Cadaveric assessment of a 3D-printed aiming device for implantation of a hinged elbow external fixator.

INTRODUCTION: Proper implantation of a hinged external elbow fixator (HEEF) is demanding since it requires precise alignment between the flexion-extension's and HEEF's axis. In order to optimize this alignment, we have developed a 3D-printed aiming device. The primary goal of the study was to compare the aiming device-based technique with the conventional pin technique. The secondary goal was to determine whether it is possible to share the aiming device with the surgical community. MATERIALS AND METHODS: A HEEF was implanted in cadavers with either the aiming device (n = 6) or the conventional pin technique (n = 6). For both techniques the duration of the procedure, the radiation exposure as well as the offset and angular divergence between the HEEF's and flexion-extension's axis were compared. To achieve the secondary goal, two surgeons used aiming devices 3D-printed from files sent by email in order to implant HEEF on cadaveric specimens (n = 6). RESULTS: Duration of the procedure was not significantly different between both techniques. However, the aiming device allowed for reduction of the number of image intensifier shots (p = 0.005), angular divergence (p = 0.02) and offset between both axes (p = 0.05). The aiming devices have been delivered less than 15 days after ordering, and they have allowed proper implantation of six HEEF. CONCLUSION: The 3D-printed aiming device allowed less irradiant and more accurate implantation of HEEF. It is possible to share it with other surgeons.

Cementless Total Hip Arthroplasty With Metasul Bearings Provides Good Results in Active Young Patients: A Concise Followup.

BACKGROUND: A primary concern of younger, more active patients who have undergone total hip arthroplasty (THA) is the longevity of the implant. Cementless fixation and hard-on-hard bearings are recognized as options to enhance THA durability. Earlier, we published a series of 83 cementless primary THAs using 28-mm metal-on-metal (MoM) bearings in patients aged 50 years or younger; here we provide concise followup on that same group after an additional 8-year survey period. QUESTIONS/PURPOSES: (1) What is the long-term survivorship of cementless primary THA using 28-mm MoM bearings in patients aged 50 years or younger? (2) What are the clinical and radiographic results of cementless THA in this active patient population? (3) Can any of the observed implant failures or adverse events be attributed to the metallic nature of the bearing couple? METHODS: We retrospectively reviewed 83 cementless THAs performed in three institutions over a decade (1995-2004) in 68 patients with 28-mm MoM articulation. All patients (15 bilateral) had a median age of 42 years (range, 24-50 years) at the time of the index procedure and 56 of them (82% [70 hips]) had activity level graded Devane 4 or 5 before significant hip pain. A 28-mm Metasul™ articulation was used with an Alloclassic-SL™ cementless stem in all cases paired with three different cementless titanium acetabular components (one threaded and two press-fit cups) from the same manufacturer. Survivorship analysis was calculated according to Dobbs life table, patient clinical results were evaluated with use of the Postel-Merle d'Aubigné scoring system, radiographic analysis was performed by independent observers, and cobalt level was determined in whole blood. RESULTS: The 15-year survivorship (33 hips at risk) for revision for any reasons (four hips) and for aseptic loosening (one hip) was 96% (95% confidence interval [CI], 81%-99%) and 99% (95% CI, 85%-99.9%), respectively. The median Merle d'Aubigné-Postel score remained stable at 17 points (range, 10-18). Thus far, we have not observed pseudotumors or other adverse reactions to metallic debris. Eight hips have undergone reoperation: trochanteric suture removal (one), psoas tendon impingement (two), and five revisions for periprosthetic fracture (one), late infection (two), acetabular osteolysis (one, as a result of polyethylene backside wear), and one hydroxyapatite-coated cup for aseptic loosening. None of the complications, failures, or revisions observed so far could directly be related to the metallic nature of the 28-mm Metasul bearings used in this selected group of patients. CONCLUSIONS: The current survey at 13-year median followup has not yet indicated any long-term deleterious effects related to dissemination of metallic ions. Two senior authors continue to use 28- or 32-mm Metasul™ bearings with cementless THA components in young and active patient populations. Longer followup with a more sophisticated imaging study is necessary to confirm this so far positive report. LEVEL OF EVIDENCE: Level IV, therapeutic study.