Opening Wedge Distal Femoral Osteotomy Research Articles

Medial Closing Wedge High Tibial Osteotomy Accurately Corrects Genu Valgum without Iatrogenic Deformity or Complications: A Consecutive Series of Thirty-one Procedures.

Angular deformities of the tibia and femur lead to mechanical axis deviation (MAD) of the lower limb and malorientation of the joints adjacent to the deformity. The current study analyses the outcomes of using a medial closing wedge high tibial osteotomy (MCWHTO) for the management of genu valgum with high medial proximal tibial angle (MPTA), and combined MCWHTO with lateral opening-wedge distal femoral osteotomy (LOWDFO) in the setting of concomitant genu varum with low lateral distal femoral angle (LDFA). There were 18 high tibial osteotomy (HTO)-only and 13 combined HTO + distal femoral osteotomy (DFO) procedures performed. The primary radiographic outcome variables included postoperative MPTA and MAD (in mm). The accuracy of MAD correction was expressed as a percentage. The postoperative posterior proximal tibial angle (PPTA) and limb length discrepancy (LLD) were also measured as secondary radiographic outcome variables. The clinical outcome variables included intraoperative surgical complications (e.g., hinge fracture), all-causes for revision, union rate, time to union, and postoperative knee range of motion. Functional outcomes used included the LDSRS, PROMIS, and EuroQOL scores. The mean preoperative MPTA was 92.9° (SD = 1.81, range: 88-96). After surgical correction, the mean MPTA was 86.0° (SD = 1.80, range: 83-90) (p < 0.0001). The mean preoperative MAD was 32.5 mm (SD = 20.16, range: 10-77) lateral to the centre of the knee joint. The mean postoperative MAD was 2.44 mm medial to the centre of the joint (SD = 7.13, range: 13 medial - 15 lateral) (p < 0.0001). The mean change in MAD achieved through surgical correction was 38.16 mm (SD = 17.94, range: 13-77). The accuracy of MAD correction was 96.1% (SD = 0.06%, range: 81.25-100%). The time to unassisted WB was a mean of 75 days (SD = 44.5, range: 44-242).There was a single stable hinge fracture and one case of chronic regional pain syndrome diagnosed. There were no cases of non-union and no indications for revision surgery in any case. Medial closing wedge high tibial osteotomy is an effective surgical procedure for the management of genu valgum deformity. The MPTA, LDFA, and MAD can be accurately corrected without significantly altering PPTA or limb length. It may be combined with open lateral distal femoral osteotomy for cases with femoral and tibial contributions to deformity without significantly impacting clinical outcomes. Functional outcomes, specifically relating to self-image are significantly improved after the MCWHTO has been performed. Sheridan GA, Page BJ, Greenstein MD, et al. Medial Closing Wedge High Tibial Osteotomy Accurately Corrects Genu Valgum without Iatrogenic Deformity or Complications: A Consecutive Series of Thirty-one Procedures. Strategies Trauma Limb Reconstr 2024;19(2):82-86.

Ten-year minimal follow-up of lateral opening wedge distal femoral osteotomy for lateral femorotibial osteoarthritis: Good survivorship and high patient satisfaction.

This study aimed (1) to determine complications and survival rates of lateral opening wedge distal femoral osteotomy (LOW-DFO) in the long term, (2) to assess their clinical outcomes in the long term and (3) to identify risk factors of failure. Between 1991 and 2011, 62 LOW-DFOs were performed in the same department. Inclusion criteria were all isolated LOW-DFO performed for isolated lateral tibiofemoral osteoarthritis and valgus malalignment, with a minimum 10-year follow-up. Thirty-eight patients were included, with a mean age of 48 ± 9 years. All patients had clinical and radiological assessments. The survival curves were calculated based on the following endpoints: unicompartmental or total knee arthroplasty. The mean follow-up was 15.2 ± 4.4 [10-29] years. The mean preoperative mechanical FemoroTibial Axis (mFTA) was 188.8° ± 3.2° [184°-197°], primarily due to femur deformity (mean lateral distal femoral axis [LDFA] 83.2° ± 2.8°). Bone union was achieved in 89.5% of patients (n = 34) at a mean delay of 6.5 ± 6.7 months. The complication rate was 26% (five stiffness, one nonunion, three secondary displacements and one deep vein thrombosis). Nine revision surgeries (24%) were recorded. Survival rates at 5 and 10 years were 92.1% and 78.9%, respectively. The mean delay between DFO and total knee arthroplasty (TKA) was 11.6 ± 5.7 [1-27] years. Nineteen patients (50%) were free of TKA at the last follow-up. KSS scores were improved significantly. Return to sports was obtained in 92% of cases (n = 35), with a mean delay of 11 ± 8 months. Seventy-four per cent of patients were satisfied or very satisfied with the surgery. Eighty-four per cent would be willing to undergo the surgery again. Older age (p = 0.032) was a significant risk factor for TKA conversion. LOW-DFO is an efficient procedure to manage lateral knee osteoarthritis in young patients with valgus deformity, with a good survival rate at 10 years and high patient satisfaction. Level III.

