Three-dimensional corrective osteotomies of complex malunited humeral fractures using patient-specific guides

Shape-matching-based fracture reduction aid concept exemplified on the proximal humerus-a pilot study

PURPOSE

Optimizing fracture reduction quality is key to achieve successful osteosynthesis, especially for epimetaphyseal regions such as the proximal humerus (PH), but can be challenging, partly due to the lack of a clear endpoint. We aimed to develop the prototype for a novel intraoperative C-arm-based aid to facilitate true anatomical reduction of fractures of the PH.

METHODS

The proposed method designates the reduced endpoint position of fragments by superimposing the outer boundary of the premorbid bone shape on intraoperative C-arm images, taking the mirrored intact contralateral PH from the preoperative CT scan as a surrogate. The accuracy of the algorithm was tested on 60 synthetic C-arm images created from the preoperative CT images of 20 complex PH fracture cases (Dataset A) and on 12 real C-arm images of a prefractured human anatomical specimen (Dataset B). The predicted outer boundary shape was compared with the known exact solution by (1) a calculated matching error and (2) two experienced shoulder trauma surgeons.

RESULTS

A prediction accuracy of 88% (with 73% 'good') was achieved according to the calculation method and an 87% accuracy (68% 'good') by surgeon assessment in Dataset A. Accuracy was 100% by both assessments for Dataset B.

CONCLUSION

By seamlessly integrating into the standard perioperative workflow and imaging, the intuitive shape-matching-based aid, once developed as a medical device, has the potential to optimize the accuracy of the reduction of PH fractures while reducing the number of X-rays and surgery time. Further studies are required to demonstrate the applicability and efficacy of this method in optimizing fracture reduction quality.

A review of novel methods to assist digital planning and execution of osteotomy for upper limb deformities

Corrective osteotomy for upper limb deformities caused by fractures, trauma, or degeneration necessitates detailed preoperative planning to ensure accurate anatomical alignment, restore limb length, and correct angular deformities. This review evaluates the effectiveness of a three-dimensional (3D) preoperative planning program and an image fusion system designed for intraoperative guidance during corrective osteotomy procedures. The application processes and clinical outcomes observed with these technologies in various surgical scenarios involving the upper extremities were summarized. The systems proved beneficial in allowing surgeons to visualize surgical steps and optimize implant placement. However, despite these technological advancements, we found no significant impact on clinical outcomes compared to conventional methods. This indicates a need for further enhancements in system efficiency and user-friendliness to significantly improve patient results. Future developments should focus on addressing these limitations to enhance the practical utility of such advanced systems.

Optimizing Reduction Guide Stability in Osteotomy Using Patient-Specific Instrumentation: A Basic Guideline

Background

The use of patient-specific instruments (PSIs) for osteotomies is becoming more popular in orthopaedic surgery for correcting mechanical axis and posttraumatic deformities. However, the PSI reduction guides have great potential for intraoperative deformation, which adversely affects the accuracy of the procedure.

Purpose

To conduct a finite element analysis (FEA) to analyze different design parameters to improve the intraoperative stability of the reduction guides.

Study Design

Descriptive laboratory study.

Methods

A reduction guide with a rectangular cross section and four 4-mm K-wire slots was simplified, and the following parameters were modified: width, height, profile design, K-wire thickness, and positions. Bending and torsional moments were applied to the guide construct and guide deformation and equivalent stress were determined using FEA.

Results

Increasing the profile height by 25% resulted in a 44% reduction in guide deformation for bending (37% for torsion). A 25% increase in profile width led to an 18% deformation reduction for bending (22% for torsion). Transverse K-wire slots resulted in 51% less deformation in torsion compared with longitudinally oriented slots. Placing the central K-wire slots 25% closer to the osteotomy reduced guide deformation by 20% for bending and 11% for torsion.

Conclusion

The most effective methods to increase reduction guide stability are to increase the guide height and reduce the central K-wire distance to the osteotomy.

Clinical Relevance

When performing opening or closing wedge osteotomies, which mainly involve bending of the guide, a high-profile guide and longitudinally oriented K-wire slots should be used. When torque is expected as in rotational osteotomies, the K-wire holes in guides should be oriented transversely to reduce intraoperative deformation.

Dome versus single-cut osteotomies for correction of long bone deformities-technical considerations

Corrective osteotomy allows to improve joint loading, pain and function. In complex deformities, the biggest challenge is to define the optimal surgical solution, while considering anatomical, technical and biomechanical factors. While the single-cut osteotomy (SCOT) and focal dome osteotomy (FDO) are well-established treatment options, their mathematical relationship remain largely unclear. The aim of the study was (1) to describe the close mathematical relationship between the SCOT and FDO and (2) to analyze and introduce a novel technique-the stepped FDO-as a modification of the classic FDO. The mathematical background and relationship of SCOT and FDO are described for the example of a femoral deformity correction and visualized using a 3D surface model taking into account the benefits for the clinical application. The novel modifications of the stepped FDO are introduced and its technical and clinical feasibility demonstrated. Both, SCOT and FDO, rely on the same deformity axis that defines the rotation axis k for a 3D deformity correction. To achieve the desired correction using a SCOT, the resulting cutting plane is perpendicular to k, while using a FDO will result in a cylindrical cut with a central axis parallel to k. The SCOT and FDO demonstrate a strong mathematical relation, as both methods rely on the same deformity axis, however, resulting in different cutting planes. These characteristics enable a complementary use when defining the optimal type of osteotomy. This understanding enables a more versatile planning approach when considering factors as the surgical approach, biomechanical characteristics of fixation or soft tissue conditions. The newly introduced stepped FDO facilitates an exact reduction of the bone fragments and potentially expands the clinical applicability of the FDO.

Augmented reality-guided pelvic osteotomy of Ganz: feasibility in cadavers

INTRODUCTION

The periacetabular osteotomy is a technically demanding procedure with the goal to improve the osseous containment of the femoral head. The options for controlled execution of the osteotomies and verification of the acetabular reorientation are limited. With the assistance of augmented reality, new possibilities are emerging to guide this intervention. However, the scientific knowledge regarding AR navigation for PAO is sparse.

METHODS

In this cadaveric study, we wanted to find out, if the execution of this complex procedure is feasible with AR guidance, quantify the accuracy of the execution of the three-dimensional plan, and find out what has to be done to proceed to real surgery. Therefore, an AR guidance for the PAO was developed and applied on 14 human hip cadavers. The guidance included performance of the four osteotomies and reorientation of the acetabular fragment. The osteotomy starting points, the orientation of the osteotomy planes, as well as the reorientation of the acetabular fragment were compared to the 3D planning.

RESULTS

The mean 3D distance between planned and performed starting points was between 9 and 17 mm. The mean angle between planned and performed osteotomies was between 6° and 7°. The mean reorientation error between the planned and performed rotation of the acetabular fragment was between 2° and 11°.

CONCLUSION

The planned correction can be achieved with promising accuracy and without serious errors. Further steps for a translation from the cadaver to the patient have been identified and must be addressed in future work.

Computer-assisted planning vs. conventional surgery for the correction of symptomatic mid-shaft clavicular nonunion and malunion

Background

The aim of this study was to compare the clinical and radiographic outcomes of treatment of symptomatic mal- and/or nonunion of midshaft clavicle fractures using radiographically based free-hand open reduction and internal fixation (ORIF) or computer-assisted 3D-planned, personalized corrective osteotomies performed using patient-specific instrumentation (PSI) and ORIF. The hypotheses were that (1) patients treated with computer-assisted planning and PSI would have a better clinical outcome, and (2) computer-assisted surgical planning would achieve a more accurate restoration of anatomy compared to the free-hand technique.

Methods

Between 1998 and 2020, 13 patients underwent PSI, and 34 patients underwent free-hand ORIF and/or corrective osteotomy. After application of exclusion criteria, 12/13 and 11/34 patients were included in the study. The clinical examination included measurement of the active range of motion and assessment of the absolute and relative Constant-Murley Scores and the subjective shoulder value. Subjective satisfaction with the cosmetic result was assessed on a Likert scale from 0 to 100 (subjective aesthetic value). 11/13 and 6/11 patients underwent postoperative computed tomography evaluation of both clavicles. Computed tomography scans were segmented to generate 3D surface models. After projection onto the mirrored contralateral side, displacement analysis was performed. Finally, bony union was documented. The average follow-up time was 43 months in the PSI and 50 months in the free-hand cohort.

