Radiostereometric analysis for monitoring percutaneous physiodesis. A preliminary study

Are percutaneous epiphysiodesis and Phemister technique effective in the treatment of leg-length discrepancy? A systematic review

Epiphysiodesis is considered the preferred treatment for children predicted to have leg length discrepancies (LLDs) 2-5 cm at maturity. The aim of this study was to systematically review the existing literature on the effectiveness of permanent epiphysiodesis for LLD treatment, and secondarily to address the reported complications of permanent epiphysiodesis techniques. This systematic review was performed according to PRISMA guidelines. We searched MEDLINE (PubMed), Embase, Cochrane Library, Web of Science and Scopus for studies on skeletally immature patients with LLD treated with permanent epiphysiodesis. The extracted outcome categories were effectiveness of epiphysiodesis (LLD measurements pre/post-operatively, successful/unsuccessful), physeal fusion/arrest, and complications that were graded on severity. Forty-nine studies (3051 patients) were included, 1550 underwent Phemister/modified Phemister epiphysiodesis and 1501 percutaneous epiphysiodesis (PE). Total successful permanent epiphysiodesis surgeries (16 studies) were 73.7% (516/700). Only 13 out of 23 studies had a mean final LLD of less than 1.5 cm. In total, 17.5% (513/2936) of complications were reported. 57 angular deformities were reported (1.9%). Phemister technique had higher percentage of complications (39%) than PE (19.1%) in total, but when failure to achieve adequate reduction in LLD was not included, complication rates for both were close to 14%. However, severe complications were 10.2% for Phemister group and 5.1% for PE. The high complication rates and the relative low success rate call for optimization of the timing and the applied techniques when treating LLD with permanent epiphysiodesis. Phemister technique was found to have higher percentage of severe complications than PE. Registration: PROSPERO (CRD42023435177).

Angular deformities after percutaneous epiphysiodesis for leg length discrepancy

PURPOSE

The purpose of this study was to systematically analyze the presence of secondary angular deformities after percutaneous epiphysiodesis based on long-standing radiographs, and to see if the occurrence and magnitude of angular deformities after percutaneous epiphysiodesis correlated with the amount of remaining growth at the time of surgery.

METHODS

From a local Health Register consisting of patients investigated using the Moseley Straight-Line Graph, we identified 269 patients who had undergone percutaneous epiphysiodesis from 2002 until 2020. Radiographic analysis included the measurement of mechanical axis and joint orientation angles on long-standing anterior-posterior radiographs. Remaining growth was analyzed based on the Menelaus method.

RESULTS

One hundred and forty epiphysiodeses (71 femurs and 69 tibiae) in 88 patients (39 girls and 49 boys) could be included in the study. Mean age at surgery was 13.2 (10-16.8) years, and mean skeletal age at surgery was 13.0 (9.8-15.7) years. A change of the MA (Mechanical axis) ≥10 mm was found in eight patients (9%). Secondary frontal plane deformities after percutaneous epiphysiodesis correlated significantly with the remaining growth at the time of surgery (p = 0.003).

CONCLUSION

We found a high rate of secondary angular deformities after percutaneous epiphysiodesis, and the magnitude of the deformities correlated with the amount of remaining growth at the time of surgery. A modification of the original surgical method for percutaneous epiphysiodesis to also include ablation of central parts of the growth plate might be considered. Patients should be enrolled in a systematic follow-up scheme which allows for the early detection of possible angular deformities.

LEVEL OF EVIDENCE

level III study.

Postoperative growth rate affects time to growth arrest after percutaneous physiodesis: A radiostereometric analysis

PURPOSE

The aim of this study was to determine the time at which physeal arrest is achieved after percutaneous physiodesis, and whether immediate postoperative growth rate affects the time to reach physeal arrest.

METHODS

Radiostereometric analysis, with implantation of tantalum balls as radiographic markers on each side of the physes, was used to measure residual longitudinal growth in 21 children (10 boys and 11 girls) after percutaneous physiodesis for leg length discrepancy or extreme tall stature. In total, 25 femoral and 20 tibial physes were operated on. Median age at surgery was 13.9 years (range = 11.4-16.1). Radiostereometric analysis was performed postoperatively and after 3, 6, 9, 12, 26, and 52 weeks. Longitudinal growth rate <50 µm per week was defined as physeal arrest. Descriptive statistics were used for evaluation.

