Reconstruction of Patellar Tendon With Achilles’ Tendon Allograft for Patella Baja After Infected Anterior Cruciate Ligament Repair

Abstract

Patella baja in patients presents with limited range of motion, pain in the patellofemoral joint, and decreased functionality of the knee. Patella baja can be a result of previous surgeries due to an alteration in the knee anatomy, infection, and adhesions, and it is usually accompanied by robust scarring. Possible surgical treatments of patella baja include arthroscopic debridement of adhesions, patellar tendon lengthening, excision of the inferior pole of the patella, and patellar tendon reconstruction using autografts or allografts. This Technical Note describes a technique for patellar tendon reconstruction in the setting of patella baja using an Achilles’ tendon allograft after an infected prior anterior cruciate ligament repair.

Patella baja is often described as a postoperative complication secondary to a change in native knee anatomy, especially scarring and contracture, which may restrict knee motion and be a cause of limited range of motion (ROM), instability, pain, weakness, and an extensor lag in a patient’s knee; this may subsequently cause a patient to have difficulty performing activities of daily living, including ambulation and squatting.¹ Diagnosis is often made with a Caton-Deschamps Index <0.6 or a Caton-Deschamps Index that is 10% to 15% lower than the patient’s contralateral knee.^1,2 Further scar can also form as a result of infection in the knee. These processes may cause a decrease in patella tendon length and, consequently, a decrease in patella height, leading to weakness in the extensor mechanism.³ Patella baja also influences the ability for the patella to engage the trochlea, which may cause impingement and contribute to a patient’s pain, dysfunction, and, sometimes, an extensor lag.⁴ Moreso, it may predispose patients to accelerated degenerative changes in the patellofemoral compartment.⁵

Once nonoperative treatments of patella baja are exhausted, surgical management is often indicated, including patellar tendon lengthening, patellar tendon reconstruction, arthroscopic lysis of adhesions with retinacular lengthening, removal of the distal third of the patella, or, lastly, patellectomy.¹ It has been noted that Achilles’ tendon allografts are especially effective in patellar tendon reconstruction as they provide mechanical strength and allow host tissue to eventually grow into the network of fibers laid by the allograft.⁶ In this Technical Note, we describe our technique for patellar tendon reconstruction with Achilles’ tendon allograft for patella baja after infected anterior cruciate ligament (ACL) repair.

Surgical Technique

Patient Evaluation and Indications

Patellar tendon reconstruction is indicated in patients with patella baja who have had unsuccessful conservative treatment and/or surgical intervention and have persistent symptoms, such as a decreased ROM after extensive lysis of adhesions following an infected ACL repair, as seen in this case (Video 1). The infection from prior surgery was eradicated prior to allograft reconstruction. Preoperative x-rays are shown in Figure 1.

Fig 1.

Preoperative imaging. Preoperative x-rays show a right knee with patellar baja and a previous anterior cruciate ligament repair in the anteroposterior (A) and lateral (B) views.

Patient Positioning and Anesthesia

A preoperative nerve block and general anesthetic are administered. The patient is positioned in a supine position with a post for knee arthroscopy with a tourniquet on the thigh. The operative knee is prepped and draped in a standard sterile orthopaedic fashion, typical weight-based antibiotics are given, and a surgical time-out is performed. An examination under anesthesia is performed to assess ROM, stability to varus/valgus stress, Lachman’s test, and posterior drawer test.

Diagnostic Arthroscopy

Two portals are placed anteromedially and anterolaterally in a standard fashion using a No. 11 blade to prepare for diagnostic arthroscopy. Intraoperative synovial samples are taken and sent for culture due to the patient’s previous diagnosis of Cutibacterium acnes. Arthroscopic evaluation is typically performed; however, we are unable to due to an immediate encounter of a thick anterior scar with loss of the anterior interval and significant stiffness.

Open Debridement of Contracted Patellar Tendon Fascia and Bone

An anterior midline incision is made, and the skin and subcutaneous tissue are excised. Full-thickness medial and lateral flaps are created to expose the extensor mechanism (Fig 2). The medial and lateral borders of the scar tissue and patellar tendon are defined from the tibial tubercle to the patella. This is done to accommodate the Achilles’ allograft bone plug into the tibia. Alternatively, the patella tendon can be excised from the patella and a soft tissue allograft utilized. After deeming the patellar tendon to be of insufficient length and quality for a Z-plasty, it is tenotomized from the tibial tubercle, and the adjacent fascia and retinacular tissue are removed. An open release of the scarred tissue is performed to ensure adequate excursion of the quadriceps. Once there is adequate debridement to nearby native tissues, 3 suture tapes are run down the length of the native patellar tendon, which are used to act as an internal brace in a locking Krakow fashion with a Scorpion (Arthrex) suture passer. Two vertical bone tunnels are created with a 3.5-mm drill from the inferior pole to the superior pole of the patella, and the sutures are shuttled through the bone tunnels.

