Plate-related results of opening wedge high tibial osteotomy with a carbon fiber reinforced poly-ether-ether-ketone (CF-PEEK) plate fixation: a retrospective case series of 346 knees

Medial opening wedge high tibial osteotomy performs similarly irrespective of body mass index

PURPOSE

This study investigates the effect of the body mass index (BMI) on the early (2 years) to midterm (5 years) results of medial opening wedge high tibial osteotomy (MOWHTO).

METHODS

A prospectively maintained single-centre database of 1138 knee osteotomies, between 2002 and 2022, was retrospectively reviewed. Adult patients who underwent MOWHTO for symptomatic unicompartmental medial knee osteoarthritis (OA), with varus knee malalignment, having failed conservative management, were included. Patients were categorized into three groups according to their BMI as per the classification from the National Institute for Health and Care Excellence (NICE): the healthy weight (HW) group (BMI of 18.5-24.9 kg/m2), the overweight (OW) (BMI of 25-29.9 kg/m2), and the obesity (OB) group (BMI ≥ 30 kg/m2). Multiple patient-reported outcome measures (n = 6) were recorded preoperatively and at 2 and 5 years postoperatively. Deformity analysis was undertaken preoperatively and postoperatively. The relative risk (RR) of the complications between the HW, OW and OB groups was calculated. The rate of conversion to arthroplasty, and 5 and 10 years survivorship were recorded, as well as the hazard ratio (HR) of BMI on survivorship.

RESULTS

A total of 574 cases were included in the study: the HW group (n = 96), the OW group (n = 233) and the OB group (n = 245), with a mean BMI of 23 ± 1.5 kg/m2, 27.4 ± 1.4 kg/m2 and 34.4 ± 3.8 kg/m2, respectively. The mean follow-up was 13.3 years (4.8-20.3). The mean mechanical tibiofemoral angle corrections were in the HW group: 7.1 ± 3°, OW group: 6.6 ± 3.5° and OB group: 7.1 ± 3.8°, with no intergroup significant difference (p = n.s.). Clinically, despite lower preoperative scores in the OW and OB groups, no difference was observed postoperatively amongst the three groups. The overall complication rate was 12.5% in the HW group, 6.8% in the OW group, and 9.8% in the OB group. There was no significant difference in the RR of complications between the HW and OW groups (RR = 0.6, 95% confidence interval [CI] = 0.3-1.3) (p = 0.2), and the HW and OB groups (RR = 0.8; 95% CI = 0.3-2.2) (p = 0.7). There was no overall significant difference in survival outcomes based on the BMI between the three groups (p = 0.4). The HR of conversion to arthroplasty between the HW and OW groups was 1.4 [95% CI = 0.6-3.5](p = 0.5) and between the HW and OB groups was 1.8 [95% CI = 0.8-4.4] (p = 0.2).

CONCLUSION

BMI has no significant effect on either the radiological corrections, clinical outcomes, complications or survivorship of MOWHTO at short- to medium-term follow-up. No specific cutoff point for BMI can be recommended as a contraindication to MOWHTO.

LEVEL OF EVIDENCE

Level IV, Retrospective cohort study.

Comparison of the use of biocompatible materials and titanium in the treatment of midshaft clavicle fractures with a patient-specific plate: a finite element analysis study

BACKGROUND

Clavicular midshaft fractures treated with titanium plates may encounter complications like implant failure. We assess if alternative biocompatible materials suchs as PLA, PLA/HA, PEEK offer comparable stability. Our study evaluates the biomechanical performance of these materials in surgical management of midshaft clavicle fractures.

METHODS

We simulated a personalized fixation implant with four different materials and conducted finite element analysis in ANSYS to assess maximum von Mises stress (MvMs).

RESULTS

The MvMs occurring on the plates, screws, clavicle, and fracture site were recorded. MvMs on titanium material at the 6th hole level (764.79 MPa) and the 6th screw level (503.38 MPa), with the highest stresses observed at 48.52 MPa on the lateral clavicle at the 1st hole level and 182.27 MPa on the medial clavicle at the 6th hole level. In PLA material analyses, the highest MvMs were observed at the 3rd hole level (340.6 MPa) and the 3rd screw level (157.83 MPa), with peak stresses at 379.63 MPa on the lateral clavicle fracture line and 505.44 MPa on the medial clavicle fracture line. In PLA/HA material analyses, the highest MvMs were at the 3rd hole (295.99 MPa) and 3rd screw (128.27 MPa), with peak stresses at 220.33 MPa on the lateral clavicle and 229.63 MPa on the medial clavicle fracture line. In PEEK material analyses, the highest MvMs were at the 3rd hole (234.74 MPa) and 6th screw (114.48 MPa), with peak stresses at 184.36 MPa on the lateral clavicle and 180.1 MPa on the medial clavicle.

