Medial patellofemoral ligament is a part of the vastus medialis obliquus and vastus intermedius aponeuroses attaching to the medial epicondyle

PURPOSE

This study aimed to investigate the bony surface characteristic of the femoral attachment of the medial patellofemoral ligament (MPFL) and the correlation between the relevant layered structures, including muscular aponeurosis and the joint capsule, which contribute to patellofemoral joint (PFJ) stability.

METHODS

The morphology of the medial aspect of the medial condyle using micro-computed tomography and analysed cortical bone thickening in 24 knees was observed. For the macroscopic and histological analyses, 21 and 3 knees were allocated, respectively. The Kruskal-Wallis one-way analysis of variance test with Dunn post hoc testing was performed for statistical analysis.

RESULTS

At the level of the adductor tubercle, there were no significant differences in cortical bone thickness. At the level of the medial epicondyle (MEC), cortical bone thickness was considerably greater than that in other areas of the medial condyle (mean ± standard deviation, 0.60 ± 0.20 mm; p < 0.0001). Macroscopic analysis revealed that the deep aponeurosis of the vastus medialis obliquus and the tendinous arch of the vastus intermedius distally formed the composite membrane and adjoined to the joint capsule to firmly attach to MEC, which was located at 41.3 ± 5.7 mm posterior and 14.2 ± 3.1 mm superior to the joint cartilage. Histological analysis showed a composite membrane and adjoining capsule attached to MEC via fibrocartilage.

CONCLUSION

MPFL could be interpreted as part of the deep aponeurosis of the vastus medialis obliquus (VMO) and the tendinous arch of the vastus intermedius, which combined with the joint capsule to attach to MEC. The cortical bone thickening indicated that the tensile stresses were loaded on MEC in aged cadavers. Involvement of VMO and vastus intermedius aponeuroses in restored graft of MPFL could utilise the dynamic stability of surrounding muscles to mimic a native structure.

Joint line reestablishment in revision total knee arthroplasty

Background

In this study, the traditional “Anatomical Landmark-Distance Method (AL-DM)” in the formation of joint line (JL) was compared with “Adductor Tubercle-Ratios method” (AT-RM), and the effect of reestablishment of JL on clinical and functional outcomes were evaluated.

Materials and methods

16 revision total knee arthroplasties (rTKAs) were performed by using “AT-RM” (group 1) and 16 rTKA by using “AL-DM” (group 2) in our clinic between 2015 and 2018. The data were prospectively collected and a total of 32 knees of 31 patients were analyzed. At the final follow-up, knee functions were evaluated by using Knee Society Score (KSS) knee and function, Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, Short Form-36 (SF-36) questionnaires and physical examinations.

Results

Postoperative flexion arc was higher in Group 1. KSS knee and function scores were better in group 1. In group1, JL was reestablished successfully in all revision rTKAs in terms of ATJL and the tibial tubercle TT-JL ratios. The improvement in KSS knee and function scores and WOMAC scores were also better in group 1. Measurements showed that the improvement in KSS scores increased as AT-JL and TT-JL distances approached the calculated values.

Conclusion

“AT-RM” was shown to be superior to the traditional distance method in terms of JL reestablishment. Functional results and patient satisfaction increased when JL was reestablished.

The adductor tubercle can be a radiographic landmark for joint line position determination: an anatomic-radiographic correlation study

Background

The adductor tubercle (AT) has been used intraoperatively as a landmark to evaluate the joint line position in knee arthroplasty. The purpose of this study was to determine whether the AT could be clearly identified on radiographic imaging as well as if the AT to joint line distance could be accurately measured for use as a radiographic landmark.

Methods

The distance from the AT to the joint line was measured on each of 78 knees during total knee arthroplasty. Next, the AT was marked with a metal marker for radiographic analysis. On the postoperative radiograph, the location of the AT was determined by tracing the metal marker. Subsequently, the radiographic joint line distance (RJLD) was measured and compared with the intraoperative joint line distance (IJLD) to test the agreement of the measurements.

Results

Location analysis indicated that the inflection point on the radiographic contour of the distal femur was the predicted location for the AT. The mean IJLD was 45 ± 3 mm and the RJLD was 45 ± 4 mm. The intraclass correlation coefficient was used to evaluate the inter-rater reliability between the two methods; that coefficient was 0.751, indicating good agreement between them. Measurements on the radiograph were comparable to the intraoperative measurements of the operated knees.

Conclusions

In addition to being an intraoperative landmark, the AT may also be an eligible radiographic landmark for analyzing joint line level. The RJLD measurement may be obtained to plan the joint line position in knees with significant bone loss preoperatively and to follow up the results of surgery postoperatively.