Results

The clinical outcomes of both groups did not differ significantly. Median subjective shoulder value was 97.5% (70; 100) in the PSI group vs. 90% (0; 100) in the free-hand group; subjective aesthetic value was 86.4% (±10.7) vs. 75% (±18.7); aCS was 82.3 (±10.3) points vs. 74.9 (±26) points; and rCS was 86.7 (±11.3) points vs. 81.9 (±28.1) points. In the free-hand group, 2/11 patients had a postoperative neurological complication. In the PSI cohort, the 3D angle deviation was significantly smaller (PSI/planned vs. free-hand/contralateral: 10.8° (3.1; 23.8) vs. 17.4° (11.6; 42.4); P = .020)). There was also a trend toward a smaller 3D shift, which was not statistically significant (PSI/planned vs. free-hand/contralateral: 6 mm (3.4; 18.3) vs. 9.3 mm (5.1; 18.1); P = .342). There were no other significant differences. A bony union was achieved in all cases.

Conclusion

Surgical treatment of nonunion and malunions of the clavicle was associated with very good clinical results and a 100% union rate. This study, albeit in a relatively small cohort with a follow-up of 4 years, could not document any clinically relevant advantage of 3D planning and personalized operative templating over conventional radiographic planning and free-hand surgical fixation performed by experienced surgeons.

[Osteotomies around the knee: preoperative planning using CT-based three-dimensional analysis, patient-specific cutting and reduction guides]

OBJECTIVE

The goal of osteotomy is either to restore pretraumatic anatomic conditions or to shift the load to less affected compartments.

INDICATIONS

Indications for computer-assisted 3D analysis and the use of patient-specific osteotomy and reduction guides include "simple" deformities and, in particular, multidimensional complex (especially posttraumatic) deformities.

CONTRAINDICATIONS

General contraindications for performing a computed tomography (CT) scan or for an open approach for performing the surgery.

SURGICAL TECHNIQUE

Based on CT examinations of the affected and, if necessary, the contralateral healthy extremity as a healthy template (including hip, knee, and ankle joints), 3D computer models are generated, which are used for 3D analysis of the deformity as well as for calculation of the correction parameters. For the exact and simplified intraoperative implementation of the preoperative plan, individualized guides for the osteotomy and the reduction are produced by 3D printing.

POSTOPERATIVE MANAGEMENT

Partial weight-bearing from the first postoperative day. Increasing load after the first x‑ray control 6 weeks postoperatively. No limitation of the range of motion.

RESULTS

There are several studies that have analyzed the accuracy of the implementation of the planned correction for corrective osteotomies around the knee joint with the use of patient-specific instruments with promising results.

The periacetabular osteotomy: angulation of the supraacetabular osteotomy for quantification of correction

BACKGROUND

Malcorrection of the acetabular fragment in periacetabular osteotomy (PAO) is associated with inferior outcomes. 2-dimensional radiographic parameters are being used for intraoperative verification of a satisfactory result. After reorientation of the fragment, the acetabular version must be verified with an intraoperative radiograph. In the case of an unsatisfactory correction, a reorientation would be required. A slim and radiation-free intraoperative navigation method to directly quantify the correction is highly desirable.

AIM

To find out whether the measurable angulation of the supraacetabular osteotomy can be used for this purpose.

METHODS

To determine the angulation, 13 consecutive patients who underwent a PAO were investigated. The preoperative and postoperative standard radiographs as well as CT scans were available. The surgically produced alteration of radiographic parameters was correlated to tilting and spreading of the supraacetabular osteotomy planes.

RESULTS

Tilting of the supraacetabular osteotomy planes correlates strongly to alteration of the lateral centre-edge angle (LCEA) and the acetabular index (ACI), whereas spreading of the same planes showed also a strong correlation, but to the LCEA only. 1° of tilting resulted in a 0.2° alteration of the LCEA and a 0.5° alteration of the ACI, whereas 1° of spreading resulted in a 0.5° alteration of the LCEA.

CONCLUSIONS

This study shows that the measurable angulation of the supraacetabular osteotomy planes can be used to monitor the three-dimensional reorientation of the acetabular fragment in PAO. As long as sophisticated modalities are lacking, this technique offers an easy way to intraoperatively navigate the correction in PAO.

Automatic 3D Postoperative Evaluation of Complex Orthopaedic Interventions

In clinical practice, image-based postoperative evaluation is still performed without state-of-the-art computer methods, as these are not sufficiently automated. In this study we propose a fully automatic 3D postoperative outcome quantification method for the relevant steps of orthopaedic interventions on the example of Periacetabular Osteotomy of Ganz (PAO). A typical orthopaedic intervention involves cutting bone, anatomy manipulation and repositioning as well as implant placement. Our method includes a segmentation based deep learning approach for detection and quantification of the cuts. Furthermore, anatomy repositioning was quantified through a multi-step registration method, which entailed a coarse alignment of the pre- and postoperative CT images followed by a fine fragment alignment of the repositioned anatomy. Implant (i.e., screw) position was identified by 3D Hough transform for line detection combined with fast voxel traversal based on ray tracing. The feasibility of our approach was investigated on 27 interventions and compared against manually performed 3D outcome evaluations. The results show that our method can accurately assess the quality and accuracy of the surgery. Our evaluation of the fragment repositioning showed a cumulative error for the coarse and fine alignment of 2.1 mm. Our evaluation of screw placement accuracy resulted in a distance error of 1.32 mm for screw head location and an angular deviation of 1.1° for screw axis. As a next step we will explore generalisation capabilities by applying the method to different interventions.

Anatomical variation in humeri: gender and side comparison using statistical shape modelling

PURPOSE

The surgical management of proximal humeral fractures remains challenging. Anatomical reduction of the fracture has been reported as the keystone for a sufficient surgical fixation and successful outcome. However, mostly there is no example of its premorbid state. Literature suggests that the mirrored contralateral side can be used as a reconstruction template. But is this a correct technique to use? The purpose of this study is to define anatomical variation between humeri based on gender and side comparison.

METHODS

Two different statistical shape models of the humerus were created and their modes of variation were described. One model contained 110 unpaired humeri. The other model consisted of 65 left and corresponding right humeri.

RESULTS

The compactness of the statistical shape model containing 110 humeri showed that two principal components explain more than 95% of the variation and the generalization showed that a random humerus can be described with an accuracy of 0.39 mm. For only three parameters, statistically significant differences were observed between left and right. However, comparing the mean of the different metrics on the humeri of men and women, almost all were significant.

CONCLUSION

Since there were only small differences between left and right humeri, using the mirrored contralateral side as a reconstruction template for fracture reduction can be defended. The variable anatomy between men and women could explain why locking plates not always fit to the bone.

Registration based assessment of femoral torsion for rotational osteotomies based on the contralateral anatomy

Background

Computer-assisted techniques for surgical treatment of femoral deformities have become increasingly important. In state-of-the-art 3D deformity assessments, the contralateral side is used as template for correction as it commonly represents normal anatomy. Contributing to this, an iterative closest point (ICP) algorithm is used for registration. However, the anatomical sections of the femur with idiosyncratic features, which allow for a consistent deformity assessment with ICP algorithms being unknown. Furthermore, if there is a side-to-side difference, this is not considered in error quantification.

The aim of this study was to analyze the influence and value of the different sections of the femur in 3D assessment of femoral deformities based on the contralateral anatomy.

Material and methods

3D triangular surface models were created from CT of 100 paired femurs (50 cadavers) without pathological anatomy. The femurs were divided into sections of eponymous anatomy of a predefined percentage of the whole femoral length. A surface registration algorithm was applied to superimpose the ipsilateral on the contralateral side. We evaluated 3D femoral contralateral registration (FCR) errors, defined as difference in 3D rotation of the respective femoral section before and after registration to the contralateral side. To compare this method, we quantified the landmark-based femoral torsion (LB FT). This was defined as the intra-individual difference in overall femoral torsion using with a landmark-based method.

Results

Contralateral rotational deviation ranged from 0° to 9.3° of the assessed femoral sections, depending on the section. Among the sections, the FCR error using the proximal diaphyseal area for registration was larger than any other sectional error. A combination of the lesser trochanter and the proximal diaphyseal area showed the smallest error. The LB FT error was significantly larger than any sectional error (p < 0.001).

Conclusion

We demonstrated that if the contralateral femur is used as reconstruction template, the built-in errors with the registration-based approach are smaller than the intraindividual difference of the femoral torsion between both sides. The errors are depending on the section and their idiosyncratic features used for registration. For rotational osteotomies a combination of the lesser trochanter and the proximal diaphyseal area sections seems to allow for a reconstruction with a minimal error.