Paper 32: Leg Length Changes Following Distal Femoral Osteotomy: Validation of a Predictive Tool and Comparison of Lateral Opening Wedge and Medial Closing Wedge Techniques

Objectives: A DFO can be performed via two techniques: a lateral opening wedge (LOW) osteotomy and a medial closing wedge (MCW) osteotomy. Small case series have looked at how leg length is affected by a lateral opening wedge DFO, however, there is a lack of research comparing these leg length changes to medial closing DFO. Additionally, no studies have presented a model for predicting the leg length changes that will occur following DFO of either technique. Given that limb length differences can lead to accelerated osteoarthritis, back pain, hip pain, and other issues, being able to predict which technique can help prevent this pathology without a secondary procedure would be an important finding. Finally, the medial closing wedge osteotomy can allow for immediate weight-bearing while the lateral opening wedge does not and typically has associated cost with bone grafting. Therefore, we designed this study to validate a tool designed to predict leg length changes after distal femoral osteotomy (DFO) and compare changes following medial closing wedge (MCW) and lateral opening wedge (LOW) techniques. Methods: A collaborative retrospective review was performed of patients from Rush and Mayo Clinic databases who received a DFO and had full-length standing radiographs both pre-and postoperatively. For each preoperative radiograph, the region on the medial (for LOW) or lateral (for MCW) distal femur cortex that would be the “hinge point” during DFO was identified. The distances from the center of the femoral head to the hinge point (“A”), from the hinge point to the center of the tibial plafond (“B”), and the resultant angle at the hinge point (“α”) were measured (Figure 1). Figure 2 demonstrates the equation used to plot a graph of the predicted leg length changes corresponding to the change in α angle produced by DFO. Final leg length was calculated on postoperative radiographs, and the difference between predicted and true leg length changes was compared using paired Wilcoxon signed rank exact tests. Results: 10 MCW and 10 LOW patients were included. For both LOW (n=10) and MCW (n=10) osteotomies, the predicted leg length change was equivalent to the true change measured on postoperative radiographs (LOW P=0.16; MCW P=0.85). LOW DFO’s had 5.10 ± 2.77 mm (range: 1.45-10.87 mm) of leg lengthening, compared to 2.61 ± 1.25 mm (range: 0.50-4.56 mm) of leg shortening (p&lt;0.001) for MCW (Figure 3). On average, there was 0.85 mm of lengthening (range 0.5-1.3 mm) for every 1° of mechanical axis correction with LOW DFO, compared to 0.45 mm of shortening (range: 0.1-1.4 mm) per 1° of MCW correction. Conclusions: This study presents a tool to accurately and reliably predict the leg length changes seen after both medial closing and lateral opening wedge DFO’s. Knowing what leg length changes to expect with each DFO technique is a useful tool that surgeons can utilize during surgical planning. Preoperative radiographic imaging can be used to predict leg length change following DFO with high reliability and accuracy. Surgeons can expect approximately 0.85mm of lengthening per 1° of DFO correction when performing LOW, compared to 0.45mm of shortening per 1° correction for MCW osteotomies.

Valgus malalignment causes increased forces on a medial collateral ligament reconstruction under dynamic valgus loading: Abiomechanical study.

To investigate the forces on a medial collateral ligament (MCL) reconstruction (MCLR) relative to the valgus alignment of the knee. Eight fresh-frozen human cadaveric knees were subjected to dynamic valgus loading at 400 N using a custom-made kinematics rig. After resection of the superficial medial collateral ligament, a single-bundle MCLR with a hamstring tendon autograft was performed. A medial opening wedge distal femoral osteotomy was performed and fixed with an external fixator to gradually adjust the alignment in 5°increments from 0° to 10° valgus. For each degree of valgus deformity, the resulting forces acting on the MCLR were measured through a force sensor and captured in 15° increments from 0° to 60° of knee flexion. Irrespective of the degree of knee flexion, increasing valgus malalignment resulted in significantly increased forces acting on the MCLR compared to neutral alignment (p < 0.05). Dynamic loading at 5° valgus resulted in increased forces on the MCLR at all flexion angles ranging between 16.2 Nand 18.5 N (p < 0.05 from 0° to 30°; p < 0.01 from 45° to 60°). A 10° valgus malalignment further increased the forces on the MCLR at all flexion angles ranging between 29.4 Nand 40.0 N (p < 0.01 from 0° to 45°, p < 0.05 at 60°). Valgus malalignment of the knee caused increased forces acting on the reconstructed MCL. In cases of chronic medial instabilities accompanied by a valgus deformity ≥ 5°, a realigning osteotomy should be considered concomitantly to the MCLR to protect the graft and potentially reduce graft failures. Level III.

Biomechanical Comparison of Uniplanar versus Biplanar Lateral Opening-wedge Distal Femoral Osteotomy Techniques in Terms of Risk for Medial Hinge Fracture.

