Matching precision of the reverse contralateral radial head in generating of the individualized prosthesis from the surface registration in tuberosity-neck and in tuberosity-diaphysis

Radial head replacement with the 3D-printed patient-specific titanium prosthesis: Preliminary results of a multi-centric prospective study

PURPOSE

To report preliminary clinical results and safety of 3D-printed patient-specific titanium radial head (RH) prosthesis in treatment of the irreparable RH fractures.

MATERIAL AND METHODS

This multi-centric prospective study included 10 patients (6 men and four women, mean age 41 years (range, 25-64 years)). Three cases were classified as Mason type III and 7 cases as type IV. Patients were assessed preoperatively, intraoperatively, and at 1, 6, 12, 24, 36, and 48 weeks postoperatively. Range of motion (ROM), visual analog scale (VAS) score, Disabilities of the Arm, Shoulder and Hand (DASH) score, Mayo Elbow Performance Score (MEPS), radiology imaging, and laboratory blood and urine testing were evaluated.

RESULTS

The prostheses were implanted utilizing cemented stems in 5 patients and cementless stems in 5 patients. Intraoperatively, well congruency of a prosthesis with capitellum and radial notch of ulna was observed in all cases. All patients had improvement of ROM, VAS score, DASH score, and MEPS during the postoperative follow-ups. At the final follow-up, mean elbow extension was 6.5° (range, 0°-30°), flexion 145° (range, 125°-150°), supination 79° (range, 70°-80°), and pronation 73.5° (range, 45°-80°). Mean VAS score was 0.3 (range, 0-3), DASH score was 12.35 (range, 1.7-23.3), and MEPS was 99.5 (range, 95-100). Postoperative radiographs demonstrated heterotopic ossification in 2 cases, periprosthetic radiolucency in 2 cases, and proximal radial neck resorption in 2 cases. No one had the evidence of capitellar erosion, implant failure, malpositioning, overstuffing, or symptomatic stem loosening. There was no significant alteration of laboratory results or adverse events related to the 3D-printed prosthesis implantation.

CONCLUSION

The preliminary results demonstrated that implantation of the 3D-printed patient-specific titanium RH prosthesis is safe and may be a potential treatment option for irreparable RH fracture.

Anthropometric Study of Proximal Radius in Below-Average Height Thai Women and Its Correlation with Commercially Available Radial Head Prostheses

Background: Most radial head prostheses were designed in Western countries based on the anatomical characteristics of Western populations. We hypothesised that these prostheses are too large for below-average height Thai women. The objective of this study is to evaluate the anthropometric parameters of the proximal radius in such a population and its correlation with commercially available prostheses.

Methods: Dominant elbows of 124 Thai women whose height was <155 cm were studied. Using the standard anteroposterior and lateral radiographic images, the head diameter and thickness, the distance between the articular surface and radial tuberosity, the narrowest intra-medullary canal diameter and the narrowest outer diameter of the radial neck were measured. Correlations between body height and each radiographic parameter were assessed using the Pearson correlation coefficient (PCC). The specifications of the commercial metallic radial head implants were reviewed and used to evaluate the relevant radiographic parameters.

Results: Mean of the minimum and maximum head diameter was 18.54 ± 1.11 mm and 19.13 ± 1.17 mm, respectively; the thickness was 7.43 ± 0.69 mm, the distance between the articular surface and tuberosity was 19.05 ± 1.45 mm, the intra-medullary canal diameter was 7.63 ± 1.2 mm and the outer diameter of the radial neck was 11.13 ± 1.26 mm. There is a poor correlation between the participant’s height and each parameter (PCC ≤ 0.50). In 24.2% of the participants, the smallest size of prosthetic designs with a head diameter of 20 mm is larger than +2 mm in reference to minor diameter. The minimum prosthetic head thickness is greater than the average value of the participants in 12 out of 15 designs. One participant has an outer neck diameter smaller than the smallest stem diameter of three designs.

Conclusions: Surgeons must be aware that commercially available radial head replacement implants may be too large for below-average height Thai women.

