2.1 History

A complete history should include a characterization of the pain. Were the patient’s symptoms completely resolved after the correction? How long was the pain-free interval? Where is the localization of the pain? The pain history should also exclude other sources of pain, like referred pain from a hip or spinal disease. Bursitis or tendinitis are other sources of extraarticular knee pain. An intraarticular injection with a local anesthetic might help to differentiate knee pain from other sources of pain. The most important questions are summarized in Table 16-1 .

Also of great importance is the patient’s social history. Are there issues of litigation or worker’s compensation? Mont et al have already described factors such as worker’s compensation, reflex sympathetic dystrophy, pain relief of less than 1 year, multiple surgical procedures, and employment as a laborer to be associated with poor outcome [7].

2.2 Clinical examination

The patient’s gait pattern, eg, antalgic gait or a varus thrust during stance, must be observed ( Fig 16-1 ). A Trendelenburg gait points to hip pathology.

The alignment of the lower limb in stance and the soft-tissue condition including previous scars must be examined. Knee effusion suggests intraarticular pathology. The ligamentous laxity of the knee must be evaluated. In knees with a gross malalignment or gross laxity a more constrained type of knee prosthesis might be indicated. Also, one should check for signs of reflex sympathetic dystrophy, like skin temperature changes and skin hypersensitivity ( Table 16-2 ).

2.3 Radiographical work-up

Radiographic examination includes standard standing AP and lateral x-rays, and also a patellar view ( Fig 16-2a-c, 16-3a-b ). The alignment of the leg is evaluated on a weight-bearing AP view of the whole leg ( Fig 16-2d, 16-3c ). In case of suspected ligamentous laxity, stress x-rays can be of use.

On the AP x-ray the progression of the osteoarthritic process can be assessed. At the site of the osteotomy the presence of a nonunion must be excluded. One should look for the presence of (stress) fractures. The tibiofemoral alignment should be assessed regarding over- or undercorrection. Also the presence of hardware should be noted.

Other radiographic peculiarities will be discussed in the surgical technique section.

It is important to determine whether the radiographic findings can explain the patient’s complaints.

2.4   Further preoperative diagnostics

Occasionally, other investigations can be of use. A scintigraphy may be useful in the diagnosis of infection or neoplasm. Magnetic resonance imaging (MRI) can be employed if an intraarticular pathology is suspected, eg, loose bodies or a meniscal tear. In case of a suspected nonunion, a computed tomography (CT) scan is mandatory.

In case of a suspected infection, a blood analysis with ESR, CRP, and white cell count can be useful. A culture sample should also be obtained either through tissue biopsy or knee punction aspirate. Infection scan (eg, IgG, labelled white blood cells) is indicated in these cases.

Diagnostic arthroscopy can be useful to determine the progression of the osteoarthritis or to treat meniscal tears or loose bodies.

If patient history, physical examination, and radiographic views do not explain the patient’s symptoms, a conservative management is preferable. Only when conservative treatment is insufficient and the patient’s complaints are caused by progressive degenerative changes, TKA is indicated.

3.1 Preoperative planning

On examining the knee x-rays after HTO, three major changes in anatomy can be observed. In the AP plane there is an increased valgus angulation of the proximal tibia, resulting in a higher medial plateau and a relative “depression” of the lateral plateau ( Fig 16-4 ). Due to this anatomy the lateral plateau cannot be used as a reference for the position of the joint line. Especially after a lateral closed-wedge HTO, the tibial shaft is displaced medially relative to the tibial plateau. This step-off can cause problems in fitting the tibial component since the tibial stem might interfere with the lateral cortex. In cases of severe depression of the lateral tibial plateau, tibial augments are needed.

On the lateral x-ray, a decrease of the tibial slope or even a negative slope after HTO is sometimes observed ( Fig 16-5 ). This influences balancing of the TKA, as the tibial slope needs to be corrected to obtain equal flexion and extension gaps.

The third anatomical change is the presence of a patella infera in up to 80% of patients after HTO ( Fig 16-6 ) [8–10]. This causes problems with exposure and impingement of the patella against the prosthesis.

In the authors’ experience these anatomical changes are not present or are less severe after a medial open-wedge HTO than after lateral closed-wedge techniques. Patella infera is less frequent when combining a medial open-wedge HTO with a distal tuberosity osteotomy [11].

On AP x-rays the tibial resection needs to be planned to restore the anatomical tibial angle. Note that in most cases there is a very small amount of bone to be resected on the lateral side (see Fig 16-4, Fig 16-7 ). In case of a severe lateral depression, augments should be used rather than lowering the level of resection and consecutively the joint line. Also consider the medial displacement of the tibial shaft. One might need to place the component slightly more medial to prevent impingement of the tibial stem on the lateral cortex. In order to prevent overhang on the medial side sometimes a smaller tibial metal back must be implanted. In cases of severe medial displacement one might use offset stems or even a custom-made prosthesis. On the lateral x-ray the tibial slope and patellar height must be evaluated to be aware of overresection of the posterior tibia and difficulties of exposure.

The presence of gross ligament laxity might need for more constrained implants or ligament retensioning procedures. open-wedge procedures can be used to tighten the ligaments at the medial or lateral side of the knee, obviating the need for a constrained implant ( Fig 16-8 ).