Anteromedialization Tibial Tubercle Osteotomy Improves Patellar Contact Forces: A Cadaveric Model of Patellofemoral Dysplasia

BACKGROUND

Patellofemoral (PF) dysplasia is common in patients with recurrent patellar instability. Tibial tubercle osteotomy (TTO) is performed with goals of correcting patellar maltracking and redistributing contact forces across the PF joint. The biomechanical effects of TTO in the setting of PF dysplasia have not been quantified.

PURPOSE/HYPOTHESIS

To quantify patellar contact mechanics and kinematics after TTO in the setting of PF dysplasia. We hypothesized that a simulated anteromedialization (AMZ) TTO would improve PF contact mechanics as compared with a pure medialization TTO.

STUDY DESIGN

Controlled laboratory study.

METHODS

PF dysplasia with Dejour type D classification was simulated in 7 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic polymeric patellar and trochlear implants. On each specimen, a flat TTO was fixed in 3 distinct positions simulating a pathologic lateralized tubercle (pathologic condition), a medialized tubercle (Elmslie Trillat), and an AMZ tubercle. The sum of forces acting on the medial and lateral patellar facet and patellar kinematics was computed for each knee for each condition from 0° to 70° of flexion at 10° increments.

RESULTS

Relative to the pathologic condition, AMZ TTO decreased contact forces across the lateral facet (20°-50° and 70° of flexion). Relative to the pathologic condition, Elmslie Trillat TTO had no effect on contact forces on either compartment. Relative to the Elmslie Trillat TTO, the AMZ TTO had significantly decreased contact forces across the medial facet (at 40°, 60°, and 70° of flexion). No significant differences in joint kinematics occurred across any groups.

CONCLUSION

Of all groups studied, AMZ TTO resulted in significantly decreased patellar contact forces in simulated dysplastic PF joints. AMZ may be considered in certain patients with PF dysplasia to avoid medial compartment PF chondral overload.

CLINICAL RELEVANCE

PF dysplasia is common in patients with recurrent patellar instability who warrant surgical intervention to prevent subsequent recurrence. Numerous interventions to treat this condition, including various TTOs, have been proposed without a clear consensus. This cadaveric biomechanical study demonstrates that AMZ TTO resulted in more favorable PF contact mechanics than Elmslie Trillat TTO in a model representing PF dysplasia. AMZ TTO may be considered for patients in the setting of recurrent instability with PF dysplasia to avoid cartilage overload on the medial compartment of the PF joint.

[Functional results in isolated patellofemoral arthrosis treated by arthroscopy plus Fulkerson osteotomy vs patellofemoral arthroplasty]

OBJECTIVE

To Compare the clinical outcomes of patellofemoral arthroplasty and Fulkerson osteotomy.

MATERIAL AND METHODS

32 patients with the diagnosis of isolated patellofemoral arthrosis were treated, 16 patients with patellofemoral Arthroplasty and 16 patients with Fulkerson type osteotomy. Being a non-probabilistic sample of convenience and quota with random allocation. The indications for surgery were osteoarthritis patellofemoral grade III-IV of the classification Kellgren-Lawrence, treated with pharmacological therapy and physical rehabilitation without improvement of the symptomatology. Clinical evaluations were performed prior to surgical procedure at six months, one year and two years. With the questionnaires of Japanese Knee Injury and Osteoarthritis Outcome Score, Lysholm Knee Score and analogue visual scale.

RESULTS

Significant improvement was found in both groups The pain component improved significantly in both groups at six months, one year and at two years (p 0.001 for both), daily activities (p = 0.001), sports (p = 0.001). The quality of life improved (p = 0.001). correlation between one-year follow-up score in the group of patients treated with patellofemoral arthroplasty on the Lysholm scale and the KOOS pain subscale (R2 = 0.8508). A moderate correlation in pain and sport dimensions on the KOOS scale (R2 = 0.783).

DISCUSSION

In our study group, patellofemoral arthroplasty exhibits better function as well as a decrease in pain compared to arthroscopy and Fulkersons osteotomy at all stages of follow-up.

Tibial tubercle osteotomy: A biomechanical comparison of two techniques

PURPOSE

The purpose of this study was to determine whether a modified step-cut tibial tubercle osteotomy (Maquet-Fulkerson hybrid) might produce comparable or better results than a standard oblique anteromedialization tibial tubercle osteotomy (Fulkerson type) and thus warrant the surgical need for additional cuts.

METHODS

Six pairs of cadaveric knees were evaluated prior to and after tibial tubercle osteotomies. Simulation was done via a shallow knee bend simulator through 20 to 70° of knee flexion for the intact specimens and following the surgical procedures. The variables tested were trochlear contact forces and pressures and patellar motion.

RESULTS

Testing showed a decreased force (P=0.027), peak contact pressure (P=0.01) and contact area (P=0.034) on the lateral trochlea of the femur for both types of osteotomies. There was no significant difference in the lateral femoral peak pressure or in the medial femoral peak pressure between the oblique cut and the step-cut. Also, there was no difference in patellar motion after either procedure.

CONCLUSION

We conclude that both osteotomies decrease lateral patellofemoral trochlear pressure. The oblique osteotomy may decrease lateral pressure to a greater extent. Regarding biomechanical testing, there was no demonstrable advantage to performing a step-cut osteotomy.

The modified tibial tubercle osteotomy for anterior knee pain due to chondromalacia patellae in adults: A five-year prospective study

OBJECTIVES

To assess the effectiveness of a modified tibial tubercle osteotomy as a treatment for arthroscopically diagnosed chondromalacia patellae.

METHODS

A total of 47 consecutive patients (51 knees) with arthroscopically proven chondromalacia, who had failed conservative management, underwent a modified Fulkerson tibial tubercle osteotomy. The mean age was 34.4 years (19.6 to 52.2). Pre-operatively, none of the patients exhibited signs of patellar maltracking or instability in association with their anterior knee pain. The minimum follow-up for the study was five years (mean 72.6 months (62 to 118)), with only one patient lost to follow-up.

RESULTS

A total of 50 knees were reviewed. At final follow-up, the Kujala knee score improved from 39.2 (12 to 63) pre-operatively to 57.7 (16 to 89) post-operatively (p < 0.001). The visual analogue pain score improved from 7.8 (4 to 10) pre-operatively to 5.0 (0 to 10) post-operatively. Overall patient satisfaction with good or excellent results was 72%. Patients with the lowest pre-operative Kujala score benefitted the most. Older patients benefited less than younger ones. The outcome was independent of the grade of chondromalacia. Six patients required screw removal. There were no major complications.

CONCLUSIONS

We conclude that this modification of the Fulkerson procedure is a safe and useful operation to treat anterior knee pain in well aligned patellofemoral joints due to chondromalacia patellae in adults, when conservative measures have failed.