7 The Knee

10.1055/b-0038-160357

7 The Knee

S. Sell, S. Rehart, V. Crnic, A. Schoeniger

7.1 Arthroscopic Synovectomy/Baker’s Cyst

Indication

Larsen 0–III destruction. There must be no significant knee joint instability.

Specific disclosures for patient consent

Recurrence. Infection.

Position

The Baker’s cyst is usually excised first with the patient secured in the lateral position with two pelvic supports. Tilting the table and internally rotating the knee provides a good starting position for a posterior approach to the knee joint.

The pelvic supports are removed following the extirpation, and the patient is turned supine. Arthroscopic synovectomy can then be performed using the same drapes.

Specifics

Preoperative ultrasound of the popliteal fossa (on the day before surgery) to determine the cyst dimensions (Fig. 7‑1 ).

Surgical technique

Baker’s cyst extirpation

Approach, see Fig. 7‑2 . Surgical technique, see Fig. 7‑3, Fig. 7‑4.

Arthroscopic synovectomy

Approach, see Fig. 7‑5 . Surgical technique, see Fig. 7‑6, Fig. 7‑7, Fig. 7‑8, Fig. 7‑9, Fig. 7‑10, Fig. 7‑11, Fig. 7‑12 . For clinically significant synovitis, arthroscopic synovectomy is combined with radiosynoviorthesis 6 weeks postoperatively.

Postoperative aftercare

As a rule, this procedure is followed by radiosynoviorthesis 6 weeks postoperatively.

Fig. 7.1 Preoperative ultrasound examination. Multilocular cyst. The exact size of the cyst dictates the size of the incision and can be determined preoperatively.

Fig. 7.2 A curvilinear or S-shaped (Trickey’s) approach to the Baker’s cyst.

Fig. 7.3 Most often, as in this case, a curvilinear approach is sufficient and can be extended distally if needed. The lower leg fascia is divided.

Fig. 7.4 The cyst normally lies between the semimembranosus muscle and the medial head of the gastrocnemius. A large multilocular cyst is pictured. These can usually be detached by blunt dissection with scissors. Better visualization of very large cysts can be achieved by releasing some of the fluid after part of the cyst has been dissected. The stalk connected to the joint is first exposed and then closed.

Fig. 7.5 Classic anteromedial and anterolateral approaches. Entry points are frequently made somewhat more proximal than those for a standard arthroscopy. This facilitates a more effective synovectomy of the superior recess, where most of the synovitis masses are commonly located. Synovectomy is performed with a combination of various-sized burs. A vaporizer may be needed for significant bleeding. Two portals are typically sufficient, but more (even dorsal portals) should be used if needed.

Fig. 7.6 Synovial fluid analysis is always performed if there is no definitive diagnosis.

Fig. 7.7 Arthroscopic synovectomy of the suprapatellar recess with the knee in extension.

Fig. 7.8 Synovitis in the suprapatellar recess.

Fig. 7.9 Pronounced synovitis in the suprapatellar recess.

Fig. 7.10 Suprapatellar recess following synovectomy.

Fig. 7.11 Instruments must be frequently switched between the portals, particularly when performing a synovectomy of the lateral recess.

Fig. 7.12 Synovitis around the cruciate ligament is typically removed using small burs.

7.2 Knee Endoprosthesis

Total knee replacement is one of the most common procedures in rheumatoid patients. The knee joint is affected in 90% of patients.

Indication

Larsen III–V destruction with significant clinical symptoms.

Principles for determining treatment

Treatment is initiated in rheumatoid patients earlier than in osteoarthritis patients. This lessens the likelihood of having to treat multiple joints simultaneously in progressive forms, and thereby avoids the lengthy phases of treatment needed to restore mobility.

Regular and relatively close clinical and radiographic monitoring is important if surgical intervention is deferred for a rapidly progressive inflammatory form. It is not uncommon for these progressive forms to develop significant bone degeneration in the space of 3 to 6 months. This significantly worsens the underlying conditions requiring surgical correction. It is also essential to monitor the supporting ligaments. Progressive laxity of the medial collateral ligament poses a difficult problem surgically, particularly in a knee with valgus deformity.

