Accuracy of mandible-independent maxillary repositioning using pre-bent locking plates: a pilot study

The double splint method is considered the gold standard for maxillary repositioning, but the procedure is lengthy and prone to error. Recent splintless methods have shown high repositioning accuracy; however, high costs and technical demands make them inaccessible to many patients. Therefore, a new cost-effective method of mandible-independent maxillary repositioning using pre-bent locking plates is proposed. Plates are bent on maxillary models in the planned position prior to surgery. The locations of the plate holes are replicated during surgery using osteotomy guides made from thermoplastic resin sheets. Pre-bent plates are subsequently fitted onto the maxilla, and plate holes are properly set to reposition the maxilla. The purpose of this study was to evaluate the accuracy of this method for maxillary repositioning and the reproducibility of the plate holes. Fifteen orthognathic surgery patients were evaluated retrospectively by superimposing preoperative simulations over their postoperative computed tomography models. The median deviations in maxillary repositioning and plate hole positioning between the preoperative plan and postoperative results were 0.43mm (range 0-1.55mm) and 0.33mm (range 0-1.86mm), respectively. There was no significant correlation between these deviations, suggesting that the method presented here allows highly accurate and reliable mandible-independent maxillary repositioning.

Individual resection and reconstruction of pelvic tumor with three-dimensional printed customized hemi-pelvic prosthesis: A case report

RATIONALE

Pelvic tumor had great impact on patients' quality of life. After tumor resection, how to accurately fill bone defect remained challenging for orthopedic surgeons. Due to lack of individual design, high incidence of prosthetic mismatching, and loosening were reported in pelvic reconstruction surgery with conventional modular prostheses. Nowadays, with rapid development of three-dimensional (3D) print technology, pelvic prostheses could be designed according to patients' own anatomy. The objective of this study was to describe the application of 3D printed customized hemi-pelvic prosthesis for patients with pelvic tumor.

PATIENT CONCERNS

A 62-year-old female had developed severe right joint pain without obvious inducement from 5 months before she sought medical advice. Pain, swelling, and limited range of motion of right joint were founded during physical examination.

DIAGNOSIS

The patients were diagnosed as "right acetabulum metastatic carcinoma" INTERVENTION:: 3D printed titanium alloy hemi-pelvic prosthesis was designed according the morphology of unaffected side hemi-pelvis and subsequently implanted in surgery to reconstruct the pelvis. 3D printed osteotomy guide and pelvic model were also manufactured and applied to improve accuracy of osteotomy and reduce operation time. X-Ray of pelvis, Harris score, musculoskeletal tumor society score (MSTS) and The MOS item short from health survey (SF-36) were recorded during the period of preoperation, 1, 3, 6, 12 months follow-up after operation.

OUTCOMES

3D printed hemi-pelvic prosthesis matched precisely with pelvis and implanted successfully. There was no sign of prosthetic loosening within 12 months' follow-up. No sign of peri-prosthetic infection from laboratory examination. Harris score, MSTS, and SF-36 were gradually increasing during follow-up period.

LESSONS

Satisfactory effect of pelvic reconstruction could be achieved by 3D printed hemi-pelvic prostheses. It also provided a promising way to the treatment of pelvic tumor in similar cases.

Clinical accuracy of a patient-specific femoral osteotomy guide in minimally-invasive posterior hip arthroplasty

INTRODUCTION

Patient specific guides can be a valuable tool in improving the precision of planned femoral neck osteotomies, especially in minimally invasive hip surgery, where bony landmarks are often inaccessible. The aim of our study was to validate the accuracy of a novel patient specific femoral osteotomy guide for THR through a minimally invasive posterior approach, the direct superior approach (DSA).

METHODS

As part of our routine preoperative planning 30 patients underwent low dose CT scans of their arthritic hip. 3D printed patient specific femoral neck osteotomy guides were then produced. Intraoperatively, having cleared all soft tissue from the postero-lateral neck of the enlocated hip, the guide was placed and pinned onto the posterolateral femoral neck. The osteotomy was performed using an oscillating saw and the uncemented hip components were implanted as per routine. Postoperatively, the achieved level of the osteotomy at the medial calcar was compared with the planned level of resection using a 3D/2D matching analysis (Mimics X-ray module, Materialise, Belgium).

RESULTS

A total of 30 patients undergoing uncemented Trinity acetabular and TriFit TS femoral component arthroplasty (Corin, UK) were included in our analysis. All but one of our analysed osteotomies were found to be within 3 mm from the planned height of osteotomy. In one patient the level of osteotomy deviated 5 mm below the planned level of resection.

CONCLUSION

Preoperative planning and the use of patient specific osteotomy guides provides an accurate method of performing femoral neck osteotomies in minimally invasive hip arthroplasty using the direct superior approach.

LEVEL OF EVIDENCE

IV (Case series).

Bilateral shoulder arthrodesis in a Pekinese using three-dimensional printed patient-specific osteotomy and reduction guides

OBJECTIVE

To report the use of computer-aided design software for virtual surgical planning and design of three-dimensional printed patient-specific osteotomy and reduction guides for facilitation of bilateral shoulder arthrodesis in a dog.

METHODS

A three-year-old male entire Pekinese was presented unable to walk due to bilateral severe medial shoulder instability. Computed tomographic data was processed to yield three-dimensional mesh representations of the humeri and scapulae which could be manipulated in computer-aided design software. Key virtual surgical planning steps included joint realignment, osteotomies of the glenoid and humeral head, and reduction. Virtual osteotomy and reduction guides were designed, three-dimensionally printed, and used intra-operatively.

RESULTS

Appropriate alignment, reduction and fixation of the humeri and scapulae were achieved bilaterally. The patient regained the ability to walk unassisted after two weeks and was subsequently able to exercise normally without lameness.

CLINICAL SIGNIFICANCE

Patient-specific, three-dimensional printed osteotomy and reduction guides facilitated accurate bilateral shoulder arthrodeses.

Three-dimensional corrective osteotomy using a patient-specific osteotomy guide and bone plate based on a computer simulation system: accuracy analysis in a cadaver study

BACKGROUND

The accuracy of three-dimensional (3-D) corrective osteotomy using a patient-specific osteotomy guide and bone plate based on computer simulation was investigated.

METHODS

Six fresh-frozen cadaver upper limbs were used. A patient-specific osteotomy guide designed to realize a preplanned osteotomy was set on the distal humerus and distal radius, and the error in the setting location was evaluated. After the osteotomy, the surgical site was fixed using a patient-specific bone plate designed to exactly fit the anatomical shape of the postoperative bone model. The postoperative results were compared with the preoperative simulation.

RESULTS

The errors in the guide location on the humerus and radius were <1.5° and 1.0 mm and <1.0° and 1.0 mm, respectively. The plate fixation errors of the humerus and radius were <2.0° and 1.5 mm and <1.0° and 1.0 mm, respectively.

CONCLUSIONS

The system is sufficiently feasible to realize precise 3-D deformity correction of a limb.