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Three-dimensional postoperative accuracy of extra-articular forearm osteotomies using CT-scan based patient-specific surgical guides.

Vlachopoulos L, Schweizer A, Graf M, Nagy L, Fürnstahl P - BMC Musculoskelet Disord (2015)

Bottom Line: However, the difference between planned and performed reduction is difficult to assess with conventional radiographs.The technique demonstrated high accuracy in performing closing wedge (or single-cut) osteotomies.However, for opening wedge osteotomies with extensive lengthening, probably due to the fact that precise reduction was difficult to achieve or maintain, the final corrections were less accurate.

View Article: PubMed Central - PubMed

Affiliation: Computer Assisted Research and Development Group, Balgrist University Hospital, University of Zurich, Zurich, Switzerland. lvlachopoulos@card.balgrist.ch.

ABSTRACT

Background: Computer assisted corrective osteotomy of the diaphyseal forearm and the distal radius based on computer simulation and patient-specific guides has been described as a promising technique for accurate reconstruction of forearm deformities. Thereby, the intraoperative use of patient-specific drill and cutting guides facilitate the transfer of the preoperative plan to the surgery. However, the difference between planned and performed reduction is difficult to assess with conventional radiographs. The aim of this study was to evaluate the accuracy of this surgical technique based on postoperative three-dimensional (3D) computed tomography (CT) data.

Methods: Fourteen patients (mean age 23.2 (range, 12-58) years) with an extra-articular deformity of the forearm had undergone computer assisted corrective osteotomy with the healthy anatomy of the contralateral uninjured side as a reconstruction template. 3D bone surface models of the pathological and contralateral side were created from CT data for the computer simulation. Patient-specific drill and cutting guides including the preoperative planned screw direction of the angular-stable locking plates and the osteotomy planes were used for the intraoperative realization of the preoperative plan. There were seven opening wedge osteotomies and nine closing wedge (or single-cut) osteotomies performed. Eight-ten weeks postoperatively CT scans were obtained to assess bony consolidation and additionally used to generate a 3D model of the forearm. The simulated osteotomies- preoperative bone models with simulated correction - and the performed osteotomies - postoperative bone models - were analyzed for residual differences in 3D alignment.

Results: On average, a significant higher residual rotational deformity was observed in opening wedge osteotomies (8.30° ± 5.35°) compared to closing wedge osteotomies (3.47° ± 1.09°). The average residual translation was comparable small in both groups, i.e., below 1.5 mm and 1.1 mm for opening and closing wedge osteotomies, respectively.

Conclusions: The technique demonstrated high accuracy in performing closing wedge (or single-cut) osteotomies. However, for opening wedge osteotomies with extensive lengthening, probably due to the fact that precise reduction was difficult to achieve or maintain, the final corrections were less accurate.

No MeSH data available.


Related in: MedlinePlus

Preoperative Plan. Outline of the investigated computer-assisted planning approach. a Quantification of the malunion by superimposing the proximal part of the pathological bone (orange) with the mirrored contralateral bone (green). b Simulated reduction of the distal fragment (violet) and positioning of the fixation plate. The (beige) cylinders represent the angular-stable locking screws. c The screw models are transformed back to the pathological bone by applying the inverse transformation. The patient-specific drill and cutting guide (beige) is designed based on this information
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Fig1: Preoperative Plan. Outline of the investigated computer-assisted planning approach. a Quantification of the malunion by superimposing the proximal part of the pathological bone (orange) with the mirrored contralateral bone (green). b Simulated reduction of the distal fragment (violet) and positioning of the fixation plate. The (beige) cylinders represent the angular-stable locking screws. c The screw models are transformed back to the pathological bone by applying the inverse transformation. The patient-specific drill and cutting guide (beige) is designed based on this information

