Rebound phenomenon and its risk factors after hemiepiphysiodesis using tension band plate in children with coronal angular deformity

Simultaneous MPFL reconstruction and guided growth result in low rates of recurrent patellofemoral instability

PURPOSE

Implant-mediated guided growth (IMGG) is used to address coronal plane deformity in skeletally immature patients. Few studies have reported on IMGG and simultaneous medial patellofemoral ligament (MPFL) reconstruction for paediatric patients with concurrent genu valgum and patellofemoral instability (PFI). This study aimed to report on the outcomes of these simultaneous procedures.

MATERIALS AND METHODS

This was a retrospective review of paediatric patients undergoing simultaneous MPFL reconstruction and IMGG between 2016 and 2023. Mechanical lateral distal femoral angle (mLDFA), hip-knee-ankle angle (HKA) and mechanical axis deviation (MAD) were measured on full-length hip-to-ankle plain radiographs. Measurements were taken preoperatively, prior to implant removal and/or at final follow-up with minimum 1-year clinical follow-up.

RESULTS

A total of 25 extremities in 22 patients (10 female) underwent simultaneous IMGG and MPFL reconstruction. The mean age at surgery was 12.6 ± 1.7 years. The mean duration of implant retention was 18.6 ± 11.3 months. Nineteen extremities (76%) underwent implant removal by final follow-up. Preoperative HKA corrected from a mean of 5.8 ± 2.3° to -0.8 ± 4.5° at implant removal or final follow-up (p < 0.001), with mLDFA and MAD similarly improving (both p < 0.001). HKA corrected a mean of 0.7 ± 0.9° per month, while mLDFA and MAD corrected a mean of 0.5 ± 0.6°/month and 2 ± 3 mm/month, respectively. At the time of implant removal or final follow-up, 88% of patients demonstrated alignment within 5° of neutral. Only one extremity experienced subsequent PFI (4%). For 14 patients who underwent implant removal with further imaging at a mean of 7.8 ± 4.9 months, only one patient (7%) had a valgus rebound to an HKA > 5°.

CONCLUSION

Simultaneous MPFL reconstruction and IMGG provided successful correction of lower extremity malalignment with only one recurrence of PFI. This approach is a reliable surgical option for skeletally immature patients with genu valgum and PFI.

LEVEL OF EVIDENCE

Level 4 case series.

Factors Affecting Postoperative Courses After Removal of Transphyseal Screws Inserted for Correction of Genu Valgum

BACKGROUND

The aim of this study was to investigate factors determining the final outcomes of hemipercutaneous epiphysiodesis using transphyseal screw (PETS) for the genu valgum, especially focusing on postoperative courses after screw removal.

METHODS

Fifty-five patients with idiopathic genu valgum treated with hemi-PETS were included. The mechanical lateral distal femoral angle (mLDFA) and medial proximal tibial angle (MPTA) were measured to calculate the degree of correction and rebound. Regarding factors related to surgical techniques, the number of screw threads beyond the physis, the moment arm of the screw, and screw insertion angles were measured.

RESULTS

In 54 femoral segments (randomly selected in bilateral cases), hemi-PETS was performed with a growth remaining of 2.0±0.6 years. The screw was removed after 6.5±2.1 months, and the degree of correction was 5.0±1.5 degrees. The mean rebound angle was -0.4±2.4 (the negative value means further correction after screw removal). A late time of surgery and an extreme peripheral position of a screw were associated with the growth inhibition. In 50 tibial segments (also randomly selected in bilateral cases), a screw was inserted with a growth remaining of 2.0±0.6 years and removed after 6.3±1.9 months. The degree of correction was 2.9±1.7 degrees during the interval, and the rebound angle was 0.8±1.7 degrees. An earlier time of surgery and a greater correction angle before screw removal were associated with the rebound phenomenon.

CONCLUSIONS

Growth inhibition of >1.6 degrees was observed in about one-fourth of femoral segments. An extreme peripheral position of a screw should be avoided when performing hemi-PETS at the distal femur. We also recommend not performing hemi-PETS at distal femur with too short a period of growth remaining.

LEVEL OF EVIDENCE

Level III-retrospective comparative series.

