Complex Patellofemoral Reconstruction for Recurrent Instability

Background: Patellofemoral instability is due to a combination of bony and soft tissue factors. While recurrent patellar dislocations are rare, evaluation and treatment of these conditions require addressing patellar height and lateralization of the tibial tubercle (TT), restraint to lateral patellar subluxation, and trochlear dysplasia. Other factors to consider are coronal limb-length alignment outside of the physiologic 5 to 8° of valgus, which may significantly alter the Q angle and contribute to lateral instability. Other ligaments around the patella contribute to soft-tissue restraint, including the medial and lateral patellotibial ligaments, patellomeniscal ligaments, and the medial quadriceps tendon femoral ligament. Patellar tilt is assessed with and without quadriceps contraction to further evaluate the patella’s relationship to the trochlear groove. The Caton-Deschamps Index, as well as patellar trochlear index (PTI), are used to measure patellar height for patella alta or baja. Technique Description: The technique is to surgically manage a patient in neutral mechanical alignment on standing limb radiographs, with moderate-to-severe DeJour type B trochlear dysplasia and a trochlear sulcus angle of around 145°, patella alta with a Caton-Deschamps Index of 1.6 and PTI of 0.22, a TT to trochlear groove (TT-TG) distance of 8 mm, and a deficient medial patellofemoral ligament (MPFL). The MPFL reconstruction is done first, with harvesting of the ipsilateral quadriceps tendon and maintenance of its distal attachment on the superior patellar pole. The quadriceps tendon graft is folded medially upon its distal attachment and fixed in this position with suture anchors. Tibial tubercle osteotomy is accomplished by spacing drill holes 2 mm apart, medially and laterally, on the TT and connecting the drill holes with an osteotome and reciprocating saw. A distalized location to secure the TT is selected and superficial bone is excised. A medial parapatellar arthrotomy is performed, and bur attachments are used to drill into the subchondral bone beneath the femoral articular surface to create a V-shaped flap of trochlear cartilage. An arthroscope is inserted under the trochlear flap during this process to visualize the appropriate depth. The trochlear flap is then secured with screws passed over guide pins to secure the flap to the desired location. Cannulated screws and washers are then used to secure the TT to its distalized and/or medialized position, with fluoroscopic verification of screw depth and location. The arthrotomy is then closed with the knee at 45°. The quadriceps graft is passed through a subretinacular channel and secured with suture anchors, adjacent to the adductor tubercle, to complete the MPFL reconstruction. Before closure, appropriate tracking and translation of the patella is verified. Results: Sulcus-deepening trochleoplasty, with or without MPFL reconstruction, has been reported to obtain satisfactory outcomes at 2 years, with close to 85% return to sport and 100% return to work, with improvements in International Knee Documentation Committee (IKDC) scores from 50.8 to 79.1 in some studies. MPFL reconstruction with tibial tubercle osteotomy (TTO) has yielded a 94.5% patient satisfaction rate in the literature. Discussion/Conclusion: In patients with recurrent patellar instability and DeJour types B-D trochlear dysplasia, MPFL reconstruction with TTO and sulcus-deepening trochleoplasty provides excellent subjective outcomes and restores patellar tracking with elimination of recurrent subluxation.

Patellar MACI With Tibial Tubercle Osteotomy

Background: Chondral pathology is frequently encountered during knee arthroscopies with a prevalence rate of 63% to 66%. Prior studies have demonstrated that unaddressed or excised fragments result in poor knee function and arthritis. As a result, chondral-related procedures have increased in popularity, and now more than 200,000 procedures are performed annually. Indications: We present a case of an active 32-year-old woman, prior collegiate basketball player, with persistent left knee pain noted to have a full-thickness patellar articular cartilage defect and maltracking. Technique: A patellar autologous matrix-induced chondrocyte is implanted with a concomitant tibial tubercle osteotomy (TTO) and lateral retinacular lengthening. Results: At 9 weeks, the patient had no knee pain with full range of motion symmetric to the contralateral side while slowly progressing with quadriceps strengthening. Discussion/Conclusion: Successful outcomes addressing large patellar chondral defects and maltracking can be achieved with matrix autologous chondrocyte implantation and concomitant TTO with lateral retinacular lengthening.