The effect of osteotomy type on the initial stiffness of the bone-implant construct in lateral opening-wedge distal femoral osteotomy (LOWDFO) using a uniplanar compared with a biplanar technique has been investigated. However, no study has explored the biomechanical risk factors for medial hinge fracture. This study aimed to compare the biomechanical strength of uniplanar versus biplanar LOWDFO regarding the risk for medial hinge fracture during gap opening. Twelve composite femora were divided into two groups (six in each group) based on the distal femoral osteotomy technique: uniplanar versus biplanar LOWDFO. All LOWDFO models were subjected to incremental static loading. The gap distance was expanded by 1 mm, and displacement values were recorded as anterior and posterior gap distances (mm). The average force values of all samples at certain gap distances were recorded, and the head distance was measured. The uniplanar group had higher load values than the biplanar group at all anterior gap distances. These differences were only significant at 2- and 3-mm gap distances (p = 0.025 and 0.037). At all posterior gap distances, the uniplanar group had higher load values than the biplanar group, but these differences only reached statistical significance at 2 mm (p = 0.037). Both groups had similar anterior, posterior, and average gap distances (p = 0.75, 0.522, 0.873). The uniplanar group had a higher head insertion distance (15.3 ± 5.7) than the biplanar group (14.7 ± 2.9), but it was not significant (p = 0.87). The uniplanar group had a lower average load before medial hinge fracture (46.41 ± 13.91 N) than the biplanar group (54.92 ± 31.94, p = 0.81). The biplanar group had an average maximum load value of 64.18 ± 25.6 N, while the uniplanar group had 57.90 ± 12.21 N (p = 0.81). This study revealed that the biplanar osteotomy technique allows a wider opening wedge gap with less risk of a medial hinge fracture than uniplanar LOWDFO.Level of evidence was level 3, case-control series.

Varus osteotomy as a salvage procedure for young patients with symptomatic patellofemoral arthritis and valgus malalignment at short- to mid-term follow-up: a case series

PurposeThe purpose of the study was to report the clinical, functional and radiological outcome following varus osteotomy as a salvage procedure in young to middle-aged patients with patellofemoral arthritis (PFA) and associated valgus malalignment. It was hypothesized that a significant improvement in knee function and reduction in pain would be achieved. Moreover, no conversion to patellofemoral joint arthroplasty could be observed.Material and methodsPatients (< 50 years of age) that underwent varus osteotomy between 08/2012 and 01/2020 for the treatment of symptomatic PFA and associated valgus malalignment were consecutively included (minimum follow-up: 24 months). Patient-reported outcome measures (PROM; International Knee Documentation Committee subjective knee form [IKDC]), Visual Analog Scale [VAS] for pain, Tegner Activity Scale [TAS], and satisfaction with the postoperative results (1–10-scale, 10 = highest satisfaction) and weight-bearing whole-leg anteroposterior radiographs were conducted pre- and postoperatively. The change in PROM and femorotibial angle (FTA) were tested for statistical significance.ResultsIn total, 12 patients (14 knees) were included (66.7% female; mean age: 33.8 ± SD 6.6 years). In ten cases, lateral opening-wedge distal femoral osteotomies (DFO) were performed, of which three cases included a concomitant femoral derotation. Three medial closing-wedge DFO and one medial closing-wedge high tibial osteotomy were performed. At follow-up (55.3 ± 29.3 months), a significant improvement in knee function (IKDC: 56.4 ± 14.4 to 69.1 ± 11.2, p = 0.015) and reduction in pain (VAS for pain: 3.5 [interquartile range 2.3–5.8] to 0.5 [0–2.0], p = 0.018) were observed. Patients were able to reach their preoperative sporting activity level (TAS: 3.0 [3.0–4.0] to 3.5 [3.0–4.0], p = 0.854) and were highly satisfied with the postoperative result (9.0 [6.5–10]). Additionally, a significant correction of valgus malalignment was observed (5.0° ± 2.9° valgus to 0.7° ± 3.2° varus, p < 0.001). Regarding complications, two re-osteosyntheses were performed due to loss of correction and delayed union. No conversion to patellofemoral arthroplasty occurred.ConclusionIn patients with symptomatic PFA and associated valgus malalignment, varus osteotomy as a salvage procedure achieved a significant improvement in knee function and reduction in pain. No conversion to patellofemoral joint arthroplasty occurred at short- to mid-term follow-up.Level of evidenceRetrospective case series, Level IV.

Bilateral Distal Femoral Osteotomy for Valgus Knee Deformity May Result in Improved Patient-Reported Outcome Scores

Background: The lateral opening wedge distal femoral osteotomy (DFO) is an effective treatment for genu valgum to improve mechanical alignment, decrease lateral compartment loads, and decrease the risk of knee osteoarthritis. Multiple studies have utilized outcome scores assessing functional changes related to pain and joint stability, with a focus solely on knee pain and functional outcomes. Questions/purposes: The primary aim of this study was to evaluate patient-reported outcome measures (PROMs) that assessed knee function, pain, patient’s perception of body image, and limb deformity-related quality of life, both preoperatively and at least 1-year postoperatively. Methods: In a retrospective review of nontraumatic genu valgum patients who underwent bilateral DFO, preoperative and postoperative radiographs were evaluated. Routinely collected preoperative and 1-year postoperative PROMs scores were analyzed, using the Knee Injury and Osteoarthritis Outcome Score Jr. (KOOS-JR) and the Limb Deformity-Modified Scoliosis Research Society (LD-SRS) score, in 72 limbs (36 patients): 7 men (19.44%) and 29 women (80.56%) with an average age of 35.34 ± 13.57 years. The mean follow-up time was 36.85 ± 24.43 months. Results: Overall mechanical axis deviation, lateral distal femoral angle, and mechanical axis alignment angle were significantly improved after DFO in all patients. Both PROMs also improved significantly from preoperative to postoperative scores: LD-SRS (3.10 ± 0.56 vs 4.19 ± 0.44, respectively) and KOOS-JR (63.02 ± 19.25 vs 78.06 ± 16.29, respectively). Conclusion: This retrospective review suggests that bilateral lateral opening-wedge DFOs in patients with symptomatic valgus knee deformity may be associated with improved overall knee health, limb deformity-related quality of life, and patients’ body image. Further study is needed.

