Case report
A 32-year-old Thai female presented with left elbow deformity for 24 years. She had a history of injury, including a fall from a chair at age 6 that resulted in being treated with a conservative method by a traditional doctor. Afterward, she noticed a progressive gunstock deformity of her left elbow without pain, numbness, or weakness in her left upper extremities. However, per patient report, due to the appearance of the deformity, she lacked confidence and did not wear sleeveless shirts or vests. Physical examination of left elbow showed a 20o varus deformity with elbow range of motion (ROM) as flexion of 125o, extension of -10o, supination of 85o, and pronation of 80o (Fig. 1). There was no muscle atrophy of the left hand, and the distal neurovascular status of the left upper extremity was intact. The preoperative radiographs (Fig. 2) and 3D CT analysis (Fig. 3) showed a 15o varus deformity and 10o hyperextension deformity without rotational deformity. Therefore, she was diagnosed as having a cubitus varus and recurvatum deformity of the left distal humerus.
The treatment option for her deformity was discussed. The planned operation was a corrective biplanar Chevron osteotomy with a customized osteotomy guide and an innovative patient-matched monoblock crosslink titanium plate (Fig. 4). In this case, we decided to use the 3D printing technology to create the customized osteotomy guide and the patient-matched plate due to the effective accuracy of this technology for osteotomy compared to the conventional technique and due to the better plate profile on the patient’s anatomy. The customized osteotomy guide was specifically designed for the position of k-wire fixation at the same position of the screw holes on the patient-matched plate. Through these aspects, this specific design can assist the surgeon with bone reduction after osteotomy via application of the plate through the k-wire position, which has the predrilled hole for screw insertion. Moreover, we also designed the plate configuration as a monoblock crosslink plate, by placing the plate on the medial and posterolateral side of the distal humerus with the built-in metal crosslink between both sides. This plate design would be helpful for the reduction osteotomy due to the easier and better intraoperative plate position adjustment, compared to the conventional dual plating technique. We also felt the crosslink would improve the biomechanical property of the plate and the stability after fixation compared to the separate dual plates, just like in spinal surgery [14]. Therefore, using both the innovative plate design with these combined advantages and the 3D printing technology would be helpful for the complex osteotomy operation by reducing the operative time related to the bone reduction step and improving the accuracy of the osteotomy.
Preparation of customized osteotomy guide and patient-matched monoblock crosslink plate
To fabricate the patient-matched plate and customized osteotomy guide, a simulation of the deformity correction was done through 3D reconstruction and image processing of DICOM files, taken from CT scans, via Avizo software (Thermo Fisher Scientific, MA, USA). A corrective biplanar Chevron osteotomy was planned, as shown in Fig. 4A, to divide the affected bone into 3 separated fragments (Fig. 4B, C). The distal fragment of bone (dark blue) was then reduced to match the mirrored image of the contralateral bone (green), as displayed in Fig. 4D. The design of the customized osteotomy guide and the patient-matched monoblock crosslink plate were then developed based on anatomical bone geometry and the surgeon’s requirements using ANSYS software (Ansys Inc., PA, USA).
The osteotomy guide was designed to fit over the distal surfaces (posterior, lateral, and medial supracondylar ridge) of the defected bone, except the area over the olecranon fossa (Fig. 4E, F). The cutting slots and drilling sleeves were designed to match the cutting planes and the plate’s screw holes, respectively. The patient-specific plate with the monoblock crosslink was designed to fit over the corrected humerus bone with an overall thickness of 2 mm (Fig. 4G, H). The structural strength of the plate was also confirmed by finite element analysis.
Upon the surgeon’s approval of the design, the patient-specific implant was 3D-printed by selective laser melting using medical grade Ti-6Al-4V alloy (Meticuly Co., Ltd., Thailand). Subsequent post-processing techniques, including surface polishing and sterilization, were performed according to routine standards. For osteotomy guides and bone models, fused filament fabrication was used for the 3D printing of biocompatible high-impact polystyrene. The entire fabrication process was certified by the ISO13485 standard for the design, manufacturing, and sterilization of medical devices. Finally, the customized osteotomy guide was printed, and the trial osteotomy was simulated on the real-sized plastic bone model (Fig. 5).
Surgical technique and postoperative care
The operation, a corrective biplanar Chevron osteotomy of the distal humerus, was performed by the orthopedic trauma expert (PS), who has more than 10 years of experience in orthopedic reconstruction surgery. The standard posterior paratricipital surgical approach was used. After combined general anesthesia and an ultrasound-guided supraclavicular nerve block, the patient was placed in the right lateral decubitus position. A 20-cm posterior midline incision was made (Fig. 6A). The triceps muscle was exposed, and then the ulnar nerve was identified. The muscle was elevated from the posterior surface of the distal humerus, and the customized osteotomy guide was placed and fixed with multiple K-wires (Fig. 6B). After complete osteotomy, the guide and bone blocks were removed (Fig. 6C), and the plate was inserted under the triceps using the screw fixation based on the predrilled screw holes (Fig. 6D). The intraoperative flexion/extension ROM was 135o/0o. The intraoperative fluoroscopic images were checked to confirm the post-reduction alignment (Fig. 6E) before wound closure without nerve transposition. The total operative time was 116 minutes. The initial postoperative radiographs showed good alignment and adequate fixation stability in both AP and lateral views (Fig. 6F).
After surgery, the routine postoperative care was pain control with multimodal analgesia and the application of intermittent cold compressions. Antibiotic prophylaxis was given for 24 hours. The patient was immobilized with an arm sling for 6 weeks and was allowed to perform active assisted-ROM exercises of the wrist, elbow, and shoulder joints as tolerated. During admission, she reported only minimal pain on motion with mild paresthesia on the ulnar side of the left hand. She was discharged from the hospital 3 days postoperatively and was then scheduled for follow-up visits at the orthopedic clinic. On the follow-up, the clinical examination showed nearly normal alignment of the left elbow compared to the right side. The ROM for flexion/extension and pronation/supination of the left elbow were 130o/0o and 90o/90o, respectively (the right elbow ROM was 130o/0o and 85o/90o, respectively). The normal sensation had completely returned at 6 weeks, and the osteotomy had healed uneventfully at 3 months postoperatively. The postoperative radiographs demonstrated the improved humerus-elbow-wrist angle from 15o varus to 7o valgus (compared to 8o valgus on the right side) (Fig. 7). Through the last follow-up visit, at 18 months postoperatively, she reported being highly satisfied with the clinical outcome and did not report feeling any pain, swelling, or implant irritation. Therefore, we did not advise to remove the implant in this case.
Patient has given informed consent for data allowance and publication. The present study has been reviewed and approved by the Institutional Review Board at Mahidol University, based on the Declaration of Helsinki.