RESULTS

Physeal arrest was obtained in 19 of the 21 children (40 physes) within 12 weeks postoperatively. One child was reoperated on in three out of four physes because of continued growth, and in one child, delayed physeal arrest was present at 26 weeks postoperatively. Time to physeal arrest was longer in physes with a higher immediate postoperative growth rate.

CONCLUSION

Postoperative follow-up with radiostereometric analysis at 12 and 15 weeks can determine whether physeal arrest has been achieved. The immediate postoperative growth rate after physiodesis seems to affect the time to physeal arrest. This implies that the risk for complications is greater for children during an accelerated growth period, for example, in boys, younger children and in distal femoral physes.

LEVEL OF EVIDENCE

level III.

Reliability and Reproducibility of Subject Positioning with EOS Low-Dose Biplanar X-ray

BACKGROUND

EOS low-dose biplanar X-ray used with tantalum bead implantation is an appealing imaging modality to evaluate limb length and physeal growth due its relatively low radiation exposure, excellent inter- and intra-observer reliability, and minimal magnification/shrinkage error.

QUESTIONS/PURPOSES

The purpose of this study was to establish the error in total length and inter-bead distances using EOS and tantalum beads due to variable positioning in the EOS gantry, by assessing variation in measurements made on the same subject repeatedly positioning by one positioner (intra-positioner measurement error) and variation in measurements made on the same subject with positioning by multiple positioners (inter-positioner measurement error).

METHODS

Tantalum bead markers were placed about the distal femoral physis of a cadaveric lamb femur. Three investigators positioned the femur in the EOS gantry 10 times, totaling 30 EOS scans. Total limb length and inter-bead distances were measured on AP and lateral views; mean and standard error were calculated. A random effects analysis of variance for nested data was used to determine the proportion of variation due to differences between positioners and differences between positioning by the same positioner.

RESULTS

Intra-positioner measurement error ranged from 0.01 to 0.06 mm. Inter-positioner measurement error ranged from 0.00 to 0.09 mm.

CONCLUSIONS

EOS has relatively low radiation and allows standing assessment of limb length and alignment. In this study, length measurements and inter-bead distances demonstrated minimal error due to positioning in the EOS gantry, documenting that there is minimal error from positioning, minimal magnification/shrinkage error, and exceptional inter and intra-rater reliability. EOS is the preferred method for length and angular measurements, and with tantalum beads, is ideal for measuring growth about the physis.

Stability and migration across femoral varus derotation osteotomies in children with neuromuscular disorders

Background and purpose - Studies have indicated that one-third of children with cerebral palsy (CP) develop dislocation of the hip that needs surgical intervention. When hip dislocation occurs during childhood surgical treatment consists of tenotomies, femoral varus derotation osteotomy (VDRO), and acetabuloplasty. Relapse is observed in one-fifth of cases during adolescence. In this prospective cohort study, we performed a descriptive evaluation of translation and rotation across VDROs in children with neuromuscular disorders and syndromes by radiostereometric analysis (RSA). We assessed "RSA stability" and migration across the VDROs. Patients and methods - Children with a neuromuscular disorder were set up for skeletal corrective surgery of the hip. RSA follow-ups were performed postoperatively, at 5 weeks, and 3, 6, and 12 months after surgery. Results - 27 femoral VDROs were included; 2 patients were excluded during the study period. RSA data showed stability across the VDRO in the majority of cases within the first 5 weeks. At the 1-year follow-up, the mean translations (SD) of the femoral shaft distal to the VDRO were 0.51 (1.12) mm medial, 0.69 (1.61) mm superior, and 0.21 (1.28) mm posterior. The mean rotations were 0.39° (2.90) anterior tilt, 0.02° (3.07) internal rotation, and 2.17° (2.29) varus angulation. Interpretation - The migration stagnates within the first 5 weeks, indicating stability across the VDRO in most patients.