Technical Considerations for an Anteromedializing Tibial Tubercle Osteotomy

Background: Tibial tubercle osteotomy and distal realignment allows for adjustment to the patellofemoral articulation in order to improve patellar tracking and redistribute patellar contract pressures. Indications: A healthy, active 39-year-old woman status post right knee tibial tubercle osteotomy presented with >2 years of patellar instability symptoms in the left knee. Imaging revealed a tibial tubercle to trochlear groove (TT-TG) distance of 21 mm and patellar tendon lateral trochlear ridge (PT-LTR) distance of 14 mm. Technique Description: After knee arthroscopy is performed, an open incision is made along the inferomedial patellar tendon. Two pilot holes are created before a sagittal saw is used to make the tibial tubercle osteotomy, before completing it with an osteotome. Anteromedialization and/or distalization of the osteotomy is performed relative to templated values in order to improve patellar articulation. After correction, 3 bicortical screws are placed to achieve stable fixation. Results: There were no immediate complications following surgery. Surgical management led to improvement of the patient’s patellofemoral pain, which allowed return to prior baseline level of function. Discussion/Conclusion: The preferred technique for an anteromedialzing tibial tubercle osteotomy is presented. An anteromedializing tibial tubercle osteotomy is an effective surgical option for patients with evidence of patellar maltracking or central or lateral patellar chondromalacia whom have failed conservative management. This case demonstrates the efficacy of an anteromedializing tibial tubercle osteotomy to provide pain relief by improving patellar tracking and offloading patellar contact pressures on areas of prominent chondral wear.

Tibial tubercle osteotomy (Fulkerson procedure) on women athlete with anterior knee pain: a case series

Anterior knee pain (AKP) is one of the most frequent complaints in knee conditions of adolescent and young adult patients. Tibial tuberosity osteotomy (Fulkerson procedure) is a well-described treatment option for a broad range of patellofemoral joint disorders. This study aimed to evaluate the clinical outcomes of tibial tubercle osteotomy and prognostic factors correlated with the outcomes in adolescents’ athletes affected by anterior knee pain. Three patients treated with tibial tubercle osteotomy for anterior knee pain were prospectively evaluated using the Anterior Knee Pain Scale (AKPS), The Western Ontario and McMaster Universities Arthritis Index (WOMAC) and the part of the International Knee Documentation Committee (IKDC) score to find different potential risk factors as an objective evaluation. The three cases are showing improvement in overall scores, both in six months (WOMAC 72.4; KUJALA 64.6%; IKDC 52.1%) and after one year (WOMAC 82.6; KUJALA 83.3%; IKDC 70.3%) following the surgical procedure. Patient 1 and patient 2 obeyed the physiotherapy schedules and checked their condition regularly. Their scores indicate an immense improvement than patient 3, who did not comply with the physiotherapy nor the check-up. However, the comparison analysis shows a significant increase of the scores for all three assessment methods (WOMAC, KUJALA and IKDC), that implies a good result of clinical outcome may still be achieved even without a close follow up. Even though the Fulkerson procedure was the treatment option for a broad range of AKP, a different comprehensive range result of the scores was found.

Biomechanical consequences of tibial tubercle osteotomy in a 3D-printed model of patellofemoral dysplasia (207)

