ORIGINAL ARTICLE
Growth Modulation in Achondroplasia Philip K. McClure, MD, Eray Kilinc, MD, and John G. Birch, MD
Introduction: Achondroplasia is the most common skeletal dysplasia with a rate of nearly 1/10,000. The development of lower extremity deformity is well documented, and various modes of correction have been reported. There are no reports on the use of growth modulation to correct angular deformity in achondroplasia. Methods: Medical Records from 1985 to 2015 were reviewed for the diagnosis of achondroplasia and growth modulation procedures. Patients who had been treated for angular deformity of the legs by growth modulation were identified. A detailed analysis of their medical record and preoperative and final lower extremity radiographs was completed. Results: Four patients underwent growth modulation procedures, all to correct existing varus deformity of the legs. Three of the 4 patients underwent bilateral distal femoral and proximal tibial growth modulation. The remaining patient underwent tibial correction only. Two of the 4 patients had a combined proximal fibular epiphysiodesis. All limbs had some improvement of alignment; however, 1 patient went on to bilateral osteotomies. Only 1 limb corrected to a neutral axis with growth modulation alone at last follow-up, initial implantation was done before 5 years of age. Conclusions: Growth modulation is an effective means for deformity correction in the setting of achondroplasia. However implantation may need to be done earlier than would be typical for patients without achondroplasia. Osteotomy may still be required after growth modulation for incomplete correction. Key Words: achondroplasia, growth modulation, deformity correction, genu varum
Typically a varus deformity is noted once patients start to stand, and progresses throughout early childhood.4 Hunter et al5 have noted that 10% of children demonstrate marked varus by 5 years of age, but continued progression results in approximately 40% of adults being affected, with up to 22% undergoing osteotomy in adolescence or early adulthood. Multiple corrective procedures are available, including fibular epiphysiodesis, tibial osteotomy, and gradual correction through distraction osteogenesis.6,7 Growth modulation to correct angular deformity in children has been growing in popularity, with predictable results across multiple settings. The use of growth modulation in the setting of other dwarfing skeletal dysplasias has been reported in a few isolated cases, with positive results.8,9 No reports are available regarding growth modulation in individuals with achondroplasia.
METHODS After obtaining approval from the institutional Review Board, medical records were reviewed from 1985 to 2015. Four patients were identified that satisfied inclusion criteria of growth modulation in the setting of achondroplasia. Records were reviewed for date of implantation and removal, as well as additional surgical care. Radiographs were measured for the following data points: mechanical axis deviation, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), lateral distal tibial angle, distal femoral physeal width, proximal tibial physeal width, femoral and tibial bone segment length, and the zone of intersection of the mechanical axis at the knee.
(J Pediatr Orthop 2017;37:e384–e387)
RESULTS
A
chondroplasia is the most common skeletal dysplasia, with a rate of 0.36 to 0.6/10,000 live births, and approximately 250,000 affected individuals worldwide.1,2 The development of lower extremity deformity in achondroplasia is widely known; the American Academy of Pediatrics has developed guidelines to help primary care physicians and optimize involvement of orthopedists based on age. Referral is encouraged as early as age 1 to 5 if difficulty walking or pain are present.3 From the Texas Scottish Rite Hospital, Dallas, TX. No funding was received for this work. The authors declare no conflicts of interest. Reprints: Philip K. McClure, MD, Texas Scottish Rite Hospital, 2222 Welborn Street, Dallas, TX 75219. E-mail: [email protected]. Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/BPO.0000000000001045
e384 | www.pedorthopaedics.com
Four patients were identified who fit the inclusion criteria (Table 1). No patients were identified who had growth modulation with staples before the introduction of tension band plates. Each patient had long leg radiographs immediately before initiation of growth modulation and at the time of completion of treatment or last follow-up. The average age at implantation was 8.9 years, with a range from 4 years 8 months to 10 years 8 months. All implants were unlocked plates with a single screw in the metaphysis and epiphysis. The average mechanical axis deviation immediately before implantation was 5.2 cm medial, in zone 3. The range of mechanical axis deviation was 4.1 to 8.1 cm medial. Varus was noted to come from both the femur and tibia with average mLDFA of 100 degrees (range, 89 to 107 degrees) and average MPTA of 74 degrees (range, 66 to 77 degrees). All patients had internal tibial torsion, although records were J Pediatr Orthop
