Kyung Wook Nha

In Vivo Patellar Tracking: Clinical Motions and Patellofemoral Indices

Patellar tracking during in vivo weightbearing knee function is not well understood. This study investigated patellar tracking of eight subjects during a full range of weightbearing flexion using magnetic resonance imaging and dual orthogonal fluoroscopy. The data were reported using a clinical description based on patellar and femoral joint coordinate systems and using patellar indices based on geometrical features of the femur and patella. The mean patellar shift was within 3 mm over the entire range of flexion. The patella tilted laterally from 0° to 75°, and then tilted medially beyond 75° of flexion. The mean tilt was within 6°. Similarly, the mean patellar rotation was small at early flexion, and the mean total excursion of patellar rotation was about 8°. The patellofemoral indices showed that the mean sulcus angle and congruence angle varied within 8° over the entire flexion range. The mean lateral patellar displacement was within 6 mm. A consistent decrease in lateral patellar tilt and an increase in lateral patellofemoral angle were observed with knee flexion. In conclusion, patellar motion is relatively small with respect to the femur during in vivo weightbearing knee flexion. These data may provide baseline knowledge for understanding normal patellar tracking.

The In Vivo Kinematics of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament During Weightbearing Knee Flexion

Background Recently, double-bundle anterior cruciate ligament reconstruction has been advocated. However, there are little data on the in vivo biomechanics of the anteromedial and posterolateral bundles of the anterior cruciate ligament. Our objective was to measure the kinematics of the 2 bundles during weightbearing flexion. Study Design Descriptive laboratory study. Hypothesis The bundles of the anterior cruciate ligament are longest at low flexion angles during in vivo weightbearing flexion. Methods Magnetic resonance images from 7 healthy subjects were used to create 3-dimensional models of the knee. The attachments of the anteromedial and posterolateral bundles were outlined on each model. Next, the subjects performed a quasi-static lunge from full extension to 135° while being imaged using a dual orthogonal fluoroscopic system. The models and fluoroscopic images were used to reproduce the motion of the knee. The length, elevation, deviation, and twist of the functional bundles were measured. Results The anteromedial and posterolateral bundles were longest at low flexion angles and shortened significantly with increasing flexion. The elevation and deviation angles of both bundles were similar at low flexion angles (<45°). The twist of the bundles was minimal (<5°) at low flexion. Conclusion With in vivo flexion, the anteromedial and posterolateral bundles did not demonstrate the reciprocal behavior noted in previous cadaveric studies. Both bundles were parallel and maximally elongated at low flexion angles. Our data suggest that if a double-bundle reconstruction is performed, 2 tunnels might need to be drilled in the femur and tibia to reproduce the orientation of the anterior cruciate ligament. Both anteromedial and posterolateral grafts should be fixed at low flexion angles to prevent over-constraint.

Function of Posterior Cruciate Ligament Bundles during in Vivo Knee Flexion

Background The biomechanical functions of the anterolateral and posteromedial bundles of the posterior cruciate ligament over the range of flexion of the knee joint remain unclear. Hypothesis The posterior cruciate ligament bundles have minimal length at low flexion angles and maximal length at high flexion angles. Study Design Descriptive laboratory study. Methods Seven knees from normal, healthy subjects were scanned with magnetic resonance, and 3-dimensional models of the femur, tibia, and posterior cruciate ligament attachment sites were created. The lines connecting the centroids of the corresponding bundle attachment sites on the femur and tibia represented the anterolateral and posteromedial bundles of the posterior cruciate ligament. Each knee was imaged during weightbearing flexion (from 0° to maximal flexion) using a dual-orthogonal fluoroscopic system. The length, elevation, deviation, and twist of the posterior cruciate ligament bundles were measured as a function of flexion. Results The lengths of the anterolateral and posteromedial bundles increased with flexion from 0° to 120° and decreased beyond 120° of flexion. The posteromedial bundle had a lower elevation angle than the anterolateral bundle beyond 60° of flexion. The anterolateral bundle had a larger deviation angle than the posteromedial bundle beyond 75° of flexion. The femoral attachment of the posterior cruciate ligament twisted externally with increasing flexion and reached a maximum of 86.4° ± 14.7° at 135° of flexion (P < .05). Conclusion These data suggest that there is no reciprocal function of the bundles with flexion, which is contrary to previous findings. The orientation of the anterolateral and posteromedial bundles suggests that at high flexion, the anterolateral bundle might play an important role in constraining the mediolateral translation, whereas the posteromedial bundle might play an important role in constraining the anteroposterior translation of the tibia. Clinical Relevance These data provide a better understanding of the biomechanical function of the posterior cruciate ligament bundles and may help to improve the design of the 2-bundle reconstruction techniques of the ruptured posterior cruciate ligament.