Proximal humerus fracture sequelae: are corrective osteotomies still a taboo? The role of three-dimensional preoperative planning and patient-specific surgical guides for proximal humerus corrective osteotomy in combination with reverse shoulder arthroplasty

Background

Symptomatic proximal humeral fracture sequelae (PHFS) represent a surgical challenge due to the altered bone and soft tissue morphology. The purpose of this study was to report the outcome of Multiplanar Corrective Humeral Osteotomies (MCHOs) in combination with reverse total shoulder arthroplasty (rTSA) performed following a three-dimensional (3D) preoperative planning and using a 3D-printed patient-specific surgical instrumentation (PSI) in type 1C, 1D, and 4 PHFS.

Methods

In this prospective monocentric study, we enrolled patients affected by symptomatic PHFS type 1C, 1D, or 4 of Boileau's classification, treated between 2018 and 2019 with rTSA associated to MCHO and followed-up at 12 and 24 mo. The preoperative and postoperative Constant Score (CS), visual analog scale, and Disabilities of the Arm, Shoulder and Hand (DASH) score were recorded. All patients underwent a preoperative computed tomography, then a dedicated software was used to run a segmentation algorithm on computed tomography images. Metaphyseal bone cuts were virtually performed before surgery in all patients, and a 3D-printed PSI was used to reproduce the planned osteotomies in vivo.

Results

Twenty patients completed a 2-y follow-up. The mean (± standard deviation) CS, visual analog scale, and DASH values improve from 24.3 (± 8.8), 6.5 (± 1.3), 60.7 (± 9.6) preoperatively, to 67.7 (± 11.4), 1.6 (± 0.8), 24.1 (± 13.1) points after surgery, respectively. The minimally clinical important difference for CS and DASH score was achieved in 95% of patients. No major complication was observed. One patient showed an unexplained worsening of clinical scores between the 12 and the 24-mo follow-up, while in one patient bone resorption of the greater tuberosity was observed on radiographs at 2 y, with no clinical impact.

Conclusion

The combination of preoperative 3D planning and intraoperative use of 3D-printed PSI to perform MCHO as concurrent procedure in the context of rTSA in the treatment of Boileau type 1C, 1D, and 4 PHFS may lead to a satisfactory clinical outcome at 2 y of follow-up.

Use of 3D Planning and Patient-specific Guides for Proximal Humerus Corrective Osteotomy Associated With Shoulder Prosthesis Implantation in Proximal Humeral Varus Malunion

Humeral stem prosthesis implantation in case of proximal humerus varus malunion (type 1D fracture sequelae) is often complicated by greater tuberosity fracture and by posterosuperior rotator cuff iatrogenic damage. Moreover, the varus malunited humeral head could lead to scapular impingement and reduce the range of motion. To address this problem, we introduced a new surgical procedure consisting in a proximal humerus osteotomy, planned with three-dimensional (3D) preoperative virtual surgery, and performed with patient-specific surgical guides, to correct humerus deformity before the implantation of the prosthetic humeral stem. A 3D evaluation of the deformity, based on the comparison to the healthy contralateral side or to anatomical standard values, is firstly performed. The metaphyseal osteotomy is then planned and virtually performed. To faithfully reproduce the planned correction, 3D printed surgical guides are prepared. Before the surgery, it is advisable to perform a simulation of the planned osteotomies to verify their real feasibility and to find any critical issues. Preliminary outcomes of this surgical technique are encouraging, but formal studies are warranted to validate its clinical utility and longevity of results.

Restoration of the patient-specific anatomy of the distal fibula based on a novel three-dimensional contralateral registration method

Purpose

Posttraumatic fibular malunion alters ankle joint biomechanics and may lead to pain, stiffness, and premature osteoarthritis. The accurate restoration is key for success of reconstructive surgeries. The aim of this study was to analyze the accuracy of a novel three-dimensional (3D) registration algorithm using different segments of the contralateral anatomy to restore the distal fibula.

Methods

Triangular 3D surface models were reconstructed from computed tomographic data of 96 paired lower legs. Four segments were defined: 25% tibia, 50% tibia, 75% fibula, and 75% fibula and tibia. A surface registration algorithm was used to superimpose the mirrored contralateral model on the original model. The accuracy of distal fibula restoration was measured.

Results

The median rotation error, 3D distance (Euclidean distance), and 3D angle (Euler’s angle) using the distal 25% tibia segment for the registration were 0.8° (− 1.7–4.8), 2.1 mm (1.4–2.9), and 2.9° (1.9–5.4), respectively. The restoration showed the highest errors using the 75% fibula segment (rotation error 3.2° (0.1–8.3); Euclidean distance 4.2 mm (3.1–5.8); Euler’s angle 5.8° (3.4–9.2)). The translation error did not differ significantly between segments.

Conclusion

3D registration of the contralateral tibia and fibula reliably approximated the premorbid anatomy of the distal fibula. Registration of the 25% distal tibia, including distinct anatomical landmarks of the fibular notch and malleolar colliculi, restored the anatomy with increasing accuracy, minimizing both rotational and translational errors. This new method of evaluating malreductions could reduce morbidity in patients with ankle fractures.

Level of evidence

IV

Biomechanical stability of complex coronal plane fracture fixation of the capitellum

INTRODUCTION

Coronal plane fractures of the distal humerus are relatively rare and can be challenging to treat due to their complexity and intra-articular nature. There is no gold standard for surgical management of these complex fractures. The purpose of this study was to compare the biomechanical stability and strength of two different internal fixation techniques for complex coronal plane fractures of the capitellum with posterior comminution.

MATERIALS AND METHODS

Fourteen fresh frozen, age- and gender-matched cadaveric elbows were 3D-navigated osteotomized simulating a Dubberley type IIB fracture. Specimens were randomized into one of two treatment groups and stabilized with an anterior antiglide plate with additional anteroposterior cannulated headless compression screws (group antiGP + HCS) or a posterolateral distal humerus locking plate with lateral extension (group PLP). Cyclic testing was performed with 75 N over 2000 cycles and ultimately until construct failure. Data were analyzed for displacement, construct stiffness, and ultimate load to failure.

RESULTS

There was no significant difference in displacement during 2000 cycles (p = 0.291), stiffness (310 vs. 347 N/mm; p = 0.612) or ultimate load to failure (649 ± 351 vs. 887 ± 187 N; p = 0.140) between the two groups.

CONCLUSIONS

Posterolateral distal humerus locking plate achieves equal biomechanical fixation strength as an anterior antiglide plate with additional anteroposterior cannulated headless compression screws for fracture fixation of complex coronal plane fractures of the capitellum. These results support the use of a posterolateral distal humerus locking plate considering the clinical advantages of less invasive surgery and extraarticular metalware.

LEVEL OF EVIDENCE

Biomechanical study.

A Bibliometric Analysis of the Field of Computer-Assisted Orthopedic Surgery during 2002–2021

Background

This study aimed to investigate the characteristics of research articles and research trends in computer-assisted orthopedic surgery (CAOS) by conducting bibliometric analyses.

Methods

CAOS-related research articles published in international journals from 2002 to 2021 were collected using the PubMed database and analyzed using the bibliometric method. Their publication year, journal name, corresponding author's country name, and the number of citations of all collected articles were noted. Contents of the articles were analyzed to evaluate the time point and anatomical site at which the digital technique was applied. Further, the 20-year period was divided into two halves of 10 years each to analyze the research trends.

Results

A total of 639 CAOS-related articles were identified. An average of 32.0 CAOS-related articles were published annually, with an average of 20.6 and 43.3 published in the first half and second half, respectively. Of all articles, 47.6% were published in the top 10 journals, and 81.2% were written in the top 10 countries. The total numbers of citations were 11.7 and 6.3 in the first and second halves, respectively, but the average annual number of citations was higher in the second half than in the first one. Articles on application of digital techniques during surgery were 62.3% and those on pre-surgery application were 36.9%. Further, articles in the knee (39.0%), spine (28.5%), and hip and pelvis (21.5%) fields accounted for 89.0% of the total publications. But the increase in publications in the said period was highest in the fields of the hand and wrist (+1,300.0%), ankle (+466.7%), and shoulder (+366.7%).

Conclusions

Over the last 20 years, the publication of CAOS-related research articles in international journals has grown steadily. Although the knee, spine, hip, and pelvis fields account for most CAOS-related research, research in new fields is also increasing. This study analyzed the types of articles and trends in CAOS-related research and provided useful information for future research in the field of CAOS.

Osteochondral Allograft Reconstruction of the Tibia Plateau for Posttraumatic Defects-A Novel Computer-Assisted Method Using 3D Preoperative Planning and Patient-Specific Instrumentation

Background  Surgical treatment of posttraumatic defects of the knee joint is challenging. Osteochondral allograft reconstruction (OCAR) is an accepted procedure to restore the joint congruity and for pain relief, particularly in the younger population. Preoperative three-dimensional (3D) planning and patient-specific instrumentation (PSI) are well accepted for the treatment of posttraumatic deformities for several pathologies. The aim of this case report was to provide a guideline and detailed description of the preoperative 3D planning and the intraoperative navigation using PSI in OCAR for posttraumatic defects of the tibia plateau. We present the clinical radiographic results of a patient who was operated with this new technique with a 3.5-year follow-up.

