18 Osteotomies for failed osteotomies around the knee
A failed osteotomy can be defined as an osteotomy of which the goal aimed at preoperative planning of correction was not reached as a result of intraoperative or postoperative complications. Although osteotomies around the knee are the most frequently performed osteotomies in the limbs, only few references can be found in the literature regarding failed osteotomies treated with recorrective osteotomies [1–3]. The complications that may lead to a failed high-tibial osteotomy (HTO) have been described [4–8]. In a previous publication the complications in a large series of high-tibial osteotomies were presented . These complications include the following:
Fracture of the medial cortex with opening medially in closed-wedge HTO
Nonunion or delayed union
Loss of fixation
Late plateau fracture
Deep venous thrombosis
Almost all of these complications also apply to the distal femur osteotomies (DFO).
Malunited osteotomies may have been caused by many [1–5, 7–12] of the above mentioned complications. Depending on the time of presentation of a patient with a malunited osteotomy around the knee, there still may be the possibility of performing a recorrective osteotomy. However, in some patients joint- preserving surgery is not possible and the deformity can only be corrected during total knee replacement. The treatment of total knee replacement after osteotomies is discussed in chapter 16 “Total knee arthroplasty after osteotomy around the knee”. In this chapter the bone corrections of failed osteotomies around the knee by recorrective osteotomies is described.
2 Causes of failure
Malunited osteotomies can result from inaccurate preoperative planning, intraoperative technical errors, and failure of fixation of the osteotomy . In addition, mistakes can be made in postoperative rehabilitation jeopardizing the stability after the correction and the bone healing (eg, functional aftertreatment and early full weight bearing after osteotomies fixed with less stable implants).
Preoperative planning of osteotomies is mandatory and has been discussed in chapter 4 “Basic principles of osteotomies around the knee” and chapter 5 “Detailed planning algorithm for high-tibial osteotomy”. Failed osteotomies due to inadequate planning may be caused by planning of correction in the wrong bone, ie, a HTO is performed to correct varus in a leg where (part of) the deformity is localized in the femur. Deformity analysis included as part of the preoperative planning will help to find whether the correction should be performed in the femur or the tibia or in both ( Fig 18-1 ) [9, 10].
Another cause of failure that can be attributed to preoperative planning is the increased joint-line obliquity (see also chapter 14 “Double osteotomies of the femur and the tibia”).
Intraoperative technical errors include imprecise intraoperative measurements, improper use of instrumentation, and errors in performing bone cuts . In addition, specific pitfalls of the osteotomy technique chosen may increase the risk of failure. Imprecise intraoperative measurements can be reduced by using fluoroscopy, rigid alignment bars, fluoroscopy grids, rulers and goniometers, or use of computer navigation during surgery. Improper use of instrumentation and errors in performing bone cuts must be attributed to the skills of the surgeon. Saw guides that allow for guiding of the saw blade have been suggested as very helpful in improving the accuracy of bone cuts. Instead of K-wires used as guides for bone cuts it is advisable to use drill bits as these maintain a straight line through the bone as opposed to K-wires.
Specific pitfalls of the closed-wedge as well as open-wedge osteotomy techniques are frequently found as causes of failure. In closed-wedge osteotomies the position of the hinge point near the contralateral cortex is critical. If the hinge point is not chosen close enough to the cortex the remaining bridge of bone will be broken rather than bent, thus creating an unstable fracture . If the opposing cortex breaks, not only is stability lost but it may spring open after wedge closing, thus increasing the correction greatly over what was planned. This is an important cause of overcorrection in closed-wedge osteotomies. Loss of cortical contact may be a cause of undercorrection as well as overcorrection. If there is loss of cortical contact on the opposite side, the distal cortex may drop inside the proximal cortex when it settles into the cancellous bone, thus losing correction. However, if the distal cortex falls inside of the proximal cortex on the other side an increase in correction is caused after closing and compression of the osteotomy. Inadequate medial buttress of the fixation material inserted may lead to collapse of the opposite cortex after weight bearing is started and result in undercorrection ( Fig 18-3 ).
In open-wedge osteotomies integrity of the opposite cortex is equally important. If the opposite cortex cracks during opening of the wedge, there is no bone stability because there is only point contact . As the wedge is opened the osteotomy may become unstable in rotation as Hohmann retractors inserted to facilitate exposure cause rotation forces in the distal femur as well as the proximal tibia. A specific problem may be encountered regarding plate positioning. When the plate is positioned too anterior or too posterior, flexion respectively extension may be introduced in the osteotomy ( Fig 18-4 ). In addition, a specific problem may be encountered when blade plates are used during wedge opening in osteoporotic bone: during distraction the plate instead of pushing open the osteotomy may sink into the osteoporotic fragment preventing further opening of the wedge. After fracture of the opposite cortex, stability can be regained by bone grafting and compression of the grafted osteotomy. However, if the bone graft is compressed back beyond the planned correction, the wedge must be reopened and more graft inserted and recompressed until enough graft is added under compression to give stability at the desired position.
