on the affected sides than in controls: 70.0 versus 80.1 (p < 0.001) and 128.5 versus 121.8 (p Z 0.02). The affected sides demonstrated more obtuse Lateral Orbital Rim and Fronto-Orbital Zygomatic angles when compared to controls: 113.8 versus 109.1 (p Z 0.005) and 131.0 versus 122.3 (p < 0.001). Comparison of volumetric ratios of normal control and UCS zygomata were found to be similar at 0.96 and 0.96, respectively (p Z 0.87) (Supplemental Table 1). With the exception of zygomatic volume, comparison of the unaffected side to normal controls demonstrated a high
Table 2
degree of similarity among all measurements (Table 5). The zygomata of the unaffected side trended toward a reduced volume compared to controls at 1639.9 mm3 and 1933.9 mm3 (p Z 0.078), respectively. The Zygomaticosphenoid and Frontal Zygomatic angles differed slightly compared to controls: 77.9 versus 80.1 (p Z 0.400) and 124.4 versus 128.5 (p Z 0.125). Lastly, the measurements of the Lateral Orbital Rim and Fronto-Orbital Zygomatic angles of the unaffected side and controls were 107.9 and 109.1 (p Z 0.985) and 121.9 and 122.3 (p Z 0.853), respectively. Stratification by age revealed that zygomatic bone volume of the affected and unaffected sides within the age range of 0e2 months old was 1278.5 mm3 and 1394.4 mm3 (p Z 0.064), 1319.7 mm3 and 1315.1 mm3 at 3e6 months old (p Z 0.956), and 2031.7 mm3 and 2075.9 mm3 at 7e12 months old (p Z 0.673) (Table 6 and Supplemental Figure 3). Normal control zygomatic volume at 3e6 months of age were 1832.7 mm3 (versus affected side: p Z 0.032; versus unaffected side: p Z 0.038) and 1998.5 mm3 at 7e13 months of age (versus affected side: p Z 0.706; versus unaffected side: p Z 0.973). The Zygomaticosphenoid angle of the affected and unaffected sides within the age range of 0e2 months old was 72.0 and 89.2 (p < 0.001), 69.5 and 77.9 at 3e6 months of age (p Z 0.361), and 66.3 and 75.1 at 7e13 months of age (p Z 0.077), respectively. The normal control Zygomaticosphenoid angle at 3e6 months of age was 80.6 (versus affected side: p Z 0.029; versus unaffected side: p Z 0.554), 80.3 at 7e13 months of age (versus affected side: p Z 0.001; versus unaffected side: p Z 0.156). The Frontal Zygomatic angle of the affected and unaffected sides was 120.1 and 122.0 at 0e2 months of age (p Z 0.302), 120.7 and 126.6 at 3e6 months of age
Morphometric measurements.
Measurements
Definition
Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle, *
Volume of the zygoma Angle formed between Angle formed between Angle formed between Angle formed between
*, Measurement performed on 2-dimensional lateral image.
line line line line
ZM to FZ and line FZ to Z ZM to ZB and line ZB to Z ZM to LO and line LO to FZ SOr and Or
Zygomatic dysmorphology in UCS Table 3
1099
Affected versus unaffected zygomata.
Measurement
Affected 3
Zygomatic volume, mm Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Unaffected
P
N
Mean
SD
Range
N
Mean
SD
Range
22 22 22 21 21
1484.8 70.6 121.6 114.6 125.8
418.7 8.6 8.0 4.7 10.2
846.1e2654.9 57.2e92.1 104.9e138.9 103.9e123.4 100.44e140.8
22 22 22 21 21
1551.3 83.8 124.2 109.7 113.9
441.9 10.0 7.0 7.4 11.9
958.9e2776.8 59.8e100.9 109.2e135.5 90.8e123.6 89.7e132.5
0.104 <0.001 0.126 <0.001 0.002
N, Number of zygomata; SD, standard deviation.