Volume 37, Number 6, September 2017
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 37, Number 6, September 2017
Growth Modulation in Achondroplasia
not adequate to determine if this changed throughout the treatment course. Three patients underwent growth modulation of the both the distal femur and proximal tibia, one of these 3 underwent concomitant proximal fibular epiphysiodesis. One underwent growth modulation of the proximal tibias only, which was paired with proximal fibular arrest. At the time of initial intervention, this patient had normal mLDFA on one side, and 8 degrees of varus on the contralateral side. At last follow-up 4.35 years later, bilateral distal femoral varus had developed (mLDFA of 99 and 97). At the termination of treatment, 1 patient had undergone osteotomy, 1 patient had neutralization of the mechanical axis in one leg, and improvement of the other. The remaining 2 patients had improvement of mechanical alignment at the time of last radiograph and last follow-up at the ages of 13 and 14 and a half. Figures 1 and 2 demonstrate the course of treatment in a patient who experienced improvement but not full correction after implantation at 9 years and 8 months of age. All patients had improvement of their mechanical axis as well as joint line angles. Other than incomplete correction, no surgical
FIGURE 2. Postoperative x-ray at age 13+7 of the same patient after growth modulation. Improvement of the mechanical axis is noted. A mature pelvis is noted, with some narrowing the remaining physes of the lower extremity.
complications were encountered in our series. Mechanical distal tibial angle was measured in all cases, but change at the end of treatment was minimal, with the largest change being 7 degrees, and an average change of 0.3 degrees.
DISCUSSION
FIGURE 1. Preoperative x-ray at age 10+7 before implantation of growth modulation device. Genu varum is present, with the mechanical axis of the lower extremity passing well medial to the joint. Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Varus deformity is very common in achondroplasia, multiple treatment methods are available and have been reported. Beals and Stanley reviewed 22 patients who were treated for genu varum through proximal tibial osteotomy, either opening wedge, closing wedge, or through distraction osteogenesis. All were effective, but carried approximately 15% risk of transient peroneal nerve palsy.6 Another series focusing on limb deformity correction through a hexapod fixator included 3 patients with achondroplasia, no specific differences were noted in the treatment of patients affected by achondroplasia compared with the remainder of the cohort.10 Complications of growth modulation have been reported in the literature. High rates of complications www.pedorthopaedics.com |
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
e385
J Pediatr Orthop
McClure et al
Volume 37, Number 6, September 2017
TABLE 1. Preimplantation and Final Follow-up Measurements 1 Age at Implantation (y)
Procedures Implantation MAD mLDFA mMPTA mLDTA Zone Final follow-up MAD mLDFA mMPTA mLDTA Zone Change MAD mLDFA mMPTA mLDTA Outcome Duration (mo)
2
3
4
4+8 10+7 10+8 Male Male Male Bilateral Growth Mod.: Bilateral Growth Mod.: Distal Bilateral Growth Mod.: Distal Fem. and Proximal Fem. and Proximal Tib. Proximal Tib. Bilateral Fib. Tib. Bilateral Fib. Epiphysiodesis Epiphysiodesis
10+0 Female Bilateral Growth Mod.: Distal Fem. and Proximal Tib.
Right
Left
Right
Left
Right
Left
Right
Left
45.4 104 77 99 3
48.8 112 76 88 3
49.2 94 75 3
58 103 77 114 3
44.7 96 74 98 3
41.8 89 77 100 3
81 107 66 112 3
52 97 72 101 3
30 83 71 94 3
0 78 91 91 1
23 87 80 100 2
21 91 82 107 2
39.5 99 86 105 3
26 97 93 107 2
62 103 73 109 3
48 100 78 101 3
26.2 7 5 * Continue
37 12 5 7 Continue
5.2 3 12 7 Continue
15.8 8 16 7 Continue
19 4 7 3 Osteotomy
4 3 6 0 Osteotomy
15.4 21 6 5 Continue
48.8 34 15 3 Removal 49
36
52
15
Duration (mo): duration of growth modulation in months of treatment. *Angle unable to be measured on last follow up film. F indicates female; Fem., femoral; M, male; MAD, mechanical axis deviation; mLDFA, mechanical lateral distal femoral angle (normal 87 degrees); mLDTA, mechanical lateral distal tibial angle (normal 90 degrees); mMPTA, medial proximal tibial angle (normal 87 degrees); Mod, modulation; Tib, tibial.