CONCLUSION

Our findings indicate that titanium material shows significantly higher stresses on plates and screws compared to those on the clavicle, suggesting a risk of implant failure. PLA and PLA/HA were inadequate for fixation. Although stress on the plate with PEEK material is higher than on the clavicle, it remains lower than titanium, indicating potential stability at fracture site. Further research is needed to confirm these findings.

Obesity does not impact complications and conversion to total knee arthroplasty after high tibial osteotomy: A systematic review

PURPOSE

The purpose of this systematic review is to consolidate outcomes of obese patients undergoing high tibial osteotomy and to investigate the effect of obesity on postoperative outcomes, including symptomatic relief and time to conversion to arthroplasty.

METHODS

Medline, Embase and Cochrane Library were searched from database inception up to April 2023 according to PRISMA guidelines by two reviewers. Search terms including 'obesity', 'BMI', 'osteotomy' and 'high tibial osteotomy (HTO)' were included to identify all relevant articles. Only studies that explicitly reported outcomes for obese patients were included. Disagreements in study inclusion or quality assessment were resolved by a senior third reviewer. Metrics compared include time to arthroplasty, preoperative and postoperative mechanical tibiofemoral angle (mTFA), patient-reported satisfaction scores and postoperative complications.

RESULTS

Nine studies comparing 973 patients were included. The mean age was 52.7 ± 4.2 years old and 38.4% were male. Six studies performed the medial opening-wedge HTO, and three utilized the medial wedge closing technique. Most studies indicated significant improvement following surgical intervention with satisfactory outcomes in obese and nonobese patients. In addition, differences in complication rates were minimal between obese and nonobese patients (n.s.), while functional scores did not vary significantly. Conversion to total knee arthroplasty was not found to increase in obese patients (n.s.).

CONCLUSION

Obesity does not appear to carry a greater complication risk or worse outcomes following high tibial osteotomies, and surgeons should consider HTO a viable option for young obese patients with symptomatic unicompartmental chondral wear with coronal limb malalignment.

LEVEL OF EVIDENCE

Level IV.

Polyetheretherketone development in bone tissue engineering and orthopedic surgery

Polyetheretherketone (PEEK) has been widely used in the medical field as an implant material, especially in bone tissue engineering and orthopedic surgery, in recent years. This material exhibits superior stability at high temperatures and is biosecured without harmful reactions. However, the chemical and biological inertness of PEEK still limits its applications. Recently, many approaches have been applied to improve its performance, including the modulation of physical morphology, chemical composition and antimicrobial agents, which advanced the osteointegration as well as antibacterial properties of PEEK materials. Based on the evolution of PEEK biomedical devices, many studies on the use of PEEK implants in spine surgery, joint surgery and trauma repair have been performed in the past few years, in most of which PEEK implants show better outcomes than traditional metal implants. This paper summarizes recent studies on the modification and application of biomedical PEEK materials, which provides further research directions for PEEK implants.

Is a Complete Anatomical Fit of the Tomofix Plate Biomechanically Favorable? A Parametric Study Using the Finite Element Method

BACKGROUND

The opening wedge high tibial osteotomy (HTO) fixation using the Tomofix system is at the risk of mechanical failure due to unstable fixation, lateral hinge fracture, and hardware breakage. This study aimed to investigate the effect of the level of anatomical fit (LOF) of the plate on the failure mechanisms of fixation.

METHODS

A finite element model of the HTO with a correction angle of 12 degrees was developed. The LOF of the TomoFix plate was changed parametrically by altering the curvature of the plate in the sagittal plane. The effect of the LOF on the fixation performance was studied in terms of the factor of safety (FOS) against failure mechanisms. The FOSs were found by 1) dividing the actual stiffness of the plate-bone construct by the minimum allowable one for unstable fixation, 2) dividing the compressive strength of the cortical bone by the actual maximum pressure at the lateral hinge for the lateral hinge fracture, and 3) the Soderberg criterion for fatigue fracture of the plate and screws.

RESULTS

The increase of the LOF by applying a larger bent to the plate changed the fixation stiffness slightly. However, it reduced the lateral hinge pressure substantially (from 182 MPa to 71 MPa) and increased the maximum equivalent stresses in screws considerably (from 187 MPa to 258 MPa). Based on the FOS-LOF diagram, a gap smaller than 2.3 mm was safe, with the highest biomechanical performance associated with a 0.5 mm gap size.

CONCLUSION

Although a high LOF is necessary for the Tomofix plate fixation to avoid mechanical failure, a gap size of 0.5mm is favored biomechanically over complete anatomical fit.