A highly individualized approach is needed when determining indications for endoprosthesis placement in the lower extremities. Certain basic principles, however, have proved successful:

Reconstruction of a knee and hip on the same extremity in order to achieve a strong functional leg.
Proximal before distal: frequently the hips are replaced first.
For significant flexion contracture of the knee and hip, evidence suggests that it is necessary to address the other ipsilateral joint within a very short period of time so as to avoid the formation of a fixed flexion contracture postoperatively.

In specific situations (such as rapid deterioration of multiple joints), unilateral procedures on multiple joints are possible.

Specific disclosures for patient consent

Prosthetic loosening. Bone fracture/perforation. Approximately 3-fold increase in risk of infection. Skin injury (steroid atrophy).

Instruments

Prosthesis system from the manufacturer of choice. Uncoupled (cruciate retaining [CR], anterior stabilized [AS], posterior stabilized [PS]), partially coupled, coupled.

Position

Supine. Leg holder or sandbag with leg support. A radiograph may be needed.

Surgical technique

Synovitis

See Fig. 7‑13, Fig. 7‑14, Fig. 7‑15.

Fig. 7.15 Severe osteophyte formation. All osteophytes should be removed. There are varying forms of disease progression, ranging from minimal to prolific osteophyte formation. Heavy osteophyte production is very common in spondyloarthritis. It is important to be very conscientious about the aftercare of these patients as their knees often stiffen progressively.

Posterior cruciate ligament (PCL)

There are no general guidelines as to whether the PCL should be resected or preserved. This ultimately depends upon the operative findings.

Alignment of the components

Rotational alignment is commonly complicated by considerable bone destruction that is found in a number of rheumatoid patients.

Femoral components: Rotational adjustments are made using multiple reference lines simultaneously. See also Fig. 7‑16.

Valgus deformities of up to 20° are often associated with a 5° external rotation with respect to the dorsal femoral condyles. This external rotation can also be significantly greater in more severe deformities. See Fig. 7‑17, Fig. 7‑18, Fig. 7‑19.

Tibial components: In rheumatoid patients, a functional alignment is used for the tibial component. Following implantation of the trial component, the knee is fully mobilized and the position marked.

In addition, an anatomical alignment is carried out based on anatomical landmarks: using the middle of the tibial prosthesis at the junction of the middle third of the patellar ligament as a guide, externally rotate toward the posterior margin of the tibial plateau.

Fig. 7.16 Rotational alignment using the posterior condyles is particularly difficult in valgus destruction associated with destroyed or hypoplastic lateral condyles. In this case the placement of the reference guide must be accurately evaluated to ensure that it is far enough posterior. Otherwise, there is a risk of internal rotation of the femoral component. Bone destruction and missing cartilage lining must be taken into account when comparing and calculating the rotation for alignment.

Fig. 7.17 **(a,b)** Whiteside’s line is marked (for example, with electrocautery) after the joint is opened and before any bone resection. The projected rotation alignment is produced with a chisel by rotating the components after the anchor holes are drilled. In this manner, it can be easily assessed with respect to the Whiteside’s line. The epicondyle axis **(b)** is frequently very difficult to palpate, particularly when the destruction is severe.
We therefore often alter our surgical procedure for a severe valgus knee deformity: the tibia is osteotomized first, and is then reconstructed. For difficult femoral anatomical landmarks, rotational alignment of the femur is based on the tibia with the aid of the reference lines: Whiteside’s line, epicondyle axis, line of the dorsal condyles.

Fig. 7.18 Spacers are used for alignment following tibial resection.

Fig. 7.19 After obtaining sufficient alignment in extension, the flexion gap is adjusted by performing additional dissection of the femoral condyle. Spacers are used to assess the rotational alignment in flexion as well.

Aligning

Knee prostheses are implanted with stronger fixation in rheumatoid patients than in osteoarthritis patients. Our experience has shown that knee prostheses have a tendency to loosen again after 5 to 7 years in patients with inflammatory disease. The opposite is true, however, for men with spondyloarthritis. They tend to develop stiffness in the affected knee joint and, therefore, their ligaments should never be tightened excessively during the procedure.

Rheumatoid valgus knee deformity

Rheumatoid valgus knee deformity is more difficult to address than varus deformity.