have been noted in some disease entities, particularly Blount’s—however, the complication rate has been correlated with increased body mass index, and is not felt to be intrinsic to the technique.11 No complications were encountered in our series. However, small sample size prevents meaningful interpretation of this finding. Fibular overgrowth has been correlated with genu varum throughout skeletal development in the setting of achondroplasia, but conclusions regarding whether this is the driver of genu varum is unclear.12 Lee and colleagues related fibular overgrowth to decreased MPTA and increased medial axis deviation. Deviation of the LDFA was not associated with fibular overgrowth.13 Using a different analysis method, Ain et al14 found genu varum to be independent of fibular overgrowth. The role of intervention regarding the fibular overgrowth in the setting of genu varum is unclear. Unfortunately our series does not have the appropriate power to evaluate, though we did see improvement in the mechanical axis through growth modulation both with and without proximal fibular epiphysiodesis. Growth modulation is dependent entirely on the growth of the physis, though the rate of correction is difficult to predict. Delayed bone age has been found in children with achondroplasia, with the authors concluding that physeal interventions should be delayed as a result.15 However, based on our limited data in this series with prolonged correction after growth modulation, we would advocate for early use of reversible techniques for angular correction if deformity is symptomatic or is felt to be unacceptable.
e386 | www.pedorthopaedics.com
In addition to the weaknesses inherent to a retrospective study, the additional weakness of only having radiographic analysis available is present. It has been demonstrated that in the setting of achondroplasia that dynamic lower extremity alignment as shown through gait analysis does not correlate well with radiographic parameters.16 It has not been demonstrated in the literature what the optimal alignment is for these patients. Given these differences, it would be reasonable to continue with treatment until symptoms have resolved (pain, gait disturbance, etc.), and then undergo further discussion on whether radiographically neutral axes should be pursued. Although growth modulation is intrinsically a growth limiting procedure, the impact of growth modulation on final height has not been established. While some surgeons and patients may be reluctant to pursue growth modulation in skeletal dysplasia due to this concern, it is unclear if this represents a significant negative effect of the technique. A recent report of growth modulation in skeletal dysplasia did not report in overall loss of height.9 Even if some loss of height occurs, many patients may prefer growth modulation to avoid more complex alignment procedures.
CONCLUSIONS Growth modulation can be an effective treatment method for genu varum in the setting of achondroplasia. In contrast to previous literature in which delayed bone maturation in achondroplasia has been demonstrated, however the impact on growth modulation is unknown. Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 37, Number 6, September 2017
Consideration should be given to early intervention to allow complete correction. REFERENCES 1. Horton WA, Hall JG, Hecht JT. Achondroplasia. Lancet (Lond, Engl). 2007;370:162–172. 2. Waller DK, Correa A, Vo TM, et al. The population-based prevalence of achondroplasia and thanatophoric dysplasia in selected regions of the US. Am J Med Genet A. 2008;146A:2385–2389. 3. Trotter TL, Hall JG. American Academy of Pediatrics Committee on Genetics. Health supervision for children with achondroplasia. Pediatrics. 2005;116:771–783. 4. Kopits SE. Orthopedic aspects of achondroplasia in children. Basic Life Sci. 1988;48:189–197. 5. Hunter AG, Bankier A, Rogers JG, et al. Medical complications of achondroplasia: a multicentre patient review. J Med Genet. 1998;35:705–712. 6. Beals RK, Stanley G. Surgical correction of bowlegs in achondroplasia. J Pediatr Orthop Part B. 2005;14:245–249. 7. Kaissi AA, Farr S, Ganger R, et al. Treatment of varus deformities of the lower limbs in patients with achondroplasia and hypochondroplasia. Open Orthop J. 2013;7:33–39. 8. Al Kaissi A, Ganger R, Roetzer KM, et al. Re-alignmentprocedures for skeletal dysplasia in three patients with genetically diverse syndromes. Orthop Surg. 2013;5:33–39.
Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Growth Modulation in Achondroplasia
9. Yilmaz G, Oto M, Thabet AM, et al. Correction of lower extremity angular deformities in skeletal dysplasia with hemiepiphysiodesis: a preliminary report. J Pediatr Orthop. 2014;34:336–345. 10. Blondel B, Launay F, Glard Y, et al. Limb lengthening and deformity correction in children using hexapodal external fixation: Preliminary results for 36 cases. Orthop Traumatol Surg Res. 2009; 95:425–430. 11. Funk SS, Mignemi ME, Schoenecker JG, et al. Hemiepiphysiodesis implants for late-onset tibia vara: a comparison of cost, surgical success, and implant failure. J Pediatr Orthop. 2016;36:29–35. 12. Ponseti IV. Bone Formation in Achondroplasia. In: Nicoletti B, Kopits SE, Ascani E, McKusick VA, Dryburgh SC, eds. Human Achondroplasia Basic Life Sciences. Plenum Press, New York, NY: Springer US; 1988:109–122. Available at: http://link.springer.com/ chapter/10.1007/978-1-4684-8712-1_15. Accessed August 22, 2016. 13. Lee ST, Song HR, Mahajan R, et al. Development of genu varum in achondroplasia: relation to fibular overgrowth. J Bone Joint Surg Br. 2007;89:57–61. 14. Ain MC, Shirley ED, Pirouzmanesh A, et al. Genu varum in achondroplasia. J Pediatr Orthop. 2006;26:375–379. 15. Lee S-H, Modi HN, Song H-R, et al. Deceleration in maturation of bone during adolescent age in achondroplasia—a retrospective study using RUS scoring system. Skeletal Radiol. 2009;38:165–170. 16. Inan M, Thacker M, Church C, et al. Dynamic lower extremity alignment in children with achondroplasia. J Pediatr Orthop. 2006; 26:526–529.
www.pedorthopaedics.com |
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
e387
Growth Modulation in Achondroplasia Philip K. McClure, MD, Eray Kilinc, MD, and John G. Birch, MD
Introduction: Achondroplasia is the most common skeletal dysplasia with a rate of nearly 1/10,000. The development of lower extremity deformity is well documented, and various modes of correction have been reported. There are no reports on the use of growth modulation to correct angular deformity in achondroplasia. Methods: Medical Records from 1985 to 2015 were reviewed for the diagnosis of achondroplasia and growth modulation procedures. Patients who had been treated for angular deformity of the legs by growth modulation were identified. A detailed analysis of their medical record and preoperative and final lower extremity radiographs was completed. Results: Four patients underwent growth modulation procedures, all to correct existing varus deformity of the legs. Three of the 4 patients underwent bilateral distal femoral and proximal tibial growth modulation. The remaining patient underwent tibial correction only. Two of the 4 patients had a combined proximal fibular epiphysiodesis. All limbs had some improvement of alignment; however, 1 patient went on to bilateral osteotomies. Only 1 limb corrected to a neutral axis with growth modulation alone at last follow-up, initial implantation was done before 5 years of age. Conclusions: Growth modulation is an effective means for deformity correction in the setting of achondroplasia. However implantation may need to be done earlier than would be typical for patients without achondroplasia. Osteotomy may still be required after growth modulation for incomplete correction. Key Words: achondroplasia, growth modulation, deformity correction, genu varum
Typically a varus deformity is noted once patients start to stand, and progresses throughout early childhood.4 Hunter et al5 have noted that 10% of children demonstrate marked varus by 5 years of age, but continued progression results in approximately 40% of adults being affected, with up to 22% undergoing osteotomy in adolescence or early adulthood. Multiple corrective procedures are available, including fibular epiphysiodesis, tibial osteotomy, and gradual correction through distraction osteogenesis.6,7 Growth modulation to correct angular deformity in children has been growing in popularity, with predictable results across multiple settings. The use of growth modulation in the setting of other dwarfing skeletal dysplasias has been reported in a few isolated cases, with positive results.8,9 No reports are available regarding growth modulation in individuals with achondroplasia.
