Mal-angulation of femoral rotational osteotomies causes more postoperative sagittal mechanical leg axis deviation in supracondylar than in subtrochanteric procedures

A surface registration-based approach for assessment of 3D angles in guided growth interventions in the growing femur

Purpose

Postoperative assessment of surgical interventions for correcting femoral rotational deformities necessitates a comparative analysis of femoral rotation pre- and post-surgery. While 2D assessment methods are commonly employed, ongoing debate surrounds their accuracy and reliability. To address the limitations associated with 2D analysis, we introduced and validated a 3D model-based analysis method for quantifying the angular and rotational impact of corrective rotational osteotomy in the growing femur.

Methods

The method is based on surface registration of the pre- and post-intervention 3D femoral models. To this end, 3D triangulated surface models were generated using CT images for the right femurs of 11 skeletally immature pigs, each scanned at two distinct time points with a 12-week interval between scans. In our validation procedures, femoral corrective rotational osteotomy of the post-12-week femur was simulated at varying angles of 5, 10, 15 and 20 degrees in three dimensions. Subsequently, a surface 3D/3D registration-based approach was applied to determine the 3D femoral angulation and rotation between the two models to assess the method's detection accuracy of the predefined twist angles as ground truth references.

Results

The results document the precision and accuracy of the registration-based method in evaluating rotation angles. Consistently high accuracy was observed across all angles, with an accuracy rate of 92.97% and a coefficient of variance of 8.14%.

Conclusion

This study has showcased the potential for improving post-operative assessments with significant implications for experimental studies evaluating the effects of correcting rotational deformities in the growing femur.

Level of Evidence

Not applicable.

Changes in sagittal and axial plane alignment in medial opening wedge high tibial osteotomy: a prospective observational study

PURPOSE

Deformity correction during high tibial osteotomy is generally based on coronal plane alignment. The aim of this study was to measure changes in sagittal and axial plane alignment following medial opening wedge high tibial osteotomy [mHTO], using pre- and postoperative computed tomography [CT] scans, and correlate them with changes in coronal plane. The secondary objective was to correlate changes in functional outcomes with changes in alignment in each plane. The null hypothesis was that sagittal and axial plane alignment does not change significantly following mHTO.

METHODS

This was a prospective, observational study including 30 patients of isolated medial compartment osteoarthritis of the knee joint, between 30 and 60 years of age. Preoperative and postoperative computed tomography scan of bilateral lower limbs from hip to ankle was performed. Varus angle, mechanical axis deviation [MAD] of the lower limb, medial proximal tibial angle [MPTA], tibial torsion and posterior proximal tibial angle [PPTA] were measured. Visual Analogue Scale [VAS 0-10 cm scale] was used for assessment of pain. Functional outcomes were evaluated using Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], 12 Item Short Form Survey [SF 12] and Tegner Lysholm knee scoring scale.

RESULTS

Mean age of patients was 44.59 ± 8.157 years. Mean preoperative varus deformity was 11.13 ± 1.5 degrees, which got corrected to a mean valgus alignment of 3.8 ± 0.93 degrees postoperatively. The mechanical axis deviation was 4.32 ± 1.76 mm lateral to the knee joint center postoperatively. Preoperatively, all knees had external tibial torsion [27.08 ± 2.18 degrees] which was corrected to a mean external tibial torsion of 19.80 ± 3.72 degree after the surgery [P < 0.001]. The overall decrease in sagittal alignment in the present study was 3.70 ± 3.14 degree, 3.97 ± 3.06 degree, 3.92 ± 2.33 degree, for medial, middle and lateral cuts, respectively. There was a significant correlation between change in varus/valgus angle and change in TT and PPTA. Significant positive correlation was seen between change in coronal alignment and functional outcome scores.

CONCLUSION

This study has shown that mHTO significantly changes torsional and sagittal alignment. This is the first study to establish relation between correction in coronal plane and associated changes in sagittal and torsional alignments.

Sagittal Plane Assessment in Deformity Correction Planning: The Sagittal Joint Line Angle

Aim

Evaluate the validity of a recent approach to calculate the knee flexion or extension contracture contributing to the overall sagittal deformity using the sagittal mechanical axis angle (SMAA) for the overall alignment assessment and sagittal joint line angle (SJLA) for soft tissue contribution. The methods of evaluating these angles and their clinical applications are discussed.

Materials and methods

In total, 107 normal limbs met the criteria and were divided into two groups: skeletally mature and immature. Sagittal alignment was evaluated using the Bone Ninja iPad application, and the posterior distal femoral angle (PDFA), posterior proximal tibial angle (PPTA), SMAA and SJLA were recorded.

Results

In skeletally immature patients, mean SJLA was 13.46° [standard deviation (SD), 4.55°], and in mature patients, it was 16.91° (SD, 2.948°). The PDFA and PPTA were consistent with previously published measurements.

Conclusion

The SJLA method is a practical way to quantify the soft tissue contribution and degree of contracture. It can also be used for monitoring deterioration or improvement of knee range of motion during lengthening or physical therapy.

Clinical significance

All patients in this study presented to our clinic with symptoms on the contralateral side. This, in addition to the retrospective nature, was a limitation in our study.We recommend a validity study to compare our SJLA method to the classic anterior cortical line angle (ACL) method in addition to an inter-observer and intra-observer reliability study for the SJLA. We also recommend a study on completely normal asymptomatic subjects to better standardise the angle measurements in skeletally immature patients at different ages.

How to cite this article

Abalkhail TB, McClure PK. Sagittal Plane Assessment in Deformity Correction Planning: The Sagittal Joint Line Angle. Strategies Trauma Limb Reconstr 2022;17(3):159-164.

Correction of complex three-dimensional deformities at the proximal femur using indirect reduction with angle blade plate and patient-specific instruments: a technical note

BACKGROUND

Corrective osteotomies for complex proximal femoral deformities can be challenging; wherefore, subsidies in preoperative planning and during surgical procedures are considered helpful. Three-dimensional (3D) planning and patient-specific instruments (PSI) are already established in different orthopedic procedures. This study gives an overview on this technique at the proximal femur and proposes a new indirect reduction technique using an angle blade plate.

METHODS

Using computed tomography (CT) data, 3D models are generated serving for the preoperative 3D planning. Different guides are used for registration of the planning to the intraoperative situation and to perform the desired osteotomies with the following reduction task. A new valuable tool to perform the correction is the use of a combined osteotomy and implant-positioning guide, with indirect deformity reduction over an angle blade plate.

RESULTS

An overview of the advantages of 3D planning and the use of PSI in complex corrective osteotomies at the proximal femur is provided. Furthermore, a new technique with indirect deformity reduction over an angle blade plate is introduced.

CONCLUSION

Using 3D planning and PSI for complex corrective osteotomies at the proximal femur can be a useful tool in understanding the individual deformity and performing the aimed deformity reduction. The indirect reduction over the implant is a simple and valuable tool in achieving the desired correction, and concurrently, surgical exposure can be limited to a subvastus approach.