Modified Z-plasty of the Patellar Ligament with Reinforcement of the Quadriceps Tendon in the Treatment of Patella Baja

Patella baja is an infrequent knee pathology, but it is limiting due to joint stiffness and localized pain in the anterior region of the knee. It may occur after trauma, prolonged immobilization or local surgical intervention. The striking pathological finding is the shortening and increase in thickness of the patellar ligament. Several surgical techniques have been described for its treatment, and there is no standardized treatment. We describe the case of a 73-year-old female patient who presented with knee stiffness, significant functional deficit, and patella baja after total knee arthroplasty. She underwent a recently described soft tissue surgical procedure, with excellent functional evolution, improving from a Lysholm Knee Score of 16 to 81 points, allowing early mobilization and return to daily life activities.


Case Report
A 73-year-old patient presented with knee stiffness with flexion deficit and, radiologically, patella baja after total arthroplasty of the right knee.The functional limitation, according to the Lysholm Knee Score, was 16 points, with a maximum flexion of 45°, pain and weakness of the extensor apparatus, being resistant to conservative treatment.Initially, the Caton-Deschamps index was 0.49 (►Fig. 1).

Surgical Technique and Rehabilitation
The patient underwent a combined surgical procedure of patellar ligament repair for lengthening and reinforcement with part of the quadriceps tendon.The polyethylene on the upper articular surface of the tibia was replaced with a thinner one, and the patellar component was removed.
As the patellar ligament thickened, the technique involved dividing the ligament in its thickness, obtaining an anterior and a posterior component of equal thickness. 6The anterior component was detached, distally, at the level of the anterior tibial tuberosity, and the posterior component, proximally, at the level of the patella 6 (►Fig.2).With the knee at 90°of flexion, the two ligament ends were fixed with at least 5mm of overlap with absorbable suture 6 (►Figs.3 and 4).A bundle of the superficial quadriceps tendon, approximately 1cm wide and 10cm long, was isolated (►Fig.5) and mobilized distally to reinforce the patellar ligament 6 (►Fig.6).Quadriceps excision site was reinforced with absorbable sutures, presenting low morbidity. 6uring the first month, immediate mobilization and rehabilitation treatment were necessary to strengthen the quadriceps and prevent relapse of the patella baja, being  limited to partial load and maximum flexion of 45°. 6,9uscle strengthening and joint rehabilitation was maintained with the support of physical medicine and rehabilitation for three months.At six months of follow-up, the functional results were excellent, with functional results of Lysholm Knee Score of 81 points, maximum flexion of 110°a nd Caton-Deschamps index of 1.17 (►Fig.7).The patient resumed her daily activities after the first month after the surgery.

Discussion
5][6][7]9 Modified Z-plasty has the advantages of obtaining greater elongation and maintenance of alignment of tendon fibers,   keeping the vector of forces and blood vascularization unaltered. 6Other advantages of this surgical technique are the prevention of subcutaneous and tendon defects, which leads to a lower risk of complications and early rehabilitation. 6[3][4][5][6][7][8][9][10] There are several surgical techniques for the treatment of patella baja, however there is no standard treatment.The surgical technique presented has the advantages of approach-ing the underlying pathology, ease of execution and reproducibility, mobilization, recovery and return to daily activities after the first month after surgery, as described in the case presented.

Financial Support
This study received no financial support from public, commercial, or non-profit sources.

Fig. 1
Fig. 1 Lateral radiograph of the knee showing the preoperative Caton-Deschamps index 0.49.

Fig. 2
Fig.2Scheme of the surgical procedure: patellar ligament was divided in two, according to its thickness.The anterior bundle (dark blue) was detached anteriorly at the level of the anterior tibial tuberosity, the posterior bundle (light blue) was detached at the level of the distal apex of the patella.Also note the acquisition of a bundle of the quadriceps tendon (gray).(1-Quadriceps Tendon; 2-Patella; 3-Patellar Ligament).

Fig. 3 Fig. 4
Fig. 3 Scheme of the surgical procedure: suture of the two bundles of the patellar ligament (dark blue and light blue), with at least 5 mm of overlap.Note the ligament reinforcement with a quadriceps tendon bundle (dark grey).(1-Quadriceps Tendon; 2-Patella; 3-Patellar Ligament)

Fig. 5
Fig. 5 Intraoperative image demonstrating mobilization of the quadriceps tendon bundle.

Fig. 6
Fig. 6 Intraoperative image demonstrating reinforcement of the patellar ligament with a quadriceps tendon bundle.(yellow arrow)

Fig. 7
Fig. 7 Lateral radiograph of the knee showing a Caton-Deschamps index of 1.17 postoperatively.