METHODS After obtaining approval from the institutional Review Board, medical records were reviewed from 1985 to 2015. Four patients were identified that satisfied inclusion criteria of growth modulation in the setting of achondroplasia. Records were reviewed for date of implantation and removal, as well as additional surgical care. Radiographs were measured for the following data points: mechanical axis deviation, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), lateral distal tibial angle, distal femoral physeal width, proximal tibial physeal width, femoral and tibial bone segment length, and the zone of intersection of the mechanical axis at the knee.
(J Pediatr Orthop 2017;37:e384–e387)
RESULTS
A
chondroplasia is the most common skeletal dysplasia, with a rate of 0.36 to 0.6/10,000 live births, and approximately 250,000 affected individuals worldwide.1,2 The development of lower extremity deformity in achondroplasia is widely known; the American Academy of Pediatrics has developed guidelines to help primary care physicians and optimize involvement of orthopedists based on age. Referral is encouraged as early as age 1 to 5 if difficulty walking or pain are present.3 From the Texas Scottish Rite Hospital, Dallas, TX. No funding was received for this work. The authors declare no conflicts of interest. Reprints: Philip K. McClure, MD, Texas Scottish Rite Hospital, 2222 Welborn Street, Dallas, TX 75219. E-mail: [email protected]. Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/BPO.0000000000001045
e384 | www.pedorthopaedics.com
Four patients were identified who fit the inclusion criteria (Table 1). No patients were identified who had growth modulation with staples before the introduction of tension band plates. Each patient had long leg radiographs immediately before initiation of growth modulation and at the time of completion of treatment or last follow-up. The average age at implantation was 8.9 years, with a range from 4 years 8 months to 10 years 8 months. All implants were unlocked plates with a single screw in the metaphysis and epiphysis. The average mechanical axis deviation immediately before implantation was 5.2 cm medial, in zone 3. The range of mechanical axis deviation was 4.1 to 8.1 cm medial. Varus was noted to come from both the femur and tibia with average mLDFA of 100 degrees (range, 89 to 107 degrees) and average MPTA of 74 degrees (range, 66 to 77 degrees). All patients had internal tibial torsion, although records were J Pediatr Orthop
Volume 37, Number 6, September 2017
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 37, Number 6, September 2017
Growth Modulation in Achondroplasia
not adequate to determine if this changed throughout the treatment course. Three patients underwent growth modulation of the both the distal femur and proximal tibia, one of these 3 underwent concomitant proximal fibular epiphysiodesis. One underwent growth modulation of the proximal tibias only, which was paired with proximal fibular arrest. At the time of initial intervention, this patient had normal mLDFA on one side, and 8 degrees of varus on the contralateral side. At last follow-up 4.35 years later, bilateral distal femoral varus had developed (mLDFA of 99 and 97). At the termination of treatment, 1 patient had undergone osteotomy, 1 patient had neutralization of the mechanical axis in one leg, and improvement of the other. The remaining 2 patients had improvement of mechanical alignment at the time of last radiograph and last follow-up at the ages of 13 and 14 and a half. Figures 1 and 2 demonstrate the course of treatment in a patient who experienced improvement but not full correction after implantation at 9 years and 8 months of age. All patients had improvement of their mechanical axis as well as joint line angles. Other than incomplete correction, no surgical
FIGURE 2. Postoperative x-ray at age 13+7 of the same patient after growth modulation. Improvement of the mechanical axis is noted. A mature pelvis is noted, with some narrowing the remaining physes of the lower extremity.
complications were encountered in our series. Mechanical distal tibial angle was measured in all cases, but change at the end of treatment was minimal, with the largest change being 7 degrees, and an average change of 0.3 degrees.