Evaluating Length: The Use of Low-dose Biplanar Radiography (EOS) and Tantalum Bead Implantation

BACKGROUND

Low-dose biplanar radiography (EOS) is an appealing imaging modality for use in children given its low radiation and ease of use. The goal of this study was to determine the accuracy and reliability of EOS compared with CT scanogram for measurement of leg length and to assess interrater and intrarater reliability of measured interbead distances for EOS and CT scanogram after insertion of tantalum beads into lamb femurs.

METHODS

Tantalum beads (0.8 mm) were inserted into the cortex on both the medial and lateral sides of 10 skeletally immature lamb femurs. CT scanogram and EOS imaging were obtained. Measurements of total length and distance between bead pairs were recorded on anteroposterior and lateral views by 2 orthopaedic surgeons on 2 separate occasions. Pearson correlations were performed for statistical comparisons.

RESULTS

EOS measurements showed near-perfect correlation to those of CT scanogram (r>0.96, P<0.001). Intrarater reliability was excellent for all measurements with EOS (r>0.98, P<0.001) and CT scanogram (r>0.99, P<0.001) as was interrater reliability for EOS (r>0.98, P<0.001) and CT scanogram (r>0.99, P<0.001).

CONCLUSIONS

EOS is comparable with CT scanogram in the assessment of limb length and the distance between 2 radiopaque markers. Reliability was excellent for all measurements. The combination of EOS imaging and tantalum bead implantation may be an effective way to evaluate physeal growth following procedures such as epiphysiodesis and physeal bar resection.

LEVEL OF EVIDENCE

Level II—diagnostic

Percutaneous epiphysiodesis in the proximal tibia by a single-portal approach: evaluation by radiostereometric analysis

PURPOSE

We modified the method for tibial epiphysiodesis by solely using a lateral approach to the physis. From this small-incision approach, the lateral as well as the medial part of the tibial physis were ablated. The aim of our study was to see if this operative technique might be as effective as a bilateral approach, and reduce the operation time and usage time of the image intensifier. The epiphysiodeses were monitored by radiostereometric analysis (RSA), which is a well-established method for the analysis of micro movements and has been used to monitor percutaneous epiphysiodesis with the bilateral approach. There are no reports in the literature comparing single- with double-portal approaches for percutaneous epiphysiodesis evaluated by RSA.

METHODS

Twenty children were treated by percutaneous epiphysiodesis for leg length discrepancies ranging from 15 to 70 mm, comprising 14 boys and 6 girls with a mean age of 13 (11-15) years. The timing of epiphysiodesis was determined by using Moseley's straight-line graph and Paley's multiplier method. For the tibial epiphysiodesis, ten patients were operated with a single surgical approach from the lateral side (Group I) and ten patients were operated with a surgical approach from both the medial and the lateral sides (Group II). The percutaneous epiphysiodesis was monitored by RSA, a method which allows analysis of the three-dimensional dynamics of the epiphysis relative to the metaphysics. RSA examinations were performed postoperatively and after 6 weeks, 12 weeks, and 6 months.

RESULTS

From 0 to 6 weeks after epiphysiodesis, the mean longitudinal growth across the operated physis in the tibia in Group I was 0.26 (0.01-0.6) mm. In Group II, the mean growth for the first 6 weeks after surgery was 0.17 (0.01-0.5) mm. During the time period from 6 weeks to 12 weeks after surgery, there was a mean growth of 0.06 (0.00-0.18) mm in Group I and 0.03 (0.00-0.2) mm in Group II. The mean growth from 0 to 6 weeks after epiphysiodesis for all patients was 0.22 mm, which corresponds to 30 % of the normal growth rate. From 6 to 12 weeks, the mean growth for all patients was 0.046 mm, i.e., 6 % of the normal growth rate. From 12 weeks to 24 weeks, no significant growth across the operated physis was observed in neither Group I nor Group II. The mean surgical time was 26 (21-30) min in Group I and 43 (35-48) min in Group II. This difference was statistically significant (p = 0.006). The mean time for use of the image intensifier during surgery was 202 (191-236) s in Group I and 229 (185-289) s in Group II (p = 0.013).

CONCLUSIONS

In our study, a single-portal technique from the lateral side for percutaneous epiphysiodesis of the proximal tibia was as effective as the double-portal technique. Actual growth arrest appeared within 12 weeks after surgery. A single-portal technique for epiphysiodesis of the tibia is a safe technique, with less surgical time and less time for image intensification compared to the double-portal technique.