Distal Femoral Osteotomy for the Management of Coronal Deformity Following Total Knee Arthroplasty: A Report of 2 Cases.

We present 2 cases demonstrating the management of coronal malalignment with an existing total knee arthroplasty using opening wedge distal femur osteotomy. The mechanical axis was corrected, and the primary total knee implants were maintained. Patients resumed full activity 3 to 4 months after surgery. In certain cases, opening wedge distal femoral osteotomy is an option to correct coronal malalignment with an existing total knee arthroplasty without revising the implant.

Lateral Opening-Wedge Distal Femoral Osteotomy Made Easy: Tips and Tricks

A lateral opening-wedge distal femoral osteotomy is useful to offload the lateral tibiofemoral compartment for focal chondral defects or isolated lateral compartment arthritis. Although beneficial for these lateral compartment disorders, a distal femoral osteotomy requires careful forethought to optimize correction accuracy and safety. We recommend the following for effective execution of a distal femoral osteotomy: (1) Plan the desired correction preoperatively while accounting for an individual patient’s anatomy and femoral width. (2) Perform an iliotibial band Z-lengthening for large deformity corrections to not overconstrain the lateral structures. (3) Use the plate to help guide the level of the osteotomy, which will facilitate bony contact after the osteotomy and decrease plate prominence. (4) Perform the osteotomy with a saw anteriorly and an osteotome posteriorly for safety and stop the osteotomy approximately 1 cm short of the far cortex. (5) Fashion tricortical wedge grafts at the height of the planned correction to maintain reduction and facilitate plate placement. (6) Control the plate position to lie optimally at the level of the osteotomy, ensuring it is not proud and is parallel with the femoral shaft. With these presurgical and intraoperative steps, a lateral opening-wedge distal femoral osteotomy can be performed effectively.

Additional Plate Fixation of Hinge Fractures After Varisation Distal Femoral Osteotomies Provides Favorable Torsional Stability: A Biomechanical Study

Background: Hinge fractures are considered risk factors for delayed or nonunion of the osteotomy gap in distal femoral osteotomies (DFOs). Limited evidence exists regarding the treatment of hinge fractures after DFO, which could improve stability and thus bone healing. Purpose: To (1) examine the effect of hinge fractures on the biomechanical properties of the bone-implant construct, (2) evaluate the biomechanical advantages of an additional fixation of a hinge fracture, and (3) test the biomechanical properties of different types of varisation DFOs. Study Design: Controlled laboratory study. Methods: A total of 32 fresh-frozen human distal femora equally underwent medial closing wedge DFO or lateral opening wedge DFO using a unilateral locking compression plate. The following conditions were serially tested: (1) preserved hinge; (2) hinge fracture along the osteotomy plane; (3) screw fixation of the hinge fracture; and (4) locking T-plate fixation of the hinge fracture. Using a servo-hydraulic materials testing machine, we subjected each construct to 15 cycles of axial compression (400 N; 20 N/s) and internal and external rotational loads (10 N·m; 0.5 N·m/s) to evaluate the stiffness. The axial and torsional hinge displacement was recorded using a 3-dimensional optical measuring system. Repeated-measures 1-way analysis of variance and post hoc Bonferroni correction were used for multiple comparisons. Statistical significance was set at P < .05. Results: Independent from the type of osteotomy, a fractured hinge significantly (P < .001) increased rotational displacement and reduced stiffness of the bone-implant construct, resulting in ≥1.92 mm increased displacement and ≥70% reduced stiffness in each rotational direction, while the axial stiffness remained unchanged. For both procedures, neither a screw nor a plate could restore intact rotational stiffness (P < .01), while only the plate was able to restore intact rotational displacement. However, the plate always performed better compared with the screw, with significantly higher and lower values for stiffness (+38% to +53%; P < .05) and displacement (–55% to −72%; P < .01), respectively, in ≥1 rotational direction. At the same time, the type of osteotomy did not significantly affect axial and torsional stability. Conclusion: Hinge fractures after medial closing wedge DFO and lateral opening wedge DFO caused decreased bone-implant construct rotational stiffness and increased fracture-site displacement. In contrast, the axial stiffness remained unchanged in the cadaveric model. Clinical Relevance: When considering an osteosynthesis of a hinge fracture in a DFO, an additional plate fixation was the construct with the highest stiffness and least displacement, which could restore intact hinge rotational displacement.