DISCUSSION
FIGURE 1. Preoperative x-ray at age 10+7 before implantation of growth modulation device. Genu varum is present, with the mechanical axis of the lower extremity passing well medial to the joint. Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Varus deformity is very common in achondroplasia, multiple treatment methods are available and have been reported. Beals and Stanley reviewed 22 patients who were treated for genu varum through proximal tibial osteotomy, either opening wedge, closing wedge, or through distraction osteogenesis. All were effective, but carried approximately 15% risk of transient peroneal nerve palsy.6 Another series focusing on limb deformity correction through a hexapod fixator included 3 patients with achondroplasia, no specific differences were noted in the treatment of patients affected by achondroplasia compared with the remainder of the cohort.10 Complications of growth modulation have been reported in the literature. High rates of complications www.pedorthopaedics.com |
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
e385
J Pediatr Orthop
McClure et al
Volume 37, Number 6, September 2017
TABLE 1. Preimplantation and Final Follow-up Measurements 1 Age at Implantation (y)
Procedures Implantation MAD mLDFA mMPTA mLDTA Zone Final follow-up MAD mLDFA mMPTA mLDTA Zone Change MAD mLDFA mMPTA mLDTA Outcome Duration (mo)
2
3
4
4+8 10+7 10+8 Male Male Male Bilateral Growth Mod.: Bilateral Growth Mod.: Distal Bilateral Growth Mod.: Distal Fem. and Proximal Fem. and Proximal Tib. Proximal Tib. Bilateral Fib. Tib. Bilateral Fib. Epiphysiodesis Epiphysiodesis
10+0 Female Bilateral Growth Mod.: Distal Fem. and Proximal Tib.
Right
Left
Right
Left
Right
Left
Right
Left
45.4 104 77 99 3
48.8 112 76 88 3
49.2 94 75 3
58 103 77 114 3
44.7 96 74 98 3
41.8 89 77 100 3
81 107 66 112 3
52 97 72 101 3
30 83 71 94 3
0 78 91 91 1
23 87 80 100 2
21 91 82 107 2
39.5 99 86 105 3
26 97 93 107 2
62 103 73 109 3
48 100 78 101 3
26.2 7 5 * Continue
37 12 5 7 Continue
5.2 3 12 7 Continue
15.8 8 16 7 Continue
19 4 7 3 Osteotomy
4 3 6 0 Osteotomy
15.4 21 6 5 Continue
48.8 34 15 3 Removal 49
36
52
15
Duration (mo): duration of growth modulation in months of treatment. *Angle unable to be measured on last follow up film. F indicates female; Fem., femoral; M, male; MAD, mechanical axis deviation; mLDFA, mechanical lateral distal femoral angle (normal 87 degrees); mLDTA, mechanical lateral distal tibial angle (normal 90 degrees); mMPTA, medial proximal tibial angle (normal 87 degrees); Mod, modulation; Tib, tibial.
have been noted in some disease entities, particularly Blount’s—however, the complication rate has been correlated with increased body mass index, and is not felt to be intrinsic to the technique.11 No complications were encountered in our series. However, small sample size prevents meaningful interpretation of this finding. Fibular overgrowth has been correlated with genu varum throughout skeletal development in the setting of achondroplasia, but conclusions regarding whether this is the driver of genu varum is unclear.12 Lee and colleagues related fibular overgrowth to decreased MPTA and increased medial axis deviation. Deviation of the LDFA was not associated with fibular overgrowth.13 Using a different analysis method, Ain et al14 found genu varum to be independent of fibular overgrowth. The role of intervention regarding the fibular overgrowth in the setting of genu varum is unclear. Unfortunately our series does not have the appropriate power to evaluate, though we did see improvement in the mechanical axis through growth modulation both with and without proximal fibular epiphysiodesis. Growth modulation is dependent entirely on the growth of the physis, though the rate of correction is difficult to predict. Delayed bone age has been found in children with achondroplasia, with the authors concluding that physeal interventions should be delayed as a result.15 However, based on our limited data in this series with prolonged correction after growth modulation, we would advocate for early use of reversible techniques for angular correction if deformity is symptomatic or is felt to be unacceptable.
e386 | www.pedorthopaedics.com
In addition to the weaknesses inherent to a retrospective study, the additional weakness of only having radiographic analysis available is present. It has been demonstrated that in the setting of achondroplasia that dynamic lower extremity alignment as shown through gait analysis does not correlate well with radiographic parameters.16 It has not been demonstrated in the literature what the optimal alignment is for these patients. Given these differences, it would be reasonable to continue with treatment until symptoms have resolved (pain, gait disturbance, etc.), and then undergo further discussion on whether radiographically neutral axes should be pursued. Although growth modulation is intrinsically a growth limiting procedure, the impact of growth modulation on final height has not been established. While some surgeons and patients may be reluctant to pursue growth modulation in skeletal dysplasia due to this concern, it is unclear if this represents a significant negative effect of the technique. A recent report of growth modulation in skeletal dysplasia did not report in overall loss of height.9 Even if some loss of height occurs, many patients may prefer growth modulation to avoid more complex alignment procedures.