Eight plate should not be used for treating leg length discrepancy

PURPOSE

The Blount staple has been widely used for treating angular deformities and leg length discrepancy (LLD) of the lower limbs. In recent years, the Eight plate has replaced the Blount staple for treating angular deformities in many centres. Although not described in the literature, it has been proposed that the Eight plate could also be used for treating LLD. We studied the effectiveness of the device for this indication.

METHODS

Ten patients with LLD were included prospectively. Medial and lateral plates were inserted for symmetrical growth reduction and the patients were followed by radiostereometric analysis (RSA) 0, 3, 6, 9, 12, 24, 52 and 80 weeks postoperatively. The error of measurement with this technique is less than 0.05 mm.

RESULTS

Case 1 continued to grow an average of 0.08 mm per week (6.7 mm longitudinal growth in 1.5 years) postoperatively, while Case 2 showed 0.07 mm longitudinal growth per week (5.6 mm longitudinal growth in 1.5 years). The longitudinal growth, in both children, showed only slight growth retardation throughout the follow-up period. The study was interrupted and no further subjects were included after the results indicated that only minor growth reduction had occurred in both patients.

CONCLUSION

The Eight plate does not significantly reduce growth when applied both medially and laterally in a symmetrical way at the proximal tibial physis.

Negative correlation between extent of physeal ablation after percutaneous permanent physiodesis and postoperative growth: volume computer tomography and radiostereometric analysis of 37 physes in 27 patients

BACKGROUND AND PURPOSE

Percutaneous physiodesis in the knee region is a well-established method for treating leg-length inequality. Longitudinal growth in the physis is believed to stop almost immediately after the operation. The extent of physis ablation required has never been investigated by any kind of tomography in humans. Using radiostereometric analysis (RSA), we determined when definite growth arrest occurred after surgery. We also studied the correlation between the extent of physis ablation and postoperative growth. Finally, we assessed any bone bridging across the physis.

METHODS

6, 12, and 30 weeks after surgery, we used RSA to measure longitudinal growth in 27 patients (37 physes) with a mean age of 13 years. CT scanning of the knee region was performed 12 weeks after surgery to measure the percentage of the ablated physis and to determine the distribution of bone bridges across the physis.

RESULTS

RSA showed that growth rate was reduced to less than half of the expected rate after 6 weeks. During the next 6 weeks, the growth ceased completely. CT scans revealed a large variation in the extent of ablated physes (17-69%). In the ablated areas, tissues of various densities were mixed with mature bone. Bridges were found both laterally and medially across the physes in all of the patients. There was a negative correlation between the extent of ablation and total postoperative growth (rho = -0.37, p = 0.03).

INTERPRETATION

Growth across the physis is effectively stopped by percutaneous physiodesis. RSA is well-suited for observation of this phenomenon. Volume CT scanning can be used to detect bone bridges that cross the physis and to calculate the extent of physis ablation.

Controlled longitudinal bone growth by temporary tension band plating

Permanent growth arrest of the longer bone is an option in the treatment of minor leg-length discrepancies. The use of a tension band plating technique to produce a temporary epiphysiodesis is appealing as it avoids the need for accurate timing of the procedure in relation to remaining growth. We performed an animal study to establish if control of growth in a long bone is possible with tension band plating. Animals (pigs) were randomised to temporary epiphysiodesis on either the right or left tibia. Implants were removed after ten weeks. Both tibiae were examined using MRI at baseline, and after ten and 15 weeks. The median interphyseal distance was significantly shorter on the treated tibiae after both ten weeks (p = 0.04) and 15 weeks (p = 0.04). On T1-weighted images the metaphyseal water content was significantly reduced after ten weeks on the treated side (p = 0.04) but returned to values comparable with the untreated side at 15 weeks (p = 0.14). Return of growth was observed in all animals after removal of implants.

Temporary epiphysiodesis can be obtained using tension band plating. The technique is not yet in common clinical practice but might avoid the need for the accurate timing of epiphysiodesis.

Cite this article: Bone Joint J 2013;95-B:855–60.