Objectives: Trochlear dysplasia and an increased tibial tubercle-trochlear groove (TT-TG) distance are two major contributing factors to patellar instability and are often found concurrently. Patellar morphology is also abnormal in the setting of trochlear dysplasia. Indications for tibial tubercle osteotomy (TTO) include recurrent patellar instability in the setting of an increased TT-TG distance. While anteromedialization (AMZ) TTO has been shown to decrease overall PF contact stresses and improve patellar tracking, this has never been demonstrated in a model of PF dysplasia. Due in part to a lack of available dysplastic cadaveric specimens, few studies have investigated the consequences of PF dysplasia on PF biomechanics. Our previous work has demonstrated that when compared to normal morphology, PF dysplasia results in a lateral shift but negligible increases in patellar contact forces. This prompted the question of how TTO affects contact mechanics in this setting. The objective of this study was to quantify contact mechanics and kinematics following TTO using a 3D-printed PF dysplasia model. We hypothesized that an anterior tubercle position simulating AMZ TTO would best improve PF contact mechanics. Methods: Five fresh frozen cadaveric knees were dissected free of all soft tissues except the extensor mechanism. Computed tomography (CT) scan of each specimen confirmed no trochlear dysplasia or patella alta and a normal TT-TG distance (<10 mm). Dysplastic bone geometries were derived from patient CT scans selected by the senior orthopaedic surgeon who specializes in PF surgery. Segmentation was performed using Mimics (Materialise Figure 1A&B). Cadaveric knees were grouped based on the medial and lateral epicondylar distance (ML distance), and the implants were scaled to the size of each group. Scaling was done using Geomagic Studio (3D Systems), and implants were printed using a Form2 SLA 3D printer (Formlabs). Durable resin (Formlabs) was used to minimize wear between the printed components (Figure 1C). Cadaveric bony resection was performed using Biomet Vanguard (Zimmer Biomet) equipment. The amount of bone resected matched the 3D implant dimensions. A 6° distal femoral valgus cut angle was utilized. For femoral rotation, posterior referencing was utilized (no lateral insufficiency was observed), and cuts were made with 3° of external rotation in relation to the transepicondylar axis. The 3D implant was then fixed flush to the distal femur and native trochlea using screws. A metered patellar reamer was used for patellar preparation. The patellar implant was pressed into a central peg hole and fixed with a screw placed through the anterior patella. A flat tibial tubercle osteotomy cut, matching the aforementioned femoral rotation, was made with a shingle thickness of 1 cm and length of 6 cm. Each knee was mounted to a custom fixture on a servo-hydraulic load frame (MTS, Eden Prairie, MN) and cycled 5 times from 0° to 70° by pulling on the quadriceps tendon using a pulley system (Figure 1D). The shingle was fixed to the tibia using two 1.57mm K-wires. For each specimen, testing was repeated for each of three tibial tubercle positions: Native tubercle position (“normal”), 1 cm lateral to native (“lateral”), and 1 cm anterior to native (“anterior”) (Figure 2A-C). For the anterior position, a 1 cm thick plastic bone block was placed between the shingle and the tibia while maintaining its native position in the coronal plane. The lateral position was intended to represent the presurgical pathologic state (increased TT-TG), the native position a postsurgical medialized state, and the anterior position a postsurgical anteromedialized state. PF contact pressures were recorded using an electronic pressure sensor (sensor #5040, Tekscan, Boston, MA). Contact data was separated to the medial and lateral facets by identifying the median patellar ridge on the sensor. Within each facet, the sum of forces and center of pressure (weighted average of position of all acting forces within the facet relative to the median patellar ridge) was computed. Kinematics were recorded using a reflective marker motion capture system (Cortex, Motion Analysis Corporation, Santa Rosa, CA). Repeated measures ANOVA with post hoc Bonferroni analysis was used to determine differences in contact force and center of pressure location for each tubercle position. Statistical significance was defined as p<0.05. Results: There was a significant increase in the lateral facet, medial facet, and total patellar contact forces with lateral tubercle position compared to the anterior position (Figure 3). There was also a significant increase in medial facet and total patellar contact forces with the native tubercle position compared to the anterior position. There were no significant differences in lateral facet, medial facet, or total patellar contact forces when comparing the native and lateral tubercle positions. There was a trend toward an increased (lateralized) lateral facet center of pressure when comparing the lateral and anterior tubercle positions (Figure 4). Conclusions: Using a model capable of quantifying kinematics and contact mechanics for dysplastic trochleae and patellae, we demonstrated that an anterior tubercle position resulted in decreased patellar contact forces when compared to lateralized and native tubercle positions. These findings suggest that when an AMZ TTO is performed in the setting of an increased TT-TG distance and PF dysplasia, overall patellar contact forces are reduced. This may improve PF biomechanics and potentially decrease the likelihood of future PF OA. Similar findings were not observed for the native tubercle position, suggesting that anterorization is a critical consideration in improving PF biomechanics in this setting.

Suture Tape Augmentation of Screw Fixation Reduces Fragment Migration in Tibial Tubercle Osteotomy: A Biomechanical Study

Background: Tibial tubercle osteotomy (TTO) is a complex surgical procedure with a significant risk of complications, which include nonunion and tibial fracture. Purpose: To determine whether an additional suture tape augmentation can provide better biomechanical stability compared with standard screw fixation. Study Design: Controlled laboratory study. Methods: Five matched pairs of human cadaveric knees were divided into 2 groups: the first group underwent standard TTO fixation with 2 parallel screws (standard group). The second group underwent a novel fixation technique, in which a nonabsorbable suture tape (FiberTape) in a figure-of-8 construct was added to the standard screw fixation for extra stabilization in the inferior-superior direction (augmented group). The specimens were biomechanically tested using a multistep cyclic loading protocol from 400 N up to 800 N to simulate the rehabilitation process. Tubercular fragment migration of >50% of the initial distalization length was defined as clinical failure. A pull-to-failure test was applied to the specimens that survived cyclic loading. Tubercular fragment displacement during cyclic loading and pull-to-failure force were recorded and compared between the 2 groups. Results: Two specimens of the standard group exhibited clinical failure during cyclic loading to 400 N. All other specimens survived cyclic loading to 800 N. The augmented group showed less cyclic tubercular fragment displacement after every load level compared with the standard group, with statistically significant differences starting from 500 N ( P < .05; power > 0.8). Mean ± standard deviation tubercular fragment displacement at the end of cyclic loading was 2.56 ± 0.82 mm for the augmented group and 5.21 ± 0.51 mm for the standard group. Mean ultimate failure load after the pull-to-failure test was 2475 ± 554 N for the augmented group and 1475 ± 280 N for the standard group. Conclusion: The specimens that underwent suture tape augmentation showed less tubercular fragment displacement during cyclic loading and higher ultimate failure forces compared with those that underwent standard screw fixation. Clinical Relevance: The augmentation technique could potentially increase the success of a TTO.