CONCLUSIONS Growth modulation can be an effective treatment method for genu varum in the setting of achondroplasia. In contrast to previous literature in which delayed bone maturation in achondroplasia has been demonstrated, however the impact on growth modulation is unknown. Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 37, Number 6, September 2017
Consideration should be given to early intervention to allow complete correction. REFERENCES 1. Horton WA, Hall JG, Hecht JT. Achondroplasia. Lancet (Lond, Engl). 2007;370:162–172. 2. Waller DK, Correa A, Vo TM, et al. The population-based prevalence of achondroplasia and thanatophoric dysplasia in selected regions of the US. Am J Med Genet A. 2008;146A:2385–2389. 3. Trotter TL, Hall JG. American Academy of Pediatrics Committee on Genetics. Health supervision for children with achondroplasia. Pediatrics. 2005;116:771–783. 4. Kopits SE. Orthopedic aspects of achondroplasia in children. Basic Life Sci. 1988;48:189–197. 5. Hunter AG, Bankier A, Rogers JG, et al. Medical complications of achondroplasia: a multicentre patient review. J Med Genet. 1998;35:705–712. 6. Beals RK, Stanley G. Surgical correction of bowlegs in achondroplasia. J Pediatr Orthop Part B. 2005;14:245–249. 7. Kaissi AA, Farr S, Ganger R, et al. Treatment of varus deformities of the lower limbs in patients with achondroplasia and hypochondroplasia. Open Orthop J. 2013;7:33–39. 8. Al Kaissi A, Ganger R, Roetzer KM, et al. Re-alignmentprocedures for skeletal dysplasia in three patients with genetically diverse syndromes. Orthop Surg. 2013;5:33–39.
Copyright
r
2017 Wolters Kluwer Health, Inc. All rights reserved.
Growth Modulation in Achondroplasia
9. Yilmaz G, Oto M, Thabet AM, et al. Correction of lower extremity angular deformities in skeletal dysplasia with hemiepiphysiodesis: a preliminary report. J Pediatr Orthop. 2014;34:336–345. 10. Blondel B, Launay F, Glard Y, et al. Limb lengthening and deformity correction in children using hexapodal external fixation: Preliminary results for 36 cases. Orthop Traumatol Surg Res. 2009; 95:425–430. 11. Funk SS, Mignemi ME, Schoenecker JG, et al. Hemiepiphysiodesis implants for late-onset tibia vara: a comparison of cost, surgical success, and implant failure. J Pediatr Orthop. 2016;36:29–35. 12. Ponseti IV. Bone Formation in Achondroplasia. In: Nicoletti B, Kopits SE, Ascani E, McKusick VA, Dryburgh SC, eds. Human Achondroplasia Basic Life Sciences. Plenum Press, New York, NY: Springer US; 1988:109–122. Available at: http://link.springer.com/ chapter/10.1007/978-1-4684-8712-1_15. Accessed August 22, 2016. 13. Lee ST, Song HR, Mahajan R, et al. Development of genu varum in achondroplasia: relation to fibular overgrowth. J Bone Joint Surg Br. 2007;89:57–61. 14. Ain MC, Shirley ED, Pirouzmanesh A, et al. Genu varum in achondroplasia. J Pediatr Orthop. 2006;26:375–379. 15. Lee S-H, Modi HN, Song H-R, et al. Deceleration in maturation of bone during adolescent age in achondroplasia—a retrospective study using RUS scoring system. Skeletal Radiol. 2009;38:165–170. 16. Inan M, Thacker M, Church C, et al. Dynamic lower extremity alignment in children with achondroplasia. J Pediatr Orthop. 2006; 26:526–529.
www.pedorthopaedics.com |
Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.
e387