(p Z 0.369), and 123.9 and 125.8 at 7e13 months of age (p Z 0.242), respectively. The Frontal Zygomatic angle in controls within the age range of 3e6 months was 125.9 (versus affected side: p Z 0.202; versus unaffected side: p Z 0.850) and 130.6 at 7e13 months of age (versus affected side: p Z 0.136; versus unaffected side: p Z 0.233). The Lateral Orbital Rim angle of the affected and unaffected sides was 114.9 and 110.8 at 0e2 months of age (p Z 0.020), 115.0 and 106.2 at 3e6 months of age (p Z 0.108), and 114.1 and 111.0 at 7e13 months of age (p Z 0.231). In normal controls, the Lateral Orbital Rim angle at 3e6 months of age was 109.8 (versus affected side: p Z 0.023; versus unaffected side: p Z 0.091), and 111.0 at 7e13 months of age (versus affected side: p Z 0.233; versus unaffected side: p Z 0.710). Lastly, Fronto-Orbital Zygomatic angle in the affected and unaffected side at 0e2 months of age was 120.7 and 105.7 (p < 0.001), 131.2 and 120.7 at 3e6 months of age (p Z 0.046), and 131.8 and 123.8 at 7e13 months of age (p Z 0.034), respectively. In controls, the Fronto-Orbital Zygomatic angle was 120.4 at 3e6 months of age (versus affected side: p Z 0.021; versus unaffected side: p Z 0.953) and 123.2 at 7e13 months of age (versus affected side: p Z 0.002; versus unaffected side: p Z 0.798).
Discussion Zygomatic growth is a complex process driven by the developing cranial base, intrinsic bone growth, and functional stress produced by the surrounding associated soft tissues. Facial width and anteroposterior growth of the upper and mid-facial skeleton are determined in part by bone growth that occurs along the synchondroses (i.e. sphenoethmoidal synchondrosis) of the cranial base, which
Table 4
also influence anterior cranial fossa development.17,18 Zygomatic bone growth is also dependent upon bone deposition along the posterior surface of the malar body with concomitant resorption along the anterior (facial) surface that occurs in coordination with maxillary growth.11,12 Furthermore, skeletal responses to functional stress (or lack thereof) placed on the bone by the associated soft tissues may contribute to zygomatic morphology.19 Premature suture fusion in UCS imparts a fronto-facial deformity, most notably of the supra-orbital and forehead regions; however, maxillary, nasal, and mandibular abnormalities also exist.37,10,14,20,21 Furthermore, as documented in previous reports3,4,15 and objectively analyzed in the present study, the zygomata of UCS patients also demonstrate dysmorphic features. It is posited that restricted development of the ipsilateral cranial vault drives compensatory expansion of the squamous temporal bone; the effect is anterior displacement of the body of the zygoma, resulting in a more forward-projecting malar eminence.15 Moreover, superolateral elevation of the orbital rim (Harlequin deformity) on the affected side, a consequence of restricted downward movement of the lateral aspect of the greater wing of the sphenoid, results in asymmetrical vertical growth of the sphenoid process of the zygoma (lateral orbital rim).5,7 Interestingly, the severity of this deformity may also be dictated by fusion of the frontosphenoidal suture.22 In UCS, the cranial base and anterior cranial fossa are notably maldeveloped,23e25 and, as a result, may influence abnormal growth of the developing zygomata. As with other facial bones, zygomatic growth is in part influenced by the surrounding soft tissue stresses, especially the muscle of mastication.16,26 In UCS, mandibular and temporomandibular joint displacement, with corresponding malocclusion and asymmetry, have been documented.14,21 Such
Affected versus normal control zygomata*.
Measurement Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Affected
Normal Control
P
N
Mean
SD
Range
N
Mean
SD
Range
12 12 12 12 12
1624.0 70.0 121.8 113.8 131.0
454.4 9.7 9.3 4.3 5.5
1058.6e2776.8 57.2e92.1 104.9e139.0 103.9e121.1 121.6e140.8
24 24 24 24 24
1933.9 80.1 128.5 109.1 122.3
420.5 6.0 6.7 4.3 5.8
1015.3e2574.1 66.8e87.1 114.0e140.0 98.1e114.9 112.05e134.1
N, Number of zygomata analyzed; *, Age- and sex-matched comparison.
0.057 <0.001 0.021 0.005 <0.001
1100 Table 5
M.J. Pfaff et al. Unaffected versus normal control zygomata*.
