[Prevention of lateral cortex fractures in open wedge high tibial osteotomies : The anteroposterior drill hole approach]

Surgical strategy and complication management of osteotomy around the painful degenerative varus knee: ESSKA Formal Consensus Part II

PURPOSE

The purpose of the European consensus was to provide recommendations for the treatment of patients with a painful degenerative varus knee using a joint preservation approach. Part II focused on surgery, rehabilitation and complications after tibial or femoral correction osteotomy.

METHODS

Ninety-four orthopaedic surgeons from 24 countries across Europe were involved in the consensus, which focused on osteotomies around the knee. The consensus was performed according to the European Society for Sports Traumatology, Knee Surgery and Arthroscopy consensus methodology. The steering group designed the questions and prepared the statements based on the experience of the experts and the evidence of the literature. The statements were evaluated by the ratings of the peer-review groups before a final consensus was released.

RESULTS

The ideal hinge position for medial opening wedge high tibial osteotomy (MOW HTO) should be at the upper level of the proximal tibiofibular joint, and for lateral closing wedge distal femoral osteotomy (LCW DFO) just above the medial femoral condyle. Hinge protection is not mandatory. Biplanar osteotomy cuts provide more stability and quicker bony union for both MOW HTO and LCW DFO and are especially recommended for the latter. Osteotomy gap filling is not mandatory, unless structural augmentation for stability is required. Patient-specific instrumentation should be reserved for complex cases by experienced hands. Early full weight-bearing can be adopted after osteotomy, regardless of the technique. However, extra caution should be exercised in DFO patients. Osteotomy patients should return to sports within 6 months.

CONCLUSION

Clear recommendations for surgical strategy, rehabilitation and complications of knee osteotomies for the painful degenerative varus knee were demonstrated. In Part 2 of the consensus, high levels of agreement were reached by experts throughout Europe, under variable working conditions. Where science is limited, the collated expertise of the collaborators aimed at providing guidance for orthopaedic surgeons developing an interest in the field and highlighting areas for potential future research.

LEVEL OF EVIDENCE

Level II, consensus.

A systematic approach to managing complications after proximal tibial osteotomies of the knee

Proximal tibial osteotomy (PTO) is an effective procedure for active and young adult patients with symptomatic unicompartmental osteoarthritis and malalignment. They were considered technically demanding and prone to various complications related to the surgical technique, biomechanical or biological origin. Among the most important are hinge fractures and delayed or non-healing, neurovascular complications, loss of correction, implant-related problems, patellofemoral complaints, biological complications and changes in limb length. Being aware of these problems can help minimizing their prevalence and improve the results of the procedure.The aim of this narrative review is to discuss the potential complications that may occur during and after proximal tibial osteotomies, their origin and ways to prevent them.

Three-dimensional analysis of lateral cortical hinge in medial open-wedge high tibial osteotomy: A computational simulation study of adult cadavers

PURPOSE

The objective of this study was to improve the three-dimensional (3D) understanding of optimal lateral cortical hinge in medial open-wedge high tibial osteotomy (MOWHTO) via a computational cadaveric simulation of actual size.

METHODS

The computed tomography data of 117 adult cadavers were imported into Mimics® software to design 3D models of tibia and fibula. To simulate the MOWTHO, a virtual cutting plane was developed inside the safe zone based on established landmarks. After splitting and distracting through the cutting plane, the 10-mm cylinder (Ø 30 mm; height 10 mm) was placed vertically to be occupied properly in the nonosteotomized lateral cortex. The cross points between the round cylinder and cutting plane represented the anterior and posterior hinge points, which were used to validate the 3D position and direction of cortical hinge.

RESULTS

A 10-mm cylinder did not violate the proximal tibiofibular joint (PTFJ) and the protruding segment of the condylar area was less than 2 mm in 115 models. The connecting line between anterior and posterior hinge points was an average of 12.1° (range 0-24.1°, SD 4.64) to the lateral side. In the nonoverlapping anteroposterior projection between proximal fibula and tibia, the posterior hinge point was laid over the PTFJ as close as possible. Based on free 360° rotation and magnification without any tilt, no posterior cortical disruption of PTFJ was observed while securing a minimum width of 10 mm.

