Patella and/or Extensor Mechanism Allograft Reconstruction

William H. Warden III

Douglas W. Jackson

INDICATIONS

A chronic dysfunctional extensor mechanism with an associated symptomatic extensor lag that persists after multiple repair or reconstruction attempts may be amenable to allograft reconstruction. Potential allograft techniques for reconstructing a portion or all of the extensor mechanism involve using an allograft that includes the quadriceps tendon with or without a patella, patellar tendon, and tibial tubercle. The allograft is used to fill defects and provide continuity by replacing or supplementing deficient tissue. If the patient’s patella is usable, we prefer using an Achilles tendon allograft with attached bone block to replace the nonfunctional quadriceps and/or patellar tendon.

Extensor mechanism disruption can occur as result of a traumatic event, tendon degeneration, or as a complication of knee surgery. Primary and secondary techniques for repair or reconstruction of specific portions of a deficient extensor mechanism have been described and are often successful. If multiple attempts at direct repair and reconstruction fail and the patient still has an extensor lag, allograft replacement of the extensor mechanism becomes a consideration.

The main indication is a symptomatic extension lag related to a deficiency in the extensor mechanism that has failed at least one primary repair and/or reconstruction using autogenous tissue, for example, failed quadriceps and patellar tendon repairs with large palpable tendon defects. Other causes of irreparable extensor deficits include disruption of the extensor mechanism during or following procedures such as:

patellectomy
total knee arthroplasty
patellar realignment procedures
lysis of adhesions for arthrofibrosis
correction of patella infera or infrapatellar adhesions

CONTRAINDICATIONS

Current infection in the knee or underlying bone
An extensor mechanism that can be reconstructed using primary repair and/or reconstruction with local autogenous tissue
A patient who does not wish to accept restricted knee flexion
A patient who is unwilling to accept to accept a minimum of 6 to 8 weeks or longer of bracing and an involved postoperative rehabilitation
A patient who is averse to possibly a manipulation, arthroscopic lysis of adhesions, and/or further open repair of portions of the graft
A patient who is not willing to accept the possibility of effusion and low-grade inflammatory response that may persist for a long period after a large allograft (entire extensor mechanism)
A patient who is unwilling to accept that an allograft may fail or need to be removed

PREOPERATIVE PLANNING

A history and physical examination of the knee and extremity includes a review of the duration and severity of the patient’s symptoms and extensor mechanism dysfunction in relation to the patient’s surgical history. Particular attention is given to prior extensor mechanism procedures and includes the number performed and the success or failure of each of those surgeries. Prior operative reports are reviewed; previous history of infection is explored as well as associated potential risk factors (e.g., diabetes, renal failure, collagen diseases, immune deficiencies, chronic medications, and smoking history). These and any factors that may delay wound healing are discussed with the patient. The current symptoms related to the extensor lag, episodes and frequency of giving-way, disability with stairs, and arising from the seated position are documented.

The complete physical examination of the lower extremities includes documentation of active and passive range of motion, evaluation of the use of assisted walking devices, and gait pattern. Special attention is paid to the prior surgical incisions over and around the knee. In addition, the degree of extensor lag and any restriction in passive extension (fixed flexion contractures) are documented. The tracking of the extensor mechanism during active and passive range-of-motion testing is assessed. The ideal candidate for this reconstruction will have 120 degrees or more of active flexion.

Radiographs include four views of the knee with standing (anteroposterior and 30 degrees flexed), lateral, and Merchant views. These are evaluated for degenerative arthritis in all three compartments, as well as for patella infera, patella alta, and the presence or absence of a patella. They are also evaluated for hardware and hetereotopic bone. If an associated knee replacement has been performed, it is assessed for alignment, loosening, and the status of the patella, if present, and its alignment. Further studies may be necessary to evaluate rotational alignment if malrotation is a contributing factor to the extensor mechanism dysfunction.

Laboratory studies may include an erythrocyte sedimentation rate, serum C-reactive protein level, and white blood cell count if there is a possibility of chronic infection. If an effusion is present, a knee aspiration is performed and sent for cell count, crystal analysis, and synovial fluid cultures. Radiographs are sent to the tissue bank for sizing of the entire allograft if a patella allograft is to be part of the reconstructed extensor mechanism.

SURGERY

Technique

Ancef 1 g (or alternative antibiotic) is given intravenously 1 hour before surgery if there is no history of allergy or other contraindication. The knee to be reconstructed is marked and observed by professional staff. This is done even when the patient has multiple scars and a palpable defect at the surgical site. The patient is placed in the supine position on the operating table with a pneumatic tourniquet high around the thigh of the involved lower extremity that has been marked and again checked in the operating room by the staff and physician. The extremity is then prepped and draped separately in the usual orthopaedic manner.

The previous surgical incisions as well as a line for the incision are marked with methylene blue before the application of the Steri-Drape. Once ready for the incision, the tourniquet is inflated after extremity elevation and with the knee flexed 90 degrees. We prefer a midline skin incision if possible;
however, we may use a previous incision and extend it as needed proximally and/or distally to obtain adequate exposure. If there are multiple incisions present, it is our preference to use the most lateral incision and not cross a previous surgical incision in a manner that may compromise the blood supply to a section of skin. The dissection is carried down in the midline elevating skin and subcutaneous flaps, with consideration for blood supply preservation determining the extent of exposure. The medial and lateral patellar retinaculum, quadriceps, and patellar tendon are exposed. The medial and lateral gutters and suprapatellar pouch spaces are re-established. The defect(s) in the extensor mechanism is defined. The midline incision is carried proximally into the host quadriceps maintaining a medial and lateral margin of tendon to suture to in the repair. This can be difficult if there is minimal host quadriceps tendon remaining proximally. The incision is carried in the midline distally to expose the host tibial tubercle. It is important to maintain as much of the host soft tissue medial and lateral to the incision as possible.

The allograft specimen to be used is prepared on a side table (see Chapter 17

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