Fig 2.

Measuring the patellar tendon. An intraoperative picture of a right knee is shown, with the orientation as labeled in the figure. Exposure of the extensor mechanism—quadriceps tendon (Q), patella (P), and patellar tendon (PT)—is performed. The tibial tubercle (TT) is also identified. The patellar tendon is measured and deemed insufficient for Z-plasty.

Bone Block Preparation

A 2-cm × 3-cm area on the anterior tibia, just distal to the tibial tubercle, is decorticated to accept the Achilles’ bone block allograft (Fig 3). A matching 2-cm × 3-cm area is cut into the allograft calcaneus with intact Achilles’ tendon and then placed into the trough made in the tibia.

Fig 3.

Preparing the tibia for bone block. An intraoperative picture of a right knee is shown, with the orientation as labeled in the figure. Distal to the tibial tubercle, a 2-cm × 3-cm area is decorticated into the anterior tibia (T), where the cadaver Achilles’ bone block allograft will be placed.

Open Patellar Tendon Reconstruction Achilles’ Tendon Allograft With Bone Block

The Achilles’ tendon bone block is secured in the tibia with 3 headless compression screws (Synthes) and evaluated for good fixation (Fig 4). Medially and laterally based suture tape through the footprint of the Achilles’ soft tissue is held via two 4.75-mm SwiveLock anchors (Arthrex) after tapping and drilling (Fig 5). These anchors are placed to provide additional fixation of the bone block in addition to the headless compression screws. Once tension is correctly achieved by adjusting the amount of overlap, the suture tapes are placed to laminate the patient’s native patellar tendon and Achilles’ allograft together, once more utilizing the Scorpion suture passer at the inferior pole of the patella. Two more SwiveLock anchors are placed medially and laterally in the inferior pole of the patella to house the sutures that re-laminated the native and allograft tendons. This construct is reinforced distally adjacent to the tibial tubercle with the suture tape into a single cortical button (Arthrex), just distal to the lateral SwiveLock that was placed in the bone block. This is laminated again with a running suture tape medially and laterally (Fig 6). Then, 10 cc of platelet-rich plasma, which was prepped preoperatively, is injected into the reconstruction to stimulate healing.

Fig 4.

Attachment of the Achilles’ bone block to the anterior tibia. An intraoperative picture of a right knee is shown, with the orientation as labeled in the figure. The allograft calcaneal bone block (A) is secured to the anterior tibia just distal to the tibial tubercle in the decorticated segment (T) with 3 headless compression screws (Synthes).

Fig 5.

Laminating the Achilles’ allograft with suture tape. An intraoperative picture of a right knee is shown, with the orientation as labeled in the figure. Suture tape on the medial and lateral sides through the footprint of the Achilles’ tendon (A) is held via 2 SwiveLock anchors (Arthrex) for additional fixation to the bone block. This picture also depicts the articular surface of the patella (P) with 2 bone tunnels from the inferior pole of the patella to the mid-upper portion of the patella created with a 3.5-mm drill that houses sutures from the internal brace and laminated native and allograft tissues. (F, femur.)

Fig 6.

Fixation of native patellar tendon reinforced with Achilles’ allograft for patellar tendon reconstruction. An intraoperative picture of a right knee is shown, with the orientation as labeled in the figure. The native patellar tendon and Achilles’ allograft (PTR) are laminated with suture tapes at the inferior pole of the patella (P). Two SwiveLock anchors (Arthrex) are placed medially and laterally in the inferior pole of the patella to house the sutures. For distal reinforcement, a suture with a cortical button is placed just distal to the lateral SwiveLock anchor. A running suture is placed to secure the lateral split Achilles’ allograft that is folded over to reinforce and add volume to the patellar tendon reconstruction.

Closure and Postoperative Rehabilitation Protocol

The retinaculum is left open to prevent constraining the reconstruction. The tourniquet is deflated, the incision is copiously irrigated, and 1 g of vancomycin powder is placed in the incision. A standard layered closure is performed with 0 Vicryl (Ethicon), 2-0 Vicryl (Ethicon), and 3-0 Monocryl (Ethicon).

Postoperative Protocol

Postoperatively, the patient is made toe-touch weightbearing for 6 weeks. A ROM brace is provided with the patient moving 0° to 15° for the first 2 weeks postoperatively. This will increase by 15° each week, with a goal of 90° of flexion by 6 weeks postoperatively. Crutches are discontinued at 6 weeks postoperatively. Progressive stretching, range of motion, and strengthening are increased over the next 6 to 12 weeks (12-18 weeks postoperatively). Activities may be slowly increased and added around 4 to 5 months after surgery. Postoperative x-rays are shown in Figure 7.

