Technique for Complete Extensor Mechanism Reconstruction Using a Fresh Quadriceps Tendon–Patella–Patellar Tendon–Tibial Tubercle Allograft in a Native Knee

Abstract

Chronic extensor mechanism injuries can cause severe functional impairment and require extensive surgical intervention. Current techniques involve reconstruction of the extensor mechanism using allograft, autograft, or synthetic mesh. This Technical Note describes an extensor mechanism reconstruction utilizing a fresh complete quadriceps tendon–patella–patellar tendon–tibial tubercle allograft for patients with chronic, recurring extensor mechanism injuries.

Extensor mechanism injuries can lead to significant functional impairment and disability. Trauma, including patella fracture, patellar tendon rupture, and quadriceps tendon rupture, is the most common cause of extensor mechanism injuries.^1,2 These injuries can also be found in patients following total knee arthroplasty.³

Current surgical techniques for extensor mechanism injuries include repair versus reconstruction, utilizing autografts, allografts, or synthetic mesh. Both repair, which is preferred for acute injuries, and reconstruction have shown high complication rates.⁴ Achilles tendon allograft has been the gold standard for extensor mechanism reconstruction in the chronic setting.5, 6, 7, 8 However, complication rates between autografts, allografts, and synthetic grafts in reconstruction have been shown recently to be comparable to each other.⁴

This Technical Note describes an extensor mechanism reconstruction, utilizing a fresh complete quadriceps tendon–patella–patellar tendon–tibial tubercle allograft in a patient with chronic, recurring extensor mechanism injuries. Modifications of this technique have been described in total knee arthroplasty with extensor mechanism disruption.⁹

Surgical Technique

Patient Positioning

The patient is placed supine on a standard operative table. Preoperative femoral and sciatic peripheral nerve blocks are performed under ultrasound guidance. General anesthesia is obtained, followed by an examination under anesthesia to assess patellar tracking and range of motion. An upper thigh tourniquet is placed with a thigh post and a bump at the end of the bed to allow the knee to be placed in 35° of flexion (Fig 1). Intraoperative fluoroscopy is placed on the contralateral side of the operative extremity to assess the Caton Deschamps Index (CDI) with a goal to match the contralateral extremity after surgical reconstruction (Table 1). A fresh allograft of the entire extensor mechanism, including a size-matched patella with patellar tendon, quadriceps tendon, and tibial tubercle, is used for reconstruction and thawed on the back table (Fig 2).

Fig 1.

Intraoperative image of the left knee. An upper thigh tourniquet (red arrow) is placed with a thigh post and a bump (white arrow) at the end of the bed to allow the knee to be placed in 35° of flexion.

Table 1.

Pearls and Pitfalls

Pearls

Pitfalls

1.Size-matching the patella allograft can optimize patellar tracking 2.Obtain preoperative CT and MRI scans to assess for trochlear dysplasia and/or osteochondral defects 3.Obtain preoperative fluoroscopic images of the normal, contralateral knee to assess baseline CDI 4.Before TTO, measure the allograft tibial tubercle according to length, width, and depth 5.Following patellectomy and before TTO, lay down the allograft over the affected knee and obtain fluoroscopic images to ensure proper patellar height as compared to the contralateral extremity 6.Preserve as much native quadriceps tendon as possible as a Pulvertaft weave of the allograft quadriceps tendon can improve graft incorporation 7.When placing sutures in the native quadriceps tendon, avoid placing Krackow sutures centrally as the allograft will be woven through the native tendon in this area

1.Use of a nonfresh, non-size-matched allograft could result in graft failure and/or patellar maltracking with pain 2.Failure to match or approximate the contralateral knee CDI can result in pain and/or patellar maltracking 3.Incorrectly sizing the tibial tubercle allograft bone block can put excess pressure on the skin and affect cosmesis 4.Failure to immobilize for 12 weeks in knee extension can result in tibial tubercle fracture and nonunion

CDI, Caton Deschamps Index; CT, computed tomography; MRI, magnetic resonance imaging; TTO, tibial tubercle osteotomy.

Fig 2.

Size-matched patellar allograft (red arrow) with patellar tendon, quadriceps tendon, and tibial tubercle is used for reconstruction and thawed on the back table.