Materials and Methods  3D-triangular surface models are created based on preoperative computer tomography (CT) of the injured side and the contralateral side. We describe the preoperative 3D-analysis and planning for the reconstruction with an osteochondral allograft (OCA) of the tibia plateau. We describe the PSI as well as cutting and reduction techniques to show the intraoperative possibilities in posttraumatic knee reconstructions with OCA.

Results  Our clinical results indicate that 3D-assisted osteotomy and OCAR for posttraumatic defects of the knee may be beneficial and feasible. We illustrate the planning and execution of the osteotomy for the tibia and the allograft using PSI, allowing an accurate anatomical restoration of the joint congruency.

Discussion  With 3D-planning and PSI the OCAR might be more precise compared with conventional methods. It could improve the reproducibility and might allow less experienced surgeons to perform the precise and technically challenging osteotomy cuts of the tibia and the allograft. Further, this technique might shorten operating time because time consuming intraoperative steps such as defining the osteotomy cuts of the tibia and the allograft during surgery are not necessary.

Conclusion  OCAR of the tibia plateau for posttraumatic defects with 3D preoperative planning and PSI might allow for the accurate restoration of anatomical joint congruency, improve the reproducibility of surgical technique, and shorten the surgery time.

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.

Three-dimensional printing technology for patient-matched instrument in treatment of cubitus varus deformity: A case report

BACKGROUND

Recently, medical three-dimensional printing technology (3DPT) has demonstrated potential benefits for the treatment of cubitus varus deformity (CVD) by improving accuracy of the osteotomy through the use of an osteotomy guide, with or without a patient-mated plate. Here, we present an interesting CVD case, involving a patient who was treated with corrective biplanar chevron osteotomy using an innovative customized osteotomy guide and a newly designed patient-matched monoblock crosslink plate created with 3DPT.

CASE SUMMARY

A 32-year-old female presented with a significant CVD from childhood injury. A computer simulation was processed using images from computerized tomography scans of both upper extremities. The biplanar chevron osteotomy was designed to create identical anatomy between the mirror image of the contralateral distal humerus and the osteotomized distal humerus. Next, the customized osteotomy guide and patient-matched monoblock crosslink plate were designed and printed. A simulation osteotomy was created for the real-sized bone model, and the operation was performed using the posterior paratricipital approach with k-wire positioning from the customized osteotomy guide as a predrilled hole for screw fixation to achieve immediate control of the reduction after osteotomy. Our method allowed for successful treatment of the CVD case, significantly improving the patient’s radiographic and clinical outcomes, with satisfactory result.

CONCLUSION

3DPT-created patient-matched osteotomy guide and instrumentation provides accurate control during CVD correction.

Inter-rater variability of three-dimensional fracture reduction planning according to the educational background

Background

Computer-assisted three-dimensional (3D) planning is increasingly delegated to biomedical engineers. So far, the described fracture reduction approaches rely strongly on the performance of the users. The goal of our study was to analyze the influence of the two different professional backgrounds (technical and medical) and skill levels regarding the reliability of the proposed planning method. Finally, a new fragment displacement measurement method was introduced due to the lack of consistent methods in the literature.

Methods

3D bone models of 20 distal radius fractures were presented to nine raters with different educational backgrounds (medical and technical) and various levels of experience in 3D operation planning (0 to 10 years) and clinical experience (1.5 to 24 years). Each rater was asked to perform the fracture reduction on 3D planning software.

Results

No difference was demonstrated in reduction accuracy regarding rotational (p = 1.000) and translational (p = 0.263) misalignment of the fragments between biomedical engineers and senior orthopedic residents. However, a significantly more accurate planning was performed in these two groups compared with junior orthopedic residents with less clinical experience and no 3D planning experience (p < 0.05).

Conclusion

Experience in 3D operation planning and clinical experience are relevant factors to plan an intra-articular fragment reduction of the distal radius. However, no difference was observed regarding the educational background (medical vs. technical) between biomedical engineers and senior orthopedic residents. Therefore, our results support the further development of computer-assisted surgery planning by biomedical engineers. Additionally, the introduced fragment displacement measure proves to be a feasible and reliable method.

Level of Evidence

Diagnostic Level II

Tibial torsion analysis in computed tomography: development and validation of a real 3D measurement technique

PURPOSE

Pathological tibial torsion is known to negatively influence the functionality of the lower extremity, and therefore, its assessment might play an important role. While 3D imaging is used for many examinations of the musculoskeletal system, for the determination of tibial torsion no 3D measurement technique has been available so far. We developed a 3D measurement method and assess its interobserver reliability as well as its correlation with standard 2D measurement methods.

METHODS

CT scans of 82 tibiae in 79 patients with a mean age of 41 years were included. A novel 3D measurement technique was developed and applied. Measurements were compared with two frequently used 2D measurement methods. ICC (intraclass correlation coefficient) for the new technique was determined and compared to the 2D measurement method. Furthermore, differences between left and right legs as well as between males and females were assessed.

RESULTS

The ICC for the 2D methods was 0.917 and 0.938, respectively. For the 3D measurements, ICCs were calculated to be 0.954 and 0.950. Agreement between 2 and 3D methods was moderate to good with ICCs between 0.715 and 0.795. Torsion values for left and right legs did not differ significantly in 2D and in 3D (26.2 vs 28.5° and 27.2 vs. 25.9°). The same is true for the differences between male and female in 2D and 3D (26.2 vs. 29.6° and 25.0 vs. 31.2°).

CONCLUSION

The newly developed 3D measurement technique shows a high intraclass agreement and offers an applicable opportunity to assess the tibial torsion three-dimensionally.

Augmented Reality Based Surgical Navigation of Complex Pelvic Osteotomies—A Feasibility Study on Cadavers

Augmented reality (AR)-based surgical navigation may offer new possibilities for safe and accurate surgical execution of complex osteotomies. In this study we investigated the feasibility of navigating the periacetabular osteotomy of Ganz (PAO), known as one of the most complex orthopedic interventions, on two cadaveric pelves under realistic operating room conditions. Preoperative planning was conducted on computed tomography (CT)-reconstructed 3D models using an in-house developed software, which allowed creating cutting plane objects for planning of the osteotomies and reorientation of the acetabular fragment. An AR application was developed comprising point-based registration, motion compensation and guidance for osteotomies as well as fragment reorientation. Navigation accuracy was evaluated on CT-reconstructed 3D models, resulting in an error of 10.8 mm for osteotomy starting points and 5.4° for osteotomy directions. The reorientation errors were 6.7°, 7.0° and 0.9° for the x-, y- and z-axis, respectively. Average postoperative error of LCE angle was 4.5°. Our study demonstrated that the AR-based execution of complex osteotomies is feasible. Fragment realignment navigation needs further improvement, although it is more accurate than the state of the art in PAO surgery.

Computer-assisted open reduction internal fixation of intraarticular radius fractures navigated with patient-specific instrumentation, a prospective case series

BACKGROUND

Intra-articular fractures are associated with posttraumatic arthritis if inappropriately treated. Exact reduction of the joint congruency is the main factor to avoid the development of arthrosis. Aim of this study was to evaluate feasibility of computer-assisted surgical planning and 3D-printed patient-specific instrumentation (PSI) for treatment of distal intraarticular radius fractures.

METHOD

7 Patients who suffered a distal intraarticular radius fracture were enrolled in this prospective case series. Preoperative CT-scan was recorded, whereupon a 3D model was computed for surgical planning and design of PSI for surgical navigation. Postoperative accuracy and joint congruency were assessed. Patients were followed-up 3, 6 and 12 months postoperatively.

RESULTS

Mean follow-up was 16 months. Over all range of motion was restored and flexion, extension and pronation showed significant recovery, p < 0.05. Biggest intraarticular joint step-off and gap reduced from average 2.49 (± 1.04) to 0.8 mm (± 0.44), p < 0.05 and 6.12 mm (± 1.04) to 2.21 mm (± 1.16), p < 0.05. Average grip strength restored (3-16 months) from 20.33 kg (± 7.12) to 39.3 kg (± 19.55) p < 0.05, 100% of the healthy contralateral side. 3D-accuracy for guided fragments was 2.07 mm (± 0.64) and 8.59° (± 2.9) and 2.33 mm (± 0.69) and 12.86° (± 7.13), p > 0.05 for fragments reduced with ligamentotaxis.