CONCLUSION

If the posterior hinge point was placed immediately above the PTFJ without involvement, the nonosteotomized portion carried sufficient width greater than 10 mm, despite lateral rotation at an average hinge direction of 12.1°.

Opposite hinge fractures in high tibial osteotomy: a displacement subtype is more critical than a fracture type

PURPOSE

Analysis of the structure of the fractures of opposite hinge (FOH) after angle-stable closed-wedge (CW) and open-wedge (OW) high tibial osteotomy (HTO), and their influence on the development of tibial pseudarthrosis.

METHODS

187 CW and 94 OWHTOs were analyzed retrospectively. The FOHs in the OWHTO were classified according to Takeuchi, and in the CWHTO-according to the own classification with two types (depending on the direction of FOH). FOHs in both techniques were also subdivided into three subtypes according to displacement (A-non-displaced, B-primarily displaced, C-secondarily displaced). The statistical analysis included correlation analysis and logistic regression.

RESULTS

FOHs were found in 81 (43.3%) CW and 39 (41.2%) OWHTOs. The stable type 1 fractures predominated in OWHTO (76.9 vs. 42%, p < 0.001), the unstable type 2 FOHs prevailed in CWHTO (58 vs. 17.9%, p < 0.001). The tibial pseudarthrosis rate was higher with type 1 (20 vs. 12.9%, n.s.) and subtype A (16.7 vs. 6.8%, p = 0.048) FOHs in OWHTO, and with type 2 (20 vs. 0%, p < 0.001) and subtypes B (25 vs. 0%, p < 0.001) and C (29.4 vs. 25%, n.s.) in CWHTO (without FOHs 0.9% in CW and 1.8% in OWHTO, n.s.). Relevant correlations were detected between the pseudarthrosis rate and fracture type only in CWHTO (ρ_s = 0.298, p < 0.001, OR 24.87 for type 2) and displacement subtype in both groups (for subtype C: ρ_s = 0.345, p < 0.001, OR 43.75 and ρ_s = 0.231, p = 0.02, OR 18.0, respectively).

CONCLUSIONS

The unstable FOH types were more common in CWHTO. The displacement subtype was more predictive for the development of tibial pseudarthrosis than the fracture type, especially in OWHTO. The secondarily displaced FOHs (subtype C) represented the highest risk for the occurrence of pseudarthrosis in both techniques.

Development and validation of a finite element model to simulate the opening of a medial opening wedge high tibial osteotomy

Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure intended to alter the coronal and sagittal plane alignment of the lower limb to primarily relieve the symptoms of osteoarthritis in the medial compartment of the knee. The purpose of this work was to develop and validate a finite element model to simulate the opening of a high tibial osteotomy and determine whether a pilot hole at the cortical hinge reduces the risk of lateral cortical fracture. Fifteen models were reconstructed from CT images of eight cadaveric specimens. The validated models indicated that the addition of the pilot hole increased the stresses and likelihood of a type-I and type-II fractures during the opening of a medial open wedge high tibial osteotomy compared to the no-hole condition.

Opening-wedge high tibial osteotomy without bone grafting in severe varus osteoarthritic knee. Rate and risk factors of non-union in 41 cases

INTRODUCTION

Using locking plates in opening-wedge high tibial osteotomy (OWHTO) via a medial opening theoretically allows early weight-bearing without need for bone or bone-substitute grafting. It incurs a risk of non-consolidation in case of large correction (>10°), although rates and risk factors of non-union are not known. The present retrospective study compared OWHTO with correction <10° versus >10°, with a view to determining: (1) complications rates (non-union) according to degree of correction, and (2) risk factors for such complications.

HYPOTHESIS

OWHTO with correction greater than 10° without graft shows normal consolidation and allows early weight-bearing.