Surgical Approach

The prior midline incision is used and extended 2 cm proximal to the quadriceps tendon and 2 cm distal to the tibial tubercle (Video 1). Skin flaps are elevated both medially and laterally, followed by complete patellectomy. The native tendon should be preserved as much as possible (Fig 3). Traction sutures of No. 5 FiberWire (Arthrex) are placed in the medial/lateral retinaculum and quadriceps tendon. A lysis of adhesions is performed proximal to the quadriceps tendon, both superficial and deep to the tendon, to mobilize the extensor mechanism. Following a gentle release of the medial and lateral gutters with electric cautery, we obtained full flexion and extension of the knee joint. The pretibial recess is then elucidated.

Fig 3.

Lateral view of left knee, proximal to the right of the image. The prior midline incision is used and extended 2 cm proximal to the quadriceps tendon and 2 cm distal to the tibial tubercle. Skin flaps are elevated both medially and laterally (white arrows), followed by complete patellectomy. The native tendon should be preserved as much as possible.

In Krackow fashion, 4 No. 5 FiberWire sutures are placed along the medial and lateral edges of the native quadriceps tendon (Fig 4). Space is reserved at the central aspect of the native quadriceps tendon to allow for later incorporation of the allograft quadriceps tendon (Table 1). A tibial tubercle slot osteotomy is then performed according to the length, width, and depth of the allograft tissue, which is tapered distally (Fig 5). The allograft tibial tubercle is press-fitted into the osteotomy slot. Under fluoroscopic guidance, patellar height and the position of the graft is confirmed, followed by placement of one 4.5-mm and two 3.5-mm cortical screws (Synthes). A FiberLoop (Arthrex) is then passed through the allograft quadriceps tendon (Fig 6).

Fig 4.

Lateral view of left knee, proximal to the right of the image. In Krackow fashion, 4 No. 5 FiberWire (Arthrex) sutures (black circles) are placed along the medial and lateral edges of the native quadriceps tendon.

Fig 5.

Lateral view of left knee, proximal to the right of the image. A tibial tubercle slot osteotomy (white arrow) is then performed according to the length, width, and depth of the allograft tissue, which is tapered distally.

Fig 6.

Lateral view of left knee, proximal to the right of the image. A FiberLoop (Arthrex) is then passed through the allograft quadriceps tendon (red arrow).

We reassess the patellar height of the operative extremity at 30° of knee flexion with the allograft patella in place. Any necessary traction is applied distally using previously placed traction stitches in the native quadriceps tendon to restore adequate patellar height. After matching the CDI of the contralateral extremity, a Pulvertaft weave of the allograft quadriceps tendon through the native quadriceps tendon is performed. Following Pulvertaft weave, the allograft quadriceps tendon is tenodesed onto itself as well as onto the native quadriceps tendon with No. 2 TigerWire sutures (Arthrex). Excess allograft tissue is removed.

Additional No. 5 FiberWire sutures are placed in the medial and lateral retinaculum and then secured to any remaining quadriceps allograft and tissue surrounding the patella allograft. Four No. 5 FiberWire sutures from the medial and lateral retinaculum are brought down in a crisscross fashion over the allograft patellar tendon and inserted into 2 SwiveLock anchors (Arthrex) just lateral and medial to the tibial tubercle slot (Fig 7). Any gaps between the retinaculum and allograft tissue are filled with No. 5 FiberWire, and 0-Vicryl (Ethicon) sutures are used to tack down the sutures overlying the tendon. Construct stability is assessed with knee flexion and extension. Knee hyperextension and 45° of flexion are achieved without any undue stress on the construct. Patellar height is confirmed with intraoperative fluoroscopy (Fig 8). The tourniquet is deflated, and wounds are copiously irrigated. One gram of vancomycin powder is placed in the wound, followed by a medium Hemovac drain deep to the vastus medialis. Subcutaneous tissues and skin are closed in standard fashion, followed by placement of a negative pressure wound vacuum dressing. The operative extremity is placed in a hinged knee brace and locked in full extension.

Fig 7.

Lateral view of left knee, proximal to the right of the image. Four No. 5 FiberWire (Arthrex) sutures from the medial and lateral retinaculum are brought down in a crisscross fashion over the allograft patellar tendon and inserted into 2 SwiveLock (Arthrex) anchors just lateral and medial to the tibial tubercle slot (white arrow).

Fig 8.

Intraoperative anteroposterior and lateral fluoroscopic views confirming patellar height (black circles).