TT-TG distance decreases after open wedge distal femoral varization osteotomy in patients with genu valgum & patellar instability. A pilot 3D computed tomography simulation study

BackgroundGenu valgum is considered to be a risk factor for patellar instability. Correction of valgus alone or combined with a tibial tuberosity medialization has been described. However, changes occurring in the tibial tuberosity-trochlear groove (TT-TG) distance after a lateral distal femoral opening wedge osteotomy (LDF-OWO) are not known.PurposeThis study aimed to define changes in TT-TG distance with increasing amounts of valgus correction after LDF-OWO.MethodsThree-Dimensional Computed Tomography (3D-CT) scans of six patients (two females and four males) aged between 19 and 35 years with genu valgum and patellar instability were analyzed. 3D models of femoral, tibial, and patellar bones were created with the advanced segment option of Mimics 21® software. An oblique lateral opening wedge osteotomy of the distal femur was simulated in 2-degree increments up to 12 degrees of varus opening. Change in TT-TG distance was measured in mm on 3D models of the knee.ResultsCompared to baseline without osteotomy, the TT-TG distance decreased significantly (p < 0.05) for all corrections from 2 to 12 degrees in 2° steps. The TT-TG distance decreased by an average of 1.7 mm for every 2 degrees of varus opening.ConclusionLateral opening wedge distal femoral osteotomy causes a decrease in TT-TG distance. The surgeon should be aware of the magnitude of this change (1.7 mm decrease for every 2° increment of valgus opening).

Radiologic simulation of leg length change after double level osteotomy in preoperative surgical planning

BackgroundTo evaluate the expected postoperative total leg length change using preoperative radiographs during surgical planning of four different methods of double level osteotomy (DLO).MethodsThis study included 34 patients (44 knees) who underwent DLO for varus knee osteoarthritis. Surgical planning was performed so that the postoperative weight bearing line ratio was 62.5%. In DLO, lateral closed or medial open wedge distal femoral osteotomy (LCWDFO, MOWDFO) was performed so that the postoperative mechanical lateral distal femoral angle was 85°, and residual deformity was corrected with medial open or lateral closed wedge high tibial osteotomy (MOWHTO, LCWHTO). Pre- and surgical planning X-rays in the one-leg standing position were compared to assess the change in leg length, and the factors affecting it, in the various surgical groups. The proportion of cases in which Δ total leg length was greater than 6 mm (symptomatic change) was investigated.ResultsThe mean postoperative total leg length increased significantly with LCWDFO + MOWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, while it decreased with LCWDFO + LCWHTO. The proportion of cases with a postoperative total leg length change > 6 mm was 72.7%, 2.3%, 100%, and 6.8% in LCWDFO + MOWHTO, LCWDFO + LCWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, respectively. In addition, the preoperative hip-knee-ankle angle correlated negatively with the postoperative total leg length change in LCWDFO + MOWHTO, MOWDFO + MOWHTO, and MOWDFO + LCWHTO, but not in LCWDFO + LCWHTO.ConclusionsMOWDFO + MOWHTO had the largest postoperative leg length change and MOWDFO + LCWHTO had the smallest. Symptomatic leg length change (> 6 mm) should be considered in MOWDFO + MOWHTO and LCWDFO + MOWHTO.

Paper 23: Taking the Load Off: Effect of Varus Producing Distal Femoral Osteotomy and High Tibial Osteotomy on Compartment Pressures and Contact Area in Varying Stages of Knee Flexion

Objectives: Study Objective: Evaluate mean contact area, mean contact pressure, and peak contact pressure in the medial and lateral compartment of the knee following varus producing high tibial osteotomy and distal femoral osteotomy in varying states of knee flexion (0*, 30*, 60*, 90*). Background: Genu valgum causes mechanical pressure to be transferred to the lateral compartment. In patients with valgus alignment and a diseased lateral compartment, both lateral opening wedge distal femoral osteotomy (DFO) and high tibial closing wedge osteotomy (HTO) can be used to unload a diseased lateral compartment of the knee. To the best of our knowledge, there are no biomechanical studies investigating how a DFO and HTO affect lateral compartment contact pressure and area in varying states of flexion. Prior anatomic studies have shown that, in valgus knees, the tibial wear is posterior. Additional, biomechanical studies have indicated that DFO exerts the greatest effect in full extension but it’s effect is decreased as flexion angle rises. Hypothesis: Medial closing wedge high tibial osteotomy will significantly decrease contact area, mean contact pressure and peak contact pressure in the lateral knee compartment through knee flexion to a greater extent compared to lateral opening wedge distal femoral osteotomy. Methods: Lateral opening wedge DFO and medial closing wedge HTO was performed, correcting a mean of 8°, in 10 cadaveric knees using plate fixation. Tibio- femoral contact pressure of the medial and lateral compartment was measured in 0°, 30°, 60°, and 90° of knee flexion before and after osteotomy using thin electronic sensors (K-scan Model 4000, 1500 psi; Tekscan Inc, South Boston, MA) and load applied through an Instron device (Instron, Norwood, MA). Peak contact pressure (PCP), average contact pressure (ACP), and contact area (CA) were measured for each condition. Mixed-effects regression analyses were used to compare the change in variables before and after osteotomy and between flexion angles. Results: The lateral ACP was significantly decreased in the HTO state when compared to native in 30° (p=0.015), 60° (p=0.0199), and 90° (p&lt;0.0001) of flexion. The lateral ACP was also significantly decreased in the HTO state when compared to the DFO state in 60° (p=0.0093) and 90° of flexion (p&lt;0.0001). Following DFO, the lateral ACP returned to that of the native state in 60° (p=1.000) and 90° (p=1.000) of flexion. The medial ACP was significantly increased when compared to both the native and HTO state in 60° (p&lt;0.001; p=0.015) and 90° (p&lt;0.0001; p=0.0435) of flexion. Conclusions: With varus corrections of &lt;10°, medial closing HTO is more effective at unloading the lateral compartment than lateral opening DFO. This effect is amplified as the knee flexion angle increases.