Level of Evidence: Level IV (Prognostic)

The patient-specific implant created with 3D printing technology in treatment of a severe open distal humerus fracture with complete loss of the lateral column

The open distal humeral fracture associated with the major loss of the articular surface and bony structure is a challenging problem for orthopedic surgeons. In this case report, we describe a case of complete missing lateral column of the distal humerus with severe articular destruction of capitellum and lateral trochlear ridge which was treated with the patient-specific implant created with three-dimensional printing technology. Apart from anatomic replacement of the articular surface, the lateral collateral ligament complex and extensor muscle which are the key soft tissue stabilizers of elbow were repaired by reattaching their bony origins to the impacted iliac crest bone graft inside the implant. Due to the favorable result at 2-year follow-up, this modality is a potentially viable surgical option in treating of the severe open distal humeral fracture associated with entire lateral condylar damage.

Precision of computed tomography and cartilage-reproducing image reconstruction method in generating digital model for potential use in 3D printing of patient-specific radial head prosthesis: a human cadaver study

Background

A prosthetic replacement is a standard treatment for an irreparable radial head fracture; however, the surface mismatch of the commercially available designs is concerned for the long-term cartilage wear. The patient-specific implant created from 3D printing technology could be favorable in replicating the normal anatomy and possibly reduce such sequela. Our study aimed to assess the precision of the computed tomography (CT) and cartilage-reproducing image reconstruction method (CIRM) in generating digital models for potentially use in manufacturing the patient-specific prosthesis from 3D printing.

Methods

Eight intact  elbows (3 right and 5 left) from 7 formalin-embalmed cadavers (4 males and 3 females) with mean age of 83 years (range, 79–94 years) were used for this study. Computerized 3D models were generated from CT, and CIRM. The cartilage-reproducing image reconstruction method has compensated the cartilage profile based on the distance between the subchondral surfaces of the radial head and surrounding bones in CT images. The models of actual radial head geometry used as the gold standard was generated from CT arthrography (CTA). All models of each specimen were matched by registering the surface area of radial neck along with the tuberosity. The difference of head diameter, head thickness, and articular disc depth among three models was evaluated and analyzed by Friedman ANOVA and multiple comparison test using Bonferroni method for statistical correction. A p-value of less than 0.01 was considered statistically  significant. The difference of overall 3D geometry was measured with the root mean square of adjacent point pairs.

Results

The analysis displayed the difference of diameter, thickness, and disc depth across the models (p< 0.01). Pairwise comparisons revealed statistically significant difference of all parameters between CTA models and CT models (p< 0.01) whereas no difference was found between CTA models and CIRM models. The mean difference of overall 3D geometry between CTA models and CT models was 0.51±0.24 mm, and between CTA models and CIRM models was 0.24±0.10 mm.

Conclusions

CIRM demonstrated encouraging results in reestablish the normal anatomy and could be potentially used in production process of 3D printed patient-specific radial head prosthesis.

Fracture Pattern Influences Radial Head Replacement Size Determination Among Experienced Elbow Surgeons

BACKGROUND

Correct sizing is challenging in radial head replacement and no consensus exists on the implant's optimal height and width to avoid elbow stiffness and instability. Studies exists, suggesting how to appropriately choose the implant size, but the manner by which the fracture pattern influences the surgeons' operative choices was not investigated.

METHODS

The radial heads of four fresh-frozen cadaveric specimens were excised, measured, and fractured to simulate four patterns: three fragments (A); four fragments (B); comminuted (C); comminuted with bone loss (D). Nine examiners were asked to indicate first the maximum diameter of the radial heads with the help of dedicated sizing dishes and then the appropriate implant size with trial implants. Accuracy and precision were determined. A coefficient of variation was calculated and agreement was evaluated with the Bland-Altman method.

RESULTS

Accuracy and precision of radial head diameter estimation with dedicated sizing dish were 96.73% and 93.64%, (best pattern, D; worst, C). Accuracy and precision of radial head diameter estimation with trial implants were 99.71% and 90.66% (best pattern, A; worst, D). Frequent modifications occurred between the initial radial head size proposal based on the sizing dish and the radial head size chosen after use of the trial implants (47.2%).

CONCLUSIONS

Diameter estimation of radial heads with dedicated sizing dishes may be underestimated in comminuted fractures; when bone loss is present, this may lead to an overestimation, especially when using trial implants. Care is essential to determine the optimal size of the implant and to avoid overlenghtening and oversizing, which can be responsible for implant failure.

LEVEL OF EVIDENCE

Basic Science Study.

CLINICAL RELEVANCE

Knowledge of the manner by which the fracture pattern influences radial head replacement size estimation can help preventing overlenghtening and oversizing during this procedure.