Thermal damage during humeral reaming in total shoulder resurfacing

Proof of concept study for using UR10 robot to help total hip replacement

BACKGROUND

The demand for total hip replacement (THR) for treating osteoarthritis has grown substantially worldwide. The existing robotic systems used in THR are invasive and costly. This study aims to develop a less-invasive and low-cost robotic system to assist THR surgery.

METHODS

A preliminary robotic reaming system was developed based on a UR10 robot equipped with a reamer to cut acetabulum. A novel approach was proposed to cut through a 5 mm hole in femur such that the operation is less invasive to the patients.

RESULTS

The average error of the cutting hemisphere by the robotic reaming system is 0.1182 mm which is smaller than the average result reaming by hand (0.1301 mm).

CONCLUSION

The robotic reaming can help make THR procedures less invasive and more accurate. Moreover, the system is expected to be significantly less expensive than the robotic systems available in the market at present.

Severe Hallux Valgus Angle Attended With High Incidence of Nonunion in Arthrodesis of the First Metatarsophalangeal Joint: A Follow-Up Study

The incidence of nonunion after first metatarsophalangeal joint (MTP-1) arthrodesis was found to be high in our clinic. By raising awareness for the problem, making a uniform surgical treatment protocol, banning the commonly used convex-concave reamers, and promoting solely the use of hand instruments to prepare the joint for arthrodesis, we tried to decrease the numbers of nonunion. This prospective cohort study included all patients who underwent MTP-1 fusion between January 2018 and March 2019. Patients were treated according to a standardized protocol, using hand instruments to prepare the joint for fusion. Anthropometric and therapy-related data were collected and compared with an earlier 2015-2016 cohort that was retrospectively assessed. Furthermore, the frequency of nonunion between convex-concave reamers and hand instruments was compared. A total of 53 patients underwent MTP-1 fusion surgery. The incidence of nonunion was 3.8%, significantly lower than the 24.1% in 2015 to 2016 (p = .002). Multivariate regression analysis showed a 7.11 times higher risk of nonunion in 2015 to 2016 compared with 2018 to 2019 (95% confidence interval [CI] 1.55 to 32.55) (p = .012). Furthermore, an increase of 10° in HVA showed a 1.52 risk of occurrence of nonunion (95% CI 1.07 to 2.17) (p = .021). The use of convex/concave reamers was univariately associated with a 3.61 times higher risk of nonunion (95% CI 1.14 to 11.43) (p = .029); however, after correction for preoperative HVA, the preparation method was no longer associated with the occurrence of nonunion (p = .108). Patients suffering from severe hallux valgus had nonunion in 32.1% of cases. Incidence of nonunion after MTP-1 arthrodesis was significantly reduced by raising awareness and by standardizing the treatment protocol. There was no significant difference in nonunion frequency between the methods of joint surface preparation. Severe hallux valgus is prone to nonunion, and more research into this indication for MTP-1 fusion and outcome is needed.

Effect of Surgical Instrumentation Variables on the Osseointegration of Narrow- and Wide-Diameter Short Implants

PURPOSE

The aim of the present study was to systematically analyze how a multifactorial surgical instrumentation approach affects osseointegration on both narrow-diameter and wide-diameter short implants.

MATERIALS AND METHODS

Twelve skeletally mature female sheep were used in the study along with 144 plateau-root-form healing chamber titanium (Ti-6Al-4V) implants (Bicon LLC, Boston, MA), evenly distributed between narrow (3.5 mm) and wide (6.0 mm) diameters. The presence or the absence of irrigation, different drilling speeds, and 2 time points quantifying bone-implant contact (BIC) and bone area fraction occupancy (BAFO) to evaluate the osteogenic parameters around the implants.

RESULTS

There were no signs of inflammation, infection, or failure of the implants observed at either healing period. The narrow 3.5-mm implant, at 6 weeks, yielded significant differences in terms of BIC at a drilling speed of 50 rotations per minute (RPM), with higher values of the samples using irrigation (30.6 ± 6.1%) compared with those without (19.7 ± 6.1%). No statistical differences were detected for 500 and 1,000 RPM with or without irrigation. The wide 6-mm diameter implant showed differences with respect to drilling speed, 500 and 1,000 RPM, with higher values associated with samples subjected to irrigation. BAFO results, for both diameters, only detected statistical differences between the 2 times (3 vs 6 weeks); no statistical differences were detected when evaluating as a function of time, drilling speed, and irrigation.

CONCLUSIONS

Surgical instrumentation variables (ie, drilling speed [RPM] and irrigation) yielded to be more of an effect for BIC at longer healing time (6 weeks) for the wider implants. Furthermore, deploying narrow or wide plateau-root-form implants, where conditions allow, has shown to be a safe alternative, considering the high BIC and BAFO values observed, independent of irrigation.

Osteogenic parameters surrounding trabecular tantalum metal implants in osteotomies prepared via osseodensification drilling

Background

Surgical fixation of implants into bone for the correction of bone deformities or defects is a traditional approach for skeletal stabilization. Important measures of efficacy of implants include implant stability and osseointegration—the direct interaction between living bone and an implant. Osseointegration depends on successful implant placement and subsequent bone remodeling. This study utilized osseodensification drilling (OD) in a low bone density model using trabecular metal (TM) implants.

