Patellectomy is a relatively old and deceptively simple procedure whose results have received attention; the effect of patellectomy on the function of the knee has been a matter of controversy. 30 Of course, the patella is an integral part of the extensor mechanism of the knee and should be preserved whenever possible; however, in certain situations, patellectomy is the only solution. The purpose of the current study was to review the techniques described for doing patellectomy with special reference to the reconstructive procedures.
As reported by Cohn, 6 Putz is credited as the first surgeon to do patellectomy in 1860 for habitual dislocation. Since then, patellectomy has been used primarily for comminuted fractures, but also for infections or tumors of the patella. 15 In 1937, Brooke 4 reported 30 patellectomies and concluded that “a complete recovery of function such that a labouring man could return to full work within four to six weeks of operation”. With these clinical results and additional experimental work, he suggested that “the patella serves no important function in man. In its absence, the efficiency of the knee joint is, if anything, increased both as regards rapidity of movement and power”. 4 According to Ackroyd and Polyzoides, 1 the popularity of patellectomy increased rapidly after this report. When the adverse effects of patellectomy on the knee, especially the rapid onset of degenerative changes, was reported, 6,9 its popularity decreased during the early 1970s. In the authors’ opinion, the study by Kaufer, 14 in which he showed that the force necessary to produce full extension of the knee after patellectomy increased 15% to 30%, was a seminal paper. Many studies then were published that condemned or at least suggested caution for patellectomy. 1,5,7–10,12,14,16,17,24,25 The current trend is to use this procedure as the last resort among surgical alternatives for the treatment of patients with patellar disorders.
Although the surgical indications for patellectomy have narrowed considerably, a review of the literature revealed the following indications for patellectomy: comminuted patellar fractures, 13,16,17,27,30 patellar chondromalacia or osteoarthritis, 1,3,16,25,30 anterior knee pain, 16 recurrent dislocation, 26 infection, tumors, 15,20 and rheumatoid arthritis. 15
It must be kept in mind that patellectomy is recommended as the last choice of treatment and almost all authors advise patellectomy in severe cases in which all other treatment options are not suitable. 13,15 The reason for regarding patellectomy as the last choice is the loss of function of the patella after patellectomy. Therefore, the goal of patellectomy is to restore at least some of the function of the patella. 13
Problems After Patellectomy
The patella increases the lever arm of the quadriceps by producing anterior displacement of the quadriceps-patellar tendon unit. 14,16,24 Although this effect is observed through the entire range of motion (ROM), it increases with progressive extension. Full extension may require as much as a 30% increase in quadriceps force after patellectomy. According to Kaufer, 14 this may be beyond the capacity of some patients, particularly those with long-standing intraarticular disease, those with an advanced age, or those who have extension lag before surgery.
The patella also is a mechanical aid to the function of the knee, because the extensor unit is displaced forward, away from the point of contact between the tibia and femur, by the thickness of its bone and articualar cartilage of the patella. 8 With the absence of the patella, the magnitude and direction of forces acting at the knee are altered and result in a 14% increase in tibiofemoral reaction and a 250% increase in the tangential force in the tibiofemoral joint. 8,12 This is a paradox in that patellectomy leads to knee degeneration, but patellectomy also is used in the treatment of degenerative knee diseases.
Abrasion of the quadriceps tendon against the femoral condyle may result in a tear or a Boutonniére-type deformity. 20 The instant centers of rotation are altered after patellectomy, especially in 15° to 45° flexion. 10,23 The loss of the normal smooth gliding tibia and femur not only accelerates arthrosis, but also puts the internal structures of the knee, especially the menisci, at a greater risk of injury. 10 If a transverse repair is done after patellectomy, complete flexion of the knee is limited 3 because of the decrease in the length of the quadriceps-patellar tendon unit. By the loss of an apparent stabilizing effect of the patella, anterior instability may complicate patellectomy. 24 In the series of Scott, 22 60% of the patients treated by patellectomy experienced giving way. Lateral subluxation of the quadriceps-patellar tendon unit may occur because greater force is necessary to compensate for the smaller moment arm. 20,30 The patella provides protection to the trochlea and distal femur from direct blows, 15 and these structures are vulnerable to injury after patellectomy. Finally, cosmesis of the knee also is impaired after patellectomy. 5,13,15,30
Techniques of Patellectomy
Several techniques to do a patellectomy have been reported but none of them have been accepted universally. 1–3,7,10,12,13,15,18,21 Moreover, it can be argued that most of the techniques described are used only by the inventors. It is well known that randomized clinical trials are thought to provide the highest-quality evidence for clinical decision-making. 28 However, a careful review of the literature revealed only one prospective randomized trial, in which two forms of patellectomies were compared 13; other studies were uncontrolled clinical series or experimental studies. There are certain difficulties in the evaluation of clinical series in that the indications, patient selection criteria, techniques, postoperative regimens of care, criteria for evaluation, and followup periods are almost completely different and the results are conflicting. However, experimental studies are seldom directly applicable to clinical work.