CONCLUSION

Computer-assisted and PSI navigated intraarticular radius fracture treatment is feasible, safe and accurate. The benefits of this method, however, do not outstand the additional effort.

LEVEL OF EVIDENCE

IV.

Computer-assisted femoral head reduction osteotomies: an approach for anatomic reconstruction of severely deformed Legg-Calvé-Perthes hips. A pilot study of six patients

BACKGROUND

Legg-Calvé-Perthes (LCP) is a common orthopedic childhood disease that causes a deformity of the femoral head and to an adaptive deformity of the acetabulum. The altered joint biomechanics can result in early joint degeneration that requires total hip arthroplasty. In 2002, Ganz et al. introduced the femoral head reduction osteotomy (FHRO) as a direct joint-preserving treatment. The procedure remains one of the most challenging in hip surgery. Computer-based 3D preoperative planning and patient-specific navigation instruments have been successfully used to reduce technical complexity in other anatomies. The purpose of this study was to report the first results in the treatment of 6 patients to investigate whether our approach is feasible and safe.

METHODS

In this retrospective pilot study, 6 LCP patients were treated with FHRO in multiple centers between May 2017 and June 2019. Based on patient-specific 3D-models of the hips, the surgeries were simulated in a step-wise fashion. Patient-specific instruments tailored for FHRO were designed, 3D-printed and used in the surgeries for navigating the osteotomies. The results were assessed radiographically [diameter index, sphericity index, Stulberg classification, extrusion index, LCE-, Tönnis-, CCD-angle and Shenton line] and the time and costs were recorded. Radiologic values were tested for normal distribution using the Shapiro-Wilk test and for significance using Wilcoxon signed-rank test.

RESULTS

The sphericity index improved postoperatively by 20% (p = 0.028). The postoperative diameter of the femoral head differed by only 1.8% (p = 0.043) from the contralateral side and Stulberg grading improved from poor coxarthrosis outcome to good outcome (p = 0.026). All patients underwent acetabular reorientation by periacetabular osteotomy. The average time (in minutes) for preliminary analysis, computer simulation and patient-specific instrument design was 63 (±48), 156 (±64) and 105 (±68.5), respectively.

CONCLUSION

The clinical feasibility of our approach to FHRO has been demonstrated. The results showed significant improvement compared to the preoperative situation. All operations were performed by experienced surgeons; nevertheless, three complications occurred, showing that FHRO remains one of the most complex hip surgeries even with computer assistance. However, none of the complications were directly related to the simulation or the navigation technique.

A real 3D measurement technique for the tibial slope: differentiation between different articular surfaces and comparison to radiographic slope measurement

Background

The tibial slope plays an important role in knee surgery. However, standard radiographic measurement techniques have a low reproducibility and do not allow differentiation between medial and lateral articular surfaces. Despite availability of three-dimensional imaging, so far, no real 3D measurement technique was introduced and compared to radiographic measurement, which were the purposes of this study.

Methods

Computed tomography scans of 54 knees in 51 patients (41 males and 10 females) with a mean age of 46 years (range 22–67 years) were included. A novel 3D measurement technique was applied by two readers to measure the tibial slope of medial and lateral tibial plateau and rim. A statistical analysis was conducted to determine the intraclass correlation coefficient (ICC) for the new technique and compare it to a standard radiographic measurement.

Results

The mean 3D tibial slope for the medial plateau and rim was 7.4° and 7.6°, for the lateral plateau and rim 7.5° and 8.1°, respectively. The mean radiographic slope was 6.0°. Statistical analysis showed an ICC between both readers of 0.909, 0.987, 0.918, 0.893, for the 3D measurement of medial plateau, medial rim, lateral plateau and lateral rim, respectively, whereas the radiographic technique showed an ICC of 0.733.

Conclusions

The proposed novel measurement technique shows a high intraclass agreement and offers an applicable opportunity to assess the tibial slope three-dimensionally. Furthermore, the medial and lateral articular surfaces can be measured separately and one can differentiate the slope from the plateau and from the rim. As three-dimensional planning becomes successively more important, our measurement technique might deliver a useful supplement to the standard radiographic assessment in slope related knee surgery.

Level of evidence

Level III, diagnostic study.

The Accuracy of Three-Dimensional Planned Bone Tumor Resection Using Patient-Specific Instrument

Introduction

Although treatment of bone tumors is multidisciplinary, the complete surgical resection of bone tumors remains the mainstay of the treatment. Patient-specific instruments (PSI) are personalized tools, which help the surgeon to perform tumor resections accurately. The aim of this study is to evaluate how precise the planned resection can be intraoperatively executed with the use of PSI.

Patients and Methods

Eleven patients who underwent a resection of bone tumor using PSI were analyzed. A preoperative model of the tumor and the affected bone was created from acquired CT scans and MRI. After defining the resection planes, PSI were produced by a 3D printer. The resected piece of bone was scanned and imported in the original planning model enabling the assessment of the distance between the planned resection plane and the realized osteotomy in every direction.

Results

In overall, the combined error of an osteotomy ranges from 0.74 ± 0.96 mm to 3.60 ± 2.46 mm. The average errors observed in situations with one resection plane (simple osteotomy) are lower than in complex curved osteotomies with multiple planes, in which we also found a greater variance.

Conclusion

3D planned bone tumor resections using PSI show promising results for precise resection at different anatomical regions. Even if the found error range in this series is slightly higher than reported, PSI remain a valuable tool to facilitate complex bone tumor resections.

Malpositioning of patient-specific instruments within the possible degrees of freedom in high-tibial osteotomy has no considerable influence on mechanical leg axis correction

PURPOSE

Patient-specific instruments (PSIs) are helpful tools in high tibial osteotomy (HTO) in patients with symptomatic varus malalignment of the mechanical leg axis. However, the precision of HTO can decrease with malpositioned PSI. This study investigates the influence of malpositioned PSI on axis correction, osteotomy, and implant placement.

METHODS

With a mean three-dimensional (3D) model (0.8° varus), PSI-navigated HTOs were computer simulated. Two different guide designs, one with stabilising hooks and one without, were used. By adding rotational and translational offsets of different degrees, wrong placements of PSI were simulated. After 5° valgisation of the postoperative mechanical axis, the distance between joint-plane and osteotomy screws, respectively, were measured. The same simulations were performed in a patient with varus deformity (7.4° varus).

RESULTS

In the mean 3D model, the postoperative mechanical axis was within 3.9°-4.5° valgus with mean value of 4.1° ± 0.1° (correct axis 4.2° valgus). Surgical failure concerning osteotomy occurred in 17 of 76 HTOs. Significantly safer screw placement was observed using PSI with stabilising hooks (p = 0.012). In the case of the 3D model with 7.4° varus deformity, the postoperative mechanical axis was within 3.2°-3.9° valgus with mean value of 3.8° ± 0.2° (correct axis 3.9° valgus). Surgical failure concerning osteotomy occurred in 3 of 38 HTOs. Screws were always within the safety distance.

CONCLUSION

The clinical relevance of the presented study is that malpositioning of a PSI within the possible degrees of freedom does not have a relevant influence on the axis correction. The most vulnerable plane for surgical failure is the sagittal plane, wherefore the treating surgeon should verify correct guide placement to prevent surgical failure, particularly in this plane.

LEVEL OF EVIDENCE

III.

Accuracy of 3D-planned patient specific instrumentation in high tibial open wedge valgisation osteotomy

Purpose

High tibial osteotomy (HTO) is an effective treatment option in early osteoarthritis. However, preoperative planning and surgical execution can be challenging. Computer assisted three-dimensional (3D) planning and patient-specific instruments (PSI) might be helpful tools in achieving successful outcomes. Goal of this study was to assess the accuracy of HTO using PSI.

Methods

All medial open wedge PSI-HTO between 2014 and 2016 were reviewed. Using pre- and postoperative radiographs, hip-knee-ankle angle (HKA) and posterior tibial slope (PTS) were determined two-dimensionally (2D) to calculate 2D accuracy. Using postoperative CT-data, 3D surface models of the tibias were reconstructed and superimposed with the planning to calculate 3D accuracy.

Results

Twenty-three patients could be included. A mean correction of HKA of 9.7° ± 2.6° was planned. Postoperative assessment of HKA correction showed a mean correction of 8.9° ± 3.2°, resulting in a 2D accuracy for HKA correction of 0.8° ± 1.5°. The postoperative PTS changed by 1.7° ± 2.2°. 3D accuracy showed average 3D rotational differences of − 0.1° ± 2.3° in coronal plane, − 0.2° ± 2.3° in transversal plane, and 1.3° ± 2.1° in sagittal plane, whereby 3D translational differences were calculated as 0.1 mm ± 1.3 mm in coronal plane, − 0.1 ± 0.6 mm in transversal plane, and − 0.1 ± 0.6 mm in sagittal plane.