An Innovative Plate Concept for Rotational Guided Growth: A Porcine Pilot Study

Background Rotational deformities in children are currently treated with an osteotomy, acute de-rotation, and surgical fixation. Meanwhile, guided growth is now the gold standard in pediatric coronal deformity correction. This study aimed to evaluate the feasibility of a novel implant intended for rotational guided growth (RotOs Plate) in a large porcine animal model. Methodology A submuscular plate was inserted on the medial and lateral aspect of the distal femoral physis of the left femur in 6 pigs. Each plate was anchored with a screw in the metaphysis and epiphysis respectively. The plates were expected to rotate the femur externally. The right femur acted as a control in a paired design. The animals were housed for 12 weeks after surgery. MRI scanning of both femora was performed before euthanasia after 12 weeks. Rotation was determined as the difference in the femoral version on MRI between the operated and non-operated femur after 12 weeks. Results External rotation in all operated femurs was observed. The mean difference in the femoral version on MRI between operated and non-operated femurs was 12.5° (range 9°-16°). No significant changes in axial growth were detected. Conclusions This study shows encouraging results regarding rotational guided growth, which may replace current invasive surgical treatment options for malrotation in children. However, further studies addressing potential secondary deformities are paramount and should be carried out.

MPFL Reconstruction and Implant-Mediated Guided Growth in Skeletally Immature Patients With Patellar Instability and Genu Valgum

BACKGROUND

There is a higher rate of failure of isolated MPFL reconstruction in skeletally immature patients with patellar instability compared to skeletally mature patients. Genu valgum is a known risk factor for patellar instability. There is potential for concomitant surgical correction of genu valgum to achieve better clinical outcomes and to decrease failure rates of MPFL reconstruction.

PURPOSE

To evaluate outcomes of combined medial patellofemoral ligament (MPFL) reconstruction and implant-mediated guided growth (IMGG) in skeletally immature patients with patellar instability and genu valgum.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

In a multicenter study, all skeletally immature patients with recurrent patellar instability and genu valgum who underwent MPFL reconstruction using hamstring graft and IMGG using a transphyseal screw or tension band plate for the distal femur and/or proximal tibia were included. The knee valgus angle and mechanical axis were measured on full-length radiographs and anatomic risk factors were measured on MRI. Patients were followed until correction of their lower limb alignment and implant removal or until skeletal maturity. Clinical outcomes, including complications, were analyzed.

RESULTS

A total of 31 patients (37 knees) were included in the study. The mean age and skeletal age of the cohort were 12.4 and 12.9 years, respectively. Simultaneous MPFL reconstruction and IMGG were performed in 26 of 37 knees; 11 underwent staged procedures. Twenty knees had transphyseal screws and 17 knees had tension band plates for IMGG. The knee valgus corrected from a mean of 12.4° to 5.1° in 12.1 months. Implants were removed from 22 of 37 knees once genu valgum was corrected. There was no significant difference (P = .65) in the correction rate between plates (0.7 deg/month) and screws (0.6 deg/month). Ten complications occurred in 4 patients (7 knees) and included 5 patellar redislocations, 2 rebound valgus, 1 varus overcorrection, 1 knee arthrofibrosis, and 1 implant loosening. For children <10 years of age, 3 of 6 (50%) knees had patellar redislocations and 5 of 6 knees had a complication. This was statistically significant (P = .003) compared with patients >10 years of age. Similarly, for patients with bilateral knee involvement, 5 of 12 (42%) knees had patellar redislocations and a total of 8 complications occurred in this subset. This was statistically significant (P < .001) compared with patients with unilateral involvement.

CONCLUSION

IMGG with plates or screws in the setting of combined MPFL reconstruction improves genu valgum. Children <10 years of age and those with bilateral instability with genu valgum remain difficult subsets to treat with higher complication rates.

Effective time, correction speed and termination time of hemi-epiphysiodesis in children

In children with asymmetric growth on the medial and lateral side of limbs, if there still remains growth potential, the guided growth technique of hemi-epiphysiodesis on one side of the epiphysis is recognized as a safe and effective method. However, when the hemi-epiphysiodesis start to correct the deformities, how many degrees could hemi-epiphysiodesis bring every month and when to remove the hemi-epiphysiodesis implant without rebound phenomenon are still on debate. This article reviews the current studies focus on the effective time, correction speed and termination time of hemi-epiphysiodesis.

Isolating factors for the prediction of rebound after guided growth with tension band plating for the valgus deformity of the knee

Purpose

The conditions leading to growth rebound after hemiepiphysiodesis are still poorly understood. This article analyzes the radiographical outcomes after guided growth with tension band plating, using plates in idiopathic genu valgum patients and attempts to generate a predictive model of growth rebound.

Methods

Patients with idiopathic genu valgum deformity who received tension band plating were selected for evaluation. We only analyzed coronal plane deformities. Only patients with a long-standing X-ray before tension band plating surgery, a long-standing X-ray at tension band plating removal, and a long-standing X-ray at the latest follow-up after tension band plating removal were considered for this study. The change of mechanical axis deviation between the tension band plating removal and the last follow-up was evaluated for rebound, and ordinal logistic regression was performed to determine the relevant variables for predictive modeling rebound growth.