The defect created by the excision of the patella may be repaired in a transverse or longitudinal fashion. Kaufer 14 showed that transverse repair was superior to a longitudinal repair in that only 15% of additional force was required to extend the knee after a transverse repair compared with 30% after a longitudinal repair. The main objection to a transverse repair is that complete flexion of the knee is limited because of the decrease in the length of the quadriceps-patellar tendon unit. 3 An additional criticism is the longer period of immobilization that is needed to protect the tension on the suture line. 15
Although ROM is protected and the period of immobilization is relatively shorter after longitudinal repair, the main problem of patellectomy, using a longitudinal repair is the decrease in the quadriceps force (as much as 30%), as reported previously. 14 However, experimental results should be viewed with caution when applied to clinical practice. As reported by Wilkinson, 27 there usually can be as much as 30% difference in the power between the right and left quadriceps muscles, which does not necessarily denote dominance. If a quadriceps muscle on the surgically treated side had greater power before surgery, then the objective assessment becomes difficult. Repair of the defect by Z-plasty or cruciate-plasty 18,21,23,30 or fascia lata graft 2 have been described, and all seem to act as a longitudinal repair. In the authors’ opinion, these techniques may be useful in large defects when approximation of the ends of the quadriceps muscle is not possible.
Several techniques also have been described to reinforce the defect produced by the absence of the excised patella. In these techniques, after closure of the defect transverse 26,29 or longitudinally 13 or with a strip of proximally attached quadriceps tendon, 3 some parts of the quadriceps muscle are advanced over the site of the excised patella. These techniques provide relatively better cosmesis and better protection of the trochlea from injury. Anterior instability and lateral subluxation of the tendon also are avoided when these techniques are used. However, limitation of complete flexion by transverse repair is not expected to be restored by advancing the vastus medialis over the sutured defect, as in the techniques described by West and Soto-Hall 26 or Zaricznyj. 29
Baker and Hughston 3 reported long-term (mean, 13.8 years) results using the Miyakawa technique of pallectomy. In this technique, a strip of quadriceps tendon is pulled distally to fill the void that was left by the removal of the patella; the vastus medialis and lateralis then are advanced over the site of the excised patella. Eighteen of 20 patients were rated as having good or excellent results by objective criteria. 3
Compere et al 7 described a technique in which a tube was constructed to contain any bone regeneration within. In this technique, the medial border of quadriceps is brought underneath and sutured to the lateral aponeurotic border, creating a tube. Then the vastus medialis also is advanced. The clinical significance of calcification or ossification at the site of the patellectomy also is a matter of debate. Some regard it as a source of pain, 15 whereas others find it beneficial to substitute for the patella. 7,27 Nevertheless, the overall end results with this technique are highly successful.
Gunal et al 13 did patellectomy by combining it with the vastus medialis obliquus advancement technique. In this technique, the defect is closed longitudinally and the vastus medialis obliquus is advanced distally and laterally and distal 1 cm and is plicated to increase the angle of insertion in the sagittal plane (Fig 1). The main advantage of this technique is the use of the vastus medialis obliquus muscle, the only part of the quadriceps that has no function in knee extension. 11,19 The functional parts of the quadriceps are not impaired. Although the results of clinical and mechanical studies are promising. 10,12,13 and seem to indicate that the problems of patellectomy are overcome, this technique only has been compared with simple longitudinal repair in a prospective randomized trial 13; more trials are mandatory before a definitive conclusion can be made.
It is hard to make conclusions because of the lack of scientific evidence, especially the lack of prospective randomized trials. However, it currently is agreed that the patella is an important part of the exterior mechanism and should be preserved if possible; when patellectomy is indicated, it seems logical to combine patellectomy with reinforcement techniques as described.
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O. Sahap Atik, MD, Guest Editor