Conclusion

The use of PSI in HTO results in accurate correction of mechanical leg axis. In contrast to the known problem of unintended PTS changes in conventional HTO, just slight changes of PTS could be observed using PSI. The use of PSI in HTO might be preferable to obtain desired correction of HKA and to maintain PTS.

Corrective Osteosynthesis in Failed Proximal Humeral Fractures

Despite implant improvement and increasing standardisation of operation techniques, the rate of therapy failure of proximal humeral fracture care with primary osteosyntheses is estimated to be 10 to 20%. Most commonly failure is precipitated by: material failure, technical error, non-anatomical repositioning, avascular necrosis, lacking medial support. An additive medial stabilisation of the so-called "calcar region" can decrease failure rates significantly. An early correction osteosynthesis with the purpose of restoring the anatomy is indicated in bony, non-consolidated "fresh" fractures. Bony consolidated fractures should be classified according to Boileau and Walch. The authors of this article advice a structured and classification-adapted approach to treatment with a correction osteosynthesis. Post-traumatic deficits can be augmented utilising the following methods: correction osteosynthesis with allogeneic/autologous bone grafts, correction osteosynthesis with hydroxyapatite grafts. For the additive stabilisation of repositioned and fixated fractures, the following are described: correction osteosynthesis with an additive ventral one-third tubular plate, correction osteosynthesis with cement-augmented screws. Based on results of endoprosthetics following fractures of the proximal humerus, the correction osteosynthesis indeed represents a real therapeutic alternative in patients that are below the age of 60, a good bone mass and with relative functional requirements.

Joint-preserving tumour resection around the knee with allograft reconstruction using three-dimensional preoperative planning and patient-specific instruments

BACKGROUND

The region around the knee joint is a common location of malignant bone tumours. Limb salvage procedures, whenever possible, are preferred to amputation. Allograft reconstruction is an accepted procedure to restore large bone defects. Preoperative three-dimensional (3D) planning and patient-specific instruments (PSI) have already been introduced. The purpose of this study was to provide a technical guideline for joint preserving tumour resection and allograft reconstruction around the knee using 3D planning and PSI.

MATERIAL AND METHODS

3D triangular surface models are created based on computed tomography (CT) and magnetic resonance imaging (MRI) data, whereby tumour expansion in the bone and affection of the surrounding structures are assessed. We describe the preoperative 3D analysis and planning in tumours around the knee joint. In addition, we provide a description of different PSI as well as cutting-techniques to enlarge the toolkit and facilitate a broad range of joint preserving tumour resections with allograft reconstruction around the knee. The basic guide serves for the registration of the preoperative plan for the surgery. Reference pins facilitate the application of further guides. Different additional guide designs can be applied, such as "safety guides," "osteotomy guides," and "allograft adjustment guides."

DISCUSSION

The use of 3D planning and generation of PSI offers valuable tools in tumour resection and allograft reconstruction around the knee joint. To perform complex osteotomies and to preserve vital structures PSI seems to be helpful tools. A step-by-step guideline is provided for the use of 3D preoperative planning and sequentially applied patient-specific guides.

An Automatic Personalized Internal Fixation Plate Modeling Framework for Minimally Invasive Curved Bone Fracture Surgery Based on Preregistration With Capsule Projection Model

OBJECTIVE

In this paper, a framework to visualize and model internal fixation plates is presented for computer-aided personalized and minimally invasive curved bone fracture surgery.

METHODS

We focus on personalized reverse reconstruction of the bone fracture plate based on three-dimensional (3-D) mesh models obtained from a 3-D optical scanner. The steps of the method are as follows. First, principal component analysis and the K-means method are used to reconstruct a Bezier curve (ridge line) of broken bones. Second, based on the geometric shape of the curved broken bones, a capsule projection model of the broken bones is proposed to obtain the feature information of the broken bone sections. Third, the ordering points to identify the clustering structure (OPTICS) method is utilized for preregistration (rough registration). Fourth, a regional self-growth strategy is designed to extract the cross-section points. Fifth, the iterative closest point method is applied for the accurate registration of the fracture surface models. Finally, a personalized internal fixation plate model is reconstructed based on several user points.

RESULTS

The internal fixation plate model can be reconstructed according to the patient's bone parameters.

CONCLUSION

Clinicians can use this framework to obtain personalized and accurate internal fixation plate models that effectively represent the broken bones of patients. Via X-ray navigation, the personalized forged plate can be fixed on the target area through a small incision.

SIGNIFICANCE

This framework provides a reasonable and practicable technical approach for computer-aided minimally invasive curved bone fracture surgery.

3D planning and surgical navigation of clavicle osteosynthesis using adaptable patient-specific instruments

Background

Preoperative three-dimensional planning and intraoperative navigation by patient-specific instruments is a promising method for the exact correction of bone deformities. Nevertheless, disadvantages of current concepts are the missing options of adapting the surgical plan intraoperatively. By providing the surgeons with a controlled length adjustment through the patient-specific instruments, the application area can usefully be expanded in the treatment of clavicle osteosyntheses.

Methods

In three cases, preoperative three-dimensional surgical planning with the intraoperative use of patient-specific instruments was applied. The computer-assisted assessments of clavicle deformities, the preoperative plan, and the design of patient-specific instruments were created on the basis of computed tomography data. Reduction guides for restoring length and rotation according to the mirrored healthy contralateral side were enhanced with adaptable length adjustment functions. The screw thread of the reduction guides enabled temporary distraction of the clavicle fracture fragments and a controlled compression of the optionally used interposed bone block between clavicle fragments.

Results

Navigated clavicle osteosyntheses by enhanced patient-specific instruments was executed uneventful in all three cases. The surgeon was able to adapt clavicle length in a planned axis intraoperatively as clinically desired.

Conclusion

Computer-assisted planning of clavicle osteosynthesis and surgical navigation with additional adaptable patient-specific instruments can usefully expand the previous application areas. By using guided length adjustments, the fragments and optionally the graft can be compressed along a planned axis as desired to ensure optimal bone healing.

Level of evidence

Basic science study, Surgical technique

Electronic supplementary material

The online version of this article (10.1186/s13018-019-1151-8) contains supplementary material, which is available to authorized users.

Can objective criteria for poor tolerance of proximal humerus malunion be identified?

BACKGROUND

Malunion of the proximal humerus is common and variably tolerated. Classifications developed for proximal humerus malunion (PHM) rely on standard radiographs, which underestimate bone fragment displacement and lack accuracy. The clinical tolerance of PHM is subjective, and revision surgery is not always necessary. The primary objective of this study was to assess the reproducibility and relevance of four CT angle measurements for objectively quantifying the morphological disharmony caused by PHM in a control population then in a population with PHM. The secondary objectives were to identify angle cut-offs and to assess the correlations between angle values and the clinical tolerance of PHM.

HYPOTHESIS

Objective criteria for assessing proximal humerus malunion can be identified using CT scans.

MATERIALS AND METHODS

Four angles were chosen to quantify proximal humerus disharmony: the angles between the humeral head and the glenoid in the coronal plane (HGCo) and axial plane (HGAx), the angle of tuberosity divergence in the axial plane (TDAx), and the centrum collum diaphyseal angle (CCD). The reproducibility of measurements of the four angles on computed tomography (CT) views was evaluated in a control population and in 46 patients with PHM. To this end, the reproducibility of reference slice selection was determined and intra- and interobserver reproducibility of the angle measurements was then assessed. Patients with PHM were divided into two groups based on clinical tolerance to allow testing for disharmony parameters associated with poor clinical tolerance, which was defined as functional impairment and surgical revision.

RESULTS

Slice selection was found to be reproducible. The Bland-Altman plot indicated that the angle measurements in both the controls and the patients were reproducible within ±2 SDs. Intraclass correlation coefficient values ranged from fair to excellent for all angles in both the controls and the patients. The mean TDAx was higher in the patients than in the controls (72.0° vs. 56.1°, P<0.05) and, within the PHM group, was higher in the subgroup with good vs. poor clinical tolerance (75.8° vs. 69.5°, P<0.05). The CCD angle was greater in the controls than in the patients (129.8° [range, 128.3°-131.3°] vs. 125.9° [range, 122.9°-128.9], respectively) and was significantly greater in the PHM subgroup with good vs poor clinical tolerance (131.4° vs. 122.3°, respectively; P=0.007). The HGCo and HGAx angles were significantly greater in the patients than in the controls (HGCo: 66.6° vs. 52.2°, respectively; HGAx: 17.5° vs. 13.3°, respectively, P=0.55).