Effects of Lateral Opening-Wedge Distal Femoral Osteotomy on Meniscal Allograft Transplantation: A Biomechanical Evaluation

Background: Lateral meniscal deficiency with valgus malalignment increases the rate of lateral compartment osteoarthritis. Lateral meniscal allograft transplantation (LMAT) with a concomitant varus-producing opening-wedge distal femoral osteotomy (DFO) is an option yet to be evaluated biomechanically. Purpose/Hypothesis: The purpose of this study was to clarify the biomechanical effects of the realignment procedure in the setting of LMAT. We hypothesized that (1) given the dependence of the lateral compartment on the lateral meniscus, a DFO and increasing degrees of varus would be insufficient to restore lateral compartment pressures to normal from a lateral meniscus-deficient state, and that (2) LMAT would restore lateral compartment pressures to the intact state while DFO would decrease lateral compartment pressures for any given state of the meniscus. Study Design: Controlled laboratory study. Methods: Ten cadaveric knees underwent opening-wedge varus-producing DFO secured by an external fixator. Anatomic alignment was standardized to 6° of mechanical valgus, and each joint was tested in full extension. Submeniscal placement of thin film pressure sensors allowed for the recording of contact pressure, peak contact pressure, and contact area. The specimens were loaded on a biaxial dynamic testing machine with loading angles between 9° valgus and 6° varus of mechanical alignment. Conditions tested included intact meniscus, meniscal deficiency, and meniscal transplantation. Results: Isolated varus-producing DFO to 6° in the meniscus-deficient state failed to restore joint pressures and contact areas to the intact state, with significant changes in mean contact pressure (175%), mean peak contact pressure (135%), and contact area (–41%) (all P &lt; .05 vs intact), while LMAT restored all outcome measures (all P &gt; .05 compared with intact). After LMAT, every additional 1° of DFO correction contributed to a decrease in the mean contact pressure, peak pressure, and contact area of 5.6% (–0.0479 N/mm2), 5.9% (–0.154 N/mm2), and 1.4% (–6.99 mm2) for the lateral compartment and 7.3% (+0.034 N/mm2), 12.6% (+0.160 N/mm2), and 4.3% (+20.53 mm2) for the medial compartment, respectively. Conclusion: Isolated DFO was inadequate to restore load distribution in meniscus-deficient knees, while concomitant LMAT restored near normal forces and improved the lateral compartment biomechanical profile. Clinical Relevance Our findings support the concomitant use of LMAT and varus-producing DFO in the setting of lateral meniscal deficiency with valgus malalignment. This study provides tools for the orthopaedic surgeon to individualize the correction for each patient.

Opening-Wedge Distal Femoral Osteotomy With Concomitant Medial Meniscal Root Repair

Background: Valgus malalignment leads to excessive loading of the lateral compartment and has been associated with lateral compartment meniscal injuries and early-onset knee osteoarthritis. Distal femoral osteotomy (DFO) is a treatment option that allows correction of the mechanical access to offload the lateral compartment. Lateral opening-wedge distal femoral osteotomy and medial meniscal root repairs are both aimed to address the pathologic biomechanics of the tibiofemoral joint and when successful can delay or even prevent progression to end-stage osteoarthritic changes in the lateral and medial compartment, respectively. Indications: Distal femoral osteotomy is indicated for patients with normal metabolic bone health and valgus malalignment who may present with concurrent lateral meniscal injury, symptomatic lateral compartment arthritis, or a chronic medial collateral ligament tear/laxity. Technique Description: Long-leg alignment radiographs and preoperative magnetic resonance images are required to evaluate the degree of mechanical access deviation and to evaluate for soft tissue injury, as there is often concomitant lateral meniscal or cartilage pathology present. This technique demonstrates the optimal order of surgical steps for DFO with a concurrent medial meniscal root repair. The senior author’s preferred order is to first perform the open lateral approach and expose the lateral cortex for the placement of plate prior to arthroscopic work and excess fluid extravasation. Intra-articular work is then performed with a diagnostic arthroscopy followed by medial meniscal root repair. Finally, the osteotomy and subsequent internal fixation are performed. Results: The literature on opening-wedge DFO outcomes is heterogeneous, with variable rates of successful outcomes and complications. Saithna et al reported that International Knee Documentation Committee and the pain subdomain of Knee injury and Osteoarthritis Outcome Scores significantly improved postoperatively following lateral opening-wedge DFOs in patients with lateral compartment osteoarthritis. The 10-year success rate of varus-producing DFO has been reported to be 64% to 85%. Discussion: We describe a technique for correction of a valgus deformity with opening-wedge DFO and concurrent meniscal root repair. This surgical technique effectively restores the native femoral and tibial axis with appropriate load distribution and also concurrently restores the appropriate function of the medial meniscus which allows axial force dispersion via hoop stresses for the medial compartment. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Experimental study of risk of medial hinge fracture during distal femoral varus osteotomy