Failure of fixation as a cause of a failed osteotomy may be due either to insufficiency of the fixation material or weakness of the bone, or a combination of both. During closed-wedge osteotomies, a secondary breakage of the opposite cortex can occur when the distal cortical screws in tibial osteotomies or the proximal femoral screws are tightened. The cause could be a shift of the distal part of the tibia respectively the proximal part of the femur towards the plate if the blade were not advanced far enough into the metaphyseal fragment. Furthermore, the surgeon should be well aware of the fixation strength of the fixation material chosen to stabilize the osteotomy after correction. Less stable fixation constructs necessitate application of additional stability through casting or bracing and adjustments in postoperative rehabilitation regarding functional aftertreatment and start of full weight bearing. Osteoporotic bone may cause fixation material to sink in after which correction is lost. Important advantages of plate fixators are not only the superior mechanical strength but also the specific fixation stability even when applied in osteoporotic bone.
The gathering of documentation, preoperative x-rays (if available) planning drawings, surgical reports, fluoroscopy pictures and x-rays taken immediately postoperatively, documentation on postoperative rehabilitation, and x-rays taken at postoperative follow-ups will allow the reconstructive surgeon to gain insight in the causes of failure.
3 Symptoms, clinical findings, and planning for recorrection
Depending on the cause of failure, the patient with a malunited osteotomy presents with a wide array of complaints. It should be remembered that complaints may only develop after compensation mechanisms fail. The importance of a mobile subtalar joint to compensate for overcorrected or under-corrected frontal plane osteotomies is well known [9, 12] Generally, valgus deformity is more acceptable than varus deformity because inversion in the subtalar joint is greater than eversion . In Fig 18-5 the compensatory motions in the subtalar joint are displayed.
Malunions in the sagittal plane may be compensated for by stretching or contracture of soft tissues around the knee joint. Transverse plane malunions are not well tolerated by the knee joint as essentially the knee joint acts as a hinge and has very limited compensatory mechanisms for malrotations. Pain after a malunited osteotomy may have several causes: stretching of capsule and ligaments, overload of cartilage, subchondral and metaphyseal bone (see Fig 18-2 ), or referred pain in the knee caused by abnormal loading of a hip joint, leg-length difference, low back pain, etc.
In patients who complain about persistent pain localized at the osteotomy side, the surgeon should always rule out the existence of a nonunion as this calls for a different preoperative work up and operative treatment. In undercorrected failed osteotomies a patient presents with persistent joint pain not or only slightly improved by the osteotomy that has been performed. Persistent stretching of ligaments or created overtension of ligaments, eg, because of lack of release during open-wedge osteotomies may also cause pain. Failure of fixation material and protrusion of screws or plates is not an infrequent cause of pain. Soft-tissue scarring may be another cause of pain in the osteotomy area.
The cosmetic aspect of a failed osteotomy may pose a serious problem for the patient and should not be overlooked ( Fig 18-6 ). Generally, patients are unhappy with the cosmetic appearance of correction of more than 3–4° varus or valgus beyond neutral. Although as a general rule osteotomies should not be performed only for the purpose of cosmesis, an indication may be present for a recorrection in a patient presenting with a multiply malunited osteotomy.
On clinical examination specific findings can be noted in patients with malunited osteotomies. Gait and stance abnormalities can be inspected. A varus thrust gait ( Fig 18-7 ), antalgic limping, limping due to leg-length difference, or instability may all be found. Leg-length difference should be measured in stance and documented. Shortening always exists when bone is removed, yet with a valgization osteotomy this almost never poses a problem. Shortening is often seen when the osteotomy has sheared and when the apex of the wedge for correction has been medial to the medial cortex. Shortening is a greater clinical problem when a varization osteotomy is performed.
The position of scars around the knee should be documented as well as areas of sensory loss related to the location of the osteotomy. Calluses on the feet point at abnormal loading. Muscle atrophy may be caused by disuse or neurological deficit related to complications of the osteotomy. The range of motion of the knee joint and in most cases also of the hip joint and upper and lower ankle joints should be documented. This information will, for example, help the surgeon to find out whether a hyperextension of the knee can only be attributed only to a malunited osteotomy resulting in a negative tibial slope or is also partly caused by a stretched posterior capsule of the knee.
The rotation profile should be assessed as described in chapter 15 “Rotational osteotomies of the femur and the tibia” to document or rule out transverse plane deformities.
The laxity of the knee ligaments should be carefully examined and documented as new ligamentous laxities may be caused by the osteotomy performed or the malunited position of the bones. A special mention should be made of the laxities that can be caused by severely depressed knee compartments after closed-wedge osteotomies around the knee. Stress x-rays will help to diagnose these laxities (see Fig 18-8 ) Instability causes a major problem in these patients. Any surgical procedure that compromises the lateral ligament will compromise the result. The lateral ligaments are not easily tensioned and the proximal fibula must not be compromised. Resection of the fibular head and reattachment of the ligaments or disarticulation of the proximal tibiofibular joint allowing the tibia to slide proximally, and is a source of catastrophic failure. For salvage in these cases, the fibula may be shortened and the fibular head pulled distally to regain tension (see Fig 18-8 ).