Mentions: 3D triangular surface models of the radius and ulna of the pathological and contralateral uninjured side were generated by segmenting the bones from CT data (slice thickness 1 mm; 120 kV; Philips Brilliance 40 CT, Philips Healthcare, The Netherlands) using commercial software (Mimics, Materialise, Belgium). The CT protocol for corrective osteotomies of the forearm at our institution includes a contiguously scan of the whole forearm from the elbow to the radiocarpal joint. For segmentation, manual thresholding and region growing was applied. A senior surgeon performed the computer planning on a standard personal computer using the custom-made software application CASPA (Balgrist CARD AG, Zurich, Switzerland). To quantify the malunion in 3D, the model of the contralateral bone was mirrored and aligned with the pathological bone using the Iterative Closest Point (ICP) surface registration algorithm as previously described [5, 6] (Fig. 1a). After simulated osteotomy, the distal part was reduced to the contralateral bone using ICP. Next, a 3D model of the angular-stable locking plate was positioned on the bone surface. Dependent on the malunion, one of the following implants was chosen by the surgeon: A 2.7 mm LCP plate (Synthes, Solothurn, Switzerland), a 2.7 mm LCP ulnar shortening osteotomy plate (Synthes), a 2.4 mm LCP distal radius plate (Synthes), or an Elegantus distal radius plate (Intercus Schweiz GmbH, Aarau, Switzerland). The plate models included cylinders representing the exact position and direction of the angular-stable locking screws (Fig. 1b) in relation to the plate. The screw models placed in the distal fragment were transformed with the previously registered distal part of the bone back to the pathological bone position by applying the inverse transformation. Thereby, during surgery the final direction of the screws can be predrilled previous to the osteotomy. Additionally, when a closing wedge osteotomy was planned, we used a metallic inlay that contains a cutting slit to guide the 0.4mm thick saw blade. The inlay was inserted into a dedicated frame in the guide body for alignment according to the planned osteotomy planes. In case of an open wedge osteotomy, since all osteotomies were complete with a resulting distraction gap, the exact position of the plane is not as important as for closing wedge or single cut osteotomies. Lastly, a surgical guide with drill sleeves and the dedicated frames for the metallic inlay was designed (Fig. 1c). To achieve a unique fit, the shape of the guide body was designed to contain irregular convex and concave parts covering the bone from different directions and the undersurface of the guide to be placed on the bone as an exact replication of the surface of the bone model. The guides were manufactured by Medacta International S.A. (Castel San Pietro, Switzerland) with a selective laser sintering device.Fig. 1


Three-dimensional postoperative accuracy of extra-articular forearm osteotomies using CT-scan based patient-specific surgical guides.

Vlachopoulos L, Schweizer A, Graf M, Nagy L, Fürnstahl P - BMC Musculoskelet Disord (2015)

Preoperative Plan. Outline of the investigated computer-assisted planning approach. a Quantification of the malunion by superimposing the proximal part of the pathological bone (orange) with the mirrored contralateral bone (green). b Simulated reduction of the distal fragment (violet) and positioning of the fixation plate. The (beige) cylinders represent the angular-stable locking screws. c The screw models are transformed back to the pathological bone by applying the inverse transformation. The patient-specific drill and cutting guide (beige) is designed based on this information
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4634814&req=5