Measurement
Contralateral control 3
Zygomatic volume, mm Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
Normal control
P
N
Mean
SD
Range
N
Mean
SD
Range
12 12 12 12 12
1639.9 77.9 124.4 107.9 121.9
490.9 8.9 8.0 6.6 6.8
958.9e2654.9 59.8e90.5 109.2e135.5 90.8e114.6 108.1e132.5
24 24 24 24 24
1933.9 80.1 128.5 109.1 122.3
420.5 6.0 6.7 4.3 5.8
1015.3e2574.1 66.8e87.1 114.0e140.0 98.1e114.9 112.05e134.1
0.078 0.400 0.125 0.985 0.853
N, Number of zygomata analyzed; SD, standard deviation *, Age- and sex-matched comparison.
observations raise the possibility of masticatory aberrations contributing to zygomatic maldevelopment, in addition to temporal bone maldevelopment; however, further studies analyzing soft tissue morphology are necessary. Lastly, the zygomatic deformity, particularly the prominence of the malar eminence, may be accentuated by supraorbital flattening of the frontal bone on the affected side. Improved CT imaging has allowed for better characterization of craniofacial osseous and soft tissue dysmorphology.5e7,16,20,27e29 The present study sought to objectively evaluate the zygomatic deformity in UCS using CT-based 3D-rendered images and found that, of the 22 UCS patients, zygomatic volume of the affected side was, on average, reduced compared to the unaffected side; however, the difference did not achieve statistical significance (Table 3). Morphometric analysis of the zygoma and frontoorbital structures also demonstrated significant differences in zygomatic morphology. The zygomaticosphenoid angle was more acute on the affected side than the unaffected side. Superolateral growth of the sphenoid process of the zygoma on the affected side may be responsible for this finding as there was only a modest decrease in the
Table 6
angulation of the frontal portion of the zygoma (Frontal Zygomatic angle) when compared to the unaffected side. As expected, the lateral orbital rim angle and fronto-orbital zygomatic angle were more obtuse than the unaffected side. This observation is likely a result of superolateral elevation of the sphenoid process, frontal bone flattening, and anterior projection of the malar eminence on the affected side. When compared to age- and sex-matched normal controls, both the affected and unaffected sides were, on average, volumetrically deficient (Table 4). This observation is also supported by our comparison of the ratios of the zygomata in controls and UCS patients (Supplemental Table 1). With the exception of the frontal zygomatic angle, the morphometric measurements of the affected zygoma in UCS patients differed significantly compared to normal controls in a similar pattern when compared to the unaffected side. Again, in response to temporal bone expansion, the zygoma is projected anteriorly resulting in prominence of the malar eminence. Interestingly, we found the zygomaticofrontal angle to be more constricted on the affected side than in controls, providing further quantitative
Zygomatic growth over time.
Measurement
Age range Affected (months) side N
Zygomatic volume, mm3 Zygomaticosphenoid angle, Frontal zygomatic angle, Lateral orbital rim angle, Fronto-orbital zygomatic angle,
0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13 0e2 3e6 7e13
Value
Unaffected side SD
N
Value
Control
SD
N
Value
Affected Affected Unaffected versus versus versus unaffected control control SD
P
10 1278.5 225.6 10 1394.4 288.5 0 e e 0.064 6 1319.1 136.9 6 1315.1 256.7 10 1832.7 484.6 0.956 5 2031.7 486.1 5 2075.9 483.4 14 1998.5 338.9 0.673 10 72.0 4.3 10 89.2 6.9 0 e e <0.001 6 69.5 11.4 6 77.9 10.8 10 80.6 5.5 0.361 5 66.3 8.3 5 75.1 7.4 14 80.3 6.1 0.077 10 120.1 5.4 10 122.0 5.7 0 e e 0.302 6 120.7 8.3 6 126.6 6.3 10 125.9 6.3 0.369 5 123.9 10.6 5 125.8 8.7 14 130.6 6.4 0.242 10 114.9 4.3 10 110.8 7.3 0 e e 0.020 5 113.5 3.9 5 106.2 9.1 10 109.8 2.9 0.178 5 114.1 5.7 5 110.1 5.3 14 111.0 4.0 0.231 10 120.7 11.2 10 105.7 10.5 0 e e <0.001 5 131.2 5.4 5 120.7 8.0 10 120.4 7.6 0.046 5 131.8 5.6 5 123.8 5.4 14 123.2 3.8 0.034
N, Number of zygomata analyzed; SD, standard deviation.
