Alteration of patellofemoral contact during healing of canine patellar tendon after removal of its central third

Simultaneous Measurement of Patellofemoral Joint Kinematics and Contact Mechanics in Intact Knees: A Cadaveric Study

Objective

Patellofemoral kinematics and contact mechanics are important measurements for the assessment of patellofemoral joint (PFJ) problems. Simultaneously measuring PFJ contact pressures and kinematics is a challenging task. The purpose of this study was to simultaneously measure the kinematics and mean/peak contact pressures in the PFJs of cadaveric knees.

Methods

This was a comparative study performed on fresh cadaveric knees. The kinematic data was acquired for nine cadaveric knees using an optical tracking system. Data about the contact pressure and contact area in the PFJ was obtained at knee flexion angles of 0°, 30°, 60°, 90°, and 120° using a pressure sensor. Intraclass correlation coefficients (ICCs) and minimal detectable differences (MDDs) of six degrees of freedom (6 DOF) in the PFJs were calculated. ICCs and the MDDs of contact pressure, peak pressure, and contact area in the PFJs were also analyzed. We also compared the kinematics of the cadaveric knees before and after the insertion of the pressure sensor.

Results

All ICC values of 6 DOF in the PFJs were found to be greater than or equal to 0.924. Regarding medial–lateral rotation, the patellar showed a simplified movement pattern that demonstrated progressive lateral rotation of 4.8° ± 3.4° at 120° of knee flexion. While for patellar tilting, the patella showed medial tilting that peaked at 7.2 ± 2.5° at 30° of knee flexion. Whereas no significant differences in PFJ kinematics were found between with and without the placement of the pressure sensor at all knee flexions (P > 0.05). Most of the ICC values for contact pressure, peak contact pressure, and contact area ranged from 0.8 to 0.9. The MDDs for rotational displacement were 0.9° and 0.6 mm for translational displacement. No statistical differences in patellar kinematics were found before and after the insertion of the pressure sensor.

Conclusions

The setup in the present study enables researchers to simultaneously and synchronously collect real‐time PFJ kinematics and tibiofemoral joint (TFJ) biomechanical kinematic data with high reliability. The low MDDs enabled the researchers to obtain an accurate interpretation of the kinematic and contact mechanics measurement using the experimental setting used in the present study.

Effects of quadriceps angle on patellofemoral contact pressure

BACKGROUND

An inappropriate Q angle may affect the biomechanics of the canine patellofemoral joint.

OBJECTIVES

The purpose of this study was to evaluate the effects of changes in quadriceps angle (Q angle) on patellofemoral joint pressure distribution in dogs.

METHODS

Eight stifles were positioned at 45, 60, 75, 90, 105, and 120° of flexion in vitro, and 30% body weight was applied through the quadriceps. Patellofemoral contact pressure distribution was mapped and quantified using pressure-sensitive film. For the pressure area, mean pressure, peak pressure, medial peak pressure, and lateral peak pressure, differences between groups according to conditions for changing the Q angle were statistically compared.

RESULTS

Increases of 10° of the Q angle result in increases in the pressure area (P = 0.04), mean pressure (P = 0.003), peak pressure, and medial peak pressure (P ≤ 0.01). Increasing the Q angle by 20° increases the pressure area (P = 0.021), mean pressure (P ≤ 0.001), peak pressure (P ≤ 0.01), and medial peak pressure (P ≤ 0.01) significantly, and shows higher mean (P ≤ 0.001) and peak pressures than increasing by 10°. Decreasing the Q angle increases the mean pressure (P = 0.013), peak pressure, and lateral peak pressure (P ≤ 0.001).

CONCLUSIONS

Both increases and decreases in the Q angle were associated with increased peak patellofemoral pressure, which could contribute to the overloading of the cartilage. Therefore, the abnormal Q angle should be corrected to the physiologically normal value during patellar luxation repair and overcorrection should be avoided.

ESTUDO DA TÉCNICA INTRACAPSULAR ASSISTIDA POR ARTROSCOPIA PARA O TRATAMENTO DA RUPTURA DO LIGAMENTO CRUZADO CRANIAL EM CADÁVERES DE CÃES

Resumo O objetivo foi estudar e aprimorar a técnica intracapsular de reparação do ligamento cruzado cranial assistida por artroscopia em cadáveres de cães com a confecção dos túneis tibial e femoral e utilização de autoenxerto osso-tendão patelar-osso. Foram utilizados 10 membros pélvicos de cães > 20kg. Os túneis ósseos foram confeccionados de forma independente e na posição anatômica original dos locais de inserção do ligamento cruzado cranial. Foram realizados estudo radiográfico e tomográfico para avaliar a articulação. A coleta das porções ósseas do enxerto foi feita com osteótomo e martelo. Ocorreram fratura em três patelas e em três tuberosidades tibiais. Os enxertos apresentaram comprimento médio 7,56cm. Os túneis tibiais e os túneis femorais foram confeccionados no local de inserção do ligamento cruzado cranial em 80% e 90% das articulações, respectivamente. Os túneis tibiais apresentaram ângulo médio de 62,95º mensurado por tomografia computadorizada. Os túneis femorais foram confeccionados em posição 13hs para o joelho esquerdo (100%) e 11hs para o direito (100%). Ao final do procedimento, obteve-se gaveta negativo em 100% das articulações. Pode-se concluir que a técnica proposta é viável de ser realizada no cão, porém faz-se necessário instrumental específico devido ao pequeno tamanho da articulação canina para obter melhor acurácia.