IntroductionLateral opening wedge distal femoral osteotomy (LOWDFO) is indicated for isolated lateral osteoarthritis in the valgus morphotype. Medial hinge fracture is a factor for poor prognosis. The present study had two aims: (1) to assess the impact of a temporary K-wire on hinge fracture risk; and (2) to assess the impact of LOWDFO opening speed. HypothesisThe main study hypothesis was that a temporary hinge K-wire reduces hinge fracture risk. The second hypothesis was that faster opening speed increases fracture risk. Material and methodTwenty femurs were produced by 3D printing from a CT database, reproducing LOWDFO anatomy. The ABS® polymer showed the same breaking-point behavior as human bone. Ten specimens were included in the “K-wire” group (KW+) and 10 in the “No K-wire” group (KW−). To determine high and low speed, a motion-capture glove was used by 2 operators, providing 3D modeling of the surgeon's hand. High speed was defined as 152mm/min and low speed as 38mm/min. The KW+ and KW− groups were subdivided into high- and low-speed subgroups (HS, LS) of 5 each. Compression tests were conducted using an Instron® mechanical test machine up to hinge fracture. The main endpoint was maximum breaking-point force (N); the secondary endpoints were maximum displacement (mm) and maximum speed (min) at breaking point. ResultsThe K-wire significantly increased maximum breaking-point force (LS, 143.08N vs. 93.71N, p<0.01; and HS, 186.98N vs. 95.22N, p<0.01), but not maximum displacement (LS, 26.17mm vs. 24.11mm, p=0.31; and HS 26.18mm vs. 23.66mm, p=0.14) or maximum time (LS, 27.07s vs. 24.94s, p=0.31; and HS, 5.24s vs. 4.73s, p=0.14). Speed did not affect maximum force (KW+, 143.08N vs. 186.98N, p=0.06; and KW−, 93.71N vs. 95.22N, p=0.42) or maximum displacement (KW+, 26.17mm vs. 26.18mm, p=1; and KW−, 24.11mm vs. 23.66mm, p=0.69). Only maximum time was greater at low speed (KW+, 27.07s vs. 5.24s, p>0.01; and KW−, 24.94s vs. 4.73s, p<0.01), which is obvious for constant distance. DiscussionThe first study hypothesis was confirmed, with significantly lower hinge fracture risk with the K-wire, independently of opening speed. The second hypothesis was not confirmed. The study was performed under strict experimental conditions, unprecedented to our knowledge in the literature. However, complementary clinical studies are needed to confirm the present findings. Level of evidenceIV, experimental study.

Computer-aided Design of Distal Femoral Osteotomy for the Valgus Knee and Effect of Correction Angle on Joint Loading by Finite Element Analysis.

Lateral open-wedge distal femoral osteotomy (DFO) has been used to treat valgus deformity of the knee, with good clinical outcomes. However, there is a lack of biomechanical studies regarding the angle of correction. The objective of this study was to apply computer-aided design (CAD) for osteotomy planning in a three-dimensional (3D) anatomical model and to assess the biomechanical differences among the varying correction angles on joint loading by finite element analysis (FEA). To model different angles of lateral open-wedge DFO correction, the CAD software package Mimics 21.0 was used to accurately simulate the operated knee. The femur was cut to 0°, 2°, 4°, 6°, 8°, and 10° of varus (equivalent to hip-knee-ankle angles of 180°, 178°, 176°, 174°, 172°, and 170°, respectively). The original knee model and the corrected models were processed by FE software. Then, the FE models were subjected to an axial force to obtain the von Mises stress (VMS) and shear stress distributions within the femoral cartilages and menisci. Under a compressive load of 740 N, the highest VMS in lateral and medial compartments of the intact knee model was 3.418 and 3.303 MPa. The maximum value of both the VMS and the shear stress in the lateral compartment decreased as the varus angle increased, but the corresponding values in the medial compartment increased. When the hip-knee-ankle (HKA) angle was 180°, the VMS in the lateral and medial compartments was balanced (3.418 and 3.303MPa, respectively). Meanwhile, when the HKA angle was 178° (3.488 and 3.625MPa, respectively), the shear stress in the lateral and medial compartments was balanced. In addition, the magnitude of change in the stress was significantly higher in the medial compartment (90.9%) than in the lateral compartment (19.3%). The optimal correction angle of the valgus knee is close to neutral alignment or slightly varus (0° - 2°). Overcorrection is not recommended, as it can result in a steep increase of the stress within the medial compartment and may accelerate the process of medial compartment OA.