Results

Overall, 100 patients (189 legs) were analyzed. The mean mechanical axis deviation at tension band plating removal was 8.4 mm in varus direction, and the mean mechanical axis deviation at the last follow-up was -3.4 mm (p ≤ 0.001). However, 111 legs (59%) showed rebound growth, 57 (30%) stayed stable, and 21 (11%) showed a continuous correction. Six significant factors significantly influencing rebound were isolated which are clinically relevant: sex, age, baseline mechanical axis deviation, mechanical lateral distal femoral angle, and mechanical medial proximal tibial angle, and mechanical axis deviation correction rate. Mechanical axis deviation correction rate had the highest odds ratios. The machine learning classification model for predicting rebound growth built from the study data showed a misclassification rate of 39%.

Conclusion

There was a high rate of rebound growth in this cohort, especially for patients at a young age at implantation. The highest risk factors for rebound growth were male sex, and high correction rates, such as found during peak growth spurt. The proposed classification model needs more data to improve its predictive power before it can be used in clinics.

Level of evidence

Level III.

Predictors of Recurrent Flexion Contracture after Total Knee Arthroplasty in Osteoarthritic Knees with Greater Than 15° Flexion Contracture

Background

This study aimed to analyze the risk factors that predict recurrent flexion contracture (FC) after total knee arthroplasty (TKA) in osteoarthritic knees with FC ≥ 15°.

Methods

Data from a consecutive cohort comprising 237 TKAs in 187 patients with degenerative osteoarthritis, preoperative FC ≥ 15°, and a minimum follow-up period of 2 years were retrospectively reviewed. Preoperative FC was corrected intraoperatively from 0° to 5°. The incidence of recurrent FC (FC ≥ 10°) at 2 years postoperatively was investigated. Potential risk factors predicting recurrent FC including age, sex, body mass index, unilateral TKA, severity of preoperative FC, 3-month postoperative residual FC, γ angle, change in posterior femoral offset ratio, and lumbar degenerative kyphosis (LDK) were analyzed using logistic regression analysis. The post-hoc powers for the identified factors were then determined.

Results

Forty-one knees (17.3%) with recurrent FC were identified. Risk factors with sufficient power for recurrent FC were unilateral TKA, severity of preoperative FC, residual FC at 3 months postoperatively, and LDK (odds ratios of 3.579, 1.115, 1.274, and 3.096, respectively; p < 0.05; power ≥ 86.1).

Conclusions

Recurrent FC can occur in TKAs with the risk factors including unilateral TKA, severe preoperative FC, residual FC at 3 months postoperative, and LDK despite appropriate intraoperative correction. Surgical strategies and rehabilitation protocols used in managing FC should be applied in TKA cases with risk factors for recurrent FC.

Fusionless All-Pedicle Screws for Posterior Deformity Correction in AIS Immature Patients Permit the Restoration of Normal Vertebral Morphology and Removal of the Instrumentation Once Bone Maturity Is Reached

The aim of this study was to report the restoration of normal vertebral morphology and the absence of curve progression after the removal of instrumentation in AIS patients that underwent posterior correction of the deformity by a common all-screws construct without fusion. A series of 36 AIS immature patients (Risser 3 or less) were included in the study. Instrumentation was removed once the maturity stage was complete (Risser 5). The curve correction was assessed pre- and postoperatively, before instrumentation removal, directly post-removal, and more than two years after instrumentation was removed. Epiphyseal vertebral growth modulation was assessed by the coronal wedging ratio (WR) at the apical level of the main curve (MC). The mean preoperative coronal Cobb was corrected from 53.7° ± 7.5 to 5.5° ± 7.5° (89.7%) at the immediate postop. After implant removal (31.0 ± 5.8 months), the MC was 13.1°. T5-T12 kyphosis showed significant improvement from 19.0° before curve correction to 27.1° after implant removal (p < 0.05). Before surgery, the WR was 0.71 ± 0.06, and after removal, 0.98 ± 0.08 (p < 0.001). At the end of the follow-up, the mean sagittal range of motion (ROM) of the T12-S1 segment was 51.2 ± 21.0°. The SRS-22 scores improved from 3.31 ± 0.25 preoperatively to 3.68 ± 0.25 at the final assessment (p < 0.001). In conclusion, a fusionless posterior approach using common all-pedicle screws correctly constructed satisfactory scoliotic main curves and permitted the removal of instrumentation once bone maturity was reached. The final correction was highly satisfactory, and an acceptable ROM of the previously lower instrumented segments was observed.