Material and Methods

Three osteotomy sites, Regular, OD-CW (clockwise), and OD-CCW (counterclockwise), were prepared in each ilium of three female sheep. Drilling was performed at 1100rpm with saline irrigation. Trabecular metal (TM) (Zimmer®, Parsippany, NJ, USA) implants measuring 3.7mm in diameter x 10mm length were placed into respective osteotomies. A three-week period post-surgery was given to allow for healing to take place after which all three sheep were euthanized and the ilia were collected. Samples were prepared, qualitatively and quantitatively analyzed using histology micrographs and image analysis software (ImageJ, NIH, Bethesda, MD). Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were quantified to evaluate the osseointegration parameters.

Results

All implants exhibit successful bone formation in the peri-implant environment as well as within the open spaces of the trabecular network. Osseointegration within the TM (quantified by %BIC) as a function of drilling technique was more pronounced in OD samples(p>0.05). The %BAFO however shows a significant difference (p=0.036) between the CCW and R samples. Greater bone volume and frequency of bone chips are observed in OD samples.

Conclusions

The utilization of OD as a design for improved fixation of hardware was supported by increased levels of stability, both primary and secondary. Histological data with OD provided notably different results from those of the regular drilling method.

Key words:Osseodensification drilling, trabecular tantalum metal, osteotomies, implants, subtractive drilling.

Atemporal osseointegration: Early biomechanical stability through osseodensification

Osseointegration, the direct functional and structural connection between device and bone is influenced by multiple factors such as implant macrogeometry and surgical technique. This study investigated the effects of osseodensification drilling techniques on implant stability and osseointegration using trabecular metal (TM) and tapered-screw vent (TSV) implants in a low-density bone. Six skeletally mature sheep were used where six osteotomy sites were prepared in each of the ilia, (n = 2/technique: Regular [R] (subtractive), clockwise [CW], and counterclockwise [CCW]). One TM and one TSV implant was subsequently placed with R osteotomy sites prepared using a conventional (subtractive) drilling protocol as recommended by the implant manufacturer for low density bone. CW and CCW drilling sites were subjected to osseodensification (OD) (additive) drilling. Evaluation of insertion torque as a function of drilling technique showed implants subjected to R drilling yielded a significant lower insertion torque relative to samples implanted in OD (CW/CCW) sites (p < 0.05). Histomorphometric analysis shows that the osseodensification demonstrates significantly greater values for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Histological analysis shows the presence of bone remnants, which acted as nucleating surfaces for osteoblastic bone deposition, facilitating the bridging of bone between the surrounding native bone and implant surface, as well as within the open spaces of the trabecular network in the TM implants. Devices that were implanted via OD demonstrated atemporal biomechanical stability and osseointegration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2516-2523, 2018.

Experimental analysis of the process parameters affecting bone burring operations

The experimental quantification of the process parameters associated with bone burring represents a desirable outcome both from the perspective of an optimized surgical procedure as well as that of a future implementation into the design of closed-loop controllers used in robot-assisted bone removal operations. Along these lines, the present study presents an experimental investigation of the effects that tool type, rotational speed of the tool, depth of cut, feed rate, cutting track overlap, and tool angle (to a total of 864 total unique combinations) have on bone temperature, tool vibration, and cutting forces associated with superficial bone removal operations. The experimental apparatus developed for this purpose allowed a concurrent measurement of bone temperature, tool vibration, and cutting forces as a function of various process parameter combinations. A fully balanced experimental design involving burring trials performed on a sawbone analog was carried out to establish process trends and subsets leading to local maximums and minimums in temperature and vibration were further investigated. Among the parameters tested, a spherical burr of 6 mm turning at 15,000 r/min and advancing at 2 mm/s with a 50% overlap between adjacent tool paths was found to yield both low temperatures at the bone/tool interface and minimal vibrations. This optimal set of parameters enables a versatile engagement between tool and bone without sacrificing the optimal process outcomes.

Osseodensification for enhancement of spinal surgical hardware fixation

Integration between implant and bone is an essential concept for osseous healing requiring hardware placement. A novel approach to hardware implantation, termed osseodensification, is described here as an effective alternative. 12 sheep averaging 65kg had fixation devices installed in their C2, C3, and C4 vertebral bodies; each device measured 4mm diameter×10mm length. The left-sided vertebral body devices were implanted using regular surgical drilling (R) while the right-sided devices were implanted using osseodensification drilling (OD). The C2 and C4 vertebra provided the t=0 in vivo time point, while the C3 vertebra provided the t=3 and t=6 week time points, in vivo. Structural competence of hardware was measured using biomechanical testing of pullout strength, while the quality and degree of new bone formation and remodeling was assessed via histomorphometry. Pullout strength demonstrated osseodensification drilling to provide superior anchoring when compared to the control group collapsed over time with statistical significance (p<0.01). On Wilcoxon rank signed test, C2 and C4 specimens demonstrated significance when comparing device pullout (p=0.031) for both, and C3 pullout tests at 3 and 6 weeks collapsed over time had significance as well (p=0.027). Percent bone-to-implant contact (%BIC) analysis as a function of drilling technique demonstrated an OD group with significantly higher values relative to the R group (p<0.01). Similarly, percent bone-area-fraction-occupancy (BAFO) analysis presented with significantly higher values for the OD group compared to the R group (p=0.024). As a function of time, between 0 and 3 weeks, a decrease in BAFO was observed, a trend that reversed between 3 and 6 weeks, resulting in a BAFO value roughly equivalent to the t=0 percentage, which was attributed to an initial loss of bone fraction due to remodeling, followed by regaining of bone fraction via production of woven bone. Histomorphological data demonstrated autologous bone chips in the OD group with greater frequency relative to the control, which acted as nucleating surfaces promoting new bone formation around the implants, providing superior stability and greater bone density. This alternative approach to a critical component of hardware implantation encourages assessment of current surgical approaches to hardware implantation.