An unambiguous technique for locating the adductor tubercle and using it to identify the joint line

BACKGROUND

If the adductor tubercle could be accurately located, it would be a useful landmark for identifying the joint line during knee arthroplasty. This study aimed to develop an intraoperative technique to improve its locating accuracy.

METHODS

Evaluation of bone specimens and cadaveric knees revealed that the proximal slope of the adductor tubercle (PSAT) turns from the medial surface vertically into the superior surface of the medial condyle, which forms a distinctive edge. This provided an ideal landmark that could be unambiguously engaged using a tipped instrument. Using the PSAT as a reference point, we measured the distance to the joint line (the proximal-distal condylar length; PDCL) in eight pairs of cadaveric knees, and evaluated the inter-observer variability. Next, we measured 120 knees undergoing total knee arthroplasty to test this technique in a normal population. Finally, we divided each PDCL by the respective anterior-posterior condylar length (APCL) to create a ratio that could predict the PDCL regardless of knee size.

RESULTS

The intra-class correlation coefficient (ICC) was 0.86 for the cadaveric measurements. The mean PDCL from the operated knees was 46mm (coefficient of variance (CV): eight percent). The mean PDCL/APCL ratio was 0.77 (CV: six percent). The high ICC and low CV indicated that using the PSAT was a reliable technique.

CONCLUSION

The PSAT is an ideal surgical landmark. The tipped instrument engagement technique with it may help to unambiguously locate the adductor tubercle in order to identify the joint line during knee arthroplasty.

The adductor tubercle: an important landmark to determine the joint line level in revision total knee arthroplasty

PURPOSE

The restoration of the physiological femoro-tibial joint line (JL) is important to obtain a good outcome in revision total knee arthroplasty (RTKA). However, its assessment is challenging. The ratio of the distance between the adductor tubercle (AT) JL (ATJL) and the trans-epicondylar femoral width (FW) was proposed as a reliable method. The purpose of this study was to check whether this ratio is a reliable tool to restore the prosthetic JL height in challenging prosthetic revision cases.

METHODS

Twenty-one patients (mean age 65.8 years) were recruited. During surgery, FW was measured and ATJL distance was calculated using 0.53 (SD 0.03) as the ratio. After implant positioning, the obtained ATJL line was measured to verify the accuracy of the surgical procedure. Thirteen patients presented a healthy contralateral knee: a comparative radiograph examination was performed to verify the appropriateness of the restored JL height.

RESULTS

The intra-operatively calculated ATJL was not significantly different with respect to the measured ATJL obtained after prosthetic component implantation. The comparative analysis between the restored JL and the JL of the contralateral not operated knee was also not statistically significant, thus confirming the appropriateness of the restored JL height.

CONCLUSIONS

This study shows that the method which uses an AT to JL distance/FW ratio to determine the JL level, previously applied in primary TKA, is valid when using intra-operatively acquired measurements in RTKA. This is clinically relevant since it represents a reliable tool which helps surgeons to restore the JL level in challenging prosthetic revision cases.

LEVEL OF EVIDENCE

Case series, Level IV.

Joint line restoration during revision total knee arthroplasty: an accurate and reliable method

During revision total knee arthroplasty, the joint line is frequently malpositioned, due to the disappearance of the anatomical landmarks following previous interventions. This leads to decreased clinical outcome and increased risk of re-intervention. Many methods have been proposed to restore the joint line, but none of them has shown itself to be reliable. We describe an accurate and precise method to localize the exact position of the joint line which guarantees a better clinical knee score. The adductor tubercle (AT) is recognized to be the most reliable landmark used to localize the knee joint line (JL). The distance from the AT to the JL on antero-posterior radiographs (ATJL) and the femoral diameter (FD) on true lateral views were measured on 200 randomly selected normal knees. These measurements were tested for intra- and inter-observer differences. Then, the relationship between these two measurements was studied. A significant correlation and linear regression between FD and ATJL was found (p < 0.001), making the adductor tubercle a valid landmark to accurately position the prosthetic joint within 4 mm from the normal position. No significant difference was noted in the intra and inter-observer measurements (F test not significant). Sex was found to be an intervening variable (p ˂ 0.001). The correlation and regression between ATJL and FD had to be adjusted accordingly. Once the ATJL was determined preoperatively, the JL level is found during surgery by using a caliper that is held on the easily palpable AT. Knowing the femoral diameter, we can easily locate the joint line level surgically, using the adductor tubercle as a landmark. This method leads to better clinical outcomes and a reduced risk of re-intervention following revision total knee arthroplasty.