P
P
e 0.032 0.706 e 0.029 0.001 e 0.202 0.136 e 0.067 0.233 e 0.021 0.002
e 0.038 0.973 e 0.554 0.156 e 0.850 0.233 e 0.278 0.710 e 0.953 0.798
Zygomatic dysmorphology in UCS evidence of anterior zygomatic displacement or repositioning. All measurements of the unaffected side were similar to normal controls. In UCS, the contralateral frontal bone inferior border (superior orbital rim) is thought to be depressed and would therefore produce a larger angle than in normal controls; however, unexpectedly, the Frontoorbital angle was similar to controls (Table 5). When stratified by age, zygomatic volume differed most significantly earlier in life, with the affected side trending smaller than the unaffected side and differing significantly compared to normal controls (Table 6). In addition, the unaffected side was significantly smaller than controls. By 7e13 months of age, however, the volumes of the affected and unaffected sides reached that of normal values. This finding is similar to the observation seen by Langford and colleagues20: maxillary volume, although deficient at an early age when compared to controls, approached that of normal values by seven months of age. Differences in craniometric measurements followed in a similar pattern, with the exception of the Fronto-orbital Zygomatic angle on the affected side. Zygomatic morphometry differed the greatest within the earlier age period between the affected side when compared to the unaffected side and to normal controls with the exception of the Fronto-Orbital Zygomatic angle, which differed significantly in all time periods. Measurements of the unaffected side were similar in all time points when compared to controls. These observed differences in zygomatic volume and morphometry at an earlier age, however, may be confounded by the fact that those who presented with more severe craniofacial distortion were as a result diagnosed at an earlier age. The aim of surgical intervention in UCS is to restore the craniofacial skeleton and prevent developmental and functional deficits. A multitude of surgical techniques have been proposed, all sharing the common goal of releasing the fused suture with concomitant correction of the frontoorbital deformity to establish normal contour and symmetry.15,30e35 It remains unclear whether commonly employed treatment approaches that alter the cranial vault and, in effect, normalize cranial base morphology,24 influence normal zygomatic growth and positioning. A similar concern was raised by Hansen and Mulliken regarding the deviated nasal root in UCS.31,35 With the held belief that traditional approaches not addressing the nasal root deformity would fail to ameliorate nasal root angulation, Hansen and Mulliken described a bilateral fronto-orbital procedure incorporating the nasal bones within the supraorbital bar; post-operative nasal root angulation significantly improved in UCS patients when compared to those that underwent other procedures that did not involve nasal radix reconstruction.31 Although a parallel may be drawn between the nasal radix and the zygomatic deformities, reconstruction of the zygoma may not be necessary (or technically feasible). Furthermore, the observation that zygomatic volume and morphometry (except the Frontoorbital Zygomatic angle) trended toward normal values over time (Table 6) suggests that the deformity may improve with time, thus obviating the need for surgical reconstruction. Further analyses studying the effects of surgical intervention on the degree of zygomatic dysmorphology and whether these changes relate to cranial base normalization would be welcomed.
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Conclusion In unicoronal synostosis, the affected zygomata were volumetrically deficient and morphometrically different compared to unaffected and normal control sides. The contralateral unaffected side were similar to normal controls, with the exception of a deficient zygomatic volume. These differences in zygomatic morphology appear to be greatest at an earlier age interval.
Support This work was supported by the Charles Ohse Grant from the Department of Surgery, Yale University School of Medicine.
Financial disclosures All authors have no commercial associations or disclosures that may pose or create a conflict of interest with the information presented within this manuscript.
Product used in this study Materialise Surgicase CMF Pro Version 8.0 for Windows; Leuven, Belgium.
Appendix A. Supplementary data Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.bjps.2013.04.025.
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