Poster 216: The Effects of Lateral Opening Wedge Distal Femoral Osteotomy on Meniscus Allograft Transplantation: A Biomechanical Evaluation

Objectives:Lateral meniscus deficiency with valgus malalignment increases the risk and rate of lateral compartment osteoarthritis. Lateral meniscus allograft transplantation (LMAT) with concomitant varus-producing lateral opening wedge distal femoral osteotomy (LOWDFO) is an available option to treat this pathology. No biomechanical data currently exists evaluating the effect on joint forces with these combined procedures. The purpose of this study is to evaluate the effects of LMAT with concomitant varus-producing LOWDFO on lateral and medial compartment biomechanics. We hypothesize that LMAT restores lateral compartment biomechanics back to native intact forces, varus-producing LOWDFO improves lateral compartment forces following LMAT, and medial compartment forces change to a lesser degree in response to mechanical varus.Methods:Ten human cadaveric knees underwent varus-producing LOWDFO and were placed in an external fixator. Anatomic alignment was standardized for each knee and utilized as a proxy for mechanical alignment. Thin film Tekscan pressure sensors were placed sub-meniscal and specimens were loaded on a biaxial dynamic testing machine to 800N within a custom designed apparatus, with loading angles between 9° valgus and 6° varus of mechanical alignment. Testing conditions included the intact meniscus, lateral meniscus deficiency, and LMAT. Statistical analysis was performed by creating two-factor random-intercepts linear mixed-effects models to compare peak pressure and contact area among the three experimental meniscus conditions.Results:Isolated varus-producing LOWDFO to 6° varus in the setting of meniscus deficiency was unable to restore joint forces to the level of the intact meniscus in neutral alignment (Mean Contact Pressure: 175%, Peak Pressure 135%, Contact Area -41%, P>0.05). LMAT restored mean contact and peak pressures, with no significant differences compared to the intact meniscus (P<0.05). LMAT resulted in significantly lower contact areas from 9° valgus to 0° (P>0.05), but this was restored to intact state at 3° and 6° varus (P<0.05). Within the lateral compartment following LMAT, every additional 1° of DFO correction contributes to a decreased in mean contact pressure of 5.6% (-0.0479 N/mm2)(Figure 1), a decrease in peak pressure of 5.9% (-0.154 N/mm2)(Figure 2), and a decrease in contact area of 1.4% (6.99 mm2)(Figure 3), as compared to forces in neutral alignment. Within the medial compartment following LMAT, every additional 1° of DFO correction contributes to an increase in mean contact pressure of 7.3% (+0.034 N/mm2), an increase in peak pressure of 12.6% (+0.160 N/mm2), and an increase in contact area of 4.3% (20.53 mm2), as compared to forces in neutral alignment. However, baseline forces in the medial compartment are significantly lower at baseline compared to lateral compartment forces (P>0.05).Conclusions:This is the first biomechanical study evaluating the effects of concomitant LMAT and varus-producing LOWDFO. Isolated varus-producing LOWDFO is inadequate to restore forces in the meniscus deficient knee. LMAT restores near normal forces, and concomitant LOWDFO improves the lateral compartment biomechanical profile. Although to a smaller magnitude, force changes in the medial compartment are significant with varus-producing LOWDFO. Unloading to 0° following LMAT may be ideal. Overall, this study provides tools to for the surgeon to individualize alignment correction for each patient to optimize outcomes.Figure 1.Mean Contact PressureFigure 2.Peak Contact PressureFigure 3.Contact Area

Osteochondral Allograft Transplantation of the Lateral Femoral Condyle and Distal Femoral Osteotomy in the Setting of Failed Osteochondritis Dissecans Fixation

Osteochondritis dissecans (OCD) is a pathologic condition, most commonly affecting the knee joint in adolescents and young adults, although pathology can also be found at the elbow and ankle. Lesions to the medial femoral condyle are classically associated with varus alignment, while lesions to the lateral femoral condyle are seen in patients with valgus malalignment. Common risk factors for failed fixation of OCD lesions include unstable lesions to the lateral femoral condyle, screw breakage, older age, and closed physes. The purpose of this technical note is to describe the preoperative planning and step-by-step surgical approach for treatment of failed fixation of an OCD lesion of the posterior aspect of the lateral femoral condyle in young, active patients using an osteochondral allograft, a lateral opening wedge distal femoral osteotomy to correct malalignment, and a tibial tubercle osteotomy to facilitate access to the lesion.

Basics of Coronal Plane Deformity Correction

High tibial osteotomy (HTO) and distal femoral osteotomy (DFO) are utilized to correct knee malalignment in patients with coronal plane deformities. Identifying the deformity of the lower extremity using a standardized, reproducible approach is critical prior to correction of lower limb malalignment with an osteotomy procedure. Appropriate radiographs, including bilateral long-leg standing films, are critical to measure the anatomical and/or mechanical axes and calculate the required degree of correction. The femoral and tibial mechanical axes, malalignment (varus or valgus), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) should be measured during coronal plane deformity analysis and accounted for during surgical planning. This paper focuses on the surgical technique for medial opening and lateral closing wedge HTO, as well as medial closing and lateral opening wedge DFO.