Classification of valgus knee deformity

Grade I: mild valgus deformity. Stable medial ligament. Synovectomy of the knee joint. Standard approach.
Grade II: lateral contracture, medially still stable. A release of the lateral contracted elements is essential. Testing is performed in both flexion and extension.
Grade III: severe lateral contracture.
Grade IIIa: medial laxity, can be realigned (usually up to approximately 40° deformity under load). Intraoperatively, the femoral and tibial weight-bearing surfaces are first resected. Next, spacers are placed, and the knee is initially released in extension. A coupled prosthesis is used if the knee cannot be adequately aligned in extension.
Grade IIIb: severe medial laxity.
Grade IV: severe medial and lateral laxity.

A coupled prosthesis is specifically indicated in patients with rapidly progressive and highly inflammatory forms. Approximately 1 to 2% of rheumatoid knee joints fall into this category.

Realigning the contracted lateral structures

Extension contracture: the flexion gap is expanded with a bent Hohmann retractor with the knee placed in flexion. The osteophytes are removed by keeping the osteotome continually aimed toward the bone and as perpendicular to the femur as possible. The posterior capsule is elevated off the femur and pushed proximal with a curved rasp. See Fig. 7‑20 for alternative.

Fig. 7.20 Aligning the contracted lateral structures. As an alternative: The posterior capsule is perforated with stab incisions and then expanded by applying pressure using a Hohmann elevator. Care should be taken around the peroneal nerve, particular with a valgus knee deformity.

Iliotibial band

The iliotibial band is dissected extra-articularly. This is accomplished by identifying and exposing the iliotibial band extra-articularly at the level of the joint. The most severely contracted fibers are palpated and released with stab incisions. The tract is then manually stretched. This is repeated until adequate alignment is achieved.

Alternatively, the tract can be exposed intra-articularly; however, the operative view is significantly reduced, so much so that we use this approach only for mild contractures. See also Fig. 7‑21.

Fig. 7.21 **(a,b)** Aligning the contracted lateral structures. Flexion contracture: First the tension of the posterior cruciate ligament is examined. If it is contracted, it is carefully incised along the posterior edge of the tibia and stripped off. The ligament is then checked for residual tension. Alternatively, it can be punctured with sharp scissors (see approach for posterior capsule). If contracture persists, the ligament is completely severed. This can result in a 1 to 4-mm expansion of the flexion gap.

If an underlying lateral contracture persists, and the situation warrants, the popliteal tendon is then released.

The lateral ligament is addressed next. An initial release is performed by making stab incisions with subsequent re-expansion. If this is not adequate, the ligament itself can be released or the bones can be osteotomized and subsequently refixed. The latter, however, requires that the remaining joint stabilizers be of sufficient caliber.

Rheumatoid varus knee deformity

Rheumatoid varus knee deformity with medial ligament contracture is less common. See Fig. 7‑22.

Anchoring

Bone cement should be used for fixation of prosthesis components because most patients have preexisting osteopenia.

For severe osteoporosis, the shaft of the tibial component is cemented. If necessary, the stability of the entire assembly can be increased with a tibial shaft extension. An overall extension of 80 mm is usually adequate, even in complex cases. See Fig. 7‑23.

Fig. 7.23 A severely sclerotic tibial plateau can be drilled open for better cementation.

Bony defects

Multiple techniques can be used for reconstruction of tibial defects. Very small, contained defects are filled with cancellous bone or cement. Reconstruction of large defects is often performed with resected bone/transplants taken from the opposite side of the tibia. Augmentations for repair of large defects have also become commonplace. See Fig. 7‑24, Fig. 7‑25, Fig. 7‑26, Fig. 7‑27, Fig. 7‑28, Fig. 7‑29.

Fig. 7.24 A very deep medial tibial defect.

Fig. 7.25 The joint line is first identified on the lateral side and osteotomized accordingly. Further resection is performed on the medial side until the largest part of the defect can be covered with a bone augmentation block.

Fig. 7.26 After medial tibial resection, the remaining small residual posterior defect comprises less than one-quarter of the joint surfaces.

Fig. 7.27 Trial implant with fully balanced medial augmentation block.

Fig. 7.28 **(a,b)** A small bony defect.

Fig. 7.29 **(a,b)** Pre- and postoperative radiographs of the affected knee. A large bone defect.

Complex instability

See Fig. 7‑30, Fig. 7‑31, Fig. 7‑32, Fig. 7‑33.

Retropatellar facet replacement

According to the literature, rheumatoid patients have slightly better clinical results if they also undergo retropatellar facet replacement. For us, the amount of clinical destruction plays an important role in determining surgical indications.