Unfavorable Results of Partial Meniscectomy for Complete Posterior Medial Meniscus Root Tear With Early Osteoarthritis: A 5- to 8-Year Follow-Up Study

PURPOSE The aim of this retrospective study was to evaluate the clinical and radiographic outcomes of arthroscopic partial meniscectomy for complete posterior medial meniscus root tear (PMMRT) in patients with early radiographic evidence of knee osteoarthritis at a minimum follow-up of 5 years. METHODS Forty-six cases had complete PMMRT with follow-up of at least 5 years and were treated with arthroscopic partial meniscectomy. On the basis of medical records, we reviewed the arthroscopic findings of joint degeneration (Outerbridge grading), clinical results using the modified Lysholm (ML) knee score and a patient questionnaire, and radiographic evaluation of degeneration using Kellgren-Lawrence (KL) grading. RESULTS The incidence of complete PMMRT in the study population was 15%. At a mean follow-up of 78 months (range, 60 to 103 months), the mean ML score significantly improved from 72 (range, 62 to 78) preoperatively to 77 (range, 70 to 98) at final follow-up (P < .01), 16 patients (35%) showed progression of degeneration from KL grade 0 to 2 preoperatively to KL grade 2 to 4, 56% of patients indicated improvement in pain, 67% of patients were satisfied with the results of the procedure, and 19% of patients underwent reoperation. There was a significant negative correlation between chondral wear during arthroscopy (ρ = -0.516, P = .002) and preoperative KL grade (ρ = -0.429, P = .004) with ML score at final follow-up. CONCLUSIONS Although arthroscopic partial meniscectomy for complete PMMRT significantly improved ML scores postoperatively, only 56% of patients had improvement in pain, 67% were satisfied with the outcome of the procedure, and 35% showed radiographic progression of osteoarthritis at a mean follow-up of 77 months. LEVEL OF EVIDENCE Level IV, therapeutic study.

Effect of Posterior Cruciate Ligament Deficiency on in vivo Translation and Rotation of the Knee during Weightbearing Flexion

Background The effect of posterior cruciate ligament (PCL) deficiency on 6 degrees of freedom in vivo knee-joint kinematics is unclear. Hypothesis In addition to constraining anterior-posterior translation, the PCL also functions to constrain the medial-lateral translation and rotation of the knee during weightbearing flexion of the knee. Study Design Controlled laboratory study. Methods Eight patients with a PCL injury in 1 knee and the other intact were scanned with magnetic resonance imaging, and 3-dimensional models of the femur and tibia were created for both knees. Each knee was imaged during quasistatic weightbearing flexion (from 0° to 105°) using a dual-orthogonal fluoroscopic system. The translation and rotation of the PCL-deficient knee were compared with the intact contralateral control. Results Posterior cruciate ligament deficiency caused an increase in posterior tibial translation beyond 30° of flexion compared with the intact contralateral knees. At 90° of flexion, PCL deficiency increased posterior tibial translation by 3.5 mm (P < .05). In the medial-lateral direction, PCL deficiency resulted in a 1.1 mm increase in lateral tibial translation at 90° of flexion (P < .05). With regard to rotation, PCL deficiency caused a significantly lower varus rotation (on average, 0.6° lower) at 90° of flexion. Posterior cruciate ligament deficiency caused a decreased internal tibial rotation throughout the range of flexion, but no significant difference was detected. Conclusions This study quantitatively describes the effect of PCL injury on 6 degrees of freedom kinematics of the knee during quasistatic weightbearing flexion. Using the intact contralateral side as a control, we found that PCL injuries not only affect anterior-posterior tibial translation but also medial-lateral translation and rotation of the knee. Clinical Relevance These data provide baseline knowledge of the in vivo kinematics of the knee after PCL injury. Surgical reconstruction of the injured PCL, either using single-bundle or double-bundle technique, should not only focus on restoration of posterior stability of the knee but also the medial-lateral stability as well as the rotational stability. These findings may help to explain the long-term degenerative changes seen in PCL-deficient knees.