DISCUSSION

The measurement method described here provides a quantitative assessment of postfracture disharmony based on four angles, the HGCo, HGAx, and TDAx. Measurement of these four angles on CT images was found to have good intra- and interobserver reproducibility. The angle values were significantly greater in the patients with PHM than in the controls. Within the patient group, the subgroup with poor clinical tolerance had smaller values of the TDAx, CCD, and HGAx angles and a greater value of the HGCo angle.

LEVEL OF EVIDENCE

IV, retrospective observational study.

Improving accuracy of opening-wedge osteotomies of distal radius using a patient-specific ramp-guide technique

BACKGROUND

Opening-wedge osteotomies of the distal radius, performed with three-dimensional printed patient-specific instruments, are a promising technique for accurate correction of malunions. Nevertheless, reports of residual malalignments and discrepancies in the plate and screw position from the planned fixation exist. Consequently, we developed a patient-specific ramp-guide technique, combining navigation of plate positioning, osteotomy cutting, and reduction. The aim of this study is to compare the accuracy of navigation of three-dimensional planned opening-wedge osteotomies, using a ramp-guide, over state-of-the-art guide techniques relying solely on pre-drilled holes.

METHODS

A retrospective analysis was carried out on opening-wedge osteotomies of the distal radius, performed between May 2016 and April 2017, with patient-specific instruments. Eight patients were identified in which a ramp-guide for the distal plate fixation was used. We compared the reduction accuracy with a control group of seven patients, where the reduction was performed with pre-drilled screw holes placed with the patient-specific instruments. The navigation accuracy was assessed by comparing the preoperative plans with the postoperative segmented, computed tomography scans. The accuracy was expressed using a 3D angle and in measurements of all six degrees of freedom (3 translations, 3 rotations), with respect to an anatomical coordinate system.

RESULTS

The duration of the surgery of the ramp-guide group was significantly shorter compared to the control group. Significantly less rotational and translational residual malalignment error was observed in the open-wedged osteotomies, where patient-specific instruments with ramp-guides were used. On average, a residual rotational malalignment error of 2.0° (± 2.2°) and a translational malalignment error of 0.6 mm (± 0.2 mm) was observed in the ramp-guide group, as compared to the 4.2° (± 15.0°) and 1.0 mm (± 0.4 mm) error in the control group. The used plate was not significantly positioned more accurately, but significantly fewer screws (15.6%) were misaligned in the distal fragment compared to the control group (51.9%).

CONCLUSION

The use of the presented ramp-guide technique in opening-wedge osteotomies is improving reduction accuracy, screw position, and surgical duration, compared to the existing patient-specific instrument based navigation methods.

Corrective osteotomy for hyperextended elbow with limited flexion due to supracondylar fracture malunion

BACKGROUND

Extension deformity of the distal humerus after a malunited supracondylar fracture can restrict elbow flexion. Here we report a computer-assisted operative procedure and review the results of clinical cases in which corrective surgery was performed.

METHODS

The medical records of the patients who underwent corrective osteotomy for hyperextended elbow malunion of the distal humerus with limited elbow flexion (flexion angle ≤100°) were reviewed retrospectively. Osteotomy was performed using patient-specific instruments designed based on preoperative 3-dimensional computer simulation.

RESULTS

Three patients, a 55-year-old woman and two 12-year-old boys, met the inclusion criteria. The angles of hyperextension of the affected distal humerus were 29°, 29°, and 25°, respectively. The range of flexion/extension of the elbow motion in the first patient improved from 95°/25° preoperatively to 140°/-10° postoperatively, in the second patient from 100°/20° to 145°/5°, and in the third patient from 80°/25° to 140°/10°. Bone union was achieved in all patients. There were no major complications. The corrective operations not only improved elbow flexion but also increased the total range of motion in the elbow by rebuilding the anterior curve of the distal humerus.

CONCLUSIONS

Correction of the extension deformity of the distal humerus after a malunited supracondylar fracture is a reasonable option for patients older than 10 years with restricted elbow flexion. Preoperative computer simulation and the use of patient-specific instruments can be a useful alternative that enables accurate deformity correction and improves the total range of motion.

Is the contralateral tibia a reliable template for reconstruction: a three-dimensional anatomy cadaveric study

PURPOSE

The contralateral anatomy is regularly used as a reconstruction template for corrective osteotomies of several deformities and pathological conditions. However, there is lack of evidence that the intra-individual differences between both tibiae are sufficiently small to use the contralateral tibia as a 3D reconstruction template for complex osteotomies. The aim of this study was to evaluate the intra-individual side differences of the tibia in length, torsion, angulation, and translation using 3D measurement techniques.

METHODS

3D surface models of both tibiae were created from computed tomography data of 51 cadavers. The (mirrored) models of the right tibiae were divided into two halves at the centre of the shaft. Thereafter, the proximal and distal segments were aligned to the left (contralateral) tibia in an automated fashion. The relative 3D transformation between both aligned segments was measured to quantify the side difference in 6° of freedom (3D translation vector, 3 angles of rotation).

RESULTS

The mean side difference in tibia length was 2.1 mm (SD 1.3 mm; range 0.2-5.9 mm). The mean side difference in torsion was 4.9° (SD 4.1°; range 0.2°-17.6°). The mean side difference in the coronal and sagittal planes was 1.1° (SD 0.9°; range 0.0°-4.6°) and 1.0° (SD 0.8°; range 0.1°-2.9°), respectively.

CONCLUSION

The present study confirms small side differences in torsion between the left and right tibia, while the side differences in the coronal and sagittal plane are probably negligible. The contralateral tibia seems to be a reliable reconstruction template for the 3D preoperative planning of complex corrective osteotomies of the tibia. However, torsional differences should be interpreted with caution, as a single cut-off value of a clinically relevant torsional side difference cannot be defined. The presented results are relevant to surgeons considering the contralateral tibia as a 3D reconstruction template for corrective osteotomies of the tibia.

LEVEL OF EVIDENCE

Basic science.

A Novel Method for the Approximation of Humeral Head Retrotorsion Based on Three-Dimensional Registration of the Bicipital Groove

BACKGROUND

The accurate restoration of premorbid anatomy is key for the success of reconstructive surgeries of the proximal part of the humerus. The bicipital groove has been proposed as a landmark for the prediction of humeral head retrotorsion. We hypothesized that a novel method based on bilateral registration of the bicipital groove yields an accurate approximation of the premorbid anatomy of the proximal part of the humerus.

METHODS

Three-dimensional (3D) triangular surface models were created from computed tomographic data of 100 paired humeri (50 cadavers). Segments of the distal part of the humerus and the humeral shaft of prespecified lengths were defined. A surface registration algorithm was applied to superimpose the models onto the mirrored contralateral humeral model based on the defined segments. We evaluated the 3D proximal humeral contralateral registration (p-HCR) errors, defined as the difference in 3D rotation of the humeral head between the models when superimposed. For comparison, we quantified the landmark-based retrotorsion (LBR) error, defined as the intra-individual difference in retrotorsion, measured with a landmark-based 3D method.

RESULTS

The mean 3D p-HCR error using the most proximal humeral shaft (bicipital groove) segment for the registration was 2.8° (standard deviation [SD], 1.5°; range, 0.6° to 7.4°). The mean LBR error of the reference method was 6.4° (SD, 5.9°; range, 0.5° to 24.0°).

CONCLUSIONS

Bilateral 3D registration of the bicipital groove is a reliable method for approximating the premorbid anatomy of the proximal part of the humerus.

CLINICAL RELEVANCE

The accurate approximation of the premorbid anatomy is a key for the successful restoration of the premorbid anatomy of the proximal part of the humerus.

Restoration of the Patient-Specific Anatomy of the Proximal and Distal Parts of the Humerus: Statistical Shape Modeling Versus Contralateral Registration Method

BACKGROUND

In computer-assisted reconstructive surgeries, the contralateral anatomy is established as the best available reconstruction template. However, existing intra-individual bilateral differences or a pathological, contralateral humerus may limit the applicability of the method. The aim of the study was to evaluate whether a statistical shape model (SSM) has the potential to predict accurately the pretraumatic anatomy of the humerus from the posttraumatic condition.

