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An 81-year-old woman with right knee pain

Issue: February 2014

ByAndrew R. Hsu, MD

ByMarc A. Zussman, MD

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Sanjeev Bhatia

 

Andrew R. Hsu

An 81-year-old woman who was a baseline community ambulator without an assistive device was brought into the emergency room after being in a motor vehicle accident. The patient complained of diffuse right knee pain with ecchymosis, swelling and discomfort with active or passive range of motion. The patient’s medical history was significant for chronic obstructive pulmonary disease.

The patient had moderate knee effusion and no open lesions or lacerations in the soft compartments of the right thigh and lower leg. Motor and sensation was grossly intact throughout the right lower extremity with palpable posterior tibial and dorsalis pedis pulses. Ligamentous exam was stable, but limited due to pain and patient compliance. She was placed in a well-padded knee immobilizer and made non-weight-bearing with strict elevation and ice to the right knee to help decrease swelling.

Figures 1a and 1b. Preoperative AP (a) and lateral radiographs (b) of the right knee demonstrate a lateral tibial plateau split-depressed fracture.

Images: Hsu AR and Zussman MA

Anteroposterior (AP) and lateral radiographs of the right knee demonstrated a split-depressed fracture of the lateral tibial plateau consistent with a Schatzker II fracture pattern (Figure 1). There was evidence of mild osteopenia and degenerative joint disease. A CT of the knee was obtained to further evaluate the fracture pattern and showed a minimally displaced split fracture with an associated >1 cm depressed area of the lateral tibial plateau with comminution of the articular surface (Figure 2).

Figures 2a, 2b and 2c. Preoperative coronal (a), sagittal (b) and axial CT scan cuts (c) further delineate the degree of articular incongruity and comminution of the lateral tibial plateau articular surface.

What is your management?

See answer on next page.

Open reduction and internal fixation with grafting

Tibial plateau fractures are common injuries in young patients due to high-energy trauma and in elderly patients due to low-energy falls, most commonly affecting the lateral articular surface. The lateral tibial plateau is convex in shape and located proximal to the medial plateau. The osteology of the lateral tibial plateau contributes to the increased incidence of lateral meniscus tears in the setting of lateral split-depressed fractures.

Marc A. Zussman

Key aspects of the physical exam include circumferential inspection of the extremity to rule out open or concominant injury, serial compartment checks, ligamentous stress testing of the knee and a thorough neurovascular exam with ankle-brachial index (ABI) if needed. Recommended imaging includes AP, lateral and oblique radiographs of the knee with an optional 10° caudal tilt view to better visualize the plateau articular surface. It is important to note any posteromedial fracture lines as this will affect surgical planning and fixation techniques. Medial plateau fractures are high-energy in nature and can often be associated with an unrecognized knee dislocation. Therefore, careful attention must be paid to ligamentous testing, ABIs and possible further vascular studies. Advanced imaging with CT can better identify articular incongruity and comminution, and MRI can be employed if meniscal or ligamentous pathology is suspected.

Treatment options

Nonoperative management consisting of a hinged knee brace, partial weight-bearing for 8 weeks to 12 weeks and early passive range of motion can be used for minimally displaced split or depressed fractures, stable low-energy fractures or nonambulatory patients. Spanning external fixation with pins in the distal femur and middle to distal tibia can initially be used in cases of significant soft tissue injury, polytrauma, fracture shortening and comminution, and open fractures. Open reduction and internal fixation (ORIF) is generally indicated for fractures with articular displacement >3 mm, condylar widening >5 mm, knee instability, and for medial and bicondylar fractures. Restoration of joint stability is the strongest predictor of long-term clinical success, and inferior results have been found in cases of ligamentous instability, meniscectomy and altered limb mechanical axis >5°. Malalignment of the mechanical axis by >5° has been found to triple the rate of degenerative osteoarthritis (27% malaligned vs. 9% well-aligned), and worse outcomes have been reported with increasing age at time of injury.

ORIF can be performed using a lateral and/or posteromedial incision depending on fracture pattern. The articular surface is restored with direct visualization and/or indirect reduction using fluoroscopy. The metaphyseal bone void can be filled with a variety of grafts including autogenous iliac crest, allograft chips, demineralized bone matrix (DBM), structural allograft (i.e., fibula cortical allograft) and calcium phosphate cement. Screws can be used alone for simple non-displaced split fractures with the addition of non-locked buttress plates or locked fixed-angle plates with subarticular rafting screws for definitive fixation of more complex fracture patterns.

Patients are made non-weight-bearing in a hinged knee brace or knee immobilizer for 6 weeks to 8 weeks with gentle early passive range of motion until evidence of fracture union is seen on radiographs. Weight-bearing status is advanced based on clinical exam and radiographic healing typically to partial weight-bearing (50%) at 8 weeks to 10 weeks and full weight-bearing at roughly 12 weeks. Progressive stretching and strengthening exercises should be instituted throughout the rehabilitation process. Treatment plans should be tailored individually to patients and potential complications should be discussed.