Evaluation of the Reliability of the Dial Test for Posterolateral Rotatory Instability: A Cadaveric Study Using an Isotonic Rotation Machine

PURPOSE The purpose of our study was to evaluate the reliability of the dial test by assessing the correlation between the severity of posterolateral corner injuries and the amount of external rotation of the tibia. METHODS Fourteen paired cadaveric legs were fixed into a custom-made isotonic rotation machine with the knee flexed at 30 degrees . For group I (7 right knees), the lateral collateral ligament, popliteofibular ligament, popliteus tendon, and posterior cruciate ligament (PCL) were cut serially. For group II (7 left knees), the PCL, lateral collateral ligament, popliteofibular ligament, and popliteus tendon were cut. The external rotation angles were measured with a 6-Nm rotational torque. RESULTS For group I, the mean increase in the external rotation angle after cutting of the 3 posterolateral ligament structures was 17.9 degrees +/- 6.4 degrees. The additional increase in mean external rotation after cutting of the PCL was 4.7 degrees +/- 2.1 degrees. For group II, the mean increase in the external rotation angle after cutting of the PCL was 8 degrees +/- 4 degrees. Cutting the 3 posterolateral ligament structures increased the external rotation by 10.7 degrees +/- 5.3 degrees. The increase in external rotation was significant in group I after cutting of the 3 posterolateral structures and in group II after cutting of the PCL and 2 posterolateral structures (P = .05, Duncan test). CONCLUSIONS The dial test may be a valuable diagnostic method in cases of injury to 3 posterolateral structures or combined injuries to the PCL and 2 posterolateral structures. However, posterolateral instability with injuries to only 1 or 2 posterolateral structures may not be clinically detected by the dial test. CLINICAL RELEVANCE In the case of posterolateral instability with only 1 or 2 structure injuries, comprehensive diagnostic methods including the patients history, other physical examinations, radiographs, and magnetic resonance imaging should be used to diagnose posterolateral rotatory instability.

The Coupled Motion of the Femur and Patella During In Vivo Weightbearing Knee Flexion

The movement of the knee joint consists of a coupled motion between the tibiofemoral and patellofemoral articulations. This study measured the six degrees-of-freedom kinematics of the tibia, femur, and patella using dual-orthogonal fluoroscopy and magnetic resonance imaging. Ten normal knees from ten living subjects were investigated during weightbearing flexion from full extension to maximum flexion. The femoral and the patellar motions were measured relative to the tibia. The femur externally rotated by 12.9 deg and the patella tilted laterally by 16.3 deg during the full range of knee flexion. Knee flexion was strongly correlated with patellar flexion (R(2)=0.91), posterior femoral translation was strongly correlated to the posterior patellar translation (R(2)=0.87), and internal-external rotation of the femur was correlated to patellar tilt (R(2)=0.73) and medial-lateral patellar translation (R(2)=0.63). These data quantitatively indicate a kinematic coupling between the tibia, femur, and patella, and provide base line information on normal knee joint kinematics throughout the full range of weightbearing flexion. The data also suggest that the kinematic coupling of tibia, femur, and patella should be considered when investigating patellar pathologies and when developing surgical techniques to treat knee joint diseases.