Fig1: Preoperative Plan. Outline of the investigated computer-assisted planning approach. a Quantification of the malunion by superimposing the proximal part of the pathological bone (orange) with the mirrored contralateral bone (green). b Simulated reduction of the distal fragment (violet) and positioning of the fixation plate. The (beige) cylinders represent the angular-stable locking screws. c The screw models are transformed back to the pathological bone by applying the inverse transformation. The patient-specific drill and cutting guide (beige) is designed based on this information
Mentions: 3D triangular surface models of the radius and ulna of the pathological and contralateral uninjured side were generated by segmenting the bones from CT data (slice thickness 1 mm; 120 kV; Philips Brilliance 40 CT, Philips Healthcare, The Netherlands) using commercial software (Mimics, Materialise, Belgium). The CT protocol for corrective osteotomies of the forearm at our institution includes a contiguously scan of the whole forearm from the elbow to the radiocarpal joint. For segmentation, manual thresholding and region growing was applied. A senior surgeon performed the computer planning on a standard personal computer using the custom-made software application CASPA (Balgrist CARD AG, Zurich, Switzerland). To quantify the malunion in 3D, the model of the contralateral bone was mirrored and aligned with the pathological bone using the Iterative Closest Point (ICP) surface registration algorithm as previously described [5, 6] (Fig. 1a). After simulated osteotomy, the distal part was reduced to the contralateral bone using ICP. Next, a 3D model of the angular-stable locking plate was positioned on the bone surface. Dependent on the malunion, one of the following implants was chosen by the surgeon: A 2.7 mm LCP plate (Synthes, Solothurn, Switzerland), a 2.7 mm LCP ulnar shortening osteotomy plate (Synthes), a 2.4 mm LCP distal radius plate (Synthes), or an Elegantus distal radius plate (Intercus Schweiz GmbH, Aarau, Switzerland). The plate models included cylinders representing the exact position and direction of the angular-stable locking screws (Fig. 1b) in relation to the plate. The screw models placed in the distal fragment were transformed with the previously registered distal part of the bone back to the pathological bone position by applying the inverse transformation. Thereby, during surgery the final direction of the screws can be predrilled previous to the osteotomy. Additionally, when a closing wedge osteotomy was planned, we used a metallic inlay that contains a cutting slit to guide the 0.4mm thick saw blade. The inlay was inserted into a dedicated frame in the guide body for alignment according to the planned osteotomy planes. In case of an open wedge osteotomy, since all osteotomies were complete with a resulting distraction gap, the exact position of the plane is not as important as for closing wedge or single cut osteotomies. Lastly, a surgical guide with drill sleeves and the dedicated frames for the metallic inlay was designed (Fig. 1c). To achieve a unique fit, the shape of the guide body was designed to contain irregular convex and concave parts covering the bone from different directions and the undersurface of the guide to be placed on the bone as an exact replication of the surface of the bone model. The guides were manufactured by Medacta International S.A. (Castel San Pietro, Switzerland) with a selective laser sintering device.Fig. 1

Bottom Line: However, the difference between planned and performed reduction is difficult to assess with conventional radiographs.The technique demonstrated high accuracy in performing closing wedge (or single-cut) osteotomies.However, for opening wedge osteotomies with extensive lengthening, probably due to the fact that precise reduction was difficult to achieve or maintain, the final corrections were less accurate.

View Article: PubMed Central - PubMed

Affiliation: Computer Assisted Research and Development Group, Balgrist University Hospital, University of Zurich, Zurich, Switzerland. lvlachopoulos@card.balgrist.ch.

ABSTRACT

Background: Computer assisted corrective osteotomy of the diaphyseal forearm and the distal radius based on computer simulation and patient-specific guides has been described as a promising technique for accurate reconstruction of forearm deformities. Thereby, the intraoperative use of patient-specific drill and cutting guides facilitate the transfer of the preoperative plan to the surgery. However, the difference between planned and performed reduction is difficult to assess with conventional radiographs. The aim of this study was to evaluate the accuracy of this surgical technique based on postoperative three-dimensional (3D) computed tomography (CT) data.

Methods: Fourteen patients (mean age 23.2 (range, 12-58) years) with an extra-articular deformity of the forearm had undergone computer assisted corrective osteotomy with the healthy anatomy of the contralateral uninjured side as a reconstruction template. 3D bone surface models of the pathological and contralateral side were created from CT data for the computer simulation. Patient-specific drill and cutting guides including the preoperative planned screw direction of the angular-stable locking plates and the osteotomy planes were used for the intraoperative realization of the preoperative plan. There were seven opening wedge osteotomies and nine closing wedge (or single-cut) osteotomies performed. Eight-ten weeks postoperatively CT scans were obtained to assess bony consolidation and additionally used to generate a 3D model of the forearm. The simulated osteotomies- preoperative bone models with simulated correction - and the performed osteotomies - postoperative bone models - were analyzed for residual differences in 3D alignment.

Results: On average, a significant higher residual rotational deformity was observed in opening wedge osteotomies (8.30° ± 5.35°) compared to closing wedge osteotomies (3.47° ± 1.09°). The average residual translation was comparable small in both groups, i.e., below 1.5 mm and 1.1 mm for opening and closing wedge osteotomies, respectively.

Conclusions: The technique demonstrated high accuracy in performing closing wedge (or single-cut) osteotomies. However, for opening wedge osteotomies with extensive lengthening, probably due to the fact that precise reduction was difficult to achieve or maintain, the final corrections were less accurate.

No MeSH data available.


Related in: MedlinePlus