Guided growth: angular deformity correction through temporary hemiepiphysiodesis with a novel flexible staple (FlexTack)

Temporary hemiepiphysiodesis (HED) is applied to children and adolescents to correct angular deformities (ADs) in long bones through guided growth. Traditional Blount staples or two-hole plates are mainly used for this indication. Despite precise surgical techniques and attentive postoperative follow-up, implant-associated complications are frequently described. To address these pitfalls, a flexible staple was developed to combine the advantages of the established implants. This study provides the first results of guided growth using the new implant and compares these with the established two-hole plates and Blount staples. Between January 2013 and December 2016, 138 patients (22 children, 116 adolescents) with genu valgum or genu varum were treated with 285 flexible staples. The minimum follow-up was 24 months. These results were compared with 98 patients treated with 205 two-hole plates and 92 patients treated with 535 Blount staples. In long-standing anteroposterior radiographs, mechanical axis deviations (MADs) were measured before and during treatment to analyze treatment efficiency. The evaluation of the new flexible staple was performed according to the idea, development, evaluation, assessment, long-term (IDEAL) study framework (Stage 2a). Overall, 79% (109/138) of patients treated with flexible staples achieved sufficient deformity correction. The median treatment duration was 16 months (interquartile range (IQR) 8 to 21). The flexible staples achieved a median MAD correction of 1.2 mm/month/HED site (IQR 0.6 to 2.0) in valgus deformities and 0.6 mm/month/HED site (IQR 0.2 to 1.5) in varus deformities. Wound infections occurred in 1%, haematomas and joint effusions in 4%, and implant-associated complications in 1% of patients treated with flexible staples. Valgus AD were corrected faster using flexible staples than two-hole plates and Blount staples. Furthermore, the median MAD after treatment was lower in varus and valgus AD, fewer implant-associated complications were detected, and reduced implantation times were recorded using flexible staples. The flexible staple seems to be a viable option for guided growth, showing comparable or possibly better results regarding correction speed and reducing implant-associated complications. Further comparative studies are required to substantiate these findings.

Growth modulation for angular knee deformities: a practical guideline

PURPOSE OF REVIEW

This study aimed to review the established concepts and advances related to growth modulation for treating knee angular deformities. Although they are considered well tolerated procedures, careful indications and accurate techniques are necessary to ensure good results.

RECENT FINDINGS

In addition to general clinical and radiographic evaluations, new tools such as two-dimensional low-dose radiography and gait analysis have been used to clarify angular and torsional combinations and the impact of mild angulations on the knee joint. Temporary epiphysiodesis is commonly the choice, and it can be performed with different implants such as staples, tension band plates (TBP), percutaneous transphyseal screws (PETS), sutures, and screws.

SUMMARY

Considering its principles, TBP has been preferred for younger children. Cost can be a limitation, and research for alternative implants such as screws and nonabsorbable sutures indicate they might be an alternative in the future. In adolescents, PETS becomes an attractive alternative; however, its reversible character has been controversial, and further studies are needed to establish limits in younger patients.

Indications and Timing of Guided Growth Techniques for Pediatric Upper Extremity Deformities: A Literature Review

Osseous deformities in children arise due to progressive angular growth or complete physeal arrest. Clinical and radiological alignment measurements help to provide an impression of the deformity, which can be corrected using guided growth techniques. However, little is known about timing and techniques for the upper extremity. Treatment options for deformity correction include monitoring of the deformity, (hemi-)epiphysiodesis, physeal bar resection, and correction osteotomy. Treatment is dependent on the extent and location of the deformity, physeal involvement, presence of a physeal bar, patient age, and predicted length inequality at skeletal maturity. An accurate estimation of the projected limb or bone length inequality is crucial for optimal timing of the intervention. The Paley multiplier method remains the most accurate and simple method for calculating limb growth. While the multiplier method is accurate for calculating growth prior to the growth spurt, measuring peak height velocity (PHV) is superior to chronological age after the onset of the growth spurt. PHV is closely related to skeletal age in children. The Sauvegrain method of skeletal age assessment using elbow radiographs is possibly a simpler and more reliable method than the method by Greulich and Pyle using hand radiographs. PHV-derived multipliers need to be developed for the Sauvegrain method for a more accurate calculation of limb growth during the growth spurt. This paper provides a review of the current literature on the clinical and radiological evaluation of normal upper extremity alignment and aims to provide state-of-the-art directions on deformity evaluation, treatment options, and optimal timing of these options during growth.