METHODS

Three-dimensional (3D) triangular surface models were extracted from the computed tomographic data of 100 paired cadaveric humeri without a pathological condition. An SSM was constructed, encoding the characteristic shape variations among the individuals. To predict the patient-specific anatomy of the proximal (or distal) part of the humerus with the SSM, we generated segments of the humerus of predefined length excluding the part to predict. The proximal and distal humeral prediction (p-HP and d-HP) errors, defined as the deviation of the predicted (bone) model from the original (bone) model, were evaluated. For comparison with the state-of-the-art technique, i.e., the contralateral registration method, we used the same segments of the humerus to evaluate whether the SSM or the contralateral anatomy yields a more accurate reconstruction template.

RESULTS

The p-HP error (mean and standard deviation, 3.8° ± 1.9°) using 85% of the distal end of the humerus to predict the proximal humeral anatomy was significantly smaller (p = 0.001) compared with the contralateral registration method. The difference between the d-HP error (mean, 5.5° ± 2.9°), using 85% of the proximal part of the humerus to predict the distal humeral anatomy, and the contralateral registration method was not significant (p = 0.61). The restoration of the humeral length was not significantly different between the SSM and the contralateral registration method.

CONCLUSIONS

SSMs accurately predict the patient-specific anatomy of the proximal and distal aspects of the humerus. The prediction errors of the SSM depend on the size of the healthy part of the humerus.

CLINICAL RELEVANCE

The prediction of the patient-specific anatomy of the humerus is of fundamental importance for computer-assisted reconstructive surgeries.

Corrective osteotomy in symptomatic clavicular malunion using computer-assisted 3-D planning and patient-specific surgical guides

Surgical correction of a symptomatic clavicular malunion requires simultaneous adjustment of the translation as well as the rotation in multiple planes. We describe a corrective osteotomy for a clavicle malunion using 3-D computer assisted preoperative-planning combined with patient-specific surgical guides, along with the benefits and disadvantages of this approach. This method enabled quantifying the malunion by comparing the malunited bone with the normal contralateral clavicle as a template. The postoperative results were encouraging with symmetrical shoulder anatomy and functional improvement. Therefore, we recommend this technique in patients with a symptomatic clavicle malunion, as it allows successful correction of the deformity.

A Novel Registration-Based Approach for 3D Assessment of Posttraumatic Distal Humeral Deformities

BACKGROUND

With current 3-dimensional (3D) computer-based methods for the assessment of deformities, a surface registration method is applied to superimpose a computer model of the pathological bone onto a mirrored computer model of the contralateral side. However, because of bilateral differences, especially in humeral torsion, such template-based approaches may introduce bias in the assessment of a distal humeral deformity. We hypothesized that a novel registration approach might prove superior to the current approach in reducing such bias, thus yielding improved accuracy of 3D assessment of distal humeral deformities.

METHODS

Three-dimensional triangular surface models were generated from computed tomographic (CT) data of 100 paired humeri without a pathological condition. Humeral segments of varying, predetermined lengths, excluding the distal part of the humerus, were defined. A surface registration algorithm was applied to superimpose the humeral models of both sides based on each selected segment. Humeral contralateral registration (HCR) errors, defined as the residual differences in apparent 3D orientation between the distal parts, were evaluated.

RESULTS

The mean HCR error (and standard deviation) using the distal-most humeral shaft segment to assess the angular orientation was 2.3° ± 1.1 (range, 0.5° to 5.8°). Including the humeral head in the surface registration algorithm, however, as is done currently, resulted in a higher HCR error (p < 0.001). The HCR error using the proximal-most segment was >10° in 20% of the cases and between 5° and 10° in an additional 50% of the cases. By comparison, using the proposed distal-most humeral shaft segment, the HCR error was between 5° and 10° in only 2% of cases, and was never >10°. The proximal segments are nevertheless used in the proposed method for registering humeral length.

CONCLUSIONS

The proposed new approach yields a deformity assessment that is less prone to bias arising from inherent bilateral differences and therefore is more accurate than current surface registration approaches.

CLINICAL RELEVANCE

Accurate 3D assessment is of fundamental importance if computer-based methods are applied in the correction of posttraumatic deformities.

Corrective Osteotomy for Symptomatic Clavicle Malunion Using Patient-specific Osteotomy and Reduction Guides

Midshaft clavicular fractures are often treated nonoperatively with good reported clinical outcome in a majority of patients. However, malunion with shortening of the affected clavicle is not uncommon. Shortening of the clavicle has been shown to affect shoulder strength and kinematics with alteration of scapular position. Whereas the exact clinical impact of these factors is unknown, the deformity may lead to cosmetic and functional impairment as for example pain with weight-bearing on the shoulder girdle. Other reported complications of clavicular malunion include thoracic outlet syndrome, subclavicular vein thrombosis, and axillary plexus compression. Corrective osteotomy has therefore been recommended for symptomatic clavicular malunions, generally using plain x-rays for planning the necessary elongation. Particularly in malunited multifragmentary fractures it may be difficult to exactly determine the plane of osteotomy intraoperatively to restore the precise anatomic shape of the clavicle. We present a technique for corrective osteotomy using preoperative computer planning and 3-dimensional printed patient-specific intraoperative osteotomy and reduction guides based on the healthy contralateral clavicle.

Computer-assisted planning and patient-specific guides for the treatment of midshaft clavicle malunions

BACKGROUND

The surgical treatment of malunions after midshaft clavicle fractures is associated with a number of potential complications and the surgical procedure is challenging. However, with appropriate and meticulous preoperative surgical planning, the surgical correction yields satisfactory results. The purpose of this study was to provide a guideline and detailed overview for the computer-assisted planning and 3-dimensional (3D) correction of malunions of the clavicle.

METHODS

The 3D bone surface models of the pathologic and contralateral sides were created on the basis of computed tomography data. The computer-assisted assessment of the deformity, the preoperative plan, and the design of patient-specific guides enabling compression plating are described.

RESULTS

We demonstrate the benefit and versatility of computer-assisted planning for corrective osteotomies of malunions of the midshaft clavicle. In combination with patient-specific guides and compression plating technique, the correction can be performed in a more standardized fashion. We describe the determination of the contact-optimized osteotomy plane. An osteotomy along this plane facilitates the correction and enlarges the contact between the fragments at once. We further developed a technique of a stepped osteotomy that is based on the calculation of the contact-optimized osteotomy plane. The stepped osteotomy enables the length to be restored without the need of structural bone graft. The application of the stepped osteotomy is presented for malunions of the clavicle with shortening and excessive callus formation.

CONCLUSIONS

The 3D preoperative planning and patient-specific guides for corrective osteotomies of the clavicle may help reduce the number of potential complications and yield results that are more predictable.

Prediction of the pre-morbid 3D anatomy of the proximal humerus based on statistical shape modelling

Aims

Restoring the pre-morbid anatomy of the proximal humerus is a goal of anatomical shoulder arthroplasty, but reliance is placed on the surgeon’s experience and on anatomical estimations. The purpose of this study was to present a novel method, ‘Statistical Shape Modelling’, which accurately predicts the pre-morbid proximal humeral anatomy and calculates the 3D geometric parameters needed to restore normal anatomy in patients with severe degenerative osteoarthritis or a fracture of the proximal humerus.

Materials and Methods

From a database of 57 humeral CT scans 3D humeral reconstructions were manually created. The reconstructions were used to construct a statistical shape model (SSM), which was then tested on a second set of 52 scans. For each humerus in the second set, 3D reconstructions of four diaphyseal segments of varying lengths were created. These reconstructions were chosen to mimic severe osteoarthritis, a fracture of the surgical neck of the humerus and a proximal humeral fracture with diaphyseal extension. The SSM was then applied to the diaphyseal segments to see how well it predicted proximal morphology, using the actual proximal humeral morphology for comparison.

Results

With the metaphysis included, mimicking osteoarthritis, the errors of prediction for retroversion, inclination, height, radius of curvature and posterior and medial offset of the head of the humerus were 2.9° (± 2.3°), 4.0° (± 3.3°), 1.0 mm (± 0.8 mm), 0.8 mm (± 0.6 mm), 0.7 mm (± 0.5 mm) and 1.0 mm (± 0.7 mm), respectively. With the metaphysis excluded, mimicking a fracture of the surgical neck, the errors of prediction for retroversion, inclination, height, radius of curvature and posterior and medial offset of the head of the humerus were 3.8° (± 2.9°), 3.9° (± 3.4°), 2.4 mm (± 1.9 mm), 1.3 mm (± 0.9 mm), 0.8 mm (± 0.5 mm) and 0.9 mm (± 0.6 mm), respectively.

Conclusion

This study reports a novel, computerised method that accurately predicts the pre-morbid proximal humeral anatomy even in challenging situations. This information can be used in the surgical planning and operative reconstruction of patients with severe degenerative osteoarthritis or with a fracture of the proximal humerus. Cite this article: Bone Joint J 2017;99-B:927–33.