Rehabilitation/Follow-Up

The patient is made strictly non-weightbearing, locked in full extension in a hinged knee brace for 8 weeks postoperatively. At 8 weeks, the patient begins gentle range of motion and may be full-weightbearing in the hinged knee brace. At 12 weeks, the brace is discontinued, and open-chain extension exercises are allowed. A biologic medication protocol for arthrofibrosis prophylaxis is given, including daily 75 mg indomethacin, 200 U intranasal calcitonin, and 100 mg losartan for 30 days postoperatively. Postoperative radiographs are obtained at 2, 6, and 12 weeks postoperatively (Fig 9), followed by a computed tomography scan to assess graft healing at 4 months postoperatively.

Fig 9.

Anteroposterior and lateral postoperative radiographs are obtained at 2, 6, and 12 weeks postoperatively, showing maintained patellar height (white circle) and intact hardware (red circle) with interval healing.

Discussion

In the setting of acute ruptures of the quadriceps or patellar tendon, primary repair is the preferred technique, with rerupture rates ranging from 2% to 50%.10, 11, 12 However, in revision scenarios for failed primary repairs, patella fracture nonunion, or chronic extensor mechanism injuries, the optimal technique for reconstruction is an ongoing investigation. Our technique using a fresh quadriceps tendon, size-matched patella, patellar tendon, and tibial tubercle allograft provides a method for reconstruction of extensor mechanism failure. Drexler et al.¹³ described a similar technique using an allograft patella, patellar tendon, and tibial tubercle to reconstruct a chronic extensor mechanism injury. Our technique differs through the use of a fresh, size-matched allograft patella with the addition of a quadriceps tendon. A size-matched fresh patella allograft provides an articular surface for proper patellar-trochlear tracking. The addition of the quadriceps tendon and patella tendon with tibial tubercle bone block provides additional tissue for graft healing, extensor mechanism function, and incorporation into the native tissue.

There are disadvantages associated with our technique, specifically related to complete patellectomy (Table 2). The downsides of a patellectomy include a decrease in the moment arm of the extensor mechanism, a loss of up to 30% of the quadriceps force for full extension that results in an extensor lag, and changes in the forces acting on the patellofemoral and tibiofemoral joints.^14,15 The goal of size-matching the patella and restoring the CDI compared to the contralateral extremity may combat these disadvantages associated with patellectomy. Patients should have a clear understanding of their anticipated postoperative course as arthrofibrosis is highly anticipated following this surgery. Patients should understand this is a salvage procedure, and a joint replacement may be required in the future.

Table 2.

Advantages and Disadvantages

Advantages	Disadvantages
1.A size-matched patella allograft allows for a smooth cartilage surface for proper patellar tracking 2.A fresh allograft optimizes the chances for graft incorporation 3.Sutures placed in the native quadriceps tendon can be fixed distally in anchors adjacent to the tibial tubercle for additional points of fixation	1.High cost of a fresh entire extensor mechanism allograft 2.Patients must understand the importance of strict non-weightbearing with their knee locked in extension for 12 weeks 3.High risk of arthrofibrosis with limited revision surgical options following complete patellectomy

In general, complications of extensor mechanism reconstruction include arthrofibrosis, infection, donor site morbidity, failure, revision with conversion to arthroplasty, fusion, and amputation. In the arthroplasty literature, entire extensor mechanism allograft reconstruction has a failure rate as high as 33%, comparable to mesh reconstruction.¹⁶ In the native knee joint, options for reconstruction include a combination of allograft, autograft, or mesh with variable success rates.^17,18 Predictors of failure include younger age at the time of reconstruction and improper tensioning of the graft.¹⁹

Limitations of the study include short-term data and only 2 patients. Additionally, a fresh entire extensor mechanism allograft with a size-matched patella is not readily available on a global scale. Regardless, we believe this technique is reproducible and may be a viable salvage procedure in the setting of multiple failed extensor mechanism reconstructions or chronic patella fracture nonunion/malunion.

Disclosures

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: G.F.R.H. is a paid consultant and a paid presenter or speaker for Arthrex. All other authors (A.P.D., E.H.L., C.L.F., P.S., A.A., W.L.) 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

Complete extensor mechanism reconstruction using a quadriceps tendon–patella–patellar tendon–tibial tubercle allograft.