Management of our patient

In this case, significant articular communition and depressed fragments were key aspects that needed to be addressed using grafting to achieve anatomic reduction and prevent articular subsidence. The patient was counseled about the risks and benefits of nonoperative and operative treatment, and informed consent was obtained for ORIF. The patient was positioned supine on a radiolucent table with a bump under the right hip and a standard anterolateral approach to the proximal tibia was performed. An oblique incision over Gerdy’s tubercle was used, which extended distally traversing approximately 1 cm lateral to the tibial crest and extending proximally over the lateral femoral condyle. Full thickness flaps were elevated off of Gerdy’s tubercle ,and the fascia was incised 1cm lateral to its insertion over the tibia shaft.

The fracture site was identified and hematoma was evacuated. Submeniscal sutures were placed to aid retraction and the nondisplaced split portion of the plateau fracture was “opened” like a book to allow visualization of the joint. Two primary pieces of the articular surface were attached to a thin rim of subchondral bone and depressed into the metaphysis. Under direct visualization, the metaphyseal bone under the most medial articular fragment was elevated with a bone tamp using the lateral femoral condyle as a template. The articular surface was provisionally held with a 0.062 K-wire, but lacked any substantial underlying bony support to hold it in place.

At this time, a 10-cc packet of biocomposite bone graft was prepared (Plexur M; Medtronic, Minneapolis, Minn.). This biocomposite graft is quick to setup and apply, and easily moldable after heating on a warming device for 5 minutes to 10 minutes. It is drillable when hard and incorporates into surrounding bone. It is composed of cortical fibers, extracellular matrix proteins, calcium, phosphate, and trace elements suspended in a resorbable polymer matrix (L-lactide-co-glycolide). This type of graft in a non-moldable form (Plexur P; Medtronic, Minneapolis, Minn.) has been found to have good compressive strength and efficacy at maintaining articular reduction and preventing subsidence in a preliminary series of 29 Schatzker II tibial plateau fractures without complications. Articular subsidence was found to be <2 mm in all cases at 6-month radiographic follow-up, a significant improvement from published results using autogenous iliac crest graft and calcium phosphate cement.

Figures 3a, 3b and 3c. Intraoperative AP notch radiograph shows provisional reduction and fixation of the medial aspect of the lateral plateau articular surface with biocomposite grafting under the articular fragment was used for increased bony support and pinning with 0.062 K-wires (a). Reduction and pinning of the lateral aspect of the articular surface (b) followed by final grafting of the metaphyseal void and closure of the open book (c) is shown.

In our case, the graft was heated on a warming device for 8 minutes and then molded under the medial aspect of the articular surface to form an initial structural support that hardened in 3 minutes to 4 minutes. This technique allowed the medial aspect of the articular surface to be more easily elevated and securely pinned into anatomic position with two 0.062 K-wires (Figure 3).

Figures 4a and 4b. Intraoperative AP notch (a) and lateral radiographs (b) show the final open reduction and internal fixation construct with proximal rafting screw fixation through biocomposite graft and native bone.

Attention was then turned to the more lateral articular fragment, which was provisionally reduced and pinned in place with K-wires. Using the same technique described above, a rim of biocomposite graft was reheated in its sterile packaging, molded, and placed under the articular surface to provide initial structural support. The remaining metaphyseal bone defect was then filled with reheated graft until hardened and the open book portion of the fracture was closed without difficulty. K-wires were used to hold the lateral portion of the plateau fracture closed and a 6-hole buttress plate (Peri-Loc VLP; Smith & Nephew, Memphis, Tenn.) was placed. Non-locked 3.5-mm cortical screws were used distally to bring the plate down to the bone and buttress the fracture.

We used 5-mm fully threaded cancellous screws for additional fixation in the metaphyseal bone as well as for proximal rafting screws. Of note, the proximal rafting screws were drilled through the hardened biocomposite graft and native bone without difficulty and achieved secure purchase and fixation in both. Two 3.5-mm fully threaded locked screws were used to secure the final construct given her bone quality (Figure 4). The wound was copiously irrigated, fascia was closed and the submeniscal incision repaired through the screw holes of the plate. After closure, soft dressings were applied and the patient was placed in a knee immobilizer and made non-weight-bearing.

Figures 5a and 5b. Postoperative AP (a) and lateral radiographs (b) 5 weeks after surgery demonstrate hardware in good alignment with initial incorporation of the subarticular biocomposite graft material used for initial structural support.

At 5-week follow-up the patient’s incision was healed and benign appearing, and she had decreased pain with good range of motion. Radiographs revealed intact hardware with maintenance of good fracture alignment. Initial incorporation of the biocomposite graft material used to support the articular surface and fill the metaphyseal void was noted (Figure 5). In our experience, we have not found any increased drainage or sterile abscess formation associated with use of this biocomposite graft. The patient will remain non-weight-bearing until 9-week follow-up.