Intraoperative patellar kinematics following resection of the central one-third of the patellar tendon in the ovine stifle joint

Objectives: The bone-patellar tendon-bone complex is routinely harvested for anterior cruciate ligament reconstruction in humans. Patella infera may ensue. However, the contribution from resection of the central one-third of the patellar tendon (PT) to potentially altered patellofemoral kinematics, in addition to those induced by a positional shift of the patella, are yet to be distinguished. Objectives of this study were to characterize changes in intraoperative patellar kinematics and PT length in nine sheep immediately following unilateral resection of the central one-third PT, and again at six, 12 and 24 weeks postoperatively.

Methods: Following implantation of bone-screws into the patella and tibia, electromagnetic receivers were anchored to these, and then passively-induced, unloaded patellar kinematics were captured. Patellar kinematics were referenced to the tibial coordinate frame and analysed using non-parametric tests (Wilcoxon Signed Rank Test).

Results: Resection alone did cause significant alteration in kinematics at the time of surgery (p <0.05). Postoperatively, a mean increase in PT length of 2.6 mm was detected in the operated stifles, reflected partly as a net 2.8 mm proximal patellar shift (p <0.001). This was accompanied by a mean net six degree medial shift in the patellar tilt pattern (p <0.001). Significant changes to patellar spin in the latter parts of flexion were also observed (p <0.005). Kinematic and length changes did not recover up to 24 weeks postoperatively.

Clinical significance: The data obtained in this study suggests that both the patellar height and integrity of the PT are important determinants of patellar kinematics in the ovine stifle joint.

Effects of patellar position and defect healing on in vitro stifle joint kinematics following removal of the central one-third of the patellar tendon in an ovine model

Harvest of the central one-third of the patella tendon (PT) is routinely performed for anterior cruciate ligament reconstruction (ACLR). Patella infera may ensue. In this study we unilaterally resected the central one-third of the PT in 20 sheep, without reconstructing or defunctionalizing the native ACL, and examined the effects at 3, 6, 12, and 24 weeks postoperatively on PT length, histological appearance of the donor defect and in vitro stifle joint kinematics. Mean length increases (p > 0.263) in the operated tendons of 0.3%, 2.8%, 0.5%, and 2.4% were observed at 3, 6, 12, and 24 weeks. A significant proximal shift of the patella correlated well with a mean 2.35° retardation of patellar flexion (r = 0.440, p = 0.001). A mean net 4.9° decrease in medial patellar tilt was also observed (p < 0.001), but was not coupled with changes in tibial rotation. Donor defect tissue showed a distinct progression of healing with time, remodeling from dense scar tissue at 3 weeks to bundles of well-organized collagen enveloped by vascularized loose connective tissue at 24 weeks but was not associated with the restoration of kinematics. These results suggest that resection of the central one-third of the PT and leaving the defect open in the ovine stifle joint may be associated with increased PT length and changes in patellar kinematics which do not recover 6 months postoperatively. The lack of patella infera may render this animal model unsuitable for the interpretation of joint kinematics following PT resection for human ACLR.

Severity of patellar luxation and frequency of concomitant cranial cruciate ligament rupture in dogs: 162 cases (2004-2007)

OBJECTIVE

To evaluate severity of medial patellar luxation (MPL) and frequency of concomitant cranial cruciate ligament rupture (CCLR) in dogs.

DESIGN

Retrospective case series.

ANIMALS

162 dogs (266 stifle joints).

PROCEDURES

Medical records of 162 small-breed dogs with MPL were reviewed. Signalment, body weight, luxation grade, bilateral or unilateral MPL, CCLR, and difference in luxation grades between stifle joints were evaluated. Association between severity of MPL and CCLR was investigated.

RESULTS

58 dogs had unilateral MPL, and 104 dogs had bilateral MPL. Dogs ranged from 8.4 months to 16.7 years of age (mean, 5.7 years), and mean body weight was 5.45 kg (12 lb). Forty-one percent of all dogs had concomitant CCLR. Mean age for dogs with MPL alone was 3.0 years, which differed significantly from mean age of dogs with MPL and concomitant CCLR (7.8 years). Dogs with grade IV MPL were significantly more likely to have concomitant CCLR than were dogs with any other grade of MPL. In dogs with bilateral MPL and unilateral CCLR, there was a significantly higher grade of luxation in the stifle joint with CCLR.

CONCLUSIONS AND CLINICAL RELEVANCE

Small-breed dogs with MPL and concomitant CCLR were older than were dogs with only MPL. Dogs with grade IV MPL were more likely to have CCLR than were dogs with other grades of MPL. Most dogs with concomitant CCLR had a higher MPL grade in the affected stifle joint than in the intact joint. These findings should be beneficial in client education and clinical diagnosis.

Sensate scaffolds can reliably detect joint loading

Treatment of cartilage defects is essential to the prevention of osteoarthritis. Scaffold-based cartilage tissue engineering shows promise as a viable technique to treat focal defects. Added functionality can be achieved by incorporating strain gauges into scaffolds, thereby providing a real-time diagnostic measurement of joint loading. Strain-gauged scaffolds were placed into the medial femoral condyles of 14 adult canine knees and benchtop tested. Loads between 75 and 130 N were applied to the stifle joints at 30 degrees, 50 degrees, and 70 degrees of flexion. Strain-gauged scaffolds were able to reliably assess joint loading at all applied flexion angles and loads. Pressure sensitive films were used to determine joint surface pressures during loading and to assess the effect of scaffold placement on joint pressures. A comparison of peak pressures in control knees and joints with implanted scaffolds, as well as a comparison of pressures before and after scaffold placement, showed that strain-gauged scaffold implantation did not significantly alter joint pressures. Future studies could possibly use strain-gauged scaffolds to clinically establish normal joint loads and to determine loads that are damaging to both healthy and tissue-engineered cartilage. Strain-gauged scaffolds may significantly aid the development of a functional engineered cartilage tissue substitute as well as provide insight into the native environment of cartilage.