Fig 7.

Postoperative imaging. Postoperative x-rays show a right knee following patellar reconstruction with an Achilles’ allograft in the anteroposterior (A) and lateral (B) views. This postoperative x-ray shows reconstruction with 2 headless compression screws (Synthes) instead of 3, as described in the technique.

Discussion

Patella baja is a challenging condition to treat, causing significant stiffness, pain, and restricted range of motion. It is especially important to treat this condition as it not only presents with persistent symptoms but also leads to increased risk of later pathology. In a cadaveric model, Yang et al.⁵ showed that patella baja increased contact pressures in early knee flexion, which may accelerate degenerative changes in the joint.

Most studies focus on treatments of the conditions following arthroplasty and trauma, including the use of tibial tubercle osteotomies and Z-plasties.7, 8, 9 Use of allografts has been described as well. Kyriakidis et al.¹⁰ showed significant improvements in ROM, extension lag, and patient-reported outcomes after using Achilles’ tendon allograft for the treatment of patellar tendon rupture in patients with infected total knee arthroplasty. Moreover, a recent systematic review found that Achilles’ tendon allografts were a reliable treatment option for extensor mechanism reconstruction in total knee arthroplasty, with substantial improvements in ROM, good clinical outcomes, and low failure rates.⁶

Limited studies exist regarding patellar reconstruction in nonarthroplasty knees. Several treatment options may be used for this situation, including hamstring autograft, bone–patellar tendon–bone allograft or autograft, or Achilles’ allograft, which have high efficacy for improved ROM and restoration of the extensor mechanism.^1,10,11 While associated with an increased cost, the use of allografts is especially useful and indicated in patients with limited native tissue and tissue of poor quality.¹² The Achilles’ tendon is an especially good option for these situations. A study by Karas and colleagues² showed excellent ROM, strength, and improvement in pain and patient-reported outcomes at a mean 52-month follow-up when utilizing an Achilles’ or whole bone–tendon–bone allograft for the treatment of extensor mechanism injuries; however, it was noted that 5 patients had residual extensor lag, with an average of 8° in these patients. Similarly, a case study of 2 patients found that use of both an Achilles’ tendon allograft and a semitendinosus autograft for the treatment of patellar tendon rupture was able to adequately restore knee motion, and patients were able to return to daily activities.¹² Hence, patellar tendon reconstruction with the use of Achilles’ tendon allograft and bone block has been assessed as a viable treatment option for extensor mechanism failure and patella baja, and we describe this technique as a treatment option for patella baja in the context of an infected ACL repair. (Tables 1 and 2).

Table 1.

Pearls and Pitfalls

Pearls	Pitfalls
Use of allograft allows significant collagen volume autograft harvest for large defects not bridgeable with Z-lengthening.	Inadequate fixation of reconstruction due to poor bone quality and native tissues. Use multiple fixation techniques, including compression screws and suture bridges.
Must consider soft tissue balance with continual assessment of intraoperative range of motion with each step of reconstruction.	If soft tissue balance is not carefully considered, surgery can create more scarring and adhesions, which may lead to recurrent patella baja.
Redundancy of reconstruction components is necessary, with high rates of failure possible with these operations.
Create fixation that can be trusted with early, progressive range of motion to prevent additional recurrent adhesions and stiffness.

Table 2.

Advantages and Disadvantages

Advantages	Disadvantages
Avoids donor site morbidity, especially beneficial in patients with multiple ligamentous knee injuries, prior surgeries, or local tissue infection	Increased complication rate including infection, graft failure, and persistent patella baja
Provides added mechanical strength when host tissue is of poor quality or extensively damaged, allowing for strength and range of motion to improve postoperatively, as outlined in various systematic reviews	Additional cost and technical demands of allograft procedures, including bone block preparation
Allows a structural base where host tissue can grow into, when minimal healthy tissue is available
Appropriate for complex cases with multiple prior surgeries and failed attempts at previous repair/autograft and/or poor quality/limited host tissue remains

Disclosures

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: M.T.P. is a consultant or advisor for Arthrex, Arthrosurface, Anika Therapeutics, and JRF Ortho; has received travel reimbursement from Arthrex; has received funding grants from Arthrex, US Department of Defense, and National Institutes of Health; is a board member of the Arthroscopy Association of North America, American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, American Shoulder and Elbow Surgeons, San Diego Shoulder Institute, and Society of Military Orthopaedic Surgeons; and is an Editorial Board Member for Arthroscopy. All other authors (I.A.B., F.A.U., N.J.D., M.M., J.S., R.F.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

Video demonstration of a right knee reconstruction of the patellar tendon with Achilles’ tendon allograft for patella baja after infected anterior cruciate ligament repair.