MATERIAL AND METHOD

Forty-one patients treated by OWHTO for medial osteoarthritis of the knee between January 2101 and November 2015 were included in a retrospective study. HKA angle was assessed by long-leg axis radiographs, preoperatively and at 3 months. Clinical and radiological follow-up at 6 weeks, 3 months and 6 months assessed consolidation in terms of >40% filling of the osteotomy site. Partial (contact) weight-bearing was allowed from the first postoperative day, with full weight-bearing at 6 weeks.

RESULTS

Mean patient age was 59±5 years. Mean body-mass index (BMI) was 30.3±5.2; 17 patients (41.5%) had BMI >30. Mean initial HKA angle was 173.5°±3° (range, 167-178°) and mean correction was 10.7°±2.7° (range, 5-15°). There were 27 corrections of 10° or more, and 14 less than 10°. At 3 months, mean HKA was 182.9°±2.5° (range, 178-187°). Twelve cases showed lateral tibial cortex fracture after opening. Thirty-six patients (87.8%) showed consolidation, at a mean 5±3 months. Five patients showed osteotomy site non-union; in all these cases, the lateral cortex was broken initially (P=0.003); all had BMI >30 (mean, 37.2±3.8; P<0.03); none were smokers. On univariate analysis, lateral tibial cortex fracture (OR=10; 95% CI, (1.59-196.30)), BMI >30 (OR=1.18; 95% CI, (1.03-1.41)) and correction ≥10° (OR=10.50; 95% CI, (2.49-53.86)) were associated with delayed consolidation. On multivariate analysis, only degree of osteotomy was significantly associated with delayed consolidation (OR=11.51; 95% CI, (2.13-95.74)).

DISCUSSION/CONCLUSION

Obesity and initial lateral cortex fracture appeared as risk factors for non-consolidation of OWHTO with large correction. Systematic bone or bone-substitute grafting may therefore be considered in this population in case of >10° correction.

LEVEL OF EVIDENCE

IV, prospective cohort study.

Mechanical strength assessment of a drilled hole in the contralateral cortex at the end of the open wedge for high tibial osteotomy

Background

This study aimed to investigate, by means of finite element analysis, the effect of a drill hole at the end of a horizontal osteotomy to reduce the risk of lateral cortex fracture while performing an opening wedge high tibial osteotomy (OWHTO). The question was whether drilling a hole relieves stress and increases the maximum correction angle without fracture of the lateral cortex depending on the ductility of the cortical bone.

Methods

Two different types of osteotomy cuts were considered; one with a drill hole (diameter 5 mm) and the other without the hole. The drill holes were located about 20 mm distally to the tibial plateau and 6 mm medially to the lateral cortex, such that the minimal thickness of the contralateral cortical bone was 5 mm. Based on finite element calculations, two approaches were used to compare the two types of osteotomy cuts considered: (1) Assessing the static strength using local stresses following the idea of the FKM-guideline, subsequently referred to as the “FKM approach” and (2) limiting the total strain during the opening of the osteotomy wedge, subsequently referred to as “strain approach”. A critical opening angle leading to crack initiation in the opposite lateral cortex was determined for each approach and was defined as comparative parameter. The relation to bone aging was investigated by considering the material parameters of cortical bones from young and old subjects.

Results

The maximum equivalent (von-Mises) stress was smaller for the cases with a drill hole at the end of the osteotomy cut. The critical angle was approximately 1.5 times higher for the specimens with a drill hole compared to those without. This corresponds to an average increase of 50%. The calculated critical angle for all approaches is below 5°. The critical angle depends on the used approach, on patient’s age and assumed ductility of the cortical bone.

Conclusions

Drilling a hole at the end of the osteotomy reduces the stresses in the lateral cortex and increases the critical opening angle prior to cracking of the opposite cortex in specimen with small correction angles. But the difference from having a drill hole or not is not so significant, especially for older patients. The ductility of the cortical bone is the decisive parameter for the critical opening angle.