Patient specific instrumentation in ACL reconstruction: a proof-of-concept cadaver experiment assessing drilling accuracy when using 3D printed guides.

INTRODUCTION: Accurate positioning of the femoral tunnel in ACL reconstruction is of the utmost importance to reduce the risk of graft failure. Limited visibility during arthroscopy and a wide anatomical variance attribute to femoral tunnel malposition using conventional surgical techniques. The purpose of this study was to determine whether a patient specific 3D printed surgical guide allows for in vitro femoral tunnel positioning within 2 mm of the planned tunnel position. MATERIALS AND METHODS: A patient specific guide for femoral tunnel positioning in ACL reconstruction was created for four human cadaveric knee specimens based on routine clinical MRI data. Fitting properties were judged by two orthopedic surgeons. MRI scanning was performed both pre- and post-procedure. The planned tunnel endpoint was compared to the actual drilled femoral tunnel. RESULTS: This patient specific 3D printed guide showed a mean deviation of 5.0 mm from the center of the planned femoral ACL origin. CONCLUSION: In search to improve accuracy and consistency of femoral tunnel positioning in ACL reconstruction, the use of a patient specific 3D printed surgical guide is a viable option to explore further. The results are comparable to those of conventional techniques; however, further design improvements are necessary to improve accuracy and enhance reproducibility.

No clinical difference between large metal-on-metal total hip arthroplasty and 28-mm-head total hip arthroplasty?

PURPOSE: We aimed to test the claim of greater range of motion (ROM) with large femoral head metal-on-metal total hip arthroplasty. METHODS: We compared 28-mm metal-on-polyethylene (MP) total hip arthroplasty with large femoral head metal-on-metal (MM) total hip arthroplasty in a randomised clinical trial. ROM one year postoperatively was determined in 50 patients. Mean head sizes were 28 mm (MP) and 48 mm (MM). RESULTS: After one year, the large head MM group showed greater improvement in internal rotation (14 degrees) than the 28 mm group (seven degrees).There were no significant differences in the absolute values of postoperative internal rotation, external rotation, flexion, extension, abduction and abduction. CONCLUSIONS: Absolute postoperative range of motion did not differ between the two groups. The improvement in internal rotation was greater after large femoral head metal-on-metal total hip arthroplasty. It is however questionable whether this difference is clinically relevant.

Effect of ACL Reconstruction on Range of Tibial Rotation: A Systematic Review of Current Literature and a Recommendation for a Standard Measuring Protocol.

BACKGROUND: Tibial rotation is an important topic in anterior cruciate ligament (ACL) surgery, and many efforts are being made to address rotational stability. The exact role of the ACL in controlling tibial rotation in clinical studies is unknown. PURPOSE: To quantify the effect of ACL reconstruction on the amount of tibial rotation based on the current available literature. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: A literature search of the PubMed and EMBASE databases was performed in August 2019. Two independent reviewers reviewed titles and abstracts as well as full-text articles. A total of 2383 studies were screened for eligibility. After screening of titles and abstracts, 178 articles remained for full-text assessment. Ultimately, 13 studies were included for analysis. A quality assessment was performed by means of the RoB 2.0 (revised tool for Risk of Bias in randomized trials) and the ROBINS-I (Risk Of Bias In Non-randomized Studies-of Interventions) tools. RESULTS: According to the studies using computer-assisted surgery that were included in this review, ACL reconstruction resulted in an average reduction in tibial rotation of 17% to 32% compared with preoperatively; whether the range of tibial rotation returned to preinjury levels remained unclear. In the current literature, a gold standard for measuring tibial rotation is lacking. Major differences between the study protocols were found. Several techniques for measuring tibial rotation were used, each with its own limitations. Most studies lacked proper description of accompanying injuries. CONCLUSION: ACL reconstruction reduced the range of tibial rotation by 17% to 32%. Normal values for the range of tibial rotation in patients with ACL deficiency and those who undergo ACL reconstruction could not be provided based on the current available literature owing to a lack of uniform measuring techniques and protocols. Therefore, we advocate uniformity in measuring tibial rotation.

Acetabular bone density and metal ions after metal-on-metal versus metal-on-polyethylene total hip arthroplasty; short-term results.

Information on periprosthetic acetabular bone density is lacking for metal-on-metal total hip arthroplasties. These bearings use cobalt-chromium instead of titanium acetabular components, which could lead to stress shielding and hence periprosthetic bone loss. Cobalt and chromium ions have detrimental effects on bone. It is unknown whether serum metal ion levels affect bone density clinically. We compared cementless large femoral head (mean 48 mm) metal-on-metal total hip arthroplasties (M2a-Magnum, Biomet) to cementless 28 mm metal-on-polyethylene total hip arthroplasties (Mallory-Head, Biomet) in a randomised clinical trial. We evaluated periprosthetic acetabular bone density and serum metal ion levels at 1 year postoperatively. Acetabular bone density was analyzed with dual energy x-ray absorptiometry in four horizontal regions of interest in 70 patients. After one year, acetabular bone density decreased (-3.5% to -7.8%) in three of four regions of interest in metal-on-polyethylene patients, but was retained in metal-on-metal patients. Bone density preservation was most pronounced superior to the metal-on-metal cup (+1% versus -3.7%). Serum cobalt, chromium and titanium ion levels were not related to bone density, nor to acetabular inclination or femoral head size. Oxford and Harris hip scores were similar in both groups. Contrary to our hypothesis, acetabular bone density was retained with metal-on-metal total hip arthroplasty, compared to metal-on-polyethylene arthroplasty. Bone preservation was most pronounced in the area superior to the cup. This could be a benefit during future revision surgery.