In vivo knee kinematics during high flexion after a posterior-substituting total knee arthroplasty

The objective of this study was to investigate biomechanics of TKA patients during high flexion. Six patients (seven knees) with a posterior-substituting TKA and weight-bearing flexion >130° were included in the study. The six degree-of-freedom kinematics, tibiofemoral contact, and cam-post contact were measured during a deep knee bend using dual-plane fluoroscopy. The patients achieved average weight-bearing flexion of 139.5 ± 4.5°. Posterior femoral translation and internal tibial rotation increased steadily beyond 90° flexion, and a sharp increase in varus rotation was noted at maximum flexion. Initial cam-post engagement was observed at 100.3 ± 6.7° flexion. Five knees had cam-post disengagement before maximum flexion. Lateral femoral condylar lift-off was found in five out of seven knees at maximum flexion, and medial condylar lift-off was found in one knee. Future studies should investigate if the kinematic characteristics of posterior-substituting TKA knees noted in this study are causative factors of high knee flexion.

Biomechanical Properties of a New Anatomical Locking Metal Block Plate for Opening Wedge High Tibial Osteotomy: Uniplane Osteotomy

Purpose The purpose of this study was to evaluate the biomechanical properties of a new anatomical locking metal block plate by comparing the initial biomechanical stability of three different fixation constructs for open wedge high tibial osteotomy (HTO). Materials and Methods Sawbones composite tibiae were used to make a 10-mm opening osteotomy model with uniplane technique. The osteotomy was secured with three different types of plates: Group I, new osteotomy plate without a metal block (n=5); Group II, new osteotomy plate with a 10-mm metal block (n=5); and Group III, two short metal block plates (n=5). Single load to failure test and staircase load-controlled cyclical failure test were performed. In the single load to failure test, the yield load, maximum failure load, and the displacement of the osteotomy gap were measured. In the staircase cyclical load to failure test, the total number of cycles to failure was recorded. Failure modes were observed during both single and cyclic load tests. Results Group II showed the highest yield and ultimate loads (1829±319 N, 3493±1250 N) compared to Group I (1512±157 N, 2422±769 N) and Group III (1369±378 N, 2157±210 N, p<0.05). The displacement of the opening gap in Group II (0.34±0.35 mm) was significantly lesser than the other groups (p<0.05). In the staircase cyclical load to failure test, the total number of cycles to failure was 12,860 at 950 N in Group III, 20,280 at 1,140 N in Group I, and 42,816 at 1,330 N in Group II (p<0.05). All the specimens showed complete fracture of the intact lateral sawbones area and slight displacement of the distal fragment of the specimens in the single load to test. None of the specimens showed deformed or broken screws and plates during the single load to test. During the fatigue test with staircase cyclic loading, no fracture of the lateral sawbones area was observed. Conclusions This study demonstrated that the new anatomical locking metal block plate could provide sufficient primary stability for open wedge HTO. The addition of a metal block to this new plate can increase the stability of the osteotomy compared to the one without a metal block.

Pseudoaneurysm of the Popliteal Artery Complicating Medial Opening Wedge High Tibial Osteotomy

The popliteal artery is vulnerable to injury during surgeries performed around the knee joint. Pseudoaneurysm of the popliteal artery following a high tibial osteotomy is rare. Few case reports describe the development of this complication after a lateral closing wedge high tibial osteotomy. Our patient underwent an uneventful medial opening wedge high tibial osteotomy and autogenous bone grafting fixed with dual plating for medial osteoarthritis of the knee. The procedure was performed under tourniquet control, which was released only once after the wound closure. Postoperatively, the dressing was soaked, and a large volume of hemorrhagic collection was present in the suction drain. The patient experienced decreased sensation over the sole, which was successfully treated conservatively with medication. Other clinical parameters like motor function and distal pulses were normal. The patient was discharged after 2 weeks. Two days later, the patient presented with pain and numbness over the entire lower limb and a pulsatile swelling in the popliteal fossa. A femoral angiogram revealed a pseudoaneurysm arising from the popliteal artery just below the osteotomy site. Open vascular surgery with resection of the pseudoaneurysm and end-to-end anastomosis using contralateral saphenous vein interposition graft was performed. During the vascular surgery, a pinhead-sized tear was clearly identified on the anterior wall of the popliteal artery, which may have occurred while using the oscillating saw during opening wedge high tibial osteotomy. Careful placement of retractors around the osteotomy site during sawing and flexing the knee to displace the popliteal artery away are recommended to prevent this complication. To our knowledge, this is the first report of a popliteal artery pseudoaneurysm occurring after a medial opening wedge high tibial osteotomy.